Diagnostic and therapeutic difficulties in MEN 1 syndrome

MEN 1 syndrome (Multiple Endocrine Neoplasia type 1) is a rare endocrine disorder characterized by the association of tumors in several endocrine glands, mainly in parathyroids, gut and pituitary. At our institution in the years 1982-2004 we have followed 26 patients with MEN 1 syndrome belonging to 19 families. The diagnosis of MEN 1 was based on Gubbio Consensus (JCEM 86: 5658-5671, 2001). Mean age at the diagnosis of MEN 1 was 35 years. Primary hyperparathyroidism was the most frequent pathology, which was diagnosed in 25 of 26 patients (96%). Gut endocrine tumors were found in 20 patients (77%), while pituitary tumors in 18 (70%). Non-functioning gut tumors were most frequent (n=9), followed by insulinoma (n=7) and gastrinoma (n=4). Prolactinoma was the most frequent pituitary tumor found in 12 patients (67%). Three patients died during the observation period - all of them of generalized gut endocrine tumor (gastrinoma in 2 cases and foregut carcinoid in one case). The management of MEN 1 is not easy and careful analysis of clinical picture is necessary in each individual case. Several important observations can be made on the basis of own experience and the literature: 1. In each sporadic pathology, which may be a part of MEN 1, one should consider. the possibility of MEN 1. The individual MEN 1 abnormalities are often diagnosed after 40 and later 2. MEN 1 tumor are usually multiple thus necessitating a different therapeutic approach (more radical surgery) 3. The most valuable screening tests are: Ca++, PP, CgA and prolactin 4. Endoscopic ultrasound is the most specific method for the localization of pancreatic endocrine tumors. 5. The results of surgical treatment of MEN 1 tumors are worse than that of sporadic tumors. 6. Prognosis in MEN 1 is determined by the behaviour of gut neuroendocrine tumor 7. No genotype/phenotype correlation in MEN 1 syndrome was found so far. In summary, it should be underlined that MEN 1 syndrome is an endocrine disorder, in which early diagnosis and optimal treatment may significantly improve the prognosis.     

Molecular and genetic mechanisms of tumorigenesis in multiple endocrine neoplasia type-1

Multiple endocrine neoplasia type 1 (MEN1) is a rare but informative syndrome for endocrine tumorigenesis. Since its isolation, several groups have begun to determine the role of menin, the protein product of MEN1, in sporadic endocrine tumors as well as tumors of the MEN1 syndrome. Mutations of menin have been reported in more than 400 families and tumors, most of which are truncating mutations, thus supporting the function of menin as a tumor suppressor. The exact function of menin is unknown, but overexpression of menin inhibits proliferation of Ras-transformed NIH3T3 cells. Since menin interacts with proteins from both the TGF beta and AP-1 signaling pathways, perhaps its tumor suppressor function is related to these key cell growth pathways. In this review we will discuss the various clinical manifestations of MEN1 syndrome, potential mechanisms of MEN1 tumorigenesis, and mutations associated with MEN and sporadic endocrine tumors.     

1型多发性内分泌腺肿瘤综合征Men1基因变异

1型多发性内分泌瘤综合征（multiple endocrine neoplasia type1,MEN1）是一种主要以累及甲状旁腺、胰岛细胞和垂体的家族性常染色体显性遗传性肿瘤疾病,其致病基因是Men1的基因突变。目前在MEN1患者中发现了大量Men1基因突变位点,其中9个位点突变频率较高,占据所有胚系细胞突变的20％,同时,MEN1患者中还存在Men1基因大片段的外显子缺失,具有外显率高和临床表现多样化的特点,与1型多发性内分泌瘤以及零散型内分泌肿瘤都可能相关。因此,在部分疑似MEN1患者中开展Men1基因变异分析可辅助确诊,在Men1基因突变携带者及其家属中开展Men1变异筛选将有助于对MEN1发生做好提前预防和治疗。     

Heterozygous Men1 mutant mice develop a range of endocrine tumors mimicking multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary syndrome characterized by the occurrence of multiple endocrine tumors of the parathyroid, pancreas, and anterior pituitary in patients. To study tumorigenesis related to the MEN1 syndrome, we have generated Men1 knockout mice using the gene targeting approach. Heterozygous Men1 mutant mice developed the same range of major endocrine tumors as is seen in MEN1 patients, affecting the parathyroid, pancreatic islets, pituitary and adrenal glands, as well as the thyroid, and exhibiting multistage tumor progression with metastatic potential. In particular, extrapancreatic gastrinoma, pancreatic glucagonoma, and mixed hormone-producing tumors in islets were observed. In addition, there was a high incidence of gonadal tumors of endocrine origin, i.e. Leydig cell tumors, and ovary sex-cord stromal cell tumors in heterozygous Men1 mutant mice. Hormonal disturbance, such as abnormal PTH and insulin levels, was also observed in these mice. These tumors were associated with loss of heterozygosity of the wild-type Men1 allele, suggesting that menin is involved in suppressing the development of these endocrine tumors. All of these features are reminiscent of MEN1 symptoms in humans and establish heterozygous Men1 mutant mice as a suitable model for this disease.     

Fine-scale mapping of the gene responsible for multiple endocrine neoplasia type 1 (MEN 1).

We have constructed a high-resolution genetic linkage map in the vicinity of the gene responsible for multiple endocrine neoplasia type 1 (MEN1). The mutation causing this disease, inherited as an autosomal dominant, predisposes carriers to development of neoplastic tumors in the parathyroid, the endocrine pancreas, and the anterior lobe of the pituitary. The 12 markers on the genetic linkage map reported here span nearly 20 cM, and linkage analysis of MEN1 pedigrees has placed the MEN1 locus within the 8-cM region between D11S480 and D11S546. The markers on this map will be useful for prenatal or presymptomatic diagnosis of individuals in families that segregate a mutant allele of the MEN1 gene.     

GSK-3β Protein Phosphorylates and Stabilizes HLXB9 Protein in Insulinoma Cells to Form a Targetable Mechanism of Controlling Insulinoma Cell Proliferation

Insulinomas (pancreatic islet β cell tumors) are the most common type of functioning pancreatic neuroendocrine tumors that occur sporadically or as a part of the MEN1 syndrome that is caused by germ line mutations in MEN1. Tissue-specific tumor predisposition from germ line mutations in ubiquitously expressed genes such as MEN1 could occur because of functional consequences on tissue-specific factors. We previously reported the proapoptotic β cell differentiation factor HLXB9 as a downstream target of menin (encoded by MEN1). Here we show that GSK-3β inactivates the proapoptotic activity of HLXB9 by phosphorylating HLXB9 at Ser-78/Ser-80 (pHLXB9). Although HLXB9 is found in the nucleus and cytoplasm, pHLXB9 is predominantly nuclear. Both pHLXB9 and active GSK-3β are elevated in β cells with menin knockdown, in MEN1-associated β cell tumors (insulinomas), and also in human sporadic insulinomas. Pharmacologic inhibition of GSK-3β blocked cell proliferation in three different rodent insulinoma cell lines by arresting the cells in G₂/M phase and caused apoptosis. Taken together, these data suggest that the combination of GSK-3β and pHLXB9 forms a therapeutically targetable mechanism of insulinoma pathogenesis. Our results reveal that GSK-3β and pHLXB9 can serve as novel targets for insulinoma treatment and have implications for understanding the pathways associated with β cell proliferation.     

Manifestations cliniques et diagnostic échoendoscopique des tumeurs endocrines digestives

Gastroenteropancreatic endocrine tumors are rare and need a multidisciplinary approach. Some of them are only found in the pancreas: insulinomas, glucagonomas and VIPomas wether other are located in the duodenum or in the small intestine. Clinical presentation depends on the site of the primary tumor and whether they are functioning tumors. Best known functioning tumors are those secreting gastrin with the so-called Zollinger–Ellison syndrome. Endoscopic ultrasonography is not used in the first place. It is particularly sensitive for identification of small tumor like pancreatic insulinomas and in the context of MEN1. Fine-needle aspiration may give diagnosis but also prognosis informations.     

Genome-wide characterization of menin-dependent H3K4me3 reveals a specific role for menin in the regulation of genes implicated in MEN1-like tumors

Inactivating mutations in the MEN1 gene predisposing to the multiple endocrine neoplasia type 1 (MEN1) syndrome can also cause sporadic pancreatic endocrine tumors. MEN1 encodes menin, a subunit of MLL1/MLL2-containing histone methyltransferase complexes that trimethylate histone H3 at lysine 4 (H3K4me3). The importance of menin-dependent H3K4me3 in normal and transformed pancreatic endocrine cells is unclear. To study the role of menin-dependent H3K4me3, we performed in vitro differentiation of wild-type as well as menin-null mouse embryonic stem cells (mESCs) into pancreatic islet-like endocrine cells (PILECs). Gene expression analysis and genome-wide H3K4me3 ChIP-Seq profiling in wild-type and menin-null mESCs and PILECs revealed menin-dependent H3K4me3 at the imprinted Dlk1-Meg3 locus in mESCs, and all four Hox loci in differentiated PILECs. Specific and significant loss of H3K4me3 and gene expression was observed for genes within the imprinted Dlk1-Meg3 locus in menin-null mESCs and the Hox loci in menin-null PILECs. Given that the reduced expression of genes within the DLK1-MEG3 locus and the HOX loci is associated with MEN1-like sporadic tumors, our data suggests a possible role for menin-dependent H3K4me3 at these genes in the initiation and progression of sporadic pancreatic endocrine tumors. Furthermore, our investigation also demonstrates that menin-null mESCs can be differentiated in vitro into islet-like endocrine cells, underscoring the utility of menin-null mESC-derived specialized cell types for genome-wide high-throughput studies.     

Haploinsufficient and predominant expression of multiple endocrine neoplasia type 1 (MEN1)-related genes, MLL, p27Kip1 and p18Ink4C in endocrine organs

Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominantly inherited syndrome characterized by parathyroid, gastro-entero-pancreatic and anterior pituitary tumors. Although the tissue selectivity of tumors in specific endocrine organs is the very essence of MEN1, the mechanisms underlying the tissue-selectivity of tumors remain unknown. The product of the Men1 gene, menin, and mixed lineage leukemia (MLL) have been found to cooperatively regulate p27(Kip1)/CDKN1B (p27) and p18(Ink4C)/CDKN2C (p18) genes. However, there are no reports on the tissue distribution of these MEN1-related genes. We investigated the expression of these genes in the endocrine and non-endocrine organs of wild-type, Men1 knockout and MLL knockout mice. Men1 mRNA was expressed at a similar level in endocrine and non-endocrine organs. However, MLL, p27 and p18 mRNAs were predominantly expressed in the endocrine organs. Notably, p27 and MLL mRNAs were expressed in the pituitary gland at levels approximately 12- and 17-fold higher than those in the liver. The heterozygotes of Men1 knockout mice the levels of MLL, p27 and p18 mRNAs did not differ from those in the wild-type mice. In contrast, heterozygotes of MLL knockout mice showed significant reductions in p27 mRNA as well as protein levels in the pituitary and p27 and p18 in the pancreatic islets, but not in the liver. This study demonstrated for the first time the predominant expression MEN1-related genes, particularly MLL and p27, in the endocrine organs, and a tissue-specific haploinsuffiency of MLL, but not menin, may lead to a decrease in levels of p27 and p18 mRNAs in endocrine organs. These findings may provide basic information for understanding the mechanisms of tissue selectivity of the tumorigenesis in patients with MEN1.     

Pancreatic polypeptide-related tumors

PP-producing tumors are mostly located in the pancreas and may present as three pathologic lesions: pure PP-omas, mixed tumors with minor PP cell population, and PP-cell hyperplasia. These tumors are among the most common multiple adenomas frequently found in patients with multiple endocrine neoplasia type 1. Hypersecretion and high circulating levels of PP are frequently found. They are symptomless but may be useful for the identification of the pancreatic tumors. Numerous types of extrapancreatic endocrine tumors are able to synthesize and secrete PP. They occur mostly but not exclusively in the gastrointestinal tract, particularly in the rectum. The inactivation of the MEN 1 gene at 11q13 appears to be involved in the development of pancreatic but not of rectal PP-producing tumors.     

Mapping of a novel MEN-like syndrome locus to rat Chromosome 4

Multiple endocrine neoplasia-like syndrome (MENX) is a hereditary cancer syndrome in the rat characterized by inborn cataract and multiple tumors affecting the neuroendocrine system developed within the first year of life. The spectrum of affected organs is intermediate between MEN type 1 (MEN1) and MEN type 2 (MEN2) syndromes in human, but, in contrast to them, MENX is inherited in a recessive fashion. Here we report the mapping of the MENX locus to rat Chromosome (Chr) 4 by a genome-wide linkage analysis. This analysis was done in 41 animals obtained from a (Wistar/Nhg × SD^we) × SD^we interstrain backcross, where SD^we (Sprague-Dawley white eye) indicates the affected animals. The MENX disease locus was ultimately mapped to a ~22-cM interval on Chr 4 that includes the rat homolog of the human RET proto-oncogene. As activating point mutations of RET are known to be responsible for MEN2 in human, we analyzed several markers located in the proximity of Ret for linkage to the disease phenotype. Our data exclude Ret involvement in MENX and establish that a second gene, playing a role in endocrine tumor formation, lies within the distal part of rat Chr 4. Although heritable human endocrine tumors are quite rare, sporadic tumors of MEN-affected tissues occur at a much higher frequency, and their pathogenesis is poorly understood. The identification of the MENX gene should contribute to our understanding of the genetic mechanisms of neuroendocrine tissue tumorigenesis and may assist in developing new and more appropriate therapeutic strategies for these diseases.     

Clinical and genetic profile of patients with medullary thyroid cancer treated in the Cancer Centre--Institute of Oncology in Warsaw

INTRODUCTION: The aim of this study was to analyse the distribution and frequency of mutations and their correlations with clinical phenotypes of patients with MTC, to reveal the differences between sporadic and familial type of MTC, and to describe the phenotypes of patients. MATERIALS AND METHODS: 212 patients with medullary thyroid cancer (MTC) were treated in Cancer Centre in Warsaw between 1997 and 2005. In most patients, DNA isolated from peripheral blood leukocytes was tested for RET gene mutations by sequencing and accordingly MTC form was assessed. Genetic testing was performed in the relatives of patients with familial MTC in order to distinguish asymptomatic mutation carriers from noncarriers. RESULTS: RET gene mutations were identified in 46 patients (22%). The others were found noncarriers and sporadic MTC was diagnosed. MEN 2A/FMTC syndrome (multiple endocrine neoplasia type 2A/ familial type of MTC) was diagnosed in 44 patients, MEN 2B syndrome (multiple endocrine neoplasia type 2B) in 2 patients. In patients with sporadic and familial MTC, age at diagnosis and multifocal occurrence was analysed, and the results were found to be in accordance with those of other research centres. However, the distribution and frequency of mutations, as well as some clinical data, such as the frequency of pheochromocytoma occurrence as the first manifestation of MEN syndrome, differed from the published data, and further studies are necessary to reveal the reasons of these differences. CONCLUSIONS: DNA testing for RET gene mutations is reliable as a diagnostic tool and therefore it should be performed for screening of all patients with MTC or other diseases of MEN syndrome.     

Synchronous Thymoma and Thymic Carcinoid in A Woman With Multiple Endocrine Neoplasia Type 1: Case Report and Review

ObjectiveTo report a rare case of multiple endocrine neoplasia type 1 (MEN 1) in conjunction with concomitant thymoma and thymic carcinoid.MethodsWe describe a never before reported case involving a 63-year-old female patient with MEN 1 who had synchronous thymoma and thymic carcinoid tumors. A review of the pertinent literature is also undertaken.ResultsAlthough prognosis is stage dependent for patients with thymoma, patients with thymic carcinoids and MEN 1 have been reported to have an extremely poor prognosis, with many patients dying of complications from thymic carcinoid rather than dying of other manifestations of MEN 1. Our patient underwent successful surgical treatment and remains under surveillance for all aspects of the MEN 1 syndrome.ConclusionThymic tumors are rare, and thymic carcinoids, while very rare in occurrence overall, have a definite association with MEN 1. Thus, it is important for practitioners to screen for thymic tumors routinely in patients with MEN 1 and to treat such tumors aggressively when found because they can be a major cause of mortality. Many thymic carcinoids are far advanced before diagnosis, and optimal screening for and treatment of thymic carcinoid are still being developed. (Endocr Pract. 2008;14:713-716)     

Description of the first two seemingly unrelated Greek Cypriot families with a common C618R RET proto-oncogene mutation

Germ-line mutations of the RET proto-oncogene cause three different cancer syndromes: multiple endocrine neoplasia type 2A (MEN2A), multiple endocrine neoplasia type 2B, and familial medullary thyroid carcinoma (FMTC). The objective of the present study was the clinical and molecular characterization of the first two Greek Cypriot families diagnosed with MEN2A and FMTC. The clinical diagnosis of the probands was based on clinical presentation and supported with laboratory findings (calcitonin and carcinoembryonic antigen tumor marker levels). We screened the RET gene by direct DNA sequencing of exons 10, 11, and 16 using genomic DNA as templates. After identification of the mutation, we also developed the amplification refractory mutation system (ARMS) as an alternative method to direct sequencing for genetic diagnosis of 22 additional individuals from both families. We identified the germ-line missense mutation T --> C of codon 618 of exon 10 (C618R) in the probands of both families. By using ARMS, two members of the MEN2A family and five members of the FMTC family were also found positive for the C618R mutation. These are the first seemingly unrelated families in Cyprus investigated clinically and molecularly in detail and shown to transmit this common RET proto-oncogene mutation.     

Classification et aspects anatomopathologiques des tumeurs endocrines digestives

Gastrointestinal and pancreatic endocrine tumors GIPET are rare and represent only 2 % of malignant tumors. Beyond their common features, endocrine tumors are characterized by a marked diversity, which results from the large functional, structural and embryological heterogeneity of normal endocrine cells. Despite the rational basis for predicting prognosis provided by the WHO classification, there is no reliable means of predicting the clinical course of patients with gastrointestinal and pancreatic endocrine tumors. The current criteria used for the definition of the tumor grade remain unsatisfactory. According to the WHO classification system, pathologists vary significantly in their reporting of endocrine tumors. Recently, the European Neuroendocrine Tumour Society (ENETS) has proposed a TNM (tumor–node–metastasis) classification for gastrointestinal and pancreatic endocrine tumors. The use of this classification is considered simple and valuable. It is hoped that the combination of WHO classification, with anatomical staging systems TNM, and possibly incorporating molecular features of gastrointestinal and pancreatic endocrine tumors will provide clinicians with effective means of classification and prognostication of patients with these tumors.     

Pheochromocytoma and Paraganglioma

Objective: Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are neural crest cell tumors associated with catecholamine production and assessed by a metanephrine/methoxytyramine measurement. This review summarizes the genetics of these tumors.Methods: Case presentation, review of the relevant literature, and bullet point conclusions.Results: Genetic research over the past 10 years has led to a better understanding of the pathogenesis of these tumors, currently associated with 20 susceptibility genes (both somatic and germ-line mutations). Although most of these genes can be divided into two clusters (clusters 1 and 2), recent data suggest that all mutations converge on the hypoxia-inducible factor signaling pathway. Most of the susceptibility genes are well characterized and associated with specific clinical presentations, including biochemical phenotype, tumor location and behavior, as well as neoplasms or similar characteristics. Correct and early detection of hereditary PHEO/PGL is paramount, as early diagnosis leads to improved and focused treatment, along with better outcomes. However, missed or delayed diagnosis of hereditary PHEO/PGL forestalls proper treatment and results in multiple, recurrent, or metastatic tumors and avoidable complications in some patients.Conclusion: Early diagnosis allows prompt screening for potentially lethal cancers associated with specific gene mutations and makes genetic testing more readily available to first-degree and other relatives of an index patient. Thus, understanding the genetics of these tumors is an essential part of endocrinology.Abbreviations: HIF2A = hypoxia-inducible factor 2α MAX = Myc-associated factor X MEN2 = multiple endocrine neoplasia type 2 NF1 = neurofibromatosis type 1 PGL = paraganglioma PHEO = pheochromocytoma SDHAF2 = succinate dehydrogenase complex assemble factor 2 TMEM127 = transmembrane protein 127 VHL = von Hippel-Lindau     

The Importance of Periodical Screening for Primary Hyperparathyroidism in a Pituitary Tumor Cohort in Searching Patients With MEN1 and Its Genetic Profile

ObjectiveMultiple endocrine neoplasia type 1 (MEN1) is a rare genetic syndrome characterized by parathyroid, anterior pituitary, and/or duodenopancreatic neuroendocrine tumors. Studies have indicated that investigating primary hyperparathyroidism (pHPT) with subsequent genetic screening may be an essential tool for the early diagnosis of MEN1 in patients with pituitary tumors (PTs). This study aimed to investigate the presence of pHPT in patients with PTs and, subsequently, to screen for genetic mutations and related tumors in patients with MEN1 syndrome.MethodsThis study included 255 patients with PTs who were assessed for the presence of MEN1 by serum calcium and parathyroid hormone measurements. Mutation screening of the MEN1, CDKN1B, and AIP genes was performed in the index cases showing the MEN1 phenotype.ResultsFive patients with PTs presented a clinical condition compatible with MEN1. These patients had a younger age of onset and a more severe clinical condition. Genetic analysis identified a frameshift mutation in the MEN1 gene in one of the cases with the MEN1 phenotype, but point mutations in CDKN1B and AIP were not detected in any of these patients.ConclusionOur results show that periodic screening for pHPT in patients with PTs may be useful to detect MEN1 syndrome; thus, it is recommended in those patients with both findings a genetic analysis of MEN1 gene and an additional search of related tumors. By contrast, our data suggest that CDKN1B and AIP mutations do not seem to play a relevant role in the pathogenesis of MEN1.     

Menin represses malignant phenotypes of melanoma through regulating multiple pathways

Substantial genetic evidence suggests that chromosome 11q is involved in regulating initiation and progression of malignant melanomas. Mutations of the MEN1 gene, located in chromosome 11q13, predispose individuals to the multiple endocrine neoplasia type 1 (MEN1) familial syndrome. MEN1 patients develop primary malignant melanoma, suggesting a potential link between MEN1 syndrome and development of melanomas, but the precise molecular mechanism is poorly understood. Here we show that the MEN1 gene suppresses malignant phenotypes of melanoma cells through multiple signalling pathways. Ectopic expression of menin, the product of MEN1 gene, significantly inhibited melanoma cell proliferation and migration in vitro and in vivo. The inhibition was partly achieved through suppressing expression of growth factor pleiotrophin (PTN) and receptor protein tyrosine phosphatase (RPTP) β/ζ, accompanied with the reduced expression of phosphatidylinositol 3-kinase (pI3K) and decreased phosphorylation of focal adhesion kinase (FAK) and extracellular signal regulated kinase (ERK1/2). Interestingly, reduced expression of menin was associated with hypermethylation of the CpG islands of the MEN1 promoter in melanoma cells. Taken together, these findings suggest a previously unappreciated function for menin in suppressing malignant phenotypes of melanomas and unravel a novel mechanism involving in regulating PTN signalling by menin in development and progression of melanomas.