Tumor invasion and metastasis regulated by microRNA-184 and microRNA-574-5p in small-cell lung cancer

Small-cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor that has an extremely poor clinical prognosis. Metastasis is the key event in SCLC progression, but its mechanism has not been fully elucidated. MicroRNAs (miRNAs) have been proven to participate in cancer processes, but their function in SCLC has not been thoroughly studied either. Here, we performed microarray and quantitative real-time PCR (qRT-PCR) analyses to identify the miRNAs associated with metastasis and prognosis in SCLC as well as the correlation between serum and tissue. We also explored these miRNAs' promising molecular mechanisms by 3'UTR reporter assay and immunoblotting. We showed that miR-184 significantly attenuated the metastasis of SCLC, whereas miR-574-5p enhanced it. Both miRNAs were found to participate in β-catenin signaling by suppressing protein tyrosine phosphatase receptor type U (PTPRU) or endothelial PAS domain protein 1 (EPAS1). Furthermore, miR-574-5p was verified as an independent prognostic risk factor for SCLC. Taken together, our findings provide a comprehensive analysis of the miRNA expression pattern in SCLC and indicate that miRNAs may serve as potential therapeutic and prognostic predictors in SCLC.