Studies have shown that
microRNAs (
miRNAs) are involved in the malignant progression of human
cancer. However, little is known about the potential role of
miRNAs in breast
carcinogenesis. miR-124 expression in
breast cancer tissue was measured by quantitative real-time PCR (qRT-PCR). Target prediction algorithms and
luciferase reporter gene assays were used to investigate the target of miR-124.
Breast cancer cells growth was regulated by overexpression or knockdown miR-124. At the end of the study,
tumor-bearing mice were tested to confirm the function of miR-124 in
breast cancer. In this study, we demonstrated that the expression of miR-124 was significantly downregulated in
breast cancer tissues compared with matched adjacent non-neoplastic tissues. We identified and confirmed that
cyclin-dependent kinase 4 (CDK4) was a direct target of miR-124. Overexpression of miR-124 suppressed
CDK4 protein expression and attenuated cell viability, proliferation, and cell cycle progression in MCF-7 and MDA-MB-435S
breast cancer cells in vitro. Overexpression of CDK4 partially rescued the inhibitory effect of miR-124 in the
breast cancer cells. Moreover, we found that miR-124 overexpression effectively repressed
tumor growth in xenograft animal experiments. Our results demonstrate that miR-124 functions as a growth-suppressive
miRNA and plays an important role in inhibiting
tumorigenesis by targeting CDK4.