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Venkataramany AS, Schieffer KM, Lee K, Cottrell CE, Wang PY, Mardis ER, Cripe TP, Chandler DS. Alternative RNA Splicing Defects in Pediatric Cancers: New Insights in Tumorigenesis and Potential Therapeutic Vulnerabilities. Ann Oncol 2022; 33:578-592. [PMID: 35339647 DOI: 10.1016/j.annonc.2022.03.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 03/15/2022] [Accepted: 03/16/2022] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Compared to adult cancers, pediatric cancers are uniquely characterized by a genomically stable landscape and lower tumor mutational burden. However, alternative splicing, a global cellular process that produces different mRNA/protein isoforms from a single mRNA transcript, has been increasingly implicated in the development of pediatric cancers. DESIGN We review the current literature on the role of alternative splicing in adult cancer, cancer predisposition syndromes, and pediatric cancers. We also describe multiple splice variants identified in adult cancers and confirmed through comprehensive genomic profiling in our institutional cohort of rare, refractory and relapsed pediatric and adolescent young adult cancer patients. Finally, we summarize the contributions of alternative splicing events to neoantigens and chemoresistance and prospects for splicing-based therapies. RESULTS Published dysregulated splicing events can be categorized as exon inclusion, exon exclusion, splicing factor upregulation, or splice site alterations. We observe these phenomena in cancer predisposition syndromes (Lynch syndrome, Li-Fraumeni syndrome, CHEK2) and pediatric leukemia (B-ALL), sarcomas (Ewing sarcoma, rhabdomyosarcoma, osteosarcoma), retinoblastoma, Wilms tumor, and neuroblastoma. Within our institutional cohort, we demonstrate splice variants in key regulatory genes (CHEK2, TP53, PIK3R1, MDM2, KDM6A, NF1) that resulted in exon exclusion or splice site alterations, which were predicted to impact functional protein expression and promote tumorigenesis. Differentially spliced isoforms and splicing proteins also impact neoantigen creation and treatment resistance, such as imatinib or glucocorticoid regimens. Additionally, splice-altering strategies with the potential to change the therapeutic landscape of pediatric cancers include antisense oligonucleotides, adeno-associated virus gene transfers, and small molecule inhibitors. CONCLUSIONS Alternative splicing plays a critical role in the formation and growth of pediatric cancers, and our institutional cohort confirms and highlights the broad spectrum of affected genes in a variety of cancers. Further studies that elucidate the mechanisms of disease-inducing splicing events will contribute toward the development of novel therapeutics.
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Affiliation(s)
- A S Venkataramany
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, Ohio, United States; Medical Scientist Training Program, The Ohio State University, Columbus, Ohio, United States
| | - K M Schieffer
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, United States
| | - K Lee
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, United States; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, United States; Department of Pathology, The Ohio State University College of Medicine, Columbus, Ohio, United States
| | - C E Cottrell
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, United States; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, United States; Department of Pathology, The Ohio State University College of Medicine, Columbus, Ohio, United States
| | - P Y Wang
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, United States; Center for Childhood Cancer and Blood Diseases, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
| | - E R Mardis
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, United States; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, United States
| | - T P Cripe
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, United States; Center for Childhood Cancer and Blood Diseases, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States; Division of Hematology, Oncology and Blood and Marrow Transplant, Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States
| | - D S Chandler
- Center for Childhood Cancer and Blood Diseases, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States; Molecular, Cellular and Developmental Biology Graduate Program and The Center for RNA Biology, The Ohio State University, Columbus, Ohio, United States.
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Klein AM, de Queiroz RM, Venkatesh D, Prives C. The roles and regulation of MDM2 and MDMX: it is not just about p53. Genes Dev 2021; 35:575-601. [PMID: 33888565 PMCID: PMC8091979 DOI: 10.1101/gad.347872.120] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this review, Klein et al. discuss the p53-independent roles of MDM2 and MDMX. First, they review the structural and functional features of MDM2 and MDMX proteins separately and together that could be relevant to their p53-independent activities. Following this, they summarize how these two proteins are regulated and how they can function in cells that lack p53. Most well studied as proteins that restrain the p53 tumor suppressor protein, MDM2 and MDMX have rich lives outside of their relationship to p53. There is much to learn about how these two proteins are regulated and how they can function in cells that lack p53. Regulation of MDM2 and MDMX, which takes place at the level of transcription, post-transcription, and protein modification, can be very intricate and is context-dependent. Equally complex are the myriad roles that these two proteins play in cells that lack wild-type p53; while many of these independent outcomes are consistent with oncogenic transformation, in some settings their functions could also be tumor suppressive. Since numerous small molecules that affect MDM2 and MDMX have been developed for therapeutic outcomes, most if not all designed to prevent their restraint of p53, it will be essential to understand how these diverse molecules might affect the p53-independent activities of MDM2 and MDMX.
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Affiliation(s)
- Alyssa M Klein
- Integrated Program in Cellular, Molecular, and Biomedical Studies, Columbia University, New York, New York 10032, USA
| | | | - Divya Venkatesh
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Carol Prives
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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Kim JY, Lee R, Xiao G, Forbes D, Bargonetti J. MDM2-C Functions as an E3 Ubiquitin Ligase. Cancer Manag Res 2020; 12:7715-7724. [PMID: 32904724 PMCID: PMC7457725 DOI: 10.2147/cmar.s260943] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 08/02/2020] [Indexed: 12/21/2022] Open
Abstract
Background Mouse double minute 2 (MDM2) is an E3 ubiquitin ligase that is over-expressed in many cancers and regulates target proteins through ubiquitination. Full-length MDM2 (MDM2-FL) is best known for targeting wild-type p53 for degradation by the proteasome, but the functions of the many splice variants of MDM2 are under-explored. The three well-studied alternative MDM2 isoforms are MDM2-A/ALT2, MDM2-B/ALT1, and MDM2-C/ALT3. MDM2-A and MDM2-B are capable of down-regulating MDM2-FL activity and have transforming activity in cancers with mutant p53. The MDM2 isoform MDM2-C is over-expressed in breast cancer and correlates with decreased survival in the context of mutant p53 expression. Therefore, MDM2-C requires further study to determine if it has biochemical activities similar to MDM2-FL. Hypothesis: We hypothesized that like MDM2-FL, the MDM2-C isoform (lacking exons 5–9 and containing a full C-terminal RING finger sequence) would maintain E3 ubiquitin ligase activity. Materials and Methods In order to explore the biochemical function of MDM2-C, we used an in vitro ubiquitination assay and a glutaraldehyde cross-linking assay. Results Here we report, for the first time, that MDM2-C has E3 auto-ubiquitin ligase activity, which can promote ubiquitination of wild-type p53 and mutant p53 R273H, and also can form a protein–protein interaction with p53 proteins. Conclusion This information strongly positions MDM2-C as a protein with biochemical activities that may explain the varied outcomes observed in patients with high-level expression of MDM2-C in the presence of wild-type p53 versus mutant p53.
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Affiliation(s)
- Jun Yeob Kim
- The Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Rusia Lee
- The Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA.,Biology PhD Program, The Graduate Center of Biology, City University of New York, New York, NY, USA
| | - Gu Xiao
- The Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Dominique Forbes
- The Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Jill Bargonetti
- The Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA.,Biology PhD Program, The Graduate Center of Biology, City University of New York, New York, NY, USA.,Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10021, USA
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Li W, Peng X, Lang J, Xu C. Targeting Mouse Double Minute 2: Current Concepts in DNA Damage Repair and Therapeutic Approaches in Cancer. Front Pharmacol 2020; 11:631. [PMID: 32477121 PMCID: PMC7232544 DOI: 10.3389/fphar.2020.00631] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 04/21/2020] [Indexed: 01/14/2023] Open
Abstract
Defects in DNA damage repair may cause genome instability and cancer development. The tumor suppressor gene p53 regulates cell cycle arrest to allow time for DNA repair. The oncoprotein mouse double minute 2 (MDM2) promotes cell survival, proliferation, invasion, and therapeutic resistance in many types of cancer. The major role of MDM2 is to inhibit p53 activity and promote its degradation. In this review, we describe the influence of MDM2 on genomic instability, the role of MDM2 on releasing p53 and binding DNA repair proteins to inhibit repair, and the regulation network of MDM2 including its transcriptional modifications, protein stability, and localization following DNA damage in genome integrity maintenance and in MDM2-p53 axis control. We also discuss p53-dependent and p53 independent oncogenic function of MDM2 and the outcomes of clinical trials that have been used with clinical inhibitors targeting p53-MDM2 to treat certain cancers.
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Affiliation(s)
- Wen Li
- Cancer Clinical Research Center & Integrative Cancer Center, Sichuan Cancer Hospital & Institute Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Xinhao Peng
- Cancer Clinical Research Center & Integrative Cancer Center, Sichuan Cancer Hospital & Institute Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.,Radiation Oncology Key Laboratory of Sichuan Province, Sichuan Cancer Hospital & Institute Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Jinyi Lang
- Cancer Clinical Research Center & Integrative Cancer Center, Sichuan Cancer Hospital & Institute Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.,Radiation Oncology Key Laboratory of Sichuan Province, Sichuan Cancer Hospital & Institute Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Chuan Xu
- Cancer Clinical Research Center & Integrative Cancer Center, Sichuan Cancer Hospital & Institute Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
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Gajan A, Martin CE, Kim S, Joshi M, Michelhaugh SK, Sloma I, Mittal S, Firestine S, Shekhar MPV. Alternative Splicing of RAD6B and Not RAD6A is Selectively Increased in Melanoma: Identification and Functional Characterization. Cells 2019; 8:E1375. [PMID: 31683936 PMCID: PMC6912459 DOI: 10.3390/cells8111375] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/28/2019] [Accepted: 10/31/2019] [Indexed: 12/31/2022] Open
Abstract
Rad6B, a principal component of the translesion synthesis pathway, and activator of canonical Wnt signaling, plays an essential role in cutaneous melanoma development and progression. As Rad6 is encoded by two genes, namely, UBE2A (RAD6A) and UBE2B (RAD6B), in humans, we compared their expressions in melanomas and normal melanocytes. While both genes are weakly expressed in normal melanocytes, Rad6B is more robustly expressed in melanoma lines and patient-derived metastatic melanomas than RAD6A. The characterization of RAD6B transcripts revealed coexpression of various splice variants representing truncated or modified functional versions of wild-type RAD6B in melanomas, but not in normal melanocytes. Notably, two RAD6B isoforms with intact catalytic domains, RAD6BΔexon4 and RAD6Bintron5ins, were identified. We confirmed that RAD6BΔexon4 and RAD6Bintron5ins variants are expressed as 14 and 15 kDa proteins, respectively, with functional in vivo ubiquitin conjugating activity. Whole exome sequence analysis of 30 patient-derived melanomas showed RAD6B variants coexpressed with wild-type RAD6B in all samples analyzed, and RAD6Bintron5ins variants were found in half the cases. These variants constitute the majority of the RAD6B transcriptome in contrast to RAD6A, which was predominantly wild-type. The expression of functional RAD6B variants only in melanomas reveals RAD6B's molecular heterogeneity and its association with melanoma pathogenesis.
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Affiliation(s)
- Ambikai Gajan
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Carly E Martin
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Seongho Kim
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Milap Joshi
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Sharon K Michelhaugh
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Ido Sloma
- Champions Oncology, Rockville, MD 20850, USA.
| | - Sandeep Mittal
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Steven Firestine
- Pharmaceutical Sciences, Wayne State University, Detroit, MI 48201, USA.
| | - Malathy P V Shekhar
- Karmanos Cancer Institute, Detroit, MI 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
- Department of Pathology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
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Evaluating dose-limiting toxicities of MDM2 inhibitors in patients with solid organ and hematologic malignancies: A systematic review of the literature. Leuk Res 2019; 86:106222. [PMID: 31522038 DOI: 10.1016/j.leukres.2019.106222] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 08/30/2019] [Accepted: 09/05/2019] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Mouse double minute 2 protein (MDM2), a negative regulator of the p53 tumour suppressor gene, is frequently amplified in malignancies. MDM2 antagonists have shown efficacy in treating malignancies with MDM2 overexpression and can overcome chemoresistance in acute myeloid leukemia. We systematically evaluated the safety profile of MDM2 inhibitors in the treatment of solid organ and hematologic malignancies. MATERIALS AND METHODS We searched Medline and EMBASE from January 1947 to November 2018 for prospective clinical studies, in English or French, investigating any MDM2 inhibitor in pediatric or adult cancers, and reporting dose and toxicity outcomes. Primary outcome was dose-limiting toxicity (DLT) and secondary outcome was death. RESULTS The search yielded 493 non-duplicate citations. Eighteen studies of 10 inhibitors met inclusion criteria (total N = 1005 patients). Two-thirds of included studies did not define DLTs and the reporting of toxicities was highly variable. The most commonly reported DLTs were cytopenias, gastrointestinal toxicity, metabolic disturbances, fatigue and cardiovascular toxicity; there was one death attributed to treatment toxicity. CONCLUSION MDM2 antagonists have been studied in a variety of malignancies with toxicities similar to other commonly used chemotherapy agents and may represent a safe adjuvant treatment for further study in in acute leukemia.
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Coomer AO, Black F, Greystoke A, Munkley J, Elliott DJ. Alternative splicing in lung cancer. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:194388. [PMID: 31152916 DOI: 10.1016/j.bbagrm.2019.05.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 05/20/2019] [Indexed: 12/21/2022]
Abstract
Lung cancer has the highest mortality rate of all cancers worldwide. Lung cancer is a very heterogeneous disease that is often diagnosed at later stages which have a poor prognosis. Aberrant alternative splicing patterns found in lung cancer contribute to important cell functions. These include changes in splicing for the BCL2L1, MDM2, MDM4, NUMB and MET genes during lung tumourigenesis, to affect pathways involved in apoptosis, cell proliferation and cellular cohesion. Global analyses of RNASeq datasets suggest there may be many more potentially influential aberrant splicing events that need to be investigated in lung cancer. Changes in expression of the splicing factors that regulate alternative splicing events have also been identified in lung cancer. Of these, changes in expression of QKI, RBM4, RBM5, RBM6, RBM10 and SRSF1 proteins regulate many of the most frequently referenced aberrant splicing events in lung cancer. The expanding list of genes known to be aberrantly spliced in lung cancer along with the altered expression of splicing factors that regulate them are providing new clues as to how lung cancer develops, and how these events can be exploited for better treatment. This article is part of a Special Issue entitled: RNA structure and splicing regulation edited by Francisco Baralle, Ravindra Singh and Stefan Stamm.
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Affiliation(s)
- Alice O Coomer
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne NE1 3BZ, United Kingdom of Great Britain and Northern Ireland.
| | - Fiona Black
- Cellular Pathology Department, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP, United Kingdom of Great Britain and Northern Ireland
| | - Alastair Greystoke
- Northern Institute for Cancer Research, Paul O'Gorman Building, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom of Great Britain and Northern Ireland
| | - Jennifer Munkley
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne NE1 3BZ, United Kingdom of Great Britain and Northern Ireland
| | - David J Elliott
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne NE1 3BZ, United Kingdom of Great Britain and Northern Ireland.
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Loo LWM, Gao C, Shvetsov YB, Okoro DR, Hernandez BY, Bargonetti J. MDM2, MDM2-C, and mutant p53 expression influence breast cancer survival in a multiethnic population. Breast Cancer Res Treat 2018; 174:257-269. [PMID: 30470976 DOI: 10.1007/s10549-018-5065-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/17/2018] [Indexed: 11/24/2022]
Abstract
PURPOSE The purpose of the study was to examine the association between expression of mutant p53 (mtp53), full-length MDM2 (MDM2), and MDM2 isoform C (MDM2-C) and survival in multiethnic breast cancer patients. METHODS A total of 787 invasive breast tumors included in a clinically annotated multiethnic population-based tissue microarray (TMA) were screened utilizing commercially available antibodies to p53 and MDM2, and a newly developed monoclonal antibody recognizing MDM2-C. RESULTS Mutant p53 (mtp53) was more common in younger (< 50 years) breast cancer patients. Among the 787 cases included in the study, mtp53, MDM2, and MDM2-C expression were not significantly associated with risk of overall or breast cancer-specific mortality. However when associations within individual racial/ethnic groups (White, Japanese, and Native Hawaiian) were examined, expression of MDM2-C was found to be associated with lower risk of breast cancer-specific mortality exclusively for White patients HR 0.32, 95% CI 0.15-0.69 and mtp53 expression was associated with higher overall mortality in Japanese patients (HR 1.63, 95% CI 1.02-2.59). Also, Japanese patients positive for the joint expression of MDM2-C and mtp53 had a greater than twofold risk of overall mortality (HR 2.15, 95% CI 1.04-4.48); and White patients with positive MDM2-C and wild-type p53 expression (HR 0.28, 95% CI 0.08-0.96) were at lower risk of mortality when compared to patients with negative MDM2-C and wild-type p53 expression in their respective racial/ethnic group. CONCLUSION Racial/ethnic differences in expression profiles of mtp53, MDM2, and MDM2-C and associations with breast cancer-specific and overall mortality. MDM2-C may have a positive or negative role in breast tumorigenesis depending on mtp53 expression.
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Affiliation(s)
- Lenora W M Loo
- Cancer Epidemiology Program, University of Hawaii Cancer Center, Honolulu, HI, USA.
| | - Chong Gao
- Department of Biological Sciences Hunter College, The Graduate Center Departments of Biology and Biochemistry, City University of New York, New York, NY, 10016, USA
| | - Yurii B Shvetsov
- Cancer Epidemiology Program, University of Hawaii Cancer Center, Honolulu, HI, USA
| | - Danielle R Okoro
- Department of Biological Sciences Hunter College, The Graduate Center Departments of Biology and Biochemistry, City University of New York, New York, NY, 10016, USA
| | - Brenda Y Hernandez
- Cancer Epidemiology Program, University of Hawaii Cancer Center, Honolulu, HI, USA
| | - Jill Bargonetti
- Department of Biological Sciences Hunter College, The Graduate Center Departments of Biology and Biochemistry, City University of New York, New York, NY, 10016, USA
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Lymphomas driven by Epstein-Barr virus nuclear antigen-1 (EBNA1) are dependant upon Mdm2. Oncogene 2018; 37:3998-4012. [PMID: 29691476 PMCID: PMC6054874 DOI: 10.1038/s41388-018-0147-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 12/07/2017] [Accepted: 12/19/2017] [Indexed: 12/22/2022]
Abstract
Epstein-Barr virus (EBV) associated Burkitt’s lymphoma is characterised by the deregulation of c-Myc expression and a restricted viral gene expression pattern in which the EBV nuclear antigen-1 (EBNA1) is the only viral protein to be consistently expressed. EBNA1 is required for viral genome propagation and segregation during latency. However, it has been much debated whether the protein plays a role in viral-associated tumourigenesis. We show that the lymphomas which arise in EµEBNA1 transgenic mice are unequivocally linked to EBNA1 expression and that both C-Myc and Mdm2 deregulation are central to this process. Tumour cell survival is supported by IL-2 and there is a skew towards CD8 positive T-cells in the tumour environment, while the immune check-point protein PD-L1 is upregulated in the tumours. Additionally, several isoforms of Mdm2 are upregulated in the EµEBNA1 tumours, with increased phosphorylation at ser166, an expression pattern not seen in Eµc-Myc transgenic tumours. Concomitantly, E2F1, Xiap, Mta1, C-Fos and Stat1 are upregulated in the tumours. Using four independent inhibitors of Mdm2 we demonstrate that the EµEBNA1 tumour cells are dependant upon Mdm2 for survival (as they are upon c-Myc) and that Mdm2 inhibition is not accompanied by upregulation of p53, instead cell death is linked to loss of E2F1 expression, providing new insight into the underlying tumourigenic mechanism. This opens a new path to combat EBV-associated disease.
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Saadatzadeh MR, Elmi AN, Pandya PH, Bijangi-Vishehsaraei K, Ding J, Stamatkin CW, Cohen-Gadol AA, Pollok KE. The Role of MDM2 in Promoting Genome Stability versus Instability. Int J Mol Sci 2017; 18:ijms18102216. [PMID: 29065514 PMCID: PMC5666895 DOI: 10.3390/ijms18102216] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 10/06/2017] [Accepted: 10/11/2017] [Indexed: 02/07/2023] Open
Abstract
In cancer, the mouse double minute 2 (MDM2) is an oncoprotein that contributes to the promotion of cell growth, survival, invasion, and therapeutic resistance. The impact of MDM2 on cell survival versus cell death is complex and dependent on levels of MDM2 isoforms, p53 status, and cellular context. Extensive investigations have demonstrated that MDM2 protein–protein interactions with p53 and other p53 family members (p63 and p73) block their ability to function as transcription factors that regulate cell growth and survival. Upon genotoxic insults, a dynamic and intricately regulated DNA damage response circuitry is activated leading to release of p53 from MDM2 and activation of cell cycle arrest. What ensues following DNA damage, depends on the extent of DNA damage and if the cell has sufficient DNA repair capacity. The well-known auto-regulatory loop between p53-MDM2 provides an additional layer of control as the cell either repairs DNA damage and survives (i.e., MDM2 re-engages with p53), or undergoes cell death (i.e., MDM2 does not re-engage p53). Furthermore, the decision to live or die is also influenced by chromatin-localized MDM2 which directly interacts with the Mre11-Rad50-Nbs1 complex and inhibits DNA damage-sensing giving rise to the potential for increased genome instability and cellular transformation.
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Affiliation(s)
- M Reza Saadatzadeh
- Department of Pediatrics (Division of Hematology/Oncology), Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University Simon Cancer Center, 1044 West Walnut Street R4 302, Indianapolis, IN 46202-5525, USA.
| | - Adily N Elmi
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
| | - Pankita H Pandya
- Department of Pediatrics (Division of Hematology/Oncology), Indianapolis, IN 46202, USA.
| | | | - Jixin Ding
- Department of Pediatrics (Division of Hematology/Oncology), Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University Simon Cancer Center, 1044 West Walnut Street R4 302, Indianapolis, IN 46202-5525, USA.
| | - Christopher W Stamatkin
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University Simon Cancer Center, 1044 West Walnut Street R4 302, Indianapolis, IN 46202-5525, USA.
| | | | - Karen E Pollok
- Department of Pediatrics (Division of Hematology/Oncology), Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
- Herman B. Wells Center for Pediatric Research, Indiana University Simon Cancer Center, 1044 West Walnut Street R4 302, Indianapolis, IN 46202-5525, USA.
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11
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Alternative splicing and cell survival: from tissue homeostasis to disease. Cell Death Differ 2016; 23:1919-1929. [PMID: 27689872 DOI: 10.1038/cdd.2016.91] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 05/26/2016] [Accepted: 07/15/2016] [Indexed: 12/17/2022] Open
Abstract
Most human genes encode multiple mRNA variants and protein products through alternative splicing of exons and introns during pre-mRNA processing. In this way, alternative splicing amplifies enormously the coding potential of the human genome and represents a powerful evolutionary resource. Nonetheless, the plasticity of its regulation is prone to errors and defective splicing underlies a large number of inherited and sporadic diseases, including cancer. One key cellular process affected by alternative splicing is the programmed cell death or apoptosis. Many apoptotic genes encode for splice variants having opposite roles in cell survival. This regulation modulates cell and tissue homeostasis and is implicated in both developmental and pathological processes. Furthermore, recent evidence has also unveiled splicing-mediated regulation of genes involved in autophagy, another essential process for tissue homeostasis. In this review, we highlight some of the best-known examples of alternative splicing events involved in cell survival. Emphasis is given to the role of this regulation in human cancer and in the response to chemotherapy, providing examples of how alternative splicing of apoptotic genes can be exploited therapeutically.
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Kozlov AP. Expression of evolutionarily novel genes in tumors. Infect Agent Cancer 2016; 11:34. [PMID: 27437030 PMCID: PMC4949931 DOI: 10.1186/s13027-016-0077-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 05/18/2016] [Indexed: 01/29/2023] Open
Abstract
The evolutionarily novel genes originated through different molecular mechanisms are expressed in tumors. Sometimes the expression of evolutionarily novel genes in tumors is highly specific. Moreover positive selection of many human tumor-related genes in primate lineage suggests their involvement in the origin of new functions beneficial to organisms. It is suggested to consider the expression of evolutionarily young or novel genes in tumors as a new biological phenomenon, a phenomenon of TSEEN (tumor specifically expressed, evolutionarily novel) genes.
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Affiliation(s)
- A. P. Kozlov
- The Biomedical Center and Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
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Inoue K, Fry EA. Aberrant splicing of the DMP1-ARF-MDM2-p53 pathway in cancer. Int J Cancer 2016; 139:33-41. [PMID: 26802432 PMCID: PMC5047959 DOI: 10.1002/ijc.30003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 01/01/2016] [Indexed: 12/11/2022]
Abstract
Alternative splicing (AS) of mRNA precursors is a ubiquitous mechanism for generating numerous transcripts with different activities from one genomic locus in mammalian cells. The gene products from a single locus can thus have similar, dominant-negative or even opposing functions. Aberrant AS has been found in cancer to express proteins that promote cell growth, local invasion and metastasis. This review will focus on the aberrant splicing of tumor suppressor/oncogenes that belong to the DMP1-ARF-MDM2-p53 pathway. Our recent study shows that the DMP1 locus generates both tumor-suppressive DMP1α (p53-dependent) and oncogenic DMP1β (p53-independent) splice variants, and the DMP1β/α ratio increases with neoplastic transformation of breast epithelial cells. This process is associated with high DMP1β protein expression and shorter survival of breast cancer (BC) patients. Accumulating pieces of evidence show that ARF is frequently inactivated by aberrant splicing in human cancers, demonstrating its involvement in human malignancies. Splice variants from the MDM2 locus promote cell growth in culture and accelerate tumorigenesis in vivo. Human cancers expressing these splice variants are associated with advanced stage/metastasis, and thus have negative clinical impacts. Although they lack most of the p53-binding domain, their activities are mostly dependent on p53 since they bind to wild-type MDM2. The p53 locus produces splice isoforms that have either favorable (β/γ at the C-terminus) or negative impact (Δ40, Δ133 at the N-terminus) on patients' survival. As the oncogenic AS products from these loci are expressed only in cancer cells, they may eventually become targets for molecular therapies.
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Affiliation(s)
- Kazushi Inoue
- The Department of Pathology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157 USA
| | - Elizabeth A. Fry
- The Department of Pathology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157 USA
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Rosso M, Polotskaia A, Bargonetti J. Homozygous mdm2 SNP309 cancer cells with compromised transcriptional elongation at p53 target genes are sensitive to induction of p53-independent cell death. Oncotarget 2015; 6:34573-91. [PMID: 26416444 PMCID: PMC4741474 DOI: 10.18632/oncotarget.5312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 09/07/2015] [Indexed: 11/25/2022] Open
Abstract
A single nucleotide polymorphism (T to G) in the mdm2 P2 promoter, mdm2 SNP309, leads to MDM2 overexpression promoting chemotherapy resistant cancers. Two mdm2 G/G SNP309 cancer cell lines, MANCA and A875, have compromised wild-type p53 that co-localizes with MDM2 on chromatin. We hypothesized that MDM2 in these cells inhibited transcription initiation at the p53 target genes p21 and puma. Surprisingly, following etoposide treatment transcription initiation occurred at the compromised target genes in MANCA and A875 cells similar to the T/T ML-1 cell line. In all cell lines tested there was equally robust recruitment of total and initiated RNA polymerase II (Pol II). We found that knockdown of MDM2 in G/G cells moderately increased expression of subsets of p53 target genes without increasing p53 stability. Importantly, etoposide and actinomycin D treatments increased histone H3K36 trimethylation in T/T, but not G/G cells, suggesting a G/G correlated inhibition of transcription elongation. We therefore tested a chemotherapeutic agent (8-amino-adenosine) that induces p53-independent cell death for higher clinically relevant cytotoxicity. We demonstrated that T/T and G/G mdm2 SNP309 cells were equally sensitive to 8-amino-adenosine induced cell death. In conclusion for cancer cells overexpressing MDM2, targeting MDM2 may be less effective than inducing p53-independent cell death.
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Affiliation(s)
- Melissa Rosso
- The Department of Biological Sciences Hunter College at The Belfer Research Building and The Graduate Center Biology PhD Program, CUNY, New York, NY 10021, USA
| | - Alla Polotskaia
- The Department of Biological Sciences Hunter College at The Belfer Research Building and The Graduate Center Biology PhD Program, CUNY, New York, NY 10021, USA
| | - Jill Bargonetti
- The Department of Biological Sciences Hunter College at The Belfer Research Building and The Graduate Center Biology PhD Program, CUNY, New York, NY 10021, USA
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