Anticarcinogenic Activity of Green Tea Polyphenols

The main physiologically active polyphenol in green tea extractis (–)-epigallocatechin gallate (EGCG). Green tea extracthas an advantage over EGCG as a cancer chemopreventive agentfor humans, as is apparent from the Japanese custom of injestinggreen tea on a daily basis. Green tea extract similarly inhibitedprotein kinase C activation by teleocidin, a tumor promoter,as did EGCG. In addition, EGCG and green tea extract showedinhibitory effects on the growth of lung and mammary cancercell lines with similar potencies. An experiment using the estrogen-dependentMCF-7 cell line showed the mechanisms of action of these compoundsto be inhibiting the interaction of estrogen with its receptors.Considering our previous results of a single application ofEGCG to mouse skin inhibiting the specific binding of ³H-12-0-tetradecanoylphorbol-13-acetate(³H-TPA) and ³H-okadaic acid, we postulated that EGCG and compoundsin green tea extracts would block the interaction of tumor promoters,hormones and growth factors with their receptors: a kind ofsealing effect. The sealing effect would account for reversiblegrowth arrest, and may be induced by various kinds of compond.