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Acute myeloid leukemias (AML), the most lethal forms of blood cancer, are genomic instability disorders primarily driven by somatic mutations that greatly impact proliferation and survival of mutant clones1. The multistep mechanism of disease progression can be attributed, in part, to the defects in one or more pathways involving responses to, or repair of, damaged DNA (DD) and base excision repair (BER). The basal levels of DD and BER are higher in myeloid leukemias due to higher levels of reactive oxygen species (ROS)-mediated accumulation of 8-oxyguanine (8-OG)2. Poly(ADP) Ribosylation (PARylation) by PAR polymerases (PARPs) is one of the early key steps in sensing and repairing ROS-induced DNA damage response (DDR) 3. Consistent with recent findings4,5 here we report that 2'-5'oligoadenylate synthases (OASs), a family of latent 2'-5'-adenylyl transferases, otherwise involved in cellular antiviral responses6, are also involved in PAR remodeling of the DDR in MDS and AML cells. The 2'-hydroxyl group of PAR ribose acts as an acceptor for 2'AMP in the OAS enzymatic reaction and terminates chain elongation (Fig. A). OAS1 over expression can increase genomic instability by increasing the flux of PARP-mediated DNA repair, promoting cellular proliferation (Fig. B)5. Expression analysis of OASs in AML patients (n=451, Beat AML) showed that OAS1 is upregulated (2-fold) in AML patients compared to normal bone marrow-derived CD34+ hematopoietic stem and progenitor cells (HSPC)(Fig. C). Knockout of OAS1 and OAS2 using Crispr-Cas9 in MDS-L cells (Fig. D), a cell line derived from an MDS patient, confers sensitivity to H2O2-induced DNA damage-mediated cell death; however, OAS3 has no effect. Conversely, ectopic over expression of OAS1 or OAS2 but not OAS3 in HEK293 cells provides protection against H2O2-induced cell death (Fig. E-F). Proteomic analysis of the OAS1 and OAS2 interactome using LCMS/MS suggests that over expression of OAS1 and OAS2 perturbs the differentiation program of HSPCs that may result in neoplastic evolution. Thus, OASs modify PAR chains, promoting speedy DNA repair and cell survival along with the induction of a differentiation block in HSPCs that leads to clonal expansion. In summary, an overburdened DDR may contribute to AML pathogenesis. Therefore, inhibiting this stimulator of BER/DDR can provide a novel therapeutic avenue in myeloid neoplasms. The current study points to the probable utility of a novel therapeutic approach of targeting OAS in combination with DNA damaging agents to prevent relapse and resistance in the treatment of leukemias. References 1. Abelson S, Collord G, Ng SWK, et al. Prediction of acute myeloid leukaemia risk in healthy individuals. Nature. 2018;559(7714):400-404. doi:10.1038/s41586-018-0317-6 2. Jankowska AM, Gondek LP, Szpurka H, Nearman ZP, Tiu RV, Maciejewski JP. Base excision repair dysfunction in a subgroup of patients with myelodysplastic syndrome. Leukemia. 2008;22(3):551-558. doi:10.1038/sj.leu.2405055 3. Rogge RA, Gibson BA, Kraus WL. Identifying Genomic Sites of ADP-Ribosylation Mediated by Specific Nuclear PARP Enzymes Using Click-ChIP. Methods Mol Biol. 2018;1813:371-387. doi:10.1007/978-1-4939-8588-3_25 4. Khodarev NN, Minn AJ, Efimova EV, et al. Signal transducer and activator of transcription 1 regulates both cytotoxic and prosurvival functions in tumor cells. Cancer Res. 2007;67(19):9214-9220. doi:10.1158/0008-5472.CAN-07-1019 5. Kondratova AA, Cheon H, Dong B, et al. Suppressing PARylation by 2',5'-oligoadenylate synthetase 1 inhibits DNA damage-induced cell death. EMBO J. 2020;39(11):e101573. doi:10.15252/embj.2019101573 6. Chakrabarti A, Jha BK, Silverman RH. New insights into the role of RNase L in innate immunity. J Interferon Cytokine Res. 2011;31(1):49-57. doi:10.1089/jir.2010.0120 Disclosures Saunthararajah: EpiDestiny: Consultancy, Current equity holder in private company, Patents & Royalties: University of Illinois at Chicago.

Nonmyeloablative allogeneic transplantation (NMAT) infrequently cures active chemoresistant, bulky, or aggressive B-cell lymphoma (B-cell non-Hodgkin lymphoma [B-NHL]). We hypothesized that 90Y-ibritumomab tiuxetan–based NMAT would facilitate early cytoreduction in such patients promoting improved long-term disease control by the allogeneic graft. Forty high-risk B-NHL patients with persistent disease received 0.4 mCi/kg (maximum, 32 mCi/kg) 90Y-ibritumomab tiuxetan, fludarabine, and 2 Gy total body irradiation and matched-related (15) or unrelated (25) transplantation. Baseline features included: median age, 58 years (range, 29-69 years); median prior regimens, 6 (range, 3-12); chemosensitive disease, 6 (15%); bulk > 5 cm, 17 (range, 5.2-18.6 cm, 43%); diffuse large B-cell lymphoma, 14 (35%); and comorbidity score > zero, 34 (85%). Early responses were observed in 24 (60%, 14 complete remission/complete remission unconfirmed, 10 partial response) patients, including 17 of 29 (59%) with chemotherapy-resistant disease and 10 (59%) with bulk > 5 cm. The estimated 30-month survival, progression-free survival, and nonrelapse mortality were 54.1%, 31.1%, and 15.9%, respectively. Early response, baseline platelet counts over 25 000/μL, indolent histology, and related donors were associated with improved survival. The addition of 90Y-ibritumomab tiuxetan to NMAT is safe and yields early responses and prolonged disease control in some of the highest-risk B-NHL patients. This trial was registered at www.clinicaltrials.gov as #NCT00119392.

Background: The impact of second line therapies on health related quality of life (HRQoL) and fatigue in pediatric patients with ITP is not well studied. Objective: To describe the impact of second line therapies on HRQoL and fatigue in North American pediatric patients with ITP. Methods: A longitudinal observational cohort of 120 children with ITP starting second line treatments was enrolled from 2013-2015 at 21 ICON centers. Enrollment requirements included age 1-17y and starting a second line treatment (not IVIG, corticosteroids or anti-D immunoglobulin) as monotherapy. HRQoL (Kids ITP Tool - KIT) and fatigue (Hockenberry Fatigue Scale - FS) surveys were completed prior to starting treatment (baseline) and 1 and 12 months after starting treatment by patient/caregiver. KIT is scored from 0 (worst) to 100 (best), and the FS scores were re-scaled so that 0 is no fatigue and 100 is highest fatigue. At the same time points as the patient/caregiver surveys, physicians assessed the perceived effect of treatment on patient HRQoL using a 7-point scale. ANOVA was used to compare the baseline means of the treatment groups. This study specifically compared change from baseline to 1 month in the KIT and FS using paired t-tests within each treatment group. The 12 month timepoint was not used in the paired analysis of individual treatments due to attrition between 1 and 12 months. Results: The median age at enrollment was 11.3 y (1.2-17.8), and 16% (19/120) had newly diagnosed ITP, 31% (37/120) had persistent ITP, and 53% (64/120) had chronic ITP. The median number of prior treatments was 3 (range: 1-9). Fifty-eight (48%) patients had received at least one prior second line treatment. Treatments selected for second line treatment included: rituximab (n=43), romiplostim (n=31), eltrombopag (n=20), oral immunosuppressants (n=19), splenectomy (n=4), and dapsone (n=3). The child and parent proxy KIT scores significantly improved on rituximab (p As previously described, at enrollment, physicians reported that ITP had impacted the patients' HRQoL severely in 15%, significantly in 45%, moderately in 38%, and almost not at all in 3%. Physicians reported that HRQoL improved in 68% (range: 64-75%) of patients while on treatment from baseline to 1 month with no significant difference by treatment group (p=0.46). The physician's assessment of the patient's baseline HRQoL significantly correlated with the child and parent proxy KIT report (p At enrollment, the median FS-Child score (n=54) was 18.5 (range 0-85), the median FS-Adolescent score (n=42) was 20.2 (0-73), and the median FS-Parent (n= 100) score was 35 (7-81). One month FS-Child improved for those who were treated with rituximab (p=0.03); there was no significant change in fatigue on the other treatments. One month FS-Parent significantly improved for those treated with rituximab (p=0.015) and eltrombopag (p=0.009). Conclusions: In this pediatric cohort, all second line treatments appear to significantly improve HRQoL in ITP. Rituximab had the greatest impact in decreasing fatigue at one month. Physician assessment of patient HRQoL did not correlate well with patient assessment after treatment was started, suggesting there may be challenges in ascertaining the effect of treatment on HRQoL. Future analysis of ICON1 will consider the impact of treatment on HRQoL and fatigue while also accounting for the treatment effect on bleeding and platelet count. Disclosures Grace: Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Klaassen: Amgen: Consultancy; Hoffman-La Roche LTD: Consultancy; Octapharma: Honoraria; Baxalta: Honoraria; Biogen Canada LTD: Consultancy; Agios Pharmaceuticals: Consultancy. Despotovic: Sanofi: Consultancy; Schell Cooley LLP: Other: Expert witness. Bussel: Protalex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Momenta: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Rothman: Pfizer: Consultancy; Agios Pharmaceuticals: Honoraria. Haley: Genentech: Honoraria; Baxalta: Honoraria; CSL Behring: Honoraria. Neufeld: Octapharma: Consultancy, Honoraria; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Lambert: Educational Concepts in Medicine: Honoraria; Novartis: Honoraria; AstraZeneca: Research Funding.

A cell culture system consisting of mouse S17 stromal cells supplemented with cytokines was developed for hematopoietic differentiation of rhesus monkey embryonic stem (ES) cells. The differentiated colonies that formed contained clusters of hematopoietic-like cells, as well as structures similar in appearance to embryonic blood islands. When this culture system was supplemented with bone morphogenetic protein 4 (BMP-4), the numbers of primary hematopoietic clusters increased by an average of 15 fold. The primary hematopoietic clusters containing clonogenic precursors (expandable hematopoietic clusters) increased by 18 fold. Immunofluorescence analysis showed that a substantial percentage of the hematopoietic-like cells were CD34+, with morphologic features of undifferentiated blast cells. Enrichment of the CD34+ cells was associated with enhanced stromal-dependent, cytokine-driven formation of cobblestone colonies on secondary plating. The hematopoietic identity of the precursors was further indicated by their expression of genes associated with hematopoietic differentiation, as well as morphologic assessments that showed erythroid and myeloid lineages among the progeny cells. In addition, reverse transcriptase–polymerase chain reaction analysis of BMP-4–treated rhesus monkey ES cells demonstrated an up-regulation of early-expressed genes responsible for embryonic hematopoiesis and angiogenesis during the first 7 days of culture. These observations suggest that embryonic mesoderm regulatory protein may mimic physiologic signals that are required for the onset of embryonic hematopoiesis and stem cell formation in rhesus monkey ES cells.

The relapse rate in childhood acute lymphoblastic leukemia (ALL) is approximately 30% but few reinduction regimens have investigated the intensive use of polyethylene glycol Escherichia coliasparaginase (PEG-Asp). Therefore, we assessed the pharmocokinetics and efficacy of PEG-Asp in this setting. Children with B-precursor ALL, in first marrow and/or extramedullary relapse were eligible. Reinduction included doxorubicin on day 1, prednisone for 28 days, vincristine weekly for 4 weeks, and PEG-Asp either weekly or biweekly by randomization. Asparaginase levels and antibody to both E coli asparaginase and PEG-asp were measured weekly just before each PEG-asp dose. Overall, 129 of 144 patients (pts) (90%) achieved a complete remission (CR). There was a highly significant difference in CR rates between weekly (69 of 71; 97%) and biweekly (60 of 73; 82%) PEG-Asp dosing (P = .003). Grade 3 or 4 infectious toxicity was common (50%), but only 4 pts died of sepsis during induction. Other toxicities were infrequent and hypersensitivity was rare (6 of 144; 4%). Low asparaginase levels were associated with high antibody titers to either native (P = .024) or PEG asp (P = .0013). The CR rate was significantly associated with higher levels of asparaginase (P = .012). Patients with ALL in first relapse receiving weekly PEG-Asp had a higher rate of second remission compared with biweekly dosing. Low levels of asparaginase were associated with high antibody titers. Increased asparaginase levels may correlate with an improved CR rate. The use of intensive PEG-Asp should be explored further in the treatment of ALL.

The optimal management of prolonged priapism for patients with sickle cell anemia (SCA) has not been established. We prospectively studied in an outpatient setting the efficacy and safety of a procedure that employs aspiration of blood from the corpora cavernosa and irrigation with a dilute epinephrine solution under local anesthesia to relieve priapism in young patients with SCA. If hydration and analgesics failed to produce detumescence or if priapism had lasted >4 hours, the protocol was activated in the emergency room or clinic. Fifteen patients with homozygous SCA (Hb SS) were treated on 39 occasions; 10 patients were treated once, 1 patient twice, 2 patients 3 times, 1 patient 6 times, and 1 patient 15 times. Median age of patients at first treatment was 14.3 years (range, 3.9-18.3 years). The procedure was successful in producing immediate detumescence on 37 of 39 occasions (95% efficacy, 95% confidence intervals (CI): 81%-99%). No serious immediate or long-term side effects were observed. None of the patients who demonstrated detumescence required hospitalization. The 2 patients whose priapism persisted after aspiration and irrigation presented with episodes lasting >24 hours. All evaluable patients whose priapism resolved after aspiration and irrigation self-reported normal erectile function at a median of 40 months (range, 3-58 months) after the last procedure. Thus, aspiration of the corpora cavernosa followed by irrigation with dilute epinephrine is effective in producing immediate and sustained detumescence and should be the initial therapy employed for patients with SCA and prolonged priapism. (Blood, 2000; 95:78-82)

Acute chest syndrome (ACS) in patients with sickle cell disease (SCD) has historically been managed with oxygen, antibiotics, and blood transfusions. Recently high-dose corticosteroid therapy was shown to reduce the duration of hospitalization in children with SCD and vaso-occlusive crisis. Therefore, we chose to assess the use of glucocorticoids in ACS. We conducted a randomized, double-blind placebo-controlled trial to evaluate the efficacy and toxicity of intravenous dexamethasone (0.3 mg/kg every 12 hours × 4 doses) in children with SCD hospitalized with mild to moderately severe ACS. Forty-three evaluable episodes of ACS occurred in 38 children (median age, 6.7 years). Twenty-two patients received dexamethasone and 21 patients received placebo. There were no statistically significant differences in demographic, clinical, or laboratory characteristics between the two groups. Mean hospital stay was shorter in the dexamethasone-treated group (47 hours v 80 hours; P = .005). Dexamethasone therapy prevented clinical deterioration and reduced the need for blood transfusions (P < .001 and = .013, respectively). Mean duration of oxygen and analgesic therapy, number of opioid doses, and the duration of fever was also significantly reduced in the dexamethasone-treated patients. Of seven patients readmitted within 72 hours after discharge (six after dexamethasone; P = .095), only one had respiratory complications (P = 1.00). No side effects clearly related to dexamethasone were observed. In a stepwise multiple linear regression analysis, gender and previous episodes of ACS were the only variables that appeared to predict response to dexamethasone, as measured by lengh of hospital stay. Intravenous dexamethasone has a beneficial effect in children with SCD hospitalized with mild to moderately severe acute chest syndrome. Further study of this therapeutic modality is indicated.© 1998 by The American Society of Hematology.

Extracellular adenosine triphosphate (ATP) and adenosine diphosphate (ADP) activate multiple types of P2-nucleotide receptors expressed in platelets or leukocytes. Electrophysiological and biochemical studies have indicated expression of the P2X1 receptor, an ATP-gated cation channel, in human and rat platelets, rat basophilic leukemia (RBL) cells, and phorbol myristate acetate (PMA)-differentiated HL-60 myeloid cells. Although these findings suggest that P2X1 receptors are present in both blood leukocytes and blood platelets, the relative levels of P2X1receptor expression and function in human blood leukocytes and platelets have not been directly characterized. On the basis of both immunoblot analysis and functional assays of P2X1receptor-mediated ionic fluxes, we report that there is significant expression of P2X1 receptors in human platelets, but not in neutrophils, monocytes, or blood lymphocytes. Thus, unlike platelets and myeloid progenitor cell lines, fully differentiated human blood leukocytes do not express functionally significant numbers of P2X1 receptors, suggesting the downregulation of P2X1 receptor gene expression during the differentiation of phagocytic leukocytes. By contrast, P2X1 receptor expression is strongly maintained during megakaryocytic differentiation and platelet release. Immunoblot analysis indicated that the platelet P2X1 receptor migrates as an approximately 60-kD protein during SDS-electrophoresis under reducing or nonreducing conditions. Treatment of platelet membranes with endoglycosidase-F causes the P2X1 receptor band to migrate as a 46-kD protein, verifying the highly glycosylated nature of the mature receptor protein. Additional studies of nucleotide-induced changes in Ca2+influx/mobilization demonstrated that the platelet P2X1receptors are pharmacologically distinct from the well-characterized ADP receptors of these cells. This finding suggests a unique role for these ATP-gated ion channels during hemostasis or thrombosis.

Since the initial observations by Kaiser and Edelman, interest in the role of calcium in ACS-induced apoptosis has wavered, in part because of the fact that extracellular calcium is only necessary for induction of apoptosis in thymocytes, but not in peripheral lymphocytes or lymphoma cells. Now, as result of molecular evidence implicating two separate ligand-gated calcium channels in ACS-induced apoptosis, interest in the role of calcium is sure to be renewed. The major challenge lies in determining the signal transduction pathway through which ACS-induced calcium fluxes mediate apoptosis.

The proliferation and differentiation of neutrophils is regulated by granulocyte-specific colony-stimulating factor (G-CSF ). G-CSF uses a receptor of the cytokine receptor superfamily and, in common with all members of the family, induces the tyrosine phosphorylation and activation of members of the Janus protein tyrosine kinase (Jak) family. In both myeloid cells and a human fibrosarcoma cell line expressing the G-CSF receptor, G-CSF induces the tyrosine phosphorylation and activation of Jak1, Jak2, and Tyk2. In addition, G-CSF induces the tyrosine phosphorylation of the receptor and members of the signal transducers and activators of transcription (Stat) family, including Stat3, as well as Stat1 and Stat5, depending on the cells involved. Using mutant cell lines lacking various Jaks, we show here that Jak1 is critical for G-CSF–mediated Stat activation, whereas Jak2 or Tyk2 are either not required or play redundant or ancillary roles. In the absence of Jak1, G-CSF induces activation of Jak2 and Tyk2, but fails to induce receptor tyrosine phosphorylation and induces dramatically reduced levels of Stat activation. A kinase-inactive Jak2, when overexpressed in cells lacking endogenous Jak2, can suppress Jak1 activation, receptor phosphorylation, and Stat activation, suggesting competition in the receptor complex either for Jak1 binding or substrates. Because the requirement for Jak1 is very similar to that previously shown for interleukin-6 signaling, the data support the concept that the G-CSF receptor and gp130 are both structurally and functionally similar.

Human hemoglobins (Hbs) are known to be immunogenic, and both normal and variant forms of Hb have been shown to stimulate antibody formation in a variety of animal species. In patients who are homozygous for the sickle Hb (HbS) mutation, transfusion of normal, HbA-containing erythrocytes provides a potential stimulus for HbA alloimmunization. We tested serum samples for the presence of anti-Hb antibody by a solid-phase enzyme-linked immunosorbent assay (ELISA) using Hb-coated polystyrene microtiter plates. Hb-bound antibody was identified using an antihuman IgG antibody. Serum samples from 89 patients with sickle cell disease were initially tested for evidence of Hb antibody. The serum from three individuals exhibited antibody activity against HbA with little or no activity against HbS. Only one of them, a multiply transfused adult with HbSS, was available for further study. When this patient's antibody was tested against a variety of normal and mutant Hbs using antibody either to human IgG or to κ chains, the anti-Hb antibody demonstrated specificity for the region of the Hb β chain corresponding to the site of the amino acid substitution of HbS. The level of activity of the patient's anti-HbA showed no significant change over 1.5 years of observation. The transfusion of erythrocytes containing Hb structurally different from that of the recipient appeared to be capable of stimulating the production of Hb-specific alloimmune antibody.

Background: The indications for treating children with immune thrombocytopenia (ITP) remain controversial. A valid and reliable bleeding assessment tool could assist in objectively quantifying bleeding and influence treatment decisions. Both the ITP Bleeding Score (IBLS) and the ITP-Bleeding Assessment Tool (BAT) have been developed to assess bleeding severity in ITP. The IBLS scores bleeding severity using an 11-item tool with grading from 0 to 2 and the 18-item BAT grades from 0 to 3 or 4. The BAT includes some types of bleeding not represented on the IBLS, such has intramuscular hematomas. To date, no data describe how these two measures compare when measuring bleeding associated with ITP. Objective: To describe and compare bleeding as assessed by both the IBLS and BAT and to correlate bleeding severity with platelet counts in a cohort of children with ITP. Methods: A longitudinal observational cohort of children ages >1 and < 18 years with ITP, were enrolled from 2013-2015 in the Pediatric ITP Consortium of North America ICON1 trial. All children were enrolled prior to starting a new second line monotherapy (not IVIG, steroids or anti-D). At enrollment, bleeding was assessed using the IBLS in all children. A subset of children also underwent a BAT assessment. Grades of bleeding were described and compared between tools and agreement in grading was assessed. Severity was correlated with platelet count using Spearman's correlation calculation. Results: 118 children were enrolled from 21 ICON centers. 54% had chronic ITP and the median age was 11.4y (range 1.2-17.8). The mean platelet count was 28 x 109/l (SD 57) and 88% had a baseline platelet count of Conclusion: The IBLS and BAT were similarly effective at identifying bleeding symptoms, although neither tool showed strong correlation with the platelet count. There were moderate correlations noted between skin bleeding scores and platelet counts for both tools. A major limitation of this comparison is the different definitions of bleeding severity between the two measures. For sites where the items were more detailed, agreement declined (i.e. adding specificity reduced generalizability). While no patients in our cohort exhibited significant grade 3 or 4 bleeding outside of skin findings, we conclude that in the setting of clinical trials, the ability to capture very severe bleeding might be an important distinction that supports using the more complicated BAT, but for clinical practice, a simplified assessment such as the IBLS may suffice. Disclosures Grace: Agios Pharmaceuticals: Other: Scientific Advisor, Research Funding. Neufeld:Novartis: Consultancy. Bussel:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; UpToDate: Patents & Royalties; Protalex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genzyme: Research Funding; Ligand: Membership on an entity's Board of Directors or advisory committees, Research Funding; Symphogen: Membership on an entity's Board of Directors or advisory committees; Rigel Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Shionogi: Membership on an entity's Board of Directors or advisory committees; Sysmex: Research Funding; Momenta Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Immunomedics: Research Funding; Eisai: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer Ingelheim: Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cangene: Research Funding; Prophylix Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Physicians Education Resource: Speakers Bureau; BiologicTx: Research Funding. Haley:CSL Behring: Honoraria; Baxalta: Membership on an entity's Board of Directors or advisory committees. Thompson:Celgene: Research Funding; ApoPharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Mast: Research Funding; Amgen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Amgen: Research Funding; Baxalta (now part of Shire): Research Funding; bluebird bio: Consultancy, Research Funding; Baxalta (now part of Shire): Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; bluebird bio: Consultancy, Research Funding; Mast: Research Funding; ApoPharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Eli Lily: Research Funding; Eli Lily: Research Funding.

Background: Decision-making in selecting second-line therapies for pediatric patients with immune thrombocytopenia (ITP) has not been studied. Using data collected from physicians experienced in treating ITP, we developed a conceptual model of factors that informed treatment choice. This study was a component of ICON1, a prospective, observational, longitudinal cohort study of second line treatments for childhood ITP performed by the Pediatric ITP Consortium of North America (ICON). Methods: Physicians who enrolled patients in ICON1 were asked to rank the top three reasons they chose a specific treatment so as to weight each factor. Those choices that were ranked 1, 2, or 3 were weighted to develop a propensity scored decisional model. In other questions, physicians were asked about all factors that may have influenced decisions to begin a particular second line therapy and this data was then used to examine additional factors that influenced therapy choices and to compare between therapies. Results: ICON1 enrolled 118 patients; 101 had primary ITP and 53 were receiving their first second line therapy. The majority of physicians in the study saw eleven or more patients per year, and the time since completion of fellowship ranged from 1 to 44 years (mean 12.5 (SD 11)). The most important factors guiding treatment decisions in propensity weighted modeling were "patient preference factors": patient/parental preference (40%), and treatment-related factors: possibility of remission (38%), side effect profile (36%), efficacy (27%), long-term toxicity (33%), and ease of administration (30%). Physician factors, such as experience and adhering to published guidelines, rarely influenced decision-making with only 2% of physicians giving published guidelines as a reason for choice of therapy, and there being no difference in choice based on years since fellowship or experience in treating ITP patients. However, 28% of physicians stated their comfort level with a treatment strongly influenced their choice. Additionally, 38% of physicians did not endorse any patient clinical factors (e.g. frequency of bleeding, expected compliance, response to other therapies, age, comorbidities) as key in their decision-making. Health system factors, such as insurance approval or distance from the closest medical center, rarely influenced treatment choice. Treatments could be categorized into five groups: oral immunosuppressive agents, rituximab, romiplostim, eltrombopag or splenectomy. A significant determinant of choosing splenectomy or rituximab was the "possibility of long-term remission" (p Conclusions: This first analysis of physician decision making regarding second line therapies shows that patient preference and physician perception of treatment characteristics (efficacy, side effects, possibility of long term remission) are primary drivers of physician choice in contrast to guidelines, clinical characteristics and health system factors. Future comparative effectiveness studies are necessary to better inform patient and physician choice. Disclosures Lambert: Novartis: Consultancy. Grace:Agios Pharmaceuticals: Other: Scientific Advisor, Research Funding. Bussel:Cangene: Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ligand: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sysmex: Research Funding; Symphogen: Membership on an entity's Board of Directors or advisory committees; BiologicTx: Research Funding; Shionogi: Membership on an entity's Board of Directors or advisory committees; Physicians Education Resource: Speakers Bureau; Protalex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Immunomedics: Research Funding; Rigel Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer Ingelheim: Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; UpToDate: Patents & Royalties; Momenta Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Prophylix Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genzyme: Research Funding; Eisai: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Haley:Baxalta: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Honoraria. Neufeld:Novartis: Consultancy.

The incidence of functional asplenia in sickle-hemoglobin C (SC) disease has not been defined, and the use of prophylactic penicillin to prevent life-threatening septicemia in this disorder is controversial. The percentage of red blood cells with pits (pit count) is a reliable assay of splenic function in other disorders but has not been validated in hemoglobin SC disease. To address these issues, we conducted a prospective, multicenter study of splenic function in persons with hemoglobin SC disease. Baseline clinical data were recorded, and red blood cell pit counts were performed on 201 subjects, aged 6 months to 90 years, with hemoglobin SC; 43 subjects underwent radionuclide liver-spleen scanning. Pit counts greater than 20% were associated with functional asplenia as assessed by liver-spleen scan, whereas pit counts less than 20% were found in subjects with preserved splenic function. Pit counts greater than 20% were present in 0 of 59 subjects (0%) less than 4 years of age, in 19 of 86 subjects (22%) 4 to 12 years of age, and in 25 of 56 subjects (45%) greater than 12 years of age. Other subjects with hemoglobin SC, who had previously undergone surgical splenectomy, had higher pit counts (59.7% +/- 9.5%) than splenectomized subjects without hemoglobinopathy (38.5% +/- 8.8%) or with sickle cell anemia (20.5% +/- 1.9%; P < .001). Two subjects with hemoglobin SC disease (not splenectomized), ages 14 and 15 years, with pit counts of 40.3% and 41.7% died from pneumococcal septicemia. These data indicate that functional asplenia occurs in many patients with hemoglobin SC disease, but its development is usually delayed until after 4 years of age. The pit count is a reliable measure of splenic function in hemoglobin SC disease, but values indicative of functional asplenia (> 20% in our laboratory) are higher than in other disorders. The routine administration of prophylactic penicillin to infants and young children with hemoglobin SC disease may not be necessary.

Bryostatins, macrocyclic lactones from the marine bryozoan Bugula neritina, are potent antineoplastic agents and multi-potential stimulators of immune cells. We have examined the effects of bryostatins on mediator release from human basophilic leukocytes and human tissue mast cells. Bryostatins 1, 2, and 5 (10 to 3,000 nmol/L) induced histamine secretion from purified and unpurified peripheral blood basophils, whereas they caused no release of peptide-leukotriene C4 from these cells. The rate of histamine release caused by bryostatin 1 was slower than that caused by anti-IgE (t1/2 +/- SEM = 38.2 +/- 4.7 minutes v 8.9 +/- 0.2 minutes; P < .01), whereas the temperature dependence was similar (optimum release at 37 degrees C, approximately 30% less at 30 degrees C, and no release at 22 degrees C or 4 degrees C). The addition of increasing concentrations of extracellular Ca2+ to the medium caused histamine release in the presence of bryostatins. Subeffective concentrations of bryostatins and anti-IgE produced a synergistic effect on histamine release from basophils. Staurosporine, chelerythrine, and calphostin C (0.1 to 10 nmol/L), which are protein kinase C inhibitors, inhibited the histamine secretion activated by bryostatin 1 and tetradecanoylphorbol-acetate (TPA). Preincubation with granulocyte-monocyte colony-stimulating factor (GM-CSF; 1 and 5 nmol/L) and interleukin-3 (IL-3; 10 ng/mL) potentiated the activation of human basophils induced by bryostatin 1. Neither bryostatin 1 nor bryostatin 2 induced the release of histamine from mast cells isolated from human lung or skin tissues. However, brief (10 minutes) preincubation with bryostatin 1 (3 to 300 nmol/L) potently inhibited the histamine secretion induced by anti-IgE from skin or lung mast cells. Bryostatin 1 was a more potent (by approximately 30 times) inhibitor of IgE- mediated histamine release than was TPA. The heterogeneous effects exerted by bryostatins on human basophils and mast cells can be of interest for those designing therapeutic trials using these agents.

We hypothesized that the silent cerebral infarcts (SCI), which affect up to 40% of children with sickle cell disease (SCD), could occur in the setting of acute anemic events. In a prospective observational study of children with and without SCD hospitalized for an illness associated with acute anemia, we identified acute silent cerebral ischemic events (ASCIE) in 4 (18.2%) of 22 with SCD and in 2 (6.7%) of 30 without SCD, using diffusion-weighted magnetic resonance imaging. Children with ASCIE had lower hemoglobin concentration than those without (median 3.1 vs 4.4 g/dL, P = .003). The unique temporal features of stroke on diffusion-weighted magnetic resonance imaging permit estimation of incidence rates for ASCIE of 421 (95% confidence interval, 155-920) per 100 patient-years during acute anemic events for all patients. For children with SCD, the estimated incidence was 663 (95% confidence interval, 182-1707) which is much higher than previously reported. Acute anemic events are common in children with SCD and prevalence could partially account for the high SCI. Some ASCIE (1 of 4 in our study) may be reversible. Alterations in management may be warranted for children with severe anemia to identify unrecognized ischemic brain injury that may have permanent neurocognitive sequelae.

We have examined the in vivo radioprotective effects of the macrocyclic lactone protein kinase C (PK-C) activator, bryostatin 1, administered either alone or in conjunction with recombinant murine granulocyte- macrophage colony-stimulating factor (rmGM-CSF), in Balb/c and C3H/HeN mice subjected to lethal total body irradiation (TBI). When administered alone on a divided dose schedule (24 hours and 30 minutes before TBI), rmGM-CSF (20 micrograms/kg) was ineffective in increasing survival in either strain. However, in Balb/c mice, bryostatin 1 alone (1 microgram) permitted the long-term survival (60 days) of 70% of the animals following TBI, and 80% when administered in conjunction with rmGM-CSF. Bryostatin 1 administered alone according to this schedule exerted minimal radioprotective effects in C3H/HeN mice, but, when combined with a subeffective dose of rmGM-CSF, allowed 50% of the animals to survive. Treatment of Balb/c mice with bryostatin 1 administered as a single dose 4 hours before TBI resulted in a 20% survival rate, and 45% when administered with rmGM-CSF; corresponding values for the C3H/HeN strain were 60% and 40%, respectively. Lastly, the survival rates of Balb/c mice treated with bryostatin 1 administered as a single dose 4 hours following TBI was 20%, and 25% with rmGM-CSF; corresponding values were 50% and 25% for C3H/HeN mice. These findings indicate that the PK-C activator bryostatin 1 exhibits intrinsic in vivo radioprotective effects in lethally irradiated Balb/c and C3H/HeN mice, and may, under some circumstances, augment the radioprotective capacity of rmGM-CSF. They also underscore the critical role that strain differences and scheduling considerations play in determining the in vivo radioprotective capacity of bryostatin 1, as well as its interactions with rmGM-CSF.

Alteration of the TAL1 locus is the most common nonrandom genetic defect in childhood T-cell acute lymphoblastic leukemia (T-ALL). To determine if rearrangements of the TAL1 proto-oncogene confer a distinct leukemic phenotype, we studied leukemic peripheral blood or bone marrow samples from 182 children with newly diagnosed T-ALL enrolled on Pediatric Oncology Group treatment protocols. Forty-eight (26%) of the samples had a local rearrangement of the TAL1 locus. Demographic and clinical features were compared for patient subgroups with and without TAL1 rearrangements. The only clinical correlates that were significantly associated with TAL1 gene rearrangements were higher white blood cell count (P = .017) and higher hemoglobin (P = .007) at diagnosis. Immunophenotypically, samples with altered TAL1 were more likely to be CD2+ (P = .001) and lack CD10 (cALLa) expression (P = .007) than those without the rearrangement. There was a trend toward improved event-free survival (EFS) in patients with TAL1 rearrangements (4-year EFS was 44% +/- 7% for patients without the rearrangements v 59% +/- 11% for those with rearrangements), but the difference was not significant (P = .34). The role of TAL1 in leukemogenesis has yet to be clearly defined, and the prognostic significance of TAL1 gene rearrangements in T-ALL deserves further study.

Children with acute lymphoblastic leukemia (ALL) who have completed 2.5 to 3 years of initial chemotherapy have an off-therapy relapse rate of approximately 20%. In an attempt to improve the survival of children with a late bone marrow (BM) relapse (ie, occurring greater than 6 months after cessation of primary therapy), the Pediatric Oncology Group designed a randomized study to compare the efficacy of doxorubicin/prednisone and cytarabine/teniposide in a multidrug retreatment chemotherapy program. Treatment consisted of remission reinduction with vincristine, prednisone, and doxorubicin, central nervous system prophylaxis with triple intrathecal chemotherapy, and continuation therapy (for 132 weeks) with alternating cycles of oral 6- mercaptopurine/methotrexate and intravenous vincristine/cyclophosphamide. Patients received intermittent courses of either prednisone/doxorubicin (regimen 1) or teniposide/cytarabine (regimen 2) during continuation therapy and a late intensification phase with either vincristine, prednisone, and doxorubicin (regimen 1) or teniposide and cytarabine (regimen 2). One hundred two of 105 evaluable patients (97%) achieved a second complete remission. Twenty- eight of 50 patients on regimen 1 have failed compared with 28 or 52 patients on regimen 2 (log-rank analysis, P = .68), indicating that this trial was inconclusive as to which treatment regimen was superior. The overall 4-year event-free survival for children with a late BM relapse was 37% +/- 6%. Age less than 10 years at initial diagnosis (P < or = .001), white blood cell count less than 5,000/microL at relapse (P = .036) and duration of first remission greater than 54 months (P = .039) were independently associated with a more favorable outcome. While the randomized trial was inconclusive, prolonged second complete remissions were secured in more than one-third of children with a late BM relapse of ALL. The prognostic factors identified may help select children with a late BM relapse who can be successfully retreated with chemotherapy alone.

The activity of protein kinase C (PK-C) has been implicated in the regulation of the growth and differentiation of both normal and neoplastic hematopoietic cells. We have examined the effects of the PK- C-activating agents phorbol 12,13-dibutyrate (PDBu), mezerein, and bryostatin 1 on the proliferation and lineage commitment of CD34+ human myeloid progenitor cells stimulated by recombinant interleukin-3 (rIL- 3) and/or recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). Although each of the PK-C activators administered alone induced no colony formation, coadministration of these agents with plateau concentrations of each cytokine (eg, 50 ng/mL) increased the number of day 14 granulocyte-macrophage colony-forming units by 100% to 150%. The number of pure and mixed neutrophil and macrophage colonies was substantially enhanced in the presence of PK-C activators, whereas the percentage and, in most cases, the absolute number of eosinophilic colonies was significantly reduced. The inhibition of eosinophilic colony formation was not overcome by the addition of rIL-5. Although addition of bryostatin 1 24 hours before rIL-3 abrogated the increase in total colony formation observed with simultaneous administration of factors, the inhibition of eosinophilic colonies and the increase in neutrophil/macrophage colonies persisted under these conditions. The addition of bryostatin 1 for up to 144 hours after rIL-3 continued to potentiate total colony formation, whereas the inhibition of eosinophilic commitment was lost after 120 hours. Together, these results suggest that pharmacologic interventions at the level of PK-C may regulate both the proliferation as well as the lineage commitment of human hematopoietic progenitors exposed to rGM-CSF and rIL-3.

A mutation in the γ-glutamyl carboxylase gene leading to a combined congenital deficiency of all vitamin K-dependent coagulation factors was identified in a Lebanese boy. He is the first offspring of consanguineous parents and was homozygous for a unique point mutation in exon 11, resulting in the conversion of a tryptophan codon (TGG) to a serine codon (TCG) at amino acid residue 501. Oral vitamin K1 administration resulted in resolution of the clinical symptoms. Screening of several family members on this mutation with an RFLP technique revealed 10 asymptomatic members who were heterozygous for the mutation, confirming the autosomal recessive pattern of inheritance of this disease. In 50 nonrelated normal subjects, the mutation was not found. This is the second time a missense mutation in the γ-glutamyl carboxylase gene is described that has serious impact on normal hemostasis.

A mutation in the γ-glutamyl carboxylase gene leading to a combined congenital deficiency of all vitamin K-dependent coagulation factors was identified in a Lebanese boy. He is the first offspring of consanguineous parents and was homozygous for a unique point mutation in exon 11, resulting in the conversion of a tryptophan codon (TGG) to a serine codon (TCG) at amino acid residue 501. Oral vitamin K1 administration resulted in resolution of the clinical symptoms. Screening of several family members on this mutation with an RFLP technique revealed 10 asymptomatic members who were heterozygous for the mutation, confirming the autosomal recessive pattern of inheritance of this disease. In 50 nonrelated normal subjects, the mutation was not found. This is the second time a missense mutation in the γ-glutamyl carboxylase gene is described that has serious impact on normal hemostasis.

Murine erythroleukemia (MEL) cells are a useful model for studying the processes that regulate erythroid differentiation because exposure of these cells to a variety of chemical inducing agents results in expression of erythroid-specific genes and the resultant loss of cellular immortality. Previously it has been suggested that the calcium ionophore, A23187, has effects on the early cellular events that lead to the commitment of these cells to differentiation, but was not in itself sufficient to induce differentiation. We demonstrate here that A23187, as well as another calcium ionophore, ionomycin, are capable of inducing commitment to differentiation. Unlike other inducing agents, continual exposure to A23187 inhibits transcription of the erythroid- specific genes, beta-globin and Band 3. This effect is not attributable to an increase in cytosolic calcium concentration, because cells induced by ionomycin produce normal amounts of hemoglobin. These effects of A23187 on MEL cells confirm that commitment to differentiation is a distinct event from the subsequent transcriptional activation of erythroid genes. The ability of both ionophores to induce commitment to differentiation suggests that an increase in cytosolic calcium can trigger commitment to differentiation. These agents should prove useful in investigating the cellular processes that are responsible for commitment to differentiation.

We report the nonrandom occurrence, frequency, and degree of immunophenotype association of the t(1;14)(p34;q11) in children with acute lymphoblastic leukemia (ALL). This chromosomal abnormality occurred in leukemia cells from 5 of 1,630 (0.3%) consecutive children with newly diagnosed ALL who were entered on a single Pediatric Oncology Group classification study (POG 8600) between January 1986 and February 1989. The frequency of the t(1;14) was 3% (5 of 168 cases) in children with T-cell ALL. All five cases had pseudodiploid karyotypes, and in 3 cases the t(1;14) was accompanied by a deletion of the long arm of chromosome 6. This translocation is of special interest because the breakpoint on chromosome 14 in band q11 corresponds to the assigned locus of the T-cell receptor alpha/delta chain gene. All five of our patients and three cases reported previously have had T-cell ALL. These findings, considered together, suggest that this translocation is specific for T-cell ALL and that a gene in the 1p34 region may play an important role in malignant transformation of thymocytes.

Background The standard first line therapy for iron deficiency anemia (IDA) is oral iron. Yet, many patients fail to respond to oral iron due to poor adherence and/or adverse effects. Intravenous (IV) iron is an effective means of treating IDA in patients with malabsorption of iron or who are non-adherent and/or experience adverse effects with oral iron. Some IV iron preparations carry an FDA-mandated black box warning and/or require a test dose or prolonged infusion. Ferric carboxymaltose (FCM, Injectafer®) is a relatively new IV iron preparation with demonstrated safety and efficacy in adults with IDA. The manufacturer recommended dosing is 15 mg/kg/dose (maximum 750 mg) x2 doses administered at least 7 days apart, and each individual infusion can be administered over 10 to 15 minutes, without the need for a test dose. Limited data exist on its use in children. Our objective was to assess the hematologic response and adverse effects of IV FCM in a diverse population of infants, children and adolescents with IDA who failed oral iron therapy. Method All children with IDA who received FCM at Children's Health from June 1, 2014 through June 10, 2015 were included. Subjects were identified via search of pharmacy records. All patients received at least one dose of FCM 15 mg/kg (maximum 750 mg) administered as a 15-minute IV infusion (without test dose or pre-medications). Patient characteristics, adverse effects and hematologic response were retrospectively collected from the electronic medical record. Results During the study frame, one hundred twenty-five infusions of FCM were administered to 87 patients (71% female) with a median age of 14 years (range 9 months to 20.8 years). The most common racial/ethnic group was Caucasian/White (Latino) at 45% followed by African American/Black and Caucasian/White (Non-Latino), each at 22%. The primary etiologies were heavy menstrual bleeding (38%), nutritional (24%), and GI bleeding and/or malabsorption (20%) with the remaining 18% representing other/mixed causes of IDA (e.g., inflammatory). The median dose administered during a single infusion was 750 mg (range 132 to 750 mg). No adverse effects were noted during or following the infusion in 77 subjects. Two patients had transient tingling, nausea and/or mild abdominal pain. Five others developed generalized pruritis and/or urticaria and received diphenhydramine and/or hydrocortisone, with prompt resolution. Two adolescents had more clinically significant reactions, 1 with nausea/vomiting post-infusion (likely psychogenic) requiring admission, and 1 with dyspnea 2 minutes into the infusion, requiring its immediate termination and administration of diphenhydramine, hydrocortisone and normal saline with prompt symptom resolution. One patient experienced asymptomatic extravasation during the second infusion which resulted in localized iron-staining of the skin. Median pre-infusion hemoglobin concentration for all patients was 9.1 g/dL (range 3.9 to 13.3 g/dL) (Table). A follow-up measurement was available for 76 patients at a median time of 6 weeks (range 1 to 30 weeks) post-initial infusion with a median hemoglobin increase of 3.3 g/dL (range -1.5 to 9.5 g/dL). Conclusion Intravenous FCM, administered in an outpatient infusion setting as one or two short IV infusions and without need for a test dose, was safe and effective in most children and adolescents with IDA refractory to oral iron therapy. Further clinical data are necessary to more fully characterize the extent of adverse effects in young patients. Prospective studies of IV FCM in children are indicated to assess clinical efficacy, including outcomes such as health related quality of life and fatigue. Table. *Hematologic Response to FCM Pre-Infusion **Post-Infusion Hemoglobin concentration (g/dL) All Etiologies, Pre (n=87), Post (n=76) Heavy menstrual bleeding, Pre (n=33), Post (n=26) Nutritional, Pre (n=21), Post (n=20) - 9.1 (3.9 to 13.3) 9.3 (4.2 to 13.3) 8.8 (4.9 to 12.2) - 12.2 (7.1 to 16) 12.7 (8.8 to 16) 12.2 (10.5 to 13.7) Mean corpuscular volume (fl), Pre (n=87), Post (n=76) 71.6 (49.5 to 97.4) 80.9 (53.3 to 102) Serum ferritin (ng/mL), Pre (n=80), Post (n=60) 5.2 (0.6 to 288.6) 115.7 (2.3 to 679.3) *Median laboratory values are reported. **Follow-up laboratory testing occurred at median time of 6 weeks (range 1 to 30 weeks) post-infusion. Disclosures Powers: Gensavis Pharmaceuticals, LLC: Research Funding. McCavit:Pfizer: Research Funding; Gensavis LLC: Research Funding; Novartis: Speakers Bureau. Adix:Gensavis Pharmaceuticals, LLC: Research Funding. Buchanan:Gensavis Pharmaceuticals, LLC: Research Funding.