GREEN TEA CONSTITUENT EPIGALLOCATECHIN-3-GALLATE AND INDUCTION OF APOPTOSIS AND CELL-CYCLE ARREST IN HUMAN CARCINOMA-CELLS

Background and Purpose: The polyphenolic compounds present in green te a show cancer chemopreventive effects in many animal tumor models, Epi demiologic studies have also suggested that green tea consumption migh t be effective in the prevention of certain human cancers, We investig ated the effect of green tea polyphenols and the major constituent, ep igallocatechin-3-gallate, on the induction of apoptosis (programmed ce ll death) and regulation of cell cycle in human and mouse carcinoma ce lls, Methods: Human epidermoid carcinoma cells (cell line A431), human carcinoma keratinocyte (cell line HaCaT), human prostate carcinoma ce lls (cell line DU145), mouse lymphoma cells (cell line L5178Y), and no rmal human epidermal keratinocytes (NHEKs) were used, Apoptosis was as sessed by 1) the formation of internucleosomal DNA fragments by agaros e gel electrophoresis, 2) confocal microscopy, and 3) flow cytometry a fter tagging the DNA fragments by fluorescence label, The distribution of cells in different phases of the cell cycle was analyzed by flow c ytometry, Results: Treatment of A431 cells with green tea polyphenols and its components, epigallocatechin-3-gallate, epigallocatechin, and epicatechin-3-gallate, resulted in the formation of internucleosomal D NA fragments, characteristic of apoptosis, Treatment with epigallocate chin-3-gallate also resulted in apoptosis in HaCaT, L5178Y, and DU145 cells, but not in NHEK. Confocal microscopy and flow cytometry confirm ed the findings, The DNA cell cycle analysis showed that in A431 cells , epigallocatechin-3-gallate treatment resulted in arrest in the G(0)- G(1) phase of the cell cycle and a dose-dependent apoptosis. Conclusio ns: Green tea may protect against cancer by causing cell cycle arrest and inducing apoptosis, It needs to be evaluated in human trials.