RESUMO
Earlier studies conducted in our laboratory have shown that a polyphenolic fraction isolated from green tea (GTP) possesses anti-skin tumor initiating and anti-skin tumor promoting activity in the two-stage skin tumorigenesis protocol in SENCAR mouse. We have also shown that topical application of GTP inhibits tumor promoter-caused induction of epidermal ornithine decarboxylase activity in SENCAR mice in a dose-dependent manner, and that its oral feeding in drinking water to SKH-1 hairless mice enhances antioxidant and phase II enzyme activity in liver, lung, small bowel and skin. In this study, we show that single or multiple applications of GTP on SENCAR mouse ear prior to or after the application of 12-O-tetradecanoylphorbol-13-acetate (TPA) afford significant protection (P < 0.05) against TPA-induced edema. Pre-application of GTP also afforded significant protection against TPA-induced hyperplasia in the ear skin. The percentage protection by GTP both in terms of epidermal thickness and vertical cell layers was 75 and 90% respectively (P < 0.005). In further studies, we assessed the protective effect of GTP against TPA-caused infiltration of neutrophils in the ear skin of SENCAR mouse, by determining a naturally occurring constituent of neutrophils, myeloperoxidase, as a quantitative marker of tissue neutrophil content. Prior application of GTP resulted in significant protection against TPA-caused infiltration of neutrophils (P < 0.005). These results suggest that GTP possesses potential as a cancer chemopreventive agent against stage I tumor promotion.