Chemopreventive effects of cabbage on 7,12-dimethylbenz(a)-anthracene-induced hepatocarcinogenesis in toads (Bufo viridis).

Hepatocellular carcinoma was induced in the toad, Bufo viridis, in 29 out of 100 cases by the administration of 0.5 mg of 7,12-dimethylbenz(a)anthracene (DMBA)/toad, 3 times/week for 12 weeks. In contrast, toads treated with DMBA and cabbage diet 1 or 2 ml (3 h prior to the carcinogen)/toad, every day for 12 weeks showed a lower incidence of liver tumors: 15 and 12 cases out of 100. However, cabbage diet (2 ml/toad, every day for 12 weeks) was ineffective when administered 3 h after the carcinogen (DMBA) in 27 out of 100 cases. Neither tumor growth nor neoplastic changes were observed in toads treated with olive oil alone or with cabbage diet. It is concluded that a cabbage diet during initiation has an inhibitory effect on hepatocarcinogenesis in toads.