Exosome-Encapsulated microRNAs as Potential Circulating Biomarkers in Colon Cancer

Exosome-encapsulated microRNAs are being suggested as a new class novel biomarker as diagnostic and predictive markers in colorectal cancer. These particles are released from many cell types into the extracellular space upon fusion of multivesicular bodies (MVB) with the plasma membrane. They contain a wide variety of information, including proteins, lipids, RNAs, non-transcribed RNAs, microRNAs, which can be circulated in various body fluids (e.g., blood, salvia, ascites, urine). Exosomes can be taken up by neighboring or distant cells and thereby modulate the functional of recipient cells and play a key role in disease progression or facilitate metastasis in cancers. The aim of current review is to give an overview about origin and trafficking of exosomes between cells, techniques to isolate exosomal microRNAs as well as the potential applications of exosome-encapsulated microRNAs as diagnostic markers in clinical settings in colorectal cancer. There is growing body of evidence showing the prognostic and diagnostic value of some exosomal microRNAs in colon cancer (e.g., miR-150, miR-21, miR-192, let-7a, miR-223, and miR-23a). These findings provide a new insight on novel application of these markers as being novel non-invasive biomarkers for early detection and risk assessment of patients with colorectal cancer, although further investigations in larger population are required to explore the clinical utility of exosomal microRNAs in colorectal cancer patients.