PDCD1 and cancer: Immune checkpoint inhibitors (ICIs) have broadened treatment horizons across multiple cancer types, offering substantial survival benefits and prolonged response durations by targeting the programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) to enhance anti-tumoral immune response [1].