Abstract: BACKGROUND AND AIM: In this study we tried to evaluate the possible effects on chemosensitization of bladder cancer cell line BIU-87. MATERIALS AND METHODS: The expression of estrogen receptor(ER) was evaluated by immunohistochemical S-P method.In vitro chemosensitivity tests were done with bladder cancer cell line BIU-87 and Doxorubicin(0.1,1,10 μmol/L) in the presence or absence of graded concentrations of Tamoxifen(1,5,10 μmol/L). The growth and the sensitivity to Tamoxifen of cells were investigated by MTT assay. The level of bcl-2 gene mRNA expression was determined by in situ hybridization. RESULTS: Immunohistochemistry showed positive ER in BIU-87 cells. Tamoxifen stimulated a concentration- dependent and time-dependent decrease in bcl-2 mRNA.Tamoxifen at concentrations of 5 and 10 μmol/L significantly enhanced the cytotoxicity of the chemotherapeutic agent to the cell lines. Tamoxifen alone caused significant toxic effects to BIU-87 at 10 μmol/L. Tamoxifen at 5 and 10 μmol/L down-regulated the secretion of bcl-2 in a concentration-dependent manner. The effect of chemosensitization was evident in cells treated with 1,5 and 10 μmol/L Tamoxifen plus Doxonubicin in which 1.77 to 6.96-fold IC50 reduction was observed. CONCLUSION: Tamoxifen increased the chemosensitivity of Tamoxifen in human bladder cancer BIU-87 cell line in vitro,inhibited cell proliferation and promoted apoptosis.

Key words: Tamoxifen, bladder neoplasms, bcl-2, estrogen receptor