Prevalence of minisatellite and microsatellite instability in radiation-induced post-Chernobyl pediatric thyroid...

Exposure to ionizing radiation induces different forms of genomic instability in cultured cells and experimental animals. A higher rate of germline mutations at human hypervariable minisatellite loci was reported in children born from parents exposed to radiation after Chernobyl, implicating genome destabilization as a possible mechanism responsible for late radiation effects in humans. To test if radiation-induced carcinogenesis in the thyroid gland may be associated with somatic minisatellite instability or microsatellite instability, we utilized a PCR-based approach to study normal and tumor DNA from 17 pediatric post-Chernobyl papillary thyroid carcinomas for mutations at three different minisatellite loci (D1S80, D17S30, ApoB), and 27 microsatellite loci of di-, tri-, or tetranucleotide repeats. Minisatellite instability was found in three (18%) tumors, with one of them exhibiting mutations in all three minisatellite loci, whereas two others showed mutations in one of two informative markers. By contrast, none of 20 sporadic thyroid cancers from patients with no history of radiation exposure was positive for minisatellite instability. Microsatellite analysis of post-Chernobyl tumors revealed a mutation in one (6%) tumor only at the locus of D10S1412, whereas all other 26 microsatellite markers showed identical patterns in each normal/tumor pair. Our results suggest that somatic cell microsatellite instability does not contribute to radiation-induced thyroid carcinogenesis. However, somatic minisatellite mutation events are present in a subset of radiation-induced, but not sporadic, thyroid cancers, suggesting that this type of genomic instability may play a role in radiation-induced tumorigenesis in the thyroid gland.