Expression In Myeloid Cells Research Articles

Dissecting the Prognostic Significance and Functional Role of Progranulin in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is known for its strong dependency on the tumor microenvironment. We found progranulin (GRN), a protein that has been linked to inflammation and cancer, to be upregulated in the serum of CLL patients compared to healthy controls, and increased GRN levels to be associated with an increased hazard for disease progression and death. This raised the question of whether GRN is a functional driver of CLL. We observed that recombinant GRN did not directly affect viability, activation, or proliferation of primary CLL cells in vitro. However, GRN secretion was induced in co-cultures of CLL cells with stromal cells that enhanced CLL cell survival. Gene expression profiling and protein analyses revealed that primary mesenchymal stromal cells (MSCs) in co-culture with CLL cells acquire a cancer-associated fibroblast-like phenotype. Despite its upregulation in the co-cultures, GRN treatment of MSCs did not mimic this effect. To test the relevance of GRN for CLL in vivo, we made use of the Eμ-TCL1 CLL mouse model. As we detected strong GRN expression in myeloid cells, we performed adoptive transfer of Eμ-TCL1 leukemia cells to bone marrow chimeric Grn−/− mice that lack GRN in hematopoietic cells. Thereby, we observed that CLL-like disease developed comparable in Grn−/− chimeras and respective control mice. In conclusion, serum GRN is found to be strongly upregulated in CLL, which indicates potential use as a prognostic marker, but there is no evidence that elevated GRN functionally drives the disease.

Increased FLYWCH1 Expression is Negatively Correlated with Wnt/β-catenin Target Gene Expression in Acute Myeloid Leukemia Cells.

Acute myeloid leukaemia (AML) is a heterogeneous clonal malignancy of hematopoietic progenitor cells. The Wnt pathway and its downstream targets are tightly regulated by β-catenin. We recently discovered a new protein, FLYWCH1, which can directly bind nuclear β-catenin. Herein, we studied the FLYWCH1/β-catenin pathway in AML cells using qRT-PCR, Western blot, and immunofluorescence assays. In addition, the stemness activity and cell cycle were analysed by the colony-forming unit (CFU) using methylcellulose-based and Propidium iodide/flow cytometry assays. We found that FLYWCH1 mRNA and protein were differentially expressed in the AML cell lines. C-Myc, cyclin D1, and c-Jun expression decreased in the presence of higher FLYWCH1 expression, and vice versa. There appeared to be the loss of FLYWCH1 expression in dividing cells. The sub-G0 phase was prolonged and shortened in the low and high FLYWCH1 expression cell lines, respectively. The G0/G1 arrest correlated with FLYWCH1-expression, and these cell lines also formed colonies, whereas the low FLYWCH1 expression cell lines could not. Thus, FLYWCH1 functions as a negative regulator of the Wnt/β-catenin pathway in AML.

PF245 METFORMIN INHIBITS THE GROWTH OF MYELOID LEUKEMIA CELLS PARTLY DUE TO SUPPRESSION OF TYRO3 EXPRESSION

Background:Metformin, an anti‐diabetic drug, is known to inhibit leukemia cell growth mainly through activation of AMP‐activated protein kinase (AMPK), resulting in inhibition of mTORC1 signaling. Meanwhile, TYRO3 is a member of the TAM family (TYRO3, AXL, and MERTK) of receptor tyrosine kinases. While the roles of activated AXL and MERTK in leukemia cell growth have been reported by us and others, the roles of TYRO3 have not been well elucidated.Aims:We examined the involvement of TYRO3 in anti‐leukemia effects of metformin.Methods:Four myeloid leukemia cell lines (OCI‐AML2, OCI‐AML3, AA, and K562) expressing TYRO3 protein were used. AA is a human cell line derived from pure erythroid leukemia. All cell lines were cultured with increasing concentrations of metformin. To knockdown TYRO3 expression, small interfering RNA (siRNA) against TYRO3 or control siRNA was transfected using an electroporation system. Cell growth was assessed with a colorimetric assay after culturing for three days. Expression levels and the activation of various signaling proteins in lysates from cultured cells were examined using immunoblotting. Expression levels of mRNA were examined by quantitative RT‐PCR.Results:Treatment with metformin suppressed the growth of these four cell lines in a dose‐dependent manner. Immunoblotting revealed that metformin increased phosphorylated AMPK while decreased phosphorylation of mTOR and the downstream proteins such as 4E‐BP1 and P70S6K without affecting expression levels of those proteins in general. Moreover, metformin treatment decreased expression levels of TYRO3 and c‐MYC and phosphorylation of TYRO3, STAT3, and ERK1/2. In K562 cells treated with metformin, decrease in phosphorylated TYRO3 was more evident than decrease in TYRO3 expression levels. In OCI‐AML2, OCI‐AML3, and K562 cells, which express AXL, metformin treatment also decreased expression levels and phosphorylation of AXL. Quantitative RT‐PCR analysis showed that expression of TYRO3 and MYC mRNA decreased by metformin treatment. Next, siRNA experiments showed that TYRO3 knockdown suppressed the cell growth to approximately 50% of the control. It also suppressed phosphorylation of STAT3 and ERK1/2, which are downstream molecules of TYRO3 signaling, while it did not obviously suppress the phosphorylation of mTOR.Summary/Conclusion:We revealed that metformin treatment suppressed TYRO3 expression in myeloid leukemia cells for the first time. We also found that TYRO3 is involved in leukemia cell growth because TYRO3 knockdown suppressed the growth. From these findings, we showed that growth inhibition by metformin might be partly due to its suppression of TYRO3. In leukemia cells expressing AXL, suppression of AXL expression might also be involved in growth inhibition by metformin. It is widely speculated that growth inhibition by metformin is mainly due to inhibition of mTORC1 signaling through AMPK activation and some AMPK‐independent mechanisms. We showed here that suppression of TYRO3 and/or AXL by metformin might also be involved in growth inhibition, although the individual effects of AMPK‐mTORC1 and TYRO3/AXL pathways are not clearly distinguished because mTOR is one of the downstream molecules of TYRO3/AXL pathway. In clinical settings in the future, metformin treatment might be effective for patients with leukemia cells expressing TYRO3 and/or AXL proteins as well as mTOR. Detection of expression and activation of these proteins can be done to select the appropriate patients for administration of metformin.image

The histone deacetylase inhibitor Romidepsin induces as a cascade of differential gene expression and altered histone H3K9 marks in myeloid leukaemia cells.

Myelodysplastic syndromes (MDS) are a heterogeneous, clonal haematopoietic disorder, with ~1/3 of patients progressing to acute myeloid leukaemia (AML). Many elderly MDS patients do not tolerate intensive therapeutic regimens, and therefore have an unmet need for better tolerated therapies.Epigenetics is important in the pathogenesis of MDS/AML with DNA methylation, and histone acetylation the most widely studied modifications. Epigenetic therapeutic agents have targeted the reversible nature of these modifications with some clinical success. The aim of this study was to characterise the molecular consequences of treatment of MDS and AML cells with the histone deacetylase inhibitor (HDACi) Romidepsin.Romidepsin as a single agent induced cell death with an increasing dose and time profile associated with increased acetylation of histone H3 lysine 9 (H3K9) and decreased HDAC activity. Gene expression profiling, qPCR, network and pathway analysis recognised that oxidation-reduction was involved in response to Romidepsin. ROS was implicated as being involved post-treatment with the involvement of TSPO and MPO.Genomic analysis uncoupled the differences in protein-DNA interactions and gene regulation. The spatial and temporal transcriptional differences associated with acetylated, mono- and tri-methylated H3K9, representative of two activation and a repression mark respectively, were identified. Bioinformatic analysis uncovered positional enrichment and transcriptional differences between these marks; a degree of overlap with increased/decreased gene expression that correlates to increased/decreased histone modification. Overall, this study has unveiled a number of underlying mechanisms of the HDACi Romidepsin that could identify potential drug combinations for use in the clinic.

Longevity-Associated Variant of BPIFB4 Mitigates Monocyte-Mediated Acquired Immune Response.

One of the basis of exceptional longevity is the maintaining of the balance between inflammatory and anti-inflammatory networks. The monocyte-macrophages activation plays a major role in tuning the immune responses, by oscillating between patrolling-protective to inflammatory status. Longevity-associated variant (LAV) of bactericidal/permeability-increasing fold-containing family B member 4 (BPIFB4) activates calcium, PKC-alpha, and eNOS, rescuing endothelial dysfunction in aged mice and inducing revascularization. The BPIFB4's increment in serum of healthy long-living individuals (LLIs) compared to nonhealthy ones, its therapeutic potential in improving vascular homeostasis, which depends on immune system, together with its expression in bone marrow myeloid cells, suggests that LAV-BPIFB4 may improve immune regulation. Here we show that human monocytes exposed to LAV-BPIFB4 protein increased co-stimulatory molecules in resting state and reduced pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) after activating stimuli. Accordingly, a low percentage of CD69+ activated lymphocytes are found among LAV-BPIFB4-treated peripheral blood mononuclear cells (PBMCs). Moreover, human monocyte-derived dendritic cells (DCs) generated in presence of LAV-BPIFB4 secreted higher anti-(IL-10 and TGF-β) and lower pro-inflammatory (TNF-α and IL-1β) cytokines. Accordingly, LLIs' plasma showed higher levels of circulating IL-10 and of neutralizing IL-1 receptor antagonist (IL-1RA) compared to controls. Thus, LAV-BPIFB4 effects on myeloid compartment could represent one example of a genetic predisposition carried by LLIs to protect from immunological dysfunctions.

Crosstalk between lung epithelial cells and myeloid cells in innate immune defense

Abstract Pathogens have evolved a wide range of strategies to allow survival and subsequently cause disease in humans. However, it is still poorly understood how the immune system successfully overcomes pathogen-induced disturbance and enable robust immune responses against infection. The intracellular bacterium Legionella pneumophila has the ability to block global protein synthesis in target macrophages, but the host can still strongly evoke an IL-1-dependent inflammatory response that clears infection. Here, we show that IL-1 signals directly to alveolar epithelial cells, which potently drives granulocyte-macrophage colony-stimulating factor (GM-CSF) production by these cells. Importantly, GM-CSF-mediated JAK2/STAT5 signaling promotes inflammatory gene expression in myeloid cells. We found that STAT5 was enriched at the 5′ upstream regions of inflammatory cytokine genes. In addition, GM-CSF metabolically reprogrammed myeloid cells to undergo aerobic glycolysis, which was required for maximal inflammatory cytokine production. Our findings reveal that lung epithelial cells act as a key intermediary to facilitate communication between infected and bystander myeloid cells and orchestrate antimicrobial defense.

Pulmonary involvement in a mouse model of Sjögren’s syndrome induced by activation of the STING pathway

Abstract Sjögren’s Syndrome (SS) is a chronic autoimmune disorder characterized by an increased type 1 interferon gene signature, autoantibody production, and salivary gland inflammation. Engagement of Stimulator of interferon genes (STING) induces type 1 interferon production. Gain of function mutations in TMEM173, encoding STING, results in a severe vasculopathy affecting the skin and lungs. We have previously reported that activation of the STING pathway in mice, using a STING agonist DMXAA, causes an SS-like disease characterized by sialoadenitis and salivary gland dysfunction. Considering that lungs are affected in 9–20% of SS patients, this study was undertaken to investigate lung involvement in DMXAA treated mice. Female C57BL/6 mice injected with DMXAA rapidly upregulated expression of IFNβ, IFNγ, and Mx1 in the lungs at 4 hours. This was followed by an increase in type 1 innate lymphoid cells on day 8. Histopathologic analysis showed the presence of peri-bronchial inflammatory infiltrates on day 35, which persisted until day 57. The lung inflammation was associated with an increased expression of multiple pro-inflammatory genes including CCl20, CXCl10, CXCl9, and IL17α. In addition, there was an increased frequency of lymphatic endothelial cells, suggestive of lymphangiogenesis. Although STING expression was seen in bronchial epithelium and alveolar cells in the lung, bone marrow chimeras between STING KO and wild type mice suggest that STING expression in myeloid cells was critical for lung inflammation. Our results show that systemic activation of the STING pathway might play an essential role in lung inflammation in SS patients.

BRCA1 Promoter Methylation Is Linked to Defective Homologous Recombination Repair and Elevated miR-155 to Disrupt Myeloid Differentiation in Myeloid Malignancies.

Defective homologous recombination (HR) has been reported in multiple myeloid disorders, suggesting a shared dysregulated pathway in these diverse malignancies. Because targeting HR-defective cancers with PARP inhibition (PARPi) has yielded clinical benefit, improved understanding of HR defects is needed to implement this treatment modality. We used an ex vivo irradiation-based assay to evaluate HR repair, HR gene promoter methylation, and mRNA expression in primary myeloid neoplastic cells. In vitro BRCA1 gene silencing was achieved to determine the consequences on HR repair, sensitivity to PARPi, and expression of miR-155, an oncogenic miRNA. Impaired HR repair was frequently detected in myeloid neoplasm samples (9/21, 43%) and was linked to promoter methylation-mediated transcriptional repression of BRCA1, which was not observed for other members of the HR pathway (BRCA2, ATM, ATR, FANC-A). In vitro BRCA1 knockdown increased sensitivity to PARP inhibition, and BRCA1 expression is inversely correlated with miR-155 expression, a finding reproduced in vitro with BRCA1 knockdown. Increased miR-155 was associated with PU.1 and SHIP1 repression, known myeloid differentiation factors that are frequently downregulated during leukemic transformation. This study demonstrates frequent defective HR, associated with BRCA1 epigenetic silencing, in a broad range of myeloid neoplasms. The increased prevalence of BRCA1 promoter methylation, resulting in repressed BRCA1, may have an additional role in leukemogenesis by increasing miR-155 expression, which then inhibits transcription factors associated with normal myeloid differentiation. Further study of HR defects may facilitate the identification of HR-defective myeloid neoplasms sensitive to PARPi.

Oncogenic potential of truncated RXR\u03b1 during colitis-associated colorectal tumorigenesis by promoting IL-6-STAT3 signaling

Retinoid X receptor-alpha (RXRα) is a potent regulator of inflammatory responses; however, its therapeutic potential for inflammatory cancer remains to be explored. We previously discovered that RXRα is abnormally cleaved in tumor cells and tissues, producing a truncated RXRα (tRXRα). Here, we show that transgenic expression of tRXRα in mice accelerates the development of colitis-associated colon cancer (CAC). The tumorigenic effect of tRXRα is primarily dependent on its expression in myeloid cells, which results in interleukin-6 (IL-6) induction and STAT3 activation. Mechanistic studies reveal an extensive interaction between tRXRα and TRAF6 in the cytoplasm of macrophages, leading to TRAF6 ubiquitination and subsequent activation of the NF-κB inflammatory pathway. K-80003, a tRXRα modulator derived from nonsteroidal anti-inflammatory drug (NSAID) sulindac, suppresses the growth of tRXRα-mediated colorectal tumor by inhibiting the NF-κB-IL-6-STAT3 signaling cascade. These results provide new insight into tRXRα action and identify a promising tRXRα ligand for treating CAC.

Histone Methylation Directs Myeloid TLR4 Expression and Regulates Wound Healing following Cutaneous Tissue Injury.

Myeloid cells are critical for orchestrating regulated inflammation during wound healing. TLRs, particularly TLR4, and its downstream-signaling MyD88 pathway play an important role in regulating myeloid-mediated inflammation. Because an initial inflammatory phase is vital for tissue repair, we investigated the role of TLR4-regulated, myeloid-mediated inflammation in wound healing. In a cutaneous tissue injury murine model, we found that TLR4 expression is dynamic in wound myeloid cells during the course of normal wound healing. We identified that changes in myeloid TLR4 during tissue repair correlated with increased expression of the histone methyltransferase, mixed-lineage leukemia 1 (MLL1), which specifically trimethylates the histone 3 lysine 4 (H3K4me3) position of the TLR4 promoter. Furthermore, we used a myeloid-specific Mll1 knockout (Mll1f/fLyz2Cre+ ) to determine MLL1 drives Tlr4 expression during wound healing. To understand the critical role of myeloid-specific TLR4 signaling, we used mice deficient in Tlr4 (Tlr4-/- ), Myd88 (Myd88 -/-), and myeloid-specific Tlr4 (Tlr4f/fLyz2Cre+) to demonstrate delayed wound healing at early time points postinjury. Furthermore, in vivo wound myeloid cells isolated from Tlr4-/- and Myd88 -/- wounds demonstrated decreased inflammatory cytokine production. Importantly, adoptive transfer of monocyte/macrophages from wild-type mice trafficked to wounds with restoration of normal healing and myeloid cell function in Tlr4-deficient mice. These results define a role for myeloid-specific, MyD88-dependent TLR4 signaling in the inflammatory response following cutaneous tissue injury and suggest that MLL1 regulates TLR4 expression in wound myeloid cells.

Augmentation of iNOS expression in myeloid progenitor cells expedites neutrophil differentiation.

Neutrophils play important role in immunity and inflammation through diverse mechanisms. Reports from this lab and others have demonstrated involvement of NO in neutrophil adhesion, chemotaxis, bacterial killing, reactive oxygen species generation, neutrophil extracellular traps' formation, and apoptosis. Constitutive expression of iNOS in human neutrophils has also been documented. The role of NO-iNOS in neutrophil differentiation however remains ill-defined. The present study was undertaken to understand the role of NO generated from iNOS in the neutrophil differentiation by using iNOS-overexpressing K562 cells (K562iNOS ) and iNOS-deficient murine progenitor cells (lineage negative cells; lin-ve ). We observed that iNOS overexpression led to increased neutrophilic differentiation in K562 cells; more specifically an early and accelerated neutrophilic differentiation was spotted in K562iNOS . These observations were further validated using iNOS knockout lin-ve cells or hematopoietic progenitor cells that exhibited delayed neutrophil differentiation in comparison to its wild-type counterpart. In addition, a significant increase in the gene expression of iNOS during neutrophilic differentiation of CD34+ hematopoietic stem and progenitor cells derived from human bone marrow further substantiates importance of iNOS in neutrophil differentiation. Moreover, a significant increase in NO generation during neutrophil differentiation was observed and enhanced neutrophil differentiation with NO donor was also observed, implying the importance of NO in neutrophil differentiation. Collectively, using alternative approaches, we demonstrated that neutrophil differentiation is significantly influenced by iNOS or NO, suggesting the possibility of exploiting this novel link for therapeutic aspects of NO generated from iNOS and neutrophil differentiation in hematopoiesis-related disorders.

Regulation of FOXP3 expression in myeloid cells in response to all-trans-retinoic acid, interleukin 2 and transforming growth factor β

FoxP3 is a transcription factor essential for differentiation and function of T regulatory cells (Tregs). There are two major subsets of Tregs: natural Tregs (nTregs) generated in thymus and inducible Tregs (iTregs) produced in peripheral immune system. It has been documented that iTreg development is dependent on soluble mediators including interleukin 2 (IL2), transforming growth factor β (TGFβ) and all-trans-retinoic acid (ATRA). In our experiments we performed a gene expression array, followed by Real-time PCR experiments to study expression of genes regulated by ATRA in cells of myeloid origin. Our experiments revealed that ATRA alone, but also a cocktail of mediators consisting of IL2, TGFβ and ATRA, upregulate expression of FOXP3 gene in normal and leukemic myeloid cells. Our results indicate that signaling pathways which are used at the late steps of T cell differentiation, are also active in the cells of myeloid lineage.

Overexpression of Tumor Necrosis Factor-Like Ligand 1 A in Myeloid Cells Aggravates Liver Fibrosis in Mice.

Macrophages are the master regulator of the dynamic fibrogenesis–fibrosis resolution paradigm. TNF-like ligand 1 aberrance (TL1A) was found to be able to induce intestinal inflammation and fibrosis. Furthermore, significantly increased TL1A had been detected in liver tissues and mononuclear cells of patients with primary biliary cirrhosis (PBC). This study was to investigate the effect of myeloid cells with constitutive TL1A expression on liver fibrogenesis. We found that TL1A expressions in liver tissues and macrophages were significantly increased in mice with liver fibrosis induced by injection of carbon tetrachloride (CCl4). TL1A overexpression in myeloid cells induced liver function injury, accelerated the necrosis and apoptosis of hepatocytes, recruited macrophages, and promoted activation of hepatic stellate cells (HSCs) and fibrosis. In vitro results of our study showed that TL1A overexpression in macrophages promoted secretion of platelet-derived growth factor-BB (PDGF-BB), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β). Culturing macrophages with TL1A overexpression could accelerate the activation and proliferation of primary HSCs. These results indicated that constitutive TL1A expression in myeloid cells exacerbated liver fibrosis, probably through macrophage recruitment and secretion of proinflammatory and profibrotic cytokines.

Mutant huntingtin expression in microglia is neither required nor sufficient to cause the Huntington's disease-like phenotype in BACHD mice.

Huntington's disease (HD) is caused by a CAG repeat expansion in the HTT gene and is characterized by early and selective striatal neurodegeneration. The huntingtin (HTT) protein is ubiquitously expressed in many tissues and the cellular pathogenesis of the disease is not fully understood. Immune cell dysfunction due to mutant HTT (mHTT) expression and aberrant immune system activation in HD patients suggests that inflammatory processes may contribute to HD pathogenesis. Here we used the BACHD mouse model of HD, which carries a conditional transgene expressing full-length human mHTT, to selectively deplete mHTT expression in myeloid lineage cells, including microglia, and evaluated the effects on HD-related behavior and neuropathology. In the converse experiment, we depleted mHTT expression in the majority of cells in the brain but specifically excluding microglia and again evaluated behavior and neuropathology. In mice with myeloid-specific mHTT-depletion, we observed no significant rescue of any behavioral or neuropathological outcome measures, while neural-specific knockout mice showed significant rescue of body weight, rotarod performance and striatal volume. We conclude that mHTT expression in microglia, though clearly affecting specific aspects of microglia function, does not alter disease pathogenesis in the BACHD mouse model. This may have implications for current or future therapeutic trials testing immune-modulating drugs in HD patients.

GADD45b Plays an Essential Role in the G-CSF Triggered Granulocytic Differentiation of Human Hematopoietic Cells

The mechanism of maturation arrest of bone marrow myeloid progenitors in severe congenital neutropenia (CN) patients is not fully elucidated. We found, that treatment of healthy individuals with G-CSF induces mRNA expression of GADD45b (Growth Arrest and DNA-Damage-inducible, beta) in CD33+ bone marrow myeloid progenitors. However, the expression of GADD45b was not activated in CD33+ cells of G-CSF treated CN patients. GADD45b functions as stress sensor downstream of G-CSF signaling and is essential in stress-induced murine myelopoiesis. Less is known about the function of GADD45b in the myeloid differentiation of human HSPCs. We hypothesized, that the inability of G-CSF to induce GADD45b expression might be a cause of diminished granulopoiesis in CN patients. To test this hypothesis, we inhibited GADD45b expression in CD34+ cells and iPSCs of healthy donors by introducing indels in exon 1 of the GADD45B gene using specific CRISPR/Cas9-gRNA ribonucleoprotein (RNP). We evaluated G-CSF-triggered myeloid differentiation of GADD45b-deficient iPSCs using embryoid body (EB)-based method and found that iPSCs cells present with severely diminished granulocytic differentiation upon GADD45b knockout, as assessed by FACS, CFU assay and morphological examination of cytospin slides. We also observed reduced G-CSF-mediated granulocytic differentiation of GADD45b-deficient CD34+ cells of healthy individuals in colony-forming units (CFU) assay and liquid culture differentiation followed by FACS analysis on day 7 and day 14.Importantly, rescue of GADD45b in HSPCs of one CN patient by lentivirus-based transduction of GADD45B cDNA restored defective granulocytic differentiation, as compared to control transduced cells. These data strongly support the essential role of GADD45b in G-CSF-mediated granulocytic differentiation. GADD45b rescue analysis of additional CN patients cells is ongoing.To study the mechanism of GADD45b activation upon G-CSF stimulation of hematopoietic cells, we performed in silico analysis of GADD45B promoter and found putative binding sites for G-CSF responsive hematopoietic transcription factors, including CEBPA, CEBPB, KLF4, STAT3 and STAT5. Using the dual luciferase reporter assay with 1.6 kb region of the GADD45B gene promoter, we found that KLF4, STAT5, CEBPA and CEBPB activate GADD45b expression in a dose-dependent manner. Intriguingly, CEBPA expression is severely diminished in myeloid cells of CN patients (Skokowa et al., 2006) and we assumed that G-CSF is not able to activate GADD45b expression in CN patients because of defective CEBPA. To study the mechanism by which GADD45b mediates myeloid differentiation, we performed RNA sequencing of WT or GADD45b-deficient CD34+ HSPCs treated or not with G-CSF. Interestingly, in GADD45b-deficient cells, G-CSF failed to induce mRNA expression of several genes essential for granulocytic differentiation and granulocyte functions including GLI1, CAMP/LL37, MMP8, CD16, LCN2, OLFM4, CX3CR1, SIGLEC5, as compared to WT cells. Reactome and Gene Set Enrichment Analysis (GSEA) of RNA-Seq data sets also revealed deregulation of the “myeloid CEBPA network”, “GLI proteins pathway” and “neutrophil degranulation pathway” in G-CSF-treated GADD45b-deficient CD34+ cells, as compared to control G-CSF-exposed cells. Of note, severely diminished expression of plasma CAMP/LL37 levels is a unique feature of CN patients (Y. Ye et al. 2015).In summary, our data suggest that GADD45b plays an essential role in granulocytic differentiation of human hematopoietic cells and inability of G-CSF to induce GADD45b expression in myeloid cells of CN patients may be a reason for the defective granulopoiesis. DisclosuresNo relevant conflicts of interest to declare.

Checkpoint Inhibition in CSF3R Mutated Chronic Neutrophilic Leukemia

Mutations in the colony-stimulating factor 3 receptor (CSF3R) have been identified in 90% of chronic neutrophilic leukemia (CNL) and lower frequency in atypical chronic myeloid leukemia (aCML). It was shown recently, that signaling of the different types of CSF3R mutations varies, but a central role of the JAK/STAT pathway activation by oncogenic CSF3R membrane proximal point mutations has been anticipated. However, the exact downstream signaling pathways mediated by CSF3R mutations are still not completely understood. Recent studies in JAK mutated myeloproliferative diseases uncovered the vital importance of JAK/STAT signaling in PD-L1 mediated immune escape, thereby suggesting a possible role and mechanistic link for PD-1/PD-L1 immune checkpoint regulation in CNL and aCML.To investigate the dependence of the oncogenic CSF3R signaling cascade on an activated JAK/STAT axis, we performed Ruxolitinib treatment in MTT assays with BaF3 cells retrovirally infected with pMIG-R1 vectors harboring either CSF3R point or truncation mutations. Our data indicate, that both, CSF3R point and truncation mutations induced cell growth could be inhibited by Ruxolitinib treatment. To narrow down the involvement of the different JAK family kinases, we included CSF3R mutation transduced JAK1 deficient U4C, JAK2 deficient y2A and TYK2 deficient U1A cell lines in combination with different JAK inhibitors. Interestingly, here we were able to show that CSF3R point mutations require functional JAK1/TYK2-STAT3 signaling for oncogenic potential, whereas truncation mutations depend on all JAK kinases through STAT3/5 for activation.To further study potential therapeutic strategies, we examined checkpoint inhibition in CSF3R mutated disease. In this regard we demonstrate a significant induction of PD-L1 expression in murine cell lines upon expression of CSF3R point mutations T615A or T618I. To investigate the impact of PD-L1 upregulation in vivo, we used a retroviral murine bone marrow (BM) transplantation model where we infected BM of Balb/c mice with a vector carrying CSF3R T618I point mutation and transplanted it into lethally irradiated recipients. Transplanted mice developed a CSF3R driven leukemia and died by leukocytosis and organ infiltration, whereas mice transplanted with BM harboring CSF3RT618I and additional ADA mutation failed to induce leukemia. To test checkpoint inhibition as a potential therapeutic strategy in vivo, CSF3RT618I transplanted mice were treated regularly with anti-PD-L1-antibody or isotype control. Interestingly, checkpoint inhibition led to reduced EGFP burden and prolonged survival of responder mice suggesting a treatment response of immunooncologic agents in these rare diseases.In immunophenotypic analyses of primary patient material, we were able to show increased PD-L1 expression in primary diseased myeloid cells isolated from peripheral blood of CNL and aCML patients, thereby defining this structure as a possible new therapeutic target.To summarize, our data expand the knowledge of oncogenic CSF3R signaling pathways and implicate an immunotherapeutic strategy by checkpoint inhibition in CSF3R driven CNL and atypical CML. DisclosuresLubbert:Teva: Other: Study drug; Celgene: Other: Travel Grant; Janssen: Honoraria, Research Funding.

TLR4/NF-κB axis induces fludarabine resistance by suppressing TXNIP expression in acute myeloid leukemia cells

Overcoming drug resistance is one of key issues in treating refractory acute myeloid leukemia (AML). The Toll-like receptor 4 (TLR4) signaling pathway is involved in many aspects of biological functions of AML cells, including the regulation of pro-inflammatory cytokine products, myeloid differentiation, and survival of AML cells. Thus, targeting TLR4 of AML patients for therapeutic purposes should be carefully addressed. In this regard, we investigated the possible role of TLR4 as a regulatory factor against fludarabine (FA) cytotoxicity activity. Here, we identified the differential expression of TLR4 and CD14 receptors in AML cell lines and examined their relationship to FA sensitivity. We found that the stimulation of TLR4 with lipopolysaccharide (LPS) in a TLR4-expressing cell line, THP-1, increased cell viability under FA treatment condition and showed that TLR4 stimulation overcame FA sensitivity through the activation of NF-κB, which subsequently upregulated several anti-apoptotic genes. The inhibition of TLR4/NF-κB signaling could partially or completely reverse LPS-induced cell survival under FA treatment conditions. Interestingly, we found that the expression of thioredoxin-interacting protein (TXNIP), a well-known tumor suppressor, was induced by FA treatment; however, it was suppressed by LPS treatment. Furthermore, the expression level of TXNIP was critical for FA-induced cytotoxicity or LPS-induced FA resistance of THP-1 cells. Our data suggest that TXNIP plays an important role in FA-induced cytotoxicity and TLR4/NF-κB-mediated FA resistance of AML cells. Therefore, TXNIP may be a potential therapeutic target for AML treatment.

E3 ligase FBXW7 aggravates TMPD-induced systemic lupus erythematosus by promoting cell apoptosis.

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease, and the pathogenesis of SLE has not been fully elucidated. The E3 ubiquitin ligase FBXW7 has been well characterized in cancer as a tumor suppressor that can promote the ubiquitination and subsequent degradation of various oncoproteins; however, the potential role of FBXW7 in autoimmune diseases is unclear. In the present study, we identified that FBXW7 is a crucial exacerbating factor for SLE development and progression in a mouse model induced by 2, 6, 10, 14-tetramethylpentadecane (TMPD). Myeloid cell-specific FBXW7-deficient (Lysm+FBXW7f/f) C57BL/6 mice showed decreased immune complex accumulation, glomerulonephritis, glomerular mesangial cell proliferation, and base-membrane thickness in the kidney. Lysm+FBXW7f/f mice produced fewer anti-Sm/RNP and anti-ANA autoantibodies and showed a decreased MHC II expression in B cells. In Lysm+FBXW7f/f mice, we observed that cell apoptosis was reduced and that fewer CD11b+Ly6Chi inflammatory monocytes were recruited to the peritoneal cavity. Consistently, diffuse pulmonary hemorrhage (DPH) was also decreased in Lysm+FBXW7f/f mice. Mechanistically, we clarified that FBXW7 promoted TMPD-induced cell apoptosis by catalyzing MCL1 degradation through K48-linked ubiquitination. Our work revealed that FBXW7 expression in myeloid cells played a crucial role in TMPD-induced SLE progression in mice, which may provide novel ideas and theoretical support for understanding the pathogenesis of SLE.

Association of Novel Inflammatory Markers TREM1 & TREM2 with Vitamin D Levels in Inflammatory Bowel Disease

Introduction: AIM: To study the association between vitamin D (Vit D) and Vitamin D receptor (VDR) in Inflammatory bowel disease (IBD) patients in Nebraska. To study the association of novel inflammatory markers TREM1(Triggering receptor expressed on myeloid cells 1) and TREM 2(Triggering receptor expressed on myeloid cells) expression in tissue biopsy specimens from terminal ileum(TI) and rectum(R) in Inflammatory Bowel Disease patients vs controls. Methods: The study included 8 cases of IBD and 11 controls who are matched to age and sex. They are healthy controls from the same geographical area visiting for colon cancer screening. Cases are already documented IBD patients visiting an endoscopy clinic for a colon cancer screening surveillance. Patients with IBD are already on a treatment plan. Vitamin D levels in the blood were measured and studied. VDR expression was studied in the biopsy specimens obtained from the terminal ileum and rectum of the cases and controls using immunohistochemistry. Histology and degree of inflammation was also studied from the tissue sections of the biopsy specimens from terminal ileum and rectum. The expression of TREM 1 and TREM 2 in the tissue specimens from the TI and R is studied using immunofluorescence. Results: The Vit D levels were not significantly different between the cases and control population. cases:29.5 ± 9.32ng/ml controls:30.82 ± 18.24ng/ml. Cases showed significantly higher expression of TREM 1 in TI and R sections (TI: P<.04, R: P<.02). TREM 2 expression is higher in cases but the expression is not significant (TI: P<0.93 R: P<0.45). The expression of VDR is insignificant between cases and controls (TI: P<0.13, R: P<0.83). When the cases were grouped into Vit D insufficient and Vit D sufficient levels, Vit D insufficient showed higher expression of TREM 1 and Vit D sufficient showed higher expression of TREM 2. Conclusion: Though cases and controls showed insignificant Vit D levels, they showed increased expression of TREM 1 and TREM in TI and rectum sections of biopsy. With insufficient Vit D levels, there is increased inflammatory state compared to the sufficient Vit D levels, which correlates with increased TREM1 which is a pro-inflammatory marker and decreased TREM2 which is an anti-inflammatory marker.683_A Figure 1. Expression of TREM1 in Vitamin D insufficient IBD patient.683_B Figure 2. Levels of Vitamin D in cases and controls683_C Figure 3. Histology of IBD tissue

NOTCH activation promotes glycosyltransferase expression in human myeloid leukemia cells.

NOTCH signaling diversely regulates the growth of acute myeloid leukemia (AML) cells. It is known that glycosylation of NOTCH receptors modulates NOTCH activation. However, little is known about glycosylation of NOTCH in AML cells. We examined the effects of ligand-induced NOTCH activation on the expression of NOTCHmodifying glycosyltransferases in two AML cell lines, THP-1 and TMD7. The cells were stimulated with recombinant NOTCH ligands JAGGED1 and DELTA1, and subjected to immunoblot analysis to evaluate the expression levels of glycosyltransferases. Ligand stimulation promoted the expression of POFUT1, LFNG, MFNG, RFNG, GXYLT1, GXYLT2, and XXYLT1 in THP-1 cells, and that of RFNG and GXYLT1 in TMD7 cells. We found that NOTCH activation promoted the expression of several glycosyltransferases in AML cells. This suggests that NOTCH activation modulates its sensitivity to NOTCH ligands by increased glycosylation of NOTCH receptors in AML cells. Further investigation is needed to elucidate its biological significance.