Growth Inhibition of Rat Mammary Carcinoma Induced by Cis-Platinum Diamminodichloride-II

Summary

Cis-platinum diamminodichloride-II (cis-Pt-II) was highly effective in promoting regression of mammary tumors (MT) induced by 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats. Dose schedules of cis-Pt-II most significant in inhibiting MT growth were 6 mg/kg body weight administered once or 4 mg/kg body weight administered thrice, every 12 days. The former dose was more efficacious than the latter. Pretreatment of DMBA-induced MT-bearing rats with Cytoxan (50 mg/kg body weight) markedly enhanced the effectiveness of cis-Pt-II. The 6-mg dose of cis-Pt-II induced a 19% decrease in body weight 7 days after treatment, but body weight returned to pretreatment values at 21 days. The cis-Pt-II-treated rats were compared with a food-restricted control group that lost a comparable or greater amount of body weight. Thus a significant inhibitory effect of cls-Pt-II on growth of DMBA-induced rat MT, an autochthonous experimental tumor system closely resembling human breast cancer, was demonstrated.