Down-regulated miR-22 as predictive biomarkers for prognosis of epithelial ovarian cancer

Background: Recent studies have demonstrated that microRNA-22 (miR-22) was deregulated in many types of cancers and was involved in various cellular processes related to carcinogenesis. However, the clinical significance and prognostic value of miR-22 in epithelial ovarian cancer (EOC) haven't been investigated. Methods: 109 pairs of fresh EOC tissue and matched adjacent normal tissue specimens were collected between May 2007 and March 2013. Real-time quantitative RT-PCR assay was performed to evaluate the expression levels of miR-22. The chi-square test was used to assess miR-22 expression with respect to clinicopathological parameters. The survival curves of the patients were determined using the Kaplan-Meier method and Cox regression, and the log-rank test was used for statistical evaluations. Results: miR-22 expression in EOC tissues was significantly lower than that in matched normal adjacent tissues (mean +/- SD: 1.944 +/- 1.026 vs. 4.981 +/- 1.507, P < 0.0001). Low miR-22 expression level was correlated with FIGO stage (P = 0.006), tumor grade (P = 0.03), and lymph node metastases (P = 0.01). Kaplan-Meier analysis with the log-rank test indicated that low miR-22 expression had a significant impact on overall survival (44.4% vs. 64.5%; P = 0.005) and progression-free survival (23.5% vs. 52.6%; P = 0.004). Conclusions: Our data demonstrated that the expression of miR-22 was downregulated in EOC, and associated with overall survival as well as progression-free survival, suggesting that miR-22 could serve as an efficient prognostic factor for EOC patients.