title: Isolation and characterization of a mitomycin C-resistant variant of human colon carcinoma HT-29 cells.
abstract: To investigate the resistant mechanisms against MMC in human tumor cells, we isolated an MMC-resistant variant (HT-29/MMC) of HT-29 human colon carcinoma cells. HT-29/MMC cells showed 5-fold resistance to MMC as compared with the parental cell line but did not show cross-resistance to Adriamycin, vincristine, ACNU, bleomycin, or cisplatin. Treatment of the cells with dicoumarol, an inhibitor of DT-diaphorase, reduced the cytotoxicity of MMC in DT-diaphorase proficient HT-29 cells but not in HT-29/MMC cells. HT-29/MMC cells were 5 times more sensitive than HT-29 cells to menadione, which is detoxified by DT-diaphorase, DT-diaphorase was deficient in HT-29/MMC cells as determined by the enzyme activity and immunoblot analysis of the cytoplasmic proteins. Levels of cytochrome P-450 reductase and glutathione S-transferase, however, were comparable in both cell lines. The amount of [3H]-MMC found covalently bound to chromosomal DNA in HT-29/MMC cells was one-fourth that detected in HT-29 cells. Treatment with dicoumarol reduced the DNA-bound MMC in HT-29 cells but not in HT-29/MMC cells. These results indicate that the deficiency in DT-diaphorase, an activating enzyme of MMC, is one of the mechanisms of resistance in HT-29/MMC cells.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Naito
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
mesh_terms: D000332:Aerobiosis; D000478:Alkylation; D001711:Biotransformation; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D004273:DNA, Neoplasm / Q000378:metabolism; D001728:Dicumarol / Q000494:pharmacology; D004351:Drug Resistance; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D016685:Mitomycin / Q000378:metabolism / Q000494:pharmacology*; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010084:Oxidation-Reduction; D014407:Tumor Cells, Cultured; D014812:Vitamin K / Q000494:pharmacology
chemical_list: D004273:DNA, Neoplasm; D014812:Vitamin K; D016685:Mitomycin; D001728:Dicumarol; D009251:NADPH-Ferrihemoprotein Reductase; D016660:NAD(P)H Dehydrogenase (Quinone); D005982:Glutathione Transferase