Many studies have shown that microRNAs have important roles in the development and progression of various cancers. Recent studies also showed that microRNA-21 expression may be associated with the prognosis of patients with several common cancers. However, there was still lack of evidence for the prognostic role of microRNA-21 expression in brain tumors. We performed a systemic review and meta-analysis of published and unpublished studies to assess the prognostic role of microRNA-21 expression in patients with brain tumors. PubMed, Embase, and Google Scholar databases were searched for eligible studies with data assessing the prognostic role of microRNA-21 expression in brain tumors. Pooled hazard ratios (HRs) of microRNA-21 expression for overall survival and 95% confidence intervals (CI) were calculated. Six studies from five publications were finally included into the meta-analysis. Those six studies included a total of 747 patients with brain tumors and 654 patients with gliomas. For overall survival, the pooled HR of higher microRNA-21 expression in patients with brain tumors was 1.82 (95% CI 1.29-2.58, P = 0.001). In patients with gliomas, the HR for overall survival of higher microRNA-21 expression was 1.83 (95% CI 1.09-3.09, P = 0.023). Sensitivity analysis by omitting one study by turns also showed there was no obvious influence of individual study on the pooled HRs. There was no obvious risk of publication bias in the meta-analysis. The present meta-analysis suggests that microRNA-21 is associated with the prognosis of patients with brain tumors, and high expression of microRNA-21 can predict poor prognosis in patients with brain tumors.
Keywords: Brain tumors; Glioma; Survival; microRNA-21.