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NITRIC OXIDE IN COLITIS-ASSOCIATED COLONIC NEOPLASIA: ROLE OF WNT-INDUCED SECRETED PROTEIN-1 (WISP-1)

H Wang, R Zhang, DM McCafferty, PL Beck, SJ Urbanski, WK MacNaughton
Mucosal and Gastrointestinal Research Groups, Departments of Physiology and Biophysics, Medicine, and Pathology and Laboratory Medicine, University of Calgary, Calgary, Alberta

Nitric oxide (NO) derived from the inducible NO synthase (iNOS) is an important inflammatory mediator in ulcerative colitis (UC) and has been implicated in the development of colorectal cancer (CRC). However, the role that NO plays in tumorigenesis is not clear. Members of the Wnt signaling pathway, such as beta-catenin and APC, have been implicated in colorectal cancer. Recently, Wnt-inducible secreted protein-1 (WISP-1), a member of the connective tissue growth factor family, was shown to be overexpressed in 84% of tumours compared with patient-matched normal mucosa. In this study, we aimed to test the effect of iNOS/NO on WISP-1 expression in the normal colon, UC and CRC. Endoscopic colonic biopsy samples were obtained from UC and CRC patients. The expression of mRNA for iNOS and WISP-1 was determined by semiquantitative RT-PCR. Both were higher in ulcerative colitis samples compared with those from uninflamed colon (p<0.05). Immuno-histochemistry revealed positive WISP-1 staining in UC and CRC samples. In separate cell culture studies, the NO donor, DETA-NONOate (0.05-0.5 mM), significantly elevated WISP-1 mRNA expression in several human colonic epithelial cell lines (HT-29, RKO and Caco-2). Furthermore, the NO donor activated the cyclic AMP response element binding protein (CREB), a potent transcriptional regulator of WISP-1 expression, by stimulating the phosphorylation of CREB at ser-133. Finally, WISP-1 expression was assessed in mouse models of colitis. TNBS colitis was induced in both wild type and iNOS-deficient mice. In addition, colitis associated with IL-10 deficiency was observed in 3-month old IL-10 knockout mice and IL-10/iNOS double knockouts. Colitis was associated with a significant increase in WISP-1 expression. However, the absence of functional iNOS significantly blocked the colitis-related WISP-1 increase. Taken together, the data suggest that during colitis, iNOS-derived NO increases WISP-1 expression through a CREB-dependent pathway. The demonstration of an interaction between iNOS/NO and WISP-1 in inflamed gut implicates a new mechanism whereby iNOS and NO participate in tumorigenesis in ulcerative colitis.
H Wang is supported by a CAG-CCFC Fellowship

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