METHODOLOGY/PRINCIPAL FINDINGS: We evaluated the effects of dietary
lycopene (250 mg/kg diet),
selenium (
methylselenocysteine, 1 mg/kg diet), and
vitamin E (
gamma-tocopherol, 200 mg/kg diet) alone and in combination on the growth of
androgen-dependent Dunning R3327-H rat prostate
adenocarcinomas in male, Copenhagen rats. AIN-93G diets containing these
micronutrients were prefed for 4 to 6 weeks prior to
tumor implantation by
subcutaneous injection.
Tumors were allowed to grow for approximately 18 weeks. Across diet groups,
methylselenocysteine consumption decreased final
tumor area (P = 0.003),
tumor weight (P = 0.003), and the
tumor weight/body weight ratio (P = 0.003), but
lycopene and
gamma-tocopherol consumption intake did not alter any of these measures. There were no significant interactions among nutrient combinations on
tumor growth.
Methylselenocysteine consumption also led to small, but significant decreases in
body weight (P = 0.007), food intake (P = 0.012), and
body weight gain/food intake ratio (P = 0.022). However, neither
body weight nor gain/food intake ratio was correlated with
tumor weight.
Methylselenocysteine,
lycopene, and
gamma-tocopherol consumed alone and in combination did not alter serum
testosterone or
dihydrotestosterone concentrations;
tumor proliferation or apoptosis rates. In addition, the diets also did not alter
tumor or prostate
androgen receptor,
probasin,
selenoprotein 15,
selenoprotein P, or
selenium binding protein 2
mRNA expression. However, using
castration and
finasteride-treated tissues from a previous study, we found that
androgen ablation altered expression of these
selenium-associated
proteins.
CONCLUSIONS: