**Background:** Colorectal cancer (CRC) is the second most deadly cancer in women and the third most prevalent in men, with approximately 576,858 deaths worldwide in 2020. Current diagnostic methods, including colonoscopy and tissue biopsy, are invasive and unsuitable for repeated testing. The carcinoembryonic antigen (CEA) biomarker lacks sufficient sensitivity and specificity. Extracellular vesicles (EVs)—lipid bilayer-enclosed sacs (30–10,000 nm) secreted from cells—carry pathophysiological signatures of parent cells, including RNAs protected from nuclease degradation. This review evaluates the potential of EV-derived RNAs as noninvasive biomarkers for CRC diagnosis, prognosis, and chemotherapy resistance monitoring.
**Methods:** The authors reviewed recent literature on EV-RNA biology, including mechanisms of RNA sorting into EVs, EV-mediated intercellular communication, characterization techniques, and clinical applications in CRC. They summarized data from multiple independent studies reporting AUC values, sensitivity, and specificity for various EV-RNA biomarkers. Characterization methods discussed include RT-PCR, microarray, next-generation sequencing, microfluidic devices, and emerging CRISPR-based approaches.
**Key Results:** Multiple EV-miRNAs are significantly overexpressed in CRC patients compared to healthy individuals. Serum-derived EV-miR-23a showed an AUC of 0.95 for metastasis detection, EV-miR-1246 an AUC of 0.94 for cytoskeleton remodeling, and EV-miR-21 an AUC of 0.91 for cell proliferation. Plasma-derived EV-miR-29a showed an AUC of 0.82 for ECM remodeling. For chemotherapy resistance, overexpression of EV-miR-1246, miR-21-5p, miR-96-5p, and miR-1229-5p was found in 5-fluorouracil resistant CRC. EV-lncRNA CRNDE-h showed an AUC of 0.892, and lncRNA GAS5 showed an AUC of 0.964. In clinical trials, miR-1246 demonstrated 84% specificity and 95.5% sensitivity (n=88), miR-23a showed 81% specificity and 92% sensitivity (n=88), and miR-135 showed 95% specificity but only 46.2% sensitivity (n=315). EV-miR203 was associated with poor prognosis, and EV-miR19a was also linked to poor outcomes. Hypoxia-specific EV-miRNAs (miR-30d-5p, miR-30e-5p, miR-31-5p, miR-194-5p) were identified as potential early CRC biomarkers. EV-circular RNAs were found to be six times higher in EVs than in cells, with circRNA KLDHC10 overexpressed in CRC-derived exosomes.
**Clinical Implications:** EV-RNAs offer significant advantages over traditional biomarkers due to their stability in the nuclease-rich blood, noninvasive isolation from body fluids, and ability to reflect tumor heterogeneity. The high AUC values of several EV-miRNAs (close to 1.0) suggest strong diagnostic potential. EV-RNAs are also implicated in immune evasion mechanisms—for example, EV-miR203 activates M2-tumor-associated macrophages, and mutant TP53-secreted EV-miR1246 converts macrophages into tumor-associated macrophages (TAMs). EV-miR-21 and EV-miR-155 target BRG1 to increase metastatic potential. However, the lack of standardized EV isolation and characterization techniques limits clinical translation. The authors note that the global point-of-care (POC) diagnostic market is expected to reach $36 billion by 2028, and multiplex EV sensing devices incorporating machine learning algorithms are under development. Large-scale clinical trials are needed to validate these biomarkers across diverse populations by gender, age, and geographical location.