MiR-200b expression in breast cancer: a prognostic marker and act on cell proliferation and apoptosis by targeting Sp1.

MicroRNAs (miRNAs) have been identified as important post-transcriptional regulators involved in various biological and pathological processes of cells. In the present study, we investigated the roles and mechanisms of miR-200b in human breast cancer (BC). MiR-200b expression was carried out by qRT-PCR in human BC cell lines and clinical samples and the prognostic potential of miR-200b expression was further evaluated. In vitro, effects of miR-200b on BC cell proliferation, apoptosis and cell cycle distribution were tested by CCK-8 kit, flow cytometric analysis respectively. Luciferase assay and Western blot analysis were performed to validate the potential targets of miR-200b after the preliminary screening by employing open access software. We found that miR-200b was significantly down-regulated in both BC tissues and cell lines. The low expression of miR-200b was correlated with late TNM stage, negative oestrogen receptor and positive HER-2 status. Multivariate analysis showed that miR-200b expression was an independent prognostic predictor for BC patients. Integrated analysis identified Sp1 as a direct and functional target of miR-200b. Knockdown of Sp1 inhibited cell proliferation, induce apoptosis and act on cell cycle resembling that of miR-200b high expression. Our data demonstrates that miR-200b has potential to serve as prognostic biomarker and tumour suppressor for BC patients. As a direct and functional target of miR-200b, Sp1 and miR-200b both could be an exciting target for BC treatment strategy.