Indeed, compared to Hiltonol treatment, HELA-Exo treatment had a more robust priming effect on CD8+ T cells, as evidenced by higherproduction of granzyme B and perforin, increased expression of CD69 (activation marker) and lower expression of PD1 in CD8+ T cells (Fig. 3E and F), which induce specific cytotoxic activity against breast cells, rather than lung cancer cells or normal breast cells in vitro (Fig. S2C). Here, PRF1 is linked to lung carcinoma.