Synergetic cytotoxicity of bleomycin and polyhydric alcohols: DNA strand breakage evaluated by "comet assay"

DNA strand breakage induced in cultured cells by bleomycin (BLM) was remarkably enhanced in the presence of glycerol or polyvinyl alcohol which produces an enhancement effect on BLM cytotoxicity, but not in the presence of alcohols such as methanol, ethanol, or polyethylene glycol which do not produce enhanced cytotoxicity. The comet assay, a useful analytical method for evaluating DNA strand breakage, clearly demonstrated that combinations of BLM and polyhydric alcohols induced serious DNA damage in the whole cell populations compared with those induced by treatment with BLM alone. The comet assay also successfully showed distributions of cell populations with various degrees of DNA damage. These results suggested that an increase in DNA damage induced in the presence of polyhydric alcohols might be responsible for the enhancement of BLM cytotoxicity.