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Zhu H, Gao H, Ji Y, Zhou Q, Du Z, Tian L, Jiang Y, Yao K, Zhou Z. Targeting p53-MDM2 interaction by small-molecule inhibitors: learning from MDM2 inhibitors in clinical trials. J Hematol Oncol 2022; 15:91. [PMID: 35831864 PMCID: PMC9277894 DOI: 10.1186/s13045-022-01314-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 07/07/2022] [Indexed: 12/17/2022] Open
Abstract
p53, encoded by the tumor suppressor gene TP53, is one of the most important tumor suppressor factors in vivo and can be negatively regulated by MDM2 through p53–MDM2 negative feedback loop. Abnormal p53 can be observed in almost all tumors, mainly including p53 mutation and functional inactivation. Blocking MDM2 to restore p53 function is a hotspot in the development of anticancer candidates. Till now, nine MDM2 inhibitors with different structural types have entered clinical trials. However, no MDM2 inhibitor has been approved for clinical application. This review focused on the discovery, structural modification, preclinical and clinical research of the above compounds from the perspective of medicinal chemistry. Based on this, the possible defects in MDM2 inhibitors in clinical development were analyzed to suggest that the multitarget strategy or targeted degradation strategy based on MDM2 has the potential to reduce the dose-dependent hematological toxicity of MDM2 inhibitors and improve their anti-tumor activity, providing certain guidance for the development of agents targeting the p53–MDM2 interaction.
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Affiliation(s)
- Haohao Zhu
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China
| | - Hui Gao
- Jiangyin People's Hospital, Wuxi, 214400, Jiangsu, China
| | - Yingying Ji
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China
| | - Qin Zhou
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China
| | - Zhiqiang Du
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China
| | - Lin Tian
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China
| | - Ying Jiang
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China.
| | - Kun Yao
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China.
| | - Zhenhe Zhou
- The Affiliated Wuxi Mental Health Center of Jiangnan University, Wuxi Tongren International Rehabilitation Hospital, Wuxi, 214151, Jiangsu, China.
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HAUSP Is a Key Epigenetic Regulator of the Chromatin Effector Proteins. Genes (Basel) 2021; 13:genes13010042. [PMID: 35052383 PMCID: PMC8774506 DOI: 10.3390/genes13010042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 12/18/2022] Open
Abstract
HAUSP (herpes virus-associated ubiquitin-specific protease), also known as Ubiquitin Specific Protease 7, plays critical roles in cellular processes, such as chromatin biology and epigenetics, through the regulation of different signaling pathways. HAUSP is a main partner of the “Epigenetic Code Replication Machinery,” ECREM, a large protein complex that includes several epigenetic players, such as the ubiquitin-like containing plant homeodomain (PHD) and an interesting new gene (RING), finger domains 1 (UHRF1), as well as DNA methyltransferase 1 (DNMT1), histone deacetylase 1 (HDAC1), histone methyltransferase G9a, and histone acetyltransferase TIP60. Due to its deubiquitinase activity and its ability to team up through direct interactions with several epigenetic regulators, mainly UHRF1, DNMT1, TIP60, the histone lysine methyltransferase EZH2, and the lysine-specific histone demethylase LSD1, HAUSP positions itself at the top of the regulatory hierarchies involved in epigenetic silencing of tumor suppressor genes in cancer. This review highlights the increasing role of HAUSP as an epigenetic master regulator that governs a set of epigenetic players involved in both the maintenance of DNA methylation and histone post-translational modifications.
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Venkatesh D, O'Brien NA, Zandkarimi F, Tong DR, Stokes ME, Dunn DE, Kengmana ES, Aron AT, Klein AM, Csuka JM, Moon SH, Conrad M, Chang CJ, Lo DC, D'Alessandro A, Prives C, Stockwell BR. MDM2 and MDMX promote ferroptosis by PPARα-mediated lipid remodeling. Genes Dev 2020; 34:526-543. [PMID: 32079652 PMCID: PMC7111265 DOI: 10.1101/gad.334219.119] [Citation(s) in RCA: 149] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 01/21/2020] [Indexed: 12/21/2022]
Abstract
Here, Venkatesh et al. investigated the p53-independent roles of MDMX and the MDM2–MDMX complex. They found that MDM2 and MDMX facilitate ferroptosis in cells with or without p53, and that PPARα activity is essential for MDM2 and MDMX to promote ferroptosis, suggesting that the MDM2–MDMX complex regulates lipids through altering PPARα activity. MDM2 and MDMX, negative regulators of the tumor suppressor p53, can work separately and as a heteromeric complex to restrain p53's functions. MDM2 also has pro-oncogenic roles in cells, tissues, and animals that are independent of p53. There is less information available about p53-independent roles of MDMX or the MDM2–MDMX complex. We found that MDM2 and MDMX facilitate ferroptosis in cells with or without p53. Using small molecules, RNA interference reagents, and mutant forms of MDMX, we found that MDM2 and MDMX, likely working in part as a complex, normally facilitate ferroptotic death. We observed that MDM2 and MDMX alter the lipid profile of cells to favor ferroptosis. Inhibition of MDM2 or MDMX leads to increased levels of FSP1 protein and a consequent increase in the levels of coenzyme Q10, an endogenous lipophilic antioxidant. This suggests that MDM2 and MDMX normally prevent cells from mounting an adequate defense against lipid peroxidation and thereby promote ferroptosis. Moreover, we found that PPARα activity is essential for MDM2 and MDMX to promote ferroptosis, suggesting that the MDM2–MDMX complex regulates lipids through altering PPARα activity. These findings reveal the complexity of cellular responses to MDM2 and MDMX and suggest that MDM2–MDMX inhibition might be useful for preventing degenerative diseases involving ferroptosis. Furthermore, they suggest that MDM2/MDMX amplification may predict sensitivity of some cancers to ferroptosis inducers.
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Affiliation(s)
- Divya Venkatesh
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Nicholas A O'Brien
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Fereshteh Zandkarimi
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - David R Tong
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Michael E Stokes
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Denise E Dunn
- Center for Drug Discovery, Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Everett S Kengmana
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Allegra T Aron
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Alyssa M Klein
- Integrated Program in Cellular, Molecular, and Biomedical Studies, Columbia University, New York, New York 10032, USA
| | - Joleen M Csuka
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Sung-Hwan Moon
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Marcus Conrad
- Helmholtz Zentrum München, Institute of Metabolism and Cell Death, Neuherberg 85764, Germany
| | - Christopher J Chang
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA.,Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Donald C Lo
- Center for Drug Discovery, Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, Colorado 80045, USA
| | - Carol Prives
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Brent R Stockwell
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA.,Department of Chemistry, Columbia University, New York, New York 10027, USA
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Stark M, Heinrich SD, Sivashanmugam R, Mackey D, Wasilewska E, Craver R. Pediatric Chondromyxoid Fibroma-Like Osteosarcoma. Fetal Pediatr Pathol 2017; 36:154-161. [PMID: 27935335 DOI: 10.1080/15513815.2016.1259376] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Chondromyxoid fibroma-like osteosarcoma (CMF-OS) is a low-grade osteosarcoma, often misdiagnosed on initial biopsy as a benign lesion, with five cases previously described. We report a 13-year-old male with an intramedullary lytic CMF-OS of the right tibial proximal metaphysis with cortical destruction and soft tissue extension. Diagnosis was based on malignant new bone formation, increased mitotic figures, lamellar bone permeation with bony destruction, and correlation with imaging studies. There were no metastasis at presentation and the tumor showed good response to standard chemotherapy with >95% necrosis.
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Affiliation(s)
- Matthew Stark
- a Department of Pathology , Children's Hospital New Orleans , New Orleans , LA , USA
| | | | | | - Dane Mackey
- d Department of Radiology , LSUHSC , New Orleans , LA , USA
| | - Ewa Wasilewska
- e Department of Radiology , Children's Hospital New Orleans , New Orleans , LA , USA
| | - Randall Craver
- a Department of Pathology , Children's Hospital New Orleans , New Orleans , LA , USA.,f Department of Pathology , LSUHSC , New Orleans , LA , USA
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Eischen CM. Role of Mdm2 and Mdmx in DNA repair. J Mol Cell Biol 2017; 9:69-73. [PMID: 27932484 PMCID: PMC5439402 DOI: 10.1093/jmcb/mjw052] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 11/07/2016] [Accepted: 12/02/2016] [Indexed: 11/21/2022] Open
Abstract
Mdm2 and Mdmx are critical regulators of the p53 tumour suppressor and are overexpressed in many human malignancies. However, in recent years, their impact on genome instability was shown to be at least, in part, independent of p53. Both Mdm2 and Mdmx inhibit DNA break repair through their association with the Mre11/Rad50/Nbs1 DNA repair complex. Recent evidence indicates that harnessing Mdm2 and/or Mdmx-mediated inhibition of DNA break repair in cancer cells could provide a therapeutic opportunity, particularly for those malignancies that have lost functional p53.
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Affiliation(s)
- Christine M. Eischen
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA19107, USA
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Tan BX, Liew HP, Chua JS, Ghadessy FJ, Tan YS, Lane DP, Coffill CR. Anatomy of Mdm2 and Mdm4 in evolution. J Mol Cell Biol 2017; 9:3-15. [PMID: 28077607 PMCID: PMC6372010 DOI: 10.1093/jmcb/mjx002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 11/24/2016] [Accepted: 01/10/2017] [Indexed: 01/09/2023] Open
Abstract
Mouse double minute (Mdm) genes span an evolutionary timeframe from the ancient eukaryotic placozoa Trichoplax adhaerens to Homo sapiens, implying a significant and possibly conserved cellular role throughout history. Maintenance of DNA integrity and response to DNA damage involve many key regulatory pathways, including precise control over the tumour suppressor protein p53. In most vertebrates, degradation of p53 through proteasomal targeting is primarily mediated by heterodimers of Mdm2 and the Mdm2-related protein Mdm4 (also known as MdmX). Both Mdm2 and Mdm4 have p53-binding regions, acidic domains, zinc fingers, and C-terminal RING domains that are conserved throughout evolution. Vertebrates typically have both Mdm2 and Mdm4 genes, while analyses of sequenced genomes of invertebrate species have identified single Mdm genes, suggesting that a duplication event occurred prior to emergence of jawless vertebrates about 550-440 million years ago. The functional relationship between Mdm and p53 in T. adhaerens, an organism that has existed for 1 billion years, implies that these two proteins have evolved together to maintain a conserved and regulated function.
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Affiliation(s)
- Ban Xiong Tan
- p53 Laboratory, Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos #06-06, Singapore138648, Singapore
| | - Hoe Peng Liew
- p53 Laboratory, Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos #06-06, Singapore138648, Singapore
| | - Joy S. Chua
- p53 Laboratory, Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos #06-06, Singapore138648, Singapore
| | - Farid J. Ghadessy
- p53 Laboratory, Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos #06-06, Singapore138648, Singapore
| | - Yaw Sing Tan
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), 30 Biopolis St, #07-01,Singapore138671, Singapore
| | - David P. Lane
- p53 Laboratory, Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos #06-06, Singapore138648, Singapore
| | - Cynthia R. Coffill
- p53 Laboratory, Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos #06-06, Singapore138648, Singapore
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Abstract
It is now clear that functional p53 is critical to protect the genome from alterations that lead to tumorigenesis. However, with the myriad of cellular stresses and pathways linked to p53 activation, much remains unknown about how p53 maintains genome stability and the proteins involved. The current understanding of the multiple ways p53 contributes to genome stability and how two of its negative regulators, Mdm2 and Mdmx, induce genome instability will be described.
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Affiliation(s)
- Christine M Eischen
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37212
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Karni-Schmidt O, Lokshin M, Prives C. The Roles of MDM2 and MDMX in Cancer. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2016; 11:617-44. [PMID: 27022975 DOI: 10.1146/annurev-pathol-012414-040349] [Citation(s) in RCA: 200] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
For more than 25 years, MDM2 and its homolog MDMX (also known as MDM4) have been shown to exert oncogenic activity. These two proteins are best understood as negative regulators of the p53 tumor suppressor, although they may have additional p53-independent roles. Understanding the dysregulation of MDM2 and MDMX in human cancers and how they function either together or separately in tumorigenesis may improve methods of diagnosis and for assessing prognosis. Targeting the proteins themselves, or their regulators, may be a promising therapeutic approach to treating some forms of cancer.
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Affiliation(s)
- Orit Karni-Schmidt
- Department of Biological Sciences, Columbia University, New York, NY 10027;
| | - Maria Lokshin
- Department of Biological Sciences, Columbia University, New York, NY 10027;
| | - Carol Prives
- Department of Biological Sciences, Columbia University, New York, NY 10027;
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Abstract
Various experimental strategies aim to (re)activate p53 signalling in cancer cells. The most advanced clinically are small-molecule inhibitors of the autoregulatory interaction between p53 and MDM2 (murine double minute 2). Different MDM2 inhibitors are currently under investigation in clinical trials. As for other targeted anti-cancer therapy approaches, relatively rapid resistance acquisition may limit the clinical efficacy of MDM2 inhibitors. In particular, MDM2 inhibitors were shown to induce p53 mutations in experimental systems. In the present article, we summarize what is known about MDM2 inhibitors as anti-cancer drugs with a focus on the acquisition of resistance to these compounds.
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Carrillo AM, Hicks M, Khabele D, Eischen CM. Pharmacologically Increasing Mdm2 Inhibits DNA Repair and Cooperates with Genotoxic Agents to Kill p53-Inactivated Ovarian Cancer Cells. Mol Cancer Res 2015; 13:1197-205. [PMID: 25964101 DOI: 10.1158/1541-7786.mcr-15-0089] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 05/02/2015] [Indexed: 11/16/2022]
Abstract
UNLABELLED The Mdm2 oncogene is a negative regulator of the p53 tumor suppressor and recently identified inhibitor of DNA break repair. Nutlin-3 is a small-molecule inhibitor of Mdm2-p53 interaction that can induce apoptosis in cancer cells through activation of p53. Although this is a promising therapy for those cancers with wild-type p53, half of all human cancers have inactivated p53. Here, we reveal that a previously unappreciated effect of Nutlin is inhibition of DNA break repair, stemming from its ability to increase Mdm2 protein levels. The Nutlin-induced increase in Mdm2 inhibited DNA double-strand break repair and prolonged DNA damage response signaling independent of p53. Mechanistically, this effect of Nutlin required Mdm2 and acted through Nbs1 of the Mre11-Rad50-Nbs1 DNA repair complex. In ovarian cancer cells, where >90% have inactivated p53, Nutlin combined with the genotoxic agents, cisplatin or etoposide, had a cooperative lethal effect resulting in increased DNA damage and apoptosis. Therefore, these data demonstrate an unexpected consequence of pharmacologically increasing Mdm2 levels that when used in combination with genotoxic agents induces synthetic lethality in ovarian cancer cells, and likely other malignant cell types, that have inactivated p53. IMPLICATIONS Data reveal a therapeutically beneficial effect of pharmacologically increasing Mdm2 levels combined with chemotherapeutic agents for malignancies that have lost functional p53.
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Affiliation(s)
- Alexia M Carrillo
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Mellissa Hicks
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Dineo Khabele
- Department of Obstetrics and Gynecology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Christine M Eischen
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee.
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Carrillo AM, Bouska A, Arrate MP, Eischen CM. Mdmx promotes genomic instability independent of p53 and Mdm2. Oncogene 2015; 34:846-56. [PMID: 24608433 PMCID: PMC4160436 DOI: 10.1038/onc.2014.27] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 12/02/2013] [Accepted: 12/18/2013] [Indexed: 12/26/2022]
Abstract
The oncogene Mdmx is overexpressed in many human malignancies, and together with Mdm2, negatively regulates the p53 tumor suppressor. However, a p53-independent function of Mdmx that impacts genome stability has been described, but this function is not well understood. In the present study, we determined that of the 13 different cancer types evaluated, 6-90% of those that had elevated levels of Mdmx had concurrent inactivation (mutated or deleted) of p53. We show elevated levels of Mdmx-inhibited double-strand DNA break repair and induced chromosome and chromatid breaks independent of p53, leading to genome instability. Mdmx impaired early DNA damage-response signaling, such as phosphorylation of the serine/threonine-glutamine motif, mediated by the ATM kinase. Moreover, we identified Mdmx associated with Nbs1 of the Mre11-Rad50-Nbs1 (MRN) DNA repair complex, and this association increased upon DNA damage and was detected at chromatin. Elevated Mdmx levels also increased cellular transformation in a p53-independent manner. Unexpectedly, all Mdmx-mediated phenotypes also occurred in cells lacking Mdm2 and were independent of the Mdm2-binding domain (RING) of Mdmx. Therefore, Mdmx-mediated inhibition of the DNA damage response resulted in delayed DNA repair and increased genome instability and transformation independent of p53 and Mdm2. Our results reveal a novel p53- and Mdm2-independent oncogenic function of Mdmx that provides new insight into the many cancers that overexpress Mdmx.
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Affiliation(s)
- Alexia M. Carrillo
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - Alyssa Bouska
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE
| | - Maria Pia Arrate
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - Christine M. Eischen
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
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12
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Eischen CM, Lozano G. The Mdm network and its regulation of p53 activities: a rheostat of cancer risk. Hum Mutat 2014; 35:728-37. [PMID: 24488925 DOI: 10.1002/humu.22524] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 01/31/2014] [Indexed: 11/07/2022]
Abstract
The potent transcriptional activity of p53 (Trp53, TP53) must be kept in check for normal cell growth and survival. Tumors, which drastically deviate from these parameters, have evolved multiple mechanisms to inactivate TP53, the most prevalent of which is the emergence of TP53 missense mutations, some of which have gain-of-function activities. Another important mechanism by which tumors bypass TP53 functions is via increased levels of two TP53 inhibitors, MDM2, and MDM4. Studies in humans and in mice reveal the complexity of TP53 regulation and the exquisite sensitivity of this pathway to small changes in regulation. Here, we summarize the factors that impinge on TP53 activity and thus cell death/arrest or tumor development.
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Affiliation(s)
- Christine M Eischen
- Vanderbilt University Medical Center, Department of Pathology, Microbiology and Immunology, Nashville, Tennessee
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13
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Abstract
Discovered in 1987 and 1997 respectively, Mdm2 and MdmX represent two critical cellular regulators of the p53 tumor suppressor. This chapter reviews each from initial discovery to our current understanding of their deregulation in human cancer with a focus on how each regulator impacts p53 function. While p53 independent activities of Mdm2 and MdmX are noted the reader is directed to other reviews on this topic. The chapter concludes with an examination of the various mechanisms of Mdm-deregulation and an assessment of the current therapeutic approaches to target Mdm2 and MdmX overexpression.
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Zhang X, Hagen J, Muniz VP, Smith T, Coombs GS, Eischen CM, Mackie DI, Roman DL, Van Rheeden R, Darbro B, Tompkins VS, Quelle DE. RABL6A, a novel RAB-like protein, controls centrosome amplification and chromosome instability in primary fibroblasts. PLoS One 2013; 8:e80228. [PMID: 24282525 PMCID: PMC3839920 DOI: 10.1371/journal.pone.0080228] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 10/01/2013] [Indexed: 12/18/2022] Open
Abstract
RABL6A (RAB-like 6 isoform A) is a novel protein that was originally identified based on its association with the Alternative Reading Frame (ARF) tumor suppressor. ARF acts through multiple p53-dependent and p53-independent pathways to prevent cancer. How RABL6A functions, to what extent it depends on ARF and p53 activity, and its importance in normal cell biology are entirely unknown. We examined the biological consequences of RABL6A silencing in primary mouse embryo fibroblasts (MEFs) that express or lack ARF, p53 or both proteins. We found that RABL6A depletion caused centrosome amplification, aneuploidy and multinucleation in MEFs regardless of ARF and p53 status. The centrosome amplification in RABL6A depleted p53−/− MEFs resulted from centrosome reduplication via Cdk2-mediated hyperphosphorylation of nucleophosmin (NPM) at threonine-199. Thus, RABL6A prevents centrosome amplification through an ARF/p53-independent mechanism that restricts NPM-T199 phosphorylation. These findings demonstrate an essential role for RABL6A in centrosome regulation and maintenance of chromosome stability in non-transformed cells, key processes that ensure genomic integrity and prevent tumorigenesis.
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Affiliation(s)
- Xuefeng Zhang
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
| | - Jussara Hagen
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
| | - Viviane P. Muniz
- The Molecular and Cellular Biology Graduate Program, University of Iowa, Iowa City, Iowa, United States of America
| | - Tarik Smith
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
| | - Gary S. Coombs
- Department of Biology, Waldorf College, Forest City, Iowa, United States of America
| | - Christine M. Eischen
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Duncan I. Mackie
- Division of Medicinal and Natural Products Chemistry, University of Iowa, Iowa City, Iowa, United States of America
| | - David L. Roman
- Division of Medicinal and Natural Products Chemistry, University of Iowa, Iowa City, Iowa, United States of America
| | - Richard Van Rheeden
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Benjamin Darbro
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Van S. Tompkins
- Department of Pathology, University of Iowa, Iowa City, Iowa, United States of America
| | - Dawn E. Quelle
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
- The Molecular and Cellular Biology Graduate Program, University of Iowa, Iowa City, Iowa, United States of America
- Department of Pathology, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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