Cytokine Regulation of the Trefoil Factor Family Binding Protein GKN2 (GDDR/TFIZ1/blottin) in Human Gastrointestinal Epithelial Cells

Trefoil factor family (TFF) peptides are major secretory products of mucous epithelia and play a multifunctional role in cytoprotection, apoptosis, and immune response. Recently, a TFF2-binding protein was discovered in mice and named blottin. It is down-regulated in gastric cancer (GDDR), abundant in human gastric surface (TFIZ1) and its similarity to gastrokine-1 led to the gene's name GKN2. To investigate the mode of GKN2 regulation activity of a luciferase reporter gene, controlled by the GKN2 promoter, was monitored upon treatment with various pro-inflammatory (TNF-alpha, IL-1beta, IL-6, IFN-gamma) and anti-inflammatory (TGF-beta1) cytokines using gastric (AGS, KATO III) and colonic (HT-29) cell lines. To assess the direct role of transcription factors (NFkappaB, HNF-3beta, hGATA6) in regulating GKN2 we performed transient co-transfection of their expression plasmids and the reporter gene construct. GKN2 gene was down-regulated by pro-inflammatory cytokines in all tested cell lines while up-regulated by TGF-beta1 only in the colonic cell line. GKN2 expression was significantly reduced in both gastric adenocarcinoma cell lines by the active form of NFkappaB transcription factor, whereas in the colonic cell line an up-regulation was noticed. Down-regulation by IL-6 was mediated by C/EBPbeta transcription factor in case of HT-29 but not of KATO III cells. We conclude that the regulation of GKN2 parallels that of TFF genes, indicating that together they may play an important role in maintaining the homeostasis of the gastrointestinal tract.