Project description:Abstract: We obtained a global view of gene expression in both cell lines and pediatric acute lymphoblastic leukemia (ALL) samples that harbor one of several selected chromosomal abnormalities. When the cell lines were studied alone, we found that these chromosomal abnormalities were associated with the predominant variation in transcriptional programs across the set of cell lines studied. When cell lines and clinical samples were studied together, we found that each chromosomal abnormality (TEL/AML1, BCR/ABL, or MLL abnormalities) was associated with a characteristic gene expression signature that was shared by both cell lines and clinical samples. However, BCR/ABL was associated with a much more heterogeneous pattern of expression than were TEL/AML1 and MLL abnormalities. This observation has important implications for the study of BCR/ABL ALL. In addition, we systematically identified genes whose expression was associated with TEL/AML1, BCR/ABL, or MLL abnormalities in both clinical samples and cell lines. Although some of these genes have previously been described, many have not previously been reported to be associated with one of these chromosomal abnormalities. Notably, we found that the erythropoietin receptor (EPOR) is consistently highly expressed in TEL/AML1 ALL compared with BCR/ABL or MLL. This SuperSeries is composed of the SubSeries listed below.
Project description:B-cell acute lymphoblastic leukemia (B-ALL) is the most prevailing childhood cancer. As predicated by its prenatal origin, infant B-ALL (iB-ALL) show a silent mutational landscape irrespective of the MLL rearrangement/status, suggesting that other regulatory mechanisms might be impaired in the context of the disease. Here we used the most recent Illumina MethylationEPIC Beadchip platform to describe the genome-wide DNA methylation changes observed in a total of 69 de novo MLL-AF4+, MLL-AF9+ and non-rearranged MLL iB-ALL leukemias uniformly treated according to Interfant 99/06 protocol. Please note that samples X8 and X9 (pool of B cells and BCP) correspond to samples 200340580160_R08C01 and 200340580161_R07C01 from study E-MTAB-6315, respectively.
Project description:Genome editing provides a potential approach to model de novo leukemogenesis in primary human hematopoietic stem and progenitor cells (HSPCs) through induction of chromosomal translocations by targeted DNA double-strand breaks. However, very low efficiency of translocations and lack of markers for translocated cells serve as barriers to their characterization and model development. Here we utilized TALENs to generate t(9;11) chromosomal translocations encoding MLL-AF9 and reciprocal AF9-MLL fusion products in CD34+ human cord blood cells. Selected cytokine combinations enabled monoclonal outgrowth and immortalization of initially rare translocated cells, which were distinguished by elevated MLL target gene expression, high surface CD9 expression, and increased colony forming ability. Subsequent transplantation into immune-compromised mice induced myeloid leukemias within 48 weeks, whose pathologic and molecular features extensively overlap with de novo patient MLL-rearranged leukemias. No evidence of secondary pathogenic mutations was revealed by targeted exome sequencing and whole genome RNA-seq analyses, suggesting the genetic sufficiency of t(9;11) translocation for leukemia development from human HSPCs. Thus, genome editing enables modeling of human acute MLL-rearranged leukemia in vivo reflecting the genetic simplicity of this disease and provides an experimental platform for biological and disease modeling applications.
Project description:Transcriptome analysis by single cell sequencing provides valuable information on intratumor heterogeneity and developmental stages of acute myeloid leukemia (AML) as well as interactions of tumor cells with the microenvironment. However, it has been hardly applied to the subgroup of cases with translocations of the mixed lineage leukemia (MLL) gene for which the enhancer of mRNA decapping 4 (EDC4) gene was recently identified as a novel fusion partner (MLL-EDC4). Here, we compared different MLL translocation by single cell RNA sequencing of cells derived from peripheral blood. The AML MLL-EDC4 patient almost exclusively showed a transcriptional profile of hematopoietic progenitor cells while leukemic cells while the MLLT3-MLL and MLL-ELL fusions exhibited a more differentiated phenotype. The MLL-EDC4 progenitor state was characterized by the upregulation of key transcriptional regulators in AML (RUNX1, SOX4, HOPX), target genes of MYC and interferon signaling as well as other genes known to play a critical role in hematopoiesis or leukemic stem cell activation (CDK6, FLT3, NPM1). In addition, we detected an enrichment of a normal and putatively immunosuppressive monocyte population in the patient with MLL-EDC4. Thus, the MLL-EDC4 translocation was associated with unique transcriptional and microenvironmental features.
Project description:microRNA are aberrantly expressed in acute myeloid leukemia (AML), and clinically may have diagnostic, prognostic, and therapeutic value. We identify one such microRNA, miR-196b, is essential for MLL-AF9 leukemia initiation and maintenance. To discover how miR-196b contributes to leukemogenesis, we utilized multiple unbiased approaches that identified and functionally screened miR-196b target activity in AML. Our studies resolved how conflicting networks of miRNA-regulated targets are integrated during leukemogenesis. This work uncovered two miR-196b direct targets, the cell cycle regulator Cdkn1b (p27Kip1) and Polycomb group member Phc2, that independently cooperate with MLL-AF9 to promote leukemogenesis by regulating stem cell transcriptional programs. Finally, we found that therapeutic disruption of miR-196b direct targeting of Cdkn1b suppresses leukemogenesis.
Project description:microRNA are aberrantly expressed in acute myeloid leukemia (AML), and clinically may have diagnostic, prognostic, and therapeutic value. We identify one such microRNA, miR-196b, is essential for MLL-AF9 leukemia initiation and maintenance. To discover how miR-196b contributes to leukemogenesis, we utilized multiple unbiased approaches that identified and functionally screened miR-196b target activity in AML. Our studies resolved how conflicting networks of miRNA-regulated targets are integrated during leukemogenesis. This work uncovered two miR-196b direct targets, the cell cycle regulator Cdkn1b (p27Kip1) and Polycomb group member Phc2, that independently cooperate with MLL-AF9 to promote leukemogenesis by regulating stem cell transcriptional programs. Finally, we found that therapeutic disruption of miR-196b direct targeting of Cdkn1b suppresses leukemogenesis.
Project description:The goals of this study aim to reveal microRNA expression profiles of leukemia-associated macrophages and regulatory mechanism in response to the microenvironmental cues in mouse MLL-AF9 acute myelogenous leukemia
Project description:Recurrent chromosomal translocations involving the mixed lineage leukemia gene (MLL) give rise to highly aggressive acute leukemia associated with poor clinical outcomes. The preferential involvement of chromatin-associated factors in MLL rearrangements belies a dependency on transcriptional control. To identify new targets for therapeutic development in MLL, we performed a genome-scale CRISPR-Cas9 knockout screen in MLL-AF4 leukemia. Among validated targets, we identified the transcriptional regulator, ENL, as an unrecognized dependency particularly indispensable for proliferation. To explain the mechanistic role for ENL in leukemia pathogenesis and the dynamic role in transcription control, we pursued a chemical genetic strategy utilizing targeted protein degradation. ENL loss suppresses transcription initiation and elongation genome-wide, with pronounced effects at genes featuring disproportionate ENL load. Importantly, ENL-dependent leukemic growth was contingent upon an intact YEATS epigenomic reader domain. These findings reveal a novel dependency in acute leukemia and a first mechanistic rationale for disrupting YEATS domains in disease.
Project description:Recurrent chromosomal translocations involving the mixed lineage leukemia gene (MLL) give rise to highly aggressive acute leukemia associated with poor clinical outcomes. The preferential involvement of chromatin-associated factors in MLL rearrangements belies a dependency on transcriptional control. To identify new targets for therapeutic development in MLL, we performed a genome-scale CRISPR-Cas9 knockout screen in MLL-AF4 leukemia. Among validated targets, we identified the transcriptional regulator, ENL, as an unrecognized dependency particularly indispensable for proliferation. To explain the mechanistic role for ENL in leukemia pathogenesis and the dynamic role in transcription control, we pursued a chemical genetic strategy utilizing targeted protein degradation. ENL loss suppresses transcription initiation and elongation genome-wide, with pronounced effects at genes featuring disproportionate ENL load. Importantly, ENL-dependent leukemic growth was contingent upon an intact YEATS epigenomic reader domain. These findings reveal a novel dependency in acute leukemia and a first mechanistic rationale for disrupting YEATS domains in disease.
Project description:The aim of the study was to investigate the role of TGIF1 in MLL-AF9 transformed cells Members of the TALE (Three-amino acid loop extension) family of atypical homeodomain-containing transcription factors are prominent downstream effectors of oncogenic fusion proteins generated from translocations involving the mixed lineage leukemia (MLL) gene. A particular well-characterized member of this protein family is MEIS1, which together with HOXA proteins, orchestrates a transcriptional program required for the maintenance of MLL-rearranged acute myeloid leukemia (AML). Although TALE family proteins are mainly described as transcriptional activators TGIF1 (TGF-β induced factor) / TGIF2 are considered as transcriptional repressors. However, as their function in MLL-rearranged AML is largely unknown, we tested the potential importance of TGIF1 in the maintenance of MLL-rearranged AML. We find that expression of TGIF1 in MLL-AF9 transformed cells (MAF9) leads to cell cycle exit and differentiation in vitro and delayed leukemic onset in vivo. In accordance, MLL-rearranged patient blasts display lower levels of TGIF1 and TGIF1 expression in general correlates positively with survival. Mechanistically, we show that TGIF1 interferes with a MEIS1-dependent transcriptional program by associating to MEIS1-bound region in a competitive manner. Collectively, these findings demonstrate that TALE family members can act both positively and negatively on transcriptional programs responsible for the maintenance of MLL-rearranged AML.