Clinical potential role of circulating microRNAs in early diagnosis of colorectal cancer patients

Current procedures for diagnosis and biomarker examination of colorectal cancer (CRC) are invasive and unpleasant. There is a great need to identify sensitive and specific biomarkers for early diagnosis of CRC. Circulating microRNAs (miRNAs) are promising molecular markers for CRC prediction. We performed a comprehensive meta-analysis to integrate an evaluation index for diagnostic accuracy of circulating miRNAs in diagnosing CRC patients. Furthermore, we conducted an independent validation set of 49 CRC patients and 49 healthy controls. In our meta-analysis, we found that miR-21 yielded a pooled area under ROC curve (AUC) of 0.867 (sensitivity: 76%, specificity: 82%) in discriminating CRC from controls, and miR-92a yielded a summary AUC of 0.803 (sensitivity: 77%, specificity: 68%); miR-21 had a higher diagnostic efficiency than miR-92a. In the further validation, plasma miR-21 levels in CRC patients were significantly higher than levels observed in healthy subjects. A ROC curve analysis showed a consistent result. However, this phenotype was not present in miR-92a. Moreover, the expression trend of miR-21 in plasma samples was in line with that of tissue samples, along with the cellular level. Current evidences suggest that plasma miR-21 could be a reliable and non-invasive biomarker for CRC diagnosis. Studies with larger cohorts that include the diagnostic value of plasma miR-21 for CRC are warranted.