Prognostic significance of tissue miR-345 downregulation in non-small cell lung cancer

Background: MiRNAs might function as oncogenes or tumor suppressor genes in the tumorigenesis process. Dysregulation of miR-345 is a frequent event in many types of human cancers. However, the tissue miR-345 expression level in non-small cell lung cancer (NSCLC) and its potential clinical significance remains unknown. Materials and methods: Real-time PCR was conducted to evaluate the expression level of miR-345 in NSCLC tissues as well as cell lines. Then the association between tissue miR-345 expression level and clinical outcome was investigated. Results: The expression level of miR-345 was significantly decreased in NSCLC tissues and cell lines compared with the controls (P< 0.05; P< 0.01). Tissue miR-345 expression level was associated with various clinicopathological parameters including LN metastasis (P= 0.012), distant metastasis (P= 0.007), TNM stage (P= 0.008) and grade (P= 0.030). In addition, the NSCLC patients in the low tissue miR-345 expression group had significantly shorter 5-year overall survival time than those in the high tissue miR-345 expression group (P= 0.016). Multivariate analysis showed that tissue miR-345 was an independent risk factor for NSCLC (HR= 3.921, 95% CI: 2.285-10.540; P= 0.008). Conclusions: The expression level of miR-345 was reduced in NSCLC tissues and cell lines. Low tissue miR-345 expression was associated with progression and poor prognosis of NSCLC, indicating that tissue miR-345 may serve as a novel prognostic marker in NSCLC.