In this study, we report new, unrelated Brazilian individuals with germline RETY791F-only: two tumour-free elderly controls; two individuals with sporadic MTC whose Y791F-carrying relatives did not show any evidence of tumours; and a 74-year-old phaeochromocytoma patient without MTC.
We hypothesised that PC/PGLs containing SDHx or VHL mutations, and succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumours (GISTs), would overexpress miR-210 relative to non-SDH or -VHL-mutated counterparts. miR-210 was analysed by quantitative PCR in i) 39 PC/PGLs, according to genotype (one SDHA, five SDHB, seven VHL, three NF1, seven RET, 15 sporadic, one unknown) and pathology (18 benign, eight atypical, 11 malignant, two unknown); ii) 18 GISTs, according to SDHB immunoreactivity (nine SDH-deficient and nine SDH-proficient) and iii) two novel SDHB-mutant neurosphere cell lines. miR-210 was higher in SDHx- or VHL-mutated PC/PGLs (7.6-fold) compared with tumours without SDHx or VHL mutations (P=0.0016). miR-210 was higher in malignant than in unequivocally benign PC/PGLs (P=0.05), but significance was lost when benign and atypical tumours were combined (P=0.08).
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.
The primary syndromes (and genes) addressed here include multiple endocrine neoplasia types 1 and 2 (MEN1 and RET genes), Cowden syndrome (PTEN), hereditary pheochromocytoma/paraganglioma syndromes (multiple genes), and von Hippel-Lindau disease (VHL).
Familial medullary thyroid cancer is now viewed as a phenotypic variant of MEN2A with decreased penetrance for PHEO and PHPT rather than a distinct entity.
Of these, 59 patients (subgroup 1) with RET codon 634 mutations were compared to 48 patients (group 2) with RET codon 634 mutations, but without MEN2-associated PHEO.
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).
Transcriptome studies indeed revealed that pheochromocytomas and paragangliomas can be classified into two major clusters depending on their gene expression profile: Cluster 1 comprises samples associated with a hypoxic signature such as SDHx- and VHL-related tumors and cluster 2 includes RET, NF1, and TMEM127-mutated tumors, as well as most of sporadic tumors.
Patients with a D631YRET mutation typically present with pheochromocytoma and medullary thyroid carcinoma appears to occur with a later onset than reported with other RET mutations.
In this short review article, we comment on our previous report of a large multiple endocrine neoplasia type 2A kindred with the same Cys609Ser germline RET mutation in which, conversely, the syndrome was characterized by a slightly aggressive, highly penetrant form of medullary thyroid carcinoma that was associated with low penetrance of pheochromocytoma and primary hyperparathyroidism.
Transcriptome and immunohistochemical analyses showed that TMEM127-related pheochromocytoma clusterized with NF1-related and RET-related tumors in a large series of pheochromocytomas and paragangliomas, exhibited a reduced TMEM127 mRNA expression and displayed a low vascularization.
Pheochromocytomas and paragangliomas are neuroendocrine tumors that occur in the context of inherited cancer syndromes in ∼30% of cases and are linked to germline mutations in the VHL, RET, NF1, SDHA, SDHB, SDHC, SDHD, SDHAF2 and TMEM127 genes.
Moreover, we report the first case of pheochromocytoma among the RETp.G533C-carriers in this Brazilian family and explore the RET mutational status in DNA isolated from pheochromocytoma.
A novel de novo germ-line V292M mutation in the extracellular region of RET in a patient with phaeochromocytoma and medullary thyroid carcinoma: functional characterization.
Up to 30% of pheochromocytomas and paragangliomas are associated with germline RET, Von Hippel-Lindau (VHL), neurofibromatosis type I (NF1), and succinate dehydrogenase subunits (SDHB, SDHC, and SDHD) mutations.