Thus, we assessed the association of a panel of five marker genes to study their association to MSI subgroup, CIMP-phenotype, and GC-progression, as well as the role of RUNX3 as a conflicting TSG [21–23] compared to a known TSG, ARID1A, in GC pathogenesis, H. pylori infection, MSI, and the tumor immune microenvironment. The gene discussed is RUNX3; the disease is gastric cancer.