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Mancarella C, Morrione A, Scotlandi K. Extracellular Interactors of the IGF System: Impact on Cancer Hallmarks and Therapeutic Approaches. Int J Mol Sci 2024; 25:5915. [PMID: 38892104 PMCID: PMC11172729 DOI: 10.3390/ijms25115915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Revised: 05/24/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024] Open
Abstract
Dysregulation of the insulin-like growth factor (IGF) system determines the onset of various pathological conditions, including cancer. Accordingly, therapeutic strategies have been developed to block this system in tumor cells, but the results of clinical trials have been disappointing. After decades of research in the field, it is safe to say that one of the major reasons underlying the poor efficacy of anti-IGF-targeting agents is derived from an underestimation of the molecular complexity of this axis. Genetic, transcriptional, post-transcriptional and functional interactors interfere with the activity of canonical components of this axis, supporting the need for combinatorial approaches to effectively block this system. In addition, cancer cells interface with a multiplicity of factors from the extracellular compartment, which strongly affect cell destiny. In this review, we will cover novel extracellular mechanisms contributing to IGF system dysregulation and the implications of such dangerous liaisons for cancer hallmarks and responses to known and new anti-IGF drugs. A deeper understanding of both the intracellular and extracellular microenvironments might provide new impetus to better decipher the complexity of the IGF axis in cancer and provide new clues for designing novel therapeutic approaches.
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Affiliation(s)
- Caterina Mancarella
- Laboratory of Experimental Oncology, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy
| | - Andrea Morrione
- Sbarro Institute for Cancer Research and Molecular Medicine and Center for Biotechnology, Department of Biology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA;
| | - Katia Scotlandi
- Laboratory of Experimental Oncology, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy
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2
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Natsume M, Niwa M, Ichikawa S, Okamoto T, Tsutsui H, Usukura D, Murata T, Abe R, Shimonaka M, Nishida T, Shiina I, Obata Y. Brefeldin A and M-COPA block the export of RTKs from the endoplasmic reticulum via simultaneous inactivation of ARF1, ARF4, and ARF5. J Biol Chem 2024; 300:107327. [PMID: 38679330 PMCID: PMC11127164 DOI: 10.1016/j.jbc.2024.107327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 03/20/2024] [Accepted: 04/17/2024] [Indexed: 05/01/2024] Open
Abstract
Normal receptor tyrosine kinases (RTKs) need to reach the plasma membrane (PM) for ligand-induced activation, whereas its cancer-causing mutants can be activated before reaching the PM in organelles, such as the Golgi/trans-Golgi network (TGN). Inhibitors of protein export from the endoplasmic reticulum (ER), such as brefeldin A (BFA) and 2-methylcoprophilinamide (M-COPA), can suppress the activation of mutant RTKs in cancer cells, suggesting that RTK mutants cannot initiate signaling in the ER. BFA and M-COPA block the function of ADP-ribosylation factors (ARFs) that play a crucial role in ER-Golgi protein trafficking. However, among ARF family proteins, the specific ARFs inhibited by BFA or M-COPA, that is, the ARFs involved in RTKs transport from the ER, remain unclear. In this study, we showed that M-COPA blocked the export of not only KIT but also PDGFRA/EGFR/MET RTKs from the ER. ER-retained RTKs could not fully transduce anti-apoptotic signals, thereby leading to cancer cell apoptosis. Moreover, a single knockdown of ARF1, ARF3, ARF4, ARF5, or ARF6 could not block ER export of RTKs, indicating that BFA/M-COPA treatment cannot be mimicked by the knockdown of only one ARF member. Interestingly, simultaneous transfection of ARF1, ARF4, and ARF5 siRNAs mirrored the effect of BFA/M-COPA treatment. Consistent with these results, in vitro pulldown assays showed that BFA/M-COPA blocked the function of ARF1, ARF4, and ARF5. Taken together, these results suggest that BFA/M-COPA targets at least ARF1, ARF4, and ARF5; in other words, RTKs require the simultaneous activation of ARF1, ARF4, and ARF5 for their ER export.
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Affiliation(s)
- Miyuki Natsume
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan; Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Mariko Niwa
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan; Faculty of Science, Department of Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Sho Ichikawa
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan; Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Takuma Okamoto
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan; Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Hisazumi Tsutsui
- Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Daiki Usukura
- Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Takatsugu Murata
- Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Ryo Abe
- Tokyo University of Science, Noda, Chiba, Japan
| | - Motoyuki Shimonaka
- Faculty of Science, Department of Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Toshirou Nishida
- National Cancer Center Hospital, Chuo-ku, Tokyo, Japan; Laboratory of Nuclear Transport Dynamics, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Isamu Shiina
- Faculty of Science, Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan
| | - Yuuki Obata
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan.
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3
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Scalia P, Marino IR, Asero S, Pandini G, Grimberg A, El-Deiry WS, Williams SJ. Autocrine IGF-II-Associated Cancers: From a Rare Paraneoplastic Event to a Hallmark in Malignancy. Biomedicines 2023; 12:40. [PMID: 38255147 PMCID: PMC10813354 DOI: 10.3390/biomedicines12010040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Revised: 12/18/2023] [Accepted: 12/20/2023] [Indexed: 01/24/2024] Open
Abstract
The paraneoplastic syndrome referred in the literature as non-islet-cell tumor hypoglycemia (NICTH) and extra-pancreatic tumor hypoglycemia (EPTH) was first reported almost a century ago, and the role of cancer-secreted IGF-II in causing this blood glucose-lowering condition has been widely established. The landscape emerging in the last few decades, based on molecular and cellular findings, supports a broader role for IGF-II in cancer biology beyond its involvement in the paraneoplastic syndrome. In particular, a few key findings are constantly observed during tumorigenesis, (a) a relative and absolute increase in fetal insulin receptor isoform (IRA) content, with (b) an increase in IGF-II high-molecular weight cancer-variants (big-IGF-II), and (c) a stage-progressive increase in the IGF-II autocrine signal in the cancer cell, mostly during the transition from benign to malignant growth. An increasing and still under-exploited combinatorial pattern of the IGF-II signal in cancer is shaping up in the literature with respect to its transducing receptorial system and effector intracellular network. Interestingly, while surgical and clinical reports have traditionally restricted IGF-II secretion to a small number of solid malignancies displaying paraneoplastic hypoglycemia, a retrospective literature analysis, along with publicly available expression data from patient-derived cancer cell lines conveyed in the present perspective, clearly suggests that IGF-II expression in cancer is a much more common event, especially in overt malignancy. These findings strengthen the view that (1) IGF-II expression/secretion in solid tumor-derived cancer cell lines and tissues is a broader and more common event compared to the reported IGF-II association to paraneoplastic hypoglycemia, and (2) IGF-II associates to the commonly observed autocrine loops in cancer cells while IGF-I cancer-promoting effects may be linked to its paracrine effects in the tumor microenvironment. Based on these evidence-centered considerations, making the autocrine IGF-II loop a hallmark for malignant cancer growth, we here propose the functional name of IGF-II secreting tumors (IGF-IIsT) to overcome the view that IGF-II secretion and pro-tumorigenic actions affect only a clinical sub-group of rare tumors with associated hypoglycemic symptoms. The proposed scenario provides an updated logical frame towards biologically sound therapeutic strategies and personalized therapeutic interventions for currently unaccounted IGF-II-producing cancers.
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Affiliation(s)
- Pierluigi Scalia
- The ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA 19102, USA; 93100 Caltanissetta, Italy
| | - Ignazio R. Marino
- Department of Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Salvatore Asero
- The ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA 19102, USA; 93100 Caltanissetta, Italy
- ARNAS Garibaldi, UOC Chirurgia Oncologica, Nesima, 95122 Catania, Italy
| | - Giuseppe Pandini
- The ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA 19102, USA; 93100 Caltanissetta, Italy
| | - Adda Grimberg
- Perelman School of Medicine, University of Pennsylvania, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Wafik S. El-Deiry
- Legorreta Cancer Center, Brown University, Providence, RI 02903, USA
| | - Stephen J. Williams
- The ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA 19102, USA; 93100 Caltanissetta, Italy
- Department of Biology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA
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4
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Soni UK, Jenny L, Hegde RS. IGF-1R targeting in cancer - does sub-cellular localization matter? J Exp Clin Cancer Res 2023; 42:273. [PMID: 37858153 PMCID: PMC10588251 DOI: 10.1186/s13046-023-02850-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 10/03/2023] [Indexed: 10/21/2023] Open
Abstract
The insulin-like growth factor receptor (IGF-1R) was among the most intensively pursued kinase targets in oncology. However, even after a slew of small-molecule and antibody therapeutics reached clinical trials for a range of solid tumors, the initial promise remains unfulfilled. Mechanisms of resistance to, and toxicities resulting from, IGF-1R-targeted drugs are well-catalogued, and there is general appreciation of the fact that a lack of biomarker-based patient stratification was a limitation of previous clinical trials. But no next-generation therapeutic strategies have yet successfully exploited this understanding in the clinic.Currently there is emerging interest in re-visiting IGF-1R targeted therapeutics in combination-treatment protocols with predictive biomarker-driven patient-stratification. One such biomarker that emerged from early clinical trials is the sub-cellular localization of IGF-1R. After providing some background on IGF-1R, its drugging history, and the trials that led to the termination of drug development for this target, we look more deeply into the correlation between sub-cellular localization of IGF-1R and susceptibility to various classes of IGF-1R - targeted agents.
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Affiliation(s)
- Upendra K Soni
- Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Liam Jenny
- Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Rashmi S Hegde
- Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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5
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Obata Y, Kurokawa K, Tojima T, Natsume M, Shiina I, Takahashi T, Abe R, Nakano A, Nishida T. Golgi retention and oncogenic KIT signaling via PLCγ2-PKD2-PI4KIIIβ activation in gastrointestinal stromal tumor cells. Cell Rep 2023; 42:113035. [PMID: 37616163 DOI: 10.1016/j.celrep.2023.113035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 06/19/2023] [Accepted: 08/11/2023] [Indexed: 08/25/2023] Open
Abstract
Most gastrointestinal stromal tumors (GISTs) develop due to gain-of-function mutations in the tyrosine kinase gene, KIT. We recently showed that mutant KIT mislocalizes to the Golgi area and initiates uncontrolled signaling. However, the molecular mechanisms underlying its Golgi retention remain unknown. Here, we show that protein kinase D2 (PKD2) is activated by the mutant, which causes Golgi retention of KIT. In PKD2-inhibited cells, KIT migrates from the Golgi region to lysosomes and subsequently undergoes degradation. Importantly, delocalized KIT cannot trigger downstream activation. In the Golgi/trans-Golgi network (TGN), KIT activates the PKD2-phosphatidylinositol 4-kinase IIIβ (PKD2-PI4KIIIβ) pathway through phospholipase Cγ2 (PLCγ2) to generate a PI4P-rich membrane domain, where the AP1-GGA1 complex is aberrantly recruited. Disruption of any factors in this cascade results in the release of KIT from the Golgi/TGN. Our findings show the molecular mechanisms underlying KIT mislocalization and provide evidence for a strategy for inhibition of oncogenic signaling.
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Affiliation(s)
- Yuuki Obata
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
| | - Kazuo Kurokawa
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Takuro Tojima
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Miyuki Natsume
- Laboratory of Intracellular Traffic & Oncology, National Cancer Center Research Institute, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan; Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo 162-8601, Japan
| | - Isamu Shiina
- Department of Applied Chemistry, Tokyo University of Science, Shinjuku-ku, Tokyo 162-8601, Japan
| | - Tsuyoshi Takahashi
- Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Ryo Abe
- Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Akihiko Nakano
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Toshirou Nishida
- National Cancer Center Hospital, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan; Laboratory of Nuclear Transport Dynamics, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka 567-0085, Japan
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6
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Chakraborty S, Bhat AM, Mushtaq I, Luan H, Kalluchi A, Mirza S, Storck MD, Chaturvedi N, Lopez-Guerrero JA, Llombart-Bosch A, Machado I, Scotlandi K, Meza JL, Ghosal G, Coulter DW, Jordan Rowley M, Band V, Mohapatra BC, Band H. EHD1-dependent traffic of IGF-1 receptor to the cell surface is essential for Ewing sarcoma tumorigenesis and metastasis. Commun Biol 2023; 6:758. [PMID: 37474760 PMCID: PMC10359273 DOI: 10.1038/s42003-023-05125-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 07/10/2023] [Indexed: 07/22/2023] Open
Abstract
Overexpression of the EPS15 Homology Domain containing 1 (EHD1) protein has been linked to tumorigenesis but whether its core function as a regulator of intracellular traffic of cell surface receptors plays a role in oncogenesis remains unknown. We establish that EHD1 is overexpressed in Ewing sarcoma (EWS), with high EHD1 mRNA expression specifying shorter patient survival. ShRNA-knockdown and CRISPR-knockout with mouse Ehd1 rescue established a requirement of EHD1 for tumorigenesis and metastasis. RTK antibody arrays identified IGF-1R as a target of EHD1 regulation in EWS. Mechanistically, we demonstrate a requirement of EHD1 for endocytic recycling and Golgi to plasma membrane traffic of IGF-1R to maintain its surface expression and downstream signaling. Conversely, EHD1 overexpression-dependent exaggerated oncogenic traits require IGF-1R expression and kinase activity. Our findings define the RTK traffic regulation as a proximal mechanism of EHD1 overexpression-dependent oncogenesis that impinges on IGF-1R in EWS, supporting the potential of IGF-1R and EHD1 co-targeting.
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Affiliation(s)
- Sukanya Chakraborty
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Aaqib M Bhat
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Insha Mushtaq
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Incyte Corporation, Wilmington, DE, USA
| | - Haitao Luan
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Achyuth Kalluchi
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Sameer Mirza
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Department of Chemistry, College of Science, United Arab Emirates University, Al Ain, UAE
| | - Matthew D Storck
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Nagendra Chaturvedi
- Department of Pediatrics, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | | | - Antonio Llombart-Bosch
- Department of Pathology, University of Valencia, Avd. Blasco Ibáñez 15, 46010, Valencia, Spain
| | - Isidro Machado
- Department of Pathology, University of Valencia, Avd. Blasco Ibáñez 15, 46010, Valencia, Spain
| | - Katia Scotlandi
- Laboratory of Experimental Oncology, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Jane L Meza
- Department of Biostatistics, College of Public Health, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Gargi Ghosal
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Donald W Coulter
- Department of Pediatrics, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - M Jordan Rowley
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Vimla Band
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Bhopal C Mohapatra
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
| | - Hamid Band
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
- Department of Genetics, Cell Biology & Anatomy, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
- Department of Biostatistics, College of Public Health, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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7
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Chakraborty S, Bhat AM, Mushtaq I, Luan H, Kalluchi A, Mirza S, Storck MD, Chaturvedi N, Lopez-Guerrero JA, Llombart-Bosch A, Machado I, Scotlandi K, Meza JL, Ghosal G, Coulter DW, Rowley JM, Band V, Mohapatra BC, Band H. EHD1-dependent traffic of IGF-1 receptor to the cell surface is essential for Ewing sarcoma tumorigenesis and metastasis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.15.524130. [PMID: 36711452 PMCID: PMC9882098 DOI: 10.1101/2023.01.15.524130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Overexpression of EPS15 Homology Domain containing 1 (EHD1) has been linked to tumorigenesis but whether its core function as a regulator of intracellular traffic of cell surface receptors plays a role in oncogenesis remains unknown. We establish that EHD1 is overexpressed in Ewing sarcoma (EWS), with high EHD mRNA expression specifying shorter patient survival. ShRNA and CRISPR-knockout with mouse Ehd1 rescue established a requirement of EHD1 for tumorigenesis and metastasis. RTK antibody arrays identified the IGF-1R as a target of EHD1 regulation in EWS. Mechanistically, we demonstrate a requirement of EHD1 for endocytic recycling and Golgi to plasma membrane traffic of IGF-1R to maintain its surface expression and downstream signaling. Conversely, EHD1 overexpression-dependent exaggerated oncogenic traits require IGF-1R expression and kinase activity. Our findings define the RTK traffic regulation as a proximal mechanism of EHD1 overexpression-dependent oncogenesis that impinges on IGF-1R in EWS, supporting the potential of IGF-1R and EHD1 co-targeting.
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8
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Emerging Role of IGF-1 in Prostate Cancer: A Promising Biomarker and Therapeutic Target. Cancers (Basel) 2023; 15:cancers15041287. [PMID: 36831629 PMCID: PMC9954466 DOI: 10.3390/cancers15041287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/15/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
Prostate cancer (PCa) is a highly heterogeneous disease driven by gene alterations and microenvironmental influences. Not only enhanced serum IGF-1 but also the activation of IGF-1R and its downstream signaling components has been increasingly recognized to have a vital driving role in the development of PCa. A better understanding of IGF-1/IGF-1R activity and regulation has therefore emerged as an important subject of PCa research. IGF-1/IGF-1R signaling affects diverse biological processes in cancer cells, including promoting survival and renewal, inducing migration and spread, and promoting resistance to radiation and castration. Consequently, inhibitory reagents targeting IGF-1/IGF-1R have been developed to limit cancer development. Multiple agents targeting IGF-1/IGF-1R signaling have shown effects against tumor growth in tumor xenograft models, but further verification of their effectiveness in PCa patients in clinical trials is still needed. Combining androgen deprivation therapy or cytotoxic chemotherapeutics with IGF-1R antagonists based on reliable predictive biomarkers and developing and applying novel agents may provide more desirable outcomes. This review will summarize the contribution of IGF-1 signaling to the development of PCa and highlight the relevance of this signaling axis in potential strategies for cancer therapy.
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9
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Tan W, Zhang Q, Hong P, Xu B. A Self-Assembling Probe for Imaging the States of Golgi Apparatus in Live Single Cells. Bioconjug Chem 2022; 33:1983-1988. [PMID: 35312281 PMCID: PMC9489815 DOI: 10.1021/acs.bioconjchem.2c00084] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Despite the enormous progress in genomics and proteomics, it is still challenging to assess the states of organelles in living cells with high spatiotemporal resolution. Based on our recent finding of enzyme-instructed self-assembly of a thiophosphopeptide that targets the Golgi Apparatus (GA) instantly, we use the thiophosphopeptide, which is enzymatically responsive and redox active, as an integrative probe for revealing the state of the GA of live cells at the single cell level. By imaging the probe in the GA of live cells over time, our results show that the accumulation of the probe at the GA depends on cell types. By comparison to a conventional Golgi probe, this self-assembling probe accumulates at the GA much faster and are sensitive to the expression of alkaline phosphatases. In addition, subtle changes of the fluorophore results in slightly different GA responses. This work illustrates a novel class of active molecular probes that combine enzyme-instructed self-assembly and redox reaction for high-resolution imaging of the states of subcellular organelles over a large area and extended times.
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Affiliation(s)
- Weiyi Tan
- Department of Chemistry, Brandeis University, 415 South St., Waltham, MA 02454, USA
| | - Qiuxin Zhang
- Department of Chemistry, Brandeis University, 415 South St., Waltham, MA 02454, USA
| | - Pengyu Hong
- Department of Computer Science, Brandeis University, 415 South St., Waltham, MA 02453, USA
| | - Bing Xu
- Department of Chemistry, Brandeis University, 415 South St., Waltham, MA 02454, USA
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10
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Tan W, Zhang Q, Quiñones-Frías MC, Hsu AY, Zhang Y, Rodal A, Hong P, Luo HR, Xu B. Enzyme-Responsive Peptide Thioesters for Targeting Golgi Apparatus. J Am Chem Soc 2022; 144:6709-6713. [PMID: 35404599 PMCID: PMC9069992 DOI: 10.1021/jacs.2c02238] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The Golgi apparatus (GA) is the hub of intracellular trafficking, but selectively targeting GA remains a challenge. We show an unconventional types of peptide thioesters, consisting of an aminoethyl thioester and acting as substrates of thioesterases, for instantly targeting the GA of cells. The peptide thioesters, above or below their critical micelle concentrations, enter cells mainly via caveolin-mediated endocytosis or macropinocytosis, respectively. After being hydrolyzed by GA-associated thioesterases, the resulting thiopeptides form dimers and accumulate in the GA. After saturating the GA, the thiopeptides are enriched in the endoplasmic reticulum (ER). Their buildup in ER and GA disrupts protein trafficking, thus leading to cell death via multiple pathways. The peptide thioesters target the GA of a wide variety of cells, including human, murine, and Drosophila cells. Changing d-diphenylalanine to l-diphenylalanine in the peptide maintains the GA-targeting ability. In addition, targeting GA redirects protein (e.g., NRAS) distribution. This work illustrates a thioesterase-responsive and redox-active molecular platform for targeting the GA and controlling cell fates.
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Affiliation(s)
- Weiyi Tan
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02453, USA
| | - Qiuxin Zhang
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02453, USA
| | | | - Alan Y. Hsu
- Department of Pathology, Harvard Medical School and Department of Laboratory Medicine, Children’s Hospital Boston and Dana-Farber/Harvard Cancer Center, Boston, MA 02115, USA
| | - Yichi Zhang
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02453, USA
| | - Avital Rodal
- Department of Biology, Brandeis University, Waltham, MA 02453, USA
| | - Pengyu Hong
- Department of Computer Science, Brandeis University, Waltham, MA 02453, USA
| | - Hongbo R. Luo
- Department of Pathology, Harvard Medical School and Department of Laboratory Medicine, Children’s Hospital Boston and Dana-Farber/Harvard Cancer Center, Boston, MA 02115, USA
| | - Bing Xu
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02453, USA
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11
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Zhang Q, Tan W, Xu B. Enzymatic Noncovalent Synthesis for Targeting Subcellular Organelles. Chempluschem 2022; 87:e202200060. [PMID: 35420712 PMCID: PMC9508291 DOI: 10.1002/cplu.202200060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/23/2022] [Indexed: 11/09/2022]
Abstract
Enzymatic noncovalent synthesis (ENS) exploits enzymatic reactions to produce spatially organized higher-order supramolecular assemblies that modulate cellular processes. While ENS is a general mechanism to create higher-order assemblies of proteins for diverse cellular functions, the exploration of ENS of other bioactive molecules, such as peptides or small organic molecules, is rather limited. Since ENS generates non-diffusive supramolecular assemblies locally, it provides a unique approach to targeting subcellular organelles. In this Review, we highlight the recent progress of the application of ENS of peptide assemblies for targeting subcellular organelles. After a brief introduction of the concept of ENS, we introduce the case of generating artificial filaments by ENS in cell cytosol, then discuss the use of ENS for targeting endoplasmic reticulum, mitochondria, Golgi apparatus, and lysosomes, and finally we describe the targeting of nucleus by ENS. We hope to illustrate the promise of ENS, as a localized molecular process in an open system, for understanding diseases, controlling cell behaviors, and developing new therapeutics.
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Affiliation(s)
- Qiuxin Zhang
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | - Weiyi Tan
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | - Bing Xu
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02454, USA
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12
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Martin A, Fernandez MC, Cattaneo ER, Schuster CD, Venara M, Clément F, Berenstein A, Lombardi MG, Bergadá I, Gutierrez M, Martí MA, Gonzalez-Baro MR, Pennisi PA. Type 1 Insulin-Like Growth Factor Receptor Nuclear Localization in High-Grade Glioma Cells Enhances Motility, Metabolism, and In Vivo Tumorigenesis. Front Endocrinol (Lausanne) 2022; 13:849279. [PMID: 35574033 PMCID: PMC9094447 DOI: 10.3389/fendo.2022.849279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/11/2022] [Indexed: 11/16/2022] Open
Abstract
Gliomas are the most frequent solid tumors in children. Among these, high-grade gliomas are less common in children than in adults, though they are similar in their aggressive clinical behavior. In adults, glioblastoma is the most lethal tumor of the central nervous system. Insulin-like growth factor 1 receptor (IGF1R) plays an important role in cancer biology, and its nuclear localization has been described as an adverse prognostic factor in different tumors. Previously, we have demonstrated that, in pediatric gliomas, IGF1R nuclear localization is significantly associated with high-grade tumors, worst clinical outcome, and increased risk of death. Herein we explore the role of IGF1R intracellular localization by comparing two glioblastoma cell lines that differ only in their IGF1R capacity to translocate to the nucleus. In vitro, IGF1R nuclear localization enhances glioblastoma cell motility and metabolism without affecting their proliferation. In vivo, IGF1R has the capacity to translocate to the nucleus and allows not only a higher proliferation rate and the earlier development of tumors but also renders the cells sensitive to OSI906 therapy. With this work, we provide evidence supporting the implications of the presence of IGF1R in the nucleus of glioma cells and a potential therapeutic opportunity for patients harboring gliomas with IGF1R nuclear localization.
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Affiliation(s)
- Ayelen Martin
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | - María Celia Fernandez
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | - Elizabeth R. Cattaneo
- Instituto de Investigaciones Bioquímicas de La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Claudio D. Schuster
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEyN-UBA) e Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Pabellòn 2 de Ciudad Universitaria, Ciudad de Buenos Aires, Argentina
| | - Marcela Venara
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | - Florencia Clément
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | - Ariel Berenstein
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
- Instituto Multidisciplinario de Investigaciones en Patologías Pediátricas, CONICET, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | | | - Ignacio Bergadá
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | - Mariana Gutierrez
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
| | - Marcelo A. Martí
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEyN-UBA) e Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Pabellòn 2 de Ciudad Universitaria, Ciudad de Buenos Aires, Argentina
| | - María R. Gonzalez-Baro
- Instituto de Investigaciones Bioquímicas de La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Patricia A. Pennisi
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” CONICET—FEI—División de Endocrinología, Hospital de Niños R. Gutierrez, Buenos Aires, Argentina
- *Correspondence: Patricia A. Pennisi,
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13
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Revising Endosomal Trafficking under Insulin Receptor Activation. Int J Mol Sci 2021; 22:ijms22136978. [PMID: 34209489 PMCID: PMC8268289 DOI: 10.3390/ijms22136978] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 06/25/2021] [Accepted: 06/27/2021] [Indexed: 02/06/2023] Open
Abstract
The endocytosis of ligand-bound receptors and their eventual recycling to the plasma membrane (PM) are processes that have an influence on signalling activity and therefore on many cell functions, including migration and proliferation. Like other tyrosine kinase receptors (TKR), the insulin receptor (INSR) has been shown to be endocytosed by clathrin-dependent and -independent mechanisms. Once at the early endosome (EE), the sorting of the receptor, either to the late endosome (LE) for degradation or back to the PM through slow or fast recycling pathways, will determine the intensity and duration of insulin effects. Both the endocytic and the endosomic pathways are regulated by many proteins, the Arf and Rab families of small GTPases being some of the most relevant. Here, we argue for a specific role for the slow recycling route, whilst we review the main molecular mechanisms involved in INSR endocytosis, sorting and recycling, as well as their possible role in cell functions.
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Tan W, Zhang Q, Wang J, Yi M, He H, Xu B. Enzymatic Assemblies of Thiophosphopeptides Instantly Target Golgi Apparatus and Selectively Kill Cancer Cells*. Angew Chem Int Ed Engl 2021; 60:12796-12801. [PMID: 33783926 PMCID: PMC8159897 DOI: 10.1002/anie.202102601] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 03/19/2021] [Indexed: 01/01/2023]
Abstract
Changing an oxygen atom of the phosphoester bond in phosphopeptides by a sulfur atom enables instantly targeting Golgi apparatus (GA) and selectively killing cancer cells by enzymatic self-assembly. Specifically, conjugating cysteamine S-phosphate to the C-terminal of a self-assembling peptide generates a thiophosphopeptide. Being a substrate of alkaline phosphatase (ALP), the thiophosphopeptide undergoes rapid ALP-catalyzed dephosphorylation to form a thiopeptide that self-assembles. The thiophosphopeptide enters cells via caveolin-mediated endocytosis and macropinocytosis and instantly accumulates in GA because of dephosphorylation and formation of disulfide bonds in Golgi by themselves and with Golgi proteins. Moreover, the thiophosphopeptide potently and selectively inhibits cancer cells (HeLa) with the IC50 (about 3 μM), which is an order of magnitude more potent than that of the parent phosphopeptide.
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Affiliation(s)
- Weiyi Tan
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
| | - Qiuxin Zhang
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
| | - Jiaqing Wang
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
| | - Meihui Yi
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
| | - Hongjian He
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
| | - Bing Xu
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
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15
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Tan W, Zhang Q, Wang J, Yi M, He H, Xu B. Enzymatic Assemblies of Thiophosphopeptides Instantly Target Golgi Apparatus and Selectively Kill Cancer Cells**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102601] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Weiyi Tan
- Department of Chemistry Brandeis University 415 South Street Waltham MA 02453 USA
| | - Qiuxin Zhang
- Department of Chemistry Brandeis University 415 South Street Waltham MA 02453 USA
| | - Jiaqing Wang
- Department of Chemistry Brandeis University 415 South Street Waltham MA 02453 USA
| | - Meihui Yi
- Department of Chemistry Brandeis University 415 South Street Waltham MA 02453 USA
| | - Hongjian He
- Department of Chemistry Brandeis University 415 South Street Waltham MA 02453 USA
| | - Bing Xu
- Department of Chemistry Brandeis University 415 South Street Waltham MA 02453 USA
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Werner H, Sarfstein R, Laron Z. The Role of Nuclear Insulin and IGF1 Receptors in Metabolism and Cancer. Biomolecules 2021; 11:biom11040531. [PMID: 33918477 PMCID: PMC8065599 DOI: 10.3390/biom11040531] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/24/2021] [Accepted: 04/01/2021] [Indexed: 12/22/2022] Open
Abstract
Insulin (InsR) and insulin-like growth factor-1 (IGF1R) receptors mediate the metabolic and growth-promoting actions of insulin and IGF1/IGF2, respectively. Evidence accumulated in recent years indicates that, in addition to their typical cell-surface localization pattern and ligand-activated mechanism of action, InsR and IGF1R are present in the cell nucleus of both normal and transformed cells. Nuclear translocation seems to involve interaction with a small, ubiquitin-like modifier protein (SUMO-1), although this modification is not always a prerequisite. Nuclear InsR and IGF1R exhibit a number of biological activities that classically fit within the definition of transcription factors. These nuclear activities include, among others, sequence-specific DNA binding and transcriptional control. Of particular interest, nuclear IGF1R was capable of binding and stimulating its cognate gene promoter. The physiological relevance of this autoregulatory mechanism needs to be further investigated. In addition to its nuclear localization, studies have identified IGF1R in the Golgi apparatus, and this particular distribution correlated with a migratory phenotype. In summary, the newly described roles of InsR and IGF1R as gene regulators, in concert with their atypical pattern of subcellular distribution, add a further layer of complexity to traditional models of cell signaling. Furthermore, and in view of the emerging role of IGF1R as a potential therapeutic target, a better understanding of the mechanisms responsible for nuclear IGF1R transport and identification of IGF1R interactors might help optimize target directed therapies in oncology.
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Affiliation(s)
- Haim Werner
- Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel;
- Shalom and Varda Yoran Institute for Human Genome Research, Tel Aviv University, Tel Aviv 69978, Israel
- Correspondence:
| | - Rive Sarfstein
- Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel;
| | - Zvi Laron
- Endocrine and Diabetes Research Unit, Schneider Children’s Medical Center, Petah Tikva 49292, Israel;
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Crudden C, Girnita L. The tale of a tail: The secret behind IGF-1R's oncogenic power. Sci Signal 2020; 13:13/633/eabb7887. [PMID: 32457114 DOI: 10.1126/scisignal.abb7887] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The C-terminal tail of insulin-like growth factor 1 receptor (IGF-1R) has long been appreciated to drive much of this receptor's oncogenic power. In this issue of Science Signaling, Rieger et al. have shown that Tyr1250 and Tyr1251 of IGF-1R are autophosphorylated in a cell adhesion-dependent manner, uncovering a previously unknown plasma membrane-Golgi trafficking route for IGF-1R in migratory cells, an integral part of the malignant phenotype.
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Affiliation(s)
- Caitrin Crudden
- Department of Oncology and Pathology, BioClinicum, Karolinska Institutet and Karolinska University Hospital, 17164 Stockholm, Sweden.,Department of Pathology, Cancer Center Amsterdam, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Leonard Girnita
- Department of Oncology and Pathology, BioClinicum, Karolinska Institutet and Karolinska University Hospital, 17164 Stockholm, Sweden.
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18
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Rieger L, O’Connor R. Controlled Signaling-Insulin-Like Growth Factor Receptor Endocytosis and Presence at Intracellular Compartments. Front Endocrinol (Lausanne) 2020; 11:620013. [PMID: 33584548 PMCID: PMC7878670 DOI: 10.3389/fendo.2020.620013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 12/02/2020] [Indexed: 12/16/2022] Open
Abstract
Ligand-induced activation of the IGF-1 receptor triggers plasma-membrane-derived signal transduction but also triggers receptor endocytosis, which was previously thought to limit signaling. However, it is becoming ever more clear that IGF-1R endocytosis and trafficking to specific subcellular locations can define specific signaling responses that are important for key biological processes in normal cells and cancer cells. In different cell types, specific cell adhesion receptors and associated proteins can regulate IGF-1R endocytosis and trafficking. Once internalized, the IGF-1R may be recycled, degraded or translocated to the intracellular membrane compartments of the Golgi apparatus or the nucleus. The IGF-1R is present in the Golgi apparatus of migratory cancer cells where its signaling contributes to aggressive cancer behaviors including cell migration. The IGF-1R is also found in the nucleus of certain cancer cells where it can regulate gene expression. Nuclear IGF-1R is associated with poor clinical outcomes. IGF-1R signaling has also been shown to support mitochondrial biogenesis and function, and IGF-1R inhibition causes mitochondrial dysfunction. How IGF-1R intracellular trafficking and compartmentalized signaling is controlled is still unknown. This is an important area for further study, particularly in cancer.
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