Extracellular vesicles in the tumor immune microenvironment

Extracellular vesicles (EVs) have gained significant attention in recent decades as major mediators of intercellular communication that are involved in various essential physiological and pathological processes. They are secreted by almost all cell types and carry bioactive materials, such as proteins, lipids and nucleic acids, that can be transmitted from host cells to recipient cells, thereby eliciting phenotypic and functional alterations in the recipient cells. Recent evidence shows that EVs play essential roles in remodeling the tumor immune microenvironment (TIME). EVs derived from tumor cells and immune cells mediate mutual communication at proximal and distal sites, which determines tumor fate and antitumor therapeutic effectiveness. In this review, the current understanding of EVs and their roles in remodeling the TIME and modulating tumor-specific immunity are summarized. We mainly discuss the mutual regulation between tumor cells and tumor-infiltrating immune cells through the delivery of EVs in the TIME. We also describe the limitations of current studies and discuss directions for further research.