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Camilletti MA, Abeledo-Machado A, Perez PA, Faraoni EY, De Fino F, Rulli SB, Ferraris J, Pisera D, Gutierrez S, Thomas P, Díaz-Torga G. mPRs represent a novel target for PRL inhibition in experimental prolactinomas. Endocr Relat Cancer 2019; 26:497-510. [PMID: 30856609 DOI: 10.1530/erc-18-0409] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 03/11/2019] [Indexed: 12/15/2022]
Abstract
Membrane progesterone receptors are known to mediate rapid nongenomic progesterone effects in different cell types. Recent evidence revealed that mPRα is highly expressed in the rat pituitary, being primarily localized in lactotrophs, acting as an intermediary of P4-inhibitory actions on prolactin secretion. The role of mPRs in prolactinoma development remains unclear. We hypothesize that mPR agonists represent a novel tool for hyperprolactinemia treatment. To this end, pituitary expression of mPRs was studied in three animal models of prolactinoma. Expression of mPRs and nuclear receptor was significantly decreased in tumoral pituitaries compared to normal ones. However, the relative proportion of mPRα and mPRβ was highly increased in prolactinomas. Interestingly, the selective mPR agonist (Org OD 02-0) significantly inhibited PRL release in both normal and tumoral pituitary explants, displaying a more pronounced effect in tumoral tissues. As P4 also regulates PRL secretion indirectly, by acting on dopaminergic neurons, we studied mPR involvement in this effect. We found that the hypothalamus has a high expression of mPRs. Interestingly, both P4 and OrgOD 02-0 increased dopamine release in hypothalamus explants. Moreover, in an in vivo treatment, that allows both, pituitary and hypothalamus actions, the mPR agonist strongly reduced the hyperprolactinemia in transgenic females carrying prolactinoma. Finally, we also found and interesting gender difference: males express higher levels of pituitary mPRα/β, a sex that does not develop prolactinoma in these mice models. Taken together, these findings suggest mPRs activation could represent a novel tool for hyperprolactinemic patients, especially those that present resistance to dopaminergic drugs.
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Affiliation(s)
| | | | - Pablo A Perez
- Centro de Microscopia Electrónica, Instituto de Investigaciones en Ciencias de la Salud (INICSA-CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Erika Y Faraoni
- Instituto de Biología y Medicina Experimental (IBYME), CONICET, Buenos Aires, Argentina
| | - Fernanda De Fino
- Instituto de Investigaciones Farmacológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Susana B Rulli
- Instituto de Biología y Medicina Experimental (IBYME), CONICET, Buenos Aires, Argentina
| | - Jimena Ferraris
- Instituto de Investigaciones Biomédicas (INBIOMED), Facultad de Medicina, UBA-CONICET, Buenos Aires, Argentina
| | - Daniel Pisera
- Instituto de Investigaciones Biomédicas (INBIOMED), Facultad de Medicina, UBA-CONICET, Buenos Aires, Argentina
| | - Silvina Gutierrez
- Centro de Microscopia Electrónica, Instituto de Investigaciones en Ciencias de la Salud (INICSA-CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Peter Thomas
- Marine Science Institute, University of Texas at Austin, Port Aransas, Texas, USA
| | - Graciela Díaz-Torga
- Instituto de Biología y Medicina Experimental (IBYME), CONICET, Buenos Aires, Argentina
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2
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Roof AK, Trudeau T, Gutierrez-Hartmann A. Pituitary somatolactotropes evade an oncogenic response to Ras. Mol Cell Endocrinol 2018; 476:165-172. [PMID: 29753028 PMCID: PMC6120793 DOI: 10.1016/j.mce.2018.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 05/07/2018] [Accepted: 05/08/2018] [Indexed: 10/16/2022]
Abstract
Distinct cell types have been shown to respond to activated Ras signaling in a cell-specific manner. In contrast to its pro-tumorigenic role in some human epithelial cancers, oncogenic Ras triggers differentiation of pheochromocytoma cells and medullary thyroid carcinoma cells. Furthermore, we have previously demonstrated that in pituitary somatolactotropes, activated Ras promotes differentiation and is not sufficient to drive tumorigenesis. These findings demonstrate that lactotrope cells have the ability to evade the tumorigenic fate that is often associated with persistent activation of Ras/ERK signaling, and suggest that there may be differential expression of inhibitory signaling molecules or negative cell cycle regulators that act as a brake to prevent the tumorigenic effects of sustained Ras signaling. Here we aim to gain further insight into the mechanisms that allow GH4T2 cells to evade an oncogenic response to Ras. We show that Ral, but likely not menin, plays a key role in directing Ras-mediated differentiation of somatolactotropes, which may allow these cells to escape the tumorigenic fate that is often associated with activated Ras signaling. We also show that dominant negative Ras expression results in reduced GH4T2 cell proliferation and transformation, but does not influence differentiation. Taken together, the data presented here begin to shed light on the mechanisms by which pituitary somatolactotropes evade an oncogenic response to persistently activated Ras signaling and suggest that the architecture of the Ras signaling cascade in some endocrine cell types may be distinct from that of cells that respond to Ras in an oncogenic manner.
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Affiliation(s)
- Allyson K Roof
- Program in Integrated Physiology and Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States; Division of Endocrinology, Metabolism, and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States
| | - Tammy Trudeau
- Division of Endocrinology, Metabolism, and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States; Departments of Medicine and of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States
| | - Arthur Gutierrez-Hartmann
- Program in Integrated Physiology and Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States; Division of Endocrinology, Metabolism, and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States; Departments of Medicine and of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, United States.
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3
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Recouvreux MV, Faraoni EY, Camilletti MA, Ratner L, Abeledo-Machado A, Rulli SB, Díaz-Torga G. Sex differences in the pituitary TGFβ1 system: The role of TGFβ1 in prolactinoma development. Front Neuroendocrinol 2018; 50:118-122. [PMID: 29074127 DOI: 10.1016/j.yfrne.2017.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 09/21/2017] [Accepted: 10/11/2017] [Indexed: 02/07/2023]
Abstract
Prolactinomas are the most frequent functioning pituitary adenomas, and sex differences in tumor size, behavior and incidence have been described. These differences have been associated with earlier diagnosis in woman, as well as with serum estradiol levels. Experimental models of prolactinomas in rodents also show a higher incidence in females, and recent findings suggest that gender differences in the transforming growth factor beta 1 (TGFβ1) system might be involved in the sex-specific development of prolactinomas in these models. The aim of this review is to summarize the literature supporting the important role of TGFβ1 as a local modulator of pituitary lactotroph function and to provide recent evidence for TGFβ1 involvement in the sex differences found in prolactinoma development in animal models.
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Affiliation(s)
- M Victoria Recouvreux
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina; Tumor Initiation and Maintenance Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd, La Jolla, CA 92037, United States.
| | - Erika Y Faraoni
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina.
| | - M Andrea Camilletti
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina.
| | - Laura Ratner
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina.
| | - Alejandra Abeledo-Machado
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina.
| | - Susana B Rulli
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina.
| | - Graciela Díaz-Torga
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, V. Obligado 2490, 1428 Buenos Aires, Argentina.
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4
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Spoletini M, Taurone S, Tombolini M, Minni A, Altissimi G, Wierzbicki V, Giangaspero F, Parnigotto PP, Artico M, Bardella L, Agostinelli E, Pastore FS. Trophic and neurotrophic factors in human pituitary adenomas (Review). Int J Oncol 2017; 51:1014-1024. [PMID: 28902350 DOI: 10.3892/ijo.2017.4120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 07/17/2017] [Indexed: 11/06/2022] Open
Abstract
The pituitary gland is an organ that functionally connects the hypothalamus with the peripheral organs. The pituitary gland is an important regulator of body homeostasis during development, stress, and other processes. Pituitary adenomas are a group of tumors arising from the pituitary gland: they may be subdivided in functional or non-functional, depending on their hormonal activity. Some trophic and neurotrophic factors seem to play a key role in the development and maintenance of the pituitary function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. Several lines of evidence suggest that trophic and neurotrophic factors may be involved in pituitary function, thus suggesting a possible role of the trophic and neurotrophic factors in the normal development of pituitary gland and in the progression of pituitary adenomas. Additional studies might be necessary to better explain the biological role of these molecules in the development and progression of this type of tumor. In this review, in light of the available literature, data on the following neurotrophic factors are discussed: ciliary neurotrophic factor (CNTF), transforming growth factors β (TGF‑β), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), vascular endothelial growth inhibitor (VEGI), fibroblast growth factors (FGFs) and epidermal growth factor (EGF) which influence the proliferation and growth of pituitary adenomas.
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Affiliation(s)
- Marialuisa Spoletini
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, 'Sapienza' University of Rome, Rome, Italy
| | - Samanta Taurone
- Department of Sensory Organs, 'Sapienza' University of Rome, Rome, Italy
| | - Mario Tombolini
- Department of Sensory Organs, 'Sapienza' University of Rome, Rome, Italy
| | - Antonio Minni
- Department of Sensory Organs, 'Sapienza' University of Rome, Rome, Italy
| | | | | | - Felice Giangaspero
- Department of Radiology, Oncology and Anatomic Pathology, 'Sapienza' University of Rome, Rome, Italy
| | - Pier Paolo Parnigotto
- Foundation for Biology and Regenerative Medicine, Tissue Engineering and Signaling (TES) Onlus, Padua, Italy
| | - Marco Artico
- Department of Sensory Organs, 'Sapienza' University of Rome, Rome, Italy
| | - Lia Bardella
- Department of Neurology and Psychiatry, 'Sapienza' University of Rome, Rome, Italy
| | - Enzo Agostinelli
- Department of Biochemical Sciences 'A. Rossi Fanelli', 'Sapienza' University of Rome, Rome, Italy
| | - Francesco Saverio Pastore
- Department of Systems' Medicine, Division of Neurosurgery, University of Rome 'Tor Vergata', Rome, Italy
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5
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Skaper SD. Nerve growth factor: a neuroimmune crosstalk mediator for all seasons. Immunology 2017; 151:1-15. [PMID: 28112808 PMCID: PMC5382350 DOI: 10.1111/imm.12717] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 01/16/2017] [Accepted: 01/18/2017] [Indexed: 12/13/2022] Open
Abstract
Neurotrophic factors comprise a broad family of biomolecules - most of which are peptides or small proteins - that support the growth, survival and differentiation of both developing and mature neurons. The prototypical example and best-characterized neurotrophic factor is nerve growth factor (NGF), which is widely recognized as a target-derived factor responsible for the survival and maintenance of the phenotype of specific subsets of peripheral neurons and basal forebrain cholinergic nuclei during development and maturation. In addition to being active in a wide array of non-nervous system cells, NGF is also synthesized by a range of cell types not considered as classical targets for innervation by NGF-dependent neurons; these include cells of the immune-haematopoietic lineage and populations in the brain involved in neuroendocrine functions. NGF concentrations are elevated in numerous inflammatory and autoimmune states such as multiple sclerosis, chronic arthritis, systemic lupus erythematosus and mastocytosis, in conjunction with increased accumulation of mast cells. Intriguingly, NGF seems to be linked also with diabetic pathology and insulin homeostasis. Mast cells and NGF appear involved in neuroimmune interactions and tissue inflammation. As mast cells are capable of producing and responding to NGF, this suggests that alterations in mast cell behaviour could provoke maladaptive neuroimmune tissue responses, including those of an autoimmune nature. Moreover, NGF exerts a modulatory role on sensory nociceptive nerve physiology in the adult, which appears to correlate with hyperalgesic phenomena occurring in tissue inflammation. NGF can therefore be viewed as a multifactorial modulator of neuro-immune-endocrine functions.
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Affiliation(s)
- Stephen D. Skaper
- Department of Pharmaceutical and Pharmacological SciencesUniversity of PaduaPaduaItaly
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6
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Booth A, Trudeau T, Gomez C, Lucia MS, Gutierrez-Hartmann A. Persistent ERK/MAPK activation promotes lactotrope differentiation and diminishes tumorigenic phenotype. Mol Endocrinol 2015; 28:1999-2011. [PMID: 25361391 DOI: 10.1210/me.2014-1168] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The signaling pathways that govern the lactotrope-specific differentiated phenotype, and those that control lactotrope proliferation in both physiological and pathological lactotrope expansion, are poorly understood. Moreover, the specific role of MAPK signaling in lactotrope proliferation vs differentiation, whether activated phosphorylated MAPK is sufficient for prolactinoma tumor formation remain unknown. Given that oncogenic Ras mutations and persistently activated phosphorylated MAPK are found in human tumors, including prolactinomas and other pituitary tumors, a better understanding of the role of MAPK in lactotrope biology is required. Here we directly examined the role of persistent Ras/MAPK signaling in differentiation, proliferation, and tumorigenesis of rat pituitary somatolactotrope GH4 cells. We stimulated Ras/MAPK signaling in a persistent, long-term manner (over 6 d) in GH4 cells using two distinct approaches: 1) a doxycycline-inducible, oncogenic V12Ras expression system; and 2) continuous addition of exogenous epidermal growth factor. We find that long-term activation of the Ras/MAPK pathway over 6 days promotes differentiation of the bihormonal somatolactotrope GH4 precursor cell into a prolactin-secreting, lactotrope cell phenotype in vitro and in vivo with GH4 cell xenograft tumors. Furthermore, we show that persistent activation of the Ras/MAPK pathway not only fails to promote cell proliferation, but also diminishes tumorigenic characteristics in GH4 cells in vitro and in vivo. These data demonstrate that activated MAPK promotes differentiation and is not sufficient to drive tumorigenesis, suggesting that pituitary lactotrope tumor cells have the ability to evade the tumorigenic fate that is often associated with Ras/MAPK activation.
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Affiliation(s)
- Allyson Booth
- Program in Reproductive Sciences and Integrated Physiology (A.B., A.G.-H.) and Departments of Medicine and of Biochemistry and Molecular Genetics (T.T., C.G., A.G.-H.) and Pathology (M.S.L.), University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado 80045
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7
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Gu W, Fukuda T, Isaji T, Hang Q, Lee HH, Sakai S, Morise J, Mitoma J, Higashi H, Taniguchi N, Yawo H, Oka S, Gu J. Loss of α1,6-Fucosyltransferase Decreases Hippocampal Long Term Potentiation: IMPLICATIONS FOR CORE FUCOSYLATION IN THE REGULATION OF AMPA RECEPTOR HETEROMERIZATION AND CELLULAR SIGNALING. J Biol Chem 2015; 290:17566-75. [PMID: 25979332 DOI: 10.1074/jbc.m114.579938] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Indexed: 01/01/2023] Open
Abstract
Core fucosylation is catalyzed by α1,6-fucosyltransferase (FUT8), which transfers a fucose residue to the innermost GlcNAc residue via α1,6-linkage on N-glycans in mammals. We previously reported that Fut8-knock-out (Fut8(-/-)) mice showed a schizophrenia-like phenotype and a decrease in working memory. To understand the underlying molecular mechanism, we analyzed early form long term potentiation (E-LTP), which is closely related to learning and memory in the hippocampus. The scale of E-LTP induced by high frequency stimulation was significantly decreased in Fut8(-/-) mice. Tetraethylammonium-induced LTP showed no significant differences, suggesting that the decline in E-LTP was caused by postsynaptic events. Unexpectedly, the phosphorylation levels of calcium/calmodulin-dependent protein kinase II (CaMKII), an important mediator of learning and memory in postsynapses, were greatly increased in Fut8(-/-) mice. The expression levels of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) in the postsynaptic density were enhanced in Fut8(-/-) mice, although there were no significant differences in the total expression levels, implicating that AMPARs without core fucosylation might exist in an active state. The activation of AMPARs was further confirmed by Fura-2 calcium imaging using primary cultured neurons. Taken together, loss of core fucosylation on AMPARs enhanced their heteromerization, which increase sensitivity for postsynaptic depolarization and persistently activate N-methyl-d-aspartate receptors as well as Ca(2+) influx and CaMKII and then impair LTP.
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Affiliation(s)
- Wei Gu
- From the Division of Regulatory Glycobiology and
| | | | - Tomoya Isaji
- From the Division of Regulatory Glycobiology and
| | - Qinglei Hang
- From the Division of Regulatory Glycobiology and
| | - Ho-hsun Lee
- From the Division of Regulatory Glycobiology and
| | - Seiichiro Sakai
- the Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577
| | - Jyoji Morise
- the Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, and
| | - Junya Mitoma
- the Division of Glyco-Signal Research, Tohoku Pharmaceutical University, Sendai, Miyagi, 981-8558
| | - Hideyoshi Higashi
- the Division of Glyco-Signal Research, Tohoku Pharmaceutical University, Sendai, Miyagi, 981-8558
| | | | - Hiromu Yawo
- the Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577
| | - Shogo Oka
- the Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, and
| | - Jianguo Gu
- From the Division of Regulatory Glycobiology and
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Zhao WJ, Jiang Q, Mei JP. Neurohypophyseal Neuregulin 1 Is Derived from the Hypothalamus as a Potential Prolactin Modulator. Neuroendocrinology 2015; 102:288-299. [PMID: 26043804 DOI: 10.1159/000431377] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Accepted: 05/14/2015] [Indexed: 02/05/2023]
Abstract
Although neuregulin 1 (Nrg1) has been identified in the rat hypothalamus, the localisation of Nrg1 in the hypothalamus-hypophyseal structure and its functions remain unclear and require further elucidation. In this study, we identified the existence of Nrg1β types I-III in the rat hypothalamus. We demonstrated that Nrg1 was partially localised in somatostatin-positive cells in the periventricular nucleus. It was also co-localised with arginine vasopressin in the supraoptic nucleus, median eminence and pituitary stalk. Nrg1 was also extensively distributed in the posterior pituitary (PP), including the projected neuronal fibres that surround the vascular structure and Herring bodies. Western blotting confirmed that these signals were primarily produced by soluble Nrg1 derived from a 45-kDa Nrg1 precursor mainly identified in the hypothalamus. Similar to Nrg1α, Nrg1β increased the prolactin (PRL) expression in rat pituitary RC-4B/C cells, which can be inhibited by an Akt inhibitor. In addition, Nrg1β had no apparent effect on growth hormone expression at the mRNA or protein levels. Collectively, we conclude that hypothalamic Nrg1 may be transported to the PP as the β form. We further hypothesise that Nrg1β may function via the regulation of PRL expression through a paracrine mechanism.
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Affiliation(s)
- Wei-Jiang Zhao
- Center for Neuroscience, Shantou University Medical College, Shantou, China
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9
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Booth AK, Gutierrez-Hartmann A. Signaling pathways regulating pituitary lactotrope homeostasis and tumorigenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 846:37-59. [PMID: 25472533 DOI: 10.1007/978-3-319-12114-7_2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Dysregulation of the signaling pathways that govern lactotrope biology contributes to tumorigenesis of prolactin (PRL)-secreting adenomas, or prolactinomas, leading to a state of pathological hyperprolactinemia. Prolactinomas cause hypogonadism, infertility, osteoporosis, and tumor mass effects, and are the most common type of neuroendocrine tumor. In this review, we highlight signaling pathways involved in lactotrope development, homeostasis, and physiology of pregnancy, as well as implications for signaling pathways in pathophysiology of prolactinoma. We also review mutations found in human prolactinoma and briefly discuss animal models that are useful in studying pituitary adenoma, many of which emphasize the fact that alterations in signaling pathways are common in prolactinomas. Although individual mutations have been proposed as possible driving forces for prolactinoma tumorigenesis in humans, no single mutation has been clinically identified as a causative factor for the majority of prolactinomas. A better understanding of lactotrope-specific responses to intracellular signaling pathways is needed to explain the mechanism of tumorigenesis in prolactinoma.
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Affiliation(s)
- Allyson K Booth
- Program in Reproductive Sciences and Integrated Physiology, University of Colorado Denver Anschutz Medical Campus, Aurora, Colorado, USA
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10
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Zhao W, Ren SG. Neuregulin-1 (Nrg1) is mainly expressed in rat pituitary gonadotroph cells and possibly regulates prolactin (PRL) secretion in a juxtacrine manner. J Neuroendocrinol 2011; 23:1252-62. [PMID: 21919974 DOI: 10.1111/j.1365-2826.2011.02223.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The binding of Neuregulin-1 (Nrg1) to its cognate receptors ErbB-3 and -4 mediates intercellular and intracellular communication. In vitro, this interaction has been shown to control prolactin (PRL) secretion from pituitary tumour cells. However, Nrg1/ErbB signalling and its function in vivo are not well understood. In the present study, we demonstrated that type I and III Nrg1 isoforms were expressed in the rat anterior pituitary. We observed that Nrg1 positive gonadotrophs can form contacts with lactotrophs, which are positive for ErbB-3 receptor. In addition, we show that gonadotroph cell-derived Nrg1 regulates the secretion of an 18 kDa form of PRL from pituitary lactosomatotroph GH3 cells in vitro. The results obtained strongly suggest that gonadotrophs are the major source of Nrg1 in the normal anterior pituitary and that Nrg1 may function as a paracrine/juxtacrine regulator of PRL secretion.
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Affiliation(s)
- W Zhao
- Shantou University Medical College, Center for Neuroscience, Shantou, Guangdong Province 515041, China.
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11
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Abstract
Prolactin (PRL) is a 23-kDa protein hormone that binds to a single-span membrane receptor, a member of the cytokine receptor superfamily, and exerts its action via several interacting signaling pathways. PRL is a multifunctional hormone that affects multiple reproductive and metabolic functions and is also involved in tumorigenicity. In addition to being a classical pituitary hormone, PRL in humans is produced by many tissues throughout the body where it acts as a cytokine. The objective of this review is to compare and contrast multiple aspects of PRL, from structure to regulation, and from physiology to pathology in rats, mice, and humans. At each juncture, questions are raised whether, or to what extent, data from rodents are relevant to PRL homeostasis in humans. Most current knowledge on PRL has been obtained from studies with rats and, more recently, from the use of transgenic mice. Although this information is indispensable for understanding PRL in human health and disease, there is sufficient disparity in the control of the production, distribution, and physiological functions of PRL among these species to warrant careful and judicial extrapolation to humans.
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Affiliation(s)
- Nira Ben-Jonathan
- Department of Cell and Cancer Biology, University of Cincinnati, Cincinnati, Ohio 45255, USA.
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12
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Ishida M, Takahashi W, Itoh S, Shimodaira S, Maeda S, Arita J. Estrogen actions on lactotroph proliferation are independent of a paracrine interaction with other pituitary cell types: a study using lactotroph-enriched cells. Endocrinology 2007; 148:3131-9. [PMID: 17412817 DOI: 10.1210/en.2006-1484] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The mitogenic action of estrogen on estrogen-responsive tissues is suggested to be mediated by paracrine growth factors secreted from neighboring estrogen receptor-positive cells. Using pituitary lactotrophs in primary culture, on which estrogen exerts both mitogenic and antimitogenic actions in a cell context-dependent manner, we investigated whether a paracrine cell-to-cell interaction with other pituitary cell types was required for estrogen action. In pituitary cells, enriched for lactotrophs by 85% using differential sedimentation on a discontinuous Percoll gradient, 17beta-estradiol (E2) showed an antimitogenic action on lactotrophs in the presence of IGF-I, which was similar to that in control unenriched cells. Mitogenic actions were also seen in lactotroph-enriched cells when E2 was administered alone, in combination with serum, or in combination with the adenylate cyclase activator forskolin. Similar results were obtained in 90% lactotroph-enriched cells collected by fluorescence-activated cell sorting from transgenic rats expressing enhanced green fluorescent protein under the control of the prolactin promoter. The putative role of basic fibroblast growth factor (bFGF) as a paracrine factor mediating the mitogenic action of estrogen was not supported by the results that: 1) bFGF inhibited lactotroph proliferation; 2) immunoneutralization of bFGF failed to block E2-induced proliferation; and 3) cellular bFGF levels were not altered by E2 treatment. These results suggest that the antimitogenic and mitogenic actions of estrogen on lactotrophs do not require paracrine signals from other pituitary cell types and that estrogen directly influences lactotroph proliferation.
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Affiliation(s)
- Maho Ishida
- Department of Physiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi 409-3898, and Division of Blood Transfusion, Shinshu University Hospital, Nagano, Japan
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13
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Abstract
Prolactinomas account for approximately 40% of all pituitary adenomas and are an important cause of hypogonadism and infertility. The ultimate goal of therapy for prolactinomas is restoration or achievement of eugonadism through the normalization of hyperprolactinemia and control of tumor mass. Medical therapy with dopamine agonists is highly effective in the majority of cases and represents the mainstay of therapy. Recent data indicating successful withdrawal of these agents in a subset of patients challenge the previously held concept that medical therapy is a lifelong requirement. Complicated situations, such as those encountered in resistance to dopamine agonists, pregnancy, and giant or malignant prolactinomas, may require multimodal therapy involving surgery, radiotherapy, or both. Progress in elucidating the mechanisms underlying the pathogenesis of prolactinomas may enable future development of novel molecular therapies for treatment-resistant cases. This review provides a critical analysis of the efficacy and safety of the various modes of therapy available for the treatment of patients with prolactinomas with an emphasis on challenging situations, a discussion of the data regarding withdrawal of medical therapy, and a foreshadowing of novel approaches to therapy that may become available in the future.
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Affiliation(s)
- Mary P Gillam
- Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
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14
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Asa SL. Transgenic and Knockout Mouse Models Clarify Pituitary Development, Function and Disease. Brain Pathol 2006. [DOI: 10.1111/j.1750-3639.2001.tb00406.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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15
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Abstract
Numerous factors have been shown to govern adenohypophysial cell proliferation. Human and animal models have documented that the hypothalamic trophic hormone growth hormone-releasing hormone stimulates cell proliferation, and prolonged stimulation leads to tumor formation. Similarly, lack of dopaminergic inhibition of lactotrophs and lack of feedback suppression by adrenal, gonadal or thyroid hormones are implicated, perhaps through hypothalamic stimulatory mechanisms, in pituitary adenoma formation superimposed on hyperplasia. However, most pituitary tumors are not associated with underlying hyperplasia. Overexpression of growth factors and their receptors, such as EGF, TGFalpha, EGF-R and VEGF has been identified in pituitary adenomas, and reduction of follistatin expression has been implicated in gonadotroph adenomas. Aberrant expression of members of the FGF family, an FGF antisense gene and FGF receptors have all been described in pituitary adenomas. The clonal composition of pituitary adenomas attests to the molecular basis of pituitary tumorigenesis, however, the evidence suggests that these various hypophysiotropic hormones and growth factors likely play a role as promoters of tumor cell growth in genetically transformed cells.
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Affiliation(s)
- S Ezzat
- Department of Medicine, University of Toronto, and The Freeman Centre for Endocrine Oncology, Mount Sinai Hospital, Ontario, Canada.
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16
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Sarkar DK. Genesis of prolactinomas: studies using estrogen-treated animals. FRONTIERS OF HORMONE RESEARCH 2006; 35:32-49. [PMID: 16809921 PMCID: PMC2882189 DOI: 10.1159/000094307] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Prolactin-secreting adenomas (prolactinomas) are the most prevalent form of pituitary tumors in humans. Our knowledge of the formation of these tumors is limited. Experimental work in animal has uncovered that estradiol exposure leads to prolactinoma formation via orchestrated events involving dopamine D2 receptors, transforming growth factor-beta(TGF-beta) isoforms and their receptors, as well as factors secondary to TGF-beta action. Additionally, these studies determined that TGF-beta and b-FGF interact to facilitate the communication between lactotropes and folliculo-stellate cells that is necessary for the mitogenic action of estradiol. The downstream signaling that governs lactotropic cell proliferation involves activation of the MAP kinase p44/42-dependent pathway.
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Affiliation(s)
- Dipak K Sarkar
- Endocrine Program, Biomedical Division of the Center of Alcohol Studies and Department of Animal Sciences, Rutgers, State University of New Jersey, New Brunswick, N.J., USA
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17
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Abstract
The anterior pituitary gland integrates the repertoire of hormonal signals controlling thyroid, adrenal, reproductive, and growth functions. The gland responds to complex central and peripheral signals by trophic hormone secretion and by undergoing reversible plastic changes in cell growth leading to hyperplasia, involution, or benign adenomas arising from functional pituitary cells. Discussed herein are the mechanisms underlying hereditary pituitary hypoplasia, reversible pituitary hyperplasia, excess hormone production, and tumor initiation and promotion associated with normal and abnormal pituitary differentiation in health and disease.
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Affiliation(s)
- Shlomo Melmed
- Cedars-Sinai Medical Center, David Geffen School of Medicine, University of California, 8700 Beverly Boulevard, Room 2015, Los Angeles, California 90048, USA.
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18
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Abstract
The majority of pituitary adenomas are trophically stable and change relatively little in size over many years. A comparatively small proportion behave more aggressively and come to clinical attention through inappropriate hormone secretion or adverse effects on surrounding structures. True malignant behaviour with metastatic spread is very atypical. Pituitary adenomas that come to surgery are predominantly monoclonal in origin and roughly half are aneuploid, indicating either ongoing genetic instability or transition through a period of genetic instability at some time during their development. Few are associated with the classical mechanisms of tumour formation but it is generally believed that the majority harbour quantitative if not qualitative differences in molecular composition compared to the normal pituitary. Despite their prevalence and the ready availability of biopsy material, at the present time, the precise molecular pathogenesis of the majority of pituitary adenomas remains unclear. This review summarizes current thinking.
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Affiliation(s)
- Andy Levy
- University Research Centre for Neuroendocrinology, Bristol University, Jenner Yard, Bristol BS2 8HW, UK.
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19
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Iaccarino C, Samad TA, Mathis C, Kercret H, Picetti R, Borrelli E. Control of lactotrop proliferation by dopamine: essential role of signaling through D2 receptors and ERKs. Proc Natl Acad Sci U S A 2002; 99:14530-5. [PMID: 12391292 PMCID: PMC137917 DOI: 10.1073/pnas.222319599] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dopamine is thought to exert a negative control on lactotrop cell proliferation and prolactin production. Indeed, mice lacking the D2 receptor develop pituitary tumors of lactotrop origin. Because lactotrops express two isoforms of D2R, D2L, and D2S, in a specific ratio, we decided to explore the physiological importance of their relative abundance in vivo. Thus, we generated transgenic animals overexpressing either D2L or D2S in lactotrops. Increased expression of D2S, but not of D2L, leads to mitogen-activated protein kinase (MAPK) induction, which results in pituitary hypoplasia. On the other hand, levels of phosphorylated MAPKs are drastically reduced in pituitary tumors generated by the absence of D2-dependent signaling. These results underline a critical role of D2-mediated MAPK activation in lactotrop proliferation. Furthermore, whereas D2S overexpression results to a drastic reduction of prolactin, D2L overexpression elevates it. Our findings underscore a different role of the two D2R isoforms in the pituitary gland physiology.
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Affiliation(s)
- Ciro Iaccarino
- Institut de Génétique et de Biologie Cellulaire et Moléculaire, Institut National de la Santé et de la Recherche Médicale/Centre National de la Recherche Scientifique/Université Louis Pasteur, BP 10142, 67404 Illkirch Cedex, France
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20
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21
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Abstract
Dopamine is a small and relatively simple molecule that fulfills diverse functions. Within the brain, it acts as a classical neurotransmitter whose attenuation or overactivity can result in disorders such as Parkinson's disease and schizophrenia. Major advances in the cloning and characterization of biosynthetic enzymes, transporters, and receptors have increased our knowledge regarding the metabolism, release, reuptake, and mechanism of action of dopamine. Dopamine reaches the pituitary via hypophysial portal blood from several hypothalamic nerve tracts that are regulated by PRL itself, estrogens, and several neuropeptides and neurotransmitters. Dopamine binds to type-2 dopamine receptors that are functionally linked to membrane channels and G proteins and suppresses the high intrinsic secretory activity of the pituitary lactotrophs. In addition to inhibiting PRL release by controlling calcium fluxes, dopamine activates several interacting intracellular signaling pathways and suppresses PRL gene expression and lactotroph proliferation. Thus, PRL homeostasis should be viewed in the context of a fine balance between the action of dopamine as an inhibitor and the many hypothalamic, systemic, and local factors acting as stimulators, none of which has yet emerged as a primary PRL releasing factor. The generation of transgenic animals with overexpressed or mutated genes expanded our understanding of dopamine-PRL interactions and the physiological consequences of their perturbations. PRL release in humans, which differs in many respects from that in laboratory animals, is affected by several drugs used in clinical practice. Hyperprolactinemia is a major neuroendocrine-related cause of reproductive disturbances in both men and women. The treatment of hyperprolactinemia has greatly benefited from the generation of progressively more effective and selective dopaminergic drugs.
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Affiliation(s)
- N Ben-Jonathan
- Department of Cell Biology, Neurobiology, and Anatomy, University of Cincinnati Medical Center, Cincinnati, Ohio 45267, USA.
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22
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Williams JC, Stone D, Smith-Arica JR, Morris ID, Lowenstein PR, Castro MG. Regulated, adenovirus-mediated delivery of tyrosine hydroxylase suppresses growth of estrogen-induced pituitary prolactinomas. Mol Ther 2001; 4:593-602. [PMID: 11735344 DOI: 10.1006/mthe.2001.0499] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prolactin-secreting adenomas are one of the most common types of intracranial neoplasm found in humans. The modalities of clinical treatment currently in use include D(2)-dopamine receptor agonists, surgery, and radiotherapy, and the success rates for treatment are good. However, there are prolactinomas that are difficult to treat. As an alternative, we have developed a gene therapy strategy in which the rate-limiting enzyme in dopamine synthesis, tyrosine hydroxylase (TH), is overexpressed in the anterior pituitary (AP) gland. Because dopamine is known to have an inhibitory effect on lactotroph growth and prolactin secretion, we developed a system that would enable its local synthesis from freely available precursor amino acids. A dual adenovirus tetracycline-regulatable expression system was generated to control the production of TH. In the absence but not presence of the tetracycline analog doxycycline, TH expression was observed in AP tumor cell lines AtT20, GH3, and MMQ. In both primary AP cell cultures and the AP gland, in situ expression of TH was seen in lactotrophs, somatotrophs, corticotrophs, thyrotrophs, and gonadotrophs in the absence but not presence of doxycycline. The ability of this system to inhibit hyperprolactinemia and pituitary lactotroph hyperplasia was then assessed in a model of estrogen- or estrogen/sulpiride-induced pituitary tumors. In the absence but not presence of doxycycline, a 49% reduction in pituitary growth and 58% reduction in the increase of circulating prolactin levels were observed in estrogen, but not estrogen/sulpiride, treated rats. These results indicate that in situ dopamine enhancement gene therapy can be a useful tool for the treatment of prolactinoma. Dopamine synthesis can be tightly regulated and the therapeutic benefit of the system is only inhibited when local dopamine signaling is impaired.
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Affiliation(s)
- J C Williams
- Molecular Medicine and Gene Therapy Unit, School of Medicine, University of Manchester, Room 1.302, Stopford Building, Oxford Road, Manchester M13 9PT, UK
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23
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Abstract
Nerve growth factor (NGF) is widely recognized as a target-derived factor responsible for the survival and maintenance of the phenotype of specific subsets of peripheral neurons and basal forebrain cholinergic nuclei during development and maturation. Other NGF-responsive cells are now known to belong to the hemopoietic-immune system and to populations in the brain involved in neuroendocrine functions. The concentration of NGF is elevated in a number of inflammatory and autoimmune states in conjunction with increased accumulation of mast cells. Mast cells and NGF appear to be involved in neuroimmune interactions and tissue inflammation. Mast cells themselves are capable of producing and responding to NGF, suggesting that alterations in mast cell behavior may trigger maladaptive neuroimmune tissue responses, including those of an autoimmune nature. Moreover, NGF exerts a modulatory role on sensory nociceptive nerve physiology in the adult, and appears to correlate with hyperalgesic phenomena occurring in tissue inflammation. NGF can thus be viewed as a multifactorial modulator of neuroimmune-endocrine functions.
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Affiliation(s)
- S D Skaper
- Neurology Centre of Excellence for Drug Discovery, GlaxoSmithKline Pharmaceuticals, North, Harlow, Essex, UK.
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24
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Abstract
Pituitary tumors are the result of a monoclonal outgrowth where the intrinsic genetic defects involve oncogenes, tumor suppressor genes (TSG), and most likely genes responsible for differentiation. In addition, hypothalamic and intrapituitary derived growth factors are imposed upon these aberrant cells, contributing to their growth characteristics. While histological examination will not identify those tumors likely to progress toward an invasive phenotype or those destined toward recurrence recent advances in the molecular pathology of these tumors holds significant promise for prediction of recurrence and the design of novel treatment strategies. Moreover, emerging data clearly indicate that different molecular mechanisms are involved in the pathogenesis of the various pituitary tumor subtypes. Until recently the gsp oncogene was the only oncogene significantly associated with pituitary tumors; however, emerging data have describe a role for PTTG and cyclin D1 in pituitary tumorigenesis. For known and putative TSG loci, allelic losses on the long arms of chromosomes 10, 11, and 13 are significantly associated with the transition from the noninvasive to the invasive and metastatic phenotype, while losses on chromosome 9p occur early in pituitary tumorigenesis. Studies of known TSG at these loci, including the menin gene and RB1, would suggest a limited role, if any, in pituitary tumors. However, loss of pRB is evident in a proportion of somatotropinomas but is not associated with allelic loss of an RB1 intragenic marker. The gene encoding p16/CDKN2A is neither deleted nor mutated in pituitary tumors; however, its associated CpG island is frequently methylated and is associated with a loss of p16 protein expression. Allelic losses on chromosome 9p, frequent methylation, and loss of p16 protein appear as early changes in nonfunctional tumors, whereas they are infrequent events in somatotropinomas. The functional consequence of enforced expression of p16/CDKN2A in the mouse corticotroph cell line AtT20 has shown that it is responsible for a profound reduction in cell proliferation and the mechanism is a G(1) arrest, mimicking the in vivo role of this cell cycle regulator in most tissues. The combined data from several groups show that the allelic losses reported at known TSG loci are not accompanied by mutation in the retained allele. However, since abnormal methylation patterns may precede and predispose toward genetic instability this could account for the allelic losses on these chromosomes. Equally, since DNA methylation may lead to reduced expression of a gene it might also account for the reduced expression of as yet unidentified TSGs implicated in pituitary tumorigenesis. Collectively these studies hold significant promise as markers predictive of tumor behavior and point to novel treatment strategies, which may include the reactivation of TSGs that are intact but silenced through epigenetic mechanisms.
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Affiliation(s)
- W E Farrell
- Centre for Cell and Molecular Medicine, University of Keele, North Staffordshire Hospital Thornburrow Drive, Stoke on Trent, ST4 7QB, United Kingdom.
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25
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Abstract
Many growth factors are expressed in normal pituitary cells and pituitary tumors. They are involved in gene expression for pituitary hormones and in cell proliferation. Some appear to be important for prognosis or treatment. Strong overexpression of some growth factors may indicate a more rapid growth. The significance of the different growth factors for pituitary function and pathology is discussed.
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26
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Cai A, Hayes JD, Patel N, Hyde JF. Targeted overexpression of galanin in lactotrophs of transgenic mice induces hyperprolactinemia and pituitary hyperplasia. Endocrinology 1999; 140:4955-64. [PMID: 10537119 DOI: 10.1210/endo.140.11.7120] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We generated transgenic mice that carry 4.6 kb of the mouse galanin gene fused to 2.5 kb of the rat PRL promoter. In all transgenic lines that carried and transmitted the transgene, there were significant increases in galanin messenger RNA and peptide levels in the anterior pituitary in both male and female transgenic mice, and the elevation of galanin was restricted to the anterior lobe. Furthermore, galanin release from pituitary cells in vitro of both male and female transgenic mice was dramatically increased compared with that in control mice. At 2-4 months of age, pituitary PRL contents in female transgenic mice were increased compared with those in normal controls. Moreover, PRL messenger RNA levels were increased in female transgenic mice. However, plasma levels of PRL in female transgenic mice were not significantly higher until 6 months of age. By 11 months of age, cell numbers in the anterior pituitary were increased in female, but not male, transgenic mice. The percentage of lactotrophs in female transgenic mice as well as PRL gene expression per cell were significantly higher. No differences were detected in PRL content, gene expression, or release between normal and transgenic male mice. Six weeks of estrogen treatment significantly increased anterior pituitary weights and PRL secretion in male transgenic mice compared with that in normal male mice. In addition, anterior pituitary weights and PRL secretion were decreased in female transgenic mice compared with controls 6 weeks after ovariectomy. We conclude that overexpression of galanin in lactotrophs stimulates PRL synthesis and secretion and acts as a growth factor resulting in the formation of pituitary hyperplasia and hyperprolactinemia. Furthermore, estrogen appears critical for these galanin-mediated events.
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Affiliation(s)
- A Cai
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington 40536-0084, USA
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27
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Suzuki S, Yamamoto I, Arita J. Mitogen-activated protein kinase-dependent stimulation of proliferation of rat lactotrophs in culture by 3',5'-cyclic adenosine monophosphate. Endocrinology 1999; 140:2850-8. [PMID: 10342877 DOI: 10.1210/endo.140.6.6775] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Intracellular cAMP regulates cell proliferation as a second messenger of extracellular signals in a number of cell types. We investigated, by pharmacological means, whether an increase in intracellular cAMP levels changes proliferation rates of lactotrophs in primary culture, whether there are interactions between signal transduction pathways of cAMP and the growth factor insulin, and where the dopamine receptor agonist bromocriptine acts in the cAMP pathway to inhibit lactotroph proliferation. Rat anterior pituitary cells, cultured in serum-free medium, were treated with cAMP-increasing agents, followed by 5-bromo-2'-deoxyuridine (BrdU) to label proliferating pituitary cells. BrdU-labeling indices indicative of the proliferation rate of lactotrophs were determined by double immunofluorescence staining for PRL and BrdU. Treatment with forskolin (an adenylate cyclase activator) or (Bu)2cAMP (a membrane-permeable cAMP analog) increased BrdU-labeling indices of lactotrophs in a dose- and incubation time-dependent manner. The cAMP-increasing agents were also effective in increasing BrdU-labeling indices in populations enriched for lactotrophs by differential sedimentation. The stimulatory action of forskolin was observed, regardless of concentrations of insulin that were added in combination with forskolin. Inhibition of the action of endogenous cAMP by H89 or KT5720, a protein kinase A inhibitor, attenuated an increase in BrdU-labeling indices by insulin treatment. On the other hand, the specific mitogen-activated protein kinase inhibitor PD98059, which was effective in blocking the mitogenic action of insulin, markedly suppressed the forskolin-induced increase in BrdU-labeling indices. (Bu)2cAMP antagonized not only inhibition of BrdU labeling indices but also changes in cell shape induced by bromocriptine treatment, although forskolin did not have such an antagonizing effect. These results suggest that: 1) intracellular cAMP plays a stimulatory role in the regulation of lactotroph proliferation; 2) cAMP and insulin/mitogen-activated protein kinase signalings require each other for their mitogenic actions; and 3) the antimitogenic action of bromocriptine is, at least in part, caused by inhibition of cAMP production.
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Affiliation(s)
- S Suzuki
- Department of Physiology, Yamanashi Medical University, Japan
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28
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Abstract
Prolactin-secreting tumors are the most frequently occurring neoplasms in the human pituitary. Although the clinical syndrome associated with prolactinomas is well recognized the molecular and cellular mechanisms leading to cell transformation and development of these tumors remain elusive. In this paper we summarize recent evidence suggesting that both hypothalamic and intrapituitary defects can be involved in the development of prolactinomas. In particular alterations of the hypothalamo-pituitary dopaminergic transmission result in the dysregulation of the proliferative activity of lactotrope cells leading to tumor development. Similarly changes in the expression and activity of resident growth factors also play a role in pituitary tumorigenesis. In particular both overexpression of TGF alpha and loss of NGF production appear to be involved in the development and progression of prolactin-secreting tumors.
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Affiliation(s)
- C Missale
- Department of Biomedical Sciences and Biotechnology, University of Brescia, Italy.
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29
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Scheithauer BW, Horvath E, Kovacs K, Lloyd RV, Stefaneanu L, Buchfelder M, Fahlbusch R, von Werder K, Lyons DF. Prolactin-producing pituitary adenoma and carcinoma with neuronal components--a metaplastic lesion. Pituitary 1999; 1:197-205. [PMID: 11081198 DOI: 10.1023/a:1009913303109] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recent studies indicate that cells of various epithelial tumors are capable of transformation to neurons. Observing both neurons and neuropil in two prolactin-producing adenohypophyseal tumors, one benign and one malignant, we sought to assess their cellular differentiation, the presence of nerve growth factor receptor, and expression of the dopamine receptor gene using immunocytochemistry, electron microscopy, and in situ hybridization. Light and electron microscopy clearly revealed cells morphologically transitional between adenoma/carcinoma cells and neurons. Large neurons lacked proliferative activity. Neurons in varying number showed immunoreactivity for pituitary hormones including prolactin, growth hormone and alpha subunit in the adenoma and prolactin alone in the carcinoma. The distribution of nerve growth factor receptor staining was similar. In both tumors, in situ hybridization showed mRNAs for prolactin and dopamine receptor within adenohypophyseal cells and neurons. Our results indicate that the occurrence of neurons and neuropil in growth hormone and prolactin-producing pituitary tumors appears to be the result of metaplasia. The process is not limited to benign tumors and may be due to the production of tropic substances by the adenohypophysial cells, which by paracrine/autocrine mechanisms result in transformation of adenoma cells to nerve cells.
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Affiliation(s)
- B W Scheithauer
- Department of Laboratory Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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30
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Affiliation(s)
- P L Dahia
- Department of Endocrinology, St. Bartholomew's Hospital, London, United Kingdom
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31
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Westphal CH, Muller L, Zhou A, Zhu X, Bonner-Weir S, Schambelan M, Steiner DF, Lindberg I, Leder P. The neuroendocrine protein 7B2 is required for peptide hormone processing in vivo and provides a novel mechanism for pituitary Cushing's disease. Cell 1999; 96:689-700. [PMID: 10089884 DOI: 10.1016/s0092-8674(00)80579-6] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The neuroendocrine protein 7B2 has been implicated in activation of prohormone convertase 2 (PC2), an important neuroendocrine precursor processing endoprotease. To test this hypothesis, we created a null mutation in 7B2 employing a novel transposon-facilitated technique and compared the phenotypes of 7B2 and PC2 nulls. 7B2 null mice have no demonstrable PC2 activity, are deficient in processing islet hormones, and display hypoglycemia, hyperproinsulinemia, and hypoglucagonemia. In contrast to the PC2 null phenotype, these mice show markedly elevated circulating ACTH and corticosterone levels, with adrenocortical expansion. They die before 9 weeks of severe Cushing's syndrome arising from pituitary intermediate lobe ACTH hypersecretion. We conclude that 7B2 is indeed required for activation of PC2 in vivo but has additional important functions in regulating pituitary hormone secretion.
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Affiliation(s)
- C H Westphal
- Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, Boston Massachusetts 02115, USA
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32
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Affiliation(s)
- S L Asa
- Department of Pathology, Mount Sinai Hospital, Toronto, Ontario, Canada.
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33
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Denef C. Autocrine/Paracrine Intermediates in Hormonal Action and Modulation of Cellular Responses to Hormones. Compr Physiol 1998. [DOI: 10.1002/cphy.cp070118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
The secrets of anterior pituitary development and cell lineage determination have been revealed mostly by genetic analyses. The requirement for three homeobox genes, Lbx3, Lbx4 and Titf1, during early organogenesis was proven by gene targeting. Spontaneous mouse mutations revealed two additional homeobox genes, Pit1 and Prop1, that are critical for specialization and proliferation of subsets of the five differentiated cell types. Analysis of patients with pituitary insufficiency has demonstrated the importance of these two genes in human pituitary function. Recently, several other homeobox genes have been identified and implicated in pituitary organogenesis. Genetic manipulations of these genes will undoubtedly add to the emerging genetic hierarchy regulating the ontogeny of this major hormone-producing gland.
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Affiliation(s)
- D E Watkins-Chow
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor 48109-0638, USA
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35
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Ueta Y, Levy A, Powell MP, Lightman SL, Kinoshita Y, Yokota A, Shibuya I, Yamashita H. Neuronal nitric oxide synthase gene expression in human pituitary tumours: a possible association with somatotroph adenomas and growth hormone-releasing hormone gene expression. Clin Endocrinol (Oxf) 1998; 49:29-38. [PMID: 9797844 DOI: 10.1046/j.1365-2265.1998.00399.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Nitric oxide (NO) has been implicated in the control of the secretory response to growth hormone-releasing hormone (GHRH) and may also modify GH release in response to excitatory aminoacids. Although rat and mouse pituitary cell lines have been shown to express neuronal NO synthase (nNOS), there has until now been no information on nNOS gene expression in human pituitary adenomas. Our objective was to provide such data and correlate the presence of nNOS transcripts with GHRH transcripts. PATIENTS Pituitary adenoma tissue was obtained from a random selection of 32 patients with somatotrophadenomas, 16 patients with corticotroph adenomas, 39 patients with endocrinologically inactive adenomas and nine patients with macroprolactinomas undergoing transsphenoidal hypophysectomy. MEASUREMENTS Transcripts for nNOS and GHRH were identified in frozen tissue sections by in situ hybridization histochemistry using synthetic 35S-labelled oligodeoxynucleotide probes with 100% homology to the target transcript. RESULTS Neuronal NOS transcripts were identified in one of 16 corticotroph adenomas (6%), one of nine macroprolactinomas (11%), six of 39 endocrinologically inactive adenomas (15%) and 13 of 32 somatotroph adenomas (41%). GHRH transcripts were found in a similar distribution to nNOS transcripts in 10 of the 13 nNOS-expressing somatotroph adenomas, and in three of the four remaining adenomas from which suitable tissue was available. Cross-hybridization of the nNOS and GHRH probes to the same target was excluded by including rat brain sections cut through the arcuate nucleus as hybridization controls. Furthermore, two different nNOS oligodeoxynucleotide probes complementary to different regions of the target transcript produced identical results. CONCLUSIONS These results suggest that there is a close correlation between nNOS gene expression and 'ectopic' expression of GHRH in human pituitary tumours, especially somatotroph adenomas. The relevance of these findings from a functional or pathologenic viewpoint remains unclear, but the data again emphasize that it is not just GH secretion that distinguishes somatotroph adenomas from other pituitary tumours.
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Affiliation(s)
- Y Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
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36
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Affiliation(s)
- C Missale
- Department of Biomedical Sciences and Biotechnologies, University of Brescia, Italy
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37
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Davis BM, Goodness TP, Soria A, Albers KM. Over-expression of NGF in skin causes formation of novel sympathetic projections to trkA-positive sensory neurons. Neuroreport 1998; 9:1103-7. [PMID: 9601676 DOI: 10.1097/00001756-199804200-00027] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Previous studies have shown that transgenic mice over-expressing NGF in the skin have novel sympathetic 'basket-like' projections to sensory neurons similar to that seen in models of chronic pain. Since only a subset of sensory neurons in the NGF-transgenic mice received the sympathetic projections, we hypothesized that sympathetic sprouting was targeted to those neurons affected by increased levels of NGF. To test this, double-label immunohistochemistry for the NGF receptor (trkA) and sympathetic baskets was performed. Thirty-nine percent of all neurons in transgenic trigeminal ganglia were trkA-positive. Moreover, of the population of sensory neurons that received sympathetic input, 84% were trkA-positive. These results indicate that retrogradely transported NGF can induce and direct growth of sympathetic axons in vivo.
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Affiliation(s)
- B M Davis
- Department of Anatomy, University of Kentucky College of Medicine, Lexington 40536-0084, USA
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38
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Abstract
Cells in the anterior pituitary originate from a common pluripotent precursor whose phenotypic development is determined by intrapituitary transcription factors as well as by hypothalamic and peripheral signals. A rapidly growing body of evidence revealed that essential to the differentiation and proliferation of pituitary cells are an array of growth factors that are produced within the pituitary and act mainly through autocrine mechanisms. Growth factors are polypeptides that are released in carefully measured amounts by some cells to regulate cell growth and differentiation by activating specific tyrosine kinase receptors in the plasma membrane of target cells. Both overproduction of mitogenic growth factors and loss of factors inhibiting cell proliferation result in uncontrolled cell growth and tumor development. There is now increasing evidence that disruption of the calibrated signalling network activated by pituitary growth factors plays a central role in pituitary tumorigenesis. This paper is focussed on the role of nerve growth factor (NGF) in pituitary physiology and pathology. In particular, we propose that NGF plays a dual role in the gland: a local one as a stimulator of differentiation and proliferation of lactotrope cells during pituitary development and a systemic one as a neurohormone which is cosecreted with prolactin into the bloodstream. Furthermore, we discuss the evidence that NGF is an autocrine differentiation factor for prolactin-secreting cells. Escape from NGF control appears to be one of the mechanisms involved in the development and progression of prolactinomas. Along the same line, exposure of prolactinomas refractory to dopaminergic therapy to exogenous NGF results in their differentiation into lactotrope-like cells reexpressing the D2 receptor protein. This observation may open the way to a sequential therapy with NGF and bromocriptine for patients refractory to the conventional therapy.
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Affiliation(s)
- C Missale
- Department of Biomedical Sciences and Biotechnology, University of Brescia, Italy
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39
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Aguado F, Majó G, Gómez de Aranda I, Ferrer I. Trk neurotrophin receptor family immunoreactivity in rat and human pituitary tissues. Neurosci Lett 1998; 243:13-6. [PMID: 9535101 DOI: 10.1016/s0304-3940(98)00074-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Several lines of evidence suggest that neurotrophins may be involved in pituitary function. By immunocytochemical methods we analyzed the cellular distribution of their functional receptors in the pituitary gland. In the rat pituitary gland Trks were differentially distributed. Punctate immunoreactivity for TrkA was observed within the neural lobe, whereas numerous nerve endings were immunostained for TrkB and TrkC in the intermediate lobe. Endocrine cells of the intermediate lobe exhibited intense immunoreactivity for the three Trks, whereas scattered endocrine cells of the anterior lobe displayed a robust immunostaining for TrkC. In addition, TrkA and TrkB immunoreactivity was located in normal and neoplastic endocrine cells from human pituitary adenomas. The differential distribution of Trks in the hypophysis suggests a potential role of different neurotrophins in pituitary functions.
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Affiliation(s)
- F Aguado
- Departament de Biologia Cel.lular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona, Spain
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40
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Abstract
The last several years have seen a significant increase in our understanding of the molecular and biochemical changes associated with pituitary tumour initiation and progression. The combined data, from several groups, now allow a tentative map to be drawn showing that reduction to hemizygosity at several chromosomal loci (10q, 11q13 and 13q) is associated with the transition to the invasive phenotype, while loss on chromosome 9p and methylation of the tumour suppressor gene p16 appear to occur early in pituitary tumorigenesis. Changes in the expression/status of several genes and/or proteins including p53, the cAMP response element-binding factor (CREB), growth hormone-releasing hormone (GHRH), nm23, p16 and p27 have also been identified along this multi-step pathway. Prospective studies will determine whether these markers are truly predictive of subsequent tumour behaviour and can be used to aid clinical management in a manner not possible when current histological criteria are used.
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Affiliation(s)
- W E Farrell
- The Centre for Cell and Molecular Medicine, University of Keele, North Staffordshire Hospital, Stoke on Trent, UK
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41
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Proesmans M, Van Bael A, Andries M, Denef C. Mitogenic effects of nerve growth factor on different cell types in reaggregate cell cultures of immature rat pituitary. Mol Cell Endocrinol 1997; 134:119-27. [PMID: 9426155 DOI: 10.1016/s0303-7207(97)00175-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Treatment of reaggregate pituitary cell cultures of 14-day-old female rats with nerve growth factor (NGF) augmented the number of [3H]thymidine ([3H]T)-incorporating lactotrophs in a dose-dependent manner (0.03-3 nM). At least during short-term treatment NGF increased the total number of cells expressing prolactin (PRL) mRNA and enlarged the cytoplasmic area occupied by PRL mRNA but did not affect the number of cells and the cytoplasmic area containing PRL, suggesting that NGF recruits lactotrophs expressing PRL mRNA but not yet PRL. NGF also stimulated [3H]T incorporation in ACTH cells but not in somatotrophs, thyrotrophs and gonadotrophs. In addition, NGF augmented the total number of [3H]T-incorporating cells to a much higher extent than was expected from its effect on lactotrophs and ACTH cells, suggesting NGF also stimulates [3H]T-incorporation in non-hormone producing cells (progenitors or stem cells?). Around 40% of these [3H]T-incorporating cells in both control and NGF treated cultures showed immunoreactivity for the transcription factor Pit-1 in the nuclei, which is twice the percentage expected (18%) if these [3H]T-incorporating cells were the only known Pit-1 expressing cells in the pituitary i.e. lactotrophs, somatotrophs and thyrotrophs. The present data suggest that NGF has a mitogenic effect on several cell lineages in the pituitary: lactotrophs, corticotrophs and non-hormone-containing cells. The high proportion of mitotic non-hormone containing cells that express Pit-1 is consistent with the proposed role of Pit-1 in cell proliferation in the developing lactosomatotroph lineage.
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Affiliation(s)
- M Proesmans
- Laboratory of Cell Pharmacology, University of Leuven, School of Medicine, Campus Gasthuisberg (O&N), Belgium
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42
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Calzà L, Giardino L, Aloe L. NGF content and expression in the rat pituitary gland and regulation by thyroid hormone. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1997; 51:60-8. [PMID: 9427507 DOI: 10.1016/s0169-328x(97)00213-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The involvement of nerve growth factor (NGF) in neuroendocrine regulation is supported by several lines of evidence. In this paper, we investigated the NGF content and expression in the pituitary gland and other endocrine organs during dysendocrine states (thyroidectomized, adrenalectomized and gonadectomized male rats). We found an increase of NGF-IR in the pituitary gland and testis of hypothyroid rats whereas no differences were found in the adrenal gland and blood. Also, NGF mRNA expression had increased in the anterior pituitary of hypothyroid rats whereas it had not changed after adrenalectomy and gonadectomy. Moreover, other neurotrophins and neurotrophin high-affinity receptors were unchanged in the anterior pituitary of hypothyroid rats. These data indicate that pituitary NGF is selectively modulated by thyroid status of the animal, further supporting a close link between NGF and thyroid hormone.
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Affiliation(s)
- L Calzà
- Institute for Human Physiology, University of Cagliari, Italy.
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43
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Abstract
The classical image of the endocrine system is that secretory function of a gland is regulated from outside that gland by other organs. Focused on the pituitary gland, hormone secretion by the anterior lobe is under control of peptides and biogenic amines produced by the hypothalamus. About a decade ago, our group launched the new idea that functioning of the anterior pituitary (AP) is also regulated from within, i.e., that the constituent cell types inter-communicate to control hormone secretion. Extensive in vitro research has now provided a body of evidence that paracrine communication plays an important role, not only in regulation of hormone secretion but also in development, growth, and differentiation of the AP [reviewed in Denef (1994) The Pituitary Gland, pp. 351-378]. It further revealed that crosstalk between the cells is mediated by local, paracrine, factors. The main objective of our research is to identify those factors, their actions and the producing and target cell type(s) in order to unravel the paracrine communication network that is functional in the AP. Equally important, we set the step towards in vivo examination of the results obtained in vitro using transgenic mice. In the present article, we will review the technology used, three examples of AP cell-to-cell interactions studied, and we will discuss the value of transgenic animal models in the study of AP paracrine communication.
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Affiliation(s)
- H Vankelecom
- Laboratory of Cell Pharmacology School of Medicine, University of Leuven, Belgium
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44
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Stefaneanu L, Kovacs K. Transgenic models of pituitary diseases. Microsc Res Tech 1997; 39:194-204. [PMID: 9361270 DOI: 10.1002/(sici)1097-0029(19971015)39:2<194::aid-jemt10>3.0.co;2-m] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Transgenic mice are valuable experimental models of human endocrine diseases. Targeted ablation of specific cell lineages or insertion of genes coding for releasing factors, hormones, growth factors, and oncogenes fused with appropriate promoters, or mutated genes, can induce several pituitary disorders. Various hyposecretory and hypersecretory states have been induced, some of them due to functioning pituitary adenomas. Adenohypophysial changes in such disorders have been thoroughly investigated in many of the transgenic lines. Functioning and silent pituitary adenomas resemble those seen in human patients, and are invaluable models of tumorigenesis. The available models have not been sufficiently exploited and new models are expected in the near future. In this review, the morphologic changes of the pituitary are described in transgenic mice and, when available, the ultrastructural alterations are included.
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Affiliation(s)
- L Stefaneanu
- Department of Pathology, St. Michael's Hospital, University of Toronto, Ontario, Canada
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45
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Saiardi A, Bozzi Y, Baik JH, Borrelli E. Antiproliferative role of dopamine: loss of D2 receptors causes hormonal dysfunction and pituitary hyperplasia. Neuron 1997; 19:115-26. [PMID: 9247268 DOI: 10.1016/s0896-6273(00)80352-9] [Citation(s) in RCA: 159] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The function of dopamine (DA) in the nervous system is paralleled by its neuroendocrine control of pituitary gland functions. Here, we document the neuroendocrine function of dopamine by studying the pituitary gland of mice lacking DA D2 receptors (D2R). These mice present a striking, progressive increase in lactotroph number, which ultimately leads to tumors in aged animals. Females develop tumors much earlier than males. An estrogen-mediated lactotroph proliferation cannot account for this sexual dimorphism, since D2R-null females are hypoestrogenic and, thus, have estrogen levels similar to males. In contrast, prolactin levels are six times higher in females than in males. We show that active prolactin receptors are present in the pituitary and their expression increases in concomitance with tumor expansion. These results point to prolactin as an autocrine proliferative factor in the pituitary gland. Additionally, they demonstrate an antiproliferative function for DA regulated through D2 receptor activation.
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Affiliation(s)
- A Saiardi
- Institut de Génétique et de Biologie Moléculaire et Cellulaire CNRS/INSERM/ULP, BP 163, Illkirch, C.U. de Strasbourg, France
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46
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Kelly MA, Rubinstein M, Asa SL, Zhang G, Saez C, Bunzow JR, Allen RG, Hnasko R, Ben-Jonathan N, Grandy DK, Low MJ. Pituitary lactotroph hyperplasia and chronic hyperprolactinemia in dopamine D2 receptor-deficient mice. Neuron 1997; 19:103-13. [PMID: 9247267 DOI: 10.1016/s0896-6273(00)80351-7] [Citation(s) in RCA: 304] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Dopamine secreted from hypophysial hypothalamic neurons is a principal inhibitory regulator of pituitary hormone secretion. Mice with a disrupted D2 dopamine receptor gene had chronic hyperprolactinemia and developed anterior lobe lactotroph hyperplasia without evidence of adenomatous transformation. Unexpectedly, the mutant mice had no hyperplasia of the intermediate lobe melanotrophs. Aged female D2 receptor -/- mice developed uterine adenomyosis in response to prolonged prolactin exposure. These data reveal a critical role of hypothalamic dopamine in controlling pituitary growth and support a multistep mechanism for the induction and perpetuation of lactotroph hyperplasia, involving the lack of dopamine signaling, a low androgen/estrogen ratio, and a final autocrine or paracrine "feed-forward" stimulation of mitogenesis, probably by prolactin itself.
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Affiliation(s)
- M A Kelly
- Vollum Institute, Oregon Health Sciences University, Portland 97201, USA
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47
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Bossé R, Fumagalli F, Jaber M, Giros B, Gainetdinov RR, Wetsel WC, Missale C, Caron MG. Anterior pituitary hypoplasia and dwarfism in mice lacking the dopamine transporter. Neuron 1997; 19:127-38. [PMID: 9247269 DOI: 10.1016/s0896-6273(00)80353-0] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Deletion of the dopamine transporter (DAT) results in increased dopaminergic tone, anterior pituitary hypoplasia, dwarfism, and an inability to lactate. DAT elimination alters the spatial distribution and dramatically reduces the numbers of lactotrophs and somatotrophs in the pituitary. Despite having normal circulating levels of growth hormone and prolactin in blood, hypoplastic glands from DAT-/- mice fail to respond to secretagog stimulation. The effects of DAT deletion on pituitary function result from elevated DA levels that down-regulate the lactotroph D2 DA receptors and depress hypothalamic growth hormone-releasing hormone content. These results reveal an unexpected and important role or DA in the control of developmental events in the pituitary gland and assign a critical role for hypothalamic DA reuptake in regulating these events.
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Affiliation(s)
- R Bossé
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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48
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Abstract
The complex range of pituitary regulatory mechanisms reviewed here underlies the critical function of the pituitary in sustaining all higher life forms. Thus, the ultimate net secretion of pituitary hormones is determined by signal integration from all three tiers of pituitary control. It is clear from our current knowledge that the trophic hormone cells of the anterior pituitary are uniquely specialized to respond to these signals. Unravelling their diversity and complexity will shed light upon the normal function of the master gland. Understanding these control mechanisms will lead to novel diagnosis and therapy of disordered pituitary function (357).
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Affiliation(s)
- D Ray
- Cedars-Sinai Research Institute, UCLA School of Medicine 90048-1865, USA
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49
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Aguzzi A, Brandner S, Isenmann S, Steinbach JP, Sure U. Transgenic and gene disruption techniques in the study of neurocarcinogenesis. Glia 1995; 15:348-64. [PMID: 8586469 DOI: 10.1002/glia.440150314] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Transgenic technologies have come of age, and the field of carcinogenesis has profited extensively from the availability of these methods. Both the inappropriate expression of dominant oncogenes in specific tissues and the ability to "knock out" tumor suppressor genes in mammalian organisms have enabled substantial advancements of our understanding of development and progression of the neoplastic phenotype. In the first part of this article, we review the most popular techniques for modification of the mammalian genome in vivo, i.e. microinjection of fertilized eggs, retrovirus-mediated gene transfer, and targeted gene deletion through homologous recombination. Subsequently, we attempt a critical evaluation of the available models of neurocarcinogenesis, and discuss their impact and future potential for the study of cancer in the nervous system.
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Affiliation(s)
- A Aguzzi
- Institute of Neuropathology, University Hospital of Zürich, Switzerland
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50
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Davis BM, Albers KM, Seroogy KB, Katz DM. Overexpression of nerve growth factor in transgenic mice induces novel sympathetic projections to primary sensory neurons. J Comp Neurol 1994; 349:464-74. [PMID: 7852636 DOI: 10.1002/cne.903490310] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Peripheral nerve crush induces novel projections from noradrenergic sympathetic neurons to sensory ganglia, and it has been suggested that these projections provide an anatomical substrate for chronic pain syndromes that occur after nerve injury. The present study demonstrates that novel sympathetic projections to sensory neurons are also induced in transgenic mice that overexpress nerve growth factor (NGF) in the skin. Specifically, a large proportion of trigeminal neurons in NGF transgenic mice were innervated by tyrosine hydroxylase (TH)-positive pericellular arborizations that were seen only rarely in controls. Electron microscopic analysis of NGF transgenic mice revealed that trigeminal neurons were surrounded by numerous axonal varicosities containing synaptic specializations. Removal of the superior cervical ganglion abolished TH-immunoreactive arborizations in the ipsilateral trigeminal ganglion confirming that these fibers were sympathetic axons. A two-site enzyme-linked immunosorbent assay revealed that transgenic ganglia contained a tenfold increase in NGF peptide compared to controls. However, reverse transcriptase polymerase chain reaction analysis showed no apparent expression of transgene mRNA in sensory ganglia, suggesting that the additional NGF was derived from increased NGF expression in the skin. These results indicate that NGF can induce novel sympathetic projections to sensory neurons in vivo and suggests a model in which increased NGF expression plays a role in the development of sympathetic hyperalgesia after nerve injury.
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Affiliation(s)
- B M Davis
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington 40536
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