PDCD1 and neoplasm: Notably, we here find that synergy is also observed even though the oncolytic virus is unable to successfully infect and directly lyse tumor cells, suggesting that the synergistic effect between oncolytic viruses and PD-1 blockade probably depends on the capability of oncolytic viruses to turn the tumor cells from the “self” state into the “nonself” state, rather than the capability of oncolytic viruses to lyse tumor cells.