A comparison of dietary supplementation with tomato extract, tomato powder, or lycopene on the tissue distribution of lycopene and LNCaP prostate tumor growth in mice

Studies have suggested that increased consumption of lycopene-rich tomato products is associated with a lower risk of prostate cancer (PCa). In order to elucidate the role of tomato products and lycopene in prostate tumor growth, we established a murine model employing athymic Swiss nu/nu mice bearing xenografts of the poorly-differentiated androgen-sensitive LNCaP human prostate carcinoma. Mice were randomly assigned to one of 5 diets based upon the AIN76 formulation: control, lycopene-rich tomato extract, freeze-dried tomato powder, pure lycopene and a vehicle placebo that deliver 0, 0.6, 0.006, 0.6 and 0% dietary lycopene, respectively. Mice were fed for 2 wk prior to s.c. inoculation with 3.6 x 10^-6 LNCAP cells. We observed no significant difference in tumor appearance rate, growth rate, or survival based upon diet over 10 wks. Cis -trans lycopene isomer content and patterns in the the LNCaP tumor were similar to those in the human prostate. The concentrations of lycopene in murine tissues was greatest in liver, followed by spleen, testes and tumor. This study suggests that increased consumption of tomato products or lycopene supplementation will not benefit men with advanced high-grade PCa. However, the hypothesis that tomato products or lycopene may inhibit earlier stages of the PCa cascade or the more well differentiated tumors commonly found in men remains to be investigated.