Early diagnosis of cancer is critical to reduce mortality.1–3 As substances overexpressed in the presence of cancer in the body, cancer biomarkers are potentially valuable for early cancer diagnosis, accurate pre-treatment staging and predicting the recurrence of cancer.4,5 For instance, carcinoembryonic antigen (CEA) is a glycoprotein with a molecular weight of about 180 kDa. The gene discussed is CEACAM5; the disease is cancer.