title: Bleomycin and X-ray-hypersensitive Chinese hamster ovary cell mutants: genetic analysis and cross-resistance to neocarzinostatin.
abstract: We have previously reported the isolation of 3 mutants of Chinese hamster ovary cells which exhibit hypersensitivity to bleomycin. 2 mutants were isolated on the basis of bleomycin-sensitivity [designated BLM-1 and BLM-2, Robson et al., Cancer Res., 45 (1985) 5304-5309] and 1 as adriamycin-sensitive [ADR-1, Robson et al., Cancer Res., 47 (1987) 1560-1565]. Because bleomycin generates DNA-strand breaks via a free-radical mechanism, we have studied the survival response of these mutants to a range of drugs which also generate free radicals and consequently DNA-strand breaks. The mutants are all hypersensitive to phleomycin, which differs from bleomycin in being unable to intercalate due to a modified bithiazole moiety. However, BLM-2 cells alone are hypersensitive to pepleomycin, a semi-synthetic bleomycin analogue. In contrast, BLM-1 cells are more sensitive than BLM-2 to streptonigrin (which operates via a hydroquinone intermediate). ADR-1 cells show wild-type resistance to streptonigrin. The results obtained with neocarzinostatin, an antibiotic requiring thiol activation, are unusual in that both BLM-1 and BLM-2 are approximately 3-fold more resistant than parental cells. However, the steady-state intracellular level of the major non-protein thiol, glutathione, is not altered in BLM-1 or BLM-2 cells. ADR-1 cells show essentially wild-type resistance to neocarzinostatin. Analysis of cell hybrids shows that BLM-1 and BLM-2 cells are phenotypically recessive in combination with parental CHO-K1 cells and represent different genetic complementation groups not only from one another, but also from the bleomycin-sensitive mutant xrs-6, isolated on the basis of X-ray sensitivity by Jeggo and Kemp [Mutation Res., 112 (1983) 313-319]. These results indicate that at least 3 gene products are involved in cellular protection against bleomycin toxicity in mammalian cells.
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001761:Bleomycin / Q000633:toxicity*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004351:Drug Resistance; D005816:Genetic Complementation Test; D005978:Glutathione / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects; D009154:Mutation; D017663:Peplomycin; D010692:Phleomycins / Q000633:toxicity; D014965:X-Rays; D009353:Zinostatin / Q000494:pharmacology*
chemical_list: D000903:Antibiotics, Antineoplastic; D010692:Phleomycins; D001761:Bleomycin; D017663:Peplomycin; D009353:Zinostatin; D005978:Glutathione