1
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Pourebrahim R, Montoya RH, Akiyama H, Ostermann L, Khazaei S, Muftuoglu M, Baran N, Zhao R, Lesluyes T, Liu B, Khoury JD, Gagea M, Van Loo P, Andreeff M. Age-specific induction of mutant p53 drives clonal hematopoiesis and acute myeloid leukemia in adult mice. Cell Rep Med 2024; 5:101558. [PMID: 38733986 PMCID: PMC11148800 DOI: 10.1016/j.xcrm.2024.101558] [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: 08/16/2023] [Revised: 02/18/2024] [Accepted: 04/17/2024] [Indexed: 05/13/2024]
Abstract
The investigation of the mechanisms behind p53 mutations in acute myeloid leukemia (AML) has been limited by the lack of suitable mouse models, which historically have resulted in lymphoma rather than leukemia. This study introduces two new AML mouse models. One model induces mutant p53 and Mdm2 haploinsufficiency in early development, showing the role of Mdm2 in myeloid-biased hematopoiesis and AML predisposition, independent of p53. The second model mimics clonal hematopoiesis by inducing mutant p53 in adult hematopoietic stem cells, demonstrating that the timing of p53 mutation determines AML vs. lymphoma development. In this context, age-related changes in hematopoietic stem cells (HSCs) collaborate with mutant p53 to predispose toward myeloid transformation rather than lymphoma development. Our study unveils new insights into the cooperative impact of HSC age, Trp53 mutations, and Mdm2 haploinsufficiency on clonal hematopoiesis and the development of myeloid malignancies.
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Affiliation(s)
- Rasoul Pourebrahim
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Rafael Heinz Montoya
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Hiroki Akiyama
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Lauren Ostermann
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Shayuan Khazaei
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Muharrem Muftuoglu
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Natalia Baran
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Ran Zhao
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Tom Lesluyes
- Cancer Genomics Laboratory, The Francis Crick Institute, London, UK
| | - Bin Liu
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Joseph D Khoury
- Department of Pathology, Microbiology, and Immunology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Mihai Gagea
- Department of Veterinary Medicine and Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Peter Van Loo
- Cancer Genomics Laboratory, The Francis Crick Institute, London, UK; Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA; Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Michael Andreeff
- Section of Molecular Hematology and Therapy, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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Lien S, Whitbread TP, Shastri SO, Contreras JA, Zhao R, Zhu Y. Cancer-associated MDM2 W329G mutant attenuates ribosomal stress-mediated p53 responses to promote cell survival and glycolysis. Am J Cancer Res 2024; 14:2141-2156. [PMID: 38859834 PMCID: PMC11162693 DOI: 10.62347/qifc4021] [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: 01/03/2024] [Accepted: 02/04/2024] [Indexed: 06/12/2024] Open
Abstract
Although amplification/overexpression is the predominant mechanism for the oncogenic properties of MDM2, an increasing number of MDM2 somatic missense mutations were identified in cancer patients with the recent advances in sequencing technology. Here, we characterized an MDM2 cancer-associated mutant variant W329G identified from a patient sample that contains a wild-type p53 gene. Trp329 is one of residues that were reported to be critical to MDM2's binding to ribosomal protein L11 (RPL11). We found that the MDM2 W329G mutant was resistant to the inhibitory effect of RPL11 on MDM2-mediated p53 ubiquitination and degradation, in line with its defect on RPL11 binding. Using isogenic U2OS cells with or without endogenous MDM2 W329G mutation, we demonstrated that the expression of classic p53 targets induced by ribosomal stress signals was reduced in mutant cells. RNA-seq analysis revealed that upon 5-FU treatment, the p53 response was significantly impaired. Also, the 5-FU-mediated repression of genes in cell cycle progression and DNA replication was diminished in W329G mutant-containing cells. Physiologically, U2OS W329G cells were more resistant to cell growth inhibition induced by ribosomal stress and exhibited higher glycolytic rates upon 5-FU treatment. Together, our data indicated that cancer-associated MDM2 W329G mutant attenuates ribosomal stress-mediated p53 responses to promote cell survival and glycolysis.
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Affiliation(s)
- Sally Lien
- Department of Biological Sciences, St. John’s UniversityQueens, NY 11439, USA
| | - Thomas P Whitbread
- Department of Biological Sciences, St. John’s UniversityQueens, NY 11439, USA
| | - Shiva O Shastri
- Department of Biological Sciences, St. John’s UniversityQueens, NY 11439, USA
| | - Jamie A Contreras
- Department of Biological Sciences, St. John’s UniversityQueens, NY 11439, USA
| | - Ruiying Zhao
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at HoustonHouston, TX 77030, USA
| | - Yan Zhu
- Department of Biological Sciences, St. John’s UniversityQueens, NY 11439, USA
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3
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Xu Y, Zheng C, Ashaq MS, Zhou Q, Li Y, Lu C, Zhao B. Regulatory role of E3 ubiquitin ligases in normal B lymphopoiesis and B-cell malignancies. Life Sci 2023; 331:122043. [PMID: 37633415 DOI: 10.1016/j.lfs.2023.122043] [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: 07/03/2023] [Revised: 08/14/2023] [Accepted: 08/23/2023] [Indexed: 08/28/2023]
Abstract
E3 ubiquitin ligases play an essential role in protein ubiquitination, which is involved in the regulation of protein degradation, protein-protein interactions and signal transduction. Increasing evidences have shed light on the emerging roles of E3 ubiquitin ligases in B-cell development and related malignances. This comprehensive review summarizes the current understanding of E3 ubiquitin ligases in B-cell development and their contribution to B-cell malignances, which could help explore the molecular mechanism of normal B-cell development and provide potential therapeutic targets of the related diseases.
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Affiliation(s)
- Yan Xu
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Chengzu Zheng
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Muhammad Sameer Ashaq
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Qian Zhou
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Yuan Li
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Chunhua Lu
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Baobing Zhao
- Key Lab of Chemical Biology (MOE), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; NMPA Key Laboratory for Technology Research and Evaluation of Drug Products, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China; Department of Pharmacology, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China.
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4
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Winkler R, Piskor EM, Kosan C. Lessons from Using Genetically Engineered Mouse Models of MYC-Induced Lymphoma. Cells 2022; 12:cells12010037. [PMID: 36611833 PMCID: PMC9818924 DOI: 10.3390/cells12010037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/06/2022] [Accepted: 12/15/2022] [Indexed: 12/25/2022] Open
Abstract
Oncogenic overexpression of MYC leads to the fatal deregulation of signaling pathways, cellular metabolism, and cell growth. MYC rearrangements are found frequently among non-Hodgkin B-cell lymphomas enforcing MYC overexpression. Genetically engineered mouse models (GEMMs) were developed to understand MYC-induced B-cell lymphomagenesis. Here, we highlight the advantages of using Eµ-Myc transgenic mice. We thoroughly compiled the available literature to discuss common challenges when using such mouse models. Furthermore, we give an overview of pathways affected by MYC based on knowledge gained from the use of GEMMs. We identified top regulators of MYC-induced lymphomagenesis, including some candidates that are not pharmacologically targeted yet.
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Grieb BC, Eischen CM. MTBP and MYC: A Dynamic Duo in Proliferation, Cancer, and Aging. BIOLOGY 2022; 11:biology11060881. [PMID: 35741402 PMCID: PMC9219613 DOI: 10.3390/biology11060881] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 05/29/2022] [Accepted: 06/02/2022] [Indexed: 12/21/2022]
Abstract
The oncogenic transcription factor c-MYC (MYC) is highly conserved across species and is frequently overexpressed or dysregulated in human cancers. MYC regulates a wide range of critical cellular and oncogenic activities including proliferation, metabolism, metastasis, apoptosis, and differentiation by transcriptionally activating or repressing the expression of a large number of genes. This activity of MYC is not carried out in isolation, instead relying on its association with a myriad of protein cofactors. We determined that MDM Two Binding Protein (MTBP) indirectly binds MYC and is a novel MYC transcriptional cofactor. MTBP promotes MYC-mediated transcriptional activity, proliferation, and cellular transformation by binding in a protein complex with MYC at MYC-bound promoters. This discovery provided critical context for data linking MTBP to aging as well as a rapidly expanding body of evidence demonstrating MTBP is overexpressed in many human malignancies, is often linked to poor patient outcomes, and is necessary for cancer cell survival. As such, MTBP represents a novel and potentially broad reaching oncologic drug target, particularly when MYC is dysregulated. Here we have reviewed the discovery of MTBP and the initial controversy with its function as well as its associations with proliferation, MYC, DNA replication, aging, and human cancer.
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Affiliation(s)
- Brian C. Grieb
- Vanderbilt-Ingram Cancer Center, Division of Hematology/Oncology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA;
- Department of Cell & Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Christine M. Eischen
- Department of Cancer Biology and the Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
- Correspondence:
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6
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Ilic VK, Egorova O, Tsang E, Gatto M, Wen Y, Zhao Y, Sheng Y. Hinokiflavone Inhibits MDM2 Activity by Targeting the MDM2-MDMX RING Domain. Biomolecules 2022; 12:biom12050643. [PMID: 35625571 PMCID: PMC9138535 DOI: 10.3390/biom12050643] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/17/2022] [Accepted: 04/22/2022] [Indexed: 02/04/2023] Open
Abstract
The proto-oncogene MDM2 is frequently amplified in many human cancers and its overexpression is clinically associated with a poor prognosis. The oncogenic activity of MDM2 is demonstrated by its negative regulation of tumor suppressor p53 and the substrate proteins involved in DNA repair, cell cycle control, and apoptosis pathways. Thus, inhibition of MDM2 activity has been pursued as an attractive direction for the development of anti-cancer therapeutics. Virtual screening was performed using the crystal structure of the MDM2-MDMX RING domain dimer against a natural product library and identified a biflavonoid Hinokiflavone as a promising candidate compound targeting MDM2. Hinokiflavone was shown to bind the MDM2-MDMX RING domain and inhibit MDM2-mediated ubiquitination in vitro. Hinokiflavone treatment resulted in the downregulation of MDM2 and MDMX and induction of apoptosis in various cancer cell lines. Hinokiflavone demonstrated p53-dependent and -independent tumor-suppressive activity. This report provides biochemical and cellular evidence demonstrating the anti-cancer effects of Hinokiflavone through targeting the MDM2-MDMX RING domain.
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Affiliation(s)
- Viktoria K. Ilic
- Department of Biology, York University, Room 327B Life Science Building, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; (V.K.I.); (O.E.); (E.T.); (M.G.); (Y.W.)
| | - Olga Egorova
- Department of Biology, York University, Room 327B Life Science Building, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; (V.K.I.); (O.E.); (E.T.); (M.G.); (Y.W.)
| | - Ernest Tsang
- Department of Biology, York University, Room 327B Life Science Building, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; (V.K.I.); (O.E.); (E.T.); (M.G.); (Y.W.)
| | - Milena Gatto
- Department of Biology, York University, Room 327B Life Science Building, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; (V.K.I.); (O.E.); (E.T.); (M.G.); (Y.W.)
| | - Yi Wen
- Department of Biology, York University, Room 327B Life Science Building, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; (V.K.I.); (O.E.); (E.T.); (M.G.); (Y.W.)
| | - Yong Zhao
- Beijing Computing Center, Beijing Academy of Science and Technology, Beijing, 100094, China;
| | - Yi Sheng
- Department of Biology, York University, Room 327B Life Science Building, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; (V.K.I.); (O.E.); (E.T.); (M.G.); (Y.W.)
- Correspondence: ; Tel.: 1-416-7362100 (ext. 33521)
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7
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Vecchio E, Fiume G, Correnti S, Romano S, Iaccino E, Mimmi S, Maisano D, Nisticò N, Quinto I. Insights about MYC and Apoptosis in B-Lymphomagenesis: An Update from Murine Models. Int J Mol Sci 2020; 21:E4265. [PMID: 32549409 PMCID: PMC7352788 DOI: 10.3390/ijms21124265] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 01/18/2023] Open
Abstract
The balance between cell survival and cell death represents an essential part of human tissue homeostasis, while altered apoptosis contributes to several pathologies and can affect the treatment efficacy. Impaired apoptosis is one of the main cancer hallmarks and some types of lymphomas harbor mutations that directly affect key regulators of cell death (such as BCL-2 family members). The development of novel techniques in the field of immunology and new animal models has greatly accelerated our understanding of oncogenic mechanisms in MYC-associated lymphomas. Mouse models are a powerful tool to reveal multiple genes implicated in the genesis of lymphoma and are extensively used to clarify the molecular mechanism of lymphoma, validating the gene function. Key features of MYC-induced apoptosis will be discussed here along with more recent studies on MYC direct and indirect interactors, including their cooperative action in lymphomagenesis. We review our current knowledge about the role of MYC-induced apoptosis in B-cell malignancies, discussing the transcriptional regulation network of MYC and regulatory feedback action of miRs during MYC-driven lymphomagenesis. More importantly, the finding of new modulators of apoptosis now enabling researchers to translate the discoveries that have been made in the laboratory into clinical practice to positively impact human health.
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Affiliation(s)
- Eleonora Vecchio
- Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, 88100 Catanzaro, Italy; (G.F.); (S.C.); (S.R.); (E.I.); (S.M.); (D.M.); (N.N.)
| | | | | | | | | | | | | | | | - Ileana Quinto
- Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, 88100 Catanzaro, Italy; (G.F.); (S.C.); (S.R.); (E.I.); (S.M.); (D.M.); (N.N.)
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8
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Hashiguchi T, Bruss N, Best S, Lam V, Danilova O, Paiva CJ, Wolf J, Gilbert EW, Okada CY, Kaur P, Drew L, Cidado J, Hurlin P, Danilov AV. Cyclin-Dependent Kinase-9 Is a Therapeutic Target in MYC-Expressing Diffuse Large B-Cell Lymphoma. Mol Cancer Ther 2019; 18:1520-1532. [DOI: 10.1158/1535-7163.mct-18-1023] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 12/10/2018] [Accepted: 06/20/2019] [Indexed: 11/16/2022]
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9
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Bowen ME, Attardi LD. The role of p53 in developmental syndromes. J Mol Cell Biol 2019; 11:200-211. [PMID: 30624728 PMCID: PMC6478128 DOI: 10.1093/jmcb/mjy087] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 11/22/2018] [Accepted: 01/06/2019] [Indexed: 12/17/2022] Open
Abstract
While it is well appreciated that loss of the p53 tumor suppressor protein promotes cancer, growing evidence indicates that increased p53 activity underlies the developmental defects in a wide range of genetic syndromes. The inherited or de novo mutations that cause these syndromes affect diverse cellular processes, such as ribosome biogenesis, DNA repair, and centriole duplication, and analysis of human patient samples and mouse models demonstrates that disrupting these cellular processes can activate the p53 pathway. Importantly, many of the developmental defects in mouse models of these syndromes can be rescued by loss of p53, indicating that inappropriate p53 activation directly contributes to their pathogenesis. A role for p53 in driving developmental defects is further supported by the observation that mouse strains with broad p53 hyperactivation, due to mutations affecting p53 pathway components, display a host of tissue-specific developmental defects, including hematopoietic, neuronal, craniofacial, cardiovascular, and pigmentation defects. Furthermore, germline activating mutations in TP53 were recently identified in two human patients exhibiting bone marrow failure and other developmental defects. Studies in mice suggest that p53 drives developmental defects by inducing apoptosis, restraining proliferation, or modulating other developmental programs in a cell type-dependent manner. Here, we review the growing body of evidence from mouse models that implicates p53 as a driver of tissue-specific developmental defects in diverse genetic syndromes.
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Affiliation(s)
- Margot E Bowen
- Division of Radiation and Cancer Biology in the Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
| | - Laura D Attardi
- Division of Radiation and Cancer Biology in the Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
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10
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Puccetti MV, Adams CM, Kushinsky S, Eischen CM. Smarcal1 and Zranb3 Protect Replication Forks from Myc-Induced DNA Replication Stress. Cancer Res 2019; 79:1612-1623. [PMID: 30610086 DOI: 10.1158/0008-5472.can-18-2705] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 11/08/2018] [Accepted: 12/27/2018] [Indexed: 02/01/2023]
Abstract
The cellular DNA replication stress response functions to stabilize DNA replication forks and inhibits genome instability and tumorigenesis induced by oncogenes. However, the specific proteins required for resolving oncogenic stress remain poorly understood. Here we report that Smarcal1 and Zranb3, closely related replication fork-remodeling proteins, have nonredundant functions in resolving Myc-induced DNA replication stress. In Myc-overexpressing primary cells, significant differences in replication fork stalling, collapse, and DNA damage were detected between cells deficient in Smarcal1 or Zranb3, leading to changes in proliferation and apoptosis. These differences were also reflected in Myc-induced lymphoma development; haploinsufficiency of Smarcal1 resulted in accelerated lymphomagenesis, whereas haploinsufficiency of Zranb3 inhibited lymphoma development. Complete loss of either protein resulted in disparate survival outcomes. Our results reveal that endogenous replication stress from Myc in primary cells requires both alleles of Smarcal1 and Zranb3 and demonstrate the requirement of both proteins to stabilize replication forks upon Myc dysregulation in a nonredundant manner. SIGNIFICANCE: Smarcal1 and Zranb3 are essential, but nonredundant, for responding to DNA replication stress and stabilizing replication forks following Myc overexpression.See related commentary by Sotiriou and Halazonetis, p. 1297.
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Affiliation(s)
- Matthew V Puccetti
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania.,Medical Scientist Training Program, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Clare M Adams
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Saul Kushinsky
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Christine M Eischen
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania.
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11
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MDMX acidic domain inhibits p53 DNA binding in vivo and regulates tumorigenesis. Proc Natl Acad Sci U S A 2018; 115:E3368-E3377. [PMID: 29581299 DOI: 10.1073/pnas.1719090115] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The MDM2 homolog MDMX oncoprotein is indispensable for inhibition of p53 during normal embryonic development and malignant transformation, yet how MDMX harnesses p53 functions is unclear. In addition to a canonical N-terminal p53-binding domain, recent work suggests the central acidic domain of MDMX regulates p53 interaction through intramolecular mimicry and engages in second-site interaction with the p53 core domain in vitro. To test the physiological relevance of these interactions, we generated an MDMX knockin mouse having substitutions in a conserved WW motif necessary for these functions (W201S/W202G). Notably, MDMXSG cells have normal p53 level but increased p53 DNA binding and target gene expression, and rapidly senesce. In vivo, MDMXSG inhibits early-phase disease in Eµ-Myc transgenic mice but accelerates the onset of lethal lymphoma and shortens overall survival. Therefore, MDMX is an important regulator of p53 DNA binding, which complements the role of MDM2 in regulating p53 level. Furthermore, the results suggest that the WW motif has dual functions that regulate p53 and inhibit Myc-driven lymphomas independent of p53.
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12
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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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13
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Adams CM, Kim AS, Mitra R, Choi JK, Gong JZ, Eischen CM. BCL-W has a fundamental role in B cell survival and lymphomagenesis. J Clin Invest 2017; 127:635-650. [PMID: 28094768 DOI: 10.1172/jci89486] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/22/2016] [Indexed: 12/29/2022] Open
Abstract
Compromised apoptotic signaling is a prerequisite for tumorigenesis. The design of effective therapies for cancer treatment depends on a comprehensive understanding of the mechanisms that govern cell survival. The antiapoptotic proteins of the BCL-2 family are key regulators of cell survival and are frequently overexpressed in malignancies, leading to increased cancer cell survival. Unlike BCL-2 and BCL-XL, the closest antiapoptotic relative BCL-W is required for spermatogenesis, but was considered dispensable for all other cell types. Here, however, we have exposed a critical role for BCL-W in B cell survival and lymphomagenesis. Loss of Bcl-w conferred sensitivity to growth factor deprivation-induced B cell apoptosis. Moreover, Bcl-w loss profoundly delayed MYC-mediated B cell lymphoma development due to increased MYC-induced B cell apoptosis. We also determined that MYC regulates BCL-W expression through its transcriptional regulation of specific miR. BCL-W expression was highly selected for in patient samples of Burkitt lymphoma (BL), with 88.5% expressing BCL-W. BCL-W knockdown in BL cell lines induced apoptosis, and its overexpression conferred resistance to BCL-2 family-targeting BH3 mimetics. Additionally, BCL-W was overexpressed in diffuse large B cell lymphoma and correlated with decreased patient survival. Collectively, our results reveal that BCL-W profoundly contributes to B cell lymphoma, and its expression could serve as a biomarker for diagnosis and aid in the development of better targeted therapies.
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MESH Headings
- Animals
- Apoptosis
- Apoptosis Regulatory Proteins
- B-Lymphocytes/metabolism
- B-Lymphocytes/pathology
- Burkitt Lymphoma/diagnosis
- Burkitt Lymphoma/genetics
- Burkitt Lymphoma/metabolism
- Burkitt Lymphoma/pathology
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Gene Expression Regulation, Neoplastic
- Humans
- Lymphoma, Large B-Cell, Diffuse/diagnosis
- Lymphoma, Large B-Cell, Diffuse/genetics
- Lymphoma, Large B-Cell, Diffuse/metabolism
- Mice
- Mice, Knockout
- Proteins/genetics
- Proteins/metabolism
- Proto-Oncogene Proteins c-myc/genetics
- Proto-Oncogene Proteins c-myc/metabolism
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14
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Abstract
This perspective will focus on the physiological impact of wild-type and mutant p53 activities. In particular, the tissue-specific nature of activation of p53 targets and their subsequent effects on cell behavior will be discussed. Because mutations in p53 are common in human cancers, the regulation and physiological consequences of mutant p53 proteins will also be discussed.
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15
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Carr MI, Jones SN. Regulation of the Mdm2-p53 signaling axis in the DNA damage response and tumorigenesis. Transl Cancer Res 2016; 5:707-724. [PMID: 28690977 PMCID: PMC5501481 DOI: 10.21037/tcr.2016.11.75] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The p53 tumor suppressor acts as a guardian of the genome in mammalian cells undergoing DNA double strand breaks induced by a various forms of cell stress, including inappropriate growth signals or ionizing radiation. Following damage, p53 protein levels become greatly elevated in cells and p53 functions primarily as a transcription factor to regulate the expression a wide variety of genes that coordinate this DNA damage response. In cells undergoing high amounts of DNA damage, p53 can promote apoptosis, whereas in cells undergoing less damage, p53 promotes senescence or transient cell growth arrest and the expression of genes involved in DNA repair, depending upon the cell type and level of damage. Failure of the damaged cell to undergo growth arrest or apoptosis, or to respond to the DNA damage by other p53-coordinated mechanisms, can lead to inappropriate cell growth and tumorigenesis. In cells that have successfully responded to genetic damage, the amount of p53 present in the cell must return to basal levels in order for the cell to resume normal growth and function. Although regulation of p53 levels and function is coordinated by many proteins, it is now widely accepted that the master regulator of p53 is Mdm2. In this review, we discuss the role(s) of p53 in the DNA damage response and in tumor suppression, and how post-translational modification of Mdm2 regulates the Mdm2-p53 signaling axis to govern p53 activities in the cell.
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Affiliation(s)
- Michael I Carr
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Stephen N Jones
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
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16
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Oliner JD, Saiki AY, Caenepeel S. The Role of MDM2 Amplification and Overexpression in Tumorigenesis. Cold Spring Harb Perspect Med 2016; 6:cshperspect.a026336. [PMID: 27194168 DOI: 10.1101/cshperspect.a026336] [Citation(s) in RCA: 149] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mouse double minute 2 (MDM2) is a critical negative regulator of the tumor suppressor p53, playing a key role in controlling its transcriptional activity, protein stability, and nuclear localization. MDM2 expression is up-regulated in numerous cancers, resulting in a loss of p53-dependent activities, such as apoptosis and cell-cycle arrest. Genetic amplification and inheritance of MDM2 promoter single-nucleotide polymorphisms (SNPs) are the two best-studied mechanisms for up-regulating MDM2 activity. This article provides an overview of these events in human cancer, highlighting the frequent occurrence of MDM2 amplification in sarcoma and the role of SNP309 and SNP285 in regulating MDM2 expression and cancer risk. The availability of large-scale genomic profiling datasets, like those from The Cancer Genome Atlas Research Network, have provided the opportunity to evaluate the consequences of MDM2 amplification and SNP inheritance across high-quality tumor samples from diverse cancer indications.
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Affiliation(s)
| | - Anne Y Saiki
- Oncology Research, Amgen, Thousand Oaks, California 91320
| | - Sean Caenepeel
- Oncology Research, Amgen, Thousand Oaks, California 91320
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17
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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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18
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Tonsing-Carter E, Bailey BJ, Saadatzadeh MR, Ding J, Wang H, Sinn AL, Peterman KM, Spragins TK, Silver JM, Sprouse AA, Georgiadis TM, Gunter TZ, Long EC, Minto RE, Marchal CC, Batuello CN, Safa AR, Hanenberg H, Territo PR, Sandusky GE, Mayo LD, Eischen CM, Shannon HE, Pollok KE. Potentiation of Carboplatin-Mediated DNA Damage by the Mdm2 Modulator Nutlin-3a in a Humanized Orthotopic Breast-to-Lung Metastatic Model. Mol Cancer Ther 2015; 14:2850-63. [PMID: 26494859 DOI: 10.1158/1535-7163.mct-15-0237] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 09/30/2015] [Indexed: 12/31/2022]
Abstract
Triple-negative breast cancers (TNBC) are typically resistant to treatment, and strategies that build upon frontline therapy are needed. Targeting the murine double minute 2 (Mdm2) protein is an attractive approach, as Mdm2 levels are elevated in many therapy-refractive breast cancers. The Mdm2 protein-protein interaction inhibitor Nutlin-3a blocks the binding of Mdm2 to key signaling molecules such as p53 and p73α and can result in activation of cell death signaling pathways. In the present study, the therapeutic potential of carboplatin and Nutlin-3a to treat TNBC was investigated, as carboplatin is under evaluation in clinical trials for TNBC. In mutant p53 TMD231 TNBC cells, carboplatin and Nutlin-3a led to increased Mdm2 and was strongly synergistic in promoting cell death in vitro. Furthermore, sensitivity of TNBC cells to combination treatment was dependent on p73α. Following combination treatment, γH2AX increased and Mdm2 localized to a larger degree to chromatin compared with single-agent treatment, consistent with previous observations that Mdm2 binds to the Mre11/Rad50/Nbs1 complex associated with DNA and inhibits the DNA damage response. In vivo efficacy studies were conducted in the TMD231 orthotopic mammary fat pad model in NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) mice. Using an intermittent dosing schedule of combined carboplatin and Nutlin-3a, there was a significant reduction in primary tumor growth and lung metastases compared with vehicle and single-agent treatments. In addition, there was minimal toxicity to the bone marrow and normal tissues. These studies demonstrate that Mdm2 holds promise as a therapeutic target in combination with conventional therapy and may lead to new clinical therapies for TNBC.
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Affiliation(s)
- Eva Tonsing-Carter
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Barbara J Bailey
- In Vivo Therapeutics Core, Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana. Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - M Reza Saadatzadeh
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana. Goodman Campbell Brain and Spine, Department of Neurosurgery, Indiana University School of Medicine, Indianapolis, Indiana
| | - Jixin Ding
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana. Goodman Campbell Brain and Spine, Department of Neurosurgery, Indiana University School of Medicine, Indianapolis, Indiana
| | - Haiyan Wang
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - Anthony L Sinn
- In Vivo Therapeutics Core, Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - Kacie M Peterman
- In Vivo Therapeutics Core, Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - Tiaishia K Spragins
- In Vivo Therapeutics Core, Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - Jayne M Silver
- In Vivo Therapeutics Core, Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - Alyssa A Sprouse
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - Taxiarchis M Georgiadis
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana
| | - T Zachary Gunter
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana
| | - Eric C Long
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana
| | - Robert E Minto
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana
| | - Christophe C Marchal
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - Christopher N Batuello
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - Ahmad R Safa
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Helmut Hanenberg
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana. Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana. Department of Otorhinolaryngology and Head/Neck Surgery, Heinrich Heine University, Düsseldorf, Germany
| | - Paul R Territo
- Indiana Institute for Biomedical Sciences Imaging, Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - George E Sandusky
- Department of Pathology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Lindsey D Mayo
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana. Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Christine M Eischen
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Harlan E Shannon
- Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - Karen E Pollok
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana. In Vivo Therapeutics Core, Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana. Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana.
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19
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Xie JL, Yang JL, Liu DS, Xie YG, Ji P. Impact of MDM2 single nucleotide polymorphism on oral squamous cell carcinoma risk. Cell Biochem Biophys 2015; 71:993-8. [PMID: 25323564 DOI: 10.1007/s12013-014-0298-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Mouse Double Minute 2 (MDM2) has emerged as a pivotal cellular antagonist of p53 by destructing the suppressive function of p53 against tumorigenesis. The MDM2 309 T > G polymorphism has been studied for its association with oral squamous cell carcinoma (OSCC) susceptibility, but the evidence was confusing and inconclusive. Here, we performed a meta-analysis to estimate the effects of the 309 T > G polymorphism on the development of OSCC. The relevant studies were searched on both PubMed and Embase. We estimated the risk of OSCC using odds ratio (OR) and 95 % confidence interval (CI). In addition, between-study heterogeneity was measured by the χ (2)-based statistic test; sensitivity analysis, and the funnel plots and Egger's test were also performed in this meta-analysis. Based on five case-control studies with a total of 1,369 OSCC cases and 2,167 control subjects, the meta-analysis result showed neither increased nor decreased risk of OSCC associated with any genetic model of the 309 T > G polymorphism. Similar results were observed in the subgroup of Asians. No significant heterogeneity and publication bias were detected in the meta-analysis. The evidence provided in our study indicated that the 309 T > G polymorphism might have no significant contribution to susceptibility toward OSCC.
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Affiliation(s)
- Jian-Li Xie
- School of Stomatology, Shandong University, Wenhuaxi Road, Jinan, 250012, Shandong, China
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20
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Urso L, Calabrese F, Favaretto A, Conte P, Pasello G. Critical review about MDM2 in cancer: Possible role in malignant mesothelioma and implications for treatment. Crit Rev Oncol Hematol 2015; 97:220-30. [PMID: 26358421 DOI: 10.1016/j.critrevonc.2015.08.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 07/02/2015] [Accepted: 08/18/2015] [Indexed: 02/07/2023] Open
Abstract
The tumor suppressor p53 regulates genes involved in DNA repair, metabolism, cell cycle arrest, apoptosis and senescence. p53 is mutated in about 50% of the human cancers, while in tumors with wild-type p53 gene, the protein function may be lost because of overexpression of Murine Double Minute 2 (MDM2). MDM2 targets p53 for ubiquitylation and proteasomal degradation. p53 reactivation through MDM2 inhibitors seems to be a promising strategy to sensitize p53 wild-type cancer cells to apoptosis. Moreover, additional p53-independent molecular functions of MDM2, such as neoangiogenesis promotion, have been suggested. Thus, MDM2 might be a target for anticancer treatment because of its antiapoptotic and proangiogenetic role. Malignant pleural mesothelioma (MPM) is an aggressive asbestos-related tumor where wild-type p53 might be present. The present review gives a complete landscape about the role of MDM2 in cancer pathogenesis, prognosis and treatment, with particular focus on Malignant Pleural Mesothelioma.
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Affiliation(s)
- Loredana Urso
- Department of Surgery, Oncology and Gastroenterology, University of Padova, Italy
| | - Fiorella Calabrese
- Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Italy
| | - Adolfo Favaretto
- Medical Oncology 2, Istituto Oncologico Veneto IRCCS, Padova, Italy
| | - PierFranco Conte
- Department of Surgery, Oncology and Gastroenterology, University of Padova, Italy; Medical Oncology 2, Istituto Oncologico Veneto IRCCS, Padova, Italy
| | - Giulia Pasello
- Medical Oncology 2, Istituto Oncologico Veneto IRCCS, Padova, Italy.
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21
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Whole-genome sequencing reveals oncogenic mutations in mycosis fungoides. Blood 2015; 126:508-19. [PMID: 26082451 DOI: 10.1182/blood-2014-11-611194] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 06/03/2015] [Indexed: 12/30/2022] Open
Abstract
The pathogenesis of mycosis fungoides (MF), the most common cutaneous T-cell lymphoma (CTCL), is unknown. Although genetic alterations have been identified, none are considered consistently causative in MF. To identify potential drivers of MF, we performed whole-genome sequencing of MF tumors and matched normal skin. Targeted ultra-deep sequencing of MF samples and exome sequencing of CTCL cell lines were also performed. Multiple mutations were identified that affected the same pathways, including epigenetic, cell-fate regulation, and cytokine signaling, in MF tumors and CTCL cell lines. Specifically, interleukin-2 signaling pathway mutations, including activating Janus kinase 3 (JAK3) mutations, were detected. Treatment with a JAK3 inhibitor significantly reduced CTCL cell survival. Additionally, the mutation data identified 2 other potential contributing factors to MF, ultraviolet light, and a polymorphism in the tumor suppressor p53 (TP53). Therefore, genetic alterations in specific pathways in MF were identified that may be viable, effective new targets for treatment.
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22
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Reed SM, Hagen J, Muniz VP, Rosean TR, Borcherding N, Sciegienka S, Goeken JA, Naumann PW, Zhang W, Tompkins VS, Janz S, Meyerholz DK, Quelle DE. NIAM-deficient mice are predisposed to the development of proliferative lesions including B-cell lymphomas. PLoS One 2014; 9:e112126. [PMID: 25393878 PMCID: PMC4231569 DOI: 10.1371/journal.pone.0112126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 10/12/2014] [Indexed: 01/10/2023] Open
Abstract
Nuclear Interactor of ARF and Mdm2 (NIAM, gene designation Tbrg1) is a largely unstudied inhibitor of cell proliferation that helps maintain chromosomal stability. It is a novel activator of the ARF-Mdm2-Tip60-p53 tumor suppressor pathway as well as other undefined pathways important for genome maintenance. To examine its predicted role as a tumor suppressor, we generated NIAM mutant (NIAMm/m) mice homozygous for a β-galactosidase expressing gene-trap cassette in the endogenous gene. The mutant mice expressed significantly lower levels of NIAM protein in tissues compared to wild-type animals. Fifty percent of aged NIAM deficient mice (14 to 21 months) developed proliferative lesions, including a uterine hemangioma, pulmonary papillary adenoma, and a Harderian gland adenoma. No age-matched wild-type or NIAM+/m heterozygous animals developed lesions. In the spleen, NIAMm/m mice had prominent white pulp expansion which correlated with enhanced increased reactive lymphoid hyperplasia and evidence of systemic inflammation. Notably, 17% of NIAM mutant mice had splenic white pulp features indicating early B-cell lymphoma. This correlated with selective expansion of marginal zone B cells in the spleens of younger, tumor-free NIAM-deficient mice. Unexpectedly, basal p53 expression and activity was largely unaffected by NIAM loss in isolated splenic B cells. In sum, NIAM down-regulation in vivo results in a significant predisposition to developing benign tumors or early stage cancers. These mice represent an outstanding platform for dissecting NIAM's role in tumorigenesis and various anti-cancer pathways, including p53 signaling.
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Affiliation(s)
- Sara M. Reed
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
- Medical Scientist Training Program, 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
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
- Molecular and Cellular Biology Program, University of Iowa, Iowa City, Iowa, United States of America
| | - Timothy R. Rosean
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, Iowa, United States of America
| | - Nick Borcherding
- Department of Pathology, University of Iowa, Iowa City, Iowa, United States of America
| | - Sebastian Sciegienka
- Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America
| | - J. Adam Goeken
- Department of Pathology, University of Iowa, Iowa City, Iowa, United States of America
| | - Paul W. Naumann
- Department of Pathology, University of Iowa, Iowa City, Iowa, United States of America
| | - Weizhou Zhang
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, Iowa, United States of America
- Department of Pathology, 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
| | - Siegfried Janz
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, Iowa, United States of America
- Department of Pathology, University of Iowa, Iowa City, Iowa, United States of America
| | - David K. Meyerholz
- 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
- Medical Scientist Training Program, University of Iowa, Iowa City, Iowa, United States of America
- Molecular and Cellular Biology 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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23
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Lee MY, Marina M, King JL, Saavedra HI. Differential expression of centrosome regulators in Her2+ breast cancer cells versus non-tumorigenic MCF10A cells. Cell Div 2014; 9:3. [PMID: 25278993 PMCID: PMC4181616 DOI: 10.1186/1747-1028-9-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/08/2014] [Indexed: 12/26/2022] Open
Abstract
Centrosome amplification (CA) amongst particular breast cancer subtypes (Her2+ subtype) is associated with genomic instability and aggressive tumor phenotypes. However, changes in signaling pathways associated with centrosome biology have not been fully explored in subtype specific models. Novel centrosome regulatory genes that are selectively altered in Her2+ breast cancer cells are of interest in discerning why CA is more prevalent in this subtype. To determine centrosome/cell cycle genes that are altered in Her2+ cells that display CA (HCC1954) versus non-tumorigenic cells (MCF10A), we carried out a gene microarray. Expression differences were validated by real-time PCR and Western blotting. After the microarray validation, we pursued a panel of upregulated and downregulated genes based on novelty/relevance to centrosome duplication. Functional experiments measuring CA and BrdU incorporation were completed after genetic manipulation of targets (TTK, SGOL1, MDM2 and SFRP1). Amongst genes that were downregulated in HCC1954 cells, knockdown of MDM2 and SFRP1 in MCF10A cells did not consistently induce CA or impaired BrdU incorporation. Conversely, amongst upregulated genes in HCC1954 cells, knockdown of SGOL1 and TTK decreased CA in breast cancer cells, while BrdU incorporation was only altered by SGOL1 knockdown. We also explored the Kaplan Meier Plot resource and noted that MDM2 and SFRP1 are positively associated with relapse free survival in all breast cancer subtypes, while TTK is negatively correlated with overall survival of Luminal A patients. Based on this functional screen, we conclude that SGOL1 and TTK are important modulators of centrosome function in a breast cancer specific model.
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Affiliation(s)
- Mi-Young Lee
- Department of Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, C3084, 1365C Clifton Road NE, Atlanta, GA 30322, USA
| | - Mihaela Marina
- Department of Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, C3084, 1365C Clifton Road NE, Atlanta, GA 30322, USA
| | - Jamie L King
- Department of Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, C3084, 1365C Clifton Road NE, Atlanta, GA 30322, USA.,Cancer Biology Graduate Program, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322, USA
| | - Harold I Saavedra
- Department of Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, C3084, 1365C Clifton Road NE, Atlanta, GA 30322, USA
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24
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Xiong X, Zhao Y, Tang F, Wei D, Thomas D, Wang X, Liu Y, Zheng P, Sun Y. Ribosomal protein S27-like is a physiological regulator of p53 that suppresses genomic instability and tumorigenesis. eLife 2014; 3:e02236. [PMID: 25144937 PMCID: PMC4163686 DOI: 10.7554/elife.02236] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 08/20/2014] [Indexed: 12/24/2022] Open
Abstract
Cell-based studies showed that several Mdm2-binding ribosomal proteins, upon overexpression, stabilize and activate p53. In contrast, here we show in a mouse knockout study that Mdm2-binding ribosomal protein S27-like (Rps27l), upon disruption, activates p53. Germline inactivation of Rps27l triggers ribosomal stress to stabilize Mdm2, which degrades Mdm4 to reduce Mdm2-Mdm4 E3 ligase towards p53, leading to p53-dependent apoptotic depletion of hematopoietic stem cells and postnatal death, which is rescued by Trp53 deletion. Paradoxically, while increased p53 is expected to inhibit tumorigenesis, Rps27l−/−;Trp53+/− mice develop lymphomas at higher incidence with p53 loss-of-heterozygosity and severe genome aneuploidy, suggesting that Rps27l disruption impose a selection pressure against p53. Thus, Rps27l has dual functions in p53 regulation: under Trp53+/+ background, Rps27l disruption triggers ribosomal stress to induce p53 and apoptosis, whereas under Trp53+/− background, Rps27l disruption triggers genomic instability and Trp53 deletion to promote tumorigenesis. Our study provides a new paradigm of p53 regulation. DOI:http://dx.doi.org/10.7554/eLife.02236.001 There are over a hundred different types of cancer that can affect humans; but, in general, all cancers are caused by mutations that cause cells to grow and divide abnormally. ‘Tumor suppressor genes’ are genes that normally protect a cell from genetic changes that can lead a cell towards becoming cancerous. About half of all cancers in humans have a mutation in one of the two copies of a tumor suppressor gene that encodes a protein called p53, which helps to control how and when cells grow and divide. In normal cells, the p53 protein can be activated in various ways. Damage to a cell's DNA triggers p53 to stop the cell growing, which gives the cell time to repair the DNA damage. However, if the damage is too severe and cannot be repaired, p53 essentially causes the cell to kill itself, via a process called apoptosis. Furthermore, if a cell has problems building new copies of its protein-making machinery, some of the parts (called ribosomal proteins) that make up these molecular machines can also lead to p53 being activated. By deleting the gene for a protein called Rps27l that is a newly characterized ribosomal protein, Xiong et al. have discovered that, in mice, Rps27I regulates the p53 protein in two different ways. In normal cells, Rps27l appears to inhibit p53, which is likely to encourage cancer to develop. But, if a cell has already lost a copy of the p53 gene—a situation that would normally encourage the cells to accrue further mutations and become cancerous—Rps27l acts as a tumor suppressor. In these mutated cells, the Rps27l protein helps to maintain the stability of the genome and prevent the loss of the second copy of gene for p53, and so protects the cell from becoming cancerous. Thus Rps27l can either activate or inactivate p53 activity depending on how many copies of the gene for p53 remain intact. The next challenge is to investigate if Rps27l levels determine the early-onset of tumor development in cancer-prone cells seen in patients with Li-Fraumeni syndrome, who are born with a mutated copy of the p53 gene. DOI:http://dx.doi.org/10.7554/eLife.02236.002
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Affiliation(s)
- Xiufang Xiong
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, United States
| | - Yongchao Zhao
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, United States
| | - Fei Tang
- Center for Cancer and Immunology Research, Children's National Medical Center, Washington, United States
| | - Dongping Wei
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, United States
| | - Daffyd Thomas
- Department of Pathology, University of Michigan Medical School, Ann Arbor, United States
| | - Xiang Wang
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, United States
| | - Yang Liu
- Center for Cancer and Immunology Research, Children's National Medical Center, Washington, United States
| | - Pan Zheng
- Center for Cancer and Immunology Research, Children's National Medical Center, Washington, United States
| | - Yi Sun
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, United States
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25
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Adams CM, Eischen CM. Inactivation of p53 is insufficient to allow B cells and B-cell lymphomas to survive without Dicer. Cancer Res 2014; 74:3923-34. [PMID: 24840646 DOI: 10.1158/0008-5472.can-13-1866] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Inactivation of p53, the master regulator of cellular stress and damage signals, often allows cells that should die or senesce to live. Loss of Dicer, an RNase III-like enzyme critical in microRNA biogenesis, causes embryonic lethality and activation of the p53 pathway. Several nonhematopoietic cell types that contain inactivated p53 have been shown to survive Dicer deletion, suggesting that p53 loss may protect cells from the negative consequences of Dicer deletion. However, here, we report that loss of p53 did not provide a survival advantage to B cells, as they underwent rapid apoptosis upon Dicer deletion. Moreover, a deficiency in p53 neither rescued the Dicer deletion-induced delay in Myc-driven B-cell lymphomagenesis, nor allowed a single B-cell lymphoma to develop with biallelic deletion of Dicer. A p53 deficiency did, however, restore the pre-B/B-cell phenotype and CD19 surface expression of the lymphomas that emerged in conditional Dicer knockout Eμ-myc transgenic mice. Moreover, p53 loss in transformed B cells did not confer protection from apoptosis, as Dicer deletion in established p53-null B-cell lymphomas induced apoptosis, and all of the 1,260 B-cell lymphoma clones analyzed that survived Cre-mediated Dicer deletion retained at least one allele of Dicer. Moreover, Dicer deletion in lymphomas in vivo reduced tumor burden and prolonged survival. Therefore, inactivation of p53 is insufficient to allow untransformed B cells and B-cell lymphomas to survive without Dicer, presenting a potential therapeutic opportunity for the treatment of B-cell lymphomas.
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Affiliation(s)
- Clare M Adams
- Authors' Affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Christine M Eischen
- Authors' Affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
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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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Nag S, Zhang X, Srivenugopal K, Wang MH, Wang W, Zhang R. Targeting MDM2-p53 interaction for cancer therapy: are we there yet? Curr Med Chem 2014; 21:553-74. [PMID: 24180275 PMCID: PMC6690199 DOI: 10.2174/09298673113206660325] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 10/02/2013] [Accepted: 10/22/2013] [Indexed: 11/22/2022]
Abstract
Inactivation of the tumor suppressor p53 and/or overexpression of the oncogene MDM2 frequently occur in human cancers, and are associated with poor prognosis, advanced forms of the disease, and chemoresistance. MDM2, the major negative regulator of p53, induces p53 degradation and inactivates its tumor suppressing activity. In turn, p53 regulates MDM2 expression. This MDM2-p53 negative feedback loop has been widely studied and presents an attractive target for cancer therapy, with a few of the inhibitors of this interaction already having advanced into clinical trials. Additionally, there is an increasing interest in understanding MDM2's p53-independent activities in carcinogenesis and cancer progression, which may also have implications for cancer therapy. This review aims to highlight the various roles that the MDM2-p53 interaction plays in cancer, the p53 independent oncogenic activities of MDM2 and the various strategies that may be used to target MDM2 and the MDM2-p53 interaction. We will summarize the major preclinical and clinical evidences of MDM2 inhibitors for human cancer treatment and make suggestions to further improve efficacy and safety of this interesting class of cancer therapeutics.
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Affiliation(s)
- S. Nag
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - X. Zhang
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - K.S. Srivenugopal
- Department of Biomedical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
- Cancer Biology Center, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - M.-H. Wang
- Department of Biomedical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
- Cancer Biology Center, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - W. Wang
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
- Cancer Biology Center, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - R. Zhang
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
- Cancer Biology Center, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
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miR-223 regulates cell growth and targets proto-oncogenes in mycosis fungoides/cutaneous T-cell lymphoma. J Invest Dermatol 2013; 134:1101-1107. [PMID: 24304814 PMCID: PMC3961555 DOI: 10.1038/jid.2013.461] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Revised: 10/01/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022]
Abstract
The pathogenesis of the cutaneous T-cell lymphoma (CTCL), mycosis fungoides (MF) is unclear. MicroRNA (miRNA) are small non-coding RNA that target mRNA leading to reduced mRNA translation. Recently, specific miRNA were shown to be altered in CTCL. We identified significantly reduced expression of miR-223 in early stage MF skin, and the levels of miR-223 diminished further in advanced stage disease. CTCL peripheral blood mononuclear cells and cell lines also had reduced miR-223 as compared to controls. Elevated expression of miR-223 in these cell lines reduced cell growth and clonogenic potential, whereas inhibition of miR-223 increased cell numbers. Investigations into putative miR-223 targets with oncogenic function, including E2F1 and MEF2C, and the predicted miR-223 target, TOX, revealed all three are targeted by miR-223 in CTCL. E2F1, MEF2C, and TOX proteins were decreased with miR-223 overexpression, while miR-223 inhibition led to increased protein levels in CTCL. In addition, we showed the 3′-UTR of TOX mRNA was a genuine target of miR-223. Therefore, reduced levels of miR-223 in MF/CTCL lead to increased expression of E2F1, MEF2C, and TOX, which likely contribute to the development and/or progression of CTCL. Thus, miR-223 and its targets may be useful for the development of new therapeutics for MF/CTCL.
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Ramaiah MJ, Pushpavalli SNCVL, Lavanya A, Bhadra K, Haritha V, Patel N, Tamboli JR, Kamal A, Bhadra U, Pal-Bhadra M. Novel anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates modulate the expression of p53-MYCN associated micro RNAs in neuroblastoma cells and cause cell cycle arrest and apoptosis. Bioorg Med Chem Lett 2013; 23:5699-706. [PMID: 23992861 DOI: 10.1016/j.bmcl.2013.08.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/07/2013] [Accepted: 08/05/2013] [Indexed: 12/14/2022]
Abstract
It has previously been shown that anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates activate p53 and cause apoptosis in cervical cancer cells such as HeLa and SiHa. Here we establish the role of these conjugates in activating p53 pathway by phosphorylation at Ser15, 20 and 46 residues and downregulate key oncogenic proteins such as MYCN and Mdm2 in IMR-32 neuroblastoma cells. Compounds decreased the proliferation rate of neuroblastoma cells such as IMR-32, Neuro-2a, SK-N-SH. Compound treatment resulted in G2/M cell cycle arrest. The expression of p53 dependent genes such as p21, Bax, caspases was increased with concomitant decrease of the survival proteins as well as anti-apoptotic proteins such as Akt1, E2F1 and Bcl2. In addition the expression of important microRNAs such as miR-34a, c, miR-200b, miR-107, miR-542-5p and miR-605 were significantly increased that eventually lead to the activation of apoptotic pathway. Our data revealed that conjugates of this nature cause cell cycle arrest and apoptosis in IMR-32 cells [MYCN (+) with intact wild-type p53] by activating p53 signalling and provides a lead for the development of anti-cancer therapeutics.
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Affiliation(s)
- M Janaki Ramaiah
- Department of Chemical Biology, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500 007, India
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Abstract
The MDM2 and MDMX (also known as HDMX and MDM4) proteins are deregulated in many human cancers and exert their oncogenic activity predominantly by inhibiting the p53 tumour suppressor. However, the MDM proteins modulate and respond to many other signalling networks in which they are embedded. Recent mechanistic studies and animal models have demonstrated how functional interactions in these networks are crucial for maintaining normal tissue homeostasis, and for determining responses to oncogenic and therapeutic challenges. This Review highlights the progress made and pitfalls encountered as the field continues to search for MDM-targeted antitumour agents.
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Affiliation(s)
- Mark Wade
- Center for Genomic Science of IIT@SEMM, Fondazione Istituto Italiano di Tecnologia, Via Adamello 16, 20139 Milan, Italy
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Nussey DH, Froy H, Lemaitre JF, Gaillard JM, Austad SN. Senescence in natural populations of animals: widespread evidence and its implications for bio-gerontology. Ageing Res Rev 2013; 12:214-25. [PMID: 22884974 PMCID: PMC4246505 DOI: 10.1016/j.arr.2012.07.004] [Citation(s) in RCA: 404] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 07/24/2012] [Accepted: 07/30/2012] [Indexed: 10/28/2022]
Abstract
That senescence is rarely, if ever, observed in natural populations is an oft-quoted fallacy within bio-gerontology. We identify the roots of this fallacy in the otherwise seminal works of Medawar and Comfort, and explain that under antagonistic pleiotropy or disposable soma explanations for the evolution of senescence there is no reason why senescence cannot evolve to be manifest within the life expectancies of wild organisms. The recent emergence of long-term field studies presents irrefutable evidence that senescence is commonly detected in nature. We found such evidence in 175 different animal species from 340 separate studies. Although the bulk of this evidence comes from birds and mammals, we also found evidence for senescence in other vertebrates and insects. We describe how high-quality longitudinal field data allow us to test evolutionary explanations for differences in senescence between the sexes and among traits and individuals. Recent studies indicate that genes, prior environment and investment in growth and reproduction influence aging rates in the wild. We argue that - with the fallacy that wild animals do not senesce finally dead and buried - collaborations between bio-gerontologists and field biologists can begin to test the ecological generality of purportedly 'public' mechanisms regulating aging in laboratory models.
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Affiliation(s)
- Daniel H Nussey
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, UK.
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Chen L, Tweddle DA. p53, SKP2, and DKK3 as MYCN Target Genes and Their Potential Therapeutic Significance. Front Oncol 2012; 2:173. [PMID: 23226679 PMCID: PMC3508619 DOI: 10.3389/fonc.2012.00173] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 11/01/2012] [Indexed: 12/15/2022] Open
Abstract
Neuroblastoma is the most common extra-cranial solid tumor of childhood. Despite significant advances, it currently still remains one of the most difficult childhood cancers to cure, with less than 40% of patients with high-risk disease being long-term survivors. MYCN is a proto-oncogene implicated to be directly involved in neuroblastoma development. Amplification of MYCN is associated with rapid tumor progression and poor prognosis. Novel therapeutic strategies which can improve the survival rates whilst reducing the toxicity in these patients are therefore required. Here we discuss genes regulated by MYCN in neuroblastoma, with particular reference to p53, SKP2, and DKK3 and strategies that may be employed to target them.
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Affiliation(s)
- Lindi Chen
- Newcastle Cancer Centre, Northern Institute for Cancer Research, Newcastle University Newcastle, UK
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33
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Abstract
The contribution of Mdm2, and its recently identified family member Mdmx (Mdm4), to tumorigenesis has primarily focused on their negative regulation of the p53 tumor suppressor. Although Mdm2 and Mdmx clearly inhibit p53, which can lead to tumor development, both have also been shown to affect tumorigenesis independent of p53. Given that Mdm2 and/or Mdmx overexpression is common and likely underestimated in human cancers, understanding the functions of these proteins beyond p53 control is critical. In recent years, new functions of Mdm2 and Mdmx that lead to genome instability, a hallmark of malignancy, have emerged. Specifically, roles in the DNA damage response that are distinct from their regulation of p53 have been identified. Inhibition of p53 as well as other components of the DNA damage response by Mdm2 and Mdmx can result in delayed DNA repair and increased genome instability, making Mdm2 and Mdmx a danger to the genome when aberrantly expressed. However, the genome instability caused by altered levels of Mdm2 and Mdmx could be used therapeutically for the treatment of cancer. Specifically, drugs/small molecules that target the interaction between Mdm2 and p53 can stabilize Mdm2, resulting in negative consequences on the genome that could be exploited for cancer treatment, particularly malignancies lacking functional p53.
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Affiliation(s)
- Alexia N Melo
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
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Eischen CM, Boyd K. Decreased Mdm2 expression inhibits tumor development and extends survival independent of Arf and dependent on p53. PLoS One 2012; 7:e46148. [PMID: 23029416 PMCID: PMC3461014 DOI: 10.1371/journal.pone.0046148] [Citation(s) in RCA: 11] [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: 07/11/2012] [Accepted: 08/27/2012] [Indexed: 11/22/2022] Open
Abstract
Inactivation of the Arf-Mdm2-p53 tumor suppressor pathway is a necessary event for tumorigenesis. Arf controls Mdm2, which in turn regulates p53, but Arf and Mdm2 also have p53-independent functions that affect tumor development. Moreover, inhibition of oncogene-induced tumorigenesis relies on Arf and p53, but the requirements of Arf and p53 in tumor development initiated in the absence of overt oncogene overexpression and the role of Mdm2 in this process remain unclear. In a series of genetic experiments in mice with defined deficiencies in Arf, Mdm2 and/or p53, we show Mdm2 haploinsufficiency significantly delayed tumorigenesis in mice deficient in Arf and p53. Mdm2 heterozygosity significantly inhibited tumor development in the absence of Arf, and in contrast to Myc oncogene-driven cancer, this delay in tumorigenesis could not be rescued with the presence of one allele of Arf. Notably, Mdm2 haploinsufficieny blocked the accelerated tumor development in Arf deficient mice caused by p53 heterozygosity. However, tumorigenesis was not inhibited in Mdm2 heterozygous mice lacking both alleles of p53 regardless of Arf status. Surprisingly, loss of Arf accelerated tumor development in p53-null mice. Tumor spectrum was largely dictated by Arf and p53 status with Mdm2 haploinsufficiency only modestly altering the tumor type in some of the genotypes and not the number of primary tumors that arose. Therefore, the significant effects of Mdm2 haploinsufficiency on tumor latency were independent of Arf and required at least one allele of p53, and an Mdm2 deficiency had minor effects on the types of tumors that developed. These data also demonstrate that decreased levels of Mdm2 are protective in the presence of multiple genetic events in Arf and p53 genes that normally accelerate tumorigenesis.
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Affiliation(s)
- Christine M Eischen
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
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Abstract
Aberrations in the p53 tumor suppressor pathway are associated with hematologic malignancies. p53-dependent cell cycle control, senescence, and apoptosis functions are actively involved in maintaining hematopoietic homeostasis under normal and stress conditions. Whereas loss of p53 function promotes leukemia and lymphoma development in humans and mice, increased p53 activity inhibits hematopoietic stem cell function and results in myelodysplasia. Thus, exquisite regulation of p53 activity is critical for homeostasis. Most of our understanding of p53 function in hematopoiesis is derived from genetically engineered mice. Here we summarize some of these models, the various mechanisms that disrupt the regulation of p53 activity, and their relevance to human disease.
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Abstract
Neoplastic transformation requires the elimination of key tumor suppressors, which may result from E3 ligase-mediated proteasomal degradation. We previously demonstrated a key role for the E3 ubiquitin ligase E6AP in the regulation of promyelocytic leukemia protein (PML) stability and formation of PML nuclear bodies. Here, we report the involvement of the E6AP-PML axis in B-cell lymphoma development. A partial loss of E6AP attenuated Myc-induced B-cell lymphomagenesis. This tumor suppressive action was achieved by the induction of cellular senescence. B-cell lymphomas deficient for E6AP expressed elevated levels of PML and PML-nuclear bodies with a concomitant increase in markers of cellular senescence, including p21, H3K9me3, and p16. Consistently, PML deficiency accelerated the rate of Myc-induced B-cell lymphomagenesis. Importantly, E6AP expression was elevated in ∼ 60% of human Burkitt lymphomas, and down-regulation of E6AP in B-lymphoma cells restored PML expression with a concurrent induction of cellular senescence in these cells. Our findings demonstrate that E6AP-mediated down-regulation of PML-induced senescence is essential for B-cell lymphoma progression. This provides a molecular explanation for the down-regulation of PML observed in non-Hodgkin lymphomas, thereby suggesting a novel therapeutic approach for restoration of tumor suppression in B-cell lymphoma.
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Gu L, Zhang H, He J, Li J, Huang M, Zhou M. MDM2 regulates MYCN mRNA stabilization and translation in human neuroblastoma cells. Oncogene 2012; 31:1342-53. [PMID: 21822304 PMCID: PMC3213308 DOI: 10.1038/onc.2011.343] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The MYCN gene has a critical role in determining the clinical behavior of neuroblastoma. Although it is known that genomic amplification occurs in high-risk subsets, it remains unclear how MYCN expression is regulated in the pathogenesis of neuroblastomas. Here, we report that MYCN expression was regulated by the oncoprotein MDM2 at the post-transcriptional level and was associated with neuroblastoma cell growth. Increasing MDM2 by ectopic overexpression in the cytoplasm enhanced both mRNA and protein expression of MYCN. Mechanistic studies found that the C-terminal RING domain of the MDM2 protein bound to the MYCN mRNA's AREs within the 3'UTR and increased MYCN 3'UTR-mediated mRNA stability and translation. Conversely, MDM2 silencing by specific siRNA rendered the MYCN mRNA unstable and reduced the abundance of the MYCN protein in MYCN-amplified neuroblastoma cell lines. Importantly, this MDM2 silencing resulted in a remarkable inhibition of neuroblastoma cell growth and induction of cell death through a p53-independent pathway. Our results indicate that MDM2 has a p53-independent role in the regulation of both MYCN mRNA stabilization and its translation, suggesting that MDM2-mediated MYCN expression is one mechanism associated with growth of MYCN-associated neuroblastoma and disease progression.
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Affiliation(s)
- L Gu
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
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Abstract
Mdm2 is an essential regulator of the p53 tumor suppressor. Mdm2 is modified at transcriptional, post-transcriptional, and post-translational levels to control p53 activity in normal versus stressed cells. Importantly, errors in these regulatory mechanisms can result in aberrant Mdm2 expression and failure to initiate programmed cell death in response to DNA damage. Such errors can have severe consequences as evidenced by tumor phenotypes resulting from amplification at the Mdm2 locus and changes in post-transcriptional and post-translational regulation of Mdm2. Although Mdm2 mediated inhibition of p53 is well characterized, Mdm2 interacts with many additional proteins and also targets many of these for proteosomal degradation. Mdm2 also has E3-ligase independent functions and p53-independent functions that have important implications for genome stability and cancer.
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Affiliation(s)
- Maurisa F Riley
- Department of Genetics, University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
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Suppression of Ras/Mapk pathway signaling inhibits Myc-induced lymphomagenesis. Cell Death Differ 2012; 19:1220-7. [PMID: 22301919 DOI: 10.1038/cdd.2012.1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Although the Myc transcription factor has been shown necessary for the oncogenic function of Ras, the contribution of Ras pathway signaling to the oncogenic function of Myc remains unresolved. We report the novel findings that Myc alone induced Ras/Mapk pathway signaling, and increased signaling following growth factor stimulation. Deletion of the scaffold protein kinase suppressor of Ras 1 (Ksr1) attenuated signaling through the Ras/Mapk pathway, including activation following Myc induction. B cells that lacked Ksr1 exhibited reduced proliferation and increased cytokine deprivation-induced apoptosis. Overexpression of Myc rescued the proliferation defect of Ksr1-null B cells, but loss of Ksr1 increased sensitivity of B cells to Myc-induced apoptosis. Notably, there was a significant delay in lymphoma development in Ksr1-null mice overexpressing Myc in B cells (Eμ-myc transgenic mice). There was an elevated frequency of p53 inactivation, indicative of increased selective pressure to bypass the p53 tumor suppressor pathway, in Ksr1-null Eμ-myc lymphomas. Therefore, loss of Ksr1 inhibits Ras/Mapk pathway signaling leading to increased Myc-induced B-cell apoptosis, and this results in reduced B-cell transformation and lymphoma development. Our data indicate that suppression of Myc-induced Ras/Mapk pathway signaling significantly impairs Myc oncogenic function. These results fill a significant gap in knowledge about Myc and should open new avenues of therapeutic intervention for Myc-overexpressing malignancies.
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Abstract
The iconic history of the Myc oncoprotein encompasses 3 decades of intense scientific discovery. There is no question that Myc has been a pioneer, advancing insight into the molecular basis of cancer as well as functioning as a critical control center for several diverse biological processes and regulatory mechanisms. This narrative chronicles the journey and milestones that have defined the understanding of Myc, and it provides an opportunity to consider future directions in this challenging yet rewarding field.
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Affiliation(s)
- Amanda R Wasylishen
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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41
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The cooperating mutation or “second hit” determines the immunologic visibility toward MYC-induced murine lymphomas. Blood 2011; 118:4635-45. [DOI: 10.1182/blood-2010-10-313098] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractIn Eμ-myc transgenic animals lymphoma formation requires additional genetic alterations, which frequently comprise loss of p53 or overexpression of BCL-2. We describe that the nature of the “second hit” affects the ability of the immune system to contain lymphoma development. Tumors with disrupted p53 signaling killed the host more rapidly than BCL-2 overexpressing ones. Relaxing immunologic control, using Tyk2−/− mice or by Ab-mediated depletion of CD8+ T or natural killer (NK) cells accelerated formation of BCL-2–overexpressing lymphomas but not of those lacking p53. Most strikingly, enforced expression of BCL-2 prolonged disease latency in the absence of p53, whereas blocking p53 function in BCL-2–overexpressing tumors failed to accelerate disease. This shows that blocking apoptosis in p53-deficient cells by enforcing BCL-2 expression can mitigate disease progression increasing the “immunologic visibility.” In vitro cytotoxicity assays confirmed that high expression of BCL-2 protein facilitates NK and T cell–mediated killing. Moreover, we found that high BCL-2 expression is accompanied by significantly increased levels of the NKG2D ligand MULT1, which may account for the enhanced killing. Our findings provide first evidence that the nature of the second hit affects tumor immunosurveillance in c-MYC–driven lymphomas and define a potential shortcoming of antitumor therapies targeting BCL-2.
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Abstract
MYCN amplification is a major biomarker of poor prognosis, occurring in 25-30% of neuroblastomas. MYCN plays contradictory roles in promoting cell growth and sensitizing cells to apoptosis. We have recently shown that p53 is a direct transcriptional target of MYCN in neuroblastoma and that p53-mediated apoptosis may be an important mechanism of MYCN-induced apoptosis. Although p53 mutations are rare in neuroblastoma at diagnosis, the p53/MDM2/p14ARF pathway is often inactivated through MDM2 amplification or p14ARF inactivation. We hypothesised that reactivation of p53 by inhibition of its negative regulator MDM2, using the MDM2-p53 antagonists Nutlin-3 and MI-63, will result in p53-mediated growth arrest and apoptosis especially in MYCN amplified cells. Using the SHEP Tet21N MYCN regulatable system, MYCN(−) cells were more resistant to both Nutlin-3 and MI-63 mediated growth inhibition and apoptosis compared to MYCN(+) cells and siRNA mediated knockdown of MYCN in 4 MYCN amplified cell lines resulted in decreased p53 expression and activation, as well as decreased levels of apoptosis following treatment with MDM2-p53 antagonists. In a panel of 18 neuroblastoma cell lines treated with Nutlin-3 and MI-63, the sub-set amplified for MYCN had a significantly lower mean GI50 value and increased caspase 3/7 activity compared to the non MYCN amplified group of cell lines, but p53 mutant cell lines were resistant to the antagonists regardless of MYCN status. We conclude that amplification or overexpression of MYCN sensitizes neuroblastoma cell lines with wildtype p53 to MDM2-p53 antagonists and that these compounds may therefore be particularly effective in treating high risk MYCN amplified disease.
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Terzian T, Dumble M, Arbab F, Thaller C, Donehower LA, Lozano G, Justice MJ, Roop DR, Box NF. Rpl27a mutation in the sooty foot ataxia mouse phenocopies high p53 mouse models. J Pathol 2011; 224:540-52. [PMID: 21674502 DOI: 10.1002/path.2891] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 02/28/2011] [Accepted: 03/04/2011] [Indexed: 01/06/2023]
Abstract
Ribosomal stress is an important, yet poorly understood, mechanism that results in activation of the p53 tumour suppressor. We present a mutation in the ribosomal protein Rpl27a gene (sooty foot ataxia mice), isolated through a sensitized N-ethyl-N-nitrosourea (ENU) mutagenesis screen for p53 pathway defects, that shares striking phenotypic similarities with high p53 mouse models, including cerebellar ataxia, pancytopenia and epidermal hyperpigmentation. This phenocopy is rescued in a haploinsufficient p53 background. A detailed examination of the bone marrow in these mice identified reduced numbers of haematopoietic stem cells and a p53-dependent c-Kit down-regulation. These studies suggest that reduced Rpl27a increases p53 activity in vivo, further evident with a delay in tumorigenesis in mutant mice. Taken together, these data demonstrate that Rpl27a plays a crucial role in multiple tissues and that disruption of this ribosomal protein affects both development and transformation.
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Post SM, Quintás-Cardama A, Pant V, Iwakuma T, Hamir A, Jackson JG, Maccio DR, Bond GL, Johnson DG, Levine AJ, Lozano G. A high-frequency regulatory polymorphism in the p53 pathway accelerates tumor development. Cancer Cell 2010; 18:220-30. [PMID: 20832750 PMCID: PMC2944041 DOI: 10.1016/j.ccr.2010.07.010] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 05/21/2010] [Accepted: 07/20/2010] [Indexed: 12/17/2022]
Abstract
MDM2, a negative regulator of p53, is elevated in many cancers that retain wild-type p53. A single nucleotide polymorphism (SNP) in the human MDM2 promoter increases the affinity of Sp1 resulting in elevated MDM2 levels. We generated mice carrying either the MDM2(SNP309T) or the MDM2(SNP309G) allele to address the impact of MDM2(SNP309G) on tumorigenesis. Mdm2(SNP309G/G) cells exhibit elevated Mdm2 levels, reduced p53 levels, and decreased apoptosis. Importantly, some Mdm2(SNP309G/G) mice succumbed to tumors before 1 year of age, suggesting that this allele increases tumor risk. Additionally, the Mdm2(SNP309G) allele potentiates the tumor phenotype and alters tumor spectrum in mice inheriting a p53 hot-spot mutation. These data provide causal evidence for increased cancer risk in carriers of the Mdm2(SNP309G) allele.
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Affiliation(s)
- Sean M. Post
- The University of Texas M. D. Anderson Cancer Center, Department of Genetics, Houston, TX, 77030, USA
| | - Alfonso Quintás-Cardama
- The University of Texas M. D. Anderson Cancer Center, Department of Genetics, Houston, TX, 77030, USA
- The University of Texas M. D. Anderson Cancer Center, Department of Leukemia, Houston, TX, 77030, USA
| | - Vinod Pant
- The University of Texas M. D. Anderson Cancer Center, Department of Genetics, Houston, TX, 77030, USA
| | - Tomoo Iwakuma
- Louisiana State University Health Sciences Center, Department of Genetics/Cancer Center, New Orleans, LA, 70112, USA
| | - Amir Hamir
- The University of Texas M. D. Anderson Cancer Center, Department of Veterinary Medicine and Surgery, Houston, TX, 77030, USA
| | - James G. Jackson
- The University of Texas M. D. Anderson Cancer Center, Department of Genetics, Houston, TX, 77030, USA
| | - Daniela R. Maccio
- The University of Texas M. D. Anderson Cancer Center, Department of Genetics, Houston, TX, 77030, USA
| | - Gareth L. Bond
- Ludwig Institute for Cancer Research, University of Oxford, Oxford, OX1 3DW, United Kingdom
| | - David G. Johnson
- The University of Texas M. D. Anderson Cancer Center, Department of Carcinogenesis, Smithville, TX, 78956, USA
| | - Arnold J. Levine
- The Simons Center for Systems Biology, The Institute for Advanced Study, Princeton, NJ, 08540, USA
| | - Guillermina Lozano
- The University of Texas M. D. Anderson Cancer Center, Department of Genetics, Houston, TX, 77030, USA
- Correspondence:
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Phillips A, Teunisse A, Lam S, Lodder K, Darley M, Emaduddin M, Wolf A, Richter J, de Lange J, Verlaan-de Vries M, Lenos K, Böhnke A, Bartel F, Blaydes JP, Jochemsen AG. HDMX-L is expressed from a functional p53-responsive promoter in the first intron of the HDMX gene and participates in an autoregulatory feedback loop to control p53 activity. J Biol Chem 2010; 285:29111-27. [PMID: 20659896 DOI: 10.1074/jbc.m110.129726] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The p53 regulatory network is critically involved in preventing the initiation of cancer. In unstressed cells, p53 is maintained at low levels and is largely inactive, mainly through the action of its two essential negative regulators, HDM2 and HDMX. p53 abundance and activity are up-regulated in response to various stresses, including DNA damage and oncogene activation. Active p53 initiates transcriptional and transcription-independent programs that result in cell cycle arrest, cellular senescence, or apoptosis. p53 also activates transcription of HDM2, which initially leads to the degradation of HDMX, creating a positive feedback loop to obtain maximal activation of p53. Subsequently, when stress-induced post-translational modifications start to decline, HDM2 becomes effective in targeting p53 for degradation, thus attenuating the p53 response. To date, no clear function for HDMX in this critical attenuation phase has been demonstrated experimentally. Like HDM2, the HDMX gene contains a promoter (P2) in its first intron that is potentially inducible by p53. We show that p53 activation in response to a plethora of p53-activating agents induces the transcription of a novel HDMX mRNA transcript from the HDMX-P2 promoter. This mRNA is more efficiently translated than that expressed from the constitutive HDMX-P1 promoter, and it encodes a long form of HDMX protein, HDMX-L. Importantly, we demonstrate that HDMX-L cooperates with HDM2 to promote the ubiquitination of p53 and that p53-induced HDMX transcription from the P2 promoter can play a key role in the attenuation phase of the p53 response, to effectively diminish p53 abundance as cells recover from stress.
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Affiliation(s)
- Anna Phillips
- Southampton Cancer Research UK Centre, University of Southampton School of Medicine, Southampton General Hospital, Southampton SO16 6YD, United Kingdom
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Arrate MP, Vincent T, Odvody J, Kar R, Jones SN, Eischen CM. MicroRNA biogenesis is required for Myc-induced B-cell lymphoma development and survival. Cancer Res 2010; 70:6083-92. [PMID: 20587524 DOI: 10.1158/0008-5472.can-09-4736] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Many tumor cells express globally reduced levels of microRNAs (miRNA), suggesting that decreased miRNA expression in premalignant cells contributes to their tumorigenic phenotype. In support of this, Dicer, an RNase III-like enzyme that controls the maturation of miRNA, was recently shown to function as a haploinsufficient tumor suppressor in nonhematopoietic cells. Because the Myc oncoprotein, a critical inducer of B-cell lymphomas, was reported to suppress the expression of multiple miRNAs in lymphoma cells, it was presumed that a deficiency of Dicer and subsequent loss of miRNA maturation would accelerate Myc-induced lymphoma development. We report here that, surprisingly, a haploinsufficiency of Dicer in B cells failed to promote B-cell malignancy or accelerate Myc-induced B-cell lymphomagenesis in mice. Moreover, deletion of Dicer in B cells of CD19-cre(+)/Emicro-myc mice significantly inhibited lymphomagenesis, and all lymphomas that did arise in these mice lacked functional Cre expression and retained at least one functional Dicer allele. Uncharacteristically, the lymphomas that frequently developed in the CD19-cre(+)/Dicer(fl/fl)/Emicro-myc mice were of very early precursor B-cell origin, a stage of B-cell development prior to Cre expression. Therefore, loss of Dicer function was not advantageous for lymphomagenesis, but rather, Dicer ablation was strongly selected against during Myc-induced B-cell lymphoma development. Moreover, deletion of Dicer in established B-cell lymphomas resulted in apoptosis, revealing that Dicer is required for B-cell lymphoma survival. Thus, Dicer does not function as a haploinsufficient tumor suppressor in B cells and is required for B-cell lymphoma development and survival.
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Affiliation(s)
- Maria Pia Arrate
- Department of Pathology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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Mendrysa SM, Akagi K, Roayaei J, Lien WH, Copeland NG, Jenkins NA, Eisenman RN. An Integrated Genetic-Genomic Approach for the Identification of Novel Cancer Loci in Mice Sensitized to c-Myc-Induced Apoptosis. Genes Cancer 2010; 1:465-479. [PMID: 20927200 DOI: 10.1177/1947601910374875] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Deregulated c-Myc is associated with a wide range of human cancers. In many cell types, overexpression of c-Myc potently promotes cell growth and proliferation concomitant with the induction of apoptosis. Secondary genetic events that shift this balance either by increasing growth and proliferation or limiting apoptosis are likely to cooperate with c-Myc in tumorigenesis. Here, the authors have performed large-scale insertional mutagenesis in Eμ-c-myc mice that, through mdm2 loss of function mutations, are sensitized to apoptosis. The authors chose to use this genetic background based on the hypothesis that the high level of apoptosis induced by c-Myc overexpression in MDM2-deficient mice would act as a rate-limiting barrier for lymphoma development. As a result, it was predicted that the spectrum of retroviral insertions would be shifted toward loci that harbor antiapoptotic genes. Nine novel common insertion sites (CISs) specific to mice with this sensitized genetic background were identified, suggesting the presence of novel antiapoptotic cancer genes. Moreover, cross-comparing the data to the Retroviral Tagged Cancer Gene Database, the authors identified an additional 23 novel CISs. Here, evidence is presented that 2 genes, ppp1r16b and hdac6, identified at CISs, are bona fide cellular oncogenes. This study highlights the power of combining unique sensitized genetic backgrounds with large-scale mutagenesis as an approach for identifying novel cancer genes.
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Affiliation(s)
- Susan M Mendrysa
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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49
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Waning DL, Lehman JA, Batuello CN, Mayo LD. Controlling the Mdm2-Mdmx-p53 Circuit. Pharmaceuticals (Basel) 2010; 3:1576-1593. [PMID: 20651945 PMCID: PMC2907906 DOI: 10.3390/ph3051576] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The p53 tumor suppressor is a key protein in maintaining the integrity of the genome by inducing either cell cycle arrest or apoptosis following cellular stress signals. Two human family members, Mdm2 and Mdmx, are primarily responsible for inactivating p53 transcription and targeting p53 protein for ubiquitin-mediated degradation. In response to genotoxic stress, post-translational modifications to p53, Mdm2 and Mdmx stabilize and activate p53. The role that phosphorylation of these molecules plays in the cellular response to genotoxic agents has been extensively studied with respect to cancer biology. In this review, we discuss the main phosphorylation events of p53, Mdm2 and Mdmx in response to DNA damage that are important for p53 stability and activity. In tumors that harbor wild-type p53, reactivation of p53 by modulating both Mdm2 and Mdmx signaling is well suited as a therapeutic strategy. However, the rationale for development of kinase inhibitors that target the Mdm2-Mdmx-p53 axis must be carefully considered since modulation of certain kinase signaling pathways has the potential to destabilize and inactivate p53.
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Affiliation(s)
- David L. Waning
- Herman B Wells Center for Pediatric Research, 980 West Walnut, Walther Hall R3-C548, Indianapolis, IN 46202, USA
| | - Jason A. Lehman
- Herman B Wells Center for Pediatric Research, 980 West Walnut, Walther Hall R3-C548, Indianapolis, IN 46202, USA
| | - Christopher N. Batuello
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS 4053, Indianapolis, IN 46202, USA
| | - Lindsey D. Mayo
- Herman B Wells Center for Pediatric Research, 980 West Walnut, Walther Hall R3-C548, Indianapolis, IN 46202, USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS 4053, Indianapolis, IN 46202, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-317-278-3173; Fax: +1-317-274-8046
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50
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Li B, Cheng Q, Li Z, Chen J. p53 inactivation by MDM2 and MDMX negative feedback loops in testicular germ cell tumors. Cell Cycle 2010; 9:1411-20. [PMID: 20372076 DOI: 10.4161/cc.9.7.11255] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Testicular germ cell tumors (TGCT) are unique in their excellent response to DNA-damaging chemotherapy. Mutation of p53 is rare in both untreated and relapsed TGCTs, suggesting that p53 fails to respond effectively against malignant transformation in germ cells. Previous studies implicated the presence of a poorly defined TGCT-specific mechanism of p53 inactivation. Here we show that disruption of p53-MDM2 binding using the MDM2-specific inhibitor Nutlin activates p53 in TGCT cells and is sufficient to induce strong apoptosis. Knockdown of MDMX cooperates with Nutlin to activate p53. Surprisingly, we found that p53 activation induced a two-fold increase in MDMX mRNA and protein expression in TGCT cells. A p53-responsive promoter is identified in MDMX intron 1 that contains a functional p53-binding site, suggesting that MDMX also functions as a negative feedback regulator of p53 in a cell line-dependent fashion. These findings suggest that MDM2 and MDMX are responsible for the functional inactivation of p53 in TGCT. Furthermore, TGCT cells are unique in having a strong apoptosis response to p53. Direct activation of p53 by targeting MDM2 and MDMX may provide a backup approach for the treatment of TGCTs resistant to DNA-damaging drugs.
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Affiliation(s)
- Baozong Li
- Molecular Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
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