ENHANCEMENT OF GAP JUNCTIONAL INTERCELLULAR COMMUNICATION IN TUMOR PROMOTER-TREATED CELLS BY COMPONENTS OF GREEN TEA

Green tea (Camellia sinensis) has been reported to inhibit tumor promo tion in vivo and in vitro. Many tumor promoters inhibit gap junctional intercellular communication (GJIC) which may be an important mechanis m of promotion. In the present study, we hypothesized that green tea w ould enhance GJIC in promoter-treated cells. An aqueous extract of gre en tea (GTE) and several of its constituents were tested for their eff ects on GJIC in p,p'-dichlorodiphenyltrichloroethane (DDT)-, 12-O-tetr adecanoylphorbol-13-acetate (TPA)- and dieldrin-treated WB-F344 rat li ver epithelial cells. All three promoters inhibited GJIC in a dose-res ponsive manner at non-cytolethal concentrations. GTE (10-80 gamma/ml) enhanced GJIC 20-80% in promoter-treated cells. (-)-Epigallocatechin g allate and (-)-epicatechin gallate also enhanced GJIC in DDT-treated c ells, but no effects were seen with (+)-catechin, (-)-epicatechin, (-) -epigallocatechin, caffeine, or theobromine. These data suggest GTE ma y inhibit tumor promotion by enhancing GJIC and that the most active c omponents are the catechin gallates.