Effects of EGCG on the Expression of Connexin43 and Gap Junction Intercellular Communication of the Bladder Cancer Cell Line BIU-87

BACKGROUND AIM:To investigate the effects of(-)-epigallocatechin-3-gallate(EGCG,the major phytochemical in green tea) on the expression of connexin43(Cx43) gene and the intercellular communication of the human bladder cancer cell line BIU-87,and to explore its possible mechanisms of prevention and cure of the bladder tumor.MATERIALS AND METHODS:The methyl thiazolyl tetrazolium and Annexin-V/PI double-labeled flow cytometry methods were used to examine the growth inhibitory rate(IR) and apoptosis rate(AR) of BIU-87 cells treated by EGCG at different concentrations(0,5,10,20 mg/L).The reverse transcription-polymerase chain reaction(RT-PCR) and Western Blot analysis were used to measure the relative expression levels of the Cx43 mRNA and its protein.The scrape-loading fluorescence dye transfer method was used to assess the gap junction intercellular communication(GJIC) through fluorescence microscopy.RESULTS:EGCG at concentrations of 10 mg/L and 20 mg/L could both significantly inhibit the proliferation and induce the apoptosis of BIU-87 cells.The IR and AR were(15.67±1.15)%,(18.33±1.53)% and(42.00±4.34)%,(27.33±3.21)%,respectively.And EGCG could significantly up-regulate the expression of Cx43 mRNA and its protein,enhance the GJIC of BIU-87 cells compared with groups of 0 and 5 mg/L(P0.05).The effects showed significant correlation with the dose of EGCG.CONCLUSION:EGCG(10,20 mg/L) could effectively up-regulate Cx43 expression and enhance the GJIC of BIU-87 cells,thereby inducing bladder tumor cells apoptosis and inhibiting its growth.This provides experimental evidence for the mechanism of chemical prevention and cure of the bladder tumor by EGCG.