Prostate cancer is the second most commonly occurring cancer in men in the United States. Generally, an extended period of time is needed for a mutation to develop into a full scale tumor. Because of this long latency period, lifestyle and environmental factors, such as diet, may play an important role in the development and progression of the disease. Diet is one factor that has been implicated in the risk for developing prostate cancer. We previously showed that diets high in soy isoflavones and selenium (Se) decreased androgen receptor expression and expression of androgen regulated genes in healthy rat prostates. The purpose of this study was to determine whether treatment of soy isoflavones and/or supplemental Se provide chemopreventive effects in the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model of prostate cancer, and whether the timing of the introduction of these nutrients determines protective effects. Male hemizygous C57/BL6 x FVB TRAMP mice were exposed to a diet high in isoflavones, a 4 mg/kg daily bolus of supplemental Se as methylselenocysteine (MSC), or the combination of high isoflavones and MSC starting at one of two time points: conception or 6 weeks of age, and were killed and dissected for prostate tissue, liver, and serum at either 4 weeks or 12 weeks of age (n per dietary treatment = 20: total mice = 240). Treatment with MSC resulted in decreased urogenital tract weight at 4 and 12 weeks. Treatment with MSC and isoflavones, both individually and as a combination, resulted in decreased androgen receptor expression, 5 alpha-reductase levels, and aromatase levels. The combination of MSC and a basal diet high in isoflavones resulted in decreased serum IGF-1 levels in 12 week TRAMP mice. Treatment from conception resulted in greater decreases in urogenital tract weight, 5 alpha-reductase expression, and aromatase expression than treatment from 6 weeks. This study demonstrated that in 12 week TRAMP mice, reductions in risk factors for prostate cancer by treatments of high isoflavones and supplemental Se are maximized by introduction to treatments at conception.



College and Department

Life Sciences; Nutrition, Dietetics, and Food Science



Date Submitted


Document Type





TRAMP, androgen receptor, IGF-1, 5 alpha-reductase, aromatase