Ornithine decarboxylase (ODC) is the rate-limiting enzyme in polyamine biosynthesis and restricts M1 macrophage activation in gastrointestinal (GI) infections, which augments epithelial injury-associated colitis and colitis-associated carcinogenesis (CAC) by impairing M1 responses that stimulate epithelial repair, anti-microbial defence, and anti-tumour immunity [117]. This evidence concerns the gene ODC1 and colitis.