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1

Interaction of tamoxifen with the multidrug resistance P-glycoprotein.  

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Tamoxifen is an anti-oestrogen which is currently being assessed as a prophylactic for women at high risk of breast cancer. Taxoxifen has also been shown to reverse multidrug resistance in P-glycoprotein (P-gp)-expressing cells, although the mechanism of action is unknown. In this study we demonstrate that tamoxifen interacts directly with P-gp. Plasma membranes from P-gp-expressing cells bound [3H]tamoxifen in a specific and saturable fashion. A 180 kDa membrane protein in these membranes, l...

Callaghan, R.; Higgins, C. F.

1995-01-01

2

Amino acid substitutions in the sixth transmembrane domain of P-glycoprotein alter multidrug resistance.  

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Eukaryotic cells can display resistance to a wide range of natural-product chemotheraputic agents by the expression of P-glycoprotein (pgp), a putative plasma membrane transporter that is thought to mediate the efflux of these agents from cells. We have identified, in cells selected for multidrug resistance with actinomycin D, a mutant form of pgp that contains two amino acid substitutions within the putative sixth transmembrane domain. In transfection experiments, this altered pgp confers a ...

Devine, S. E.; Ling, V.; Melera, P. W.

1992-01-01

3

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

4

Essential features of the P-glycoprotein pharmacophore as defined by a series of reserpine analogs that modulate multidrug resistance.  

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We have shown previously that reserpine is an effective "modulator" of P-glycoprotein-associated multidrug resistance (MDR). In addition to enhancing drug cytotoxicity in our multidrug-resistant human leukemia cell line, CEM/VLB100, reserpine strongly competes with a photoactivatible analog of vinblastine, N-(p-azido-3-[125I]iodosalicyl)-N'-(beta-aminoethyl)vindesine, for binding to P-glycoprotein. We also demonstrated previously that there are three substructural domains present in many comp...

Pearce, H. L.; Safa, A. R.; Bach, N. J.; Winter, M. A.; Cirtain, M. C.; Beck, W. T.

1989-01-01

5

Reversal of P-glycoprotein-mediated multidrug resistance by XR9051, a novel diketopiperazine derivative.  

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XR9051 (N-(4-(2-(6,7-Dimethoxy-1,2,3,4-tetrahydro-2-isoquinolyl)ethyl)phe nyl)-3-((3Z,6Z)-6-benzylidene-1-methyl-2,5-dioxo-3-pipera zinylidene) methylbenzamide) was identified as a potent modulator of P-glycoprotein-mediated multidrug resistance (MDR) following a synthetic chemistry programme based on a natural product lead compound. The activity of XR9051 was determined using a panel of human and murine drug-resistant cell lines (H69/LX4, 2780AD, EMT6/AR 1.0, MC26 and P388/DX Johnson). XR905...

1998-01-01

6

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

Science.gov (United States)

Multidrug resistance (MDR) in mammalian cells and tumors is associated with overexpression of an approximately 170 kDa 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 (t1/2 approximately 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. Median effective concentrations (EC50; microM) were as follows: vinblastine, 13; daunomycin, 55; idarubicin, 65; actinomycin D, 235; colchicine, minimal inhibition; adriamycin, no effect. P-glycoprotein modulators generally demonstrated significantly greater potency (EC50; microM): SDZ PSC 833, 0.08; cyclosporin A, 1.3; verapamil, 4.1; quinidine, 6.4; prazosin, > 300. Modulator-induced enhancement up to 100-fold was observed with Hill coefficients approximately 1, consistent with simple Michaelis-Menten kinetics. Vanadate was an efficacious transport inhibitor, while agents usually not included in the MDR phenotype were without effect. Scatchard analysis showed quinidine to be a noncompetitive inhibitor of P-glycoprotein-mediated Tc-SESTAMIBI transport, indicating allosteric effector sites on P-glycoprotein. The lipid bilayer adsorbing agents tetraphenyl borate and phloretin induced large increases in final Tc-SESTAMIBI accumulation, showing maximal accumulations 2-fold greater than classic MDR modulators and Hill coefficients > 2. In V79 and 77A cells, modulators of PKC activity altered Tc-SESTAMIBI accumulation, while there was no indication of modulation of P-glycoprotein-mediated Tc-SESTAMIBI transport by hypotonic buffer, extracellular ATP, Cl-, or K+ (membrane potential). While recognized and avidly transported by the P-glycoprotein at buffer concentrations as low as 7 pM, Tc-SESTAMIBI at up to 100 microM only minimally modulated the cytotoxic action of colchicine, doxorubicin, or vinblastine in MDR cells. In conclusion, transport analysis with Tc-SESTAMIBI is a sensitive assay for detecting functional expression of low levels of P-glycoprotein and for the quantitative characterization of transporter modulation and regulation. The biochemical data favor a high Km, high capacity allosterically modulated translocation mechanism for P-glycoprotein-mediated transport of this organometallic cation. PMID:7547962

Piwnica-Worms, D; Rao, V V; Kronauge, J F; Croop, J M

1995-09-26

7

Genistein modulates the decreased drug accumulation in non-P-glycoprotein mediated multidrug resistant tumour cells.  

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In tumour cells the pharmacological basis for multidrug resistance (MDR) often appears to be a reduced cellular cytostatic drug accumulation caused by the drug efflux protein, P-glycoprotein (Pgp MDR), or by other drug transporters (non-Pgp MDR). Here we report the reversal of the decreased daunorubicin (DNR) accumulation in five non-Pgp MDR cell lines (GLC4/ADR, SW-1573/2R120, HT1080/DR4, MCF7/Mitox and HL60/ADR) by genistein. Genistein inhibited the enhanced DNR efflux in the GLC4/ADR cells...

Versantvoort, C. H.; Schuurhuis, G. J.; Pinedo, H. M.; Eekman, C. A.; Kuiper, C. M.; Lankelma, J.; Broxterman, H. J.

1993-01-01

8

Polyaromatic alkaloids from marine invertebrates as cytotoxic compounds and inhibitors of multidrug resistance caused by P-glycoprotein.  

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The effects of several members of the family of lamellarins, polyaromatic alkaloids isolated from tunicates belonging to the genus Didemnum, on the growth of several tumour cell lines and on P-glycoprotein (P-gp)-mediated multidrug resistance (MDR), were investigated. Cytotoxicity experiments of lamellarins were performed on a panel of tumour cell lines, including two multidrug-resistant cell lines. Some lamellarins showed good anti-tumour activity, with similar levels of cytotoxicity against...

Quesada, A. R.; Garci?a Gra?valos, M. D.; Ferna?ndez Puentes, J. L.

1996-01-01

9

P-glycoprotein gene amplification and expression in multidrug-resistant murine P388 and B16 cell lines.  

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P-glycoprotein gene (mdrl) amplification and expression were examined in murine leukaemia P388/DX and melanoma B16VDXR cell lines, which exhibit a high level of resistance to a selecting agent, doxorubicin, and express a multidrug-resistant phenotype because they are cross-resistant to multiple cytotoxic drugs. The multidrug-resistant phenotype was obtained in different conditions of selection (in vivo and in vitro for P388/DX and B16VDXR, respectively). In both multidrug-resistant cell lines...

1989-01-01

10

Parallel functional and immunological detection of human multidrug resistance proteins, P-glycoprotein and MRP1.  

Science.gov (United States)

The proper assessment of the expression and drug extrusion activity of multidrug resistance proteins in various tumor cells is a challenging clinical laboratory problem. Recently, we have introduced a fluorescent dye (calcein) accumulation assay for the estimation of the functional expression of both P-glycoprotein (MDR1) and the multidrug resistance-associated protein (MRP1). Since both MDR1 and MRP1 decrease the intracellular accumulation of the fluorescent free calcein, by applying appropriate inhibitors of MDR1 and MRP1, the transport activity of these proteins could be quantitatively and selectively estimated in fluorometry or flow-cytometry assays. In the present work single-cell fluorescence digital imaging has been applied to characterize the kinetics and inhibitor-sensitivity of calcein accumulation in a mixture of HL60 MRP1 and NIH 3T3 MDR1 cells. Subsequent immunofluorescence labeling was performed by the anti-MDR1 monoclonal antibody (mAb) UIC2 in the same cell population. We report that the double labeling approach, based on the single cell calcein accumulation assay and an immunofluorescence detection, provides good sensitivity and selectivity for the simultaneous functional and immunological detection of cellular MDR1 and MRP1. PMID:9713496

Holló, Z; Homolya, L; Hegedûs, T; Müller, M; Szakács, G; Jakab, K; Antal, F; Sarkadi, B

1998-01-01

11

Generation of multidrug resistant lymphoma cell lines stably expressing P-glycoprotein.  

Science.gov (United States)

The objective of this study was to generate new P-glycoprotein (P-gp)-expressing multidrug resistant (MDR) cell lines by drug selection. Since our previous studies have been carried out with cells infected with a P-gp-containing vector, it was important to confirm our findings in cells generated by drug selection. In this report, we describe three B-lymphoma cell lines which became drug-resistant by stepwise exposure to vincristine (VCR): Raji cells resistant to 18 nM VCR (R18V), Namalwa cells resistant to 21 nM VCR (N21V) and DHL-4 cells resistant to 12 nM VCR (DHL-4/12V). Cells overexpressed P-gp and continued to express CD19, CD20 and CD22, all of which are targets for monoclonal antibody (MAb) therapy. The P-gp pump in these new cells was functional as determined by the efflux of Rhodamine 123 and DIOC2, and the three cell lines were resistant to several chemotherapeutic drugs. We further determined that their P-gp phenotype was stable in xenografted SCID mice and that the tumors were also resistant to chemotherapy. We will now use these new MDR cells to determine whether monoclonal antibodies against CD19 and -20 can reverse P-gp, as we previously demonstrated using Namalwa cells infected with a human mdr1 gene-containing retrovirus. PMID:18357372

Pop, Iliodora; Pop, Laurentiu; Vitetta, Ellen S; Ghetie, Maria-Ana

2008-04-01

12

Inhibition of the multidrug resistance P-glycoprotein: time for a change of strategy?  

Science.gov (United States)

P-glycoprotein (P-gp) is a key player in the multidrug-resistant phenotype in cancer. The protein confers resistance by mediating the ATP-dependent efflux of an astonishing array of anticancer drugs. Its broad specificity has been the subject of numerous attempts to inhibit the protein and restore the efficacy of anticancer drugs. The general strategy has been to develop compounds that either compete with anticancer drugs for transport or act as direct inhibitors of P-gp. Despite considerable in vitro success, there are no compounds currently available to "block" P-gp-mediated resistance in the clinic. The failure may be attributed to toxicity, adverse drug interaction, and numerous pharmacokinetic issues. This review provides a description of several alternative approaches to overcome the activity of P-gp in drug-resistant cells. These include 1) drugs that specifically target resistant cells, 2) novel nanotechnologies to provide high-dose, targeted delivery of anticancer drugs, 3) compounds that interfere with nongenomic transfer of resistance, and 4) approaches to reduce the expression of P-gp within tumors. Such approaches have been developed through the pursuit of greater understanding of resistance mediators such as P-gp, and they show considerable potential for further application. PMID:24492893

Callaghan, Richard; Luk, Frederick; Bebawy, Mary

2014-04-01

13

A new method for a quantitative assessment of P-glycoprotein-related multidrug resistance in tumour cells.  

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A rapid, functional and quantitative diagnostic method for the estimation of the P-glycoprotein (P-gp)-dependent multidrug resistance is required in the clinical treatment of human tumours, as chemotherapy protocols and resistance-reversing agents could be applied accordingly. In the present work, by using a calcein accumulation method in combination with immunorecognition and drug-resistance studies, a new method is described for the quantitative estimation of the expression and function of ...

Homolya, L.; Hollo?, M.; Mu?ller, M.; Mechetner, E. B.; Sarkadi, B.

1996-01-01

14

Cortisol is transported by the multidrug resistance gene product P-glycoprotein  

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The physiology of the multidrug transporter P-glycoprotein (Pgp) is still poorly understood. We now show evidence that cell lines with a high expression of Pgp display a reduced accumulation of cortisol and an ATP-dependent outward transport of the hormone. Cortisol efflux from Pgp negative cells does not have such an active component. Further we show that the steroid hormones cortisol, testosterone, and progesterone cause an immediate, dose-dependent increase of daunorubicin accumulation in ...

Kalken, C. K.; Broxterman, H. J.; Pinedo, H. M.; Feller, N.; Dekker, H.; Lankelma, J.; Giaccone, G.

1993-01-01

15

P-glycoprotein mediates the collateral sensitivity of multidrug resistant cells to steroid hormones.  

Science.gov (United States)

The overexpression of P-glycoprotein (P-gp, ABCB1) in cancer cells often leads to multidrug resistance (MDR) through reduced drug accumulation. However, certain P-gp-positive cells display hypersensitivity, or collateral sensitivity, to certain compounds that are believed to induce Pgp-dependent oxidative stress. We have previously reported that MDR P-gp-positive CHO cells are collaterally sensitive to verapamil (VRP; Laberge et al. (2009) [1]). In this report we extend our previous findings and show that drug resistant CHO cells are also collaterally sensitive to physiologic levels of progesterone (PRO) and deoxycorticosterone (DOC). Both PRO and DOC collateral sensitivities in CH(R)C5 cells are dependent on P-gp-expression and ATPase, as knockdown of P-gp expression with siRNA or inhibition of P-gp-ATPase with PSC833 reverses PRO- and DOC-induced collateral sensitivity. Moreover, the mitochondrial complexes I and III inhibitors (antimycin-A and rotenone, respectively) synergize with PRO and DOC-induced collateral sensitivity. We also show that VRP inhibits PRO and DOC collateral sensitivity, consistent with earlier findings relating to the VRP's modulation of PRO and DOC-stimulation of P-gp ATPase. The findings of this study demonstrate a P-gp-dependent collateral sensitivity of MDR cells in the presence of physiologically achievable concentrations of progesterone and deoxycorticosterone. PMID:24747077

Laberge, Rémi-Martin; Ambadipudi, Raghuram; Georges, Elias

2014-05-16

16

Efflux pump inhibitors: a strategy to combat P-glycoprotein and the NorA multidrug resistance pump.  

Science.gov (United States)

Multidrug resistance (MDR) is the cause of an ever-increasing number of problems in the treatment of cancers and bacterial infections. The active efflux of drugs contributes significantly to this phenomenon. This minireview summarizes recent advances in combating MDR, with particular emphasis on natural and synthetic efflux pump inhibitors of P-glycoprotein in resistant tumor cells and of the NorA MDR pump in Staphylococcus aureus. PMID:20373322

Zhang, Ling; Ma, Shutao

2010-06-01

17

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

Science.gov (United States)

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. PMID:24095875

Jara, Gabriel E; Vera, D Mariano A; Pierini, Adriana B

2013-11-01

18

Reversal of P-glycoprotein-mediated multidrug resistance by Alisol B 23-acetate.  

Science.gov (United States)

Herbal drugs were screened for their activity in reversing multidrug resistance (MDR) in P-glycoprotein (P-gp) over-expressing cancer cells. Through bio-assay guided fractionation an active compound was isolated from Rhizoma Alismatis, the underground part of Alisma orientale and the chemical structure of the isolate compound was confirmed by HPLC, LC-MS and NMR as Alisol B 23-acetate (ABA). ABA restored the sensitivity of MDR cell lines HepG2-DR and K562-DR to anti-tumor agents that have different modes of action but are all P-gp substrates. It restored the activity of vinblastine, a P-gp substrate, in causing G2/M arrest in MDR cells. In a dose-dependent manner, ABA increased doxorubicin accumulation and slowed down the efflux of rhodamin-123 from MDR cells. ABA inhibited the photoaffinity labeling of P-gp by [125I]iodoarylazidoprazosin and stimulated the ATPase activity of P-gp in a concentration-dependent manner, suggesting that it could be a transporter substrate for P-gp. In addition, ABA was also a partial non-competitive inhibitor of P-gp when verapamil was used as a substrate. Our results suggest that ABA may be a potential MDR reversal agent and could serve as a lead compound in the development of novel drugs. PMID:15294447

Wang, Cheng; Zhang, Jin-Xia; Shen, Xiao-Ling; Wan, Chi-Keung; Tse, Anfernee Kai-Wing; Fong, Wang-Fun

2004-09-01

19

Characterization of multidrug resistance 1a/P-glycoprotein knockout rats generated by zinc finger nucleases.  

Science.gov (United States)

The development of zinc finger nuclease (ZFN) technology has enabled the genetic engineering of the rat genome. The ability to manipulate the rat genome has great promise to augment the utility of rats for biological and pharmacological studies. A Wistar Hannover rat model lacking the multidrug resistance protein Mdr1a P-glycoprotein (P-gp) was generated using a rat Mdr1a-specific ZFN. Mdr1a was completely absent in tissues, including brain and small intestine, of the knockout rat. Pharmacokinetic studies with the Mdr1a P-gp substrates loperamide, indinavir, and talinolol indicated that Mdr1a was functionally inactive in the blood-brain barrier and intestine in Mdr1a(-/-) rats. To identify possible compensatory mechanisms in Mdr1a(-/-) rats, the expression levels of drug-metabolizing enzyme and transporter-related genes were compared in brain, liver, kidney, and intestine of male and female Mdr1a(-/-) and control rats. In general, alterations in gene expression of these genes in Mdr1a(-/-) rats seemed to be modest, with more changes in female than in male rats. Taken together, our studies demonstrate that the ZFN-generated Mdr1a(-/-) rat will be a valuable tool for central nervous system drug target validation and determining the role of P-gp in drug absorption and disposition. PMID:22049154

Chu, Xiaoyan; Zhang, Zuo; Yabut, Jocelyn; Horwitz, Sarah; Levorse, John; Li, Xiang-qing; Zhu, Lei; Lederman, Harmony; Ortiga, Rachel; Strauss, John; Li, Xiaofang; Owens, Karen A; Dragovic, Jasminka; Vogt, Thomas; Evers, Raymond; Shin, Myung K

2012-02-01

20

Cytotoxic effect of the cyclosporin PSC 833 in multidrug-resistant leukaemia cells with increased expression of P-glycoprotein.  

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Multidrug resistance (MDR) to anti-cancer agents is frequently associated with overexpression of the drug efflux transporter P-glycoprotein (Pgp) in cancer cells, ensuing drug expulsion and maintenance of tolerable intracellular levels of certain cytotoxic drugs. Pgp may also be present in normal tissue, providing protection against toxic substances, but the physiological role of Pgp is not fully understood. Recently, it was shown that Pgp also takes part in the transport of certain growth-re...

Lehne, G.; Rugstad, H. E.

1998-01-01

 
 
 
 
21

Nilotinib Counteracts P-Glycoprotein-Mediated Multidrug Resistance and Synergizes the Antitumoral Effect of Doxorubicin in Soft Tissue Sarcomas  

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The therapeutic effect of doxorubicin (DXR) in the treatment of soft tissue sarcomas (STS) is limited by its toxicity and the development of multidrug resistance (MDR), the latter mainly induced by high expression of efflux pumps (e.g., P-glycoprotein [P-gp]). Therefore, the search for alternative therapies, which sensitize these tumors to chemotherapy while maintaining a low toxicity profile, is a rational approach. We assessed efficacy and molecular mechanisms involved in the antiproliferat...

Villar, Victor Hugo; Vo?gler, Oliver; Marti?nez-serra, Jordi; Ramos, Rafael; Calabuig-farin?as, Silvia; Gutie?rrez, Antonio; Barcelo?, Francisca; Marti?n-broto, Javier; Alemany, Regina

2012-01-01

22

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-09-01

23

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

International Nuclear Information System (INIS)

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

1990-01-01

24

P-glycoprotein antagonists confer synergistic sensitivity to short-chain ceramide in human multidrug resistant cancer cells  

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P-glycoprotein (P-gp) antagonists inhibit ceramide metabolism at the juncture of glycosylation. The purpose of this study was to test whether targeting P-gp would be a viable alternative to targeting glucosylceramide synthase (GCS) for enhancing ceramide cytotoxicity. A2780 wild-type, and multidrug resistant 2780AD and NCI/ADR-RES human ovarian cancer cell lines and the cell-permeable ceramide analog, C6-ceramide (C6-cer), were employed. Compared to P-gp-poor A2780 cells, P-gp-rich 2780AD cel...

Chapman, Jacqueline V.; Gouaze?-andersson, Vale?rie; Karimi, Ramin; Messner, Maria C.; Cabot, Myles C.

2011-01-01

25

Inhibition of N-linked glycosylation of P-glycoprotein by tunicamycin results in a reduced multidrug resistance phenotype.  

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Characterisation of altered glycosylation of P-glycoprotein (P-gp) found associated with the absence of a multidrug resistance (MDR) phenotype in cell lines prompted an investigation to assess the role of post-translational processing in establishing P-gp efflux pump functionally. The clone A cell line used in this study displays a strong MDR phenotype mediated by high constitutive levels of expression of P-gp. Incubation of clone A cells with tunicamycin for different periods resulted in a t...

Kramer, R.; Weber, T. K.; Arceci, R.; Ramchurren, N.; Kastrinakis, W. V.; Steele, G.; Summerhayes, I. C.

1995-01-01

26

Polyaromatic alkaloids from marine invertebrates as cytotoxic compounds and inhibitors of multidrug resistance caused by P-glycoprotein.  

Science.gov (United States)

The effects of several members of the family of lamellarins, polyaromatic alkaloids isolated from tunicates belonging to the genus Didemnum, on the growth of several tumour cell lines and on P-glycoprotein (P-gp)-mediated multidrug resistance (MDR), were investigated. Cytotoxicity experiments of lamellarins were performed on a panel of tumour cell lines, including two multidrug-resistant cell lines. Some lamellarins showed good anti-tumour activity, with similar levels of cytotoxicity against both the resistant and their corresponding parental cell lines. Two lamellarins displayed a high potency against lung carcinoma cells. Studies of the resistance modifier activity of the different lamellarins at non-toxic concentrations were also carried out in cells exhibiting MDR, and lamellarin I was selected for the highest chemosensitising activity. At non-toxic doses, verapamil and lamellarin I effectively increased the cytotoxicity of doxorubicin, vinblastine and daunorubicin in a concentration-dependent manner in multidrug-resistant cells, but the potency of lamellarin I as a MDR modulator was 9- to 16-fold higher than that of verapamil. In vitro measurements of rhodamine 123 accumulation in the multidrug-resistant Lo Vo/Dx cells suggest that lamellarin I reverses MDR by directly inhibiting the P-gp-mediated drug efflux. This work underscores the possibility of using these marine-derived compounds as a potential new source of anti-tumoral drugs active on resistant cells as well as of non-toxic modulators of the MDR phenotype. PMID:8795567

Quesada, A R; García Grávalos, M D; Fernández Puentes, J L

1996-09-01

27

Multidrug resistance proteins: role of P-glycoprotein, MRP1, MRP2, and BCRP (ABCG2) in tissue defense  

International Nuclear Information System (INIS)

In tumor cell lines, multidrug resistance is often associated with an ATP-dependent decrease in cellular drug accumulation which is attributed to the overexpression of certain ATP-binding cassette (ABC) transporter proteins. ABC proteins that confer drug resistance include (but are not limited to) P-glycoprotein (gene symbol ABCB1), the multidrug resistance protein 1 (MRP1, gene symbol ABCC1), MRP2 (gene symbol ABCC2), and the breast cancer resistance protein (BCRP, gene symbol ABCG2). In addition to their role in drug resistance, there is substantial evidence that these efflux pumps have overlapping functions in tissue defense. Collectively, these proteins are capable of transporting a vast and chemically diverse array of toxicants including bulky lipophilic cationic, anionic, and neutrally charged drugs and toxins as well as conjugated organic anions that encompass dietary and environmental carcinogens, pesticides, metals, metalloids, and lipid peroxidation products. P-glycoprotein, MRP1, MRP2, and BCRP/ABCG2 are expressed in tissues important for absorption (e.g., lung and gut) and metabolism and elimination (liver and kidney). In addition, these transporters have an important role in maintaining the barrier function of sanctuary site tissues (e.g., blood-brain barrier, blood-cerebral spinal fluid barrier, blood-testis barrier and the maternal-fetal barrier or placenta). Thus, these ABC transporters are increasingly recognized for their ability to modulate the absorption, distribution, metabolism, excretion, and toxicity of xenobiotics. In this review, the role of these four ABC transporter proteins in protecting tissues from a variety of toxicants is discussed. Species variations in substrate specificity and tissue distribution of these transporters are also addressed since these properties have implications for in vivo models of toxicity used for drug discovery and development

2005-05-01

28

Macelignan: a new modulator of P-glycoprotein in multidrug-resistant cancer cells.  

Science.gov (United States)

The effect of macelignan, a phytoestrogen, on P-gp function was investigated using multidrug resistant cancer cells overexpressing P-gp (NCI/ADR-RES) and the fluorescent P-gp substrates, daunorubicin and rhodamine 123. Macelignan (40 microM) increased the cellular accumulation of daunorubicin by approximately threefold in NCI/ADR-RES cells, whereas it did not alter the cellular accumulation of daunorubicin in MCF-7/sensitive cells. Similarly, the presence of macelignan also enhanced significantly (P macelignan. Those results suggest that macelignan has inhibitory effects on P-gp mediated cellular efflux. However, P-gp activity did not affect the cellular accumulation of macelignan itself. Taken all together, macelignan was identified as a novel inhibitor of P-gp activity and may be a promising lead compound for the rational design of more efficacious drugs to reverse multidrug resistance in cancer. PMID:19838926

Im, Young Bin; Ha, Ilho; Kang, Keon Wook; Lee, Moo-Yeol; Han, Hyo-Kyung

2009-01-01

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A new method for a quantitative assessment of P-glycoprotein-related multidrug resistance in tumour cells.  

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A rapid, functional and quantitative diagnostic method for the estimation of the P-glycoprotein (P-gp)-dependent multidrug resistance is required in the clinical treatment of human tumours, as chemotherapy protocols and resistance-reversing agents could be applied accordingly. In the present work, by using a calcein accumulation method in combination with immunorecognition and drug-resistance studies, a new method is described for the quantitative estimation of the expression and function of the multidrug transporter. MDR1-transfected and drug-selected tumour cell lines with various levels of drug resistance were examined. The expression of P-gp and its cell-surface appearance were assessed by quantitative immunoblotting and by immunofluorescence cytometry. The transport function of the P-gp was assessed by measuring the extrusion of calcein acetoxymethyl ester (AM) with fluorometry and flow cytometry, while in parallel experiments drug resistance was directly examined in cell survival assays. The MDR1 activity factor (MAF), calculated from the calcein AM extrusion assay, is demonstrated to provide a reliable quantitative measure for MDR1 specific activity, reflecting cellular drug resistance. This relatively simple and rapid new functional P-gp assay surpasses the formerly used techniques in both sensitivity and reproducibility. PMID:8611394

Homolya, L; Holló, M; Müller, M; Mechetner, E B; Sarkadi, B

1996-04-01

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

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

Yan Xu

2012-10-01

31

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

International Nuclear Information System (INIS)

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

2005-02-01

32

Dynamic and intracellular trafficking of P-glycoprotein-EGFP fusion protein: Implications in multidrug resistance in cancer.  

Science.gov (United States)

In our present study, a P-glycoprotein-EGFP (P-gp-EGFP) fusion plasmid was constructed and functionally expressed in HeLa cells to investigate the intracellular localization and trafficking of P-glycoprotein (P-gp). Using immunocytochemistry and fluorescent confocal microscopy techniques, colocalization studies showed that after transfection, P-gp-EGFP was progressively transported from the endoplasmic reticulum (ER) to the Golgi and finally to the plasma membrane within 12-48 hr. The degree of intracellular accumulation of daunorubicin was related to the particular localization of P-gp-EGFP. Significant daunorubicin accumulation occurred in transfected cells when P-gp-EGFP was localized predominantly within the ER, and accumulation remained high when P-gp-EGFP was mainly localized in the Golgi. However, there was little or no intracellular accumulation of daunorubicin when P-gp-EGFP was localized predominantly on the plasma membrane. Blocking the intracellular trafficking of P-gp-EGFP with brefeldin A (BFA) and monensin resulted in inhibition of traffic of P-gp-EGFP and retention of P-gp-EGFP intracellularly. Intracellular accumulation of daunorubicin also increased in the presence of BFA or monensin. Our study shows that P-gp-EGFP can be used to define the dynamics of P-gp traffic in a transient expression system, and demonstrates that localization of P-gp on the plasma membrane is associated with the highest level of resistance to daunorubicin accumulation in cells. Modulation of intracellular localization of P-gp with agents designed to selectively modify its traffic may provide a new strategy for overcoming multidrug resistance in cancer cells. PMID:14750166

Fu, Dong; Bebawy, Mary; Kable, Eleanor P W; Roufogalis, Basil D

2004-03-20

33

Astragaloside ? reduces the expression level of P?glycoprotein in multidrug?resistant human hepatic cancer cell lines.  

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Astragaloside is a saponin widely used in traditional Chinese medicine and has been reported to be a potent multidrug resistance (MDR) reversal agent. The present study investigated the role of astragaloside ? (ASIV) in the regulation of P?glycoprotein (P?gp, encoded by the mdr1 gene) and its effect on the reversal of MDR. The activity of ASIV was evaluated using human hepatic cancer cells Bel?7402 and the corresponding 5?fluorouracil (5?FU) resistant cells Bel?7402/FU. ASIV (0.08 mg/ml) potentiated the cytotoxicity of 5?FU which was demonstrated using the MTT assay on Bel?7402/FU cells. ASIV reduced the expression of P?gp as was revealed by immunocytochemistry. Accumulation and efflux studies with the P?gp substrate, rhodamine 123 (Rh123), demonstrated that ASIV inhibited P?gp?mediated drug efflux. Furthermore, it was demonstrated that AS? enhanced the drug accumulation of 5?FU using a high performance liquid chromatography (HPLC) assay for drug resistant cells. Furthermore, ASIV may downregulate the expression of P?gp, which was examined using western blot analysis and polymerase chain reaction. In conclusion, the results of the present study indicated that ASIV reverses the drug resistance of Bel?7402/FU cells by downregulating the expression of mdr1. ASIV may represent a potent modulator of P?gp?mediated MDR in hepatic cancer therapy. PMID:24676670

Wang, Pei-Pei; Xu, Du-Juan; Huang, Can; Wang, Wei-Ping; Xu, Wen-Ke

2014-06-01

34

Overexpression of P-glycoprotein but not its mRNA in multidrug resistant cells selected with hydroxyrubicin.  

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Previous studies have revealed that cultured cells treated with lipophilic natural products containing aromatic rings and basic amino group usually yielded multidrug resistant (MDR) variants. These MDR cells overexpress P-glycoprotein (P-gp), most often due to gene amplification or transcriptional activation of mdr/P-gp genes. Doxorubicin (Dox) is an anthracycline that belongs to this group of compounds. To explore the possible resistance mechanism(s) to anthracyclines that do not involve P-gp, we use a Dox analog, hydroxyrubicin (HyR) or WP159, which contains a C3' hydroxy group in replacement of the amino group in the sugar moiety of Dox thereby reducing basicity and eliminating positive charge in the parental compound to establish HyR-resistant cell lines. These resistant cells displayed the MDR phenotype and overexpressed P-gp as analyzed by Western blot analyses and immunohistochemical staining using two different anti-P-gp antibodies. Strikingly, the levels of P-gp mRNA in the majority of these MDR cells remained comparable to those in the drug-sensitive counterparts by slot blot hybridization. These results implicate that the basic center of the selecting agent is a critical determinant for generating diverse MDR variants, and that HyR may have a posttranscriptional effect on P-gp biosynthesis. This is the first report suggesting that cultured cells exposed to a particular selecting agent may give rise to particular subtype of MDR variants. PMID:7531410

Zhao, J Y; Savaraj, N; Song, R; Priebe, W; Kuo, M T

1994-01-01

35

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

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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 res...

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

2004-01-01

36

Reversion of P-glycoprotein-mediated multidrug resistance by diallyl trisulfide in a human osteosarcoma cell line.  

Science.gov (United States)

Diallyl trisulfide (DATS), the main sulfuric compound in garlic, has been shown to have antitumor effects. The present study aimed to ascertain whether DATS reverses the drug resistance of human osteosarcoma cells in vitro and to investigate its potential mechanisms. Human osteosarcoma U2-OS cells were treated with different concentrations of DATS. Cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, while P-glycoprotein (P-gp) expression and the proportion of apoptotic cells were measured by flow cyto-metry. Morphological changes were observed under an optical microscope. ?uclear factor-?B (NF-?B) and inhibitor of NF-?B (I?B) activities were measured by PCR and western blot analysis. Results showed that the proliferation of U2-OS cells treated with different concentrations of DATS was signi-ficantly decreased in a concentration- and time-dependent manner. DATS increased the toxic effect of adriamycin on U2-OS cells. Moreover, P-gp expression was decreased and the apoptosis rate was increased in a concentration-dependent manner following treatment of DATS. Additionally, NF-?B activity was inhibited by DATS while expression of I?B was increased. Our data clearly suggest that DATS has significant anticancer effects on human osteosarcoma cells. The potential mechanisms include reducing the multidrug resistance and inducing apoptosis. NF-?B suppression may be involved in DATS-induced inhibition of cell proliferation. PMID:24788927

Wang, Zhiyong; Xia, Qing; Cui, Jia; Diao, Yutao; Li, Jianmin

2014-06-01

37

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

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

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

2014-01-01

38

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

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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 assa...

2009-01-01

39

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

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Cellular expression of ATP-binding cassette (ABC) transport proteins, such as P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP1), or ABCG2, is known to confer a drug-resistant phenotype. Thus, the development of effective transporter inhibitors could be of value to cancer treatment. CBT-1® is a bisbenzylisoquinoline plant alkyloid currently in development as a Pgp inhibitor. We characterized its interactions with the three major ABC transporters associated with drug resista...

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

2008-01-01

40

SDZ 280-446, a novel semi-synthetic cyclopeptolide: in vitro and in vivo circumvention of the P-glycoprotein-mediated tumour cell multidrug resistance.  

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SDZ 280-446 is a semi-synthetic derivative of a natural cyclic peptolide. Its ability to sensitise in vitro tumour cells whose resistance is due to P-glycoprotein-mediated anticancer-drug efflux was shown using four different pairs of parental drug-sensitive (Par-) and multidrug-resistant (MDR-) cell lines, from three different species (mouse, human, Chinese hamster) representing four different cell lineages (monocytic leukaemia, nasopharyngeal epithelial carcinoma, colon epithelial carcinoma...

1992-01-01

 
 
 
 
41

Lamellarins as inhibitors of P-glycoprotein-mediated multidrug resistance in a human colon cancer cell line.  

Science.gov (United States)

Chemical analysis of a Didemnum sp. (CMB-01656) collected during scientific Scuba operations off Wasp Island, New South Wales, yielded five new lamellarins A1 (1), A2 (2), A3 (3), A4 (4) and A5 (5) and eight known lamellarins C (6), E (7), K (8), M (9), S (10), T (11), X (12) and ? (13). Analysis of a second Didemnum sp. (CMB-02127) collected during scientific trawling operations along the Northern Rottnest Shelf, Western Australia, yielded the new lamellarin A6 (14) and two known lamellarins G (15) and Z (16). Structures were assigned to 1-16 on the basis of detailed spectroscopic analysis with comparison to literature data and authentic samples. Access to this unique library of natural lamellarins (1-16) provided a rare opportunity for structure-activity relationship (SAR) investigations, probing interactions between lamellarins and the ABC transporter efflux pump P-glycoprotein (P-gp) with a view to reversing multidrug resistance in a human colon cancer cell line (SW620 Ad300). These SAR studies, which were expanded to include the permethylated lamellarin derivative (17) and a series of lamellarin-inspired synthetic coumarins (19-24) and isoquinolines (25-26), successfully revealed 17 as a promising new non-cytotoxic P-gp inhibitor pharmacophore. PMID:22473938

Plisson, Fabien; Huang, Xiao-Cong; Zhang, Hua; Khalil, Zeinab; Capon, Robert J

2012-06-01

42

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

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

Hai-chang Zhang

2012-06-01

43

Glutathione and thiolated chitosan inhibit multidrug resistance P-glycoprotein activity in excised small intestine.  

Science.gov (United States)

The aim of the present study was to evaluate the influence of glutathione (GSH), the thiomer chitosan-4-thiobutylamidine (chitosan-TBA) and a combination of both compounds on P-glycoprotein (P-gp) activity. Permeation studies were performed with freshly excised guinea pig ileum mounted in Ussing chambers using the fluorescent dye rhodamine-123 (Rho-123) as P-gp substrate. Apparent permeability coefficients (Papp) as well as efflux ratios (secretory Papp/absorptive Papp) were calculated and compared with values gained from experiments with the well-established P-gp inhibitors terfenadine and verapamil. In the presence of terfenadine, verapamil as well as GSH, the absorptive transport of Rho-123 across intestinal tissue increased, while the secretory decreased with efflux ratios around 1.0. Chitosan-TBA and especially chitosan-TBA/GSH not only enhanced absorption of Rho-123, but also reduced the basolateral to apical secretion of Rho-123 resulting in efflux ratios of 1.1, 0.8 and 0.5. The study indicates that chitosan-TBA/GSH is a potentially valuable tool for inhibiting the ATPase activity of P-gp in the intestine. PMID:16377016

Werle, Martin; Hoffer, Martin

2006-03-10

44

Cysteine-scanning mutagenesis provides no evidence for the extracellular accessibility of the nucleotide-binding domains of the multidrug resistance transporter P-glycoprotein.  

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Multidrug resistance of cancer cells is, at least in part, conferred by overexpression of P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) superfamily of active transporters. P-gp actively extrudes chemotherapeutic drugs from cells, thus reducing their efficacy. As a typical ABC transporter, P-gp has four domains: two transmembrane domains, which form a pathway through the membrane through which substrates are transported, and two hydrophilic nucleotide-binding domains (NBDs)...

Blott, E. J.; Higgins, C. F.; Linton, K. J.

1999-01-01

45

P-glycoprotein antagonists confer synergistic sensitivity to short-chain ceramide in human multidrug-resistant cancer cells.  

Science.gov (United States)

P-glycoprotein (P-gp) antagonists inhibit ceramide metabolism at the juncture of glycosylation. The purpose of this study was to test whether targeting P-gp would be a viable alternative to targeting glucosylceramide synthase (GCS) for enhancing ceramide cytotoxicity. A2780 wild-type, and multidrug-resistant 2780AD and NCI/ADR-RES human ovarian cancer cell lines and the cell-permeable ceramide analog, C6-ceramide (C6-cer), were employed. Compared to P-gp-poor A2780 cells, P-gp-rich 2780AD cells converted 3.7-fold more C6-cer to nontoxic C6-glucosylceramide (C6-GC), whereas cell-free GCS activities were equal. 2780AD cells displayed resistance to C6-cer (10 ?M) that was reversed by inclusion of the P-gp antagonist tamoxifen (5 ?M) but not by inclusion of a GCS inhibitor. Co-administration of C6-cer and P-gp antagonists was also effective in NCI/ADR-RES cells. For example, C6-cer, VX-710 (Biricodar), and cyclosporin A (cyc A) exposure resulted in viabilities of ~90% of control; however, C6-cer/VX-710 and C6-cer/cyc A additions were synergistic and resulted in viabilities of 22% and 17%, respectively. Further, whereas C6-ceramide and cyc A imparted 1.5- and 0-fold increases in caspase 3/7 activity, the combination produced a 3.5-fold increase. Although the upstream elements of cell death have not been elucidated, the novel C6-ceramide/P-gp antagonist combination merits further study and assessment of clinical translational potential. PMID:21396934

Chapman, Jacqueline V; Gouazé-Andersson, Valérie; Karimi, Ramin; Messner, Maria C; Cabot, Myles C

2011-07-15

46

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

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

Douglas J. Swartz

2014-06-01

47

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

Science.gov (United States)

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

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

2014-01-01

48

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

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

Lee Sung-Hack

2004-05-01

49

Nilotinib counteracts P-glycoprotein-mediated multidrug resistance and synergizes the antitumoral effect of doxorubicin in soft tissue sarcomas.  

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The therapeutic effect of doxorubicin (DXR) in the treatment of soft tissue sarcomas (STS) is limited by its toxicity and the development of multidrug resistance (MDR), the latter mainly induced by high expression of efflux pumps (e.g., P-glycoprotein [P-gp]). Therefore, the search for alternative therapies, which sensitize these tumors to chemotherapy while maintaining a low toxicity profile, is a rational approach. We assessed efficacy and molecular mechanisms involved in the antiproliferative effects of the tyrosine kinase inhibitors, nilotinib and imatinib, as single agents or in combination with DXR, in human synovial sarcoma SW982 and leiomyosarcoma SK-UT-1 cells. As single compound nilotinib (1-10 µM) was more potent than imatinib inhibiting the growth of SK-UT-1 and SW982 cells by 33.5-59.6%, respectively. Importantly, only nilotinib synergized the antitumoral effect of DXR (0.05-0.5 µM) by at least 2-fold, which clearly surpassed the mere sum of effects according to isobolographic analysis. Moreover, nilotinib in combination with DXR had a sustained effect on cell number (-70.3±5.8%) even 12 days after withdrawal of drugs compared to DXR alone. On the molecular level, only nilotinib fully blocked FBS-induced ERK1 and p38 MAPK activation, hence, reducing basal and DXR-induced up-regulation of P-gp levels. Moreover, efflux activity of the MDR-related proteins P-gp and MRP-1 was inhibited, altogether resulting in intracellular DXR retention. In high-risk STS tumors 53.8% and 15.4% were positive for P-gp and MRP-1 expression, respectively, with high incidence of P-gp in synovial sarcoma (72.7%). In summary, nilotinib exhibits antiproliferative effects on cellular models of STS and sensitizes them to DXR by reverting DXR-induced P-gp-mediated MDR and inhibiting MRP-1 activity, leading to a synergistic effect with potential for clinical treatment. PMID:22662203

Villar, Victor Hugo; Vögler, Oliver; Martínez-Serra, Jordi; Ramos, Rafael; Calabuig-Fariñas, Silvia; Gutiérrez, Antonio; Barceló, Francisca; Martín-Broto, Javier; Alemany, Regina

2012-01-01

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

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

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

1995-05-01

51

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

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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.

Kong Siu-Kai

2009-07-01

52

Selective modulation of P-glycoprotein-mediated drug resistance  

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Multidrug resistance associated with the overexpression of the multidrug transporter P-glycoprotein is a serious impediment to successful cancer treatment. We found that verapamil reversed resistance of CEM/VLB 100 cells to vinblastine and fluorescein-colchicine, but not to colchicine. Chlorpromazine reversed resistance to vinblastine but not to fluorescein-colchicine, and it increased resistance to colchicine. Initial influx rates of fluorescein-colchicine were similar in resistant and paren...

Bebawy, M.; Morris, M. B.; Roufogalis, B. D.

2001-01-01

53

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

Scientific Electronic Library Online (English)

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

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

54

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

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

Apte Shireesh Prakash

2010-12-01

55

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

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

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

2003-02-01

56

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

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

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

2012-06-01

57

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

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

Webb Glenn

2011-01-01

58

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

DEFF Research Database (Denmark)

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

Wielinga, Pieter; Westerhoff, Hans V.

2000-01-01

59

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

Science.gov (United States)

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

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

2010-09-01

60

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

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

Linardi Renata Lehn

2006-01-01

 
 
 
 
61

Interaction of forskolin with the P-glycoprotein multidrug transporter  

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

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

1991-08-27

62

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

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

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

2009-03-01

63

Oleanolic and maslinic acid sensitize soft tissue sarcoma cells to doxorubicin by inhibiting the multidrug resistance protein MRP-1, but not P-glycoprotein.  

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The pentacyclic triterpenes oleanolic acid (OLA) and maslinic acid (MLA) are natural compounds present in many plants and dietary products consumed in the Mediterranean diet (e.g., pomace and virgin olive oils). Several nutraceutical activities have been attributed to OLA and MLA, whose antitumoral effects have been extensively evaluated in human adenocarcinomas, but little is known regarding their effectiveness in soft tissue sarcomas (STS). We assessed efficacy and molecular mechanisms involved in the antiproliferative effects of OLA and MLA as single agents or in combination with doxorubicin (DXR) in human synovial sarcoma SW982 and leiomyosarcoma SK-UT-1 cells. As single compound, MLA (10-100 ?M) was more potent than OLA, inhibiting the growth of SW982 and SK-UT-1 cells by 70.3 ± 1.11% and 68.8 ± 1.52% at 80 ?M, respectively. Importantly, OLA (80 ?M) or MLA (30 ?M) enhanced the antitumoral effect of DXR (0.5-10 ?M) by up to 2.3-fold. On the molecular level, efflux activity of the multidrug resistance protein MRP-1, but not of the P-glycoprotein, was inhibited. Most probably as a consequence, DXR accumulated in these cells. Kinetic studies showed that OLA behaved as a competitive inhibitor of substrate-mediated MRP-1 transport, whereas MLA acted as a non-competitive one. Moreover, none of both triterpenes induced a compensatory increase in MRP-1 expression. In summary, OLA or MLA sensitized cellular models of STS to DXR and selectively inhibited MRP-1 activity, but not its expression, leading to a higher antitumoral effect possibly relevant for clinical treatment. PMID:24491315

Villar, Victor Hugo; Vögler, Oliver; Barceló, Francisca; Gómez-Florit, Manuel; Martínez-Serra, Jordi; Obrador-Hevia, Antònia; Martín-Broto, Javier; Ruiz-Gutiérrez, Valentina; Alemany, Regina

2014-04-01

64

Molecular analysis of the multidrug transporter, P-glycoprotein  

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Inherent or acquired resistance of tumor cells to cytotoxic drugs represents a major limitation to the successful chemotherapeutic treatment of cancer. During the past three decades dramatic progress has been made in the understanding of the molecular basis of this phenomenon. Analyses of drug-selected tumor cells which exhibit simultaneous resistance to structurally unrelated anti-cancer drugs have led to the discovery of the human MDR1 gene product, P-glycoprotein, as one of the mechanisms ...

Germann, Ursula A.; Chambers, Timothy C.

1998-01-01

65

Involvement of the multidrug resistance P-glycoprotein in acetaminophen-induced toxicity in hepatoma-derived HepG2 and Hep3B cells.  

Science.gov (United States)

Acetaminophen overdose causes severe hepatic failure. Although the mechanisms of acetaminophen hepatotoxicity have been well investigated, little is known about the involvement of the P-glycoprotein in acetaminophen transport and toxicity. P-Glycoprotein is a membrane efflux pump, playing a significant role in regulating absorption, excretion, and tissue distribution of many drugs. To evaluate the contribution of P-glycoprotein transporter in the course of acetaminophen-induced toxicity, HepG2 and Hep3B cells with different P-glycoprotein expression and activity, were treated by acetaminophen (1-10 mM) for different time periods, with or without the P-glycoprotein inhibitor verapamil. P-Glycoprotein activity was determined by rhodamine 123 efflux assay and western blot analysis. To assess the acetaminophen-induced toxicity and effect of verapamil, we investigated cellular redox status, phosphatidylserine externalization, nuclear fragmentation and ultrastructural changes. Verapamil markedly enhanced acetaminophen-induced oxidative damage and cell death. Moreover, verapamil revealed acetaminophen toxicity even at subtoxic levels. High acetaminophen concentrations increased P-glycoprotein activity and content in both HepG2 and Hep3B cells. These observations suggest the involvement of P-glycoprotein in acetaminophen transport. Notwithstanding the differences of the investigated hepatoma cell lines in P-glycoprotein function, acetaminophen-induced toxicity was similar, possibly due to different functions of drug-metabolizing systems. We conclude that acetaminophen is a P-glycoprotein substrate and P-glycoprotein is involved in acetaminophen transport and toxicity in HepG2 and Hep3B cells. This study establishes the fact that acetaminophen can modulate P-glycoprotein in tumour cells, suggesting that its routine use in cancer patients in combination with anticancer drugs, may influence the result of chemotherapy. PMID:16930294

Manov, Irena; Bashenko, Yulia; Hirsh, Mark; Iancu, Theodore C

2006-09-01

66

The multidrug transporter, P-glycoprotein, actively mediates cholesterol redistribution in the cell membrane  

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P-glycoprotein (P-gp) is a plasma membrane ATP-binding cassette transporter, responsible for multidrug resistance in tumor cells. P-gp catalyzes the ATP hydrolysis-dependent efflux of numerous amphiphilic compounds of unrelated chemical structures. In the absence of any identified substrate, P-gp exhibits an apparently futile, basal ATPase activity. By using native membrane vesicles containing high amounts of P-gp, we show here that (i) this basal ATPase activity is tightly dependent on the p...

Garrigues, Alexia; Escargueil, Alexandre E.; Orlowski, Ste?phane

2002-01-01

67

Crystal structure of the multidrug transporter P-glycoprotein from C. elegans  

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P-glycoprotein (P-gp) is an ATP-binding cassette (ABC) transporter that confers multidrug resistance in cancer cells1,2. It also affects the absorption, distribution, and clearance of cancer-unrelated drugs and xenobiotics. For these reasons, the structure and function of P-gp have been studied extensively for decades3. Here we present biochemical characterization of P-gp from C. elegans and its crystal structure at 3.4 Å resolution. This work provides the following new information towards a...

Jin, Mi Sun; Oldham, Michael L.; Zhang, Qiuju; Chen, Jue

2012-01-01

68

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

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

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

2003-08-01

69

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

International Nuclear Information System (INIS)

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

2003-08-01

70

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

Science.gov (United States)

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

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

2013-01-01

71

The synthesis and evaluation of a solution phase indexed combinatorial library of non-natural polyenes for reversal of P-glycoprotein mediated multidrug resistance.  

Science.gov (United States)

A combinatorial library of polyenes, based on (-)-stipiamide, has been constructed and evaluated for the discovery of new multidrug resistance reversal agents. A palladium coupling was used to react each individual vinyl iodide with a mixture of the seven acetylenes at near 1:1 stoichiometry. The coupling was also used to react each individual acetylene with the mixture of six vinyl iodides to create 13 pools indexed in two dimensions for a total of 42 compounds. Individual compounds were detected at equimolar concentration. The vinyl iodides, made initially using a crotylborane addition to generate the anti1,2-hydroxylmethyl products, were now made using a more efficient norephedrine propionate boron enolate aldol reaction. The indexed approach, ideally suited for cellular assays that involve membrane-bound targets, allowed for the rapid identification of reversal agents using assays with drug-resistant human breast cancer MCF7-adrR cells. Intersections of potent pools identified new compounds with promising activity. Aryl dimension pools showed R = ph and naphthyl as the most potent. The acetylene dimension had R' = phenylalaninol and alaninol as the most potent. Isolated individual compounds, both active and nonpotent, were assayed to confirm the library results. The most potent new compound was 4ek (R = naphthyl, R' = phenylaninol) at 1.45 microM. Other nonnatural individual naphthyl-amide compounds showed potent MDR reversal including the morpholino-amide 4ej (1.69 microM). Synergistic activities attributed to the two ends of the molecule were also identified. Direct interaction with Pgp was established by ATPase and photoaffinity displacement assays. The results indicate that both ends of the polyene reversal agent are involved in Pgp interaction and can be further modified for increased potency. PMID:10956480

Andrus, M B; Turner, T M; Sauna, Z E; Ambudkar, S V

2000-08-11

72

Sequence analysis of bile salt export pump (ABCB11) and multidrug resistance p-glycoprotein 3 (ABCB4, MDR3) in patients with intrahepatic cholestasis of pregnancy.  

Science.gov (United States)

Intrahepatic cholestasis of pregnancy (ICP) is a liver disorder associated with increased risk of intrauterine fetal death and prematurity. There is increasing evidence that genetically determined dysfunction in the canalicular ABC transporters bile salt export pump (BSEP, ABCB11) and multidrug resistance protein 3 (MDR3, ABCB4) might be risk factors for ICP development. This study aimed to (i). describe the extent of genetic variability in BSEP and MDR3 in ICP and (ii). identify new disease-causing mutations. Twenty-one women with ICP and 40 women with uneventful pregnancies were recruited between April 2001 and April 2003. Sequencing of BSEP and MDR3 spanned 8-10 kb per gene and comprised the promoter region and 100-350 bp of the flanking intronic region around each exon. DNA sequencing of polymerase chain reaction fragments was performed on an ABI3700 capillary sequencer. MDR3 promoter activity of promoter constructs carrying different ICP-specific mutations was studied using reporter assays. A total of 37 and 51 variant sites were detected in BSEP and MDR3, respectively. Three non-synonymous sites in codons for evolutionarily conserved amino acids were specific for the ICP collective (BSEP, N591S; MDR3, S320F and G762E). Furthermore, four ICP-specific splicing mutations were detected in MDR3 [intron 21, G(+1)A; intron 25, G(+5)C and C(-3)G; and intron 26, T(+2)A]. Activity of the mutated MDR3 promoter was similar to that observed for the wild-type promoter. Our data further support an involvement of MDR3 genetic variation in the pathogenesis of ICP, whereas analysis of BSEP sequence variation indicates that this gene is probably less important for the development of pregnancy-associated cholestasis. PMID:15077010

Pauli-Magnus, Christiane; Lang, Thomas; Meier, Yvonne; Zodan-Marin, Tina; Jung, Diana; Breymann, Christian; Zimmermann, Roland; Kenngott, Silke; Beuers, Ulrich; Reichel, Christoph; Kerb, Reinhold; Penger, Anja; Meier, Peter J; Kullak-Ublick, Gerd A

2004-02-01

73

Recognition of Sulfonylurea Receptor (ABCC8/9) Ligands by the Multidrug Resistance Transporter P-glycoprotein (ABCB1): FUNCTIONAL SIMILARITIES BASED ON COMMON STRUCTURAL FEATURES BETWEEN TWO MULTISPECIFIC ABC PROTEINS  

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ATP-sensitive K+ (KATP) channels are the target of a number of pharmacological agents, blockers like hypoglycemic sulfonylureas and openers like the hypotensive cromakalim and diazoxide. These agents act on the channel regulatory subunit, the sulfonylurea receptor (SUR), which is an ABC protein with homologies to P-glycoprotein (P-gp). P-gp is a multidrug transporter expressed in tumor cells and in some healthy tissues. Because these two ABC proteins both exhibit multispecific recognition pro...

Bessadok, Anis; Garcia, Elisabeth; Jacquet, He?le?ne; Martin, Solenne; Garrigues, Alexia; Loiseau, Nicolas; Andre?, Franc?ois; Orlowski, Ste?phane; Vivaudou, Michel

2011-01-01

74

An anti-CD19 antibody inhibits the interaction between P-glycoprotein (P-gp) and CD19, causes P-gp to translocate out of lipid rafts, and chemosensitizes a multidrug-resistant (MDR) lymphoma cell line.  

Science.gov (United States)

We have previously demonstrated that an anti-CD19 monoclonal antibody (MAb; HD37) inhibits the function of the P-glycoprotein (P-gp) pump in a multidrug-resistant (MDR) B-lymphoma cell line, Namalwa/MDR1, and that this effect is not due to the recognition of a cross-reactive epitope on P-gp. In this study, we have used the same cell line to define the mechanisms responsible for the effect of HD37 on the P-gp pump. Using fluorescence resonance energy transfer (FRET), we show that CD19 and P-gp are constitutively associated in cells. In the absence of treatment with anti-CD19, 40% of P-gp molecules expressed by Namalwa/MDR1 cells reside in the low-density lipid (ie, cholesterol-rich) microdomains (lipid rafts). Following treatment of the cells with HD37 and disruption of the interactions between P-gp and CD19, P-gp translocated out of lipid rafts and CD19 translocated into lipid rafts. The effect of chemosensitization on Namalwa/MDR1 cells was specific for CD19; an anti-CD22 MAb had no such effect, although the cells express CD22. These results suggest that anti-CD19 might chemosensitize P-gp(+) cells by interfering with interactions between CD19 and P-gp, rapidly resulting in the translocation of P-gp into a compartment on the plasma membrane where it is no longer active. PMID:15001473

Ghetie, Maria-Ana; Marches, Radu; Kufert, Stephanie; Vitetta, Ellen S

2004-07-01

75

Rituximab but not other anti-CD20 antibodies reverses multidrug resistance in 2 B lymphoma cell lines, blocks the activity of P-glycoprotein (P-gp), and induces P-gp to translocate out of lipid rafts.  

Science.gov (United States)

The objective of this study was to investigate the ability of the anti-CD20 antibody, Rituximab (RTX), to inhibit the activity of P-glycoprotein (P-gp), and reverse multidrug resistance (MDR) in 2 P-gp/CD20 lymphoma cell lines. We determined whether RTX would chemosensitize the 2 P-gp cell lines in vitro, and inhibit the ability of the cells to efflux Rhodamine 123. One cell line was infected with an MDR1 vector and the other was generated by drug selection. We also determined whether RTX induced P-gp to translocate out of lipid rafts. RTX chemosensitized 2 different MDR cell lines, inhibited the activity of P-gp in both, and induced P-gp to translocate out of lipid rafts in the 1 cell line that was studied in greater detail. In contrast, 3 other anti-CD20 antibodies did not chemosensitize, inhibit the activity of P-gp, or induce it to translocate out of rafts, despite the fact that 1 antibody recognized the same epitope on CD20. Our results suggest that RTX can chemosensitize 2 CD20/P-gp cell lines in vitro by inhibiting the activity of the P-gp pump. The inhibition of P-gp activity correlated with the ability of RTX to induce P-gp to translocate out of lipid rafts. Although the mechanisms by which RTX effects P-gp translocation and activity are not yet known, they are not associated with acid-sphingomyelinase activation in raft microdomains, as described for the antiproliferative activity of RTX. PMID:16971809

Ghetie, Maria-Ana; Crank, Michelle; Kufert, Stephanie; Pop, Iliodora; Vitetta, Ellen

2006-01-01

76

Human hepatoma cells rich in P-glycoprotein are sensitive to aclarubicin and resistant to three other anthracyclines.  

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Drug resistance is a major obstacle to successful chemotherapy of primary liver cancer, which is associated with high expression of the multidrug resistance (MDR) gene product P-glycoprotein (Pgp), a multidrug efflux transporter. The most effective single agents in treatment of primary liver carcinoma belong to the anthracycline family, yet several anthracyclines are known to be substrates for Pgp. In the present study, we compared four anthracyclines with respect to cell growth inhibition, i...

Lehne, G.; Angelis, P.; Clausen, O. P.; Rugstad, H. E.

1996-01-01

77

Modulation of P-glycoprotein expression by triptolide in adriamycin-resistant K562/A02 cells  

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Multidrug resistance is a serious obstacle encountered in leukemia treatment. Previous studies have found drug resistance in human leukemia is mainly associated with overexpression of the multidrug resistance gene 1 (MDR1). The aim of the present study was to investigate the modulation of P-glycoprotein expression by triptolide in adriamycin-resistant K562/A02 cells. The reverse effects of triptolide on drug resistance in K562/A02 cells were assessed by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphe...

Li, Hao; Hui, Lulu; Xu, Wenlin; Shen, Huiling; Chen, Qiaoyun; Long, Lulu; Zhu, Xiaolan

2012-01-01

78

P-glycoprotein positive, drug resistant invasive lymphoepithelial thymoma: treatment response to chemotherapy with cyclosporin and quinine.  

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A case of invasive drug resistant thymoma, expressing P-glycoprotein, which showed noticeable clinical response to chemotherapy and the multidrug resistance modulating agents cyclosporin and quinine is reported. A 46 year old man presented with severe left shoulder pain and a diagnosis of invasive lymphoepithelial thymoma was made following chest x ray and a computed tomography scan. The patient underwent extensive chemotherapy without resolution of the tumour. More than 90% of the malignant ...

1995-01-01

79

Complex Interplay between the P-Glycoprotein Multidrug Efflux Pump and the Membrane: Its Role in Modulating Protein Function  

Science.gov (United States)

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

Sharom, Frances Jane

2014-01-01

80

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

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5?-fluorosulfonylbenzonyl 5?-adenosine (FSBA) is an ATP analog that covalently modifies several residues in the nucleotide-binding domains (NBDs) of several ATPases, kinases and other proteins. P-glycoprotein (P-gp, ABCB1) is a member of the ATP-binding cassette (ABC) transporter superfamily that utilizes energy from ATP hydrolysis for the efflux of amphipathic anticancer agents from cancer cells. We investigated the interactions of FSBA with P-gp to study the catalytic cycle of ATP hydro...

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

2011-01-01

 
 
 
 
81

Functional expression of P-glycoprotein in Saccharomyces cerevisiae confers cellular resistance to the immunosuppressive and antifungal agent FK520.  

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We have recently reported that expression in yeast cells of P-glycoprotein (P-gp) encoded by the mouse multidrug resistance mdr3 gene (Mdr3) can complement a null ste6 mutation (M. Raymond, P. Gros, M. Whiteway, and D. Y. Thomas, Science 256:232-234, 1992). Here we show that Mdr3 behaves as a fully functional drug transporter in this heterologous expression system. Photolabelling experiments indicate that Mdr3 synthesized in yeast cells binds the drug analog [125I]iodoaryl azidoprazosin, this...

Raymond, M.; Ruetz, S.; Thomas, D. Y.; Gros, P.

1994-01-01

82

Overcoming Multidrug Resistance in Human Cancer Cells by Natural Compounds  

Directory of Open Access Journals (Sweden)

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

Tomohiro Nabekura

2010-05-01

83

A monoclonal antibody-Pseudomonas toxin conjugate that specifically kills multidrug-resistant cells.  

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One form of multidrug resistance is due to the expression of a 170-kDa energy-dependent drug efflux pump called P-glycoprotein in the plasma membranes of human cancer cells. We have prepared conjugates of Pseudomonas toxin with the anti-P-glycoprotein monoclonal antibody MRK-16. These anti-P-glycoprotein-toxin conjugates specifically kill multidrug-resistant human KB cells. Similar conjugates could be useful in cancer therapy to reduce or eliminate multidrug-resistant tumor populations in tum...

Fitzgerald, D. J.; Willingham, M. C.; Cardarelli, C. O.; Hamada, H.; Tsuruo, T.; Gottesman, M. M.; Pastan, I.

1987-01-01

84

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 SciELO Brazil | Language: English 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, rat [...] os, 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. 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 t [...] his 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.

85

Expression of P-glycoprotein in HeLa cells confers resistance to ceramide cytotoxicity.  

Science.gov (United States)

The role of glucosylceramide synthase (GCS) in regulating ceramide-induced apoptosis has been widely studied. The purpose of this investigation was to evaluate the role of P-glycoprotein (P-gp) in regulating ceramide cytotoxicity by using C6-ceramide. To accomplish this, we employed HeLa cells with conditional expression of the multidrug resistance gene 1/P-gp. HeLa cells expressing P-gp (P-gp/on cells) challenged with [14C]C6-ceramide (6 µM), synthesized 4.5-fold the amount of C6-glucosylceramide (GC) compared to HeLa cells with suppressed expression of P-gp (P-gp/off cells), whereas the generated levels of C6-sphingomyelin were almost equal (33 and 29% of intracellular 14C, respectively). Tamoxifen, a P-gp antagonist, decreased the C6-GC levels from 3.5-1.0% in the P-gp/off and from 17-2.8% of the total lipid 14C levels in the P-gp/on cells. Tamoxifen did not inhibit cell-free C6-GC synthesis in the P-gp/off or P-gp/on homogenates. However, a specific GCS inhibitor, ethylenedioxy-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol (ethylenedioxy-P4), blocked synthesis by 90%. In the cytotoxicity assays, the P-gp/off cells were sensitive to C6-ceramide and the P-gp/on cells were resistant. Resistance to C6-ceramide in the P-gp/on cells was reversed by tamoxifen but not by ethylenedioxy-P4. Experiments in another cervical cancer model showed that multidrug-resistant P-gp-rich KB-V1 cells synthesized 3-fold more C6-GC from C6-ceramide than the parental, P-gp-poor KB-3-1 cells, and whereas tamoxifen had no effect on the C6-GC synthesis in the KB-3-1 cells, it inhibited synthesis by 70% in the KB-V1 cells. This study demonstrates that P-gp potentiates C6-ceramide glycosylation and if antagonized augments C6-ceramide sensitivity, both features previously ascribed to GCS. We propose that P-gp can be an effective target for enhancing short-chain ceramide cytotoxicity in the treatment of drug-resistant cancer. PMID:21042729

Chapman, Jacqueline V; Gouazé-Andersson, Valérie; Cabot, Myles C

2010-12-01

86

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  

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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 Benzopyran...

Jabeen, Ishrat; Wetwitayaklung, Penpun; Chiba, Peter; Pastor, Manuel; Ecker, Gerhard F.

2013-01-01

87

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

Scientific Electronic Library Online (English)

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

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

88

Functional expression of murine multidrug resistance in Xenopus laevis oocytes  

International Nuclear Information System (INIS)

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

1990-01-01

89

Functional expression of murine multidrug resistance in Xenopus laevis oocytes  

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

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

1990-06-01

90

A Novel Non-Natural Nucleoside that Influences P-glycoprotein Activity and Mediates Drug Resistance  

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Multi drug resistance during cancer chemotherapy is commonly acquired by overexpression of the ATP binding cassette transporter, P-glycoprotein (P-gp). As such, inhibitors that target P-gp activity represent potential therapeutic agents against this form of drug resistance. This study evaluated the ability of various non-natural nucleosides that mimic the core structure of adenosine to modulate drug resistance by inhibiting the ATPase activity to P-gp. Of several analogs tested, only one nove...

Eng, Kevin T.; Berdis, Anthony J.

2010-01-01

91

Liposome-encapsulated doxorubicin reverses drug resistance by inhibiting P-glycoprotein in human cancer cells.  

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The most frequent drawback of doxorubicin is the onset of drug resistance, due to the active efflux through P-glycoprotein (Pgp). Recently formulations of liposome-encapsulated doxorubicin have been approved for the treatment of tumors resistant to conventional anticancer drugs, but the molecular basis of their efficacy is not known. To clarify by which mechanisms the liposome-encapsulated doxorubicin is effective in drug-resistant cancer cells, we analyzed the effects of doxorubicin and doxo...

Bosia, Amalia; Ghigo, Dario Antonio; Costamagna, Costanzo; Kopecka, Joanna; Riganti, Chiara; Voena, Claudia

2011-01-01

92

Macrocyclic diterpenes resensitizing multidrug resistant phenotypes.  

Science.gov (United States)

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

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

2014-07-15

93

Altered intracellular pH regulation in cells with high levels of P-glycoprotein expression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

P-glycoprotein is an ATP-binding-cassette transporter that pumps many structurally unrelated drugs out of cells through an ATP-dependent mechanism. As a result, multidrug-resistant cells that overexpress P-glycoprotein have reduced intracellular steady-state levels of a variety of chemotherapeutic agents. In addition, increased cytosolic pH has been a frequent finding in multidrug-resistant cells that express P-glycoprotein, and it has been proposed that this consequence of P-glycoprotein exp...

2011-01-01

94

Modulation of p-glycoprotein and breast cancer resistance protein by some prescribed corticosteroids.  

Science.gov (United States)

Efflux transporters, p-glycoprotein and breast cancer resistance protein (BCRP), located at barrier sites such as the blood-brain barrier may affect distribution of steroids used for treating chronic inflammatory conditions and thus the extent to which they may perturb the hypothalamic-pituitary-adrenal axis. In the present study, six different glucocorticoids were investigated for their possible interactions with these efflux transporters. Beclomethasone dipropionate, mometasone furoate and ciclesonide active principle but not fluticasone propionate or triamcinolone, (all at 0.1 to 10 microM) caused inhibition of efflux, resulting in increased accumulation of mitoxantrone in BCRP-expressing MCF7/MR breast cancer cells and of calcein in p-glycoprotein-expressing SW620/R colon carcinoma cell. At 5 microM the same three increased sensitivity of p-glycoprotein-expressing SW620/R to doxorubicin and stimulated ATPase activity associated with BCRP expressed in bacterial membrane vesicles. Budesonide also stimulated ATPase activity. These data demonstrate the capacity of some clinically used glucocorticoids to interact with efflux transporters. PMID:16442095

Cooray, Hiran C; Shahi, Sanjay; Cahn, Anthony P; van Veen, Hendrik W; Hladky, Stephen B; Barrand, Margery A

2006-02-15

95

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

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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-metho...

Campos, Mo?nica Caroline Oliveira; Castro-pinto, Denise Barc?ante; Ribeiro, Grazielle Alves; Berredo-pinho, Ma?rcia Moreira; Gomes, Leonardo Henrique Ferreira; Da Silva Bellieny, Myrtes Santos; Goulart, Carla Marins; Echevarria, A?urea; Leon, Leonor Laura

2013-01-01

96

Multidrug resistance related molecules in human and murine lung  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Aims: Transporter proteins known to mediate multidrug resistance (MDR) in tumour cells—MDR1 P-glycoprotein (P-gp) and multidrug resistance related protein 1 (MRP1)—are thought to be involved in protecting the lungs against inhaled toxic pollutants. Recently, several new transporter family members have been identified—for example, MRP2, MRP3, and breast cancer resistance protein (BCRP). To study the possible contribution of these proteins and the earlier defined MDR1 and MDR3 P-gp molecu...

Scheffer, G. L.; Pijnenborg, A. C. L. M.; Smit, E. F.; Mu?ller, M.; Postma, D. S.; Timens, W.; Valk, P.; Vries, E. G. E.; Scheper, R. J.

2002-01-01

97

Multidrug resistance in Lactococcus lactis: evidence for ATP-dependent drug extrusion from the inner leaflet of the cytoplasmic membrane.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lactococcus lactis possesses an ATP-dependent drug extrusion system which shares functional properties with the mammalian multidrug resistance (MDR) transporter P-glycoprotein. One of the intriguing aspects of both transporters is their ability to interact with a broad range of structurally unrelated amphiphilic compounds. It has been suggested that P-glycoprotein removes drugs directly from the membrane. Evidence is presented that this model is correct for the lactococcal multidrug transport...

1996-01-01

98

Intracellular trafficking of P-glycoprotein  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Fu, Dong; Arias, Irwin M.

2012-01-01

99

P-glycoprotein and alloimmune T-cell activation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2003-01-01

100

Dendritic cells require multidrug resistance protein 1 (ABCC1) transporter activity for differentation  

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Dendritic cells (DC) express the ATP-binding cassette (ABC) transporters P-glycoprotein (ABCB1) and multidrug resistance protein 1 (MRP1; ABCC1). Functionally, both these transporters have been described to be required for efficient DC and T cell migration. In this study, we report that MRP1 activity is also crucial for differentiation of DC. Inhibition of MRP1, but not P-glycoprotein, transporter activity with specific antagonists during in vitro DC differentiation interfered with early DC d...

2006-01-01

 
 
 
 
101

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

Directory of Open Access Journals (Sweden)

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

Wan CP

2013-01-01

102

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

103

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

Scientific Electronic Library Online (English)

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

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

104

Interaction of Transported Drugs with the Lipid Bilayer and P-Glycoprotein through a Solvation Exchange Mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Broad substrate specificity of human P-glycoprotein (ABCB1) is an essential feature of multidrug resistance. Transport substrates of P-glycoprotein are mostly hydrophobic and many of them have net positive charge. These compounds partition into the membrane. Utilizing the energy of ATP hydrolysis, P-glycoprotein is thought to take up substrates from the cytoplasmic leaflet of the plasma membrane and to transport them to the outside of the cell. We examined this model by molecular dynamics sim...

Omote, Hiroshi; Al-shawi, Marwan K.

2006-01-01

105

Phosphorylation of the multidrug resistance associated glycoprotein  

Energy Technology Data Exchange (ETDEWEB)

Drug-resistant cell lines derived from the mouse macrophage-like cell line J774.2 express the multidrug resistant phenotype which includes the overexpression of a membrane glycoprotein (130-140 kilodaltons). Phosphorylation of this resistant-specific glycoprotein (P-glycoprotein) in intact cells and in cell-free membrane fractions has been studied. The phosphorylated glycoprotein can be immunoprecipitated by a rabbit polyclonal antibody specific for the glycoprotein. Phosphorylation studies done with partially purified membrane fractions derived from colchicine-resistant cells indicated that (a) phosphorylation of the glycoprotein in 1 mM MgCl/sub 2/ was enhanced a minimum of 2-fold by 10 ..mu..M cAMP and (b) the purified catalytic subunit of the cAMP-dependent protein kinase (protein kinase A) phosphorylated partially purified glycoprotein that was not phosphorylated by (..gamma..-/sup 32/P)ATP alone, suggesting that autophosphorylation was not involved. These results indicate that the glycoprotein is a phosphoprotein and that at least one of the kinases responsible for its phosphorylation is a membrane-associated protein kinase A. The state of phosphorylation of the glycoprotein, which is a major component of the multidrug resistance phenotype, may be related to the role of the glycoprotein in maintaining drug resistance.

Mellado, W.; Horwitz, S.B.

1987-11-03

106

Research of 99Tcm-MIBI SPECT imaging for assessment of multidrug resistance in bone tumor  

International Nuclear Information System (INIS)

There has a overexpression of multidrug resistance (MDR) gene in most tumor. It is very important that it's expression product P-glycoprotein (P-gp) in multidrug resistance machine of tumor. The acceptation for P-gp expression is significance for chemotherapy. The conveying analysis of 99Tcm-sestamibi (99Tcm-MIBI) is a sensitiveness index for low-level P-gp expression. (authors)

2005-07-01

107

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1998-01-01

108

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

Science.gov (United States)

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

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

2013-12-01

109

Multidrug-resistant tumor cells remain sensitive to a recombinant interleukin-4-Pseudomonas exotoxin, except when overexpressing the multidrug resistance protein MRP1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Tumor cells may become resistant to conventional anticancer drugs through the occurrence of transmembrane transporter proteins such as P-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), or members of the multidrug resistance-associated protein family (MRP1¿MRP5; ABCC1¿ABCC5). In this report, we studied whether tumor cells that are cytostatic drug resistant because of overexpression of one of the above mentioned proteins are sensitive to a new anticancer agent, interleukin-4 t...

2003-01-01

110

Multidrug resistant Acinetobacter  

Directory of Open Access Journals (Sweden)

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

Manchanda Vikas

2010-01-01

111

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 characteris...

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

1999-01-01

112

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 m??ltipla 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

2001-03-01

113

Expression of a human multidrug resistance cDNA (MDR1) in the bone marrow of transgenic mice: resistance to daunomycin-induced leukopenia.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The human multidrug resistance gene (MDR1) encodes a drug efflux pump glycoprotein (P-glycoprotein) responsible for resistance to multiple cytotoxic drugs. A plasmid carrying a human MDR1 cDNA under the control of a chicken beta-actin promoter was used to generate transgenic mice in which the transgene was mainly expressed in bone marrow and spleen. Immunofluorescence localization studies showed that P-glycoprotein was present on bone marrow cells. Furthermore, leukocyte counts of the transge...

Galski, H.; Sullivan, M.; Willingham, M. C.; Chin, K. V.; Gottesman, M. M.; Pastan, I.; Merlino, G. T.

1989-01-01

114

A multidrug resistance transporter from human MCF-7 breast cancer cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

MCF-7/AdrVp is a multidrug-resistant human breast cancer subline that displays an ATP-dependent reduction in the intracellular accumulation of anthracycline anticancer drugs in the absence of overexpression of known multidrug resistance transporters such as P glycoprotein or the multidrug resistance protein. RNA fingerprinting led to the identification of a 2.4-kb mRNA that is overexpressed in MCF-7/AdrVp cells relative to parental MCF-7 cells. The mRNA encodes a 663-aa member of the ATP-bind...

Doyle, L. Austin; Yang, Weidong; Abruzzo, Lynne V.; Krogmann, Tammy; Gao, Yongming; Rishi, Arun K.; Ross, Douglas D.

1998-01-01

115

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

Scientific Electronic Library Online (English)

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

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

116

Schistosoma mansoni express higher levels of multidrug resistance-associated protein 1 (SmMRP1) in juvenile worms and in response to praziquantel  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ATP-binding cassette (ABC) superfamily of proteins comprises several ATP-dependent efflux pumps involved in transport of toxins and xenobiotics from cells. These transporters are essential components of normal physiology, and a subset is associated with development of multidrug resistance. P-glycoprotein (Pgp) and the multidrug resistance-associated proteins (MRPs) represent two classes of these multidrug resistance (MDR) transporters. MRP1 is one type of mammalian MRP, which preferential...

2010-01-01

117

Enhanced Brain Disposition and Effects of ?9-Tetrahydrocannabinol in P-Glycoprotein and Breast Cancer Resistance Protein Knockout Mice  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ABC transporters P-glycoprotein (P-gp, Abcb1) and breast cancer resistance protein (Bcrp, Abcg2) regulate the CNS disposition of many drugs. The main psychoactive constituent of cannabis ?9-tetrahydrocannabinol (THC) has affinity for P-gp and Bcrp, however it is unknown whether these transporters modulate the brain accumulation of THC and its functional effects on the CNS. Here we aim to show that mice devoid of Abcb1 and Abcg2 retain higher brain THC levels and are more sensitive to can...

Spiro, Adena S.; Wong, Alexander; Boucher, Aure?lie A.; Arnold, Jonathon C.

2012-01-01

118

Multidrug-resistant cancer cells are preferential targets of the new antineoplastic lanthanum compound KP772 (FFC24)  

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Recently, we have introduced [tris(1,10-phenanthroline)lanthanum(III)] trithiocyanate (KP772, FFC24) as a new lanthanum compound which has promising anticancer properties in vivo and in vitro. Aim of this study was to investigate the impact of ABC transporter-mediated multidrug resistance (MDR) on the anticancer activity of KP772. Here, we demonstrate that all MDR cell models investigated, overexpressing ABCB1 (P-glycoprotein), ABCC1 (multidrug resistance protein 1), or ABCG2 (breast cancer r...

Heffeter, P.; Jakupec, M. A.; Ko?rner, W.; Chiba, P.; Pirker, C.; Dornetshuber, R.; Elbling, L.; Sutterlu?ty, H.; Micksche, M.; Keppler, B. K.; Berger, W.

2007-01-01

119

Guggulsterone of Commiphora mukul resin reverses drug resistance in imatinib-resistant leukemic cells by inhibiting cyclooxygenase-2 and P-glycoprotein.  

Science.gov (United States)

The purpose of this study was to investigate the effects of guggulsterone on cyclooxygenase-2 and P-glycoprotein mediated drug resistance in imatinib-resistant K562 cells (K562/IMA). MTT cytotoxicity assay, flow cytometry, western blot analysis, and ELISA were performed to investigate the anti-proliferative effect, the reversal action of drug resistance, and the inhibitory effect on cyclooxygenase-2, P-glycoprotein, BCR/ABL kinase, and PGE2 release in K562/IMA cells by guggulsterone. The results showed that co-administration of guggulsterone resulted in a significant increase in chemo-sensitivity of K562/IMA cells to imatinib, compared with imatinib treatment alone. Rhodamine123 accumulation in K562/IMA cells was significantly enhanced after incubation with guggulsterone (60, 120?M), compared with untreated K562/IMA cells (pimatinib (1?M) was combined with guggulsterone (60, 120?M), the mean apoptotic population of K562/IMA cells was 15.47% and 24.91%. It was increased by 3.82 and 6.79 times, compared with imatinib (1?M) treatment alone. Furthermore, guggulsterone had significantly inhibitory effects on the levels of cyclooxygenase-2, P-glycoprotein and prostaglandin E2. However, guggulsterone had little inhibitory effect on the activity of BCR/ABL kinase. The present study indicates guggulsterone induces apoptosis by inhibiting cyclooxygenase-2 and down-regulating P-glycoprotein expression in K562/IMA cells. PMID:24680616

Xu, Hong-Bin; Xu, Lu-Zhong; Mao, Xia-Ping; Fu, Jun

2014-06-15

120

Altered intracellular pH regulation in cells with high levels of P-glycoprotein expression.  

Science.gov (United States)

P-glycoprotein is an ATP-binding-cassette transporter that pumps many structurally unrelated drugs out of cells through an ATP-dependent mechanism. As a result, multidrug-resistant cells that overexpress P-glycoprotein have reduced intracellular steady-state levels of a variety of chemotherapeutic agents. In addition, increased cytosolic pH has been a frequent finding in multidrug-resistant cells that express P-glycoprotein, and it has been proposed that this consequence of P-glycoprotein expression may contribute to the lower intracellular levels of chemotherapeutic agents. In these studies, we measured intracellular pH and the rate of acid extrusion in response to an acid load in two cells with very different levels of P-glycoprotein expression: V79 parental cells and LZ-8 multidrug resistant cells. Compared to the wild-type V79 cells, LZ-8 cells have a lower intracellular pH and a slower recovery of intracellular pH after an acid load. The data also show that LZ-8 cells have reduced ability to extrude acid, probably due to a decrease in Na(+)/H(+) exchanger activity. The alterations in intracellular pH and acid extrusion in LZ-8 cells are reversed by 24-h exposure to the multidrug-resistance modulator verapamil. The lower intracellular pH in LZ-8 indicates that intracellular alkalinization is not necessary for multidrug resistance. The reversal by verapamil of the decreased acid-extrusion suggests that P-glycoprotein can affect other membrane transport mechanism. PMID:22003434

Young, Gregory; Reuss, Luis; Altenberg, Guillermo A

2011-01-01

 
 
 
 
121

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2011-01-01

122

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

P-glycoprotein (P-gp), an efflux transporter, controls the pharmacokinetics of various compounds under physiological conditions. P-gp-mediated drug efflux has been suggested as playing a role in various disorders, including multidrug-resistant cancer and medication-refractory epilepsy. However, P-gp inhibition has had, to date, little or no clinically significant effect in multidrug-resistant cancer. To enhance our understanding of its in vivo function under pathophysiological conditions, sub...

Kannan, P.; John, C.; Zoghbi, Ss; Halldin, C.; Gottesman, Mm; Innis, Rb; Hall, Md

2009-01-01

123

Chemosensitisation by verapamil and cyclosporin A in mouse tumour cells expressing different levels of P-glycoprotein and CP22 (sorcin).  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The relationships between resistance to adriamycin, vincristine, colchicine and etopside, expression of P-glycoprotein and CP22 (sorcin), and resistance modification by verapamil and cyclosporin A have been studied in a panel of multidrug-resistant (MDR) mouse tumour cell lines. Whereas there was a generally good correlation between the degree of resistance and the amount of P-glycoprotein, no relationship between resistance and CP22 expression was seen. At 3.3 microM verapamil, the sensitisa...

1990-01-01

124

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

International Nuclear Information System (INIS)

The development of the multidrug resistance (MDR) phenotype in mammals is often mediated by the overexpression of the P-glycoprotein1 (Pgp, ABCB1) or multidrug resistance-associated protein (MRP)-like ABC transport proteins. A similar phenomenon has also been observed and considered as an important part of the multixenobiotic resistance (MXR) defence system in aquatic organisms. We have recently demonstrated the presence of ABC transporters in the widely used in vitro fish model, the PLHC-1 hepatoma cell line. In the present study we were able to select a highly resistant PLHC-1 sub-clone (PLHC-1/dox) by culturing the wild-type cells in the presence of 1 ?M doxorubicin. Using quantitative PCR a 42-fold higher expression of ABCB1 gene was determined in the PLHC-1/dox cells compared to non-selected wild-type cells (PLHC-1/wt). The efflux rates of model fluorescent Pgp1 substrates rhodamine 123 and calcein-AM were 3- to 4-fold higher in the PLHC-1/dox in comparison to the PLHC-1/wt cells. PLHC-1/dox were 45-fold more resistant to doxorubicin cytotoxicity than PLHC-1/wt. Similarly to mammalian cell lines, typical cross-resistance to cytotoxicity of other chemotherapeutics such as daunorubicin, vincristine, vinblastine, etoposide and colchicine, occurred. Furthermore, cyclosporine A, verapamil and PSC833, specific inhibitors of Pgp1 transport activity, completely reversed resistance of PLHC-1/dox cells to all tested drugs, resulting in EC50 values similar to the EC50 values found for PLHC-1/wt. In contrast, MK571, a specific inhibitor of MRP type of efflux transporters, sensitized PLHC-1/dox cells, neither to doxorubicin, nor to any other of the chemotherapeutics used in the study. These data demonstrate for the first time that a specific Pgp1-mediated doxorubicin resistance mechanism is present in the PLHC-1 fish hepatoma cell line. In addition, the fact that low micromolar concentrations of specific inhibitors may completely reverse a highly expressed doxorubicin resistance points to the fragility of Pgp1-mediated MXR defence mechanism in fish

2008-03-01

125

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

Scientific Electronic Library Online (English)

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

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

126

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

2011-01-01

127

Effects of Rifampin and Multidrug Resistance Gene Polymorphism on Concentrations of Moxifloxacin?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Treatment regimens combining moxifloxacin and rifampin for drug-susceptible tuberculosis are being studied intensively. However, rifampin induces enzymes that transport and metabolize moxifloxacin. We evaluated the effect of rifampin and the human multidrug resistance gene (MDR1) C3435T polymorphisms (P-glycoprotein) on moxifloxacin pharmacokinetic parameters. This was a single-center, sequential design study with 16 volunteers in which sampling was performed after four daily oral doses of mo...

Weiner, Marc; Burman, William; Luo, Chi-cheng; Peloquin, Charles A.; Engle, Melissa; Goldberg, Stefan; Agarwal, Vipin; Vernon, Andrew

2007-01-01

128

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 respo...

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

129

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Reports showing susceptibility of multidrug resistant (MDR) cancer cells to immune effectors, together with P-glycoprotein (P-gp) expression in immune effector subsets, including immature natural killer (NK) cells, and some activated T cells, suggest P-gp or some changes associated with it, have implications in immune-mediated mechanisms. A series of experiments were done to determine the nature of alterations associated with susceptibility to immune effector cells of MDR t...

Savas Burhan; Kerr Pauline E; Pross Hugh F

2006-01-01

130

Synthesis, activity and pharmacophore development for isatin-?-thiosemicarbazones with selective activity towards multidrug resistant cellsa  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have recently identified a new class of compounds that selectively kill cells that express P-glycoprotein (P-gp, MDR1), the ATPase efflux pump that confers multidrug resistance on cancer cells. Several isatin-?-thiosemicarbazones from our initial study have been validated, and a range of analogs synthesized and tested. A number demonstrated improved MDR1-selective activity over the lead, NSC73306 (1). Pharmacophores for cytotoxicity and MDR1-selectivity were generated to delineate the str...

Hall, Matthew D.; Salam, Noeris K.; Hellawell, Jennifer L.; Fales, Henry M.; Kensler, Caroline B.; Ludwig, Joseph A.; Szakacs, Gergely; Hibbs, David E.; Gottesman, Michael M.

2009-01-01

131

Can flavonoids from honey alter multidrug resistance?  

Science.gov (United States)

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

Jaganathan, Saravana Kumar

2011-04-01

132

A Novel ATP-Binding Cassette Transporter Involved in Multidrug Resistance in the Phytopathogenic Fungus Penicillium digitatum  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Demethylation inhibitor (DMI)-resistant strains of the plant pathogenic fungus Penicillium digitatum were shown to be simultaneously resistant to cycloheximide, 4-nitroquinoline-N-oxide (4NQO), and acriflavine. A PMR1 (Penicillium multidrug resistance) gene encoding an ATP-binding cassette (ABC) transporter (P-glycoprotein) was cloned from a genomic DNA library of a DMI-resistant strain (LC2) of Penicillium digitatum by heterologous hybridization with a DNA fragment containing an ABC-encoding...

1998-01-01

133

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

International Nuclear Information System (INIS)

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

2007-09-21

134

Marine Natural Products with P-Glycoprotein Inhibitor Properties  

Directory of Open Access Journals (Sweden)

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

Dioxelis Lopez

2014-01-01

135

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.

Huiqin Guo

2012-10-01

136

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

Science.gov (United States)

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

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

2013-12-01

137

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

138

PEITC reverse multi-drug resistance of human gastric cancer SGC7901/DDP cell line.  

Science.gov (United States)

Gastric cancer is one of the leading causes of cancer death in the world and nearly all patients who respond initially to cisplatin later develop drug resistance, indicating multi-drug resistance is an essential aspect of the failure of treatment. Phenethyl isothiocyanate (PEITC) has been implicated in inhibiting metastasis of several types of human cancer. However, the effect and potential mechanism of PEITC reversed multi-drug resistance of human gastric cancer is not fully clear. We have identified the role of PEITC in multi-drug resistance reversal of human gastric cancer SGC7901/DDP cell line. PEITC inhibited cisplatin-resistant human SGC7901/DDP cell growth in a dose-dependent manner, causing increased apoptosis, ROS generation, glutathione depletion, accumulation of Rhodamine-123, decreased expression of P-glycoprotein and cell cycle arrest. mRNA and protein expression of the multi-drug resistance gene (MDR1), multi-drug resistance-associated protein (MRP1), excision repair cross-complementing gene 1 (ERCC1), survivin, and Mad2 was decreased, and phosphorylation of Akt and transcriptional activation of NF-?B were suppressed. PEITC may be useful as the therapeutic strategy for overcoming multi-drug resistance through suppressing the PI3K-Akt pathway in human gastric cancer. PMID:23956061

Tang, Tao; Song, Xin; Liu, Yu-Fen; Wang, Wen-Yue

2014-04-01

139

Phenylsulfonylfuroxans as Modulators of Multidrug-Resistance-Associated Protein-1 and P-Glycoprotein  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A series of furoxan derivatives were studied for their ability to interact with P-gp and MRP1 transporters in MDCK cells overexpressing these proteins. 3-Phenylsulfonyl substituted furoxans emerged as the most interesting compounds. All of them were capable of inhibiting P-gp, and a few also MRP1. Substituents at the 4-position of 3-phenylsulfonylfuroxan scaffold were able to modulate the selectivity and the intensity of inhibition. In some cases, they reverted MRP1 inhibitor activity, namely...

2010-01-01

140

Proteins in cancer multidrug resistance.  

Science.gov (United States)

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

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

2014-01-01

 
 
 
 
141

P-glycoprotein-dependent trafficking of nanoparticle-drug conjugates.  

Science.gov (United States)

P-glycoprotein (P-gp) is considered to be the most prevalent and single most important cause of multidrug-resistance (MDR) in humans. Although the protein is well known to modulate the cellular trafficking of small molecule fluorophores, antimicrobials, and up to 50% of all cytotoxic chemotherapeutics, little is known about its interactions with nanoscale drug conjugates. Here, we use P-gp substrate-conjugated gold nanorods as model drug carriers to investigate P-gp-dependent cellular trafficking of nanoparticles. PMID:24616407

Dreaden, Erik C; Raji, Idris O; Austin, Lauren A; Fathi, Shaghayegh; Mwakwari, Sandra C; Humphries, William H; Kang, Bin; Oyelere, Adegboyega K; El-Sayed, Mostafa A

2014-05-01

142

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

143

Non-glucocorticoid steroid analogues (21-aminosteroids) sensitize multidrug resistant cells to vinblastine.  

Science.gov (United States)

Several members of a group of compounds developed to treat stroke and trauma of the central nervous system are shown also to reverse multidrug resistance in human KB-V1 cells. The most potent reversal agents studied are 21-aminosteroid derivatives (lazaroids), tirilazad mesylate (tirilazad, U-74006F) and U-74389F. Tirilazad sensitizes resistant human cells (KB-V1) to killing by vinblastine by 66-fold, but does not change the sensitivity of the nonresistant parental line, KB-3-1, to vinblastine. KB-V1 cell membranes have high levels of P-glycoprotein, a protein that acts as an efflux pump and is thought to be the major cause of multidrug resistance in these cells. Tirilazad inhibits the photoaffinity labeling of P-glycoprotein with [3H]azidopine in KB-V1 cells more effectively than does verapamil, a standard reversal agent. In addition, tirilazad causes the increased accumulation of [3H]vinblastine in multidrug resistant KB-V1 cells. Studies of the resistance reversal potential of related compounds suggest that the complex amine portion of tirilazad is important for its reversal activity, while the steroid portion is less important. PMID:8097968

Abraham, I; Wolf, C L; Sampson, K E

1993-01-01

144

Clarithromycin increases linezolid exposure in multidrug-resistant tuberculosis patients.  

Science.gov (United States)

The use of linezolid for the treatment of multidrug-resistant tuberculosis is limited by dose- and time-dependent toxicity. Recently, we reported a case of pharmacokinetic drug-drug interaction between linezolid and clarithromycin that resulted in increased linezolid exposure. The aim of this prospective pharmacokinetic study is to quantify the effect of clarithromycin on the exposure of linezolid. Subjects were included in an open-label, single-centre, single-arm, fixed-order pharmacokinetic interaction study. All subjects received 300 mg linezolid twice daily during the entire study, consecutively co-administered with 250 mg and 500 mg clarithromycin once daily. Steady-state serum curves of linezolid and clarithromycin were analysed using validated methods, and differences between pharmacokinetic parameters were calculated. Linezolid exposure increased by a median (interquartile range) of 44% (23-102%, p=0.043) after co-administration of 500 mg clarithromycin (n=5) compared to baseline, whereas 250 mg clarithromycin had no statistically significant effect. Co-administration was well tolerated by most patients; none experienced severe adverse effects. One patient reported common toxicity criteria grade 2 gastrointestinal adverse events. In this study, we showed that clarithromycin significantly increased linezolid serum exposure after combining clarithromycin with linezolid in multidrug-resistant tuberculosis patients. The drug-drug interaction is possibly P-glycoprotein-mediated. Due to large interpatient variability, therapeutic drug monitoring is advisable to determine individual effect size. PMID:23520311

Bolhuis, Mathieu S; van Altena, Richard; van Soolingen, Dick; de Lange, Wiel C M; Uges, Donald R A; van der Werf, Tjip S; Kosterink, Jos G W; Alffenaar, Jan-Willem C

2013-12-01

145

Functional imaging of the multidrug resistance in vivo  

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-07-01

146

ATP-dependent transport of vinblastine in vesicles from human multidrug-resistant cells  

International Nuclear Information System (INIS)

Resistance of human cancer cells to multiple cytotoxic hydrophobic agents (multidrug resistance) is due to overexpression of the MDR1 gene, whose product is the plasma membrane P-glycoprotein. Plasma membrane vesicles partially purified from multidrug-resistant human KB carcinoma cells, but not from drug-sensitive cells, accumulate [3H]vinblastine in an ATP-dependent manner. This transport is osmotically sensitive, with an apparent Km of 38 ?M for ATP and of ? 2 ?M for vinblastine. The nonhydrolyzable analog adenosine 5'-[?,?-imido]triphosphate does not substitute for ATP but is a competitive inhibitor of ATP for the transport process. Vanadate, and ATPase inhibitor, is a potent noncompetitive inhibitor of transport. These results indicate that hydrolysis of ATP is probably required for active transport vinblastine. Several other drugs to which multidrug-resistant cell lines are resistant inhibit transport, with relative potencies as follows: vincristine > actinomycin D > daunomycin > colchicine = puromycin. Verapamil and quinidine, which reverse the multidrug-resistance phenotype, are good inhibitors of the transport process. These results confirm that multidrug-resistant cells express an energy-dependent plasma membrane transporter for hydrophobic drugs, and establish a system for the detailed biochemical analysis of this transport process

1988-01-01

147

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

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Vipin Saxena, M Delwar HussainDepartment of Pharmaceutical Sciences, Irma Lerma Rangel College of Pharmacy, Texas A&M Health Science Center, Kingsville, TX, USABackground: Delivery of a high concentration of anticancer drugs specifically to cancer cells remains the biggest challenge for the treatment of multidrug-resistant cancer. Poloxamers and D-?-Tocopheryl polyethylene glycol 1000 succinate (TPGS) are known inhibitors of P-glycoprotein (P-gp). Mixed micelles prepared from Poloxa...

Saxena V; Md, Hussain

2012-01-01

148

Multidrug resistance reversal by co-delivery of tariquidar (XR9576) and paclitaxel using long-circulating liposomes  

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One of the major obstacles to the success of cancer chemotherapy is the multidrug resistance (MDR) often resulting due to the overexpression of drug efflux transporter pumps such as P-glycoprotein (P-gp). Highly efficacious third generation P-gp inhibitors, like tariquidar, have shown promising results in overcoming the MDR. However, P-gp is also expressed in normal tissues like blood brain barrier, gastrointestinal track, liver, spleen and kidney. To maximize the efficacy of P-gp inhibitor a...

Patel, Niravkumar R.; Rathi, Alok; Mongayt, Dmitriy; Torchilin, Vladimir P.

2011-01-01

149

Imaging of multidrug resistance in cancer  

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Primary intrinsic and/or acquired multidrug resistance (MDR) is the main obstacle to successful cancer treatment. Functional molecular imaging of MDR in cancer using single photon or positron emitters may be helpful to identify multidrug-resistant tumours and predict not only those patients who are resistant to treatment, with a clinically unfavourable prognosis, but also those who are susceptible to the development of drug toxicity or even certain tumours . Variations in the mdr1 gene produc...

Dizdarevic, S.; Peters, A. M.

2011-01-01

150

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

151

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

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

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

2011-01-01

152

A Novel Approach for Predicting P-glycoprotein (ABCB1) Inhibition Using Molecular Interaction Fields  

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P-glycoprotein (Pgp or ABCB1) is an ABC transporter protein involved in intestinal absorption, drug metabolism and brain penetration, and its inhibition can seriously alter a drug's bioavailability and safety. In addition, inhibitors of Pgp can be used to overcome multidrug resistance. Given this dual-purpose, reliable in silico procedures to predict Pgp inhibition are of great interest. A large and accurate literature collection yielded more than 1200 structures; a model was then constructed...

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

2011-01-01

153

Inhibition of Human P-glycoprotein Transport and Substrate Binding Using a Galantamine Dimer  

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The human multidrug resistance transporter P-glycoprotein (P-gp) prevents the entry of compounds into the brain by an active efflux mechanism at the blood brain barrier (BBB). Treatment of neurodegenerative diseases, therefore, has become a challenge and the development of new reversible inhibitors of P-gp is pertinent to overcome this problem. We report the design and synthesis of a crosslinked agent based on the Alzheimer’s disease treatment galantamine (Gal-2) that inhibits P-gp-mediated...

Namanja, Hilda A.; Emmert, Dana; Pires, Marcos M.; Hrycyna, Christine A.; Chmielewski, Jean

2009-01-01

154

Ceramide and glucosylceramide upregulate expression of the multidrug resistance gene MDR1 in cancer cells  

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In the present study we used human breast cancer cell lines to assess the influence of ceramide and glucosylceramide (GC) on expression of MDR1, the multidrug resistance gene that codes for P-glycoprotein (P-gp), because GC has been shown to be a substrate for P-gp. Acute exposure (72 h) to C8-ceramide (5 µg/ml culture medium), a cell-permeable ceramide, increased MDR1 mRNA levels by 3-and 5-fold in T47D and in MDA-MB-435 cells, respectively. Acute exposure of MCF-7 and MDA-MB-231 cells to C...

Gouaze?-andersson, Vale?rie; Yu, Jing Y.; Kreitenberg, Adam J.; Bielawska, Alicja; Giuliano, Armando E.; Cabot, Myles C.

2007-01-01

155

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

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Bo Li1, Hui Xu2, Zhen Li1, Mingfei Yao1, Meng Xie1, Haijun Shen1, Song Shen1, Xinshi Wang1, Yi Jin11College of Pharmaceutical sciences, Zhejiang University, Hangzhou, 2No. 202 Hospital of People's Liberation Army, Shenyang, ChinaBackground: Multidrug resistance (MDR) mediated by the overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), remains one of the major obstacles to effective cancer chemotherapy. In this study, lipid/part...

2012-01-01

156

Cells resistant to HTI-286 do not overexpress P-glycoprotein but have reduced drug accumulation and a point mutation in alpha-tubulin.  

Science.gov (United States)

HTI-286, a synthetic analogue of hemiasterlin, depolymerizes microtubules and is proposed to bind at the Vinca peptide site in tubulin. It has excellent in vivo antitumor activity in human xenograft models, including tumors that express P-glycoprotein, and is in phase II clinical evaluation. To identify potential mechanisms of resistance induced by HTI-286, KB-3-1 epidermoid carcinoma cells were exposed to increasing drug concentrations. When maintained in 4.0 nmol/L HTI-286, cells had 12-fold resistance to HTI-286. Cross-resistance was observed to other Vinca peptide-binding agents, including hemiasterlin A, dolastatin-10, and vinblastine (7- to 28-fold), and DNA-damaging drugs, including Adriamycin and mitoxantrone (16- to 57-fold), but minimal resistance was seen to taxanes, epothilones, or colchicine (1- to 4-fold). Resistance to HTI-286 was retained when KB-HTI-resistant cells were grown in athymic mice. Accumulation of [(3)H]HTI-286 was lower in cells selected in intermediate (2.5 nmol/L) and high (4.0 nmol/L) concentrations of HTI-286 compared with parental cells, whereas accumulation of [(14)C]paclitaxel was unchanged. Sodium azide treatment partially reversed low HTI-286 accumulation, suggesting involvement of an ATP-dependent drug pump. KB-HTI-resistant cells did not overexpress P-glycoprotein, breast cancer resistance protein (BCRP/ABCG2/MXR), MRP1, or MRP3. No mutations were found in the major beta-tubulin isoform. However, 4.0 nmol/L HTI-286-selected cells had a point mutation in alpha-tubulin that substitutes Ser for Ala(12) near the nonexchangeable GTP-binding site of alpha-tubulin. KB-HTI-resistant cells removed from drug became less resistant to HTI-286, no longer had low HTI-286 accumulation, and retained the Ala(12) mutation. These data suggest that HTI-286 resistance may be partially mediated by mutation of alpha-tubulin and by an ATP-binding cassette drug pump distinct from P-glycoprotein, ABCG2, MRP1, or MRP3. PMID:15486199

Loganzo, Frank; Hari, Malathi; Annable, Tami; Tan, Xingzhi; Morilla, Daniel B; Musto, Sylvia; Zask, Arie; Kaplan, Joshua; Minnick, Albert A; May, Michael K; Ayral-Kaloustian, Semiramis; Poruchynsky, Marianne S; Fojo, Tito; Greenberger, Lee M

2004-10-01

157

Calcein assay for multidrug resistance reliably predicts therapy response and survival rate in acute myeloid leukaemia.  

Science.gov (United States)

In this study, we evaluated the suitability of the calcein assay as a routine clinical laboratory method for the identification of multidrug-resistant phenotype in acute leukaemia. This study presents the results of the calcein tests obtained in two large haematological centres in Hungary. Assays were performed with blast cells of 93 de novo acute leukaemia patients, including 65 patients with acute myeloid leukaemia (AML). Results were expressed as multidrug resistance activity factor (MAF) values. AML patients were divided into responders and non-responders and MAF values were calculated for each group. In both centres, responder patients displayed significantly lower MAF values than non-responders (P = 0.0045 and P = 0.0454). Cut-off values were established between the MAFR + SEM and MAFNR - SEM values. On the basis of these cut-off levels, multidrug resistance (MDR) negativity showed a 72% predictive value for the response to chemotherapy, whereas MDR positivity was found to have an average predictive value of 69% for therapy failure. MDR activity was a prognostic factor for survival rate and the test was suitable for detecting patients at relapse. The calcein assay can be used as a quantitative, standardized, inexpensive screening test in a routine clinical laboratory setting. The assay detects both P-glycoprotein and multidrug resistance-associated protein activities, and identifies AML patients with unfavourable therapy responses. PMID:11167823

Karászi, E; Jakab, K; Homolya, L; Szakács, G; Holló, Z; Telek, B; Kiss, A; Rejtô, L; Nahajevszky, S; Sarkadi, B; Kappelmayer, J

2001-02-01

158

Detection of multidrug resistance using molecular nuclear technique  

Energy Technology Data Exchange (ETDEWEB)

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

159

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

Directory of Open Access Journals (Sweden)

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

Buddhasukh Duang

2004-04-01

160

Chemotoxicity of doxorubicin and surface expression of P-glycoprotein (MDR1) is regulated by the Pseudomonas aeruginosa toxin Cif  

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P-glycoprotein (Pgp), a member of the adenosine triphosphate-binding cassette (ABC) transporter superfamily, is a major drug efflux pump expressed in normal tissues, and is overexpressed in many human cancers. Overexpression of Pgp results in reduced intracellular drug concentration and cytotoxicity of chemotherapeutic drugs and is thought to contribute to multidrug resistance of cancer cells. The involvement of Pgp in clinical drug resistance has led to a search for molecules that block Pgp ...

Ye, Siying; Maceachran, Daniel P.; Hamilton, Joshua W.; O Toole, George A.; Stanton, Bruce A.

2008-01-01

 
 
 
 
161

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

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

Chen Tingfu

2010-07-01

162

Treatment options for multidrug-resistant bacteria.  

Science.gov (United States)

As a consequence of antibiotic overuse and misuse, nosocomial infections caused by multidrug-resistant bacteria represent a physician's nightmare throughout the world. No newer antimicrobials active against Pseudomonas aeruginosa, the main multidrug-resistant nosocomial pathogen, are available or under investigation. The only exceptions are linezolid, some newer glycopeptides (dalbavancin, oritavancin and telavancin) and daptomycin (a lipopeptide), which are active against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) strains, as well as tigecycline, a potent in vitro glycylcycline against MRSA, VRE, Acinetobacter baumannii and entended-spectrum beta-lactamase (ESBL)+ Enterobacteriaceae. Colistin, an antibiotic of the 1950s has been rediscovered by intensive care unit physicians for use against ESBL+ Enterobacteriaceae, as well as against multidrug-resistant P. aeruginosa and A. baumannii isolates. Although success rates with colistin range between 50 and 73%, almost all studies are retrospective. Immunostimulation efforts against S. aureus are still under development. As antibiotic research and development stagnate, rational policies for prescribing existing antibiotics plus strict infection control are the current mainstay efforts for preventing and combating multidrug-resistant bacterial infections. PMID:17009940

Giamarellou, Helen

2006-08-01

163

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

164

Accelerated evolution of resistance in multidrug environments  

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The emergence of resistance during multidrug chemotherapy impedes the treatment of many human diseases, including malaria, TB, HIV, and cancer. Although certain combination therapies have long been known to be more effective in curing patients than single drugs, the impact of such treatments on the evolution of drug resistance is unclear. In particular, very little is known about how the evolution of resistance is affected by the nature of the interactions—synergy or antagonism—between dr...

Hegreness, Matthew; Shoresh, Noam; Damian, Doris; Hartl, Daniel; Kishony, Roy

2008-01-01

165

Abamectin resistance in Drosophila is related to increased expression of P-glycoprotein via the dEGFR and dAkt pathways.  

Science.gov (United States)

Many insects have evolved resistance to abamectin but the mechanisms involved in this resistance have not been well characterized. P-glycoprotein (P-gp), an ATP-dependent drug-efflux pump transmembrane protein, may be involved in abamectin resistance. We investigated the role of P-gp in abamectin (ABM) resistance in Drosophila using an ABM-resistant strain developed in the laboratory. A toxicity assay, Western blotting analysis and a vanadate-sensitive ATPase activity assay all demonstrated the existence of a direct relationship between P-gp expression and ABM resistance in these flies. Our observations indicate that P-gp levels in flies' heads were higher than in their thorax and abdomen, and that both P-gp levels and LC(50) values were higher in resistant than in susceptible and P-gp-deficient strains. In addition, P-gp levels in the blood-brain barrier (BBB) of resistant flies were higher than in susceptible and P-gp-deficient flies, which is further evidence that a high level of P-gp in the BBB is related to ABM resistance. Furthermore, we found greater expression of Drosophila EGFR (dEGFR) in the resistant strain than in the susceptible strain, and that the level of Drosophila Akt (dAkt) was much higher in resistant than in susceptible flies, whereas that in P-gp-deficient flies was very low. Compared to susceptible flies, P-gp levels in the resistant strain were markedly suppressed by the dEGFR and dAkt inhibitors lapatinib and wortmannin. These results suggest that the increased P-gp in resistant flies was regulated by the dEGFR and dAkt pathways and that increased expression of P-gp is an important component of ABM resistance in insects. PMID:23648830

Luo, Liang; Sun, Ying-Jian; Wu, Yi-Jun

2013-08-01

166

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.)

2009-08-01

167

Precipitous Release of Methyl-CpG Binding Protein 2 and Histone Deacetylase 1 from the Methylated Human Multidrug Resistance Gene (MDR1) on Activation†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Overexpression of the human multidrug resistance gene 1 (MDR1) is a negative prognostic factor in leukemia. Despite intense efforts to characterize the gene at the molecular level, little is known about the genetic events that switch on gene expression in P-glycoprotein-negative cells. Recent studies have shown that the transcriptional competence of MDR1 is often closely associated with DNA methylation. Chromatin remodeling and modification targeted by the recognition of methylated DNA provid...

2002-01-01

168

Synthesis and structure-activity evaluation of isatin-?-thiosemicarbazones with improved selective activity towards multidrug-resistant cells expressing P-glycoproteina  

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Cancer multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters presents a significant unresolved clinical challenge. One strategy to resolve MDR is to develop compounds that selectively kill cells over-expressing the efflux transporter P-glycoprotein (MDR1, P-gp, ABCB1). We have previously reported structure-activity studies based around the lead compound NSC73306 (1, 1-isatin-4-(4?-methoxyphenyl)-3-thiosemicarbazone, 4.3-fold selective). Here we sought to extend this...

Hall, Matthew D.; Brimacombe, Kyle R.; Varonka, Matthew S.; Pluchino, Kristen M.; Monda, Julie K.; Li, Jiayang; Walsh, Martin J.; Boxer, Matthew B.; Warren, Timothy H.; Fales, Henry M.; Gottesman, Michael M.

2011-01-01

169

Predicting P-Glycoprotein-Mediated Drug Transport Based On Support Vector Machine and Three-Dimensional Crystal Structure of P-glycoprotein  

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Human P-glycoprotein (P-gp) is an ATP-binding cassette multidrug transporter that confers resistance to a wide range of chemotherapeutic agents in cancer cells by active efflux of the drugs from cells. P-gp also plays a key role in limiting oral absorption and brain penetration and in facilitating biliary and renal elimination of structurally diverse drugs. Thus, identification of drugs or new molecular entities to be P-gp substrates is of vital importance for predicting the pharmacokinetics,...

Bikadi, Zsolt; Hazai, Istvan; Malik, David; Jemnitz, Katalin; Veres, Zsuzsa; Hari, Peter; Ni, Zhanglin; Loo, Tip W.; Clarke, David M.; Hazai, Eszter; Mao, Qingcheng

2011-01-01

170

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. 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...

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

2010-01-01

171

Differential chemosensitization of P-glycoprotein overexpressing K562/Adr cells by withaferin A and Siamois polyphenols  

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Abstract Background Multidrug resistance (MDR) is a major obstacle in cancer treatment and is often the result of overexpression of the drug efflux protein, P-glycoprotein (P-gp), as a consequence of hyperactivation of NF?B, AP1 and Nrf2 transcription factors. In addition to effluxing chemotherapeutic drugs, P-gp also plays a specific role in blocking caspase-dependent apoptotic pathways. One feature that cytotoxic treatments of cancer have in common is activation of the tra...

2010-01-01

172

Fluoxetine potentiates chloroquine and mefloquine effect on multidrug-resistant Plasmodium falciparum in vitro.  

Science.gov (United States)

Fluoxetine (FLX), a P-glycoprotein inhibitor with antimalarial activity, is promising candidate for reversing chloroquine/mefloquine (CQ/MQ) resistance. The Dd2 strain of CQ- and MQ-resistant Plasmodium falciparum was synchronized and assayed with various concentrations of CQ/MQ individually and in combination with FLX or verapamil (VPL). Our results indicated the 50% inhibitory concentration values of CQ and MQ were greatly lowered when FLX was used simultaneously. Isobolograms indicated that CQ-FLX combinations are more synergistic (mean fractional inhibitory concentration [FIC] index 0.55) than MQ-FLX (mean FIC index 0.64), and their synergistic effect was better than or at par with CQ-VPL (mean FIC index 0.88) and MQ-VPL (mean FIC index 0.60) combinations. We conclude that the FLX potentiates the CQ and MQ response on multidrug-resistant P. falciparum at clinically achievable concentrations. PMID:17060702

Khairul, Mohd Fadzli Mustaffa; Min, Tan Hooi; Low, Jen Hou; Nasriyyah, Che Husin Che; A'shikin, Azahri Noor; Norazmi, Mohd Nor; Ravichandran, Manickam; Raju, Suraparaju Sivachandra

2006-10-01

173

[Travellers and multi-drug resistance bacteria].  

Science.gov (United States)

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

Takeshita, Nozomi

2012-02-01

174

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

2012-05-01

175

Multidrug resistance in pediatric urinary tract infections.  

Science.gov (United States)

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). PMID:16922629

Gaspari, Romolo J; Dickson, Eric; Karlowsky, James; Doern, Gary

2006-01-01

176

Comparative tissue pharmacokinetics and efficacy of moxidectin, abamectin and ivermectin in lambs infected with resistant nematodes: Impact of drug treatments on parasite P-glycoprotein expression?  

Science.gov (United States)

The high level of resistance to the macrocyclic lactones has encouraged the search for strategies to optimize their potential as antiparasitic agents. There is a need for pharmaco-parasitological studies addressing the kinetic-dynamic differences between various macrocyclic lactones under standardized in vivo conditions. The current work evaluated the relationship among systemic drug exposure, target tissue availabilities and the pattern of drug accumulation within resistant Haemonchus contortus for moxidectin, abamectin and ivermectin. Drug concentrations in plasma, target tissues and parasites were measured by high performance liquid chromatography. Additionally, the efficacy of the three molecules was evaluated in lambs infected with resistant nematodes by classical parasitological methods. Furthermore, the comparative determination of the level of expression of P-glycoprotein (P-gp2) in H. contortus recovered from lambs treated with each drug was performed by real time PCR. A longer persistence of moxidectin (P moxidectin concentrations were recovered within adult H. contortus compared to abamectin and ivermectin at day 2 post-treatment. However, the efficacy against H. contortus was 20.1% (ivermectin), 39.7% (abamectin) and 89.6% (moxidectin). Only the ivermectin treatment induced an enhancement on the expression of P-gp2 in the recovered adult H. contortus, reaching higher values at 12 and 24 h post-administration compared to control (untreated) worms. This comparative pharmacological evaluation of three of the most used macrocyclic lactones compounds provides new insights into the action of these drugs.

Lloberas, Mercedes; Alvarez, Luis; Entrocasso, Carlos; Virkel, Guillermo; Ballent, Mariana; Mate, Laura; Lanusse, Carlos; Lifschitz, Adrian

2012-01-01

177

Inhibition of multidrug resistance by adamantylgb3, a globotriaosylceramide analog.  

Science.gov (United States)

Multidrug resistance (MDR) via the ABC drug transporter (ABCB1), P-glycoprotein (P-gp/MDR1) overexpression, is a major obstacle in cancer chemotherapy. Many inhibitors reverse MDR but, like cyclosporin A (CsA), have significant toxicities. MDR1 is also a translocase that flips glucosylceramide inside the Golgi to enhance neutral glycosphingolipid (GSL) synthesis. We observed partial MDR1/globotriaosylceramide (Gb3) cell surface co-localization, and GSL removal depleted cell surface MDR1. MDR1 may therefore interact with GSLs. AdamantylGb3, a water-soluble Gb3 mimic, but not other GSL analogs, reversed MDR1-MDCK cell drug resistance. Cell surface MDR1 was up-regulated 1 h after treatment with CsA or adaGb3, but at 72 h, cell surface expression was lost. Intracellular MDR1 accumulated throughout, suggesting long term defects in plasma membrane MDR1 trafficking. AdaGb3 or CsA rapidly reduced rhodamine 123 cellular efflux. MDR1 also mediates gastrointestinal epithelial drug efflux, restricting oral bioavailability. Vinblastine apical-to-basal transport in polarized human intestinal C2BBe1 cells was significantly increased when adaGb3 was added to both sides, or to the apical side only, comparable with verapamil, a standard MDR1 inhibitor. Disulfide cross-linking of mutant MDR1s showed no binding of adaGb3 to the MDR1 verapamil/cyclosporin-binding site between surface proximal helices of transmembrane segments (TM) 6 and TM7, but rather to an adjacent site nearer the center of TM6 and the TM7 extracellular face, i.e. close to the bilayer leaflet interface. Verotoxin-mediated Gb3 endocytosis also up-regulated total MDR1 and inhibited drug efflux. Thus, a functional interplay between membrane Gb3 and MDR1 provides a more physiologically based approach to MDR1 regulation to increase the bioavailability of chemotherapeutic drugs. PMID:18003606

De Rosa, María Fabiana; Ackerley, Cameron; Wang, Bernice; Ito, Shinya; Clarke, David M; Lingwood, Clifford

2008-02-22

178

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)

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

2001-08-01

179

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

180

[Active efflux as the multidrug resistance mechanism].  

Science.gov (United States)

Active efflux is a common resistance mechanism in a wide range of bacterial pathogens. It is responsible for the transport of such toxic compounds as drugs, toxins, and detergents. Pumps with broad substrate profiles promote the emergence of multidrug-resistant bacterial pathogens that are a particular threat to contemporary medicine, such as Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Salmonella enterica sv Typhimurium. One can distinguish five major class of transport systems on the basis of their structure and function: MFS (major facilitator superfamily), SMR (small multidrug-resistance family), MATE (multidrug and toxic compound extrusion family), ABC (ATP binding cassette superfamily), and RND (resistance nodulation cell division family). Substrate transport may include hydrogen proton exchange or energy generated via ATP hydrolysis. The transport is effectively regulated by local regulatory proteins.such as BmrR from Bacillus subtilis, or by the global bacterial regulatory system. Investigations into efflux pumps and their substrate profiles and regulatory mechanisms have led to the discovery of new therapeutics and pump inhibitors that could potentially become alternative and effective antimicrobial drugs. Additionally, some alternative therapies such as photodynamic inactivation could be more effective if the synergistic action of efflux pump inhibitors are used.Thus research into efflux transport systems seems to be an important element of contemporary medicine . PMID:19373193

Wasaznik, Anna; Grinholc, Mariusz; Bielawski, Krzysztof P

2009-01-01

 
 
 
 
181

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

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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 (vincristine, vinblastine) was semiquantitatively assessed by scanning Northern blots on a phosphorimager. The relative level of mdr1 expression was expressed as ratio of mdr1 to the internal RNA (actin)...

1995-01-01

182

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

183

Effect of multidrug resistance modulators on the activity of ivermectin and moxidectin against selected strains of Haemonchus contortus infective larvae Efeito de drogas moduladoras da resistência múltipla na atividade da ivermectina e moxidectina contra larvas infectantes selecionadas de Haemonchus contortus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Molento, Marcelo B.; Prichard, Roger K.

2001-01-01

184

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.)

2009-03-01

185

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

186

Reversal effects of antifungal drugs on multidrug resistance in MDR1-overexpressing HeLa cells.  

Science.gov (United States)

In this study, the antiproliferative effects of vinblastine (VLB), paclitaxel (TXL), doxorubicin (DXR), daunorubicin (DNR) and 5-fluorouracil (5-FU) were assessed in the human cervical carcinoma cell line HeLa-Ohio (HeLa) and Hvr100-6 cells, established by growing the parental HeLa cells in the presence of progressively greater concentrations of VLB in the culture medium. Flow cytometric analysis indicated the induction of MDR1 (P-glycoprotein) in Hvr100-6 cells with no alterations in levels of multidrug resistance-associated protein (MRP). Resistance to VLB, TXL, DXR and DNR was found in Hvr100-6 cells with relative resistances of ca. 300, 4000, 50 and 200, respectively, whereas no resistance was found to 5-FU. The reversal effects of antifungal drugs, fluconazole, itraconazole, ketoconazole, miconazole and amphotericin B on multidrug resistance were also assessed using Hvr100-6 cells. Itraconazole was found to have potent reversal effect on the resistance to VLB and TXL, but the others had no such effect. This reversal effect of itraconazole was concentration-dependent, with dose modifying factors of 3.2, 10.1 and 435.7 at 0.1, 0.25 and 0.5 microM of itraconazole, respectively. In addition, this reversal effect of itraconazole was explained by the inhibition of accumulation of the anticancer drugs. PMID:11558564

Iida, N; Takara, K; Ohmoto, N; Nakamura, T; Kimura, T; Wada, A; Hirai, M; Sakaeda, T; Okumura, K

2001-09-01

187

Reversal of multidrug resistance by morning glory resin glycosides in human breast cancer cells.  

Science.gov (United States)

Reversal of multidrug resistance (MDR) by thirty resin glycosides from the morning glory family (Convolvulaceae) was evaluated in vinblastine-resistant human breast carcinoma cells (MCF-7/Vin). The effects of these amphipathic compounds on the cytotoxicity and P-glycoprotein (P-gp)-mediated MDR were estimated with the sulforhodamine B colorimetric assay. Active noncytotoxic compounds exerted a potentiation effect of vinblastine susceptibility by 1- to over 1906-fold at tested concentrations of 5 and 25 ?g/mL. Murucoidin V (1) enhanced vinblastine activity 255-fold when incorporated at 25 ?g/mL and also, based on flow cytometry, significantly increased the intracellular accumulation of rhodamine 123 with the use of reserpine as a positive control for a MDR reversal agent. Incubation of MCF-7/Vin cells with 1 caused an increase in uptake and notably lowered the efflux rate of rhodamine 123. Decreased expression of P-glycoprotein by compound 1 was detected by immunofluorescence flow cytometry after incubation with an anti-P-gp monoclonal antibody. These results suggest that resin glycosides represent potential efflux pump inhibitors for overcoming MDR in cancer therapy. PMID:22148475

Figueroa-González, Gabriela; Jacobo-Herrera, Nadia; Zentella-Dehesa, Alejandro; Pereda-Miranda, Rogelio

2012-01-27

188

Study of multidrug resistance and radioresistance  

International Nuclear Information System (INIS)

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

1999-01-01

189

Study of multidrug resistance and radioresistance  

Energy Technology Data Exchange (ETDEWEB)

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

Kang, Yoon Koo; Yoo, Young Do

1999-04-01

190

Terpenoids from Maytenus species and assessment of their reversal activity against a multidrug-resistant Leishmania tropica line.  

Science.gov (United States)

The phytochemical analysis of the root bark extracts of the Chilean Maytenus, M. chubutensis, and M. magellanica (Celastraceae), led to the isolation of one phenolic nortriterpene, 1, and one diterpene with a nor-ent-kaurene skeleton, 2. In addition, four known compounds were isolated, among which compound 3 has been isolated for the first time from a natural source. Their structures were elucidated by spectroscopic methods, including 1D- and 2D-NMR (COSY, ROESY, HSQC, and HMBC) experiments, comparison with data reported in the literature, and chemical correlations. The isolated compounds were assayed for their reversal activity against a multidrug-resistant Leishmania tropica line, overexpressing a P-glycoprotein related transporter. Compound 1 showed moderate multidrug-resistance reversal activity. PMID:22162167

Kennedy, María L; Llanos, Gabriel G; Castanys, Santiago; Gamarro, Francisco; Bazzocchi, Isabel L; Jiménez, Ignacio A

2011-12-01

191

Imaging and Targeted Therapy of Multidrug Resistance. Final Report  

International Nuclear Information System (INIS)

One focus area of DOE Office of Science was the Imaging of Gene Expression in Health and Disease in real time in tissue culture, whole animals and ultimately patients. Investigators of the Molecular Imaging Group, Washington University Medical School, ascribed to this objective and a major focus of this group directly tied into the DOE program through their efforts targeting the multidrug resistance gene (MDR1). Our plans for continuation of the program were to extend and build on this line of investigation, incorporating new molecular tools into our methodology to selectively inhibit MDR1 gene expression with novel modulation strategies. Two approaches were to be pursued: (1) high throughput screening of compounds that disrupted mutant p53 transactivation of the MDR1 promoter, and (2) knockdown of MDR1 messenger RNA with retroviral-mediated delivery of small interfering RNA constructs. These would be combined with our continuing effort to synthesize ligands and examine structure-activity relationships of bis-salicylaldehydes labeled with gallium-68 to generate PET agents for imaging MDR1 P-glycoprotein function. We would be uniquely positioned to correlate therapeutic modulation of MDR1 gene expression and protein function in the same systems in vivo using PET and bioluminescence reporters. Use of animal models such as the mdr1a/1b(-/-) gene deleted mice would also have enabled refined analysis of modulation and tracer pharmacokinetics in vivo. Overall, this DOE program and resultant tools would enable direct monitoring of novel therapeutic strategies and the MDR phenotype in relation to gene expression and protein function in vivo.

2009-01-01

192

Fingerprint-based in silico models for the prediction of P-glycoprotein substrates and inhibitors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

P-Glycoprotein (P-gp, ABCB1) plays a significant role in determining the ADMET properties of drugs and drug candidates. Substrates of P-gp are not only subject to multidrug resistance (MDR) in tumor therapy, they are also associated with poor pharmacokinetic profiles. In contrast, inhibitors of P-gp have been advocated as modulators of MDR. However, due to the polyspecificity of P-gp, knowledge on the molecular basis of ligand–transporter interaction is still poor, which renders the predict...

Poongavanam, Vasanthanathan; Haider, Norbert; Ecker, Gerhard F.

2012-01-01

193

Comparison of an immunoperoxidase "sandwich" staining method and western blot detection of P-glycoprotein in human cell lines and sarcomas.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The applicability of a multilayer immunoperoxidase "sandwich" method (IpS) developed by Chan14 for the amplified detection of P-glycoprotein (Pgp) was investigated. The authors examined 15 formalin-fixed cell lines, as well as formalin-fixed, paraffin-embedded sections from single biopsies of 46 sarcomas. The cell lines included sensitive and multidrug resistant sublines (KB, A2780, MCF-7, HeLa) with various relative degrees of resistance to doxorubicin (Dox). The sarcoma biopsy specimens wer...

To?th, K.; Vaughan, M. M.; Slocum, H. K.; Fredericks, W. J.; Chen, Y. F.; Arredondo, M. A.; Harstrick, A.; Karakousis, C.; Baker, R. M.; Rustum, Y. M.

1992-01-01

194

Polymorphisms in the multiple drug resistance protein 1 and in P-glycoprotein 1 are associated with time to event outcomes in patients with advanced multiple myeloma treated with bortezomib and pegylated liposomal doxorubicin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Single nucleotide polymorphisms (SNPs) in the multiple drug resistance protein 1 (MRP1) and P-glycoprotein 1 (MDR1) genes modulate their ability to mediate drug resistance. We therefore sought to retrospectively evaluate their influence on outcomes in relapsed and/or refractory myeloma patients treated with bortezomib or bortezomib with pegylated liposomal doxorubicin (PLD). The MRP1/R723Q polymorphism was found in five subjects among the 279 patient study population, all of whom received PLD...

2010-01-01

195

Effects of highly purified anthraquinoid compounds from Aloe vera on sensitive and multidrug resistant leukemia cells.  

Science.gov (United States)

Folk medicine has attributed antitumor properties to preparations from Aloe vera. We have studied the effects of five purified compounds from the plant on human K562 leukemia and on its multidrug resistant (MDR) variant, K562/R. The glycosides aloin A and B, aloesin and aloeresin were devoid of antitumor activity up to 200 mu M concentrations. Only the aglycone aloe emodin produced reproducible antitumor effects, which, interestingly, were more pronounced in the MDR, P-glycoprotein overexpressing, cell line. Its IC50 was in fact 29 mu M in K562 and 10.5 mu M in K562/R. Aloe emodine caused mainly cytostasis and accumulation of the cells in the S and G(2)-M phases of the cell cycle during the first 48 h of treatment. Thereafter, massive cell death ensued. Research on the antitumor activity of compounds extracted from Aloe vera probably deserves continuation. PMID:21590055

Grimaudo, S; Tolomeo, M; Gancitano, R; Dalessandro, N; Aiello, E

1997-01-01

196

Cellular communication via microparticles: role in transfer of multidrug resistance in cancer.  

Science.gov (United States)

Multidrug resistance (MDR) continues to be a major impediment to the successful treatment of cancer. The two efflux transporters, P-glycoprotein (P-gp) and MRP1 are major contributors to cancer MDR clinically. The upregulation of P-gp leading to MDR was initially understood to occur via pre- and post-transcriptional mechanisms only. However, we demonstrated that microparticles mediate the intercellular exchange and trafficking of bioactive material, including functional P-gp and selected modulatory miRNAs. This exchange of P-gp leads to the dissemination of MDR within a cancer cell population. These findings have significant implications in understanding the cellular basis governing the intercellular acquisition of deleterious traits in cancers, serving to substantially advance our understanding of the molecular basis of the emergence of MDR in cancer clinically. PMID:24754595

Jaiswal, Ritu; Raymond Grau, Georges Emile; Bebawy, Mary

2014-03-01

197

Reversal of multidrug resistance in cancer cells by Rhizoma Alismatis extract.  

Science.gov (United States)

Prolonged chemotherapy may lead to the selective proliferation of multidrug resistant (MDR) cancer cells. In MDR HepG2-DR and K562-DR cells that over-expressed P-glycoprotein (Pgp), the extract of the rhizomes of Alisma orientalis (Sam) Juzep. showed a synergistic growth inhibitory effect with cancer drugs that are Pgp substrates including actinomycin D, puromycin, paclitaxel, vinblastine and doxorubicin. At the same toxicity levels the herbal extract was more effective than verapamil, a standard Pgp inhibitor, in enhancing cellular doxorubicin accumulation and preventing the efflux of rhodamin-123 from the MDR cells. The extract restored the effect of vinblastine on the induction of G(2)/M arrest in MDR cells. Our data suggest that A. orientalis may contain components that are effective inhibitors of Pgp. PMID:16713217

Fong, W-F; Wang, C; Zhu, G-Y; Leung, C-H; Yang, M-S; Cheung, H-Y

2007-02-01

198

Constituents of Carpobrotus edulis inhibit P-glycoprotein of MDR1-transfected mouse lymphoma cells.  

Science.gov (United States)

A bioassay-guided separation protocol, including the testing of the extracts, fractions and pure compounds for their ability to inhibit P-glycoprotein (the efflux pump responsible for the multidrug resistance of the used cell line) of mouse lymphoma cells containing the human efflux pump gene MDR1, led to the isolation of seven compounds from the chloroform and ethyl acetate soluble fractions of the methanolic extract of Carpobrotus edulis. The compounds were identified by 1D, 2D NMR and MS investigations as triterpens (beta-amyrin, uvaol and oleanolic acid), monogalactosyldiacylglycerol, catechin, epicatechin and procyanidin B5. Uvaol was the most effective and promising compound in the reversal of multidrug resistance in MDR mouse lymphoma cell line. PMID:20393003

Martins, A; Vasas, A; Schelz, Zs; Viveiros, M; Molnár, J; Hohmann, J; Amaral, L

2010-03-01

199

Oroxylin A reverses P-glycoprotein-mediated multidrug resistance of MCF7/ADR cells by G2/M arrest.  

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Oroxylin A is a naturally occurring monoflavonoid isolated from the root of Scutellaria baicalensis Georgi, which has been used in traditional Chinese medicine for its anti-tumor, anti-inflammatory and anti-bacterial properties. The purpose of this study is to investigate the reversal effect and the fundamental mechanisms of oroxylin A in MCF7/ADR cells. Data indicated that oroxylin A showed strong reversal potency in MCF7/ADR cells and the reversal fold (RF) reached 4.68. After treatment with oroxylin A, MCF7/ADR cells displayed reduced functional activity and expression of MDR1 at both the protein and mRNA levels. Meanwhile, oroxylin A induced cells G2/M arrest in a concentration-dependent manner by increasing the expression of p-Chk2 (Thr68). Moreover, western blot and EMSA assays were used to reveal the inhibition of NF-?B in nucleus and the suppression of NF-?B binding activity by oroxylin A. NSC 109555 ditosylate-Chk2 inhibitor partly dismissed G2/M arrest induced by oroxylin A, reversed the increased trend of p-Chk2 and p-P53 (Ser20), inhibited the decreasing effect of oroxylin A on the expression of P-gp and decreased the reversal fold of 90 ?M oroxylin A from 4.68 fold to 1.73 fold. In conclusion, we suggested that oroxylin A reversed MDR by G2/M arrest and the underlying mechanism attributed to the suppression of P-gp expression via Chk2/P53/NF-?B signaling pathway. PMID:23470866

Zhu, Litao; Zhao, Li; Wang, Hu; Wang, Yu; Pan, Di; Yao, Jing; Li, Zhiyu; Wu, Guanzhong; Guo, Qinglong

2013-05-23

200

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.

2011-07-01

 
 
 
 
201

ABC transporters in multidrug resistance and pharmacokinetics, and strategies for drug development.  

Science.gov (United States)

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 complete clinical trials thus far have showen that those tested chemosensitizers only add 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. PMID:23688078

Choi, Young Hee; Yu, Ai-Ming

2014-01-01

202

Human multidrug resistance ABCB and ABCG transporters: participation in a chemoimmunity defense system.  

Science.gov (United States)

In this review we give an overview of the physiological functions of a group of ATP binding cassette (ABC) transporter proteins, which were discovered, and still referred to, as multidrug resistance (MDR) transporters. Although they indeed play an important role in cancer drug resistance, their major physiological function is to provide general protection against hydrophobic xenobiotics. With a highly conserved structure, membrane topology, and mechanism of action, these essential transporters are preserved throughout all living systems, from bacteria to human. We describe the general structural and mechanistic features of the human MDR-ABC transporters and introduce some of the basic methods that can be applied for the analysis of their expression, function, regulation, and modulation. We treat in detail the biochemistry, cell biology, and physiology of the ABCB1 (MDR1/P-glycoprotein) and the ABCG2 (MXR/BCRP) proteins and describe emerging information related to additional ABCB- and ABCG-type transporters with a potential role in drug and xenobiotic resistance. Throughout this review we demonstrate and emphasize the general network characteristics of the MDR-ABC transporters, functioning at the cellular and physiological tissue barriers. In addition, we suggest that multidrug transporters are essential parts of an innate defense system, the "chemoimmunity" network, which has a number of features reminiscent of classical immunology. PMID:17015488

Sarkadi, Balázs; Homolya, László; Szakács, Gergely; Váradi, András

2006-10-01

203

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

Science.gov (United States)

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

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

2013-06-15

204

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

Science.gov (United States)

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

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

2009-07-26

205

P-GLYCOPROTEIN QUANTITATION IN ACUTE LEUKEMIA  

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

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

2003-01-01

206

Insight into the Cooperation of P-glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2) at the Blood-Brain Barrier: A Case Study Examining Sorafenib Efflux Clearance  

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The ATP-binding cassette transporters p-glycoprotein and breast cancer resistance protein have been shown to be critical determinants limiting drug transport across the BBB into the brain. Several therapeutic agents have been shown to be substrates for these two transporters, and as a result they have limited distribution to the brain. Recently, it has been shown that these two drug transporters cooperate at the BBB and brain penetration of dual substrates increase significantly only when bot...

Agarwal, Sagar; Elmquist, William F.

2012-01-01

207

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

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The objective of this study was to quantitatively examine the protein expression of relevant transporters and other proteins in the brain capillary endothelial cells isolated from wild-type mice and P-glycoprotein (P-gp), breast cancer resistance protein (Bcrp), and P-gp/Bcrp knockout mice. After the isolation of brain capillary endothelial cells, a highly sensitive liquid chromatography-tandem mass spectrometry method with multiple reaction monitoring was used to determine the quantitative e...

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

2012-01-01

208

Thiorhodamines Containing Amide and Thioamide Functionality as Inhibitors of the ATP-Binding Cassette Drug Transporter P-glycoprotein (ABCB1)  

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Twelve thiorhodamine derivatives have been examined for their ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His10, to promote uptake of calcein AM and vinblastine into multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells. The thiorhodamine derivatives have structural diversity from amide and thioamide functionality (N,N-diethyl and N-piperidyl)...

Orchard, Alexandra; Schamerhorn, Gregory A.; Calitree, Brandon D.; Sawada, Geri A.; Loo, Tip W.; Bartlett, M. Claire; Clarke, David M.; Dettya, Michael R.

2012-01-01

209

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

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

Hussain MD

2012-02-01

210

Comparative tissue pharmacokinetics and efficacy of moxidectin, abamectin and ivermectin in lambs infected with resistant nematodes: Impact of drug treatments on parasite P-glycoprotein expression.  

Science.gov (United States)

The high level of resistance to the macrocyclic lactones has encouraged the search for strategies to optimize their potential as antiparasitic agents. There is a need for pharmaco-parasitological studies addressing the kinetic-dynamic differences between various macrocyclic lactones under standardized in vivo conditions. The current work evaluated the relationship among systemic drug exposure, target tissue availabilities and the pattern of drug accumulation within resistant Haemonchus contortus for moxidectin, abamectin and ivermectin. Drug concentrations in plasma, target tissues and parasites were measured by high performance liquid chromatography. Additionally, the efficacy of the three molecules was evaluated in lambs infected with resistant nematodes by classical parasitological methods. Furthermore, the comparative determination of the level of expression of P-glycoprotein (P-gp2) in H. contortus recovered from lambs treated with each drug was performed by real time PCR. A longer persistence of moxidectin (P < 0.05) concentrations in plasma was observed. The concentrations of the three compounds in the mucosal tissue and digestive contents were significant higher than those measured in plasma. Drug concentrations were in a range between 452 ng/g (0.5 day post-treatment) and 32 ng/g (2 days post-treatment) in the gastrointestinal (GI) contents (abomasal and intestinal). Concentrations of the three compounds in H. contortus were in a similar range to those observed in the abomasal contents (positive correlation P = 0.0002). Lower moxidectin concentrations were recovered within adult H. contortus compared to abamectin and ivermectin at day 2 post-treatment. However, the efficacy against H. contortus was 20.1% (ivermectin), 39.7% (abamectin) and 89.6% (moxidectin). Only the ivermectin treatment induced an enhancement on the expression of P-gp2 in the recovered adult H. contortus, reaching higher values at 12 and 24 h post-administration compared to control (untreated) worms. This comparative pharmacological evaluation of three of the most used macrocyclic lactones compounds provides new insights into the action of these drugs. PMID:24533290

Lloberas, Mercedes; Alvarez, Luis; Entrocasso, Carlos; Virkel, Guillermo; Ballent, Mariana; Mate, Laura; Lanusse, Carlos; Lifschitz, Adrian

2013-12-01

211

Relationship between P-glycoprotein positivity, doxorubicin binding ability and histologic response to chemotherapy in osteosarcomas.  

Science.gov (United States)

We previously reported that the doxorubicin binding ability detected by the doxorubicin (adriamycin) binding assay was closely correlated with the chemosensitivity of human osteosarcomas. In this study, we undertook to clarify the relationship between P-glycoprotein positivity (%PPG) and doxorubicin binding ability (%DB) in human osteosarcomas in order to determine which is a more sensitive index of histologic response to chemotherapy. Ten primary osteosarcomas were analyzed by the doxorubicin binding assay and by immunofluorescence to detect cellular P-glycoprotein positivity. Three good responders to chemotherapy containing doxorubicin showed a %DB greater than 90% (average: 96.43%), whereas the seven poor responders had values less than 80% (average: 35.31%). The difference between the two groups was statistically significant (P = 0.0167). However, the average %PPG of the three good responders was 6.73%, whereas the %PPG of the seven poor responders was 14.27%. There was no significant difference in %PPG between the two groups (P = 0.3051). No negative correlation between the %DB and the %PPG of all osteosarcomas (r = 0.536, P = 0.1104) was found, although there was a trend that those tumors with a high %PPG showed a low %DB. These results suggest that osteosarcomas showing a low %DB and %PPG with poor response to chemotherapy, may have multidrug resistance mechanisms other than P-glycoprotein. Therefore, we conclude that doxorubicin binding ability, which reflects all of the doxorubicin-resistant mechanisms, was more sensitive than P-glycoprotein positivity in predicting the chemosensitivity of human osteosarcoma. PMID:10378794

Kusuzaki, K; Hirata, M; Takeshita, H; Murata, H; Hashiguchi, S; Ashihara, T; Hirasawa, Y

1999-04-26

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A REVISED ROLE FOR P-GLYCOPROTEIN IN THE BRAIN DISTRIBUTION OF DEXAMETHASONE, CORTISOL, AND CORTICOSTERONE IN WILD TYPE AND ABCB1A/B-DEFICIENT MICE  

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The ABCB1-type multi-drug resistance efflux transporter P-glycoprotein (P-gp) has been hypothesized to regulate hypothalamic-pituitary-adrenal (HPA) axis activity by limiting the access of glucocorticoids to the brain. In vivo systemic administration studies using P-gp-deficient mice have shown increased glucocorticoid entry to the brain compared with wild-type controls. However, these studies did not control for the presence of radiolabeled drug in the capillaries, verify an intact blood-bra...

Mason, Brittany L.; Pariante, Carmine M.; Thomas, Sarah A.

2008-01-01

213

Multi-drug resistance (MDR1) gene expression in de novo acute leukemia cells: correlations with CD surface markers and treatment outcome.  

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One important mechanism of drug resistance in acute leukemia is the overexpression of the multi-drug resistance (MDR1) gene that encodes a 170-kDa membrane protein called P-glycoprotein. To estimate the incidence and role of MDR1 gene expression in patients with acute leukemia, we investigated the expression of MDR1 by using the RT-PCR method in blast cells from 40 cases of de novo acute leukemia. We found a high frequency of MDR1 gene expression: 10 out of 20 with de novo acute myeloid leuke...

1998-01-01

214

Fluorescent cellular indicators are extruded by the multidrug resistance protein.  

Science.gov (United States)

In this report we show that NIH-3T3 mouse fibroblasts stably expressing the human multidrug transporter (MDR1 or P-glycoprotein), in contrast to the control NIH-3T3 cells, actively extrude the hydrophobic acetoxymethyl ester (AM) derivatives used for cellular loading of various fluorescent calcium and pH indicators. This dye extrusion is blocked by competing substrates and inhibitors of the multidrug transporters, e.g. by verapamil, vincristine, sodium orthovanadate, oligomycin, and a monoclonal anti-MDR1 antibody. The hydrophilic free acid forms of the indicators are not exported by MDR1. We also demonstrate that in isolated cell membranes the MDR1-ATPase, similar to that by known substrates of the transporter, is stimulated by the AM derivatives of fluorescent dyes whereas the free acid forms of the dyes are without effect. Since (i) the AM derivatives of the fluorescent indicators rapidly permeate the cell membrane and are readily cleaved by high activity and large capacity cytoplasmic esterases and (ii) the free acid forms are not substrates for export by MDR1, the observations above suggest that dye extrusion by MDR1 may occur without a cytoplasmic appearance of the AM compounds. These data also call attention to the possible interaction of widely used hydrophobic fluorescent indicators with MDR1 and offer an efficient detection of MDR1-expressing tumor cells as well as a screening method for examining drug interactions with the multidrug transporter. PMID:8104940

Homolya, L; Holló, Z; Germann, U A; Pastan, I; Gottesman, M M; Sarkadi, B

1993-10-15

215

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

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

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

2009-01-01

216

Successful treatment of multidrug resistant Acinetobacter baumannii meningitis  

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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

2007-12-01

217

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

Science.gov (United States)

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

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

2011-10-01

218

Multidrug resistant yeasts in synanthropic wild birds  

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

Somanath Sushela

2010-03-01

219

Multi-drug resistance gene (MDR1) and opioid analgesia in horses Gene de resistência múltipla aos fármacos e analgesia opióide em eqüinos  

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Opioid absorption in the intestinal tract as well as its effects in the central nervous system is modulated by the P-glycoprotein (P-gp) encoded in the Multi-drug Resistance gene (MDR1) also named ATP-binding cassete, subfamily B, member 1 (ABCB1). This MDR1 gene acts as a selective pump. The expression of this protein in humans and rodents inhibits cellular uptake of substrate opioids. The presence of the intestinal iso-enzyme CYP3A4 associated with MDR1 gene decreases the opioid analgesic a...

Cláudio Corrêa Natalini; Anderson Fávaro da Cunha; Renata Lehn Linardi

2006-01-01

220

Identification of multi-drug resistance gene (MDR1) in equine ileum Identificação do gene de resistência múltipla aos fármacos no íleo de eqüinos  

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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 ...

Cláudio Corrêa Natalini; Renata Lehn Linardi

2006-01-01

 
 
 
 
221

mdm2 gene mediates the expression of mdr1 gene and P-glycoprotein in a human glioblastoma cell line.  

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The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumours. The mechanism by which mdr1 gene and P-gp are overexpressed in human tumours, however, is not yet clear. In this report, we show that the mdm2 (murine double minute 2) gene induced the expression of the mdr1 gene and P-gp in human glioblastoma U87-MG cells, which did not express the MDM2 protein or P-gp. The mdm2 gene, in addition...

Kondo, S.; Kondo, Y.; Hara, H.; Kaakaji, R.; Peterson, J. W.; Morimura, T.; Takeuchi, J.; Barnett, G. H.

1996-01-01

222

Differential chemosensitization of P-glycoprotein overexpressing K562/Adr cells by withaferin A and Siamois polyphenols  

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Background: Multidrug resistance (MDR) is a major obstacle in cancer treatment and is often the result of overexpression of the drug efflux protein, P-glycoprotein (P-gp), as a consequence of hyperactivation of NF-kappa B, AP1 and Nrf2 transcription factors. In addition to effluxing chemotherapeutic drugs, P-gp also plays a specific role in blocking caspase-dependent apoptotic pathways. One feature that cytotoxic treatments of cancer have in common is activation of the transcription factor NF...

Suttana, Wipob; Mankhetkorn, Samlee; Poompimon, Wilart; Palagani, Ajay; Zhokhov, Sergey; Gerlo, Sarah; Haegeman, Guy; Vanden Berghe, Wim

2010-01-01

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

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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 (<45%) and remaining failed to interact with P-gp, indicating that there may be multiple mechanisms for MDR. (author)

1999-01-01

224

Establishment of a human hepatoma multidrug resistant cell line in vitro  

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Full Text Available AIM: To establish a multidrug-resistant hepatoma cell line (SK-Hep-1, and to investigate its biological characteristics.METHODS: A highly invasive SK-Hep-1 cell line of human hepatocellular carcinoma, also known as malignant hepatoma was incubated with a high concentration of cisplatin (CDDP to establish a CDDP-resistant cell subline (SK-Hep-1/CDDP. The 50% inhibitory dose (IC50 values and the resistance indexes [(IC50 SK-Hep-1/CDDP/(IC50 SK-Hep-1] for other chemotherapeutic agents and the growth curve of cells were all evaluated using cell counting kit-8 assays. The distribution of the cell cycles were detected by flow cytometry. Expression of acquired multidrug resistance P-glycoprotein (MDR1, ABCB1 and multidrug resistance-associated protein 1 (MRP1, ABCC1 was compared with that in parent cells by Western blotting and immunofluorescence combined with laser scanning confocal microscopy.RESULTS: The SK-Hep-1/CDDP cells (IC50 = 70.61 ± 1.06 ?g/mL was 13.76 times more resistant to CDDP than the SK-Hep-1 cells (IC50 = 5.13 ± 0.09 ?g/mL, and CDDP-resistant cells also demonstrated cross-resistance to many anti-tumor agents such as doxorubicin, 5-fluorouracil and vincristine. Similar morphologies were determined in both SK-Hep-1 and SK-Hep-1/CDDP groups. The cell cycle distribution of the SK-Hep-1/CDDP cell line exhibited a significantly increased percentage of cells in S (42.2% ± 2.65% vs 27.91% ± 2.16%, P < 0.01 and G2/M (20.67% ± 5.69% vs 12.14% ± 3.36%, P < 0.01 phases in comparison with SK-Hep-1 cells, while the percentage of cells in the G0/G1 phase decreased (37.5% ± 5.05% vs 59.83% ± 3.28%, P < 0.01. The levels of MDR1 and MRP1 were overexpressed in the SK-Hep-1/CDDP cells exhibiting the MDR phenotype.CONCLUSION: Multiple drug resistance of multiple drugs in the human hepatoma cell line SK-Hep-1/CDDP was closely related to the overexpression of MDR1 and MRP1.

Yuan Zhou, Xian-Long Ling, Shi-Wei Li, Xin-Qiang Li, Bin Yan

2010-05-01

225

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

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

Li B

2012-01-01

226

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

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

Ramin Miri

2007-06-01

227

Salvage therapy for multidrug-resistant tuberculosis.  

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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. PMID:23991934

Seung, K J; Becerra, M C; Atwood, S S; Alcántara, F; Bonilla, C A; Mitnick, C D

2014-05-01

228

Combination of tunicamycin with anticancer drugs synergistically enhances their toxicity in multidrug-resistant human ovarian cystadenocarcinoma cells  

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Full Text Available Abstract Background The pharmacologic modulatory effects of the antibiotic, tunicamycin (TM, on multidrug-resistant human UWOV2 ovarian cancer cells are reported. The UWOV2 cell line was derived from a cystadenocarcinoma in a patient refractory to combination chemotherapy with actinomycin D, vincristine (VCR, cis-diaminedichloroplatinum (II (CDDP and doxorubicin (DXR. In an attempt to explain drug resistance in this cell line, we examined the effects of TM on their sensitivity to various anticancer drugs, the uptake, efflux and retention of [3H]VCR, and their ability to bind [14C]DXR and [3H]azidopine (AZD, a photoaffinity label of the multidrug transporter, P-glycoprotein (Pgp. Results TM effectively decreased the EC50 for DXR, EXR, VCR and CDDP, thus enhancing their cytotoxicity. The antibiotic also prolonged the intracellular retention time of [3H]VCR and increased the binding of both [14C]DXR and [3H]AZD to the cells. Conclusion It is concluded that the pharmacomodulatory effects of TM in these cells are mediated by global inhibition of protein and glycoprotein synthesis and synergistic interaction with antineoplastic drugs. The ability of TM to enhance the sensitivity of drug resistant tumour cells may have impact on the design and optimization of novel resistance modifiers to improve the efficacy of combination treatment of intractable neoplasms.

Gabriels Gary A

2007-04-01

229

Radiosensitivity in multidrug-resistant and cisplatin-resistant human carcinoma cell lines.  

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The radiosensitivity of a multidrug-resistant (MDR) clone and a cisplatin-resistant clone was compared with that of their parental chemosensitive cell lines. The LoVo cell line was derived from a human colon carcinoma, and LoVo-R was the MDR clone. The MDR phenotype is attributable to an increased drug efflux mediated by the P-glycoprotein and involves several classes of structurally unrelated drugs. The 2008 cell line was derived from a human ovary carcinoma and C13 was the cisplatin-resistant clone. Reduced cisplatin accumulation and elevated plasma membrane potential partially account for the drug resistance of C13 cells. The chemoresistance of LoVo-R and C13 cells was confirmed by cytotoxicity tests consisting of 24-hour paclitaxel and 1-hour cisplatin incubation, respectively. The radiosensitivity was evaluated by a clonogenic test. The dose-reducing cell survival fraction from 1 to 0.37 (D(0)), the quasi-threshold dose (Dq), and the survival fraction (SF) after 2 or 4 Gy were determined for each cell line. D(0), Dq, and SF(2) were 1.3 +/- 0.4 Gy, 2.1 +/- 0.6 Gy, and 43 +/- 4% for the LoVo cell line and 1.0 +/- 0.2 Gy, 1.7 +/- 0.4 Gy, and 45 +/- 8%, respectively, for the LoVo-R cell line. D(0), Dq, and SF(4) were 1.7 +/- 0.3 Gy, 3.1 +/- 0.4 Gy, and 43 +/- 12% for 2008 cells and 2.6 +/- 0.5 Gy, 4.3 +/- 0.6 Gy, and 53 +/- 11%, respectively for C13 cells. No significant differences were found between LoVo and LoVo-R cells, whereas C13 cells showed a significantly greater D(0,) Dq, and SF(4) than 2008 cells (p <0.05). Incubation of 2008 and C13 cells with subcytotoxic buthionine (BSO) before and after irradiation partially restored C13 radiosensitivity. In fact, D(0) dropped from 2.8 +/- 0.1 to 2.0 +/- 0.3 Gy in C13 cells with and without BSO, whereas it was 1.9 +/- 0.2 Gy in 2008 cells in the absence and presence of BSO. The total glutathione content (GSH) of C13 cells was 1.5-fold higher than that of 2008 cells. BSO treatment caused a partial depletion of GSH in 2008 and C13 cells, but their radiosensitivity did not change accordingly. PMID:12902902

Gigante, Marco; Toffoli, Giuseppe; Bertola, Antonella; Biscontin, Gabriella; Dassie, Andrea; Zanelli, Giuseppe D; Zanin, Enzo; Trovò, Mauro G; Muzzio, Pier Carlo

2003-08-01

230

Multidrug-resistant Mycobacterium tuberculosis, Bangui, Central African Republic  

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We investigated multidrug-resistant (MDR) Mycobacterium tuberculosis strains in Bangui, Central African Republic. We found 39.6% with the same spoligotype and synonymous single nucleotide polymorphism in the mutT1 gene. However, strains had different rpoB mutations responsible for rifampin resistance. MDR strains in Bangui may emerge preferentially from a single, MDR-prone family.

Nouvel, Laurent X.; Kassa-kelembho, Eric; Dos Vultos, Tiago; Zandanga, Germain; Rauzier, Jean; Lafoz, Carmen; Martin, Carlos; Blazquez, Jesus; Talarmin, Antoine; Gicquel, Brigitte

2006-01-01

231

Reversal of MDR1 gene-dependent multidrug resistance using low concentration of endonuclease-prepared small interference RNA.  

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Multidrug resistance following initial chemotherapy is commonly associated with MDR1 gene encoding for P-glycoprotein (P-gp). RNA interference of MDR1 gene expression was used as a strategy to reverse MDR1-mediated multidrug resistance phenotypes. Here we report that endonuclease-prepared small interfering RNA (esiRNA) at concentrations as low as 10 ng/ml (about 0.7 nM) can decrease MDR1 expression and increase chemosensitivity in the Adriamycin-induced resistant MCF-7/R cells. When MCF-7/R cells were transiently transfected with esiRNA of MDR1 (esiMDR1), the MDR1 mRNA was reduced by about 50%, drug accumulation increased by about 30%, and the IC50 for daunorubicin was reduced from 4.5 to 1.2 microM. These results provide evidence that esiRNA of MDR1 could be an alternative to P-gp inhibitors with the advantage of avoiding non-specific suppression with a lower effective dosage than using a single siRNA duplex, offering a potential therapeutic application of siRNA. PMID:16564522

Li, Lin; Xu, Jianfeng; Min, Taishan; Huang, Weida

2006-04-24

232

Sinomenine Sensitizes Multidrug-Resistant Colon Cancer Cells (Caco-2) to Doxorubicin by Downregulation of MDR-1 Expression  

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Chemoresistance in multidrug-resistant (MDR) cells over expressing P-glycoprotein (P-gp) encoded by the MDR1 gene, is a major obstacle to successful chemotherapy for colorectal cancer. Previous studies have indicated that sinomenine can enhance the absorption of various P-gp substrates. In the present study, we investigated the effect of sinomenine on the chemoresistance in colon cancer cells and explored the underlying mechanism. We developed multidrug-resistant Caco-2 (MDR-Caco-2) cells by exposure of Caco-2 cells to increasing concentrations of doxorubicin. We identified overexpression of COX-2 and MDR-1 genes as well as activation of the NF-?B signal pathway in MDR-Caco-2 cells. Importantly, we found that sinomenine enhances the sensitivity of MDR-Caco-2 cells towards doxorubicin by downregulating MDR-1 and COX-2 expression through inhibition of the NF-?B signaling pathway. These findings provide a new potential strategy for the reversal of P-gp-mediated anticancer drug resistance.

Liu, Zhen; Duan, Zhi-Jun; Chang, Jiu-Yang; Zhang, Zhi-feng; Chu, Rui; Li, Yu-Ling; Dai, Ke-Hang; Mo, Guang-quan; Chang, Qing-Yong

2014-01-01

233

Tariquidar and Elacridar Are Dose-Dependently Transported by P-Glycoprotein and Bcrp at the Blood-Brain Barrier: A Small-Animal Positron Emission Tomography and In Vitro Study  

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Elacridar (ELC) and tariquidar (TQD) are generally thought to be nontransported inhibitors of P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP), but recent data indicate that they may also be substrates of these multidrug transporters (MDTs). The present study was designed to investigate potential transport of ELC and TQD by MDTs at the blood-brain barrier at tracer doses as used in positron emission tomography (PET) studies. We performed PET scans with carbon-11-labeled ELC an...

Bankstahl, Jens P.; Bankstahl, Marion; Roemermann, Kerstin; Wanek, Thomas; Stanek, Johann; Windhorst, Albert D.; Fedrowitz, Maren; Erker, Thomas; Mueller, Markus; Loescher, Wolfgang; Langer, Oliver; Kuntner, Claudia

2013-01-01

234

(Patho)physiological function of the Multidrug Resistance protein MRP1  

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Overexpression of the multidrug resistance protein MRP1 confer multidrug resistance (MDR) to cancer cells. The contents of this thesis describe the involvement of MRP1 in MDR and its importance as transporter for physiological phase II detoxification conjugates. ...

2000-01-01

235

Ceramide and glucosylceramide upregulate expression of the multidrug resistance gene MDR1 in cancer cells.  

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In the present study we used human breast cancer cell lines to assess the influence of ceramide and glucosylceramide (GC) on expression of MDR1, the multidrug resistance gene that codes for P-glycoprotein (P-gp), because GC has been shown to be a substrate for P-gp. Acute exposure (72 h) to C8-ceramide (5 microg/ml culture medium), a cell-permeable ceramide, increased MDR1 mRNA levels by 3- and 5-fold in T47D and in MDA-MB-435 cells, respectively. Acute exposure of MCF-7 and MDA-MB-231 cells to C8-GC (10 microg/ml culture medium), a cell-permeable analog of GC, increased MDR1 expression by 2- and 4- fold, respectively. Chronic exposure of MDA-MB-231 cells to C8-ceramide for extended periods enhanced MDR1 mRNA levels 45- and 390-fold at passages 12 and 22, respectively, and also elicited expression of P-gp. High-passage C8-ceramide-grown MDA-MB-231 (MDA-MB-231/C8cer) cells were more resistant to doxorubicin and paclitaxel. Incubation with [1-(14)C]C6-ceramide showed that cells converted short-chain ceramide into GC, lactosylceramide, and sphingomyelin. When challenged with 5 mug/ml [1-(14)C]C6-ceramide, MDA-MB-231, MDA-MB-435, MCF-7, and T47D cells took up 31, 17, 21, and 13%, respectively, and converted 82, 58, 62, and 58% of that to short-chain GC. Exposing cells to the GCS inhibitor, ethylenedioxy-P4, a substituted analog of 1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol, prevented ceramide's enhancement of MDR1 expression. These experiments show that high levels of ceramide and GC enhance expression of the multidrug resistance phenotype in cancer cells. Therefore, ceramide's role as a messenger of cytotoxic response might be linked to the multidrug resistance pathway. PMID:18035065

Gouazé-Andersson, Valérie; Yu, Jing Y; Kreitenberg, Adam J; Bielawska, Alicja; Giuliano, Armando E; Cabot, Myles C

2007-12-01

236

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.

Haddadin William J

2011-07-01

237

Expression of multidrug resistance membrane transporter (Pgp) and p53 protein in canine mammary tumours.  

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The aim of this study was to determine the expression rate of P-glycoprotein (Pgp), a multidrug resistance marker and the p53 tumour-suppressor protein in canine mammary tumours. A total of 30 tumours were examined in parallel to patient history. The tumours were allotted to four groups: tubulopapillar carcinomas, complex carcinomas, benign tumours, and other malignant tumours. A monoclonal mouse antibody (C494) was used for the immunohistochemical evaluation of Pgp and a polyclonal rabbit antibody for p53. We found that the intact ductal epithelium and connective tissue showed pronounced Pgp expression. The most intensive staining was detected in tubulopapillar carcinomas for both Pgp and p53. The expression rate of Pgp and p53 differed significantly between tubulopapillar carcinoma and complex carcinoma, and between tubulopapillar carcinoma and benign mammary tumour, respectively. The expressions of Pgp and p53 highly correlated statistically; therefore, both can determine malignancy in a similar manner. In the case of tubulopapillar carcinomas, more relapsed tumours occurred than in relation to complex carcinomas and other malignant tumours. Pgp expression rate was proportional to the probability of the tumour becoming recidivant postoperatively, as well. These results suggest that routine evaluation of Pgp expression in canine mammary tumours may be prognostically helpful. PMID:24659714

Koltai, Zsófia; Vajdovich, Péter

2014-06-01

238

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

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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, Seethalakshmi; Ravichandran, Sathyabaarathi; Vetrivel, Umashankar; Krishnakumar, Subramanian

2013-01-01

239

In Vivo Evaluation of Eclipta alba Extract as Anticancer and Multidrug Resistance Reversal Agent.  

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The present study investigates the anticancer and multidrug resistance (MDR) reversal potential of hydro-alcoholic Eclipta alba extract (EAE) through in vivo experiments. Diethylnitrosamine (DEN) and 2-acetylaminofluorene (AAF) were used for liver cancer induction in animal model, whereas for MDR induction, AAF was used. The level of antioxidant enzymes was studied in serum along with biochemical parameters. Cancer and MDR-induced liver cells have higher levels of reactive oxygen species (ROS) and, in turn, are responsible for the maintenance of the cancer phenotype. Treatment with EAE declines the ROS level and revealed the ROS scavenging properties. Alfa feto protein levels were found to increase significantly in cancer-induced animals confirming induction and progression of liver cancer, EAE treatment was found to bring back the altered levels within normal range indicating the therapeutic effect of plant extract over liver cancer. Zymogram showed the inhibition of MMPs and RT-PCR analysis revealed that the mRNA expression of nuclear factor-kB was markedly decreased upon EAE treatment. Further, our results showed that EAE could significantly inhibit mdr1 gene encode P-glycoprotein expression. Our data suggest that EAE is a novel anticancer and potent MDR reversal agent and may be a potential adjunctive agent for tumor chemotherapy. PMID:24896195

Chaudhary, Harshita; Jena, Prasant Kumar; Seshadri, Sriram

2014-07-01

240

A Novel MDR1 GT1292-3TG (Cys431Leu) Genetic Variation and Its Effect on P-glycoprotein Biologic Functions  

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P-glycoprotein (P-gp) is a membrane-bound transporter protein that is encoded by the human multidrug resistance gene MDR1 (ABCB1). P-gp recognizes a wide range of xenobiotics, is pivotal in mediating cancer drug resistance, and plays an important role in limiting drug penetration across the blood–brain barrier. MDR1 genetic variation can lead to changes in P-gp function and may have implications on drug pharmacokinetics. We have identified a novel MDR1GT1292-3TG (Cys431Leu) genetic variatio...

Crouthamel, Matthew H.; Wu, Daniel; Yang, Ziping; Ho, Rodney J. Y.

2010-01-01

 
 
 
 
241

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.  

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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 (P0.05). 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. PMID:23483136

Sun, Yanhui; Li, Qin; Xu, Youhua; Pu, Conglun; Zhao, Lihua; Guo, Zhenhua; Ding, Xionghui; Jin, Xianqing

2013-05-01

242

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

2012-01-01

243

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 occur, contrasts with isolates from eastern Cambodia, where this combination therapy remains highly effective.

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

2008-01-01

244

Ecological aspects of the multidrug resistance to chemotherapy agents ????????????? ????????????? ???????????? ?????????? ?????? ? ???????????????????? ??????????. ????????????? ???????  

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Full Text Available This paper presents generalized and analyzed literature data concerning the main mechanisms of the development of multidrug resistance (MDR produced by tumour cells to chemotherapeutic agents. The conclusion is made about the biological role of acquired MDR phenotype for the tumour cell population.? ?????? ???????? ? ???????????????? ???????????? ??????, ?????????? ???????? ?????????? ???????? ???????? ????????????? ????????????? ???????????? (??? ?????????? ?????? ? ???????????????????? ??????????. ??????? ?????????? ? ????????????? ???? ?????????????? ???????? ??? ??? ????????? ?????????? ?????? ? ?????.

Volkova Tatyana

2012-07-01

245

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

2013-09-01

246

P-GLYCOPROTEIN QUANTITATION IN ACUTE LEUKEMIA  

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Full Text Available Multi drug resistance(MDR is a major problem in the treatment of cancer and hemalological malignancies. This resistance is multi factorial and is the result of decreased intra cellular drug accumulation. This is partly due to the presence of a 170KD intra membranous protein termed P-glycoprotein(P-gp that is an energy-dependent efflux pump which has increased expression on drug-resistance cells. In this study we identified the presence of P-gp by staining with Fluorescent Iso Thio Cyanate (FITC conjugated anti P-gp in acute leukemia patients and flow cytometry in addition to performing immunophenotype analysis and French, American British (FAB classification. Results revealed that one fifth of leuke¬mic patients expressed P-gp and this phenotype was more prevalent in Acute Undifferentiated Leukemia(AUL and Acute Myelogenous Leukemia (AML than in Acute Lymphoblastic Leukemia(ALL. Other findings showed a logical rela¬tionship between this phenotype and age groups. There was not any association between P-gp+ phenotype and FAB and Immunophenotyping sub classification, but there was a linear relationship between CD34 and CD7 expression and P-gp+ phenotype. The accumulation of P-gp molecule that was stated as Mean Fluores¬cence Intensity (MFI on the blasts1 membrane of AUL and AML patients showed marked increase in comparison to ALL. Furthermore MFI in P-gp+ relapsed patients was much more than P-gp+ pretreatment patients.

A.A. Pourfathollali

2003-06-01

247

Inhibition of tetramethylpyrazine on P-gp, MRP2, MRP3 and MRP5 in multidrug resistant human hepatocellular carcinoma cells.  

Science.gov (United States)

Some membrane transporters in liver, such as P-glycoprotein, multidrug resistance-associated protein 2 (MRP2), MRP3, and MRP5 can lead to a complex multidrug resistance (MDR) to antineoplastic agents. How to inhibit these proteins is still an issue. Tetramethylpyrazine is a bioactive constituent isolated from the root of Ligusticum chuanxiong Hort, a Chinese herb. Recent studies showed that it can enhance the chemosensitivity effects of a drug on human hepatocellular carcinoma cells, acting as a multidrug resistance modulator. In this study, the reversal effect of TMP on MDR was evaluated and its activity mechanism in vitro was explored. The IC50 value shows that TMP reversed the multidrug resistance of BEL-7402/ADM cells 9.23-fold (P<0.01) at the concentration of 600 microM. The mean fluorescence intensity of ADM in BEL-7402/ADM cells with TMP was found to be 163.78+/-39.5% (P<0.01) versus in BEL-7402/ADM cells without TMP by flow cytometry and 126.73+/-28.72% in BEL-7402/ADM cells with TMP versus in BEL-7402/ADM cells without TMP (P<0.01) by high performance liquid chromatography, respectively. It was also found that the mRNA level of multidrug resistant gene MDR1, MRP2, MRP3 and MRP5 and the level of the proteins they encode were decreased after treatment with TMP, indicating that TMP can effectively reverse the MDR in BEL-7402/ADM cells, and its activity mechanism may be correlated with the down-regulation of expression in these transporters. PMID:19956884

Wang, Xuan-Bin; Wang, Shan-Shan; Zhang, Qiu-Fang; Liu, Ming; Li, Hong-Liang; Liu, Ying; Wang, Jia-Ning; Zheng, Fei; Guo, Ling-Yun; Xiang, Ji-Zhou

2010-01-01

248

[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 (p< 0.01), amikacin-kanamycin (p= 0.01) and streptomycin-ethionamide (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

249

Influence of exogenous RAR alpha gene on MDR1 expression and P-glycoprotein function in human and rodent cell lines.  

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The goal of our study was to obtain direct evidence of co-ordinated regulation of P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) and differentiation in tumour cells and to study some signalling pathways involved in joint regulation of these two cell phenotypes. The sublines of human melanoma (mS) and hepatoma (human HepG2 and rat McA RH 7777) cell lines were obtained by retroviral infection of the wild-type cells with the cDNA of the human retinoic acid receptor alpha (RAR alpha). ...

Stromskaya, T. P.; Rybalkina, E. Y.; Shtil, A. A.; Zabotina, T. N.; Filippova, N. A.; Stavrovskaya, A. A.

1998-01-01

250

Tunicamycin Depresses P-Glycoprotein Glycosylation Without an Effect on Its Membrane Localization and Drug Efflux Activity in L1210 Cells  

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P-glycoprotein (P-gp), also known as ABCB1, is a member of the ABC transporter family of proteins. P-gp is an ATP-dependent drug efflux pump that is localized to the plasma membrane of mammalian cells and confers multidrug resistance in neoplastic cells. P-gp is a 140-kDa polypeptide that is glycosylated to a final molecular weight of 170 kDa. Our experimental model used two variants of L1210 cells in which overexpression of P-gp was achieved: either by adaptation of parental cells (S) to vin...

Mário Šereš; Dana Cholujová; Tatiana Buben?íkova; Albert Breier; Zdenka Sulová

2011-01-01

251

Tariquidar-induced P-glycoprotein inhibition at the rat blood-brain barrier studied with (R)-11C-verapamil and PET  

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The multidrug efflux transporter P-glycoprotein (P-gp) is expressed in high concentrations at the blood-brain barrier (BBB) and believed to be implicated in resistance to central nervous system drugs. We used small-animal positron emission tomography (PET) and (R)-11C-verapamil together with tariquidar, a new-generation P-gp modulator, to study the functional activity of P-gp at the BBB of rats. To enable a comparison with human PET data we performed kinetic modeling to estimate the rate cons...

Bankstahl, Jens P.; Kuntner, Claudia; Abrahim, Aiman; Karch, Rudolf; Stanek, Johann; Wanek, Thomas; Wadsak, Wolfgang; Kletter, Kurt; Mu?ller, Markus; Lo?scher, Wolfgang; Langer, Oliver

2008-01-01

252

P-glycoprotein effect on the properties of its natural lipid environment probed by Raman spectroscopy and Langmuir-Blodgett technique.  

Science.gov (United States)

Behavior of P-glycoprotein (Pgp) natural lipid environment within the membrane of CEM cells expressing Pgp in the quantities varying from 0% to 32% of the total amount of all membrane proteins is described for the first time. Observed cooperative effect of Pgp-induced increase of membrane stability, decrease of the temperature of gel-to-crystal lipids transition and predominance of the lipid liquid crystalline phase at physiological temperatures should have an impact in development of multidrug resistance phenotype of tumor cells by favoring the Pgp intercellular transfer and Pgp ATPase activity. PMID:16930597

Oleinikov, Vladimir A; Fleury, Fabrice; Ianoul, Anatoli; Zaitsev, Sergey; Nabiev, Igor

2006-09-01

253

Using Rhodamine 123 Accumulation in CD8+ Cells as a Surrogate Indicator to Study the P-Glycoprotein Modulating Effect of Cepharanthine Hydrochloride In Vivo  

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The purpose of this study was the use of rhodamine 123 (Rho123) accumulation in peripheral blood CD8+cells as a surrogate indicator to evaluate the modulating effect of P-glycoprotein (P-gp) inhibitors in the multidrug resistance (MDR) tumor-bearing mouse model. Rho123 was administered to mice, and the fluorescence level in CD8+ cells was measured. Cepharanthine hydrochloride (CH) and verapamil (VER), two P-gp inhibitors, were administered to mice 1 hour prior to Rho123 administration in vivo...

Li, Han; Yan, Zhang; Ning, Wang; Xiao-juan, Guo; Cai-hong, Zang; Jin-hua, Jiang; Fang, Ma; Qing-duan, Wang

2011-01-01

254

The drug-transporter gene MDR1 C3435T and G2677T/A polymorphisms and the risk of multidrug-resistant epilepsy in Turkish children.  

Science.gov (United States)

One-third of all individuals with epilepsy are resistant to antiepileptic drug (AED) treatment. Antiepileptic treatment response has been suggested to be modulated by genetic polymorphisms of drug efflux transporters. Several polymorphic variants within the multidrug resistance 1 (MDR1) gene, which encodes the major transmembrane efflux transporter P-glycoprotein, have been proposed to be associated with AED resistance in epilepsy patients. The aim of this study was to evaluate the effect of C3435T and G2677T/A polymorphisms of MDR1 on AED resistance in Turkish children with epilepsy. MDR1 C3435T and G2677T/A were genotyped in 152 patients with epilepsy, classified as drug-resistant in 69 and drug-responsive in 83. Genotypes of the C3435T and G2677T/A polymorphisms were determined by polymerase chain reaction followed by restriction fragment length polymorphism. Genotype and allele frequencies of C3435T and G2677T/A polymorphisms of the MDR1 gene did not differ between drug-resistant and drug-responsive epilepsy patients. Our results suggest that MDR1 C3435T and G2677T/A polymorphisms are not associated with AED resistance in Turkish epileptic patients. To clarify the exact clinical implication of the MDR1 polymorphisms on the multidrug resistance in epilepsy, further investigations in various ethnic populations would be necessary. PMID:24213830

Seven, Mehmet; Batar, Bahadir; Unal, Selin; Yesil, Gozde; Yuksel, Adnan; Guven, Mehmet

2014-01-01

255

Effect of methylglyoxal on multidrug-resistant Pseudomonas aeruginosa  

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

KunihikoNishino

2014-04-01

256

Effect of methylglyoxal on multidrug-resistant Pseudomonas aeruginosa.  

Science.gov (United States)

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

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

2014-01-01

257

Overcoming multidrug resistance of small-molecule therapeutics through conjugation with releasable octaarginine transporters  

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Many cancer therapeutic agents elicit resistance that renders them ineffective and often produces cross-resistance to other drugs. One of the most common mechanisms of resistance involves P-glycoprotein (Pgp)-mediated drug efflux. To address this problem, new agents have been sought that are less prone to inducing resistance and less likely to serve as substrates for Pgp efflux. An alternative to this approach is to deliver established agents as molecular transporter conjugates into cells thr...

Dubikovskaya, Elena A.; Thorne, Steve H.; Pillow, Thomas H.; Contag, Christopher H.; Wender, Paul A.

2008-01-01

258

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

259

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

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

Kerr Pauline E

2006-11-01

260

H-NS Modulates Multidrug Resistance of Salmonella enterica Serovar Typhimurium by Repressing Multidrug Efflux Genes acrEF?  

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Screening of Salmonella mutants for the ability to increase ?-lactam resistance has led to the identification of a mutation in hns, which codes for the histone-like nucleoid structuring protein (H-NS). In this study, we report that H-NS modulates multidrug resistance through repression of the genes that encode the AcrEF multidrug efflux pump in Salmonella enterica serovar Typhimurium.

2009-01-01

 
 
 
 
261

H-NS modulates multidrug resistance of Salmonella enterica serovar Typhimurium by repressing multidrug efflux genes acrEF.  

Science.gov (United States)

Screening of Salmonella mutants for the ability to increase beta-lactam resistance has led to the identification of a mutation in hns, which codes for the histone-like nucleoid structuring protein (H-NS). In this study, we report that H-NS modulates multidrug resistance through repression of the genes that encode the AcrEF multidrug efflux pump in Salmonella enterica serovar Typhimurium. PMID:19506059

Nishino, Kunihiko; Hayashi-Nishino, Mitsuko; Yamaguchi, Akihito

2009-08-01

262

Chemosensitization of a multidrug-resistant Leishmania tropica line by new sesquiterpenes from Maytenus magellanica and Maytenus chubutensis.  

Science.gov (United States)

Parasite resistance to drugs has emerged as a major problem in current medicine, and therefore, there is great clinical interest in developing compounds that overcome these resistances. In an intensive study of South American medicinal plants, herein we report the isolation, structure elucidation, and biological activity of dihydro-beta-agarofuran sesquiterpenes from the roots of Maytenus magellanica (1-14) and M. chubutensis (14-17). This type of natural products may be considered as privileged structures. The structures of 10 new compounds, 1, 3, 6-9, and12-15, were determined by means of (1)H and (13)C NMR spectroscopic studies, including homonuclear (COSY and ROESY) and heteronuclear correlation experiments (HMQC and HMBC). The absolute configurations of eight hetero- and homochromophoric compounds, 1, 3,6-9, 12, and 13, were determined by means of CD studies. Fourteen compounds, 1-3 and 6-16, have been tested on a multidrug-resistant Leishmania tropica line overexpressing a P-glycoprotein-like transporter to determine their ability to revert the resistance phenotype and to modulate intracellular drug accumulation. From this series, 1, 2, 3, 14, and 15 showed potent activity, 1 being the most active compound. The structure-activity relationships of the different compounds are discussed. PMID:11741484

Kennedy, M L; Cortés-Selva, F; Pérez-Victoria, J M; Jiménez, I A; González, A G; Muñoz, O M; Gamarro, F; Castanys, S; Ravelo, A G

2001-12-20

263

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

2009-02-01

264

Farnesiferol A from Ferula persica and galbanic acid from Ferula szowitsiana inhibit P-glycoprotein-mediated rhodamine efflux in breast cancer cell lines.  

Science.gov (United States)

In multidrug resistance (MDR), cancer cells exposed to anticancer agents develop resistance to a wide variety of chemicals and chemotherapeutic agents. Sesquiterpene coumarins are reported to inhibit P-glycoprotein and/or increase cytotoxicity of anticancer drugs in P-gp-overexpressing cell lines. In the current study, we investigated the effects of galbanic acid (from the roots of Ferula szowitsiana) and farnesiferol A (from the roots of Ferula persica) on functionality of the drug transporter P-glycoprotein (P-gp) using a rhodamine 123 efflux assay in a doxorubicin resistant breast cancer cell line (MCF7/Adr). Compared to verapamil, the well-known inhibitor of P-gp, galbanic acid (5, 10, and 25 µg/mL), significantly inhibited the P-gp activity. In inhibition of the P-gp transporter, farnesiferol A (0.5?µg/mL) was more potent than verapamil at 15 min exposure. Our results indicate that the plant derived sesquiterpene coumarins, farnesiferol A and galbanic acid, may be promising candidates to be considered for further studies on the reversal of multidrug resistance phenotype in chemotherapy of cancer patients. PMID:21484672

Hanafi-Bojd, Mohammad Yahya; Iranshahi, Mehrdad; Mosaffa, Fatemeh; Tehrani, Shahireh Omidvar; Kalalinia, Fatemeh; Behravan, Javad

2011-09-01

265

Inhibition of P-glycoprotein activity by limonin and other secondary metabolites from Citrus species in human colon and leukaemia cell lines.  

Science.gov (United States)

P-glycoprotein (P-gp), a membrane transporter encoded by the MDR1 gene in human cells, mediates drug efflux from cells and plays a major role in causing multidrug resistance; which is one of the most accepted mechanisms for failure of chemotherapy in cancer treatment. In this study, we investigated the effects of nine naturally occurring compounds isolated from Citrus jambhiri Lush and Citrus pyriformis Hassk (Rutaceae) for their potential to modulate the activity of P-gp in the multidrug-resistant human leukaemia cell line CEM/ADR5000. Limonin, deacetylnomilin, hesperidin, neohesperidin, stigmasterol and ss-sitosterol-O-glucoside inhibited the efflux of the P-gp substrate rhodamine 123 in a concentration-dependent manner. Some of these compounds were more active than verapamil, which was used as a positive control. Treatment of drug-resistant Caco-2 cells with the most active C. jambhiri and C. pyriformis compounds increased their sensitivity to doxorubicin and completely reversed doxorubicin resistance, which agrees with a decreased P-gp activity. Limonin was the most potent P-glycoprotein inhibitor - when it was applied at a non-toxic concentration of 20 microM, it significantly enhanced doxorubicin cytotoxicity 2.98-fold (PCitrus compounds could be considered as good candidates for the development of novel P-gp/MDR1 reversal agents which may enhance the accumulation and efficacy of chemotherapy agents. PMID:19782062

El-Readi, Mahmoud Zaki; Hamdan, Dalia; Farrag, Nawal; El-Shazly, Assem; Wink, Michael

2010-01-25

266

A bacterial model system for understanding multi-drug resistance.  

Science.gov (United States)

Mankind stands at the crossroads, recognizing the need for a radical change in bacterial disease management. The development of several antimicrobial agents in the 1940s and 1950s allowed man to gain the upper hand in controlling these diseases. However, the horizon is now clouded by the activation in bacteria of cryptic multi-drug resistance (MDR) genes and the spread of plasmid- and integron-born MDR genes through bacterial populations. Unless remedial measures are taken, nearly all currently available antimicrobial agents are likely to soon lose their efficacies. We briefly review the bacterial MDR phenomenon and focus on a recently emerging family of small multi-drug resistance (SMR) pumps which may provide an ideal model system for understanding the MDR phenomenon in general. PMID:9442481

Saier, M H; Paulsen, I T; Matin, A

1997-01-01

267

Overview of P-glycoprotein inhibitors: a rational outlook  

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P-glycoprotein (P-gp), a transmembrane permeability glycoprotein, is a member of ATP binding cassette (ABC) super family that functions specifically as a carrier mediated primary active efflux transporter. It is widely distributed throughout the body and has a diverse range of substrates. Several vital therapeutic agents are substrates to P-gp and their bioavailability is lowered or a resistance is induced because of the protein efflux. Hence P-gp inhibitors were explored for overcoming multi...

Kale Mohana Raghava Srivalli; Lakshmi, P. K.

2012-01-01

268

Interaction of Common Azole Antifungals with P Glycoprotein  

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Both eucaryotic and procaryotic cells are resistant to a large number of antibiotics because of the activities of export transporters. The most studied transporter in the mammalian ATP-binding cassette transporter superfamily, P glycoprotein (P-gp), ejects many structurally unrelated amphiphilic and lipophilic xenobiotics. Observed clinical interactions and some in vitro studies suggest that azole antifungals may interact with P-gp. Such an interaction could both affect the disposition and ex...

Wang, Er-jia; Lew, Karen; Casciano, Christopher N.; Clement, Robert P.; Johnson, William W.

2002-01-01

269

Anthelmintics Are Substrates and Activators of Nematode P Glycoprotein?  

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P glycoproteins (Pgp), members of the ABC transporter superfamily, play a major role in chemoresistance. In nematodes, Pgp are responsible for resistance to anthelmintics, suggesting that they are Pgp substrates, as they are in mammalian cells. However, their binding to nematode Pgp and the functional consequences of this interaction have not been investigated. Our study showed that levamisole and most of the macrocyclic lactones (MLs) are Pgp substrates in nematodes. Ivermectin, although a v...

Kerboeuf, Dominique; Gue?gnard, Fabrice

2011-01-01

270

Expression of mdr-1/P-glycoprotein in human neuroblastoma.  

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Increased expression of the mdr-1 gene encoding the drug efflux pump P-glycoprotein is a well-established mediator of acquired drug resistance in vitro, and a similar role has been hypothesized in vivo in human malignancy. Because expression of mdr-1 is increased in neuroblastoma cell lines by differentiating agents, the authors hypothesized a similar correlation with differentiation in vivo in neuroblastomas. In 12 tumors from 11 patients, total RNA analysis demonstrated no correlation with ...

Bates, S. E.; Shieh, C. Y.; Tsokos, M.

1991-01-01

271

Hepatic expression of multidrug resistance protein 2 in biliary atresia  

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Abstract Background Biliary atresia (BA) is an idiopathic inflammatory obliterative cholangiopathy of neonates, leading to progressive biliary cirrhosis. Hepatoportoenterostomy (Kasai procedure) can cure jaundice in 30% to 80% of patients. Postoperative clearance of jaundice is one of the most important factors influencing long-term outcomes of BA patients. Multidrug resistance protein 2 (MRP2) is one of the canalicular export pumps located in hepatocytes; it exports organic ...

2011-01-01

272

Paclitaxel Nanocrystals for Overcoming Multidrug Resistance in Cancer  

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Here we described a paclitaxel (PTX) nanocrystals formulation using D-?-tocopheryl polyethylene glycol 1000 succinate (TPGS) as the sole excipient for overcoming multidrug resistance (MDR), a key challenge in current cancer therapy. To the best of our knowledge, it is the first report on PTX nanocrystals which can reverse MDR. TPGS serves as a surfactant to stabilize the nanocrystals and a P-gp inhibitor to reverse MDR. The size and morphology of the nanocrystals were studied by transmission...

2010-01-01

273

Genes Required for Intrinsic Multidrug Resistance in Mycobacterium avium  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Genes required for intrinsic multidrug resistance by Mycobacterium avium were identified by screening a library of transposon insertion mutants for the inability to grow in the presence of ciprofloxacin, clarithromycin, and penicillin at subinhibitory concentrations. Two genes, pks12 and Maa2520, were disrupted in multiple drug-susceptible mutants. The pks12 gene (Maa1979), which may be cotranscribed with a downstream gene (Maa1980), is widely conserved in the actinomycetes. Its ortholog in M...

2004-01-01

274

Multidrug-Resistant Tuberculosis (MDR TB)  

Science.gov (United States)

... or more of the primary drugs (isoniazied and rifampin) used for the treatment of tuberculosis. Extensively drug- ... is TB resistant to at least isoniazid and rifampin among the first-line anti-TB drugs and ...

275

Sequestration of doxorubicin in vesicles in a multidrug-resistant cell line (LZ-100).  

Science.gov (United States)

A multidrug-resistant Chinese hamster cell line, LZ-8, was subcultured in increasing levels of doxorubicin (DOX) until capable of growth in 100 micrograms/mL DOX. This new derivative, designated LZ-100, is the most DOX-resistant line in the LZ series, based on a comparison of Ki-1 values from cell survival studies. This increased level of drug resistance in LZ-100 cells did not result from (i) higher levels of P-glycoprotein (P-gp) in the plasma membrane compared with LZ-8 cells, since this protein constitutes approximately 20% of the total plasma membrane protein in both cell lines, or (ii) more efficient drug pumping by the same amount of P-gp, since efflux of rhodamine 123 and DOX was comparable in the two cell lines. However, an altered drug distribution was observed in LZ-100 cells compared with wild-type V79 cells; in LZ-100 cells DOX was largely excluded from the nucleus and was sequestered in vesicles in the cytoplasm. The number of vesicles per cell seen after DOX exposure corresponded with the level of drug resistance achieved by the LZ cell lines studied. DOX concentration-response experiments revealed that vesicle formation exhibited a biphasic relationship, with an initial rapid increase followed by a plateau where no further increase was observed. Time-course studies in LZ-100 cells revealed that the maximum number of DOX-containing vesicles per cell occurred 3-4 hr following initiation of DOX treatment. Radiation exposure (10 Gy) immediately preceding DOX treatment decreased the number of vesicles formed in LZ-100 cells by more than one-half and altered the subcellular distribution of DOX from an almost exclusively cytoplasmic to a homogeneous nuclear/cytoplasmic distribution. This redistribution was not a result of radiation inhibition of P-gp efflux. The inhibitory effect of radiation on vesicle formation increased with increasing radiation dose up to 10 Gy. Drug-containing vesicles were also observed in LZ-100 cells following exposure to mitoxantrone or daunorubicin (to which LZ-100 cells are also resistant), but fewer vesicles were observed than with DOX. These studies demonstrate that the drug sequestration phenomenon (i) occurs in cells exhibiting widely different levels of drug resistance, (ii) correlates with the level of drug resistance in LZ cell lines, (iii) occurs rapidly following exposure to DOX, mitoxantrone, or daunorubicin, and (iv) can be inhibited by irradiation.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7914406

Sognier, M A; Zhang, Y; Eberle, R L; Sweet, K M; Altenberg, G A; Belli, J A

1994-07-19

276

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

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

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

2005-01-01

277

Emr, an Escherichia coli locus for multidrug resistance.  

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An Escherichia coli chromosomal DNA fragment cloned on a multicopy plasmid conferred resistance to carbonylcyanide m-chlorophenylhydrazone, nalidixic acid, and a number of other toxic compounds. The sequence of the cloned emr locus located at minute 57.5 of the chromosome revealed two open reading frames, emrA and emrB. emrB encodes a highly hydrophobic 56.2-kDa peptide, with 14 potential alpha-helices to span the inner membrane. The peptide is homologous to QacA, a multidrug-resistant pump f...

Lomovskaya, O.; Lewis, K.

1992-01-01

278

Gene expression in the development of multidrug resistance  

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Molecular processes involved in the development of malignancy have a role to play in the establishment of the multidrug resistant (MDR) phenotype. Analysis of oncogene expression, at the mRNA level using RT-PCR, in resistant variants of the human squamous lung cell line, DLKP, and the human ovarian carcinoma cell line, OAW42, was carried out in this study. Analysis of gene expression, by RT-PCR and in situ hybridisation, on tumours from breast cancer patients was also carried out on fresh and...

Nicamhlaoibh, Roisin

1997-01-01

279

Functional expression of yeast artificial chromosome-human multidrug resistance genes in mouse cells.  

Science.gov (United States)

Multidrug resistance (MDR) genes, which are ATP-binding cassette family genes, encode the cell surface glycoprotein, P-glycoprotein, which functions as an energy-dependent drug efflux pump. Two relevant human genes, PGY1 and PGY3, are located on human chromosome 7, and three relevant mouse genes, mdr1a, mdr1b, and mdr2, are located on mouse chromosome 5. An LMD1 cell line was established after the transfer of a 580-kb yeast artificial chromosome (YAC) clone carrying the human MDR locus into mouse L cells; the cell line was shown to have stably integrated YAC DNA in an apparent intact form. Using LMD1 cells as the parental cell line, five vincristine-resistant sublines, designated LMD1-V50, LMD1-V100, LMD1-V200, LMD1-V500, and LMD1-V1000, were isolated by exposure to increasing concentrations of the drug. LMD1-V50, LMD1-V100, LMD1-V200, LMD1-V500, and LMD1-V1000 showed 3-, 7-, 13-, 45-, and 110-fold higher resistance to the cytotoxic effects of vincristine, respectively, than their parental counterpart, LMD1. Immunofluorescence, Western blot, and Northern blot analyses revealed that the human PGY1 gene or its product was overexpressed, accompanied by gene amplification. The human PGY3 gene was also overexpressed in the LMD1-V20, LMD1-V100, and LMD1-V1000 cell lines. Southern blot and fluorescence in situ hybridization (FISH) analyses demonstrated that although essentially the entire YAC DNA was integrated in mouse genome and amplified, the endogenous mouse mdr genes were not amplified in these drug-resistant cell lines. Similar results were obtained by the analyses of vincristine-resistant cell lines isolated from four independent subclones of LMD1 cells. Thus, in contrast to their mouse counterparts, the integrated human MDR genes retained susceptibility to both gene activation and amplification, during the selection of drug-resistant mouse cell lines. The possibility that transferred YACs may retain regulatory properties observed in the cells of origin, and may have a chromatin structure that favors augmented expression, is discussed. PMID:8593612

Kusaba, H; Kohno, K; Asakuno, K; Kuwano, M; Okumura, K; Green, E D; Schlessinger, D; Wada, M

1995-10-01

280

Tuberculosis Multidrogoresistente / Multidrug-resistant tuberculosis  

Scientific Electronic Library Online (English)

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

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

 
 
 
 
281

New Antibiotics in Development Against Multidrug-Resistant Bacteria  

Directory of Open Access Journals (Sweden)

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

Soner Yýlmaz

2013-05-01

282

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

283

Profiles of Multidrug Resistance Protein-1 in the Peripheral Blood Mononuclear Cells of Patients with Refractory Epilepsy  

Science.gov (United States)

Background About one third of patients with epilepsy become refractory to therapy despite receiving adequate medical treatment, possibly from multidrug resistance. P-glycoprotein, encoded by multidrug resistance protein-1 (MDR1) gene, at the blood brain barrier is considered as a major factor mediating drug efflux and contributing to resistance. Given that peripheral blood mononuclear cells (PBMNCs) express MDR1, we investigated a MDR1 status of PBMNCs in various subsets of epilepsy patients and demonstrated their association with clinical characteristics. Methodology/Principal Findings Clinical and MDR1 data were collected from 140 patients with epilepsy, 30 healthy volunteers, and 20 control patients taking anti-epileptic drugs. PBMNCs were isolated, and basal MDR1 levels and MDR1 conformational change levels were measured by flow cytometry. MDR1 profiles were analyzed according to various clinical parameters, including seizure frequency and number of medications used in epilepsy patients. Epilepsy patients had a higher basal MDR1 level than non-epilepsy groups (p<0.01). Among epilepsy patients, there is a tendency for higher seizure frequency group to have higher basal MDR1 level (p?=?0.059). The MDR1 conformational change level was significantly higher in the high-medication-use group than the low-use group (p?=?0.028). Basal MDR1 (OR?=?1.16 [95% CI: 1.060–1.268]) and conformational change level (OR?=?1.11 [95% CI: 1.02–1.20]) were independent predictors for seizure frequency and number of medications, respectively. Conclusions/Significance The MDR1 profile of PBMNCs is associated with seizure frequency and medication conditions in patients with epilepsy.

Chu, Kon; Lee, Soon-Tae; Jeon, Daejong; Park, Kyung-Il; Moon, Hye-Jin; Kim, Hyeyun; Kim, Sunghun; Lee, Sang Kun; Roh, Jae-Kyu

2012-01-01

284

Risk factors for acquired multidrug-resistant tuberculosis  

Directory of Open Access Journals (Sweden)

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

Barroso Elizabeth Clara

2003-01-01

285

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 patients. To optimise cellular transport characteristics, a number of chemical families that have been found to be substrates of Pgp and other drug efflux pumps, will be investigated. In the first instance, a series of drugs based on the flavonol natural product, Quercetin will be developed, screened for MDR and radiolabelled with PET and SPECT isotopes. Quercetin and related flavonol derivatives have been selected for this project because of their moderate to good affinity for Pgp. With the assistance of molecular modeling and in vitro studies, structural modification will be undertaken to improve the specificity and affinity for PgP. This generic structure also offers the flexibility to prepare a wide range of molecules that are readily suitable for halogenation with either Iodine-123 or F-18 for radiopharmaceutical development. Finally these phenolic type of molecules based on Quercetin are relatively less toxic than equivalent drugs. In this proposal an extensive research program is required to develop specific drugs for the different efflux pumps present in the body, which represent multi drug resistance. A successful outcome is critically dependent on the initial synthesis of a large number of compounds for screening. The combined effort of the three institutions will boost resources significantly to a critical level required to competitively produce successful outcomes in the project. Optimisation studies on derivatives of these flavonols will be made in parallel with the assistance of in vitro studies by measuring the binding of compounds to the ATP sites of Pgp. An extensive in vitro screening program has been established in Paris, prior to radiolabelling and in vivo evaluation. Structural optimisation and attachment of radionuclides to promising molecular targets will be explored using molecular modelling. Initially computational chemistry using Sybyl will be undertaken to develop a pharmacophore and to assist with the incorporation of the radionuclide in the appropriate position. In vivo evaluation will be undertaken in specific animal models both at the University of Tours in France as well as at the Sydney Cancer Centre in Australia. PET functional imaging studies may be undertaken on successful candidates at the SHFJ in Orsay, France whilst SPECT imaging will be undertaken in both Tours and in Sydney. In addition to intellectual property and potential commercial product(s), specific PET or SPECT radiopharmaceuticals can provide valuable information on the assessment of MDR in cancer patients through functional, non-invasive, imaging and therefore make significant contributions to the understanding of MDR. Scientific and clinical researchers from both countries identified the

2002-04-29

286

Delamanid improves outcomes and reduces mortality in multidrug-resistant tuberculosis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Multidrug-resistant and extensively drug-resistant tuberculosis (TB) are associated with worse treatment outcomes for patients, including higher mortality, than for drug-sensitive tuberculosis. Delamanid (OPC-67683) is a novel anti-TB medication with demonstrated activity against multidrug-resistant disease.

Skripconoka, Vija; Danilovits, Manfred; Pehme, Lea; Tomson, Tarmo; Skenders, Girts; Kummik, Tiina; Cirule, Andra; Leimane, Vaira; Kurve, Anu; Levina, Klavdia; Geiter, Lawrence J.; Manissero, Davide; Wells, Charles D.

2013-01-01

287

Diversity and evolution of the small multidrug resistance protein family  

Directory of Open Access Journals (Sweden)

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

Turner Raymond J

2009-06-01

288

A tamoxifen derivative, N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine, selectively targets P-glycoprotein-positive multidrug resistant Chinese hamster cells.  

Science.gov (United States)

DPPE, a tamoxifen derivative with antihistamine activity, was previously shown to potentiate the toxicity of chemotherapeutic drugs. Recently, a Phase III clinical study using doxorubicin with DPPE demonstrated significant increase in the overall survival of breast cancer patients. In this study we examined the effects of DPPE alone on the growth of drug sensitive and P-gp positive CHO cell line. Our results demonstrate DPPE is selectively toxic to P-gp positive cells and the sensitivity to DPPE alone correlated with the levels of P-gp expression. Moreover, in MDR cells, DPPE-induced apoptosis was significantly reduced with Bcl2 overexpression and in the presence of P-gp ATPase inhibitor, PSC833. Furthermore, knockdown of P-gp expression in MDR cells with P-gp-siRNA reversed DPPE sensitivity and increased their sensitivity to doxorubicin and taxol but not to cisplatin. The addition of DPPE to membrane fractions led to dose-dependent increase in P-gp ATPase that was inhibited with PSC833. Moreover, incubation of P-gp positive cells with DPPE led to a significant increase in superoxide levels and a drop in cellular ATP and GSH pools that were reversible with inhibitors of P-gp ATPase. The combined presence of DPPE and the mitochondria electron transport complex III inhibitor, antimycin A, synergized in their effects on the growth of MDR cells but had no effect on the growth of parental drug sensitive cells. Collectively, the results of this study provide a possible mechanism that may be relevant to the clinical results of DPPE in breast cancer trial and demonstrates DPPE as P-gp collateral sensitivity drug. PMID:24821111

Georges, Elias; Lian, Jing; Laberge, Remi

2014-07-15

289

Effect of P-glycoprotein on flavopiridol sensitivity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2001-01-01

290

Changes in Multidrug Resistance of Enteric Bacteria following an Intervention To Reduce Antimicrobial Resistance in Dairy Calves ?  

Science.gov (United States)

An intervention study was conducted to determine whether discontinuing the feeding of milk replacer medicated with oxytetracycline and neomycin to preweaned calves reduced antimicrobial resistance in Salmonella, Campylobacter, and Escherichia coli bacteria. Results demonstrated that the intervention did reduce multidrug resistance in these bacteria but that other factors also influenced multidrug resistance.

Kaneene, John B.; Warnick, Lorin D.; Bolin, Carole A.; Erskine, Ronald J.; May, Katherine; Miller, RoseAnn

2009-01-01

291

Inhibition of the Emergence of Ciprofloxacin Resistance in Streptococcus pneumoniae by the Multidrug Efflux Inhibitor Reserpine  

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Recent evidence supports the contribution of a multidrug efflux mechanism to fluoroquinolone resistance in Streptococcus pneumoniae. In this paper I show that reserpine, an inhibitor of multidrug transporters in gram-positive bacteria, dramatically suppresses the in vitro emergence of ciprofloxacin-resistant variants of S. pneumoniae, suggesting that the combination of a fluoroquinolone with an inhibitor of multidrug transport may help preserve the efficacy of this class of antibiotics.

Markham, Penelope N.

1999-01-01

292

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

International Nuclear Information System (INIS)

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

2011-05-06

293

Moxidectin has a lower neurotoxic potential but comparable brain penetration in P-glycoprotein-deficient CF-1 mice compared to ivermectin.  

Science.gov (United States)

The anti-parasitic drugs ivermectin (IVM) and moxidectin (MOX) normally show limited brain penetration in vertebrates because of effective drug efflux at the blood-brain barrier by P-glycoprotein, encoded by the multi-drug resistance (MDR1) gene. However, dogs with homozygous nt230(del4) mutation in the MDR1 gene do not express a functionally active P-glycoprotein and show increased brain penetration of these drugs, resulting in neurological toxicity to different degrees. Thus, whereas IVM provokes neurological toxicity at 0.1 mg/kg, MOX is tolerated at this dosage. To investigate whether this difference is attributable to lower brain penetration of MOX in the absence of P-glycoprotein or to their neurotoxic potential, we applied IVM and MOX to P-glycoprotein-deficient CF-1 mice and comparatively analysed the absolute drug concentrations in the brain. Furthermore, we quantified drug-induced neurotoxicity by measuring the walking performance of the mice on a rotarod setup. We found that at a dosage of 0.2 mg/kg, representing 0.23 ?mol/kg IVM and 0.31 ?mol/kg MOX, the absolute drug concentrations in the brain were comparable with 100.8 pmol/g and 140.2 pmol/g, respectively. However, MOX induced the same degree of neurotoxicosis at the higher dosage of 1.09 ?mol/kg (0.7 mg/kg) compared with IVM at 0.40 ?mol/kg (0.35 mg/kg), demonstrating the 2.7-fold lower neurotoxic potential of MOX compared to IVM. This could be explained by a lower binding affinity or lower intrinsic activity of MOX at the relevant central nervous system receptors compared with IVM. PMID:22834856

Janko, C; Geyer, J

2013-06-01

294

Tuberculosis: burning issues: multidrug resistance and HIV-coinfection.  

Science.gov (United States)

Tuberculosis is an infection of respiratory tract and Mycobacterium tuberculosis is the causative agent. Multidrug resistance and HIV-coinfection are the burning issues for tuberculosis. The management of drug resistance to tuberculosis is the necessity of the day so by taking effective and controlled measures and giving high doses of 2nd line drugs, we can minimize the death rate in TB. For the HIV-related TB infection, it is necessary to treat TB infection first so that effectiveness of antiretroviral therapy may not be altered and the transmission of M. tuberculosis to other healthy individuals of community could be prevented. All HIV positive individuals who are at a greater risk of acquiring TB infection, either due to suppressed immune system or unhealthy circumstances, must be investigated and if indicated must be treated effectively at immediate basis so that latent TB infection may not progress to active TB. PMID:22421086

Janbaz, Khalid Hussain; Qadir, M Imran; Ahmad, Bashir; Sarwar, Abida; Yaqoob, Nazish; Masood, Muhammad Irfan

2012-11-01

295

Functional imaging of multidrug resistance in an orthotopic model of osteosarcoma using {sup 99m}Tc-sestamibi  

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The purpose of this work was the development of an orthotopic model of osteosarcoma based on luciferase-expressing tumour cells for the in vivo imaging of multidrug resistance (MDR) with {sup 99m}Tc-sestamibi. Doxorubicin-sensitive (143B-luc{sup +}) and resistant (MNNG/HOS-luc{sup +}) osteosarcoma cell lines expressing different levels of P-glycoprotein and carrying a luciferase reporter gene were inoculated into the tibia of nude mice. Local tumour growth was monitored weekly by bioluminescence imaging and X-ray. After tumour growth, a {sup 99m}Tc-sestamibi dynamic study was performed. A subset of animals was pre-treated with an MDR inhibitor (PSC833). Images were analysed for calculation of {sup 99m}Tc-sestamibi washout half-life (t{sub 1/2}), percentage washout rate (%WR) and tumour/non-tumour (T/NT) ratio. A progressively increasing bioluminescent signal was detected in the proximal tibia after 2 weeks. The t{sub 1/2} of {sup 99m}Tc-sestamibi was significantly shorter (p < 0.05) in drug-resistant MNNG/HOS-luc{sup +} tumours (t{sub 1/2} = 87.3 {+-} 15.7 min) than in drug-sensitive 143B-luc{sup +} tumours (t{sub 1/2} = 161.0 {+-} 47.4 min) and decreased significantly with PSC833 (t{sub 1/2} = 173.0 {+-} 24.5 min, p < 0.05). No significant effects of PSC833 were observed in 143B-luc{sup +} tumours. The T/NT ratio was significantly lower (p < 0.05) in MNNG/HOS-luc{sup +} tumours than in 143B-luc{sup +} tumours at early (1.55 {+-} 0.22 vs 2.14 {+-} 0.36) and delayed times (1.12 {+-} 0.11 vs 1.62 {+-} 0.33). PSC833 had no significant effects on the T/NT ratios of either tumour. The orthotopic injection of tumour cells provides an animal model suitable for functional imaging of MDR. In vivo bioluminescence imaging allows the non-invasive monitoring of tumour growth. The kinetic analysis of {sup 99m}Tc-sestamibi washout provides information on the functional activity of MDR related to P-glycoprotein expression and its pharmacological inhibition in osteosarcoma. (orig.)

Gomes, Celia M.F. [Leiden University Medical Center, Department of Radiology, Section of Nuclear Medicine, Leiden (Netherlands); Institute of Biophysics/Biomathematics, IBILI - Faculty of Medicine, Coimbra (Portugal); Welling, Mick; Pauwels, Ernest K.J. [Leiden University Medical Center, Department of Radiology, Section of Nuclear Medicine, Leiden (Netherlands); Que, Ivo; Henriquez, Niek V.; Pluijm, Gabri van der [Leiden University Medical Center, Department of Endocrinology, Leiden (Netherlands); Romeo, Salvatore; Hogendoorn, Pancras C.W.; Cleton-Jansen, Anne M. [Leiden University Medical Center, Department of Pathology, Leiden (Netherlands); Abrunhosa, Antero J.; Botelho, M.F. [Institute of Biophysics/Biomathematics, IBILI - Faculty of Medicine, Coimbra (Portugal)

2007-11-15

296

Reversal effect of bufalin on multidrug resistance in human hepatocellular carcinoma BEL-7402/5-FU cells.  

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Multidrug resistance (MDR) is a major obstacle to chemotherapy in patients with hepatocellular carcinoma (HCC). To overcome MDR and improve chemotherapeutic efficacy, novel reversal agents with higher efficacy and lower toxicity are urgently needed for HCC. The present study was designed to examine the potential reversal activity of bufalin, a toxic ligand isolated from the traditional Chinese medicine 'Chansu' and to elucidate the possible related mechanisms. A multidrug-resistant HCC cell line, BEL-7402/5-FU, was used as the cell model. The working concentration of bufalin as an effective reversal agent, and the cell viability in the reversal experiments were determined by MTT assay. The effects of bufalin at a non-cytotoxic dose on cell cycle distribution, apoptosis and drug efflux pump activity were measured by flow cytometry. Qualitative observation of apoptosis was also carried out by confocal microscopy. Furthermore, the effects of bufalin on the expression of potential genes involved in MDR of BEL-7402/5-FU cells, including thymidylate synthase (TS), P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), B-cell lymphoma-extra large (Bcl-xL) and Bcl-2-associated X protein (Bax), were determined using real-time PCR and western blot analysis. The results showed that bufalin at a concentration of 1 nM enhanced the chemosensitivity of BEL-7402/5-FU cells to 5-FU with a reversal fold of 3.8 which was similar to that of 1 µM verapamil. Bufalin significantly arrested the cell cycle at the G?/G? phase, induced apoptosis through an increase in the Bax/Bcl-xL ratio, inhibited drug efflux pump activity via downregulation of MRP1, and reduced the expression of TS in BEL-7402/5-FU cells. The present study revealed that bufalin effectively reversed MDR in BEL-7402/5-FU cells through multiple pathways. The combination of bufalin with cytotoxic drugs may serve as a promising strategy for the chemotherapy of HCC. PMID:24173654

Gu, Wei; Liu, Long; Fang, Fan-Fu; Huang, Feng; Cheng, Bin-Bin; Li, Bai

2014-01-01

297

Overexpression of cyclooxygenase-2 in childhood ependymomas: role of COX-2 inhibitor in growth and multi-drug resistance in vitro.  

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The management of ependymomas remains one of the most frustrating issues in pediatric neuro-oncology. Gross total resection is not always possible, and intensive chemotherapy and craniospinal radiotherapy have made no clear advances. Moreover, the chemoresistance of ependymomas may be explained by the expression of membrane transport molecule P-glycoprotein (P-gp). In this study the expression of cyclooxygenase 2 (COX-2) and the role of the specific COX-2 inhibitor NS-398 in growth and multi-drug resistance of ependymomas were investigated. COX-2 protein expression was assessed in 19 ependymomas immunohistochemically, and the effect of NS-398 on growth and multi-drug resistance was investigated using two primary cultured ependymoma cell lines. COX-2 protein expression was observed in 15 (79%) of the 19 ependymomas. NS-398 was found to reduce the proliferation of monolayer cell cultures in a dose- and time-dependent manner and to induce apoptosis and lower bcl-2 protein levels. After NS-398 treatment, Western blotting showed reduced P-gp expression and a rhodamine 123 efflux assay demonstrated a significant decrease in P-gp activity. Our findings demonstrate that COX-2 is overexpressed in ependymomas and that NS-398 is able to induce apoptosis and suppress P-gp expression and activity. PMID:15254709

Kim, Seung-Ki; Lim, Su-Young; Wang, Kyu-Chang; Kim, Young-Yim; Chi, Je G; Choi, Yoon La; Shin, Hyung Jin; Cho, Byung-Kyu

2004-08-01

298

BBA, a Synthetic Derivative of 23-hydroxybutulinic Acid, Reverses Multidrug Resistance by Inhibiting the Efflux Activity of MRP7 (ABCC10)  

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Natural products are frequently used for adjuvant chemotherapy in cancer treatment. 23-O-(1,4'-bipiperidine-1-carbonyl) betulinic acid (BBA) is a synthetic derivative of 23-hydroxybutulinic acid (23-HBA), which is a natural pentacyclic triterpene and the major active constituent of the root of Pulsatillachinensis. We previously reported that BBA could reverse P-glycoprotein (P-gp/ABCB1)-mediated multidrug resistance (MDR). In the present study, we investigated whether BBA has the potential to reverse multidrug resistance protein 7 (MRP7/ABCC10)-mediated MDR. We found that BBA concentration-dependently enhanced the sensitivity of MRP7-transfected HEK293 cells to paclitaxel, docetaxel and vinblastine. Accumulation and efflux experiments demonstrated that BBA increased the intracellular accumulation of [3H]-paclitaxel by inhibiting the efflux of [3H]-paclitaxel from HEK293/MRP7 cells. In addition, immunoblotting and immunofluorescence analyses indicated no significant alteration of MRP7 protein expression and localization in plasma membranes after treatment with BBA. These results demonstrate that BBA reverses MRP7-mediated MDR through blocking the drug efflux function of MRP7 without affecting the intracellular ATP levels. Our findings suggest that BBA has the potential to be used in combination with conventional chemotherapeutic agents to augment the response to chemotherapy.

Chen, Jun-Jiang; Patel, Atish; Sodani, Kamlesh; Xiao, Zhi-Jie; Tiwari, Amit K.; Zhang, Dong-Mei; Li, Ying-Jie; Yang, Dong-Hua; Ye, Wen-Cai; Chen, Si-Dong; Chen, Zhe-Sheng

2013-01-01

299

Characterization and Identification of Multidrug Resistant Bacteria from Some Egyptian Patients  

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

Seham Abdel-Shafi

2013-01-01

300

Influence of Intermittent Hypoxia on Myocardial and Hepatic P-glycoprotein Expression  

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Study Objective The purpose of this study was to determine if intermittent hypoxia that mimics obstructive sleep apnea would upregulate myocardial and hepatic p-glycoprotein protein and Abcb1a/Abcb1b mRNA expression. Design Prospective, randomized, blinded, parallel designed animal study Setting University Research Laboratory Participants Thirty adult, male Sprague-Dawley rats Intervention We assigned rats to either two weeks of intermittent hypoxia similar to sleep apnea (N=12) or control treatment (N=18) (no hypoxia). Measurements and Main Results After intermittent hypoxia or normoxia exposure, rats were anesthetized and the heart and liver were harvested and small samples were taken from the left ventricle (heart) and the liver for analysis. P-glycoprotein protein expression was measured by Western blotting, while Abcb1a/Abcb1b mRNA expression (genes that code for P-glycoprotein) was assessed by real-time polymerase chain reaction. Band density of myocardial (but not hepatic) p-glycoprotein protein expression (standardized by ?-actin) was higher in hypoxic compared to control rats (p=0.03). Quantitative polymerase chain reaction revealed that myocardial and hepatic Abcb1a and myocardial Abcb1b mRNA expression were increased in hypoxic rats compared to controls. Conclusions Myocardial P-glycoprotein expression and myocardial and hepatic Abcb1a mRNA expression are significantly increased by two weeks of intermittent hypoxia. Hypoxia-induced increases in p-glycoprotein expression may partially explain drug resistant cardiovascular disease in OSA.

Dopp, John M.; Moran, John J.; Abel, Nicole J.; Wiegert, Nicholas A.; Cowgill, John B.; Olson, E. Burt; Sims, J. Jason

2010-01-01

 
 
 
 
301

Etoposide-resistance in the multidrug-resistant LZ-8 cells.  

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The multidrug-resistant LZ-8 cells were found to exhibit marked resistance to etoposide compared to wild-type, parental V79 cells. The multidrug resistant phenotype did not significantly contribute to this etoposide-resistance. Following exposure of LZ-8 cells and V79 cells to equivalent concentrations of etoposide, there was a dramatic reduction in the number of etoposide-induced stabilized DNA-topoisomerase II complexes in the LZ-8 cells compared to V79 cells, however, this reduction was not found when nuclei isolated from LZ-8 and V79 cells were exposed to equivalent concentrations of etoposide. These results suggest that cytoplasmic factors are involved in the etoposide-resistance of LZ-8 cells. PMID:7866304

Liengswangwong, V; Haddock, M G; Sognier, M A; Belli, J A; Bonner, J A

1994-10-01

302

Chemoprevention and inhibition of P-glycoprotein in cancer cells by Chinese medicinal herbs.  

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Many of the herbal extracts used in the Chinese clinical medical routine inhibit the growth of tumor cells. In the present work, extracts of 12 selected herbs were prepared with methanol, chloroform, ethyl acetate and water, and the effects of these on the multidrug resistance (MDR) and P-glycoprotein of mouse lymphoma cells transfected with the human mdr1 gene and on a human lung alveolar epithelial cell line were investigated. The extracts were tested for antiproliferative effects, and the reversal of MDR in mouse lymphoma cells. The possible chemopreventive effect of the chloroform extracts was studied on the expression of cytomegalovirus (CMV) immediate-early (IE) antigen in human lung cancer cells (A549). The antimicrobial effects of the extracts were tested on some representative micro-organisms. Certain of the chloroform extracts of the plant materials were the most effective compounds on the reversal of MDR. Two of the chloroform extracts enhanced the antiproliferative effect of doxorubicin on MDR mouse lymphoma cells. The selected extracts did not show any antibacterial effect with the agar diffusion method. Certain chloroform extracts decreased the intermediate IE antigen expression of CMV in A459 cells. PMID:18690658

Engi, Helga; Hohmann, Judit; Gang, Geng; Pusztai, Rozália; Rédei, Dóra; Kovács, Orsolya; Schelz, Zsuzsanna; Molnár, Joseph

2008-12-01

303

The network of P-glycoprotein and microRNAs interactions.  

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Overexpression of P-glycoprotein (P-gp) contributes to the multidrug resistance (MDR) phenotype found in many cancer cells. P-gp has been identified as a promising molecular target, although attempts to find successful therapies to counteract its function as a drug efflux pump have largely failed to date. Apart from its role in drug efflux, P-gp may have other cellular functions such as being involved in apoptosis, and is found in various locations in the cell. Its expression is highly regulated, namely by microRNAs (miRNAs or miRs). In addition, P-gp may regulate the expression of miRs in the cell. Furthermore, both P-gp and miRs may be found in microvesicles or exosomes and may be transported to neighboring, drug-sensitive cells. Here, we review this current issue together with recent evidence of this network of interactions between P-gp and miRs. PMID:24122334

Lopes-Rodrigues, Vanessa; Seca, Hugo; Sousa, Diana; Sousa, Emília; Lima, Raquel T; Vasconcelos, M Helena

2014-07-15

304

A multifaceted analysis of HIV-1 protease multidrug resistance phenotypes  

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Full Text Available Abstract Background Great strides have been made in the effective treatment of HIV-1 with the development of second-generation protease inhibitors (PIs that are effective against historically multi-PI-resistant HIV-1 variants. Nevertheless, mutation patterns that confer decreasing susceptibility to available PIs continue to arise within the population. Understanding the phenotypic and genotypic patterns responsible for multi-PI resistance is necessary for developing PIs that are active against clinically-relevant PI-resistant HIV-1 variants. Results In this work, we use globally optimal integer programming-based clustering techniques to elucidate multi-PI phenotypic resistance patterns using a data set of 398 HIV-1 protease sequences that have each been phenotyped for susceptibility toward the nine clinically-approved HIV-1 PIs. We validate the information content of the clusters by evaluating their ability to predict the level of decreased susceptibility to each of the available PIs using a cross validation procedure. We demonstrate the finding that as a result of phenotypic cross resistance, the considered clinical HIV-1 protease isolates are confined to ~6% or less of the clinically-relevant phenotypic space. Clustering and feature selection methods are used to find representative sequences and mutations for major resistance phenotypes to elucidate their genotypic signatures. We show that phenotypic similarity does not imply genotypic similarity, that different PI-resistance mutation patterns can give rise to HIV-1 isolates with similar phenotypic profiles. Conclusion Rather than characterizing HIV-1 susceptibility toward each PI individually, our study offers a unique perspective on the phenomenon of PI class resistance by uncovering major multidrug-resistant phenotypic patterns and their often diverse genotypic determinants, providing a methodology that can be applied to understand clinically-relevant phenotypic patterns to aid in the design of novel inhibitors that target other rapidly evolving molecular targets as well.

Doherty Kathleen M

2011-12-01

305

An enhanced ability for transforming adriamycin into a noncytotoxic form in a multidrug-resistant cell line (LZ-8).  

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Multidrug-resistant LZ-8 cells are 9000-fold more resistant to Adriamycin (ADRM) exposure than wild-type V79 cells. To understand more about the mechanisms producing such high level resistance, we tested whether LZ-8 cells inactivate ADRM toxicity to a greater extent than wild-type V79 cells. ADRM was recovered from (1) culture media of wild-type V79 and ADRM-resistant LZ-8 cells; (2) V79 and LZ-8 cells; and (3) LZ-8 cell plasma membrane, and the cytotoxicity was determined by treating V79 cells for 1 hr with a known concentration of the recovered ADRM. ADRM obtained from LZ-8 cells or its culture medium exhibited less cytotoxicity than that recovered from V79 cells or its culture medium. ADRM extracted from LZ-8 cell plasma membrane was noncytotoxic. HPLC analysis revealed that the extracted ADRM was structurally changed compared to stock ADRM. The retention time in the column was 7 min for stock ADRM, and 23 min for the recovered ADRM. Thus, LZ-8 cells have an increased ability to transform ADRM into a noncytotoxic form compared to wild-type V79 cells. This transformation involves structural conversion into a previously unidentified ADRM metabolite. The greatly increased survival of LZ-8 cells compared to V79 cells after ADRM treatment is due to at least two mechanisms: (1) an enhanced ability to inactivate the cytotoxicity of ADRM, and (2) increased drug efflux resulting from the amplification and overexpression of the pgp 1 gene in these cells. Our results suggest the possibility that P-glycoprotein participates in drug binding/inactivation in addition to serving as a drug efflux pump. PMID:1360214

Zhang, Y; Sweet, K M; Sognier, M A; Belli, J A

1992-11-01

306

Establishment of a Multidrug Resistance Cell Line A549/cDDP of Human Lung Adenocarcinoma and Expression Analysis of Multidrug Resistance-Associated Genes  

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Full Text Available Background and objective It has been proven that chemotherapy failure caused by multidrug resistance in lung tumor cells is the main cause for the patient's survival rate. The aim of this study is to establish a multidrug resistance cell line of human lung adenocarcinoma and study the mechanism of multidrug resistance. Methods Human lung adenocarcinoma cell line A549 was induced to multidrug resistance cell line A549/cDDP by intermittentadministration of high dose of cisplatin (cDDP. The multidrug resistance was detected by using MTT assay. The levels of expression of MDR-1 gene-coded P-glycoportein (P-gp, multidrug resistance-associated protein (MRP, and GSH/GST were examined by flow cytometric assay. The levels of expression of MDR and MRP gene were also detected by RTPCR in both A549/cDDP and A549 cell lines. Results A549/cDDP was resistant to many anti-tumor agents. The IC50 of A549/cDDP was 16.87 times higher than that of A549. The expressions of P-gp and MRP in A549/cDDP were increased significantly to (70.5±4.9? and (29.4±2.9?, respectively, vs (42.4±5.6? and (21.4±3.5? in A549. There was no difference of the GSH/GST expression between A549/cDDPand A549 cells. Conclusion A549/cDDP is a model with multidrug resistance and the levels of MDR and MRP mRNA expressions are remarkably higher in A549/cDDP than those in A549.

Yongcheng PAN

2009-03-01

307

Overview of P-glycoprotein inhibitors: a rational outlook  

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

Kale Mohana Raghava Srivalli

2012-09-01

308

Epstein-Barr virus-negative aggressive natural killer-cell leukaemia with high P-glycoprotein activity and phosphorylated extracellular signal-regulated protein kinases 1 and 2  

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Aggressive natural killer-cell leukaemia (ANKL) is a rare type of disease with fulminant course and poor outcome. The disease is more prevalent among Asians than in other ethnic groups and shows strong association with Epstein-Barr virus (EBV) and P-glycoprotein (P-gp) expression associated with multidrug resistance. Here we present a case of a 47 year old Caucasian female with a prior medical history of azathioprine treated ulcerative colitis who developed EBV-negative form of ANKL. The pati...

2012-01-01

309

Inhibitory effects of terpenoids on multidrug resistance-associated protein 2- and breast cancer resistance protein-mediated transport.  

Science.gov (United States)

The possibility of interactions between natural products/supplements and conventional prescription medicines is one of the most important issues in pharmacotherapeutic safety. Recently, we reported that some terpenoids such as (R)-(+)-citronellal and glycyrrhetic acid, which are present in herbal medicines, can act as inhibitors of P-glycoprotein (MDR1/ABCB1). In the present study, the effects of seven terpenoids on multidrug resistance-associated protein 2 (MRP2/ABCC2) and breast cancer resistance protein (BCRP/ABCG2)-mediated transport were investigated in vitro. Membrane vesicles were prepared from MRP2 cDNA transfected Sf9 cells derived from pupal ovarian tissue of Spodoptera frugiperda, a fall armyworm, and BCRP cDNA transfected LLC-PK1 cells derived from porcine kidney. MRP2- or BCRP-mediated efflux transport was measured as ATP-dependent accumulation of [(3)H]estradiol 17-beta-d-glucuronide (E(2)17betaG) into membrane vesicles collected by a rapid filtration technique. The effects of (R)-(+)-citronellal, (S)-(-)-beta-citronellol, alpha-terpinene, terpinolene, (-)-beta-pinene, abietic acid, and glycyrrhetic acid on the intravesicular accumulation of [(3)H]E(2)17betaG were examined. Large decreases in the [(3)H]E(2)17betaG accumulation into vesicles from MRP2-overexpressing Sf9 cells were observed in the presence of glycyrrhetic acid and abietic acid, and their IC(50) values were about 20 and 51 microM, respectively. [(3)H]E(2)17betaG accumulation into vesicles from BCRP-overexpressing LLC-PK1 cells was suppressed by only glycyrrhetic acid, with an IC(50) value of about 39 microM. Other terpenoids used in this study did not alter the ATP-dependent accumulation of [(3)H]E(2)17betaG. These findings suggest that glycyrrhetic acid and abietic acid can potently inhibit MRP2- or BCRP-mediated membrane transport and may interact with their substrates in pharmacokinetic processes. PMID:18436619

Yoshida, Naoko; Takada, Tappei; Yamamura, Yoshikazu; Adachi, Isao; Suzuki, Hiroshi; Kawakami, Junichi

2008-07-01

310

Multidrug resistance 1 gene polymorphisms may determine Crohn's disease behavior in patients from Rio de Janeiro  

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OBJECTIVES: Conflicting data from studies on the potential role of multidrug resistance 1 gene polymorphisms in inflammatory bowel disease may result from the analysis of genetically and geographically distinct populations. Here, we investigated whether multidrug resistance 1 gene polymorphisms are associated with inflammatory bowel diseases in patients from Rio de Janeiro. METHODS: We analyzed 123 Crohn's disease patients and 83 ulcerative colitis patients to determine the presence of the multidrug resistance 1 gene polymorphisms C1236T, G2677T and C3435T. In particular, the genotype frequencies of Crohn's disease and ulcerative colitis patients were analyzed. Genotype-phenotype associations with major clinical characteristics were established, and estimated risks were calculated for the mutations. RESULTS: No significant difference was observed in the genotype frequencies of the multidrug resistance 1 G2677T/A and C3435T polymorphisms between Crohn's disease and ulcerative colitis patients. In contrast, the C1236T polymorphism was significantly more common in Crohn's disease than in ulcerative colitis (p?=?0.047). A significant association was also found between the multidrug resistance 1 C3435T polymorphism and the stricturing form of Crohn's disease (OR: 4.13; p?=?0.009), whereas no association was found with penetrating behavior (OR: 0.33; p?=?0.094). In Crohn's disease, a positive association was also found between the C3435T polymorphism and corticosteroid resistance/refractoriness (OR: 4.14; p?=?0.010). However, no significant association was found between multidrug resistance 1 gene polymorphisms and UC subphenotypic categories. CONCLUSION: The multidrug resistance 1 gene polymorphism C3435T is associated with the stricturing phenotype and an inappropriate response to therapy in Crohn's disease. This association with Crohn's disease may support additional pathogenic roles for the multidrug resistance 1 gene in regulating gut-microbiota interactions and in mediating fibrosis. Understanding the effects of several drugs associated with multidrug resistance 1 gene variants may aid in the selection of customized therapeutic regimens.

Carvalho, Ana Teresa P; Froes, Renata S B; Esberard, Barbara C; Santos, Juliana C V C; Rapozo, Davy C. M.; Grinman, Ana B; Simao, Tatiana A; Neto, Pedro Nicolau; Luiz, Ronir R; Carneiro, Antonio Jose V; de Souza, Heitor S P; Ribeiro-Pinto, Luis Felipe

2014-01-01

311

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

Science.gov (United States)

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

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

2014-02-01

312

Bisbenzylisoquinolines as modulators of chloroquine resistance in Plasmodium falciparum and multidrug resistance in tumor cells.  

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Ten naturally occurring bisbenzylisoquinolines (BBIQ) and two dihydro derivatives belonging to five BBIQ subgroups were evaluated in vitro for their ability to inhibit Plasmodium falciparum growth and, in drug combination, to reverse the resistance to chloroquine of strain FcB1. The same alkaloids were also assessed in vitro for their potentiating activity against vinblastine with the multidrug-resistant clone CCRF-CEM/VLB, established from lymphoblastic acute leukemia. Three of the BBIQ test...

1996-01-01

313

Effect of NlpE Overproduction on Multidrug Resistance in Escherichia coli?  

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

2010-01-01

314

Virulence Properties of Multidrug Resistant Ocular Isolates of Acinetobacter baumannii.  

Science.gov (United States)

Abstract Purpose: Acinetobacter (A.) baumannii is an opportunistic pathogen and has been reported as a causative agent of ocular infections. The aim of this study is to identify virulence properties (biofilm formation, adhesion, invasion and cytotoxicity) and antibiotic resistance among A. baumannii isolates recovered from the eye. Materials and Methods: The Microscan Walk-Away®, an automated bacterial identification and susceptibility testing system was used to determine antibiotic resistance. Clonal relatedness was assessed by Pulsed-field gel electrophoresis (PFGE) and plasmid profile analysis. Conjugation experiments were carried out to determine the transfer of antibiotic resistance genes and PCR was used to confirm gene transfer. Virulence properties of the isolates were determined by biofilm formation using crystal violet and immunofluorescence staining, adherence and internalization using cultured corneal epithelial cells, and cytotoxicity by TUNEL-staining and LDH release assays. Results: All ocular isolates (n?=?12) exhibited multidrug resistant (MDR) phenotype and one of the isolate (AB12) was resistant to 18 antibiotics (?-lactam, aminoglycosides, tetracycline, chloramphenicol and quinolones). The plasmid profile analysis showed the presence of multiple plasmids in each isolate and a total of 10 different profiles were observed. However, PFGE analysis was more discriminatory which revealed 12 distinct genotypes. Antibiotic resistance (tetracycline and quinolone) was transferable from the isolate AB12 to a recipient Escherichia coli J53. Ten isolates were strong biofilm producers and the remaining two (AB5 and AB7) were moderate producers. All isolates demonstrated adherence and invasive properties towards HCECs. A similar trend was observed in their ability to cause cell death and toxicity. Conclusions: Our results indicate that ocular isolates of A. baumannii are biofilm producers and adherent and invasive to corneal epithelium, a first step in the pathogenesis of ocular infection. In addition, they demonstrated plasmid-mediated transfer of MDR traits making them a reservoir of resistance genes at ocular surface. PMID:24502411

Talreja, Deepa; Muraleedharan, Chithra; Gunathilaka, Gayathri; Zhang, Yifan; Kaye, Keith S; Walia, Satish K; Kumar, Ashok

2014-07-01

315

Characterization of a multidrug resistant Teladorsagia circumcincta isolate from Spain.  

Science.gov (United States)

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

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

2012-05-01

316

In vitro modulation of P-glycoprotein, MRP-1 and BCRP expression by mangiferin in doxorubicin-treated MCF-7 cells.  

Science.gov (United States)

The multidrug resistance phenotype is one of the major problems in development of cancer cell resistance to chemotherapy. Some natural compounds from medicinal plants have demonstrated promising capacity in enhancing anticancer effects in drug resistant cancer cells. We aimed to investigate whether mangiferin might have an ability to re-sensitize MCF-7 breast cancer cells previously treated with short-term doxorubicin in vitro, through the modulation of efflux transporters, P-glycoprotein (P-gp), MRP1 and BCRP. We exposed MCF-7 breast cancer cells pretreated with doxorubicin for 10 days to mangiferin (10, 25 or 50 ?M) for 96 hours. Afterwards, we evaluated influence on cell viability and level of mRNA expression of P-gp, MRP1 and BCRP. Doxorubicin given in combination with mangiferin at low concentrations (10 and 25 ?M) failed to give significant reduction in cell viability, while at the highest concentrations, the combination significantly reduced cell viability. The mRNA expression analysis of P-gp, MRP1 and BCRP showed that mangiferin had inhibitory effects on P-gp but no effects on MRP1 and BCRP. In conclusion, we suggest that mangiferin at high concentrations can be used as chemosensitizer for doxorubicin therapy. This effect might be attributed by inhibitory effects of mangiferin on P-glycoprotein expression. PMID:24641381

Louisa, Melva; Soediro, Tjahjani Mirawati; Suyatna, Frans Dhyanagiri

2014-01-01

317

Rapid detection of multidrug-resistant Mycobacterium tuberculosis using the mycobacteria growth indicator tube (MGIT) system  

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The emergence of multidrug-resistant strains of Mycobacterium tuberculosis has increased the need for rapid drug susceptibility tests, which are needed for adequate patient treatment. The objective of the present study was to evaluate the mycobacteria growth indicator tube (MGIT) system to detect multidrug-resistant M. tuberculosis strains. The MGIT system was compared with two standard methods (proportion and resistance ratio methods). One hundred clinical M. tuberculosis isolates [25 suscep...

Telles, M. A. S.; Bori, A.; Amorim, A. B. R.; Cruz, A. F.; Pini, M. I. T.; Sato, D. N.

2002-01-01

318

Nrf2 Pathway Regulates Multidrug-Resistance-Associated Protein 1 in Small Cell Lung Cancer  

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Although multidrug-resistance-associated protein-1 (MRP1) is a major contributor to multi-drug resistance (MDR), the regulatory mechanism of Mrp1 still remains unclear. Nrf2 is a transcription factor that regulates cellular defense response through antioxidant response elements (AREs) in normal tissues. Recently, Nrf2 has emerged as an important contributor to chemo-resistance in tumor tissues. In the present study, the role of Nrf2-ARE pathway on regulation of Mrp1 was investigated. Compared...

2013-01-01

319

Expression of a drug resistance gene in human neuroblastoma cell lines: modulation by retinoic acid-induced differentiation.  

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Expression of a multidrug resistance gene (mdr1) and its protein product, P-glycoprotein (Pgp), has been correlated with the onset of multidrug resistance in vitro in human cell lines selected for resistance to chemotherapeutic agents derived from natural products. Expression of this gene has also been observed in normal tissues and human tumors, including neuroblastoma. We therefore examined total RNA prepared from human neuroblastoma cell lines before and after differentiation with retinoic...

Bates, S. E.; Mickley, L. A.; Chen, Y. N.; Richert, N.; Rudick, J.; Biedler, J. L.; Fojo, A. T.

1989-01-01

320

Cloning and heterologous expression of the ovine (Ovis aries) P-glycoprotein (Mdr1) in Madin-Darby canine kidney (MDCK) cells.  

Science.gov (United States)

P-glycoprotein (P-gp) plays a crucial role in the multidrug resistance of pathogenic helminths in sheep (Ovis aries) as well as in antiparasitic drug pharmacokinetics in the host. We cloned sheep P-gp cDNA and expressed it stably in Madin-Darby canine kidney (MDCK) cells. The open reading frame consists of 3858 nucleotides coding for a 1285 amino acids containing protein. The sequence shows high homology to the orthologs of other mammalian species, especially cattle. Both ruminant DNA sequences show a 9 bp insertion that is lacking in all other investigated sequences. Expressed in MDCK cells, the protein displays a size of 170 kDa on Western analysis. Transfection of MDCK cells with sheep P-gp resulted in 10- to 50-fold resistance to the cytotoxic P-gp substrates colchicin and daunorubicin, and in reduced digoxin accumulation. PMID:20557448

Zahner, D; Alber, J; Petzinger, E

2010-06-01

 
 
 
 
321

Prevalence of Multidrug Resistant Mycobacterium tuberculosis by Mycobacteria growth  

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

Livani S

2012-01-01

322

Nanodrugs: optimism for emerging trend of multidrug resistance  

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Full Text Available Asad U KhanMedical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, IndiaThis is with reference to an article published recently in your journal regarding the antibiotic activity of chitosan-coated silver nanoparticles.1 This is an inspiring move towards control of infection caused by multidrug-resistant bacteria which has become a serious problem for clinicians and physicians worldwide.2 At the moment, carbapenems are being used as the drugs of choice to combat infections. However, the emergence of carbapenem resistance has changed current remedial approaches in the management of serious infections. One of the latest enzymes, NDM-1 (New Delhi metallo-?-lactamase-1, first identified in a Swedish patient of Indian origin in 2008,3 has been key in the development of resistance to almost all antibiotics. Infection caused by NDM-1 producers is widespread on the Indian subcontinent,4 and is now emerging in the US and other countries throughout the world.5View original paper by Jena and colleagues.

Khan AU

2012-08-01

323

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

Science.gov (United States)

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

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

2008-02-01

324

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

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

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

1994-05-01

325

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

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

ScottMoye-Rowley

2014-04-01

326

Selective photodynamic inactivation of a multidrug transporter by a cationic photosensitising agent.  

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We have characterised sites of photodamage catalysed by the cationic photosensitiser tetrabromorhodamine 123, using P388 murine leukaemia cells and a subline (P388/ADR) which has a multidrug resistance phenotype and hyperexpresses mdr1 mRNA for P-glycoprotein. Fluorescence emission spectra were consistent with sensitiser localisation in hydrophobic regions of the P388 cell, and in more aqueous loci in P388/ADR. Subsequent irradiation resulted in photodamage to the P388 cells, resulting in los...

1995-01-01

327

P-glycoprotein polymorphism in hypo- and hyper-thyroidism patients.  

Science.gov (United States)

P-glycoprotein (Pgp) is encoded by the multidrug resistance gene (MDR1) in humans and is the product of MDR1. It is expressed in various tissues and is related to drug distribution in intestinal erythrocytes, capillary endotel of brain, proximal tubules cells of kidneys and liver canalicular cells. Expression of Pgp is affected by Pgp polymorphism, and exon 26 C3435T polymorphism is the most common one. It has been thought that expression of Pgp is high in C-allele subjects and this situation is responsible for the resistance against some drugs and substances. Pgp may have a role in the distribution of thyroid hormones, drugs used for hypo- and hyperthyroidism and the resistance occurred. For this purpose possible relationship between T and C alleles and frequency of Pgp polymorphism as well as thyroid hormone distribution in patients with hypo- and hyperthyroidism was investigated. Thirty five hyperthyroidism patients diagnosed as Graves' disease, 78 hypothyroidism patients diagnosed as Hashimoto's thyroiditis and 100 healthy volunteers were included in the study. According to the results obtained no statistically significant difference was found in Pgp C3435T polymorphism between hypo- and hyperthyroidism patients. In addition, the serum free T3 levels of hyperthyroidism patients with C alleles was higher than those of subjects with T alleles. No statistically significant difference was seen in the CC, CT and TT genotype frequencies between the patients and control groups. In conclusion, it seems that Pgp polymorphism is not a predictor factor for the occurrence of hypo- and hyperthyroidism. There is a significant relationship between Pgp and the elevated serum free T3 levels of hyperthyroidism patients, and further research will help understand this situation. PMID:17891478

Turgut, Günfer; Ba?temir, Mehmet; Turgut, Sebahat; Akin, Fulya; Kursunluoglu, Raziye; Kaptano?lu, Bünyamin

2008-12-01

328

Measurement of P-Glycoprotein expression in human neuroblastoma xenografts using in vitro quantitative autoradiography  

International Nuclear Information System (INIS)

P-glycoprotein (P-gp) has a role in multidrug resistance (MDR) encountered in human cancers. In this study, we used the colchicine-resistant cell line BE(2)-C/CHCb(0.2), a strain of neuroblastoma cell line BE(2)-C, as a model to measure variations of P-gp expression in cells grown in vitro and in vivo. Cells were cultured in the medium supplemented with colchicine. At the beginning of the study the drug was withdrawn and, after 22 days, added back to the culture medium. Cells were harvested at various time points and xenografted in nude mice. P-gp content in cells was measured by self-competitive binding assay and in tumors, by quantitative autoradiography (QAR). Both assays were carried out using 125I-labeled monoclonal antibody MRK16, reactive with P-gp. Concentration of P-gp in cells varied from a maximum of 1,361 pmol/g in the presence of colchicine to a minimum of 374 pmol/g in the absence of colchicine in the culture medium. P-gp concentration in the tumors ranged from 929 to 188 pmol/g, which correlated with P-gp content in the cells at the time of their injection in the mice. QAR is an accurate and reliable method to quantify P-gp expression in tumors. Changes in colchicine concentration in the ambient medium of BE(2)-C/CHCb(0.2) cells growing in vitro resulted in a change in phenotype of P-gp expression, which was stable under conditions of in vivo growth over approximately 9 cell divisions in nude mice xenografts. Therefore, P-gp content in xenografts depends only on the level of resistance of the cells at the time of their injection in the mice

1999-01-01

329

Measurement of P-Glycoprotein expression in human neuroblastoma xenografts using in vitro quantitative autoradiography  

Energy Technology Data Exchange (ETDEWEB)

P-glycoprotein (P-gp) has a role in multidrug resistance (MDR) encountered in human cancers. In this study, we used the colchicine-resistant cell line BE(2)-C/CHCb(0.2), a strain of neuroblastoma cell line BE(2)-C, as a model to measure variations of P-gp expression in cells grown in vitro and in vivo. Cells were cultured in the medium supplemented with colchicine. At the beginning of the study the drug was withdrawn and, after 22 days, added back to the culture medium. Cells were harvested at various time points and xenografted in nude mice. P-gp content in cells was measured by self-competitive binding assay and in tumors, by quantitative autoradiography (QAR). Both assays were carried out using {sup 125}I-labeled monoclonal antibody MRK16, reactive with P-gp. Concentration of P-gp in cells varied from a maximum of 1,361 pmol/g in the presence of colchicine to a minimum of 374 pmol/g in the absence of colchicine in the culture medium. P-gp concentration in the tumors ranged from 929 to 188 pmol/g, which correlated with P-gp content in the cells at the time of their injection in the mice. QAR is an accurate and reliable method to quantify P-gp expression in tumors. Changes in colchicine concentration in the ambient medium of BE(2)-C/CHCb(0.2) cells growing in vitro resulted in a change in phenotype of P-gp expression, which was stable under conditions of in vivo growth over approximately 9 cell divisions in nude mice xenografts. Therefore, P-gp content in xenografts depends only on the level of resistance of the cells at the time of their injection in the mice.

Fonti, Rosa; Levchenko, Andrey; Mehta, Bipin M.; Zhang Jiaju; Tsuruo, Takashi; Larson, Steven M

1999-01-01

330

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

Scientific Electronic Library Online (English)

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

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

331

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

Directory of Open Access Journals (Sweden)

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

Mariana V. Arnoni

2007-04-01

332

Multi-drug resistant Acinetobacter ventilator-associated pneumonia  

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Full Text Available Background: Ventilator-associated pneumonia (VAP due to a multi-drug resistant (MDR Acinetobacter is one of the most dreadful complications, which occurs in the critical care setting. Aims and objectives: To find out the incidence of Acinetobacter infection in VAP cases, to determine various risk factors responsible for acquisition of Acinetobacter infection and to determine the antimicrobial susceptibility pattern of Acinetobacter. Materials and Methods: A total of 60 endotracheal aspirate specimens from intubated patients diagnosed clinically and microscopically as VAP were studied bacteriologically. All clinical details and prior exposure to antibiotics were recorded. Results: An incidence of 11.6% of Acinetobacter VAP cases was recorded. Various underlying conditions like head injury, cerebral hemorrhage and chronic obstructive pulmonary disease (COPD were found to be associated with Acinetobacter VAP. Acinetobacter strains exhibited MDR pattern. Conclusion: Strict infection control measures, judicious prescribing of antibiotics, antibiotic resistance surveillance programs and antibiotic cycling should be adopted to control infections due to these bacteria in patients admitted to intensive care units.

Shete Vishal

2010-01-01

333

ANTIBIOTIC SYNERGY TEST: CHECKERBOARD METHOD ON MULTIDRUG RESISTANT PSEUDOMONAS AERUGINOSA  

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

Spoorthi N. Jain

2011-12-01

334

Multidrug-resistant tuberculosis in an adult with cystic fibrosis.  

Science.gov (United States)

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

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

2013-01-01

335

Global dissemination of a multidrug resistant Escherichia coli clone  

Science.gov (United States)

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

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

2014-01-01

336

Molecular patterns of multidrug resistance of Mycobacterium tuberculosis in Georgia  

Science.gov (United States)

Background Tuberculosis (TB) infections caused by multidrug-resistant Mycobacterium tuberculosis (MDR MTB) remain a significant public health concern worldwide. Georgia has a high prevalence of MDR MTB. The genetic mechanisms underlying the emergence of MDR MTB strains in this region are poorly understood and need to be determined for developing better strategies for TB control. This study investigated the frequency of major drug resistance mutations across rpoB, katG and inhA loci of Georgian MDR MTB strains and explored differences between new and previously treated patients. A total of 634 MTB strains were examined for which an MDR phenotype had been previously determined by the proportions method. The GenoType®MTBDRplus system was applied to screen the strains for the presence of rpoB (S531L, H526D, H526Y, and D516V), katG (S315T) and inhA promoter region (C15T and T8C) mutations. The target loci were amplified by PCR and then hybridized with the respective site-specific and wild type (control) probes. Results Out of the 634 isolates tested considered by phenotypic testing to be resistant to RIF and INH, this resistance was confirmed by the GenoType®MTBDRplus assay in 575 (90.7%) isolates. RIF resistance was seen in 589 (92.9%) and INH resistance was seen in 584 (92.1%); 67.2% and 84.3% of MDR strains harbored respectively rpoB S531L and katG S315T mutations (generally known as having low or no fitness cost in MTB). The inhA C15T mutation was detected in 22.6% of the strains, whereas rpoB H526D, rpoB H526Y, rpoB D516V and inhA T8C were revealed at a markedly lower frequency (?5.2%). The specific mutations responsible for the RIF resistance of 110 isolates (17.4%) could not be detected as no corresponding mutant probe was indicated in the assay. There was no specific association of the presence of mutations with the gender/age groups. All types of prevailing mutations had higher levels in new cases. A great majority of the Georgian MDR MTB strains have a strong preference for the drug resistance mutations carrying no or low fitness cost. Thus, it can be suggested that MDR MTB strains with such mutations will continue to arise in Georgia at a high frequency even in the absence of antibiotic pressure.

Shubladze, N.; Tadumadze, N.; Bablishvili, N.

2014-01-01

337

Hospital costs of nosocomial multi-drug resistant Pseudomonas aeruginosa acquisition  

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Full Text Available Abstract Background We aimed to assess the hospital economic costs of nosocomial multi-drug resistant Pseudomonas aeruginosa acquisition. Methods A retrospective study of all hospital admissions between January 1, 2005, and December 31, 2006 was carried out in a 420-bed, urban, tertiary-care teaching hospital in Barcelona (Spain. All patients with a first positive clinical culture for P. aeruginosa more than 48 h after admission were included. Patient and hospitalization characteristics were collected from hospital and microbiology laboratory computerized records. According to antibiotic susceptibility, isolates were classified as non-resistant, resistant and multi-drug resistant. Cost estimation was based on a full-costing cost accounting system and on the criteria of clinical Activity-Based Costing methods. Multivariate analyses were performed using generalized linear models of log-transformed costs. Results Cost estimations were available for 402 nosocomial incident P. aeruginosa positive cultures. Their distribution by antibiotic susceptibility pattern was 37.1% non-resistant, 29.6% resistant and 33.3% multi-drug resistant. The total mean economic cost per admission of patients with multi-drug resistant P. aeruginosa strains was higher than that for non-resistant strains (15,265 vs. 4,933 Euros. In multivariate analysis, resistant and multi-drug resistant strains were independently predictive of an increased hospital total cost in compared with non-resistant strains (the incremental increase in total hospital cost was more than 1.37-fold and 1.77-fold that for non-resistant strains, respectively. Conclusions P. aeruginosa multi-drug resistance independently predicted higher hospital costs with a more than 70% increase per admission compared with non-resistant strains. Prevention of the nosocomial emergence and spread of antimicrobial resistant microorganisms is essential to limit the strong economic impact.

Morales Eva

2012-05-01

338

Structure of the multidrug resistance efflux transporter EmrE from Escherichia coli  

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Multidrug resistance efflux transporters threaten to reverse the progress treating infectious disease by extruding a wide range of drug and other cytotoxic compounds. One such drug transporter, EmrE, from the small multidrug resistance family, utilizes proton gradients as an energy source to drive substrate translocation. In an effort to understand the molecular structural basis of this transport mechanism, we have determined the structure of EmrE from Escherichia coli to 3.8 Å. EmrE is a te...

Ma, Che; Chang, Geoffrey

2004-01-01

339

Discovering Natural Product Modulators to Overcome Multidrug Resistance in Cancer Chemotherapy  

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Multidrug resistance caused by the overexpression of ABC drug transporters is a major obstacle in clinical cancer chemotherapy. For several years, it appeared that direct inhibition of ABC transporters would be the cheapest and most efficient way to combat this problem. Unfortunately, progress in finding a potent, selective inhibitor to modulate ABC transporters and restore drug sensitivity in multidrug-resistant cancer cells has been slow and challenging. Candidate drugs should ideally be se...

Wu, Chung-pu; Ohnuma, Shinobu; Ambudkar, Suresh V.

2011-01-01

340

Population Pharmacokinetics and Pharmacodynamics of Ofloxacin in South African Patients with Multidrug-Resistant Tuberculosis  

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Despite the important role of fluoroquinolones and the predominant use of ofloxacin for treating multidrug-resistant tuberculosis in South Africa, there are limited data on ofloxacin pharmacokinetics in patients with multidrug-resistant tuberculosis, no ofloxacin pharmacokinetic data from South African patients, and no direct assessment of the relationship between ofloxacin pharmacokinetics and the MIC of ofloxacin of patient isolates. Our objectives are to describe ofloxacin pharmacokinetics...

Chigutsa, Emmanuel; Meredith, Sandra; Wiesner, Lubbe; Padayatchi, Nesri; Harding, Joe; Moodley, Prashini; Mac Kenzie, William R.; Weiner, Marc; Mcilleron, Helen; Kirkpatrick, Carl M. J.

2012-01-01

 
 
 
 
341

Reversal of intrinsic multidrug resistance in Chinese hamster ovary cells by amiloride analogs.  

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A number of amiloride analogs can sensitise wild type Chinese Hamster ovary (CHO) cells to the cytotoxic action of vinblastine, daunomycin, puromycin or colchicine. Some of these analogs also have weak sensitising effects on the multidrug resistant CHO cell line, CHRC5. The unusual feature of most of the active amiloride analogs is that they are more potent in reversing the intrinsic multidrug resistance (MDR) phenotype of CHO cells than their acquired MDR characteristic. Human HeLa cells tha...

Epand, R. F.; Epand, R. M.; Gupta, R. S.; Cragoe, E. J.

1991-01-01

342

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

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The aim of this study was to identify the risk factors for nosocomial bloodstream infections by multidrug resistant Gram-negative bacilli. From November 2001 to December 2003, in the Pediatric Department of the Santa Casa de São Paulo, a retrospective case-control study was developed concerning patients who had nosocomial bloodstream infection caused by Gram-negative bacilli. Patients with multidrug resistant infections were designated as case patients, and control patients were those with a...

Arnoni, Mariana V.; Berezin, Eitan N.; Martino, Marine?s D. V.

2007-01-01

343

Pyrazinamide Resistance among South African Multidrug-Resistant Mycobacterium tuberculosis Isolates?  

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Pyrazinamide is important in tuberculosis treatment, as it is bactericidal to semidormant mycobacteria not killed by other antituberculosis drugs. Pyrazinamide is also one of the cornerstone drugs retained in the treatment of multidrug-resistant tuberculosis (MDR-TB). However, due to technical difficulties, routine drug susceptibility testing of Mycobacterium tuberculosis for pyrazinamide is, in many laboratories, not performed. The objective of our study was to generate information on pyrazi...

2008-01-01

344

Reversal of the multidrug resistance by drug combination using multifunctional liposomes  

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One of the major obstacles to the success of cancer chemotherapy is the multi-drug resistance (MDR) that results due mainly to the over-expression of drug efflux transporter pumps such as P-glycoprotein (P-gp). Highly efficacious third generation P-gp inhibitors, like tariquidar, have shown promising results against MDR. However, P-gp is also expressed in normal tissues like the blood-brain barrier, gastrointestinal tract, liver and kidney. It is therefore important to limit the exposure of P-gp inhibitors to normal tissues and increase their co-localization with anticancer agents in tumor tissues to maximize the efficacy of a P-gp inhibitor. To minimize non-specific binding and increase its delivery to tumor tissues, liposomes, self-assembling phospholipid vesicles, were chosen as a drug delivery vehicle. The liposome has been identified as a system capable of carrying molecules with diverse physicochemical properties. It can also alter the pharmacokinetic profile of loaded molecules which is a concern with both tariquidar and paclitaxel. Liposomes can easily be surface-modified rendering them cell-specific as well as organelle-specific. The main objective of present study was to develop an efficient liposomal delivery system which would deliver therapeutic molecules of interest to tumor tissues and avoid interaction with normal tissues. In this study, the co-delivery of tariquidar and paclitaxel into tumor cells to reverse the MDR using long-circulating cationic liposomes was investigated. SKOV-3TR, the resistant variant of SKOV-3 and MCF-7/ADR, the resistant variant of MCF-7 were used as model cell lines. Uniform liposomal formulations were generated with high incorporation efficiency and no apparent decrease in tariquidar potency towards P-gp. Tariquidar- and paclitaxel- co-loaded long-circulating liposomes showed significant re-sensitization of SKOV-3TR and MCF-7/ADR for paclitaxel in vitro. Further modification of these liposomes with antitumor 2C5 resulted in increased cell association with these cancer cells. The 2C5-modified immunoliposomes, along with unmodified liposomes co-loaded with tariquidar and paclitaxel were tested for their antitumor effects in vivo. Significant tumor growth inhibition occurred with combination therapy in resistant as well as sensitive cell lines. However, immunoliposomes failed to increase antitumor effect in vivo as spontaneous accumulation of liposomes at added dose may have saturated tumor accumulation. We were also interested in evaluating physiological factors responsible for the MDR. Spheroids grown in vitro provided platform to demonstrate many characteristics of tumor tissues such as cell-cell interaction, a hypoxic core, low pH environment at core and a relevant genetic profile. In this study, spheroids were utilized to evaluate paclitaxel cytotoxity and to evaluate effects of 2C5 modification on cellular uptake. Lack of cytotoxicity was observed in spheroids treated with paclitaxel alone as well as in combination with tariquidar. Likely explanations could be the presence of cells in diverse cell cycle stages and limited penetration. Also, increased uptake was observed in spheroids when treated with 2C5-modified Rh-labeled liposomes compared to UPC10-modified Rh-labeled liposomes. Such results have clearly demonstrated the importance of using this novel research model in cancer research.

Patel, Niravkumar R.

345

Modulating P-glycoprotein regulation: Future perspectives for pharmacoresistant epilepsies?  

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P>Enhanced brain efflux of antiepileptic drugs by the blood-brain barrier transporter P-glycoprotein is discussed as one mechanism contributing to pharmacoresistance of epilepsies. P-glycoprotein overexpression has been proven to occur as a consequence of seizure activity. Therefore, blocking respective signaling events should help to improve brain penetration and efficacy of P-glycoprotein substrates. A series of recent studies revealed key signaling factors involved in seizure-associated tr...

2010-01-01

346

Differential chemosensitization of P-glycoprotein overexpressing K562/Adr cells by withaferin A and Siamois polyphenols  

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Full Text Available Abstract Background Multidrug resistance (MDR is a major obstacle in cancer treatment and is often the result of overexpression of the drug efflux protein, P-glycoprotein (P-gp, as a consequence of hyperactivation of NF?B, AP1 and Nrf2 transcription factors. In addition to effluxing chemotherapeutic drugs, P-gp also plays a specific role in blocking caspase-dependent apoptotic pathways. One feature that cytotoxic treatments of cancer have in common is activation of the transcription factor NF?B, which regulates inflammation, cell survival and P-gp expression and suppresses the apoptotic potential of chemotherapeutic agents. As such, NF?B inhibitors may promote apoptosis in cancer cells and could be used to overcome resistance to chemotherapeutic agents. Results Although the natural withanolide withaferin A and polyphenol quercetin, show comparable inhibition of NF?B target genes (involved in inflammation, angiogenesis, cell cycle, metastasis, anti-apoptosis and multidrug resistance in doxorubicin-sensitive K562 and -resistant K562/Adr cells, only withaferin A can overcome attenuated caspase activation and apoptosis in K562/Adr cells, whereas quercetin-dependent caspase activation and apoptosis is delayed only. Interestingly, although withaferin A and quercetin treatments both decrease intracellular protein levels of Bcl2, Bim and P-Bad, only withaferin A decreases protein levels of cytoskeletal tubulin, concomitantly with potent PARP cleavage, caspase 3 activation and apoptosis, at least in part via a direct thiol oxidation mechanism. Conclusions This demonstrates that different classes of natural NF?B inhibitors can show different chemosensitizing effects in P-gp overexpressing cancer cells with impaired caspase activation and attenuated apoptosis.

Gerlo Sarah

2010-05-01

347

Lipopolysaccharide increases cell surface P-glycoprotein that exhibits diminished activity in intestinal epithelial cells.  

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Increasingly, it is recognized that commensal microflora regulate epithelial cell processes through the dynamic interaction of pathogen-associated molecular patterns and host pattern recognition receptors such as Toll-like receptor 4 (TLR4). We therefore investigated the effects of bacterial lipopolysaccharide (LPS) on intestinal P-glycoprotein (P-gp) expression and function. Human SW480 (P-gp+/TLR4+) and Caco-2 (P-gp+/TLR4-) cells were treated with medium control or LPS (100 ng/ml) for 24 h prior to study. P-gp function was assessed by measuring the intracellular concentration of rhodamine 123 (Rh123). To confirm P-gp-specific effects, breast cancer resistance protein (BCRP/ABCG2) and multidrug resistance-associated protein 2 (MRP-2/ABCC2) were also analyzed. Treatment of SW480 cells with LPS led to diminished P-gp activity, which could be prevented with polymyxin B (control: 207+/-16 versus LPS: 402+/-22 versus LPS+polymyxin B: 238+/-26 pmoles Rh123/mg protein, p<0.05 control versus LPS). These effects could be blocked by using polymyxin B and were not seen in the P-gp+/TLR4--Caco-2 cell line (control: 771+/-28 versus LPS: 775+/-59 pmoles Rh123/mg protein). Total cellular levels of P-gp did not change in LPS-treated SW480 cells; however, a significant increase in cell surface P-gp was detected. No change in activity, total protein, or apically located MRP-2 was detected following LPS treatment. Sequence analysis confirmed wild-type status of SW480 cells. These data suggest that activation of TLR4 in intestinal epithelial cells leads to an increase in plasma membrane P-gp that demonstrates a diminished capacity to transport substrate. PMID:18687802

Mishra, Jayshree; Zhang, Qiuye; Rosson, Jessica L; Moran, John; Dopp, John M; Neudeck, Brien L

2008-10-01

348

Differential sensitivities of the human ATP-binding cassette transporters ABCG2 and P-glycoprotein to cyclosporin A.  

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Several ATP-binding cassette (ABC) transporters can confer multidrug resistance to cancer cells by functioning as energy-dependent efflux pumps. The half-transporter ABCG2 and the widely studied P-glycoprotein (P-gp) are two ABC transporters that, when overexpressed, are capable of extruding a variety of structurally unrelated chemotherapy agents from cells. In this study, we demonstrate that human ABCG2 and P-glycoprotein, despite overlapping substrate specificities, differ in sensitivity to the immunomodulator cyclosporin A. In this study, we used human ABCG2 and human P-gp, each expressed separately in drug-selected MCF-7 sublines and transiently transfected HeLa cells. By flow cytometric analysis using the fluorescent substrates rhodamine 123 and mitoxantrone, we showed that cyclosporin A inhibits P-gp function at low micromolar concentrations, whereas ABCG2 function was unaffected. Furthermore, P-gp, but not ABCG2, was able to transport [3H]cyclosporin A directly in intact cells. We also demonstrated, for the first time, that [125I]iodoarylazidoprazosin, a photoaffinity analog of the substrate prazosin, labels multiple variants of ABCG2 specifically and that this labeling, although competed by some ABCG2 substrates, is unaffected by cyclosporin A. These labeling data also suggest the presence of multiple drug binding sites in ABCG2. In addition, cyclosporin A had no effect on the basal or prazosin-stimulated ATPase activity of ABCG2, whereas both the basal and verapamil-stimulated ATPase activities of P-gp were inhibited markedly. Together, our results suggest that cyclosporin A is neither a substrate nor an inhibitor of the human ABCG2 transporter, under the conditions and concentrations examined. PMID:15598974

Ejendal, Karin F K; Hrycyna, Christine A

2005-03-01

349

Multidrug Resistance and Cancer Stem Cells in Neuroblastoma and Hepatoblastoma  

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Full Text Available Chemotherapy is one of the major modalities in treating cancers. However, its effectiveness is limited by the acquisition of multidrug resistance (MDR. Several mechanisms could explain the up-regulation of MDR genes/proteins in cancer after chemotherapy. It is known that cancer stem cells (CSCs play a role as master regulators. Therefore, understanding the mechanisms that regulate some traits of CSCs may help design efficient strategies to overcome chemoresistance. Different CSC phenotypes have been identified, including those found in some pediatric malignancies. As solid tumors in children significantly differ from those observed in adults, this review aims at providing an overview of the mechanistic relationship between MDR and CSCs in common solid tumors, and, in particular, focuses on clinical as well as experimental evidence of the relations between CSCs and MDR in neuroblastoma and hepatoblastoma. Finally, some novel approaches, such as concomitant targeting of multiple key transcription factors governing the stemness of CSCs, as well as nanoparticle-based approaches will also be briefly addressed.

Anna Alisi

2013-12-01

350

Multidrug resistance and cancer stem cells in neuroblastoma and hepatoblastoma.  

Science.gov (United States)

Chemotherapy is one of the major modalities in treating cancers. However, its effectiveness is limited by the acquisition of multidrug resistance (MDR). Several mechanisms could explain the up-regulation of MDR genes/proteins in cancer after chemotherapy. It is known that cancer stem cells (CSCs) play a role as master regulators. Therefore, understanding the mechanisms that regulate some traits of CSCs may help design efficient strategies to overcome chemoresistance. Different CSC phenotypes have been identified, including those found in some pediatric malignancies. As solid tumors in children significantly differ from those observed in adults, this review aims at providing an overview of the mechanistic relationship between MDR and CSCs in common solid tumors, and, in particular, focuses on clinical as well as experimental evidence of the relations between CSCs and MDR in neuroblastoma and hepatoblastoma. Finally, some novel approaches, such as concomitant targeting of multiple key transcription factors governing the stemness of CSCs, as well as nanoparticle-based approaches will also be briefly addressed. PMID:24351843

Alisi, Anna; Cho, William C; Locatelli, Franco; Fruci, Doriana

2013-01-01

351

Protein phosphatase complex PP5/PPP2R3C dephosphorylates P-glycoprotein/ABCB1 and down-regulates the expression and function.  

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P-glycoprotein (P-gp)/ABCB1 is a key molecule of multidrug resistance in cancer. Protein phosphatase (PP) 2A, regulatory subunit B, gamma (PPP2R3C), which is a regulatory subunit of PP2A and PP5, was identified as a binding candidate to P-gp. Immunoprecipitation-western blotting revealed that PP5 and PPP2R3C were coprecipitated with P-gp, while PP2A was not. PP5/PPP2R3C dephosphorylated protein kinase A/protein kinase C-phosphorylation of P-gp. Knockdown of PP5 and/or PPP2R3C increased P-gp expression and lowered the sensitivity to vincristine and doxorubicin. Consequently, our results indicate that PP5/PPP2R3C negatively regulates P-gp expression and function. PMID:24333728

Katayama, Kazuhiro; Yamaguchi, Miho; Noguchi, Kohji; Sugimoto, Yoshikazu

2014-04-01

352

Dominance of multidrug resistant CC271 clones in macrolide-resistant streptococcus pneumoniae in Arizona  

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Full Text Available Abstract Background Rates of resistance to macrolide antibiotics in Streptococcus pneumoniae are rising around the world due to the spread of mobile genetic elements harboring mef(E and erm(B genes and post-vaccine clonal expansion of strains that carry them. Results Characterization of 592 clinical isolates collected in Arizona over a 10 year period shows 23.6% are macrolide resistant. The largest portion of the macrolide-resistant population, 52%, is dual mef(E/erm(B-positive. All dual-positive isolates are multidrug-resistant clonal lineages of Taiwan19F-14, mostly multilocus sequence type 320, carrying the recently described transposon Tn2010. The remainder of the macrolide resistant S. pneumoniae collection includes 31% mef(E-positive, and 9% erm(B-positive strains. Conclusions The dual-positive, multidrug-resistant S. pneumoniae clones have likely expanded by switching to non-vaccine serotypes after the heptavalent pneumococcal conjugate vaccine release, and their success limits therapy options. This upsurge could have a considerable clinical impact in Arizona.

Bowers Jolene R

2012-01-01

353

Principles for designing future regimens for multidrug-resistant tuberculosis.  

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Fewer than 20% of patients with multidrug-resistant (MDR) tuberculosis are receiving treatment and there is an urgent need to scale up treatment programmes. One of the biggest barriers to scale-up is the treatment regimen, which is lengthy, complex, ineffective, poorly tolerated and expensive. For the first time in over 50 years, new drugs have been developed specifically to treat tuberculosis, with bedaquiline and potentially delamanid expected to be available soon for treatment of MDR cases. However, if the new drugs are merely added to the current treatment regimen, the new regimen will be at least as lengthy, cumbersome and toxic as the existing one. There is an urgent need for strategy and evidence on how to maximize the potential of the new drugs to improve outcomes and shorten treatment. We devised eight key principles for designing future treatment regimens to ensure that, once they are proven safe in clinical trials, they will be clinically effective and programmatically practicable. Regimens should contain at least one new class of drug; be broadly applicable for use against MDR and extensively drug-resistant Mycobacterium tuberculosis complex strains; contain three to five effective drugs, each from a different drug class; be delivered orally; have a simple dosing schedule; have a good side-effect profile that allows limited monitoring; last a maximum of 6 months; and have minimal interaction with antiretrovirals. Following these principles will maximize the potential of new compounds and help to overcome the clinical and programmatic disadvantages and scale-up constraints that plague the current regimen. PMID:24391302

Brigden, Grania; Nyang'wa, Bern-Thomas; du Cros, Philipp; Varaine, Francis; Hughes, Jennifer; Rich, Michael; Horsburgh, C Robert; Mitnick, Carole D; Nuermberger, Eric; McIlleron, Helen; Phillips, Patrick P J; Balasegaram, Manica

2014-01-01

354

Emergence of fluoroquinolones-resistant strains of Salmonella typhi: Watch on multidrug-resistant isolates  

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Full Text Available Subhash C Arya, Nirmala Agarwal, Shekhar Agarwal, Dolly WadhwaSant Parmanand Hospital, Delhi, IndiaEmergence of multidrug-resistant Salmonella typhi has been responsible for clinical challenges for clinicians. Recently, frequent isolation and dissemination of fluoroquinolones-resistant strains of S. enterica in Surabaya, Indonesia was in the news. Subsequently, Yangai and colleagues1 recommended regular communications between laboratory professionals and clinicians. Collaboration between laboratory personnel and clinicians would be essential to offer a rational empiric antibiotic recipe while awaiting antibiotic susceptibility test results (AST for any patient.

Subhash C Arya

2010-05-01

355

Cytosolic superoxide dismutase activity after photodynamic therapy, intracellular distribution of Photofrin II and hypericin, and P-glycoprotein localization in human colon adenocarcinoma.  

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Full Text Available In photodynamic therapy (PDT, a tumor-selective photosensitizer is administered and then activated by exposure to a light source of applicable wavelength. Multidrug resistance (MDR is largely caused by the efflux of therapeutics from the tumor cell by means of P-glycoprotein (P-gp, resulting in reduced efficacy of the anticancer therapy. This study deals with photodynamic therapy with Photofrin II (Ph II and hypericin (Hyp on sensitive and doxorubicin-resistant colon cancer cell lines. Changes in cytosolic superoxide dismutase (SOD1 activity after PDT and the intracellular accumulation of photosensitizers in sensitive and resistant colon cancer cell lines were examined. The photosensitizers' distributions indicate that Ph II could be a potential substrate for P-gp, in contrast to Hyp. We observed an increase in SOD1 activity after PDT for both photosensitizing agents. The changes in SOD1 activity show that photodynamic action generates oxidative stress in the treated cells. P-gp appears to play a role in the intracellular accumulation of Ph II. Therefore the efficacy of PDT on multidrug-resistant cells depends on the affinity of P-gp to the photosensitizer used. The weaker accumulation of photosensitizing agents enhances the antioxidant response, and this could influence the efficacy of PDT.

Anna Marcinkowska

2007-06-01

356

Pharmacological functions of multidrug transporters: studies employing combination transporter knockout mice  

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ATP-binding cassette (ABC) multidrug transporters are drug efflux pumps located in the plasma membrane that utilize the energy of ATP hydrolysis to extrude a wide spectrum of endogenous and exogenous compounds from cells, including numerous (anticancer) drugs and/or their metabolites. The studies described in this thesis focus on the pharmacological functions of the ABC transporters: P-glycoprotein (P-gp/ABCB1), the Multidrug Resistance Proteins 2 and 3 (MRP2/ABCC2 and MRP3/ABCC3) and the Bre...

Lagas, J. S.

2009-01-01

357

Histone deacetylase inhibitor (HDACI) PCI-24781 enhances chemotherapy induced apoptosis in multidrug resistant sarcoma cell lines  

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The anti-tumor activity of histone deacetylase inhibitors (HDACI) on multi-drug resistant sarcoma cell lines has never been previously described. Four multidrug resistant sarcoma cell lines treated with HDACI PCI-24781 resulted in dose-dependent accumulation of acetylated histones, p21 and PARP cleavage products. Growth of these cell lines was inhibited by PCI-24781 at IC50 of 0.43 to 2.7. When we looked for synergy of PCI-24781 with chemotherapeutic agents, we found that PCI-24781 reverses drug resistance in all four multidrug resistant sarcoma cell lines and synergizes with chemotherapeutic agents to enhance caspase-3/7 activity. Expression of RAD51 (a marker for DNA double-strand break repair) was inhibited and the expression of GADD45? (a marker for growth arrest and DNA-damage) was induced by PCI-24781 in multidrug resistant sarcoma cell lines. In conclusion, HDACI PCI-24781 synergizes with chemotherapeutic drugs to induce apoptosis and reverses drug resistance in multidrug resistant sarcoma cell lines.

Yang, Cao; Choy, Edwin; Hornicek, Francis J.; Wood, Kirkham B; Schwab, Joseph H; Liu, Xianzhe; Mankin, Henry; Duan, Zhenfeng

2013-01-01

358

ABC transporters during epilepsy and mechanisms underlying multidrug resistance in refractory epilepsy.  

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It is estimated 20-25% of the epileptic patients fails to achieve good control with the different antiepileptic drugs (AEDs) treatments, developing refractory epilepsy (RE). Discovered first in cancer, the activity of P-glycoprotein (P-gp) and others ABC transporters as multidrug-resistance-associated proteins (MRPs) and breast cancer resistant protein (BCRP) are directly related with the refractoriness. We have observed the overexpression of these all transporters in the brain of patients with RE, and according with other authors, all these data suggests an active drug efflux from brain. Both constitutive and seizure induced brain P-gp overexpression was also suggested. As confirmation of these clinical evidences, different models of experimental epilepsy have demonstrated P-gp overexpression on blood brain barrier (BBB) and brain parenchyma cells, as astrocytes and neurons. In our model, early P-pg detection in vessel-related cells and later additional P-gp detection in neurons, correlated with the gradual loss of protective effect of phenytoin. The progressive neuronal P-gp expression, depending on intensity and time-constancy of seizure-injury, was in agreement with the development of "P-gp-positive seizure-axis" proposed by Kwan & Brodie, who also showed that the development of RE directly correlated with the number and frequency of seizures before initiation of drug therapy. P-gp expression in excretory organs suggests that P-gp have a central role in drug elimination. Persistent low levels of AEDs in plasma and P-gp brain overexpression in several RE pediatric patients were reported. We also observed in adult RE patients, an increased liver clearance of 99mTc-hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) (a P-gp substrate), and the surgically treated cases showed P-gp brain overexpression. These results suggest the systemic hyperactivity of P-gp in RE patients, including brain P-gp over-expression should be suspected when persistent subtherapeutic levels of AEDs in plasma are detected. P-gp neuronal expression described in both clinical and experimental reports indicates that additional mechanisms could be operative from seizure-affected P-gp-positive neurons, due to AEDs targets are expressed at membrane level. An alternative mechanism was demonstrated in P-gp-expressed cells that exhibit lower membrane potential (Deltapsi(0)=-10 to -20) compared to normal physiological Deltapsi(0) of -60 mV. Under this situation and irrespective to the P-gp pharmacoresistant property or type of drug treatment selected, P-gp-expressed neurons could increase their sensitivity to new seizures perhaps as an epileptogenic mechanism. The understanding of properties of these ABC transporters can offer new tools for better selection of more effective preventive or therapeutic strategies and avoid the invasive surgical treatments for RE. PMID:17910594

Lazarowski, Alberto; Czornyj, Liliana; Lubienieki, Fabiana; Girardi, Elena; Vazquez, Silvia; D'Giano, Carlos

2007-01-01

359

Uncovering Scaling Laws to Infer Multi-drug Response of Resistant Microbes and Cancer Cells  

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Drug resistance in bacterial infections and cancers constitutes a major threat to human health. Treatments often include several interacting drugs, but even potent therapies can become ineffective in resistant mutants. Here we simplify the picture of drug resistance by identifying scaling laws that unify the multi-drug responses of drug sensitive and drug resistant cells. Based on these scaling relationships, we are able to infer the two-drug response of resistant mutants in previously unsamp...

Wood, Kevin B.; Wood, Kris C.; Nishida, Satoshi; Cluzel, Philippe

2014-01-01

360

Multidrug resistance 1 gene polymorphisms may determine Crohn's disease behavior in patients from Rio de Janeiro  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english OBJECTIVES: Conflicting data from studies on the potential role of multidrug resistance 1 gene polymorphisms in inflammatory bowel disease may result from the analysis of genetically and geographically distinct populations. Here, we investigated whether multidrug resistance 1 gene polymorphisms are [...] associated with inflammatory bowel diseases in patients from Rio de Janeiro. METHODS: We analyzed 123 Crohn's disease patients and 83 ulcerative colitis patients to determine the presence of the multidrug resistance 1 gene polymorphisms C1236T, G2677T and C3435T. In particular, the genotype frequencies of Crohn's disease and ulcerative colitis patients were analyzed. Genotype-phenotype associations with major clinical characteristics were established, and estimated risks were calculated for the mutations. RESULTS: No significant difference was observed in the genotype frequencies of the multidrug resistance 1 G2677T/A and C3435T polymorphisms between Crohn's disease and ulcerative colitis patients. In contrast, the C1236T polymorphism was significantly more common in Crohn's disease than in ulcerative colitis (p?=?0.047). A significant association was also found between the multidrug resistance 1 C3435T polymorphism and the stricturing form of Crohn's disease (OR: 4.13; p?=?0.009), whereas no association was found with penetrating behavior (OR: 0.33; p?=?0.094). In Crohn's disease, a positive association was also found between the C3435T polymorphism and corticosteroid resistance/refractoriness (OR: 4.14; p?=?0.010). However, no significant association was found between multidrug resistance 1 gene polymorphisms and UC subphenotypic categories. CONCLUSION: The multidrug resistance 1 gene polymorphism C3435T is associated with the stricturing phenotype and an inappropriate response to therapy in Crohn's disease. This association with Crohn's disease may support additional pathogenic roles for the multidrug resistance 1 gene in regulating gut-microbiota interactions and in mediating fibrosis. Understanding the effects of several drugs associated with multidrug resistance 1 gene variants may aid in the selection of customized therapeutic regimens.

Ana Teresa P., Carvalho; Renata S.B., Fróes; Barbara C., Esberard; Juliana C.V.C., Santos; Davy C. M., Rapozo; Ana B., Grinman; Tatiana A., Simão; Pedro, Nicolau Neto; Ronir R., Luiz; Antonio José V., Carneiro; Heitor S.P. de, Souza; Luis Felipe, Ribeiro-Pinto.

 
 
 
 
361

Function-Altering SNPs in the Human Multidrug Transporter Gene ABCB1 Identified Using a Saccharomyces-Based Assay  

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The human ABCB1 (MDR1)-encoded multidrug transporter P-glycoprotein (P-gp) plays a major role in disposition and efficacy of a broad range of drugs including anticancer agents. ABCB1 polymorphisms could therefore determine interindividual variability in resistance to these drugs. To test this hypothesis we developed a Saccharomyces-based assay for evaluating the functional significance of ABCB1 polymorphisms. The P-gp reference and nine variants carrying amino-acid–altering single nucleotid...

Jeong, Hotcherl; Herskowitz, Ira; Kroetz, Deanna L.; Rine, Jasper

2007-01-01

362

Radiation- and chemoinduced multidrug resistance in colon carcinoma cells  

International Nuclear Information System (INIS)

Background and purpose: radiation can induce multidrug resistance (MDR) and thus interfere with simultaneous or subsequent chemotherapy. In SW620 colon carcinoma cells, the interrelation of various biological endpoints of MDR was analyzed and the potential of fractionated irradiation and chemoselection to evoke MDR was compared. Material and methods: to induce/select an MDR phenotype, SW620 were exposed to either 27 Gy in 1.8-Gy daily fractions or to 50% inhibiting concentrations of doxorubicin or cisplatin, given over 6-15 weeks. Expression of genes involved in MDR, including glutathione metabolism, was determined by semiquantitative RT-PCR (reverse transcription-polymerase chain reaction). Efflux was analyzed by flow cytometry after staining with rhodamine-123 or 5-chloromethyl fluorescein diacetate. Apoptosis was monitored after pulse exposure to doxorubicin or cisplatin. Colony-forming assays were performed under continuous drug exposure. Results: a pronounced gene induction was found in MRP2 after cisplatin selection and up to 3 weeks after radiation. LRP was activated only shortly after radiation. Radiation enhanced rhodamine-123 efflux to a similar extent as short-term chemoselection but not as much as long-term drug exposure. Drug-induced apoptosis was slightly delayed in preirradiated cells. Clonogenic growth in the progeny of irradiated cells was less sensitive to cisplatin but not to doxorubicin. Conclusion: fractionated radiation can induce an MDR phenotype in SW620. However, long-term drug exposure establishes a more efficient selection. Various endpoints are not fully concordant regarding the extent of MDR. Posttranscriptional modifications, pleiotropic regulation, and alternative pathways may cause these discrepancies. (orig.)

2009-12-01

363

Radiation- and chemoinduced multidrug resistance in colon carcinoma cells  

Energy Technology Data Exchange (ETDEWEB)

Background and purpose: radiation can induce multidrug resistance (MDR) and thus interfere with simultaneous or subsequent chemotherapy. In SW620 colon carcinoma cells, the interrelation of various biological endpoints of MDR was analyzed and the potential of fractionated irradiation and chemoselection to evoke MDR was compared. Material and methods: to induce/select an MDR phenotype, SW620 were exposed to either 27 Gy in 1.8-Gy daily fractions or to 50% inhibiting concentrations of doxorubicin or cisplatin, given over 6-15 weeks. Expression of genes involved in MDR, including glutathione metabolism, was determined by semiquantitative RT-PCR (reverse transcription-polymerase chain reaction). Efflux was analyzed by flow cytometry after staining with rhodamine-123 or 5-chloromethyl fluorescein diacetate. Apoptosis was monitored after pulse exposure to doxorubicin or cisplatin. Colony-forming assays were performed under continuous drug exposure. Results: a pronounced gene induction was found in MRP2 after cisplatin selection and up to 3 weeks after radiation. LRP was activated only shortly after radiation. Radiation enhanced rhodamine-123 efflux to a similar extent as short-term chemoselection but not as much as long-term drug exposure. Drug-induced apoptosis was slightly delayed in preirradiated cells. Clonogenic growth in the progeny of irradiated cells was less sensitive to cisplatin but not to doxorubicin. Conclusion: fractionated radiation can induce an MDR phenotype in SW620. However, long-term drug exposure establishes a more efficient selection. Various endpoints are not fully concordant regarding the extent of MDR. Posttranscriptional modifications, pleiotropic regulation, and alternative pathways may cause these discrepancies. (orig.)

Bartkowiak, Detlef; Stempfhuber, Michael; Wiegel, Thomas; Bottke, Dirk [Dept. of Radiotherapy and Radiooncology, Univ. of Ulm (Germany)

2009-12-15

364

Keratinocyte growth factor-2 stimulates P-glycoprotein expression and function in intestinal epithelial cells.  

Science.gov (United States)

Intestinal P-glycoprotein (Pgp/multidrug resistance 1), encoded by the ATP-binding cassette B1 gene, is primarily involved in the transepithelial efflux of toxic metabolites and xenobiotics from the mucosa into the gut lumen. Reduced Pgp function and expression has been shown to be associated with intestinal inflammatory disorders. Keratinocyte growth factor-2 (KGF2) has emerged as a potential target for modulation of intestinal inflammation and maintenance of gut mucosal integrity. Whether KGF2 directly regulates Pgp in the human intestine is not known. Therefore, the present studies were undertaken to determine the modulation of Pgp by KGF2 using Caco-2 cells. Short-term treatment of Caco-2 cells with KGF2 (10 ng/ml, 1 h) increased Pgp activity (~2-fold, P < 0.05) as measured by verapamil-sensitive [(3)H]digoxin flux. This increase in Pgp function was associated with an increase in surface Pgp levels. The specific fibroblast growth factor receptor (FGFR) antagonist PD-161570 blocked the KGF2-mediated increase in Pgp activity. Inhibition of the mitogen-activated protein kinase (MAPK) pathway by PD-98059 attenuated the stimulatory effects of KGF2 on Pgp activity. Small-interfering RNA knockdown of Erk1/2 MAPK blocked the increase in surface Pgp levels by KGF2. Long-term treatment with KGF2 (10 ng/ml, 24 h) also significantly increased PgP activity, mRNA, protein expression, and promoter activity. The long-term effects of KGF2 on Pgp promoter activity were also blocked by the FGFR antagonist and mediated by the Erk1/2 MAPK pathway. In conclusion, our findings define the posttranslational and transcriptional mechanisms underlying stimulation of Pgp function and expression by KGF2 that may contribute to the beneficial effects of KGF2 in intestinal inflammatory disorders. PMID:23328208

Saksena, Seema; Priyamvada, Shubha; Kumar, Anoop; Akhtar, Maria; Soni, Vikas; Anbazhagan, Arivarasu Natarajan; Alakkam, Anas; Alrefai, Waddah A; Dudeja, Pradeep K; Gill, Ravinder K

2013-03-15

365

In silico model for P-glycoprotein substrate prediction: insights from molecular dynamics and in vitro studies.  

Science.gov (United States)

P-glycoprotein (P-gp) is a plasma membrane efflux transporter belonging to ATP-binding cassette superfamily, responsible for multidrug resistance in tumor cells. Over-expression of P-gp in cancer cells limits the efficacy of many anticancer drugs. A clear understanding of P-gp substrate binding will be advantageous in early drug discovery process. However, substrate poly-specificity of P-gp is a limiting factor in rational drug design. In this investigation, we report a dynamic trans-membrane model of P-gp that accurately identified the substrate binding residues of known anticancer agents. The study included homology modeling of human P-gp based on the crystal structure of C. elegans P-gp, molecular docking, molecular dynamics analyses and binding free energy calculations. The model was further utilized to speculate substrate propensity of in-house anticancer compounds. The model demonstrated promising results with one anticancer compound (NSC745689). As per our observations, the molecule could be a potential lead for anticancer agents devoid of P-gp mediated multiple drug resistance. The in silico results were further validated experimentally using Caco-2 cell lines studies, where NSC745689 exhibited poor permeability (P app 1.03 ± 0.16 × 10(-6) cm/s) and low efflux ratio of 0.26. PMID:23612916

Prajapati, Rameshwar; Singh, Udghosh; Patil, Abhijeet; Khomane, Kailas S; Bagul, Pravin; Bansal, Arvind K; Sangamwar, Abhay T

2013-04-01

366

Antitumor Agents 286. Design, Synthesis and Structure-Activity Relationships of 3?R,4?R-Disubstituted-2?,2?-dimethyldihydropyrano[2,3-f]chromone (DSP) Analogs as Potent Chemosensitizers to Overcome Multidrug Resistance  

Science.gov (United States)

In this study, various 3?R,4?R-disubstituted-2?,2?-dimethydihydropyrano[2,3-f]chromone (DSP) derivatives were discovered as potent chemosensitizers in the treatment of multidrug resistant cancer cells. Twenty-four DSP analogs (5–28) were synthesized and evaluated against a multi-drug resistant (MDR) cell line (KB-Vin) with and without vincristine (VCR). All DSP analogs exhibited low intrinsic cytotoxicity. However, in combination treatment, most DSPs reversed resistance to VCR and lowered the GI50 value of VCR by 12–349-fold. At a concentration of 1?g/mL, three compounds, 11, 14 and 21, fully reversed resistance to VCR in KB-Vin cancer cells, a twofold increase compared to verapamil, a first generation chemosensitizer. Detailed structure-activity relationship (SAR) conclusions were established based on 3? and 4? substitutions. Moreover, a preliminary mechanism study indicated that the chemosensitizing activity of DSP analogs results from inhibition of P-glycoprotein (P-gp) over-expressed in MDR cancer cells.1

Zhou, Ting; Shi, Qian; Bastow, Kenneth F.; Lee, Kuo-Hsiung

2010-01-01

367

In vivo detection of multidrug-resistant (MDR1) phenotype by technetium-99m sestamibi scan in untreated breast cancer patients  

International Nuclear Information System (INIS)

Technetium-99m sestamibi is a transport substrate recognised by the multidrug-resistant P-glycoprotein (Pgp). To test whether 99mTc-sestamibi efflux is enhanced in breast carcinomas overexpressing Pgp, w