Clinicopathological and prognostic significance of microRNA-107 and its relationship to DICER1 mRNA expression in gastric cancer.

microRNAs (miRNAs) are small non-coding RNAs that regulate target gene expression. It is known that miRNA-107 (miR-107) promotes cancer invasion and metastasis. However, the relationship between clinicopathological factors and the prognostic significance of miR-107 for gastric cancer patients remains elusive. In this study, we evaluated the prognostic value of miR-107 using tissue samples from gastric cancer patients. Furthermore, the relationship between miR-107 and the mRNA levels of its target gene DICER1 was examined. The expression levels of miR-107 and DICER1 mRNA in tumor tissues and adjacent normal tissues of 161 gastric cancer patients were examined (TNM stage I, 29 patients; stage II, 31 patients; stage III, 51 patients and stage IV, 50 patients). miR-107 levels were measured by Taqman microRNA assays, and DICER1 mRNA levels were measured by the Taqman real-time RT-PCR method. In the analysis by real-time PCR-based miRNA arrays using pooled RNA samples from five gastric cancer patients, expression of miR-107, miR-21, miR-196a, miR-26b, miR-9, miR-142-3p, miR-30b, miR-150, miR-191 and miR-17 was found to be upregulation. The mean expression level of miR-107 was significantly higher in the tumor tissues compared to that of normal tissues. In the comparison of clinicopathological factors, miR-107 expression showed significant association with depth of tumor invasion, lymph node metastasis and stage. In Kaplan-Meier survival curve analysis, overall survival rates (OS) and disease-free survival rates (DFS) of patients with high miR-107 expression were significantly worse than those of patients with low miR-107 expression. In the Cox multivariate analysis, it was shown that miR-107 expression in gastric cancer tissues was an independent prognostic factor for OS and DFS. Significant inverse correlations were demonstrated between miR-107 and DICER1 mRNA. Our results indicate that miR-107 may be useful as an effective biomarker for prediction of a poor prognosis in gastric cancer patients.