Transformation of hematopoietic cells and activation of JAK2-V617F by IL-27R, a component of a heterodimeric type I cytokine receptor

Tannic acid and quaternized chitosan mediated puerarin-loaded octacalcium phosphate /sodium alginate scaffold for bone tissue engineering

Current limitations in mechanical performance and foreign body reactions (FBR) often lead to implant failure, restricting the application of bioceramic scaffolds. This study presents a novel 3D-printed scaffold that combines the release of anti-inflammatory drugs with osteogenic stimulation. Initially, the inorganic and organic phases were integrated to ensure the scaffold's mechanical integrity through catechol chemistry and the electrostatic interactions between tannic acid and quaternary ammonium chitosan. Subsequently, layers of polydopamine-encapsulated puerarin-loaded zeolitic imidazolate framework-8 (ZIF-8) were self-assembled onto the stent's surface, creating the drug-loaded scaffold that improved drug release without altering the scaffold's structure. Compared with unloaded scaffolds, the puerarin-loaded scaffold demonstrated excellent osteogenic differentiation properties along with superior anti-inflammatory and osteogenic effects in a range of in vitro and in vivo studies. RNA sequencing clarified the role of the TNF and NF/κB signaling pathways in these effects, further supporting the scaffold's osteogenic potential. This study introduces a novel approach for creating drug-loaded scaffolds, providing a unique method for treating cancellous bone defects.

Exploring the role of interleukin-27 as a regulator of neuronal survival in central nervous system diseases

Interleukin-27 is a pleiotropic cytokine that is involved in tissue responses to infection, cell stress, neuronal disease, and tumors. Recent studies in various tissues indicate that interleukin-27 has complex activating and inhibitory properties in innate and acquired immunity. The availability of recombinant interleukin-27 protein and mice with genetic deletions of interleukin-27, its receptors and signaling mediators have helped define the role of interleukin-27 in neurodegenerative diseases. Interleukin-27 has been well-characterized as an important regulator of T cell activation and differentiation that enhances or suppresses T cell responses in autoimmune conditions in the central nervous system. Evidence is also accumulating that interleukin-27 has neuroprotective activities in the retina and brain. Interleukin-27 is secreted from and binds to infiltrating microglia, macrophage, astrocytes, and even neurons and it promotes neuronal survival by regulating pro- and anti-inflammatory cytokines, neuroinflammatory pathways, oxidative stress, apoptosis, autophagy, and epigenetic modifications. However, interleukin-27 can have the opposite effect and induce inflammation and cell death in certain situations. In this review, we describe the current understanding of regulatory activities of interleukin-27 on cell survival and inflammation and discuss its mechanisms of action in the brain, spinal cord, and retina. We also review evidence for and against the therapeutic potential of interleukin-27 for dampening harmful neuroinflammatory responses in central nervous system diseases.

Enhancing Prednisone-Based Arthritis Therapy with Targeted IL-27 Gene Delivery

Rheumatoid arthritis (RA) is a chronic autoimmune disease which is characterized primarily by synovial hyperplasia and accumulation of several types of immune infiltrates that promote progressive destruction of the articular structure. Glucocorticoids are often prescribed to treat RA because of their strong anti-inflammatory and immunosuppressive effects. However, their application must be limited to the short-term due to a risk of adverse events. In the present study, we examined the potential combination of low-dose prednisone with gene delivery of an agent of promising and complementary effectiveness in RA, interleukin (IL)-27. IL-27 has been shown to have anti-inflammatory potential, while also acting as an effective bone-normalization agent in prior reports. The present report examined a version of IL-27 targeted at the C-terminus with a short ‘peptide L’ (pepL, LSLITRL) that binds the interleukin 6 receptor α (IL-6Rα) upregulated during inflammation. By focusing on this targeted form, IL-27pepL or 27pL, we examined whether the anti-inflammatory potential of prednisone (at a relatively low dose and short duration) could be further enhanced in the presence of 27pL as a therapy adjuvant. Our results indicate that 27pL represents a novel tool for use as an adjuvant with current therapeutics, such as prednisone, against inflammatory conditions.

Interleukin 27 Signaling in Rheumatoid Arthritis Patients: Good or Evil?

The occurrence and development of rheumatoid arthritis (RA) is regulated by numerous cytokines. Interleukin 27 (IL-27) is a soluble cytokine that exerts biological effects by regulating the Janus tyrosine kinase (JAK)/signal transducer and activator of the transcription (STAT) signaling pathway via the IL-27 receptor. IL-27 is known for its pleiotropic roles in modulating inflammatory responses. Previous studies found that IL-27 levels are elevated in RA blood, synovial fluid, and rheumatoid nodules. Cellular and animal experiments indicated that IL-27 exerts multiple regulatory functions in RA patients via different mechanisms. IL-27 inhibits ectopic-like structure (ELS) formation and CD4⁺ T helper type 2 (Th2) cell, CD4⁺ T helper type 17 (Th17) cell, and osteoclast differentiation in RA, contributing to alleviating RA. However, IL-27 promotes Th1 cell differentiation, which may exacerbate RA synovitis. Moreover, IL-27 also acts on RA synovial fibroblasts (RA-FLSs) and regulatory T cells (Tregs), but some of its functions are unclear. There is currently insufficient evidence to determine whether IL-27 promotes or relieves RA. Targeting IL-27 signaling in RA treatment should be deliberate based on current knowledge.

Synergistic Effects of Toll-Like Receptor 1/2 and Toll-Like Receptor 3 Signaling Triggering Interleukin 27 Gene Expression in Chikungunya Virus-Infected Macrophages

Chikungunya virus (CHIKV) is the etiological agent of chikungunya fever (CHIKF), a self-limiting disease characterized by myalgia and severe acute or chronic arthralgia. CHIKF is associated with immunopathology and high levels of pro-inflammatory factors. CHIKV is known to have a wide range of tropism in human cell types, including keratinocytes, fibroblasts, endothelial cells, monocytes, and macrophages. Previously, we reported that CHIKV-infected monocytes-derived macrophages (MDMs) express high levels of interleukin 27 (IL27), a heterodimeric cytokine consisting of IL27p28 and EBI3 subunits, that triggers JAK-STAT signaling and promotes pro-inflammatory and antiviral response, in interferon (IFN)-independent manner. Based on the transcriptomic analysis, we now report that induction of IL27-dependent pro-inflammatory and antiviral response in CHIKV-infected MDMs relies on two signaling pathways: an early signal dependent on recognition of CHIKV-PAMPs by TLR1/2-MyD88 to activate NF-κB-complex that induces the expression of EBI3 mRNA; and second signaling dependent on the recognition of intermediates of CHIKV replication (such as dsRNA) by TLR3-TRIF, to activate IRF1 and the induction of IL27p28 mRNA expression. Both signaling pathways were required to produce a functional IL27 protein involved in the induction of ISGs, including antiviral proteins, cytokines, CC- and CXC- chemokines in an IFN-independent manner in MDMs. Furthermore, we reported that activation of TLR4 by LPS, both in human MDMs and murine BMDM, results in the induction of both subunits of IL27 that trigger strong IL27-dependent pro-inflammatory and antiviral response independent of IFNs signaling. Our findings are a significant contribution to the understanding of molecular and cellular mechanisms of CHIKV infection.

Modeling pediatric AML FLT3 mutations using CRISPR/Cas12a- mediated gene editing

Clustered regularly interspaced palindromic repeats (CRISPR) with the associated (Cas) nuclease complexes have democratized genetic engineering through their precision and ease-of-use. We have applied a variation of this technology, known as CRISPR-directed mutagenesis (CDM), to reconstruct genetic profiles within the FLT3 gene of AML patients. We took advantage of the versatility of CDM and built expression vectors that, in combination with a specifically designed donor DNA fragment, recapitulate simple and complex mutations within the FLT3 gene. We generate insertions and point mutations including combinations of these mutations originating from individual patient samples. We then analyze how these complex genetic profiles modulate transformation of Ba/F3 cells. Our results show that FLT3 expression plasmids bearing patient-specific single or multiple mutations recapitulate cellular transformation properties induced by FLT3 ITDs and modify their sensitivity or resistance in response to established AML drugs as a function of these complex mutations.

IL-27, a pleiotropic cytokine for fine-tuning the immune response in cancer

Interleukin (IL)-27, a member of the IL-6/IL-12 family, has an important role in modulating inflammation in partnership with innate and adaptive immune cells. IL-27 binding to IL-27R starts downstream signaling based on the target cells. It can instigate inflammation by inducing CD4⁺ T cell proliferation, Th1 polarization, cytotoxic T cell activation, generation of the natural killer cell, and macrophage and dendritic cell activation. However, by inducing programmed cell death and suppression of effector cells, IL-27 can suppress inflammation and return the immune response to hemostasis. Altogether, IL-27 displays multifaceted dual functions, which may result in either pro- or anti-inflammatory effects. Recent investigations indicated the antitumor activity of IL-27 via inducing Th1, and CTL responses and generating NK cells. On the other hand, IL-27 also can promote tumor cells' proliferation, survival, and angiogenesis. In the present review, we'll discuss recent advances concerning the role of IL-27 in inflammatory diseases such as infections, autoimmune diseases with a focus on cancer.

IL-12 and IL-23-Close Relatives with Structural Homologies but Distinct Immunological Functions

Cytokines of the IL-12 family show structural similarities but have distinct functions in the immune system. Prominent members of this cytokine family are the pro-inflammatory cytokines IL-12 and IL-23. These two cytokines share cytokine subunits and receptor chains but have different functions in autoimmune diseases, cancer and infections. Accordingly, structural knowledge about receptor complex formation is essential for the development of new therapeutic strategies preventing and/or inhibiting cytokine:receptor interaction. In addition, intracellular signaling cascades can be targeted to inhibit cytokine-mediated effects. Single nucleotide polymorphisms can lead to alteration in the amino acid sequence and thereby influencing protein functions or protein–protein interactions. To understand the biology of IL-12 and IL-23 and to establish efficient targeting strategies structural knowledge about cytokines and respective receptors is crucial. A highly efficient therapy might be a combination of different drugs targeting extracellular cytokine:receptor assembly and intracellular signaling pathways.

Ligand-Mediated Targeting of Cytokine Interleukin-27 Enhances Its Bioactivity In Vivo

We have examined the role of a novel targeted cytokine, interleukin-27 (IL-27), modified at the C terminus with a dual targeting and therapeutic heptapeptide, in treating prostate cancer. IL-27 has shown promise in halting tumor growth and mediating tumor regression in several cancer models, including prostate cancer. We describe our findings on the effects of targeted IL-27 gene delivery on prostate cancer cells in vitro and in vivo and how the targeting enhances bioactivity of the IL-27 cytokine. We applied the IL-27 gene delivery protocol utilizing sonoporation (sonodelivery) with the goal of reducing prostate tumor growth in an immunocompetent TC2R C57/BL6 model. The reduction in tumor growth and effector cellular profiles implicate targeted IL-27 as more effective than an untargeted version of IL-27 in promoting bioactivity, as assessed by STAT1 and IFN-γ reporter genes. Moreover, enhanced antitumor effects and significantly higher accumulation of natural killer T (NKT) and CD8 effector cells in the tumors were observed. These results support a novel IL-27-based targeting strategy that is promising since it shows improved therapeutic efficacy while utilizing simple and effective sonodelivery methods.

Interleukin-27 Gene Delivery Targeting IL-6Rα-Expressing Cells as a Stress Response Therapy

Interleukin-27 (IL-27) has shown promise in halting tumor growth and mediating tumor regression in several models, including prostate cancer. We describe our findings on the effects of IL-27 on the gene expression changes of TC2R prostate adenocarcinoma cells. We utilized RNAseq to assess profile differences between empty vector control, vector delivering IL-27 modified at its C-terminus with a non-specific peptide, and IL-27 modified at the C-terminus with a peptide targeting the IL-6-Rα. The targeted IL-27 had higher bioactivity and activity in vivo in a recent study by our group, but the mechanisms underlying this effect had not been characterized in detail at the gene expression level on tumor cells. In the present work, we sought to examine potential mechanisms for targeted IL-27 enhanced activity directly on tumor cells. The targeted IL-27 appeared to modulate several changes that would be consistent with an anti-tumor effect, including upregulation in the Interferon (IFN) and Interferon regulatory factor (IRF), oxidative phosphorylation, Janus kinase/Signal transducers and activators of transcription (JAK/STAT), and eukaryotic initiation factor 2 (EIF2) signaling. Of these signaling changes predicted by ingenuity pathway analyses (IPA), the novel form also with the highest significance (-log(Benjamini-Hochberg (B-H)) p-value) was the EIF2 signaling upregulation. We validated this predicted change by assaying for eukaryotic initiation factor 2 alpha (eIF2α), or phosphorylated eIF2α (p-eIF2α), and caspase-3 levels. We detected an increase in the phosphorylated form of eIF2α and in the cleaved caspase-3 fraction, indicating that the EIF2 signaling pathway was upregulated in these prostate tumor cells following targeted IL-27 gene delivery. This approach of targeting cytokines to enhance their activity against cancer cells is a novel approach to help augment IL-27's bioactivity and efficacy against prostate tumors and could be extended to other conditions where it could help interfere with the EIF2α pathway and promote caspase-3 activation.

The Immunobiology of the Interleukin-12 Family: Room for Discovery

The discovery of interleukin (IL)-6 and its receptor subunits provided a foundation to understand the biology of a group of related cytokines: IL-12, IL-23, and IL-27. These family members utilize shared receptors and cytokine subunits and influence the outcome of cancer, infection, and inflammatory diseases. Consequently, many facets of their biology are being therapeutically targeted. Here, we review the landmark discoveries in this field, the combinatorial biology inherent to this family, and how patient datasets have underscored the critical role of these pathways in human disease. We present significant knowledge gaps, including how similar signals from these cytokines can mediate distinct outcomes, and discuss how a better understanding of the biology of the IL-12 family provides new therapeutic opportunities.

JAK2V617F but not CALR mutations confer increased molecular responses to interferon-α via JAK1/STAT1 activation

Pegylated interferon-α (peg-IFNa) treatment induces molecular responses (MR) in patients with myeloproliferative neoplasms (MPNs), including partial MR (PMR) in 30-40% of patients. Here, we compared the efficacy of IFNa treatment in JAK2V617F- vs. calreticulin (CALR)-mutated cells and investigated the mechanisms of differential response. Retrospective analysis of MPN patients treated with peg-IFNa demonstrated that patients harboring the JAK2V617F mutation were more likely to achieve PMR than those with mutated CALR (p = 0.004), while there was no significant difference in hematological response. In vitro experiments confirmed an upregulation of IFN-stimulated genes in JAK2V617F-positive 32D cells as well as patient samples (peripheral blood mononuclear cells and CD34+ hematopoietic stem cells) compared to their CALR-mutated counterparts, and higher IFNa doses were needed to achieve the same IFNa response in CALR- as in JAK2V617F-mutant 32D cells. Additionally, Janus-activated kinase-1 (JAK1) and signal transducers and activators of transcription 1 (STAT1) showed constitutive phosphorylation in JAK2V617F-mutated but not CALR-mutated cells, indicating priming towards an IFNa response. Moreover, IFN-induced growth arrest was counteracted by selective JAK1 inhibition but enhanced by JAK2 inhibition. In conclusion, our data suggest that, clinically, higher doses of IFNa are needed in CALR-mutated vs. JAK2V617F-positive patients and we suggest a model of JAK2V617F-JAK1/STAT1 crosstalk leading to a priming of JAK2V617F-positive cells to IFNa resulting in differential sensitivity.

Cancer stem cells and differentiation therapy

Cancer stem cells can generate tumors from only a small number of cells, whereas differentiated cancer cells cannot. The prominent feature of cancer stem cells is its ability to self-renew and differentiate into multiple types of cancer cells. Cancer stem cells have several distinct tumorigenic abilities, including stem cell signal transduction, tumorigenicity, metastasis, and resistance to anticancer drugs, which are regulated by genetic or epigenetic changes. Like normal adult stem cells involved in various developmental processes and tissue homeostasis, cancer stem cells maintain their self-renewal capacity by activating multiple stem cell signaling pathways and inhibiting differentiation signaling pathways during cancer initiation and progression. Recently, many studies have focused on targeting cancer stem cells to eradicate malignancies by regulating stem cell signaling pathways, and products of some of these strategies are in preclinical and clinical trials. In this review, we describe the crucial features of cancer stem cells related to tumor relapse and drug resistance, as well as the new therapeutic strategy to target cancer stem cells named "differentiation therapy."

The cross talk between cervical carcinoma cells and vascular endothelial cells mediated by IL-27 restrains angiogenesis

PROBLEM

To explore whether cervical carcinoma cell-derived interleukin-27 (IL-27) modulates the angiogenesis of vascular endothelial cells.

METHOD OF STUDY

The expression of IL-27 in cervical cancer tissues and cervical cell lines was analyzed by immunohistochemistry, ELISA and flow cytometry. Then, the effects of IL-27 on the proliferation and apoptosis-related molecules and angiogenesis in vitro of human umbilical vein endothelial cells (HUVECs) were investigated. Finally, in vivo experiment was performed to further confirm the effects of IL-27.

RESULTS

Compared with cervicitis, the cervical cancer tissues highly expressed IL-27. Both HeLa and CaSki cells secreted IL-27, and HUVECs expressed low levels of IL-27 receptors (IL-27R). However, the co-culture of cervical cell lines and HUVECs led to a significant elevation of IL-27R on HUVECs. Co-culturing with IL-27-overexpressed HeLa cells downregulated Ki-67 and Bcl-2 and upregulated Fas expression in HUVECs. In addition, overexpression of IL-27 in HeLa cells and CasKi cells secreted less IL-8 and could further restrict angiogenesis compared with control cells in vitro. In the subcutaneous tumorous model of C57/BL6 mouse, there were decreased vessel density and tumor volume when inoculation with IL-27-overexpressed TC-1 cells.

CONCLUSION

This study indicates that IL-27 secreted by cervical carcinoma cells restricts the angiogenesis in a paracrine manner in the pathogenesis of cervical cancer.

Drug-Loaded Polymeric Nanoparticles for Cancer Stem Cell Targeting

Cancer stem cells (CSCs) have been reported to play critical roles in tumor initiation, propagation, and regeneration of cancer. Nano-size vehicles are employed to deliver drugs to target the CSCs for cancer therapy. Polymeric nanoparticles have been considered as the most efficient vehicles for drug delivery due to their excellent pharmacokinetic properties. The CSCs specific antibodies or ligands can be conjugated onto the surface or interior of nanoparticles to successfully target and finally eliminate CSCs. In this review, we focus on the approaches of polymeric nanoparticles design for loading drug, and their potential application for CSCs targeting in cancer therapy.

Myeloproliferative Neoplasms: Molecular Drivers and Therapeutics

Activating mutations in genes that drive neoplastic cell growth are numerous and widespread in cancer, and specific genetic alterations are associated with certain types of cancer. For example, classic myeloproliferative neoplasms (MPNs) are hematopoietic stem cell disorders that affect cells of the myeloid lineage, including erythrocytes, platelets, and granulocytes. An activating mutation in the JAK2 tyrosine kinase is prevalent in these diseases. In MPN patients that lack such a mutation, other genetic changes that lead to activation of the JAK2 signaling pathway are present, indicating deregulation of JAK2 signaling plays an etiological driving role in MPNs, a concept supported by significant evidence from in vivo experimental MPN systems. Thus, small molecules that inhibit JAK2 activity are ideal drugs to impede the progression of disease in MPN patients. However, even though JAK inhibitors provide significant symptomatic relief, they have failed as a remission-inducing therapy. Nonetheless, the progress made understanding the molecular etiology of MPNs since 2005 is significant and has provided insight for the development and testing of novel molecular targeted therapeutic approaches. The current understanding of driver mutations in MPNs and an overview of current and potential therapeutic strategies for MPN patients will be discussed.

Interleukin-27 as a Novel Therapy for Inflammatory Bowel Disease: A Critical Review of the Literature

Inflammatory bowel disease (IBD) is an inflammatory disorder of the intestine that affects an estimated 329 per 100,000 people in the United States and is increasing in incidence within a number of cultures worldwide. Likely due to its incompletely understood pathophysiology and etiology, the standard treatments for IBD are only efficacious in subsets of patients and often do not induce lasting remission. As a result, novel therapies are needed. The success of anti-tumor necrosis factor-α treatment in a subset of patients with IBD demonstrated that therapy targeting a single cytokine could be efficacious in IBD, and clinical trials investigating the blockade of a variety of cytokines have commenced. Interleukin (IL) 27 is a relatively recently discovered type I cytokine with established roles in infectious disease, autoimmunity, and cancer in a variety of organs. IL-27 was identified as a candidate gene for IBD, and a number of studies in mouse models of IBD have demonstrated that IL-27 therapy is protective. However, in contrast to these investigations, genetic deletion of the IL-27 receptor has been shown to be protective in some mouse models of IBD. The purpose of this review is to highlight the recent literature investigating the role of IL-27 in IBD and to discuss the possible explanations for the sometimes conflicting results of these studies. Evidence supporting IL-27 therapy as a treatment for IBD will also be discussed.

Cancer Stem Cells: Formidable Allies of Cancer

Cancer stem cells (CSC) represent the subpopulation of cells within a tumour showing two fundamental properties of stem cells - self-renewal (the ability to make more of their own kind) and differentiation (the ability to generate diverse cell types present within a tissue). The CSC hypothesis posits that CSCs play an important role in tumour initiation, maintenance and progression. Furthermore, owing to their intrinsic drug resistance, they remain refractory to currently used therapy, thereby contributing to tumour relapse. Thus, targeting or taming CSCs can lead to more effective cancer treatment in the coming decades. In this review, we will discuss about the origin of CSC hypothesis, evidence showing their existence, clinical relevance and translational significance.

IL-27 Promotes Proliferation of Human Leukemic Cell Lines Through the MAPK/ERK Signaling Pathway and Suppresses Sensitivity to Chemotherapeutic Drugs

IL-27 is a pleiotropic cytokine of the IL-6/IL-12 family with diverse biological functions. Previous in vivo studies have suggested the antitumor activities of IL-27 in animal models, whereas clinical observations indicate the link of IL-27 in tumor progression. IL-27 has recently been shown to cause inhibition of proliferation on primary leukemic cells from pediatric patients, but information on its role in human leukemic cell lines is limited. In the present study, we investigated the ability of IL-27 to regulate cell growth and survival of various human leukemic cell lines. Our results showed that in human leukemic cell lines coexpressing both IL-27R chains, IL-27Rα and gp130, IL-27 did not inhibit cell growth, but caused dose-dependent proliferation of the acute myeloid leukemic cell line, OCI-AML5, and the erythroleukemic cell lines, TF-1, UT-7, and UT-7/EPO. Consistent with this, IL-27 promoted cell survival and reduced TNF-α-induced apoptosis of the leukemic cell lines. IL-27 also decreased the responsiveness of the leukemic cells to chemotherapeutic drugs, cytarabine and daunorubicin. We observed that IL-27 induced the activation of STAT1/3 and ERK1/2 in the leukemic cells. Growth stimulation by IL-27 was suppressed by the specific MEK inhibitor, U0126, indicating that IL-27-induced cell proliferation is mainly mediated through the activation of the MAPK/ERK signaling pathway. The present study is the first demonstration of the proliferative and antichemotherapeutic properties of IL-27 in human leukemic cell lines, suggesting that IL-27 can play an unfavorable role in tumor growth and can be an important determinant in the chemoresponsiveness of certain subtypes of human leukemia.

Potential clinical application of interleukin-27 as an antitumor agent

Cancer immunotherapies such as sipuleucel-T and ipilimumab are promising new treatments that harness the power of the immune system to fight cancer and achieve long-lasting remission. Interleukin (IL)-27, a member of the IL-12 heterodimeric cytokine family, has pleiotropic functions in the regulation of immune responses with both pro-inflammatory and anti-inflammatory properties. Evidence obtained using a variety of preclinical mouse models indicates that IL-27 possesses potent antitumor activity against various types of tumors through multiple mechanisms without apparent adverse effects. These mechanisms include those mediated not only by CD8⁺ T cells, natural killer cells and macrophages, but also by antibody-dependent cell-mediated cytotoxicity, antiangiogenesis, direct antiproliferative effects, inhibition of expression of cyclooxygenase-2 and prostaglandin E₂, and suppression of epithelial–mesenchymal transition, depending on the characteristics of individual tumors. However, the endogenous role of IL-27 subunits and one of its receptor subunits, WSX-1, in the susceptibility to tumor development after transplantation of tumor cell lines or endogenously arising tumors seems to be more complicated. IL-27 functions as a double-edged sword: IL-27 increases IL-10 production and the expression of programmed death ligand 1 and T-cell immunoglobulin and mucin domain-3, and promotes the generation of regulatory T cells, and IL-27 receptor α singling enhances transformation; IL-27 may augment protumor effects as well. Here, we review both facets of IL-27, antitumor effects and protumor effects, and discuss the potential clinical application of IL-27 as an antitumor agent.

Interleukin-27 and IFNγ regulate the expression of CXCL9, CXCL10, and CXCL11 in hepatitis

Interleukin-27 (IL-27) belongs to the IL-6/IL-12 family of cytokines, associated with different inflammatory diseases and orchestrates its biological activity via common heterodimeric receptor composed of WSX-1 (IL-27Rα) and gp130. The present study was aimed to investigate the regulation of CXCL9, CXCL10, and CXCL11 chemokines in hepatic cells (human LX-2 cell line derived from normal human stellate cells (HSC), primary human hepatocytes, HSC, and HepG2 cells) and concanavalin A (ConA)-induced liver inflammation. We demonstrated that IL-27, but not IL-6, induced/up-regulated CXCR3 ligand genes (CXCL9, CXCL10, and CXCL11; out of 26 selected genes) in a STAT1-dependent manner in hepatic cells in vitro both at transcript and protein levels. In ConA-induced T cell-mediated hepatic model, we showed that soluble IL-27/IFNγ was elevated following ConA hepatitis in association with increased CXCL9, CXCL10, and CXCL11 expression in the liver. The exogenous IL-27 administration induced CXCR3 ligands in mouse liver at 4 h with any significant effect on recruitment of CXCR3(+) immune cells in the liver. The neutralization of IL-27 during ConA hepatitis differentially modulated (transcript vs protein expression) CXCR3 ligands and IFNγ during ConA-induced hepatitis with down-regulated expression of CXCL9 and CXCL10 at transcript level. The IFNγ, complementary regulated the expression of CXCR3 ligands as their up-regulation during ConA hepatitis, was abolished in IFNγ KO mice. In summary, IL-27 up-regulated the CXCL9, CXCL10, and CXCL11 chemokine expression in hepatic cells. IL-27 regulated CXCR3 ligand expression in IFNγ-dependent manner during acute hepatitis suggesting a complementary role of IL-27 and IFNγ to moderate liver inflammation via regulation of CXCR3 ligands.

KEY MESSAGE

IL-27 up-regulated CXCR3 ligand expression in human hepatic cells in vitro. IL-27 up-regulated CXCR3 ligand expression and secretion in ConA hepatitis in vivo. CXCR3 ligand expression was down-regulated by blocking IL-27 or IFNγ deficiency. IL-27 modulated liver injury by regulation of CXCR3 ligands in IFNγ-dependent manner.

How does JAK2V617F contribute to the pathogenesis of myeloproliferative neoplasms?

A decade on from the discovery of the JAK2V617F mutation in the majority of patients with myeloproliferative neoplasms (MPNs), JAK2V617F is now firmly installed in the hematology curriculum of medical students and the diagnostic-testing algorithm of clinicians. Furthermore, the oral JAK1/JAK2 inhibitor ruxolitinib, rationally designed to target activated JAK2 signaling in MPN, has been approved by the Food and Drug Administration (FDA) of the United States for the past 3 years for the treatment of intermediate- and advanced-phase myelofibrosis. Notwithstanding this, JAK2V617F continues to stimulate the MPN research community and novel insights into understanding the mechanisms by which JAK2V617F contributes to the pathogenesis of MPN are continually emerging. In this chapter, we focus on recent advances in 4 main areas: (1) the molecular processes coopted by JAK2V617F to induce MPN, (2) the role that JAK2V617F plays in phenotypic diversity in MPN, (3) the functional impact of JAK2V617F on hematopoietic stem cells, and (4) therapeutic strategies to target JAK2V617F. Although great strides have been made, significant deficits still exist in our understanding of the precise mechanisms by which JAK2V617F-mutant hematopoietic stem cells emerge and persist to engender clonal hematopoiesis in MPN and in developing strategies to preferentially target the JAK2V617F-mutant clone therapeutically. Critically, although myelofibrosis remains arguably the greatest clinical challenge in JAK2V617F-mediated MPN, the current understanding of myelofibrosis-specific disease biology remains quite rudimentary. Therefore, many important biological questions pertaining to JAK2V617F will continue to engage and challenge the MPN research community in the coming decade.

Expression of IL-27 by tumor cells in invasive cutaneous and metastatic melanomas [corrected]

Interleukin (IL)-27 is a cytokine of the IL-12 family that displays either immunostimulatory or immunosuppressive functions depending on the context. In various murine tumor models including melanoma models, ectopic expression of IL-27 has been shown to play an anti-tumoral role and to favor tumor regression. In this study, we investigated whether IL-27 might play a role in the development of melanoma in humans. We analyzed the in situ expression of IL-27 in melanocytic lesions (n = 82) representative of different stages of tumor progression. IL-27 expression was not observed in nevus (n = 8) nor in in situ melanoma (n = 9), but was detected in 28/46 (61%) cases of invasive cutaneous melanoma, notably in advanced stages (19/23 cases of stages 3 and 4). In most cases, the main source of IL-27 was tumor cells. Of note, when IL-27 was detected in primary cutaneous melanomas, its expression was maintained in metastatic lesions. These in situ data suggested that the immunosuppressive functions of IL-27 may dominate in human melanoma. Consistent with this hypothesis, we found that IL-27 could induce suppressive molecules such as PD-L1, and to a lesser extent IL-10, in melanoma cells, and that the in situ expression of IL-27 in melanoma correlated with those of PD-L1 and IL-10.

Understanding and targeting cancer stem cells: therapeutic implications and challenges

Cancer stem cells (CSCs) have been identified as rare cell populations in many cancers, including leukemia and solid tumors. Accumulating evidence has suggested that CSCs are capable of self-renewal and differentiation into various types of cancer cells. Aberrant regulation of gene expression and some signaling pathways has been observed in CSCs compared to other tumor cells. CSCs are thought to be responsible for cancer initiation, progression, metastasis, recurrence and drug resistance. The CSC hypothesis has recently attracted much attention due to the potential for discovery and development of CSC-related therapies and the identification of key molecules involved in controlling the unique properties of CSC populations. Over the past several years, a tremendous amount of effort has been invested in the development of new drugs, such as nanomedicines, that can take advantage of the "Achilles' heel" of CSCs by targeting cell-surface molecular markers or various signaling pathways. Novel compounds and therapeutic strategies that selectively target CSCs have been identified, some of which have been evaluated in preclinical and clinical studies. In this article, we review new findings related to the investigation of the CSC hypothesis, and discuss the crucial pathways involved in regulating the development of CSC populations and the advances in studies of drug resistance. In addition, we review new CSC-targeted therapeutic strategies aiming to eradicate malignancies.

Interleukin-27: balancing protective and pathological immunity

It has been more than 15 years since the identification of individual interleukin-27 (IL-27) and IL-27 receptor components. The last decade has seen the description of the signaling pathways engaged by IL-27, and an appreciation has emerged that this cytokine can modulate the intensity and duration of many classes of T cell responses. Here we provide an overview of the immunobiology of IL-27 and review advances in understanding the functions of individual IL-27 and IL-27 receptor subunits and the role of IL-27 in dictating the balance between protective and pathological immunity. Additionally, this cytokine has been proposed as a therapy to modify inflammatory conditions or to promote antitumor responses, and situations where experimental and clinical data sets implicate IL-27 in the outcome of disease are highlighted.

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.

Small-molecule inhibitors in myeloproliferative neoplasms: are we aiming for the right targets?

The ATP-binding pocket of the kinase domain of JAK2 is the major target of the present treatment of myeloproliferative neoplasms. Several inhibitors of JAK2 that are ATP competitive have been developed, but they do not discriminate between wild-type and mutant JAK2. These inhibitors have been used in myelofibrosis and, for the first time, treatment induced a reduction in spleen size and in constitutional symptoms. However, no dramatic effects on BM fibrosis, allele burden, or peripheral blast numbers were observed. These data indicate that other avenues should be explored that would either target mutant molecules (JAKs or receptors) more specifically and spare wild-type JAK2 or that would address other pathways that contribute to the malignant proliferation. Future success in treating myeloproliferative neoplasms will depend on advances of the understanding of JAK-STAT signaling and also on a better understanding of the disease pathogenesis, especially the role that mutants in spliceosome factors and epigenetic regulators play in the phenotype of the disease and the precise mechanism of fibrosis development.

The cytokines interleukin 27 and interferon-γ promote distinct Treg cell populations required to limit infection-induced pathology

Interferon-γ (IFN-γ) promotes a population of T-bet(+) CXCR3(+) regulatory T (Treg) cells that limit T helper 1 (Th1) cell-mediated pathology. Our studies demonstrate that interleukin-27 (IL-27) also promoted expression of T-bet and CXCR3 in Treg cells. During infection with Toxoplasma gondii, a similar population emerged that limited T cell responses and was dependent on IFN-γ in the periphery but on IL-27 at mucosal sites. Transfer of Treg cells ameliorated the infection-induced pathology observed in Il27(-/-) mice, and this was dependent on their ability to produce IL-10. Microarray analysis revealed that Treg cells exposed to either IFN-γ or IL-27 have distinct transcriptional profiles. Thus, IFN-γ and IL-27 have different roles in Treg cell biology and IL-27 is a key cytokine that promotes the development of Treg cells specialized to control Th1 cell-mediated immunity at local sites of inflammation.

Identification of a novel function of the clathrin-coated structure at the plasma membrane in facilitating GM-CSF receptor-mediated activation of JAK2

It is well known that ligand binding to the high-affinity GM-CSF receptor (GMR) activates JAK2. However, how and where this event occurs in a cellular environment remains unclear. Here, we demonstrate that clathrin- but not lipid raft-mediated endocytosis is crucial for GMR signaling. Knockdown expression of clathrin heavy chain or intersectin 2 (ITSN2) attenuated GMR-mediated activation of JAK2, whereas inhibiting clathrin-coated pits or plagues to bud off the membrane by the dominant-negative mutant of dynamin enhanced such event. Moreover, unlike the wild-type receptor, an ITSN2-non-binding mutant of GMR defective in targeting to clathrin-coated pits or plagues [collectively referred to as clathrin-coated structures (CCSs) here] failed to activate JAK2 at such locations. Additional experiments demonstrate that ligand treatment not only enhanced JAK2/GMR association at CCSs, but also induced a conformational change of JAK2 which is required for JAK2 to be activated by CCS-localized CK2. Interestingly, ligand-independent activation of the oncogenic mutant of JAK2 (JAK2V617F) also requires the targeting of this mutant to CCSs. But JAK2V617F seems to be constitutively in an open conformation for CK2 activation. Together, this study reveals a novel functional role of CCSs in GMR signaling and the oncogenesis of JAK2V617F.

Interleukin-27 inhibits the growth of pediatric acute myeloid leukemia in NOD/SCID/Il2rg-/- mice

PURPOSE

Acute myeloid leukemia (AML) accounts for more than half of fatal cases in all pediatric leukemia patients; this observation highlights the need of more effective therapies. Thus, we investigated whether interleukin (IL)-27, an immunomodulatory cytokine, functions as an antitumor agent against pediatric AML cells.

EXPERIMENTAL DESIGN

Expression of WSX-1 and gp130 on AML cells from 16 pediatric patients was studied by flow cytometry. Modulation of leukemia cell proliferation or apoptosis upon IL-27 treatment in vitro was tested by bromodeoxyuridine/propidium iodide (PI) and Ki67, or Annexin V/PI staining and flow cytometric analysis. The angiogenic potential of AML cells treated or not with IL-27 was studied by chorioallantoic membrane assay and PCR array. In vivo studies were carried out using nonobese diabetic/severe combined immunodeficient (NOD/SCID)/Il2rg(-/-) mice injected intravenously with five pediatric AML cell samples. Leukemic cells engrafted in PBS and IL-27-treated animals were studied by immunohistochemical/morphologic analysis and by PCR array for expression angiogenic/dissemination-related genes.

RESULTS

We provided the first demonstration that (i) AML cells injected into NOD/SCID/Il2rg(-/-) mice gave rise to leukemia dissemination that was severely hampered by IL-27, (ii) compared with controls, leukemia cells harvested from IL-27-treated mice showed significant reduction of their angiogenic and spreading related genes, and (iii) similarly to what was observed in vivo, IL-27 reduced in vitro AML cell proliferation and modulated the expression of different genes involved in the angiogenic/spreading process.

CONCLUSION

These results provide an experimental rationale for the development of future clinical trials aimed at evaluating the toxicity and efficacy of IL-27.

ALK-activating homologous mutations in LTK induce cellular transformation

Leukocyte tyrosine kinase (LTK) is a receptor tyrosine kinase reported to be overexpressed in human leukemia. Though much regarding the function of LTK remains unknown, it shares a high degree of similarity with anaplastic lymphoma kinase (ALK), which is found mutated in human cancer. In order to determine if LTK has transforming potential, we created two LTK mutants, F568L and R669Q, that correspond to two well-characterized activating mutations of ALK (F1174L and R1275Q). LTK-F568L, but not wildtype LTK or LTK-R669Q, transformed hematopoietic cells to cytokine independence. LTK-F568L exhibited a stronger ability to induce loss of contact inhibition and anchorage-independent growth of epithelial cells compared to LTK-R669Q, while wildtype LTK was non-transforming in the same cells. Likewise, LTK-F568L induced greater neurite outgrowth of PC12 cells than R669Q, while wildtype LTK could not. Correlating with transforming activity, LTK-F568L displayed significantly enhanced tyrosine phosphorylation compared to wildtype LTK and LTK-R668Q and induced activation of various signaling proteins including Shc, ERK and the JAK/STAT pathway. Expression of wildtype LTK or LTK-R669Q generally led to weaker activation of signaling proteins than expression of LTK-F568L, or no activation at all. Thus, mutating LTK at residue F568, and to a lesser extent at R669, activates the receptor tyrosine kinase, inducing cell signaling that results in transforming properties. These studies suggest that aberrant activation of LTK may contribute to neoplastic cell growth.

The immunobiology of IL-27

Like many cytokines, IL-27 has pleiotropic properties that can limit or enhance ongoing immune responses depending on context. Thus, under certain circumstances, IL-27 can promote TH1 differentiation and has been linked to the activation of CD8(+) T cells and enhanced humoral responses. However, IL-27 also has potent inhibitory properties and mice that lack IL-27 mediated signaling develop exaggerated inflammatory responses in the context of infection or autoimmunity. This chapter reviews in depth the biology of IL-27, including the initial discovery, characterization, and signaling mediated by IL-27 as well as more recent insights into the molecular and cellular basis for its pleiotropic effects. Many of these advances are relevant to human diseases and highlight the potential of therapies that harness the regulatory properties of IL-27.

IL-27 enhances LPS-induced proinflammatory cytokine production via upregulation of TLR4 expression and signaling in human monocytes

IL-27, which is produced by activated APCs, bridges innate and adaptive immunity by regulating the development of Th cells. Recent evidence supports a role for IL-27 in the activation of monocytic cells in terms of inflammatory responses. Indeed, proinflammatory and anti-inflammatory activities are attributed to IL-27, and IL-27 production itself is modulated by inflammatory agents such as LPS. IL-27 primes LPS responses in monocytes; however, the molecular mechanism behind this phenomenon is not understood. In this study, we demonstrate that IL-27 priming results in enhanced LPS-induced IL-6, TNF-α, MIP-1α, and MIP-1β expression in human primary monocytes. To elucidate the molecular mechanisms responsible for IL-27 priming, we measured levels of CD14 and TLR4 required for LPS binding. We determined that IL-27 upregulates TLR4 in a STAT3- and NF-κB-dependent manner. Immunofluorescence microscopy revealed enhanced membrane expression of TLR4 and more distinct colocalization of CD14 and TLR4 upon IL-27 priming. Furthermore, IL-27 priming enhanced LPS-induced activation of NF-κB family members. To our knowledge, this study is the first to show a role for IL-27 in regulating TLR4 expression and function. This work is significant as it reveals new mechanisms by which IL-27 can enhance proinflammatory responses that can occur during bacterial infections.

Mutations in the transmembrane and juxtamembrane domains enhance IL27R transforming activity

Cytokines and their receptors regulate haemopoiesis by controlling cellular growth, survival and differentiation. Thus it is not surprising that mutations of cytokine receptors contribute to the formation of haemopoietic disorders, including cancer. We recently identified transforming properties of IL27R, the ligand-binding component of the receptor for interleukin-27. Although wild-type IL27R exhibits transforming properties in haemopoietic cells, in the present study we set out to determine if the transforming activity of IL27R could be enhanced by mutation. We identified three mutations of IL27R that enhance its transforming activity. One of these mutations is a phenylalanine to cysteine mutation at residue 523 (F523C) in the transmembrane domain of the receptor. The two other mutations identified involve deletions of amino acids in the cytoplasmic juxtamembrane region of the receptor. Expression of each of these mutant IL27R proteins led to rapid cytokine-independent transformation in haemopoietic cells. Moreover, the rate of transformation induced by these mutants was significantly greater than that induced by wild-type IL27R. Expression of these IL27R mutants also induced enhanced activation of JAK (Janus kinase)/STAT (signal transducer and activator of transcription) signalling compared with wild-type. An activating deletion mutation of IL27R enhanced homodimerization of the receptor by a mechanism that may involve disulfide bonding. These transforming IL27R mutants displayed equal or greater transforming activity than bona fide haemopoietic oncogenes such as BCR-ABL (breakpoint cluster region-Abelson murine leukaemia viral oncogene homologue) and JAK2-V617F. Since IL27R is expressed on haemopoietic stem cells, lymphoid cells and myeloid cells, including acute myeloid leukaemia blast cells, mutation of this receptor has the potential to contribute to a variety of haemopoietic neoplasms.

A potential role of ruxolitinib in leukemia

INTRODUCTION

An increased understanding of cellular signaling pathways, like the JAK?STAT pathway, and the identification of the JAK2 V617F mutation in the classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), has generated great interest in the development of targeted JAK2 inhibitors. In a recently completed Phase I?II study, ruxolitinib, a selective orally available JAK1 and JAK2 inhibitor, has shown efficacy in patients with advanced myelofibrosis. Constitutive activation of the JAK?STAT pathway has also been implicated in other hematological malignancies suggesting a potential role of JAK kinase inhibitors in these malignancies.

AREAS COVERED

This article reviews the chemistry, pharmacodynamics, pharmacokinetics, clinical efficacy, safety and tolerability of ruxolitinib. The literature for this article was retrieved from PubMed database searches using the keywords ?ruxolitinib?, ?INCB 018424?, ?JAK2 inhibitors? and ?leukemia?.

EXPERT OPINION

The JAK?STAT signaling pathway plays a vital role in leukemogenesis. Ruxolitinib, a potent JAK1 and JAK2 inhibitor, known to decrease spleen size and alleviate constitutional symptoms in myelofibrosis, represents a potentially promising agent for the treatment of leukemias by inhibiting the JAK?STAT signaling. Further studies of ruxolitinib, in patients with acute and chronic leukemias, are now needed to establish the clinical usefulness of this promising drug.

WSX1 expression in tumors induces immune tolerance via suppression of effector immune cells

Crosstalk between tumor cells and the cognate microenvironment plays a crucial role in tumor initiation and progression. However, only a few genes are known to affect such a crosstalk. This study reveals that WSX1 plays such a role when highly expressed in tumor cells. The expression of WSX1 in Lewis Lung Carcinoma (LLC) and the melanoma cell line AGS induces the death of T cells and inhibits the production of the effector cytokine IFNγ from NK and T cells, resulting in the promotion of tumor growth. These pro-tumorigenic properties of WSX1 are independent of IL27. This key observation reveals a new pathway of tumor-host interaction, which will ultimately lead to better strategies in immune therapy to reverse tumor tolerance.

Functional characterization of FLT3 receptor signaling deregulation in acute myeloid leukemia by single cell network profiling (SCNP)

Background

Molecular characterization of the FMS-like tyrosine kinase 3 receptor (FLT3) in cytogenetically normal acute myeloid leukemia (AML) has recently been incorporated into clinical guidelines based on correlations between FLT3 internal tandem duplications (FLT3-ITD) and decreased disease-free and overall survival. These mutations result in constitutive activation of FLT3, and FLT3 inhibitors are currently undergoing trials in AML patients selected on FLT3 molecular status. However, the transient and partial responses observed suggest that FLT3 mutational status alone does not provide complete information on FLT3 biological activity at the individual patient level. Examination of variation in cellular responsiveness to signaling modulation may be more informative.

Methodology/Principal Findings

Using single cell network profiling (SCNP), cells were treated with extracellular modulators and their functional responses were quantified by multiparametric flow cytometry. Intracellular signaling responses were compared between healthy bone marrow myeloblasts (BMMb) and AML leukemic blasts characterized as FLT3 wild type (FLT3-WT) or FLT3-ITD. Compared to healthy BMMb, FLT3-WT leukemic blasts demonstrated a wide range of signaling responses to FLT3 ligand (FLT3L), including elevated and sustained PI3K and Ras/Raf/Erk signaling. Distinct signaling and apoptosis profiles were observed in FLT3-WT and FLT3-ITD AML samples, with more uniform signaling observed in FLT3-ITD AML samples. Specifically, increased basal p-Stat5 levels, decreased FLT3L induced activation of the PI3K and Ras/Raf/Erk pathways, decreased IL-27 induced activation of the Jak/Stat pathway, and heightened apoptotic responses to agents inducing DNA damage were observed in FLT3-ITD AML samples. Preliminary analysis correlating these findings with clinical outcomes suggests that classification of patient samples based on signaling profiles may more accurately reflect FLT3 signaling deregulation and provide additional information for disease characterization and management.

Conclusions/Significance

These studies show the feasibility of SCNP to assess modulated intracellular signaling pathways and characterize the biology of individual AML samples in the context of genetic alterations.

CRLF2 and JAK2 in B-progenitor acute lymphoblastic leukemia: a novel association in oncogenesis

Expression of cytokine receptor-like factor 2 (CRLF2) has recently been shown to be upregulated as well as mutated in populations of B-progenitor acute lymphoblastic leukemia (B-ALL), including Down syndrome (DS-ALL) patients, lacking recurring chromosomal translocations. Increased CRLF2 expression associates with JAK2 mutation, a combination that transforms hematopoietic cells, suggesting that mutant JAK2 and CRLF2 may cooperate to contribute to B-ALL formation. Importantly, elevated CRLF2 expression correlates with poor outcome in high-risk B-ALL patients. Therefore, CRLF2 may provide a new prognostic marker for high-risk B-ALL, and inhibition of CRLF2/JAK2 signaling may represent a therapeutic approach for this population of ALL patients.

Preclinical characterization of the selective JAK1/2 inhibitor INCB018424: therapeutic implications for the treatment of myeloproliferative neoplasms

Constitutive JAK2 activation in hematopoietic cells by the JAK2V617F mutation recapitulates myeloproliferative neoplasm (MPN) phenotypes in mice, establishing JAK2 inhibition as a potential therapeutic strategy. Although most polycythemia vera patients carry the JAK2V617F mutation, half of those with essential thrombocythemia or primary myelofibrosis do not, suggesting alternative mechanisms for constitutive JAK-STAT signaling in MPNs. Most patients with primary myelofibrosis have elevated levels of JAK-dependent proinflammatory cytokines (eg, interleukin-6) consistent with our observation of JAK1 hyperactivation. Accordingly, we evaluated the effectiveness of selective JAK1/2 inhibition in experimental models relevant to MPNs and report on the effects of INCB018424, the first potent, selective, oral JAK1/JAK2 inhibitor to enter the clinic. INCB018424 inhibited interleukin-6 signaling (50% inhibitory concentration [IC(50)] = 281nM), and proliferation of JAK2V617F(+) Ba/F3 cells (IC(50) = 127nM). In primary cultures, INCB018424 preferentially suppressed erythroid progenitor colony formation from JAK2V617F(+) polycythemia vera patients (IC(50) = 67nM) versus healthy donors (IC(50) > 400nM). In a mouse model of JAK2V617F(+) MPN, oral INCB018424 markedly reduced splenomegaly and circulating levels of inflammatory cytokines, and preferentially eliminated neoplastic cells, resulting in significantly prolonged survival without myelosuppressive or immunosuppressive effects. Preliminary clinical results support these preclinical data and establish INCB018424 as a promising oral agent for the treatment of MPNs.

Activation of JAK2-V617F by components of heterodimeric cytokine receptors

The JAK2-V617F mutation is an important etiologic factor for the development of myeloproliferative neoplasms. The mechanism by which this mutated tyrosine kinase initiates deregulated signals in cells is not completely understood. It is believed that JAK2-V617F requires interactions with homodimeric cytokine receptors to elicit its transforming signal. In this study, we demonstrate that components of heterodimeric cytokine receptors can also activate JAK2-V617F. Expression of IL27Ra, a heterodimeric receptor component, enhanced the activation of JAK2-V617F and subsequent downstream signaling to activation of STAT5 and ERK. In addition, expression of components of the interleukin-3 receptor, IL3Ra and the common beta chain, activated JAK2-V617F as well as STAT5 and ERK. Importantly, expression of IL27Ra functionally replaced the requirement of a homodimeric cytokine receptor to promote the activation and transforming activity of JAK2-V617F in BaF3 cells. Tyrosine phosphorylation of IL27Ra was not required to induce activation of JAK2-V617F or STAT5, or to enhance the transforming activity of JAK2-V617F. Expression of IL3Ra or the common beta chain in BaF3 cells also enhanced the ability of JAK2-V617F to transform these hematopoietic cells. However, the heterodimeric receptor component IL12RB1 did not enhance the activation or transforming signals of JAK2-V617F in BaF3 cells. IL27Ra also activated the K539L and R683G JAK2 mutants. Together our data demonstrate that in addition to homodimeric receptors, some heterodimeric receptor components can support the activation and transforming signals of JAK2-V617F and other JAK2 mutants. Therefore, heterodimeric receptors may play unappreciated roles in JAK2 activation in the development of hematopoietic diseases including myeloproliferative neoplasms.

Combined inhibition of Janus kinase 1/2 for the treatment of JAK2V617F-driven neoplasms: selective effects on mutant cells and improvements in measures of disease severity

PURPOSE

Deregulation of the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway is a hallmark for the Philadelphia chromosome-negative myeloproliferative diseases polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We tested the efficacy of a selective JAK1/2 inhibitor in cellular and in vivo models of JAK2-driven malignancy.

EXPERIMENTAL DESIGN

A novel inhibitor of JAK1/2 was characterized using kinase assays. Cellular effects of this compound were measured in cell lines bearing the JAK2V617F or JAK1V658F mutation, and its antiproliferative activity against primary polycythemiavera patient cells was determined using clonogenic assays. Antineoplastic activity in vivo was determined using a JAK2V617F-driven xenograft model, and effects of the compound on survival, organomegaly, body weight, and disease-associated inflammatory markers were measured.

RESULTS

INCB16562 potently inhibited proliferation of cell lines and primary cells from PV patients carrying the JAK2V617F or JAK1V658F mutation by blocking JAK-STAT signaling and inducing apoptosis. In vivo, INCB16562 reduced malignant cell burden, reversed splenomegaly and normalized splenic architecture, improved body weight gains, and extended survival in a model of JAK2V617F-driven hematologic malignancy. Moreover, these mice suffered from markedly elevated levels of inflammatory cytokines, similar to advanced myeloproliferative disease patients, which was reversed upon treatment.

CONCLUSIONS

These data showed that administration of the dual JAK1/2 inhibitor INCB16562 reduces malignant cell burden, normalizes spleen size and architecture, suppresses inflammatory cytokines, improves weight gain, and extends survival in a rodent model of JAK2V617F-driven hematologic malignancy. Thus, selective inhibitors of JAK1 and JAK2 represent a novel therapy for the patients with myeloproliferative diseases and other neoplasms associated with JAK dysregulation.

Expression of WSX1 in tumors sensitizes IL-27 signaling-independent natural killer cell surveillance

It is well known that the interleukin (IL)-27 receptor WSX1 is expressed in immune cells and induces an IL-27-dependent immune response. Opposing this conventional dogma, this study reveals a much higher level of WSX1 expression in multiple types of epithelial tumor cells when compared with normal epithelial cells. Expression of exogenous WSX1 in epithelial tumor cells suppresses tumorigenicity in vitro and inhibits tumor growth in vivo. Different from the role of WSX1 in immune cells, the antitumor activity of WSX1 in epithelial tumor cells is independent of IL-27 signaling but is mainly dependent on natural killer (NK) cell surveillance. Deficiency of either the IL-27 subunit EBV-induced gene 3 or the IL-27 receptor WSX1 in the host animals had no effect on tumor growth inhibition induced by WSX1 expression in tumor cells. Expression of WSX1 in epithelial tumor cells enhances NK cell cytolytic activity against tumor cells, whereas the absence of functional NK cells impairs the WSX1-mediated inhibition of epithelial tumor growth. The underlying mechanism by which WSX1 expression in tumor cells enhances NK cytolytic activity is dependent on up-regulation of NKG2D ligand expression. Our results reveal an IL-27-independent function of WSX1: sensitizing NK cell-mediated antitumor surveillance via a NKG2D-dependent mechanism.

The Stat3-activating Tyk2 V678F mutant does not up-regulate signaling through the type I interferon receptor but confers ligand hypersensitivity to a homodimeric receptor

Tyk2 is a Jak family member involved in cytokine signaling through heterodimeric-type receptors. Here, we analyzed the impact of the Val(678)-to-Phe substitution on Tyk2 functioning. This mutation is homologous to the Jak2 Val(617)-to-Phe mutation, implicated in myeloproliferative disorders. We studied ligand-independent and ligand-dependent Jak/Stat signaling in cells expressing Tyk2 V678F. Moreover, the effect of Tyk2 V678F was monitored in the context of the native heterodimeric interferon alpha receptor and in the context of a homodimeric receptor chimera, EpoR/R1, containing the ectodomain of the erythropoietin receptor. We show that Tyk2 V678F has increased catalytic potential in vivo and in vitro and more so when it is anchored to the homodimeric receptor. Tyk2 V678F leads to constitutive Stat3 phosphorylation but has no notable effect on the canonical interferon alpha-induced signaling. However, if anchored to the homodimeric EpoR/R1, the mutant confers to the cell increased sensitivity to erythropoietin. Thus, despite the catalytic gain of function of Tyk2 V678F, the effect on ligand-induced signaling is manifest only when two mutant enzymes are juxtaposed via the homodimeric receptor.