Abstract: BACKGROUND ＆ AIM: To observe the effects of arsenic trioxide (As2O3) on the growth of human bladder cancer cells EJ and illustrate its mechanism. MATERAIL AND METHODS: The cell proliferation inhibition was measured by (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromid,MTT) colorimetric assay. Morphological changes of EJ cells were observed by fluorescence staining of Hoechst 33258. Cell cycle and apoptosis were analyzed by flow cytometry (FCM). The expression of caspase-3 in EJ cells was observed by immunocytochemistry staining. RESULTS：There was obviously a concentration-dependent relationship between As2O3 and the inhibition of EJ cells proliferation IC50 was 22.51 μmol/L. Morphological observation by fluorescence staining and FCM indicated that As2O3 induced apoptosis of EJ cells. The apoptosis rate was increased from 3.37 ％ to 19.07 ％. Immunocytochemistry demonstrated that the expression of caspase-3 in EJ cells was enhanced after treated by As2O3. CONCLUSION： The results suggest that As2O3 can inhibits human bladder cancer cells EJ growth by means of cell proliferation inhibition, expression of caspase-3 and apoptosis.

Key words: arsenic trioxide, human bladder cancer cell line EJ, inhibition in proliferation, caspase-3, apoptosis