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Lockbaum GJ, Henes M, Talledge N, Rusere LN, Kosovrasti K, Nalivaika EA, Somasundaran M, Ali A, Mansky LM, Yilmaz NK, Schiffer CA. Inhibiting HTLV-1 Protease: A Viable Antiviral Target. ACS Chem Biol 2021; 16:529-538. [PMID: 33619959 PMCID: PMC8126997 DOI: 10.1021/acschembio.0c00975] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) is a retrovirus that can cause severe paralytic neurologic disease and immune disorders as well as cancer. An estimated 20 million people worldwide are infected with HTLV-1, with prevalence reaching 30% in some parts of the world. In stark contrast to HIV-1, no direct acting antivirals (DAAs) exist against HTLV-1. The aspartyl protease of HTLV-1 is a dimer similar to that of HIV-1 and processes the viral polyprotein to permit viral maturation. We report that the FDA-approved HIV-1 protease inhibitor darunavir (DRV) inhibits the enzyme with 0.8 μM potency and provides a scaffold for drug design against HTLV-1. Analogs of DRV that we designed and synthesized achieved submicromolar inhibition against HTLV-1 protease and inhibited Gag processing in viral maturation assays and in a chronically HTLV-1 infected cell line. Cocrystal structures of these inhibitors with HTLV-1 protease highlight opportunities for future inhibitor design. Our results show promise toward developing highly potent HTLV-1 protease inhibitors as therapeutic agents against HTLV-1 infections.
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Affiliation(s)
- Gordon J. Lockbaum
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Mina Henes
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Nathaniel Talledge
- Institute for Molecular Virology, Masonic Cancer Center, University of Minnesota – Twin Cities, Minneapolis, Minnesota 55455, United States
| | - Linah N. Rusere
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Klajdi Kosovrasti
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Ellen A. Nalivaika
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Mohan Somasundaran
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Akbar Ali
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Louis M. Mansky
- Institute for Molecular Virology, Masonic Cancer Center, University of Minnesota – Twin Cities, Minneapolis, Minnesota 55455, United States
| | - Nese Kurt Yilmaz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
| | - Celia A. Schiffer
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, United States
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Polymorphic Nature of Human T-Cell Leukemia Virus Type 1 Particle Cores as Revealed through Characterization of a Chronically Infected Cell Line. J Virol 2017; 91:JVI.00369-17. [PMID: 28615198 DOI: 10.1128/jvi.00369-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 05/05/2017] [Indexed: 12/18/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 cell-to-cell transmission is dependent on the release of infectious virus particles into the virological synapse. The HTLV-1 particle structure is still poorly understood, and previous studies analyzed viruses produced by transformed lymphocytic cell lines chronically infected with HTLV-1, particularly the MT-2 cell line, which harbors truncated proviruses and expresses aberrant forms of the Gag protein. In this study, we demonstrate that the chronically infected SP cell line harbors a relatively low number of proviruses, making it a more promising experimental system for the study of the HTLV-1 particle structure. We first identified the genomic sites of integration and characterized the genetic structure of the gag region in each provirus. We also determined that despite encoding a truncated Gag protein, only the full-length Gag protein was incorporated into virus particles. Cryo-transmission electron microscopy analyses of the purified virus particles revealed three classes of particles based upon capsid core morphology: complete cores, incomplete cores, and particles without distinct electron densities that would correlate with the capsid region of a core structure. Observed cores were generally polygonal, and virus particles were on average 115 nm in diameter. These data corroborate particle morphologies previously observed for MT-2 cells and provide evidence that the known poor infectivity of HTLV-1 particles may correlate with HTLV-1 particle populations containing few virus particles possessing a complete capsid core structure.IMPORTANCE Studies of retroviral particle core morphology have demonstrated a correlation between capsid core stability and the relative infectivity of the virus. In this study, we used cryo-transmission electron microscopy to demonstrate that HTLV-1 particles produced from a distinct chronically infected cell line are polymorphic in nature, with many particles lacking organized electron densities that would correlate with a complete core structure. These findings have important implications for infectious HTLV-1 spread, particularly in the context of cell-to-cell transmission, a critical step in HTLV-1 transmission and pathogenesis.
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RNA stability regulates human T cell leukemia virus type 1 gene expression in chronically-infected CD4 T cells. Virology 2017; 508:7-17. [PMID: 28478312 DOI: 10.1016/j.virol.2017.04.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 04/25/2017] [Accepted: 04/26/2017] [Indexed: 11/22/2022]
Abstract
Regulation of expression of HTLV-1 gene products from integrated proviruses plays an important role in HTLV-1-associated disease pathogenesis. Previous studies have shown that T cell receptor (TCR)- and phorbol ester (PMA) stimulation of chronically infected CD4 T cells increases the expression of integrated HTLV-1 proviruses in latently infected cells, however the mechanism remains unknown. Analysis of HTLV-1 RNA and protein species following PMA treatment of the latently HTLV-1-infected, FS and SP T cell lines demonstrated rapid induction of tax/rex mRNA. This rapid increase in tax/rex mRNA was associated with markedly enhanced tax/rex mRNA stability while the stability of unspliced or singly spliced HTLV-1 RNAs did not increase. Tax/rex mRNA in the HTLV-1 constitutively expressing cell lines exhibited high basal stability even without PMA treatment. Our data support a model whereby T cell activation leads to increased HTLV-1 gene expression at least in part through increased tax/rex mRNA stability.
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Einsiedel LJ, Pham H, Woodman RJ, Pepperill C, Taylor KA. The prevalence and clinical associations of HTLV-1 infection in a remote Indigenous community. Med J Aust 2017; 205:305-9. [PMID: 27681971 DOI: 10.5694/mja16.00285] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 06/28/2016] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Hospital and laboratory data indicate that human T-lymphotropic virus type 1 (HTLV-1) is endemic to central Australia, but no community-based studies of its prevalence or disease burden have been reported. We determined the prevalence rates of HTLV-1 infection and of HTLV-1-associated diseases in a remote Indigenous community. SETTING A remote Northern Territory community. DESIGN All residents were asked to complete a health survey and offered a limited clinical examination, together with serological tests for HTLV-1 and Strongyloides, and HTLV-1 proviral load (PVL) assessment. MAIN OUTCOME MEASURES HTLV-1 seropositivity rates; HTLV-1 PVL (copies/105 peripheral blood leucocytes [PBL]); presentation with HTLV-1-related clinical disease. RESULTS HTLV-1 serostatus was determined for 97 of 138 residents (70%). The prevalence of HTLV-1 infection was significantly higher among adults (30 of 74 people tested) than children (1 of 23; P = 0.001). Nine of 30 HTLV-1-positive adults had a clinical syndrome that was potentially attributable to HTLV-1 infection (chronic lung disease, seven; symptomatic strongyloidiasis, two). The median HTLV-1 PVL was significantly higher for adults with chronic lung disease than for those who were asymptomatic (chronic lung disease, 649 copies/105 PBL [IQR, 162-2220]; asymptomatic adults, 40 copies/105 PBL [IQR, 0.9-229]; P = 0.017). Ten of 72 adults tested were seropositive for Strongyloides (six of 28 HTLV-1-positive participants and four of 44 HTLV-1-negative participants; P = 0.17), as were three of 15 children tested; the three children were HTLV-1-negative. CONCLUSION The prevalence of HTLV-1 infection and the rate of disease potentially attributable to HTLV-1 were high among adults in this remote community.
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Affiliation(s)
- Lloyd J Einsiedel
- Northern Territory Rural Clinical School, Flinders University, Alice Springs, NT
| | - Hai Pham
- Baker IDI Heart and Diabetes Institute, Alice Springs, NT
| | - Richard J Woodman
- Flinders Centre for Epidemiology and Biostatistics, Flinders University, Adelaide, SA
| | | | - Kerry A Taylor
- Poche Centre for Indigenous Health, Flinders University, Alice Springs, NT
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Witzens-Harig M, Giaisi M, Köhler R, Krammer PH, Li-Weber M. HTLV-1-associated adult T cell leukemia is highly susceptible to Navitoclax due to enhanced Bax expression. Int J Cancer 2015; 138:507-14. [PMID: 26260669 DOI: 10.1002/ijc.29726] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 07/28/2015] [Accepted: 08/03/2015] [Indexed: 11/09/2022]
Abstract
Over-expression of Bcl-2, Bcl-xL and Bcl-w is frequently associated with cancer resistance to chemotherapy. Navitoclax (ABT-263), an orally bio-available small-molecule mimetic of the Bcl-2 homology domain 3, specifically inhibits Bcl-2, Bcl-xL and Bcl-w. Despite promising results obtained from the clinical trials, the use of Navitoclax in patients is dose-limited due to induction of death of platelets via inhibition of Bcl-xL and subsequent thrombocytopenia. This side effect limits the use of Navitoclax in low doses and to very sensitive tumors. In this study, we show that HTLV-1-associated adult T-cell leukemia/lymphoma (ATL) cells, which over-express Bcl-2, Bcl-xL and Bcl-w, show a 10- to 20-fold higher sensitivity (EC50 = ∼ 25-50 nM) to Navitoclax compared to non-HTLV-1-associated leukemic cells (EC50 = ∼ 1 μM). Investigation of the molecular mechanisms revealed that the HTLV-1 oncogenic protein Tax up-regulates expression of the pro-apoptotic protein Bax which enhances the therapeutic efficacy of Navitoclax. In addition, we show that agents that inhibit the transcription elongation or translation initiation such as Wogonin and Roc-A can further decrease the effective dose of Navitoclax. Our study suggests that HTLV-1 ATL may be a good candidate disease for low dose Navitoclax therapy and probably with less risk of thrombocytopenia.
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Affiliation(s)
- Mathias Witzens-Harig
- Medizinische Klinik V, Hematology, Oncology Und Rheumatology, University Heidelberg, Heidelberg, 69120, Germany
| | - Marco Giaisi
- Tumorimmunology Program (D030), German Cancer Research Center (DKFZ), Heidelberg, D-69120, Germany
| | - Rebecca Köhler
- Tumorimmunology Program (D030), German Cancer Research Center (DKFZ), Heidelberg, D-69120, Germany
| | - Peter H Krammer
- Tumorimmunology Program (D030), German Cancer Research Center (DKFZ), Heidelberg, D-69120, Germany
| | - Min Li-Weber
- Tumorimmunology Program (D030), German Cancer Research Center (DKFZ), Heidelberg, D-69120, Germany
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6
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Tax contributes apoptosis resistance to HTLV-1-infected T cells via suppression of Bid and Bim expression. Cell Death Dis 2014; 5:e1575. [PMID: 25522269 PMCID: PMC4649845 DOI: 10.1038/cddis.2014.536] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 10/28/2014] [Accepted: 11/05/2014] [Indexed: 12/21/2022]
Abstract
The human T-lymphotropic virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia (ATL). HTLV-1 Tax has been shown to have a prosurvival role in infected T cells by enhancing expression of the Bcl-2 family of antiapoptotic proteins. In this study, we show that the expression of proapoptotic BH3-only proteins Bim (Bcl-2-interacting mediator of cell death) and Bid (BH3-interacting domain death agonist) is diminished in HTLV-1-infected leukemic cells. Using a Tax-inducible system and a transient overexpression approach, we demonstrate that Tax downregulates Bid and Bim expression at the transcriptional level. We show that reinforced expression of Bim and Bid in HTLV-1-infected T-cell lines sensitizes CD95/TRAIL- and anticancer drug-induced apoptosis. Furthermore, we show that Tax suppresses Bid and Bim expression by enhancing hypoxia-inducible factor-1α (HIF-1α) protein expression. siRNA knockdown of HIF-1α or chemical inhibition of the transactivation activity of HIF-1α resulted in an increase in Bid and Bim expression and, consequently, in an increase in CD95/TRAIL- and anticancer drug-induced apoptosis in HTLV-1-infected leukemic T-cell lines. Our study provides evidence that besides upregulation of prosurvival Bcl-2 proteins, Tax may also confer apoptosis resistance to HTLV-1-infected T cells by suppressing the expression of the proapoptotic BH3-only proteins Bim and Bid.
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Bourkoula K, Englert C, Giaisi M, Köhler R, Krammer PH, Li-Weber M. The Wilms' tumor suppressor WT1 enhances CD95L expression and promotes activation-induced cell death in leukemic T cells. Int J Cancer 2013; 134:291-300. [DOI: 10.1002/ijc.28379] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 06/25/2013] [Accepted: 06/27/2013] [Indexed: 12/12/2022]
Affiliation(s)
- Konstantina Bourkoula
- Tumor Immunology Program (D030); German Cancer Research Center (DKFZ); Heidelberg Germany
| | - Christoph Englert
- Leibniz Institute for Age Research-Fritz Lipmann Institute e.V. (FLI); Jena Germany
| | - Marco Giaisi
- Tumor Immunology Program (D030); German Cancer Research Center (DKFZ); Heidelberg Germany
| | - Rebecca Köhler
- Tumor Immunology Program (D030); German Cancer Research Center (DKFZ); Heidelberg Germany
| | - Peter H. Krammer
- Tumor Immunology Program (D030); German Cancer Research Center (DKFZ); Heidelberg Germany
| | - Min Li-Weber
- Tumor Immunology Program (D030); German Cancer Research Center (DKFZ); Heidelberg Germany
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8
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Ding J, Polier G, Köhler R, Giaisi M, Krammer PH, Li-Weber M. Wogonin and related natural flavones overcome tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein resistance of tumors by down-regulation of c-FLIP protein and up-regulation of TRAIL receptor 2 expression. J Biol Chem 2011; 287:641-649. [PMID: 22086925 DOI: 10.1074/jbc.m111.286526] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent that kills various tumor cells without damaging normal tissues. However, many cancers remain resistant to TRAIL. To overcome TRAIL resistance, combination therapies using sensitizers of the TRAIL pathway would be an efficacious approach. To investigate potential sensitizers of TRAIL-induced apoptosis, we used TRAIL-resistant human T cell leukemia virus type 1 (HTLV-1)-associated adult T cell leukemia/lymphoma (ATL) cells as a model system. So far, HTLV-1-associated ATL is incurable by presently known therapies. Here, we show that wogonin and the structurally related natural flavones apigenin and chrysin break TRAIL resistance in HTLV-1-associated ATL by transcriptional down-regulation of c-FLIP, a key inhibitor of death receptor signaling, and by up-regulation of TRAIL receptor 2 (TRAIL-R2). This effect is mediated through transcriptional inhibition of the p53 antagonist murine double minute 2 (Mdm2), leading to an increase in p53 levels and, consequently, to up-regulation of the p53 target gene TRAIL-R2. We also show that these flavones can sensitize to TNFα- and CD95-mediated cell death. Furthermore, we show that wogonin, apigenin, and chrysin also enhance TRAIL-mediated apoptosis in other human cancer cell lines including breast cancer cell line MDA-MB-231, colon cancer cell line HT-29, hepatocellular carcinoma cell line HepG2, melanoma cell line SK-MEL-37, and pancreatic carcinoma cell line Capan-1 by the same mechanism. Thus, our study suggests the potential use of these flavones as an adjuvant for TRAIL-mediated anticancer therapy.
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Affiliation(s)
- Jie Ding
- Tumor Immunology Program (D030), German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany
| | - Gernot Polier
- Tumor Immunology Program (D030), German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany
| | - Rebecca Köhler
- Tumor Immunology Program (D030), German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany
| | - Marco Giaisi
- Tumor Immunology Program (D030), German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany
| | - Peter H Krammer
- Tumor Immunology Program (D030), German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany
| | - Min Li-Weber
- Tumor Immunology Program (D030), German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany.
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9
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Zhou M, Lu H, Park H, Wilson-Chiru J, Linton R, Brady JN. Tax interacts with P-TEFb in a novel manner to stimulate human T-lymphotropic virus type 1 transcription. J Virol 2006; 80:4781-91. [PMID: 16641271 PMCID: PMC1472077 DOI: 10.1128/jvi.80.10.4781-4791.2006] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) encodes a transcriptional activator, Tax, whose function is essential for viral transcription and replication. Tax transactivates the viral long-terminal repeat through a series of protein-protein interactions which facilitate CREB and CBP/p300 binding. In addition, Tax dissociates transcription repressor histone deacetylase 1 interaction with the CREB response element. The subsequent events through which Tax interacts and communicates with RNA polymerase II and cyclin-dependent kinases (CDKs) are not clearly understood. Here we present evidence that Tax recruits positive transcription elongation factor b (P-TEFb) (CDK9/cyclin T1) to the viral promoter. This recruitment likely involves protein-protein interactions since Tax associates with P-TEFb in vitro as demonstrated by glutathione S-transferase fusion protein pull-down assays and in vivo as shown by co-immunoprecipitation assays. Functionally, small interfering RNA directed toward CDK9 inhibited Tax transactivation in transient assays. Consistent with these findings, the depletion of CDK9 from nuclear extracts inhibited Tax transactivation in vitro. Reconstitution of the reaction with wild-type P-TEFb, but not a kinase-dead mutant, recovered HTLV-1 transcription. Moreover, the addition of the CDK9 inhibitor flavopiridol blocked Tax transactivation in vitro and in vivo. Interestingly, we found that Tax regulates CDK9 kinase activity through a novel autophosphorylation pathway.
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Affiliation(s)
- Meisheng Zhou
- Virus Tumor Biology Section, Laboratory of Cellular Oncology, Center for Cancer Research, NCI/NIH, , Bethesda, MD 20892, USA
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10
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Krueger A, Fas SC, Giaisi M, Bleumink M, Merling A, Stumpf C, Baumann S, Holtkotte D, Bosch V, Krammer PH, Li-Weber M. HTLV-1 Tax protects against CD95-mediated apoptosis by induction of the cellular FLICE-inhibitory protein (c-FLIP). Blood 2006; 107:3933-9. [PMID: 16403915 DOI: 10.1182/blood-2005-06-2567] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The HTLV-1 transactivator protein Tax is essential for malignant transformation of CD4 T cells, ultimately leading to adult T-cell leukemia/lymphoma (ATL). Malignant transformation may involve development of apoptosis resistance. In this study we investigated the molecular mechanisms by which HTLV-1 Tax confers resistance toward CD95-mediated apoptosis. We show that Tax-expressing T-cell lines derived from HTLV-1-infected patients express elevated levels of c-FLIP(L) and c-FLIP(S). The levels of c-FLIP correlated with resistance toward CD95-mediated apoptosis. Using an inducible system we demonstrated that both resistance toward CD95-mediated apoptosis and induction of c-FLIP are dependent on Tax. In addition, analysis of early cleavage of the BH3-only Bcl-2 family member Bid, a direct caspase-8 substrate, revealed that apoptosis is inhibited at a CD95 death receptor proximal level in Tax-expressing cells. Finally, using siRNA we directly showed that c-FLIP confers Tax-mediated resistance toward CD95-mediated apoptosis. In conclusion, our data suggest an important mechanism by which expression of HTLV-1 Tax may lead to immune escape of infected T cells and, thus, to persistent infection and transformation.
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Affiliation(s)
- Andreas Krueger
- Tumorimmunology Program, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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11
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Cheng J, Zhang D, Zhou C, Marasco WA. Down-regulation of SHP1 and up-regulation of negative regulators of JAK/STAT signaling in HTLV-1 transformed cell lines and freshly transformed human peripheral blood CD4+ T-cells. Leuk Res 2004; 28:71-82. [PMID: 14630083 DOI: 10.1016/s0145-2126(03)00158-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Adult T-cell leukemia (ATL) is an aggressive malignancy that is associated with human T-cell lymphotropic virus I (HTLV-I) infection. HTLV-I transformed T-cell lines and fresh ATL cells are characterized by constitutive activation of the interleukin-2 receptor (IL-2R) signaling pathway however, the mechanism(s) responsible for constitutive IL-2R activation are unknown. To further examine the cause of this signaling pathway deregulation, we measured mRNA and protein expression levels by real-time PCR and Western blots, respectively, of four negative regulators of the IL-2R signaling pathway including src homology 2 (SH2)-containing phosphatase (SHP1), cytokine-inducible (CIS) SH2-containing protein, suppressor of cytokine signaling-1 (SOCS1) and protein inhibitor of activated signal transducer and activator of transcription 3 (STAT3) (PIAS3) in six HTLV-1 negative and seven HTLV-1 positive T-cell leukemia lines. The activation status of the JAK/STAT pathway was also examined. SHP1 mRNA and protein expression levels were selectively down regulated in all HTLV-1-infected transformed cell lines, while CIS, SOCS1, and PIAS3 protein expression were markedly but variably upregulated and the cells showed evidence of constitutive STAT3 activation. In acutely HTLV-1 infected primary CD4+ T-cells there was a gradual loss of SHP1 expression over 10 weeks in culture which correlated with progression from immortalization to transformation and loss of IL-2 dependence for growth. Two transformed cell lines that were established following HTLV-1 infection showed loss of SHP1 expression and overexpression of CIS, SOCS1, PIAS3. However, this overexpression was not adequate to block constitutive activation of the JAK/STAT pathway. Thus, multiple levels of IL-2 receptor signal deregulation are found in HTLV-1 transformed cells, which may be a result of early loss of SHP1 expression.
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Affiliation(s)
- Jihua Cheng
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA
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12
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Guyot DJ, Newbound GC, Lairmore MD. Signaling via the CD2 receptor enhances HTLV-1 replication in T lymphocytes. Virology 1997; 234:123-9. [PMID: 9234953 DOI: 10.1006/viro.1997.8636] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Human T lymphotropic virus type 1 (HTLV-1) is considered the etiologic agent of adult T cell leukemia/lymphoma and several chronic progressive immune-mediated diseases. Approximately 1-4% of infected individuals develop disease, generally decades following infection. Increased proviral transcription, mediated by the viral 40-kDa trans-activating protein, Tax, has been implicated in the pathogenesis of HTLV-1-associated diseases. Since the HTLV-1 promoter contains sequences responsive to cyclic AMP and protein kinase C, we hypothesized that lymphocyte activation signals initiated through the TCR/CD3 complex or CD2 receptor promote viral replication in HTLV-1-infected lymphocytes. We demonstrate that mAbs directed against the CD2, but not the CD3 receptor increase viral p24 capsid protein 1.5- to 5.7-fold in CD2/CD3+ HTLV-1-infected cell culture supernatants. Northern blot analysis demonstrated a 2.5- to 4-fold increase in all species of viral mRNA following CD2 cross-linking of OSP2/4 cells, an immortalized HTLV-1 cell line. Consistent with transcriptional regulation, reporter gene activity increased approximately 11-fold in CD2-stimulated Jurkat T cells cotransfected with a Tax-expressing plasmid and a CAT reporter gene construct under control of the HTLV-1 promoter. These data suggest a possible physiologic mechanism, whereby CD2-mediated cell adhesion and lymphocyte activation may promote viral transcription in infected lymphocytes.
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Affiliation(s)
- D J Guyot
- Center for Retrovirus Research and Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210-1093, USA
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13
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Collins ND, Newbound GC, Ratner L, Lairmore MD. In vitro CD4+ lymphocyte transformation and infection in a rabbit model with a molecular clone of human T-cell lymphotrophic virus type 1. J Virol 1996; 70:7241-6. [PMID: 8794375 PMCID: PMC190781 DOI: 10.1128/jvi.70.10.7241-7246.1996] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We transfected human and rabbit peripheral blood mononuclear cells (PBMC) with the ACH molecular clone of human T-cell lymphotropic virus type 1 (HTLV-1) to study its in vitro and in vivo properties. PBMC transfected with ACH were shown to transfer infection to naive PBMC. ACH transformed rabbit PBMC, as indicated by interleukin-2-independent proliferation of a transfectant culture. This transformant culture was shown by flow cytometric analysis to be a CD4+ CD25+ T-lymphocyte population containing, as determined by Southern blot analysis, at least three integrated HTLV-1 proviral copies. HTLV-1 infection was produced in rabbits inoculated with ACH-transfected, irradiated PBMC. Inoculated rabbits seroconverted to positivity for antibodies against HTLV-1 and had steady or rising HTLV-1 enzyme-linked immunosorbent assay antibody titers. Western blot (immunoblot) analysis revealed sustained seroconversion of rabbits to positivity for antibodies against all major viral antigenic determinants. Infection of rabbits was further demonstrated by antigen capture assay of p24 in PBMC and lymph node cultures and PCR amplification of proviral sequences from PBMC. These data suggest that ACH, like wild-type HTLV-1, infects and transforms primary CD4+ T lymphocytes and is infectious in vivo. This clone will facilitate investigations into the role of viral genes on biological properties of HTLV-1 in vitro and in vivo.
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Affiliation(s)
- N D Collins
- Center for Retrovirus Research, Ohio State University, Columbus 43210-1092, USA
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