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•Children living in extreme poverty during maintenance therapy for childhood ALL experience a 1.9-fold greater hazard of relapse.•Lower proportion of children with ALL living in extreme poverty achieve critical adherence (95%) to oral mercaptopurine.

CRLF2-rearranged (CRLF2r) acute lymphoblastic leukemia (ALL) accounts for more than half of Philadelphia chromosome-like (Ph-like) ALL and is associated with a poor outcome in children and adults. Overexpression of CRLF2 results in activation of Janus kinase (JAK)-STAT and parallel signaling pathways in experimental models, but existing small molecule inhibitors of JAKs show variable and limited efficacy. Here, we evaluated the efficacy of proteolysis-targeting chimeras (PROTACs) directed against JAKs. Solving the structure of type I JAK inhibitors ruxolitinib and baricitinib bound to the JAK2 tyrosine kinase domain enabled the rational design and optimization of a series of cereblon (CRBN)-directed JAK PROTACs utilizing derivatives of JAK inhibitors, linkers, and CRBN-specific molecular glues. The resulting JAK PROTACs were evaluated for target degradation, and activity was tested in a panel of leukemia/lymphoma cell lines and xenograft models of kinase-driven ALL. Multiple PROTACs were developed that degraded JAKs and potently killed CRLF2r cell lines, the most active of which also degraded the known CRBN neosubstrate GSPT1 and suppressed proliferation of CRLF2r ALL in vivo, e.g. compound 7 (SJ988497). Although dual JAK/GSPT1-degrading PROTACs were the most potent, the development and evaluation of multiple PROTACs in an extended panel of xenografts identified a potent JAK2-degrading, GSPT1-sparing PROTAC that demonstrated efficacy in the majority of kinase-driven xenografts that were otherwise unresponsive to type I JAK inhibitors, e.g. compound 8 (SJ1008030). Together, these data show the potential of JAK-directed protein degradation as a therapeutic approach in JAK-STAT–driven ALL and highlight the interplay of JAK and GSPT1 degradation activity in this context.

Acute erythroid leukemia (AEL) is characterized by a distinct morphology, mutational spectrum, lack of preclinical models, and poor prognosis. Here, using multiplexed genome editing of mouse hematopoietic stem and progenitor cells and transplant assays, we developed preclinical models of AEL and non-erythroid acute leukemia and describe the central role of mutational cooperativity in determining leukemia lineage. Different combination of mutations in Trp53, Bcor, Dnmt3a, Rb1, and Nfix resulted in the development of leukemia with an erythroid phenotype, accompanied by the acquisition of alterations in signaling and transcription factor genes that recapitulate human AEL by cross-species genomic analysis. Clonal expansion during tumor evolution was driven by mutational cooccurrence, with clones harboring a higher number of founder and secondary lesions (eg, mutations in signaling genes) showing greater evolutionary fitness. Mouse and human AEL exhibited deregulation of genes regulating erythroid development, notably Gata1, Klf1, and Nfe2, driven by the interaction of mutations of the epigenetic modifiers Dnmt3a and Tet2 that perturbed methylation and thus expression of lineage-specific transcription factors. The established mouse leukemias were used as a platform for drug screening. Drug sensitivity was associated with the leukemia genotype, with the poly (ADP-ribose) polymerase inhibitor talazoparib and the demethylating agent decitabine efficacious in Trp53/Bcor–mutant AEL, CDK7/9 inhibitors in Trp53/Bcor/Dnmt3a–mutant AEL, and gemcitabine and bromodomain inhibitors in NUP98-KDM5A leukemia. In conclusion, combinatorial genome editing has shown the interplay of founding and secondary genetic alterations in phenotype and clonal evolution, epigenetic regulation of lineage-specific transcription factors, and therapeutic tractability in erythroid leukemogenesis.

•High antimetabolite dose intensity during maintenance therapy for childhood ALL is associated with elevated odds of hematologic toxicities.•Among those who adhere to 6-mercaptopurine, high antimetabolite dose intensity is associated with significantly elevated hazard of relapse.

INTRODUCTION

Introduction: Current COG protocols for childhood ALL recommend increasing 6-mercaptopurine (6MP) and methotrexate (MTX) dose intensity (DI=prescribed therapy dose/ planned protocol dose) to >100% during maintenance for patients exhibiting inadequate myelosuppression (surrogate for systemic exposure to 6MP/MTX). Whether increasing DI >100% (high DI) to achieve myelosuppression is associated with increased toxicity is not clear. Additionally, whether high DI influences relapse risk, and the direction of that association, remains unknown. Nonadherence to 6MP results in inadequate myelosuppression and prompts clinicians to increase the prescribed dose. Nonadherence to 6MP is also associated with relapse (Bhatia, JAMA Onc2015). Prior literature examining the association between high DI and relapse risk did not consider adherence to chemotherapy. Here, we examined whether high 6MP/MTX DI affects toxicity or relapse, taking 6MP adherence into consideration.

Introduction: Computerized tomography (CT) scans of the sinus, chest, abdomen, and pelvis are often performed in children prior to hematopoietic stem cell transplantation (HSCT) to evaluate for occult infections. Identification of infectious abnormalities could allow for pre- or post-HSCT infection prophylaxis to reduce morbidity or mortality. However, the association of abnormal pre-HSCT and adverse outcomes post-HSCT has not been previously examined. Additionally, routine imaging may identify incidental non-infectious findings, potentially necessitating additional diagnostic workup and unnecessary radiation exposure. In this study, we sought to investigate the prevalence of abnormal findings on CT scans in children undergoing HSCT and their association with post-HSCT length of stay (LOS) and early non-relapse mortality (NRM).

INTRODUCTION

INTRODUCTION

Introduction:Race significantly influences phenotypic and genetic diversity in hematological diseases, consequently affecting disease prognosis, Human Leukocyte Antigen-matching and Hematopoietic Stem Cell Transplant (HSCT) outcomes. To ensure the development of novel transplant strategies effective for patients from diverse backgrounds, all racial groups must have equal opportunities to take part in HSCT clinical trials.

Introduction:Metabolic syndrome (MS) comprises a cluster of cardiovascular risk factors, including central obesity, dysglycemia, elevated blood pressure (BP), increased triglyceride levels (HyperTG), and low HDL cholesterol levels. Epidemiologic and clinical data suggest that MS may be an important etiologic factor in the progression of certain cancer types. These studies have excluded patients with myelodysplastic syndromes (MDS), but MS may be relevant in these patients owing to the link between cardiovascular disease and MDS derived from clonal hematopoiesis. We conducted a population-based analysis to define the prevalence of MS and its components among patients with MDS and explore the effect of MS on MDS outcomes.

Nonmyeloablative conditioning using total lymphoid irradiation (TLI) and rabbit antithymocyte serum (ATS) (the murine preclinical equivalent of antithymocyte globulin [ATG]) facilitates immune tolerance after bone marrow transplantation (BMT) across major histocompatibility complex (MHC) disparities and may be a useful strategy for nonmalignant disorders. We previously reported that donor effector T-cell function and graft-versus-host disease (GVHD) are regulated via recipient invariant natural killer T-cell (iNKT) interleukin-4–driven expansion of donor Foxp3+ naturally occurring regulatory T cells (Tregs). This occurs via recipient iNKT- and STAT6-dependent expansion of recipient myeloid dendritic cells (MDCs) that induce contact-dependent expansion of donor Treg through PD-1/PD ligand signaling. After TLI/ATS + BMT, Gr-1lowCD11c+ MDCs and Gr-1highCD11cneg myeloid-derived suppressor cells (MDSCs) were enriched in GVHD target organs. We now report that the recovery of both recipient MDSCs (P < .01) and MDCs (P < .01) is significantly increased when the alkylator cyclophosphamide (CTX) is added to TLI/ATS conditioning. In a BALB/c → B6 lethal GVHD model, adoptive transfer of MDSCs from TLI/ATS/CTX-conditioned recipients is associated with significantly improved GVHD colitis and survival (P < .001), conversion of MDSCs to PD ligand–expressing MDCs, and increased donor naturally occurring Treg recovery (P < .01) compared with control treatment. Using BALB/c donors and β-thalassemic HW-80 recipients, we found significantly improved rates of engraftment and GVHD following TLI/ATS/CTX compared with TLI/ATS, lethal or sublethal total body irradiation/ATS/CTX, or CTX/ATS conditioning. These data provide preclinical support for trials of TLI/ATG/alkylator regimens for MHC-mismatched BMT for hemoglobinopathies. The data also delineate innate immune mechanisms by which TLI/ATS/CTX conditioning may augment transplantation tolerance.

No relevant conflicts of interest to declare.

Activation of the serine/threonine kinase Akt and the regulation of its activation are recognized as critical in controlling proliferative/survival signals via many hematopoietic receptors. In B lymphocytes, the B-cell receptor (BCR)-mediated activation of Akt is attenuated by co–cross-linking of BCR with the inhibitory receptor Fc?RIIB1, and the binding of the SH2 domain-containing inositol phosphatase, SHIP, to Fc?RIIB1. Because SHIP dephosphorylates phosphatidylinositol 3,4,5-trisphosphate (PIP3) and activation of Akt requires PIP3, the destruction of this phospholipid has been proposed as the mechanism for Akt inhibition. However, upstream kinases that activate Akt, such as PDK1, also require PIP3 for activation. In this report, we addressed whether SHIP inhibits Akt directly at the level of Akt recruitment to the membrane, indirectly through PDK recruitment/phosphorylation of Akt, or both. We generated stable B-cell lines expressing a regulatable, but constitutively membrane-bound Akt that still required PDK-dependent phosphorylation for activation. Several lines of evidence suggested that activation of this membrane-targeted Akt is not inhibited by Fc?RIIB1/SHIP and that PDK is not a target for SHIP-mediated inhibition. These data demonstrate that SHIP inhibits Akt primarily through regulation of Akt membrane localization. We also observed during these studies that Fc?RIIB1/SHIP does not inhibit p70S6k activation, even though several other PIP3-dependent events were down-regulated. Because the enhanced activation of Akt in the absence of SHIP correlates with hyperproliferation in the myeloid lineage, our data have implications for SHIP and Akt-dependent regulation of proliferation in the hematopoietic lineage.

Pediatric Acute Myeloid Leukemia (AML) is a rare, but deadly cancer. Outcomes over the last 20 years have remained stagnant with an overall 5-year survival rate < 70% and relapse rates around 50%. Further, few new therapies have been successfully introduced to improve these outcomes. Here we report that exploiting deficiencies in DNA damage repair (DDR) is a potential therapeutic strategy for AML. Poly-ADP Ribose Polymerase (PARP) inhibitors were initially developed to target deficient homologous recombination (HR) in BRCA1/2mutated cancers by blocking single stranded base repair following DNA damage, leading to an accumulation of double stranded DNA breaks, thereby inducing apoptosis.

Background:Moderate mitochondrial stress induced by multiple mediators but most notably ROS can lead to activation of persistent mito-protective mechanisms termed “Mitohormesis”. As a result of massive protein synthesis, malignant plasma cells (PCs) from MM patients (pts) undergo substantial ER stress but in addition high rates of Ig synthesis contributes to overproduction of ROS. We hypothesized that MM cells exploit mitohormesis to maintain ROS in the hometic zone, thereby increasing mitochondrial fitness to avoid apoptosis. We therefore set out to determine if the processes of mitohormesis are activated in MM and whether unmitigated mitochondrial stress can be exploited as a therapeutic strategy in MM.

Introduction:Clinicians in academia face four major career challenges:

Background: The projected 5y survival rates for pediatric hematologic malignancies exceed 85% (SEER statistics, 2017), in large part due to risk-stratified intensive multi-agent therapeutic approaches. However, these regimens result in chemotoxicity, often requiring hospitalization. However, the burden of chemotoxicity-related hospitalizations in children with hematologic malignancies remains understudied.

Interleukin-4 (IL-4) has distinct hematopoietic activities, primarily as a costimulant with other cytokines to enhance colony formation of hematopoietic progenitors. We investigated the influence of IL-4 on stromal cell-supported long-term cultures (LTCs) of normal human bone marrow. Addition of IL-4 to LTCs of unseparated bone marrow or highly enriched CD34+ cells resulted in a significant increase of myeloid progenitors in the nonadherent, as well as in the stromal cell-adherent cell populations. In contrast, the total cell number was not influenced by IL-4, suggesting a selective effect on primitive progenitor cells. Cord blood cells or CD34+ bone marrow cells were incubated with stem cell factor (SCF) and/or IL-4 in stromal cell-free cultures. In these experiments, a twofold to fivefold increase of myeloid progenitor cells was observed in the presence of SCF and IL-4 as compared with SCF alone. Preincubation of the stromal cell cultures with IL-4 resulted in an enhanced adherence of CD34+ cells to the stromal layer. Secretion of hematopoietic growth factors produced by the stromal cells, such as granulocyte-macrophage colony-stimulating factor (G-CSF), and IL-1, was inhibited by IL-4. Thus, the increase of hematopoietic progenitors in LTCs, as observed in the presence of IL-4, can be at least partially explained by a costimulation of SCF and IL-4 on primitive progenitor cells and by an enhancement of hematopoietic cells to stroma. The downregulation of CSFs by IL-4 might prevent the expansion of the mature hematopoietic cell compartment.

In the present study, we investigated the effect of interf eron-α (IFN-α) on the expression of interleukin-10 (IL-10) mRNA and protein synthesis in human monocytes and CD4+T cells. In mononuclear cells, IFN-α induced expression of IL-10 mRNA and further enhanced lipopolysaccharide (LPS)-stim-ulated IL-10 expression. In purified monocytes, a strong expression of IL-10 mRNA induced by LPS was not further enhanced by IFN-α. In highly purified CD4+T cells, IFN-α upregulated IL-10 mRNA upon activation with phytohemag-glutinin and phorbol myristate acetate. In purified monocytes, an effect of IFN-α on IL-10 protein synthesis was dependent on costimulation with LPS. Maximal stimulation of IL-10 protein by IFN-α was seen after prolonged incubation periods of 48 to 96 hours, whereas IFN-γ reduced IL-10 production in the early incubation period. Similar effects of IFN-α were observed in CD4+T cells activated with CD3 and CD28 monoclonal antibodies. Addition of IFN-α caused an increase of IL-10 in culture supernatants of activated T-helper cells of more than 100% after 96 hours of incubation. In contrast, other cytokines, including IFN-γ and IL-4, had no influence on IL-10 secretion stimulated by CD3 and CD28 in CD4+T cells. In serum samples of IFN-α-treated individuals, we failed to detect an influence of cytokine treatment on IL-10 serum levels, confirming the requirement of additional activating signals for IFN-α—mediated effects on IL-10 synthesis. In conclusion, IFN-α enhances the late induction of IL-10, which physiologically occurs upon stimulation of monocytes and T cells. Biologically, this effect might enhance the negative-feedback mechanism ascribed to IL-10, which limits inflammatory reactions.

We investigated the effects of interferon-alpha (IFN-alpha) on the expression of cytokines by human bone marrow stromal cells. Production of granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte-CSF (G-CSF), and interleukin-1 beta (IL-1 beta) in stromal cell layers was induced by incubation with IL-1 alpha, tumor necrosis factor (TNF), or lipopolysaccharide (LPS). Addition of IFN-alpha to such stimulated cultures resulted in a strong downregulation of mRNA expression of GM-CSF and IL-1 beta. Similarly, the protein levels of GM- CSF and IL-1 beta were significantly reduced by IFN-alpha, whereas G- CSF production was only moderately inhibited. In contrast, IFN-alpha markedly stimulated the production of IL-1 receptor antagonist (IL-1RA) by stromal cells. The inhibition of cytokine expression resulted in a reduced hematopoietic activity of stromal cells, indicated by a reduced proliferation of the factor dependent cell line MO7e on IFN-alpha- treated stromal cells. In the presence of cycloheximide (CHX), IFN- alpha failed to inhibit IL-1 mRNA expression, whereas the regulation of GM-CSF and IL-1RA by IFN-alpha was not affected. Our results indicate that the myelosuppressive effects of IFN-alpha, as observed in therapeutic applications or associated with viral infections, are, in part, indirectly mediated by inhibition of the paracrine production of hematopoietic growth factors.

Neoplastic populations from 25 cases of B-lymphocytic leukemia (B-LL) were investigated in an attempt to define the stages of maturation arrest represented in this disease and the relationship, if any, to various clinical parameters. Intrinsic to this study was the expression of a number of B-cell antigens defined by monoclonal antibodies. These included antibodies to B1 and B2, both expressed exclusively on B lymphocytes, but with the latter probably restricted to a narrow window of differentiation, BB-1 and LB-1, both markers of activated lymphocytes, and 38.13, a monoclonal antibody raised against and recognizing an epitope expressed on Burkitt lymphoma cells. While the patterns of reactivities were complex, the cases could be classified into various groups on the basis of the phenotypes revealed. These were termed “pre-B,” “early-B,” “intermediate-B,xyc “mature-B,” and “secretory- B” from their patterns of immunoglobulin (Ig) isotype expression and their capacity to secrete Ig in short-term culture. Although B1 was detected on neoplastic cells from all but one case, its intensity of expression varied markedly, being strongest on the “mature-B” and “secretory-B” cases and weakest on the “pre-B” type. The expression of B2 was essentially restricted to the “intermediate-B,” “mature-B,” and “secretory-B” cases and was usually, but not invariably, accompanied by the coexpression of surface IgM and IgD. While expression of BB-1 was restricted to a few cases with mature features, LB-1 was more frequently detected and found predominantly on “intermediate-B” and “mature-Bxyc cases. The 38.13 antibody was found to react weakly with a number of the populations coexpressing IgM and IgD. The export of large amounts of whole Ig was restricted to three “secretory-B” cases all of which were associated with a serum M-component corresponding to the Ig isotype secreted in vitro. In contrast, the secretion of free Ig light chains was a consistent feature of all B-LL, and the amounts detected did not vary considerably between the different types. No correlation between immunologic cell-type and the stage of the disease was apparent. Classification of the cases into “true” B-chronic lymphocytic leukemia and immunocytoma similarly revealed no strict association of these histopathologic entities with any particular phenotypic group, although those cases with the more mature features tended to be immunocytomas. The findings are discussed within the context of normal B-cell differentiation pathways.

In the present study, we investigated the effect of interferon-alpha (IFN-alpha) on the expression of interleukin-10 (IL-10) mRNA and protein synthesis in human monocytes and CD4+ T cells. In mononuclear cells, IFN-alpha induced expression of IL-10 mRNA and further enhanced lipopolysaccharide (LPS)-stimulated IL-10 expression. In purified monocytes, a strong expression of IL-10 mRNA induced by LPS was not further enhanced by IFN-alpha. In highly purified CD4+ T cells, IFN- alpha upregulated IL-10 mRNA upon activation with phytohemagglutinin and phorbol myristate acetate. In purified monocytes, an effect of IFN- alpha on IL-10 protein synthesis was dependent on costimulation with LPS. Maximal stimulation of IL-10 protein by IFN-alpha was seen after prolonged incubation periods of 48 to 96 hours, whereas IFN-gamma reduced IL-10 production in the early incubation period. Similar effects of IFN-alpha were observed in CD4+ T cells activated with CD3 and CD28 monoclonal antibodies. Addition of IFN-alpha caused an increase of IL-10 in culture supernatants of activated T-helper cells of more than 100% after 96 hours of incubation. In contrast, other cytokines, including IFN-gamma and IL-4, had no influence on IL-10 secretion stimulated by CD3 and CD28 in CD4+ T cells. In serum samples of IFN-alpha-treated individuals, we failed to detect an influence of cytokine treatment on IL-10 serum levels, confirming the requirement of additional activating signals for IFN-alpha-mediated effects on IL-10 synthesis. In conclusion, IFN-alpha enhances the late induction of IL- 10, which physiologically occurs upon stimulation of monocytes and T cells. Biologically, this effect might enhance the negative-feedback mechanism ascribed to IL-10, which limits inflammatory reactions.

We investigated the production of cytokines by highly purified T helper cells from B-cell chronic lymphocytic leukemia (B-CLL) patients stimulated by different activation pathways, and we studied the influence of various accessory cell populations on the pattern of the secretion of cytokines, including interleukin (IL)-2, IL-4, interferon- gamma (IFN-gamma), and IL-10. Neither a qualitative nor a quantitative difference in cytokine production and proliferative capacity was observed in CLL-derived purified T cells compared with normal individuals, when T cells were stimulated by different pathways, including CD3, CD2, and costimulation with CD28. Addition of autologous accessory cells (aAC), however, dramatically influenced the cytokine pattern of normal versus B-CLL-derived T cells. CLL cells as aAC caused a marked increase of IL-2, whereas IFN-gamma was only slightly induced and IL-4 was not influenced. In contrast, in normal individuals addition of aAC, which predominantly consisted of monocytes, resulted in a significant increase of IFN-gamma and a reduction of IL-4 secretion. IL-2 production was inhibited by higher concentrations of aAC. The increased stimulation of IL-2 production by CLL cells was not specific to the leukemic cell population, as purified B cells from normal individuals had the same effect. On the other hand, purified monocytes from CLL patients and controls both induced IFN-gamma production and inhibited IL-4 secretion. After antigen-specific stimulation with tetanus toxoid, cytokine secretion was influenced by the type of aAC in a similar pattern. We conclude that T helper cells derived from patients with B-CLL are intrinsically normal and that the predominance of B cells as accessory cells in CLL significantly alters the immune function of T helper cells in vitro.

nterleukin-8 (IL-8) is produced by many cell types upon stimulation with bacterial products or inflammation-associated cytokines such as tumor necrosis factor-alpha and IL-1. Interferons (IFNs) represent another group of cytokines that are induced by similar stimuli in inflammatory reactions. We show now that type-I IFNs are potent inhibitors of IL-8 expression in vitro and in vivo. A significant reduction of both secretion of IL-8 protein and accumulation of IL-8 mRNA in vitro was observed in several cell types comprising peripheral blood mononuclear cells (PBMNC) from healthy donors and from patients with chronic myelogenous leukemia (CML), the myelomonocytic cell line THP-1, and bone marrow (BM) stromal cells as a representative model for BM microenvironment. By contrast, in lipopolysaccharide-stimulated polymorphonuclear phagocytes IFN failed to suppress IL-8 expression. In untreated patients with CML, a constitutive expression of IL-8 mRNA was detected in freshly isolated PBMNC that was markedly reduced 5 hours after therapeutic application of IFN-alpha. The mechanism of IL-8 downregulation was studied more in detail in the THP-1 cell line. The experiments showed that de novo protein synthesis was not required for the inhibitory effect. RNA decay analysis and nuclear run-on assays suggest that in THP-1 cell line the inhibition of IL-8 expression is predominantly regulated at the posttranscriptional level.

Mullighan: Loxo Oncology: Research Funding; Amgen: Honoraria, Other: speaker, sponsored travel; Illumina: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: sponsored travel; AbbVie: Research Funding; Pfizer: Honoraria, Other: speaker, sponsored travel, Research Funding.

Chromosomal translocations are common in acute myeloid leukemia (AML), causing gene fusions that encode oncogenic proteins. The NUP98gene participates in chromosomal rearrangements with over 30 fusion partners and comprises 6-10% of de novocases of pediatric AML. These fusions are associated with poor prognosis in children and adults. Among them, NUP98-KDM5Ais further enriched in specific subpopulations, found in 15% of non-Down syndrome acute megakaryoblastic leukemia cases and 20% of pediatric acute erythroleukemia. Despite these associations, the direct impact of NUP98-KDM5Aon the growth and differentiation of human hematopoietic cells has not been systemically studied.

Mullighan: Abbvie: Research Funding; Amgen: Honoraria, Speakers Bureau; Loxo Oncology: Research Funding; Cancer Prevention and Research Institute of Texas: Consultancy; Pfizer: Honoraria, Research Funding, Speakers Bureau.

Sintim: KinaRx, LLC: Other: Founder and Scientific Advisor. Aman:KinaRx, LLC: Other: Founder. Holtsberg:KinaRx, LLC: Other: Founder. Emadi:NewLink Genetics: Research Funding. Lapidus:KinaRx, LLC: Other: Founder and Scientific Advisor.

Introduction

Maji: Case Western Reserve University: Patents & Royalties: Licensed to XaTek, Inc. . Mohseni:Case Western Reserve University: Patents & Royalties: Licensed to XaTek, Inc.; XaTek, Inc.: Consultancy. Suster:XaTek, Inc.: Consultancy; Case Western Reserve University: Patents & Royalties: licensed to XaTek, Inc..

Genes encoding epigenetic regulators are commonly mutated at relapse in acute lymphoblastic leukemia, but the way in which such mutations promote drug resistance, and their potential for therapeutic targeting is largely unknown. We previously identified mutations in CREBBP, encoding CREBBP-binding protein, a histone and non-histone acetyl transferase and transcriptional coregulatorin relapsed ALL and non-Hodgkin lymphoma. In view of the known role of CREBBP in mediating the transcriptional response to glucocorticoids, we hypothesized that CREBBPmutations promote glucocorticoid resistance, and sought to comprehensively define the prevalence and spectrum of mutations in relapsed ALL, and elucidate their role in resistance.

No relevant conflicts of interest to declare.

Wang: Fluorinov Pharma Inc.: Employment. Dove:Fluorinov Pharma Inc.: Employment. Hadri:Fluorinov Pharma Inc.: Employment. O'Neill:Fluorinov Pharma Inc.: Employment. Slassi:Fluorinov Pharma Inc.: Employment.

Hemolysis, oxidative stress, inflammation, vaso-occlusion, and organ infarction are hallmarks of sickle cell disease (SCD). Hemolysis releases free hemoglobin (Hb) and Hb-containing microparticles into the vasculature that upon oxidation to methemoglobin frees heme from the globin, which in turn can promote oxidative stress and activate toll-like receptor 4 (TLR4) signaling. Hemopexin (HPX), a plasma β1-glycoprotein, binds heme with a very high affinity (Kd< 10-12M), and transports it to the liver for catabolism via CD91 receptor-mediated uptake. SCD patients have low serum HPX levels likely due to chronic hemolysis leading to increased HPX catabolism with insufficient compensatory increase in synthesis. We and others have shown that HPX transports heme to the liver, and inhibits heme toxicity and the activation of endothelial, leukocyte and platelet TLR4 signaling. Acute studies have shown HPX infusion prior to a heme challenge protects sickle mice from vaso-occlusion and developing acute pulmonary injury while chronic HPX infusion therapy modified heme toxicity to endothelium. We hypothesize that in SCD mice, hepatic overexpression of HPX will bind the proximal mediator of vascular activation, heme, and will inhibit inflammation and microvascular stasis (vaso-occlusion). To examine the protective role of HPX in SCD, we transplanted bone marrow from NY1DD SCD mice into HPX-/-or normal C57BL/6 mice. After 12 weeks, conversion to the HbS phenotype was confirmed by isoelectric focusing. Dorsal skin fold chambers (DSFC) were implanted in week 13 and microvascular stasis (% non-flowing venules) assessed in response to heme (3.2 µmol/kg) infusion. HPX-/-sickle mice had 34% ± 3% and 24% ± 2% at 1h and 4h post heme, significantly greater than HPX+/+C57BL/6 sickle mice which had 21% ± 5% and 13% ± 8% at 1 and 4 h, (mean ± SD, p<.05), demonstrating the protective role of HPX in SCD. To further test our hypothesis, we utilized Sleeping Beauty (SB)transposon-mediated gene therapy to overexpress rat HPX in NY1DD and Townes-SS SCD mice. Rat HPX plasmid (pT2/Caggs-HPX) was delivered with an SBtransposase plasmid (pK/CMV-SB100X) and luciferase (LUC) plasmid (pT2/Caggs-LUC, as tracer) in trans into NY1DD or Townes-SS SCD mice by hydrodynamic tail vein injections. Control SCD mice were infused with the same volume of lactated Ringer's solution (LRS) or LUC plasmid with SBtransposase plasmid in trans. One week later, the mice LUC bioluminescence imaging showed the liver was the primary location of expression. Four weeks later, the HPX SCD mice had marked increases in hepatic rat HPX mRNA (300-2000 copies/5ng total RNA) comparing to LRS and SB-LUC controls (0-44 copies/5ng total RNA). Plasma and hepatic HPX were significantly increased compared to LRS and SB-LUC controls. In vitroexpression of the rat HPX plasmid in Chinese Hamster Ovary cells, and protein purification confirmed heme binding activity by spectroscopic scan absorbance shifts of rat HPX-heme complexes at 414nm.

No relevant conflicts of interest to declare.

Wang: Fluorinov Pharma Inc.: partial salary/fellowship support Other. Dove:Fluorinov Pharma Inc.: Employment. Climie:Fluorinov Pharma Inc.: Employment. O'Neill:Fluorinov Pharma Inc.: Employment. Slassi:Fluorinov Pharma Inc.: Employment.

Proteasome inhibitors (PIs), such as bortezomib and carfilzomib, are often associated with serious toxicities, poor pharmacokinetics (PK), and the inconvenience of intravenous administration. Therefore, there is a need for safer and more effective orally active PIs. Applying a novel fluorine-based medicinal chemistry technology, we designed, synthesized and tested novel proprietary analogs of epoxyketone-based PIs. Our initial screening identified a lead orally bioavailable PI, FV-162, which had superior potency in proteasome activity inhibition, cytotoxicity in cultured human multiple myeloma (MM) cells and metabolic stability in mouse liver microsomes, compared to an oral PI currently under clinical evaluation, ONX-0912.

Abstract 4853 was withdrawn on April 3, 2009 by authors' request.