PD-L1 is overexpressed in up to 50% of gastric cancers [237,238] and a large number of clinical trials are evaluating the efficacy of mAbs anti-PD-1 (i.e., nivolumab, pembrolizumab) (Table S1) and anti-PD-L1 (i.e., atezolizumab, avelumab, durvalumab) (Table S2) as monotherapy or in combination with anti-CTLA-4 (i.e., ipilimumab) or targeted therapies in the management of advanced-stage gastric cancer. This evidence concerns the gene CTLA4 and gastric cancer.