Granulocyte-macrophage Progenitor Cells Research Articles

Revealing common differential mRNAs, signaling pathways, and immune cells in blood, glomeruli, and tubulointerstitium of lupus nephritis patients based on transcriptomic data

Lupus nephritis (LN) is a potentially fatal autoimmune disease. The purpose of this study was to find potential key molecular markers of LN to aid in the early diagnosis and management of the disease. Datasets GSE99967_blood, GSE32591_glomeruli, and GSE32591_tubulointerstitium were included in this study. Differentially expressed mRNAs (DEmRNAs) were identified between the normal control and LN groups using the limma package in R. Common DEmRNAs in the three datasets were taken. Subsequently, functional enrichment analysis, immune correlation analysis, receiver operating characteristic (ROC) curve analysis and real-time polymerase chain reaction (RT-PCR) verification were performed. In this study, 11 common DEmRNAs were obtained and all of them were up-regulated. In protein–protein interaction (PPI) networks, we found that MX dynamin like GTPase 1 (MX1) and radical S-adenosyl methionine domain containing 2 (RSAD2) had the highest interaction score (0.997). Functional enrichment analysis revealed that MX1 and RSAD2 were enriched in influenza A and hepatitis C signaling pathways. The area under the curve (AUC) values of interferon-induced protein 44 (IFI44) and MX1 in GSE32591_glomeruli and GSE32591_tubulointerstitium datasets are 1, which is worthy of further study on their diagnostic value and molecular mechanism. The xCell analysis showed abnormal distribution of granulocyte-macrophage progenitor (GMP) cells in blood, glomeruli, and tubulointerstitium. Pearson’s correlation analysis found that GMP cells were significantly correlated with lactotransferrin (LTF) and cell cycle. Identification of common DEmRNAs and key pathways in the blood, glomeruli, and tubulointerstitium of patients with LN provides potential research directions for exploring the molecular mechanisms of the disease.

Integrating RNA-seq and scRNA-seq to explore the biological significance of NAD + metabolism-related genes in the initial diagnosis and relapse of childhood B-cell acute lymphoblastic leukemia.

Nicotinamide Adenine Dinucleotide (NAD) depletion is reported to be a potential treatment for B-cell Acute Lymphoblastic Leukemia (B-ALL), but the mechanism of NAD metabolism-related genes (NMRGs) in B-ALL relapse remains unclear. Transcriptome data (GSE3912), and single-cell sequencing data (GSE130116) of B-ALL patients were downloaded from Gene Expression Omnibus (GEO) database. NMRGs were sourced from Kyoto Encyclopedia of Genes and Genomes (KEGG) and Reactome databases. Further, the differentially expressed NMRGs (DE-NMRGs) were selected from the analysis between initial diagnosis and relapse B-ALL samples, which further performed functional enrichment analyses. The biomarkers were obtained through random forest (RF) algorithm and repeated cross validation. Additionally, cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm was used to evaluate the immune cell differences between the initial diagnosis and relapse samples, and the correlations between biomarkers and gene markers of differential immune cells were analyzed. Furthermore, single cell RNA sequencing was conducted in the GSE130116 dataset to find key cell clusters. In addition, according to biomarkers expressions, cell clusters were categorized into high and low biomarker expression groups, and Gene Set Enrichment Analysis (GSEA) analysis was performed on them. Finally, the cell clusters with the highest expression of biomarkers were selected to explore the roles of biomarkers in different cell clusters and identify transcription factors (TFs) influencing biological markers. 23 DE-NMRGs were screened out, which were mainly enriched in nucleoside phosphate metabolic process, nucleotide metabolic process, and Nicotinate and nicotinamide metabolism. Moreover, 3 biomarkers (NADSYN1, SIRT3, and PARP6) were identified from the machine learning. CIBERSORT results demonstrated that four types of immune cells (B Cells naive, Monocyte, Neutrophils, and T cells CD4 memory Activated) were significantly different between the initial diagnosis and the relapse B-ALL samples, and there were strong correlations between biomarkers and differential immune cells such as positive correlation between NADSYN1 and B Cells naive. The single cell analyses showed that the biomarkers were highly expressed in common myeloid progenitors (CMP), granulocyte-macrophage progenitor (GMP), and megakaryocyte-erythroid progenitor (MEP) cell clusters. Gene set enrichment analysis (GSEA) results indicated that 55 GO terms and 3 KEGG pathways were enriched by the genes in high and low biomarker expression groups. It was found that TF CREB3L2(+) was significantly reduced in the high expression group, which may be the TF affecting biomarkers in the high expression group. This study identified NADSYN1, SIRT3, and PARP6 as the biomarkers of B-ALL, explored biological significance of NMRGs in the initial diagnosis and relapse of B-ALL, and revealed mechanism of biomarkers at the level of the single cell.

Abstract 3201: Single-cell trajectory analysis reveals a melanoma-driven distinct hematopoietic response in murine spleen

Abstract Growing evidence suggests that tumor progression can interfere with normal hematopoiesis and skew the host system to undergo myeloid biased changes. Hematopoietic stem and progenitor cells (HSPCs) are a rare population of precursor cells giving rise to progeny that replenish blood cells throughout life. HSPCs are mainly localized in the bone marrow niche in healthy adults, however pathophysiological conditions such as cancer can cause extramedullary hematopoiesis in organs like the spleen. In this study, we investigated tumor-driven phenotypic and molecular alterations in the HSPC compartment at a single-cell level during extramedullary hematopoiesis using single-cell multiomics. We used a B16-F10 melanoma mouse model to uncover the tumor-mediated changes. Mice with tumor-burden showed splenomegaly and alterations in the composition of the HSPC compartment in the spleen consistent with extramedullary hematopoiesis. We then isolated four HSPC populations, including Lin- Sca1+ cKit+ (LSK), common myeloid progenitor (CMP), granulocyte-macrophage progenitor (GMP) and megakaryocyte-erythrocyte progenitor (MEP) cells from the spleen and bone marrow of melanoma-burdened mice using the BD FACSMelody™ Cell Sorter. Next, we used an integrated workflow on the BD Rhapsody™ Single-Cell Analysis System for the downstream single-cell multiomics analysis. We utilized oligo-conjugated antibodies for NGS-based sample multiplexing and protein detection (BD® Single-Cell Multiplexing Kit, BD® AbSeq Assay), along with whole transcriptome analysis for a comprehensive analysis of mRNA expression. Data analysis using the X-shift algorithm paired with single-cell force-directed layout visualization enabled delineation of the developmental trajectories of HSPC populations and exploration of phenotypic and transcriptomic changes across different hematopoietic subpopulations and across distinct anatomic sites. The analysis also identified unique hematopoietic cell clusters present during melanoma-driven extramedullary hematopoiesis in the spleen. Overall, our findings highlight melanoma-driven perturbations in hematopoiesis by utilizing advanced single-cell multiomics technology. Disclaimers: For Research Use Only. Not for use in diagnostic or therapeutic procedures. Class 1 Laser Product. BD-23277 (v1.0) 1120 BD, the BD Logo, FACSMelody and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2020 BD. All rights reserved. Citation Format: Nihan Kara, Nikolay Samusik, Xiaoshan Shi, Chip Lomas, Stephanie Widmann, Aaron J. Tyznik. Single-cell trajectory analysis reveals a melanoma-driven distinct hematopoietic response in murine spleen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3201.

A Novel Model of Human Hemopoiesis Based on Single Cell Functional and Transcriptional Analysis of Lympho-Myeloid Progenitors

Introduction: Human hemopoiesis produces 10 billion new, terminally mature blood cells daily; a production that is also rapidly responsive to external stimuli. Dysregulation of this complex process can lead to hemopoietic and immune deficiencies and blood cancers. In humans, the hemopoietic progenitor hierarchy producing lymphoid and myeloid lineages is unclear. Multiple progenitor populations give rise to lymphoid and myeloid cells but they remain incompletely characterized at the immunophenotypic, transcriptional and functional level. Here, we aim to understand the clonal functional output and transcriptional programs of primary human lympho-myeloid progenitor populations - the lymphoid-primed multipotent progenitor (LMPP) (Goardon et al., Cancer Cell, 2011), the multi-lymphoid progenitor (MLP) (Doulatov et al., Nature Immunology, 2010) and the granulocyte-macrophage progenitor (GMP).Methods: We devised a FACS strategy to prospectively purify eight human hemopoietic stem and progenitor cell populations. We functionally compared the LMPP, MLP and GMP in vitro by quantitative CFU assays, three different single cell liquid cultures or limit dilution analysis and in vivo by transplantation into a humanized ossicle mouse model (Reinisch et al., Nature Medicine, 2016). We performed population and single cell RNA sequencing and Fluidigm qRT-PCR to understand the relationship between the functional and transcriptional heterogeneity within human lympho-myeloid progenitor populations.Results: Our study comprehensively characterized the LMPP, MLP and GMP lympho-myeloid progenitor populations. Both LMPP and MLP are very rare within the mononuclear fraction (1 in 104 and 1 in 105 cells in CB and BM, respectively). We cultured 4357 single LMPP, GMP and MLP cells (isolated from 25 cord blood units and equivalent to ~1010 mononuclear cells) under three different culture conditions, one of which is described for the first time. We observed marked functional heterogeneity in the three lympho-myeloid progenitor populations. Focusing on the wells that gave single cell-initiated cultures, the majority of cells from LMPP, MLP and GMP gave uni-lineage output (60-90%). Bi-lineage output was less common (up to 35%), while multi-lineage output was the least frequent and only observed from LMPP and GMP cells (up to 15%). In vivo transplantation using the humanized ossicle mouse model increased the engraftment of lympho-myeloid progenitors 10-fold compared to previous reports. In vivo, the LMPP and GMP gave robust engraftment but the MLP substantially less engraftment. The LMPP gave rise to both myeloid and B cell engraftment, the GMP to myeloid engraftment and the MLP mainly to B cell output. Population RNA sequencing revealed distinct transcriptional signatures of these populations: MLP signature was enriched for lymphoid-affiliated genes, GMP for myeloid-affiliated genes and LMPP had a hybrid lympho-myeloid signature. Single cell RNA sequencing of 320 LMPP, MLP and GMP cells showed that the 3 progenitor populations form a transcriptional continuum. Linking the single cell gene expression to FACS indexing allowed exclusive purification of lymphoid- and myeloid-only progenitors from the current LMPP and GMP populations.Conclusions: These data change our understanding of human hematopoiesis and offer a radically new model of human lympho-myeloid progenitor specification. This model may have important implications for human immune deficiencies and hemopoietic malignancies.BS and DK contributed equally to this work. FH and AR contributed equally to this work. DisclosuresQuek:Celgene Corporation: Research Funding. Vyas:Jazz Pharmaceuticals: Speakers Bureau; Celgene Corporation: Speakers Bureau.

MUFAs in High-Fat Diets Protect against Obesity-Induced Bias of Hematopoietic Cell Lineages.

The role of dietary fatty acids in the generation of bone marrow (BM) immune cells and their trafficking to extramedullary compartments in the obesity is not yet fully understood. C57BL/6J mice are randomly assigned to isocaloric high-fat diets (HFDs) formulate with dietary fats rich in saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) or MUFAs fortified with eicosapentaenoic and docosahexaenoic acids for 20 weeks, followed by profiling of the obese metabolic phenotype and immunophenotypic features of immune cells in blood, spleen, and BM. All HFDs induce an obese phenotype, but it becomes largely less disruptive after the HFDs are enriched in MUFAs, which also induce signs of granulopoiesis and an expansion of long-term hematopoietic stem and granulocyte-macrophage progenitor cells in BM. In contrast, a HFD enriched in SFAs disturbs the fitness of medullary lymphocytes and promotes monopoiesis in favor of pro-inflammatory activated subsets. The reshaping of the fatty acid pools with MUFAs from the diet serves to manipulate the generation and trafficking of immune cells that are biased during obesity. These findings reveal a novel strategy by which dietary MUFAs may be instrumental in combating HFD-induced dysfunctional immune systems.

MYC-induced human acute myeloid leukemia requires a continuing IL-3/GM-CSF costimulus

AbstractHematopoietic clones with leukemogenic mutations arise in healthy people as they age, but progression to acute myeloid leukemia (AML) is rare. Recent evidence suggests that the microenvironment may play an important role in modulating human AML population dynamics. To investigate this concept further, we examined the combined and separate effects of an oncogene (c-MYC) and exposure to interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and stem cell factor (SCF) on the experimental genesis of a human AML in xenografted immunodeficient mice. Initial experiments showed that normal human CD34+ blood cells transduced with a lentiviral MYC vector and then transplanted into immunodeficient mice produced a hierarchically organized, rapidly fatal, and serially transplantable blast population, phenotypically and transcriptionally similar to human AML cells, but only in mice producing IL-3, GM-CSF, and SCF transgenically or in regular mice in which the cells were exposed to IL-3 or GM-CSF delivered using a cotransduction strategy. In their absence, the MYC+ human cells produced a normal repertoire of lymphoid and myeloid progeny in transplanted mice for many months, but, on transfer to secondary mice producing the human cytokines, the MYC+ cells rapidly generated AML. Indistinguishable diseases were also obtained efficiently from both primitive (CD34+CD38−) and late granulocyte-macrophage progenitor (GMP) cells. These findings underscore the critical role that these cytokines can play in activating a malignant state in normally differentiating human hematopoietic cells in which MYC expression has been deregulated. They also introduce a robust experimental model of human leukemogenesis to further elucidate key mechanisms involved and test strategies to suppress them.

Abstract 4497: A single-cell multiomics approach to study tumor-driven perturbations during hematopoiesis in mice

Abstract Cancer is associated with concomitant myeloid cell responses that are characterized by an expansion of tumor associated myeloid cells including, myeloid derived suppressor cells (MDSCs), tumor associated macrophages (TAMs) and neutrophils (TANs). These myeloid derived cells are known to modulate immune responses that enhance cancer cell stemness, angiogenesis, metastasis, invasion and immune escape. The prevailing paradigm is that cancer interferes with hematopoiesis and skews the host system to generate cells of myeloid origin with tumor-promoting functions. Intriguingly, tumor derived factors can perturbate normal bone marrow hematopoiesis and promote extramedullary hematopoiesis in organs such as the spleen. Advances in single cell multiomic technologies now enable the analysis of high dimensional protein and mRNA expression from thousands of cells simultaneously. Using the power of the BD Rhapsody™ Single-Cell Analysis system, we have carefully investigated melanoma associated extramedullary hematopoiesis in mice. To do this, we isolated four hematopoietic stem and progenitor cell populations simultaneously, including Lin- Sca-1+ c-Kit+ (LSK), common myeloid progenitor (CMP), granulocyte-macrophage progenitor (GMP) and megakaryocyte-erythrocyte progenitor (MEP) cells from the spleen and bone marrow of melanoma-bearing mice using the BD FACSMelody™ cell sorter in combination with a multiplex BD® AbSeq Oligos panel for surface protein expression and a single-cell whole transcriptome analysis. Using advanced analysis plugins in SeqGeq™ software, we were able to delineate the developmental trajectories of these hematopoietic stem and progenitor cells in this systemic immuno-suppressive myeloid environment. These advanced technologies are critical to uncover tumor mediated abnormalities in hematopoiesis. Disclaimers: For Research Use Only. Not for use in diagnostic or therapeutic procedures. Class 1 Laser Product. BD, the BD Logo, FACSMelody and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2019 BD. All rights reserved. Citation Format: Nihan Kara, Xiaoshan Shi, Nikolay Samusik, Stephanie Widmann, Aaron J. Tyznik. A single-cell multiomics approach to study tumor-driven perturbations during hematopoiesis in mice [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4497.

A single-cell multiomics approach to study tumor-driven perturbations during hematopoiesis in mice

Abstract Cancer is associated with concomitant myeloid cell responses that are characterized by an expansion of tumor associated myeloid cells, including myeloid derived suppressor cells, tumor associated macrophages and neutrophils. The prevailing paradigm is that cancer interferes with normal hematopoiesis by skewing the generation of myeloid cells with tumor promoting functions and promoting extramedullary hematopoiesis in organs such as the spleen. Advances in single cell multiomic technologies now enable the analysis of high dimensional protein and mRNA expression from thousands of cells simultaneously. Using the power of the BD Rhapsody™ Single-Cell Analysis System, we have carefully investigated melanoma associated extramedullary hematopoiesis in mice. To do this, we isolated 4 hematopoietic stem and progenitor cell populations simultaneously, including Lin− Sca-1+ c-Kit+, common myeloid progenitor, granulocyte-macrophage progenitor, and megakaryocyte-erythrocyte progenitor cells from the spleen and bone marrow of melanoma bearing mice using the BD FACSMelody™ cell sorter in combination with a multiplex BD® AbSeq Oligos panel for surface protein expression and a single-cell whole transcriptome analysis. Using advanced analysis plugins in SeqGeq™ software, we were able to delineate the developmental trajectories of these hematopoietic stem and progenitor cells in this systemic immuno-suppressive myeloid environment. These advanced technologies are critical to uncover tumor mediated abnormalities in hematopoiesis. Disclaimers: For Research Use Only. Class 1 Laser Product. BD, the BD Logo, FACSMelody and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2019 BD. All rights reserved.

Ionizing radiation induces ferroptosis in granulocyte-macrophage hematopoietic progenitor cells of murine bone marrow

Purpose: To study whether radiation-induced bleeding in the bone marrow induced iron accumulation, and subsequently caused ferroptosis in granulocyte-macrophage hematopoietic progenitor cells.Materials and methods: Male mice were subjected to different doses (0, 4, 8, or 10 Gy) of gamma radiation from a 137Cs source. The changes in iron metabolism or ferroptosis-related parameters of irradiated bone marrow were accessed with biochemical, histopathological, and antibody methods. Hematocytes were detected with a hematology analyzer. The counts of granulocyte-macrophage hematopoietic progenitor cells were measured with the granulocyte-macrophage colony-forming unit.Results: Iron accumulation occurred in the bone marrow, which caused by radiation-induced hemorrhage. The iron accumulation triggered an iron regulatory protein-ferroportin 1 axis to increase serum iron levels. Using LDN193189, radiation-induced iron accumulation was demonstrated to decrease white blood cell counts at least partly through a decrease in the counts of granulocyte-macrophage hematopoietic progenitor cells. The reduction in the counts of granulocyte-macrophage hematopoietic progenitor cells was subsequently demonstrated to attribute to ferroptosis with the use of ferroptosis inhibitors and through the detection of ferroptosis related-parameters. The survival rate of irradiated mice was improved using Ferrostatin-1 or LDN193189.Conclusions: These findings suggest that radiation-induced hemorrhage in the bone marrow causes ferroptosis in granulocyte-macrophage hematopoietic progenitor cells, and anti-ferroptosis has the potential to be a radioprotective strategy to ameliorate radiation-induced hematopoietic injury.

Reveal the Neutrophil: Elucidating the Role of a Neutrophil-Specific JAK2-V617F Mutation

Introduction: Myeloproliferative neoplasms (MPN) are characterized by monoclonal proliferation of myeloid cells. The clinical presentation of classic BCR-ABL negative MPN includes blood count changes, splenomegaly, chronic inflammation and, prognostically relevant, thrombosis. Within polycythemia vera, essential thrombocythemia and primary myelofibrosis, the most frequent genetic alteration is the point mutation V617F (VF) in the Jak2 gene. Due to an activation of leucocyte β1 and β2 integrins, in particular on neutrophils, JAK2-VF is driving thrombus formation (Edelmann et al., JCI, 2018). Thus, understanding the role of neutrophils within JAK2-VF-positive MPN is of special interest. We developed a murine JAK2-VF Catchup model of MPN that is characterized by the neutrophil-specific expression of JAK2-VF in combination with the fluorescent protein tdTomato allowing in-vivo two-photon microscopy. Neutrophil-specificity was achieved through a knock-in allele of Cre recombinase and tdTomato replacing exon 1 of Ly6G (Hasenberg et al., Nat Methods, 2015). Methods: The murine JAK2-VF Catchup model was developed by crossing JAK2+/loxP-VF-loxP mice and Ly6G+/Cre-tdTomato CatchupIVM-red mice. Experiments were performed in 12 weeks old JAK2+/loxP-VF-loxP Ly6G+/Cre-tdTomato CatchupIVM-red (JAK2+/VF Catchup) mice (n=5) and JAK2+/+ Ly6G+/Cre-tdTomato CatchupIVM-red (JAK2+/+ Catchup) mice (n=5) as wildtype (WT) controls. Whole blood cell counts and spleen weight were determined. Bone marrow (BM) cells were harvested from hind limbs followed by isolation of granulocytes using negative selection. In order to determine hematopoietic stem and progenitor cells (HSPCs), BM and spleen cell suspensions were analyzed by flow cytometry (FC). Using ICAM-1, VCAM-1, E-selectin and P-selectin, each with and without Fc-tag, adhesion properties of the isolated granulocytes were examined by either FC or microplate reader analysis. The expression of β1 integrin was further analyzed by FC. Results and Discussion: JAK2+/VF Catchup mice showed a slight but significant increase in platelet counts [1544±58.02 Gpt/l; WT: 1190±90.50 Gpt/l; p=0.011], with the mean value still remaining within the normal range. Hematocrit, red blood cell, white blood cell and neutrophil count as well as spleen weight were also within the normal range showing no differences from their WT controls. Interestingly, neutrophil and platelet counts of JAK2+/VF Catchup mice significantly correlated with one another [p=0.0251; R2=0.8529]. MPN-typical changes in number and composition of c-Kit+ HSPCs in either BM or spleen could not be found in JAK2+/VF Catchup mice. Directly compared to reliably MPN-developing Vav-1-Cre JAK2+/VF mice, JAK2+/VF Catchup mice showed significantly less megakaryocyte-erythroid progenitor (MEP), Lin- Sca1+ c-Kit+ (LSK) and multipotent progenitor cells (MPP) in the BM. In spleen of JAK2+/VF Catchup mice, the fractions of Lin- c-Kit+ (LK) and granulocyte-macrophage progenitor cells (GMP) were significantly lower compared to Vav-1-Cre JAK2+/VF mice. Thus, the neutrophil-specific JAK2-VF mutation does not lead to apparent numerical or compositional changes of HSPCs. These results show that a neutrophil-specific JAK2-VF mutation is not sufficient to induce a characteristic phenotype of JAK2-VF-positive MPN. The expression of β1 integrin on granulocytes was significantly increased in JAK2+/VF Catchup mice [fold change vs. control; 1.126±0.041; WT: 1.0±0.011; p=0.0194]. Unexpectedly, despite increased β1 integrin expression, the binding of granulocytes from JAK2+/VF Catchup mice to either ICAM-1, VCAM-1, E-selectin or P-selectin corresponded to that of their WT controls. Static adhesion and soluble ligand binding assays showed similar results. Since adhesion of granulocytes appeared unchanged in-vitro, we hypothesize that expression of JAK2-VF in neutrophils is not sufficient to overactivate integrins but secondary extrinsic signals (e.g. cytokines) may play a dominant role. Further experimentation is under way to elucidate this molecular mechanism. Conclusions: In order to dissect the properties of JAK2-VF-positive neutrophils, the JAK2-VF Catchup model represents a promising murine model of MPN. Herewith, the initiation of thrombosis and the development of other granulocyte-driven disease manifestations of JAK2-VF induced MPN can be thoroughly examined. Disclosures No relevant conflicts of interest to declare.

The Impact of Integrin β2 on Granulocyte/Macrophage Progenitor Proliferation.

Previously, we reported that although the HSPC frequency in bone marrow cells (BMC) was comparable between β2−/− and β2+/+ mice, transplantation of β2−/− BMC into lethally irradiated CD45.1 recipient resulted in more myeloid cell production than β2+/+ BMC. The objective of this study is to address if integrin β2 deficiency skews granulocyte/macrophage progenitor (GMP) proliferation. FACS analysis demonstrated that GMP frequency and cell number were higher and megakaryocyte/erythrocyte progenitor frequency and cell number were lower in β2−/− mice than β2+/+ mice. However, the common myeloid progenitors (CMP) frequency and cell number were similar between the two groups. The increased GMP number was due to GMP proliferation as evidenced by the percentage of BrdU‐incorporating GMP. Whole genome transcriptome analysis identified increased FcεRIα expression in β2−/− CMP compared to β2+/+ CMP. FcεRIα expression on β2−/− GMP was detected increased in β2−/− mice by qRT‐PCR and FACS. Although transplantation of FcεRIαhi GMP or FcεRIαlo GMP into lethally irradiated CD45.1 recipient resulted in comparable myeloid cell production, transplantation of β2 deficient FcεRIαhi GMP generated more myeloid cells than β2+/+ FcεRIαhi GMP. GATA2 expression was increased in β2−/− GMP. Using a luciferase reporter assay, we demonstrated that mutation of the GATA2 binding site in the FcεRIα promoter region diminished FcεRIα transcription. In vitro, the addition of IgE, the ligand of FcεRIα, promoted GMP expansion, which was abrogated by inhibition of JNK phosphorylation. Integrin β2 deficiency promoted GMP proliferation and myeloid cell production, which was mediated via FcεRIα/IgE‐induced JNK phosphorylation in GMP. Stem Cells 2019;37:430–440

CCAAT/enhancer-binding protein alpha (CEBPA) gene haploinsufficiency does not alter hematopoiesis or induce leukemia in Lck-CALM/AF10 transgenic mice.

Although rare, CALM/AF10 is a chromosomal rearrangement found in immature T-cell acute lymphoblastic leukemia (T-ALL), acute myeloid leukemia, and mixed phenotype acute leukemia of T/myeloid lineages with poor prognosis. Moreover, this translocation is detected in 50% of T-ALL patients with gamma/delta T cell receptor rearrangement, frequently associated with low expression of transcription factor CCAAT/enhancer-binding protein alpha (CEBPA). However, the relevance of CEBPA low expression for CALM/AF10 leukemogenesis has not yet been evaluated. We generated double mutant mice, which express the Lck-CALM/AF10 fusion gene and are haploinsufficient for the Cebpa gene. To characterize the hematopoiesis, we quantified hematopoietic stem cells, myeloid progenitor cells, megakaryocyte-erythrocyte progenitor cells, common myeloid progenitor cells, and granulocyte-macrophage progenitor cells. No significant difference was detected in any of the progenitor subsets. Finally, we tested if Cebpa haploinsufficiency would lead to the expansion of Mac-1+/B220+/c-Kit+ cells proposed as the CALM/AF10 leukemic progenitor. Less than 1% of bone marrow cells expressed Mac-1, B220, and c-Kit with no significant difference between groups. Our results showed that the reduction of Cebpa gene expression in Lck-CALM/AF10 mice did not affect their hematopoiesis or induce leukemia. Our data corroborated previous studies suggesting that the CALM/AF10 leukemia-initiating cells are early progenitors with lymphoid/myeloid differentiating potential.

Rap1 Gtpases Regulate the Retention and Engraftment of Hematopoietic Stem and Progenitor Cells

Signaling molecules that control the homing and mobilization of hematopoietic stem and progenitor cells (HSC/Ps) are poorly understood. Rap1, a small-molecular-weight GTP-binding protein belongs to the Ras-like superfamily of GTPases and regulates several signal transduction cascades. Rap1 cycles between a GDP-bound inactive and a GTP-bound active form and exists in two isoforms - Rap1a and Rap1b, which have been implicated in the regulation of actin based functions in non-hematopoietic cells. Although Rap1 has been involved in regulating several hematologic disorders including chronic lymphocytic leukemia, myeloproliferative stem cell disorders, polycythemia vera and sickle cell anemia, its role in the development and function of HSC/Ps has not been investigated. We have generated a mouse model in which both Rap1a and Rap1b isoforms were conditionally deleted in HSC/Ps individually or in combination (double knockout; DKO). Our results demonstrate that deletion of both isoforms of Rap1 results in profound mobilization of primitive hematopoietic stem cells in peripheral blood. In the bone marrow, Rap1ab deficiency shows increased frequency of LSK cells, HPC-1 (LSK CD150-CD48+), HPC-2 (LSK CD150+CD48+) along with an increase in granulocyte-macrophage progenitor cell (GMP) population. Furthermore, spleen size and cellularity were significantly enhanced in DKO mice relative to controls. We hypothesized that Rap1 plays an essential role in regulating the retention of HSC/Ps in the bone marrow (BM) and that loss of Rap1 might inhibit the interaction of HSC/Ps with the BM niche cells, leading to egress of HSC/Ps and thus creating empty space(s) in the marrow for enhanced engraftment of donor derived cells when transplanted under non-myeloablative conditions. To test this, we performed BM transplantation using Rap1ab DKO mice as recipients and WT GFP expressing HSC/Ps as donors in the absence of any myeloablative conditioning. Our long-term engrfatment results showed significantly greater donor derived reconstitution of GFP positive cells in peripheral blood of DKO recipients compared to WT controls (WT: 19.2% vs DKO: 82.18% n=3, *p<0.05), suggesting that loss of Rap1ab creates functional open niche(s) in the BM due to mobilization of endogenous HSC/Ps. To better understand the mechanism behind this observation and to determine whether the GFP donor cells localize closer to the endosteal or vascular niche, we transplanted GFP positive cells into unconditioned (non-myeloablative) WT and Rap1ab DKO mice as described above. We measured the median distance of engrafted GFP cells from the bone surface and vasculature as a measure of proximity utilizing intravital microscopy. DKO recipients, transplanted with WT HSC/Ps preferentially localized to the vascular niche compared to control WT recipients (WT: 8µm vs DKO: 3 µm) and compared to osteoblastic niche, which was comparable in the two recipients, suggesting that GFP+ donor HSC/Ps preferentially localize and engraft near vascular niches providing indirect evidence to suggest that loss of Rap1ab leads to egress of hematopoietic cells from the vascular niche as opposed to osteoblastic niche. We next assessed the potential of Rap1ab deficient cells to engraft in a lethally irradiated host in a competitive repopulation assay. Rap1ab DKO HSC/Ps showed a defect in engraftment as well as multi-lineage reconstitution when transplanted into lethally irradiated hosts compared to WT controls. The defect in engraftment was largely due to impaired homing of DKO HSC/Ps. To assess which specific isoform of Rap1 is essential for mobilization and engraftment/homing of HSC/Ps, we induced deletion in Rap1a and Rap1b separately (single knock out mice) and assessed these mice for peripheral blood cell counts. We found no significant changes in the peripheral WBC counts in single Rap1a KO mice relative to controls; and only a modest increase in single Rap1b KO mice; suggesting that mobilization of HSC/Ps was relatively unperturbed in these mice and requires the loss of both isoforms of Rap1. In contrast, engraftment of HSC/Ps derived from the single KOs of Rap1a and Rap1b was impaired to the same extent as DKO HSC/Ps. These data suggest that loss of single Rap1 isoform contributes similarly to the engraftment of HSC/Ps, whereas the combined loss of both isoforms is required for efficient mobilization of HSC/Ps. DisclosuresNo relevant conflicts of interest to declare.

The Depletion of TGF-β Co-Receptor CD109 Induces Erythroid Differentiation of TF-1 Cells: A Model of Preferential Commitment of PIGA-Mutated Hematopoietic Stem Cells in Immune-Mediated Bone Marrow Failure

[Background] Glycosylphosphatidylinositol-anchored proteins (GPI-APs) on hematopoietic stem progenitor cells (HSPCs) may play an important role in the regulation of the HSPC commitment, given the fact that a lack of GPI-APs due to PIGA mutations allows HSPCs to preferentially undergo commitment into mature blood cells under immune pressure against HSPCs in patients with acquired aplastic anemia. CD109, one of the GPI-APs expressed by keratinocytes and HSPCs in humans, serves as a TGF-β co-receptor and is reported to inhibit TGF-β signaling in keratinocytes; however, the role of CD109 on HSPCs has not been clarified. TF-1 is one of a few myeloid leukemia cell lines that express CD109, the proliferation of which is dependent on GM-CSF. Since TF-1 undergoes erythroid differentiation in response to δ-5-aminolevulinic acid (δ-ALA), and its differentiation is reportedly inhibited by TGF-β, a lack of GPI-APs due to PIGA mutation and/or the knockout (KO) of CD109 may affect the differentiation of TF-1 cells. [Objectives/Methods] To gain insights into the role of GPI-APs on HSPCs, we established a PIGA-mutated TF-1 cell line by culturing TF-1 in the presence of α-toxin for several months, and a CD109 KO TF-1 cell line using a CRISPR-Cas 9 system. The erythroid differentiation of the cells was assessed by testing the expression of glycophorin A (GPA) on TF-1 cells using flow cytometry (FCM) and iron staining. We also determined the CD109 expression by HSPCs from healthy individuals and C57BL/6 mice using FCM and a quantitative PCR. [Results] Both GPI-AP-deficient TF-1 cells that had a PIGA mutation (7 nucleotide deletion at position 291-297 [TTGTCAC] in exon 2) and CD109 KO TF-1 cells showed slower proliferation than wild-type (WT) TF-1 cells. Similarly to TF-1 cells treated with δ-ALA, both mutant cells expressed GPA, exhibited erythroid morphology, and were positive for iron granules, suggesting that GPI-APs inhibited the erythroid differentiation of WT TF-1 cells that were cultured in RPMI1640 containing 10% fetal bovine serum (FBS), and that the GPI-AP that plays a key role in the inhibition of erythroid differentiation is CD109. Since low levels (1-2 ng/ml) of TGF-β in the serum-containing culture medium were suspected to inhibit the erythroid differentiation of WT TF-1 through its binding to CD109, WT TF-1 cells were cultured in a serum-free medium Expi293 Expression Medium for 10 days. While control TF-1 cells cultured in the serum-containing RPMI1640 were negative for the expression of GPA, 77.0-84.5% of the cultured TF-1 cells expressed GPA and exhibited erythroid morphology. CD109 was expressed by 12.1-18.3% of CD34+CD38- cells, 4.5-7.4% of common myeloid progenitor cells (CMPs), 20.8-42.4% of megakaryocyte-erythrocyte progenitor cells (MEPs), and 14.2-22.0% of granulocyte macrophage progenitor cells (GMPs) in the bone marrow of healthy individuals, while murine CD48-CD150+CD34- LSK cells were negative for either CD109 protein or mRNA. [Conclusions] CD109 protects TF-1 cells from differentiating into erythroid cells in serum-containing culture. In contrast to keratinocytes, the CD109 on TF-1 cells, and possibly on HSPCs, may enhance TGF-β signaling, and the lack of the GPI-AP might make PIGA-mutated HSPCs insensitive to TGF-β, leading to the preferential commitment of mutant HSPCs to mature blood cells in immune-mediated bone marrow failure. [Display omitted] DisclosuresNakao:Kyowa Hakko Kirin Co., Ltd.: Honoraria; Novartis: Honoraria; Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria.

Postnatal Administration of Lactobacillus rhamnosus HN001 Ameliorates Perinatal Broad-Spectrum Antibiotic-Induced Reduction in Myelopoiesis and T Cell Activation in Mouse Pups.

This study addresses whether administration of Lactobacillus rhamnosus HN001 could mitigate the effects of a compromised gut microbiota on the composition of mature leukocytes and granulocyte-macrophage progenitor cells (GMPs) in newborn mice. Pregnant dams receive oral broad-spectrum antibiotics, which dramatically decrease the gut microbial composition analyzed by 16S rRNA sequencing. Perinatal antibiotic treatment decreases the proportions of bone marrow (BM) GMPs (postnatal day (PND2): 0.5% vs 0.8%, PND4: 0.2% to 0.6%) and mature granulocytes (33% vs 24% at PND2), and spleen granulocytes (7% vs 17% at PND2) and B cells (PND2:18% vs 28%, PND4:11% vs 22%). At PND35, T helper (Th) cells (20% vs 14%) and cytotoxic T (Tc) cells (10% vs 8%) decrease in the spleen. Oral administration of L. rhamnosus HN001 to neonatal pups (PND1-7) restores the antibiotic-induced changes of GMPs and granulocytes in BM and spleen, and further increases splenic granulocytes in control pups. At PND35, splenic proportions of B and Th but not Tc cells are restored. Postnatal administration of a single bacterial strain efficiently restores granulopoiesis and most T cell activation in neonatal mice that suffer from a perinatal antibiotic-induced compromised gut microbiota at birth.

Granulocyte-macrophage progenitor cells response to magnetite nanoparticles in a static magnetic field

The ability to modulate the life process of stem cells conjugated with MNPs via a magnetic field is promising as multifunctional tool in biomedicine. Experiment on mice demonstrates the high accumulation of iron ions measured via stripping voltammetry in the bone marrow in respect to bone, liver or kidney. Therefore, the potential cytotoxic effects of iron oxide magnetic nanoparticles (MNPs) on bone marrow cells become more predictable in comparison with the other examined cells. This study examined in vitro responses of mouse bone marrow-derived granulocyte–macrophage committed stem cells (colony-forming units of granulocytes and macrophages, CFU-GM) to a controlled amount of MNPs prepared by the exploding wire method; and to a moderate static magnetic field (SMF) of about 160 Oe. The moderate SMF did not affect CFU-GM capacity. Two different regimes of bone marrow cells cultivation with MNPs were investigated. Remarkably, adding MNPs to cells either decreased (1st cultivation regime, 6 pg MNPs per 1 cell) or enhanced (2nd regime, 20 pg MNPs per 1 cell) the colony-forming activity of CFU-GM, depending on the regimes of cultivation. The action of a moderate SMF on cells cultivated with MNPs inverts their effects on stem cell colony formation. Possible mechanisms of these phenomena are discussed. The main pathway was explained by a change in the presence of iron, either inside or outside of the cell, following the formation of free radicals susceptible to SMFs. Nanoscale magnetite activity within the pool of bipotent hemopoietic stem cells supports its proposed usage as supplement in cell technologies, theranostics, bone marrow repair and regenerative medicine. Further study is necessary to examine the intra- and intercellular mechanisms of the SMF’s modulating effect on stem cell activity caused by magnetite MNPs.

DNA damage tolerance in hematopoietic stem and progenitor cells in mice

DNA damage tolerance (DDT) enables bypassing of DNA lesions during replication, thereby preventing fork stalling, replication stress, and secondary DNA damage related to fork stalling. Three modes of DDT have been documented: translesion synthesis (TLS), template switching (TS), and repriming. TLS and TS depend on site-specific PCNA K164 monoubiquitination and polyubiquitination, respectively. To investigate the role of DDT in maintaining hematopoietic stem cells (HSCs) and progenitors, we used PcnaK164R/K164R mice as a unique DDT-defective mouse model. Analysis of the composition of HSCs and HSC-derived multipotent progenitors (MPPs) revealed a significantly reduced number of HSCs, likely owing to increased differentiation of HSCs toward myeloid/erythroid-associated MPP2s. This skewing came at the expense of the number of lymphoid-primed MPP4s, which appeared to be compensated for by increased MPP4 proliferation. Furthermore, defective DDT decreased the numbers of MPP-derived common lymphoid progenitor (CLP), common myeloid progenitor (CMP), megakaryocyte-erythroid progenitor (MEP), and granulocyte-macrophage progenitor (GMP) cells, accompanied by increased cell cycle arrest in CMPs. The HSC and MPP phenotypes are reminiscent of premature aging and stressed hematopoiesis, and indeed progressed with age and were exacerbated on cisplatin exposure. Bone marrow transplantations revealed a strong cell intrinsic defect of DDT-deficient HSCs in reconstituting lethally irradiated mice and a strong competitive disadvantage when cotransplanted with wild-type HSCs. These findings indicate a critical role of DDT in maintaining HSCs and progenitor cells, and in preventing premature aging.

Abstract 5595: HDAC inhibitor Entinostat disrupts function of PMN-MDSC

Abstract Myeloid-derived suppressor cells (MDSCs), consisting of subpopulations of polymorphonuclear (PMN; CD11b+Ly6G+Ly6Clo) and monocytic (M; CD11b+Ly6G-Ly6Chi) MDSCs play a major role as immune suppressors in cancer. MDSC-targeted therapy has not been developed yet. Histone deacetylases (HDAC) are critically involved in epigenetic regulation of multiple genes and may regulate MDSC number and function. The purpose of this study was to evaluate the effect of the class I HDAC inhibitor, entinostat on differentiation and function of MDSCs in mouse tumor models of lung cancer (Lewis Lung Carcinoma, LLC) and colon cancer (CT26). LLC and CT26 tumor-bearing mice were treated with entinostat (10 mg/kg, p.o. daily for two weeks). Entinostat caused significant increase in the presence of CD45+ CD11b+ myeloid cells in bone marrow, spleen and tumors. This increase was largely due to accumulation of Ly6ClowLy6G+ PMN. Unexpectedly, this was associated with a small decrease in the presence of common myeloid progenitor (CMP) and granulocyte-macrophage progenitor (GMP) cells in bone marrow. This suggests that entinostat affects differentiation of PMN downstream of GMP. Experiments in vitro demonstrated that entinostat increased differentiation of enriched hematopoietic progenitor cells (HPC) to PMN in the presence of tumor explant supernatant (TES), which supported the in vivo result. To assess the effect of entinostat on the function of PMN-MDSCs, Ly6G+ cells were purified from spleen and tumor of LLC tumor-bearing mice treated with entinostat or vehicle alone and tested for their ability to suppress antigen-specific T cell. As expected Ly6G+ PMN-MDSC from tumor-bearing mice treated with vehicle alone had strong suppressive activity. In contrast, Ly6G+ cells from spleen and tumor of entinostat-treated LLC tumor-bearing mice show significantly reduced suppressive activity. This result was confirmed in experiments with Ly6G+ cells differentiated from HPC culture with/without entinostat treatment. To determine whether entinostat inhibition of PMN-MDSC immunosuppressive function could enhance immune checkpoint activity, entinostat combined with an anti-PD-1 antibody was evaluated using the LLC tumor-bearing mice. These mice were treated with entinostat (10 mg/kg, p.o., daily) and anti-mouse PD-1 rat antibody (10 mg/kg, i.p., twice a week). Entinostat or PD-1 antibody alone did not significantly inhibit the tumor growth. In striking contrast, the combination treatment blocked tumor progression. Our data demonstrate that entinostat increases a population of PMN-MDSCs that are no longer immunosuppressive leading to enhanced anti-tumor activity when combined with an immune checkpoint inhibitor. This novel phenomenon provides further rationale for combination therapy of entinostat with anti-PD-1 antibody or other checkpoint inhibitors in clinical settings. Citation Format: Ayumi Hashimoto, Vinit Kumar, Peter Ordentlich, Dmitry I. Gabrilovich. HDAC inhibitor Entinostat disrupts function of PMN-MDSC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5595. doi:10.1158/1538-7445.AM2017-5595

Inhibition of Pol I transcription treats murine and human AML by targeting the leukemia-initiating cell population

AbstractDespite the development of novel drugs, the prospects for many patients with acute myeloid leukemia (AML) remain dismal. This study reveals that the selective inhibitor of RNA polymerase I (Pol I) transcription, CX-5461, effectively treats aggressive AML, including mixed-lineage leukemia-driven AML, and outperforms standard chemotherapies. In addition to the previously characterized mechanism of action of CX-5461 (ie, the induction of p53-dependent apoptotic cell death), the inhibition of Pol I transcription also demonstrates potent efficacy in p53null AML in vivo. This significant survival advantage in both p53WT and p53null leukemic mice treated with CX-5461 is associated with activation of the checkpoint kinases 1/2, an aberrant G2/M cell-cycle progression and induction of myeloid differentiation of the leukemic blasts. The ability to target the leukemic-initiating cell population is thought to be essential for lasting therapeutic benefit. Most strikingly, the acute inhibition of Pol I transcription reduces both the leukemic granulocyte-macrophage progenitor and leukemia-initiating cell (LIC) populations, and suppresses their clonogenic capacity. This suggests that dysregulated Pol I transcription is essential for the maintenance of their leukemia-initiating potential. Together, these findings demonstrate the therapeutic utility of this new class of inhibitors to treat highly aggressive AML by targeting LICs.

BCAP inhibits proliferation and differentiation of myeloid progenitors in the steady state and during demand situations

AbstractB-cell adaptor for phosphatidylinositol 3-kinase (BCAP) is a signaling adaptor expressed in mature hematopoietic cells, including monocytes and neutrophils. Here we investigated the role of BCAP in the homeostasis and development of these myeloid lineages. BCAP−/− mice had more bone marrow (BM) monocytes than wild-type (WT) mice, and in mixed WT:BCAP−/− BM chimeras, monocytes and neutrophils skewed toward BCAP−/− origin, showing a competitive advantage for BCAP−/− myeloid cells. BCAP was expressed in BM hematopoietic progenitors, including lineage−Sca-1+c-kit+ (LSK), common myeloid progenitor, and granulocyte/macrophage progenitor (GMP) cells. At the steady state, BCAP−/− GMP cells expressed more IRF8 and less C/EBPα than did WT GMP cells, which correlated with an increase in monocyte progenitors and a decrease in granulocyte progenitors among GMP cells. Strikingly, BCAP−/− progenitors proliferated and produced more myeloid cells of both neutrophil and monocyte/macrophage lineages than did WT progenitors in myeloid colony-forming unit assays, supporting a cell-intrinsic role of BCAP in inhibiting myeloid proliferation and differentiation. Consistent with these findings, during cyclophosphamide-induced myeloablation or specific monocyte depletion, BCAP−/− mice replenished circulating monocytes and neutrophils earlier than WT mice. During myeloid replenishment after cyclophosphamide-induced myeloablation, BCAP−/− mice had increased LSK proliferation and increased numbers of LSK and GMP cells compared with WT mice. Furthermore, BCAP−/− mice accumulated more monocytes and neutrophils in the spleen than did WT mice during Listeria monocytogenes infection. Together, these data identify BCAP as a novel inhibitor of myelopoiesis in the steady state and of emergency myelopoiesis during demand conditions.