PDCD1 and neoplasm: ICIs, such as antibodies targeting programmed cell death protein 1 (PD-1) or its ligand PD-L1, and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), function by releasing the brakes on the host immune system, enabling T cells to recognize and attack tumor cells (Mivehchi et al., 2025).