The effect of lycopene on the cyclooxygenase (cox-2), caspase-3, caspase-9, bax, bcl-2, p53 protein expression and DNA damage in rats with azoxhymethane-induced colorectal cancer

Tomatoes and tomato products are the major dietary source of lycopene. Because dietary intake of tomato powder (TP) has been associated with a reduced risk of a variety of human cancers, in this thesis we investigated the effects of TP supplementation on the development of azoxymethane (AOM)-induced colorectal cancer in the Wistar rats. We also assessed colorectal tissue expression levels of cyclooxygenase-2 (cox-2), bax, bcl-2, caspase-3, caspase-9, p53 protein by Western blotting and we assessed tissue DNA damage by DNA agarose gel electrophoresis. Sixty rats were divided into four groups. Each group consists of fifteen animals. Thirty Wistar rats (AOM group and AOM + TP group) were injected once a week with azoxymethane (15mg/kg body weight subcutaneously) for a total of 3 weeks. Rats were fed either a basal diet (contol group and AOM group) or the basal diet supplemented of 5% tomato powder per kilogram of diet. The animals were sacrificed after 20 weeks and the colorectal tumors were identified. Tomato powder supplementation, significantly differences in the AOM +DT group expression levels of cox-2, bcl-2, caspase-3, caspase-9, p53 compared with AOM group (p<0.05). Expression levels of caspase-3 and bcl-2 increased, whereas expression levels of caspase-9 and p53 decreased with tomato powder supplementation (p<0.05). But There were no significant differences in the AOM +DT group expression levels of bax compared with AOM group (p>0.05). TP supplementation, decreased in the AOM +DT group rate of DNA damage compared with AOM group. In addition, while we found 8 adenocarcinomas and 3 dysplasia in AOM group, we found 2 adenocarcinomas and 5 dysplasia in AOM+TP group (p<0.05). The results indicate that dietary supplementation with TP reduces the incidence and size of AOM-induced colorectal cancer occurring of in the Wistar rats and these findings should be conducted to investigate the efficacy of TP supplementation in the prevention of colorectal cancer in humans.Key Words: Lycopene, apoptosis, DNA damage, cox-2, p53, caspase-3, caspase-9, bax, bcl-2, colorectal cancer.