MicroRNA-9 as a novel prognostic biomarker in human laryngeal squamous cell carcinoma

In the present study, we aimed to detect microRNA-9 (miR-9) expression level and its clinical significance in laryngeal squamous cell carcinomas (LSCC). 103 patients who were diagnosed with LSCC and treated between March 2010 and June 2013 were enrolled in this study. Expression levels of miR-9 were detected by real-time quantitative RT-PCR assay. Survival curves were estimated using the Kaplan-Meier method, and differences between them were evaluated by the log-rank test. Cox proportional hazard regression test was used to estimate univariate and multivariate hazard ratios for prognosis. We found that miR-9 levels were significantly higher in LSCC tissues compared with matched non-cancerous tissues [4.55 (164-6.75) vs. 2.07 (0.89-2.65), P < 0.05]. The level of miR-9 in LSCC was strongly correlated with tumor differentiation (P = 0.031), thyroid cartilage invasion (P = 0.024), lymph node metastasis (P = 0.009) and clinical TNM stage (P = 0.011). The log-rank test showed that the survival time was significantly different between groups with high and low expression of miR-9 (Log Rank test, P = 0.014). Furthermore, Cox regression multivariate analysis demonstrated that miR-9 expression was an independent prognostic factor of outcomes in patients with LSCC after tumour resection (HR = 3.18, 95% CI = 2.19-11.91, P = 0.012). In conclusion, miR-9 expression was up-regulated in LSCC and was significantly associated with the progression and poorer prognosis of LSCC. Therefore, it might be utilized as a useful prognostic biomarker for LSCC.