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.     

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.     

Studies on the distribution of PHI in mammals

We have developed a sensitive and specific radioimmunoassay to PHI and investigated its distribution in four mammalian species (man, cat, guinea-pig and rat). PHI was present in high concentrations, not only in intestine but also in brain, respiratory tract, urogenital tract and other peripheral tissues. Its distribution was similar to that of VIP and in each tissue examined there was always a significant correlation between the concentrations of these two peptides. In a survey of endocrine tumours, PHI was found to be produced only in those tumours that also produced VIP. In addition PHI was only elevated in the plasma of patients that also had high plasma VIP concentrations. This parallel distribution and release was found to be due to the co-synthesis of VIP and PHI in the same pro-hormone peptide. However, the variable ratio of VIP/PHI in different anatomical areas suggest that in these areas there is a different post-translational enzyme processing of the precursor protein.     

G691S/S904S polymorphism in the RET protooncogene of a 25-year-old medical student with bilateral pheochromocytoma

The case of a 25-year-old medical student with bilateral pheochromocytoma is described. Following diagnostic testing, tumors were surgically removed. Genetic analysis revealed that the patient is a heterozygote with the following mutations on opposite homologs: G691S (exon 11) and S904S (TCC-TCG, exon 15), suggesting the diagnosis of multiple endocrine neoplasia 2A (MEN2A). A diagnosis of MEN2 would be an indication of thyroidectomy in this patient. Although this mutation is described in the literature, it has no known connection to pheochromocytomas. Therefore, it is unknown whether there is a causal connection between the G691S genotype and the pheochromocytomas in this patient. If so, G691S is to be added to the list of genotypes causing MEN2A. Here, the procedure of sequencing the RET protooncogene is described and a possible association between the G691S genotype and MEN2A is discussed.     

A multihormonal tumor of the pancreas producing neurotensin associated with the WDHA syndrome. Histology, histochemistry and origin

A pancreatic tumor associated with severe WDHA syndrome has been studied histologically and immunohistochemically. Light microscopy revealed that the growth pattern of the tumor varied greatly from zone to zone but with prevailing solid arrangement of the tumoral cells. The majority of the endocrine cells showed numerous eosinophilic, PTAH-positive, and argyrophilic secretory granules, that were ultrastructurally similar to those of normal and tumoral neurotensin-containing cells. A minority of the endocrine cells had secretory granules ultrastructurally different from the aforementioned ones, but these were not diagnostic on purely morphological grounds. Inside the tumor, immunohistochemistry demonstrated a majority of neurotensin-immunoreactive cells, sparse and small clusters of VIP-immunoreactive cells and few, dispersed pancreatic polypeptide-immunoreactive cells. Some structural and ultrastructural aspects of the tumoral stroma have also been reported. Ducts and solid masses of duct-like cells were also found, and small clusters and singly dispersed duct-like cells were seen invading the endocrine tissue and undergoing mitoses. Such features suggest that the tumor originated from precursors located in the medium-sized and small pancreatic ducts. Because of the multihormonal nature of the tumor, the role of neurotensin and VIP in producing the patient's symptoms is discussed and a synergistic action of the two hormones is suggested in causing the particularly severe WDHA syndrome.     

Loss of heterozygosity on chromosome 11 in sporadic gastrinomas

Summary Gastrinomas are pancreatic endocrine neoplasms that arise either sporadically or are inherited as part of the multiple endocrine neoplasia type I syndrome (MEN I). Loss of heterozygosity (LOH) in the region flanking the MEN I gene at chromosome 11q13 has been documented in a few sporadic and familial pancreatic endocrine tumors, but not previously in sporadic gastrinomas. It has therefore been suggested that gastrinomas develop by a mechanism different from other tumors associated with the MENI syndsrome. We report LOH on chromosome 11 in 5 of 11 sporadic gastrinomas. Four of these tumors have LOH for markers flanking the MEN I region. Molecular evaluation of segments of chromosomes 3, 13, and 17 known to contain cloned or putative tumor suppressor genes fail to show LOH except at one locus in one tumor. These data suggest that a tumor suppressor DNA segment exists at 11q13 that may be involved in the development of sporadic gastrinomas.     

Zebrafish model of KRAS-initiated pancreatic endocrine tumor

Pancreatic cancer constitutes a genetic disease in which somatic mutations in the KRAS proto-oncogene are detected in 95% of cases. Activation of the KRAS proto-oncogene represents an initiating event in pancreatic tumorigenesis. Here, we established a zebrafish pancreatic neoplasia model that recapitulates human pancreatic tumors. Toward this end, we generated a stable CRE/Lox-based zebrafish model system to express oncogenic KRAS^G12D  in the elastase3I domain of the zebrafish pancreas. Lineage tracing experiments showed that early KRAS^G12D -responsive pancreatic progenitors contribute to endocrine in addition to exocrine cells. In this system, 10% and 40% of zebrafish developed pancreatic tumors by 6 and 12 months, respectively. The histological profiles of these experimental tumors bore a striking resemblance to those of pancreatic endocrine tumors. Immunohistochemical analysis including the endocrine cell-specific marker confirmed the pancreatic tumor region as a characteristic endocrine tumor. Taken together, our zebrafish model data revealed that pancreatic endocrine tumors originate from early KRAS^G12D -responsive pancreatic progenitor cells. These findings demonstrated that this zebrafish model may be suitable as an experimental and preclinical system to evaluate different strategies for targeting pancreatic endocrine tumors and ultimately improve the outcome for patients with pancreatic endocrine tumors.     

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.     

Sequence analysis of the MEN I gene in two patients with multiple cutaneous lipomas and endocrine tumors.

The discovery of mutations of the menin gene in a few multiple endocrine neoplasma type 1 (MEN I)-associated lipomas and loss of heterozygosity (LOH) on chromosome 11q13 in some sporadic lipomas has stimulated the hypothesis that lipomas may belong to the group of sporadic tumors caused by defects of the gene responsible for MEN I. Since it is unclear if the above hypothesis applies to all patients with lipoma or just to specific subsets, we searched to enlarge the database on this topic. For this purpose, we identified two patients with multiple cutaneous lipomas. One had an additional pituitary adenoma and familial presentation of multiple lipomas, the other had recurrent goiter in the setting of a family history of adenomatous goiter. Deoxyribonucleic acid (DNA) was analyzed by complete direct DNA sequencing of all coding exons and splice junctions of the MEN I gene. No mutation was identified in the coding exons of the menin gene. In contrast to former data on sporadic lipomas, these data are the first to render evidence that mutations of the MEN I gene may not be responsible for the formation of multiple lipomas, even if they appear in the context of other endocrine tumors.     

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.     

Differential expression of the regulated catecholamine secretory pathway in different hereditary forms of pheochromocytoma

Pheochromocytomas in patients with von Hippel-Lindau (VHL) syndrome and multiple endocrine neoplasia type 2 (MEN 2) differ in the types and amounts of catecholamines produced and the resulting signs and symptoms. We hypothesized the presence of different processes of catecholamine release reflecting differential expression of components of the regulated secretory pathway among the two types of hereditary tumors. Differences in catecholamine secretion from tumors in patients with VHL syndrome (n = 47) and MEN 2 (n = 32) were examined using measurements of catecholamines in tumor tissue, urine, and plasma, the last of which was under baseline conditions in all subjects and in a subgroup of patients who received intravenous glucagon to provoke catecholamine release. Microarray and proteomics analyses, quantitative PCR, and Western blotting were used to assess expression of tumor tissue secretory pathway components. The rate constant for baseline catecholamine secretion was 20-fold higher in VHL than in MEN 2 tumors (0.359 +/- 0.094 vs. 0.018 +/- 0.009 day(-1)), but catecholamine release was responsive only to glucagon in MEN 2 tumors. Compared with tumors from MEN 2 patients, those from VHL patients were characterized by reduced expression of numerous components of the regulated secretory pathway (e.g., SNAP25, syntaxin, rabphilin 3A, annexin A7, calcium-dependent secretion activator). The mutation-dependent differences in expression of secretory pathway components indicate a more mature regulated secretory pathway in MEN 2 than VHL tumors. These data provide a unique mechanistic link to explain how variations in the molecular machinery governing exocytosis may contribute to clinical differences in the secretion of neurotransmitters or hormones and the subsequent presentation of a disease.     

Differential loss of heterozygosity in familial, sporadic, and uremic hyperparathyroidism

Various genetic loci harboring oncogenes, tumor suppressor genes, and genes for calcium receptors have been implicated in the development of parathyroid tumors. We have carried out loss of heterozygosity (LOH) studies in chromosomes 1p, 1q, 3q, 6q, 11q, 13q, 15q, and X in a total of 89 benign parathyroid tumors. Of these, 28 were sporadic parathyroid adenomas from patients with no family history of the disease, 41 were secondary parathyroid tumors, 5 were from patients with a history of previous irradiation to the neck, 12 were from patients with a family history of hyperparathyroidism, and 3 were parathyroid tumors related to multiple endocrine neoplasia type 1 (MEN1). In addition, we determined the chromosomal localization of a second putative calcium-sensing receptor, CaS, for inclusion in the LOH studies. Based on analysis of somatic cell hybrids and fluorescent in situ hybridization to metaphase chromsomes, the gene for CaS was mapped to chromosomal region 2q21-q22. The following results were obtained from the LOH studies: (1) out of the 24 tumors that showed LOH, only 4 had more than one chromosomal region involved, (2) in the tumours from uremic patients, LOH of chromosome 3q was detected in a subset of the tumors, (3) LOH of the MEN1 region at 11q13 was the most common abnormality found in both MEN1-related and sporadic parathyroid tumours but was not a feature of the other forms of parathyroid tumors, (4) LOH in 1p and 6q was not as frequent as previously reported, and (5) tumor suppressor genes in 1q and X might have played a role, particularly on the X chromosome, in the case of familial parathyroid adenomas. We therefore conclude that the tumorigenesis of familial, sporadic, and uremic hyperparathyroidism involves different genetic triggers in a non-progressive pattern. Received: 28 October 1996 / Revised: 16 November 1996     

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.     

Multiple Endocrine Neoplasia Syndromes

The multiple endocrine neoplasia (MEN) syndromes consist of three distinct disease entities. They have in common adenomatous, carcinomatous or hyperplastic involvement of a variety of endocrine glands, and an autosomal dominant inheritance. MEN I includes hyperparathyroidism, islet cell and pituitary tumors. The components of MEN IIa are hyperparathyroidism, medullary thyroid carcinoma and pheochromocytoma. MEN IIb includes multiple neuromas, medullary thyroid carcinoma and pheochromocytoma. Effective tests are available for the early detection of components of the syndromes in potentially affected patients. Screening can lead to therapeutic intervention before clinical sequelae ensue.     

Primary hyperparathyroidism in patients with multiple endocrine neoplasia type 1: comparison with sporadic parathyroid adenomas.

A prospective study on the natural course of primary hyperparathyroidism has recently been reported. Since hyperparathyroidism in multiple endocrine neoplasia type 1 (MEN 1) is genetically distinct from most forms of sporadic hyperparathyroidism, it is important to know the natural course of hyperparathyroidism in MEN 1 for better clinical management. For this purpose, we retrospectively reviewed clinical parameters of patients with MEN 1 when they were diagnosed as having hyperparathyroidism, and compared them with those of patients with sporadic primary hyperparathyroidism. In patients with MEN 1: 1) levels of intact PTH (i-PTH) gradually increased with age, which accelerated over 40 years; 2) compared to the steep rise in i-PTH levels in aged patients, increase in serum calcium or decrease of serum inorganic phosphate concentration was relatively mild, and 3) the high concentrations of i-PTH in aged patients were not due to renal insufficiency. These features were not observed in patients with sporadic primary parathyroid adenomas. Clinical features of untreated hyperparathyroidism in MEN 1 may be significantly affected by the age of the patient. The effect, if any, of age-dependent deterioration on recurrence rate after subtotal or total parathyroidectomy requires further elucidation.     

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.     

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。     

血管活性肠多肽结合核苷酸性质的研究

采用光亲和技术检测了血管活性肠多肽(VIP)与核苷酸之间的相互作用,发现VIP可以特异性结合同位素标记的GTP,还发现未标记的GTP以及其它三磷酸核苷抑制这种结合,这意味着VIP与上述三磷酸核苷之间的结合是一种典型的可逆性的结合反应.发现低浓度的GDP,GMP不但不抑制VIP与同位素标记GTP的结合反应,反而增强这种结合.联系到其它研究者关于GTP影响VIP与其受体结合反应的结果,可认为VIP能可逆性地连接一种三磷酸核苷,这种连接受反应系统中不同核苷酸比例影响,通过这种连接来调节VIP与其受体之间的反应.