Molecular tools for presymptomatic testing in multiple endocrine neoplasia type 1

Transcriptional alterations in hereditary and sporadic nonfunctioning pancreatic neuroendocrine tumors according to genotype

BACKGROUND

Nonfunctioning pancreatic neuroendocrine tumors (NFPanNETs) may be sporadic or inherited because of germline mutations associated with von Hippel-Lindau disease (VHL) or multiple endocrine neoplasia type 1 (MEN1). The clinical behavior of NFPanNETs is difficult to predict, even in tumors of the same stage and grade. The authors analyzed genotype-specific patterns of transcriptional messenger RNA (mRNA) levels of NFPanNETs to understand the molecular features that determine PanNET phenotype.

METHODS

Thirty-two samples were included for genome-wide mRNA gene expression analysis (9 VHL-associated, 10 MEN1-associated, and 9 sporadic NFPanNETs and 4 purified normal islet cell [NIC] samples). Validation of genes was performed by real-time polymerase chain reaction analysis and immunohistochemistry. Gene expression profiles were analyzed by tumor genotype, and pathway analysis was curated.

RESULTS

Consensus clustering of mRNA expression revealed separate clustering of NICs, VHL-associated NFPanNETs, and MEN1-associated NFPanNETs; whereas some sporadic tumors clustered with MEN1. Four of 5 MEN1-like sporadic PanNET subtypes had loss of heterozygosity at the MEN1 gene locus. Pathway analysis demonstrated subtype-specific pathway activation, comprising angiogenesis and immune response in VHL; neuronal development in MEN1; protein ubiquitination in the new MEN1/sporadic subtype; and cytokinesis and cilium/microtubule development in sporadic NFPanNETs. Among many genes, platelet-derived growth factor receptor β (PDGFRB), lymphoid enhancer-binding factor-1 (Lef-1), cyclin-dependent kinase 4 (CDK4), and CDK6 were upregulated in VHL or MEN1 NFPanNETs, providing potential subtype-specific treatment targets.

CONCLUSIONS

Distinct mRNA expression patterns were identified in sporadic-associated, VHL-associated, and MEN1-associated NFPanNETs. The current results uncover new pathways involved in NFPanNETs that are subtype-specific and provide potential new diagnostic or therapeutic targets based on tumor subtype. Cancer 2018;124:636-47. © 2017 American Cancer Society.

Multiple endocrine neoplasms

Multiple endocrine neoplasia type 1 (MEN1) and type 2 (MEN2) are rare autosomal-dominant disorders characterized by primary tumours in at least two different endocrine tissues. Both syndromes present as sporadic (a single case with two of the characteristic endocrine tumours) or familial form (an MEN case plus at least one first-degree relative showing one of the characteristic endocrine tumours). MEN1 is characterized by the occurrence of parathyroid, gastro-entero-pancreatic and anterior pituitary tumours, but it can include various combinations of more than 20 endocrine and non-endocrine tumours. Generally, tumours in MEN1 are benign, although gastrinomas and foregut carcinoids may exhibit a malignant course. MEN2 is characterized by medullary thyroid carcinoma (MTC), uni- or bi-lateral pheochromocytoma, and other tumours of different endocrine tissues. If not diagnosed precociously, MTC can be fatal. MEN1 develops after tissue inactivation of both MEN1 gene copies. Activating mutations of c-RET proto-oncogene causes MEN2.

A kindred of familial acromegaly without evidence for linkage to MEN-1 locus

Familial acromegaly (FA) is a rare inherited disease characterized by clustering of somatotrophic adenomas and acromegaly within a family without other manifestations of multiple endocrine neoplasia-type 1 (MEN-1). The genetic basis of this pituitary-specific phenotype is largely unknown, and its relationship to the MEN-1 locus on chromosome 11q13 also remains unclear. To test the hypothesis that FA results from a germline mutation of the MEN-1 locus, we performed a linkage analysis in a Japanese family with 2 members showing manifestations of acromegaly due to somatotroph adenomas. We also examined the adenoma of one patient for loss of heterozygosity (LOH) at 11q13 locus and for the presence of mutations of codon 201 and 227 in the gene for Gsalpha. Our results provided no evidence that either germline alterations of the MEN-1 locus, LOH at 11q13, or somatic mutation of Gsalpha plays a causative role in the development of somatotroph adenomas in our FA family. Together with the previous reports, these results suggest that there are at least two distinct subgroups of FA: one that results from a mutation in MEN-1 locus and the other whose causative gene is located outside the 11q13 locus.

Loss of heterozygosity of the MEN1 gene in a large series of TSH-secreting pituitary adenomas

Thyrotropin-secreting pituitary adenomas (TSH-omas) are rare tumors (0.5% of all pituitary adenomas) showing an invasive behavior and usually sporadic, although a few cases are associated with multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant inherited syndrome. This disorder is linked to loss of heterozygosity (LOH) on 11q13 and inactivating mutations of MEN1 gene, which is located in the same chromosomal region. As other types of anterior pituitary adenomas, TSH-omas are the result of a monoclonal outgrowth where the intrinsic genetic defects involving oncogenes or tumor suppressor genes occur in a progenitor cell. However, so far no activating mutations of particular oncogenes or inactivating mutations of tumor suppressor genes have been identified. Starting from the observation that 3-30% of sporadic pituitary adenomas show LOH on 11q13, and that allelic losses on the long arms of chromosome 11, beside 10 and 13, are significantly associated with the transition from the non-invasive to the invasive phenotype, we decided to investigate LOH on 11q13 and mutations of menin in a large series of TSH-omas. Thirteen tumors were evaluated. DNA was extracted from tumors by standard methods and genomic DNA from peripheral blood leukocytes was used as control. LOH was screened by using 3 polymorphic markers on 11q13: D11S956, PYGM, INT-2. In 3 out of 15 cases we could demonstrate LOH on 11q13, but none of the tumors showed menin mutation after sequence analysis. These data strongly suggest that menin does not play a causative role in the development of TSH-omas, and are in agreement with other studies demonstrating a limited role of menin in pituitary sporadic tumorigenesis.

Common ancestral mutation in the MEN1 gene is likely responsible for the prolactinoma variant of MEN1 (MEN1Burin) in four kindreds from Newfoundland

Familial multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder with affected individuals developing parathyroid, gastrointestinal (GI) endocrine, and anterior pituitary tumors. Four large kindreds from the Burin peninsula/Fortune Bay area of Newfoundland with prominent features of prolactinomas, carcinoids, and parathyroid tumors (referred to as MEN1Burin) have been described, and they show linkage to 11q13, the same locus as that of MEN1. Haplotype analysis with 16 polymorphic markers now reveals that representative affected individuals from all four families share a common haplotype over a 2.5 Mb region. A nonsense mutation in the MEN1 gene has been found to be responsible for the disease in the affected members in all four of the MEN1Burin families, providing convincing evidence of a common founder.

Type 1 multiple endocrine neoplasia (MEN1): contribution of genetic analysis to the screening and follow-up of a large French kindred

OBJECTIVE

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal genetic disorder, the clinical phenotype of which includes tumours of the parathyroids and/or anterior pituitary and/or endocrine pancreas. The genetic defect has been mapped to the chromosome 11q13 and the MEN1 gene has been recently identified, thus allowing genetic screening in affected kindreds. The aim of this study was to establish the usefulness of genetic screening in the follow-up of a large MEN1 kindred.

PATIENTS

We describe a large kindred of 91 members, of whom 56 had clinical, biochemical and genetic screening. Twenty eight of them have been tested annually for the last 5 years.

RESULTS

Although the precise mutation is still undetermined in this kindred, genotypic determination confirmed linkage with the MEN1 gene in affected members and excluded 28 members from annual testing. By drawing our attention to susceptible subjects, genetic screening improved the evaluation of age-related penetrance of the disease in the 3 generations from this kindred. For instance, annual screening showed conversion from unaffected to affected phenotype in 4 subjects aged 14, 14, 15, and 17 years. Moreover, genetics helped us to evaluate the specificity of clinical or biochemical markers, and thus to discard useless investigations. So far however, the genetics have not helped to explain the phenotypic heterogeneity and particularly low incidence of pancreatic tumours in this kindred.

CONCLUSION

Genetic screening is very useful in detecting high risk individuals for MEN 1, since it avoids time-consuming and expensive investigations in non-affected subjects. By providing better understanding of the age-related penetrance of this syndrome, it improves the efficiency of screening. Genetic studies allow differentiation between clinical and biochemical features that are useful in follow-up and other confusing or unhelpful parameters.

Parathyroid MEN1 gene mutations in relation to clinical characteristics of nonfamilial primary hyperparathyroidism

Biochemical signs and severity of symptoms of primary hyperparathyroidism (pHPT) differ among patients, and little is known of any coupling of clinical characteristics of nonfamilial pHPT to genetic abnormalities in the parathyroid tumors. Mutations in the recently identified MEN1 gene at chromosome 11q13 have been found in parathyroid tumors of nonfamilial pHPT. Using microsatellite analysis for loss of heterozygosity (LOH) at 11q13 and DNA sequencing of coding exons, the MEN1 gene was studied in 49 parathyroid lesions of patients with divergent symptoms, operative findings, histopathological diagnosis, and biochemical signs of nonfamilial pHPT. Allelic loss at 11q13 was detected in 13 tumors, and 6 of them demonstrated previously unrecognized somatic missense and frameshift deletion mutations of the MEN1 gene. Many of the detected mutations would most likely result in a nonfunctional menin protein, consistent with a tumor suppressor mechanism. Clinical and biochemical characteristics of HPT were apparently unrelated to the presence or absence of LOH and the MEN1 gene mutations. However, the demonstration of LOH at 11q13 and MEN1 gene mutations in small parathyroid adenomas of patients with slight hypercalcemia and normal serum PTH levels suggest that altered MEN1 gene function may also be important for the development of mild sporadic pHPT.

Germ-line mutation analysis in patients with multiple endocrine neoplasia type 1 and related disorders

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant syndrome predisposing to tumors of the parathyroid, endocrine pancreas, anterior pituitary, adrenal glands, and diffuse neuroendocrine tissues. The MEN1 gene has been assigned, by linkage analysis and loss of heterozygosity, to chromosome 11q13 and recently has been identified by positional cloning. In this study, a total of 84 families and/or isolated patients with either MEN1 or MEN1-related inherited endocrine tumors were screened for MEN1 germ-line mutations, by heteroduplex and sequence analysis of the MEN1 gene-coding region and untranslated exon 1. Germ-line MEN1 alterations were identified in 47/54 (87%) MEN1 families, in 9/11 (82%) isolated MEN1 patients, and in only 6/19 (31.5%) atypical MEN1-related inherited cases. We characterized 52 distinct mutations in a total of 62 MEN1 germ-line alterations. Thirty-five of the 52 mutations were frameshifts and nonsense mutations predicted to encode for a truncated MEN1 protein. We identified eight missense mutations and five in-frame deletions over the entire coding sequence. Six mutations were observed more than once in familial MEN1. Haplotype analysis in families with identical mutations indicate that these occurrences reflected mainly independent mutational events. No MEN1 germ-line mutations were found in 7/54 (13%) MEN1 families, in 2/11 (18%) isolated MEN1 cases, in 13/19 (68. 5%) MEN1-related cases, and in a kindred with familial isolated hyperparathyroidism. Two hundred twenty gene carriers (167 affected and 53 unaffected) were identified. No evidence of genotype-phenotype correlation was found. Age-related penetrance was estimated to be >95% at age >30 years. Our results add to the diversity of MEN1 germ-line mutations and provide new tools in genetic screening of MEN1 and clinically related cases.

Identification and characterization of the multiple endocrine neoplasia type 1 (MEN1) gene

For nearly a decade since the mapping of the multiple endocrine neoplasia type 1 (MEN1) locus to 11q13 and the suggestion that it is a tumour suppressor gene, efforts have been made to identify the gene responsible for this familial cancer syndrome. Recently, we have identified the MEN1 gene by the positional cloning approach. This effort involved construction of a 2.8-Mb physical map (D11S480-D11S913) based primarily on a bacterial clone contig. Using these resources, 20 new polymorphic markers were isolated which helped to reduce the interval for candidate genes by haplotype analysis in families and by loss of heterozygosity (LOH) studies in approximately 200 tumours, utilizing laser-assisted microdissection to obtain tumour cells with minimal or no admixture by normal cells. The interval was narrowed by LOH to only 300 kb, and nearly 20 new transcripts that map to this region of 11q13 were isolated and characterized. One of the transcripts was found by dideoxyfingerprinting and cycle sequencing to harbour deleterious germline mutations in affected individuals from MEN-1 kindreds and therefore identified as the MEN1 gene. The type of germline mutations and the identification of mutations in sporadic tumours support the Knudson's two-hit model of tumorigenesis for MEN-1. Efforts are being made to identify the function of the MEN1 gene-encoded protein, menin, and to study its role in tumorigenesis.

Characterization of mutations in patients with multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors of the parathyroids, pancreatic islets, and anterior pituitary. The MEN1 gene, on chromosome 11q13, has recently been cloned, and mutations have been identified. We have characterized such MEN1 mutations, assessed the reliability of SSCP analysis for the detection of these mutations, and estimated the age-related penetrance for MEN1. Sixty-three unrelated MEN1 kindreds (195 affected and 396 unaffected members) were investigated for mutations in the 2,790-bp coding region and splice sites, by SSCP and DNA sequence analysis. We identified 47 mutations (12 nonsense mutations, 21 deletions, 7 insertions, 1 donor splice-site mutation, and 6 missense mutations), that were scattered throughout the coding region, together with six polymorphisms that had heterozygosity frequencies of 2%-44%. More than 10% of the mutations arose de novo, and four mutation hot spots accounted for >25% of the mutations. SSCP was found to be a sensitive and specific mutational screening method that detected >85% of the mutations. Two hundred and one MEN1 mutant-gene carriers (155 affected and 46 unaffected) were identified, and these helped to define the age-related penetrance of MEN1 as 7%, 52%, 87%, 98%, 99%, and 100% at 10, 20, 30, 40, 50, and 60 years of age, respectively. These results provide the basis for a molecular-genetic screening approach that will supplement the clinical evaluation and genetic counseling of members of MEN1 families.

Loss of heterozygosity at 11q13: analysis of pituitary tumors, lung carcinoids, lipomas, and other uncommon tumors in subjects with familial multiple endocrine neoplasia type 1

Loss of heterozygosity (LOH) for polymorphic markers flanking the multiple endocrine neoplasia type 1 (MEN-1) gene in parathyroid and pancreatic islet tumors from subjects with familial MEN-1 (FMEN-1) has been well documented and has led to the hypothesis that the MEN-1 gene functions as a tumor suppressor. To assess the role of the MEN-1 gene in the pathogenesis of tumors less commonly associated with MEN-1, we employed a large number of highly informative polymorphic markers closely linked to the MEN-1 gene to study a series of 13 such tumors from subjects with FMEN-1 for LOH at 11q13. We were able to identify LOH for 1 or more 11q13 markers in 2 of 3 pituitary tumors, 3 lung carcinoids, and 1 of 2 lipomas. In every case studied, the allele lost represented the normal allele inherited from the unaffected parent. No LOH was detected in 3 skin angiofibromas, an esophageal leiomyoma, or a renal angiomyolipoma despite the presence of at least 2 informative markers for each tumor. Our results suggest that, like that for parathyroid and pancreatic islet tumors, the pathogenesis of pituitary tumors, lung carcinoids, and lipomas occurring in subjects with FMEN-1 probably involves loss of the normal tumor suppressor function of the MEN-1 gene. Our inability to detect 11q13 LOH in skin angiofibromas, leiomyoma, and angiomyolipoma from subjects with FMEN-1 is consistent with the possibility that these neoplasms arose independently by a mechanism unrelated to the MEN-1 gene, but a role for the MEN-1 gene in the pathogenesis of these tumors cannot be definitively excluded until the gene itself is identified and evaluated for small intragenic deletions or point mutations in such tumors.

Parathyroid glands and the multiple endocrine neoplasia syndromes and familial hypocalciuric hypercalcemia

Hypercalcemia is a variable feature of inherited endocrine disorders. In the multiple endocrine neoplasia (MEN) syndromes, generalized hyperparathyroidism is a common feature. It occurs much more frequently in patients with MEN type 1 as compared to patients with MEN type 2A. Unlike the MEN syndromes, patients with familial hypocalciuric hypercalcemia (FHH) have only hypercalcemia with no associated endocrinopathies. The hyperparathyroidism in patients with either of the MEN syndromes is managed by parathyroidectomy, whereas patients with FHH are managed nonoperatively. The specific genetic defects associated with MEN type 2 syndromes and FHH have been identified. They explain, in part, the clinical and pathophysiologic features of these diseases. The genetic defect causative of MEN type 1 will doubtless soon be found and thereby provide further insights into the molecular basis of calcium homeostasis. We will review the clinical presentation and the management of patients with these disorders. We will also review the recent molecular discoveries in MEN 2A, MEN 2B, and FHH, and define how they have altered the management of patients who have these syndromes.

Clinicopathologic studies of thymic carcinoids in multiple endocrine neoplasia type 1

Thymic carcinoid is part of the multiple endocrine neoplasia type 1 (MEN1) syndrome occurring predominantly in male patients who were heavy smokers, presenting most commonly in middle age. In contrast with metastatic midgut carcinoids, MEN1-related thymic carcinoid is not associated with carcinoid syndrome, nor is it associated with Cushing syndrome, in contrast with sporadic thymic carcinoids. Local invasion and metastasis are common. Prognosis is poor because of late detection, lack of effective treatment, and the aggressive nature of the tumor. All patients with thymic carcinoids should be investigated for MEN1, including thorough clinical evaluation and family studies. Anterior mediastinal lesions in MEN1 male patients should be considered thymic carcinoids until proven otherwise. All male MEN1 patients and asymptomatic gene carriers should be warned of the risk of thymic carcinoids and the possible link to smoking. Computed tomography (CT) of the chest is recommended on first screening for MEN1 in male patients more than 25 years of age, followed by yearly chest X-rays and chest CT every 3 years. Prophylactic thymectomy should be carried out during subtotal or total parathyroidectomy on MEN1 patients.