Genetics of inflammatory bowel disease and associated cancers

Abstract

The inflammatory bowel diseases (IBD), Crohn’s disease and ulcerative colitis, result from an altered host response to intestinal flora, and genome-wide searches have identified a number of disease susceptibility alleles, such as NOD2/CARD15. IBD confers a high risk of development of a number of malignancies, especially colorectal cancer, and this risk is related to chronic inflammation. Genomic instability in the form of gross chromosomal changes is common, with microsatellite instability occurring in a small subset of colitis-associated lesions. The carcinogenesis pathway in colitis-associated cancers is less clearly understood than its sporadic counterpart. Mutations in the APC gene appear to be less frequent and occur later, whereas inflammation-induced p53 mutations are found early in nondysplastic tissue. Selection and clonal expansion of inflammation-induced mutations is likely to account for the high mutational load seen in carcinoma tissue. Development of an effective biomarker to predict development of malignancy in colitis has so far been unsuccessful.