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1

Combating P-glycoprotein-Mediated Multidrug Resistance Using Therapeutic Nanoparticles.  

UK PubMed Central (United Kingdom)

The development of multidrug resistance (MDR) to chemotherapy is a major obstacle for the successful treatment of cancer. A number of mechanisms have been postulated to account for MDR in cancer. The most common and best-studied mechanism of resistance is mediated through the drug efflux protein P-glycoprotein (P-gp), which is overexpressed in drug-resistant cancer cells and is responsible for the removal of many chemotherapeutic agents. Therapeutic nanoparticles (NPs) have emerged as an innovative and promising option to combat P-gp-mediated MDR, and they have shown enhanced therapeutic efficacy and reduced toxicity compared to their small molecule counterparts. This review focuses on recent studies using therapeutic NPs to circumvent P-gp-mediated MDR in cancer therapy. The advantages and strategies by which therapeutic NPs were used to overcome P-gp-mediated MDR in cancer are discussed.

Zhang Q; Li F

2013-04-01

2

Photoaffinity labeling of the multidrug-resistance-related P-glycoprotein with photoactive analogs of verapamil  

Energy Technology Data Exchange (ETDEWEB)

Verapamil, a phenylalkylamine calcium channel blocker, has been shown to reverse multidrug resistance in tumor cells, possibly by increasing drug retention through interaction with an outward drug transporter of the resistant cells. In this study two photoactive radioactive analogs of verapamil, N-(p-azido(3,5-{sup 3}H)benzoyl)aminomethyl verapamil and N-(p-azido(3-{sup 125}I)salicyl)aminomethyl verapamil, were synthesized and used to identify the possible biochemical target(s) for verapamil in multidrug-resistance DC-3F/VCRd-5L Chinese hamster lung cells selected for resistance to vincristine. The results show that a specifically labeled 150- to 180-kDa membrane protein in resistant cells was immunoprecipitated with a monoclonal antibody specific for P-glycoprotein. Phenylalkylamine binding specificity was established by competitive blocking of specific photolabeling with the nonradioactive photoactive analogs as well as with verapamil. Photoaffinity labeling was also inhibited by 50 {mu}M concentrations of the calcium channel blockers nimodipine, nifedipine, nicardipine, azidopine, bepridil, and diltiazem and partially by prenylamine. Moreover, P-glycoprotein labeling was inhibited in a dose-dependent manner by vinblastine with half-maximal inhibition at 0.2 {mu}M compared to that by verapamil at 8 {mu}M. These data provide direct evidence that P-glycoprotein has broad drug recognition capacity and that it serves as a molecular target for calcium channel blocker action in reversing multidrug resistance.

Safa, A.R. (Univ. of Chicago Medical Centers, IL (USA))

1988-10-01

3

Photoaffinity labeling of the multidrug-resistance-related P-glycoprotein with photoactive analogs of verapamil  

International Nuclear Information System (INIS)

Verapamil, a phenylalkylamine calcium channel blocker, has been shown to reverse multidrug resistance in tumor cells, possibly by increasing drug retention through interaction with an outward drug transporter of the resistant cells. In this study two photoactive radioactive analogs of verapamil, N-(p-azido[3,5-3H]benzoyl)aminomethyl verapamil and N-(p-azido[3-125I]salicyl)aminomethyl verapamil, were synthesized and used to identify the possible biochemical target(s) for verapamil in multidrug-resistance DC-3F/VCRd-5L Chinese hamster lung cells selected for resistance to vincristine. The results show that a specifically labeled 150- to 180-kDa membrane protein in resistant cells was immunoprecipitated with a monoclonal antibody specific for P-glycoprotein. Phenylalkylamine binding specificity was established by competitive blocking of specific photolabeling with the nonradioactive photoactive analogs as well as with verapamil. Photoaffinity labeling was also inhibited by 50 ?M concentrations of the calcium channel blockers nimodipine, nifedipine, nicardipine, azidopine, bepridil, and diltiazem and partially by prenylamine. Moreover, P-glycoprotein labeling was inhibited in a dose-dependent manner by vinblastine with half-maximal inhibition at 0.2 ?M compared to that by verapamil at 8 ?M. These data provide direct evidence that P-glycoprotein has broad drug recognition capacity and that it serves as a molecular target for calcium channel blocker action in reversing multidrug resistance

1988-01-01

4

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 99m}Tc-agents to image P-glycoprotein function in human tumors in vivo has been proposed. Net tumor cell content of {sup 99m}Tc-Sestamibi, {sup 99m}Tc-Tetrofosmin and several {sup 99m}Tc-Q-complexes ({sup 99m}Tc-Q58 and {sup 99m}Tc-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.

Bae, K. T.; Piwnica-Worms, D. [St. Louis, Washington Univ. (United States). Mallinckrodt Institute of Radiology. Lab. of Molecular Radiopharmacology]|[St. Louis, Washington Univ. (United States). Dept. of Molecular Biology and Pharmacology

1997-06-01

5

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

Energy Technology Data Exchange (ETDEWEB)

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

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.

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

2003-01-01

7

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 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 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 (more) 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.; Calado, R.T.; Garcia, A.B.; Falcão, R.P.

2003-12-01

8

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

1988-01-01

9

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

Energy Technology Data Exchange (ETDEWEB)

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

10

Inhibition of P-glycoprotein mediated multidrug resistance by stemofoline derivatives.  

UK PubMed Central (United Kingdom)

Resistance to chemotherapy in cancer patients has been correlated to the overexpression of the ATP-binding cassette (ABC) drug transporters including P-glycoprotein (P-gp) that actively efflux chemotherapeutic drugs from cancer cells. We examined the multidrug resistance reversing property of stemofoline derivatives in drug-resistance human cervical carcinoma (KB-V1) and human leukemic (K562/Adr) cell lines that overexpress P-gp. Didehydrostemofoline and eleven of its derivatives were synthesized and the cytotoxicity and their effect on doxorubicin, vinblastine and paclitaxel sensitivity in drug resistant (KB-V1 and K562/Adr) and drug sensitive (KB-3-1 and K562) cell lines by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were determined. We found that three out of the twelve stemofoline derivatives including OH-A1, NH-B6 and NH-D6 showed commitment efficiency to increase sensitivity to doxorubicin, vinblastine and paclitaxel in KB-V1 cells and increase sensitivity to doxorubicin, and paclitaxel in K562/Adr cells whereas the effects have not been seen in their parental sensitive cancer cell lines (KB-3-1 and K562). These results indicate that stemofoline derivatives reversed P-gp-mediated multidrug resistance in vitro, and thus could be developed as effective chemosensitizers to treat multidrug-resistant cancers. The molecular mechanism of modulation of P-gp would be further determined.

Umsumarng S; Pintha K; Pitchakarn P; Sastraruji K; Sastraruji T; Ung AT; Jatisatienr A; Pyne SG; Limtrakul P

2013-01-01

11

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

Directory of Open Access Journals (Sweden)

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; Dandekar V.D

2010-01-01

12

Multidrug resistance in mucoepidermoid carcinoma of the parotid gland--immunohistochemical investigations of P-glycoprotein expression.  

UK PubMed Central (United Kingdom)

Abstract Conclusion: P-glycoprotein is abundantly expressed in certain parotid mucoepidermoid carcinoma tissues, known historically to be multidrug resistant. This discovery may be important in incrementally advancing our ability to develop alternative pharmacologic strategies to improve multi-modality tumor control. Objective: P-glycoprotein plays a functional role in promoting the efflux of drug metabolites in certain malignant tumors. With this understanding we immunohistochemically investigated the expression of P-glycoprotein in parotid mucoepidermoid carcinoma tissues and examined prognostic factors that contribute to the treatment of parotid cancer. Methods: Thirteen patients with mucoepidermoid carcinoma of the parotid gland were included. P-glycoprotein expression was immunohistochemically investigated by a modified avidin-biotin-peroxidase complex method using four different antibodies. Results: P-glycoprotein expression was observed in a higher percentage of patients with higher grade malignancy. The tumor size-related difference in P-glycoprotein expression was only significant for staining with one antibody, and no significant differences were observed with or without induction chemotherapy.

Furusaka T; Sasaki CT; Matsuda A; Susaki Y; Matsuda H; Ikeda M

2013-05-01

13

Multidrug resistance in mucoepidermoid carcinoma of the parotid gland--immunohistochemical investigations of P-glycoprotein expression.  

Science.gov (United States)

Abstract Conclusion: P-glycoprotein is abundantly expressed in certain parotid mucoepidermoid carcinoma tissues, known historically to be multidrug resistant. This discovery may be important in incrementally advancing our ability to develop alternative pharmacologic strategies to improve multi-modality tumor control. Objective: P-glycoprotein plays a functional role in promoting the efflux of drug metabolites in certain malignant tumors. With this understanding we immunohistochemically investigated the expression of P-glycoprotein in parotid mucoepidermoid carcinoma tissues and examined prognostic factors that contribute to the treatment of parotid cancer. Methods: Thirteen patients with mucoepidermoid carcinoma of the parotid gland were included. P-glycoprotein expression was immunohistochemically investigated by a modified avidin-biotin-peroxidase complex method using four different antibodies. Results: P-glycoprotein expression was observed in a higher percentage of patients with higher grade malignancy. The tumor size-related difference in P-glycoprotein expression was only significant for staining with one antibody, and no significant differences were observed with or without induction chemotherapy. PMID:23350593

Furusaka, Tohru; Sasaki, Clarence T; Matsuda, Akira; Susaki, Yasuhiko; Matsuda, Hiroshi; Ikeda, Minoru

2013-01-28

14

Binding of modulators to mouse and human multidrug resistance P-glycoprotein. A computational study.  

UK PubMed Central (United Kingdom)

The human multidrug resistance (MDR) P-glycoprotein (P-gp) mediates the extrusion of chemotherapeutic drugs from cancer cells. Modulators are relevant pharmaceutical targets since they are intended to control or to inhibit its pumping activity. In the present work, a common binding site for Rhodamine 123 and modulators with different modulation activity was found by molecular docking over the crystal structure of the mouse P-gp. The modulators involved a family of compounds, including derivatives of propafenone (3-phenylpropiophenone nucleus) and XR9576 (tariquidar). Our results showed that the relative binding energies estimated by molecular docking were in good correlation with the experimental activities. Preliminary classical molecular dynamics results on selected P-gp/modulator complexes were also performed in order to understand the nature of the prevalent molecular interactions and the possible main molecular features that characterize a modulator. Besides, the results obtained with a human P-gp homology model from the mouse structure are also presented and analyzed. Our observations suggest that the hydrophobicity and molecular flexibility are the main features related to the inhibitory activity. The latter factor would increase the modulator ability to fit the aromatic rings inside the transmembrane domain.

Jara GE; Vera DM; Pierini AB

2013-09-01

15

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±0.01; 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.)

2003-01-01

16

Reversal of chemoresistance in malignant gliomas by calcium antagonists: correlation with the expression of multidrug-resistant p-glycoprotein.  

UK PubMed Central (United Kingdom)

Resistance to multiple drugs is often observed in malignant gliomas. The authors used a microtiter tetrazolium test to analyze primary in vitro chemoresistance and chemosensitivity of 15 early cultures of human malignant glioma exposed to 50 micrograms/ml (1,4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a (ACNU), 50 micrograms/ml cisplatin, 1 microgram/ml vincristine, or combinations of these chemotherapeutic agents. Primary chemoresistance was observed in 87% of tumors for ACNU, in 87% for cisplatin, and in 83% for vincristine. All tumors were examined for expression of multidrug-resistant p-glycoprotein, a transport protein of 170,000 D, by means of immunohistochemical staining with the JSB-1 antibody on paraffinized tumor sections. Eight of 15 specimens (53%) showed positive staining for the monoclonal antibody. Primary chemoresistance was overcome by addition of the calcium antagonists verapamil or nimodipine to the cultures if the original tumor expressed p-glycoprotein (p < 0.01 for verapamil, p < 0.05 for nimodipine). In tumors not expressing p-glycoprotein, addition of calcium antagonists to the cell cultures did not influence primary chemoresistance. It is concluded from these data that addition of calcium antagonists to the adjuvant chemotherapy of malignant gliomas might overcome primary chemoresistance in tumors expressing the multidrug-resistant phenotype.

Kiwit JC; Hertel A; Matuschek AE

1994-10-01

17

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

2003-01-01

18

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

Energy Technology Data Exchange (ETDEWEB)

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

19

Phosphorylation of the multidrug resistant associated glycoprotein (p-glycoprotein): Preparation and characterization of 7-acetyltaxol  

Energy Technology Data Exchange (ETDEWEB)

To assess the role of phosphorylation in P-glycoprotein function, phosphorylation of P-glycoprotein in intact cells and in cell-free membrane fractions has been studied. Results obtained with cell-free membrane fractions indicate that P-glycoprotein is a substrate for a membrane-associated protein kinase A (PK-A). To assess whether P-glycoprotein was phosphorylated in vivo by PK-A, MDR cells were incubated with ({sup 32}P)Pi in the presence or absence of 100 uM 8Br-cAMP. The tryptic phosphopeptides of six P-glycoproteins from five independently derived MDR cell lines were analyzed by HPLC. A similar analysis carried out with two other P-glycoproteins (from J7.V3-1 and the lower band of J7.T1-50) demonstrated a major phosphopeptide with a retention time of 26 min. Fraction 26 was resolved as a single phosphopeptide by 2-D mapping. The phosphorylation of fraction 26 which was derived from P-glycoprotein in J7.V3-1 or the J7.T1-50 lower band was enhanced when the cells were treated with 8BrcAMP.

Mellado, W.

1988-01-01

20

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

 
 
 
 
21

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

UK PubMed Central (United Kingdom)

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.

Sumizawa T; Chuman Y; Sakamoto H; Iemura K; Almquist KC; Deeley RG; Cole SP; Akiyama S

1994-09-01

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Multidrug resistance after retroviral transfer of the human MDR1 gene correlates with P-glycoprotein density in the plasma membrane and is not affected by cytotoxic selection.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Multidrug resistance (MDR) in mammalian cells is associated with the expression of the MDR1 gene encoding P-glycoprotein (P-gp), an and active efflux pump for various lipophilic compounds. MDR transfectants can be isolated after MDR1 gene transfer and selection with cytotoxic drugs; low levels of dr...

Choi, K; Frommel, T O; Stern, R K; Perez, C F; Kriegler, M; Tsuruo, T; Roninson, I B

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

Directory of Open Access Journals (Sweden)

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-dimethoxyphenylethylamino)propane 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; Feng Zhi; Guangming Xu; Xiaolei Tang; Sheng Lu; Jinhui Wu; Yiqiao Hu

2012-01-01

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HZ08 inhibits the multi-drug resistance on multiple sites as the substrate of p-glycoprotein.  

UK PubMed Central (United Kingdom)

Overexpression of p-glycoprotein (p-gp) leads to the production of multi-drug resistance (MDR) which could discharge various anti-tumor chemicals with structural heterogeneity. HZ08, a novel tetrahydroisoquinoline derivate, was discovered to modulate the MDR. What was confirmed is its definite inhibition of multi-drug resistance caused by p-gp and its promotion for the intracellular cytotoxins accumulation in the previous study. In order to explore whether HZ08 is the substrate of p-gp and on which sites it exerts its function, RNAi to mdr1 was introduced and the interaction between HZ08 and some classic agents (verapamil, rhodamine 123) with clearly binding sites was also investigated. Experimental results revealed that HZ08 is the most probable substrate of p-gp and may share the same modulation sites located at the p-gp with verapamil. Data obtained also indicated that there is a common binding site shared by rhodamine 123 and HZ08, but negative competition showed between HZ08 and adriamycin. In conclusion, HZ08 may be the substrate of p-gp and acts as a multiple target modulator to invert the efflux function of p-gp.

Feng Y; Hu Y; Cen J; Darshika KN; Fang W; Li Y; Huang W

2013-07-01

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Reversal of P-glycoprotein-mediated multidrug resistance is induced by mollugin in MCF-7/adriamycin cells.  

UK PubMed Central (United Kingdom)

P-glycoprotein (P-gp), an important efflux transporter, is encoded by the MDR1 class of genes and is a central element of the multidrug resistance (MDR) phenomenon in cancer cells. In the present study, we investigated whether mollugin, purified from roots of Rubica cordifolia L., down-regulated MDR1 expression in MCF-7/adriamycin (MCF-7/adr) cells, a human breast multidrug-resistant cancer cell line. Mollugin treatment significantly inhibited MDR1 expression by blocking MDR1 transcription. Mollugin treatment also significantly increased intracellular accumulation of the fluorescently-tagged P-gp substrate, rhodamine-123. The suppression of MDR1 promoter activity and protein expression was mediated through mollugin-induced activation of AMP-activated protein kinase (AMPK). Furthermore, mollugin inhibited MDR1 expression through the suppression of NF-?B and CREB activation. Interestingly, mollugin also inhibited COX-2 expression. These results suggest that mollugin treatment enhanced suppression of P-gp expression by inhibiting the NF-?B signaling pathway and COX-2 expression, as well as attenuating CRE transcriptional activity through AMPK activation.

Tran TP; Kim HG; Choi JH; Na MK; Jeong HG

2013-05-01

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Parguerenes: Marine red alga bromoditerpenes as inhibitors of P-glycoprotein (ABCB1) in multidrug resistant human cancer cells.  

UK PubMed Central (United Kingdom)

High intrinsic or acquired expression of membrane spanning, adenosine triphosphate binding cassette (ABC) transporter proteins, such as P-glycoprotein (P-gp), in cancers represents a major impediment to chemotherapy, with accelerated drug efflux leading to multi-drug resistance (MDR). Although ABC transporter inhibitors offer the prospect of reversing the MDR phenotype, no inhibitors have advanced to the clinic. We employed a range of intracellular fluorescence and radio-ligand accumulation and efflux assays, together with cytotoxicity and MDR reversal assays, as well as flow cytometry, fluorescence microscopy and radioimmunoprecipitation, to discover and evaluate new P-gp inhibitors from a unique library of southern Australian and Antarctic marine natural products. This study successfully characterized two rare bromoditerpenes, parguerenes I and II, sourced from a southern Australian collection of the red alga Laurencia filiformis, as P-gp inhibitors. We determined that the parguerenes were non-cytotoxic, dose-dependent inhibitors of P-gp mediated drug efflux, that modify the extracellular antibody binding epitope of P-gp in a manner that differs markedly from that of the known inhibitors verapamil and cyclosporine A. We confirmed that parguerenes were capable of reversing P-gp mediated vinblastine, doxorubicin and paclitaxel MDR, that inhibitory properties span both P-gp and multidrug resistant protein 1 (MRP1), but do not extend to breast cancer resistance protein (BCRP), and that parguerene II is superior (more potent) to verapamil. Our investigations validate the proposition that marine natural products can deliver new ABC transporter inhibitor scaffolds, with structure characteristics fundamentally different from existing inhibitor classes.

Huang XC; Sun YL; Salim AA; Chen ZS; Capon RJ

2013-05-01

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Parguerenes: Marine red alga bromoditerpenes as inhibitors of P-glycoprotein (ABCB1) in multidrug resistant human cancer cells.  

Science.gov (United States)

High intrinsic or acquired expression of membrane spanning, adenosine triphosphate binding cassette (ABC) transporter proteins, such as P-glycoprotein (P-gp), in cancers represents a major impediment to chemotherapy, with accelerated drug efflux leading to multi-drug resistance (MDR). Although ABC transporter inhibitors offer the prospect of reversing the MDR phenotype, no inhibitors have advanced to the clinic. We employed a range of intracellular fluorescence and radio-ligand accumulation and efflux assays, together with cytotoxicity and MDR reversal assays, as well as flow cytometry, fluorescence microscopy and radioimmunoprecipitation, to discover and evaluate new P-gp inhibitors from a unique library of southern Australian and Antarctic marine natural products. This study successfully characterized two rare bromoditerpenes, parguerenes I and II, sourced from a southern Australian collection of the red alga Laurencia filiformis, as P-gp inhibitors. We determined that the parguerenes were non-cytotoxic, dose-dependent inhibitors of P-gp mediated drug efflux, that modify the extracellular antibody binding epitope of P-gp in a manner that differs markedly from that of the known inhibitors verapamil and cyclosporine A. We confirmed that parguerenes were capable of reversing P-gp mediated vinblastine, doxorubicin and paclitaxel MDR, that inhibitory properties span both P-gp and multidrug resistant protein 1 (MRP1), but do not extend to breast cancer resistance protein (BCRP), and that parguerene II is superior (more potent) to verapamil. Our investigations validate the proposition that marine natural products can deliver new ABC transporter inhibitor scaffolds, with structure characteristics fundamentally different from existing inhibitor classes. PMID:23415901

Huang, Xiao-Cong; Sun, Yue-Li; Salim, Angela A; Chen, Zhe-Sheng; Capon, Robert J

2013-02-13

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Targeting of multidrug-resistant human ovarian carcinoma cells with anti-P-glycoprotein antibody conjugates.  

UK PubMed Central (United Kingdom)

A monoclonal antibody (mAb) to P-glycoprotein (Pgp), UIC2, is used as a targeting moiety for N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer/drug [(meso chlorin e(6) mono(N-2-aminoethylamide) (Mce(6)) or doxorubicin (DOX)] conjugates to investigate their cytotoxicity towards the Pgp-expressing human ovarian carcinoma cell line A2780/AD. The binding, internalization, and subcellular trafficking of a fluorescein labeled UIC2 targeted HPMA copolymer are studied and show localization to the plasma membrane with limited internalization. The specificity of the UIC2-targeted HPMA copolymer/drug conjugates are confirmed using the sensitive cell line A2780 that does not express Pgp.

Fowers KD; Kope?ek J

2012-04-01

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Targeting of multidrug-resistant human ovarian carcinoma cells with anti-P-glycoprotein antibody conjugates.  

Science.gov (United States)

A monoclonal antibody (mAb) to P-glycoprotein (Pgp), UIC2, is used as a targeting moiety for N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer/drug [(meso chlorin e(6) mono(N-2-aminoethylamide) (Mce(6)) or doxorubicin (DOX)] conjugates to investigate their cytotoxicity towards the Pgp-expressing human ovarian carcinoma cell line A2780/AD. The binding, internalization, and subcellular trafficking of a fluorescein labeled UIC2 targeted HPMA copolymer are studied and show localization to the plasma membrane with limited internalization. The specificity of the UIC2-targeted HPMA copolymer/drug conjugates are confirmed using the sensitive cell line A2780 that does not express Pgp. PMID:22278817

Fowers, Kirk D; Kope?ek, Jind?ich

2012-01-25

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Inhibition of P-glycoprotein-induced multidrug resistance by a clerodane-type diterpenoid from Sindora sumatrana.  

UK PubMed Central (United Kingdom)

The aim of the present study was to investigate the effects of di- and sesquiterpenoids isolated from the pods of Sindora sumatrana Miq. (Leguminosae) on P-glycoprotein (P-gp) function in an adriamycin-resistant human breast cancer cell line, MCF-7/ADR. Over-expression of P-gp is known to be one of the mechanisms involved in multidrug resistance (MDR), which is a major obstacle in clinical cancer treatment. Among six di- and sesquiterpenoids extracted from S. sumatrana, (+)-7beta-acetoxy-15,16-epoxycleroda-3,13(16),14-trien-18-oic acid (1) showed a strong P-gp inhibitory effect, as great as that of verapamil, a representative P-gp inhibitor. Compound 1 enhanced daunomycin accumulation more than fourfold and significantly decreased daunomycin efflux compared with control, resulting in a decrease in the IC(50) value for daunomycin. These results suggest that compound 1 inhibits the functioning of P-gp and, therefore, can be developed as an MDR-reversing agent.

Jung HJ; Chung SY; Nam JW; Chae SW; Lee YJ; Seo EK; Lee HJ

2010-08-01

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Modulation of P-glycoprotein expression and function by curcumin in multidrug-resistant human KB cells.  

UK PubMed Central (United Kingdom)

Multidrug resistance (MDR) is a phenomenon that is often associated with decreased intracellular drug accumulation in the tumor cells of a patient, resulting from enhanced drug efflux. It is often related to the overexpression of P-glycoprotein (Pgp) on the surface of tumor cells, thereby reducing drug cytotoxicity. In this study, curcumin was tested for its potential ability to modulate the expression and function of Pgp in the multidrug-resistant human cervical carcinoma cell line KB-V1. Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) showed that treatment with 1, 5, and 10 microM curcumin for up to 72hr was able to significantly lower Pgp expression in KB-V1 cells. Curcumin (1-10 microM) decreased Pgp expression in a concentration-dependent manner and was also found to have the same effect on MDR1 mRNA levels. The effect of curcumin on Pgp function was demonstrated by rhodamine 123 (Rh123) accumulation and efflux in Pgp-expressing KB-V1 cells. Curcumin increased Rh123 accumulation in a concentration-dependent manner (1-55 microM) and inhibited the efflux of Rh123 from these cells, but did not affect the efflux of Rh123 from the wild-type drug-sensitive KB-3-1 cells. Treatment of drug-resistant KB-V1 cells with curcumin increased their sensitivity to vinblastine, which was consistent with an increased intracellular accumulation of Rh123. In addition, curcumin inhibited verapamil-stimulated ATPase activity and the photoaffinity labeling of Pgp with the prazosin analog [125I]iodoarylazidoprazosin in a concentration-dependent manner, demonstrating that curcumin interacts directly with the transporter. Thus, curcumin seems to be able to modulate the in vitro expression and function of Pgp in multidrug-resistant human KB-V1 cells. In summary, this study describes the duel modulation of MDR1 expression and Pgp function by the phytochemical curcumin, which may be an attractive new agent for the chemosensitization of cancer cells.

Anuchapreeda S; Leechanachai P; Smith MM; Ambudkar SV; Limtrakul PN

2002-08-01

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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; Fei Zhang; Bing Wu; Jing-hua Han; Wei Ji; Yan Zhou; Rui-fang Niu

2012-01-01

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Transport properties of P-glycoprotein in plasma membrane vesicles from multidrug-resistant Chinese hamster ovary cells.  

UK PubMed Central (United Kingdom)

Multidrug resistant (MDR) cells overexpress a 170-180 kDa membrane glycoprotein, the P-glycoprotein, which is believed to export drugs in an ATP-dependent manner. Plasma membrane vesicles from the MDR CHRC5 cell line, but not the AuxB1 drug-sensitive parent, showed uptake of [3H]colchicine and [3H]vinblastine that was stimulated by the presence of ATP and an ATP-regenerating system. Steady-state uptake of drugs was achieved by 10 min and was stable for greater than 30 min. Non-hydrolysable ATP analogues were unable to support drug uptake, indicating that ATP hydrolysis is essential for transport. ATP-stimulated drug uptake appeared to result from drug transport into inside-out vesicles, since uptake was osmotically sensitive and could be prevented by detergent permeabilization. Steady-state uptake was half-maximal at 100 microM colchicine and 200 nM vinblastine and was inhibited by a 10-100-fold excess of MDR drugs and chemosensitizers, in the order vinblastine greater than verapamil greater than daunomycin greater than colchicine. In addition to being vanadate-sensitive, drug uptake was inhibited by 10-200 microM concentrations of several sulfhydryl-modifying reagents, suggesting that cysteine residues play an important role in drug transport. Vesicular colchicine was rapidly exchanged by an excess of unlabelled drug, demonstrating that drug association is the net result of opposing colchicine fluxes across the membrane.

Doige CA; Sharom FJ

1992-08-01

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

International Nuclear Information System (INIS)

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

2001-11-15

35

Binding diversity of antibodies against external and internal epitopes of the multidrug resistance gene product P-glycoprotein  

Energy Technology Data Exchange (ETDEWEB)

P-glycoprotein (Pgp) is a trans-membraneous protein that is associated with multidrug resistance (MDR) in human cancer, including hepatocellular carcinomas and leukemia. There is no consensus regarding methods of choice for analysis of Pgp expression, and development of reliable analytical methods is now essential. We have studied the Pgp expression in human hepatoma and leukemia cell lines using flow cytometry. The aim of the study was to compare binding properties of anti-Pgp antibodies reacting with surface (MRK16, UIC2) and cytoplasmic (C219, JSB-1) epitopes to assess which antibody performed best with respect to fluorescence discrimination. By histogram subtraction the fractions of resistant human hepatoma cells positive for Pgp were 99% (MRK16), 97% (UIC2), 77% (USB-1), and 51% (C219), demonstrating variations in antibody reactivity. The resolution in detecting decreasing levels of Pgp in hepatoma cells was superior for the externally binding antibodies, showing that there is a correlation between antibody reactivity and fluorescence discrimination. Similar results were obtained for parental and resistant KG1a human leukemia cell lines. The Pgp epitopes remained reactive to the anti-Pgp MAbs after methanol fixation and cryopreservation. By dual parameter flow cytometry it was shown that Pgp expression in viable cells may be assessed together with uptake of epirubicin, which was low in cells expressing high levels of Pgp and vice versa. In conclusion, all tested antibodies proved useful for flow cytometric detection of high levels of Pgp, but the externally binding ones were superior in detection of low and variable levels of Pgp. 36 refs., 8 figs., 1 tab.

Lehne, G.; De Angelis, P.; Clausen, O.P.F.; Egeland, T.; Rugstad, H.E. [National Hospital, Oslo (Norway)] [and others

1995-07-01

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

Directory of Open Access Journals (Sweden)

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.

Lalloo Anita K; Luo Feng R; Guo Ailan; Paranjpe Pankaj V; Lee Sung-Hack; Vyas Viral; Rubin Eric; Sinko Patrick J

2004-01-01

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

Directory of Open Access Journals (Sweden)

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; Cintia H. Maruiama; Wanda P. Almeida

2010-01-01

38

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 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 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 (more) now are shortly discussed. Physicochemical and structural properties of MDR modulators, measures of the MDR reversal, and QSAR studies are included.

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

2010-01-01

39

Jatrophane diterpenoids from the latex of Euphorbia dendroides and their anti-P-glycoprotein activity in human multi-drug resistant cancer cell lines.  

UK PubMed Central (United Kingdom)

Thirteen jatrophane diterpenoids (1-10, 13-15), three previously isolated (11, 12, 16) and a known tigliane (17) were isolated from the latex of Euphorbia dendroides. The structures and relative configurations of compounds were elucidated by spectroscopic techniques. The P-glycoprotein (P-gp) inhibiting activities of the representative set of jatrophanes (1-6 and 11-16) have been assessed. Jatrophanes 2 and 5 demonstrated the most powerful inhibition of P-gp, higher than R(+)-verapamil and tariquidar in colorectal multi-drug resistant (MDR) cells (DLD1-TxR).

Jadranin M; Peši? M; Aljan?i? IS; Milosavljevi? SM; Todorovi? NM; Podolski-Reni? A; Bankovi? J; Tani? N; Markovi? I; Vajs VE; Teševi? VV

2013-02-01

40

Jatrophane diterpenoids from the latex of Euphorbia dendroides and their anti-P-glycoprotein activity in human multi-drug resistant cancer cell lines.  

Science.gov (United States)

Thirteen jatrophane diterpenoids (1-10, 13-15), three previously isolated (11, 12, 16) and a known tigliane (17) were isolated from the latex of Euphorbia dendroides. The structures and relative configurations of compounds were elucidated by spectroscopic techniques. The P-glycoprotein (P-gp) inhibiting activities of the representative set of jatrophanes (1-6 and 11-16) have been assessed. Jatrophanes 2 and 5 demonstrated the most powerful inhibition of P-gp, higher than R(+)-verapamil and tariquidar in colorectal multi-drug resistant (MDR) cells (DLD1-TxR). PMID:23079764

Jadranin, Milka; Peši?, Milica; Aljan?i?, Ivana S; Milosavljevi?, Slobodan M; Todorovi?, Nina M; Podolski-Reni?, Ana; Bankovi?, Jasna; Tani?, Nikola; Markovi?, Ivanka; Vajs, Vlatka E; Teševi?, Vele V

2012-10-15

 
 
 
 
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Photodynamic therapy inhibits p-glycoprotein mediated multidrug resistance via JNK activation in human hepatocellular carcinoma using the photosensitizer pheophorbide a  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Multidrug resistance (MDR) is frequently observed after prolonged treatment in human hepatoma with conventional anti-tumor drugs, and photodynamic therapy (PDT) is a recently suggested alternative to overcome MDR. The therapeutic potential of PDT was evaluated in a multidrug resistance (MDR) human hepatoma cell line R-HepG2 with photosensitizer pheophorbide a (Pa). Results Our results demonstrated that intracellular accumulation of Pa was not reduced by the overexpression of P-glycoprotein. Pa-based PDT (Pa-PDT) significantly inhibited the growth of R-HepG2 cells with an IC50 value of 0.6 ?M. Mechanistic study demonstrated that genomic DNA fragmentation and phosphatidylserine externalization occurred where increase of intracellular singlet oxygen level triggers the phosphorylation of c-Jun N-terminal Kinase (JNK) and leads to activation of intrinsic apoptotic caspases cascade during the Pa-PDT treatment. The cytotoxicity of Pa-PDT, accumulation of sub-G1 population, and depolarization of mitochondrial membrane could be inhibited by JNK inhibitor in the Pa-PDT treated cells. Interestingly, the Pa-PDT induced JNK activation showed inhibitory effect on MDR by the down-regulation of P-glycoprotein in R-HepG2 cells in a dose-dependent manner. In addition, significant reduction of tumor size was obtained in Pa-PDT treated R-HepG2-bearing nude mice with no significant damages in liver and heart. Conclusion In summary, our findings provided the first evidence that PDT could inhibit the MDR activity by down-regulating the expression of P-glycoprotein via JNK activation using pheophorbide a as the photosensitizer, and our work proved that Pa-PDT inhibited the growth of MDR hepatoma cells by mitochondrial-mediated apoptosis induction.

Tang Patrick; Zhang Dong-Mei; Xuan Ngoc-Ha; Tsui Stephen; Waye Mary; Kong Siu-Kai; Fong Wing-Ping; Fung Kwok-Pui

2009-01-01

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Association between reversal of multidrug resistance by methyl jasmonate and P-glycoprotein ATPase activity in hepatocellular carcinoma.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To study the effects of methyl jasmonate on multidrug resistance in a mouse model of hepatocellular carcinoma. METHODS: Multidrug resistant H22 (H22/FAP) hepatocellular carcinoma cells were produced in vitro by continuous exposure to increasing doses of doxorubicin, cisplatin and 5-fluorouracil (FAP regimen). Cell toxicity was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolum bromide (MTT) assay. Survival time was calculated for BALB/c mice that received intraperitoneal injections of H22/FAP cells followed by treatment with methyl jasmonate or verapamil in combination with FAP for 7 days. Adenosine triphosphate (ATP) hydrolysis was used to measure the activity of permeability-glycoprotein (P-gp) ATPase activity in plasma membranes. RESULTS: The MTT assay showed that methyl jasmonate significantly enhanced the cytotoxicity of the FAP regimen in multidrug resistant H22/FAP cells. Methyl jasmonate (10 mg/kg and 5 mg/kg) combined with FAP significantly increased survival time in BALB/c mice by 44.25% and 48.01%, respectively, compared with FAP. Methyl jasmonate increased P-gp ATPase activity. CONCLUSION: The combined use of methyl jasmonate and the FAP regimen might be a novel strategy for overcoming the multidrug resistance often observed in hepatocellular carcinoma.

Wang CF; Wang YQ; Huang FZ; Nie WP; Liu XY; Jiang XZ

2013-08-01

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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

2010-01-01

44

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

International Nuclear Information System (INIS)

99mTc-sestamibi(MIBI) and 99mTc-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 99mTc-MIBI and 99mTc-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 (?

2005-01-01

45

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

46

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

UK PubMed Central (United Kingdom)

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.

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

2012-07-01

47

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

48

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

Directory of Open Access Journals (Sweden)

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; Natalini Cláudio Corrêa

2006-01-01

49

Thioridazine induces apoptosis of multidrug-resistant mouse lymphoma cells transfected with the human ABCB1 and inhibits the expression of P-glycoprotein.  

UK PubMed Central (United Kingdom)

AIM: Chlorpromazine has activity against a large variety of cancer types. However, this phenothiazine produces a plethora of serious side-effects. We have studied thioridazine (TZ), a phenothiazine neuroleptic that is much milder, for activity against multidrug-resistant (MDR) cancer cells, as well as against the overexpressed ABCB1 transporter (P-glycoprotein) that is the cause for the MDR phenotype of these cancer cells. MATERIALS AND METHODS: MDR mouse T-lymphoma cells, transfected with the human gene ABCB1 that codes for the transporter ABCB1, were incubated with TZ for various periods of time and examined for evidence of apoptosis. Concentrations of TZ were evaluated for activity against the ABCB1 transporter with the aid of an automated ethidium bromide (EB) method. RESULTS: TZ induces apoptosis of MDR cancer cell line, as well as inhibits the activity of the overexpressed ABCB1 transporter of these cells. CONCLUSION: Because thioridazine has been in moderately safe use for over 40 years for the therapy of psychosis, it has the potential to serve as an adjuvant with anticancer agents, rendering the a priori MDR cancer cells susceptible to the anticancer agent.

Spengler G; Molnar J; Viveiros M; Amaral L

2011-12-01

50

Interaction of forskolin with the P-glycoprotein multidrug transporter  

Energy Technology Data Exchange (ETDEWEB)

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

51

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

Directory of Open Access Journals (Sweden)

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; Samlee Mankhetkorn

2009-01-01

52

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

Hong LIANG; Yu ZHANG

2007-01-01

53

P-glycoprotein, multidrug-resistance associated protein 2, Cyp3a, and carboxylesterase affect the oral availability and metabolism of vinorelbine.  

UK PubMed Central (United Kingdom)

We investigated the interactions of the anticancer drug vinorelbine with drug efflux transporters and cytochrome P450 3A drug-metabolizing enzymes. Vinorelbine was transported by human multidrug-resistance associated protein (MRP) 2, and Mrp2 knockout mice displayed increased vinorelbine plasma exposure after oral administration, suggesting that Mrp2 limits the intestinal uptake of vinorelbine. Using P-glycoprotein (P-gp), Cyp3a-, and P-gp/Cyp3a knockout mice, we found that the absence of P-gp or Cyp3a resulted in increased vinorelbine plasma exposure, both after oral and intravenous administration. Surprisingly, P-gp/Cyp3a knockout mice displayed markedly lower vinorelbine plasma concentrations than wild-type mice upon intravenous administration but higher concentrations upon oral administration. This could be explained by highly increased formation of 4'-O-deacetylvinorelbine, an active vinorelbine metabolite, especially in P-gp/Cyp3a knockout plasma. Using wild-type and Cyp3a knockout liver microsomes, we found that 4'-O-deacetylvinorelbine formation was 4-fold increased in Cyp3a knockout liver and was not mediated by Cyp3a or other cytochrome P450 enzymes. In vitro incubation of vinorelbine with plasma revealed that vinorelbine deacetylation in Cyp3a and especially in P-gp/Cyp3a knockout mice but not in P-gp-deficient mice was strongly up-regulated. Metabolite formation in microsomes and plasma could be completely inhibited with the nonspecific carboxylesterase (CES) inhibitor bis(4-nitrophenyl) phosphate and partly with the CES2-specific inhibitor loperamide, indicating that carboxylesterase Ces2a, which was appropriately up-regulated in Cyp3a and especially in P-gp/Cyp3a knockout liver was responsible for the 4'O-deacetylvinorelbine formation. Such compensatory up-regulation can complicate the interpretation of knockout mouse data. Nonetheless, P-gp, Mrp2, Cyp3a, and Ces2a clearly restricted vinorelbine availability in mice. Variation in activity of their human homologs may also affect vinorelbine pharmacokinetics in patients.

Lagas JS; Damen CW; van Waterschoot RA; Iusuf D; Beijnen JH; Schinkel AH

2012-10-01

54

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.

2002-10-02

55

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.

2002-10-02

56

HIV-1 integrase inhibitors are substrates for the multidrug transporter MDR1-P-glycoprotein  

Science.gov (United States)

Background The discovery of diketoacid-containing derivatives as inhibitors of HIV-1 Integrase (IN) (IN inhibitors, IINs) has played a major role in validating this enzyme as an important target for antiretroviral therapy. Since the in vivo efficacy depends on access of these drugs to intracellular sites where HIV-1 replicates, we determined whether the IINs are recognized by the multidrug transporter MDR1-P-glycoprotein (P-gp) thereby reducing their intracellular accumulation. To address the effect of IINs on drug transport, nine quinolonyl diketo acid (DKA) derivatives active on the HIV-1 IN strand transfer (ST) step and with EC50 ranging from 1.83 to >50 ?m in cell-based assays were tested for their in vitro interaction with P-gp in the CEM-MDR cell system. IINs were investigated for the inhibition and induction of the P-gp function and expression as well as for multidrug resistance (MDR) reversing ability. Results The HIV-1 IINs act as genuine P-gp substrates by inhibiting doxorubicin efflux and inducing P-gp functional conformation changes as evaluated by the modulation of UIC2 mAb epitope. Further, IINs chemosensitize MDR cells to vinblastine and induce P-gp expression in drug sensitive revertants of CEM-MDR cells. Conclusion To our knowledge, this is the first demonstration that HIV-1 IINs are P-gp substrates. This biological property may influence the absorption, distribution and elimination of these novels anti HIV-1 compounds.

Cianfriglia, Maurizio; Dupuis, Maria Luisa; Molinari, Agnese; Verdoliva, Antonio; Costi, Roberta; Galluzzo, Clementina Maria; Andreotti, Mauro; Cara, Andrea; Di Santo, Roberto; Palmisano, Lucia

2007-01-01

57

Technetium-99m sestamibi single photon emission computed tomography findings correlated with p-glycoprotein expression, encoded by the multidrug resistance gene-1 messenger ribonucleic acid, in intracranial meningiomas  

International Nuclear Information System (INIS)

The present study evaluated whether technetium-99m sestamibi (99mTc-MIBI) single photon emission computed tomography (SPECT) characteristics of intracranial meningioma are correlated with the histological malignancy, proliferative potential, and P-glycoprotein (Pgp) expression, encoded by the multidrug resistance gene-1 (MDR-1) messenger ribonucleic acid (mRNA). Twenty-one patients with intracranial meningiomas, including 17 benign and four nonbenign meningiomas, underwent 99mTc-MIBI SPECT imaging at 15 minutes (early) and 3 hours (delayed) after injection. The tumor-to-normal pituitary gland ratio was calculated on both early (ER) and delayed (DR) images. Retention index (RI) was calculated using the following formula: (DR-ER)/ER x 100%. Meningioma specimens were examined by immunohistochemistry using anti-Pgp and MIB-1 monoclonal antibody. MDR-1 mRNA expression was also investigated using reverse transcription-polymerase chain reaction assay. 99mTc-MIBI was highly accumulated and retained in the tumors. 99mTc-MIBI SPECT findings were not related to MIB-1 labeling index. 99mTc-MIBI SPECT RI of the Pgp-positive group (-9.12±22.27%) was significantly lower than that of the Pgp-negative group (28.79±22.80%) (p=0.0016). No significant difference was seen in ER and DR between the positive and negative groups. These results show that 99mTc-MIBI may not be useful for determining proliferative potential and histological malignancy, but could predict anticancer drug resistance related to the expression of MDR-1 mRNA and its gene product Pgp in patients with intracranial meningiomas. (author)

2003-01-01

58

Structure-activity relationships studies in a series of N,N-bis(alkanol)amine aryl esters as P-glycoprotein (Pgp) dependent multidrug resistance (MDR) inhibitors.  

Science.gov (United States)

As a continuation of a previous research, a series of N,N-bis(alkanol)amine aryl esters, as Pgp-dependent MDR inhibitors, was designed and synthesized. The aromatic ester portions are suitably modulated, and new aryl rings (Ar(1) and Ar(2)) were combined with trans-3-(3,4,5-trimethoxyphenyl)vinyl, 3,4,5-trimethoxybenzyl and anthracene moieties that were present in the most potent previously studied compounds. The new compounds showed a wide range of potencies and efficacies on doxorubicin-resistant erythroleukemia K562 cells (K562/DOX) in the pirarubicin uptake assay. Selected compounds (5, 6, 8, 9, and 21) were further studied, evaluating their action on doxorubicin cytotoxicity potentiation on K562 cells; they significantly enhanced doxorubicin cytotoxicity on K562/DOX cells, confirming the results obtained with pirarubicin. Compound 9 shows the most promising properties as it was able to nearly completely reverse Pgp-dependent pirarubicin extrusion at nanomolar doses and increased the cytotoxicity of doxorubicin with a reversal fold (RF) of 19.1 at 3 microM dose. PMID:20104851

Martelli, Cecilia; Coronnello, Marcella; Dei, Silvia; Manetti, Dina; Orlandi, Francesca; Scapecchi, Serena; Novella Romanelli, Maria; Salerno, Milena; Mini, Enrico; Teodori, Elisabetta

2010-02-25

59

Overexpression of lung resistance-related protein and P-glycoprotein and response to induction chemotherapy in acute myelogenous leukemia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lung resistance-related protein (LRP) and P-glycoprotein (P-gp) are associated with multidrug resistance. P-gp overexpression reduces intracellular anticancer drug concentrations and is correlated with low remission rates. However, whether the presence of LRP influences the response to induction che...

Kazue Tsuji; Yan-Hua Wang; Minoko Takanashi; Tsuyoshi Odajima; Gabriel A. Lee; Hiroki Sugimori; Toshiko Motoji

60

Grape Seed Procyanidin Reversal of P-glycoprotein Associated Multi-Drug Resistance via Down-regulation of NF-?B and MAPK/ERK Mediated YB-1 Activity in A2780/T Cells.  

UK PubMed Central (United Kingdom)

The expression and function of P-glycoprotein (P-gp) is associated with the phenotype of multi-drug resistance (MDR), leading chemotherapy failure of patients suffered with cancer. Grape seed procyanidin(GSP) is a natural polyphenol supplement with anti-inflammatory effect. Present study assessed a new use of GSP on the MDR reversal activity and its possible molecular mechanisms in MDR1-overpressing paclitaxel resistant ovarian cancer cells. Our results showed GSP significantly enhanced the cytotoxicity of paclitaxel and adriamycin in paclitaxel resistant A2780/T cells but its parental A2780 cells. Furthermore, GSP strongly inhibited P-gp expression by blocking MDR1 gene transcription, as well as, increased the intracellular accumulation of the P-gp substrate rhodamine-123 in A2780/T cells. Nuclear factor-?B(NF-?B) activity, I?B degradation level and NF-?B/p65 nuclear translocation induced by lipopolysaccharide (LPS) and receptor activator for nuclear factor-?B ligand (RANKL) were markedly inhibited by pre-treatment with GSP. Meanwhile, GSP inhibited MAPK/ERK pathway by decreasing the phosphorylation of ERK1/2, resulting in reduced the Y-box binding protein 1 (YB-1) activation with blocking its nuclear translocation. Moreover, the up-regulation of P-gp expression, the activation of AKT/NF-?B and MAPK/ERK pathway induced by LPS was attenuated by GSP administration. Compared with PDTC and U1026, inhibitor of NF-?B and MAPK/ERK respectively, GSP showed the same tendency of down-regulating NF-?B and MAPK/ERK mediated YB-1 activities. Thus, GSP reverses P-gp associated MDR by inhibiting the function and expression of P-gp through down-regulation of NF-?B activity and MAPK/ERK pathway mediated YB-1 nuclear translocation, offering insight into the mechanism of reversing MDR by natural polyphenol supplement compounds. GSP could be a new potential MDR reversal agent used for combination therapy with chemotherapeutics in clinic.

Zhao BX; Sun YB; Wang SQ; Duan L; Huo QL; Ren F; Li GF

2013-01-01

 
 
 
 
61

Grape Seed Procyanidin Reversal of P-glycoprotein Associated Multi-Drug Resistance via Down-regulation of NF-?B and MAPK/ERK Mediated YB-1 Activity in A2780/T Cells  

Science.gov (United States)

The expression and function of P-glycoprotein (P-gp) is associated with the phenotype of multi-drug resistance (MDR), leading chemotherapy failure of patients suffered with cancer. Grape seed procyanidin(GSP) is a natural polyphenol supplement with anti-inflammatory effect. Present study assessed a new use of GSP on the MDR reversal activity and its possible molecular mechanisms in MDR1-overpressing paclitaxel resistant ovarian cancer cells. Our results showed GSP significantly enhanced the cytotoxicity of paclitaxel and adriamycin in paclitaxel resistant A2780/T cells but its parental A2780 cells. Furthermore, GSP strongly inhibited P-gp expression by blocking MDR1 gene transcription, as well as, increased the intracellular accumulation of the P-gp substrate rhodamine-123 in A2780/T cells. Nuclear factor-?B(NF-?B) activity, I?B degradation level and NF-?B/p65 nuclear translocation induced by lipopolysaccharide (LPS) and receptor activator for nuclear factor-?B ligand (RANKL) were markedly inhibited by pre-treatment with GSP. Meanwhile, GSP inhibited MAPK/ERK pathway by decreasing the phosphorylation of ERK1/2, resulting in reduced the Y-box binding protein 1 (YB-1) activation with blocking its nuclear translocation. Moreover, the up-regulation of P-gp expression, the activation of AKT/NF-?B and MAPK/ERK pathway induced by LPS was attenuated by GSP administration. Compared with PDTC and U1026, inhibitor of NF-?B and MAPK/ERK respectively, GSP showed the same tendency of down-regulating NF-?B and MAPK/ERK mediated YB-1 activities. Thus, GSP reverses P-gp associated MDR by inhibiting the function and expression of P-gp through down-regulation of NF-?B activity and MAPK/ERK pathway mediated YB-1 nuclear translocation, offering insight into the mechanism of reversing MDR by natural polyphenol supplement compounds. GSP could be a new potential MDR reversal agent used for combination therapy with chemotherapeutics in clinic.

Wang, Sheng-qi; Duan, Lian; Huo, Qi-lu; Ren, Fei; Li, Guo-feng

2013-01-01

62

Grape Seed Procyanidin Reversal of P-glycoprotein Associated Multi-Drug Resistance via Down-regulation of NF-?B and MAPK/ERK Mediated YB-1 Activity in A2780/T Cells.  

Science.gov (United States)

The expression and function of P-glycoprotein (P-gp) is associated with the phenotype of multi-drug resistance (MDR), leading chemotherapy failure of patients suffered with cancer. Grape seed procyanidin(GSP) is a natural polyphenol supplement with anti-inflammatory effect. Present study assessed a new use of GSP on the MDR reversal activity and its possible molecular mechanisms in MDR1-overpressing paclitaxel resistant ovarian cancer cells. Our results showed GSP significantly enhanced the cytotoxicity of paclitaxel and adriamycin in paclitaxel resistant A2780/T cells but its parental A2780 cells. Furthermore, GSP strongly inhibited P-gp expression by blocking MDR1 gene transcription, as well as, increased the intracellular accumulation of the P-gp substrate rhodamine-123 in A2780/T cells. Nuclear factor-?B(NF-?B) activity, I?B degradation level and NF-?B/p65 nuclear translocation induced by lipopolysaccharide (LPS) and receptor activator for nuclear factor-?B ligand (RANKL) were markedly inhibited by pre-treatment with GSP. Meanwhile, GSP inhibited MAPK/ERK pathway by decreasing the phosphorylation of ERK1/2, resulting in reduced the Y-box binding protein 1 (YB-1) activation with blocking its nuclear translocation. Moreover, the up-regulation of P-gp expression, the activation of AKT/NF-?B and MAPK/ERK pathway induced by LPS was attenuated by GSP administration. Compared with PDTC and U1026, inhibitor of NF-?B and MAPK/ERK respectively, GSP showed the same tendency of down-regulating NF-?B and MAPK/ERK mediated YB-1 activities. Thus, GSP reverses P-gp associated MDR by inhibiting the function and expression of P-gp through down-regulation of NF-?B activity and MAPK/ERK pathway mediated YB-1 nuclear translocation, offering insight into the mechanism of reversing MDR by natural polyphenol supplement compounds. GSP could be a new potential MDR reversal agent used for combination therapy with chemotherapeutics in clinic. PMID:23967153

Zhao, Bo-Xin; Sun, Ya-Bin; Wang, Sheng-Qi; Duan, Lian; Huo, Qi-Lu; Ren, Fei; Li, Guo-Feng

2013-08-15

63

HIV-1 integrase inhibitors are substrates for the multidrug transporter MDR1-P-glycoprotein  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The discovery of diketoacid-containing derivatives as inhibitors of HIV-1 Integrase (IN) (IN inhibitors, IINs) has played a major role in validating this enzyme as an important target for antiretroviral therapy. Since the in vivo efficacy depends on access of these drugs to intracellular sites where HIV-1 replicates, we determined whether the IINs are recognized by the multidrug transporter MDR1-P-glycoprotein (P-gp) thereby reducing their intracellular accumulation. To address the effect of IINs on drug transport, nine quinolonyl diketo acid (DKA) derivatives active on the HIV-1 IN strand transfer (ST) step and with EC50 ranging from 1.83 to >50 ?m in cell-based assays were tested for their in vitro interaction with P-gp in the CEM-MDR cell system. IINs were investigated for the inhibition and induction of the P-gp function and expression as well as for multidrug resistance (MDR) reversing ability. Results The HIV-1 IINs act as genuine P-gp substrates by inhibiting doxorubicin efflux and inducing P-gp functional conformation changes as evaluated by the modulation of UIC2 mAb epitope. Further, IINs chemosensitize MDR cells to vinblastine and induce P-gp expression in drug sensitive revertants of CEM-MDR cells. Conclusion To our knowledge, this is the first demonstration that HIV-1 IINs are P-gp substrates. This biological property may influence the absorption, distribution and elimination of these novels anti HIV-1 compounds.

Cianfriglia Maurizio; Dupuis Maria; Molinari Agnese; Verdoliva Antonio; Costi Roberta; Galluzzo Clementina; Andreotti Mauro; Cara Andrea; Di Santo Roberto; Palmisano Lucia

2007-01-01

64

Influence of the multidrug transporter P-glycoprotein on the intracellular pharmacokinetics of vandetanib.  

Science.gov (United States)

Efflux transporters play an important role in the resistance of tumor cells against anticancer agents. Interaction between these transporters, including P-glycoprotein (P-gp), and drugs might influence their pharmacological properties and toxicities. The aim of this study was to investigate whether vandetanib (Caprelsa(®)), a small tyrosine kinase inhibitor, could interact with the multidrug transporter P-gp. Interaction of vandetanib with the P-gp was investigated using the parental cell line (IGROV1) and the P-gp doxorubicin-resistant (IGROV1-DXR) cell line, derived from the parental drug-sensitive IGROV1 cells. Cytotoxicity tests were assessed in both cell lines to examine the impact of P-gp on the cell survival after a vandetanib treatment. The effects of P-gp on vandetanib intracellular pharmacokinetics were investigated. To this aim, we developed a quantitative liquid chromatography tandem mass spectrometry to quantify vandetanib in cell medium. Results showed that overexpression of P-gp confers resistance to vandetanib in the IGROV1-DXR cell line. Using a LC-MS/MS assay validated in cell medium, cellular pharmacokinetic studies revealed that in cells overexpressing the P-gp intracellular concentrations of vandetanib were decreased compared to parental cell line. For the first time, vandetanib is described as a substrate of P-gp. In tumor cells, P-gp could be responsible for cellular resistance to vandetanib. It may be relevant to the clinical efficacy of vandetanib. Moreover, interaction of vandetanib with P-gp could modify the pharmacodynamics of other conventional chemotherapeutics, substrates of P-gp. It could impact on the overall response to anticancer therapy. PMID:23446814

Jovelet, C; Deroussent, A; Broutin, S; Paci, A; Farinotti, R; Bidart, J M; Gil, S

2013-02-28

65

Influence of the multidrug transporter P-glycoprotein on the intracellular pharmacokinetics of vandetanib.  

UK PubMed Central (United Kingdom)

Efflux transporters play an important role in the resistance of tumor cells against anticancer agents. Interaction between these transporters, including P-glycoprotein (P-gp), and drugs might influence their pharmacological properties and toxicities. The aim of this study was to investigate whether vandetanib (Caprelsa(®)), a small tyrosine kinase inhibitor, could interact with the multidrug transporter P-gp. Interaction of vandetanib with the P-gp was investigated using the parental cell line (IGROV1) and the P-gp doxorubicin-resistant (IGROV1-DXR) cell line, derived from the parental drug-sensitive IGROV1 cells. Cytotoxicity tests were assessed in both cell lines to examine the impact of P-gp on the cell survival after a vandetanib treatment. The effects of P-gp on vandetanib intracellular pharmacokinetics were investigated. To this aim, we developed a quantitative liquid chromatography tandem mass spectrometry to quantify vandetanib in cell medium. Results showed that overexpression of P-gp confers resistance to vandetanib in the IGROV1-DXR cell line. Using a LC-MS/MS assay validated in cell medium, cellular pharmacokinetic studies revealed that in cells overexpressing the P-gp intracellular concentrations of vandetanib were decreased compared to parental cell line. For the first time, vandetanib is described as a substrate of P-gp. In tumor cells, P-gp could be responsible for cellular resistance to vandetanib. It may be relevant to the clinical efficacy of vandetanib. Moreover, interaction of vandetanib with P-gp could modify the pharmacodynamics of other conventional chemotherapeutics, substrates of P-gp. It could impact on the overall response to anticancer therapy.

Jovelet C; Deroussent A; Broutin S; Paci A; Farinotti R; Bidart JM; Gil S

2013-09-01

66

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

67

[Multidrug resistance of malignant tumors  

UK PubMed Central (United Kingdom)

The development of resistance to chemotherapy is a major problem in the treatment of malignant tumors. Clinically, this is characterized by short periods of remission and failure to respond to subsequent therapy. Multidrug-resistance or pleiotropic resistance describes the simultaneous expression of cellular resistance to a vide range of structurally unrelated drugs (e.g. alkaloids, anthracyclines, antibiotics, etc.). The most frequently reported alteration of multidrug-resistant cells is the overexpression of a 170 kD glycoprotein (P--170 or P-glycoprotein) encoding by the MDR gene family. A great deal of evidence has suggested that the P-glycoprotein is, in fact, an energy-dependent drug efflux pump. Pharmacological overcome of MDR may indicate to circumvent clinically observed drug resistance.

Bak M

1991-10-01

68

Effects of Devil's Claw (Harpagophytum procumbens) on the multidrug transporter ABCB1/P-glycoprotein.  

UK PubMed Central (United Kingdom)

UNLABELLED: Devil's Claw (Harpagophytum procumbens) a plant native to Southern Africa, has historically been used in traditional medicine to treat a wide range of diseases and currently is widely employed as anti-inflammatory and pain-relieving natural remedy in Europe and other parts of the world. AIM OF THE STUDY: Little is known about possible herb-drug interactions arising from effects of Devil's Claw on the major drug metabolizing enzymes or transporters. This study evaluated in vitro the effects of Devil's Claw on the multidrug transporter ABCB1/P-glycoprotein. MATERIALS AND METHODS: The effects of three commercially available Devil's Claw preparations and that of pure harpagoside were studied in the human kidney (HK-2) proximal tubule cell line, constitutively expressing ABCB1/P-glycoprotein (P-gp). Pgp activity and expression were tested by the calcein-AM test and by Western blotting, respectively. RESULTS: Commercial preparations inhibited P-gp activity, even if to a different extent, while pure harpagoside was almost ineffective. In cells cultured for three days in the presence of Devil's Claw preparations or pure harpagoside, a dose-dependent P-gp upregulation was found. CONCLUSIONS: Our results demonstrate for the first time that Devil's Claw may interact with the multidrug transporter ABCB1/P-gp, the effect not appearing strictly related to the harpagoside relative content. Modulation of both P-gp activity and P-gp expression by Devil's Claw raise the possibility of herb-drug interactions, to be further explored in depth.

Romiti N; Tramonti G; Corti A; Chieli E

2009-12-01

69

Inhibition of P-glycoprotein functionality by vandetanib may reverse cancer cell resistance to doxorubicin.  

Science.gov (United States)

P-glycoprotein belongs to the ATP binding cassette transporters, responsible for the multidrug resistance of cancer cells. These transporters efflux hydrophobic drugs outside cells and decrease their therapeutic efficacy. The aim of this study was to investigate the effect of vandetanib, an oral tyrosine kinase inhibitor of EGFR, VEGFR 2 and RET kinases, on the functionality of P-gp after a 24h-treatment at therapeutic concentration (2?M), and its ability to increase the cytotoxicity of chemotherapeutic agents in multidrug resistance cancer cells. In this study we found that IGROV1-DXR and IGROV1-CDDP cells were resistant to doxorubicin and cisplatin respectively, compare to parental cell line IGROV1. The parental sensitive and the two resistant cell lines similarly expressed MRP1 and did not express BCRP. Moreover, in contrast to the IGROV1 and IGROV1-CDDP cells, IGROV1-DXR cell line overexpressed P-gp. Functional activity studies demonstrated that MRP1 was not functional and the MDR phenotype in IGROV1-DXR cells was linked to P-gp functionality. Results also showed that vandetanib reversed resistance to doxorubicin in IGROV1-DXR cells, but not to cisplatin in IGROV1-CDDP cells. After 24h of treatment, vandetanib increased the accumulation of rhodamine 123 and calcein AM, demonstrating a functional inhibition of the transporter. In IGROV1-DXR cell line, vandetanib reverse resistance to doxorubicin by inhibiting the functionality of P-gp. In conclusion, vandetanib should be an option for drug combination in patients already developing a P-gp mediated multidrug resistance. PMID:22484209

Jovelet, C; Bénard, J; Forestier, F; Farinotti, R; Bidart, J M; Gil, S

2012-03-30

70

Inhibition of P-glycoprotein functionality by vandetanib may reverse cancer cell resistance to doxorubicin.  

UK PubMed Central (United Kingdom)

P-glycoprotein belongs to the ATP binding cassette transporters, responsible for the multidrug resistance of cancer cells. These transporters efflux hydrophobic drugs outside cells and decrease their therapeutic efficacy. The aim of this study was to investigate the effect of vandetanib, an oral tyrosine kinase inhibitor of EGFR, VEGFR 2 and RET kinases, on the functionality of P-gp after a 24h-treatment at therapeutic concentration (2?M), and its ability to increase the cytotoxicity of chemotherapeutic agents in multidrug resistance cancer cells. In this study we found that IGROV1-DXR and IGROV1-CDDP cells were resistant to doxorubicin and cisplatin respectively, compare to parental cell line IGROV1. The parental sensitive and the two resistant cell lines similarly expressed MRP1 and did not express BCRP. Moreover, in contrast to the IGROV1 and IGROV1-CDDP cells, IGROV1-DXR cell line overexpressed P-gp. Functional activity studies demonstrated that MRP1 was not functional and the MDR phenotype in IGROV1-DXR cells was linked to P-gp functionality. Results also showed that vandetanib reversed resistance to doxorubicin in IGROV1-DXR cells, but not to cisplatin in IGROV1-CDDP cells. After 24h of treatment, vandetanib increased the accumulation of rhodamine 123 and calcein AM, demonstrating a functional inhibition of the transporter. In IGROV1-DXR cell line, vandetanib reverse resistance to doxorubicin by inhibiting the functionality of P-gp. In conclusion, vandetanib should be an option for drug combination in patients already developing a P-gp mediated multidrug resistance.

Jovelet C; Bénard J; Forestier F; Farinotti R; Bidart JM; Gil S

2012-08-01

71

Structure-activity relationships, ligand efficiency, and lipophilic efficiency profiles of benzophenone-type inhibitors of the multidrug transporter P-glycoprotein.  

UK PubMed Central (United Kingdom)

The drug efflux pump P-glycoprotein (P-gp) has been shown to promote multidrug resistance (MDR) in tumors as well as to influence ADME properties of drug candidates. Here we synthesized and tested a series of benzophenone derivatives structurally analogous to propafenone-type inhibitors of P-gp. Some of the compounds showed ligand efficiency and lipophilic efficiency (LipE) values in the range of compounds which entered clinical trials as MDR modulators. Interestingly, although lipophilicity plays a dominant role for P-gp inhibitors, all compounds investigated showed LipE values below the threshold for promising drug candidates. Docking studies of selected analogues into a homology model of P-glycoprotein suggest that benzophenones show an interaction pattern similar to that previously identified for propafenone-type inhibitors.

Jabeen I; Pleban K; Rinner U; Chiba P; Ecker GF

2012-04-01

72

Synthesis of 5-oxyquinoline derivatives for reversal of multidrug resistance  

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The inhibition of ABC (ATP binding cassette) transporters is considered a powerful tool to reverse multidrug resistance. Zosuquidar featuring a difluorocyclopropyl-annulated dibenzosuberyl moiety has been found to be an inhibitor of the P-glycoprotein, one of the best-studied multidrug efflux pumps....

Torsten Dittrich; Nils Hanekop; Nacera Infed; Lutz Schmitt; Manfred Braun

73

[The efflux of intracellular vincristine in drug-resistant human lung cancer cells is not mediated by P-glycoprotein  

UK PubMed Central (United Kingdom)

A subline (PC-9/VCR) of the human lung adenocarcinoma cell line (PC-9), derived by in vitro exposure to vincristine (VCR), exhibited a 10-12-fold resistance to VCR by MTT and HTCA assay. Compared to the parental cell line (PC-9), PC-9/VCR-resistant cells displayed a reduced accumulation of VCR. The rate of VCR efflux was shown to be enhanced by PC-9/VCR. Unlike multidrug resistance, this efflux was independent of P-glycoprotein overexpression as determined by the Northern blotting method. In addition, PC-9/VCR showed no collateral sensitivity to verapamil. This resistant subline only showed 6.9-fold and 2.5-fold cross resistance to colchicine and vinblastine, respectively. This preliminary result indicates that defective drug accumulation in PC-9/VCR is due to other mechanisms possibly involving the microtubule assembly.

Song EJ; Chiang CD; Chao CC; Cheng V

1993-06-01

74

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

2010-01-01

75

Multi-drug resistance (MDR1) gene and P-glycoprotein influence on pharmacokinetic and pharmacodymanic of therapeutic drugs/ Influência do gene de resistência múltipla (MDR1) e da P-glicoproteína na farmacocinética e farmacodinâmica de drogas terapêuticas  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese P-glicoproteína (P-gp) é um transportador de membrana ligado ao gene de resistência múltipla (MDR1), expressado em células tumorais e também em tecidos normais como intestino, fígado, rins, membranas hematoencefálica, hemo-placentária e medula espinhal. A P-gp já foi identificada em camundongos, ratos, bovinos, macacos, roedores e seres humanos e tem ganhado relevância clínica particular em função de sua expressão limitar o acesso de drogas ao cérebro e in (more) terferir com a absorção intestinal quando administradas pela via oral. Esta proteína participa da função protetora do organismo contra uma grande variedade de substratos, evitando a entrada de drogas no sistema nervoso central. A P-gp interfere também com a biodisponibilidade dos fármacos, incluindo absorção, distribuição, metabolização e excreção, influenciando assim, a farmacocinética e dinâmica dos mesmos. Desta maneira, a modulação da P-gp pode explicar alguns efeitos adversos no sistema nervoso central, induzidos por alguns fármacos após administração intravenosa, e a pobre resposta após administração oral em pacientes. A alteração na expressão ou função da P-glicoproteína tem sido associada a uma maior susceptibilidade a diversas doenças em humanos e animais. Estudos adicionais relacionados à expressão e à função da P-gp espécie-específica têm implicação clínica importante em termos de eficiência de tratamento. Abstract in english (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, avoi (more) ding 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; Natalini, Cláudio Corrêa

2006-02-01

76

Multi-drug resistance (MDR1) gene and P-glycoprotein influence on pharmacokinetic and pharmacodymanic of therapeutic drugs Influência do gene de resistência múltipla (MDR1) e da P-glicoproteína na farmacocinética e farmacodinâmica de drogas terapêuticas  

Directory of Open Access Journals (Sweden)

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.P-glicoproteína (P-gp) é um transportador de membrana ligado ao gene de resistência múltipla (MDR1), expressado em células tumorais e também em tecidos normais como intestino, fígado, rins, membranas hematoencefálica, hemo-placentária e medula espinhal. A P-gp já foi identificada em camundongos, ratos, bovinos, macacos, roedores e seres humanos e tem ganhado relevância clínica particular em função de sua expressão limitar o acesso de drogas ao cérebro e interferir com a absorção intestinal quando administradas pela via oral. Esta proteína participa da função protetora do organismo contra uma grande variedade de substratos, evitando a entrada de drogas no sistema nervoso central. A P-gp interfere também com a biodisponibilidade dos fármacos, incluindo absorção, distribuição, metabolização e excreção, influenciando assim, a farmacocinética e dinâmica dos mesmos. Desta maneira, a modulação da P-gp pode explicar alguns efeitos adversos no sistema nervoso central, induzidos por alguns fármacos após administração intravenosa, e a pobre resposta após administração oral em pacientes. A alteração na expressão ou função da P-glicoproteína tem sido associada a uma maior susceptibilidade a diversas doenças em humanos e animais. Estudos adicionais relacionados à expressão e à função da P-gp espécie-específica têm implicação clínica importante em termos de eficiência de tratamento.

Renata Lehn Linardi; Cláudio Corrêa Natalini

2006-01-01

77

Enhanced complement resistance in drug-selected P-glycoprotein expressing multi-drug-resistant ovarian carcinoma cells  

Science.gov (United States)

Multi-drug resistance (MDR) is a major obstacle in cancer chemotherapy. There are contrasting data on a possible correlation between the level of expression of the drug transporter P-glycoprotein (P-gp) and susceptibility to complement-dependent cytotoxicity (CDC). We therefore investigated the sensitivity of human ovarian carcinoma cells and their P-gp expressing MDR variants to complement. Chemoselected P-gp expressing MDR cells showed increased resistance to CDC associated with overexpression of membrane-bound complement regulatory proteins (mCRP) and increased release of the soluble inhibitors C1 inhibitor and factor I. MDR1 gene transfection alone did not alter the susceptibility of P-gp expressing A2780-MDR and SKOV3-MDR cells to CDC. However, subsequent vincristine treatment conferred an even higher resistance to complement to these cells, again associated with increased expression of mCRP. Blocking the function of P-gp with verapamil, cyclosporine A or the anti-P-gp-antibody MRK16 had no impact on their complement resistance, whereas blocking of mCRP enhanced their susceptibility to complement. These results suggest that enhanced resistance of chemoselected MDR ovarian carcinoma cells to CDC is not conferred by P-gp, but is due at least partly to overexpression of mCRP, probably induced by treatment with the chemotherapeutic agents.

Odening, K E; Li, W; Rutz, R; Laufs, S; Fruehauf, S; Fishelson, Z; Kirschfink, M

2009-01-01

78

Enhanced complement resistance in drug-selected P-glycoprotein expressing multi-drug-resistant ovarian carcinoma cells.  

UK PubMed Central (United Kingdom)

Multi-drug resistance (MDR) is a major obstacle in cancer chemotherapy. There are contrasting data on a possible correlation between the level of expression of the drug transporter P-glycoprotein (P-gp) and susceptibility to complement-dependent cytotoxicity (CDC). We therefore investigated the sensitivity of human ovarian carcinoma cells and their P-gp expressing MDR variants to complement. Chemoselected P-gp expressing MDR cells showed increased resistance to CDC associated with overexpression of membrane-bound complement regulatory proteins (mCRP) and increased release of the soluble inhibitors C1 inhibitor and factor I. MDR1 gene transfection alone did not alter the susceptibility of P-gp expressing A2780-MDR and SKOV3-MDR cells to CDC. However, subsequent vincristine treatment conferred an even higher resistance to complement to these cells, again associated with increased expression of mCRP. Blocking the function of P-gp with verapamil, cyclosporine A or the anti-P-gp-antibody MRK16 had no impact on their complement resistance, whereas blocking of mCRP enhanced their susceptibility to complement. These results suggest that enhanced resistance of chemoselected MDR ovarian carcinoma cells to CDC is not conferred by P-gp, but is due at least partly to overexpression of mCRP, probably induced by treatment with the chemotherapeutic agents.

Odening KE; Li W; Rutz R; Laufs S; Fruehauf S; Fishelson Z; Kirschfink M

2009-02-01

79

Structure-activity relationship of natural and synthetic coumarins inhibiting the multidrug transporter P-glycoprotein.  

Science.gov (United States)

A set of 32 natural and synthetic coumarins were tested in order to evaluate their activity on human leukemic cells (K562/R7) overexpressing P-glycoprotein (P-gp). Their ability to reduce the P-gp-mediated drug efflux of daunorubicin out of cells was evaluated at 10 microM. Four natural compounds, previously isolated from Calophyllum dispar (Clusiaceae) and substituted by a common alpha-(hydroxyisopropyl)dihydrofuran moiety, exhibited a significant inhibitory effect on P-gp when compared to the positive control cyclosporin A. A 3D-quantitative structure-activity relationship (3D-QSAR) analysis of the coumarins was performed using the biological results obtained by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) of P-gp. Results showed a favorable electrostatic and steric volume, like the alpha-(hydroxyisopropyl)dihydrofuran moiety, beside C(5)-C(6) or C(7)-C(8) positions. In addition, the analysis revealed an important hydrophobic, neutral charge group, like phenyl, in position C(4) on the coumarinic ring. PMID:16824763

Raad, Imad; Terreux, Raphael; Richomme, Pascal; Matera, Eva-Laure; Dumontet, Charles; Raynaud, Jean; Guilet, David

2006-07-07

80

Potential contribution of P-glycoproteins to macrocyclic lactone resistance in the cattle parasitic nematode Cooperia oncophora.  

UK PubMed Central (United Kingdom)

Resistance against macrocyclic lactones such as ivermectin is widespread among parasitic gastrointestinal nematodes of small ruminants and is rapidly increasing in cattle parasites. ABC transporters of the subfamily B, the so-called P-glycoproteins (Pgps) have been frequently implicated in ivermectin resistance and are a major cause of multi-drug resistance in protozoa and helminths. The Pgp inhibitor verapamil (VPL) dramatically enhanced susceptibility of the cattle parasitic nematode Cooperia oncophora to ivermectin in vitro as measured in a larval developmental assay and a larval migration inhibition assay using third stage larvae. Moreover, VPL completely restored susceptibility to ivermectin in a resistant isolate resulting in virtually identical dose-response curves of susceptible and resistant isolates in the presence of VPL. Further characterisation of the molecular mechanisms resulting in Pgp-mediated ivermectin resistance is still hampered by the lack of molecular and biochemical information for Pgps of parasitic nematodes. Using PCR with degenerate primers, fragments of four different C. oncophora Pgps could be amplified and the Conpgp-2, previously implicated in macrocyclic lactone resistance in Haemonchus contortus, and Conpgp-3 full-length cDNAs were obtained by RACE PCR. The pgp sequences presented here contribute important data required to systematically screen resistant C. oncophora isolates for up- or down-regulation of Pgps and for the detection of single nucleotide polymorphisms in Pgps to detect selection of specific Pgp alleles by anthelmintics as early as possible.

Demeler J; Krücken J; AlGusbi S; Ramünke S; De Graef J; Kerboeuf D; Geldhof P; Pomroy WE; von Samson-Himmelstjerna G

2013-03-01

 
 
 
 
81

Potential contribution of P-glycoproteins to macrocyclic lactone resistance in the cattle parasitic nematode Cooperia oncophora.  

Science.gov (United States)

Resistance against macrocyclic lactones such as ivermectin is widespread among parasitic gastrointestinal nematodes of small ruminants and is rapidly increasing in cattle parasites. ABC transporters of the subfamily B, the so-called P-glycoproteins (Pgps) have been frequently implicated in ivermectin resistance and are a major cause of multi-drug resistance in protozoa and helminths. The Pgp inhibitor verapamil (VPL) dramatically enhanced susceptibility of the cattle parasitic nematode Cooperia oncophora to ivermectin in vitro as measured in a larval developmental assay and a larval migration inhibition assay using third stage larvae. Moreover, VPL completely restored susceptibility to ivermectin in a resistant isolate resulting in virtually identical dose-response curves of susceptible and resistant isolates in the presence of VPL. Further characterisation of the molecular mechanisms resulting in Pgp-mediated ivermectin resistance is still hampered by the lack of molecular and biochemical information for Pgps of parasitic nematodes. Using PCR with degenerate primers, fragments of four different C. oncophora Pgps could be amplified and the Conpgp-2, previously implicated in macrocyclic lactone resistance in Haemonchus contortus, and Conpgp-3 full-length cDNAs were obtained by RACE PCR. The pgp sequences presented here contribute important data required to systematically screen resistant C. oncophora isolates for up- or down-regulation of Pgps and for the detection of single nucleotide polymorphisms in Pgps to detect selection of specific Pgp alleles by anthelmintics as early as possible. PMID:23384738

Demeler, Janina; Krücken, Jürgen; AlGusbi, Salha; Ramünke, Sabrina; De Graef, Jessie; Kerboeuf, Dominique; Geldhof, Peter; Pomroy, William E; von Samson-Himmelstjerna, Georg

2013-02-04

82

P-glycoprotein in adriamycin-resistant cells functions as an efflux pump for benzopyrene, a chemical carcinogen  

Energy Technology Data Exchange (ETDEWEB)

The physiological function of multidrug resistant gene (MDR 1) coded P-glycoprotein 170 (P-gp) in normal tissues remains unknown. The authors propose that P-gp functions as an efflux pump in normal tissues for benzopyrene and other xenobiotic substances. To examine their hypothesis the authors used a series of MDR human breast cancer MCF-7 cells with increasing degrees of drug resistance, expression of MDR and levels of P-gp. First, they found the IC{sub 50} for benzopyrene is linearly correlated with the levels of P-gp at different stages of adriamycin resistant MCF-7 cells. Using P-gp ({sup 3}H)azidopine labeling as a measurement of P-gp they found benzopyrene competes for labeling of P-gp. Finally, they directly measured cellular efflux of benzopyrene with adherent cell laser cytometry and found that resistant cells expressing high levels of P-gp showed rapid efflux of benzopyrene. By contrast, drug sensitive wild type cells with undetectable P-gp showed negligible efflux. They conclude that P-gp can function as an efflux pump for benzopyrene and suggest that P-gp may be a cellular mechanism for resistance to carcinogens.

Chao Yeh, G.; Poore, C.M.; Lopaczynska, J.; Phang, J.M. (NCI-FCRDC, Frederick, MD (United States))

1991-03-15

83

Effects of Zuccagnia punctata extracts and their flavonoids on the function and expression of ABCB1/P-glycoprotein multidrug transporter.  

UK PubMed Central (United Kingdom)

ETHNOPHARMACOLOGICAL RELEVANCE: Zuccagnia punctata extracts (ZpE) are used in ethnomedicine as antimicrobial and anti-inflammatory drugs. The pharmacological properties of ZpE and their polyphenolic components suggest that they may be used as potential modulators on the P-glycoprotein (P-gp) multidrug transporter. P-gp is well known for its role in the acquired drug resistance by tumors following chemotherapy, causing a low drug bioavailability by extruding them out of the cells. AIM OF STUDY: To evaluate the effects of ZpE and three of their phenolic components: 7-hydroxyflavanone (HF), 3,7-dihydroxyflavone (DHF) and 2',4'-dihydroxychalcone (DHC) on P-gp activity and expression. MATERIAL AND METHODS: The effects of natural products on ABCB1/P-gp function and expression were evaluated by R-123 accumulation assay and western blot analysis using HK-2 cells as experimental model. The ABCB1 mRNA content was determined by SQRT-PCR. RESULTS: The accumulation of R-123 in HK-2 cells was significantly increased by ZpE and DHF, and to a lesser extent by DHC, indicating their roles on the efflux transporter activity. However, HF did not show any effect. HK-2 cells maintained in the presence of ZpE or DHF for 72 h, showed an increase in P-gp expression whereas activity was unchanged or decreased. No changes were observed in ABCB1 mRNA content. Furthermore, in these assay conditions, more sensibility of HK-2 cells to the cytotoxic action of cyclosporine A (P-gp substrate) was observed. CONCLUSION: These results may suggest an impact of Zuccagnia punctata and some of its components on the pharmacokinetics of drugs that are P-gp substrates, as well as a potential role on multidrug resistance modulation.

Chieli E; Romiti N; Catiana Zampini I; Garrido G; Inés Isla M

2012-12-01

84

Effects of grapefruit juice on the multidrug transporter P-glycoprotein in the human proximal tubular cell line HK-2.  

UK PubMed Central (United Kingdom)

The multidrug transporter MDR-1 P-glycoprotein (Pgp) has been recently pointed out as an important mechanism underlying chemical interaction between drugs and many commonly ingested substances, including grapefruit juice (GFJ). Modulation of intestinal Pgp dependent transport by GFJ may lead to changes in bioavailability of drugs that are substrates of Pgp itself, by affecting their presystemic clearance. Since other cellular sites expressing Pgp and devoted to drug disposition, like kidney proximal tubules, could be involved in these pharmacokinetic interactions, we investigated the effect of GFJ on the expression and activity of Pgp in the human immortalized tubular cell line HK-2. Two flavonoid compounds related to GFJ, kaempferol and naringenin, were also tested for their effects on HK-2 Pgp. HK-2 cells cultured for 4 days in the presence of GFJ, showed a dose-dependent decrease in Pgp immunoblottable amount as well as a decrease in MDR-1 mRNA level, as shown by western blot analysis and RT-PCR, respectively. Both kaempferol and naringenin were also able to significantly decrease Pgp immunoblottable amount. To test whether the downregulation of HK-2 Pgp due to GFJ exposition could influence the cell sensitivity to drugs that are transported by Pgp itself, HK-2 cells precultured with GFJ were exposed to scalar concentrations of Cyclosporin A or Vinblastine and cell viability examined 36 hours later. The cytotoxicity of both drugs was increased. The calcein-AM test in untreated cells showed that GFJ, kaempferol or naringenin inhibited Pgp activity. Downregulation of Pgp as well inhibition of its function by GFJ or its related components in tubular cells could have a role in changing disposition kinetics of some important therapeutic agents.

Romiti N; Tramonti G; Donati A; Chieli E

2004-12-01

85

Effects of grapefruit juice on the multidrug transporter P-glycoprotein in the human proximal tubular cell line HK-2.  

Science.gov (United States)

The multidrug transporter MDR-1 P-glycoprotein (Pgp) has been recently pointed out as an important mechanism underlying chemical interaction between drugs and many commonly ingested substances, including grapefruit juice (GFJ). Modulation of intestinal Pgp dependent transport by GFJ may lead to changes in bioavailability of drugs that are substrates of Pgp itself, by affecting their presystemic clearance. Since other cellular sites expressing Pgp and devoted to drug disposition, like kidney proximal tubules, could be involved in these pharmacokinetic interactions, we investigated the effect of GFJ on the expression and activity of Pgp in the human immortalized tubular cell line HK-2. Two flavonoid compounds related to GFJ, kaempferol and naringenin, were also tested for their effects on HK-2 Pgp. HK-2 cells cultured for 4 days in the presence of GFJ, showed a dose-dependent decrease in Pgp immunoblottable amount as well as a decrease in MDR-1 mRNA level, as shown by western blot analysis and RT-PCR, respectively. Both kaempferol and naringenin were also able to significantly decrease Pgp immunoblottable amount. To test whether the downregulation of HK-2 Pgp due to GFJ exposition could influence the cell sensitivity to drugs that are transported by Pgp itself, HK-2 cells precultured with GFJ were exposed to scalar concentrations of Cyclosporin A or Vinblastine and cell viability examined 36 hours later. The cytotoxicity of both drugs was increased. The calcein-AM test in untreated cells showed that GFJ, kaempferol or naringenin inhibited Pgp activity. Downregulation of Pgp as well inhibition of its function by GFJ or its related components in tubular cells could have a role in changing disposition kinetics of some important therapeutic agents. PMID:15531381

Romiti, Nadia; Tramonti, Gianfranco; Donati, Andrea; Chieli, Elisabetta

2004-12-01

86

Progesterone-adenine hybrids as bivalent inhibitors of P-glycoprotein-mediated multidrug efflux: design, synthesis, characterization and biological evaluation.  

UK PubMed Central (United Kingdom)

Bivalent ligands were designed on the basis of the described close proximity of the ATP-site and the putative steroid-binding site of P-glycoprotein (ABCB1). The syntheses of 19 progesterone-adenine hybrids are described. Their abilities to inhibit P-glycoprotein-mediated daunorubicin efflux in K562/R7 human leukemic cells overexpressing P-glycoprotein were evaluated versus progesterone. The hybrid with a hexamethylene linker chain showed the best inhibitory potency. The efficiency of these progesterone-adenine hybrids depends on two main factors: (i) the nature of the linker and (ii) its attachment point on the steroid skeleton.

Zeinyeh W; Mahiout Z; Radix S; Lomberget T; Dumoulin A; Barret R; Grenot C; Rocheblave L; Matera EL; Dumontet C; Walchshofer N

2012-10-01

87

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

UK PubMed Central (United Kingdom)

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.

Stordal B; Hamon M; McEneaney V; Roche S; Gillet JP; O'Leary JJ; Gottesman M; Clynes M

2012-01-01

88

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

2012-07-11

89

P-glycoprotein efflux pump plays an important role in Trypanosoma cruzi drug resistance.  

UK PubMed Central (United Kingdom)

Drug resistance in protozoan parasites has been associated with the P-glycoprotein (Pgp), an energy-dependent efflux pump that transports substances across the membrane. Interestingly, the genes TcPGP1 and TcPGP2 have been described in Trypanosoma cruzi, although the function of these genes has not been fully elucidated. The main goal of this work was to investigate Pgp efflux pump activity and expression in T. cruzi lines submitted to in vitro induced resistance to the compounds 4-N-(2-methoxy styryl)-thiosemicarbazone (2-Meotio) and benznidazole (Bz) and to verify the stability of the resistant phenotypes during the parasite life cycle. We observed that the EC50 values for the treatment of epimastigotes with 2-Meotio or Bz were increased at least 4.7-fold in resistant lines, and this phenotype was maintained in metacyclic trypomastigotes, cell-derived trypomastigotes, and intracellular amastigotes. However, in epimastigotes, 2-Meotio resistance is reversible, but Bz resistance is irreversible. When compared with the parental line, the resistant lines exhibited higher Pgp efflux activity, reversion of the resistant phenotypes in the presence of Pgp inhibitors, cross-resistance with Pgp modulators, higher basal Pgp ATPase activity, and overexpression of the genes TcPGP1 and TcPGP2. In conclusion, the resistance induced in T. cruzi by the compounds 2-Meotio and Bz is maintained during the entire parasite life cycle. Furthermore, our data suggest the participation of the Pgp efflux pump in T. cruzi drug resistance.

Campos MC; Castro-Pinto DB; Ribeiro GA; Berredo-Pinho MM; Gomes LH; da Silva Bellieny MS; Goulart CM; Echevarria A; Leon LL

2013-06-01

90

MDRO - Multidrug-Resistant Organisms  

Science.gov (United States)

... Information Downloads Healthcare Wide Hazards MDRO - Multidrug-Resistant Organisms Potential Hazard Exposure of employees to infections from multidrug resistant organisms such as "staph" and "strep" bacteria in the ...

91

Overexpression of lung resistance-related protein and P-glycoprotein and response to induction chemotherapy in acute myelogenous leukemia  

Directory of Open Access Journals (Sweden)

Full Text Available Lung resistance-related protein (LRP) and P-glycoprotein (P-gp) are associated with multidrug resistance. P-gp overexpression reduces intracellular anticancer drug concentrations and is correlated with low remission rates. However, whether the presence of LRP influences the response to induction chemotherapy remains controversial. Therefore, we investigated the relationship of LRP and P-gp overexpression with the response to induction chemotherapy. Univariate analysis revealed that there was a significant difference between complete remission rates for acute myelogenous leukemia patients depending on their blast cell expressions, between LRP positive versus negative, P-gp positive versus negative, and LRP/P-gp double positive versus other groups. Crude odds ratios (ORs) for complete remission were 0.390, 0.360, and 0.307 for LRP positive, for P-gp positive, and LRP/P- gp double positive patients, respectively. After controlling the confounding variables by stepwise multivariate logistical regression analysis, the presence of LRP/P-gp double positivity and P-gp positivity were found to be independent prognostic factors; adjusted ORs were 0.233 and 0.393, respectively. Furthermore, the monoclonal antibody against LRP significantly increased daunorubicin acumulation (P=0.004) in the nuclei of leukemic blast cells with LRP positivity in more than 10% of the cells. An LRP reversing agent, PAK-104P, was found to increase the daunorubicin content with marginal significance (P=0.060). The present results suggest that not only the presence of P-gp, but also LRP in leukemic blast cells is a risk factor for resistance to induction chemotherapy. Inhibiting LRP function, similar to the inhibition of P-gp function, will be necessary to improve the effectiveness of induction chemotherapy.

Kazue Tsuji; Yan-Hua Wang; Minoko Takanashi; Tsuyoshi Odajima; Gabriel A. Lee; Hiroki Sugimori; Toshiko Motoji

2012-01-01

92

Can P-glycoprotein mediate resistance to nilotinib in human leukaemia cells?  

UK PubMed Central (United Kingdom)

The effect of P-glycoprotein (P-gp, ABCB1, MDR1) expression on cell resistance to nilotinib was studied in human leukaemia cells. We used K562/Dox cells overexpressing P-gp and their variants (subclones) with a gradually decreased P-gp expression. These subclones were established by stable transfection of K562/Dox cells with a plasmid vector expressing shRNA targeting the ABCB1 gene. Functional analysis of P-gp using a specific fluorescent probe indicated gradually decreased dye efflux which was proportional to the P-gp expression. We observed that K562/Dox cells overexpressing P-gp contained a significantly reduced intracellular level of nilotinib when compared to their counter partner K562 cells, which do not express P-gp. This effect was accompanied by a decreased sensitivity of the K562/Dox cells to nilotinib. Importantly, cells with downregulated expression of P-gp gradually lost their ability to decrease the intracellular level of nilotinib although they still significantly decreased the intracellular level of daunorubicin (DNR). Accordingly, cells with the reduced expression of P-gp concomitantly failed to provide resistance to nilotinib, however, they exhibited a significant resistance to DNR. Taken together, we demonstrated that the conclusion as to whether P-gp is involved in nilotinib resistance or not strongly depends on its expression at protein level.

Kosztyu P; Dolezel P; Mlejnek P

2013-01-01

93

Can P-glycoprotein mediate resistance to nilotinib in human leukaemia cells?  

Science.gov (United States)

The effect of P-glycoprotein (P-gp, ABCB1, MDR1) expression on cell resistance to nilotinib was studied in human leukaemia cells. We used K562/Dox cells overexpressing P-gp and their variants (subclones) with a gradually decreased P-gp expression. These subclones were established by stable transfection of K562/Dox cells with a plasmid vector expressing shRNA targeting the ABCB1 gene. Functional analysis of P-gp using a specific fluorescent probe indicated gradually decreased dye efflux which was proportional to the P-gp expression. We observed that K562/Dox cells overexpressing P-gp contained a significantly reduced intracellular level of nilotinib when compared to their counter partner K562 cells, which do not express P-gp. This effect was accompanied by a decreased sensitivity of the K562/Dox cells to nilotinib. Importantly, cells with downregulated expression of P-gp gradually lost their ability to decrease the intracellular level of nilotinib although they still significantly decreased the intracellular level of daunorubicin (DNR). Accordingly, cells with the reduced expression of P-gp concomitantly failed to provide resistance to nilotinib, however, they exhibited a significant resistance to DNR. Taken together, we demonstrated that the conclusion as to whether P-gp is involved in nilotinib resistance or not strongly depends on its expression at protein level. PMID:23103446

Kosztyu, Petr; Dolezel, Petr; Mlejnek, Petr

2012-10-26

94

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

95

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 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 domain 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 (more) 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.

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

1999-08-01

96

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 domain 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.

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

1999-01-01

97

[Multidrug-resistant tuberculosis].  

UK PubMed Central (United Kingdom)

The emergence and spread of Mycobacterium tuberculosis strains resistant to multiple drugs represent a threat for global tuberculosis control. The World Health Organization (WHO) estimates that almost 500,000 cases of M. tuberculosis resistant to isoniazid and rifampicin (multidrug-resistant, or MDR-TB), at least, emerged in 2006. In addition, new cases of extensively drug-resistant tuberculosis (XDR-TB), defined as MDR-TB with resistance to a fluoroquinolone and at least one second line injectable agent, have been reported in 45 countries in all five continents. Multidrug-resistant tuberculosis is an emerging problem in Spain but the impact of this disease is limited: the WHO estimates that 0.1% of new cases of tuberculosis and 4.3% of previously treated cases are MDR-TB. Treatment of MDR-TB is especially complicated, since this disease requires the use of drugs that are less effective and more toxic, requiring treatment to be administered over longer periods and severely reducing the probability of success. This situation poses a serious problem for low income countries, especially those with a high prevalence of human immunodeficiency virus type 1 (HIV-1) infection. MDR-TB and XDR-TB are also of special concern in wealthy countries, due to mass immigration. Therefore, tuberculosis resistant to multiple drugs should be given high priority in global public health and biomedical research.

Alcaide F; Santín M

2008-11-01

98

[Multidrug-resistant tuberculosis].  

Science.gov (United States)

The emergence and spread of Mycobacterium tuberculosis strains resistant to multiple drugs represent a threat for global tuberculosis control. The World Health Organization (WHO) estimates that almost 500,000 cases of M. tuberculosis resistant to isoniazid and rifampicin (multidrug-resistant, or MDR-TB), at least, emerged in 2006. In addition, new cases of extensively drug-resistant tuberculosis (XDR-TB), defined as MDR-TB with resistance to a fluoroquinolone and at least one second line injectable agent, have been reported in 45 countries in all five continents. Multidrug-resistant tuberculosis is an emerging problem in Spain but the impact of this disease is limited: the WHO estimates that 0.1% of new cases of tuberculosis and 4.3% of previously treated cases are MDR-TB. Treatment of MDR-TB is especially complicated, since this disease requires the use of drugs that are less effective and more toxic, requiring treatment to be administered over longer periods and severely reducing the probability of success. This situation poses a serious problem for low income countries, especially those with a high prevalence of human immunodeficiency virus type 1 (HIV-1) infection. MDR-TB and XDR-TB are also of special concern in wealthy countries, due to mass immigration. Therefore, tuberculosis resistant to multiple drugs should be given high priority in global public health and biomedical research. PMID:19100168

Alcaide, Fernando; Santín, Miguel

2008-11-01

99

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

UK PubMed Central (United Kingdom)

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.

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

2013-01-01

100

Interaction of CJZ3, a lomerizine derivative, with ATPase activity of human P-glycoprotein in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells.  

Science.gov (United States)

P-Glycoprotein, a 170-180 kDa membrane glycoprotein that mediates multidrug resistance, hydrolyses ATP to efflux a broad spectrum of hydrophobic agents. To observe the interaction of a P-gp reversal agent with P-gp ATPase activity should provide further insights into the mechanisms of P-gp modulator. In this study, we analysed the effect of CJZ3, a lomerizine derivative, on the adenosine triphosphatase (ATPase) activity of human P-glycoprotein. The results showed that the basal P-gp ATPase activity was increased by CJZ3 with half-maximal activity concentration (Km) of 6.8 +/- 1.5 microM, CJZ3 may interact with P-gp with a higher affinity and exhibit a more potent effect than verapamil (Ver). Kinetic analysis indicated a noncompetitive inhibition of Ver-stimulated P-gp ATPase activity and a competitive inhibition of CJX2-stimulated P-gp ATPase activity by CJZ3, moreover, the effect of CsA on CJZ3-stimulated and Ver-stimulated P-gp ATPase activity showed a non-competitive and a competitive inhibition respectively. CJZ3 and CJX2 can bind P-gp either on overlapping sites or distinct but interacting sites, while CJZ3 and Ver as well as CsA can bind P-gp on separated sites in K562/DOX cells. PMID:20662321

Ji, Bian-Sheng; Li, Ming; He, Ling

2010-07-01

 
 
 
 
101

Interaction of CJZ3, a lomerizine derivative, with ATPase activity of human P-glycoprotein in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells.  

UK PubMed Central (United Kingdom)

P-Glycoprotein, a 170-180 kDa membrane glycoprotein that mediates multidrug resistance, hydrolyses ATP to efflux a broad spectrum of hydrophobic agents. To observe the interaction of a P-gp reversal agent with P-gp ATPase activity should provide further insights into the mechanisms of P-gp modulator. In this study, we analysed the effect of CJZ3, a lomerizine derivative, on the adenosine triphosphatase (ATPase) activity of human P-glycoprotein. The results showed that the basal P-gp ATPase activity was increased by CJZ3 with half-maximal activity concentration (Km) of 6.8 +/- 1.5 microM, CJZ3 may interact with P-gp with a higher affinity and exhibit a more potent effect than verapamil (Ver). Kinetic analysis indicated a noncompetitive inhibition of Ver-stimulated P-gp ATPase activity and a competitive inhibition of CJX2-stimulated P-gp ATPase activity by CJZ3, moreover, the effect of CsA on CJZ3-stimulated and Ver-stimulated P-gp ATPase activity showed a non-competitive and a competitive inhibition respectively. CJZ3 and CJX2 can bind P-gp either on overlapping sites or distinct but interacting sites, while CJZ3 and Ver as well as CsA can bind P-gp on separated sites in K562/DOX cells.

Ji BS; Li M; He L

2010-07-01

102

Effect of mitoxantrone liposomes on multidrug-resistant breast cancer cells.  

UK PubMed Central (United Kingdom)

A major obstacle in efficacy of breast cancer chemotherapy is the emergence of multidrug resistance. We investigated modulation of multidrug resistance by liposome-encapsulated mitoxantrone in a drug resistant human breast MCF7R cell line and the influence of liposome composition. Neutral high phase-transition temperature and anionic low phase-transition temperature phospholipid liposomes, reduced the resistance factor from 142 to 15 and 38, respectively. The higher cytotoxicity obtained with mitoxantrone-encapsulation was not necessarily related to higher intracellular uptake. Our data suggest that liposomes, according to their lipid composition, may alter the P-glycoprotein function by plasma membrane stabilization and modulate multidrug resistance in human cancer.

Poujol S; Tilleul P; Astre C; Martel P; Fabbro M; Pinguet F

1999-07-01

103

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 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 medicame (more) nto 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 activation, 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 stress (more) ed: (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.

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

2005-06-01

104

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; Sanchaita Sinha; Singh N

2010-01-01

105

Clinical imaging of multidrug resistance in cancer  

Energy Technology Data Exchange (ETDEWEB)

The most well-characterized mechanism of multidrug resistance (MDR) involves P-glycoprotein (Pgp), a transmembrane protein acting as an ATP-dependent drug efflux pump. The recognition of {sup 9}9mTc-Sestamibi and other lipophilic cations as transport substrates for Pgp provided the necessary tool for the clinical assessment of Pgp function in patients with cancer. Many clinical studies from different institutions and trials including variety of malignancies indicate that both tumor uptake and clearance of {sup 9}9mTc-Sestamibi are correlate with Pgp expression and may be used for the phenotypic assessment of multidrug resistance. Although both parameters may predict tumor responsible to chemotherapy, the extraction of efflux rate constants appeared o provide a more direct index of Pgp function as compared tp tracer uptake ratio allowing to trace a continuous spectrum of drug transport activity. Preliminary studies the use of MDR imaging agents to monitor the modulating ability of revertant compounds. Although the results support the feasibility of this approach, the alteration of tracer pharmacokinetics induced by the modulators certainly constitute a challenge in the development of a simple functional test suitable in clinical practice. The extension of the acquired imaging methodology to tumors with redundant intrinsic resistant mechanism. Due to multifactorial nature of phenomenon, the development of new tracers with substrate specificity for other known the complex array of cellular mechanisms contributing to treatment failure.

Del Vecchi, S.; Ciarmiello, A.; Salvatore, M. [Naples Univ. Federico 2. (Italy). Medicina Nucleare. Dipt. di Scienze Biomorfologiche e Funzionali

1999-06-01

106

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.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. Estudos 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.

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

2001-01-01

107

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

Scientific Electronic Library Online (English)

Full Text Available 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. Estudos de mecanismos de resistência múltipla a fármacos têm dependido da análise de linhagens celulares tumorais que foram selecionadas e apresentam reatividade (more) 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 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 (more) 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.; TRINDADE, GILMA S.; WAGNER-SOUZA, KAREN; MELETTI-DE-OLIVEIRA, MICHELE C.; MARQUES-SANTOS, LUIS F.; MAIA, RAQUEL C.; CAPELLA, MÁRCIA A. M.

2001-03-01

108

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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), t...

Limtrakul Pornngarm; Anuchapreeda Songyot; Buddhasukh Duang

109

Involvement of Multidrug Resistance-Associated Protein 2 in Intestinal Secretion of Grepafloxacin in Rats  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigated the contribution of multidrug resistance-associated protein 2 (MRP2) to the secretory transport of grepafloxacin and compared its functional role with that of P-glycoprotein (P-gp) by using Sprague-Dawley rats (SDRs) and Eisai hyperbilirubinemic rats (EHBRs), in which MRP2 is heredit...

Naruhashi, Kazumasa; Tamai, Ikumi; Inoue, Natsuko; Muraoka, Hiromi; Sai, Yoshimichi; Suzuki, Nagao; Tsuji, Akira

110

Evaluation of toremifene for reversal of multidrug resistance in renal cell cancer patients treated with vinblastine.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Expression of P-glycoprotein (Pgp), which confers the multidrug resistance (MDR) phenotype, is thought to contribute to the insensitivity of renal cell cancer (RCC) to chemotherapy. The development of Pgp inhibitors for clinical application has been hampered by unacceptable toxicity at doses require...

Braybrooke, JP; Vallis, KA; Houlbrook, S; Rockett, H; Ellmén, J

111

Synthesis of 5-oxyquinoline derivatives for reversal of multidrug resistance  

Directory of Open Access Journals (Sweden)

Full Text Available The inhibition of ABC (ATP binding cassette) transporters is considered a powerful tool to reverse multidrug resistance. Zosuquidar featuring a difluorocyclopropyl-annulated dibenzosuberyl moiety has been found to be an inhibitor of the P-glycoprotein, one of the best-studied multidrug efflux pumps. Twelve 5-oxyisoquinoline derivatives, which are analogues of zosuquidar wherein the dibenzosuberyl-piperazine moiety is replaced by either a diarylaminopiperidine or a piperidone-derived acetal or thioacetal group, have been synthesized as pure enantiomers. Their inhibitory power has been evaluated for the bacterial multidrug-resistance ABC transporter LmrCD and fungal Pdr5. Four of the newly synthesized compounds reduced the transport activity to a higher degree than zosuquidar, being up to fourfold more efficient than the lead compound in the case of LmrCD and about two times better for Pdr5.

Torsten Dittrich; Nils Hanekop; Nacera Infed; Lutz Schmitt; Manfred Braun

2012-01-01

112

Low-level doxorubicin resistance in P-glycoprotein-negative human pancreatic tumour PSN1/ADR cells implicates a brefeldin A-sensitive mechanism of drug extrusion.  

Science.gov (United States)

The human pancreatic tumour cell line PSN1/ADR, stepwise selected in 17-510 nM doxorubicin, displayed a multidrug resistance not conferred by P-glycoprotein (P-gp). Resistance to 17-51 nM doxorubicin was accompanied by overexpression of the vesicular marker lung resistance-related protein (LRP). Further selection in 170 nM doxorubicin led to the activation of multidrug resistance-associated protein (MRP) and to the development of drug accumulation/retention defects sensitive to verapamil. In addition, these defects were reversible by the vesicular traffic inhibitors brefeldin A, fluoroaluminate and nocodazole. In contrast, in human ovarian H134AD cells that are resistant to 1700 nM doxorubicin and used as P-gp-positive controls, the drug efflux was inhibited only by verapamil. The tyrosine kinase inhibitor genistein was a potent blocker of doxorubicin efflux in the PSN1/ADR cells but showed no activity in the H134 AD cells. The doxorubicin cytotoxicity in the PSN1/ADR cells was enhanced both by verapamil and brefeldin A, whereas in the parental PSN1 cells they demonstrated the opposite effects, being respectively sensitising and protecting. The P-gp-negative PSN1/ADR cells adapted to 510 nM doxorubicin retained brefeldin A-sensitive doxorubicin accumulation defects while MRP declined. The persistence of brefeldin A-responsive phenotype on the background of variable MRP expression suggests this agent as a useful functional probe for non-P-gp-mediated resistance to plasma-achievable doxorubicin concentrations. Images Figure 2

Verovski, V. N.; Van den Berge, D. L.; Delvaeye, M. M.; Scheper, R. J.; De Neve, W. J.; Storme, G. A.

1996-01-01

113

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

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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.

Sylwia Borska; Miroslaw Sopel; Magdalena Chmielewska; Maciej Zabel; Piotr Dziegiel

2010-01-01

114

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.

Zager Ellen M; McNerney Ruth

2008-01-01

115

Multidrug-resistant tuberculosis.  

Science.gov (United States)

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. PMID:23477764

Lemos, Antônio Carlos Moreira; Matos, Eliana Dias

2013-03-09

116

Multidrug-resistant tuberculosis  

Directory of Open Access Journals (Sweden)

Full Text Available 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

2013-01-01

117

Multidrug-resistant tuberculosis.  

UK PubMed Central (United Kingdom)

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.

Lemos AC; Matos ED

2013-03-01

118

Multidrug-resistant tuberculosis  

Scientific Electronic Library Online (English)

Full Text Available 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 (more) 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.

Lemos, Antônio Carlos Moreira; Matos, Eliana Dias

2013-04-01

119

Reversing resistance of multidrug-resistant hepatic carcinoma cells with parthenolide.  

UK PubMed Central (United Kingdom)

AIM: To investigate the mechanism of reversing resistance of a hepatic carcinoma multidrug-resistant cell BEL-7402/5-FU with parthenolide (PTL). MATERIALS & METHODS: BEL-7402/5-FU cells were treated with different concentrations of PTL and/or 5-fluorouracil. The proliferation inhibition rates, NF-?B, P-glycoprotein, MRP, Bcl-2, WNT1 and p53 levels were determined. RESULTS: The results showed that PTL did not only have proliferation inhibition influence on BEL-7402/5-FU in a concentration-dependent manner, but also significantly increased the proliferation inhibition role of 5-fluorouracil on BEL-7402/5-FU, to reverse the resistance of hepatic carcinoma-resistant cells. PTL could also inhibit the NF-?B activity and the expression of P-glycoprotein, MRP, Bcl-2 and WNT1, and increase the expression of p53. CONCLUSION: Our research suggests that clinical administration of PTL may be useful for hepatic carcinoma patients.

Liu D; Liu Y; Liu M; Ran L; Li Y

2013-04-01

120

Structure and expression of the human MDR (P-glycoprotein) gene family.  

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The human MDR (P-glycoprotein) gene family is known to include two members, MDR1 and MDR2. The product of the MDR1 gene, which is responsible for resistance to different cytotoxic drugs (multidrug resistance), appears to serve as an energy-dependent efflux pump for various lipophilic compounds. The ...

Chin, J E; Soffir, R; Noonan, K E; Choi, K; Roninson, I B

 
 
 
 
121

Nocardioazines: a novel bridged diketopiperazine scaffold from a marine-derived bacterium inhibits P-glycoprotein.  

UK PubMed Central (United Kingdom)

An Australian marine sediment-derived isolate, Nocardiopsis sp. (CMB-M0232), yielded a new class of prenylated diketopiperazine, indicative of the action of a uniquely regioselective diketopiperazine indole prenyltransferase. The bridged scaffold of nocardioazine A proved to be a noncytotoxic inhibitor of the membrane protein efflux pump P-glycoprotein, reversing doxorubicin resistance in a multidrug resistant colon cancer cell.

Raju R; Piggott AM; Huang XC; Capon RJ

2011-05-01

122

Nocardioazines: a novel bridged diketopiperazine scaffold from a marine-derived bacterium inhibits P-glycoprotein.  

Science.gov (United States)

An Australian marine sediment-derived isolate, Nocardiopsis sp. (CMB-M0232), yielded a new class of prenylated diketopiperazine, indicative of the action of a uniquely regioselective diketopiperazine indole prenyltransferase. The bridged scaffold of nocardioazine A proved to be a noncytotoxic inhibitor of the membrane protein efflux pump P-glycoprotein, reversing doxorubicin resistance in a multidrug resistant colon cancer cell. PMID:21513295

Raju, Ritesh; Piggott, Andrew M; Huang, Xiao-Cong; Capon, Robert J

2011-04-22

123

[Multidrug resistance: diagnostic approaches and difficulties].  

UK PubMed Central (United Kingdom)

During the mid sixties scientists recognized that tumour cells can be resistant to a variety of chemotherapeutical drugs of different chemical structure simultaneously. They named this phenomenon multidrug resistance (MDR). Following this observation, number of in vitro and in vivo experiments proved that transmembrane proteins of the cell membrane are responsible for the mechanism. Many details of the underlying biochemical mechanisms were explored during the past decade. Nowadays the importance of MDR is well appreciated in different walks of medical science. MDR is an important problem during the treatment of many haematological conditions and solid organ tumors. Also, MDR is an important factor during immunosuppressant therapy of the transplanted patients. In spite of extensive research there are many uncertainties around MDR. This brief review describes the present options in the investigation of MDR. Based upon the MDR genotyping and expression level the likelihood of drug resistance may be predicted with reasonable accuracy. Additional information may be obtained by measuring the P-glycoprotein expression on the cell surface and the outward transport of test molecules from the cells. Although the tests described above provide significant help in predicting MDR or in the confirmation of existing MDR there is no consensus about the laboratory diagnosis.

Rideg O; Csutora P; Magyarlaki T; Teibert A; Nagy T; Kovács LG; Miseta A

2005-05-01

124

2D- and 3D-QSAR studies of a series of benzopyranes and benzopyrano[3,4b][1,4]-oxazines as inhibitors of the multidrug transporter P-glycoprotein.  

UK PubMed Central (United Kingdom)

The ATP-binding cassette efflux transporter P-glycoprotein (P-gp) is notorious for contributing to multidrug resistance in antitumor therapy. Due to its expression in many blood-organ barriers, it also influences the pharmacokinetics of drugs and drug candidates and is involved in drug/drug- and drug/nutrient interactions. However, due to lack of structural information the molecular basis of ligand/transporter interaction still needs to be elucidated. Towards this goal, a series of Benzopyranes and Benzopyrano[3,4b][1,4]oxazines have been synthesized and pharmacologically tested for their ability to inhibit P-gp mediated daunomycin efflux. Both quantitative structure-activity relationship (QSAR) models using simple physicochemical and novel GRID-independent molecular descriptors (GRIND) were established to shed light on the structural requirements for high P-gp inhibitory activity. The results from 2D-QSAR showed a linear correlation of vdW surface area (Å(2)) of hydrophobic atoms with the pharmacological activity. GRIND (3D-QSAR) studies allowed to identify important mutual distances between pharmacophoric features, which include one H-bond donor, two H-bond acceptors and two hydrophobic groups as well as their distances from different steric hot spots of the molecules. Activity of the compounds particularly increases with increase of the distance of an H-bond donor or a hydrophobic feature from a particular steric hot spot of the benzopyrane analogs.

Jabeen I; Wetwitayaklung P; Chiba P; Pastor M; Ecker GF

2013-02-01

125

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

Directory of Open Access Journals (Sweden)

Full Text Available 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<0.05), and the expression of the multidrug resistance gene and P-glycoprotein were significantly suppressed (p<0.05). The combination of curcumin and vincristine significantly inhibited xenograft growth. The expression of the multidrug resistance protein 1 and survivin genes was significantly reduced in xenografts of curcumin-treated mice and mice treated with both curcumin and vincristine relative to control mice. CONCLUSION: Curcumin has strong reversal effects on the multidrug resistance of human colon carcinoma in vitro and in vivo.

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

2013-01-01

126

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

Scientific Electronic Library Online (English)

Full Text Available 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 sur (more) vivin 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<0.05), and the expression of the multidrug resistance gene and P-glycoprotein were significantly suppressed (p<0.05). The combination of curcumin and vincristine significantly inhibited xenograft growth. The expression of the multidrug resistance protein 1 and survivin genes was significantly reduced in xenografts of curcumin-treated mice and mice treated with both curcumin and vincristine relative to control mice. CONCLUSION: Curcumin has strong reversal effects on the multidrug resistance of human colon carcinoma in vitro and in vivo.

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

2013-05-01

127

Effects of multidrug resistance gene expression in acute erythroleukemia.  

Science.gov (United States)

Acute erythroleukemia is a relatively rare disorder of a multilineal nature. Patients with this type of leukemia traditionally have been treated with a standard myeloid protocol, with a wide variation in prognosis between M6a, which has a similar prognosis to acute myelogenous leukemias, and M6b, with an extremely poor outcome despite aggressive therapy. Forty-eight archival cases of acute erythroleukemia, subtypes M6a (the traditional FAB-M6), M6b (pure erythroleukemia), and M6c (>30% myeloblasts and >30% pronormoblasts by FAB exclusion criteria), were evaluated for multidrug resistance gene (MDR-1) status. Findings were correlated with clinical course and karyotypes. Immunohistochemical stain for the protein product of MDR-1, P-glycoprotein, was variably positive in 11 of 23 patients with M6a, as well as in all of the patients with M6b (strongly positive) and M6c (weakly positive). P-glycoprotein expression positively correlated with unfavorable cytogenetic aberrations, poor response to chemotherapeutic agents, and short survival. Most significant was that P-glycoprotein expression demonstrated a negative additive effect on response to treatment and prognosis with unfavorable cytogenetic anomalies. P-glycoprotein expression and multiple cytogenetic anomalies most probably contribute to the resistance to chemotherapy and poor survival characteristic of the patients with M6b (mean survival, 3.15 +/- 4.2 mo) and M6c (mean survival, 10.5 +/- 12.7 mo). Because patients with M6b and M6c have increased numbers of pronormoblasts in their bone marrow and past chemotherapeutic attempts have failed, chemotherapy directed at these cells is appropriate. Additional therapy directed toward the MDR-1 gene and its protein product seems indicated from our findings. PMID:10786807

Mazzella, F M; Kowal-Vern, A; Shrit, M A; Rector, J T; Cotelingam, J D; Schumacher, H R

2000-04-01

128

Effects of multidrug resistance gene expression in acute erythroleukemia.  

UK PubMed Central (United Kingdom)

Acute erythroleukemia is a relatively rare disorder of a multilineal nature. Patients with this type of leukemia traditionally have been treated with a standard myeloid protocol, with a wide variation in prognosis between M6a, which has a similar prognosis to acute myelogenous leukemias, and M6b, with an extremely poor outcome despite aggressive therapy. Forty-eight archival cases of acute erythroleukemia, subtypes M6a (the traditional FAB-M6), M6b (pure erythroleukemia), and M6c (>30% myeloblasts and >30% pronormoblasts by FAB exclusion criteria), were evaluated for multidrug resistance gene (MDR-1) status. Findings were correlated with clinical course and karyotypes. Immunohistochemical stain for the protein product of MDR-1, P-glycoprotein, was variably positive in 11 of 23 patients with M6a, as well as in all of the patients with M6b (strongly positive) and M6c (weakly positive). P-glycoprotein expression positively correlated with unfavorable cytogenetic aberrations, poor response to chemotherapeutic agents, and short survival. Most significant was that P-glycoprotein expression demonstrated a negative additive effect on response to treatment and prognosis with unfavorable cytogenetic anomalies. P-glycoprotein expression and multiple cytogenetic anomalies most probably contribute to the resistance to chemotherapy and poor survival characteristic of the patients with M6b (mean survival, 3.15 +/- 4.2 mo) and M6c (mean survival, 10.5 +/- 12.7 mo). Because patients with M6b and M6c have increased numbers of pronormoblasts in their bone marrow and past chemotherapeutic attempts have failed, chemotherapy directed at these cells is appropriate. Additional therapy directed toward the MDR-1 gene and its protein product seems indicated from our findings.

Mazzella FM; Kowal-Vern A; Shrit MA; Rector JT; Cotelingam JD; Schumacher HR

2000-04-01

129

A Semisynthetic Taxane Yg-3-46a Effectively Evades P-glycoprotein and ?-III Tubulin Mediated Tumor Drug Resistance in vitro.  

UK PubMed Central (United Kingdom)

Tumor resistance, especially that mediated by P-glycoprotein (P-gp) and ?-III tubulin, is a major obstacle to the efficacy of most microtubule-targeting anticancer drugs in clinics. A novel semisynthetic taxane, 2-debenzoyl-2-(3-azidobenzyl)-10-propionyldocetaxel (Yg-3-46a) was shown to be highly cytotoxic to breast cancer cell lines MCF-7 and MCF/ADR which overexpressed P-gp via long term culture with doxorubicin, and cervical cancer cell lines Hela and Hela/?III which overexpressed ?III-tubulin via stable transfection with TUBB3 gene. siRNA transfection experiments also confirmed that Yg-3-46a can circumvent P-gp and ?-III tubulin mediated drug resistance. In addition, its cytotoxicity was lower than that of paclitaxel in the human mammary cell line HBL-100 and the human telomerase-immortalized retinal pigment epithelium cell line (hTERT-RPE1), suggesting a better safety margin for this compound in vivo. It exhibited more potent microtubule polymerization ability than paclitaxel in vitro, and also induced G2/M phase arrest in MCF-7/ADR cells. Moreover, it was found to induce apoptosis in MCF-7/ADR cells through the caspase-dependent death-receptor pathway by enhancing levels of Fas and FasL, and activating caspase-8 and 3. Yg-3-46a was found to be a poorer substrate of P-gp compared to paclitaxel, in both binding and ATPase experiments, which is likely responsible for its ability to circumvent P-gp mediated multidrug resistance (MDR). All of these results indicate that Yg-3-46a is a novel microtubule-stabilizing agent that has the potential to evade drug resistance mediated by P-gp and ?-III tubulin overexpression.

Cai P; Lu P; Sharom FJ; Fang WS

2013-08-01

130

Rapid up-regulation of mdr1 expression by anthracyclines in a classical multidrug-resistant cell line.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studies were carried out in a variant human multidrug-resistant (MDR) cell line CEM/A7R, which expresses very low levels of mdr1 mRNA and P-glycoprotein (P-gp). The induction of mdr1 RNA expression by three anthracyclines, (doxorubicin, daunorubicin, epirubicin), VP-16 and two vinca alkaloids (vincr...

Hu, X. F.; Slater, A.; Wall, D. M.; Kantharidis, P.; Parkin, J. D.; Cowman, A.; Zalcberg, J. R.

131

The three mouse multidrug resistance (mdr) genes are expressed in a tissue-specific manner in normal mouse tissues.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The gene responsible for multidrug resistance (mdr), which encodes the P-glycoprotein, is a member of a multigene family. We have identified distinct mdr gene transcripts encoded by three separate mdr genes in the mouse. Expression levels of each mdr gene are dramatically different in various mouse ...

Croop, J M; Raymond, M; Haber, D; Devault, A; Arceci, R J; Gros, P; Housman, D E

132

Direct interaction between verapamil and doxorubicin causes the lack of reversal effect of verapamil on P-glycoprotein mediated resistance to doxorubicin in vitro using L1210/VCR cells  

International Nuclear Information System (INIS)

Mouse leukemic cell sub-line L 1210/VCR exerts expressive multidrug resistance (MDR) that is mediated by P-glycoprotein. Cells originally adapted to vincristine are also extremely resistant to doxorubicin. Resistance to both vincristine and doxorubicin is connected with depression of drug uptake. While resistance of L 121 O cells to vincristine could be reversed by verapamil as chemo-sensitizer, resistance of cells to doxorubicin was insensitive to verapamil. Action of verapamil (well-known inhibitor of PGP activity) on multidrug resistance was often used as evidence that MDR is mediated by PGP. From this point it may be possible that the resistance of L1210/VCR cells to vincristine is mediated by PGP and the resistance to doxorubicin is mediated by other PGP-independent system. Another and more probable explanation of different effect of verapamil on resistance of L1210/VCR cells to vincristine and doxorubicin may be deduced from the following fact: Using UV spectroscopy we found that doxorubicin dissolved in water buffered medium interacts effectively with verapamil. This interaction may be responsible for the decrease of concentration of both drugs in free effective form and consequently for higher survival of cells. In contrast to doxorubicin vincristine does not give any interaction with verapamil that is measurable by UV spectroscopy and resistance of L1210/VCR cells to vincristine may be fully reversed by verapamil. (authors)

1998-01-01

133

Enhanced absorption of pour-on ivermectin formulation in rats by co-administration of the multidrug-resistant-reversing agent verapamil.  

UK PubMed Central (United Kingdom)

The effect of verapamil, a multidrug-resistance (Mdr)-reversing agent on the absorption of a pour-on formulation of ivermectin was evaluated in rats. Absorption of ivermectin was effectively enhanced (40%) by the presence of verapamil, suggesting that absorption of ivermectin involves Mdr-P-glycoprotein and that verapamil should act as a competitive inhibitor for the transport and extrusion of ivermectin by P-glycoprotein. This hypothesis is consistent with other studies describing verapamil as a blocking agent of P-glycoprotein involved in the efflux of ivermectin in a resistant strain of Haemonchus contortus.

Alvinerie M; Dupuy J; Eeckhoutte C; Sutra JF

1999-11-01

134

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 o...

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

135

Nanoparticles attenuate P-glycoprotein/MDR1 function in A549 human alveolar epithelial cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

P-glycoprotein/MDR1 (P-gp) is a well characterised membrane transporter relevant in drug disposition and multi-drug resistance. In this study, we aimed to investigate in how far nanoparticulates impair the function of the P-gp transport system, and which particle properties govern these interactions...

EHRHARDT, CARSTEN

136

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

UK PubMed Central (United Kingdom)

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.

Liu R; Zhang Y; Chen Y; Qi J; Ren S; Xushi MY; Yang C; Zhu H; Xiong D

2010-07-01

137

Effect of Thai plant extracts on P-glycoprotein function and viability in paclitaxel-resistant HepG2 cells.  

UK PubMed Central (United Kingdom)

The effects of ethanol extracts from Thai plants on P-glycoprotein (P-gp) function and cell viability were examined using paclitaxel-resistant HepG2 (PR-HepG2) cells. KP018 from Ellipeiopsis cherrevensis and AT80 from Ancistrocladus tectorius increased both rhodamine 123, a typical P-gp substrate, and [(3)H]paclitaxel uptake in PR-HepG2 cells. However, some extracts such as MT80 from Microcos tomentosa increased rhodamine 123, but not [(3)H]paclitaxel, uptake, while MM80 from Micromelum minutum increased only [(3)H]paclitaxel uptake. Thus, the effects of extracts of Thai plants on rhodamine 123 uptake were not necessarily the same as those on [(3)H]paclitaxel uptake. Purified compounds such as bergapten did not affect the uptake of either substrate. KP018, AT80, and MM80 increased [(3)H]paclitaxel uptake and decreased the cell viability in a concentration-dependent manner. Among these extracts, KP018 showed the most potent cytotoxicity. The cytotoxic potency of KP018 on PR-HepG2 cells was similar to that on wild-type HepG2 cells, and was not potentiated by verapamil. At concentrations resulting in no cytotoxicity, AT80 and MM80 potentiated paclitaxel-induced cytotoxicity in PR-HepG2 cells. These results indicate that K018 may be a useful source to search for a new anticancer drug, while AT80 and MM80 may be useful as modulators of P-gp-mediated multidrug resistance in cancer cells.

Kawami M; Yumoto R; Nagai J; Junyaprasert VB; Soonthornchareonnon N; Patanasethanont D; Sripanidkulchai BO; Takano M

2010-01-01

138

Olomoucine II, but Not Purvalanol A, Is Transported by Breast Cancer Resistance Protein (ABCG2) and P-Glycoprotein (ABCB1)  

Science.gov (United States)

Purine cyclin-dependent kinase inhibitors have been recognized as promising candidates for the treatment of various cancers; nevertheless, data regarding interaction of these substances with drug efflux transporters is still lacking. Recently, we have demonstrated inhibition of breast cancer resistance protein (ABCG2) by olomoucine II and purvalanol A and shown that these compounds are able to synergistically potentiate the antiproliferative effect of mitoxantrone, an ABCG2 substrate. In this follow up study, we investigated whether olomoucine II and purvalanol A are transported by ABCG2 and ABCB1 (P-glycoprotein). Using monolayers of MDCKII cells stably expressing human ABCB1 or ABCG2, we demonstrated that olomoucine II, but not purvalanol A, is a dual substrate of both ABCG2 and ABCB1. We, therefore, assume that pharmacokinetics of olomoucine II will be affected by both ABCB1 and ABCG2 transport proteins, which might potentially result in limited accumulation of the compound in tumor tissues or lead to drug-drug interactions. Pharmacokinetic behavior of purvalanol A, on the other hand, does not seem to be affected by either ABCG2 or ABCB1, theoretically favoring this drug in the potential treatment of efflux transporter-based multidrug resistant tumors. In addition, we observed intensive sulfatation of olomoucine II in MDCKII cell lines with subsequent active efflux of the metabolite out of the cells. Therefore, care should be taken when performing pharmacokinetic studies in MDCKII cells, especially if radiolabeled substrates are used; the generated sulfated conjugate may largely contaminate pharmacokinetic analysis and result in misleading interpretation. With regard to chemical structures of olomoucine II and purvalanol A, our data emphasize that even drugs with remarkable structure similarity may show different pharmacokinetic behavior such as interactions with ABC transporters or biotransformation enzymes.

Hofman, Jakub; Kucera, Radim; Cihalova, Daniela; Klimes, Jiri; Ceckova, Martina; Staud, Frantisek

2013-01-01

139

[Expression of breast cancer resistance protein and p-glycoprotein in residual breast cancer tissue after chemotherapy and its correlation with cancer stem cells].  

UK PubMed Central (United Kingdom)

OBJECTIVE: To compare the expression differences of breast cancer resistance protein(BCRP/ABCG2) and P-glycoprotein(P-gp) in breast cancer tissue before chemotherapy and in residual breast cancer tissue, and to explore its correlation with breast cancer stem cells. METHODS: Immunohistochemistry was used to detect the expression of ABCG2, P-gp, and breast cancer stem cells(BCSCs) markers(CD44 and CD24) in breast cancer tissue before chemotherapy and residual breast cancer tissue after chemotherapy. Immunofluorescence was applied for determination of the CD44 and CD24 protein expressions of BCSCs microspheres cells. The monoclone-forming ability of BCSCs microspheres cells was detected by limited dilution assay. The expressions of ABCG2, P-gp, CD44, and CD24 proteins were detected by Western blot. RESULTS: Compared with those in breast cancer tissue before chemotherapy, the expression levels of ABCG2 and P-gp were positively correlated with the expression level of CD44 protein(?(2)=41.34, r=0.83;?(2)=22.81, r=0.61) in residual breast cancer tissue after chemotherapy;meanwhile, they were negatively correlated with the expression of CD24 protein(?(2)=-21.25, r=0.72;?(2)=-17.26, r=0.65) (all P<0.05) .The diameter of BCSCs microspheres were increased significantly after chemotherapy.The content of BCSCs increased by about 2.5 times after chemotherapy.The expressions of ABCG2, P-gp and CD44 proteins significantly increased and that of CD24 protein significantly declined(P<0.05) . CONCLUSION: Chemotherapy endows residual breast cancer tissue with cancer stem cells-like features, leading to multidrug resistance of breast cancer.

Qu HB; Fan YM; Han ML; Luo HJ; Xie J; Liu H; Liu H; Wu CY; Tang WX

2013-04-01

140

P-glycoprotein (MDR1/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) restrict brain accumulation of the JAK1/2 inhibitor, CYT387.  

UK PubMed Central (United Kingdom)

CYT387 is an orally bioavailable, small molecule inhibitor of Janus family of tyrosine kinases (JAK) 1 and 2. It is currently undergoing Phase I/II clinical trials for the treatment of myelofibrosis and myeloproliferative neoplasms. We aimed to establish whether the multidrug efflux transporters P-glycoprotein (P-gp; MDR1; ABCB1) and breast cancer resistance protein (BCRP;ABCG2) restrict oral availability and brain penetration of CYT387. In vitro, CYT387 was efficiently transported by both human MDR1 and BCRP, and very efficiently by mouse Bcrp1 and its transport could be inhibited by specific MDR1 inhibitor, zosuquidar and/or specific BCRP inhibitor, Ko143. CYT387 (10mg/kg) was orally administered to wild-type (WT), Bcrp1(-/-), Mdr1a/1b(-/-) and Bcrp1;Mdr1a/1b(-/-) mice and plasma and brain concentrations were analyzed. Over 8h, systemic exposure of CYT387 was similar between all the strains, indicating that these transporters do not substantially limit oral availability of CYT387. Despite the similar systemic exposure, brain accumulation of CYT387 was increased 10.5- and 56-fold in the Bcrp1;Mdr1a/1b(-/-) mice compared to the WT strain at 2 and 8h after CYT387 administration, respectively. In single Bcrp1(-/-) mice, brain accumulation of CYT387 was more substantially increased than in Mdr1a/1b(-/-) mice, suggesting that CYT387 is a slightly better substrate of Bcrp1 than of Mdr1a at the blood-brain barrier. These results indicate a marked and additive role of Bcrp1 and Mdr1a/1b in restricting brain penetration of CYT387, potentially limiting efficacy of this compound against brain (micro) metastases positioned behind a functional blood-brain barrier.

Durmus S; Xu N; Sparidans RW; Wagenaar E; Beijnen JH; Schinkel AH

2013-07-01

 
 
 
 
141

Effect of mitoxantrone liposomes on multidrug-resistant breast cancer cells.  

Science.gov (United States)

A major obstacle in efficacy of breast cancer chemotherapy is the emergence of multidrug resistance. We investigated modulation of multidrug resistance by liposome-encapsulated mitoxantrone in a drug resistant human breast MCF7R cell line and the influence of liposome composition. Neutral high phase-transition temperature and anionic low phase-transition temperature phospholipid liposomes, reduced the resistance factor from 142 to 15 and 38, respectively. The higher cytotoxicity obtained with mitoxantrone-encapsulation was not necessarily related to higher intracellular uptake. Our data suggest that liposomes, according to their lipid composition, may alter the P-glycoprotein function by plasma membrane stabilization and modulate multidrug resistance in human cancer. PMID:10652629

Poujol, S; Tilleul, P; Astre, C; Martel, P; Fabbro, M; Pinguet, F

142

Current Status on Marine Products with Reversal Effect on Cancer Multidrug Resistance  

Directory of Open Access Journals (Sweden)

Full Text Available The resistance of tumor cells to a broad range of anticancer agents continues to be a problem for the success of cancer chemotherapy. Multidrug resistance (MDR) is due in part to three drug transporter proteins: ABCB1/P-glycoprotein (P-gp), ABCC1/multidrug resistance protein 1 (MRP1) and ABCG2/breast cancer resistance protein (BCRP). These transporters are part of the ATP-binding cassette (ABC) superfamily, whose members function as ATP-dependent drug-efflux pumps. Their activity can be blocked by various drugs such as verapamil (calcium channel blocker) and cyclosporin A (immunosuppressive agent), etc. These compounds are called MDR modulators or reversals. This review highlights several marine natural products with reversal effect on multidrug resistance in cancer, including agosterol A, ecteinascidin 743, sipholane triterpenoids, bryostatin 1, and welwitindolinones.

Ioana Abraham; Khalid El Sayed; Zhe-Sheng Chen; Huiqin Guo

2012-01-01

143

Drugs reverting multidrug resistance (chemosensitizers)  

Energy Technology Data Exchange (ETDEWEB)

Drug resistance is a phenomenon that frequently impairs proper treatment of cancer. Multidrug resistance (MDR) is a particular case of acquired drug resistance, resulting from overexpression of a protein (P-170) that functions as a pump, clearing cells from the chemotherapic. The P-170 protein functions can be inhibited by a variety of lipophilic drugs containing a hydrophilic nitrogen, protonated at physiological pH. A considerable effort is underway to identify new drugs able to reverse MDR. Few of these molecules are already undergoing clinical trials.

Gualtieri, F. [Florence Univ. (Italy). Dip. di Scienze Farmaceutiche

1996-12-01

144

Phase IB study of doxorubicin in combination with the multidrug resistance reversing agent S9788 in advanced colorectal and renal cell cancer.  

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S9788 is a new triazineaminopiperidine derivate capable of reversing multidrug resistance (MDR) in cells resistant to chemotherapeutic agents such as doxorubicin. It does not belong to a known class of MDR revertants, but its action involves the binding of P-glycoprotein. Thirty-eight evaluable pati...

Punt, C. J.; Voest, E. E.; Tueni, E.; Van Oosterom, A. T.; Backx, A.; De Mulder, P. H.; Hecquet, B.; Lucas, C.; Gerard, B.

145

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

2013-01-23

146

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

UK PubMed Central (United Kingdom)

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.

Dulin JN; Moore ML; Grill RJ

2013-02-01

147

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

148

P-glycoprotein and breast cancer resistance protein in acute myeloid leukaemia cells treated with the Aurora-B Kinase Inhibitor barasertib-hQPA  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Aurora kinases play an essential role in orchestrating chromosome alignment, segregation and cytokinesis during mitotic progression, with both aurora-A and B frequently over-expressed in a variety of human malignancies. Over-expression of the ABC drug transporter proteins P-glycoprotein (Pgp) and Breast cancer resistance protein (BCRP) is a major obstacle for chemotherapy in many tumour types with Pgp conferring particularly poor prognosis in acute myeloid leukaemia (AML). Barasertib-hQPA is a highly selective inhibitor of aurora-B kinase that has shown tumouricidal activity against a range tumour cell lines including those of leukaemic AML origin. Methods Effect of barasertib-hQPA on the pHH3 biomarker and cell viability was measured in a panel of leukaemic cell lines and 37 primary AML samples by flow cytometry. Pgp status was determined by flow cytometry and BCRP status by flow cytometry and real-time PCR. Results In this study we report the creation of the cell line OCI-AML3DNR, which over-expresses Pgp but not BCRP or multidrug resistance-associated protein (MRP), through prolonged treatment of OCI-AML3 cells with daunorubicin. We demonstrate that Pgp (OCI-AML3DNR and KG-1a) and BCRP (OCI-AML6.2) expressing AML cell lines are less sensitive to barasertib-hQPA induced pHH3 inhibition and subsequent loss of viability compared to transporter negative cell lines. We also show that barasertib-hQPA resistance in these cell lines can be reversed using known Pgp and BCRP inhibitors. We report that barasertib-hQPA is not an inhibitor of Pgp or BCRP, but by using 14[C]-barasertib-hQPA that it is effluxed by these transporters. Using phosphoHistone H3 (pHH3) as a biomarker of barasertib-hQPA responsiveness in primary AML blasts we determined that Pgp and BCRP positive primary samples were less sensitive to barasertib-hQPA induced pHH3 inhibition (p = 50 inhibition of pHH3 by barasertib-hQPA was achieved in 94.6% of these samples after 1 hour drug treatment, in contrast to the resistance of the cell lines. Conclusion We conclude that Pgp and BCRP status and pHH3 down-regulation in patients treated with barasertib should be monitored in order to establish whether transporter-mediated efflux is sufficient to adversely impact on the efficacy of the agent.

Grundy Martin; Seedhouse Claire; Russell Nigel H; Pallis Monica

2011-01-01

149

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

150

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

UK PubMed Central (United Kingdom)

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.

Ishii K; Tanaka S; Kagami K; Henmi K; Toyoda H; Kaise T; Hirano T

2010-03-01

151

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

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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. Chromat...

Shengnan He; Feng Liu; Zhenhua Xie; Xuyu Zu; Wei Xu; Yuyang Jiang

152

Detection of expression and modulation of multidrug-resistance (MDR) and establishment of a new bioassay  

International Nuclear Information System (INIS)

The present thesis deals with the resistance of human malignant cells against cellular toxicity of anticancer drugs, a phenomenon representing one of the major obstacles to successful chemotherapy. One mechanism underlying a cross-resistance to different drugs called multidrug resistance (MDR) is characterized by the expression of an active transport protein (P-glycoprotein), causing decreased intracellular drug retention and cytotoxicity. The main subjects of the present work were to establish different detection methods for MDR and its modulation (by substances blocking activity of P-glycoprotein) including immunological methods (immunocytochemistry, radioimmunoassay), molecular biology (slot-blot analysis, in-situ hybridization) and functional assays (drug-accumulation analysis, drug-cytotoxicity analysis). The methods were evaluated and compared using human and mouse MDR control cell lines and human tumor cell lines established in our laboratory. In cell lines derived from human melanoma - a malignancy insensitive to chemotherapy - expression of P-glycoprotein of relatively low transporting activity was detected by different methods in 8 of 33 cases. Furthermore a new sensitive in vitro assay for the functional detection of MDR was established using the biological features of cytochalasins, a microfilament disrupting substance group. These compounds were shown to be substrates for the P-glycoprotein efflux pump and their effects on cell division (blockade of cytokinesis resulting in multinucleate cells) correlated with MDR-activity of the tested cells. With this new assay P-glycoprotein activity can be demonstrated and analysed over a wide range of resistance against different cytotoxic drugs. Therefore it may by a suitable tool for research and diagnosis in the field of drug resistance

1993-01-01

153

Vaults are up-regulated in multidrug-resistant cancer cell lines.  

Science.gov (United States)

Vaults are 13-MDa ribonucleoprotein particles composed largely of a 104-kDa protein, termed major vault protein or MVP, and a small vault RNA, vRNA. While MVP levels have been found to increase up to 15-fold in non-P-glycoprotein multidrug-resistant cell lines, the levels of vault particles have not been investigated. As both the function of vault particles and the mechanism of drug resistance in non-P-glycoprotein cells are unknown, we decided to determine whether vault synthesis was coupled to MDR. By cloning the human gene for vRNA and careful quantitation of the MVP and vRNA levels in MDR cells, we find that vRNA is in considerable excess to MVP. Sedimentation measurements of vault particles in multidrug resistance cells have indeed revealed up to a 15-fold increase in vault synthesis, coupled with a comparable shift of associated vRNA, demonstrating that vault formation is limited by expression of MVP or the minor vault proteins. The observation that vault synthesis is linked directly to multidrug resistance supports a direct role for vaults in drug resistance. PMID:9535882

Kickhoefer, V A; Rajavel, K S; Scheffer, G L; Dalton, W S; Scheper, R J; Rome, L H

1998-04-10

154

Vaults are up-regulated in multidrug-resistant cancer cell lines.  

UK PubMed Central (United Kingdom)

Vaults are 13-MDa ribonucleoprotein particles composed largely of a 104-kDa protein, termed major vault protein or MVP, and a small vault RNA, vRNA. While MVP levels have been found to increase up to 15-fold in non-P-glycoprotein multidrug-resistant cell lines, the levels of vault particles have not been investigated. As both the function of vault particles and the mechanism of drug resistance in non-P-glycoprotein cells are unknown, we decided to determine whether vault synthesis was coupled to MDR. By cloning the human gene for vRNA and careful quantitation of the MVP and vRNA levels in MDR cells, we find that vRNA is in considerable excess to MVP. Sedimentation measurements of vault particles in multidrug resistance cells have indeed revealed up to a 15-fold increase in vault synthesis, coupled with a comparable shift of associated vRNA, demonstrating that vault formation is limited by expression of MVP or the minor vault proteins. The observation that vault synthesis is linked directly to multidrug resistance supports a direct role for vaults in drug resistance.

Kickhoefer VA; Rajavel KS; Scheffer GL; Dalton WS; Scheper RJ; Rome LH

1998-04-01

155

Are altered pHi and membrane potential in hu MDR 1 transfectants sufficient to cause MDR protein-mediated multidrug resistance?  

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Multidrug resistance (MDR) mediated by overexpression of the MDR protein (P-glycoprotein) has been associated with intracellular alkalinization, membrane depolarization, and other cellular alterations. However, virtually all MDR cell lines studied in detail have been created via protocols that invol...

156

Differential recognition of mdr1a and mdr1b gene products in multidrug resistant mouse tumour cell lines by different monoclonal antibodies.  

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An immunocytochemical method was used to test the reactivity of the anti-P-glycoprotein antibodies, C219, MRK 16, JSB-1 and 265/F4 against multidrug resistant (MDR) variants derived from the human small cell lung carcinoma line, NCI-H69, the mouse fibrosarcoma line, RIF-1 and the mouse mammary tumou...

Barrand, M. A.; Twentyman, P. R.

157

Amplification and expression of mdr1 gene in a multidrug resistant variant of small cell lung cancer cell line NCI-H69.  

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Amplification and expression of the mdr1 gene encoding P-glycoprotein have been studied in H69/LX4 a multidrug resistant variant (MDR) of small cell lung cancer (SCLC) cell line NCI-H69. Recently a second independently derived MDR variant of this cell line designated H69/AR was found by others not t...

Reeve, J. G.; Rabbitts, P. H.; Twentyman, P. R.

158

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

International Nuclear Information System (INIS)

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

1997-01-01

159

Enhancement of cellular uptake and cytotoxicity of curcumin-loaded PLGA nanoparticles by conjugation with anti-P-glycoprotein in drug resistance cancer cells.  

UK PubMed Central (United Kingdom)

AIM: To compare the anti-cancer activity and cellular uptake of curcumin (Cur) delivered by targeted and non-targeted drug delivery systems in multidrug-resistant cervical cancer cells. METHODS: Cur was entrapped into poly (DL-lactide-co-glycolide) (PLGA) nanoparticles (Cur-NPs) in the presence of modified-pluronic F127 stabilizer using nano-precipitation technique. On the surface of Cur-NPs, the carboxy-terminal of modified pluronic F127 was conjugated to the amino-terminal of anti-P-glycoprotein (P-gp) (Cur-NPs-APgp). The physical properties of the Cur-NPs, including particle size, zeta potential, particle morphology and Cur release kinetics, were investigated. Cellular uptake and specificity of the Cur-NPs and Cur-NPs-APgp were detected in cervical cancer cell lines KB-V1 (higher expression of P-gp) and KB-3-1 (lower expression of P-gp) using fluorescence microscope and flow cytometry, respectively. Cytotoxicity of the Cur-NPs and Cur-NPs-APgp was determined using MTT assay. RESULTS: The particle size of Cur-NPs and Cur-NPs-APgp was 127 and 132 nm, respectively. The entrapment efficiency and actual loading of Cur-NPs-APgp (60% and 5 ?g Cur/mg NP) were lower than those of Cur-NPs (99% and 7 ?g Cur/mg NP). The specific binding of Cur-NPs-APgp to KB-V1 cells was significantly higher than that to KB-3-1 cells. Cellular uptake of Cur-NPs-APgp into KB-V1 cells was higher, as compared to KB-3-1 cells. However, the cellular uptake of Cur-NPs and Cur-NPs-IgG did not differ between the two types of cells. Besides, the cytotoxicity of Cur-NPs-APgp in KB-V1 cells was higher than those of Cur and Cur-NPs. CONCLUSION: The results demonstrate that Cur-NPs-APgp targeted to P-gp on the cell surface membrane of KB-V1 cells, thus enhancing the cellular uptake and cytotoxicity of Cur.

Punfa W; Yodkeeree S; Pitchakarn P; Ampasavate C; Limtrakul P

2012-06-01

160

Management of multidrug resistant tuberculosis.  

UK PubMed Central (United Kingdom)

Drug-resistant strains of Mycobacterium tuberculosis have emerged as a major threat to global tuberculosis control. Despite the availability of curative antituberculosis therapy for nearly half a century, inappropriate and inadequate treatment has allowed M. tuberculosis to acquire resistance to our most important antituberculosis drugs. The epidemic of drug-resistant tuberculosis has spread quickly in some areas due to the convergence of resistant strains of M. tuberculosis in high-risk patients (e.g., those with human immunodeficiency virus/acquired immunodeficiency syndrome) and high-risk environments (e.g., hospitals and prisons). The World Health Organization (WHO) estimates that there were 650,000 cases of multidrug resistant tuberculosis (MDR-TB) in 2010, defined as strains that are resistant to at least isoniazid (INH) and rifampicin (RIF). Globally, WHO estimates that 3.7% of new tuberculosis cases and 20% of re-treatment cases have MDR-TB. By the end of 2012, 84 countries had reported at least one case of extensively drug resistant strains (XDR-TB), which are MDR-TB strains that have acquired additional resistance to fluoroquinolones and at least one second-line injectable. Recently, cases of "totally drug resistant" tuberculosis have been reported. It is estimated that only 10% of all MDR-TB cases are currently receiving therapy and only 2% are receiving quality-assured drugs. This article reviews the management of MDR and XDR-TB and highlights the updated 2011 WHO guidelines on the programmatic management of drug-resistant tuberculosis.

Daley CL; Caminero JA

2013-02-01

 
 
 
 
161

Management of multidrug resistant tuberculosis.  

Science.gov (United States)

Drug-resistant strains of Mycobacterium tuberculosis have emerged as a major threat to global tuberculosis control. Despite the availability of curative antituberculosis therapy for nearly half a century, inappropriate and inadequate treatment has allowed M. tuberculosis to acquire resistance to our most important antituberculosis drugs. The epidemic of drug-resistant tuberculosis has spread quickly in some areas due to the convergence of resistant strains of M. tuberculosis in high-risk patients (e.g., those with human immunodeficiency virus/acquired immunodeficiency syndrome) and high-risk environments (e.g., hospitals and prisons). The World Health Organization (WHO) estimates that there were 650,000 cases of multidrug resistant tuberculosis (MDR-TB) in 2010, defined as strains that are resistant to at least isoniazid (INH) and rifampicin (RIF). Globally, WHO estimates that 3.7% of new tuberculosis cases and 20% of re-treatment cases have MDR-TB. By the end of 2012, 84 countries had reported at least one case of extensively drug resistant strains (XDR-TB), which are MDR-TB strains that have acquired additional resistance to fluoroquinolones and at least one second-line injectable. Recently, cases of "totally drug resistant" tuberculosis have been reported. It is estimated that only 10% of all MDR-TB cases are currently receiving therapy and only 2% are receiving quality-assured drugs. This article reviews the management of MDR and XDR-TB and highlights the updated 2011 WHO guidelines on the programmatic management of drug-resistant tuberculosis. PMID:23460005

Daley, Charles L; Caminero, Jose A

2013-03-04

162

Identification of multi-drug resistance gene (MDR1) in equine ileum  

Directory of Open Access Journals (Sweden)

Full Text Available P-glycoprotein (P-gp) is a membrane transporter encoded in the Multi-drug Resistance (MDR1) gene expressed in several normal tissues and over expressed in tumor cells. P-gp was already identified in different species but not yet in equine. MDR1 gene and P-gp are able to interfere with bioavailability and disposition of several drugs, altering pharmacokinetic and pharmacodinamic of drugs. The presence of the MDR1 and P-gp in the central nervous system blocks the entry of certain drugs in this tissue and reduces drug absorption and enhances drug elimination when P-gp and MDR1 are presented in the gastrointestinal tract. This study showed that the MDR1 gene is present in equine ileum. Future studies on the impact of the P-glycoprotein encoded gene MDR1 on drugs pharmacologic effects in horses are granted.

Natalini Cláudio Corrêa; Linardi Renata Lehn

2006-01-01

163

Reversal of multidrug resistance-associated protein-mediated drug resistance by the pyridine analog PAK-104P.  

UK PubMed Central (United Kingdom)

Three agents, verapamil, cepharanthine, and 2-[4-(diphenylmethyl)-1-piperazinyl]ethyl-5-(trans-4,6-dimethyl-1, 3,2-dioxaphosphorinan-2-yl)-2,6-dimethyl-4-(3-nitrophenyl)-3-py ridinecarboxylate P-oxide (PAK-104P), that reverse drug resistance in P-glycoprotein (P-Gp)-mediated multidrug-resistant cells were examined for their activity to reverse drug resistance in multidrug resistance-associated protein (MRP)-mediated multidrug-resistant C-A120 cells. Agents other than PAK-104P could not reverse the resistance to doxorubicin in C-A120 cells. PAK-104P moderately reversed the doxorubicin resistance. In contrast, PAK-104P almost completely reversed the resistance to vincristine (VCR) in C-A120 cells as well as in KB-8-5 cells, and other agents moderately reversed the VCR resistance in C-A120 cells. PAK-104P at 10 microM enhanced the accumulation of VCR in C-A120 cells to the level of that in KB-3-1 cells without the agent. PAK-104P competitively inhibited the ATP-dependent [3H]leukotriene C4 uptake in membrane vesicles isolated from C-A120 cells. These findings demonstrate that PAK-104P can completely reverse the resistance to VCR in both P-Gp- and MRP-mediated multidrug-resistant cells and that PAK-104P directly interacts with MRP and inhibits the transporting activity of MRP.

Sumizawa T; Chen ZS; Chuman Y; Seto K; Furukawa T; Haraguchi M; Tani A; Shudo N; Akiyama SI

1997-03-01

164

Drug resistance in epithelial ovarian cancer: P-glycoprotein and glutation S-transferase. Can they play an important role in detecting response to platinum-based chemotherapy as a first-line therapy.  

UK PubMed Central (United Kingdom)

OBJECTIVE: Drug resistance is important for the treatment of ovarian cancer. P-glycoprotein and glutation S-transferase as resistance markers play an important role in the effectivity of chemotherapeutical agents. The role of P-glycoprotein and glutation S-transferase in the treatment of epithelial ovarian cancer is not well understood. We investigated the relation between P-glycoprotein and glutation S-transferase level for response to platinum-based chemotherapy in epithelial ovarian cancer. MATERIAL AND METHODS: We reviewed 30 cases diagnosed as epithelial ovarian cancer and treated with platinum-based chemotherapy in the Department of Obstetrics and Gynecology, Akdeniz University School of Medicine. The material was attained from initial parafin-embeded blocks stained for P-glycoprotein and glutation S-transferase. The cases that were diagnosed and treated before attending our clinic were not enrolled in the study. RESULTS: Mean age was 58.2 (25-70) and mean gravida 4.1 (0-10). Twenty-four patients (80%) were glutation S-transferase positive. Three cases (10%) out of 30 had positive reaction for P-glycoprotein. No difference was revealed regarding chemotherapy response rate among the cases showing glutation S-transferase positivity and P-glycoprotein negativity. CONCLUSION: Detection of glutation S-transferase and P-glycoprotein levels in epithelial ovarian cancer tissue is not important for response to platinum-based chemotherapy as a first line.

Sim?ek T; Ozbilim G; Gülkesen H; Kaya H; Sargin F; Karaveli S

2001-01-01

165

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

166

Constitutive overexpression of P-glycoprotein, rather than breast cancer resistance protein or organic cation transporter 1, contributes to acquisition of imatinib-resistance in K562 cells.  

UK PubMed Central (United Kingdom)

PURPOSE: The purpose of this study was to investigate the contribution of drug transporters in acquired imatinib-resistance. Specifically, we focused on the efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), and an influx transporter, organic cation transporter 1 (OCT1). MATERIALS AND METHODS: We established imatinib-resistant K562 cells (K562/IM). Real-time PCR or Western blot analyses were performed to examine the mRNA or protein levels. Alamar blue method was used in the cytotoxicity assay. The transport activities and intracellular imatinib levels were measured by flow cytometry and HPLC, respectively. RESULTS: K562/IM displayed a 47-fold increase in resistance to imatinib over the parent K562 cells. Both P-gp and BCRP were overexpressed in K562/IM relative to K562. Furthermore, the intracellular imatinib level was markedly reduced in K562/IM. Interestingly, cyclosporin A, a P-gp inhibitor, but not fumitremorgin C, a BCRP inhibitor, restored both imatinib-sensitivity and the intracellular imatinib level. By contrast, no significant difference in the expression and function of OCT1 was observed between K562/IM and K562. CONCLUSIONS: P-gp, rather than BCRP or OCT1, is partially responsible for the development of imatinib-resistance due to constitutive and functional overexpression, leading to reduced intracellular accumulation of imatinib in K562/IM.

Hirayama C; Watanabe H; Nakashima R; Nanbu T; Hamada A; Kuniyasu A; Nakayama H; Kawaguchi T; Saito H

2008-04-01

167

Multidrug-resistant Mycobacterium tuberculosis: molecular perspectives.  

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Multidrug-resistant strains of Mycobacterium tuberculosis seriously threaten tuberculosis (TB) control and prevention efforts. Molecular studies of the mechanism of action of antitubercular drugs have elucidated the genetic basis of drug resistance in M. tuberculosis. Drug resistance in M. tuberculo...

Rattan, A.; Kalia, A.; Ahmad, N.

168

Expression of P-glycoprotein-mediated drug resistance in CHO cells surviving a single X-ray dose of 30 Gy  

Energy Technology Data Exchange (ETDEWEB)

The authors reported previously that Chinese hamster ovary (CHO) cells surviving exposure to repeated doses of 9 Gy of X-irradiation in vitro expressed a multiple drug resistance phenotype characterized by cross-resistance to epipodophyllotoxins and to Vinca alkaloids, and by P-glycoprotein (Pgp) overexpression. They now show that exposure of these CHO cells to a single 30-Gy X-ray dose similarly resulted in the survivors expressing resistance to vincristine and to etoposide and overexpressing Pgp. In agreement with data obtained on cells which received repeated X-ray exposures, this Pgp overexpression occurred in the absence of any significant elevation of Pgp mRNA. However, the reduced ability to accumulate rhodamine 123 identified in these sublines, and the ability of verapamil to reverse this accumulation defect, implies that the Pgp which was overexpressed was functional. (author).

McClean, S.; Hosking, L.K.; Hill, B.T. (Imperial Cancer Research Fund, London (United Kingdom). Labs.)

1993-06-01

169

Expression of P-glycoprotein-mediated drug resistance in CHO cells surviving a single X-ray dose of 30 Gy  

International Nuclear Information System (INIS)

The authors reported previously that Chinese hamster ovary (CHO) cells surviving exposure to repeated doses of 9 Gy of X-irradiation in vitro expressed a multiple drug resistance phenotype characterized by cross-resistance to epipodophyllotoxins and to Vinca alkaloids, and by P-glycoprotein (Pgp) overexpression. They now show that exposure of these CHO cells to a single 30-Gy X-ray dose similarly resulted in the survivors expressing resistance to vincristine and to etoposide and overexpressing Pgp. In agreement with data obtained on cells which received repeated X-ray exposures, this Pgp overexpression occurred in the absence of any significant elevation of Pgp mRNA. However, the reduced ability to accumulate rhodamine 123 identified in these sublines, and the ability of verapamil to reverse this accumulation defect, implies that the Pgp which was overexpressed was functional. (author)

1993-01-01

170

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

Science.gov (United States)

Background 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.

Ren, Yanyan; Zhang, Haijun; Chen, Baoan; Cheng, Jian; Cai, Xiaohui; Liu, Ran; Xia, Guohua; Wu, Weiwei; Wang, Shuai; Ding, Jiahua; Gao, Chong; Wang, Jun; Bao, Wen; Wang, Lei; Tian, Liang; Song, Huihui; Wang, Xuemei

2012-01-01

171

Molecular characterization of the ldmdr1 multidrug resistance gene from Leishmania donovani.  

UK PubMed Central (United Kingdom)

The ldmdr1 gene that confers resistance to multiple structurally dissimilar hydrophobic drugs in Leishmania donovani has been isolated within a 5.4-kb XmaI fragment from a genomic library of L. donovani DNA and its protein coding region sequenced. The longest open reading frame within ldmdr1 encodes a 146.5-kDa protein of 1341 amino acids, designated LDMDR1. The primary structure and predicted membrane topology of LDMDR1 indicates that it is a member of the P-glycoprotein superfamily with the greatest homology to the mammalian multidrug resistance P-glycoproteins. A 2.3-kb SalI fragment derived from a second ldmdr1 allele was also cloned from the L. donovani library. Nucleotide sequence analysis of a portion of the SalI insert revealed 5 single base differences from its counterpart within the 5.4-kb XmaI fragment, one of which created a PvuI restriction site polymorphism. Southern blots of PvuI-digested DNA divulged that the amplified ldmdr1 gene copies in a multidrug-resistant L. donovani strain were all derived from the single ldmdr1 allele whose protein coding segment was sequenced in its entirety.

Hendrickson N; Sifri CD; Henderson DM; Allen T; Wirth DF; Ullman B

1993-07-01

172

Treatment options for multidrug-resistant nonfermenters.  

UK PubMed Central (United Kingdom)

Multidrug-resistant nonfermenters are a worldwide threat. Pseudomonas aeruginosa and Acinetobacter baumannii have been associated with high mortality and treatment failures. In addition, therapeutic options are increasingly narrowed, mainly due to widespread resistance in these pathogens and a shortage of new antimicrobial compounds. Hence, old, potent but toxic antibiotics such as the polymyxins are re-emerging as therapeutic options. Maximizing pharmacokinetics/pharmacodynamics with existing agents is also a worthwhile approach to explore. This problem exemplifies the critical need for new drug development for multidrug-resistant Gram-negative microorganisms.

Briceño DF; Quinn JP; Villegas MV

2010-03-01

173

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

174

Detection of multidrug resistance using molecular nuclear technique  

International Nuclear Information System (INIS)

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. 99m-Tc-MIBI and other 99m-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 11C 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-(11C)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.

2004-01-01

175

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.

Limtrakul Pornngarm; Anuchapreeda Songyot; Buddhasukh Duang

2004-01-01

176

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.

2011-01-15

177

P-glycoprotein activity and biological response  

International Nuclear Information System (INIS)

P-glycoprotein (P-gp) is a transmembrane drug efflux pump encoded by the MDR-1 gene in humans. Most likely P-gp protects organs against endogenous and exogenous toxins by extruding toxic compounds such as chemotherapeutics and other drugs. Many drugs are substrates for P-gp. Since P-gp is also expressed in the blood-brain barrier, P-gp substrates reach lower concentrations in the brain than in P-gp-negative tissues. Failure of response to chemotherapy of malignancies can be due to intrinsic or acquired drug resistance. Many tumors are multidrug resistant (MDR); resistant to several structurally unrelated chemotherapeutic agents. Several mechanisms are involved in MDR of which P-gp is studied most extensively. P-gp extrudes drugs out of tumor cells resulting in decreased intracellular drug concentrations, leading to the MDR phenotype. Furthermore, the MDR-1 gene exhibits several single nucleotide polymorphisms, some of which result in different transport capabilities. P-gp functionality and the effect of P-gp modulation on the pharmacokinetics of novel and established drugs can be studied in vivo by positron emission tomography (PET) using carbon-11 and fluorine-18-labeled P-gp substrates and modulators. PET may demonstrate the consequences of genetic differences on tissue pharmacokinetics. Inhibitors such as calcium-channel blockers (verapamil), cyclosporin A, ONT-093, and XR9576 can modulate the P-gp functionality. With PET the effect of P-gp modulation on the bioavailability of drugs can be investigated in humans in vivo. PET also allows the measurement of the efficacy of newly developed P-gp modulators

2005-09-01

178

Synthesis of 2-methyl N10-substituted acridones as selective inhibitors of multidrug resistance (MDR) associated protein in cancer cells.  

Science.gov (United States)

A series of N10-substituted-2-methyl acridone derivatives are synthesized and are examined for its ability to reverse P-glycoprotein (P-gp) mediated multidrug resistance (MDR) in breast cancer cell lines MCF-7 and MCF-7/Adr. The structural requirement of in-vitro anti-cancer and reversal of drug resistance are studied. The results showed that compound 16 with four carbon spacer exhibited promising in-vitro anti-cancer and reversal of drug resistance in comparison to the other analogues. PMID:18782042

Mayur, Y C; Ahmad, Osman; Prasad, V V S Rajendra; Purohit, M N; Srinivasulu, N; Kumar, S M Shanta

2008-09-01

179

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

Directory of Open Access Journals (Sweden)

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

2005-01-01

180

P-glycoprotein and breast cancer resistance protein restrict apical-to-basolateral permeability of human brain endothelium to amyloid-beta.  

UK PubMed Central (United Kingdom)

The clearance of amyloid beta (Abeta) from the brain represents a novel therapeutic target for Alzheimer's disease. Conflicting data exist regarding the contribution of adenosine triphosphate-binding cassette transporters to the clearance of Abeta through the blood-brain barrier. Therefore, we investigated whether Abeta could be a substrate for P-glycoprotein (P-gp) and/or for breast cancer resistance protein (BCRP) using a human brain endothelial cell line, hCMEC/D3. Inhibition of P-gp and BCRP increased apical-to-basolateral, but not basolateral-to-apical, permeability of hCMEC/D3 cells to (125)I Abeta 1-40. Our in vitro data suggest that P-gp and BCRP might act to prevent the blood-borne Abeta 1-40 from entering the brain.

Tai LM; Loughlin AJ; Male DK; Romero IA

2009-06-01

 
 
 
 
181

P-glycoprotein and breast cancer resistance protein restrict apical-to-basolateral permeability of human brain endothelium to amyloid-beta.  

Science.gov (United States)

The clearance of amyloid beta (Abeta) from the brain represents a novel therapeutic target for Alzheimer's disease. Conflicting data exist regarding the contribution of adenosine triphosphate-binding cassette transporters to the clearance of Abeta through the blood-brain barrier. Therefore, we investigated whether Abeta could be a substrate for P-glycoprotein (P-gp) and/or for breast cancer resistance protein (BCRP) using a human brain endothelial cell line, hCMEC/D3. Inhibition of P-gp and BCRP increased apical-to-basolateral, but not basolateral-to-apical, permeability of hCMEC/D3 cells to (125)I Abeta 1-40. Our in vitro data suggest that P-gp and BCRP might act to prevent the blood-borne Abeta 1-40 from entering the brain. PMID:19367293

Tai, Leon M; Loughlin, A Jane; Male, David K; Romero, Ignacio A

2009-04-15

182

The multidrug resistance 1 (MDR1) gene polymorphism G-rs3789243-A is not associated with disease susceptibility in Norwegian patients with colorectal adenoma and colorectal cancer; a case control study  

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Background: Smoking, dietary factors, and alcohol consumption are known life style factors contributing to gastrointestinal carcinogenesis. Genetic variations in carcinogen handling may affect cancer risk. The multidrug resistance 1(MDR1/ABCB1) gene encodes the transport protein P-glycoprotein (a ph...

Andersen, Vibeke; Agerstjerne, Lene; Jensen, Dorte; Østergaard, Mette; Saebo, Mona; Hamfjord, Julian; Kure, Elin

183

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

UK PubMed Central (United Kingdom)

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.

Shi R; Peng H; Yuan X; Zhang X; Zhang Y; Fan D; Liu X; Xiong D

2013-08-01

184

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

185

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.

Zhao Lihua; Jin Xianqing; Xu Youhua; Guo Yuxia; Liang Rui; Guo Zhenhua; Chen Tingfu; Sun Yanhui; Ding Xionghui

2010-01-01

186

Clinical importance of P-glycoprotein-related resistance in leukemia and myelodysplastic syndromes--first experience with their reversal.  

Science.gov (United States)

P-glycoprotein (P-gp) expression in mononuclear bone marrow cells was analyzed in 119 patients, including 60 with chronic myelogenous leukemia (CML), 48 with myelodysplastic syndromes (MDS), and 11 with acute myelogenous leukemia (AML). For P-gp measurement an immunocytological method using monoclonal antibodies C219, 4E3, and MRK 16 and the reverse transcription-polymerase chain reaction technique were applied. According to our results obtained in healthy volunteers using the immunocytological method, the limit for P-gp overexpression was set at > or = 10% P-gp-positive mononuclear bone marrow cells and at > or = 30% P-gp-positive mononuclear peripheral blood cells. All 42 CML patients in chronic phase had normal P-gp expression. P-gp overexpression was demonstrated in four of six patients in accelerated myelogenous blast cell phase and in four of 12 CML-BC patients. Of eight CML patients in blast crisis (BC) with normal P-gp expression, partial remission was achieved in three and minor response in five after prednisone/vindesine therapy. All four of the 12 CML-BC patients with P-gp overexpression did not respond to this therapy. Normal P-gp expression was seen in 41 (85.4%) of 48 untreated MDS patients. While P-gp overexpression did not develop during therapy in any of the myelodysplastic syndrome patients treated with low-dose ara-C alone, four of eight treated with low-dose ara-C plus GM-CSF and four of 11 treated with low-dose ara-C and IL-3 developed P-gp overexpression after therapy. Furthermore, 11 AML patients at primary diagnosis, including five AML patients with P-gp overexpression, who were treated with idarubicin, vepesid, and cytarabine V (ara-C) showed a complete remission. Additionally, one daunorubicin-cytarabine-pretreated refractory AML patient was treated with the oral form of the P-gp modulator drug dexniguldipine and achieved complete remission for a duration of 7 months. Our results suggest that in CML patients in BC, P-gp expression influences outcome after therapy. Further more, studies in a larger series of patients are necessary to prove the efficacy and toxicity of idarubicin/vepesid and cytardbine--or dexniguldipine-containing--therapy in relation to P-gp expression of AML patients. PMID:7914749

Nüssler, V; Pelka-Fleischer, R; Zwierzina, H; Nerl, C; Beckert, B; Gullis, E; Gieseler, F; Bock, S; Bartl, R; Petrides, P E

1994-01-01

187

Clinical importance of P-glycoprotein-related resistance in leukemia and myelodysplastic syndromes--first experience with their reversal.  

UK PubMed Central (United Kingdom)

P-glycoprotein (P-gp) expression in mononuclear bone marrow cells was analyzed in 119 patients, including 60 with chronic myelogenous leukemia (CML), 48 with myelodysplastic syndromes (MDS), and 11 with acute myelogenous leukemia (AML). For P-gp measurement an immunocytological method using monoclonal antibodies C219, 4E3, and MRK 16 and the reverse transcription-polymerase chain reaction technique were applied. According to our results obtained in healthy volunteers using the immunocytological method, the limit for P-gp overexpression was set at > or = 10% P-gp-positive mononuclear bone marrow cells and at > or = 30% P-gp-positive mononuclear peripheral blood cells. All 42 CML patients in chronic phase had normal P-gp expression. P-gp overexpression was demonstrated in four of six patients in accelerated myelogenous blast cell phase and in four of 12 CML-BC patients. Of eight CML patients in blast crisis (BC) with normal P-gp expression, partial remission was achieved in three and minor response in five after prednisone/vindesine therapy. All four of the 12 CML-BC patients with P-gp overexpression did not respond to this therapy. Normal P-gp expression was seen in 41 (85.4%) of 48 untreated MDS patients. While P-gp overexpression did not develop during therapy in any of the myelodysplastic syndrome patients treated with low-dose ara-C alone, four of eight treated with low-dose ara-C plus GM-CSF and four of 11 treated with low-dose ara-C and IL-3 developed P-gp overexpression after therapy. Furthermore, 11 AML patients at primary diagnosis, including five AML patients with P-gp overexpression, who were treated with idarubicin, vepesid, and cytarabine V (ara-C) showed a complete remission. Additionally, one daunorubicin-cytarabine-pretreated refractory AML patient was treated with the oral form of the P-gp modulator drug dexniguldipine and achieved complete remission for a duration of 7 months. Our results suggest that in CML patients in BC, P-gp expression influences outcome after therapy. Further more, studies in a larger series of patients are necessary to prove the efficacy and toxicity of idarubicin/vepesid and cytardbine--or dexniguldipine-containing--therapy in relation to P-gp expression of AML patients.

Nüssler V; Pelka-Fleischer R; Zwierzina H; Nerl C; Beckert B; Gullis E; Gieseler F; Bock S; Bartl R; Petrides PE

1994-01-01

188

Nuclear Multidrug-Resistance Related Protein 1 Contributes to Multidrug-Resistance of Mucoepidermoid Carcinoma Mainly via Regulating Multidrug-Resistance Protein 1: A Human Mucoepidermoid Carcinoma Cells Model and Spearman's Rank Correlation Analysis  

Science.gov (United States)

Background Multidrug resistance-related protein 1 (MRP1/ABCC1) and multidrug resistance protein 1 (MDR1/P-glycoprotein/ABCB1) are both membrane-bound drug transporters. In contrast to MDR1, MRP1 also transports glutathione (GSH) and drugs conjugated to GSH. Due to its extraordinary transport properties, MRP1/ABCC1 contributes to several physiological functions and pathophysiological incidents. We previously found that nuclear translocation of MRP1 contributes to multidrug-resistance (MDR) of mucoepidermoid carcinoma (MEC). The present study investigated how MRP1 contributes to MDR in the nuclei of MEC cells. Methods Western blot and RT-PCR was carried out to investigate the change of multidrug-resistance protein 1 (MDR1) in MC3/5FU cells after MRP1 was downregulated through RNA interference (RNAi). Immunohistochemistry (IHC) staining of 127 cases of MEC tissues was scored with the expression index (EI). The EI of MDR1 and MRP1 (or nuclear MRP1) was analyzed with Spearman's rank correlation analysis. Using multiple tumor tissue assays, the location of MRP1 in other tissues was checked by HIC. Luciferase reporter assays of MDR1 promoter was carried out to check the connection between MRP1 and MDR1 promoter. Results MRP1 downregulation led to a decreased MDR1 expression in MC3/5FU cells which was caused by decreased activity of MDR1 promoter. IHC study of 127 cases of MEC tissues demonstrated a strong positive correlation between nuclear MRP1 expression and MDR1 expression. Furthermore, IHC study of multiple tumor tissue array sections showed that although nuclear MRP1 widely existed in MEC tissues, it was not found in normal tissues or other tumor tissues. Conclusions Our findings indicate that nuclear MRP1 contributes to MDR mainly through regulating MDR1 expression in MEC. And the unique location of MRP1 made it an available target in identifying MEC from other tumors.

Liu, Yuan; Xu, Xiaofang; Guan, Sumin; Wu, Junzheng; Liu, Yanpu

2013-01-01

189

Nuclear Multidrug-Resistance Related Protein 1 Contributes to Multidrug-Resistance of Mucoepidermoid Carcinoma Mainly via Regulating Multidrug-Resistance Protein 1: A Human Mucoepidermoid Carcinoma Cells Model and Spearman's Rank Correlation Analysis.  

UK PubMed Central (United Kingdom)

BACKGROUND: Multidrug resistance-related protein 1 (MRP1/ABCC1) and multidrug resistance protein 1 (MDR1/P-glycoprotein/ABCB1) are both membrane-bound drug transporters. In contrast to MDR1, MRP1 also transports glutathione (GSH) and drugs conjugated to GSH. Due to its extraordinary transport properties, MRP1/ABCC1 contributes to several physiological functions and pathophysiological incidents. We previously found that nuclear translocation of MRP1 contributes to multidrug-resistance (MDR) of mucoepidermoid carcinoma (MEC). The present study investigated how MRP1 contributes to MDR in the nuclei of MEC cells. METHODS: Western blot and RT-PCR was carried out to investigate the change of multidrug-resistance protein 1 (MDR1) in MC3/5FU cells after MRP1 was downregulated through RNA interference (RNAi). Immunohistochemistry (IHC) staining of 127 cases of MEC tissues was scored with the expression index (EI). The EI of MDR1 and MRP1 (or nuclear MRP1) was analyzed with Spearman's rank correlation analysis. Using multiple tumor tissue assays, the location of MRP1 in other tissues was checked by HIC. Luciferase reporter assays of MDR1 promoter was carried out to check the connection between MRP1 and MDR1 promoter. RESULTS: MRP1 downregulation led to a decreased MDR1 expression in MC3/5FU cells which was caused by decreased activity of MDR1 promoter. IHC study of 127 cases of MEC tissues demonstrated a strong positive correlation between nuclear MRP1 expression and MDR1 expression. Furthermore, IHC study of multiple tumor tissue array sections showed that although nuclear MRP1 widely existed in MEC tissues, it was not found in normal tissues or other tumor tissues. CONCLUSIONS: Our findings indicate that nuclear MRP1 contributes to MDR mainly through regulating MDR1 expression in MEC. And the unique location of MRP1 made it an available target in identifying MEC from other tumors.

Cai B; Miao Y; Liu Y; Xu X; Guan S; Wu J; Liu Y

2013-01-01

190

Reversal of multidrug resistance by surfactants.  

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Cremophor EL, a pharmacologically inactive solubilising agent, has been shown to reverse multidrug resistance (MDR). Using flow cytometric evaluation of equilibrium intracellular levels of daunorubicin (DNR), we found that eight other surface active agents will also reverse MDR. All the active deter...

Woodcock, D. M.; Linsenmeyer, M. E.; Chojnowski, G.; Kriegler, A. B.; Nink, V.; Webster, L. K.; Sawyer, W. H.

191

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

Energy Technology Data Exchange (ETDEWEB)

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

192

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

International Nuclear Information System (INIS)

Multidrug resistance, aggressiveness and accelerated choline metabolism are hallmarks of malignancy and have motivated the development of new PET tracers like 18F-FCH, an analogue of choline. Our aim was to study the relationship of multidrug resistance of cultured glioma cell lines and 18F-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.)

2009-01-01

193

Reversal of multidrug resistance-associated protein-mediated drug resistance by the pyridine analog PAK-104P.  

Science.gov (United States)

Three agents, verapamil, cepharanthine, and 2-[4-(diphenylmethyl)-1-piperazinyl]ethyl-5-(trans-4,6-dimethyl-1, 3,2-dioxaphosphorinan-2-yl)-2,6-dimethyl-4-(3-nitrophenyl)-3-py ridinecarboxylate P-oxide (PAK-104P), that reverse drug resistance in P-glycoprotein (P-Gp)-mediated multidrug-resistant cells were examined for their activity to reverse drug resistance in multidrug resistance-associated protein (MRP)-mediated multidrug-resistant C-A120 cells. Agents other than PAK-104P could not reverse the resistance to doxorubicin in C-A120 cells. PAK-104P moderately reversed the doxorubicin resistance. In contrast, PAK-104P almost completely reversed the resistance to vincristine (VCR) in C-A120 cells as well as in KB-8-5 cells, and other agents moderately reversed the VCR resistance in C-A120 cells. PAK-104P at 10 microM enhanced the accumulation of VCR in C-A120 cells to the level of that in KB-3-1 cells without the agent. PAK-104P competitively inhibited the ATP-dependent [3H]leukotriene C4 uptake in membrane vesicles isolated from C-A120 cells. These findings demonstrate that PAK-104P can completely reverse the resistance to VCR in both P-Gp- and MRP-mediated multidrug-resistant cells and that PAK-104P directly interacts with MRP and inhibits the transporting activity of MRP. PMID:9058594

Sumizawa, T; Chen, Z S; Chuman, Y; Seto, K; Furukawa, T; Haraguchi, M; Tani, A; Shudo, N; Akiyama, S I

1997-03-01

194

Quantitative analysis of MDR1 (multidrug resistance) gene expression in human tumors by polymerase chain reaction  

International Nuclear Information System (INIS)

The resistance of tumor cells ot chemotheraprutic drugs is a major obstacle to successful cancer chemotherapy. In human cells, expression of the MDR1 gene, encoding a transmembrane efflux pump (P-glycoprotein), leads to decreased intracellular accumulation and resistance to a variety of lipophilic drugs (multidrug resistance; MDR). The levels of MDR in cell lines selected in bitro have been shown to correlate with the steady-state levels of MDR1 mRNA and P-glycoprotein. In cells with a severalfold increase in cellular drug resistance, MDR1 expression levels are close to the limits of detection by conventional assays. MDR1 expression has been frequently observed in human tumors after chemotherapy and in some but not all types of clinically refactory tumors untreated with chemotherapeutic drugs. The authors have devised a highly sensitive, specific, and quantitative protocol for measuring the levels of MDR1 mRNA in clincal samples, based on the polymerase chain reaction. They have used this assay to measure MDR1 gene expression in MDR cell lines and >300 normal tissues, tumor-derived cell lines, and clinical specimens of untreated tumors of the types in which MDR1 expression was rarely observed by standard assays. Low levels of MDR1 expression were found by polymerase chain reaction in most solid tumors and leukemias tested. The frequency of samples without detectable MDR1 expression varied among different types of tumors; MDR1-negative samples were ost common among tumor types known to be relatively responsive to chemotherapy.

1990-01-01

195

Quantitative analysis of MDR1 (multidrug resistance) gene expression in human tumors by polymerase chain reaction  

Energy Technology Data Exchange (ETDEWEB)

The resistance of tumor cells ot chemotheraprutic drugs is a major obstacle to successful cancer chemotherapy. In human cells, expression of the MDR1 gene, encoding a transmembrane efflux pump (P-glycoprotein), leads to decreased intracellular accumulation and resistance to a variety of lipophilic drugs (multidrug resistance; MDR). The levels of MDR in cell lines selected in bitro have been shown to correlate with the steady-state levels of MDR1 mRNA and P-glycoprotein. In cells with a severalfold increase in cellular drug resistance, MDR1 expression levels are close to the limits of detection by conventional assays. MDR1 expression has been frequently observed in human tumors after chemotherapy and in some but not all types of clinically refactory tumors untreated with chemotherapeutic drugs. The authors have devised a highly sensitive, specific, and quantitative protocol for measuring the levels of MDR1 mRNA in clincal samples, based on the polymerase chain reaction. They have used this assay to measure MDR1 gene expression in MDR cell lines and >300 normal tissues, tumor-derived cell lines, and clinical specimens of untreated tumors of the types in which MDR1 expression was rarely observed by standard assays. Low levels of MDR1 expression were found by polymerase chain reaction in most solid tumors and leukemias tested. The frequency of samples without detectable MDR1 expression varied among different types of tumors; MDR1-negative samples were ost common among tumor types known to be relatively responsive to chemotherapy.

Noonan, K.E.; Beck, C.; Holzmayer, T.A.; Chin, J.E.; Roninson, I.B. (Univ. of Illinois, Chicago (USA)); Wunder, J.S.; Andrulis, I.L. (Mount Sinai Hospital, Toronto, Ontario (Canada)); Gazdar, A.F. (National Cancer Inst., Bethesda, MD (USA)); Willman, C.L.; Griffith, B. (Univ. of New Mexico, Albuquerque (USA)); Von Hoff, D.D. (Univ. of Texas, San Antonio (USA))

1990-09-01

196

[Travellers and multi-drug resistance bacteria].  

UK PubMed Central (United Kingdom)

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.

Takeshita N

2012-02-01

197

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

Directory of Open Access Journals (Sweden)

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; Zhang H; Chen B; Cheng J; Cai X; Liu R; Xia G; Wu W; Wang S; Ding J; Gao C; Wang J; Bao W; Wang L; Tian L; Song H; Wang X

2012-01-01

198

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  

Energy Technology Data Exchange (ETDEWEB)

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

199

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  

International Nuclear Information System (INIS)

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. 99mTc-MIBI efflux rates were measured using a gamma camera in three Brca1 -/-; p53 -/- 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 99mTc-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.)

2009-01-01

200

Multidrug resistance in pediatric urinary tract infections.  

UK PubMed Central (United Kingdom)

Urinary tract infections (UTIs) represent a common infection in the pediatric population. Escherichia coli is the most common uropathogen in children, and antimicrobial resistance in this species complicates the treatment of pediatric UTIs. Despite the impact of resistance on empiric antibiotic choice, there is little data on multidrug resistance in pediatric patients. In this paper, we describe characteristics of multidrug-resistant E. coli in pediatric patients using a large national database of uropathogens antimicrobial sensitivities. Antimicrobial susceptibility patterns to commonly prescribed antibiotics were performed on uropathogens isolated from children presenting to participating hospitals between 1999 and 2001. Data were analyzed separately for four pediatric age groups. Single and multidrug resistance to ampicillin, amoxicillin-clavulanate, cefazolin, ciprofloxacin, nitrofurantoin, and trimethoprim-sulfamethoxazole (TMP-SMX) were performed on all specimens. There were a total of 11,341 E. coli urine cultures from 343 infants (0-4 weeks), 1,801 toddlers (5 weeks-24 months), 6,742 preteens (2-12 years), and 2,455 teens (13-17 years). E. coli resistance to ampicillin peaked in toddlers (52.8%) but was high in preteens (52.1%), infants (50.4%), and teens (40.6%). Resistance to two or more antibiotics varied across age groups, with toddlers (27%) leading preteens (23.1%), infants (21%), and teens (15.9%). Resistance to three or more antibiotics was low in all age groups (range 3.1-5.2%). The most common co-resistance in all age groups was ampicillin/TMP-SMZ. In conclusion, less than half of all pediatric UTIs are susceptible to all commonly used antibiotics. In some age groups, there is a significant percentage of co-resistance between the two most commonly used antibiotics (ampicillin and TMP-SMZ).

Gaspari RJ; Dickson E; Karlowsky J; Doern G

2006-01-01

 
 
 
 
201

A lack of Adriamycin (ADR) resistance in Chinese hamster ovary (CHO) cells overexpressing P-glycoprotein (Pgp) following in vitro exposure to fractionated X-irradiation  

Energy Technology Data Exchange (ETDEWEB)

Using x-ray pretreated CHO cells, the authors demonstrated differing accumulation of adriamycin and vincristine in cells overexpressing P-glycoprotein. Response was also varied by the addition of calcium channel antagonist verapamil. (author).

Whelan, R.D.H.; Hosking, L.K.; Hill, B.T. (Imperial Cancer Research Fund, London (United Kingdom). Labs.)

1991-04-01

202

A lack of Adriamycin (ADR) resistance in Chinese hamster ovary (CHO) cells overexpressing P-glycoprotein (Pgp) following in vitro exposure to fractionated X-irradiation  

International Nuclear Information System (INIS)

Using x-ray pretreated CHO cells, the authors demonstrated differing accumulation of adriamycin and vincristine in cells overexpressing P-glycoprotein. Response was also varied by the addition of calcium channel antagonist verapamil. (author).

1991-01-01

203

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.  

Science.gov (United States)

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

2012-10-18

204

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.  

UK PubMed Central (United Kingdom)

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.

Durmus S; Sparidans RW; Wagenaar E; Beijnen JH; Schinkel AH

2012-11-01

205

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

International Nuclear Information System (INIS)

[en] 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

2001-01-01

206

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

Energy Technology Data Exchange (ETDEWEB)

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

207

Bacillus licheniformis bacitracin-resistance ABC transporter: relationship to mammalian multidrug resistance.  

UK PubMed Central (United Kingdom)

The nucleotide sequence of the Bacillus licheniformis bacitracin-resistance locus was determined. The presence of three open reading frames, bcrA, bcrB and bcrC, was revealed. The BcrA protein shares a high degree of homology with the hydrophilic ATP-binding components of the ABC family of transport proteins. The bcrB and bcrC genes were found to encode hydrophobic proteins, which may function as membrane components of the permease. Apart from Bacillus subtilis, these genes also confer resistance upon the Gram-negative Escherichia coli. The presumed function of the Bcr transporter is to remove the bacitracin molecule from its membrane target. In addition to the homology of the nucleotide-binding sites, BcrA protein and mammalian multidrug transporter or P-glycoprotein share collateral detergent sensitivity of resistant cells and possibly the mode of Bcr transport activity within the membrane. The advantage of the resistance phenotype of the Bcr transporter was used to construct deletions within the nucleotide-binding protein to determine the importance of various regions in transport.

Podlesek Z; Comino A; Herzog-Velikonja B; Zgur-Bertok D; Komel R; Grabnar M

1995-06-01

208

Bacillus licheniformis bacitracin-resistance ABC transporter: relationship to mammalian multidrug resistance.  

Science.gov (United States)

The nucleotide sequence of the Bacillus licheniformis bacitracin-resistance locus was determined. The presence of three open reading frames, bcrA, bcrB and bcrC, was revealed. The BcrA protein shares a high degree of homology with the hydrophilic ATP-binding components of the ABC family of transport proteins. The bcrB and bcrC genes were found to encode hydrophobic proteins, which may function as membrane components of the permease. Apart from Bacillus subtilis, these genes also confer resistance upon the Gram-negative Escherichia coli. The presumed function of the Bcr transporter is to remove the bacitracin molecule from its membrane target. In addition to the homology of the nucleotide-binding sites, BcrA protein and mammalian multidrug transporter or P-glycoprotein share collateral detergent sensitivity of resistant cells and possibly the mode of Bcr transport activity within the membrane. The advantage of the resistance phenotype of the Bcr transporter was used to construct deletions within the nucleotide-binding protein to determine the importance of various regions in transport. PMID:7476193

Podlesek, Z; Comino, A; Herzog-Velikonja, B; Zgur-Bertok, D; Komel, R; Grabnar, M

1995-06-01

209

TFPI-2 downregulates multidrug resistance protein in 5-FU-resistant human hepatocellular carcinoma BEL-7402/5-FU cells.  

Science.gov (United States)

Tissue factor pathway inhibitor-2 (TFPI-2) is known to induce apoptosis and to suppress tumor metastasis in several types of cancer cells. However, there is little known about its reversal effect on chemoresistant tumor cells. This study investigated the effect of TFPI-2 in 5-fluorouracil (5-FU)-resistant human hepatocellular cancer BEL-7402/5-FU cells in vitro. We constructed TFPI-2 overexpression BEL-7402/5-FU cell lines and explored resistance index (RI) of 5-FU, function of the P-glycoprotein (P-gp) efflux pump, and the mRNA and protein expression of drug resistance gene, including multidrug resistance gene (MDR1), lung-resistance protein (LRP), multidrug resistance-associated protein (MRP1), glutathione-S-transferase-? (GST-?), excision repair cross-complementing gene 1 (ERCC1), and p38 phosphorylation. We found that TFPI-2 improved the RI of 5-FU and inhibited P-gp function. Western blotting and real-time PCR revealed that TFPI-2 also decreased mRNA and protein expression of MDR1, LRP, MRP1, GST-?, and ERCC1, whereas p38 phosphorylation was increased. We considered that TFPI-2 reduces 5-FU resistance in BEL-7402/5-FU cells, and the mechanism appears to involve p38-mediated downregulation of drug resistance gene expression such as MDR1, LRP, MRP1, GST-?, and ERCC1. PMID:23125179

Lu, Fei; Hou, Yong-Qiang; Song, Ying; Yuan, Zheng-Jiang

2012-11-04

210

TFPI-2 downregulates multidrug resistance protein in 5-FU-resistant human hepatocellular carcinoma BEL-7402/5-FU cells.  

UK PubMed Central (United Kingdom)

Tissue factor pathway inhibitor-2 (TFPI-2) is known to induce apoptosis and to suppress tumor metastasis in several types of cancer cells. However, there is little known about its reversal effect on chemoresistant tumor cells. This study investigated the effect of TFPI-2 in 5-fluorouracil (5-FU)-resistant human hepatocellular cancer BEL-7402/5-FU cells in vitro. We constructed TFPI-2 overexpression BEL-7402/5-FU cell lines and explored resistance index (RI) of 5-FU, function of the P-glycoprotein (P-gp) efflux pump, and the mRNA and protein expression of drug resistance gene, including multidrug resistance gene (MDR1), lung-resistance protein (LRP), multidrug resistance-associated protein (MRP1), glutathione-S-transferase-? (GST-?), excision repair cross-complementing gene 1 (ERCC1), and p38 phosphorylation. We found that TFPI-2 improved the RI of 5-FU and inhibited P-gp function. Western blotting and real-time PCR revealed that TFPI-2 also decreased mRNA and protein expression of MDR1, LRP, MRP1, GST-?, and ERCC1, whereas p38 phosphorylation was increased. We considered that TFPI-2 reduces 5-FU resistance in BEL-7402/5-FU cells, and the mechanism appears to involve p38-mediated downregulation of drug resistance gene expression such as MDR1, LRP, MRP1, GST-?, and ERCC1.

Lu F; Hou YQ; Song Y; Yuan ZJ

2013-01-01

211

The three mouse multidrug resistance (mdr) genes are expressed in a tissue-specific manner in normal mouse tissues  

Energy Technology Data Exchange (ETDEWEB)

The gene responsible for multidrug resistance (mdr), which encodes the P-glycoprotein, is a member of a multigene family. The authors have identified distinct mdr gene transcripts encoded by three separate mdr genes in the mouse. Expression levels of each mdr gene are dramatically different in various mouse tissues. Specific mdr RNA transcripts of approximately 4.5, 5 and 6 kilobases have been detected. Each of the mdr genes has a specific RNA transcript pattern. These results should be considered in relation to understanding the normal physiological function of the mdr multigene family.

Croop, J.M.; Arceci, R.J. (Children' s Hospital Corp., Boston, MA (USA)); Raymond, M.; Gros, P.; Devault, A. (McGill Univ., Montreal, PQ (Canada). Dept. of Chemistry); Haber, D. (Harvard Medical School, Boston, MA (USA)); Housman, D.E. (Massachusetts Inst. of Tech., Cambridge, MA (USA))

1989-03-01

212

Chromosomal Instability Confers Intrinsic Multidrug Resistance  

DEFF Research Database (Denmark)

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

213

[Reoperation for Multidrug-resistant Pulmonary Tuberculosis].  

UK PubMed Central (United Kingdom)

We have performed pulmonary resection combined with chemotherapy for multidrug-resistant tuberculosis (MDR-TB). Postoperative complications of pulmonary resection for MDR-TB include space problem, prolonged air leak, bronchopleural fistula with or without empyema, chylothorax, and relapse. Indication, surgical technique, postoperative management, and follow-up of reoperation (thoracoplasty and muscle plombage, clousure of bronchopleural fistula, resuture of bronchial stump, open window thoracostomy, and 2nd pulmonary resection) for these complications are described.

Katsuragi N; Shiraishi Y

2013-07-01

214

Multidrug resistant malaria in splenectomized patient  

Directory of Open Access Journals (Sweden)

Full Text Available Malaria is a dangerous infection in splenectomized individuals. In endemic areas, managing malaria in such individuals is a clinical challenge. In the tropics, death from malaria after splenectomy has been reported, but no formal study has been undertaken. Here we discuss a case of multidrug resistant malaria in a splenectomized patient, managed by antimalarial drugs and exchange transfusion with a successful outcome.

Tauro L; Roshan M; Hegde N; Bhat K; Vivek

2006-01-01

215

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

Directory of Open Access Journals (Sweden)

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.

Becker Jean-Paul; Depret Grégoire; Van Bambeke Françoise; Tulkens Paul M; Prévost Martine

2009-01-01

216

(-)-Roemerine, an aporphine alkaloid from Annona senegalensis that reverses the multidrug-resistance phenotype with cultured cells.  

UK PubMed Central (United Kingdom)

A known aporphine alkaloid, (-)-roemerine [1], isolated from the leaves of Annona senegalensis, was found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB-V1 cells. In the absence of vinblastine, no significant cytotoxicity was observed with KB-3 or KB-V1 cells (ED50 > 20 micrograms/ml), and several other human tumor cell lines were also relatively insensitive. As indicated by its ability to inhibit ATP-dependent [3H]vinblastine binding to multidrug-resistant KB-V1 cell membrane vesicles, (-)-roemerine appears to function by interacting with P-glycoprotein. In addition to alkaloid 1, three inactive compounds [the aporphine alkaloid(-)-isocorydine (reported in the levo-configuration for the first time), and the lignans (+/-)-8,8'-bisdihydrosiringenin [2] (a new natural product), and (+)-syringaresinol] were also isolated.

You M; Wickramaratne DB; Silva GL; Chai H; Chagwedera TE; Farnsworth NR; Cordell GA; Kinghorn AD; Pezzuto JM

1995-04-01

217

(-)-Roemerine, an aporphine alkaloid from Annona senegalensis that reverses the multidrug-resistance phenotype with cultured cells.  

Science.gov (United States)

A known aporphine alkaloid, (-)-roemerine [1], isolated from the leaves of Annona senegalensis, was found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB-V1 cells. In the absence of vinblastine, no significant cytotoxicity was observed with KB-3 or KB-V1 cells (ED50 > 20 micrograms/ml), and several other human tumor cell lines were also relatively insensitive. As indicated by its ability to inhibit ATP-dependent [3H]vinblastine binding to multidrug-resistant KB-V1 cell membrane vesicles, (-)-roemerine appears to function by interacting with P-glycoprotein. In addition to alkaloid 1, three inactive compounds [the aporphine alkaloid(-)-isocorydine (reported in the levo-configuration for the first time), and the lignans (+/-)-8,8'-bisdihydrosiringenin [2] (a new natural product), and (+)-syringaresinol] were also isolated. PMID:7623038

You, M; Wickramaratne, D B; Silva, G L; Chai, H; Chagwedera, T E; Farnsworth, N R; Cordell, G A; Kinghorn, A D; Pezzuto, J M

1995-04-01

218

Cytogenetic and molecular characterization of random chromosomal rearrangements activating the drug resistance gene, MDR1/P-glycoprotein, in drug-selected cell lines and patients with drug refractory ALL.  

Science.gov (United States)

Drug resistance, both primary and acquired, is a major obstacle to advances in cancer chemotherapy. In vitro, multidrug resistance can be mediated by P-glycoprotein (PGY1), a cell surface phosphoglycoprotein that acts to efflux natural products from cells. PGY1 is encoded by the MDR1 gene located at 7q21.1. Overexpression of MDR1 has been demonstrated in many cancers, both in patient tumors and in cell lines selected with a variety of chemotherapeutic agents. Recent studies in drug-selected cell lines and patients samples have identified hybrid mRNAs comprised of an active, but apparently random, gene fused 5' to MDR1. This observation indicates that random chromosomal rearrangements, such as translocations and inversions, leading to "capture" of MDR1 by constitutively expressed genes may be a mechanism for activation of this gene following drug exposure. In this study, fluorescence in situ hybridization (FISH) using whole chromosome paints (WCP) and bacterial artificial chromosome (BAC)-derived probes showed structural rearrangements involving 7q in metaphase and interphase cells, and comparative genomic hybridization (CGH) revealed high levels of amplification at chromosomal breakpoints. In an adriamycin-selected resistant colon cancer line (S48-3s/Adr), WCP4/WCP7 revealed t(4;7)(q31;q21) and BAC-derived probes demonstrated that the breakpoint lay between MDR1 and sequences 500-1000 KB telomeric to it. Similarly, in a subline isolated following exposure to actinomycin D (S48-3s/ActD), a hybrid MDR1 gene composed of heme oxygenase-2 sequences (at 16p13) fused to MDR1 was identified and a rearrangement confirmed with WCP7 and a subtelomeric 16p probe. Likewise, in a paclitaxel-selected MCF-7 subline where CASP sequences (at 7q22) were shown to be fused to MDR1, WCP7 showed an elongated chromosome 7 with a homogeneously staining regions (hsr); BAC-derived probes demonstrated that the hsr was composed of highly amplified MDR1 and CASP sequences. In all three selected cell lines, CGH demonstrated amplification at breakpoints involving MDR1 (at 7q21) and genes fused to MDR1 at 4q31, 7q22, and 16p13.3. Finally, in samples obtained from two patients with drug refractory ALL, BAC-derived probes applied to archived marrow cells demonstrated that a breakpoint occurred between MDR1 and sequences 500-1000 KB telomeric to MDR1, consistent with a random chromosomal rearrangement. These results support the proposal that random chromosomal rearrangement leading to capture and activation of MDR1 is a mechanism of acquired drug resistance. PMID:9713996

Knutsen, T; Mickley, L A; Ried, T; Green, E D; du Manoir, S; Schröck, E; Macville, M; Ning, Y; Robey, R; Polymeropoulos, M; Torres, R; Fojo, T

1998-09-01

219

Cytogenetic and molecular characterization of random chromosomal rearrangements activating the drug resistance gene, MDR1/P-glycoprotein, in drug-selected cell lines and patients with drug refractory ALL.  

UK PubMed Central (United Kingdom)

Drug resistance, both primary and acquired, is a major obstacle to advances in cancer chemotherapy. In vitro, multidrug resistance can be mediated by P-glycoprotein (PGY1), a cell surface phosphoglycoprotein that acts to efflux natural products from cells. PGY1 is encoded by the MDR1 gene located at 7q21.1. Overexpression of MDR1 has been demonstrated in many cancers, both in patient tumors and in cell lines selected with a variety of chemotherapeutic agents. Recent studies in drug-selected cell lines and patients samples have identified hybrid mRNAs comprised of an active, but apparently random, gene fused 5' to MDR1. This observation indicates that random chromosomal rearrangements, such as translocations and inversions, leading to "capture" of MDR1 by constitutively expressed genes may be a mechanism for activation of this gene following drug exposure. In this study, fluorescence in situ hybridization (FISH) using whole chromosome paints (WCP) and bacterial artificial chromosome (BAC)-derived probes showed structural rearrangements involving 7q in metaphase and interphase cells, and comparative genomic hybridization (CGH) revealed high levels of amplification at chromosomal breakpoints. In an adriamycin-selected resistant colon cancer line (S48-3s/Adr), WCP4/WCP7 revealed t(4;7)(q31;q21) and BAC-derived probes demonstrated that the breakpoint lay between MDR1 and sequences 500-1000 KB telomeric to it. Similarly, in a subline isolated following exposure to actinomycin D (S48-3s/ActD), a hybrid MDR1 gene composed of heme oxygenase-2 sequences (at 16p13) fused to MDR1 was identified and a rearrangement confirmed with WCP7 and a subtelomeric 16p probe. Likewise, in a paclitaxel-selected MCF-7 subline where CASP sequences (at 7q22) were shown to be fused to MDR1, WCP7 showed an elongated chromosome 7 with a homogeneously staining regions (hsr); BAC-derived probes demonstrated that the hsr was composed of highly amplified MDR1 and CASP sequences. In all three selected cell lines, CGH demonstrated amplification at breakpoints involving MDR1 (at 7q21) and genes fused to MDR1 at 4q31, 7q22, and 16p13.3. Finally, in samples obtained from two patients with drug refractory ALL, BAC-derived probes applied to archived marrow cells demonstrated that a breakpoint occurred between MDR1 and sequences 500-1000 KB telomeric to MDR1, consistent with a random chromosomal rearrangement. These results support the proposal that random chromosomal rearrangement leading to capture and activation of MDR1 is a mechanism of acquired drug resistance.

Knutsen T; Mickley LA; Ried T; Green ED; du Manoir S; Schröck E; Macville M; Ning Y; Robey R; Polymeropoulos M; Torres R; Fojo T

1998-09-01

220

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Lalloo Anita K; Luo Feng R; Guo Ailan; Paranjpe Pankaj V; Lee Sung-Hack; Vyas Viral; Rubin Eric; Sinko Patrick J

 
 
 
 
221

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 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.

2011-01-01

222

Polymeric mixed micelles for delivery of curcumin to multidrug resistant ovarian cancer.  

Science.gov (United States)

The biggest challenge for the treatment of multidrug resistance cancer is to deliver high concentration of anticancer drugs specifically to cancer cells for longer period of time. Poloxamers and D-alpha-Tocopheryl polyethylene glycol 1000 succinate (TPGS) are known inhibitors of P-glycoprotein. Mixed micelles prepared from Poloxamer 407 and TPGS may increases the therapeutic efficacy of drug by delivering high concentration of drug inside the cells and inhibition of P-gp. Curcumin (CUR) is a naturally derived novel anticancer agent but poor solubility limited its clinical use. In this study, we have developed Poloxamer 407 and TPGS mixed micelle encapsulating CUR for treatment of multidrug-resistant ovarian cancer. CUR-loaded Poloxamer 407/TPGS mixed micelles were prepared by thin film hydration method and their physicochemical properties were characterized. Cellular uptake and in vitro cytotoxicity of the CUR-loaded Poloxamer 407/TPGS mixed micelles were studied in multidrug-resistant ovarian cancer (NCI/ADR-RES) cells. The diameter of CUR-loaded Poloxamer 407/TPGS mixed micelles was about 21.4 +/- 0.3 nm and a zeta potential of -11.56 +/- 0.7 mV. The encapsulation efficiency of CUR was ranged from 95-86% with drug loading was about 1-9%. Differential scanning calorimetry and X-ray powder diffraction studies confirmed that CUR was encapsulated by the polymers. The in vitro release studies showed that mixed micelles sustained the release of CUR for more than 9 days. Results from cellular uptake studies indicated that CUR-loaded Poloxamer 407/TPGS mixed micelles had increased cellular uptake of CUR in NCI/ADR-RES cells. Cytotoxicity of CUR-loaded Poloxamer 407/TPGS mixed micelles was found to be 3 folds more than free CUR after 48 of incubations. Conclusion: This study suggests that Poloxamer 407/TPGS mixed micelles might be a suitable nanocarrier for curcumin to treat multidrug resistant ovarian cancer. PMID:23909128

Saxena, Vipin; Hussain, Muhammad Delwar

2013-07-01

223

Circumvention of multi-drug resistance of cancer cells by Chinese herbal medicines  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Multi-drug resistance (MDR) of cancer cells severely limits therapeutic outcomes. A proposed mechanism for MDR involves the efflux of anti-cancer drugs from cancer cells, primarily mediated by ATP-binding cassette (ABC) membrane transporters including P-glycoprotein. This article reviews the recent progress of using active ingredients, extracts and formulae from Chinese medicine (CM) in circumventing ABC transporters-mediated MDR. Among the ABC transporters, Pgp is the most extensively studied for its role in MDR reversal effects. While other MDR reversal mechanisms remain unclear, Pgp inhibition is a criterion for further mechanistic study. More mechanistic studies are needed to fully establish the pharmacological effects of potential MDR reversing agents.

Chai Stella; To Kenneth KW; Lin Ge

2010-01-01

224

PTRF/cavin-1 is essential for multidrug resistance in cancer cells.  

UK PubMed Central (United Kingdom)

Since detergent-resistant lipid rafts play important roles in multidrug resistance (MDR), their comprehensive proteomics could provide new insights to understand the underlying molecular mechanism of MDR in cancer cells. In the present work, lipid rafts were isolated from MCF-7 and adriamycin-resistant MCF-7/ADR cells and their proteomes were analyzed by label-free quantitative proteomics. Polymerase I and transcript release factor (PTRF)/cavin-1 was measured to be upregulated along with multidrug-resistant P-glycoprotein, caveolin-1, and serum deprivation protein response/cavin-2 in the lipid rafts of MCF-7/ADR cells. PTRF knockdown led to reduction in the amount of lipid rafts on the surface of MCF7/ADR cells as determined by cellular staining with lipid raft-specific dyes such as S-laurdan2 and FITC-conjugated cholera toxin B. PTRF knockdown also reduced MDR in MCF-7/ADR cells. These data indicate that PTRF is necessary for MDR in cancer cells via the fortification of lipid rafts.

Yi JS; Mun DG; Lee H; Park JS; Lee JW; Lee JS; Kim SJ; Cho BR; Lee SW; Ko YG

2013-02-01

225

Zoledronic Acid Restores Doxorubicin Chemosensitivity and Immunogenic Cell Death in Multidrug-Resistant Human Cancer Cells  

Science.gov (United States)

Durable tumor cell eradication by chemotherapy is challenged by the development of multidrug-resistance (MDR) and the failure to induce immunogenic cell death. The aim of this work was to investigate whether MDR and immunogenic cell death share a common biochemical pathway eventually amenable to therapeutic intervention. We found that mevalonate pathway activity, Ras and RhoA protein isoprenylation, Ras- and RhoA-downstream signalling pathway activities, Hypoxia Inducible Factor-1alpha activation were significantly higher in MDR+ compared with MDR? human cancer cells, leading to increased P-glycoprotein expression, and protection from doxorubicin-induced cytotoxicity and immunogenic cell death. Zoledronic acid, a potent aminobisphosphonate targeting the mevalonate pathway, interrupted Ras- and RhoA-dependent downstream signalling pathways, abrogated the Hypoxia Inducible Factor-1alpha-driven P-glycoprotein expression, and restored doxorubicin-induced cytotoxicity and immunogenic cell death in MDR+ cells. Immunogenic cell death recovery was documented by the ability of dendritic cells to phagocytise MDR+ cells treated with zoledronic acid plus doxorubicin, and to recruit anti-tumor cytotoxic CD8+ T lymphocytes. These data indicate that MDR+ cells have an hyper-active mevalonate pathway which is targetable with zoledronic acid to antagonize their ability to withstand chemotherapy-induced cytotoxicity and escape immunogenic cell death.

Riganti, Chiara; Castella, Barbara; Kopecka, Joanna; Campia, Ivana; Coscia, Marta; Pescarmona, Gianpiero; Bosia, Amalia; Ghigo, Dario; Massaia, Massimo

2013-01-01

226

Zoledronic acid restores doxorubicin chemosensitivity and immunogenic cell death in multidrug-resistant human cancer cells.  

UK PubMed Central (United Kingdom)

Durable tumor cell eradication by chemotherapy is challenged by the development of multidrug-resistance (MDR) and the failure to induce immunogenic cell death. The aim of this work was to investigate whether MDR and immunogenic cell death share a common biochemical pathway eventually amenable to therapeutic intervention. We found that mevalonate pathway activity, Ras and RhoA protein isoprenylation, Ras- and RhoA-downstream signalling pathway activities, Hypoxia Inducible Factor-1alpha activation were significantly higher in MDR+ compared with MDR- human cancer cells, leading to increased P-glycoprotein expression, and protection from doxorubicin-induced cytotoxicity and immunogenic cell death. Zoledronic acid, a potent aminobisphosphonate targeting the mevalonate pathway, interrupted Ras- and RhoA-dependent downstream signalling pathways, abrogated the Hypoxia Inducible Factor-1alpha-driven P-glycoprotein expression, and restored doxorubicin-induced cytotoxicity and immunogenic cell death in MDR+ cells. Immunogenic cell death recovery was documented by the ability of dendritic cells to phagocytise MDR+ cells treated with zoledronic acid plus doxorubicin, and to recruit anti-tumor cytotoxic CD8+ T lymphocytes. These data indicate that MDR+ cells have an hyper-active mevalonate pathway which is targetable with zoledronic acid to antagonize their ability to withstand chemotherapy-induced cytotoxicity and escape immunogenic cell death.

Riganti C; Castella B; Kopecka J; Campia I; Coscia M; Pescarmona G; Bosia A; Ghigo D; Massaia M

2013-01-01

227

Impact of P-Glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2) Gene Dosage on Plasma Pharmacokinetics and Brain Accumulation of Dasatinib, Sorafenib, and Sunitinib.  

UK PubMed Central (United Kingdom)

Low brain accumulation of anticancer drugs due to efflux transporters may limit chemotherapeutic efficacy, necessitating a better understanding of the underlying mechanisms. P-glycoprotein (Abcb1a/1b) and breast cancer resistance protein (Abcg2) combination knockout mice often display disproportionately increased brain accumulation of shared drug substrates compared with single transporter knockout mice. Recently developed pharmacokinetic models could explain this phenomenon. To experimentally test these models and their wider relevance for tyrosine kinase inhibitors and other drugs, we selected dasatinib, sorafenib, and sunitinib because of their divergent oral availability and brain accumulation profiles: the brain accumulation of dasatinib is mainly restricted by Abcb1, that of sorafenib mainly by Abcg2, and that of sunitinib equally by Abcb1 and Abcg2. We analyzed the effect of halving the efflux activity of these transporters at the blood-brain barrier by generating heterozygous Abcb1a/1b;Abcg2 knockout mice and testing the plasma and brain levels of the drugs after oral administration at 10 mg/kg. Real-time reverse transcription-polymerase chain reaction analysis confirmed the ?2-fold decreased expression of both transporters in brain. Interestingly, whereas complete knockout of the transporters caused 24- to 36-fold increases in brain accumulation of the drugs, the heterozygous mice only displayed 1.6- to 1.9-fold increases of brain accumulation relative to wild-type mice. These results are well in line with the predictions of the pharmacokinetic models and provide strong support for their validity for a wider range of drugs. Moreover, retrospective analysis of fetal accumulation of drugs across the placenta in Abcb1a/1b heterozygous knockout pups suggests that these models equally apply to the maternal-fetal barrier.

Tang SC; de Vries N; Sparidans RW; Wagenaar E; Beijnen JH; Schinkel AH

2013-09-01

228

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

2009-05-09

229

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

UK PubMed Central (United Kingdom)

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.

Venn AA; Quinn J; Jones R; Bodnar A

2009-07-01

230

Impact of P-Glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2) Gene Dosage on Plasma Pharmacokinetics and Brain Accumulation of Dasatinib, Sorafenib, and Sunitinib.  

Science.gov (United States)

Low brain accumulation of anticancer drugs due to efflux transporters may limit chemotherapeutic efficacy, necessitating a better understanding of the underlying mechanisms. P-glycoprotein (Abcb1a/1b) and breast cancer resistance protein (Abcg2) combination knockout mice often display disproportionately increased brain accumulation of shared drug substrates compared with single transporter knockout mice. Recently developed pharmacokinetic models could explain this phenomenon. To experimentally test these models and their wider relevance for tyrosine kinase inhibitors and other drugs, we selected dasatinib, sorafenib, and sunitinib because of their divergent oral availability and brain accumulation profiles: the brain accumulation of dasatinib is mainly restricted by Abcb1, that of sorafenib mainly by Abcg2, and that of sunitinib equally by Abcb1 and Abcg2. We analyzed the effect of halving the efflux activity of these transporters at the blood-brain barrier by generating heterozygous Abcb1a/1b;Abcg2 knockout mice and testing the plasma and brain levels of the drugs after oral administration at 10 mg/kg. Real-time reverse transcription-polymerase chain reaction analysis confirmed the ?2-fold decreased expression of both transporters in brain. Interestingly, whereas complete knockout of the transporters caused 24- to 36-fold increases in brain accumulation of the drugs, the heterozygous mice only displayed 1.6- to 1.9-fold increases of brain accumulation relative to wild-type mice. These results are well in line with the predictions of the pharmacokinetic models and provide strong support for their validity for a wider range of drugs. Moreover, retrospective analysis of fetal accumulation of drugs across the placenta in Abcb1a/1b heterozygous knockout pups suggests that these models equally apply to the maternal-fetal barrier. PMID:23843632

Tang, Seng Chuan; de Vries, Niels; Sparidans, Rolf W; Wagenaar, Els; Beijnen, Jos H; Schinkel, Alfred H

2013-07-10

231

Emerging therapies for multidrug resistant Acinetobacter baumannii.  

UK PubMed Central (United Kingdom)

The global emergence of multidrug resistant Acinetobacter baumannii has reduced the number of clinically available antibiotics that retain activity against this pathogen. For this reason, the development of novel prevention and treatment strategies for infections caused by A. baumannii is necessary. Several studies have begun to characterize nonantibiotic approaches that utilize novel mechanisms of action to achieve antibacterial activity. Recent advances in phage therapy, iron chelation therapy, antimicrobial peptides, prophylactic vaccination, photodynamic therapy, and nitric oxide (NO)-based therapies have all been shown to have activity against A. baumannii. However, before these approaches can be used clinically there are still limitations and remaining questions that must be addressed.

García-Quintanilla M; Pulido MR; López-Rojas R; Pachón J; McConnell MJ

2013-03-01

232

Trends in multidrug-resistant tuberculosis  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Multidrug-resistant tuberculosis (MDR-TB) is an increasing global problem. The extent and burden of MDR-TB varies significantly from country to country and region to region. Globally, about three per cent of all newly diagnosed patients have MDR-TB and the proportion is higher in patients who had previously received anti-tuberculosis (anti-TB) treatment reflecting the failure of programs designed to ensure complete cure of patients with tuberculosis. The management of MDR (more) -TB is a challenge that should be undertaken by experienced clinicians at centers equipped with reliable laboratory services and implementation of DOTS-Plus strategy.

Dias-Baptista, I. M. F.; Usó, S. M. R. S.; Marcondes-Machado, J.

2008-01-01

233

Trends in multidrug-resistant tuberculosis  

Directory of Open Access Journals (Sweden)

Full Text Available Multidrug-resistant tuberculosis (MDR-TB) is an increasing global problem. The extent and burden of MDR-TB varies significantly from country to country and region to region. Globally, about three per cent of all newly diagnosed patients have MDR-TB and the proportion is higher in patients who had previously received anti-tuberculosis (anti-TB) treatment reflecting the failure of programs designed to ensure complete cure of patients with tuberculosis. The management of MDR-TB is a challenge that should be undertaken by experienced clinicians at centers equipped with reliable laboratory services and implementation of DOTS-Plus strategy.

I. M. F. Dias-Baptista; S. M. R. S. Usó; J. Marcondes-Machado

2008-01-01

234

Substrate versus inhibitor dynamics of P-glycoprotein.  

Science.gov (United States)

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 simulations to examine the behaviour of P-gp. In agreement with previous reports, we found that P-gp undergoes large conformational changes which tended to result in the nucleotide-binding domains coming closer together. In all simulations, the approach of the NBDs was asymmetrical in agreement with previous observations for other ABC transporter proteins. To validate the simulations, we make extensive comparison to previous cross-linking data. Our results show very good agreement with the available data. We then went on to compare the influence of inhibitor compounds bound with simulations of a substrate (daunorubicin) bound. Our results suggest that inhibitors may work by keeping the NBDs apart, thus preventing ATP-hydrolysis. On the other hand, repeat simulations of daunorubicin (substrate) in one particular binding pose suggest that the approach of the NBDs is not impaired and that the structure would be still be competent to perform ATP hydrolysis, thus providing a model for inhibition or substrate transport. Finally we compare the latter to earlier QSAR data to provide a model for the first part of substrate transport within P-gp. Proteins 2013. © 2013 Wiley Periodicals, Inc. PMID:23670856

Ma, Jerome; Biggin, Philip C

2013-06-17

235

ABC Transporters in Multidrug Resistance and Pharmacokinetics, and Strategies for Drug Development.  

UK PubMed Central (United Kingdom)

Multidrug resistance (MDR) is a serious problem that hampers the success of cancer pharmacotherapy. A common mechanism is the overexpression of ATP-binding cassette (ABC) efflux transporters in cancer cells such as P-glycoprotein (P-gp/ABCB1), multidrug resistance-associated protein 1 (MRP1/ABCC1) and breast cancer resistance protein (BCRP/ABCG2) that limit the exposure to anticancer drugs. One way to overcome MDR is to develop ABC efflux transporter inhibitors to sensitize cancer cells to chemotherapeutic drugs. The completed clinical trials thus far have showed that those tested chemosensitizers add only limited or no benefits to cancer patients. Some MDR modulators are merely toxic, and others induce unwanted drug-drug interactions. Actually, many ABC transporters are also expressed abundantly in the gastrointestinal tract, liver, kidney, brain and other normal tissues, and they largely determine drug absorption, distribution and excretion, and affect the overall pharmacokinetic properties of drugs in humans. In addition, ABC transporters such as P-gp, MRP1 and BCRP co-expressed in tumors show a broad and overlapped specificity for substrates and MDR modulators. Thus reliable preclinical assays and models are required for the assessment of transporter-mediated flux and potential effects on pharmacokinetics in drug development. In this review, we provide an overview of the role of ABC efflux transporters in MDR and pharmacokinetics.Preclinical assays for the assessment of drug transport and development of MDR modulators are also discussed.

Choi YH; Yu AM

2013-05-01

236

Biological variability and the emergence of multidrug-resistant tuberculosis.  

UK PubMed Central (United Kingdom)

A new study demonstrates that bacterial mutation rates associated with the Mycobacterium tuberculosis lineage most commonly linked to multidrug-resistant tuberculosis are multifold higher than shown in previous studies. This discovery, when considered together with recent findings on pharmacokinetic variability in patients, leads to new models of how multidrug-resistant tuberculosis arises, with direct therapeutic implications.

Gumbo T

2013-07-01

237

[Managing multi-drug resistant bacteria in nursing homes].  

UK PubMed Central (United Kingdom)

The application of standard and sometimes additional hygiene precautions also concerns nursing homes, in order to prevent the transmission of multi-drug resistant bacteria. If a resident is a carrier or infected by a multi-drug resistant bacteria, the care must be organised accordingly but geographic confinement is rarely adapted.

Novakova I; Neveur M

2013-06-01

238

Biological variability and the emergence of multidrug-resistant tuberculosis.  

Science.gov (United States)

A new study demonstrates that bacterial mutation rates associated with the Mycobacterium tuberculosis lineage most commonly linked to multidrug-resistant tuberculosis are multifold higher than shown in previous studies. This discovery, when considered together with recent findings on pharmacokinetic variability in patients, leads to new models of how multidrug-resistant tuberculosis arises, with direct therapeutic implications. PMID:23800865

Gumbo, Tawanda

2013-07-01

239

Interaction of 11C-Tariquidar and 11C-Elacridar with P-Glycoprotein and Breast Cancer Resistance Protein at the Human Blood-Brain Barrier.  

UK PubMed Central (United Kingdom)

UNLABELLED: The adenosine triphosphate-binding cassette transporters P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) are 2 major gatekeepers at the blood-brain barrier (BBB) that restrict brain distribution of several clinically used drugs. In this study, we investigated the suitability of the radiolabeled Pgp/BCRP inhibitors (11)C-tariquidar and (11)C-elacridar to assess Pgp density in the human brain with PET. METHODS: Healthy subjects underwent a first PET scan of 120-min duration with either (11)C-tariquidar (n = 6) or (11)C-elacridar (n = 5) followed by a second PET scan of 60-min duration with (R)-(11)C-verapamil. During scan 1 (at 60 min after radiotracer injection), unlabeled tariquidar (3 mg/kg) was intravenously administered. Data were analyzed using 1-tissue 2-rate-constant (1T2K) and 2-tissue 4-rate-constant (2T4K) compartment models and either metabolite-corrected or uncorrected arterial input functions. RESULTS: After injection of (11)C-tariquidar or (11)C-elacridar, the brain PET signal corrected for radioactivity in the vasculature was low (?0.1 standardized uptake value), with slow washout. In response to tariquidar injection, a moderate but statistically significant rise in brain PET signal was observed for (11)C-tariquidar (+27% ± 15%, P = 0.014, paired t test) and (11)C-elacridar (+21% ± 15%, P = 0.014) without changes in plasma activity concentrations. Low levels of radiolabeled metabolites (<25%) were detected in plasma up to 60 min after injection of (11)C-tariquidar or (11)C-elacridar. The 2T4K model provided better data fits than the 1T2K model. Model outcome parameters were similar when metabolite-corrected or uncorrected input functions were used. There was no significant correlation between distribution volumes of (11)C-tariquidar or (11)C-elacridar and distribution volumes of (R)-(11)C-verapamil in different brain regions. CONCLUSION: The in vivo behavior of (11)C-tariquidar and (11)C-elacridar was consistent with that of dual Pgp/BCRP substrates. Both tracers were unable to visualize cerebral Pgp density, most likely because of insufficiently high binding affinities in relation to the low density of Pgp in human brain (?1.3 nM). Despite their inability to visualize Pgp density, (11)C-tariquidar and (11)C-elacridar may find use as a new class of radiotracers to study the interplay of Pgp and BCRP at the human BBB in limiting brain uptake of dual substrates.

Bauer M; Karch R; Zeitlinger M; Stanek J; Philippe C; Wadsak W; Mitterhauser M; Jäger W; Haslacher H; Müller M; Langer O

2013-08-01

240

Reversal effect of rosmarinic acid on multidrug resistance in SGC7901/Adr cell.  

UK PubMed Central (United Kingdom)

Multidrug resistance (MDR) has been a major problem in cancer chemotherapy. In this study, the aim was to explore the reversal effect and its potential mechanism of rosmarinic acid (RA) on SGC7901/Adr cells. 3-(4,5-Dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to investigate the reversal index of RA in SGC7901/Adr cell line. The intracellular accumulation of adriamycin, rhodamine123 (Rh123), and the expression of P-glycoprotein (P-gp) were assayed by flow cytometry. The influence of RA on the transcription of MDR1 gene was determined by reverse transcription-polymerase chain reaction. The results showed that RA could reverse the MDR of SGC7901/Adr cells, increase the intracellular accumulation of Adr and Rh123, and decrease the transcription of MDR1 gene and the expression of P-gp in SGC7901/Adr cells. These results indicated that RA was a potential multidrug resistance-reversing agent and warranted further investigations.

Li FR; Fu YY; Jiang DH; Wu Z; Zhou YJ; Guo L; Dong ZM; Wang ZZ

2013-01-01

 
 
 
 
241

Reversal effect of rosmarinic acid on multidrug resistance in SGC7901/Adr cell.  

Science.gov (United States)

Multidrug resistance (MDR) has been a major problem in cancer chemotherapy. In this study, the aim was to explore the reversal effect and its potential mechanism of rosmarinic acid (RA) on SGC7901/Adr cells. 3-(4,5-Dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to investigate the reversal index of RA in SGC7901/Adr cell line. The intracellular accumulation of adriamycin, rhodamine123 (Rh123), and the expression of P-glycoprotein (P-gp) were assayed by flow cytometry. The influence of RA on the transcription of MDR1 gene was determined by reverse transcription-polymerase chain reaction. The results showed that RA could reverse the MDR of SGC7901/Adr cells, increase the intracellular accumulation of Adr and Rh123, and decrease the transcription of MDR1 gene and the expression of P-gp in SGC7901/Adr cells. These results indicated that RA was a potential multidrug resistance-reversing agent and warranted further investigations. PMID:23421517

Li, Fa-Rong; Fu, Yan-Yan; Jiang, Dan-Hong; Wu, Zhen; Zhou, Yang-Jing; Guo, Ling; Dong, Zhong-Min; Wang, Zhe-Zhi

2013-02-19

242

Expression and clinical significance of multidrug resistance proteins in brain tumors  

Directory of Open Access Journals (Sweden)

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; Zhu Jin; Zhao Lihua; Luo Qing; Jin Xianqing

2010-01-01

243

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

Energy Technology Data Exchange (ETDEWEB)

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.

Chun, K. A.; Lee, J.; Chun, S. H.; Sohn, S. K.; Yi, C. K.; Lee, K. B. [College of Medicine, Kyungpook National Univ., Taegu (Korea, Republic of); Kim, J. H. [College of Medicine, Youngnam Univ., Taegu (Korea, Republic of)

1997-07-01

244

Hyaluronan oligosaccharides sensitize lymphoma resistant cell lines to vincristine by modulating P-glycoprotein activity and PI3K/Akt pathway.  

UK PubMed Central (United Kingdom)

Multidrug resistance (MDR) is one of the main reasons for failure of cancer therapy. It may be mediated by overexpression of ATP-dependent efflux pumps or by alterations in survival or apoptotic pathways. Fragments generated by enzymatic degradation of hyaluronan (oHA) were able to modulate growth and cell survival and sensitize MDR breast cancer cells to cytotoxic drugs. In this work the relationship between oHA and MDR in lymphoid malignancies was analyzed using murine lymphoma cell lines resistant to doxorubicin (LBR-D160) or vincristine (LBR-V160) and a sensitive line (LBR-). After oHA treatment, higher apoptosis levels were observed in the resistant cell lines than in the sensitive one. Besides, oHA sensitized LBR-D160 and LBR-V160 to vincristine showing increased apoptosis induction when used in combination with vincristine. Native hyaluronan failed to increase apoptosis levels. As different survival factors could be modulated by hyaluronan, we investigated the PI3K/Akt pathway through PIP3 production and phosphorylated Akt (p-Akt) and survivin expression was also evaluated. Our results showed that oHA decreased p-Akt in the 3 cell lines while anti-CD44 treatment abolished this effect. Besides, survivin was downregulated only in LBR-V160 by oHA. When Pgp function was evaluated, we observed that oHA were able to inhibit Pgp efflux in murine and human resistant cell lines in a CD44-dependent way. In summary, we report for the first time that oHA per se modulate MDR in lymphoma cells by decreasing p-Akt as well as Pgp activity, thus suggesting that oHA could be useful in combination with classical chemotherapy in MDR hematological malignancies.

Cordo Russo RI; García MG; Alaniz L; Blanco G; Alvarez E; Hajos SE

2008-03-01

245

Hyaluronan oligosaccharides sensitize lymphoma resistant cell lines to vincristine by modulating P-glycoprotein activity and PI3K/Akt pathway.  

Science.gov (United States)

Multidrug resistance (MDR) is one of the main reasons for failure of cancer therapy. It may be mediated by overexpression of ATP-dependent efflux pumps or by alterations in survival or apoptotic pathways. Fragments generated by enzymatic degradation of hyaluronan (oHA) were able to modulate growth and cell survival and sensitize MDR breast cancer cells to cytotoxic drugs. In this work the relationship between oHA and MDR in lymphoid malignancies was analyzed using murine lymphoma cell lines resistant to doxorubicin (LBR-D160) or vincristine (LBR-V160) and a sensitive line (LBR-). After oHA treatment, higher apoptosis levels were observed in the resistant cell lines than in the sensitive one. Besides, oHA sensitized LBR-D160 and LBR-V160 to vincristine showing increased apoptosis induction when used in combination with vincristine. Native hyaluronan failed to increase apoptosis levels. As different survival factors could be modulated by hyaluronan, we investigated the PI3K/Akt pathway through PIP3 production and phosphorylated Akt (p-Akt) and survivin expression was also evaluated. Our results showed that oHA decreased p-Akt in the 3 cell lines while anti-CD44 treatment abolished this effect. Besides, survivin was downregulated only in LBR-V160 by oHA. When Pgp function was evaluated, we observed that oHA were able to inhibit Pgp efflux in murine and human resistant cell lines in a CD44-dependent way. In summary, we report for the first time that oHA per se modulate MDR in lymphoma cells by decreasing p-Akt as well as Pgp activity, thus suggesting that oHA could be useful in combination with classical chemotherapy in MDR hematological malignancies. PMID:17985348

Cordo Russo, Rosalía I; García, Mariana G; Alaniz, Laura; Blanco, Guillermo; Alvarez, Elida; Hajos, Silvia E

2008-03-01

246

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

UK PubMed Central (United Kingdom)

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.

Yang S; Liu J; Chen Y; Jiang J

2012-04-01

247

In vitro antileukaemic activity of extracts from berry plant leaves against sensitive and multidrug resistant HL60 cells.  

Science.gov (United States)

The aim of the present study was to determine in vitro antileukaemic activity of extracts obtained from selected berry plant leaves (Fragaria x ananassa Duch. cv Elsanta, raspberry Rubus ideus L. cv Polana and blueberry Vaccinium corymbosum L. cv Bluecrop) against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the blueberry extract was the most efficient against sensitive HL60 cell line (about 2-fold more active than strawberry and raspberry extracts) but presented much lower activity towards resistant cells. In contrast, strawberry and raspberry extracts exhibited the high cytotoxic activity against sensitive leukaemia HL60 cell line as well as its MDR sublines. The values of resistance factor (RF) found for these extracts were very low lying in the range 0.32/2.0. PMID:16039042

Skupie?, Katarzyna; Oszmia?ski, Jan; Kostrzewa-Nowak, Dorota; Tarasiuk, Jolanta

2005-07-20

248

In vitro antileukaemic activity of extracts from berry plant leaves against sensitive and multidrug resistant HL60 cells.  

UK PubMed Central (United Kingdom)

The aim of the present study was to determine in vitro antileukaemic activity of extracts obtained from selected berry plant leaves (Fragaria x ananassa Duch. cv Elsanta, raspberry Rubus ideus L. cv Polana and blueberry Vaccinium corymbosum L. cv Bluecrop) against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the blueberry extract was the most efficient against sensitive HL60 cell line (about 2-fold more active than strawberry and raspberry extracts) but presented much lower activity towards resistant cells. In contrast, strawberry and raspberry extracts exhibited the high cytotoxic activity against sensitive leukaemia HL60 cell line as well as its MDR sublines. The values of resistance factor (RF) found for these extracts were very low lying in the range 0.32/2.0.

Skupie? K; Oszmia?ski J; Kostrzewa-Nowak D; Tarasiuk J

2006-05-01

249

Successful treatment of multidrug resistant Acinetobacter baumannii meningitis  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Acinetobacter baumannii is a major cause of nosocomial infections in many hospitals and appears to have a propensity for developing multiple antimicrobial resistance rapidly.Cases: We report two cases with post-surgical meningitis due to multidrug resistant A. baumannii which were successfully treated with high-dose intravenous meropenem therapy.Conclusions: Multidrug resistant Acinetobacter spp. in intensive care units are a growing concern. High-dose meropenem is used in the treatment of these infections.

Acinetobacter baumannii, Post-surgical meningitis, High dose meropenem

2007-01-01

250

Effect of phenoxazine MDR modulators on photoaffinity labeling of P-glycoprotein by [3H] azidopine: an approach to understand drug resistance in cancer chemotherapy  

International Nuclear Information System (INIS)

P-glycoprotein (P-gp) rich membrane fractions from KB-VI cells were isolated and the interaction of [3H] azidopine with membrane fractions in the presence of 25, 50 and 100 ?M concentration of each of the twenty N10 -substituted phenoxazines, was under taken and the extent of competition was compared to a standard modulator, verapamil. Competition data showed that only two modulators 4 and 6 exhibited the maximum competition (>50%). Among the compounds examined, three of them interact strongly (>50%), six marginally (

1999-01-01

251

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-resistant cells. This may occur through modulation of an efflux pump by protein phosphorylation.

1988-01-01

252

Phorbol esters induce multidrug resistance in human breast cancer cells.  

UK PubMed Central (United Kingdom)

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 parent cells. Exposure of drug-sensitive cells to the phorbol ester phorbol 12,13-dibutyrate [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 accompanied 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 plays a role in the drug-transport changes in multidrug-resistant cells. This may occur through modulation of an efflux pump by protein phosphorylation.

Fine RL; Patel J; Chabner BA

1988-01-01

253

Phorbol esters induce multidrug resistance in human breast cancer cells  

Energy Technology Data Exchange (ETDEWEB)

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

254

Drug resistance pattern in multidrug resistance pulmonary tuberculosis patients  

International Nuclear Information System (INIS)

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)

2010-01-01

255

Drug resistance pattern in multidrug resistance pulmonary tuberculosis patients.  

UK PubMed Central (United Kingdom)

OBJECTIVE: 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.

Rao NA; Irfan M; Soomro MM; Mehfooz Z

2010-04-01

256

In vitro antileukaemic activity of extracts from chokeberry (Aronia melanocarpa [Michx] Elliott) and mulberry (Morus alba L.) leaves against sensitive and multidrug resistant HL60 cells.  

Science.gov (United States)

The aim of the present study was to determine in vitro antileukaemic activities of extracts obtained from chokeberry (Aronia melanocarpa [Michx] Elliot) and mulberry (Morus alba L.) leaves against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the extracts from chokeberry and mulberry leaves were active against the sensitive leukaemic cell line HL60 and retained the in vitro activity against multidrug resistant sublines (HL60/VINC and HL60/DOX). The values of resistance factor (RF) found for these extracts were very low lying in the range 1.2-1.6. PMID:18350513

Skupie?, Katarzyna; Kostrzewa-Nowak, Dorota; Oszmia?ski, Jan; Tarasiuk, Jolanta

2008-05-01

257

In vitro antileukaemic activity of extracts from chokeberry (Aronia melanocarpa [Michx] Elliott) and mulberry (Morus alba L.) leaves against sensitive and multidrug resistant HL60 cells.  

UK PubMed Central (United Kingdom)

The aim of the present study was to determine in vitro antileukaemic activities of extracts obtained from chokeberry (Aronia melanocarpa [Michx] Elliot) and mulberry (Morus alba L.) leaves against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the extracts from chokeberry and mulberry leaves were active against the sensitive leukaemic cell line HL60 and retained the in vitro activity against multidrug resistant sublines (HL60/VINC and HL60/DOX). The values of resistance factor (RF) found for these extracts were very low lying in the range 1.2-1.6.

Skupie? K; Kostrzewa-Nowak D; Oszmia?ski J; Tarasiuk J

2008-05-01

258

Multi-Drug Resistant Tuberculosis: Occurrence in US and ...  

Science.gov (United States)

Text Version... HIV Infection and multidrug-resistant tuberculosis - the perfect storm. J Infect Dis 2007;196:S86-S107 Page 6. Patient characteristics No. (%) ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

259

The imaging feature of multidrug-resistant tuberculosis  

International Nuclear Information System (INIS)

Objective: To evaluate the imaging features of multidrug-resistant tuberculosis by collecting multidrug-resistant tuberculosis verified by test of drug-sensitivity, which defined as resistance to three anti-tuberculosis drugs. Methods:Fifty-one cases of multidrug-resistant tuberculosis were categorized as group of observed, and 46 cases of drug sensitive tuberculosis were categorized as control. Cultures were positive for Mycobacterium tuberculosis in all cases with no other illness such as diabetes mellitus. All patients had chest radiographs available for review, while 64 cases had tomography and 30 cases had CT during the same time. All images were analyzed by three of the radiologists, disagreement among them was discussed and a consensus was reached. Results: There was no difference in the distribution of lesions between the multidrug-resistant tuberculosis group and control group. However, the radiological findings in the multidrug-resistant tuberculosis group were significantly more common than in control group, such as multiple nodules (10 cases), disseminated foci (23 cases), cavity (9 cases), and complications (10 cases). Comparing the dynamic cases, deteriorating cases were more commonly seen in observed group than in control group, while improved cases were less in observed group than in control group. Conclusion: Multidrug-resistant tuberculosis is the most serious tuberculosis, which is characterized with significant activity, more disseminated foci, cavity, and complications. The lesion deteriorated while correct anti-tuberculosis treatment is applied. (authors)

2004-01-01

260

Multidrug resistant yeasts in synanthropic wild birds  

Directory of Open Access Journals (Sweden)

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.

Lord Alexander; Mohandas Kavitha; Somanath Sushela; Ambu Stephen

2010-01-01

 
 
 
 
261

Multidrug resistant yeasts in synanthropic wild birds.  

UK PubMed Central (United Kingdom)

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.

Lord AT; Mohandas K; Somanath S; Ambu S

2010-01-01

262

Combating apoptosis and multidrug resistant cancers by targeting lysosomes.  

UK PubMed Central (United Kingdom)

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.

Groth-Pedersen L; Jäättelä M

2013-05-01

263

Novel tubulin polymerization inhibitors overcome multidrug resistance and reduce melanoma lung metastasis.  

UK PubMed Central (United Kingdom)

PURPOSE: To evaluate abilities of 2-aryl-4-benzoyl-imidazoles (ABI) to overcome multidrug resistance (MDR), define their cellular target, and assess in vivo antimelanoma efficacy. METHODS: MDR cell lines that overexpressed P-glycoprotein, MDR-associated proteins, and breast cancer resistance protein were used to evaluate ABI ability to overcome MDR. Cell cycle analysis, molecular modeling, and microtubule imaging were used to define ABI cellular target. SHO mice bearing A375 human melanoma xenograft were used to evaluate ABI in vivo antitumor activity. B16-F10/C57BL mouse melanoma lung metastasis model was used to test ABI efficacy to inhibit tumor lung metastasis. RESULTS: ABIs showed similar potency to MDR cells compared to matching parent cells. ABIs were identified to target tubulin on the colchicine binding site. After 31 days of treatment, ABI-288 dosed at 25 mg/kg inhibited melanoma tumor growth by 69%; dacarbazine at 60 mg/kg inhibited growth by 52%. ABI-274 dosed at 25 mg/kg showed better lung metastasis inhibition than dacarbazine at 60 mg/kg. CONCLUSIONS: This new class of antimitotic compounds can overcome several clinically important drug resistant mechanisms in vitro and are effective in inhibiting melanoma lung metastasis in vivo, supporting their further development.

Wang Z; Chen J; Wang J; Ahn S; Li CM; Lu Y; Loveless VS; Dalton JT; Miller DD; Li W

2012-11-01

264

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

Directory of Open Access Journals (Sweden)

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.

Ahmadreza Mehdipour; Katayoun Javidnia; Bahram Hemmateenejad; Ramin Miri

2007-01-01

265

Salvage therapy for multidrug-resistant tuberculosis.  

UK PubMed Central (United Kingdom)

Treatment of multidrug-resistant tuberculosis (MDR-TB), defined as Mycobacterium tuberculosis resistant to both isoniazid and rifampicin, is challenging under the best of circumstances, and particularly in resource-limited settings. For patients who remain persistently sputum-culture-positive despite therapy with second-line TB drugs, treatment options are limited, especially if disease is too advanced for resective surgery. Salvage therapy refers to the design of a regimen combining new and previously used drugs in a final effort to attain sputum conversion before declaring treatment to have failed. We retrospectively evaluated the outcomes of salvage therapy in 213 Peruvian patients. Salvage regimens included a median of two new drugs (range 1-6) and nine (range 5-13) total (new plus previously used) drugs. The most frequently used new drug was moxifloxacin, followed by capreomycin, amoxicillin-clavulanate, kanamycin and clarithromycin. Culture conversion occurred in 65 (30.5%) patients. Salvage regimens that included moxifloxacin were significantly more likely to be followed by culture conversion (OR 2.2; p 0.02). Later-generation fluoroquinolones such as moxifloxacin should be used in salvage therapy but also in the initial treatment of MDR-TB, if the best clinical strategy is to use the most effective drugs when the patient has the best chance for cure. New TB drugs are most likely to be initially used in salvage patients, in conditions similar to those described here. Close bacteriological monitoring of these patients will be essential, as useful information about the best way to use these new drugs can be gained from analysis of salvage therapy cohorts.

Seung KJ; Becerra MC; Atwood SS; Alcántara F; Bonilla CA; Mitnick CD

2013-07-01

266

Silencing of P-glycoprotein increases mortality in temephos-treated Aedes aegypti larvae.  

UK PubMed Central (United Kingdom)

Re-emergence of vector-borne diseases such as dengue and yellow fever, which are both transmitted by the Aedes aegypti mosquito, has been correlated with insecticide resistance. P-glycoproteins (P-gps) are ATP-dependent efflux pumps that are involved in the transport of substrates across membranes. Some of these proteins have been implicated in multidrug resistance (MDR). In this study, we identified a putative P-glycoprotein in the Ae.?aegypti database based on its significantly high identity with Anopheles gambiae, Culex quinquefasciatus, Drosophila melanogaster and human P-gps. The basal ATPase activity of ATP-binding cassette transporters in larvae was significantly increased in the presence of MDR modulators (verapamil and quinidine). An eightfold increase in Ae.?aegypti P-gp (AaegP-gp) gene expression was detected in temephos-treated larvae as determined by quantitative PCR. To analyse the potential role of AaegP-gp in insecticide efflux, a temephos larvicide assay was performed in the presence of verapamil. The results showed an increase of 24% in temephos toxicity, which is in agreement with the efflux reversing effect. RNA interference (RNAi)-mediated silencing of the AaegP-gp gene caused a significant increase in temephos toxicity (57%). In conclusion, we have demonstrated for the first time in insects that insecticide-induced P-gp expression can be involved in the modulation of insecticide efflux.

Figueira-Mansur J; Ferreira-Pereira A; Mansur JF; Franco TA; Alvarenga ES; Sorgine MH; Neves BC; Melo AC; Leal WS; Masuda H; Moreira MF

2013-08-01

267

Lipid-functionalized dextran nanosystems to overcome multidrug resistance in cancer: a pilot study.  

UK PubMed Central (United Kingdom)

BACKGROUND: The toxicity of anticancer agents and the difficulty in delivering drugs selectively to tumor cells pose a challenge in overcoming multidrug resistance (MDR). Recently, nanotechnology has emerged as a powerful tool in addressing some of the barriers to drug delivery, including MDR in cancer, by utilizing alternate routes of cellular entry and targeted delivery of drugs and genes. However, it is unclear whether doxorubicin (Dox) can be delivered by nanotechnologic approaches. QUESTIONS/PURPOSES: We asked whether (1) Dox-loaded lipid-functionalized dextran-based biocompatible nanoparticles (Dox/NP) can reverse MDR, (2) Dox/NP has more potent cytotoxic effect on MDR tumors than poly(ethylene glycol)-modified liposomal Dox (PLD), and (3) multidrug resistance protein 1 (MDR1) small interfering RNA loaded in these nanoparticles (siMDR1/NP) can modulate MDR. METHODS: To create stable Dox/NP and siMDR1/NP, we used two different lipid-modified dextran derivatives. The effect of Dox or Dox/NP was tested on drug-sensitive osteosarcoma (KHOS) and ovarian cancer (SKOV-3) cell cultures in triplicate and their respective MDR counterparts KHOS(R2) and SKOV-3(TR) in triplicate. We determined the effects on drug retention, transfection efficacy of siMDR1/NP, and P-glycoprotein expression and the antiproliferative effect between Dox/NP and PLD in MDR tumor cells. RESULTS: Fluorescence microscopy revealed efficient uptake of the Dox/NP and fluorescently tagged siMDR1/NP. Dox/NP showed five- to 10-fold higher antiproliferative activity at the 50% inhibitory concentration than free Dox in tumor cells. Dox/NP showed twofold higher activity than PLD in MDR tumor cells. siMDR1/NP (100 nM) suppressed P-glycoprotein expression in KHOS(R2). CONCLUSIONS: Dextran-lipid nanoparticles are a promising platform for delivering Dox and siRNAs. CLINICAL RELEVANCE: Biocompatible dextran-based nanoparticles that are directly translatable to clinical medicine may lead to new potential therapeutics for reversing MDR in patients with cancer.

Kobayashi E; Iyer AK; Hornicek FJ; Amiji MM; Duan Z

2013-03-01

268

Nilotinib potentiates anticancer drug sensitivity in murine ABCB1-, ABCG2-, and ABCC10-multidrug resistance xenograft models.  

UK PubMed Central (United Kingdom)

A panel of clinically used tyrosine kinase inhibitors were compared and nilotinib was found to most potently sensitize specific anticancer agents by blocking the functions of ABCB1/P-glycoprotein, ABCG2/BCRP and ABCC10/MRP7 transporters involved in multi-drug resistance. Nilotinib appreciably enhanced the antitumor response of (1) paclitaxel in the ABCB1- and novel ABCC10-xenograft models, and (2) doxorubicin in a novel ABCG2-xenograft model. With no apparent toxicity observed in the above models, nilotinib attenuated tumor growth synergistically and increased paclitaxel concentrations in ABCB1-overexpressing tumors. The beneficial actions of nilotinib warrant consideration as viable combinations in the clinic with agents that suffer from MDR-mediated insensitivity.

Tiwari AK; Sodani K; Dai CL; Abuznait AH; Singh S; Xiao ZJ; Patel A; Talele TT; Fu L; Kaddoumi A; Gallo JM; Chen ZS

2013-01-01

269

High-Level ?-Lactam Resistance Associated with Acquired Multidrug Resistance in Helicobacter pylori  

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Four clinical Helicobacter pylori isolates with high-level resistance to ?-lactams exhibited low- to moderate-level resistance to the structurally and functionally unrelated antibiotics ciprofloxacin, chloramphenicol, metronidazole, rifampin, and tetracycline. This pattern of multidrug resistance wa...

Kwon, Dong H.; Dore, M. P.; Kim, J. J.; Kato, M.; Lee, M.; Wu, J. Y.; Graham, D. Y.

270

Cediranib (recentin, AZD2171) reverses ABCB1- and ABCC1-mediated multidrug resistance by inhibition of their transport function.  

UK PubMed Central (United Kingdom)

PURPOSE: Cediranib (recentin, AZD2171) is an oral small-molecule multiple receptor tyrosine kinases inhibitor. Here we investigate the ability of cediranib to reverse tumor multidrug resistance (MDR) due to overexpression of ABCB1 (P-glycoprotein) and ABCC1 (MRP1) transporters. METHODS: KBv200,MCF-7/adr, C-A120 and their parental sensitive cell lines KB, MCF-7 and KB-3-1 were used for reversal study. The intracellular accumulations of doxorubicin and rhodamine 123 were determined by flow cytometry. The expressions levels of ABCB1 and ABCC1 were investigated by Western blot and RT-PCR analyses. ATPase activity assay were performed by Luminescence. The functions of ERK in MCF-7/adr were investigated by RNA interference. RESULTS: Cediranib significantly enhanced the sensitivity of ABCB1 or ABCC1 substrates in MDR cells, with no effect found on sensitive cells. However, the expressions of these transporters were not affected and the reversal activity of cediranib was not related to the phosphorylation of AKT or ERK1/2. Further studies showed that cediranib inhibited ATPase activity of ABCB1 (P-glycoprotein) in a dose-dependent manner. CONCLUSIONS: Cediranib reverses ABCB1- and ABCC1-mediated MDR by directly inhibiting their drug efflux function. These findings may be useful for cancer combinational therapy with cediranib in the clinic.

Tao LY; Liang YJ; Wang F; Chen LM; Yan YY; Dai CL; Fu LW

2009-10-01

271

Reactive oxygen species participate in mdr1b mRNA and P-glycoprotein overexpression in primary rat hepatocyte cultures.  

UK PubMed Central (United Kingdom)

P-glycoproteins encoded by multidrug resistance type 1 (mdr1) genes mediate ATP-dependent efflux of numerous lipophilic xenobiotics, including several anticancer drugs, from cells. Overexpression of mdr1-type transporters in tumour cells contributes to a multidrug resistance phenotype. Several factors shown to induce mdr1 overexpression (UV irradiation, epidermal growth factor, tumour necrosis factor alpha, doxorubicin) have been associated with the generation of reactive oxygen species (ROS). In the present study, primary rat hepatocyte cultures that exhibit time-dependent overexpression of the mdr1b gene were used as a model system to investigate whether ROS might participate in the regulation of intrinsic mdr1b overexpression. Addition of H2O2 to the culture medium resulted in a significant increase in mdrlb mRNA and P-glycoprotein after 3 days of culture, with maximal (approximately 2-fold) induction being observed with 0.5-1 mM H2O2. Furthermore, H2O2 led to activation of poly(ADP-ribose) polymerase, a nuclear enzyme activated by DNA strand breaks, indicating that ROS reached the nuclear compartment. Thus, extracellularly applied H2O2 elicited intracellular effects. Treatment of rat hepatocytes with the catalase inhibitor 3-amino-1,2,4-triazole (2-4 mM for 72 h or 10 mM for 1 h following the hepatocyte attachment period) also led to an up-regulation of mdrlb mRNA and P-glycoprotein expression. Conversely, antioxidants (1 mM ascorbate, 10 mM mannitol, 2% dimethyl sulphoxide, 10 mM N-acetylcysteine) markedly suppressed intrinsic mdr1b mRNA and P-glycoprotein overexpression. Intracellular steady-state levels of the mdrl substrate rhodamine 123, determined as parameter of mdr1-type transport activity, indicated that mdr1-dependent efflux was increased in hepatocytes pretreated with H2O2 or aminotriazole and decreased in antioxidant-treated cells. The induction of mdr1b mRNA and of functionally active mdr1-type P-glycoproteins by elevation in intracellular ROS levels and the repression of intrinsic mdrlb mRNA and P-glycoprotein overexpression by antioxidant compounds support the conclusion that the expression of the mdr1b P-glycoprotein is regulated in a redox-sensitive manner.

Ziemann C; Bürkle A; Kahl GF; Hirsch-Ernst KI

1999-03-01

272

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

International Nuclear Information System (INIS)

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

2004-01-01

273

Brain penetration of ivermectin and selamectin in mdr1a,b P-glycoprotein- and bcrp- deficient knockout mice.  

UK PubMed Central (United Kingdom)

P-glycoprotein, which is encoded by the multi-drug resistance gene (MDR1), highly restricts the entry of ivermectin into the brain by an ATP-driven efflux mechanism at the blood-brain barrier. In dogs with a homozygous MDR1 mutation though, ivermectin accumulates in the brain and provokes severe signs of neurotoxicosis and even death. In contrast to ivermectin, selamectin is safer in the treatment of MDR1 mutant dogs, suggesting that selamectin is transported differently by P-glycoprotein across the blood-brain barrier. To test this, we applied selamectin to mdr1-deficient mdr1a,b(-/-) knockout mice and wild-type mice. Brain penetration, organ distribution, and plasma kinetics were analyzed after intravenous, oral, and dermal spot-on application in comparison with ivermectin. We found that in vivo both macrocyclic lactone compounds are substrates of P-glycoprotein and that these strongly accumulate in the brain of mdr1a,b(-/-) knockout mice compared with wild-type mice at therapeutic doses of 12 mg/kg selamectin and 0.2 mg/kg ivermectin. However, selamectin accumulates to a much lesser degree (5-10 times) than ivermectin (36-60 times) in the absence of P-glycoprotein. This could explain the broader margin of safety of selamectin in MDR1 mutant dogs. In liver, kidney, and testes, ivermectin and selamectin accumulated less than four times as much in mdr1a,b mutant mice as in wild-type mice. Breast cancer resistance protein (Bcrp)-deficient bcrp(-/-) knockout mice were also included in the application studies, but showed no differences in brain concentrations or organ distribution of either ivermectin or selamectin compared with wild-type mice. This indicates that Bcrp is not a relevant efflux carrier for these macrocyclic lactone compounds in vivo at the blood-brain barrier.

Geyer J; Gavrilova O; Petzinger E

2009-02-01

274

Brain penetration of ivermectin and selamectin in mdr1a,b P-glycoprotein- and bcrp- deficient knockout mice.  

Science.gov (United States)

P-glycoprotein, which is encoded by the multi-drug resistance gene (MDR1), highly restricts the entry of ivermectin into the brain by an ATP-driven efflux mechanism at the blood-brain barrier. In dogs with a homozygous MDR1 mutation though, ivermectin accumulates in the brain and provokes severe signs of neurotoxicosis and even death. In contrast to ivermectin, selamectin is safer in the treatment of MDR1 mutant dogs, suggesting that selamectin is transported differently by P-glycoprotein across the blood-brain barrier. To test this, we applied selamectin to mdr1-deficient mdr1a,b(-/-) knockout mice and wild-type mice. Brain penetration, organ distribution, and plasma kinetics were analyzed after intravenous, oral, and dermal spot-on application in comparison with ivermectin. We found that in vivo both macrocyclic lactone compounds are substrates of P-glycoprotein and that these strongly accumulate in the brain of mdr1a,b(-/-) knockout mice compared with wild-type mice at therapeutic doses of 12 mg/kg selamectin and 0.2 mg/kg ivermectin. However, selamectin accumulates to a much lesser degree (5-10 times) than ivermectin (36-60 times) in the absence of P-glycoprotein. This could explain the broader margin of safety of selamectin in MDR1 mutant dogs. In liver, kidney, and testes, ivermectin and selamectin accumulated less than four times as much in mdr1a,b mutant mice as in wild-type mice. Breast cancer resistance protein (Bcrp)-deficient bcrp(-/-) knockout mice were also included in the application studies, but showed no differences in brain concentrations or organ distribution of either ivermectin or selamectin compared with wild-type mice. This indicates that Bcrp is not a relevant efflux carrier for these macrocyclic lactone compounds in vivo at the blood-brain barrier. PMID:19161460

Geyer, J; Gavrilova, O; Petzinger, E

2009-02-01

275

Multidrug-resistant tuberculosis, Somalia, 2010-2011.  

UK PubMed Central (United Kingdom)

In a nationwide survey in 2011, multidrug-resistant tuberculosis (MDR TB) was found in 5.2% and 40.8% of patients with new and previously treated TB, respectively. These levels of drug resistance are among the highest ever documented in Africa and the Middle East. This finding presents a serious challenge for TB control in Somalia.

Sindani I; Fitzpatrick C; Falzon D; Suleiman B; Arube P; Adam I; Baghdadi S; Bassili A; Zignol M

2013-03-01

276

Heteroresistance to Colistin in Multidrug-Resistant Acinetobacter baumannii  

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Multidrug-resistant Acinetobacter baumannii has emerged as a significant clinical problem worldwide and colistin is being used increasingly as “salvage” therapy. MICs of colistin against A. baumannii indicate its significant activity. However, resistance to colistin in A. baumannii has been reported...

Li, Jian; Rayner, Craig R.; Nation, Roger L.; Owen, Roxanne J.; Spelman, Denis; Tan, Kar Eng; Liolios, Lisa

277

Reversal of anticancer multidrug resistance by the ardeemins  

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Two “reverse prenyl” hexahydropyrroloindole alkaloids, 5-N-acetylardeemin and 5-N-acetyl-8-demethylardeemin, were evaluated as reversal agents in cells exhibiting a multidrug resistant (MDR) phenotype. These ardeemins (i) reversed drug resistance to vinblastine (VBL) or to taxol as much as 700-fold ...

Chou, Ting-Chao; Depew, Kristopher M.; Zheng, Yu-Huang; Safer, Michelle L.; Chan, Daniel; Helfrich, Barbara; Zatorska, Danuta

278

HIF-1 activation induces doxorubicin resistance in MCF7 3-D spheroids via P-glycoprotein expression: a potential model of the chemo-resistance of invasive micropapillary carcinoma of the breast.  

UK PubMed Central (United Kingdom)

BACKGROUND: Invasive micropapillary carcinoma (IMPC) of the breast is a distinct and aggressive variant of luminal type B breast cancer that does not respond to neoadjuvant chemotherapy. It is characterized by small pseudopapillary clusters of cancer cells with inverted cell polarity. To investigate whether hypoxia-inducible factor-1 (HIF-1) activation may be related to the drug resistance described in this tumor, we used MCF7 cancer cells cultured as 3-D spheroids, which morphologically simulate IMPC cell clusters. METHODS: HIF-1 activation was measured by EMSA and ELISA in MCF7 3-D spheroids and MCF7 monolayers. Binding of HIF-1? to MDR-1 gene promoter and modulation of P-glycoprotein (Pgp) expression was evaluated by ChIP assay and FACS analysis, respectively. Intracellular doxorubicin retention was measured by spectrofluorimetric assay and drug cytotoxicity by annexin V-FITC measurement and caspase activity assay. RESULTS: In MCF7 3-D spheroids HIF-1 was activated and recruited to participate to the transcriptional activity of MDR-1 gene, coding for Pgp. In addition, Pgp expression on the surface of cells obtained from 3-D spheroids was increased. MCF7 3-D spheroids accumulate less doxorubicin and are less sensitive to its cytotoxic effects than MCF7 cells cultured as monolayer. Finally, HIF-1? inhibition either by incubating cells with 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (a widely used HIF-1? inhibitor) or by transfecting cells with specific siRNA for HIF-1? significantly decreased the expression of Pgp on the surface of cells and increased the intracellular doxorubicin accumulation in MCF7 3-D spheroids. CONCLUSIONS: MCF7 breast cancer cells cultured as 3-D spheroids are resistant to doxorubicin and this resistance is associated with an increased Pgp expression in the plasma membrane via activation of HIF-1. The same mechanism may be suggested for IMPC drug resistance.

Doublier S; Belisario DC; Polimeni M; Annaratone L; Riganti C; Allia E; Ghigo D; Bosia A; Sapino A

2012-01-01

279

HIF-1 activation induces doxorubicin resistance in MCF7 3-D spheroids via P-glycoprotein expression: a potential model of the chemo-resistance of invasive micropapillary carcinoma of the breast  

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Full Text Available Abstract Background Invasive micropapillary carcinoma (IMPC) of the breast is a distinct and aggressive variant of luminal type B breast cancer that does not respond to neoadjuvant chemotherapy. It is characterized by small pseudopapillary clusters of cancer cells with inverted cell polarity. To investigate whether hypoxia-inducible factor-1 (HIF-1) activation may be related to the drug resistance described in this tumor, we used MCF7 cancer cells cultured as 3-D spheroids, which morphologically simulate IMPC cell clusters. Methods HIF-1 activation was measured by EMSA and ELISA in MCF7 3-D spheroids and MCF7 monolayers. Binding of HIF-1? to MDR-1 gene promoter and modulation of P-glycoprotein (Pgp) expression was evaluated by ChIP assay and FACS analysis, respectively. Intracellular doxorubicin retention was measured by spectrofluorimetric assay and drug cytotoxicity by annexin V-FITC measurement and caspase activity assay. Results In MCF7 3-D spheroids HIF-1 was activated and recruited to participate to the transcriptional activity of MDR-1 gene, coding for Pgp. In addition, Pgp expression on the surface of cells obtained from 3-D spheroids was increased. MCF7 3-D spheroids accumulate less doxorubicin and are less sensitive to its cytotoxic effects than MCF7 cells cultured as monolayer. Finally, HIF-1? inhibition either by incubating cells with 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (a widely used HIF-1? inhibitor) or by transfecting cells with specific siRNA for HIF-1? significantly decreased the expression of Pgp on the surface of cells and increased the intracellular doxorubicin accumulation in MCF7 3-D spheroids. Conclusions MCF7 breast cancer cells cultured as 3-D spheroids are resistant to doxorubicin and this resistance is associated with an increased Pgp expression in the plasma membrane via activation of HIF-1. The same mechanism may be suggested for IMPC drug resistance.

Doublier Sophie; Belisario Dimas C; Polimeni Manuela; Annaratone Laura; Riganti Chiara; Allia Elena; Ghigo Dario; Bosia Amalia; Sapino Anna

2012-01-01

280

The heterogeneous evolution of multidrug-resistant Mycobacterium tuberculosis.  

UK PubMed Central (United Kingdom)

Recent surveillance data of multidrug-resistant tuberculosis (MDR-TB) reported the highest rates of resistance ever documented. As further amplification of resistance in MDR strains of Mycobacterium tuberculosis occurs, extensively drug-resistant (XDR) and totally drug-resistant (TDR) TB are beginning to emerge. Although for the most part, the epidemiological factors involved in the spread of MDR-TB are understood, insights into the bacterial drivers of MDR-TB have been gained only recently, largely owing to novel technologies and research in other organisms. Herein, we review recent findings on how bacterial factors, such as persistence, hypermutation, the complex interrelation between drug resistance and fitness, compensatory evolution, and epistasis affect the evolution of multidrug resistance in M. tuberculosis. Improved knowledge of these factors will help better predict the future trajectory of MDR-TB, and contribute to the development of new tools and strategies to combat this growing public health threat.

Müller B; Borrell S; Rose G; Gagneux S

2013-03-01

 
 
 
 
281

The heterogeneous evolution of multidrug-resistant Mycobacterium tuberculosis.  

Science.gov (United States)

Recent surveillance data of multidrug-resistant tuberculosis (MDR-TB) reported the highest rates of resistance ever documented. As further amplification of resistance in MDR strains of Mycobacterium tuberculosis occurs, extensively drug-resistant (XDR) and totally drug-resistant (TDR) TB are beginning to emerge. Although for the most part, the epidemiological factors involved in the spread of MDR-TB are understood, insights into the bacterial drivers of MDR-TB have been gained only recently, largely owing to novel technologies and research in other organisms. Herein, we review recent findings on how bacterial factors, such as persistence, hypermutation, the complex interrelation between drug resistance and fitness, compensatory evolution, and epistasis affect the evolution of multidrug resistance in M. tuberculosis. Improved knowledge of these factors will help better predict the future trajectory of MDR-TB, and contribute to the development of new tools and strategies to combat this growing public health threat. PMID:23245857

Müller, Borna; Borrell, Sonia; Rose, Graham; Gagneux, Sebastien

2012-12-13

282

PHARMACOGENOINFORMATICS: MODELING OF P-GLYCOPROTEIN AND NOVEL APPROACH OF In Silico DRUG DESIGNING BASED ON GENETIC VARIATION OF MDR1 GENE INVOLVED IN STATIN RESISTANCE  

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Full Text Available Statins are the most prescribed drugs, highly effective in reducing the risk of cardiovascular and cerebrovascular events, primarily by lowering low density lipoprotein (LDL) cholesterol. Although large clinical trials found a 27% average relative risk reduction of major coronary events, there is large variability in benefits from statin therapy. Researchers have found three SNPs (C3435T, G2677T/A, C1236T) of MDR1gene, which codes for P-Glycoprotein (P-gp) (a drug efflux transporter), responsible for the reduced bioavailability of statins. We aimed to design a new drug molecule based on synonymous and nonsynonymous SNPs of MDR1 gene, which is not a substrate to P-gp and acts directly on ßhydroxy methylglutaryl coenzyme A reductase (HMG-CoA), a target site for statins, using Insilico tools. Structural changes in mRNA due to synonymous and nonsynonymous SNPs were evaluated by SNPfold. The 3D structures of normal and mutant proteins of P-gp and HMG-CoA reductase were modeled by Molecular Operating Environment (MOE). A new lead molecule was designed from native structure by VegaZZ and parameters of drug were validated with HyperChem and Pharmacophore mapping was done using LigandScout. We docked the lead molecule with normal and mutant P-gp and found no interactions with P-gp showing that it is not a substrate for P-gp. However, it forms clear hydrogen bond interactions with HMG-CoA reductase. This is a novel approach in the field of bioinformatics and pharmacogenomics (pharmacogenoinformatics) for the development of new drug molecules based on the SNPs of genes involved in drug metabolism in a particular population.

Sai Babu M., Venkateswara Rao A., Lakshman Teja G., Subash Kaul, Jyothy A. and Anjana Munshi

2012-01-01

283

Multidrug resistant tuberculosis diagnosed by synovial fluid analysis.  

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Tuberculosis remains a major public health problem worldwide. HIV co-infection is contributing to an increased incidence of the disease, particularly that caused by multidrug resistant strains of Mycobacterium tuberculosis (MT). We describe an HIV-infected patient with pleural and lymph node tuberculosis diagnosed by pleural effusion characteristics and biopsy specimens, without MT identification, that further presented with knee-joint involvement. Arthrocentesis allowed MT isolation and drug susceptibility testing, resulting in a diagnosis of multidrug-resistant tuberculosis and an appropriate treatment regimen. MT identification and drug susceptibility tests are very important, especially for HIV co-infected patients. PMID:22421741

van Zeller, M; Monteiro, R; Ramalho, J; Almeida, I; Duarte, R

2012-03-14

284

Multidrug resistant tuberculosis diagnosed by synovial fluid analysis.  

UK PubMed Central (United Kingdom)

Tuberculosis remains a major public health problem worldwide. HIV co-infection is contributing to an increased incidence of the disease, particularly that caused by multidrug resistant strains of Mycobacterium tuberculosis (MT). We describe an HIV-infected patient with pleural and lymph node tuberculosis diagnosed by pleural effusion characteristics and biopsy specimens, without MT identification, that further presented with knee-joint involvement. Arthrocentesis allowed MT isolation and drug susceptibility testing, resulting in a diagnosis of multidrug-resistant tuberculosis and an appropriate treatment regimen. MT identification and drug susceptibility tests are very important, especially for HIV co-infected patients.

van Zeller M; Monteiro R; Ramalho J; Almeida I; Duarte R

2012-09-01

285

Modulation of multidrug resistance 1 expression and function in retinoblastoma cells by curcumin.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To determine the possible interaction of curcumin with P-glycoprotein (P-gp) expression and function by in vitro and in silico studies. MATERIALS AND METHODS: In this study, curcumin was compared for its potential to modulate the expression and function of P-gp in Y79 RB cells by western blot, RT-PCR (reverse transcription polymerase chain reaction) and functional assay. Further, in silico molecular modeling and docking simulations were performed to deduce the inhibitory binding mode of curcumin. RESULTS: Western blot and RT-PCR analysis decreased the expression of P-gp in a dose-dependent manner. The effect of curcumin on P-gp function was demonstrated by Rhodamine 123 (Rh123) accumulation and efflux study. Curcumin increased the accumulation of Rh123 and decreased its efflux in retinoblastoma (RB) cells. In addition, curcumin inhibited verapamil stimulated ATPase activity and photoaffinity labeling study showed no effect on the binding of 8-azido-ATP-biotin, indicating its interaction at the substrate binding site. Moreover, molecular docking studies concurrently infer the binding of curcumin into the substrate binding site of P-gp with a binding energy of -7.66 kcal/mol. CONCLUSION: These findings indicate that curcumin suppresses the MDR1 expression and function, and therefore may be useful as modulators of multidrug resistance in RB tumor.

Sreenivasan S; Ravichandran S; Vetrivel U; Krishnakumar S

2013-04-01

286

Multi-drug resistance 1 genetic polymorphism and prediction of chemotherapy response in Hodgkin's Lymphoma  

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Full Text Available Abstract Background The human multi-drug resistance gene (MDR1), which encodes the major trans-membrane transporter P-glycoprotein (P-gp), was found to be associated with susceptibility to cancer and response to chemotherapy. The C3435T Polymorphism of MDR1 gene was correlated with expression levels and functions of P-gp. Here, we studied the association between MDR1 C3435T polymorphism and susceptibility to Hodgkin lymphoma (HL) and patient's response to ABVD chemotherapy regimen. Methods a total of 130 paraffin embedded tissue samples collected from HL patients were analyzed to identify the C3435T polymorphism. As a control group, 120 healthy subjects were enrolled in the study. The C3435T Polymorphism was genotyped by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method. Data analysis was carried out using the statistical package SPSS version 17 to compute all descriptive statistics. Chi-square and Fisher exact tests were used to evaluate the genotype distribution and allele frequencies of the studied polymorphism. Results these studies revealed that the frequency of T allele was significantly higher in HL patients compared to the controls (P 0.05). Conclusions these results suggest that MDR1 C3435T polymorphism might play a role in HL occurrence; however this polymorphism is not correlated with the clinical response to ABVD.

Mhaidat Nizar M; Alshogran Osama Y; Khabour Omar F; Alzoubi Karem H; Matalka Ismail I; Haddadin William J; Mahasneh Ibraheem O; Aldaher Ahmad N

2011-01-01

287

Overexpression of the multidrug resistance gene product in adult rat hepatocytes during primary culture.  

UK PubMed Central (United Kingdom)

Expression of P-glycoprotein (P-gp), the product of multidrug resistance gene(s), was investigated in primary cultures of normal adult rat hepatocytes. Levels of P-gp mRNAs determined by Northern blotting and of P-gp measured by immunoblotting increased in parallel with time in culture. As in normal liver, P-gp was found to be localized on the membrane of bile canaliculus-like structures. This increased expression of P-gp was associated with decreased intracellular retention of doxorubicin, which could be restored by compounds such as verapamil and cyclosporin; doxorubicin (and also vincristine) was more cytotoxic to early than to late cultures. As in preneoplastic and neoplastic liver, overexpression of P-gp in cultured hepatocytes was associated with differential changes in drug-metabolizing enzymes, including increased glutathione S-transferase 7-7. Functional P-gp over-expression was observed in the absence of xenobiotic exposure or cell division; it could be linked to cellular stress occurring during cell isolation and plating. Increased expression of P-gp was blocked by actinomycin D, indicating its dependence on increased transcription, while cycloheximide led to a superinduction suggesting negative regulation by a protein factor.

Fardel O; Ratanasavanh D; Loyer P; Ketterer B; Guillouzo A

1992-04-01

288

Multidrug resistance modulation and apoptosis induction of cancer cells by terpenic compounds isolated from Euphorbia species.  

UK PubMed Central (United Kingdom)

BACKGROUND: One of the most promising strategies to overcome multidrug resistance (MDR) is to use compounds that can modulate P-glycoprotein and restore the cytotoxicity of anticancer drugs. Furthermore, the search for compounds that regulate and overcome apoptosis deficiency of cancer cells is also of great therapeutic importance. MATERIALS AND METHODS: Seven known pentacyclic triterpenes and one steroid were isolated from Euphorbia lagascae methanolic extracts and identified by physical and spectroscopic methods. These compounds, together with eleven terpenoids previously isolated from Euphorbia lagascae and E. tuckeyana were tested for their MDR-reversing and/or apoptosis induction activities by flow cytometry on L5178 human MDR1 gene-transfected mouse lymphoma cells. RESULTS: Four taraxastane-type triterpenes: 21alpha-hydroxytaraxasterol, 21alpha-hydroxytaraxasterol acetate, 3beta,30-dihydroxy-20(21)-taraxastene and 3beta-hydroxy-20-taraxasten-30-al, and two steroids: stigmastane-3,6-dione and ergosterol peroxide exhibited a significant MDR-Pgp modulation activity. Some aspects of structure-activity relationships are discussed. Regarding apoptosis induction, the most significant results were obtained for the polycyclic diterpenes ent-16alpha,17-dihydroxykauran-3-one and ent-16alpha,17-dihydroxyatisan-3-one.

Duarte N; Ramalhete C; Varga A; Molnár J; Ferreira MJ

2009-11-01

289

[Reversal of multidrug resistance by lomerizine in K562/ADM cells].  

UK PubMed Central (United Kingdom)

AIM: To study the effect of lomerizine (Lom) on the reversal of multidrug resistance (MDR) in K562/ADM cells and its mechanism. METHODS: MTT assay was used to determine the influence of Lom on the cytotoxicity of adriamycin (ADM). The effect of Lom on the apoptosis induced by ADM and vincristine (VCR) in K562/ADM cells was detected using flow cytometry. Intracellular accumulation of ADM was measured by fluorescence spectrophotometry. Flow cytometry was used to investigate the efflux of rhodamine 123 (Rh123) and the expression of P-glycoprotein (P-gp) in K562/ADM cells. RESULTS: Lom increased the cytotoxicity of ADM and the apoptosis induced by ADM or VCR in K562/ADM cells. At the concentration of 3, 10 and 30 micromol x L(-1), Lom reduced the IC50 value of ADM from 79.03 micromol x L(-1) to 28.14, 8.16 and 3.16 micromol x L(-1), respectively. Lom increased the intracellular accumulation of ADM and inhibited the efflux of Rh123 in K562/ ADM cells. No change in P-gp expression was observed after the treatment of Lom for 72 h. CONCLUSION: Lom had strong reversal effect on MDR in K562/ADM cells by inhibiting P-gp function.

Zhu HJ; Wu YL; Liu GQ

2004-05-01

290

Study of the mechanisms underlying the reversal of multidrug resistance of human neuroblastoma multidrug-resistant cell line SK-N-SH/MDR1 by low-intensity pulsed ultrasound.  

UK PubMed Central (United Kingdom)

The aim of the present study was to investigate the underlying mechanism(s) involved in reversing multidrug resistance (MDR) of SK-N-SH/MDR1 by low-intensity pulsed ultrasound (LIPUS). Membrane alteration of SK-N-SH/MDR1 cells exposed to LIPUS was analyzed by scanning electron microscopy (SEM). Immunofluorescence and western blotting were used\\ to detect changes in the expression of the MDR-related proteins P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1) and glutathione-s-transferase-? (GST-?) after the optimum ultrasonic. The optimum ultrasonic conditions were 0.3 MHz, 1.0 W/cm², 40 sec and the chemosensitivity of SK-N-SH/MDR1 cells was significantly increased (P<0.05). The optimum ultrasonic-induced perforation of the irradiated cell membranes was observed by SEM. The expression of P-gp was significantly decreased in the group treated by optimum ultrasonic (P<0.05), but not the expressions of MRP1 or GST-? (P>0.05). We demonstrated that LIPUS effectively reverses the MDR of SK-N-SH/MDR1, presumably via augmenting membrane permeability and decreasing the P-gp expression of SK-N-SH/MDR1.

Sun Y; Li Q; Xu Y; Pu C; Zhao L; Guo Z; Ding X; Jin X

2013-05-01

291

Effect of magnetic nanoparticles of Fe3O4 and wogonin on the reversal of multidrug resistance in K562/A02 cell line  

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Full Text Available Jian Cheng,1,* Lin Cheng,1,* Baoan Chen,1,2 Guohua Xia,1 Chong Gao,1 Huihui Song,1 Wen Bao,1 Qinglong Guo,3 Haiwei Zhang,3 Xuemei Wang41Department of Hematology, Key Medical Disciplines of Jiangsu Province, Zhongda Hospital, Medical School of Southeast University, 2Department of Oncology of Southeast University, 3Key Laboratory of Carcinogenesis and Intervention of Jiangsu Province, China Pharmaceutical University, 4State Key Laboratory of Bioelectronics, Southeast University, Nanjing, People's Republic of China *These authors contributed equally to this workBackground: Multidrug resistance is the main obstacle to the efficiency of systemic chemotherapy against hematologic malignancy. This study investigated the reversible effect of the copolymer wogonin and daunorubicin coloaded into Fe3O4 magnetic anoparticles, and the mechanism potentially involved.Methods: The growth inhibition rate of K562/A02 cells was investigated by MTT assay, and apoptosis of cells and the intracellular daunorubicin concentration were detected by flow cytometry. Distribution of nanoparticles taken up by K562/A02 cells was observed under a transmission electron microscope and demonstrated by Prussian blue staining. The transcription level of MDR1 mRNA and expression of P-glycoprotein were determined by reverse transcriptase polymerase chain reaction and Western blotting assay, respectively.Results: The reversible effect of daunorubicin-wogonin magnetic nanoparticles was 8.87-fold that of daunorubicin + wogonin and of daunorubicin magnetic nanoparticles. Transmission electron microscopy and Prussian blue staining revealed that the nanoparticles were located in the endosome vesicles of cytoplasm. Also, the apoptosis rate and accumulation of intracellular daunorubicin in the daunorubicin-wogonin magnetic nanoparticle group were significantly higher than that in the daunorubicin, daunorubicin + wogonin, and daunorubicin magnetic nanoparticle groups. Furthermore, transcription of MDR1 mRNA and expression of P-glycoprotein in K562/A02 cells were significantly downregulated in the daunorubicin-wogonin magnetic nanoparticle group compared with the other groups.Conclusion: These findings suggest that the remarkable effects of the novel daunorubicin-wogonin magnetic nanoparticle formulation on multidrug resistant K562/A02 leukemia cells would be a promising strategy for overcoming multidrug resistance.Keywords: magnetic nanoparticles, Fe3O4, wogonin, multidrug resistance, daunorubicin, P-glycoprotein

Cheng J; Cheng L; Chen B; Xia G; Gao C; Song H; Bao W; Guo Q; Zhang H; Wang X

2012-01-01

292

Relation between expression pattern of wild-type p53 and multidrug resistance proteins in human nephroblastomas.  

UK PubMed Central (United Kingdom)

One of the best characterized resistance mechanisms of human cancer is multidrug resistance (MDR) mediated by P-glycoprotein (Pgp/MDR1) and multidrug-resistant related protein (MRP1). In addition to Pgp/MDR1 and MRP1, p53 inactivation or mutation might play a relevant role in therapeutic failure. This study involved 25 children (17 girls and 8 boys) aged 7 months to 10 years treated for unilateral Wilms' tumor. 25 tissue samples of Wilms' tumor and 5 samples of normal human kidneys were obtained from the Department of Pathological Anatomy, Jessenius Faculty of Medicine in Martin, Slovak Republic. We used an indirect immunohistochemical method to determine expression of Pgp/MDR1, MRP1 and wild-type p53 in 25 tissue samples of nephroblastoma. The minority of nephroblastoma specimens showed positivity for both MDR proteins, as well as for wild-type p53. 24% of tissue samples revealed positive results for Pgp/MDR1, 48% for MRP1 and 8% for wild-type p53. Furthermore, our study showed a statistically significant difference between p53 and MRP1 protein expression (p<0.01), but not between p53 and Pgp/MDR1 (p>0.05). No correlation was found between the expression of both multidrug resistance proteins (Pgp/MDR1 and MRP1) and the expression of wild-type p53. Immunohistochemical detection of the expression of MDR proteins and wild-type p53 at the time of diagnosis might assist in choosing specific chemotherapeutics to improve prognosis and therapy.

Hodorová I; Rybárová S; Vecanová J; Solár P; Plank L; Mihalik J

2013-04-01

293

Multidrug-resistant tuberculosis in Port-au-Prince, Haiti.  

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OBJECTIVE: To determine the prevalence of multidrug-resistant tuberculosis (MDR-TB) among patients with new smear-positive pulmonary TB in Port-au-Prince, Haiti. METHODS: Sputum samples were cultured from 1 006 patients newly diagnosed with TB in 2008. The core region of the rpoB gene that is associ...

Ocheretina, Oksana; Morose, Willy; Gauthier, Marie; Joseph, Patrice; D'Meza, Richard; Escuyer, Vincent E; Rastogi, Nalin

294

Molecular fingerprinting of multidrug-resistant Salmonella enterica serotype Typhi.  

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For epidemiologic investigations, the primary subdivision of Salmonella Typhi is vi-phage typing; 106 Vi-phage types are defined. For multidrug-resistant strains the most common types have been M1 (Pakistan) and E1 (India, Pakistan, Bangladesh, and the Arabian Gulf); a strain untypable with the Vi p...

Hampton, M. D.; Ward, L. R.; Rowe, B.; Threlfall, E. J.

295

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...

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

296

Inhibitors of multidrug resistance (MDR) have affinity for MDR substrates.  

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Multidrug-resistance (MDR) occurs in many bacterial species and tumour cells. MDR functions by membrane proteins which export drugs from cells, resulting in a low ineffective concentration of the drug. We have shown by molecular modelling that inhibitors of MDR have affinity for substrates of MDR tr...

Zloh, M; Kaatz, GW; Gibbons, S

297

Multidrug-Resistant Tuberculosis Management in Resource-Limited Settings  

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Evidence of successful management of multidrug-resistant tuberculosis (MDRTB) is mainly generated from referral hospitals in high-income countries. We evaluate the management of MDRTB in 5 resource-limited countries: Estonia, Latvia, Peru, the Philippines, and the Russian Federation. All projects we...

Nathanson, Eva; Lambregts-van Weezenbeek, Catharina; Gupta, Rajesh; Blöndal, Kai; Caminero, José A.; Cegielski, J. Peter

298

Molecular Surveillance for Multidrug-Resistant Plasmodium falciparum, Cambodia  

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We conducted surveillance for multidrug-resistant Plasmodium falciparum in Cambodia during 2004–2006 by assessing molecular changes in pfmdr1. The high prevalence of isolates with multiple pfmdr1 copies found in western Cambodia near the Thai border, where artesunate–mefloquine therapy failures occu...

Shah, Naman K.; Alker, Alisa P.; Sem, Rithy; Susanti, Agustina Ika; Muth, Sinuon; Maguire, Jason D.; Duong, Socheat

299

Molecular surveillance for multidrug-resistant Plasmodium falciparum, Cambodia.  

UK PubMed Central (United Kingdom)

We conducted surveillance for multidrug-resistant Plasmodium falciparum in Cambodia during 2004-2006 by assessing molecular changes in pfmdr1. The high prevalence of isolates with multiple pfmdr1 copies found in western Cambodia near the Thai border, where artesunate-mefloquine therapy failures occur, contrasts with isolates from eastern Cambodia, where this combination therapy remains highly effective.

Shah NK; Alker AP; Sem R; Susanti AI; Muth S; Maguire JD; Duong S; Ariey F; Meshnick SR; Wongsrichanalai C

2008-10-01

300

Molecular surveillance for multidrug-resistant Plasmodium falciparum, Cambodia.  

Science.gov (United States)

We conducted surveillance for multidrug-resistant Plasmodium falciparum in Cambodia during 2004-2006 by assessing molecular changes in pfmdr1. The high prevalence of isolates with multiple pfmdr1 copies found in western Cambodia near the Thai border, where artesunate-mefloquine therapy failures occur, contrasts with isolates from eastern Cambodia, where this combination therapy remains highly effective. PMID:18826834

Shah, Naman K; Alker, Alisa P; Sem, Rithy; Susanti, Agustina Ika; Muth, Sinuon; Maguire, Jason D; Duong, Socheat; Ariey, Frederic; Meshnick, Steven R; Wongsrichanalai, Chansuda

2008-10-01

 
 
 
 
301

Functional imaging of multidrug resistance gene expression in patients with recurrent tumor following definitive irradiation  

International Nuclear Information System (INIS)

Purpose/Objective: Definitive irradiation remains the cornerstone of management for high-grade glial tumors. If failure occurs, then salvage chemotherapy regimens (eg. PCV) are often considered. Tl-201 brain SPECT is a well-established diagnostic method to assess the recurrent or residual viable tumor. Tc-99m-MIBI is a lipophilic, cationic agent and a transport substrate recognized by the multidrug resistance (MDR) P-glycoprotein. This study investigates the feasibility of imaging P-glycoprotein expression by dual isotope Tl-201 and Tc-MIBI scintigraphy and attempts to predict expression of the multidrug resistance gene (MDR) expression in patients with malignant glioma prior to chemotherapy. Material and Methods: Twenty-seven patients with malignant glioma were evaluated with sequential Tl-201 and Tc-MIBI brain SPECT for recurrent brain tumor. Seventeen patients (group 1) were treated with surgery, radiation therapy and chemotherapy. Ten (group 2) were treated with surgery and radiation therapy. There were 6 patients with anaplastic and 21 patients with glioblastoma, ages ranging from 29 to 74 years old (median age:41). Tumor uptake was visually graded by two interpreters and scored with respect to the degree of uptake to determine the concordance and discordance between two tracers. Brain SPECT findings were correlated with clinical follow-up, or a biopsy defined as recurrent or stable at the time of the brain SPECT. Results: Twenty-five of 27 patients showed recurrent brain tumor. Among these, five patients showed discordant findings: two patients had markedly positive thallium tumor uptake without Tc-MIBI uptake. Northern blotting of the resected tumor specimen depicted the expression of multidrug resistance gene. Both patients were proven to have glioblastoma. One patient was in group 1 and another patient was in group 2. Three patients showed partial discordance, namely thallium tumor uptake greater than Tc-MIBI uptake. Two patients were in group 1 and one was in group 2. Conclusion: Our study suggests that the absence of Tc-MIBI tumor uptake in the presence of Tl-201 tumor uptake indicates MDR gene expression in the recurrent brain tumor. The frequency of MDR occurred in 2 out of 9 patients with recurrent brain tumor without chemotherapy and in 3 of 17 patients treated with chemotherapy. The partial discordance finding in 3 out of 5 cases implies that MDR can express heterogenously (partially) within the tumor. Utilizing the dual isotope technique, Tl-201 and Tc-99m-MIBI brain SPECT, it may be feasible to monitor the MDR expression in-vivo and predict MDR gene expression in a patient with recurrent brain tumor before and during chemotherapy. Patients with MDR gene expression should be considered for alternative salvage strategies. (e.g. radiosurgery)

1996-01-01

302

Carbapenem-resistance mechanisms of multidrug-resistant Pseudomonas aeruginosa.  

Science.gov (United States)

Clonal dissemination of multidrug-resistant Pseudomonas aeruginosa (MDRPA) is a major concern worldwide. The aim of this study was to explore the mechanisms leading to the carbapenem resistance of an MDRPA clone. Isolates were obtained from a surgical wound, sputum, urine and a blood culture. Pulsed-field gel electrophoresis (PFGE) showed high genomic homogeneity of these isolates and confirmed the circulation of an endemic clone belonging to serotype O4. Outer membrane protein (OMP) bands were visualized by SDS-PAGE, meropenem accumulation was measured in a bioassay and integrons were detected by PCR. Efflux pumps were studied for several antimicrobial agents and synergic combinations thereof in the presence or absence of both carbonyl cyanide m-chlorophenylhydrazone (CCCP) and Phe-Arg-?-naphthylamide (PA?N) at final concentrations of 10 and 40 mg l(-1), respectively. On OMP electrophoretic profiles, MDRPA showed a reduction of outer membrane porin D (OprD) and PCR demonstrated the presence of a class 1 integron with a cassette encoding aminoglycoside adenyltransferase B (aadB). Meropenem accumulation was slightly higher in bacilli than in the filamentous cells that formed in the presence of antibiotics. Overexpression of the efflux pump MexAB-OprM and a functional MexXY-OprM were detected in all isolates. PMID:23722434

Fusté, Ester; López-Jiménez, Lídia; Segura, Concha; Gainza, Eusebio; Vinuesa, Teresa; Viñas, Miguel

2013-05-30

303

Reversal of mdr1-mediated multidrug resistance in human leukemia cells by a new spin-labeled derivative of podophyllotoxin.  

UK PubMed Central (United Kingdom)

GP7 (4-[4"-(2", 2", 6", 6"-tetramethyl-l"-piperidinyloxy) amino]-4'-demethyl epipodophyllotoxin) is a promising anticancer drug of the podophyllotoxin class. However, little is known about its anti-multidrug resistance effects. In the present study, we investigated the effects of GP7 on P-glycoprotein (P-gp) overexpression multidrug-resistant human leukemia K562/ADM cells with the comparison of VP-16 and K562 cells. GP7 inhibited the proliferation of K562/ADM cells in a concentration- or time-dependent manner, and the inhibitory effect of GP7 on K562/ADM cells was 1.50-fold higher than that of VP-16. GP7 caused G2/M phase accumulation but VP-16 caused S phase accumulation in K562/ADM and K562 cells. GP7 could induce apoptosis of both K562/ADM and K562 cell lines, but there was no significant difference between GP7- and VP-16-induced apoptotic ratios. GP7 could also induce typical apoptotic morphological changes and internucleosomal DNA fragmentation of K562/ADM and K562 cells, but DNA fragmentation induced by GP7 in K562/ADM cells was weaker than that in K562 cells. When treated with GP7 or VP-16 for 48 h, 128-256 microM GP7 induced more DNA fragmentation than VP-16 did, but 32-64 microM GP7 induced less DNA fragmentation than VP-16 did. GP7 could down-regulate the expression of P-gp in K562/ADM cells but VP-16 could not. Our findings suggest that GP7 may reverse multidrug resistance in human leukemia K562/ADM cells via down-regulation of P-gp expression.

Qi SN; Song LJ; Chen Y; Jing YX

2010-02-01

304

Reversal of mdr1-mediated multidrug resistance in human leukemia cells by a new spin-labeled derivative of podophyllotoxin.  

Science.gov (United States)

GP7 (4-[4"-(2", 2", 6", 6"-tetramethyl-l"-piperidinyloxy) amino]-4'-demethyl epipodophyllotoxin) is a promising anticancer drug of the podophyllotoxin class. However, little is known about its anti-multidrug resistance effects. In the present study, we investigated the effects of GP7 on P-glycoprotein (P-gp) overexpression multidrug-resistant human leukemia K562/ADM cells with the comparison of VP-16 and K562 cells. GP7 inhibited the proliferation of K562/ADM cells in a concentration- or time-dependent manner, and the inhibitory effect of GP7 on K562/ADM cells was 1.50-fold higher than that of VP-16. GP7 caused G2/M phase accumulation but VP-16 caused S phase accumulation in K562/ADM and K562 cells. GP7 could induce apoptosis of both K562/ADM and K562 cell lines, but there was no significant difference between GP7- and VP-16-induced apoptotic ratios. GP7 could also induce typical apoptotic morphological changes and internucleosomal DNA fragmentation of K562/ADM and K562 cells, but DNA fragmentation induced by GP7 in K562/ADM cells was weaker than that in K562 cells. When treated with GP7 or VP-16 for 48 h, 128-256 microM GP7 induced more DNA fragmentation than VP-16 did, but 32-64 microM GP7 induced less DNA fragmentation than VP-16 did. GP7 could down-regulate the expression of P-gp in K562/ADM cells but VP-16 could not. Our findings suggest that GP7 may reverse multidrug resistance in human leukemia K562/ADM cells via down-regulation of P-gp expression. PMID:20225656

Qi, She-Ning; Song, Li-Juan; Chen, Yan; Jing, Yuan-Xue

2010-02-01

305

Verapamil induces upregulation of P-glycoprotein expression on human monocyte derived dendritic cells.  

UK PubMed Central (United Kingdom)

Overexpression of P-glycoprotein, a transmembrane drug efflux pump that mediates efflux of chemotherapeutic agents contributes to drug resistance in many leukaemia and other cancerous cells. Non-malignant cells including leukocytes also express P-glycoprotein, but physiologic functions for P-glycoprotein are poorly defined. Recently, P-glycoprotein expression has been described in human mononuclear phagocytes and Langerhans cells. It has been shown to play a role in phagocytic cell transmigration through endothelial-lined vessels in an ablumenal-lumenal direction, a process that mimics their migration into lymphatic vessels. Using the monoclonal antibody 4E3, and the P-glycoprotein antagonist, verapamil, the expression of P-glycoprotein on human monocyte-derived dendritic cells was evaluated. Dendritic cells used in this study were CD1a+, CD11c+, CD14-, CD80+, CD83+, CD86+ and MHC-II(High). The expression of these markers increased significantly as the cells matured. P-glycoprotein expression was upregulated as the dendritic cells matured as well as in the presence of the "inflammatory stress" of the pathogenic bacteria Strept. pyogenes. Addition of verapamil or Strept. pyogenes to the culture medium during the final 24 hours significantly upregulated P-glycoprotein expression. Immortalized cell lines did not upregulate P-glycoprotein in the presence of verapamil. Evaluation of other normal cells showed that P-glycoprotein upregulation in the presence of verapamil was also a characteristic of macrophages. This novel observation of the upregulation of P-glycoprotein in the presence of verapamil appears to be a characteristic of activated myeloid derived antigen presenting cells and suggest that P-glycoprotein is essential for these cells as when it is blocked, they respond by increasing expression of this protein. In summary, this work describes that human dendritic cells generated from plastic-adherent monocytes rapidly upregulate expression of P-glycoprotein as they mature, and in the presence of inflammatory stress and the pharmacological agent verapamil, which blocks P-glycoprotein activity, suggesting that P-glycoprotein may play a role in activation as well as in migration of dendritic cells.

Ishri RK; Menzies S; Halliday GM

2006-01-01

306

Differential inhibitory effects of two Raf-targeting drugs, sorafenib and PLX4720, on the growth of multidrug-resistant cells.  

UK PubMed Central (United Kingdom)

B-Raf is the most frequently mutated protein kinase in the MAPK signaling cascade in human cancers, making it an important therapeutic target. Here, we describe the differential effects of two Raf-targeting drugs, sorafenib and PLX4720, on multidrug-resistant v-Ha-ras-transformed cells (Ras-NIH 3T3/Mdr). We demonstrate that the growth of the NIH 3T3/Mdr cell line was affected in a dose-dependent manner more significantly by the pan-Raf inhibitor sorafenib than by the selective mutant B-Raf inhibitor PLX4720. Despite their differential effects on LKB1/AMPK phosphorylation, both sorafenib and PLX4720 inhibited downstream mTOR signaling with concomitant induction of autophagy, implying that the differential effects of sorafenib and PLX4720 on multidrug-resistant cells might not be due to different levels of autophagy and apoptosis. Interestingly, sorafenib caused a dose-dependent increase in rhodamine 123 uptake and retention. More importantly, sorafenib reversed the resistance to paclitaxel in Ras-NIH 3T3/Mdr cells. Moreover, MEK/ERK signaling was hyperactivated by the selective mutant B-Raf inhibitor PLX4720 and inhibited by the pan-Raf inhibitor sorafenib. Our data suggest that sorafenib sensitivity in MDR cells is mediated through the inhibition of P-glycoprotein activity following strong inhibition of Raf/MEK/ERK signaling. Thus, Raf inhibition with sorafenib might be a promising approach to abrogate the multidrug resistance of cancer cells.

Eum KH; Ahn SK; Kang H; Lee M

2013-01-01

307

Reversal of multidrug resistance by small interfering RNA (siRNA) in doxorubicin-resistant MCF-7 breast cancer cells.  

UK PubMed Central (United Kingdom)

PURPOSE: Resistance to anticancer drugs is a serious obstacle to cancer chemotherapy. A common form of multidrug resistance (MDR) is caused by the overexpression of transmembrane transporter proteins P-glycoprotein (P-gp) and multidrug resistance-associated protein-1 (MRP1), encoded by MDR1 and MRP1 genes, respectively. These proteins lead to reduced intracellular drug concentration and decreased cytotoxicity by means of their ability to pump the drugs out of the cells. Breast cancer tumor resistance is mainly associated with overexpression of P-gp/MDR1. Although some chemical MDR modulators aim to overcome MDR by interfering functioning of P-gp, their toxicities limit their usage in clinics. Consequently, RNA interference mediated sequence specific inhibition of the expression of P-gp/MDR1 mRNA may be an efficient tool to reverse MDR phenotype and increase the success of chemotherapy. Aim of this study was resensitizing doxorubicin-resistant breast cancer cells to anticancer agent doxorubicin by selective downregulation of P-gp/MDR1 mRNA. METHODS: The effect of the selected MDR1 siRNA, and MRP1 expression after MDR1 silencing was determined by qPCR analysis. Intracellular drug accumulation and localization was investigated by confocal laser scanning microscopy after treatment with MDR1 siRNA. XTT cell proliferation assay was performed to determine the effect of MDR1 silencing on doxorubicin sensitivity. RESULTS: The results demonstrated that approximately 90% gene silencing occurred by the selected siRNA targeting MDR1 mRNA. However, the level of MRP1 mRNA did not change after MDR1 downregulation. Silencing of P-gp encoding MDR1 gene resulted in almost complete restoration of the intracellular doxorubicin accumulation and relocalization of the drug in the nuclei. Introduction of siRNA resulted in about 70% resensitization to doxorubicin. CONCLUSIONS: Selected siRNA duplex was shown to effectively inhibit MDR1 gene expression, restore doxorubicin accumulation and localization, and enhance chemosensitivity of resistant cells, which makes it a suitable candidate for therapeutic applications.

Dönmez Y; Gündüz U

2011-03-01

308

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

Science.gov (United States)

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

309

Mass spectrometry reveals synergistic effects of nucleotides, lipids, and drugs binding to a multidrug resistance efflux pump.  

UK PubMed Central (United Kingdom)

Multidrug resistance is a serious barrier to successful treatment of many human diseases, including cancer, wherein chemotherapeutics are exported from target cells by membrane-embedded pumps. The most prevalent of these pumps, the ATP-Binding Cassette transporter P-glycoprotein (P-gp), consists of two homologous halves each comprising one nucleotide-binding domain and six transmembrane helices. The transmembrane region encapsulates a hydrophobic cavity, accessed by portals in the membrane, that binds cytotoxic compounds as well as lipids and peptides. Here we use mass spectrometry (MS) to probe the intact P-gp small molecule-bound complex in a detergent micelle. Activation in the gas phase leads to formation of ions, largely devoid of detergent, yet retaining drug molecules as well as charged or zwitterionic lipids. Measuring the rates of lipid binding and calculating apparent KD values shows that up to six negatively charged diacylglycerides bind more favorably than zwitterionic lipids. Similar experiments confirm binding of cardiolipins and show that prior binding of the immunosuppressant and antifungal antibiotic cyclosporin A enhances subsequent binding of cardiolipin. Ion mobility MS reveals that P-gp exists in an equilibrium between different states, readily interconverted by ligand binding. Overall these MS results show how concerted small molecule binding leads to synergistic effects on binding affinities and conformations of a multidrug efflux pump.

Marcoux J; Wang SC; Politis A; Reading E; Ma J; Biggin PC; Zhou M; Tao H; Zhang Q; Chang G; Morgner N; Robinson CV

2013-06-01

310

Mass spectrometry reveals synergistic effects of nucleotides, lipids, and drugs binding to a multidrug resistance efflux pump.  

Science.gov (United States)

Multidrug resistance is a serious barrier to successful treatment of many human diseases, including cancer, wherein chemotherapeutics are exported from target cells by membrane-embedded pumps. The most prevalent of these pumps, the ATP-Binding Cassette transporter P-glycoprotein (P-gp), consists of two homologous halves each comprising one nucleotide-binding domain and six transmembrane helices. The transmembrane region encapsulates a hydrophobic cavity, accessed by portals in the membrane, that binds cytotoxic compounds as well as lipids and peptides. Here we use mass spectrometry (MS) to probe the intact P-gp small molecule-bound complex in a detergent micelle. Activation in the gas phase leads to formation of ions, largely devoid of detergent, yet retaining drug molecules as well as charged or zwitterionic lipids. Measuring the rates of lipid binding and calculating apparent KD values shows that up to six negatively charged diacylglycerides bind more favorably than zwitterionic lipids. Similar experiments confirm binding of cardiolipins and show that prior binding of the immunosuppressant and antifungal antibiotic cyclosporin A enhances subsequent binding of cardiolipin. Ion mobility MS reveals that P-gp exists in an equilibrium between different states, readily interconverted by ligand binding. Overall these MS results show how concerted small molecule binding leads to synergistic effects on binding affinities and conformations of a multidrug efflux pump. PMID:23690617

Marcoux, Julien; Wang, Sheila C; Politis, Argyris; Reading, Eamonn; Ma, Jerome; Biggin, Philip C; Zhou, Min; Tao, Houchao; Zhang, Qinghai; Chang, Geoffrey; Morgner, Nina; Robinson, Carol V

2013-05-20

311

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

UK PubMed Central (United Kingdom)

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.

Tang SC; Lankheet NA; Poller B; Wagenaar E; Beijnen JH; Schinkel AH

2012-04-01

312

FG020326 Sensitized Multidrug Resistant Cancer Cells to Docetaxel-Mediated Apoptosis via Enhancement of Caspases Activation  

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Full Text Available Apoptotic resistance is the main obstacle for treating cancer patients with chemotherapeutic drugs. Multidrug resistance (MDR) is often characterized by the expression of P-glycoprotein (P-gp), a 170-KD ATP-dependent drug efflux protein. Functional P-gp can confer resistance to activate caspase-8 and -3 dependent apoptosis induced by a range of different stimuli, including tumor necrosis and chemotherapeutic drugs such as docetaxel and vincristine. We demonstrated here that comparison of sensitive KB cells, P-gp positive (P-gp+ve) KBv200 cells were extremely resistant to apoptosis induced by docetaxel. FG020326, a pharmacological inhibitor of P-gp function, could enhance concentration-dependently the effect of docetaxel on cell apoptosis and sensitize caspase-8, -9 and -3 activation in P-gp overexpressing KBv200 cells, but not in KB cells. Therefore, the enhancement of caspase-8, -9 and -3 activation induced by docetaxel may be one of the key mechanisms of the reversal of P-gp mediated docetaxel resistance by FG020326.

Xiu-Wen Wang; Xiao-Kun Wang; Xu Zhang; Yong-Ju Liang; Zhi Shi; Li-Ming Chen; Li-Wu Fu

2012-01-01

313

FG020326 sensitized multidrug resistant cancer cells to docetaxel-mediated apoptosis via enhancement of caspases activation.  

UK PubMed Central (United Kingdom)

Apoptotic resistance is the main obstacle for treating cancer patients with chemotherapeutic drugs. Multidrug resistance (MDR) is often characterized by the expression of P-glycoprotein (P-gp), a 170-KD ATP-dependent drug efflux protein. Functional P-gp can confer resistance to activate caspase-8 and -3 dependent apoptosis induced by a range of different stimuli, including tumor necrosis and chemotherapeutic drugs such as docetaxel and vincristine. We demonstrated here that comparison of sensitive KB cells, P-gp positive (P-gp(+ve)) KBv200 cells were extremely resistant to apoptosis induced by docetaxel. FG020326, a pharmacological inhibitor of P-gp function, could enhance concentration-dependently the effect of docetaxel on cell apoptosis and sensitize caspase-8, -9 and -3 activation in P-gp overexpressing KBv200 cells, but not in KB cells. Therefore, the enhancement of caspase-8, -9 and -3 activation induced by docetaxel may be one of the key mechanisms of the reversal of P-gp mediated docetaxel resistance by FG020326.

Wang XW; Wang XK; Zhang X; Liang YJ; Shi Z; Chen LM; Fu LW

2012-01-01

314

Transmitted multidrug resistant HIV-1: new and investigational therapeutic approaches.  

UK PubMed Central (United Kingdom)

The increasing prevalence of transmitted drug-resistant HIV-1 has highlighted the challenging issue of the optimal management of antiretroviral-naïve, newly infected patients with multidrug-resistant HIV-1. This review discusses current trends in the evolution and transmission of HIV-1 with reduced susceptibility to multiple antiretroviral agents. In most cases, clinical strategies for the management of such patients with stable virological and immunological parameters involve deferment of therapy until clinically indicated. When a decision is made to initiate therapy, the process of selecting a regimen should consider baseline viral genotype and phenotype results, as well as the inclusion of novel agents with diverse mechanisms of action, in order to achieve a more complete suppression of viral replication. A summary of established and investigational antiretroviral agents is presented in this review, together with novel therapeutic approaches to decrease the burden of viral replication and maintain immunological status in cases of transmitted multidrug-resistant HIV-1 infection.

Shet A; Markowitz M

2006-08-01

315

The role of P-glycoprotein in human gastric cancer xenografts in response to chemotherapy.  

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To clarify the contribution of P-glycoprotein (P-GP) to drug resistance of gastric cancer, the correlation between chemosensitivity of the tumor and expression of P-GP was examined using human gastric cancer xenografts in nude mice.

Monden, N; Abe, S; Hishikawa, Y; Yoshimura, H; Kinugasa, S; Dhar, DK; Tachibana, M; Nagasue, N

316

Different modalities of intercellular membrane exchanges mediate cell-to-cell p-glycoprotein transfers in MCF-7 breast cancer cells.  

UK PubMed Central (United Kingdom)

Multi-drug resistance (MDR) is a phenomenon by which tumor cells exhibit resistance to a variety of chemically unrelated chemotherapeutic drugs. The classical form of multidrug resistance is connected to overexpression of membrane P-glycoprotein (P-gp), which acts as an energy dependent drug efflux pump. P-glycoprotein expression is known to be controlled by genetic and epigenetic mechanisms. Until now processes of P-gp gene up-regulation and resistant cell selection were considered sufficient to explain the emergence of MDR phenotype within a cell population. Recently, however, "non-genetic" acquisitions of MDR by cell-to-cell P-gp transfers have been pointed out. In the present study we show that intercellular transfers of functional P-gp occur by two different but complementary modalities through donor-recipient cells interactions in the absence of drug selection pressure. P-glycoprotein and drug efflux activity transfers were followed over 7 days by confocal microscopy and flow cytometry in drug-sensitive parental MCF-7 breast cancer cells co-cultured with P-gp overexpressing resistant variants. An early process of remote transfer was established based on the release and binding of P-gp-containing microparticles. Microparticle-mediated transfers were detected after only 4 h of incubation. We also identify an alternative mode of transfer by contact, consisting of cell-to-cell P-gp trafficking by tunneling nanotubes bridging neighboring cells. Our findings supply new mechanistic evidences for the extragenetic emergence of MDR in cancer cells and indicate that new treatment strategies designed to overcome MDR may include inhibition of both microparticles and Tunneling nanotube-mediated intercellular P-gp transfers.

Pasquier J; Galas L; Boulangé-Lecomte C; Rioult D; Bultelle F; Magal P; Webb G; Le Foll F

2012-03-01

317

Defective autophagy in multidrug resistant cells may lead to growth inhibition by BH3-mimetic gossypol.  

UK PubMed Central (United Kingdom)

The clinical efficacy of many chemotherapeutic agents has been reduced due to the development of drug resistance. In this article, we aimed to validate gossypol, a natural BH3 mimetic found in cottonseeds, as a potential therapeutic to overcome multidrug resistance (MDR). Gossypol was found to retain its efficacy in v-Ha-ras-transformed NIH 3T3 cells that overexpressed P-glycoprotein (Ras-NIH 3T3/Mdr), which was similar to the efficacy observed in their parental counterparts (Ras-NIH 3T3). A rhodamine assay revealed that the alteration of MDR activity did not contribute to the cytotoxic effect of gossypol. Gossypol caused a G2 /M arrest by the induction of p21(Cip1) and the down-regulation of p27(Kip1) expression in Ras-NIH 3T3 cells, whereas no significant G2 /M arrest was exhibited in Ras-NIH 3T3/Mdr cells. Surprisingly, a 48-h treatment with gossypol induced apoptotic cell death in Ras-NIH 3T3 cells; however, gossypol induced both apoptosis and necrosis in Ras-NIH 3T3/Mdr cells, as determined with flow cytometry analysis. More notably, gossypol preferentially induced autophagy in Ras-NIH 3T3 cells but not in Ras-NIH 3T3/Mdr cells. Coimmunoprecipitation and flow cytometric analysis revealed that gossypol-induced autophagy is independent of the dissociation of Beclin 1 from Bcl-2 in Ras-NIH 3T3 cells. Taken together, these results suggest that the antiproliferative activity of gossypol appears to be due to cell-cycle arrest at the G2 /M phase, with the induction of apoptosis in Ras-NIH 3T3 cells. In addition, defective autophagy might contribute to apoptotic and necrotic cell death in response to gossypol in Ras-NIH 3T3/Mdr cells.

Ahn JH; Jang GH; Lee M

2013-07-01

318

Imaging of activity of multidrug resistance-associated protein 1 in the lungs.  

Science.gov (United States)

Multidrug resistance-associated protein 1 (MRP1) transports various xenobiotics and metabolites across cell membranes, and the alteration of MRP1 expression is associated with certain lung diseases. This study sought to examine the feasibility of imaging pulmonary MRP1 activity using 6-bromo-7-[(11)C]methylpurine ([(11)C]1). A positron emission tomography study with [(11)C]1 was performed in wild-type, Mrp1 knockout (KO), and P-glycoprotein/breast cancer resistance protein (Pgp/Bcrp) KO mice. Lung radioactivity in wild-type and Mrp1 KO mice reached a maximum level immediately after the administration of [(11)C]1. Thereafter, radioactivity rapidly decreased in the lungs of wild-type mice, whereas it was mostly retained in the lungs of Mrp1 KO mice. The kinetics in the lungs of Pgp/Bcrp KO mice was quite similar to that of wild-type mice. Analysis of the chemical form confirmed that radioactive compounds in the lungs of Mrp1 KO mice were nearly completely composed of a glutathione conjugate, a MRP1 substrate, 5 minutes after the intravenous administration of [(11)C]1. The effect of an MRP1 inhibitor, MK571, on the kinetics of [(11)C]1 was also examined. Treatment with MK571 delayed the elimination of radioactivity from the lungs, compared with control mice. These results suggest that [(11)C]1 diffuses into the lung tissue after administration and undergoes conversion into the hydrophilic conjugate, which is then specifically expelled by MRP1. In conclusion, [(11)C]1 allows for the imaging of in vivo MRP1 activity in lungs. PMID:23596979

Okamura, Toshimitsu; Kikuchi, Tatsuya; Okada, Maki; Wakizaka, Hidekatsu; Zhang, Ming-Rong

2013-09-01

319

Imaging of activity of multidrug resistance-associated protein 1 in the lungs.  

UK PubMed Central (United Kingdom)

Multidrug resistance-associated protein 1 (MRP1) transports various xenobiotics and metabolites across cell membranes, and the alteration of MRP1 expression is associated with certain lung diseases. This study sought to examine the feasibility of imaging pulmonary MRP1 activity using 6-bromo-7-[(11)C]methylpurine ([(11)C]1). A positron emission tomography study with [(11)C]1 was performed in wild-type, Mrp1 knockout (KO), and P-glycoprotein/breast cancer resistance protein (Pgp/Bcrp) KO mice. Lung radioactivity in wild-type and Mrp1 KO mice reached a maximum level immediately after the administration of [(11)C]1. Thereafter, radioactivity rapidly decreased in the lungs of wild-type mice, whereas it was mostly retained in the lungs of Mrp1 KO mice. The kinetics in the lungs of Pgp/Bcrp KO mice was quite similar to that of wild-type mice. Analysis of the chemical form confirmed that radioactive compounds in the lungs of Mrp1 KO mice were nearly completely composed of a glutathione conjugate, a MRP1 substrate, 5 minutes after the intravenous administration of [(11)C]1. The effect of an MRP1 inhibitor, MK571, on the kinetics of [(11)C]1 was also examined. Treatment with MK571 delayed the elimination of radioactivity from the lungs, compared with control mice. These results suggest that [(11)C]1 diffuses into the lung tissue after administration and undergoes conversion into the hydrophilic conjugate, which is then specifically expelled by MRP1. In conclusion, [(11)C]1 allows for the imaging of in vivo MRP1 activity in lungs.

Okamura T; Kikuchi T; Okada M; Wakizaka H; Zhang MR

2013-09-01

320

Effect of multidrug resistance modulators on the activity of ivermectin and moxidectin against selected strains of Haemonchus contortus infective larvae  

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Full Text Available Nematode parasites have shown resistance to the anthelmintics, ivermectin and moxidectin, and there is evidence that the over-expression of parasite P-glycoprotein (P-gp) may account, at least in part, for resistance to ivermectin. The objective of this study was to evaluate whether the multidrug resistance (MDR) modulators, verapamil, CL 347.099 (an analog of verapamil) and cyclosporin A, would enhance the efficacy of ivermectin and moxidectin against selected strains of Haemonchus contortus using an in vitro larval migration assay. The modulators had no effects on the number of migrating larvae when used alone. Ivermectin and moxidectin showed a significant (P<0.05) increase in its efficacy by 52.8 and 58.5% respectively, when used in association with verapamil against a moxidectin-selected strain. CL 347,099 also increased significantly (P<0.05) the ivermectin and moxidectin efficacy by 24.2 and 40.0% respectively, against an ivermectin-selected strain and by 40.0 and 75.6% respectively, against an moxidectin-selected strain. At the concentrations tested cyclosporin A showed a variable effect on increasing the efficacy of the anthelmintics against the susceptible and resistant strains.

Molento Marcelo B.; Prichard Roger K.

2001-01-01

 
 
 
 
321

PI3K/Akt inhibition modulates multidrug resistance and activates NF-kappaB in murine lymphoma cell lines.  

Science.gov (United States)

Upregulation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway has been described in some tumors related to multidrug resistance (MDR). The aim of this work was to analyze the relationship between PI3K/Akt, MDR and NF-kappaB in murine lymphoma cell lines resistant to vincristine (LBR-V160) and doxorubicin (LBR-D160) as well as in the sensitive line (LBR-). PI3K/Akt activity, analyzed by phosphatidylinositol trisphosphate production and phosphorylated Akt (p-Akt) expression, was higher in the resistant cell lines than in the sensitive one and inhibition with wortmannin or LY294002 improved apoptosis in the resistant cell lines. Vincristine but not doxorubicin increased p-Akt expression whereas co-treatment with PI3K inhibitors and vincristine increased apoptosis in the three cell lines. Wortmannin and LY294002 inhibited P-glycoprotein (Pgp) function and also increased NF-kappaB activity. We concluded that the PI3K/Akt pathway is involved in MDR in lymphoma cell lines and PI3K/Akt inhibition correlates down-regulation of NF-kappaB activity and inhibition Pgp function. PMID:18640717

García, Mariana G; Alaniz, Laura D; Cordo Russo, Rosalía I; Alvarez, Elida; Hajos, Silvia E

2008-07-21

322

PI3K/Akt inhibition modulates multidrug resistance and activates NF-kappaB in murine lymphoma cell lines.  

UK PubMed Central (United Kingdom)

Upregulation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway has been described in some tumors related to multidrug resistance (MDR). The aim of this work was to analyze the relationship between PI3K/Akt, MDR and NF-kappaB in murine lymphoma cell lines resistant to vincristine (LBR-V160) and doxorubicin (LBR-D160) as well as in the sensitive line (LBR-). PI3K/Akt activity, analyzed by phosphatidylinositol trisphosphate production and phosphorylated Akt (p-Akt) expression, was higher in the resistant cell lines than in the sensitive one and inhibition with wortmannin or LY294002 improved apoptosis in the resistant cell lines. Vincristine but not doxorubicin increased p-Akt expression whereas co-treatment with PI3K inhibitors and vincristine increased apoptosis in the three cell lines. Wortmannin and LY294002 inhibited P-glycoprotein (Pgp) function and also increased NF-kappaB activity. We concluded that the PI3K/Akt pathway is involved in MDR in lymphoma cell lines and PI3K/Akt inhibition correlates down-regulation of NF-kappaB activity and inhibition Pgp function.

García MG; Alaniz LD; Cordo Russo RI; Alvarez E; Hajos SE

2009-02-01

323

Different Strategies to Overcome Multidrug Resistance in Cancer.  

UK PubMed Central (United Kingdom)

The risk of acquisition of resistance to chemotherapy remains a major hurdle in the management of various types of cancer patients. Several cellular and noncellular mechanisms are involved in developing both intrinsic and acquired resistance in cancer cells toward chemotherapy. This review covers the various multidrug resistance (MDR) mechanisms observed in cancer cells as well as the various strategies developed to overcome these MDR mechanisms. Extensive studies have been conducted during the last several decades to enhance the efficacy of chemotherapy by suppressing or evading these MDR mechanisms including the use of new anticancer drugs that could escape from the efflux reaction, MDR modulators or chemosensitizers, multifunctional nanocarriers, and RNA interference (RNAi) therapy.

Saraswathy M; Gong S

2013-06-01

324

Regulation of multidrug resistance in pathogenic fungi.  

UK PubMed Central (United Kingdom)

Infections by opportunistic pathogenic fungi, especially Candida species, Cryptococcus neoformans, and Aspergillus fumigatus, are a serious medical problem in immunocompromised patients. Different classes of antimycotic drugs are available to treat fungal infections, but the pathogens can develop resistance to all these agents. A major mechanism of antifungal drug resistance is the overexpression of efflux pumps of the ABC transporter and major facilitator superfamilies, which confer resistance to many structurally and functionally unrelated toxic compounds. For some pathogenic fungi, like Candida albicans and Candida glabrata, the most important drug transporters, transcription factors controlling their expression, and mutations that cause the constitutive upregulation of the efflux pumps in drug-resistant clinical isolates have been identified. For other important pathogens comparatively little is known about the role of transporters in antimycotic resistance. This review summarizes our current knowledge about efflux pump-mediated drug resistance and its regulation in human-pathogenic fungi.

Morschhäuser J

2010-02-01

325

Human ABCB1 (P-glycoprotein) and ABCG2 mediate resistance to BI 2536, a potent and selective inhibitor of Polo-like kinase 1.  

Science.gov (United States)

The overexpression of the serine/threonine specific Polo-like kinase 1 (Plk1) has been detected in various types of cancer, and thus has fast become an attractive therapeutic target for cancer therapy. BI 2536 is the first selective inhibitor of Plk1 that inhibits cancer cell proliferation by promoting G2/M cell cycle arrest at nanomolar concentrations. Unfortunately, alike most chemotherapeutic agents, the development of acquired resistance to BI 2536 is prone to present a significant therapeutic challenge. One of the most common mechanisms for acquired resistance in cancer chemotherapy is associated with the overexpression of ATP-binding cassette (ABC) transporters ABCB1, ABCC1 and ABCG2. Here, we discovered that overexpressing of either ABCB1 or ABCG2 is a novel mechanism of acquired resistance to BI 2536 in human cancer cells. Moreover, BI 2536 stimulates the ATPase activity of both ABCB1 and ABCG2 in a concentration-dependent manner, and inhibits the drug substrate transport mediated by these transporters. More significantly, the reduced chemosensitivity and BI 2536-mediated G2/M cell cycle arrest in cancer cells overexpressing either ABCB1 or ABCG2 can be significantly restored in the presence of selective inhibitor or other chemotherapeutic agents that also interact with ABCB1 and ABCG2, such as tyrosine kinase inhibitors nilotinib and lapatinib. Taken together, our findings indicate that in order to circumvent ABCB1 or ABCG2-mediated acquired resistance to BI 2536, a combined regimen of BI 2536 and inhibitors or clinically active drugs that potently inhibit the function of ABC drug transporters, should be considered as a potential treatment strategy in the clinic. PMID:23962445

Wu, Chung-Pu; Hsiao, Sung-Han; Sim, Hong-May; Luo, Shi-Yu; Tuo, Wei-Cherng; Cheng, Hsing-Wen; Li, Yan-Qing; Huang, Yang-Hui; Ambudkar, Suresh V

2013-08-17

326

Human ABCB1 (P-glycoprotein) and ABCG2 mediate resistance to BI 2536, a potent and selective inhibitor of Polo-like kinase 1.  

UK PubMed Central (United Kingdom)

The overexpression of the serine/threonine specific Polo-like kinase 1 (Plk1) has been detected in various types of cancer, and thus has fast become an attractive therapeutic target for cancer therapy. BI 2536 is the first selective inhibitor of Plk1 that inhibits cancer cell proliferation by promoting G2/M cell cycle arrest at nanomolar concentrations. Unfortunately, alike most chemotherapeutic agents, the development of acquired resistance to BI 2536 is prone to present a significant therapeutic challenge. One of the most common mechanisms for acquired resistance in cancer chemotherapy is associated with the overexpression of ATP-binding cassette (ABC) transporters ABCB1, ABCC1 and ABCG2. Here, we discovered that overexpressing of either ABCB1 or ABCG2 is a novel mechanism of acquired resistance to BI 2536 in human cancer cells. Moreover, BI 2536 stimulates the ATPase activity of both ABCB1 and ABCG2 in a concentration-dependent manner, and inhibits the drug substrate transport mediated by these transporters. More significantly, the reduced chemosensitivity and BI 2536-mediated G2/M cell cycle arrest in cancer cells overexpressing either ABCB1 or ABCG2 can be significantly restored in the presence of selective inhibitor or other chemotherapeutic agents that also interact with ABCB1 and ABCG2, such as tyrosine kinase inhibitors nilotinib and lapatinib. Taken together, our findings indicate that in order to circumvent ABCB1 or ABCG2-mediated acquired resistance to BI 2536, a combined regimen of BI 2536 and inhibitors or clinically active drugs that potently inhibit the function of ABC drug transporters, should be considered as a potential treatment strategy in the clinic.

Wu CP; Hsiao SH; Sim HM; Luo SY; Tuo WC; Cheng HW; Li YQ; Huang YH; Ambudkar SV

2013-10-01

327

Multidrug resistant miliary tuberculosis during infliximab therapy despite tuberculosis screening.  

UK PubMed Central (United Kingdom)

We describe an unusual case of multidrug-resistant miliary tuberculosis diagnosed 9 months after the commencement of infliximab treatment for psoriasis despite negative pretreatment tuberculosis screening, including chest X-ray and interferon-gamma release assay. After 4 months' treatment with amikacin, ethambutol, pyrazinamide and moxifloxacin, infliximab was restarted with concomitant anti-TB medications. No recurrence of tuberculosis has been detected 12 months after recommencing infliximab.

Gin A; Dolianitis C

2013-05-01

328

Increase in doxorubicin cytotoxicity by inhibition of P-glycoprotein activity with lomerizine.  

Science.gov (United States)

Acquired resistance to chemotherapy is a major problem during cancer treatment. One mechanism for drug resistance is overexpression of the MDR (multidrug resistance)1 gene encoding the transmembrane efflux pump, P-glycoprotein (P-gp). Calcium channel blockers such as verapamil, nifedipine and nicardipine have been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux. This study evaluated whether a new calcium channel blocker, lomerizine, influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. Verapamil, and even more markedly, lomerizine, increased cellular uptake of calcein transported by P-gp in a P-gp-expressing erythroleukemia cell line, K562-Dox. Ten microM of lomerizine reduced the IC50 of doxorubicin in the K562-Dox from 60000 ng/ml to 800 ng/ml, whereas the IC50 of doxorubicin in the K562 subline was only marginally affected by these drugs. Lomerizine showed greater reduction in P-gp efflux than verapamil at an equimolar concentration. These results suggest that lomerizine has the clinical potential to reverse tumor MDR involving the efflux protein P-gp. PMID:11379779

Shiraki, N; Hamada, A; Ohmura, T; Tokunaga, J; Oyama, N; Nakano, M

2001-05-01

329

Increase in doxorubicin cytotoxicity by inhibition of P-glycoprotein activity with lomerizine.  

UK PubMed Central (United Kingdom)

Acquired resistance to chemotherapy is a major problem during cancer treatment. One mechanism for drug resistance is overexpression of the MDR (multidrug resistance)1 gene encoding the transmembrane efflux pump, P-glycoprotein (P-gp). Calcium channel blockers such as verapamil, nifedipine and nicardipine have been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux. This study evaluated whether a new calcium channel blocker, lomerizine, influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. Verapamil, and even more markedly, lomerizine, increased cellular uptake of calcein transported by P-gp in a P-gp-expressing erythroleukemia cell line, K562-Dox. Ten microM of lomerizine reduced the IC50 of doxorubicin in the K562-Dox from 60000 ng/ml to 800 ng/ml, whereas the IC50 of doxorubicin in the K562 subline was only marginally affected by these drugs. Lomerizine showed greater reduction in P-gp efflux than verapamil at an equimolar concentration. These results suggest that lomerizine has the clinical potential to reverse tumor MDR involving the efflux protein P-gp.

Shiraki N; Hamada A; Ohmura T; Tokunaga J; Oyama N; Nakano M

2001-05-01

330

Prognostic significance of multidrug-resistance protein (MDR-1) in renal clear cell carcinomas: A five year follow-up analysis  

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Full Text Available Abstract Background A large number of renal cancer patients shows poor or partial response to chemotherapy and the mechanisms have not been still understood. Multi-drug resistance is the principal mechanism by which many cancers develop resistance to chemotherapic drugs. The role of the multi-drug resistant transporter (MDR-1/P-glycoprotein), the gene product of MDR-1, and that one of the so-called multi-drug resistance associated protein (MRP), two energy-dependent efflux pumps, are commonly known to confer drug resistance. We studied MDR-1 expression in selected cases of renal cell carcinoma (RCC), clear cell type, with long-term follow-up, in order to establish its prognostic role and its possible contribution in the choice of post-surgical therapy. Methods MDR-1 has been studied by standard LSAB-HRP immunohistochemical technique, in paraffin embedded RCC samples. Protein expression has been compared to clinical and histopathological data and to disease specific survival of RCC patients, by Kaplan-Meier curve and Cox multivariate regression analyses. Results Two groups of RCCs were obtained by esteeming MDR-1 expression and disease specific survival (obtained with Kaplan-Meier curve and Cox multivariate regression analyses): the first one presents low or absent MDR-1 expression and good survival; the second one is characterized by high MDR-1 expression and significant poor outcome (p p p p Conclusion In our opinion, the results of this study well prove the relationship between MDR-1 expression and worse clinical prognosis in RCC, because MDR-1 over-expressing RCCs can be considered a group of tumours with a more aggressive behavior. This finding outlines a possible role of MDR-1 as prognostic factor, dependent and independent of multidrug resistance. These results could be useful to predict cancer evolution and to choose the appropriate treatment: this is another step that can stimulate further promising and interesting investigations on broader study population.

Mignogna Chiara; Staibano Stefania; Altieri Vincenzo; De Rosa Gaetano; Pannone Giuseppe; Santoro Angela; Zamparese Rosanna; D'Armiento Massimino; Rocchetti Romualdo; Mezza Ernesto; Nasti Mario; Strazzullo Viviana; Montanaro Vittorino; Mascolo Massimo; Bufo Pantaleo

2006-01-01

331

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.  

UK PubMed Central (United Kingdom)

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.

Natarajan K; Bhullar J; Shukla S; Burcu M; Chen ZS; Ambudkar SV; Baer MR

2013-02-01

332

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.  

Science.gov (United States)

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

2012-12-19

333

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

International Nuclear Information System (INIS)

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

2004-01-01

334

Emerging of Multidrug Resistance Human Pathogens from Urinary Tract Infections  

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Full Text Available The present study aimed to ascertain the current situation of antimicrobial resistance of Urinary Tract Infections (UTIs) caused by human pathogens. Ten midstream urine samples were collected from adult patients were analyzed for Multidrug Resistant (MDR) strain isolation and identified. The result was clear that E. coli was the predominant pathogen (31.5%) causing UTI, followed by Staphylococcus aureus (20.5%), Klebsiella pneumonia (15.8%), Proteus sp. (7.4%) and Pseudomonas aeruginosa (7.5%). The percentages of resistance of all isolates to the antimicrobial agents were: 83.3% to SXT, 80.6% to Nalidixic acid, 67.3% to Amoxycillin, 61% to Cotrimoxazole, 48.8% to Gentamycin, 46% to ciprofloxacin and 43% to Cephalexin. Isolated UTI strains were tested for susceptibility against antibiotics, few of the antibiotics were sensitive but most of antibiotics showed resistant to the MDR strains. Among this E. coli, K. pneumoniae and P. aeruginosa were highly resistance to most of the antibiotics, whereas Staphylococcus sp. and Serratia marcescens exhibited sensitive to Cephalexin, Ciprofloxacin and Gentamycin. The present study was evaluated for the prevalence of micrograms implicated in UTI to ascertain their antimicrobial resistance patterns and indicates emerging multidrug resistance among UTI bacterial pathogens.

S. Manikandan; S. Ganesapandian; Manoj Singh; A.K. Kumaraguru

2011-01-01

335

Multi-drug resistant childhood tuberculosis.  

Science.gov (United States)

Emergence of drug resistant tuberculosis is one of the major challenges faced by health community globally. Tuberculosis is an important cause of morbidity and mortality among children in endemic areas, yet little is known regarding epidemiology of pediatric tuberculosis and even far lesser information is available about epidemiology, diagnosis, management and treatment outcome of drug resistant tuberculosis in children. Despite limited data and difficulties in its management, drug resistant tuberculosis can be successfully treated even in resource poor settings with proper use of existing technologies. A high index of suspicion and early drug susceptibility testing is the key to early diagnosis and good treatment outcome. Difficulties in establishing the diagnosis, drug toxicities and absence of pediatric formulations add challenges to the management of Pediatric MDR TB Cases. Active research is required to answer the unresolved issues of finding optimal diagnostic tools, treatment regimens and duration and chemoprophylaxis in pediatric drug resistant tuberculosis. PMID:21193973

Singh, Varinder; Kaur, Satnam

2010-12-31

336

Multi-drug resistant childhood tuberculosis.  

UK PubMed Central (United Kingdom)

Emergence of drug resistant tuberculosis is one of the major challenges faced by health community globally. Tuberculosis is an important cause of morbidity and mortality among children in endemic areas, yet little is known regarding epidemiology of pediatric tuberculosis and even far lesser information is available about epidemiology, diagnosis, management and treatment outcome of drug resistant tuberculosis in children. Despite limited data and difficulties in its management, drug resistant tuberculosis can be successfully treated even in resource poor settings with proper use of existing technologies. A high index of suspicion and early drug susceptibility testing is the key to early diagnosis and good treatment outcome. Difficulties in establishing the diagnosis, drug toxicities and absence of pediatric formulations add challenges to the management of Pediatric MDR TB Cases. Active research is required to answer the unresolved issues of finding optimal diagnostic tools, treatment regimens and duration and chemoprophylaxis in pediatric drug resistant tuberculosis.

Singh V; Kaur S

2011-04-01

337

Multidrug-resistant nosocomial Citrobacter in a hospital in Kathmandu.  

UK PubMed Central (United Kingdom)

Citrobacter sp. is a commensal flora and an infrequent nosocomial pathogen to cause nuisance in hospital settings. Recently, the isolation of this pathogen in health care setting is rising and the multidrug resistant strains are emerging. This pathogen cause wide array of infections and the mortality rate is unexpectedly high of 30.0-60.0%. Extended spectrum cephalosporins have been used to treat this pathogen and due to the emergence of resistant strains to these drugs newer treatment protocols have to be devised. Epidemiology and antibiotic susceptibility pattern of clinical isolates of Citrobacter sp. isolated in a hospital were investigated. Specimens were collected from patients and implicated pathogens were isolated. Disk diffusion test was performed on these isolates and resistant patterns were. Antibiogram typing was used to resolve the clones of the isolated bacteria. The results showed that Citrobacter sp. was highly prevalent and commonly isolated from the sputum sample of patients diagnosed as Chronic Obstructive Pulmonary Disease (COPD). The antibiogram pattern suggested the circulation of three clones of Citrobacter sp. They were multidrug resistant and were sensitive to only cefoperazone and sulbactam suggesting the production of â-lactamse inhibitors sensitive molecular class A and D extended spectrum â-lactamases (ESBL). In conclusion, although, ESBL producers are always treated with carbapenems, we recommend to use combination therapy of â-lactam and â-lactamse inhibitors to treat this multidrug resistant Citrobacter sp. and carbapenems should be kept as a reserve drug and we should aim to prevent the spread of this resistant pathogen between different patients to decrease the morbidity and mortality associated with this pathogen.

Thapa B; Adhikari P; Mahat K; Chhetri MR; Joshi LN

2009-09-01

338

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)

2004-01-01

339

Changes in the localization of ileal P-glycoprotein induced by intestinal ischemia/reperfusion.  

UK PubMed Central (United Kingdom)

P-glycoprotein is one of the most important transporters in the ATP binding cassette transporter. Moreover, it is well known that the efficacy of immunosuppressants, which are used after organ transplantation, is controlled by P-glycoprotein (P-gp). We investigated how ischemia/reperfusion (I/R), which occurs after transplantation, influences the expression level and function of P-gp. To clarify the influence of intestinal I/R on the localization of P-gp, an intestinal ischemia model was produced using a spring scale and surgical sutures for 1 h, followed by reperfusion for 24 h. The expression levels of mRNA and protein of P-gp were examined. The protein expression levels of P-gp in ileal homogenate and the brush border membrane (BBM) were significantly decreased until 3 h after reperfusion. While the protein expression level of P-gp in homogenate showed a tendency to increase, that in the BBM continued to significantly decrease until 24 h after reperfusion. In contrast, the protein expression level of P-gp in the basolateral membrane (BLM) increased significantly until 24 h after reperfusion. While no significant change in multidrug resistance (mdr)-1a mRNA was found, the levels of mdr-1b and mdr-2 significantly increased during intestinal I/R. In addition, the levels of inflammatory cytokines mRNA and nitric oxide (NO) also significantly increased. It was shown that mdr-1b and mdr-2 mRNA strongly participate in the recovery of P-gp protein level after intestinal I/R. We detected the abnormal localization of P-gp in the ileal membrane during intestinal I/R, suggesting NO and/or inflammatory cytokines participate in the abnormal localization of P-gp.

Takizawa Y; Kishimoto H; Kitazato T; Tomita M; Hayashi M

2011-01-01

340

Changes in the localization of ileal P-glycoprotein induced by intestinal ischemia/reperfusion.  

Science.gov (United States)

P-glycoprotein is one of the most important transporters in the ATP binding cassette transporter. Moreover, it is well known that the efficacy of immunosuppressants, which are used after organ transplantation, is controlled by P-glycoprotein (P-gp). We investigated how ischemia/reperfusion (I/R), which occurs after transplantation, influences the expression level and function of P-gp. To clarify the influence of intestinal I/R on the localization of P-gp, an intestinal ischemia model was produced using a spring scale and surgical sutures for 1 h, followed by reperfusion for 24 h. The expression levels of mRNA and protein of P-gp were examined. The protein expression levels of P-gp in ileal homogenate and the brush border membrane (BBM) were significantly decreased until 3 h after reperfusion. While the protein expression level of P-gp in homogenate showed a tendency to increase, that in the BBM continued to significantly decrease until 24 h after reperfusion. In contrast, the protein expression level of P-gp in the basolateral membrane (BLM) increased significantly until 24 h after reperfusion. While no significant change in multidrug resistance (mdr)-1a mRNA was found, the levels of mdr-1b and mdr-2 significantly increased during intestinal I/R. In addition, the levels of inflammatory cytokines mRNA and nitric oxide (NO) also significantly increased. It was shown that mdr-1b and mdr-2 mRNA strongly participate in the recovery of P-gp protein level after intestinal I/R. We detected the abnormal localization of P-gp in the ileal membrane during intestinal I/R, suggesting NO and/or inflammatory cytokines participate in the abnormal localization of P-gp. PMID:21372393

Takizawa, Yusuke; Kishimoto, Hisanao; Kitazato, Takuya; Tomita, Mikio; Hayashi, Masahiro

2011-01-01

 
 
 
 
341

Multidrug-resistant tuberculosis in children: evidence from global surveillance.  

Science.gov (United States)

Multidrug-resistant tuberculosis (MDR-TB) can affect persons of any age, but it remains unknown whether children are more or less likely than adults to have MDR-TB. Representative drug resistance surveillance data reported to the World Health Organization between 1994 and 2011 were analysed to test the association between MDR-TB and age group (children aged childhood tuberculosis, our analysis suggests that proportions of MDR-TB in children and adults are similar in many settings. Of particular concern is the association found between age <15 years and MDR-TB in southern African countries with high HIV prevalence. PMID:23222872

Zignol, Matteo; Sismanidis, Charalambos; Falzon, Dennis; Glaziou, Philippe; Dara, Masoud; Floyd, Katherine

2012-12-06

342

Expression of protein kinase C in multidrug resistant cells of colorectal carcinoma  

International Nuclear Information System (INIS)

Objective: To detect the expression of protein kinase C (PKC) in multidrug resistant cells of colorectal carcinoma after ionizing irradiation and observe the effect of PKC on occurrence and development of the multidrug resistant. Methods: The effect of PKC on multidrug resistant HCG-8 cells of colorectal carcinoma after treated with X-ray was detected by indirect immunofluorescence technique and flow cytometry. Results: Compared with sham- irradiation group, the positive percentage of PKC was increased significantly (P

2008-01-01

343

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

Science.gov (United States)

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. PMID:20957096

He, Shengnan; Liu, Feng; Xie, Zhenhua; Zu, Xuyu; Xu, Wei; Jiang, Yuyang

2010-08-27

344

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.

Shengnan He; Feng Liu; Zhenhua Xie; Xuyu Zu; Wei Xu; Yuyang Jiang

2010-01-01

345

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

UK PubMed Central (United Kingdom)

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.

He S; Liu F; Xie Z; Zu X; Xu W; Jiang Y

2010-01-01

346

New Antibiotics in Development Against Multidrug-Resistant Bacteria  

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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

2013-01-01

347

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

International Nuclear Information System (INIS)

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

2005-03-01

348

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; Mota Rosa Maria Salani; Santos Raimunda Oliveira; Sousa Ana Lúcia Oliveira; Barroso Joana Brasileiro; Rodrigues Jorge Luís Nobre

2003-01-01

349

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

International Nuclear Information System (INIS)

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.

2004-12-01

350

Clinical evaluation of multidrug resistance associated protein expression by FDG PET and MIBI SPECT in lung cancer  

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[en] Multidrug resistance is one of the major obstacles in the successful anticancer therapy. The aim of this study is to evaluate whether FDG PET and MIBI SPECT can be markers for p-glycoprotein (Pgp), multidrug resistance-associated protein (MRP), lung resistance protein (LRP) expression in lung cancer tissues. Eighty-eight patients with 92 lung cancer lesions were enrolled in this study. Before surgery, FDG PET imaging was performed 40 min after injection of FDG 185 MBq, and standardized uptake values (SUVs) were obtained. MIBI SPECT imaging was performed 15 min and 3 hour after injection of MIBI 370 MBq. Early ratio (ER), delayed ratio (DR), and washout rate (WR) were obtained. Pgp, MRP, and LRP expression in lung cancer tissues were determined by immunohistochemical staining. No significant correlations were observed between MIBI uptake and expression of Pgp, MRP and LRP. FDG uptake significantly correlated with expression of Pgp and LRP. The lung cancer with high degree of Pgp and LRP expression had significantly low FDG uptake. However, there is no correlation between FDG uptake and MRP expression. Pgp and LRP expression of adenocarcinomas were significantly higher than that of squamous cell carcinomas. FDG uptake of adenocarcinomas were significantly lower than that of squamous cell carcinomas. In lung adenocarcinomas, Pgp and LRP expression of bronchioloalveolar carcinomas were significantly higher than that of poorly differentiated adenocarcinomas. In contrast, FDG uptake of bronchioloalveolar carcinomas were significantly low when compared with that of poorly differentiated adenocarcinomas. In addition, it was also suggested that biological behavior of LRP expression was similar to that of Pgp expression. FDG uptake may be a marker for Pgp and LRP expression but not for MRP expression in patients with lung cancer. Both Pgp, LRP expression and FDG uptake correlate with cellular differentiation and histological type. (author)

2002-01-01

351

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

352

Development of PET and SPECT radiopharmaceuticals to study multi-drug resistance (MDR)  

International Nuclear Information System (INIS)

Full text: Cellular resistance or Multidrug Resistance (MDR) to cytotoxic agents is the major cause of treatment failure in many human cancers. P-glycoprotein (Pgp), a Mr 17,0000 transmembrane protein and Multi Resistance Protein (MRP) are two proteins that are over expressed and confer resistance to a large number of chemotherapeutic agents by enhancing their extracellular transport. P-glycoprotein is expressed at a relative high level in treated and untreated human malignant tumours, including renal, colonic, adrenal, hepatocellular carcinoma and a considerable percentage of breast carcinomas. 99mTc-Sestamibi, a lipophilic cationic complex is a transport substrate for Pgp. In clinical studies of human neoplasms it was found that tumour uptake and clearance of this tracer correlate with Pgp expression and may be used for the phenotypic assessment of MDR. However, new tracers with better substrate specificity for Pgp and other drug transporters would greatly assist in optimising chemotherapeutic treatment and improving patient management by predicting tumour response to therapy and to assist in the development of antagonists, which may reverse or halt MDR. The aim of this project is therefore to develop PET and SPECT radiopharmaceuticals with improved affinity and selectivity for Pgp and MRP for the clinical evaluation of MDR in cancer patie