Inflammation rapidly recruits mammalian GMP and MDP from bone marrow into regional lymphatics.

Innate immune cellular effectors are actively consumed during systemic inflammation, but the systemic traffic and the mechanisms that support their replenishment remain unknown. Here, we demonstrate that acute systemic inflammation induces the emergent activation of a previously unrecognized system of rapid migration of granulocyte-macrophage progenitors and committed macrophage-dendritic progenitors, but not other progenitors or stem cells, from bone marrow (BM) to regional lymphatic capillaries. The progenitor traffic to the systemic lymphatic circulation is mediated by Ccl19/Ccr7 and is NF-κB independent, Traf6/IκB-kinase/SNAP23 activation dependent, and is responsible for the secretion of pre-stored Ccl19 by a subpopulation of CD205+/CD172a+ conventional dendritic cells type 2 and upregulation of BM myeloid progenitor Ccr7 signaling. Mature myeloid Traf6 signaling is anti-inflammatory and necessary for lymph node myeloid cell development. This report unveils the existence and the mechanistic basis of a very early direct traffic of myeloid progenitors from BM to lymphatics during inflammation.

When the body becomes infected with disease-causing pathogens, such as bacteria, the immune system activates various mechanisms which help to fight off the infection. One of the immune system's first lines of defense is to launch an inflammatory response that helps remove the pathogen and recruit other immune cells. However, this response can become overactivated, leading to severe inflammatory conditions that damage healthy cells and tissues. A second group of cells counteract this over inflammation and are different to the ones involved in the early inflammatory response. Both types of cells ­ inflammatory and anti-inflammatory ­ develop from committed progenitors, which, unlike stem cells, are already destined to become a certain type of cell. These committed progenitors reside in the bone marrow and then rapidly travel to secondary lymphoid organs, such as the lymph nodes, where they mature into functioning immune cells. During this journey, committed progenitors pass from the bone marrow to the lymphatic vessels that connect up the different secondary lymphoid organs, and then spread to all tissues in the body. Yet, it is not fully understood what exact route these cells take and what guides them towards these lymphatic tissues during inflammation. To investigate this, Serrano-Lopez, Hegde et al. used a combination of techniques to examine the migration of progenitor cells in mice that had been treated with lethal doses of a bacterial product that triggers inflammation. This revealed that as early as one to three hours after the onset of infection, progenitor cells were already starting to travel from the bone marrow towards lymphatic vessels. Serrano-Lopez, Hegde et al. found that a chemical released by an "alarm" immune cell already residing in secondary lymphoid organs attracted these progenitor cells towards the lymphatic tissue. Further experiments showed that the progenitor cells travelling to secondary lymphoid organs were already activated by bacterial products. They then follow the chemical released by alarm immune cells ready to respond to the immune challenge and suppress inflammation. These committed progenitors were also found in the inflamed lymph nodes of patients. These findings suggest this rapid circulation of progenitors is a mechanism of defense that contributes to the fight against severe inflammation. Altering how these cells migrate from the bone marrow to secondary lymphoid organs could provide a more effective treatment for inflammatory conditions and severe infections. However, these approaches would need to be tested further in the laboratory and in clinical trials.

Describing the evolution of myeloid-derived leucocytes in treated B-lineage paediatric acute lymphoblastic leukaemia with a data-driven granulocyte-monocyte-blast model.

Acute lymphoblastic leukaemia (ALL) is associated with a compromised myeloid system. Understanding the state of granulopoiesis in a patient during treatment, places the clinician in an advantageous position. Mathematical models are aids able to present the clinician with insight into the behaviour of myeloid-derived leucocytes. The main objective of this investigation was to determine whether a proposed model of ALL during induction therapy would be a usable descriptor of the system. The model assumes the co-occurrence of the independent leukaemic and normal marrow populations. It is comprised of four delay-differential equations, capturing the fundamental characteristics of the blood and bone marrow myeloid leucocytes and B-lineage lymphoblasts. The effect of treatment was presumed to amplify cell loss within both populations. Clinical data was used to inform the construction, calibration and examination of the model. The model is promising-presenting a good foundation for the development of a clinical supportive tool. The predicted parameters and forecasts aligned with clinical expectations. The starting assumptions were also found to be sound. A comparative investigation highlighted the differing responses of similarly diagnosed patients during treatment and further testing on patient data emphasized patient specificity. Model examination recommended the explicit consideration of the suppressive effects of treatment on the normal population production. Additionally, patient-related factors that could have resulted in such different responses between patients need to be considered. The parameter estimates require refinement to incorporate the action of treatment. Furthermore, the myeloid populations require separate consideration. Despite the model providing explanation, incorporating these recommendations would enhance both model usability and predictive capacity.

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.

CXCR2 expression on granulocyte and macrophage progenitors under tumor conditions contributes to mo-MDSC generation via SAP18/ERK/STAT3.

Myeloid-derived suppressor cells (MDSCs) comprise a critical component of the tumor environment and CXCR2 reportedly plays a key role in the pathophysiology of various inflammatory diseases. Here, CXCR2 expression on granulocyte and macrophage progenitor cells (GMPs) was found to participate in myeloid cell differentiation within the tumor environment. In CXCR2-deficient tumor-bearing mice, GMPs exhibited fewer macrophage and dendritic cell progenitor cells than wild-type tumor-bearing mice, thereby decreasing monocytic MDSCs (mo-MDSCs) expansion. CXCR2 deficiency increased SAP18 expression in tumor-bearing mice, which reduced STAT3 phosphorylation through restraining ERK1/2 activation. Our findings reveal a critical role for CXCR2 in regulating hematopoietic progenitor cell differentiation under tumor conditions, and SAP18 is a key negative regulator in this process. Thus, inhibiting CXCR2 expression may alter the tumor microenvironment and attenuate tumor progression.

Reduction of CFU-GM and circulating hematopoietic progenitors in a subgroup of children with chronic neutropenia associated with severe infections and delayed recovery.

Myelopoiesis was evaluated in 66 pediatric patients with chronic neutropenia who were positive for anti-neutrophil antibodies (median age at diagnosis: 11 months, median neutrophil count at diagnosis: 419/µl). Other causes of neutropenia were excluded. Bone marrow morphology, clonogenic tests and/or the peripheral blood CD 34+ cell count, and apoptotic rate were evaluated in 61 patients with neutropenia lasting > 12 months or severe infections. The peripheral blood CD 34+ cell count and apoptotic rate were evaluated in five patients with shorter neutropenia. The median follow-up time was 29 months (range 7-180 months). Forty-seven patients (71.2%) had a spontaneous recovery after 7-180 months (median 29 months). The group of patients younger than 24 months at diagnosis (n = 50) had a higher probability of recovery (40/50 vs. 7/16 χ2 p<0.01) with a shorter period of neutropenia (median 26 versus 47 months, Kaplan-Meier analysis p = 0.001). The colony-forming units-granulocyte-macrophage (CFU-GM) were significantly decreased in 26/35 patients (74%) evaluated for clonogenic tests. All patients with normal CFU-GM recovered (9/9 patients); whereas, neutropenia persisted in 12/26 patients with reduced CFU-GM (46%, Pearson χ2 p = 0.02). In 36/55 (65%) patients evaluated by flow cytometry we observed reduced circulating CD34+ cells compared with controls of the same age. An increase in the circulating CD34+ cell apoptotic rate was observed in 28/55 patients (51%). Infections requiring hospitalization were observed in 9/18 (50%; Pearson χ2, p = 0.03) patients with both decreased circulating CD34+ cells and increased CD34+ apoptotic rates. In the group aged < 24 months, we observed a significant correlation between the persistence of neutropenia and decreased circulating CD34+ cells (Pearson χ2 p = 0.008). In conclusion, reduced CFU-GM and circulating hematopoietic progenitors were observed in a subgroup of children with chronic neutropenia who were positive for anti-neutrophil antibodies and had a higher incidence of severe infections and delayed spontaneous remission.

Hedgehog/GLI1 activation leads to leukemic transformation of myelodysplastic syndrome in vivo and GLI1 inhibition results in antitumor activity.

Myelodysplastic syndromes (MDSs) are stem cell disorders with risk of transformation to acute myeloid leukemia (AML). Gene expression profiling reveals transcriptional expression of GLI1, of Hedgehog (Hh) signaling, in poor-risk MDS/AML. Using a murine model of MDS we demonstrated that constitutive Hh/Gli1 activation accelerated leukemic transformation and decreased overall survival. Hh/Gli1 activation resulted in clonal expansion of phenotypically defined granulocyte macrophage progenitors (GMPs) and acquisition of self-renewal potential in a non-self-renewing progenitor compartment. Transcriptome analysis of GMPs revealed enrichment in gene signatures of self-renewal pathways, operating via direct Gli1 activation. Using human cell lines we demonstrated that in addition to canonical Hh signaling, GLI1 is activated in a Smoothened-independent manner. GLI1 knockdown or inhibition with GANT61 resulted in decreased proliferation and clonogenic potential. Our data suggest that GLI1 activation is frequent in MDS during disease progression and inhibition of GLI1 is an attractive therapeutic target for a subset of patients.

Sepsis Induces a Long-Lasting State of Trained Immunity in Bone Marrow Monocytes.

Innate immune memory describes the functional reprogramming of innate immune cells after pathogen contact, leading to either a boosted (trained immunity) or a diminished (immune tolerance) response to a secondary stimulus. Immune tolerance or "sepsis-induced immunosuppression" is a typical hallmark of patients after sepsis survival, characterized by hypo-responsiveness of the host's immune system. This condition renders the host vulnerable for a persisting infection or the occurrence of secondary, often opportunistic infections, along with an increased mortality rate. The mechanisms involved in the maintenance of this long-lasting condition are not examined yet. Polymicrobial abdominal sepsis was induced in 12 week old male C57BL/6 mice by cecal ligation and puncture. Mice were euthanized 3 months after insult. Immune cell composition of the spleen and whole blood, as well as stem and progenitor cells of the bone marrow, were assessed by flow cytometry. Whole blood and bone marrow monocytes were stimulated with LPS and supernatant levels of TNF and IL-6 detected by ELISA. Furthermore, naïve bone marrow monocytes were analyzed for metabolic (Seahorse technology) and transcriptomic (RNA sequencing) changes. Flow cytometric analysis revealed an increase of inflammatory monocytes and regulatory T cells in the spleen, whereby immune composition of whole blood kept unchanged. Granulocyte-monocyte progenitor cells are increased in sepsis survivors. Systemic cytokine response was unchanged after LPS challenge. In contrast, cytokine response of post-septic naïve bone marrow monocytes was increased. Metabolic analysis revealed enhanced glycolytic activity, whereas mitochondrial indices were not affected. In addition, RNA sequencing analysis of global gene expression in monocytes revealed a sustained signature of 367 differentially expressed genes. We here demonstrate that sepsis via functional reprogramming of naïve bone marrow monocytes induces a cellular state of trained immunity, which might be counteracted depending on the compartmental localization of the cell. These findings shed new light on the complex aftermath of sepsis and open up a new pathophysiological framework in need for further research.

Lead Transiently Promotes Granulocyte-Macrophage Progenitor Differentiation and Subsequently Suppresses Common Myeloid Progenitor Differentiation.

Lead (Pb) is a toxic heavy metal affecting human health; it is known to be harmful to various organs or systems, yet the mechanisms by which Pb influences immune cell development remain to be defined. In this study, we show that Pb exposure (1250 ppm via drinking water) selectively impacted the development of myeloid cells (myelopoiesis). After Pb treatment of adult C57BL/6 mice, the numbers of granulocyte-macrophage progenitors (GMP) were consistently reduced, whereas the numbers of myeloid cells were increased at week (wk) 1 and decreased at wk8 after initiating the Pb exposure. Functional assays indicate that Pb accelerated GMP differentiation in a reactive oxygen species-dependent manner after treatment for 1 week and inhibited common myeloid progenitor differentiation by upregulating interferon regulatory factor 8 (IRF8) expression after treatment for 8 weeks. Consistent with the distinct Pb influences on myeloid cells observed at wk1 and wk8, Pb caused an inflammatory environment in vivo at wk8, but not at wk1. Furthermore, like the observations in mice during the Pb exposure, bloods from humans occupationally exposed to Pb had their numbers of monocytes, neutrophils and GMP negatively associated with the Pb concentration, whereas IRF8 expression in common myeloid progenitor, but not GMP, was positively correlated with the Pb concentration. These data suggest an occupationally relevant level of Pb exposure preferentially influences myelopoiesis involving reactive oxygen species and IRF8, which may contribute to the current understanding of the hematopoietic toxicology of Pb.

Myeloid progenitor cluster formation drives emergency and leukaemic myelopoiesis.

Although many aspects of blood production are well understood, the spatial organization of myeloid differentiation in the bone marrow remains unknown. Here we use imaging to track granulocyte/macrophage progenitor (GMP) behaviour in mice during emergency and leukaemic myelopoiesis. In the steady state, we find individual GMPs scattered throughout the bone marrow. During regeneration, we observe expanding GMP patches forming defined GMP clusters, which, in turn, locally differentiate into granulocytes. The timed release of important bone marrow niche signals (SCF, IL-1ß, G-CSF, TGFß and CXCL4) and activation of an inducible Irf8 and ß-catenin progenitor self-renewal network control the transient formation of regenerating GMP clusters. In leukaemia, we show that GMP clusters are constantly produced owing to persistent activation of the self-renewal network and a lack of termination cytokines that normally restore haematopoietic stem-cell quiescence. Our results uncover a previously unrecognized dynamic behaviour of GMPs in situ, which tunes emergency myelopoiesis and is hijacked in leukaemia.

Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage.

Our understanding of the perturbation of normal cellular differentiation hierarchies to create tumor-propagating stem cell populations is incomplete. In human acute myeloid leukemia (AML), current models suggest transformation creates leukemic stem cell (LSC) populations arrested at a progenitor-like stage expressing cell surface CD34. We show that in ∼25% of AML, with a distinct genetic mutation pattern where >98% of cells are CD34(-), there are multiple, nonhierarchically arranged CD34(+) and CD34(-) LSC populations. Within CD34(-) and CD34(+) LSC-containing populations, LSC frequencies are similar; there are shared clonal structures and near-identical transcriptional signatures. CD34(-) LSCs have disordered global transcription profiles, but these profiles are enriched for transcriptional signatures of normal CD34(-) mature granulocyte-macrophage precursors, downstream of progenitors. But unlike mature precursors, LSCs express multiple normal stem cell transcriptional regulators previously implicated in LSC function. This suggests a new refined model of the relationship between LSCs and normal hemopoiesis in which the nature of genetic/epigenetic changes determines the disordered transcriptional program, resulting in LSC differentiation arrest at stages that are most like either progenitor or precursor stages of hemopoiesis.

Deletion of Stat3 enhances myeloid cell expansion and increases the severity of myeloproliferative neoplasms in Jak2V617F knock-in mice.

The JAK2V617F mutation commonly found in myeloproliferative neoplasms (MPNs) induces constitutive phosphorylation/activation of the signal transducer and activator of transcription 3 (Stat3). However, the contribution of Stat3 in MPN evoked by JAK2V617F remains unknown. To determine the role of Stat3 in JAK2V617F-induced MPN, we generated Stat3-deficient Jak2V617F-expressing mice. Whereas expression of Jak2V617F resulted in a polycythemia vera-like disease characterized by increased red blood cells (RBCs), hematocrit, neutrophils and platelets in the peripheral blood of Jak2V617F knock-in mice, deletion of Stat3 slightly reduced RBC and hematocrit parameters and modestly increased platelet numbers in Jak2V617F knock-in mice. Moreover, deletion of Stat3 significantly increased the neutrophil counts/percentages and markedly reduced the survival of mice expressing Jak2V617F. These phenotypic manifestations were reproduced upon bone marrow (BM) transplantation into wild-type animals. Flow cytometric analysis showed increased hematopoietic stem cell and granulocyte-macrophage progenitor populations in the BM and spleens of Stat3-deficient Jak2V617F mice. Stat3 deficiency also caused a marked expansion of Gr-1+/Mac-1+ myeloid cells in Jak2V617F knock-in mice. Histopathologic analysis revealed marked increase in granulocytes in the BM, spleens and livers of Stat3-deficient Jak2V617F-expressing mice. Together, these results suggest that deletion of Stat3 increases the severity of MPN induced by Jak2V617F.

Myelotoxicity of carboplatin is increased in vivo in db/db mice, the animal model of obesity-associated diabetes mellitus.

PURPOSE: Some authors observed increased carboplatin-associated myelotoxicity in obese patients which was exclusively attributed to elevated AUC. To investigate the potential contribution of functional changes of cells primarily responsible for myelopoiesis, granulocyte-macrophage progenitors (CFU-GM) were studied in obesity-associated diabetes mellitus (DMT2). METHODS: The most frequently used animal model of human obesity with DMT2 is db/db mouse. Cellularity, frequency of CFU-GM and total CFU-GM content of femoral bone marrow were measured after 100 mg/kg dose of carboplatin in vivo. To exclude influence of pharmacokinetic changes, direct toxicity of carboplatin on CFU-GM was also determined in vitro and was compared with other anticancer agents, namely doxorubicin, 5-fluorouracil and 4-thiouridylate. RESULTS: After intraperitoneal administration of carboplatin, each measured characteristics of bone marrow function was more significantly suppressed and the induced neutropenia was more serious in db/db mice than in the controls. The increased myelotoxicity seemed to be a direct effect on myeloid progenitor cells since their increased in vitro sensitivity was found in db/db mice. This was not specific for carboplatin, a similar double to fivefold increase in myelotoxicity of each cytotoxic drug with different mechanism of action was observed. Four-thiouridylate, a promising antileukemic molecule with good therapeutic index, was by far the least toxic for CFU-GM of db/db mice. CONCLUSIONS: A serious disorder of CFU-GM progenitors was suggested in obese mice with DMT2, which eventually might lead to more severe myelotoxicity and neutropenia. Weight loss and normalization of glucose homeostasis may be important before chemotherapy of malignant diseases in obesity with DMT2.

High spontaneous granulocyte/macrophage-colony formation in patients with myelofibrosis.

Unstimulated methylcellulose cultures in 25 myelofibrosis (MF) patients were performed to better understand the role of cytokines in the proliferation of MF cells. Compared to controls MF patients show a variable but highly increased spontaneous CFU-GM formation (66 vs 4.8/10(5) PBMNC). There was a marked reduction of autonomous CFU-GM growth by the cytokine-synthesis-inhibiting molecule IL-10 as well as by antibodies against GM-CSF whereas antibodies against IL-3, G-CSF, M-CSF and IL-1ß showed heterogeneous effects. Spontaneous CFU-GM growth >100/10(5) PBMNC predicted shorter survival. Constitutive release of GM-CSF seems to contribute to proliferation of MF cells in vitro and possibly in vivo.

Long-term cadmium exposure leads to the enhancement of lymphocyte proliferation via down-regulating p16 by DNA hypermethylation.

Cadmium (Cd) is a well-established carcinogen, however, the underlying mechanism, especially the role of epigenetics in it, is still poorly understood. Our previous work has disclosed that when rats were exposed to 0.5mg CdCl2 (kgd) for 8 and 12 weeks, the growth of peripheral white blood cells (WBC) was obviously stimulated but no over-proliferation of granulocyte-monocyte (GM) progenitor cells was observed in the bone marrow, suggesting that the over-proliferation of lymphocyte was promoted by Cd exposure. Is DNA-methylation involved in this Cd-stimulated cell proliferation? The present study found that when human B lymphoblast HMy2.CIR cells were exposed to Cd with a dose lower than 0.1µM for 3 months, both cell proliferation and mRNA expressions of DNA methyltransferases of DNMT1 and DNMT3b were increased, while the mRNA of tumor suppressor gene p16 was remarkably decreased. Furthermore, the level of genomic DNA methylation was increased and the CpG island in p16 promoter was hypermethylated in the Cd-exposed cells. A DNA demethylating agent, 5-aza-2'-deoxycytidine (5-aza-dC), diminished Cd-stimulated cell proliferation associated with p16 overexpression. Our results suggested that the chronic exposure of low dose Cd could induce hypermethylation of p16 promoter and hence suppress p16 expression and then promote cell proliferation, which might contribute to Cd-induced carcinogenesis.

Investigation of Ehrlich ascites tumor cell death mechanisms induced by Synadenium umbellatum Pax.

ETHNOPHARMACOLOGICAL RELEVANCE: Synadenium umbellatum Pax. is widely found in South America and empirically used in Brazil for the treatment of several diseases, mainly cancer. The aim of the study was to investigate cell death mechanisms induced by Synadenium umbellatum Pax. using Ehrlich ascites tumor (EAT) cells, as well as the myelotoxicity potential of this plant. MATERIALS AND METHODS: S. umbellatum cytotoxicity was evaluated in EAT cells by trypan blue exclusion and MTT reduction test and the mechanisms involved in EAT cell death were investigated by light and fluorescence microscopy, flow cytometry and immunocytochemistry. Investigation of S. umbellatum myelotoxicity was performed by clonogenic assay of colony forming unit- granulocyte macrophage (CFU-GM). RESULTS AND CONCLUSION: Our results demonstrated that S. umbellatum decreased the viability of EAT cells using both methods. Morphological analyses revealed that S. umbellatum-treatment induced EAT cell death by apoptotic pathway. We demonstrated the occurrence of reactive oxygen species (ROS) overgeneration, increased intracellular Ca(2+) concentration, alteration in mitochondrial membrane potential, phosphatydylserine externalization, and activation of caspases 3, 8, and 9. However, S. umbellatum produced myelotoxicity in bone marrow cells in a concentration-dependent manner. In comparison to EAT cells, the effects of S. umbellatum in bone marrow cells were 8-fold lower. Taken together, our results showed that S. umbellatum induced apoptosis in EAT cells at several levels and seems more toxic to tumor cells than to normal bone marrow cells.

Functional analysis of the NUP98-CCDC28A fusion protein.

BACKGROUND: The nucleoporin gene NUP98 is rearranged in more than 27 chromosomal abnormalities observed in childhood and adult, de novo and therapy-related acute leukemias of myeloid and T-lymphoid origins, resulting in the creation of fusion genes and the expression of chimeric proteins. We report here the functional analysis of the NUP98-coiled-coil domain-containing protein 28A (NUP98-CCDC28A) fusion protein, expressed as the consequence of a recurrent t(6;11)(q24.1;p15.5) translocation. DESIGN AND METHODS: To gain insight into the function of the native CCDC28A gene, we collected information on any differential expression of CCDC28A among normal hematologic cell types and within subgroups of acute leukemia. To assess the in vivo effects of the NUP98-CCDC28A fusion, NUP98-CCDC28A or full length CCDC28A were retrovirally transduced into primary murine bone marrow cells and transduced cells were next transplanted into sub-lethally irradiated recipient mice. RESULTS: Our in silico analyses supported a contribution of CCDC28A to discrete stages of murine hematopoietic development. They also suggested selective enrichment of CCDC28A in the French-American-British M6 class of human acute leukemia. Primary murine hematopoietic progenitor cells transduced with NUP98-CCDC28A generated a fully penetrant and transplantable myeloproliferative neoplasm-like myeloid leukemia and induced selective expansion of granulocyte/macrophage progenitors in the bone marrow of transplanted recipients, showing that NUP98-CCDC28A promotes the proliferative capacity and self-renewal potential of myeloid progenitors. In addition, the transformation mediated by NUP98-CCDC28A was not associated with deregulation of the Hoxa-Meis1 pathway, a feature shared by a diverse set of NUP98 fusions. CONCLUSIONS: Our results demonstrate that the recurrent NUP98-CCDC28A is an oncogene that induces a rapid and transplantable myeloid neoplasm in recipient mice. They also provide additional evidence for an alternative leukemogenic mechanism for NUP98 oncogenes.

Cell of origin in AML: susceptibility to MN1-induced transformation is regulated by the MEIS1/AbdB-like HOX protein complex.

Pathways defining susceptibility of normal cells to oncogenic transformation may be valuable therapeutic targets. We characterized the cell of origin and its critical pathways in MN1-induced leukemias. Common myeloid (CMP) but not granulocyte-macrophage progenitors (GMP) could be transformed by MN1. Complementation studies of CMP-signature genes in GMPs demonstrated that MN1-leukemogenicity required the MEIS1/AbdB-like HOX-protein complex. ChIP-sequencing identified common target genes of MN1 and MEIS1 and demonstrated identical binding sites for a large proportion of their chromatin targets. Transcriptional repression of MEIS1 targets in established MN1 leukemias demonstrated antileukemic activity. As MN1 relies on but cannot activate expression of MEIS1/AbdB-like HOX proteins, transcriptional activity of these genes determines cellular susceptibility to MN1-induced transformation and may represent a promising therapeutic target.

IL-1ß-driven neutrophilia preserves antibacterial defense in the absence of the kinase IKKß.

Transcription factor NF-κB and its activating kinase IKKß are associated with inflammation and are believed to be critical for innate immunity. Despite the likelihood of immune suppression, pharmacological blockade of IKKß-NF-κB has been considered as a therapeutic strategy. However, we found neutrophilia in mice with inducible deletion of IKKß (Ikkß(Δ) mice). These mice had hyperproliferative granulocyte-macrophage progenitors and pregranulocytes and a prolonged lifespan of mature neutrophils that correlated with the induction of genes encoding prosurvival molecules. Deletion of interleukin 1 receptor 1 (IL-1R1) in Ikkß(Δ) mice normalized blood cellularity and prevented neutrophil-driven inflammation. However, Ikkß(Δ)Il1r1(-/-) mice, unlike Ikkß(Δ) mice, were highly susceptible to bacterial infection, which indicated that signaling via IKKß-NF-κB or IL-1R1 can maintain antimicrobial defenses in each other's absence, whereas inactivation of both pathways severely compromises innate immunity.

Leukemic stromal hematopoietic microenvironment negatively regulates the normal hematopoiesis in mouse model of leukemia.

BACKGROUND AND OBJECTIVE: Leukemic microenvironment has a major role in the progression of leukemia. Leukemic cells can induce reversible changes in microenvironmental components, especially the stromal function which results in improved growth conditions for maintaining the malignant leukemic cells. This study aimed to investigate the survival advantage of leukemic cells over normal hematopoietic cells in stromal microenvironment in long term. METHODS: The mice were injected intraperitoneally with N-N' ethylnitrosourea (ENU) to induce leukemia; the mice received injection of normal saline were used as control. At 180 days after ENU induction, the mice were killed and the bone marrows were cultured for 19 days. Colony-forming assays were used to analyze the formation of various cell colonies. The expression of Sca-1, CD146, VEGFR2, CD95, pStat3, pStat5, and Bcl-xL in marrow cells were detected by flow cytometry. RESULTS: Long-term leukemic bone marrow culture showed abnormal elongated stromal fibroblasts with almost absence of normal hematopoietic cells. Adherent cell colonies were increased, but CFU-F and other hematopoietic cell colonies were significantly decreased in leukemia group (P<0.001). Primitive progenitor-specific Sca-1 receptor expression was decreased with subsequent increased expression of CD146 and VEGFR-2 in leukemic bone marrow cells. Decreased Fas antigen expression with increased intracellular pStat3, pStat5 and Bcl-xL proteins were observed in leukemic bone marrow cells. CONCLUSIONS: Stromal microenvironment shows altered morphology and decreased maturation in leukemia. Effective progenitor cells are decreased in leukemia with increased leukemia-specific cell population. Leukemic microenvironment plays a role in promoting and maintaining the leukemic cell proliferation and survivability in long term.