Currently widely used serum tumor markers for GC, such as carcinoembryonic antigen (CEA), cancer antigen 125 (CA125), and carbohydrate antigen 19–9 (CA19-9), are glycoproteins (proteins with attached carbohydrate chains) that may be elevated in GC patients, but due to their low sensitivity and specificity, their diagnostic utility is limited (Xia and Aadam 2022). Here, CEACAM5 is linked to gastric cancer.