Effects of trilostane on 7,12-dimethylbenz[a]anthracene-induced rat mammary cancers and body weight of rats in relation to estrogen receptors.

Effects of trilostane (TLS) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancers and body weight of rats were examined in relation to estrogen receptors (ER) in 103 female Sprague-Dawley rats with DMBA-induced cancers. The inhibitory effects of the treated groups on the growth of DMBA-induced rat mammary cancers were significantly stronger than those of the control group at many points during the treatment, demonstrating a more remarkable inhibitory effect in the high-dose groups of 300 and 500 mg/kg. In the high-dose groups, the inhibitory effects of TLS tended to be slightly stronger in the ER-negative groups than in the ER-positive groups. These results suggest that the mechanisms of action of TLS are not influenced by the presence or absence of ER, but are due to complicated hormonal changes induced by the inhibition of steroid biosynthesis.