Interaction of c-Myb with p300 is required for the induction of acute myeloid leukemia (AML) by human AML oncogenes
ABSTRACT: The MYB oncogene is widely expressed in acute leukemias and is important for the continued proliferation of leukemia cells, raising the possibility that MYB may be a therapeutic target. However realization of this potential requires (i) a significant therapeutic window for MYB inhibition, given its essential role in normal hematopoiesis; and (ii) an approach for developing an effective therapeutic. We previously showed that the interaction of Myb with the coactivator CBP/p300 is essential for its transforming activity. Here we use hematopoietic cells from the Booreana mouse strain, which carries a mutation in Myb that prevents interaction with CBP/p300, to examine the requirement for this interaction in myeloid transformation and leukemogenesis. Using this strain and a strain (plt6) carrying a “complementary” mutation in p300, we show that the Myb-p300 interaction is essential for in vitro transformation by the myeloid leukemia oncogenes AML1-ETO, AML1-ETO9a, MLL-ENL, and MLL-AF9. We further show that unlike cells from wild-type (WT) mice, Booreana cells fail to induce leukemia upon transplantation into irradiated recipients following transduction with an AML1-ETO9a retrovirus. These data highlight disruption of the Myb-p300 interaction as a potential therapeutic strategy for AML and suggest that such a strategy would have a useable therapeutic index since Booreana mice, unlike Myb null mice, are viable. Finally we have begun to explore the molecular basis of the these observations by gene expression profiling; this highlighted several genes previously implicated in myeloid leukemogenesis as being differentially expressed between WT and Booreana cells transduced with AML1-ETO9a. Total RNA was obtained from FACS sorted GFP+;c-Kit+ primary bone marrow cells from WT and Booreana mouse strains which had been cultured for 48 hours post-transduction with Control or AML1-ETO9a retroviruses. RNA was extracted from each of 4 samples per group and used to probe Illumina mouse Beadchips array.
Project description:MEIS2 collaborates with AML1-ETO in inducing acute myeloid leukemia in a murine bone marrow transplantation model We employed RNA-seq to assess similarities/differences among murine leukemic bone marrow samples transduced with either AML1-ETO/Meis2, AML1-ETO9a/Meis2, or AML1-ETO9a
Project description:Leukemogenesis requires enhanced self-renewal activity, which is induced by specific oncogenes. The underlying molecular mechanisms remain incompletely understood. We transduced mouse lineage negative bone marrow cells (enriched for hematopoietic stem and progenitor cells) with retrovirus expressing leukemic oncogene AML1-ETO9a, MYC and MLL-AF9 as well as empty vector (MIG). We found that all three oncogenes enhanced snoRNA formation. High abundance of snoRNAs was observed in primary human AML specimens with the notable exception of NPM1 mutant AML. Leukemogenesis by AML1-ETO required expression of the groucho related Amino Enhancer of Split (AES). AES functioned by inducing snoRNA/RNP formation via interaction with the RNA helicase DDX21. Similarly, loss of C/D box snoRNAs with concomitant loss of rRNA 2’-O-methylation resulted in decreased leukemia self-renewal potential.In summary, we identified C/D box snoRNAs and rRNA 2’-O-methylation as critical determinants of leukemic stem cell activity. Overall design: We used small RNA-Seq to determine the expression profile of small nucleolar RNA (snoRNA) in 63 primary AML patient samples. To further investigate the role of AES and DDX21 in snoRNA formation we also analyzed kasumi-1 cell lines with shRNA based downregulation of AES or DDX21. Furthermore, we show that mouse snoRNAs are induced by leukemia oncogene AML-ETO9a, MLL-AF9 and MYC in mouse lineage negative bone marrow cells.
Project description:Combined gene expression and DNA occupancy profiling identifies JAK/STAT signaling as a valid therapeutic target of t(8;21) AML t(8;21) is commonly associated with acute myeloid leukemia (AML). The resulting AML1-ETO fusion proteins are involved in the pathogenesis of AML. To identify novel molecular and therapeutic targets, we performed combined gene expression and promoter occupancy profiling using a primary leukemia initiating cell-enriched population induced by AML1-ETO9a (AE9a). CD45, a negative regulator of cytokine/growth factor receptor and JAK/STAT signaling, is greatly downregulated; furthermore JAK1 and JAK2 are upregulated in these leukemia cells. Consequently, JAK/STAT signaling is enhanced in the AE9a leukemia cells. Importantly, AE9a leukemia cells are highly susceptible to perturbation of JAK/STAT signaling, and a JAK2-selective inhibitor, TG101209, effectively targets these leukemia cells in vivo, suggesting the potential efficacy of JAK2 inhibitors in treating t(8;21) AML. Overall design: Wild-type or AE9a leukemic samples in triplicate.
Project description:Microarray gene profilling indentified snoRNAs are downstream target of Amino Enhancer of Split (AES) and are essential for AML1-ETO9a induced leukemia. Amino Enhancer of Split (Aes) is strongly induced by leukemia oncogenes AML1-ETO, PML-RARα and PLZF-RARα. With a conditional AES knockout mouse model we showed that AES is essential for AML1-ETO9a indeced leukemia. We performed gene expression microarray using mouse primary AML1-ETO9a transformed AES wildtype and knockout and showed that snoRNAs were downregulated in AES knockout cells. We found that SnoRNA induction is a common mechanism shared by distinct oncogenes including AML1-ETO, MYC and MLL-AF9. Suppression of C/D box snoRNA complexes or deletion of several single C/D box snoRNAs inhibit clonogenic growth of leukemia cells. These findings suggest that enhancement of snoRNA levels is a critical mechanism of leukemic transformation. Overall design: AES wildtype or knockout AML1-ETO9a transformed cells in triplicates
Project description:Combined gene expression and DNA occupancy profiling identifies JAK/STAT signaling as a valid therapeutic target of t(8;21) AML t(8;21) is commonly associated with acute myeloid leukemia (AML). The resulting AML1-ETO fusion proteins are involved in the pathogenesis of AML. To identify novel molecular and therapeutic targets, we performed combined gene expression and promoter occupancy profiling using a primary leukemia initiating cell-enriched population induced by AML1-ETO9a (AE9a). CD45, a negative regulator of cytokine/growth factor receptor and JAK/STAT signaling, is greatly downregulated; furthermore JAK1 and JAK2 are upregulated in these leukemia cells. Consequently, JAK/STAT signaling is enhanced in the AE9a leukemia cells. Importantly, AE9a leukemia cells are highly susceptible to perturbation of JAK/STAT signaling, and a JAK2-selective inhibitor, TG101209, effectively targets these leukemia cells in vivo, suggesting the potential efficacy of JAK2 inhibitors in treating t(8;21) AML. Wild-type or AE9a leukemic samples in triplicate.
Project description:Human histone deacetylase 3 (HDAC3) plays an important role in gene transcription in diseased human cells, such as leukemia. The t(8;21) chromosomal translocation is one of the most commonly observed genetic abnormalities associated with acute myeloid leukemia. This translocation generates the AML1-ETO fusion protein between the wild-type RUNX1 transcription factor and wild-type ETO transcriptional corepressor. To better understand the role of HDAC3 in t(8;21) leukemogenesis, the human HDAC3-containing complexes were isolated from stably-transfected HeLa cells by using anti-FLAG immunoprecipitation. The resulting complexes were resolved in SDS-PAGE. The components of the complexes were identified using LC-MS/MS. We report here that the human RUNX1 transcription is a component of the HDAC3 complexes. We demonstrate that HDAC3 and RUNX1 collaboratively repress AML1-ETO-mediated transcription. These results reveal new insight into how AML1-ETO, RUNX1, and HDAC3 crosstalk to deregulate gene transcription in t(8;21) leukemia cells.
Project description:Transcription profiling by array of wild type and p300 KIX/KIX; CBP +/KIX primary mouse embryonic fibroblasts (MEFs) transduced with either MSCV-c-Myb_IRES-GFP or MSCV-IRES-GFP retrovirus to determine the effect of mutating the KIX domain of CBP and p300 on c-Myb regulated gene expression. CBP KIX mutation (MGI:3578129) and p300 KIX mutation (MGI:3578128).
Project description:The clustered homeobox proteins play crucial roles in development, hematopoiesis and leukemia yet the targets they regulate and their mechanisms of action are poorly understood. Here, we identified the binding sites for Hoxa9 and the Hox cofactor Meis1 on a genome-wide level and profiled their associated epigenetic modifications and transcriptional targets. Hoxa9 and the Hox cofactor Meis1 co-bind at hundreds of highly evolutionarily-conserved sites, most of which are distant from transcription start sites. These sites show high levels of histone H3K4 monomethylation and CBP/P300 binding characteristic of enhancers. Furthermore, a subset of these sites shows enhancer activity in transient transfection assays. Many Hoxa9 and Meis1 binding sites are also bound by PU.1 and other lineage-restricted transcription factors previously implicated in establishment of myeloid enhancers. Conditional Hoxa9 activation is associated with CBP/P300 recruitment, histone acetylation and transcriptional activation of a network of proto-oncogenes including Erg, Flt3, Lmo2, Myb and Sox4. Collectively this work suggests that Hoxa9 regulates transcription by interacting with enhancers of genes important for hematopoiesis and leukemia. To identify the genome-wide binding sites for Hoxa9 and the Hox cofactor Meis1
Project description:Chromatin organization is a highly orchestrated process that influences gene expression, in part by modulating access of regulatory factors to DNA and nucleosomes. We found that the chromatin accessibility regulator HMGN1, a target of recurrent DNA copy gains in leukemia, controls myeloid differentiation. HMGN1 amplification was associated with increased accessibility, expression, and histone H3K27 acetylation of loci important for hematopoietic stem cell (HSC) function and AML, such as HoxA cluster genes. In vivo, HMGN1 overexpression was linked to decreased quiescence and increased HSC activity in bone marrow transplantation. HMGN1 overexpression also cooperated with the AML-ETO9a fusion oncoprotein to impair myeloid differentiation and enhance leukemia stem cell (LSC) activity. Inhibition of histone acetyltransferases CBP/p300 relieved the HMGN1-associated differentiation block. These data nominate factors that modulate chromatin accessibility as regulators of HSCs and LSCs and suggest that targeting HMGN1 or its downstream effects on histone acetylation could be therapeutically active in AML.
Project description:AML1-ETO, a fusion protein generated by the t(8;21) translocation in acute myeloid leukemia, is a transcription factor implicated in both gene repression and activation. We now show that, in leukemic cells, AML1-ETO resides in and functions through a stable protein complex (AETFC) that contains several hematopoietic transcription factors and cofactors. In conjunction with biochemical and leukemia pathological studies, the ChIP-seq and RNA-seq analyses of the AETFC components in leukemic cells reveal that these components stabilize the complex through multivalent interactions, provide multiple DNA-binding domains for diverse target genes, colocalize genome-wide, cooperatively regulate gene expression, and contribute to leukemogenesis. RNA-seq analyses gene expression upon knockdown of each AETFC component, including AML1-ETO, HEB, E2A, LYL1, LDB1 and LMO2, and double-knockdown of HEB and E2A, in Kasumi-1 cells. ChIP-seq analyses of four AETFC components, namely AML1-ETO, HEB, E2A and LMO2, in Kasumi-1 cells.