BMC Cancer：雌二醇抑制microRNA诱导乳腺癌细胞增殖

在对雌激素有反应的MCF-7细胞中，雌二醇（E2）结合雌激素受体α参与调控细胞增殖和生存基因的转录。微小RNA（miRNA的）已经成为重要的转录后基因表达调控因子。

近日，BMC Cancer杂志上的一项研究探讨了miRNA是否参与激素调节雌激素受体基因的表达。研究人员采用Western blot和定量PCR分别来确定雌激素应答基因和miRNA的表达。荧光素酶报告基因检测和转染miRNA的模仿或抑制miRNA来确定miRNA所调控的靶基因表达。常规MTS检测细胞增殖活性。

结果发现E2通过抑制MCF-7细胞中一系列miRNA（miR-16, miR-143和miR-203）水平，进而显著诱导Bcl-2，cyclin D1和Survivin的表达。miRNA转染技术和荧光素酶检测证实Bcl-2由miR-16和miR-143调节，cyclinD1由miR-16的调控。

重要的是，miR-16, miR-143, miR-203都靶向调控蛋白survivin。E2的调节作用可被抗雌激素制剂，雷洛昔芬或雌激素受体alpha转染siRNA后所消除，这说明调控依赖于雌激素受体alpha。

为了研究这些miRNAs在雌激素受体细胞中的功能意义，用miRNA转染MCF-7细胞。这些miRNA表达过高抑制E2诱导细胞增殖。进一步研究表明，miR-16，miR-143和miR-203高表达于三重阳性乳腺癌组织中（乳腺癌的亚型分为HER2阳性、雌激素受体阳性、以及三种受体均为阴性等），这表明这些miRNA在ER阳性乳腺癌中是一个潜在的肿瘤抑制因子。总之结果表明，E2通过调控miRNA诱导Bcl-2，cyclin D1和survivin表达下调。

拓展阅读：

BMC Cancer：雌激素或影响汉族男性结直肠癌风险

AACR：单纯雌激素替代治疗也增加乳腺癌风险

Lancet Oncol：雌激素替代疗法不会助长乳腺癌

Lancet Oncol:雌激素对乳腺癌有长期预防作用

Nature：雌激素受体改变“工作路线”致乳腺癌耐药

Nature：雌激素受体可致乳腺癌患者出现耐药性

雌激素或决定绝经前乳腺癌预后

JAMA:雌激素和孕激素与绝经后女性乳腺癌发病率和死亡率的研究

doi:10.1186/1471-2407-12-29
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Induction of cell proliferation and survival genes by estradiol-repressed microRNAs in breast cancer cells

Xinfeng Yu1*, Xuemei Zhang2, Ishwori B Dhakal3, Marjorie Beggs3, Susan Kadlubar3 and Dali Luo1

Background

In estrogen responsive MCF-7 cells, estradiol (E₂) binding to ERα leads to transcriptional regulation of genes involved in the control of cell proliferation and survival. MicroRNAs (miRNAs) have emerged as key post-transcriptional regulators of gene expression. The aim of this study was to explore whether miRNAs were involved in hormonally regulated expression of estrogen responsive genes.

Methods

Western blot and QPCR were used to determine the expression of estrogen responsive genes and miRNAs respectively. Target gene expression regulated by miRNAs was validated by luciferase reporter assays and transfection of miRNA mimics or inhibitors. Cell proliferation was evaluated by MTS assay.

Results

E₂ significantly induced bcl-2, cyclin D1 and survivin expression by suppressing the levels of a panel of miRNAs (miR-16, miR-143, miR-203) in MCF-7 cells. MiRNA transfection and luciferase assay confirmed that bcl-2 was regulated by miR-16 and miR-143, cyclinD1 was modulated by miR-16. Importantly, survivin was found to be targeted by miR-16, miR-143, miR-203. The regulatory effect of E₂ can be either abrogated by anti-estrogen ICI 182, 780 and raloxifene pretreatment, or impaired by ERα siRNA, indicating the regulation is dependent on ERα. In order to investigate the functional significance of these miRNAs in estrogen responsive cells, miRNAs mimics were transfected into MCF-7 cells. It revealed that overexpression of these miRNAs significantly inhibited E₂-induced cell proliferation. Further study of the expression of the miRNAs indicated that miR-16, miR-143 and miR-203 were highly expressed in triple positive breast cancer tissues, suggesting a potential tumor suppressing effect of these miRNAs in ER positive breast cancer.

Conclusions

These results demonstrate that E₂ induces bcl-2, cyclin D1 and survivin by orchestrating the coordinate downregulation of a panel of miRNAs. In turn, the miRNAs manifest growth suppressive effects and control cell proliferation in response to E₂. This sheds a new insight into the integral post-transcriptional regulation of cell proliferation and survival genes by miRNAs, a potential therapeutic option for breast cancer.