miR-145-5p Suppresses Breast Cancer Progression by Inhibiting SOX2

Abstract Background In this study, we aimed to investigate the expression and clinical significance of miR-145-5p and its tumor-suppressive effect in breast cancer patients. Methods We used luciferase reporter assay, real-time quantitative reverse transcription polymerase chain reaction and Western blot to identify sex-determining region Y-box2 (SOX2) as the target gene of miR-145-5p. Their expression levels in breast cancer tissues ( n  = 122) were detected by real-time quantitative polymerase chain reaction. We also applied 3-(4,5-dimethyl- 2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay and flow cytometry to reveal the effect of miR-145-5p on proliferation in breast cancer. Results miR-145-5p expression is downregulated in breast cancer tissues and negatively correlated with SOX2 expression. Decreased miR-145-5p expression was significantly associated with larger tumor size, distal metastasis, higher Ki67 expression level, and shorter overall survival. miR-145-5p inhibits breast cancer cell proliferation via targeting SOX2, and multivariate regression showed that both miR-145-5p and SOX2 were unfavorable prognostic factors. Conclusions miR-145-5p played a suppressive role in the proliferation of breast cancer cells by targeting SOX2, and miR-145-5p is a putative biomarker for risk assessment in patients with breast cancer.