Clinical Significance and Tumor-Suppressive Function of miR-516b in Nonsmall Cell Lung Cancer

Background: MicroRNA-516b (miR-516b) has been recently reported to be downregulated in nonsmall cell lung cancer (NSCLC). However, its clinical significance and biological function in NSCLC remain to be clarified. Materials and Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of miR-516b in 82 paired fresh primary tumor tissues and NSCLC cell lines. The association of miR-516b expression with clinicopathological factors and prognosis was statistically analyzed by SPSS 21.0 software, Kaplan-Meier method, and Cox regression analyses. Cell Counting Kit-8, colony formation, flow cytometric, Transwell migration, and invasion assays were used to evaluate the proliferation, cell cycle, apoptosis, migration, and invasion of NSCLC cells after miR-516b mimics or negative control of mimics transfection. Results: The expression level of miR-516b was found to be significantly lower in NSCLC tissues and cell lines than in corresponding normal tissues and cells. Decreased miR-516b expression was significantly associated with tumor size (p = 0.004), Tumor Node Metastasis (TNM) stage (p = 0.016), and shorter overall survival (p = 0.0039). Multivariate analysis suggested that miR-516b was an independent risk factor for NSCLC (hazard ratio = 2.435, 95% confidence interval: 1.423-2.457; p = 0.003). Furthermore, overexpression of miR-516b could inhibit NSCLC cell proliferation, cell cycle progression, migration and invasion, and promoted cell apoptosis. The qRT-PCR results indicated that overexpressing miR-516b reduced the mRNA expression of CDK2, MMP-2, and MMP-9, whereas increased BAX mRNA expression in NSCLC cells. Their protein expression levels presented similar trends, as confirmed by Western blotting. Conclusions: Findings in this study demonstrated for the first time that miR-516b expression might be a novel diagnostic and prognostic factor, as well as a promising target for NSCLC.