Some effects of inhibitors of polyamine synthesis on experimental prostatic cancer.

Difluoromethylornithine (DFMO) and methylglyoxal-bis(guanyl-hydrazone) (MGBG), inhibitors of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AMDC), respectively, were tested in two experimental prostatic cancer models. DFMO resulted in a reduction in tumor size in both the rapidly growing R-3327 rat prostatic adenocarcinoma (30.5 +/- 15 versus 61 +/- 9.5 in control animals) and the human DU-145 adenocarcinomas (1.7 ml versus 3.3 ml in control animals) in nude mice. MGBG was tested only in the rat tumor, where it induced a reduction of 22.9 +/- 9.5 ml versus 61 +/- 9.5 in control animals in tumor size but was highly toxic. Flutamide or 9-B-D-arabinofuranosyladenine (Ara-A) proved ineffective per se in reducing tumor growth of the human DU-145 or of the R-3327-G strain, respectively, but increased the efficacy of DFMO against the DU-145 tumor had a high level of ODC which was reduced by DFMO of by Ara-A; the R-3327 tumor had a low level of ODC which was too low to be decreased by DFMO.