Altered Expression of the Epithelial Mucin MUC1 Accompanies Endoscopic Recurrence of Postoperative Crohn's Disease.

BACKGROUND: MUC1-glycoprotein is expressed at low levels and in fully glycosylated form on epithelial cells. Inflammation causes MUC1 overexpression and hypoglycosylation. We hypothesized that overexpression of hypoglycosylated MUC1 would be found in postoperative Crohn's disease (CD) recurrence and could be considered an additional biomarker of recurrence severity. METHODS: We examined archived neo-terminal ileum biopsies from patients with prior ileocecal resection who had postoperative endoscopic assessment of CD recurrence and given a Rutgeerts ileal recurrence score. Consecutive tissue sections were stained using 2 different anti-MUC1 antibodies, HMPV that recognizes all forms of MUC1 and 4H5 that recognizes only inflammation-associated hypoglycosylated MUC1. RESULTS: A total of 71 postoperative CD patients were evaluated. There was significant increase in MUC1 expression of both glycosylated/normal (P<0.0001) and hypoglycosylated/abnormal (P<0.0001) forms in patients with severe endoscopic CD recurrence (i3+i4), ileal score i2, compared with patients in endoscopic remission (i0+i1). Results were similar regardless of anti-TNF-alpha use. Although MUC1 expression and Rutgeerts scores were in agreement when characterizing the majority of cases, there were a few exceptions where MUC1 expression was characteristic of more severe recurrence than implied by Rutgeerts score. CONCLUSIONS: MUC1 is overexpressed and hypoglycosylated in neo-terminal ileum tissue of patients with postoperative CD recurrence. Increased levels are associated with more severe endoscopic recurrence scores, and this is not influenced by anti-TNF-alpha use. Discrepancies found between Rutgeerts scores and MUC1 expression suggest that addition of MUC1 as a biomarker of severity of postoperative CD recurrence may improve categorization of recurrence status and consequently treatment decisions.