Apoptosis induction by epigallocatechin gallate involves its binding to Fas

Epigallocatechin gallate (EGCG) is known to induce apoptosis in various typ es of tumor cells, but the precise mechanism by which EGCG induces apoptosi s remains to be elucidated. The Fas-Fas ligand system is one of the major p athways operating in the apoptotic cascade. The aim of this study was to ex amine the possibility that EGCG-binding to Fas triggers the Fas-mediated ap optosis. The EGCG treatment of human monocytic leukemia U937 cells resulted in elevation of caspase 8 activity and fragmentation of caspase 8. The DNA ladder formation caused by the EGCG treatment was inhibited by the caspase 8 inhibitor. These findings suggested the involvement of the Fas-mediated cascade in the EGCG-induced apoptosis in U937 cells. Affinity chromatograph y revealed the binding between EGCG and Fas. Thus, the results suggest that EGCG-binding to Fas, presumably on the cell surface, triggers the Fas-medi ated apoptosis in U937 cells. (C) 2001 Academic Press.