Chinese hamster ovary cell lines resistant to mitomycin C under aerobic but not hypoxic conditions are deficient in DT-diaphorase.
We have previously reported the isolation of CHO cell lines resistant to mitomycin C under aerobic conditions of drug exposure. Here it is reported that these cell lines have the same response to mitomycin C under hypoxic conditions as do controls. The cells are shown to have lower levels of DT-diaphorase activity than controls, but similar levels of activity of NADPH:cytochrome c reductase, another enzyme involved in the metabolism of mitomycin C. Evidence for molecular defects in the DT-diaphorase gene or gene transcript is presented for the deficient cell lines. The consequences of this DT-diaphorase deficiency is further explored by testing the toxicity of menadione, an established enzyme substrate. The isolation of CHO cell lines deficient in DT-diaphorase activity and resistant to mitomycin C under aerobic but not hypoxic conditions suggests that mitomycin C reduction by this enzyme has a significant impact on cytotoxicity under aerobic but not hypoxic conditions. Similarly, DT-diaphorase metabolism of menadione does not appear to have a significant impact on cytotoxicity in CHO cells.
Dulhanty
A M
AM
Physics Division of the Ontario Cancer Institute, Canada.
Whitmore
G F
GF
D000818:Animals; D015139:Blotting, Southern; D015687:Cell Hypoxia; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000032:analysis; D004351:Drug Resistance; D005796:Genes; D016685:Mitomycin; D008937:Mitomycins / Q000378:metabolism* / Q000633:toxicity; D011808:Quinone Reductases / Q000172:deficiency* / Q000235:genetics
D008937:Mitomycins; D016685:Mitomycin; D004247:DNA; D011808:Quinone Reductases