1. ¹Department of Pathology, University of Chicago, Chicago, IL, USA
2. ²Department of Medicine, University of Chicago, Chicago, IL, USA

Correspondence: Dr JR Turner, MD, PhD, Department of Pathology, University of Chicago, 5841 South Maryland Avenue, MC 1089, Chicago, IL 60637, USA. E-mail: jturner@bsd.uchicago.edu

³These authors contributed equally to this work.

Received 21 June 2008; Revised 11 July 2008; Accepted 14 July 2008; Published online 18 August 2008.

Abstract

Patients with inflammatory bowel disease (IBD) are at increased risk of developing colorectal adenocarcinoma. The factors that result in IBD-associated carcinogenesis are not understood. We hypothesized that altered expression of intestinal epithelial tight junction proteins might contribute to neoplastic progression. Semiquantitative immunohistochemical staining of human biopsies was used to assess expression of the tight junction proteins claudin-1, claudin-2, claudin-4, and occludin in IBD, IBD-associated dysplasia, acute, self-limited colitis (ASLC), and sporadic adenomas. Claudin-1 and claudin-2 expression was elevated in active IBD, adenomas, and IBD-associated dysplasia, but not ASLC. In contrast, claudin-4 expression was elevated in both active IBD and ASLC. Occludin expression was similar to control in all cases. Importantly, in IBD, claudin-1 and claudin-2 expression correlated positively with inflammatory activity. To investigate mechanisms underlying altered claudin expression, -catenin activation was assessed as nuclear localization. Like claudin-1 and claudin-2, -catenin was markedly activated in IBD, sporadic dysplasia, and IBD-associated dysplasia, but was only slightly activated in ASLC. Taken together, these data suggest that -catenin transcriptional activity is elevated in chronic injury and that this may contribute to increased claudin-1 and claudin-2 expression. We speculate that increased claudin-1 and claudin-2 expression may be involved at early stages of transformation in IBD-associated neoplasia.