PDCD1 and cancer: Among them, ICIs such as cytotoxic T-lymphocyte antigen 4 (CTLA-4) inhibitors, programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1) have shown great therapeutic effects on various kinds of malignant tumors with fewer side effects than traditional therapy, especially in treating melanoma and hematologic malignancies (Luke et al., 2022; Mei et al., 2022).