MicroRNA-374b-5p Functions as a Tumor Suppressor in Non-Small Cell Lung Cancer by Targeting FOXP1 and Predicts Prognosis of Cancer Patients

Background: Lung cancer remains the most frequent malignancy worldwide with increasing morbidity and mortality. This study aimed to assess the expression of microRNA-374b-5p (miR-374b-5p) in tissues and cell lines of non-small cell lung cancer (NSCLC) and to evaluate the prognostic value of miR-374b-5p as well as its biological function in tumor progression. Materials and Methods: Expression of miR-374b-5p in NSCLC patients and cells was estimated using quantitative real-time PCR. The prognostic value of miR-374b-5p was evaluated using Kaplan- Meier method and Cox regression analysis. Gain-of-function and loss-of-function cell experiments were performed to examine the effects of miR-374b-5p on NSCLC cell proliferation, migration and invasion. A luciferase activity assay was used to confirm the target gene of miR-374b-5p. Results: miR-374b-5p expression levels were decreased in tumorous tissues and cell lines compared with the normal tissues or cells (P < 0.05). The expression of miR-374b-5p was associated with the patients' tumor size, lymph node metastasis and TNM stage (all P < 0.05). Patients with low miR-374b-5p expression have a shorter survival time (log-rank P = 0.001), and the downregulated expression of miR-374b-5p was determined to be an independent prognostic indicator of NSCLC. In NSCLC cells, the overexpression of miR-374b-5p could inhibit NSCLC cell proliferation, migration and invasion and could directly target FOXP1. Conclusion: This study found that the decreased miR-374b-5p predicts poor prognosis of NSCLC, and the upregulation of miR-374b-5p can inhibit NSCLC cell proliferation, migration and invasion. The data obtained from this study provide a novel candidate prognostic biomarker and a potential therapeutic target for NSCLC.