Exosomal MicroRNAs in Cancer: Mechanisms, Clinical Applications, and Challenges in Biomarker Discovery

Exosomal microRNAs (miRNAs) have emerged as promising candidates for cancer biomarker discovery due to their unique properties as stable, non-invasive, and informative molecules in body fluids. These small, membrane-bound vesicles play critical roles in intercellular communication by transferring miRNAs, which regulate gene expression and influence various biological processes, including cancer progression, metastasis, and drug resistance. Recent advancements in exosome isolation and miRNA profiling technologies have unveiled their potential for early cancer detection, prognosis, and therapeutic monitoring. Exosomal miRNAs offer several advantages over traditional biomarkers, including ease of detection in liquid biopsies (e.g., blood, urine), the ability to reflect the molecular landscape of tumors, and their association with both primary and metastatic cancer sites. However, despite the growing body of evidence supporting their utility, challenges such as standardization of isolation methods, variability in miRNA expression across cancer types, and the need for large-scale clinical validation remain significant barriers to clinical translation. This review highlights the biological mechanisms by which exosomal miRNAs influence cancer biology, their clinical applications in cancer diagnosis and therapy, and the technological advancements driving their profiling. Additionally, we discuss the current challenges and future directions for harnessing exosomal miRNAs in precision oncology.