Lack of inhibitory effect of lycopene on dysplastic lesions induced by 7,12-dimethyl-benz[a]anthracene in hamster buccal pouch

It is widely known that oxidative damage caused by free radical imbalance in tissues plays a major role in the carcinogenesis processes of initiation and promotion. Natural antioxidants present in the diet are useful protectors against lipid, protein, and DNA oxidative damage. In this study, we evaluated the effects of lycopene, a red pigment largely found in tomatoes, on dysplastic lesions induced by 7,12-dimethyl-benz[a]anthracene (DMBA) in hamster buccal pouch mucosa. The extent of lipid peroxidation and liver reduced glutathione concentrations were used to assess overall oxidative levels. Thirty animals received topical application of a 0.5% solution of DMBA in mineral oil in the left buccal pouches, 3 times per week for 10 weeks. Ten animals were euthanized 1 day after the last DMBA application and the remaining 20 were divided into 2 groups, which received a standard AIN-93M diet or this diet supplemented with 20 ppm lycopene for the next 11 weeks. Ten animals remained untreated throughout the entire experiment as negative controls. Levels of thiobarbituric acid–reactive substances were significantly lower in the group that received DMBA and lycopene as compared to the group treated with DMBA but did not significantly alter liver levels of glutathione. Incidences of carcinoma were 80% and 70% (P > .05), respectively, in groups B (DMBA only) and C (DMBA and lycopene). The present data suggest that the antioxidant activity of lycopene may not be sufficient to suppress tumor formation in a postinitiation phase.