S150 Poster presentations P036 A novel p53-mediated mouse model of inflammatory bowel disease-associated colorectal cancer A.M. Churchhouse* 1 , C.V. Billard 1 , M.J. Arends 2 , K.B. Myant 1 1 The Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK, 2 Division of Pathology, Centre for Comparative Pathology, Cancer Research UK Edinburgh Centre, The Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK Background: Current mouse models of colitis-associated cancer often utilise a combination of APC mutation, Dextran sulphate sodium (DSS) and azoxymethane administration. However, only 13% of human in- flammatory bowel disease (IBD)-associated cancers is associated with an APC mutation 1 . Instead, they are frequently associated with mutation of p53 (occurring in 63% of human cancers 1 ). Whilst some models of IBD-associated cancer using either global p53 loss or mutant p53 have been described, we felt that a more pathophysiologically relevant model would be represented using p53 loss solely in the colonic epithelium. Methods: Colonic epithelial p53 floxing in Vil-Cre ERT2 p53 fl/fl mice was achieved through intraperitoneal injection of 120 and 80 mg/kg tamoxifen on two consecutive days. After 16 days, mice were started on a chronic DSS treatment protocol. Chronic DSS-induced colitis involved three 5-day cycles of low-dose DSS (1.5% initially and subsequently 1% for the remaining two cycles), interspersed with normal drinking water for 2 weeks to facilitate recovery. After three cycles of DSS, mice were aged to 164 days. Results: At 164 days post induction of DSS, 100% of mice had devel- oped adenomata with low-grade dysplasia (n = 4). Adenomata in 50% of these mice (n = 2) also had features of high-grade dysplasia. There were between one and three adenomata in each animal. No features of invasive adenocarcinoma were demonstrated. There was partial β-catenin nuclear localisation in these tumours. Background chronic colitis was evident, even though the experiment ended over 3 months after the DSS treatment finished. Conclusion: To the best our knowledge, this is the first mouse model of colitis-associated cancer using p53 loss in the colonic epithelium together with chronic colitis induction using DSS. The experiment ended over 3 months after the DSS treatment finished, showing that the resultant chronic colitis can persist long after the initial insult is given. The fact that β-catenin is partially, but not fully nuclear localised suggests an alternative pathway to tumour formation in this p53fl/fl model, and may therefore be more pathophysiologically relevant to human IBD-associated colo- rectal cancers. Further work is now being carried out to both validate and further evaluate this novel mouse model, including assessment of stem cell dynamics in response to colitis in the context of p53 loss. Reference 1. Robles, A. I. et al. Whole-Exome Sequencing Analyses of Inflam- matory Bowel Disease-Associated Colorectal Cancers. Gastro- enterology 150, 931–943 (2016). P037 Antagonism of chemokine receptor CCR9 synergises with anti-TNFα immunotherapy to reduce inflammation in the MDR1a −/− mouse model of colitis J. Campbell* 1 , L. Ertl 1 , K. Ebsworth 1 , J. McMahon 2 , P. Zhang 2 , V. Chhina 1 , I. Charo 1 , T. Schall 1 1 Department of Biology, ChemoCentryx, Inc., Mountain View, CA, USA, 2 Department of Chemistry, ChemoCentryx, Inc., Mountain View, CA, USA Background: The development of anti-TNFα immunotherapies has led to great advances in quality of life for Crohn’s and colitis patients and has allowed a reduction in steroid use for these dis- eases. However, a significant proportion of IBD patients is resistant to anti-TNFα agents, or becomes resistant to such treatments over time. Preclinical research and clinical trials have suggested that CCR9 antagonism can effectively reduce colon inflammation. CCR9 is expressed on a subset of T cells dedicated to monitoring the immune status of the intestine. When activated by its only known chemokine ligand, CCL25/TECK, CCR9 triggers the adhesion of gut-specific T cells to vascular endothelium and the subsequent in- gress of these cells to intestinal tissues. Antagonism of this receptor inhibits the accumulation of T cells within inflamed intestinal epithe- lium and lamina propria. Since anti-TNFα and CCR9 antagonists act through entirely different mechanisms, we asked whether these two approaches might synergise and expand the effectiveness and scope of each therapy. Methods: We used a piroxicam-accelerated version of the MDR1a −/− spontaneous colitis model in mice. In this model, 7week MDR1a −/− mice (or WT FVB controls) receive piroxicam in powdered chow for 10 days. Mice are monitored both during and after the piroxicam feeding period, for a total of 21 days. Treatment groups (eight mice each) include an antibody (a saturating dose of either anti-TNFα or its isotype-matched control) and a CCR9 antagonist (or its vehicle alone as a control). Body weight and diarrhoea score were recorded throughout the entire 21 days period, after which colons were obtained from sacrificed animals for weighing, length measurement and imaging. Results: We have found that combined dosing of piroxicam-fed MDR1a −/− mice with a CCR9 antagonist and an anti-TNFα MAb significantly reverses loss of body weight, diarrhoea score and colon inflammation. The combined dosing was more effective than anti- TNFα or CCR9 antagonist alone, as measured by colon length/ weight ratio, neutrophil accumulation in the colonic epithelium and reversal of the loss in body weight characteristic of this model. Conclusion: These data suggest that combining a CCR9 antagonist with existing anti-TNFα treatment regimens may extend the benefits of anti-TNFα immunotherapy to a larger class of patients suffering from IBD and may prolong the effectiveness of anti-TNFα immuno- therapy for those patients already undergoing such treatments. P038 A single-cell transcriptomics approach reveals high-resolution cellular signatures in Crohn’s disease A. Garrido Trigo* 1 , A.M. Corraliza 1 , M. Veny 1 , J. Lozano 2 , E. Ricart 3 , I. Ordás 3 , M.C. Masamunt 3 , J. Panés 3 , M. Hemberg 4 , A. Salas 1 1 IDIBAPS, Inflammatory Bowel Disease Unit, Barcelona, Spain, 2 Ciberehd, Bioinformatics, Barcelona, Spain, 3 Hospital Clinic de Barcelona, Gastroenterology, Barcelona, Spain, 4 Wellcome Trust Sanger Institute, Bioinformatics, Hinxton, UK Background: Single-cell RNA sequencing (sc-RNAseq) provides high-resolution analysis of individual cells and cell clusters within complex tissues like the intestinal mucosa. No study to date has applied this novel technology to understand the complexity of Downloaded from https://academic.oup.com/ecco-jcc/article/14/Supplement_1/S150/5705769 by guest on 30 August 2024