Yunxia Li, Xiaomei Cui, Yongdeng Li, Tingting Zhang, Shuyun Li

Non-small-cell lung cancer (NSCLC) represents the most frequent subtype of lung cancer. MicroRNAs (miRNAs) have attracted a lot of attention with regard to their clinical significance and crucial biological functions in various human cancers. This study aimed to investigate the prognostic significance of microRNA-421 (miR-421) and its correlation with tumor progression in NSCLC. Expression levels of miR-421 in both serum and tissue samples were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The prognostic value of miR-421 was evaluated using Kaplan-Meier survival analysis and Cox regression assay. To explore the functional role of miR-421 during NSCLC progression, cell experiments were carried out. Expression of serum and tissue miR-421 was upregulated in the NSCLC patients compared with the normal controls (all P<0.001), and the expression showed a significant correlation between the serum samples and tissues (R=0.475, P<0.001). The increased miR-421 expression was associated with positive lymph-node metastasis and advanced TNM stage (all P<0.05). Moreover, patients with high miR-421 expression had poor overall survival compared with those with low expression (log-rank P=0.007). The overexpression of miR-421 proved to be an independent prognostic factor for NSCLC (HR=1.991, 95% CI=1.046-3.791, P=0.036). According to the cell experiments, the proliferation, migration and invasion of NSCLC cells were suppressed by knockdown of miR-421. Overexpression of miR-421 serves as a prognostic biomarker and may be involved in the promotion of tumor progression in NSCLC.