Clinical relevance of serum miR-9 in resected non-small cell lung cancer patients

Background: MiRNAs can be released from cancer cells to body fluids via secreting exosomes particles. MicroRNA-9 (MiR-9) was over expressed in non-small-cell lung cancer (NSCLC), and identified as promising prognostic markers in NSCLC. In the present study, we analyzed whether levels of serum miR-9 can be used as prognostic or predictive biomarkers in radically resected NSCLC patients. Methods: Serum samples from 161 radically resected NSCLC patients and 161 controls was collected. We used quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) assays to measure miR-9 and assess its association with clinicopathological parameters. KaplanMeier survival analysis and Cox proportional hazards models were used to estimate the serum miR-9 expression on survival. Results: The data showed that the serum levels of miR-9 was significantly upregulated in NSCLC patients compared with the healthy controls. MiR-9 expression was significantly correlated with the lymphy node metastasis (P=0.0026), high II+III stage (P=0.0038) and recurrence (P=0.0001). Univariate analysis showed that advanced p-stage (P=0.002), an advanced regional lymph node metastasis status (P<0.001), lymphatic permeation (P<0.001), poor tumor differentiation (P=0.046), pleural involvement (P=0.012), vascular invasion (P=0.003) and high miR-9 expression (P=0.003) were significant prognostic factors. Multivariate analysis identified lymph node metastasis status (HR, 5.643; 95% CI, 2.315-13.76; P<0.001) and high miR-9 expression (HR, 4.08; 95% CI, 1.452-6.36; P=0.002) were as independent prognostic factors. Using univariate analysis, the low miR-9 expression patients had a significantly higher OS rate than did the low miR-9 expression patients (P=0.0016). Conclusions: Serum miR9 was increased in NSCLC patients, and high serum miR-9 level was associated with poor outcomes in completely resected NSCLC patients.