Extracellular Vesicles as Biomarkers for Cancer

Because of the minimally invasive nature of biofluid collection, extracellular vesicles (EVs) have promising applications in the diagnosis, management, surveillance, and prognosis of malignancies. Emerging evidence has shown that EVs derived from biofluids can reflect their cells of origin and thus may be utilized as noninvasive cancer biomarkers. Many molecules in EVs differ significantly in biofluids from patients with cancer compared with those from healthy individuals, allowing for biomarker identification in many cancer types. EVs contain different forms of RNA, including mRNA, chimeric RNA, rRNA, and long and small noncoding RNA, such as microRNAs, tRNA fragments, piwi-interacting RNAs, vault RNAs, and Y RNAs. In addition to RNAs, EVs are enriched in tumor-derived DNA and proteins. Moreover, the presence of a membrane ensures that the EV molecular cargo is highly stable, thereby avoiding variation due to exogenous factors. In this chapter, we outline EV biomarkers in cancers of the digestive tract, mammary reproductive system, hematologic system, urinary system, and other types of cancer. This chapter provides an overview of the EV concentrations detected in clinical practice and challenges associated with the utilization of EVs as biomarkers in cancer.