Four circulating exosomal miRNAs as novel potential biomarkers for the early diagnosis of human colorectal cancer

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths worldwide. Our study aimed to identify novel circulating miRNAs as early diagnostic biomarkers of CRC. The Gene Expression Omnibus (GEO) datasets were analyzed by using the online tool GEO2R. Isolated exosomes were verified by using the transmission electron microscope (TEM), Nanosight, and western blot. qRT-PCR was implemented to examine miRNA expression. The diagnostic value of circulating exosomal miRNAs was identified by using the receiver operating characteristic curve (ROC). In this study, we found that serum exosomal miRNAs are more suitable for diagnosing CRC when compared to serum miRNAs. Furthermore, we identified four exosomal miRNAs (miR-126, miR-1290, miR-23a, and miR-940) in the serum of CRC patients as novel potential biomarkers for the early diagnosis of CRC because they showed high diagnostic values to differentiate CRC patients at TNM stage I from healthy controls (HCs). In addition, our data suggested that CRC cells may secrete miRNAs into the extracellular environment through exosomes regardless of intracellular miRNA expression. In conclusion, we identified serum exosomal miR-126, miR-1290, miR-23a, and miR-940 as novel potential biomarkers for the early diagnosis of CRC.