Abstract

Ultra-Sensitive Liquid Biopsy of Circulating Extracellular Vesicles (EVs) by ExoScreen Method

Takahiro Ochiya, Chief, National Cancer Center Research Institute Japan

EVs are small membraneous vesicles that differ in their cellular origin, abundance and biogenesis8, and are naturally secreted by almost all cell types to transport bioactive molecules intercellularly. EVs are positive for tetraspanin family proteins, such as CD63, CD81 and CD9, and contain cell surface proteins as well as both mRNA and microRNA. Conventional methods of analyzing EVs generally require large quantities of EVs to be concentrated and processed via time-consuming immunoblotting or enzyme-linked immunosorbent assay (ELISA) assays; these methods are impractical in most clinical settings. In this study, we establish a highly sensitive and rapid analytical technique for profiling surface proteins in EVs from patient blood that can be used to identify biomarkers of colorectal cancer, named ExoScreen. ExoScreen could monitor circulating EVs in serum without the need for purification step. In addition, we show that ExoScreen is superior for the detection of EVs to conventional methods, immunoblotting and ELISA. Furthermore, our results demonstrate that ExoScreen can be a tool for detection of EVs from as little as 5?microliters of cancer patients’ serum to detect circulating cancer-derived EVs.