PDCD1 and neoplasm: Many studies have shown that the combination of PD-L1 on the surface of tumor cells and PD-1 on the surface of T cells initiates the programmed death of T cells, enabling tumor cells to achieve “immune escape”, and that PD-1/PD-L1 immune checkpoint inhibitors can restore the antitumor activity of T cells by blocking the binding of PD-1 to PD-L1 (Doroshow et al., 2021; Yamaguchi et al., 2022).