The immune checkpoint proteins programmed cell death 1 ligand 1 (PD-L1) and programmed cell death 1 protein (PD-1) appear to play significant roles in GC/GEJC pathobiology, with PD-L1 being expressed in 30–45% of GC/GEJC tumors [14, 15]. This evidence concerns the gene PDCD1 and gastric cancer.