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Lanigan LG, Hildreth BE, Dirksen WP, Simmons JK, Martin CK, Werbeck JL, Thudi NK, Papenfuss TL, Boyaka PN, Toribio RE, Ward JM, Weilbaecher KN, Rosol TJ. In Vivo Tumorigenesis, Osteolytic Sarcomas, and Tumorigenic Cell Lines from Transgenic Mice Expressing the Human T-Lymphotropic Virus Type 1 (HTLV-1) Tax Viral Oncogene. THE AMERICAN JOURNAL OF PATHOLOGY 2021; 191:335-352. [PMID: 33181139 PMCID: PMC7863134 DOI: 10.1016/j.ajpath.2020.10.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 09/17/2020] [Accepted: 10/13/2020] [Indexed: 12/12/2022]
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) causes adult T-cell leukemia, a disease commonly associated with hypercalcemia and osteolysis. There is no effective treatment for HTLV-1, and the osteolytic mechanisms are not fully understood. Mice expressing the HTLV-1 oncogene Tax, driven by the human granzyme B promoter (Tax+), develop osteolytic tumors. To investigate the progression of the bone-invasive malignancies, wild-type, Tax+, and Tax+/interferon-γ-/- mice were assessed using necropsy, histologic examination, IHC analysis, flow cytometry, and advanced imaging. Tax+ and Tax+/interferon-γ-/- malignancies of the ear, tail, and foot comprised poorly differentiated, round to spindle-shaped cells with prominent neutrophilic infiltrates. Tail tumors originated from muscle, nerve, and/or tendon sheaths, with frequent invasion into adjacent bone. F4/80+ and anti-mouse CD11b (Mac-1)+ histiocytic cells predominated within the tumors. Three Tax+/interferon-γ-/- cell lines were generated for in vivo allografts, in vitro gene expression and bone resorption assays. Two cell lines were of monocyte/macrophage origin, and tumors formed in vivo in all three. Differences in Pthrp, Il6, Il1a, Il1b, and Csf3 expression in vitro were correlated with differences in in vivo plasma calcium levels, tumor growth, metastasis, and neutrophilic inflammation. Tax+ mouse tumors were classified as bone-invasive histiocytic sarcomas. The cell lines are ideal for further examination of the role of HTLV-1 Tax in osteolytic tumor formation and the development of hypercalcemia and tumor-associated inflammation.
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Affiliation(s)
- Lisa G Lanigan
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio; Tox Path Specialists, a StageBio Company, Fredrick, Maryland
| | - Blake E Hildreth
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio; Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Wessel P Dirksen
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Jessica K Simmons
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Chelsea K Martin
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio; Department of Pathology and Microbiology, University of Prince Edward Island, Atlantic Veterinary College, Prince Edward Island, Canada
| | - Jillian L Werbeck
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Nandu K Thudi
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Tracey L Papenfuss
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Prosper N Boyaka
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Ramiro E Toribio
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | | | - Katherine N Weilbaecher
- Division of Molecular Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Thomas J Rosol
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio; Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio.
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Cook L, Melamed A, Yaguchi H, Bangham CR. The impact of HTLV-1 on the cellular genome. Curr Opin Virol 2017; 26:125-131. [PMID: 28822906 DOI: 10.1016/j.coviro.2017.07.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 06/12/2017] [Accepted: 07/18/2017] [Indexed: 10/19/2022]
Abstract
Human T-lymphotropic virus type-1 (HTLV-1) is the causative agent of adult T-cell leukaemia/lymphoma (ATL), an aggressive CD4+ T-cell malignancy. The mechanisms of leukaemogenesis in ATL are incompletely understood. Insertional mutagenesis has not previously been thought to contribute to the pathogenesis of ATL. However, the recent discovery that HTLV-1 binds the key chromatin architectural protein CTCF raises the hypothesis that HTLV-1 deregulates host gene expression by causing abnormal chromatin looping, bringing the strong HTLV-1 promoter-enhancer near to host genes that lie up to 2Mb from the integrated provirus. Here we review current opinion on the mechanisms of oncogenesis in ATL, with particular emphasis on the local and distant impact of HTLV-1 on the structure and expression of the host genome.
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Affiliation(s)
- Lucy Cook
- Section of Virology, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom; National Centre for Human Retrovirology, Imperial College Healthcare NHS Trust, London, United Kingdom; Department of Haematology, Imperial College Healthcare NHS Trust, United Kingdom
| | - Anat Melamed
- Section of Virology, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom
| | - Hiroko Yaguchi
- Section of Virology, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom
| | - Charles Rm Bangham
- Section of Virology, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom.
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Nicot C. HTLV-I Tax-Mediated Inactivation of Cell Cycle Checkpoints and DNA Repair Pathways Contribute to Cellular Transformation: "A Random Mutagenesis Model". ACTA ACUST UNITED AC 2015; 2. [PMID: 26835512 DOI: 10.13188/2377-9292.1000009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To achieve cellular transformation, most oncogenic retroviruses use transduction by proto-oncogene capture or insertional mutagenesis, whereby provirus integration disrupts expression of tumor suppressors or proto-oncogenes. In contrast, the Human T-cell leukemia virus type 1 (HTLV-I) has been classified in a separate class referred to as "transactivating retroviruses". Current views suggest that the viral encoded Tax protein transactivates expression of cellular genes leading to deregulated growth and transformation. However, if Tax-mediated transactivation was indeed sufficient for cellular transformation, a fairly high frequency of infected cells would eventually become transformed. In contrast, the frequency of transformation by HTLV-I is very low, likely less than 5%. This review will discuss the current understanding and recent discoveries highlighting critical functions of Tax in cellular transformation. HTLV-I Tax carries out essential functions in order to override cell cycle checkpoints and deregulate cellular division. In addition, Tax expression is associated with increased DNA damage and genome instability. Since Tax can inhibit multiple DNA repair pathways and stimulate unfaithful DNA repair or bypass checkpoints, these processes allow accumulation of genetic mutations in the host genome. Given this, a "Random Mutagenesis" transformation model seems more suitable to characterize the oncogenic activities of HTLV-I.
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Affiliation(s)
- Christophe Nicot
- Department of Pathology and Laboratory Medicine, Center for Viral Oncology, University of Kansas Medical Center, USA
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Baydoun HH, Cherian MA, Green P, Ratner L. Inducible nitric oxide synthase mediates DNA double strand breaks in Human T-Cell Leukemia Virus Type 1-induced leukemia/lymphoma. Retrovirology 2015; 12:71. [PMID: 26265053 PMCID: PMC4534112 DOI: 10.1186/s12977-015-0196-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 07/30/2015] [Indexed: 01/23/2023] Open
Abstract
Background Adult T-cell leukemia/lymphoma (ATLL) is an aggressive and fatal malignancy of CD4+ T-lymphocytes infected by the Human T-Cell Virus Type 1 (HTLV-1). The molecular mechanisms of transformation in ATLL have not been fully elucidated. However, genomic instability and cumulative DNA damage during the long period of latency is believed to be essential for HTLV-1 induced leukemogenesis. In addition, constitutive activation of the NF-κB pathway was found to be a critical determinant for transformation. Whether a connection exists between NF-κB activation and accumulation of DNA damage is not clear. We recently found that the HTLV-1 viral oncoprotein, Tax, the activator of the NF-κB pathway, induces DNA double strand breaks (DSBs). Results Here, we investigated whether any of the NF-κB target genes are critical in inducing DSBs. Of note, we found that inducible nitric oxide synthase (iNOS) that catalyzes the production of nitric oxide (NO) in macrophages, neutrophils and T-cells is over expressed in HTLV-1 infected and Tax-expressing cells. Interestingly, we show that in HTLV-1 infected cells, iNOS expression is Tax-dependent and specifically requires the activation of the classical NF-κB and JAK/STAT pathways. A dramatic reduction of DSBs was observed when NO production was inhibited, indicating that Tax induces DSBs through the activation of NO synthesis. Conclusions Determination of the impact of NO on HTLV-1-induced leukemogenesis opens a new area for treatment or prevention of ATLL and perhaps other cancers in which NO is produced.
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Affiliation(s)
- Hicham H Baydoun
- Division of Molecular Oncology, Department of Medicine Campus, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO, 63110, USA.
| | - Mathew A Cherian
- Division of Molecular Oncology, Department of Medicine Campus, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO, 63110, USA.
| | - Patrick Green
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, USA.
| | - Lee Ratner
- Division of Molecular Oncology, Department of Medicine Campus, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO, 63110, USA. .,Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA.
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Shembade N, Harhaj EW. Role of post-translational modifications of HTLV-1 Tax in NF-κB activation. World J Biol Chem 2010; 1:13-20. [PMID: 21540989 PMCID: PMC3083931 DOI: 10.4331/wjbc.v1.i1.13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 12/17/2009] [Accepted: 12/24/2009] [Indexed: 02/05/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiological agent of adult-T-cell leukemia/lymphoma. The HTLV-1 encoded Tax protein is a potent oncoprotein that deregulates gene expression by constitutively activating nuclear factor-κB (NF-κB). Tax activation of NF-κB is critical for the immortalization and survival of HTLV-1-infected T cells. In this review, we summarize the present knowledge on mechanisms underlying Tax-mediated NF-κB activation, with an emphasis on post-translational modifications of Tax.
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Affiliation(s)
- Noula Shembade
- Noula Shembade, Edward W Harhaj, Department of Microbiology and Immunology, Sylvester Comprehensive Cancer Center, University of Miami, Miller School of Medicine, Miami, FL 33136, United States
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Rauch D, Gross S, Harding J, Bokhari S, Niewiesk S, Lairmore M, Piwnica-Worms D, Ratner L. T-cell activation promotes tumorigenesis in inflammation-associated cancer. Retrovirology 2009; 6:116. [PMID: 20017942 PMCID: PMC2806367 DOI: 10.1186/1742-4690-6-116] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 12/17/2009] [Indexed: 02/03/2023] Open
Abstract
Chronic inflammation has long been associated with a wide range of malignancies, is now widely accepted as a risk factor for development of cancer, and has been implicated as a promoter of a variety of cancers including hematopoietic malignancies. We have described a mouse model uniquely suited to examine the link between inflammation and lymphoma in which the Tax oncogene, expressed in activated T and NK cells, perpetuates chronic inflammation that begins as microscopic intraepithelial lesions and develops into inflammatory nodules, subcutaneous tumors, and large granular lymphocytic leukemia. The use of bioluminescent imaging in these mice has expanded our ability to interrogate aspects of inflammation and tumorigenesis non-invasively. Here we demonstrate that bioluminescence induction in these mice correlated with inflammation resulting from wounding, T cell activation, and exposure to chemical agents. In experiments in which long-term effects of inflammation on disease outcome were monitored, the development of lymphoma was promoted by an inflammatory stimulus. Finally we demonstrated that activation of T-cells in T-cell receptor (TCR) transgenic TAX-LUC animals dramatically exacerbated the development of subcutaneous TCR- CD16+ LGL tumors. The role of activated T-cells and acquired immunity in inflammation-associated cancers is broadly applicable to hematopoietic malignancies, and we propose these mice will be of use in dissecting mechanisms by which activated T-cells promote lymphomagenesis in vivo.
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Affiliation(s)
- Dan Rauch
- Department of Medicine, Division of Molecular Oncology, Washington University School of Medicine, St Louis, MO 63110, USA.
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Imaging spontaneous tumorigenesis: inflammation precedes development of peripheral NK tumors. Blood 2008; 113:1493-500. [PMID: 18971418 DOI: 10.1182/blood-2008-07-166462] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Early events in tumor development are spontaneous, microscopic, and affected by the microenvironment. We developed a mouse model of spontaneous lymphoma in which malignant transformation is coupled with light emission that can be detected noninvasively using bioluminescent imaging. The human T-cell leukemia virus (HTLV) type 1 transcriptional transactivator Tax is an oncogene sufficient to produce lymphoma in transgenic animal models. Using the granzyme B promoter to restrict Tax expression to the mature natural killer (NK)/T-cell compartment, we have reproduced many elements of HTLV-associated adult T-cell leukemia/lymphoma. Tax activates signaling cascades associated with transformation, inflammation, and tumorigenesis. Here, we report that Tax-mediated activation of luciferase in long terminal repeat-luciferase (LTR-LUC) mice serves as a reporter for imaging these processes in vivo. Using bioluminescent imaging (BLI), we discovered that microscopic intraepithelial lesions precede the onset of peripheral subcutaneous tumors, tumorigenesis progresses through early reversible stages, and Tax is sufficient for inducing tumors. Based on these findings, we propose that Tax expression in activated lymphocytes initiates a cascade of events that leads to NK/T cell recruitment, activation, and transformation. The use of BLI expands our ability to interrogate the role of Tax in tumorigenesis in vivo and has made the association of inflammation with tumor initiation amenable for study.
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Abstract
Human T cell leukemia virus type I (HTLV-I) is the causative agent of a fatal malignancy known as adult T cell leukemia (ATL). The HTLV-I Tax protein is thought to play a significant role in the initiation and pathogenesis of HTLV-I-mediated disease. Tax is a potent oncogene that deregulates cellular gene expression by persistently activating signaling pathways such as NF-kappaB. Tax activation of NF-kappaB is critical for the immortalization and survival of HTLV-I-infected T cells. In this review, we describe recent insights into the mechanisms employed by Tax to activate the canonical and noncanonical NF-kappaB signaling pathways. The adaptor function of Tax appears to be a common and important mechanism for the pathological activation of both NF-kappaB pathways.
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Affiliation(s)
- Edward W Harhaj
- Department of Microbiology and Immunology, Sylvester Comprehensive Cancer Center, The University of Miami School of Medicine, Miami, FL 33136, USA.
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Gao L, Deng H, Zhao H, Hirbe A, Harding J, Ratner L, Weilbaecher K. HTLV-1 Tax transgenic mice develop spontaneous osteolytic bone metastases prevented by osteoclast inhibition. Blood 2005; 106:4294-302. [PMID: 16118323 PMCID: PMC1895233 DOI: 10.1182/blood-2005-04-1730] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One in 20 carriers of human T-cell leukemia virus type 1 (HTLV-1) will develop adult T-cell leukemia/lymphoma (ATL), a disease frequently associated with hypercalcemia, bone destruction, and a fatal course refractory to current therapies. Overexpression of the HTLV-1-encoded Tax oncoprotein under the human granzyme B promoter causes large granular lymphocytic leukemia/lymphomas in mice. We found that Tax+ mice spontaneously developed hypercalcemia, high-frequency osteolytic bone metastases, and enhanced osteoclast activity. We evaluated Tax tumors for the production of osteoclast-activating factors. Purification of Tax+ tumor cells and nonmalignant tumor-infiltrating lymphocytes demonstrated that each of these populations expressed transcripts for distinct osteoclast-activating factors. We then evaluated the effect of osteoclast inhibition on tumor formation. Mice doubly transgenic for Tax and the osteoclast inhibitory factor, osteoprotegerin, were protected from osteolytic bone disease and developed fewer soft-tissue tumors. Likewise, osteoclast inhibition with bone-targeted zoledronic acid protected Tax+ mice from bone and soft-tissue tumors and prolonged survival. Tax+ mice represent the first animal model of high-penetrance spontaneous osteolytic bone metastasis and underscore the critical role of nonmalignant host cells recruited by tumor cells in the process of cancer progression and metastasis.
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Affiliation(s)
- Ling Gao
- Department of Medicine, Division of Oncology, Washington University School of Medicine, 660 S Euclid Ave, Box 8069, St Louis, MO 63110, USA
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Kehn K, Fuente CDL, Strouss K, Berro R, Jiang H, Brady J, Mahieux R, Pumfery A, Bottazzi ME, Kashanchi F. The HTLV-I Tax oncoprotein targets the retinoblastoma protein for proteasomal degradation. Oncogene 2005; 24:525-40. [PMID: 15580311 DOI: 10.1038/sj.onc.1208105] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Human T-cell leukemia virus type-I (HTLV-I), the etiologic agent of adult T-cell leukemia (ATL), is estimated to affect 10-20 million people worldwide. The transforming ability of HTLV-I has been largely attributed to the viral protein Tax, which modulates the activity of several well-known cell cycle regulators. An important cell cycle regulator, the retinoblastoma (Rb) protein, is often inactivated in many cancers including virally induced cancers. Upon examination of Rb status, we observed a decrease in Rb protein expression in HTLV-1-infected cell lines as well as in ex vivo ATL patient samples. Transient transfection assays indicated that decreased Rb protein levels were Tax dependent. Here, we demonstrate for the first time that Tax directly associates with Rb. This interaction was localized within the B pocket of Rb and the C-terminus of Tax (aa 245-353). Within the C-terminus of Tax, we have identified an LXCXE-like motif, that when mutated resulted in the loss of Tax/Rb interaction. Furthermore, through the use of proteasome inhibitors, such as MG-132, in vivo and proteasome degradation assays in vitro, we found that Tax destabilizes the hypo-phosphorylated (active) form of Rb via the proteasome pathway. Therefore, we propose a model whereby Tax targets Rb to the proteasome by acting as a molecular bridge bringing Rb into contact with the proteasome for degradation.
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Affiliation(s)
- Kylene Kehn
- Department of Biochemistry and Molecular Biology, The George Washington University School of Medicine, Washington, DC 20037, USA
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Abstract
The pathogenesis of human T-cell leukemia virus (HTLV)-induced adult T-cell leukemia-lymphoma (ATLL) was explored using an infectious molecular viral clone and a transgenic mouse model. Activation of nuclear factor-kappaB by the HTLV transcriptional transactivator protein Tax was found to be important for lymphocyte immortalization and tumorigenesis. Interferon-gamma regulates tumor development owing primarily to angiostatic effects. Translational clinical studies of chemotherapy, interferon-alpha, and nucleoside reverse transcriptase inhibitors have also assisted in identifying the pathogenic features of ATLL.
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Affiliation(s)
- Lee Ratner
- Division of Molecular Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Costa CM, De Figueiredo EG, Santos TJ, Frota CH, Lobo CC, Santos FJ, Alcântara RN, Ramos RS, Rocha TT, Nogueira TF. Experimental HTLV-I infection and associated myelopathy. ARQUIVOS DE NEURO-PSIQUIATRIA 1998; 56:494-7. [PMID: 9754436 DOI: 10.1590/s0004-282x1998000300024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
HTLV-I infection and associated myelopathy has been reproduced experimentally in vitro and in vivo and these studies have shown the possibility of creating several lines of infective cells and of detecting minor and major clinical expressions of HTLV-I associated myelopathy in rabbits and rats.
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Affiliation(s)
- C M Costa
- Department of Physiology and Pharmacology, Federal University of Ceará (UFC), Brazil
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Ravandi-Kashani F, Sriswasdi C, Lynott A, Giles FJ. HTLV-1 and Adult T-Cell Leukemia/Lymphoma: A Review. Hematology 1998; 3:429-41. [PMID: 27420330 DOI: 10.1080/10245332.1998.11746417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Infection with the human T-lymphotropic virus type 1 (HTLV-1) has been shown to be fundamental to the etiology of Adult T-cell Leukemia/Lymphoma (ATL). The disease is endemic in specific geographic areas but is increasingly reported from non-endemic regions. With increasing number of patients with this entity, the diversity in the clinical features has become apparent. In the past treatment strategies using combination chemotherapy have been unsatisfactory, but more recent trials using adenosine analouges, interferons, and combination of interferons and AZT have shown promise. With increased understanding of the etiology and molecular basis of the disease more effective therapies can be anticipated.
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Affiliation(s)
- F Ravandi-Kashani
- a Department of Leukemia , University of Texas , M.D. Anderson Cancer Center , Houston , Texas
| | - C Sriswasdi
- a Department of Leukemia , University of Texas , M.D. Anderson Cancer Center , Houston , Texas
| | - A Lynott
- b International Oncology Study Group , Houston , Texas
| | - F J Giles
- a Department of Leukemia , University of Texas , M.D. Anderson Cancer Center , Houston , Texas
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