Cross-resistance to methotrexate and metals in human cisplatin-resistant cell lines results from a pleiotropic defect in accumulation of these compounds associated with reduced plasma membrane binding proteins.
Cross-resistance to a wide array of toxic chemicals is a common phenomenon in cisplatin-resistant cell lines. In this study, two independently isolated cisplatin-resistant cell lines derived from a human hepatoma and a cervical adenocarcinoma were shown to be cross-resistant to methotrexate (MTX) and several metal salts, such as sodium arsenite, sodium arsenate, antimony potassium tartrate, and cadmium chloride. A pleiotropic defect resulting in reduced accumulation of cisplatin, 3[H]MTX, 73As3+, and 73As5+ was found in both cisplatin-resistant cell lines. Analysis by immunoblot, indirect immunofluorescence, and Northern hybridization showed dramatically reduced expression of the folate binding protein that mediates MTX uptake in both human cisplatin-resistant cell lines. By photoaffinity labeling with UV irradiation, specific binding proteins of Mr 230,000 and Mr 48,000 for 73As3+ and Mr 190,000 for 73As5+ were found in enriched plasma membrane of both human cisplatin-sensitive parental cell lines. Expression of these specific binding proteins was decreased in cells selected for cisplatin resistance. A protein band at Mr 36,000 that binds to 73As3+ was overexpressed in both human cisplatin-resistant cell lines. The finding of loss of distinct binding proteins for MTX, arsenate, and arsenite in association with decreased accumulation of these agents in cisplatin-resistant cells suggests a pleiotropic, possibly regulatory, alteration in these cells.
Shen
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Laboratory of Cell Biology, National Cancer Institute, NIH, Bethesda, Maryland 20892-4255, USA.
Pastan
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I
Gottesman
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MM
D000970:Antineoplastic Agents / Q000633:toxicity*; D001152:Arsenicals / Q000493:pharmacokinetics / Q000494:pharmacology; D015152:Blotting, Northern; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002945:Cisplatin / Q000633:toxicity*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D019084:Fluorescent Antibody Technique, Indirect; D058973:Folate Receptors, GPI-Anchored; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D008670:Metals / Q000378:metabolism* / Q000633:toxicity; D008727:Methotrexate / Q000378:metabolism* / Q000633:toxicity; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D001152:Arsenicals; D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D008565:Membrane Proteins; D008670:Metals; D009363:Neoplasm Proteins; D011956:Receptors, Cell Surface; D002945:Cisplatin; D008727:Methotrexate