Abstract
Breast cancer is the most common type of malignant cancer in females. An increasing number of studies have revealed that microRNAs (miR), which belong to a class of small non-coding RNAs, serve an important role in a number of human cancer subtypes. In the present study, the role of miR-194 in breast cancer cells and its underlying mechanisms were investigated. The results demonstrated that the serum levels of miR-194 were significantly higher in patients of the poorly differentiated and well-differentiated groups, compared with in healthy adults. Additionally, the serum level of miR-194 was significantly higher in the poorly differentiated group compared with in the well-differentiated group. In order to further investigate the role of miR-194 in breast cancer cells, the present study transfected two breast cancer cell lines, MCF-7 and MDA-MB-231, with an empty vector (control), miR-194 (overexpression), antagomiR-194 (inhibitor, functional knock down) or antagomiR-194 and miR-194. An MTT assay was performed in order to detect the proliferation of breast cancer cells in the various groups. The results revealed that the overexpression of miR-194 significantly accelerated cell proliferation, whereas the inhibition of miR-194 significantly decelerated the proliferation of MCF-7 and MDA-MB-231 cells. Furthermore, the expression levels of cyclin D and cyclin E were significantly upregulated in miR-194 overexpressing cells, and the expression levels of cyclin D and cyclin E were significantly downregulated in miR-194 inhibited cells, as compared with in control cells. No significant change was observed in the level of proliferation of cells co-transfected with miR-194 and antagomiR-194, compared with in the control cells. According to the hypothesis suggesting possible target genes of miR-194, the present study proposed that F-box/WD repeat-containing protein 7 (Fbxw-7) may be a direct target of miR-194, which was confirmed by a luciferase reporter assay. The present study suggested that miR-194 expression promoted the proliferation of breast cancer cells by targeting Fbxw-7, and may serve as a biomarker and a novel target for breast cancer therapy.