Microsatellite instability and loss of heterozygosity in radiation-associated thyroid carcinomas of Belarussian children and adults

DNA from 129 paired thyroid tumorous and non-tumorous tissue samples of Bel arussian children (102 patients; age at surgery less than or equal to 18 ye ars) and adults (27 patients; age at surgery 19-35 years), who had been exp osed to radioactive fallout from the Chernobyl reactor accident in 1986, wa s examined for microsatellite instability (MSI) and loss of heterozygosity (LOH), Twenty-eight microsatellite markers were chosen because of their vic inity to DNA repair genes or genes involved in tumorigenesis as well as reg ions of chromosomal breakpoints in thyroid tumours, In 40 patients (31% of 129) we detected a total of 73 alterations, 80% of which were classified as LOH and only 20% as MSI, Amongst these 40 patients we identified a subgrou p of 11, mainly young female patients (8.5% of 129), exhibiting alterations in at least two microsatellite markers, For comparison we examined samples from spontaneous thyroid carcinomas without radiation history from 20 adul t patients from Munich (mean age at surgery 56 +/- 13 Sears). None of the t umour samples investigated showed evidence of alterations in the 28 microsa tellite markers tested. Taken together our data indicate an increased insta bility of microsatellite markers in thyroid cancers from Belarussian patien ts. At present, it is uncertain whether the increased genome instability ob served in Belarussian patients is the result of the exposure to radioactive iodine from the Chernobyl reactor accident or due to the young age of the patients.