Transcriptional regulation of the human trefoil factor, TFF1, by gastrin.

Abstract

This study aimed to identify gastrin-sensitive genes that may mediate the effects of this hormone on gastric epithelial architecture. Gastrin-sensitive genes were identified by messenger RNA (mRNA) differential display of the gastric fundus from gastrin-deficient (GAS-KO) or wild-type mice. Gastrin-stimulated expression of the trefoil peptide TFF1 in mouse fundus and in the gastric cancer cell line AGS-G(R) was determined by Northern blot and real-time polymerase chain reaction. Transcriptional regulation of TFF1 in AGS-G(R) cells was studied using promoter-reporter assays and electrophoretic mobility shift assay. Expression of TFF1 and the cholecystokinin(B) receptor in response to gastric mucosal injury was determined by immunohistochemistry. mRNA differential display identified TFF1 as a gastrin-regulated gene. TFF1 mRNA was reversibly reduced in GAS-KO mice and increased in a hypergastrinemic transgenic strain versus respective background strains. TFF1 mRNA expression was rapidly and potently induced by gastrin in a gastric cancer cell line that expresses the gastrin/cholecystokinin(B) receptor. Gastrin responsiveness of the human TFF1 promoter mapped to a G-C rich region 300 base pairs upstream of the transcriptional start site. This region bound the transcription factors SP3 and MAZ. Gastrin activated transcription through a Raf-, Mek- and Erk-dependent but Ras-independent pathway. TFF1 expression was induced both directly and by transactivation between neighboring cells. Neither direct nor indirect gastrin-induced TFF1 expression required activation of the epidermal growth factor receptor. Gastrin exerts tonic control of TFF1 expression but also has the potential for rapid up-regulation of this trefoil factor. TFF1 is a potential candidate to counterbalance the proliferative effects of gastrin.