Low expression of let-7 predicts poor prognosis in patients with multiple cancers: a meta-analysis

The connection between microRNA expression and cancers has been identified, and microRNAs may be considered as important prognostic biomarkers. However, it is still inconsistent whether expression of let-7 can predict prognosis in patients with multiple cancers. A meta-analysis was performed by searching PubMed, EMBASE, and ISI Web of Science databases. All data were extracted from articles comparing prognosis in patients with multiple cancers having low expression of let-7 with those having high expression. Pooled hazard ratios (HRs) and corresponding 95 % confidence intervals (CIs) were calculated. Subgroup analyses were conducted for cancer type and ethnicity. A total of 1,757 cases of multiple cancers were involved for this meta-analysis. The HR of low let-7 expression in multiple cancers was 1.80 (95 % CI 1.18–2.76), and that in lung cancer was 1.99 (95 % CI 1.17–3.40). A subgroup analysis was performed on ethnicity; combined HR was 1.61 (95 % CI 0.84–3.11) for Asians and 1.94 (95 % CI 1.11–3.39) for non-Asians. Low expression of let-7 might predict poor prognosis in patients with multiple cancers, especially in lung cancer. Furthermore, let-7 might be a biomarker in non-Asian patients with favorable prognosis.