Induction of cell proliferation and survival genes by estradiol-repressed microRNAs in breast cancer cells

Abstract

BackgroundIn 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.MethodsWestern 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.ResultsE2 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.ConclusionsThese 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.

MiR-203 inhibits estrogen-induced viability, migration and invasion of estrogen receptor α-positive breast cancer cells

“…In the present study, it was found that treatment with E2 induced a significant decrease in miR-203 levels in breast cancer cells, suggesting that it may be involved in E2-mediated malignant progression of breast cancer MCF-7 cells. Yu et al also reported that E2 significantly induced bcl-2, cyclin D1 and survivin expression by suppressing the levels of miR-16, miR-143 and miR-203 in MCF-7 cells (35), consistent with the current findings.…”

Excessive Cellular Proliferation Negatively Impacts Reprogramming Efficiency of Human Fibroblasts

“…Our findings are consistent with previous studies [18] reporting increased expression of cell survival genes (AKT1, BCL2, XIAP, and BCL-XL) during increased proliferation. Consistent with the observation that insulin is a potent inducer of cell proliferation during development [19], we detected an upregulation of phosphorylated AKT and of proteins in the insulin/IGF-1 signaling pathway, including PI3K, IRS1, and S6K, in fibroblasts grown in defined Ax medium.…”

The cooked meat-derived mammary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) elicits estrogenic-like microRNA responses in breast cancer cells

“…It has been suggested that the repression of miRNA by E2 is involved in the increased proliferation of mammary cells when stimulated with the hormone (Maillot et al, 2009;Yu et al, 2012).…”