Bleomycin cytotoxicity is prevented by superoxide dismutase in vitro

The cytotoxicity of the antitumor antibiotic bleomycin (BLM) on Chinese hamster ovary cells in vitro was studied. Approximately 50% of the cells were killed by exposure to 9.6 micrograms/ml BLM for 1 h. The cytotoxicity could be partially reversed by the prior addition of superoxide dismutase (SOD) or catalase, but not with the addition of mannitol or histidine. These results indicate that superoxide anion and hydrogen peroxide but not hydroxyl radical are involved in the cytotoxic action of BLM.