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* = Presenting author

P406 AlphaE+ cells have increased expression of inflammatory markers and are correlated in the ileum and colon

R. Ichikawa1, J. Eastham-Anderson1, A. Scherl1, J. Hackney1, L. Orozco1, W. Faubian2, J. Mansfield3, 4, J. Kirby3, C. Lamb3, 5, M. Keir*1

1Genentech, Inc, a member of the Roche Group, South San Francisco, California, United States, 2Mayo Clinic, Division of Gastroenterology & Hepatology, Rochester, Minnesota, United States, 3Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, United Kingdom, 4Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, United Kingdom, 5Department of Gastroenterology, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, United Kingdom

Background

Etrolizumab, a humanised monoclonal antibody against beta7 integrin, blocks both alpha4beta7: MAdCAM-1 and alphaEbeta7: E-cadherin interactions. AlphaE gene expression and alphaE+ cell quantification showed promise as potential predictive biomarkers for response to etrolizumab in ulcerative colitis (UC) and the role of alphaE+ cells in inflammation is of interest. Biopsy-based alphaE biomarkers may help identify patients more likely to respond to etrolizumab but are limited by accessibility in inflammatory bowel disease (IBD) patients with disease outside the reach of the endoscope, such as patients with ileal Crohn’s disease (CD); in addition, disease activity and concomitant medications may affect alphaE levels. To address this, paired ileal and colonic biopsies were used to determine the correlation of colonic and ileal alphaE expression in IBD patients in different inflammatory and treatment settings.

Methods

Gene expression differences were evaluated in sorted intestinal alphaE+ and alphaE- T-cells from IBD (n = 4) and non-IBD (n = 4) patients. AlphaE gene expression levels were measured by qPCR in paired ileal and colonic biopsies from an observational IBD study [UC (n = 31), CD (n = 67), and healthy (n = 12) subjects]. AlphaE+ cells were identified by immunohistochemistry and enumerated by automated image analysis in paired colonic and ileal biopsies from a retrospective IBD cohort [UC (n = 87), CD (n = 57), and healthy (n = 95) subjects].

Results

An increase in effector molecules, including granzyme A and B, and decreased expression of FOXP3 were found in alphaE+ cells relative to alphaE- cells. Paired biopsies showed significant positive correlation between the ileum and colon using both alphaE gene expression (rho = 0.38, p < 0.01) and number of alphaE+ cells (rho = 0.49, p < 0.0001). AlphaE gene expression levels and alphaE+ cell numbers were not different in patients with active disease in comparison to patients with inactive disease. Similarly, levels of alphaE gene expression and alphaE+ cells were not different in patients on immunosuppressants and/or steroids, independent of disease activity.

Conclusion

Although colonic alphaE+ cell counts are similar between healthy subjects and IBD patients, alphaE+ T- cells from IBD patients have higher effector gene expression levels in IBD patients than in healthy subjects, suggesting alphaE+ T-cells may be involved in inflammation. AlphaE gene expression and alphaE+ cell numbers are higher in the ileum and correlated in paired colonic biopsies, suggesting that predictive biomarker analysis may be possible in patients where ileal biopsies cannot be obtained. Further evaluation of alphaE as a predictive biomarker for response to etrolizumab is underway in ongoing Phase III studies.