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Diamond Blackfan Anemia (DBA) is associated with a hypoproliferative anemia, congenital abnormalities, and cancer. The disease typically presents within the first year of life with the majority of patients carrying mutations in one of at least 17 ribosomal proteins, with RPS19 being the most common. Current therapies for DBA have undesirable side effects, including iron overload from repeated red cell transfusions, chronic effects from long term corticosteroid use, or complications from stem cell transplantation. The serine threonine kinase Nemo-like Kinase (NLK) is an atypical member of the MAP kinase family of enzymes and has been shown to be chronically hyper-activated in RPS19- and RPL11-haploinsufficient murine and human models of DBA, as well as in erythroid progenitors from DBA patients. In RPS19-insufficient human hematopoietic stem and progenitor cells, genetic silencing of NLK by shRNA increased erythroid expansion by 220.3% (SD = 6.6%), indicating that aberrant NLK activation may contribute to the pathogenesis of the disease and is a potential target for DBA therapy. A number of clinically approved or advanced compounds have been developed to inhibit MAP kinases with various degrees of cross reactivity among its family members. We therefore screened a number of compounds that inhibit NLK as an off-target and found that these NLK inhibitors improved erythroid expansion in DBA models. Of these inhibitors, OTS-167 performed optimally, improving erythropoiesis by 2-fold at 300nM, with an EC50 of 146nM. Previous studies of OTS-167 in xenograft models of neuroblastoma for one month did not result in neutropenia, suggesting very little to no toxicity to myeloid cells. The goal in treating DBA patients with NLK inhibitors is to sufficiently raise the hemoglobin to prevent the need for chronic red cell transfusions or treatment with steroids. Our results suggest that pharmacologic inhibition of NLK is a potential approach to treat patients with DBA. We are currently investigating other NLK inhibitors in preclinical models for future clinical application. Disclosures Glader: Agios: Consultancy.

Diamond Blackfan Anemia (DBA) is an inherited bone marrow failure syndrome that is typically associated with mutations in one of at least 20 ribosomal genes and is associated with anemia, congenital abnormalities, and cancer predisposition. The current treatment for DBA is associated with toxicities including iron overload from repeated transfusions, immune suppression from chronic corticosteroid therapy or consequences from stem cell transplantation. Developing new therapies for DBA remains a challenge, since it is a rare disease and the connection between faulty ribosomes and defects in erythropoiesis is still being explored. As such, repurposing existing, approved drugs is one approach to find new ways to treat this disease. We recently identified that Nemo-like Kinase (NLK) is hyper-activated and contributes to disease pathogenesis in the erythroid progenitors of patients with DBA, irrespective of the genetic mutation. NLK is an atypical member of the MAPK family of kinases. Due to a high degree of conservation, kinase inhibitors that specifically target NLK are not currently available, although several small molecules inhibit NLK as an off-target. We are actively pursuing a number of these compounds as potential therapies for DBA. In addition to known kinase inhibitors, we have examined the active components of widely available nutritional supplements. Although rigorous clinical evaluation is required, these supplements are well tolerated and offer an alternative or a complement to conventional drug therapy for DBA. Ginsenoside Rb1, an active component of ginseng, increases erythropoiesis in in vitro models of DBA (2.6-fold) at 50mM (p=0.048) with an EC 50 of 2.3mM. Importantly, ginsenoside Rb1 does not impact healthy erythropoiesis or other hematopoietic lineages and is nontoxic to normal cells. Our results demonstrate that ginsenoside Rb1 does not inhibit NLK kinase activity directly, but rather induces a microRNA (miR-208) that binds to NLK mRNA leading to degradation of transcript by 35.9% (p=0.007) before the protein can be translated. Another nutritional supplement that has been indicated to improve erythropoiesis (in DBA and non-diseased models) and is currently in clinical trials is the amino acid leucine. In DBA progenitors, 5mM leucine increases erythropoiesis from 8.8 to 16.3% of healthy controls. Leucine acts by stimulating the activity of mTORC1 but similar to erythropoiesis, mTORC1 activity is only stimulated from 26.4 to 57.2% of controls in DBA progenitors. Our results demonstrate that leucine does not impact NLK expression or activity directly. Aberrantly activated NLK phosphorylates and inhibits the activation of mTORC1 (target of leucine). The suppression of NLK by 50mM ginsenoside Rb1 restored mTORC1 activity to basal (94.7% of non-diseased control) but also restored leucine sensitivity (from 57.2 to 88.1% of non-diseased controls). Importantly, combining 5mM leucine and 50mM ginsenoside Rb1 increased erythropoiesis from 1.9-fold and 2.6-fold when used alone, to 8.9-fold (or 78.3% of healthy controls) together in our in vitro models of DBA (CI=0.31). Ginseng and leucine offer promising alternatives to steroids and other immunosuppressive drugs for DBA patients. The goal of these studies is to raise the hemoglobin in DBA patients to avoid the need for red cell transfusions. As nutritional supplements are widely available and well tolerated, this class of compounds provides alternatives to currently approved drugs to treat DBA. Disclosures Glader: Agios: Consultancy.

Diamond Blackfan Anemia (DBA) is a rare genetic disease predominantly caused by mutations carried within one of at least 20 ribosomal genes. DBA is characterized by red blood cell aplasia and normal myeloid and megakaryocyte progenitors, indicating that early uncommitted progenitors are relatively unaffected by the mutations. In DBA, the formation of BFU-E colonies and subsequent erythroblasts are severely restricted and indicate a defect in one of the earliest stages of erythroid expansion. To identify critical molecular mechanisms that may regulate early erythropoiesis, we used shRNAs against the ribosomal protein RPS19 (the most commonly mutated gene in DBA) in cord blood derived CD34+ hematopoietic stem and progenitor cells (HSPCs) and performed bulk RNA-seq. After 3 days in an erythroid culture media, the transcriptomes in CD71+ erythroid progenitors were examined. We found that the special AT binding protein 1 (SATB1) was downregulated in RPS19-insufficient HSPCs compared to healthy cord blood HSPCs. SATB1 is modestly expressed in hematopoietic stem cells but is induced during lymphoid expansion and has been previously reported to suppress myeloid/erythroid progenitor (MEP) expansion. Our results showed that maintaining SATB1 expression is required for optimal expansion of MEP progenitors and that the premature loss of SATB1 in DBA contributes to the anemia phenotype. SATB1 binds to 3 specific regions upstream of the 5'UTR of the HSP70 genes and induces the formation of 2 chromatin loops. An enhancer element associates with the proximal promoters of the two HSP70 genes and facilitates the induction of HSP70. In DBA, HSP70 is not induced and contributes to DBA pathogenesis. HSPA1A is induced 4.3-fold while HSPA1B is induced 3.1-fold. Increased expression of the master erythroid transcription factor GATA1 during erythropoiesis occurs in two phases. The first induction precedes a more dramatic induction that accompanies later stages of erythroid differentiation. The absence of SATB1 or HSP70 reduced the earlier GATA1 induction that accompany MEP expansion by 46.1% and 49.3% respectively. The number of MEPs in SATB1 knockdown HSPCs was reduced, resulting in a 24.5% reduction in CD235+ erythroid and 20.8% reduction in CD41+ megakaryocytes. While SATB1-independent effects of RPS19-insufficiency contribute more significantly to erythroid defects in DBA, we have uncovered that SATB1 contributes to regulation of the earliest stages of erythropoiesis by facilitating the induction of HSP70 and subsequent stabilization of an early induction of GATA1. Disclosures No relevant conflicts of interest to declare.

[Introduction] Infant AML has been defined as AML in patients aged [Methods] This study enrolled patients aged [Results] We first analyzed the distribution of fusion genes and FAB classification in 503 patients with clinical samples. Fusion genes were found in >50% of the patients in each age group. RUNX1-RUNX1T1, KMT2A-R, and CBFB-MYH11 were present in almost all age groups. RUNX1-RUNX1T1 was the most frequently identified fusion gene in all age groups excluding those Furthermore, we analyzed the prognosis of KMT2A-R and CBFB-MYH11 in all 723 patients and confirmed that these fusions had significantly different prognoses between patients In patients with KMT2A-R (n = 131), no molecular markers were identified as prognostic markers in combination with age; however, high WBC counts were related to poor prognosis regardless of age. Particularly, among patients 3-10,000/µL (n = 37) had a significantly poorer prognosis than those with WBC In patients with CBFB-MYH11 with clinical samples (n = 39), NRAS-mutated patients (n = 13) had significantly better 5y EFS and CIR than NRAS-wild-type patients (n = 26) (100% vs 60.5%, p = 0.012, and 0% vs 35.7%, respectively). Moreover, the combination of NRAS status with age identified the worst prognosis in NRAS-wild-type patients [Conclusions] Although age has not been used for the risk stratification of recent pediatric AML clinical trials, it might be a useful prognostic maker of this disease in combination with some molecular makers. Disclosures No relevant conflicts of interest to declare.

Umbilical cord blood (UCB) has been used as a potential source of various kinds of stem cells, including hematopoietic stem cells, mesenchymal stem cells, and endothelial progenitor cells (EPCs), for a variety of cell therapies. Recently, EPCs were introduced for restoring vascularization in ischemic tissues. An appropriate procedure for isolating EPCs from UCB is a key issue for improving therapeutic efficacy and eliminating the unexpected expansion of nonessential cells. Here we report a novel method for isolating EPCs from UCB by a combination of negative immunoselection and cell culture techniques. In addition, we divided EPCs into 2 subpopulations according to the aldehyde dehydrogenase (ALDH) activity. We found that EPCs with low ALDH activity (Alde-Low) possess a greater ability to proliferate and migrate compared to those with high ALDH activity (Alde-High). Moreover, hypoxia-inducible factor proteins are up-regulated and VEGF, CXCR4, and GLUT-1 mRNAs are increased in Alde-Low EPCs under hypoxic conditions, while the response was not significant in Alde-High EPCs. In fact, the introduction of Alde-Low EPCs significantly reduced tissue damage in ischemia in a mouse flap model. Thus, the introduction of Alde-Low EPCs may be a potential strategy for inducing rapid neovascularization and subsequent regeneration of ischemic tissues.

Vascular endothelial growth factor A (VEGF-A) is upregulated during hypoxia and is the major regulator of angiogenesis. VEGF-A expression has also been found to recruit myeloid cells to ischemic tissues where they contribute to angiogenesis. This study investigates the mechanisms underlying neutrophil recruitment to VEGF-A as well as the characteristics of these neutrophils. A previously undefined circulating subset of neutrophils shown to be CD49d(+)VEGFR1(high)CXCR4(high) was identified in mice and humans. By using chimeric mice with impaired VEGF receptor 1 (VEGFR1) or VEGFR2 signaling (Flt-1tk(-/-), tsad(-/-)), we found that parallel activation of VEGFR1 on neutrophils and VEGFR2 on endothelial cells was required for VEGF-A-induced recruitment of circulating neutrophils to tissue. Intravital microscopy of mouse microcirculation revealed that neutrophil recruitment by VEGF-A versus by the chemokine macrophage inflammatory protein 2 (MIP-2 [CXCL2]) involved the same steps of the recruitment cascade but that an additional neutrophil integrin (eg, VLA-4 [CD49d/CD29]) played a crucial role in neutrophil crawling and emigration to VEGF-A. Isolated CD49d(+) neutrophils featured increased chemokinesis but not chemotaxis compared with CD49d(-) neutrophils in the presence of VEGF-A. Finally, by targeting the integrin α4 subunit (CD49d) in a transplantation-based angiogenesis model that used avascular pancreatic islets transplanted to striated muscle, we demonstrated that inhibiting the recruitment of circulating proangiogenic neutrophils to hypoxic tissue impairs vessel neoformation. Thus, angiogenesis can be modulated by targeting cell-surface receptors specifically involved in VEGF-A-dependent recruitment of proangiogenic neutrophils without compromising recruitment of the neutrophil population involved in the immune response to pathogens.

The mechanism of commencement of hematopoiesis in blood islands of the yolk sac and the aorta-gonad-mesonephros (AGM) region during primate embryogenesis remains elusive. In this study, we demonstrated that VE-cadherin+CD45− endothelial cells derived from nonhuman primate embryonic stem cells are able to generate primitive and definitive hematopoietic cells sequentially, as revealed by immunostaining of floating erythrocytes and colony-forming assay in cultures. Single bipotential progenitors for hematopoietic and endothelial lineages are included in this endothelial cell population. Furthermore, hemogenic activity of these endothelial cells is observed exclusively in the α4-integrin+ subpopulation; bipotential progenitors are 4-fold enriched in this subpopulation. The kinetics of this hemogenic subpopulation is similar to that of hemogenic endothelial cells previously reported in the yolk sac and the AGM region in vivo in that they emerge for only a limited time. We suggest that VE-cadherin+CD45−α4-integrin+ endothelial cells are involved in primitive and definitive hematopoiesis during primate embryogenesis, though VE-cadherin−CD45−α4-integrin+ cells are the primary sources for primitive hematopoiesis.

Vascular endothelial growth factor (VEGF) is a major growth factor for developing endothelial cells (ECs). Embryonic lethality due to haploinsufficiency of VEGF in the mouse highlighted the strict dose dependency of VEGF on embryonic vascular development. Here we investigated the dose-dependent effects of VEGF on the differentiation of ES cell–derived fetal liver kinase 1 (Flk-1)/VEGF receptor 2+ (VEGFR2+) mesodermal cells into ECs on type IV collagen under a chemically defined serum-free condition. These cells could grow even in the absence of VEGF, but differentiated mostly into mural cells positive for α-smooth muscle actin. VEGF supported in a dose-dependent manner the differentiation into ECs defined by the expression of VE-cadherin, platelet-endothelial cell adhesion molecule 1 (PECAM-1)/ CD31, CD34, and TIE2/TEK. VEGF requirement was greater at late than at early phase of culture during EC development, whereas response of VEGFR2+ cells to VEGF-E, which is a virus-derived ligand for VEGFR2 but not for Flt-1/VEGFR1, was not dose sensitive even at late phase of culture. Delayed expression of VEGFR1 correlated with increased dose dependency of VEGF. These results suggested that greater requirement of VEGF in the maintenance than induction of ECs was due to the activity of VEGFR1 sequestering VEGF from VEGFR2 signal. The chemically defined serum-free culture system described here provides a new tool for assessing different factors for the proliferation and differentiation of VEGFR2+ mesodermal cells.

Hematopoietic system is maintained by the differentiation and proliferation of hematopoietic stem/progenitor cells (HSPCs) and their commitment to the mature blood cells should be tightly controlled by gene regulatory networks (GRNs) governed by transcription factors (TFs). To keep the homeostasis, GRNs should respond to the environmental changes, such as infection. However, the precise mechanism of such a system remains to be elucidated. TFs Bach1 and Bach2 belong to the basic region-leucine zipper family and recognize Maf-recognition elements containing AP-1 site (Oyake et al., 1996). We have previously shown that Bach1-/-Bach2-/-(DKO; double knockout) mice show erythropoiesis disorders with increased myelopoiesis from common myeloid progenitors (CMPs), which is an erythro-myeloid bifurcation point (ASH2015; Abstract ID# 81562) (Akashi et al., 2000). Since this phenotype is similar to that of LPS treated mice (O'Connell et al., 2008), we hypothesized that Bach factors work as sensors for infection. First, to evaluate the cell-intrinsic function of Bach factors, WT or DKO bone marrow cells were depleted of mature differentiated cells and transplanted to lethally irradiated WT mice. After 8 weeks, DKO donor cells showed greater myelopoiesis and lesser lymphogenesis compared to WT, suggesting Bach factors are necessary to suppress myelopoiesis to the appropriate level in regenerating hematopoiesis. To reveals the function of Bach factors in HSPCs from other aspect, LSKs (Lin-Sca1+c-kit+) were infected with retroviruses expressing Bach1-IRES-eGFP or Bach2-IRES-eGFP and transplanted to lethally irradiated WT mice. Cells derived from transgene induced LSKs were monitored by GFP fluorescence. After 2 weeks, Bach1 overexpressing LSKs did not show any difference in erythropoiesis and myelopoiesis. This might be explained by the high Bach1 expression levels in HSPCs according to the previous report (Lara-Astiaso et al., 2014). On the other hand, Bach2 overexpressing LSKs showed increased erythropoiesis and decreased myelopoiesis, suggesting that Bach2 regulates the erythro-myeloid lineage specification as expected by the observations of DKO mice. To assess the function of Bach factors under infection, we used M1 murine myeloid leukemia cells that differentiate to macrophage-like cells by LPS stimulation. LPS stimulation reduced expressions of Bach1, Bach2 and erythroid gene Gata1, and induced those of myeloid genes such as Cebpb and Csf1rin a dose-dependent manner. To determine if down-regulation of Bach factors is necessary for myeloid differentiation, Bach1 or Bach2 were transgenically overexpressed in M1 cells. Both of the M1 cells overexpressing Bach1 or Bach2 showed lower expression levels of myeloid marker CD11b compared to control under LPS stimulation. Thus, reductions of the expression of Bach factors in response to LPS were necessary for appropriate myeloid differentiation. To identify the direct target genes of Bach factors, Bach1 or Bach2 ChIP-seq data of M1 cells (Ebina-Shibuya et al., 2016) were merged with results of expression profile of WT and DKO CMPs. Several myeloid or inflammatory genes such as Cebpb, Fcgr1 and Tlr4 were identified as putative repressed target genes and several erythroid or lymphoid genes such as Klf1, Rag1 and Rag2 were identified as putative activated target genes. In addition, when Bach1 or Bach2 ChIP-seq data were merged by that of C/EBPb, which also possesses AP-1 site as its target motif, obtained from ENCODE database (ENCSR000AIB), we found that there were several co-localized regions of Bach and C/EBPb near the myeloid genes such as Cebpa, Il6 and Fcgr1. These observations suggest that Bach factors repress myeloid genes by competitively working with C/EBPb at same genomic regions. This is particularly interesting in the light of the latest findings showing the Bach2 function on AP-1 site in lymphoid cells (Sidwell et al., 2016). These results reveal a novel mechanism by which how the differentiation of erythro-myeloid bifurcation is controlled by responding to environmental changes. Bach factors regulate erythro-myeloid competitive differentiation by promoting and repressing erythroid and myeloid differentiation, respectively. We suggest that infection promote myelopoiesis at the expense of erythropoiesis by reducing the expression of Bach factors. Therefore, Bach factors may function as sensors for environmental changes. Disclosures No relevant conflicts of interest to declare.

The significant function of cytokines includes maintenance of cell survival as well as induction of cell differentiation and/or proliferation. We demonstrate here that interferon-γ (IFN-γ) plays a role for progression of Epstein-Barr virus (EBV)-infected natural killer cell leukemia (NK leukemia) through maintaining cell survival. NK leukemia cells obtained from 7 patients had clonal episomal forms of EBV, indicating that the leukemic cells were of clonal origin. Although normal NK cells constitutively expressed Bcl-2, the EBV-infected NK leukemia cells lacked endogenous Bcl-2 expression and were hypersensitive to apoptosis in vitro. The addition of IFN-γ to the culture significantly inhibited their spontaneous apoptosis without inducing cell proliferation or upregulation of Bcl-2. The NK leukemia cells constitutively secreted IFN-γ, and the patients’ sera contained a high concentration of IFN-γ, levels that were high enough to prevent NK leukemia cells from apoptosis. Bcl-XL was not involved in the IFN-γ–induced NK leukemia cell survival. These data suggest that the acquisition of IFN-γ–mediated autocrine survival signals, other than Bcl-2 or BCL-XL, might be important for the development of EBV-infected NK leukemia.

application/pdf, The poliovirus receptor CD155 and its family member CD112 (nectin-2) are the ligands for the activating cell-surface receptor DNAM-1 on CD8(+) T cells and natural killer (NK) cells. Here, we demonstrate that, whereas the RMA tumor grew in syngeneic mice, DNAM-1 ligand-transduced RMA was rejected, in which CD8(+) T cells and NK cells played an essential role. Importantly, CD8(+) memory cytotoxic T cells to parental RMA were generated in these mice. We found that DNAM-1 was also expressed on CD8 alpha(+), rather than CD8 alpha(-), dendritic cells (DCs). Cross-linking DNAM-1 induced maturation of CD8 alpha(+) DCs. Antigen presentation by these stimulated DCs drove Th1 cells. Moreover, the rejection of DNAM-1 ligand-transduced RMA was canceled in CD4(+) T-cell-depleted and major histocompatibility complex class II-deficient mice. Taken together, these results suggest that DNAM-1 ligands stimulate innate immunity by CD8 alpha(+) DCs as well as NK cells, which efficiently prime cell-mediated tumor-specific immunity.

Recurrent translocation t(10;11) has been reported to be associated with acute myeloid leukemia (AML). Recently, two types of chimeric transcripts, MLL-AF10 in t(10;11)(p12;q23) andCALM-AF10 in t(10;11)(p13;q14), were isolated. t(10;11) is strongly associated with complex translocations, including invins(10;11) and inv(11)t(10;11), because the direction of transcription of AF10 is telomere to centromere. We analyzed a patient of AML with t(10;11)(p11.2;q23) and identified ABI-1 on chromosome 10p11.2, a human homolog to mouse Abl-interactor 1 (Abi-1), fused with MLL. Whereas the ABI-1 gene bears no homology with the partner genes of MLL previously described, the ABI-1 protein exhibits sequence similarity to protein of homeotic genes, contains several polyproline stretches, and includes asrc homology 3 (SH3) domain at the C-terminus that is required for binding to Abl proteins in mouse Abi-1 protein. Recently, e3B1, an eps8 SH3 binding protein 1, was also isolated as a human homolog to mouse Abi-1. Three types of transcripts of ABI-1 gene were expressed in normal peripheral blood. Although e3B1 was considered to be a full-length ABI-1, the MLL-ABI-1fusion transcript in this patient was formed by an alternatively spliced ABI-1. Others have shown that mouse Abi-1 suppresses v-ABL transforming activity and that e3B1, full-length ABI-1, regulates cell growth. In-frame MLL-ABI-1 fusion transcripts combine the MLL AT-hook motifs and DNA methyltransferase homology region with the homeodomain homologous region, polyproline stretches, and SH3 domain of alternatively spliced transcript of ABI-1. Our results suggest that the ABI-1 gene plays a role in leukemogenesis by translocating to MLL. © 1998 by The American Society of Hematology.

Previous studies have shown that daily multiple administration of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) markedly stimulates thrombopoiesis and effectively ameliorates thrombocytopenia, and in most cases anemia and neutropenia, in myelosuppressed animals. In this study, we evaluated the effects of a single intravenous injection of PEG-rHuMGDF on hematopoietic recovery after sublethal total-body irradiation in mice. A single injection of PEG-rHuMGDF (1 to 640 μg/kg) 1 hour after irradiation accelerated platelet, red blood cell (RBC), and white blood cell (WBC) recovery in a dose-dependent fashion. In the bone marrow of vehicle-treated mice, megakaryocytic, erythroid, and myeloid progenitors, as well as day 12 colony-forming unit–spleen (CFU-S), were dramatically decreased much earlier than the nadirs of peripheral blood cells, whereas megakaryocytes were modestly decreased. Treatment with PEG-rHuMGDF (80 μg/kg, an optimal dose) 1 hour after irradiation resulted in more rapid recovery of these four hematopoietic progenitors and also significantly facilitated megakaryocyte recovery. In addition, the same PEG-rHuMGDF administration schedule expanded bone marrow cells capable of rescuing lethally irradiated recipient mice. As the interval between irradiation and PEG-rHuMGDF treatment was longer, its effects on hematopoietic recovery were attenuated. In contrast to the effects of PEG-rHuMGDF, a single injection of recombinant human granulocyte colony-stimulating factor (rhG-CSF) 1 hour after irradiation exclusively accelerated WBC recovery, but only to a similar extent as PEG-rHuMGDF (80 μg/kg) treatment even when rhG-CSF doses were escalated to 1,000 μg/kg. This appeared related to different pharmacokinetics of these two factors after a single injection in irradiated mice. The concentrations of PEG-rHuMGDF after injection persisted in the plasma for a longer time compared with rhG-CSF. These results indicate that a single injection of PEG-rHuMGDF at an early time after irradiation is able to effectively improve thrombocytopenia, anemia, and leukopenia with concomitant accelerated recovery of both primitive and committed hematopoietic progenitors in irradiated mice. Our data also show that compared with the rhG-CSF shown to exert multilineage effects on hematopoiesis, PEG-rHuMGDF has more wide-ranging effects on peripheral blood cell recovery.

Background: Erythrocyte and granulocyte/macrophage develop from common myeloid progenitor (CMP) (Akashi et al., 2000). Differentiation of hematopoietic progenitor cells is precisely controlled by multiple transcription factors, among which GATA1, C/EBPα, C/EBPβ and Spi-C play pivotal roles in erythrocyte and granulocyte/macrophage differentiation (Mancini et al., 2012; Pongubala et al., 2008; Hirai et al., 2006; Haldar et al., 2014). However, the mechanism by which the differentiation of CMP controlled under infectious condition has been unclear. Bach1 and Bach2 belong to the basic region-leucine zipper family and recognize Maf-recognition elements (Oyake et al., 1996). They promote B cell development by repressing the myeloid genes such as Cebpb and Spic in common lymphoid progenitor cells (Itoh-Nakadai et al., 2014). In addition, Bach1 regulates several target genes related to iron/heme homeostasis such as globin genes and hemeoxygenase-1, and Bach2 may similarly regulate these genes (Igarashi, 2014). Therefore, it is expected that both Bach1 and Bach2 play redundant roles in erythropoiesis. To figure out their roles in erythroid and myeloid cell differentiation, we performed hematological and transcriptomics analyses using Bach1-/- Bach2-/- (double-deficient; DD) mice. Methods: The generation of DD mice on the C57BL/6J background and Bach2 reporter mice with red fluorescent protein coding cDNA inserted in the Bach2 locus were described previously (Itoh-Nakadai et al., 2014). Mice between 8-12 weeks old were analyzed in the present study. Bone marrow (BM) cells were stained with specific combinations of antibodies to identify erythroid/myeloid progenitor and mature cells (Sheila et al., 2008; Cornelis et al., 2007; Socolovsky et al., 2001). Flow cytometry analysis and cell sorting were performed by using FACSAriaⅡ(BD) and FlowJo software (TreeStar). For infectious simulation of CMP, sorted CMPs were incubated with 1μg/ml LPS (Sigma) for 48h and RNA was purified with RNeasy micro kit (Qiagen). Quantitative PCR by using SuperscriptⅢ reverse transcriptase (Invitrogen) and Light Cycler system (Roche) was performed according to manufacturer's instructions. Microarray analysis by using Sure-Print G3 mouse GE microarray slide (Agilent) was performed as previously described (Itoh-Nakadai et al., 2014) and the results were analyzed by using GeneSpring software (Agilent). We used Gene Set Enrichment Analysis (GSEA) to interpret gene expression data (Subramanian et al., 2005; Mootha et al., 2003). LPS stimulation (50 μg/body) of mice was performed as previously described (Ryan et al., 2008). Data were analyzed by the two-sided Student's t-test and p - values of Results: DD mice show mild normocytic anemia compered to wild-type (WT), Bach1-/-, and Bach2-/- mice (hemoglobin; 14.4±0.2, 14.0±0.3, 13.5±0.3 and 11.9±0.7 g/dl, for WT, Bach1-/-, Bach2-/- and DD, respectively, p Conclusions: Bach1 and Bach2 control the differentiation of CMP to erythroid cell or myeloid cell by repressing myeloid genes such as Cebpb and Spic. Infectious stimuli may promote myeloid cell differentiation by reducing the expression of Bach1 and Bach2 in CMP. Disclosures Fujiwara: Chugai Pharmaceutical CO., LTD: Research Funding. Harigae:Chugai Pharmaceutical CO., LTD: Research Funding.

We investigated the effects of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and recombinant human granulocyte- CSF (rhG-CSF) on the generation of natural killer (NK) cells in vitro. NK cells were cultured from selected human bone marrow cells obtained after the elimination of mature T and NK cells. rhGM-CSF significantly suppressed the generation of CD56+ cells and NK activity (P less than .01) in a dose-dependent manner. The generation of large granular lymphocytes (LGL) was also suppressed in the presence of rhGM-CSF (P less than .01). In contrast, rhG-CSF had no effect on LGL (P greater than .05). Both rhGM-CSF and rhG-CSF had no influence on the CD56+ cell count in the peripheral blood. These results suggest that rhGM-CSF suppresses the in vitro generation of NK cells.

We investigated the effects of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and recombinant human granulocyte colony-stimulating factor (rhG-CSF) therapy on the natural killer (NK) cell lineage in patients with aplastic anemia and myelodysplastic syndrome. Selected bone marrow (BM) cells were prepared by the elimination of nylon wool-adherent cells and mature T and NK cells from BM cells. The frequency of BM NK progenitors relative to BM cells selected was significantly decreased 4 weeks after the start of rhGM- CSF therapy (P less than .01), while the peripheral blood NK cell count and NK activity were also significantly decreased (P less than .05). A return to the pretreatment levels was seen 4 weeks after the cessation of treatment in all cases. No suppressive effect was noted in the patients who received rhG-CSF therapy. These results suggest that rhGM- CSF therapy suppresses the generation of NK cells from human BM NK progenitors.

We have established a new nonlymphoid leukemic cell ine from a patient with myelodysplastic syndrome (MDS), which progressed to overt leukemia. The parental cell line and a subline derived from this line have absolute dependency on several cytokines for their long-term survival and growth. The parental line designated F-36P requires granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) for continuous growth, while a subline designated F-36E can be maintained in the presence of erythropoietin (Epo) alone. When these cytokines are depleted, both the parental and the subline cells die within several days, even in medium supplemented with fetal calf serum (FCS). F-36E, maintained in the presence of Epo, constitutively synthesizes hemoglobin at a significant level. F-36P, which is usually maintained in the presence of GM-CSF or IL-3, can be induced to synthesize hemoglobin when GM-CSF or IL-3 is substituted by Epo. The surface marker profile shows that the F-36P cells are positive for the leukocyte common antigen (CD45) and some common multilineage markers such as CD13, CD33, and CD34, and negative for T- and B-cell antigens and mature myelomonocytic antigens. However, some monoclonal antibodies recognizing erythroid and platelet glycoproteins react with these cells. Thus, this cell line has a multilineage phenotype, suggesting that the transformation event occurred in a multipotent stem cell. It is also evident that the F-36 cells can be induced to differentiate into the erythroid lineage in the presence of Epo. This, to our knowledge, is the first description of a human leukemic cell line that can be stimulated to synthesize hemoglobin by Epo.

Vascular endothelial growth factor (VEGF) and VEGF receptor-1 (VEGFR-1/Flt-1) were shown to be involved in pathological angiogenesis, particularly rheumatoid arthritis (RA). However, the molecular basis of their actions is not fully understood. Here we report that in a murine model of RA, deletion of the tyrosine kinase (TK) domain of VEGFR-1 decreased the incidence and clinical symptoms of RA. Pathological symptoms, such as synovial hyperplasia, inflammatory infiltrates, pannus formation, and cartilage/bone destruction, became milder in Vegfr-1 tk–/– mice compared with wild-type (Wt) mice in the human T-cell leukemia virus-1 (HTLV-1) pX–induced chronic models. VEGFR-1 TK-deficient bone marrow cells showed a suppression of multilineage colony formation. Furthermore, macrophages induced to differentiate in vitro showed a decrease in immunologic reactions such as phagocytosis and the secretion of interleukin-6 (IL-6) and VEGF-A. Treatment of this RA model with a small molecule inhibitor for VEGFR TK, KRN951, also attenuated the arthritis. These results indicate that the VEGFR-1 TK signaling modulates the proliferation of bone marrow hematopoietic cells and immunity of monocytes/macrophages and promotes chronic inflammation, which may be a new target in the treatment of RA.

Natural killer (NK) cells can be cultured in interleukin-2 (IL-2)- containing medium from selected human bone marrow (BM) cells obtained after the elimination of mature T and NK cells. To isolate and characterize IL-2-responsive NK progenitors in the selected BM cells, we investigated the expression of IL-2 receptors (IL-2R) on these cells. Neither CD25 (IL-2R alpha) nor IL-2R beta antigen was observed on the selected BM cells before culture. However, CD25+ cells without detectable levels of IL-2R beta antigen appeared 24 hours after culture in IL-2-containing medium. Cells were sorted from each fraction of the selected BM cells 24 hours after culture after staining with anti-CD33, anti-CD34, and anti-CD25 monoclonal antibodies. The generation of NK cells (CD3- CD56+ cells) and NK activity were observed only from the CD33-/CD34-/CD25+ cell fraction after culture in IL-2-containing medium. The frequency of IL-2-responsive NK progenitors relative to the fraction was 1/231 (95% confidence range, 1/156 to 1/289), which corresponded to the frequency relative to the total number of selected BM cells when the frequency relative to the CD33-/CD34-/CD25+ cell- fraction was converted according to the percentage of these cells in the total number of selected BM cells. These results indicated that IL- 2-responsive NK progenitors were enriched in the CD33-/CD34-/CD25+ cell fraction.

Flt-1, also known as vascular endothelial growth factor receptor 1 (VEGFR-1), is a high-affinity tyrosine kinase receptor for VEGF and is expressed almost exclusively on vascular endothelial cells. As an exception, Flt-1 transcript was recently found to be expressed in human peripheral blood monocytes. However, the protein of the Flt-1 receptor on the cell surface of monocytes is yet to be identified, and whether the Flt-1 protein is expressed during the differentiation of monocyte-macrophage lineage cells has not been examined. Using monoclonal antibodies against 2 different antigenic epitopes on the Flt-1 extracellular domain, this study found that the major population of the monocyte-marker CD97+ cells in human peripheral blood express Flt-1 as a cell surface molecule. VEGFR-2 (KDR/Flk-1) was not expressed at detectable levels in these cells. An Flt-1 neutralizing monoclonal antibody significantly suppressed VEGF-induced migration of the monocytes, suggesting an important role for Flt-1 in the biologic function of monocytes. Furthermore, CD34+cells in human cord blood, originally negative for the Flt-1 expression, differentiated into Flt-1+ cells in association with the appearance of monocyte-macrophage markers after a 2-week culture in the presence of hematopoietic cytokines. In addition, the Flt-1+CD11b+ cell fraction from CD34+ cells was found to efficiently differentiate into multinuclear osteoclasts in the presence of macrophage colony-stimulating factor and osteoclast differentiation factor. These results strongly suggest that Flt-1 is a novel cell surface marker as well as a biologically functional molecule for monocyte-macrophage lineages in humans.

It has been reported that clinically significant heart involvement affected 5% to 10% of patients undergoing bone marrow transplantation (BMT) after pretreatment with CY and TBI[1][1] and that life-threatening or fatal cardiac toxicity occurred in about 1%-5% of patients receiving CY-containing

The significant function of cytokines includes maintenance of cell survival as well as induction of cell differentiation and/or proliferation. We demonstrate here that interferon-gamma (IFN-gamma) plays a role for progression of Epstein-Barr virus (EBV)-infected natural killer cell leukemia (NK leukemia) through maintaining cell survival. NK leukemia cells obtained from 7 patients had clonal episomal forms of EBV, indicating that the leukemic cells were of clonal origin. Although normal NK cells constitutively expressed Bcl-2, the EBV-infected NK leukemia cells lacked endogenous Bcl-2 expression and were hypersensitive to apoptosis in vitro. The addition of IFN-gamma to the culture significantly inhibited their spontaneous apoptosis without inducing cell proliferation or upregulation of Bcl-2. The NK leukemia cells constitutively secreted IFN-gamma, and the patients' sera contained a high concentration of IFN-gamma, levels that were high enough to prevent NK leukemia cells from apoptosis. Bcl-XL was not involved in the IFN-gamma-induced NK leukemia cell survival. These data suggest that the acquisition of IFN-gamma-mediated autocrine survival signals, other than Bcl-2 or BCL-XL, might be important for the development of EBV-infected NK leukemia.

Recurrent translocation t(10;11) has been reported to be associated with acute myeloid leukemia (AML). Recently, two types of chimeric transcripts, MLL-AF10 in t(10;11)(p12;q23) and CALM-AF10 in t(10;11)(p13;q14), were isolated. t(10;11) is strongly associated with complex translocations, including invins(10;11) and inv(11)t(10;11), because the direction of transcription of AF10 is telomere to centromere. We analyzed a patient of AML with t(10;11)(p11.2;q23) and identified ABI-1 on chromosome 10p11.2, a human homolog to mouse Abl-interactor 1 (Abi-1), fused with MLL. Whereas the ABI-1 gene bears no homology with the partner genes of MLL previously described, the ABI-1 protein exhibits sequence similarity to protein of homeotic genes, contains several polyproline stretches, and includes a src homology 3 (SH3) domain at the C-terminus that is required for binding to Abl proteins in mouse Abi-1 protein. Recently, e3B1, an eps8 SH3 binding protein 1, was also isolated as a human homolog to mouse Abi-1. Three types of transcripts of ABI-1 gene were expressed in normal peripheral blood. Although e3B1 was considered to be a full-length ABI-1, the MLL-ABI-1 fusion transcript in this patient was formed by an alternatively spliced ABI-1. Others have shown that mouse Abi-1 suppresses v-ABL transforming activity and that e3B1, full-length ABI-1, regulates cell growth. In-frame MLL-ABI-1 fusion transcripts combine the MLL AT-hook motifs and DNA methyltransferase homology region with the homeodomain homologous region, polyproline stretches, and SH3 domain of alternatively spliced transcript of ABI-1. Our results suggest that the ABI-1 gene plays a role in leukemogenesis by translocating to MLL.

A novel cell line was established from a patient with a leukemic-state nasal angiocentric natural killer (NK) cell lymphoma with systemic skin infiltration. The morphology of the leukemic cells was large-granular-lymphocyte (LGL), and their immunophenotype was CD2+, CD3−, CD5+, CD7+, CD16−, CD56+, and CD57−. The presence of Epstein-Barr viral (EBV) genome was shown in specimens from the patient’s nose, skin, and peripheral blood by in situ hybridization using an EBV-encoded small RNA-1 probe or by Southern blotting using a terminal-repeat probe of the EBV genome. Leukemic cells were cocultured with a mouse stromal cell line (SPY3-2) in the presence of 100 U/mL recombinant human interleukin-2 and a novel stromal cell-independent cell line, NK-YS, was established. The NK-YS cells showed LGL morphology and expressed surface CD2, CD5, CD7, CD25, CD56, and CD95. The NK-YS cells retained cytotoxicity against K562 and Jurkat cells. A Southern blotting using a terminal-repeat probe of EBV showed that NK-YS and fresh leukemic cells had a clonal EBV genome, whereas the T-cell receptor β and γ chain genes of NK-YS were not rearranged. In an immunocytochemical analysis, the NK-YS cells showed a type-II latent infection of EBV. The NK-YS cells preserved the original characteristics of NK cell lymphoma/leukemia and will be a useful tool for the study of biological characteristics of EBV-associated nasal angiocentric NK cell lymphoma/leukemia. © 1998 by The American Society of Hematology.

We investigated the expression of an apoptosis-associated antigen (Fas) (CD95) on hematopoietic progenitor cells in the presence or absence of interferon-gamma (IFN-gamma) and/or tumor necrosis factor-alpha (TNF- alpha). CD34+ cells freshly isolated from bone marrow did not express Fas. However, IFN-gamma and/or TNF-alpha induced the expression of both the mRNA of Fas and Fas itself in a dose-dependent fashion on the surface of CD34+ cells after 48 hours of serum-free culture. IFN-gamma and TNF-alpha had a synergistic effect on the induction of Fas, when both cytokines were added to the culture. The TNF-alpha-induced Fas expression is mediated by p55 TNF-alpha receptor. CD34+ cells cultured in medium alone or with stem cell factor (SCF) showed some slight expression of Fas. When anti-Fas antibody (IgM) was added to CD34+ cells after the induction of Fas expression, CD34+ cells underwent apoptosis, as shown by a decrease in the number of viable cells, morphologic changes, the induction of DNA fragmentation, and a decrease in the number of colony-forming cells (CFC) including colony-forming unit granulocytes/macrophages (CFU-GM) and burst-forming unit erythroids (BFU-E). These observations indicate that IFN-gamma and/or TNF-alpha, well known as negative hematopoietic regulators, induce functional Fas on hematopoietic progenitor cells. The suppression of hematopoiesis by negative hematopoietic regulators may be mediated in part by Fas induction.

We have established a cell culture system without stromal cells that allows the CD34+ hematopoietic progenitor cells (HPC) to differentiate into natural killer (NK) cells. CD34+Lin (CD3, CD16, CD56)-cells were purified using fluorescence-activated cell sorting from normal adult bone marrow (BM) and cultured for 28 days in medium supplemented with interleukin-2 (IL-2) and stem cell factor (SCF). NK (CD3-CD16-CD56+) cells were generated in a dose-dependent manner in response to SCF. NK cells originated from CD34+CD33+Lin- cells, but they were barely detectable in cultures of CD34+CD33-Lin- cells. However, on addition of IL-3, an induced differentiation of NK cells from CD34+CD33-Lin- cells was observed, although at a lower frequency. Supplementing of the cell cultures with SCF alone or both SCF and IL-3 for the first 7 days followed by IL-2 for the next 21 days is essential for production of NK cells from CD34+CD33+Lin- cells and from CD34+CD33-Lin- cells, respectively. These data provide direct evidence that NK cells arise from CD34+HPC and show the minimum lymphokine requirement for their differentiation.

Abstract 4656 Introduction Cyclosporine A (CyA), a calcineurin inhibitor, is widely used as an immunosuppressor for the prevention of acute graft-versus-host disease (aGVHD) in allogeneic hematopoietic stem cell transplantation (alloHSCT). However, the optimal regimen of CyA has not yet been unequivocally established. Among liver transplant patients, it is important to maintain a peak CyA concentration and to monitor area under the concentration-time curve (AUC) and 2 h after CyA dosing (C2) for prophylaxis against graft rejection. We investigated the pharmacokinetics of CyA delivered by twice-daily infusion and oral administration maintained with a peak level above 1000 ng/ml to keep AUC 0-24 higher than 10000 ng-h/ml in 10 patients with hematological malignancy who underwent alloHSCT. Methods CyA was started as a twice-daily infusion at 1.5 mg/kg and then orally administered at twice the infusion dose in order to maintain the trough blood concentration between 200 and 500 ng/ml and with a peak level above 1000 ng/ml. Serial blood samples were collected at 0, 1, 2, 3, 5, 8, and 12 h after CyA dosing (C0,C1,C2,C3,C5,C8,C12) on days 14-21 after transplantation and on days 7-14 after switching to oral administration, and the AUC was calculated. Results The mean AUC0-12 for twice-daily infusion and oral administration was 7443±998.5 ng-h/ml and 7185±1714 ng-h/ml, respectively. Among all the patients, the AUC0-24 for both CyA twice-daily infusion and oral administration was higher than 10000 ng-h/ml. Two close relationships were observed between AUC0-12 and the C3 level for infusion and between AUC0-12 and the C8 level for oral administration. Engraftment was achieved in all cases, and two patients suffered from grade 2 aGVHD. None of the patients had grades 3-4 aGVHD or other serious complications. Conclusion This strategy was well tolerated, and the C3 level for twice-daily infusion and the C8 level for oral administration were the optimal points for monitoring of CyA concentration in the early phase of alloHSCT. Disclosures: No relevant conflicts of interest to declare.

We have established a new nonlymphoid leukemic cell ine from a patient with myelodysplastic syndrome (MDS), which progressed to overt leukemia. The parental cell line and a subline derived from this line have absolute dependency on several cytokines for their long-term survival and growth. The parental line designated F-36P requires granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) for continuous growth, while a subline designated F-36E can be maintained in the presence of erythropoietin (Epo) alone. When these cytokines are depleted, both the parental and the subline cells die within several days, even in medium supplemented with fetal calf serum (FCS). F-36E, maintained in the presence of Epo, constitutively synthesizes hemoglobin at a significant level. F-36P, which is usually maintained in the presence of GM-CSF or IL-3, can be induced to synthesize hemoglobin when GM-CSF or IL-3 is substituted by Epo. The surface marker profile shows that the F-36P cells are positive for the leukocyte common antigen (CD45) and some common multilineage markers such as CD13, CD33, and CD34, and negative for T- and B-cell antigens and mature myelomonocytic antigens. However, some monoclonal antibodies recognizing erythroid and platelet glycoproteins react with these cells. Thus, this cell line has a multilineage phenotype, suggesting that the transformation event occurred in a multipotent stem cell. It is also evident that the F-36 cells can be induced to differentiate into the erythroid lineage in the presence of Epo. This, to our knowledge, is the first description of a human leukemic cell line that can be stimulated to synthesize hemoglobin by Epo.

We studied the effects of interleukin-4 (IL-4) and IL-6 on the growth of leukemic blasts from 40 patients with acute myelogenous leukemia (AML). Patients were selected on the basis of negativity for a series of B-cell antigens including CD10 and CD19. Twenty-one cases were CD34- positive (CD34+) (greater than 15% of blasts) and the remaining 19 were CD34-negative (CD34-) (less than 3% of blasts). IL-4 alone (100 U/ml) could stimulate either DNA synthesis (with greater than 2.0 stimulation index) or leukemic blast colony formation in 24 of 40 AML patients. In the presence of other growth factors, IL-4 showed divergent effects on IL-3-, granulocyte-macrophage colony-stimulating factor-, granulocyte colony-stimulating factor-, or erythropoietin-dependent colony formation. These effects of IL-4 were observed in both CD34+ and CD34- AML cases. IL-6 (100 U/mL) alone could not stimulate DNA synthesis and blast colony formation except for one CD34+ case. On the other hand, IL- 6 showed synergistic effects on IL-3- and IL-4-dependent blast colony formation in 10 of 12 and 7 of 9 CD34+ AML cases, respectively. Among CD34- AML cases, such synergism was seen only in 1 of 12 cases for IL-3- dependent colony formation and in 3 of 7 cases for IL-4-dependent colony formation. The divergent effect of IL-4 and the synergistic effect of IL-6 were also observed in purified CD34+ leukemic blast populations, indicating that these phenomena are not mediated by accessory cells. The present study suggests that IL-4, alone or in combination with other growth factors, has divergent effects on the growth of AML progenitors irrespective of the CD34 expression, and that IL-6 acts synergistically with IL-3 or IL-4 on the growth of leukemic progenitors preferentially in CD34+ AML.

In cynomolgus monkeys, twice daily subcutaneous injections of recombinant human interleukin-6 (rhIL-6) at doses of 5 to 80 micrograms/kg/d for 14 consecutive days caused dose-dependent increases in platelet count, usually continuing for more than 1 week after cessation of the injections. The count reached a level approximately twofold or more above the preinjection level even at 5 micrograms/kg/d, and at doses of more than 20 micrograms/kg/d, the increase became biphasic with a higher second peak 3 days after cessation of the injections. Morphologic analysis of the bone marrow after the 7 day- injections with 80 micrograms/kg/d revealed a marked increment in size of megakaryocytes compared with control, indicating the promotion of megakaryocyte maturation. Other changes attributable to the rhIL-6 treatment include dose-dependent loss of body weight, anemia, neutrophilia and monocytosis, elevation of serum C-reactive protein and alpha-1 acid glycoprotein levels, and decrease of serum albumin; all of which returned to normal within 1 week after cessation of the injections and were tolerable at doses of less than 10 micrograms/kg/d. These findings suggest that rhIL-6 may be an effective strategy for the treatment of thrombocytopenia.