Identification of five novel germline mutations of the MEN1 gene in Japanese multiple endocrine neoplasia type 1 (MEN1) families

SET domain containing 1B gene is mutated in primary hepatic neuroendocrine tumors

Primary hepatic neuroendocrine tumors (PHNETs) are extremely rare NETs originating from the liver. These tumors are associated with heterogeneous prognosis, and few treatment targets for PHNETs have been identified. Because the major genetic alterations in PHNET are still largely unknown, we performed whole-exome sequencing of 22 paired tissues from PHNET patients and identified 22 recurring mutations of somatic genes involved in the following activities: epigenetic modification (BPTF, MECP2 and WDR5), cell cycle (TP53, ATM, MED12, DIDO1 and ATAD5) and neural development (UBR4, MEN1, GLUL and GIGYF2). Here, we show that TP53 and the SET domain containing the 1B gene (SETD1B) are the most frequently mutated genes in this set of samples (3/22 subjects, 13.6%). A biological analysis suggests that one of the three SETD1B mutants, A1054del, promotes cell proliferation, migration and invasion compared to wild-type SETD1B. Our work unveils that SETD1B A1054del mutant is functional in PHNET and implicates genes including TP53 in the disease. Our findings thus characterize the mutational landscapes of PHNET and implicate novel gene mutations linked to PHNET pathogenesis and potential therapeutic targets.

Molecular genetics of syndromic and non-syndromic forms of parathyroid carcinoma

Parathyroid carcinoma (PC) may occur as part of a complex hereditary syndrome or an isolated (i.e., non-syndromic) non-hereditary (i.e., sporadic) endocrinopathy. Studies of hereditary and syndromic forms of PC, which include the hyperparathyroidism-jaw tumor syndrome (HPT-JT), multiple endocrine neoplasia types 1 and 2 (MEN1 and MEN2), and familial isolated primary hyperparathyroidism (FIHP), have revealed some genetic mechanisms underlying PC. Thus, cell division cycle 73 (CDC73) germline mutations cause HPT-JT, and CDC73 mutations occur in 70% of sporadic PC, but in only ∼2% of parathyroid adenomas. Moreover, CDC73 germline mutations occur in 20%-40% of patients with sporadic PC and may reveal unrecognized HPT-JT. This indicates that CDC73 mutations are major driver mutations in the etiology of PCs. However, there is no genotype-phenotype correlation and some CDC73 mutations (e.g., c.679_680insAG) have been reported in patients with sporadic PC, HPT-JT, or FIHP. Other genes involved in sporadic PC include germline MEN1 and rearranged during transfection (RET) mutations and somatic alterations of the retinoblastoma 1 (RB1) and tumor protein P53 (TP53) genes, as well as epigenetic modifications including DNA methylation and histone modifications, and microRNA misregulation. This review summarizes the genetics and epigenetics of the familial syndromic and non-syndromic (sporadic) forms of PC.

Genetic basis of familial isolated hyperparathyroidism: a case series and a narrative review of the literature

Primary hyperparathyroidism is a heterogeneous clinical entity. In the clinical setting, the diagnosis and management of familial isolated hyperparathyroidism (FIHP) and other familial hyperparathyroidism (FHPT) forms continue to rely on clinical, laboratory, and histological findings, with careful examination of the family. In this article, we report a case series of FIHP in a four-generation Greek family, with no identifiable gene mutations. Clinical approach and long-term follow-up are discussed and a narrative review of the genetic basis of this entity has been performed.

Achieving eugastrinemia in MEN1 patients: both duodenal inspection and formal lymph node dissection are important

BACKGROUND

Controversy exists regarding the role and extent of operation for patients with multiple endocrine neoplasia type 1 (MEN1) and hypergastrinemia.

METHODS

An institutional MEN1 database was reviewed to identify patients with evidence of hypergastrinemia. The relationship of extent of resection to achievement of eugastrinemia was evaluated.

RESULTS

Operation was performed in 20 patients with MEN1 and hypergastrinemia with a median follow-up of 71 months. Duodenal gastrinomas were identified in 85% of patients who underwent duodenal evaluation. Nodal metastases were identified in 80%. Patients who underwent anatomic regional lymph node dissection (RLND) had a median of 16 nodes removed, vs 1 in patients who did not undergo a formal regional lymphadenectomy. Eugastrinemia was achieved in 12 patients (60%), and 8 (40%) had persistent hypergastrinemia. Compared with patients with persistent hypergastrinemia, patients rendered eugastrinemic more often underwent duodenal evaluation (11/12 vs 2/8; P = .01) and RLND (11/12 vs 3/8; P = .03); there was no relationship between pancreatic resection and achievement of eugastrinemia (P = .32).

CONCLUSION

For patients with MEN1-associated hypergastrinemia selected for operative treatment, a strategy including duodenal evaluation and anatomic regional lymphadenectomy is associated with long-term eugastrinemia. In contrast, the extent of pancreatic resection should be dictated by the extent and distribution of pancreatic neuroendocrine neoplasms, rather than by the presence of hypergastrinemia.

Correlation of mutant menin stability with clinical expression of multiple endocrine neoplasia type 1 and its incomplete forms

Germline mutations of the tumor suppressor gene MEN1 are found not only in typical multiple endocrine neoplasia type 1 (MEN1) but also in its incomplete forms such as familial isolated hyperparathyroidism (FIHP) and apparently sporadic parathyroid tumor (ASPT). No definitive genotype-phenotype correlation has been established between these clinical forms and MEN1 gene mutations. We previously demonstrated that mutant menin proteins associated with MEN1 are rapidly degraded by the ubiquitin-proteasome pathway. To examine whether the intracellular stability of mutant menin is correlated with clinical phenotypes, we developed a method of evaluating menin stability and examined 20 mutants associated with typical MEN1 (17 missense, two in-frame deletion, one nonsense) and 21 mutants associated with FIHP or ASPT (19 missense, two in-frame deletion). All tested mutants associated with typical MEN1 showed reduced stability. Some missense and in-frame deletion mutants (G28A, R171W, T197I, E255K, E274A, Y353del and E366D) associated with FIHP or ASPT were almost as stable as or only slightly less stable than wild-type menin, while others were as unstable as those associated with typical MEN1. Some stable mutants exhibited substantial biological activities when tested by JunD-dependent transactivation assay. These findings suggest that certain missense and in-frame mutations are fairly stable and retain intrinsic biological activity, and might be specifically associated with incomplete clinical phenotypes. The menin stability test will provide useful information for the management of patients carrying germline MEN1 mutations especially when they have missense or in-frame variants of ambiguous clinical significance.

Co-existence of glucagonoma with recurrent insulinoma in a patient with multiple endocrine neoplasia-type 1 (MEN-1)

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors of the parathyroid glands, the anterior pituitary, and the endocrine pancreas. Our patient was a 58-year-old man who manifested typical features of MEN-1 including primary hyperparathyroidism, lung carcinoid, and lipomas and insulinoma. He was admitted to our hospital because of recurrent hypoglycemia and a growth of pancreatic tumors. The first operation for insulinoma was performed when he was 20 years old. We found a germline mutation of the MEN1 gene (E45G, exon 2) in this patient. According to these examinations and his clinical course, the patient was diagnosed as having a recurrence of insulinoma. He subsequently underwent surgery for the pancreatic tumors. The majority of these tumor cells were immunohistochemically positive for insulin and negative for glucagon. A few nodules showed immunohistochemical staining positivity for glucagon but they were negative for insulin. Although it is uncommon for patients with MEN1 to exhibit insulinoma and glucagonoma, this case suggests the need for careful analysis of pancreatic tumors in patients with MEN1.

Management of pancreatic endocrine tumors in multiple endocrine neoplasia type 1

INTRODUCTION

Pancreatic endocrine tumors (PETs) occur in at least 50% of patients with multiple endocrine neoplasia type 1 (MEN1) and are the leading cause of disease-specific mortality. However, the timing and extent of surgery for MEN1-related PETs is controversial owing to the indolent tumor growth seen in most patients and the desire to avoid complications associated with insulin dependence. To help resolve this controversy, we retrospectively analyzed the clinical characteristics, surgical treatment, and clinical outcome of patients with MEN1-related PETs.

METHODS

All patients had histologic or radiographic confirmation of a PET in the setting of MEN1. Disease progression was defined radiographically as the development of new pancreatic tumors or distant metastases. Progression-free survival (PFS) and overall survival (OS) were used as the endpoints of this analysis.

RESULTS

We identified 98 patients with MEN1, 55 (56%) of whom had PETs, including 27 women and 28 men with a median age of 37 years (range 8-69 years) at the time of diagnosis. Functioning PETs were present in 35 (64%) of 55 patients, and nonfunctioning tumors were present in 20 (36%). Pancreatic surgery was performed in 38 (69%) of the 55 patients; and the first operation included enucleation (n = 4), total pancreatectomy (n = 3), Whipple procedure (n = 4), and distal pancreatectomy (n = 27). The median size of the resected tumors was 2.8 cm (range 0.6-11.0 cm). Recurrent disease developed in the residual pancreas in 7 (20%) of 35 at-risk patients a median of 7.8 years after the first operation, and distant metastases occurred in 5 (14 %) of 36 surgically treated patients without distant metastasis (2 patients had distant metastases when surgery on the primary tumor was performed) at a median of 2.7 years following surgery. At last follow-up, 16 (29%) of 55 patients with PETs had died, 12 (22%) were alive with disease, 26 (47%) were alive without evidence of disease, and 1 (2%) was lost to follow-up. The median OS was 19.5 years (range 13-26 years) and was significantly longer for patients who had functioning PETs versus those with nonfunctioning tumors (P = 0.0007), for patients who underwent surgical resection of their PETs versus those who did not (P = 0.0043), and for patients with localized versus metastatic PETs at the time of diagnosis (P < 0.0001). Multivariate analysis revealed that younger age, hormonal function, and PET resection were independently associated with longer OS.

CONCLUSIONS

Our data suggest that early diagnosis and surgical excision of MEN1-related PETs improves survival. However, translating these data into a surveillance strategy for the early detection of PETs is complex owing to the potential morbidity of pancreatic resection and the risk of long-term insulin dependence.

Multiple endocrine neoplasia type 1

Multiple Endocrine Neoplasia type 1 (MEN1) is a rare autosomal dominant hereditary cancer syndrome presented mostly by tumours of the parathyroids, endocrine pancreas and anterior pituitary, and characterised by a very high penetrance and an equal sex distribution. It occurs in approximately one in 30,000 individuals. Two different forms, sporadic and familial, have been described. The sporadic form presents with two of the three principal MEN1-related endocrine tumours (parathyroid adenomas, entero-pancreatic tumours and pituitary tumours) within a single patient, while the familial form consists of a MEN1 case with at least one first degree relative showing one of the endocrine characterising tumours. Other endocrine and non-endocrine lesions, such as adrenal cortical tumours, carcinoids of the bronchi, gastrointestinal tract and thymus, lipomas, angiofibromas, collagenomas have been described. The responsible gene, MEN1, maps on chromosome 11q13 and encodes a 610 aminoacid nuclear protein, menin, with no sequence homology to other known human proteins. MEN1 syndrome is caused by inactivating mutations of the MEN1 tumour suppressor gene. This gene is probably involved in the regulation of several cell functions such as DNA replication and repair and transcriptional machinery. The combination of clinical and genetic investigations, together with the improving of molecular genetics knowledge of the syndrome, helps in the clinical management of patients. Treatment consists of surgery and/or drug therapy, often in association with radiotherapy or chemotherapy. Currently, DNA testing allows the early identification of germline mutations in asymptomatic gene carriers, to whom routine surveillance (regular biochemical and/or radiological screenings to detect the development of MEN1-associated tumours and lesions) is recommended.

A novel germline mutation of MEN 1 gene in a patient with acromegaly and multiple endocrine tumors

Germline mutations of the MEN 1 gene are responsible for multiple endocrine neoplasia type 1 (MEN 1), a dominantly inherited cancer syndrome characterized by tumors of the parathyroids, gastro-intestinal endocrine tissue, anterior pituitary and other endocrine tissues. We report on a 55-yr old woman, presenting with active acromegaly (due to GH-secreting microadenoma), associated to bilateral adrenal adenomatosis and Hürthle-cell thyroid neoplasia. No evidence of hyperparathyroidism or gastrin-secreting tumor was found. Peripheral blood genomic DNA was extracted, amplified by PCR, purified and analyzed by direct sequencing. The analysis revealed a heterozygous mutation in exon 4 of the MEN 1 gene: a G to A missense mutation at codon 229 (CGC-->CAC), which changes arginine to histidine. This mutation causes loss of the Hhal restriction site and can thus be employed for a rapid familiar screening. This case represents a newly recognized germline mutation of the MEN 1 gene.

Multiple endocrine neoplasia type 1 (MEN1) germline mutations in familial isolated primary hyperparathyroidism

BACKGROUND

Familial isolated hyperparathyroidism (FIHP) is an autosomal dominant disorder characterized by uniglandular or multiglandular parathyroid tumours that occur in the absence of other endocrine tumours. The disorder may represent either an early stage of multiple endocrine neoplasia type 1 (MEN1), or an allelic variant of MEN1, or a distinct entity involving another locus. We have explored these possibilities in seven families in whom primary hyperparathyroidism occurred as the sole endocrinopathy.

METHODS

Seven FIHP families were ascertained and venous blood samples obtained from 35 members (17 affected and 18 unaffected) for DNA sequence analysis of the MEN1 gene. The mean (+/- SD) follow-up period in the 17 affected members was 15.06 (+/- 8.83) years.

RESULTS

Four heterozygous germline mutations of the MEN1 gene were identified. These consisted of two 4-bp intragenic deletions that would result in prematurely truncated proteins, and two missense (Asp153Val and Ala411Pro) mutations. Furthermore, analysis of parathyroid tumour DNA from one individual revealed a loss of the wild-type allele and retention of the mutant allele, consistent with Knudson's 'two-hit' model of hereditary cancer and a tumour suppressor role for MEN1 in FIHP.

CONCLUSIONS

Our results provide further support for FIHP being a distinct allelic variant of MEN1, and an analysis of the 16 mutations reported to date indicate that FIHP is associated with a higher frequency of missense MEN1 mutations.

The MEN1 gene and associated diseases: an update

Heterozygous germline mutations of the tumor suppressor gene MEN1 are responsible for multiple endocrine neoplasia type 1 (MEN1), a dominantly inherited familial cancer syndrome characterized by the combined occurrence of pituitary, parathyroid, and enteropancreatic tumors. Various types of mutations likely causing loss of the gene function have been identified throughout the entire gene region in patients with MEN1 and related disorders including a small fraction of familial isolated hyperparathyroidism (FIHP). Neither mutation hot spot nor phenotype-genotype correlation has been established in classical MEN1, although some missense mutations may be specifically associated with a phenotype of FIHP. Familial isolated pituitary tumor and atypical familial MEN1 consisting of only pituitary tumor and hyperparathyroidism usually lack germline MEN1 mutations, suggesting that these familial endocrine tumor syndromes are genetic entities distinct from MEN1. DNA test for MEN1 germline mutations is a robust tool for diagnosis of predisposition to MEN1, and will be useful for the counseling and management of patients and their families. In this review, we will summarize the most recent findings on the MEN1 gene, focusing primarily on germline mutations and associated diseases.

Large and asymptomatic pancreatic islet cell tumor in a patient with multiple endocrine neoplasia type 1

The major phenotypes of multiple endocrine neoplasia type 1 (MEN 1) consist of three lesions characterized by hyperparathyroidism, pituitary tumors, and endocrine pancreatic tumors. The endocrine pancreatic tumors are a significant cause of disease-related mortality in MEN 1. Although symptomatic pancreatic tumors such as insulinoma and gastrinoma should be resected, the management of asymptomatic pancreatic tumors is not established. In asymptomatic pancreatic tumors, the most important factor is the propensity for malignant transformation of the tumors. Although there are no means to foresee it, the size of the pancreatic tumors might be predictive of malignant development in MEN 1. We report here a patient with MEN 1 who had a large asymptomatic pancreatic tumor. The patient (72-yr-old man) was diagnosed with primary hyperparathyroidism and underwent a total parathyroidectomy. Genetic examination showed a germline mutation of the MEN1 gene (E45G). Abdominal magnetic resonance imaging revealed a large (>6 cm) tumor with a heterogeneous pattern in the tail of the pancreas. No metastases of the tumor were evident. Serum levels of insulin, gastrin, and glucagon were normal, and the patient had no symptoms. Operative resection was performed, and microscopic examination revealed that the tumor was an islet cell tumor stained with multiple hormones. This is a case indicating that asymptomatic pancreatic tumors associated with MEN 1 might be indolent independent of their size.

Multiple endocrine neoplasia type 1

Combined clinical and laboratory investigations of MEN-1 have resulted in an increased understanding of this disorder, which may be inherited as an autosomal dominant condition. Defining the features of each disease manifestation in MEN-1 has improved patient management and treatment and has facilitated a screening protocol. Application of the techniques of molecular biology has enabled the identification of the gene causing MEN-1 and the detection of mutations in patients. The protein encoded by the MEN1 gene has been shown to be involved in the regulation of JunD-mediated transcription, but much still remains to be elucidated. Recent advances permit the identification of mutant MEN1 gene carriers who are at a high risk for this disorder and who require regular and biochemical screening to detect the development of endocrine tumors.

Multiple endocrine neoplasia type 1

The recent cloning of the gene responsible for multiple endocrine neoplasia type 1 (MEN 1) has opened new avenues for both clinical and basic science research in the field of endocrine oncology. A large amount of genetic information, particularly those in relation to germline and somatic mutations, has since been published during the last 2 years. This new knowledge has provided important insights into its gene function. The significance of these advances in relation to clinical management and future directions for research is discussed.

Expression of menin in parathyroid tumors

The multiple endocrine neoplasia type 1 (MEN1) gene seems to be a tumor suppressor that encodes a 610-amino acid protein termed menin and that plays an important role in the development of MEN1 syndrome. Recent reports indicate that heterozygous germline mutations of this gene are responsible for the disease onset of MEN1. In this study we examined the expression of menin in parathyroid tumors from primary hyperparathyroidism (PHP), secondary hyperparathyroidism (SHP), and MEN1 and thyroid tumors including Basedow's disease, thyroid cancer, and adrenocortical tumors. Both ribonucleic acid and protein from these tumors were applied to RT-PCR and Western blotting, respectively. Primers for RT-PCR were designed to amplify the sequence between exons 2 and 3 of the MEN1 gene. Specific antibody against menin was generated in guinea pigs immunized with the recombinant peptide from amino acid residues 443-535 of menin made by using glutathione-S-transferase (GST) gene fusion. Menin messenger ribonucleic acid was strongly expressed on RT-PCR analysis in the parathyroid tumors from both PHP and SHP. Western blotting revealed a specific band of approximately 67 kDa in parathyroid tumors from PHP and SHP, with a much weaker such band detected in thyroid tumors. Menin expression was down-regulated in MEN1 samples, including nonsense mutation and deletion mutant. These findings suggest that menin is predominantly synthesized and stored in parathyroid tumors resulting from PHP and SHP.

A newly recognized germline mutation of MEN1 gene identified in a patient with parathyroid adenoma and carcinoma

We report on a patient with primary hyperparathyroidism, owing to the concurrence of parathyroid adenoma with carcinoma, who had a newly recognized germline mutation of the multiple endocrine neoplasia type 1 gene (MEN1 gene). The patient underwent total parathyroidectomy, and histological examination revealed parathyroid carcinoma and multiple adenoma of the other three glands. Genetic analysis revealed a newly recognized heterozygous germline mutation (842delC, exon 4) of the MEN1 gene. Both imaging studies and laboratory data showed no evidence of MEN1 in the patient. Four family members--three sisters and one daughter--had neither clinical features of MEN1 nor genetic evidence of the MEN1 gene. This is the first report of a germline mutation of the MEN1 gene found in a patient who exhibited the concurrence of parathyroid adenoma with carcinoma, suggesting that long-term hyperactivity of the parathyroids may result in the formation of carcinoma.

Clinical aspects of hyperparathyroidism in Japanese multiple endocrine neoplasia type 1

We describe here the clinical aspects of hyperparathyroidism (HP) in Japanese multiple endocrine neoplasia type 1 (MEN 1). The total number of MEN 1 patients was 37, and they originated from ten unrelated Japanese families. Nine of the ten families were proven to have heterozygous germline mutations of the MEN 1 gene. The incidence of HP, pituitary tumors, and pancreatic tumors in 37 MEN 1 patients was 91.9%, 32.4%, and 45.9%, respectively. The age-related penetrances of HP were 50%, 79%, 84%, by 20, 30, and 40 years of age, respectively. Of these MEN 1 patients, we used 28 individuals, diagnosed with HP at our hospitals, to study the clinical aspects of MEN 1-associated HP. The mean age was 40 years, and the mean was much lower in the sporadic (non-MEN 1) HP patients. The mean levels of calcium, phosphate, and intact PTH were 10.8 mg/dL, 2.3 mg/dL, and 178.0 pg/mL, respectively, and these were not different from those of sporadic HP patients. The levels of intact PTH were positively correlated with age, suggesting that HP may be progressive with time in MEN 1. The percentage of symptomatic HP was 36% in MEN 1, whereas it was 55% in sporadic HP patients. Although histopathological findings revealed that all four parathyroid glands were involved in hyperplasia, imaging studies showed an enlargement of only the single parathyroid gland in most patients. The combination of total parathyroidectomy and autoplantation succeeding in improving HP in MEN 1.

Gene diagnosis and clinical management of multiple endocrine neoplasia type 1 (MEN1)

Identification of the MEN1 gene as a disease gene for multiple endocrine neoplasia type 1 (MEN1) has made it possible to predict whether a family member of an MEN1 patient will suffer from the same disease. MEN1 mutations have been found in almost all cases with familial MEN 1, but in fewer cases with sporadic MEN1. We analyzed MEN1 mutations in the largest number of Japanese MEN1 patients, 17 families and 21 sporadic cases, and found 54 MEN1 mutant carriers and 30 non-carriers. Furthermore, we identified a MEN1 phenocopy: GH-secreting pituitary tumor and primary hyperparathyroidism, which develops at older ages. In this article, we discuss how to utilize MEN1 gene diagnostics for the clinical management of MEN 1 patients and MEN1 mutation carriers.

Clinical features of multiple endocrine neoplasia type 1 (MEN1) phenocopy without germline MEN1 gene mutations: analysis of 20 Japanese sporadic cases with MEN1

OBJECTIVE

Multiple endocrine neoplasia type 1 (MEN1) is a familial tumour syndrome of endocrine tumours involving parathyroids, anterior pituitary and enteropancreatic neuroendocrine tissues, and is inherited in an autosomal dominant manner with high penetrance. Recently, the gene responsible for this syndrome, MEN1, was positionally cloned from chromosome 11q13.

PATIENTS

To characterize sporadic MEN1 patients, we analysed the MEN1 gene by direct sequencing of the entire open reading frame from 20 individuals.

RESULTS

We identified heterozygous germline mutations of the MEN1 gene in 8 of 20 (40%) cases. Seven were novel MEN1 germline mutations. Three mutations were splicing abnormalities, and all were confirmed to be splicing defects by RT-PCR. The clinical significance of detecting germline MEN1 mutations, not only in familial MEN1 but also in sporadic MEN1, was confirmed by the finding of asymptomatic mutant carriers among family members of the sporadic MEN1 patients. Seven of 8 cases with MEN1 mutations had enteropancreatic lesions in contrast to 4 of 12 (P < 0.018) in those cases with no mutation. Ten of the 12 cases without MEN1 mutation were more than 50-year-old. Six of these 10 cases had the same clinical features; primary hyperparathyroidism and a GH-secreting pituitary tumour.

CONCLUSIONS

It is likely that the six cases without mutations were MEN1 phenocopies due to (i) two kinds of tumours with high natural incidence in older subjects developed by chance (ii) another familial tumour syndrome with low penetrance, e. g. familial acromegaly with primary hyperparathyroidism by mutation of another gene, or (iii) somatic mutation during early embryonic stages.

Characterization of high-grade neuroendocrine tumors of the lung in relation to menin mutations

It has been suggested that mutations in the menin gene play a role in the development of multiple endocrine neoplasia type 1 (MEN1)-associated and of sporadic forms of low- and intermediate-grade neuroendocrine tumors of the lung. In the present study, eight tumor specimens of large cell neuroendocrine carcinoma (LCNEC) and 13 of small cell lung cancer (SCLC), which represent a high-grade category of neuroendocrine tumors, were examined for the potential involvement of menin alterations as well as for the expression of various neuroendocrine markers and p53 and Rb abnormalities. All specimens expressed multiple neuroendocrine markers as expected and almost invariably carried p53 and Rb alterations. Unexpectedly, however, mutations in the menin gene were not detected in any of the high-grade neuroendocrine tumors examined. We thus conclude that menin mutations do not play a crucial role in the pathogenesis of high-grade subsets, in contrast to their suggested significant role in the development of low- and intermediate-grade subsets. Interestingly, loss of heterozygosity (LOH) in the menin gene appeared to be more prevalent in LCNEC (50%) than in SCLC (22%), suggesting a possible distinction between SCLC and LCNEC.

Large goiter and multiple rib tumors

We report an interesting case of a 47-yr-old who had a large goiter and multiple rib tumors. The patient was initially suspected of having thyroid cancer, which had metastasized on the ribs, based on imaging studies. However, laboratory tests revealed a high level of ionized calcium and parathyroid hormone (PTH). The large goiter was diagnosed as having parathyroid tumors owing to the high level of PTH in the tissue fluid. The biopsy specimen from a rib tumor was diagnosed as containing brown tumors associated with primary hyperparathyroidism (PHP). The patient also had prolactinoma and pancreatic gastrinoma. Her daughter had both prolactinoma and PHP, and her brother and her father had PHP. Thus, the patient was diagnosed as having multiple endocrine neoplasia type 1.

Molecular pathology of multiple endocrine neoplasia type I: two novel germline mutations and updated classification of mutations affecting MEN1 gene

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the combined development of tumors in several endocrine glands and other tissues. The MEN1 gene was recently identified and isolated by positional cloning. This gene was screened in two unrelated MEN1 Spanish kindreds (with four affected members and seven asymptomatic members) using single-strand conformation polymorphism, DNA sequencing, and restriction enzyme analysis. Two novel germline mutations were identified: a missense in exon 2 (H139R) and a splice-site in intron 9 (1461-2A>C). These findings allowed us to identify the MEN1 carriers among the seven asymptomatic members analyzed. An updated review of the mutations and polymorphisms found in the analysis of the MEN1 gene is provided. The report of all germline mutations causing MEN1 and easy access to this updated information are both of special diagnostic interest, because this greatly facilitates the task of attributing the disorder to a specific mutation found in a given MEN1 family. This is especially helpful in the critical differentiation of missense mutations from nonsynonymous polymorphisms that fit the pattern of segregation of the disease, but do not cause it.

Structure and distribution of rat menin mRNA

Menin is a protein product of a tumor suppressor gene MEN1, mutations of which are responsible for multiple endocrine neoplasia type 1, an autosomal dominant familial cancer syndrome. We isolated rat menin cDNA clones from a fetal rat brain cDNA library. We also determined the nucleotide sequence of the protein coding region of mouse menin cDNA, which was partly registered in the expressed sequence tag (EST) database. Deduced amino acid sequences of rat and mouse menin are highly homologous to human menin. All of the previously reported disease-associated missense mutations and single amino acid deletions were observed at the residues that are conserved among these three species. Rat MEN1 transcripts were detected not only in the endocrine tissues but also in the tissues of the nervous, digestive, reproductive and immune systems. The MEN1 transcripts were abundantly expressed in the developing rat brain on day 14-18 of gestation. Immunoblotting and immunocytochemical analysis of the COS-7 cells transfected with a rat menin-expression vector revealed that the translated product has a molecular mass of approximately 70 kDa, and is localized mainly in the nucleus. These findings are consistent with those reported on human menin.

Analysis of the MEN1 gene in sporadic pituitary adenomas from Japanese patients

An autosomal-dominant syndrome known as multiple endocrine neoplasia type 1 (MEN1) is characterized by tumors in parathyroid glands, pancreatic endocrine tissues and the anterior pituitary gland. The predisposing gene was identified at 11q13 when germline mutations in the MEN1 gene were detected in affected pedigrees. To investigate a possible role of this gene in tumorigenesis of non-familial pituitary adenomas, we examined 24 sporadic tumors from Japanese patients for loss of heterozygosity (LOH) at the 11q13 region and for somatic mutations in the entire coding region and exon-intron boundaries of MEN1. Although three common sequence variants were detected, none of the tumors exhibited either LOH or somatic mutations of this gene. Our results indicate that inherited and sporadic forms of pituitary adenomas are different in terms of the genetic events that contribute to their development, and that other loci associated with pituitary neoplasia must still be sought.

Review: multiple endocrine neoplasia type 1, sporadic neuroendocrine tumors, and MENIN

Since the identification and cloning of the gene responsible for the inherited syndrome multiple endocrine neoplasia type 1 (MEN1) in 1997, important advances in the understanding of the disease, the encoded protein (MENIN) and its role in the development of sporadic neuroendocrine and other neoplasms have been made. In this review, the most important recently published data on the pathology of the MEN1 syndrome, alterations of the MEN1 gene in affected families, and sporadic neuroendocrine tumors and the possible function of MENIN will be summarized.