A germline hMSH2 alteration is unrelated to colonic microsatellite instability in patients with ulcerative colitis

Recently, a polymorphism in the hMSH2 DNA mismatch repair gene has been associated with the development of dysplasia in ulcerative colitis (UC) patients. This polymorphism is of interest because DNA mismatch repair defects result in alterations in microsatellite stability. The current study was designed to determine whether this hMSH2 polymorphism associates with the development of microsatellite instability and dysplasia in UC patients. The hMSH2 genotype of 96 UC patients was determined by direct DNA sequencing. In addition, we examined 363 samples of colonic mucosa from 93 of these UC patients for microsatellite mutation by polymerase chain reaction (PCR) at eight loci. Three cases had insufficient DNA for microsatellite instability studies. The hMSH2 polymorphism was identified in 13 of the 96 patients examined (13.5%). The polymorphism was observed in 7 of 46 patients with dysplasia (15.2%), and in 6 of 50 patients without dysplasia (12.0%). Microsatellite instability was identified in 35 tissue samples (25 regenerative, one indefinite for dysplasia, eight dysplasias, and one invasive carcinoma) from 26 patients. Two patients with microsatellite instability had the hMSH2 alteration. The 11 remaining patients had the hMSH2 polymorphism, but no evidence of microsatellite mutations with any of the markers tested. We were unable to confirm the previously reported findings that the specific germline hMSH2 alteration represents a marker for increased risk of dysplasia in patients with UC, nor is it responsible for the development of microsatellite instability in these patients.