CD274 and gastric cancer: Biomarkers such as microsatellite instability (MSI), HER2, and programmed death-ligand 1 (PD-L1) have already made an impact in the treatment of gastric cancer, and new biomarkers have recently been identified, such as claudin 18.2 (CLDN18.2) and fibroblast growth receptor 2 (FGFR2) [4,5].