Exosomes for the treatment of human malignancies

Exosomes are nanometer particles (50-100 nm) secreted by most living cells. The first description of exosomes was made in 1987 by Rose Johnstone, who described a vesicle formation during the maturation process of reticulocytes. At this time it has been suggested that exosome release could represent a major route for the externalization of obsolete membrane proteins. A renewed vision of exosome function was raised when Graça Raposo demonstrated in 1996 that exosomes derived from B cells could have immunogenic capacities. Since then, exosomes have been described in numerous cell types in vitro, including hematopoietic and nonhematopoietic cells. The physiological relevance of exosomes in vivo still remains unclear. Studies have demonstrated that exosomes can play a role in the physiology of originating cells (i.e., reticulocyte-derived exosomes). Furthermore, exosomes can act on intercellular communication by allowing exchange of proteins, lipids, and also mRNA between cells. Finally, exosomes have been shown to modulate the immune system (i.e., dendritic cells, B cells, and tumor cells). In the present review, we have focused on the potential therapeutic role of exosomes as a cell free vaccine in cancer.