Genistein attenuates peritoneal metastasis of azoxymethane-induced intestinal adenocarcinomas in Wistar rats.

The effects of the soybean isoflavonoid genistein on the development of bombesin-enhanced peritoneal metastasis from intestinal adenocarcinomas induced by azoxymethane (AOM) were investigated in male inbred Wistar rats. From the beginning of the experiment, rats were given 10 weekly s.c. injections of AOM (7.4 mg/kg body weight) and s.c. injections of bombesin (40 microg/kg body weight) every other day, and from week 16, s.c. injections of genistein (5 or 10 mg/kg body weight) every other day until the end of the experiment in week 45. Bombesin significantly increased the incidence of intestinal tumors and of cancer metastasis to the peritoneum. Although genistein administered at either dose had little or no effect on the enhancement of intestinal carcinogenesis by bombesin or on the location, histologic type, depth of involvement, labeling index, or growth pattern of intestinal cancers, it significantly decreased the incidence of cancer metastasis. Genistein also significantly decreased the incidence of lymphatic vessel invasion of adenocarcinomas, which was enhanced by bombesin. Our findings indicate that genistein attenuates cancer metastasis by inhibiting cancer cell invasion into lymphatic vessels through activities that do not affect the growth of intestinal cancers. Copyright 2000 Wiley-Liss, Inc.