The therapeutic mechanism of ICIs is based on targeting certain immunoregulatory signaling molecules, including cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death 1 (PD-1), and its ligand 1 (PD-L1), which activate T cells and inhibit the growth of tumor cells (Ribas and Wolchok, 2018). Here, PDCD1 is linked to neoplasm.