PDCD1 and gastric cancer: MSI-GC frequently express PD-L1 (Fig. 1) (Böger et al. 2016; Cho et al. 2021), and anti-PD-1 agents with or without chemotherapy significantly and consistently improved overall survival, progression free survival, and objective response rate vs. chemotherapy alone in the subgroup of patients with advanced MSI-GC (Pietrantonio et al. 2021).