CHEMOPREVENTION BY LYCOPENE OF MOUSE LUNG NEOPLASIA AFTER COMBINED INITIATION TREATMENT WITH DEN, MNU AND DMH

An investigation was conducted to assess the chemopreventive potential of lycopene (LP), a naturally occurring hydrocarbon carotenoid found in tomatoes and their products, administered during the post-initiatio n stage in a multiorgan carcinogenesis model. One hundred eighteen B6C 3F(1) mice of both sexes were subjected tb combined treatment with die thylnitrosamine (DEN), N-methyl-N-nitrosourea (MNU) and 1,2-dimethylhy drazine (DMH) from day 11 after birth to week 9 (DMD treatment) (group s I and 2) or their vehicles (group 3). Then group 1 received LP (25 o r 50 ppm in drinking water)for 21 weeks from weeks 11 to 32. Group 2 s erved as a carcinogen alone control and group 3 was given only LP (25 or 50 ppm). All surviving animals were sacrificed at week 32 and the m ajor organs, including the Liver, lung, kidney and colon, were histolo gically examined. The incidences and multiplicities of lung adenomas p lus carcinomas combined in male mice in group 1 receiving 50 ppm LP we re significantly decreased as compared to the DMD alone or DMD and 25 ppm LP groups (75.0 versus 18.8%, P < 0.02; 0.94 +/- 0.17 Versus 0.25 +/- 0.14, P < 0.001). No such effect was observed for females. Althoug h hepatocellular carcinomas were lacking in the DMD and LP groups whil e two cases were found in the DMD alone group, this difference was not statistically significant. The values for aberrant crypt foci (ACF) a nd tumors in the colon and kidney did not show any significant variati on among the carcinogen-treated subgoups. The results suggest that LP exerts a chemopreventive effect limited to male lung carcinogenesis wh en given in the post-initiation stage to B6C3F(1) mice. (C) 1997 Elsev ier Science Ireland Ltd.