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Among adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia, treatment with the bispecific anti-CD19 and anti-CD3 monoclonal antibody blinatumomab resulted in longer overall survival and higher remission rates than did chemotherapy. The prognosis for adults with newly diagnosed acute lymphoblastic leukemia (ALL) has improved over the past three decades. With the use of intensive chemotherapy regimens, complete remission rates are 85 to 90% and long-term survival rates are 30 to 50%. 1 – 4 Still, most adults with B-cell precursor ALL will have a relapse and will die from complications of resistant disease or associated treatment. Among adults with relapsed or refractory ALL, remission rates are 18 to 44% with the use of standard salvage chemotherapy, but the duration of remission is typically short. 5 – 10 A major goal in this population is to . . .

T and B cell receptor loci undergo combinatorial rearrangement, generating a diverse immune receptor repertoire, which is vital for recognition of potential antigens. Here we use a multiplex PCR with a mixture of primers targeting the rearranged variable and joining segments to capture receptor diversity. Differential hybridization kinetics can introduce significant amplification biases that alter the composition of sequence libraries prepared by multiplex PCR. Using a synthetic immune receptor repertoire, we identify and minimize such biases and computationally remove residual bias after sequencing. We apply this method to a multiplex T cell receptor gamma sequencing assay. To demonstrate accuracy in a biological setting, we apply the method to monitor minimal residual disease in acute lymphoblastic leukaemia patients. A similar methodology can be extended to any adaptive immune locus. Immunosequencing enables cost-effective sequencing of repertoires of immune cells, but it often suffers from amplification biases when attempting cell quantification. Here, the authors present a powerful multiplex PCR assay that allows for quantitative and unbiased analysis of frequency of different T cell receptors.

Adolescent and young adult (AYA) patients 16–30 years old with high-risk acute lymphoblastic leukemia (HR-ALL) have inferior outcomes compared to younger HR-ALL patients. AALL0232 was a Phase 3 randomized Children’s Oncology Group trial for newly diagnosed HR B-ALL (1–30 years). Between 2004 and 2011, 3154 patients enrolled with 3040 eligible and evaluable for induction. AYA patients comprised 20% of patients (16–21 years, n = 551; 22–30 years, n = 46). 5-year event-free survival and overall survival was 65.4 ± 2.2% and 77.4 ± 2.0% for AYA patients compared to 78.1 ± 0.9% and 87.3 ± 0.7% for younger patients (p < 0.0001). Five-year cumulative incidence of relapse was 18.5 ± 1.7% for AYA patients and 13.5 ± 0.7% for younger patients (p = 0.006), largely due to increased marrow relapses (14.0 ± 1.5% versus 9.1 ± 0.6%; p < 0.0001). Additionally, induction failure rate was higher in AYA (7.2 ± 1.1% versus 3.5 ± 0.4%; p < 0.001) and post-induction remission deaths were significantly higher in AYA (5.7 ± 1.0% versus 2.4 ± 0.3%; p < 0.0001). AALL0232 enrolled the largest number of AYA B-ALL patients to date, demonstrating significantly inferior survival and greater rates of treatment-related toxicities compared to younger patients. Although treatment intensification has improved outcomes in younger patients, they have not been associated with the same degree of improvement for older patients.

Pluripotent stem cells (PSCs) represent an alternative hematopoietic stem cell (HSC) source for treating hematopoietic disease. The limited engraftment of human PSC-derived (hPSC-derived) multipotent progenitor cells (MPP) has hampered the clinical application of these cells and suggests that MPP require additional cues for definitive hematopoiesis. We hypothesized that the presence of a vascular niche that produces Notch ligands jagged-1 (JAG1) and delta-like ligand-4 (DLL4) drives definitive hematopoiesis. We differentiated hes2 human embryonic stem cells (hESC) and Macaca nemestrina-induced PSC (iPSC) line-7 with cytokines in the presence or absence of endothelial cells (ECs) that express JAG1 and DLL4. Cells cocultured with ECs generated substantially more CD34+CD45+ hematopoietic progenitors compared with cells cocultured without ECs or with ECs lacking JAG1 or DLL4. EC-induced cells exhibited Notch activation and expressed HSC-specific Notch targets RUNX1 and GATA2. EC-induced PSC-MPP engrafted at a markedly higher level in NOD/SCID/IL-2 receptor γ chain-null (NSG) mice compared with cytokine-induced cells, and low-dose chemotherapy-based selection further increased engraftment. Long-term engraftment and the myeloid-to-lymphoid ratio achieved with vascular niche induction were similar to levels achieved for cord blood-derived MPP and up to 20-fold higher than those achieved with hPSC-derived MPP engraftment. Our findings indicate that endothelial Notch ligands promote PSC-definitive hematopoiesis and production of long-term engrafting CD34+ cells, suggesting these ligands are critical for HSC emergence.

Errors in chromosome segregation during gametogenesis, such as nondisjunction (NDJ) errors, have severe consequences in human reproduction, and a better understanding of their etiology is of fundamental interest in genetics. Mapping NDJ errors to meiotic/mitotic stages typically requires proband-parent comparison, limiting its applicability. Herein, we develop Mis-segregation Error Identification through Hidden Markov Models (MeiHMM), a method for inferring NDJ error stage and crossover events based on only genomic data of trisomic probands. Guided by triallelic genotype/haplotype configurations, MeiHMM discerns the allelic origin at each locus, which informs NDJ error during gamete formation, without identifying the parental origin of the trisomy. In 152 Down syndrome (DS) cases, MeiHMM achieved an accuracy of 96.1% in classifying NDJ errors, with a sensitivity of 91.6% in crossover identification, compared to proband-parents trio analysis. 17% of Meiosis II errors were misclassified as Meiosis I, mainly due to small proximal crossover events. Applying MeiHMM to 509 children with DS-associated childhood leukemia, we demonstrate that NDJ error is associated with the age of disease onset, somatic genomic abnormalities, and prognosis. Thus, MeiHMM is an effective method for trisomic NDJ error classification and crossover identification that can be applied broadly to study the etiology of congenital aneuploidy conditions. The authors report a computational framework for determining the meiotic/mitotic origin of nondisjunction (NDJ) in trisomies without parental data. Applying this to Down syndrome, they uncover links between NDJ error stage and leukemia genomics.

Charles Mullighan, Stephen Hunger, Jinghui Zhang and colleagues report a genomic analysis of 264 pediatric and young adult T-lineage acute lymphoblastic leukemia (T-ALL) samples. They identify 106 candidate driver genes, 53 of which have not been described previously in pediatric T-ALL, as well as associations between mutations and disease stage or subtype. Genetic alterations that activate NOTCH1 signaling and T cell transcription factors, coupled with inactivation of the INK4/ARF tumor suppressors, are hallmarks of T-lineage acute lymphoblastic leukemia (T-ALL), but detailed genome-wide sequencing of large T-ALL cohorts has not been carried out. Using integrated genomic analysis of 264 T-ALL cases, we identified 106 putative driver genes, half of which had not previously been described in childhood T-ALL (for example, CCND3 , CTCF , MYB , SMARCA4 , ZFP36L2 and MYCN ). We describe new mechanisms of coding and noncoding alteration and identify ten recurrently altered pathways, with associations between mutated genes and pathways, and stage or subtype of T-ALL. For example, NRAS / FLT3 mutations were associated with immature T-ALL, JAK3 / STAT5B mutations in HOXA1 deregulated ALL, PTPN2 mutations in TLX1 deregulated T-ALL, and PIK3R1 / PTEN mutations in TAL1 deregulated ALL, which suggests that different signaling pathways have distinct roles according to maturational stage. This genomic landscape provides a logical framework for the development of faithful genetic models and new therapeutic approaches.

Lineage switch (LS) refers to the immunophenotypic transformation of one leukemia lineage to another (ie, lymphoid to myeloid) with retention of baseline genetics. This phenomenon was originally observed in infants with B-lymphoblastic leukemia (B-ALL) with KMT2A rearrangements following chemotherapy, but is now increasingly being observed as a form of immune escape following targeted therapies among children and adults with B-ALL with and without KMT2A rearrangements. In this report, we present two cases of adolescents with B-ALL harboring CRLF2 rearrangements (Philadelphia-like phenotype) who developed LS to acute myeloid leukemia following CD19 targeted therapy. To our knowledge, these are the first cases of LS to be reported in patients with CRLF2 rearranged acute lymphoblastic leukemia. In addition to raising awareness that this genetic mutation may associate with lineage plasticity, our cases illustrate the importance of multi-modal disease surveillance in the diagnosis of LS.

B-cell acute lymphoblastic leukemia (B-cell ALL) is the most common childhood cancer. Despite a high overall cure rate, relapsed B-cell ALL remains a leading cause of cancer-related death among children. The addition of the bispecific T-cell engager molecule blinatumomab (an anti-CD19 and anti-CD3 single-chain molecule) to therapy for newly diagnosed standard-risk (as defined by the National Cancer Institute) B-cell ALL in children may improve outcomes. We conducted a phase 3 trial involving children with newly diagnosed standard-risk B-cell ALL who had an average or higher risk of relapse. Patients were randomly assigned to receive chemotherapy alone or chemotherapy plus two nonsequential 28-day cycles of blinatumomab. The primary end point was disease-free survival. The data and safety monitoring committee reviewed the results from the first interim efficacy analysis, which included 1440 patients who had undergone randomization (722 to chemotherapy alone and 718 to blinatumomab and chemotherapy) and recommended early termination of randomization. At a median follow-up of 2.5 years, the estimated 3-year disease-free survival (±SE) was 96.0±1.2% with blinatumomab and chemotherapy and 87.9±2.1% with chemotherapy alone (difference in restricted mean survival time, 72 days; 95% confidence interval, 36 to 108; P<0.001 by stratified log-rank test). The estimated 3-year disease-free survival among patients with an average relapse risk was 97.5±1.3% with blinatumomab and chemotherapy and 90.2±2.3% with chemotherapy alone; among those with a higher relapse risk, the corresponding values were 94.1±2.5% and 84.8±3.8%. Cytokine release syndrome, seizures, and sepsis of grade 3 or higher were rare during blinatumomab cycles, but the overall incidence of nonfatal sepsis and catheter-related infections was significantly higher among patients with an average relapse risk who had been assigned to receive blinatumomab and chemotherapy than among those assigned to receive chemotherapy alone. Adding blinatumomab to combination chemotherapy in patients with newly diagnosed childhood standard-risk B-cell ALL of average or higher risk of relapse significantly improved disease-free survival. (Funded by the National Institutes of Health and others; AALL1731 ClinicalTrials.gov number, NCT03914625.).

Background The recently updated European LeukemiaNet risk stratification guidelines combine cytogenetic abnormalities and genetic mutations to provide the means to triage patients with acute myeloid leukemia for optimal therapies. Despite the identification of many prognostic factors, relatively few have made their way into clinical practice. Methods In order to assess and improve the performance of the European LeukemiaNet guidelines, we developed novel prognostic models using the biomarkers from the guidelines, age, performance status and select transcript biomarkers. The models were developed separately for mononuclear cells and viable leukemic blasts from previously untreated acute myeloid leukemia patients (discovery cohort, N  = 185) who received intensive chemotherapy. Models were validated in an independent set of similarly treated patients (validation cohort, N  = 166). Results Models using European LeukemiaNet guidelines were significantly associated with clinical outcomes and, therefore, utilized as a baseline for comparisons. Models incorporating age and expression of select transcripts with biomarkers from European LeukemiaNet guidelines demonstrated higher area under the curve and C-statistics but did not show a substantial improvement in performance in the validation cohort. Subset analyses demonstrated that models using only the European LeukemiaNet guidelines were a better fit for younger patients (age < 55) than for older patients. Models integrating age and European LeukemiaNet guidelines visually showed more separation between risk groups in older patients. Models excluding results for ASXL1 , CEBPA , RUNX1 and TP53 , demonstrated that these mutations provide a limited overall contribution to risk stratification across the entire population, given the low frequency of mutations and confounding risk factors. Conclusions While European LeukemiaNet guidelines remain a critical tool for triaging patients with acute myeloid leukemia, the findings illustrate the need for additional prognostic factors, including age, to improve risk stratification.

T-lineage acute lymphoblastic leukaemia (T-ALL) is a high-risk tumour 1 that has eluded comprehensive genomic characterization, which is partly due to the high frequency of noncoding genomic alterations that result in oncogene deregulation 2 , 3 . Here we report an integrated analysis of genome and transcriptome sequencing of tumour and remission samples from more than 1,300 uniformly treated children with T-ALL, coupled with epigenomic and single-cell analyses of malignant and normal T cell precursors. This approach identified 15 subtypes with distinct genomic drivers, gene expression patterns, developmental states and outcomes. Analyses of chromatin topology revealed multiple mechanisms of enhancer deregulation that involve enhancers and genes in a subtype-specific manner, thereby demonstrating widespread involvement of the noncoding genome. We show that the immunophenotypically described, high-risk entity of early T cell precursor ALL is superseded by a broader category of ‘early T cell precursor-like’ leukaemia. This category has a variable immunophenotype and diverse genomic alterations of a core set of genes that encode regulators of hematopoietic stem cell development. Using multivariable outcome models, we show that genetic subtypes, driver and concomitant genetic alterations independently predict treatment failure and survival. These findings provide a roadmap for the classification, risk stratification and mechanistic understanding of this disease. Comprehensive genomic and transcriptomics analyses of more than 1,300 cases of childhood T-lineage acute lymphoblastic leukaemia identify 15 distinct subtypes that are associated with specific outcomes.