Diet and the duration of testosterone-dependent prostate cancer in Lobund–Wistar rats

Hormone-related cancers in the prostate, breast, endometrium, ovary and testicle account for 30% of malignancies in humans. We have developed a unique model of spontaneous prostate cancer (PC) in Lobund–Wistar [L–W] rats that shares many of its characteristics with the natural history of PC in man, including (a) inherent predisposition, high production of testosterone and aging risk factors, (b) endogenous tumorigenic mechanisms, and (c) early stage testosterone-dependent and late stage testosterone-independent tumors. About 30% of L–W rats on diet L-485 develop spontaneous palpable cancer in the anterior prostate-seminal vesicle (P-SV) complex in average of 20.5 months. At age 12 months early stage spontaneous PC was prevented or reversed by testosterone-deprivation through change of diet from L-485 to soy protein isolate/isoflavone (SPII) diet, thereby preventing the late lethal clinical disease: about 75% of rats at risk of developing testosterone-independent P-SV tumors were free of detectable cancer and about 25% had developed testosterone-independent cancer at age 12 months. The duration of the dependent stage exceeded age 12 months in 75% of the rats at risk. Dietary soymeal, found in most natural ingredient diets, may promote PC tumorigenesis, but only in L–W rats.