Senescent cell-derived extracellular vesicles are critical elements in senescence surveillance by recruiting antigen-presenting cells

Abstract

Abstract Cellular senescence is a tumor suppressor mechanism that arrests cell cycle and initiates immune-mediated removal of senescent cells, a process known as senescence surveillance (SS). Senescent cells interact with their microenvironment through senescence-associated secretory phenotype (SASP). Current knowledge about the SASP has focused on soluble elements like cytokines. Extracellular vesicles (EVs) are membrane-bound, nanometer-sized particles that are emerging as a novel class of SASP factors. Whether EVs play a role in SS is unknown. Elucidating the role of EVs in SS will open new avenues for therapeutically targeting cellular senescence. In order to study if and how EVs contribute to SS, we inhibited EV release from senescent cells using dominant-negative mutant Rab35. This approach preserved secretion of soluble SASP elements while decreasing >95% the release of EVs from senescent cells. C57BL6 mice were challenged with EV-inhibited senescent cells and their numbers at the site of injection as well as immune infiltrates were quantified. Interfering with EV release led to the reduction of antigen-presenting cells including dendritic cells, macrophages, and B cells, which may contribute to the observed persistence of senescent cells. Interestingly, EV-inhibition reverted cellular senescence, promoted proliferation and tumor formation. Proteomic analysis revealed 35 proteins that were exclusively present on senescent cell-derived EVs, compared to those from their non-senescence counterparts. These results suggest that EVs have critical role in SS possibly via signaling to immune cells. Future work will explore whether T cells respond to EV-bound senescent cell antigens. Integrated Training in Quantitative and Experimental Cancer Systems Biology, 5T32CA254888-02 and CRUK/OHSU A29681