PDCD1 and neoplasm: Immune checkpoint blockade (ICB) has been identified as a promising treatment option for malignancies [7], based on the finding that the programmed cell death protein 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) signaling pathways play a key role in tumor immune escape.