Abstract: 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 (P<0.05). 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.

Key words: (－)_epigallocatechin_3_gallate, bladder tumor, connexin43, intercellular communication