251 Ulcerative Colitis Gene Signature Distinguishes Patients Harboring Remote Dysplasia

Background: Individuals with ulcerative colitis (UC) are at increased risk for colorectal cancer (CRC), although underlying mechanisms are incompletely understood.The current standard for premalignant surveillance, however, is invasive and limited as it samples only a tiny fraction of colonic mucosa.Genetic changes can occur in non-dysplastic mucosa in UC patients who harbor a dysplastic lesion.We sought to identify a potential gene signature in non-dysplastic distal mucosa that as a "genetic field effect" could indicate remote dysplastic lesions.Identification of genes associated with dysplasia could also advance understanding of the pathogenesis of IBD neoplasia.Methods: Colonic biopsies, obtained from healthy controls and patients with chronic UC (> 7 years), were taken 20 cm from the anal verge and stored in RNAlater.All patients with UC had quiescent or mildly active histological colitis in the sigmoid colon.RNA was extracted using Ambion RNeasy kit and amplified using One-Cycle cDNA Synthesis Kit (Affymetrix).cDNA was hybridized on HT HG-U133 PM Affymetrix chips.Normalization was done using the Robust Multi-array Average (RMA) method.Gene expression differences were calculated using Significance Analysis of Microarrays (SAM).Hierarchical clustering was performed with dChip using the Pearson correlation for distance with a centroid-linkage method.Results: Gene expression was analyzed in 5 normal controls, 4 UC patients without dysplasia, and 11 UC patients with dysplasia.Controls and UC patients were comparable in age.Median disease duration was 13.5 years in UC patients with dysplasia and 20 years in UC patients without dysplasia.One hundred thirty-two genes were significantly up-regulated and 205 genes were significantly downregulated >2-fold in UC patients with dysplasia compared to UC patients without dysplasia.Thirteen genes (CLC, S100A9, CCL4, THBD, ACSL1, CREM, BIRC3, ELTD1, CLU, ANXA3, v-MAF, TPD52L1, and FGG) were progressively and significantly up-regulated from controls to quiescent non-dysplastic UC to UC with dysplasia.Genes belonged to pathways regulating inflammation, proliferation, apoptosis, and angiogenesis.Real time PCR studies to confirm array changes and immunostaining to assess expression levels of proteins encoded by these genes are in progress.Conclusion: Gene expression changes unrelated to disease duration were seen as 'field effects' in UC patients harboring dysplasia.Confirmatory prospective studies to validate these gene changes are needed.These gene identifications will elucidate mechanisms driving colonic tumorigenesis and provide biomarkers for risk assessment of dysplasia in UC patients.