沉默Bmi-1表达可促进MCF-7乳腺癌细胞凋亡并抑制其侵袭

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

目的探讨B细胞特异的Moloney鼠白血病病毒插入位点1(Bmi-1)基因沉默对细胞增殖与侵袭的影响及可能的分子机制。方法收集经病理确诊的乳腺癌及癌旁组织,采用实时荧光定量PCR检测Bmi-1的表达差异;采用LipofectamineRNAi MAX转染试剂将靶向Bmi-1基因的小干扰RNA(siRNA)转染MCF-7细胞,流式细胞术检测Bmi-1沉默后细胞周期和凋亡的改变,Western blot法检测凋亡相关基因P21、Bax、Bcl-2的表达变化。TranswellTM侵袭实验检测MCF-7细胞侵袭力变化,Western blot法检测上皮钙黏素(E-cadherin),神经钙黏素(N-cadherin)、波形蛋白(vimentin)的表达水平。结果乳腺癌组织Bmi-1 mRNA表达量高于癌旁组织,沉默Bmi-1基因可使MCF-7细胞周期阻滞于G1期,凋亡细胞增多;与空白对照组、阴性对照siRNA转染组相比,Bmi-1-siRNA组中P21与Bax的表达水平明显上调,Bcl-2明显下调。沉默Bmi-1基因表达可抑制MCF-7细胞的侵袭力,与对照组相比,下调Bmi-1可增强E-cadherin的表达,减少N-cadherin、vimentin的表达。结论下调Bmi-1的表达可引起MCF-7细胞G1期阻滞,促进细胞凋亡,与P21表达上调,Bax/Bcl-2比率升高有关;下调Bmi-1水平可抑制MCF-7细胞侵袭性,与抑制肿瘤细胞上皮间质转化有关。

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-l-siRNA was transfected into MCF-7 cells by a Lipofectamine RNAiMAX transfection reagent. Flow cytometry was used to detect cell cycle and apoptosis of MCF-1 cells transfected by Bmi-I-siRNA. Western blotting was performed to detect the protein levels of P21, Bax and Bcl-2. Matrigel TranswellTM 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 GI/S phase and promoted the apoptosis of MCF-7 cells. Compared with blank control group or negative control group, the Bmi-l-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-1 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.