EGF is a critical regulator of the interleukin‐33 in intestinal epithelial cells

Abstract IL-33 is a novel cytokine that is believed to be involved in inflammation and carcinogenesis; however, its source, its production and its secretion process remain unclear. Recently we have reported that interleukin-33(IL-33) is up regulated in dextran sulfate sodium (DSS) colitis in mice. We examined how IL-33 is produced from intestinal tissue using the murine azoxymethane (AOM)/DSS-induced cancer model and IEC-6 epithelial cells. Mice with AOM/DSS-induced colitis expressed all the characteristic symptoms of colon cancer pathology. Immunohistochemical analysis demonstrated epithelial derived IL-33 in the colon tissues in AOM/DSS colitis mice. RT-PCR and quantitative PCR analysis of colon tissues revealed that AOM/DSS colitis tissues expressed upregulated IL-1β, IL-33, TGF-β, and EGF mRNA. Gefitinib, an EGFR inhibitor, inhibited IL-33 mRNA expression in AOM/DSS colitis mice. The pathophysiological role of IL-33 in rat IEC-6 epithelial cells was then investigated. We found that EGF, but not TGF-β1 or PDGF, greatly enhanced mRNA expression of IL-33 and its receptor ST2. In accordance with the gene expression and immunohistochemical analysis of IL-33 levels, ELISA based analysis of cytoplasmic and nuclear extracts showed increased IL-33 protein levels in IEC-6 cells after treatment with EGF. Our results suggest that EGF is a key growth factor that triggers IL-33 production and ST2 receptor expression during intestinal inflammation and carcinogenesis. The EGF/IL-33/ST2 axis represents a novel therapeutic target of colon cancer.