DAO and colorectal carcinoma: Eight weeks after the first injection of DMH, the activity of polyamine metabolism-related enzymes, including ODC, OAZ1, DAO (diamine oxidase, which catalyses the biotransformation of putrescine into γ-aminobutyric acid), ADC (arginine decarboxylase, which catalyses the biotransformation of arginine into agmatine) and PAO (polyamine oxidase, one of the key enzymes in catalytic polyamine degradation) were significantly increased in CRC rats compared with normal rats.