Somatic mutations of the ret protooncogene in sporadic medullary thyroid carcinoma are not restricted to exon 16 and are associated with tumor recurrence

Cristina Romei, Rossella Elisei, Aldo Pinchera, Isabella Ceccherini, Eleonora Molinaro, Francesco Mancusi, Enio Martino, Giovanni Romeo, Furio Pacini

Research output: Contribution to journalArticle

Abstract

Germline point mutations in exons 10, 11, and 16 of the ret protooncogene have been identified as causative in multiple endocrine neoplasia type 2 and in familial medullary thyroid carcinoma (MTC). Somatic point mutations of the same gene, exclusively associated with codon 918 of exon 16, have also been reported in few cases of sporadic medullary thyroid carcinoma. We analyzed the blood and tumor DNA of 19 patients with sporadic MTC and 6 patients with primary parathyroid adenoma for point mutations at exons 10, 11, and 16 of the ret protooncogene by restriction analysis of the PCR-amplified product and by sequence analysis of exons 10 and 11. A Cys634→Tyr mutation was found in both the tumoral and blood DNA of one patient, indicating that he was affected by an hereditary form of MTC, erroneously considered sporadic. In the other 18 patients with MTC, somatic point mutations of ret were found in 8 cases (44.4%). In 5 cases the mutation affected exon 16 (Met918→Thr), and in 3 cases it affected exon 11 (Cys634→Arg in 1 and Cys634→Trp in 2); these 3 mutations were confirmed by sequence analysis. The remaining 10 patients had no mutation in exon 10 by either restriction analysis or sequence analysis. Clinical data showed that 75% of the patients whose tumor carried ret mutation had tumor recurrence and/or increased serum calcitonin concentrations during the postsurgical follow-up period as opposed to 10% of the patients without mutations (P <0.02, by χ2 analysis). No ret mutation was found in the tumoral DNA from parathyroid adenomas. Our findings indicate that the somatic ret point mutation frequently found in sporadic MTC may affect not only exon 16 but also exon 11 and is associated with less favorable clinical outcome.

Original languageEnglish
Pages (from-to)1619-1622
Number of pages4
JournalJournal of Clinical Endocrinology and Metabolism
Volume81
Issue number4
DOIs
Publication statusPublished - 1996

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

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