Senescent host-derived extracellular vesicles potentiate antitumor immunity via bystander T cell activation

Extracellular vesicles (EVs) are key mediators of intercellular communication, and those from the plasma of aged individuals are typically viewed as drivers of aging or even cancer. Here, we uncover a latent, potent antitumor capacity inherent to EVs derived from aged hosts. Specifically, we demonstrate that extracellular vesicles from the plasma of aged mice (A-EVs) exhibit robust tumor-suppressive activity in young tumor-bearing recipients. Mechanistically, A-EVs engage a dual mode of action: they directly induce senescence in cancer cells, enhancing their immunogenicity. More importantly, they concurrently activate non-tumor-specific bystander CD8 T cells within the tumor microenvironment via cross-presentation of pathogen-derived antigens, thereby reshaping the immunosuppressive tumor microenvironment. This synergistic interplay potently reinvigorates antitumor immunity and sensitizes tumors to PD-L1 checkpoint blockade. Our findings establish A-EVs as a novel class of endogenous immunomodulators with broad therapeutic potential for cancer immunotherapy.