[The siRNA-mediated silencing of Bmi-1 promotes apoptosis and inhibits invasion of MCF-7 breast cancer cells].

Objective To investigate the effect of small interfering RNA (siRNA)-mediated silencing of the Bmi-1 gene on cell proliferation and invasion of MCF-7 human mammary carcinoma cell line and the potential molecular mechanisms. Methods Real-time quantitative PCR was used to detect the levels of Bmi-1 mRNA in the paired breast cancer and adjacent noncancerous breast tissues which were confirmed by pathological diagnosis. Bmi-1-siRNA was transfected into MCF-7 cells by a Lipofectamine(R) RNAiMAX transfection reagent. Flow cytometry was used to detect cell cycle and apoptosis of MCF-7 cells transfected by Bmi-1-siRNA. Western blotting was performed to detect the protein levels of P21, Bax and Bcl-2. Matrigel Transwell(TM) invasion assay was used to determine the cell invasion of MCF-7 cells with Bmi-1 silencing. The protein levels of E-cadherin, N-cadherin, vimentin were tested by Western blotting. Results The expression of Bmi-1 mRNA in the breast cancer tissues was higher than that in the adjacent noncancerous breast tissues. Bmi-1 silencing significantly suppressed the cell growth, arrested the cells in the G1/S phase and promoted the apoptosis of MCF-7 cells. Compared with blank control group or negative control group, the Bmi-1-silenced group showed the increased expressions of P21 and Bax and the decreased expression of Bcl-2. In addition, Bmi-1 silencing significantly suppressed the cell invasion and promoted the expression of E-cadherin as well as downregulated the expressions of N-cadherin and vimentin in MCF-7 cells. Conclusion The invasion of MCF-7 cells can be inhibited by Bmi-1 silencing, of which the molecular regulation mechanism might be associated with the inhibition of tumor cell epithelial-mesenchymal transition.