A germline substitution in the human MSH2 gene is associated with high-grade dysplasia and cancer in ulcerative colitis

Abstract

Background & Aims: The DNA mismatch repair gene human MSH2 shows a germline mutation in certain family members with hereditary nonpolyposis colorectal cancer. There is an increased risk of colorectal cancer in patients with ulcerative colitis (UC) with extensive disease of >8 years' duration; however, specific constitutional predisposing genetic abnormalities have not yet been identified. Methods: A germline human MSH2 abnormality was sought in patients with UC with high-grade dysplasia or carcinoma. Results: After direct sequencing of exon 13 and flanking regions of human MSH2, a germline T to C substitution was shown at the −6 intronic splice acceptor site of exon 13. This substitution was found in 14 of 53 patients with UC with high-grade dysplasia or carcinoma (26%) compared with 4 of 36 high-risk patients with UC without dysplasia or cancer (11%) ( P ≤ 0.04) and in 7 of 80 healthy adult blood donors (9%) ( P ≤ 0.003). The patients with UC who had the substitution were three times more likely to develop neoplasia than patients with UC who did not carry it. Conclusions: An intronic splice-site substitution in the human MSH2 gene is present in the general population but may predispose to cancer in the setting of UC.