We detected the levels of total serum Cat S in the healthy controls (n = 99) and the patients with a variety of cancers (n = 347) that included gastric cancer (n = 119), esophageal cancer (n = 45), liver cancer (n = 46), colorectal cancer (n = 48), nasopharyngeal cancer (n = 47), and lung cancer (n = 42) by ELISA. The gene discussed is CAT; the disease is colorectal cancer.