TUMOR SUPPRESSIVE ROLE OF MIR-199A-5P IN TRIPLE-NEGATIVE BREAST CANCER

Abstract

Background: Triple-negative breast cancer (TNBC) is defined by lack of expression in estrogen, progesterone receptors and human epidermal growth factor receptor 2. TNBC exhibited a more aggressive phenotype than other subtypes. Our previous study identified miR-199a-5p as TNBC-specific circulating marker, so we further investigated its role in breast cancer. Methods: MTT, migration/invasion assay, cell cycle analysis, single-cell clonogenic assay and aldehyde dehydrogenase (ALDH) activity were performed in TNBC cell line MDA-MB-231 transfected with miR-199a-5p mimic. Gene expression level was investigated by real-time PCR. Results: Overexpression of miR-199a-5p significantly inhibited cell proliferation, migration and invasion leading to G0/G1 phase arrest, early apoptosis and alteration in epithelial-mesenchymal transition-related genes in MDA-MB-231. Also, miR-199a-5p correlated with stemness characteristics by inhibiting single cell colony formation and decreasing CD24-/CD44+ subpopulation and ALDH activity. ALDH1A3 had a higher expression in breast cancer plasma especially in TNBC when compared to normal individuals. Furthermore, luciferase assay identified that PIK3CD is the potential downstream target of miR-199a-5p. Conclusions: Our data implicated that miR-199a-5p confers tumor suppressive role in TNBC, which inhibited stemness characteristics. These findings may help the development of novel therapeutic strategies towards this highly malignant disease.