NDRG2通过抑制β-catenin表达和入核调控乳腺癌细胞增殖

NDRG2 inhibits the proliferation of breast cancer cells via regulating β-catenin expression and nuclear translocation

背景与目的:乳腺癌是女性发病率最高的恶性肿瘤之一,肿瘤细胞的恶性增殖是造成患者死亡的重要原因。本研究利用具有相同遗传背景但不同增殖能力的乳腺癌细胞模型,研究N-myc下游调节基因2(N-myc downstream regulated gene 2,NDRG2)调控乳腺癌细胞增殖的作用及分子机制。方法:通过蛋白[质]印迹法(Western blot)检测MCF-7/LM-MCF-7细胞中NDRG2蛋白表达水平;构建NDRG2真核表达载体及si RNA干扰片段,通过转染上调或沉默NDRG2表达,流式细胞实验检测细胞增殖能力,Western blot检测β-连环蛋白(β-catenin)表达,免疫荧光染色检测β-catenin细胞定位;共转染MCF-7细胞NDRG2 si RNA和pCMV-Tcfδ,流式细胞实验检测细胞增殖能力。结果:NDRG2的蛋白表达水平同乳腺癌细胞增殖能力负相关;在增殖的LMMCF-7细胞中上调NDRG2表达,细胞增殖指数(proliferation index,PI)由47.18%下降至31.78%(P<0.001);在低增殖的MCF-7细胞中沉默NDRG2表达,PI由32.00%上升至52.59%(P<0.001);Western blot及免疫荧光结果显示,NDRG2可抑制β-catenin表达,并抑制其聚集入核;流式细胞检测结果显示,共转染si RNA和pCMV-Tcfδ的MCF-7细胞增殖能力未增强,进一步说明NDRG2是通过抑制β-catenin的转录调节作用抑制肿瘤细胞增殖。结论:在乳腺癌细胞中,NDRG2的表达水平下调,导致β-catenin聚集入核,并激活下游靶基因,促进乳腺癌细胞增殖。此分子机制对阐明乳腺癌细胞增殖调控机制具有重要意义。

Background and purpose： Breast cancer is one of the most common malignant diseases in women and its malignant proliferation is the major cause of death. To investigate the effects of N-myc downstream regulated gene 2 （NDRG2） on proliferation of breast cancer cells by using two parallel cell lines （MCF-7 and LM-MCF-7） with different metastatic abilities. Methods： The expression level of NDRG2 in breast cancer cells was detected by Western blot. The effects of overexpressing （or down-regulating） NDRG2 on proliferation of breast cancer cells were investigated by flow cytometry. The expression and location of β-catenin were detected by Western blot and immunofluorescence respectively. NDRG2 blocking the transcription activity of β-catenin was investigated via co-transfecting MCF-7 cells with NDRG2 siRNA and pCMV-Tcfδ （lacking the portion responsible for the protein binding to DNA）. Results： The expression level of NDRG2 was negatively related to the proliferation ability of breast cancer cells. Over-expressing NDRG2 （or down-regulating） via transfecting LM-MCF-7 （or MCF-7） cells with pCMV-NDRG2 （or NDRG2 siRNA） could inhibit （or promote） cell proliferation. Interestingly, the results of Western blot, immunofluorescence and flow cytometry revealed that down-regulation of NDRG2 resulted from the down-regulation of β-catenin and blocking its nuclear translocation, which led to losing control of the proliferation of breast cancer cells. Conclusion： NDRG2 inhibit the proliferation of breast cancer cells via down-regulating the expression of β-catenin and blocking its nuclear translocation, which is significant for exploring the molecular mechanism of proliferation of breast cancer cells.