12-o-tetradeca-2-4-6-8-tetranoylphorbol-13-acetate and epigallocatechin-gallate

Our research objective is to develop nontoxic cancer chemopreventive agents and to apply these agents in treating humans. We are identifying agents that inhibit the process of tumor promotion in two-stage carcinogenesis experiments on mouse skin.. We review (a) the inhibitory effect of penta-O-galloyl-beta-D-glucose (5GG) on tumor promotion by teleocidin, one of the 12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoters (5GG is structurally similar to (-)-epigallocatechin gallate (EGCG) and is isolated from hydrolyzed tannic acid); (b) the inhibitory effects of EGCG, the main constituent of Japanese green tea, on tumor promotion with two tumor promoters, teleocidin and okadaic acid, a non-TPA-type tumor promoter; (c) the mechanisms of action of EGCG, a single application of which reduced the specific binding of [3H]TPA and [3H]okadaic acid to a particulate fraction of mouse skin; and (d) the anticarcinogenic effects of EGCG on duodenal carcinogenesis induced by N-ethyl-N'-nitro-N-nitrosoguanidine in male C57BL/6 mice. EGCG is a nontoxic compound.. We believe that the main constituent of Japanese green tea, EGCG, is a practical cancer chemopreventive agent available in everyday life.

Topics: Animals; Anticarcinogenic Agents; Catechin; Hydrolyzable Tannins; Male; Mice; Mice, Inbred C57BL; Skin; Skin Neoplasms; Tannins; Tea; Tetradecanoylphorbol Acetate

Polyphenol components isolated from green tea showed strong antioxidant activity. The green tea extract (GTE) significantly inhibited the promoting effect of TPA in BALB/3T3 cell transformation assays. In in vivo experiments, GTE inhibited edema induced by TPA in mouse ear. The inhibitory effect of GTE on the induction of ornithine decarboxylase activity was also found in mouse skin treated with TPA. GTE decreased the frequency of SCE induced by oxygen radical in IAR 20 liver cells treated with hypoxanthine and xanthine oxidase. Mechanisms of the antipromoting effect of GTE are discussed. Our experimental results suggest that GTE may have some practical use in cancer prevention.

Topics: Animals; Antioxidants; Catechin; Cell Transformation, Neoplastic; Edema; Female; Mice; Mice, Inbred BALB C; Ornithine Decarboxylase; Sister Chromatid Exchange; Tea; Tetradecanoylphorbol Acetate