SLC15A1 and colitis: While PepT1 expression is normally restricted to the small intestine, our studies in mice show that overexpression of human PepT1 in the colon exacerbates experimental colitis, whereas a PepT1 deficiency (PepT1−/− mice) is sufficient to protect against dextran sulfate sodium (DSS)-induced colitis and colitis-associated cancer (CAC)5,6.