Inhibition by Ergocornine of Initiation and Growth of 7,12-Dimethylbenzanthracene-Induced Mammary Tumors in Rats: Effect of Tumor Size

Summary

Administration of ergocornine 11 days before, and 5 days after, treatment with DMBA significantly inhibited the induction of mammary tumors in rats. Ergocornine caused rapid and complete (to palpation) regression of 62% of established, DMBA-induced mammary tumors. Examination of sites where tumors had completely regressed to palpation, 2 months after ergocornine treatment was discontinued, revealed that 64% of the tumors did not recur. The effectiveness of ergocornine in regressing tumors was found to be related to initial tumor size. Tumors with volumes up to 1.8 cm³ regressed rapidly after ergocornine; whereas tumors approximately 14.1 cm³ and over did not respond to treatment. Tumors intermediate between these two sizes showed growth inhibition, and many showed regression in varying degrees. Therefore, mammary tumors start to lose their hormonal dependence as they become larger, and eventually may lose it completely. In view of these results, we suggest that prolactin inhibitors may cause regression of breast cancer in its early stages and may prevent formation of tumors through prophylactic treatment.