Developing Effective Screening Strategies in Multiple Endocrine Neoplasia Type 1 (MEN 1) on the Basis of Clinical and Sequencing Data of German Patients with MEN 1

An Update on the Genetic Drivers of Corticotroph Tumorigenesis

The genetic landscape of corticotroph tumours of the pituitary gland has dramatically changed over the last 10 years. Somatic changes in the USP8 gene account for the most common genetic defect in corticotrophinomas, especially in females, while variants in TP53 or ATRX are associated with a subset of aggressive tumours. Germline defects have also been identified in patients with Cushing's disease: some are well-established (MEN1, CDKN1B, DICER1), while others are rare and could represent coincidences. In this review, we summarise the current knowledge on the genetic drivers of corticotroph tumorigenesis, their molecular consequences, and their impact on the clinical presentation and prognosis.

Genetic diagnosis in acromegaly and gigantism: From research to clinical practice

It is usually considered that only 5% of all pituitary neuroendocrine tumours are due to inheritable causes. Since this estimate was reported, however, multiple genetic defects driving syndromic and nonsyndromic somatotrophinomas have been unveiled. This heterogeneous genetic background results in overlapping phenotypes of GH excess. Genetic tests should be part of the approach to patients with acromegaly and gigantism because they can refine the clinical diagnoses, opening the possibility to tailor the clinical conduct to each patient. Even more, genetic testing and clinical screening of at-risk individuals have a positive impact on disease outcomes, by allowing for the timely detection and treatment of somatotrophinomas at early stages. Future research should focus on determining the actual frequency of novel genetic drivers of somatotrophinomas in the general population, developing up-to-date disease-specific multi-gene panels for clinical use, and finding strategies to improve access to modern genetic testing worldwide.

[Comparative analysis of bone complications/manifestations in sporadic and MEN1-related primary hyperparathyroidism]

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN1) - is a rare syndrome with an autosomal dominant inheritance pattern caused by a mutation in the tumor suppressor gene (MEN1). Parathyroid involvement is the most common MEN1 manifestation resulting in primary hyperparathyroidism (mPHPT). Data on the prevalence and structure of bone disease in mPHPT compared to sporadic one (sPHPT) are often incomplete and contradictory.

AIM

The purpose of this study was to compare the severity of bone involvement between mPHPT and sPHPT.

MATERIALS AND METHODS

A single-center retrospective study was conducted among young patients in the active phase of PHPT and without prior parathyroidectomy in anamnesis. The analysis included the main parameters of calcium-phosphorus metabolism, bone remodeling markers, as well as an assessment of disease complications. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA) at sites of lumbar spine, femur and radius. Trabecular bone score (TBS) was applied to estimate trabecular microarchitecture. All patients included in the study underwent genetic testing.

RESULTS

Group 1 (mPHPT) included 26 patients, and group 2 (sSHPT) included 30 age-matched patients: the median age in group 1 was 34.5 years [25; 39], in group 2 - 30.5 years [28; 36], (p=0.439, U-test). Within group 1, the subgroup 1A (n=21) was formed with patients without other hormone-produced neuroendocrine neoplasms (NEN) in the gastrointestinal tract (GI) and the anterior pituitary gland. The duration of PHPT was comparable in both groups: mPHPT - 1 year [0; 3] versus sPHPT - 1 year [0; 1], (p=0.533, U-test). There were no differences in the main parameters of calcium-phosphorus metabolism, as well as in the prevalence of kidney complications. In the mPHPT group, bone abnormalities were observed significantly more often compared to sPHPT: 54 vs 10% (p=<0.001; F-test). Statistically significant differences were revealed both in BMD and in Z-score values of the femoral neck and total hip, which were lower in the mPHPT group. These differences remained significant when comparing subgroup 1A with sPHPT.

CONCLUSION

MEN1-associated PHPT may be accompanied by a more severe decrease in BMD in the femoral neck and total hip compared to sPHPT regardless of the other hormone-producing NEN. Clarifying the role of mutation in the MEN1 gene in these processes requires further study.

[Casuistic cases of parathyroid carcinoma with a verified mutation in the MEN1 gene]

Parathyroid cancer (PTC) is usually sporadic; however, it could be presented as a component of hereditary syndromes. The prevalence of PTC among patients with primary hyperparathyroidism (PHPT) is about 1% cases. The lack of reliable preoperative predictors significantly complicates the diagnosis of PTC. The clinical course is non-specific and in most cases is determined by severe hypercalcemia. The final diagnosis can only be made on the basis of invasive histopathologic features, while an analysis immunohistochemical (IHC) one can be used only as an additional method. Given the rarity the diagnosis of MEN1-related PTC a challenge. We present two clinical cases of patients with PTC and a verified heterozygous mutation in the MEN1 gene. The described cases demonstrate the complexity of morphological diagnosis for PTC, the heterogeneity of clinical manifestations in patients with the MEN1 mutation, as well as the need for timely screening to identify other components of MEN1 syndrome and mutations of the MEN1 gene among first-line relatives.

Novel PRUNE2 Germline Mutations in Aggressive and Benign Parathyroid Neoplasms

Parathyroid tumors are mostly sporadic but can also occur in familial forms, including different kinds of genetic syndromes with varying phenotypes and penetrance. Recently, somatic mutations of the tumor suppressor gene PRUNE2 were found to be frequent in parathyroid cancer (PC). The germline mutation status of PRUNE2 was investigated in a large cohort of patients with parathyroid tumors from the genetically homogenous Finnish population, 15 of which had PC, 16 atypical parathyroid tumors (APT), and 6 benign parathyroid adenomas (PA). Mutations in previously established hyperparathyroidism-related genes were screened with a targeted gene panel analysis. Nine PRUNE2 germline mutations with a minor allele frequency (MAF) of <0.05 were found in our cohort. Five of these were predicted to be potentially damaging and were identified in two patients with PC, two with APT, and three with PA. The mutational status was not associated with the tumor group nor related to the clinical picture or severity of the disease. Still, the frequent finding of rare germline mutations of PRUNE2 may point to the gene playing a role in the pathogenesis of parathyroid neoplasms.

[The clinical practice guidelines for primary hyperparathyroidism, short version]

Primary hyperparathyroidism (PHPT) is an endocrine disorder of parathyroid glands characterized by excessive secretion of parathyroid hormone (PTH) with an upper normal or elevated blood calcium level. Classical PHPT refers to a symptomatic, multi-system disorder, wich can lead to a significant decrease in the quality of life, disability of patients, and even an increased risk of premature death. Hypercalcemia and the catabolic effect of PTH on various cells are considered as the main pathogenetic mechanisms of the PHPT associated complications. In the last two decades, there has been an increase in the incidence of PHPT, mainly due to the mild forms of the disease, primarily due to the routine calcium screening in North America, Western Europe and, Asia. High prevalence of the disease, as well as the variety of clinical manifestations, cause the attention of different specialists - physicians, rheumatologists, urologists, nephrologists, cardiologists and other doctors. This review cover the main issues of Russian guidelines for the management of PHPT, approved in 2020, including laboratory and instrumental methods, differential diagnosis, surgical and conservative approach, short-term and long-term follow-up. This guidelines also include the recommendations for special groups of patients with hereditary forms of PHPT, parathyroid carcinoma, PHPT during pregnancy.

Patients' perception on the quality of care for multiple endocrine neoplasia disorders in Europe: an online survey from a patient support group

PURPOSE

European Patient Advocacy Groups (ePAGs) within the Endo-ERN identified a lack of knowledge about quality of care (QoC) of patients with multiple endocrine neoplasia (MEN). The aim of this study was to identify inequalities in care and to encourage improvements.

METHODS

The European MEN Alliance (EMENA) developed and conducted a survey, using the European Commissions' EUSurvey platform. Patient groups and healthcare professionals (HCPs) distributed the survey.

RESULTS

A total of 288 participants completed the survey (MEN1 n = 203, MEN2 n = 67, MEN3 n = 18) from 18 European countries. The majority of respondents were recruited via patient groups (58%), aged between 41 and 60 years (53%) and were female (67%). All participants reported having been diagnosed on average 5.58 years (95%-CI: 4.45-6.60) after first symptoms occurred. This timeframe was lower in the group with MEN2 (2.97 years, 95%-CI: 1.37-4.57). Most of the participants (67%) received their diagnosis by a positive gene test after presenting with one or more MEN-related tumours. Overall QoC was rated as either "good" (43%) or "excellent" (36%).

CONCLUSION

The results of this unique Europe-wide, patient-driven survey on QoC of patients with MEN show that ratings for overall QoC were lower than ratings for different aspects of care. This may be because of the complex nature of care for genetic syndromes. Furthermore, patients who connect with patient groups may be deemed "expert patients" whose answers are not representative of the overall MEN patient community. We hope that Endo-ERN can support further education and training for HCPs based on these results.

[Hereditary syndromal and nonsyndromal forms of primary hyperparathyroidism]

Primary hyperparathyroidism is a common disorder of mineral homeostasis, characterized by overproduction of parathyroid hormone and upper normal or elevated calcium levels due to hyperplasia or a tumor of parathyroid gland. 90&minus;95% of cases of primary hyperparathyroidism are sporadic, while hereditary genetic forms occur in 5&ndash;10% of all cases. Primary hyperparathyroidism as the component of hereditary syndromes can present in various clinical forms (asymptomatic, symptomatic), can be associated with other endocrine or non-endocrine diseases, and require special approaches to treatment. Given that primary hyperparathyroidism is one of the most common components of these syndromes, it can be used as an important diagnostic tool in identifying affected families. This review is devoted to modern ideas about the clinical course and genetic characteristics of hereditary variants of primary hyperparathyroidism and the diagnostic and treatment algorithms recommended today. The review considers primary hyperparathyroidism as a component of hereditary syndromes including multiple endocrine neoplasias types 1, 2A and 4 and syndrome of hyperparathyroidism with a jaw tumor. Also non-syndromic hereditary forms are descripted, such as familial isolated hyperparathyroidism, familial hypocalciuric hypercalcemia, and severe neonatal primary hyperparathyroidism.

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.

A novel germline mutation at exon 10 of MEN1 gene: a clinical survey and positive genotype-phenotype analysis of a MEN1 Italian family, including monozygotic twins

CONTEXT

Clinical phenotype variability in MEN1 syndrome exists and evidence for an established genotype-phenotype is lacking. However, a higher aggressiveness of MEN1-associated gastro-entero-pancreatic (GEP) (neuro)endocrine tumours (NETs) tumours has been reported when MEN1 gene truncating mutations are detected. We found a novel germline truncating mutation of MEN1 gene at exon 10 in a subject with an aggressive clinical behavior of GEP-NETs. Successively, other two mutant-affected familial members have been identified.

OBJECTIVE

The aim of this observational study was to investigate genotype-phenotype correlation in these three members, with attention to GPE-NETs behavior over the years.

DESIGN

The genetic and clinical data obtained and the follow-up screening program (2012-2016) were according to the International Guidelines in a multidisciplinary academic reference center. The familial history collected strongly suggested MEN1 GEP-NETs in at least other four members from different generations.

PATIENTS

Three MEN1 patients (aged 30-69 years at MEN1 diagnosis) were clinically screened for MEN1 GEP-NETs, both functioning and nonfunctioning.

METHODS

Biochemical, imaging, and nuclear medicine tests and fine-needle agobiopsy were performed, depending on found/emerging clinical symptoms/biochemical abnormalities, and made when necessary.

RESULTS

Our clinical survey found strong genotype-phenotype correlation with aggressive MEN1 GEP-NETs (G1, G2-NETs, and multiple ZES/gastrinomas) over the years. The familial history strongly suggested ZES/gastrinoma in progenitors from previous generations.

CONCLUSIONS

This novel MEN1 truncating mutation correlates with an aggressive evolution and behavior of MEN1 GEP-NETs in studied affected subjects, confirming the need for MEN1 individuals to be evaluated by a skilled multidisciplinary team, as also stated by International Guidelines.

Expression of p27Kip1 and p18Ink4c in human multiple endocrine neoplasia type 1-related pancreatic neuroendocrine tumors

PURPOSE

Pancreatic neuroendocrine tumors are a major manifestation of multiple endocrine neoplasia type 1 (MEN1). This tumor syndrome is caused by germline mutations in MEN1, encoding menin. Insight into pathogenesis of these tumors might lead to new biomarkers and therapeutic targets for these patients. Several lines of evidence point towards a role for p27^Kip1 and p18^Ink4c in MEN1-related tumor development in animal models for MEN1, but their contribution to human MEN1-related pancreatic neuroendocrine tumor development is not known.

METHODS

In this study, we characterized protein expression of p27^Kip1 and p18^Ink4c in human MEN1-related PanNETs by immunohistochemistry. From the nationwide DutchMEN1 Study Group database including > 90% of the Dutch MEN1 population, MEN1-patients, who underwent pancreatic surgery, were selected. A tissue micro-array was constructed with available paraffin tissue blocks, and PanNETs from 61 MEN1 patients were eligible for analysis.

RESULTS

Expression of p27^Kip1 was high in 57 (93%) PanNETs and 67% of the tumors showed low expression of p18^Ink4c (67.3%). No association was found between expression of either p27^Kip1 or p18^Ink4c and clinic-pathological characteristics.

CONCLUSIONS

These findings indicate that loss of p18^Ink4c, but not p27^Kip1, is a common event in the development of MEN1-related PanNETs. Restoration of p18^Ink4c function through CDK4/6 inhibitors could be a therapeutic option for MEN1-related PanNETs.

Current and emerging therapies for PNETs in patients with or without MEN1

Pancreatic neuroendocrine tumours (PNETs) might occur as a non-familial isolated endocrinopathy or as part of a complex hereditary syndrome, such as multiple endocrine neoplasia type 1 (MEN1). MEN1 is an autosomal dominant disorder characterized by the combined occurrence of PNETs with tumours of the parathyroids and anterior pituitary. Treatments for primary PNETs include surgery. Treatments for non-resectable PNETs and metastases include biotherapy (for example, somatostatin analogues, inhibitors of receptors and monoclonal antibodies), chemotherapy and radiological therapy. All these treatments are effective for PNETs in patients without MEN1; however, there is a scarcity of clinical trials reporting the efficacy of the same treatments of PNETs in patients with MEN1. Treatment of PNETs in patients with MEN1 is challenging owing to the concomitant development of other tumours, which might have metastasized. In recent years, preclinical studies have identified potential new therapeutic targets for treating MEN1-associated neuroendocrine tumours (including PNETs), and these include epigenetic modification, the β-catenin-wingless (WNT) pathway, Hedgehog signalling, somatostatin receptors and MEN1 gene replacement therapy. This Review discusses these advances.

Is Routine Screening of Young Asymptomatic MEN1 Patients Necessary?

BACKGROUND

Recent clinical practice guidelines recommend that routine screening of MEN1 mutation carriers should start at the age of 5 years. The occurrence of clinically relevant MEN1 organ manifestations in children (≤18 years) was evaluated.

METHODS

Two prospective collected databases of MEN1 patients (n = 166) who underwent annual screening were retrospectively analyzed for organ manifestations in MEN1 patients ≤18 years. The follow-up was based on the most recent screening examination until December 2015.

RESULTS

Twenty [11 females, 9 males, (12%)] of 166 MEN1 patients were diagnosed with at least one organ manifestation at age ≤18 years. The most frequent manifestation was mild asymptomatic pHPT (n = 9, 45%, age range 8-18 years). Eight (40%) young patients had pNENs (three non-functioning pNENs, five insulinomas, age range 9-18 years). All five insulinomas were diagnosed based on hypoglycemic symptoms. The other organ manifestations were asymptomatic pituitary adenomas in six patients (30%, age range 15-18 years) and a bronchial carcinoid in one 15-year-old patient. Only six (30%) patients ≤18 years had clinically relevant organ manifestations.

CONCLUSION

Symptomatic or severe manifestations in MEN1 patients rarely occur below the age of 16 years. With regard to psychological burden and cost-effectiveness, routine screening of asymptomatic MEN1 patients should be postponed at least until the age of 16 years.

Neuroendocrine Tumors in the Stomach, Duodenum, and Pancreas Accompanied by Novel MEN1 Gene Mutation

Multiple endocrine neoplasia type 1 (MEN1) syndrome is a relatively rare disease, characterized by the occurrence of multiple endocrine tumors in the parathyroid and pituitary glands as well as the pancreas. Here, we report a case of MEN1 with neuroendocrine tumors (NETs) in the stomach, duodenum, and pancreas. A 53-year-old man visited our hospital to manage gastric NET. Five years prior to his visit, he had undergone surgery for incidental meningioma. His brother had pancreatic nodules and a history of surgery for adrenal adenoma. His brother's daughter also had pancreatic nodules, but had not undergone surgery. The lesion was treated by endoscopic submucosal dissection and diagnosed as a grade 1 NET. Another small NET was detected in the second duodenal portion, resected by endoscopic submucosal dissection, which was also diagnosed as a grade 1 NET. During evaluation, three nodules were detected in the pancreas, and no evidence of pituitary, parathyroid tumors, or metastasis was observed. After surgery, the pancreatic lesions were diagnosed as NETs, with the same immunohistochemical patterns as those of the stomach and duodenum. Genetic testing was performed, and a heterozygous mutation was detected in the MEN1 gene, which is located on 11q13.

MEN1 redefined, a clinical comparison of mutation-positive and mutation-negative patients

BACKGROUND

Multiple Endocrine Neoplasia type 1 (MEN1) is diagnosed when two out of the three primary MEN1-associated endocrine tumors occur in a patient. Up to 10-30 % of those patients have no mutation in the MEN1 gene. It is unclear if the phenotype and course of the disease of mutation-negative patients is comparable with mutation-positive patients and if these patients have true MEN1. The present study aims to describe and compare the clinical course of MEN1 mutation-negative patients with two out of the three main MEN1 manifestations and mutation-positive patients during long-term follow-up.

METHODS

This is a cohort study performed using the Dutch MEN1 database, including > 90 % of the Dutch MEN1 population.

RESULTS

A total of 293 (90.7 %) mutation-positive and 30 (9.3 %) mutation-negative MEN1 patients were included. Median age of developing the first main MEN1 manifestation was higher in mutation-negative patients (46 vs. 33 years) (P = 0.007). Mutation-negative patients did not develop a third main MEN1 manifestation in the course of follow-up compared to 48.3 % of mutation-positive patients (P < 0.001). Median survival in mutation-positive patients was estimated at 73.0 years (95 % CI, 69.5-76.5) compared to 87.0 years (95 % CI not available) in mutation-negative patients (P = 0.001).

CONCLUSIONS

Mutation-positive and mutation-negative MEN1 patients have a different phenotype and clinical course. Mutation-negative patients develop MEN1 manifestations at higher age and have a life expectancy comparable with the general population. The apparent differences in clinical course suggest that MEN1 mutation-negative patients do not have true MEN1, but another MEN1-like syndrome or sporadic co-incidence of two neuro-endocrine tumors.

Thoracic and duodenopancreatic neuroendocrine tumors in multiple endocrine neoplasia type 1: natural history and function of menin in tumorigenesis

Mutations of the multiple endocrine neoplasia type 1 (MEN1) gene lead to loss of function of its protein product menin. In keeping with its tumor suppressor function in endocrine tissues, the majority of the MEN1-related neuroendocrine tumors (NETs) show loss of heterozygosity (LOH) on chromosome 11q13. In sporadic NETs, MEN1 mutations and LOH are also reported, indicating common pathways in tumor development. Prevalence of thymic NETs (thNETs) and pulmonary carcinoids in MEN1 patients is 2-8%. Pulmonary carcinoids may be underreported and research on natural history is limited, but disease-related mortality is low. thNETs have a high mortality rate. Duodenopancreatic NETs (dpNETs) are multiple, almost universally found at pathology, and associated with precursor lesions. Gastrinomas are usually located in the duodenal submucosa while other dpNETs are predominantly pancreatic. dpNETs are an important determinant of MEN1-related survival, with an estimated 10-year survival of 75%. Survival differs between subtypes and apart from tumor size there are no known prognostic factors. Natural history of nonfunctioning pancreatic NETs needs to be redefined because of increased detection of small tumors. MEN1-related gastrinomas seem to behave similar to their sporadic counterparts, while insulinomas seem to be more aggressive. Investigations into the molecular functions of menin have led to new insights into MEN1-related tumorigenesis. Menin is involved in gene transcription, both as an activator and repressor. It is part of chromatin-modifying protein complexes, indicating involvement of epigenetic pathways in MEN1-related NET development. Future basic and translational research aimed at NETs in large unbiased cohorts will clarify the role of menin in NET tumorigenesis and might lead to new therapeutic options.

Enucleation and limited pancreatic resection provide long-term cure for insulinoma in multiple endocrine neoplasia type 1

AIM

To assess the characteristics and long-term outcome after surgery in patients with multiple endocrine neoplasia type 1 (MEN1)-associated insulinoma.

METHODS

Retrospective analysis of prospectively collected data of MEN1 patients with organic hyperinsulinism at a tertiary referral center.

RESULTS

Thirteen (17%) of 74 patients with MEN1 had organic hyperinsulinism. The median age at diagnosis was 27 (range 9-48) years. In 7 patients insulinoma was the first manifestation of the syndrome. All patients had at least one pancreatic neuroendocrine neoplasm (pNEN) upon imaging, including CT, MRI or endoscopic ultrasonography. Seven patients had solitary lesions upon imaging, 4 patients had one dominant tumor with coexisting multiple small pNENs, and 2 patients had multiple lesions without dominance. Eight patients had limited resections (1 segmental resection, 7 enucleations), 4 subtotal distal pancreatectomies, and 1 patient a partial duodenopancreatectomy. There was no postoperative mortality. Six patients experienced complications, including pancreatic fistula in 5 patients. Pathological examination revealed median three (range 1-14) macro-pNENs sized between 6 and 40 mm, and a total of 14 potentially benign insulinomas were detected in the 13 patients. After median follow-up of 156 months, only 1 patient developed recurrent hyperinsulinism after initial enucleation. Twelve patients developed new pNENs in the pancreatic remnant and 4 patients underwent reoperations (3 for metastatic ZES, 1 for recurrent hyperinsulinism). One of 5 patients with an initial extended pancreatic resection developed insulin-dependent diabetes mellitus.

CONCLUSION

Enucleation and limited resection provide long-term cure for MEN1 insulinoma in patients with solitary or dominant tumors. Subtotal distal pancreatectomy should thus be preserved for patients with multiple pNENs without dominance given the risk of exocrine and endocrine pancreas insufficiency in the mostly young patients.

Recent results of basic and clinical research in MEN1: opportunities to improve early detection and treatment

Due to the variable expression of multiple endocrine neoplasia type 1 (MEN1), it is difficult to predict the course of the disease. However, knowledge about the normal function of the MEN1 gene product, together with the effects of cellular derangement by subsequent genetic events, has increased considerably. At first, the possible existence of a genotype-phenotype correlation is discussed. Thus, mild- and late-onset phenotypes may be distinguished from more malignant phenotypes depending on the character of the primary MEN1 disease gene mutation. Subsequently, tumor-promoting factors such as gender, additional genetic mutations and ecogenetic factors may contribute to the course of the disease. New developments in management are based on the knowledge and experience of the multidisciplinary teams involved. Finally, the metabolic effects of MEN1 mutations in aged patients are discussed. Early identification of predisposition to the disease, together with knowledge about the natural history of specific mutations, risks of additional mutations and periodic clinical monitoring, allow early treatment and may improve life expectancy and quality of life.

Menin missense mutants encoded by the MEN1 gene that are targeted to the proteasome: restoration of expression and activity by CHIP siRNA

CONTEXT

In multiple endocrine neoplasia type 1 (MEN1) characterized by tumors of parathyroid, enteropancreas, and anterior pituitary, missense mutations in the MEN1 gene product, menin, occur in a subset of cases. The mutant proteins are degraded by the proteasome. However, whether their expression and activity can be restored is not known.

OBJECTIVE

Our objective was to functionally characterize a panel of 16 menin missense mutants, including W423R and S443Y identified in new MEN1 families, with respect to protein stability, targeting to the proteasome and restoration of expression by proteasome inhibitors and expression and function by small interfering RNA technology.

METHODS

Flag-tagged wild-type (WT) and missense menin mutant expression vectors were transiently transfected in human embryonic kidney (HEK293) and/or rat insulinoma (Rin-5F) cells.

RESULTS

The majority of mutants were short-lived, whereas WT menin was stable. Proteasome inhibitors MG132 and PS-341 and inhibition of the chaperone, heat-shock protein 70 (Hsp70), or the ubiquitin ligase, COOH terminus of Hsp70-interacting protein (CHIP), by specific small interfering RNA, restored the levels of the mutants, whereas that of WT menin was largely unaffected. Inhibition of CHIP restored the ability of mutants to mediate normal functions of menin: TGF-β up-regulation of the promoters of its target genes, the cyclin-dependent kinase inhibitors p15 and p21 as well as TGF-β inhibition of cell numbers.

CONCLUSION

When the levels of missense menin mutants that are targeted to the proteasome are normalized they may function similarly to WT menin. Potentially, targeting specific components of the proteasome chaperone pathway could be beneficial in treating a subset of MEN1 cases.

Variable clinical expression in patients with a germline MEN1 disease gene mutation: clues to a genotype-phenotype correlation

Multiple endocrine neoplasia type 1 is an inherited endocrine tumor syndrome, predominantly characterized by tumors of the parathyroid glands, gastroenteropancreatic tumors, pituitary adenomas, adrenal adenomas, and neuroendocrine tumors of the thymus, lungs or stomach. Multiple endocrine neoplasia type 1 is caused by germline mutations of the multiple endocrine neoplasia type 1 tumor suppressor gene. The initial germline mutation, loss of the wild-type allele, and modifying genetic and possibly epigenetic and environmental events eventually result in multiple endocrine neoplasia type 1 tumors. Our understanding of the function of the multiple endocrine neoplasia type 1 gene product, menin, has increased significantly over the years. However, to date, no clear genotype-phenotype correlation has been established. In this review we discuss reports on exceptional clinical presentations of multiple endocrine neoplasia type 1, which may provide more insight into the pathogenesis of this disorder and offer clues for a possible genotype-phenotype correlation.

Long-term results of surgery for pancreatic neuroendocrine neoplasms in patients with MEN1

PURPOSE

This study was made to evaluate long-term results of an aggressive surgical approach for pancreaticoduodenal neuroendocrine neoplasms (pNENs) in patients with multiple endocrine neoplasia type 1 (MEN1).

METHODS

MEN1 patients with either biochemical evidence of functioning or non-functioning pNENs larger than 1 cm in size on imaging underwent duodenopancreatic surgery. Since 1997, patients were followed annually by biochemical testing and imaging studies.

RESULTS

Thirty-eight genetically confirmed MEN1 patients underwent duodenopancreatic resection for functioning (n = 22) or non-functioning (n = 16) pNENs, nine patients were yet not operated. Malignant disease occurred in 12 (35%) patients defined by either lymph node (12 patients) and/or distant metastases (2 patients). Six patients with Zollinger-Ellison syndrome (ZES) required pylorus-preserving pancreaticoduodenectomy (PPPD) as initial or redo procedure and 32 patients underwent other duodenopancreatic resections. Ten (26%) patients underwent up to four reoperations for either recurrent or metastatic disease that resulted in completion pancreatectomy in four patients. After median 109 months, 44 patients were alive and three patients died, one due to thymic carcinoid and two of unrelated causes. All eight patients with organic hyperinsulinism and 7 of 13 patients with ZES were biochemically cured. However, 24 of 38 (78%) patients developed new pNENs in the pancreatic remnant, but none developed distant metastases.

CONCLUSIONS

Early resection of pNENs in MEN1 may prevent the development of distant metastases. However, the majority of patients develop new pNENs in the duodenopancreatic remnant which may require completion pancreatectomy in the long term.

Neuroendocrine tumors and tumor syndromes in childhood

Endocrine and neuroendocrine cells form a large and diverse array of cell types. They are present in the form of specialized organs, such as the pituitary, parathyroid, thyroid, and adrenal gland, or in the form of the diffuse neuroendocrine system in the respiratory and digestive tracts. Neuroendocrine tumors are a heterogeneous group of neoplasms, yet they present certain unifying features. These include frequent hormonal overproduction that leads to specific symptoms and a typical immunohistochemical staining profile with chromogranin A and synaptophysin reactivity. Over the past decades, many neuroendocrine tumors have been described in the context of heritable tumor syndromes, and there exist several syndromes that are almost entirely composed of neuroendocrine tumors. Tumors occurring as part of these hereditary syndromes are characterized by specific genetic abnormalities that have helped our understanding of tumorigenesis, and they frequently appear at a young age. It is therefore important for the pediatric pathologist to be aware of specific histologic characteristics of neuroendocrine tumors in childhood and of their association with specific tumor syndromes. This may alert other clinicians to the possibility of multiple tumors in the patient or his family members. This review focuses on hereditary syndromes with neuroendocrine tumors, including multiple endocrine neoplasia types 1 and 2, Von Hippel-Lindau disease, neurofibromatosis type 1, Carney complex, pheochromocytoma-paraganglioma syndrome, and familial nonmedullary thyroid carcinoma. In addition, several individual neuroendocrine tumors are described, such as medullary thyroid carcinoma, gastroenteropancreatic tumors, pheochromocytoma, and paraganglioma, emphasizing specific histopathologic characteristics.

DNA-based test: when and why to apply it to primary hyperparathyroidism clinical phenotypes

Several cancer-related genes have been discovered and molecular test for the cancer genetic risk assessment has been widely increasing. Disorders such as Multiple Endocrine Neoplasia syndromes have received benefits from the identification of the responsible genes whose mutations account for the genetic susceptibility to develop endocrine tumours. Primary hyperparathyroidism (PHPT)is a clinical phenotype frequently associated to Multiple Endocrine Neoplasia syndromes, but it can also represent the unique endocrinopathy recurring as a familial cluster. In recent years, care options have been made available to patients and families with hereditary PHPT, and the process of systematically assessing the genetic risk has been becoming increasingly important. This review aims to help health providers not frequently dealing with genetic testing use and it will introduce some general concepts concerning genetic diagnosis issues. As an example the role and the practical usefulness of DNA-based diagnosis in patients affected by different forms of congenital PHPT is described, with a close look on why, when and how genetic testing should be performed in these subjects and their relatives. Some practical recommendations and suggestions concerning on how to deal when a suspect or known case of familial PHPT has to be faced conclude this manuscript.

Multiple endocrine neoplasia type 1 (MEN1): its manifestations and effect of genetic screening on clinical outcome

OBJECTIVE

Effect of genetic screening on outcome in multiple endocrine neoplasia type 1 (MEN1) remains unclear. Expression of MEN1 is described using currently available diagnostic techniques. Manifestations and outcome are compared in patients diagnosed because of clinical expression with those diagnosed by genetic screening.

DESIGN

Retrospective cohort study. Patients are divided into two groups: patients with a (i) clinical MEN1 diagnosis and (ii) MEN1 diagnosis by genetic screening.

PATIENTS AND MEASUREMENTS

Demographic and clinical data were collected on MEN1 patients treated in the UMCU up to 1 January 2008. Results of mutation analysis were obtained from the Department of Medical Genetics.

RESULTS

A total of 74 patients was included (median follow-up 5.5 year); 78% had hyperparathyroidism, 46% a pancreatic neuro-endocrine tumour (NET), 38% a pituitary abnormality, 8% a NET of other origin and 16% an adrenal adenoma at the end of follow-up. Of the patients 18% had no manifestation. All five MEN1-related tumours were seen as first manifestation. Compared with patients identified by genetic screening, patients with a clinical MEN1 diagnosis had significantly more manifestations at diagnosis (P < 0.001) and at end of follow-up (P = 0.002). Eleven of 30 patients with a genetic MEN1 diagnosis (mean age at diagnosis 30.0 years) already had manifestations at diagnosis. No malignancy or death was seen in genetically diagnosed patients.

CONCLUSIONS

MEN1 is a syndrome with high morbidity. Genetic diagnosis is associated with less morbidity at diagnosis and at follow-up. Early genetic diagnosis might therefore lead to improvement of long-term outcome.

[Indication and performance of endocrine surgery. The significance of molecular genetic examination]

The molecular genetic changes from certain endocrine tumors are already understood, reflecting as they do the etiology of these sporadic familial disorders. This already has clinical consequences to the treatment of familial endocrine tumors, which often appear in the course of syndromatic disorders. These consequences consist in slight changes to surgical technique, the search for other active and usually endocrinal tumors, and examination of family members for other gene carriers (of disease-specific mutations) and the most suitable prophylactic tumor therapy. In contrast, for sporadic endocrine tumors there exists far less clinically relevant knowledge. Starting with anamnesis and clinical findings of active endocrine tumors, we discuss the current possibilities for molecular genetic determination of disease-specific mutations (germline and tumor DNA) and their effect on surgical procedure.