The presence of germ-line RET mutations in four living relatives demonstrates that the original patient and her family had multiple endocrine neoplasia type 2 and provides molecular evidence that she had pheochromocytoma.
They showed RET transcript, protein amounts as well as Ret-associated phosphotyrosine levels similar to those measured in MEN-2A-associated pheochromocytomas.
However, mutations 630 and 634 activate RET more strongly than mutations 609, 618 or 620 as demonstrated by quantitative assays in rodent fibroblasts and pheochromocytoma PC12 cells.
The group of pheochromocytoma susceptibility genes includes, along with the tumor suppressor genes VHL and NF1, the proto-oncogene RET and the genes encoding succinate dehydrogenase subunit D and succinate dehydrogenase subunit B.
MEN2B is a very rare autosomal dominant hereditary tumor syndrome associated with medullary thyroid carcinoma (MTC) in 100% cases, pheochromocytoma in 50% cases and multiple extra-endocrine features, many of which can be quite disabling.
The remaining 15 RET mutation carriers did not exhibit CLA; of these, 1 presented with MTC and pheochromocytoma, 9 with MTC only, 2 with elevated serum calcitonin, and 3 younger subjects with normal serum calcitonin levels.
An intriguing hypothesis proposes that mutations of RET, NF1, VHL, or SDH predispose to hereditary pheochromocytoma/ paraganglioma by causing defective apoptotic culling of cells that would normally be destroyed during embryogenesis.
Detection of RET proto-oncogene point mutations in paraffin-embedded pheochromocytoma specimens by nonradioactive single-strand conformation polymorphism analysis and direct sequencing.
We conclude that, in all families with MEN 2, mutational analysis of the RET proto-oncogene should be performed, both to identify gene carriers for MEN 2 and to identify specific mutations that are more strongly associated with pheochromocytoma.
Among the members of the three families with MEN 2A and RET 634 mutation, the incidence of CLA was 36%, a figure similar to that reported in the literature for phaeochromocytoma (30-50%) and even higher than that for hyperparathyroidism (10-20%).
The findings propose a classification of 15 of the 26 VUS in RET without any well-defined risk profiles and suggest that the G691S SNP, or a combination of SNPs, may be associated with the development of PHEO.
The human ret proto-oncogene (proto-ret), encoding a receptor tyrosine kinase, is highly expressed in neuroblastomas, medullary thyroid carcinomas (MTCs) and pheochromocytomas, which are all tumors of cells originating from the neural crest.
Herein, we report that each RET isoform activated by MEN 2A or MEN 2B mutation was transforming in fibroblasts and induced neuronal differentiation of pheochromocytoma PC12 cells.
The relationship between the presence of pheochromocytoma (PC) and/or hiperparathyroidism (HPT) in carriers of the same RET mutation, and the genotype for the specific variants was also studied.
However, on genotyping a group of 172 sporadic or familial pheochromocytomas, we characterized four unrelated probands with familial pheochromocytomas without any sequence variants of RET (exons 8, 10, 11, 13, 14, 15, and 16) or the entire coding sequence of VHL, SDHB, SDHC, SDHD, and EGLN3 (exon-intron boundaries included).
In contrast to the previously held belief that only 10% of cases had a genetic component, currently about one-third of all aPCA/eFPGL cases are thought to be attributable to germline mutations in at least nine genes (NF1, RET, SDHA, SDHB, SDHC, SDHD, TMEM127, MAX and VHL).
RET, a transmembrane receptor tyrosine kinase and a receptor for the glial cell-derived neurotrophic factor family ligands, was one of the first oncogenes to be identified, and has been shown to be an oncogene in thyroid cancer and pheochromocytoma.
Global transcription analysis of KIF1B beta mutant pheochromocytomas revealed that these tumors are transcriptionally related to pheochromocytomas with RET and NF1 mutations but independent from SDH- and VHL-associated tumors.
The diagnosis of MEN-II should be confirmed by molecular genetic analysis and the diagnosis of VHL syndrome should be considered for families with an absence of RET mutations and a preponderance of pheochromocytomas.