GKN1 and gastric cancer: As shown in Figure 1A and Table 1, the serum GKN1 protein concentrations were significantly lower in the gastric cancer patients (median: 3.48 ng/μL, IQR: 2.90‐4.11 ng/μL) compared with healthy individuals (median: 6.34 ng/μL, IQR: 5.66‐7.54 ng/μL; P < .0001).