Extracellular vesicles in cancer: current status and challenges

Small membranous vesicles released from the cell surface, which can be frequently observed by electron microscopy, were considered as just an artifact for a long time (Figure 1). The hypothesis that these vesicles, now called extracellular vesicles (EVs), are not mere artifacts but important and primitive cell-cell communication tools, was proposed for the first time in 1984 (1). An Increasing number of studies have demonstrated that EVs contain a variety of biomolecules such as proteins, mRNAs and microRNAs, and that their profiles reflect the state of their donor cells.