Circulating exosomes and their cargos in blood as novel biomarkers for cancer

Exosomes, the bilayer-lipid-membrane microvesicles are well known for intercellular communications. They are considered to be involved in tumorigenesis, progression and chemotherapy resistance via horizontal transfer of their functional biomolecules (i.e., proteins and nucleic acids) to neighboring or distant cells. Thus, circulating exosomes are becoming a new star among existing liquid biopsies [circulating tumor cells (CTCs); disseminated tumor cells (DTCs); cell-free DNAs; cell-free miRNAs]. The detection of circulating exosomes, in particular tumor-specific exosomes, along with the profiling of their contents are expected to facilitate early detection of tumor, prediction of prognosis and monitoring therapy response in cancer. In this review, the clinical relevance of circulating exosomes and their cargos in blood as novel diagnostic and prognostic biomarkers for caner is summarized. Additionally, exosomes as therapeutic target and drug delivery vehicle in clinical applications are also highlighted.