Project description:High hyperdiploid acute lymphoblastic leukemia (ALL) is one of the most common malignancies in children. It is characterized by gain of chromosomes, typically +X, +4, +6, +10, +14, +17, +18, and +21,+21; little is known about additional genetic aberrations. Approximately 20% of the patients relapse; therefore it is clinically important to identify risk-stratifying markers. We used SNP array analysis to investigate a consecutive series of 74 cases of high hyperdiploid ALL. We show that the characteristic chromosomal gains are even more frequent than previously believed, indicating that karyotyping mistakes are common, and that almost 80% of the cases display additional abnormalities detectable by SNP array analysis. Subclonality analysis strongly implied that the numerical aberrations were primary and arose before structural events, suggesting that step-wise evolution of the leukemic clone is common. An association between duplication of 1q and +5 was seen (P = 0.003). Other frequent abnormalities included whole-chromosome uniparental isodisomies (wUPIDs) 9 and 11, gain of 17q not associated with isochromosome formation, extra gain of part of 21q, deletions of ETS variant 6 (ETV6), cyclin-dependent kinase inhibitor 2A (CKDN2A) and paired box 5 (PAX5), and PAN3 poly(A) specific ribonuclease subunit homolog (PAN3) microdeletions. Comparison of whole-chromosome and partial UPID9 suggested different pathogenetic outcomes, with the former not involving CDKN2A. Finally, two cases had partial deletions of AT rich interactive domain 5B (ARID5B), indicating that acquired as well as constitutional variants in this locus may be associated with pediatric ALL. Here we provide a comprehensive characterization of the genetic landscape of high hyperdiploid childhood ALL, including the heterogeneous pattern of secondary genetic events.
Project description:Proteogenomic analysis and genomic profiling, RNA-sequencing, and mass spectrometry-based analysis of High hyperdiploid childhood acute lymphoblastic leukemia.
Project description:High hyperdiploidy (HD) is the most common cytogenetic subtype of childhood acute lymphoblastic leukemia (ALL), and a higher incidence of HD has been reported in ALL patients with congenital cancer syndromes. We assessed the frequency of predisposing germline mutations in 57 HD-ALL patients from the California Childhood Leukemia Study via targeted sequencing of cancer-relevant genes. Three out of 57 patients (5.3%) harbored confirmed germline mutations that were likely causal, in NBN, ETV6, and FLT3, with an additional six patients (10.5%) harboring putative predisposing mutations that were rare in unselected individuals (<0.01% allele frequency in the Exome Aggregation Consortium, ExAC) and predicted functional (scaled CADD score ≥ 20) in known or potential ALL predisposition genes (SH2B3, CREBBP, PMS2, MLL, ABL1, and MYH9). Three additional patients carried rare and predicted damaging germline mutations in GAB2, a known activator of the ERK/MAPK and PI3K/AKT pathways and binding partner of PTPN11-encoded SHP2. The frequency of rare and predicted functional germline GAB2 mutations was significantly higher in our patients (2.6%) than in ExAC (0.28%, P = 4.4 × 10-3 ), an observation that was replicated in ALL patients from the TARGET project (P = .034). We cloned patient GAB2 mutations and expressed mutant proteins in HEK293 cells and found that frameshift mutation P621fs led to reduced SHP2 binding and ERK1/2 phosphorylation but significantly increased AKT phosphorylation, suggesting possible RAS-independent leukemogenic effects. Our results support a significant contribution of rare, high penetrance germline mutations to HD-ALL etiology, and pinpoint GAB2 as a putative novel ALL predisposition gene.
Project description:High hyperdiploidy (HD), the most common cytogenetic subtype of B-cell acute lymphoblastic leukemia (B-ALL), is largely curable but significant treatment-related morbidity warrants investigating the biology and identifying novel drug targets. Targeted deep-sequencing of 538 cancer-relevant genes was performed in 57 HD-ALL patients lacking overt KRAS and NRAS hotspot mutations and lacking common B-ALL deletions to enrich for discovery of novel driver genes. One-third of patients harbored damaging mutations in epigenetic regulatory genes, including the putative novel driver DOT1L (n=4). Receptor tyrosine kinase (RTK)/Ras/MAPK signaling pathway mutations were found in two-thirds of patients, including novel mutations in ROS1, which mediates phosphorylation of the PTPN11-encoded protein SHP2. Mutations in FLT3 significantly co-occurred with DOT1L (p=0.04), suggesting functional cooperation in leukemogenesis. We detected an extraordinary level of tumor heterogeneity, with microclonal (mutant allele fraction <0.10) KRAS, NRAS, FLT3, and/or PTPN11 hotspot mutations evident in 31/57 (54.4%) patients. Multiple KRAS and NRAS codon 12 and 13 microclonal mutations significantly co-occurred within tumor samples (p=4.8x10-4), suggesting ongoing formation of and selection for Ras-activating mutations. Future work is required to investigate whether tumor microheterogeneity impacts clinical outcome and to elucidate the functional consequences of epigenetic dysregulation in HD-ALL, potentially leading to novel therapeutic approaches.
Project description:Proteogenomic analysis and genomic profiling, RNA-sequencing, and mass spectrometry-based analysis of High hyperdiploid childhood acute lymphoblastic leukemia.
Project description:Hyperdiploidy, i.e. gain of whole chromosomes, is one of the most common genetic features of childhood acute lymphoblastic leukemia (ALL), but its pathogenetic impact is poorly understood. Here, we report a proteogenomic analysis on matched datasets from genomic profiling, RNA-sequencing, and mass spectrometry-based analysis of >8,000 genes and proteins as well as Hi-C of primary patient samples from hyperdiploid and ETV6/RUNX1-positive pediatric ALL. We show that CTCF and cohesin, which are master regulators of chromatin architecture, display low expression in hyperdiploid ALL. In line with this, a general genome-wide dysregulation of gene expression in relation to topologically associating domain (TAD) borders were seen in the hyperdiploid group. Furthermore, Hi-C of a limited number of hyperdiploid childhood ALL cases revealed that 2/4 cases displayed a clear loss of TAD boundary strength and 3/4 showed reduced insulation at TAD borders, with putative leukemogenic effects.
Project description:In precursor B-cell acute lymphoblastic leukemia (ALL), whole chromosome uniparental isodisomy (wUPD) occurs almost uniquely in the high hyperdiploid (51-67 chromosomes) (HH) subtype. Comparison of 26 HH with wUPD with 31 with noUPD, showed a higher modal number of chromosomes and gains of 5+ in wUPD. Mutations in genes within epigenetic pathways with upregulation of genes involved in cellular response to stress and stimuli, and mutations in RAS/RTK pathways and upregulation of genes in RNA Polymerase III pathway were seen in wUPD and noUPD respectively. Though overall outcomes were similar in patient with and without wUPD, those with noUPD were more likely to have residual disease after treatment. Differential gene expression between the two groups showed upregulation of genes involved in thiopurine drug resistance in wUPD. Genome-wide differences between HH ALL with and without UPD identified plausible biological explanations for the heterogeneity in therapeutic response in HH ALL.
Project description:Development of B-acute lymphoblastic leukemia accompanies with multiple variable mutations. Beside the structural and chromosomal alterations, especially mutations in the regulators of B cell differentiation are common. Around 60% of the B-ALL show deletions of these genes.
Project description:BCR-ABL1 lymphoblastic leukaemia is characterized by the deletion of Ikaros. The Philadelphia chromosome, encoding BCR-ABL1, is the defining lesion of chronic myelogenous leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL) cases. To define oncogenic lesions that cooperate with BCR-ABL1 to induce ALL, we performed genome-wide analysis of leukemic samples from 23 CML cases and 304 ALL cases, including 43 BCR-ABL1 B-ALL cases. IKZF1 (encoding the transcription factor Ikaros) was deleted in 83.7% of BCR-ABL1 B-ALL cases, but not in chronic phase CML. Deletion of IKZF1 was also identified as an acquired lesion in lymphoid blast crisis of CML. The IKZF1 deletions resulted in haploinsufficiency, expression of a dominant negative Ikaros isoform or the complete loss of Ikaros expression. Sequencing of IKZF1 deletion breakpoints suggested that aberrant V(D)J recombination is responsible for the deletions. These findings suggest that genetic lesions resulting in the loss of Ikaros function are a key event in the development of BCR-ABL1 ALL. *** Due to privacy concerns, the primary SNP array data is no longer available with unrestricted access. Individuals wishing to obtain this data for research purposes may request access using the Web links below. *** This SuperSeries is composed of the SubSeries listed below.
Project description:Despite their apparently good prognosis ?15% of high hyperdiploid (HD) childhood acute lymphoblastic leukemia (ALL) cases relapse. To search for responsible risk factors we determined copy number aberrations as well as copy neutral loss of heterozygosity (LOH) in 13 matched diagnosis and relapse samples and added the data of the only three available cases from the literature. Deletions and copy neutral LOH in 3 and 2 of the 16 cases directed us to the histone-modifying CREB-binding protein (CREBBP) gene, whose functional impairment is implicated in drug resistance. We therefore screened all samples for mutations in this gene and discovered 9 acquired sequence mutations in 7/16 cases, leading to an overall frequency of somatic CREBBP aberrations in HD ALL relapse cases of 63% that is considerably higher than that of the reported, mainly non-HD ALL (18.3%). Moreover, mutations in HD cases occur almost exclusively in the HAT domain (8/9; 89%). Hot spot mutations are present at diagnosis in 18.8% of relapsing HD ALL cases but in none of 40 respective cases remaining in long-term remission. Thus, the particular high incidence of CREBBP mutations in relapse-prone HD ALL cases could eventually be exploited for refined risk stratification and customized treatment in this genetic subgroup.