MEN1 gene mutations in Hungarian patients with multiple endocrine neoplasia type 1

Clinical and molecular features of four Brazilian families with multiple endocrine neoplasia type 1

OBJECTIVE

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant syndrome characterized by its clinical variability and complexity in diagnosis and treatment. We performed both clinical and molecular descriptions of four families with MEN1 in a follow-up at a tertiary center in Brasília.

METHODS

From a preliminary review of approximately 500 medical records of patients with pituitary neuroendocrine tumor (PitNET) from the database of the Neuroendocrinology Outpatient Clinic of the University Hospital of Brasília, a total of 135 patients met the criteria of at least two affected family members. From this cohort, we have identified 34 families: only four with a phenotype of MEN1 and the other 30 families with the phenotype of familial isolated pituitary adenoma (FIPA). Eleven patients with a clinical diagnosis of MEN1 from these four families were selected.

RESULTS

Variants in MEN1 gene were identified in all families. One individual from each family underwent genetic testing using targeted high-throughput sequencing (HTS). All patients had primary hyperparathyroidism (PHPT), and the second most common manifestation was PitNET. One individual had well-differentiated liposarcoma, which has been previously reported in a single case of MEN1. Three variants previously described in the database and a novel variant in exon 2 have been found.

CONCLUSIONS

The study allowed the genotypic and phenotypic characterization of families with MEN1 in a follow-up at a tertiary center in Brasília.

True MEN1 or phenocopy? Evidence for geno-phenotypic correlations in MEN1 syndrome

PURPOSE

Multiple endocrine neoplasia type 1 is a rare tumor syndrome caused by germline mutations of MEN1 gene. Phenotype varies widely, and no definitive correlation with the genotype has been observed. Mutation-negative patients with MEN1-associated tumors represent phenocopies. By comparing mutation-positive and mutation-negative patients, we aimed to identify phenotype features predictive for a positive genetic test and to evaluate the role of MEN1 mutations in phenotype modulation.

METHODS

Mutation screeening of MEN1 gene by Sanger sequencing and assessment of clinical data of 189 consecutively enrolled probands and relatives were performed at our national and European Reference Center. Multiple ligation probe amplification analysis of MEN1 gene and Sanger sequencing of CDKN1B were carried out in clinically suspicious but MEN1-negative cases.

RESULTS

Twenty-seven probands and twenty family members carried MEN1 mutations. Five mutations have not been described earlier. Pronouncedly high number of phenocopies (>70%) was observed. Clinical suspicion of MEN1 syndrome emerged at significantly earlier age in MEN1-positive compared to MEN1-negative probands. Gastroenteropancreatic neuroendocrine tumors developed significantly earlier and more frequently in carriers compared to non-carriers. Probands with high-impact (frameshift, nonsense, large deletions) mutations, predicted to affect menin function significantly, developed GEP-NETs more frequently compared to low-impact (inframe and missense) mutation carriers.

CONCLUSIONS

MEN1 phenocopy is common and represents a significant confounder for the genetic testing. GEP-NET under 30 years best predicted a MEN1 mutation. The present study thus confirmed a previous proposal and suggested that GEP-NET under 30 years should be considered as a part of the indication criteria for MEN1 mutational analysis.

Novel Mutations in Serbian MEN1 Patients: Genotype-phenotype Correlation

Background

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant cancer syndrome characterized by the occurrence of primary hyperparathyroidism (PHPT), pituitary adenoma (PA) and pancreatic neuroendocrine tumor (pNET). Whether the underlying mutations in MEN1 gene predict clinical presentation of affected heterozygotes or not, is still a matter of a debate.

Methods

Clinical and genetic analysis of 90 consecutive MEN1 patients was performed in a retrospective, single – center study.

Results

MEN1 mutation was found in 67 (74.4%) patients belonging to 31 different families. Twenty nine different heteozygous mutations were found, including 6 novel point mutations (W220G, 941delG, 1088del7, 1184insA, 1473del10, 1602del17) and one large deletion of exon 8. Truncating mutations predicted development of pNETs (OR=5.8, 95% CI 1.7 – 19.7%) and PHPT (OR=4.3, 95% CI 1.5 – 12.4%).

Conclusions

Large number of novel mutations among MEN1 patients confirmed previously reported data. PNETs and PHPT were more frequent in patients with truncating mutations.

Mutational and large deletion study of genes implicated in hereditary forms of primary hyperparathyroidism and correlation with clinical features

The aim of this study was to carry out genetic screening of the MEN1, CDKN1B and AIP genes, both by direct sequencing of the coding region and multiplex ligation-dependent probe amplification (MLPA) assay in the largest monocentric series of Italian patients with Multiple Endocrine Neoplasia type 1 syndrome (MEN1) and Familial Isolated Hyperparathyroidism (FIHP). The study also aimed to describe and compare the clinical features of MEN1 mutation-negative and mutation-positive patients during long-term follow-up and to correlate the specific types and locations of MEN1 gene mutations with onset and aggressiveness of the main MEN1 manifestations. A total of 69 index cases followed at the Endocrinology Unit in Pisa over a period of 19 years, including 54 MEN1 and 15 FIHP kindreds were enrolled. Seven index cases with MEN1 but MEN1 mutation-negative, followed at the University Hospital of Cagliari, were also investigated. FIHP were also tested for CDC73 and CaSR gene alterations. MEN1 germline mutations were identified in 90% of the index cases of familial MEN1 (F-MEN1) and in 23% of sporadic cases (S-MEN1). MEN1 and CDC73 mutations accounted for 13% and 7% of the FIHP cohort, respectively. A CDKN1B mutation was identified in one F-MEN1. Two AIP variants of unknown significance were detected in two MEN1-negative S-MEN1. A MEN1 positive test best predicted the onset of all three major MEN1-related manifestations or parathyroid and gastro-entero-pancreatic tumors during follow-up. A comparison between the clinical characteristics of F and S-MEN1 showed a higher prevalence of a single parathyroid disease and pituitary tumors in sporadic compared to familial MEN1 patients. No significant correlation was found between the type and location of MEN1 mutations and the clinical phenotype. Since all MEN1 mutation-positive sporadic patients had a phenotype resembling that of familial MEN1 (multiglandular parathyroid hyperplasia, a prevalence of gastro-entero-pancreatic tumors and/or the classic triad) we might hypothesize that a subset of the sporadic MEN1 mutation-negative patients could represent an incidental coexistence of sporadic primary hyperparathyroidism and pituitary tumors or a MEN1 phenocopy, in our cohort, as in most cases described in the literature.

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 variants in familial pituitary tumour syndrome genes are common in young patients and families with additional endocrine tumours

OBJECTIVE

Familial pituitary tumour syndromes (FPTS) account for 5% of pituitary adenomas. Multi-gene analysis via next-generation sequencing (NGS) may unveil greater prevalence and inform clinical care. We aimed to identify germline variants in selected patients with pituitary adenomas using a targeted NGS panel.

DESIGN

We undertook a nationwide cross-sectional study of patients with pituitary adenomas with onset ≤40 years of age and/or other personal/family history of endocrine neoplasia. A custom NGS panel was performed on germline DNA to interrogate eight FPTS genes. Genome data were analysed via a custom bioinformatic pipeline, and validation was performed by Sanger sequencing. Multiplex ligation-dependent probe amplification (MLPA) was performed in cases with heightened suspicion for MEN1, CDKN1B and AIP mutations. The main outcomes were frequency and pathogenicity of rare variants in AIP, CDKN1B, MEN1, PRKAR1A, SDHA, SDHB, SDHC and SDHD.

RESULTS

Forty-four patients with pituitary tumours, 14 of whom had a personal history of other endocrine tumours and/or a family history of pituitary or other endocrine tumours, were referred from endocrine tertiary-referral centres across Australia. Eleven patients (25%) had a rare variant across the eight FPTS genes tested: AIP (p.A299V, p.R106C, p.F269F, p.R304X, p.K156K, p.R271W), MEN1 (p.R176Q), SDHB (p.A2V, p.S8S), SDHC (p.E110Q) and SDHD (p.G12S), with two patients harbouring dual variants. Variants were classified as pathogenic or of uncertain significance in 9/44 patients (20%). No deletions/duplications were identified in MEN1, CDKN1B or AIP.

CONCLUSIONS

A high yield of rare variants in genes implicated in FPTS can be found in selected patients using an NGS panel. It may also identify individuals harbouring more than one rare variant.

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.

Genetic and epigenetic analysis in korean patients with multiple endocrine neoplasia type 1

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN1) is a familial syndrome characterized by the parathyroid, pancreas and pituitary tumors. Parathyroid tumors are the most common clinical manifestations, occurring in more than 90% of MEN1 patients. Heterozygous germline mutations of the MENIN gene underlie the tumorigenesis in MEN1 and epigenetic alterations along with germline mutations may contribute to tumorigenesis. Here, we investigated the associations between genotype and phenotype in Korean MEN1 patients.

METHODS

We analyzed medical records from 14 unrelated MEN1 patients who had newly confirmed MENIN germline mutations, together with 14 previous reports in Korea. Aberrant DNA methylations were also examined in MEN1-related parathyroid tumors using the Infinium HumanMethylation 450 BeadChip.

RESULTS

Total 28 germline mutations of MENIN were relatively highly concentrated in exons 7 and 8 compared to previous reports from Western countries. Six mutations (c.111dupT/p.S38Ffs(*)79, c.225_226insT/p.T76Yfs(*)41, c.383_398del16/p.S128Tfs(*)52, c.746dupT/p.H250Afs(*)20, c.1150G>T/p.E384(*), and c.1508G>A/p.G503N) were newly found in the present study. Of interest, four patients (15%) showed unusual initial presentations and three patients were diagnosed incidentally at the general medical checkup. We also found three distinct sites in exon 2 of MENIN were significantly hypomethylated in the MEN1 parathyroid tumors, comparing correspondent blood samples.

CONCLUSION

We also have found a lack of genotype/phenotype correlation in Korean MEN1 patients. There were not a few unusual initial manifestations in MEN1 patients, thus, genetic testing for the MENIN germline mutations can provide important information for the better prognosis. Further studies are warranted to investigate altered DNA methylations in the MENIN gene involved in tumorigenesis.

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.

Assessment of p27 (cyclin-dependent kinase inhibitor 1B) and aryl hydrocarbon receptor-interacting protein (AIP) genes in multiple endocrine neoplasia (MEN1) syndrome patients without any detectable MEN1 gene mutations

OBJECTIVE

Germline mutations in the MEN1 gene predispose to the multiple endocrine neoplasia (MEN1) syndrome; however, approximately 10-20% of patients with MEN1 do not have a detectable MEN1 mutation. A rat strain with multiple endocrine tumours, a phenotypic overlap of both MEN1 and MEN2, has been reported to have a homozygous germline p27 (CDKN1B) mutation. Recently, two MEN1 mutation-negative MEN1 syndrome patients have been identified to harbour a germline CDKN1B mutation. The recently identified gene AIP can also cause familial isolated pituitary adenoma, but no other specific tumour is associated with this syndrome. The objective of this study was to evaluate the possible contribution of CDKN1B and AIP germline mutations in a cohort of MEN1 mutation-negative MEN1 syndrome patients.

PATIENTS

Eighteen sporadic and three familial cases of MEN1 mutation-negative MEN1 syndrome were studied (18 pituitary adenomas, 12 hyperparathyroidism, 10 neuroendocrine tumours including 2 ACTH-secreting lesions and one adrenal nodular hyperplasia). Clinical data and genomic DNA were analysed for mutations in the CDKN1B and AIP genes.

RESULTS

There were no mutations in the coding region or exon/intron junction of the CDKN1B and AIP genes in any patient. Although we have a limited number of patients in our cohort, our data is consistent with others in the literature suggesting that CDKN1B and AIP mutations are extremely rare in MEN1 syndrome.

CONCLUSION

Our results suggest that mutations in the CDKN1B and AIP genes are relatively uncommon in MEN1 mutation-negative MEN1 syndrome patients.

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

Reverse referral: from pathology to endocrinology

Establishing a diagnosis of multiple endocrine neoplasia type 1 (MEN1) especially in children, adolescents, and young adults can be challenging because of phenotypic heterogeneity even among family members. We report an adolescent girl diagnosed to have MEN1 following presentation with multiple collagenomas. Histological evaluation of her cutaneous lesions revealed >70 collagenomas. Hormonal evaluation included calcium, phosphate, and parathormone measurements. Exons 2-10 of the MEN1 gene and flanking intron-exon borders were sequenced and revealed a novel nonsense mutation, Y222X. Following the identification of the cutaneous lesions as collagenomas by the pathologist, the patient was referred for an endocrine evaluation which revealed asymptomatic primary hyperparathyroidism. The patient elected to have surgery at which time she was found to have parathyroid hyperplasia. This case emphasizes the usefulness of cutaneous findings for the diagnosis and management of MEN1.