MPO and colitis: In mouse models of inflammation-associated colon cancer caused by AOM and DSS, colons of HCA2−/− mice shrink with highly increased myeloperoxidase activity, upregulated expression of colon cancer-promoting genes such as cyclin-D1, cyclin-B1, and cyclin-dependent kinase 1, decreased tight junction proteins expression and decreased expression of genes that inhibit colitis and colon carcinogenesis, such as transforming growth factor beta (Tgfb)1, Tgfb2, Solute Carrier Family 5 Member 8 (Slc5a8), MutS Homolog (Msh)2, and Msh3 (34) (Figure 3C).