The inhibitory effect of genistein on the growth and metastasis of a transplantable rat accessory sex gland carcinoma

Background: A cell line (K1) derived from a carcinogen-induced accessory sex gland carcinoma was used to examine the effects of the soybean extract, genistein, on tumor growth and metastasis. Methods: Male Lobund–Wistar rats were injected s.c. with 20 million K1 cells; genistein (50 mg/kg BW) or the vehicle was administered s.c. every 12 h for 31 days. Results: Genistein significantly inhibited tumor growth. Compared with controls, fewer genistein-treated rats developed invasive tumors (11% vs. 44%) or lymph node metastases (44% vs. 89%). No lung metastases were found in genistein-treated animals in contrast to controls (0% vs. 44%). Estrogenic side effects were precipitated in genistein-treated rats, including decreased accessory sex gland complex weight, increased pituitary weight, decreased testis weight, and decreased (BW). Serum testosterone was undetectable and serum prostate-specific acid phosphatase activity was 38% lower in genistein-treated rats compared with controls. Genistein concentrations in the solid tumors (2 nmol/g) were one-third those in blood. Conclusions: These data suggest that genistein may be a useful chemotherapeutic agent to inhibit the growth and metastasis of accessory sex gland cancers, such as those derived from the prostate.