Endocrine Abstracts

Multiple endocrine neoplasia (MEN) is characterized by the occurrence of tumors involving two or more endocrine glands; MEN 2 is defined by medullary thyroid carcinoma in association with phaeochromocytoma and appears in several clinical variants, which may be inherited as autosomal dominant syndromes. Mutational analysis of RET protooncogene has been use in the diagnosis and management of patients and families with MEN 2 variants.

Aim: In this study, we retrospectively analyzed 20 patients with MEN 2 from 14 different families for relevance of specific mutations in the RET proto-oncogene.

Materials and methods: Genomic DNA was extracted from peripheral leukocytes using a Promega blood minikit and two fragments covering the exons 10 and 11 of the RET gene were amplified by polymerase chain reaction using specific oligonucleotide primers (exon 10: 5′-GCCTATGCTTGCGACACCAGTTG-3′, exon 11: 5′-CATGAGGCAGAGCATACGCA-3′) and the following protocol; 95CX 10 min followed by 30 cycles 95CX 1 min, 64CX 1 min, 62CX 30 s and a final extension at 72C for 7 min. The resulting fragments were sequenced directly with the Big Dye R Terminator v 3.1 cycle sequencing kit using a ABI Prism 310 Genetic Analyser.

Results: In 13 of 20 examined MEN 2 cases, missense mutation of codon 634 from exon 11 of the RET proto-oncogene were detected. Nine of the MEN 2 samples proved to have an identical base sequence change TGC-TGG resulting in the substitution of Cys with Trp, two of the samples have the change TGC-GGC resulting in the substitution of Cys with Gly and other two samples have the change TGC-CGC resulting in the substitution of Cys with Arg. We cannot detect mutations in exon 10 or 11 of RET protooncogenes in 7 patients with specific tumors associations.

Conclusion: We conclude that, in all families with MEN 2, mutational analysis of the RET proto-oncogene should be performed both to identify specific mutations and to prove gene carrier status for MEN 2.