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

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.

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.

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.

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.