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Role of P-Glycoprotein for Resistance of Tumors to Anticancer Drugs: From Bench to Bedside. RESISTANCE TO TARGETED ANTI-CANCER THERAPEUTICS 2015. [DOI: 10.1007/978-3-319-09801-2_1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Frede J, Fraser SP, Oskay-Özcelik G, Hong Y, Ioana Braicu E, Sehouli J, Gabra H, Djamgoz MB. Ovarian cancer: Ion channel and aquaporin expression as novel targets of clinical potential. Eur J Cancer 2013; 49:2331-44. [DOI: 10.1016/j.ejca.2013.03.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 01/29/2013] [Accepted: 03/10/2013] [Indexed: 01/11/2023]
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Rajendra Prasad V, Deepak Reddy G, Appaji D, Peters G, Mayur Y. Chemosensitizing acridones: In vitro calmodulin dependent cAMP phosphodiesterase inhibition, docking, pharmacophore modeling and 3D QSAR studies. J Mol Graph Model 2013; 40:116-24. [PMID: 23388503 DOI: 10.1016/j.jmgm.2012.12.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 11/30/2012] [Accepted: 12/17/2012] [Indexed: 10/27/2022]
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Germann UA, Chambers TC. Molecular analysis of the multidrug transporter, P-glycoprotein. Cytotechnology 2012; 27:31-60. [PMID: 19002782 DOI: 10.1023/a:1008023629269] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
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 responsible for multidrug resistance. Overexpression of this 170 kDa N-glycosylated plasma membrane protein in mammalian cells has been associated with ATP-dependent reduced drug accumulation, suggesting that P-glycoprotein may act as an energy-dependent drug efflux pump. P-glycoprotein consists of two highly homologous halves each of which contains a transmembrane domain and an ATP binding fold. This overall architecture is characteristic for members of the ATP-binding cassette or ABC superfamily of transporters. Cell biological, molecular genetic and biochemical approaches have been used for structure-function studies of P-glycoprotein and analysis of its mechanism of action. This review summarizes the current status of knowledge on the domain organization, topology and higher order structure of P-glycoprotein, the location of drug- and ATP binding sites within P-glycoprotein, its ATPase and drug transport activities, its possible functions as an ion channel, ATP channel and lipid transporter, its potential role in cholesterol biosynthesis, and the effects of phosphorylation on P-glycoprotein activity.
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Affiliation(s)
- U A Germann
- Vertex Pharmaceuticals Incorporated, 130 Waverly Street, Cambridge, MA, 02139-4242, U.S.A.,
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Eichhorn T, Efferth T. P-glycoprotein and its inhibition in tumors by phytochemicals derived from Chinese herbs. JOURNAL OF ETHNOPHARMACOLOGY 2012; 141:557-570. [PMID: 21963565 DOI: 10.1016/j.jep.2011.08.053] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 08/19/2011] [Accepted: 08/25/2011] [Indexed: 05/31/2023]
Abstract
P-glycoprotein belongs to the family of ATP-binding cassette (ABC) transporters. It functions in cellular detoxification, pumping a wide range of xenobiotic compounds, including anticancer drugs out of the cell. In cancerous cells, P-glycoprotein confers resistance to a broad spectrum of anticancer agents, a phenomenon termed multidrug resistance. An attractive strategy for overcoming multidrug resistance is to block the transport function of P-glycoprotein and thus increase intracellular concentrations of anticancer drugs to lethal levels. Efforts to identify P-glycoprotein inhibitors have led to numerous candidates, none of which have passed clinical trials with cancer patients due to their high toxicity. The search for naturally inhibitory products from traditional Chinese medicine may be more promising because natural products are frequently less toxic than chemically synthesized substances. In this review, we give an overview of molecular and clinical aspects of P-glycoprotein and multidrug resistance in the context of cancer as well as Chinese herbs and phytochemicals showing inhibitory activity towards P-glycoprotein.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Animals
- Antineoplastic Agents, Phytogenic/adverse effects
- Antineoplastic Agents, Phytogenic/therapeutic use
- Drug Resistance, Neoplasm
- Drugs, Chinese Herbal/adverse effects
- Drugs, Chinese Herbal/therapeutic use
- Humans
- Neoplasms/drug therapy
- Neoplasms/metabolism
- Plants, Medicinal
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Affiliation(s)
- Tolga Eichhorn
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz, Germany
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Chen L, Tu Z, Voloshchuk N, Liang JF. Lytic peptides with improved stability and selectivity designed for cancer treatment. J Pharm Sci 2012; 101:1508-17. [PMID: 22227945 DOI: 10.1002/jps.23043] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 11/22/2011] [Accepted: 12/14/2011] [Indexed: 11/10/2022]
Abstract
Lytic peptides are a group of membrane-acting peptides, which have excellent activity to drug-resistant cells. In this study, the stability and tumor selectivity of newly designed pH-activated lytic peptides were studied. We found that despite varied secondary structures, pH-induced structure changes could not be directly linked to the activity and pH sensitivity of peptides. On the contrary, formation of aggregates had great impacts on peptide binding and insertion into the lipid bilayer of cell membrane. It was found that the pH controlled peptide aggregation and dissolution was responsible for the pH-dependent membrane lysis activity of peptides. One peptide (PTP-7c) formed stable amyloid fibrils, which did not completely dissolve under acidic conditions. As a result, PTP-7c had the lowest membrane lysis and cell killing activities among tested lytic peptides. As solid tumors have consistently low extracellular pHs, peptides with acid-activation features showed improved selectivity to cancer cells. In addition, self-assembled lytic peptides were found to become more stable and showed dramatically increased half lives (up to 11 h) in human plasma. These new lytic peptides with good stability and acid-activated cell lysis activity will have wide biomedical applications especially for the treatment of cancers in which drug resistance has developed.
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Affiliation(s)
- Long Chen
- Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA
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Christophe Minier, Nancy Eufemia, D. The multi-xenobiotic resistance phenotype as a tool to biomonitor the environment. Biomarkers 2008; 4:442-54. [DOI: 10.1080/135475099230606] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Han QL, Zhang LF, Zhang XD, Jin XW, Yang L, Wang X, Ding J. Role of Ss-A/Ro ribonucleoprotein 60 ku subunit variant 1 in multi-drug resistance of gastric cancer. Shijie Huaren Xiaohua Zazhi 2008; 16:814-818. [DOI: 10.11569/wcjd.v16.i8.814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the possible role of Ro 60 variant 1 in multi-drug resistance (MDR) of gastric cancer.
METHODS: Ro 60 variant 1 encoding gene was cloned using RT-PCR method. Ro 60 variant 1 sense eukaryotic expression vector was constructed using DNA recombination technique and transfected into SGC7901 cells with LipofectamineTM 2000. Drug sensitivity was detected by MTT assay. IC50 values of gastric cancer cells for chemotherapy drugs were calculated. Intracellular accumulation of adriamycin in gastric cancer cells was measured by sorting fluorescence- activated cells.
RESULTS: The expression level of Ro 60 variant 1 in SGC7901 cells was increased after transfection with sense genes. In vitro drug sensitivity assay showed that the sensitivity of SGC7901 cells transfected with Ro 60 variant 1 genes was significantly decreased compared with SGC7901 and SGC7901-pcDNA3.1 cells on vincristine (IC50: 2.87 ± 0.10 mg/L vs 0.47 ± 0.07 mg/L, 0.63 ± 0.08 mg/L, P < 0.01), 5-FU(IC50: 3.89 ± 0.12 mg/L vs 0.59 ± 0.17 mg/L, 0.92 ± 0.12 mg/L, P<0.01), mitomycin (IC50: 1.02 ± 0.06 mg/L vs 0.50 ± 0.04 mg/L, 0.73 ± 0.09 mg/L, P < 0.05), cisplatin (IC50: 1.15 ± 0.06 mg/L vs 0.46 ± 0.04 mg/L, 0.52 ± 0.05 mg/L, P < 0.01) and adriamycin (IC50: 0.45 ± 0.03 mg/L vs 0.15 ± 0.03 mg/L, 0.16 ± 0.02 mg/L, P < 0.01). Flow cytometry revealed that accumulation of adriamycin in SGC7901 cells transfected with Ro 60 variant 1 gene was decreased (50.39 ± 2.09 mg/L vs 94.99 ± 4.07 mg/L, 88.06 ± 2.67 mg/L, P < 0.01), when compared with SGC7901 and SGC7901-pcDNA3.1 cells.
CONCLUSION: SGC7901 cells transfected with Ro 60 variant 1 sense genes exhibit MDR. Ro 60 variant 1 might play a certain role in MDR of gastric cancer.
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Coley HM, Labeed FH, Thomas H, Hughes MP. Biophysical characterization of MDR breast cancer cell lines reveals the cytoplasm is critical in determining drug sensitivity. Biochim Biophys Acta Gen Subj 2006; 1770:601-8. [PMID: 17270349 DOI: 10.1016/j.bbagen.2006.12.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 11/27/2006] [Accepted: 12/12/2006] [Indexed: 11/25/2022]
Abstract
Dielectrophoresis (DEP) was used to examine a panel of MCF-7 cell lines comprising parental MCF-7 cells and MDR derivatives: MCF-7TaxR (paclitaxel-resistant, P-glycoprotein (P-gp) positive), MCF-7DoxR (doxorubicin-resistant MRP2 positive) plus MCF-7MDR1 (MDR1 transfected, P-gp positive). MCF-7DoxR and MCF-7MDR1 were broadly cross-resistant to natural product anticancer agents, whereas MCF-7TaxR cells were not, contrary to P-gp expression. Whilst DEP revealed modest membrane changes in MDR sub-lines, we saw significant changes in their cytoplasmic conductivity: MCF-7TaxR<MCF-7<MCF-7MDR1<MCF-7DoxR (range 0.14-0.40 S/m). Cytoplasmic conductivity is affected by the movement of molecules e.g. as in intracellular trafficking MCF-7TaxR showed a reduced membrane potential, whereas MCF-7DoxR and MCF-7MDR1 showed an increase. Thus, altered membrane potential is associated with an MDR phenotype, but in a complex manner. DEP data suggest a model whereby relative increases in cytoplasmic conductivity are correlated with MDR, whilst relative decreases equate with a sensitised phenotype e.g. MCF-7TaxR. Moreover, extent of anthracycline accumulation was inversely related to cytoplasmic conductivity. These data are representative of a model where drug sensitivity is associated with low ionic conductance (reduced cellular trafficking and ion transport) and substantial anthracycline accumulation. For classical MDR i.e. MCF-7MDR1, we saw the reverse picture. Thus, the drug resistance phenotypes of this panel of MCF-7 lines can be delineated by assessment of cytoplasmic biophysical properties using DEP.
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Affiliation(s)
- Helen M Coley
- Division of Oncology, Postgraduate Medical School, School, University of Surrey, Guildford, Surrey GU2 7WG, UK.
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Han QL, Zhang XD, Ding J, Jin XW, Yang L, Wang X, Zhang XY, Fan DM. Reversal of multidrug resistance in gastric cancer cell line by Ss-A/Ro ribonucleoprotein 60-ku subunit antisense nucleic acid. Shijie Huaren Xiaohua Zazhi 2006; 14:2668-2672. [DOI: 10.11569/wcjd.v14.i27.2668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the possible function of Ro 60 antisense nucleic acid in multidrug resistant cell line of gastric cancer.
METHODS: Ro 60 antisense eukaryotic expression vector was constructed using DNA recombination technique, then transfected into SGC7901-VCR by LipofectamineTM2000. Drug sensitivity assay was performed using MTT assay, and IC50 values of gastric cancer cells to chemotherapy drugs were calculated. The intracellular accumulation of adriamycin in gastric cancer cells was measured using fluorescence-activated cell sorting.
RESULTS: The expression level of Ro 60 in SGC7901-VCR cells was decreased after transfection with antisense genes. In vitro drug sensitivity assay show that SGC7901-VCR cells transfected with Ro 60 antisense genes showed significantly increased sensitivity to vincristine (IC50: 7.66 ± 0.45 mg/L vs 19.56 ± 0.38, 17.48 ± 0.85 mg/L, P < 0.01), mitomycin (IC50: 0.84 ± 0.03 mg/L vs 1.62 ± 0.06, 1.80 ± 0.03 mg/L, P < 0.01), cisplatin (IC50: 0.51 ± 0.03 mg/L vs 0.87 ± 0.03, 0.88 ± 0.03 mg/L, P < 0.01) and adriamycin (IC50: 0.22 ± 0.01 mg/L vs 0.52 ± 0.02, 0.43 ± 0.03 mg/L, P < 0.01), as compared with SGC7901-VCR and SGC7901-VCR-pcDNA3.1 cells. As showed by flow cytometry, the intracellular accumulation of adriamycin in the cells transfected with Ro 60 antisense gene was markedly increased in comparison with that in SGC7901-VCR or SGC7901-VCR-pcDNA3.1 cells (51.94 ± 1.26 mg/L vs 36.27 ± 0.98, 37.01 ± 0.91 mg/L, P < 0.01).
CONCLUSION: After transfected into multidrug resistant cell line of gastric cancer, Ro 60 antisense nucleic acid can inhibit the multidrug resistant phenotype of gastric cancer.
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Abstract
This report describes the pH measurement of individual acidic organelles isolated from the human leukemia CCRF-CEM and CEM/C2 cells. These cells were allowed to endocytose fluorescein tetramethylrhodamine dextran (FRD), a ratiometric probe that has fluorescein as a pH-dependent fluorophore and tetramethylrhodamine as a pH-independent fluorophore. Isolated organelle fractions from these cells were then subjected to capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) analysis. The detection of individual organelle fluorescence at two different wavelengths, selected on the basis of the emission range of the FRD probe, gives a fluorescence intensity ratio used to calculate the pH from a calibration curve. This curve was constructed from CE-LIF measurements of individual liposomes loaded with several pH buffer standards. The respective median pH values are 5.1 +/- 0.2 in CEM/C2 cells and 6.1 +/- 0.4 in CCRF-CEM cells. These measurements compare well with pixel-based epifluorescence microscopy measurements of whole cells where the corresponding average pH values are 5.0 +/- 0.6 (n = 15) and 6.2 +/- 0.7 (n = 15). A pH comparison between the two cell types suggests that the lower pH in the CEM/C2 cells may be relevant to the protonation and sequestration of weak base anticancer drugs such as doxorubicin. The determination of the pH of individual vesicles, liposomes, and acidic organelles is a new resource for measuring and investigating the role of the acid-base properties of subcellular-size compartments.
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Affiliation(s)
- Yun Chen
- Department of Chemistry, University of Minnesota, Minneapolis, 55455, USA
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Han QL, Ding J, Guo CC, Wang X, Qiao TD, Zhang XY, Fan DM. Expression of Ss-A/Ro ribonucleoprotein 60 ku subunit and its variants in drug-resistant gastric cancer cells. Shijie Huaren Xiaohua Zazhi 2005; 13:2788-2790. [DOI: 10.11569/wcjd.v13.i23.2788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To clone the encoding gene of Ss-A/Ro ribonucle-oprotein 60 ku subunit, and to detect the expression of Ss-A/Ro 60 ku subunit and its variants in the drug resi-stance gastric cancer cells.
METHODS: The encoding gene of Ss-A/Ro ribonucl-eoprotein 60 ku subunit was cloned by reverse transcri-ption-polymerase chain reaction. The expression of Ss-A/Ro 60 ku subunit and its variants in the gastric cancer cells were analyzed by semi-quantitative RT-PCR.
RESULTS: The Ss-A/Ro 60 ku subunit was successful-ly cloned, and its two transcription variants, with a length of 52 and 41 bp, respectively, were found out. The expression of Ss-A/Ro 60 ku subunit and its two variants in the SGC7901/VCR cells was higher than that in the SGC7901 ones (P = 0.000 1, P = 0.001).
CONCLUSION: The Ss-A/Ro 60 ku subunit and its variants are multi-drug resistance-related molecules.
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Sawicka M, Kalinowska M, Skierski J, Lewandowski W. A review of selected anti-tumour therapeutic agents and reasons for multidrug resistance occurrence. J Pharm Pharmacol 2004; 56:1067-81. [PMID: 15324475 DOI: 10.1211/0022357044265] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
It is assumed that proteins from the ABC family (i.e., glycoprotein P (Pgp)) and a multidrug resistance associated protein (MRP) play a main role in the occurrence of multidrug resistance (MDR) in tumour cells. Other factors that influence the rise of MDR are mechanisms connected with change in the effectiveness of the glutathione cycle and with decrease in expression of topoisomerases I and II. The aim of this review is to characterize drugs applied in anti-tumour therapy and to describe the present state of knowledge concerning the mechanisms of MDR occurrence, as well as the pharmacological agents applied in reducing this phenomenon.
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Affiliation(s)
- M Sawicka
- Department of Chemistry, Biatystok Technical University, Zamenhofa 29, 15-435 Biatystok, Poland
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Dragomir A, Roomans GM. Increased chloride efflux in colchicine-resistant airway epithelial cell lines. Biochem Pharmacol 2004; 68:253-61. [PMID: 15193997 DOI: 10.1016/j.bcp.2004.03.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Accepted: 03/15/2004] [Indexed: 11/30/2022]
Abstract
Colchicine has been proposed as a treatment to alleviate chronic lung inflammation in cystic fibrosis patients and clinical trials are ongoing. Our aim was to investigate whether chronic exposure of cystic fibrosis cells to colchicine can affect their ability to transport chloride in response to cAMP. Colchicine-resistant cells were selected by growing in medium containing nanomolar concentrations of the drug. While microtubuli were affected by acute exposure to colchicine, they appeared normal in colchicine-resistant cells. Colchicine-resistant clones had higher expression of multidrug resistance proteins compared to untreated cells. Cystic fibrosis transmembrane conductance regulator (CFTR) labelling by immunocytochemistry showed no significant changes. The intracellular chloride concentration and basal chloride efflux of the cystic fibrosis treated cells increased significantly compared with untreated cells, while for the cAMP-stimulated Cl-efflux there was no significant change. The results suggest that colchicine promotes chloride efflux via alternative chloride channels. Since this is an accepted strategy for pharmacological treatment of cystic fibrosis, the results strengthen the notion that colchicine would be beneficial to these patients.
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Affiliation(s)
- Anca Dragomir
- Department of Medical Cell Biology, University of Uppsala, Box 571, 751 23 Uppsala, Sweden.
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Sankatsing SUC, Beijnen JH, Schinkel AH, Lange JMA, Prins JM. P glycoprotein in human immunodeficiency virus type 1 infection and therapy. Antimicrob Agents Chemother 2004; 48:1073-81. [PMID: 15047504 PMCID: PMC375313 DOI: 10.1128/aac.48.4.1073-1081.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- Sanjay U C Sankatsing
- Department of Internal Medicine, Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical Center, University of Amsterdam, The Netherlands
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Joseph B, Bhargava KK, Malhi H, Schilsky ML, Jain D, Palestro CJ, Gupta S. Sestamibi is a substrate for MDR1 and MDR2 P-glycoprotein genes. Eur J Nucl Med Mol Imaging 2003; 30:1024-31. [PMID: 12536246 DOI: 10.1007/s00259-002-1111-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Technetium-99m sestamibi has attracted interest for assessment of the function of P-glycoproteins, which are well expressed in the liver and have roles in biliary transport and the removal of chemotherapeutic drugs. To further examine the cross-reactivity of (99m)Tc-sestamibi for P-glycoprotein family members, we conducted studies in animals. Hepatobiliary secretion of (99m)Tc-sestamibi was determined in normal FVB/N mice, mutant mice with specific P-glycoprotein deficiencies in the FVB/N background, normal Long-Evans Agouti (LEA) rats, and Long-Evans Cinnamon (LEC) rats with abnormal copper transport and liver disease but intact P-glycoprotein expression. After intrasplenic injection, (99m)Tc-sestamibi was rapidly incorporated in the mouse and rat liver, with maximal accumulation after 102+/-31 and 109+/-16 s, respectively ( P=NS). In normal mice and rats, 55%+/-11% and 55%+/-6%, respectively, of the maximal sestamibi activity was retained in the liver after 1 h ( P=NS). In double knockout mice lacking both mdr1a and mdr1b homologs of the human MDR1 ( ABCB1) gene, 88%+/-11% of maximal sestamibi activity was retained in the liver after 1 h ( P<0.001). In knockout mice deficient in either mdr1a gene or mdr2 ( ABCB4) gene, biliary sestamibi excretion was also impaired, although this impairment was relatively less pronounced in ABCB4-deficient mice than in double knockout mice lacking both ABCB1 gene homologs ( P<0.03). Hepatobiliary sestamibi excretion in LEC rats was not different from that in control normal rats, despite the presence of significant liver disease in the former. Hepatobiliary sestamibi excretion requires P-glycoproteins and is unperturbed in chronic liver disease. Sestamibi appears to be a substrate for both ABCB1 and ABCB4 genes, although the former utilizes it far more efficiently. Assessment of P-glycoprotein activity with sestamibi should consider how regulation of ABCB1 and related family members might modulate sestamibi incorporation.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B/deficiency
- ATP Binding Cassette Transporter, Subfamily B/genetics
- ATP Binding Cassette Transporter, Subfamily B/metabolism
- ATP Binding Cassette Transporter, Subfamily B, Member 1/deficiency
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Animals
- Liver/cytology
- Liver/diagnostic imaging
- Liver/metabolism
- Metabolic Clearance Rate
- Mice
- Mice, Knockout
- Radionuclide Imaging
- Rats
- Rats, Inbred LEC
- Substrate Specificity
- Technetium Tc 99m Sestamibi/pharmacokinetics
- ATP-Binding Cassette Sub-Family B Member 4
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Affiliation(s)
- Brigid Joseph
- Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Ullmann 625, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Sietsma H, Dijkhuis AJ, Kamps W, Kok JW. Sphingolipids in neuroblastoma: their role in drug resistance mechanisms. Neurochem Res 2002; 27:665-74. [PMID: 12374201 DOI: 10.1023/a:1020228117739] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Disseminated neuroblastoma usually calls for chemotherapy as the primary approach for treatment. Treatment failure is often attributable to drug resistance. This involves a variety of cellular mechanisms, including increased drug efflux through expression of ATP-binding cassette transporters (e.g., P-glycoprotein) and the inability of tumor cells to activate or propagate the apoptotic response. In recent years it has become apparent that sphingolipid metabolism and the generation of sphingolipid species, such as ceramide, also play a role in drug resistance. This may involve an autonomous mechanism, related to direct effects of sphingolipids on the apoptotic response, but also a subtle interplay between sphingolipids and ATP-binding cassette transporters. Here, we present an overview of the current understanding of the multiple levels at which sphingolipids function in drug resistance, with an emphasis on sphingolipid function in neuroblastoma and how modulation of sphingolipid metabolism may be used as a novel treatment paradigm.
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Affiliation(s)
- Hannie Sietsma
- Department of Pathology and Laboratory Medicine, University Hospital Groningen, The Netherlands
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Harguindey S. Integrating fields of cancer research through pivotal mechanisms and synthetic final pathways: a unifying and creative overview. Med Hypotheses 2002; 58:444-52. [PMID: 12323109 DOI: 10.1054/mehy.2001.1415] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
From cancer etiopathogenesis to selective apoptosis, from multiple drug resistance to oncogen activation and from the phenomena of spontaneous regression of cancer to certain aspects of cancer chemotherapy, all these subfields of biology and oncology research share some deep-seated, both basic and clinical, essential features and characteristics. Certain apoptosis-inducing agents of unrelated families, ranging from ether lipids to Na(+)/H(+)-antiporter inhibitors to Delta(9)-tetrahydrocannabinol all have been reported to induce selective cancer-cell death. Behind a wide array of intermediary factors and mechanisms involved in their activity, they seem to share common pivotal and/or final pathways in inducing cell death mediated by a 'pathological' accumulation of intracellular hydrogen ions as a mechanism underlying core changes in intracellular signaling pathways. An H(+)-concentration initial perspective indicates that from pathogenesis to apoptosis and multiple drug resistance, as well as oncogen activity, tumor progression and even the phenomenon of spontaneous regression, all can be interpreted from their deep (H(+))-related basic and clinical essential characteristics. This speculative review discusses the potential integration of these previously disparate subfields of cancer research, through a model which also seems to lead toward improving understanding of the fundamental nature of malignant processes. It is concluded that this synthetic and universal approach allows advancement toward a combining of different areas of oncology into deeper and more comprehensive forms of rational understanding, with the hope of paving the way towards more selective, effective and all-encompassing forms of treatment.
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Affiliation(s)
- S Harguindey
- Department of Clinical Oncology, Clinica USP-La Esperanza, Vitoria, Spain.
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Porcelli AM, Scotlandi K, Strammiello R, Gislimberti G, Baldini N, Rugolo M. Intracellular pH regulation in U-2 OS human osteosarcoma cells transfected with P-glycoprotein. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1542:125-38. [PMID: 11853886 DOI: 10.1016/s0167-4889(01)00173-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The molecular mechanisms responsible for intracellular pH regulation in the U2-OS osteosarcoma cell line were investigated by loading with 2',7'-bis(2-carboxyethyl)-5(6) carboxyfluorescein ester and manipulation of Cl(-) and Na(+) gradients, both in HEPES- and HCO(3)(-)/CO(2)-buffered media. Both acidification and alkalinisation were poorly sensitive to 4,4'-diisothiocyanate dihydrostilbene-2,2'-disulfonic acid, inhibitor of the anion exchanger, but sensitive to amiloride, inhibitor of the Na(+)/H(+) exchanger. In addition to the amiloride-sensitive Na(+)/H(+) exchanger, another H(+) extruding mechanism was detected in U-2 OS cells, the Na(+)-dependent HCO(3)(-)/Cl(-) exchanger. No significant difference in resting pH(i) and in the rate of acidification or alkalinisation was observed in clones obtained from U-2 OS cells by transfection with the MDR1 gene and overexpressing P-glycoprotein. However, both V(max) and K' values for intracellular [H(+)] of the Na(+)/H(+) exchanger were significantly reduced in MDR1-transfected clones, in the absence and/or presence of drug selection, in comparison to vector-transfected or parental cell line. NHE1, NHE5 and at a lower extent NHE2 mRNA were detected in similar amount in all U2-OS clones. It is concluded that, although overexpression of P-glycoprotein did not impair pH(i) regulation in U-2 OS cells, the kinetic parameters of the Na(+)/H(+) exchanger were altered, suggesting a functional relationship between the two membrane proteins.
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Affiliation(s)
- Anna Maria Porcelli
- Dipartimento di Biologia Evoluzionistica Sperimentale, Università di Bologna, Italy
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20
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Pantić VR. Biology of kidney cells: ontogeny-recapitulating phylogeny. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 206:155-212. [PMID: 11407760 DOI: 10.1016/s0074-7696(01)06022-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Biology of kidney cells can be used as a model for further understanding of ontogeny-recapitulating phylogeny. The common and species-specific structural and functional relationship between blood capillaries and the environment via a filtration barrier of nephrons is a biological phenomenon resulting from renal cell memory acquired through evolution. Genetically programmed development, a subsequent series of gene expression, and inductive interactions played a key role in differentiation and maintenance of specific activities of kidneys in birds and mammals. Various environmental factors may alter kidney development and specific activities at the levels of gene expression, repression, or derepression, and defensive mechanisms involved in reaction to risk factors are developed. Autoimmunity and cancerogenesis are closely dependent on a variety of environmental agents, such as antigens originating from infections with some viruses and toxins, or irradiation, advanced industrialization, and progress of civilization. As a result of gene mutation, delation, rearrangement, and/or susceptibility to different agents, renal cell memory is altered. Instead of cell-specific activities, the abilities for regeneration, and other genetically programmed activities, the genesis of kidney diseases are common. Balkan endemic nephropathy, as regional disease, is an important example of the role, of environmental agents, at the level of genes. Research programs on molecular genetics will contribute to our efforts both to prevent infections and to elucidate the genesis, diagnosis, prognosis, prevention, and therapy of kidney diseases.
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Affiliation(s)
- V R Pantić
- Serbian Academy of Sciences and Arts, Belgrade, Yugoslavia
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21
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Skatrud PL. The impact of multiple drug resistance (MDR) proteins on chemotherapy and drug discovery. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2002; 58:99-131. [PMID: 12079203 DOI: 10.1007/978-3-0348-8183-8_3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Transportation of molecules across the cell membrane in living organisms is a critical aspect of life. Transportation includes importation of nutrients from the environment and exportation of toxic compounds. When export includes therapeutic compounds, then the practice of clinical medicine may become compromised. Often efflux of therapeutic compounds is mediated by a large superfamily of proteins referred to as multidrug resistance (MDR) proteins. The initial sections of this chapter are focused on MDR proteins and their negative impact on clinical medicine in cancer chemotherapy as well as infectious diseases mediated by bacteria, fungi and parasites. A brief description of major classes of MDR proteins found in microbes is followed by a more exhaustive treatment of ABC transporters in lower eukaryotes and parasites as well as cancerous mammalian cells. Later sections deal with potential and real positive aspects and applications brought about by a growing knowledge of MDR proteins. Examples described include improved antibiotic production, leveraging MDR proteins in drug discovery, new therapeutic options, dual therapy in treatment of cancer and infectious diseases, and finally MDR proteins as targets for new classes of therapeutic compounds.
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Affiliation(s)
- Paul L Skatrud
- Elanco Animal Health Science, Eli Lilly and Company, Greenfield, Indiana 46140, USA.
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22
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Sauna ZE, Smith MM, Müller M, Kerr KM, Ambudkar SV. The mechanism of action of multidrug-resistance-linked P-glycoprotein. J Bioenerg Biomembr 2001; 33:481-91. [PMID: 11804190 DOI: 10.1023/a:1012875105006] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
P-glycoprotein (Pgp), the ATP-binding cassette (ABC) transporter, confers multidrug resistance to cancer cells by extruding cytotoxic natural product amphipathic drugs using the energy of ATP hydrolysis. Our studies are directed toward understanding the mechanism of action of Pgp and recent work deals with the assessment of interaction between substrate and ATP sites and elucidation of the catalytic cycle of ATP hydrolysis. The kinetic analyses of ATP hydrolysis by reconstituted purified Pgp suggest that ADP release is the rate-limiting step in the catalytic cycle and the substrates exert their effect by modulating ADP release. In addition, we provide evidence for two distinct roles for ATP hydrolysis in a single turnover of Pgp, one in the transport of drug and the other in effecting conformational changes so as to reset the transporter for the next catalytic cycle. Detailed kinetic measurements determined that both nucleotide-binding domains behave symmetrically and during individual hydrolysis events the ATP sites are recruited in a random manner. Furthermore, only one nucleotide site hydrolyzes ATP at any given time, causing (in this site) a conformational change that drastically decreases (>30-fold) the affinity of the second site for ATP-binding. Thus, the blocking of ATP-binding to the second site while the first one is in catalytic conformation appears to be the basis for the alternate catalytic cycle of ATP hydrolysis by Pgp, and this may be applicable as well to other ABC transporters linked with the development of multidrug resistance.
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Affiliation(s)
- Z E Sauna
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
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23
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Abstract
P-glycoprotein (P-gp) is an energy dependent drug pump responsible for multidrug resistance (MDR) in human cancers. While it is irrefutable that P-gp can efflux xenobiotics out of cells, the biological function of P-gp in multicellular organisms has yet to be firmly established. The question of what, if anything, P-gp does when not effluxing drugs has been raised by recent reports indicating that P-gp may regulate apoptosis, chloride channel activity, cholesterol metabolism and immune cell function. There is now a lively debate regarding the possible role of P-gp in regulating cell differentiation, proliferation and survival.
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Affiliation(s)
- R W Johnstone
- Cellular Cytotoxicity Laboratory, The Austin Research Institute, Australia, Victoria.
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24
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Zheleznova EE, Markham P, Edgar R, Bibi E, Neyfakh AA, Brennan RG. A structure-based mechanism for drug binding by multidrug transporters. Trends Biochem Sci 2000; 25:39-43. [PMID: 10664577 DOI: 10.1016/s0968-0004(99)01514-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Multidrug transporters bind chemically dissimilar, potentially cytotoxic compounds and remove them from the cell. How these transporters carry out either of these functions is unknown. On the basis of crystal structures of the multidrug-binding domain of the transcription activator BmrR and mutagenesis studies on the bacterial multidrug transporter MdfA, we propose a possible mechanism for the binding of cationic lipophilic drugs by multidrug transporters. The key element of this mechanism includes a conformational change in the transporter that exposes a buried charged residue in the substrate-binding pocket and allows access to this site by only those drugs that are its steric and electrostatic complements.
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Affiliation(s)
- E E Zheleznova
- Dept of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, OR, USA
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25
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Demeule M, Jodoin J, Gingras D, Béliveau R. P-glycoprotein is localized in caveolae in resistant cells and in brain capillaries. FEBS Lett 2000; 466:219-24. [PMID: 10682831 DOI: 10.1016/s0014-5793(00)01087-5] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A significant proportion of P-glycoprotein (P-gp) and caveolin was co-localized in caveolae isolated from resistant (CH(R)C5) cells overexpressing P-gp and from drug-sensitive Chinese hamster ovary cells (AuxB1). The proportion of P-gp and caveolin associated with caveolar microdomains was higher in CH(R)C5 cells grown in the presence of P-gp substrates (cyclosporin A or colchicine) than in untreated CH(R)C5 cells. Coimmunoprecipitation of P-gp and caveolin from CH(R)C5 lysates suggests that there is a physical interaction between them. Furthermore, co-localization of P-gp and caveolin was found in caveolae from brain capillaries, indicating that this association also takes place in vivo.
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Affiliation(s)
- M Demeule
- Laboratoire de Médecine Moléculaire, Centre de Cancérologie Charles Bruneau-UQAM, Département de Chimie-Biochimie, Montréal, Canada
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26
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Ferté J. Analysis of the tangled relationships between P-glycoprotein-mediated multidrug resistance and the lipid phase of the cell membrane. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:277-94. [PMID: 10632698 DOI: 10.1046/j.1432-1327.2000.01046.x] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
P-glycoprotein (Pgp), the so-called multidrug transporter, is a plasma membrane glycoprotein often involved in the resistance of cancer cells towards multiple anticancer agents in the multidrug-resistant (MDR) phenotype. It has long been recognized that the lipid phase of the plasma membrane plays an important role with respect to multidrug resistance and Pgp because: the compounds involved in the MDR phenotype are hydrophobic and diffuse passively through the membrane; Pgp domains involved in drug binding are located within the putative transmembrane segments; Pgp activity is highly sensitive to its lipid environment; and Pgp may be involved in lipid trafficking and metabolism. Unraveling the different roles played by the membrane lipid phase in MDR is relevant, not only to the evaluation of the precise role of Pgp, but also to the understanding of the mechanism of action and function of Pgp. With this aim, I review the data from different fields (cancer research, medicinal chemistry, membrane biophysics, pharmaceutical research) concerning drug-membrane, as well as Pgp-membrane, interactions. It is emphasized that the lipid phase of the membrane cannot be overlooked while investigating the MDR phenotype. Taking into account these aspects should be useful in the search of ways to obviate MDR and could also be relevant to the study of other multidrug transporters.
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Affiliation(s)
- J Ferté
- Service de Biophysique des Protéines et des Membranes, DSV-DBCM-SBPM, CEA, Centre de Saclay, Gif-sur-Yvette, France.
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27
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Kabasakal L, Halaĉ M, Nisli C, Oguz O, Onsel C, Civi G, Uslu I. The effect of P-glycoprotein function inhibition with cyclosporine A on the biodistribution of Tc-99m sestamibi. Clin Nucl Med 2000; 25:20-3. [PMID: 10634525 DOI: 10.1097/00003072-200001000-00005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE The failure to cure persons with cancer is caused primarily by the development of drug resistance by overexpression of p-glycoprotein. Diverse groups of drugs have been identified, including cyclosporine A, which can reverse drug resistance by inhibiting P-glycoprotein transport. Tc-99m sestamibi is a substrate for P-glycoprotein. P-glycoprotein is normally expressed in biliary canalicular surfaces of hepatocytes and is responsible for the excretion of cationic metabolites from the liver. The aim of the current study was to evaluate the effect of cyclosporine A on the biological distribution of Tc-99m sestamibi in vivo. METHODS Five patients with alopecia and two renal transplant patients who were treated with cyclosporine A were selected for the study. All patients were examined before and at least 2 weeks after administration of cyclosporine A. Tc-99m sestamibi scintigraphy was performed by obtaining planar abdominal images at 5, 30, 60, 120, and 180 minutes after injection, and the liver-heart ratios were calculated. RESULTS Plasma cyclosporine A, bilirubin levels, liver enzymes, and creatinine clearance values were obtained from all patients. In three, the plasma cyclosporine A level was increased to more than 400 pg/dl. The liver-heart ratio was increased significantly after cyclosporine A administration (P < 0.01). After cyclosporine A administration Tc-99m sestamibi excretion was delayed and the uptake in the liver was increased. The difference was 17% at 5 minutes and 38% at 180 minutes. Liver retention was greatest in patients with cyclosporine A toxicity. CONCLUSIONS With a limited number of patients, this study suggests that Tc-99m sestamibi excretion from the liver is mediated by P-glycoprotein, and inhibition of P-glycoprotein transport not only delays liver excretion but also increases the liver uptake of Tc-99m sestamibi. Because this observation deserves further investigation, the inhibition of P-glycoprotein function with nontoxic multidrug-resistance reversing agents may be used as an intervention to increase the tumor uptake of Tc-99m sestamibi and to increase the sensitivity of Tc-99m sestamibi tumor imaging.
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Affiliation(s)
- L Kabasakal
- Cerrahpasa Medical Faculty, Istanbul, Turkey.
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28
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Zimniak P, Pikula S, Bandorowicz-Pikula J, Awasthi YC. Mechanisms for xenobiotic transport in biological membranes. Toxicol Lett 1999; 106:107-18. [PMID: 10403654 DOI: 10.1016/s0378-4274(99)00061-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- P Zimniak
- Department of Internal Medicine, University of Arkansas for Medical Sciences, and McClellan VA Hospital Medical Research, Little Rock, USA
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29
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Ambudkar SV, Dey S, Hrycyna CA, Ramachandra M, Pastan I, Gottesman MM. Biochemical, cellular, and pharmacological aspects of the multidrug transporter. Annu Rev Pharmacol Toxicol 1999; 39:361-98. [PMID: 10331089 DOI: 10.1146/annurev.pharmtox.39.1.361] [Citation(s) in RCA: 1503] [Impact Index Per Article: 60.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Considerable evidence has accumulated indicating that the multidrug transporter or P-glycoprotein plays a role in the development of simultaneous resistance to multiple cytotoxic drugs in cancer cells. In recent years, various approaches such as mutational analyses and biochemical and pharmacological characterization have yielded significant information about the relationship of structure and function of P-glycoprotein. However, there is still considerable controversy about the mechanism of action of this efflux pump and its function in normal cells. This review summarizes current research on the structure-function analysis of P-glycoprotein, its mechanism of action, and facts and speculations about its normal physiological role.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/drug effects
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Animals
- Cell Membrane/metabolism
- Drug Resistance, Multiple/genetics
- Drug Resistance, Neoplasm/genetics
- Humans
- Neoplasms/genetics
- Neoplasms/metabolism
- Protein Conformation
- Structure-Activity Relationship
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Affiliation(s)
- S V Ambudkar
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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30
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Fritz F, Howard EM, Hoffman MM, Roepe PD. Evidence for altered ion transport in Saccharomyces cerevisiae overexpressing human MDR 1 protein. Biochemistry 1999; 38:4214-26. [PMID: 10194338 DOI: 10.1021/bi981929n] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recently [Hoffman, M. M., and Roepe, P. D. (1997) Biochemistry 36, 11153-11168] we presented evidence for a novel Na+- and Cl--dependent H+ transport process in LR73/hu MDR 1 CHO transfectants that likely explains pHi, volume, and membrane potential changes in eukaryotic cells overexpressing the hu MDR 1 protein. To further explore this process, we have overexpressed human MDR 1 protein in yeast strain 9.3 following a combination of approaches used previously [Kuchler, K., and Thorner, J. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 2302-2306; Ruetz, S., et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 11588-11592]. Thus, a truncated hu MDR 1 cDNA was cloned behind a tandem array of sterile 6 (Ste6) and alchohol dehydrogenase (Adh) promoters to create the yeast expression vector pFF1. Valinomycin resistance of intact cells and Western blot analysis with purified yeast plasma membranes confirmed the overexpression of full length, functional, and properly localized hu MDR 1 protein in independently isolated 9.3/pFF1 colonies. Interestingly, relative valinomycin resistance and growth of the 9.3/hu MDR 1 strains are found to strongly depend on the ionic composition of the growth medium. Atomic absorption reveals significant differences in intracellular K+ for 9.3/hu MDR 1 versus control yeast. Transport assays using [3H]tetraphenylphosphonium ([3H]TPP+) reveal perturbations in membrane potential for 9.3/hu MDR 1 yeast that are stimulated by KCl and alkaline pHex. ATPase activity of purified plasma membrane fractions from yeast strains and LR73/hu MDR 1 CHO transfectants constructed previously [Hoffman, M. M., et al. (1996) J. Gen. Physiol. 108, 295-313] was compared. MDR 1 ATPase activity exhibits a higher pH optimum and different salt dependencies, relative to yeast H+ ATPase. Inside-out plasma membrane vesicles (ISOV) fabricated from 9.3/hu MDR 1 and control strains were analyzed for formation of H+ gradients +/- verapamil. Similar pharmacologic profiles are found for verapamil stimulation of MDR 1 ATPase activity and H+ pumping in 9.3/hu MDR 1 ISOV. In sum, these experiments strongly support the notion that hu MDR 1 catalyzes H+ transport in some fashion and lowers membrane potential in yeast when K+ contributes strongly to that potential. In the accompanying paper [Santai, C. T., Fritz, F., and Roepe, P. D. (1999) Biochemistry 38, XXXX-XXXX] the effects of ion gradients on H+ transport by hu MDR 1 are examined.
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Affiliation(s)
- F Fritz
- Department of Chemistry, Lombardi Cancer Center Program in Tumor Biology, Georgetown University, Washington, D.C. 20057, USA
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31
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Loo TW, Clarke DM. Molecular dissection of the human multidrug resistance P-glycoprotein. Biochem Cell Biol 1999. [DOI: 10.1139/o99-014] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The human multidrug resistance P-glycoprotein is an ATP-dependent drug pump that extrudes a broad range of cytotoxic agents from the cell. Its physiological role may be to protect the body from endogenous and exogenous cytotoxic agents. The protein has clinical importance because it contributes to the phenomenon of multidrug resistance during chemotherapy. In this review, we discuss some of the results obtained by using molecular biology and protein chemistry techniques for studying this important and intriguing protein.Key words: P-glycoprotein, ABC transporters, drug transport, dibromobimane, mutagenesis, disulfide crosslinking, metal-chelate chromatography, ATPase activity.
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32
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Abstract
The need for new antimalarials comes from the widespread resistance to those in current use. New antimalarial targets are required to allow the discovery of chemically diverse, effective drugs. The search for such new targets and new drug chemotypes will likely be helped by the advent of functional genomics and structure-based drug design. After validation of the putative targets as those capable of providing effective and safe drugs, targets can be used as the basis for screening compounds in order to identify new leads, which, in turn, will qualify for lead optimization work. The combined use of combinatorial chemistry--to generate large numbers of structurally diverse compounds--and of high throughput screening systems--to speed up the testing of compounds--hopefully will help to optimize the process. Potential chemotherapeutic targets in the malaria parasite can be broadly classified into three categories: those involved in processes occurring in the digestive vacuole, enzymes involved in macromolecular and metabolite synthesis, and those responsible for membrane processes and signalling. The processes occurring in the digestive vacuole include haemoglobin digestion, redox processes and free radical formation, and reactions accompanying haem release followed by its polymerization into haemozoin. Many enzymes in macromolecular and metabolite synthesis are promising potential targets, some of which have been established in other microorganisms, although not yet validated for Plasmodium, with very few exceptions (such as dihydrofolate reductase). Proteins responsible for membrane processes, including trafficking and drug transport and signalling, are potentially important also to identify compounds to be used in combination with antimalarial drugs to combat resistance.
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Affiliation(s)
- P L Olliaro
- UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, Geneva, Switzerland
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33
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Demant EJ, Friche E. Kinetics of anthracycline accumulation in multidrug-resistant tumor cells: relationship to drug lipophilicity and serum albumin binding. Biochem Pharmacol 1998; 56:1209-17. [PMID: 9802333 DOI: 10.1016/s0006-2952(98)00255-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A multidrug-resistant Ehrlich ascites tumor cell line (EHR2/DNR+) was used to examine the membrane transport kinetics of lipophilic anthracycline derivatives in the presence of serum albumin. We present a model for theoretical data analysis with consideration of drug-albumin complex formation. For a set of five derivatives (doxorubicin, daunorubicin, 4-demethoxydaunorubicin, 4'-deoxy-4'-iododoxorubicin, and 13-dihydro-4'-deoxy-4'-iododoxorubicin), data were given on the rates of diffusional drug uptake, and membrane permeability coefficients of the noncharged molecules were estimated. Both the initial rates and the steady-state levels of drug uptake were found to decrease by addition of BSA at concentrations ranging from 5 to 75 mg/mL. For each drug, this effect of serum albumin could be accounted for by the altered distribution between free and protein-bound drug molecules in the bulk aqueous medium. A good fit of theoretical accumulation curves to the experimental data was obtained. It was concluded that a mathematical simulation method makes it possible to predict the uptake characteristics of lipophilic anthracycline compounds into tumor cells under serum conditions.
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Affiliation(s)
- E J Demant
- Department of Medical Biochemistry and Genetics, The Panum Institute, University of Copenhagen, Denmark
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34
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Nakaune R, Adachi K, Nawata O, Tomiyama M, Akutsu K, Hibi T. A novel ATP-binding cassette transporter involved in multidrug resistance in the phytopathogenic fungus Penicillium digitatum. Appl Environ Microbiol 1998; 64:3983-8. [PMID: 9758830 PMCID: PMC106589 DOI: 10.1128/aem.64.10.3983-3988.1998] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
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 region from Botrytis cinerea. Sequence analysis revealed significant amino acid homology to the primary structures of PMR1 (protein encoded by the PMR1 gene) and ABC transporters of Saccharomyces cerevisiae (PDR5 and SNQ2), Schizosaccharomyces pombe (HBA2), Candida albicans (CDR1), and Aspergillus nidulans (AtrA and AtrB). Disruption of the PMR1 gene of P. digitatum DMI-resistant strain LC2 demonstrated that PMR1 was an important determinant of resistance to DMIs. The effective concentrations inhibiting radial growth by 50% (EC50s) and the MICs of fenarimol and bitertanol for the PMR1 disruptants (Deltapmr1 mutants) were equivalent to those for DMI-sensitive strains. Northern blot analysis indicated that severalfold more PMR1 transcript accumulated in the DMI-resistant strains compared with those in DMI-sensitive strains in the absence of fungicide. In both DMI-resistant and -sensitive strains, transcription of PMR1 was strongly enhanced within 10 min after treatment with the DMI fungicide triflumizole. These results suggested that the toxicant efflux system comprised of PMR1 participates directly in the DMI resistance of the fungus.
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Affiliation(s)
- R Nakaune
- Department of Agricultural and Environmental Biology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
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35
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Kamp D, Haest CW. Evidence for a role of the multidrug resistance protein (MRP) in the outward translocation of NBD-phospholipids in the erythrocyte membrane. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1372:91-101. [PMID: 9651491 DOI: 10.1016/s0005-2736(98)00049-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Phosphatidylserine (PS) containing a 7-nitrobenz-2-oxa-1, 3-diazol-4-yl- (NBD-) hexanoyl residue, like native PS, preferentially distributes into the inner membrane leaflet of human erythrocytes. In the case of NBD-PS, this preference results from two opposite active processes, an inward translocation mediated by the aminophospholipid flippase and an outward translocation mediated by an ill-defined floppase. Selective inhibition of this floppase by alkylating reagents or cationic and anionic drugs increases the extent of accumulation of NBD-PS in the inner membrane leaflet from about 70% in control cells to about 90%. Different inhibitor sensitivities of the flippase and the floppase strongly suggest that both represent different entities. The floppase was characterized in further detail by comparing inhibitory effects of various compounds on this translocase with their effects on known primary active transport systems for amphiphilic compounds. The inhibitory effects of various drugs, glutathione conjugates and GSSG on the floppase activity closely correlate with those reported for the active transport by the multidrug resistance protein (MRP) while only poorly going parallel with those for the active transport by the low affinity pump for glutathione conjugates and the multidrug resistance MDR1 P-glycoprotein. The NBD-phospholipid floppase activity of the erythrocyte is thus probably a function of MRP.
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Affiliation(s)
- D Kamp
- Institut für Physiologie, Universitätsklinikum, Pauwelsstrasse 30, D-52057 Aachen, Germany
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36
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Smit JW, Schinkel AH, Müller M, Weert B, Meijer DK. Contribution of the murine mdr1a P-glycoprotein to hepatobiliary and intestinal elimination of cationic drugs as measured in mice with an mdr1a gene disruption. Hepatology 1998; 27:1056-63. [PMID: 9537446 DOI: 10.1002/hep.510270422] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
In the mouse, both the mdr1a and the mdr1b gene encode drug-transporting P-glycoproteins. The mdr1a P-glycoprotein is expressed in epithelial cells of, among others, the liver and the intestine. Furthermore, the mdr1b gene product is found in the liver but is not detectable in the intestine. To establish the potential involvement of P-glycoprotein in the elimination of cationic amphiphilic drugs from the body, we investigated biliary, intestinal, and urinary excretion in mice with a homozygous disruption of the mdr1a gene (mdr1a(-/-) mice). These mice are fully viable under laboratory conditions and have normal bile flow. Cumulative biliary excretion (expressed as percent of the intravenously administered dose excreted over a 1-hour period) of several cationic compounds was decreased as follows in mdr1a(-/-) mice compared with the wild-type animals: tri-n-butylmethylammonium (TBuMA), 0.7% versus 2.1%; azidoprocainamide methoiodide (APM), 3.8% versus 7.6%; and vecuronium, 22.7% versus 41.3%. The luminal secretion of both TBuMA and APM in the small intestine was profoundly decreased, respectively 4.6-fold (1.8% vs. 8.2% in the wild-type) and 7.9-fold (1.6% vs. 10.3% in the wild-type) in mdr1a(-/-) mice. Thus mdr1a P-glycoprotein contributes substantially to the removal of a wide variety of cationic agents from the body through intestinal and hepatobiliary secretion, but it evidently acts in concert with other transport system(s). These processes probably provide a protective mechanism limiting the overall rate of absorption as well as the bioavailability of potentially toxic organic amines.
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Affiliation(s)
- J W Smit
- Department of Pharmacokinetics and Drug Delivery, University Center for Pharmacy, Groningen Institute for Drug Studies, The Netherlands
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37
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Bray PG, Ward SA. A comparison of the phenomenology and genetics of multidrug resistance in cancer cells and quinoline resistance in Plasmodium falciparum. Pharmacol Ther 1998; 77:1-28. [PMID: 9500157 DOI: 10.1016/s0163-7258(97)00083-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Plasmodium falciparum is the causative agent of the most deadly form of human malaria. Chemotherapy traditionally has been the main line of defense against this parasite, and chloroquine, the drug of choice, has been one of the most successful drugs ever developed. Unfortunately, the evolution and spread of resistance to chloroquine and other quinoline-containing drugs means that these compounds are now virtually useless in many endemic areas. Future prospects for the use of quinoline compounds improved considerably when it was demonstrated that chloroquine resistance could be circumvented in vitro by a number of structurally and functionally unrelated compounds such as verapamil and desipramine. The phenomenon of resistance reversal by compounds such as verapamil is also a key feature of drug resistance in mammalian cells, and this has raised the possibility that the underlying mechanisms of drug resistance of the two cell types could be similar. This hypothesis has prompted a large number of studies into the genetics and biochemistry of resistance to quinoline-containing drugs in P. falciparum. Both the genetic and the biochemical studies have raised issues of controversy and stimulated much debate. These issues are discussed in this review, in the context of a comparison with the genetics and biochemistry of multidrug resistance in mammalian cells.
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Affiliation(s)
- P G Bray
- Department of Pharmacology and Therapeutics, University of Liverpool, UK
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38
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Hoffman MM, Roepe PD. Analysis of ion transport perturbations caused by hu MDR 1 protein overexpression. Biochemistry 1997; 36:11153-68. [PMID: 9287158 DOI: 10.1021/bi970530g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In previous work [Luz et al. (1994) Biochemistry 33, 7239-7249; Roepe et al. (1994) Biochemistry 33, 11008-11015] we measured changes in Cl- and HCO3--dependent pHi regulation for LR73 Chinese hamster ovary fibroblasts overexpressing mu MDR 1 protein. However, only one clonal cell line overexpressing the protein but not previously exposed to chemotherapeutic drug (i.e., a "true" transfectant) was examined, since very few MDR cell lines of this nature have been constructed. Recently [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313] we derived a series of true LR73/hu MDR 1 transfectants that are valuable for defining the MDR phenotype mediated by MDR protein alone, without the additional complexities introduced by exposing cells to chemotherapeutic drugs. Several independently derived clones from these and additional transfection experiments exhibit expression of MDR protein that is higher than that found in other true transfectants, and that is similar to the highest level of overexpression yet recorded for drug selected MDR cells. We examined altered Cl--dependent pHi regulation for these clones using improved single-cell photometry (SCP) techniques. Short-term isotonic Cl- substitution experiments performed in the presence of CO2/HCO3- reveal that mild overexpression of hu MDR 1 protein alters anion exchange (Cl-/HCO3- exchange or AE) for LR73 cells, as expected on the basis of previous work [Luz et al. (1994) Biochemistry 33, 7239-7249]. Interestingly, we now find that several independently selected high-level MDR 1 overexpressing clones acidify quite extensively upon isotonic exchange of Cl- and then rapidly alkalinize upon restoring normal [Cl-]. These data suggest that MDR protein may effectively compete against AE. The MDR protein effect is not dependent on HCO3-/CO2 or K+, is partially inhibited by verapamil, is completely inhibited by substituting K+ or N-methylglucamine (NMG+) for Na+ in the SCP perfusate but is not affected by 100 microM levels of amiloride, bumetanide, chlorothiazide, or stilbene. ATP depletion inhibits the MDR 1 effect. We are unable to restore normal AE activity for the MDR clones via manipulation of Cl- or HCO3- gradients. We thus suggest that MDR protein overexpression provides a novel Na+- and Cl--dependent pathway for transmembrane H+ transport. From analysis of ion dependency and inhibitor sensitivities, we conclude the transport is not via altered regulation of any known K+/H+, Na+/H+, or Cl-/HCO3- antiporters, Na+:K+:2Cl-, Na+:K+:2HCO3-, K+:HCO3-, or Na+:HCO3- co-transporters, or any combination of these. Thus, it appears to represent a novel ATP and Na+-dependent Cl-/H+ antiport process that (1) may be directly mediated by the MDR protein, (2) may represent the modulation of one or more currently unidentified ion transport proteins by MDR protein, (3) may be due to some combination of direct ion transport and regulation of ion transport, or (4) may represent unusual passive H+ movement in response to a novel Cl--dependent electrical perturbation that occurs during our Cl- substitution protocol. The results have important implications for understanding drug resistance mediated by MDR 1 overexpression, as well as the physiologic function of endogenously expressed MDR protein.
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Affiliation(s)
- M M Hoffman
- Molecular Pharmacology and Therapeutics Program at the Raymond and Beverly Sackler Foundation Laboratory, Memorial Sloan-Kettering Cancer Center, Cornell University Medical College, New York, New York 10021, USA
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Robinson LJ, Roberts WK, Ling TT, Lamming D, Sternberg SS, Roepe PD. Human MDR 1 protein overexpression delays the apoptotic cascade in Chinese hamster ovary fibroblasts. Biochemistry 1997; 36:11169-78. [PMID: 9287159 DOI: 10.1021/bi9627830] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Several laboratories have reported that overexpression of the multidrug resistance (MDR) protein is associated with intracellular alkalinization, and several investigators have reported that cells induced to undergo programmed cell death (apoptosis) acidify quite significantly. Because it is difficult to fully explain the resistance to apoptosis-inducing chemotherapeutic drugs that is exhibited by MDR tumor cells solely via altered drug transport alone [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313], we have investigated whether overexpression of the hu MDR 1 protein alters progression of the apoptotic cascade. LR73 fibroblasts induced to undergo apoptosis either via treatment with the chemotherapeutic drug colchicine or by serum withdrawal exhibit cellular volume changes, intracellular acidification, nuclear condensation, and chromosomal digestion ("ladder formation"), characteristic of apoptosis, in a temporally well-defined pattern. However, multidrug resistant LR73/20E or LR73/27 hu MDR 1 transfectants recently created in our laboratory without selection on chemotherapeutic drug are significantly delayed in the onset of apoptosis as defined by the above criteria, regardless of whether apoptosis is induced by colchicine treatment or by serum withdrawal. Thus, the delay cannot simply be due to the well-known ability of MDR protein overexpression to lower chemotherapeutic drug accumulation in MDR cells. LR73/27V500 "selectants", exhibiting similar levels of MDR protein overexpression but higher multidrug resistance due to selection with the chemotherapeutic drug vincristine, exhibit a slightly longer delay in the progression of apoptosis. Normal apoptotic cascade kinetics are partially restored by pre-treatment of the MDR cells with the MDR protein inhibitor verapamil. Untransfected LR73 cells not expressing MDR protein but elevated in pHi via manipulation of CO2/HCO3- as described [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313] are inhibited in DNA ladder formation, similar to LR73/hu MDR 1 transfectants. These results uncover an additional mechanism whereby MDR protein overexpression may promote the survival of tumor cells and further support the notion that in some systems intracellular acidification may be either causal or permissive for proper progression of the apoptotic cascade.
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Affiliation(s)
- L J Robinson
- Molecular Pharmacology and Therapeutics Program at the Raymond and Beverly Sackler Foundation Laboratory, Memorial Sloan-Kettering Cancer Center, Pharmacology, Cornell University Medical College, New York, New York 10021, USA
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Baggetto LG. Biochemical, genetic, and metabolic adaptations of tumor cells that express the typical multidrug-resistance phenotype. Reversion by new therapies. J Bioenerg Biomembr 1997; 29:401-13. [PMID: 9387101 DOI: 10.1023/a:1022459100409] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Among the genetic and metabolic alterations that cancer cells undergo, several allow their survival under extreme environmental conditions. The resulting aberrant metabolism is compatible with tumor progression at the expenses of high energy needs, especially for maintaining high division rate. When treated with chemotherapeutic drugs many cancer cells take advantage of their ability to develop a resistance phenotype, as part of an adaptative mechanism. Two main actors of this multidrug phenotype (MDR) are represented by the P-glycoprotein and by the more recently discovered multidrug-resistance associated protein (MRP), two membrane proteins of the ABC superfamily of transporters that can extrude chemotherapeutic drugs under an ATP-dependent mechanism. We will briefly review the major metabolic aberrations that several cancers develop, followed by the molecular, genetic, structural, and functional aspects related mainly to P-glycoprotein, with a concern for the regulation of mdr gene expression. We will point out the role that membrane cholesterol may play in the MDR phenotype, relate this phenotype to bioenergetic considerations, and review the ways of modulating it by the use of new therapeutic approaches.
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41
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Mao Q, Scarborough GA. Purification of functional human P-glycoprotein expressed in Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1327:107-18. [PMID: 9247172 DOI: 10.1016/s0005-2736(97)00050-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A system for expression and facile purification of the human P-glycoprotein (Pgp) from the yeast Saccharomyces cerevisiae is described. The wild-type human mdr1 cDNA was cloned into a high copy number yeast expression vector under the control of the constitutive promoter of the yeast plasma membrane H+-ATPase. Western blots of membranes from the stable transformants confirmed that the Pgp is expressed in yeast cells in amounts approximately 0.4% of the total yeast membrane protein. Density gradient sedimentation analysis of the yeast membranes indicated that the expressed Pgp is localized in the plasma membrane. Yeast cells transformed with the Pgp expression plasmid acquire increased resistance to valinomycin, suggesting that the expressed Pgp is properly folded and functional. The expressed Pgp can be solubilized from the yeast membranes with lysophosphatidylcholine, and when tagged with ten histidines at its C-terminus, can be readily purified to about 90% homogeneity by Ni2+ affinity chromatography. About 50 microg of the Pgp can be purified from 20 mg of crude yeast membranes. The purified human Pgp exhibits a verapamil-stimulated ATPase activity and the maximal activity is 2.5 +/- 0.5 micromol/min per mg of Pgp, suggesting that the purified Pgp from yeast is highly functional. The Pgp expressed in yeast has the same electrophoretic mobility (ca. 130 kDa) as the Pgp produced in Sf9 insect cells and is unaffected by N-glycosidase treatment, suggesting that it is not glycosylated. Because of the relative ease of growing yeast in massive quantities this expression system appears to be excellent for producing this membrane transporter at levels sufficient for further biochemical and biophysical studies, and for site-directed mutagenesis studies as well.
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Affiliation(s)
- Q Mao
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill 27599, USA
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42
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Abstract
Mammalian P-glycoproteins are plasma membrane proteins belonging to the superfamily of ATP-binding cassette transporters. They were discovered as drug pumps in multidrug-resistant cancer cells, but are also present in many normal tissues. Genetic approaches have helped to dissect the physiological functions and mode of action of P-glycoproteins. Disruption of both genes for the drug-transporting P-glycoproteins in mice has no effect on the normal sheltered life of these mice, but renders them hypersensitive to many drugs. P-glycoprotein appears to be especially important in protecting the brain and in limiting uptake of hydrophobic drugs from the gut. Recent experiments with polarized cells support the idea that drug-transporting P-glycoproteins act by flipping drugs from the inner to the outer leaflet of the plasma membrane.
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Affiliation(s)
- P Borst
- The Netherlands Cancer Institute, Department of Molecular Biology, Amsterdam, The Netherlands
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Barrand MA, Bagrij T, Neo SY. Multidrug resistance-associated protein: a protein distinct from P-glycoprotein involved in cytotoxic drug expulsion. GENERAL PHARMACOLOGY 1997; 28:639-45. [PMID: 9184795 DOI: 10.1016/s0306-3623(96)00284-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
1. Multidrug resistance (MDR) is a phenomenon originally seen in cultured tumor cells that, following selection for resistance to a single anticancer agent, become resistant to a range of chemically diverse anticancer agents. These MDR cells show a decrease in intracellular drug accumulation due to active efflux by transporter proteins. The transporter best characterized is P-glycoprotein (Pgp). This protein has been identified in many cancers and has been the target for agents able to inhibit its action, thereby reversing resistance. 2. More recently, another transporter, multidrug resistance-associated protein (MRP) has been identified in a number of MDR human tumor cell lines that do not apparently express Pgp. The presence of MRP at the cell surface of these cells is associated with alterations in drug accumulation and distribution. 3. The gene-encoding MRP has been cloned and sequenced and shown by transfection studies to be able to confer resistance and changes in drug accumulation in sensitive tumor cells. The profile of anticancer drugs expelled in the presence of MRP is similar, but not identical, to that of Pgp. 4. MRP has been identified in a number of different types of cancers, but it is not yet clear to what extent it is involved with clinical resistance. Furthermore, resistance modulators useful against Pgp are less effective in reversing MRP-mediated resistance. 5. It is not fully understood how MRP brings about drug efflux, but it is clear that the underlying mechanisms are different from those responsible for Pgp-mediated drug efflux. In particular, glutathione (GSH) is required for the effective expulsion of the anticancer agents. 6. Unlike Pgp, MRP is able to transport metallic oxyanions and glutathione and other conjugates, including peptidyl leukotrienes. Agents that inhibit organic anion transport, such as probenecid, can block MRP activity. 7. Like Pgp, MRP is expressed not only in resistant tumor cells, but also in normal human tissues. These include the epithelial cells lining the airways and the gastrointestinal tract. In cells in normal tissues, MRP appears to be located within the cytoplasm, which may mean that it functions here in a manner slightly different to that in malignant cells. It is now also recognized in cells and tissues from other species, such as the rat and mouse.
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Affiliation(s)
- M A Barrand
- Department of Pharmacology, University of Cambridge
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44
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Hepatobiliary elimination of cationic drugs: the role of P-glycoproteins and other ATP-dependent transporters. Adv Drug Deliv Rev 1997. [DOI: 10.1016/s0169-409x(97)00498-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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45
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Klyachko KA, Schuldiner S, Neyfakh AA. Mutations affecting substrate specificity of the Bacillus subtilis multidrug transporter Bmr. J Bacteriol 1997; 179:2189-93. [PMID: 9079903 PMCID: PMC178954 DOI: 10.1128/jb.179.7.2189-2193.1997] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Bacillus subtilis multidrug transporter Bmr, a member of the major facilitator superfamily of transporters, causes the efflux of a number of structurally unrelated toxic compounds from cells. We have shown previously that the activity of Bmr can be inhibited by the plant alkaloid reserpine. Here we demonstrate that various substitutions of residues Phe143 and Phe306 of Bmr not only reduce its sensitivity to reserpine inhibition but also significantly change its substrate specificity. Cross-resistance profiles of bacteria expressing mutant forms of the transporter differ from each other and from the cross-resistance profile of cells expressing wild-type Bmr. This result strongly suggests that Bmr interacts with its transported drugs directly, with residues Phe143 and Phe306 likely to be involved in substrate recognition.
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Affiliation(s)
- K A Klyachko
- Department of Medicinal Chemistry and Pharmacognosy, University of Illinois, Chicago 60607, USA
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46
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Wadkins RM, Roepe PD. Biophysical aspects of P-glycoprotein-mediated multidrug resistance. INTERNATIONAL REVIEW OF CYTOLOGY 1997; 171:121-65. [PMID: 9066127 DOI: 10.1016/s0074-7696(08)62587-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In the 45 years since Burchenal's observation of chemotherapeutic drug resistance in tumor cells, many investigators have studied the molecular basis of tumor drug resistance and the phenomenon of tumor multidrug resistance (tumor MDR). Examples of MDR in microorganisms have also become topics of intensive study (e.g., Plasmodium falciparum MDR and various types of bacterial MDR) and these emerging fields have, in some cases, borrowed language, techniques, and theories from the tumor MDR field. Serendipitously, the cloning of MDR genes overexpressed in MDR tumor cells has led to elucidation of a large family of membrane proteins [the ATP-binding cassette (ABC) proteins], an important subset of which confer drug resistance in many different cells and microorganisms. In trying to decipher how ABC proteins confer various forms of drug resistance, studies on the structure and function of both murine and human MDR1 protein (also called P-glycoprotein or P-gp) have often led the way. Although various theories of P-gp function have become popular, there is still no precise molecular-level description for how P-gp overexpression lowers intracellular accumulation of chemotherapeutic drugs. In recent years, controversy has developed over whether the protein protects cells by translocating drugs directly (as some type of drug pump) or indirectly (through modulating biophysical parameters of the cell). In this ongoing debate over P-gp function, detailed consideration of biophysical issues is critical but has often been neglected in considering cell biological and pharmacological issues. In particular, P-gp overexpression also changes plasma membrane electrical potential (delta psi zero) and intracellular pH (pHi), and these changes will greatly affect the cellular flux of a large number of compounds to which P-gp overexpression confers resistance. In this chapter, we highlight these biophysical issues and describe how delta psi zero and pHi may in fact be responsible for many MDR-related phenomena that have often been hypothesized to be due to direct drug translocation (e.g., drug pumping) by P-gp.
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Affiliation(s)
- R M Wadkins
- Raymond & Beverly Sackler Foundation Laboratory, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
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47
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Fillpits M, Suchomel RW, Dekan G, Stiglbauer W, Haider K, Depisch D, Pirker R. Expression of the multidrug resistance-associated protein (MRP) gene in colorectal carcinomas. Br J Cancer 1997; 75:208-12. [PMID: 9010028 PMCID: PMC2063277 DOI: 10.1038/bjc.1997.35] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
To determine the clinical significance of MRP in patients with colorectal carcinomas, we have studied the expression of the MRP gene by reverse transcription-polymerase chain reaction (RT-PCR) (n = 105) and by immunohistochemistry (n = 30). MRP mRNA expression was observed in 92 (88%) tumour specimens. Positive MRP staining with monoclonal antibodies QCRL-1 and QCRL-3 was detected in all samples studied with strong staining in seven (23%) and weak staining in 23 (77%) specimens. Strong MRP staining in these samples did not appear to be related to the age and sex of the patients, localization of the primary tumour, histological grade, tumour size, lymph node metastasis, distant metastasis and tumour stage. Strong MRP staining was not associated with MDR1 RNA or P-glycoprotein (P-gp) expression. Kaplan-Meier curves revealed that overall survival of patients with strong MRP-staining tumours was similar to the survival of patients with weak-staining tumours. These data indicate that the MRP gene is expressed in primary colorectal carcinomas but is neither related to known prognostic factors nor a prognostic factor by itself.
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Affiliation(s)
- M Fillpits
- Department of Oncology, University of Vienna Medical School, Austria
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Roepe PD, Wei LY, Hoffman MM, Fritz F. Altered drug translocation mediated by the MDR protein: direct, indirect, or both? J Bioenerg Biomembr 1996; 28:541-55. [PMID: 8953386 DOI: 10.1007/bf02110444] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Overexpression of the MDR protein, or p-glycoprotein (p-GP), in cells leads to decreased initial rates of accumulation and altered intracellular retention of chemotherapeutic drugs and a variety of other compounds. Thus, increased expression of the protein is related to increased drug resistance. Since several homologues of the MDR protein (CRP, ItpGPA, PDR5, sapABCDF) are also involved in conferring drug resistance phenomena in microorganisms, elucidating the function of the MDR protein at a molecular level will have important general applications. Although MDR protein function has been studied for nearly 20 years, interpretation of most data is complicated by the drug-selection conditions used to create model MDR cell lines. Precisely what level of resistance to particular drugs is conferred by a given amount of MDR protein, as well as a variety of other critical issues, are not yet resolved. Data from a number of laboratories has been gathered in support of at least four different models for the MDR protein. One model is that the protein uses the energy released from ATP hydrolysis to directly translocate drugs out of cells in some fashion. Another is that MDR protein overexpression perturbs electrical membrane potential (delta psi) and/or intracellular pH (pHi) and thereby indirectly alters translocation and intracellular retention of hydrophobic drugs that are cationic, weakly basic, and/or that react with intracellular targets in a pHi or delta psi-dependent manner. A third model proposes that the protein alternates between drug pump and Cl- channel (or channel regulator) conformations, implying that both direct and indirect mechanisms of altered drug translocation may be catalyzed by MDR protein. A fourth is that the protein acts as an ATP channel. Our recent work has tested predictions of these models via kinetic analysis of drug transport and single-cell photometry analysis of pHi, delta psi, and volume regulation in novel MDR and CFTR transfectants that have not been exposed to chemotherapeutic drugs prior to analysis. This paper reviews these data and previous work from other laboratories, as well as relevant transport physiology concepts, and summarizes how they either support or contradict the different models for MDR protein function.
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Affiliation(s)
- P D Roepe
- Molecular Pharmacology and Therapeutics Program, Raymond & Beverly Sackler Foundation Laboratory, Memorial Sloan Kettering Cancer Center, New York, New York, USA
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49
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Stein U, Walther W, Shoemaker RH. Modulation of mdr1 expression by cytokines in human colon carcinoma cells: an approach for reversal of multidrug resistance. Br J Cancer 1996; 74:1384-91. [PMID: 8912533 PMCID: PMC2074774 DOI: 10.1038/bjc.1996.553] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Reversal of multidrug resistance (MDR) may offer a means of increasing the effectiveness of tumour chemotherapy. A variety of recent evidence indicates that cytokines may be particularly useful in this endeavour. To investigate the molecular mechanism by which cytokines may sensitise multidrug-resistant colon carcinoma cells, HCT15 and HCT116, to treatment with MDR-related drugs, we evaluated the effects of the human cytokines tumour necrosis factor alpha (TNF alpha), interleukin 2 (IL-2) and interferon gamma (IFN gamma) on mdr1 gene expression at the mRNA level by reverse transcription-polymerase chain reaction (RT-PCR) and at the protein level with monoclonal antibodies by immuno flow cytometry. P-glycoprotein function was examined after accumulation of the fluorescent drug, doxorubicin, by flow cytometry. Chemosensitivity to doxorubicin and vincristine was analysed using the XTT assay. All three cytokines were found to modulate the MDR characteristics on mdr1 expression levels, P-glycoprotein function and measured chemosensitivity to MDR-associated anti-cancer drugs. This cytokine-induced reversal of MDR was strongly time dependent, with maximal effects after 48 and 72 h of cytokine treatment. If similar modulation of MDR phenotype can be obtained in in vivo models, it may be possible to verify the time course for modulation by cytokine treatment and to design appropriate clinical trials of this strategy for MDR reversal.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/drug effects
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Antibiotics, Antineoplastic/metabolism
- Antineoplastic Agents/pharmacology
- Colonic Neoplasms/genetics
- Colonic Neoplasms/metabolism
- Doxorubicin/metabolism
- Gene Expression Regulation, Neoplastic/drug effects
- Genes, MDR/drug effects
- Humans
- Interferon-gamma/pharmacology
- Interleukin-2/pharmacology
- Neoplasm Proteins/drug effects
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Tumor Cells, Cultured/drug effects
- Tumor Cells, Cultured/metabolism
- Tumor Necrosis Factor-alpha/pharmacology
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Affiliation(s)
- U Stein
- Laboratory of Drug Discovery Research and Development, Division of Cancer Treatment, National Cancer Institute, Frederick, Maryland 21702-1201, USA
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50
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Robinson LJ, Roepe PD. Effects of membrane potential versus pHi on the cellular retention of doxorubicin analyzed via a comparison between cystic fibrosis transmembrane conductance regulator (CFTR) and multidrug resistance (MDR) transfectants. Biochem Pharmacol 1996; 52:1081-95. [PMID: 8831728 DOI: 10.1016/0006-2952(96)81736-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Recently (Wei et al., Biophys J 69: 883-895, 1995), several 3T3/hu cystic fibrosis transmembrane conductance regulator (CFTR) transfectant clones were found to exhibit a low-level multidrug resistance (MDR) phenotype. This phenotype is similar, but not identical to that found for MDR transfectants not previously exposed to chemotherapeutic drugs. Both MDR and CFTR transfectants are depolarized (exhibit lower plasma membrane delta psi ), but the former have alkaline pHi whereas the latter are acidic. It has been proposed (Roepe et al., Biochemistry 32: 11042-11056, 1993) that both decreased delta psi and increased pHi contribute to altered cellular retention of chemotherapeutic drugs in MDR tumor cells, but the relative contribution of each to altered cellular drug accumulation, drug retention, and drug efflux has not been studied in detail. We therefore examined doxorubicin transport for hu CFTR and mu MDR 1 transfectants using sensitive continuous monitoring of fluorescence techniques. Both CFTR and MDR transfectants exhibited significantly reduced doxorubicin accumulation, relative to drug-sensitive control cells. Plots of the initial rate of accumulation versus doxorubicin concentration were linear for the control cells and the CFTR and MDR transfectants between 0.1 to 0.5 microM drug, but better fit by a quadratic between 0.1 to 1.5 microM drug. The slopes of these curves were proportional to measured delta psi. Low-level selection of either CFTR or MDR transfectants with chemotherapeutic drug did not decrease further the initial rate of drug accumulation or change delta psi. Accumulation experiments for control cells performed in the presence of various concentrations of K+ further suggests that the rate of accumulation is related to delta psi. By measuring the kinetics of doxorubicin release for CFTR and MDR transfectants preloaded with drug, we concluded that alkaline pHi perturbations are more important for determining relative intracellular binding efficiency. We also concluded, similar to the case previously made for MDR protein (Roepe, Biochemistry 31: 12555-12564, 1992) that CFTR overexpression does not enhance the rate of drug efflux. These data better define the role of lowered delta psi and elevated pHi in altering the cellular retention of doxorubicin in MDR tumor cells.
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Affiliation(s)
- L J Robinson
- Molecular Pharmacology and Therapeutics Program, Raymond & Beverly Sackler Foundation Laboratory, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
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