MEN1 is a syndrome of parathyroid adenomas, gastrinomas, prolactinomas, and other endocrine tumors. Collagenomas and facial angiofibromas are newly recognized but common skin expressions. Many tumors in MEN1 are benign; however, many entero-pancreatic neuroendocrine tumors and foregut carcinoid tumors are malignant. MEN1 is thus the expression of a cancer gene but without available prevention or cure for malignancy. Hereditary (as compared to sporadic) endocrine tumors show early onset age and multiplicity, because each cell of the body has "one hit" by inheritance. Multiple neoplasia syndromes with endocrine tumor(s) all include nonendocrine components; their known defective genes seem mainly to disturb cell accumulation. Hereditary neoplasia/hyperplasia of one endocrine tissue reflects a defect that is tissue selective and directed at cell secretion. Though the hereditary endocrine neoplasias are rare, most of their identified genes also contribute to common sporadic endocrine neoplasms. Hereditary tumors may be caused by activation of an oncogene (e.g., RET) or, more often, by inactivation of a tumor suppressor gene (e.g., P53, MEN1). Recently, MEN1 was identified by positional cloning. This strategy included narrowing the gene candidate interval, identifying many or all genes in that interval, and testing the newly identified candidate genes for mutation in MEN1 cases. MEN1 was identified because it showed mutation in 14 of 15 MEN1 cases. NIH testing showed germline MEN1 mutations in 47 of 50 MEN1 index cases and in seven of eight cases with sporadic MEN1. Despite proven capacity to find germline MEN1 mutation, NIH testing found no MEN1 mutation among five families with isolated hyperparathyroidism, suggesting that this often arises from mutation of other gene(s). Analogous studies in Japan found that familial isolated pituitary tumors also did not show MEN1 germline mutation. MEN1 mutation testing can now be considered for cases of MEN1 and its phenocopies and for asymptomatic members of families with known MEN1 mutation. Germline MEN1 testing does not have the urgency of RET testing in MEN2a and 2b, as MEN1 testing does not commonly lead to an important intervention. Somatic MEN1 mutation was found in sporadic tumors: parathyroid adenoma (21%), gastrinoma (33%), insulinoma (17%), and bronchial carcinoid (36%). For each of these, MEN1 was the known gene most frequently mutated. MEN1 has a widely expressed mRNA that encodes a protein (menin) of 610 amino acids. The protein sequence is not informative about domains or functions. The protein was mainly nuclear. Menin binds to JunD, an AP-1 transcription factor, inhibiting JunD's activation of transcription. Most of the germline and somatic MEN1 mutations predict truncation of menin, a likely destructive change. Inactivating MEN1 mutations in germline and in sporadic neoplasms support prior predictions that MEN1 is a tumor suppressor gene. Germline MEN1 mutation underlies all or most cases of MEN1 (familial or sporadic). Somatic MEN1 mutation is the most common gene mutation in many sporadic endocrine tumor types.
"MEN1 is an autosomal dominant genetic disease caused by an inactivating mutation of the tumor suppressor gene MEN1 on chromosome 11q13,. The function of the encoded protein, menin, has been extensively studied, but the role of menin in tumor suppression is not entirely clear. "
[Show abstract][Hide abstract] ABSTRACT: Pancreatic neuroendocrine tumors (PNETs), a group of endocrine tumors arising in the pancreas, are among the most common neuroendocrine tumors. The genetic causes of familial and sporadic PNETs are understood to some degree while the molecular pathogenesis of PNETs is still unclear. Most PNETs are indolent but have malignant potential. The biological behavior of an individual PNET is not readily predictable; higher tumor grade, lymph node and liver metastasis, and larger tumor size generally portend less favorable prognosis. Endocrine testing, imaging, and histological evidence are needed for accurate diagnosis of PNETs. An "aggressive" treatment approach with 4 components: surgery, locoregional therapy, systemic therapy, and complication control, has becomes a trend in academic centers throughout the world. The optimal use of the multiple modalities of systemic therapy is still being developed; efficacy, safety, availability, and cost should be considered when treating a specific patient. Clinical presentation, diagnosis, and treatment of specific types of PNETs and familial PNET syndromes, including a novel Mahvash disease, are summarized.
Chinese journal of cancer 12/2012; 32(6). DOI:10.5732/cjc.012.10295 · 2.16 Impact Factor
"Both spontaneous and familial cases of human MEN1 mutation result in predisposition to a range of tumour types, predominantly in endocrine organs such as parathyroid, pituitary and enteropancreatic sites . Several groups have published mouse models of MEN1, which replicate the human syndrome and result in tumour development, most commonly in endocrine pancreas, pituitary, parathyroid and thyroid glands, adrenals, in the gonads in some models, as well as other rarer sites [9-12]. "
[Show abstract][Hide abstract] ABSTRACT: While it is now more than a decade since the first description of the gene mutation underlying the tumour predisposition syndrome multiple endocrine neoplasia type 1 (MEN1), the mechanism by which its protein product menin acts to prevent development of tumours is still poorly understood.
We undertook a genetic experiment to assess whether menin synergises with p53. Mice carrying various combinations of Men1 and Trp53 mutations were generated then survival and pathology assessed.
While homozygous loss of Trp53 in mice resulted in early onset, aggressive tumours and profoundly reduced lifespan, heterozygous loss of either Trp53 or Men1 caused later onset disease, with a spectrum of tumours characteristic of each tumour suppressor gene. Loss of one copy of Men1 in animals also lacking both alleles of Trp53 did not exacerbate phenotype, based on survival, animal weight or sites of pathology, compared to Trp53 deletion alone. Dual heterozygous deletion of Men1 and Trp53 resulted in a small reduction in lifespan compared to the individual mutations, without new tumour sites. In the adrenal, we observed development of cortical tumours in dual heterozygous animals, as we have previously seen in Men1+/- animals, and there was loss of heterozygosity at the Men1 allele in these tumours. Median number of pathology observations per animal was increased in dual heterozygous animals compared with heterozygous loss of Trp53 alone.
Simultaneous heterozygous deletion of Men1 in animals with either heterozygous or homozygous deletion of Trp53 did not result in formation of tumours at any new sites, implying additive rather than synergistic effects of these pathways. Mice that were Men1+/- in addition to Trp53+/- had tumours in endocrine as well as other sites, implying that increase in total tumour burden, at sites typically associated with either Men1 or Trp53 loss, contributed to the slight decrease in survival in Men1+/-: Trp53+/- animals in comparison with their littermates.
BMC Cancer 06/2012; 12:252. DOI:10.1186/1471-2407-12-252 · 3.36 Impact Factor
"Up to now 459 different germline mutations have been reported in the literature and recently summarized . Most of the mutations identified in MEN-1 subjects cause either absence or low availability of menin [28, 29]. A complete loss of menin has been described in tumours from patients with MEN-1 or from mouse models of MEN-1 [30, 31]. "
[Show abstract][Hide abstract] ABSTRACT: Primary hyperparathyroidism may occur as a part of an inherited syndrome in a combination with pancreatic endocrine tumours and/or pituitary adenoma, which is classified as Multiple Endocrine Neoplasia type 1 (MEN-1). This syndrome is caused by a germline mutation in MEN-1 gene encoding a tumour-suppressor protein, menin. Primary hyperparathyroidism is the most frequent clinical presentation of MEN-1, which usually appears in the second decade of life as an asymptomatic hypercalcemia and progresses through the next decades. The most frequent clinical presentation of MEN-1-associated primary hyperparathyroidism is bone demineralisation and recurrent kidney stones rarely followed by chronic kidney disease. The aim of this paper is to present the pathomechanism, screening procedures, diagnosis, and management of primary hyperparathyroidism in the MEN-1 syndrome. It also summarises the recent advances in the pharmacological therapy with a new group of drugs-calcimimetics.
International Journal of Endocrinology 01/2010; 2010:928383. DOI:10.1155/2010/928383 · 1.95 Impact Factor
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