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Abstract
The SV40 viral oncogene has been used since the 1970s as a reliable and reproducible method to generate transgenic mouse models. This seminal discovery has taught us an immense amount about how tumorigenesis occurs, and its success has led to the evolution of many mouse models of cancer. Despite the development of more modern and targeted approaches for developing genetically engineered mouse models of cancer, SV40-induced mouse models still remain frequently used today. This review discusses a number of cancer types in which SV40 mouse models of cancer have been developed and highlights their relevance and importance to preclinical research.
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Affiliation(s)
- Amanda L Hudson
- Amanda L. Hudson, PhD, is a Sydney Neuro-Oncology Group postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia. Emily K. Colvin is a Cancer Institute NSW postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia
| | - Emily K Colvin
- Amanda L. Hudson, PhD, is a Sydney Neuro-Oncology Group postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia. Emily K. Colvin is a Cancer Institute NSW postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia
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2
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Khabaz MN, Nedjadi T, Gari MA, Al-Maghrabi JA, Atta HM, Basuni AA, Elderwi DA, Bakarman M. Simian virus 40 is not likely involved in the development of colorectal adenocarcinoma. Future Virol 2016. [DOI: 10.2217/fvl-2015-0020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aim: The purpose of this study is to investigate the role of simian virus 40 (SV40) in colorectal cancer development by assessing the presence of DNA and protein product of SV40 in colorectal cancer. Materials & methods: Extracted DNA from 83 archival colorectal adenocarcinoma samples and 35 control samples of noncancerous colon tissue was analyzed for SV40 using PCR-based techniques. The expression of the protein product was assessed using immunohistochemical staining. Results: All tested tumors and control cases failed to detect SV40 DNA in PCR assays. Furthermore, immunohistochemical staining did not show any viral proteins in both cancer and control cases. Conclusion: These results indicated that there is no association between SV40 and the development of colorectal adenocarcinomas.
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Affiliation(s)
- Mohamad Nidal Khabaz
- Department of Pathology, Rabigh Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Taoufik Nedjadi
- King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Mamdooh A Gari
- Centre of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Jaudah A Al-Maghrabi
- Department of Pathology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Hazem M Atta
- Department of Clinical Biochemistry, Rabigh Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
- Department of Medical Biochemistry, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Ashraf A Basuni
- Department of Clinical Biochemistry, Rabigh Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
- Department of Clinical Biochemistry, Liver Institute, Menofiya University, Egypt
| | - Douaa A Elderwi
- Department of Pediatric Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
- Department of Public Health & Community Medicine, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Marwan Bakarman
- Department of Family & Community Medicine, Rabigh Faculty of Medicine, King Abdulaziz University, 21589 Jeddah, Saudi Arabia
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3
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Expression of the small T antigen of Lymphotropic Papovavirus is sufficient to transform primary mouse embryo fibroblasts. Virology 2015; 487:112-20. [PMID: 26517398 DOI: 10.1016/j.virol.2015.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/25/2015] [Accepted: 10/02/2015] [Indexed: 01/17/2023]
Abstract
Polyomaviruses induce cell proliferation and transformation through different oncoproteins encoded within the early region (ER): large T antigen (LT), small T antigen (sT) and, in some cases, additional components. Each virus utilizes different mechanisms to achieve transformation. For instance, the LTs of Simian virus 40 (SV40), BK and/or JC virus can induce transformation; but Merkel Cell Polyomavirus (MCPyV) requires expression of sT. Lymphotropic Papovavirus (LPV) is closely related to Human Polyomavirus 9 (HuPyV9) and, under similar conditions, mice expressing LPV.ER exhibit higher rates of tumor formation than mice expressing SV40.ER. We have investigated the contributions of individual LPV.ER components to cell transformation. In contrast to SV40, LPV.ER transforms mouse embryonic fibroblasts (MEFs), but expression of LPV LT is insufficient to transform MEFs. Furthermore, LPV sT induces immortalization and transformation of MEFs. Thus, in the case of LPV, sT is the main mediator of oncogenesis.
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Giacobbi NS, Gupta T, Coxon AT, Pipas JM. Polyomavirus T antigens activate an antiviral state. Virology 2015; 476:377-385. [PMID: 25589241 DOI: 10.1016/j.virol.2014.12.032] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 11/18/2014] [Accepted: 12/19/2014] [Indexed: 01/12/2023]
Abstract
Ectopic expression of Simian Virus 40 (SV40) large T antigen (LT) in mouse embryonic fibroblasts (MEFs) increased levels of mRNAs encoding interferon stimulated genes (ISGs). The mechanism by which T antigen increases levels of ISGs in MEFs remains unclear. We present evidence that expression of T antigen from SV40, Human Polyomaviruses BK (BKV) or JC (JCV) upregulate production of ISGs in MEFs, and subsequently result in an antiviral state, as determined by inhibition of VSV or EMCV growth. The first 136 amino acids of LT are sufficient for these activities. Furthermore, increased ISG expression and induction of the antiviral state requires STAT1. Finally, the RB binding motif of LT is necessary for activation of STAT1. We conclude that the induction of the STAT1 mediated innate immune response in MEFs is a common feature shared by SV40, BKV and JCV.
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Affiliation(s)
- Nicholas S Giacobbi
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Tushar Gupta
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Andrew T Coxon
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - James M Pipas
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Removal of a small C-terminal region of JCV and SV40 large T antigens has differential effects on transformation. Virology 2014; 468-470:47-56. [PMID: 25129438 DOI: 10.1016/j.virol.2014.07.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2014] [Revised: 06/23/2014] [Accepted: 07/21/2014] [Indexed: 01/12/2023]
Abstract
The large T antigen (LT) protein of JCV and SV40 polyomaviruses is required to induce tumors in rodents and transform cells in culture. When both LTs are compared side-by-side in cell culture assays, SV40 shows a more robust transformation phenotype even though the LT sequences are highly conserved. A complete understanding of SV40׳s enhanced transforming capabilities relative to JCV is lacking. When the least conserved region of the LT proteins, the variable linker and host range region (VHR), was removed, changes in T antigen expression and cellular p53 post-translational modifications occurred, but interaction with the pRB pathway was unaffected. Transformation assessed by growth in low serum was reduced after VHR truncation of the SV40, but not the JCV, T antigen. Conversely, anchorage independent transformation was enhanced only by truncation of the JCV VHR. This is the first report to link the SV40 or JCV VHR region to transformation potential.
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Sáenz Robles MT, Chong JL, Koivisto C, Trimboli A, Liu H, Leone G, Pipas JM. Viral oncogene expression in the stem/progenitor cell compartment of the mouse intestine induces adenomatous polyps. Mol Cancer Res 2014; 12:1355-64. [PMID: 24994749 DOI: 10.1158/1541-7786.mcr-14-0166] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
UNLABELLED Genetic and epigenetic events that alter gene expression and/or protein function or localization are thought to be the primary mechanism that drives tumorigenesis and governs the clinical behavior of cancers. Yet, a number of studies have shown that the effects of oncogene expression or tumor suppressor ablation are highly dependent on cell type. The molecular basis for this cell-type specificity and how it contributes to tumorigenesis are unknown. Here, expression of a truncated SV40 large T antigen in murine intestinal crypts promoted the formation of numerous adenomatous polyps in the colon and small intestine. In contrast, when the same T-antigen construct is expressed in villous enterocytes, the consequences are limited to hyperplasia and dysplasia. The T-antigen-induced polyps show high levels of the proto-oncogene c-Myc protein even though there is no transport of β-catenin to the nucleus. Targeting the expression of viral oncogenes to intestinal crypts or villi provides a murine model system for studying cell-type specific effects in tumorigenesis, and is particularly relevant to the study of APC/β-catenin-independent pathways contributing to the generation of intestinal polyps. IMPLICATIONS This mouse model system describes the formation of colon polyps in the absence of Wnt/β-catenin signaling.
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Affiliation(s)
| | - Jean Leon Chong
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Christopher Koivisto
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Anthony Trimboli
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Huayang Liu
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Gustavo Leone
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - James M Pipas
- Department of Biological Sciences, University of Pittsburgh. Pittsburgh, Pennsylvania.
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A retinoblastoma allele that is mutated at its common E2F interaction site inhibits cell proliferation in gene-targeted mice. Mol Cell Biol 2014; 34:2029-45. [PMID: 24662053 DOI: 10.1128/mcb.01589-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The retinoblastoma protein (pRB) is best known for regulating cell proliferation through E2F transcription factors. In this report, we investigate the properties of a targeted mutation that disrupts pRB interactions with the transactivation domain of E2Fs. Mice that carry this mutation endogenously (Rb1(ΔG)) are defective for pRB-dependent repression of E2F target genes. Except for an accelerated entry into S phase in response to serum stimulation, cell cycle regulation in Rb1(ΔG/ΔG) mouse embryonic fibroblasts (MEFs) strongly resembles that of the wild type. In a serum deprivation-induced cell cycle exit, Rb1(ΔG/ΔG) MEFs display a magnitude of E2F target gene derepression similar to that of Rb1(-/-) cells, even though Rb1(ΔG/ΔG) cells exit the cell cycle normally. Interestingly, cell cycle arrest in Rb1(ΔG/ΔG) MEFs is responsive to p16 expression and gamma irradiation, indicating that alternate mechanisms can be activated in G1 to arrest proliferation. Some Rb1(ΔG/ΔG) mice die neonatally with a muscle degeneration phenotype, while the others live a normal life span with no evidence of spontaneous tumor formation. Most tissues appear histologically normal while being accompanied by derepression of pRB-regulated E2F targets. This suggests that non-E2F-, pRB-dependent pathways may have a more relevant role in proliferative control than previously identified.
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Two independent regions of simian virus 40 T antigen increase CBP/p300 levels, alter patterns of cellular histone acetylation, and immortalize primary cells. J Virol 2013; 87:13499-509. [PMID: 24089570 DOI: 10.1128/jvi.02658-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Simian virus 40 (SV40) large T antigen (SVT) interferes with normal cell regulation and thus has been used to identify cellular components controlling proliferation and homeostasis. We have previously shown that SVT-mediated transformation requires interaction with the histone acetyltransferases (HATs) CBP/p300 and now report that the ectopic expression of SVT in several cell types in vivo and in vitro results in a significant increase in the steady-state levels of CBP/p300. Furthermore, SVT-expressing cells contain higher levels of acetylated CBP/p300, a modification that has been linked to increased HAT activity. Concomitantly, the acetylation levels of histone residues H3K56 and H4K12 are markedly increased in SVT-expressing cells. Other polyomavirus-encoded large T antigens also increase the levels of CBP/p300 and sustain a rise in the acetylation levels of H3K56 and H4K12. SVT does not affect the transcription of CBP/p300, but rather, alters their overall levels through increasing the loading of CBP/p300 mRNAs onto polysomes. Two distinct regions within SVT, one located in the amino terminus and one in the carboxy terminus, can independently alter both the levels of CBP/p300 and the loading of CBP/p300 transcripts onto polysomes. Within the amino-terminal fragment, a functional J domain is necessary for increasing CBP/p300 and specific histone acetylation levels, as well as for immortalizing primary cells. These studies uncover the action of polyomavirus T antigens on cellular CBP/p300 and suggest that additional mechanisms are used by T antigens to induce cell immortalization and transformation.
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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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Comparative analysis of SV40 17kT and LT function in vivo demonstrates that LT's C-terminus re-programs hepatic gene expression and is necessary for tumorigenesis in the liver. Oncogenesis 2012; 1:e28. [PMID: 23552841 PMCID: PMC3503294 DOI: 10.1038/oncsis.2012.27] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Transformation by Simian Virus 40 (SV40) large T antigen (LT) is mediated in large part by its interaction with a variety of cellular proteins at distinct binding domains within LT. While the interaction of LT's N-terminus with the tumor suppressor Rb is absolutely required for LT-dependent transformation, the requirement for the interaction of LT's C-terminus with p53 is less clear and cell- and context-dependent. Here, we report a line of transgenic mice expressing a doxycycline-inducible liver-specific viral transcript that produces abundant 17kT, a naturally occurring SV40 early product that is co-linear with LT for the first 131 amino acids and that binds to Rb, but not p53. Comparative analysis of livers of transgenic mice expressing either 17kT or full length LT demonstrates that 17kT stimulates cell proliferation and induces hepatic hyperplasia but is incapable of inducing hepatic dysplasia or promoting hepatocarcinogenesis. Gene expression profiling demonstrates that 17kT and LT invoke a set of shared molecular signatures consistent with the action of LT's N-terminus on Rb-E2F-mediated control of hepatocyte transcription. However, 17kT also induces a unique set of genes, many of which are known transcriptional targets of p53, while LT actively suppresses them. LT also uniquely deregulates the expression of a subset of genes within the imprinted network and rapidly re-programs hepatocyte gene expression to a more fetal-like state. Finally, we provide evidence that the LT/p53 complex provides a gain-of-function for LT-dependent transformation in the liver, and confirm the absolute requirement for LT's C-terminus for liver tumor development by demonstrating that phosphatase and tensin homolog (PTEN)-deficiency readily cooperates with LT, but not 17kT, for tumorigenesis. These results confirm independent and inter-dependent functions for LT's N- and C-terminus and emphasize differences in the requirements for LT's C-terminus in cell-type dependent transformation.
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Zhang L, Zhao CG, Li DL, Wang JY, Li Q, Fan ZZ. Construction and identification of ATP4B-SV40T-IRES-GFP transgenic vector. Shijie Huaren Xiaohua Zazhi 2012; 20:314-318. [DOI: 10.11569/wcjd.v20.i4.314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To construct and identify ATP4B-SV40T-IRES-GFP transgenic vector.
METHODS: The mouse ATP4B gene promoter was amplified and inserted into IRES-GFP vector after the addition of restriction enzyme sites to result in ATP4B-IRES-GFP. After restriction enzyme digestion, the SV40T gene sequence was inserted into ATP4B-IRES-GFP. The resultant recombinant plasmid was identified by digestion with restriction enzymes PstI and AseⅠ.
RESULTS: The recombinant plasmids ATP4B-IRES-GFP and ATP4B-SV40T-IRES-GFP have been successfully constructed and can be used to generate transgenic mice.
CONCLUSION: The recombinated plasmid ATP4B-SV40T-IRES-GFP was constructed successfully and it could be used to construct the transgenic mice with primary gastric cancer.
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Sáenz Robles MT, Case A, Chong JL, Leone G, Pipas JM. The retinoblastoma tumor suppressor regulates a xenobiotic detoxification pathway. PLoS One 2011; 6:e26019. [PMID: 22022495 PMCID: PMC3192141 DOI: 10.1371/journal.pone.0026019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 09/15/2011] [Indexed: 11/22/2022] Open
Abstract
The retinoblastoma tumor suppressor (pRb) regulates cell cycle entry, progression and exit by controlling the activity of the E2F-family of transcription factors. During cell cycle exit pRb acts as a transcriptional repressor by associating with E2F proteins and thereby inhibiting their ability to stimulate the expression of genes required for S phase. Indeed, many tumors harbor mutations in the RB gene and the pRb-E2F pathway is compromised in nearly all types of cancers. In this report we show that both pRb and its interacting partners, the transcriptional factors E2F1-2-3, act as positive modulators of detoxification pathways important for metabolizing and clearing xenobiotics—such as toxins and drugs—from the body. Using a combination of conventional molecular biology techniques and microarray analysis of specific cell populations, we have analyzed the detoxification pathway in murine samples in the presence or absence of pRb and/or E2F1-2-3. In this report, we show that both pRb and E2F1-2-3 act as positive modulators of detoxification pathways in mice, challenging the conventional view of E2F1-2-3 as transcriptional repressors negatively regulated by pRb. These results suggest that mutations altering the pRb-E2F axis may have consequences beyond loss of cell cycle control by altering the ability of tissues to remove toxins and to properly metabolize anticancer drugs, and might help to understand the formation and progression rates of different types of cancer, as well as to better design appropriate therapies based on the particular genetic composition of the tumors.
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Affiliation(s)
- Maria Teresa Sáenz Robles
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Ashley Case
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Jean-Leon Chong
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, College of Biological Sciences and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, United States of America
| | - Gustavo Leone
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, College of Biological Sciences and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, United States of America
| | - James M. Pipas
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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Campello C, Comar M, D'Agaro P, Minicozzi A, Rodella L, Poli A. A molecular case-control study of the Merkel cell polyomavirus in colon cancer. J Med Virol 2011; 83:721-4. [DOI: 10.1002/jmv.22004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Rathi AV, Cantalupo PG, Sarkar SN, Pipas JM. Induction of interferon-stimulated genes by Simian virus 40 T antigens. Virology 2010; 406:202-11. [PMID: 20692676 PMCID: PMC2939315 DOI: 10.1016/j.virol.2010.07.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/22/2010] [Accepted: 07/09/2010] [Indexed: 12/24/2022]
Abstract
Simian virus 40 (SV40) large T antigen (TAg) is a multifunctional oncoprotein essential for productive viral infection and for cellular transformation. We have used microarray analysis to examine the global changes in cellular gene expression induced by wild-type T antigen (TAg(wt)) and TAg-mutants in mouse embryo fibroblasts (MEFs). The expression profile of approximately 800 cellular genes was altered by TAg(wt) and a truncated TAg (TAg(N136)), including many genes that influence cell cycle, DNA-replication, transcription, chromatin structure and DNA repair. Unexpectedly, we found a significant number of immune response genes upregulated by TAg(wt) including many interferon-stimulated genes (ISGs) such as ISG56, OAS, Rsad2, Ifi27 and Mx1. Additionally, we also observed activation of STAT1 by TAg(wt). Our genetic studies using several TAg-mutants reveal an unexplored function of TAg and indicate that the LXCXE motif and p53 binding are required for the upregulation of ISGs.
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Affiliation(s)
- Abhilasha V. Rathi
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Paul G. Cantalupo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Saumendra N. Sarkar
- University of Pittsburgh Cancer Institute, Hillman Cancer Research Pavilion, 5117 Centre Avenue, Pittsburgh, PA 15213
| | - James M. Pipas
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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Klein A, Li N, Nicholson JM, McCormack AA, Graessmann A, Duesberg P. Transgenic oncogenes induce oncogene-independent cancers with individual karyotypes and phenotypes. ACTA ACUST UNITED AC 2010; 200:79-99. [PMID: 20620590 DOI: 10.1016/j.cancergencyto.2010.04.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 03/24/2010] [Accepted: 04/01/2010] [Indexed: 11/25/2022]
Abstract
Cancers are clones of autonomous cells defined by individual karyotypes, much like species. Despite such karyotypic evidence for causality, three to six synergistic mutations, termed oncogenes, are generally thought to cause cancer. To test single oncogenes, they are artificially activated with heterologous promoters and spliced into the germ line of mice to initiate cancers with collaborating spontaneous oncogenes. Because such cancers are studied as models for the treatment of natural cancers with related oncogenes, the following must be answered: 1) which oncogenes collaborate with the transgenes in cancers; 2) how do single transgenic oncogenes induce diverse cancers and hyperplasias; 3) what maintains cancers that lose initiating transgenes; 4) why are cancers aneuploid, over- and underexpressing thousands of normal genes? Here we try to answer these questions with the theory that carcinogenesis is a form of speciation. We postulate that transgenic oncogenes initiate carcinogenesis by inducing aneuploidy. Aneuploidy destabilizes the karyotype by unbalancing teams of mitosis genes. This instability thus catalyzes the evolution of new cancer species with individual karyotypes. Depending on their degree of aneuploidy, these cancers then evolve new subspecies. To test this theory, we have analyzed the karyotypes and phenotypes of mammary carcinomas of mice with transgenic SV40 tumor virus- and hepatitis B virus-derived oncogenes. We found that (1) a given transgene induced diverse carcinomas with individual karyotypes and phenotypes; (2) these karyotypes coevolved with newly acquired phenotypes such as drug resistance; (3) 8 of 12 carcinomas were transgene negative. Having found one-to-one correlations between individual karyotypes and phenotypes and consistent coevolutions of karyotypes and phenotypes, we conclude that carcinogenesis is a form of speciation and that individual karyotypes maintain cancers as they maintain species. Because activated oncogenes destabilize karyotypes and are dispensable in cancers, we conclude that they function indirectly, like carcinogens. Such oncogenes would thus not be valid models for the treatment of cancers.
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Affiliation(s)
- Andreas Klein
- Charité-Universitätsmedizin Berlin, Campus Charité Mitte, Institut für Biochemie, Monbijoustrasse 2, Berlin, Germany
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Abstract
Over 50 years of polyomavirus research has produced a wealth of insights into not only general biologic processes in mammalian cells, but also, how conditions can be altered and signaling systems tweaked to produce transformation phenotypes. In the past few years three new members (KIV, WUV, and MCV) have joined two previously known (JCV and BKV) human polyomaviruses. In this review, we present updated information on general virologic features of these polyomaviruses in their natural host, concentrating on the association of MCV with human Merkel cell carcinoma. We further present a discussion on advances made in SV40 as the prototypic model, which has and will continue to inform our understanding about viruses and cancer.
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Affiliation(s)
- Ole Gjoerup
- Cancer Virology Program, Hillman Cancer Research Pavilion, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
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17
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Campello C, Comar M, Zanotta N, Minicozzi A, Rodella L, Poli A. Detection of SV40 in colon cancer: A molecular case-control study from Northeast Italy. J Med Virol 2010; 82:1197-200. [DOI: 10.1002/jmv.21798] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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García-Escudero V, García-Gómez A, Gargini R, Martín-Bermejo MJ, Langa E, de Yébenes JG, Delicado A, Avila J, Moreno-Flores MT, Lim F. Prevention of senescence progression in reversibly immortalized human ensheathing glia permits their survival after deimmortalization. Mol Ther 2009; 18:394-403. [PMID: 19935779 DOI: 10.1038/mt.2009.268] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Reversible immortalization holds great potential for primary tissue expansion to develop cell-based therapies as well as for basic research. Human olfactory ensheathing glia (hOEG) are promising candidates for treating spinal cord injury and for studying extrinsic neuroregenerative mechanisms. We used lentivectors with Cre/loxP technology to achieve reversible gene transfer of BMI1, SV40 large T antigen (TAg), a short hairpin RNA against p53 (shp53), and the catalytic subunit of telomerase (TERT) in primary cultures of hOEG from human donor cadaver olfactory bulbs. Several combinations of these genes were able to immortalize hOEG, conserving their antigenic markers and neuroregenerative properties but only those transduced by BMI1/TERT did not accumulate karyotypic alterations or increase senescence marker levels. Strikingly, these were also the only cells which continued to proliferate after transgene removal by Cre recombinase delivery, whereas hOEG immortalized by shp53 or TAg in combination with TERT entered into growth arrest and died. These data support the idea that immortalization and halting senescent changes are separate processes; hOEG immortalized by BMI1/TERT can revert back to their former primary cell replicative state when deimmortalized, whereas those transduced by the other combinations depend on the presence of these transgenes to maintain their aberrant proliferative state.
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Affiliation(s)
- Vega García-Escudero
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, Madrid, Spain
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19
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Simian virus 40 T-antigen-mediated gene regulation in enterocytes is controlled primarily by the Rb-E2F pathway. J Virol 2009; 83:9521-31. [PMID: 19570859 DOI: 10.1128/jvi.00583-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Simian virus 40 large T antigen (TAg) contributes to cell transformation, in part, by targeting two well-characterized tumor suppressors, pRb and p53. TAg expression affects the transcriptional circuits controlled by Rb and by p53. We have performed a microarray analysis to examine the global change in gene expression induced by wild-type TAg (TAg(wt)) and TAg mutants, in an effort to link changes in gene expression to specific transforming functions. For this analysis we have used enterocytes from the mouse small intestine expressing TAg. Expression of TAg(wt) in the mouse intestine results in hyperplasia and dysplasia. Our analysis indicates that practically all gene expression regulated by TAg in enterocytes is dependent upon its binding and inactivation of the Rb family proteins. To further dissect the role of the Rb family in the induction of intestinal hyperplasia, we have screened several lines of transgenic mice expressing a truncated TAg (TAg(N136)), which is able to interfere with the Rb pathway but lacks the functions associated with the carboxy terminus of the protein. This analysis confirmed the pivotal association between the Rb pathway and the induction of intestinal hyperplasia and revealed that upregulation of p53 target genes is not associated with the tumorigenic phenotype. Furthermore, we found that TAg(N136) was sufficient to induce intestinal hyperplasia, although the appearance of dysplasia was significantly delayed.
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20
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Sáenz Robles MT, Pipas JM. T antigen transgenic mouse models. Semin Cancer Biol 2009; 19:229-35. [PMID: 19505650 DOI: 10.1016/j.semcancer.2009.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/03/2009] [Accepted: 02/06/2009] [Indexed: 01/12/2023]
Abstract
The study of polyomavirus has benefited immensely from two scientific methodologies, cell culture and in vitro studies on one side and the use of transgenic mice as experimental models on the other. Both approaches allowed us to identify cellular products targeted by the viruses, the consequences of these interactions at the phenotypic and molecular level, and thus the potential roles of the targets within their normal cellular context. In particular, cell culture and in vitro reports suggest a model explaining partially how SV40 large T antigen contributes to oncogenic transformation. In most cases, T antigen induces cell cycle entry by inactivation of the Rb proteins (pRb, p130, and p107), thus activating E2F-dependent transcription and subsequent S-phase entry. Simultaneously, T antigen blocks p53 activity and therefore prevents the ensuing cell-cycle arrest and apoptosis. For the most part, studies of T antigen expression in transgenic mice support this model, but the use of T antigen mutants and their expression in different tissue and cell type settings have expanded our knowledge of the model system and raised important questions regarding tumorigenic mechanisms functioning in vivo.
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21
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Cantalupo PG, Sáenz-Robles MT, Rathi AV, Beerman RW, Patterson WH, Whitehead RH, Pipas JM. Cell-type specific regulation of gene expression by simian virus 40 T antigens. Virology 2009; 386:183-91. [PMID: 19201438 DOI: 10.1016/j.virol.2008.12.038] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 12/02/2008] [Accepted: 12/26/2008] [Indexed: 10/21/2022]
Abstract
SV40 transforms cells through the action of two oncoproteins, large T antigen and small t antigen. Small t antigen targets phosphatase PP2A, while large T antigen stimulates cell proliferation and survival by action on multiple proteins, including the tumor suppressors Rb and p53. Large T antigen also binds components of the transcription initiation complex and several transcription factors. We examined global gene expression in SV40-transformed mouse embryo fibroblasts, and in enterocytes obtained from transgenic mice. SV40 transformation alters the expression of approximately 800 cellular genes in both systems. Much of this regulation is observed in both MEFs and enterocytes and is consistent with T antigen action on the Rb-E2F pathway. However, the regulation of many genes is cell-type specific, suggesting that unique signaling pathways are activated in different cell types upon transformation, and that the consequences of SV40 transformation depends on the type of cell targeted.
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Affiliation(s)
- Paul G Cantalupo
- Department of Biological Sciences, 559 Crawford Hall, University of Pittsburgh Pittsburgh, Pennsylvania 15260, USA
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22
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Pipas JM. SV40: Cell transformation and tumorigenesis. Virology 2008; 384:294-303. [PMID: 19070883 DOI: 10.1016/j.virol.2008.11.024] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 11/18/2008] [Indexed: 10/21/2022]
Abstract
The story of SV40-induced tumorigenesis and cellular transformation is intimately entwined with the development of modern molecular biology. Because SV40 and other viruses have small genomes and are relatively easy to manipulate in the laboratory, they offered tractable systems for molecular analysis. Thus, many of the early efforts to understand how eukaryotes replicate their DNA, regulate expression of their genes, and translate mRNA were focused on viral systems. The discovery that SV40 induces tumors in certain laboratory animals and transforms many types of cultured cells offered the first opportunity to explore the molecular basis for cancer. The goal of this article is to highlight some of the experiments that have led to our current view of SV40-induced transformation and to provide some context as to how they contributed to basic research in molecular biology and to our understanding of cancer.
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Affiliation(s)
- James M Pipas
- Department of Biological Sciences, University of Pittsburgh, PA 15260, USA.
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23
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Sáenz-Robles MT, Markovics JA, Chong JL, Opavsky R, Whitehead RH, Leone G, Pipas JM. Intestinal hyperplasia induced by simian virus 40 large tumor antigen requires E2F2. J Virol 2007; 81:13191-9. [PMID: 17855529 PMCID: PMC2169091 DOI: 10.1128/jvi.01658-07] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The simian virus 40 large T antigen contributes to neoplastic transformation, in part, by targeting the Rb family of tumor suppressors. There are three known Rb proteins, pRb, p130, and p107, all of which block the cell cycle by preventing the transcription of genes regulated by the E2F family of transcription factors. T antigen interacts directly with Rb proteins and disrupts Rb-E2F complexes both in vitro and in cultured cells. Consequently, T antigen is thought to inhibit transcriptional repression by the Rb family proteins by disrupting their interaction with E2F proteins, thus allowing E2F-dependent transcription and the expression of cellular genes needed for entry into S phase. This model predicts that active E2F-dependent transcription is required for T-antigen-induced transformation. To test this hypothesis, we have examined the status of Rb-E2F complexes in murine enterocytes. Previous studies have shown that T antigen drives enterocytes into S phase, resulting in intestinal hyperplasia, and that the induction of enterocyte proliferation requires T-antigen binding to Rb proteins. In this paper, we show that normal growth-arrested enterocytes contain p130-E2F4 complexes and that T-antigen expression destroys these complexes, most likely by stimulating p130 degradation. Furthermore, unlike their normal counterparts, enterocytes expressing T antigen contain abundant levels of E2F2 and E2F3a. Concomitantly, T-antigen-induced intestinal proliferation is reduced in mice lacking either E2F2 alone or both E2F2 and E2F3a, but not in mice lacking E2F1. These studies support a model in which T antigen eliminates Rb-E2F repressive complexes so that specific activator E2Fs can drive S-phase entry.
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Affiliation(s)
- M Teresa Sáenz-Robles
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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24
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Rathi AV, Sáenz Robles MT, Pipas JM. Enterocyte proliferation and intestinal hyperplasia induced by simian virus 40 T antigen require a functional J domain. J Virol 2007; 81:9481-9. [PMID: 17581980 PMCID: PMC1951414 DOI: 10.1128/jvi.00922-07] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Transgenic mice expressing the simian virus 40 large T antigen (TAg) in enterocytes develop intestinal hyperplasia that progresses to dysplasia with age. This induction requires TAg action on the retinoblastoma (Rb) family of tumor suppressors and is independent of the p53 pathway. In cell culture systems, the inactivation of Rb proteins requires both a J domain in TAg that interacts with hsc70 and an LXCXE motif that directs association with Rb proteins. Together these elements are sufficient to release E2Fs from their association with Rb family members. We have generated transgenic mice that express a J domain mutant (D44N) in villus enterocytes. In contrast to wild-type TAg, the D44N mutant is unable to induce enterocyte proliferation. Histological and morphological examination revealed that mice expressing the J domain mutant have normal intestines without loss of growth control. Unlike mice expressing wild-type TAg, mice expressing D44N do not reduce the protein levels of p130 and are also unable to dissociate p130-E2F DNA binding complexes. Furthermore, mice expressing D44N in a null p130 background are still unable to develop hyperplasia. These studies demonstrate that the ectopic proliferation of enterocytes by TAg requires a functional J domain and suggest that the J domain is necessary to inactivate all three pRb family members.
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Affiliation(s)
- Abhilasha V Rathi
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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25
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Ahuja D, Sáenz-Robles MT, Pipas JM. SV40 large T antigen targets multiple cellular pathways to elicit cellular transformation. Oncogene 2005; 24:7729-45. [PMID: 16299533 DOI: 10.1038/sj.onc.1209046] [Citation(s) in RCA: 405] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
DNA tumor viruses such as simian virus 40 (SV40) express dominant acting oncoproteins that exert their effects by associating with key cellular targets and altering the signaling pathways they govern. Thus, tumor viruses have proved to be invaluable aids in identifying proteins that participate in tumorigenesis, and in understanding the molecular basis for the transformed phenotype. The roles played by the SV40-encoded 708 amino-acid large T antigen (T antigen), and 174 amino acid small T antigen (t antigen), in transformation have been examined extensively. These studies have firmly established that large T antigen's inhibition of the p53 and Rb-family of tumor suppressors and small T antigen's action on the pp2A phosphatase, are important for SV40-induced transformation. It is not yet clear if the Rb, p53 and pp2A proteins are the only targets through which SV40 transforms cells, or whether additional targets await discovery. Finally, expression of SV40 oncoproteins in transgenic mice results in effects ranging from hyperplasia to invasive carcinoma accompanied by metastasis, depending on the tissue in which they are expressed. Thus, the consequences of SV40 action on these targets depend on the cell type being studied. The identification of additional cellular targets important for transformation, and understanding the molecular basis for the cell type-specific action of the viral T antigens are two important areas through which SV40 will continue to contribute to our understanding of cancer.
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Affiliation(s)
- Deepika Ahuja
- Department of Biological Sciences, University of Pittsburgh, PA 15260, USA
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