Johann Hitzler

Fusion of two novel genes, RBM15 and MKL1, in the t(1;22)(p13;q13) of acute megakaryoblastic leukemia.

t(1;22) is the principal translocation of acute megakaryoblastic leukemias. Here we show this chromosomal rearrangement to result in the fusion of two novel genes, RNA-binding motif protein-15 (RBM15), an RNA recognition motif-encoding gene with homology to Drosophila spen, and Megakaryoblastic Leukemia-1 (MKL1), a gene encoding an SAP (SAF-A/B, Acinus and PIAS) DNA-binding domain.

Origins of leukaemia in children with Down syndrome

Transient megakaryoblastic leukaemia is found in 10% of newborns with Down syndrome, characterized by constitutional trisomy 21. Although in most cases the leukaemic cells disappear spontaneously after the first months of life, irreversible acute megakaryoblastic leukaemia develops in 20% of these individuals within 4 years. The leukaemic cells typically harbour somatic mutations of the gene encoding GATA1, an essential transcriptional regulator of normal megakaryocytic differentiation. Leukaemia that specifically arises in the context of constitutional trisomy 21 and somatic GATA1 mutations is a unique biological model of the incremental process of leukaemic transformation.

Comparison of Long-Term Neurocognitive Outcomes in Young Children With Acute Lymphoblastic Leukemia Treated With Cranial Radiation or High-Dose or Very High-Dose Intravenous Methotrexate

PURPOSE Cranial radiation therapy (CRT) is associated with neurocognitive morbidity in survivors of childhood acute lymphoblastic leukemia (ALL). For most patients, CRT has been replaced with intensified systemic and intrathecal chemotherapy, often including methotrexate (MTX). The impact of chemotherapy-only protocols on neurocognitive outcomes is unclear, and the importance of systemic MTX dose has not been established. PATIENTS AND METHODS Seventy nine of 120 eligible children diagnosed with high-risk ALL between the ages of 1.0 and 4.9 years participated in this retrospective cohort study. All patients were treated on a uniform chemotherapy protocol with one of three modalities of CNS prophylaxis, depending on their treatment era. In addition to intrathecal therapy, CNS-directed therapy consisted of CRT (18 Gy in 10 fractions) in 25 patients, high-dose intravenous (IV) MTX (8 g/m2 x 3 doses) in 32 patients and very high-dose IV MTX (33.6 g/m2 x 3 doses) in 22 patients. Participants completed tests of intelligence, academic achievement, attention, and memory. RESULTS Neurocognitive assessment was conducted at least 5 years after diagnosis (mean, 10.5 years, standard deviation, 2.7 years). No difference was detected on any neurocognitive measure between children treated with high-dose or very high-dose IV MTX. The combined MTX groups scored near the population mean on 17/18 measures. Children treated with CRT performed more poorly than the MTX group on most measures. CONCLUSION Treatment strategies for young children with ALL that avoid CRT are associated with good long-term neurocognitive outcomes. In this cohort, the dose of IV MTX did not influence these outcomes.

Methylation of the TERT promoter and risk stratification of childhood brain tumours: an integrative genomic and molecular study

BACKGROUND Identification of robust biomarkers of malignancy and methods to establish disease progression is a major goal in paediatric neuro-oncology. We investigated whether methylation of the TERT promoter can be a biomarker for malignancy and patient outcome in paediatric brain tumours. METHODS For the discovery cohort, we used samples obtained from patients with paediatric brain tumours and individuals with normal brain tissues stored at the German Cancer Research Center (Heidelberg, Germany). We used methylation arrays for genome-wide assessment of DNA. For the validation cohort, we used samples obtained from several tissues for which full clinical and follow-up data were available from two hospitals in Toronto (ON, Canada). We did methylation analysis using quantitative Sequenom and pyrosequencing of an identified region of the TERT promoter. We assessed TERT expression by real-time PCR. To establish whether the biomarker could be used to assess and predict progression, we analysed methylation in paired samples of tumours that transformed from low to high grade and from localised to metastatic, and in choroid plexus tumours of different grades. Finally, we investigated overall survival in patients with posterior fossa ependymomas in which the identified region was hypermethylated or not. All individuals responsible for assays were masked to the outcome of the patients. FINDINGS Analysis of 280 samples in the discovery cohort identified one CpG site (cg11625005) in which 78 (99%) of 79 samples from normal brain tissues and low-grade tumours were not hypermethylated, but 145 (72%) of 201 samples from malignant tumours were hypermethylated (>15% methylated; p<0.0001). Analysis of 68 samples in the validation cohort identified a subset of five CpG sites (henceforth, upstream of the transcription start site [UTSS]) that was hypermethylated in all malignant paediatric brain tumours that expressed TERT but not in normal tissues that did not express TERT (p<0.0001). UTSS had a positive predictive value of 1.00 (95% CI 0.95-1.00) and a negative predictive value of 0.95 (0.87-0.99). In two paired samples of paediatric gliomas, UTSS methylation increased during transformation from low to high grade; it also increased in two paired samples that progressed from localised to metastatic disease. Two of eight atypical papillomas that had high UTSS methylation progressed to carcinomas, while the other six assessed did not progress or require additional treatment. 5-year overall survival was 51% (95% CI 31-71) for 25 patients with hypermethylated UTSS posterior fossa ependymomas and 95% (86-100) for 20 with non-hypermethylated tumours (p=0.0008). 5-year progression-free survival was 86% (68-100) for the 25 patients with non-hypermethylated UTSS tumours and 30% (10-50) for those with hypermethylated tumours (p=0.0008). INTERPRETATION Hypermethylation of the UTSS region in the TERT promoter is associated with TERT expression in cancers. In paediatric brain tumours, UTSS hypermethylation is associated with tumour progression and poor prognosis. This region is easy to amplify, and the assay to establish hypermethylation can be done on most tissues in most clinical laboratories. Therefore the UTSS region is a potentially accessible biomarker for various cancers. FUNDING The Canadian Institute of Health Research and the Terry Fox Foundation.

Use of Allogeneic Hematopoietic Stem-Cell Transplantation Based on Minimal Residual Disease Response Improves Outcomes for Children With Relapsed Acute Lymphoblastic Leukemia in the Intermediate-Risk Group

PURPOSE In children with intermediate risk of relapse of acute lymphoblastic leukemia (ALL), it is essential to identify patients in need of treatment intensification. We hypothesized that the prognosis of patients with unsatisfactory reduction of minimal residual disease (MRD) can be improved by allogeneic hematopoietic stem-cell transplantation (HSCT). PATIENTS AND METHODS In the Acute Lymphoblastic Leukemia-Relapse Study of the Berlin-Frankfurt-Münster Group (ALL-REZ BFM) 2002, patients with an MRD level of ≥ 10(-3) (n = 99) at the end of induction therapy were allocated to HSCT, whereas those with an MRD level less than 10(-3) (n = 109) continued to receive chemotherapy. MRD was quantified by real-time polymerase chain reaction for clone-specific T-cell receptor/immunoglobulin gene rearrangements. RESULTS The probability of event-free survival for patients with MRD ≥ 10(-3) was 64% ± 5% in ALL-REZ BFM 2002 compared with 18% ± 7% in the predecessor study ALL-REZ BFM P95/96 (P < .001). This was mainly achieved by reducing the cumulative incidence of subsequent relapse (CIR) at 8 years from 59% ± 9% to 27% ± 5% (P < .001). The favorable prognosis of patients with MRD less than 10(-3) could be confirmed in those with a late combined or isolated bone marrow B-cell precursor (BCP) -ALL relapse (CIR, 20% ± 5%), whereas patients with an early combined BCP-ALL relapse had an unfavorable outcome (CIR, 63% ± 13%; P < .001). CONCLUSION Allogeneic HSCT markedly improved the prognosis of patients with intermediate risk of relapse of ALL and unsatisfactory MRD response. As a result, outcomes in this group approximated those of patients with favorable MRD response. Patients with early combined relapse require treatment intensification even in case of favorable MRD response, demonstrating the prognostic impact of time to relapse.

The genomic landscape of juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative neoplasm (MPN) of childhood with a poor prognosis. Mutations in NF1, NRAS, KRAS, PTPN11 or CBL occur in 85% of patients, yet there are currently no risk stratification algorithms capable of predicting which patients will be refractory to conventional treatment and could therefore be candidates for experimental therapies. In addition, few molecular pathways aside from the RAS-MAPK pathway have been identified that could serve as the basis for such novel therapeutic strategies. We therefore sought to genomically characterize serial samples from patients at diagnosis through relapse and transformation to acute myeloid leukemia to expand knowledge of the mutational spectrum in JMML. We identified recurrent mutations in genes involved in signal transduction, splicing, Polycomb repressive complex 2 (PRC2) and transcription. Notably, the number of somatic alterations present at diagnosis appears to be the major determinant of outcome.

Leukapheresis and low-dose chemotherapy do not reduce early mortality in acute myeloid leukemia hyperleukocytosis: a systematic review and meta-analysis.

The role of leukapheresis and low-dose chemotherapy is unclear in decreasing early mortality in acute myeloid leukemia (AML) patients with hyperleukocytosis. This systematic review was conducted to describe early mortality (deaths during first induction) in patients with AML with an initial white blood count≥100×10(9)L(-1) stratified by the approach to leukapheresis and hydroxyurea/low-dose chemotherapy. Twenty-one studies were included. Weighted mean early deaths rate (20 studies, 1354 patients) was 20.1% (95% confidence interval 15.0-25.1). Neither leukapheresis strategy (p=0.67) nor hydroxyurea/low-dose chemotherapy (p=0.23) influenced the early death rate. Early mortality related to hyperleukocytosis in AML is not influenced by universal or selected use of leukapheresis or hydroxyurea/low-dose chemotherapy.

Risk of late effects of treatment in children newly diagnosed with standard-risk acute lymphoblastic leukaemia: a report from the Childhood Cancer Survivor Study cohort

BACKGROUND Treatment of patients with paediatric acute lymphoblastic leukaemia has evolved such that the risk of late effects in survivors treated in accordance with contemporary protocols could be different from that noted in those treated decades ago. We aimed to estimate the risk of late effects in children with standard-risk acute lymphoblastic leukaemia treated with contemporary protocols. METHODS We used data from similarly treated members of the Childhood Cancer Survivor Study cohort. The Childhood Cancer Survivor Study is a multicentre, North American study of 5-year survivors of childhood cancer diagnosed between 1970 and 1986. We included cohort members if they were aged 1·0-9·9 years at the time of diagnosis of acute lymphoblastic leukaemia and had received treatment consistent with contemporary standard-risk protocols for acute lymphoblastic leukaemia. We calculated mortality rates and standardised mortality ratios, stratified by sex and survival time, after diagnosis of acute lymphoblastic leukaemia. We calculated standardised incidence ratios and absolute excess risk for subsequent neoplasms with age-specific, sex-specific, and calendar-year-specific rates from the Surveillance, Epidemiology and End Results Program. Outcomes were compared with a sibling cohort and the general US population. FINDINGS We included 556 (13%) of 4329 cohort members treated for acute lymphoblastic leukaemia. Median follow-up of the survivors from 5 years after diagnosis was 18·4 years (range 0·0-33·0). 28 (5%) of 556 participants had died (standardised mortality ratio 3·5, 95% CI 2·3-5·0). 16 (57%) deaths were due to causes other than recurrence of acute lymphoblastic leukaemia. Six (1%) survivors developed a subsequent malignant neoplasm (standardised incidence ratio 2·6, 95% CI 1·0-5·7). 107 participants (95% CI 81-193) in each group would need to be followed-up for 1 year to observe one extra chronic health disorder in the survivor group compared with the sibling group. 415 participants (376-939) in each group would need to be followed-up for 1 year to observe one extra severe, life-threatening, or fatal disorder in the group of survivors. Survivors did not differ from siblings in their educational attainment, rate of marriage, or independent living. INTERPRETATION The prevalence of adverse long-term outcomes in children treated for standard risk acute lymphoblastic leukaemia according to contemporary protocols is low, but regular care from a knowledgeable primary-care practitioner is warranted. FUNDING National Cancer Institute, American Lebanese-Syrian Associated Charities, Swiss Cancer Research.

cDNA cloning and characterization of a novel gene encoding the MLF1-interacting protein MLF1IP

Myelodysplasia/acute myeloid leukemia (MDS/AML) is characterized by a t(3;5)(q25.1;q34) chromosomal translocation that forms a fusion gene between nucleophosmin (NPM) and MDS/myeloid leukemia factor 1 (MLF1). We identified a novel protein, MLF1-interacting protein (MLF1IP), that specifically associates with MLF1 by yeast two-hybrid analysis and in pulldown assays, and colocalizes with it in both the nuclei and cytoplasm of cells. The MLF1IP gene locus is at chromosome 4q35.1 and is composed of 14 exons spanning 75.8 kb of genomic DNA. The MLF1IP cDNA encodes a 46-kDa protein that contains two bipartite and two classical nuclear localization signals, two nuclear receptor-binding motifs (LXXLL), two leucine zippers, two PEST residues and several potential phosphorylation sites. MLF1IP transcripts are expressed in a variety of tissues (e.g. fetal liver, bone marrow, thymus and testis). MLF1IP appears to be a lineage-specific gene whose expression is confined exclusively to the CFU-E erythroid precursor cells, but not in mature erythrocytes. These observations, together with previous data demonstrating a role for MLF1 in suppressing red cell maturation, suggest a possible role for MLF1IP and MLF1 deregulation in the genesis of erythroleukemias.

Long-term results of an ultra low-dose cytarabine-based regimen for the treatment of acute megakaryoblastic leukaemia in children with Down syndrome.

Children with acute megakaryoblastic leukaemia (AMKL) and Down syndrome (DS) show a favourable response to chemotherapy, probably due to increased sensitivity of the leukaemic blasts to cytarabine. In contrast, dose‐intensive approaches have resulted in disproportionate treatment‐related mortality in this group. The survival of children with AMKL and DS was retrospectively compared following treatment with a low‐dose chemotherapy protocol, consisting of cytarabine (10 mg/m2/dose), retinylpalmitate and vincristine or standard chemotherapy. Event‐free (67 ± 11%) and overall survival (77 ± 10%) at 5 years were not significantly different in both groups. Further reduction of treatment intensity in AMKL of children with DS, therefore, appears feasible.