Biochemical characterization of a mitomycin C‐resistant human bladder cancer cell line

• Published in: International journal of cancer Vol. 65; no. 6; pp. 852 - 857
• Main Authors: Singh, Shivendra V., Scalamogna, Domenic, Xia, Hong, O'Toole, Stacy, Roy, Deodutta, Emerson, Erling O., Gupta, Vicram, Zaren, Howard A.
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 15.03.1996; Wiley-Liss
• Subjects: Antibiotics, Antineoplastic - pharmacokinetics; Antibiotics, Antineoplastic - pharmacology; Antineoplastic agents; Biological and medical sciences; Biotransformation; Cell Survival - drug effects; DNA Polymerase I - metabolism; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; General aspects; Glutathione - metabolism; Glutathione Transferase - metabolism; Humans; Medical sciences; Mitomycin - pharmacokinetics; Mitomycin - pharmacology; Pharmacology. Drug treatments; RNA, Messenger - metabolism; Tumor Cells, Cultured; Urinary Bladder Neoplasms - drug therapy; Urinary Bladder Neoplasms - metabolism; Urinary Bladder Neoplasms - pathology; Antineoplastic agent; Human; Urinary system disease; Urinary tract disease; Malignant tumor; Cell subpopulation; Mechanism; Alkylating agent; Antibiotic; Urinary bladder; Established cell line; Bladder disease; Negative therapeutic reaction
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/(SICI)1097-0215(19960315)65:6<852::AID-IJC24>3.0.CO;2-4

This study describes characteristics of a mitomycin C (MMC)‐resistant human bladder cancer cell line, J82/MMC‐2, which was established by repeated in vitro exposures of a 6‐fold MMC‐resistant variant (J82/MMC) to 18 nM MMC. A 9.6‐fold higher concentration of MMC was required to kill 50% of the J82/MMC‐2 sub‐line compared with parental cells (J82/WT). NADPH cytochrome P450 reductase and DT‐diaphorase activities were significantly lower in J82/MMC‐2 cells compared with J82/WT, suggesting that reduced sensitivity of J82/MMC‐2 cells to MMC resulted from impaired drug activation. Consistent with this hypothesis, the formation of MMC‐alkylating metabolites was significantly lower in J82/MMC‐2 cells compared with J82/WT. Furthermore, DT‐diaphorase activity in J82/MMC‐2 cells was significantly lower compared with the 6‐fold MMC‐resistant variant. Glutathione (GSH) levels were comparable in all 3 cell lines. Although GSH transferase (GST) activity was significantly higher in the J82/MMC‐2 cells compared with J82/WT, this enzyme activity did not differ between 6‐ and 9.6‐fold MMC‐resistant variants. Whereas DNA polymerase α mRNA expression was comparable in these cell lines, levels of DNA ligase I mRNA were slightly lower in both MMC‐resistant variants relative to J82/WT. However, the DNA polymerase β mRNA level was markedly higher in the J82/MMC‐2 cell line compared with either J82/WT or J82/MMC. Thus, emergence of a higher level of resistance to MMC in J82/MMC‐2 cells compared with J82/MMC may be attributed to (i) impaired drug activation through further reduction in DT‐diaphorase activity and (ii) enhanced DNA repair through over‐expression of DNA polymerase β. © 1996 Wiley‐Liss, Inc.