title: Characterization of a human bladder cancer cell line selected for resistance to mitomycin C.
abstract: This study describes characteristics of a human bladder cancer cell line J82/MMC that is 6-fold more resistant to mitomycin C (MMC) than the parental cells. The J82/MMC subline was isolated by repeated continuous exposures of the J82/WT cells to increasing concentrations of MMC. The J82/MMC cell line showed (1) collateral sensitivity to taxol, 5-FU and topoisomerase II inhibitors; and (2) cross-resistance to cisplatin, melphalan and MMC analogues BMY 25282 and BMY 25067. Levels of two key MMC activation enzymes, NADPH cytochrome P450 reductase and DT-diaphorase, were significantly lower in J82/MMC cells compared with J82/WT, suggesting that lower sensitivity of J82/MMC cells to MMC may result from deficient drug activation. Further support is indicated by: 1) reduction in the differential in toxicity between the 2 cell lines by BMY 25282; and 2) a higher effect of DT-diaphorase inhibitor dicumarol on the wild-type cells compared with J82/MMC. Although glutathione (GSH) levels did not differ in these cells, a small but significant increase in GSH transferase (GST) activity was noticed in J82/MMC cells. GST inhibitor ethacrynic acid significantly enhanced MMC cytotoxicity in the J82/MMC cell line. A small but significant increase in the level of anti-oxidative enzyme catalase, but not GSH peroxidase, was also observed in J82/MMC cell line compared with J82/WT. Thus, the possibility that relatively lower sensitivity of J82/MMC cells to MMC may result from reduced oxygen radical generation cannot be ruled out. MMC-induced DNA interstrand cross-linking was markedly lower in the J82/MMC cell line compared with J82/WT. Our results suggest that the MMC resistance in the J82/MMC cell line may be multifactorial.
authors.affiliation: Mercy Cancer Center, Mercy Hospital, Pittsburgh, PA 15219.
authors.forename: B H
authors.initials: BH
authors.lastname: Xu
authors.forename: V
authors.initials: V
authors.lastname: Gupta
authors.forename: S V
authors.initials: SV
authors.lastname: Singh
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D002277:Carcinoma / Q000473:pathology / Q000503:physiopathology*; D002374:Catalase / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004351:Drug Resistance; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D016685:Mitomycin / Q000633:toxicity*; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000473:pathology / Q000503:physiopathology*
chemical_list: D000970:Antineoplastic Agents; D016685:Mitomycin; D002374:Catalase; D005978:Glutathione