PersonALL: a genetic scoring guide for personalized risk assessment in pediatric B-cell precursor acute lymphoblastic leukemia.

BACKGROUND: Recurrent genetic lesions provide basis for risk assessment in pediatric acute lymphoblastic leukemia (ALL). However, current prognostic classifiers rely on a limited number of predefined sets of alterations. METHODS: Disease-relevant copy number aberrations (CNAs) were screened genome-wide in 260 children with B-cell precursor ALL. Results were integrated with cytogenetic data to improve risk assessment. RESULTS: CNAs were detected in 93.8% (n = 244) of the patients. First, cytogenetic profiles were combined with IKZF1 status (IKZF1normal, IKZF1del and IKZF1plus) and three prognostic subgroups were distinguished with significantly different 5-year event-free survival (EFS) rates, IKAROS-low (n = 215): 86.3%, IKAROS-medium (n = 27): 57.4% and IKAROS-high (n = 18): 37.5%. Second, contribution of genetic aberrations to the clinical outcome was assessed and an aberration-specific score was assigned to each prognostically relevant alteration. By aggregating the scores of aberrations emerging in individual patients, personalized cumulative values were calculated and used for defining four prognostic subgroups with distinct clinical outcomes. Two favorable subgroups included 60% of patients (n = 157) with a 5-year EFS of 96.3% (excellent risk, n = 105) and 87.2% (good risk, n = 52), respectively; while 40% of patients (n = 103) showed high (n = 74) or ultra-poor (n = 29) risk profile (5-year EFS: 67.4% and 39.0%, respectively). CONCLUSIONS: PersonALL, our conceptually novel prognostic classifier considers all combinations of co-segregating genetic alterations, providing a highly personalized patient stratification.

Next-Generation Sequencing-Based Genomic Profiling of Children with Acute Myeloid Leukemia.

Pediatric acute myeloid leukemia (AML) represents a major cause of childhood leukemic mortality, with only a limited number of studies investigating the molecular landscape of the disease. Here, we present an integrative analysis of cytogenetic and molecular profiles of 75 patients with pediatric AML from a multicentric, real-world patient cohort treated according to AML Berlin-Frankfurt-Münster protocols. Targeted next-generation sequencing of 54 genes revealed 17 genes that were recurrently mutated in >5% of patients. Considerable differences were observed in the mutational profiles compared with previous studies, as BCORL1, CUX1, KDM6A, PHF6, and STAG2 mutations were detected at a higher frequency than previously reported, whereas KIT, NRAS, and KRAS were less frequently mutated. Our study identified novel recurrent mutations at diagnosis in the BCORL1 gene in 9% of the patients. Tumor suppressor gene (PHF6, TP53, and WT1) mutations were found to be associated with induction failure and shorter event-free survival, suggesting important roles of these alterations in resistance to therapy and disease progression. Comparison of the mutational landscape at diagnosis and relapse revealed an enrichment of mutations in tumor suppressor genes (16.2% versus 44.4%) and transcription factors (35.1% versus 55.6%) at relapse. Our findings shed further light on the heterogeneity of pediatric AML and identify previously unappreciated alterations that may lead to improved molecular characterization and risk stratification of pediatric AML.

Integrative phosphoproteomics defines two biologically distinct groups of KMT2A rearranged acute myeloid leukaemia with different drug response phenotypes.

Acute myeloid leukaemia (AML) patients harbouring certain chromosome abnormalities have particularly adverse prognosis. For these patients, targeted therapies have not yet made a significant clinical impact. To understand the molecular landscape of poor prognosis AML we profiled 74 patients from two different centres (in UK and Finland) at the proteomic, phosphoproteomic and drug response phenotypic levels. These data were complemented with transcriptomics analysis for 39 cases. Data integration highlighted a phosphoproteomics signature that define two biologically distinct groups of KMT2A rearranged leukaemia, which we term MLLGA and MLLGB. MLLGA presented increased DOT1L phosphorylation, HOXA gene expression, CDK1 activity and phosphorylation of proteins involved in RNA metabolism, replication and DNA damage when compared to MLLGB and no KMT2A rearranged samples. MLLGA was particularly sensitive to 15 compounds including genotoxic drugs and inhibitors of mitotic kinases and inosine-5-monosphosphate dehydrogenase (IMPDH) relative to other cases. Intermediate-risk KMT2A-MLLT3 cases were mainly represented in a third group closer to MLLGA than to MLLGB. The expression of IMPDH2 and multiple nucleolar proteins was higher in MLLGA and correlated with the response to IMPDH inhibition in KMT2A rearranged leukaemia, suggesting a role of the nucleolar activity in sensitivity to treatment. In summary, our multilayer molecular profiling of AML with poor prognosis and KMT2A-MLLT3 karyotypes identified a phosphoproteomics signature that defines two biologically and phenotypically distinct groups of KMT2A rearranged leukaemia. These data provide a rationale for the potential development of specific therapies for AML patients characterised by the MLLGA phosphoproteomics signature identified in this study.

Dissection of subclonal evolution by temporal mutation profiling in chronic lymphocytic leukemia patients treated with ibrutinib.

The Bruton's tyrosine kinase (BTK) inhibitor ibrutinib is inducing durable responses in chronic lymphocytic leukemia (CLL) patients with refractory/relapsed disease or with TP53 defect, with BTK and phospholipase C gamma 2 (PLCG2) mutations representing the predominant mechanisms conferring secondary ibrutinib resistance. To understand the landscape of genomic changes and the dynamics of subclonal architecture associated with ibrutinib treatment, an ultra-deep next-generation sequencing analysis of 30 recurrently mutated genes was performed on sequential samples of 20 patients, collected before and during single-agent ibrutinib treatment. Mutations in the SF3B1, MGAand BIRC3 genes were enriched during ibrutinib treatment, while aberrations in the BTK, PLCG2, RIPK1, NFKBIE and XPO1 genes were exclusively detected in posttreatment samples. Besides the canonical mutations, four novel BTK mutations and three previously unreported PLCG2 variants were identified. BTK and PLCG2 mutations were backtracked in five patients using digital droplet PCR and were detectable on average 10.5 months before clinical relapse. With a median follow-up time of 36.5 months, 7/9 patients harboring BTK mutations showed disease progression based on clinical and/or laboratory features. In conclusion, subclonal heterogeneity, dynamic clonal selection and various patterns of clonal variegation were identified with novel resistance-associated BTK mutations in individual patients treated with ibrutinib.

Comprehensive profiling of disease-relevant copy number aberrations for advanced clinical diagnostics of pediatric acute lymphoblastic leukemia.

Acute lymphoblastic leukemia is the most common pediatric cancer characterized by a heterogeneous genomic landscape with copy number aberrations occurring at various stages of pathogenesis, disease progression, and treatment resistance. In this study, disease-relevant copy number aberrations were profiled in bone marrow samples of 91 children with B- or T-cell precursor acute lymphoblastic leukemia using digital multiplex ligation-dependent probe amplification (digitalMLPATM). Whole chromosome gains and losses, subchromosomal copy number aberrations, as well as unbalanced alterations conferring intrachromosomal gene fusions were simultaneously identified with results available within 36 hours. Aberrations were observed in 96% of diagnostic patient samples, and increased numbers of copy number aberrations were detected at the time of relapse as compared with diagnosis. Comparative scrutiny of 24 matching diagnostic and relapse samples from 11 patients revealed three different patterns of clonal relationships with (i) one patient displaying identical copy number aberration profiles at diagnosis and relapse, (ii) six patients showing clonal evolution with all lesions detected at diagnosis being present at relapse, and (iii) four patients displaying conserved as well as lost or gained copy number aberrations at the time of relapse, suggestive of the presence of a common ancestral cell compartment giving rise to clinically manifest leukemia at different time points during the disease course. A newly introduced risk classifier combining cytogenetic data with digitalMLPATM-based copy number aberration profiles allowed for the determination of four genetic subgroups of B-cell precursor acute lymphoblastic leukemia with distinct event-free survival rates. DigitalMLPATM provides fast, robust, and highly optimized copy number aberration profiling for the genomic characterization of acute lymphoblastic leukemia samples, facilitates the decipherment of the clonal origin of relapse and provides highly relevant information for clinical prognosis assessment.

Elevated HOX gene expression in acute myeloid leukemia is associated with NPM1 mutations and poor survival.

Acute myeloid leukemia (AML) is a clonal disorder of hematopoietic progenitor cells and the most common malignant myeloid disorder in adults. Several gene mutations such as in NPM1 (nucleophosmin 1) are involved in the pathogenesis and progression of AML. The aim of this study was to identify genes whose expression is associated with driver mutations and survival outcome. Genotype data (somatic mutations) and gene expression data including RNA-seq, microarray, and qPCR data were used for the analysis. Multiple datasets were utilized as training sets (GSE6891, TCGA, and GSE1159). A new clinical sample cohort (Semmelweis set) was established for in vitro validation. Wilcoxon analysis was used to identify genes with expression alterations between the mutant and wild type samples. Cox regression analysis was performed to examine the association between gene expression and survival outcome. Data analysis was performed in the R statistical environment. Eighty-five genes were identified with significantly altered expression when comparing NPM1 mutant and wild type patient groups in the GSE6891 set. Additional training sets were used as a filter to condense the six most significant genes associated with NPM1 mutations. Then, the expression changes of these six genes were confirmed in the Semmelweis set: HOXA5 (P = 3.06E-12, FC = 8.3), HOXA10 (P = 2.44E-09, FC = 3.3), HOXB5 (P = 1.86E-13, FC = 37), MEIS1 (P = 9.82E-10, FC = 4.4), PBX3 (P = 1.03E-13, FC = 5.4) and ITM2A (P = 0.004, FC = 0.4). Cox regression analysis showed that higher expression of these genes - with the exception of ITM2A - was associated with worse overall survival. Higher expression of the HOX genes was identified in tumors harboring NPM1 gene mutations by computationally linking genotype and gene expression. In vitro validation of these genes supports their potential therapeutic application in AML.