PDCD1 and neoplasm: Immunotherapies targeting the checkpoint molecules expressed on immune or tumor cells, including cytotoxic T-lymphocyte antigen 4 (CTLA-4), PD-1, and programmed death-ligand 1 (PD-L1), have demonstrated outstanding clinical efficacies in recent studies and clinical trials, laying the groundwork for the development of standard ITM treatments [15,19,32,33,34].