Trefoil Factor 1 (TFF1), also known as pS2, is one of three structurally related secreted proteins that contain trefoil domains. These domains adopt a three-leaved conformation held together by conserved intrachain disulfide bonds. TFF1 is an approximately 7 kDa peptide that plays an important role in epithelial regeneration and wound healing (1). Mature human TFF1 shares 67% amino acid sequence identity with mouse and rat TFF1. It is expressed by goblet cells of the gastric and intestinal mucosa and by conjunctival goblet cells (2-5). TFF1 is a copper-binding protein that can form disulfide-linked homodimers, associate into disulfide-linked complexes with Gastrokine 2, and form non-covalent complexes with the mucin MUC5AC (4, 6-8). Copper enhances TFF1 homodimerization as well as its ability to promote epithelial cell motility, wound healing, and the colonization of H. pylori in stomach and colon epithelia (9, 10). TFF1 is down-regulated during the progression from gastritis to gastric dysplasia to gastric cancer, although it is up-regulated in breast and prostate cancers (11-13). TFF1 inhibits the formation of calcium oxalate crystals, and its excretion in the urine is reduced in patients with kidney stones (14).