Constitutively activated Jak-STAT pathway in T cells transformed with HTLV-I

Non-clinical safety assessment of novel drug modalities: Genome safety perspectives on viral-, nuclease- and nucleotide-based gene therapies

Gene therapies have emerged as promising treatments for various conditions including inherited diseases as well as cancer. Ensuring their safe clinical application requires the development of appropriate safety testing strategies. Several guidelines have been provided by health authorities to address these concerns. These guidelines state that non-clinical testing should be carried out on a case-by-case basis depending on the modality. This review focuses on the genome safety assessment of frequently used gene therapy modalities, namely Adeno Associated Viruses (AAVs), Lentiviruses, designer nucleases and mRNAs. Important safety considerations for these modalities, amongst others, are vector integrations into the patient genome (insertional mutagenesis) and off-target editing. Taking into account the constraints of in vivo studies, health authorities endorse the development of novel approach methodologies (NAMs), which are innovative in vitro strategies for genotoxicity testing. This review provides an overview of NAMs applied to viral and CRISPR/Cas9 safety, including next generation sequencing-based methods for integration site analysis and off-target editing. Additionally, NAMs to evaluate the oncogenicity risk arising from unwanted genomic modifications are discussed. Thus, a range of promising techniques are available to support the safe development of gene therapies. Thorough validation, comparisons and correlations with clinical outcomes are essential to identify the most reliable safety testing strategies. By providing a comprehensive overview of these NAMs, this review aims to contribute to a better understanding of the genome safety perspectives of gene therapies.

Prognostic and therapeutic potential of STAT3: Opportunities and challenges in targeting HPV-mediated cervical carcinogenesis

Cervical cancer (CaCx) ranks as the fourth most prevalent cancer among women globally. Persistent infection of high-risk human papillomaviruses (HR-HPVs) is major etiological factor associated with CaCx. Signal Transducer and Activator of Transcription 3 (STAT3), a prominent member of the STAT family, has emerged as independent oncogenic driver. It is a target of many oncogenic viruses including HPV. How STAT3 influences HPV viral gene expression or gets affected by HPV is an area of active investigation. A better understanding of host-virus interaction will provide a prognostic and therapeutic window for CaCx control and management. In this comprehensive review, we delve into carcinogenic role of STAT3 in development of HPV-induced CaCx. With an emphasis on fascinating interplay between STAT3 and HPV genome, the review explores the diverse array of opportunities and challenges associated with this field to harness the prognostic and therapeutic potential of STAT3 in CaCx.

Exploring Novel Frontiers: Leveraging STAT3 Signaling for Advanced Cancer Therapeutics

Signal Transducer and Activator of Transcription 3 (STAT3) plays a significant role in diverse physiologic processes, including cell proliferation, differentiation, angiogenesis, and survival. STAT3 activation via phosphorylation of tyrosine and serine residues is a complex and tightly regulated process initiated by upstream signaling pathways with ligand binding to receptor and non-receptor-linked kinases. Through downstream deregulation of target genes, aberrations in STAT3 activation are implicated in tumorigenesis, metastasis, and recurrence in multiple cancers. While there have been extensive efforts to develop direct and indirect STAT3 inhibitors using novel drugs as a therapeutic strategy, direct clinical application remains in evolution. In this review, we outline the mechanisms of STAT3 activation, the resulting downstream effects in physiologic and malignant settings, and therapeutic strategies for targeting STAT3. We also summarize the pre-clinical and clinical evidence of novel drug therapies targeting STAT3 and discuss the challenges of establishing their therapeutic efficacy in the current clinical landscape.

HTLV-1 Tax Tug-of-War: Cellular Senescence and Death or Cellular Transformation

Human T cell leukemia virus type 1 (HTLV-1) is a retrovirus associated with a lymphoproliferative disease known as adult T cell leukemia/lymphoma (ATLL). HTLV-1 infection efficiently transforms human T cells in vivo and in vitro. The virus does not transduce a proto-oncogene, nor does it integrate into tumor-promoting genomic sites. Instead, HTLV-1 uses a random mutagenesis model, resulting in cellular transformation. Expression of the viral protein Tax is critical for the immortalization of infected cells by targeting specific cellular signaling pathways. However, Tax is highly immunogenic and represents the main target for the elimination of virally infected cells by host cytotoxic T cells (CTLs). In addition, Tax expression in naïve cells induces pro-apoptotic signals and has been associated with the induction of non-replicative cellular senescence. This review will explore these conundrums and discuss the mechanisms used by the Tax viral oncoprotein to influence life-and-death cellular decisions and affect HTLV-1 pathogenesis.

Strategies to therapeutically modulate cytokine action

Cytokines are secreted or membrane-presented molecules that mediate broad cellular functions, including development, differentiation, growth and survival. Accordingly, the regulation of cytokine activity is extraordinarily important both physiologically and pathologically. Cytokine and/or cytokine receptor engineering is being widely investigated to safely and effectively modulate cytokine activity for therapeutic benefit. IL-2 in particular has been extensively engineered, to create IL-2 variants that differentially exhibit activities on regulatory T cells to potentially treat autoimmune disease versus effector T cells to augment antitumour effects. Additionally, engineering approaches are being applied to many other cytokines such as IL-10, interferons and IL-1 family cytokines, given their immunosuppressive and/or antiviral and anticancer effects. In modulating the actions of cytokines, the strategies used have been broad, including altering affinities of cytokines for their receptors, prolonging cytokine half-lives in vivo and fine-tuning cytokine actions. The field is rapidly expanding, with extensive efforts to create improved therapeutics for a range of diseases.

Human T-Cell Leukemia Virus Type 1 Oncogenesis between Active Expression and Latency: A Possible Source for the Development of Therapeutic Targets

The human T-cell leukemia virus type 1 (HTLV-1) is the only known human oncogenic retrovirus. HTLV-1 can cause a type of cancer called adult T-cell leukemia/lymphoma (ATL). The virus is transmitted through the body fluids of infected individuals, primarily breast milk, blood, and semen. At least 5-10 million people in the world are infected with HTLV-1. In addition to ATL, HTLV-1 infection can also cause HTLV-I-associated myelopathy (HAM/TSP). ATL is characterized by a low viral expression and poor prognosis. The oncogenic mechanism triggered by HTLV-1 is extremely complex and the molecular pathways are not fully understood. However, viral regulatory proteins Tax and HTLV-1 bZIP factor (HBZ) have been shown to play key roles in the transformation of HTLV-1-infected T cells. Moreover, several studies have shown that the final fate of HTLV-1-infected transformed Tcell clones is the result of a complex interplay of HTLV-1 oncogenic protein expression with cellular transcription factors that subvert the cell cycle and disrupt regulated cell death, thereby exerting their transforming effects. This review provides updated information on the mechanisms underlying the transforming action of HTLV-1 and highlights potential therapeutic targets to combat ATL.

Defining the Basal and Immunomodulatory Mediator-Induced Phosphoprotein Signature in Pediatric B Cell Acute Lymphoblastic Leukemia (B-ALL) Diagnostic Samples

It is theorized that dysregulated immune responses to infectious insults contribute to the development of pediatric B-ALL. In this context, our understanding of the immunomodulatory-mediator-induced signaling responses of leukemic blasts in pediatric B-ALL diagnostic samples is rather limited. Hence, in this study, we defined the signaling landscape of leukemic blasts, as well as normal mature B cells and T cells residing in diagnostic samples from 63 pediatric B-ALL patients. These samples were interrogated with a range of immunomodulatory-mediators within 24 h of collection, and phosflow analyses of downstream proximal signaling nodes were performed. Our data reveal evidence of basal hyperphosphorylation across a broad swath of these signaling nodes in leukemic blasts in contrast to normal mature B cells and T cells in the same sample. We also detected similarities in the phosphoprotein signature between blasts and mature B cells in response to IFNγ and IL-2 treatment, but significant divergence in the phosphoprotein signature was observed between blasts and mature B cells in response to IL-4, IL-7, IL-10, IL-21 and CD40 ligand treatment. Our results demonstrate the existence of both symmetry and asymmetry in the phosphoprotein signature between leukemic and non-leukemic cells in pediatric B-ALL diagnostic samples.

The implications of IL-15 trans-presentation on the immune response

Interleukin-15 is a pleiotropic cytokine type I four alpha-helical bundle cytokine that along with IL-2, IL-4, IL-7, IL-9, and IL-21 shares the common cytokine receptor γ chain, γ_c. IL-15 is vital for the development, survival, and expansion of natural killer cells and for the development of CD8⁺ memory T cells. Whereas other family γ_c cytokines signal by directly binding to their target cells, IL-15 is distinctive in that it binds to IL-15Rα, a sushi domain containing binding protein that is expressed on a number of cell types, including monocytes and dendritic cells as well as T cells, and then is trans-presented to responding cells that express IL-2Rβ and γ_c. This distinctive mechanism for IL-15 relates to its role in signaling in the context of cell-cell interactions and signaling synapses. The actions of IL-15 and ways of manipulating its actions to potential therapeutic benefit are discussed.

The JAK-STAT pathway at 30: Much learned, much more to do

The discovery of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway arose from investigations of how cells respond to interferons (IFNs), revealing a paradigm in cell signaling conserved from slime molds to mammals. These discoveries revealed mechanisms underlying rapid gene expression mediated by a wide variety of extracellular polypeptides including cytokines, interleukins, and related factors. This knowledge has provided numerous insights into human disease, from immune deficiencies to cancer, and was rapidly translated to new drugs for autoimmune, allergic, and infectious diseases, including COVID-19. Despite these advances, major challenges and opportunities remain.

An acquired phosphatidylinositol 4-phosphate transport initiates T-cell deterioration and leukemogenesis

Lipid remodeling is crucial for malignant cell transformation and tumorigenesis, but the precise molecular processes involved and direct evidences for these in vivo remain elusive. Here, we report that oxysterol-binding protein (OSBP)-related protein 4 L (ORP4L) is expressed in adult T-cell leukemia (ATL) cells but not normal T-cells. In ORP4L knock-in T-cells, ORP4L dimerizes with OSBP to control the shuttling of OSBP between the Golgi apparatus and the plasma membrane (PM) as an exchanger of phosphatidylinositol 4-phosphate [PI(4)P]/cholesterol. The PI(4)P arriving at the PM via this transport machinery replenishes phosphatidylinositol 4,5-bisphosphate [PI(4,5)P₂] and phosphatidylinositol (3,4,5) trisphosphate [PI(3,4,5)P₃] biosynthesis, thus contributing to PI3K/AKT hyperactivation and T-cell deterioration in vitro and in vivo. Disruption of ORP4L and OSBP dimerization disables PI(4)P transport and T-cell leukemogenesis. In summary, we identify a non-vesicular lipid transport machinery between Golgi and PM maintaining the oncogenic signaling competence initiating T-cell deterioration and leukemogenesis.

The oxysterol-binding protein-related protein 4 (ORP4L) is expressed in T-cell acute lymphoblastic leukemia and is required for leukemogenesis. Here the authors show that ORP4L orchestrates the transport of the phospholipid PI(4)P from Golgi to the plasma membrane, contributing to PI3K/AKT hyperactivation and T-cell leukemogenesis.

Dual-target Janus kinase (JAK) inhibitors: Comprehensive review on the JAK-based strategies for treating solid or hematological malignancies and immune-related diseases

Janus kinases (JAKs) are the non-receptor tyrosine kinases covering JAK1, JAK2, JAK3, and TYK2 which regulate signal transductions of hematopoietic cytokines and growth factors to play essential roles in cell growth, survival, and development. Dysregulated JAK activity leading to a constitutively activated signal transducers and activators of transcription (STAT) is strongly associated with immune-related diseases and cancers. Targeting JAK to interfere the signaling of JAK/STAT pathway has achieved quite success in the treatment of these diseases. However, inadequate clinical response and serious adverse events come along by the treatment of monotherapy of JAK inhibitors. With better and deeper understanding of JAK/STAT pathway in the pathogenesis of diseases, researchers start to show huge interest in combining inhibition of JAK and other oncogenic targets to realize a broader regulation on pathological processes to block disease development and progression, which has hastened extensive research of dual JAK inhibitors over the past decades. Until now, studies of dual JAK inhibitors have added BTK, SYK, FLT3, HDAC, Src, and Aurora kinases to the overall inhibitory profile and demonstrated significant advantage and superiority over single-target inhibitors. In this review, we elucidated the possible mechanism of synergic effects caused by dual JAK inhibitors and briefly describe the development of these agents.

Pediatric T-ALL type-1 and type-2 relapses develop along distinct pathways of clonal evolution

The mechanisms underlying T-ALL relapse remain essentially unknown. Multilevel-omics in 38 matched pairs of initial and relapsed T-ALL revealed 18 (47%) type-1 (defined by being derived from the major ancestral clone) and 20 (53%) type-2 relapses (derived from a minor ancestral clone). In both types of relapse, we observed known and novel drivers of multidrug resistance including MDR1 and MVP, NT5C2 and JAK-STAT activators. Patients with type-1 relapses were specifically characterized by IL7R upregulation. In remarkable contrast, type-2 relapses demonstrated (1) enrichment of constitutional cancer predisposition gene mutations, (2) divergent genetic and epigenetic remodeling, and (3) enrichment of somatic hypermutator phenotypes, related to BLM, BUB1B/PMS2 and TP53 mutations. T-ALLs that later progressed to type-2 relapses exhibited a complex subclonal architecture, unexpectedly, already at the time of initial diagnosis. Deconvolution analysis of ATAC-Seq profiles showed that T-ALLs later developing into type-1 relapses resembled a predominant immature thymic T-cell population, whereas T-ALLs developing into type-2 relapses resembled a mixture of normal T-cell precursors. In sum, our analyses revealed fundamentally different mechanisms driving either type-1 or type-2 T-ALL relapse and indicate that differential capacities of disease evolution are already inherent to the molecular setup of the initial leukemia.

Januskinase-Inhibitoren: Next-Generation-Therapie der Uveitis

Viele PatientInnen mit visusgefährdender nicht infektiöser Uveitis bedürfen, um eine Remission ihrer Uveitis zu erreichen, einer Behandlung mit DMARDs. Obwohl herkömmliche DMARD-Therapien in einem großen Teil dieser PatientInnen eine hochpotente Therapie darstellen, ist in einzelnen Fällen aufgrund eines unzureichenden Ansprechens oder unerwünschter Wirkungen ein Therapiewechsel erforderlich. Januskinase-Inhibitoren (JAKI) sind in der Rheumatologie, Gastroenterologie und Dermatologie bereits für mehrere autoimmune Erkrankungen zugelassen. Nun steht ein Zulassungsprozess für ausgewählte Uveitisentitäten an. Wirkmechanismus: JAKI üben ihre Wirkung über die Hemmung der Phosphorylierung von Transmembranproteinen, den Januskinasen aus. Dies führt zu einer fehlenden Aktivierung von Transkriptionsfaktoren und damit zur verminderten Zytokinexpression und Entzündungshemmung. JAKI stellen in der Rheumatologie, Gastroenterologie und Dermatologie einen äußerst effektiven neuen therapeutischen Ansatz dar. Sie sind zur Behandlung bei rheumatoider Arthritis, Psoriasis-Arthritis, ankylosierender Spondylitis, Colitis ulcerosa und dem atopischen Ekzem bereits zugelassen. In bisherigen Vergleichsstudien zu etablierten Biologika konnte teilweise ein besseres therapeutisches Ansprechen beschrieben werden. Aus publizierten Fallberichten wurde auch bei Uveitispatienten, die auf klassische und biologische DMARDs unzureichend ansprachen, eine Kortisoneinsparung und Reizfreiheit erzielt. Zulassungsstudien bei JIA-assoziierter und ANA-positiver anteriorer Uveitis sind im Prozess. Zusammenfassend stellen JAKI eine innovative Therapieoption bei Patienten mit nicht infektiöser Uveitis dar, bei denen Kontraindikationen gegen die Verwendung oder ein unzureichender Effekt von DMARDs bestehen.

Inhibition of ATL cell proliferation by polymerized proanthocyanidin from blueberry leaves through JAK proteolysis

We have previously reported that the proanthocyanidin (PAC) fraction of blueberry leaf extract (BB-PAC) inhibits the proliferation of human T lymphotropic retrovirus (HTLV-1)-infected adult T-cell leukemia (ATL) by inducing apoptosis. In the present study, we further analyzed the structure of BB-PAC and elucidated the molecular mechanism underlying the inhibitory function of HTLV-1 infected and ATL cells. After hot water extraction with fractionation with methanol-acetone, BB-PAC was found to be concentrated in fractions 4 to 7 (Fr 7). The strongest inhibition of ATL cell growth was observed with Fr7, which contained the highest BB-PAC polymerization degree of 14. The basic structure of BB-PAC is mainly B-type bonds, with A-type bonds (7.1%) and cinchonain I units as the terminal unit (6.1%). The molecular mechanism of cytotoxicity observed around Fr7 against ATL cells was the degradation of JAK1 to 3 and the dephosphorylation of STAT3/5, which occurs by proteasome-dependent proteolysis, confirming that PAC directly binds to HSP90. JAK degradation was caused by proteasome-dependent proteolysis, and we identified the direct binding of PAC to HSP90. In addition, the binding of cochaperone ATPase homolog 1 (AHA1) to HSP90, which is required for activation of the cofactor HSP90, was inhibited by BB-PAC treatment. Therefore, BB-PAC inhibited the formation of the HSP90/AHA1 complex and promoted the degradation of JAK protein due to HSP90 dysfunction. These results suggest that the highly polymerized PAC component from blueberry leaves has great potential as a preventive and therapeutic agent against HTLV-1 infected and ATL cells.

Transcription Independent Stimulation of Telomerase Enzymatic Activity by HTLV-I Tax Through Stimulation of IKK

The persistence and spreading of HTLV-I infected cells relies upon their clonal expansion through cellular replication. The development of adult T cell leukemia (ATLL) occurs decades following primary infection by HTLV-I. Moreover, identical provirus integration sites have been found in samples recovered several years apart from infected individuals. These observations suggest that infected cells persist in the host for an extended period of time. To endure long term proliferation, HTLV-I pre-leukemic cells must acquire critical oncogenic events, two of which are the bypassing of apoptosis and replicative senescence. In the early stages of disease, interleukin-2 (IL-2)/IL-2R signaling likely plays a major role in combination with activation of anti-apoptotic pathways. Avoidance of replicative senescence in HTLV-I infected cells is achieved through reactivation of human telomerase (hTERT). We have previously shown that HTLV-I viral Tax transcriptionally activates the hTERT promoter. In this study we demonstrate that Tax can stimulate hTERT enzymatic activity independently of its transcriptional effects. We further show that this occurs through Tax-mediated NF-KB activating functions. Our results suggest that in ATLL cells acquire Tax-transcriptional and post-transcriptional events to elevate telomerase activity.

Involvement of EZH2 inhibition in lenalidomide and pomalidomide-mediated growth suppression in HTLV-1-infected cells

Immunomodulatory imide drugs (IMiDs), such as lenalidomide and pomalidomide, exert pleiotropic effects, e.g., antitumor effects in multiple myeloma, by binding the protein Cereblon and altering its substrate specificity. Lenalidomide is approved for the treatment of adult T-cell leukemia/lymphoma (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1), although the precise mechanisms responsible for its effectiveness have not been fully elucidated. Here, we used HTLV-1-infected cell lines to investigate how IMiDs exert anti-ATL effects. In three of four tested HTLV-1-infected cell lines, the cells treated with lenalidomide or pomalidomide exhibited mild growth suppression without apoptosis, which was associated with decreased IRF4, c-Myc, and phosphorylated STAT3 levels as well as enhanced SOCS3 expression. Additionally, the levels of enhancer of zeste homolog 2 (EZH2) and trimethyl histone 3 Lys27 (H3K27me3) were decreased following IMiD treatment in all three susceptible cell lines. An IMiD-mediated reduction of EZH2 and H3K27me3 levels was also observed in a multiple myeloma cell line. Furthermore, treatment with an EZH2-inhibitor reproduced the IMiD-mediated effects in HTLV-1-infected cells and multiple myeloma cells. These findings strongly suggest that a reduction of EZH2 expression is involved in the mechanism underlying the antitumor effects of IMiD.

Carbazole Derivatives as STAT Inhibitors: An Overview

The carbazole class is made up of heterocyclically structured compounds first isolated from coal tar. Their structural motif is preponderant in different synthetic materials and naturally occurring alkaloids extracted from the taxonomically related higher plants of the genus Murraya, Glycosmis, and Clausena from the Rutaceae family. Concerning the biological activity of these compounds, many research groups have assessed their antiproliferative action of carbazoles on different types of tumoral cells, such as breast, cervical, ovarian, hepatic, oral cavity, and small-cell lung cancer, and underlined their potential effects against psoriasis. One of the principal mechanisms likely involved in these effects is the ability of carbazoles to target the JAK/STATs pathway, considered essential for cell differentiation, proliferation, development, apoptosis, and inflammation. In this review, we report the studies carried out, over the years, useful to synthesize compounds with carbazole moiety designed to target these kinds of kinases.

miRNAs as novel immunoregulators in cancer

The immune system is a well-known vital regulator of tumor growth, and one of the main hallmarks of cancer is evading the immune system. Immune system deregulation can lead to immune surveillance evasion, sustained cancer growth, proliferation, and metastasis. Tumor-mediated disruption of the immune system is accomplished by different mechanisms that involve extensive crosstalk with the immediate microenvironment, which includes endothelial cells, immune cells, and stromal cells, to create a favorable tumor niche that facilitates the development of cancer. The essential role of non-coding RNAs such as microRNAs (miRNAs) in the mechanism of cancer cell immune evasion has been highlighted in recent studies. miRNAs are small non-coding RNAs that regulate a wide range of post-transcriptional gene expression in a cell. Recent studies have focused on the function that miRNAs play in controlling the expression of target proteins linked to immune modulation. Studies show that miRNAs modulate the immune response in cancers by regulating the expression of different immune-modulatory molecules associated with immune effector cells, such as macrophages, dendritic cells, B-cells, and natural killer cells, as well as those present in tumor cells and the tumor microenvironment. This review explores the relationship between miRNAs, their altered patterns of expression in tumors, immune modulation, and the functional control of a wide range of immune cells, thereby offering detailed insights on the crosstalk of tumor-immune cells and their use as prognostic markers or therapeutic agents.

IL-6 in inflammation, autoimmunity and cancer

IL-6 is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is an NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6-STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6-STAT3 axis is a critical target for treating diseases.

Non-Hodgkin Lymphomas: Malignancies Arising from Mature B Cells

Non-Hodgkin lymphomas (NHLs) are a diverse group of entities, both clinically and molecularly. Here, we review the evolution of classification schemes in B-cell lymphoma, noting the now standard WHO classification system that is based on immune cell-of-origin and molecular phenotypes. We review how lymphomas arise throughout the B-cell development process as well as the molecular and clinical features of prominent B-cell lymphomas. We provide an overview of the major progress that has occurred over the past decade in terms of our molecular understanding of these diseases. We discuss treatment options available and focus on a number of the diverse research tools that have been employed to improve our understanding of these diseases. We discuss the problem of heterogeneity in lymphomas and anticipate that the near future will bring significant advances that provide a measurable impact on NHL outcomes.

The Multifaced Role of STAT3 in Cancer and Its Implication for Anticancer Therapy

Signal transducer and activator of transcription (STAT) 3 is one of the most complex regulators of transcription. Constitutive activation of STAT3 has been reported in many types of tumors and depends on mechanisms such as hyperactivation of receptors for pro-oncogenic cytokines and growth factors, loss of negative regulation, and excessive cytokine stimulation. In contrast, somatic STAT3 mutations are less frequent in cancer. Several oncogenic targets of STAT3 have been recently identified such as c-myc, c-Jun, PLK-1, Pim1/2, Bcl-2, VEGF, bFGF, and Cten, and inhibitors of STAT3 have been developed for cancer prevention and treatment. However, despite the oncogenic role of STAT3 having been widely demonstrated, an increasing amount of data indicate that STAT3 functions are multifaced and not easy to classify. In fact, the specific cellular role of STAT3 seems to be determined by the integration of multiple signals, by the oncogenic environment, and by the alternative splicing into two distinct isoforms, STAT3α and STAT3β. On the basis of these different conditions, STAT3 can act both as a potent tumor promoter or tumor suppressor factor. This implies that the therapies based on STAT3 modulators should be performed considering the pleiotropic functions of this transcription factor and tailored to the specific tumor type.

Immunopathogenesis and Cellular Interactions in Human T-Cell Leukemia Virus Type 1 Associated Myelopathy/Tropical Spastic Paraparesis

HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) is a neuropathological disorder in 1–3% of individuals infected with Human T-lymphotropic virus 1 (HTLV-1). This condition is characterized by progressive spastic lower limb weakness and paralysis, lower back pain, bladder incontinence, and mild sensory disturbances resembling spinal forms of multiple sclerosis. This disease also causes chronic disability and is therefore associated with high health burden in areas where HTLV-1 infection is endemic. Despite various efforts in understanding the virus and discovery of novel diagnostic markers, and cellular and viral interactions, HAM/TSP management is still unsatisfactory and mainly focused on symptomatic alleviation, and it hasn’t been explained why only a minority of the virus carriers develop HAM/TSP. This comprehensive review focuses on host and viral factors in association with immunopathology of the disease in hope of providing new insights for drug therapies or other forms of intervention.

The Dynamic Interface of Viruses with STATs

Viruses commonly antagonize the antiviral type I interferon response by targeting signal transducer and activator of transcription 1 (STAT1) and STAT2, key mediators of interferon signaling. Other STAT family members mediate signaling by diverse cytokines important to infection, but their relationship with viruses is more complex. Importantly, virus-STAT interaction can be antagonistic or stimulatory depending on diverse viral and cellular factors. While STAT antagonism can suppress immune pathways, many viruses promote activation of specific STATs to support viral gene expression and/or produce cellular conditions conducive to infection. It is also becoming increasingly clear that viruses can hijack noncanonical STAT functions to benefit infection. For a number of viruses, STAT function is dynamically modulated through infection as requirements for replication change. Given the critical role of STATs in infection by diverse viruses, the virus-STAT interface is an attractive target for the development of antivirals and live-attenuated viral vaccines. Here, we review current understanding of the complex and dynamic virus-STAT interface and discuss how this relationship might be harnessed for medical applications.

Transcription Factors in Cancer Development and Therapy

Cancer is a multi-step process and requires constitutive expression/activation of transcription factors (TFs) for growth and survival. Many of the TFs reported so far are critical for carcinogenesis. These include pro-inflammatory TFs, hypoxia-inducible factors (HIFs), cell proliferation and epithelial-mesenchymal transition (EMT)-controlling TFs, pluripotency TFs upregulated in cancer stem-like cells, and the nuclear receptors (NRs). Some of those, including HIFs, Myc, ETS-1, and β-catenin, are multifunctional and may regulate multiple other TFs involved in various pro-oncogenic events, including proliferation, survival, metabolism, invasion, and metastasis. High expression of some TFs is also correlated with poor prognosis and chemoresistance, constituting a significant challenge in cancer treatment. Considering the pivotal role of TFs in cancer, there is an urgent need to develop strategies targeting them. Targeting TFs, in combination with other chemotherapeutics, could emerge as a better strategy to target cancer. So far, targeting NRs have shown promising results in improving survival. In this review, we provide a comprehensive overview of the TFs that play a central role in cancer progression, which could be potential therapeutic candidates for developing specific inhibitors. Here, we also discuss the efforts made to target some of those TFs, including NRs.

Transcription Factors in Cancer Development and Therapy

Cancer is a multi-step process and requires constitutive expression/activation of transcription factors (TFs) for growth and survival. Many of the TFs reported so far are critical for carcinogenesis. These include pro-inflammatory TFs, hypoxia-inducible factors (HIFs), cell proliferation and epithelial-mesenchymal transition (EMT)-controlling TFs, pluripotency TFs upregulated in cancer stem-like cells, and the nuclear receptors (NRs). Some of those, including HIFs, Myc, ETS-1, and β-catenin, are multifunctional and may regulate multiple other TFs involved in various pro-oncogenic events, including proliferation, survival, metabolism, invasion, and metastasis. High expression of some TFs is also correlated with poor prognosis and chemoresistance, constituting a significant challenge in cancer treatment. Considering the pivotal role of TFs in cancer, there is an urgent need to develop strategies targeting them. Targeting TFs, in combination with other chemotherapeutics, could emerge as a better strategy to target cancer. So far, targeting NRs have shown promising results in improving survival. In this review, we provide a comprehensive overview of the TFs that play a central role in cancer progression, which could be potential therapeutic candidates for developing specific inhibitors. Here, we also discuss the efforts made to target some of those TFs, including NRs.

Molecular targeting of PD-1 signaling pathway as a novel therapeutic approach in HTLV-1 infection

HTLV-1, the first human oncogenic retrovirus, is a type C retrovirus that belongs to the Deltaretrovirus genus. The HTLV-1 genome has 8.5 kbp length, and consists of major genes such as gag, pol, pro, env, and pX region. This retrovirus is considered as one of the most deadly infectious agent for peripheral-blood mononuclear cells (PBMC). The infection of HTLV-1 can lead to dangerous complications, such as infective dermatitis (ID), uveitis, arthritis, lymphadenitis, arthropathies, Sjögren's Syndrome (SS), and particularly HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) or Adult T-Cell Leukemia Lymphoma (ATLL). At the moment, Zidovudine (AZT) plus IFN-α is the only treatment available for HTLV-1 infections. Based on scientific studies, alongside the therapeutic regimens, intrinsic mechanisms also play a determinant role in reducing the signs of disease. Programmed cell death-1 (PD-1) signaling pathway, one of the most important checkpoints, has recently received interest, such as the development of a novel generation of anti-tumors. In the present study, we discuss the role of PD-1 signaling pathway in HTLV-1 infection as well as its application as a novel approach for treatment of HTLV-1 infections.

STAT3 Mutation Is Associated with STAT3 Activation in CD30+ ALK- ALCL

Peripheral T-cell lymphomas (PTCL) are a heterogeneous, and often aggressive group of non-Hodgkin lymphomas. Recent advances in the molecular and genetic characterization of PTCLs have helped to delineate differences and similarities between the various subtypes, and the JAK/STAT pathway has been found to play an important oncogenic role. Here, we aimed to characterize the JAK/STAT pathway in PTCL subtypes and investigate whether the activation of the pathway correlates with the frequency of STAT gene mutations. Patient samples from AITL (n = 30), ALCL (n = 21) and PTCL-NOS (n = 12) cases were sequenced for STAT3, STAT5B, JAK1, JAK3, and RHOA mutations using amplicon sequencing and stained immunohistochemically for pSTAT3, pMAPK, and pAKT. We discovered STAT3 mutations in 13% of AITL, 13% of ALK⁺ ALCL, 38% of ALK⁻ ALCL and 17% of PTCL-NOS cases. However, no STAT5B mutations were found and JAK mutations were only present in ALK^- ALCL (15%). Concurrent mutations were found in all subgroups except ALK⁺ ALCL where STAT3 mutations were always seen alone. High pY-STAT3 expression was observed especially in AITL and ALCL samples. When studying JAK-STAT pathway mutations, pY-STAT3 expression was highest in PTCLs harboring either JAK1 or STAT3 mutations and CD30⁺ phenotype representing primarily ALK⁻ ALCLs. Further investigation is needed to elucidate the molecular mechanisms of JAK-STAT pathway activation in PTCL.

IL-2/IL-2 Receptor Pathway Plays a Crucial Role in the Growth and Malignant Transformation of HTLV-1-Infected T Cells to Develop Adult T-Cell Leukemia

T cells infected with human T-cell leukemia virus type 1 (HTLV-1) transform into malignant/leukemic cells and develop adult T-cell leukemia (ATL) after a long latency period. The tax (transactivator from the X-gene region) and HBZ (HTLV-1 bZIP factor) genes of HTLV-1 play crucial roles in the development of ATL. The process and mechanism by which HTLV-1-infected T cells acquire malignancy and develop ATL remain to be elucidated. Constitutive expression of interleukin-2 (IL-2) receptor α-chain (IL-2Rα/CD25), induced by the tax and HBZ genes of HTLV-1, on ATL cells implicates the involvement of IL-2/IL-2R pathway in the growth and development of ATL cells in vivo. However, the leukemic cells in the majority of ATL patients appeared unresponsive to IL-2, raising controversies on the role of this pathway for the growth of ATL cells in vivo. Here, we report the establishment of 32 IL-2-dependent T-cell lines infected with HTLV-1 from 26 ATL patients, including eight leukemic cell lines derived from five ATL patients, while no T-cell lines were established without IL-2. We have shown that the IL-2-dependent ATL cell lines evolved into IL-2-independent/-unresponsive growth phase, resembling ATL cells in vivo. Moreover, the IL-2-dependent non-leukemic T-cell lines infected with HTLV-1 acquired IL-2-independency and turned into tumor-producing cancer cells as with the ATL cell lines. HTLV-1-infected T cells in vivo could survive and proliferate depending on IL-2 that was produced in vivo by the HTLV-1-infected T cells of ATL patients and patients with HTLV-1-associated diseases and, acts as a physiological molecule to regulate T-cell growth. These results suggest that ATL cells develop among the HTLV-1-infected T cells growing dependently on IL-2 and that most of the circulating ATL cells progressed to become less responsive to IL-2, acquiring the ability to proliferate without IL-2.

Targeting STAT-3 signaling pathway in cancer for development of novel drugs: Advancements and challenges

Signal transducers and activators of transcription 3 (STAT-3) is a transcription factor that regulates the gene expression of several target genes. These factors are activated by the binding of cytokines and growth factors with STAT-3 specific receptors on cell membrane. Few years ago, STAT-3 was considered an acute phase response element having several cellular functions such as inflammation, cell survival, invasion, metastasis and proliferation, genetic alteration, and angiogenesis. STAT-3 is activated by several types of inflammatory cytokines, carcinogens, viruses, growth factors, and oncogenes. Thus, the STAT3 pathway is a potential target for cancer therapeutics. Abnormal STAT-3 activity in tumor development and cellular transformation can be targeted by several genomic and pharmacological methodologies. An extensive review of the literature has been conducted to emphasize the role of STAT-3 as a unique cancer drug target. This review article discusses in detail the wide range of STAT-3 inhibitors that show antitumor effects both in vitro and in vivo. Thus, targeting constitutive STAT-3 signaling is a remarkable therapeutic methodology for tumor progression. Finally, current limitations, trials and future perspectives of STAT-3 inhibitors are also critically discussed.

EGFR Promotes the Development of Triple Negative Breast Cancer Through JAK/STAT3 Signaling

Purpose

To investigate the role of EGFR and STAT3 in breast cancer development and progression.

Methods

Through bioinformatics analysis differently expressed genes (DEGs) including EGFR and STAT3 were identified in breast cancer tissue. QRT-PCR and Western blot analysis were used to investigate EGFR and STAT3 levels in breast cancer tissues and cells. The influence of EGFR and STAT3 on the breast cancer cell proliferation (CCK-8 assay, clone formation assays), migration (wound healing assays) and invasion (transwell assays) were investigated. The influence of EGFR on breast cancer in vivo was examined by Nude mouse transplantation tumor experiments and immunohistochemistry (IHC) staining. The effects of EGFR on breast cancer signaling were assessed via Western blot.

Results

Both EGFR and p-STAT3 were up-regulated in breast cancer tissues and cell lines. EGFR expression was positively associated with p-STAT3. Moreover, EGFR and p-STAT3 activity enhanced the proliferation and invasion of tumor cells. Breast cancer cell growth was dramatically inhibited by EGFR silencing in vivo.

Conclusion

EGFR promotes breast cancer progression via STAT3 phosphorylation and JAK/STAT3 signaling.

Role of HTLV-1 orf-I encoded proteins in viral transmission and persistence

The human T cell leukemia virus type 1 (HTVL-1), first reported in 1980 by Robert Gallo's group, is the etiologic agent of both cancer and inflammatory diseases. Despite approximately 40 years of investigation, the prognosis for afflicted patients remains poor with no effective treatments. The virus persists in the infected host by evading the host immune response and inducing proliferation of infected CD4⁺ T-cells. Here, we will review the role that viral orf-I protein products play in altering intracellular signaling, protein expression and cell-cell communication in order to escape immune recognition and promote T-cell proliferation. We will also review studies of orf-I mutations found in infected patients and their potential impact on viral load, transmission and persistence. Finally, we will compare the orf-I gene in HTLV-1 subtypes as well as related STLV-1.

Accelerated cancer aggressiveness by viral oncomodulation: New targets and newer natural treatments for cancer control and treatment

An infectious etiology for a number of cancers has been entertained for over 100 years and modern studies have confirmed that a number of viruses are linked to cancer induction. While a large number of viruses have been demonstrated in a number of types of cancers, most such findings have been dismissed in the past as opportunistic infections, especially with persistent viruses with high rates of infectivity of the world’s populations. More recent studies have clearly shown that while not definitely causing these cancers, these viruses appear capable of affecting the biology of these tumors in such a way as to make them more aggressive and more resistant to conventional treatments. The term oncomodulatory viruses has been used to describe this phenomenon. A number of recent studies have shown a growing number of ways these oncomodulatory viruses can alter the pathology of these tumors by affecting cell-signaling, cell metabolism, apoptosis mechanisms, cell-cell communication, inflammation, antitumor immunity suppression, and angiogenesis. We are also learning that much of the behavior of tumors depends on cancer stem cells and stromal cells within the tumor microenvironment, which participate in extensive, dynamic crosstalk known to affect tumor behavior. Cancer stem cells have been found to be particularly susceptible to infection by human cytomegalovirus. In a number of studies, it has been shown that while only a select number of cells are actually infected with the virus, numerous viral proteins are released into cancer and stromal cells in the microenvironment and these viral proteins are known to affect tumor behavior and aggressiveness.

Essential Role of Human T Cell Leukemia Virus Type 1 orf-I in Lethal Proliferation of CD4+ Cells in Humanized Mice

Human T cell leukemia virus type 1 (HTLV-1) is the ethological agent of adult T cell leukemia/lymphoma (ATLL) and a number of lymphocyte-mediated inflammatory conditions, including HTLV-1-associated myelopathy/tropical spastic paraparesis. HTLV-1 orf-I encodes two proteins, p8 and p12, whose functions in humans are to counteract innate and adaptive responses and to support viral transmission. However, the in vivo requirements for orf-I expression vary in different animal models. In macaques, the ablation of orf-I expression by mutation of its ATG initiation codon abolishes the infectivity of the molecular clone HTLV-1_p12KO In rabbits, HTLV-1_p12KO is infective and persists efficiently. We used humanized mouse models to assess the infectivity of both wild-type HTLV-1 (HTLV-1_WT) and HTLV-1_p12KO We found that NOD/SCID/γ_C ^-/- c-kit⁺ mice engrafted with human tissues 1 day after birth (designated NSG-1d mice) were highly susceptible to infection by HTLV-1_WT, with a syndrome characterized by the rapid polyclonal proliferation and infiltration of CD4⁺ CD25⁺ T cells into vital organs, weight loss, and death. HTLV-1 clonality studies revealed the presence of multiple clones of low abundance, confirming the polyclonal expansion of HTLV-1-infected cells in vivo HTLV-1_p12KO infection in a bone marrow-liver-thymus (BLT) mouse model prone to graft-versus-host disease occurred only following reversion of the orf-I initiation codon mutation within weeks after exposure and was associated with high levels of HTLV-1 DNA in blood and the expansion of CD4⁺ CD25⁺ T cells. Thus, the incomplete reconstitution of the human immune system in BLT mice may provide a window of opportunity for HTLV-1 replication and the selection of viral variants with greater fitness.IMPORTANCE Humanized mice constitute a useful model for studying the HTLV-1-associated polyclonal proliferation of CD4⁺ T cells and viral integration sites in the human genome. The rapid death of infected animals, however, appears to preclude the clonal selection typically observed in human ATLL, which normally develops in 2 to 5% of individuals infected with HTLV-1. Nevertheless, the expansion of multiple clones of low abundance in these humanized mice mirrors the early phase of HTLV-1 infection in humans, providing a useful model to investigate approaches to inhibit virus-induced CD4⁺ T cell proliferation.

Expression of STAT3-regulated genes in circulating CD4+ T cells discriminates rheumatoid arthritis independently of clinical parameters in early arthritis

OBJECTIVES

Dysregulated signal transduction and activator of transcription-3 (STAT3) signalling in CD4+ T cells has been proposed as an early pathophysiological event in RA. We sought further evidence for this observation, and to determine its clinical relevance.

METHODS

Microarray technology was used to measure gene expression in purified peripheral blood CD4+ T cells from treatment-naïve RA patients and disease controls newly recruited from an early arthritis clinic. Analysis focused on 12 previously proposed transcripts, and concurrent STAT3 pathway activation was determined in the same cells by flow cytometry. A pooled analysis of previous and current gene expression findings incorporated detailed clinical parameters and employed multivariate analysis.

RESULTS

In an independent cohort of 161 patients, expression of 11 of 12 proposed signature genes differed significantly between RA patients and controls, robustly validating the earlier findings. Differential regulation was most pronounced for the STAT3 target genes PIM1, BCL3 and SOCS3 (>1.3-fold difference; P < 0.005), each of whose expression correlated strongly with paired intracellular phospho-STAT3. In a meta-analysis of 279 patients the same three genes accounted for the majority of the signature's ability to discriminate RA patients, which was found to be independent of age, joint involvement or acute phase response.

CONCLUSION

The STAT3-mediated dysregulation of BCL3, SOCS3 and PIM1 in circulating CD4+ T cells is a discriminatory feature of early RA that occurs independently of acute phase response. The mechanistic and functional implications of this observation at a cellular level warrant clarification.

Fine-Tuning Cytokine Signals

Cytokines are secreted or otherwise released polypeptide factors that exert autocrine and/or paracrine actions, with most cytokines acting in the immune and/or hematopoietic system. They are typically pleiotropic, controlling development, cell growth, survival, and/or differentiation. Correspondingly, cytokines are clinically important, and augmenting or attenuating cytokine signals can have deleterious or therapeutic effects. Besides physiological fine-tuning of cytokine signals, altering the nature or potency of the signal can be important in pathophysiological responses and can also provide novel therapeutic approaches. Here, we give an overview of cytokines, their signaling and actions, and the physiological mechanisms and pharmacologic strategies to fine-tune their actions. In particular, the differential utilization of STAT proteins by a single cytokine or by different cytokines and STAT dimerization versus tetramerization are physiological mechanisms of fine-tuning, whereas anticytokine and anticytokine receptor antibodies and cytokines with altered activities, including cytokine superagonists, partial agonists, and antagonists, represent new ways of fine-tuning cytokine signals.

[HSP90 inhibitor 17-AAG plays an important role in JAK3/STAT5 signaling pathways in HTLV-1 infection cell line HUT-102]

Objective: To analyze whether heat-shock protein 90 (HSP90) be involved in a permanently abnormal activated JAK/STAT signaling in ATL cells in vitro. Methods: The effect of 17-AAG on proliferation of ATL cell lines HUT-102 was assessed using CCK8 at different time points. Cell apoptosis was measured by flow cytometry. The specific proteins HSP90, STAT5, p-STAT5 and JAK3 were detected by Western blotting. Results: Overexpression of HSP90 in HUT-102 cell lines was disclosed (P<0.05) , and constitutive activation of JAK3/STAT5 signaling was observed in HTLV-1-infected T-cell lines but not in normal PBMCs; Treatment of ATL cell lines with 17-AAG led to reduced cell proliferation, but there was no significant change in terms of cell proliferation when the concentration of 17-AAG between 2 000-8 000 nmol/L (P>0.05) . 17-AAG induced cell apoptosis in different time-points and concentrations. 17-AAG don't affect the expression of JAK3 gene. Conclusion: This study indicated that JAK3 as HSP90 client protein was aberrantly activated in HTLV-1-infected T-cell lines, leading to constitutive activation of p-STAT5 in JAK/STAT signal pathway, which demonstrated that HSP90-inhibitors 17-AAG inhibited the growth of HTLV-1-infected T-cell lines by reducing cell proliferation and inducing cell apoptosis.

Janus kinases to jakinibs: from basic insights to clinical practice

Cytokines are critical mediators of diverse immune and inflammatory diseases. Targeting cytokines and cytokine receptors with biologics has revolutionized the treatment of many of these diseases, but targeting intracellular signalling with Janus kinase (JAK) inhibitors (jakinibs) now represents a major new therapeutic advance. We are still in the first decade since these drugs were approved and there is still much to be learned about the mechanisms of action of these drugs and the practical use of these agents. Herein we will review cytokines that do, and just as importantly, do not signal by JAKs, as well as explain how this relates to both efficacy and side effects in various diseases. We will review new, next-generation selective jakinibs, as well as the prospects and challenges ahead in targeting JAKs.

Transcriptional analysis distinguishes breast implant-associated anaplastic large cell lymphoma from other peripheral T-cell lymphomas

Breast implant-associated anaplastic large cell lymphoma is a new provisional entity in the revised World Health Organization classification of lymphoid malignancies, the pathogenesis and cell of origin of which are still unknown. We performed gene expression profiling of microdissected breast implant-associated anaplastic large cell lymphoma samples and compared their transcriptional profiles with those previously obtained from normal T-cells and other peripheral T-cell lymphomas and validated expression of selected markers by immunohistochemistry. Our results indicate that most breast implant-associated anaplastic large cell lymphomas exhibit an activated CD4+ memory T-cell phenotype, which is associated with CD25 and FoxP3 expression. Gene ontology analyses revealed upregulation of genes involved in cell motility programs (e.g., CCR6, MET, HGF, CXCL14) in breast implant-associated anaplastic large cell lymphomas compared to normal CD4+ T-cells and upregulation of genes involved in myeloid cell differentiation (e.g., PPARg, JAK2, SPI-1, GAB2) and viral gene transcription (e.g., RPS10, RPL17, RPS29, RPL18A) compared to other types of peripheral T-cell lymphomas. Gene set enrichment analyses also revealed shared features between the molecular profiles of breast implant-associated anaplastic large cell lymphomas and other types of anaplastic large cell lymphomas, including downregulation of T-cell receptor signaling and STAT3 activation. Our findings provide novel insights into the biology of this rare disease and further evidence that breast implant-associated anaplastic large cell lymphoma represents a distinct peripheral T-cell lymphoma entity.

Cytokine Networks Dysregulation during HTLV-1 Infection and Associated Diseases

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of a neural chronic inflammation, called HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and of a malignant lymphoproliferation, called the adult T-cell leukemia/lymphoma (ATLL). The mechanisms through which the HTLV-1 induces these diseases are still unclear, but they might rely on immune alterations. HAM/TSP is associated with an impaired production of pro-inflammatory cytokines and chemokines, such as IFN-γ, TNF-α, CXCL9, or CXCL10. ATLL is associated with high levels of IL-10 and TGF-β. These immunosuppressive cytokines could promote a protumoral micro-environment. Moreover, HTLV-1 infection impairs the IFN-I production and signaling, and favors the IL-2, IL-4, and IL-6 expression. This contributes both to immune escape and to infected cells proliferation. Here, we review the landscape of cytokine dysregulations induced by HTLV-1 infection and the role of these cytokines in the HTLV-1-associated diseases progression.

Cytokines in Cancer Immunotherapy

Cytokines that control the immune response were shown to have efficacy in preclinical murine cancer models. Interferon (IFN)-α is approved for treatment of hairy cell leukemia, and interleukin (IL)-2 for the treatment of advanced melanoma and metastatic renal cancer. In addition, IL-12, IL-15, IL-21, and granulocyte macrophage colony-stimulating factor (GM-CSF) have been evaluated in clinical trials. However, the cytokines as monotherapy have not fulfilled their early promise because cytokines administered parenterally do not achieve sufficient concentrations in the tumor, are often associated with severe toxicities, and induce humoral or cellular checkpoints. To circumvent these impediments, cytokines are being investigated clinically in combination therapy with checkpoint inhibitors, anticancer monoclonal antibodies to increase the antibody-dependent cellular cytotoxicity (ADCC) of these antibodies, antibody cytokine fusion proteins, and anti-CD40 to facilitate tumor-specific immune responses.

North American ATLL has a distinct mutational and transcriptional profile and responds to epigenetic therapies

Adult T-cell leukemia lymphoma (ATLL) is a rare T cell neoplasm that is endemic in Japanese, Caribbean, and Latin American populations. Most North American ATLL patients are of Caribbean descent and are characterized by high rates of chemo-refractory disease and worse prognosis compared with Japanese ATLL. To determine genomic differences between these 2 cohorts, we performed targeted exon sequencing on 30 North American ATLL patients and compared the results with the Japanese ATLL cases. Although the frequency of TP53 mutations was comparable, the mutation frequency in epigenetic and histone modifying genes (57%) was significantly higher, whereas the mutation frequency in JAK/STAT and T-cell receptor/NF-κB pathway genes was significantly lower. The most common type of epigenetic mutation is that affecting EP300 (20%). As a category, epigenetic mutations were associated with adverse prognosis. Dissimilarities with the Japanese cases were also revealed by RNA sequencing analysis of 9 primary patient samples. ATLL samples with a mutated EP300 gene have decreased total and acetyl p53 protein and a transcriptional signature reminiscent of p53-mutated cancers. Most importantly, decitabine has highly selective single-agent activity in the EP300-mutated ATLL samples, suggesting that decitabine treatment induces a synthetic lethal phenotype in EP300-mutated ATLL cells. In conclusion, we demonstrate that North American ATLL has a distinct genomic landscape that is characterized by frequent epigenetic mutations that are targetable preclinically with DNA methyltransferase inhibitors.

Anti-adult T‑cell leukemia/lymphoma activity of cerdulatinib, a dual SYK/JAK kinase inhibitor

Adult T‑cell leukemia/lymphoma (ATLL) constitutes an aggressive malignancy caused by human T‑cell leukemia virus type 1 (HTLV‑1) that is resistant to available chemotherapeutics. The constitutive activation of Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling is an important feature of ATLL, and spleen tyrosine kinase (SYK) is overexpressed in HTLV‑1-transformed T‑cell lines. In this study, we evaluated the effects of SYK- (PRT060318) or JAK- (JAK inhibitor 1) selective inhibitors and the dual SYK/JAK inhibitor, cerdulatinib, on the viability of HTLV‑1-transformed and ATLL-derived T‑cell lines. Cell proliferation, viability, cell cycle, apoptosis and intracellular signaling cascades were analyzed by the water-soluble tetrazolium-8 assay, flow cytometry and western blot analysis. HTLV‑1-infected T‑cell lines were sensitive to both SYK-selective and pan-JAK inhibitors, whereas cerdulatinib more potently suppressed cell proliferation and reduced cell viability than either of these agents alone. By contrast, the cytotoxic effects of cerdulatinib on uninfected T‑cell lines and peripheral blood mononuclear cells from a healthy donor were less pronounced. Cerdulatinib induced cell cycle arrest in the G2/M phase, which was associated with a decreased cyclin-dependent kinase 1 and cyclin B1, and an increased p21 and p27 expression. Hoechst staining revealed chromatin condensation and nuclear fragmentation in the cells treated with cerdulatinib, and an increased fraction of apoptotic APO2.7-stained cells was detected by flow cytometry. This corresponded to the activation of caspase-8, -9 and -3, and decreased levels of the anti-apoptotic factors, Bcl-xL, survivin, X-linked inhibitor of apoptosis (XIAP) and c‑FLIP. The cerdulatinib-induced decrease in cell viability was partly reversed by the caspase inhibitor, z‑VAD‑FMK. These anti-ATLL effects were associated with the suppression of SYK and JAK/STAT signaling, along with that of the downstream factors, AKT, ERK, activator protein‑1 and nuclear factor-κB. Finally, oral dosing with cerdulatinib lowered the tumor burden in a murine model of ATLL. Thus, our findings indicate that the simultaneous inhibition of therapeutically relevant targets, such as SYK and JAK is a more effective approach than single-agent therapy for the treatment of ATLL.

HTLV-1-Mediated Epigenetic Pathway to Adult T-Cell Leukemia-Lymphoma

Human T-cell leukemia virus type 1 (HTLV-1), the first reported human oncogenic retrovirus, is the etiologic agent of highly aggressive, currently incurable diseases such as adult T-cell leukemia-lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 proteins, including Tax and HBZ, have been shown to have critical roles in HTLV-1 pathogenicity, yet the underlying mechanisms of HTLV-1-driven leukemogenesis are unclear. The frequent disruption of genetic and epigenetic gene regulation in various types of malignancy, including ATL, is evident. In this review, we illustrate a focused range of topics about the establishment of HTLV-1 memory: (1) genetic lesion in the Tax interactome pathway, (2) gene regulatory loop/switch, (3) disordered chromatin regulation, (4) epigenetic lock by the modulation of epigenetic factors, (5) the loss of gene fine-tuner microRNA, and (6) the alteration of chromatin regulation by HTLV-1 integration. We discuss the persistent influence of Tax-dependent epigenetic changes even after the disappearance of HTLV-1 gene expression due to the viral escape from the immune system, which is a remaining challenge in HTLV-1 research. The summarized evidence and conceptualized description may provide a better understanding of HTLV-1-mediated cellular transformation and the potential therapeutic strategies to combat HTLV-1-associated diseases.

Translational and clinical advances in JAK-STAT biology: The present and future of jakinibs

In this era, it is axiomatic that cytokines have critical roles in cellular development and differentiation, immune homeostasis, and host defense. Equally, dysregulation of cytokines is known to contribute to diverse inflammatory and immune-mediated disorders. In fact, the past 20 years have witnessed the rapid translation of basic discoveries in cytokine biology to multiple successful biological agents (mAbs and recombinant fusion proteins) that target cytokines. These targeted therapies have not only fundamentally changed the face of multiple immune-mediated diseases but have also unequivocally established the role of specific cytokines in human disease; cytokine biologists have many times over provided remarkable basic advances with direct clinical benefit. Numerous cytokines rely on the JAK-STAT pathway for signaling, and new, safe, and effective small molecule inhibitors have been developed for a range of disorders. In this review, we will briefly summarize basic discoveries in cytokine signaling and briefly comment on some major unresolved issues. We will review clinical data pertaining to the first generation of JAK inhibitors and their clinical indications, discuss additional opportunities for targeting this pathway, and lay out some of the challenges that lie ahead.

Signal Transducers and Activators of Transcription: Novel Targets for Anticancer Therapeutics

Background

Through specific activation of gene expression, the family of proteins known as signal transducers and activators of transcription (STATs) converts extracellular stimuli into diverse biological responses. Beyond the normal signaling functions of STATs, recent evidence indicates that aberrant activation of STATs contributes to neoplastic transformation.

Methods

Current literature pertaining to the role of STAT proteins in oncogenesis is presented. Also, the rationale for developing novel approaches to disrupt STAT signaling is discussed, and the potential of STATs as anticancer targets in treating human cancer is reviewed.

Results

The discovery that certain oncoproteins constitutively activate specific STATs, coupled with observations that elevated STAT activity occurs frequently in a spectrum of human tumors, establishes a direct link between STAT activation and neoplastic transformation. Significantly, abrogation of STAT signaling blocks oncogenesis in model in vitro and in vivo systems. These results make STATs attractive targets for rational design of small molecule inhibitors and gene therapy approaches to disrupt STAT signaling.

Conclusions

As a result of genetic, biochemical, and crystallographic analyses, the functional domains of STAT proteins have been well characterized. Based on these data, selective inhibitors of STAT function can be designed. Because disrupting STAT signaling has proven effective in blocking neoplastic transformation, it is proposed that STAT proteins represent promising targets for development of novel molecular therapeutics to treat human cancer.

JAK/STAT pathway directed therapy of T-cell leukemia/lymphoma: Inspired by functional and structural genomics

Abnormal activation of the γc cytokine JAK/STAT signaling pathway assessed by STAT3 or STAT5b phosphorylation was present in a proportion of many T-cell malignancies. Activating mutations of STAT3/STAT5b and JAK1/3 were present in some but not in all cases with constitutive signaling pathway activation. Using shRNA analysis pSTAT malignant T-cell lines were addicted to JAKs/STATs whether they were mutated or not. Activating JAK/STAT mutations were not sufficient to support leukemic cell proliferation but only augmented upstream pathway signals. Functional cytokine receptors were required for pSTAT expression. Combining a JAK1/2 inhibitor with a Bcl-xL inhibitor navitoclax provided additive/synergistic activity with IL-2 dependent ATLL cell lines and in a mouse model of human IL-2 dependent ATLL. The insight that disorders of the γc/JAK/STAT system are pervasive suggests approaches including those that target gamma cytokines, their receptors or that use JAK kinase inhibitors may be of value in multicomponent therapy for T-cell malignancies.

Disorders of the JAK/STAT Pathway in T Cell Lymphoma Pathogenesis: Implications for Immunotherapy

Common gamma receptor-dependent cytokines and their JAK/STAT pathways play pivotal roles in T cell immunity. Abnormal activation of this system was pervasive in diverse T cell malignancies assessed by pSTAT3/pSTAT5 phosphorylation. Activating mutations were described in some but not all cases. JAK1 and STAT3 were required for proliferation and survival of these T cell lines whether or not JAKs or STATs were mutated. Activating JAK and STAT mutations were not sufficient to initiate leukemic cell proliferation but rather only augmented signals from upstream in the cytokine pathway. Activation required the full pathway, including cytokine receptors acting as scaffolds and docking sites for required downstream JAK/STAT proteins. JAK kinase inhibitors have depressed leukemic T cell line proliferation. The insight that JAK/STAT system activation is pervasive in T cell malignancies suggests novel therapeutic approaches that include antibodies to common gamma cytokines, inhibitors of cytokine-receptor interactions, and JAK kinase inhibitors that may revolutionize therapy for T cell malignancies.