Thermal enhancement of dna strand breakage in mammalian cells treated with bleomycin

Abstract

Chinese hamster ovary cells were treated with various doses of Bleomycin (BLM) for 1 hr at 37° or 43°C and the effects of these treatments in terms of cell killing and DNA strand breakage were determined. The technique of alkaline elution was utilized for the sensitive detection of the DNA strand breaks thus allowing the use of doses of BLM which also permit the measurement of cell survival. The results of these experiments showed that both the cytotoxic effects and DNA strand breakage were enhanced when the treatments were conducted at 43°C compared to 37°C. However, when the data were plotted as the degree of strand breakage vs the fraction of cells surviving, it appeared that the strand breaks produced under hypertbermic conditions were more effective for cell killing. While most of the breaks were rapidly repaired following treatment at 37°C, the rate of red was reduced and the amount of residual unrepalred breaks was greater when the drug treatment was at 43°C. Thus, it would appear that the repair of BLM induced DNA strand breaks is important for cell survival.