Genetic analysis of the TSH receptor gene in differentiated human thyroid carcinomas

Somatic mutations of the TSH receptor (TSHR) gene have been identified as t he major cause of toxic thyroid adenoma, Recently, point mutations of the s ame gene have also been described in some differentiated thyroid carcinomas . The aim of the present study was to investigate the presence TSHR gene mu tations in a series of thyroid specimens obtained from 22 consecutive patie nts with differentiated thyroid carcinomas (8 follicular and 14 papillary). Genomic DNA was extracted from fresh-frozen or paraffin-embedded tumor and normal surrounding parenchyma. Two fragments corresponding to the entire e xon 10 and one fragment corresponding to exon 9 were amplified by PCR using biotinylated primers. PCR products were purified on streptavidin-coated ma gnetic beads and subjected to direct sequencing with Sequenase and 35(3)-la beled d-ATP-alpha S. Adenyl-cyclase activity in membrane preparations of 10 papillary carcinomas was also determined. No TSHR mutations were detected in these tumors. A polymorphism that encoded a single amino acid change Asp 727Glu was identified in two follicular thyroid carcinomas. Adenyl-cyclase activity was normal in the ten papillary thyroid carcinomas we analyzed. In conclusion, our results suggest that clonal somatic mutations of the TSHR gene do not play a role in the pathogenesis of differentiated thyroid carci noma. (J. Endocrinol. Invest. 22: 273-278, 1999) (C)1999, Editrice Kurtis.