Prevention of chinese green tea on 3,4-benzopyrene-induced lung cancer and its mechanism in animal mode.

Abstract

Chinese green tea is one of the daily consumption beverages in the world and is considered a promising cancer chemopreventive agent. In the present study, we investigate the role of lung cancer prevention by green tea and its mechanism. Three groups of female SD rats were kept with the same feed. Rats in group A were administrated with 1% green tea drinking, while in group B and group C with water only. Animals in group A and group B were given 3,4-benzopyrene-corn oil mixture pulmonary injection fortnightly for 4 times, while in group C corn oil only. Rats were sacrificed 1 year after the first injection under narcotism. Lung tumors and lung tissues were performed H&E staining for cancer identification. Each case of lung cancer was examined for expression of p53 and Bcl-2 with in situ hybridization analysis and immunohistochemistry staining. No cancer was found in rats in group C. However, in group B, 15 out of 20 rats were found generating lung cancer, and in group A, 6 out of 20 rats inducing lung cancer were recorded. The rate of lung carcinogenesis in rats was decreased from 75% to 30% by 1% chinese green tea oral administration (Chi-Square=8.12, P <0.01). Higher level of p53 expression in lung cancer tissues of group A was observed under microscope than that of group B, but the difference has no statistic significance (P >0.05). However, significantly lower level of Bcl-2 expression was found in lung cancer tissues of group A than that of group B (P <0.05). The results indicate that chinese green tea inhibits lung carcinogenesis. Chinese green tea can slightly upregulate expression of p53, but significantly downregulate expression of Bcl-2 in lung cancer, and this may be related to the mechanism of lung cancer prevention.