Prognostic role of microRNA-21 in various carcinomas: a systematic review andmeta-analysis

Background Recent studies have shown that microRNAs (miRNA) could play a potential role as diagnostic and prognostic biomarkers of cancers. The aim of this meta-analysis is to summarize the global predicting role of miR-21 for survival in patients with a variety of carcinomas. Design Eligible studies were identified and assessed for quality through multiple search strategies. Data were collected from studies comparing overall, relapse-free or cancer-specific survival (CSS) in patients with cancer having higher miR-21 expression with those having lower levels. Pooled hazard ratios (HRs) of miR-21 for survival were calculated. Results A total of 17 studies dealing with various carcinomas were included for this global meta-analysis. For overall survival (OS), the pooled hazard ratio (HR) of higher miR-21 expression in cancerous tissue was 1.69 (95% CI: 1.33-2.16, P < 0.001), which could significantly predict poorer survival in general carcinomas. For relapse-free or CSS, elevated miR-21 was also a significant predictor, with a pooled HR of 1.48 (95% CI: 1.03-2.11, P = 0.033). Importantly, subgroup analysis suggested that higher expression of miR-21 correlated with worse OS in head and neck squamous cell carcinoma (HNSCC) (HR 1.46, 95% CI: 1.13-1.87, P = 0.004) and carcinomas in digestion system (HR 1.56, 95% CI: 1.08-2.26, P = 0.018). Conclusions Our findings suggest that miR-21 detection has a prognostic value in patients with cancer, especially in HNSCC and digestion system cancers.