Su1969 Interleukin-33 and Its Receptor, ST2, Are Dysregulated in Gastritis and Gastric Cancer and May Influence Gastric Epithelial Proliferation

Background and aims: Gastric cancer is still a relevant cause of death. Interleukin (IL)-1 family cytokines play key roles in promoting gastric cancer growth. IL-33, a novel member of the IL-1 family, binds to the receptor ST2 and induces prominent epithelial hyperplasia in the gut. Aim of this study is to characterize IL-33 and ST2 expression modifications throughout the progression from healthy gastric mucosa to cancer and obtain insights on the potential involvement of the IL-33/ST2 axis in regulating gastric epithelial proliferation. Methods: Biopsies from normal gastric mucosa (CONT) (N=7), Helicobacter pylori (Hp)(N=8) and non Hp-related gastritis (N=8), gastric intestinal metaplasia (IM) (N=4), gastric cancer (GC) (N=11) and normal tissue close to cancer lesions (N=11) were collected from patients undergoing upper gastrointestinal endoscopies. IL-33 and ST2 expression was evaluated by WB and qRT-PCR. AGS gastric epithelial cell were cultured with growing concentration of rIL-33 (0 ng/ml-10 ng/ml). Cell proliferation was assessed by means of XTT and CFSE assay using 0, 6 and 24h, or 4, 6 and 8 days' timepoints, respectively. Wound-healing scratch test was performed on AGS monolayers. Caspase-Glo 3/7 luminescent assay evaluated AGS apoptosis. Results: WB for IL-33 showed both full-length (30 kD) and cleaved (22 kD) forms in all the experimental groups; IL-33 mRNA transcripts were increased in non Hprelated gastritis (9.1±3.2 fold increase; p=0.04), compared to CONT (set as 1), not significantly changed in gastric cancer, whereas a trend towards reduction was detected in Hp-related gastritis and IM. WB for ST2 demonstrated both the soluble sST2 and the transmembrane ST2L variants in all the experimental groups; qRT-PCR for sST2 showed no significant changes in the different experimental groups; ST2L mRNA was more abundant in the normal tissue close to cancer lesions (34.2±4.3 fold increase, p=0.05) and in gastric cancer (9.7±4.6 fold increase, p=0.14), compared to CONT (set as 1). The XTT proliferation assay, wound healing experiments and CFSE assay showed an inhibitory effect of IL-33 on AGS in a dose-dependent way. In addition, apoptosis increased consensually to IL-33 concentrations. Conclusions: These data suggest that IL-33/ST2 axis is dysregulated during the progression from gastritis to gastric cancer and may inhibit pathologic gastric epithelial growth.