Consistent with the TCGA-STAD training cohort, the expressions of the NOX4 and FKBP10 were significantly up-regulated, while the expressions of the MAOA and ALDH3A2 were significantly down-regulated in STAD in GSE66229 validation cohort (Additional file 2: Fig. S2D). The gene discussed is NOX4; the disease is gastric adenocarcinoma.