How to explain the contradiction of microRNA 200c expression and survival in solid tumors? A meta-analysis

MicroRNA 200c is a microRNA 200 family member that plays an important role in regulation of the epithelial- to-mesenchymal transition (EMT). The prognostic value of microRNA 200c in solid tumors remains controversial because of inconsistent data. Here, we report a meta-analysis of the association of microRNA 200c expression and survival in patients with solid tumors. Pubmed was searched up to November 2013 for studies investigating microRNA 200c expression and overall survival (OS) in solid tumors. Hazard ratios (HRs) with 95% confidence intervals (CIs) for OS were extracted from each study. Pooled HR and CIs were calculated using the Mantel- Haenszel fixed-effects models. A total of five studies evaluating colorectal cancer, gastric cancer, ovarian cancer, pancreatic cancer and endometrial cancer were included in the analysis. Data were divided into tissue microRNA 200c expression group and serum microRNA 200c expression group. The combined HRs [95%CIs] estimated for OS were 0.62 [0.42-0.91] and 2.16 [1.32-3.52] respectively. Low expression of microRNA 200c in tumor tissue and high expression of microRNA 200c in serum are associated with worse survival in solid tumors. Further study is needed to elucidate this contradiction.