Extracellular vesicles and co-isolated endogenous retroviruses from murine cancer cells differentially affect dendritic cells

Cells secrete extracellular vesicles (EVs) and non-vesicular extracellular (nano)particles (NVEPs or ENPs) that may play a role in intercellular communication. Tumor-derived EVs have been proposed to induce immune priming of antigen presenting cells or to be immuno-suppressive agents. We suspect that such disparate functions are due to variable compositions in EV subtypes and ENPs. We aimed to characterize the array of secreted EVs and ENPs of murine tumor cell lines. Unexpectedly, we identified virus-like particles (VLPs) from endogenous murine leukemia virus in preparations of EVs produced by many tumor cells. We established a protocol to separate small EVs from VLPs and ENPs. We compared their protein composition and analyzed their functional interaction with target dendritic cells. ENPs were poorly captured and did not affect dendritic cells. Small EVs specifically induced dendritic cell death. A mixed large/dense EV/VLP preparation was most efficient to induce dendritic cell maturation and antigen presentation. Our results call for systematic re-evaluation of the respective proportions and functions of non-viral EVs and VLPs produced by murine tumors and their contribution to tumor progression. imageTumor-derived extracellular vesicles have been proposed to induce immune priming of antigen presenting cells, or to act as immuno-suppressive agents. This study presents a comprehensive analysis of distinct subpopulations of extracellular vesicles (EVs) and non-vesicular extracellular particles released by murine tumor cells and reveals presence of endogenous retrovirus-derived components.Murine tumor cell lines commonly release endogenous retrovirus-derived virus-like particles (VLPs) alongside other EVs.Tumor-derived VLPs and other EVs exhibit distinct effects on dendritic cells, with a mixed EV preparation, including larger vesicles and VLPs, proving most efficient for antigen transfer and dendritic cell-mediated T cell activation.Non-vesicular extracellular particles are ineffective in inducing antigen presentation and T cell activation by antigen-presenting cells. A comprehensive analysis of distinct subpopulations of extracellular particles released by murine tumor cells reveals presence of endogenous retrovirus-derived components.image