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

Somatic mutations of the TSH receptor (TSHR) gene have been identified as the major cause of toxic thyroid adenoma. Recently, point mutations of the same gene have also been described in some differentiated thyroid carcinomas. The aim of the present study was to investigate the presence TSHR gene mutations in a series of thyroid specimens obtained from 22 consecutive patients 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 exon 10 and one fragment corresponding to exon 9 were amplified by PCR using biotinylated primers. PCR products were purified on streptavidin-coated magnetic beads and subjected to direct sequencing with Sequenase and 35(3)-labeled d-ATP-alphaS. 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 Asp727Glu 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 carcinoma.