The use of checkpoint inhibitors, such as nivolumab, atezolizumab, or durvalumab [133,134,135], by regulating the programmed death ligand 1/programmed cell death 1 (PD-L1/PD-1) axis, also enhanced the anti-tumor activity of T-cells [136] to modify tumor microenvironment [137]. The gene discussed is PDCD1; the disease is neoplasm.