Abstract 5113: Discovery and application of a biomarker cassette to inflammatory bowel disease

Abstract

Inflammatory bowel disease (IBD) results from intermittent and severe activation of the mucosal immune system in the gastrointestinal tract to promote a chronic state of inflammation. Crohn's disease (CD) and ulcerative colitis (UC) are the two major forms of IBD. Infiltration of gut tissue by lymphocytes, neutrophils, and macrophages results in prolonged exposure to chemical agents such as pro-inflammatory cytokines and reactive oxygen/nitrogen species. Chronic exposure to these inflammation products leads to mis-regulated cell signaling, altered protein expression, and chemical damage to lipids, protein, and nucleic acids. IBD is a significant risk factor for colon cancer. IBD exhibits phases of active disease (active inflammation) and remission, which complicate therapeutic intervention. Clinical biomarkers currently in use are not predictive of the transition from remission to active disease. Our laboratory has conducted an unbiased, four-pronged approach to IBD biomarker identification in human serum utilizing proteomic discovery of acute phase proteins, cytokine profiling, quantification of oxidative tyrosine modifications (chlorotyrosine (Cl-Tyr), bromotyrosine (Br-Tyr), and nitrotyrosine (NO-Tyr)–markers of neutrophil activity), and measurement of carbonylated proteins. One hundred and ten human serum samples were analyzed. This network of data was analyzed by orthogonormalized partial least squares (OPLS) analysis to identify covariance in the data set. Variable importance in projection (VIP) scores were determined to identify which variables were most predictive of clinically diagnosed disease score (VIP >1). Using data available from the cytokine and oxidative tyrosine analysis, the data set was stratified to clinically diagnosed active and inactive disease, with the intent of identifying serum markers that were predictive of this transition. Several variables for UC and CD demonstrated strong covariance with disease score. The top VIP scores identified for UC were: Interleukin-8 (IL-8), granulocyte-colony stimulating factor (G-CSF), IL-6, and Cl-Tyr. The top VIP scores identified for CD were: Cl-Tyr, macrophage inflammatory protein-1β (MIP-1β), inflammatory chemokine-10 (IP-10), IL-6, and IL-1 receptor antagonist (IL-1ra). A Total Score was generated for each UC and CD serum sample by normalizing the raw data to a base-10 spread, scaling by the VIP factor, and summing the total. Based on the Total Score the calculated specificity and sensitivity for identifying active UC was 81.8% and 84.2%, respectively, while the specificity and sensitivity for identifying active CD was 87.5% and 75%, respectively. We anticipate that the addition of acute phase and cabonylated protein analysis will improve the Total Score assessment. Results from this study strongly suggest that a cassette of in vivo serum markers may be predictive of the transition from remission to active disease in IBD. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5113. doi:10.1158/1538-7445.AM2011-5113