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Synthetic fused silica, exposed to high-power KrF excimer laser irradiation, shows the well-known induced absorption at 210 nm owing to E′ center generation. Time-resolved absorption spectroscopy reveals that this induced absorption is transient in nature. The generation rate of E′ centers depends strongly on the irradiation history, the OH content, and previous high-temperature processes. In order to explain the experimental observations, a nonabsorbing state of the E′ center is postulated. The recovery of the induced optical absorption in high-OH fused silica is explained as a conversion from E′ centers to these nonabsorbing centers.

Leukemia is the most common cancer in children. Sequencing data from identical twins suggests that the first genetic alterations in childhood leukemia occur in utero. Children with Down syndrome (Trisomy 21, T21) have an increased risk of childhood leukemia. In 30% of newborns with Down syndrome, a transient pre-leukemia disease occurs, which is characterized by a clonal proliferation of immature megakaryocytes carrying somatic mutations in the GATA1 transcription factor. These acquired GATA1 mutations lead to the expression of an N-terminal truncated protein (GATA1-Short). In 20% of the cases, acute megakaryoblastic leukemia (AMKL) evolves from the pre-leukemia by acquisition of additional genetic mutations in the transient leukemia clone, predominantly in genes of the cohesin complex. It is hypothesized that this represents a multi-step process of leukemogenesis with three distinct genetic events: T21, GATA1-Short and additional cohesin mutations. Yet, it remains unclear how an extra copy of chromosome 21 predisposes towards leukemia, the mechanisms of leukemic transformation and the interplay between each genetic component. Therefore, we wanted to establish a tractable human model system to investigate the initiation and evolution of transient leukemia and AMKL using CRISPR/Cas9 genome editing in primary human hematopoietic stem cells (HSCs).

Druley: Washington University: Employment; ArcherDX Inc.: Employment, Equity Ownership. Loken:Hematologics, Inc: Employment, Equity Ownership. Eidenschink Brodersen:Hematologics, Inc: Employment.

Grupp: Jazz Pharmaceuticals: Consultancy; Adaptimmune: Consultancy; University of Pennsylvania: Patents & Royalties; Novartis Pharmaceuticals Corporation: Consultancy, Research Funding. Maude:Novartis Pharmaceuticals Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees.

No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

This editorial introduction summarizes the seven guest‐edited contributions to AI Magazine that explore opportunities and challenges arising from transferring and adapting sema.ntic web technologies to the big data quest.

Continuous Friedel–Crafts alkylation of mesitylene, C6H3Me3, and anisole, C6H5OMe, with propene or propan-2-ol has been carried out in supercritical propene or CO2 using a heterogeneous polysiloxane-supported solid acid Deloxan® catalyst in a small fixed bed reactor (10 ml volume); 100% selectivity for mono-alkylated products with 50% conversion could be obtained by adjusting the reaction parameters, e.g. temperature, pressure, flow rates, etc.

No relevant conflicts of interest to declare.

Wilson: Hematologics: Employment. Brodersen:Hematologics: Employment. Zehentner:Hematologics: Employment, Equity Ownership. Pardo:Hematologics, Inc: Employment. Wells:Hematologics: Employment, Equity Ownership. Loken:Hematologics: Employment, Equity Ownership.

Gupta: Incyte: Honoraria, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Hunger: Sigma Tau: Consultancy; Jazz Pharmaceuticals: Consultancy; Merck: Equity Ownership; Spectrum Pharmaceuticals: Consultancy.

Background: Acute promyelocytic leukemia (APL) is a rare subtype of childhood acute myeloid leukemia (AML). Bleeding complications occur in 80% of patients at diagnosis and contribute to a higher incidence of early death (ED) in APL compared to other AML subtypes. However, estimates of ED in pediatric APL are imprecise and factors associated with ED in children with APL are unknown.

A small flow reactor (5 ml volume) is used for continuous hydrogenation in supercritical CO2 or propane with polysiloxane-supported noble metal catalysts; a wide range of organic functionalities can be hydrogenated with good throughput (up to 1200 ml h-1 in favourable cases) and the various parameters (temperature, pressure, concentration of H2, etc.) can be controlled independently to optimise the selectivity for a particular product.

No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

Pre-BCR–independent activation of spleen tyrosine kinase plays a pathogenic role in high-risk B cell acute lymphoblastic leukemia.

No relevant conflicts of interest to declare.

Hyperleukocytosis in acute myeloid leukemia (AML) is associated with early deaths, typically related to respiratory failure and intracranial ischemia/hemorrhage. Various interventions for leukoreduction including leukapheresis, low-dose chemotherapy and hydroxyurea have been used in an attempt to decrease mortality. However, there are no randomized trials and observational trials are biased. We undertook a systematic review and meta-analysis to evaluate the effect of these interventions using an “intent-to-treat” approach and classifying studies as always, sometimes and never using these interventions.The primary objective was to describe the proportion of early deaths in patients with AML with an initial WBC ≥ 100,000x109/L stratified by the approach to leukapheresis and hydroxyurea/low dose chemotherapy (universal, sometimes or never). The secondary objective was to compare the proportion of early deaths in patients who did and did not receive leukapheresis.Electronic searches of Ovid Medline from 1980 to July 12, 2013, EMBASE from 1980 to July 12, 2013 and Cochrane Central Register of Controlled Trials until June 2013 were conducted. Studies were included if: (1) Population included patients with AML; and (2) Either described the proportion of patients with early deaths in patients with an initial WBC ≥ 100,000x109/L or compared the proportion of early deaths by receipt of leukapheresis in patients using the same initial WBC threshold. Studies including solely acute promyelocytic leukemia (APML) patients were excluded. The pre-specified subgroups in the evaluation of early death proportions were whether leukapheresis and low-dose chemotherapy/hydroxyurea were intended to be applied universally, sometimes or never in hyperleukocytosis. These subgroups were defined based on the study’s stated policy independent of the number of patients actually receiving the intervention. Two investigators assessed the quality of the included studies for selection and confounding bias using the Hayden framework. Synthesis of proportions was conducted using RevMan. Meta-regression was conducted in which the natural log of the proportion of early deaths was modelled. Heterogeneity was assessed by visual inspection and I2.Twenty studies representing 1427 patients were included in the final meta-analysis. Overall, the proportion of early deaths (19 studies, 1281 patients) was 19.9% (95% CI: 14.7-25.1). Table 1 illustrates that neither leukapheresis strategy nor hydroxyurea/low dose chemotherapy influenced the early death rate. Meta-regression evaluating the percent of patients receiving leukapheresis showed no relationship with early death rate (odds ratio 1.01, 95% CI: 0.99-1.02; P=0.249). Evaluation of leukapheresis within studies included 7 studies of which 6 were at high risk of confounding bias and sufficiently heterogeneous to not permit synthesis.Early mortality related to hyperleukocytosis is high and is not influenced by universal or selected use of leukapheresis or low-dose chemotherapy/hydroxyurea. This meta-analysis does not support these interventions for patients with AML and hyperleukocytosis. Novel approaches are required to decrease mortality.Lehrnbecher: Gilead: Honoraria; MSD: Honoraria; Pfizer: Honoraria; Astellas: Honoraria.

Young children with Down syndrome (DS; constitutional trisomy 21) have a 150-fold higher risk of developing acute myeloid leukemia (AML). Blast cells are detectable in the peripheral blood of approximately 10% of newborns with DS; these indicate the frequent presence of a preleukemic disorder termed transient leukemia (TL)/transient myeloproliferative disorder (TMD). This disorder of fetal hematopoiesis is triggered by somatic mutations of the hematopoietic transcription factor GATA1 exclusively in the context of cellular trisomy 21. The majority of TL cases undergo spontaneous resolution by unknown mechanisms. In contrast, approximately 1 of 5 cases progress to AML within a defined postnatal window (first 4 years of life). We hypothesized that the resolution of TL results from the absence of essential environmental cues following the developmental transition from prenatal fetal liver (FL) hematopoiesis to postnatal blood cell formation in the bone marrow (BM). We previously observed that primary blasts of human TL lack the proliferative expansion in the bone marrow environment of xenotransplant recipients that is observed for blasts of DS-AML. Consequently, we aimed to identify the signals provided by the FL niche that support the survival and proliferation of human TL cells.To determine the differential impact of the hematopoietic niche provided by FL and postnatal BM on TL cells, we cultured primary human TL cells on murine stromal cell lines that were derived either from FL (AFT024) or adult BM (MS-5). The absolute number of primary TL cells increased >80-fold during culture on FL-derived stromal cells for 2 weeks. In contrast, BM-derived MS-5 stromal cells supported only a moderate expansion (<10-fold), which was associated with enhanced induction of apoptotic cell death and evidence of partial myeloid differentiation. Direct interaction between TL and stromal cells – acting co-operatively with soluble growth factors – appears indispensable for the maintenance of TL cell survival and stimulation of proliferation. Functional studies identified the very late antigen-4 [VLA-4 (CD49d)]/vascular cell adhesion molecule-1 (VCAM-1) binding partners as putative mediator of this interaction. Furthermore, insulin-like growth factor 2 (IGF-2) supplementation augmented the proliferation of TL cells specifically in the context of the FL niche. Neither IGF-2 alone or in combination with BM-derived stroma promoted expansion of TL cells. Work currently underway aims at identification of additional molecular pathways involved in TL-cell regulation, including elucidating the potential role of Notch signaling in development and maintenance of TL cells.Cooperative signals that are preferentially provided by the hematopoietic environment of the fetal liver support the survival and proliferation of human TL cells.These signals consist of a combination of cell-cell contact, in part mediated by VLA-4/ VCAM1, and soluble growth factors such as IGF-2. The identification and disruption of signaling pathways that are essential for the survival and expansion of TL blasts has the potential to prevent development of AML in children with Down syndrome by targeted elimination of the preleukemic TL clone.No relevant conflicts of interest to declare.

Hennig: European Patent Office: Patents & Royalties.

Children with Down syndrome (DS) have a higher risk for developing not only acute lymphoblastic leukemia (ALL) but also significant adverse effects of chemotherapy compared to the overall pediatric population. Currently, it is unknown how children with DS, who develop a relapse of ALL, respond to treatment protocols that were optimized in the pediatric population without DS. We hypothesized that a concomitant diagnosis of DS is an independent prognostic factor of survival after treatment for relapsed ALL and that decreased tolerance of therapy impairs the success of relapse treatment in children with DS.The probability of event-free (EFS) and overall survival (OS) and the causes of treatment failure were determined for 51 children with DS and a matched cohort of 102 children without DS among 2736 children and young adults (up to 22 years of age) who were treated for relapsed ALL on a series of clinical trials conducted by the ALL-REZ-BFM Study Group between 1983 and 2012.Among children with DS, who were enrolled on clinical trials of the ALL-REZ-BFM Study Group, ALL relapse more frequently exhibited favorable prognostic characteristics compared to the unmatched population of 2579 patients without DS. High risk forms of relapse were less frequent among children with DS (risk group S4, 10 vs. 28%, p<0.001) including relapse at a very early and early time point (35 vs. 56%, p<0.001). A higher proportion of relapse in DS involved the bone marrow (94 vs. 83% p<0.001). Transcripts of ETV6-RUNX1 or BCR-ABL1 were detected in none of the cases of relapsed ALL in DS compared to 20% (231/895, p<0.001) and 6% (83/1379, p=0.02) of cases in the population without DS. Treatment for relapsed ALL in children with DS less frequently included irradiation (of the central nervous system or total body) and hematopoietic stem cell transplantation compared to the matched non-DS group (28 vs. 70%, p<0.001, and 15 vs. 40%, p=0.002), respectively. Despite the apparent favorable risk profile, EFS and OS were lower in children with DS than the matched control group without DS (EFS 16 ± 08% vs. 39 ± 06%, p=0.005; OS 17 ± 08% vs. 48 ± 06%, p<0.001). Fatal adverse events of treatment developed more frequently in children with DS than the control group (36 ± 07% vs. 9 ± 03%, p<0.001). In contrast, the cumulative incidence of a subsequent relapse was similar in both groups (32 ± 07%, DS vs. 36 ± 05%, non-DS, p=0.373). The proportion of children with DS registered on clinical trials for relapsed ALL after frontline treatment on ALL-BFM trials showed an increase over time (from 1 registered vs. 1 non registered patient in ALL-BFM 81 to 18 registered vs. 8 non registered patients in ALL-BFM 2000). Furthermore, the proportion of patients with high risk relapse features (S4 group) and DS increased from 5 to 15%. During the more recent study period (2000–2012) EFS and OS were no longer significantly different in children with and without DS (EFS 30 ± 09% vs. 35 ± 09%, p=0.403; OS 30 ± 11% vs. 51 ± 08%, p=0.158).DS was an independent prognostic factor of outcome after relapse of ALL in multivariate analysis.A higher rate of induction deaths and treatment-related mortality was the main barrier to successful outcomes of relapse therapy in children with DS whereas relapse rates were not different from patients without DS. An increased representation of children with DS including those with high risk features in recent time suggests that access to clinical trials for relapsed ALL has been successfully broadened for children with DS. Specific optimization of treatment modifications and supportive care have improved survival in children with DS and are suggested to further decrease the number of fatal treatment-related events during relapse therapy in this group.No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

Children with relapsed ALL are at a high risk for treatment failure and require improvement of induction and consolidation therapy. Subsequent ALL-REZ BFM trials have been conducted with the aim to define risk factors and to determine adequate intensity and duration of therapy, risk-adapted SCT indication and preventive/therapeutic CNS irradiation. Short course high intensity multiagent chemotherapy elements (R-courses) have been developed as standard of care consolidation therapy of relapsed childhood ALL in countries using ALL-REZ BFM protocols. A conventionally dosed, anthracycline-containing reinduction regimen, termed “Protocol II”, which has resulted in a striking improvement of outcomes in patients with primary ALL treated with BFM protocols, may also be considered as effective consolidation therapy of relapsed childhood ALL.Aim of the study: The multi-centre prospective randomized study ALL-REZ BFM 2002 was designed to compare the efficacy and toxicity of R-courses and Protocol II-Idarubicin (Prot II-IDA) as post-induction therapy in children with relapsed ALL.Patients and methods: A total of 538 children and adolescents aged 1–18 years with first relapse of acute lymphoblastic leukaemia were enrolled in approximately 100 hospitals in Germany, Austria, Switzerland, Czech Republic and Toronto, Canada. 420 patients (78%) were randomized to receive either Prot II-IDA or R-courses as post-induction therapy after uniform induction with F1/2 courses. Further treatment was stratified according to risk groups S1-4: Patients in group S1 (late isolated extramedullary relapse) received 3 more R-courses, local irradiation and maintenance chemotherapy. Patients in group S3/4 (early and very early precursor B cell and any T cell bone marrow relapse) received allogeneic hematopoietic stem cell transplantation (HSCT) from any donor. Patients in group S2 (intermediate risk, all others) were stratified according to the level of minimal residual disease (MRD) in the bone marrow after induction therapy, measured with a PCR-based, centrally reviewed assay: MRD good responders (<10e-3) received 5 additional R-courses followed by maintenance chemotherapy. MRD poor responders (≥10e-3) went on to HSCT from a well matched allogeneic donor.210 patients were allocated to Prot II-IDA course and 210 patients were allocated to R-courses. The randomized groups were well-balanced with respect to relevant clinical parameters including the proportion of patients receiving stem cell transplantation. The estimated 5-year probabilities of event-free survival (pEFS) of the two randomized groups (Prot II-IDA: 0.60 ± 0.04 vs. R-courses: 0.53 ± 0.04, P = 0.30) and overall survival (pOS, Prot II-IDA: 0.69 ± 0.04 vs. R-courses: 0.63 ± 0.04, P = 0.46) were not significantly different. However, the cumulative incidence of subsequent relapse was significantly lower in the Prot II-IDA arm (0.21 ± 0.01) compared to patients treated with R-courses (0.30 ± 0.01, p = 0.03). Treatment-related mortality was mainly associated with HSCT and not different in both arms (0.05 vs. 0.03). Whereas hematological toxicity was higher with Prot II-IDA, more patients suffered from mucositis with R-courses.More than 50% of children with relapsed ALL could be cured with the ALL-REZ BFM 2002 strategy. Post-induction therapy with Protocol II-IDA was associated with fewer subsequent relapses compared to R-courses. Toxicity was acceptable and EFS/OS probabilities were not different in both study arms. Protocol II-IDA will be taken forward as standard post-induction therapy in future ALL-REZ BFM trials.No relevant conflicts of interest to declare.

Transient leukemia (TL), a disorder of fetal hematopoiesis, occurs in approximately 10% of infants with Down syndrome and in one fifth of cases is followed by the development of acute myeloid leukemia. The diagnosis of TL is based on the detection of a spontaneously resolving population of blasts in the peripheral blood of newborns with DS and, more recently, the detection of clone-specific somatic mutations of the hematopoietic transcription factor GATA1. The alternative terms for this condition, transient myeloproliferative disorder (TMD) and transient abnormal myelopoiesis (TAM), reflect the observation that the peripheral blood of affected infants frequently shows an expansion of immature granulocytic precursor cells at various stages of development as well as nucleated erythroid precursors in addition to a population of blast cells. We hypothesized that the immature myeloid precursor cells observed in TL arise from the same hematopoietic cell clone that is defined by the specific GATA1 mutation found in TL blasts.Cryopreserved mononuclear cells from peripheral blood samples of three male infants with TL of Down syndrome were stained at a density of 106 cells/100ul with the following antibodies: CD45-Alexa Flour 700, CD61-PE, CD11b-PE-Cy5, CD235a-PE-Cy7, CD3-APC, CD34-APC-Cy7, CD15-Pacific Blue. In addition, aliquots of these cell populations were fixed, permeabilized and stained with for intracellular myeloperoxidase (MPO-FITC). Fractions of cells corresponding to different hematopoietic lineages were prepared by fluorescence activated cell sorting (FACSAriaII, BD Biosciences, San Jose, CA) both as bulk populations and single cells (sorted into 96-well plates). Morphology of sorted cell populations was determined by Giemsa staining. Lineage-specific hematopoietic colonies were cultured from primary mononuclear cell samples in a standard CFC assay. DNA of sorted bulk and single cell populations as well as individual lineage-specific hematopoietic colonies was used to detect GATA1 mutations in exon 2 by PCR, restriction enzyme analysis or sequencing of PCR products, or nested PCR. The location of the GATA1 gene on the X chromosome and the use of samples derived from males meant that wild type GATA1 alleles were not derived from TL cells.Primary TL blood samples could be fractionated in a blast cell (CD45+CD34+and/or CD61+), erythroid (CD45-CD235a+), immature myeloid (CD45+CD15+MPO+) and lymphoid (CD45+CD3+) cell population. Cell morphology was consistent with this sorting strategy. The cell fraction designed to enrich TL blasts in all cases showed the presence of cells harboring only the mutant GATA1 allele indicating a high degree of purity of the blast fraction. As expected, the lymphoid cell populations contained in the CD3+ fractions exclusively harbored wild type alleles. Similarly, both sorted erythroid cell populations and individual erythroid colonies (Bfu-E) derived from unsorted input cells harbored only wild type GATA1 alleles. In contrast, CD15+ and/or MPO+ myeloid cell fractions consistently showed the presence of both mutant and wild type GATA1 alleles. Quantification by single cell PCR is in progress.Somatic GATA1 mutations which result in the translation of a N-terminally truncated mutant protein (GATA1s), are pathognomonic for TL and myeloid leukemia of Down syndrome. Published data do not determine if the cell clone harboring GATA1 mutations in TL extends beyond the population of blast cells and megakaryocytic lineage. We confirmed the presence of GATA1 mutations in TL blasts and their expected absence from lymphoid cell populations. The absence of mutations from cells of erythroid lineage suggests that the altered GATA1 function induced by mutations found in TL is incompatible with erythroid differentiation. The detection of clone-specific GATA1 mutations in myeloid cells expressing MPO was unexpected and raises the possibility that either the progenitor cells giving rise to TL blasts or the blasts themselves retain myeloid lineage differentiation potential. The finding lends support to definitions of TL and myeloid leukemia in Down syndrome that are based on the specific mutational and cellular mechanism and transcend a megakaryoblastic blast phenotype.No relevant conflicts of interest to declare.

Abstract 2562