Exploring Extracellular Vesicles as a Potential Source of Biomarkers for the Diagnosis of Colorectal Cancer and Its Current Challenges

Colorectal cancer (CRC), a common cancer that affects people all around the world, has high rates of morbidity and mortality rates. The disease stage is the key indicator of the long-term survival of CRC patients during diagnosis. The most important indicator of long-term survival of CRC patients is the disease stage at the time of diagnosis. Unfortunately, early-stage CRC usually displays no symptoms; it is mainly diagnosed where long-term survival chances might drop as low as 14%. Current screening methods, including stool-based tests (fecal immunochemical test, fecal occult blood test, and stool DNA test), CT colonography, flexible sigmoidoscopy, and colonoscopies, suffer from limited adherence, which diminishes the overall effectiveness of CRC screening. Blood tests are often more readily accepted as a primary screening method compared to stool tests or colonoscopy. Hence, there is a pressing need to identify blood biomarkers for detecting CRC. The extracellular vesicles (EVs) derived from tumors serve as a valuable tool for liquid biopsy as well as a potential source of several biomarkers, such as miRNA, circular RNA, long-noncoding RNA, and protein, for CRC diagnosis. In CRC, EVs have been found to be involved in cargo transfer, such as DNA, RNA, proteins, and lipids, to the recipient cancer cells, leading to tumorigenesis and drug resistance, and also regulating intercellular communication. Recent studies have documented that tumor-derived extracellular vesicles (EVs) can serve as a valuable tool for liquid biopsy. EVs play a significant role in intercellular communication in CRC via transfer of cargo lipids, proteins, DNA, and RNAs to the recipient tumor cells, driving tumorigenesis, facilitating progression, and fostering drug resistance. This review delves into the potential of EVs as diagnostic biomarkers for CRC, exploring their clinical applications along with existing challenges in the field.