IDO1 and gastritis: We intersected and overlapped genes related to the transformation of gastritis-to-cancer with differentially expressed genes in GC and ultimately identified 12 driver genes (PLA2G7, CXCL1, CXCL6, CHI3L1, SPP1, MMP12, TREM1, MMP7, CXCL5, IDO1, CCL20, KRT23) that ultimately lead to carcinogenesis (Fig. 2C).