Exosome-mediated drug resistance in cancer: the near future is here.

Drug resistance exerts a crucial role in several cancer treatments. Understanding the resistance mechanisms against different therapeutic agents can be helpful to determine the prognosis, but remains a tricky task. In this context, tumor- derived exosomes (TDEs) may give crucial answers about these resistance mechanisms. Exosomes are biological nanovesicles with an average size around 30–100 nm of diameter (Figure 1) that originate from the endocytic path- way by the inward budding of multivesicular bod- ies (MVB), and they function as cell-free messengers, involved in the cell–cell communica- tion [Kowal et al. 2014].