CEACAM5 and colorectal cancer: Chen et al. reported a specific metabolite, 1-methyladenosine, as biomarker in hepatocellular carcinoma patients using metabonomics [26]; Leichtle et al. investigated the levels of 26 amino acids in the blood of colorectal cancer patients and found that the cancer patients had lower concentration for 11 amino acids and proposed a carcinoembryonic antigen- (CEA-) glycine-tyrosine tri-biomarker, the best model for the diagnosis of the disease [27].