PRF1 and lung cancer: 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).