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1

Aureobasidins as new inhibitors of P-glycoprotein in multidrug resistant tumor cells.  

Science.gov (United States)

Cyclic depsipeptide antibiotic aureobasidin A (AbA) and its analogs were tested for the inhibitory activity of P-glycoprotein in multidrug resistant cancer cells as well as for the antifungal activity. Some analogs with lower antifungal activity than AbA showed higher inhibition of P-glycoproteins indicating difference of the structure-activity relationships between the two activities. Among AbA analogs tested, [D-beta-hydroxy-methylvalyl9]-AbA newly prepared by chemical synthesis, which had much lower antifungal activity than AbA, showed 10-fold higher inhibitory activity of P-glycoprotein than AbA. PMID:9589072

Kurome, T; Takesako, K; Kato, I

1998-03-01

2

Flurazepam inhibits the P-glycoprotein transport function: an insight to revert multidrug-resistance phenotype.  

Science.gov (United States)

P-glycoprotein mediated drug transport may lead to a multidrug resistance phenotype often associated with a poor response to the successful treatment of a variety of human disorders. Several agents have been found to modulate P-glycoprotein drug resistance, most probably by blocking its transport function. The aim of this study was to examine the effects of some benzodiazepines (bromazepam, chlordiazepoxide, diazepam and flurazepam) able to bind to P-glycoprotein in proteoliposomes on its transport function and ATPase activity in the human cancer cell line, KB-V1. The toxicity of the benzodiazepines drugs towards KB-V1 cells was first evaluated and the non toxic drugs concentrations were used to assess the drug efflux and the ATPase activity. Using the flow cytometry approach, the accumulation and efflux of daunorubicin were followed by measuring the daunorubicin associated geometric mean fluorescence intensity. Vanadate was employed as a comparative inhibitory compound. Flurazepam was able to inhibit the daunorubicin efflux in 80%. ATPase activity determined by a colorimetric assay revealed that flurazepam inhibits the P-glycoprotein enzymatic activity, indicating coupling between drug transport and ATP hydrolysis. Bromazepam, chlordiazepoxide and diazepam behaved as activators of the P-glycoprotein ATPase activity, suggesting a role as transported substrates and did not interfere in the daunorubicin transport. PMID:18190907

Lima, Sofia A C; Tavares, Joana; Gameiro, Paula; de Castro, Baltazar; Cordeiro-da-Silva, Anabela

2008-02-26

3

Pharmacokinetic modeling of multidrug resistance P-glycoprotein transport of gamma-emitting substrates  

International Nuclear Information System (INIS)

P-glycoprotein, the human multidrug resistance (MDR1) gene product, is an integral membrane protein expressed on the plasma membrane of MDR tumor cells and is the best characterized of a family of efflux transporters that confer chemotherapeutic resistance. The use of gamma-emitting 99mTc-agents to image P-glycoprotein function in human tumors in vivo has been proposed. Net tumor cell content of 99mTc-Sestamibi, 99mTc-Tetrofosmin and several 99mTc-Q-complexes 99mTc-Q58 and 99mTc-Q63) are function of passive potential-dependent influx and MDR1 P-glycoprotein-mediated active extrusion. To better understand the overall fidelity of these P-glycoprotein substrates to report MDR activity in vivo in relation to tissue perfusion, a compartmental model of tracer pharmacokinetics was developed. Modeling indicates that tissue perfusion will impact pharmacokinetics in vivo in a manner that will tend to diminish P-glycoprotein-mediated phenotypic differences between tissues when they are perfusion-limited. However, dynamic imaging to extract efflux rate constants is independent of perfusion and may represent the highest quality methodology for collecting the desired information regarding activity of the efflux transporter. Much work remains to translate these concepts and biological targeting properties into clinical practice

4

Characterization of multidrug resistance P-glycoprotein transport function with an organotechnetium cation  

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Multidrug resistance (MDR) in mammalian cells and tumors is associated with overexpression of an {approximately}170 integral membrane efflux transporter, the MDR1 P-glycoprotein. Hexakis(2-methoxyisobutyl isonitrile) technetium(I) (Tc-SESTAMIBI), a {gamma}-emitting lipophilic cationic metallopharmaceutical, has recently been shown to be a P-glycoprotein transport substrate. Exploiting the negligible lipid membrane adsorption properties of this organometallic substrate, we studied the transport kinetics, pharmacology, drug binding, and modulation of P-glycoprotein in cell preparations derived from a variety of species and selection strategies, including SW-1573, V79, Alex, and CHO drug-sensitive cells and in 77A, LZ-8, and Alex/A.5 MDR cells. Rapid cell accumulation (T{sub 1/2} {approx} 6 min) of the agent to a steady state was observed which was inversely proportional to immunodetectable levels of P-glycoprotein. Many MDR cytotoxic agents inhibited P-glycoprotein-mediated Tc-SESTAMIBI efflux, thereby enhancing organometallic cation accumulation. 70 refs., 7 figs., 2 tabs.

Piwnica-Worms, D.; Vallabhaneni, V.R. [Washington Univ. Medical School, St. Louis, MO (United States); Kronauge, J.F. [Harvard Medical School, Boston, MA (United States)] [and others

1995-09-26

5

The expression and significance of P-glycoprotein, lung resistance protein and multidrug resistance-associated protein in gastric cancer  

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Abstract Background To detect the expression of multidrug resistance molecules P-glycoprotein (P-gp), Lung resistnce protein (LRP) and Multidrug resistance-associated protein (MRP) and analyze the relationship between them and the clinico-pathological features. Methods The expressions of P-gp, LRP and MRP in formalin-fixed paraffin-embedded tissue sections from 59 gastric cancer patients were determined by a labbelled Streptavidin-Peroxidase (SP) immunohistochem...

Li Yan; Peng Chun-Wei; Hu Wen-Qing

2009-01-01

6

Age-related changes of the multidrug resistance P-glycoprotein function in normal human peripheral blood T lymphocytes  

Directory of Open Access Journals (Sweden)

Full Text Available The multidrug resistance P-glycoprotein is a transmembrane efflux pump expressed by lymphocytes and is involved in their cytolytic activity. In the present study, we investigated the age-related changes of P-glycoprotein function in normal peripheral blood lymphocytes. Blood samples from 90 normal volunteers (age range, 0 to 86 years were analyzed. P-glycoprotein function was assessed by the flow cytometric rhodamine 123 assay. P-glycoprotein function was highest in cord blood and progressively declined with age in peripheral blood T CD4+ and CD8+ cells. In contrast, P-glycoprotein function did not vary with age in CD19+ B or CD16+CD56+ natural killer cells. These data suggest that the decline in P-glycoprotein function in T CD4+ and CD8+ lymphocytes as a function of age may contribute to the decrease in T cell cytolytic activity with aging.

Machado C.G.

2003-01-01

7

Nuclear immunolocalization of P-glycoprotein in multidrug-resistant cell lines showing similar mechanisms of doxorubicin distribution.  

Science.gov (United States)

The MDR1 gene product P-glycoprotein is a plasma membrane efflux pump which is responsible for multiple drug resistance of cancer cells. Although the ability of multidrug-resistant cells to exclude drugs from the nucleus is a distinctive and possibly the main mechanism for resistance against a number of drugs, including doxorubicin, this phenomenon is not entirely understood. In this paper, the relationship between doxorubicin subcellular distribution and P-glycoprotein activity at different cell sites has been investigated by different techniques. Cytofluorometry and confocal microscopy were used to study doxorubicin subcellular distribution in U-2 OS human osteosarcoma cells and in the multidrug-resistant variant U-2 OS/DX580. Stable levels of doxorubicin accumulation were found in the nuclei of sensitive cells, whereas the absence of detectable levels of drug in the nuclei of resistant cells could be attributed to an energy-dependent mechanism. Moreover, in resistant cells, inhibition of P-glycoprotein activity was able to induce drug accumulation in the nuclei of resistant cells and to achieve cytotoxic effects comparable to those observed in sensitive cells. Similar results were also found in isolated nuclei from U-2 OS/DX580 cells. The expression of P-glycoprotein in U-2 OS/DX580 and in two other multidrug-resistant cell lines (SW948-R-300 and LoVo-R-100) was investigated by confocal microscopy and immunoelectron microscopy, by using a panel of monoclonal antibodies directed against this protein. Higher levels of P-glycoprotein expression, not only in the plasma membrane and inside the cytoplasm, but also in the nucleus, were found in U-2 OS/DX580 and in LoVo-R-100 multidrug-resistant cells compared to their corresponding sensitive cells. SW948-R-300 cells, featuring increased amounts of MDR1 mRNA but lacking P-glycoprotein expression at the cell surface, showed a higher P-glycoprotein immunolabeling only in the nucleus and in the cytoplasm. The localization of P-glycoprotein in the nucleus of multidrug-resistant cells was confirmed also by studies on isolated nuclei and nuclear matrices, and by Western blot analysis on total cell and isolated nuclear extracts. These findings, suggesting the possible involvement of nuclear P-glycoprotein in the regulation of subcellular doxorubicin distribution in multidrug-resistant cells, open new insights on the mechanisms of P-glycoprotein-mediated resistance to anticancer drugs. PMID:8603675

Baldini, N; Scotlandi, K; Serra, M; Shikita, T; Zini, N; Ognibene, A; Santi, S; Ferracini, R; Maraldi, N M

1995-11-01

8

Most drugs that reverse multidrug resistance also inhibit photoaffinity labeling of P-glycoprotein by a vinblastine analog  

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Multidrug-resistant human KB carcinoma cells express a 170,000-dalton membrane glycoprotein (P-glycoprotein) that can be photoaffinity labeled with the vinblastine analog N-(p-azido-(3-/sup 125/I)salicyl)-N'-(beta-aminoethyl)vindesine. Several agents that suppress the multidrug-resistant phenotype, including N-solanesyl-N,N'-bis(3,4-dimethylbenzyl)ethylenediamine, cepharanthine, quinidine, and reserpine, were found to inhibit photolabeling of P-glycoprotein at doses comparable to those that reverse multidrug resistance. However, the phenothiazines chlorpromazine and trifluoperazine, which also effectively reverse multidrug resistance, were poor inhibitors of the photoaffinity labeling of P-glycoprotein. Chloroquine, propranolol, or atropine, which only partially reversed the drug resistance, also did not inhibit photolabeling. Naphthalene sulfonamide calmodulin inhibitors, W7 and W5, as well as many other drugs that did not circumvent multidrug resistance, did not inhibit photolabeling. These studies suggest that most, but not all, agents that phenotypically suppress multidrug resistance also inhibit drug binding to a site on P-glycoprotein with which a photoaffinity analog of vinblastine interacts.

Akiyama, S.; Cornwell, M.M.; Kuwano, M.; Pastan, I.; Gottesman, M.M.

1988-02-01

9

Most drugs that reverse multidrug resistance also inhibit photoaffinity labeling of P-glycoprotein by a vinblastine analog  

International Nuclear Information System (INIS)

Multidrug-resistant human KB carcinoma cells express a 170,000-dalton membrane glycoprotein (P-glycoprotein) that can be photoaffinity labeled with the vinblastine analog N-(p-azido-[3-125I]salicyl]-N'-(beta-aminoethyl)vindesine. Several agents that suppress the multidrug-resistant phenotype, including N-solanesyl-N,N'-bis(3,4-dimethylbenzyl)ethylenediamine, cepharanthine, quinidine, and reserpine, were found to inhibit photolabeling of P-glycoprotein at doses comparable to those that reverse multidrug resistance. However, the phenothiazines chlorpromazine and trifluoperazine, which also effectively reverse multidrug resistance, were poor inhibitors of the photoaffinity labeling of P-glycoprotein. Chloroquine, propranolol, or atropine, which only partially reversed the drug resistance, also did not inhibit photolabeling. Naphthalene sulfonamide calmodulin inhibitors, W7 and W5, as well as many other drugs that did not circumvent multidrug resistance, did not inhibit photolabeling. These studies suggest that most, but not all, agents that phenotypically suppress multidrug resistance also inhibit drug binding to a site on P-glycoprotein with which a photoaffinity analog of vinblastine interacts

10

Modulation of P-Glycoprotein Mediated Multidrug Resistance (Mdr in Cancer Using Chemosensitizers.  

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Full Text Available Multidrug resistance (MDR is one of the main obstacles in the chemotherapy of cancer. MDR is associated with the over expression of P-glycoprotein (P-gp, resulting in increased efflux of chemotherapy from cancer cells. Inhibiting P-gp as a method to reverse MDR in cancer patients has been studied extensively, but the results have generally been disappointing. First-generation agents were limited by unacceptable toxicity, whereas second-generation agents had bettertolerability but were confounded by unpredictable pharmacokinetic interactions and interactions with other transporter proteins. Third-generation inhibitors have high potency and specificity for P-gp. Furthermore, pharmacokinetic studies to date have shown no appreciable impact on drug metabolism and no clinically significant drug interactions with common chemotherapy agents. Third-generation P-gp inhibitors have shown promise in clinical trials. The continued development of these agents may establish the true therapeutic potential of P-gp-mediated MDR reversal.

Velingkar V.S

2010-03-01

11

Age-related changes of the multidrug resistance P-glycoprotein function in normal human peripheral blood T lymphocytes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The multidrug resistance P-glycoprotein is a transmembrane efflux pump expressed by lymphocytes and is involved in their cytolytic activity. In the present study, we investigated the age-related changes of P-glycoprotein function in normal peripheral blood lymphocytes. Blood samples from 90 normal v [...] olunteers (age range, 0 to 86 years) were analyzed. P-glycoprotein function was assessed by the flow cytometric rhodamine 123 assay. P-glycoprotein function was highest in cord blood and progressively declined with age in peripheral blood T CD4+ and CD8+ cells. In contrast, P-glycoprotein function did not vary with age in CD19+ B or CD16+CD56+ natural killer cells. These data suggest that the decline in P-glycoprotein function in T CD4+ and CD8+ lymphocytes as a function of age may contribute to the decrease in T cell cytolytic activity with aging.

C.G., Machado; R.T., Calado; A.B., Garcia; R.P., Falcão.

12

In vivo and in vitro multitracer analyses of P-glycoprotein expression-related multidrug resistance  

International Nuclear Information System (INIS)

P-glycoprotein (Pgp) is an ABC (ATP binding cassette) transporter that is often overexpressed in tumours, contributing significantly to their multidrug resistance. In this study, we explored whether the radiotracers used in tumour diagnostics can be used for in vivo visualisation of Pgp-related multidrug resistance. We also examined the effects of different Pgp modulators on the accumulation of these radioligands in tumours with or without Pgp expression. In a SCID BC-17 mouse model, cells of the drug-sensitive KB-3-1 (MDR-) and the KB-V1 Pgp-expressing (MDR+) human epidermoid carcinoma cell lines were inoculated to yield tumours in opposite flanks. For in vivo scintigraphic (biodistribution) and positron emission tomography (PET) examinations, the mice were injected with technetium-99m hexakis-2-methoxybutylisonitrile (99mTc-MIBI), carbon-11 labelled methionine and fluorine-18 fluoro-2-deoxy-d-glucose (18FDG). For validation, in vitro cell studies with 99mTc-MIBI,99mTc-tetrofosmin, [11C]methionine and 18FDG were carried out using a gamma counter. The expression and function of the MDR product were proved by immunohistochemistry and spectrofluorimetry. 99mTc-MIBI uptake was significantly lower in KB-V1 cells as compared with KB-3-1-derived tumours in vivo (Pgp+/Pgp- =0.61±0.13; P+/Pgp- =0.08±0.01p+/Pgp- =0.08±0.01; P99mTc-MIBI uptake in the Pgp+ cells, while verapamil failed to modify it. 18FDG uptake was significantly higher in KB-V1 tumours (Pgp+/Pgp- =1.36±0.05; P+/Pgp-=1.52 ±0.12; P + and MDR - cell lines, verapamil significantly increased it. When the animals were treated with verapamil, the ratio of 99mTc-MIBI uptake in the MDR + tumours to that in the MDR - tumours decreased to 0.38 ±0.05 (P 18FDG uptake increased to 2.1 ±0.3 (P 11C]methionine uptake in the MDR + and MDR - tumours and cell lines, nor was [ 11C]methionine accumulation modified by cyclosporin A. Parallel administration of 18FDG and 99mTc-MIBI combined with verapamil treatment seems to be a good candidate as a non-invasive marker for the diagnosis of MDR-related Pgp expression in tumours. (orig.)

13

Molecular basis of preferential resistance to colchicine in multidrug-resistant human cells conferred by Gly-185 ? Val-185 substitution in P-glycoprotein  

International Nuclear Information System (INIS)

Expression of P-glycoprotein, encoded by the human MDR1 gene, results in cross-resistance to many lipophilic cytotoxic drugs (multidrug resistance). P-glycoprotein is believed to function as an energy-dependent efflux pump that is responsible for decreased drug accumulation in multidrug-resistant cells. Previous work showed that preferential resistance to colchicine in a colchicine-selected multidrug-resistant cell line was caused by spontaneous mutations in the MDR1 gene that resulted in a Gly-185 ? Val-185 substitution in P-glycoprotein. The authors have now compared transfectant cell lines expressing the wild-type Gly-185 or the mutant Val-185 P-glycoprotein with regard to their levels of resistance to and accumulation and binding of different drugs. In cells expressing the mutant protein, increased resistance to colchicine and decreased resistance to vinblastine correlated with a decreased accumulation of colchicine and increased accumulation of vinblastine. Expression of the mutant P-glycoprotein also resulted in significantly increased resistance to epipodophyllotoxin and decreased resistance to vincristine and actinomycin D; smaller changes in resistance were observed for several other drugs. Unexpectedly, the mutant P-glycoprotein showed increased binding of photoactive analogs of vinblastine and verapamil and the photoactive compound azidopine and decreased binding of a photoactive colchicine analog. These results suggest that the Gly-185 ? Val-185 substitution affects not the initial drug-binding site of P-glycoprotein but another site, associated with the release of P-glycoprotein-bound drugs to the outside of the cell

14

Molecular basis of preferential resistance to colchicine in multidrug-resistant human cells conferred by Gly-185 yields Val-185 substitution in P-glycoprotein  

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Expression of P-glycoprotein, encoded by the human MDR1 gene, results in cross-resistance to many lipophilic cytotoxic drugs (multidrug resistance). P-glycoprotein is believed to function as an energy-dependent efflux pump that is responsible for decreased drug accumulation in multidrug-resistant cells. Previous work showed that preferential resistance to colchicine in a colchicine-selected multidrug-resistant cell line was caused by spontaneous mutations in the MDR1 gene that resulted in a Gly-185 {yields} Val-185 substitution in P-glycoprotein. The authors have now compared transfectant cell lines expressing the wild-type Gly-185 or the mutant Val-185 P-glycoprotein with regard to their levels of resistance to and accumulation and binding of different drugs. In cells expressing the mutant protein, increased resistance to colchicine and decreased resistance to vinblastine correlated with a decreased accumulation of colchicine and increased accumulation of vinblastine. Expression of the mutant P-glycoprotein also resulted in significantly increased resistance to epipodophyllotoxin and decreased resistance to vincristine and actinomycin D; smaller changes in resistance were observed for several other drugs. Unexpectedly, the mutant P-glycoprotein showed increased binding of photoactive analogs of vinblastine and verapamil and the photoactive compound azidopine and decreased binding of a photoactive colchicine analog. These results suggest that the Gly-185 {yields} Val-185 substitution affects not the initial drug-binding site of P-glycoprotein but another site, associated with the release of P-glycoprotein-bound drugs to the outside of the cell.

Safa, A.R.; Stern, R.K.; Choi, Kyunghee; Agresti, M.; Tamai, Ikumi; Mehta, N.D.; Roninson, I.B. (Univ. of Chicago, IL (USA))

1990-09-01

15

Effects of chemosensitizer on 99Tcm-MIBI uptake of P-glycoprotein induced multidrug-resistant carcinoma cells  

International Nuclear Information System (INIS)

Objective: To observe the changes of 99Tcm-methoxyisobutylisonitrile (MIBI) uptake kinetics and P-glycoprotein levels after using verapamil in multidrug-resistant (MDR) human breast cells MCF-7/Adr, and to establish a method to evaluate the effects of chemosensitizer on P-glycoprotein using 99Tcm-MIBI. Methods: MDR breast carcinoma cells, MCF-7/Adr, were incubated at 37 degree C. 1)Verapamil (10?mol/L), a chemosensitizer, was added into cell culture medium used for verapamil group, while for control group, the same quotient of DMEM. Cells were harvested after 2 h incubation with 99Tcm-MIBI. 2)Verapamil (10 ?mol/L) was added into cell culture medium for verapamil group and incubated for 20, 40, 60, 80 min, 8, 24, 48 and 72 h respectively. Cells were harvested after 2 h incubation with 99Tcm-MIBI. The radioactivity and P-glycoprotein expression levels were determined. Results: 1) After 2 h incubation with verapamil the 99Tcm-MIBI uptake was remarkably higher in verapamil group than in control group (t=2.33, P0.05). 2) In verapamil group, 99Tcm-MIBI uptake increased with incubation time prolonging (F=58.2, P99Tcm-MIBI uptake negatively correlated to the P-glycoprotein expression levels (r=- 0.73, P99Tcm-MIBI accumulation and P-glycoprotein levels (r=0.16, P>0.05). Conclusion: Chemosensitizers may impact the cellular uptake of 99Tcm-MIBI in P-glycoprotein over-expressing MDR tumor cells

16

In vivo and in vitro multitracer analyses of P-glycoprotein expression-related multidrug resistance  

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P-glycoprotein (Pgp) is an ABC (ATP binding cassette) transporter that is often overexpressed in tumours, contributing significantly to their multidrug resistance. In this study, we explored whether the radiotracers used in tumour diagnostics can be used for in vivo visualisation of Pgp-related multidrug resistance. We also examined the effects of different Pgp modulators on the accumulation of these radioligands in tumours with or without Pgp expression. In a SCID BC-17 mouse model, cells of the drug-sensitive KB-3-1 (MDR{sup -}) and the KB-V1 Pgp-expressing (MDR{sup +}) human epidermoid carcinoma cell lines were inoculated to yield tumours in opposite flanks. For in vivo scintigraphic (biodistribution) and positron emission tomography (PET) examinations, the mice were injected with technetium-99m hexakis-2-methoxybutylisonitrile ({sup 99m}Tc-MIBI), carbon-11 labelled methionine and fluorine-18 fluoro-2-deoxy-d-glucose ({sup 18}FDG). For validation, in vitro cell studies with {sup 99m}Tc-MIBI,{sup 99m}Tc-tetrofosmin, [{sup 11}C]methionine and {sup 18}FDG were carried out using a gamma counter. The expression and function of the MDR product were proved by immunohistochemistry and spectrofluorimetry. {sup 99m}Tc-MIBI uptake was significantly lower in KB-V1 cells as compared with KB-3-1-derived tumours in vivo (Pgp{sup +}/Pgp{sup -} =0.61{+-}0.13; P<0.01) and cells in vitro (Pgp{sup +}/Pgp{sup -} =0.08{+-}0.01; P<0.001).Cyclosporin A reversed {sup 99m}Tc-MIBI uptake in the Pgp+ cells, while verapamil failed to modify it. {sup 18}FDG uptake was significantly higher in KB-V1 tumours (Pgp{sup +}/Pgp{sup -} =1.36{+-}0.05; P<0.01) and cells (Pgp{sup +}/Pgp{sup -}=1.52 {+-}0.12; P <0.001). Whereas cyclosporin A eliminated the difference between FDG uptake in MDR {sup +} and MDR {sup -} cell lines, verapamil significantly increased it. When the animals were treated with verapamil, the ratio of {sup 99m}Tc-MIBI uptake in the MDR {sup +} tumours to that in the MDR {sup -} tumours decreased to 0.38 {+-}0.05 (P <0.01), while the ratio of {sup 18}FDG uptake increased to 2.1 {+-}0.3 (P <0.001). There were no significant differences in the [ {sup 11}C]methionine uptake in the MDR {sup +} and MDR {sup -} tumours and cell lines, nor was [ {sup 11}C]methionine accumulation modified by cyclosporin A. Parallel administration of {sup 18}FDG and {sup 99m}Tc-MIBI combined with verapamil treatment seems to be a good candidate as a non-invasive marker for the diagnosis of MDR-related Pgp expression in tumours. (orig.)

Marian, Terez; Balkay, Laszlo; Mikecz, Pal; Tron, Lajos [PET Center, University of Debrecen (Hungary); Szabo, Gabor; Goda, Katalin; Nagy, Henrietta; Krasznai, Zoltan [Department of Biophysics and Cell Biology, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen (Hungary); Szincsak, Nora; Juhasz, Istvan [Department of Dermatology, University of Debrecen (Hungary); Galuska, Laszlo [Center of Nuclear Medicine, University of Debrecen (Hungary)

2003-08-01

17

Non-P-glycoprotein-mediated multidrug-resistant human KB cells selected in medium containing adriamycin, cepharanthine, and mezerein.  

Science.gov (United States)

Human epidermoid KB cell lines resistant to high levels of adriamycin, C-A90, C-A120, C-A500, and C-A1000, were isolated in selection medium containing increasing concentrations of adriamycin, 1 microgram/ml of cepharanthine, a multidrug-resistance (MDR) reversing agent, and 100 nM of mezerein, a protein kinase C activating agent. One of the adriamycin-resistant KB cell lines, C-A500, was cross-resistant to drugs that typify the classical multidrug resistance phenotype, such as vincristine, actinomycin D, VP-16, and colchicine. The accumulation of adriamycin and vincristine was decreased in C-A500 cells and the efflux of adriamycin from C-A500 was enhanced compared with parental KB-3-1 cells. These adriamycin-resistant KB cells did not contain detectable levels of P-glycoprotein or overexpress MDR1. Multidrug-resistance-associated protein (MRP) and MRP mRNA were expressed in the adriamycin-resistant KB cells, C-A120, C-A500, and C-A1000, but not in parental KB-3-1 and revertant C-AR cells. The MRP gene was amplified in all the MDR cells that overexpressed MRP mRNA. DNA topoisomerase II levels were markedly decreased in C-A500 and C-A1000 cells but only slightly decreased in C-A120 cells. These results indicate that MRP overexpressed in the resistant cells may be responsible for the reduced accumulation of adriamycin and vincristine and that both the increased expression of MRP and decreased levels of topoisomerase II underlie the drug resistance in C-A120, C-A500, and C-A1000 cell lines. PMID:7825064

Sumizawa, T; Chuman, Y; Sakamoto, H; Iemura, K; Almquist, K C; Deeley, R G; Cole, S P; Akiyama, S

1994-09-01

18

Overcoming multidrug-resistance in vitro and in vivo using the novel P-glycoprotein inhibitor 1416  

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Full Text Available MDR (multidrug-resistance represents a major obstacle to successful cancer chemotherapy and is usually accomplished by overexpression of P-gp (P-glycoprotein. Much effort has been devoted to developing P-gp inhibitors to modulate MDR. However, none of the inhibitors on the market have been successful. 1416 [1-(2,6-dimethylphenoxy-2-(3,4-dimethoxyphenylethylaminopropane hydrochloride (phenoprolamine hydrochloride] is a new VER (verapamil analogue with a higher IC50 for blocking calcium channel currents than VER. In the present paper, we examined the inhibition effect of 1416 on P-gp both in vitro and in vivo. 1416 significantly enhanced cytotoxicity of VBL (vinblastine in P-gp-overexpressed human multidrug-resistant K562/ADM (adriamycin and KBV cells, but had no such effect on the parent K562 and KB cells. The MDR-modulating function of 1416 was further confirmed by increasing intracellular Rh123 (rhodanmine123 content in MDR cells. Human K562/ADM xenograft-nude mice model verified that 1416 potentiates the antitumour activity of VBL in vivo. RT-PCR (reverse transcriptase-PCR and FACS analysis demonstrated that the expression of MDR1/P-gp was not affected by 1416 treatment. All these observations suggest that 1416 could be a promising agent for overcoming MDR in cancer chemotherapy.

Yan Xu

2012-10-01

19

Modulation of P-glycoprotein-mediated multidrug resistance in K562 leukemic cells by indole-3-carbinol  

International Nuclear Information System (INIS)

Resistance to chemotherapeutic drugs is one of the major problems in the treatment of cancer. P-glycoprotein (P-gp) encoded by the mdr gene is a highly conserved protein, acts as a multidrug transporter, and has a major role in multiple drug resistance (MDR). Targeting of P-gp by naturally occurring compounds is an effective strategy to overcome MDR. Indole-3-carbinol (I3C), a glucosinolates present in cruciferous vegetables, is a promising chemopreventive agent as it is reported to possess antimutagenic, antitumorigenic, and antiestrogenic properties in experimental studies. In the present investigation, the potential of I3C to modulate P-gp expression was evaluated in vinblastine (VBL)-resistant K562 human leukemic cells. The resistant K562 cells (K562/R10) were found to be cross-resistant to vincristine (VCR), doxorubicin (DXR), and other antineoplastic agents. I3C at a nontoxic dose (10 x 10-3 M) enhanced the cytotoxic effects of VBL time dependently in VBL-resistant human leukemia (K562/R10) cells but had no effect on parent-sensitive cells (K562/S). The Western blot analysis of K 562/R 10 cells showed that I3C downregulates the induced levels of P-gp in resistant cells near to normal levels. The quantitation of immunocytochemically stained K562/R10 cells showed 24%, 48%, and 80% decrease in the levels of P-gp by I3C for 24, 48, and 72 h of incubation. The above features thus indicate that I3C could be used as a novel modulator of P-gp-mediated multidrug resistance in vitro and may be effective as a dietary adjuvant in the treatment of MDR cancers

20

P-glycoprotein inhibition as a therapeutic approach for overcoming multidrug resistance in cancer: current status and future perspectives.  

Science.gov (United States)

One of the major causes of failure in cancer chemotherapy is multidrug resistance (MDR), where cancer cells simultaneously become resistant to different anticancer drugs. Over-expression of membrane efflux pumps like P-glycoprotein (P-gp) that recognizes different chemotherapeutic agents and transports them out of the cell, plays a major role in MDR. The shortcoming of P-gp inhibitors in clinic has been attributed to their non-specific action on P-gp and/or non-selective distribution to non-target organs that leads to intolerable side effects by the P-gp inhibitor at doses required for P-gp inhibition upon systemic administration. Another major issue is the reduced elimination of P-gp substrates (e.g. anticancer drugs) and intolerable toxicities by anticancer drugs when co-administered with P-gp inhibitors. To overcome these shortcomings, new generation of P-gp inhibitors with improved specificity for P-gp have been developed. More recently, attention has been paid to the use of drug delivery systems primarily to restrict P-gp inhibition to tumor and reduce the non-selective inhibition of P-gp in non-target organs. This review will provide an overview and update on the status of P-gp inhibition approaches and the role of drug delivery systems in overcoming P-gp mediated MDR. PMID:23369096

Binkhathlan, Ziyad; Lavasanifar, Afsaneh

2013-03-01

 
 
 
 
21

Effect of calcium antagonists on the chemosensitivity of two multidrug-resistant human tumour cell lines which do not overexpress P-glycoprotein.  

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We have examined the ability of eight compounds to enhance adriamycin (ADM) sensitivity of two human tumour cell lines (a small cell lung cancer cell line, NCI-H69, and a fibrosarcoma cell line, HT1080) and their multidrug-resistant variants. The resistant cell lines (H69AR and HT1080/DR4) do not overexpress P-glycoprotein. Verapamil, nicardipine, perhexiline maleate, chloroquine, tamoxifen, clomiphene, prenylamine and trifluoperazine were tested alone and in combination with ADM for their cy...

Cole, S. P.; Downes, H. F.; Slovak, M. L.

1989-01-01

22

HIF-1? Inhibition Reverses Multidrug Resistance in Colon Cancer Cells via Downregulation of MDR1/P-Glycoprotein  

Science.gov (United States)

Background Multidrug resistance (MDR) is one of the major reasons chemotherapy-based treatments fail. Hypoxia is generally associated with tumor chemoresistance. However, the correlation between the heterodimeric hypoxia-inducible factor-1 (HIF-1) and the multidrug resistance (MDR1) gene/transporter P-glycoprotein (P-gp) remains unclear. This study aims to explore the molecular mechanisms of reversing colon cancer MDR by focusing on the target gene HIF-1?. Methods A chemotherapeutic sensitivity assay was used to observe the efficiency of MDR reversal in LoVo multicellular spheroids (MCS). The apoptotic level induced by different drugs was examined by flow cytometry (FCM). Binding of HIF-1? to the MDR1 gene promoter was evaluated by Chromatin immunoprecipitation (ChIP). The relationship between HIF-1?/P-gp expression and sensitivity to chemotherapy was analyzed. Results The sensitivity of LoVo MCS to all four chemotherapy drugs was decreased to varying degrees under hypoxic conditions. After silencing the HIF-1? gene, the sensitivities of LoVo MCS to all four chemotherapy drugs were restored. The apoptotic levels that all the drugs induced were all decreased to various extents in the hypoxic group. After silencing HIF-1?, the apoptosis level induced by all four chemotherapy drugs increased. The expression of HIF-1? and P-gp was significantly enhanced in LoVo MCS after treatment with hypoxia. Inhibiting HIF-1? significantly decreased the expression of MDR1/P-gp mRNA or protein in both the LoVo monolayers and LoVo MCS. The ChIP assay showed that HIF-1? was bound to the MDR1 gene promoter. Advanced colon carcinoma patients with expression of both HIF-1? and P-gp were more resistant to chemotherapy than that with non expression. Conclusions HIF-1? inhibition reverses multidrug resistance in colon cancer cells via downregulation of MDR1/P-gp. The expression of HIF-1? and MDR1/P-gp can be used as a predictive marker for chemotherapy resistance in colon cancer. PMID:24901645

Peng, Yonghai; Pan, Feng; Li, Jianjun; Zou, Lan; Zhang, Yanling; Liang, Houjie

2014-01-01

23

Identification of the Interaction between P-Glycoprotein and Anxa2 in Multidrug-resistant Human Breast Cancer Cells  

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Full Text Available Objective To explore the interaction of Anxa2 with P- Glycoprotein (P-gp in the migration and invasion of the multidrug-resistant (MDR human breast cancer cell line MCF-7/ADR. Methods A pair of short hairpin RNA (shRNA targeting P-gp was transfected into MCF-7/ADR cells, and monoclonal cell strains were screened. The expression of P-gp was detected by Western blot. Transwell chambers were used to observe the cell migration capacity and invasion ability. The interaction between P-gp and Anxa2 was examined by immunoprecipitation and immunofluorescence confocal microscopy analyses. Results P-gp expression was significantly knocked down, and there were notable decreasing trends in the migration and invasion capability of MDR breast cancer cells (P<0.05. There was a close interaction between Anxa2 and P-gp.Conclusions MCF-7/ADR is an MDR human breast cancer cell line with high migration and invasion abilities. The knockdown of P-gp notably impaired the migration and invasion abilities of the tumor cells. The interaction of Anxa2 with P-pg may play an important role in the enhanced invasiveness of MDR human breast cancer cells.

Hai-chang Zhang

2012-06-01

24

N-ethylmaleimide increases P-glycoprotein photoaffinity labeling with iodoaryl-azidoprazosin in multidrug resistant cells.  

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P-glycoprotein (P-gp) mediates a multidrug resistance (MDR) phenotype in tumor cell lines selected with lipophilic cytotoxic drugs. Transport studies using purified P-glycoprotein reconstituted into defined liposomes have shown energy-dependent drug efflux of structurally dissimilar drugs. In this report, we have examined the effects of N-ethylmaleimide, a potent inhibitor of the P-gp ATPase, on P-gp drug binding in intact MDR cells and in plasma membranes. Our results show that short term treatment of MDR cells with 1-50 microM N-ethylmaleimide led to a concentration dependent increase in P-gp photoaffinity labeling with iodoaryl-azidoparazosin (IAAP). In addition, N-ethylmaleimide increases [3H] vinblastine accumu-lation in drug-resistant but not in sensitive cells. Comparison of IAAP photolabeled P-gp from intact cells with or without N-ethylmaleimide treatment did not show differences in the pattern of IAAP photolabeled peptides. Thus, the observed increase in P-gp photolabeling with IAAP in N-ethylmaleimide treated cells is not due to photolabeling at different sites. Incubation of MDR cells with [14C] N-ethylmaleimide showed that P-gp is directly modified at several Cysteine residues, as found from a complete proteolytic digestion of [14C] Nethylmaleimide labeled P-gp. The comparison of V8 staphylococcus aureas peptides from [14C] Nethylmaleimide or IAAP modified P-gp showed some peptides to co-migrate on SDS PAGE. However, modification of plasma membranes from drug resistant cells treated with N-ethylmaleimide did not show a dose-dependent increase in P-gp photolabeling with IAAP as seen with intact MDR cells. Interestingly, N-ethylmaleimide increases P-gp phosphorylation by inhibiting the turnover of Pgp phosphates. However, inhibition of P-gp phosphorylation with calyculin A did not show an increase in P-gp photolabeling in MDR cells. Taken together, the results of this study suggest that N-ethylmaleimide potentiates P-gp photolabeling with IAAP by inhibiting P-gp ATPase thereby increasing the local concentration of IAAP in intact MDR cells. Furthermore, inhibition of P-gp ATPase by N-ethylmaleimide does not lead to conformational changes that affects P-gp drug binding. PMID:9066677

Wang, Y; Georges, E

1997-01-01

25

Expression of P-glycoprotein and multidrug resistance associated protein in Ehrlich ascites tumor cells after fractionated irradiation  

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PURPOSE: To characterize irradiated murine tumor cells with respect to drug resistance, drug kinetics, and ATPase activity, and to evaluate the possible role of P-glycoprotein (PGP) and murine multidrug resistance associated protein (Mrp1) in the drug-resistant phenotype of these cells. METHODS AND MATERIALS: Sensitive Ehrlich ascites tumor cells (EHR2) were in vitro exposed to fractionated irradiation (60 Gy). Western blot analysis was performed for determination of PGP and Mrp1, reverse transcriptase-polymerase chain reaction (RT-PCR) for determination of mdr1a + b mRNA, and semiquantitative RT-PCR for Mrp1 mRNA. The clonogenic assay was applied to investigate sensitivity, whereas the steady-state drug accumulation of daunorubicin (DNR), 3H-vincristine (VCR), and 3H-etoposide (VP16) was measured by spectrofluorometry and scintillation counting, respectively. For determining of ATPase activity, the release of inorganic phosphate from ATP was quantified using a colorimetric method. RESULTS: Compared with EHR2, the irradiated cell line EHR2/irr showed increased expression of PGP (threefold), Mrp1 (eightfold), and Mrp1 mRNA (sixfold), and a slight reduction of mdr1b mRNA, whereas mdr1a was present in EHR2 but could not be detected in EHR2/irr. EHR2/irr developed sixfold resistance to VP16, twofold resistance to vincristine, but remained sensitive to DNR. Addition of the PGP inhibitor, verapamil (VER) or depletion of glutathione by buthionine sulfoximine (BSO) partly reversed the resistance in EHR2/irr. In EHR2/irr, the steady-state accumulation of 3H-VCR and 3H-VP16 was significantly decreased as compared with EHR2, whereas the accumulation of DNR was unchanged. The ATPase activity of plasma membrane vesicles prepared from EHR2/irr cells was similar to that of wild-type EHR2 cells. The ATPase activity was neither stimulated by vinblastine nor VER. CONCLUSION: Irradiation induced a multidrug-resistant phenotype in sensitive tumor cells. This phenotype was characterized by increased expression of Mrp1 mRNA, Mrp1, and PGP but decreased expression of mdr1a + b mRNA. The influence of irradiation on PGP and Mrp1 expression seemed to be different.

Nielsen, D; Maare, C

2001-01-01

26

Correlation between reversing of multidrug resistance and inhibiting of [3H]azidopine photolabeling of P-glycoprotein by newly synthesized dihydropyridine analogues in a human cell line.  

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Ten synthetic dihydropyridine analogues were investigated for their ability to reverse drug resistance in a multidrug-resistant human carcinoma cell line, KB-Cl. Four dihydropyridine analogues completely reversed the resistance, three lowered the resistance, and three had little effect. The radioactive photoactive dihydropyridine calcium channel blocker, [3H]azidopine, photolabels P-glycoprotein in membrane vesicles from KB-Cl cells. This photolabeling was almost completely inhibited by excess dihydropyridine analogues that reversed or lowered drug resistance. In contrast, the labeling was not significantly inhibited by analogues that do not reverse resistance. Among other reversing agents, cepharanthine and reserpine inhibited the [3H]azidopine photolabeling, but thioridazine did not. N-Solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine slightly inhibited the labeling at 100 microM. An anticancer agent, vinblastine, also inhibited the labeling. The correlation between the reversing of the drug resistance and the inhibition of the [3H]azidopine photolabeling of P-glycoprotein by dihydropyridine analogues suggests a role for P-glycoprotein in multidrug resistance and also the reversing of the resistance by dihydropyridine analogues. PMID:2566378

Kamiwatari, M; Nagata, Y; Kikuchi, H; Yoshimura, A; Sumizawa, T; Shudo, N; Sakoda, R; Seto, K; Akiyama, S

1989-06-15

27

In vivo imaging and specific targeting of P-glycoprotein expression in multidrug resistant nude mice xenografts with [125I]MRK-16 monoclonal antibody  

International Nuclear Information System (INIS)

Multidrug resistance (MDR) in tumors is associated with P-glycoprotein (Pgp) expression. In vivo quantitation of Pgp may allow MDR to be evaluated noninvasively prior to treatment planning. The purpose of this study was to radiolabel MRK-16, a monoclonal antibody that targets an external epitope of P-glycoprotein, and perform in vivo quantitation of P-glycoprotein in a MDR xenograft nude mouse model. MRK-16 was labeled with 125I by the iodogen method, with subsequent purification by size exclusion chromatography. Groups of 10 Balb/c mice were each xenografted with colchicine-resistant or -sensitive neuroblastoma cell lines, respectively. Whole body clearance and tumor uptake over time was quantitated by gamma camera imaging, and biodistribution studies were performed with [125]MRK-16 and an isotype matched control antibody, A33. Quantitative autoradiography and immunohistochemistry analysis of tumors was also evaluated to confirm specific targeting of [125I]MRK-16. Peak tumor uptake was at 2-3 days post-injection, and was significantly greater in resistance compared to sensitive tumors (mean % injected dose/g ± SD) (18.76 ± 2.94 vs 10.93 ± 0.96; p 125I]MRK-16 was confirmed by comparison to [131I]A33 in biodistribution studies, and localized to cellular components of tissue stroma by colar components of tissue stroma by comparison of histologic and autoradiographic sections of sensitive and resistant tumors. Immunoblot analysis demonstrated a 4.5-fold difference in P-glycoprotein expression between sensitive and resistant cell lines without colchicine selective pressure. We conclude that in vivo quantitation of P-glycoprotein in MDR tumors can be performed with [125I]MRK-16. These findings suggest a potential clinical application for radiolabeled MRK-16 in the in vivo evaluation of multidrug resistance in tumors

28

Directed evolution of P-glycoprotein cysteines reveals site-specific, non-conservative substitutions that preserve multidrug resistance  

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Full Text Available Pgp (P-glycoprotein is a prototype ABC (ATP-binding-cassette transporter involved in multidrug resistance of cancer. We used directed evolution to replace six cytoplasmic Cys (cysteine residues in Pgp with all 20 standard amino acids and selected for active mutants. From a pool of 75000 transformants for each block of three Cys, we identified multiple mutants that preserved drug resistance and yeast mating activity. The most frequent substitutions were glycine and serine for Cys427 (24 and 20%, respectively and Cys1070 (37 and 25% of the Walker A motifs in the NBDs (nucleotide-binding domains, Cys1223 in NBD2 (25 and 8% and Cys638 in the linker region (24 and 16%, whereas close-by Cys669 tolerated glycine (16% and alanine (14%, but not serine (absent. Cys1121 in NBD2 showed a clear preference for positively charged arginine (38% suggesting a salt bridge with Glu269 in the ICL2 (intracellular loop 2 may stabilize domain interactions. In contrast, three Cys residues in transmembrane ?-helices could be successfully replaced by alanine. The resulting CL (Cys-less Pgp was fully active in yeast cells, and purified proteins displayed drug-stimulated ATPase activities indistinguishable from WT (wild-type Pgp. Overall, directed evolution identified site-specific, non-conservative Cys substitutions that allowed building of a robust CL Pgp, an invaluable new tool for future functional and structural studies, and that may guide the construction of other CL proteins where alanine and serine have proven unsuccessful.

Douglas J. Swartz

2014-06-01

29

Directed evolution of P-glycoprotein cysteines reveals site-specific, non-conservative substitutions that preserve multidrug resistance  

Science.gov (United States)

Pgp (P-glycoprotein) is a prototype ABC (ATP-binding-cassette) transporter involved in multidrug resistance of cancer. We used directed evolution to replace six cytoplasmic Cys (cysteine) residues in Pgp with all 20 standard amino acids and selected for active mutants. From a pool of 75000 transformants for each block of three Cys, we identified multiple mutants that preserved drug resistance and yeast mating activity. The most frequent substitutions were glycine and serine for Cys427 (24 and 20%, respectively) and Cys1070 (37 and 25%) of the Walker A motifs in the NBDs (nucleotide-binding domains), Cys1223 in NBD2 (25 and 8%) and Cys638 in the linker region (24 and 16%), whereas close-by Cys669 tolerated glycine (16%) and alanine (14%), but not serine (absent). Cys1121 in NBD2 showed a clear preference for positively charged arginine (38%) suggesting a salt bridge with Glu269 in the ICL2 (intracellular loop 2) may stabilize domain interactions. In contrast, three Cys residues in transmembrane ?-helices could be successfully replaced by alanine. The resulting CL (Cys-less) Pgp was fully active in yeast cells, and purified proteins displayed drug-stimulated ATPase activities indistinguishable from WT (wild-type) Pgp. Overall, directed evolution identified site-specific, non-conservative Cys substitutions that allowed building of a robust CL Pgp, an invaluable new tool for future functional and structural studies, and that may guide the construction of other CL proteins where alanine and serine have proven unsuccessful. PMID:24825346

Swartz, Douglas J.; Mok, Leo; Botta, Sri K.; Singh, Anukriti; Altenberg, Guillermo A.; Urbatsch, Ina L.

2014-01-01

30

Recent attempts at RNAi-mediated P-glycoprotein downregulation for reversal of multidrug resistance in cancer.  

Science.gov (United States)

Multidrug resistance (MDR) is among the major mechanisms leading to failure in chemotherapy of cancer patients. The ATP-binding cassette proteins are major contributors to MDR, involved in the active efflux of xenobiotics out of cancer cells. Among them, P-glycoprotein (P-gp) is the most dominant protein involved in the efflux of drugs. For more than 30 years, scientists have searched for the ideal P-gp inhibitor to modulate drug resistance activity of P-gp. This inhibitor should be tissue and cell specific with side effects on other tissues, must not provoke immune responses from the host, should provide sustained inhibition, and must be synthesized readily with low cost. Chemical P-gp inhibitors tested to date, have shown nonspecific toxic effects limiting their clinical applications. Sequence-specific P-gp gene silencing by RNA interference (RNAi) may provide a more effective approach for downregulation of specific protein targets due to high specificity, limited toxicity and immunogenicity, and relative ease in synthesis. RNAi can be implemented by delivery of synthetic small interfering RNAs (siRNAs) or by gene expression of short hairpin RNAs using gene expressing vectors. Specific delivery systems and expression vectors have been designed for this purpose and many researchers have explored their effectiveness for P-gp downregulation. In this report, we review the efficiency of various methods for siRNA delivery and transfection for P-gp downregulation in cancer cells for MDR reversal. Novel ideas and observations by different research groups were discussed for future improvement in this essential field. PMID:21523793

Abbasi, Meysam; Lavasanifar, Afsaneh; Uludag, Hasan

2013-01-01

31

Directed evolution of P-glycoprotein cysteines reveals site-specific, non-conservative substitutions that preserve multidrug resistance.  

Science.gov (United States)

Pgp (P-glycoprotein) is a prototype ABC (ATP-binding-cassette) transporter involved in multidrug resistance of cancer. We used directed evolution to replace six cytoplasmic Cys (cysteine) residues in Pgp with all 20 standard amino acids and selected for active mutants. From a pool of 75000 transformants for each block of three Cys, we identified multiple mutants that preserved drug resistance and yeast mating activity. The most frequent substitutions were glycine and serine for Cys427 (24 and 20%, respectively) and Cys1070 (37 and 25%) of the Walker A motifs in the NBDs (nucleotide-binding domains), Cys1223 in NBD2 (25 and 8%) and Cys638 in the linker region (24 and 16%), whereas close-by Cys669 tolerated glycine (16%) and alanine (14%), but not serine (absent). Cys1121 in NBD2 showed a clear preference for positively charged arginine (38%) suggesting a salt bridge with Glu269 in the ICL2 (intracellular loop 2) may stabilize domain interactions. In contrast, three Cys residues in transmembrane ?-helices could be successfully replaced by alanine. The resulting CL (Cys-less) Pgp was fully active in yeast cells, and purified proteins displayed drug-stimulated ATPase activities indistinguishable from WT (wild-type) Pgp. Overall, directed evolution identified site-specific, non-conservative Cys substitutions that allowed building of a robust CL Pgp, an invaluable new tool for future functional and structural studies, and that may guide the construction of other CL proteins where alanine and serine have proven unsuccessful. PMID:24825346

Swartz, Douglas J; Mok, Leo; Botta, Sri K; Singh, Anukriti; Altenberg, Guillermo A; Urbatsch, Ina L

2014-01-01

32

Membrane transport of camptothecin: facilitation by human P-glycoprotein (ABCB1 and multidrug resistance protein 2 (ABCC2  

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Full Text Available Abstract Background The purpose of the present study was to continue the investigation of the membrane transport mechanisms of 20-(S-camptothecin (CPT in order to understand the possible role of membrane transporters on its oral bioavailability and disposition. Methods The intestinal transport kinetics of CPT were characterized using Caco-2 cells, MDCKII wild-type cells and MDCKII cells transfected with human P-glycoprotein (PGP (ABCB1 or human multidrug resistance protein 2 (MRP2 (ABCC2. The effects of drug concentration, inhibitors and temperature on CPT directional permeability were determined. Results The absorptive (apical to basolateral and secretory (basolateral to apical permeabilities of CPT were found to be saturable. Reduced secretory CPT permeabilities with decreasing temperatures suggests the involvement of an active, transporter-mediated secretory pathway. In the presence of etoposide, the CPT secretory permeability decreased 25.6%. However, inhibition was greater in the presence of PGP and of the breast cancer resistant protein inhibitor, GF120918 (52.5%. The involvement of additional secretory transporters was suggested since the basolateral to apical permeability of CPT was not further reduced in the presence of increasing concentrations of GF120918. To investigate the involvement of specific apically-located secretory membrane transporters, CPT transport studies were conducted using MDCKII/PGP cells and MDCKII/MRP2 cells. CPT carrier-mediated permeability was approximately twofold greater in MDCKII/PGP cells and MDCKII/MRP2 cells than in MDCKII/wild-type cells, while the apparent Km values were comparable in all three cell lines. The efflux ratio of CPT in MDCKII/PGP in the presence of 0.2 ?M GF120918 was not completely reversed (3.36 to 1.49. However, the decrease in the efflux ratio of CPT in MDCKII/MRP2 cells (2.31 to 1.03 suggests that CPT efflux was completely inhibited by MK571, a potent inhibitor of the Multidrug Resistance Protein transporter family. Conclusions The current results provide evidence that PGP and MRP2 mediate the secretory transport of CPT in vitro. However, the involvement of other transporters cannot be ruled out based on these studies. Since these transporters are expressed in the intestine, liver and kidney variations in their expression levels and/or regulation may be responsible for the erratic oral absorption and biliary excretion of CPT observed in human subjects.

Lee Sung-Hack

2004-05-01

33

Technetium-99m methoxyisobutylisonitrile imaging for parathyroid adenoma: relationship to P-glycoprotein or multidrug resistance-related protein expression  

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Gland size has been reported to have a major influence on localisation of parathyroid adenomas by technetium-99m methoxyisobutylisonitrile ({sup 99m}Tc-MIBI) imaging. It has also been suggested that P-glycoprotein (Pgp) expression in parathyroid adenomas may influence localisation because false negative studies have been reported with large tumours and true positives with very small tumours. Therefore, the purpose of this study was to retrospectively evaluate the relationship between {sup 99m}Tc-MIBI parathyroid imaging results and Pgp or multidrug resistance-related protein (MRP) expression in parathyroid adenomas. Before surgery, 47 patients with large parathyroid adenomas (larger than 1.5 g) underwent early and delayed parathyroid imaging, 10 min and 2 h after intravenous injection of {sup 99m}Tc-MIBI. Immunohistochemical analyses (IHA) were performed, using multiple non-consecutive sections of the operative specimens, to detect Pgp or MRP expression. According to the results of IHA, the 34 parathyroid adenomas were separated into four groups: (1) three adenomas positive for both Pgp and MRP expression, (2) one adenoma positive for Pgp but negative for MRP expression, (3) four adenomas negative for Pgp but positive for MRP expression and (4) 39 adenomas with negative for both Pgp and MRP expression. All 39 adenomas in group 4 could be detected by {sup 99m}Tc-MIBI parathyroid imaging. None of the eight adenomas in groups 1-3 could be detected by {sup 99m}Tc-MIBI parathyroid imaging (P<0.05). It is concluded that not only the size of parathyroid adenomas but also significant Pgp or MRP expression limits the sensitivity of {sup 99m}Tc-MIBI imaging in localising parathyroid adenomas preoperatively. (orig.)

Kao, Albert [Departments of Nuclear Medicine and Medical Research, China Medical College Hospital, No. 2, Yuh-Der Road, Taichung 404 (Taiwan); Shiau, Yu-Chien [Department of Nuclear Medicine, Far Eastern Memorial Hospital, Institute of Biomedical Engineering, College of Electrical Engineering, National Taiwan University, Taipei (Taiwan); Tsai, Shih-Chuan [Department of Nuclear Medicine, Show-Chwan Memorial Hospital, Chunghua (Taiwan); Wang, Jhi-Joung [Department of Medical Research, Chi-Mei Medical Center, Tainan (Taiwan); Ho, Shung-Tai [School of Medicine, National Defense Medical Center, Taipe (Taiwan)

2002-08-01

34

Technetium-99m methoxyisobutylisonitrile imaging for parathyroid adenoma: relationship to P-glycoprotein or multidrug resistance-related protein expression  

International Nuclear Information System (INIS)

Gland size has been reported to have a major influence on localisation of parathyroid adenomas by technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) imaging. It has also been suggested that P-glycoprotein (Pgp) expression in parathyroid adenomas may influence localisation because false negative studies have been reported with large tumours and true positives with very small tumours. Therefore, the purpose of this study was to retrospectively evaluate the relationship between 99mTc-MIBI parathyroid imaging results and Pgp or multidrug resistance-related protein (MRP) expression in parathyroid adenomas. Before surgery, 47 patients with large parathyroid adenomas (larger than 1.5 g) underwent early and delayed parathyroid imaging, 10 min and 2 h after intravenous injection of 99mTc-MIBI. Immunohistochemical analyses (IHA) were performed, using multiple non-consecutive sections of the operative specimens, to detect Pgp or MRP expression. According to the results of IHA, the 34 parathyroid adenomas were separated into four groups: (1) three adenomas positive for both Pgp and MRP expression, (2) one adenoma positive for Pgp but negative for MRP expression, (3) four adenomas negative for Pgp but positive for MRP expression and (4) 39 adenomas with negative for both Pgp and MRP expression. All 39 adenomas in group 4 could be detected by 99mTc-MIBI parathyroid imaging. None of the eight adenomas in groups 1-3 could be detected by enomas in groups 1-3 could be detected by 99mTc-MIBI parathyroid imaging (P99mTc-MIBI imaging in localising parathyroid adenomas preoperatively. (orig.)

35

Glicoproteína-P, resistência a múltiplas drogas (MDR e relação estrutura-atividade de moduladores P-glycoprotein and multidrug resistance: structure-activity relationships of modulators  

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Full Text Available Multidrug resistance, MDR is a major obstacle for cancer chemotherapy. MDR can be reversed by drugs that vary in their chemical structure and main biological activity. Many efforts have been done to overcome MDR based on studies of structure-activity relationships and in this review we summarize some aspects of MDR mediated by P-glycoprotein (P-gp, as the most experimentally and clinically tested form of drug resistance. The most significant MDR mechanisms revealed until now are shortly discussed. Physicochemical and structural properties of MDR modulators, measures of the MDR reversal, and QSAR studies are included.

Paula C. Huber

2010-01-01

36

In vivo imaging and specific targeting of P-glycoprotein expression in multidrug resistant nude mice xenografts with [{sup 125}I]MRK-16 monoclonal antibody  

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Multidrug resistance (MDR) in tumors is associated with P-glycoprotein (Pgp) expression. In vivo quantitation of Pgp may allow MDR to be evaluated noninvasively prior to treatment planning. The purpose of this study was to radiolabel MRK-16, a monoclonal antibody that targets an external epitope of P-glycoprotein, and perform in vivo quantitation of P-glycoprotein in a MDR xenograft nude mouse model. MRK-16 was labeled with {sup 125}I by the iodogen method, with subsequent purification by size exclusion chromatography. Groups of 10 Balb/c mice were each xenografted with colchicine-resistant or -sensitive neuroblastoma cell lines, respectively. Whole body clearance and tumor uptake over time was quantitated by gamma camera imaging, and biodistribution studies were performed with [{sup 125}]MRK-16 and an isotype matched control antibody, A33. Quantitative autoradiography and immunohistochemistry analysis of tumors was also evaluated to confirm specific targeting of [{sup 125}I]MRK-16. Peak tumor uptake was at 2-3 days post-injection, and was significantly greater in resistance compared to sensitive tumors (mean % injected dose/g {+-} SD) (18.76 {+-} 2.94 vs 10.93 {+-} 0.96; p < 0.05). Quantitative autoradiography verified these findings (19.13 {+-} 0.622 vs 12.08 {+-} 0.38, p < 0.05). Specific binding of [{sup 125}I]MRK-16 was confirmed by comparison to [{sup 131}I]A33 in biodistribution studies, and localized to cellular components of tissue stroma by comparison of histologic and autoradiographic sections of sensitive and resistant tumors. Immunoblot analysis demonstrated a 4.5-fold difference in P-glycoprotein expression between sensitive and resistant cell lines without colchicine selective pressure. We conclude that in vivo quantitation of P-glycoprotein in MDR tumors can be performed with [{sup 125}I]MRK-16. These findings suggest a potential clinical application for radiolabeled MRK-16 in the in vivo evaluation of multidrug resistance in tumors.

Scott, Andrew M.; Rosa, Eddie; Mehta, Bippin M.; Divgi, Chaitanya R.; Finn, Ronald D.; Biedler, June L.; Tsuruo, Takashi; Kalaigian, Hovannes; Larson, Steven M

1995-05-01

37

Possibility of the reversal of multidrug resistance and the avoidance of side effects by liposomes modified with MRK-16, a monoclonal antibody to P-glycoprotein.  

Science.gov (United States)

For cancer chemotherapy, avoiding the side effects of chemotherapeutic agents is difficult. Multidrug resistance is one of the major obstacles to successful cancer chemotherapy. P-Glycoprotein (P-gp) serves as an efflux pump and plays a key role in the multidrug resistance. We examined the effect of MRK-16, a monoclonal antibody against P-gp, modified liposomes (MRK-Lip) on the human myelogenous leukemia K-562 cells and its adriamycin resistance cell line K-562/ADM cells to avoid the side effects and to reverse the multidrug resistance. The uptake of vincristine (VCR) by K-562/ADM cells was lower than that by K-562 cells. This low uptake was increased in the presence of verapamil and MRK-16, however, it was not increased in the presence of control antibody, IgG2A. The binding of MRK-Lip to K-562/ADM cells was higher than that of IgG2A-modified liposome (IgG-Lip) and liposome without modification (Cont-Lip). Moreover, the cytotoxicity of VCR-encapsulated MRK-Lip to K-562/ADM cells was higher than that of VCR-encapsulated IgG-Lip and Cont-Lip. These results suggest that the interaction between liposomes and multidrug resistance cells was increased by the modification of liposomes with MRK-16. Consequently, the usefulness of MRK-Lip in cancer chemotherapy as a potent carrier was suggested. PMID:11689261

Matsuo, H; Wakasugi, M; Takanaga, H; Ohtani, H; Naito, M; Tsuruo, T; Sawada, Y

2001-11-01

38

Multi-drug resistance in a canine lymphoid cell line due to increased P-glycoprotein expression, a potential model for drug-resistant canine lymphoma.  

Science.gov (United States)

Canine lymphoma is routinely treated with a doxorubicin-based multidrug chemotherapy protocol, and although treatment is initially successful, tumor recurrence is common and associated with therapy resistance. Active efflux of chemotherapeutic agents by transporter proteins of the ATP-Binding Cassette superfamily forms an effective cellular defense mechanism and a high expression of these transporters is frequently observed in chemotherapy-resistant tumors in both humans and dogs. In this study we describe the ABC-transporter expression in a canine lymphoid cell line and a sub-cell line with acquired drug resistance following prolonged exposure to doxorubicin. This sub-cell line was more resistant to doxorubicin and vincristine, but not to prednisolone, and had a highly increased P-glycoprotein (P-gp/abcb1) expression and transport capacity for the P-gp model-substrate rhodamine123. Both resistance to doxorubicin and vincristine, and rhodamine123 transport capacity were fully reversed by the P-gp inhibitor PSC833. No changes were observed in the expression and function of the ABC-transporters MRP-1 and BCRP. It is concluded that GL-40 cells represent a useful model for studying P-gp dependent drug resistance in canine lymphoid neoplasia, and that this model can be used for screening substances as potential P-gp substrates and their capacity to modulate P-gp mediated drug resistance. PMID:24975508

Zandvliet, M; Teske, E; Schrickx, J A

2014-12-01

39

Impact of BCRP/MXR, MRP1 and MDR1/P-Glycoprotein on thermoresistant variants of atypical and classical multidrug resistant cancer cells  

DEFF Research Database (Denmark)

The impact of the ABC transporters breast cancer resistance protein/mitoxantrone resistance associated transporter (BCRP/MXR), multidrug resistance-associated protein 1 (MRP1) and multidrug resistance gene-1/P-glycoprotein (MDR1/PGP) on the multidrug resistance (MDR) phenotype in chemoresistance and thermoresistance was investigated in the parental human gastric carcinoma cell line EPG85-257P, the atypical MDR subline EPG85-257RNOV, the classical MDR subline EPG85-257RDB and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RNOV-TR and EPG85-257RDB-TR. Within the atypical MDR subline EPG85-257RNOV expression of BCRP/MXR and of MRP1 were clearly enhanced (vs. parental and classical MDR lines). MDR1/PGP expression was distinctly elevated in the classical MDR subline EPG85-257RDB (vs. parental and atypical MDR sublines). In all thermoresistant counterparts basal expression of BCRP/MXR, MRP1 and MDR1/PGP was increased relative to thermosensitive sublines. Although it could be shown that the overexpressedABC transporters were functionally active, however, no decreased drug accumulations of doxorubicin, mitoxantrone and rhodamine 123 were observed. Thus, expression of BCRP/MXR, MRP1 and MDR1/PGP was found to be dependent on the appropriate type of chemoresistance; correlating with a classical or atypical MDR phenotype. Within the thermoresistant variants, however, the increase in ABC transporter expression did obviously not influence the MDR phenotype.

Stein, Ulrike; Lage, Hermann

2002-01-01

40

Glicoproteína-P, resistência a múltiplas drogas (MDR) e relação estrutura-atividade de moduladores / P-glycoprotein and multidrug resistance: structure-activity relationships of modulators  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english Multidrug resistance, MDR is a major obstacle for cancer chemotherapy. MDR can be reversed by drugs that vary in their chemical structure and main biological activity. Many efforts have been done to overcome MDR based on studies of structure-activity relationships and in this review we summarize som [...] e aspects of MDR mediated by P-glycoprotein (P-gp), as the most experimentally and clinically tested form of drug resistance. The most significant MDR mechanisms revealed until now are shortly discussed. Physicochemical and structural properties of MDR modulators, measures of the MDR reversal, and QSAR studies are included.

Paula C., Huber; Cintia H., Maruiama; Wanda P., Almeida.

 
 
 
 
41

Reversal of P-glycoprotein-mediated multidrug resistance in vitro by milbemycin compounds in adriamycin-resistant human breast carcinoma (MCF-7/adr) cells.  

Science.gov (United States)

The effects of milbemycin A(4) (MB A(4)), milbemycin oxime A(4) (MBO A(4)) and milbemycin beta(1) (MB beta(1)) on reversing multidrug resistance (MDR) of tumor cells were firstly conducted according to the following research, including MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, the accumulation of adriamycin, the accumulation and efflux of rhodamine 123 (Rh123), the regulations of MDR1 gene, and expression of P-gp. The three milbemycins (5muM) showed strong potency to increase adriamycin cytotoxicity toward adriamycin-resistant human breast carcinoma cells MCF-7/adr with reversal fold (RF) of 21.42, 19.06 and 14.89, respectively. In addition, the mechanisms of milbemycins on P-glycoprotein (P-gp)-mediated MDR demonstrated that the milbemycins significantly increased the intracellular accumulations of adriamycin and Rh123 via inhibiting P-gp transport function. Based on the analysis of the P-gp and MDR1 gene expression using flow cytometry and RT-PCR, the results revealed that milbemycin compounds, particularly MB A(4), could regulate down the expression of the P-gp and MDR1 gene. These findings suggest that the milbemycins probably represent promising agents for overcoming MDR in cancer therapy, and especially MB A(4) is better modulator with the lowest toxicity. PMID:20656007

Xiang, Wensheng; Gao, Aili; Liang, Hongsheng; Li, Changyu; Gao, Jiguo; Wang, Qing; Shuang, Bao; Zhang, Ji; Yan, Yijun; Wang, Xiangjing

2010-09-01

42

An isoquinoline alkaloid from the Chinese herbal plant Corydalis yanhusuo W.T. Wang inhibits P-glycoprotein and multidrug resistance-associate protein 1.  

Science.gov (United States)

Overexpression of P-glycoprotein (P-gp) and multidrug resistance-associate protein 1 (MRP1) is a major mechanism leading to multidrug resistance (MDR) of cancer cells. These transporters expel anti-cancer drugs and greatly impair therapeutic efficacy of chemotherapy. A Chinese herbal plant Yanhusuo (Corydalis yanhusuo W.T. Wang, YHS) is frequently used in functional food and traditional Chinese medicine to improve the efficacy of chemotherapy. The objective of this work was to study effects of glaucine, an alkaloid component of YHS, on P-gp and MRP1 in resistant cancer cells. The resistant cancer cell line, MCF-7/ADR and corresponding parental sensitive cells were employed to determine reversal properties of glaucine. Glaucine inhibits P-gp and MRP1-mediated efflux and activates ATPase activities of the transporters, indicating that it is a substrate and inhibits P-gp and MRP1 competitively. Furthermore, glaucine suppresses expression of ABC transporter genes. It reverses the resistance of MCF-7/ADR to adriamycin and mitoxantrone effectively. PMID:23194502

Lei, Yu; Tan, Juan; Wink, Michael; Ma, Yonggang; Li, Na; Su, Guannan

2013-02-15

43

Selecting surfactants for the maximum inhibition of the activity of the multidrug resistance efflux pump transporter, P-glycoprotein: conceptual development.  

Directory of Open Access Journals (Sweden)

Full Text Available Amphiphilic excipients, such as surfactants, have been shown to be inhibitors of the multidrug resistance (MDR efflux pump transporter protein, P-glycoprotein (Pgp. In vitro studies using manysurfactants have demonstrated that those with an optimum hydrophilic-lipophilic balance (HLB exhibit greater efflux pump inhibition than those that are either very hydrophobic, or very hydrophilic, although the correlation of HLB to Pgp inhibition activity remains weak. Using the data from multiple in vitro studies, a model has been conceptualized that underscores the attributes of both the HLB and the critical micellar concentration (CMC, occurring in tandem, and unable of being varied independently, as key determinants toward prediction of surfactant Pgp inhibition activity. The algorithm that formalizes this concept provides a ‘semi-rational’ method of choosingsurfactants for a specific type of cancer for maximum inhibition of MDR.

Apte Shireesh Prakash

2010-12-01

44

Effect of P-glycoprotein and multidrug resistance associated protein gene expression on Tc-99m MIBI imaging in hepatocellular carcinoma  

Energy Technology Data Exchange (ETDEWEB)

P-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP) expressions as well as Tc-99m methoxisobutylisonitrile (MIBI) images were assessed in 25 patients hepatocellular carcinoma (HCC). Tc-99m MIBI imaging was performed 10 minutes after intravenous injection of 20 mCi Tc-99m MIBI. Using immunohistochemical staining, 60% of the HCC lesions showed positive for Pgp and 64% showed positive for MRP. In 3 patients with MIBI uptake, immunohistochemical study of tumor tissue showed no Pgp stained cells. Nevertheless, they were all positive for MRP. The result of Tc-99m MIBI imaging is more related to the expression of Pgp than MRP gene. It is possible that other membrane transporters as well as Pgp and MRP are involved in the efflux of Tc-99m MIBI.

Chang, C.-S. E-mail: changcs@vghtc.gov.tw; Huang, W.-T.; Yang, S.-S.; Yeh, H.-Z.; Kao, C.-H.; Chen, G.-H

2003-02-01

45

Reversal of P-glycoprotein-mediated multidrug resistance in human hepatoma cells by hedyotiscone A, a compound isolated from Hedyotis corymbosa.  

Science.gov (United States)

Multidrug resistance is a major problem in hepatocellular carcinoma. Hedyotiscone A, a compound isolated from Chinese herbal medicine Hedyotis corymbosa (HC, family Rubiaceae), was used as the chemical marker to distinguish between HC and an anticancer herb Hedyotis diffusa (HD) in our previous study. The present study aimed to investigate whether HA exhibited antiproliferative activities in multidrug-resistant hepatocellular carcinoma cells R-HepG2 and the parental cells HepG2 using MTT assay and [(3)H]-thymidine incorporation assay. Our results showed that HA could significantly inhibit cell proliferation in R-HepG2 and HepG2 (IC(50)?=?43.7 and 56.3 µg/mL, respectively), but not in normal human liver cells WRL-68 (IC(50) > 100 µg/mL) cells, suggesting its selective cytotoxic effects. Besides, HA induced apoptosis in R-HepG2 cells, as confirmed by annexin-V & propidium iodide staining, and DNA fragmentation assay. The caspase cascade was activated as shown by a significant increase of cleaved caspases-3, -7 and -9 in HA-treated R-HepG2 cells. The activities and protein expression of P-glycoprotein as well as mRNA expression of MDR1 were also decreased in HA-treated R-HepG2 cells. Our study demonstrated for the first time the antiproliferative activities of hedyotiscone A in multidrug-resistant R-HepG2 cells. The findings revealed the potential of this compound in treating multidrug-resistant tumor. PMID:22352391

Yue, Grace Gar-Lee; Kin-Ming Lee, Julia; Cheng, Ling; Chung-Lap Chan, Ben; Jiang, Lei; Fung, Kwok-Pui; Leung, Ping-Chung; Bik-San Lau, Clara

2012-06-01

46

[Correlation between reversing effect of cepharanthine hydrochloride on multidrug resistance and P-glycoprotein expression and function of K562/ADR cells].  

Science.gov (United States)

In this study, cepharanthine hydrochloride (CH) was tested for its potential ability to modulate the expression and function of P-glycoprotein (P-gp) in the multidrug-resistant human chronic myelogenous leukemia cell line K562/ADR. Cytotoxicity of adriamycin (ADR) alone or in combination with CH or verapamil (VER) in K562 and K562/ADR cells was determined by MTT assay. Based on flow cytometric technology, the effect of CH or VER on the uptake and efflux of rhodamine123 (Rho123) and the accumulation of ADR in these cells was detected by measuring Rho123 or ADR-associated mean fluorescence intensity (MFI). The effects of CH and VER on P-glycoprotein (P-gp) expression in K562 and K562/ADR cells were also measured using a flow cytometry with PE-conjugated P-glycoprotein antibody. The results show that CH significantly enhanced the sensitivity of K562/ADR cells to ADR, 4 micromol x L(-1) of CH enhanced the sensitivity of K562/ADR cells to ADR by 7.43 folds, the reversal activity was 3.19 times higher than that of verapamil. However, CH had no effect on drug-sensitive K562 cells (P < 0.05). CH increased Rho123 and ADR accumulation in a concentration-dependent manner (2-8 micromol x L(-1)) and inhibited the efflux of Rho123 from these cells, but did not affect the accumulation and efflux of Rho123 from the wild-type drug-sensitive K562 cells. The inhibition effect of CH on P-gp expression in K562/ADR cells is in a time- and concentration-dependent manner. The reversal activity of CH is possibility related to inhibition of P-gp function and expression, which lead to an increased intracellular accumulation of anticancer drugs. PMID:22812001

Peng, You-Mei; Wang, Ning; Wang, Ya-Feng; Han, Li; Zhang, Yan; Jiang, Jin-Hua; Zhou, Yu-Bing; Wang, Qing-Duan

2012-05-01

47

Modulation of multidrug resistance P-glycoprotein activity by antiemetic compounds in human doxorubicin-resistant sarcoma cells (MES-SA/Dx-5): implications on cancer therapy.  

Science.gov (United States)

Multidrug resistance (MDR) in cancer cells is often caused by the high expression of the plasma membrane drug transporter P-glycoprotein (Pgp) associated with an elevated intracellular glutathione (GSH) content in various human tumors. Several chemosensitizers reverse MDR but have significant toxicities. Antiemetic medications are often used for controlling chemotherapy-induced nausea and vomiting in cancer patient. In this in vitro study we investigated if the effects of two common antiemetic drugs such as dimenhydrinate (dime) and ondansentron (onda) and a natural compound (6)-gingerol (ginger), the active principle of ginger root, interfere on Pgp activity and intracellular GSH content in order to evaluate their potential use as chemosensitizing agents in anticancer chemotherapy. The human doxorubicin (doxo) resistant uterine sarcoma cells (MES-SA/Dx5) that overexpress Pgp, were treated with each antiemetic alone (1, 10 and 20 microM) or in combination with different doxo concentrations (2, 4, and 8 microM). We measured the intracellular accumulation and cytotoxicity of doxo (MTT assay), the cellular GSH content (GSH assay) and ROS production (DFC-DA assay), in comparison with verapamil (Ver), a specific inhibitor for Pgp, used as reference molecule. We found that exposure at 2, 4 and 8 microM doxo concentrations in the presence of dime, onda and ginger enhanced significantly doxo accumulation and cytotoxicity on resistant MES-SA/Dx5 cells when compared with doxo alone. Moreover, treatment with ginger (20 microM) increased cellular GSH content (greater than 10 percent) in resistant cells, while ROS production remained below the control values for all antiemetic compounds at all concentrations. These findings provide the rationale for innovative clinical trials of antiemetics or their derivatives as a new potential generation of chemosensitizers to improve effectiveness of the anticancer drugs in MDR human tumours. PMID:24382184

Angelini, A; Conti, P; Ciofani, G; Cuccurullo, F; Di Ilio, C

2013-01-01

48

Reversion of multidrug resistance in the P-glycoprotein positive breast cancer cell line (MCF-7/ADR) by introduction of hammerhead ribozyme.  

Science.gov (United States)

A hammerhead ribozyme which site-specifically cleaved the GUC position in codon 880 of the mdr1 mRNA was designed. The target site was chosen between the two ATP binding sites, which may be important for the function of the P-Gp as an ATP-dependent pump. A DNA sequence encoding the ribozyme gene was then incorporated into a eukaryotic expression vector (pH beta Apr-1 neo) and transfected into the breast cancer cell line MCF-7/Adr, which is resistant to adriamycin and expresses the MDR phenotype. The ribozyme was stably expressed in the cell line by the RNA dot blotting assay. The result of Northern blot assay showed that the expressed ribozyme could decrease the level of mdr1 mRNA expression by 83.5%; and the expressed ribozyme could inhibit the formation of P-glycoprotein detected by immuno-cytochemistry assay and could reduce the cell's resistance to adriamycin; this means that the resistant cells were 1,000-fold more resistant than the parental cell line (MCF-7), whereas those cell clones that showed ribozyme expression were only 6-fold more resistant than the parental cell line. These results show that a potentially useful tool is at hand which may inactivate MDR1 mRNA and revert the multidrug resistance phenotype. PMID:11717919

Yuan, Y; Zhang, J; Scanlon, K J; Lu, Z; Qi, G

1998-03-01

49

Expression and localization of p-glycoprotein, multidrug resistance protein 4, and breast cancer resistance protein in the female lower genital tract of human and pigtailed macaque.  

Science.gov (United States)

Abstract Antiretroviral drug absorption and disposition in cervicovaginal tissue is important for the effectiveness of vaginally or orally administered drug products in preexposure prophylaxis (PrEP) of HIV-1 sexual transmission to women. Therefore, it is imperative to understand critical determinants of cervicovaginal tissue pharmacokinetics. This study aimed to examine the mRNA expression and protein localization of three efflux transporters, P-glycoprotein (P-gp), multidrug resistance-associated protein 4 (MRP4), and breast cancer resistance protein (BCRP), in the lower genital tract of premenopausal women and pigtailed macaques. Along the human lower genital tract, the three transporters were moderately to highly expressed compared to colorectal tissue and liver, as revealed by real-time reverse transcriptase polymerase chain reaction (RT-PCR). In a given genital tract segment, the transporter with the highest expression level was either BCRP or P-gp, while MRP4 was always expressed at the lowest level among the three transporters tested. The immunohistochemical staining showed that P-gp and MRP4 were localized in multiple cell types including epithelial cells and vascular endothelial cells. BCRP was predominantly localized in the vascular endothelial cells. Differences in transporter mRNA level and localization were observed among endocervix, ectocervix, and vagina. Compared to human tissues, the macaque cervicovaginal tissues displayed comparable expression and localization patterns of the three transporters, although subtle differences were observed between the two species. The role of these cervicovaginal transporters in drug absorption and disposition warrants further studies. The resemblance between human and pigtailed macaque in transporter expression and localization suggests the utility of the macaque model in the studies of human cervicovaginal transporters. PMID:24803409

Zhou, Tian; Hu, Minlu; Pearlman, Andrew; Patton, Dorothy; Rohan, Lisa

2014-11-01

50

Consequences of cell-to-cell P-glycoprotein transfer on acquired multidrug resistance in breast cancer: a cell population dynamics model  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Cancer is a proliferation disease affecting a genetically unstable cell population, in which molecular alterations can be somatically inherited by genetic, epigenetic or extragenetic transmission processes, leading to a cooperation of neoplastic cells within tumoural tissue. The efflux protein P-glycoprotein (P-gp is overexpressed in many cancer cells and has known capacity to confer multidrug resistance to cytotoxic therapies. Recently, cell-to-cell P-gp transfers have been shown. Herein, we combine experimental evidence and a mathematical model to examine the consequences of an intercellular P-gp trafficking in the extragenetic transfer of multidrug resistance from resistant to sensitive cell subpopulations. Methodology and Principal Findings We report cell-to-cell transfers of functional P-gp in co-cultures of a P-gp overexpressing human breast cancer MCF-7 cell variant, selected for its resistance towards doxorubicin, with the parental sensitive cell line. We found that P-gp as well as efflux activity distribution are progressively reorganized over time in co-cultures analyzed by flow cytometry. A mathematical model based on a Boltzmann type integro-partial differential equation structured by a continuum variable corresponding to P-gp activity describes the cell populations in co-culture. The mathematical model elucidates the population elements in the experimental data, specifically, the initial proportions, the proliferative growth rates, and the transfer rates of P-gp in the sensitive and resistant subpopulations. Conclusions We confirmed cell-to-cell transfer of functional P-gp. The transfer process depends on the gradient of P-gp expression in the donor-recipient cell interactions, as they evolve over time. Extragenetically acquired drug resistance is an additional aptitude of neoplastic cells which has implications in the diagnostic value of P-gp expression and in the design of chemotherapy regimens. Reviewers This article was reviewed by Leonid Hanin, Anna Marciniak-Czochra and Marek Kimmel.

Webb Glenn

2011-01-01

51

Inhibition of P-glycoprotein-mediated transport by S-adenosylmethionine and cynarin in multidrug-resistant human uterine sarcoma MES-SA/Dx5 cells.  

Science.gov (United States)

Multidrug resistance (MDR) to anticancer chemotherapy is often mediated by the overexpression of the plasma membrane drug transporter P-glycoprotein (Pgp) encoded by multidrug resistance gene (MDR1). Various chemosensitizing agents are able to inhibit Pgp activity but their clinical application is limited by their toxicity. Furthermore, hepatotoxicity related to chemotherapy causes delays of treatment in cancer patients and often requires supplementation of anti-tumour therapy with hepatoprotective agents. In this in vitro study, we investigated the effectiveness of an endogenous hepatoprotective agent, S-adenosylmethionine (SAMe), and a natural hepatoprotective compound, Cynarin (Cyn), to inhibit Pgp activity in order to evaluate their potential use as chemosensitizing agents. Human doxorubicin (doxo) resistant uterine sarcoma cells (MES-SA/Dx5) expressing high levels of Pgp were treated with two hepatoprotectors at various concentrations (1, 5 and 10 microM) that are clinically achievable, in the presence or absence of three different concentrations of doxo (2, 4 and 8 microM). In order to evaluate the effects of both hepatoprotectors, we measured the intracellular accumulation and cytotoxicity of doxo, the cellular GSH level, ROS production and catalase (CAT) activity. We found that treatment with 2, 4 and 8 microM doxo in the presence of SAMe or Cyn significantly increased the doxo accumulation and cytotoxicity on MES-SA/Dx5 cells, when compared to control cells receiving doxo alone. Moreover, treatment with SAMe or Cyn significantly increased GSH content, greater than 80 percent and 60 percent, respectively) and CAT activity greater than 60 and 150 percent, respectively) in resistant cancer cells, while ROS production was below the values of corresponding untreated control cells. Our in vitro findings provide a rationale for the potential clinical use of these hepatoprotectors both as chemosensitizing agents, to reverse Pgp-mediated MDR, and as antioxidants to protect normal cells from chemotherapy-induced cytotoxixity. PMID:23034269

Angelini, A; Di Pietro, R; Centurione, L; Castellani, M L; Conti, P; Porreca, E; Cuccurullo, F

2012-01-01

52

The relative importance of passive and P-glycoprotein mediated anthracycline efflux from multidrug-resistant cells  

DEFF Research Database (Denmark)

For the four anthracyclines idarubicin, daunorubicin, epirubicin and doxorubicin the passive and active efflux rates in intact multidrug resistant cells were compared. Although highly similar structurally, these anti-tumor agents differ in lipophilicity and membrane permeability (k). The method we used was based on the continuous measurement of the cellular efflux and determination of the ratio (RVp) of transport rates just before and just after inhibition of the active transport with verapamil (Vp). Hence, RVp ? 1 should reflect the active transport rate relative to the passive transport rate. If cells were single, well-stirred compartments, RVp ? 1 should equal Vmax/(k·Km), where Vmax is the maximal pumping rate and Km is the Michaelis constant. However, using the plasma membrane permeabilizing agent digitonin, we found an effective intracellular anthracycline store. Particularly, when the efflux was fast, e.g. with idarubicin or in intensively pumping cells, the intracellular transport began to control thecellular efflux. Under these conditions, k underestimated the true plasma membrane permeability (k0) and RVp ? 1 underestimated Vmax/(k·Km). Based on the effects of digitonin on the efflux rates in pumping and nonpumping cells, we developed an index (RVp,corrected ? 1) which should equal Vmax/(k0·Km). The term Vmax/(k0·Km) varied substantially between the drugs. It appears that differences in lipophilicity between the drugs do not affect passive efflux and pumping equally. This demonstrates that passive permeation plays a substantial and independent role in determining the drug resistance for these anthracyclines. The methods developed here enable dissection of this role from that of drug pumping and intracellular subcompartmentation.

Wielinga, Pieter; Westerhoff, Hans V.

2000-01-01

53

Comparative uptake of Tc-99m sestamibi and Tc-99m tetrofosmin in cancer cells and tissue expressing P-Glycoprotein or multidrug resistance associated protein  

Energy Technology Data Exchange (ETDEWEB)

{sup 99m}Tc-sestamibi(MIBI) and {sup 99m}Tc-tetrofosmin have been used as substrates for P-glycoprotein (Pgp) and multidrug resistance associated protein (MRP), which are closely associated with multidrug resistance of the tumors. To understand different handling of radiotracers in cancer cell lines expressing Pgp and MRP, we compared cellular uptakes of {sup 99m}Tc-MIBI and {sup 99m}Tc-tetrofosmin. The effects of cyclosporin A (CsA), well-known multidrug resistant reversing agent, on the uptake of both tracers were also compared. HCT15/CL02 human colorectal cancer cells for Pgp expressing cells, and human non-small cell lung cancer A549 cells for MRP expressing cells, were used for in vitro and in vivo studies. RT-PCR, western blot analysis and immunohistochemistry were used for detection of Pgp and MRP. MDR-reversal effect with CsA was evaluated at different drug concentrations after incubation with MIBI or tetrofosmin. Radioactivities of supernatant and pellet were measured with gamma well counter. Tumoral uptake of the tracers were measured from tumor bearing nude mice treated with or without CsA. RT-PCR, western blot analysis of the cells and immunochemical staining revealed selective expression of Pgp and MRP for HCT15/CL02 and A549 cells, respectively. There were no significant difference in cellular uptakes of both tracers in HCT15/CL02 cells, but MIBI uptake was slightly higher than that of tetrofosmin in A549 cells. Co-incubation with CsA resulted in a increase in cellular uptakes of MIBI and tetrofosmin. Uptake of MIBI or tetrofosmin in HCT15/CL02 cells was increased by 10-and 2.4-fold, and by 7.5 and 6.3-fold in A549 cells, respectively. Percentage increase of MIBI was higher than that of tetrofosmin with CsA for both cells ({rho} < 0.05). In vivo biodistribution study showed that MIBI (114% at 10 min, 257% at 60 min, 396% at 24C min) and tetrofosmin uptake (110% at 10 min, 205% at 60 min, 410% at 240 min) were progressively increased by the time, up to 240 min with CsA. But increases in tumoral uptake were not significantly different between MIBI and tetrofosmin for both tumors. MIBI seems to be a better tracer than tetrofosmin for evaluating MDR reversal effect of the modulators in vitro, but these differences were not evident in vivo tumoral uptake. Both MIBI and tetrofosmin seem to be suitable tracers for imaging Pgp-and MRP=mediated drug resistance in tumors.

Cho, Jung Ah; Lee, Jae Tae; Yoo, Jung Ah [School of Medicine, Kyungpook National University, Daegu (Korea, Republic of)] (and others)

2005-02-15

54

Chalcogenopyrylium compounds as modulators of the ATP-binding cassette transporters P-glycoprotein (P-gp/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1).  

Science.gov (United States)

Twenty-seven chalcogenopyrylium derivatives varying in the heteroatom of the pyrylium core and substituents at the 2-, 4-, and 6-positions were examined for their effect on human MRP1-mediated uptake of tritiated estradiol glucuronide into inside-out membrane vesicles, their affinity for and ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His(10), and their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant cells. Differences in their effects on MRP1 and P-gp activity were noted, and a second set of thiopyrylium compounds with systematic substituent changes was examined to refine these differences further. Derivatives with tert-butyl substituents in the 2- and 6-positions had the lowest inhibitory activity toward both transporters. Derivatives with thioamide functionality in the 4-position were more active against MRP1 than derivatives with amide functionality. Conversely, derivatives with amide functionality in the 4-position were more active in P-gp than derivatives with thioamide functionality. PMID:22533905

Ebert, Sean P; Wetzel, Bryan; Myette, Robert L; Conseil, Gwenaëlle; Cole, Susan P C; Sawada, Geri A; Loo, Tip W; Bartlett, M Claire; Clarke, David M; Detty, Michael R

2012-05-24

55

Why the xanthine derivatives are used to study of P-glycoprotein-mediated multidrug resistance in L1210/VCR line cells.  

Science.gov (United States)

There is generally well known that various xanthines occur frequently in natural products, e.g. black coffee, black tea, green tea, natural dyes etc. Xanthine molecules are good tolerated and metabolised by organisms. Moreover, natural xanthines and/or sythesized xanthines may recall a lot positive affects (hemorheologic properties, anti-inflammatory properties, tracheal smooth muscle relaxant, positive chronotropic and central nervous system-stimulating, etc.) and may even induce a quantity of changes on the molecular level (inhibition of cyclic nucleotide phosphodiesterases, inhibition of the synthesis of tumor necrosis factor (TNF-alpha), cellular Ca(2+) homeostasis, etc.). In our previous paper we showed that some xanthine derivatives (pentoxifylline and its derivatives) depress P-glycoprotein (P-gp) mediated multidrug resistance of the mouse leukemic cells. Other authors, first of all Sadzuka and co-workers, confirm this usefulness of long side substituted xanthines as biochemical modulators. However, the mechanism of molecular action of xanthine derivatives has not been clarified. One of the possible ways to chemosensitize the cancer cells is direct competiting in defence mechanism - inhibition of efflux pump (P-gp). Interaction of xanthine derivatives with binding site of P-gp is a question which could be solved by experiment; although, molecular modelling may clear up this matter. But, each dynamic and static program for molecular simulation of P-gp action is dividing on input variable, considering mechanistic view of insight drug transport. PMID:20817945

Do?olomanský, Peter; Bohá?ová, Viera; Baran?ík, Miroslav; Breier, Albert

2010-09-01

56

Up-regulation of CD147 and matrix metalloproteinase-2, -9 induced by P-glycoprotein substrates in multidrug resistant breast cancer cells.  

Science.gov (United States)

Treatment of animals bearing multidrug resistant (MDR) tumor cells with P-glycoprotein (P-gp) substrates could worsen host survival. It is assumed that this is due to increased tumor metastasis. To clarify the mechanism(s) underlying this observation, the MDR human breast cancer cell line, MCF-7/AdrR, and its sensitive parental line, MCF-7, was treated with various concentrations of P-gp substrate drugs (vincristine, paclitoxel, adriamycin) and a P-gp non-substrate drug (bleomycin) in serum-free media. Increased production of CD147, and matrix metalloproteinases (MMP)-2, -9 was observed only in MDR cancer cells exposed to P-gp substrates, as determined using real-time polymerase chain reaction, western blotting and zymography. Correspondingly, P-gp substrates significantly enhanced the in vitro invasion abilities of MCF-7/Adr cells. It was also found that the drug-induced promotion of CD147, and MMP-2, -9 was consistent with increased expression of epidermal growth factor receptor (EGFR) and that inhibition of either EGFR or P-gp activity could significantly interrupt the downstream effects, and so inhibit in vitro invasion abilities motivated by P-gp substrates. These results imply that treatment of MDR tumors with P-gp substrates could adversely affect therapeutic outcomes through modulating the production of CD147, MMP-2, -9, and EGFR, and suggest that this effect may be initiated by the transporter function of P-gp. PMID:17725804

Li, Qing-Quan; Wang, Wen-Juan; Xu, Jing-Da; Cao, Xi-Xi; Chen, Qi; Yang, Jin-Ming; Xu, Zu-De

2007-11-01

57

Detecting parathyroid adenoma using technetium-99m tetrofosmin: comparison with P-glycoprotein and multidrug resistance related protein expression--a preliminary report  

Energy Technology Data Exchange (ETDEWEB)

The aim of this study was to investigate the relationships among technetium-99m tetrofosmin (Tc-TF) accumulation in parathyroid adenoma and the expression of P-glycoprotein (Pgp) or multidrug resistance related protein (MRP). Before operation, 33 patients with parathyroid adenomas (larger than 1.5 gm) were studied with parathyroid scintigraphy 10 minutes and 2 hours after intravenous injection of Tc-TF before operation. Immunohistochemical analyses (IHA) were performed on multiple nonconsecutive sections of operative parathyroid specimens to detect Pgp or MRP expression. According to the results of IHA, the 33 parathyroid adenomas were separated into four groups: (1) 2 adenomas with both positive Pgp and positive MRP expression, (2) 1 adenomas with positive Pgp but negative MRP expression, (3) 2 adenomas with negative Pgp but positive MRP expression, and (4) 28 adenomas with both negative Pgp and negative MRP expression. All of 28 adenomas in the group 4 could be detected by Tc-TF parathyroid imaging. All of 5 adenomas in the groups 1 to 3 could not be detected by TcTF parathyroid imaging (p < 0.05). Not only the size of parathyroid adenomas, but also significant Pgp or MRP expression limited the sensitivity of Tc-TF parathyroid imaging to localize parathyroid adenomas before operation.

Shiau, Y.C.; Tsai, S.C.; Wang, J.J.; Ho, S.T.; Kao, A. E-mail: albertkaotw@yahoo.com.tw

2002-04-01

58

Detecting parathyroid adenoma using technetium-99m tetrofosmin: comparison with P-glycoprotein and multidrug resistance related protein expression--a preliminary report  

International Nuclear Information System (INIS)

The aim of this study was to investigate the relationships among technetium-99m tetrofosmin (Tc-TF) accumulation in parathyroid adenoma and the expression of P-glycoprotein (Pgp) or multidrug resistance related protein (MRP). Before operation, 33 patients with parathyroid adenomas (larger than 1.5 gm) were studied with parathyroid scintigraphy 10 minutes and 2 hours after intravenous injection of Tc-TF before operation. Immunohistochemical analyses (IHA) were performed on multiple nonconsecutive sections of operative parathyroid specimens to detect Pgp or MRP expression. According to the results of IHA, the 33 parathyroid adenomas were separated into four groups: (1) 2 adenomas with both positive Pgp and positive MRP expression, (2) 1 adenomas with positive Pgp but negative MRP expression, (3) 2 adenomas with negative Pgp but positive MRP expression, and (4) 28 adenomas with both negative Pgp and negative MRP expression. All of 28 adenomas in the group 4 could be detected by Tc-TF parathyroid imaging. All of 5 adenomas in the groups 1 to 3 could not be detected by TcTF parathyroid imaging (p < 0.05). Not only the size of parathyroid adenomas, but also significant Pgp or MRP expression limited the sensitivity of Tc-TF parathyroid imaging to localize parathyroid adenomas before operation

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Multi-drug resistance (MDR1 gene and P-glycoprotein influence on pharmacokinetic and pharmacodymanic of therapeutic drugs  

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Full Text Available (MDR1 gene expressed in tumor cells and also in several normal tissues, such as intestine, liver, kidney, blood-brain barrier, spinal cord, and placenta. P-gp has been identified in mice, rat, bovine, monkey, rodents, and human beings and has been receiving a particular clinical relevance because this protein expression limits brain access and intestinal absorption of many drugs. This protein plays a role as a protective barrier against a wide variety of substrates, avoiding drug entry into the central nervous system. P-glycoprotein also interferes with drug bioavailability and disposition, including absorption, distribution, metabolization, and excretion, influencing pharmacokinetic and pharmacodynamic of drugs. Modulation of P-gp may help the efficacy of treatment of several diseases and can explain some adverse central nervous system effects induced by drugs after intravenous administration and the poor response of oral administration in patients. Alteration in P-gp expression or function has been associated with several diseases susceptibility in humans and animals. Furthermore, additional studies relating MDR1 and P-gp expression has an important clinical implication also in terms of treatment efficacy.

Linardi Renata Lehn

2006-01-01

60

Inhibition of P-glycoprotein (ABCB1)- and multidrug resistance-associated protein 1 (ABCC1)-mediated transport by the orally administered inhibitor, CBT-1((R)).  

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Cellular expression of ATP-binding cassette (ABC) transport proteins, such as P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP1), or ABCG2, is known to confer a drug-resistant phenotype. Thus, the development of effective transporter inhibitors could be of value to cancer treatment. CBT-1 is a bisbenzylisoquinoline plant alkyloid currently in development as a Pgp inhibitor. We characterized its interactions with the three major ABC transporters associated with drug resistance - Pgp, MRP1 and ABCG2 - and compared it to other known inhibitors. CBT-1 completely inhibited rhodamine 123 transport from Pgp-overexpressing cells at a concentration of 1muM. Additionally, 1 microM completely reversed Pgp-mediated resistance to vinblastine, paclitaxel and depsipeptide in SW620 Ad20 cells. CBT-1 was found to compete [(125)I]-IAAP labeling of Pgp with an IC(50) of 0.14 microM, and low concentrations of CBT-1 (<1 microM) stimulated Pgp-mediated ATP hydrolysis. In MRP1-overexpressing cells, 10 microM CBT-1 was found to completely inhibit MRP1-mediated calcein transport. CBT-1 at 25 microM did not have a significant effect on ABCG2-mediated pheophorbide a transport. Serum levels of CBT-1 in samples obtained from eight patients receiving CBT-1 increased intracellular rhodamine 123 levels in CD56+ cells 2.1- to 5.7-fold in an ex vivo assay. CBT-1 is able to inhibit the ABC transporters Pgp and MRP1, making it an attractive candidate for clinical trials in cancers where Pgp and/or MRP1 might be overexpressed. Further clinical studies with CBT-1 are warranted. PMID:18234154

Robey, Robert W; Shukla, Suneet; Finley, Elizabeth M; Oldham, Robert K; Barnett, Daryl; Ambudkar, Suresh V; Fojo, Tito; Bates, Susan E

2008-03-15

 
 
 
 
61

Inhibition of P-glycoprotein (ABCB1)- and multidrug resistance-associated protein 1 (ABCC1)-mediated transport by the orally administered inhibitor, CBT-1(R)  

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Cellular expression of ATP-binding cassette (ABC) transport proteins, such as P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP1), or ABCG2, is known to confer a drug-resistant phenotype. Thus, the development of effective transporter inhibitors could be of value to cancer treatment. CBT-1® is a bisbenzylisoquinoline plant alkyloid currently in development as a Pgp inhibitor. We characterized its interactions with the three major ABC transporters associated with drug resistance--Pgp, MRP1 and ABCG2—and compared it to other known inhibitors. CBT-1® completely inhibited rhodamine 123 transport from Pgp-overexpressing cells at a concentration of 1 ?M. Additionally, 1 ?M completely reversed Pgp-mediated resistance to vinblastine, paclitaxel and depsipeptide in SW620 Ad20 cells. CBT-1® was found to compete [125I]-IAAP labeling of Pgp with an IC50 of 0.14 ?M, and low concentrations of CBT-1® (< 1 ?M) stimulated Pgp-mediated ATP hydrolysis. In MRP1-overexpressing cells, 10 ?M CBT-1® was found completely inhibit MRP1-mediated calcein transport. CBT-1® at 25 ?M did not have a significant effect on ABCG2-mediated pheophorbide a transport. Serum levels of CBT-1® in samples obtained from eight patients receiving CBT-1® increased intracellular rhodamine 123 levels in CD56+ cells 2.1- to 5.7-fold in an ex vivo assay. CBT-1® is able to inhibit the ABC transporters Pgp and MRP1, making it an attractive candidate for clinical trials in cancers where Pgp and/or MRP1 might be overexpressed. Further clinical studies with CBT-1® are warranted. PMID:18234154

Robey, Robert W.; Shukla, Suneet; Finley, Elizabeth M.; Oldham, Robert K.; Barnett, Daryl; Ambudkar, Suresh V.; Fojo, Tito; Bates, Susan E.

2008-01-01

62

Diatrizoate, Iopromide and Iotrolan Enhanced Cytotoxicity of Daunorubicin in Multidrug Resistant K562/adr Cells: Impaired the Mitochondrial and Inhibited the P-Glycoprotein Function  

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Full Text Available Multidrug resistance was an obstacle in cancer chemotherapy because the cells decreased their intracellular drug accumulation by energy-dependent compounds efflux pumps such as P-glycoprotein (P-gp. This study observed some iodinated radiographic contrast media, diatrizoate, iopromide and iotrolan affected the cellular energetic state and the kinetics of P-gp in drug-sensitive K562 and drug resistant K562/adr cell lines using spectrophotometer and spectrofluorometer. By colorimetric MTT assay, it was found that contrast media (0-3500 µM had no effect on both K562 and K562/adr cell viabilities, but in co-treatment with daunorubicin (DNR, diatrizoate decreased cell viability in K562/adr cells by decreasing ICso of DNR from 610.7 ±74.5 nM to 360±108.9 nM. The change in cellular energetic state was studied using rhodamine B as a probe to estimate mitochondrial membrane potential (??m. The results showed that 3500 µM diatrizoate decreased ??m from 162.2±0.3 mV to 86.9±9.9 mV in K562/adr cells. The kinetics of P-gp-mediated efflux of DNR could be reduced by diatrizoate from 0 (no inhibition to 0.65±0.11. This inhibition could be partially prevented in co-incubation with 20 nM concanamycin A or 10 µM cytochalasin B. Among the three molecules, diatrizoate showed the best efficiency. It could be proposed for further studies that diatrizoate could be used as MDR identification or MDR imaging and also acted as MDR sensitizing agent in cancer treatments.

Nitaya S.N. Ayudhya

2009-01-01

63

Interaction of forskolin with the P-glycoprotein multidrug transporter  

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Forskolin and 1,9-dideoxyforskolin, an analogue that does not activate adenylyl cyclase, were tested for their ability to enhance the cytotoxic effects of adriamycin in human ovarian carcinoma cells, SKOV3, which are sensitive to adriamycin and express low levels of P-glycoprotein, and a variant cell line, SKVLB, which overexpresses the P-glycoprotein and has the multidrug reing ance (MDR) phenotype. Forskolin and 1,9-dideoxyforskolin both increased the cytotoxic effects of adriamycin in SKVLB cells, yet had no effect on SKOV3 cells. Two photoactive derivatives of forskolin have been synthesized, 7-O-((2-(3-(4-azido-3-({sup 125}I)iodophenyl)propionamido)ethyl)carbamyl)forskolin, {sup 125}I-6-AIPP-Fsk, and 6-O-((2-(3-(4-azido-3-({sup 125}I)iodophenyl)propionamido)ethyl)carbamyl)forskolin, {sup 125}I-6-AIPP-Fsk, which exhibit specificity for labeling the glucose transporter and aing lyl cyclase, respectively. Both photolabels identified a 140-kDa protein in membranes from SKVLB cells whose labeling was inhibited by forskolin and 1,9-dideoxyforskolin. The data are consistent with forskolin binding to the P-glycoprotein analogous to that of other chemosensitizing drugs that have been shown to partially reverse MDR. The ability of forskolin photolabels to specifically label the transporter, the adenylyl cyclase, and the P-glycoprotein suggests that these proteins may share a common biing g domain for forskolin analogues.

Ming s, D.I.; Seamon, K.B. (Food and Drug Administration, Bethesda, MD (United States)); Speicher, L.A.; Tew, K.D. (Fox Chase Cancer Research Center, Philadelphia, PA (United States)); Ruoho, A.E. (Univ. of Wisconsin, Madison (United States))

1991-08-27

64

Down-regulation of extracellular signal-regulated kinase 1/2 activity in P-glycoprotein-mediated multidrug resistant hepatocellular carcinoma cells  

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Full Text Available AIM: To study the expression and phosphorylation of extracellular signal-regulated kinase (ERK 1 and ERK2 in multidrug resistant (MDR hepatocellular carcinoma (HCC cells.METHODS: MDR HCC cell lines, HepG2/adriamycin (ADM and SMMC7721/ADM, were developed by exposing parental cells to stepwise increasing concentrations of ADM. MTT assay was used to determine drug sensitivity. Flow cytometry was employed to analyze cell cycle distribution and measure cell P-glycoprotein (P-gp and multidrug resistant protein 1 (MRP1 expression levels. ERK1 and ERK2 mRNA expression levels were measured by quantitative real-time PCR (QRT-PCR. Expression and phosphorylation of ERK1 and ERK2 were analyzed by Western blot.RESULTS: MTT assay showed that HepG2/ADM and SMMC7721/ADM were resistant not only to ADM, but also to multiple anticancer drugs. The P-gp expression was over 10-fold higher in HepG2/ADM cells than in HepG2 cells (8.92% ± 0.22% vs 0.88% ± 0.05%, P < 0.001 and over 4-fold higher in SMMC7721/ADM cells than in SMMC7721 cells (7.37% ± 0.26% vs 1.74% ± 0.25%, P < 0.001. However, the MRP1 expression was not significantly higher in HepG2/ADM and SMMC7721/ADM cells than in parental cells. In addition, the percentage of MDR HepG2/ADM and SMMC7721/ADM cells was significantly decreased in the G0/G1 phase and increased in the the S phase or G2/M phase. QRT-PCR analysis demonstrated that the ERK1 and ERK2 mRNA expression increased apparently in HepG2/ADM cells and decreased significantly in SMMC7721/ADM cells. Compared with the expression of parental cells, ERK1 and ERK2 protein expressions were markedly decreased in SMMC7721/ADM cells. However, ERK2 protein expression was markedly increased while ERK1 protein expression had no significant change in HepG2/ADM cells. Phosphorylation of ERK1 and ERK2 was markedly decreased in both HepG2/ADM and SMMC7721/ADM MDR cells.CONCLUSION: ERK1 and ERK2 activities are down-regulated in P-gp-mediated MDR HCC cells. ERK1 or ERK2 might be a potential drug target for circumventing MDR HCC cells.

Feng Yan, Xiao-Min Wang, Chao Pan, Quan-Ming Ma

2009-03-01

65

P-Glycoprotein-Mediated Efflux and Drug Sequestration in Lysosomes Confer Advantages of K562 Multidrug Resistance Sublines to Survive Prolonged Exposure to Cytotoxic Agents  

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Full Text Available Problem statement: Cellular drug resistance to anticancer agents is major obstacle in cancer chemotherapy and the mechanisms by which these MDR cells possess for protecting themselves to survive prolonged exposure to cytotoxic agents still debating. The study aimed to clarify the role of P-glycoprotein (Pgp and enhanced drug sequestration in lysosomes to confer the multidrug resistance K562 cells with varied degree of Pgp expression. Approach: Erythromyelogenous leukemic K562 and its corresponding Pgp-over expression K562/adr (RF = 26.5 and K562/10000 (RF = 39.6 cells were used. The transport of intrinsic fluorescence molecules including acridine orange and pirarubicin across plasma membrane of living cells was performed by using spectrofluorometric and flow cytometric analysis. Results: Pirarubicin passively diffused through the plasma membrane of K562, K562/adr and K562/10000 cells with the same values of k+ = 3.4±0.3 pL. s-1.cell-1. Similar results were found for acridine orange, which passively diffused through plasma membrane of these cell lines about 30-fold faster than pirarubicin. The mean rate of Pgp-mediated efflux coefficient (ka of pirarubicin was equal to 2.6 ± 0.9 pL.s-1.cell-1 for K562/adr and 4.7 ± 1.0 pL.s-1.cell-1 for K562/10000 cells. The Pgp-mediated efflux of acridine orange could not be determined for K562/adr cells while an enhancement of exocytosis in K562/10000 cells was characterized. The acridine orange exhibited antiproliferative activity and IC50 for K562, K562/adr and K562/10000 cells was 447±40, 715±19 and 1,719±258 nM, respectively. Cytotoxicity of acridine orange was increased by 2-fold in the presence of and 25 nM monensin. Conclusion: The results clearly demonstrated for the first time that by using the same methods and cell lines. The predominant cellular defense mechanism determined in multidrug resistant cells depends upon the nature of molecular probes used. As molecular probe, pirarubicin clearly showed that the Pgp-mediated efflux of drug play as predominant mechanism while AO clearly demonstrated the role of drug sequestration in lysosomes following an enhance exocytosis in both MDR sublines.

Nathupakorn Dechsupa

2009-01-01

66

Effects of arsenic trioxide on expressions of vascular endothelial growth factor and P-glycoprotein in multidrug resistant leukemia cell line K562/A02  

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Full Text Available Objective: To investigate the effects of arsenic trioxide (ATO on the expressions of vascular endothelial growth factor (VEGF and P-glycoprotein (P-gp in K562/A02 cells and to explore the correlation between VEGF and P-gp.Methods: The inhibition rate of K562/A02 cell proliferation was detected by using methyl thiazolyl tetrazolium assay (MTT; the level of VEGF was detected by enzyme-linked immunosorbent assay (ELISA and the expression rate of P-gp was determined by flow cytometry (FCM.Results: 0.05 ?mol/L ATO had no influences on the cell proliferation and the expression of VEGF in K562/A02 cells; 0.4 and 3.2 ?mol/L ATO could significantly inhibit the K562/A02 cell proliferation and down-regulate the expression of VEGF in K562/A02 cells (P<0.05. The expression of P-gp did not changed after being exposed to 0.05 and 0.4 ?mol/L ATO for 24, 48 and 72 hours (P?0.05. 3.2 ?mol/L ATO could remarkably reduce the expression of P-gp in K562/A02 cells after 48- and 72-hour incubation with ATO (P<0.05.Conclusions: The down-regulation of P-gp and VEGF after being exposed to ATO probably contributes to the reversion of multidrug resistance in K562/A02 cells. The level of VEGF may be related to the expression rate of P-gp in K562/A02 cells

Yu ZHANG

2007-11-01

67

Intestinal absorption of HMG-CoA reductase inhibitor pitavastatin mediated by organic anion transporting polypeptide and P-glycoprotein/multidrug resistance 1.  

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The purpose of this study was to investigate the involvement of organic anion transporting polypeptide (OATP/Oatp) and P-glycoprotein (P-gp)/multidrug resistance 1 (MDR1/Mdr1) in intestinal absorption of pitavastatin. Pitavastatin was found to be a substrate for human OATP1A2, OATP2B1, and MDR1 and rat Oatp1a5, Oatp2b1, and Mdr1a in experiments using transporter-expressing Xenopus oocytes and LLC-PK1 cell systems. Naringin inhibited Oatp1a5- and Mdr1a-mediated transport of pitavastatin with IC(50) values of 18.5 and 541 µM, respectively. The difference in the IC(50) values of naringin for Oatp1a5 and Mdr1a-mediated pitavastatin transport may account for the complex concentration-dependent effect of naringin on the intestinal absorption of pitavastatin. Rat intestinal permeability of pitavastatin measured by the in situ closed-loop perfusion method was indeed significantly reduced by 200 µM naringin, but was significantly increased by 1000 µM naringin. Furthermore, the permeability was significantly increased by elacridar, a potent inhibitor of Mdr1, while the permeability was significantly decreased in the presence of both elacridar and naringin, suggesting that Oatp1a5 and Mdr1a are both involved in intestinal absorption of pitavastatin. Our present results indicate that OATP/Oatp and MDR1/Mdr1 play roles in the intestinal absorption of pitavastatin as influx and efflux transporters, respectively. PMID:21206133

Shirasaka, Yoshiyuki; Suzuki, Kensuke; Shichiri, Megumi; Nakanishi, Takeo; Tamai, Ikumi

2011-01-01

68

Comparison of staurosporine and four analogues: their effects on growth, rhodamine 123 retention and binding to P-glycoprotein in multidrug-resistant MCF-7/Adr cells.  

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The potent kinase inhibitor staurosporine and its protein kinase C (PKC)-selective analogue CGP 41251 are known to sensitise cells with the multidrug resistance (MDR) phenotype mediated by P-glycoprotein (P-gp) to cytotoxic agents. Here four PKC-selective staurosporine cogeners, CGP 41251, UCN-01, RO 31 8220 and GF 109203X, were compared with staurosporine in terms of their MDR-reversing properties and their susceptibility towards P-gp-mediated drug efflux from MCF-7/Adr cells. Staurosporine was the most potent and the bisindolylmaleimides RO 31 8220 and GF 109203X the least potent cytostatic agents. When compared with MCF-7 wild-type cells, MCF-7/Adr cells were resistant towards the growth-arresting properties of RO 31 8220 and UCN-01, with resistance ratios of 12.6 and 7.0 respectively. This resistance could be substantially reduced by inclusion of the P-gp inhibitor reserpine. The ratios for GF 109203X, staurosporine and CGP 41251 were 1.2, 2.0 and 2.9 respectively, and they were hardly affected by reserpine. These results suggest that RO 31 8220 and UCN-01 are avidly transported by P-gp but that the other compounds are not. Staurosporine and CGP 41251 at 10 and 20 nM, respectively, decreased efflux of the P-gp probe rhodamine 123 (R123) from MCF-7/Adr cells, whereas RO 31 8220 and GF 109203X at 640 nM were inactive. CGP 41251 was the most effective and GF 109203X the least effective inhibitor of equilibrium binding of [3H]vinblastine to its specific binding sites, probably P-gp, in MCF-7/Adr cells. Overall, the results imply that for this class of compound the structural properties that determine susceptibility towards P-gp-mediated substrate transport are complex. Comparison with ability to inhibit PKC suggests that the kinase inhibitors affect P-gp directly and not via inhibition of PKC. Among these compounds CGP 41251 was a very potent MDR-reversing agent with high affinity for P-gp and least affected by P-gp-mediated resistance, rendering it an attractive drug candidate for clinical development. PMID:8624264

Budworth, J; Davies, R; Malkhandi, J; Gant, T W; Ferry, D R; Gescher, A

1996-05-01

69

Assessment of the in vitro and in vivo properties of a {sup 99m}Tc-labeled inhibitor of the multidrug resistant gene product P-glycoprotein  

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Overexpression of P-glycoprotein (Pgp), which is present in the plasma membrane of various tumor cells and in several normal cell types, contributes to the multidrug resistance (MDR) phenotype of many human cancers. As a prerequisite for therapy, the expression of Pgp must be studied. The available clinical radiopharmaceuticals for studying the expression of Pgp include the lipophilic {sup 99m}Tc cations (sestamibi, tetrofosmin) as well as [{sup 99m}Tc]Q57, [{sup 99m}Tc]Q58, and [{sup 99m}Tc]Q63. Here we describe the in vitro and in vivo properties of the structurally different complex (3-thiapentane-1,5-dithiolato)[[N-(3-phenylpropyl)-N-2(3-quinazoline-2,4 -dionyl)-ethyl]amino-ethylthiolato] oxotechnetium(V) ({sup 99/99m}Tc1) as a potential inhibitor of Pgp. {sup 99}Tc1 enhances the net cell accumulation of Pgp substrates [{sup 3}H]vinblastine, [{sup 3}H]vincristine, [{sup 3}H]colchicine, [{sup 99m}Tc]sestamibi, and [{sup 99m}Tc]tetrofosmin in rat brain endothelial cells (RBE4), an immortalized endothelial cell line that expresses Pgp. In addition, the cell accumulation of {sup 99m}Tc1 could be increased by verapamil and reserpine, which are known Pgp inhibitors. A multitracer approach was used to study the side effects of {sup 99}Tc1 on cell metabolism. The cells were simultaneously incubated with [{sup 99m}Tc]sestamibi, 2-[{sup 18}F]fluoro-2-deoxyglucose ([{sup 18}F]FDG), and various {sup 3}H-labeled tracers. Two-dimensional scatter plots of [{sup 99m}Tc]sestamibi uptake/[{sup 18}F]FDG uptake show typical changes of known Pgp inhibitors including {sup 99}Tc1. The effects of {sup 99}Tc1 on the in vivo distribution of [{sup 99m}Tc]sestamibi and [{sup 18}F]FDG in rats also are comparable with the effects of verapamil, an established Pgp inhibitor and calcium channel blocker. We conclude that {sup 99/99m}Tc1 is a transport substrate and a potential inhibitor of Pgp. Our approach may be useful in the design of further radiotracers with specificity to Pgp.

Bergmann, R. E-mail: R.Bergmann@fz-rossendorf.de; Brust, P.; Scheunemann, M.; Pietzsch, H.-J.; Seifert, S.; Roux, F.; Johannsen, B

2000-02-01

70

Using 99mTc-MIBI to evaluate the effects of chemosensitizer on P-glycoprotein in multidrug-resistant carcinoma cells  

International Nuclear Information System (INIS)

Purpose: The changes of 99'mTc-MIBI uptake kinetics and P-glycoprotein levels were observed after using verapamil in MDR human breast cells MCF-7/Adr, in order to establish a method to evaluate the impacts of the chemosensitizer on P-glycoprotein using 99mTc-MIBI and thereby to assess the effects of chemosensitizer. Methods: MDR breast carcinoma cells, MCF-7/Adr were incubated at 370C. (1) Verapamil (10?mol/L), was added into cell culture medium, while in control group, the same quotient of DMEM. Cells were harvested after 2h incubation with 99mTc-MIBI. (2) Verapamil (10?mol/L) was added into cell culture medium and incubated for 20min, 40min, 60min, 80min, 8h, 24h, 48h and 72h respectively. Cells were harvested after 2h incubation with 99mTc-MIBI. The radioactivity and P-glycoprotein expression levels were determined. Results: (1) after 2h incubation with verapamil the cellular uptake of 99mTc-MIBI in verapamil group was remarkably higher than control (t=2.33, P99mTc-MIBI uptake increased with incubation time prolonging (F=58.2,P99mTc-MIBI uptake negatively correlated to the P-glycoprotein expression levels (r=0.73,P99mTc-MIBI accumulation and P-glycoprotein levels(r=0.16,P>0.05). Conclusions: 99mTc-MIBI may be used to evaluate the effects of chemosensitizer on P-glycoprotein expression levels

71

Using 99mTc-MIBI to evaluate the effects of chemosensitizer on P-glycoprotein in multidrug-resistant carcinoma cells  

International Nuclear Information System (INIS)

Aim: In order to explore the possibility of 99mTc-MIBI to evaluate the impacts of chemosensitizer on P-glycoprotein and thereby to assess the effects of chemosensitizer, the changes of 99mTc-MIBI uptake kinetics and P-glycoprotein levels were observed after using verapamil in MDR human breast cells MCF-7/Ad in the present study. Material and Methods: MDR breast carcinoma cells, MCF-7/Adr were incubated at 37 deg. C. (1) Verapamil (10?mol/L), a chemosensitizer, was added into cell culture medium, while in control group, the same quotient of DMEM. Cells were harvested after 2h incubation with 99mTc-MIBI. (2) Verapamil (10?mol/L) was added into cell culture medium and incubated for 20min, 40min, 60min, 80min, 8h, 24h, 48h, and 72h respectively. Cells were harvested after 2h incubation with 99mTc-MIBI. The radioactivity and P-glycoprotein expression levels were determined. Results: (1) After 2h incubation with verapamil the cellular uptake of 99mTc-MIBI was remarkably higher control group than (t=2.33, P99mTc-MIBI uptake increased with incubation time prolonging (F=58.2 P99mTc-MIBI uptake negatively correlated to the P-glycoprotein expression levels (r= 0.73 P99mTc-MIBI accumulation and P-glycoprotein levels(r=0.16 P>0.05). Conclusion: 99mTc-MIBI may be potentially used to evaluate the effects of chemosensitizer on P-glycoprotein expression levels

72

To predict response chemotherapy using technetium-99m tetrofosmin chest images in patients with untreated small cell lung cancer and compare with p-glycoprotein, multidrug resistance related protein-1, and lung resistance-related protein expression  

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Our preliminary studies found technetium-99m tetrofosmin (Tc- TF) chest imaging was related to Pgp or MRP1 expression and successfully predict chemotherapy response and in SCLC in human. However, there was no published literature to study relationship of Tc-TF chest images and LRP expression in SCLC patients. Therefore, the aim of this study was to investigate the relationships among Tc- TF accumulation in untreated small cell lung cancer (SCLC), the expression of P-glycoprotein (Pgp), multidrug resistance related protein-1 (MRP1), and lung resistance-related protein (LRP), as well as the response to chemotherapy in patients with untreated SCLC. Thirty patients with SCLC were studied with chest images 15 to 30 minutes after intravenous injection of Tc-TF before chemotherapeutic induction. Tumor-to-background (T/B) ratios were obtained on the static and plantar Tc-TF chest images. The response to chemotherapy was evaluated upon completion of chemotherapy by clinical and radiological methods. These patients were separated into 15 patients with good response and 15 patients with poor response. No significant differences of prognostic factors (Karnofsky performance status, tumor size, or tumor stage) were found between the patients with good and poor responses. Immunohistochemical analyses were performed on multiple nonconsecutive sections of biopsy specimens to detect Pgp, MRP1, and LRP expression. The difference in T/B ratios on the Tc-TF chest images of the patients with good versus poor response was significant. The differences in T/B ratios of the patients with positive versus negative Pgp expression and with positive versus negative MRP1 expression were significant. The difference in T/B ratios of the patients with positive versus negative LRP expression was not significant. We concluded that Tc-TF chest images could accurately predict chemotherapy response of patients with SCLC. In addition, The Tc-TF tumor uptake was related to Pgp or MRP1 but not LPR expression in SCLC.

Kuo, T.-H.; Liu, F.-Y.; Chuang, C.-Y.; Wu, H.-S.; Wang, J.-J.; Kao, Albert E-mail: albertkaotw@yahoo.com.tw

2003-08-01

73

Coniferyl Ferulate, a Strong Inhibitor of Glutathione S-Transferase Isolated from Radix Angelicae sinensis, Reverses Multidrug Resistance and Downregulates P-Glycoprotein.  

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Glutathione S-transferase (GST) is the key enzyme in multidrug resistance (MDR) of tumour. Inhibition of the expression or activity of GST has emerged as a promising therapeutic strategy for the reversal of MDR. Coniferyl ferulate (CF), isolated from the root of Angelica sinensis (Oliv.) Diels (Radix Angelicae sinensis, RAS), showed strong inhibition of human placental GST. Its 50% inhibition concentration (IC50) was 0.3? ? M, which was greater than a known GSTP1-1 inhibitor, ethacrynic acid (EA), using the established high-throughput screening model. Kinetic analysis and computational docking were used to examine the mechanism of GST inhibition by CF. Computational docking found that CF could be fully docked into the gorge of GSTP1-1. The further exploration of the mechanisms showed that CF was a reversible noncompetitive inhibitor with respect to GSH and CDNB, and it has much less cytotoxicity. Apoptosis and the expression of P-gp mRNA were evaluated in the MDR positive B-MD-C1 (ADR+/+) cell line to investigate the MDR reversal effect of CF. Moreover, CF showed strong apoptogenic activity and could markedly decrease the overexpressed P-gp. The results demonstrated that CF could inhibit GST activity in a concentration-dependent manner and showed a potential MDR reversal effect for antitumour adjuvant therapy. PMID:24058374

Chen, Chang; Wu, Chuanhong; Lu, Xinhua; Yan, Zhiyong; Gao, Jian; Zhao, Hui; Li, Shaojing

2013-01-01

74

Contribution of glial cells and pericytes to the mRNA profiles of P-glycoprotein and multidrug resistance-associated proteins in an in vitro model of the blood-brain barrier.  

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P-glycoprotein (P-gp) and the multidrug resistance-associated proteins (MRP), whose expression is associated with multidrug resistance, have been recently located in the brain capillary endothelial cells (BCEC) forming the blood-brain barrier (BBB), without taking into account a possible influence or contribution of glial cells and pericytes. Using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), the present study analysed the transcriptional expression of P-gp and the seven homologues of MRP transporters in BCECs in solo culture or in an in vitro model of the BBB consisting of a co-culture of BCECs and glial cells. Pericytes, glial cells, isolated brain capillaries and bovine grey matter extracts were also tested. P-gp mRNA, absent in glial cells, was found in brain capillaries and in co-cultured BCECs with an increased signal compared to the in solo culture. No amplification was observed in pericytes or grey matter. While MRP2, MRP3 and MRP7 remained undetected, MRP1, absent in capillaries or grey matter, was amplified in BCECs, glial cells and pericytes. MRP4 gave a low signal in most cultures. MRP5 was ubiquitously expressed, displaying a potent signal in all conditions. In spite of its presence in cultured glial cells, MRP6 mRNA expression appeared to be restricted to BCECs, with the same upregulation in the co-cultured condition as observed with P-gp. Moreover, MRP6 was the only transporter whose endothelial mRNA expression was influenced by the presence of pericytes. The tissue distribution of the expression of these transporters and the contribution of the different cell populations are discussed. PMID:15262198

Berezowski, Vincent; Landry, Christophe; Dehouck, Marie-Pierre; Cecchelli, Roméo; Fenart, Laurence

2004-08-20

75

The packing of the transmembrane segments of human multidrug resistance P-glycoprotein is revealed by disulfide cross-linking analysis.  

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Residues from several transmembrane (TM) segments of P-glycoprotein (P-gp) likely form the drug-binding site(s). To determine the organization of the TM segments, pairs of cysteine residues were introduced into the predicted TM segments of a Cys-less P-gp, and the mutant protein was subjected to oxidative cross-linking. In SDS gels, the cross-linked product migrated with a slower mobility than the native protein. The cross-linked products were not detected in the presence of dithiothreitol. Cross-linking was observed in 12 of 125 mutants. The pattern of cross-linking suggested that TM6 is close to TMs 10, 11, and 12, while TM12 is close to TMs 4, 5, and 6. In some mutants the presence of drug substrate colchicine, verapamil, cyclosporin A, or vinblastine either enhanced or inhibited cross-linking. Cross-linking was inhibited in the presence of ATP plus vanadate. These results suggest that the TM segments critical for drug binding must be close to each other and exhibit different conformational changes in response to binding of drug substrate or vanadate trapping of nucleotide. Based on these results, we propose a model for the arrangement of the TM segments. PMID:10681495

Loo, T W; Clarke, D M

2000-02-25

76

Medicated serum prepared with Chinese herbal medicine Zhizhen Recipe down-regulates activity of nuclear factor-?B and expression of P-glycoprotein in human colorectal cancer multidrug-resistant cell line HCT-8/VCR  

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Full Text Available Objective: To investigate the effects of medicated serum prepared with Chinese herbal medicine Zhizhen Recipe (ZZR on activity of nuclear factor-?B (NF-?B and expression and function of P-glycoprotein (P-gp in human colorectal cancer multidrug-resistant cell line HCT-8/VCR.Methods: The multidrug resistance of HCT-8/VCR cells was detected by cell counting kit-8 method, and the experimental concentrations of ZZR-medicated serum were determined by the same way. HCT-8 and HCT-8/VCR cells were treated with ZZR-medicated serum of medium dose for 24 h. The activity of NF-?B was determined by enzyme-linked immunosorbent assay. The intracellular distribution of P-gp was detected by laser scanning confocal microscopy, and the mean fluorescence intensity of rhodamine 123 was detected by flow cytometry.Results: ZZR-medicated sera with volume fraction of 8%, 16% and 32% of medium dose were confirmed as the experimental sera. Compared with the untreated group, NF-?B activities of the ZZR-medicated serum groups (ZZR-medicated serum with volume fraction of 8%, 16% and 32% of medium dose were obviously down-regulated (P<0.01, which had a negative correlation with the concentrations. After interfering HCT-8/VCR with ZZR-medicated serum of different concentrations for 24 h, P-gp in HCT-8/VCR transmitted gradually from cell membrane to cytoplasm and nuclei. Nuclei became pyknotic and cracking. Compared with the untreated group, the mean fluorescence intensities of ZZR-medicated serum groups declined with concentration gradients (P<0.01. The efflux of intracellular rhodamine 123 decreased, the wave crest shifted to right, and the intracellular fluorescence intensity strengthened (P<0.01.Conclusion: ZZR-medicated sera of experimental concentrations down-regulate activity of NF-?B and expression and function of P-gp in human colorectal cancer multidrug-resistant cell line HCT-8/VCR and the effect is related to the concentrations.

Song-bai Cai

2011-12-01

77

Modulation of function of three ABC drug transporters, P-glycoprotein (ABCB1), mitoxantrone resistance protein (ABCG2) and multidrug resistance protein 1 (ABCC1) by tetrahydrocurcumin, a major metabolite of curcumin.  

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Many studies have been performed with the aim of developing effective resistance modulators to overcome the multidrug resistance (MDR) of human cancers. Potent MDR modulators are being investigated in clinical trials. Many current studies are focused on dietary herbs due to the fact that these have been used for centuries without producing any harmful side effects. In this study, the effect of tetrahydrocurcumin (THC) on three ABC drug transporter proteins, P-glycoprotein (P-gp or ABCB1), mitoxantrone resistance protein (MXR or ABCG2) and multidrug resistance protein 1 (MRP1 or ABCC1) was investigated, to assess whether an ultimate metabolite form of curcuminoids (THC) is able to modulate MDR in cancer cells. Two different types of cell lines were used for P-gp study, human cervical carcinoma KB-3-1 (wild type) and KB-V-1 and human breast cancer MCF-7 (wild type) and MCF-7 MDR, whereas, pcDNA3.1 and pcDNA3.1-MRP1 transfected HEK 293 and MXR overexpressing MCF7AdrVp3000 or MCF7FL1000 and its parental MCF-7 were used for MRP1 and MXR study, respectively. We report here for the first time that THC is able to inhibit the function of P-gp, MXR and MRP1. The results of flow cytometry assay indicated that THC is able to inhibit the function of P-gp and thereby significantly increase the accumulation of rhodamine and calcein AM in KB-V-1 cells. The result was confirmed by the effect of THC on [(3)H]-vinblastine accumulation and efflux in MCF-7 and MCF-7MDR. THC significantly increased the accumulation and inhibited the efflux of [(3)H]-vinblastine in MCF-7 MDR in a concentration-dependent manner. This effect was not found in wild type MCF-7 cell line. The interaction of THC with the P-gp molecule was clearly indicated by ATPase assay and photoaffinity labeling of P-gp with transport substrate. THC stimulated P-gp ATPase activity and inhibited the incorporation of [(125)I]-iodoarylazidoprazosin (IAAP) into P-gp in a concentration-dependent manner. The binding of [(125)I]-IAAP to MXR was also inhibited by THC suggesting that THC interacted with drug binding site of the transporter. THC dose dependently inhibited the efflux of mitoxantrone and pheophorbide A from MXR expressing cells (MCF7AdrVp3000 and MCF7FL1000). Similarly with MRP1, the efflux of a fluorescent substrate calcein AM was inhibited effectively by THC thereby the accumulation of calcein was increased in MRP1-HEK 293 and not its parental pcDNA3.1-HEK 293 cells. The MDR reversing properties of THC on P-gp, MRP1, and MXR were determined by MTT assay. THC significantly increased the sensitivity of vinblastine, mitoxantrone and etoposide in drug resistance KB-V-1, MCF7AdrVp3000 and MRP1-HEK 293 cells, respectively. This effect was not found in respective drug sensitive parental cell lines. Taken together, this study clearly showed that THC inhibits the efflux function of P-gp, MXR and MRP1 and it is able to extend the MDR reversing activity of curcuminoids in vivo. PMID:16960658

Limtrakul, Pornngarm; Chearwae, Wanida; Shukla, Suneet; Phisalphong, Chada; Ambudkar, Suresh V

2007-02-01

78

Usefulness of technetium-99m tetrofosmin liver imaging to detect hepatocellular carcinoma and related to expression of P-glycoprotein or multidrug resistance associated protein-a preliminary report  

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Technetium-99m Tetrofsomin (Tc-TF) has been shown to be useful in identifying several types of tumors, such as breast, lung, and thyroid cancers. There was no report in the literature for Tc-TF uptake in hepatocellular carcinoma (HCC). The aim of this study was to evaluate the usefulness of Tc-TF liver imaging to detect HCC and investigate the relationship between Tc-TF liver imaging findings and P-glycoprotein (Pgp) and multidrug resistance associated protein (MRP) expression. Before any therapy, 22 patients with HCC were enrolled in this study. Tc-TF liver images were performed l0 minutes after intravenous injection of 20mCi Tc-TF. All patients had liver biopsy or surgery within l week after Tc-TF liver imaging. Immunohistochemical study of the biopsy or resected HCC specimens was performed using anti-human Pgp and MRP antibodies. Twenty of the 22 (90.9%) patients showed negative Tc-TF liver imaging results without significant Tc-TF uptake in HCC, whereas only the remaining 2 (9.1%) patients showed positive Tc-TF liver imaging results with significant Tc-TF uptake in HCC. Positive Pgp expression was observed in 13 of 20 patients with negative Tc-TF liver imaging results, whereas positive MRP expression was observed in 6 of the remaining 7 patients with negative both Tc-TF liver imaging results and Pgp expression. However, negative Pgp expression but positive MRP expression was observed in all of the remaining 2 patients with positive Tc-TF liver imaging results. The correlation between Tc-TF liver imaging findings and Pgp expression was significant and better than between Tc-TF liver imaging findings and MRP expression. Pgp or MRP expression in HCC may induce no significant Tc-TF uptake in HCC resulting in negative Tc-TF liver imaging findings. Therefore, Tc-TF liver imaging is potential to be a non-invasive method to predict Pgp or MRP expression in HCC. However, further studies with a larger series of patients and longer follow-up time are necessary to confirm our findings.

Ding, H.J.; Huang, W.T.; Tsai, C.S.; Chang, C.S.; Kao, A. E-mail: albertkaotw@yahoo.com.tw

2003-05-01

79

A novel way to spread drug resistance in tumor cells: functional intercellular transfer of P-glycoprotein (ABCB1)  

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Intercellular transfer of proteins is a mode of communication between cells that is crucial for certain physiological processes. Chemotherapy is the treatment of choice for ~50% of all cancers. However, multidrug resistance mediated by drug-efflux pumps such as P-glycoprotein (Pgp) minimizes the effectiveness of such therapy in a large number of patients. A new study demonstrates the functional intercellular transfer of Pgp. Non-genetic transfer of the multidrug resistance phenotype raises fascinating questions about the mechanism and regulation of cell-surface membrane-protein-mediated spread of traits. PMID:15978680

Ambudkar, Suresh V.; Sauna, Zuben E.; Gottesman, Michael M.; Szakacs, Gergely

2005-01-01

80

P-Glycoprotein and Drug Resistance in Systemic Autoimmune Diseases  

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Autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are chronic inflammatory disorders of unknown etiology characterized by a wide range of abnormalities of the immune system that may compromise the function of several organs, such as kidney, heart, joints, brain and skin. Corticosteroids (CCS), synthetic and biologic immunosuppressive agents have demonstrated the capacity to improve the course of autoimmune diseases. However, a significant number of patients do not respond or develop resistance to these therapies over time. P-glycoprotein (P-gp) is a transmembrane protein that pumps several drugs out of the cell, including CCS and immunosuppressants; thus, its over-expression or hyper-function has been proposed as a possible mechanism of drug resistance in patients with autoimmune disorders. Recently, different authors have demonstrated that P-gp inhibitors, such as cyclosporine A (CsA) and its analogue Tacrolimus, are able to reduce P-gp expression and or function in SLE, RA and PsA patients. These observations suggest that P-gp antagonists could be adopted to revert drug resistance and improve disease outcome. The complex inter-relationship among drug resistance, P-gp expression and autoimmunity still remains elusive. PMID:24658440

Picchianti-Diamanti, Andrea; Rosado, Maria Manuela; Scarsella, Marco; Laganà, Bruno; D’Amelio, Raffaele

2014-01-01

 
 
 
 
81

Complex interplay between the P-glycoprotein multidrug efflux pump and the membrane: its role in modulating protein function  

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Full Text Available Multidrug resistance in cancer is linked to expression of the P-glycoprotein multidrug transporter (Pgp, ABCB1, which exports many structurally diverse compounds from cells. Substrates first partition into the bilayer and then interact with a large flexible binding pocket within the transporter’s transmembrane regions. Pgp has been described as a hydrophobic vacuum cleaner or an outwardly-directed drug/lipid flippase. Recent X-ray crystal structures have shed some light on the nature of the drug-binding pocket and suggested routes by which substrates can enter it from the membrane. Detergents have profound effects on Pgp function, and several appear to be substrates. Biochemical and biophysical studies in vitro, some using purified reconstituted protein, have explored the effects of the membrane environment. They have demonstrated that Pgp is involved in a complex relationship with its lipid environment, which modulates the behaviour of its substrates, as well as various functions of the protein, including ATP hydrolysis, drug binding and drug transport. Membrane lipid composition and fluidity, phospholipid headgroup and acyl chain length all influence Pgp function. Recent studies focusing on thermodynamics and kinetics have revealed some important principles governing Pgp-lipid and substrate-lipid interactions, and how these affect drug binding and transport. In some cells, Pgp is associated with cholesterol-rich microdomains which may modulate its functions. The relationship between Pgp and cholesterol remains an open question; however it clearly affects several aspects of its function in addition to substrate-membrane partitioning. The action of Pgp modulators appears to depend on their membrane permeability, and membrane fluidizers and surfactants reverse drug resistance, likely via an indirect mechanism. A detailed understanding of how the membrane affects Pgp substrates and Pgp’s catalytic cycle may lead to new strategies to combat clinical drug resistance.

FrancesJaneSharom

2014-03-01

82

Overcoming Multidrug Resistance in Human Cancer Cells by Natural Compounds  

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Full Text Available Multidrug resistance is a phenomenon whereby tumors become resistant to structurally unrelated anticancer drugs. P-glycoprotein belongs to the large ATP-binding cassette (ABC transporter superfamily of membrane transport proteins. P-glycoprotein mediates resistance to various classes of anticancer drugs including vinblastine, daunorubicin, and paclitaxel, by actively extruding the drugs from the cells. The quest for inhibitors of anticancer drug efflux transporters has uncovered natural compounds, including (--epigallocatechin gallate, curcumin, capsaicin, and guggulsterone, as promising candidates. In this review, studies on the effects of natural compounds on P-glycoprotein and anticancer drug efflux transporters are summarized.

Tomohiro Nabekura

2010-05-01

83

Inhibition of Multidrug Resistance-Linked P-Glycoprotein (ABCB1) Function by 5?-Fluorosulfonylbenzoyl 5?-Adenosine: Evidence for an ATP Analog That Interacts With Both Drug-Substrate- and Nucleotide-Binding Sites†  

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5?-fluorosulfonylbenzonyl 5?-adenosine (FSBA) is an ATP analog that covalently modifies several residues in the nucleotide-binding domains (NBDs) of several ATPases, kinases and other proteins. P-glycoprotein (P-gp, ABCB1) is a member of the ATP-binding cassette (ABC) transporter superfamily that utilizes energy from ATP hydrolysis for the efflux of amphipathic anticancer agents from cancer cells. We investigated the interactions of FSBA with P-gp to study the catalytic cycle of ATP hydrolysis. Incubation of P-gp with FSBA inhibited ATP hydrolysis (IC50= 0.21 mM) and the binding of 8-azido[?–32P]ATP (IC50= 0.68 mM). In addition, 14C-FSBA crosslinks to P-gp, suggesting that FSBA-mediated inhibition of ATP hydrolysis is irreversible due to covalent modification of P-gp. However, when the NBDs were occupied with a saturating concentration of ATP prior to treatment, FSBA stimulated ATP hydrolysis by P-gp. Furthermore, FSBA inhibited the photocrosslinking of P-gp with [125I]-Iodoaryl-azidoprazosin (IAAP; IC50 = 0.17 mM). As IAAP is a transport substrate for P-gp, this suggests that FSBA affects not only the NBDs, but also the transport-substrate site in the transmembrane domains. Consistent with these results, FSBA blocked efflux of rhodamine 123 from P-gp-expressing cells. Additionally, mass spectrometric analysis identified FSBA crosslinks to residues within or nearby the NBDs but not in the transmembrane domains and docking of FSBA in a homology model of human P-gp NBDs supports the biochemical studies. Thus, FSBA is an ATP analog that interacts with both the drug-binding and ATP-binding sites of P-gp, but fluorosulfonyl-mediated crosslinking is observed only at the NBDs. PMID:21452853

Ohnuma, Shinobu; Chufan, Eduardo; Nandigama, Krishnamachary; Miller Jenkins, Lisa M.; Durell, Stewart R.; Appella, Ettore; Sauna, Zuben E.; Ambudkar, Suresh V.

2011-01-01

84

Inhibition of multidrug resistance-linked P-glycoprotein (ABCB1) function by 5'-fluorosulfonylbenzoyl 5'-adenosine: evidence for an ATP analogue that interacts with both drug-substrate-and nucleotide-binding sites.  

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5'-Fluorosulfonylbenzonyl 5'-adenosine (FSBA) is an ATP analogue that covalently modifies several residues in the nucleotide-binding domains (NBDs) of several ATPases, kinases, and other proteins. P-glycoprotein (P-gp, ABCB1) is a member of the ATP-binding cassette (ABC) transporter superfamily that utilizes energy from ATP hydrolysis for the efflux of amphipathic anticancer agents from cancer cells. We investigated the interactions of FSBA with P-gp to study the catalytic cycle of ATP hydrolysis. Incubation of P-gp with FSBA inhibited ATP hydrolysis (IC(50 )= 0.21 mM) and the binding of 8-azido[?-(32)P]ATP (IC(50) = 0.68 mM). In addition, (14)C-FSBA cross-links to P-gp, suggesting that FSBA-mediated inhibition of ATP hydrolysis is irreversible due to covalent modification of P-gp. However, when the NBDs were occupied with a saturating concentration of ATP prior to treatment, FSBA stimulated ATP hydrolysis by P-gp. Furthermore, FSBA inhibited the photo-cross-linking of P-gp with [(125)I]iodoarylazidoprazosin (IAAP; IC(50) = 0.17 mM). As IAAP is a transport substrate for P-gp, this suggests that FSBA affects not only the NBDs but also the transport-substrate site in the transmembrane domains. Consistent with these results, FSBA blocked efflux of rhodamine 123 from P-gp-expressing cells. Additionally, mass spectrometric analysis identified FSBA cross-links to residues within or nearby the NBDs but not in the transmembrane domains, and docking of FSBA in a homology model of human P-gp NBDs supports the biochemical studies. Thus, FSBA is an ATP analogue that interacts with both the drug-binding and ATP-binding sites of P-gp, but fluorosulfonyl-mediated cross-linking is observed only at the NBDs. PMID:21452853

Ohnuma, Shinobu; Chufan, Eduardo; Nandigama, Krishnamachary; Jenkins, Lisa M Miller; Durell, Stewart R; Appella, Ettore; Sauna, Zuben E; Ambudkar, Suresh V

2011-05-10

85

Functional expression of murine multidrug resistance in Xenopus laevis oocytes  

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The development of multidrug resistance (MDR) is associated with the overproduction of a plasma membrane glycoprotein, P glycoprotein. Here the authors report the functional expression of a member of the murine MDR family of proteins and show that Xenopus oocytes injected with RNA encoding the mouse mdr1b P glycoprotein develop a MDR-like phenotype. Immunological analysis indicated that oocytes injected with the mdr1b RNA synthesized a protein with the size and immunological characteristics of the mouse mdr1b P glycoprotein. These oocytes exhibited a decreased accumulation of ({sup 3}H)vinblastine and showed an increased capacity to extrude the drug compared to control oocytes not expressing the P glycoprotein. In addition, competition experiments indicated that verapamil, vincristine, daunomycin, and quinidine, but not colchicine, can overcome the rapid drug efflux conferred by the expression of the mouse P glycoprotein.

Castillo, G.; Vera, J.C.; Rosen, O.M. (Memorial Sloan-Kettering Cancer Research Center, New York, NY (USA)); Yang, Chiaping Huang; Horwitz, S.B. (Albert Einstein College of Medicine, Bronx, NY (USA))

1990-06-01

86

Functional expression of murine multidrug resistance in Xenopus laevis oocytes  

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The development of multidrug resistance (MDR) is associated with the overproduction of a plasma membrane glycoprotein, P glycoprotein. Here the authors report the functional expression of a member of the murine MDR family of proteins and show that Xenopus oocytes injected with RNA encoding the mouse mdr1b P glycoprotein develop a MDR-like phenotype. Immunological analysis indicated that oocytes injected with the mdr1b RNA synthesized a protein with the size and immunological characteristics of the mouse mdr1b P glycoprotein. These oocytes exhibited a decreased accumulation of [3H]vinblastine and showed an increased capacity to extrude the drug compared to control oocytes not expressing the P glycoprotein. In addition, competition experiments indicated that verapamil, vincristine, daunomycin, and quinidine, but not colchicine, can overcome the rapid drug efflux conferred by the expression of the mouse P glycoprotein

87

P-glycoprotein mediates drug resistance via a novel mechanism involving lysosomal sequestration.  

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Localization of the drug transporter P-glycoprotein (Pgp) to the plasma membrane is thought to be the only contributor of Pgp-mediated multidrug resistance (MDR). However, very little work has focused on the contribution of Pgp expressed in intracellular organelles to drug resistance. This investigation describes an additional mechanism for understanding how lysosomal Pgp contributes to MDR. These studies were performed using Pgp-expressing MDR cells and their non-resistant counterparts. Using confocal microscopy and lysosomal fractionation, we demonstrated that intracellular Pgp was localized to LAMP2-stained lysosomes. In Pgp-expressing cells, the Pgp substrate doxorubicin (DOX) became sequestered in LAMP2-stained lysosomes, but this was not observed in non-Pgp-expressing cells. Moreover, lysosomal Pgp was demonstrated to be functional because DOX accumulation in this organelle was prevented upon incubation with the established Pgp inhibitors valspodar or elacridar or by silencing Pgp expression with siRNA. Importantly, to elicit drug resistance via lysosomes, the cytotoxic chemotherapeutics (e.g. DOX, daunorubicin, or vinblastine) were required to be Pgp substrates and also ionized at lysosomal pH (pH 5), resulting in them being sequestered and trapped in lysosomes. This property was demonstrated using lysosomotropic weak bases (NH4Cl, chloroquine, or methylamine) that increased lysosomal pH and sensitized only Pgp-expressing cells to such cytotoxic drugs. Consequently, a lysosomal Pgp-mediated mechanism of MDR was not found for non-ionizable Pgp substrates (e.g. colchicine or paclitaxel) or ionizable non-Pgp substrates (e.g. cisplatin or carboplatin). Together, these studies reveal a new mechanism where Pgp-mediated lysosomal sequestration of chemotherapeutics leads to MDR that is amenable to therapeutic exploitation. PMID:24062304

Yamagishi, Tetsuo; Sahni, Sumit; Sharp, Danae M; Arvind, Akanksha; Jansson, Patric J; Richardson, Des R

2013-11-01

88

P-glycoprotein Mediates Drug Resistance via a Novel Mechanism Involving Lysosomal Sequestration*  

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Localization of the drug transporter P-glycoprotein (Pgp) to the plasma membrane is thought to be the only contributor of Pgp-mediated multidrug resistance (MDR). However, very little work has focused on the contribution of Pgp expressed in intracellular organelles to drug resistance. This investigation describes an additional mechanism for understanding how lysosomal Pgp contributes to MDR. These studies were performed using Pgp-expressing MDR cells and their non-resistant counterparts. Using confocal microscopy and lysosomal fractionation, we demonstrated that intracellular Pgp was localized to LAMP2-stained lysosomes. In Pgp-expressing cells, the Pgp substrate doxorubicin (DOX) became sequestered in LAMP2-stained lysosomes, but this was not observed in non-Pgp-expressing cells. Moreover, lysosomal Pgp was demonstrated to be functional because DOX accumulation in this organelle was prevented upon incubation with the established Pgp inhibitors valspodar or elacridar or by silencing Pgp expression with siRNA. Importantly, to elicit drug resistance via lysosomes, the cytotoxic chemotherapeutics (e.g. DOX, daunorubicin, or vinblastine) were required to be Pgp substrates and also ionized at lysosomal pH (pH 5), resulting in them being sequestered and trapped in lysosomes. This property was demonstrated using lysosomotropic weak bases (NH4Cl, chloroquine, or methylamine) that increased lysosomal pH and sensitized only Pgp-expressing cells to such cytotoxic drugs. Consequently, a lysosomal Pgp-mediated mechanism of MDR was not found for non-ionizable Pgp substrates (e.g. colchicine or paclitaxel) or ionizable non-Pgp substrates (e.g. cisplatin or carboplatin). Together, these studies reveal a new mechanism where Pgp-mediated lysosomal sequestration of chemotherapeutics leads to MDR that is amenable to therapeutic exploitation. PMID:24062304

Yamagishi, Tetsuo; Sahni, Sumit; Sharp, Danae M.; Arvind, Akanksha; Jansson, Patric J.; Richardson, Des R.

2013-01-01

89

Expression of P-glycoprotein, multidrug resistance-associated protein, glutathione-S-transferase pi and p53 in canine transmissible venereal tumor / Expressão da glicoproteína-P, proteína associada à múltiplas drogas, glutationa-S-transferase pi e p53 no tumor venéreo transmissível canino  

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Full Text Available SciELO Brazil | Language: English Abstract in portuguese A superexpressão das proteínas glicoproteína-P (Gp-P), proteína associada à resistência à múltiplas drogas 1 (MRP1) e p53 mutante e a enzima glutationa-S-transferase pi (GSTpi) está relacionada com resistência à quimioterapia em neoplasias humanas e caninas. Este estudo avaliou a expressão, por meio [...] da imuno-histoquímica desses marcadores em espécimes de TVT caninos sem histórico de quimioterapia prévia (TVT1, n=9) e em TVT caninos que apresentaram resposta clínica insatisfatória ao sulfato de vincristina (TVT2, n=5). A porcentagem de espécimes positivos para Gp-P, MRP1, GSTpi e p53 foram, respectivamente 88,8%, 0%, 44,5% e 22,2% no grupo TVT1 e 80%, 0%, 80% e 0% no grupo TVT2. No TVT1, um espécime apresentou expressão positiva para três marcadores e quatro para dois marcadores. No TVT2, três espécimes expressaram a Gp-P e GSTpi. Em conclusão, os TVTs caninos estudados expressaram os quatro marcadores avaliados, no entanto apenas a Gp-P e GSTpi foram significativamente expressas, principalmente no citoplasmas e no citoplasma e no núcleo, respectivamente, tanto antes da quimioterapia quanto após à exposição ao sulfato de vincristina. Estudos futuros são necessários para demonstrar a função desses dois marcadores em conferir resistência à multiplas drogas (RMD) ou predizer a resposta a quimioterapia no TVT canino. Abstract in english The overexpression of proteins P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP1), mutant p53, and the enzyme glutathione-S-transferase (GSTpi) are related to resistance to chemotherapy in neoplasms. This study evaluated the expression of these markers by immunohistochemistry in t [...] wo groups of canine TVT, without history of prior chemotherapy (TVT1, n=9) and in TVTs presented unsatisfactory clinical response to vincristine sulfate (TVT2, n=5). The percentage of specimens positively stained for P-gp, MRP1, GSTpi and p53 were, respectively 88.8%, 0%, 44.5% and 22.2% in TVT1 and 80%, 0%, 80% and 0% in TVT2. In TVT1, one specimen presented positive expression for three markers and four specimens for two markers. In TVT2, three specimens expressed P-gp and GSTpi. In conclusion, the canine TVTs studied expressed the four markers evaluated, but just P-gp and GSTpi were significantly expressed, mainly at cytoplasm and cytoplasm and nuclei, respectively, either before chemotherapy as after vincristine sulfate exposure. Future studies are needed to demonstrate the function of these two markers in conferring multidrug resistance (MDR) or predict the response to chemotherapy in canine TVT.

Daniel G., Gerardi; Mirela, Tinucci-Costa; Ana Carolina T., Silveira; Juliana V., Moro.

2014-01-01

90

Expression of P-glycoprotein, multidrug resistance-associated protein, glutathione-S-transferase pi and p53 in canine transmissible venereal tumor / Expressão da glicoproteína-P, proteína associada à múltiplas drogas, glutationa-S-transferase pi e p53 no tumor venéreo transmissível canino  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A superexpressão das proteínas glicoproteína-P (Gp-P), proteína associada à resistência à múltiplas drogas 1 (MRP1) e p53 mutante e a enzima glutationa-S-transferase pi (GSTpi) está relacionada com resistência à quimioterapia em neoplasias humanas e caninas. Este estudo avaliou a expressão, por meio [...] da imuno-histoquímica desses marcadores em espécimes de TVT caninos sem histórico de quimioterapia prévia (TVT1, n=9) e em TVT caninos que apresentaram resposta clínica insatisfatória ao sulfato de vincristina (TVT2, n=5). A porcentagem de espécimes positivos para Gp-P, MRP1, GSTpi e p53 foram, respectivamente 88,8%, 0%, 44,5% e 22,2% no grupo TVT1 e 80%, 0%, 80% e 0% no grupo TVT2. No TVT1, um espécime apresentou expressão positiva para três marcadores e quatro para dois marcadores. No TVT2, três espécimes expressaram a Gp-P e GSTpi. Em conclusão, os TVTs caninos estudados expressaram os quatro marcadores avaliados, no entanto apenas a Gp-P e GSTpi foram significativamente expressas, principalmente no citoplasmas e no citoplasma e no núcleo, respectivamente, tanto antes da quimioterapia quanto após à exposição ao sulfato de vincristina. Estudos futuros são necessários para demonstrar a função desses dois marcadores em conferir resistência à multiplas drogas (RMD) ou predizer a resposta a quimioterapia no TVT canino. Abstract in english The overexpression of proteins P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP1), mutant p53, and the enzyme glutathione-S-transferase (GSTpi) are related to resistance to chemotherapy in neoplasms. This study evaluated the expression of these markers by immunohistochemistry in t [...] wo groups of canine TVT, without history of prior chemotherapy (TVT1, n=9) and in TVTs presented unsatisfactory clinical response to vincristine sulfate (TVT2, n=5). The percentage of specimens positively stained for P-gp, MRP1, GSTpi and p53 were, respectively 88.8%, 0%, 44.5% and 22.2% in TVT1 and 80%, 0%, 80% and 0% in TVT2. In TVT1, one specimen presented positive expression for three markers and four specimens for two markers. In TVT2, three specimens expressed P-gp and GSTpi. In conclusion, the canine TVTs studied expressed the four markers evaluated, but just P-gp and GSTpi were significantly expressed, mainly at cytoplasm and cytoplasm and nuclei, respectively, either before chemotherapy as after vincristine sulfate exposure. Future studies are needed to demonstrate the function of these two markers in conferring multidrug resistance (MDR) or predict the response to chemotherapy in canine TVT.

Daniel G., Gerardi; Mirela, Tinucci-Costa; Ana Carolina T., Silveira; Juliana V., Moro.

91

Effect of pentoxifylline on P-glycoprotein mediated vincristine resistance of L1210 mouse leukemic cell line  

International Nuclear Information System (INIS)

Effect of pentoxifylline (PTX) on vincristine (VCR) resistance of multidrug resistant L1210/VCR mouse leukemic cell line was studied. Reversal effect of PTX (in concentration 50-150 mg dm-3) on vincristine resistance, i.e. potentiation of vincristine cytotoxicity on L1210/VCR cells by PTX was found. PTX alone in the above concentration did not exert any significant effect on sensitive or resistant cell lines in the absence of vincristine. Resistance of L1210/VCR cell line was found previously to be accompanied with overexpression of drug transporting P-glycoprotein. Indeed, lower level of 3H-vincristine accumulation by resistant L1210/VCR cell line in comparison with sensitive L1210 cell line was observed. Accumulation of 3H-vincristine by L1210/VCR cell line was significantly increased in the presence of PTX. PTX in the same condition did not exert any considerable effect on accumulation of 3H-vincristine by nonresistant L1210 cells. Observable morphological damage was observed in 1210/VCR cells cultivated in medium containing vincristine (0.2 mg dm-3) and pentoxifylline (100 mg dm-3) in comparison with the non-damaged cells in the presence of vincristine or pentoxifylline alone. The results obtained indicate that pentoxifylline may be considered as a reversal agent in multidrug resistance. (author)

92

Multidrug resistance in tumour cells: characterisation of the multidrug resistant cell line K562-Lucena 1  

Directory of Open Access Journals (Sweden)

Full Text Available Multidrug resistance to chemotherapy is a major obstacle in the treatment of cancer patients. The best characterised mechanism responsible for multidrug resistance involves the expression of the MDR-1 gene product, P-glycoprotein. However, the resistance process is multifactorial. Studies of multidrug resistance mechanisms have relied on the analysis of cancer cell lines that have been selected and present cross-reactivity to a broad range of anticancer agents. This work characterises a multidrug resistant cell line, originally selected for resistance to the Vinca alkaloid vincristine and derived from the human erythroleukaemia cell K562. This cell line, named Lucena 1, overexpresses P-glycoprotein and have its resistance reversed by the chemosensitisers verapamil, trifluoperazine and cyclosporins A, D and G. Furthermore, we demonstrated that methylene blue was capable of partially reversing the resistance in this cell line. On the contrary, the use of 5-fluorouracil increased the resistance of Lucena 1. In addition to chemotherapics, Lucena 1 cells were resistant to ultraviolet A radiation and hydrogen peroxide and failed to mobilise intracellular calcium when thapsigargin was used. Changes in the cytoskeleton of this cell line were also observed.

RUMJANEK VIVIAN M.

2001-01-01

93

Macrocyclic diterpenes resensitizing multidrug resistant phenotypes.  

Science.gov (United States)

Herein, collateral sensitivity effect was exploited as a strategy to select effective compounds to overcome multidrug resistance in cancer. Thus, eleven macrocyclic diterpenes, namely jolkinol D (1), isolated from Euphorbia piscatoria, and its derivatives (2-11) were evaluated for their activity on three different Human cancer entities: gastric (EPG85-257), pancreatic (EPP85-181) and colon (HT-29) each with a variant selected for resistance to mitoxantrone (EPG85-257RN; EPP85-181RN; HT-29RN) and one to daunorubicin (EPG85-257RD; EPP85-181RD; HT-29RD). Jolkinol D (1) and most of its derivatives (2-11) exhibited significant collateral sensitivity effect towards the cell lines EPG85-257RN (associated with P-glycoprotein overexpression) and HT-29RD (altered topoisomerase II expression). The benzoyl derivative, jolkinoate L (8) demonstrated ability to target different cellular contexts with concomitant high antiproliferative activity. These compounds were previously assessed as P-glycoprotein modulators, at non-cytotoxic doses, on MDR1-mouse lymphoma cells. A regression analysis between the antiproliferative activity presented herein and the previously assessed P-glycoprotein modulatory effect showed a strong relation between the compounds that presented both high P-glycoprotein modulation and cytotoxicity. PMID:24864039

Reis, Mariana A; Paterna, Angela; Ferreira, Ricardo J; Lage, Hermann; Ferreira, Maria-José U

2014-07-15

94

Marine Natural Products with P-Glycoprotein Inhibitor Properties  

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P-glycoprotein (P-gp) is a protein belonging to the ATP-binding cassette (ABC) transporters superfamily that has clinical relevance due to its role in drug metabolism and multi-drug resistance (MDR) in several human pathogens and diseases. P-gp is a major cause of drug resistance in cancer, parasitic diseases, epilepsy and other disorders. This review article aims to summarize the research findings on the marine natural products with P-glycoprotein inhibitor properties. Natural compounds that...

Dioxelis Lopez; Sergio Martinez-Luis

2014-01-01

95

Substrate versus inhibitor dynamics of P-glycoprotein.  

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By far the most studied multidrug resistance protein is P-glycoprotein. Despite recent structural data, key questions about its function remain. P-glycoprotein (P-gp) is flexible and undergoes large conformational changes as part of its function and in this respect, details not only of the export cycle, but also the recognition stage are currently lacking. Given the flexibility, molecular dynamics (MD) simulations provide an ideal tool to examine this aspect in detail. We have performed MD si...

Ma, J.; Biggin, Pc

2013-01-01

96

Multidrug resistance: Physiological principles and nanomedical solutions.  

Science.gov (United States)

Multidrug resistance (MDR) is a pathophysiological phenomenon employed by cancer cells which limits the prolonged and effective use of chemotherapeutic agents. MDR is primarily based on the over-expression of drug efflux pumps in the cellular membrane. Prominent examples of such efflux pumps, which belong to the ATP-binding cassette (ABC) superfamily of proteins, are Pgp (P-glycoprotein) and MRP (multidrug resistance-associated protein), nowadays officially known as ABCB1 and ABCC1. Over the years, several strategies have been evaluated to overcome MDR, based not only on the use of low-molecular-weight MDR modulators, but also on the implementation of 1-100(0) nm-sized drug delivery systems. In the present manuscript, after introducing the most important physiological principles of MDR, we summarize prototypic nanomedical strategies to overcome multidrug resistance, including the use of carrier materials with intrinsic anti-MDR properties, the use of nanomedicines to modify the mode of cellular uptake, and the co-formulation of chemotherapeutic drugs together with low- and high-molecular-weight MDR inhibitors within a single drug delivery system. While certain challenges still need to be overcome before such constructs and concepts can be widely applied in the clinic, the insights obtained and the progress made strongly suggest that nanomedicine formulations hold significant potential for improving the treatment of multidrug-resistant malignancies. PMID:24120954

Kunjachan, Sijumon; Rychlik, B?a?ej; Storm, Gert; Kiessling, Fabian; Lammers, Twan

2013-11-01

97

Resistance to paclitaxel in a cisplatin-resistant ovarian cancer cell line is mediated by P-glycoprotein.  

Science.gov (United States)

The IGROVCDDP cisplatin-resistant ovarian cancer cell line is also resistant to paclitaxel and models the resistance phenotype of relapsed ovarian cancer patients after first-line platinum/taxane chemotherapy. A TaqMan low-density array (TLDA) was used to characterise the expression of 380 genes associated with chemotherapy resistance in IGROVCDDP cells. Paclitaxel resistance in IGROVCDDP is mediated by gene and protein overexpression of P-glycoprotein and the protein is functionally active. Cisplatin resistance was not reversed by elacridar, confirming that cisplatin is not a P-glycoprotein substrate. Cisplatin resistance in IGROVCDDP is multifactorial and is mediated in part by the glutathione pathway and decreased accumulation of drug. Total cellular glutathione was not increased. However, the enzyme activity of GSR and GGT1 were up-regulated. The cellular localisation of copper transporter CTR1 changed from membrane associated in IGROV-1 to cytoplasmic in IGROVCDDP. This may mediate the previously reported accumulation defect. There was decreased expression of the sodium potassium pump (ATP1A), MRP1 and FBP which all have been previously associated with platinum accumulation defects in platinum-resistant cell lines. Cellular localisation of MRP1 was also altered in IGROVCDDP shifting basolaterally, compared to IGROV-1. BRCA1 was also up-regulated at the gene and protein level. The overexpression of P-glycoprotein in a resistant model developed with cisplatin is unusual. This demonstrates that P-glycoprotein can be up-regulated as a generalised stress response rather than as a specific response to a substrate. Mechanisms characterised in IGROVCDDP cells may be applicable to relapsed ovarian cancer patients treated with frontline platinum/taxane chemotherapy. PMID:22792399

Stordal, Britta; Hamon, Marion; McEneaney, Victoria; Roche, Sandra; Gillet, Jean-Pierre; O'Leary, John J; Gottesman, Michael; Clynes, Martin

2012-01-01

98

Multidrug-Resistant Tuberculosis  

Centers for Disease Control (CDC) Podcasts

In this podcast, Dr. Oeltmann discusses multidrug-resistant tuberculosis. An outbreak occurred in Thailand, which led to 45 cases in the U.S. This serious illness can take up to 2 years to treat. MDR TB is a real threat and a serious condition.  Created: 10/28/2008 by Emerging Infectious Diseases.   Date Released: 10/28/2008.

2008-10-28

99

Intracellular trafficking of P-glycoprotein  

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Overexpression of P-glycoprotein (P-gp) is a major cause of multidrug resistance in cancer. P-gp is mainly localized in the plasma membrane and can efflux structurally and chemically unrelated substrates, including anticancer drugs. P-gp is also localized in intracellular compartments, such as ER, Golgi, endosomes and lysosomes, and cycles between endosomal compartments and the plasma membrane in a microtubular-actin dependent manner. Intracellular trafficking pathways for P-gp and participat...

Fu, Dong; Arias, Irwin M.

2012-01-01

100

P-glycoprotein and alloimmune T-cell activation  

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P-glycoprotein (P-gp), the human multidrug resistant (MDR1) gene product and cancer multidrug resistance-associated adenosine triphosphate (ATP)-binding cassette (ABC) transporter, is physiologically expressed on peripheral blood mononuclear cells, but its role in cellular immunity is only beginning to be elucidated. A role of P-gp in the secretion of several T-cell and antigen presenting cell-derived cytokines has been described, and additional functions of the molecule have been identified ...

Pendse, Shona S.; Briscoe, David M.; Frank, Markus H.

2003-01-01

 
 
 
 
101

The combined use of paclitaxel-loaded nanoparticles with a low-molecular-weight copolymer inhibitor of P-glycoprotein to overcome drug resistance  

Directory of Open Access Journals (Sweden)

Full Text Available Chung Ping Leon Wan,* Kevin Letchford,* John K Jackson, Helen M Burt Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada*These authors contributed equally to this workAbstract: Two types of nanoparticles were prepared using the diblock copolymer methoxy poly(ethylene glycol-block-poly(caprolactone (MePEG-b-PCL, with either a short PCL block length, which forms micelles, or with a longer PCL block length, which forms kinetically "frozen core" structures termed nanospheres. Paclitaxel (PTX-loaded micelles and nanospheres were evaluated for their cytotoxicity, cellular polymer uptake, and drug accumulation in drug-sensitive (Madin–Darby Canine Kidney [MDCK]II and multidrug-resistant (MDR P-glycoprotein (P-gp-overexpressing (MDCKII-MDR1 cell lines. Both types of PTX-loaded nanoparticles were equally effective at inhibiting proliferation of MDCKII cells, but PTX-loaded micelles were more cytotoxic than nanospheres in MDCKII-MDR1 cells. The intracellular accumulation of both PTX and the diblock copolymers were similar for both nanoparticles, suggesting that the difference in cytotoxicity might be due to the different drug-release profiles. Furthermore, the cytotoxicity of these PTX-loaded nanoparticles was enhanced when these systems were subsequently or concurrently combined with a low-molecular-weight MePEG-b-PCL diblock copolymer, which we have previously demonstrated to be an effective P-gp inhibitor. These results suggest that the dual functionality of MePEG-b-PCL might be useful in delivering drug intracellularly and in modulating P-gp in order to optimize the cytotoxicity of PTX in multidrug-resistant cells.Keywords: multidrug resistance, paclitaxel, nanoparticles, micelles, nanospheres, P-glycoprotein

Wan CP

2013-01-01

102

Reversal of P-glycoprotein-mediated paclitaxel resistance by new synthetic isoprenoids in human bladder cancer cell line.  

Science.gov (United States)

We isolated a paclitaxel-resistant cell line (KK47/TX30) from a human bladder cancer cell line (KK47/WT) in order to investigate the mechanism of and reversal agents for paclitaxel resistance. KK47/TX30 cells exhibited 700-fold resistance to paclitaxel and cross-resistance to vinca alkaloids and topoisomerase II inhibitors. Tubulin polymerization assay showed no significant difference in the ratio of polymerized alpha- and beta-tubulin between KK47/WT and KK47/TX30 cells. Western blot analysis demonstrated overexpression of P-glycoprotein (P-gp) and lung resistance-related protein (LRP) in KK47/TX30 cells. Drug accumulation and efflux studies showed that the decreased paclitaxel accumulation in KK47/TX30 cells was due to enhanced paclitaxel efflux. Cell survival assay revealed that verapamil and cepharanthine, conventional P-gp modulators, could completely overcome paclitaxel resistance. To investigate whether new synthetic isoprenoids could overcome paclitaxel resistance, we synthesized 31 isoprenoids based on the structure of N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine (SDB), which could reverse multidrug resistance (MDR), as shown previously. Among those examined, trans-N,N'-bis(3,4-dimethoxybenzyl)-N-solanesyl-1,2-diaminocyclohexane (N-5228) could completely reverse paclitaxel resistance in KK47/TX30 cells. N-5228 inhibited photoaffinity labeling of P-gp by [(3)H]azidopine, suggesting that N-5228 could bind to P-gp directly and could be a substrate of P-gp. Next, we investigated structural features of these 31 isoprenoids in order to determine the structural requirements for the reversal of P-gp-mediated paclitaxel resistance, suggesting that the following structural features are important for overcoming paclitaxel resistance: (1) a basic structure of 8 to 10 isoprene units, (2) a cyclohexane ring or benzene ring within the framework, (3) two cationic sites in close proximity to each other, and (4) a benzyl group with 3,4-dimethoxy functionalities, which have moderate electron-donating ability. These findings may provide valuable information for the development of P-gp-mediated MDR-reversing agents. PMID:12359058

Enokida, Hideki; Gotanda, Takenari; Oku, Shoichi; Imazono, Yoshiharu; Kubo, Hiroyuki; Hanada, Toshikatsu; Suzuki, Shigenori; Inomata, Kouhei; Kishiye, Takao; Tahara, Yoshiyuki; Nishiyama, Kenryu; Nakagawa, Masayuki

2002-09-01

103

P-glycoprotein-mediated resistance to chemotherapy in cancer cells: using recombinant cytosolic domains to establish structure-function relationships  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Resistance to chemotherapy in cancer cells is mainly mediated by overexpression of P-glycoprotein (Pgp), a plasma membrane ATP-binding cassette (ABC) transporter which extrudes cytotoxic drugs at the expense of ATP hydrolysis. Pgp consists of two homologous halves each containing a transmembrane dom [...] ain and a cytosolic nucleotide-binding domain (NBD) which contains two consensus Walker motifs, A and B, involved in ATP binding and hydrolysis. The protein also contains an S signature characteristic of ABC transporters. The molecular mechanism of Pgp-mediated drug transport is not known. Since the transporter has an extraordinarily broad substrate specificity, its cellular function has been described as a "hydrophobic vacuum cleaner". The limited knowledge about the mechanism of Pgp, partly due to the lack of a high-resolution structure, is well reflected in the failure to efficiently inhibit its activity in cancer cells and thus to reverse multidrug resistance (MDR). In contrast to the difficulties encountered when studying the full-length Pgp, the recombinant NBDs can be obtained in large amounts as soluble proteins. The biochemical and biophysical characterization of recombinant NBDs is shown here to provide a suitable alternative route to establish structure-function relationships. NBDs were shown to bind ATP and analogues as well as potent modulators of MDR, such as hydrophobic steroids, at a region close to the ATP site. Interestingly, flavonoids also bind to NBDs with high affinity. Their binding site partly overlaps both the ATP-binding site and the steroid-interacting region. Therefore flavonoids constitute a new promising class of bifunctional modulators of Pgp.

A., Di Pietro; G., Dayan; G., Conseil; E., Steinfels; T., Krell; D., Trompier; H., Baubichon-Cortay; J.-M., Jault.

104

Subcellular distribution of daunorubicin in P-glycoprotein-positive and -negative drug-resistant cell lines using laser-assisted confocal microscopy.  

Science.gov (United States)

Four well defined multidrug-resistant cell lines and their drug-sensitive counterparts were examined for intracellular distribution of daunorubicin (DNR) by laser-assisted confocal fluorescence microscopy: P-glycoprotein-negative HL-60/AR cells, and P-glycoprotein-positive P388/ADR, KBV-1, and MCF-7/ADR cells. Both drug sensitive cell lines (HL-60/S, P388/S, KB3-1, and MCF-7/S) and drug-resistant cell lines (HL-60/AR, P388/ADR, KBV-1, and MCF-7/ADR) exposed to DNR showed a similar rapid distribution of drug from the plasma membrane to the perinuclear region within the first 2 min. From 2-10 min, the drug sensitive HL-60/S, P388/S, and MCF-7/S cells redistributed drug to the nucleus and to the cytoplasm in a diffuse pattern. In contrast, drug-resistant HL-60/AR, P388/ADR, and MCF-7/ADR redistributed DNR from the perinuclear region into vesicles distinct from nuclear structures, thereby assuming a "punctate" pattern. This latter redistribution could be inhibited by glucose deprivation (indicating energy dependence), or by lowering the temperature of the medium below 18 degrees C. The differences in distribution between sensitive and resistant cells did not appear to be a function of intracellular DNR content, nor the result of drug cytotoxicity. Drug-sensitive KB3-1 and -resistant KBV-1 cells did not fully follow this pattern in that they demonstrated an intracellular DNR distribution intermediate between HL-60/S and HL-60/AR cells with both "punctate" and nuclear/cytoplasmic uptake sometimes in the same cell. These data indicate that the intracellular distribution of DNR is an important determinant of drug resistance regardless of the overexpression of P-glycoprotein. The intracellular movement of drug requires the presence of glucose and a temperature above 18 degrees C, implicating energy-dependent processes and vesicle fusion in the distribution process. This intracellular transport of DNR away from the nucleus in multidrug-resistant cells may protect putative cell targets such as DNA against drug toxicity. PMID:1680024

Gervasoni, J E; Fields, S Z; Krishna, S; Baker, M A; Rosado, M; Thuraisamy, K; Hindenburg, A A; Taub, R N

1991-09-15

105

Benzodiazepine-mediated structural changes in the multidrug transporter P-glycoprotein: an intrinsic fluorescence quenching analysis.  

Science.gov (United States)

P-glycoprotein expressed in Pichia pastoris was used to study the drug binding sites of different benzodiazepines. The effect of bromazepam, chlordiazepoxide, diazepam and flurazepam on P-glycoprotein structure was investigated by measuring the intrinsic fluorescence of the transporter tryptophan residues. Purified mouse mdr1a transporter in mixed micelles of 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonic acid and 1,2-dimiristoyl-sn-glycerol-3-phosphocholine emitted fluorescence at 340 nm indicative of the fluorophores in a relatively apolar environment. Acrylamide and iodide ion were used as collisional quenchers toward distinct regions of the transporter, the protein and the interface protein-surface, respectively. Binding of ATP induced conformational changes at the protein surface level in accordance with the location of the nucleotide binding sites. Bromazepam interaction with the transporter was located at the protein-surface interface, diazepam at the membrane region and chlordiazepoxide at the protein surface. Only the flurazepam interaction site was not detected by the quenchers used. All benzodiazepines were able to elicit reorientation of the protein fluorophores on the P-glycoprotein-ATP complex. PMID:18791834

Lima, Sofia A C; Cordeiro-da-Silva, Anabela; de Castro, Baltazar; Gameiro, Paula

2008-06-01

106

Reversal of vinblastine transport by chlorpromazine in membrane vesicles from multidrug-resistant human CCRF-CEM leukaemia cells.  

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The mechanism of action of 2-chlorpromazine (2-chloro-10-(3-dimethylaminopropyl)-phenothiazine) as a reversal agent for P-glycoprotein-mediated multidrug resistance was investigated using inside out-orientated membrane vesicles prepared from vinblastine-resistant human CCRF-CEM leukaemia cells (VBL1000). 2-Chlorpromazine (10 microM) completely inhibited ATP-dependent P-glycoprotein-mediated vinblastine accumulation in the vesicles. Whereas in the absence of added ligands VBL transport was des...

Syed, S. K.; Christopherson, R. I.; Roufogalis, B. D.

1998-01-01

107

Multidrug resistance in leukaemia.  

Science.gov (United States)

Multidrug resistance hampers successful chemotherapy in many haematological neoplasms and is mediated by several cellular proteins. In some cases, the genes encoding these proteins have been shown to confer resistance on transfer to drug-sensitive cell lines. This is true for the efflux pump product of the MDR1 gene, P-170. Upregulation of enzymes such as GST has been observed, although the contribution of this enzyme in drug resistance expressed by malignant haematopoietic cells is still uncertain. Cells also appear to be able to downregulate enzymes which are drug targets. Examples include the decrease in Topo II which accompanies the resistance shown by cells to VP-16 and VM-26. Although many reports include both presentation and relapsed patients, there are few data on samples drawn from the same patients before and after chemotherapy. While P-170 and GST appear to be raised more often in cells from resistant and relapsed disease, it is quite clear that such mechanisms can be active in de novo malignancy and do not necessarily emerge as a consequence of prior chemotherapy. Methods of detecting drug resistance are reviewed here; these include in vitro cellular assays for drug toxicity, and molecular, immunological and functional detection of P-170 or Topo II. The clinical evaluation of such assays is only just beginning and some of the data are contradictory. To some extent, this may reflect the complex way in which the various resistance mechanisms may interact. Nevertheless, there are some encouraging early signs that the application of these assays to clinical material will yield valuable data on the relative contributions of these mechanisms and on ways in which they may be overcome. At present, much attention has focused on the potential of agents which prevent the P-170 efflux pump from exporting cytotoxics from the cell. This is likely to be only the first of new therapies arising from an improved understanding of multidrug resistance. More immediately, assays for multidrug resistance and its parameters may find their place as routine diagnostic and prognostic tools in the laboratory. PMID:1364045

Baines, P; Cumber, P; Padua, R A

1992-10-01

108

Multidrug resistant Acinetobacter  

Directory of Open Access Journals (Sweden)

Full Text Available Emergence and spread of Acinetobacter species, resistant to most of the available antimicrobial agents, is an area of great concern. It is now being frequently associated with healthcare associated infections. Literature was searched at PUBMED, Google Scholar, and Cochrane Library, using the terms ?Acinetobacter Resistance, multidrug resistant (MDR, Antimicrobial Therapy, Outbreak, Colistin, Tigecycline, AmpC enzymes, and carbapenemases in various combinations. The terms such as MDR, Extensively Drug Resistant (XDR, and Pan Drug Resistant (PDR have been used in published literature with varied definitions, leading to confusion in the correlation of data from various studies. In this review various mechanisms of resistance in the Acinetobacter species have been discussed. The review also probes upon the current therapeutic options, including combination therapies available to treat infections due to resistant Acinetobacter species in adults as well as children. There is an urgent need to enforce infection control measures and antimicrobial stewardship programs to prevent the further spread of these resistant Acinetobacter species and to delay the emergence of increased resistance in the bacteria.

Manchanda Vikas

2010-01-01

109

First evidence of the P-glycoprotein gene expression and multixenobiotic resistance modulation in earthworm.  

Science.gov (United States)

Multixenobiotic resistance (MXR) is an important mechanism of cellular efflux mediated by ATP binding cassette (ABC) transporters that bind and actively remove toxic substrates from the cell. This study was the first to identify ABC transporter P-glycoprotein (P-gp/ABCB1) as a representative of the MXR phenotype in earthworm (Eisenia fetida). The identified partial cDNA sequence of ABCB1 overlapped with ABCB1 homologues of other organisms from 58.5 % to 72.5 %. We also studied the effect of five modulators (verapamil, cyclosporine A, MK571, probenecid, and orthovanadate) on the earthworm's MXR activity by measuring the accumulation of model substrates rhodamine B and rhodamine 123 in whole body tissue of the adult earthworm. MK571, orthovanadate, and verapamil significantly inhibited MXR activity, and rhodamine 123 turned out to better reflect MXR activity in that species than rhodamine B. Our results show that E. fetida can serve well as a test organism for environmental pollutants that inhibit MXR activity. PMID:24622780

Bošnjak, Ivana; Bielen, Ana; Babi?, Sanja; Sver, Lidija; Popovi?, Natalija Topi?; Strunjak-Perovi?, Ivan?ica; Což-Rakovac, Rozelinda; Klobu?ar, Roberta Sauerborn

2014-03-01

110

Masitinib reverses doxorubicin resistance in canine lymphoid cells by inhibiting the function of P-glycoprotein.  

Science.gov (United States)

Overexpression of ABC-transporters including Pgp, MRP1, and BCRP has been associated with multidrug resistance (MDR) in both human and canine oncology. Therapeutic interventions to reverse MDR are limited, but include multidrug protocols and the temporary concomitant use of inhibitors of ABC-transporters. Recently, the use of tyrosine kinase inhibitors has been proposed to overcome MDR in human oncology. One of the tyrosine kinase inhibitors, masitinib, is licensed for veterinary use in the treatment of canine mast cell tumors. Therefore, this study aimed to assess the potential of masitinib to revert MDR in canine malignant lymphoma using an in vitro model with canine lymphoid cell lines. Masitinib had a mild antiproliferative effect on lymphoid cells, inhibited Pgp function at concentrations equal to or exceeding 1 ?m and was able to reverse doxorubicin resistance. The current findings provide the rationale for a combined use of masitinib with doxorubicin in the treatment of dogs with doxorubicin-resistant malignant lymphoma but await confirmation in clinical trials. PMID:23363222

Zandvliet, M; Teske, E; Chapuis, T; Fink-Gremmels, J; Schrickx, J A

2013-12-01

111

alpha-(3,4-dimethyoxyphenyl)-3,4-dihydro-6,7-dimethoxy-alpha- [(4-methylphenyl)thio]-2(1H)-isoquinolineheptanenitrile (CL 329,753): a novel chemosensitizing agent for P-glycoprotein-mediated resistance with improved biological properties compared with verapamil and cyclosporine A.  

Science.gov (United States)

Agents that inhibit P-glycoprotein may restore sensitivity to some antitumor drugs in cancer patients. Optimization of the specificity and potency of one class of chemosensitizing agents related to verapamil has led to the identification of alpha-(3,4-dimethyoxyphenyl)-3,4-dihydro-6, 7-dimethoxy-alpha-[(4-methylphenyl) thio]-2(1H)-isoquinolineheptanenitrile, designated CL 329,753. In vitro, 0.1 to 2.0 microM CL 329,753 restored sensitivity to drugs in the multidrug resistance (MDR) phenotype in cell lines that overexpress P-glycoprotein. CL 329,753 was greater than 10-fold more potent and efficacious than cyclosporine A or verapamil in vitro, particularly in cells that express high levels of P-glycoprotein. The enhanced activity of CL 329,753 may be related to its inability to be transported by P-glycoprotein, since low drug accumulation of cyclosporine or verapamil but not CL 329,753 was found in P-glycoprotein-containing cells, yet all three agents inhibited vinblastine binding to membranes containing P-glycoprotein and inhibited photoaffinity labeling of P-glycoprotein. In vivo, CL 329,753 resensitized drug-resistant tumors to vinblastine or doxorubicin in an ascitic or solid tumor model, respectively. No alteration in the plasma pharmacokinetic profile of doxorubicin by CL 329,753 has been found. Furthermore, the compound had 70-fold less calcium channel antagonistic activity compared with verapamil. PMID:8884813

Greenberger, L M; Collins, K I; Annable, T; Boni, J P; May, M K; Lai, F M; Kramer, R; Citeralla, R V; Hallett, W A; Powell, D

1996-01-01

112

Multidrug-resistant tuberculosis  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background With almost 9 million new cases each year, tuberculosis remains one of the most feared diseases on the planet. Led by the STOP-TB Partnership and WHO, recent efforts to combat the disease have made considerable progress in a number of countries. However, the emergence of mutated strains of Mycobacterium tuberculosis that are resistant to the major anti-tuberculosis drugs poses a deadly threat to control efforts. Multidrug-resistant tuberculosis (MDR-TB has been reported in all regions of the world. More recently, extensively drug resistant-tuberculosis (XDR-TB that is also resistant to second line drugs has emerged in a number of countries. To ensure that adequate resources are allocated to prevent the emergence and spread of drug resistance it is important to understand the scale of the problem. In this article we propose that current methods of describing the epidemiology of drug resistant tuberculosis are not adequate for this purpose and argue for the inclusion of population based statistics in global surveillance data. Discussion Whereas the prevalence of tuberculosis is presented as the proportion of individuals within a defined population having disease, the prevalence of drug resistant tuberculosis is usually presented as the proportion of tuberculosis cases exhibiting resistance to anti-tuberculosis drugs. Global surveillance activities have identified countries in Eastern Europe, the former Soviet Union and regions of China as having a high proportion of MDR-TB cases and international commentary has focused primarily on the urgent need to improve control in these settings. Other regions, such as sub-Saharan Africa have been observed as having a low proportion of drug resistant cases. However, if one considers the incidence of new tuberculosis cases with drug resistant disease in terms of the population then countries of sub-Saharan Africa have amongst the highest rates of transmitted MDR-TB in the world. We propose that inclusion of population based statistics in global surveillance data is necessary to better inform debate on the control of drug resistant tuberculosis. Summary Re-appraisal of global MDR-TB data to include population based statistics suggests that the problem of drug resistant tuberculosis in sub-Saharan Africa is more critical than previously perceived.

McNerney Ruth

2008-01-01

113

Multidrug resistance in tumour cells: characterisation of the multidrug resistant cell line K562-Lucena 1  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A resistência a múltiplos fármacos é o principal obstáculo no tratamento de pacientes com câncer. O mecanismo responsável pela resistência múltipla mais bem caracterizado envolve a expressão do produto do gene MDR-1, a glicoproteína P. Entretanto, o processo de resistência tem fatores múltiplos. Est [...] udos de mecanismos de resistência múltipla a fármacos têm dependido da análise de linhagens celulares tumorais que foram selecionadas e apresentam reatividade cruzada a uma ampla faixa de agentes anti-tumorais. Este trabalho caracteriza uma linhagem celular com múltipla resistência a fármacos, selecionada originalmente pela resistência ao alcalóide de Vinca vincristina e derivado da linhagem eritro-leucêmica K562. Esta linhagem celular, denominada Lucena 1, super-expressa a glicoproteína P e tem sua resistência revertida pelos quimio-sensibilizantes verapamil, trifluoperazina e ciclosporinas A, D e G. Ademais, demonstramos que o azul de metileno era capaz de reverter parcialmente a resistência nesta linhagem celular. Em contraste, o uso de 5-flúor-uracil aumentava a resistência de Lucena 1. Adicionalmente aos quimioterápicos, células Lucena 1 eram resistentes radiação ultra-violeta A e peróxido de hidrogênio e deixavam de mobilizar o cálcio intra-celular quando se usava tapsigargina. Mudanças no cito-esqueleto desta linhagem foram também observadas. Abstract in english Multidrug resistance to chemotherapy is a major obstacle in the treatment of cancer patients. The best characterised mechanism responsible for multidrug resistance involves the expression of the MDR-1 gene product, P-glycoprotein. However, the resistance process is multifactorial. Studies of multidr [...] ug resistance mechanisms have relied on the analysis of cancer cell lines that have been selected and present cross-reactivity to a broad range of anticancer agents. This work characterises a multidrug resistant cell line, originally selected for resistance to the Vinca alkaloid vincristine and derived from the human erythroleukaemia cell K562. This cell line, named Lucena 1, overexpresses P-glycoprotein and have its resistance reversed by the chemosensitisers verapamil, trifluoperazine and cyclosporins A, D and G. Furthermore, we demonstrated that methylene blue was capable of partially reversing the resistance in this cell line. On the contrary, the use of 5-fluorouracil increased the resistance of Lucena 1. In addition to chemotherapics, Lucena 1 cells were resistant to ultraviolet A radiation and hydrogen peroxide and failed to mobilise intracellular calcium when thapsigargin was used. Changes in the cytoskeleton of this cell line were also observed.

VIVIAN M., RUMJANEK; GILMA S., TRINDADE; KAREN, WAGNER-SOUZA; MICHELE C., MELETTI-DE-OLIVEIRA; LUIS F., MARQUES-SANTOS; RAQUEL C., MAIA; MÁRCIA A. M., CAPELLA.

114

Multidrug resistance in tumour cells: characterisation of the multidrug resistant cell line K562-Lucena 1  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A resistência a múltiplos fármacos é o principal obstáculo no tratamento de pacientes com câncer. O mecanismo responsável pela resistência múltipla mais bem caracterizado envolve a expressão do produto do gene MDR-1, a glicoproteína P. Entretanto, o processo de resistência tem fatores múltiplos. Est [...] udos de mecanismos de resistência múltipla a fármacos têm dependido da análise de linhagens celulares tumorais que foram selecionadas e apresentam reatividade cruzada a uma ampla faixa de agentes anti-tumorais. Este trabalho caracteriza uma linhagem celular com múltipla resistência a fármacos, selecionada originalmente pela resistência ao alcalóide de Vinca vincristina e derivado da linhagem eritro-leucêmica K562. Esta linhagem celular, denominada Lucena 1, super-expressa a glicoproteína P e tem sua resistência revertida pelos quimio-sensibilizantes verapamil, trifluoperazina e ciclosporinas A, D e G. Ademais, demonstramos que o azul de metileno era capaz de reverter parcialmente a resistência nesta linhagem celular. Em contraste, o uso de 5-flúor-uracil aumentava a resistência de Lucena 1. Adicionalmente aos quimioterápicos, células Lucena 1 eram resistentes radiação ultra-violeta A e peróxido de hidrogênio e deixavam de mobilizar o cálcio intra-celular quando se usava tapsigargina. Mudanças no cito-esqueleto desta linhagem foram também observadas. Abstract in english Multidrug resistance to chemotherapy is a major obstacle in the treatment of cancer patients. The best characterised mechanism responsible for multidrug resistance involves the expression of the MDR-1 gene product, P-glycoprotein. However, the resistance process is multifactorial. Studies of multidr [...] ug resistance mechanisms have relied on the analysis of cancer cell lines that have been selected and present cross-reactivity to a broad range of anticancer agents. This work characterises a multidrug resistant cell line, originally selected for resistance to the Vinca alkaloid vincristine and derived from the human erythroleukaemia cell K562. This cell line, named Lucena 1, overexpresses P-glycoprotein and have its resistance reversed by the chemosensitisers verapamil, trifluoperazine and cyclosporins A, D and G. Furthermore, we demonstrated that methylene blue was capable of partially reversing the resistance in this cell line. On the contrary, the use of 5-fluorouracil increased the resistance of Lucena 1. In addition to chemotherapics, Lucena 1 cells were resistant to ultraviolet A radiation and hydrogen peroxide and failed to mobilise intracellular calcium when thapsigargin was used. Changes in the cytoskeleton of this cell line were also observed.

VIVIAN M., RUMJANEK; GILMA S., TRINDADE; KAREN, WAGNER-SOUZA; MICHELE C., MELETTI-DE-OLIVEIRA; LUIS F., MARQUES-SANTOS; RAQUEL C., MAIA; MÁRCIA A. M., CAPELLA.

2001-03-01

115

Transmembrane domain (TM) 9 represents a novel site in P-glycoprotein that affects drug resistance and cooperates with TM6 to mediate [125I]iodoarylazidoprazosin labeling.  

Science.gov (United States)

The multidrug resistant cell line DC-3F/ADII was obtained by stepwise selection for growth in actinomycin D (ActD). Compared with parental cells, it displays high resistance to ActD and vincristine and low resistance to colchicine and daunorubicin. These cells overexpress a form of P-glycoprotein (Pgp1) containing a double mutation, I837L and N839I, in transmembrane domain (TM) 9; when transfected into DC-3F, this mutation confers the DC-3F/ADII phenotype. We have shown previously that another cell line, DC-3F/ADX, also displays this phenotype and overexpresses a mutant form of Pgp1 containing a double mutation in TM6 (G338A, A339P). Hence, mutations in TM9 and TM6 are independently capable of conferring the same cross-resistance phenotype. The TM6 mutations inhibit the ability of cyclosporin A to reverse cross-resistance and to block labeling of the protein by [125I]iodoarylazidoprazosin (IAAP), whereas the TM9 mutations do not show similar effects. A chimeric protein containing both pairs of mutations confers twice the level of resistance to ActD than expected from the sum of the individual mutations, but it cannot be labeled to detectable levels with [125I]IAAP. Thus, TM9 represents a novel site that cooperates with TM6 to mediate drug resistance and [125I]IAAP labeling. PMID:11455011

Song, J; Melera, P W

2001-08-01

116

Primary multidrug resistant tuberculosis  

Directory of Open Access Journals (Sweden)

Full Text Available A 37-year old man presented at our institution with back pain, low-grade fever and weight-loss. X-ray of chest (postero-anterior view showed multiple opacities with erosion of right 2nd and left 6th ribs. CT-scan of thorax and CT-guided FNAC con-firmed the diagnosis of tuberculosis of ribs. Even after 5-months of treatment with four first line drugs, the patient developed a cold abscess at the back. Mycobacterial culture and drug sensitivity of material aspirated by Radiometric method from the cold abscess showed growth of Mycobacterium tuberculosis, and those bacilli were resistant to both isoniazide and rifampicin. The patient did not have anti-tubercu-lar medication in the past, and that established the diagnosis of primary multidrug resistant tuberculosis of ribs. Patient was treated successfully with 2nd line drugs at the cost of moderate degree of hearing loss. After one and half years of treatment X-ray of chest (PA view showed complete healing of rib erosions with new bone formation.

Sarkar Supriya

2007-01-01

117

Multidrug-resistant tuberculosis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Despite the efforts made worldwide to reduce the number of cases of drug-susceptible tuberculosis, multidrug-resistant tuberculosis (MDR-TB) constitutes an important public health issue. Around 440,000 new cases of MDR-TB are estimated annually, although in 2008 only 7% of these (29,423 cases) were [...] notified. The laboratory tests for diagnosing resistance may be phenotypic (based on culture growth in the presence of drugs) or genotypic (i.e. identification of the presence of mutations that confer resistance). The urgent need for a rapid means of detecting resistance to anti-TB drugs has resulted in the development of many genotypic methods over recent years. The treatment of MDR-TB is expensive, complex, prolonged (18-24 months) and associated with a higher incidence of adverse reactions. Some basic principles must be observed when prescribing an adequate treatment regimen for MDR-TB: (a) the association of at least four drugs (three of which should not have been used previously); (b) use of a fluoroquinolone; and (c) use of an injectable anti-TB drug. In Brazil, the therapeutic regimen for MDR-TB has been standardized and consists of five drugs: terizidone, levofloxacin, pyrazinamide, ethambutol and an aminoglycoside (streptomycin or amikacin). Pulmonary resection is an important tool in the coadjuvant treatment of MDR-TB. While a recent meta-analysis revealed an average cure rate of MDR-TB of 69%, clinical studies are currently being conducted with new drugs and with drugs already available on the market but with a new indication for TB, with encouraging results that will enable more effective treatment regimens to be planned in the future.

Antônio Carlos Moreira, Lemos; Eliana Dias, Matos.

2013-04-01

118

Breast cancer resistance protein and P-glycoprotein limit sorafenib brain accumulation.  

Science.gov (United States)

Sorafenib is a second-generation, orally active multikinase inhibitor that is approved for the treatment of patients with advanced renal cell carcinoma and patients with unresectable hepatocellular carcinoma. We studied active transport of sorafenib in MDCK-II cells expressing human P-glycoprotein (P-gp/ABCB1) or ABCG2 (breast cancer resistance protein) or murine Abcg2. Sorafenib was moderately transported by P-gp and more efficiently by ABCG2 and Abcg2. Because sorafenib is taken orally, we orally administered sorafenib to wild-type, Abcb1a/1b(-/-), Abcg2(-/-), and Abcb1a/1b;Abcg2(-/-) mice, completely lacking functional Abcb1a/1b, Abcg2, or both, respectively, and we studied plasma pharmacokinetics and brain accumulation. The systemic exposure on oral administration was not different among all strains. However, brain accumulation was 4.3-fold increased in Abcg2(-/-) mice and 9.3-fold increased in Abcb1a/1b;Abcg2(-/-) mice. Moreover, when wild-type mice were treated with sorafenib in combination with the dual P-gp and ABCG2 inhibitor elacridar, brain accumulation was similar to that observed for Abcb1a/1b;Abcg2(-/-) mice. These results show that the brain accumulation of sorafenib is primarily restricted by ABCG2. This contrasts with previous studies using shared ABCG2 and P-gp substrates, which all suggested that P-gp dominates at the blood-brain barrier, and that an effect of ABCG2 is only evident when both transporters are absent. Interestingly, for sorafenib, it is the other way around, that is, ABCG2, and not P-gp, plays the dominant role in restricting its brain accumulation. Clinically, our findings may be relevant for the treatment of renal cell carcinoma patients with central nervous system relapses, as a dual ABCG2 and P-gp inhibitor might improve the central nervous system entry and thereby the therapeutic efficacy of sorafenib. PMID:20103600

Lagas, Jurjen S; van Waterschoot, Robert A B; Sparidans, Rolf W; Wagenaar, Els; Beijnen, Jos H; Schinkel, Alfred H

2010-02-01

119

An atomic detail model for the human ATP binding cassette transporter P-glycoprotein derived from disulfide cross-linking and homology modeling.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The multidrug resistance P-glycoprotein mediates the extrusion of chemotherapeutic drugs from cancer cells. Characterization of the drug binding and ATPase activities of the protein have made it the paradigm ATP binding cassette (ABC) transporter. P-glycoprotein has been imaged at low resolution by electron cryo-microscopy and extensively analyzed by disulphide cross-linking, but a high resolution structure solved ab initio remains elusive. Homology models of P-glycoprotein were generated usi...

Stenham, Dr; Campbell, Jd; Sansom, Ms; Higgins, CF; Kerr, Id; Linton, Kj

2003-01-01

120

Quercetin as a Potential Modulator of P-Glycoprotein Expression and Function in Cells of Human Pancreatic Carcinoma Line Resistant to Daunorubicin  

Directory of Open Access Journals (Sweden)

Full Text Available P-glycoprotein (P-gp is one of the ABC transporters responsible for the resistance of several tumours to successful chemotherapy. Numerous agents are capable of interfering with the P-gp-mediated export of drugs but unfortunately most of them produce serious side effects. Some plant polyphenols, including the flavonol quercetin (Q, manifest anti-neoplastic activity mainly due to their influence on cell cycle control and apoptosis. Reports are also available which show that Q may intensify action of cytostatic drugs and suppress the multidrug resistance (MDR phenomenon. The study aimed at determination if Q sensitizes cells resistant to daunorubicin (DB through its effect on P-gp expression and action. The experiments were conducted on two cell lines of human pancreatic carcinoma, resistant to DB EPP85-181RDB and sensitive EPP85-181P as a comparison. Cells of both lines were exposed to selected concentrations of Q and DB, and then membranous expression of P-gp and its transport function were examined. The influence on expression of gene for P-gp (ABCB1 was also investigated. Results of the studies confirmed that Q affects expression and function of P-gp in a concentration-dependent manner. Moreover it decreased expression of ABCB1. Thus, Q may be considered as a potential modulator of P-gp.

Piotr Dziegiel

2010-02-01

 
 
 
 
121

The effect of the plasticizer diethylhexyl phthalate on transport activity and expression of P-glycoprotein in parental and doxo-resistant human sarcoma cell lines.  

Science.gov (United States)

Multidrug resistance (MDR) to cancer therapy is frequently associated with the over-expression of the multidrug transporter MDR1 gene product P-glycoprotein (Pgp) in several types of human tumours. Various chemosensitizers have been used to inhibit Pgp activity but toxicity limits their clinical application. Di(2-ethylhexyl)phthalate (DEHP) is a plasticizer that is released from polyvinyl chloride (PVC) medical devices. Therefore, cancer patients undertaking chemotherapy are exposed to a clinically important amount of DEHP through blood and blood component transfusions, apheresis products, intravenous chemotherapy, parenteral nutrition and other medical treatments. The present study was designed to investigate the effects of DEHP on transport activity and expression of Pgp in order to evaluate its potential use as a chemosensitizer in cancer therapy. Human doxorubicin (doxo) resistant sarcoma cells (MES-SA/Dx5) that over-express Pgp were treated with different doses of doxo (2, 4 and 8 ?M) in the presence or absence of various concentrations of DEHP (3, 6 and 12 ?M) that were clinically achievable in vivo. Our results show that co-treatment with 2, 4 and 8 ?M doxo in the presence of the lowest concentration of DEHP (3 ?M) enhanced significantly doxo accumulation in MES-SA/Dx5 cells and, consistently increased the sensitivity to doxo, when compared to controls receiving only doxo. In contrast, higher DEHP concentrations (6 and 12 ?M) induced MES-SA/Dx5 to extrude doxo decreasing doxo cytotoxicity toward resistant cells below control values. These results are consistent with the increase in Pgp expression levels in parental MES-SA cells treated with 3, 6 and 12 ?M DEHP for 24 h and compared to untreated controls. All in all, these findings suggest a potential clinical application of DEHP as a chemosensitizer to improve effectiveness of the antineoplastic drugs in MDR human tumours. PMID:21880209

Angelini, A; Centurione, L; Sancilio, S; Castellani, M L; Conti, P; Di Ilio, C; Porreca, E; Cuccurullo, F; Di Pietro, R

2011-01-01

122

Inhibition of vincristine binding to plasma membrane vesicles from daunorubicin-resistant Ehrlich ascites cells by multidrug resistance modulators.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The multidrug resistance (MDR) phenotype is presumed to be mostly dependent on changes in the resistant cell plasma membrane, notably the emergence of a 170 kDa glycoprotein called P-glycoprotein, which facilitate increased drug efflux. We have previously demonstrated that ATP-enhanced binding of vincristine (VCR) to plasma membrane vesicles is much greater in MDR than in wild type cells. The present study has shown that VCR binding to MDR Ehrlich ascites tumour cell plasma membrane vesicles ...

Sehested, M.; Jensen, P. B.; Skovsgaard, T.; Bindslev, N.; Demant, E. J.; Friche, E.; Vindela?¸v, L.

1989-01-01

123

Synthesis and characterization of reversible mometasone furoate dimers as P-glycoprotein inhibitors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several ABC (ATP-binding cassette) transporters, including P-glycoprotein (P-gp), breast cancer resistance protein (BCRP, ABCG2), and the multidrug resistance proteins (MRPs) are expressed in tissues important for the uptake, metabolism, and elimination of xenobiotics. Their function protects tissues from the potentially toxic effects of foreign compounds. Transporter efflux also limits the access of numerous pharmaceuticals to their target tissues. P-gp is the best-characterized multidrug tr...

Ivers, Jenna Manby

2011-01-01

124

A novel calmodulin antagonist O-(4-ethoxyl-butyl)-berbamine overcomes multidrug resistance in drug-resistant MCF-7/ADR breast carcinoma cells.  

Science.gov (United States)

Multidrug resistance (MDR) mediated by the overexpression of the drug efflux protein P-glycoprotein is one of the major obstacles to successful cancer chemotherapy. The development of safe and effective MDR-reversing agents is an important approach to addressing this problem clinically. In this study, we evaluated the P-gp-modulatory potential of O-(4-ethoxyl-butyl)-berbamine (EBB), a novel calmodulin antagonist and derivative of bisbenzylisoquinoline alkaloid, which significantly improved the chemosensitivity of P-glycoprotein-mediated multidrug-resistant cells to doxorubicin compared with the efficacy of a conventional P-glycoprotein inhibitor, verapamil. EBB not only blocked the function of P-glycoprotein confirmed by the fact that EBB increased intracellular accumulation of rhodamine 123 and doxorubicin but also inhibited the expression of P-glycoprotein actualized by downregulating P-glycoprotein. Furthermore, our results showed that cotreatment with EBB and doxorubicin resulted in marked G(2)/M arrest and apoptosis of MCF-7/ADR cells, accompanied by down-regulation of the proteins cdc2/p34 and cyclin B1 and increased the levels of calcium ions. Taken together, these results suggest that cotreatment with EBB and doxorubicin could strongly potentiate the antitumor activity of doxorubicin, thus may have significant clinical application in cancer chemotherapy. PMID:20112430

Liu, Rong; Zhang, Yanjun; Chen, Yanhong; Qi, Jing; Ren, Simei; Xushi, Ming Yang; Yang, Chunzheng; Zhu, Huifang; Xiong, Dongsheng

2010-07-01

125

Leishmania: papel de la glicoproteína P en la mediación de resistencia a medicamentos y estrategias de reversión / Leishmania: role of P glycoprotein in drug resistance and reversion strategies  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish Actualmente, los parásitos protozoarios son uno de los principales agentes causantes de morbilidad y mortalidad en el mundo, un problema complicado, además, por la aparición de resistencia a medicamentos en estos organismos. La resistencia a medicamentos observada en parásitos protozoarios se debe a [...] diferentes mecanismos como la disminución de la entrada del medicamento a la célula por cambios en el transportador requerido, la pérdida de la activación del medicamento por parte del hospedero, las alteraciones en el blanco del medicamento y la expresión exagerada del transportador múltiple de medicamentos o glicoproteína P (Pgp). En esta revisión, nos centramos en: 1) el papel de las glicoproteínas P (Pgp) de la familia de proteínas ABC (ATP binding cassette) como los transportadores de múltiples medicamentos en la mediación de resistencia en protozoarios, especialmente en Leishmania, y en el desarrollo de resistencia cruzada para medicamentos estructural y funcionalmente no relacionados, y 2) en algunos conceptos relacionados con los mecanismos moduladores que podrían revertir la resistencia a medicamentos por fármacos y productos naturales. Numerosos moduladores o quimiosensibilizadores son conocidos por alterar la capacidad de las glicoproteínas P para mantener concentraciones intracelulares subtóxicas del medicamento; algunos ejemplos incluyen los bloqueadores de los canales de calcio como el verapamilo; sin embargo, se requieren altas concentraciones para una inhibición eficiente y duradera, las cuales producen efectos adversos indeseables. Por tanto, se necesitan más investigaciones relacionadas con los moduladores naturales para Pgp, los cuales podrían presentar menor toxicidad para el hospedero. Abstract in english Protozoan parasites are important causative agents of morbidity and mortality throughout the world -a problem further complicated by the emergence of drug resistance in these parasites. Mechanisms of drug resistance include the following: decreased uptake of the drug into the cell, loss of drug acti [...] vation, alterations in the drug target, and over-expression of a well-known multiple drug transporter proteins. In this review, two critical components of resistance are stressed: (1) the role of ATP binding cassette proteins, such as P-glycoproteins, in mediating drug resistance in Leishmania and other protozoans, followed by development of cross-resistance to many structurally and functionally unrelated drugs, and (2) some concepts concerning the reversal mechanism of multidrug resistance by drugs and natural products. Several modulators or chemosensitizers alter the capacity of P-glycoproteins to maintain subtoxic intracellular drug concentrations. Calcium channel blockers such as verapamil act in this mode; however, high concentrations are required for an efficient and effective inhibition and, in addition, produce undesirable side effects. The discovery of new, natural product modulators of P-glycoproteins is stressed. This category of modulators offer potentially improved efficacy and lowered toxicity for the mammalian host.

Edison J, Osorio; Sara M, Robledo; Gabriel J, Arango; Carlos E, Muskus.

2005-06-01

126

Can flavonoids from honey alter multidrug resistance?  

Science.gov (United States)

Cancer is one of the deadly diseases that burdens the society since long-time. Although design of chemotherapy is well-advanced, still it could not prevent the cancer death by hundred percent. One of the major stumbling blocks for cancer chemotherapy is multidrug resistance (MDR) developed by cancer cells. Role of ABC family of transporter proteins is well recognized in MDR. P-glycoprotein (P-gp), member of ABC transporter family, has been described for drug resistance and a low bioavailability of drugs by pumping structurally unrelated drugs out of the cells at the cost of ATP hydrolysis. Recently various P-gp inhibitors (chemosensitizers) are studied extensively to reverse MDR. In this scenario, we propose honey with multitude of polyphenolic flavonoids as a plausible candidate for inhibiting the P-gp proteins. Common flavonoids of honey like chrysin, genistein, biochanin, quercetin, kaempferol, and naringenin have found to interact with P-gp transporters. Generally chemosensitizers bind with transmembrane domain (TMD) in the P-gp transporter but flavonoids are bi-functional in reversing the MDR. Flavonoids can inhibit the ATPases activity involved in drug efflux and also it may serve as substrates for P-gp transporters, thereby causing competitive inhibition towards other substrates. This dual-mode of flavonoids interaction with P-gp transporter enhances the therapeutic index. Hence we promulgate honey with rich flavonoid content as a potential candidate for reversing MDR. If our hypothesis is true, honey a novel chemosensitizer will reduce the huge amount invested in developing new chemosensitizers to overcome the burden of chemo-resistance. PMID:21247706

Jaganathan, Saravana Kumar

2011-04-01

127

Localization of P-glycoprotein at the nuclear envelope of rat brain cells  

International Nuclear Information System (INIS)

P-Glycoprotein is a plasma membrane drug efflux protein implicated in extrusion of cytotoxic compounds out of a cell. There is now evidence that suggests expression of this transporter at several subcellular sites, including the nucleus, mitochondria, and Golgi apparatus. This study investigated the localization and expression of P-glycoprotein at the nuclear membrane of rat brain microvessel endothelial (RBE4) and microglial (MLS-9) cell lines. Immunocytochemistry at the light and electron microscope levels using P-glycoprotein monoclonals antibodies demonstrated the localization of the protein at the nuclear envelope of RBE4 and MLS-9 cells. Western blot analysis revealed a single band of 170-kDa in purified nuclear membranes prepared from isolated nuclei of RBE4 and MLS-9 cells. These findings indicate that P-glycoprotein is expressed at the nuclear envelope of rat brain cells and suggest a role in multidrug resistance at this subcellular site

128

The multidrug-resistant phenotype associated with overexpression of the new ABC half-transporter, MXR (ABCG2)  

DEFF Research Database (Denmark)

Mechanisms of drug resistance other than P-glycoprotein are of increasing interest as the list of newly identified members of the ABC transport family has grown. We sought to characterize the phenotype of the newly discovered ABC transporter encoded by the mitoxantrone resistance gene, MXR, also known as ABCP1 or BCRP. The pharmacodynamics of mitoxantrone and 12 other fluorescent drugs were evaluated by confocal microscopy in four multidrug-resistant human colon (S1) and breast (MCF-7) cancer cell lines. We utilized two sublines, MCF-7 AdVp3000 and S1-M1-80, and detected overexpression of MXR by PCR, immunoblot assay and immunohistochemistry. These MXR overexpressing sublines were compared to cell lines with P-glycoprotein- and MRP-mediated resistance. High levels of cross-resistance were observed for mitoxantrone, the anthracyclines, bisantrene and topotecan. Reduced levels of mitoxantrone, daunorubicin, bisantrene, topotecan, rhodamine 123 and prazosin were observed in the two sublines with high MXR expression. Neither the P-glycoprotein substrates vinblastine, paclitaxel, verapamil and calcein-AM, nor the MRP substrate calcein, were extruded from MCF-7 AdVp3000 and S1-M1-80 cells. Thus, the multidrug-resistant phenotype due to MXR expression is overlapping with, but distinct from, that due to P-glycoprotein. Further, cells that overexpress the MXR protein seem to be more resistant to mitoxantrone and topotecan than cells with P-glycoprotein-mediated multidrug resistance. Our studies suggest that the ABC half-transporter, MXR, is a potent, new mechanism for conferring multiple drug resistance. Definition of its mechanism of transport and its role in clinical oncology is required.

Litman, Thomas; Brangi, M

2000-01-01

129

Visualization of multidrug resistance in vivo  

Energy Technology Data Exchange (ETDEWEB)

Various mechanisms are involved in multidrug resistance (MDR) for chemotherapeutic drugs, such as the drug efflux pumps, P-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP). In this review the mechanisms involved in MDR are described and results are reviewed with particular attention to the in vivo imaging of Pgp and MRP. Various detection assays provide information about the presence of drug efflux pumps at the mRNA and protein levels. However, these methods do not yield information about the dynamic function of Pgp and MRP in vivo. For the study of Pgp- and MRP-mediated transport, single-photon emission tomography (SPET) and positron emission tomography (PET) are available. Technetium-99m sestamibi is a substrate for Pgp and MRP, and has been used in clinical studies for tumour imaging, and to visualize blockade of Pgp-mediated transport after modulation of the Pgp pump. Other {sup 99m}Tc radiopharmaceuticals, such as {sup 99m}Tc-tetrofosmin and several {sup 99}Tc-Q complexes, are also substrates for Pgp, but to date only results from in vitro and animal studies are available for these compounds. Several agents, including [{sup 11}C]colchicine, [{sup 11}C]verapamil and [{sup 11}C]daunorubicin, have been evaluated for the quantification of Pgp-mediated transport with PET in vivo. The results suggest that radiolabelled colchicine, verapamil and daunorubicin are feasible substrates with which to image Pgp function in tumours. Uptake of [{sup 11}C]colchicine and [{sup 11}C]verapamil is relatively high in the chest area, reducing the value of both tracers for monitoring Pgp-mediated drug transport in tumours located in this region. In addition, it has to be borne in mind that only comparison of Pgp-mediated transport of radioalabelled substrates in the absence and in the presence of Pgp blockade gives quantitative information on Pgp-mediated pharmacokinetics. Leukotrienes are specific substrates for MRP. Therefore, N-[{sup 11}C]acetyl-leukotriene E{sub 4} provides an opportunity to study MRP function non-invasively. Results obtained in MRP{sub 2} mutated GY/TR rats have demonstrated visualization of MRP-mediated transport. This tracer permits the study of MRP transport function abnormalities in vivo, e.g. in Dubin-Johnson patients, who are MRP{sub 2} gene deficient. Results obtained show the feasibility of using SPET and PET to study the functionality of MDR transporters in vivo. (orig.) With 3 figs., 91 refs.

Hendrikse, N.H. [PET Center, University Hospital, Groningen (Netherlands)]|[Department of Internal Medicine, Division of Medical Oncology, University Hospital, Groningen (Netherlands); Franssen, E.J.F. [PET Center, University Hospital, Groningen (Netherlands)]|[Department of Nuclear Medicine, University Hospital, Groningen (Netherlands); Graaf, W.T.A. van der; Vries, E.G.E. de [Department of Internal Medicine, Division of Medical Oncology, University Hospital, Groningen (Netherlands); Vaalburg, W. [PET Center, University Hospital, Groningen (Netherlands)

1999-03-01

130

Bispecific antibodies reactive with the multidrug-resistance-related glycoprotein and CD3 induce lysis of multidrug-resistant tumor cells.  

Science.gov (United States)

We describe the lysis of multidrug-resistant (MDR) tumor cells by various lymphocytic effector cells, retargeted with bispecific antibodies (heteroconjugates). The Ab-heteroconjugate used was prepared by chemically cross-linking the OKT3 monoclonal antibody (MAb) reactive with CD3 antigen on T lymphocytes, with the MRK16 MAb, which recognizes the MDR-associated P-glycoprotein. Cloned TCR alpha beta/CD3+ T lymphocytes, OKT3-activated peripheral-blood mononuclear cells and peripheral-blood mononuclear blood lymphocytes, stimulated with allogeneic irradiated cells in a mixed lymphocyte culture, could be induced to lyse MDR ovarian tumor cells in the presence of Ab-heteroconjugate CD3/MRK16, whereas the drug-sensitive parental tumor cells lacking the P-glycoprotein were not lysed by these retargeted effector cells. Cloned TCR gamma delta/CD3+ T lymphocytes showed a high MHC-unrestricted lysis of MDR tumor cells. Addition of Ab-heteroconjugate CD3/MRK16 could therefore not enhance target-cell lysis. Melanoma tumor cells transfected with the mdr-I gene which codes for the P-glycoprotein were also efficiently lysed by Ab-heteroconjugate retargeted cloned TCR alpha beta/CD3+ T cells. Tumor cell lines derived from organs known to express the P-glycoprotein also were lysable by the retargeted effector cells. PMID:2793246

Van Dijk, J; Tsuruo, T; Segal, D M; Bolhuis, R L; Colognola, R; van de Griend, R J; Fleuren, G J; Warnaar, S O

1989-10-15

131

Marine Natural Products with P-Glycoprotein Inhibitor Properties  

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Full Text Available P-glycoprotein (P-gp is a protein belonging to the ATP-binding cassette (ABC transporters superfamily that has clinical relevance due to its role in drug metabolism and multi-drug resistance (MDR in several human pathogens and diseases. P-gp is a major cause of drug resistance in cancer, parasitic diseases, epilepsy and other disorders. This review article aims to summarize the research findings on the marine natural products with P-glycoprotein inhibitor properties. Natural compounds that modulate P-gp offer great possibilities for semi-synthetic modification to create new drugs and are valuable research tools to understand the function of complex ABC transporters.

Dioxelis Lopez

2014-01-01

132

Stimulatory effect of insecticides on partially purified P-glycoprotein ATPase from the resistant pest Helicoverpa armigera.  

Science.gov (United States)

A P-glycoprotein-like protein (Ha-Pgp) was detected in a membrane preparation from the insecticide-resistant pest Helicoverpa armigera (Lepidoptera: Noctüidae) using C219 antibodies that are directed towards an epitope in the nucleotide-binding domains. This protein was partially purified and found to be a glycoprotein displaying ATPase activity. SDS-PAGE confirmed that a high molecular mass glycoprotein (150 kDa) was overexpressed in resistant pests, but was not detected in susceptible pests. The partially purified Ha-Pgp ATPase was reconstituted into proteoliposomes and it was found that some insecticides, namely, monocrotophos, endosulfan, cypermethrin, fenvalerate, and methylparathion, stimulated the ATPase activity. The effect of various inhibitors on partially purified Ha-Pgp showed that orthovanadate is a potent inhibitor of its ATPase activity, inhibiting it by 90% at a concentration of 2 mmol/L. Other inhibitors, such as EDTA, sodium azide, and molybdate resulted in only a 20% decrease in activity. Details of the structure and function of Ha-Pgp will be important in the development of strategies to overcome insecticide resistance in this pest. PMID:17215890

Aurade, Ravindra; Jayalakshmi, Senigala K; Sreeramulu, Kuruba

2006-12-01

133

Acetylcholine receptor subunit and P-glycoprotein transcription patterns in levamisole-susceptible and -resistant Haemonchus contortus.  

Science.gov (United States)

The mechanism of resistance to the anthelmintic levamisole in parasitic nematodes is poorly understood, although there is some evidence implicating changes in expression of nicotinic acetylcholine receptor (nAChR) subunit genes. Hence, in order to define levamisole resistance mechanisms in some Australian field-derived isolates of Haemonchus contortus we examined gene expression patterns and SNPs in nAChR subunit genes, as well as expression levels for P-glycoprotein (P-gp) and receptor ancillary protein genes, in various life stages of one levamisole-sensitive and three levamisole-resistant isolates of this species. Larvae of two isolates showed high-level resistance to levamisole (resistance ratios at the IC50 > 600) while the third isolate showed a degree of heterogeneity, with a resistance factor of only 1.1-fold at the IC50 alongside the presence of a resistant subpopulation. Transcription patterns for nAChR subunit genes showed a great degree of variability across the different life stages and isolates. The most consistent observation was the down-regulation of Hco-unc-63a in adults of all resistant isolates. Transcription of this gene was also reduced in the L3 stage of the two most resistant isolates, highlighting its potential as a resistance marker in the readily accessible free-living stages. There was down regulation of all four Hco-unc-29 paralogs in adults of one resistant isolate. There were no consistent changes in expression of P-gps or ancillary protein genes across the resistant isolates. The present study has demonstrated a complex pattern of nAChR subunit gene expression in H. contortus, and has highlighted several instances where reduced expression of subunit genes (Hco-unc-63a, Hco-unc-29) may be associated with the observed levamisole resistance. The data also suggests that it will be difficult to detect resistance using gene transcription-based methods on pooled larval samples from isolates containing only a resistant subpopulation due to the averaging of gene expression data across the whole population. PMID:24533293

Sarai, Ranbir S; Kopp, Steven R; Coleman, Glen T; Kotze, Andrew C

2013-12-01

134

In vivo evaluation of P-glycoprotein and breast cancer resistance protein modulation in the brain using [{sup 11}C]gefitinib  

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Gefitinib (Iressa) is a selective inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase. Recent studies confirmed that gefitinib interacted with the breast cancer resistance protein (BCRP) at submicromolar concentrations, whereas other multidrug transporters, including P-glycoprotein (P-gp), showed much lower reactivity toward gefitinib. Recently, many tracers for positron emission tomography (PET) have been prepared to study P-gp function in vivo; however, PET tracers had not been evaluated for both P-gp and BCRP modulation in the brain. Therefore, we evaluated in vivo brain penetration-mediated P-gp and BCRP in mice using [{sup 11}C]gefitinib. Co-injection with gefitinib (over 50 mg/kg), a nonspecific P-gp modulator cyclosporin A (50 mg/kg), and the dual P-gp and BCRP modulator GF120918 (over 5 mg/kg) induced an increase in the brain uptake of [{sup 11}C]gefitinib in mice 30 min after injection. In the PET study of mice, the radioactivity level in the brain with co-injection of GF120918 (5 mg/kg) was three- to fourfold higher than that in control after initial uptake. The radioactivity level in the brain in P-gp and Bcrp knockout mice was approximately eightfold higher than that in wild-type mice 60 min after injection. In conclusion, [{sup 11}C]gefitinib is a promising PET tracer to evaluate the penetration of gefitinib into the brain by combined therapy with P-gp or BCRP modulators, and into brain tumors. Furthermore, PET study with GF120918 is a promising approach for evaluating brain penetration-mediated P-gp and BCRP.

Kawamura, Kazunori [Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan)], E-mail: kawamur@nirs.go.jp; Yamasaki, Tomoteru; Yui, Joji; Hatori, Akiko; Konno, Fujiko; Kumata, Katsushi; Irie, Toshiaki; Fukumura, Toshimitsu; Suzuki, Kazutoshi; Kanno, Iwao; Zhang Mingrong [Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan)

2009-04-15

135

[Proteins in cancer multidrug resistance].  

Science.gov (United States)

Multidrug Resistance (MDR) is defined as insensitivity to administered medicines that are structurally unrelated and have different molecular targets. Cancers possess numerous mechanisms of drug resistance, involving various aspects of cell biology. A pivotal role in this phenomenon is played by proteins--enzymatic or structural parts of the cell. Membrane transporters, including the main members of ABC protein family--P-gp, MRP1 and BCRP, as well as LRP, which builds structure of vaults, determine the multidrug-resistant phenotype by decreasing drug concentration within the cell or modifying its distribution to intracellular compartments. The ? isoform of protein enzyme--glutathione S-transferase (GSTP-1), is responsible for excessive intensity of detoxification of cytostatics. A common example of altered drug target site that does not respond to chemotherapy is topoisomerase II ? (TopoIIa). Alterations of programmed cell death result from expression of metallothionein (MT)--inhibitor of the process, and cytokeratin 18 (CK18), which, if in high concentration, also prevents apoptosis of cells. Several methods of decreasing activity of these proteins have been developed, aiming to overcome MDR in cancer cells. However, for a variety of reasons, their clinical suitability is still very low, leading to continuous increase in death rate among patients. This paper presents current state of knowledge on the most important examples of proteins responsible for MDR of cancer cells and molecular mechanisms of their action. PMID:24864112

Pop?da, Marta; P?uciennik, El?bieta; Bednarek, Andrzej K

2014-01-01

136

Inhibition of anticancer drug efflux transporter P-glycoprotein by rosemary phytochemicals.  

Science.gov (United States)

The effects of dietary antioxidative and chemopreventive rosemary phytochemicals on the function of the human drug efflux transporter P-glycoprotein (MDR1, ABCB1) and multidrug resistance protein 1 (MRP1, ABCC1) were investigated using P-glycoprotein-overexpressing human carcinoma KB-C2 cells and human MRP1 gene-transfected KB/MRP cells. The effects of natural phytochemicals found in rosemary such as carnosic acid, carnosol, rosmarinic acid, and ursolic acid were investigated. The accumulation of daunorubicin or rhodamine 123, fluorescent substrates of P-glycoprotein, in KB-C2 cells increased in the presence of carnosic acid, carnosol, and ursolic acid in a concentration-dependent manner. In contrast, carnosic acid, carnosol, rosmarinic acid, and ursolic acid had no effects on the accumulation of calcein, a fluorescent substrate of MRP1, in KB/MRP cells. The ATPase activities of P-glycoprotein were stimulated by carnosic acid, carnosol, and ursolic acid. KB-C2 cells were sensitized to vinblastine cytotoxicity by carnosic acid, showing that carnosic acid reverses multidrug resistance. These results suggest that rosemary phytochemicals, such as carnosic acid, have inhibitory effects on anticancer drug efflux transporter P-glycoprotein and may become useful to enhance the efficacy of cancer chemotherapy. PMID:19944162

Nabekura, Tomohiro; Yamaki, Takeshi; Hiroi, Takashi; Ueno, Kazuyuki; Kitagawa, Shuji

2010-03-01

137

Impact of genetic deficiencies of P-glycoprotein and breast cancer resistance protein on pharmacokinetics of aripiprazole and dehydroaripiprazole.  

Science.gov (United States)

Abstract 1.?We investigated how deficiencies in P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) affect the pharmacokinetics of atypical antipsychotics aripiprazole and its active metabolite (dehydroaripiprazole) using normal Friend leukemia virus strain B (FVB) mice, BCRP knockout (Bcrp[-/-]) mice, and P-gp and BCRP triple knockout (Mdr1a/1b[-/-]Bcrp[-/-]) mice. 2.?While plasma concentrations of aripiprazole and dehydroaripiprazole after oral administration were slightly higher in both Bcrp(-/-) and Mdr1a/1b(-/-)/Bcrp(-/-) mice than in normal FVB mice, the difference was not marked. The increase in absolute bioavailability (F) compared with normal mice (approximately 1.3-fold increase) was comparable between Bcrp(-/-) and Mdr1a/1b(-/-)/Bcrp(-/-) mice. This finding suggests that BCRP may be involved in the intestinal absorption of aripiprazole in mice, albeit with minimal contribution to absorption at best. 3.?In contrast, the brain-to-plasma concentration ratio (Kp,brain) for aripiprazole and dehydroaripiprazole after oral administration was significantly higher in Mdr1a/1b(-/-)/Bcrp(-/-) mice than in normal mice, whereas Bcrp(-/-) mice exhibited Kp,brain values similar to those in normal mice. In addition, the Kp,brain values in Mdr1a/1b(-/-)/Bcrp(-/-) mice were not drastically different from those previously reported in Mdr1a/1b(-/-) mice, suggesting that brain penetration of aripiprazole and dehydroaripiprazole can be affected by P-gp, but with little synergistic effect of BCRP. PMID:24666334

Nagasaka, Yasuhisa; Sano, Tomokazu; Oda, Kazuo; Kawamura, Akio; Usui, Takashi

2014-10-01

138

The multidrug resistance P-glycoprotein modulates cell regulatory volume decrease.  

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Cell volume is frequently down-regulated by the activation of anion channels. The role of cell swelling-activated chloride channels in cell volume regulation has been studied using the patch-clamp technique and a non-invasive microspectrofluorimetric assay for changes in cell volume. The rate of activation of these chloride channels was shown to limit the rate of regulatory volume decrease (RVD) in response to hyposmotic solutions. Expression of the human MDR1 or mouse mdr1a genes, but not th...

Valverde, Ma; Bond, Td; Hardy, Sp; Taylor, Jc; Higgins, CF; Altamirano, J.; Alvarez-leefmans, Fj

1996-01-01

139

Effect of curcumin on human colon cancer multidrug resistance in vitro and in vivo  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english OBJECTIVE: To determine whether curcumin reverses the multidrug resistance of human colon cancer cells in vitro and in vivo. METHODS: In a vincristine-resistant cell line of human colon cancer, the cell viability of curcumin-treated cells was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5- [...] diphenyltetrazolium bromide assay. Rhodamine123 efflux was evaluated to detect P-glycoprotein transporter activity, and expression of the multidrug resistance protein 1 and survivin genes was analyzed by reverse transcription polymerase chain reaction and western blotting. In addition, xenograft mouse tumors were grown and treated with curcumin. The morphology of the xenografts was investigated by hematoxylin-eosin staining. The in vivo expression of the multidrug resistance gene and P-glycoprotein and survivin genes and proteins was observed using reverse transcription-polymerase chain reaction and western blotting, respectively. RESULTS: Curcumin was not obviously toxic to the vincristine-resistant human colon cancer cells at concentrations less than 25 ?M, but the growth of cells was significantly inhibited. At concentrations greater than 25 ?M, curcumin was toxic in a concentration-dependent manner. The sensitivity of cells to vincristine, cisplatin, fluorouracil, and hydroxycamptothecin was enhanced, intracellular Rhodamine123 accumulation was increased (p

Wei-Dong, Lu; Yong, Qin; Chuang, Yang; Lei, Li.

2013-05-01

140

The dual cyclooxygenase/5-lipoxygenase inhibitor licofelone attenuates p-glycoprotein-mediated drug resistance in the injured spinal cord.  

Science.gov (United States)

There are currently no proven effective treatments that can improve recovery of function in spinal cord injury (SCI) patients. Many therapeutic compounds have shown promise in pre-clinical studies, but clinical trials have been largely unsuccessful. P-glycoprotein (Pgp, Abcb1b) is a drug efflux transporter of the blood-spinal cord barrier that limits spinal cord penetration of blood-borne xenobiotics. Pathological Pgp upregulation in diseases such as cancer causes heightened resistance to a broad variety of therapeutic drugs. Importantly, several drugs that have been evaluated for the treatment of SCI, such as riluzole, are known substrates of Pgp. We therefore examined whether Pgp-mediated pharmacoresistance diminishes delivery of riluzole to the injured spinal cord. Following moderate contusion injury at T10 in male Sprague-Dawley rats, we observed a progressive, spatial spread of increased Pgp expression from 3 days to 10 months post-SCI. Spinal cord uptake of i.p.-delivered riluzole was significantly reduced following SCI in wild type but not Abcb1a-knockout rats, highlighting a critical role for Pgp in mediating drug resistance following SCI. Because inflammation can drive Pgp upregulation, we evaluated the ability of the new generation dual anti-inflammatory drug licofelone to promote spinal cord delivery of riluzole following SCI. We found that licofelone both reduced Pgp expression and enhanced riluzole bioavailability within the lesion site at 72?h post-SCI. This work highlights Pgp-mediated drug resistance as an important obstacle to therapeutic drug delivery for SCI, and suggests licofelone as a novel combinatorial treatment strategy to enhance therapeutic drug delivery to the injured spinal cord. PMID:22947335

Dulin, Jennifer N; Moore, Meredith L; Grill, Raymond J

2013-02-01

 
 
 
 
141

Down-regulation of P-glycoprotein expression in MDR breast cancer cell MCF-7/ADR by honokiol.  

Science.gov (United States)

P-glycoprotein accounts for the most intrinsic and acquired cancer multidrug resistance. To inhibit the expression of P-glycoprotein is one of the effective ways to reverse cancer drug resistance. Honokiol, a naturally occurring compound, has been demonstrated to combat cancer through mechanisms including inhibition of angiogenesis and induction of apoptosis. Here, we show that honokiol down-regulated the expression of P-glycoprotein at mRNA and protein levels in MCF-7/ADR, a human breast MDR cancer cell line. The down-regulation of P-glycoprotein was accompanied with a partial recovery of the intracellular drug accumulation, and of the sensitivities toward adriamycin. This study reveals a novel function of honokiol as an anti-cancer agent. PMID:16406853

Xu, Dong; Lu, Qinghua; Hu, Xun

2006-11-18

142

Functional imaging of the multidrug resistance in vivo  

Energy Technology Data Exchange (ETDEWEB)

Although diverse mechanisms are involved in multidrug resistance for chemotherapeutic drugs, the development of cellular P-glycoprotein(Pgp) and multidrug-resistance associated protein (MRP) are improtant factors in the chemotherapy failure to cancer. Various detection assays provide information about the presence of drug efflux pumps at the mRNA and protein levels. However these methods do not yield information about dynamic function of Pgp and MRP in vivo. Single photon emission tomograpy (SPECT) and positron emission tomograpy (PET) are available for the detection of Pgp and MRP-mediated transport. {sup 99m}Tc-sestaMIBI and other {sup 99m}Tc-radiopharmaceuticals are substrates for Pgp and MRP, and have been used in clinical studies of tumor imaging, and to visualize blockade of Pgp-mediated transport after modulation of Pgp pump. Colchicine, verapamil and daunorubicin labeled with {sup 11}C have been evaluated for the quantification of Pgp-mediated transport with PET in vivo and reported to be feasible substrates with which to image Pgp function in tumors. Leukotrienes are specific substrates for MRP and N-{sup (11}C]acetyl-leukotriene E4 provides an opportunity to study MRP function non-invasively in vivo. Results obtained from recent publications are reviewed to confirm the feasibility of using SPECT and PET to study the functionality of MDR transportes in vivo.

Lee, Jae Tae [College of Medicine, Kyungpook National Univ., Taegu (Korea, Republic of)

2001-07-01

143

Effects of dietary ingredients on function and expression of P-glycoprotein in human intestinal epithelial cells.  

Science.gov (United States)

The present study was conducted to investigate the functional and transcriptional modulation of P-glycoprotein (MDR-1) by several dietary ingredients (piperine, capsaicin, daidzein, genistein, sesamin, curcumin, taurine) in vinblastine-resistant colon carcinoma LS-180 cells (LS-180V cells). The amount of rhodamine 123 accumulated in LS-180V cells was significantly increased by capsaicin, piperine and sesamin, whereas it was significantly reduced by daidzein and genistein which stimulated the efflux of rhodamine 123. These results suggest that the P-glycoprotein-mediated efflux is inhibited by piperine, capsaicin and sesamin and stimulated by daidzein and genistein. The concurrent addition of piperine and capsaicin seemed to inhibit synergistically the P-glycoprotein-mediated efflux. Pretreatment with sesamin for 48 h caused a significant increase in MDR1 mRNA expression without a significant effect on the expression of P-glycoprotein or accumulation of rhodamine 123. Similar pretreatment with other ingredients had little effect on the expression of MDR1 mRNA or P-glycoprotein, suggesting that they do not cause transcriptional modulation of P-glycoprotein. Piperine, genistein and curcumin have been suggested to stimulate P-glycoprotein-mediated efflux without increasing P-glycoprotein expression. In LS-180V cells, significant increases in mRNA levels of multi-drug resistance associated protein 1 (MRP1) or MRP3 were observed on pretreatment with capsaicin, daidzein, piperine and sesamin. In conclusion, our results suggest that P-glycoprotein-mediated efflux is significantly affected by dietary ingredients. Also, capsaicin, daidzein, piperine and sesamin increased significantly the mRNA expression of MRP1 or MRP3. Thus, the present study provides further evidence that repeated exposure to dietary ingredients can cause drug-food interactions by affecting the function and mRNA expression of intestinal transporters such as P-glycoprotein. PMID:20118549

Okura, Takashi; Ibe, Michiko; Umegaki, Keizo; Shinozuka, Kazumasa; Yamada, Shizuo

2010-01-01

144

Effects of naturally occurring polymethyoxyflavonoids on cell growth, p-glycoprotein function, cell cycle, and apoptosis of daunorubicin-resistant T lymphoblastoid leukemia cells.  

Science.gov (United States)

Effects of polymethoxyflavonoids tangeretin and nobiletin and the related polyphenolic compounds baicalein, wogonin, quercetin, and epigallocatechin gallate on the cell growth, P-glycoprotein function, apoptosis, and cell cycle of human T lymphoblastoid leukemia MOLT-4 and its daunorubicin-resistant cells were investigated. The IC50 values of these compounds on the cell growth were 7.1-32.2 micromol/L, and the inhibitory effects were observed to be almost equal to the parent MOLT-4 and the daunorubicin-resistant cells. Tangeretin and nobiletin showed the strongest effects with the IC50 values of 7.1-14.0 micromol/L. These polymethoxyflavonoids inhibited the P-glycoprotein function and significantly influenced the cell cycle (p<.05), whereas they did not induce apoptosis. PMID:19863351

Ishii, Kimiko; Tanaka, Sachiko; Kagami, Keisuke; Henmi, Kayo; Toyoda, Hiroo; Kaise, Toshikazu; Hirano, Toshihiko

2010-03-01

145

Multidrug resistance proteins expression in glioma patients with epilepsy.  

Science.gov (United States)

Epilepsy occurs in glioma, especially in low-grade glioma (LGG), but also in glioblastoma (GBM). In about 20 % of patients pharmacological treatment with anti-epileptic drugs (AEDs) fails. Refractory epilepsy is a multifactorial phenomenon not yet completely understood. The multidrug resistance phenotype was initially associated to P-glycoprotein (Pgp), an ATP-dependent transporter belonging to the same superfamily of multidrug resistance-associated proteins (MRPs). Glutathione-S-transferase-? (GST-?) is also involved in refractory epilepsy. In the present work we investigated the expression of Pgp, MRP1, MRP3 and GST-? in surgical specimens obtained from 35 patients with glioma and epilepsy. We observed MRP1 expression in tumor and endothelial cells (EC), MRP3 and Pgp expression mainly in ECs and GST-? predominantly in tumor cells (TC). MRP1 and MRP3 were more expressed in high grade glioma (HGG) than in LGG. In 6 cases we could compare tumor and periphery detecting the same MRP1 and Pgp expression, while MRP3 was mainly expressed in the tumor. We observed a trend of a better outcome in seizure control associated with a lower expression of MRP1 and MRP3. MRP3 was statistically more expressed in TCs of HGG than LGG (p = 0.0401) and more expressed in tumor than in periphery, in agreement with recent works that identify MRP3 as a potential target in GBM. Moreover, MRP3 was investigated in association with refractory epilepsy for the first time in our study and it was less expressed in patients with complete response to AEDs (p = 0.0550). Our preliminary data show an association between multidrug resistance transporters and refractory epilepsy in glioma. PMID:22832898

Calatozzolo, Chiara; Pollo, Bianca; Botturi, Andrea; Dinapoli, Loredana; Carosi, Mariantonia; Salmaggi, Andrea; Maschio, Marta

2012-10-01

146

Facing multi-drug resistant tuberculosis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Multi-drug resistant tuberculosis (MDR-TB) is caused by Mycobacterium tuberculosis strains resistant to at least two of the most effective anti-tuberculosis drugs (i.e., isoniazid and rifampicin). Therapeutic regimens based on second- and third-line anti-tuberculosis medicines showed poor efficacy, safety, and tolerability profiles. It was estimated that in 2012 the multi-drug resistant tuberculosis incidence ranged from 300,000 to 600,000 cases, mainly diagnosed in the E...

Sotgiu, Giovanni; Migliori, Giovanni Battista

2014-01-01

147

Identification of the cyclosporin-binding site in P-glycoprotein.  

Science.gov (United States)

The binding site of cyclosporin A to P-glycoprotein was characterized by using a multidrug-resistant Chinese hamster ovary cell line. P-glycoprotein photolabeled with diazirine-cyclosporin A analogue was purified by a two-step process involving continuous elution electrophoresis followed by wheat germ agglutinin-agarose precipitation. The cyclosporin A covalently bound to P-glycoprotein and to subsequent proteolytic fragments was detected by Western blot analysis using a monoclonal antibody against cyclosporin A. Proteolytic digestion of purified P-glycoprotein by V8 generated a major fragment of 15 kDa photolabeled by cyclosporin A, while proteolysis of P-glycoprotein photolabeled by [125I]-iodoaryl azidoprazosin generated a major fragment of 7 kDa. Limited proteolysis of cyclosporin A-photolabeled P-glycoprotein with trypsin indicated that the major binding site for cyclosporin A was in the C-terminal half of the protein. This cyclosporin A binding site was further characterized with chemical agents (N-chlorosuccinimide, cyanogen bromide, and 2-nitro-5-thiocyanobenzoate). These three chemical agents established a proteolytic profile of P-glycoprotein for fragments photolabeled with cyclosporin A and for fragments that contained the C494 and C219 epitopes. The smallest fragments generated by these chemical agents include the transmembrane domains (TMs) 10, 11, and 12 of P-glycoprotein. When the fragments generated by these chemical agents are aligned, the region that binds cyclosporin A is reduced to the 953-1007 residues. These combined results suggest that the major binding site of cyclosporin A occurs between the end of TM 11 and the end of TM 12. PMID:9922180

Demeule, M; Laplante, A; Murphy, G F; Wenger, R M; Béliveau, R

1998-12-22

148

Nanodrug Delivery in Reversing Multidrug Resistance in Cancer Cells  

Directory of Open Access Journals (Sweden)

Full Text Available Different mechanisms in cancer cells become resistant to one or more chemotherapeutics is known as multidrug resistance(MDR which hinders chemotherapy efficacy. Potential factors for MDR includes enhanced drug detoxification, decreased drug uptake, increased intracellular nucleophiles levels, enhanced repair of drug induced DNA damage, overexpression of drug transporter such as P-glycoprotein(P-gp, multidrug resistance-associated proteins(MRP1, MRP2 and breast cancer resistance protein(BCRP. Currently nanoassemblies such as polymeric/solid lipid/inorganic/metal nanoparticles, quantum dots, dendrimers, liposomes, micelles has emerged as an innovative, effective and promising platforms for treatment of drug resistant cancer cells. Nanocarriers have potential to improve drug therapeutic index, ability for multifunctionality, divert ABC-transporter mediated drug efflux mechanism and selective targeting to tumor cells, cancer stem cells, tumor initiating cells or cancer microenvironment. Selective nanocarrier targeting to tumor overcomes dose-limiting side effects, lack of selectivity, tissue toxicity, limited drug access to tumor tissues, high drug doses and emergence of multiple drug resistance with conventional or combination chemotherapy. Current review highlights various nanodrug delivery systems to overcome mechanism of MDR by neutralizing, evading or exploiting the drug efflux pumps and those independent of drug efflux pump mechanism by silencing Bcl-2 and HIF1? gene expressions by siRNA and miRNA, modulating ceramide levels and targeting NF-?B. “Theragnostics” combining a cytotoxic agent, targeting moiety, chemosensitizing agent and diagnostic imaging aid are highlighted as effective and innovative systems for tumor localization and overcoming MDR. Physical approaches such as combination of drug with thermal/ultrasound/photodynamic therapies to overcome MDR are focused. The review focuses on newer drug delivery systems developed to overcome MDR in cancer cell

MayurYergeri

2014-07-01

149

Nanodrug delivery in reversing multidrug resistance in cancer cells.  

Science.gov (United States)

Different mechanisms in cancer cells become resistant to one or more chemotherapeutics is known as multidrug resistance (MDR) which hinders chemotherapy efficacy. Potential factors for MDR includes enhanced drug detoxification, decreased drug uptake, increased intracellular nucleophiles levels, enhanced repair of drug induced DNA damage, overexpression of drug transporter such as P-glycoprotein(P-gp), multidrug resistance-associated proteins (MRP1, MRP2), and breast cancer resistance protein (BCRP). Currently nanoassemblies such as polymeric/solid lipid/inorganic/metal nanoparticles, quantum dots, dendrimers, liposomes, micelles has emerged as an innovative, effective, and promising platforms for treatment of drug resistant cancer cells. Nanocarriers have potential to improve drug therapeutic index, ability for multifunctionality, divert ABC-transporter mediated drug efflux mechanism and selective targeting to tumor cells, cancer stem cells, tumor initiating cells, or cancer microenvironment. Selective nanocarrier targeting to tumor overcomes dose-limiting side effects, lack of selectivity, tissue toxicity, limited drug access to tumor tissues, high drug doses, and emergence of multiple drug resistance with conventional or combination chemotherapy. Current review highlights various nanodrug delivery systems to overcome mechanism of MDR by neutralizing, evading, or exploiting the drug efflux pumps and those independent of drug efflux pump mechanism by silencing Bcl-2 and HIF1? gene expressions by siRNA and miRNA, modulating ceramide levels and targeting NF-?B. "Theragnostics" combining a cytotoxic agent, targeting moiety, chemosensitizing agent, and diagnostic imaging aid are highlighted as effective and innovative systems for tumor localization and overcoming MDR. Physical approaches such as combination of drug with thermal/ultrasound/photodynamic therapies to overcome MDR are focused. The review focuses on newer drug delivery systems developed to overcome MDR in cancer cell. PMID:25071577

Kapse-Mistry, Sonali; Govender, Thirumala; Srivastava, Rohit; Yergeri, Mayur

2014-01-01

150

Collateral Sensitivity of Multidrug-Resistant Cells to the Orphan Drug Tiopronin  

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A major challenge in the treatment of cancer is multidrug resistance (MDR) that develops during chemotherapy. Here we demonstrate that tiopronin (1), a thiol-substituted N-propanoylglycine derivative, was selectively toxic to a series of cell lines expressing the drug efflux pump P-glycoprotein (P-gp, ABCB1) and MRP1 (ABCC1). Treatment of MDR cells with 1 led to instability of the ABCB1 mRNA and consequently a reduction in P-gp protein, despite functional assays demonstrating that tiopronin d...

Goldsborough, Andrew S.; Handley, Misty D.; Dulcey, Andre?s E.; Pluchino, Kristen M.; Kannan, Pavitra; Brimacombe, Kyle R.; Hall, Matthew D.; Griffiths, Gary; Gottesman, Michael M.

2011-01-01

151

The inhibitory and combinative mechanism of HZ08 with P-glycoprotein expressed on the membrane of Caco-2 cell line  

International Nuclear Information System (INIS)

Recently, the research and development of agents to reverse the phenomenon of multidrug resistance has been an attractive goal as well as a key approach to elevating the clinical survival of cancer patients. Although three generations of P-glycoprotein modulators have been identified, poor clearance and metabolism render these agents too toxic to be used in clinical application. HZ08, which has been under investigation for several years, shows a dramatic reversal effect with low cytotoxicity. For the first time, we aimed to describe the interaction between HZ08 and P-glycoprotein in Caco-2 cell line in which P-glycoprotein is overexpressed naturally. Cytotoxicity and multidrug resistance reversal assays, together with flow cytometry, fluorescence microscopy and siRNA interference as well as Caco-2 monolayer transport model were employed in this study to evaluate the interaction between HZ08 and P-glycoprotein. This study revealed that HZ08 was capable of reversing adriamycin resistance mediated by P-glycoprotein as a result of intracellular enhancement of adriamycin accumulation, which was found to be superior to verapamil. In addition, we confirmed that HZ08 suppressed the transport of Rhodamine123 in the Caco-2 monolayer model but had little effect on P-glycoprotein expression. The transport of HZ08 was diminished by P-glycoprotein inhibitors (verapamil and LY335979) and its accumulation was increased via siRNA targeting MDR1 in Caco-2 cells. Furthermore, considering the binding site of P-glycoprotein, verapamil performed as a competitive inhibitor with HZ08. In conclusion, as a P-glycoprotein substrate, HZ08 inhibited P-glycoprotein activity and may share the same binding site of verapamil to P-glycoprotein. - Highlights: • The cytotoxicity and reversing effect of HZ08 was measured in Caco-2 cell line. • HZ08 inhibited the transport of Rhodamine123 across Caco-2 cell monolayer. • The efflux ratio of HZ08 was dropped when combined with P-glycoprotein inhibitors. • The accumulation of HZ08 increased via gene interference targeting P-glycoprotein. • HZ08 competitively bound to P-glycoprotein under the presence of verapamil

152

Human intestinal P-glycoprotein activity estimated by the model substrate digoxin  

DEFF Research Database (Denmark)

P-glycoprotein (Pgp) plays a part in the intestinal uptake of xenobiotics and has been associated with susceptibility to ulcerative colitis. The aim of this study was to examine Pgp activity in relation to age, gender, medical treatment (rifampicin or ketoconazole) and the multidrug resistance (MDR1) gene single nucleotide polymorphisms (SNPs) G2677T and C3435T using the model drug digoxin.

Larsen, U L; Hyldahl Olesen, L

2007-01-01

153

Exhaustive Sampling of Docking Poses Reveals Binding Hypotheses for Propafenone Type Inhibitors of P-Glycoprotein  

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Overexpression of the xenotoxin transporter P-glycoprotein (P-gp) represents one major reason for the development of multidrug resistance (MDR), leading to the failure of antibiotic and cancer therapies. Inhibitors of P-gp have thus been advocated as promising candidates for overcoming the problem of MDR. However, due to lack of a high-resolution structure the concrete mode of interaction of both substrates and inhibitors is still not known. Therefore, structure-based design studies have to r...

Klepsch, Freya; Chiba, Peter; Ecker, Gerhard F.

2011-01-01

154

Anthracyclines, proteasome activity and multi-drug-resistance  

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Abstract Background P-glycoprotein is responsible for the ATP-dependent export of certain structurally unrelated compounds including many chemotherapeutic drugs. Amplification of P-glycoprotein activity can result in multi-drug resistance and is a common cause of chemotherapy treatment failure. Therefore, there is an ongoing search for inhibitors of P-glycoprotein. Observations that cyclosporin A, and certain other substances, inhibit both the proteasome and P-glycoprotein le...

2005-01-01

155

Detection of multidrug resistance using molecular nuclear technique  

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Although the outcome of cancer patients after cytotoxic chemotherapy is related diverse mechanisms, multidrug resistance (MDR) for chemotherapeutic drugs due to cellular P-glycoprotein (Pgp) or multidrug-resistance associated protein (MRP) is most important factor in the chemotherapy failure to cancer. A large number of pharmacologic compounds, including verapamil, quinidine, tamoxifen, cyclosporin A and quinolone derivatives have been reported to overcome MDR. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are available for the detection of Pgp and MRP-mediated transporter. {sup 99}m-Tc-MIBI and other {sup 99}m-Tc-radiopharmaceuticals are substrates for Pgp and MRP, and have been used in clinical studies for tumor imaging, and to visualize blockade of Pgp-mediated transport after modulation of Pgp pump. Colchicine, verapamil and daunorubicin labeled with {sup 11}C have been evaluated for the quantification of Pgp-mediated transport with PET in vivo and reported to be feasible substrates with which to image Pgp function in tumors. Leukotrienes are specific substrates for MRP and N-({sup 11}C)acetyl-leukotriene E4 provides an opportunity to study MRP function non-invasively in vivo. SPECT and PET pharmaceuticals have successfully used to evaluate pharmacologic effects of MDR modulators. Imaging of MDR and reversal of MDR with bioluminescence in a living animal is also evaluated for future clinical trial. We have described recent advances in molecular imaging of MDR and reviewed recent publications regarding feasibility of SPECT and PET imaging to study the functionality of MDR transporters in vivo.

Lee, Jae Tae; Ahn, Byeong Cheol [School of Medicine, Kyungpook National Univ., Daegu (Korea, Republic of)

2004-04-01

156

Modulation of human multidrug-resistance MDR-1 gene by natural curcuminoids  

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Full Text Available Abstract Background Multidrug resistance (MDR is a phenomenon that is often associated with decreased intracellular drug accumulation in patient's tumor cells resulting from enhanced drug efflux. It is related to the overexpression of a membrane protein, P-glycoprotein (Pgp-170, thereby reducing drug cytotoxicity. A variety of studies have tried to find MDR modulators which increase drug accumulation in cancer cells. Methods In this study, natural curcuminoids, pure curcumin, demethoxycurcumin and bisdemethoxycurcumin, isolated from turmeric (Curcuma longa Linn, were compared for their potential ability to modulate the human MDR-1 gene expression in multidrug resistant human cervical carcinoma cell line, KB-V1 by Western blot analysis and RT-PCR. Results Western blot analysis and RT-PCR showed that all the three curcuminoids inhibited MDR-1 gene expression, and bisdemethoxycurcumin produced maximum effect. In additional studies we found that commercial grade curcuminoid (approximately 77% curcumin, 17% demethoxycurcumin and 3% bisdemthoxycurcumin decreased MDR-1 gene expression in a dose dependent manner and had about the same potent inhibitory effect on MDR-1 gene expression as our natural curcuminoid mixtures. Conclusion These results indicate that bisdemethoxycurcumin is the most active of the curcuminoids present in turmeric for modulation of MDR-1 gene. Treatment of drug resistant KB-V1 cells with curcumin increased their sensitivity to vinblastine, which was consistent with a decreased MDR-1 gene product, a P-glycoprotein, on the cell plasma membrane. Although many drugs that prevent the P-glycoprotein function have been reported, this report describes the inhibition of MDR-1 expression by a phytochemical. The modulation of MDR-1 expression may be an attractive target for new chemosensitizing agents.

Buddhasukh Duang

2004-04-01

157

Microvesicles mediate transfer of P-glycoprotein to paclitaxel-sensitive A2780 human ovarian cancer cells, conferring paclitaxel-resistance.  

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The overexpression of P-glycoprotein (P-gp) causes resistance to chemotherapy in human ovarian cancer. However, the underlying mechanism remains unclear. In the present study, we showed that, at membrane-bound protein level, P-gp was 'shared' between human ovarian cancer cells by the intercellular transfer of microvesicles (MVs). Paclitaxel-resistant human ovarian cancer cells (A2780/PTX) readily formed and released P-gp-containing MVs into the extracellular space compared with the wild-type parental line (A2780/WT). Shedding MVs bound to the chemosensitive A2780/WT cells in a time- and dose-dependent manner, transferring P-gp via the microenvironment. MV-mediated transfer of P-gp led to redistribution of the chemotherapeutic drug adriamycin in recipient cells (A2780/WT), which displayed 5- and 5-fold higher resistance to adriamycin and paclitaxel, respectively. Thus, these findings demonstrate a new mechanism of drug-resistance acquisition via MVs. PMID:24877693

Zhang, Fang-fang; Zhu, Yi-fei; Zhao, Qian-nan; Yang, Dan-tong; Dong, Ye-ping; Jiang, Li; Xing, Wei-xing; Li, Xi-yuan; Xing, Hui; Shi, Mei; Chen, Yun; Bruce, Iain C; Jin, Jian; Ma, Xin

2014-09-01

158

Poly(ethylene glycol)-conjugated multi-walled carbon nanotubes as an efficient drug carrier for overcoming multidrug resistance  

International Nuclear Information System (INIS)

The acquisition of multidrug resistance poses a serious problem in chemotherapy, and new types of transporters have been actively sought to overcome it. In the present study, poly(ethylene glycol)-conjugated (PEGylated) multi-walled carbon nanotubes (MWCNTs) were prepared and explored as drug carrier to overcome multidrug resistance. The prepared PEGylated MWCNTs penetrated into mammalian cells without damage plasma membrane, and its accumulation did not affect cell proliferation and cell cycle distribution. More importantly, PEGylated MWCNTs accumulated in the multidrug-resistant cancer cells as efficient as in the sensitive cancer cells. Intracellular translocation of PEGylated MWCNTs was visualized in both multidrug-resistant HepG2-DR cells and sensitive HepG2 cells, as judged by both fluorescent and transmission electron microscopy. PEGylated MWCNTs targeted cancer cells efficiently and multidrug-resistant cells failed to remove the intracellular MWCNTs. However, if used in combination with drugs without conjugation, PEGylated MWCNTs prompted drug efflux in MDR cells by stimulating the ATPase activity of P-glycoprotein. This study suggests that PEGylated MWCNTs can be developed as an efficient drug carrier to conjugate drugs for overcoming multidrug resistance in cancer chemotherapy.

159

ABC transporters as multidrug resistance mechanisms and the development of chemosensitizers for their reversal  

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Full Text Available Abstract One of the major problems related with anticancer chemotherapy is resistance against anticancer drugs. The ATP-binding cassette (ABC transporters are a family of transporter proteins that are responsible for drug resistance and a low bioavailability of drugs by pumping a variety of drugs out cells at the expense of ATP hydrolysis. One strategy for reversal of the resistance of tumor cells expressing ABC transporters is combined use of anticancer drugs with chemosensitizers. In this review, the physiological functions and structures of ABC transporters, and the development of chemosensitizers are described focusing on well-known proteins including P-glycoprotein, multidrug resistance associated protein, and breast cancer resistance protein.

Choi Cheol-Hee

2005-10-01

160

Functional study of the novel multidrug resistance gene HA117 and its comparison to multidrug resistance gene 1  

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Full Text Available Abstract Background The novel gene HA117 is a multidrug resistance (MDR gene expressed by all-trans retinoic acid-resistant HL-60 cells. In the present study, we compared the multidrug resistance of the HA117 with that of the classical multidrug resistance gene 1 (MDR1 in breast cancer cell line 4T1. Methods Transduction of the breast cancer cell line 4T1 with adenoviral vectors encoding the HA117 gene and the green fluorescence protein gene (GFP (Ad-GFP-HA117, the MDR1 and GFP (Ad-GFP-MDR1 or GFP (Ad-GFP was respectively carried out. The transduction efficiency and the multiplicity of infection (MOI were detected by fluorescence microscope and flow cytometry. The transcription of HA117 gene and MDR1 gene were detected by reverse transcription polymerase chain reaction (RT-PCR. Western blotting analysis was used to detect the expression of P-glycoprotein (P-gp but the expression of HA117 could not be analyzed as it is a novel gene and its antibody has not yet been synthesized. The drug-excretion activity of HA117 and MDR1 were determined by daunorubicin (DNR efflux assay. The drug sensitivities of 4T1/HA117 and 4T1/MDR1 to chemotherapeutic agents were detected by Methyl-Thiazolyl-Tetrazolium (MTT assay. Results The transducted efficiency of Ad-GFP-HA117 and Ad-GFP-MDR1 were 75%-80% when MOI was equal to 50. The transduction of Ad-GFP-HA117 and Ad-GFP-MDR1 could increase the expression of HA117 and MDR1. The drug resistance index to Adriamycin (ADM, vincristine (VCR, paclitaxel (Taxol and bleomycin (BLM increased to19.8050, 9.0663, 9.7245, 3.5650 respectively for 4T1/HA117 and 24.2236, 11.0480, 11.3741, 0.9630 respectively for 4T1/MDR1 as compared to the control cells. There were no significant differences in drug sensitivity between 4T1/HA117 and 4T1/MDR1 for the P-gp substrates (ADM, VCR and Taxol (P Conclusions These results confirm that HA117 is a strong MDR gene in both HL-60 and 4T1 cells. Furthermore, our results indicate that the MDR mechanism of the HA117 gene may not be similar to that of MDR1.

Chen Tingfu

2010-07-01

 
 
 
 
161

P-glycoprotein alters blood–brain barrier penetration of antiepileptic drugs in rats with medically intractable epilepsy  

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Full Text Available Aimei Ma,1,* Cuicui Wang,2,3,* Yinghui Chen,2,3 Weien Yuan4 1Department of Neurology, The People's Hospital of Shanxi Province, Taiyuan, 2Department of Neurology, Jinshan Hospital, Fudan University, 3Department of Neurology, Shanghai Medical College, Shanghai, 4School of Pharmacy, Shanghai JiaoTong University, Shanghai, People's Republic of China *These authors contributed equally to this work Abstract: P-glycoprotein is one of the earliest known multidrug transporters and plays an important role in resistance to chemotherapeutic drugs. In this study, we detected levels of P-glycoprotein and its mRNA expression in a rat brain model of medically intractable epilepsy established by amygdala kindling and drug selection. We investigated whether inhibition of P-glycoprotein affects the concentration of antiepileptic drugs in cortical extracellular fluid. We found that levels of P-glycoprotein and its mRNA expression were upregulated in epileptic cerebral tissue compared with cerebral tissue from normal rats. The concentrations of two antiepileptic drugs, carbamazepine and phenytoin, were very low in the cortical extracellular fluid of rats with medically intractable epilepsy, and were restored after blockade of P-glycoprotein by verapamil. These results show that increased P-glycoprotein levels alter the ability of carbamazepine and phenytoin to penetrate the blood–brain barrier and reduce the concentrations of these agents in extracellular cortical fluid. High P-glycoprotein levels may be involved in resistance to antiepileptic drugs in medically intractable epilepsy. Keywords: P-glycoprotein, medically intractable epilepsy, antiepileptic drugs, amygdala kindling, verapamil

Ma A

2013-12-01

162

Overcoming of P-glycoprotein mediated vincristine resistance of L1210/VCR mouse leukemic cells could be induced by pentoxifyline but not by theophylline and caffeine.  

Science.gov (United States)

Effects of xanthine derivatives (pentoxifylline, caffeine, theophylline, 1-methyl-3-isobutylxanthine) on P-glycoprotein mediated vincristine resistance of L1210/VCR mouse leukemic cell subline were studied. From the applied xanthines only PTX was found to reverse the vincristine resistance of the above cells. Moreover, only PTX, but not other xanthine, increased the accumulation of [3H]vincristine by L1210/VCR cells. Thus it may be concluded that PTX-induced reversal of vincristine resistance could not be explained from the point of known pharmacological effects of PTX that are common for other xanthines such as inhibition of phosphodiesterase activity, calcium mobilizing effect, inhibition of tumor necrosis factor alpha (TNF), etc. PMID:8843953

Stefanková, Z; Barancík, M; Breier, A

1996-01-01

163

Overcoming of P-glycoprotein mediated vincristine resistance of L1210/VCR mouse leukemic cells could be induced by pentoxifylline but not by theophylline and caffeine  

International Nuclear Information System (INIS)

Effects of xanthine derivatives (pentoxifylline (PTX), caffeine, theophylline, 1-methyl-3-isobutylxanthine) on P-glycoprotein mediated vincristine resistance of L1210/VCR mouse leukemic cell sub-line were studied. From the applied xanthines only PTX was found to reverse the vincristine resistance of the above cells. Moreover, only PTX, but not other xanthine, increased the accumulation of [3H]vincristine by L1210/VCR cells. Thus it may be concluded that PTX-induced reversal of vincristine (VCR) resistance could not be explained from the point of known pharmacological effects of PTX that are common for other xanthines such as inhibition of phosphodiesterase activity, calcium mobilizing effect, inhibition of tumor necrosis factor ? (TNF), etc. (author)

164

Schistosoma mansoni P-glycoprotein levels increase in response to praziquantel exposure and correlate with reduced praziquantel susceptibility  

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One potential physiological target for new antischistosomals is the parasite’s system for excretion of wastes and xenobiotics. P-glycoprotein (Pgp), a member of the ATP-binding cassette superfamily of proteins, is an ATP-dependent efflux pump involved in transport of toxins and xenobiotics from cells. In vertebrates, increased expression of Pgp is associated with multidrug resistance in tumor cells. Pgp may also play a role in drug resistance in helminths. In this report, we examine the rel...

Messerli, Shanta M.; Kasinathan, Ravi S.; Morgan, William; Spranger, Stefani; Greenberg, Robert M.

2009-01-01

165

Kinetic Validation of the Models for P-Glycoprotein ATP Hydrolysis and Vanadate-Induced Trapping. Proposal for Additional Steps  

Science.gov (United States)

P-Glycoprotein, a member of the ATP-binding cassette (ABC) superfamily, is a multidrug transporter responsible for cellular efflux of hundreds of structurally unrelated compounds, including natural products, many clinically used drugs and anti-cancer agents. Expression of P-glycoprotein has been linked to multidrug resistance in human cancers. ABC transporters are driven by ATP hydrolysis at their two cytoplasmic nucleotide-binding domains, which interact to form a closed ATP-bound sandwich dimer. Intimate knowledge of the catalytic cycle of these proteins is clearly essential for understanding their mechanism of action. P-Glycoprotein has been proposed to hydrolyse ATP by an alternating mechanism, for which there is substantial experimental evidence, including inhibition of catalytic activity by trapping of ortho-vanadate at one nucleotide-binding domain, and the observation of an asymmetric occluded state. Despite many studies of P-glycoprotein ATPase activity over the past 20 years, no comprehensive kinetic analysis has yet been carried out, and some puzzling features of its behaviour remain unexplained. In this work, we have built several progressively more complex kinetic models, and then carried out simulations and detailed analysis, to test the validity of the proposed reaction pathway employed by P-glycoprotein for ATP hydrolysis. To establish kinetic parameters for the catalytic cycle, we made use of the large amount of published data on ATP hydrolysis by hamster P-glycoprotein, both purified and in membrane vesicles. The proposed kinetic scheme(s) include a high affinity priming reaction for binding of the first ATP molecule, and an independent pathway for ADP binding outside the main catalytic cycle. They can reproduce to varying degrees the observed behavior of the protein's ATPase activity and its inhibition by ortho-vanadate. The results provide new insights into the mode of action of P-glycoprotein, and some hypotheses about the nature of the occluded nucleotide-bound state. PMID:24897122

Lugo, Miguel Ramón; Sharom, Frances Jane

2014-01-01

166

The ABCs of multidrug resistance in malaria.  

Science.gov (United States)

Expanding drug resistance could become a major problem in malaria treatment, as only a limited number of effective antimalarials are available. Drug resistance has been associated with single nucleotide polymorphisms and an increased copy number of multidrug resistance protein 1 (MDR1), an ATP-binding cassette (ABC) protein family member. Many ABC transport proteins are membrane transporters that actively translocate a wide range of structurally and functionally diverse amphipathic compounds. The Plasmodium falciparum ABC family consists of 16 members and current knowledge of their physiological function and contribution to antimalarial drug resistance is limited. Here, we give an overview of the Plasmodium ABC family members with reference to their possible role in multidrug resistance. PMID:20541973

Koenderink, Jan B; Kavishe, Reginald A; Rijpma, Sanna R; Russel, Frans G M

2010-09-01

167

Multidrug resistant yeasts in synanthropic wild birds  

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Abstract Background The aim of this study was to investigate the presence of multidrug resistant yeasts in the faeces of synanthropic wild birds from the Bangsar suburb of Kuala Lumpur. Methods Species characterisations of yeast isolates and determinations of antimycotic susceptibility profiles were undertaken using the commercial characterization kit, Integral System Yeasts Plus (Liofilchem, Italy). Results Fourteen species of yeasts were detected...

Somanath Sushela; Mohandas Kavitha; Lord Alexander; Ambu Stephen

2010-01-01

168

Regulation of Multidrug Efflux Systems Involved in Multidrug and Metal Resistance of Salmonella enterica Serovar Typhimurium?  

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Multidrug-resistant strains of Salmonella are now encountered frequently, and the rates of multidrug resistance have increased considerably in recent years. Here, we report that the two-component regulatory system BaeSR increases multidrug and metal resistance in Salmonella through the induction of drug efflux systems. Screening of random fragments of genomic DNA for the ability to increase ?-lactam resistance in Salmonella enterica led to the isolation of a plasmid containing baeR, which co...

Nishino, Kunihiko; Nikaido, Eiji; Yamaguchi, Akihito

2007-01-01

169

Influence of multidrug resistance on {sup 18}F-FCH cellular uptake in a glioblastoma model  

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Multidrug resistance, aggressiveness and accelerated choline metabolism are hallmarks of malignancy and have motivated the development of new PET tracers like {sup 18}F-FCH, an analogue of choline. Our aim was to study the relationship of multidrug resistance of cultured glioma cell lines and {sup 18}F-FCH tracer uptake. We used an in vitro multidrug-resistant (MDR) glioma model composed of sensitive parental U87MG and derived resistant cells U87MG-CIS and U87MG-DOX. Aggressiveness, choline metabolism and transport were studied, particularly the expression of choline kinase (CK) and high-affinity choline transporter (CHT1). FCH transport studies were assessed in our glioblastoma model. As expected, the resistant cell lines express P-glycoprotein (Pgp), multidrug resistance-associated protein isoform 1 (MRP1) and elevated glutathione (GSH) content and are also more mobile and more invasive than the sensitive U87MG cells. Our results show an overexpression of CK and CHT1 in the resistant cell lines compared to the sensitive cell lines. We found an increased uptake of FCH (in % of uptake per 200,000 cells) in the resistant cells compared to the sensitive ones (U87MG: 0.89{+-}0.14; U87MG-CIS: 1.27{+-}0.18; U87MG-DOX: 1.33{+-}0.13) in line with accelerated choline metabolism and aggressive phenotype. FCH uptake is not influenced by the two ATP-dependant efflux pumps: Pgp and MRP1. FCH would be an interesting probe for glioma imaging which would not be effluxed from the resistant cells by the classic MDR ABC transporters. Our results clearly show that FCH uptake reflects accelerated choline metabolism and is related to tumour aggressiveness and drug resistance. (orig.)

Vanpouille, Claire; Jeune, Nathalie le; Clotagatide, Anthony; Dubois, Francis [Universite de Lyon, Universite Jean Monnet-Cancer Research Group IFRESIS 143, Saint-Etienne (France); Kryza, David; Janier, Marc [Hospice Civils de Lyon, Quai Des Celestins, CREATIS, UMR CNRS, Lyon (France); Perek, Nathalie [Universite de Lyon, Universite Jean Monnet-Cancer Research Group IFRESIS 143, Saint-Etienne (France); Laboratoire de Biophysique, Faculte de Medecine, Saint-Etienne (France)

2009-08-15

170

An atomic detail model for the human ATP binding cassette transporter P-glycoprotein derived from disulfide cross-linking and homology modeling.  

Science.gov (United States)

The multidrug resistance P-glycoprotein mediates the extrusion of chemotherapeutic drugs from cancer cells. Characterization of the drug binding and ATPase activities of the protein have made it the paradigm ATP binding cassette (ABC) transporter. P-glycoprotein has been imaged at low resolution by electron cryo-microscopy and extensively analyzed by disulphide cross-linking, but a high resolution structure solved ab initio remains elusive. Homology models of P-glycoprotein were generated using the structure of a related prokaryotic ABC transporter, the lipid A transporter MsbA, as a template together with structural data describing the dimer interface of the nucleotide binding domains (NBDs). The first model, which maintained the NBD:transmembrane domain (TMD) interface of MsbA, did not satisfy previously published cross-linking data. This suggests that either P-glycoprotein has a very different structure from MsbA or that the published E. coli MsbA structure does not reflect a physiological state. To distinguish these alternatives, we mapped the interface between the two TMDs of P-glycoprotein experimentally by chemical cross-linking of introduced triple-cysteine residues. Based on these data, a plausible atomic model of P-glycoprotein could be generated using the MsbA template, if the TMDs of MsbA are reoriented with respect to the NBDs. This model will be important for understanding the mechanism of P-glycoprotein and other ABC transporters. PMID:14563687

Stenham, Daniella R; Campbell, Jeff D; Sansom, Mark S P; Higgins, Christopher F; Kerr, Ian D; Linton, Kenneth J

2003-12-01

171

Down-regulation of c-fos by shRNA sensitizes adriamycin-resistant MCF-7/ADR cells to chemotherapeutic agents via P-glycoprotein inhibition and apoptosis augmentation.  

Science.gov (United States)

Multidrug resistance (MDR) is a major hurdle in the treatment of cancer. Research indicated that the main mechanisms of most cancers included so-called "pump" (P-glycoprotein, P-gp) and "non-pump" (apoptosis) resistance. Identification of novel signaling molecules associated with both P-gp and apoptosis will facilitate the development of more effective strategies to overcome MDR in tumor cells. Since the proto-oncogene c-fos has been implicated in cell adaptation to environmental changes, we analyzed its role in mediating "pump" and "non-pump" resistance in MCF-7/ADR, an adriamycin (ADR)-selected human breast cancer cell line with the MDR phenotype. Elevated expression of c-fos in MCF-7/ADR cells and induction of c-fos by ADR in the parental drug-sensitive MCF-7 cells suggested a link between c-fos and MDR phenotype. Down-regulation of c-fos expression via shRNA resulted in sensitization of MCF-7/ADR cells to chemotherapeutic agents, including both P-gp and non-P-gp substrates. Further results proved that c-fos down-regulation in MCF-7/ADR cells resulted in decreased P-gp expression and activity, enhanced apoptosis, and altered expression of apoptosis-associated proteins (i.e., Bax, Bcl-2, p53, and PUMA). All above facts indicate that c-fos is involved in both P-gp- and anti-apoptosis-mediated MDR of MCF-7/ADR cells. Based on these results, we propose that c-fos may represent a potential molecular target for resistant cancer therapy, and suppressing c-fos gene expression may therefore be an effective means to temper breast cancer cell's MDR to cytotoxic chemotherapy. PMID:23494858

Shi, Ruizan; Peng, Hongwei; Yuan, Xiangfei; Zhang, Xiuli; Zhang, Yanjun; Fan, Dongmei; Liu, Xuyi; Xiong, Dongsheng

2013-08-01

172

[Travellers and multi-drug resistance bacteria].  

Science.gov (United States)

The number of international travellers has increased. There is enormous diversity in medical backgrounds, purposes of travel, and travelling styles among travellers. Travellers are hospitalized abroad because of exotic and common diseases via medical tourism. This is one way of transporting and importing human bacteria between countries, including multi-drug resistant organisms. In developing countries, the antimicrobial resistance in Shigella sp. and Salmonella sp. have been a problem, because of this trend, the first choice of antibiotics has changed in some countries. Community acquired infections as well as hospital acquired infections with MRSA, multi-drug resistance (MDR) Pseudomonas aeruginosa, and ESBL have been a problem. This review will discuss the risk of MDR bacterial infectious diseases for travellers. PMID:22413540

Takeshita, Nozomi

2012-02-01

173

Multifunctional magnetic Fe3O4 nanoparticles combined with chemotherapy and hyperthermia to overcome multidrug resistance  

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Full Text Available Yanyan Ren1,2,*, Haijun Zhang1,2,*, Baoan Chen1, Jian Cheng1, Xiaohui Cai1, Ran Liu1, Guohua Xia1, Weiwei Wu1, Shuai Wang1, Jiahua Ding1, Chong Gao1, Jun Wang1, Wen Bao1, Lei Wang1, Liang Tian1, Huihui Song1, Xuemei Wang1,2 1Department of Hematology and Oncology, Key Medical Discipline, Jiangsu Province, Zhongda Hospital, and Faculty of Oncology, Medical School, Nanjing, 2State Key Laboratory of Bioelectronics, Southeast University, Nanjing, People's Republic of China*These authors contributed equally to this workBackground: Multidrug resistance in cancer is a major obstacle for clinical therapeutics, and is the reason for 90% of treatment failures. This study investigated the efficiency of novel multifunctional Fe3O4 magnetic nanoparticles (Fe3O4-MNP combined with chemotherapy and hyperthermia for overcoming multidrug resistance in an in vivo model of leukemia.Methods: Nude mice with tumor xenografts were randomly divided into a control group, and the treatment groups were allocated to receive daunorubicin, 5-bromotetrandrine (5-BrTet and daunorubicin, Fe3O4-MNP, and Fe3O4-MNP coloaded with daunorubicin and 5-bromotetrandrine (Fe3O4-MNP-DNR-5-BrTet, with hyperthermia in an alternating magnetic field. We investigated tumor volume and pathology, as well as P-glycoprotein, Bcl-2, Bax, and caspase-3 protein expression to elucidate the effect of multimodal treatment on overcoming multidrug resistance.Results: Fe3O4-MNP played a role in increasing tumor temperature during hyperthermia. Tumors became significantly smaller, and apoptosis of cells was observed in both the Fe3O4-MNP and Fe3O4-MNP-DNR-5-BrTet groups, especially in the Fe3O4-MNP-DNR-5-BrTet group, while tumor volumes in the other groups had increased after treatment for 12 days. Furthermore, Fe3O4-MNP-DNR-5-BrTet with hyperthermia noticeably decreased P-glycoprotein and Bcl-2 expression, and markedly increased Bax and caspase-3 expression.Conclusion: Fe3O4-MNP-DNR-5-BrTet with hyperthermia may be a potential approach for reversal of multidrug resistance in the treatment of leukemia.Keywords: magnetic nanoparticles, daunorubicin, 5-bromotetrandrine, multidrug resistance, hyperthermia

Ren Y

2012-05-01

174

Effect of duration of exposure to verapamil on vincristine activity against multidrug-resistant human leukemic cell lines.  

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Verapamil sensitizes multidrug-resistant cell lines to various heterocyclic anticancer drugs by inhibition of energy-dependent release of drug, presumably by interaction with membrane glycoproteins involved in drug efflux. This work assessed verapamil sensitization of human multidrug-resistant lymphocytic and myeloid leukemic cell lines (CEM/VLB100, HL-60/AR) to vincristine during exposures of short duration (4 h). When cells were transferred to drug-free medium immediately after simultaneous 4-h exposures to vincristine and verapamil, the antiproliferative activity of vincristine was not altered in CEM/VLB100 cells and was only moderately increased in HL-60/AR cells. In contrast, when cells were transferred to verapamil-containing medium, vincristine activity was greatly increased against both CEM/VLB100 and HL-60/AR cells. Verapamil enhanced accumulation and inhibited release of [3H]vincristine by CEM/VLB100 and HL-60/AR cells, indicating that the sensitization was due to an increase in cell-associated vincristine after transfer of cells to vincristine-free medium. Slot blot analysis of cellular RNA with the pMDR1 probe revealed high levels of expression of the mdr1 gene in CEM/VLB100 cells but no detectable expression in HL-60/AR cells. Consistent with this finding, polypeptides (Mr 170,000 to 180,000) that were recognized by a monoclonal antibody (C219) against P-glycoprotein were greatly overexpressed in CEM/VLB100 cells, but were expressed at low levels, if at all, in HL-60/AR cells. These results demonstrate the importance of duration of exposure to verapamil in reversing multidrug resistance, not only in cells that overexpress P-glycoprotein but also in cells, such as HL-60/AR, that express little, if any, P-glycoprotein. PMID:2790792

Cass, C E; Janowska-Wieczorek, A; Lynch, M A; Sheinin, H; Hindenburg, A A; Beck, W T

1989-11-01

175

A novel anthracene derivative, MHY412, induces apoptosis in doxorubicin-resistant MCF-7/Adr human breast cancer cells through cell cycle arrest and downregulation of P-glycoprotein expression.  

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New potential chemotherapeutic strategies are required to overcome multidrug resistance (MDR) in cancer. This study investigated the anticancer effect of a novel anthracene derivative MHY412 on doxorubicin-resistant human breast cancer (MCF-7/Adr) cells. We measured cell viability and the expression of apoptosis-related genes; in addition, the antitumor activity of MHY412 was confirmed using an in vivo tumor xenograft model. MHY412 significantly inhibited the proliferation of MCF-7/Adr and MCF-7 cells in a concentration-dependent manner. Notably, the half-maximal inhibitory concentration (IC50) values of MHY412 in MCF-7/Adr (0.15 µM) and MCF-7 (0.26 µM) cells were lower than those of doxorubicin (MCF-7/Adr, 13.6 µM and MCF-7, 1.26 µM) after treatment for 48 h. MHY412 at low concentrations induced S phase arrest, but at high concentrations, the number of MCF-7/Adr cells in the sub-G1 phase significantly increased. MHY412-induced sub-G1 phase arrest was associated with inhibition of cyclin, cyclin-dependent kinase 2 (CDK2) and p21 expression in MCF-7/Adr cells. MHY412 markedly reduced P-glycoprotein (P-gp) expression and increased apoptotic cell death in MCF-7/Adr cells. Cleavage of poly-ADP ribose polymerase, reduced Bcl-2 expression, and increased in cytochrome c release in MCF-7/Adr cells confirmed the above results. In addition, MHY412 markedly inhibited tumor growth in a tumor xenograft model of MCF-7/Adr cells. Our data suggest that MHY412 exerts antitumor effects by selectively modulating the genes related to cell cycle arrest and apoptosis. In particular, MHY412 is a new candidate agent for the treatment of Bcl-2 overexpressed doxorubicin-resistant human breast cancer. PMID:24190517

De, Umasankar; Chun, Pusoon; Choi, Wahn Soo; Lee, Byung Mu; Kim, Nam Deuk; Moon, Hyung Ryong; Jung, Jee H; Kim, Hyung Sik

2014-01-01

176

Metformin reverses multidrug resistance in human hepatocellular carcinoma Bel?7402/5?fluorouracil cells.  

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Metformin exhibits anti?proliferative effects in tumor cells in vitro and in vivo. The present study investigated the ability of metformin to reverse multidrug resistance (MDR) in human hepatocellular carcinoma Bel?7402/5?fluorouracil (5?Fu; Bel/Fu) cells. The synergistic anti?proliferative effect of metformin combined with 5?Fu was evaluated using a Cell Counting kit?8 assay. The variation in apoptotic rates and cell cycle distribution were evaluated using a flow cytometric assay and variations in target gene and protein expression were monitored using reverse transcription?polymerase chain reaction and western blot analysis. The results demonstrated that metformin had a synergistic anti?proliferative effect with 5?Fu in the Bel/Fu cells. The variations in the number of apoptotic cells and distribution of the cell cycle were consistent with the variability in cell viability. Metformin targeted the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway, suppressed the expression of hypoxia?inducible factor?1? (HIF?1?) and transcriptionally downregulated the expression of multidrug resistance protein 1/P?glycoprotein (P?gp) and multidrug resistance?associated protein 1 (MRP1). Collectively, these findings suggested that metformin may target the AMPK/mTOR/HIF?1?/P?gp and MRP1 pathways to reverse MDR in hepatocellular carcinoma. PMID:25310259

Ling, Sunbin; Tian, Yu; Zhang, Haiquan; Jia, Kaiqi; Feng, Tingting; Sun, Deguang; Gao, Zhenming; Xu, Fei; Hou, Zhaoyuan; Li, Yan; Wang, Liming

2014-12-01

177

Codelivery of Chemotherapeutics via Crosslinked Multilamellar Liposomal Vesicles to Overcome Multidrug Resistance in Tumor  

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Multidrug resistance (MDR) is a significant challenge to effective cancer chemotherapy treatment. However, the development of a drug delivery system that allows for the sustained release of combined drugs with improved vesicle stability could overcome MDR in cancer cells. To achieve this, we have demonstrated codelivery of doxorubicin (Dox) and paclitaxel (PTX) via a crosslinked multilamellar vesicle (cMLV). This combinatorial delivery system achieves enhanced drug accumulation and retention, in turn resulting in improved cytotoxicity against tumor cells, including drug-resistant cells. Moreover, this delivery approach significantly overcomes MDR by reducing the expression of P-glycoprotein (P-gp) in cancer cells, thus improving antitumor activity in vivo. Thus, by enhancing drug delivery to tumors and lowering the apoptotic threshold of individual drugs, this combinatorial delivery system represents a potentially promising multimodal therapeutic strategy to overcome MDR in cancer therapy.

Joo, Kye-Il; Wong, Michael K.; Wang, Pin

2014-01-01

178

Study of tea polyphenol as a reversal agent for carcinoma cell lines' multidrug resistance (study of TP as a MDR reversal agent)  

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The aim of this study was to examine MDR1 expression product P-glycoprotein (Pgp) and study the effect and mechanism of tea polyphenol (TP) in reversion of multidrug resistance (MDR) in carcinoma cell lines. Immunocytochemical method was used for qualitative detection of Pgp. A comparative study of cytotoxicity and multidrug resistance reversion effect was made by MTT assay for tea polyphenol and quinidine in MCF-7 and MCF-7/Adr cell lines. The multidrug resistance reversion effect and mechanism were studied by measuring the uptake of 99mTc-tetrofosmin in the carcinoma cell lines. (1) The Pgp overexpression in MCF-7/Adr cells was found to be strong positive, while the Pgp expression of MCF-7 was negative. (2) Although both tea polyphenol and quinidine could not remarkably change the toxicity of adriamycin to MCF-7, they could improve the sensitivity of MCF-7/Adr to adriamycin. The reversion index of tea polyphenol and quinidine was 3 and 10 respectively. (3) The cellular uptake of 99mTc-tetrofosmin was remarkably lower in MCF-7/Adr than in MCF-7. The uptake of 99mTc-tetrofosmin in MCF-7/Adr exhibited a 4, 13, 16 fold increase in the presence of 200, 400 and 500 ?g/ml of tea polyphenol respectively. The uptake of 99mTc-tetrofosmin in MCF-7/Adr exhibited only a 4-fold increase in the presence of 200 ?M of quinidine. Immunocytochemistry can detect P-glycoprotein expression level qualitatively. Tea polyphenol is not only an anti-tumor agent, but also a multidrug resistant modulator similar to quinidine. The multidrug resistance reversion mechanism of tea polyphenol seems to be its inhibition of the activity of P-glycoprotein. Tea polyphenol has the advantage of very low toxicity in tumor treatment

179

Study of tea polyphenol as a reversal agent for carcinoma cell lines' multidrug resistance (study of TP as a MDR reversal agent)  

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The aim of this study was to examine MDR1 expression product P-glycoprotein (Pgp) and study the effect and mechanism of tea polyphenol (TP) in reversion of multidrug resistance (MDR) in carcinoma cell lines. Immunocytochemical method was used for qualitative detection of Pgp. A comparative study of cytotoxicity and multidrug resistance reversion effect was made by MTT assay for tea polyphenol and quinidine in MCF-7 and MCF-7/Adr cell lines. The multidrug resistance reversion effect and mechanism were studied by measuring the uptake of {sup 99m}Tc-tetrofosmin in the carcinoma cell lines. (1) The Pgp overexpression in MCF-7/Adr cells was found to be strong positive, while the Pgp expression of MCF-7 was negative. (2) Although both tea polyphenol and quinidine could not remarkably change the toxicity of adriamycin to MCF-7, they could improve the sensitivity of MCF-7/Adr to adriamycin. The reversion index of tea polyphenol and quinidine was 3 and 10 respectively. (3) The cellular uptake of {sup 99m}Tc-tetrofosmin was remarkably lower in MCF-7/Adr than in MCF-7. The uptake of {sup 99m}Tc-tetrofosmin in MCF-7/Adr exhibited a 4, 13, 16 fold increase in the presence of 200, 400 and 500 {mu}g/ml of tea polyphenol respectively. The uptake of {sup 99m}Tc-tetrofosmin in MCF-7/Adr exhibited only a 4-fold increase in the presence of 200 {mu}M of quinidine. Immunocytochemistry can detect P-glycoprotein expression level qualitatively. Tea polyphenol is not only an anti-tumor agent, but also a multidrug resistant modulator similar to quinidine. The multidrug resistance reversion mechanism of tea polyphenol seems to be its inhibition of the activity of P-glycoprotein. Tea polyphenol has the advantage of very low toxicity in tumor treatment.

Zhu Aizhi E-mail: zhuaizhi@263.net; Wang Xiangyun; Guo Zhenquan

2001-08-01

180

Multi-drug resistant Ewingella americana.  

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We report a case of pneumonia due to multi-drug resistant Ewingella americana in a young patient admitted in the Intensive Care Unit of Hera General Hospital, Makkah, Saudi Arabia with severe head injury in a road traffic accident. He was an Indonesian pilgrim who had traveled to the Kingdom of Saudi Arabia to perform Hajj in December 2007. Ewingella americana was identified to be the pathogen of pneumonia with clinical signs and symptoms along with positive radiological findings.

Syed Z. Bukhari

2008-07-01

 
 
 
 
181

Chromosomal Instability Confers Intrinsic Multidrug Resistance  

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Aneuploidy is associated with poor prognosis in solid tumors. Spontaneous chromosome missegregation events in aneuploid cells promote chromosomal instability (CIN) that may contribute to the acquisition of multidrug resistance in vitro and heighten risk for tumor relapse in animal models. Identification of distinct therapeutic agents that target tumor karyotypic complexity has important clinical implications. To identify distinct therapeutic approaches to specifically limit the growth of CIN tumors, we focused on a panel of colorectal cancer (CRC) cell lines, previously classified as either chromosomally unstable (CIN+) or diploid/near-diploid (CIN-), and treated them individually with a library of kinase inhibitors targeting components of signal transduction, cell cycle, and transmembrane receptor signaling pathways. CIN+ cell lines displayed significant intrinsic multidrug resistance compared with CIN- cancer cell lines, and this seemed to be independent of somatic mutation status and proliferation rate. Confirming the association of CIN rather than ploidy status with multidrug resistance, tetraploid isogenic cells that had arisen from diploid cell lines displayed lower drug sensitivity than their diploid parental cells only with increasing chromosomal heterogeneity and isogenic cell line models of CIN+ displayed multidrug resistance relative to their CIN- parental cancer cell line derivatives. In a meta-analysis of CRC outcome following cytotoxic treatment, CIN+ predicted worse progression-free or disease-free survival relative to patients with CIN- disease. Our results suggest that stratifying tumor responses according to CIN status should be considered within the context of clinical trials to minimize the confounding effects of tumor CIN status on drug sensitivity. Cancer Res; 71(5); 1858-70. (c) 2011 AACR.

Lee, Alvin J. X.; Endesfelder, David

2011-01-01

182

Phorbol esters induce multidrug resistance in human breast cancer cells.  

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Mechanisms responsible for broad-based resistance to antitumor drugs derived from natural products (multidrug resistance) are incompletely understood. Agents known to reverse the multidrug-resistant phenotype (verapamil and trifluoperazine) can also inhibit the activity of protein kinase C. When we assayed human breast cancer cell lines for protein kinase C activity, we found that enzyme activity was 7-fold higher in the multidrug-resistant cancer cells compared with the control, sensitive pa...

Fine, R. L.; Patel, J.; Chabner, B. A.

1988-01-01

183

Proteome analysis of multidrug-resistant, breast cancer–derived microparticles  

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Full Text Available Cancer multidrug resistance (MDR occurs when cancer cells evade the cytotoxic actions of chemotherapeutics through the active efflux of drugs from within the cells. Our group have previously demonstrated that multidrug-resistant breast cancer cells spontaneously shed microparticles (MPs and that these MPs can transfer resistance to drug-responsive cells and confer MDR on those cells in as little as 4 h. Furthermore, we also showed that, unlike MPs derived from leukaemia cells, breast cancer–derived MPs display a tissue selectivity in the transfer of P-glycoprotein (P-gp, transferring the resistance protein only to malignant breast cells. This study aims to define the proteome of breast cancer–derived MPs in order to understand the differences in protein profiles between those shed from drug-resistant versus drug-sensitive breast cancer cells. In doing so, we detail the protein cargo required for the intercellular transfer of MDR to drug-sensitive recipient cells and the factors governing the transfer selectivity to malignant breast cells. We describe the first proteomic analysis of MPs derived from human breast cancer cells using SDS PAGE and liquid chromatography–tandem mass spectrometry (LC/MS/MS, in which we identify 120 unique proteins found only in drug-resistant, breast cancer–derived MPs. Our results demonstrate that the MP-mediated transfer of P-gp to recipient cells occurs alongside CD44; the Ezrin, Radixin and Moesin protein family (ERM; and cytoskeleton motor proteins within the MP cargo.

Deep Pokharel

2014-08-01

184

Study of multidrug resistance and radioresistance  

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We investigated the mechanism of 5-FU, adriamycin, radiation resistance in Korean gastric cancer cells. First we investigated the relation between Rb and multidrug resistance. Rb stable transfectants exhibited 5- to 10- fold more resistance to adriamycin than the control cells. These Rb transfectants showed increased MDR1 expression. We also investigated up-regulation in radiation-resistant tumor tissues. HSP27, MRP-8, GST, and NKEF-B were up-regulated in radiation resistant tumor. Expression of NKEF-B was also increased by radiation exposure in Head and Neck cells. These results demonstrated that NKEF-B is a stress response protein and it may have an important role in radiation resistance

185

Study of multidrug resistance and radioresistance  

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We investigated the mechanism of 5-FU, adriamycin, radiation resistance in Korean gastric cancer cells. First we investigated the relation between Rb and multidrug resistance. Rb stable transfectants exhibited 5- to 10- fold more resistance to adriamycin than the control cells. These Rb transfectants showed increased MDR1 expression. We also investigated up-regulation in radiation-resistant tumor tissues. HSP27, MRP-8, GST, and NKEF-B were up-regulated in radiation resistant tumor. Expression of NKEF-B was also increased by radiation exposure in Head and Neck cells. These results demonstrated that NKEF-B is a stress response protein and it may have an important role in radiation resistance.

Kang, Yoon Koo; Yoo, Young Do

1999-04-01

186

Role of p-glycoprotein expression in predicting response to neoadjuvant chemotherapy in breast cancer-a prospective clinical study  

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Full Text Available Abstract Background Neoadjuvant chemotherapy (NACT is an integral part of multi-modality approach in the management of locally advanced breast cancer. It is vital to predict response to chemotherapy in order to tailor the regime for a particular patient. The prediction would help in avoiding the toxicity induced by an ineffective chemotherapeutic regime in a non-responder and would also help in the planning of an alternate regime. Development of resistance to chemotherapeutic agents is a major problem and one of the mechanisms considered responsible is the expression of 170-k Da membrane glycoprotein (usually referred to as p-170 or p-glycoprotein, which is encoded by multidrug resistance (MDR1 gene. This glycoprotein acts as an energy dependent pump, which actively extrudes certain families of chemotherapeutic agents from the cells. The expression of p-glycoprotein at initial presentation has been found to be associated with refractoriness to chemotherapy and a poor outcome. Against this background a prospective study was conducted using C219 mouse monoclonal antibody specific for p-glycoprotein to ascertain whether pretreatment detection of p-glycoprotein expression could be utilized as a reliable predictor of response to neoadjuvant chemotherapy in patients with breast cancer. Patients and methods Fifty cases of locally advanced breast cancer were subjected to trucut® biopsy and the tissue samples were evaluated immunohistochemically for p-glycoprotein expression and ER, PR status. The response to neoadjuvant chemotherapy was assessed clinically and by using ultrasound after three cycles of FAC regime (cyclophosphamide 600 mg/m2, Adriamycin 50 mg/m2, 5-fluorourail 600 mg/m2 at an interval of three weeks. The clinical response was correlated with both the pre and post chemotherapy p-glycoprotein expression. Descriptive studies were performed with SPSS version 10. The significance of correlation between tumor response and p-glycoprotein expression was determined with chi square test. Results A significant relationship was found between the pretreatment p-glycoprotein expression and clinical response. The positive p-glycoprotein expression was associated with poor clinical response rates. When the clinical response was correlated with p-glycoprotein expression, a statistically significant negative correlation was observed between the clinical response and p- glycoprotein expression (p Conclusion The study concluded that pretreatment p-glycoprotein expression predicts and indicates a poor clinical response to NACT. Patients with positive p-glycoprotein expression before initiation of NACT were found to be poor responders. Thus pretreatment detection of p-glycoprotein expression may be utilized, as a reliable predictor of response to NACT in patients with breast cancer The chemotherapy induced p-glycoprotein positivity observed in the study could possibly explain the phenomenon of acquired chemoresistance and may also serve as an intermediate end point in evaluating drug response particularly if the adjuvant therapy is planned with the same regime.

Bhatia Ashima

2005-09-01

187

Noninvasive functional imaging of P-glycoprotein-mediated doxorubicin resistance in a mouse model of hereditary breast cancer to predict response, and assign P-gp inhibitor sensitivity  

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Using a ''spontaneous'' mammary mouse tumor model we set out to develop diagnostic approaches for non-invasive P-glycoprotein (P-gp) staging and response prediction. {sup 99m}Tc-MIBI efflux rates were measured using a gamma camera in three Brca1 {sup -/-}; p53 {sup -/-} mouse mammary tumors that have different Mdr1a/b expression levels. The efflux rates were quantified in the 10-30-min period after injection. In addition to the P-gp-mediated efflux measurements in untreated tumors, efflux measurements were performed in the presence of the P-gp inhibitor tariquidar. Volumetric doxorubicin response patterns for the different tumors were determined and correlated with the efflux rates. Combined pre- and post-inhibitor treatment imaging of P-gp-mediated efflux correlated with Mdr1a/b expression: basal (0.0026, p = 0.16), 3-fold Mdr1a/b (0.0074, p = 0.02), and 17-fold Mdr1a and 46-fold Mdr1b (0.012, p = 0.002). Based on the doxorubicin response of these tumors, we generated a computer-aided diagnosis model that predicts the likelihood of drug resistance. Quantified {sup 99m}Tc-MIBI efflux has potential to: (1) noninvasively assign Mdr1 expression levels, (2) predict the therapeutic impact of a P-gp inhibitor, and (3) noninvasively assess the probability of drug resistance. (orig.)

Leeuwen, Fijs W.B. van; Buckle, Tessa; Gilhuijs, Kenneth G.A. [The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Departments of Radiology and Nuclear Medicine, Amsterdam (Netherlands); Kersbergen, Ariena; Rottenberg, Sven [The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Department of Molecular Biology, Amsterdam (Netherlands)

2009-03-15

188

Oral availability and brain penetration of the B-RAFV600E inhibitor vemurafenib can be enhanced by the P-GLYCOprotein (ABCB1) and breast cancer resistance protein (ABCG2) inhibitor elacridar.  

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Vemurafenib (PLX4032) is a novel tyrosine kinase inhibitor that has clinical efficacy against metastatic melanoma harboring a BRAF(V600E) mutation. We aimed to establish whether oral availability and brain penetration of vemurafenib could be restricted by the multidrug efflux transporters P-glycoprotein (P-gp/ABCB1) and breast cancer resistance protein (BCRP/ABCG2), as these might limit therapeutic efficacy, especially against brain metastases. In vitro, vemurafenib was efficiently transported by both human ABCB1 and ABCG2, and very efficiently by mouse Abcg2, but not by mouse Abcc2. Upon oral administration of vemurafenib (5 mg/kg), Abcb1a/1b(-/-) mice had a 1.6-fold increased, Abcg2(-/-) mice a 2.3-fold increased, and Abcb1a/1b(-/-);Abcg2(-/-) mice a 6.6-fold increased plasma AUC, respectively, compared to wild-type (WT) mice, indicating a marked and additive role of these transporters in limiting vemurafenib oral availability. Brain-to-plasma ratios of vemurafenib (oral, 25 mg/kg) were not increased in Abcg2(-/-) mice, only 1.7-fold in Abcb1a/1b(-/-) mice, but 21.4-fold in Abcb1a/1b(-/-);Abcg2(-/-) mice, indicating pronounced overlapping functions of these transporters in reducing vemurafenib brain accumulation. Oral coadministration of the dual ABCB1 and ABCG2 inhibitor elacridar almost completely eliminated the roles of Abcb1 and Abcg2 in restricting oral availability and brain accumulation of vemurafenib. As predicted by previously described pharmacokinetic modeling, halving the amount of active efflux transport at the WT blood-brain barrier by testing heterozygous Abcb1a/1b(+/-);Abcg2(+/-) mice had little impact on vemurafenib brain accumulation. Our data suggest that elacridar coadministration may be considered to improve the therapeutic efficacy of vemurafenib, especially for brain metastases located behind a functional blood-brain barrier. PMID:23020847

Durmus, Selvi; Sparidans, Rolf W; Wagenaar, Els; Beijnen, Jos H; Schinkel, Alfred H

2012-11-01

189

Multidrug-resistant breast cancer: current perspectives  

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Full Text Available Heather L Martin,1 Laura Smith,2 Darren C Tomlinson11BioScreening Technology Group, Leeds Institutes of Molecular Medicine, University of Leeds, Leeds, UK; 2Leeds Institute of Cancer and Pathology, University of Leeds, Leeds, UKAbstract: Breast cancer is the most common cancer in women worldwide, and resistance to the current therapeutics, often concurrently, is an increasing clinical challenge. By understanding the molecular mechanisms behind multidrug-resistant breast cancer, new treatments may be developed. Here we review the recent advances in this understanding, emphasizing the common mechanisms underlying resistance to both targeted therapies, notably tamoxifen and trastuzumab, and traditional chemotherapies. We focus primarily on three molecular mechanisms, the phosphatidylinositide 3-kinase/Akt pathway, the role of microRNAs in gene silencing, and epigenetic alterations affecting gene expression, and discuss how these mechanisms can interact in multidrug resistance. The development of therapeutics targeting these mechanisms is also addressed.Keywords: PI3K/Akt, epigenetics, miRNA, ER, HER2, triple negative

Martin HL

2014-01-01

190

Inhibition of glutathione peroxidase mediates the collateral sensitivity of multidrug-resistant cells to tiopronin.  

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Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of cancer. MDR is often the result of overexpression of ATP-binding cassette transporters following chemotherapy. A common ATP-binding cassette transporter that is overexpressed in MDR cancer cells is P-glycoprotein, which actively effluxes drugs against a concentration gradient, producing an MDR phenotype. Collateral sensitivity (CS), a phenomenon of drug hypersensitivity, is defined as the ability of certain compounds to selectively target MDR cells, but not the drug-sensitive parent cells from which they were derived. The drug tiopronin has been previously shown to elicit CS. However, unlike other CS agents, the mechanism of action was not dependent on the expression of P-glycoprotein in MDR cells. We have determined that the CS activity of tiopronin is mediated by the generation of reactive oxygen species (ROS) and that CS can be reversed by a variety of ROS-scavenging compounds. Specifically, selective toxicity of tiopronin toward MDR cells is achieved by inhibition of glutathione peroxidase (GPx), and the mode of inhibition of GPx1 by tiopronin is shown in this report. Why MDR cells are particularly sensitive to ROS is discussed, as is the difficulty in exploiting this hypersensitivity to tiopronin in the clinic. PMID:24930045

Hall, Matthew D; Marshall, Travis S; Kwit, Alexandra D T; Miller Jenkins, Lisa M; Dulcey, Andrés E; Madigan, James P; Pluchino, Kristen M; Goldsborough, Andrew S; Brimacombe, Kyle R; Griffiths, Gary L; Gottesman, Michael M

2014-08-01

191

Molecular models of human P-glycoprotein in two different catalytic states  

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Full Text Available Abstract Background P-glycoprotein belongs to the family of ATP-binding cassette proteins which hydrolyze ATP to catalyse the translocation of their substrates through membranes. This protein extrudes a large range of components out of cells, especially therapeutic agents causing a phenomenon known as multidrug resistance. Because of its clinical interest, its activity and transport function have been largely characterized by various biochemical studies. In the absence of a high-resolution structure of P-glycoprotein, homology modeling is a useful tool to help interpretation of experimental data and potentially guide experimental studies. Results We present here three-dimensional models of two different catalytic states of P-glycoprotein that were developed based on the crystal structures of two bacterial multidrug transporters. Our models are supported by a large body of biochemical data. Measured inter-residue distances correlate well with distances derived from cross-linking data. The nucleotide-free model features a large cavity detected in the protein core into which ligands of different size were successfully docked. The locations of docked ligands compare favorably with those suggested by drug binding site mutants. Conclusion Our models can interpret the effects of several mutants in the nucleotide-binding domains (NBDs, within the transmembrane domains (TMDs or at the NBD:TMD interface. The docking results suggest that the protein has multiple binding sites in agreement with experimental evidence. The nucleotide-bound models are exploited to propose different pathways of signal transmission upon ATP binding/hydrolysis which could lead to the elaboration of conformational changes needed for substrate translocation. We identified a cluster of aromatic residues located at the interface between the NBD and the TMD in opposite halves of the molecule which may contribute to this signal transmission. Our models may characterize different steps in the catalytic cycle and may be important tools to understand the structure-function relationship of P-glycoprotein.

Tulkens Paul M

2009-01-01

192

Disruption of vitellogenesis and spermatogenesis by triclabendazole (TCBZ) in a TCBZ-resistant isolate of Fasciola hepatica following incubation in vitro with a P-glycoprotein inhibitor.  

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A study has been carried out to investigate whether the action of triclabendazole (TCBZ) against Fasciola hepatica is altered by inhibition of P-glycoprotein (Pgp)-linked drug efflux pumps. The Sligo TCBZ-resistant fluke isolate was used for these experiments and the Pgp inhibitor selected was R(+)-verapamil [R(+)-VPL]. In the first experiment, flukes were initially incubated for 2 h in R(+)-VPL (100 ? m), then incubated in R(+)-VPL+triclabendazole sulphoxide (TCBZ.SO) (50 ?g mL-1, or 133·1 ? m) until flukes ceased movement (at 9 h post-treatment). In a second experiment, flukes were incubated in TCBZ.SO alone and removed from the incubation medium following cessation of motility (after 15 h). In the third experiment, flukes were incubated for 24 h in R(+)-VPL on its own. Changes to the testis tubules and vitelline follicles following drug treatment and following Pgp inhibition were assessed by means of light microscope histology and transmission electron microscopy. Incubation of the Sligo isolate in either R(+)-VPL or TCBZ.SO on their own had a limited impact on the morphology of the two tissues. Greater disruption was observed when the drugs were combined, in terms of the block in development of the spermatogenic and vitelline cells and the apoptotic breakdown of the remaining cells. Sperm formation was severely affected and abnormal. Large spaces appeared in the vitelline follicles and synthesis of shell protein was disrupted. The results of this study support the concept of altered drug efflux in TCBZ-resistant flukes and indicate that drug transporters may play a role in the development of drug resistance. PMID:24889697

Savage, J; Meaney, M; Brennan, G P; Hoey, E; Trudgett, A; Fairweather, I

2014-07-01

193

Nanopreparations to overcome multidrug resistance in cancer.  

Science.gov (United States)

Multidrug resistance is the most widely exploited phenomenon by which cancer eludes chemotherapy. Broad variety of factors, ranging from the cellular ones, such as over-expression of efflux transporters, defective apoptotic machineries, and altered molecular targets, to the physiological factors such as higher interstitial fluid pressure, low extracellular pH, and formation of irregular tumor vasculature are responsible for multidrug resistance. A combination of various undesirable factors associated with biological surroundings together with poor solubility and instability of many potential therapeutic small & large molecules within the biological systems and systemic toxicity of chemotherapeutic agents has necessitated the need for nano-preparations to optimize drug delivery. The physiology of solid tumors presents numerous challenges for successful therapy. However, it also offers unique opportunities for the use of nanotechnology. Nanoparticles, up to 400 nm in size, have shown great promise for carrying, protecting and delivering potential therapeutic molecules with diverse physiological properties. In this review, various factors responsible for the MDR and the use of nanotechnology to overcome the MDR, the use of spheroid culture as well as the current technique of producing microtumor tissues in vitro are discussed in detail. PMID:23973912

Patel, Niravkumar R; Pattni, Bhushan S; Abouzeid, Abraham H; Torchilin, Vladimir P

2013-11-01

194

Imatinib resistance in multidrug-resistant K562 human leukemic cells.  

Science.gov (United States)

The multidrug resistance phenotype (MDR) is one of the major causes of failure in cancer chemotherapy and it is associated with the over-expression of P-glycoprotein (P-gp or MDR1) in tumor cell membranes. A constitutive NF-kappaB activity has been observed in several haematological malignancies and this is associated with its anti-apoptotic role. In the present work, the relationship between NF-kappaB and MDR phenotype was evaluated in wild type K562 human leukemic cells (K562-WT) and in its vincristine-resistant counterpart, K562-Vinc cells. These data showed that K562-Vinc cells, which express an active P-gp, exhibited MDR phenotype. The resistant indexes (IC(50)(K562-Vinc)/IC(50)(K562-WT)) for structurally unrelated drugs like imatinib, doxorubicin and colchicine were 8.0+/-0.3, 2.8+/-0.4 and 44.8+/-8.8, respectively. The imatinib resistance was reversed by P-gp blockade suggesting the involvement of P-gp in imatinib transport. We observed that NF-kappaB was constitutively activated in both cell lines but in a lesser extent in K562-Vinc. The inhibition of NF-kappaB with BAY 11-7082 increased the cytotoxicity of imatinib in K562-Vinc cells but not in K562-WT. Further, the co-administration of imatinib and BAY 11-7082 sensitized multidrug-resistant K562 cells to cell death as detected by increased percentage of annexin V positive cells. The induced cell death in K562-Vinc cells was associated with activation of caspases 9 and 3. Finally, we provide data showing that BAY 11-7082 down-regulates the expression of P-gp suggesting that the activity of NF-kappaB could be functionally associated to this protein in K562 cells. Our results indicate that the vincristine-resistant K562 cells which developed MDR phenotype, exhibited resistance to imatinib associated with a functional P-gp over-expression. This resistance could be partially overcome by the inhibition of NF-kappaB pathway. PMID:18977528

Assef, Yanina; Rubio, Fernanda; Coló, Georgina; del Mónaco, Silvana; Costas, Mónica A; Kotsias, Basilio A

2009-05-01

195

Poloxamer 407/TPGS mixed micelles for delivery of gambogic acid to breast and multidrug-resistant cancer  

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Full Text Available Vipin Saxena, M Delwar HussainDepartment of Pharmaceutical Sciences, Irma Lerma Rangel College of Pharmacy, Texas A&M Health Science Center, Kingsville, TX, USABackground: Delivery of a high concentration of anticancer drugs specifically to cancer cells remains the biggest challenge for the treatment of multidrug-resistant cancer. Poloxamers and D-?-Tocopheryl polyethylene glycol 1000 succinate (TPGS are known inhibitors of P-glycoprotein (P-gp. Mixed micelles prepared from Poloxamer 407 and TPGS may increase the therapeutic efficacy of the drug by delivering high concentrations inside the cells and inhibiting P-gp. Gambogic acid (GA is a naturally derived novel anticancer agent, but poor solubility and toxic side effects limit its use. In this study, we have developed Poloxamer 407 and TPGS mixed micelle-encapsulating GA for the treatment of breast and multidrug-resistant cancer.Methods: GA-loaded Poloxamer 407/TPGS mixed micelles were prepared using a thin film hydration method, and their physicochemical properties were characterized. Cellular accumulation and cytotoxicity of the GA-loaded Poloxamer 407/TPGS mixed micelles were studied in breast cancer cells, MCF-7 cells, and multidrug-resistant NCI/ADR-RES cells.Results: The diameter of GA-loaded Poloxamer 407/TPGS mixed micelles was about 17.4 ± 0.5 nm and the zeta potential -13.57 mV. The entrapment efficiency of GA was 93.1% ± 0.5% and drug loading was about 9.38% ± 0.29%. Differential scanning calorimetry and X-ray powder diffraction studies confirmed that GA is encapsulated by the polymers. The in vitro release studies showed that mixed micelles sustained the release of GA for more than 4 days. Results from cellular uptake studies indicated that GA-loaded Poloxamer 407/TPGS mixed micelles had increased cellular uptake of GA in NCI/ADR-RES cells. Cytotoxicity of GA-loaded Poloxamer 407/TPGS mixed micelles was found to be 2.9 times higher in multidrug-resistant NCI/ADR-RES cells, and 1.6 times higher in MCF-7 cells, as compared with unencapsulated GA.Conclusion: This study suggests that Poloxamer 407/TPGS mixed micelles can be used as a delivery system for GA to treat breast and multidrug-resistant cancer.Keywords: gambogic acid, Poloxamer 407, TPGS, P-glycoprotein, multidrug resistance, breast cancer

Hussain MD

2012-02-01

196

Characterization of multidrug resistance by fluorescent dyes.  

Science.gov (United States)

Fluorimetric techniques were used to examine accumulation of fluorescent probes by the P388 murine leukemia and an anthracycline-resistant subline, P388/Adriamycin(ADR), which expresses the multidrug-resistant phenotype. P388 could be differentiated from P388/ADR on the basis of fluorescence intensity measurements using 3 classes of cationic dyes that are sensitive to membrane potential differences: rhodamine esters, cyanines, and styrylpyridinium dyes. But fluorescence intensity differences were also observed with potential-insensitive dyes: zwitterionic rhodamines and an acridine orange derivative. In all cases, fluorescence intensity differences were caused by impaired dye accumulation, and could be eliminated by treatment of P388/ADR cells with verapamil. Moreover, fluorescence signals from 2 anionic potential-sensitive dyes, merocyanine 540 and a bis-oxonol, were identical in P388 and P388/ADR. None of these dyes could be used to delineate CCRF-CEM, a lymphoblastic leukemia of human origin from the CEM/VM-1 subline that exhibits a markedly atypical drug resistance pattern not based on an enhanced outward transport. But accumulation of both neutral and cationic dyes was impaired in CEM/VLB100, a subline of CCRF-CEM expressing mdr. These studies show that many cationic and neutral fluorescent probes are substrates for the enhanced outward drug transport system associated with P388/ADR cells, and cannot be used to probe membrane-potential differences in cells expressing the mdr phenotype. With several dyes, differences in fluorescence intensity were sufficient so that flow cytometry could be used to delineate P388 from P388/ADR and CCRF-CEM from CEM-VLB100. The latter technique may be useful for identifying malignant cell populations expressing multidrug resistance in patients with neoplastic disease. PMID:1873811

Kessel, D; Beck, W T; Kukuruga, D; Schulz, V

1991-09-01

197

Evaluation of the P-glycoprotein- and breast cancer resistance protein-mediated brain penetration of 11C-labeled topotecan using small-animal positron emission tomography  

International Nuclear Information System (INIS)

Introduction: Topotecan (TPT) is a camptothecin derivative and is an anticancer drug working as a topoisomerase-I-specific inhibitor. But TPT cannot penetrate through the blood-brain barrier. In this study, we synthesized a new positron emission tomography (PET) probe, [11C]TPT, to evaluate the P-glycoprotein (Pgp)- and breast cancer resistance protein (BCRP)-mediated brain penetration of [11C]TPT using small-animal PET. Methods: [11C]TPT was synthesized by the reaction of a desmethyl precursor with [11C]CH3I. In vitro study using [11C]TPT was carried out in MES-SA and doxorubicin-resistant MES-SA/Dx5 cells in the presence or absence of elacridar, a specific inhibitor for Pgp and BCRP. The biodistribution of [11C]TPT was determined using small-animal PET and the dissection method in mice. Results: The transport of [11C]TPT to the extracellular side was determined in MES-SA/Dx5 cells exhibiting the expressions of Pgp and BCRP at high levels. This transport was inhibited by coincubation with elacridar. In Mdr1a/b-/-Bcrp1-/- mice, PET results indicated that the brain uptake of [11C]TPT was about two times higher than that in wild-type mice. Similarly, the brain penetration of [11C]TPT in wild-type mice was increased by treatment with elacridar. The radioactivity in the brain of elacridar-treated mice was maintained at a certain level after t was maintained at a certain level after the injection of [11C]TPT, although the radioactivity in the blood decreased with time. Conclusions: We demonstrated the increase of brain penetration of [11C]TPT by deficiency and inhibition of Pgp and BCRP functions using small-animal PET in mice.

198

Multidrug resistance reversal and apoptosis induction in human colon cancer cells by some flavonoids present in citrus plants.  

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Multidrug resistance (MDR) of cancer cells constitutes one of the main reasons for chemotherapy failure. The search for nontoxic modulators that reduce MDR is a task of great importance. An ability to enhance apoptosis of resistant cells would also be beneficial. In the present study, the MDR reversal and apoptosis-inducing potency of three flavonoids produced by Citrus plants, namely, naringenin (1a), aromadendrin (2), and tangeretin (3), and the methylated naringenin derivatives (1b, 1c), have been studied in sensitive (LoVo) and multidrug-resistant (LoVo/Dx) human colon adenocarcinoma cells. Cytotoxicity of methoxylated flavonoids was higher as compared to hydroxylated analogues. Only 3 turned out to inhibit P-glycoprotein, as demonstrated by a rhodamine 123 accumulation assay. It also increased doxorubicin accumulation in LoVo/Dx cells and enabled doxorubicin to enter cellular nuclei. In addition, 3 was found to be an effective MDR modulator in resistant cells by sensitizing them to doxorubicin. Tangeretin-induced caspase-3 activation and elevated surface phosphatidylserine exposure demonstrated its apoptosis-inducing activity in LoVo/Dx cells, while the other flavonoids evaluated were not active. Additionally, 3 was more toxic to resistant rather than to sensitive cancer cells. Its apoptosis-inducing activity was also higher in LoVo/Dx than in LoVo cells. It was concluded that the activity of 3 against multidrug-resistant cancer cells may be enhanced by its apoptosis-inducing activity. PMID:23137376

Weso?owska, Olga; Wi?niewski, Jerzy; Sroda-Pomianek, Kamila; Bielawska-Pohl, Aleksandra; Paprocka, Maria; Du?, Danuta; Duarte, Noélia; Ferreira, Maria-José U; Michalak, Krystyna

2012-11-26

199

From MDR to MXR : new understanding of multidrug resistance systems, their properties and clinical significance  

DEFF Research Database (Denmark)

The ATP binding cassette (ABC) superfamily of membrane transporters is one of the largest protein classes known, and counts numerous proteins involved in the trafficking of biological molecules across cell membranes. The first known human ABC transporter was P-glycoprotein (P-gp), which confers multidrug resistance (MDR) to anticancer drugs. In recent years, we have obtained an increased understanding of the mechanism of action of P-gp as its ATPase activity, substrate specificity and pharmacokinetic interactions have been investigated. This review focuses on the functional characterization of P-gp, as well as other ABC transporters involved in MDR: the family of multidrug-resistance-associated proteins (MRP1-7), and the recently discovered ABC half-transporter MXR (also known as BCRP, ABCP and ABCG2). We describe recent progress in the analysis of protein structure-function relationships, and consider the conceptual problem of defining and identifying substrates and inhibitors of MDR. An in-depth discussion follows of how coupling of nucleotide hydrolysis to substrate transport takes place, and we propose a scheme for the mechanism of P-gp function. Finally, the clinical correlations, both for reversal of MDR in cancer and for drug delivery, are discussed.

Litman, Thomas; Druley, T E

2001-01-01

200

Evidence of p-glycoprotein sequence diversity in cyathostomins.  

Science.gov (United States)

P-glycoproteins (Pgps) are adenosine triphosphate-binding transporter proteins thought to be associated with multi-drug resistance in mammals and protozoans and have been suggested to be involved in the mechanism of ivermectin (IVM) resistance in Haemonchus contortus. Until now, resistance to IVM has not been reported in cyathostomins in horses in spite of its widespread and frequent use. Reasons for this might be differences in the molecular mechanism of the development of resistance. Based on this hypothesis, the present study was carried out to find homologues of Pgp in cyathostomins. A 416-bp polymerase chain reaction (PCR) product was generated using complementary DNA (cDNA) of Cylicocyclus elongatus and Cylicocyclus insigne and degenerate primers, located in the conserved Pgp nucleotide-binding domains. Resulting PCR products showed interspecific nucleotide and amino acid sequence identities of 73.3 and 76.8%, respectively. Specific primers were designed based on the Cc. elongatus sequence, and a PCR product of 268-bp was amplified from cDNA of single adults of Cylicocyclus radiatus, Cc. insigne, Cylicocyclus nassatus, Cc. elongatus, Cylicostephanus hybridus (2 individuals), Cylicostephanus goldi, Cyathostomum pateratum, Cyathostomum coronatum, and Cyathostomum catinatum. Two clusters of sequences were found representing 2 different internucleotide-binding domains (IBDs). A further distinct IBD is represented by the 416-bp PCR product of Cc. insigne. Therefore, a total of 3 clearly different sequences of the IBD were cloned and sequenced, suggesting that at least 2 Pgp genes exist in cyathostomins. PMID:15562598

Drogemuller, Michaela; Schnieder, T; von Samson-Himmelstjerna, G

2004-10-01

 
 
 
 
201

Expression and clinical significance of multidrug resistance proteins in brain tumors  

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Full Text Available Abstract Background To investigate the mechanisms of multidrug resistance of brain tumors, to identify the site of cellular expression of P-gp in human brains in situ and to morphologically determine whether an association may exist between P-gp and caveolin-1. Methods Immunohistochemistry was used to detect the expression and location of P-glycoprotein (P-gp, Multidrug resistance-associated protein (MDR, Lung resistance-related protein (LRP, Topoisomerase II (Topo II and Glutathione-S-? (GST-? in 30 patient tumor tissues and 5 normal brain tissues. The sections were subjected to double labeling for P-gp (TRITC labeled and caveolin-1 (FITC labeled. The location and characteristics of expression of the two proteins in the blood brain barrier(BBB was observed using a laser scanning microscope. Results High expression of P-gp was detected in vessel walls and the tissue surrounding the vessels. However, expression of P-gp was low in tumor cells. The expression of the other 4 multidrug resistance proteins was not observed in the vessel walls. Laser scanning microscopy showed P-gp and caveolin-1 co-expression: the two proteins co-localized either in the luminal endothelial compartment or at the border of the luminal/abluminal compartments. Conclusion Chemotherapeutics drugs are interrupted in the end-feet of neuroepithelial cells of the BBB by P-gp, which weakens the chemotherapeutic effect. P-gp marks the BBB, and the transporter is localized in the luminal endothelial compartment where it co-localizes with caveolin-1.

Guo Zhenhua

2010-09-01

202

Drug-resistance in multiple myeloma and non-Hodgkin's lymphoma: detection of P-glycoprotein and potential circumvention by addition of verapamil to chemotherapy.  

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The B-cell neoplasms, multiple myeloma and non-Hodgkin's lymphoma, frequently become drug resistant, despite initial responses to chemotherapeutic drugs. Tumor cells from eight patients with clinically drug-refractory disease were evaluated by immuno-histochemical staining for monoclonal immunoglobulin (Ig) expression, nuclear proliferation antigen, P-glycoprotein (P-gly) expression, and other cellular antigens. P-gly was detected on tumor cells from six of eight patients with drug-resistant disease. Of the six patients with P-gly-positive tumors, five patients had advanced multiple myeloma and one had a drug-refractory non-Hodgkin's lymphoma. Cellular RNA analysis confirmed the over-expression of P-gly. In an effort to overcome drug resistance, a pilot study evaluated possible verapamil enhancement of chemotherapy in these eight patients. All patients had developed progressive disease while receiving a regimen containing vincristine and doxorubicin, and seven of eight patients had previously received continuous infusion vincristine and doxorubicin plus oral dexamethasone (VAD). At the time of progressive disease, continuous infusion verapamil was added to the VAD regimen. Three of the eight patients who were refractory to vincristine and doxorubicin alone responded when verapamil was added to VAD. The three patients who responded had P-gly-positive tumors. Verapamil increased the intracellular accumulation of doxorubicin and vincristine in vitro for both a P-gly-positive myeloma cell line and tumor cells from two patients with end-stage myeloma which over-expressed P-gly. The dose-limiting side effect associated with the addition of verapamil to chemotherapy was temporary impairment of cardiac function, manifest as hypotension and cardiac arrhythmia. We conclude that P-gly expression occurs in drug-refractory B-cell neoplasms and may contribute to the development of clinical drug resistance. However, other factors, such as the proliferative activity of the tumor, may also play a role in determining response to chemotherapy. The administration of verapamil along with VAD chemotherapy may partially circumvent drug resistance in patients whose tumors over-express P-gly. PMID:2564428

Dalton, W S; Grogan, T M; Meltzer, P S; Scheper, R J; Durie, B G; Taylor, C W; Miller, T P; Salmon, S E

1989-04-01

203

Effect of multidrug resistance gene-1(MDR1) expression on in-vitro uptake of Tc-99m sestaMIBI(MIBI) in murine L1210 leukemia cells  

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Resistance of malignant tumors to multiple chemotherapeutic agents is a major cause of treatment failure and one of the most important mechanisms of multidrug resistance is an increased expression of plasma membrane P-glycoprotein. P-glycoprotein can recognize and transport a large group of cytotoxic compounds sharing little or no structural or functional similarities, other than being relatively small, hydrophobic and cationic. Recent studies have proved that Tc-99m MIBI is transported by the P-glycoprotein in insect cells with overexpression of recombinant multidrug resistance P-glycoprotein. To demonstrate that Tc-99m MIBI is recognized by the multidrug resistant P-glycoprotein, we have quantitatively measured Tc-99m MIBI uptake in cancer cells with or without expression of MDR1 gene which is responsible for P-glycoprotein. The relationship between Tc-99m MIBI uptake and expression of MDR1 gene was evaluated. Multidrug resistance cell lines were induced from murine leukemia cell line(L1210, mouse lymphocytic leukemia cell, ATCC) with continuous challenging low dose adriamycin (Adr cell) or vincristine (Vcr cell) in culture media. Expression of MDR1 RNA was measured with reverse transcriptase polymerase chain reaction (RT-PCR) using 243 base pair primer (Kizaki et al. Blood 87:725, 1996). Cellular uptake of Tc-99m MIBI was measured at 4 .deg. C and 37 .deg. C condition, and after incubating for 60-min in 37 .deg. C RPMI media with or without 50uM or 200uM verapamil. RT-PCR of Adr cells revealed an intense band corresponding expression of MDR1 RNA, whereas Vcr cells weaker linear band. In contrast, RT-PCR specimen of L1210 did not show MDR1 band. Incubation of cells with Tc-99m MIBI resulted in higher uptake with L1210 than Adr or Vcr cells in either 4 .deg. C (37% L1210 vs 17% Adr or 9% Vcr, p<0.05 respectively) or 37 .deg. C (48% vs 25% or 23%, p<0.01 respectively). In the presence of verapamil, known reverser of PgP functions, incubation with verapamil resulted in increased Tc-99m MIBI uptake in Adr cell line (from 25% to 29% with 50uM or 45% with 200uM) and Vcr cell line(from 23% to 27% with 50uM or 35% with 200uM). Tc-99m MIBI uptake was not changed with verapamil in L1210 cells. These results demonstrate that MDR1 gene expressing cell lines were effectively induced in in-vitro and Tc-99m MIBI is a transporter substrate recognized by the MDR1 P-glycoprotein. Tc-99m MIBI may be useful for characterizing P-glycoprotein expression in leukemic cells in vitro

204

Impact of P-glycoprotein and breast cancer resistance protein on the brain distribution of antiepileptic drugs in knockout mouse models.  

Science.gov (United States)

Refractory epilepsy is reportedly associated with an overexpression of ATP-binding cassette transporters such as P-glycoprotein (Pgp) and breast cancer resistance protein (Bcrp). In this study, we examined the contribution of Pgp and Bcrp to the brain distribution of 12 antiepileptic drugs (AEDs) in Mdr1a/1b(-/-) and Mdr1a/1b(-/-)/Bcrp(-/-) mice within a therapeutic concentration range. The blood concentrations were sequentially determined, and the brain concentrations were measured at 60 min after intravenous administration. The plasma concentration profiles for each AED in the Mdr1a/1b(-/-) mice were equivalent to those in the wild-type mice. In contrast, the plasma concentration profiles of phenytoin, lamotrigine, topiramate, tiagabine, and levetiracetam in the Mdr1a/1b(-/-)/Bcrp(-/-) mice were significantly lower than the corresponding ones in the wild-type mice. The brain-to-plasma concentration ratio (Kpbrain) values of phenytoin, topiramate, and tiagabine in the Mdr1a/1b(-/-) mice were significantly higher than the corresponding ones in the wild-type mice. In contrast, the Kpbrain values of phenobarbital, clobazam, zonisamide, gabapentin, tiagabine, and levetiracetam in the Mdr1a/1b(-/-)/Bcrp(-/-) mice were significantly higher than the corresponding ones in Mdr1a/1b(-/-) mice. The Kpbrain values of the 12 AEDs in the Mdr1a/1b(-/-)/Bcrp(-/-) mice, but not wild-type mice, significantly correlated with the corresponding molecular weight values. These findings suggest that both Pgp and Bcrp restrict brain access for several AEDs. Taken together, information on the contribution of each transporter may be useful in the development of strategic treatments of refractory epilepsy. PMID:23588114

Nakanishi, Haruka; Yonezawa, Atsushi; Matsubara, Kazuo; Yano, Ikuko

2013-06-15

205

Distribution of gefitinib to the brain is limited by P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2)-mediated active efflux.  

Science.gov (United States)

Gefitinib is an orally active inhibitor of the epidermal growth factor receptor approved for use in patients with locally advanced or metastatic non-small cell lung cancer. It has also been evaluated in several clinical trials for treatment of brain tumors such as high-grade glioma. In this study, we investigated the influence of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) on distribution of gefitinib to the central nervous system. In vitro studies conducted in Madin-Darby canine kidney II cells indicate that both P-gp and BCRP effectively transport gefitinib, limiting its intracellular accumulation. In vivo studies demonstrated that transport of gefitinib across the blood-brain barrier (BBB) is significantly limited. Steady-state brain-to-plasma (B/P) concentration ratios were 70-fold higher in the Mdr1a/b(-/-) Bcrp1(-/-) mice (ratio of approximately 7) compared with wild-type mice (ratio of approximately 0.1). The B/P ratio after oral administration increased significantly when gefitinib was coadministered with the dual P-gp and BCRP inhibitor elacridar. We investigated the integrity of tight junctions in the Mdr1a/b(-/-) Bcrp1(-/-) mice and found no difference in the brain inulin and sucrose space between the wild-type and Mdr1a/b(-/-) Bcrp1(-/-) mice. This suggested that the dramatic enhancement in the brain distribution of gefitinib is not due to a leakier BBB in these mice. These results show that brain distribution of gefitinib is restricted due to active efflux by P-gp and BCRP. This finding is of clinical significance for therapy in brain tumors such as glioma, where concurrent administration of a dual inhibitor such as elacridar can increase delivery and thus enhance efficacy of gefitinib. PMID:20421331

Agarwal, Sagar; Sane, Ramola; Gallardo, Jose L; Ohlfest, John R; Elmquist, William F

2010-07-01

206

P-glycoprotein (multi-xenobiotic resistance) and heat shock protein gene expression in the reef coral Montastraea franksi in response to environmental toxicants.  

Science.gov (United States)

The deleterious impacts of marine pollutants on reef corals and their symbiotic algae are an important element of global coral reef decline. In the current study we examined the impacts of toxicants on the reef coral Montastraea franksi by analysing the expression of three stress-related genes belonging to the coral host, using Taqman real-time quantitative reverse transcription-PCR. Gene expression profiles of P-glycoprotein (or multi-xenobiotic resistance protein) (P-gp); heat shock protein 70 (Hsp70) and heat shock protein 90 (Hsp90) were examined following 4 and 8h exposures to the heavy metal copper (3, 10, 30 and 100 microgL(-1)) or the third generation oil dispersant Corexit9527 (1, 5, 10 and 50 ppm). Additionally, the expression of P-gp was examined following exposure to 0.5 and 5 microM concentrations of the chemotherapeutic drug vinblastine, a classic substrate of P-gp. The expression of P-gp increased significantly in corals treated with vinblastine and also increased following exposure to copper and Corexit9527. Hsp70, and to a lesser extent Hsp90 expression increased following exposure to copper and Corexit9527 indicating a general cellular stress response. Densities of symbiotic algae in the tissues of the corals did not change significantly during the experiments, nor was any loss or paling of coral tissues observed. These findings provide important insight into how corals defend themselves against pollution and complement ongoing initiatives developing molecular biomarkers of stress in reef-building corals. PMID:19501419

Venn, Alexander A; Quinn, Jennifer; Jones, Ross; Bodnar, Andrea

2009-07-26

207

P-GLYCOPROTEIN QUANTITATION IN ACUTE LEUKEMIA  

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Multi drug resistance(MDR) is a major problem in the treatment of cancer and hemalological malignancies. This resistance is multi factorial and is the result of decreased intra cellular drug accumulation. This is partly due to the presence of a 170KD intra membranous protein termed P-glycoprotein(P-gp) that is an energy-dependent efflux pump which has increased expression on drug-resistance cells. In this study we identified the presence of P-gp by staining with Fluorescent Iso Thio Cyanate (...

Pourfathollali, A. A.; Farliadi, M.; Mali in Nikougoftar

2003-01-01

208

Reversal effect of Tween-20 on multidrug resistance in tumor cells in vitro.  

Science.gov (United States)

Multidrug resistance (MDR) is a major barrier for chemotherapy of many cancers. Non-ionic surfactants have great potential to reverse the MDR by preventing onset or delay progression of the carcinogenic process. However, the role of Tween-20 in the development of MDR remains unknown. The aim of this study was to explore the reversal effect and potential mechanism of Tween-20 on tumor cells in vitro. Alamar Blue assay was used to examine the reversal index of Tween-20 to vincristine (VCR), doxorubicin (DOX) and 5-fluorouracil (5-FU) in KBv200, HepG2/R and Bel-7402/5-FU, respectively. Morphological change was determined by Gimsa and Hoechst 33258 staining. The acumulation of DOX was confirmed by spectrofluorimetric assay. Cell cycle analysis was performed using flow cytometry. The mRNA and protein expression levels of MDR were assessed by semiquantitative RT-PCR and dot blot, respectively. The results showed that Tween-20 at concentrations of 0.0025%, 0.005%, 0.01% had little cytotoxicity. When combined with the cancer drugs, it significantly promoted the sensitivity of MDR cells. Fluorescence staining confirmed that the percentage of apoptotic cell increased when combined with Tween-20. This notion was further supported by the observation that Tween-20 treatment potentiated VIN-induced G2/M arrest of the cell cycle. Furthermore, Tween-20 treatment increased significantly intracellular accumulation of DOX. RT-PCR and dot blot revealed that Tween-20 could downregulate the expression of MDR and P-glycoprotein. Low concentrations of Tween-20 can efficiently reverse the multidrug resistance phenotype by enhancing accumulation of the anticancer drugs. The potential mechanism may be via inhibiting the multidrug-resistant gene expression. PMID:22440896

Yang, Shouhui; Liu, Jinjuan; Chen, Yongqiang; Jiang, Jihong

2012-04-01

209

Salinomycin overcomes ABC transporter-mediated multidrug and apoptosis resistance in human leukemia stem cell-like KG-1a cells  

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Leukemia stem cells are known to exhibit multidrug resistance by expression of ATP-binding cassette (ABC) transporters which constitute transmembrane proteins capable of exporting a wide variety of chemotherapeutic drugs from the cytosol. We show here that human promyeloblastic leukemia KG-1a cells exposed to the histone deacetylase inhibitor phenylbutyrate resemble many characteristics of leukemia stem cells, including expression of functional ABC transporters such as P-glycoprotein, BCRP and MRP8. Consequently, KG-1a cells display resistance to the induction of apoptosis by various chemotherapeutic drugs. Resistance to apoptosis induction by chemotherapeutic drugs can be reversed by cyclosporine A, which effectively inhibits the activity of P-glycoprotein and BCRP, thus demonstrating ABC transporter-mediated drug resistance in KG-1a cells. However, KG-1a are highly sensitive to apoptosis induction by salinomycin, a polyether ionophore antibiotic that has recently been shown to kill human breast cancer stem cell-like cells and to induce apoptosis in human cancer cells displaying multiple mechanisms of drug and apoptosis resistance. Whereas KG-1a cells can be adapted to proliferate in the presence of apoptosis-inducing concentrations of bortezomib and doxorubicin, salinomycin does not permit long-term adaptation of the cells to apoptosis-inducing concentrations. Thus, salinomycin should be regarded as a novel and effective agent for the elimination of leukemia stem cells and other tumor cells exhibiting ABC transporter-mediated multidrug resistance.

Fuchs, Dominik [Research Group Molecular Neuro-Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg (Germany); Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany); Daniel, Volker; Sadeghi, Mahmoud; Opelz, Gerhard [Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany); Naujokat, Cord, E-mail: cord.naujokat@med.uni-heidelberg.de [Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany)

2010-04-16

210

Phorbol esters induce multidrug resistance in human breast cancer cells  

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Mechanisms responsible for broad-based resistance to antitumor drugs derived from natural products (multidrug resistance) are incompletely understood. Agents known to reverse the multidrug-resistant phenotype (verapamil and trifluoperazine) can also inhibit the activity of protein kinase C. When the authors assayed human breast cancer cell lines for protein kinase C activity, they found that enzyme activity was 7-fold higher in the multidrug-resistance cancer cells compared with the control, sensitive parent cells. Exposure of drug-sensitive cells to the phorbol ester phorbol 12,13-dibutyate (P(BtO)/sub 2/) led to an increase in protein kinase C activity and induced a drug-resistance phenotype, whereas exposure of drug-resistant cells to P(BtO)/sub 2/ further increased drug resistance. In sensitive cells, this increased resistance was accomplished by a 3.5-fold increased phosphorylation of a 20-kDa particulate protein and a 35-40% decreased intracellular accumulation of doxorubicin and vincristine. P(BtO)/sub 2/ induced resistance to agents involved in the multidrug-resistant phenotype (doxorubicin and vincristine) but did not affect sensitivity to an unrelated alkylating agent (melphalan). The increased resistance was partially or fully reversible by the calcium channel blocker verapamil and by the calmodulin-antagonist trifluoperazine. These data suggest that stimulation of protein kinase C playus a role in the drug-transport changes in multidrug-resistant cells. This may occur through modulation of an efflux pump by protein phosphorylation.

Fine, R.L.; Patel, J.; Chabner, B.A.

1988-01-01

211

Drug resistance pattern in multidrug resistance pulmonary tuberculosis patients  

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To evaluate the frequency of drug resistance profiles of multidrug resistant tuberculosis (MDR-TB) isolates of pulmonary tuberculosis patients, against both the first and the second line drugs. Study Design: An observational study. Place and Duration of Study: The multidrug resistant tuberculosis (MDR-TB) ward of Ojha Institute of Chest Diseases (OICD), Karachi, from 1996 to 2006. Methodology: Culture proven MDR-TB cases (resistant to both isoniazid and Rifampicin) were retrospectively reviewed. Susceptibility testing was performed at the clinical laboratory of the Aga Khan University. Sensitivity against both first and second line anti-tuberculosis drugs was done. Susceptibility testing was performed using Agar proportion method on enriched middle brook 7H10 medium (BBL) for Rifampicin, Isoniazid, Streptomycin, Ethambutol, Ethionamide, Capreomycin and Ciprofloxacin. Pyrazinamide sensitivity was carried out using the BACTEC 7H12 medium. During the study period MTB H37Rv was used as control. Results: Out of total 577 patients, all were resistant to both Rifampicin and Isoniazid (INH). 56.5% isolates were resistant to all five first line drugs. Resistances against other first line drugs was 76.60% for Pyrazinamide, 73% for Ethambutol and 68.11% for Streptomycin. Five hundred and ten (88%) cases were MDR plus resistant to one more first line drug. Forty (07%) isolates were MDR plus Quinolone-resistant. They were sensitive to Capreomycin but sensitivity against Amikacin and Kanamycin were not tested. Conclusion: There were high resistance rates in MDR-TB to remaining first line and second line drugs. Continuous monitoring of drug resistance pattern especially of MDR isolates and treatment in specialized centers is a crucial need for future TB control in Pakistan. (author)

212

Multidrug resistant yeasts in synanthropic wild birds  

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Full Text Available Abstract Background The aim of this study was to investigate the presence of multidrug resistant yeasts in the faeces of synanthropic wild birds from the Bangsar suburb of Kuala Lumpur. Methods Species characterisations of yeast isolates and determinations of antimycotic susceptibility profiles were undertaken using the commercial characterization kit, Integral System Yeasts Plus (Liofilchem, Italy. Results Fourteen species of yeasts were detected in the bird faecal samples.Candida albicans was present in 28.89% of bird faecal samples, Candida krusei (13.33%, Candida tropicalis (4.44%, Candida glabrata (4.44%, Candida parapsilosis (2.22%, Candida lambica (2.22%, Candida stellatoidea (2.22%, Candida rugosa (2.22% and Candida lusitaniae (2.22%. Amongst the non-candidal yeast isolates, Cryptococcus laurentii was present in 6.67% of bird faecal samples, Cryptococcus uniguttulatus (4.44%, Saccharomyces cerevisiae (4.44%, Trichosporon pullulans (2.22%, Trichosporon pullulans/Cryptococcus albidus (8.89% and Rhodotorula rubra/Rhodotorula glutinis (4.44%. Of the isolated yeasts, 18.1% (or 26/144 were found to be resistant to all 11 antimycotic agents they were tested against i.e. Nystatin, Amphotericin B, Flucytosine, Econazole, Ketoconazole, Clotrimazole, Miconazole, Itraconazole, Voriconazole, Fluconazole 16 and Fluconazole 64. 45.8% (or 66/144 of the bird faecal yeast isolates were resistant to four or more of the 11 antimycotic agents they were tested against. Conclusions This finding is of public health significance as these synanthropic wild birds may be reservoirs for transmission of drug resistant yeast infections to humans.

Somanath Sushela

2010-03-01

213

Radiosynthesis and in vivo evaluation of 1-[18F]fluoroelacridar as a positron emission tomography tracer for P-glycoprotein and breast cancer resistance protein.  

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Aim of this study was to label the potent dual P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) inhibitor elacridar (1) with (18)F to provide a positron emission tomography (PET) radiotracer to visualize Pgp and BCRP. A series of new 1- and 2-halogen- and nitro-substituted derivatives of 1 (4a-e) was synthesized as precursor molecules and reference compounds for radiolabelling and shown to display comparable in vitro potency to 1 in increasing rhodamine 123 accumulation in a cell line overexpressing human Pgp (MDCKII-MDR1). 1-[(18)F]fluoroelacridar ([(18)F]4b) was synthesized in a decay-corrected radiochemical yield of 1.7±0.9% by a 1-step no-carrier added nucleophilic aromatic (18)F-substitution of 1-nitro precursor 4c. Small-animal PET imaging of [(18)F]4b was performed in naïve rats, before and after administration of unlabelled 1 (5 mg/kg, n=3), as well as in wild-type and Mdr1a/b((-/-))Bcrp1((-/-)) mice (n=3). In PET experiments in rats, administration of unlabelled 1 increased brain activity uptake by a factor of 9.5 (p=0.0002, 2-tailed Student's t-test), whereas blood activity levels remained unchanged. In Mdr1a/b((-/-))Bcrp1((-/-)) mice, the mean brain-to-blood ratio of activity at 60 min after tracer injection was 7.6 times higher as compared to wild-type animals (p=0.0002). HPLC analysis of rat brain tissue extracts collected at 40 min after injection of [(18)F]4b revealed that 93±7% of total radioactivity in brain was in the form of unchanged [(18)F]4b. In conclusion, the in vivo behavior of [(18)F]4b was found to be similar to previously described [(11)C]1 suggesting transport of [(18)F]4b by Pgp and/or BCRP at the rodent BBB. However, low radiochemical yields and a significant degree of in vivo defluorination will limit the utility of [(18)F]4b as a PET tracer. PMID:21419632

Dörner, Bernd; Kuntner, Claudia; Bankstahl, Jens P; Wanek, Thomas; Bankstahl, Marion; Stanek, Johann; Müllauer, Julia; Bauer, Florian; Mairinger, Severin; Löscher, Wolfgang; Miller, Donald W; Chiba, Peter; Müller, Markus; Erker, Thomas; Langer, Oliver

2011-04-01

214

Mesoporous silica nanoparticles loading doxorubicin reverse multidrug resistance: performance and mechanism  

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Multidrug resistance (MDR) is one of the major obstacles for successful chemotherapy in cancer. One of the effective approaches to overcome MDR is to use nanoparticle-mediated drug delivery to increase drug accumulation in drug resistant cancer cells. In this work, we first report that the performance and mechanism of an inorganic engineered delivery system based on mesoporous silica nanoparticles (MSNs) loading doxorubicin (DMNs) to overcome the MDR of MCF-7/ADR (a DOX-resistant and P-glycoprotein (P-gp) over-expression cancer cell line). The experimental results showed that DMNs could enhance the cellular uptake of doxorubicin (DOX) and increase the cell proliferation suppression effect of DOX against MCF-7/ADR cells. The IC50 of DMNs against MCF-7/ADR cells was 8-fold lower than that of free DOX. However, an improved effect of DOX in DMNs against MCF-7 cells (a DOX-sensitive cancer cell line) was not found. The increased cellular uptake and nuclear accumulation of DOX delivered by DMNs in MCF-7/ADR cells was confirmed by confocal laser scanning microscopy, and could result from the down-regulation of P-gp and bypassing the efflux action by MSNs themselves. The cellular uptake mechanism of DMNs indicated that the macropinocytosis was one of the pathways for the uptake of DMNs by MCF-7/ADR cells. The in vivo biodistribution showed that DMNs induced a higher accumulation of DOX in drug resistant tumors than free DOX. These results suggested that MSNs could be an effective delivery system to overcome multidrug resistance.

Shen, Jianan; He, Qianjun; Gao, Yu; Shi, Jianlin; Li, Yaping

2011-10-01

215

Artemisinin induces doxorubicin resistance in human colon cancer cells via calcium-dependent activation of HIF-1alpha and P-glycoprotein overexpression  

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BACKGROUND AND PURPOSE: Artemisinin is an antimalarial drug exerting pleiotropic effects, such as the inhibition of the transcription factor nuclear factor-kappa B and of the sarcoplasmic/endoplasmic reticulum Ca(++)-ATPase (SERCA) of P. falciparum. As the sesquiterpene lactone thapsigargin, a known inhibitor of mammalian SERCA, enhances the expression of P-glycoprotein (Pgp) by increasing the intracellular Ca(++) ([Ca(++)](i)) level, we investigated whether artemisinin and its structural hom...

Bosia, Amalia; Pescarmona, Gianpiero; Ghigo, Dario Antonio; Miraglia, Erica; Doublier, Sophie; Riganti, Chiara

2009-01-01

216

Combating apoptosis and multidrug resistant cancers by targeting lysosomes.  

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Acquired therapy resistance is one of the prime obstacles for successful cancer treatment. Partial resistance is often acquired already during an early face of tumor development when genetic changes causing defects in classical caspase-dependent apoptosis pathway provide transformed cells with a growth advantage by protecting them against various apoptosis inducing stimuli including transforming oncogenes themselves and host immune system. Apoptosis defective cells are further selected during tumor progression and finally by apoptosis inducing treatments. Another form of resistance, multidrug resistance, arises during cancer treatment when cancer cells with effective efflux of cytotoxic agents escape the therapy. Remarkably, induction of lysosomal membrane permeabilization has recently emerged as an effective way to kill apoptosis resistant cancer cells and some lysosome targeting drugs can also re-sensitize multidrug resistant cells to classical chemotherapy. In this review, we highlight recent data on lysosomal cell death pathways and their implications for the future treatment of apoptosis defective and multidrug resistant aggressive tumors. PMID:20598437

Groth-Pedersen, Line; Jäättelä, Marja

2013-05-28

217

Bypassing multidrug resistance in human breast cancer cells with lipid/polymer particle assemblies  

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Full Text Available Bo Li1, Hui Xu2, Zhen Li1, Mingfei Yao1, Meng Xie1, Haijun Shen1, Song Shen1, Xinshi Wang1, Yi Jin11College of Pharmaceutical sciences, Zhejiang University, Hangzhou, 2No. 202 Hospital of People's Liberation Army, Shenyang, ChinaBackground: Multidrug resistance (MDR mediated by the overexpression of adenosine triphosphate (ATP-binding cassette (ABC transporters, such as P-glycoprotein (P-gp, remains one of the major obstacles to effective cancer chemotherapy. In this study, lipid/particle assemblies named LipoParticles (LNPs, consisting of a dimethyldidodecylammonium bromide (DMAB-modified poly(lactic-co-glycolic acid (PLGA nanoparticle core surrounded by a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC shell, were specially designed for anticancer drugs to bypass MDR in human breast cancer cells that overexpress P-gp.Methods: Doxorubicin (DOX, a chemotherapy drug that is a P-gp substrate, was conjugated to PLGA and encapsulated in the self-assembled LNP structure. Physiochemical properties of the DOX-loaded LNPs were characterized in vitro. Cellular uptake, intracellular accumulation, and cytotoxicity were compared in parental Michigan Cancer Foundation (MCF-7 cells and P-gp-overexpressing, resistant MCF-7/adriamycin (MCF-7/ADR cells.Results: This study found that the DOX formulated in LNPs showed a significantly increased accumulation in the nuclei of drug-resistant cells relative to the free drug, indicating that LNPs could alter intracellular traffic and bypass drug efflux. The cytotoxicity of DOX loaded-LNPs had a 30-fold lower half maximal inhibitory concentration (IC50 value than free DOX in MCF-7/ADR, measured by the colorimetric cell viability (MTT assay, correlated with the strong nuclear retention of the drug.Conclusion: The results show that this core-shell lipid/particle structure could be a promising strategy to bypass MDR.Keywords: chemotherapy, drug delivery, polymeric nanoparticles, multidrug resistance

Li B

2012-01-01

218

Phorbol esters induce multidrug resistance in human breast cancer cells  

International Nuclear Information System (INIS)

Mechanisms responsible for broad-based resistance to antitumor drugs derived from natural products (multidrug resistance) are incompletely understood. Agents known to reverse the multidrug-resistant phenotype (verapamil and trifluoperazine) can also inhibit the activity of protein kinase C. When the authors assayed human breast cancer cell lines for protein kinase C activity, they found that enzyme activity was 7-fold higher in the multidrug-resistance cancer cells compared with the control, sensitive parent cells. Exposure of drug-sensitive cells to the phorbol ester phorbol 12,13-dibutyate [P(BtO)2] led to an increase in protein kinase C activity and induced a drug-resistance phenotype, whereas exposure of drug-resistant cells to P(BtO)2 further increased drug resistance. In sensitive cells, this increased resistance was accomplished by a 3.5-fold increased phosphorylation of a 20-kDa particulate protein and a 35-40% decreased intracellular accumulation of doxorubicin and vincristine. P(BtO)2 induced resistance to agents involved in the multidrug-resistant phenotype (doxorubicin and vincristine) but did not affect sensitivity to an unrelated alkylating agent (melphalan). The increased resistance was partially or fully reversible by the calcium channel blocker verapamil and by the calmodulin-antagonist trifluoperazine. These data suggest that stimulation of protein kinase C playus a role in the drug-transport changes in multidrug-resie drug-transport changes in multidrug-resistant cells. This may occur through modulation of an efflux pump by protein phosphorylation

219

Possible effect of dihydropyridines on topoisomerase-mediated multidrug resistance, a new approach for ?designing the new reversal agents for atypical MDR  

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Full Text Available Multidrug resistance can result from several factors and processes. Some types of multidrug resistance (MDR were recognized whose patterns differ from pattern of P-glycoprotein (P-gp associated MDR in several important ways. Although, there is limited evidence for effect of DHP on atypical MDR; based on some observations like noncompetitive inhibition of topoisomerase I by a DHP derivative (Dexniguldipine, it has been hypothesized that some DHP derivatives which have essential structural feature have possible effect on altering the topoisomerase II levels or activity which results in reversing topoisomerase-mediated MDR. If this hypothesis is verified, some new dihydropyridine can be synthesized with possible dual effect on both typical and atypical MDR.

Ramin Miri

2007-06-01

220

Modulation of multidrug resistance gene expression by dexamethasone in cultured hepatoma cells.  

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Considerable evidence has accumulated indicating that overexpression of P-glycoproteins encoded by the multidrug-resistance (mdr) genes is responsible for the development of collateral resistance to a number of structurally and functionally dissimilar cytotoxic compounds in animal cells. There are three mdr genes (mdr1, mdr2, and mdr3) in the mouse genome and two (MDR1 and MDR2) in the human genome; however, only two mouse genes (mdr1 and mdr3) and one human gene (MDR1) can confer multidrug resistance upon transfection into otherwise drug-sensitive cells. Using RNase protection assay we report here that the steady-state levels of mdr1 and mdr3 messenger RNA were elevated in mouse hepatoma cells treated with dexamethasone (Dex); whereas no induction of mdr2 gene was found. Western blot analyses using anti-mdr1 and anti-mdr3 antibodies revealed that the encoded proteins appeared to be increased, but at much reduced levels. The induction was time and Dex concentration dependent. Nuclear run-on experiments demonstrated that the induction was at least in part by transcriptional control. The induction apparently required new protein synthesis since no increases in mdr1 and mdr3 transcripts was found when cultured cells were simultaneously treated with Dex and cycloheximide. Neither mdr1 nor mdr3 gene was induced in the Dex-treated nonhepatoma cell lines, LMtk- and NIH3T3. Similarly, MDR1 messenger RNA levels were elevated in the Dex-treated human hepatoma line, HepG2, but not in the nonhepatoma, HeLa. This study demonstrated that the hormonal regulation of mdr gene expression is gene and cell type specific. PMID:8102093

Zhao, J Y; Ikeguchi, M; Eckersberg, T; Kuo, M T

1993-08-01

 
 
 
 
221

Reversal of multidrug-resistance using Valspodar (PSC 833) and doxorubicin in osteosarcoma.  

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High-grade osteosarcoma is an extremely aggressive neoplasm, where over 80% of patients present with life-threatening micrometastases at diagnosis. Systemic control of the disease is therefore critical for the treatment of these patients and neoadjuvant chemotherapy using various drugs, including doxorubicin (DXR), which has been demonstrated to be the most effective regimen. Multidrug resistance (MDR) to some anticancer agents, including DXR, mediated by the MDR1 gene product P-glycoprotein (Pgp), has been shown to be a major cause of chemotherapy failure in osteosarcoma. We analyzed the effect of a cyclosporine A derivate Valspodar (PSC 833) on MDR human osteosarcoma cells. We also evaluated Pgp expression in sporadic appendicular canine osteosarcoma. Moreover, dogs were treated with combined administration of DXR and PSC 833. Several blood samples were collected for the determination of DXR and PSC 833 levels. PSC 833 induced a complete reversal of the resistant phenotype at concentrations compatible with the clinical use. Pgp was present in 12/18 (66.6%) of the cases. At the time of DXR administration, adequate blood concentrations of PSC 833, to provide a complete MDR reversal, were obtained without clinical or laboratory findings of toxicity. Combination therapy with DXR and PSC 833 allowed a 30% decrease in DXR dose infusion with equivalent therapeutic exposure. The high incidence of Pgp expression in osteosarcoma confers to the study a rationale for an effective regimen based on down-modulation of MDR. PMID:15492788

Cagliero, E; Ferracini, R; Morello, E; Scotlandi, K; Manara, M C; Buracco, P; Comandone, A; Baroetto Parisi, R; Baldini, N

2004-11-01

222

Association between DNA methylation and multidrug resistance in human glioma SHG?44 cells.  

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The aim of the present study was to evaluate the association between DNA methylation and multidrug resistance (MDR) in glioma and identify novel effectors responsible for MDR in human gliomas. An MDR glioma cell line, SGH?44/ADM, was developed using adriamycin (ADM) impulse treatment. Cryopreservation, recovery and withdrawal were performed to evaluate the stability of SGH?44/ADM cells. The adherence rate and cellular morphology were observed by microscopy, and the cell growth curve and doubling time were determined. DNA methylation was analyzed using a methylated DNA immunoprecipitation microarray chip (MeDIP?Chip). The cell cycle, Rh123 ingestion and exudation, and SGH?44/ADM apoptosis were analyzed by flow cytometry. SGH?44/ADM cells showed little difference as compared with parental cells, except that SGH?44/ADM cells were bigger in size with a wizened nucleus. Compared to SGH?44 cells, a larger proportion of SGH?44/ADM cells remained in G1 and S phase, as measured by flow cytometry. The MDR of SGH?44/ADM was associated with the upregulation of multi?drug resistance 1, prostaglandin?endoperoxide synthase 2 (COX?2); protein kinase C ? (PKC?); however, the expression of these genes was not associated with DNA methylation. In the MeDIP?Chip analysis, 74 functions were markedly enhanced, and seven significant pathways were observed. Genes including SNAP47, ARRB2, PARD6B, TGFB1, VPS4B and CBLB were identified by gene ontology analysis. The predominant molecular mechanism of MDR in SGH?44/ADM cells was identified as exocytosis and efflux. The expression of COX?2, PKC? and P?glycoprotein (Pgp) was not found to be associated with DNA methylation. Genes including SNAP47, VAMP4 and VAMP3 may serve as the downstream effectors of Pgp, COX?2 or PKC?; however, further experiments are required to verify these observations. PMID:25333456

Chen, Jin; Xu, Zhong-Ye; Wang, Feng

2015-01-01

223

Using 99Tcm-MIBI to evaluate tumor multidrug resistance and monitor the reversing of chemosensitizer  

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Objective: To study the correlation between uptake of 99Tcm-methoxyisobutylisonitrile (MIBI) and multidrug-resistant P-glycoprotein (gp), and to evaluate the effect of chemosensitizer. Methods: Tumor bearing mice model was established by implanting human cancer cell line MCF-7/Adr, the model mice were randomized into two groups: chemosensitizer verapamil group and control group. Before and after giving verapamil, 99Tcm-MIBI imaging was performed at 15, 60, 90, 120 min, respectively. Mice of the control group were sacrificed after the pre-verapamil imaging, and mice of the verapamil group were sacrificed after the post-verapamil imaging to get %ID/g of tumor and major organs. The level of P-gp was measured with immunocytochemical assay and mRNA of mdr1 gene determined with RT-PCR was obtained simultaneously. Results: After giving verapamil the TPN ratio of tumor increased significantly except on 120 min imaging. 99Tcm-MIBI uptake difference between the verapamil group and control group was obvious (P=0.045, 0.015, 0.042, respectively). The expression of mdr1 mRNA decreased significantly after verapamil reversing (t=4.873, P=0.008). The level of P-gp declined from 0.1038 ± 0.0078 to 0.0096 ± 0.0059 (t=3.579, P=0.023). The 99Tcm-MIBI uptake of tumor, liver and kidney rose obviously after reversing, %ID/g increments were 106.83%, 40.35%, 166.07%, respectively whereas it was slightly declined, -12.82%, in heart. Conclusion: 99Tcm-MIBI imaging may evaluate multidrug resistance (MDR) mediated by P-gp and be used to monitor the reversing effect of chemosensitizer in P-gp positive tumors

224

In vitro and in vivo reversal of MDR1-mediated multidrug resistance by KT-5720: implications on hematological malignancies.  

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Multidrug resistance (MDR) due to over-expression of the MDR1 (ABCB1) gene and its P-glycoprotein (Pgp) product is an obstacle in the treatment of hematological malignancies. In this study, we have evaluated the potency of KT-5720 to reverse Pgp-dependent MDR in vitro and in vivo. KT-5720 (but not its close derivatives, K252a and K252b) reversed multidrug resistance of LM1/MDR cell line at non-toxic concentrations and increased accumulation of rhodamine 123 (Rh123). KT-5720 significantly reversed MDR1-dependent resistance of primary malignant cells from patients with chronic myelogenous leukemia in blast crisis (CML-BC) and advanced multiple myeloma (MM). Moreover, KT-5720 (at 5 mg/kg) sensitized the bone marrow of MDR1 transgenic mice model towards daunorubicin (at 8 mg/kg) without general toxic effects. Therefore, KT-5720 can be considered as candidate for combination therapy in various hematological malignancies where Pgp activity is a major impediment for cure. PMID:16542724

Galski, Hanan; Sivan, Hamutal; Lazarovici, Philip; Nagler, Arnon

2006-09-01

225

Multi-drug resistance gene (MDR1 and opioid analgesia in horses  

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Full Text Available Opioid absorption in the intestinal tract as well as its effects in the central nervous system is modulated by the P-glycoprotein (P-gp encoded in the Multi-drug Resistance gene (MDR1 also named ATP-binding cassete, subfamily B, member 1 (ABCB1. This MDR1 gene acts as a selective pump. The expression of this protein in humans and rodents inhibits cellular uptake of substrate opioids. The presence of the intestinal iso-enzyme CYP3A4 associated with MDR1 gene decreases the opioid analgesic activity due to an increase in intestinal metabolism, with a predicted intestinal first pass extraction around 20% which significantly influences the oral availability of opioids. In the central nervous system, P-gp expression decreases opioid neuronal uptake diminishing the analgesic effects. It is unknown if horses have the MDR1 gene and P-gp and what are the effects on opioid absorption, metabolism, and analgesia. Identifying the MDR1 gene and P-gp status in horses is of great importance in order to better understand opioid pharmacologic effects in horses.

Natalini Cláudio Corrêa

2006-01-01

226

A novel approach for predicting P-glycoprotein (ABCB1) inhibition using molecular interaction fields.  

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P-glycoprotein (Pgp or ABCB1) is an ABC transporter protein involved in intestinal absorption, drug metabolism, and brain penetration, and its inhibition can seriously alter a drug's bioavailability and safety. In addition, inhibitors of Pgp can be used to overcome multidrug resistance. Given this dual purpose, reliable in silico procedures to predict Pgp inhibition are of great interest. A large and accurate literature collection yielded more than 1200 structures; a model was then constructed using various molecular interaction field-based technologies, considering pharmacophoric features and those physicochemical properties related to membrane partitioning. High accuracy was demonstrated internally with two different validation sets and, moreover, using a number of molecules, for which Pgp inhibition was not experimentally available but was evaluated in-house. All of the validations confirmed the robustness of the model and its suitability to help medicinal chemists in drug discovery. The information derived from the model was rationalized as a pharmacophore for competitive Pgp inhibition. PMID:21341745

Broccatelli, Fabio; Carosati, Emanuele; Neri, Annalisa; Frosini, Maria; Goracci, Laura; Oprea, Tudor I; Cruciani, Gabriele

2011-03-24

227

Multidrug-resistant Acinetobacter baumannii Harboring OXA-24 carbapenemase, Spain.  

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In February 2006, a patient colonized with a multidrug-resistant sequence type 56 Acinetobacter baumannii strain was admitted to a hospital in Madrid, Spain. This strain spread rapidly and caused a large outbreak in the hospital. Clinicians should be alert for this strain because its spread would have serious health consequences. PMID:21749771

Acosta, Joshi; Merino, Maria; Viedma, Esther; Poza, Margarita; Sanz, Francisca; Otero, Joaquín R; Chaves, Fernando; Bou, Germán

2011-06-01

228

Clonal Multidrug-Resistant Corynebacterium striatum Strains, Italy  

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We assessed the clinical relevance and performed molecular characterization of 36 multidrug-resistant strains of Corynebacterium striatum. Pulsed-field gel electrophoresis confirmed a single clone, possessing erm(X), tetA/B, cmxA/B, and aphA1 genes, but few related subclones. This strain is emerging as a pathogen in Italy.

Campanile, Floriana; Carretto, Edoardo; Barbarini, Daniela; Grigis, Annalisa; Falcone, Marco; Goglio, Antonio; Venditti, Mario; Stefani, Stefania

2009-01-01

229

Aquariums as Reservoirs for Multidrug-resistant Salmonella Paratyphi B  

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Multidrug-resistant Salmonella enterica serovar Paratyphi B dT+ isolates from patients with gastroenteritis were identical with isolates from their home aquariums. Matched isolates had identical phage types, XbaI and IS200 profiles, and Salmonella genomic island 1 (SGI1). Ornamental fish tanks are reservoirs for SGI1-containing S. Paratyphi B dT+.

Levings, Renee S.; Lightfoot, Diane; Hall, Ruth M.; Djordjevic, Steven P.

2006-01-01

230

Modulating cancer multidrug resistance by sertraline in combination with a nanomedicine.  

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Inherent and acquired multiple drug resistance (MDR) to chemotherapeutic drugs is a major obstacle in cancer treatment. The ATP Binding Cassettes (ABC) transporter super family that act as extrusion pumps such as P-glycoprotein and multidrug-resistance-associated-proteins have prominent roles in cancer MDR. One of the most efficient strategies to modulate this active drug efflux from the cells is to physically block the pump proteins and thus change the balance between drug influx and efflux toward an accumulation of drug inside the cell, which eventually cumulates into cell death. MDR modulators (also known as chemosensitizers) were found among drugs approved for non-cancer indications. Yet, toxicity, adverse effects, and poor solubility at doses required for MDR reversal prevent their clinical application. Previous reports have shown that drugs belonging to the selective serotonin reuptake inhibitors (SSRI) family, which are clinically used as antidepressants, can act as effective chemosensitizers both in vitro and in vivo in tumor bearing mouse models. Here, we set out to explore whether sertraline (Zoloft®), a molecule belonging to the SSRI family, can be used as an MDR modulator. Combining sertraline with another FDA approved drug, Doxil® (pegylated liposomal doxorubicin), is expected to enhance the effect of chemotherapy while potentially reducing adverse effects. Our findings reveal that sertraline acts as a pump modulator in cellular models of MDR. In addition, in an aggressive and highly resistant human ovarian xenograft mouse model the use of sertraline in combination with Doxil® generated substantial reduction in tumor progression, with extension of the median survival of tumor-bearing mice. Taken together, our results show that sertraline could act as a clinically relevant cancer MDR inhibitor. Moreover, combining two FDA approved drugs, DOXIL®, which favor the influx of chemotherapy inside the malignant cell with sertraline, which blocks the extrusion pumps, could readily be available for clinical translation in the battle against resistant tumors. PMID:25173796

Drinberg, Velthe; Bitcover, Rivka; Rajchenbach, Wolf; Peer, Dan

2014-11-28

231

Potent and specific inhibition of the breast cancer resistance protein multidrug transporter in vitro and in mouse intestine by a novel analogue of fumitremorgin C.  

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Inhibitors of the breast cancer resistance protein (BCRP/ABCG2) multidrug transporter are of interest as chemosensitizers for clinical drug resistance, for improving the pharmacokinetics of substrate chemotherapeutic drugs, and in functional assays of BCRP activity for tailoring chemotherapy. The fungal toxin fumitremorgin C (FTC) is a potent and specific inhibitor of BCRP, but its neurotoxic effects preclude use in vivo. We have therefore evaluated a new tetracyclic analogue of FTC, Ko143, as a practical inhibitor of BCRP, comparing it with two other analogues in the same class and with GF120918. All three FTC analogues are effective inhibitors of both mouse Bcrp1 and human BCRP, proving highly active for increasing the intracellular drug accumulation and reversing Bcrp1/BCRP-mediated multidrug resistance. Indeed, Ko143 appears to be the most potent BCRP inhibitor known thus far. In contrast, the compounds have only low activity against P-glycoprotein, the multidrug resistance-associated protein (MRP1), or other known drug transporters. They are nontoxic in vitro at useful concentrations and evinced no signs of toxicity in mice at high oral or i.p. doses. Administered p.o. to inhibit intestinal Bcrp1, Ko143 markedly increased the oral availability of topotecan in mice. It is thus the first highly potent and specific BCRP inhibitor applicable in vivo. As such, Ko143 and other FTC analogues of this type represent valuable reagents for analysis of drug resistance mechanisms and may be candidates for development as clinical BCRP inhibitors. PMID:12477054

Allen, John D; van Loevezijn, Arnold; Lakhai, Jeany M; van der Valk, Martin; van Tellingen, Olaf; Reid, Glen; Schellens, Jan H M; Koomen, Gerrit-Jan; Schinkel, Alfred H

2002-04-01

232

Pilot study on multidrug resistant tuberculosis in Nigeria  

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Full Text Available Background: Drug resistant tuberculosis (TB has lately emerged and it represents a serious public health problem. We set out to determine drug resistance among TB patients. Methods: Using automated BACTEC cultures, multidrug resistant-tuberculosis (MDR-TB was investigated in 117 diagnosed cases in Abuja, Nigeria. Results: Ten (31% of 32 culture-positive patients were resistant to at least one and four (13% to all of the four drugs tested. No association between drug resistance and human immunodeficiency virus (HIV infection was found. Conclusions: MDR-TB is present in Nigeria and larger studies are urgently required. TB clinical management and control efforts should be improved.

Lawson L

2010-09-01

233

Multidrug resistance and efflux pumps: insights from molecular dynamics simulations.  

Science.gov (United States)

Evolution of bacteria resistant to the most diverse antibiotics is posing one of the major threats to public health. Particular alarm is raised by those genetic lines that develop phenotypes simultaneously resistant to multiple drugs. Among the different mechanisms leading to multidrug resistance, multidrug efflux pumps raise particular concern. These are large macromolecular constructs localised at cell boundaries, which are able to actively bind and transport out of the cell several chemically uncorrelated substrates. In this last decade, computer modelling has proved to be a valuable tool for the investigation of multiple drug-efflux systems at the molecular level. In particular, molecular dynamics simulations unveiled several aspects of the molecular mechanisms governing the recognition and transport of drugs by these systems. Computer-aided protocols constitute a bottom-up reductionist approach that has the privilege of obtaining clean data referring intrinsically to those single parts of the efflux process explicitly taken into account. Combining computational data to the experimental determinations may therefore help in the definition of possible general criteria limiting the action of these systems against both patented and new putative antibiotic agents. Here, we review the most relevant contributions by computational scientists to the understanding of multidrug-efflux systems in the recent past. Particular care is put in the description of the dynamical features of multidrug exporters, a valuable piece of information for which computer modelling represents one of the best investigation tools available at present. PMID:24200357

Collu, Francesca; Cascella, Michele

2013-01-01

234

NANOMICELLAR PACLITAXEL INCREASES CYTOTOXICITY OF MULTIDRUG RESISTANT BREAST CANCER CELLS  

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Multidrug resistance (MDR) of breast cancer cells still represents an unmet medical need in chemotherapy. To this end, the purpose of this study was to determine efficacy of paclitaxel loaded in sterically stabilized, biocompatible and biodegradable sterically stabilized mixed phospholipid nanomicelles (SSMM; size, ~15 nm) and actively targeted vasoactive intestinal peptide-grafted SSMM (SSMM-VIP) in circumventing P-gp-mediated paclitaxel resistance in BC19/3 cells, a human breast cancer cell...

O?nyu?ksel, Hayat; Jeon, Eunjung; Rubinstein, Israel

2009-01-01

235

Rapid tests for multidrug resistant tuberculosis in low income settings  

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Tuberculosis (TB) is at epidemic levels in the resource-limited settings (RLSs) due to HIV/AIDS, poverty and insufficient TB control programmes. These factors are also contributing to TB drug resistance. Patients with multidrug drug resistant tuberculosis (MDR-TB) do not respond to first line drugs. These patients require unique drug regimens, making it necessary to routinely screen for MDR-TB. Screening for MDR-TB with the Lowenstein-Jensen proportion method (LJPM), which i...

Bwanga, Freddie

2010-01-01

236

Radioligands targeting P-glycoprotein and other drug efflux proteins at the blood-brain barrier.  

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Brain penetration of radiopharmaceuticals or therapeutic drugs may be restricted by adenosine triphosphate-binding cassette (ABC) transporters, such as P-glycoprotein (Pgp), breast cancer resistance protein (BCRP), or the multidrug resistance-associated proteins. These transporters are expressed in the luminal membrane of brain capillary endothelial cells forming the blood-brain barrier (BBB), where they actively efflux a wide range of chemically unrelated compounds from the brain back into the blood. Most efforts to visualize ABC transporters at the BBB with positron emission tomography have concentrated on Pgp. Pgp imaging probes can be classified as radiolabeled substrates or inhibitors. The radiolabeled substrates (R)-[(11) C]verapamil and [(11) C]-N-desmethyl-loperamide have been successfully used to assess Pgp function at the BBB of animals and humans. Radiolabeled Pgp inhibitors, such as [(11) C]tariquidar, [(11) C]elacridar, or [(11) C]laniquidar, were developed to measure Pgp expression levels at the BBB, which has so far remained unsuccessful as these probes were unexpectedly recognized at tracer concentrations by Pgp and BCRP as substrates resulting in low brain uptake. Studies on positron emission tomography tracers for other ABC transporters than Pgp (BCRP and multidrug resistance-associated proteins) are still in their infancy. It is hoped that the experience gained with the imaging of Pgp will be successfully translated to the development of radiotracers to visualize other ABC transporters. PMID:24285312

Wanek, Thomas; Mairinger, Severin; Langer, Oliver

2013-01-01

237

Carotenoids reverse multidrug resistance in cancer cells by interfering with ABC-transporters.  

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Proteins of the ATP-binding cassette superfamily, mainly P-glycoprotein (P-gp; MDR1), play an important role in the development of multidrug resistance (MDR) in cancer cells and thus in the potential failure of chemotherapy. A selection of carotenoids (?-carotene, crocin, retinoic acid, canthaxanthin, and fucoxanthin) was investigated whether they are substrates of P-gp, and if they can reverse MDR in resistant Caco-2 and CEM/ADR5000 cells as compared to the sensitive parent cell line CCRF-CEM. The activity of ABC transporter was determined in resistant and sensitive cells by spectrofluorometry and flow cytometry using the substrates doxorubicin, rhodamine 123, and calcein as fluorescent probes. The carotenoids increased accumulation of these P-gp substrates in a dose-dependent manner indicating that they themselves also function as substrates. Fucoxanthin and canthaxanthin (50-100 ?M) produced a 3-5-fold higher retention of the fluorescent probes than the known competitive inhibitor verapamil. Carotenoids showed a low cytotoxicity in cells with MDR with IC(50) values between 100 and 200 ?M. The combination of carotenoids with eight structurally different cytotoxic agents synergistically enhanced their cytotoxicity in Caco-2 cells, probably by inhibiting the function of the ABC transporters. For example, fucoxanthin synergistically enhanced the cytotoxicity of 5-FU 53.37-fold, of vinblastine 51.01-fold, and of etoposide 12.47-fold. RT-PCR was applied to evaluate the mRNA levels of P-gp in Caco-2 cells after treatment with carotenoids. Fucoxanthin and canthaxanthin significantly decreased P-gp levels to 12% and 24%, respectively as compared to untreated control levels (p<0.001). This study implies that carotenoids may be utilised as chemosensitisers, especially as adjuvants in chemotherapy. PMID:22770743

Eid, Safaa Yehia; El-Readi, Mahmoud Zaki; Wink, Michael

2012-08-15

238

[Investigation of extensive drug resistance in multidrug resistance tuberculosis isolates].  

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Increasing number of drug resistant tuberculosis (TB) cases, observed in recent years, is an important public health problem. Extensively drug resistant TB (XDR-TB) is the development of resistance against any fluoroquinolones and at least one of the injectable second line anti-TB drugs in addition to resistance against isoniazide and rifampicin which are the first line anti-TB drugs [definition of multidrug resistant TB (MDR-TB)]. Anti-TB therapy failed with first-line anti-TB drugs due to MDR-TB cases is being planned according to second-line anti-TB drug susceptibility test results if available and if not, standart treatment protocols are used. Although it is recommended that individual anti-TB therapy should be designed according to the isolate's susceptibility test results, standart therapeutic protocols are always needed since second-line anti-TB drug susceptibility testing generally could not be performed in developing countries like Turkey. For this reason, nationwide and regional surveillance studies to determine the resistance patterns are always needed to make decisions about the standard therapy algorithms. In this study, it was aimed to investigate the presence of extensive drug resistance among 81 MDR-TB isolates obtained from various health care facilities from Istanbul, Izmir and Manisa and to determine the XDR-TB incidence in Marmara and Aegean regions. Furthermore, we aimed to provide epidemiological data to clinicians to support their choice of second-line anti-TB drugs for MDR-TB infections. Susceptibility testing of isolates for the first and the second-line anti-TB drugs were performed by using modified Middlebrook 7H9 broth in fluorometric BACTEC MGIT 960 system (Becton Dickinson, USA). Eighty-one MDR-TB isolates included in this study were isolated from 43 (53.1%) patients residing in Istanbul, 26 (32.1%) in Izmir and 12 (14.8%) in Manisa provinces. We could not find any isolate consistent with XDR-TB definition in this study. Second-line drug resistance rates of MDR-TB isolates to amikacin and kanamycin were 1.2%, ofloxacin and levofloxacin were 2.5%, capreomycin was 14.8%, ethionamide was 37% whereas linezolid resistance was not detected. Statistically significant correlation was detected between resistance rates of these antibiotic pairs; levofloxacin-ofloxacin (pethionamide (p= 0.04). In our study, extensive drug resistance was not encountered in any MDR-TB isolates while high resistance rates was observed against ethionamide and capreomycin. It can be concluded that parenteral aminoglycosides amikasin and kanamycin, fluoroquinolones and linezolid seemed to be reliable anti-TB agents in MDR-TB treatment, however, further larger scale studies are needed. PMID:23390903

Bektöre, Bayhan; Haznedaro?lu, Tunçer; Baylan, Orhan; Ozyurt, Mustafa; Ozkütük, Nuri; Satana, Dilek; Cavu?o?lu, Cengiz; Seber, Engin

2013-01-01

239

Effect of methylglyoxal on multidrug-resistant Pseudomonas aeruginosa  

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Full Text Available Honey has a complex chemistry, and its broad-spectrum antimicrobial activity varies with floral source, climate, and harvesting conditions. Methylglyoxal was identified as the dominant antibacterial component of manuka honey. Although it has been known that methylglyoxal has antibacterial activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, there is not much information describing its activity against gram-negative bacteria. In this study, we report the effect of methylglyoxal against multidrug-resistant Pseudomonas aeruginosa (MDRP using 53 clinically isolated strains. We also assessed the effect of deleting the five multidrug efflux systems in P. aeruginosa, as well as the efflux systems in Escherichia coli and Salmonella enterica serovar Typhimurium, on MICs of methylglyoxal. Our results indicate that methylglyoxal inhibits the growth of MDRP at concentrations of 128–512 µg/ml (1.7–7.1 mM and is not recognized by drug efflux systems.

KunihikoNishino

2014-04-01

240

Effect of methylglyoxal on multidrug-resistant Pseudomonas aeruginosa.  

Science.gov (United States)

Honey has a complex chemistry, and its broad-spectrum antimicrobial activity varies with floral source, climate, and harvesting conditions. Methylglyoxal was identified as the dominant antibacterial component of manuka honey. Although it has been known that methylglyoxal has antibacterial activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, there is not much information describing its activity against gram-negative bacteria. In this study, we report the effect of methylglyoxal against multidrug-resistant Pseudomonas aeruginosa (MDRP) using 53 clinically isolated strains. We also assessed the effect of deleting the five multidrug efflux systems in P. aeruginosa, as well as the efflux systems in Escherichia coli and Salmonella enterica serovar Typhimurium, on MICs of methylglyoxal. Our results indicate that methylglyoxal inhibits the growth of MDRP at concentrations of 128-512 ?g/ml (1.7-7.1 mM) and is not recognized by drug efflux systems. PMID:24860556

Hayashi, Katsuhiko; Fukushima, Aiko; Hayashi-Nishino, Mitsuko; Nishino, Kunihiko

2014-01-01

 
 
 
 
241

Enhanced effect of pH-sensitive mixed copolymer micelles for overcoming multidrug resistance of doxorubicin.  

Science.gov (United States)

P-glycoprotein (P-gp) mediated drug efflux has been recognized as a key factor contributing to the multidrug resistance (MDR) in tumor cells. To address this issue, a new pH-sensitive mixed copolymer micelles system composed of hyaluronic acid-g-poly(l-histidine) (HA-PHis) and d-?-tocopheryl polyethylene glycol 2000 (TPGS2k) copolymers was developed to co-deliver doxorubicin (DOX) and TPGS2k into drug-resistant breast cancer MCF-7 cells (MCF-7/ADR). The DOX-loaded HA-PHis/TPGS2k mixed micelles (HPHM/TPGS2k) were characterized to have a unimodal size distribution, high DOX loading content and a pH dependent drug release profile due to the protonation of poly(l-histidine). As compared to HA-PHis micelles (HPHM), the HPHM/TPGS2k showed higher and comparable cytotoxicity against MCF-7/ADR cells and MCF-7 cells, respectively. The enhanced MDR reversal effect was attributed to the higher amount of cellular uptake of HPHM/TPGS2k in MCF-7/ADR cells than HPHM, arising from the inhibition of P-gp mediated drug efflux by TPGS2k. The measurements of P-gp expression level and mitochondrial membrane potential indicate that the blank HPHM/TPGS2k inhibited P-gp activity by reducing mitochondrial membrane potential and depletion of ATP but without inhibition of P-gp expression. In vivo study of micelles in tumor-bearing mice indicate that HPHM/TPGS2k could reach the tumor site more effectively than HPHM. The pH-sensitive mixed micelles system has been demonstrated to be a promising approach for overcoming the MDR. PMID:25201738

Qiu, Lipeng; Qiao, Mingxi; Chen, Qing; Tian, Chenmin; Long, Miaomiao; Wang, Mingyue; Li, Zhen; Hu, Wen; Li, Gang; Cheng, Liang; Cheng, Lifang; Hu, Haiyang; Zhao, Xiuli; Chen, Dawei

2014-12-01

242

Effect of prostaglandin e2 on multidrug resistance transporters in human placental cells.  

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Prostaglandin (PG) E2, a major product of cyclooxygenase (COX)-2, acts as an immunomodulator at the maternal-fetal interface during pregnancy. It exerts biologic function through interaction with E-prostanoid (EP) receptors localized to the placenta. The activation of the COX-2/PGE2/EP signal pathway can alter the expression of the ATP-binding cassette (ABC) transporters, multidrug resistance protein 1 [P-glycoprotein (Pgp); gene: ABCB1], and breast cancer resistance protein (BCRP; gene: ABCG2), which function to extrude drugs and xenobiotics from cells. In the placenta, PGE2-mediated changes in ABC transporter expression could impact fetal drug exposure. Furthermore, understanding the signaling cascades involved could lead to strategies for the control of Pgp and BCRP expression levels. We sought to determine the impact of PGE2 signaling mechanisms on Pgp and BCRP in human placental cells. The treatment of placental cells with PGE2 up-regulated BCRP expression and resulted in decreased cellular accumulation of the fluorescent substrate Hoechst 33342. Inhibiting the EP1 and EP3 receptors with specific antagonists attenuated the increase in BCRP. EP receptor signaling results in activation of transcription factors, which can affect BCRP expression. Although PGE2 decreased nuclear factor ?-light chain-enhancer of activated B activation and increased activator protein 1, chemical inhibition of these inflammatory transcription factors did not blunt BCRP up-regulation by PGE2. Though PGE2 decreased Pgp mRNA, Pgp expression and function were not significantly altered. Overall, these findings suggest a possible role for PGE2 in the up-regulation of placental BCRP expression via EP1 and EP3 receptor signaling cascades. PMID:25261564

Mason, Clifford W; Lee, Gene T; Dong, Yafeng; Zhou, Helen; He, Lily; Weiner, Carl P

2014-12-01

243

Lymphokine-activated killer cell susceptibility and adhesion molecule expression of multidrug resistant breast carcinoma  

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Full Text Available Abstract Reports showing susceptibility of multidrug resistant (MDR cancer cells to immune effectors, together with P-glycoprotein (P-gp expression in immune effector subsets, including immature natural killer (NK cells, and some activated T cells, suggest P-gp or some changes associated with it, have implications in immune-mediated mechanisms. A series of experiments were done to determine the nature of alterations associated with susceptibility to immune effector cells of MDR tumor cells. A cell line isolated from the malignant pleural effusion of a breast cancer patient was transfected with human and murine MDR1 genes, and four variants with different levels of MDR were obtained. Lymphokine-activated killer (LAK activity was measured by a 51Chromium release, and conjugate formation assays. MDR1 transfectant P-gp+ breast carcinoma lines had increased LAK susceptibility compared to their parent line. Some part of the increased LAK susceptibility of drug-resistant cell lines was at the binding/recognition level as shown by conjugate formation assays. This suggests that differences may exist between paired cell lines with respect to the expression of cell adhesion molecules (CAMs. Monoclonal antibodies (mAbs to CAMs and flow cytometry were used to quantitate these antigens. The CAMs studied were those previously found to be upregulated by stimulating NK cells with (interleukin-2 IL-2; ICAM-1 (CD54, LFA-3 (CD58, N-CAM (CD56, and the ? chain of LFA-1 (CD18. Although no differences in these CAMs were found between the breast carcinoma line and its MDR1-transfected variants, the target susceptibility results given above suggest that IL-2 treatment could be effective in combination with current protocols using chemotherapeutics, monoclonal antibodies (mAbs and stem cell transplantation.

Kerr Pauline E

2006-11-01

244

Imaging the Function of P-Glycoprotein With Radiotracers: Pharmacokinetics and In Vivo Applications  

Science.gov (United States)

P-glycoprotein (P-gp), an efflux transporter, controls the pharmacokinetics of various compounds under physiological conditions. P-gp-mediated drug efflux has been suggested as playing a role in various disorders, including multidrug-resistant cancer and medication-refractory epilepsy. However, P-gp inhibition has had, to date, little or no clinically significant effect in multidrug-resistant cancer. To enhance our understanding of its in vivo function under pathophysiological conditions, substrates of P-gp have been radiolabeled and imaged using single-photon emission computed tomography (SPECT) and positron emission tomography (PET). To accurately quantify P-gp function, a radiolabeled P-gp substrate should be selective for P-gp, produce a large signal after P-gp blockade, and generate few radiometabolites that enter the target tissue. Furthermore, quantification of P-gp function via imaging requires pharmacological inhibition of P-gp, which requires knowledge of P-gp density at the target site. By meeting these criteria, imaging can elucidate the function of P-gp in various disorders and improve the efficacy of treatments. PMID:19625998

Kannan, P; John, C; Zoghbi, SS; Halldin, C; Gottesman, MM; Innis, RB; Hall, MD

2009-01-01

245

Structural and functional properties of human multidrug resistance protein 1 (MRP1/ABCC1).  

Science.gov (United States)

Multidrug ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1) play an important role in the extrusion of drugs from the cell and their overexpression can be a cause of failure of anticancer and antimicrobial chemotherapy. Recently, the mouse P-gp/Abcb1a structure has been determined and this has significantly enhanced our understanding of the structure-activity relationship (SAR) of mammalian ABC transporters. This paper highlights our current knowledge on the structural and functional properties and the SAR of human MRP1/ABCC1. Although the crystal structure of MRP1/ABCC1 has yet to be resolved, the current topological model of MRP1/ABCC1 contains two transmembrane domains (TMD1 and TMD2) each followed by a nucleotide binding domain (NBD) plus a third NH2-terminal TMD0. MRP1/ABCC1 is expressed in the liver, kidney, intestine, brain and other tissues. MRP1/ABCC1 transports a structurally diverse array of important endogenous substances (e.g. leukotrienes and estrogen conjugates) and xenobiotics and their metabolites, including various conjugates, anticancer drugs, heavy metals, organic anions and lipids. Cells that highly express MRP1/ABCC1 confer resistance to a variety of natural product anticancer drugs such as vinca alkaloids (e.g. vincristine), anthracyclines (e.g. etoposide) and epipodophyllotoxins (e.g. doxorubicin and mitoxantrone). MRP1/ABCC1 is associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. However, most compounds that efficiently reverse P-gp/ABCB1-mediated multidrug resistance have only low affinity for MRP1/ABCC1 and there are only a few effective and relatively specific MRP1/ABCC1 inhibitors available. A number of site-directed mutagenesis studies, biophysical and photolabeling studies, SAR and QSAR, molecular docking and homology modeling studies have documented the role of multiple residues in determining the substrate specificity and inhibitor selectivity of MRP1/ABCC1. Most of these residues are located in the TMs of TMD1 and TMD2, in particular TMs 4, 6, 7, 8, 10, 11, 14, 16, and 17, or in close proximity to the membrane/cytosol interface of MRP1/ABCC1. The exact transporting mechanism of MRP1/ABCC1 is unclear. MRP1/ABCC1 and other multidrug transporters are front-line mediators of drug resistance in cancers and represent important therapeutic targets in future chemotherapy. The crystal structure of human MRP1/ABCC1 is expected to be resolved in the near future and this will provide an insight into the SAR of MRP1/ABCC1 and allow for rational design of anticancer drugs and potent and selective MRP1/ABCC1 inhibitors. PMID:21143116

He, S-M; Li, R; Kanwar, J R; Zhou, S-F

2011-01-01

246

The multidrug resistance protein breast cancer resistance protein (BCRP) protects adipose-derived stem cells against ischemic damage.  

Science.gov (United States)

Adipose tissue-derived stem cells (ASCs) are promising candidates for regenerative therapy, like after myocardial infarction. However, when transplanted into the infarcted heart, ASCs are jeopardized by the ischemic environment. Interestingly, it has been shown that multidrug resistance (MDR) proteins like the breast cancer resistance protein (BCRP) and P-glycoprotein (P-gp) have a protective effect in haematopoietic stem cells. In ASC, however, only expression of BCRP was shown until now. In this study, we therefore analysed the expression and functional activity of BCRP and P-gp and their putative function in ischemia in ASC. BCRP and P-gp protein expression was studied over time (passages 2-6) using western blot analysis and immunohistochemical staining. MDR activity was analysed using protein-specific substrate extrusion assays. Ischemia was induced using metabolic inhibition. All analyses demonstrated protein expression and activity of BCRP in ASCs. In contrast, only minor expression of P-gp was found, without functional activity. BCRP expression was most prominent in early passage ASCs (p2) and decreased during culture. Finally, ischemia induced expression of BCRP. In addition, when BCRP was blocked, a significant increase in dead ASCs was found already after 1 h of ischemia. In conclusion, ASCs expressed BCRP, especially in early passages. In addition, we now show for the first time that BCRP protects ASCs against ischemia-induced cell death. These data therefore indicate that for transplantation of ASCs in an ischemic environment, like myocardial infarction, the optimal stem cell protective effect of BCRP theoretically will be achieved with early culture passages ASCs. PMID:22801743

van Dijk, A; Naaijkens, B A; Jurgens, W J F M; Oerlemans, R; Scheffer, G L; Kassies, J; Aznou, J; Brouwer, M; van Rossum, A C; Schuurhuis, G J; van Milligen, F J; Niessen, H W M

2012-10-01

247

Using 99Tcm-MIBI to evaluate tumor multidrug resistance and monitor the reversring of chemosensitizer  

International Nuclear Information System (INIS)

Objective: To study the correlation between, uptake of 99Tcm-MIBI and multidrug-resistant P-glycoprotein and evaluate the effect of chemosensitizer. Methods: Tumor bearing mice models were established by inplanting human cancer cell line MCF-7/Adr, the mice were randomized into two groups: chemosensitizer verapamil group and control. Before and after giving verapamil, 99Tcm-MIBI scintigraphy were performed at 15 min, 60 min, 90 min, 120 min, respectively. Mice Were sacrificed after scintigraphy to get %ID/g of tumor and major organs. The level of P-gp were measured with immunocytochemical assay and mRNA of mdrl gene determined with RT-PCR were obtained simultaneously. Results: After giving verapamil the T/N ratio of tumor increased significantly except 120 min scintigraphy.The 99Tcm-MIBI uptake difference between the verapamil group and controls was obvious (P value were 0.045, 0.015, 0.042, respectively ). The expression of mdrl mRNA decreased dramastically after verapamil reversing (t=4.873, P=0.008). The level of P-gp declined from 0.1038±0.0078 to 0.0096±0.0059 (t=3.579, P=0.023). The 99Tcm-MIBI uptake of tumor, liver and kidney rose obviously after reversing, %ID/g increaments were 106.83%, 40.35%, 166.07% respectively, whereas it was slightly declined by -12.82% in heart . Conclusions: 99Tcm-MIBI scintigraphy may evaluate MDR mediated by P-gp and potentialy be used to monitor the reversing effect of chemosensitizer in P-gp positive tumors. (authors)

248

Tuberculosis Multidrogoresistente / Multidrug-resistant tuberculosis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish La tuberculosis es una enfermedad infecciosa causada por el Mycobacterium tuberculosis. En el año 2010 se registraron 8.8 millones de casos incidentes en el mundo y en los últimos años han aparecido poblaciones bacterianas de micobacterias con resistencia a los fármacos de primera línea. Se ha defin [...] ido la presencia de resistencia a rifampicina e isoniacida como multidrogoresistencia, estimándose una incidencia mundial aproximada de 3.6%. Esta revisión de tema se centrará en la situación de la tuberculosis multidrogoresistente en el mundo, incluyendo un análisis regional de la casuística Colombiana. Se comentarán los principales mecanismos de resistencia del microorganismo, los genes implicados en la misma y los factores de riesgo asociados a la generación de resistencia en algunas comunidades. Abstract in english Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis. In 2010, there were 8.8 million incident cases in the world, and, in recent years, populations of mycobacteria with resistance to first-line drugs have emerged. The resistance to rifampin and isoniazid has been defined as mu [...] ltidrugresistant tuberculosis (TB MDR). TB MDR has an incidence of approximately 3.6% in the world. This review will focus on the current stage TB MDR in the world, including a regional analysis of Colombian cases. It will discuss the mechanism of resistance of the microorganism, genes involved, and the risk factors associated with the generation of resistance in some communities

German A, Acevedo; Agustín, Vega; Wellman, Ribón.

2013-12-01

249

Draft Genome Sequences of Two Multidrug Resistant Klebsiella pneumoniae ST258 Isolates Resistant to Colistin  

Science.gov (United States)

Sequence type 258 (ST258) is the most widespread multidrug resistant (MDR) Klebsiella pneumoniae strain worldwide. Here, we report the draft genome sequences of two colistin-resistant MDR K. pneumoniae ST258 clinical strains isolated from hospital patients in Italy. These strains are resistant to ?-lactams, cephalosporins, fluoroquinolones, aminoglycosides, macrolides, tetracyclines, carbapenems, and colistin. PMID:23405348

Comandatore, Francesco; Sassera, Davide; Ambretti, Simone; Landini, Maria Paola; Daffonchio, Daniele; Marone, Piero; Sambri, Vittorio; Bandi, Claudio

2013-01-01

250

Draft Genome Sequences of Two Multidrug Resistant Klebsiella pneumoniae ST258 Isolates Resistant to Colistin  

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Sequence type 258 (ST258) is the most widespread multidrug resistant (MDR) Klebsiella pneumoniae strain worldwide. Here, we report the draft genome sequences of two colistin-resistant MDR K. pneumoniae ST258 clinical strains isolated from hospital patients in Italy. These strains are resistant to ?-lactams, cephalosporins, fluoroquinolones, aminoglycosides, macrolides, tetracyclines, carbapenems, and colistin.

Comandatore, Francesco; Sassera, Davide; Ambretti, Simone; Landini, Maria Paola; Daffonchio, Daniele; Marone, Piero; Sambri, Vittorio; Bandi, Claudio; Gaibani, Paolo

2013-01-01

251

Expression of the mutated p53 tumor suppressor protein and its molecular and biochemical characterization in multidrug resistant MCF-7/Adr human breast cancer cells.  

Science.gov (United States)

Multidrug resistance in MCF-7/Adr human breast cancer cells is mediated by several mechanisms including overexpression of the MDR1 gene product, P-glycoprotein and glutathione-related detoxifying enzymes. Mutations in the p53 tumor suppressor protein have been reported to play a role in the development of resistance to DNA damaging agents in several human cancer cells. In the present study we have assessed the mutational status of the p53 protein and its expression levels, degree of stability and cellular localization to investigate whether it is involved in modulating multidrug resistance in MCF-7/Adr cells compared to sensitive MCF-7 cells. As revealed by immunofluorescence microscopy using the anti-p53 mouse monoclonal antibody DO-1, wild-type p53 is sequestered in the cytoplasm of MCF-7 cells, whereas in MCF-7/Adr cells, the protein is localized in the nucleus. The sequencing of full-length p53 cDNA revealed a 21 bp deletion in its one of the four conserved regions within the conformational domain, spanning codons 126-133 at exon five, in MCF-7/Adr cells. Moreover, detection of ThaI polymorphism of codon 72 showed that MCF-7 cells predominantly express wild-type p53 with proline, while mutated p53 in MCF-7/Adr cells contains an arginine residue at codon 72. In addition, we demonstrate that the half-life of p53 in MCF-7 cells is less than 30 min while the mutated protein is more stable; its half-life is about 4 h in MCF-7/Adr cells. Thus, this study demonstrates that the deletion of codons 126-133 in p53 causes increased stability, overexpression and nuclear localization of the protein in multidrug resistant MCF-7/Adr cells, and further suggests that mutated p53 might be involved in the development of multidrug resistance in this cell line. PMID:9053847

Ogretmen, B; Safa, A R

1997-01-30

252

Multidrug Resistance-Associated Protein 1 (MRP1) mediated vincristine resistance: effects of N-acetylcysteine and Buthionine Sulfoximine  

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Abstract Background Multidrug resistance mediated by the multidrug resistance-associated protein 1 (MRP1) decreases cellular drug accumulation. The exact mechanism of MRP1 involved multidrug resistance has not been clarified yet, though glutathione (GSH) is likely to have a role for the resistance to occur. N-acetylcysteine (NAC) is a pro-glutathione drug. DL-Buthionine (S,R)-sulfoximine (BSO) is an inhibitor of GSH synthesis. The aim of our study was to investigate the effec...

Savas Burhan; Akca Hakan; Akan Selma; Akan Ilhan; Ozben Tomris

2005-01-01

253

New Antibiotics in Development Against Multidrug-Resistant Bacteria  

Directory of Open Access Journals (Sweden)

Full Text Available The rapid development of resistance to antimicrobial agents caused to investigate new antimicrobial agents for the treatment of various infections and new antibiotic effect mechanisms. Methicillin-resistant Staphylococcus aureus (MRSA, vancomycin-resistant enterococci (VRE, extended-spectrum beta-lactamase (ESBL Escherichia coli and Klebsiella spp., multidrug-resistant strains of Acinetobacter baumannii and Pseudomonas aeruginosa are the most important targets for new antibacterial. Development speed of new antibacterial agents decreased dramatically in the last ten years. Correct use of antibiotics should be the basic principle to avoid the development of resistance. In addition, although the development of new antibiotics is so important, the main purpose should be determining the new targets in order to minimize undesired effects and drug interactions, detecting new antibiotics effect mechanisms and developing new antibiotics for these purposes.

Soner Yýlmaz

2013-05-01

254

Risk factors for acquired multidrug-resistant tuberculosis  

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Full Text Available Multidrug-resistant tuberculosis (MDR-TB is a severe and feared problem, that is difficult to control and has shown a tendency to increase worldwide. OBJECTIVE: To analyze the risk factors for acquired MDR-TB. CASUISTIC AND METHODS: A retrospective population-based case-control study was conducted. A bacillus was considered multidrug-resistant whenever it was resistant at least to rifampin (RFP + isoniazid (INH, and a case was considered as sensitive tuberculosis (TB if it had undergone the first treatment during a similar period as the first treatment of an MDR-TB case, but was cured at the time of the interview. Case selection was made based on the list of Sensitivity Tests (ST performed at the Central Public Health Laboratory of the State of Ceará, from 1990 through 1999. The Proportion Method was used to investigate resistance to the six antituberculosis drugs (isoniazid, rifampin, pyrazinamide, ethambutol, ethionamide, streptomycin used as the standard treatment in Brazil. Controls were selected from the registry of the TB Control Program. Univariate and multivariate analysis were performed, with p < 0.05 considered significant. RESULTS: Out of the 1,500 STs performed during the studied period, 266 strains were multidrug-resistant; 153 patients were identified, 19 of which were excluded. The Group of Cases comprised 134 patients, and the Group of Controls comprised 185. Multivariate analysis helped to detect the following risk factors: lack of home sewer system, alcoholism + smoking, number of previous treatments, irregular treatment, and lung cavities. CONCLUSION: These five factors are important for the development of acquired MDR-TB, and an attempt to neutralize them might contribute to control TB.

Barroso Elizabeth Clara

2003-01-01

255

STUDIES ON ANTIBACTERIAL EFFECT OF APAMARGA (ACHYRANTHES ASPERA) ON MULTI-DRUG RESISTANT CLINICAL ISOLATES  

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Recent reports on emergence of multidrug resistant bacteria are cause of concern in medical world. Several ayurvedic drugs have been proved to contain the antimicrobial activity. Literature on effect of ayurvedic drugs on multidrug resistant bacterial pathogens is limited. Present study reports the antimicrobial effect of Achyranthes aspera (Apamarga) crude extracts on the clinical isolates of multidrug resistant bacteria. The drug was evaluated by using phytochemical tests. Crude extracts of...

Patil Usha; Sharma Mahesh Chandra

2013-01-01

256

Biodegradable cationic polymeric nanocapsules for overcoming multidrug resistance and enabling drug-gene co-delivery to cancer cells  

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Having unique architectural features, cationic polymeric nanocapsules (NCs) with well-defined covalently stabilized biodegradable structures were generated as potentially universal and safe therapeutic nanocarriers. These NCs were synthesized from allyl-functionalized cationic polylactide (CPLA) by highly efficient UV-induced thiol-ene interfacial cross-linking in transparent miniemulsions. With tunable nanoscopic sizes, negligible cytotoxicity and remarkable degradability, they are able to encapsulate doxorubicin (Dox) with inner cavities and bind interleukin-8 (IL-8) small interfering RNA (siRNA) with cationic shells. The Dox-encapsulated NCs can effectively bypass the P-glycoprotein (Pgp)-mediated multidrug resistance of MCF7/ADR cancer cells, thereby resulting in increased intracellular drug concentration and reduced cell viability. In vitro studies also showed that the NCs loaded with Dox, IL-8 siRNA and both agents can be readily taken up by PC3 prostate cancer cells, resulting in a significant chemotherapeutic effect and/or IL-8 gene silencing.Having unique architectural features, cationic polymeric nanocapsules (NCs) with well-defined covalently stabilized biodegradable structures were generated as potentially universal and safe therapeutic nanocarriers. These NCs were synthesized from allyl-functionalized cationic polylactide (CPLA) by highly efficient UV-induced thiol-ene interfacial cross-linking in transparent miniemulsions. With tunable nanoscopic sizes, negligible cytotoxicity and remarkable degradability, they are able to encapsulate doxorubicin (Dox) with inner cavities and bind interleukin-8 (IL-8) small interfering RNA (siRNA) with cationic shells. The Dox-encapsulated NCs can effectively bypass the P-glycoprotein (Pgp)-mediated multidrug resistance of MCF7/ADR cancer cells, thereby resulting in increased intracellular drug concentration and reduced cell viability. In vitro studies also showed that the NCs loaded with Dox, IL-8 siRNA and both agents can be readily taken up by PC3 prostate cancer cells, resulting in a significant chemotherapeutic effect and/or IL-8 gene silencing. Electronic supplementary information (ESI) available: Experimental section and Fig. S1-S6. See DOI: 10.1039/c3nr04804g

Chen, Chih-Kuang; Law, Wing-Cheung; Aalinkeel, Ravikumar; Yu, Yun; Nair, Bindukumar; Wu, Jincheng; Mahajan, Supriya; Reynolds, Jessica L.; Li, Yukun; Lai, Cheng Kee; Tzanakakis, Emmanuel S.; Schwartz, Stanley A.; Prasad, Paras N.; Cheng, Chong

2014-01-01

257

Pharmacology and potential physiological significance of schistosome multidrug resistance transporters.  

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Schistosomes are the causative agents of schistosomiasis, a neglected tropical disease affecting hundreds of millions worldwide and a major global health burden. Current control of schistosomiasis depends largely on a single drug, praziquantel (PZQ). One potential physiological target for new antischistosomal drugs is the parasite's excretory system, which removes wastes and xenobiotics. Multidrug resistance (MDR) transporters that are members of the ATP-binding cassette (ABC) superfamily of proteins are ATP-dependent efflux pumps involved in removal of toxins and xenobiotics from cells. They mediate the phenomenon of multidrug resistance, in which cells resistant to one drug show cross-resistance to a broad range of other agents, and are also associated with reduced drug susceptibility in parasitic helminths. In this review, we survey the different types of ABC transporter genes present within the schistosome genome, and examine recent evidence indicating that at least some of these transporters may play a role in fine-tuning susceptibility of schistosomes to PZQ. Disruption of their function may therefore provide a strategy for enhancing drug action or overcoming or attenuating drug resistance. Furthermore, dissection of the roles these transporters may play in normal schistosome physiology could potentially lead to identification of highly "druggable" targets for new antischistosomals. PMID:21420955

Kasinathan, Ravi S; Greenberg, Robert M

2012-09-01

258

P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) restrict brain accumulation of the active sunitinib metabolite N-desethyl sunitinib.  

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N-desethyl sunitinib is a major and pharmacologically active metabolite of the tyrosine kinase inhibitor and anticancer drug sunitinib. Because the combination of N-desethyl sunitinib and sunitinib represents total active drug exposure, we investigated the impact of several multidrug efflux transporters on plasma pharmacokinetics and brain accumulation of N-desethyl sunitinib after sunitinib administration to wild-type and transporter knockout mice. In vitro, N-desethyl sunitinib was a good transport substrate of human ABCB1 and ABCG2 and murine Abcg2, but not ABCC2 or Abcc2. At 5 ?M, ABCB1 and ABCG2 contributed almost equally to N-desethyl sunitinib transport. In vivo, the systemic exposure of N-desethyl sunitinib after oral dosing of sunitinib malate (10 mg/kg) was unchanged when Abcb1 and/or Abcg2 were absent. However, brain accumulation of N-desethyl sunitinib was markedly increased (13.7-fold) in Abcb1a/1b(-/-)/Abcg2(-/-) mice, but not in Abcb1a/1b(-/-) or Abcg2(-/-) mice. In the absence of the ABCB1 and ABCG2 inhibitor elacridar, brain concentrations of N-desethyl sunitinib were detectable only in Abcb1a/1b(-/-)/Abcg2(-/-) mice after sunitinib administration. Combined elacridar plus N-desethyl sunitinib treatment increased N-desethyl sunitinib plasma and brain exposures, but not brain-to-plasma ratios in wild-type mice. In conclusion, brain accumulation of N-desethyl sunitinib is effectively restricted by both Abcb1 and Abcg2. The effect of elacridar treatment in improving brain accumulation of N-desethyl sunitinib in wild-type mice was limited compared with its effect on sunitinib brain accumulation. PMID:22238213

Tang, Seng Chuan; Lankheet, Nienke A G; Poller, Birk; Wagenaar, Els; Beijnen, Jos H; Schinkel, Alfred H

2012-04-01

259

Multidrug-resistant hela cells overexpressing MRP1 exhibit sensitivity to cell killing by hyperthermia: Interactions with etoposide  

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Purpose: Multidrug resistance (MDR) remains one of the primary obstacles in cancer chemotherapy and often involves overexpression of drug efflux transporters such as P-glycoprotein and multidrug resistance protein 1 (MRP1). Regional hyperthermia is undergoing clinical investigation in combination with chemotherapy or radiotherapy. This study evaluates whether hyperthermia can reverse MDR mediated by MRP1 in human cervical adenocarcinoma (HeLa) cells. Methods and materials: Cytotoxicity of hyperthermia and/or etoposide was evaluated using sulforhodamine-B in HeLa cells overexpressing MRP1 and their drug-sensitive counterparts. Glutathione, glutathione peroxidase (GPx), and glutathione S-transferase (GST) were quantified by spectrophotometry. GST isoenzymes were quantified by immunodetection. Caspase activation was evaluated by fluorometry and chromatin condensation by fluorescence microscopy using Hoechst 33258. Necrosis was determined using propidium iodide. Results: The major finding is that HeLa and HeLaMRP cells are both sensitive to cytotoxicity of hyperthermia (41-45 deg C). Hyperthermia induced activation of caspase 3 and chromatin condensation. Although total levels of cell killing were similar, there was a switch from apoptotic to necrotic cell death in MDR cells. This could be explained by decreased glutathione and GPx in MDR cells. MDR cells also contained very low levels of GST and were resistant to etoposide-induced apoptosis. Hyperthermia caused a modest increase in etoposide-induced apoptosis in HeLa and HeLaMRP cells, which required appropriate heat-drug scheduling. Conclusions: Hyperthermia could be useful in eliminating MDR cells that overexpress MRP1

260

Diversity and evolution of the small multidrug resistance protein family  

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Full Text Available Abstract Background Members of the small multidrug resistance (SMR protein family are integral membrane proteins characterized by four ?-helical transmembrane strands that confer resistance to a broad range of antiseptics and lipophilic quaternary ammonium compounds (QAC in bacteria. Due to their short length and broad substrate profile, SMR proteins are suggested to be the progenitors for larger ?-helical transporters such as the major facilitator superfamily (MFS and drug/metabolite transporter (DMT superfamily. To explore their evolutionary association with larger multidrug transporters, an extensive bioinformatics analysis of SMR sequences (> 300 Bacteria taxa was performed to expand upon previous evolutionary studies of the SMR protein family and its origins. Results A thorough annotation of unidentified/putative SMR sequences was performed placing sequences into each of the three SMR protein subclass designations, namely small multidrug proteins (SMP, suppressor of groEL mutations (SUG, and paired small multidrug resistance (PSMR using protein alignments and phylogenetic analysis. Examination of SMR subclass distribution within Bacteria and Archaea taxa identified specific Bacterial classes that uniquely encode for particular SMR subclass members. The extent of selective pressure acting upon each SMR subclass was determined by calculating the rate of synonymous to non-synonymous nucleotide substitutions using Syn-SCAN analysis. SUG and SMP subclasses are maintained under moderate selection pressure in comparison to integron and plasmid encoded SMR homologues. Conversely, PSMR sequences are maintained under lower levels of selection pressure, where one of the two PSMR pairs diverges in sequence more rapidly than the other. SMR genomic loci surveys identified potential SMR efflux substrates based on its gene association to putative operons that encode for genes regulating amino acid biogenesis and QAC-like metabolites. SMR subclass protein transmembrane domain alignments to Bacterial/Archaeal transporters (BAT, DMT, and MFS sequences supports SMR participation in multidrug transport evolution by identifying common TM domains. Conclusion Based on this study, PSMR sequences originated recently within both SUG and SMP clades through gene duplication events and it appears that SMR members may be evolving towards specific metabolite transport.

Turner Raymond J

2009-06-01

 
 
 
 
261

Entamoeba histolytica P-glycoprotein (EhPgp) inhibition, induce trophozoite acidification and enhance programmed cell death.  

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Programmed cell death (PCD) is induced in Entamoeba histolytica by a variety of stimuli in vitro and in vivo. In mammals, intracellular acidification serves as a global switch for inactivating cellular processes and initiates molecular mechanisms implicated in the destruction of the genome. In contrast, intracellular alkalinization produced by P-glycoprotein overexpression in multidrug-resistant cells has been related to apoptosis resistance. Our previous studies showed that overexpression of E. histolytica P-glycoprotein (PGP) altered chloride-dependent currents and triggered trophozoite swelling, the reverse process of cell shrinkage produced during PCD. Here we showed that antisense inhibition of PGP expression produced a synchronous death of trophozoites and the enhancement of biochemical and morphological characteristics of PCD induced by G418. The nucleus was contracted, and the nuclear membrane was disrupted. Moreover, chromatin was extensively fragmented. Ca(2+) concentration was increased, while the intracellular pH (ipH) was acidified. In contrast, PGP overexpression prevented intracellular acidification and circumvented the apoptotic effect of G418. PMID:24012862

Medel Flores, Olivia; Gómez García, Consuelo; Sánchez Monroy, Virgina; Villalba Magadaleno, José D'Artagnan; Nader García, Elvira; Pérez Ishiwara, D Guillermo

2013-11-01

262

Draft Genome Sequence of a Multidrug-Resistant New Zealand Isolate of Mycobacterium tuberculosis Lineage 3  

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Multidrug resistance constitutes a threat worldwide to the management of tuberculosis (TB). We report the draft whole-genome sequence of a lineage 3 (East-African Indian) isolate of Mycobacterium tuberculosis which presented as multidrug resistant in New Zealand, and describe a number of single-nucleotide polymorphisms in genes relating to drug resistance. PMID:25323711

Mac Aogain, Micheal; Johari, Bushra M.; Bower, James E.

2014-01-01

263

D-?-tocopherol polyethylene glycol succinate-based redox-sensitive paclitaxel prodrug for overcoming multidrug resistance in cancer cells.  

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To overcome the multidrug resistance (MDR) of P-glycoprotein (P-gp) substrate anticancer drugs, such as paclitaxel (PTX), a novel dual-functional prodrug, D-?-tocopherol polyethylene glycol succinate (TPGS) based PTX prodrug (TPGS-S-S-PTX), was synthesized here to fulfill the synergistic effect of P-gp inhibiting and intracellular redox-sensitive release. The prodrug could self-assemble into stable micelles in physiological environment with a diameter of ?140 nm, while it disassociated in reductive condition and released PTX and TPGS active derivatives rapidly. High cell cytotoxicity in PTX-resistant human ovarian cell line A2780/T was observed with enhanced PTX accumulation due to the P-gp inhibition by the TPGS moiety. The IC50 of TPGS-S-S-PTX was 55% and 91% more effective than that of Taxol (clinical formulation of PTX) and uncleavable TPGS-C-C-PTX prodrug, respectively. This was found to be related with the increased apoptosis/necrosis and cell arrest in G2/M phase. In vivo evaluation of the TPGS-S-S-PTX prodrug exhibited an extended half-life, increased AUC (area under the concentration-time curve), enhanced tumor distribution and significant tumor growth inhibition with reduced side effects as compared to Taxol and TPGS-C-C-PTX. This prodrug has great potential in improving efficiency in the treatment of MDR tumors. PMID:25102234

Bao, Yuling; Guo, Yuanyuan; Zhuang, Xiangting; Li, Dan; Cheng, Bolin; Tan, Songwei; Zhang, Zhiping

2014-09-01

264

Effect of microRNA-21 on multidrug resistance reversal in A549/DDP human lung cancer cells.  

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Lung cancer is a predominant cause of cancer?related mortality and numerous lung cancer patients succumb to the disease due to drug resistance. A number of microRNAs (miRNAs) are upregulated in cancer and are involved in tumorigenesis, functioning as oncogenes. Several functional studies have shown that miR?21 is important in carcinogenesis; however, none of these studies has investigated multidrug resistance (MDR) reversal in human lung cancer cells. In the present study, the effect of miR?21 on MDR reversal was analyzed in A549/DDP lung cancer cells. The data demonstrated the following after miR?21 silencing: Proliferation of the tumor cells was inhibited, cell apoptosis and oxidative damage were increased, the cell cycle was blocked at the G0/G1 phase, expression levels of P?glycoprotein were reduced, accumulation of Rhodamine 123 was increased, and the MDR?related genes encoding MDR1, MPR, glutathione S?transferase??, B?cell lymphoma 2, cyclin?dependent kinase 1, cystathione and glutathione were downregulated. Further mechanistic analysis revealed that miR?21 silencing reduced AKT phosphorylation and transcriptional activation of E2F?1 and Twist. In conclusion, this study demonstrated that miR?21 silencing reversed lung cancer cell MDR by modulation of MDR?related gene expression and inhibition of the AKT signaling pathway, suggesting that miR?21 may be a potential therapeutic candidate in patients with MDR lung cancer. PMID:25323306

Dong, Zuoliang; Ren, Li; Lin, Li; Li, Jiang; Huang, Yiwen; Li, Jinhong

2015-01-01

265

Transport of the coumarin metabolite 7-hydroxycoumarin glucuronide is mediated via multidrug resistance-associated proteins 3 and 4.  

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Coumarin (1,2-benzopyrone) is a natural compound that has been used as a fragrance in the food and perfume industry and could have therapeutic usefulness in the treatment of lymphedema and different types of cancer. Several previous pharmacokinetic studies of coumarin have been performed in humans, which revealed extensive first-pass metabolism of the compound. 7-Hydroxycoumarin (7-HC) and its glucuronide (7-HC-G) are the main metabolites formed in humans, and via this route, 80 to 90% of the absorbed coumarin is excreted into urine, mainly as 7-HC-G. Active transport processes play a role in the urinary excretion of 7-HC-G; however, until now, the transporters involved remained to be elucidated. In this study, we investigated whether the efflux transporters multidrug resistance-associated proteins (MRP)1-4, breast cancer resistance protein, or P-glycoprotein play a role in 7-HC and 7-HC-G transport. For this purpose, we measured uptake of the metabolites into membrane vesicles overexpressing these transporters. Our results showed that 7-HC is not transported by any of the efflux transporters tested, whereas 7-HC-G was a substrate of MRP3 and MRP4. These results are in line with the pharmacokinetic profile of coumarin and suggest that MRP3 and MRP4 are the main transporters involved in the excretion of the coumarin metabolite 7-HC-G from liver and kidney. PMID:22415933

Wittgen, Hanneke G M; van den Heuvel, Jeroen J M W; van den Broek, Petra H H; Siissalo, Sanna; Groothuis, Geny M M; de Graaf, Inge A M; Koenderink, Jan B; Russel, Frans G M

2012-06-01

266

Reversal effects of two new milbemycin compounds on multidrug resistance in MCF-7/adr cells in vitro.  

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Development of agents to overcome multidrug resistance (MDR) is important in cancer chemotherapy, and the overexpression of P-glycoprotein (P-gp) is one of the major mechanisms of MDR. In this paper, we evaluated the effects of two new milbemycin compounds, milbemycin ?(14) and secomilbemycin D, isolated from fermentation broth of S. bingchenggensis on reversing MDR of adriamycin-resistant human breast carcinoma (MCF-7/adr) cells. We observed that the both milbemycins (5 ?M) showed strong potency to increase adriamycin cytotoxicity toward MCF-7/adr cells with reversal fold (RF) of 13.5 and 10.59, respectively. In addition, the mechanisms of milbemycins on reversing P-gp-mediated MDR demonstrated that they significantly increased the accumulations of adriamycin and Rh123 via inhibiting P-gp efflux in MCF-7/adr cells. Furthermore, the results also revealed that milbemycin ?(14) and secomilbemycin D could regulate down the expression of P-gp, but not affect the expression of MDR1 gene. In conclusion, our observations suggest that the two new milbemycin compounds probably represent the promising agents for reversing MDR in cancer therapy. PMID:21458446

Gao, Aili; Liang, Hongsheng; Wang, Xiangjing; Zhang, Xiangtong; Jing, Meng; Zhang, Ji; Yan, Yijun; Xiang, Wensheng

2011-06-01

267

Development and characterization of P-glycoprotein 1 (Pgp1, ABCB1)-mediated doxorubicin-resistant PLHC-1 hepatoma fish cell line  

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g in EC50 values similar to the EC50 values found for PLHC-1/wt. In contrast, MK571, a specific inhibitor of MRP type of efflux transporters, sensitized PLHC-1/dox cells, neither to doxorubicin, nor to any other of the chemotherapeutics used in the study. These data demonstrate for the first time that a specific Pgp1-mediated doxorubicin resistance mechanism is present in the PLHC-1 fish hepatoma cell line. In addition, the fact that low micromolar concentrations of specific inhibitors may completely reverse a highly expressed doxorubicin resistance points to the fragility of Pgp1-mediated MXR defence mechanism in fish

268

The Pim kinase inhibitor SGI-1776 decreases cell surface expression of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) and drug transport by Pim-1-dependent and -independent mechanisms.  

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Overexpression of the ATP-binding cassette (ABC) drug efflux proteins P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) on malignant cells is associated with inferior chemotherapy outcomes. Both, ABCB1 and ABCG2, are substrates of the serine/threonine kinase Pim-1; Pim-1 knockdown decreases their cell surface expression, but SGI-1776, the first clinically tested Pim inhibitor, was shown to reverse drug resistance by directly inhibiting ABCB1-mediated transport. We sought to characterize Pim-1-dependent and -independent effects of SGI-1776 on drug resistance. SGI-1776 at the Pim-1-inhibitory and non-cytotoxic concentration of 1 ?M decreased the IC(50)s of the ABCG2 and ABCB1 substrate drugs in cytotoxicity assays in resistant cells, with no effect on the IC(50) of non-substrate drug, nor in parental cells. SGI-1776 also increased apoptosis of cells overexpressing ABCG2 or ABCB1 exposed to substrate chemotherapy drugs and decreased their colony formation in the presence of substrate, but not non-substrate, drugs, with no effect on parental cells. SGI-1776 decreased ABCB1 and ABCG2 surface expression on K562/ABCB1 and K562/ABCG2 cells, respectively, with Pim-1 overexpression, but not HL60/VCR and 8226/MR20 cells, with lower-level Pim-1 expression. Finally, SGI-1776 inhibited uptake of ABCG2 and ABCB1 substrates in a concentration-dependent manner irrespective of Pim-1 expression, inhibited ABCB1 and ABCG2 photoaffinity labeling with the transport substrate [(125)I]iodoarylazidoprazosin ([(125)I]IAAP) and stimulated ABCB1 and ABCG2 ATPase activity. Thus SGI-1776 decreases cell surface expression of ABCB1 and ABCG2 and inhibits drug transport by Pim-1-dependent and -independent mechanisms, respectively. Decrease in ABCB1 and ABCG2 cell surface expression mediated by Pim-1 inhibition represents a novel mechanism of chemosensitization. PMID:23261525

Natarajan, Karthika; Bhullar, Jasjeet; Shukla, Suneet; Burcu, Mehmet; Chen, Zhe-Sheng; Ambudkar, Suresh V; Baer, Maria R

2013-02-15

269

P-glycoprotein down-regulates the X-ray-induced apoptosis of a drug-resistant tumor cell line MCF-7/Adr  

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Objective: To investigate the regulatory effect of P-gp on X-ray-induced apoptosis of drug-resistant tumor cells. Methods: Anti-P-gp McAb was applied to block P-gp function. MCF-7/Adr, a P-gp-over-expressing drug-resistant breast cancer cell line, was irradiated with X-rays. Flow cytometry was performed to examine dynamic changes of apoptotic ratio and mitochondrial membrane potential (??m) at various times after X-ray irradiation. Results: Apoptotic ratio of the P-gp-blocked group was 25.53%±2.85 %; 30.43%±2.21%; 39.03% ±2.60%, and of the control group was 16.13%±1.16%; 21.73%±1.31%; 27.53%±2.55% at 6 h,12 h, 24 h, respectively, after X-ray irradiation. The apoptotic ratio of the P-gp-blocked group was significantly up-regulated, as compared with that of the control group (P<0.01). The mitochondrial membrane potential (??m) of both the P-gp-blocked group and the control group was decreased, but the ??m of the P-gp-blocked group was significantly lower than that of the control group (P<0.01 ). Conclusion: P-gp down-regulates the X-ray-induced apoptosis of the drug-resistant MCF-7/Adr cells and elevates the mitochondrial membrane potential (??m)

270

How multidrug resistance in typhoid fever affects treatment options.  

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Salmonella enterica serotype Typhi (S. Typhi) is an enteric pathogen that causes typhoid fever. The infection can be severe, with significant morbidity and mortality, requiring antimicrobial therapy. Cases of S. Typhi infection in the United States and other developed countries are often associated with travel to endemic regions. The empirical use of first-line drugs for therapy, including ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole, has resulted in transmissible multidrug resistance. With the global increase in multidrug-resistant S. Typhi, use of ciprofloxacin, with excellent oral absorption, few side effects, and cost-effectiveness, has become popular for treatment. However, decreased ciprofloxacin susceptibility due to point mutations in the S. Typhi genes gyrA and/or parC has caused treatment failures, necessitating alternative therapeutic options. S. Typhi is typically genetically homogenous, with phylogenetic and epidemiological studies showing that identical clones and diverse S. Typhi types often coexist in the same geographic region. Studies investigating point mutations have demonstrated that selective pressure from empirical use of first-line drugs and fluoroquinolones has led to the global emergence of haplotype H-58. Antibiotic resistance is subject to high selective pressure in S. Typhi and thus demands careful use of antimicrobials. PMID:25069595

Tatavarthy, Aparna; Luna, Vicki A; Amuso, Philip T

2014-09-01

271

Differential effects of the organochlorine pesticide DDT and its metabolite p,p'-DDE on p-glycoprotein activity and expression  

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1,1-Bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) is an organochlorine pesticide. Its metabolite, 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethene (p,p'-DDE) is a persistent environmental contaminant and both compounds accumulate in animals. Because multidrug resistance transporters, such as p-glycoprotein, function as a defense against xenobiotic exposure, we analyzed the ability of DDT and p,p'-DDE to act as efflux modulators. Using a competitive intact cell assay based on the efflux of the fluorescent dye rhodamine 123, we found that DDT, but not p,p'-DDE, stimulated dye retention. Subsequent studies using verapamil as competitor suggested that DDT is a weak p-glycoprotein inhibitor. Further studies addressed the ability of DDT and p,p'-DDE to induce MDR1, the gene encoding p-glycoprotein. In HepG2 cells, we found that both compounds induced MDR1 by twofold to threefold. Similar results were observed in mouse liver after a single dose of p,p'-DDE, although some gender-specific induction differences were noted. By contrast, p,p'-DDE failed to induce MDR1 in HeLa cells, indicating some cell-specific effects for induction. Further expression studies demonstrated increased levels of the endoplasmic reticulum molecular chaperone, Bip, in response to DDT, but not p,p'-DDE. These results suggest that DDT, but not p,p'-DDE, induces an endoplasmic reticulum stress response

272

Cell-Free Microfluidic Determination of P-glycoprotein Interactions with Substrates and Inhibitors.  

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The membrane protein P-glycoprotein (P-gp) plays key roles in the oral bioavailability of drugs, their blood brain barrier passage as well as in multidrug resistance. For new drug candidates it is mandatory to study their interaction with P-gp, according to FDA and EMA regulations. The vast majority of these tests are performed using confluent cell layers of P-gp overexpressing cell lines that render these tests laborious. In this study, we introduce a cell-free microfluidic assay for the rapid testing of drug- P-gp interactions. Cell-derived vesicles are prepared from MDCKII-MDR1 overexpressing cells and immobilized on the surface of a planar microfluidic device. The drug is delivered continuously to the vesicles and calcein accumulation is monitored by means of a fluorescence assay and total internal reflection fluorescence (TIRF) microscopy. Only small amounts of compounds (~10 ?l) are required in concentrations of 5, 25 and 50 ?M for a test that provides within 5 min information on the apparent dissociation constant of the drug and P-gp. We tested 10 drugs on-chip, 9 of which are inhibitors or substrates of P-glycoprotein and one negative control. We benchmarked the measured apparent dissociation constants against an alternative assay on a plate reader and reference data from FDA. These comparisons revealed good correlations between the logarithmic apparent dissociation constants (R(2)?=?0.95 with ATPase assay, R(2)?=?0.93 with FDA data) and show the reliability of the rapid on-chip test. The herein presented assay has an excellent screening window factor (Z'-factor) of 0.8, and is suitable for high-throughput testing. PMID:24928366

Eyer, Klaus; Herger, Michael; Krämer, Stefanie D; Dittrich, Petra S

2014-12-01

273

P-Glycoprotein/MDR1 Regulates Pokemon Gene Transcription Through p53 Expression in Human Breast Cancer Cells  

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Full Text Available P-glycoprotein (Pgp, encoded by the multidrug resistance 1 (MDR1 gene, is an efflux transporter and plays an important role in pharmacokinetics. In this study, we demonstrated that the pokemon promoter activity, the pokemon mRNA and protein expression can be significantly inhibited by Pgp. Chromatin immunoprecipitation assay showed that Pgp can bind the pokemon prompter to repress pokemon transcription activity. Furthermore, Pgp regulated pokemon transcription activity through expression of p53 as seen by use of p53 siRNA transfected MCF-7 cells or p53 mutated MDA-MB-231 cells. Moreover, p53 was detected to bind with Pgp in vivo using immunoprecipitation assay. Taken together, we conclude that Pgp can regulate the expression of pokemon through the presence of p53, suggesting that Pgp is a potent regulator and may offer an effective novel target for cancer therapy.

Wei Xu

2010-08-01

274

Effects of Astragalus polysaccharides on P-glycoprotein efflux pump function and protein expression in H22 hepatoma cells in vitro  

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Full Text Available Abstract Background Astragalus polysaccharides (APS are active constituents of Astragalus membranaceus. They have been widely studied, especially with respect to their immunopotentiating properties, their ability to counteract the side effects of chemotherapeutic drugs, and their anticancer properties. However, the mechanism by which APS inhibit cancer and the issue of whether that mechanism involves the reversal of multidrug resistance (MDR is not completely clear. The present paper describes an investigation of the effects of APS on P-glycoprotein function and expression in H22 hepatoma cell lines resistant to Adriamycin (H22/ADM. Methods H22/ADM cell lines were treated with different concentrations of APS and/or the most common chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine. Chemotherapeutic drug sensitivity, P-glycoprotein function and expression, and MDR1 mRNA expression were detected using MTT assay, flow cytometry, Western blotting, and quantitative RT-PCR. Results When used alone, APS had no anti-tumor activity in H22/ADM cells in vitro. However, it can increase the cytotoxicity of certain chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine, in H22/ADM cells. It acts in a dose-dependent manner. Compared to a blank control group, APS increased intracellular Rhodamine-123 retention and decreased P-glycoprotein efflux function in a dose-dependent manner. These factors were assessed 24?h, 48?h, and 72?h after administration. APS down regulated P-glycoprotein and MDR1 mRNA expression in a concentration-dependent manner within a final range of 0.8–500?mg/L and in a time-dependent manner from 24–72?h. Conclusion APS can enhance the chemosensitivity of H22/ADM cells. This may involve the downregulation of MDR1 mRNA expression, inhibition of P-GP efflux pump function, or both, which would decrease the expression of the MDR1 protein.

Tian Qing E

2012-07-01

275

Clinical study of 99mTc-MIBI SPECT imaging for detection of multidrug resistant p-glycoprotein expression in lung cancer  

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ohistochemical staining and PCR have been developed to detect p-GP in tissue. Compared with biopsy, which was subject to sampling errors and heterogeneity of p-GP expression, the present technique was a non-invasive and independent from sampling errors. Therefore, it might serve as an effective complement to the other techniques to detect p-GP mediated MDR

276

The role of multidrug resistance-associated protein in the blood-brain barrier and opioid analgesia.  

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The blood-brain barrier protects the brain from circulating compounds and drugs. The ATP-binding cassette (ABC) transporter P-glycoprotein (Pgp) is involved with the barrier, both preventing the influx of agent from the blood into the brain and facilitating the efflux of compounds from the brain into the blood, raising the possibility of a similar role for other transporters. Multidrug resistance-associated protein (MRP), a 190 kDa protein, similar to Pgp is also ABC transporter that has been implicated in the blood-brain barrier. The current study explores its role in opioid action. Immunohistochemically, it is localized in the choroid plexus in rats and can be selectively downregulated by antisense treatment at both the level of mRNA, as shown by RT-PCR, and protein, as demonstrated immunohistochemically. Behaviorally, downregulation of MRP significantly enhances the analgesic potency of systemic morphine in MRP knockout mice and in antisense-treated rats by lowering the blood-brain barrier. Following intracerebroventricular administration, a number of compounds, including some opioids, are rapidly secreted from the brain into the blood where they contribute to the overall analgesic effects by activating peripheral systems. MRP plays a role in this efflux. Downregulating MRP expression leads to a corresponding decrease in the transport and a diminished analgesic response from opioids administered intracerebroventricularly. Thus, the transporter protein MRP plays a role in maintaining the blood-brain barrier and modulates the activity of opioids. PMID:23508590

Su, Wendy; Pasternak, Gavril W

2013-09-01

277

Anticancer effects of the organosilicon multidrug resistance modulator SILA 421.  

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1,3-dimethyl-1,3-bis(4-fluorophenyl)-1,3-bis{3-[1(4-butylpiperazinyl)]-propyl}-disiloxan-tetrahydrochlorid (SILA 421) is a compound that was developed as modulator of the ABC cassette transporter P-glycoprotein. Furthermore, it exerted antimicrobial toxicity, vascular effects, downregulation of chaperone induction and plasmid curing in bacterial cells. Here, this drug was found to possess cytotoxic activity against a panel of human cancer cell lines that do not overexpress P-gp, with 50% inhibitory concentrations ranging between 1.75±0.38 ?M for GLC14 small cell lung cancer and 34.00±4.75 ?M for PC-3 prostate cancer cells. HL-60 leukemia and MDA-MB-435 breast cancer cells exhibited cell cycle arrest and apoptotic cell death in response to SILA 421. Assessment of global gene expression of SILA 421-treated HL-60 cells was employed to identify cellular pathways affected by the compound and revealed disturbance of DNA replication, transcription and production of apparently misfolded proteins. Endoplasmatic reticulum stress and downregulation of cell cycle, cellular repair mechanisms and growth factor-related signaling cascades eventually resulted in induction of apoptosis in this cell line. In addition to the well established P-gp inhibitory effect of SILA compounds, reversal of resistance to taxanes, which had been reported for SILA 421 and the related molecule SILA 409, may be linked to downregulation of gene expression of kinesins. Interference with DNA replication and transcription seems to be the common denominator of antimicrobial activity and plasmid curing, as well as anticancer toxicity in human cell lines. Thus, in consideration of the full range of putative cellular targets found in the present work, the application of these SILA compounds for treatment of tumors should be further evaluated. PMID:22263791

Olszewski, Ulrike; Zeillinger, Robert; Kars, Meltem Demirel; Zalatnai, Attila; Molnar, Jozsef; Hamilton, Gerhard

2012-07-01

278

STUDIES ON ANTIBACTERIAL EFFECT OF APAMARGA (ACHYRANTHES ASPERA ON MULTI-DRUG RESISTANT CLINICAL ISOLATES  

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Full Text Available Recent reports on emergence of multidrug resistant bacteria are cause of concern in medical world. Several ayurvedic drugs have been proved to contain the antimicrobial activity. Literature on effect of ayurvedic drugs on multidrug resistant bacterial pathogens is limited. Present study reports the antimicrobial effect of Achyranthes aspera (Apamarga crude extracts on the clinical isolates of multidrug resistant bacteria. The drug was evaluated by using phytochemical tests. Crude extracts of aqueous, methanol, ethanol and chloroform was prepared. Antibacterial activity against clinically isolated multidrug resistant bacteria belonging to groups of bacillus, citrobacter, E.coli, klebsiella, proteus and salmonella was tested. The drug showed highest efficacy against Bacillus organism while least effectiveness on Proteus spp bacteria. Results of the study conclude that the medicinal plant A. aspera might be useful against multidrug resistance in pathogens of clinical importance.

Patil Usha

2013-04-01

279

Comparative study on reversal efficacy of SDZ PSC 833, cyclosporin a and verapamil on multidrug resistance in vitro and in vivo  

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A non-immunosuppressive cyclosporin, SDZ PSC 833 (PSC833), shows a reversal effect on multidrug resistance (MDR) by functional modulation of MDR1 gene product, P-glycoprotein. The objective of the present study was to compare the reversal efficacy of three multidrug resistance modulators, PSC833, cyclosporin A (CsA) and verapamil (Vp). PSC833 has approximately 3-10-fold greater potency than CsA and Vp with respect to the restoring effect on reduced accumulation of doxorubicin (ADM) and vincristine (VCR) in ADM-resistant K562 myelogenous leukemia cells (K562/ADM) in vitro and also on the sensitivity of K562/ADM to ADM and VCR in in vitro growth inhibition. The in vivo efficacy of a combination of modifiers (PSC833 and CsA: 50 mg/kg, Vp 100 mg/kg administered p.o. 4 h before the administration of anticancer drugs) with anticancer drugs (ADM 2.5 mg/kg i.p., Q4D days 1, 5 and 9, VCR 0.05 mg/kg i.p., QD days 1-5) was tested in ADM-resistant P388-bearing mice. PSC833 significantly enhanced the increase in life span by more than 80%, whereas CsA and Vp enhanced by less than 50%. This reversal potency, which exceeded that of CsA and Vp, was confirmed by therapeutic experiments using colon adenocarcinoma 26-bearing mice. These results demonstrated that PSC833 has significant potency to reverse MDR in vitro and in vivo, suggesting that PSC833 is a good candidate for reversing multidrug resistance in clinical situations. (orig.)

280

Evaluation of the P-glycoprotein- and breast cancer resistance protein-mediated brain penetration of {sup 11}C-labeled topotecan using small-animal positron emission tomography  

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Introduction: Topotecan (TPT) is a camptothecin derivative and is an anticancer drug working as a topoisomerase-I-specific inhibitor. But TPT cannot penetrate through the blood-brain barrier. In this study, we synthesized a new positron emission tomography (PET) probe, [{sup 11}C]TPT, to evaluate the P-glycoprotein (Pgp)- and breast cancer resistance protein (BCRP)-mediated brain penetration of [{sup 11}C]TPT using small-animal PET. Methods: [{sup 11}C]TPT was synthesized by the reaction of a desmethyl precursor with [{sup 11}C]CH{sub 3}I. In vitro study using [{sup 11}C]TPT was carried out in MES-SA and doxorubicin-resistant MES-SA/Dx5 cells in the presence or absence of elacridar, a specific inhibitor for Pgp and BCRP. The biodistribution of [{sup 11}C]TPT was determined using small-animal PET and the dissection method in mice. Results: The transport of [{sup 11}C]TPT to the extracellular side was determined in MES-SA/Dx5 cells exhibiting the expressions of Pgp and BCRP at high levels. This transport was inhibited by coincubation with elacridar. In Mdr1a/b{sup -/-}Bcrp1{sup -/-} mice, PET results indicated that the brain uptake of [{sup 11}C]TPT was about two times higher than that in wild-type mice. Similarly, the brain penetration of [{sup 11}C]TPT in wild-type mice was increased by treatment with elacridar. The radioactivity in the brain of elacridar-treated mice was maintained at a certain level after the injection of [{sup 11}C]TPT, although the radioactivity in the blood decreased with time. Conclusions: We demonstrated the increase of brain penetration of [{sup 11}C]TPT by deficiency and inhibition of Pgp and BCRP functions using small-animal PET in mice.

Yamasaki, Tomoteru; Fujinaga, Masayuki; Kawamura, Kazunori; Hatori, Akiko; Yui, Joji [Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Nengaki, Nobuki; Ogawa, Masanao; Yoshida, Yuichiro [Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); SHI Accelerator Service, Ltd., Tokyo 141-8686 (Japan); Wakizaka, Hidekatsu [Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Yanamoto, Kazuhiko [Division of Health Sciences, Graduate School of Medicine, Osaka University, Osaka 565-0871 (Japan); Fukumura, Toshimitsu [Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Zhang Mingrong, E-mail: zhang@nirs.go.jp [Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan)

2011-07-15

 
 
 
 
281

In silico screening for inhibitors of p-glycoprotein that target the nucleotide binding domains.  

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Multidrug resistances and the failure of chemotherapies are often caused by the expression or overexpression of ATP-binding cassette transporter proteins such as the multidrug resistance protein, P-glycoprotein (P-gp). P-gp is expressed in the plasma membrane of many cell types and protects cells from accumulation of toxins. P-gp uses ATP hydrolysis to catalyze the transport of a broad range of mostly hydrophobic compounds across the plasma membrane and out of the cell. During cancer chemotherapy, the administration of therapeutics often selects for cells which overexpress P-gp, thereby creating populations of cancer cells resistant to a variety of chemically unrelated chemotherapeutics. The present study describes extremely high-throughput, massively parallel in silico ligand docking studies aimed at identifying reversible inhibitors of ATP hydrolysis that target the nucleotide-binding domains of P-gp. We used a structural model of human P-gp that we obtained from molecular dynamics experiments as the protein target for ligand docking. We employed a novel approach of subtractive docking experiments that identified ligands that bound predominantly to the nucleotide-binding domains but not the drug-binding domains of P-gp. Four compounds were found that inhibit ATP hydrolysis by P-gp. Using electron spin resonance spectroscopy, we showed that at least three of these compounds affected nucleotide binding to the transporter. These studies represent a successful proof of principle demonstrating the potential of targeted approaches for identifying specific inhibitors of P-gp. PMID:25270578

Brewer, Frances K; Follit, Courtney A; Vogel, Pia D; Wise, John G

2014-12-01

282

Effect of P-glycoprotein on flavopiridol sensitivity  

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Flavopiridol is the first potent inhibitor of cyclin-dependent kinases (CDKs) to enter clinical trials. Little is known about mechanisms of resistance to this agent. In order to determine whether P-glycoprotein (Pgp) might play a role in flavopiridol resistance, we examined flavopiridol sensitivity in a pair of Chinese hamster ovary cell lines differing with respect to level of Pgp expression. The IC 50 s of flavopiridol in parental AuxB1 (lower Pgp) and colchicine-selected CHRC5 (higher Pgp)...

Boerner, S. A.; Tourne, M. E.; Kaufmann, S. H.; Bible, K. C.

2001-01-01

283

The B-cell lymphoma 2 (BCL2)-inhibitors, ABT-737 and ABT-263, are substrates for P-glycoprotein  

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Highlights: {yields} The BCL2-inhibitor ABT-263 is a substrate for P-glycoprotein. {yields} Apoptosis is inhibited by P-glycoprotein expression. {yields} Overexpression of P-glycoprotein may contribute to resistance to ABT-263 or ABT-737. -- Abstract: Inhibition of BCL2 proteins is one of the most promising new approaches to targeted cancer therapy resulting in the induction of apoptosis. Amongst the most specific BCL2-inhibitors identified are ABT-737 and ABT-263. However, targeted therapy is often only effective for a limited amount of time because of the occurrence of drug resistance. In this study, the interaction of BCL2-inhibitors with the drug efflux transporter P-glycoprotein was investigated. Using {sup 3}H labelled ABT-263, we found that cells with high P-glycoprotein activity accumulated less drug. In addition, cells with increased P-glycoprotein expression were more resistant to apoptosis induced by either ABT-737 or ABT-263. Addition of tariquidar or verapamil sensitized the cells to BCL2-inhibitor treatment, resulting in higher apoptosis. Our data suggest that the BCL2-inhibitors ABT-737 and ABT-263 are substrates for P-glycoprotein. Over-expression of P-glycoprotein may be, at least partly, responsible for resistance to these BCL2-inhibitors.

Vogler, Meike, E-mail: mv62@le.ac.uk [MRC Toxicology Unit, University of Leicester, LE1 9HN Leicester (United Kingdom); Dickens, David, E-mail: David.Dickens@liverpool.ac.uk [Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, L69 3GL Liverpool (United Kingdom); Dyer, Martin J.S., E-mail: mjsd1@le.ac.uk [MRC Toxicology Unit, University of Leicester, LE1 9HN Leicester (United Kingdom); Owen, Andrew, E-mail: aowen@liverpool.ac.uk [Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, L69 3GL Liverpool (United Kingdom); Pirmohamed, Munir, E-mail: munirp@liv.ac.uk [Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, L69 3GL Liverpool (United Kingdom); Cohen, Gerald M., E-mail: gmc2@le.ac.uk [MRC Toxicology Unit, University of Leicester, LE1 9HN Leicester (United Kingdom)

2011-05-06

284

The B-cell lymphoma 2 (BCL2)-inhibitors, ABT-737 and ABT-263, are substrates for P-glycoprotein  

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Highlights: ? The BCL2-inhibitor ABT-263 is a substrate for P-glycoprotein. ? Apoptosis is inhibited by P-glycoprotein expression. ? Overexpression of P-glycoprotein may contribute to resistance to ABT-263 or ABT-737. -- Abstract: Inhibition of BCL2 proteins is one of the most promising new approaches to targeted cancer therapy resulting in the induction of apoptosis. Amongst the most specific BCL2-inhibitors identified are ABT-737 and ABT-263. However, targeted therapy is often only effective for a limited amount of time because of the occurrence of drug resistance. In this study, the interaction of BCL2-inhibitors with the drug efflux transporter P-glycoprotein was investigated. Using 3H labelled ABT-263, we found that cells with high P-glycoprotein activity accumulated less drug. In addition, cells with increased P-glycoprotein expression were more resistant to apoptosis induced by either ABT-737 or ABT-263. Addition of tariquidar or verapamil sensitized the cells to BCL2-inhibitor treatment, resulting in higher apoptosis. Our data suggest that the BCL2-inhibitors ABT-737 and ABT-263 are substrates for P-glycoprotein. Over-expression of P-glycoprotein may be, at least partly, responsible for resistance to these BCL2-inhibitors.

285

Photoaffinity labeling of P-glycoprotein.  

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The aim of the present review is to summarize recent progress in identifying substrate binding domains of P-glycoprotein by photoaffinity labeling. Preferred substrate binding regions have been identified using a number of photoaffinity ligands, including anthracyclines, the quinazoline iodoarylazidoprazosine (IAAP), dihydropyridines, taxanes and propafenones. These studies allowed identification of protein regions, which are involved in ligand interaction. PMID:15720286

Peer, Michael; Csaszar, Edina; Vorlaufer, Elisabeth; Kopp, Stephan; Chiba, Peter

2005-02-01

286

MiR-223 modulates multidrug resistance via downregulation of ABCB1 in hepatocellular carcinoma cells.  

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Multidrug resistance (MDR) has become a major impediment to a successful treatment for liver cancer patients, and one of the common reasons for MDR is the activation of ABCB1 gene, leading to the over-expression of P-glycoprotein (P-gp), which conferred cancer cells be resistant to a broad range of anticancer drugs. MicroRNAs (miRNAs) are a class of short, non-coding RNA moleculars that can regulate gene expression at the post-transcriptional level. In the current study, the aim is to explore whether miRNA participates in the regulation of MDR mediated by ABCB1. We found that the expression of ABCB1 was correlated with the doxorubicin IC50 dose in eight hepatocellular carcinoma (HCC) cell lines: Hep3B, HCC3, LM-6, SMMC7721, Huh-7, SK-Hep-1, HepG2 and BEL-7402. Using the bioinformatics, we discovered that there were several miRNAs that can bind to the 3'UTR of ABCB1 gene. Among these candidate miRNAs, miR-223 was chosen for further study. Then, EGFP reporter assay, real-time PCR and Western blot were performed to verify that miR-223 targeted ABCB1 3'UTR directly, and miR-223 downregulated ABCB1 at both mRNA and protein levels. Finally, we found that the over-expression of miR-223 increased the HCC cell sensitivity to anticancer drugs, and the inhibition of miR-223 had the opposite effect. Importantly, the over-expression or silencing of ABCB1 can rescue the cell response to the anticancer drugs mediated by miR-223 over-expression or inhibition, respectively. In conclusion, our findings indicated that miR-223 played an important role in the regulation of MDR mediated by ABCB1, and it suggests that miR-223 may be considered as a therapeutic biomarker for HCC patients who had MDR problems induced by high expression of ABCB1. PMID:23925649

Yang, Tao; Zheng, Zhi-Min; Li, Xiao-Na; Li, Zhen-Fu; Wang, Yan; Geng, Yun-Feng; Bai, Li; Zhang, Xian-Bo

2013-09-01

287

Expression of multidrug resistance proteins in invasive ductal carcinoma of the breast  

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Chemotherapy is commonly used for the treatment of breast cancer. However, the resistance to chemotherapeutic agents, often mediated by multidrug resistance (MDR) mechanisms, is a common occurrence. The present study examined the expression of several MDR-related proteins (MRPs) in invasive ductal carcinoma (IDC) of the breast, and assessed their association with clinicopathological variables and their prognostic significance. In addition, immunohistochemistry was used to measure the expression of MRP, p-glycoprotein (P-gp), topoisomerase 2? (Topo2?), thymidylate synthase (TS) and glutathione-S-transferase ? (GST-?) in 156 resected IDCs of the breast. Pearson’s ?2 test and Spearman’s correlation coefficient were used to analyze the association between MDR protein expression and several clinicopathological variables. The association between each of the five MDR proteins was also examined. Furthermore, Kaplan-Meier analysis and Cox regression modeling were used to assess overall survival. The expression of MRP, P-gp, Topo2?, TS and GST-? was detected in 20.5% (32/156), 25.0% (39/156), 84.0% (131/156), 41.7% (65/156) and 41.0% (64/156) of cases examined, respectively. No correlation was identified between MRP and Topo-2? and the clinicopathological variables examined. By contrast, P-gp (?2=20.226; P<0.0001) and GST-? (?2=35.032; P<0.0001) were found to positively correlate with tumor grade. In addition, staining for TS was associated with axillary lymph node metastasis (?2=42.281; P<0.0001). The expression levels of P-gp and GST-? were found to be significantly correlated (r= 0.319; P<0.0001). Furthermore, GST-? expression was elevated in estrogen receptor-negative breast cancer (?2=17.407; P<0.0001). Tumor histological grade, in addition to TS and GST-? expression, were significant predictors of a poor survival outcome. TS and GST-? are consequently useful prognostic biomarkers in IDC, therefore, when establishing a personalized chemotherapeutic plan, the expression of MDR proteins must be considered.

LI, WEIQUAN; SONG, MAOMIN

2014-01-01

288

Characterization and Identification of Multidrug Resistant Bacteria from Some Egyptian Patients  

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Full Text Available The isolation of multidrug resistant bacteria from Egyptian patients showed a great interest to study such phenomenon. Hence, simple methods were followed herein to isolate and characterize the antibiotic resistant variants by the common phenotypic, morphological and biochemical characters. Out of 500 clinical bacterial cultures, 50 only were multidrug resistant bacteria with a value of drug resistance ability of about 10%. About 46% of multidrug resistant bacterial cultures tested were isolated from urine samples. The percentage values of both resistance and susceptibility of the 50 multidrug resistant bacterial isolates to 14 types of antibiotics were calculated. Based on their cultural, morphological and biochemical characteristics, the 50 multidrug resistant bacterial isolates were identified and categorized into eight groups. The identified bacterial species were arranged in a descending order according to their frequency percentage viz. Escherichia coli>Staphylococcus aureus> Pseudomonas aeruginosa> Klebsiella pneumoniae>Streptococcus pyogenes> Proteus vulgaris>Streptococcus pneumoniae> Staphylococcus saprophyticus. The relationship between pathogenic cases, symptoms and the identified multidrug bacterial pathogens was studied. A simple key was designed for easy differentiation and classification of the 50 multidrug resistant bacterial organisms. It was based on easily determinable characteristics which were used for rapid assignment of bacteria into genera and species.

Seham Abdel-Shafi

2013-01-01

289

On-line identification of P-glycoprotein substrates by monitoring of extracellular acidification and respiration rates in living cells.  

Science.gov (United States)

The influence of P-glycoprotein (ABCB1) in drug resistance as well as drug absorption and disposition is an important factor to be considered during the development of new drugs. Thus, the early identification and exclusion of compounds showing a high affinity towards P-glycoprotein can help to select drug candidates. The aim of our study was to implement a label-free assay for the identification of P-glycoprotein substrates in living cells. For this approach, a multiparametric, chip-based sensor system was used to determine extracellular acidification, cell respiration and adhesion upon stimulation with P-glycoprotein substrates. Using L-MDR1 cells, a human P-glycoprotein overexpressing cell line, the influence of P-glycoprotein activity was determined for seven different compounds, demonstrating the applicability of the system for P-glycoprotein substrate identification. Effects were concentration dependent, as shown for the P-glycoprotein substrate verapamil, and were associated with cellular acidification and respiration. P-glycoprotein ATPase activation by verapamil could be described by a Michaelis-Menten type kinetic profile showing saturation at high substrate concentrations. The Michaelis-Menten constants K(M) were determined to be 0.92?M (calculated based on extracellular acidification) and 4.9?M (calculated based on cellular respiration). Control experiments using 100nM of the P-glycoprotein inhibitor elacridar indicated that the observed effects were related to P-glycoprotein ATPase activity. In contrast, wild-type LLC-PK1 cells not expressing P-glycoprotein were not responsive towards stimulation with different P-glycoprotein substrates. Summarizing these findings, the used microsensor system is a generic system suitable for the identification of P-glycoprotein substrates. In contrast to biochemical P-glycoprotein assays, activation of the drug efflux pump can be monitored on-line in living cells to identify P-glycoprotein substrates and to study the molecular mechanisms of adenosintriphosphate-dependent active transport. PMID:21439263

Seeland, Swen; Treiber, Alexander; Hafner, Mathias; Huwyler, Jörg

2011-07-01

290

P-glycoprotein, breast cancer resistance protein, Organic Anion Transporter 3, and Transporting Peptide 1a4 during blood-brain barrier maturation: involvement of Wnt/?-catenin and endothelin-1 signaling.  

Science.gov (United States)

Our current knowledge about drug transporters in the maturational brain is very limited. In this study, we provide a comprehensive overview of the expression and activity profile of P-glycoprotein (P-gp), Breast Cancer Resistance Protein (bcrp), Organic Anion Transporter 3 (oat3), and Transporting Peptide 1a4 (oatp1a4) transporters during blood-brain barrier (BBB) maturation. Gene and protein expressions of the analyzed transporters increase as the brain matures, with no variation in their activity for P-gp and bcrp, while the transport activity of oat3 and oatp1a4 increases during brain maturation from preterm up to adulthood. For the first time, we illustrate a downregulation of nuclear ?-catenin expression in brain capillaries when bcrp, P-gp, oat3, and oatp1a4 transporters are at their highest expression levels. In vivo activation of ?-catenin in rat brains, by intracerebroventricular (ICV) injection of a GSK-3 inhibitor, enhances the activity of P-gp, bcrp, oat3, and oatp1a4. Interestingly, in an in vitro BBB model consisting of a coculture of primary endothelial brain cells with astrocytes or in vivo, activation of ?-catenin enhances the mRNA expression of ET-1. Interestingly, blocking the ETA receptor for endothelin-1 in vivo by ICV injection of a ETA antagonist decreases transporter activity mediated by the activation of ?-catenin. These findings shed light on the role of an interaction between ?-catenin and endothelin-1 signaling in the regulation of these transporters at the BBB. PMID:22998451

Harati, Rania; Benech, Henri; Villégier, Anne Sophie; Mabondzo, Aloïse

2013-05-01

291

Quantitative Proteomics of Transporter Expression in Brain Capillary Endothelial Cells Isolated from P-Glycoprotein (P-gp), Breast Cancer Resistance Protein (Bcrp), and P-gp/Bcrp Knockout Mice  

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The objective of this study was to quantitatively examine the protein expression of relevant transporters and other proteins in the brain capillary endothelial cells isolated from wild-type mice and P-glycoprotein (P-gp), breast cancer resistance protein (Bcrp), and P-gp/Bcrp knockout mice. After the isolation of brain capillary endothelial cells, a highly sensitive liquid chromatography-tandem mass spectrometry method with multiple reaction monitoring was used to determine the quantitative expression of membrane transporters at the blood-brain barrier (BBB) of the various mouse genotypes. Quantitative expression of 29 protein molecules, including 12 ATP-binding cassette transporters, 10 solute carrier transporters, five receptors, and two housekeeping proteins, was examined by quantitative proteomics in the four mouse genotypes. There was no significant difference in the expression of P-gp between the wild-type and Bcrp1(?/?) mice. Likewise, Bcrp expression was not significantly different between the wild-type and Mdr1a/b(?/?) mice. There was no significant difference in the expression of any of the measured proteins in the brain capillary endothelial cells across the genotypes, except for the lack of expression of the corresponding protein in the mice that had a genetic deletion of P-gp or Bcrp. In conclusion, using a quantitative proteomic approach, we have shown that there are no changes in the expression of several relevant transporters in brain capillary endothelial cells isolated from single and combination knockout mice. These data suggest that the mechanism behind the functional compensation between P-gp and Bcrp at the BBB is not related to compensatory changes in transporter expression. PMID:22401960

Agarwal, Sagar; Uchida, Yasuo; Mittapalli, Rajendar K.; Sane, Ramola; Terasaki, Tetsuya

2012-01-01

292

Increased oral availability and brain accumulation of the ALK inhibitor crizotinib by coadministration of the P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) inhibitor elacridar.  

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Crizotinib is an oral tyrosine kinase inhibitor approved for treating patients with non-small cell lung cancer (NSCLC) containing an anaplastic lymphoma kinase (ALK) rearrangement. We used knockout mice to study the roles of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) in plasma pharmacokinetics and brain accumulation of oral crizotinib, and the feasibility of improving crizotinib kinetics using coadministration of the dual ABCB1/ABCG2 inhibitor elacridar. In vitro, crizotinib was a good transport substrate of human ABCB1, but not of human ABCG2 or murine Abcg2. With low-dose oral crizotinib (5 mg/kg), Abcb1a/1b(-/-) and Abcb1a/1b;Abcg2(-/-) mice had an approximately twofold higher plasma AUC than wild-type mice, and a markedly (~40-fold) higher brain accumulation at 24 hr. Also at 4 hr, crizotinib brain concentrations were ?25-fold, and brain-to-plasma ratios ~14-fold higher in Abcb1a/1b(-/-) and Abcb1a/1b;Abcg2(-/-) mice than in wild-type mice. High-dose oral crizotinib (50 mg/kg) resulted in comparable plasma pharmacokinetics between wild-type and Abcb1a/1b(-/-) mice, suggesting saturation of intestinal Abcb1. Nonetheless, brain accumulation at 24 hr was still ~70-fold higher in Abcb1a/1b(-/-) than in wild-type mice. Importantly, oral elacridar coadministration increased the plasma and brain concentrations and brain-to-plasma ratios of crizotinib in wild-type mice, equaling the levels in Abcb1a/1b;Abcg2(-/-) mice. Our results indicate that crizotinib oral availability and brain accumulation were primarily restricted by Abcb1 at a non-saturating dose, and that coadministration of elacridar with crizotinib could substantially increase crizotinib oral availability and delivery to the brain. This principle might be used to enhance therapeutic efficacy of crizotinib against brain metastases in NSCLC patients. PMID:24037730

Chuan Tang, Seng; Nguyen, Luan N; Sparidans, Rolf W; Wagenaar, Els; Beijnen, Jos H; Schinkel, Alfred H

2014-03-15

293

Co-administration strategy to enhance brain accumulation of vandetanib by modulating P-glycoprotein (P-gp/Abcb1) and breast cancer resistance protein (Bcrp1/Abcg2) mediated efflux with m-TOR inhibitors.  

Science.gov (United States)

The objectives of this study were (i) to characterize the interaction of vandetanib with P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp1) in vitro and in vivo (ii) to study the modulation of P-gp and BCRP mediated efflux of vandetanib with specific transport inhibitors and m-TOR inhibitors, everolimus and temsirolimus. Cellular accumulation and bi-directional transport studies in MDCKII cell monolayers were conducted to delineate the role of efflux transporters on disposition of vandetanib. Brain distribution studies were conducted in male FVB wild-type mice with vandetanib administered intravenously either alone or in the presence of specific inhibitors and m-TOR inhibitors. In vitro studies suggested that vandetanib is a high affinity substrate of Bcrp1 but is not transported by P-gp. Interestingly, in vivo brain distribution studies in FVB wild type mice indicated that vandetanib penetration into the brain is restricted by both Bcrp1 and P-gp mediated active efflux at the blood brain barrier (BBB). Co-administration of elacridar, a dual P-gp/BCRP inhibitor increased the brain to plasma concentration ratio of vandetanib upto 5 fold. Of the two m-TOR pathway inhibitors examined; everolimus showed potent effect on modulating vandetanib brain penetration whereas no significant affect on vandetanib brain uptake was observed following temsirolimus co-administration. This finding could be clinically relevant as everolimus can provide synergistic pharmacological effect in addition to primary role of vandetanib efflux modulation at BBB for the treatment of brain tumors. PMID:22633931

Minocha, Mukul; Khurana, Varun; Qin, Bin; Pal, Dhananjay; Mitra, Ashim K

2012-09-15

294

Saturable active efflux by p-glycoprotein and breast cancer resistance protein at the blood-brain barrier leads to nonlinear distribution of elacridar to the central nervous system.  

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The study objective was to investigate factors that affect the central nervous system (CNS) distribution of elacridar. Elacridar inhibits transport mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) and has been used to study the influence of transporters on brain distribution of chemotherapeutics. Adequate distribution of elacridar across the blood-brain barrier (BBB) and into the brain parenchyma is necessary to target tumor cells in the brain that overexpress transporters and reside behind an intact BBB. We examined the role of P-gp and Bcrp on brain penetration of elacridar using Friend leukemia virus strain B wild-type, Mdr1a/b(-/-), Bcrp1(-/-), and Mdr1a/b(-/-)Bcrp1(-/-) mice. Initially, the mice were administered 2.5 mg/kg of elacridar intravenously, and the plasma and brain concentrations were determined. The brain-to-plasma partition coefficient of elacridar in the wild-type mice was 0.82, as compared with 3.5 in Mdr1a/b(-/-) mice, 6.6 in Bcrp1(-/-) mice, and 15 in Mdr1a/b(-/-)Bcrp1(-/-) mice, indicating that both P-gp and Bcrp limit the brain distribution of elacridar. The four genotypes were then administered increasing doses of elacridar, and the CNS distribution of elacridar was determined. The observed and model predicted maximum brain-to-plasma ratios (Emax) at the highest dose were not significantly different in all genotypes. However, the ED50 was lower for Mdr1a/b(-/-) mice compared with Bcrp1(-/-) mice. These findings correlate with the relative expression of P-gp and Bcrp at the BBB in these mice and demonstrate the quantitative enhancement in elacridar CNS distribution as a function of its dose. Overall, this study provides useful concepts for future applications of elacridar as an adjuvant therapy to improve targeting of chemotherapeutic agents to tumor cells in the brain parenchyma. PMID:23397054

Sane, Ramola; Agarwal, Sagar; Mittapalli, Rajendar K; Elmquist, William F

2013-04-01

295

Sensitization of multidrug resistant human ostesarcoma cells to Apo2 Ligand/TRAIL-induced apoptosis by inhibition of the Akt/PKB kinase.  

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Chemotherapeutic agents have been used for the treatment of patients with osteosarcoma (OS). However, inherent or acquired resistance to these agents is a serious problem in the management of OS patients. The emergence of the multidrug resistance (MDR) phenotype in cancer cells is often associated with the overexpression of P-glycoprotein, encoded by the multidrug resistance gene MDR-1. The administration of some of the most common chemotherapeutic agents to these cells becomes ineffective because of their P-gp-driven efflux from the cell. Apo2L/TRAIL is a member of the tumor necrosis factor (TNF) family of cytokines that is considered to induce death of cancer cells but not normal cells. Its powerful apoptotic activity is mediated through its cell surface death domain-containing receptors, TRAIL-R1/DR4 and TRAIL-R2/DR5, which in turn spread the signal in the cytosol through the activation of the caspase cascade. The Akt/PKB kinase is an important cell survival protein which is regulated by D3-phosphoinositides. High Akt expression and activity levels are well documented in many types of tumors, which very often show an altered PI3-K/Akt/PTEN pathway. In this study the U2OS human osteosarcoma cell line and its multidrug resistant (MDR) subline that overexpresses MDR-1 gene, MDR-U2OS, have been analyzed for their responsiveness to TRAIL. In conflict with the presence of active DR4 and DR5 receptors in both clones, U2OS cells exhibited only a low responsiveness to TRAIL, while the MDR-U2OS subline did exhibit a marked TRAIL sensitivity. An analysis of the post-receptor events showed that TRAIL responsiveness correlates with a reduced expression of endogenous Akt. In fact, expression in MDR-U2OS cells of a constitutively active Akt strongly decreased their sensitivity to TRAIL. The identification of Akt as a key modulator of TRAIL responsiveness could help to design TRAIL-based combinations for treatment of osteosarcoma. Moreover, the discovery that multidrug resistant osteosarcomas are highly sensitive to TRAIL-induced apoptosis indicates TRAIL as a new candidate for the treatment of multidrug resistant bone malignancies. PMID:15547696

Cenni, Vittoria; Maraldi, Nadir M; Ruggeri, Alessandra; Secchiero, Paola; Del Coco, Rosalba; De Pol, Anto; Cocco, Lucio; Marmiroli, Sandra

2004-12-01

296

Imaging multidrug resistance with 4-[{sup 18}F]fluoropaclitaxel  

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Multidrug resistance (MDR) is a cause of treatment failure in many cancer patients. MDR refers to a phenotype whereby a tumor is resistant to a large number of natural chemotherapeutic drugs. Having prior knowledge of the presence of such resistance would decrease morbidity from unsuccessful therapy and allow for the selection of individuals who may benefit from the coadministration of MDR-inhibiting drugs. The Tc-99m-labeled single-photon-emitting radiotracers sestamibi and tetrofosmin have shown some predictive value. However, positron-emitting radiotracers, which allow for dynamic quantitative imaging, hold promise for a more accurate and specific identification of MDRtumors.MDR-expressing tumors are resistant to paclitaxel, which is commonly used as a chemotherapeutic agent. 4-[{sup 18}F]Fluoropaclitaxel (FPAC) is a PET-radiolabeled analogue of paclitaxel. Preclinical studies have shown the uptake of FPAC to be inversely proportional to tumor MDR expression. FPAC PET imaging in normal volunteers shows biodistribution to be similar to that in nonhuman primates. Imaging in a breast cancer patient showed FPAC localization in a primary tumor that responded to chemotherapy, while failure to localize in mediastinal disease corresponded with only partial response.FPAC PET imaging shows promise for the noninvasive pretreatment identification of MDR-expressing tumors. While much additional work is needed, this work represents a step toward image-guided personalized medicine.

Kurdziel, Karen A. [Department of Radiology, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: kurdziel@vcu.edu; Kalen, Joseph D. [School of Medicine, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: jdkalen@vcu.edu; Hirsch, Jerry I. [School of Medicine, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: jihirsch@vcu.edu; Wilson, John D. [School of Medicine, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: wilsonjd@hsc.vcu.edu; Agarwal, Rakesh [Surgical Oncology, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: dbarrett@vcu.edu; Barrett, Daniel [School of Medicine, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: ragarwal@vcu.edu; Bear, Harry D. [Surgical Oncology, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: 9jmccumi@mail2.vcu.edu; McCumiskey, James F. [Department of Radiology, Virginia Commonwealth University, Richmond, VA (United States)], E-mail: hbear@hsc.vcu.edu

2007-10-15

297

Characterization of a multidrug resistant Teladorsagia circumcincta isolate from Spain.  

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The aim of this work was to know the anthelmintic resistance (AR) status of a Spanish sheep flock infected by gastrointestinal nematodes (GIN) and the possible cross resistance among anthelmintics of the macrocyclic lactones (ML) family. The Faecal Egg Count Reduction Test (FECRT) was carried out to check the efficacy of albendazole (Zodalben®), levamisole (LEV) (Endex®) and an oral formulation of ivermectin (IVM) (Oramec®), at the recommended dose rates. Then, the study was extended to check the cross resistance between drugs of the ML family: injectable IVM (Ivomec®), oral moxidectin (Cydectin®), injectable moxidectin (Biodectin®) and doramectin (Dectomax®), at the recommended dose rates. The GIN species were identified after faecal cultures in all groups. The FECRT showed the resistance of a Teladorsagia circumcincta isolate against LEV (39-58%), IVM (88-92%) and doramectin (85%). This study is the first report to confirm the side resistance between these MLs, which belong to the avermectin chemical group, in a Spanish sheep flock. The in vitro efficacy of LEV and IVM was measured by the Larval Feeding Inhibition Assay (LFIA) using the IC(50) measurement (concentration needed to inhibit the ingestion of 50% L1). The values of the multidrug resistant isolate were 0.25 ?g/ml for LEV and 3 ng/ml for IVM. Both results were higher than the values obtained with a susceptible isolate, which could be indicative of AR. However, further research examining the response of a greater range of susceptible and resistant nematodes isolates should be carried out to establish a discrimination threshold. PMID:22179266

Martínez-Valladares, M; Famularo, M R; Fernández-Pato, N; Cordero-Pérez, C; Castañón-Ordóñez, L; Rojo-Vázquez, F A

2012-05-01

298

Methylation of SFRP5 is related to multidrug resistance in leukemia cells.  

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Methylation of secreted frizzle-related protein (SFRP) genes activates Wnt/ß-catenin signaling and promotes tumor development. This study investigated whether SFRP5 gene methylation causes multidrug resistance (MDR) in leukemia through the Wnt/ß-catenin signaling, leading to the upregulation of the mdr1 gene and its product, P-glycoprotein (P-gp). Methylation-specific PCR identified SFRP5 gene methylation in cultured bone mononuclear cells from 7/12 patients with acute leukemia and in four human leukemia cell lines (HL-60, Raji, U937 and KG1a). Western blotting revealed absent SFRP5 protein expression in cells from 5/7 patients with SFRP5 gene methylation and in all cell lines. Treatment with a demethylation agent (DAC) rescued SFRP5 expression. mdr1 mRNA and P-gp protein were detected in cells from 3/5 patients with absent SFRP5, and in the KG1a cell line; these cells also had the highest levels of activated ß-catenin. In cells from these three patients, DAC rescued SFRP5 expression and downregulated mdr1 and P-gp. SFRP5 protein expression was rescued in transgenic KG1a/SFRP5 cells, compared with KG1a/eGFP or untransfected KG1a cells. mdr1 and P-gp in KG1a/SFRP5 cells were downregulated. Doxorubicin IC50 values were significantly lower in KG1a/SFRP5 (0.573±0.131 ?M) than in KG1a (0.963±0.115) or KG1a/eGFP (0.917±0.138) cells (P<0.05). We conclude that SFRP5 gene methylation in leukemia cells activates Wnt/ß-catenin signaling to upregulate mdr1/P-gp expression and cause MDR. Recovery of SFRP5 expression reversed MDR in the KG1a leukemia cell line. Our results suggest that modulating SFRP5 methylation could decrease MDR in leukemia patients. PMID:24434572

Wang, H; Wang, X; Hu, R; Yang, W; Liao, A; Zhao, C; Zhang, J; Liu, Z

2014-02-01

299

The radiological spectrum of pulmonary multidrug-resistant tuberculosis: in HIV-Negative patients  

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Background: Multidrug-resistant tuberculosis is a major worldwide health problem. In countries where tuberculosis is of moderate to high prevalence, the issue of Multidrug-resistant tuberculosis carries significant importance. Multidrug-resistant tuberculosis, similar to drug-sensitive tuberculosis, is contagious. Meanwhile its treatment is not only more difficult but also more expensive with lower success rates. Regarding clinical findings, there is no significant difference between Multidrug-resistant tuberculosis and drug-sensitive tuberculosis. Therefore determination of characteristic radiological findings in cases of Multidrug-resistant tuberculosis might be of help in early detection, and hence appropriate management of this disease condition. Objective: To explain the radiological spectrum of pulmonary Multidrug-resistant tuberculosis. Patients and methods: We retrospectively evaluated the radiographic images of 35 patients with clinically-and microbiologically- proven Multidrug-resistant tuberculosis admitted to our tertiary-care tuberculosis unit over a period of 13 months. The latest chest x-ray of all patients and the conventional chest CT scan without contrast of 15 patients were reviewed by three expert radiologists who rendered consensus opinion. Results: Of the 35 patients with imaging studies, 23 (66%) were male and 12 (34%) were female. The mean±SD age of participants was 38.2±17.3 (range: 16-20) years. 33 patients were known as secondary and only 2 had primary Multidrug-resistant tuberculosis. Chest radiography revealed cavitary lesion in 80% pulmonary infiltration in 89% and nodules in 80% of the cases. Pleurisy was the rarest finding observed in only 5 (14%) patients. All of 15 chest CT scans revealed cavitation, 93% of which were bilateral and multiple. Pleural involvement was seen in 93% of patients. Conclusion: Presence of multiple cavities, especially in both lungs, nodular and infiltrative lesions, and pleural effusion are main features of multidrug-resistant tuberculosis as compared to drug-sensitive tuberculosis

300

Effect of NlpE Overproduction on Multidrug Resistance in Escherichia coli?  

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NlpE, an outer membrane lipoprotein, functions during envelope stress responses in Gram-negative bacteria. In this study, we report that overproduction of NlpE increases multidrug and copper resistance through activation of the genes encoding the AcrD and MdtABC multidrug efflux pumps in Escherichia coli.

Nishino, Kunihiko; Yamasaki, Seiji; Hayashi-nishino, Mitsuko; Yamaguchi, Akihito

2010-01-01

 
 
 
 
301

Where is it and how does it get there – intracellular localization and traffic of P-glycoprotein  

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Full Text Available P-glycoprotein (P-gp, an ATP-binding cassette (ABC, is able to transport structurally and chemically unrelated substrates. Overexpression of P-gp in cancer cells significantly decreases the intercellular amount of anticancer drugs, and results in multidrug resistance in cancer cells, a major obstacle in cancer chemotherapy. P-gp is mainly localized on the plasma membrane and functions as a drug efflux pump; however, P-gp is also localized in many intracellular compartments, such as endoplasmic reticulum, Golgi, endosomes and lysosomes. P-gp moves between the intracellular compartments and the plasma membrane in a microtubule-actin dependent manner. This review highlights our current understanding of 1 the intracellular localization of P-gp; 2 the trafficking and cycling pathways among the cellular compartments as well as between these compartments and the plasma membrane; and 3 the cellular factors regulating P-gp traffic and cycling. This review also presents a potential implication in overcoming P-gp-mediated multidrug resistance by targeting P-gp traffic and cycling pathways and impairing P-gp localization on the plasma membrane.

DongFu

2013-12-01

302

Emergence of multidrug-resistant Salmonella enterica serotype Newport in Minnesota.  

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We report a concurrent increase in the number of isolates of Salmonella enterica serotype Newport and the rate of multidrug resistance in S. Newport isolates from animal and human populations in Minnesota. Antimicrobial susceptibility and pulsed-field gel electrophoresis analysis demonstrated heterogeneity of isolates and showed that 1 pulsed-field gel electrophoresis cluster contained most of the multidrug-resistant isolates with a resistance pattern and most class 1 integron isolates, implying the clonal origin of the isolates. PMID:16779749

Lopes, Vanessa C; Wedel, Stephanie D; Bender, Jeffrey B; Smith, Kirk E; Leano, Fe T; Boxrud, David J; Lauer, Dale C; Velayudhan, Binu T; Nagaraja, Kakambi V

2006-07-15

303

Aureobasidin A, an antifungal cyclic depsipeptide antibiotic, is a substrate for both human MDR1 and MDR2/P-glycoproteins.  

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The human MDR1 gene encodes the multidrug transporter P-glycoprotein (Pgp). Although the MDR2/Pgp shares about 80% identity at the amino acid level with the MDR1/Pgp, the MDR2/Pgp cannot act as a multidrug transporter. We examined the drug sensitivity of Saccharomyces cerevisiae expressing either the human MDR1/Pgp or MDR2/ Pgp. The human MDR1/Pgp conferred about 4-fold resistance to aureobasidin A, a cyclic depsipeptide antifungal antibiotic, on the drug-sensitive yeast strains. Interestingly the human MDR2/Pgp also conferred about 2.5-fold resistance to aureobasidin A. The resistance to aureobasidin A conferred by the MDR2/Pgp as well as by the MDR1/Pgp was overcome by vinblastine, verapamil, and cyclosporin A, depending on their concentrations, but not by colchicine. Aureobasidin A probably interacts directly with Pgps, because it overcame multidrug resistance of human cells and inhibited azidopine photoaffinity labeling of MDR1/Pgp in human cell membranes. These results suggest the possibility that the human MDR1 and MDR2/Pgps have conserved domain(s) for drug recognition. PMID:8980113

Kino, K; Taguchi, Y; Yamada, K; Komano, T; Ueda, K

1996-12-01

304

Molecular characterization of clinical multidrug-resistant Klebsiella pneumoniae isolates  

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Background Klebsiella pneumoniae is a frequent nosocomial pathogen, with the multidrug-resistant (MDR) K. pneumoniae being a major public health concern, frequently causing difficult-to-treat infections worldwide. The aim of this study was to investigate the molecular characterization of clinical MDR Klebsiella pneumoniae isolates. Methods A total of 27 non-duplicate MDR K. pneumoniae isolates with a CTX-CIP-AK resistance pattern were investigated for the prevalence of antimicrobial resistance genes including extended spectrum ?-lactamase genes (ESBLs), plasmid-mediated quinolone resistance (PMQR) genes, 16S rRNA methylase (16S-RMTase) genes, and integrons by polymerase chain reaction (PCR) amplification and DNA sequencing. Plasmid replicons were typed by PCR-based replicon typing (PBRT). Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were carried out to characterize the strain relatedness. Results All the isolates co-harbored 3 or more resistance determinants. OqxAB, CTX-M-type ESBLs and RmtB were the most frequent determinants, distributed among19 (70.4%),18 (66.7%) and 8 (29.6%) strains. Fourteen isolates harbored class 1 integrons, with orfD-aacA4 being the most frequent gene cassette array. Class 3 integrons were less frequently identified and contained the gene cassette array of blaGES-1-blaOXA-10-aac(6?)-Ib. IncFII replicon was most commonly found in this collection. One cluster was observed with ?80% similarity among profiles obtained by PFGE, and one sequence type (ST) by MLST, namely ST11, was observed in the cluster. Conclusion K. pneumoniae carbapenemase (KPC)–producing ST11 was the main clone detected. Of particular concern was the high prevalence of multiple resistance determinants, classs I integrons and IncFII plasmid replicon among these MDR strains, which provide advantages for the rapid development of MDR strains. PMID:24884610

2014-01-01

305

Medical treatment of pulmonary multidrug-resistant tuberculosis.  

Science.gov (United States)

Treatment of multidrug-resistant tuberculosis (MDR-TB) is challenging because of the high toxicity of second-line drugs and the longer treatment duration required compared with drug-susceptible TB. The efficacy of treatment for MDR-TB is poorer than that for drug-susceptible TB. The selection of drugs in MDR-TB is based on previous treatment history, drug susceptibility results, and TB drug resistance patterns in the each region. Recent World Health Organization guidelines recommend the use of least 4 second-line drugs (a newer fluoroquinolone, an injectable agent, prothionamide, and cycloserine or para-aminosalicylic acid) in addition to pyrazinamide. The kanamycin is the initial choice of injectable durgs, and newer fluoroquinolones include levofloxacin and moxifloxacin. For MDR-TB, especially cases that are extensively drug-resistant, group 5 drugs such as linezolid, clofazimine, and amoxicillin/clavulanate need to be included. New agents with novel mechanisms of action that can be given for shorter durations (9-12 months) for MDR-TB are under investigation. PMID:24475350

Shim, Tae Sun; Jo, Kyung-Wook

2013-12-01

306

Prevalence of Multidrug Resistant Mycobacterium tuberculosis by Mycobacteria growth  

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Full Text Available Background and objectives: Identification and monitoring ofmultidrugresistant Mycobacterium tuberculosis strains (MDR ishighlighted by the high risk of their spreading in different areas.Prevalence of these strains was evaluated in Golestan province innortheast of Iran.Material and Methods: Drug susceptibility testing to Isoniazid andrifampin was carried out for 148 clinical samples that had grown inMycobacteria growth indicator tube (MGIT system, according to themanufacturer's instructions (Becton-Dickinson, USA. The associationof drug resistance frequency with demographic characteristics andgrowth time were investigated. The appropriate statistical tests, X2 andstudent Ttest were performed for comparison of these variants. A pvalue>0.05 was considered significant in all cases.Results: The turnaround time required for growth of Mycobacteriumtuberculosis in MGIT system was between 2 to 55 days (mean16.3±10.4 days. Of all samples studied, 17.6% and 3.4% wereresistant to Isoniazid and rifampin, respectively, and 3.4% (5 sampleswere MDR (CI 95%; 1- 6%. The turnaround time required fordetermining MDR cases was 9.6 days. No statistically significantassociation was found between the resistance to the drugs and none ofthe factors including sex, age, type of clinical sample, and positivity ofthe smear.Conclusion: The prevalence of MDR in the studied region wasdetermined to be 3.4% which is similar to the country-wideevaluations. The turnaround time for Mycobacterium growth and antidrug susceptibility result can be shortened by MGIT method.Key words: Mycobacterium tuberculosis, Mycobacterium GrowthIndicator Tube, Multidrug Resistant

Livani S

2012-01-01

307

Higher Desolvation Energy Reduces Molecular Recognition in Multi-Drug Resistant HIV-1 Protease.  

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Designing HIV-1 protease inhibitors that overcome drug-resistance is still a challenging task. In this study, four clinical isolates of multi-drug resistant HIV-1 proteases that exhibit resistance to all the US FDA-approved HIV-1 protease inhibitors and also reduce the substrate recognition ability were examined. A multi-drug resistant HIV-1 protease isolate, MDR 769, was co-crystallized with the p2/NC substrate and the mutated CA/p2 substrate, CA/p2 P1'F. Both substrates display different levels of molecular recognition by the wild-type and multi-drug resistant HIV-1 protease. From the crystal structures, only limited differences can be identified between the wild-type and multi-drug resistant protease. Therefore, a wild-type HIV-1 protease and four multi-drug resistant HIV-1 proteases in complex with the two peptides were modeled based on the crystal structures and examined during a 10 ns-molecular dynamics simulation. The simulation results reveal that the multi-drug resistant HIV-1 proteases require higher desolvation energy to form complexes with the peptides. This result suggests that the desolvation of the HIV-1 protease active site is an important step of protease-ligand complex formation as well as drug resistance. Therefore, desolvation energy could be considered as a parameter in the evaluation of future HIV-1 protease inhibitor candidates. PMID:24832048

Wang, Yong; Dewdney, Tamaria G; Liu, Zhigang; Reiter, Samuel J; Brunzelle, Joseph S; Kovari, Iulia A; Kovari, Ladislau C

2012-01-01

308

Higher Desolvation Energy Reduces Molecular Recognition in Multi-Drug Resistant HIV-1 Protease  

Directory of Open Access Journals (Sweden)

Full Text Available Designing HIV-1 protease inhibitors that overcome drug-resistance is still a challenging task. In this study, four clinical isolates of multi-drug resistant HIV-1 proteases that exhibit resistance to all the US FDA-approved HIV-1 protease inhibitors and also reduce the substrate recognition ability were examined. A multi-drug resistant HIV-1 protease isolate, MDR 769, was co-crystallized with the p2/NC substrate and the mutated CA/p2 substrate, CA/p2 P1’F. Both substrates display different levels of molecular recognition by the wild-type and multi-drug resistant HIV-1 protease. From the crystal structures, only limited differences can be identified between the wild-type and multi-drug resistant protease. Therefore, a wild-type HIV-1 protease and four multi-drug resistant HIV-1 proteases in complex with the two peptides were modeled based on the crystal structures and examined during a 10 ns-molecular dynamics simulation. The simulation results reveal that the multi-drug resistant HIV-1 proteases require higher desolvation energy to form complexes with the peptides. This result suggests that the desolvation of the HIV-1 protease active site is an important step of protease-ligand complex formation as well as drug resistance. Therefore, desolvation energy could be considered as a parameter in the evaluation of future HIV-1 protease inhibitor candidates.

Ladislau C. Kovari

2012-05-01

309

Structure of P-Glycoprotein Reveals a Molecular Basis for Poly-Specific Drug Binding  

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P-glycoprotein (P-gp) detoxifies cells by exporting hundreds of chemically unrelated toxins but has been implicated in multidrug resistance (MDR) in the treatment of cancers. Substrate promiscuity is a hallmark of P-gp activity, thus a structural description of poly-specific drug-binding is important for the rational design of anticancer drugs and MDR inhibitors. The x-ray structure of apo P-gp at 3.8 angstroms reveals an internal cavity of -6000 angstroms cubed with a 30 angstrom separation of the two nucleotide-binding domains. Two additional P-gp structures with cyclic peptide inhibitors demonstrate distinct drug-binding sites in the internal cavity capable of stereoselectivity that is based on hydrophobic and aromatic interactions. Apo and drug-bound P-gp structures have portals open to the cytoplasm and the inner leaflet of the lipid bilayer for drug entry. The inward-facing conformation represents an initial stage of the transport cycle that is competent for drug binding.

Aller, Stephen G.; Yu, Jodie; Ward, Andrew; Weng, Yue; Chittaboina, Srinivas; Zhuo, Rupeng; Harrell, Patina M.; Trinh, Yenphuong T.; Zhang, Qinghai; Urbatsch, Ina L.; Chang, Geoffrey; (Scripps); (TTU)

2009-04-22

310

Selenorhodamine photosensitizers for photodynamic therapy of p-glycoprotein-expressing cancer cells.  

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We examined a series of selenorhodamines with amide and thioamide functionality at the 5-position of a 9-(2-thienyl) substituent on the selenorhodamine core for their potential as photosensitizers for photodynamic therapy (PDT) in P-glycoprotein (P-gp) expressing cells. These compounds were examined for their photophysical properties (absorption, fluorescence, and ability to generate singlet oxygen), for their uptake into Colo-26 cells in the absence or presence of verapamil, for their dark and phototoxicity toward Colo-26 cells, for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their colocalization with mitochondrial specific agents in Colo-26 cells. Thioamide derivatives 16b and 18b were more effective photosensitizers than amide derivatives 15b and 17b. Selenorhodamine thioamides 16b and 18b were useful in a combination therapy to treat Colo-26 cells in vitro: a synergistic therapeutic effect was observed when Colo-26 cells were exposed to PDT and treatment with the cancer drug doxorubicin. PMID:25250825

Hill, Jacqueline E; Linder, Michelle K; Davies, Kellie S; Sawada, Geri A; Morgan, Janet; Ohulchanskyy, Tymish Y; Detty, Michael R

2014-10-23

311

A novel areneisonitrile Tc complex inhibits the transport activity of MDR P-glycoprotein  

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P-glycoprotein (Pgp), the product of the multidrug resistance (MDR1) gene, has been an important cancer target for development of MDR modulators that act to inhibit Pgp efflux transport activity. From a series of novel substituted areneisonitrile analogues of Tc-sestamibi, a known Pgp transport substrate, emerged the hexakis(3,4,5-trimethoxyphenylisonitrile)Tc(I) complex (Tc-TMPI) as a potential modulator of Pgp. Tracer 99mTc-TMPI showed net cellular accumulation in inverse proportion to expression of Pgp and enhancement upon addition of classic MDR modulators. At pharmacological concentrations, the carrier-added 99Tc-TMPI complex showed potent inhibition of Pgp-mediated 99mTc-sestamibi transport (EC50, 1.1 ± 0.2 ?M) and displacement of a Pgp-specific photolabel in a concentration-dependent manner. We conclude that 99Tc-TMPI directly inhibited Pgp transport activity and serves as a convenient template for development of nonradioactive Re(I) analogues as novel MDR modulators

312

In vivo P-glycoprotein function before and after epilepsy surgery  

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Objectives: To study the functional activity of the multidrug efflux transporter P-glycoprotein (Pgp) at the blood-brain barrier of patients with temporal lobe epilepsy using (R)-[11C]verapamil (VPM)-PET before and after temporal lobe surgery to assess whether postoperative changes in seizure frequency and antiepileptic drug load are associated with changes in Pgp function. Methods: Seven patients with drug-resistant temporal lobe epilepsy underwent VPM-PET scans pre- and postsurgery. Patients were followed up for a median of 6 years (range 4–7) after surgery. Pgp immunoreactivity in surgically resected hippocampal specimens was determined with immunohistochemistry. Results: Optimal surgical outcome, defined as seizure freedom and withdrawal of antiepileptic drugs, was associated with higher temporal lobe Pgp function before surgery, higher Pgp-positive staining in surgically resected hippocampal specimens, and reduction in global Pgp function postoperatively, compared with nonoptimal surgery outcome. Conclusions: The data from our pilot study suggest that Pgp overactivity in epilepsy is dynamic, and complete seizure control and elimination of antiepileptic medication is associated with reversal of overactivity, although these findings will require confirmation in a larger patient cohort. PMID:25186858

Bauer, Martin; Karch, Rudolf; Zeitlinger, Markus; Liu, Joan; Koepp, Matthias J.; Asselin, Marie-Claude; Sisodiya, Sanjay M.; Hainfellner, Johannes A.; Wadsak, Wolfgang; Mitterhauser, Markus; Muller, Markus; Pataraia, Ekaterina

2014-01-01

313

Predicting the three-dimensional structure of human P-glycoprotein in absence of ATP by computational techniques embodying crosslinking data: insight into the mechanism of ligand migration and binding sites.  

Science.gov (United States)

P-glycoprotein is a membrane protein involved in the phenomenon of multidrug resistance. Its activity and transport function have been largely characterized by various biochemical studies and a low-resolution image has been obtained by electron microscopy. Obtaining a high-resolution structure is, however, still remote due to the inherent difficulties in the experimental determination of membrane protein structures. We present here a three-dimensional (3D) atomic model of P-glycoprotein in absence of ATP. This model was obtained using a combination of computational techniques including comparative modeling and rigid body dynamics simulations that embody all available cysteine disulfide crosslinking data characterizing the whole protein in absence of ATP. The model features rather well most of the experimental interresidue distances derived both in the transmembrane domains and in the nucleotide binding domains. The model is also in good agreement with electron microscopy data, particularly in terms of size and topology. It features a large cavity detected in the protein core into which seven ligands were successfully docked. Their predicted affinity correlates well with experimental values. Locations of docked ligands compare favorably with those suggested by cysteine-scanning data. The finding of different positions both for a single ligand and for different ligands corroborates the experimental evidence indicating the existence of multiple drug binding sites. The interactions identified between P-glycoprotein and the docked ligands reveal that different types of interactions such as H-bonds, pi-pi and cation-pi interactions occur in agreement with a recently proposed pharmacophore model of P-glycoprotein ligands. Furthermore, the model also displays a lateral opening located in the transmembrane domains connecting the lipid bilayer to the central cavity. This feature supports rather well the commonly admitted mechanism of substrate uptake from the lipid bilayer. We propose that this 3D model may be an important tool to understand the structure-function relationship of P-glycoprotein. PMID:16463278

Vandevuer, Stéphane; Van Bambeke, Françoise; Tulkens, Paul M; Prévost, Martine

2006-05-15

314

Overview of P-glycoprotein inhibitors: a rational outlook  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Glicoproteína-p (P-gp), uma glicoproteína de transmembrana permeável, é um membro da superfamília (ABC) de cassete de gene de ligação de ATP que funciona especificamente como um carreador mediado pelo transportador de efluxo ativo primário. É amplamente distribuído por todo o corpo e apresenta uma g [...] ama diversificada de substratos. Diversos agentes terapêuticos vitais são substratos para P-gp e sua biodisponibilidade é reduzida ou a resistência é induzida devido ao efluxo de proteínas. Portanto, os inibidores da P-gp foram explorados para a superação da resistência a múltiplas drogas e problemas de biodisponibilidade deficiente dos substratos terapêuticos da P-gp. A sensibilidade das moléculas da droga à P-gp e vice-versa, pode ser estabelecida por vários modelos experimentais in silico, in vitro e in vivo. Desde a descoberta da P-gp, diversas pesquisas identificaram várias estruturas químicas como inibidores da P-gp. O objetivo deste presente estudo foi o de enfatizar a descoberta e desenvolvimento de inibidores mais novos, inertes, atóxicos e mais eficazes, visando especificamente os da P-gp, como aqueles entre os extratos vegetais, excipientes e formulações farmacêuticas, e outras moléculas racionais de droga. As aplicações do conhecimento de biologia celular e molecular, bancos de dados estruturais in silico, estudos de modelagem molecular e análises da relação quantitativa estrutura-atividade (QSAR) no desenvolvimento de novos inibidores racionais da P-gp também foram mencionados. Abstract in english P-glycoprotein (P-gp), a transmembrane permeability glycoprotein, is a member of ATP binding cassette (ABC) super family that functions specifically as a carrier mediated primary active efflux transporter. It is widely distributed throughout the body and has a diverse range of substrates. Several vi [...] tal therapeutic agents are substrates to P-gp and their bioavailability is lowered or a resistance is induced because of the protein efflux. Hence P-gp inhibitors were explored for overcoming multidrug resistance and poor bioavailability problems of the therapeutic P-gp substrates. The sensitivity of drug moieties to P-gp and vice versa can be established by various experimental models in silico, in vitro and in vivo. Ever since the discovery of P-gp, the research plethora identified several chemical structures as P-gp inhibitors. The aim of this review was to emphasize on the discovery and development of newer, inert, non-toxic, and more efficient, specifically targeting P-gp inhibitors, like those among the natural herb extracts, pharmaceutical excipients and formulations, and other rational drug moieties. The applications of cellular and molecular biology knowledge, in silico designed structural databases, molecular modeling studies and quantitative structure-activity relationship (QSAR) analyses in the development of novel rational P-gp inhibitors have also been mentioned.

Kale Mohana Raghava, Srivalli; P. K., Lakshmi.

2012-09-01

315

Overview of P-glycoprotein inhibitors: a rational outlook  

Directory of Open Access Journals (Sweden)

Full Text Available P-glycoprotein (P-gp, a transmembrane permeability glycoprotein, is a member of ATP binding cassette (ABC super family that functions specifically as a carrier mediated primary active efflux transporter. It is widely distributed throughout the body and has a diverse range of substrates. Several vital therapeutic agents are substrates to P-gp and their bioavailability is lowered or a resistance is induced because of the protein efflux. Hence P-gp inhibitors were explored for overcoming multidrug resistance and poor bioavailability problems of the therapeutic P-gp substrates. The sensitivity of drug moieties to P-gp and vice versa can be established by various experimental models in silico, in vitro and in vivo. Ever since the discovery of P-gp, the research plethora identified several chemical structures as P-gp inhibitors. The aim of this review was to emphasize on the discovery and development of newer, inert, non-toxic, and more efficient, specifically targeting P-gp inhibitors, like those among the natural herb extracts, pharmaceutical excipients and formulations, and other rational drug moieties. The applications of cellular and molecular biology knowledge, in silico designed structural databases, molecular modeling studies and quantitative structure-activity relationship (QSAR analyses in the development of novel rational P-gp inhibitors have also been mentioned.Glicoproteína-p (P-gp, uma glicoproteína de transmembrana permeável, é um membro da superfamília (ABC de cassete de gene de ligação de ATP que funciona especificamente como um carreador mediado pelo transportador de efluxo ativo primário. É amplamente distribuído por todo o corpo e apresenta uma gama diversificada de substratos. Diversos agentes terapêuticos vitais são substratos para P-gp e sua biodisponibilidade é reduzida ou a resistência é induzida devido ao efluxo de proteínas. Portanto, os inibidores da P-gp foram explorados para a superação da resistência a múltiplas drogas e problemas de biodisponibilidade deficiente dos substratos terapêuticos da P-gp. A sensibilidade das moléculas da droga à P-gp e vice-versa, pode ser estabelecida por vários modelos experimentais in silico, in vitro e in vivo. Desde a descoberta da P-gp, diversas pesquisas identificaram várias estruturas químicas como inibidores da P-gp. O objetivo deste presente estudo foi o de enfatizar a descoberta e desenvolvimento de inibidores mais novos, inertes, atóxicos e mais eficazes, visando especificamente os da P-gp, como aqueles entre os extratos vegetais, excipientes e formulações farmacêuticas, e outras moléculas racionais de droga. As aplicações do conhecimento de biologia celular e molecular, bancos de dados estruturais in silico, estudos de modelagem molecular e análises da relação quantitativa estrutura-atividade (QSAR no desenvolvimento de novos inibidores racionais da P-gp também foram mencionados.

Kale Mohana Raghava Srivalli

2012-09-01

316

Multidrug Resistance in Fungi: Regulation of Transporter-encoding Gene Expression  

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Full Text Available A critical risk to the continued success of antifungal chemotherapy is the acquisition of resistance; a risk exacerbated by the few classes of effective antifungal drugs. Predictably, as the use of these drugs increases in the clinic, more resistant organisms can be isolated from patients. A particularly problematic form of drug resistance that routinely emerges in the major fungal pathogens is known as multidrug resistance. Multidrug resistance refers to the simultaneous acquisition of tolerance to a range of drugs via a limited or even single genetic change. This review will focus on recent progress in understanding pathways of multidrug resistance in fungi including those of most medical relevance. Analyses of multidrug resistance in Saccharomyces cerevisiae have provided the most detailed outline of multidrug resistance in a eukaryotic microorganism. Multidrug resistant isolates of S. cerevisiae typically result from changes in the activity of a pair of related transcription factors that in turn elicit overproduction of several target genes. Chief among these is the ATP-binding cassette-encoding gene PDR5. Interestingly, in the medically important Candida species, very similar pathways are involved in acquisition of multidrug resistance. In both C. albicans and C. glabrata, changes in the activity of transcriptional activator proteins elicits overproduction of a protein closely related to S. cerevisiae Pdr5 called Cdr1. The major filamentous fungal pathogen, Aspergillus fumigatus, was previously thought to acquire resistance to azole compounds (the principal antifungal drug class via alterations in the azole drug target-encoding gene cyp51A. More recent data indicate that pathways in addition to changes in the cyp51A gene are important determinants in A. fumigatus azole resistance. We will discuss findings that suggest azole resistance in A. fumigatus and Candida species may share more mechanistic similarities than previously thought.

ScottMoye-Rowley

2014-04-01

317

Multidrug resistance in fungi: regulation of transporter-encoding gene expression.  

Science.gov (United States)

A critical risk to the continued success of antifungal chemotherapy is the acquisition of resistance; a risk exacerbated by the few classes of effective antifungal drugs. Predictably, as the use of these drugs increases in the clinic, more resistant organisms can be isolated from patients. A particularly problematic form of drug resistance that routinely emerges in the major fungal pathogens is known as multidrug resistance. Multidrug resistance refers to the simultaneous acquisition of tolerance to a range of drugs via a limited or even single genetic change. This review will focus on recent progress in understanding pathways of multidrug resistance in fungi including those of most medical relevance. Analyses of multidrug resistance in Saccharomyces cerevisiae have provided the most detailed outline of multidrug resistance in a eukaryotic microorganism. Multidrug resistant isolates of S. cerevisiae typically result from changes in the activity of a pair of related transcription factors that in turn elicit overproduction of several target genes. Chief among these is the ATP-binding cassette (ABC)-encoding gene PDR5. Interestingly, in the medically important Candida species, very similar pathways are involved in acquisition of multidrug resistance. In both C. albicans and C. glabrata, changes in the activity of transcriptional activator proteins elicits overproduction of a protein closely related to S. cerevisiae Pdr5 called Cdr1. The major filamentous fungal pathogen, Aspergillus fumigatus, was previously thought to acquire resistance to azole compounds (the principal antifungal drug class) via alterations in the azole drug target-encoding gene cyp51A. More recent data indicate that pathways in addition to changes in the cyp51A gene are important determinants in A. fumigatus azole resistance. We will discuss findings that suggest azole resistance in A. fumigatus and Candida species may share more mechanistic similarities than previously thought. PMID:24795641

Paul, Sanjoy; Moye-Rowley, W Scott

2014-01-01

318

Antimicrobial resistance determinant microarray for analysis of multi-drug resistant isolates  

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The prevalence of multidrug-resistant infections in personnel wounded in Iraq and Afghanistan has made it challenging for physicians to choose effective therapeutics in a timely fashion. To address the challenge of identifying the potential for drug resistance, we have developed the Antimicrobial Resistance Determinant Microarray (ARDM) to provide DNAbased analysis for over 250 resistance genes covering 12 classes of antibiotics. Over 70 drug-resistant bacteria from different geographic regions have been analyzed on ARDM, with significant differences in patterns of resistance identified: genes for resistance to sulfonamides, trimethoprim, chloramphenicol, rifampin, and macrolide-lincosamidesulfonamide drugs were more frequently identified in isolates from sources in Iraq/Afghanistan. Of particular concern was the presence of genes responsible for resistance to many of the last-resort antibiotics used to treat war traumaassociated infections.

Taitt, Chris Rowe; Leski, Tomasz; Stenger, David; Vora, Gary J.; House, Brent; Nicklasson, Matilda; Pimentel, Guillermo; Zurawski, Daniel V.; Kirkup, Benjamin C.; Craft, David; Waterman, Paige E.; Lesho, Emil P.; Bangurae, Umaru; Ansumana, Rashid

2012-06-01

319

Binding site(s) on P-glycoprotein for a newly synthesized photoaffinity analog of agosterol A.  

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Agosterol A (AG-A) is a novel agent that reverses P-glycoprotein (P-gp) and multidrug resistance protein-1 (MRP1)-meditated multidrug resistance (MDR). We have synthesized [125I]11-azidophenyl agosterol A (azidoAG-A), a photoaffinity analog of AG-A, and characterized its binding to P-gp in membrane vesicles prepared from multidrug-resistant P-gp-overexpressing KB-C2 cells. The photoanalog photolabeled intact P-gp and both the N- and C-terminal fragments of P-gp. [125I]AzidoAG-A is transported by P-gp and the intracellular accumulation of both [125I]azidoAG-A and [3H]AG-A in KB-C2 cells was lower than that in the parental drug-sensitive KB-3-1 cells. [125I]AzidoAG-A bound to the drug binding site(s) on P-gp because photoaffinity labeling of P-gp was inhibited by a variety of known P-gp substrates, including anticancer, reversing, and anti-human immunodeficiency virus (HIV) agents. The binding of [125I]azidoAG-A to P-gp differs from the binding of other photolabeled probes such as iodoaryl-azidoprazosin (IAAP) to P-gp and from the binding of [125I]azidoAG-A to MRP1 based on the differing effects of flupentixol and glutathione (GSH) on their binding. Thus, [125I]azidoAG-A will be a useful tool to elucidate the structure and function of P-gp because it directly binds to the drug binding site(s) on P-gp, is transported by P-gp, and exhibits different P-gp binding characteristics than IAAP. PMID:14552590

Mitsuo, Masahiko; Noguchi, Tomohiro; Nakajima, Yuichi; Aoki, Shunji; Ren, Xiao-Qin; Sumizawa, Tomoyuki; Haraguchi, Misako; Kobayashi, Motomasa; Baba, Masanori; Nagata, Yukihiro; Akiyama, Shin-ichi; Furukawa, Tatsuhiko

2003-01-01

320

Effects of Mefloquine Use on Plasmodium vivax Multidrug Resistance.  

Science.gov (United States)

Numerous studies have indicated a strong association between amplification of the multidrug resistance-1 gene and in vivo and in vitro mefloquine resistance of Plasmodium falciparum. Although falciparum infection usually is not treated with mefloquine, incorrect diagnosis, high frequency of undetected mixed infections, or relapses of P. vivax infection triggered by P. falciparum infections expose non-P. falciparum parasites to mefloquine. To assess the consequences of such unintentional treatments on P. vivax, we studied variations in number of Pvmdr-1 (PlasmoDB accession no. PVX_080100, NCBI reference sequence NC_009915.1) copies worldwide in 607 samples collected in areas with different histories of mefloquine use from residents and from travelers returning to France. Number of Pvmdr-1 copies correlated with drug use history. Treatment against P. falciparum exerts substantial collateral pressure against sympatric P. vivax, jeopardizing future use of mefloquine against P. vivax. A drug policy is needed that takes into consideration all co-endemic species of malaria parasites. PMID:25272023

Khim, Nimol; Andrianaranjaka, Voahangy; Popovici, Jean; Kim, Saorin; Ratsimbasoa, Arsene; Benedet, Christophe; Barnadas, Celine; Durand, Remy; Thellier, Marc; Legrand, Eric; Musset, Lise; Menegon, Michela; Severini, Carlo; Nour, Bakri Y M; Tichit, Magali; Bouchier, Christiane; Mercereau-Puijalon, Odile; Ménard, Didier

2014-10-01

 
 
 
 
321

Multidrug-resistant tuberculosis in an adult with cystic fibrosis.  

Science.gov (United States)

Mycobacterium tuberculosis infection in patients with cystic fibrosis (CF) is rare. We report a 22-year-old CF patient with high fever, dyspnea and weight loss that progressively worsened over 2 weeks before admission. The patient suffered from liver cirrhosis, was colonized with Pseudomonas aeruginosa and had been repeatedly hospitalized for pulmonary infections. The patient was treated initially as for an exacerbation of P. aeruginosa infection, but tuberculosis (TBC) was suspected due to lack of improvement. A CT of the chest revealed enlarged bilateral cavities in the upper and middle lobes. A tuberculin skin test was positive, and M. tuberculosis nucleic acid was isolated from sputum samples. After receiving first-line anti-TBC drugs for 1 month, the patient's condition continued to worsen so molecular drug susceptibility testing was performed. Multidrug-resistant TBC was discovered, leading to a change in regimen. The patient was treated with ethionamide, moxifloxacin, linezolid, amikacin, imipenem/cilastatin and rifabutin and showed a remarkable clinical improvement. Although nontuberculous mycobacteria are more common in CF, the possibility of TBC should not be ignored. In that setting, early suspicion of infection due to resistant M. tuberculosis can be life saving. PMID:22869452

Manika, K; Giouleka, P; Zarogoulidis, K; Kioumis, I

2013-01-01

322

ANTIBIOTIC SYNERGY TEST: CHECKERBOARD METHOD ON MULTIDRUG RESISTANT PSEUDOMONAS AERUGINOSA  

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Full Text Available Pseudomonas aeruginosa is a global emergence of multidrug resistant strains leading to a wide variety of nosocomial infections in humans. The clinical use of combination of antibiotic therapy for gram negative infections is probably more effective than monotherapy. Certain combinations of antibiotic exhibit synergistic antibacterial effects. Ampicillin and Kanamycin are the commonly used potent bactericidal antibiotics, active against gram negative bacteria and also act synergistically. Antibiotic susceptibility of Pseudomonas aeruginosa showed a high level of resistance with Optochin and Rifamycin. An intermediate effect was seen to Erythromycin and Chloramphenicol, Kanamycin and Ampicillin showed different minimum inhibitory concentration (MIC. Thus, the susceptible antibiotics were used in the checker board technique, which appears useful for determining antibiotic synergism against Pseudomonas aeruginosa.. The ?FIC results showed synergy for concentrations of 80µg/ml and 40µg/ml of antibiotic combinations with fractional inhibitory concentration (FIC of 0.48 at 37?C over night incubation per ml. Thus, the combinations tested were bactericidal indicating the minimum inhibitory concentration and no growth illustrated the extensive activity of kanamycin which was enforced by the ampicillin resulting in an antibacterial effect.

Spoorthi N. Jain

2011-12-01

323

TAT-modified nanosilver for combating multidrug-resistant cancer.  

Science.gov (United States)

A nanopharmaceutical system using TAT-enhanced cell/tissue penetration strategy was developed for multidrug-resistant (MDR) cancer treatment, in which nanocrystalline silver with mean size of 8 nm modified with TAT cell-penetrating peptide (termed AgNP-TAT) displayed extraordinary antitumor activity in both MDR cells and non-resistant cells at an indiscriminating manner. Such anti-MDR effect is presumably due to the size-exclusion effect, by which the nanoparticles are too large to be pumped out. Of note, AgNP-TAT showed significant enhancement in killing tumor cells, e.g. up to 24 fold higher compared to its counterpart without TAT-modification. The animal studies further confirmed the success of our strategy that AgNP-TAT was able to effectively inhibit the tumor growth in the mice bearing malignant melanoma at a dose of 1 nmol/kg, compared with the effective dose (4.3 ?mol/kg) of doxorubicin. AgNP-TAT also showed significantly reduced adverse toxicity in vivo. It indicates AgNP-TAT could be a class of nano drug for MDR cancer treatment. PMID:22682937

Liu, Jinhua; Zhao, Yongxing; Guo, Qianqian; Wang, Zhao; Wang, Huiyuan; Yang, Yongxin; Huang, Yongzhuo

2012-09-01

324

Global dissemination of a multidrug resistant Escherichia coli clone.  

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Escherichia coli sequence type 131 (ST131) is a globally disseminated, multidrug resistant (MDR) clone responsible for a high proportion of urinary tract and bloodstream infections. The rapid emergence and successful spread of E. coli ST131 is strongly associated with several factors, including resistance to fluoroquinolones, high virulence gene content, the possession of the type 1 fimbriae FimH30 allele, and the production of the CTX-M-15 extended spectrum ?-lactamase (ESBL). Here, we used genome sequencing to examine the molecular epidemiology of a collection of E. coli ST131 strains isolated from six distinct geographical locations across the world spanning 2000-2011. The global phylogeny of E. coli ST131, determined from whole-genome sequence data, revealed a single lineage of E. coli ST131 distinct from other extraintestinal E. coli strains within the B2 phylogroup. Three closely related E. coli ST131 sublineages were identified, with little association to geographic origin. The majority of single-nucleotide variants associated with each of the sublineages were due to recombination in regions adjacent to mobile genetic elements (MGEs). The most prevalent sublineage of ST131 strains was characterized by fluoroquinolone resistance, and a distinct virulence factor and MGE profile. Four different variants of the CTX-M ESBL-resistance gene were identified in our ST131 strains, with acquisition of CTX-M-15 representing a defining feature of a discrete but geographically dispersed ST131 sublineage. This study confirms the global dispersal of a single E. coli ST131 clone and demonstrates the role of MGEs and recombination in the evolution of this important MDR pathogen. PMID:24706808

Petty, Nicola K; Ben Zakour, Nouri L; Stanton-Cook, Mitchell; Skippington, Elizabeth; Totsika, Makrina; Forde, Brian M; Phan, Minh-Duy; Gomes Moriel, Danilo; Peters, Kate M; Davies, Mark; Rogers, Benjamin A; Dougan, Gordon; Rodriguez-Baño, Jesús; Pascual, Alvaro; Pitout, Johann D D; Upton, Mathew; Paterson, David L; Walsh, Timothy R; Schembri, Mark A; Beatson, Scott A

2014-04-15

325

Global dissemination of a multidrug resistant Escherichia coli clone  

Science.gov (United States)

Escherichia coli sequence type 131 (ST131) is a globally disseminated, multidrug resistant (MDR) clone responsible for a high proportion of urinary tract and bloodstream infections. The rapid emergence and successful spread of E. coli ST131 is strongly associated with several factors, including resistance to fluoroquinolones, high virulence gene content, the possession of the type 1 fimbriae FimH30 allele, and the production of the CTX-M-15 extended spectrum ?-lactamase (ESBL). Here, we used genome sequencing to examine the molecular epidemiology of a collection of E. coli ST131 strains isolated from six distinct geographical locations across the world spanning 2000–2011. The global phylogeny of E. coli ST131, determined from whole-genome sequence data, revealed a single lineage of E. coli ST131 distinct from other extraintestinal E. coli strains within the B2 phylogroup. Three closely related E. coli ST131 sublineages were identified, with little association to geographic origin. The majority of single-nucleotide variants associated with each of the sublineages were due to recombination in regions adjacent to mobile genetic elements (MGEs). The most prevalent sublineage of ST131 strains was characterized by fluoroquinolone resistance, and a distinct virulence factor and MGE profile. Four different variants of the CTX-M ESBL–resistance gene were identified in our ST131 strains, with acquisition of CTX-M-15 representing a defining feature of a discrete but geographically dispersed ST131 sublineage. This study confirms the global dispersal of a single E. coli ST131 clone and demonstrates the role of MGEs and recombination in the evolution of this important MDR pathogen. PMID:24706808

Petty, Nicola K.; Ben Zakour, Nouri L.; Stanton-Cook, Mitchell; Skippington, Elizabeth; Totsika, Makrina; Forde, Brian M.; Phan, Minh-Duy; Gomes Moriel, Danilo; Peters, Kate M.; Davies, Mark; Rogers, Benjamin A.; Dougan, Gordon; Rodriguez-Bano, Jesus; Pascual, Alvaro; Pitout, Johann D. D.; Upton, Mathew; Paterson, David L.; Walsh, Timothy R.; Schembri, Mark A.; Beatson, Scott A.

2014-01-01

326

Efflux pump gene hefA of Helicobacter pylori plays an important role in multidrug resistance  

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Full Text Available AIM: To determine whether efflux systems contribute to multidrug resistance of H pylori.METHODS: A chloramphenicol-induced multidrug resistance model of six susceptible H pylori strains (5 isolates and H pylori NCTC11637 was developed. Multidrug-resistant (MDR strains were selected and the minimal inhibitory concentration (MIC of erythromycin, metronidazole, penicillin G, tetracycline, and ciprofloxacin in multidrug resistant strains and their parent strains was determined by agar dilution tests. The level of mRNA expression of hefA was assessed by fluorescence real-time quantitative PCR. A H pylori LZ1026 knockout mutant (?H pylori LZ1026 for (putative efflux protein was constructed by inserting the kanamycin resistance cassette from pEGFP-N2 into hefA, and its susceptibility profiles to 10 antibiotics were evaluated.RESULTS: The MIC of six multidrug-resistant strains (including 5 clinical isolates and H pylori NCTC11637 increased significantly (? 4-fold compared with their parent strains. The expression level of hefA gene was significantly higher in the MDR strains than in their parent strains (P = 0.033. A H pylori LZ1026 mutant was successfully constructed and the ?H pylori LZ1026 was more susceptible to four of the 10 antibiotics. All the 20 strains displayed transcripts for hefA that confirmed the in vitro expression of these genes.CONCLUSION: The efflux pump gene hefA plays an important role in multidrug resistance of H pylori.

Zhi-Qiang Liu, Peng-Yuan Zheng, Ping-Chang Yang

2008-09-01

327

Risk factors for nosocomial bloodstream infection caused by multidrug resistant gram-negative bacilli in pediatrics  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The aim of this study was to identify the risk factors for nosocomial bloodstream infections by multidrug resistant Gram-negative bacilli. From November 2001 to December 2003, in the Pediatric Department of the Santa Casa de São Paulo, a retrospective case-control study was developed concerning pati [...] ents who had nosocomial bloodstream infection caused by Gram-negative bacilli. Patients with multidrug resistant infections were designated as case patients, and control patients were those with an infection that did not meet the criteria for multidrug resistance. Previous use of central venous catheter and previous use of vancomycin plus third generation cephalosporins were associated to a higher chance of infections by multidrug resistant Gram-negative bacilli (Odds ratio - 5.8 and 5.2, respectively). Regarding sensitivity of the isolated agents, 47.8% were multidrug resistant, 54.2% were Klebsiella spp. ESBL producers and 36.4% were imipenem resistant Pseudomonas aeruginosa. The lethality rate was 36.9% in the studied cases and this rate was significantly higher in the group of patients with multidrug resistant infections (p=0.013). Risk factor identification as well as the knowledge of the susceptibility of the nosocomial infectious agents gave us the possibility to perform preventive and control strategies to reduce the costs and mortality related to these infections.

Mariana V., Arnoni; Eitan N., Berezin; Marinês D.V., Martino.

328

Acute-onset postoperative endophthalmitis caused by multidrug-resistant Klebsiella pneumoniae  

Science.gov (United States)

The purpose of this paper is to report outcomes of intravitreal imipenem in the treatment of multidrug-resistant Klebsiella-related postoperative endophthalmitis. This observational case series consists of three eyes from three patients seen between 2013 and 2014. Multidrug-resistant Klebsiella pneumoniae is characterized by a rapid, fulminant course and severe intraocular inflammation. Intravitreal imipenem may be used to treat such infection.

Sanghi, Shekhar; Pathengay, Avinash; Jindal, Animesh; Raval, Vishal; Nayak, Sameera; Sharma, Savitri; Bawdekar, Abhishek; Flynn, Harry W

2014-01-01

329

Influence of efflux pump inhibitors on the multidrug resistance of Helicobacter pylori  

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AIM: To evaluate the effect of efflux pump inhibitors (EPIs) on multidrug resistance of Helicobacter pylori (H. pylori).METHODS: H. pylori strains were isolated and cultured on Brucella agar plates with 10% sheep’s blood. The multidrug resistant (MDR) H. pylori were obtained with the inducer chloramphenicol by repeated doubling of the concentration until no colony was seen, then the susceptibilities of the MDR strains and their parents to 9 antibiotics were assessed with agar dilution tests...

Zhan Zhang, Zhi-qiang Liu

2010-01-01

330

P-Glycoprotein inhibitory activity of lipophilic constituents of Echinacea pallida roots in a human proximal tubular cell line.  

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The N-hexane root extracts from Echinacea pallida, Echinacea angustifolia and Echinacea purpurea were evaluated for inhibition of the multidrug transporter P-glycoprotein (Pgp) activity, the product of the ABCB1 gene, involved in cancer multidrug resistance (MDR) and in herb-drug or drug-drug interactions. The biological assay was performed using the human proximal tubule HK-2 cell line that constitutively expresses ABCB1. The N-hexane extracts of all three species reduced the efflux of the Pgp probe calcein-AM from HK-2 cells two-fold in a concentration-dependent manner, and E. pallida was found to be the most active species. For the first time, two polyacetylenes and three polyenes, isolated from the N-hexane extract of E. pallida roots by a bioassay-guided fractionation, were found to be able to reduce Pgp activity. Pentadeca-(8 Z,13 Z)-dien-11-yn-2-one was the most efficient compound, being able to decrease the calcein-AM efflux about three-fold with respect to the control at 30 microg/mL. PMID:18425719

Romiti, Nadia; Pellati, Federica; Nieri, Paola; Benvenuti, Stefania; Adinolfi, Barbara; Chieli, Elisabetta

2008-02-01

331

Ionic currents in multidrug resistant K562 human leukemic cells.  

Science.gov (United States)

In this study, the expression and functional characterization of currents through the CFTR (cystic fibrosis transmembrane regulator) and ORCC (outwardly rectifying chloride channels) were determined in wild-type K562 chronic human leukemia cells (K562-WT) and in its resistant counterpart, the vincristine resistant cell line (K562-Vinc). Expression of the CFTR and MDR1 (multidrug resistant) gene products was determined by a semi-quantitative RT-PCR protocol. The amplified products in K562-WT and K562-Vinc showed two bands corresponding to CFTR and MDR1. MDR1 mRNA increased by 20-fold in K562-Vinc whereas no change in CFTR mRNA levels was observed. CFTR and ORCC channel activity were measured with a whole cell configuration of the patch clamp technique. Forskolin (40 microM n activator of adenylate cyclase, added to the extracellular side increased the current in both cell lines. A fraction of the activated whole cell currents was inhibited by 500 microM 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS) and subsequent addition of 500 microM diphenylamine-2-carboxylate (DPC plus DIDS) further inhibited the remaining currents. The levels of forskolin-activated currents and subsequent blockade were similar in both cell lines. The effect of forskolin was prevented in cells previously exposed to 500 microM DPC. The effects of DIDS and DPC on the forskolin-activated whole cell currents support the idea that both CFTR and ORCC are generating a significant fraction of these currents with DIDS inhibiting ORCC currents and DPC inhibiting CFTR currents when the blockers are added one after another to the extracellular side. Finally, we show that exposure of K562 cells to vincristine which results in the over expression of MDR1 is not accompanied by a significant down regulation of CFTR as in other cells. PMID:16038730

Assef, Yanina A; Cavarra, Soledad M; Damiano, Alicia E; Ibarra, Cristina; Kotsias, Basilio A

2005-09-01

332

Comparison of P-glycoprotein expression in cell lines and xenogragraft sections using I-125 MRK-16 monoclonal antibody (MAB)  

Energy Technology Data Exchange (ETDEWEB)

P-glycoprotein (Pgp) is known to be associated with multidrug resistance (MDR). Quantitation of P-glycoprotein expression may permit appropriate therapy depending on Pgp expression in tumors. The present study was undertaken to evaluate the utility of quantitative autoradiography (QAR) in the quantification of MDR using MRK-16, a murine IgG mAb reactive against Pgp. Balb/c mice were xenografted with colchicine resistant BE(2)C/CHC cells. Animals with established tumors were sacrificed, and 8 {mu}m tumor sections were prepared. Mab MRK-16 was labeled with I-125 (150 {mu}Ci/0.625 nmole) by the iodogen method and subsequently purified by size exclusion chromatography. Consecutive tumor sections were incubated overnight at 4{degrees}C with serial dilutions of I-125 MRK-16. Similarly cell suspensions containing 1 X 10{sup 7} cells per ml were also incubated with serial dilutions. QAR analysis of tissue sections of BE(2)C/CHC tumors growing as xenografts in nude mice, determined the binding affinity (K{sub a}) for MRK-16 to be 1 x 10{sup 9} L/M and the number of binding sites (B{sub max}) to be 137, 700 per cell (222 picomols/g); it compared very well with the K{sub a} value of 5 x 10{sup 8} L/M and the B{sub max} value of 130,000 per cell (217 picomols/g) obtained from binding analysis with cell suspensions.

Mehta, B.M.; Kostakoglu, L.; Levchenko, A. [Kettering Cancer, New York, NY (United States)] [and others

1994-05-01

333

Demonstrating a multi-drug resistant Mycobacterium tuberculosis amplification microarray.  

Science.gov (United States)

Simplifying microarray workflow is a necessary first step for creating MDR-TB microarray-based diagnostics that can be routinely used in lower-resource environments. An amplification microarray combines asymmetric PCR amplification, target size selection, target labeling, and microarray hybridization within a single solution and into a single microfluidic chamber. A batch processing method is demonstrated with a 9-plex asymmetric master mix and low-density gel element microarray for genotyping multi-drug resistant Mycobacterium tuberculosis (MDR-TB). The protocol described here can be completed in 6 hr and provide correct genotyping with at least 1,000 cell equivalents of genomic DNA. Incorporating on-chip wash steps is feasible, which will result in an entirely closed amplicon method and system. The extent of multiplexing with an amplification microarray is ultimately constrained by the number of primer pairs that can be combined into a single master mix and still achieve desired sensitivity and specificity performance metrics, rather than the number of probes that are immobilized on the array. Likewise, the total analysis time can be shortened or lengthened depending on the specific intended use, research question, and desired limits of detection. Nevertheless, the general approach significantly streamlines microarray workflow for the end user by reducing the number of manually intensive and time-consuming processing step