1
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Li AX, Martin TA, Lane J, Jiang WG. Cellular Impacts of Striatins and the STRIPAK Complex and Their Roles in the Development and Metastasis in Clinical Cancers (Review). Cancers (Basel) 2023; 16:76. [PMID: 38201504 PMCID: PMC10777921 DOI: 10.3390/cancers16010076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/18/2023] [Accepted: 12/20/2023] [Indexed: 01/12/2024] Open
Abstract
Striatins (STRNs) are generally considered to be cytoplasmic proteins, with lower expression observed in the nucleus and at cell-cell contact regions. Together with protein phosphatase 2A (PP2A), STRNs form the core region of striatin-interacting phosphatase and kinase (STRIPAK) complexes through the coiled-coil region of STRN proteins, which is crucial for substrate recruitment. Over the past two decades, there has been an increasing amount of research into the biological and cellular functions of STRIPAK members. STRNs and the constituent members of the STRIPAK complex have been found to regulate several cellular functions, such as cell cycle control, cell growth, and motility. Dysregulation of these cellular events is associated with cancer development. Importantly, their roles in cancer cells and clinical cancers are becoming recognised, with several STRIPAK components found to have elevated expression in cancerous tissues compared to healthy tissues. These molecules exhibit significant diagnostic and prognostic value across different cancer types and in metastatic progression. The present review comprehensively summarises and discusses the current knowledge of STRNs and core STRIPAK members, in cancer malignancy, from both cellular and clinical perspectives.
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Affiliation(s)
| | - Tracey A. Martin
- Cardiff China Medical Research Collaborative, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK; (A.X.L.); (J.L.); (W.G.J.)
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2
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Denisova OV, Merisaari J, Huhtaniemi R, Qiao X, Yetukuri L, Jumppanen M, Kaur A, Pääkkönen M, von Schantz‐Fant С, Ohlmeyer M, Wennerberg K, Kauko O, Koch R, Aittokallio T, Taipale M, Westermarck J. PP2A-based triple-strike therapy overcomes mitochondrial apoptosis resistance in brain cancer cells. Mol Oncol 2023; 17:1803-1820. [PMID: 37458534 PMCID: PMC10483611 DOI: 10.1002/1878-0261.13488] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 05/08/2023] [Accepted: 07/13/2023] [Indexed: 07/27/2023] Open
Abstract
Mitochondrial glycolysis and hyperactivity of the phosphatidylinositol 3-kinase-protein kinase B (AKT) pathway are hallmarks of malignant brain tumors. However, kinase inhibitors targeting AKT (AKTi) or the glycolysis master regulator pyruvate dehydrogenase kinase (PDKi) have failed to provide clinical benefits for brain tumor patients. Here, we demonstrate that heterogeneous glioblastoma (GB) and medulloblastoma (MB) cell lines display only cytostatic responses to combined AKT and PDK targeting. Biochemically, the combined AKT and PDK inhibition resulted in the shutdown of both target pathways and priming to mitochondrial apoptosis but failed to induce apoptosis. In contrast, all tested brain tumor cell models were sensitive to a triplet therapy, in which AKT and PDK inhibition was combined with the pharmacological reactivation of protein phosphatase 2A (PP2A) by NZ-8-061 (also known as DT-061), DBK-1154, and DBK-1160. We also provide proof-of-principle evidence for in vivo efficacy in the intracranial GB and MB models by the brain-penetrant triplet therapy (AKTi + PDKi + PP2A reactivator). Mechanistically, PP2A reactivation converted the cytostatic AKTi + PDKi response to cytotoxic apoptosis, through PP2A-elicited shutdown of compensatory mitochondrial oxidative phosphorylation and by increased proton leakage. These results encourage the development of triple-strike strategies targeting mitochondrial metabolism to overcome therapy tolerance in brain tumors.
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Affiliation(s)
- Oxana V. Denisova
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | - Joni Merisaari
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
- Institute of BiomedicineUniversity of TurkuFinland
| | - Riikka Huhtaniemi
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | - Xi Qiao
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | - Laxman Yetukuri
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
- Institute for Molecular Medicine Finland (FIMM), HiLIFEUniversity of HelsinkiFinland
- Centre for Biostatistics and Epidemiology (OCBE)University of OsloNorway
| | - Mikael Jumppanen
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | - Amanpreet Kaur
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | - Mirva Pääkkönen
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | | | - Michael Ohlmeyer
- Icahn School of Medicine at Mount SinaiNew YorkNYUSA
- Atux Iskay LLCPlainsboroNJUSA
| | - Krister Wennerberg
- Institute for Molecular Medicine Finland (FIMM), HiLIFEUniversity of HelsinkiFinland
- Biotech Research & Innovation CentreUniversity of CopenhagenDenmark
| | - Otto Kauko
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
| | | | - Tero Aittokallio
- Institute for Molecular Medicine Finland (FIMM), HiLIFEUniversity of HelsinkiFinland
- Centre for Biostatistics and Epidemiology (OCBE)University of OsloNorway
- Institute for Cancer ResearchOslo University HospitalNorway
| | - Mikko Taipale
- Donnelly Centre for Cellular and Biomolecular ResearchUniversity of TorontoCanada
| | - Jukka Westermarck
- Turku Bioscience CentreUniversity of Turku and Åbo Akademi UniversityFinland
- Institute of BiomedicineUniversity of TurkuFinland
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3
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Merkel Cell Polyomavirus: Infection, Genome, Transcripts and Its Role in Development of Merkel Cell Carcinoma. Cancers (Basel) 2023; 15:cancers15020444. [PMID: 36672392 PMCID: PMC9857234 DOI: 10.3390/cancers15020444] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/23/2022] [Accepted: 12/27/2022] [Indexed: 01/13/2023] Open
Abstract
The best characterized polyomavirus family member, i.e., simian virus 40 (SV40), can cause different tumors in hamsters and can transform murine and human cells in vitro. Hence, the SV40 contamination of millions of polio vaccine doses administered from 1955-1963 raised fears that this may cause increased tumor incidence in the vaccinated population. This is, however, not the case. Indeed, up to now, the only polyomavirus family member known to be the most important cause of a specific human tumor entity is Merkel cell polyomavirus (MCPyV) in Merkel cell carcinoma (MCC). MCC is a highly deadly form of skin cancer for which the cellular origin is still uncertain, and which appears as two clinically very similar but molecularly highly different variants. While approximately 80% of cases are found to be associated with MCPyV the remaining MCCs carry a high mutational load. Here, we present an overview of the multitude of molecular functions described for the MCPyV encoded oncoproteins and non-coding RNAs, present the available MCC mouse models and discuss the increasing evidence that both, virus-negative and -positive MCC constitute epithelial tumors.
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4
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Zandi M, Shokri S, Mahmoudvand S, Hosseinzadeh Adli A, Mohammadi R, Haddadi A. Interplay between cellular metabolism and DNA viruses. J Med Virol 2022; 94:5163-5173. [PMID: 35869415 DOI: 10.1002/jmv.28018] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 07/15/2022] [Accepted: 07/21/2022] [Indexed: 12/15/2022]
Abstract
Viruses as intracellular pathogens take over the host metabolism and reprogram to facilitate optimal virus production. DNA viruses can cause alterations in several metabolic pathways, including aerobic glycolysis also known as the Warburg effect, pentose phosphate pathway activation, and amino acid catabolism such as glutaminolysis, nucleotide biosynthesis, lipid metabolism, and amino acid biosynthesis. The available energy for productive infection can be increased in infected cells via modification of different carbon source utilization. This review discusses the metabolic alterations of the DNA viruses that will be the basis for future novel therapeutic approaches.
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Affiliation(s)
- Milad Zandi
- Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Somayeh Shokri
- Research Center for Molecular Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.,Department of Medical Virology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Shahab Mahmoudvand
- Research Center for Molecular Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.,Department of Medical Virology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Ahmad Hosseinzadeh Adli
- Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Department of Bacteriology and Virology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Ramin Mohammadi
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Azita Haddadi
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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5
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Moens U, Prezioso C, Pietropaolo V. Functional Domains of the Early Proteins and Experimental and Epidemiological Studies Suggest a Role for the Novel Human Polyomaviruses in Cancer. Front Microbiol 2022; 13:834368. [PMID: 35250950 PMCID: PMC8894888 DOI: 10.3389/fmicb.2022.834368] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 01/31/2022] [Indexed: 11/13/2022] Open
Abstract
As their name indicates, polyomaviruses (PyVs) can induce tumors. Mouse PyV, hamster PyV and raccoon PyV have been shown to cause tumors in their natural host. During the last 30 years, 15 PyVs have been isolated from humans. From these, Merkel cell PyV is classified as a Group 2A carcinogenic pathogen (probably carcinogenic to humans), whereas BKPyV and JCPyV are class 2B (possibly carcinogenic to humans) by the International Agency for Research on Cancer. Although the other PyVs recently detected in humans (referred to here as novel HPyV; nHPyV) share many common features with PyVs, including the viral oncoproteins large tumor antigen and small tumor antigen, as their role in cancer is questioned. This review discusses whether the nHPyVs may play a role in cancer based on predicted and experimentally proven functions of their early proteins in oncogenic processes. The functional domains that mediate the oncogenic properties of early proteins of known PyVs, that can cause cancer in their natural host or animal models, have been well characterized and we examined whether these functional domains are conserved in the early proteins of the nHPyVs and presented experimental evidence that these conserved domains are functional. Furthermore, we reviewed the literature describing the detection of nHPyV in human tumors.
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Affiliation(s)
- Ugo Moens
- Faculty of Health Sciences, Department of Medical Biology, University of Tromsø – The Arctic University of Norway, Tromsø, Norway
- *Correspondence: Ugo Moens,
| | - Carla Prezioso
- Microbiology of Chronic Neuro-Degenerative Pathologies, IRCSS San Raffaele Roma, Rome, Italy
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy
| | - Valeria Pietropaolo
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy
- Valeria Pietropaolo,
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6
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Merkel cell polyomavirus small tumour antigen activates the p38 MAPK pathway to enhance cellular motility. Biochem J 2021; 477:2721-2733. [PMID: 32639530 PMCID: PMC7398664 DOI: 10.1042/bcj20200399] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 12/26/2022]
Abstract
Merkel cell carcinoma (MCC) is an aggressive skin cancer with high rates of recurrence and metastasis. Merkel cell polyomavirus (MCPyV) is associated with the majority of MCC cases. MCPyV-induced tumourigenesis is largely dependent on the expression of the small tumour antigen (ST). Recent findings implicate MCPyV ST expression in the highly metastatic nature of MCC by promoting cell motility and migration, through differential expression of cellular proteins that lead to microtubule destabilisation, filopodium formation and breakdown of cell-cell junctions. However, the molecular mechanisms which dysregulate these cellular processes are yet to be fully elucidated. Here, we demonstrate that MCPyV ST expression activates p38 MAPK signalling to drive cell migration and motility. Notably, MCPyV ST-mediated p38 MAPK signalling occurs through MKK4, as opposed to the canonical MKK3/6 signalling pathway. In addition, our results indicate that an interaction between MCPyV ST and the cellular phospatase subunit PP4C is essential for its effect on p38 MAPK signalling. These results provide novel opportunities for the treatment of metastatic MCC given the intense interest in p38 MAPK inhibitors as therapeutic agents.
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7
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Wei H, Zhang HL, Wang XC, Xie JZ, An DD, Wan L, Wang JZ, Zeng Y, Shu XJ, Westermarck J, Lu YM, Ohlmeyer M, Liu R. Direct Activation of Protein Phosphatase 2A (PP2A) by Tricyclic Sulfonamides Ameliorates Alzheimer's Disease Pathogenesis in Cell and Animal Models. Neurotherapeutics 2020; 17:1087-1103. [PMID: 32096091 PMCID: PMC7609734 DOI: 10.1007/s13311-020-00841-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Alzheimer's disease (AD) is a multifactorial neurodegenerative disease for which there are limited therapeutic strategies. Protein phosphatase 2A (PP2A) activity is decreased in AD brains, which promotes the hyperphosphorylation of Tau and APP, thus participate in the formation of neurofibrillary tangles (NFTs) and β-amyloid (Aβ) overproduction. In this study, the effect of synthetic tricyclic sulfonamide PP2A activators (aka SMAPs) on reducing AD-like pathogenesis was evaluated in AD cell models and AD-like hyperhomocysteinemia (HHcy) rat models. SMAPs effectively increased PP2A activity, and decreased tau phosphorylation and Aβ40/42 levels in AD cell models. In HHcy-AD rat models, cognitive impairments induced by HHcy were rescued by SMAP administration. HHcy-induced tau hyperphosphorylation and Aβ overproduction were ameliorated through increasing PP2A activity on compound treatment. Importantly, SMAP therapy also prevented neuronal cell spine loss and neuronal synapse impairment in the hippocampus of HHcy-AD rats. In summary, our data reveal that pharmacological PP2A reactivation may be a novel therapeutic strategy for AD treatment, and that the tricyclic sulfonamides constitute a novel candidate class of AD therapeutic.
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Affiliation(s)
- Hui Wei
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hui-Liang Zhang
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiao-Chuan Wang
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jia-Zhao Xie
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Dan-Dan An
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lu Wan
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian-Zhi Wang
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yi Zeng
- Clinical Laboratory, The Central Hospital of Wuhan, Wuhan, China
| | - Xi-Ji Shu
- Department of Pathology and Pathophysiology, School of Medicine, Jianghan University, Wuhan, China
| | - Jukka Westermarck
- Turku Bioscience Centre, University of Turku and Åbo Akademi University, Turku, Finland
- Institute of Biomedicine, University of Turku, Turku, Finland
| | - You-Ming Lu
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Michael Ohlmeyer
- Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Atux Iskay LLC, Plainsboro, NJ, USA.
| | - Rong Liu
- Department of Pathophysiology, Key Laboratory of Ministry of Education for Neurological Disorders, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China.
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8
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Kim JW, Berrios C, Kim M, Schade AE, Adelmant G, Yeerna H, Damato E, Iniguez AB, Florens L, Washburn MP, Stegmaier K, Gray NS, Tamayo P, Gjoerup O, Marto JA, DeCaprio J, Hahn WC. STRIPAK directs PP2A activity toward MAP4K4 to promote oncogenic transformation of human cells. eLife 2020; 9:53003. [PMID: 31913126 PMCID: PMC6984821 DOI: 10.7554/elife.53003] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/07/2020] [Indexed: 12/13/2022] Open
Abstract
Alterations involving serine-threonine phosphatase PP2A subunits occur in a range of human cancers, and partial loss of PP2A function contributes to cell transformation. Displacement of regulatory B subunits by the SV40 Small T antigen (ST) or mutation/deletion of PP2A subunits alters the abundance and types of PP2A complexes in cells, leading to transformation. Here, we show that ST not only displaces common PP2A B subunits but also promotes A-C subunit interactions with alternative B subunits (B’’’, striatins) that are components of the Striatin-interacting phosphatase and kinase (STRIPAK) complex. We found that STRN4, a member of STRIPAK, is associated with ST and is required for ST-PP2A-induced cell transformation. ST recruitment of STRIPAK facilitates PP2A-mediated dephosphorylation of MAP4K4 and induces cell transformation through the activation of the Hippo pathway effector YAP1. These observations identify an unanticipated role of MAP4K4 in transformation and show that the STRIPAK complex regulates PP2A specificity and activity. Cells maintain a fine balance of signals that promote or counter cell growth and division. Two sets of enzymes – called kinases and phosphatases – contribute to this balance. In general, kinases “switch on” other proteins by tagging them with a phosphate molecule. This process is called phosphorylation. Phosphatases, on the other hand, dephosphorylate these proteins, switching them off. Cancer cells often have mutations that activate kinases to drive cancer growth. The same cells can have mutations that inactivate the phosphatases or reduce their abundance. The roles of phosphatases in cancer are still being studied. One major hurdle in this research is that it is not always clear how they recognize the proteins they dephosphorylate. Protein phosphatase 2A (or PP2A for short) is one of the phosphatases that is often mutated or deleted in human cancers. Even just reduced levels of PP2A can promote cancer. Kim, Berrios, Kim, Schade et al. used an experimental trick to decrease the phosphatase activity of PP2A in human cells growing in a dish. Biochemical analysis of these cells showed that, as expected, many proteins were now in their phosphorylated states. Unexpectedly, however, some proteins were dephosphorylated under these conditions. One of these proteins was called MAP4K4. In the case of MAP4K4, the dephosphorylated state contributes to the growth of the cancer cell. Kim et al. carried out further genetic and biochemical experiments to show that, in these cells, PP2A and MAP4K4 stay physically connected to one another. This connection was enabled by a group of proteins called the STRIPAK complex. The STRIPAK proteins directed the remaining PP2A towards MAP4K4. Low levels or activity of PP2A could, therefore, promote cancer in a different way. Taken together, PP2A is not a single phosphatase that always turns proteins off, but rather is a dual switch that turns off some proteins while turning on others. Future experiments will explore to what extent these findings also apply in tumors. Information about how mutations in PP2A affect human cancers could suggest new targets for cancer drugs.
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Affiliation(s)
- Jong Wook Kim
- Broad Institute of Harvard and MIT, Cambridge, United States.,Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States.,Division of Medical Genetics, School of Medicine, University of California, San Diego, San Diego, United States.,Moores Cancer Center, University of California, San Diego, San Diego, United States
| | - Christian Berrios
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States.,Program in Virology, Graduate School of Arts and Sciences, Harvard University, Cambridge, United States
| | - Miju Kim
- Broad Institute of Harvard and MIT, Cambridge, United States.,Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States
| | - Amy E Schade
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States.,Program in Virology, Graduate School of Arts and Sciences, Harvard University, Cambridge, United States
| | - Guillaume Adelmant
- Department of Cancer Biology and Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, United States.,Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, United States.,Department of Oncologic Pathology, Dana-Farber Cancer Institute, Boston, United States
| | - Huwate Yeerna
- Division of Medical Genetics, School of Medicine, University of California, San Diego, San Diego, United States
| | - Emily Damato
- Broad Institute of Harvard and MIT, Cambridge, United States
| | - Amanda Balboni Iniguez
- Broad Institute of Harvard and MIT, Cambridge, United States.,Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, United States
| | - Laurence Florens
- Stowers Institute for Medical Research, Kansas City, United States
| | - Michael P Washburn
- Stowers Institute for Medical Research, Kansas City, United States.,Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, United States
| | - Kim Stegmaier
- Broad Institute of Harvard and MIT, Cambridge, United States.,Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, United States
| | - Nathanael S Gray
- Department of Cancer Biology and Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, United States
| | - Pablo Tamayo
- Division of Medical Genetics, School of Medicine, University of California, San Diego, San Diego, United States.,Moores Cancer Center, University of California, San Diego, San Diego, United States
| | - Ole Gjoerup
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States
| | - Jarrod A Marto
- Department of Cancer Biology and Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, United States.,Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, United States.,Department of Oncologic Pathology, Dana-Farber Cancer Institute, Boston, United States
| | - James DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States.,Program in Virology, Graduate School of Arts and Sciences, Harvard University, Cambridge, United States.,Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, United States
| | - William C Hahn
- Broad Institute of Harvard and MIT, Cambridge, United States.,Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, United States.,Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, United States
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9
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Perl AL, O'Connor CM, Fa P, Mayca Pozo F, Zhang J, Zhang Y, Narla G. Protein phosphatase 2A controls ongoing DNA replication by binding to and regulating cell division cycle 45 (CDC45). J Biol Chem 2019; 294:17043-17059. [PMID: 31562245 DOI: 10.1074/jbc.ra119.010432] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/20/2019] [Indexed: 11/06/2022] Open
Abstract
Genomic replication is a highly regulated process and represents both a potential benefit and liability to rapidly dividing cells; however, the precise post-translational mechanisms regulating genomic replication are incompletely understood. Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that regulates a diverse array of cellular processes. Here, utilizing both a gain-of-function chemical biology approach and loss-of-function genetic approaches to modulate PP2A activity, we found that PP2A regulates DNA replication. We demonstrate that increased PP2A activity can interrupt ongoing DNA replication, resulting in a prolonged S phase. The impaired replication resulted in a collapse of replication forks, inducing dsDNA breaks, homologous recombination, and a PP2A-dependent replication stress response. Additionally, we show that during replication, PP2A exists in complex with cell division cycle 45 (CDC45) and that increased PP2A activity caused dissociation of CDC45 and polymerase α from the replisome. Furthermore, we found that individuals harboring mutations in the PP2A Aα gene have a higher fraction of genomic alterations, suggesting that PP2A regulates ongoing replication as a mechanism for maintaining genomic integrity. These results reveal a new function for PP2A in regulating ongoing DNA replication and a potential role for PP2A in the intra-S-phase checkpoint.
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Affiliation(s)
- Abbey L Perl
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Caitlin M O'Connor
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Pengyan Fa
- Department of Radiation Oncology, Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, Ohio 43210
| | - Franklin Mayca Pozo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Junran Zhang
- Department of Radiation Oncology, Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, Ohio 43210
| | - Youwei Zhang
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Goutham Narla
- Department of Internal Medicine, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 .,Department of Internal Medicine, Division of Genetic Medicine, University of Michigan, Ann Arbor, Michigan 48105
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10
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Clark AR, Ohlmeyer M. Protein phosphatase 2A as a therapeutic target in inflammation and neurodegeneration. Pharmacol Ther 2019; 201:181-201. [PMID: 31158394 PMCID: PMC6700395 DOI: 10.1016/j.pharmthera.2019.05.016] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 05/29/2019] [Indexed: 12/11/2022]
Abstract
Protein phosphatase 2A (PP2A) is a highly complex heterotrimeric enzyme that catalyzes the selective removal of phosphate groups from protein serine and threonine residues. Emerging evidence suggests that it functions as a tumor suppressor by constraining phosphorylation-dependent signalling pathways that regulate cellular transformation and metastasis. Therefore, PP2A-activating drugs (PADs) are being actively sought and investigated as potential novel anti-cancer treatments. Here we explore the concept that PP2A also constrains inflammatory responses through its inhibitory effects on various signalling pathways, suggesting that PADs may be effective in the treatment of inflammation-mediated pathologies.
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Affiliation(s)
- Andrew R Clark
- Institute of Inflammation and Ageing, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom.
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11
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Umesalma S, Kaemmer CA, Kohlmeyer JL, Letney B, Schab AM, Reilly JA, Sheehy RM, Hagen J, Tiwari N, Zhan F, Leidinger MR, O'Dorisio TM, Dillon J, Merrill RA, Meyerholz DK, Perl AL, Brown BJ, Braun TA, Scott AT, Ginader T, Taghiyev AF, Zamba GK, Howe JR, Strack S, Bellizzi AM, Narla G, Darbro BW, Quelle FW, Quelle DE. RABL6A inhibits tumor-suppressive PP2A/AKT signaling to drive pancreatic neuroendocrine tumor growth. J Clin Invest 2019; 129:1641-1653. [PMID: 30721156 DOI: 10.1172/jci123049] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 01/24/2019] [Indexed: 12/15/2022] Open
Abstract
Hyperactivated AKT/mTOR signaling is a hallmark of pancreatic neuroendocrine tumors (PNETs). Drugs targeting this pathway are used clinically, but tumor resistance invariably develops. A better understanding of factors regulating AKT/mTOR signaling and PNET pathogenesis is needed to improve current therapies. We discovered that RABL6A, a new oncogenic driver of PNET proliferation, is required for AKT activity. Silencing RABL6A caused PNET cell-cycle arrest that coincided with selective loss of AKT-S473 (not T308) phosphorylation and AKT/mTOR inactivation. Restoration of AKT phosphorylation rescued the G1 phase block triggered by RABL6A silencing. Mechanistically, loss of AKT-S473 phosphorylation in RABL6A-depleted cells was the result of increased protein phosphatase 2A (PP2A) activity. Inhibition of PP2A restored phosphorylation of AKT-S473 in RABL6A-depleted cells, whereas PP2A reactivation using a specific small-molecule activator of PP2A (SMAP) abolished that phosphorylation. Moreover, SMAP treatment effectively killed PNET cells in a RABL6A-dependent manner and suppressed PNET growth in vivo. The present work identifies RABL6A as a new inhibitor of the PP2A tumor suppressor and an essential activator of AKT in PNET cells. Our findings offer what we believe is a novel strategy of PP2A reactivation for treatment of PNETs as well as other human cancers driven by RABL6A overexpression and PP2A inactivation.
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Affiliation(s)
| | | | | | | | | | | | - Ryan M Sheehy
- Department of Pharmacology.,Free Radical & Radiation Biology Training Program
| | | | | | | | - Mariah R Leidinger
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | - David K Meyerholz
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | - Abbey L Perl
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | | | | | | | | | - Agshin F Taghiyev
- Pediatrics, Colleges of Medicine, Engineering, or Public Health, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | - Andrew M Bellizzi
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | - Goutham Narla
- Department of Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Benjamin W Darbro
- Pediatrics, Colleges of Medicine, Engineering, or Public Health, University of Iowa, Iowa City, Iowa, USA
| | | | - Dawn E Quelle
- Department of Pharmacology.,Molecular Medicine Graduate Program.,Free Radical & Radiation Biology Training Program.,Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
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12
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Targeting SET to restore PP2A activity disrupts an oncogenic CIP2A-feedforward loop and impairs triple negative breast cancer progression. EBioMedicine 2019; 40:263-275. [PMID: 30651219 PMCID: PMC6412013 DOI: 10.1016/j.ebiom.2018.12.032] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 12/13/2018] [Accepted: 12/17/2018] [Indexed: 12/29/2022] Open
Abstract
Background Triple-negative breast cancer (TNBC) remains difficult to be targeted. SET and cancerous inhibitor of protein phosphatase 2A (CIP2A) are intrinsic protein-interacting inhibitors of protein phosphatase 2A (PP2A) and frequently overexpressed in cancers, whereas reactivating PP2A activity has been postulated as an anti-cancer strategy. Here we explored this strategy in TNBC. Methods Data from The Cancer Genome Atlas (TCGA) database was analyzed. TNBC cell lines were used for in vitro studies. Cell viability was examined by MTT assay. The apoptotic cells were examined by flow cytometry and Western blot. A SET-PP2A protein-protein interaction antagonist TD19 was used to disrupt signal transduction. In vivo efficacy of TD19 was tested in MDA-MB-468-xenografted animal model. Findings TCGA data revealed upregulation of SET and CIP2A and positive correlation of these two gene expressions in TNBC tumors. Ectopic SET or CIP2A increased cell viability, migration, and invasion of TNBC cells. Notably ERK inhibition increased PP2A activity. ERK activation is known crucial for Elk-1 activity, a transcriptional factor regulating CIP2A expression, we hypothesized an oncogenic feedforward loop consisting of pERK/pElk-1/CIP2A/PP2A. This loop was validated by knockdown of PP2A and ectopic expression of Elk-1, showing reciprocal changes in loop members. In addition, ectopic expression of SET increased pAkt, pERK, pElk-1 and CIP2A expressions, suggesting a positive linkage between SET and CIP2A signaling. Moreover, TD19 disrupted this CIP2A-feedforward loop by restoring PP2A activity, demonstrating in vitro and in vivo anti-cancer activity. Mechanistically, TD19 downregulated CIP2A mRNA via inhibiting pERK-mediated Elk-1 nuclear translocation thereby decreased Elk-1 binding to the CIP2A promoter. Interpretation These findings suggested that a novel oncogenic CIP2A-feedforward loop contributes to TNBC progression and targeting SET to disrupt this oncogenic CIP2A loop showed therapeutic potential in TNBC.
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13
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Nasser MM, Mehdipour P. Exploration of Involved Key Genes and Signaling Diversity in Brain Tumors. Cell Mol Neurobiol 2018; 38:393-419. [PMID: 28493234 DOI: 10.1007/s10571-017-0498-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Accepted: 05/02/2017] [Indexed: 02/05/2023]
Abstract
Brain tumors are becoming a major cause of death. The classification of brain tumors has gone through restructuring with regard to some criteria such as the presence or absence of a specific genetic alteration in the 2016 central nervous system World Health Organization update. Two categories of genes with a leading role in tumorigenesis and cancer induction include tumor suppressor genes and oncogenes; tumor suppressor genes are inactivated through a variety of mechanisms that result in their loss of function. As for the oncogenes, overexpression and amplification are the most common mechanisms of alteration. Important cell cycle genes such as p53, ATM, cyclin D2, and Rb have shown altered expression patterns in different brain tumors such as meningioma and astrocytoma. Some genes in signaling pathways have a role in brain tumorigenesis. These pathways include hedgehog, EGFR, Notch, hippo, MAPK, PI3K/Akt, and WNT signaling. It has been shown that telomere length in some brain tumor samples is shortened compared to that in normal cells. As the shortening of telomere length triggers chromosome instability early in brain tumors, it could lead to initiation of cancer. On the other hand, telomerase activity was positive in some brain tumors. It is suggestive that telomere length and telomerase activity are important diagnostic markers in brain tumors. This review focuses on brain tumors with regard to the status of oncogenes, tumor suppressors, cell cycle genes, and genes in signaling pathways as well as the role of telomere length and telomerase in brain tumors.
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Affiliation(s)
- Mojdeh Mahdian Nasser
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Parvin Mehdipour
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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14
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Sun D, Wan X, Pan BB, Sun Q, Ji XB, Zhang F, Zhang H, Cao CC. Bioinformatics Analysis of Genes and Pathways of CD11b +/Ly6C intermediate Macrophages after Renal Ischemia-Reperfusion Injury. Curr Med Sci 2018; 38:70-77. [PMID: 30074154 PMCID: PMC7089064 DOI: 10.1007/s11596-018-1848-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 11/08/2017] [Indexed: 12/12/2022]
Abstract
Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI), which could induce the poor prognosis. The purpose of this study was to characterize the molecular mechanism of the functional changes of CDllb+/Ly6Cintermediate macrophages after renal IRI. The gene expression profiles of CDllb+/Ly6Cintermcdiate macrophages of the sham surgery mice, and the mice 4 h, 24 h and 9 days after renal IRI were downloaded from the Gene Expression Omnibus database. Analysis of mRNA expression profiles was conducted to identify differentially expressed genes (DEGs), biological processes and pathways by the series test of cluster. Protein-protein interaction network was constructed and analysed to discover the key genes. A total of 6738 DEGs were identified and assigned to 20 model profiles. DEGs in profile 13 were one of the predominant expression profiles, which are involved in immune cell chemotaxis and proliferation. Signet analysis showed that Atp5al, Atp5o, Cox4i, Cdc42, Rac2 and Nhp2 were the key genes involved in oxidation-reduction, apoptosis, migration, M1-M2 differentiation, and proliferation of macrophages. RPS18 may be an appreciate reference gene as it was stable in macrophages. The identified DEGs and their enriched pathways investigate factors that may participate in the functional changes of CD 1lb+Ly6Cintermediate macrophages after renal IRI. Moreover, the vital gene Nhp2 may involve the polarization of macrophages, which may be a new target to affect the process of AKI.
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Affiliation(s)
- Dong Sun
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
| | - Xin Wan
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
| | - Bin-bin Pan
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
| | - Qing Sun
- Department of Nephrology, The Affiliated Sir Run Run Hospital, Nanjing Medical University, Nanjing, 211166 China
| | - Xiao-bing Ji
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
| | - Feng Zhang
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
| | - Hao Zhang
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
| | - Chang-chun Cao
- Department of Nephrology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006 China
- Department of Nephrology, The Affiliated Sir Run Run Hospital, Nanjing Medical University, Nanjing, 211166 China
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15
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Hmeljak J, Kern I, Cör A. No Implication of Simian virus 40 in pathogenesis of Malignant Pleural Mesothelioma in Slovenia. TUMORI JOURNAL 2018; 96:667-73. [DOI: 10.1177/030089161009600504] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background and aim Malignant mesothelioma is predominantly caused by asbestos exposure, although the association of Simian virus 40 in its pathogenesis is currently still under debate. Simian virus 40, a DNA rhesus monkey virus with oncogenic properties, accidentally contaminated early batches of polio vaccine in the 1960s. In the 1990s, viral sequences and proteins were discovered in several human tumors, which triggered research to find a link between Simian virus 40 and human cancers, especially malignant mesothelioma. The aim of our study was to establish an effective laboratory procedure for Simian virus 40 detection and to investigate the presence of Simian virus 40 DNA and small t antigen in mesothelioma samples from Slovenian patients. Methods and study design Paraffin-embedded malignant pleural mesothelioma specimens from 103 Slovenian patients were collected and used for total DNA isolation and real-time polymerase chain reaction for Simian virus 40 small t and large T DNA analysis. Special attention was devoted to primer design, good laboratory practice and polymerase chain reaction contamination prevention. Polymerase chain reaction products were sequenced and BLAST aligned. One 5 μm thick paraffin section from each patient's tissue block was stained with hematoxylin and eosin for histological typing and one for immunohistochemical detection of Simian virus 40 small t antigen using a monoclonal antibody against Simian virus 40 (Pab280). SV40-expressing Wi-38 cells were used as positive control in both PCR and immunohistochemistry. Results In real-time polymerase chain reaction analyses, only 4 samples gave products with primer pairs amplifying small t antigen and were inconsistent and poorly reproducible. BLAST alignment showed no homology with any deposited SV40 sequences. No immunopositive staining for SV40 small t antigen was found in any of the samples. Conclusions We found no evidence of SV40 presence in tissue samples from 103 Slovenian patients with malignant pleural mesothelioma. Asbestos exposure remains the main risk factor for malignant pleural mesothelioma in Slovenia. Free full text available at www.tumorionline.it
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Affiliation(s)
- Julija Hmeljak
- University of Primorska, College of Health Care Izola, Polje 42, Izola
| | - Izidor Kern
- University Clinic of Respiratory and Allergic Diseases, Golnik 36, Golnik, Slovenia
| | - Andrej Cör
- University of Primorska, College of Health Care Izola, Polje 42, Izola
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16
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Baez CF, Brandão Varella R, Villani S, Delbue S. Human Polyomaviruses: The Battle of Large and Small Tumor Antigens. Virology (Auckl) 2017; 8:1178122X17744785. [PMID: 29238174 PMCID: PMC5721967 DOI: 10.1177/1178122x17744785] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 10/30/2017] [Indexed: 12/17/2022] Open
Abstract
About 40 years ago, the large and small tumor antigens (LT-Ag and sT-Ag) of the polyomavirus (PyVs) simian vacuolating virus 40 have been identified and characterized. To date, it is well known that all the discovered human PyVs (HPyVs) encode these 2 multifunctional and tumorigenic proteins, expressed at viral replication early stage. The 2 T-Ags are able to transform cells both in vitro and in vivo and seem to play a distinct role in the pathogenesis of some tumors in humans. In addition, they are involved in viral DNA replication, transcription, and virion assembly. This short review focuses on the structural and functional features of the HPyVs’ LT-Ag and sT-Ag, with special attention to their transforming properties.
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Affiliation(s)
- Camila Freze Baez
- Department of Preventive Medicine, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Sonia Villani
- Department of Biomedical, Surgical and Dental Sciences, University of Milano, Milano, Italy
| | - Serena Delbue
- Department of Biomedical, Surgical and Dental Sciences, University of Milano, Milano, Italy
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17
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Janghorban M, Langer EM, Wang X, Zachman D, Daniel CJ, Hooper J, Fleming WH, Agarwal A, Sears RC. The tumor suppressor phosphatase PP2A-B56α regulates stemness and promotes the initiation of malignancies in a novel murine model. PLoS One 2017; 12:e0188910. [PMID: 29190822 PMCID: PMC5708644 DOI: 10.1371/journal.pone.0188910] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 11/15/2017] [Indexed: 01/13/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is a ubiquitously expressed Serine-Threonine phosphatase mediating 30–50% of protein phosphatase activity. PP2A functions as a heterotrimeric complex, with the B subunits directing target specificity to regulate the activity of many key pathways that control cellular phenotypes. PP2A-B56α has been shown to play a tumor suppressor role and to negatively control c-MYC stability and activity. Loss of B56α promotes cellular transformation, likely at least in part through its regulation of c-MYC. Here we report generation of a B56α hypomorph mouse with very low B56α expression that we used to study the physiologic activity of the PP2A-B56α phosphatase. The predominant phenotype we observed in mice with B56α deficiency in the whole body was spontaneous skin lesion formation with hyperproliferation of the epidermis, hair follicles and sebaceous glands. Increased levels of c-MYC phosphorylation on Serine62 and c-MYC activity were observed in the skin lesions of the B56αhm/hm mice. B56α deficiency was found to increase the number of skin stem cells, and consistent with this, papilloma initiation was accelerated in a carcinogenesis model. Further analysis of additional tissues revealed increased inflammation in spleen, liver, lung, and intestinal lymph nodes as well as in the skin lesions, resembling elevated extramedullary hematopoiesis phenotypes in the B56αhm/hm mice. We also observed an increase in the clonogenicity of bone marrow stem cells in B56αhm/hm mice. Overall, this model suggests that B56α is important for stem cells to maintain homeostasis and that B56α loss leading to increased activity of important oncogenes, including c-MYC, can result in aberrant cell growth and increased stem cells that can contribute to the initiation of malignancy.
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Affiliation(s)
- Mahnaz Janghorban
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Ellen M. Langer
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Xiaoyan Wang
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Derek Zachman
- Papé Family Pediatric Research Institute, Oregon Stem Cell Center, Department of Pediatrics, Portland, Oregon, United States of America
| | - Colin J. Daniel
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Jody Hooper
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - William H. Fleming
- Papé Family Pediatric Research Institute, Oregon Stem Cell Center, Department of Pediatrics, Portland, Oregon, United States of America
- Knight Cancer Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Anupriya Agarwal
- Knight Cancer Institute, Oregon Health & Science University, Portland, Oregon, United States of America
- Division of Hematology & Medical Oncology, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Rosalie C. Sears
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
- Knight Cancer Institute, Oregon Health & Science University, Portland, Oregon, United States of America
- Brenden-Colson Center for Pancreatic Care, Oregon Health and Science University, Portland, Oregon, United States of America
- * E-mail:
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18
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Wu CG, Chen H, Guo F, Yadav VK, Mcilwain SJ, Rowse M, Choudhary A, Lin Z, Li Y, Gu T, Zheng A, Xu Q, Lee W, Resch E, Johnson B, Day J, Ge Y, Ong IM, Burkard ME, Ivarsson Y, Xing Y. PP2A-B' holoenzyme substrate recognition, regulation and role in cytokinesis. Cell Discov 2017; 3:17027. [PMID: 28884018 PMCID: PMC5586252 DOI: 10.1038/celldisc.2017.27] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Accepted: 07/12/2017] [Indexed: 12/11/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a major Ser/Thr phosphatase; it forms diverse heterotrimeric holoenzymes that counteract kinase actions. Using a peptidome that tiles the disordered regions of the human proteome, we identified proteins containing [LMFI]xx[ILV]xEx motifs that serve as interaction sites for B′-family PP2A regulatory subunits and holoenzymes. The B′-binding motifs have important roles in substrate recognition and in competitive inhibition of substrate binding. With more than 100 novel ligands identified, we confirmed that the recently identified LxxIxEx B′α-binding motifs serve as common binding sites for B′ subunits with minor variations, and that S/T phosphorylation or D/E residues at positions 2, 7, 8 and 9 of the motifs reinforce interactions. Hundreds of proteins in the human proteome harbor intrinsic or phosphorylation-responsive B′-interaction motifs, and localize at distinct cellular organelles, such as midbody, predicting kinase-facilitated recruitment of PP2A-B′ holoenzymes for tight spatiotemporal control of phosphorylation at mitosis and cytokinesis. Moroever, Polo-like kinase 1-mediated phosphorylation of Cyk4/RACGAP1, a centralspindlin component at the midbody, facilitates binding of both RhoA guanine nucleotide exchange factor (epithelial cell transforming sequence 2 (Ect2)) and PP2A-B′ that in turn dephosphorylates Cyk4 and disrupts Ect2 binding. This feedback signaling loop precisely controls RhoA activation and specifies a restricted region for cleavage furrow ingression. Our results provide a framework for further investigation of diverse signaling circuits formed by PP2A-B′ holoenzymes in various cellular processes.
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Affiliation(s)
- Cheng-Guo Wu
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA.,Biophysics Program, University of Wisconsin at Madison, Madison, WI, USA
| | - Hui Chen
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Feng Guo
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Vikash K Yadav
- Department of Chemistry-BMC, Uppsala University, Uppsala, Sweden
| | - Sean J Mcilwain
- Biostatistics and Medical Informatics, Wisconsin Institutes of Medical Research, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Michael Rowse
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Alka Choudhary
- Department of Medicine, Hematology/Oncology, UW Carbone Cancer Center, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Ziqing Lin
- Department of Cell and Regenerative Biology, Human Proteomic Program, School of Medicine and Public Health, Madison, WI, USA
| | - Yitong Li
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Tingjia Gu
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Aiping Zheng
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Qingge Xu
- Department of Cell and Regenerative Biology, Human Proteomic Program, School of Medicine and Public Health, Madison, WI, USA
| | - Woojong Lee
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Eduard Resch
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Project Group Translational Medicine and Pharmacology TMP, Frankfurt am Main, Germany
| | - Benjamin Johnson
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Jenny Day
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Ying Ge
- Department of Cell and Regenerative Biology, Human Proteomic Program, School of Medicine and Public Health, Madison, WI, USA
| | - Irene M Ong
- Biostatistics and Medical Informatics, Wisconsin Institutes of Medical Research, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Mark E Burkard
- Department of Medicine, Hematology/Oncology, UW Carbone Cancer Center, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA
| | - Ylva Ivarsson
- Department of Chemistry-BMC, Uppsala University, Uppsala, Sweden
| | - Yongna Xing
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI, USA.,Biophysics Program, University of Wisconsin at Madison, Madison, WI, USA
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19
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Sangodkar J, Perl A, Tohme R, Kiselar J, Kastrinsky DB, Zaware N, Izadmehr S, Mazhar S, Wiredja DD, O'Connor CM, Hoon D, Dhawan NS, Schlatzer D, Yao S, Leonard D, Borczuk AC, Gokulrangan G, Wang L, Svenson E, Farrington CC, Yuan E, Avelar RA, Stachnik A, Smith B, Gidwani V, Giannini HM, McQuaid D, McClinch K, Wang Z, Levine AC, Sears RC, Chen EY, Duan Q, Datt M, Haider S, Ma'ayan A, DiFeo A, Sharma N, Galsky MD, Brautigan DL, Ioannou YA, Xu W, Chance MR, Ohlmeyer M, Narla G. Activation of tumor suppressor protein PP2A inhibits KRAS-driven tumor growth. J Clin Invest 2017; 127:2081-2090. [PMID: 28504649 DOI: 10.1172/jci89548] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 03/07/2017] [Indexed: 12/20/2022] Open
Abstract
Targeted cancer therapies, which act on specific cancer-associated molecular targets, are predominantly inhibitors of oncogenic kinases. While these drugs have achieved some clinical success, the inactivation of kinase signaling via stimulation of endogenous phosphatases has received minimal attention as an alternative targeted approach. Here, we have demonstrated that activation of the tumor suppressor protein phosphatase 2A (PP2A), a negative regulator of multiple oncogenic signaling proteins, is a promising therapeutic approach for the treatment of cancers. Our group previously developed a series of orally bioavailable small molecule activators of PP2A, termed SMAPs. We now report that SMAP treatment inhibited the growth of KRAS-mutant lung cancers in mouse xenografts and transgenic models. Mechanistically, we found that SMAPs act by binding to the PP2A Aα scaffold subunit to drive conformational changes in PP2A. These results show that PP2A can be activated in cancer cells to inhibit proliferation. Our strategy of reactivating endogenous PP2A may be applicable to the treatment of other diseases and represents an advancement toward the development of small molecule activators of tumor suppressor proteins.
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Affiliation(s)
- Jaya Sangodkar
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Abbey Perl
- Case Western Reserve University, Cleveland, Ohio, USA
| | - Rita Tohme
- Case Western Reserve University, Cleveland, Ohio, USA.,Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Janna Kiselar
- Case Western Reserve University, Cleveland, Ohio, USA
| | | | - Nilesh Zaware
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Sudeh Izadmehr
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Sahar Mazhar
- Case Western Reserve University, Cleveland, Ohio, USA
| | | | | | - Divya Hoon
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Neil S Dhawan
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Shen Yao
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | | | | | - Lifu Wang
- University of Virginia, Charlottesville, Virginia, USA
| | - Elena Svenson
- Case Western Reserve University, Cleveland, Ohio, USA
| | | | - Eric Yuan
- Case Western Reserve University, Cleveland, Ohio, USA
| | - Rita A Avelar
- Case Western Reserve University, Cleveland, Ohio, USA
| | - Agnes Stachnik
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Blake Smith
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Vickram Gidwani
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Daniel McQuaid
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Zhizhi Wang
- University of Washington, Seattle, Washington, USA
| | - Alice C Levine
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Edward Y Chen
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Qiaonan Duan
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Manish Datt
- International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Shozeb Haider
- School of Pharmacy, University College London, London, United Kingdom.,University of Washington, Seattle, Washington, USA
| | - Avi Ma'ayan
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Analisa DiFeo
- Case Western Reserve University, Cleveland, Ohio, USA
| | | | - Matthew D Galsky
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | | | - Wenqing Xu
- University of Washington, Seattle, Washington, USA
| | - Mark R Chance
- Case Western Reserve University, Cleveland, Ohio, USA
| | - Michael Ohlmeyer
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Goutham Narla
- Case Western Reserve University, Cleveland, Ohio, USA
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20
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Abstract
Observed deficits in protein phosphatase 2A (PP2A) function in a variety of human cancers have stimulated drug discovery efforts aimed at restoring PP2A function to inhibit tumor growth. Work published by Sangodkar et al. in this issue of the JCI describes the characterization of orally available small molecule activators of PP2A (SMAPs). These SMAPs attenuated mitogenic signaling and triggered apoptosis in KRAS-mutant lung cancer cells and inhibited tumor growth in murine models. Tumors with mutations in the SMAP-binding site of the PP2A A subunit displayed resistance to SMAPs. Future studies that identify the PP2A-regulated events targeted by SMAPs should guide critical decisions about which cancers might be best treated with these molecules. This study provides encouraging evidence in favor of SMAPs as potential anticancer drugs.
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21
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Korup-Schulz SV, Lucke C, Moens U, Schmuck R, Ehlers B. Large T antigen variants of human polyomaviruses 9 and 12 and seroreactivity against their N terminus. J Gen Virol 2017; 98:704-714. [PMID: 28113048 DOI: 10.1099/jgv.0.000714] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The tumour antigens (TAgs) of mammalian polyomaviruses (PyVs) are key proteins responsible for modulating the host cell cycle and are involved in virus replication as well as cell transformation and tumour formation. Here we aimed to identify mRNA sequences of known and novel TAgs encoded by the recently discovered human polyomaviruses 9 and 12 (HPyV9 and HPyV12) in cell culture. Synthetic viral genomes were transfected into human and animal cell lines. Gene expression occurred in most cell lines, as measured by quantitative PCR of cDNA copies of mRNA encoding major structural protein VP1. Large TAg- and small TAg-encoding mRNAs were detected in all cell lines, and additional spliced mRNAs were identified encoding TAg variants of 145 aa (HPyV9) and 84 aa (HPyV12). Using as antigens in ELISA the N-terminal 78 aa common to all respective TAg variants of HPyV9 and HPyV12, seroreactivity of 100 healthy blood donors, 54 patients with malignant diseases of the gastrointestinal tract (GIT) and 32 patients with non-malignant diseases of the GIT was analysed. For comparison, the corresponding TAg N termini of BK PyV (BKPyV) and Merkel cell PyV (MCPyV) were included. Frequent reactivity against HPyV9, HPyV12 and BKPyV TAgs, but not MCPyV TAg, was observed in all tested groups. This indicates expression activity of the early region of three human PyVs in healthy and diseased subjects.
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Affiliation(s)
- Sarah-Verena Korup-Schulz
- Division 12 'Measles, Mumps, Rubella, and Viruses Affecting Immunocompromised Patients', Robert Koch Institute, Berlin, Germany
| | - Claudia Lucke
- Division 12 'Measles, Mumps, Rubella, and Viruses Affecting Immunocompromised Patients', Robert Koch Institute, Berlin, Germany
| | - Ugo Moens
- Faculty of Health Sciences, Department of Medical Biology, University of Tromsø, NO-9037 Tromsø, Norway
| | - Rosa Schmuck
- General, Visceral, and Transplantation Surgery, Experimental Surgery and Regenerative Medicine, Charité-Campus Virchow, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Bernhard Ehlers
- Division 12 'Measles, Mumps, Rubella, and Viruses Affecting Immunocompromised Patients', Robert Koch Institute, Berlin, Germany
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22
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Gheit T, Dutta S, Oliver J, Robitaille A, Hampras S, Combes JD, McKay-Chopin S, Le Calvez-Kelm F, Fenske N, Cherpelis B, Giuliano AR, Franceschi S, McKay J, Rollison DE, Tommasino M. Isolation and characterization of a novel putative human polyomavirus. Virology 2017; 506:45-54. [PMID: 28342387 DOI: 10.1016/j.virol.2017.03.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 03/07/2017] [Accepted: 03/16/2017] [Indexed: 01/08/2023]
Abstract
The small double-stranded DNA polyomaviruses (PyVs) form a family of 73 species, whose natural hosts are primarily mammals and birds. So far, 13 PyVs have been isolated in humans, and some of them have clearly been associated with several diseases, including cancer. In this study, we describe the isolation of a novel PyV in human skin using a sensitive degenerate PCR protocol combined with next-generation sequencing. The new virus, named Lyon IARC PyV (LIPyV), has a circular genome of 5269 nucleotides. Phylogenetic analyses showed that LIPyV is related to the raccoon PyV identified in neuroglial tumours in free-ranging raccoons. Analysis of human specimens from cancer-free individuals showed that 9 skin swabs (9/445; 2.0%), 3 oral gargles (3/140; 2.1%), and one eyebrow hair sample (1/439; 0.2%) tested positive for LIPyV. Future biological and epidemiological studies are needed to confirm the human tropism and provide insights into its biological properties.
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Affiliation(s)
- Tarik Gheit
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - Sankhadeep Dutta
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - Javier Oliver
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - Alexis Robitaille
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - Shalaka Hampras
- Department of Cancer Epidemiology, Moffitt Cancer Center, Tampa, FL, USA
| | - Jean-Damien Combes
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - Sandrine McKay-Chopin
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | | | - Neil Fenske
- Department of Dermatology & Cutaneous Surgery, University of South Florida, Morsani College of Medicine, Tampa, FL, USA; Department of Cutaneous Oncology, Moffitt Cancer Center, Tampa, FL, USA
| | - Basil Cherpelis
- Department of Dermatology & Cutaneous Surgery, University of South Florida, Morsani College of Medicine, Tampa, FL, USA; Department of Cutaneous Oncology, Moffitt Cancer Center, Tampa, FL, USA
| | - Anna R Giuliano
- Center for Infection Research in Cancer, Moffitt Cancer Center, Tampa, FL, USA
| | - Silvia Franceschi
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - James McKay
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France
| | - Dana E Rollison
- Department of Cancer Epidemiology, Moffitt Cancer Center, Tampa, FL, USA
| | - Massimo Tommasino
- International Agency for Research on Cancer, World Health Organization, Lyon 69372, France.
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23
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XU P, YONG B, SHAO HH, SHEN JB, HE B, MA QQ, YUAN XH, WANG Y. Cloning and characterization of a serine/threonine protein phosphatase2A-encoding gene IbPP2A1 from Ipomoea batatas (L.) Lam. Turk J Biol 2017. [DOI: 10.3906/biy-1604-94] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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24
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Protein phosphatase 2A Cα regulates proliferation, migration, and metastasis of osteosarcoma cells. J Transl Med 2016; 96:1050-62. [PMID: 27617401 DOI: 10.1038/labinvest.2016.82] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 06/20/2016] [Accepted: 06/23/2016] [Indexed: 02/05/2023] Open
Abstract
Osteosarcoma is the most frequent primary bone tumor. Serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes, such as cell cycle, growth, apoptosis, and signal transduction. In this study, we examined the expression and function of PP2A Cα in osteosarcoma cells. PP2A Cα expression was expected to be higher in malignant osteosarcoma tissues. PP2A Cα expression level and PP2A activity was higher in malignant osteosarcoma LM8 cells compared with that in primary osteoblasts and in the osteoblast-like cell line MC3T3-E1. Okadaic acid, an inhibitor of PP2A, reduced cell viability and induced apoptosis in LM8 cells. PP2A Cα-knockdown LM8 cells (shPP2A) exhibited less striking filopodial and lamellipodial structures than that in original LM8 cells. Focal adhesion kinase phosphorylation and NF-κB activity decreased in shPP2A-treated cells. Sensitivity to serum deprivation-induced apoptosis increased in shPP2A-treated cells, accompanied by a lower expression level of anti-apoptotic BCL-2 in these cells. Reduction of PP2A Cα resulted in a decrease in the migration ability of LM8 cells in vitro. Reduction in PP2A Cα levels in vivo suppressed proliferation and metastasis in LM8 cells. PP2A Cα expression was also higher in human osteosarcoma MG63 and SaOS-2 cells than that in primary osteoblasts and MC3T3-E1 cells, and reduction in PP2A Cα levels suppressed the cell proliferation rate and migration ability of MG63 cells. These results indicate that PP2A Cα has a critical role in the proliferation and metastasis of osteosarcoma cells; therefore, its inhibition could potentially suppress the malignancy of osteosarcoma cells.
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25
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Wu JH, Simonette RA, Nguyen HP, Rady PL, Tyring SK. Molecular mechanisms supporting a pathogenic role for human polyomavirus 6 small T antigen: Protein phosphatase 2A targeting and MAPK cascade activation. J Med Virol 2016; 89:742-747. [PMID: 27632801 DOI: 10.1002/jmv.24688] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/12/2016] [Indexed: 02/04/2023]
Abstract
BRAF inhibitors are highly effective therapies in treating a subset of melanomas but are associated with induction of secondary cutaneous squamous cell carcinoma (cSCC). Recently, Human Polyomavirus 6 (HPyV6) was found to actively express viral proteins in BRAF inhibitor-induced cSCCs; however, the specific cellular mechanisms by which HPyV6 may facilitate neoplastic cell growth require further investigation. The current study describes a novel pathogenic mechanism of action for HPyV6 small tumor (sT) antigen which involves binding to protein phosphatase 2A (PP2A) via its WFG motif and zinc binding sites. Our findings demonstrate an important role of HPyV6 sT for activation of PP2A's downstream oncogenic pathways (MEK/ERK/c-Jun), which may underlie the pathogenesis of BRAF inhibitor-induced neoplasms. J. Med. Virol. 89:742-747, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Julie H Wu
- Department of Dermatology, University of Texas Health Science Center, Houston, Texas.,Baylor College of Medicine, Houston, Texas
| | - Rebecca A Simonette
- Department of Dermatology, University of Texas Health Science Center, Houston, Texas
| | - Harrison P Nguyen
- Department of Dermatology, University of Texas Health Science Center, Houston, Texas.,Baylor College of Medicine, Houston, Texas
| | - Peter L Rady
- Department of Dermatology, University of Texas Health Science Center, Houston, Texas
| | - Stephen K Tyring
- Department of Dermatology, University of Texas Health Science Center, Houston, Texas
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26
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The broken "Off" switch in cancer signaling: PP2A as a regulator of tumorigenesis, drug resistance, and immune surveillance. BBA CLINICAL 2016; 6:87-99. [PMID: 27556014 PMCID: PMC4986044 DOI: 10.1016/j.bbacli.2016.08.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Revised: 08/01/2016] [Accepted: 08/02/2016] [Indexed: 12/31/2022]
Abstract
Aberrant activation of signal transduction pathways can transform a normal cell to a malignant one and can impart survival properties that render cancer cells resistant to therapy. A diverse set of cascades have been implicated in various cancers including those mediated by serine/threonine kinases such RAS, PI3K/AKT, and PKC. Signal transduction is a dynamic process involving both "On" and "Off" switches. Activating mutations of RAS or PI3K can be viewed as the switch being stuck in the "On" position resulting in continued signaling by a survival and/or proliferation pathway. On the other hand, inactivation of protein phosphatases such as the PP2A family can be seen as the defective "Off" switch that similarly can activate these pathways. A problem for therapeutic targeting of PP2A is that the enzyme is a hetero-trimer and thus drug targeting involves complex structures. More importantly, since PP2A isoforms generally act as tumor suppressors one would want to activate these enzymes rather than suppress them. The elucidation of the role of cellular inhibitors like SET and CIP2A in cancer suggests that targeting these proteins can have therapeutic efficacy by mechanisms involving PP2A activation. Furthermore, drugs such as FTY-720 can activate PP2A isoforms directly. This review will cover the current state of knowledge of PP2A role as a tumor suppressor in cancer cells and as a mediator of processes that can impact drug resistance and immune surveillance.
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27
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Pusey M, Bail S, Xu Y, Buiakova O, Nestor M, Yang JJ, Rice LM. Inhibition of protein methylesterase 1 decreased cancerous phenotypes in endometrial adenocarcinoma cell lines and xenograft tumor models. Tumour Biol 2016; 37:11835-11842. [PMID: 27048286 DOI: 10.1007/s13277-016-5036-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 03/28/2016] [Indexed: 12/15/2022] Open
Abstract
Protein methylesterase 1 (PME-1) promotes cancerous phenotypes through the demethylation and inactivation of protein phosphatase 2A. We previously demonstrated that PME-1 overexpression promotes Akt, ERK, and may promote Wnt signaling and increases tumor burden in a xenograft model of endometrial cancer. Here, we show that covalent PME-1 inhibitors decrease cell proliferation and invasive growth in vitro but have no effect in vivo at the concentrations tested; however, depletion of PME-1 with shRNA in an endometrial cancer xenograft model significantly reduced tumor growth. Thus, discovery of more potent PME-1 inhibitors may be beneficial for the treatment of endometrial cancer.
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Affiliation(s)
- Michelle Pusey
- Oncoveda, Cancer Signaling and Cell Cycle Team, Medical Diagnostic Laboratories, LLC, 1000 Waterview Drive, Room 345, Hamilton, NJ, 08691, USA
| | - Sophie Bail
- Oncoveda, Cancer Signaling and Cell Cycle Team, Medical Diagnostic Laboratories, LLC, 1000 Waterview Drive, Room 345, Hamilton, NJ, 08691, USA
| | - Yan Xu
- Invivotek, LLC, 16 Black Forest Road, Hamilton, NJ, 08691, USA
| | - Olesia Buiakova
- Invivotek, LLC, 16 Black Forest Road, Hamilton, NJ, 08691, USA
| | - Mariya Nestor
- Pathology Department, Members of Genesis Biotechnology Group, LLC, Medical Diagnostic Laboratories LLC, 2439 Kuser Road, Hamilton, NJ, 08690, USA
| | - Jing-Jing Yang
- Pathology Department, Members of Genesis Biotechnology Group, LLC, Medical Diagnostic Laboratories LLC, 2439 Kuser Road, Hamilton, NJ, 08690, USA
| | - Lyndi M Rice
- Oncoveda, Cancer Signaling and Cell Cycle Team, Medical Diagnostic Laboratories, LLC, 1000 Waterview Drive, Room 345, Hamilton, NJ, 08691, USA.
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28
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Sangodkar J, Farrington C, McClinch K, Galsky MD, Kastrinsky DB, Narla G. All roads lead to PP2A: exploiting the therapeutic potential of this phosphatase. FEBS J 2016; 283:1004-24. [PMID: 26507691 PMCID: PMC4803620 DOI: 10.1111/febs.13573] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/29/2015] [Accepted: 10/21/2015] [Indexed: 12/22/2022]
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase involved in the regulation of many cellular processes. A confirmed tumor suppressor protein, PP2A is genetically altered or functionally inactivated in many cancers highlighting a need for its therapeutic reactivation. In this review we discuss recent literature on PP2A: the elucidation of its structure and the functions of its subunits, and the identification of molecular lesions and post-translational modifications leading to its dysregulation in cancer. A final section will discuss the proteins and small molecules that modulate PP2A and how these might be used to target dysregulated forms of PP2A to treat cancers and other diseases.
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Affiliation(s)
- Jaya Sangodkar
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY, USA
| | - Caroline Farrington
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Kimberly McClinch
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Matthew D. Galsky
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - David B. Kastrinsky
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Goutham Narla
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
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29
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Wang J, Li Z, Liu B, Chen G, Shao N, Ying X, Wang Y. Systematic study of cis-antisense miRNAs in animal species reveals miR-3661 to target PPP2CA in human cells. RNA (NEW YORK, N.Y.) 2016; 22:87-95. [PMID: 26577378 PMCID: PMC4691837 DOI: 10.1261/rna.052894.115] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 10/03/2015] [Indexed: 05/13/2023]
Abstract
MicroRNAs (miRNAs) suppress targeting gene expression through blocking translation or triggering mRNA degradation and, in general, act in trans, through a partially complementary interaction with the 3' untranslated region (3' UTR) or coding regions of a target gene. Although it has been reported previously that some miRNAs suppress their target genes on the opposite strand with a fully complementary sequence (i.e., natural antisense miRNAs that act in cis), there is no report to systematically study such cis-antisense miRNAs in different animal species. Here we report that cis-antisense miRNAs do exist in different animal species: 48 in Caenorhabditis elegans, 17 in Drosophila, 36 in Mus musculus, and 52 in Homo sapiens using a systematical bioinformatics approach. We show that most of these cis-antisense miRNAs can efficiently reduce the expression levels of their target genes in human cells. We further investigate hsa-miR-3661, one of the predicted cis-antisense miRNAs, in detail and demonstrate that this miRNA directly targets the coding sequence of PPP2CA located on the opposite DNA strand and inhibits the PPP2CA expression. Taken together, these results indicate that cis-antisense miRNAs are conservative and functional in animal species including humans.
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Affiliation(s)
- Jian Wang
- Department of Radiation Oncology, Emory University School of Medicine, Winship Cancer Institute of Emory University, Atlanta, Georgia 30322, USA
| | - Zongcheng Li
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Bailong Liu
- Department of Radiation Oncology, Emory University School of Medicine, Winship Cancer Institute of Emory University, Atlanta, Georgia 30322, USA The First Norman Bethune Hospital of Jilin University, Changchun 130012, China
| | - Guangnan Chen
- Department of Radiation Oncology, Emory University School of Medicine, Winship Cancer Institute of Emory University, Atlanta, Georgia 30322, USA
| | - Ningsheng Shao
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Xiaomin Ying
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Ya Wang
- Department of Radiation Oncology, Emory University School of Medicine, Winship Cancer Institute of Emory University, Atlanta, Georgia 30322, USA
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30
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Wu JH, Nguyen HP, Rady PL, Tyring SK. Molecular insight into the viral biology and clinical features of trichodysplasia spinulosa. Br J Dermatol 2015; 174:490-8. [PMID: 26479880 DOI: 10.1111/bjd.14239] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2015] [Indexed: 02/03/2023]
Abstract
Trichodysplasia spinulosa (TS) is a disfiguring skin disease that occurs most frequently in patients receiving immunosuppressive therapies, and is thus frequently associated with organ transplantation. TS is characterized clinically by folliculocentric papular eruption, keratin spine formation and development of leonine face; and histologically by expansion of the inner root sheath epithelium and high expression of the proliferative marker Ki-67. Recent discovery of the TS-associated polyomavirus (TSPyV) and emerging studies demonstrating the role of TSPyV tumour antigens in cell proliferation pathways have opened a new corridor for research on TS. In this brief review, we summarize the clinical and histological features of TS and evaluate the current options for therapy. Furthermore, we address the viral aetiology of the disease and explore the mechanisms by which TSPyV may influence TS development and progression. As reports of TS continue to rise, clinician recognition of TS, as well as accompanying research on its underlying pathogenesis and therapeutic options, is becoming increasingly important. It is our hope that heightened clinical suspicion for TS will increase rates of diagnosis and will galvanize both molecular and clinical interest in this disease.
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Affiliation(s)
- J H Wu
- Department of Dermatology, University of Texas Health Science Center at Houston, Houston, TX, U.S.A.,Baylor College of Medicine, Houston, TX, U.S.A
| | - H P Nguyen
- Department of Dermatology, University of Texas Health Science Center at Houston, Houston, TX, U.S.A.,Baylor College of Medicine, Houston, TX, U.S.A
| | - P L Rady
- Department of Dermatology, University of Texas Health Science Center at Houston, Houston, TX, U.S.A
| | - S K Tyring
- Department of Dermatology, University of Texas Health Science Center at Houston, Houston, TX, U.S.A
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31
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Hu X, Garcia C, Fazli L, Gleave M, Vitek MP, Jansen M, Christensen D, Mulholland DJ. Inhibition of Pten deficient Castration Resistant Prostate Cancer by Targeting of the SET - PP2A Signaling axis. Sci Rep 2015; 5:15182. [PMID: 26563471 PMCID: PMC4643319 DOI: 10.1038/srep15182] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 09/15/2015] [Indexed: 11/11/2022] Open
Abstract
The PP2A signaling axis regulates multiple oncogenic drivers of castration resistant prostate cancer (CRPC). We show that targeting the endogenous PP2A regulator, SET (I2PP2A), is a viable strategy to inhibit prostate cancers that are resistant to androgen deprivation therapy. Our data is corroborated by analysis of prostate cancer patient cohorts showing significant elevation of SET transcripts. Tissue microarray analysis reveals that elevated SET expression correlates with clinical cancer grading, duration of neoadjuvant hormone therapy (NHT) and time to biochemical recurrence. Using prostate regeneration assays, we show that in vivo SET overexpression is sufficient to induce hyperplasia and prostatic intraepithelial neoplasia. Knockdown of SET induced significant reductions in tumorgenesis both in murine and human xenograft models. To further validate SET as a therapeutic target, we conducted in vitro and in vivo treatments using OP449 - a recently characterized PP2A-activating drug (PAD). OP449 elicits robust anti-cancer effects inhibiting growth in a panel of enzalutamide resistant prostate cancer cell lines. Using the Pten conditional deletion mouse model of prostate cancer, OP449 potently inhibited PI3K-Akt signaling and impeded CRPC progression. Collectively, our data supports a critical role for the SET-PP2A signaling axis in CRPC progression and hormone resistant disease.
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Affiliation(s)
- Xiaoyong Hu
- The 6th People's Hospital, Shanghai Jiaotong University, Shanghai, 200233, China.,Icahn School of Medicine, Mount Sinai Medical Center, New York, NY, 10029, USA
| | - Consuelo Garcia
- Icahn School of Medicine, Mount Sinai Medical Center, New York, NY, 10029, USA
| | - Ladan Fazli
- The Prostate Centre at Vancouver General Hospital Vancouver, British Columbia, Canada
| | - Martin Gleave
- The Prostate Centre at Vancouver General Hospital Vancouver, British Columbia, Canada
| | - Michael P Vitek
- Oncotide Pharmaceuticals, Research Triangle Park, NC, 27709, USA
| | - Marilyn Jansen
- Oncotide Pharmaceuticals, Research Triangle Park, NC, 27709, USA
| | - Dale Christensen
- Oncotide Pharmaceuticals, Research Triangle Park, NC, 27709, USA.,Division of Hematology, Duke University Medical Center, Durham, NC 27710, USA
| | - David J Mulholland
- Icahn School of Medicine, Mount Sinai Medical Center, New York, NY, 10029, USA
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32
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Kauko O, Laajala TD, Jumppanen M, Hintsanen P, Suni V, Haapaniemi P, Corthals G, Aittokallio T, Westermarck J, Imanishi SY. Label-free quantitative phosphoproteomics with novel pairwise abundance normalization reveals synergistic RAS and CIP2A signaling. Sci Rep 2015; 5:13099. [PMID: 26278961 PMCID: PMC4642524 DOI: 10.1038/srep13099] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 07/06/2015] [Indexed: 11/11/2022] Open
Abstract
Hyperactivated RAS drives progression of many human malignancies. However, oncogenic activity of RAS is dependent on simultaneous inactivation of protein phosphatase 2A (PP2A) activity. Although PP2A is known to regulate some of the RAS effector pathways, it has not been systematically assessed how these proteins functionally interact. Here we have analyzed phosphoproteomes regulated by either RAS or PP2A, by phosphopeptide enrichment followed by mass-spectrometry-based label-free quantification. To allow data normalization in situations where depletion of RAS or PP2A inhibitor CIP2A causes a large uni-directional change in the phosphopeptide abundance, we developed a novel normalization strategy, named pairwise normalization. This normalization is based on adjusting phosphopeptide abundances measured before and after the enrichment. The superior performance of the pairwise normalization was verified by various independent methods. Additionally, we demonstrate how the selected normalization method influences the downstream analyses and interpretation of pathway activities. Consequently, bioinformatics analysis of RAS and CIP2A regulated phosphoproteomes revealed a significant overlap in their functional pathways. This is most likely biologically meaningful as we observed a synergistic survival effect between CIP2A and RAS expression as well as KRAS activating mutations in TCGA pan-cancer data set, and synergistic relationship between CIP2A and KRAS depletion in colony growth assays.
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Affiliation(s)
- Otto Kauko
- 1] Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland [2] Department of Pathology, University of Turku, FI-20520 Turku, Finland [3] Turku Doctoral Program of Biomedical Sciences (TuBS), Turku, Finland
| | - Teemu Daniel Laajala
- 1] Department of Mathematics and Statistics, University of Turku, FI-20014 Turku, Finland [2] Drug Research Doctoral Programme (DRDP), Turku, Finland
| | - Mikael Jumppanen
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland
| | - Petteri Hintsanen
- Institute for Molecular Medicine Finland, Tukholmankatu 8, FI-00290 Helsinki, Finland
| | - Veronika Suni
- 1] Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland [2] Turku Centre for Computer Science, FI-20520 Turku, Finland
| | - Pekka Haapaniemi
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland
| | - Garry Corthals
- 1] Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland [2] Van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Tero Aittokallio
- Institute for Molecular Medicine Finland, Tukholmankatu 8, FI-00290 Helsinki, Finland
| | - Jukka Westermarck
- 1] Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland [2] Department of Pathology, University of Turku, FI-20520 Turku, Finland
| | - Susumu Y Imanishi
- 1] Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistokatu 6, FI-20520 Turku, Finland [2] Faculty of Pharmacy, Meijo University, Yagotoyama 150, Tempaku, Nagoya 468-8503, Japan
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33
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Ramaswamy K, Spitzer B, Kentsis A. Therapeutic Re-Activation of Protein Phosphatase 2A in Acute Myeloid Leukemia. Front Oncol 2015; 5:16. [PMID: 25699237 PMCID: PMC4313608 DOI: 10.3389/fonc.2015.00016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 01/13/2015] [Indexed: 11/13/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that is required for normal cell growth and development. PP2A is a potent tumor suppressor, which is inactivated in cancer cells as a result of genetic deletions and mutations. In myeloid leukemias, genes encoding PP2A subunits are generally intact. Instead, PP2A is functionally inhibited by post-translational modifications of its catalytic C subunit, and interactions with negative regulators by its regulatory B and scaffold A subunits. Here, we review the molecular mechanisms of genetic and functional inactivation of PP2A in human cancers, with a particular focus on human acute myeloid leukemias (AML). By analyzing expression of genes encoding PP2A subunits using transcriptome sequencing, we find that PP2A dysregulation in AML is characterized by silencing and overexpression of distinct A scaffold and B regulatory subunits, respectively. We review the mechanisms of functional PP2A activation by drugs such as fingolimod, forskolin, OP449, and perphenazine. This analysis yields two non-mutually exclusive mechanisms for therapeutic PP2A re-activation: (i) allosteric activation of the phosphatase activity, and (ii) stabilization of active holo-enzyme assembly and displacement of negative regulatory factors from A and B subunits. Future studies should allow the development of specific and potent pharmacologic activators of PP2A, and definition of susceptible disease subsets based on specific mechanisms of PP2A dysregulation.
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Affiliation(s)
- Kavitha Ramaswamy
- Molecular Pharmacology and Chemistry Program, Department of Pediatrics, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University , New York, NY , USA
| | - Barbara Spitzer
- Molecular Pharmacology and Chemistry Program, Department of Pediatrics, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University , New York, NY , USA
| | - Alex Kentsis
- Molecular Pharmacology and Chemistry Program, Department of Pediatrics, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University , New York, NY , USA
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Papillomavirus E7 oncoproteins share functions with polyomavirus small T antigens. J Virol 2014; 89:2857-65. [PMID: 25540383 DOI: 10.1128/jvi.03282-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Many of the small DNA tumor viruses encode transforming proteins that function by targeting critical cellular pathways involved in cell proliferation and survival. In this study, we have examined whether some of the functions of the polyomavirus small T antigens (ST) are shared by the E6 and E7 oncoproteins of two oncogenic papillomaviruses. Using three different assays, we have found that E7 can provide some simian virus 40 (SV40) or murine polyomavirus (PyV) ST functions. Both human papillomavirus 16 (HPV16) and bovine papillomavirus (BPV1) E7 proteins are capable of partially substituting for SV40 ST in a transformation assay that also includes SV40 large T antigen, the catalytic subunit of cellular telomerase, and oncogenic Ras. Like SV40 ST, HPV16 E7 has the ability to override a quiescence block induced by mitogen deprivation. Like PyV ST, it also has the ability to inhibit myoblast differentiation. At least two of these activities are dependent upon the interaction of HPV16 E7 with retinoblastoma protein family members. For small T antigens, interaction with PP2A is needed for each of these functions. Even though there is no strong evidence that E6 or E7 share the ability of small T to interact with PP2A, E7 provides these functions related to cellular transformation. IMPORTANCE DNA tumor viruses have provided major insights into how cancers develop. Some viruses, like the human papillomaviruses, can cause cancer directly. Both the papillomaviruses and the polyomaviruses have served as tools for understanding pathways that are often perturbed in cancer. Here, we have compared the functions of transforming proteins from several DNA tumor viruses, including two papillomaviruses and two polyomaviruses. We tested the papillomavirus E6 and E7 oncoproteins in three functional assays and found that E7 can provide some or all of the functions of the SV40 small T antigen, another well-characterized oncoprotein, in two of these assays. In a third assay, papillomavirus E7 has the same effect as the murine polyomavirus small T protein. In summary, we report several new functions for the papillomavirus E7 proteins, which will contribute new insights into the roles of viruses in cancer and the cellular pathways they perturb in carcinogenesis.
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Peng B, Lei N, Chai Y, Chan EKL, Zhang JY. CIP2A regulates cancer metabolism and CREB phosphorylation in non-small cell lung cancer. MOLECULAR BIOSYSTEMS 2014; 11:105-14. [PMID: 25325377 DOI: 10.1039/c4mb00513a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The cancerous inhibitor of protein phosphatase 2A (CIP2A) is a recently characterized endogenous inhibitor of the phosphatase activity of protein phosphatase 2A (PP2A), which extends the half-life of oncogenic protein c-myc and promotes in vivo tumor growth. The function of CIP2A in cancer progression is still poorly understood. To uncover the underlying mechanism of CIP2A-mediated cell proliferation, we implemented a two-dimensional electrophoresis (2DE)-based proteomic approach to examine lung cancer cell H1299 with and without CIP2A. We found 47 proteins differentially expressed where 19 proteins were upregulated and 28 proteins were downregulated. These were categorized into functional groups such as metabolism (25%), transcriptional and translational control (23%), and the signaling pathway and protein degradation (20%). On one hand, we validate our proteomic work by measuring the metabolic change. The knockdown of CIP2A decreased the expression of LDH-A as well as the enzymatic activity, accompanying with a decreased lactate production, an increased NADH/NAD+ ratio and ROS production. On the other hand, we found that CIP2A may regulate CREB activity through bioinformatics analysis. Our following experiments showed that, CIP2A positively regulated the phosphorylation of CREB in response to the serum treatment. Therefore, our proteomic study suggested that CIP2A mediates cancer progression through the metabolic pathway and intracellular signaling cascade.
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Affiliation(s)
- Bo Peng
- Border Biomedical Research Center & Department of Biological Sciences, The University of Texas at El Paso, El Paso, Texas 79968, USA.
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36
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Verhaegen ME, Mangelberger D, Harms PW, Vozheiko TD, Weick JW, Wilbert DM, Saunders TL, Ermilov AN, Bichakjian CK, Johnson TM, Imperiale MJ, Dlugosz AA. Merkel cell polyomavirus small T antigen is oncogenic in transgenic mice. J Invest Dermatol 2014; 135:1415-1424. [PMID: 25313532 PMCID: PMC4397111 DOI: 10.1038/jid.2014.446] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 09/15/2014] [Accepted: 10/02/2014] [Indexed: 12/17/2022]
Abstract
Merkel cell carcinoma (MCC) is a rare and deadly neuroendocrine skin tumor
frequently associated with clonal integration of a polyomavirus, MCPyV, and MCC tumor
cells express putative polyomavirus oncoproteins small T antigen (sTAg) and truncated
large T antigen (tLTAg). Here, we show robust transforming activity of sTAg in
vivo in a panel of transgenic mouse models. Epithelia of pre-term
sTAg-expressing embryos exhibited hyperplasia, impaired differentiation, increased
proliferation and apoptosis, and activation of a DNA damage response. Epithelial
transformation did not require sTAg interaction with the PP2A protein complex, a tumor
suppressor in some other polyomavirus transformation models, but was strictly dependent on
a recently-described sTAg domain that binds Fbxw7, the substrate-binding component of the
SCF ubiquitin ligase complex. Postnatal induction of sTAg using a Cre-inducible transgene
also led to epithelial transformation with development of lesions resembling squamous cell
carcinoma in situ and elevated expression of Fbxw7 target proteins. Our
data establish that expression of MCPyV sTAg alone is sufficient for rapid neoplastic
transformation in vivo, implicating sTAg as an oncogenic driver in MCC
and perhaps other human malignancies. Moreover, the loss of transforming activity
following mutation of the sTAg Fbxw7 binding domain identifies this domain as crucial for in
vivo transformation.
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Affiliation(s)
| | | | - Paul W Harms
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109.,Department of Pathology, University of Michigan, Ann Arbor, MI 48109
| | - Tracy D Vozheiko
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
| | - Jack W Weick
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
| | - Dawn M Wilbert
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
| | - Thomas L Saunders
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | | | | | - Timothy M Johnson
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109.,Otolaryngology, University of Michigan, Ann Arbor, MI 48109.,Surgery, University of Michigan, Ann Arbor, MI 48109
| | | | - Andrzej A Dlugosz
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109.,Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
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Nguyen HT, Hong X, Tan S, Chen Q, Chan L, Fivaz M, Cohen SM, Voorhoeve PM. Viral small T oncoproteins transform cells by alleviating hippo-pathway-mediated inhibition of the YAP proto-oncogene. Cell Rep 2014; 8:707-13. [PMID: 25088426 DOI: 10.1016/j.celrep.2014.06.062] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 06/09/2014] [Accepted: 06/28/2014] [Indexed: 12/19/2022] Open
Abstract
Primary human cells can be transformed into tumor cells by a defined set of genetic alterations including telomerase, oncogenic Ras(V12), and the tumor suppressors p53 and pRb. SV40 small T (ST) is required for anchorage-independent growth in vitro and in vivo. Here, we identify the Hippo tumor suppressor pathway as a critical target of ST in cellular transformation. We report that ST uncouples YAP from the inhibitory activity of the Hippo pathway through PAK1-mediated inactivation of NF2. Membrane-tethered activated PAK is sufficient to bypass the requirement for ST in anchorage-independent growth. PAK acts via YAP to mediate the transforming effects of ST. Activation of endogenous YAP is required for ST-mediated transformation and is sufficient to bypass ST in anchorage-independent growth and xenograft tumor formation. Our findings uncover the Hippo tumor suppressor pathway as a final gatekeeper to transformation and tumorigenesis of primary cells.
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Affiliation(s)
- Hung Thanh Nguyen
- Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - Xin Hong
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673, Singapore; Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Sam Tan
- Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - Qingfeng Chen
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673, Singapore; Interdisciplinary Research Group in Infectious Diseases, Singapore-MIT Alliance for Research and Technology (SMART) and Department of Microbiology, National University of Singapore, Singapore 117545, Singapore
| | - Lifang Chan
- Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - Marc Fivaz
- Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore; Department of Physiology, National University of Singapore, Singapore 117597, Singapore
| | - Stephen M Cohen
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673, Singapore; Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
| | - P Mathijs Voorhoeve
- Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore
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38
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Targeting c-MYC by antagonizing PP2A inhibitors in breast cancer. Proc Natl Acad Sci U S A 2014; 111:9157-62. [PMID: 24927563 DOI: 10.1073/pnas.1317630111] [Citation(s) in RCA: 151] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The transcription factor c-MYC is stabilized and activated by phosphorylation at serine 62 (S62) in breast cancer. Protein phosphatase 2A (PP2A) is a critical negative regulator of c-MYC through its ability to dephosphorylate S62. By inactivating c-MYC and other key signaling pathways, PP2A plays an important tumor suppressor function. Two endogenous inhibitors of PP2A, I2PP2A, Inhibitor-2 of PP2A (SET oncoprotein) and cancerous inhibitor of PP2A (CIP2A), inactivate PP2A and are overexpressed in several tumor types. Here we show that SET is overexpressed in about 50-60% and CIP2A in about 90% of breast cancers. Knockdown of SET or CIP2A reduces the tumorigenic potential of breast cancer cell lines both in vitro and in vivo. Treatment of breast cancer cells in vitro or in vivo with OP449, a novel SET antagonist, also decreases the tumorigenic potential of breast cancer cells and induces apoptosis. We show that this is, at least in part, due to decreased S62 phosphorylation of c-MYC and reduced c-MYC activity and target gene expression. Because of the ubiquitous expression and tumor suppressor activity of PP2A in cells, as well as the critical role of c-MYC in human cancer, we propose that activation of PP2A (here accomplished through antagonizing endogenous inhibitors) could be a novel antitumor strategy to posttranslationally target c-MYC in breast cancer.
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39
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PP2A-mediated regulation of Ras signaling in G2 is essential for stable quiescence and normal G1 length. Mol Cell 2014; 54:932-945. [PMID: 24857551 DOI: 10.1016/j.molcel.2014.04.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 03/04/2014] [Accepted: 04/07/2014] [Indexed: 12/23/2022]
Abstract
Quiescence (G0) allows cycling cells to reversibly cease proliferation. A decision to enter quiescence is suspected of occurring early in G1, before the restriction point (R). Surprisingly, we have identified G2 as an interval during which inhibition of the protein phosphatase PP2A results in failure to exhibit stable quiescence. This effect is accompanied by shortening of the ensuing G1. The PP2A subcomplex required for stable G0 contains the B56γ B subunit. After PP2A inhibition in G2, aberrant overexpression of cyclin E occurs during mitosis and is responsible for overriding quiescence. Strikingly, suppression of Ras signaling re-establishes normal cyclin E levels during M and restores G0. These data point to PP2A-B56γ-driven Ras signaling modulation in G2 as essential for suppressing aberrant cyclin E expression during mitosis and thereby achieving normal G0 control. Thus, G2 is an interval during which the length and growth factor dependence of the next G1 interval are established.
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40
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Farrell AS, Allen-Petersen B, Daniel CJ, Wang X, Wang Z, Rodriguez S, Impey S, Oddo J, Vitek MP, Lopez C, Christensen DJ, Sheppard B, Sears RC. Targeting inhibitors of the tumor suppressor PP2A for the treatment of pancreatic cancer. Mol Cancer Res 2014; 12:924-39. [PMID: 24667985 DOI: 10.1158/1541-7786.mcr-13-0542] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
UNLABELLED Pancreatic cancer is a deadly disease that is usually diagnosed in the advanced stages when few effective therapies are available. Given the aggressive clinical course of this disease and lack of good treatment options, the development of new therapeutic agents for the treatment of pancreatic cancer is of the upmost importance. Several pathways that have shown to contribute to pancreatic cancer progression are negatively regulated by the tumor suppressor protein phosphatase 2A (PP2A). Here, the endogenous inhibitors of PP2A, SET (also known as I2PP2A) and cancerous inhibitor of PP2A (CIP2A), were shown to be overexpressed in human pancreatic cancer, contributing to decreased PP2A activity and overexpression and stabilization of the oncoprotein c-Myc, a key PP2A target. Knockdown of SET or CIP2A increases PP2A activity, increases c-Myc degradation, and decreases the tumorigenic potential of pancreatic cancer cell lines both in vitro and in vivo. Moreover, treatment with a novel SET inhibitor, OP449, pharmacologically recapitulates the phenotypes and significantly reduces proliferation and tumorigenic potential of several pancreatic cancer cell lines, with an accompanying attenuation of cell growth and survival signaling. Furthermore, primary cells from patients with pancreatic cancer were sensitive to OP449 treatment, indicating that PP2A-regulated pathways are highly relevant to this deadly disease. IMPLICATIONS The PP2A inhibitors SET and CIP2A are overexpressed in human pancreatic cancer and are important for pancreatic cancer cell growth and transformation; thus, antagonizing SET and/or CIP2A may be an innovative approach for the treatment of human pancreatic cancer.
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Affiliation(s)
- Amy S Farrell
- Authors' Affiliations: Departments of Molecular and Medical Genetics
| | | | - Colin J Daniel
- Authors' Affiliations: Departments of Molecular and Medical Genetics
| | - Xiaoyan Wang
- Authors' Affiliations: Departments of Molecular and Medical Genetics
| | - Zhiping Wang
- Authors' Affiliations: Departments of Molecular and Medical Genetics
| | - Sarah Rodriguez
- Oregon Stem Cell Center, Oregon Health and Science University, Portland, Oregon
| | - Soren Impey
- Oregon Stem Cell Center, Oregon Health and Science University, Portland, Oregon
| | - Jessica Oddo
- Oncotide Pharmaceuticals Inc., Research Triangle Park
| | - Michael P Vitek
- Oncotide Pharmaceuticals Inc., Research Triangle Park; Department of Neurology, Duke University Medical Center, Durham, North Carolina
| | | | - Dale J Christensen
- Oncotide Pharmaceuticals Inc., Research Triangle Park; Division of Hematology, Department of Medicine, and
| | | | - Rosalie C Sears
- Authors' Affiliations: Departments of Molecular and Medical Genetics,
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Abstract
The MYC oncoprotein is an essential transcription factor that regulates the expression of many genes involved in cell growth, proliferation, and metabolic pathways. Thus, it is important to keep MYC activity in check in normal cells in order to avoid unwanted oncogenic changes. Normal cells have adapted several ways to control MYC levels, and these mechanisms can be disrupted in cancer cells. One of the major ways in which MYC levels are controlled in cells is through targeted degradation by the ubiquitin-proteasome system (UPS). Here, we discuss the role of the UPS in the regulation of MYC protein levels and review some of the many proteins that have been shown to regulate MYC protein stability. In addition, we discuss how this relates to MYC transcriptional activity, human cancers, and therapeutic targeting.
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Affiliation(s)
- Amy S Farrell
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon 97239
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42
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Bortezomib congeners induce apoptosis of hepatocellular carcinoma via CIP2A inhibition. Molecules 2013; 18:15398-411. [PMID: 24335617 PMCID: PMC6269665 DOI: 10.3390/molecules181215398] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Revised: 11/20/2013] [Accepted: 11/28/2013] [Indexed: 11/18/2022] Open
Abstract
CIP2A is an oncoprotein that upregulates p-Akt and promotes cancer cell proliferation and survival. The proteasome inhibitor bortezomib has been shown to reduce CIP2A and lead to cell apoptosis. Here; we modified the functional group of bortezomib to generate a series of novel compounds and conducted a structure–activity relationship (SAR) study. The results showed that compound 1 was able to repress CIP2A expression and cell apoptosis in the same manner as bortezomib, but with less potency in inhibition of proteasome activity. This finding provides a new direction for the design of CIP2A inhibitors.
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Fan YL, Chen L, Wang J, Yao Q, Wan JQ. Over expression of PPP2R2C inhibits human glioma cells growth through the suppression of mTOR pathway. FEBS Lett 2013; 587:3892-7. [PMID: 24126060 DOI: 10.1016/j.febslet.2013.09.029] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 08/28/2013] [Accepted: 09/17/2013] [Indexed: 11/29/2022]
Abstract
PPP2R2C encodes a gamma isoform of the subunit B55 subfamily, which is a regulatory subunit of Protein phosphatase type 2A (PP2A). Our study shows that PPP2R2C is downregulated in glioma cells and human brain cancer patient samples. Overexpression of PPP2R2C inhibited cancer cell proliferation both in vitro and in vivo through the suppression of the activity of S6K in the mTOR pathway. Moreover, exogenous expression of PPP2R2C promoted the formation of a complex with the PP2A-C subunit to further enhance the binding of PP2A-C with S6K. Our results suggest that PPP2R2C is a potential tumor suppressor gene in human brain cancers. This study will provide novel insight into the development of therapeutic strategies in the treatment of human brain tumors.
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Affiliation(s)
- Yi-Ling Fan
- Department of Neurosurgery, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200127, China
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44
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Merkel cell polyomavirus small T antigen targets the NEMO adaptor protein to disrupt inflammatory signaling. J Virol 2013; 87:13853-67. [PMID: 24109239 DOI: 10.1128/jvi.02159-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Merkel cell carcinoma (MCC) is a highly aggressive nonmelanoma skin cancer arising from epidermal mechanoreceptor Merkel cells. In 2008, a novel human polyomavirus, Merkel cell polyomavirus (MCPyV), was identified and is strongly implicated in MCC pathogenesis. Currently, little is known regarding the virus-host cell interactions which support virus replication and virus-induced mechanisms in cellular transformation and metastasis. Here we identify a new function of MCPyV small T antigen (ST) as an inhibitor of NF-κB-mediated transcription. This effect is due to an interaction between MCPyV ST and the NF-κB essential modulator (NEMO) adaptor protein. MCPyV ST expression inhibits IκB kinase α (IKKα)/IKKβ-mediated IκB phosphorylation, which limits translocation of the NF-κB heterodimer to the nucleus. Regulation of this process involves a previously undescribed interaction between MCPyV ST and the cellular phosphatase subunits, protein phosphatase 4C (PP4C) and/or protein phosphatase 2A (PP2A) Aβ, but not PP2A Aα. Together, these results highlight a novel function of MCPyV ST to subvert the innate immune response, allowing establishment of early or persistent infection within the host cell.
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45
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Khanna A, Kauko O, Böckelman C, Laine A, Schreck I, Partanen JI, Szwajda A, Bormann S, Bilgen T, Helenius M, Pokharel YR, Pimanda J, Russel MR, Haglund C, Cole KA, Klefström J, Aittokallio T, Weiss C, Ristimäki A, Visakorpi T, Westermarck J. Chk1 targeting reactivates PP2A tumor suppressor activity in cancer cells. Cancer Res 2013; 73:6757-69. [PMID: 24072747 DOI: 10.1158/0008-5472.can-13-1002] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Checkpoint kinase Chk1 is constitutively active in many cancer cell types and new generation Chk1 inhibitors show marked antitumor activity as single agents. Here we present a hitherto unrecognized mechanism that contributes to the response of cancer cells to Chk1-targeted therapy. Inhibiting chronic Chk1 activity in cancer cells induced the tumor suppressor activity of protein phosphatase protein phosphatase 2A (PP2A), which by dephosphorylating MYC serine 62, inhibited MYC activity and impaired cancer cell survival. Mechanistic investigations revealed that Chk1 inhibition activated PP2A by decreasing the transcription of cancerous inhibitor of PP2A (CIP2A), a chief inhibitor of PP2A activity. Inhibition of cancer cell clonogenicity by Chk1 inhibition could be rescued in vitro either by exogenous expression of CIP2A or by blocking the CIP2A-regulated PP2A complex. Chk1-mediated CIP2A regulation was extended in tumor models dependent on either Chk1 or CIP2A. The clinical relevance of CIP2A as a Chk1 effector protein was validated in several human cancer types, including neuroblastoma, where CIP2A was identified as an NMYC-independent prognostic factor. Because the Chk1-CIP2A-PP2A pathway is driven by DNA-PK activity, functioning regardless of p53 or ATM/ATR status, our results offer explanative power for understanding how Chk1 inhibitors mediate single-agent anticancer efficacy. Furthermore, they define CIP2A-PP2A status in cancer cells as a pharmacodynamic marker for their response to Chk1-targeted therapy.
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Affiliation(s)
- Anchit Khanna
- Authors' Affiliations: Institute of Biomedical Technology and BioMediTech, University of Tampere and Tampere University Hospital; Tampere Graduate Program in Biomedicine and Biotechnology (TGPBB), University of Tampere, Tampere; Turku Centre for Biotechnology, University of Turku and Åbo Akademi University; Department of Pathology, University of Turku; Turku Doctoral Program of Biomedical Sciences (TuBS), Turku; Department of Pathology, HUSLAB and Haartman Institute, Helsinki University, Central Hospital and University of Helsinki; University of Helsinki Institute of Biomedicine and Genome-Scale Biology Research Program; Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland; Karlsruhe Institute of Technology, Campus North, Institute of Toxicology and Genetics, Karlsruhe, Germany; Adult Cancer Program, Lowy Cancer Centre and Prince of Wales Hospital, UNSW Medicine, University of New South Wales, Sydney, Australia; Department of Medical Biology and Genetics, Faculty of Medicine, Akdeniz University, Antalya, Turkey; Division of Oncology, Children's Hospital of Philadelphia; and Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia
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Comparative transcriptome profiling of an SV40-transformed human fibroblast (MRC5CVI) and its untransformed counterpart (MRC-5) in response to UVB irradiation. PLoS One 2013; 8:e73311. [PMID: 24019915 PMCID: PMC3760899 DOI: 10.1371/journal.pone.0073311] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/18/2013] [Indexed: 11/19/2022] Open
Abstract
Simian virus 40 (SV40) transforms cells through the suppression of tumor-suppressive responses by large T and small t antigens; studies on the effects of these two oncoproteins have greatly improved our knowledge of tumorigenesis. Large T antigen promotes cellular transformation by binding and inactivating p53 and pRb tumor suppressor proteins. Previous studies have shown that not all of the tumor-suppressive responses were inactivated in SV40-transformed cells; however, the underlying cause is not fully studied. In this study, we investigated the UVB-responsive transcriptome of an SV40-transformed fibroblast (MRC5CVI) and that of its untransformed counterpart (MRC-5). We found that, in response to UVB irradiation, MRC-5 and MRC5CVI commonly up-regulated the expression of oxidative phosphorylation genes. MRC-5 up-regulated the expressions of chromosome condensation, DNA repair, cell cycle arrest, and apoptotic genes, but MRC5CVI did not. Further cell death assays indicated that MRC5CVI was more sensitive than MRC-5 to UVB-induced cell death with increased caspase-3 activation; combining with the transcriptomic results suggested that MRC5CVI may undergo UVB-induced cell death through mechanisms other than transcriptional regulation. Our study provides a further understanding of the effects of SV40 transformation on cellular stress responses, and emphasizes the value of SV40-transformed cells in the researches of sensitizing neoplastic cells to radiations.
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47
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Hagen KR, Zeng X, Lee MY, Tucker Kahn S, Harrison Pitner MK, Zaky SS, Liu Y, O'Regan RM, Deng X, Saavedra HI. Silencing CDK4 radiosensitizes breast cancer cells by promoting apoptosis. Cell Div 2013; 8:10. [PMID: 23886499 PMCID: PMC3733890 DOI: 10.1186/1747-1028-8-10] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 07/18/2013] [Indexed: 11/10/2022] Open
Abstract
Background The discovery of molecular markers associated with various breast cancer subtypes has greatly improved the treatment and outcome of breast cancer patients. Unfortunately, breast cancer cells acquire resistance to various therapies. Mounting evidence suggests that resistance is rooted in the deregulation of the G1 phase regulatory machinery. Methods To address whether deregulation of the G1 phase regulatory machinery contributes to radiotherapy resistance, the MCF10A immortalized human mammary epithelial cell line, ER-PR-Her2+ and ER-PR-Her2- breast cancer cell lines were irradiated. Colony formation assays measured radioresistance, while immunocytochemistry, Western blots, and flow cytometry measured the cell cycle, DNA replication, mitosis, apoptosis, and DNA breaks. Results Molecular markers common to all cell lines were overexpressed, including cyclin A1 and cyclin D1, which impinge on CDK2 and CDK4 activities, respectively. We addressed their potential role in radioresistance by generating cell lines stably expressing small hairpin RNAs (shRNA) against CDK2 and CDK4. None of the cell lines knocked down for CDK2 displayed radiosensitization. In contrast, all cell lines knocked down for CDK4 were significantly radiosensitized, and a CDK4/CDK6 inhibitor sensitized MDA-MB-468 to radiation induced apoptosis. Our data showed that silencing CDK4 significantly increases radiation induced cell apoptosis in cell lines without significantly altering cell cycle progression, or DNA repair after irradiation. Our results indicate lower levels of phospho-Bad at ser136 upon CDK4 silencing and ionizing radiation, which has been shown to signal apoptosis. Conclusion Based on our data we conclude that knockdown of CDK4 activity sensitizes breast cancer cells to radiation by activating apoptosis pathways.
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Affiliation(s)
- Katie R Hagen
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| | - Xiangbin Zeng
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| | - Mi-Young Lee
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| | - Shannon Tucker Kahn
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| | | | - Sandra S Zaky
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| | - Yuan Liu
- Department of Biostatistics and Bioinformatics, Emory University School of Public Health, Atlanta, USA
| | - Ruth M O'Regan
- Department of Medical Oncology, Emory University School of Medicine, Atlanta, USA
| | - Xingming Deng
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| | - Harold I Saavedra
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA
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Dela Cruz FN, Giannitti F, Li L, Woods LW, Del Valle L, Delwart E, Pesavento PA. Novel polyomavirus associated with brain tumors in free-ranging raccoons, western United States. Emerg Infect Dis 2013; 19:77-84. [PMID: 23260029 PMCID: PMC3558004 DOI: 10.3201/eid1901.121078] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Tumors of any type are exceedingly rare in raccoons. High-grade brain tumors, consistently located in the frontal lobes and olfactory tracts, were detected in 10 raccoons during March 2010-May 2012 in California and Oregon, suggesting an emerging, infectious origin. We have identified a candidate etiologic agent, dubbed raccoon polyomavirus, that was present in the tumor tissue of all affected animals but not in tissues from 20 unaffected animals. Southern blot hybridization and rolling circle amplification showed the episomal viral genome in the tumors. The multifunctional nuclear protein large T-antigen was detectable by immunohistochemical analyses in a subset of neoplastic cells. Raccoon polyomavirus may contribute to the development of malignant brain tumors of raccoons.
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The B55α regulatory subunit of protein phosphatase 2A mediates fibroblast growth factor-induced p107 dephosphorylation and growth arrest in chondrocytes. Mol Cell Biol 2013; 33:2865-78. [PMID: 23716589 DOI: 10.1128/mcb.01730-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Fibroblast growth factor (FGF)-induced growth arrest of chondrocytes is a unique cell type-specific response which contrasts with the proliferative response of most cell types and underlies several genetic skeletal disorders caused by activating FGF receptor (FGFR) mutations. We have shown that one of the earliest key events in FGF-induced growth arrest is dephosphorylation of the retinoblastoma protein (Rb) family member p107 by protein phosphatase 2A (PP2A), a ubiquitously expressed multisubunit phosphatase. In this report, we show that the PP2A-B55α holoenzyme (PP2A containing the B55α subunit) is responsible for this phenomenon. Only the B55α (55-kDa regulatory subunit, alpha isoform) regulatory subunit of PP2A was able to bind p107, and this interaction was induced by FGF in chondrocytes but not in other cell types. Small interfering RNA (siRNA)-mediated knockdown of B55α prevented p107 dephosphorylation and FGF-induced growth arrest of RCS (rat chondrosarcoma) chondrocytes. Importantly, the B55α subunit bound with higher affinity to dephosphorylated p107. Since the p107 region interacting with B55α is also the site of cyclin-dependent kinase (CDK) binding, B55α association may also prevent p107 phosphorylation by CDKs. FGF treatment induces dephosphorylation of the B55α subunit itself on several serine residues that drastically increases the affinity of B55α for the PP2A A/C dimer and p107. Together these observations suggest a novel mechanism of p107 dephosphorylation mediated by activation of PP2A through B55α dephosphorylation. This mechanism might be a general signal transduction pathway used by PP2A to initiate cell cycle arrest when required by external signals.
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An P, Sáenz Robles MT, Pipas JM. Large T antigens of polyomaviruses: amazing molecular machines. Annu Rev Microbiol 2013; 66:213-36. [PMID: 22994493 DOI: 10.1146/annurev-micro-092611-150154] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The large tumor antigen (T antigen) encoded by simian virus 40 is an amazing molecular machine because it orchestrates viral infection by modulating multiple fundamental viral and cellular processes. T antigen is required for viral DNA replication, transcription, and virion assembly. In addition, T antigen targets multiple cellular pathways, including those that regulate cell proliferation, cell death, and the inflammatory response. Ectopic T antigen expression results in the immortalization and transformation of many cell types in culture and T antigen induces neoplasia when expressed in rodents. The analysis of the mechanisms by which T antigen carries out its many functions has proved to be a powerful way of gaining insights into cell biology. The accelerating pace at which new polyomaviruses are being discovered provides a collection of novel T antigens that, like simian virus 40, can be used to discover and study key cellular regulatory systems.
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Affiliation(s)
- Ping An
- Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA
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