Germline Multiple Endocrine Neoplasia Type 1 Mutations Research Articles

Comprehensive Analysis of Clinical Features in Index Cases With Multiple Endocrine Neoplasia Type 1 Refine the Risk Rate for Detection of Mutation Distinguishing Negative-Mutation (Phenocopies) and Positive-Mutation Cases

Background: Index cases clinically diagnosed with multiple endocrine neoplasia type 1 (MEN1) are declared as MEN1 phenocopies if no germline MEN1 mutation is identified. In comparison with positive-mutation cases, most phenocopies have been diagnosed in older age, mainly by association of primary hyperparathyroidism (HPT) and pituitary adenoma (PIT), with HPT predominantly diagnosed as uniglandular disease. Besides that, phenocopies rarely develop a third MEN1-related tumor and are associated with lower morbidity and longer survival. However, all these data are mainly derived of genetic studies by Sanger targeted to MEN1 gene from a strict number of MEN1 phenocopies. Objectives: to recognize strong clinical profiles capable of predicting the occurrence or absence of germline MEN1 mutation refining the clinical differentiation of phenocopies and mutation-positive cases before genetic testing disclosure. Casuistic/Methods: 143 MEN1 index cases: 87 MEN1-positive and 56 true MEN1 phenocopies (excluded mutations for MLPA assay and by a mini-painel based on long-range PCR and next generation sequencing of 6 MEN1-related genes (MEN1, p15, p18, p21, p27, AIP) covering full coding and non-coding regions. Results: High detectability rate of MEN1 mutation was associated with the presence of ≥ 4 organs affected for primary tumors (100%), association of HPT/PET (neuroendocrine pancreatic tumor)/PIT (93%), HPT/PET (81%), positive familial history (88% vs. 48%), presence of PET (84%) as malign (80%) as multifocal (95%), two different PETs (100%), multiglandular HPT (81%) and diagnosis of one MEN1-related tumor (93%) or of two/three MEN1 tumors diagnosed before 21y (100%). The combination HPT/PIT has the lowest rate of detection of mutation (33%), it is even lower if PIT was acromegaly (12%) or age at the diagnosis of HPT and PIT was, respectively, > 45y and >30y (8%) and absent if it is added uniglandular HPT (0%) or if there was association HPT/PIT (age-independent) with uniglandular HPT (0%). The prediction for detection of mutation increases if these HPT (> 45y)/PIT (> 30y) cases have multiglandular HPT (20%) and it is 100% with association HPT (< 30y)/PIT (< 21y). A p <0.05 was observed to all data above. Conclusions: By integration of phenotypic clues and full genetic analysis applied to the largest MEN1 phenocopy series, we identified strong clinical predictors capable of anticipate the potential risk rate for mutation detection revealing the estimated chance of an index case harbor a mutation or be classified as phenocopy. By their peculiarities, the management/treatment of phenocopies should potentially be different of that recommended to mutation-positive cases.

SUN-124 Are Venous Thromboembolic Events Increased in MEN1 Patients?

Background: Multiple endocrine neoplasia type 1 (MEN1) is a rare inherited disorder in which patients develop multiple simultaneous hormone-secreting tumors. Most common tumors include: anterior pituitary adenomas (50%), multi-gland parathyroid adenomas (95%), and gastroenteropancreatic neuroendocrine tumors (40-80%). Only rare MEN1 associated glucagonomas (<1%), and ACTH-producing neuroendocrine tumors (<5%) are known to increase risk of hypercoagulability. It is unknown if patients with MEN1 syndrome have increased risk of venous thrombolytic events (VTE), defined as a deep-vein thrombosis and/or pulmonary embolism. Methods: We queried a prospective natural history study of MEN1 patients who tested positive for germline MEN1 mutations (n=287) between 1991-2019 (54 patients on our current protocol were followed before 1991; the earliest was 1971). All lifetime events of VTE were included. Search terms included: DVT, thromb, embol, PE, pulmonary embolism, clot, hematology consult, anticoagulant, coumadin, lovenox, xarelto, warfarin, aspirin, rivaroxaban and apixaban. After initial screening, 10 patients were removed due to insufficient clinical data. Kaplan-Meier analysis was performed to compare age of death between the two cohorts. Results were expressed as mean ± standard deviation. Results: Thirty-four subjects (mean 57.5 years-old, 17 women) were identified with any VTE, yielding a prevalence rate of 13.4%. The incidence of VTE corresponded to 264 events per 100,000 patient-years, which was ~2-fold higher than the estimated annual incidence rate in the general population (104-183/100,000 patient years).1 Kaplan-Meier analysis revealed no significant difference in survival between the two groups (non-VTE cohort mean 81.1 years ± 2.23; VTE cohort mean 77.4 years ± 3.45; p = 0.96). Thirty-two events occurred during the surveillance period at our institution; 9 individuals had more than one VTE. At the time of VTE, 80% had hyperparathyroidism (mean PTH ± SD; 97.56 pg/mL ± 90.76), 21% had hyperprolactinemia (prolactin 25.7μg/L ± 43.41), 62.5% had hypergastrinemia (mean gastrin 1100.9 pg/mL ± 3127.8), and 84.6% had non-functional pancreatic neuroendocrine tumors. One patient was identified to have a Factor V Leiden mutation, 3 patients had lupus anti-coagulant. Eleven patients experienced events within a post-surgical period of 3 months. Conclusions: Hypercoagulability in MEN1 has been previously unidentified. Our cohort data suggests a two-fold increase in the incidence of VTE as compared to the general population, with a high risk occurring within the perioperative period. Further mechanistic investigation and validation from other cohorts are needed to confirm the increased prevalence of VTE in this population. 1Heit, John A., et al. Epidemiology of venous thromboembolism. Nat Rev Cardiol 2015 Aug;12(8): 464-474.

Genetic background influences tumour development in heterozygous Men1 knockout mice.

Multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant disorder caused by MEN1 germline mutations, is characterised by parathyroid, pancreatic and pituitary tumours. MEN1 mutations also cause familial isolated primary hyperparathyroidism (FIHP), a milder condition causing hyperparathyroidism only. Identical mutations can cause either MEN1 or FIHP in different families, thereby implicating a role for genetic modifiers in altering phenotypic expression of tumours. We therefore investigated the effects of genetic background and potential for genetic modifiers on tumour development in adult Men1+/- mice, which develop tumours of the parathyroids, pancreatic islets, anterior pituitary, adrenal cortex and gonads, that had been backcrossed to generate C57BL/6 and 129S6/SvEv congenic strains. A total of 275 Men1+/- mice, aged 5–26 months were macroscopically studied, and this revealed that genetic background significantly influenced the development of pituitary, adrenal and ovarian tumours, which occurred in mice over 12 months of age and more frequently in C57BL/6 females, 129S6/SvEv males and 129S6/SvEv females, respectively. Moreover, pituitary and adrenal tumours developed earlier, in C57BL/6 males and 129S6/SvEv females, respectively, and pancreatic and testicular tumours developed earlier in 129S6/SvEv males. Furthermore, glucagon-positive staining pancreatic tumours occurred more frequently in 129S6/SvEv Men1+/- mice. Whole genome sequence analysis of 129S6/SvEv and C57BL/6 Men1+/- mice revealed >54,000 different variants in >300 genes. These included, Coq7, Dmpk, Ccne2, Kras, Wnt2b, Il3ra and Tnfrsf10a, and qRT-PCR analysis revealed that Kras was significantly higher in pituitaries of male 129S6/SvEv mice. Thus, our results demonstrate that Kras and other genes could represent possible genetic modifiers of Men1.

SUN-046 Identification of Clinical Predictors for Detection of Mutations in Multiple Endocrine Neoplasia Type 1

Context: Guidelines has systematically suggested genetic testing for a wide spectrum of phenotypes in order to confirm or exclude surely the diagnosis of multiple endocrine neoplasia type 1 (MEN1). However, the probability of find a germline MEN1 mutation has showed extremely variable (5-95%) when different phenotypes are considered. The prompt recognition of potential clinical predictors could anticipate the result of the genetic testing in the different clinical scenarios. Objective: To investigate if specific phenotypic features may predict the presence of germline MEN1 mutations in index-cases with clinical diagnosis of MEN1 syndrome. Methods and Patients: 110 MEN1 index cases were included: amplicons based on long-range PCR covering the full MEN1 open reading frame of 94 MEN1 index cases (49 familial, 45 sporadic) were sequenced by targeted-Next Generation Sequencing (tNGS) MiSeq Illumina platform while Sanger Sequencing (SS) was approached to the other 16 MEN1 index cases (2 familial, 14 sporadic). MLPA assay was supported to 31 MEN1-negative patients by tNGS/SS whose DNA samples were available. Results: 68 index cases (62%) had germline MEN1 mutations. With the tNGS/SS/MLPA protocol, the mutation detectability rate was higher in familial MEN1 (90%, 46/51 vs. 37%; 22/59; p, < 0.05). In comparison with MEN1-positive patients, MEN1-negative cases were older (53±12 vs. 39±13; p, < 0.05) and most of them had no more than two MEN1-related tumors (76%, 32/42 vs. 10%, 7/68; p, < 0.05). Considering the subset of 59 patients with negative familial history, the 22 MEN1-positive patients revealed clinical predictors for detection of MEN1 mutation when they were compared with 37 truly non-MEN1 mutation carriers. Thus, sporadic MEN1-positive patients had higher significantly prevalence of the following predictors. 1) ≥ 3 tumors, 86% (19/22) versus 11% (4/37); 2) PETs, 86% (19/22) versus 22% (8/37); 3) which were multifocal, 100% versus 1/8 (9%); 4) with frequent synchronic association of functioning and NF/PETs, 47% (9/19) versus 0% and; 5) high frequency of malignancies, 58% (11/19) versus 5% (2/37). Indeed, there was confirmation of these predictors comparing all 68 MEN1-positive carriers against 42 MEN1-negative cases. Conclusions: The strategy adopted to support the diagnosis of MEN1 based on analysis of clinical predictors and genetic testing for tNGS/SS-MLPA underscored that the positive familial history, occurrence of three or more MEN1 tumors, presence of PETs, especially multifocal PETs, and malignancies are strong predictors to detection of MEN1 mutations.

Multiple endocrine neoplasia type 1: analysis of germline MEN1 mutations in the Italian multicenter MEN1 patient database.

Multiple endocrine neoplasia type 1 (MEN1) is caused by germline inactivating mutations of the MEN1 gene. Currently, no direct genotype-phenotype correlation is identified. We aim to analyze MEN1 mutation site and features, and possible correlations between the mutation type and/or the affected menin functional domain and clinical presentation in patients from the Italian multicenter MEN1 database, one of the largest worldwide MEN1 mutation series published to date. The study included the analysis of MEN1 mutation profile in 410 MEN1 patients [370 familial cases from 123 different pedigrees (48 still asymptomatic at the time of this study) and 40 single cases]. We identified 99 different mutations: 41 frameshift [small intra-exon deletions (28) or insertions (13)], 13 nonsense, 26 missense and 11 splicing site mutations, 4 in-frame small deletions, and 4 intragenic large deletions spanning more than one exon. One family had two different inactivating MEN1 mutations on the same allele. Gastro-entero-pancreatic tumors resulted more frequent in patients with a nonsense mutation, and thoracic neuroendocrine tumors in individuals bearing a splicing-site mutation. Our data regarding mutation type frequency and distribution are in accordance with previously published data: MEN1 mutations are scattered through the entire coding region, and truncating mutations are the most common in MEN1 syndrome. A specific direct correlation between MEN1 genotype and clinical phenotype was not found in all our families, and wide intra-familial clinical variability and variable disease penetrance were both confirmed, suggesting a role for modifying, still undetermined, factors, explaining the variable MEN1 tumorigenesis.

The future: genetics advances in MEN1 therapeutic approaches and management strategies.

The identification of the multiple endocrine neoplasia type 1 (MEN1) gene in 1997 has shown that germline heterozygous mutations in the MEN1 gene located on chromosome 11q13 predisposes to the development of tumors in the MEN1 syndrome. Tumor development occurs upon loss of the remaining normal copy of the MEN1 gene in MEN1-target tissues. Therefore, MEN1 is a classic tumor suppressor gene in the context of MEN1. This tumor suppressor role of the protein encoded by the MEN1 gene, menin, holds true in mouse models with germline heterozygous Men1 loss, wherein MEN1-associated tumors develop in adult mice after spontaneous loss of the remaining non-targeted copy of the Men1 gene. The availability of genetic testing for mutations in the MEN1 gene has become an essential part of the diagnosis and management of MEN1. Genetic testing is also helping to exclude mutation-negative cases in MEN1 families from the burden of lifelong clinical screening. In the past 20 years, efforts of various groups world-wide have been directed at mutation analysis, molecular genetic studies, mouse models, gene expression studies, epigenetic regulation analysis, biochemical studies and anti-tumor effects of candidate therapies in mouse models. This review will focus on the findings and advances from these studies to identify MEN1 germline and somatic mutations, the genetics of MEN1-related states, several protein partners of menin, the three-dimensional structure of menin and menin-dependent target genes. The ongoing impact of all these studies on disease prediction, management and outcomes will continue in the years to come.

MEN1 mutations and potentially MEN1-targeting miRNAs are responsible for menin deficiency in sporadic and MEN1 syndrome-associated primary hyperparathyroidism.

Inherited, germline mutations of menin-coding MEN1 gene cause multiple endocrine neoplasia type 1 (MEN1), while somatic MEN1 mutations are the sole main driver mutations in sporadic primary hyperparathyroidism (PHPT), suggesting that menin deficiency has a central role in the pathogenesis of PHPT. MiRNAs are small, noncoding RNAs posttranscriptionally regulating gene expression. Our aim was to investigate both the role of MEN1 mutations and potentially MEN1-targeting miRNAs as the underlying cause of menin deficiency in MEN1-associated and sporadic PHPT tissues. Fifty six PHPT tissues, including 16 MEN1-associated tissues, were evaluated. Diagnosis of MEN1 syndrome was based on identification of germline MEN1 mutations. In silico target prediction was used to identify miRNAs potentially targeting MEN1. Menin expression was determined by immunohistochemistry while expression of miRNAs was analyzed by quantitative real-time PCR. Sporadic PHPT tissues were subjected to somatic MEN1 mutation analysis as well. Lack of nuclear menin was identified in all MEN1-associated and in 28% of sporadic PHPT tissues. Somatic MEN1 mutations were found in 25% of sporadic PHPTs. The sensitivity and specificity of menin immunohistochemistry to detect a MEN1 mutation were 86 and 87%, respectively. Expression levels of hsa-miR-24 and hsa-miR-28 were higher in sporadic compared to MEN1-associated PHPT tissues; however, no difference in miRNA levels occurred between menin-positive and menin-negative PHPT tissues. Menin deficiency is the consequence of a MEN1 mutation in most menin-negative PHPT tissues. Elevated expression of hsa-miR-24 and hsa-miR-28 mark the first epigenetic changes observed between sporadic and MEN1-associated PHPT.

Germline and somatic genetic changes in multicentric tumors obtained from a patient with multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary cancer syndrome caused by germline mutations of the MEN1 gene located in chromosome 11q13. In patients with MEN1, multicentric tumors develop in the involved organs; however, precise evaluation of genetic changes in these multicentric tumors has not been performed. In the present study, using whole-exome sequencing, we analyzed germline and somatic genetic changes in blood cells, two pancreatic endocrine tumors and one duodenal tumor obtained from a patient with MEN1 gastrinoma. We found that this patient possessed a novel germline mutation of the MEN1 gene [NM_137099.2:c.1505dupA (p.Lys502Lysfs); the localization was Chr11:64572134 on Assembly GRCh37], in which an adenine insertion in codon 502 of the MEN1 gene resulted in a frame shift and a premature stop codon. In terms of heterozygosity, the mutated allele was heterozygous in blood cells, hemizygous in the two pancreatic tumors and homozygous in the duodenal tumor. Immunohistochemical staining confirmed that only truncated menin protein accumulated in the nucleus of the tumor tissues. Further evaluation of tumor-specific somatic mutations in two pancreatic tumors did not detect single-nucleotide variations (SNVs) in 609 cancer-associated genes designated by the COSMIC cancer gene census, suggesting that the germline MEN1 mutation and resultant loss of heterozygosity played a major role in tumorigenesis. In the duodenal tumor, in addition to the germline MEN1 mutation, single-nucleotide variations in two cancer-associated genes were found. Further studies are required to clarify the role of these somatic single-nucleotide variations in the progression of MEN1 tumors.

A patient with MEN1 typical features and MEN2-like features.

Multiple endocrine neoplasia (MEN) type 1 (MEN1) and 2 (MEN2) rarely co-exist in one case. Here we report a patient with features of both syndromes. The patient presented with typical MEN1 features plus pheochromocytoma and thickened corneal nerves. She had a germline 1132delG frameshift mutation in MEN1, no mutation in CDKN1B (p27) and no RET mutation, but had both RET polymorphisms Gly691Ser and Arg982Cys. This is the first case report of a combination of typical clinical findings of MEN1 harboring a germline MEN1 mutation and the MEN2-like phenotype with negative full RET gene analysis of pathogenic variants. Possible explanations include a previously unrecognized phenotype-genotype association or the influence of potential phenotypic modifying RET variants. Furthermore, the combination observed in this patient may point to a single molecular pathway, and supports the possibility of as yet unrecognized connections between the molecular pathways for MEN1/menin protein and MEN2/RET protein.

Multiple endocrine neoplasia type 1 (MEN1): An update of 208 new germline variants reported in the last nine years

This review will focus on the germline MEN1 mutations that have been reported in patients with MEN1 and other hereditary endocrine disorders from 2007 to September 2015. A comprehensive review regarding the analysis of 1336 MEN1 mutations reported in the first decade following the gene's identification was performed by Lemos and Thakker in 2008. No other similar papers are available in literature apart from these data. We also checked for the list of Locus-Specific DataBases (LSDBs) and we found five MEN1 free-online mutational databases. 151 articles from the NCBI PubMed literature database were read and evaluated and a total of 75 MEN1 variants were found. On the contrary, 67, 22 and 44 novel MEN1 variants were obtained from ClinVar, MEN1 at Café Variome and HGMD (The Human Gene Mutation Database) databases respectively. A final careful analysis of MEN1 mutations affecting the coding region was performed.

Association between the p27 rs2066827 variant and tumor multiplicity in patients harboring MEN1 germline mutations.

To date, no evidence of robust genotype-phenotype correlation or disease modifiers for multiple endocrine neoplasia type 1 (MEN1) syndrome has been described, leaving the highly variable clinical presentation of patients unaccounted for. As the CDKN1B (p27) gene causes MEN4 syndrome and it is transcriptionally regulated by the product of the MEN1 gene (menin), we sought to analyze whether p27 influences the phenotype of MEN1-mutated patients. The cohort consisted of 100 patients carrying germline MEN1 gene mutations and 855 population-matched control individuals. Genotyping of the coding p27 c.326T>G (V109G) variant was performed by sequencing and restriction site digestion, and the genotypes were associated with clinical parameters by calculating odds ratios (ORs) and their 95% CIs using logistic regression. There were significant differences in p27 V109G allele frequencies between controls and MEN1-mutated patients (OR=2.55, P=0.019, CI=1.013-5.76). Among patients who are ≥30 years old carrying truncating MEN1 mutations, the T allele was strongly associated with susceptibility to tumors in multiple glands (three to four glands affected vs one to two glands affected; OR=18.33; P=0.002, CI=2.88-16.41). This finding remained significant after the Bonferroni's multiple testing correction, indicating a robust association. No correlations were observed with the development of MEN1-related tumors such as hyperparathyroidism, pituitary adenomas, and enteropancreatic and adrenocortical tumors. Our study suggests that the p27 tumor suppressor gene acts as a disease modifier for the MEN1 syndrome associated with MEN1 germline mutations. If confirmed in independent patient cohorts, this finding could facilitate the management of this clinically complex disease.

Application of an intracellular stability test of a novel missense menin mutant to the diagnosis of multiple endocrine neoplasia type 1

Germline MEN1 mutation analysis is a powerful tool for an early diagnosis of multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant familial cancer syndrome characterized by the parathyroid, pituitary and gastroenteropancreatic endocrine tumors. However, the clinical significance of MEN1 gene variants, especially missense and in-frame mutations as well as some splicing mutations, is not always obvious. We have previously shown that mutant menin proteins associated with MEN1 are rapidly degraded by the ubiquitin-proteasome pathway. We also demonstrated by a fluorescent immunocytochemical stability test that the stability of missense and in-frame deletion mutants varies widely but that unstable mutants were found only in MEN1 and related disorders and not in normal polymorphisms. In the present study, we evaluated by this stability test the pathogenicity of a novel MEN1 missense mutation, c.1118C>T, encoding a P373L mutant menin, identified in a suspected MEN1 patient. The results demonstrated that the mutant menin is highly unstable, indicating that this mutation is causative for MEN1. These findings encouraged us to proceed with presymptomatic genetic screening for this mutation among the family members, which resulted in the identification of asymptomatic mutation carriers. Thus, the information from the menin stability test was useful for genetic diagnosis and counseling of MEN1 in the case with a previously unreported MEN1 missense mutation.

Correlation of mutant menin stability with clinical expression of multiple endocrine neoplasia type 1 and its incomplete forms

Germline mutations of the tumor suppressor gene MEN1 are found not only in typical multiple endocrine neoplasia type 1 (MEN1) but also in its incomplete forms such as familial isolated hyperparathyroidism (FIHP) and apparently sporadic parathyroid tumor (ASPT). No definitive genotype-phenotype correlation has been established between these clinical forms and MEN1 gene mutations. We previously demonstrated that mutant menin proteins associated with MEN1 are rapidly degraded by the ubiquitin-proteasome pathway. To examine whether the intracellular stability of mutant menin is correlated with clinical phenotypes, we developed a method of evaluating menin stability and examined 20 mutants associated with typical MEN1 (17 missense, two in-frame deletion, one nonsense) and 21 mutants associated with FIHP or ASPT (19 missense, two in-frame deletion). All tested mutants associated with typical MEN1 showed reduced stability. Some missense and in-frame deletion mutants (G28A, R171W, T197I, E255K, E274A, Y353del and E366D) associated with FIHP or ASPT were almost as stable as or only slightly less stable than wild-type menin, while others were as unstable as those associated with typical MEN1. Some stable mutants exhibited substantial biological activities when tested by JunD-dependent transactivation assay. These findings suggest that certain missense and in-frame mutations are fairly stable and retain intrinsic biological activity, and might be specifically associated with incomplete clinical phenotypes. The menin stability test will provide useful information for the management of patients carrying germline MEN1 mutations especially when they have missense or in-frame variants of ambiguous clinical significance.

Bone mineral density analysis in patients with primary hyperparathyroidism associated with multiple endocrine neoplasia type 1 after total parathyroidectomy

Limited data have been reported on the effect of parathyroidectomy (PTx) on bone mineral density (BMD) in the setting of patients with hyperparathyroidism (HPT) associated with multiple endocrine neoplasia type 1 (MEN1). This study investigates the impact of total PTx on BMD in patients with HPT/MEN1. A case series study was performed in a tertiary academic hospital. A total of 16 HPT/MEN1 patients from six families harbouring MEN1 germline mutations were subjected to total PTx followed by parathyroid auto-implant in the forearm. Bone mineral density values were assessed using dual-energy X-ray absorptiometry. Before PTx, reduced BMD (Z-score <-2.0) was highly prevalent in the proximal one-third of the distal radius (1/3 DR) (50%), lumbar spine (LS) (43.7%), ultradistal radius (UDR) (43.7%), femoral neck (FN) (25%) and total femur (TF) (18.7%) in the patients. Fifteen months after PTx, we observed a BMD improvement in the LS (from 0.843 to 0.909 g/cm(2); +8.4%, P = 0.001), FN (from 0.745 to 0.798 g/cm(2); +7.7%, P = 0.0001) and TF (from 0.818 to 0.874 g/cm(2); +6.9%, P < 0.0001). No significant change was noticed in the 1/3 DR and UDR after PTx. This data confirmed BMD recovery in the LS and FN after PTx in HPT/MEN1 patients. We also documented a significant BMD increase in the TF and no change in both the 1/3 DR and UDR BMD after PTx. Our data suggest that LS and proximal femur are the most informative sites to evaluate the short-term BMD outcome after PTx in HPT/MEN1 subjects.

Néoplasies endocriniennes multiples, aspects cliniques

Multiple endocrine neoplasia type 1 (MEN1) and type 2 (MEN2) are autosomal dominant inherited multiglandular diseases with familial and individual age-related penetrance and variable expression. The most frequent endocrine features of MEN1 are parathyroid involvement (> 95%), duodeno-pancreatic endocrine tissue involvement (80%), pituitary adenoma (30%), and adrenal cortex tumors (25%), with no clear syndromic variants. Identification of the germline MEN1 mutation confirms the diagnosis, but there is no phenotype-genotype correlation. All patients with MEN2 have medullary thyroid carcinoma (MTC). The most distinctive MEN2 variants are MEN2A (MTC+pheochromocytoma+hyperparathyroidism), MEN2B (MTC+pheo), and isolated familial MTC (FMTC). The prognosis of MEN2 is linked to the progression of MTC, which depends mainly on the stage at diagnosis and the quality of initial surgical treatment. This emphasizes the need for early diagnosis and management. The specific RET codon mutation correlates with the MEN2 syndromic variant and with the age of onset and aggressiveness of MTC. Consequently, RET mutational status should guide major management decisions, such as whether and when to perform thyroidectomy.

MEN1 gene and its mutations: Basic and clinical implications

Heterozygous germline mutations of the tumor-suppressor gene MEN1 are responsible for multiple endocrine neoplasia type 1 (MEN1), a dominantly inherited familial cancer syndrome characterized by pituitary, parathyroid, and enteropancreatic tumors. Various mutations have been identified throughout the entire gene region in patients with MEN1 and related disorders. Neither mutation hot spot nor phenotype–genotype correlation has been established in MEN1 although some missense mutations may be specifically associated with a phenotype of familial isolated hyperparathyroidism. The gene product menin has been implicated in multiple roles, including gene transcription, maintenance of genomic integrity, and control of cell division and differentiation. These multiple functions are likely to be conferred by association with multiple protein factors. Occurrence of MEN1-causing missense mutations throughout menin also suggests the requirement of multiple binding factors for its full tumor-suppressive activity. The effect of menin depletion is highly tissue specific, but its underlying mechanism remains to be elucidated. A DNA test for MEN1 germline mutations is a useful tool for diagnosis of MEN1 although it needs further improvements

Rare Germline Mutations in Cyclin-Dependent Kinase Inhibitor Genes in Multiple Endocrine Neoplasia Type 1 and Related States

Germline mutation in the MEN1 gene is the usual cause of multiple endocrine neoplasia type 1 (MEN1). However, the prevalence of identifiable germline MEN1 mutations in familial MEN1 cases is only 70%. Some cases may have a germline mutation in another gene such as the p27 cyclin-dependent kinase inhibitor (CDKI). The aim of the study was to investigate cases of MEN1 or related states for germline mutations in all CDKI genes. A total of 196 consecutive index cases were selected with clear or suspected MEN1 and no identifiable germline MEN1 mutation. Every case was analyzed for germline mutation in each of the seven CDKI genes. We identified benign polymorphisms of the CDKI genes and also 15 other initially unclassified sequence variants. After detailed gene/protein analysis, seven of these 15 variants were classified as probably pathological mutations. Three of these seven were probable mutations of p27. The remaining four were probable pathological mutations in three of the other CDKI genes, thereby implicating these three genes in the germline of human tumors. The identification rates for probably pathological mutations among the 196 index cases were similarly low for each of four CDKI genes: p15 (1%), p18 (0.5%), p21 (0.5%), and p27 (1.5%). No characteristic clinical subtype related to MEN1 was identified among the seven index cases and their families. Rare germline mutation in any among four (p15, p18, p21, and p27) of the seven CDKIs is a probable cause of MEN1 or of some related states.

Familial isolated primary hyperparathyroidism caused by mutations of the MEN1 gene

Familial isolated primary hyperparathyroidism (FIHP) is an autosomal dominant disorder that can represent an early stage of either the multiple endocrine neoplasia type 1 (MEN1) or hyperparathyroidism-jaw tumor (HPT-JT) syndromes; alternatively, the condition can be caused by an allelic variant of MEN1 or HRPT2 (hyperparathyroidism 2 gene), or caused by a distinct entity involving another locus. We have explored these possibilities in a patient with primary hyperparathyroidism, whose mother had a history of renal calculi and primary hyperparathyroidism. Serum biochemistry and radiological investigations for primary hyperparathyroidism, MEN1 and HPT-JT, and genetic testing for MEN1 and HRPT2 mutations were undertaken. FIHP with primary hyperparathyroidism as the sole endocrinopathy due to a previously unreported heterozygous missense germline MEN1 mutation, Tyr351Asn. In addition, another unreported heterozygous missense germline MEN1 mutation, Trp220Leu, was identified in an unrelated male patient with FIHP, whose mother and sister also had primary hyperparathyroidism. DNA from a parathyroid tumor from the sister revealed a loss of heterozygosity in which the mutant allele was retained. This is consistent with Knudson's 'two-hit' model of hereditary cancer and a tumor suppressor role for MEN1 in FIHP. The patient underwent parathyroidectomy and has remained normocalcemic over a follow-up period of 6 years. The other four patients have remained normocalcemic for a follow-up period of 4-15 years following parathyroidectomy. None has developed abnormalities of the MEN1 syndrome, providing further support that FIHP is a distinct genetic variant of the MEN1 syndrome.

Novel MEN1 germline mutations in Brazilian families with multiple endocrine neoplasia type 1

To characterize clinical features and identify MEN1 germline mutations in Brazilian families with multiple endocrine neoplasia type 1 (MEN1). Settings Non-profit academic centre. Fourteen Brazilian families with MEN1 and 141 at-risk relatives. We identified 12 different MEN1 disease-causing mutations, seven of them previously unreported: 308delC; 375del21; 549A>T (I147F); 1243delA; 1348T>G (L413R); 1351T>C (L414P) and 1523G>T (W471C). Families with the recurrent mutations 360delTCTA and L413R were shown to be unrelated by mitochondrial-DNA and Y-chromosome haplotype analyses. Most of the MEN1 single point mutations involved evolutionarily conserved residues, whereas most of the deletion/frameshift changes occurred in GC-rich repetitive regions. Genetic screening of 141 at-risk family members identified 38 MEN1 mutation carriers, 37 (97.4%) of whom had at least one major MEN1-related tumour upon clinical investigation. High frequencies of MEN1 gene mutations were detected in Brazilian families with MEN1, including seven new genetic mutations that are predicted to cause inactivation of the MEN1 tumour suppressor gene. Our data underscore the need to implement a systematic MEN1 screening programme in Brazil.

Age‐related penetrance of endocrine tumours in multiple endocrine neoplasia type 1 (MEN1): a multicentre study of 258 gene carriers

In multiple endocrine neoplasia type 1 (MEN1), age-related tumour penetrance according to the type of MEN1 germline mutation has not been investigated in-depth. This study was conducted to examine whether carriers of out-of-frame/truncating and in-frame MEN1 mutations differ in age-related tumour penetrance. A multicentre study with biochemical, hormonal and radiological screening for MEN1-associated tumours. A total of 258 MEN1 carriers from six major German tertiary referral centres averaging 43 years of age at last follow-up. Main outcome measure was time to first diagnosis of MEN1-associated tumours. Independent of the year of birth and observation period, time to first tumour diagnosis did not vary much by the type of MEN1 germline mutation or endocrine organ system, and perhaps not even by the type of endocrine tumour when the amount of time was considered by which the diagnosis probably has been advanced through the manifestation of hormonal symptoms. Parathyroid hyperplasia and adenomas developed almost twice as often as enteropancreatic and pituitary tumours (77%vs. 49-32%), and more than five to sevenfold as often as adrenal cortical tumours and carcinoids (77%vs. 15-10%), reaching penetrance rates of up to 90%, 60%, 40%, 26% and 17%, respectively. The heterogeneity of tumour penetrance was marked, ranging from 9 years to 25 years for the earliest, and from 68 years to 77 years for the latest tumour manifestation. Because of our inability of predicting tumour penetrance and malignant transformation individually, life-long follow-up of MEN1 carriers is warranted to prevent tumour morbidity.