Prognostic value of let-7 in lung cancer: systematic review and meta-analysis

Lung cancer is the leading cause of cancer-related deaths worldwide and the overall survival of patients with non-small cell lung cancer has not been improved. Let-7 family has been shown to act as tumor suppressors by inhibiting oncogenes and key regulators of mitogenic pathways, while far fewer clinical studies addressing the association between let-7 expression and the disease prognosis have been published up to date. Therefore, our meta-analysis aims to determine the prognostic significance of let-7 expression in lung cancer patients.

PubMed, EMBASE, the Web of Science and China National Knowledge Infrastructure (CNKI) databases were searched for full-text literature citations. We applied the hazard ratio (HR) with 95% confidence interval (CI) as the appropriate summarized statistics. Q-test and I2 statistic were used to estimate the level of heterogeneity. The publication bias was detected by Begg's test and Egger's test.

Seven eligible studies involving 2,262 patients were selected for this meta-analysis. The combined HR for the seven eligible studies was 0.61 (95% CI: 0.53-0.70, P<0.00001) and heterogeneity of overall prognosis was relatively high (I²=76.4%, P=0.000). We conducted a further subgroup analysis, including an evaluation of the relationship between let-7 expression, lung cancer pathology, race, and sample size. All the results revealed that a significantly low let-7 expression in patients was an indicator of poor survival. Neither Begg's test nor Egger's test found publication bias in any analysis.

The present evidence indicates that the low let-7 expression can be considered as a significant predictor of worse prognosis in patients with lung cancer. The findings of our meta-analysis may be further confirmed in the future by the use of more updated review pooling and more relevant investigations.