We created a mouse model where conditional expression of physiologic levels of an Mll-AF4 fusion oncogene induces development of acute lymphoblastic (ALL) or acute myeloid leukemias (AML). Immunophenotypic and gene expression analysis of the ALL cells demonstrated bone marrow replacement with B-precursor cells which express a gene expression profile that has significant overlap with profiles in human MLL-rearranged ALL.
H3K79 methylation profiles define murine and human MLL-AF4 leukemias.
Specimen part
View SamplesWe created a mouse model where conditional expression of physiologic levels of an Mll-AF4 fusion oncogene induces development of acute lymphoblastic (ALL) or acute myeloid leukemias (AML). Immunophenotypic and gene expression analysis of the ALL cells demonstrated bone marrow replacement with B-precursor cells which express a gene expression profile that has significant overlap with profiles in human MLL-rearranged ALL.
H3K79 methylation profiles define murine and human MLL-AF4 leukemias.
Specimen part
View SamplesThe presence of unspliced transcripts in hematopoietic stem cells (HSCs) and the proposed association of CREBBP with the constitutive production of unspliced RNA and with pre-mRNA processing prompted us to examine more closely an anomaly we had noted in microarray-based gene expression studies but had previously attributed to experimental noise. We noticed that more than half of the probe sets down-regulated in Crebbp+/- fetal liver HSCs (FLHSCs) relative to wild-type (WT) mapped entirely within introns, rather than detecting exonic or spliced sequences. We therefore set out to test whether this might be evidence that reduced CREBBP levels selectively alter the generation of full-length, unspliced pre-mRNA. We also asked whether this process might be associated with differentiation since self-renewal and lineage commitment are the both responses for which HSCs are primed.
Inactivation of a single copy of Crebbp selectively alters pre-mRNA processing in mouse hematopoietic stem cells.
Specimen part
View SamplesDeregulated Wnt/b-catenin signaling underlies the pathogenesis of a broad range of human cancers including multiple myeloma (MM). Thus, the b-catenin transcriptional complex has emerged as a high-priority pharmacologic target. The BCL9 oncogene is a critical transcriptional co-activator of b-catenin, and studies from our laboratory have implicated this transcriptional complex in MM disease initiation and progression. Micro RNAs regulate the expression of oncogenes and tumor suppressor genes, and because they play important roles as biologic inhibitors of cancer growth, they have great potential as novel therapeutic agents. Here we provide evidence for a role of miR-30s family in regulating expression of BCL9 and as a novel therapeutic agent in MM.
No associated publication
Disease, Cell line, Treatment
View SamplesPathologic activation of c-Myc plays a central role in pathogenesis of several neoplasias, including multiple myeloma. However, therapeutic targeting of c-Myc has remained elusive due to its lack of a clear ligand-binding domain. We therefore targeted c-Myc transcriptional function by another means, namely the disruption of chromatin-dependent signal transduction. Members of the bromodomain and extra-terminal (BET) subfamily of human bromodomain proteins (BRD2, BRD3 and BRD4) associate with acetylated chromatin and facilitate transcriptional activation by increasing the effective molarity of recruited transcriptional activators. Notably, BRD4 marks select M/G1 genes in mitotic chromatin for transcriptional memory and direct post-mitotic transcription, via direct interaction with the positive transcription elongation factor complex b (P-TEFb). Because c-Myc is known to regulate promoter-proximal pause release of Pol II, also through the recruitment of P-TEFb, we evaluated the selective small-molecule inhibitor of BET bromodomains, JQ1, as a chemical probe to interrogate the role of BET bromodomains in Myc-dependent transcription and to explore their role as therapeutic targets in c-Myc-driven neoplasias.
BET bromodomain inhibition as a therapeutic strategy to target c-Myc.
Specimen part, Cell line, Treatment
View SamplesFusion of the EWS gene to FLI1 produces a fusion oncoprotein that drives an aberrant gene expression program responsible for the development of Ewing sarcoma. We used a homogenous proximity assay to screen for compounds that disrupt the binding of EWS-FLI1 to its cognate DNA targets. A number of DNA-binding chemotherapeutic agents were found to non-specifically disrupt protein binding to DNA. In contrast, actinomycin D was found to preferentially disrupt EWS-FLI1 binding by comparison to p53 binding to their respective cognate DNA targets in vitro. In cell-based assays, low concentrations of actinomycin preferentially blocked EWS-FLI1 binding to chromatin, and disrupted EWS-FLI1-mediated gene expression. Higher concentrations of actinomycin globally repressed transcription. These results demonstrate that actinomycin preferentially disrupts EWS-FLI1 binding to DNA at selected concentrations. Although the window between this preferential effect and global suppression is too narrow to exploit in a therapeutic manner, these results suggest that base-preferences may be exploited to find DNA-binding compounds that preferentially disrupt subclasses of transcription factors.
Differential disruption of EWS-FLI1 binding by DNA-binding agents.
Cell line, Treatment
View SamplesMyelodysplastic syndrome (MDS) is considered a disease of hematopoietic stem cell (HSC) origin. To begin to unravel the molecular mechanisms underlying the deregulation of HSCs in MDS, we performed comparative gene expression profiling on Crebbp+/- and wild type HSCs. We chose to isolate HSCs from the fetal liver (FLHSC) because at this stage there were no differences in cell number between Crebbp+/- and wild type fetal livers, suggesting no overt hematopoietic differences. Thus, any change in gene expression found in Crebbp+/- FLHSCs is likely to reflect the initially compromised genetic program of HSC regulation, as opposed to that of Crebbp+/- HSCs in adult bone marrow, where secondary changes in gene expression may also occur as compensatory mechanisms for a compromised or failing hematopoietic system. We used day 14.5 post coitus FLHSC (Sca-1+,Lin-,AA4.1+,c-Kit++) from wild type (wt) and Crebbp heterozygous (ht) embryos to examine changes in gene expression before overt myelodysplastic disease manifestation.
No associated publication
Age, Specimen part
View SamplesStabilized Alpha-Helix peptides of BCL9 HD2 (SAH-BCL9) block BCL9 and B9L interactions with beta-catenin and specifically downregulate Wnt target gene expression.
Targeted disruption of the BCL9/β-catenin complex inhibits oncogenic Wnt signaling.
Specimen part, Cell line, Treatment
View SamplesWe created a mouse model where conditional expression of physiologic levels of an Mll-AF4 fusion oncogene induces development of acute lymphoblastic (ALL) or acute myeloid leukemias (AML). Immunophenotypic and gene expression analysis of the ALL cells demonstrated bone marrow replacement with B-precursor cells which express a gene expression profile that has significant overlap with profiles in human MLL-rearranged ALL.
H3K79 methylation profiles define murine and human MLL-AF4 leukemias.
Specimen part
View Samples