Copy number variations are progressively associated with the pathogenesis of colorectal cancer in ulcerative colitis.

Abstract

To evaluate the association of known copy number variations (CNVs) in ulcerative colitis (UC) progressing to colorectal cancer. Microsatellite instability analysis using the National Cancer Institute's panel of markers, and CNV association studies using Agilent 2 × 105 k arrays were done in tissue samples from four patient groups with UC: those at low risk (LR) or high risk of developing colorectal cancer, those with premalignant dysplastic lesions, and those with colitis-associated colorectal cancer (CAC). DNA from tissue samples of these groups were independently hybridized on arrays and analyzed. The data obtained were further subjected to downstream bioinformatics enrichment analysis to examine the correlation with CAC progression. Microarray analysis highlighted a progressive increase in the total number of CNVs [LR (n = 178) vs CAC (n = 958), 5.3-fold], gains and losses [LR (n = 37 and 141) vs CAC (n = 495 and 463), 13.4- and 3.3-fold, respectively], size [LR (964.2 kb) vs CAC (10540 kb), 10.9-fold] and the number of genes in such regions [LR (n = 119) vs CAC (n = 455), 3.8-fold]. Chromosome-wise analysis of CNVs also showed an increase in the number of CNVs across each chromosome. There were 38 genes common to all four groups in the study; 13 of these were common to cancer genes from the Genetic Disease Association dataset. The gene set enrichment analysis and ontology analysis highlighted many cancer-associated genes. All the samples in the different groups were microsatellite stable. Increasing numbers of CNVs are associated with the progression of UC to CAC, and warrant further detailed exploration.