Tomato phytochemicals and prostate cancer risk

Epidemiological studies illustrate a significant relationship between increased tomato product consumption and decreased prostate cancer risk. Lycopene is often hypothesized as the phytochemical responsible for these anticarcinogenic effects, yet human and animal studies suggest that whole tomato intake has health benefits beyond that of lycopene. The foundation of this research is that tomato phytochemicals, in addition to lycopene, contribute substantially to prostate cancer risk reduction. Studies were conducted to biosynthesize and evaluate the effects of tomato carotenoids and flavonoids on factors associated with prostate cancer.;Results show that individual flavonoid treatments of quercetin, kaempferol, and naringenin significantly inhibited cancer cell proliferation in vitro, yet significant interactions were found when combination flavonoid treatments were administered. Thus, combinations of tomato flavonoids are more beneficial in diminishing cancer growth.;As phytoene and phytofluene are not commercially available, plant cell culture methodologies utilizing the herbicide norflurazon and 14C-sucrose were developed to biosynthesize and radiolabel these carotenoids in tomato cell suspension cultures. DU 145 prostate tumor cells absorbed 14C-15- cis phytoene and an oxidized phytoene product and partially metabolized these compounds in vitro. To elucidate the biological roles of phytoene and phytofluene, it was essential to determine the biodistribution and bioavailability of these carotenoids in vivo. Male F344 rats fed a 10% tomato powder diet displayed a distinct tissue specific tomato carotenoid accumulation, such that phytofluene and lycopene had the highest carotenoid accumulation in the liver and prostate, respectively. Provision of a single oral dose of either phytoene or phytofluene resulted in an increase in the dosed carotenoid concentration in most tissues. To evaluate an interrelationship between phytofluene, lycopene, or tomato powder consumption and androgen status, castrated or sham-operated, male F344 rats were provided with oral supplementation of phytofluene or lycopene or fed a 10% tomato powder or control diet for 4 d. Results show that short-term carotenoid and tomato intake lowered serum testosterone concentrations, potentially by modulation of prostate and/or testes steroidogenic enzyme mRNA expression. These studies suggest that a variety of phytochemicals, including flavonoids and carotenoids, are collectively responsible for the bioactivity of tomatoes that is associated with prostate cancer risk reduction.