GKN1 and gastric cancer: When we compared serum GKN1 concentrations between patients with gastric cancer and patients with non‐gastric cancers, serum GKN1 concentration distinguished patients with gastric cancer from those with the foregoing non‐gastric cancers with AUC values of >0.94 (Figure 3B) and diagnostic accuracies of >0.86 (Table S2), suggesting that serum GKN1 protein may be a gastric cancer‐specific diagnostic biomarker.