Effect of coumarin on the normal rat prostate and on the R-3327H prostatic adenocarcinoma.

Coumarin, the parent compound of warfarin, has been observed to stimulate macrophages, increase phagocytosis, and induce changes in lymphocyte-mitogen responsiveness in cancer patients. Coumarin has been reported to have antitumor activity in human melanomas and renal cancer when used in conjunction with the H-2 antagonist, cimetidine. We have observed that coumarin has antiprostatic activity in rats. When coumarin was given to mature rats at a dose of 40 mg/kg, a significant decrease in the size of the prostate, seminal vesicles, and testes was observed. Testosterone levels were unchanged or slightly elevated, consistent with an antiandrogenic-like activity. Similarly, coumarin significantly inhibited the androgen-induced increase in prostatic size when administered to castrated rats receiving testosterone. Coumarin given to rats bearing the R-3327H androgen-sensitive, prostate-derived tumor decreased the size of the primary tumor. The effect was greater than that produced by castration. Coumarin is worthy of further consideration as an agent for use in controlling the normal and abnormal growth of the prostate.