Promotional effects of testosterone and dietary fat on prostate carcinogenesis in genetically susceptible rats.

Germfree (GF) Lobund strain Wistar (LW) rats, fed vegetable diet L-485, have developed prostate adenocarcinomas spontaneously (10% incidence) at average age 34 months. Conventional LW rats, implanted with testosterone at age 4 months, developed a higher incidence of prostate cancer after an average interval of 14 months: 24% had developed gross tumors, and 40% when it included microscopic tumors. Preliminary results indicate that testosterone-treated LW rats that were fed the same diet, which was supplemented with corn oil up to 20% fat, developed prostate cancer after intervals of 6-12 months. Aged GF Sprague-Dawley (SD) rats have not developed prostate cancer spontaneously. Conventional SD rats fed diet L-485 and treated with testosterone developed only prostatitis. Experimental designs should consider genetic susceptibility as a basic prerequisite for studies on experimental prostate cancer.