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Margiotta A. All Good Things Must End: Termination of Receptor Tyrosine Kinase Signal. Int J Mol Sci 2021; 22:ijms22126342. [PMID: 34198477 PMCID: PMC8231876 DOI: 10.3390/ijms22126342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 12/28/2022] Open
Abstract
Receptor tyrosine kinases (RTKs) are membrane receptors that regulate many fundamental cellular processes. A tight regulation of RTK signaling is fundamental for development and survival, and an altered signaling by RTKs can cause cancer. RTKs are localized at the plasma membrane (PM) and the major regulatory mechanism of signaling of RTKs is their endocytosis and degradation. In fact, RTKs at the cell surface bind ligands with their extracellular domain, become active, and are rapidly internalized where the temporal extent of signaling, attenuation, and downregulation are modulated. However, other mechanisms of signal attenuation and termination are known. Indeed, inhibition of RTKs’ activity may occur through the modulation of the phosphorylation state of RTKs and the interaction with specific proteins, whereas antagonist ligands can inhibit the biological responses mediated by the receptor. Another mechanism concerns the expression of endogenous inactive receptor variants that are deficient in RTK activity and take part to inactive heterodimers or hetero-oligomers. The downregulation of RTK signals is fundamental for several cellular functions and the homeostasis of the cell. Here, we will review the mechanisms of signal attenuation and termination of RTKs, focusing on FGFRs.
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Affiliation(s)
- Azzurra Margiotta
- Department of Biology, Faculty of Medicine, Masaryk University, 62500 Brno, Czech Republic;
- International Clinical Research Center, St. Anne’s University Hospital, 65691 Brno, Czech Republic
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2
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De Luca A, Esposito Abate R, Rachiglio AM, Maiello MR, Esposito C, Schettino C, Izzo F, Nasti G, Normanno N. FGFR Fusions in Cancer: From Diagnostic Approaches to Therapeutic Intervention. Int J Mol Sci 2020; 21:E6856. [PMID: 32962091 PMCID: PMC7555921 DOI: 10.3390/ijms21186856] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/15/2020] [Accepted: 09/15/2020] [Indexed: 12/11/2022] Open
Abstract
Fibroblast growth factor receptors (FGFRs) are tyrosine kinase receptors involved in many biological processes. Deregulated FGFR signaling plays an important role in tumor development and progression in different cancer types. FGFR genomic alterations, including FGFR gene fusions that originate by chromosomal rearrangements, represent a promising therapeutic target. Next-generation-sequencing (NGS) approaches have significantly improved the discovery of FGFR gene fusions and their detection in clinical samples. A variety of FGFR inhibitors have been developed, and several studies are trying to evaluate the efficacy of these agents in molecularly selected patients carrying FGFR genomic alterations. In this review, we describe the most frequent FGFR aberrations in human cancer. We also discuss the different approaches employed for the detection of FGFR fusions and the potential role of these genomic alterations as prognostic/predictive biomarkers.
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Affiliation(s)
- Antonella De Luca
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy; (A.D.L.); (R.E.A.); (A.M.R.); (M.R.M.); (C.E.)
| | - Riziero Esposito Abate
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy; (A.D.L.); (R.E.A.); (A.M.R.); (M.R.M.); (C.E.)
| | - Anna Maria Rachiglio
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy; (A.D.L.); (R.E.A.); (A.M.R.); (M.R.M.); (C.E.)
| | - Monica Rosaria Maiello
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy; (A.D.L.); (R.E.A.); (A.M.R.); (M.R.M.); (C.E.)
| | - Claudia Esposito
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy; (A.D.L.); (R.E.A.); (A.M.R.); (M.R.M.); (C.E.)
| | - Clorinda Schettino
- Clinical Trials Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy;
| | - Francesco Izzo
- Division of Surgical Oncology, Hepatobiliary Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy;
| | - Guglielmo Nasti
- SSD Innovative Therapies for Abdominal Cancers, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy;
| | - Nicola Normanno
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori-IRCCS-Fondazione G. Pascale, 80131 Naples, Italy; (A.D.L.); (R.E.A.); (A.M.R.); (M.R.M.); (C.E.)
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Levine KM, Ding K, Chen L, Oesterreich S. FGFR4: A promising therapeutic target for breast cancer and other solid tumors. Pharmacol Ther 2020; 214:107590. [PMID: 32492514 DOI: 10.1016/j.pharmthera.2020.107590] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 05/26/2020] [Indexed: 02/07/2023]
Abstract
The fibroblast growth factor receptor (FGFR) signaling pathway has long been known to cancer researchers because of its role in cell survival, proliferation, migration, and angiogenesis. Dysregulation of FGFR signaling is frequently reported in cancer studies, but most of these studies focus on FGFR1-3. However, there is growing evidence implicating an important and unique role of FGFR4 in oncogenesis, tumor progression, and resistance to anti-tumor therapy in multiple types of cancer. Importantly, there are several novel FGFR4-specific inhibitors in clinical trials, making FGFR4 an attractive target for further research. In this review, we focus on assessing the role of FGFR4 in cancer, with an emphasis on breast cancer. First, the structure, physiological functions and downstream signaling pathways of FGFR4 are introduced. Next, different mechanisms reported to cause aberrant FGFR4 activation and their functions in cancer are discussed, including FGFR4 overexpression, FGF ligand overexpression, FGFR4 somatic hotspot mutations, and the FGFR4 G388R single nucleotide polymorphism. Finally, ongoing and recently completed clinical trials targeting FGFRs in cancer are reviewed, highlighting the therapeutic potential of FGFR4 inhibition for the treatment of breast cancer.
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Affiliation(s)
- Kevin M Levine
- Women's Cancer Research Center, UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Magee-Women's Research Institute, Magee-Women's Research Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, USA; Department of Pathology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kai Ding
- Women's Cancer Research Center, UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Magee-Women's Research Institute, Magee-Women's Research Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, USA; Integrative Systems Biology Program, University of Pittsburgh, Pittsburgh, PA, USA
| | - Lyuqin Chen
- Women's Cancer Research Center, UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Magee-Women's Research Institute, Magee-Women's Research Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Steffi Oesterreich
- Women's Cancer Research Center, UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Magee-Women's Research Institute, Magee-Women's Research Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA.
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Abstract
FGF19 is a noncanonical FGF ligand that can control a broad spectrum of physiological responses, which include bile acid homeostasis, liver metabolism and glucose uptake. Many of these responses are mediated by FGF19 binding to its FGFR4/β-klotho receptor complex and controlling activation of an array of intracellular signaling events. Overactivation of the FGF19/FGFR4 axis has been implicated in tumorigenic formation, progression and metastasis, and inhibitors of this axis have recently been developed for single agent use or in combination with other anticancer drugs. Considering the critical role of this receptor complex in cancer, this review focuses on recent developments and applications of FGF19/FGFR4-targeted therapeutics.
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Heinzle C, Erdem Z, Paur J, Grasl-Kraupp B, Holzmann K, Grusch M, Berger W, Marian B. Is fibroblast growth factor receptor 4 a suitable target of cancer therapy? Curr Pharm Des 2015; 20:2881-98. [PMID: 23944363 DOI: 10.2174/13816128113199990594] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Accepted: 08/06/2013] [Indexed: 12/17/2022]
Abstract
Fibroblast growth factors (FGF) and their tyrosine kinase receptors (FGFR) support cell proliferation, survival and migration during embryonic development, organogenesis and tissue maintenance and their deregulation is frequently observed in cancer development and progression. Consequently, increasing efforts are focusing on the development of strategies to target FGF/FGFR signaling for cancer therapy. Among the FGFRs the family member FGFR4 is least well understood and differs from FGFRs1-3 in several aspects. Importantly, FGFR4 deletion does not lead to an embryonic lethal phenotype suggesting the possibility that its inhibition in cancer therapy might not cause grave adverse effects. In addition, the FGFR4 kinase domain differs sufficiently from those of FGFRs1-3 to permit development of highly specific inhibitors. The oncogenic impact of FGFR4, however, is not undisputed, as the FGFR4-mediated hormonal effects of several FGF ligands may also constitute a tissue-protective tumor suppressor activity especially in the liver. Therefore it is the purpose of this review to summarize all relevant aspects of FGFR4 physiology and pathophysiology and discuss the options of targeting this receptor for cancer therapy.
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Affiliation(s)
| | | | | | | | | | | | | | - Brigitte Marian
- Institute of Cancer Research, Department of Medicine 1, Medical University Vienna, Borschkegasse 8a, 1090 Vienna, Austria.
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Developmental pathways hijacked by osteosarcoma. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 804:93-118. [PMID: 24924170 DOI: 10.1007/978-3-319-04843-7_5] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cancer of any type often can be described by an arrest, alteration or disruption in the normal development of a tissue or organ, and understanding of the normal counterpart's development can aid in understanding the malignant state. This is certainly true for osteosarcoma and the normal developmental pathways that guide osteoblast development that are changed in the genesis of osteogenic sarcoma. A carefully regulated crescendo-decrescendo expression of RUNX2 accompanies the transition from mesenchymal stem cell to immature osteoblast to mature osteoblast. This pivotal role is controlled by several pathways, including bone morphogenic protein (BMP), Wnt/β-catenin, fibroblast growth factor (FGF), and protein kinase C (PKC). The HIPPO pathway and its downstream target YAP help to regulate proliferation of immature osteoblasts and their maturation into non-proliferating mature osteoblasts. This pathway also helps regulate expression of the mature osteoblast protein osteocalcin. YAP also regulates expression of MT1-MMP, a membrane-bound matrix metalloprotease responsible for remodeling the extracellular matrix surrounding the osteoblasts. YAP, in turn, can be regulated by the ERBB family protein Her-4. Osteosarcoma may be thought of as a cell held at the immature osteoblast stage, retaining some of the characteristics of that developmental stage. Disruptions of several of these pathways have been described in osteosarcoma, including BMP, Wnt/b-catenin, RUNX2, HIPPO/YAP, and Her-4. Further, PKC can be activated by several receptor tyrosine kinases implicated in osteosarcoma, including the ERBB family (EGFR, Her-2 and Her-4 in osteosarcoma), IGF1R, FGF, and others. Understanding these functions may aid in the understanding the mechanisms underpinning clinical observations in osteosarcoma, including both the lytic and blastic phenotypes of tumors, the invasiveness of the disease, and the tendency for treated tumors to ossify rather than shrink. Through a better understanding of the relationship between normal osteoblast development and osteosarcoma, we may gain insights into novel therapeutic avenues and improved outcomes.
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Gauglhofer C, Paur J, Schrottmaier WC, Wingelhofer B, Huber D, Naegelen I, Pirker C, Mohr T, Heinzle C, Holzmann K, Marian B, Schulte-Hermann R, Berger W, Krupitza G, Grusch M, Grasl-Kraupp B. Fibroblast growth factor receptor 4: a putative key driver for the aggressive phenotype of hepatocellular carcinoma. Carcinogenesis 2014; 35:2331-8. [DOI: 10.1093/carcin/bgu151] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Lee C, Mayfield RD, Harris RA. Altered gamma-aminobutyric acid type B receptor subunit 1 splicing in alcoholics. Biol Psychiatry 2014; 75:765-73. [PMID: 24209778 PMCID: PMC3999301 DOI: 10.1016/j.biopsych.2013.08.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 08/27/2013] [Accepted: 08/27/2013] [Indexed: 11/25/2022]
Abstract
BACKGROUND Chronic alcohol exposure can change splice variant expression. The gamma-aminobutyric acid type B (GABAB) receptor undergoes splicing and is an alcoholism treatment target, but there is little information about splicing changes in this receptor in alcoholics. We studied GABAB receptor subunit 1 (GABAB1) splicing in alcoholic postmortem brains. METHODS To maximize GABAB1 splice junction identification, we combined gene specific libraries with RNA-seq. Splice junctions and mapped reads were also found from intronic and intergenic regions. We compared GABAB1 splice junctions in prefrontal cortices from 14 alcoholic and 15 control subjects and introduced new strategies, reads per kilobase of splice junction model per million mapped reads and reads per kilobase of gene model per million mapped reads, for quantitating splice junction and gene expression. RESULTS Novel splice junction detection indicated that the GABAB1 gene is at least two times longer than the previously reported gene length. GABAB1 exon and intron expression data showed low expression at the 5' end exons and exon grouping. This indicated that there are short splicing variants in addition to GABAB receptor subunit GABAB1a, the longest known major transcript. We found that chronic alcohol altered exon/intron expression and splice junction levels. Decreased expression of the gamma-aminobutyric acid binding site, a transmembrane domain and a microRNA binding site may decrease normal GABAB1 transcript population and thereby decrease normal signal transduction in alcoholics. CONCLUSIONS We discovered novel, complex splicing of GABAB1 in human brain and showed that chronic alcohol produces additional splicing complexity.
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Affiliation(s)
- Changhoon Lee
- Waggoner Center for Alcohol and Addiction Research, Section of Neurobiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas.
| | - R Dayne Mayfield
- Waggoner Center for Alcohol and Addiction Research, Section of Neurobiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, Section of Neurobiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas
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Alternative Splicing of Fibroblast Growth Factor Receptor IgIII Loops in Cancer. J Nucleic Acids 2011; 2012:950508. [PMID: 22203889 PMCID: PMC3238399 DOI: 10.1155/2012/950508] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 07/27/2011] [Accepted: 08/07/2011] [Indexed: 02/06/2023] Open
Abstract
Alternative splicing
of the IgIII loop of fibroblast growth factor
receptors (FGFRs) 1–3 produces b- and
c-variants of the receptors with distinctly
different biological impact based on their
distinct ligand-binding spectrum. Tissue-specific expression of these splice variants
regulates interactions in embryonic development,
tissue maintenance and repair, and cancer.
Alterations in FGFR2 splicing are involved in
epithelial mesenchymal transition that produces
invasive, metastatic features during tumor
progression.
Recent research has elucidated regulatory factors that determine
the splice choice both on the level of exogenous signaling events
and on the RNA-protein interaction level. Moreover, methodology
has been developed that will enable the in depth analysis of
splicing events during tumorigenesis and provide further insight on
the role of FGFR 1–3 IIIb and IIIc in the pathophysiology of
various malignancies. This paper aims to summarize expression
patterns in various tumor types and outlines possibilities for
further analysis and application.
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Yang Y, Zhou Y, Lu M, An Y, Li R, Chen Y, Lu DR, Jin L, Zhou WP, Qian J, Wang HY. Association between fibroblast growth factor receptor 4 polymorphisms and risk of hepatocellular carcinoma. Mol Carcinog 2011; 51:515-21. [PMID: 21656577 DOI: 10.1002/mc.20805] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 05/04/2011] [Accepted: 05/04/2011] [Indexed: 12/11/2022]
Abstract
Human fibroblast growth factor receptor 4 (FGFR4) polymorphisms have recently been shown to be associated with tumor progression of various types of cancer, including cancer of the breast, colon, and prostate and sarcoma. However, their association with hepatocellular carcinoma (HCC) is unknown. We evaluated the association of FGFR4 polymorphisms with risk of HCC in a study population with HCC and with/without hepatitis B virus (HBV) infection in East China. We genotyped four FGFR4 SNPs (rs351855, rs641101, rs376618, and rs31777) in 1,451 Chinese subjects, including 711 patients with HCC, 368 controls with HBV infection and 372 controls without HBV infection, using the TaqMan genotyping assay. Unconditional logistic regression analysis was performed to evaluate associations of genotypes of each SNP with HCC risk. For the rs351855 (Arg388) locus, we observed a reduced HCC risk associated with the T variant genotypes, particularly for those whose tumors with gross portal vein tumor thrombosis (gross PVTT) (OR = 0.66; 95% confidence interval, 95% CI = 0.46-0.95 for CT + TT). Such a protective effect was also observed for those with liver cirrhosis (OR = 0.42; 95% CI = 0.20-0.88 for CT + TT). Clearly the T allele was associated with these conditions. Our findings suggest that genetic polymorphism in FGFR4 may be a marker for risk of HCC with liver cirrhosis and gross PVTT in Chinese populations.
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Affiliation(s)
- Yuan Yang
- Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai, PR China
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Chen Q, Jiang Y, An Y, Zhao N, Zhao Y, Yu C. Soluble FGFR4 extracellular domain inhibits FGF19-induced activation of FGFR4 signaling and prevents nonalcoholic fatty liver disease. Biochem Biophys Res Commun 2011; 409:651-6. [PMID: 21616061 DOI: 10.1016/j.bbrc.2011.05.059] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 05/11/2011] [Indexed: 12/30/2022]
Abstract
Fibroblast growth factor receptor 4 (FGFR4) is a transmembrane tyrosine kinase receptor that plays a crucial role in the regulation of hepatic bile acid and lipid metabolism. FGFR4 underlies high-fat diet-induced hepatic steatosis, suggesting that inhibition of FGFR4 activation may be an effective way to prevent or treat nonalcoholic fatty liver disease (NAFLD). To determine whether neutralization of FGFR4 ligands by soluble FGFR4 extracellular domain (FGFR4-ECD) can inhibit the activation of FGFR4, we constructed FGFR4-ECD expression vector and showed that FGFR4-ECD was effectively expressed in cells and secreted into culture medium. FGFR4-ECD inhibited FGF19-induced activation of FGFR4 signaling and reduced steatosis of HepG2 induced by palmitic acid in vitro. Furthermore, in a tetracycline-induced fatty liver model, expression of FGFR4-ECD in mouse liver reduced the accumulation of hepatic lipids and partially restored the expression of peroxisome proliferator-activated receptor α (PPARα), which promotes the mitochondrial fatty acid beta-oxidation but is repressed by tetracycline. Taken together, these results demonstrate that FGFR4-ECD can block FGFR4 signaling and prevent hepatic steatosis, highlighting the potential value of inhibition of FGFR4 signaling as a method for therapeutic intervention against NAFLD.
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Affiliation(s)
- Qiang Chen
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
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Identification and characterization of an inhibitory fibroblast growth factor receptor 2 (FGFR2) molecule, up-regulated in an Apert Syndrome mouse model. Biochem J 2011; 436:71-81. [DOI: 10.1042/bj20100884] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
AS (Apert syndrome) is a congenital disease composed of skeletal, visceral and neural abnormalities, caused by dominant-acting mutations in FGFR2 [FGF (fibroblast growth factor) receptor 2]. Multiple FGFR2 splice variants are generated through alternative splicing, including PTC (premature termination codon)-containing transcripts that are normally eliminated via the NMD (nonsense-mediated decay) pathway. We have discovered that a soluble truncated FGFR2 molecule encoded by a PTC-containing transcript is up-regulated and persists in tissues of an AS mouse model. We have termed this IIIa–TM as it arises from aberrant splicing of FGFR2 exon 7 (IIIa) into exon 10 [TM (transmembrane domain)]. IIIa–TM is glycosylated and can modulate the binding of FGF1 to FGFR2 molecules in BIAcore-binding assays. We also show that IIIa–TM can negatively regulate FGF signalling in vitro and in vivo. AS phenotypes are thought to result from gain-of-FGFR2 signalling, but our findings suggest that IIIa–TM can contribute to these through a loss-of-FGFR2 function mechanism. Moreover, our findings raise the interesting possibility that FGFR2 signalling may be a regulator of the NMD pathway.
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Heinzle C, Sutterlüty H, Grusch M, Grasl-Kraupp B, Berger W, Marian B. Targeting fibroblast-growth-factor-receptor-dependent signaling for cancer therapy. Expert Opin Ther Targets 2011; 15:829-46. [PMID: 21375471 DOI: 10.1517/14728222.2011.566217] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION Fibroblast growth factors (FGF) exert a combination of biological effects that contribute to four of the six essential hallmarks of cancer. It is no surprise that FGF-dependent signaling has increasingly moved to the center of cancer therapy research during the past decade. This is illustrated by the large number of publications focusing on various aspects of this theme that have been published in the past 5 years. AREAS COVERED Information from these sources as well as ongoing work from the authors' groups is used to outline the physiological functions of FGF signaling and to highlight how the high oncogenic effects of deregulated FGFs and FGFRs derive from their physiological functions. The biological effect of deregulated FGFR signaling in malignant diseases is described and the current state of therapeutic targeting of FGFR is summarized. EXPERT OPINION Strategies for targeting FGFR-signaling for cancer therapy are very promising, but need to be carefully developed based on the physiological roles of FGF signaling. Preventive measures may be necessary for protection from FGF-related side effects. Combined targeting of several receptor tyrosine kinases or combination with other therapies may be a useful way of avoiding or ameliorating side effects. FGF-related markers of prognosis and therapy response still need to be investigated.
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Affiliation(s)
- Christine Heinzle
- Medical University Vienna, Institute of Cancer Research, Department of Medicine 1, Vienna,Austria
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Lee C, Mayfield RD, Harris RA. Intron 4 containing novel GABAB1 isoforms impair GABAB receptor function. PLoS One 2010; 5:e14044. [PMID: 21124972 PMCID: PMC2987798 DOI: 10.1371/journal.pone.0014044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 10/26/2010] [Indexed: 12/24/2022] Open
Abstract
Background Gamma-aminobutyric acid type B (GABAB) receptors decrease neural activity through G protein signaling. There are two subunits, GABAB1 and GABAB2. Alternative splicing provides GABAB1 with structural and functional diversity. cDNA microarrays showed strong signals from human brain RNA using GABAB1 intron 4 region probes. Therefore, we predicted the existence of novel splice variants. Methodology/Principal Findings Based on the probe sequence analysis, we proposed two possible splice variants, GABAB1j and GABAB1k. The existence of human GABAB1j was verified by quantitative real-time PCR, and mouse GABAB1j was found from a microarray probe set based on human GABAB1j sequence. GABAB1j open reading frames (ORF) and expression patterns are not conserved across species, and they do not have any important functional domains except sushi domains. Thus, we focused on another possible splice variant, GABAB1k. After obtaining PCR evidence for GABAB1k existence from human, mouse, and rat, it was cloned from human and mouse by PCR along with three additional isoforms, GABAB1l, GABAB1m, and GABAB1n. Their expression levels by quantitative real-time PCR are relatively low in brain although they may be expressed in specific cell types. GABAB1l and GABAB1m inhibit GABAB receptor-induced G protein-activated inwardly rectifying K+ channel (GIRK) currents at Xenopus oocyte two-electrode voltage clamp system. Conclusions/Significance This study supports previous suggestions that intron 4 of GABAB1 gene is a frequent splicing spot across species. Like GABAB1e, GABAB1l and GABAB1m do not have transmembrane domains but have a dimerization motif. So, they also could be secreted and bind GABAB2 dominantly instead of GABAB1a. However, only GABAB1l and GABAB1m are N- and C-terminal truncated splicing variants and impair receptor function. This suggests that the intron 4 containing N-terminal truncation is necessary for the inhibitory action of the new splice variants.
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Affiliation(s)
- Changhoon Lee
- Section of Neurobiology and Institute for Cellular and Molecular Biology, Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
| | - R. Dayne Mayfield
- Section of Neurobiology and Institute for Cellular and Molecular Biology, Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - R. Adron Harris
- Section of Neurobiology and Institute for Cellular and Molecular Biology, Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
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Zhu X, Zheng L, Asa SL, Ezzat S. Loss of heterozygosity and DNA methylation affect germline fibroblast growth factor receptor 4 polymorphism to direct allelic selection in breast cancer. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 177:2860-9. [PMID: 21037081 DOI: 10.2353/ajpath.2010.100509] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Genome-wide association studies highlight the importance of the fibroblast growth factor (FGF) receptor as a risk factor for breast cancer development. In particular, FGFR4 has been implicated in membrane ruffling, cancer cell invasiveness, and clinical chemoresistance in breast cancer. In this work, we studied FGFR4 in both human breast cancers and cell lines. We examined primary human microdissected breast samples for FGFR4 mutations, polymorphisms, loss of heterozygosity (LOH), and DNA methylation status. We identified no activating somatic mutations of FGFR4; however, we did identify a high proportion of the FGFR4-R388 heterozygous germline polymorphism. Analysis of paired microdissected samples uncovered selective LOH at the FGFR4 locus in 50% of primary tumors. This LOH involved the FGFR4-WT allele as frequently as the cancer progression-associated FGFR4-G388R polymorphic allele. Further, we identified DNA methylation in one-third of cases that targeted the FGFR4-WT allele more often and occurred more frequently either in concert with or exclusively in lymph node metastases. The role of DNA methylation in silencing the FGFR4-WT allele was supported by azacytidine treatment findings and was also confirmed in mouse xenograft studies, demonstrating selective FGFR4-WT allelic methylation with corresponding gene down-regulation. These findings support a growth advantage function for FGFR4-R388 and underscore the complex role of DNA methylation and LOH in determining the penetrance of allelic selection in breast cancer progression. These findings therefore have critical therapeutic importance.
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Affiliation(s)
- Xuegong Zhu
- Department of Medicine, University Health Network, University of Toronto, Toronto, Ontario, Canada
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16
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Huang X, Yang C, Jin C, Luo Y, Wang F, McKeehan WL. Resident hepatocyte fibroblast growth factor receptor 4 limits hepatocarcinogenesis. Mol Carcinog 2009; 48:553-62. [PMID: 19009564 DOI: 10.1002/mc.20494] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fibroblast growth factor (FGF) family signaling mediates cell-to-cell communication in development and organ homeostasis in adults. Of the FGF receptor (FGFR) isotypes, FGFR4 is the sole resident isotype present in mature parenchymal hepatocytes. FGFR1 that is normally associated with activated nonparenchymal cells appears ectopically in hepatoma cells. Ectopic expression and chronic activity of FGFR1 in hepatocytes accelerates diethylnitrosamine (DEN)-initiated hepatocarcinogenesis by driving unrestrained cell proliferation and tumor angiogenesis. Hepatocyte FGFR4 mediates liver's role in systemic cholesterol/bile acid and lipid metabolism and affects proper hepatolobular restoration after damage without effect on cell proliferation. Here we ask whether FGFR4 plays a role in progression of hepatocellular carcinoma (HCC). We report that although spontaneous HCC was not detected in livers of FGFR4-deficient mice, the ablation of FGFR4 accelerated DEN-induced hepatocarcinogenesis. In contrast to FGFR1 that induced a strong mitogenic response and depressed rate of cell death in hepatoma cells, FGFR4 failed to induce a mitogenic response and increased the rate of cell death. FGFR1 but not FGFR4 induced cyclin D1 and repressed p27 expression. Analysis of activation of Erk, JNK, and PI3K-related AKT signaling pathways indicated that in contrast to FGFR1, FGFR4 failed to sustain Erk activation and did not activate AKT. These differences may underlie the opposing effects of FGFR1 and FGFR4. These results suggest that in contrast to ectopic FGFR1 that is a strong promoter of hepatoma, resident FGFR4 that mediates differentiated hepatocyte metabolic functions also serves to suppress hepatoma progression.
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Affiliation(s)
- Xinqiang Huang
- Center for Cancer & Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas 77030, USA
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17
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Kwiatkowski BA, Kirillova I, Richard RE, Israeli D, Yablonka-Reuveni Z. FGFR4 and its novel splice form in myogenic cells: Interplay of glycosylation and tyrosine phosphorylation. J Cell Physiol 2008; 215:803-17. [PMID: 18186042 DOI: 10.1002/jcp.21365] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The family of fibroblast growth factor receptors (FGFRs) is encoded by four distinct genes. FGFR1 and FGFR4 are both expressed during myogenesis, but whereas the function of FGFR1 in myoblast proliferation has been documented, the role of FGFR4 remains unknown. Here, we report on a new splice form of FGFR4 cloned from primary cultures of mouse satellite cells. This form, named FGFR4(-16), lacks the entire exon 16, resulting in a deletion within the FGFR kinase domain. Expression of FGFR4(-16) coincided with that of wild-type FGFR4 in all FGFR4-expressing tissues examined. Moreover, expression of both FGFR4 forms correlated with the onset of myogenic differentiation, as determined in mouse C2C12 cells and in the inducible myogenic system of 10T(1/2)-MyoD-ER cell line. Both endogenous and overexpressed forms of FGFR4 exhibited N-glycosylation. In contrast to FGFR1, induced homodimerization of FGFR4 proteins did not result in receptor tyrosine phosphorylation. Surprisingly, coexpression of FGFR4 forms and a chimeric FGFR1 protein resulted in FGFR4 tyrosine phosphorylation, raising the possibility that FGFR4 phosphorylation might be enabled by a heterologous tyrosine kinase activity. Collectively, the present study reveals novel characteristics of mouse FGFR4 gene products and delineates their expression pattern during myogenesis. Our findings suggest that FGFR4 functions in a distinctly different manner than the prototype FGFR during myogenic differentiation.
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Affiliation(s)
- Boguslaw A Kwiatkowski
- Department of Biological Structure, University of Washington School of Medicine, Seattle, Washington 98195, USA
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18
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Tomlinson DC, L'Hôte CG, Kennedy W, Pitt E, Knowles MA. Alternative splicing of fibroblast growth factor receptor 3 produces a secreted isoform that inhibits fibroblast growth factor-induced proliferation and is repressed in urothelial carcinoma cell lines. Cancer Res 2006; 65:10441-9. [PMID: 16288035 DOI: 10.1158/0008-5472.can-05-1718] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fibroblast growth factor receptors (FGFRs) are a family of receptor tyrosine kinases that play key roles in proliferation, differentiation, and tumorigenesis. FGFR3 was identified as the major family member expressed in both normal human urothelium and cultured normal human urothelial (NHU) cells and was expressed as the IIIb isoform. We also identified a splice variant, FGFR3 Delta8-10, lacking exons encoding the COOH-terminal half of immunoglobulin-like domain III and the transmembrane domain. Previous reports have assumed that this is a cancer-specific splice variant. We showed that FGFR3 Delta8-10 is a normal transcript in NHU cells and is translated, N-glycosylated, and secreted. Primary urothelium expressed high levels of FGFR3 transcripts. In culture, levels were reduced in actively proliferating cells but increased at confluence and as cells approached senescence. Cells overexpressing FGFR3 IIIb showed FGF1-induced proliferation, which was inhibited by the addition of FGFR3 Delta8-10. In bladder tumor cell lines derived from aggressive carcinomas, there were significant alterations in the relative expression of isoforms including an overall decrease in the proportion of FGFR3 Delta8-10 and predominant expression of FGFR3 IIIc in some cases. In summary, alternative splicing of FGFR3 IIIb in NHU cells represents a normal mechanism to generate a transcript that regulates proliferation and in bladder cancer, the ratio of FGFR3 isoforms is significantly altered.
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MESH Headings
- Aged
- Aged, 80 and over
- Alternative Splicing
- Base Sequence
- Carcinoma, Renal Cell/genetics
- Carcinoma, Renal Cell/metabolism
- Cell Line, Tumor
- Cloning, Molecular
- Female
- Fibroblast Growth Factors/antagonists & inhibitors
- Glycosylation
- Humans
- Kidney Neoplasms/genetics
- Kidney Neoplasms/metabolism
- Male
- Middle Aged
- Molecular Sequence Data
- Protein Isoforms
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptor, Fibroblast Growth Factor, Type 3/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 3/genetics
- Receptor, Fibroblast Growth Factor, Type 3/metabolism
- Urinary Bladder Neoplasms/genetics
- Urinary Bladder Neoplasms/metabolism
- Urologic Neoplasms/genetics
- Urologic Neoplasms/metabolism
- Urothelium/metabolism
- Urothelium/pathology
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Affiliation(s)
- Darren C Tomlinson
- Cancer Research UK Clinical Centre, St. James's University Hospital, Leeds, United Kingdom
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19
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Abstract
It is becoming increasingly evident that cell adhesion is an important determinant of organised growth and the maintenance of architectural integrity. Indeed, reduced adhesiveness between cells and with the extracellular matrix is a hallmark of neoplastic growth. In neuroendocrine tissues, neural cell adhesion molecule is implicated in modulating cell growth, migration, and differentiation. This review will focus on the molecular pathways involving key growth factor receptors that govern normal adhesive forces. The extent to which disruption of these adhesive forces contributes to the tumorigenic process in neuroendocrine tissues will be highlighted. Validation of the functional relevance of these adhesive pathways will be discussed in light of targeted pharmacotherapeutic studies that are unmasking novel approaches to the treatment of neuroendocrine tumours.
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Affiliation(s)
- S Ezzat
- Department of Medicine, University of Toronto, Endocrine Oncology Site Group, Mount Sinai and Princess Margaret Hospitals, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G-1X5.
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20
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Ezzat S, Huang P, Dackiw A, Asa SL. Dual Inhibition of RET and FGFR4 Restrains Medullary Thyroid Cancer Cell Growth. Clin Cancer Res 2005. [DOI: 10.1158/1078-0432.1336.11.3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Medullary thyroid cancer is frequently an aggressive form of carcinoma for which there are currently no effective forms of systemic therapy. These carcinomas arise as a result of activating mutations in the RET proto-oncogene transmembrane tyrosine kinase receptor. We, therefore, examined the potential efficacy of the tyrosine kinase inhibitor STI571 on the growth of human TT medullary cancer cells in vitro and in xenografted severe combined immunodeficiency mice. Treatment with STI571 resulted in inhibition of RET phosphorylation, cell proliferation, tumor growth and invasiveness. Based on the profile of expression of fibroblast growth factor receptors (FGFR), we examined the effects of FGFR tyrosine kinase inhibition using the small molecule FGFR inhibitor PD173074. This inhibitor resulted in abrogation of fibroblast growth factor-1-mediated FGFR4 phosphorylation in TT cells, an effect that was accompanied by significant arrest of cell proliferation and tumor growth in vivo. Moreover, the combination of STI571 and PD173074 resulted in greater suppression of cell proliferation in vitro and tumor control in vivo than that achieved with either agent alone. These data highlight RET and FGFR4 as therapeutic targets and suggest a potential role for the combined use of tyrosine kinase inhibitors in the management of inoperable medullary thyroid cancers.
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Affiliation(s)
| | | | - Alan Dackiw
- 2Surgery, Mount Sinai Hospital and University of Toronto, and
| | - Sylvia L. Asa
- 3Department of Pathology, University Health Network and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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21
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Yu S, Zheng L, Trinh DK, Asa SL, Ezzat S. Distinct transcriptional control and action of fibroblast growth factor receptor 4 in differentiating skeletal muscle cells. J Transl Med 2004; 84:1571-80. [PMID: 15467729 DOI: 10.1038/labinvest.3700187] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Although FGF signaling promotes myoblast proliferation and represses myogenic differentiation, one of the FGF receptors (FGFR), FGFR4, is expressed mainly in mature skeletal muscle. Disruption of FGFR4 signaling interrupts chick limb muscle formation. To determine the developmental regulation of FGFR4 expression, we compared the transcriptional control and action of FGFR4 in myoblasts and myotubes. We identified higher FGFR4 expression in differentiated myotubes than precursor myoblasts. FGFR4 promoter activity was localized within a region 115 bp upstream of the transcription start site. Overlapping fragments of this promoter displayed a distinct difference when compared by electromobility shift assay (EMSA) using nuclear extracts from myoblasts and myotubes. While fragments B (-95/-56) and C (-65/-26) formed specific complexes in both cell types, these complexes were consistently more intense in myotubes than myoblasts. These complexes were efficiently competed by an Sp-type oligonucleotide and were supershifted by Sp1 and by Sp3 antibodies. Deletions of the Sp-binding sites in fragment B (-95/-56) confirmed their critical contribution to promoter activity. Moreover, Sp1 expression correlated with FGFR4-expression in myotubes. To determine whether FGFR4 expression regulates myoblast differentiation, we infected a soluble dominant-negative FGFR4-containing adenovirus into these cells. This significantly impeded Erk1/2 phosphorylation and differentiation of myoblasts into MHC-expressing myotubes. Our findings point to distinct transcriptional regulation and action for FGFR4 in differentiating skeletal muscle cells.
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Affiliation(s)
- Shunjiang Yu
- Department of Medicine, Mount Sinai Hospital and University of Toronto, The Freeman Centre for Endocrine Oncology and The Ontario Cancer Institute, Toronto, Ontario, Canada
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22
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Abstract
Inherited and acquired changes in pre-mRNA splicing have been documented to play a significant role in human disease development and many cancer-associated genes are regulated by alternative splicing. Loss of fidelity, variation of the splicing process, even controlled switching to specific splicing alternatives may occur during tumor progression and could play a major role in carcinogenesis. Splice variants that are found predominantly in tumors have clear diagnostic value and may provide potential drug targets. Moreover, understanding the process of aberrant splicing and the detailed characterization of the splice variants may prove crucial to our understanding of malignant transformation. This review discusses the basic mechanism of alternative splicing, alternative splicing in cancer-associated genes, tools to identify splice variants, and the development of clinical tests based on alternatively spliced biomarkers.
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23
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Sørensen V, Brech A, Khnykin D, Kolpakova E, Citores L, Olsnes S. Deletion mutant of FGFR4 induces onion-like membrane structures in the nucleus. J Cell Sci 2004; 117:1807-19. [PMID: 15075241 DOI: 10.1242/jcs.01047] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of several deletion mutants of fibroblast growth factor receptor 4 (FGFR4) was studied in COS-1 cells. FGFR4-mutants lacking most of the extracellular region did not efficiently reach the plasma membrane but accumulated in the endoplasmic reticulum (ER) and Golgi body. A mutant FGFR4 lacking the kinase domain as well as most of the extracellular region (DeltaExt/R4Tth) had a distinct intracellular distribution. It localized in part to the nucleus, where it exhibited a striking spotted pattern. Ultrastructural studies showed that the nuclear spots consisted of several layers of membrane that were folded into onion-like structures at the nucleoplasmic side of the nuclear envelope. These intranuclear structures did not contain nuclear pores but were positive for the ER proteins calreticulin and protein disulfide isomerase, in addition to abundant DeltaExt/R4Tth. Formation of the intranuclear structures was sensitive to inhibition of protein kinase C. Live microscopy of a green-fluorescent-protein/DeltaExt/R4Tth fusion protein showed that the intranuclear structures were stable and immobile, suggesting that they function as deposits of the overexpressed mutant and associated membrane. The DeltaExt/R4Tth protein also induced formation of densely packed membrane stacks in the cytosol and we suggest a model were the intranuclear structures are formed by invagination of ER-derived membrane stacks into the nucleus.
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Affiliation(s)
- Vigdis Sørensen
- Institute for Cancer Research, The Norwegian Radium Hospital, Department of Biochemistry, Montebello, 0310 Oslo, Norway
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24
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Sturla LM, Merrick AE, Burchill SA. FGFR3IIIS: a novel soluble FGFR3 spliced variant that modulates growth is frequently expressed in tumour cells. Br J Cancer 2003; 89:1276-84. [PMID: 14520460 PMCID: PMC2394287 DOI: 10.1038/sj.bjc.6601249] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Fibroblast growth factor receptor 3 (FGFR3) is one of four high-affinity tyrosine kinase receptors for the FGF family of ligands, frequently associated with growth arrest and induction of differentiation. The extracellular immunoglobulin (IgG)-like domains II and III are responsible for ligand binding; alternative usage of exons IIIb and IIIc of the Ig-like domain III determining the ligand-binding specificity of the receptor. By reverse transcriptase polymerase chain reaction (RT–PCR) a novel FGFR3IIIc variant FGFR3IIIS, expressed in a high proportion of tumours and tumour cell lines but rarely in normal tissues, has been identified. Unlike recently described nonsense transcripts of FGFR3, the coding region of FGFR3IIIS remains in-frame producing a novel protein. The protein product is coexpressed with FGFR3IIIc in the membrane and soluble cell fractions; expression in the soluble fraction is decreased after exposure to bFGF but not aFGF. Knockout of FGFR3IIIS using antisense has a growth-inhibitory effect in vitro, suggesting a dominant-negative function for FGFR3IIIS inhibiting FGFR3-induced growth arrest. In summary, alternative splicing of the FGFR3 Ig-domain III represents a mechanism for the generation of receptor diversity. FGFR3IIIS may regulate FGF and FGFR trafficking and function, possibly contributing to the development of a malignant phenotype.
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MESH Headings
- Alternative Splicing
- Blotting, Southern
- Cell Division/drug effects
- DNA Primers
- Exons/genetics
- Fibroblast Growth Factor 1/pharmacology
- Fibroblast Growth Factor 2/pharmacology
- Gene Expression Regulation, Neoplastic
- Humans
- Immunoglobulins/genetics
- Neoplasms/genetics
- Neoplasms/metabolism
- Neoplasms/pathology
- Oligonucleotides, Antisense/pharmacology
- Phosphorylation
- Polymerase Chain Reaction
- Protein Isoforms
- Protein-Tyrosine Kinases
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor, Fibroblast Growth Factor, Type 3
- Receptors, Fibroblast Growth Factor/genetics
- Receptors, Fibroblast Growth Factor/metabolism
- Tissue Distribution
- Tumor Cells, Cultured
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Affiliation(s)
- L-M Sturla
- Candlelighter's Children's Cancer Research Laboratory, Cancer Research UK Clinical Centre, St. James's University Hospital, Beckett Street, Leeds LS9 7TF, UK
| | - A E Merrick
- Candlelighter's Children's Cancer Research Laboratory, Cancer Research UK Clinical Centre, St. James's University Hospital, Beckett Street, Leeds LS9 7TF, UK
| | - S A Burchill
- Candlelighter's Children's Cancer Research Laboratory, Cancer Research UK Clinical Centre, St. James's University Hospital, Beckett Street, Leeds LS9 7TF, UK
- Candlelighter's Children's Cancer Research Laboratory, Cancer Research UK Clinical Centre, St. James's University Hospital, Beckett Street, Leeds LS9 7TF, UK. E-mail:
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25
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Affiliation(s)
- Sylvia L Asa
- Department of Pathology and Laboratory Medicine, University of Toronto, University Health Network and Toronto Medical Laboratories, 610 University Avenue, Toronto, Ontario, Canada M5G 2M5.
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26
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Yu S, Zheng L, Asa SL, Ezzat S. Fibroblast growth factor receptor 4 (FGFR4) mediates signaling to the prolactin but not the FGFR4 promoter. Am J Physiol Endocrinol Metab 2002; 283:E490-5. [PMID: 12169442 DOI: 10.1152/ajpendo.00166.2002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Fibroblast growth factor receptors (FGFRs) have been implicated in a multitude of activities. Signaling of the 23 members of the FGF family is mediated through FGFR1-4. We show that FGF-19, which selectively binds FGFR4, can induce prolactin (PRL) but not growth hormone expression. FGF-19 also stimulated MAPK activation, an effect that was abrogated by a soluble dominant negative (dn) form of FGFR4. The response of the pituitary PRL promoter to FGF maps to an Ets-Pit1 binding site. We have previously shown that the hematopoietic zinc finger-containing transcription factor Ikaros (Ik) regulates FGFR4 as part of an overlapping site with that for an Ets-type factor in the FGFR4 promoter. Thus, we examined whether FGF-19 might regulate its own receptor through the Ets-Ik element in the FGFR4 promoter. Ets stimulated and dn-Ets inhibited basal FGFR4 and PRL promoter activity. In contrast, Ets enhanced FGF-19-induced PRL activation but failed to confer an effect for FGF-19 on the FGFR4 promoter. We conclude that FGFR4 mediates FGF-19 signaling to the PRL promoter. Our data also suggest a possible functional role for Ik in sorting Ets signals to the FGFR4 promoter, as distinct from the PRL promoter, where Ets partners with Pit1.
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Affiliation(s)
- Shunjiang Yu
- Department of Medicine, Mount Sinai Hospital and University of Toronto, Toronto, Ontario, Canada
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27
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Jang JH. Identification and characterization of soluble isoform of fibroblast growth factor receptor 3 in human SaOS-2 osteosarcoma cells. Biochem Biophys Res Commun 2002; 292:378-82. [PMID: 11906172 DOI: 10.1006/bbrc.2002.6668] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously reported the alternatively spliced transcripts of fibroblast growth factor 3 (FGFR3 ATs and MTs) derived by aberrant splicing and usage of cryptic splicing sites. Here, we describe a soluble variant of FGFR3 (FGFR3 AT-III) arising from skipping exons 8, 9, and 10 in human SaOS-2 osteosarcoma cell. This splicing event leads to the generation of an mRNA encoding a FGFR3 in which the COOH-terminal portion of the Ig-like-III domain and transmembrane domain are deleted while the remainder of the mature molecule is fused in-frame to the COOH-terminal cytoplasmic kinases domains. Sf9 cells transfected with the corresponding cDNA express the soluble form of FGFR3 AT-III into the condition medium and its secreted form was able to bind both FGF-1 and FGF-2 leading to loss of ligand binding specificity. These results indicate that the FGFR3 AT-III mRNAs are transcribed due to exon skipping with altered ligand binding specificity. These results suggest that the presence of soluble transcripts of FGFRs gene is a common feature due to mRNA splicing and this splicing plays an important role in the regulation of FGFRs function.
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Affiliation(s)
- Jun-Hyeog Jang
- Intellectual Biointerface Engineering Center, Seoul National University College of Dentistry, Seoul 110-768, Korea.
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28
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Ezzat S, Zheng L, Zhu XF, Wu GE, Asa SL. Targeted expression of a human pituitary tumor-derived isoform of FGF receptor-4 recapitulates pituitary tumorigenesis. J Clin Invest 2002; 109:69-78. [PMID: 11781352 PMCID: PMC150823 DOI: 10.1172/jci14036] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
It is estimated that up to one in five individuals develop pituitary gland tumors. Despite the common occurrence of these tumors, the pathogenetic mechanisms underlying their development remain largely unknown. We report the identification of a novel pituitary tumor-derived, N-terminally truncated isoform of FGF receptor-4 (ptd-FGFR4). The corresponding mRNA results from alternative transcription initiation and encodes a polypeptide that lacks a signal peptide and the first two extracellular Ig-like domains. ptd-FGFR4 has a distinctive cytoplasmic residence, is constitutively phosphorylated, and is transforming in vitro and in vivo. Here we show that targeted expression of ptd-FGFR4, but not FGFR4, results in pituitary tumors that morphologically recapitulate the human disease.
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MESH Headings
- 3T3 Cells
- Animals
- Base Sequence
- Cell Transformation, Neoplastic
- DNA, Neoplasm/genetics
- Gene Expression
- Humans
- Mice
- Mice, Nude
- Mice, Transgenic
- Molecular Sequence Data
- Peptide Fragments/genetics
- Peptide Fragments/metabolism
- Phosphorylation
- Pituitary Neoplasms/etiology
- Pituitary Neoplasms/genetics
- Pituitary Neoplasms/metabolism
- Pituitary Neoplasms/pathology
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- Receptor, Fibroblast Growth Factor, Type 4
- Receptors, Fibroblast Growth Factor/genetics
- Receptors, Fibroblast Growth Factor/metabolism
- Sequence Deletion
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Affiliation(s)
- Shereen Ezzat
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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