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Biochemical characterization of a mitomycin C‐resistant human bladder cancer cell line
Author(s) -
Singh Shivendra V.,
Scalamogna Domenic,
Xia Hong,
O'Toole Stacy,
Roy Deodutta,
Emerson Erling O.,
Gupta Vicram,
Zaren Howard A.
Publication year - 1996
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19960315)65:6<852::aid-ijc24>3.0.co;2-4
Subject(s) - mitomycin c , cell culture , medicine , cell growth , transfection , microbiology and biotechnology , biology , biochemistry , surgery , genetics
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.