Point mutations in the thyrotropin receptor in human thyroid tumors

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• Thyroid tumor cells exhibit impaired responses to thyrotropin (TSH).
• The underlying molecular mechanisms, particularly alterations in the TSH receptor (TSH-R), are not fully understood.

Purpose of the Study:

• To investigate structural changes in the TSH receptor (TSH-R) within human neoplastic thyroid tissues.
• To correlate these structural changes with the impaired TSH response observed in thyroid tumors.

Main Methods:

• Analysis of 34 thyroid tissue samples (normal, adenoma, follicular cancer, papillary cancer).
• RNA extraction, cDNA synthesis, polymerase chain reaction (PCR), and single-strand conformation polymorphism (SSCP) analysis.
• Direct sequencing of identified TSH-R fragments with altered electrophoretic mobility.

Main Results:

• Two TSH-R fragments (extracellular and cytoplasmic domains) showed mobility differences in neoplastic tissues.
• Specific amino acid substitutions (Phe197Ile, Asp219Glu) were found in the extracellular domain of papillary cancers.
• Substitutions (Asn715Asp, Lys723Met, Asp727Glu) were identified in the cytoplasmic domain across various thyroid tissues, including cancers.

Conclusions:

• Structural alterations in the TSH receptor (TSH-R) are present in a subset of thyroid neoplastic tissues.
• These TSH-R mutations may contribute to the abnormal cellular responses observed in thyroid tumors.
• Further research is warranted to elucidate the functional consequences of these TSH-R structural changes.