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

Singh, SV, Scalamogna, D, Xia, H et al. (1996). Biochemical characterization of a mitomycin C-resistant human bladder cancer cell line . 65(6), 852-857. 10.1002/(SICI)1097-0215(19960315)65:6<852::AID-IJC24>3.0.CO;2-4

cited authors

  • Singh, SV; Scalamogna, D; Xia, H; O'Toole, S; Roy, D; Emerson, EO; Gupta, V; Zaren, HA

fiu authors

abstract

  • 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 a 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 182/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 8.

publication date

  • March 15, 1996

start page

  • 852

end page

  • 857

volume

  • 65

issue

  • 6