MiR-492 Contributes to Cell Proliferation and Cell Cycle of Human Breast Cancer Cells by Suppressing SOX7 Expression

MicroRNAs (miRNAs) have emerged as important regulators that potentially play critical roles in cancer cell biological processes. Previous studies have shown that miR-492 plays an important role in cell tumorigenesis in multiple kinds of human cancer cells. However, the underlying mechanisms of this microRNA in breast cancer remain largely unknown. In the present study, we investigated miR-492's role in cell proliferation of breast cancer. MiR-492 expression was markedly upregulated in breast cancer tissues and breast cancer cells. Overexpression of miR-492 promoted the proliferation and anchorage-independent growth of breast cancer cells. Bioinformatics analysis further revealed sex-determining region Y-box 7 (SOX7), a putative tumor suppressor, as a potential target of miR-492. Data from luciferase reporter assays showed that miR-492 directly binds to the 3'-untranslated region (3'-UTR) of SOX7 messenger RNA (mRNA) and repressed expression at both transcriptional and translational levels. Ectopic expression of miR-492 led to downregulation of SOX7 protein, which resulted in the upregulation of cyclin D1 and c-Myc. In functional assays, SOX7 silenced in miR-492-in-transfected ZR-75-30 cells has positive effect to promote cell proliferation, suggesting that direct SOX7 downregulation is required for miR-492-induced cell proliferation and cell cycle of breast cancer. In sum, these results suggest that miR-492 represents a potential onco-miR and participates in breast cancer carcinogenesis by suppressing SOX7 expression.