Targeting HTLV-1 activation of NFκB in mouse models and ATLL patients

Role of miRNAs in Human T Cell Leukemia Virus Type 1 Induced T Cell Leukemia: A Literature Review and Bioinformatics Approach

Human T cell leukemia virus type 1 (HTLV-1) was identified as the first pathogenic human retrovirus and is estimated to infect 5 to 10 million individuals worldwide. Unlike other retroviruses, there is no effective therapy to prevent the onset of the most alarming diseases caused by HTLV-1, and the more severe cases manifest as the malignant phenotype of adult T cell leukemia (ATL). MicroRNA (miRNA) dysfunction is a common feature of leukemogenesis, and it is no different in ATL cases. Therefore, we sought to analyze studies that reported deregulated miRNA expression in HTLV-1 infected cells and patients’ samples to understand how this deregulation could induce malignancy. Through in silico analysis, we identified 12 miRNAs that stood out in the prediction of targets, and we performed functional annotation of the genes linked to these 12 miRNAs that appeared to have a major biological interaction. A total of 90 genes were enriched in 14 KEGG pathways with significant values, including TP53, WNT, MAPK, TGF-β, and Ras signaling pathways. These miRNAs and gene interactions are discussed in further detail for elucidation of how they may act as probable drivers for ATL onset, and while our data provide solid starting points for comprehension of miRNAs’ roles in HTLV-1 infection, continuous effort in oncologic research is still needed to improve our understanding of HTLV-1 induced leukemia.

TAX and HBZ: hFc Ɣ 1 proteins as targets for passive immunotherapy

Objective(s):

Human T leukemia virus type one (HTLV-1) causes two life-threatening diseases in around five percent of infected subjects, a T cell malignancy and a neurodegenerative disease. TAX and HBZ are the main virulence agents implicated in the manifestation of HTLV-1–associated diseases. Therefore, this study aims to produce these HTLV-1 factors as recombinant Fc fusion proteins to study the structures, their immunogenic properties as vaccines, and their capability to produce specific neutralization antibodies.

Materials and Methods:

TAX and HBZ sequences were chosen from the NCBI-nucleotide database, then designed as human Fc chimers and cloned into Pichia pastoris. Produced proteins were purified by HiTrap affinity chromatography and subcutaneously injected into rabbits. Rabbit Abs were purified by batch chromatography, and their neutralization activities for the HTLV-1-infected MT-2 cell line were assessed. Furthermore, the protective abilities of recombinant proteins were evaluated in Tax or HBZ immunized rabbits by MT-2 cell line inoculation and measurement of HTLV-1-proviral load.

Results:

Specific Abs against Tax and HBZ can eliminate 2 million MT-2 cells in 1/1000 dilution in vitro. In challenging assays, the immunization of the animals using Tax or HBZ had no protective activity as HTLV-1 PVL was still positive.

Conclusion:

The result suggests that recombinant TAX and HBZ: hFcγ1 proteins can produce a proper humoral immune response. Therefore, they could be considered a passive immunotherapy source for HTLV-1-associated diseases, while total TAX and HBZ proteins are unsuitable as HTLV-1 vaccine candidates.

Aggressive T-cell lymphomas: 2021 Updates on diagnosis, risk stratification and management

INTRODUCTION

Aggressive T-cell lymphomas continue to have a poor prognosis. There are over 27 different subtypes of peripheral T-cell lymphoma (PTCL), and we are now beginning to understand the differences between the various subtypes beyond histologic variations.

MOLECULAR PATHOGENESIS OF VARIOUS SUBTYPES OF PTCL

Gene expression profiling (GEP) can help in diagnosis and prognostication of various subtypes including PTCL-nos and anaplastic large cell lymphoma (ALCL). In addition, mutational analysis is now being incorporated in clinical trials of novel agents to evaluate various biomarkers of response to allow better therapeutic choices for patients.

TARGETED THERAPIES

There are many targeted agents currently in various stages of clinical trials for PTCL that take advantage of the differential expression of specific proteins or receptors in PTCL tumors. This includes the CD30 directed antibody drug conjugate brentuximab vedotin. Other notable targets are CD25, CCR4, inhibition of PI3kinase - m TOR and JAK/STAT pathways. The ALK inhibitors are promising for ALK expressing tumors.

IMMUNOTHERAPIES

Allogeneic stem cell transplant continues to be the curative therapy for most aggressive subtypes of PTCL. The use of checkpoint inhibitors in the treatment of PTCL is still controversial. The most promising results have been seen in cases of extranodal natural killer cell/T-cell (ENK/T) lymphomas and cutaneous T-cell lymphomas (CTCL). Bispecific antibody based treatments as well as CAR-T cell based therapies are in clinical trials.

Targeting NF-κB with Nanotherapy in a Mouse Model of Adult T-Cell Leukemia/Lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive, clonal malignancy of mature T cells caused by human T-cell leukemia virus type 1. Although it is a rare tumor type, it serves as an excellent model of a virus driven process that transforms cells and engenders a highly malignant tumor that is extraordinarily difficult to treat. The viral transcriptional transactivator (Tax) in the HTLV-1 genome directly promotes tumorigenesis, and Tax-induced oncogenesis depends on its ability to constitutively activate NF-κB signaling. Accordingly, we developed and evaluated a nano-delivery system that simultaneously inhibits both canonical (p65) and noncanonical (p100) NF-κB signaling pathways locally in tumors after systemic administration. Our results demonstrate that siRNA is delivered rapidly to ATLL tumors after either i.p. or i.v. injection. The siRNA treatment significantly reduced both p65 and p100 mRNA and protein expression. Anti-NF-κB nanotherapy significantly inhibited tumor growth in two distinct tumor models in mice: a spontaneous Tax-driven tumor model, and a Tax tumor cell transplant model. Moreover, siRNA nanotherapy sensitized late-stage ATLL tumors to the conventional chemotherapeutic agent etoposide, indicating a pleiotropic benefit for localized siRNA nanotherapeutics.

NF-κB-induced R-loop accumulation and DNA damage select for nucleotide excision repair deficiencies in adult T cell leukemia

Constitutive NF-κB activation (NF-κBCA) confers survival and proliferation advantages to cancer cells and frequently occurs in T/B cell malignancies including adult T cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1). Counterintuitively, NF-κBCA by the HTLV-1 transactivator/oncoprotein Tax induces a senescence response, and HTLV-1 infections in culture mostly result in senescence or cell-cycle arrest due to NF-κBCA How NF-κBCA induces senescence, and how ATL cells maintain NF-κBCA and avert senescence, remain unclear. Here we report that NF-κBCA by Tax increases R-loop accumulation and DNA double-strand breaks, leading to senescence. R-loop reduction via RNase H1 overexpression, and short hairpin RNA silencing of two transcription-coupled nucleotide excision repair (TC-NER) endonucleases that are critical for R-loop excision-Xeroderma pigmentosum F (XPF) and XPG-attenuate Tax senescence, enabling HTLV-1-infected cells to proliferate. Our data indicate that ATL cells are often deficient in XPF, XPG, or both and are hypersensitive to ultraviolet irradiation. This TC-NER deficiency is found in all ATL types. Finally, ATL cells accumulate R-loops in abundance. Thus, TC-NER deficits are positively selected during HTLV-1 infection because they facilitate the outgrowth of infected cells initially and aid the proliferation of ATL cells with NF-κBCA later. We suggest that TC-NER deficits and excess R-loop accumulation represent specific vulnerabilities that may be targeted for ATL treatment.

HTLV-1 Replication and Adult T Cell Leukemia Development

Human T-cell leukemia virus type 1 (HTLV-1) was discovered in 1980 as the first, and to date, the only retrovirus that causes human cancer. While HTLV-1 infection is generally asymptomatic, 3-5% of infected individuals develop a T cell neoplasm known as adult T cell leukemia/lymphoma (ATL) decades after infection. Since its discovery, HTLV-1 has served as a model for understanding retroviral oncogenesis, transcriptional regulation, cellular signal transduction, and cell-associated viral infection and spread. Much of the initial research was focused on the viral trans-activator/oncoprotein, Tax. Over the past decade, the study of HTLV-1 has entered the genomic era. With the development of new systems for studying HTLV-1 infection and pathogenesis, the completion of the whole genome, exome and transcriptome sequencing analyses of ATL, and the discovery of HBZ as another HTLV-1 oncogene, many established concepts about how HTLV-1 infects, persists and causes disease have undergone substantial revision. This chapter seeks to integrate our current understanding of the mechanisms of action of Tax and HBZ with the comprehensive genomic information of ATL to provide an overview of how HTLV-1 infects, replicates and causes leukemia.

Synergy between parthenolide and arsenic trioxide in adult T-cell leukemia/lymphoma cells in vitro

OBJECTIVES

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive lymphoid malignancy with low survival rate and distinct geographical distribution. In search for novel chemotherapeutics against ATLL, we investigated the combinatorial effects of parthenolide, a sesquiterpene lactone with valuable pharmaceutical activities, and arsenic trioxide (ATO) in vitro.

MATERIALS AND METHODS

MT2 cells, an ATLL cell line, were treated with increasing concentrations of parthenolide (1.25, 2.5, and 5 μg/ml) and ATO (2, 4, 8, and 16 µM) to determine their IC50. Then, cells were treated with a combination of sub-IC50 concentrations of parthenolide (1 μg/ml) and ATO (2 µM) for 72 hr. Cell viability and cell cycle changes were assessed by Alamar blue and PI staining, respectively. To understand the mechanisms responsible for observed effects, expression of CD44, NF-κB (REL-A), BMI-1, and C-MYC were investigated by real-time PCR.

RESULTS

Assessment of cell viability indicated that parthenolide significantly increased the toxicity of ATO, as confirmed by accumulation of MT2 cells in the sub G1 phase of the cell cycle. Moreover, molecular analysis revealed significant down-regulation of CD44, NF-κB (REL-A), BMI-1, and C-MYC upon combinatorial administration of parthenolide and ATO in comparison with relevant controls.

CONCLUSION

Taken together, present results showed that parthenolide significantly enhanced the toxicity of ATO in MT2 cells. Therefore, the future possible clinical impact of our study could be combinatorial use of parthenolide and ATO as a novel and more effective approach for ATLL.

Inhibition of IκBα phosphorylation potentiates regulated cell death induced by azidothymidine in HTLV-1 infected cells

Adult T cell leukemia/lymphoma (ATL) can be susceptible, at least transiently, to treatments with azidothymidine (AZT) plus IFNα and/or arsenic trioxide. However, the real role of AZT in this effect is still unclear. In fact, while reverse transcriptase (RT) inhibition could explain reduction of clonal expansion and of renewal of HTLV-1 infected cells during ATL progression, this effect alone seems insufficient to justify the evident and prompt decrease of the pro-viral load in treated patients. We have previously demonstrated that AZT is endowed with an intrinsic pro-apoptotic potential towards both peripheral blood mononuclear cells from healthy donors or some tumor cell lines, but this cytotoxic potential cannot be fully achieved unless IκBα phosphorylation is inhibited. Since the constitutive activation of NF-kappa B (NF-κB) appears a common biological basis of HTLV-1-infected cells, a pharmacological inhibition of IκBα phosphorylation seems a potential strategy for treating and preventing HTLV-1 related pathologies. In this study, we have demonstrated that a combination treatment with the IκBα phosphorylation inhibitor Bay 11-7085 and AZT induced increased levels of regulated cell death (RCD) by apoptosis compared to the single treatments in HTLV-1 infected cells of different origin. Importantly, levels of RCD were considerably higher in infected cells in comparison with the uninfected ones. Inhibition of NF-κB activation following the combined treatment was confirmed by analysis of both gel-shift and functional activity of the NF-κB complex proteins, p65/p52. Moreover, a transcriptional analysis revealed that the addition of Bay 11-7085 to AZT treatment in HTLV-1-infected cells modified their transcriptional profile, by inducing the upregulation of some pro-apoptotic genes together with the downregulation of some anti-apoptotic genes. Our data suggest that addition of adequate concentrations of IκBα phosphorylation inhibitor to therapeutic regimens including AZT could be a promising strategy in ATL.

HTLV-1 basic leucine zipper factor protects cells from oxidative stress by upregulating expression of Heme Oxygenase I

Adult T-cell Leukemia (ATL) is a lymphoproliferative disease of CD4+ T-cells infected with Human T-cell Leukemia Virus type I (HTLV-1). With the exception of allogeneic hematopoietic stem cell transplantation, there are no effective treatments to cure ATL, and ATL cells often acquire resistance to conventional chemotherapeutic agents. Accumulating evidence shows that development and maintenance of ATL requires key contributions from the viral protein, HTLV-1 basic leucine zipper factor (HBZ). In this study we found that HBZ activates expression of Heme Oxygenase 1 (HMOX-1), a component of the oxidative stress response that functions to detoxify free heme. Transcription of HMOX1 and other antioxidant genes is regulated by the small Mafs. These cellular basic leucine zipper (bZIP) factors control transcription by forming homo- or heterodimers among themselves or with other cellular bZIP factors that then bind Maf responsive elements (MAREs) in promoters or enhancers of antioxidant genes. Our data support a model in which HBZ activates HMOX1 transcription by forming heterodimers with the small Mafs that bind MAREs located in an upstream enhancer region. Consistent with this model, we found that HMOX-1 is upregulated in HTLV-1-transformed T-cell lines and confers these cells with resistance to heme-induced cytotoxicity. In this context, HBZ-mediated activation of HMOX-1 expression may contribute to resistance of ATL cells to certain chemotherapeutic agents. We also provide evidence that HBZ counteracts oxidative stress caused by two other HTLV-1-encoded proteins, Tax and p13. Tax induces oxidative stress as a byproduct of driving mitotic expansion of infected cells, and p13 is believed to induce oxidative stress to eliminate infected cells that have become transformed. Therefore, in this context, HBZ-mediated activation of HMOX-1 expression may facilitate transformation. Overall, this study characterizes a novel function of HBZ that may support the development and maintenance of ATL.

Absence of FLT3 mutations in Iranian adult T-cell leukemia/lymphoma patients

Background: Adult T cell leukemia lymphoma (ATLL) is a rare disease, significantly linked to the infection by the human T-cell lymphotropic virus 1(HTLV-1). ATLL is typically preceded by decades of clinical latency during which infected cells accumulate selectable traits leading to a malignant transformation. Amongst all the HTLV-1 infected carriers only about 3-5% will develop ATLL. Despite the intensive attempt to improve the overall survival, ATLL remains one of worse prognosis among the hematologic malignancies. FMS like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutations are mutations which are frequent among leukemic patients. We aimed to investigate the frequency of FLT3 mutation status in patients with acute type of ATLL which has not been studied yet.

Methods: In this case control study 38 patients with acute type of ATLL were retrospectively analyzed between February 2015 and February 2017. Forty HTLV-1 positive patients were also used as control cases. Genomic DNA was extracted according to phenolchloroform protocol and two restriction fragment length polymorphism (RFLP) PCR reactions were set up to detect FLT3/ ITD and FLT3/TKD mutations. Differences between variables were evaluated by the chi-square test and t test for categorical and continuous variables, respectively. SPSS software v. 15 was used for statistical analysis. All P values were two sided and values less than 0.05 were considered to be significant.

Results: No FLT3 mutations were detected in acute type of ATLL patients. So far, not many studies have shown the frequency of FLT3 mutation in ATLL patients

Conclusion: Therefore, we conclude that although FLT3 mutations are rather unusual in the acute type of ATLL patients, but other alternative mechanisms associated with ATLL remain to be further investigated. This study was a novel project regarding the analysis of FLT3 mutation in the field of ATLL research.

The Human T-Cell Leukemia Virus Type 1 Basic Leucine Zipper Factor Attenuates Repair of Double-Stranded DNA Breaks via Nonhomologous End Joining

Adult T-cell leukemia (ATL) is a fatal malignancy of CD4⁺ T cells infected with human T-cell leukemia virus type 1 (HTLV-1). ATL cells often exhibit random gross chromosomal rearrangements that are associated with the induction and improper repair of double-stranded DNA breaks (DSBs). The viral oncoprotein Tax has been reported to impair DSB repair but has not been shown to be consistently expressed throughout all phases of infection. The viral oncoprotein HTLV-1 basic leucine zipper (bZIP) factor (HBZ) is consistently expressed prior to and throughout disease progression, but it is unclear whether it also influences DSB repair. We report that HBZ attenuates DSB repair by nonhomologous end joining (NHEJ), in a manner dependent upon the bZIP domain. HBZ was found to interact with two vital members of the NHEJ core machinery, Ku70 and Ku80, and to be recruited to DSBs in a bZIP-dependent manner in vitro We observed that HBZ expression also resulted in a bZIP-dependent delay in DNA protein kinase (DNA-PK) activation following treatment with etoposide. Although Tax is reported to interact with Ku70, we did not find Tax expression to interfere with HBZ:Ku complex formation. However, as Tax was reported to saturate NHEJ, we found that this effect masked the attenuation of NHEJ by HBZ. Overall, these data suggest that DSB repair mechanisms are impaired not only by Tax but also by HBZ and show that HBZ expression may significantly contribute to the accumulation of chromosomal abnormalities during HTLV-1-mediated oncogenesis.IMPORTANCE Human T-cell leukemia virus type 1 (HTLV-1) infects 15 million to 20 million people worldwide. Approximately 90% of infected individuals are asymptomatic and may remain undiagnosed, increasing the risk that they will unknowingly transmit the virus. About 5% of the HTLV-1-positive population develop adult T-cell leukemia (ATL), a fatal disease that is not highly responsive to treatment. Although ATL development remains poorly understood, two viral proteins, Tax and HBZ, have been implicated in driving disease progression by manipulating host cell signaling and transcriptional pathways. Unlike Tax, HBZ expression is consistently observed in all infected individuals, making it important to elucidate the specific role of HBZ in disease progression. Here, we present evidence that HBZ could promote the accumulation of double-stranded DNA breaks (DSBs) through the attenuation of the nonhomologous end joining (NHEJ) repair pathway. This effect may lead to genome instability, ultimately contributing to the development of ATL.

From Immunodeficiency to Humanization: The Contribution of Mouse Models to Explore HTLV-1 Leukemogenesis

The first discovered human retrovirus, Human T-Lymphotropic Virus type 1 (HTLV-1), is responsible for an aggressive form of T cell leukemia/lymphoma. Mouse models recapitulating the leukemogenesis process have been helpful for understanding the mechanisms underlying the pathogenesis of this retroviral-induced disease. This review will focus on the recent advances in the generation of immunodeficient and human hemato-lymphoid system mice with a particular emphasis on the development of mouse models for HTLV-1-mediated pathogenesis, their present limitations and the challenges yet to be addressed.

Inducible nitric oxide synthase mediates DNA double strand breaks in Human T-Cell Leukemia Virus Type 1-induced leukemia/lymphoma

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.

Epigallocatechin-3-gallate inhibits tax-dependent activation of nuclear factor kappa B and of matrix metalloproteinase 9 in human T-cell lymphotropic virus-1 positive leukemia cells

Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenol molecule from green tea and is known to exhibit antioxidative as well as tumor suppressing activity. In order to examine EGCG tumor invasion and suppressing activity against adult T-cell leukemia (ATL), two HTLV-1 positive leukemia cells (HuT-102 and C91- PL) were treated with non-cytotoxic concentrations of EGCG for 2 and 4 days. Proliferation was significantly inhibited by 100 μM at 4 days, with low cell lysis or cytotoxicity. HTLV-1 oncoprotein (Tax) expression in HuT- 102 and C91-PL cells was inhibited by 25 μM and 125 μM respectively. The same concentrations of EGCG inhibited NF-kB nuclearization and stimulation of matrix metalloproteinase-9 (MMP-9) expression in both cell lines. These results indicate that EGCG can inhibit proliferation and reduce the invasive potential of HTLV-1- positive leukemia cells. It apparently exerted its effects by suppressing Tax expression, manifested by inhibiting the activation of NF-kB pathway and induction of MMP-9 transcription in HTLV-1 positive cells.

The novel IKK2 inhibitor LY2409881 potently synergizes with histone deacetylase inhibitors in preclinical models of lymphoma through the downregulation of NF-κB

PURPOSE

To evaluate the pharmacologic activity of a novel inhibitor of IκB kinase β (IKK2), LY2409881, in preclinical models of B- and T-cell lymphoma, as a single agent and in combination with histone deacetylase (HDAC) inhibitors.

EXPERIMENTAL DESIGN

The in vitro activity of LY2409881 was determined using an ATP-based growth inhibition assay and flow cytometric assay of apoptosis in lymphoma cell lines. The in vivo activity of LY2409881 was determined using SCID-beige xenograft mouse model. The mechanism of action was determined using immunoblotting, immuofluorescence, and electrophoretic mobility shift assay. Synergy of LY2409881 with other drugs active in lymphoma was determined by calculating relative risk ratio (RRR) and combination index (CI).

RESULTS

LY2409881 inhibited constitutively activated NF-κB, and caused concentration- and time-dependent growth inhibition and apoptosis in lymphoma cells. In models of diffuse large B-cell lymphoma (DLBCL), the cytotoxicity of LY2409881 correlated with the overall activation status of NF-κB, but not simply in a pattern predicted by the cell-of-origin classification of these cell lines. LY2409881 was safe to mice at three dose levels, 50, 100, and 200 mg/kg, all of which caused significant inhibition of tumor growth. LY2409881 suppressed the activity of the NF-κB subunit p65 in lymphoma cells treated by the HDAC inhibitor romidepsin, underlying a potential mechanism of the marked synergy observed of these two drugs.

CONCLUSION

Collectively, these data strongly suggest that targeting the NF-κB pathway in combination with romidepsin could represent a novel and potent regimen for the treatment of B- and T-cell lymphoma.

Tetracycline-regulated mouse models of cancer

Genetically engineered mouse models (GEMMs) have proven essential to the study of mammalian gene function in both development and disease. However, traditional constitutive transgenic mouse model systems are limited by the temporal and spatial characteristics of the experimental promoter used to drive transgene expression. To address this limitation, considerable effort has been dedicated to developing conditional and inducible mouse model systems. Although a number of approaches to generating inducible GEMMs have been pursued, several have been restricted by toxic or undesired physiological side effects of the compounds used to activate gene expression. The development of tetracycline (tet)-dependent regulatory systems has allowed for circumvention of these issues resulting in the widespread adoption of these systems as an invaluable tool for modeling the complex nature of cancer progression.

HTLV-1 and leukemogenesis: virus-cell interactions in the development of adult T-cell leukemia

Human T-cell lymphotropic virus type 1 (HTLV-1) was originally discovered in the early 1980s. It is the first retrovirus to be unambiguously linked causally to a human cancer. HTLV-1 currently infects approximately 20 million people worldwide. In this chapter, we review progress made over the last 30 years in our understanding of HTLV-1 infection, replication, gene expression, and cellular transformation.

Mechanisms of nanoparticle-mediated siRNA transfection by melittin-derived peptides

Traditional peptide-mediated siRNA transfection via peptide transduction domains exhibits limited cytoplasmic delivery of siRNA due to endosomal entrapment. This work overcomes these limitations with the use of membrane-destabilizing peptides derived from melittin for the knockdown of NFkB signaling in a model of adult T-cell leukemia/lymphoma. While the mechanism of siRNA delivery into the cytoplasmic compartment by peptide transduction domains has not been well studied, our analysis of melittin derivatives indicates that concurrent nanocomplex disassembly and peptide-mediated endosomolysis are crucial to siRNA transfection. Importantly, in the case of the most active derivative, p5RHH, this process is initiated by acidic pH, indicating that endosomal acidification after macropinocytosis can trigger siRNA release into the cytoplasm. These data provide general principles regarding nanocomplex response to endocytosis, which may guide the development of peptide/siRNA nanocomplex-based transfection.

p53 dysfunction precedes the activation of nuclear factor-κB during disease progression in mice expressing Tax, a human T-cell leukemia virus type 1 oncoprotein

Transgenic (Tg) mice expressing Tax, a human T-cell leukemia virus type 1 (HTLV-1) oncoprotein, develop mature T-cell leukemia/lymphoma. The leukemic cells in Tg mice expressing Tax show p53 dysfunction and nuclear factor-κB (NF-κB) activation, similar to that seen in adult T-cell leukemia/lymphoma (ATLL) cells from patients infected with HTLV-1. However, it is unclear when these effects occur in HTLV-1 carriers during the development of ATLL. Here, we examined p53 function and NF-κB activity before the onset of leukemia in Tax-expressing Tg (Tax-Tg) mice between 4 and 25 months of age. At 4-10 months of age, 71% of mice showed p53 inactivation, without evidence for NF-κB activation, even though tax expression was consistent from 4 to 25 months of age. The decline in p53 function resulted from decreased p53 accumulation after DNA damage. From 11 months of age onward, 75% of mice showed p53 dysfunction and 37.5% showed constitutive NF-κB activation with the components of p50 and RelB. An NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), reduced NF-κB activity (i.e. p50/RelB) but did not restore p53 function. In vivo, treatment with DHMEQ until 24 months of age prevented the onset of T-cell leukemia in Tax-Tg mice. These results suggest that the Tax-induced decline in p53 function, which is independent of NF-κB activation in the early stage, might be the first stage in the onset of ATLL. NF-κB activity is involved in the later stages of ATLL onset.

Mechanisms of human T-lymphotropic virus type 1 transmission and disease

Human T-lymphotrophic virus type-1 (HTLV-1) infects approximately 15-20 million people worldwide, with endemic areas in Japan, the Caribbean, and Africa. The virus is spread through contact with bodily fluids containing infected cells most often from mother to child through breast milk or via blood transfusion. After prolonged latency periods, approximately 3-5% of HTLV-1 infected individuals will develop either adult T-cell leukemia/lymphoma, or other lymphocyte-mediated disorders such as HTLV-1-associated myelopathy/tropical spastic paraparesis. The genome of this complex retrovirus contains typical gag, pol, and env genes, but also unique nonstructural proteins encoded from the pX region. These nonstructural genes encode the Tax and Rex regulatory proteins, as well as novel proteins essential for viral spread in vivo such as p30, p12, p13 and the antisense-encoded HTLV-1 basic leucine zipper factor (HBZ). While progress has been made in knowledge of viral determinants of cell transformation and host immune responses, host and viral determinants of HTLV-1 transmission and spread during the early phases of infection are unclear. Improvements in the molecular tools to test these viral determinants in cellular and animal models have provided new insights into the early events of HTLV-1 infection. This review will focus on studies that test HTLV-1 determinants in context to full-length infectious clones of the virus providing insights into the mechanisms of transmission and spread of HTLV-1.