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Pivonello C, De Martino MC, Negri M, Cuomo G, Cariati F, Izzo F, Colao A, Pivonello R. The GH-IGF-SST system in hepatocellular carcinoma: biological and molecular pathogenetic mechanisms and therapeutic targets. Infect Agent Cancer 2014; 9:27. [PMID: 25225571 PMCID: PMC4164328 DOI: 10.1186/1750-9378-9-27] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 06/23/2014] [Indexed: 12/15/2022] Open
Abstract
Hepatocellular carcinoma (HCC) is the sixth most common malignancy worldwide. Different signalling pathways have been identified to be implicated in the pathogenesis of HCC; among these, GH, IGF and somatostatin (SST) pathways have emerged as some of the major pathways implicated in the development of HCC. Physiologically, GH-IGF-SST system plays a crucial role in liver growth and development since GH induces IGF1 and IGF2 secretion and the expression of their receptors, involved in hepatocytes cell proliferation, differentiation and metabolism. On the other hand, somatostatin receptors (SSTRs) are exclusively present on the biliary tract. Importantly, the GH-IGF-SST system components have been indicated as regulators of hepatocarcinogenesis. Reduction of GH binding affinity to GH receptor, decreased serum IGF1 and increased serum IGF2 production, overexpression of IGF1 receptor, loss of function of IGF2 receptor and appearance of SSTRs are frequently observed in human HCC. In particular, recently, many studies have evaluated the correlation between increased levels of IGF1 receptors and liver diseases and the oncogenic role of IGF2 and its involvement in angiogenesis, migration and, consequently, in tumour progression. SST directly or indirectly influences tumour growth and development through the inhibition of cell proliferation and secretion and induction of apoptosis, even though SST role in hepatocarcinogenesis is still opened to argument. This review addresses the present evidences suggesting a role of the GH-IGF-SST system in the development and progression of HCC, and describes the therapeutic perspectives, based on the targeting of GH-IGF-SST system, which have been hypothesised and experimented in HCC.
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Affiliation(s)
- Claudia Pivonello
- Dipartimento di Medicina Clinica e Chirurgia, Università Federico II di Napoli, Via Sergio Pansini, 5, Naples 80131, Italy
| | - Maria Cristina De Martino
- Dipartimento di Medicina Clinica e Chirurgia, Università Federico II di Napoli, Via Sergio Pansini, 5, Naples 80131, Italy
| | - Mariarosaria Negri
- Dipartimento di Medicina Clinica e Chirurgia, Università Federico II di Napoli, Via Sergio Pansini, 5, Naples 80131, Italy
| | | | - Federica Cariati
- Dipartimento di Medicina Clinica e Chirurgia, Università Federico II di Napoli, Via Sergio Pansini, 5, Naples 80131, Italy
| | - Francesco Izzo
- National Cancer Institute G Pascale Foundation, Naples, Italy
| | - Annamaria Colao
- Dipartimento di Medicina Clinica e Chirurgia, Università Federico II di Napoli, Via Sergio Pansini, 5, Naples 80131, Italy
| | - Rosario Pivonello
- Dipartimento di Medicina Clinica e Chirurgia, Università Federico II di Napoli, Via Sergio Pansini, 5, Naples 80131, Italy
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Fusco A, Miele L, D'Uonnolo A, Forgione A, Riccardi L, Cefalo C, Barini A, Bianchi A, Giampietro A, Cimino V, Landolfi R, Grieco A, De Marinis L. Nonalcoholic fatty liver disease is associated with increased GHBP and reduced GH/IGF-I levels. Clin Endocrinol (Oxf) 2012; 77:531-6. [PMID: 22077984 DOI: 10.1111/j.1365-2265.2011.04291.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
INTRODUCTION Nonalcoholic fatty liver disease (NAFLD) has been described in adult GH deficiency syndrome. Furthermore, chronic liver disease can be associated with significant changes in levels of IGF-I, GH-binding protein (GHBP), IGF-binding proteins (IGFBPs) and acid-labile subunit (ALS). However, the effect of liver steatosis on the GHBP production has not been investigated yet. AIM OF THE STUDY To explore whether GH secretion and/or levels of IGF-I, IGFBP-3, ALS and GHBP could be altered in obese patients in relation to the presence of liver steatosis. MATERIALS AND METHODS A total of 115 obese patients (BMI > 30) were enrolled in the protocol (65 patients with liver steatosis and 50 age- and BMI-matched controls). In all patients, the following parameters were studied: serum levels of glucose, insulin, the HOMA index, IGF-I, GHBP, IGFBP-3, ALS and GH after GHRH and arginine stimulation test. RESULTS As expected, patients with NAFLD had blood glucose, insulin, HOMA-R significantly higher than controls, indicating a more severe insulin-resistance state in NAFLD. Furthermore, patients with NAFLD had higher levels of GHBP and IGFBP-3 and lower GH peak and IGF-I levels as compared to controls. No difference was found in ALS levels between the groups. In a multivariate analysis, GHBP was positively associated with hepatic steatosis while IGF-1 was negatively associated with hepatic steatosis. CONCLUSIONS This study demonstrates that in patients with NAFLD, the GHBP levels are increased, and that the GH/IGF-I axis is significantly altered probably leading to reduced IGF-I bioavailability at tissue level.
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Affiliation(s)
- Alessandra Fusco
- Division of Endocrinology, Catholic University, School of Medicine, Rome, Italy.
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Palau N, Rebuffat SA, Altirriba J, Piquer S, Hanzu FA, Gomis R, Barbera A. Role of IGFBP-3 in the regulation of β-cell mass during obesity: adipose tissue/β-cell cross talk. Endocrinology 2012; 153:177-87. [PMID: 22067319 DOI: 10.1210/en.2011-0181] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In obesity an increase in β-cell mass occurs to cope with the rise in insulin demand. This β-cell plasticity is essential to avoid the onset of hyperglycemia, although the molecular mechanisms that regulate this process remain unclear. This study analyzed the role of adipose tissue in the control of β-cell replication. Using a diet-induced model of obesity, we obtained conditioned media from three different white adipose tissue depots. Only in the adipose tissue depot surrounding the pancreas did the diet induce changes that led to an increase in INS1E cells and the islet replication rate. To identify the factors responsible for this proliferative effect, adipose tissue gene expression analysis was conducted by microarrays and quantitative RT-PCR. Of all the differentially expressed proteins, only the secreted ones were studied. IGF binding protein 3 (Igfbp3) was identified as the candidate for this effect. Furthermore, in the conditioned media, although the blockage of IGFBP3 led to an increase in the proliferation rate, the blockage of IGF-I receptor decreased it. Taken together, these data show that obesity induces specific changes in the expression profile of the adipose tissue depot surrounding the pancreas, leading to a decrease in IGFBP3 secretion. This decrease acts in a paracrine manner, stimulating the β-cell proliferation rate, probably through an IGF-I-dependent mechanism. This cross talk between the visceral-pancreatic adipose tissue and β-cells is a novel mechanism that participates in the control of β-cell plasticity.
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Affiliation(s)
- Nuria Palau
- Diabetes and Obesity Laboratory, Institut d'Investigations Biomediques August Pi i Sunyer, Rosselló 149-153, E-08036 Barcelona, Spain
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4
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ISOLATION, TRANSCRIPTS POLYMORPHISM AND TISSUES EXPRESSION OF GROWTH HORMONE RECEPTOR GENES IN CYPRINUS CARPIO VAR. JIAN. ACTA ACUST UNITED AC 2011. [DOI: 10.3724/sp.j.1035.2011.00218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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5
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González L, Curto LM, Miquet JG, Bartke A, Turyn D, Sotelo AI. Differential regulation of membrane associated-growth hormone binding protein (MA-GHBP) and growth hormone receptor (GHR) expression by growth hormone (GH) in mouse liver. Growth Horm IGF Res 2007; 17:104-112. [PMID: 17321774 DOI: 10.1016/j.ghir.2006.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 11/25/2006] [Accepted: 12/11/2006] [Indexed: 10/23/2022]
Abstract
Growth hormone (GH) binding to GH receptor (GHR) is the initial step that leads to the physiological functions of the hormone. Proteolytical cleavage of the GHR in humans and rabbits and alternative processing of the GHR transcript in rodents generates circulating growth hormone binding protein (GHBP). Moreover, other GHR truncated forms that result from alternative processing of the GHR mRNA transcript have been described. These GHR short forms are inserted in the plasma membrane but they are unable to transduce the signal. In rodents, membrane associated-GHBP (MA-GHBP), which accounts for a significant proportion of liver GH binding capacity, represents the main GHR short form found in membranes, and may therefore function as a negative form of the receptor. In the present study, GHR and MA-GHBP content in liver were analyzed using mutant and transgenic mice expressing different concentrations of growth hormone to evaluate the correlation between GH levels, body weight (BW), GHR and MA-GHBP expression. It was found that GH deficiency was associated with diminished BW, GHR and MA-GHBP expression, while increased GH concentration led to increased BW, GHR and MA-GHBP expression, but MA-GHBP upregulation was more pronounced than the observed increase in GHR expression. Since GHR and MA-GHBP both contribute to liver GH binding capacity, GH-induced enrichment of the dominant negative form would represent a compensatory mechanism triggered by high levels of the hormone. This attempt to attenuate the effects of supraphysiological concentrations of GH may be critical to reduce or prevent their plausible damaging effects on the organism.
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Affiliation(s)
- L González
- Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, Buenos Aires, Argentina
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6
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Fisker S. Physiology and pathophysiology of growth hormone-binding protein: methodological and clinical aspects. Growth Horm IGF Res 2006; 16:1-28. [PMID: 16359897 DOI: 10.1016/j.ghir.2005.11.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 10/01/2005] [Accepted: 11/01/2005] [Indexed: 11/20/2022]
Abstract
Circulating GH is partly bound to a high-affinity binding protein (GHBP), which in humans is derived from cleavage of the extracellular domain of the GH receptor. The precise biological function GHBP is unknown, although a regulation of GH bioactivity appears plausible. GHBP levels are determined by GH secretory status, body composition, age, and sex hormones, but the cause-effect relationships remain unclarified. In addition to the possible in vivo significance of GHBP, the interaction between GH and GHBP has methodological implications for both GH and GHBP assays. The present review concentrates on methodological aspects of GHBP measurements, GHBP levels in certain clinical conditions with a special emphasis on disturbances in the GH-IGF axis, and discusses the possible relationship between plasma GHBP and GH receptor status in peripheral tissues.
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Affiliation(s)
- Sanne Fisker
- Medical Department M (Endocrinology and Diabetes), Aarhus University Hospital, Aarhus Sygehus, Nørrebrogade 44, DK-8000 Aarhus C, Denmark.
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7
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Abstract
Prolactin (PRL) and growth hormone (GH) act by way of their receptors as either hormones (systemically) or cytokines (locally). The Jak2/Stat5 pathway is the principal route by which PRL/GH activate target genes. The availability of knockout mice for each member of this signaling cascade has provided opportunities to understand their unique interactions. Jak2 is important in alternative signal transduction schema such as the MAP kinase and PI3K/Akt pathways. The putative Jak2/RUSH pathway is based on the fact that RUSH mediates the ability of PRL to augment progesterone-dependent gene transcription. New evidence shows that suppressors, regulators, and degraders control Jak2/Stat5. This review focuses on the most recent advances in the field of PRL/GH signal transduction.
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Affiliation(s)
- Beverly S Chilton
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
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8
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Iida K, Takahashi Y, Kaji H, Yoshioka S, Murata M, Iguchi G, Okimura Y, Chihara K. Diverse regulation of full-length and truncated growth hormone receptor expression in 3T3-L1 adipocytes. Mol Cell Endocrinol 2003; 210:21-9. [PMID: 14615057 DOI: 10.1016/j.mce.2003.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two truncated forms of growth hormone (GH) receptor (GHR), 1-277 and 1-279, were reported to be normally produced in human tissues by alternative splicing in exon 9 and its boundary. We found previously that GHR-277 exerts a dominant-negative effect on full-length GHR (GHR-fl)-mediated GH signaling causing short stature. The existence of truncated GHRs (hGHR-tr) in normal tissues suggests that hGHR-tr may play a physiological role in regulation of GH action at the cellular level. To clarify the physiological significance of GHR-tr and the regulation mechanism of GHR-tr expression, we examined the expression of mouse GHR-tr (mGHR-tr) mRNA in mouse adipocyte 3T3-L1 cells, comparing with that of mouse GHR-fl (mGHR-fl). The mRNAs of two mGHR-tr, mGHR-282 and mGHR-280, were detected by RT-PCR methods using specific primers. Although the mGHR-282 and mGHR-280 mRNA levels were approximately 100 times lower than that of mGHR-fl in mature 3T3-L1 cells, quantitative analysis by competitive RT-PCR methods revealed that the mRNA levels of mGHR-280 in 3T3-L1 cells were transiently reduced and thereafter increased during differentiation from preadipocyte to adipocyte. In contrast, the mRNA levels of mGHR-fl were increased in parallel with the progress of differentiation. Stimulation by GH of differentiated 3T3-L1 mature adipocytes resulted in dose-dependent increases of the mRNA of both mGHR-fl and mGHR-282, whereas it caused a paradoxical decrease of the mRNA of mGHR-280 stimulated by high concentration of GH. These findings suggest that the expressions of truncated mGHRs were regulated in a different manner from that of mGHR-fl, thereby modulating GH action in murine adipocytes.
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Affiliation(s)
- Keiji Iida
- Division of Endocrinology/Metabolism, Neurology and Hematology/Oncology, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
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9
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Obrepalska-Steplowska A, Kedzia A, Goździcka-Józefiak A, Jakubowicz M, Korman E. Analysis of the human growth hormone receptor and IGF-I coding sequences in children with growth disorders. J Pediatr Endocrinol Metab 2003; 16:819-25. [PMID: 12948293 DOI: 10.1515/jpem.2003.16.6.819] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Analysis of GHR and IGF-I coding sequences in 47 children with normal serum levels of GH, low IGF-I and growth disorders generally did not show mutation in the genes studied. Only one boy had a mutation located in the fifth exon of the GHR gene (C-->T in codon 88). This suggests that the growth disorders in this group of children might be due to a defect in a DNA region regulating expression of the GHR and IGF1 genes or genes involved in their regulation.
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10
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Chopin LK, Veveris-Lowe TL, Philipps AF, Herington AC. Co-expression of GH and GHR isoforms in prostate cancer cell lines. Growth Horm IGF Res 2002; 12:126-136. [PMID: 12175650 DOI: 10.1054/ghir.2002.0271] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Prostate cancer is a significant cause of morbidity and mortality in Western males. While it is known that androgens play a central role in prostate cancer development and progression, other hormones and growth factors are also involved in prostate growth. Insulin-like growth factor-I (IGF-I) plasma levels have been associated with prostate cancer risk, and growth hormone (GH), a major factor regulating IGF levels, also appears to have a role in prostate cancer cell growth. Most significantly, GH has been shown to increase the rate of cell proliferation in prostate cancer cell lines. We have now demonstrated the co-expression of GH and GH receptor (GHR) mRNA isoforms in the ALVA41, PC3, DU145, LNCaP prostate cancer cells by reverse transcription polymerase chain reaction. Sequence analysis has confirmed that these cell lines express the pituitary form of GH mRNA and also the placental mRNA isoform. These prostate cancer cell lines also express the full-length mRNA for the GHR and the exon 3 deleted isoform. We have also demonstrated the presence of GH and GHR proteins in these cell lines by immunohistochemistry. GH expression has not been described previously in human prostate cancer cells. The co-expression of GH and its receptor would enable an autocrine-paracrine pathway to exist in the prostate that would be capable of stimulating prostate growth, either directly via the GHR or indirectly via IGF production. The GH axis in the prostate could therefore be an important additional target for the future development of prostate cancer therapies.
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Affiliation(s)
- L K Chopin
- Centre for Molecular Biotechnology, Queensland University of Technology, GPO Box 2434, Brisbane, Q 4001, Australia.
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12
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Zhang Y, Jiang J, Black RA, Baumann G, Frank SJ. Tumor necrosis factor-alpha converting enzyme (TACE) is a growth hormone binding protein (GHBP) sheddase: the metalloprotease TACE/ADAM-17 is critical for (PMA-induced) GH receptor proteolysis and GHBP generation. Endocrinology 2000; 141:4342-8. [PMID: 11108241 DOI: 10.1210/endo.141.12.7858] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The GH binding protein (GHBP), which exists in many vertebrates, is a circulating high affinity binding protein corresponding to the extracellular domain of the GH receptor (GHR). In humans, rabbits, and several other species, the GHBP is generated by proteolysis of the GHR and shedding of its extracellular domain. We previously showed that GHBP shedding is inducible by the phorbol ester phorbol 12-myristate,13-acetate (PMA) and inhibited by the metalloprotease inhibitor, Immunex Corp. Compound 3 (IC3). The metzincin metalloprotease, tumor necrosis factor-alpha (TNF-alpha)-converting enzyme (TACE), catalyzes the shedding of TNF-alpha from its transmembrane precursor, a process that is also inhibitable by IC3. TACE may hence be a candidate for GHBP sheddase. In this study, we reconstitute fibroblasts derived from a TACE knockout mouse (Null cells) with either the rabbit (rb) GHR alone (Null/R) or rbGHR plus murine TACE (Null/R+T). Although GHR in both cells was expressed at similar abundance, dimerized normally and caused JAK2 activation in response to GH independent of TACE expression, PMA was unable to generate GHBP from Null/R cells. In contrast, PMA caused ample GHBP generation from TACE reconstituted (Null/R + T) cells, and this GHBP shedding was substantially inhibited by IC3 pretreatment. Corresponding to the induced shedding of GHBP from Null/R + T cells, PMA treatment caused a significant loss of immunoblottable GHR in Null/R+T, but not in Null/R cells. We conclude that TACE is an enzyme required for PMA-induced GHBP shedding and that PMA-induced down-regulation of GHR abundance may in significant measure be attributable to TACE-mediated GHR proteolysis.
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Affiliation(s)
- Y Zhang
- Department of Cell Biology, University of Alabama at Birmingham, 35294, USA
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13
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Affiliation(s)
- J J Kopchick
- Edison Biotechnology Institute, Ohio University, Athens, Ohio 45701, USA
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14
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Pantel J, Machinis K, Sobrier ML, Duquesnoy P, Goossens M, Amselem S. Species-specific alternative splice mimicry at the growth hormone receptor locus revealed by the lineage of retroelements during primate evolution. J Biol Chem 2000; 275:18664-9. [PMID: 10764769 DOI: 10.1074/jbc.m001615200] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In humans, growth hormone receptor (GHR) transcripts exist in two isoforms differing by the retention (GHRfl) or exclusion (GHRd3) of exon 3, whereas in mice GHRfl is solely expressed. This species-specific expression pattern is believed to result from an alternative splice event that, on the basis of conflicting data obtained in humans, has been considered to be tissue-, developmentally, and/or individual-specific. To decipher the molecular basis of this unusual trait, we isolated a 6.8-kilobase fragment spanning exon 3 from individuals expressing GHRfl. Sequence analysis revealed the existence of two 99% identical retroelements flanking this exon. Unexpectedly, individuals expressing GHRd3 displayed a 2.7-kilobase deletion involving exon 3, which most likely results from an ancestral homologous recombination between the two retroelements. The lineage of these retroelements during primate evolution revealed the species specificity of the GHRd3 allele. These findings led us to propose a model underlying the existence of the sole GHRfl allele in most species. Such a retrovirus-mediated alternative splice mimicry, which clears up several as yet unexplained phenomena (i.e. the above-mentioned expression data, the Mendelian inheritance of GHR expression patterns, and the deletion of nonconsecutive exons in growth hormone resistant patients), represents a novel physiological mechanism accounting for protein diversity between and within species.
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Affiliation(s)
- J Pantel
- Institut National de la Santé et de la Recherche Médicale, Unité 468, Hôpital Henri Mondor, 94010 Créteil Cedex, France
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Mol JA, Lantinga-van Leeuwen IS, van Garderen E, Selman PJ, Oosterlaken-Dijksterhuis MA, Schalken JA, Rijnberk A. Mammary growth hormone and tumorigenesis--lessons from the dog. Vet Q 1999; 21:111-5. [PMID: 10567999 DOI: 10.1080/01652176.1999.9695004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022] Open
Abstract
The discovery in the early 1990s that progestin-induced growth hormone (GH) excess in the dog originates in the mammary gland can be seen as a hallmark in the research on the pathogenesis of mammary cancer in the dog. The local biosynthesis and release of GH may provide a highly proliferative environment in the mammary gland, which contributes to the development and/or progression of mammary tumours. Before final goals such as prevention of tumour formation or inhibition of tumour promotion can be achieved it is of eminent importance to elucidate the mechanism of progesterone-induced mammary GH production and the mechanism of local autocrine/paracrine action of GH. These local GH effects may be achieved through direct growth stimulating effects of GH as well as by indirect effects mediated by the stimulation of the biosynthesis of insulin-like growth factor-I (IGF-I). The biological effects of the IGFs largely depend on the presence of IGF binding proteins (IGFBPs) which may both enhance or inhibit the activity of the IGFs. This review concentrates on recent advances in the understanding of the local mammary GH-IGF axis and the lessons which can be drawn from the dog for mammary cancer research in other species.
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Affiliation(s)
- J A Mol
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
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Chang JT, Esumi N, Moore K, Li Y, Zhang S, Chew C, Goodman B, Rattner A, Moody S, Stetten G, Campochiaro PA, Zack DJ. Cloning and characterization of a secreted frizzled-related protein that is expressed by the retinal pigment epithelium. Hum Mol Genet 1999; 8:575-83. [PMID: 10072424 DOI: 10.1093/hmg/8.4.575] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Wnt/frizzled cell signaling pathway has been implicated in the determination of polarity in a number of systems, including the Drosophila retina. The vertebrate retina develops from an undifferentiated neuroepithelium into an organized and laminated structure that demonstrates a high degree of polarity at both the tissue and cellular levels. In the process of searching for molecules that are preferentially expressed by the vertebrate retinal pigment epithelium (RPE), we identified secreted frizzled-related protein 5 (SFRP5), a member of the SFRP family that appears to act by modulating Wnt signal transduction. SFRP5 is highly expressed by RPE cells, and is also expressed in the pancreas. Within the retina, the related molecule SFRP2 is expressed specifically by cells of the inner nuclear layer. Thus, photoreceptors are likely to be bathed by two opposing gradients of SFRP molecules. Consistent with SFRP5 's postulated role in modulating Wnt signaling in the retina, it inhibits the ability of Xwnt-8 mRNA to induce axis duplication in Xenopus embryos. The human SFRP5 gene consists of three coding exons and it maps to chromosome 10q24.1; human SFRP2 maps to 4q31.3. Based on the biology and complementary expression patterns of SFRP2 and SFRP5, we suggest that they may be involved in determining the polarity of photoreceptor, and perhaps other, cells in the retina.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Amino Acid Sequence
- Animals
- Base Sequence
- Body Patterning
- Cattle
- Chromosome Banding
- Chromosome Mapping
- Chromosomes, Human, Pair 10/genetics
- Chromosomes, Human, Pair 4/genetics
- Cloning, Molecular
- Embryo, Nonmammalian/metabolism
- Embryonic Development
- Exons
- Eye Proteins/genetics
- Gene Expression
- Gene Expression Regulation
- Genes/genetics
- Humans
- In Situ Hybridization
- In Situ Hybridization, Fluorescence
- Intracellular Signaling Peptides and Proteins/genetics
- Introns
- Membrane Proteins
- Mice
- Mice, Inbred Strains
- Microinjections
- Molecular Sequence Data
- Pancreas/metabolism
- Pigment Epithelium of Eye/metabolism
- Proteins
- Proto-Oncogene Proteins/genetics
- RNA, Messenger/administration & dosage
- Retina/metabolism
- Sequence Homology, Amino Acid
- Wnt Proteins
- Xenopus
- Xenopus Proteins/genetics
- Zebrafish Proteins
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Affiliation(s)
- J T Chang
- The Wilmer Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-9289, USA
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