Trefoil factor 1 is a protein that in humans is encoded by the TFF1 gene. Members of the trefoil family are characterized by having at least one copy of the trefoil motif, a 40-amino acid domain that contains three conserved disulfides. They are stable secretory proteins expressed in gastrointestinal mucosa. TFF1 expression is frequently lost in gastric carcinoma, probably through mechanism of DNA methylation, and it is therefore considered as a tumor suppressor gene.