PDCD1 and cancer: Recently, immune checkpoint inhibitors (ICIs), targeting cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and its ligand programmed death-ligand 1 (PD-L1), have significantly advanced cancer therapy, improving survival outcomes for malignancies such as melanoma, non-small cell lung cancer, and renal cell carcinoma [3].