Effects of alpha-difluromethylornithine on the development of deeply invasive urinary bladder carcinomas in mice.

alpha-Difluoromethylornithine (DFMO), was examined for its ability to suppress the development of invasive urinary bladder carcinoma in C3H/He male mice. Continuous administration of 0.2% DFMO in water following carcinogen treatment (0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine, BHBN, in drinking water for 8 weeks) was effective in suppressing urinary bladder carcinomas (P less than 0.05) as compared with the control group. However, when comparison was made based on tumors involving the entire urinary tract, protective effects could not be demonstrated. Coadministration of DFMO (0.2%) and BHBN (0.01%) did not alter tumor induction by the latter. These results were in sharp contrast to the protective effects in rats. Since bladder tumors in rats are of low grade and superficial whereas those in mice are of high grade and deeply invasive, our data indicate that DFMO has little to no effects against the development of aggressive forms of bladder carcinoma.