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Serk In Park and Laurie K McCauley

Prostate cancer remains a leading cause of cancer-related death in men, largely attributable to distant metastases, most frequently to bones. Despite intensive investigations, molecular mechanisms underlying metastasis are not completely understood. Among prostate cancer-derived factors, parathyroid hormone-related peptide (PTHrP), first discovered as an etiologic factor for malignancy-induced hypercalcemia, regulates many cellular functions critical to tumor growth, angiogenesis, and metastasis. In this study, the role of PTHrP in tumor cell survival from detachment-induced apoptosis (i.e. anoikis) was investigated. Reduction of PTHLH (encoding PTHrP) gene expression in human prostate cancer cells (PC-3) increased the percentage of apoptotic cells when cultured in suspension. Conversely, overexpression of PTHrP protected prostate cancer cells (Ace-1 and LNCaP, both typically expressing low or undetectable basal PTHrP) from anoikis. Overexpression of nuclear localization signal (NLS)-defective PTHrP failed to protect cells from anoikis, suggesting that PTHrP-dependent protection from anoikis is an intracrine event. A PCR-based apoptosis-related gene array showed that detachment increased expression of the TNF gene (encoding the proapoptotic protein tumor necrosis factor-α) fourfold greater in PTHrP-knockdown PC-3 cells than in control PC-3 cells. In parallel, TNF gene expression was significantly reduced in PTHrP-overexpressing LNCaP cells, but not in NLS-defective PTHrP overexpressing LNCaP cells, when compared with control LNCaP cells. Subsequently, in a prostate cancer skeletal metastasis mouse model, PTHrP-knockdown PC-3 cells resulted in significantly fewer metastatic lesions compared to control PC-3 cells, suggesting that PTHrP mediated antianoikis events in the bloodstream. In conclusion, nuclear localization of PTHrP confers prostate cancer cell resistance to anoikis, potentially contributing to prostate cancer metastasis.

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Dorota Dworakowska and Ashley B Grossman

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder characterised by the development of multiple hamartomas in numerous organs. It is caused by mutations of two tumour suppressor genes, TSC1 on chromosome 9q34 and TSC2 on chromosome 16p13.3, which encode for hamartin and tuberin respectively. The interaction between these two proteins, the tuberin–hamartin complex, has been shown to be critical to multiple intracellular signalling pathways, especially those controlling cell growth and proliferation. TSC may affect skin, central nervous system, kidneys, heart, eyes, blood vessels, lung, bone and gastrointestinal tract. Small series and case reports have documented that in tuberous sclerosis patients many endocrine system alterations might occur, affecting the function of the pituitary, parathyroid and other neuroendocrine tissue. There have been scattered reports of the involvement of such tissue in the pathological process of TSC, but no systematic review as to whether this is a true association. We have therefore systematically assessed all available published literature in this area. We conclude that there may be an association with pituitary and parathyroid tumours, and two recent descriptions of Cushing's disease are especially intriguing. However, the evidence seems more firm in the case of islet cell tumours, particularly insulinomas. As these latter may cause changes in mental state that may be confused with the cerebral manifestations of TSC per se, it is particularly important for physicians working with these patients to be aware of the putative and indeed likely association.

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Arthur Varoquaux, Electron Kebebew, Fréderic Sebag, Katherine Wolf, Jean-François Henry, Karel Pacak, and David Taïeb

The vagus nerve (cranial nerve X) is the main nerve of the parasympathetic division of the autonomic nervous system. Vagal paragangliomas (VPGLs) are a prime example of an endocrine tumor associated with the vagus nerve. This rare, neural crest tumor constitutes the second most common site of hereditary head and neck paragangliomas (HNPGLs), most often in relation to mutations in the succinate dehydrogenase complex subunit D (SDHD) gene. The treatment paradigm for VPGL has progressively shifted from surgery to abstention or therapeutic radiation with curative-like outcomes. Parathyroid tissue and parathyroid adenoma can also be found in close association with the vagus nerve in intra or paravagal situations. Vagal parathyroid adenoma can be identified with preoperative imaging or suspected intraoperatively by experienced surgeons. Vagal parathyroid adenomas located in the neck or superior mediastinum can be removed via initial cervicotomy, while those located in the aortopulmonary window require a thoracic approach. This review particularly emphasizes the embryology, molecular genetics, and modern imaging of these tumors.

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Brian Harding, Manuel C Lemos, Anita A C Reed, Gerard V Walls, Jeshmi Jeyabalan, Michael R Bowl, Hilda Tateossian, Nicky Sullivan, Tertius Hough, William D Fraser, Olaf Ansorge, Michael T Cheeseman, and Rajesh V Thakker

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized in man by parathyroid, pancreatic, pituitary and adrenal tumours. The MEN1 gene encodes a 610-amino acid protein (menin) which is a tumour suppressor. To investigate the in vivo role of menin, we developed a mouse model, by deleting Men1 exons 1 and 2 and investigated this for MEN1-associated tumours and serum abnormalities. Men1 +/− mice were viable and fertile, and 220 Men1 +/− and 94 Men1 +/+ mice were studied between the ages of 3 and 21 months. Survival in Men1 +/− mice was significantly lower than in Men1 +/+ mice (<68% vs >85%, P<0.01). Men1 +/− mice developed, by 9 months of age, parathyroid hyperplasia, pancreatic tumours which were mostly insulinomas, by 12 months of age, pituitary tumours which were mostly prolactinomas, and by 15 months parathyroid adenomas and adrenal cortical tumours. Loss of heterozygosity and menin expression was demonstrated in the tumours, consistent with a tumour suppressor role for the Men1 gene. Men1 +/− mice with parathyroid neoplasms were hypercalcaemic and hypophosphataemic, with inappropriately normal serum parathyroid hormone concentrations. Pancreatic and pituitary tumours expressed chromogranin A (CgA), somatostatin receptor type 2 and vascular endothelial growth factor-A. Serum CgA concentrations in Men1 +/− mice were not elevated. Adrenocortical tumours, which immunostained for 3-β-hydroxysteroid dehydrogenase, developed in seven Men1 +/− mice, but resulted in hypercorticosteronaemia in one out of the four mice that were investigated. Thus, these Men1 +/− mice are representative of MEN1 in man, and will help in investigating molecular mechanisms and treatments for endocrine tumours.

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Sandra Rodríguez-Rodero, Elías Delgado-Álvarez, Agustín F Fernández, Juan L Fernández-Morera, Edelmiro Menéndez-Torre, and Mario F Fraga

Aberrant epigenetics is a hallmark of cancer, and endocrine-related tumors are no exception. Recent research has been identifying an ever-growing number of epigenetic alterations in both genomic DNA methylation and histone post-translational modification in tumors of the endocrine system. Novel microarray and ultra-deep sequencing technologies have allowed the identification of genome-wide epigenetic patterns in some tumor types such as adrenocortical, parathyroid, and breast carcinomas. However, in other cancer types, such as the multiple endocrine neoplasia syndromes and thyroid cancer, tumor information is limited to candidate genes alone. Future research should fill this gap and deepen our understanding of the functional role of these alterations in cancer, as well as defining their possible clinical uses.

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Simona Grozinsky-Glasberg, Kate E Lines, Shani Avniel-Polak, Chas Bountra, and Rajesh V Thakker

Neuroendocrine neoplasms (NENs) occur usually as sporadic tumours; however, rarely, they may arise in the context of a hereditary syndrome, such as multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant disorder characterised by the combined development of pancreatic NENs (pNENs) together with parathyroid and anterior pituitary tumours. The therapeutic decision for sporadic pNENs patients is multi-disciplinary and complex: based on the grade and stage of the tumor, various options (and their combinations) are considered, such as surgical excision (either curative or for debulking aims), biological drugs (somatostatin analogues), targeted therapies (mTOR inhibitors or tyrosine kinases (TK)/receptors inhibitors), peptide receptor radioligand therapy (PRRT), chemotherapy, and liver-directed therapies. However, treatment of MEN1-related NENs’ patients is even more challenging, as these tumours are usually multifocal with co-existing foci of heterogeneous biology and malignant potential, rendering them more resistant to the conventional therapies used in their sporadic counterparts, and therefore associated with a poorer prognosis. Moreover, clinical data using standard therapeutic options in MEN1-related NENs are scarce. Recent preclinical studies have identified potentially new targeted therapeutic options for treating MEN1-associated NENs, such as epigenetic modulators, Wnt pathway-targeting β-catenin antagonists, Ras signalling modulators, Akt/mTOR signalling modulators, novel somatostatin receptors analogues, anti-angiogenic drugs, as well as MEN1 gene replacement therapy. The present review aims to summarize these novel therapeutic opportunities for NENs developing in the context of MEN1 syndrome, with an emphasis on pancreatic NENs, as they are the most frequent ones studied in MEN1-NENs models to date; moreover, due to the recent shifting nomenclature of ‘pituitary adenomas’ to ‘pituitary neuroendocrine neoplasms’, relevant data on MEN1-pituitary tumours, when appropriate, are briefly described.

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A Perren, S Schmid, T Locher, P Saremaslani, C Bonvin, P U Heitz, and P Komminoth

The tumorigenesis of sporadic endocrine tumors is still not fully understood. Activating point mutations of the serine/threonine kinase gene BRAF located on 7q34 are found in a wide range of malignancies, with the highest frequency (66%) occurring in malignant melanomas. Melanomas are tumors of neural-crest-derived cells as are medullary thyroid carcinomas, pheochromocytomas and paragangliomas. BRAF has not been examined in endocrine tumors of the diffuse neuroendocrine system or of neural-crest-derived cells.

We examined 130 endocrine tumors of the pancreas, parathyroid gland, adrenal medulla, paraganglia, lung and gastrointestinal tract as well as follicular and c-cell-derived thyroid tumors. We found a high rate of V559E mutations in papillary thyroid carcinomas (47%), one V599E mutation in a well-differentiated gastric endocrine carcinoma (malignant carcinoid), but no activating BRAF mutations in all other endocrine tumors examined. These results point towards different pathways in tumorigenesis of endocrine tumors of various localizations and only rare involvement of the MAP kinase (MAPK) pathway in a subset of malignant neuroendocrine tumors.

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Kerong Shi, Vaishali I Parekh, Swarnava Roy, Shruti S Desai, and Sunita K Agarwal

The multiple endocrine neoplasia type 1 (MEN1) syndrome is caused by germline mutations in the MEN1 gene encoding menin, with tissue-specific tumors of the parathyroids, anterior pituitary, and enteropancreatic endocrine tissues. Also, 30–40% of sporadic pancreatic endocrine tumors show somatic MEN1 gene inactivation. Although menin is expressed in all cell types of the pancreas, mouse models with loss of menin in either pancreatic α-cells, or β-cells, or total pancreas develop β-cell-specific endocrine tumors (insulinomas). Loss of widely expressed tumor suppressor genes may produce tissue-specific tumors by reactivating one or more embryonic-specific differentiation factors. Therefore, we determined the effect of menin overexpression or knockdown on the expression of β-cell differentiation factors in a mouse β-cell line (MIN6). We show that the β-cell differentiation factor Hlxb9 is posttranscriptionally upregulated upon menin knockdown, and it interacts with menin. Hlxb9 reduces cell proliferation and causes apoptosis in the presence of menin, and it regulates genes that modulate insulin level. Thus, upon menin loss or from other causes, dysregulation of Hlxb9 predicts a possible combined mechanism for β-cell proliferation and insulin production in insulinomas. These observations help to understand how a ubiquitously expressed protein such as menin might control tissue-specific tumorigenesis. Also, our findings identify Hlxb9 as an important factor for β-cell proliferation and insulin regulation.

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Joanna Grey and Kym Winter

Multiple endocrine neoplasia type 2 (MEN2) refers to the autosomal-dominant neuroendocrine tumour syndromes, MEN type 2A (MEN2A) and MEN type 2B (MEN2B). They are typified by the development of medullary thyroid cancer (MTC), phaeochromocytoma and parathyroid hyperplasia in MEN2A and MTC, phaeochromocytomas, ganglioneuromatosis and skeletal abnormalities in MEN2B. The aggressiveness of MTC is variable according to genotype, and although it is still the major cause of mortality in both conditions, prognosis has improved dramatically in those diagnosed and treated at a young age thanks to predictive genetic testing. Nevertheless, metastatic MTC, ganglioneuromatosis and a variety of other negative clinical and psychosocial impacts on quality of life and/or prognosis in MEN2 persist. In the absence, at the time of writing, of any large-scale research into quality of life specifically in MEN2, this review includes data from patient surveys and anonymised patient anecdotes from the records of the Association for Multiple Endocrine Neoplasia Disorders (AMEND), for whom the authors work. We recommend that these patients are cared for only in centres of expertise able to provide expert diagnosis, treatment and continuity of care, including psychological and transition support. Only in this way can the clinical advances of the last two and half decades be built upon further to ensure that the care of these complex, lifelong patients can be considered truly holistic.

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Anna Angelousi, Georgios K Dimitriadis, Georgios Zografos, Svenja Nölting, Gregory Kaltsas, and Ashley Grossman

Tumourigenesis is a relatively common event in endocrine tissues. Currently, specific guidelines have been developed for common malignant endocrine tumours, which also incorporate advances in molecular targeted therapies (MTT), as in thyroid cancer and in gastrointestinal neuroendocrine malignancies. However, there is little information regarding the role and efficacy of MTT in the relatively rare malignant endocrine tumours mainly involving the adrenal medulla, adrenal cortex, pituitary, and parathyroid glands. Due to the rarity of these tumours and the lack of prospective studies, current guidelines are mostly based on retrospective data derived from surgical, locoregional and ablative therapies, and studies with systemic chemotherapy. In addition, in many of these malignancies the prognosis remains poor with individual patients responding differently to currently available treatments, necessitating the development of new personalised therapeutic strategies. Recently, major advances in the molecular understanding of endocrine tumours based on genomic, epigenomic, and transcriptome analysis have emerged, resulting in new insights into their pathogenesis and molecular pathology. This in turn has led to the use of novel MTTs in increasing numbers of patients. In this review, we aim to present currently existing and evolving data using MTT in the treatment of adrenal, pituitary and malignant parathyroid tumours, and explore the current utility and effectiveness of such therapies and their future evolution.