STAT signaling in the pathogenesis and treatment of leukemias

Inflammation as a driver of hematological malignancies

Hematopoiesis is a tightly regulated process that produces all adult blood cells and immune cells from multipotent hematopoietic stem cells (HSCs). HSCs usually remain quiescent, and in the presence of external stimuli like infection or inflammation, they undergo division and differentiation as a compensatory mechanism. Normal hematopoiesis is impacted by systemic inflammation, which causes HSCs to transition from quiescence to emergency myelopoiesis. At the molecular level, inflammatory cytokine signaling molecules such as tumor necrosis factor (TNF), interferons, interleukins, and toll-like receptors can all cause HSCs to multiply directly. These cytokines actively encourage HSC activation, proliferation, and differentiation during inflammation, which results in the generation and activation of immune cells required to combat acute injury. The bone marrow niche provides numerous soluble and stromal cell signals, which are essential for maintaining normal homeostasis and output of the bone marrow cells. Inflammatory signals also impact this bone marrow microenvironment called the HSC niche to regulate the inflammatory-induced hematopoiesis. Continuous pro-inflammatory cytokine and chemokine activation can have detrimental effects on the hematopoietic system, which can lead to cancer development, HSC depletion, and bone marrow failure. Reactive oxygen species (ROS), which damage DNA and ultimately lead to the transformation of HSCs into cancerous cells, are produced due to chronic inflammation. The biological elements of the HSC niche produce pro-inflammatory cytokines that cause clonal growth and the development of leukemic stem cells (LSCs) in hematological malignancies. The processes underlying how inflammation affects hematological malignancies are still not fully understood. In this review, we emphasize the effects of inflammation on normal hematopoiesis, the part it plays in the development and progression of hematological malignancies, and potential therapeutic applications for targeting these pathways for therapy in hematological malignancies.

Designing patient-oriented combination therapies for acute myeloid leukemia based on efficacy/toxicity integration and bipartite network modeling

Acute myeloid leukemia (AML), a heterogeneous and aggressive blood cancer, does not respond well to single-drug therapy. A combination of drugs is required to effectively treat this disease. Computational models are critical for combination therapy discovery due to the tens of thousands of two-drug combinations, even with approved drugs. While predicting synergistic drugs is the focus of current methods, few consider drug efficacy and potential toxicity, which are crucial for treatment success. To find effective new drug candidates, we constructed a bipartite network using patient-derived tumor samples and drugs. The network is based on drug-response screening and summarizes all treatment response heterogeneity as drug response weights. This bipartite network is then projected onto the drug part, resulting in the drug similarity network. Distinct drug clusters were identified using community detection methods, each targeting different biological processes and pathways as revealed by enrichment and pathway analysis of the drugs' protein targets. Four drugs with the highest efficacy and lowest toxicity from each cluster were selected and tested for drug sensitivity using cell viability assays on various samples. Results show that ruxolitinib-ulixertinib and sapanisertib-LY3009120 are the most effective combinations with the least toxicity and the best synergistic effect on blast cells. These findings lay the foundation for personalized and successful AML therapies, ultimately leading to the development of drug combinations that can be used alongside standard first-line AML treatment.

Clinical, biological, and outcome features of P2RY8-CRLF2 and CRLF2 over-expression in pediatric B-cell precursor acute lymphoblastic leukemia according to the CCLG-ALL 2008 and 2018 protocol

OBJECTIVES

CRLF2 alterations are associated with B-cell precursor acute lymphoblastic leukemia (BCP-ALL). This study aimed to explore the clinical, biological, and outcome features of pediatric BCP-ALL with CRLF2 abnormalities.

METHODS

This study enrolled 630 childhood BCP-ALLs treated on CCLG-ALL 2008 or 2018 protocol. P2RY8-CRLF2 was determined by Sanger sequencing and CRLF2 expression was evaluated by qRT-PCR. The correlation between clinical, biological features and outcomes with P2RY8-CRLF2 or CRLF2 over-expression were analyzed.

RESULTS

P2RY8-CRLF2 and CRLF2 over-expression were found in 3.33% and 5.71% respectively. P2RY8-CRLF2 was associated with male, higher frequency of CD7 expression, high WBC and MRD before consolidation. CRLF2 over-expression showed ETV6-RUNX1^- , higher frequency of CD22, CD34, CD66c, CD86 expression, hyperdiploidy and high MRD at early treatment. The lower overall survival (OS) was found in patients with P2RY8-CRLF2 and confined only in IR group. Furthermore, adverse event-free survival and OS of P2RY8-CRLF2 were discovered comparing to those without known fusions or treated on CCLG-ALL 2008 protocol. However, P2RY8-CRLF2 was not confirmed as independent prognostic factors and no prognostic impact of CRLF2 over-expression was found.

CONCLUSIONS

These findings indicate P2RY8-CRLF2 identifies a subset of patients with specific features and adverse outcomes that could be improved by risk-directed treatment.

JAK/STAT pathway: Extracellular signals, diseases, immunity, and therapeutic regimens

Janus kinase/signal transduction and transcription activation (JAK/STAT) pathways were originally thought to be intracellular signaling pathways that mediate cytokine signals in mammals. Existing studies show that the JAK/STAT pathway regulates the downstream signaling of numerous membrane proteins such as such as G-protein-associated receptors, integrins and so on. Mounting evidence shows that the JAK/STAT pathways play an important role in human disease pathology and pharmacological mechanism. The JAK/STAT pathways are related to aspects of all aspects of the immune system function, such as fighting infection, maintaining immune tolerance, strengthening barrier function, and cancer prevention, which are all important factors involved in immune response. In addition, the JAK/STAT pathways play an important role in extracellular mechanistic signaling and might be an important mediator of mechanistic signals that influence disease progression, immune environment. Therefore, it is important to understand the mechanism of the JAK/STAT pathways, which provides ideas for us to design more drugs targeting diseases based on the JAK/STAT pathway. In this review, we discuss the role of the JAK/STAT pathway in mechanistic signaling, disease progression, immune environment, and therapeutic targets.

Stochastic dynamics of Type-I interferon responses

Interferon (IFN) activates the transcription of several hundred of IFN stimulated genes (ISGs) that constitute a highly effective antiviral defense program. Cell-to-cell variability in the induction of ISGs is well documented, but its source and effects are not completely understood. The molecular mechanisms behind this heterogeneity have been related to randomness in molecular events taking place during the JAK-STAT signaling pathway. Here, we study the sources of variability in the induction of the IFN-alpha response by using MxA and IFIT1 activation as read-out. To this end, we integrate time-resolved flow cytometry data and stochastic modeling of the JAK-STAT signaling pathway. The complexity of the IFN response was matched by fitting probability distributions to time-course flow cytometry snapshots. Both, experimental data and simulations confirmed that the MxA and IFIT1 induction circuits generate graded responses rather than all-or-none responses. Subsequently, we quantify the size of the intrinsic variability at different steps in the pathway. We found that stochastic effects are transiently strong during the ligand-receptor activation steps and the formation of the ISGF3 complex, but negligible for the final induction of the studied ISGs. We conclude that the JAK-STAT signaling pathway is a robust biological circuit that efficiently transmits information under stochastic environments.

We investigate the impact of intrinsic and extrinsic noise on the reliability of interferon signaling. Information must be transduced robustly despite existing biochemical variability and at the same time the system has to allow for cellular variability to tune it against changing environments. Getting insights into stochasticity in signaling networks is crucial to understand cellular dynamics and decision-making processes. To this end, we developed a detailed stochastic computational model based on single cell data. We are able to show that reliability is achieved despite high noise at the receptor level.

The emerging role of non-coding RNAs in the epigenetic regulation of pediatric cancers

Epigenetics is a process that involves the regulation of gene expression without altering the sequence of DNA. Numerous studies have documented that epigenetic mechanisms play a critical role in cell growth, differentiation, and cancer over the past decade. The well-known epigenetic modifications are either on DNA or at the histone proteins. Although several studies have focused on regulating gene expression by non-coding RNAs, the current understanding of their biological functions in various human diseases, particularly in cancers, is inadequate. Only about two percent of DNA is involved in coding the protein-coding genes, and leaving the rest 98 percent is non-coding and the scientific community regarded as junk or noise with no known purpose. Most non-coding RNAs are derived from such junk DNA and are known to be involved in various signaling pathways involving cancer initiation, progression, and the development of therapy resistance in many human cancer types. Recent studies have suggested that non-coding RNAs, especially microRNAs, piwi-interactingRNAs, and long non-coding RNAs, play a significant role in controlling epigenetic mechanism(s), indicating the potential effect of epigenetic modulation of non-coding RNAs on cancer progression. In this review article, we briefly presented epigenetic marks' characteristics, crosstalk between epigenetic modifications and microRNAs, piwi-interactingRNAs, and long non-coding RNAs to uncover the effect on the phenotype of pediatric cancers. Further, current knowledge on understanding the RNA epigenetics will help design novel therapeutics that target epigenetic regulatory networks to benefit cancer patients in the clinic.

Genetic Biomarkers and Their Clinical Implications in B-Cell Acute Lymphoblastic Leukemia in Children

Acute lymphoblastic leukemia (ALL) is a heterogeneous group of hematologic malignancies characterized by abnormal proliferation of immature lymphoid cells. It is the most commonly diagnosed childhood cancer with an almost 80% cure rate. Despite favorable survival rates in the pediatric population, a significant number of patients develop resistance to therapy, resulting in poor prognosis. ALL is a heterogeneous disease at the genetic level, but the intensive development of sequencing in the last decade has made it possible to broaden the study of genomic changes. New technologies allow us to detect molecular changes such as point mutations or to characterize epigenetic or proteomic profiles. This process made it possible to identify new subtypes of this disease characterized by constellations of genetic alterations, including chromosome changes, sequence mutations, and DNA copy number alterations. These genetic abnormalities are used as diagnostic, prognostic and predictive biomarkers that play an important role in earlier disease detection, more accurate risk stratification, and treatment. Identification of new ALL biomarkers, and thus a greater understanding of their molecular basis, will lead to better monitoring of the course of the disease. In this article, we provide an overview of the latest information on genomic alterations found in childhood ALL and discuss their impact on patients' clinical outcomes.

LncRNA Hmrhl regulates expression of cancer related genes in chronic myelogenous leukemia through chromatin association

Long non-coding RNA has emerged as a key regulator of myriad gene functions. One such lncRNA mrhl, reported by our group, was found to have important role in spermatogenesis and embryonic development in mouse. Recently, its human homolog, Hmrhl was shown to have differential expression in several type of cancers. In the present study, we further characterize molecular features of Hmrhl and gain insight into its functional role in leukemia by gene silencing and transcriptome-based studies. Results indicate its high expression in CML patient samples as well as in K562 cell line. Silencing experiments suggest role of Hmrhl in cell proliferation, migration & invasion. RNA-seq and ChiRP-seq data analysis further revealed its association with important biological processes, including perturbed expression of crucial TFs and cancer-related genes. Among them ZIC1, PDGRFβ and TP53 were identified as regulatory targets, with high possibility of triplex formation by Hmrhl at their promoter site. Further, overexpression of PDGRFβ in Hmrhl silenced cells resulted in rescue effect of cancer associated cellular phenotypes. In addition, we also found TAL-1 to be a potential regulator of Hmrhl expression in K562 cells. Thus, we hypothesize that Hmrhl lncRNA may play a significant role in the pathobiology of CML.

The Emerging Role of Suppressors of Cytokine Signaling (SOCS) in the Development and Progression of Leukemia

Cytokines are pleiotropic signaling molecules that execute an essential role in cell-to-cell communication through binding to cell surface receptors. Receptor binding activates intracellular signaling cascades in the target cell that bring about a wide range of cellular responses, including induction of cell proliferation, migration, differentiation, and apoptosis. The Janus kinase and transducers and activators of transcription (JAK/STAT) signaling pathways are activated upon cytokines and growth factors binding with their corresponding receptors. The SOCS family of proteins has emerged as a key regulator of cytokine signaling, and SOCS insufficiency leads to constitutive activation of JAK/STAT signaling and oncogenic transformation. Dysregulation of SOCS expression is linked to various solid tumors with invasive properties. However, the roles of SOCS in hematological malignancies, such as leukemia, are less clear. In this review, we discuss the recent advances pertaining to SOCS dysregulation in leukemia development and progression. We also highlight the roles of specific SOCS in immune cells within the tumor microenvironment and their possible involvement in anti-tumor immunity. Finally, we discuss the epigenetic, genetic, and post-transcriptional modifications of SOCS genes during tumorigenesis, with an emphasis on leukemia.

GM-CSF mediates immune evasion via upregulation of PD-L1 expression in extranodal natural killer/T cell lymphoma

Background

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a cytokine that is used as an immunopotentiator for anti-tumor therapies in recent years. We found that some of the extranodal natural killer/T cell lymphoma (ENKTL) patients with the treatment of hGM-CSF rapidly experienced disease progression, but the underlying mechanisms remain to be elucidated. Here, we aimed to explore the mechanisms of disease progression triggered by GM-CSF in ENKTL.

Methods

The mouse models bearing EL4 cell tumors were established to investigate the effects of GM-CSF on tumor growth and T cell infiltration and function. Human ENKTL cell lines including NK-YS, SNK-6, and SNT-8 were used to explore the expression of programmed death-ligand 1 (PD-L1) induced by GM-CSF. To further study the mechanisms of disease progression of ENKTL in detail, the mutations and gene expression profile were examined by next-generation sequence (NGS) in the ENKTL patient’s tumor tissue samples.

Results

The mouse-bearing EL4 cell tumor exhibited a faster tumor growth rate and poorer survival in the treatment with GM-CSF alone than in treatment with IgG or the combination of GM-CSF and PD-1 antibody. The PD-L1 expression at mRNA and protein levels was significantly increased in ENKTL cells treated with GM-CSF. STAT5A high-frequency mutation including p.R131G, p.D475N, p.F706fs, p.V707E, and p.S710F was found in 12 ENKTL cases with baseline tissue samples. Importantly, STAT5A-V706fs mutation tumor cells exhibited increased activation of STAT5A pathway and PD-L1 overexpression in the presence of GM-CSF.

Conclusions

These findings demonstrate that GM-CSF potentially triggers the loss of tumor immune surveillance in ENKTL patients and promotes disease progression, which is associated with STAT5 mutations and JAK2 hyperphosphorylation and then upregulates the expression of PD-L1. These may provide new concepts for GM-CSF application and new strategies for the treatment of ENKTL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01374-y.

Prospects for Clinical Development of Stat5 Inhibitor IST5-002: High Transcriptomic Specificity in Prostate Cancer and Low Toxicity In Vivo

Simple Summary

There is an unmet medical need for new and potent pharmacological inhibitor drugs for the protein Stat5 that would be orally bioavailable for treatment of several different cancers. Previous work has established a critical role for Stat5 in molecular and clinical progression of prostate cancer to metastatic disease and in the pathogenesis of several leukemias and blood-based disorders. Our group has developed a potent pharmacological inhibitor for Stat5, IST5-002, which targets two critical steps in the activation process of Stat5 in cancer cells. In the present work, we evaluated the characteristics of IST5-002 for further development into a cancer drug. We evaluated whether IST5-002 affects the Stat5 targets genes in prostate cancer, defined more closely its mechanisms of action, and investigated its initial toxicity as the basis for further development in order to enable its entrance into clinical testing in patients. Our study supports optimization of IST5-002 compound for oral bioavailability and for clinical development.

Abstract

Stat5 is of significant interest in the search for new therapeutics for prostate cancer (PC) and hematopoietic disorders. We evaluated the transcriptomic specificity of the Stat5a/b inhibitor IST5-002 (IST5) in PC, defined more closely its mechanisms of action, and investigated the in vivo toxicity of IST5 for further optimization for clinical development. The transcriptomic specificity of IST5 vs. genetic Stat5 knockdown was evaluated by RNA-seq analysis, which showed high similarity with the Pearson correlation coefficient ranging from 0.98–0.99. The potency of IST5 vs. its derivative lacking the phosphate group in suppressing Stat5 was evaluated in two separate but complementary assays. The inhibitory activity of IST5 against kinases was investigated in cell-free assays followed by more focused evaluation in a cell-based assay. IST5 has no specific inhibitory activity against 54 kinases, while suppressing Stat5 phosphorylation and subsequent dimerization in PC cells. The phosphate group was not critical for the biological activity of IST5 in cells. The acute, sub-chronic and chronic toxicity studies of IST5 were carried out in mice. IST5 did not cause any significant toxic effects or changes in the blood profiles. The present work supports further optimization of IST5 for oral bioavailability for clinical development for therapies for solid tumors, hematological and myeloproliferative disorders.

Ortho-Topolin Riboside Induced Differentiation through Inhibition of STAT3 Signaling in Acute Myeloid Leukemia HL-60 Cells

Objective:

We previously demonstrated that ortho-topolin riboside (oTR) as a naturally occurring cytokinin secreted from Populus × robusta has great potential anticancer effects via the mitochondrial apoptotic pathway and endoplasmic reticulum stress pathway. In the present study, we reveal that oTR induced the differentiation of acute myeloid leukemia (AML) HL-60 cells, which represent the M2 subtype of AML.

Materials and Methods:

After the incubation of HL-60 cells with oTR, its effect was analyzed with cell viability assay, Wright-Giemsa staining, CD11b protein expression analysis, western blot analysis, and polymerase chain reaction.

Results:

We found that oTR arrested the cell cycle at the S phase, upregulated the expression of myeloid surface marker CD11b, reduced the nuclear cytoplasmic ratio, and altered the horseshoe shape of nuclei, as evidenced by Wright-Giemsa staining. Furthermore, we found that the protein level of phosphorylated STAT3 was decreased when cells were treated with oTR, while phosphorylated STAT1 was activated. Moreover, the protein level of phosphorylated STAT3 and its upstream kinase, Janus kinase 2, were also inhibited when cells were treated with oTR after increased time. Additionally, the levels of phosphorylated SHP-1 were increased while phosphorylated SHP-2 was decreased.

Conclusion:

Collectively, our data indicate a differentiation-induced mechanism underlying the inhibition of STAT3 signaling upon treatment with oTR. Therefore, oTR may constitute a novel differentiation-induced therapeutic for use in clinical treatment of AML.

TGF-β2 antagonizes IL-6-promoted cell survival

Transforming growth factor beta is a key cytokine involved in the pathogenesis of fibrosis in many organs, whereas interleukin-6 plays an important role in the regulation of inflammation. They are both potent angiogenesis inducers with opposite effects on cell survival and apoptosis. TGF-β2 induces apoptosis; in contrast, IL-6 protects cells from apoptosis. The possible interaction between these two cytokines is indicated in various disease states. In this study, we have assessed the effect of TGF-β2 on IL-6 signaling and found that TGF-β2 could strongly inhibit IL-6-induced STAT3 activation and synergy with IL-6 resulting in enhanced SOCS3 expression. Interestingly, IL-6 also slows down the decay of TGF-β2 mRNA. Consistent with this mechanism, we found that TGF-β2 could antagonize IL-6 effect on cell survival in both γ-irradiation and UV light-induced apoptosis. Taken together, the finding shows that TGF-β2 serves as a negative regulator of IL-6 signaling and antagonizes the anti-apoptosis effect of IL-6.

Signal Transducer and Activator of Transcription (STATs) Proteins in Cancer and Inflammation: Functions and Therapeutic Implication

Signal Transducer and Activator of Transcription (STAT) pathway is connected upstream with Janus kinases (JAK) family protein and capable of integrating inputs from different signaling pathways. Each family member plays unique functions in signal transduction and crucial in mediating cellular responses to different kind of cytokines. STAT family members notably STAT3 and STAT5 have been involved in cancer progression whereas STAT1 plays opposite role by suppressing tumor growth. Persistent STAT3/5 activation is known to promote chronic inflammation, which increases susceptibility of healthy cells to carcinogenesis. Here, we review the role of STATs in cancers and inflammation while discussing current therapeutic implications in different cancers and test models, especially the delivery of STAT3/5 targeting siRNA using nanoparticulate delivery system.

PIM inhibitor SMI-4a induces cell apoptosis in B-cell acute lymphocytic leukemia cells via the HO-1-mediated JAK2/STAT3 pathway

OBJECTIVES

The serine/threonine PIM protein kinases are critical regulators of tumorigenesis in multiple cancers. However, whether PIMs are potential therapeutic targets for treating B-cell acute lymphocytic leukemia (B-ALL) remains unclear. Therefore, here, PIM expression was detected in B-ALL patients and the effects of SMI-4a, a pan-PIM small molecule inhibitor, were investigated in B-ALL cells.

METHODS

PIM1 and PIM2 expression in 26 newly diagnosed B-ALL cases was detected by real-time PCR and Western blot. B-ALL cells were treated with varied SMI-4a doses and the viability of treated cells was investigated using a cell-counting kit-8 (CCK-8) assay. Apoptosis and cell cycles were analyzed by flow cytometry. Western blot analysis was then used to explore the expression of apoptosis-related proteins and the JAK2/STAT3 pathway.

RESULTS

PIM1 and 2 were overexpressed in B-ALL patients with high HO-1 level. SMI-4a induced decreases in PIMs and HO-1 expressions and inhibited B-ALL cell viability. Treatment with SMI-4a induced apoptosis by downregulating Bcl-2, upregulating Bax and other antiapoptotic proteins, and decreasing protein levels of p-JAK2 and p-STAT3. In addition, upregulation of HO-1 alleviated decrease in p-JAK2 and p-STAT3 expression, reduced SMI-4a-induced apoptosis of B-ALL cells, and influenced B-ALL cell survival.

CONCLUSIONS

PIMs were highly expressed in B-ALL patients. SMI-4a inhibited B-ALL proliferation and induced apoptosis via the HO-1-mediated JAK2/STAT3 pathway. SMI-4a might be applicable for treatment of B-ALL cells.

Vasculogenesis and angiogenesis initiation under normoxic conditions through Wnt/β-catenin pathway in gliomas

The canonical Wnt/β-catenin pathway is up-regulated in gliomas and involved in proliferation, invasion, apoptosis, vasculogenesis and angiogenesis. Nuclear β-catenin accumulation correlates with malignancy. Hypoxia activates hypoxia-inducible factor (HIF)-1α by inhibiting HIF-1α prolyl hydroxylation, which promotes glycolytic energy metabolism, vasculogenesis and angiogenesis, whereas HIF-1α is degraded by the HIF prolyl hydroxylase under normoxic conditions. We focus this review on the links between the activated Wnt/β-catenin pathway and the mechanisms underlying vasculogenesis and angiogenesis through HIF-1α under normoxic conditions in gliomas. Wnt-induced epidermal growth factor receptor/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, Wnt-induced signal transducers and activators of transcription 3 (STAT3) signaling, and Wnt/β-catenin target gene transduction (c-Myc) can activate HIF-1α in a hypoxia-independent manner. The PI3K/Akt/mammalian target of rapamycin pathway activates HIF-1α through eukaryotic translation initiation factor 4E-binding protein 1 and STAT3. The β-catenin/T-cell factor 4 complex directly binds to STAT3 and activates HIF-1α, which up-regulates the Wnt/β-catenin target genes cyclin D1 and c-Myc in a positive feedback loop. Phosphorylated STAT3 by interleukin-6 or leukemia inhibitory factor activates HIF-1α even under normoxic conditions. The activation of the Wnt/β-catenin pathway induces, via the Wnt target genes c-Myc and cyclin D1 or via HIF-1α, gene transactivation encoding aerobic glycolysis enzymes, such as glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production, as the primary alternative of ATP, at all oxygen levels, even in normoxic conditions. Lactate released by glioma cells via the monocarboxylate lactate transporter-1 up-regulated by HIF-1α and lactate anion activates HIF-1α in normoxic endothelial cells by inhibiting HIF-1α prolyl hydroxylation and preventing HIF labeling by the von Hippel-Lindau protein. Increased lactate with acid environment and HIF-1α overexpression induce the vascular endothelial growth factor (VEGF) pathway of vasculogenesis and angiogenesis under normoxic conditions. Hypoxia and acidic pH have no synergistic effect on VEGF transcription.

The Role of Signal Transducer and Activator of Transcription 3 (STAT3) and Its Targeted Inhibition in Hematological Malignancies

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT protein family, can be phosphorylated by receptor-associated Janus kinases (JAKs) in response to stimulation by cytokines and growth factors. It forms homo- or heterodimers that can translocate to the cell nucleus where they act as transcription activators. Constitutive activation of STAT3 has been found to be associated with initiation and progression of various cancers. It can exert proliferative as well as anti-apoptotic effects. This review focuses on the role of STAT3 in pathogenesis i.e., proliferation, differentiation, migration, and apoptosis of hematological malignancies viz. leukemia, lymphoma and myeloma, and briefly highlights the potential therapeutic approaches developed against STAT3 activation pathway.

The effect of Ganoderma lucidum extract on immunological function and identify its anti-tumor immunostimulatory activity based on the biological network

Ganoderma lucidum extract (GLE) has shown positive effects for tumor treatment. However, the molecular mechanism of GLE treatment is unknown. In this study, a Hepa1-6-bearing C57 BL/6 mouse model was established to explore the anti-tumor and immunostimulatory activity of GLE treatment. The results showed that GLE effectively inhibited tumor growth without hepatic/renal toxicity and bone marrow suppression, and might enhancing immunological function. Based on the mRNA profiles of GLE treated and untreated mice, 302 differentially expressed (DE) mRNAs were identified and 6 kernel mRNAs were identified from the established protein-protein interaction (PPI) network. Quantitative RT-PCR and western-blot analysis indicated that 6 mRNAs have had statistically significant differences between the GLE treated and untreated mice. Furthermore, four kernel pathways were isolated from the KEGG-Target network, including the Jak-STAT signaling pathway, T cell receptor signaling pathway, PI3K-Akt signaling pathway, and cytokine-cytokine receptor interaction. Western-blot and cytokine detection results demonstrated that GLE suppressed growth and proliferation of tumors by the Jak-STAT signaling pathway, T cell receptor signaling pathway and PI3K-Akt signaling pathway, but also regulated the expression levels of serum immune cytokines and improved the anti-tumor immunostimulatory activity.

Mutations in the signal transducer and activator of transcription family of genes in cancer

In recent years, it has become clear that members of the signal transducer and activator of transcription (STAT) family of genes play an important role in cancer. The STAT family consists of seven genes, STAT1‐4,STAT5A, STAT5B and STAT6, that are involved in regulating cellular proliferation, apoptosis, angiogenesis and the immune system response. Constitutive activation of STAT3, via mutational changes, is important in oncogenesis in both solid and hematopoietic cancers. In the case of hematopoietic neoplasms, STAT3 driver mutations have been described in T‐cell large granular lymphocytic (T‐LGL) leukemia and chronic natural killer lymphoproliferative disorders (CLPD‐NK) and are seen in 30%‐40% of T‐LGL leukemia patients. STAT5B is also mutated in T‐LGL leukemia and CLPD‐NK, but in a much smaller proportion. Here we review past and current research on STAT genes in hematopoietic and solid cancers with emphasis on STAT3 and STAT5B and their roles in the pathogenesis of hematopoietic malignancies, particularly T‐LGL leukemia and CLPD‐NK.

Mediator Kinase Phosphorylation of STAT1 S727 Promotes Growth of Neoplasms With JAK-STAT Activation

Constitutive JAK-STAT signaling drives the proliferation of most myeloproliferative neoplasms (MPN) and a subset of acute myeloid leukemia (AML), but persistence emerges with chronic exposure to JAK inhibitors. MPN and post-MPN AML are dependent on tyrosine phosphorylation of STATs, but the role of serine STAT1 phosphorylation remains unclear. We previously demonstrated that Mediator kinase inhibitor cortistatin A (CA) reduced proliferation of JAK2-mutant AML in vitro and in vivo and also suppressed CDK8-dependent phosphorylation of STAT1 at serine 727. Here we report that phosphorylation of STAT1 S727 promotes the proliferation of AML cells with JAK-STAT pathway activation. Inhibition of serine phosphorylation by CA promotes growth arrest and differentiation, inhibits colony formation in MPN patient samples and reduces allele burden in MPN mouse models. These results reveal that STAT1 pS727 regulates growth and differentiation in JAK-STAT activated neoplasms and suggest that Mediator kinase inhibition represents a therapeutic strategy to regulate JAK-STAT signaling.

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CDK8/19 inhibitor cortistatin A synergizes with FDA-approved JAK1/2 ruxolitinib and inhibits ruxolitinib-persistent cells.

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CDK8/19 phosphorylation of STAT1 S727 promotes growth and suppresses differentiation.

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Cortistatin A upregulates expression of STAT1 pS727- and SE-associated genes.

Previously, it was known that cancer cells with activated JAK-STAT signaling are driven by oncogenic actions of JAK2 and tyrosine-phosphorylated STAT3 and STAT5. The FDA-approved JAK inhibitor ruxolitinib targets these dependencies, but significant challenges remain in the clinic, especially for leukemia patients. We show here that JAK2-mutant leukemia cells that become resistant to ruxolitinib are sensitive to CDK8/19 inhibitor CA and that CA synergizes with ruxolitinib, indicating that CDK8/19 inhibitors may be an effective therapeutic strategy for these cancers. Further, our studies provide insights into the mechanistic role of STAT1 serine phosphorylation by CDK8/19 in JAK2-activated leukemia.

STAT3 mediates C6-ceramide-induced cell death in chronic lymphocytic leukemia

The pathogenesis of chronic lymphocytic leukemia (CLL) is poorly understood and it remains incurable with current therapies. We have previously shown that nanoliposomal C6-ceramide (CNL) is an effective therapy in an in vivo murine model of CLL. However, the key signaling pathways mediating CNL-induced cell death in CLL remains unknown. We hypothesized that CNL targets STAT3, a critical regulator of hematopoietic biology. We observed that CNL treatment reduced phosphorylated STAT3 at both Y705 and S727 residues in CLL cell lines and patient cells. This, in turn, reduced STAT3 transcriptional activity and expression of critical STAT3-dependent survival factors like Mcl-1 and survivin. The effect of CNL on STAT3 was further confirmed ex vivo as shown by reduced STAT3 phosphorylation in xenograft tumors obtained from mice treated with CNL. CNL suppressed STAT3 phosphorylation at Y705 and S727 through reduction in BTK activity and MEK1/2 kinase/PKC activities, respectively. Moreover, a synergistic reduction in CLL cell viability was observed on co-treatment with CNL and the BTK inhibitor, ibrutinib. Expression of an oncogenic form of STAT3 conferred partial resistance to CNL, providing confirmation that STAT3 mediates CNL-induced cell death. Taken together, these findings provide the first body of evidence demonstrating ceramide regulation of STAT3 phosphorylation. These results are also the first to demonstrate an effect of ceramide on BTK, a critical kinase mediating the B-cell receptor signaling in CLL cells and suggest a novel and synergistic combination of CNL and BTK inhibitors for CLL treatment.

Ibrutinib modulates the immunosuppressive CLL microenvironment through STAT3-mediated suppression of regulatory B-cell function and inhibition of the PD-1/PD-L1 pathway

Ibrutinib, a covalent inhibitor of Bruton Tyrosine Kinase (BTK), is approved for treatment of patients with relapsed/refractory or treatment-naïve chronic lymphocytic leukemia (CLL). Besides directly inhibiting BTK, ibrutinib possesses immunomodulatory properties through targeting multiple signaling pathways. Understanding how this ancillary property of ibrutinib modifies the CLL microenvironment is crucial for further exploration of immune responses in this disease and devising future combination therapies. Here, we investigated the mechanisms underlying the immunomodulatory properties of ibrutinib. In peripheral blood samples collected prospectively from CLL patients treated with ibrutinib monotherapy, we observed selective and durable downregulation of PD-L1 on CLL cells by 3 months post-treatment. Further analysis showed that this effect was mediated through inhibition of the constitutively active signal transducer and activator of transcription 3 (STAT3) in CLL cells. Similar downregulation of PD-1 was observed in CD4+ and CD8+ T cells. We also demonstrated reduced interleukin (IL)-10 production by CLL cells in patients receiving ibrutinib, which was also linked to suppression of STAT3 phosphorylation. Taken together, these findings provide a mechanistic basis for immunomodulation by ibrutinib through inhibition of the STAT3 pathway, critical in inducing and sustaining tumor immune tolerance. The data also merit testing of combination treatments combining ibrutinib with agents capable of augmenting its immunomodulatory effects.

Interleukin-6 levels predict event-free survival in pediatric AML and suggest a mechanism of chemotherapy resistance

The tumor microenvironment can protect cancer cells from conventional anticancer therapies. Thus, targeting these protective mechanisms could eradicate therapy-resistant cancer cells and improve outcomes. Interleukin-6 (IL-6) provides extrinsic protection for several solid tumors and multiple myeloma. In pediatric acute myeloid leukemia (AML), IL-6-induced STAT3 signaling frequently becomes stronger at relapse, and increases in IL-6-induced STAT3 activity are associated with inferior survival after relapse. These findings suggested that the IL-6-induced STAT3 pathway may promote chemotherapy resistance and disease progression. Thus, we investigated the dysregulation of IL-6 levels in the bone marrow niche in pediatric patients with AML and the association between IL-6 levels and outcome. We measured levels of over 40 cytokines and growth factors in plasma from diagnostic bone marrow aspirates of 45 pediatric AML patients and 7 healthy sibling controls. Of the measured cytokines, only IL-6 levels were associated with event-free survival. Importantly, the effect of elevated IL-6 was most striking among children classified as having a low risk of relapse. In these patients, 5-year event-free survival was 82.5% ± 11% for patients with low IL-6 levels at diagnosis (n = 14) compared with 17.3% ± 11% for patients with elevated IL-6 (n = 13, log-rank P = .0003). In vitro, exogenous IL-6 reduced mitoxantrone-induced apoptosis in cell lines and primary pediatric AML samples. These results suggest that IL-6 levels at diagnosis could be used to help identify children at high risk of relapse, particularly those who are otherwise classified as low risk by current algorithms. Moreover, the IL-6 pathway could represent a target for overcoming environment-mediated chemotherapy resistance.

Wogonoside exerts growth-suppressive effects against T acute lymphoblastic leukemia through the STAT3 pathway

Wogonoside is the main flavonoid of the traditional Chinese medicinal herb Scutellaria baicalensis Georgi and has been found to induce growth suppression in myelogenous leukemia cells. However, its activity in T acute lymphoblastic leukemia (T-ALL) is still unclear. In this study, T-ALL cell lines MOLT-3 and Jurkat were exposed to different concentrations of wogonoside for 48 h, and cell viability, cell cycle distribution, and apoptosis were measured. The involvement of signal transducers and activators of transcription 3 (STAT3) signaling in the activity of wogonoside was checked. The in vivo effect of wogonoside on T-ALL growth was investigated in a xenograft mouse model. Wogonoside significantly inhibited the viability of MOLT-3 and Jurkat cells, with the IC₅₀ (the half maximal concentration) of 68.5 ± 3.8 and 52.6 ± 4.3 μM, respectively. However, healthy T lymphocytes were unaffected. Wogonoside-treated Jurkat cells exhibited a G1-phase cell cycle arrest and significant apoptosis, which was coupled with inactivation of STAT3 signaling. Overexpression of constitutively active STAT3 reversed wogonoside-mediated growth suppression and apoptosis and restored the expression of cyclin D1, Mcl-1, and Bcl-xL. In vivo studies demonstrated that wogonoside retarded tumor growth and suppressed STAT3 phosphorylation in Jurkat xenografts. In conclusion, wogonoside suppresses the growth of T-ALL through the STAT3 pathway and may have therapeutic benefits in this disease.

Single-cell epigenomic variability reveals functional cancer heterogeneity

Background

Cell-to-cell heterogeneity is a major driver of cancer evolution, progression, and emergence of drug resistance. Epigenomic variation at the single-cell level can rapidly create cancer heterogeneity but is difficult to detect and assess functionally.

Results

We develop a strategy to bridge the gap between measurement and function in single-cell epigenomics. Using single-cell chromatin accessibility and RNA-seq data in K562 leukemic cells, we identify the cell surface marker CD24 as co-varying with chromatin accessibility changes linked to GATA transcription factors in single cells. Fluorescence-activated cell sorting of CD24 high versus low cells prospectively isolated GATA1 and GATA2 high versus low cells. GATA high versus low cells express differential gene regulatory networks, differential sensitivity to the drug imatinib mesylate, and differential self-renewal capacity. Lineage tracing experiments show that GATA/CD24hi cells have the capability to rapidly reconstitute the heterogeneity within the entire starting population, suggesting that GATA expression levels drive a phenotypically relevant source of epigenomic plasticity.

Conclusion

Single-cell chromatin accessibility can guide prospective characterization of cancer heterogeneity. Epigenomic subpopulations in cancer impact drug sensitivity and the clonal dynamics of cancer evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1133-7) contains supplementary material, which is available to authorized users.

Three Tyrosine Residues in the Erythropoietin Receptor Are Essential for Janus Kinase 2 V617F Mutant-induced Tumorigenesis

The erythropoietin receptor (EpoR) regulates development of blood cells, and its full activation normally requires the cytokine erythropoietin (Epo). In the case of myeloproliferative neoplasms (MPN), Epo-independent signaling through EpoR can be caused by a point mutation, V617F, in the EpoR-interacting tyrosine kinase Janus kinase 2 (JAK2). In cells expressing the JAK2 V617F mutant, eight tyrosine residues in the intracellular domain of EpoR are phosphorylated, but the functional role of these phosphorylations in oncogenic signaling is incompletely understood. Here, to evaluate the functional consequences of the phosphorylation of these tyrosine residues, we constructed an EpoR-8YF mutant in which we substituted all eight tyrosine residues with phenylalanine. Co-expression of EpoR-8YF with the JAK2 V617F mutant failed to induce cytokine-independent cell proliferation and tumorigenesis, indicating that JAK2-mediated EpoR phosphorylation is the reason for JAK2 V617F mutant-induced oncogenic signaling. An exhaustive mutational analysis of the eight EpoR tyrosine residues indicated that three of these residues, Tyr-343, Tyr-460, and Tyr-464, are required for the JAK2 V617F mutant to exhibit its oncogenic activity. We also showed that phosphorylation at these three residues was necessary for full activation of the transcription factor STAT5, which is a critical downstream factor of JAK2 V617F-induced oncogenic signaling. In contrast, Epo stimulation could moderately stimulate the proliferation of cells expressing wild type JAK2 and EpoR-8YF, suggesting that the requirement of the phosphorylation of these three tyrosine residues seems to be specific for the oncogenic proliferation provoked by V617F mutation. Collectively, these results have revealed that phosphorylation of Tyr-343, Tyr-460, and Tyr-464 in EpoR underlies JAK2 V617F mutant-induced tumorigenesis. We propose that the targeted disruption of this pathway has therapeutic utility for managing MPN.

Prognostic significance of P2RY8-CRLF2 and CRLF2 overexpression may vary across risk subgroups of childhood B-cell acute lymphoblastic leukemia

The cytokine receptor-like factor 2 (CRLF2) gene plays an important role in early B-cell development. Aberrations in CRLF2 activate the JAK-STAT signaling pathway that contributes to B-cell acute lymphoblastic leukemia (B-ALL). The prognostic significance of CRLF2 overexpression and P2RY8-CRLF2 fusion in various B-ALL risk subgroups has not been well established. Two hundred seventy-one patients with newly diagnosed childhood B-ALL were enrolled from a Chinese population. The prevalence of CRLF2 overexpression, CRLF2-P2RY8 fusion, CRLF2 F232C mutation, and JAK2 and IL7R mutational status were analyzed, and the prognostic impact of CRLF2 overexpression and P2RY8-CRLF2 on B-ALL was evaluated by assessing their influence on overall survival and event-free survival. CRLF2 overexpression and P2RY8-CRLF2 were found in 19% and 10%, respectively, in the whole cohort. No correlation between CRLF2 overexpression and P2RY8-CRLF2 was observed. CRLF2 F322C and IL7R mutations were not detected in B-ALL cases overexpressing CRLF2, and no JAK2 mutations were found in the whole cohort either. The results showed that CRLF2 overexpression and P2RY8-CRLF2 were associated with a poor outcome in unselected B-ALL. Moreover, in an intermediate risk B-ALL subgroup P2RY8-CRLF2 was correlated with worse survival, whereas in high- and low-risk subgroups, CRLF2 overexpression predicted a poor outcome. Our findings suggest that P2RY8-CRLF2 is an independent prognostic indicator in intermediate risk B-ALL, while CRLF2 overexpression is correlated with an inferior outcome in high- or low-risk B-ALL. Our study demonstrates that the impact of P2RY8-CRLF2 and CRLF2 overexpression on B-ALL survival may differ across risk subgroups. © 2016 Wiley Periodicals, Inc.

p43 induces IP-10 expression through the JAK-STAT signaling pathway in HMEC-1 cells

p43 is a cofactor of aminoacyl-tRNA synthetase in mammals that effectively inhibits angiogenesis. However, the role of p43 in angiogenesis remains unclear. In the present study, we examined the effects of p43 on angiogenesis using human microvascular endothelial cells-1 (HMEC-1) cells as a model. Our microarray data showed that p43 regulated a number of cytokines, and the majoity of these are involved in the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. IP-10 was previously shown to inhibit angiogenesis and suppress tumor growth via the JAK-STAT signaling pathway in vitro and in vivo. Our results showed that p43 induces both the mRNA and protein expression of IP-10. Furthermore, we demonstrated that p43 exerted an effect on the JAK-STAT signaling pathway by regulating key factors of the pathway. Using a JAK inhibitor, AG490, we studied the effect of p43 on HMEC-1 cells by blocking the JAK-STAT pathway. We found that AG490 inhibited the induction of IP-10 expression by p43, and suppressed the inhibitory effect of p43 on tubule formation and cell migration in HMEC-1 cells. We concluded that p43 inhibits tubule formation and cell migration by inducing IP-10 through the JAK-STAT signaling pathway, and blocking the JAK-STAT pathway with AG490 diminishes the inhibitory effects of p43 on angiogenesis.

Gene expression-based discovery of atovaquone as a STAT3 inhibitor and anticancer agent

The oncogenic transcription factor signal transducer and activator of transcription 3 (STAT3) is frequently activated inappropriately in a wide range of hematological and solid cancers, but clinically available therapies targeting STAT3 are lacking. Using a computational strategy to identify compounds opposing the gene expression signature of STAT3, we discovered atovaquone (Mepron), an antimicrobial approved by the US Food and Drug Administration, to be a potent STAT3 inhibitor. We show that, at drug concentrations routinely achieved clinically in human plasma, atovaquone inhibits STAT3 phosphorylation, the expression of STAT3 target genes, and the viability of STAT3-dependent hematological cancer cells. These effects were also observed with atovaquone treatment of primary blasts isolated from patients with acute myelogenous leukemia or acute lymphocytic leukemia. Atovaquone is not a kinase inhibitor but instead rapidly and specifically downregulates cell-surface expression of glycoprotein 130, which is required for STAT3 activation in multiple contexts. The administration of oral atovaquone to mice inhibited tumor growth and prolonged survival in a murine model of multiple myeloma. Finally, in patients with acute myelogenous leukemia treated with hematopoietic stem cell transplantation, extended use of atovaquone for Pneumocystis prophylaxis was associated with improved relapse-free survival. These findings establish atovaquone as a novel, clinically accessible STAT3 inhibitor with evidence of anticancer efficacy in both animal models and humans.

Hsp90 inhibitor, BIIB021, induces apoptosis and autophagy by regulating mTOR-Ulk1 pathway in imatinib-sensitive and -resistant chronic myeloid leukemia cells

Development of drug resistance due to BCR-ABL point mutations and the persistence of leukemia initiating cells has become a major obstacle for tyrosine kinase inhibitors (TKIs) in the treatment of chronic myeloid leukemia (CML). The BCR-ABL protein is an important client protein of heat shock protein 90 (Hsp90). BIIB021, an orally available Hsp90 inhibitor, has activity against various cancer cells. However, little is known about the inhibitory effect of BIIB021 on CML cells. We evaluated the inhibitory effects of BIIB021 on K562, K562/G (an imatinib-resistant cell lines), as well as 32D mouse leukemic cells expressing wild-type BCR-ABL (b3a2, 32Dp210) and T315I mutant BCR-ABL (32Dp210-T315I) cells. Our data showed that BIIB021 induced significant growth inhibition and apoptosis that was predominantly mediated by the mitochondrial pathway. BIIB021 also resulted in proteasomal degradation of BCR-ABL proteins. In addition to induction of apoptosis, we report for the first time that BIIB021 induced autophagic response as evidenced by the formation of autophagosome, increased conversion of microtubule-associated protein light chain 3 (LC3)-I to LC3-II, decreased p62 (SQSTM1) protein levels. Further study suggested that Akt-mTOR-Ulk1 signaling pathway was involved in BIIB021-triggered autophagy. Moreover, blocking autophagy using pharmacological inhibitor 3-methyladenine and bafilomycin A1 significantly enhanced cell death and apoptosis induced by BIIB021, indicating the cytoprotective role of autophagy in BIIB021-treated CML cells. Collectively, these data provide possible molecular mechanisms for the antileukemic effect of BIIB021 on imatinib-sensitive and -resistant CML cells and provide new insights into the future application of BIIB021 in the clinical treatment of CML.

Constitutive activation of Pim1 kinase is a therapeutic target for adult T-cell leukemia

Human T-cell leukemia virus type 1 (HTLV-1)-associated adult T-cell leukemia and T-cell lymphoma (ATL) are aggressive diseases with poor prognoses, limited therapeutic options, and no curative treatment. In this study, we used a mouse model of ATL and restored expression of the microRNA, miR-124a, to identify in vivo downstream effectors responsible for its tumor-suppressive functions in ATL cells. Our results revealed that STAT3, a direct target of miR-124a, is constitutively activated in HTLV-I-transformed cells and ATL cells, and activating STAT3 mutations were detected in 25.5% of primary ATL patients. Interestingly, we found that the STAT3 downstream kinase effector, Pim1, is constitutively activated in ATL cells. The dependence of ATL cells to Pim1 activity was demonstrated using 2 Pim1 small inhibitors, SMI-4a and AZD1208. These studies indicated that HTLV-I-transformed and ATL cells, but not normal peripheral blood mononuclear cells, are highly sensitive to AZD1208, and the inhibition of Pim1 signaling triggers an apoptotic signal in leukemic cells. Finally, preclinical testing of AZD1208 in a mouse model of ATL resulted in significant prevention of tumor growth in vivo. In conclusion, our studies suggest that constitutive activation of the STAT3-Pim1 pathway represents a novel therapeutic target for the treatment of ATL.

STAT5 in Cancer and Immunity

Signal transducers and activators of transcription 5 (STAT5a and STAT5b) are highly homologous proteins that are encoded by 2 separate genes and are activated by Janus-activated kinases (JAK) downstream of cytokine receptors. STAT5 proteins are activated by a wide variety of hematopoietic and nonhematopoietic cytokines and growth factors, all of which use the JAK-STAT signalling pathway as their main mode of signal transduction. STAT5 proteins critically regulate vital cellular functions such as proliferation, differentiation, and survival. The physiological importance of STAT5 proteins is underscored by the plethora of primary human tumors that have aberrant constitutive activation of these proteins, which significantly contributes to tumor cell survival and malignant progression of disease. STAT5 plays an important role in the maintenance of normal immune function and homeostasis, both of which are regulated by specific members of IL-2 family of cytokines, which share a common gamma chain (γ(c)) in their receptor complex. STAT5 critically mediates the biological actions of members of the γ(c) family of cytokines in the immune system. Essentially, STAT5 plays a critical role in the function and development of Tregs, and consistently activated STAT5 is associated with a suppression in antitumor immunity and an increase in proliferation, invasion, and survival of tumor cells. Thus, therapeutic targeting of STAT5 is promising in cancer.

Molecular genetic and cytogenetic analysis of a primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma

We performed cytogenetic and molecular cytogenetic analyses of a primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma, a rare type of primary cutaneous T-cell lymphoma. G-banded analysis at initial diagnosis and recurrence revealed complex karyotype and clonal evolution reflecting genomic instability that parallels the aggressive clinical course observed. Spectral karyotyping revealed numerous structural abnormalities. SNP array-based analysis of an initial diagnostic sample revealed numerous gains and losses of chromosomal material, including loss of short arm of the chromosome 17, to which TP53 is mapped. The molecular cytogenetics and array data of this case suggest genomic instability, particularly chromosomal instability and haploinsufficiency for TP53, the latter possibly giving rise to alteration of p14ARF-Mdm2-p53 tumor suppressor protein pathway, likely to be associated with unfavorable clinical course.

STAT3 activation is associated with cerebrospinal fluid interleukin-10 (IL-10) in primary central nervous system diffuse large B cell lymphoma

Signal transducers and activators of transcription 3 (STAT3) are activated by various cytokines and oncogenes; however, the activity and pathogenesis of STAT3 in diffuse large B cell lymphoma of the central nervous system have not been thoroughly elucidated. We investigated the phosphorylation levels of STAT3 in 40 specimens of primary central nervous system diffuse large B-cell lymphoma (PCNS DLBCL) and analyzed the association between phsopho-STAT3 (pSTAT3) expression and cerebrospinal fluid (CSF) concentration of interleukin-10 (IL-10) or IL-6. Immunohistochemistry and Western blot analysis revealed that most of the specimens in PCNS DLBCL expressed pSTST3 protein, and a strong phosphorylation levels of STAT3 was statistically associated with high CSF IL-10 levels, but not with CSF IL-6 levels. Next, we demonstrated that recombinant IL-10 and CSF containing IL-10 induced the phosphorylation of STAT3 in PCNS DLBCL cells. Furthermore, molecular subtype classified by Hans' algorithm was correlated with pSTAT3 expression levels and CSF IL-10 levels. These results suggest that the STAT3 activity is correlated with CSF IL-10 level, which is a useful marker for STAT3 activity in PCNS DLBCLs.

Structure-Based Screen Identifies a Potent Small Molecule Inhibitor of Stat5a/b with Therapeutic Potential for Prostate Cancer and Chronic Myeloid Leukemia

Bypassing tyrosine kinases responsible for Stat5a/b phosphorylation would be advantageous for therapy development for Stat5a/b-regulated cancers. Here, we sought to identify small molecule inhibitors of Stat5a/b for lead optimization and therapy development for prostate cancer and Bcr-Abl-driven leukemias. In silico screening of chemical structure databases combined with medicinal chemistry was used for identification of a panel of small molecule inhibitors to block SH2 domain-mediated docking of Stat5a/b to the receptor-kinase complex and subsequent phosphorylation and dimerization. We tested the efficacy of the lead compound IST5-002 in experimental models and patient samples of two known Stat5a/b-driven cancers, prostate cancer and chronic myeloid leukemia (CML). The lead compound inhibitor of Stat5-002 (IST5-002) prevented both Jak2 and Bcr-Abl-mediated phosphorylation and dimerization of Stat5a/b, and selectively inhibited transcriptional activity of Stat5a (IC50 = 1.5μmol/L) and Stat5b (IC50 = 3.5 μmol/L). IST5-002 suppressed nuclear translocation of Stat5a/b, binding to DNA and Stat5a/b target gene expression. IST5-002 induced extensive apoptosis of prostate cancer cells, impaired growth of prostate cancer xenograft tumors, and induced cell death in patient-derived prostate cancers when tested ex vivo in explant organ cultures. Importantly, IST5-002 induced robust apoptotic death not only of imatinib-sensitive but also of imatinib-resistant CML cell lines and primary CML cells from patients. IST5-002 provides a lead structure for further chemical modifications for clinical development for Stat5a/b-driven solid tumors and hematologic malignancies.

Phase I study of OPB-51602, an oral inhibitor of signal transducer and activator of transcription 3, in patients with relapsed/refractory hematological malignancies

We carried out a multicenter dose-escalation phase I study of oral OPB-51602, a signal transducer and activator of transcription 3 phosphorylation inhibitor, in patients with relapsed or refractory hematological malignancies to evaluate the safety, maximum tolerated dose (MTD), pharmacokinetics, and preliminary antitumor activity. Twenty patients were treated with OPB-51602 at doses of 1, 2, 3, 4, and 6 mg in the “3 + 3” dose escalation design. The most common treatment-related adverse events included nausea (55%), peripheral sensory neuropathy (45%), and diarrhea (40%). The most frequently observed grade 3 or 4 drug-related adverse events were neutropenia (20%), leukopenia (15%), lymphopenia (10%), and thrombocytopenia (10%). The MTD was 6 mg, with dose-limiting toxicities of grade 3 lactic acidosis and increased blood lactic acid levels observed in one of three patients and grade 1–2 peripheral neuropathy in three of three patients. The recommended dose was determined to be 4 mg. OPB-51602 was rapidly absorbed, and exposure tended to increase in a dose-dependent manner. Accumulation of OPB-51602 was seen with 4 weeks of multiple treatments. No clear therapeutic response was observed. Durable stable disease was observed in two patients with acute myeloid leukemia and one with myeloma. In conclusion, the MTD of OPB-51602 was 6 mg. OPB-51602 was safe and well tolerated in a dose range of 1–4 mg. However, long-term administration at higher doses was difficult with the daily dosing schedule, and no response was seen. Therefore, further clinical development of OPB-51602 for hematological malignancies with a daily dosing schedule was terminated.

Zebrafish as a Model for the Study of Human Myeloid Malignancies

Myeloid malignancies are heterogeneous disorders characterized by uncontrolled proliferation or/and blockage of differentiation of myeloid progenitor cells. Although a substantial number of gene alterations have been identified, the mechanism by which these abnormalities interact has yet to be elucidated. Over the past decades, zebrafish have become an important model organism, especially in biomedical research. Several zebrafish models have been developed to recapitulate the characteristics of specific myeloid malignancies that provide novel insight into the pathogenesis of these diseases and allow the evaluation of novel small molecule drugs. This report will focus on illustrative examples of applications of zebrafish models, including transgenesis, zebrafish xenograft models, and cell transplantation approaches, to the study of human myeloid malignancies.

Gold nanoparticle-based beacon to detect STAT5b mRNA expression in living cells: a case optimized by bioinformatics screen

Messenger RNA (mRNA), a single-strand ribonucleic acid with functional gene information is usually abnormally expressed in cancer cells and has become a promising biomarker for the study of tumor progress. Hairpin DNA-coated gold nanoparticle (hDAuNP) beacon containing a bare gold nanoparticle (AuNP) as fluorescence quencher and thiol-terminated fluorescently labeled stem-loop-stem oligonucleotide sequences attached by Au-S bond is currently a new nanoscale biodiagnostic platform capable of mRNA detection, in which the design of the loop region sequence is crucial for hybridizing with the target mRNA. Hence, in this study, to improve the sensitivity and selectivity of hDAuNP beacon simultaneously, the loop region of hairpin DNA was screened by bioinformatics strategy. Here, signal transducer and activator of transcription 5b (STAT5b) mRNA was selected and used as a practical example. The results from the combined characterizations using optical techniques, flow cytometry assay, and cell microscopic imaging showed that after optimization, the as-prepared hDAuNP beacon had higher selectivity and sensitivity for the detection of STAT5b mRNA in living cells, as compared with our previous beacon. Thus, the bioinformatics method may be a promising new strategy for assisting in the designing of the hDAuNP beacon, extending its application in the detection of mRNA expression and the resultant mRNA-based biological processes and disease pathogenesis.

Natural course and biology of CML

Chronic myeloid leukaemia (CML) is a myeloproliferative disorder arising in the haemopoietic stem cell (HSC) compartment. This disease is characterised by a reciprocal t(9;22) chromosomal translocation, resulting in the formation of the Philadelphia (Ph) chromosome containing the BCR-ABL1 gene. As such, diagnosis and monitoring of disease involves detection of BCR-ABL1. It is the BCR-ABL1 protein, in particular its constitutively active tyrosine kinase activity, that forges the pathogenesis of CML. This aberrant kinase signalling activates downstream targets that reprogram the cell to cause uncontrolled proliferation and results in myeloid hyperplasia and 'indolent' symptoms of chronic phase (CP) CML. Without successful intervention, the disease will progress into blast crisis (BC), resembling an acute leukaemia. This advanced disease stage takes on an aggressive phenotype and is almost always fatal. The cell biology of CML is also centred on BCR-ABL1. The presence of BCR-ABL1 can explain virtually all the cellular features of the leukaemia (enhanced cell growth, inhibition of apoptosis, altered cell adhesion, growth factor independence, impaired genomic surveillance and differentiation). This article provides an overview of the clinical and cell biology of CML, and highlights key findings and unanswered questions essential for understanding this disease.

Matrine suppresses cell growth of human chronic myeloid leukemia cells via its inhibition of the interleukin-6/Janus activated kinase/signal transducer and activator of transcription 3 signaling cohort

Matrine, alkaloid isolated from Sophora flavescens, is known to be pleiotropic by exerting anti-inflammatory, anti-oxidation, as well as anti-cancer effects. However, the precise molecular targets or pathways responsible for its activities still remain unclear. The present study aimed to determine the underlying mechanisms of matrine in inhibiting the chronic myeloid leukemia cells (CML). It was observed that matrine treatment significantly suppressed CML cells proliferation, induced apoptosis and resulted in the accumulation of cells in the G0/G1 phase, accompanied by a significant decrease in Bcl-xL, Cyclin D1, and c-Myc expression. Western blot analyses revealed that matrine treatment resulted in the down-regulation in phospho-STAT3 and phospho-JAK2 without significantly effects on STAT3 and JAK2 protein levels. Matrine significantly reduced the expression of IL-6, a potent upstream activating factor of STAT3. These results strongly suggested the IL-6/JAK/STAT3 pathway play an important role in matrine's anti-leukemia effects in K562 cells.

The synthetic tryptanthrin analogue suppresses STAT3 signaling and induces caspase dependent apoptosis via ERK up regulation in human leukemia HL-60 cells

Tryptanthrin is a natural product which has been reported to have several medicinal properties. In this study, we tried to investigate the detailed molecular mechanism of its bromo analogue (TBr), a potent cytotoxic agent in the induction of cancer cell death. It was found that TBr primarily targets STAT3 and ERK signaling during the induction of apoptosis in several human leukemia cell lines. In HL-60 cells, TBr treatment caused early down regulation of p-STAT3 with concomitant up regulation of p-ERK which led to the activation of intrinsic and extrinsic pathways of apoptosis. The mechanism of TBr mediated inhibition of p-STAT3 was found to be due to the activation of ubiquitin dependent degradation of tyrosine 705 and serine 727 p-STAT3. As IL-6 is the main driver of the STAT3 pathway, the effect of TBr on cell death was subdued when treated in the combination with IL-6 in HL60 cells. Interestingly, PD98059 significantly reduced the apoptotic effects of TBr, thus showing the direct involvement of p-ERK in TBr mediated cell death. It was further shown that apoptotic protein Bax silencing in HL-60 cells resists TBr mediated ERK dependent apoptosis. In summary, for the first time we report the mechanism of TBr mediated cell death in human leukemia cell lines by targeting STAT3 and ERK pathways.

STAT3 supports experimental K-RasG12D-induced murine myeloproliferative neoplasms dependent on serine phosphorylation

Juvenile myelomonocytic leukemia, acute myeloid leukemia (AML), and other myeloproliferative neoplasms (MPNs) are genetically heterogeneous but frequently display activating mutations in Ras GTPases and activation of signal transducer and activator of transcription 3 (STAT3). Altered STAT3 activity is observed in up to 50% of AML correlating with poor prognosis. Activated STAT proteins, classically associated with tyrosine phosphorylation, support tumor development as transcription factors, but alternative STAT functions independent of tyrosine phosphorylation have been documented, including roles for serine-phosphorylated STAT3 in mitochondria supporting transformation by oncogenic Ras. We examined requirements for STAT3 in experimental murine K-Ras-dependent hematopoietic neoplasia. We show that STAT3 is phosphorylated on S727 but not Y705 in diseased animals. Moreover, a mouse with a point mutation abrogating STAT3 S727 phosphorylation displayed delayed onset and decreased disease severity with significantly extended survival. Activated K-Ras required STAT3 for cytokine-independent growth of myeloid progenitors in vitro, and mitochondrially restricted STAT3 and STAT3-Y705F, both transcriptionally inert mutants, supported factor-independent growth. STAT3 was dispensable for growth of normal or K-Ras-mutant myeloid progenitors in response to cytokines. However, abrogation of STAT3-S727 phosphorylation impaired factor-independent malignant growth. These data document that serine-phosphorylated mitochondrial STAT3 supports neoplastic hematopoietic cell growth induced by K-Ras.

Phosphatase of regenerating liver-3 is regulated by signal transducer and activator of transcription 3 in acute myeloid leukemia

Overexpression of protein-tyrosine phosphatase of regenerating liver 3 (PRL-3) has been identified in about 50% of patients with acute myeloid leukemia (AML). The mechanism of regulation of PRL-3 remains obscure. Signal transducer and activator of transcription 3 (STAT3), a latent transcriptional factor, has also been often found to be activated in AML. We first identified STAT3-consensus-binding sites in the promoter of PRL-3 genes. Then we experimentally validated the direct binding and transcriptional activation. We applied shRNA-mediated knockdown and overexpression approaches in STAT3(-/-) liver cells and leukemic cells to validate the functional regulation of PRL-3 by STAT3. A STAT3 core signature, derived through data mining from publicly available gene expression data, was employed to correlate PRL-3 expression in large AML patient samples. We discovered that STAT3 binds to the -201 to -210 region of PRL-3, which was conserved between human and mouse. Importantly, PRL-3 protein was significantly reduced in mouse STAT3-knockout liver cells compared with STAT3-wild type counterparts, and ectopic expression of STAT3 in these cells led to a pronounced increase in PRL-3 protein. We demonstrated that STAT3 functionally regulated PRL-3, and STAT3 core signature was enriched in AML with high PRL-3 expression. Targeting either STAT3 or PRL-3 reduced leukemic cell viability. Silencing PRL-3 impaired invasiveness and induced leukemic cell differentiation. In conclusion, PRL-3 was transcriptionally regulated by STAT3. The STAT3/PRL-3 regulatory loop contributes to the pathogenesis of AML, and it might represent an attractive therapeutic target for antileukemic therapy.

STATs profiling reveals predominantly-activated STAT3 in cholangiocarcinoma genesis and progression

BACKGROUND

We investigated the aberrant expression of the STAT family in humans and liver fluke (Opisthorchis viverrini, Ov)-induced hamster cholangiocarcinoma (CCA) tissues.

METHODS

The expression and phosphorylation of STAT1, STAT2, STAT3, STAT4, STAT5a, STAT5b and STAT6 in human hamster CCA tissues were immunohistochemistry-profiled. Localizations of STAT5 in macrophages and lipopolysaccharide (LPS)-induced macrophage-conditioned media mediated STAT3 activation in CCA cells were demonstrated.

RESULTS

The expressions of STAT 1-4 and 6 were detected in the cytoplasm of hyperplastic bile ducts and tumor cells, whereas STAT5a and STAT5b were observed in macrophages and connective tissues surrounding tumor, respectively. The expressions of STAT3 and STAT5b were significantly observed in tumors with a poorer histological differentiation. STAT3 expression was significantly associated with shorter survival of CCA patients and was predominately activated in CCA cell lines. In the CCA-hamsters, STATs expression was gradually increased along the carcinogenesis, especially at 30 days post-infection in which the inflammatory response was markedly observed, showing the correlation between the inflammation and STATs activation. Moreover, LPS-induced macrophage-conditioned media could mediate STAT3 activation in CCA cells.

CONCLUSIONS

STAT3 is the major STAT, which plays roles in the inflammation that contributes to CCA carcinogenesis and progression and may serve as a marker for a poor prognosis of CCA.