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

Updates on the genetics of multiple endocrine neoplasia

Multiple endocrine neoplasia (MEN) is a group of syndromes with a genetic predisposition to the appearance of endocrine tumors, and shows autosomal dominant transmission. The advent of molecular genetics has led to improvements in the management of MEN in terms of diagnosis, prognosis and therapy. The genetics of MEN is the subject of regular updates, which will be presented throughout this paper. MEN1, the first to be described, is associated with the MEN1 gene. MEN1 is well known in terms of the observed phenotype, with genetic analysis being conclusive in 90% of patients with a typical phenotype, but is negative in around 10% of families with MEN1. Improvement in analysis techniques and the identification of other genes responsable for phenocopies allows the resolution of some, but not all, cases, notably non-familial forms suspected to be fortuitous assocations with tumors. MEN4 is a rare phenocopy of MEN1 linked to constitutional mutations in the CDKN1B gene. Though it closely resembles the phenotype of MEN1, published data suggests the appearance of tumors is later and less frequent in MEN4. MEN2, which results from mutations in the RET oncogene, shows a strong genotype-phenotype correlation. This correlation is particularly evident in the major manifestation of MEN2, medullary thyroid carcinoma (MTC), in which disease aggressiveness is dependent on the pathogenic variant of RET. However, recent studies cast doubt on this correlation between MTC and pathogenic variant. Lastly, the recent description of families carrying a mutation in MAX, which is known to predispose to the development of pheochromocytoma and paraganglioma, and presents a phenotypic spectrum that evokes MEN, suggests the existence of another syndrome, MEN5.

Familial MEN1 Syndrome Diagnosed on Functional Imaging: A Case Report with Clinical and Genetic Correlation

Multiple endocrine neoplasia, type 1 (MEN1) syndrome is an autosomal dominant disease characterized by tumors involving parathyroid, pituitary, and pancreas. The diagnosis is mostly clinical and by the presence of MEN1 gene mutation. We present a case with initial presentation of neuroendocrine tumor of pancreas whose ancillary findings on 68 Ga-DOTATATE positron emission tomography-computed tomography helped in raising suspicion of MEN1, which was confirmed on genetic testing and family history. We emphasize the importance of using gestalt approach in such cases to avoid misdiagnosis or delay. Additionally, we describe the clinical profile of affected family members with their MEN1 gene mutation status, highlighting the gestalt approach again to uncover the unknowns.

Clinical profile and treatment outcomes among patients with sporadic and multiple endocrine neoplasia syndrome-related primary hyperparathyroidism

OBJECTIVE

Accurate demarcation between multiple endocrine neoplasia, type 1 (MEN1)- related primary hyperparathyroidism (MPHPT) and sporadic PHPT (SPHPT) is important to plan the management of primary parathyroid disease and surveillance for other endocrine and nonendocrine tumours. The objective of this study is to compare the clinical, biochemical and radiological features and surgical outcomes in patients with MPHPT versus SPHPT and to identify the predictors of MEN1 syndrome in PHPT.

DESIGN, PATIENTS AND MEASUREMENTS

This was an ambispective observationalstudy involving 251 patients with SPHPT and 23 patients with MPHPT evaluated at the endocrine clinic of All India Institute of Medical Sciences, New Delhi, India between January 2015 and December 2021.

RESULTS

The prevalence of MEN1 syndrome among patients with PHPT was 8.2% and a genetic mutation was identified by Sanger sequencing in 26.1% of patients with MPHPT. Patients with MPHPT were younger (p < .001), had lower mean serum calcium (p = .01) and alkaline phosphatase (ALP; p = .03) levels and lower bone mineral density (BMD) Z score at lumbar spine (p < .001) and femoral neck (p = .007). The prevalence of renal stones (p = .03) and their complications (p = .006) was significantly higher in MPHPT group. On multivariable analysis, factors predictive of MPHPT were hyperplasia on histopathology [OR 40.1, p < .001], ALP levels within reference range [OR 5.6, p = .02] and lumbar spine BMD [OR 0.39 per unit increase in Z score, p < .001].

CONCLUSIONS

Patients with MPHPT have more severe, frequent and early onset of bone and renal involvement despite milder biochemical features. A normal serum ALP, low BMD for age and gender at lumbar spine and histopathology evidence of hyperplasia are predictive factors for MEN1 syndrome in PHPT.

Optimized minimal genome-wide human sgRNA library

Genome-wide clustered regularly interspaced short palindromic repeats (CRISPR)-based knockout screening is revolting the genetic analysis of a cellular or molecular phenotype in question but is challenged by the large size of single-guide RNA (sgRNA) library. Here we designed a minimal genome-wide human sgRNA library, H-mLib, which is composed of 21,159 sgRNA pairs assembled based on a dedicated selection strategy from all potential SpCas9/sgRNAs in the human genome. These sgRNA pairs were cloned into a dual-gRNA vector each targeting one gene, resulting in a compact library size nearly identical to the number of human protein-coding genes. The performance of the H-mLib was benchmarked to other CRISPR libraries in a proliferation screening conducted in K562 cells. We also identified groups of core essential genes and cell-type specific essential genes by comparing the screening results from the K562 and Jurkat cells. Together, the H-mLib exemplified high specificity and sensitivity in identifying essential genes while containing minimal library complexity, emphasizing its advantages and applications in CRISPR screening with limited cell numbers.

Cutaneous lesions and other non-endocrine manifestations of Multiple Endocrine Neoplasia type 1 syndrome

Background

Multiple Endocrine Neoplasia type 1 is a rare genetic syndrome mainly caused by mutations of MEN1 gene and characterized by a combination of several endocrine and non-endocrine manifestations. The objective of this study was to describe cutaneous lesions and other non-endocrine manifestations of MEN1 in a cohort of patients with familial (F) and sporadic (S) MEN1, compare the prevalence of these manifestations between the two cohorts, and investigate the correlation with MEN1 mutation status.

Methods

We collected phenotypic and genotypic data of 185 patients with F-MEN1 and S-MEN1 followed from 1997 to 2022. The associations between F-MEN1 and S-MEN1 or MEN1 mutation-positive and mutation-negative patients and non-endocrine manifestations were determined using chi-square or Fisher's exact tests or multivariate exact logistic regression analyses.

Results

The prevalence of angiofibromas was significantly higher in F-MEN1 than in S-MEN1 in both the whole (p < 0.001) and index case (p = 0.003) cohorts. The prevalence of lipomas was also significantly higher in F-MEN1 than in S-MEN1 (p = 0.009) and in MEN1 mutation-positive than in MEN1 mutation-negative (p = 0.01) index cases. In the whole cohort, the prevalence of lipomas was significantly higher in MEN1 mutation-positive compared to MEN1 mutation-negative patients (OR = 2.7, p = 0.02) and in F-MEN1 than in S-MEN1 (p = 0.03), only after adjustment for age. No significant differences were observed for the other non-endocrine manifestations between the two cohorts. Hibernoma and collagenoma were each present in one patient (0.5%) and meningioma and neuroblastoma in 2.7% and 0.5%, respectively. Gastric leiomyoma was present in 1.1% of the patients and uterine leiomyoma in 14% of women. Thyroid cancer, breast cancer, lung cancer, basal cell carcinoma, melanoma, and colorectal cancer were present in 4.9%, 2.7%, 1.6%, 1.6%, 2.2%, and 0.5% of the whole series, respectively.

Conclusions

We found a significantly higher prevalence of angiofibromas and lipomas in F-MEN1 compared with S-MEN1 and in MEN1 mutation-positive compared to MEN1 mutation-negative patients. In patients with one major endocrine manifestation of MEN1 , the presence of cutaneous lesions might suggest the diagnosis of MEN1 and a possible indication for genetic screening.

Multiple Endocrine Neoplasia Type 1 Syndrome Pancreatic Neuroendocrine Tumor Genotype/Phenotype: Is There Any Advance on Predicting or Preventing?

Multiple endocrine neoplasia type 1 syndrome (MEN1) is a disease caused by mutations in the MEN1 tumor suppressor gene leading to hyperparathyroidism, pituitary adenomas, and entero-pancreatic neuroendocrine tumors. Pancreatic neuroendocrine tumors (PNETs) are a major cause of mortality in patients with MEN1. Identification of consistent genotype-phenotype correlations has remained elusive, but MEN1 mutations in exons 2, 9, and 10 may be associated with metastatic PNETs; patients with these mutations may benefit from more intensive surveillance and aggressive treatment. In addition, epigenetic differences between MEN1-associated PNETs and sporadic PNETs are beginning to emerge, but further investigation is required to establish clear phenotypic associations.

A Direct Comparison of Patients With Hereditary and Sporadic Pancreatic Neuroendocrine Tumors: Evaluation of Clinical Course, Prognostic Factors and Genotype-Phenotype Correlations

Introduction

Pancreatic neuroendocrine tumors (PNETs) in hereditary syndromes pose a significant challenge to clinicians. The rarity of these syndromes and PNETs itself make it difficult to directly compare them with sporadic PNETs. Despite research suggesting differences between these two entities, the same approach is used in hereditary and sporadic PNETs.

Methods

We included 63 patients with hereditary PNET (GpNET) and 145 with sporadic PNET (SpNET) in a retrospective observational study. Clinical and genetic data were collected in two Polish endocrine departments from January 2004 to February 2020. Only patients with confirmed germline mutations were included in the GpNET cohort. We attempted to establish prognostic factors of metastases and overall survival in both groups and genotype-phenotype correlations in the GpNET group.

Results

Patients with GpNET were younger and diagnosed earlier, whereas their tumors were smaller and more frequently multifocal compared with patients with SpNET. Metastases occurred more frequently in the SpNET group, and their appearance was associated with tumor size in both groups. GpNET patients had longer overall survival (OS). OS was affected by age, age at diagnosis, sex, grade, stage, tumor diameter, occurrence and localization of metastases, type of treatment, and comorbidities. In the MEN1 group, carriers of frameshift with STOP codon, splice site, and missense mutations tended to have less advanced disease, while patients with mutations in exon 2 tended to have metastases more frequently.

Conclusions

Direct comparisons of GpNET and SpNET demonstrate significant differences in the clinical courses of both entities, which should force different approaches. A larger group of patients with GpNET should be assessed to confirm genotype-phenotype correlations.

A Parathyroid-Gut Axis: Hypercalcemia and the Pathogenesis of Gastrinoma in Multiple Endocrine Neoplasia 1

Patients with multiple endocrine neoplasia 1 (MEN1) syndrome have a germline mutation in the MEN1 gene. Loss of the wild-type allele can initiate endocrine tumorigenesis. Microscopic and macroscopic pituitary, parathyroid, and pancreatic tumors (referred to as the 3 P's) show loss of the wild-type MEN1 allele up to 100%. In contrast, the duodenal gastrinoma pathogenesis in MEN1 syndrome follows a hyperplasia-to-neoplasia sequence. Gastrinomas have loss of heterozygosity of the MEN1 locus in <50%, and invariably coincide with linear, diffuse, or micronodular gastrin-cell hyperplasia. The factor initiating the gastrin-cell hyperplasia-to-neoplasia sequence is unknown. In this perspective, we argue that hypercalcemia may promote the gastrin-cell hyperplasia-to-neoplasia sequence through the calcium sensing receptor. Hypercalcemia is present in almost all patients with MEN1 syndrome due to parathyroid adenomas. We propose a parathyroid-gut axis, which could well explain why patients with MEN1 syndrome are regularly cured of duodenal gastrinoma after parathyroid surgery, and might cause MEN1 syndrome phenocopies in MEN1-mutation negative individuals with parathyroid adenomas. This perspective on the pathogenesis of the gastrin-cell hyperplasia and neoplasia sequence sheds new light on tumorigenic mechanisms in neuroendocrine tumors and might open up novel areas of gastrinoma research. It may also shift focus in the treatment of MEN1 syndrome-related gastrinoma to biochemical prevention.

Molecular genetic testing strategies used in diagnostic flow for hereditary endocrine tumour syndromes

INTRODUCTION

Although current guidelines prefer the use of targeted testing or small-scale gene panels for identification of genetic susceptibility of hereditary endocrine tumour syndromes, next generation sequencing based strategies have been widely introduced into every day clinical practice. The application of next generation sequencing allows rapid testing of multiple genes in a cost effective manner. Increasing knowledge about these techniques and the demand from health care providers and society, shift the molecular genetic testing towards using high-throughput approaches.

PURPOSE

In this expert opinion, the authors consider the molecular diagnostic workflow step by step, evaluating options and challenges of gathering family information, pre- and post-test genetic counselling, technical and bioinformatical analysis related issues and difficulties in clinical interpretation focusing on molecular genetic testing of hereditary endocrine tumour syndromes.

RESULT AND CONCLUSION

Considering all these factors, a diagnostic genetic workflow is also proposed for selection of the best approach for testing of patients with hereditary genetic tumour syndromes in order to minimalize difficult interpretation, unwanted patient anxiety, unnecessary medical interventions and cost. There are potential benefits of utilizing high throughput approaches however, important limitations have to be considered and should discussed towards the clinicians and patients.

Comprehensive Analysis of MEN1 Mutations and Their Role in Cancer

Simple Summary

Cancers are characterized by accumulation of genetic mutations in key cell cycle regulators that alter or disable the function of these genes. Such mutations can be inherited or arise spontaneously during the life of the individual. The MEN1 gene prevents uncontrolled cell division and it is considered a tumor suppressor. Inherited MEN1 mutations are associated with certain parathyroid and pancreatic syndromes while spontaneous mutations have been detected in cancer cells. We investigated whether inherited mutations appear in cancer cells which would suggest that patients with parathyroid and pancreatic syndromes have a predisposition to develop cancer. We find a weak correlation between the spectrum of inherited mutations and those appearing spontaneously. Thus, inherited MEN1 mutations may not be a good predictor of tumorigenesis.

Abstract

MENIN is a scaffold protein encoded by the MEN1 gene that functions in multiple biological processes, including cell proliferation, migration, gene expression, and DNA damage repair. MEN1 is a tumor suppressor gene, and mutations that disrupts MEN1 function are common to many tumor types. Mutations within MEN1 may also be inherited (germline). Many of these inherited mutations are associated with a number of pathogenic syndromes of the parathyroid and pancreas, and some also predispose patients to hyperplasia. In this study, we cataloged the reported germline mutations from the ClinVar database and compared them with the somatic mutations detected in cancers from the Catalogue of Somatic Mutations in Cancer (COSMIC) database. We then used statistical software to determine the probability of mutations being pathogenic or driver. Our data show that many confirmed germline mutations do not appear in tumor samples. Thus, most mutations that disable MEN1 function in tumors are somatic in nature. Furthermore, of the germline mutations that do appear in tumors, only a fraction has the potential to be pathogenic or driver mutations.

Understanding the clinical course of genotype-negative MEN1 patients can inform management strategies

BACKGROUND

It is unclear whether genotype-negative clinical multiple endocrine neoplasia type 1 patients derive equal benefit from prospective surveillance as genotype-positive patients.

METHODS

In this retrospective cohort study, we compared genotype-negative patients with clinical multiple endocrine neoplasia type 1 with genotype-positive index cases. Primary outcome was age-related penetrance of manifestations; secondary outcomes were disease-specific survival and clinical course of endocrine tumors.

RESULTS

We included 39 genotype-negative patients with clinical multiple endocrine neoplasia type 1 (Male: 33%) and 63 genotype-positive multiple endocrine neoplasia type 1 index cases (Male: 59%). Genotype-negative patients with clinical multiple endocrine neoplasia type 1 were 65 years old at last follow-up; genotype-positive multiple endocrine neoplasia type 1 index cases were 50 (P < .001). Genotype-negative patients with clinical multiple endocrine neoplasia type 1 were significantly older at their first and second primary manifestation. Only 1 developed a third primary manifestation. No genotype-negative patients with clinical multiple endocrine neoplasia type 1 with primary hyperparathyroidism and a pituitary adenoma developed a duodenopancreatic neuroendocrine tumor. Disease-specific survival was significantly better in genotype-negative patients with clinical multiple endocrine neoplasia type 1. In genotype-negative patients with clinical multiple endocrine neoplasia type 1, primary hyperparathyroidism was single-gland disease in 47% of parathyroidectomies versus 0% in genotype-positive multiple endocrine neoplasia type 1 index cases. In genotype-negative patients with clinical multiple endocrine neoplasia type 1, 17% of duodenopancreatic neuroendocrine tumors were multifocal versus 68% in genotype-positive multiple endocrine neoplasia type 1 index cases. Genotype-negative patients with clinical multiple endocrine neoplasia type 1 had more pituitary macroadenomas, fewer prolactinomas, and more somatotroph adenomas.

CONCLUSION

Genotype-negative patients with clinical multiple endocrine neoplasia type 1 have a different clinical course than genotype-positive multiple endocrine neoplasia type 1 index cases. This may support a separate classification and a tailored surveillance regimen. Of the genotype-negative patients with clinical multiple endocrine neoplasia type 1 who had parathyroidectomy, almost half had no evidence of multigland disease and may be potential candidates for a more targeted single-gland approach.

Multiple endocrine neoplasia type 1 revealed by a hip pathologic fracture

Multiple endocrine neoplasia type 1 is a rare autosomal inherited syndrome that affects a variety of endocrine tissues such as the parathyroid, endocrine pancreas, and anterior pituitary. Osseous complications are often misdiagnosed. We presented a case of a 46-year-old woman with pathological fractures of the lower limb. She had a history of type 1 diabetes and galactorrhea. Laboratory examinations showed hypercalcemia and an increased level of parathyroid hormone related to hyperparathyroidism. Serum chromogranin A level was increased at 9369 ng/mL (N < 102). A somatostatin receptor scintigraphy (octreoscan) revealed pathological uptake in the gastric wall, later cave adenopathy, and liver. The diagnosis of multiple endocrine neoplasia type 1 was made based on radiological and histological findings. The patient underwent a subtotal parathyroidectomy associated with somatostatin analog treatment leading to significant improvement. A literature review was conducted by searching PubMed using these following terms: multiple endocrine neoplasia type 1, hyperparathyroidism, fracture, menin, osteoporosis. We emphasized bone involvement related to multiple endocrine neoplasia type 1 syndrome. This diagnosis should be considered when pathological fractures occur in young patients with a history of endocrine disorder. We highlighted the importance of imaging features in making the diagnosis of multiple endocrine neoplasia type 1. Early management of this disease is necessary. Treatment including parathyroidectomy and somatostatin analogs leads to bone preservation and functional improvement.

Features of Multiple Endocrine Neoplasia Type 1 and 2A in a Patient with Both RET and MEN1 Germline Mutations

The coexistence of multiple endocrine neoplasia type 1 (MEN1) and type 2A (MEN2A) is a rare occurrence and has been reported only twice in the literature. We present a patient with primary hyperparathyroidism and medullary thyroid cancer with strong family history of both MEN1- and MEN2A-associated conditions. Genetic testing showed the patient had a novel MEN1 loss-of-function mutation, c0.525_526insTT (p.Ala176Leufs*10), and an uncommon Cys630Tyr RET mutation. This case highlights the importance of obtaining a detailed family history when heritable endocrine disorders are suspected.

Phenotypes Associated With MEN1 Syndrome: A Focus on Genotype-Phenotype Correlations

Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant inherited tumor syndrome, associated with parathyroid, pituitary, and gastro-entero-pancreatic (GEP) neuroendocrine tumors (NETs). MEN1 is usually consequent to different germline and somatic mutations of the MEN1 tumor suppressor gene, although phenocopies have also been reported. This review analyzed main biomedical databases searching for reports on MEN1 gene mutations and focused on aggressive and aberrant clinical manifestations to investigate the potential genotype-phenotype correlation. Despite efforts made by several groups, this link remains elusive to date and evidence that aggressive or aberrant clinical phenotypes may be related to specific mutations has been provided by case reports and small groups of MEN1 patients or families. In such context, a higher risk of aggressive tumor phenotypes has been described in relation to frameshift and non-sense mutations, and predominantly associated with aggressive GEP NETs, particularly pancreatic NETs. In our experience a novel heterozygous missense mutation at c.836C>A in exon 6 was noticed in a MEN1 patient operated for macro-prolactinoma, who progressively developed recurrent parathyroid adenomas, expanding gastrinomas and, long after the first MEN1 manifestation, a neuroendocrine uterine carcinoma. In conclusion, proof of genotype-phenotype correlation is limited but current evidence hints at the need for long-term interdisciplinary surveillance in patients with aggressive phenotypes and genetically confirmed MEN1.

Using Structural Analysis In Silico to Assess the Impact of Missense Variants in MEN1

Despite the rapid expansion in recent years of databases reporting either benign or pathogenic genetic variations, the interpretation of novel missense variants remains challenging, particularly for clinical or genetic testing laboratories where functional analysis is often unfeasible. Previous studies have shown that thermodynamic analysis of protein structure in silico can discriminate between groups of benign and pathogenic missense variants. However, although structures exist for many human disease‒associated proteins, such analysis remains largely unexploited in clinical laboratories. Here, we analyzed the predicted effect of 338 known missense variants on the structure of menin, the MEN1 gene product. Results provided strong discrimination between pathogenic and benign variants, with a threshold of >4 kcal/mol for the predicted change in stability, providing a strong indicator of pathogenicity. Subsequent analysis of seven novel missense variants identified during clinical testing of patients with MEN1 showed that all seven were predicted to destabilize menin by >4 kcal/mol. We conclude that structural analysis provides a useful tool in understanding the effect of missense variants in MEN1 and that integration of proteomic with genomic data could potentially contribute to the classification of novel variants in this disease.