In recent years, significant advancements have been made in cancer immunotherapy, particularly with the advent of widely used immune checkpoint inhibitors (ICIs), such as programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitors and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) inhibitors, which can prolong patient survival (1). Here, PDCD1 is linked to cancer.