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

✍ Scribed by Shivendra V. Singh; Domenic Scalamogna; Hong Xia; Stacy O'Toole; Deodutta Roy; Erling O. Emerson; Vicram Gupta; Howard A. Zaren

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: French
• Weight: 765 KB
• Volume: 65
• Category: Article
• ISSN: 0020-7136
• DOI: 10.1002/(sici)1097-0215(19960315)65:6<852::aid-ijc24>3.0.co;2-4

✦ Synopsis

This study describes characteristics of a mitomycin C (MMC)resistant human bladder cancer cell line, )82/MMC-2, which was established by repeated in vitro exposures of a 6-fold MMC-resistant variant (J82lMMC) to 18 nM MMC. A 9.6-fold higher concentration of MMC was required to kill 50% of the )82/MMC-2 sub-line compared with parental cells ()82/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 )82/MMC-2 cells to MMC resulted from impaired drug activation. Consistent with this hypothesis, the formation of MMC-alkylating metabolites was significantly lower in )82/MMC-2 cells compared with J82iWT. Furthermore, DT-diaphorase activity in J82/MMC-2 cells was significantly lower compared with the 6-fold MMCresistant variant. Glutathione (GSH) levels were comparable in all 3 cell lines. Although GSH transferase (GST) activity was significantly higher in the )82/MMC-2 cells compared with )82/WT, this enzyme activity did not differ between 6-and 9.6-fold MMC-resistant variants. Whereas DNA polymerase Q mRNA expression was comparable in these cell lines, levels of DNA ligase I mRNA were slightly lower in both MMC-resistant variants relative to )82/WT. However, the DNA polymerase p mRNA level was markedly higher in the J82/MMC-2 cell line compared with either )82/WT or )82/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 p.