Exosomes as diagnostic biomarkers in cancer

Purpose of review: Exosomes are extracellular vesicles of 30-150 nm diameter, secreted from nearly all mammalian cells through fusion of multivesicular bodies with the plasma membrane. Owing to the differences in the properties of exosomes and microvesicles released through outward budding of the plasma membrane, exosomes have recently received increasing interest. This review discusses the current status of exosome research for diagnostic biomarkers in cancers. The scope of information that can be acquired from exosomal contents potentially include tumour progression, detection of metastasis, and possible chemotherapeutic resistance, which can facilitate clinical decisions in precision medicine. Recent findings: Exosomes protect molecular components including miRNAs and proteins from enzymatic degradation during circulation and serve as stable cargo for them. miRNAs transferred by exosomes have emerged as novel regulators of cellular function in various types of cancers. In addition, exosomes contain numerous plasma membrane and cytosolic proteins and exosome-specific proteins. However, many of the experiments are limited in their methods for the isolation and purification of exosomes. Nevertheless, the physiological and pathological significance of the role of exosomes in miRNA- or protein-based cell-to-cell or tissue-to-tissue communication has been highlighted.