sLeA on CD44v6 Is a Potential Biomarker of Severity in Inflammation-Associated Mucosal Disease
Maria A Delgado, Jennifer C Brazil, Nancy A Louis, Charles A Parkos, Alton B Farris. Emory University, Atlanta, GA
Background: A paucity of effective markers limits inflammatory bowel disease (IBD) progression risk stratification and therapeutic response prediction. CD44v6 protein expression is upregulated in IBD and cancer. The tetrasaccharide glycoepitope sLeA has been described as a prognostic marker in IBD patients with primary sclerosing cholangitis associated cholangiocarcinoma. We generated a novel monoclonal antibody (GM35) that recognizes sLeA displayed on CD44v6 with great affinity. Using GM35 and an anti-peptide CD44v6 mAb, we characterized staining for CD44v6 and sLeA on CD44v6 in chronic active colitis (CAC), chronic colitis (CC) and uninvolved mucosa (UM) in ulcerative colitis (UC) and Crohn's disease (CD).
Design: IBD patients (n = 24, 13 UC and 11 CD) were included with tissue from different colonic portions ranging from severe chronic active colitis to uninvolved mucosa (21 CAC, 18 CC and 15 UM). Both biopsies and resections were included (with 1-3 representative sections/patient). Slides were immunostained with either anti-CD44v6 mAb or GM35. Apical surface, cytoplasmic, basal membrane and lateral membrane staining intensities were graded on a 5-tier scale from 0-4 in CAC, CC and UM. T-test or Chi square tests were performed.
Results: Statistically significant differences in staining patterns were found between the CD44v6 anti-peptide mAb and GM35. CD44v6 protein expression was seen at the basolateral membrane while GM35 bound to sLeA in the cytoplasm and cell apex (Table 1). Anti-CD44v6 mAb stained the mucosal lower half while GM35 stained the upper half (Chi square p = <0.0001, for the distribution). CD44v6 staining became full thickness with increasing disease severity (Chi square p = <0.0001). Further, GM35 stained neutrophils in crypt abscesses while anti-CD44v6 mAb did not. There was no statistically significant difference in staining of either molecule between UC and CD.
Conclusions: We have shown differential expression of CD44v6 and sLeA on CD44v6 (GM35) in colonic mucosa with varying severities of IBD, suggesting that post-translational modifications, and in particular the glycosylation status of CD44v6, plays an important role in inflammation. Targeting sLeA with specific mAbs such as GM35 thus warrants further investigation as an inflammation-associated disease process biomarker.
Tuesday, March 5, 2013 1:00 PM
Poster Session IV # 121, Tuesday Afternoon