From the launch of the first tumor immunotherapy drug (IFN-α) to the current immune checkpoint inhibitors (PD-1/PD-L1, CLTA-4) (15), CAR-T cell therapy (16), tumor vaccines (17), oncolytic viruses (18), and other new drugs, these drugs have shown good therapeutic effects and hence are approved for tumor immunotherapy. Here, PDCD1 is linked to neoplasm.