title: Characterization of a set of Chinese hamster ovary variant cell lines demonstrating differing sensitivity to mitomycin C.
abstract: Three related Chinese hamster ovary (CHO) cell lines derived from CHO-K1R cells (MMC3-A2, 21-1 and G1B) previously shown to differ in their sensitivity to mitomycin C (MMC), were investigated in more detail to determine the factors controlling this sensitivity. A separately maintained wild type cell line (CHO-K1TOR) was included in this study for comparison. Continuous (chronic) exposure of the five cell lines to MMC during the 10-day colony forming assay demonstrated a 15-fold range in MMC sensitivity between the most sensitive cell line (MMC3-A2) and the most resistant cell line (G1B) with CHO-K1R, 21-1 and CHO-K1TOR falling at intermediate levels. Acute aerobic exposure (0-5 h) to MMC resulted in a reduced fivefold range of sensitivities, which was further reduced to a three-fold range under hypoxic exposure conditions. These results were suggestive of differences in the aerobic enzymatic activation of MMC as a possible mechanism contributing to the varying sensitivities. There was no correlation between the one-electron reducing enzyme NADPH:cytochrome P-450 oxidoreductase (P450R) activity and cellular sensitivity to MMC. The five cell lines had similar levels of reduced glutathione (GSH), suggesting that oxygen homeostasis was not correlated with the cells, differing sensitivity to MMC. A correlation did exist between NAD(P)H:quinone oxidoreductase (DT-diaphorase) activity and cellular sensitivity to MMC under chronic exposure conditions for the cell lines. High DT-diaphorase levels were also correlated with a reduced ability of oxygen to modulate MMC toxicity. Levels of P450R and DT-diaphorase were not altered significantly during five-hour aerobic or hypoxic exposures of control cells.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: B L
authors.initials: BL
authors.lastname: Kuehl
authors.forename: M
authors.initials: M
authors.lastname: Buchwald
authors.forename: A M
authors.initials: AM
authors.lastname: Rauth
mesh_terms: D000818:Animals; D016466:CHO Cells; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004351:Drug Resistance; D005978:Glutathione / Q000032:analysis; D016685:Mitomycin / Q000494:pharmacology*; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism
chemical_list: D016685:Mitomycin; D003577:Cytochrome P-450 Enzyme System; D016660:NAD(P)H Dehydrogenase (Quinone); D005978:Glutathione