The tumor suppressor miR-124 inhibits cell proliferation by targeting STAT3 and functions as a prognostic marker for postoperative NSCLC patients.

The aim of the present study was to investigate the role of miR-124 in lung cancer and identify the potential predictive value of miR-124 in postoperative non-small cell lung cancer (NSCLC) patients. We detected miR-124 expression in A549, NCL-H460 and normal lung epithelial BEAS-2E cells and showed a significantly lower expression level of miR-124 in NSCLC cells than in BEAS-2E cells. Upregulation of miR-124 expression levels in both A549 and NCL-H460 cells by transfection with miR-124 mimics suppressed cell proliferation and induced apoptosis. Further investigation revealed that miR-124 bound directly to the 3' UTR region of STAT3, thereby inhibiting STAT3 expression. In addition, miR-124 levels detected in NSCLC tissues were lower than those in adjacent normal lung tissues, while the opposite was observed for STAT3. In NSCLC, the expression levels of miR-124 and STAT3 correlated significantly with the tumor node metastases (TNM) stage, differentiation grade and lymph node metastasis, while the levels of these molecules did not differ significantly by gender, age, location, smoking index, pleural invasion or pathological type. The expression level of miR-124 was significantly associated with disease-free survival (DFS) in both positive and negative lymph node groups. Furthermore, patients with low miR-124 or high STAT3 expression generally received a worse prognosis in terms of both overall survival (OS) and DFS. In conclusion, our findings suggest that miR-124 functions as a tumor suppressor by targeting STAT3, and that miR-124 may potentially serve as a useful biomarker for the prognosis of NSCLC patients.