【Objective】 To investigate the effect of Bmi-1 gene knockdown on the proliferation and apoptosis in human SO-RB50 cells. 【Methods】 Bmi-1 expression was examined in human retinoblastoma tissue and SO-RB50 cells by immunohistochemistry and RT-PCR. Chemically synthesized Bmi-1 siRNA was transfected into SO-RB50 cells. After Bmi-1 siRNA transfection

expression of Bmi-1 mRNA and protein in SO-RB50 cells were examined by real time RT-PCR and Western blot analysis. Cell growth and proliferation were analyzed by MTT assay. Cell apoptosis was observed by flow cytometry. 【Results】Bmi-1 was expressed in human retinoblastoma tissue and SO-RB50 cells. After Bmi-1 siRNA treatment

Bmi-1 mRNA and protein in SO-RB50 cells were dramatically decreased by (83.9±3.2)% and (82.8±1.1)% respectively. After Bmi-1 knockdown

MTT showed that Bmi-1 siRNA could significantly inhibit SO-RB50 cell proliferation. The inhibitory effect reached peak at 96 hours [(52.5±1.9)%] after transfection. Cell apoptosis rate was promoted up to (20.67±1.1)% in the siRNA treated cells while cell apoptosis rate was (1.9±0.2)% in the negative group. 【Conclusion】Specific Bmi-1 siRNA can inhibit the expression of Bmi-1 and inhibit human SO-RB50 cell growth in vitro. The effect might be attributed to promoting cell apoptosis. These results suggest that Bmi-1 may be a new therapy target in RBs.