P096 Characterization of suppressive immune cell subsets in mouse models of colitis-associated colorectal cancer

Abstract Background Chronic colonic inflammation in inflammatory bowel disease (IBD) patients increases the risk of colitis-associated cancer (CAC). Cancer development CAC is different from that observed sporadic colorectal (CRC). Most studies have focused on role pro-inflammatory immune cell subsets CAC, yet it becoming increasingly clear immunosuppression may also drive progression. We hypothesize emergence immunosuppressive as a result chronic intestinal inflammation, dampens anti-tumor responses and accelerates CAC. Methods To simulate formation background mice were treated with azoxymethane (AOM) followed by three cycles dextran sodium sulphate (DSS). Apc Min/+ AOM used to model CRC. After 10 weeks, cells proximal distal lamina propria, mesenteric lymph nodes (MLNs) tumors obtained for microscopy analyses processed obtain single suspensions flow cytometry. Immune populations studied conventional cytometry immunofluorescence. Results significant increase absolute numbers PD1+CTLA4+TIM3+ ‘exhausted’ CD4+ T propria colons compared CRC mice. Interestingly, these showed positive correlation score AOM/DSS, demonstrating associated cells. In addition, we trend higher M2-like (MHCII-CD206+) suppressive macrophages CD4+FoxP3+ regulatory (Tregs) When analysing MLNs, found decrease ratio IFNγ/IL10-producing CD8+ mice, suggesting shift towards an anti-inflammatory response Conclusion summary, increased mucosa which be dysplasia. Further functional are necessary prove IBD-associated dysplasia- carcinoma