PDCD1 and cancer: PD-1 is a type I transmembrane protein comprising 288 amino acids and belongs to the B7 receptor immunoglobulin family, which includes three domains: an immunoglobulin superfamily domain, a transmembrane domain, and an intracellular domain.307 Notably, PD-1 is highly expressed on tumour-specific T cells, indicating its critical role in the immune response to cancer.308 The interaction between the PD-1 pathway and its ligand PD-L1 is crucial for suppressing anti-tumour immune responses, which represents a substantial breakthrough in cancer therapy.