PDCD1 and cancer: In many cancers (including NSCLC), the PD-L1 signaling pathway is usually abnormally activated, and the interaction between PD-1 and PD-L1 inhibits the proliferation and activity of CD4+T cells and CD8+T cells, reducing their immune response to surrounding tissues and preventing the occurrence of autoimmune diseases (David et al., 2019; song et al., 2020).