OP13 TLR4 signaling activates the Wnt pathway in a mouse model of colitis-associated neoplasia

Abstract

s of the 7th Congress of ECCO the European Crohn’s and Colitis Organisation S7 OP13 TLR4 signaling activates the Wnt pathway in a mouse model of colitis-associated neoplasia R. Santaolalla1 *, J. Ruiz1, M. Fukata1, C. Espana1, J.M. Davies1, C. Pastorini1, D.A. Sussman1, J. Ko2, R. Dirisina2, T.A. Barrett2, M.T. Abreu1. 1University of Miami, Miller School of Medicine, Division of Gastroenterology, Miami, United States, 2Northwestern University, Feinberg School of Medicine, Division of Gastroenterology, Chicago, United States Background: In patients with colitis cancers, we have shown that there is an increased expression of toll-like receptor-4 (TLR4) in intestinal epithelial cells (IECs). The Wnt pathway regulates intestinal cell proliferation and the development of neoplasia. We have previously shown constitutive expression of TLR4 in a mouse model increases inflammation in the mucosa and drives colitis-associated tumorigenesis. We hypothesized that cross-talk between TLR4 and the Wnt pathway could have a synergistic tumorigenic effect in an inflammatory environment. Methods: Villin-TLR4 mice, which have increased TLR4 signaling in the intestinal epithelium, were compared to wild-type (WT) littermates. To induce tumorigenesis, the mice were treated with an initial injection of the genotoxic agent azoxymethane (AOM) followed by two cycles of 3% dextran sodium sulfate (DSS). Proliferation was assessed by BrDU labeling. Western blots were performed on intestinal IEC lines for total and phosphorylated b-catenin, GSK3-b and AKT. Immunohistochemistry was done for total b-catenin, active bcatenin phosphorylated at Ser552 and the Wnt target cyclin-D1. Villin-TLR4 mice were also crossed to Lgr5-EGFP mice. Lgr5 is Wnt target gene and stem cell marker. Results: Compared to WT mice, villin-TLR4 mice have a higher cell proliferation rate in the colon crypts and show a higher expression of nuclear b-catenin and cyclin-D1, indicating Wnt pathway activation. Given this, we asked whether TLR4 activity regulated expression of Lgr5. Our data demonstrate that whereas Lgr5 expression is normally located at the base of the crypts in WT mice, there is a dramatic expansion of Lgr5+ cells in the crypts of villin-TLR4 mice at baseline. To understand the mechanism underlying Wnt pathway activation, we found that TLR4 activates the phosphatidylinositide 3-kinase (PI3K)/AKT pathway to phosphorylate b-catenin at activation sites (Ser552 and Ser675). In vivo, we also see that villin-TLR4 AOM-DSS mice show increased nuclear b-catenin and phosphorylation of bcatenin at Ser552, an event associated with stem cell activation and colitis-associated cancer. Conclusions: In the intestinal mucosa, tonic stimulation of TLR4 by its ligand LPS can lead to activation of the Wnt signaling pathway and thereby promote neoplasia. In addition, TLR4 is linked to Lgr5 expression in the colon and is associated with an increase in proliferation of the colon crypts. These results highlight the role of bacterial signaling in stimulation of oncogenic pathways. OP14 Adenomas in patients with inflammatory bowel disease: Increased risk of advanced neoplasia F. van Schaik1 *, E. Mooiweer1, M. van der Have1, T. Belderbos1, F. ten Kate2, G.J. Offerhaus2, M. Schipper3, G. Dijkstra4, M. Pierik5, P. Stokkers6, C. Ponsioen7, D. de Jong8, D.W. Hommes9, A. van Bodegraven10, P. Siersema11, M. Van Oijen11, B. Oldenburg12. 1University Medical Center Utrecht, Gastroenterology and hepatology, Utrecht, Netherlands, 2University Medical Center Utrecht, Department of Pathology, Utrecht, Netherlands, 3University Medical Centre Utrecht, Department of Pathology, Utrecht, Netherlands, 4University Medical Center Groningen, Gastroenterology and Hepatology, Groningen, Netherlands, 5Maastricht University Medical Center, Dept of Gastroenterology, Maastricht, Netherlands, 6Academic Medical Center, Gastroenterology and Hepatology C2, Amsterdam, Netherlands, 7Academic Medical Center, Gastroenterology and Hepatology, Amsterdam, Netherlands, 8Universitair Medisch Centrum St Radboud, Afd Maag Darm Leverziekten, Nijmegen, Netherlands, 9UCLA, Division of Digestive Diseases, Los Angeles, United States, 10VU University Medical Center, Gastroenterology, Amsterdam, Netherlands, 11University Medical Center Utrecht, Department of Gastroenterology and Hepatology, Utrecht, Netherlands, 12University Medical Centre Utrecht, Department of Gastroenterology, Utrecht, Netherlands Background: The increased risk of colorectal cancer (CRC) in longstanding colitis is well documented, but it is unclear whether colonic adenomas in patients with inflammatory bowel disease (IBD) carry a higher risk of progression to CRC than sporadic adenomas in non-IBD patients. The aim of the current study was to evaluate the risk of high-grade dysplasia (HGD) or CRC in IBD patients compared to controls, and to compare this with age-matched IBD patients without adenomas. Methods: The nationwide pathology database (PALGA) was used to identify IBD patients with a histological diagnosis of adenoma (IBD + adenoma), age-matched IBD patients without adenoma (IBD-nonadenoma) and patients with adenoma without IBD (nonIBD + adenoma) in seven university hospitals in the Netherlands between 1995 and 2005. Medical charts and endoscopy, pathology and surgery reports were reviewed for adenoma characteristics and development of advanced neoplasia (HGD or CRC). The endoscopic appearance of adenomas was characterized as typical (solitary sessile or pedunculated) or atypical (all other descriptions). Survival analysis was used to assess the development of advanced neoplasia. Results: A total of 110 IBD + adenoma patients, 123 IBDnonadenoma patients and 179 nonIBD + adenoma patients were included. Mean duration of follow-up was 88 months (SD ±41). Polypectomy was performed in 68 IBD + adenoma patients (62%) and 146 nonIBD + adenoma patients (82%) (p < 0.01). The cumulative risks of advanced neoplasia were 16%, 7% and 4% in IBD + adenoma, IBD-nonadenoma and nonIBD + adenoma patients, respectively (p < 0.01). Atypical adenomas were identified in 28 IBD + adenoma patients (25%), which were associated with a higher cumulative risk of advanced neoplasia compared to IBD + adenoma patients with typical adenomas (29% versus 12%, p = 0.03). Conclusions: IBD patients with a histological diagnosis of adenoma have a significantly higher risk of developing advanced neoplasia during follow-up than adenoma patients without IBD and age-matched IBD patients without adenomas. This is due to a higher prevalence of atypical adenomas in IBD patients, conferring an increased risk of advanced dysplasia in these patients. by gest on A ril 2, 2016 http://eccoxfordjournals.org/ D ow nladed from