The Structural and Functional Basis of Cytokine Receptor Activation: Lessons From the Common β Subunit of the Granulocyte-Macrophage Colony-Stimulating Factor, Interleukin-3 (IL-3), and IL-5 Receptors

Matrix-Bound Hyaluronan Molecular Weight as a Regulator of Dendritic Cell Immune Potency

Hyaluronic acid (HA) is a glycosaminoglycan in the extracellular matrix with immunoregulatory properties depending on its molecular weight (MW). However, the impact of matrix-bound HA on dendritic cells (DCs) remains unclear due to varying distribution of HA MW under different physiological conditions. To investigate DCs in defined biosystems, 3D collagen matrices modified with HA of specific MW with similar microstructure and HA levels are used. It is found that HA MW influences cytokine binding to matrix, suggesting modulation of cytokine availability by the different HA MWs. These studies on DC immune potency reveal that low MW HA (8-15 kDa) enhances immature DC differentiation and antigen uptake, while medium (MMW-HA; 500-750 kDa) and high MW HA (HMW-HA; 1250-1500 kDa) increase cytokine secretion in mature DCs. The effect on DC phenotype and cytokine secretion by different MWs of HA is independent of CD44. However, blocking the CD44 receptor reveals its potential role in regulating acute inflammation through increased secretion of CCL2, CXCL8, and IL-6. Additionally, MMW- and HMW-HA matrices reduce migratory capacity of DCs, dependent on CD44. Overall, these findings provide insights into MW-dependent effects of matrix-bound HA on DCs, opening avenues for the design of DC-modulating materials to enhance DC-based therapy.

Unravelling the Influence of Host Genetic Factors on Malaria Susceptibility in Asian Populations

Malaria is a deadly blood-borne disease caused by a Plasmodium parasite. Infection results in various forms of malaria, including an asymptomatic state, uncomplicated disease, or severe disease. Severe malaria (SM) is particularly prevalent among young children and is a significant cause of mortality. SM is associated with the sequestration of parasitized erythrocytes in the microvasculature of vital host organs, disrupting the normal functioning of the immune system. Although the exact mechanisms of malaria pathogenesis are yet to be fully understood, researchers have been investigating the role of host genetics in determining the severity of the disease and the outcome of infection. The objective of this study is to identify specific host genes that have been examined for their association with malaria in Asian populations and pinpoint those most likely to influence susceptibility. Through an extensive screening process, a total of 982 articles were initially identified, and after careful review, 40 articles discussing 68 genes were included in this review. By constructing a network of protein-protein interactions (PPIs), we identified six key proteins (TNF, IL6, TLR4, IL1β, IL10, and IL8) that exhibited substantial interactions (more than 30 edges), suggesting their potential as significant targets for influencing malaria susceptibility. Notably, these six proteins have been previously identified as crucial components of the immune response, associated with malaria susceptibility, and capable of affecting different clinical forms of the disease. Identifying genes that contribute to malaria susceptibility or resistance holds the promise of enhancing the diagnosis and treatment of this debilitating illness. Such knowledge has the potential to pave the way for more targeted and effective strategies in combating malaria, particularly in Asian populations where controlling Plasmodium vivax is challenging, and India contributes the highest number of cases. By understanding the genetic factors underlying malaria vulnerability, we can develop interventions that are tailored to the specific needs of Asian populations, ultimately leading to better outcomes in the fight against this disease.

Targeting the human β c receptor inhibits inflammatory myeloid cells and lung injury caused by acute cigarette smoke exposure

Background and objective

Chronic obstructive pulmonary disease (COPD) is a devastating disease commonly caused by cigarette smoke (CS) exposure that drives tissue injury by persistently recruiting myeloid cells into the lungs. A significant portion of COPD patients also present with overlapping asthma pathology including eosinophilic inflammation. The β_c cytokine family includes granulocyte monocyte‐colony‐stimulating factor, IL‐5 and IL‐3 that signal through their common receptor subunit β_c to promote the expansion and survival of multiple myeloid cells including monocytes/macrophages, neutrophils and eosinophils.

Methods

We have used our unique human β_c receptor transgenic (hβ_cTg) mouse strain that expresses human β_c instead of mouse β_c and β_IL3 in an acute CS exposure model. Lung tissue injury was assessed by histology and measurement of albumin and lactate dehydrogenase levels in the bronchoalveolar lavage (BAL) fluid. Transgenic mice were treated with an antibody (CSL311) that inhibits human β_c signalling.

Results

hβ_cTg mice responded to acute CS exposure by expanding blood myeloid cell numbers and recruiting monocyte‐derived macrophages (cluster of differentiation 11b⁺ [CD11b⁺] interstitial and exudative macrophages [IM and ExM]), neutrophils and eosinophils into the lungs. This inflammatory response was associated with lung tissue injury and oedema. Importantly, CSL311 treatment in CS‐exposed mice markedly reduced myeloid cell numbers in the blood and BAL compartment. Furthermore, CSL311 significantly reduced lung CD11b⁺ IM and ExM, neutrophils and eosinophils, and this decline was associated with a significant reduction in matrix metalloproteinase‐12 (MMP‐12) and IL‐17A expression, tissue injury and oedema.

Conclusion

This study identifies CSL311 as a therapeutic antibody that potently inhibits immunopathology and lung injury caused by acute CS exposure.

Myeloid cells, including macrophages, neutrophils and eosinophils, are important cellular drivers of inflammation and injury. In this study, we blocked granulocyte monocyte‐colony stimulating factor, IL‐5 and IL‐3 signalling with an anti‐β_c receptor antibody (CSL311), which greatly reduced lung inflammation and injury in a pre‐clinical model of acute cigarette smoke exposure.

Blocking the human common beta subunit of the GM-CSF, IL-5 and IL-3 receptors markedly reduces hyperinflammation in ARDS models

Acute respiratory distress syndrome (ARDS) is triggered by various aetiological factors such as trauma, sepsis and respiratory viruses including SARS-CoV-2 and influenza A virus. Immune profiling of severe COVID-19 patients has identified a complex pattern of cytokines including granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin (IL)-5, which are significant mediators of viral-induced hyperinflammation. This strong response has prompted the development of therapies that block GM-CSF and other cytokines individually to limit inflammation related pathology. The common cytokine binding site of the human common beta (β_c) receptor signals for three inflammatory cytokines: GM-CSF, IL-5 and IL-3. In this study, β_c was targeted with the monoclonal antibody (mAb) CSL311 in engineered mice devoid of mouse β_c and β_IL-3 and expressing human β_c (hβ_cTg mice). Direct pulmonary administration of lipopolysaccharide (LPS) caused ARDS-like lung injury, and CSL311 markedly reduced lung inflammation and oedema, resulting in improved oxygen saturation levels in hβ_cTg mice. In a separate model, influenza (HKx31) lung infection caused viral pneumonia associated with a large influx of myeloid cells into the lungs of hβ_cTg mice. The therapeutic application of CSL311 potently decreased accumulation of monocytes/macrophages, neutrophils, and eosinophils without altering lung viral loads. Furthermore, CSL311 treatment did not limit the viral-induced expansion of NK and NKT cells, or the tissue expression of type I/II/III interferons needed for efficient viral clearance. Simultaneously blocking GM-CSF, IL-5 and IL-3 signalling with CSL311 may represent an improved and clinically applicable strategy to reducing hyperinflammation in the ARDS setting.

Molecular characterization, expression analysis and cellular location of IL-4/13 receptors in large yellow croaker (Larimichthys crocea)

Interleukin (IL)-4 and IL-13 are closely related class I cytokines that play key roles in the T helper (Th)-2 immune response via heterodimeric receptors. IL-4 signals via both the type I (IL-4Rα/γc) and type II (IL-4Rα/IL-13Rα1) receptor complexes, while IL-13 signals only via the type II receptor complex. IL-13Rα2 is traditionally considered a "decoy" receptor for IL-13. However, the IL-4/13 system and its response to pathogenic infection are still not fully understood in fish. In this study, we identified four IL-4/13 receptor subunit genes in the large yellow croaker (Larimichthys crocea): LcIL-4Rα1, LcIL-4Rα2, LcIL-13Rα1, and LcIL-13Rα2. Sequence analysis showed that these receptors possessed typical characteristic domains, including a signal peptide, two fibronectin type III (FN III)-like domains, and a transmembrane domain, but their cytoplasmic regions were not well conserved. The mRNA and protein of the four IL-4/13 receptors were constitutively expressed in all examined tissues of large yellow croaker. Their mRNAs were also detected in primary head kidney macrophages (PKMs), primary head kidney granulocytes (PKGs), and primary head kidney lymphocytes (PKLs). Immunofluorescence assay further showed that LcIL-4Rα and LcIL-13Rα1 were expressed on the membrane of IgM ⁺ B cells. After stimulation by Vibrio alginolyticus and poly (I:C) (a viral dsRNA mimic), the mRNA levels of LcIL-4/13 receptors were significantly upregulated in the head kidney and spleen. Their mRNA levels were also upregulated in head kidney leukocytes in response to poly (I:C) and lipopolysaccharide (LPS) treatment. Moreover, both recombinant LcIL-4/13A and LcIL-4/13B upregulated LcIL-4Rα1 and LcIL-4Rα2 in primary leukocytes, but only recombinant LcIL-4/13A upregulated LcIL-13Rα1 and LcIL-13Rα2. These results indicated that LcIL-4/13 receptors, containing conserved functional domains, may be involved in the IL-4/13-mediated immune response to pathogenic infections in the large yellow croaker.

Discovery of a novel potentially transforming somatic mutation in CSF2RB gene in breast cancer

The colony stimulating factor 2 receptor subunit beta (CSF2RB) is the common signaling subunit of the cytokine receptors for IL-3, IL-5, and GM-CSF. Several studies have shown that spontaneous and random mutants of CSF2RB can lead to ligand independence in vitro. To date, no report(s) have been shown for the presence of potentially transforming and oncogenic CSF2RB mutation(s) clinically in cancer patients until the first reported case of a leukemia patient in 2016 harboring a germline-activating mutation (R461C). We combined exome sequencing, pathway analyses, and functional assays to identify novel somatic mutations in KAIMRC1 cells and breast tumor specimen. The patient's peripheral blood mononuclear cell (PBMC) exome served as a germline control in the identification of somatic mutations. Here, we report the discovery of a novel potentially transforming and oncogenic somatic mutation (S230I) in the CSF2RB gene of a breast cancer patient and the cell line, KAIMRC1 established from her breast tumor tissue. KAIMRC1 cells are immortalized and shown to survive and proliferate in ligand starvation condition. Immunoblot analysis showed that mutant CSF2RB signals through JAK2/STAT and PI3K/mTOR pathways in ligand starvation conditions. Screening a small molecule kinase inhibitor library revealed potent JAK2 inhibitors against KAIMRC1 cells. We, for the first time, identified a somatic, potentially transforming, and oncogenic CSF2RB mutation (S230I) in breast cancer patients that seem to be an actionable mutation leading to the development of new therapeutics for breast cancer.

Mouse Models of CMML

Chronic myelomonocytic leukemia (CMML) is a rare and challenging type of myeloproliferative neoplasm. Poor prognosis and high mortality, associated predominantly with progression to secondary acute myeloid leukemia (sAML), is still an unsolved problem. Despite a growing body of knowledge about the molecular repertoire of this disease, at present, the prognostic significance of CMML-associated mutations is controversial. The absence of available CMML cell lines and the small number of patients with CMML make pre-clinical testing and clinical trials complicated. Currently, specific therapy for CMML has not been approved; most of the currently available therapeutic approaches are based on myelodysplastic syndrome (MDS) and other myeloproliferative neoplasm (MNP) studies. In this regard, the development of the robust CMML animal models is currently the focus of interest. This review describes important studies concerning animal models of CMML, examples of methodological approaches, and the obtained hematologic phenotypes.

ExHuMId: A curated resource and analysis of Exposome of Human Milk across India

Human milk is a vital source of nourishment for infants. However, numerous environmental contaminants also find their way into human milk, making up the major part of a newborn's external exposome. While there are chemical regulations in India and scientific literature on environmental contaminants is available, the systematic compilation, monitoring, and risk management of human milk contaminants are inadequate. We have harnessed the potential of this large body of literature to develop the Exposome of Human Milk across India (ExHuMId) version 1.0 containing detailed information on 101 environmental contaminants detected in human milk samples across 13 Indian states, compiled from 36 research articles. ExHuMId also compiles the detected concentrations of the contaminants, structural and physicochemical properties, and factors associated with the donor of the sample. We also present findings from a three-pronged analysis of ExHuMId and two other resources on human milk contaminants, with a focus on the Indian scenario. Through a comparative analysis with global chemical regulations and guidelines, we identify human milk contaminants of high concern, such as potential carcinogens, endocrine disruptors and neurotoxins. We then study the physicochemical properties of the contaminants to gain insights on their propensity to transfer into human milk. Lastly, we employ a systems biology approach to shed light on potential effects of human milk contaminants on maternal and infant health, by identifying contaminant-gene interactions associated with lactation, cytokine signalling and production, and protein-mediated transport. ExHuMId 1.0 is accessible online at: https://cb.imsc.res.in/exhumid/.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.

Orchestration of signaling by structural disorder in class 1 cytokine receptors

BACKGROUND

Class 1 cytokine receptors (C1CRs) are single-pass transmembrane proteins responsible for transmitting signals between the outside and the inside of cells. Remarkably, they orchestrate key biological processes such as proliferation, differentiation, immunity and growth through long disordered intracellular domains (ICDs), but without having intrinsic kinase activity. Despite these key roles, their characteristics remain rudimentarily understood.

METHODS

The current paper asks the question of why disorder has evolved to govern signaling of C1CRs by reviewing the literature in combination with new sequence and biophysical analyses of chain properties across the family.

RESULTS

We uncover that the C1CR-ICDs are fully disordered and brimming with SLiMs. Many of these short linear motifs (SLiMs) are overlapping, jointly signifying a complex regulation of interactions, including network rewiring by isoforms. The C1CR-ICDs have unique properties that distinguish them from most IDPs and we forward the perception that the C1CR-ICDs are far from simple strings with constitutively bound kinases. Rather, they carry both organizational and operational features left uncovered within their disorder, including mechanisms and complexities of regulatory functions.

CONCLUSIONS

Critically, the understanding of the fascinating ability of these long, completely disordered chains to orchestrate complex cellular signaling pathways is still in its infancy, and we urge a perceptional shift away from the current simplistic view towards uncovering their full functionalities and potential. Video abstract.

Targeting the alpha subunit of IL-3 receptor (CD123) in patients with acute leukemia

The IL-3 alpha chain receptor (CD123) is a cell surface protein that is widely expressed by various subtypes of acute leukemia, including acute myeloid leukemia (AML), acute lymphoblastic leukemia and blastic plasmacytoid dendritic cell neoplasm. Notably, CD123 is preferentially overexpressed in leukemia stem cells (LSC) in contrast to normal hematopoietic stem cells, and this differential expression allows for the selective eradication of LSC and leukemic blasts through therapeutic targeting of CD123, with less impact on hematopoietic cells. The level of CD123 expression in AML correlates with both treatment response and outcomes. Therefore, targeting CD123 represents a promising universal therapeutic target in advanced acute leukemias irrespective of the individual leukemia phenotype. There are currently 31 ongoing clinical trials examining the utility of CD123-based targeted therapies. Here we focus our review on current efforts to target CD123 in acute leukemia through various therapeutic constructs.

A natural bioactive feed additive alters expression of genes involved in inflammation in whole blood of healthy Angus heifers

A greater demand for food animal production without antibiotics has created the common practice of feeding food animals dietary immunomodulatory feed additives (IFA) throughout their life cycle. However, little is known about the impact of IFA on cytokine and chemokine signaling in non-stressed, non-pathogen-challenged food animals during the early feeding period. We evaluated the expression of 82 genes related to cytokine and chemokine signaling in the whole blood of growing Angus heifers to determine the effect of IFA supplementation on cytokine and chemokine signaling during the first 28 d of feeding. One gene (CCL1) was significantly up-regulated and 14 genes (17%) were significantly down-regulated by IFA feeding during the entire early feeding period including 5 of 21 (24%) evaluated chemokine and IL receptors (CCR1, CCR2, IL1R1, IL10RA, IL10RB). These data when taken together suggest providing an IFA in the diet of growing beef cattle during the early feeding period may suppress the inflammatory response through cytokine–cytokine receptor signaling.

Molecular mechanisms for stemness maintenance of acute myeloid leukemia stem cells

Human acute myeloid leukemia (AML) is a fatal hematologic malignancy characterized with accumulation of myeloid blasts and differentiation arrest. The development of AML is associated with a serial of genetic and epigenetic alterations mainly occurred in hematopoietic stem and progenitor cells (HSPCs), which change HSPC state at the molecular and cellular levels and transform them into leukemia stem cells (LSCs). LSCs play critical roles in leukemia initiation, progression, and relapse, and need to be eradicated to achieve a cure in clinic. Key to successfully targeting LSCs is to fully understand the unique cellular and molecular mechanisms for maintaining their stemness. Here, we discuss LSCs in AML with a focus on identification of unique biological features of these stem cells to decipher the molecular mechanisms of LSC maintenance.

Identification and expression analysis of IL-4/13 receptors in grass carp Ctenopharyngodon idella

Interleukin (IL)-4 and IL-13 are T helper 2 (Th2) cytokines with pleiotropic functions. IL-4 interacts with two receptors consisting of IL-4Rα/γ chain receptor (γC) and IL-4Rα/IL-13Rα1. In contrast, IL-13 binds to IL-13Rα2 but also shares the receptor complex containing IL-4Rα/IL-13Rα1. In fish, two IL-4/13 homologs have been identified but their phylogenetic relationships with IL-4 and IL-13 are ambiguous. In this study, we identified six putative IL-4/13 receptor homologs in grass carp, including γC1, γC2, IL-4Rα1, IL-13Rα1, IL-13Rα2 and a soluble form of IL-4Rα2. Comparative sequence analyses revealed that these receptors possess conserved characteristic domains and the genes encoding them share conserved gene synteny with their human counterparts. All six receptors contain a cytokine binding homology domain (CHD) and two fibronectin type Ⅲ (FNⅢ) like domains, with IL-13Rα1 and IL-13Rα2 harbouring an extra Ig-like domain preceding the CHD domain. Interestingly, grass carp IL-13Rα1 and IL-13Rα2 lack the characteristic WSXWS motif, a typical feature of mammalian type I cytokine receptors. The IL-4/13 receptor genes are differentially expressed in tissues and primary leukocytes of head kidney and can be modulated by Flavobacterium cloumnare (F. cloumnare), suggesting they are involved in immune response against F. cloumnare infection.

Monoclonal Antibody Therapies for Hematological Malignancies: Not Just Lineage-Specific Targets

Today, monoclonal antibodies (mAbs) are a widespread and necessary tool for biomedical science. In the hematological cancer field, since rituximab became the first mAb approved by the Food and Drug Administration for the treatment of B-cell malignancies, a number of effective mAbs targeting lineage-specific antigens (LSAs) have been successfully developed. Non-LSAs (NLSAs) are molecules that are not restricted to specific leukocyte subsets or tissues but play relevant pathogenic roles in blood cancers including the development, proliferation, survival, and refractoriness to therapy of tumor cells. In consequence, efforts to target NLSAs have resulted in a plethora of mAbs-marketed or in development-to achieve different goals like neutralizing oncogenic pathways, blocking tumor-related chemotactic pathways, mobilizing malignant cells from tumor microenvironment to peripheral blood, modulating immune-checkpoints, or delivering cytotoxic drugs into tumor cells. Here, we extensively review several novel mAbs directed against NLSAs undergoing clinical evaluation for treating hematological malignancies. The review focuses on the structure of these antibodies, proposed mechanisms of action, efficacy and safety profile in clinical studies, and their potential applications in the treatment of hematological malignancies.

Therapeutic antibodies against cancer stem cells: a promising approach

Monoclonal antibodies have been extensively used to treat malignancy along with routine chemotherapeutic drugs. Chemotherapy for metastatic cancer has not been successful in securing long-term remission of disease. This is in part due to the resistance of cancer cells to drugs. One aspect of the drug resistance is the inability of conventional drugs to eliminate cancer stem cells (CSCs) which often constitute less than 1-2% of the whole tumor. In some tumor types, it is possible to identify these cells using surface markers. Monoclonal antibodies targeting these CSCs are an attractive option for a new therapeutic approach. Although administering antibodies has not been effective, when combined with chemotherapy they have proved synergistic. This review highlights the potential of improving treatment efficacy using functional antibodies against CSCs, which could be combined with chemotherapy in the future.

Nitro-oleic acid regulates growth factor-induced differentiation of bone marrow-derived macrophages

Many diseases accompanied by chronic inflammation are connected with dysregulated activation of macrophage subpopulations. Recently, we reported that nitro-fatty acids (NO₂-FAs), products of metabolic and inflammatory reactions of nitric oxide and nitrite, modulate macrophage and other immune cell functions. Bone marrow cell suspensions were isolated from mice and supplemented with macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) in combination with NO₂-OA for different times. RAW 264.7 macrophages were used for short-term (1-5min) experiments. We discovered that NO₂-OA reduces cell numbers, cell colony formation, and proliferation of macrophages differentiated with colony-stimulating factors (CSFs), all in the absence of toxicity. In a case of GM-CSF-induced bone marrow-derived macrophages (BMMs), NO₂-OA acts via downregulation of signal transducer and activator of transcription 5 and extracellular signal-regulated kinase (ERK) activation. In the case of M-CSF-induced BMMs, NO₂-OA decreases activation of M-CSFR and activation of related PI3K and ERK. Additionally, NO₂-OA also attenuates activation of BMMs. In aggregate, we demonstrate that NO₂-OA regulates the process of macrophage differentiation and that NO₂-FAs represent a promising therapeutic tool in the treatment of inflammatory pathologies linked with increased accumulation of macrophages in inflamed tissues.

Harnessing the Immune System Against Leukemia: Monoclonal Antibodies and Checkpoint Strategies for AML

Acute myeloid leukemia (AML) is the most common leukemia among adults and is associated with a poor prognosis, especially in patients with adverse prognostic factors, older age, or relapsed disease. The last decade has seen a surge in successful immune-based therapies in various solid tumors; however, the role of immune therapies in AML remains poorly defined. This chapter describes the rationale, clinical data, and toxicity profiles of immune-based therapeutic modalities in AML including naked and conjugated monoclonal antibodies, bispecific T-cell engager antibodies, chimeric antigen receptor (CAR)-T cells, and checkpoint blockade via blockade of PD1/PDL1 or CTLA4. Monoclonal antibodies commonly used in AML therapy target highly expressed "leukemia" surface antigens and include (1) naked antibodies against common myeloid markers such as anti-CD33 (e.g., lintuzumab), (2) antibody-drug conjugates linked to either, (a) a highly potent toxin such as calicheamicin, pyrrolobenzodiazepine, maytansine, or others in various anti-CD33 (gemtuzumab ozogamicin, SGN 33A), anti-123 (SL-401), and anti-CD56 (lorvotuzumab mertansine) formulations, or (b) radioactive particles, such as 131I, 213Bi, or 225Ac-labeled anti-CD33 or CD45 antibodies. Novel monoclonal antibodies that recruit and promote proximity-induced cytotoxicity of tumor cells by T cells (bispecific T-cell engager [BiTE] such as anti CD33/CD3, e.g., AMG 330) or block immune checkpoint pathways such as CTLA4 (e.g., ipilimumab) or PD1/PD-L1 (e.g., nivolumab) unleashing the patients T cells to fight leukemic cells are being evaluated in clinical trials in patients with AML. The numerous ongoing clinical trials with immunotherapies in AML will improve our understanding of the biology of AML and allow us to determine the best approaches to immunotherapy in AML.

Evolution of Cytokine Receptor Signaling

Cytokines represent essential mediators of cell–cell communication with particularly important roles within the immune system. These secreted factors are produced in response to developmental and/or environmental cues and act via cognate cytokine receptors on target cells, stimulating specific intracellular signaling pathways to facilitate appropriate cellular responses. This review describes the evolution of cytokine receptor signaling, focusing on the class I and class II receptor families and the downstream JAK–STAT pathway along with its key negative regulators. Individual components generated over a long evolutionary time frame coalesced to form an archetypal signaling pathway in bilateria that was expanded extensively during early vertebrate evolution to establish a substantial “core” signaling network, which has subsequently undergone limited diversification within discrete lineages. The evolution of cytokine receptor signaling parallels that of the immune system, particularly the emergence of adaptive immunity, which has likely been a major evolutionary driver.

Identification of neutrophil surface marker changes in health and inflammation using high-throughput screening flow cytometry

Neutrophils are the most abundant white blood cell and are an essential component of the innate immune system. A complete cataloguing of cell surface markers has not been undertaken for neutrophils isolated from circulation as well as healthy and inflamed tissues. To identify cell-surface markers specific to human neutrophils, we used high-throughput flow cytometry to screen neutrophil populations isolated from blood and oral rinses from healthy and chronic periodontitis patients against a panel of 374 known cluster of differentiation (CD) antibodies. This screen identified CD11b, CD16, and CD66b as markers that are consistently expressed on neutrophils independent of the cell location, level of activation and disease state. Cell sorting against CD11b, CD16 and CD66b allowed for the enrichment of mature neutrophils, yielding neutrophil populations with up to 99% purity. These findings suggest an ideal surface marker set for isolating mature neutrophils from humans. The screen also demonstrated that tissue neutrophils from chronically inflamed tissue display a unique surface marker set compared to tissue neutrophils present in healthy, non-inflamed tissues.

Signaling via the CytoR/JAK/STAT/SOCS pathway: Emergence during evolution

Cell-cell signaling represents an essential hallmark of multicellular organisms, which necessarily require a means of communicating between different cell populations, particularly immune cells. Cytokine receptor signaling through the Janus kinase/Signal Transducer and Activator of Transcription/Suppressor of Cytokine Signaling (CytoR/JAK/STAT/SOCS) pathway embodies one important paradigm by which this is achieved. This pathway has been extensively studied in vertebrates and protostomes and shown to play fundamental roles in development and function of immune and other cells. However, our understanding of the origins of the individual pathway components and their assembly into a functional pathway has remained limited. This study examined the origins of each component of this pathway through bioinformatics analysis of key extant species. This has revealed step-wise accretion of individual components over a large evolutionary time-frame, but only in bilateria did a series of innovations allow their final coalescence to form a complete pathway. Assembly of the CytoR/JAK/STAT pathway has followed the retrograde model of pathway evolution, whereas addition of the SOCS component has adhered to the patchwork model.

Exploration of benzamidochromenone derivatives with conformational restrictor as interleukin-5 inhibitors

Novel amidochromen-4-one analogs 8a-k and 9a-f were prepared and studied for their IL-5 inhibitory activity. Among the synthesized compounds, (6-benzamido-2-cyclohexyl-4-oxo-4H-chromen-3-yl)methyl acetate (8a, 95% inhibition at 30 μM, IC50=6.1 μM) exhibited potent IL-5 inhibitory activity. The conformational restrictor at position 2 like bulky cyclohexyl group is favorable for the formation of effective conformer of side chain small ester like acetoxymethyl at position 3 of these chromenone analogs 8. In addition the hydrophobic planarity of benzamido group at position 6 should be important for the potent IL-5 inhibitory activity. Since replacing acetoxymethyl moiety with hydroxymethyl group at position 3 of chromenone decreases the activity, which indicates that the location of hydrogen bonding group should be near 4 atom distances away from chromenone ring is more optimum for the activity. Therefore, these benzamidochromen-4-one analogs 8 are novel scaffold for finding potent interleukin-5 inhibitors.

Innate immune regulation by STAT-mediated transcriptional mechanisms

The term innate immunity typically refers to a quick but non-specific host defense response against invading pathogens. The innate immune system comprises particular immune cell populations, epithelial barriers, and numerous secretory mediators including cytokines, chemokines, and defense peptides. Innate immune cells are also now recognized to play important contributing roles in cancer and pathological inflammatory conditions. Innate immunity relies on rapid signal transduction elicited upon pathogen recognition via pattern recognition receptors (PRRs) and cell:cell communication conducted by soluble mediators, including cytokines. A majority of cytokines involved in innate immune signaling use a molecular cascade encompassing receptor-associated Jak protein tyrosine kinases and STAT (signal transducer and activator of transcription) transcriptional regulators. Here, we focus on roles for STAT proteins in three major innate immune subsets: neutrophils, macrophages, and dendritic cells (DCs). While knowledge in this area is only now emerging, understanding the molecular regulation of these cell types is necessary for developing new approaches to treat human disorders such as inflammatory conditions, autoimmunity, and cancer.

Interleukin-3/granulocyte macrophage colony-stimulating factor receptor promotes stem cell expansion, monocytosis, and atheroma macrophage burden in mice with hematopoietic ApoE deficiency

OBJECTIVE

Coronary heart disease is associated with monocytosis. Studies using animal models of monocytosis and atherosclerosis such as ApoE(-/-) mice have shown bone marrow (BM) hematopoietic stem and multipotential progenitor cell (HSPC) expansion, associated with increased cell surface expression of the common β subunit of the granulocyte macrophage colony-stimulating factor/interleukin-3 receptor (CBS) on HSPCs. ApoE(-/-) mice also display increased granulocyte macrophage colony-stimulating factor-dependent monocyte production in the spleen. We investigated the role of the CBS in cholesterol-driven HSPC expansion, monocytosis, and atherosclerosis.

APPROACH AND RESULTS

Ldlr(-/-) mice were transplanted with ApoE(-/-)Cbs(-/-) or ApoE(-/-) BM followed by Western-type diet feeding. Compared with ApoE(-/-) BM-transplanted controls, ApoE(-/-)Cbs(-/-) BM-transplanted mice had reduced BM and splenic HSPC proliferation, fewer blood monocytes and neutrophils, and reduced macrophage content and area of early atherosclerotic lesions. More advanced lesions showed diminished macrophage and collagen content; however, lesion size was unchanged, reflecting an increase in necrotic core area, associated with a marked decrease in Abcg1 expression and increased macrophage apoptosis. Compared with wild-type mice, Western-type diet-fed ApoE(-/-) mice showed increased CBS expression on granulocyte macrophage colony-stimulating factor-producing innate response activator B cells and expansion of this population. ApoE(-/-)Cbs(-/-) BM-transplanted Ldlr(-/-) mice showed a marked decrease in innate response activator B cells compared with ApoE(-/-) BM-transplanted Ldlr(-/-) controls.

CONCLUSIONS

Increased levels of CBS on HSPCs and splenic innate response activator B cells lead to expansion of these populations in ApoE(-/-) BM-transplanted Ldlr(-/-) mice, contributing to monocytosis and increased lesional macrophage content. However, in more advanced lesions, the CBS also has a role in atherosclerotic plaque stabilization.

Monoclonal antibody targeting of IL-3 receptor α with CSL362 effectively depletes CML progenitor and stem cells

Despite the remarkable efficacy of tyrosine kinase inhibitors (TKIs) in eliminating differentiated chronic myeloid leukemia (CML) cells, recent evidence suggests that leukemic stem and progenitor cells (LSPCs) persist long term, which may be partly attributable to cytokine-mediated resistance. We evaluated the expression of the interleukin 3 (IL-3) receptor α subunit (CD123), an established marker of acute myeloid leukemia stem cells, on CML LSPCs and the potential of targeting those cells with the humanized anti-CD123 monoclonal antibody CSL362. Compared with normal donors, CD123 expression was higher in CD34(+)/CD38(-) cells of both chronic phase and blast crisis CML patients, with levels increasing upon disease progression. CSL362 effectively targeted CML LSPCs by selective antibody-dependent cell-mediated cytotoxicity (ADCC)-facilitated lysis of CD123(+) cells and reduced leukemic engraftment in mice. Importantly, not only were healthy donor allogeneic natural killer (NK) cells able to mount an effective CSL362-mediated ADCC response, but so were CML patients' autologous NK cells. In addition, CSL362 also neutralized IL-3-mediated rescue of TKI-induced cell death. Notably, combination of TKI- and CSL362-induced ADCC caused even greater reduction of CML progenitors and further augmented their preferential elimination over normal hematopoietic stem and progenitor cells. Thus, our data support the further evaluation of CSL362 therapy in CML.

PLC-γ and PI3K link cytokines to ERK activation in hematopoietic cells with normal and oncogenic Kras

Oncogenic K-Ras proteins, such as K-Ras(G12D), accumulate in the active, guanosine triphosphate (GTP)-bound conformation and stimulate signaling through effector kinases. The presence of the K-Ras(G12D) oncoprotein at a similar abundance to that of endogenous wild-type K-Ras results in only minimal phosphorylation and activation of the canonical Raf-mitogen-activated or extracellular signal-regulated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) signaling cascades in primary hematopoietic cells, and these pathways remain dependent on growth factors for efficient activation. We showed that phospholipase C-γ (PLC-γ), PI3K, and their generated second messengers link activated cytokine receptors to Ras and ERK signaling in differentiated bone marrow cells and in a cell population enriched for leukemia stem cells. Cells expressing endogenous oncogenic K-Ras(G12D) remained dependent on the second messenger diacylglycerol for the efficient activation of Ras-ERK signaling. These data raise the unexpected possibility of therapeutically targeting proteins that function upstream of oncogenic Ras in cancer.

SOCS-1 mediates ubiquitylation and degradation of GM-CSF receptor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and the related cytokines interleukin (IL)-3 and IL-5 regulate the production and functional activation of hematopoietic cells. GM-CSF acts on monocytes/macrophages and granulocytes, and several chronic inflammatory diseases and a number of haematological malignancies such as Juvenile myelomonocytic leukaemia (JMML) are associated with deregulated GM-CSF receptor (GMR) signaling. The downregulation of GMR downstream signaling is mediated in part by the clearance of activated GMR via the proteasome, which is dependent on the ubiquitylation of βc signaling subunit of GMR via an unknown E3 ubiquitin ligase. Here, we show that suppressor of cytokine signaling 1 (SOCS-1), best known for its ability to promote ubiquitin-mediated degradation of the non-receptor tyrosine kinase Janus kinase 2 (JAK2), also targets GMRβc for ubiquitin-mediated degradation and attenuates GM-CSF-induced downstream signaling.

Granulocyte-macrophage colony stimulating factor (GM-CSF) enhances cumulus cell expansion in bovine oocytes

BACKGROUND

The objectives of the study were to characterize the expression of the α- and β-subunits of granulocyte-macrophage colony stimulating factor (GM-CSF) receptor in bovine cumulus cells and oocytes and to determine the effect of exogenous GM-CSF on cumulus cells expansion, oocyte maturation, IGF-2 transcript expression and subsequent competence for embryonic development.

METHODS

Cumulus-oocyte complexes (COC) were obtained by aspirating follicles 3- to 8-mm in diameter with an 18 G needle connected to a vacuum pump at -50 mmHg. Samples of cumulus cells and oocytes were used to detect GM- CSF receptor by immunofluorescence. A dose-response experiment was performed to estimate the effect of GM-CSF on cumulus cell expansion and nuclear/cytoplasmic maturation. Also, the effect of GM-CSF on IGF-2 expression was evaluated in oocytes and cumulus cells after in vitro maturation by Q-PCR. Finally, a batch of COC was randomly assigned to in vitro maturation media consisting of: 1) synthetic oviductal fluid (SOF, n = 212); 2) synthetic oviductal fluid supplemented with 100 ng/ml of GM-CSF (SOF + GM-CSF, n = 224) or 3) tissue culture medium (TCM 199, n = 216) and then subsequently in vitro fertilized and cultured for 9 days.

RESULTS

Immunoreactivity for both α and β GM-CSF receptors was localized in the cytoplasm of both cumulus cells and oocytes. Oocytes in vitro matured either with 10 or 100 ng/ml of GM-CSF presented a higher (P < 0.05) cumulus cells expansion than that of the control group (0 ng/ml of GM-CSF). GM-CSF did not affect the proportion of oocytes in metaphase II, cortical granules dispersion and IGF-2 expression. COC exposed to 100 ng/ml of GM-CSF during maturation did not display significant differences in terms of embryo cleavage rate (50.4% vs. 57.5%), blastocyst development at day 7 (31.9% vs. 28.7%) and at day 9 (17.4% vs. 17.9%) compared to untreated control (SOF alone, P = 0.2).

CONCLUSIONS

GM-CSF enhanced cumulus cell expansion of in vitro matured bovine COC. However, GM-CSF did not increase oocyte nuclear or cytoplasmic maturation rates, IGF-2 expression or subsequent embryonic development.

Inhibition of SRC corrects GM-CSF hypersensitivity that underlies juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasm in children characterized by the overproduction of monocytic cells that infiltrate the spleen, lung, and liver. JMML remains a disease for which few curative therapies are available other than myeloablative hematopoietic stem cell transplant (HSCT); however, relapse remains a major cause of treatment failure and the long-term morbidities of HSCT for survivors are substantial. A hallmark feature of JMML is acquired hypersensitivity by clonal myeloid progenitor cells to granulocyte macrophage-colony stimulating factor (GM-CSF) via a largely unknown mechanism. Here, we identify c-Cbl (henceforth referred to as Cbl) as a GM-CSF receptor (GMR) adaptor protein that targets Src for ubiquitin-mediated destruction upon GM-CSF stimulation and show that a loss of negative regulation of Src is pivotal in the hyperactivation of GMR signaling in Cbl-mutated JMML cells. Notably, dasatinib, an U.S. Food and Drug Administration-approved multikinase inhibitor that also targets Src family, dramatically attenuated the spontaneous and GM-CSF-induced hypersensitive growth phenotype of mononuclear cells from peripheral blood and bone marrow collected from JMML patients harboring Cbl or other known JMML-associated mutations. These findings reveal Src kinase as a critical oncogenic driver underlying JMML.

Engineering a CD123xCD3 bispecific scFv immunofusion for the treatment of leukemia and elimination of leukemia stem cells

Engineered bispecific antibodies that recruit cytotoxic lymphocytes to kill specific tumor cells have been showing promising clinical results. Here, we describe a bispecific single-chain Fv (scFv) immunofusion or BIf to target CD123(+) leukemia, that contains an anti-CD123 scFv fused at the N-terminus of human IgG1 hinge-C(H)2-C(H)3, and an anti-CD3 scFv fused at C-terminus. When expressed from transfected CHO-S cells, CD123xCD3 BIf forms a homodimer that provides a structure of N-terminal tumor-targeting domain that closely resembles natural antibody. The CD123xCD3 dimeric structure also provides binding affinity to CD123(+) tumor cells with a Kd of 10(-10) M, one to two orders of magnitude stronger than traditional bispecific antibody constructs. The location of the anti-CD3 scFv at C-terminus of BIf reduces the binding affinity to CD3(+) T cells by two orders, which could help to prevent non-specific T-cell activation. CD123xCD3 BIf is able to achieve T-cell-mediated target cell killing activities at low pM levels with E/T ratios as low as 2. Overall, the inclusion of human IgG1 constant region in BIf construct increases target cell-binding affinity; potentially increases serum half-life by its larger size and FcRn-mediated salvage system; and includes the abilities to activate the additional antibody-mediated cellular cytotoxicities.

The receptor that tames the innate immune response

Tissue injury, hypoxia and significant metabolic stress activate innate immune responses driven by tumor necrosis factor (TNF)-α and other proinflammatory cytokines that typically increase damage surrounding a lesion. In a compensatory protective response, erythropoietin (EPO) is synthesized in surrounding tissues, which subsequently triggers antiinflammatory and antiapoptotic processes that delimit injury and promote repair. What we refer to as the sequelae of injury or disease are often the consequences of this intentionally discoordinated, primitive system that uses a "scorched earth" strategy to rid the invader at the expense of a serious lesion. The EPO-mediated tissue-protective system depends on receptor expression that is upregulated by inflammation and hypoxia in a distinctive temporal and spatial pattern. The tissue-protective receptor (TPR) is generally not expressed by normal tissues but becomes functional immediately after injury. In contrast to robust and early receptor expression within the immediate injury site, EPO production is delayed, transient and relatively weak. The functional EPO receptor that attenuates tissue injury is distinct from the hematopoietic receptor responsible for erythropoiesis. On the basis of current evidence, the TPR is composed of the β common receptor subunit (CD131) in combination with the same EPO receptor subunit that is involved in erythropoiesis. Additional receptors, including that for the vascular endothelial growth factor, also appear to be a component of the TPR in some tissues, for example, the endothelium. The discoordination of the EPO response system and its relative weakness provide a window of opportunity to intervene with the exogenous ligand. Recently, molecules were designed that preferentially activate only the TPR and thus avoid the potential adverse consequences of activating the hematopoietic receptor. On administration, these agents successfully substitute for a relative deficiency of EPO production in damaged tissues in multiple animal models of disease and may pave the way to effective treatment of a wide variety of insults that cause tissue injury, leading to profoundly expanded lesions and attendant, irreversible sequelae.

Agrin is required for survival and function of monocytic cells

Agrin, an extracellular matrix protein belonging to the heterogeneous family of heparan sulfate proteoglycans (HSPGs), is expressed by cells of the hematopoietic system but its role in leukocyte biology is not yet clear. Here we demonstrate that agrin has a crucial, nonredundant role in myeloid cell development and functions. We have identified lineage-specific alterations that affect maturation, survival and properties of agrin-deficient monocytic cells, and occur at stages later than stem cell precursors. Our data indicate that the cell-autonomous signals delivered by agrin are sensed by macrophages through the α-DC (DG) receptor and lead to the activation of signaling pathways resulting in rearrangements of the actin cytoskeleton during the phagocytic synapse formation and phosphorylation of extracellular signal-regulated kinases (Erk 1/2). Altogether, these data identify agrin as a novel player of innate immunity.

Rosacea: The cytokine and chemokine network

Rosacea is one of the most common dermatoses of adults. Recent studies have improved our understanding of the pathophysiology of rosacea. Current concepts suggest that known clinical trigger factors of rosacea such as UV radiation, heat, cold, stress, spicy food, and microbes modulate Toll-like receptor signaling, induce reactive oxygen species, as well as enhance antimicrobial peptide and neuropeptide production. Downstream of these events cytokines and chemokines orchestrate an inflammatory response that leads to the recruitment and activation of distinct leukocyte subsets and induces the characteristic histopathological features of rosacea. Here we summarize the current knowledge of the cytokine and chemokine network in rosacea and propose pathways that may be of therapeutic interest.

Down-regulating the expression of IL-3Rβ interfered with the proliferation, not differentiation in NB4 cells

The human IL-3 receptor is composed of both α and β subunits. In early studies, we showed that the level of IL-3Rβ expression was lower in patients with acute promyelocytic leukemia (APL) than healthy donors and patients in complete remission by real-time quantitative polymerase chain reaction (RT-qPCR). With the differentiation of cells, enhanced expression of IL-3Rβ was also observed in all-trans-retinoic acid (ATRA)-induced NB4 cells. To unravel the role of IL-3Rβ upregulation in NB4 cells induced with ATRA, we knocked down IL-3Rβ expression by RNA interference (RNAi). Knockdown of IL-3Rβ resulted in decreased proliferation in NB4 cells induced with or without ATRA, observed by cell growth curves, colony formation assays and cell cycle analysis. Surface expression of CD11b antigen and nitroblue tetrazolium (NBT) reduction assays were also carried out at different time points. However, no significant difference was observed between the experimental and control groups treated with ATRA. Other findings suggested that IL-3Rα was decreased in NB4-IL-3Rβ shRNA cells by western blot. Down-regulation of IL-3Rβ also caused a decrease in PML/RARα expression detected with RT-qPCR. Together, these results suggest that abnormalities of IL-3Rβ expression were observed in APL; knockdown of IL-3Rβ inhibited the proliferation of NB4 cells with or without ATRA, but no effect was detected in the cellular differentiation. When NB4 cells exposed to ATAR, the up-regulation of IL-3Rβ expression may contribute to the maintenance of proliferation rather than cell differentiation.

Endogenous oncogenic Nras mutation promotes aberrant GM-CSF signaling in granulocytic/monocytic precursors in a murine model of chronic myelomonocytic leukemia

Oncogenic NRAS mutations are frequently identified in myeloid diseases involving monocyte lineage. However, its role in the genesis of these diseases remains elusive. We report a mouse bone marrow transplantation model harboring an oncogenic G12D mutation in the Nras locus. Approximately 95% of recipient mice develop a myeloproliferative disease resembling the myeloproliferative variant of chronic myelomonocytic leukemia (CMML), with a prolonged latency and acquisition of multiple genetic alterations, including uniparental disomy of oncogenic Nras allele. Based on single-cell profiling of phospho-proteins, a novel population of CMML cells is identified to display aberrant granulocyte-macrophage colony stimulating factor (GM-CSF) signaling in both the extracellular signal-regulated kinase (ERK) 1/2 and signal transducer and activator of transcription 5 (Stat5) pathways. This abnormal signaling is acquired during CMML development. Further study suggests that aberrant Ras/ERK signaling leads to expansion of granulocytic/monocytic precursors, which are highly responsive to GM-CSF. Hyperactivation of Stat5 in CMML cells is mainly through expansion of these precursors rather than up-regulation of surface expression of GM-CSF receptors. Our results provide insights into the aberrant cytokine signaling in oncogenic NRAS-associated myeloid diseases.

Overview of novel therapeutic targets for asthma and chronic obstructive pulmonary disease

Obstructive lung diseases, in particular asthma and chronic obstructive pulmonary disease, are a worldwide health problem that is increasing in incidence. While significant progress has been made in the control of symptoms, further advances must be made in modifying the clinical situation in terms of disease progression. Numerous pathogenetic studies have demonstrated that inflammatory responses play a crucial role in the development of chronic lung obstruction, while current molecular findings have provided a myriad of new and promising therapeutic targets. The aim of this article is to provide an overview of clinically and pharmacologically relevant targets for asthma and chronic obstructive pulmonary diseases, considering currently investigated therapeutic approaches.

Monoclonal antibody-mediated targeting of CD123, IL-3 receptor alpha chain, eliminates human acute myeloid leukemic stem cells

Leukemia stem cells (LSCs) initiate and sustain the acute myeloid leukemia (AML) clonal hierarchy and possess biological properties rendering them resistant to conventional chemotherapy. The poor survival of AML patients raises expectations that LSC-targeted therapies might achieve durable remissions. We report that an anti-interleukin-3 (IL-3) receptor alpha chain (CD123)-neutralizing antibody (7G3) targeted AML-LSCs, impairing homing to bone marrow (BM) and activating innate immunity of nonobese diabetic/severe-combined immunodeficient (NOD/SCID) mice. 7G3 treatment profoundly reduced AML-LSC engraftment and improved mouse survival. Mice with pre-established disease showed reduced AML burden in the BM and periphery and impaired secondary transplantation upon treatment, establishing that AML-LSCs were directly targeted. 7G3 inhibited IL-3-mediated intracellular signaling of isolated AML CD34(+)CD38(-) cells in vitro and reduced their survival. These results provide clear validation for therapeutic monoclonal antibody (mAb) targeting of AML-LSCs and for translation of in vivo preclinical research findings toward a clinical application.

The structure of the GM-CSF receptor complex reveals a distinct mode of cytokine receptor activation

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that controls the production and function of blood cells, is deregulated in clinical conditions such as rheumatoid arthritis and leukemia, yet offers therapeutic value for other diseases. Its receptors are heterodimers consisting of a ligand-specific alpha subunit and a betac subunit that is shared with the interleukin (IL)-3 and IL-5 receptors. How signaling is initiated remains an enigma. We report here the crystal structure of the human GM-CSF/GM-CSF receptor ternary complex and its assembly into an unexpected dodecamer or higher-order complex. Importantly, mutagenesis of the GM-CSF receptor at the dodecamer interface and functional studies reveal that dodecamer formation is required for receptor activation and signaling. This unusual form of receptor assembly likely applies also to IL-3 and IL-5 receptors, providing a structural basis for understanding their mechanism of activation and for the development of therapeutics.

Role of the proteasome in modulating native G-CSFR expression

The granulocyte colony-stimulating factor receptor (G-CSFR) is a critical regulator of granulopoiesis, but the mechanisms controlling its surface expression are poorly understood. Recent studies using transfected cell lines have suggested the activated G-CSFR is routed to the lysosome and not the proteasome. Here, we examined the role of the ubiquitin/proteasome system in regulating G-CSFR surface expression in both ts20 cells that have a temperature-sensitive E1 ubiquitin-activating enzyme and in primary human neutrophils. We show that the G-CSFR is constitutively ubiquitinated, which increases following ligand binding. In the absence of a functional E1 enzyme, ligand-induced internalization of the receptor is inhibited. Pre-treatment of ts20 transfectants with either chloroquine or MG132 inhibited ligand-induced G-CSFR degradation, suggesting a role for both lysosomes and proteasomes in regulating G-CSFR surface expression in this cell line. In neutrophils, inhibition of the proteasome but not the lysosome was found to inhibit internalization/degradation of the activated G-CSFR. Collectively, these data demonstrate the requirement for a functional ubiquitin/proteasome system in G-CSFR internalization and degradation. Our results suggest a prominent role for the proteasome in physiologic modulation of the G-CSFR, and provide further evidence for the importance of the ubiquitin/proteasome system in the initiation of negative signaling by cytokine receptors.