Atiprimod blocks phosphorylation of JAK-STAT and inhibits proliferation of acute myeloid leukemia (AML) cells

Effect of AML-exosomes on the cellular and molecular properties of bone marrow mesenchymal stromal cells: Expression of JAK/STAT signaling genes

PURPOSE OF STUDY

Despite the various therapeutic options introduced for AML treatment, therapy resistance and relapse are still the main obstacles. It is well known that alterations in the bone marrow microenvironment (BMM) play a crucial role in leukemia growth and the treatment failure of AML. Evidence shows that exosomes alter the components of BMM in a way that support leukemia survival, leading to chemoresistance. In this study, we evaluated the effect of AML exosomes on the biological functions of human bone marrow mesenchymal stromal cells (h BM-MSCs), especially alteration in the expression of the JAK/STAT signaling genes, as a leukemia-favoring pathway.

METHOD

Exosomes were isolated from the HL-60 cell line and characterized using flow cytometry, Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS) technique. The exosome protein content was assessed using a bicinchoninic acid (BCA) protein assay kit in order to determine the concentration of exosomes. Subsequently, MSCs were treated with varying concentrations of AML exosomes, and data was obtained using MTT, cell cycle, apoptosis, and ki67 assays. Additionally, gene expression analysis was conducted through qRT-PCR.

RESULT

AML exosomes regulated the viability and survival of MSCs in a concentration-dependent manner. The qRT-PCR data revealed that treatment with AML exosomes at a concentration of 50 μg/mL led to a significant upregulation of JAK2, STAT3, and STAT5 genes in MSCs.

CONCLUSION

Because the JAK/STAT signaling pathway has been shown to play a role in the proliferation and survival of leukemic cells, our results suggest that AML exosomes stimulate MSCs to activate this pathway. This activation may impede AML cell apoptosis, potentially leading to chemoresistance and relapse.

The Role of the JAK-STAT Pathway in Childhood B-Cell Acute Lymphoblastic Leukemia

B-cell lymphoblastic leukemia is a hematologic neoplasm that poses a serious health concern in childhood. Genetic aberrations, such as mutations in the genes IL-7, IL7R, JAK1, JAK2, TLSP, CRLF2, and KTM2A or gene fusions involving BCR::ABL1, ETV6::RUNX1, and PAX5::JAK2, often correlate with the onset of this disease. These aberrations can lead to malfunction of the JAK-STAT signaling pathway, which is implicated in various important biological processes, including those related to immunology. Understanding the mechanisms underlying the malfunction of the JAK-STAT pathway holds potential for research on drugs targeting its components. Available drugs that interfere with the JAK-STAT pathway include fludarabine, ruxolitinib, and fedratinib.

JAK/STAT in leukemia: a clinical update

Over the past three decades, considerable efforts have been expended on understanding the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway in leukemia, following the identification of the JAK2V617F mutation in myeloproliferative neoplasms (MPNs). The aim of this review is to summarize the latest progress in our understanding of the involvement of the JAK/STAT signaling pathway in the development of leukemia. We also attempt to provide insights into the current use of JAK/STAT inhibitors in leukemia therapy and explore pertinent clinical trials in this field.

A Triazaspirane Derivative Inhibits Migration and Invasion in PC3 Prostate Cancer Cells

Cancer is a serious health problem due to the complexity of establishing an effective treatment. The purpose of this work was to evaluate the activity of a triazaspirane as a migration and invasion inhibitor in PC3 prostatic tumor cells through a possible negative regulation of the FAK/Src signal transduction pathway and decreased secretion of metalloproteinases 2 and 9. Molecular docking analysis was performed using Moe 2008.10 software. Migration (wound-healing assay) and invasion (Boyden chamber assay) assays were performed. In addition, the Western blot technique was used to quantify protein expression, and the zymography technique was used to observe the secretion of metalloproteinases. Molecular docking showed interactions in regions of interest of the FAK and Src proteins. Moreover, the biological activity assays demonstrated an inhibitory effect on cell migration and invasion, an important suppression of metalloproteinase secretion, and a decrease in the expression of p-FAK and p-Src proteins in treated PC3 cells. Triazaspirane-type molecules have important inhibitory effects on the mechanisms associated with metastasis in PC3 tumor cells.

Atiprimod triggered apoptotic cell death via acting on PERK/eIF2α/ATF4/CHOP and STAT3/NF-ΚB axis in MDA-MB-231 and MDA-MB-468 breast cancer cells

PURPOSE

The constitutive activation of STAT3 through receptor tyrosine kinases triggered breast cancer cell growth and invasion-metastasis. Atiprimod impacts anti-proliferative, anti-carcinogenic effects in hepatocellular carcinoma, lymphoma, multiple myeloma via hindering the biological activity of STAT3. Dose-dependent atiprimod evokes first autophagy as a survival mechanism and then apoptosis due to prolonged ER stress in pituitary adenoma cells. The therapeutic efficiency and mechanistic action of atiprimod in breast cancer cells have not been investigated yet. Thus, we aimed to modulate the pivotal role of ER stress in atiprimod-triggered apoptosis in MDA-MB-231 and MDA-MB-468 breast cancer cells.

RESULTS

Dose- and time-dependent atiprimod treatment inhibits cell viability and colony formation in MDA-MB-468 and MDA-MB-231 breast cancer cells. A moderate dose of atiprimod (2 μM) inhibited STAT3 phosphorylation at Tyr705 residue and also suppressed the total expression level of p65. In addition, nuclear localization of STAT1, 3, and NF-κB was prevented by atiprimod exposure in MDA-MB-231 and MDA-MB-468 cells. Atiprimod evokes PERK, BiP, ATF-4, CHOP upregulation, and PERK (Thr980), eIF2α (Ser51) phosphorylation's. However, atiprimod suppressed IRE1α-mediated Atg-3, 5, 7, 12 protein expressions and no alteration was observed on Beclin-1, p62 expression levels. PERK/eIF2α/ATF4/CHOP axis pivotal role in atiprimod-mediated G1/S arrest and apoptosis via Bak, Bax, Bim, and PUMA upregulation in MDA-MB-468 cells. Moreover, atiprimod renders MDA-MB-231 more vulnerable to type I programmed cell death by plasmid-mediated increased STAT3 expression.

CONCLUSION

Atiprimod induced prolonged ER stress-mediated apoptosis via both activating PERK/eIF2α/ATF4/CHOP axis and suppressing STAT3/NF-κB transcription factors nuclear migration in TBNC cells.

Proinflammatory cytokine profile is critical in autocrine GH-triggered curcumin resistance engulf by atiprimod cotreatment in MCF-7 and MDA-MB-231 breast cancer cells

Active growth hormone (GH) signaling triggers cellular growth and invasion-metastasis in colon, breast, and prostate cancer. Curcumin, an inhibitor of NF-ҡB pathway, is assumed to be a promising anti-carcinogenic agent. Atiprimod is also an anti-inflammatory, anti-carcinogenic agent that induces apoptotic cell death in hepatocellular carcinoma, multiple myeloma, and pituitary adenoma. We aimed to demonstrate the potential additional effect of atiprimod on curcumin-induced apoptotic cell death via cytokine expression profiles in MCF-7 and MDA-MB-231 cells with active GH signaling. The effect of curcumin and/or atiprimod on IL-2, IL-4, and IL-17A levels were measured by ELISA assay. MTT cell viability, trypan blue exclusion, and colony formation assays were performed to determine the effect of combined drug exposure on cell viability, growth, and colony formation, respectively. Alteration of the NF-ҡB signaling pathway protein expression profile was determined following curcumin and/or atiprimod exposure by RT-PCR and immunoblotting. Finally, the effect of curcumin with/without atiprimod treatment on Reactive Oxygen Species (ROS) generation and apoptotic cell death was examined by DCFH-DA and Annexin V/PI FACS flow analysis, respectively. Autocrine GH-mediated IL-6, IL-8, IL-10 expressions were downregulated by curcumin treatment. Atiprimod co-treatment increased the inhibitory effect of curcumin on cell viability, proliferation and also increased the curcumin-triggered ROS generation in each GH⁺ breast cancer cells. Combined drug exposure increased apoptotic cell death through acting on IL-2, IL-4, and IL-17A secretion. Forced GH-triggered curcumin resistance might be overwhelmed by atiprimod and curcumin co-treatment via modulating NF-ҡB-mediated inflammatory cytokine expression in MCF-7 and MDA-MB-231 cells.

Transcriptomics-Based Characterization of the Toxicity of ZnO Nanoparticles Against Chronic Myeloid Leukemia Cells

INTRODUCTION

Zinc oxide nanoparticles (ZnO NPs) have recently attracted attention as potential anti-cancer agents. To the best of our knowledge, the toxicity of ZnO NPs against human chronic myeloid leukemia cells (K562 cell line) has not been studied using transcriptomics approach.

OBJECTIVE

The goals of this study were to evaluate the capability of ZnO NPs to induce apoptosis in human chronic myeloid leukemia cells (K562 cells) and to investigate the putative mechanisms of action.

METHODS

We used viability assay and flowcytometry coupled with Annexin V-FITC and propidium iodide to investigate the toxicity of ZnO NPs on K562 cells and normal peripheral blood mononuclear cells. Next we utilized a DNA microarray-based transcriptomics approach to characterize the ZnO NPs-induced changes in the transcriptome of K562 cells.

RESULTS

ZnO NPs exerted a selective toxicity (mainly by apoptosis) on the leukemic cells (p≤0.005) and altered their transcriptome; 429 differentially expressed genes (DEGs) with fold change (FC)≥4 and p≤0.008 with corrected p≤0.05 were identified in K562 cells post treatment with ZnO NPs. The over-expressed genes were implicated in "response to zinc", "response to toxic substance" and "negative regulation of growth" (corrected p≤0.05). In contrast, the repressed genes positively regulated "cell proliferation", "cell migration", "cell adhesion", "receptor signaling pathway via JAK-STAT" and "phosphatidylinositol 3-kinase signaling" (corrected p≤0.05). Lowering the FC to ≥1.5 with p≤0.05 and corrected p≤0.1 showed that ZnO NPs over-expressed the anti-oxidant defense system, drove K562 cells to undergo mitochondrial-dependent apoptosis, and targeted NF-κB pathway.

CONCLUSION

Taken together, our findings support the earlier studies that reported anti-cancer activity of ZnO NPs and revealed possible molecular mechanisms employed by ZnO NPs to induce apoptosis in K562 cells.

Pharmacological Inhibition of Oncogenic STAT3 and STAT5 Signaling in Hematopoietic Cancers

Signal Transducer and Activator of Transcription (STAT) 3 and 5 are important effectors of cellular transformation, and aberrant STAT3 and STAT5 signaling have been demonstrated in hematopoietic cancers. STAT3 and STAT5 are common targets for different tyrosine kinase oncogenes (TKOs). In addition, STAT3 and STAT5 proteins were shown to contain activating mutations in some rare but aggressive leukemias/lymphomas. Both proteins also contribute to drug resistance in hematopoietic malignancies and are now well recognized as major targets in cancer treatment. The development of inhibitors targeting STAT3 and STAT5 has been the subject of intense investigations during the last decade. This review summarizes the current knowledge of oncogenic STAT3 and STAT5 functions in hematopoietic cancers as well as advances in preclinical and clinical development of pharmacological inhibitors.

Nanoparticles Targeting STATs in Cancer Therapy

Over the past decades, an increase in the incidence rate of cancer has been witnessed. Although many efforts have been made to manage and treat this life threatening condition, it is still one of the leading causes of death worldwide. Therefore, scientists have attempted to target molecular signaling pathways involved in cancer initiation and metastasis. It has been shown that signal transducers and activator of transcription (STAT) contributes to the progression of cancer cells. This important signaling pathway is associated with a number of biological processes including cell cycle, differentiation, proliferation and apoptosis. It appears that dysregulation of the STAT signaling pathway promotes the migration, viability and malignancy of various tumor cells. Hence, there have been many attempts to target the STAT signaling pathway. However, it seems that currently applied therapeutics may not be able to effectively modulate the STAT signaling pathway and suffer from a variety of drawbacks such as low bioavailability and lack of specific tumor targeting. In the present review, we demonstrate how nanocarriers can be successfully applied for encapsulation of STAT modulators in cancer therapy.

Mantle cell lymphoma in the era of precision medicine-diagnosis, biomarkers and therapeutic agents

Despite advances in the development of clinical agents for treating Mantle Cell Lymphoma (MCL), treatment of MCL remains a challenge due to complexity and frequent relapse associated with MCL. The incorporation of conventional and novel diagnostic approaches such as genomic sequencing have helped improve understanding of the pathogenesis of MCL, and have led to development of specific agents targeting signaling pathways that have recently been shown to be involved in MCL. In this review, we first provide a general overview of MCL and then discuss about the role of biomarkers in the pathogenesis, diagnosis, prognosis, and treatment for MCL. We attempt to discuss major biomarkers for MCL and highlight published and ongoing clinical trials in an effort to evaluate the dominant signaling pathways as drugable targets for treating MCL so as to determine the potential combination of drugs for both untreated and relapse/refractory cases. Our analysis indicates that incorporation of biomarkers is crucial for patient stratification and improve diagnosis and predictability of disease outcome thus help us in designing future precision therapies. The evidence indicates that a combination of conventional chemotherapeutic agents and novel drugs designed to target specific dysregulated signaling pathways can provide the effective therapeutic options for both untreated and relapse/refractory MCL.

The Multi-kinase Inhibitor Debio 0617B Reduces Maintenance and Self-renewal of Primary Human AML CD34+ Stem/Progenitor Cells

Acute myelogenous leukemia (AML) is initiated and maintained by leukemia stem cells (LSC). LSCs are therapy-resistant, cause relapse, and represent a major obstacle for the cure of AML. Resistance to therapy is often mediated by aberrant tyrosine kinase (TK) activation. These TKs primarily activate downstream signaling via STAT3/STAT5. In this study, we analyzed the potential to therapeutically target aberrant TK signaling and to eliminate LSCs via the multi-TK inhibitor Debio 0617B. Debio 0617B has a unique profile targeting key kinases upstream of STAT3/STAT5 signaling such as JAK, SRC, ABL, and class III/V receptor TKs. We demonstrate that expression of phospho-STAT3 (pSTAT3) in AML blasts is an independent prognostic factor for overall survival. Furthermore, phospho-STAT5 (pSTAT5) signaling is increased in primary CD34⁺ AML stem/progenitors. STAT3/STAT5 activation depends on tyrosine phosphorylation, mediated by several upstream TKs. Inhibition of single upstream TKs did not eliminate LSCs. In contrast, the multi-TK inhibitor Debio 0617B reduced maintenance and self-renewal of primary human AML CD34⁺ stem/progenitor cells in vitro and in xenotransplantation experiments resulting in long-term elimination of human LSCs and leukemia. Therefore, inhibition of multiple TKs upstream of STAT3/5 may result in sustained therapeutic efficacy of targeted therapy in AML and prevent relapses. Mol Cancer Ther; 16(8); 1497-510. ©2017 AACR.

JAK/STAT pathway regulation of GABAA receptor expression after differing severities of experimental TBI

Synaptic inhibition in the adult brain is primarily mediated by the γ-aminobutyric acid (GABA) type A receptor (GABA(A)R). The distribution, properties, and dynamics of these receptors are largely determined by their subunit composition. Alteration of subunit composition after a traumatic brain injury (TBI) may result in abnormal increased synaptic firing and possibly contribute to injury-related pathology. Several studies have shown that the Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling pathway can alter GABA(A)R subunit expression. The present study investigated changes in JAK/STAT pathway activation after two different severities of experimental TBI in the mouse using the controlled cortical impact (CCI) model. It also investigated whether modulating the activation of the JAK/STAT pathway after severe controlled cortical impact (CCI-S) with a JAK/STAT inhibitor (WP1066) alters post-traumatic epilepsy development and/or neurological recovery after injury. Our results demonstrated differential changes in both the activation of STAT3 and the expression of the GABA(A)R α1 and γ2 subunit levels that were dependent on the severity of the injury. The change in the GABA(A)R α1 subunit levels appeared to be at least partly transcriptionally mediated. We were able to selectively reverse the decrease in GABA(A)R α1 protein levels with WP1066 treatment after CCI injury. WP1066 treatment also improved the degree of recovery of vestibular motor function after injury. These findings suggest that the magnitude of JAK/STAT pathway activation and GABA(A)R α1 subunit level decrease is dependent on injury severity in this mouse model of TBI. In addition, reducing JAK/STAT pathway activation after severe experimental TBI reverses the decrease in the GABA(A)R α1 protein levels and improves vestibular motor recovery.

The Multifaceted Roles of STAT3 Signaling in the Progression of Prostate Cancer

The signal transducer and activator of transcription (STAT)3 governs essential functions of epithelial and hematopoietic cells that are often dysregulated in cancer. While the role for STAT3 in promoting the progression of many solid and hematopoietic malignancies is well established, this review will focus on the importance of STAT3 in prostate cancer progression to the incurable metastatic castration-resistant prostate cancer (mCRPC). Indeed, STAT3 integrates different signaling pathways involved in the reactivation of androgen receptor pathway, stem like cells and the epithelial to mesenchymal transition that drive progression to mCRPC. As equally important, STAT3 regulates interactions between tumor cells and the microenvironment as well as immune cell activation. This makes it a major factor in facilitating prostate cancer escape from detection of the immune response, promoting an immunosuppressive environment that allows growth and metastasis. Based on the multifaceted nature of STAT3 signaling in the progression to mCRPC, the promise of STAT3 as a therapeutic target to prevent prostate cancer progression and the variety of STAT3 inhibitors used in cancer therapies is discussed.

Role of altered growth factor receptor-mediated JAK2 signaling in growth and maintenance of human acute myeloid leukemia stem cells

Acute myeloid leukemia (AML) is sustained by small populations of leukemia stem cells (LSCs) that can resist available treatments and represent important barriers to cure. Although previous studies have shown increased signal transducer and activator of transcription (STAT)3 and STAT5 phosphorylation in AML leukemic blasts, the role of Janus kinase (JAK) signaling in primary AML compared with normal stem cells has not been directly evaluated. We show here that JAK/STAT signaling is increased in LSCs, particularly from high-risk AML. JAK2 inhibition using small molecule inhibitors or interference RNA reduced growth of AML LSCs while sparing normal stem cells both in vitro and in vivo. Increased JAK/STAT activity was associated with increased expression and altered signaling through growth factor receptors in AML LSCs, including receptor tyrosine kinase c-KIT and FMS-related tyrosine kinase 3 (FLT3). Inhibition of c-KIT and FLT3 expression significantly inhibited JAK/STAT signaling in AML LSCs, and JAK inhibitors effectively inhibited FLT3-mutated AML LSCs. Our results indicate that JAK/STAT signaling represents an important signaling mechanism supporting AML LSC growth and survival. These studies support continued evaluation of strategies for JAK/STAT inhibition for therapeutic targeting of AML LSCs.

Therapeutic modulators of STAT signalling for human diseases

The signal transducer and activator of transcription (STAT) proteins have important roles in biological processes. The abnormal activation of STAT signalling pathways is also implicated in many human diseases, including cancer, autoimmune diseases, rheumatoid arthritis, asthma and diabetes. Over a decade has passed since the first inhibitor of a STAT protein was reported and efforts to discover modulators of STAT signalling as therapeutics continue. This Review discusses the outcomes of the ongoing drug discovery research endeavours against STAT proteins, provides perspectives on new directions for accelerating the discovery of drug candidates, and highlights the noteworthy candidate therapeutics that have progressed to clinical trials.

Role of STAT3 in cancer metastasis and translational advances

Signal transducer and activator of transcription 3 (STAT3) is a latent cytoplasmic transcription factor, originally discovered as a transducer of signal from cell surface receptors to the nucleus. It is activated by tyrosine phosphorylation at position 705 leading to its dimerization, nuclear translocation, DNA binding, and activation of gene transcription. Under normal physiological conditions, STAT3 activation is tightly regulated. However, compelling evidence suggests that STAT3 is constitutively activated in many cancers and plays a pivotal role in tumor growth and metastasis. It regulates cellular proliferation, invasion, migration, and angiogenesis that are critical for cancer metastasis. In this paper, we first describe the mechanism of STAT3 regulation followed by how STAT3 is involved in cancer metastasis, then we summarize the various small molecule inhibitors that inhibit STAT3 signaling.

STAT transcription factors in hematopoiesis and leukemogenesis: opportunities for therapeutic intervention

Signal transducer and activator of transcription (STAT) proteins comprise a family of transcription factors that are activated by cytokines, hormones and growth factors. The activation of STAT proteins plays a key role in the production of mature hematopoietic cells via effects on cellular proliferation, survival and lineage-specific differentiation. Emerging evidence also demonstrates frequent, constitutive activation of STATs in primary leukemia specimens. Moreover, roles for STATs in promoting leukemia development have been delineated in numerous preclinical studies. This review summarizes our current understanding of STAT protein involvement in normal hematopoiesis and leukemogenesis, as well as recent advances in the development and testing of novel STAT inhibitors.

The role of JAK pathway dysregulation in the pathogenesis and treatment of acute myeloid leukemia

The discovery of the Janus kinase 2 (JAK2) V617F mutation has improved our understanding of the pathophysiology of myeloproliferative neoplasms such as polycythemia vera, essential thrombocythemia, and primary myelofibrosis. Before discovery of the JAK2 V617F mutation, there were no specific targeted therapies for patients with myeloproliferative neoplasms. More recently, several small-molecule inhibitors have been developed that have shown therapeutic potential in the clinical setting. There is evidence that the JAK2 pathway is dysregulated in some acute myeloid leukemias and may also represent a novel therapeutic target in this disease. In this review, we describe the preclinical, clinical, and pathophysiologic evidence for using JAK inhibitors in the treatment of acute myeloid leukemias.

Prolactin regulation of the prostate gland: a female player in a male game

Prolactin is best known for its actions on the mammary gland. However, circulating prolactin is also detected in males and its receptor (PRLR) is expressed in the prostate, suggesting that the prostate is a target of prolactin. Germline knockout of prolactin or its receptor has failed to reveal a key role for prolactin signaling in mouse prostate physiology. However, several studies involving rodent models and human prostate cell lines and specimens have supported the contribution of the canonical PRLR-Jak2-Stat5a/b pathway to prostate cancer tumorigenesis and progression. Increased expression of prolactin in the prostate itself (rather than changes in circulating prolactin levels) and crosstalk with androgen receptor (AR) signaling are potential mechanisms for increased Stat5a/b signaling in prostate cancer. In the mouse prostate, prolactin overexpression results in disorganized expansion of the basal/stem cell compartment, which has been proposed to house putative prostate tumor-initiating cells. These findings provide new insight into the molecular and cellular targets by which locally produced prolactin could contribute to prostate cancer initiation and progression. A number of pharmacological inhibitors targeting various levels of the PRLR-Jak2-Stat5a/b pathway have been developed and are entering clinical trials for advanced prostate cancer.

Prospect of JAK2 inhibitor therapy in myeloproliferative neoplasms

The discovery of the Janus kinase (JAK)2 V617F mutation in patients with myeloproliferative neoplasms was a major milestone in understanding the biology of those disorders. Several groups simultaneously reported on the high incidence of this mutation in patients with myeloproliferative neoplasms: almost all patients with polycythemia vera harbor the mutation and about 50% of patients with essential thrombocythemia and primary myelofibrosis have the mutation, making the development of JAK2 tyrosine kinase inhibitors an attractive therapeutic goal. In addition, inhibition of JAK2 kinase may have a therapeutic role in other hematologic malignancies, such as chronic myeloid leukemia or lymphoma. A number of molecules that inhibit JAK2 kinase have been described in the literature, and several are being evaluated in a clinical setting. Here, we summarize current clinical experience with JAK2 inhibitors.

A non-apoptotic function of caspase-3 in pharmacologically-induced differentiation of K562 cells

BACKGROUND AND PURPOSE

Several anticancer drugs with diverse chemical structures can induce differentiation of cancer cells. This study was undertaken to explore the potential contribution of caspase-3 to pharmacologically-induced differentiation of K562 cells.

EXPERIMENTAL APPROACH

We assessed differentiation by measuring the expression of glycophorin A and haemoglobin synthesis in K562 cells treated with low concentrations of doxorubicin, hydroxyurea, cytosine arabinoside, cisplatin and haemin. Caspase-3 activation, mitochondrial membrane potential dissipation and viability were assessed by FACS. GATA-1-binding activity was evaluated by EMSA.

KEY RESULTS

Treatment of K562 cells with low concentrations of the tested drugs activated caspase-3 but did not trigger detectable apoptosis. Instead, elevated levels of haemoglobin-positive and glycophorin A/caspase-3-double-positive cells were observed, suggesting involvement of caspase-3 in drug-induced differentiation. Inhibition of caspase-3 activity significantly reduced the ability of K562 cells to execute the differentiation programme. Mitochondrial membrane potential dissipation was observed, indicating involvement of the mitochondrial pathway. Binding activity of GATA-1, transcription factor responsible for differentiation and cell survival, was not diminished by increased caspase-3 activity during drug-stimulated differentiation.

CONCLUSIONS AND IMPLICATIONS

Our results could explain how anticancer drugs, with diverse structures and modes of action, can stimulate erythroid differentiation in leukaemic cells with appropriate genetic backgrounds. Our findings imply that some similarities exist between pharmacologically-induced differentiation of erythroleukaemic cells and normal erythropoiesis, both involving caspase-3 activation at high levels of anti-apoptotic protein Bcl-X(L) and chaperone protein Hsp70 (heat shock protein 70). Therefore, the functions of caspase-3, unrelated to cell death, can be extended to pharmacologically-induced differentiation of some cancer cells.

Jak2 inhibitors: rationale and role as therapeutic agents in hematologic malignancies

Although the Jak2-V617F mutation has generated strong awareness because of its causative role in myeloproliferative disorders, reports of Jak2 gene aberrations linked to hematologic malignancies have preceded those of V617F by nearly a decade. These malignant mutations include Jak2 amino acid substitutions, deletions, insertions, and chromosomal translocations. As a consequence, researchers are increasingly focused on identifying Jak2 inhibitors that suppress aberrant Jak2 kinase activity. Some of these inhibitors may one day become therapeutically beneficial for individuals with Jak2-related hematologic malignancies. This review summarizes various Jak2 mutations associated with hematologic malignancies and assesses some of the Jak2 inhibitors in the preclinical phase or in clinical trials. By reviewing these specific areas, we hope to have a better understanding of Jak2's role in hematologic malignancies and to shed light on the utility of Jak2 inhibitors.

Alteration of epileptogenesis genes

Retrospective studies suggest that precipitating events such as prolonged seizures, stroke, or head trauma increase the risk of developing epilepsy later in life. The process of epilepsy development, known as epileptogenesis, is associated with changes in the expression of a myriad of genes. One of the major challenges for the epilepsy research community has been to determine which of these changes contributes to epileptogenesis, which may be compensatory, and which may be noncontributory. Establishing this for any given gene is essential if it is to be considered a therapeutic target for the prevention or treatment of epilepsy. Our laboratories have examined alterations in gene expression related to inhibitory neurotransmission that have been proposed as contributing factors in epileptogenesis. The GABA(A) receptor mediates most fast synaptic inhibition, and changes in GABA(A) receptor subunit expression and function have been reported in adult animals beginning immediately after prolonged seizures (status epilepticus [SE]) and continue as animals become chronically epileptic. Prevention of GABA(A) receptor subunit changes after SE using viral gene transfer inhibits development of epilepsy in an animal model, suggesting that these changes directly contribute to epileptogenesis. The mechanisms that regulate differential expression of GABA(A) receptor subunits in hippocampus after SE have recently been identified, and include the CREB-ICER, JAK-STAT, BDNF, and Egr3 signaling pathways. Targeting signaling pathways that alter the expression of genes involved in epileptogenesis may provide novel therapeutic approaches for preventing or inhibiting the development of epilepsy after a precipitating insult.

Z3, a novel Jak2 tyrosine kinase small-molecule inhibitor that suppresses Jak2-mediated pathologic cell growth

Jak2 tyrosine kinase is essential for animal development and hyperkinetic Jak2 function has been linked to a host of human diseases. Control of this pathway using Jak2-specific inhibitors would therefore potentially serve as a useful research tool and/or therapeutic agent. Here, we used a high-throughput program called DOCK to predict the ability of 20,000 small molecules to interact with a structural pocket adjacent to the ATP-binding site of murine Jak2. One small molecule, 2-methyl-1-phenyl-4-pyridin-2-yl-2-(2-pyridin-2-ylethyl)butan-1-one (herein designated as Z3), bound to Jak2 with a favorable energy score. Z3 inhibited Jak2-V617F and Jak2-WT autophosphorylation in a dose-dependent manner but was not cytotoxic to cells at concentrations that inhibited kinase activity. Z3 selectively inhibited Jak2 kinase function with no effect on Tyk2 or c-Src kinase function. Z3 significantly inhibited proliferation of the Jak2-V617F-expressing, human erythroleukemia cell line, HEL 92.1.7. The Z3-mediated reduction in cell proliferation correlated with reduced Jak2 and STAT3 tyrosine phosphorylation levels as well as marked cell cycle arrest. Finally, Z3 inhibited the growth of hematopoietic progenitor cells isolated from the bone marrow of an essential thrombocythemia patient harboring the Jak2-V617F mutation and a polycythemia vera patient carrying a Jak2-F537I mutation. Collectively, the data suggest that Z3 is a novel specific inhibitor of Jak2 tyrosine kinase.

A severe combined immunodeficient-hu in vivo mouse model of human primary mantle cell lymphoma

PURPOSE

To establish a severe combined immunodeficient (SCID)-hu in vivo mouse model of human primary mantle cell lymphoma (MCL) for the study of the biology and novel therapy of human MCL.

EXPERIMENTAL DESIGN

Primary MCL cells were isolated from spleen, lymph node, bone marrow aspirates, or peripheral blood of six different patients and injected respectively into human bone chips, which had been s.c. implanted in SCID-hu. Circulating human beta(2)-microglobulin in mouse serum was used to monitor the engraftment and growth of patient's MCL cells. H&E staining and immunohistochemical staining with anti-human CD20 and cyclin D1 antibodies were used to confirm the tumor growth and migration.

RESULTS

Increasing levels of circulating human beta(2)-microglobulin in mouse serum indicated that the patient's MCL cells were engrafted successfully into human bone chip of SCID-hu mice. The engraftment and growth of patient's MCL cells were dependent on human bone marrow microenvironment. Immunohistochemical staining with anti-human CD20 and cyclin D1 antibodies confirmed that patient's MCL cells were able to not only survive and propagate in the bone marrow microenvironment of the human fetal bone chips, but also similar to the human disease, migrate to lymph nodes, spleen, bone marrow, and gastrointestinal tract of host mice. Treatment of MCL-bearing SCID-hu mice with atiprimod, a novel antitumor compound against the protection of bone marrow stromal cells, induced tumor regression.

CONCLUSION

This is the first human primary MCL animal model that should be useful for the biological and therapeutic research on MCL.

Deactivation of Akt and STAT3 signaling promotes apoptosis, inhibits proliferation, and enhances the sensitivity of hepatocellular carcinoma cells to an anticancer agent, Atiprimod

Atiprimod is a novel anticancer and antiangiogenic drug candidate which is currently being evaluated in patients with liver carcinoid and multiple myeloma. In this study, we report that atiprimod selectively inhibited proliferation and induced apoptosis in HCC cells that expressed either hepatitis B virus (HBV) or hepatitis C virus, through deactivation of protein kinase B (Akt) and signal transducers and activators of transcription 3 (STAT3) signaling. In HepG2 AD38 cells, which express HBV genome under the control of a tetracycline-off promoter, both Akt and STAT3 were constitutively activated in response to HBV expression. However, this constitutive activation was not sensitive to lamivudine, a drug that inhibits HBV replication without affecting its gene expression, suggesting that HBV replication per se might not be responsible for the activation. Interestingly, the electrophoretic mobility of p-STAT3 protein bands on immunoblot was slower when AD38 cells were cultured in the absence of tetracycline, suggesting a differential phosphorylation in response to HBV expression. In HCC cells, interleukin 6 stimulates the phosphorylation of STAT3 both at serine 727 and at tyrosine 705 positions. The interleukin 6-stimulated activation of STAT3 and Akt was inhibited not only by atiprimod but also by LY294002, a phosphoinositide-3-kinase-specific inhibitor, and by NS398, a cyclooxygenase-2-selective inhibitor. The combination of these compounds did not produce any additive effect, implying that the mechanisms by which HBV activates Akt and STAT3 might also involve phosphoinositide-3-kinase and cyclooxygenase-2. Collectively, these results suggest that atiprimod could be useful as a multifunctional drug candidate for the treatment of HCC in humans.

Atiprimod inhibits the growth of mantle cell lymphoma in vitro and in vivo and induces apoptosis via activating the mitochondrial pathways

Atiprimod is a novel cationic amphiphilic compound and has been shown to exert antimyeloma effects both in vitro and in mouse experiments. This study was undertaken to evaluate the therapeutic efficacy of atiprimod on mantle cell lymphoma (MCL) and elucidate the mechanism by which it induces cell apoptosis. Atiprimod inhibited the growth and induced apoptosis of MCL cell lines and freshly isolated primary tumor cells in vitro. More importantly, atiprimod significantly inhibited tumor growth in vivo and prolonged the survival of tumor-bearing mice. However, atiprimod also exhibited lower cytotoxicity toward normal lymphocytes. Atiprimod activated c-Jun N-terminal protein kinases (JNK) and up-regulated the level of Bax, Bad, and phosphorylated Bcl-2, resulting in release of apoptosis-inducing factor (AIF) and cytochrome c from mitochondria and activation and cleavage of caspase-9, caspase-3, and PARP. However, AIF, but not activation of caspases or PARP, was responsible for apoptosis in MCL cells because an AIF inhibitor, but not pan-caspase or paspase-9 inhibitors, completely abrogated atiprimod-induced apoptosis. Taken together, our results demonstrate that atiprimod displays a strong anti-MCL activity. Cell apoptosis was induced mainly via activation of the AIF pathway. These results support the use of atiprimod as a potential agent in MCL chemotherapy.