Project description:This SuperSeries is composed of the following subset Series: GSE30745: Expression data from murine acute myeloid leukemia (AML) cells following shRNA-mediated suppression of Myb GSE30746: Expression data from murine Tet-off MLL-AF9/Ras acute myeloid leukemia cell lines following withdrawal of MLL-AF9 Refer to individual Series
Project description:Using an integrative approach combining a Tet-off conditional AML mouse model, global expression profiling following suppression of the driving MLL-AF9 oncogene, and a new Tet-on conditional shRNA expression system we have identified Myb as critical mediator of addiction to MLL-AF9. Suppression of Myb in established AML in vivo terminates aberrant self-renewal and triggers a terminal myeloid differentiation program that precisely phenocopies the effects of suppressing MLL-AF9. Remarkably, suppressing Myb effectively eradicates aggressive and chemotherapy resistant AML. To further investigate Myb dependent transcriptional programs involved in mediating aberrant self-renewal in leukemia, we globally surveyed gene expression changes following acute shRNA-induced suppression of Myb in an established Tet-on competent model of MLL-AF9;NrasG12D-induced AML. To enable regulatable suppression of Myb in AML, we retrovirally transduced established Tet-on competent MLL-AF9;NrasG12D induced AML cells with TRMPV-Neo vectors (Zuber et al., Nature Biotech, 2010) harboring shRNAs targeting Myb (shMyb.2572 and shMyb.2652), a control shRNA targeting Renilla Luciferase (shRen.713), or an empty miR30 cassette of the recipient cloning vector (Rec). Following drug selection, shRNA expression was induced by doxycycline treatment and total RNA was isolated from sorted shRNA expressing (Venus+/dsRed+) leukemia cells after 3 days of dox treatment, and subjected to Affymetrix microarray expression analysis. Expression profiles following expression of two independent Myb shRNAs were compared to those observed after induction in shRen.713- and Rec-expressing control samples (each in 3 biological replicates).
Project description:Using an integrative approach combining a Tet-off conditional AML mouse model, global expression profiling following suppression of the driving MLL-AF9 oncogene, and a new Tet-on conditional shRNA expression system we have identified Myb as critical mediator of addiction to MLL-AF9. Suppression of Myb in established AML in vivo terminates aberrant self-renewal and triggers a terminal myeloid differentiation program that precisely phenocopies the effects of suppressing MLL-AF9. Remarkably, suppressing Myb effectively eradicates aggressive and chemotherapy resistant AML. To further investigate Myb dependent transcriptional programs involved in mediating aberrant self-renewal in leukemia, we globally surveyed gene expression changes following acute shRNA-induced suppression of Myb in an established Tet-on competent model of MLL-AF9;NrasG12D-induced AML.
Project description:Dysregulated gene expression is one of the most prevalent features in human cancers. Here, we show that most subtypes of acute myeloid leukemia (AML) depend on the aberrant assembly of the MYB transcriptional co-activator complex. By rapid and selective peptidomimetic interference with the binding of CBP/P300 to MYB, but not CREB or MLL1, we find that the leukemic functions of MYB are mediated by CBP/P300-mediated co-activation of a distinct set of transcriptional factor complexes that are aberrantly assembled with MYB in AML cells. This therapeutic remodeling is accompanied by dynamic redistribution of CBP/P300 complexes to genes that control cellular differentiation and growth. Thus, aberrantly organized transcription factor complexes control convergent gene expression programs in AML cells. These findings establish a compelling strategy for pharmacologic reprogramming of oncogenic gene expression that supports its targeting for leukemias and other human cancers caused by dysregulated gene control.
Project description:MLL-rearrangements (MLL-r) are recurrent genetic events in acute myeloid leukemia (AML) and frequently associate with poor prognosis. In infants, MLL-r have been suggested to be sufficient to drive transformation. However, despite the prenatal origin of MLL-r, the incidence of congenital leukemia is very low with transformation usually occurring postnatally. The influence of prenatal signals on leukemogenesis, such as those mediated by the fetal-specific RNA binding protein LIN28B, remains controversial. Here, using a dual-transgenic mouse model that co-express MLL-ENL and LIN28B, we investigated the impact of LIN28B on AML. We show that LIN28B impedes the progression of MLL-r AML through a compromised leukemia initiating cell activity and a suppression of MYB signaling. Mechanistically, rather than involving the well-studied Lin28B-let7 miR axis, we found that LIN28B directly bound MYBBP1A mRNA, a co-repressor of MYB, and that positively correlated with MYBBP1A protein levels. Overexpression of MYBBP1A in MLL-ENL driven leukemogenesis largely phenocopied the tumor suppressor effects of LIN28B. Thereby, our work proposes that the developmentally-restricted expression of LIN28B during fetal development provides a protection against MYB-dependent AML.
Project description:Hierarchical maintenance of MLL myeloid leukemia stem cells employs a transcriptional program shared with embryonic rather than adult stem cells; The genetic programs that promote retention of self-renewing leukemia stem cells (LSCs) at the apex of cellular hierarchies in acute myeloid leukemia (AML) are not known. In a mouse model of human AML, LSCs exhibit variable frequencies that correlate with the initiating MLL oncogene and are maintained in a self-renewing state by a transcriptional sub-program more akin to that of embryonic stem cells (ESCs) than adult stem cells. The transcription/chromatin regulatory factors Myb, Hmgb3 and Cbx5 are critical components of the program and suffice for Hoxa/Meis-independent immortalization of myeloid progenitors when co-expressed, establishing the cooperative and essential role of an ESC-like LSC maintenance program ancillary to the leukemia initiating MLL/Hox/Meis program. Enriched expression of LSC maintenance and ESC-like program genes in normal myeloid progenitors and poor prognosis human malignancies links the frequency of aberrantly self-renewing progenitor-like cancer stem cells to prognosis in human cancer. Experiment Overall Design: Refer to individual Series Experiment Overall Design: This SuperSeries is composed of the following subset Series: Experiment Overall Design: GSE13690: Gene expression profiling of murine MLL leukemias (whole BM) Experiment Overall Design: GSE13692: Expression profiling of MLL-AF10 myeloid leukemia cellular subsets Experiment Overall Design: GSE13693: Gene expression profiling of normal mouse myeloid cell populations
Project description:Recurring chromosomal translocation t(10;17)(p15;q21) present in a subset of human acute myeloid leukemia (AML) patients creates an aberrant fusion gene termed ZMYND11-MBTD1 (ZM); however, its function remains undetermined. Here, we show that ZM confers primary murine hematopoietic stem/progenitor cells indefinite self-renewal capability ex vivo and causes AML in vivo. Genomics profilings reveal that ZM directly binds to and maintains high expression of pro-leukemic genes including Hoxa, Meis1, Myb, Myc and Sox4. Mechanistically, ZM recruits NuA4/Tip60 histone acetyltransferase complex to cis-regulatory elements, sustaining an active chromatin state enriched in histone acetylation and devoid of repressive histone marks. Systematic mutagenesis of ZM demonstrates essential requirements of Tip60 interaction and an H3K36me3-binding PWWP domain for oncogenesis. Inhibitor of histone acetylation-‘reading’ bromodomain proteins, which act downstream of ZM, is efficacious in treating ZM-induced AML. Collectively, this study demonstrates AML-causing effects of ZM, examines its gene-regulatory roles, and reports an attractive mechanism-guided therapeutic strategy.
Project description:Deregulation of transcription factor MYB contributes to the development of leukemia and other human cancers, making MYB an attractive target for drug development. We demonstrate that the natural sesquiterpene lactone (STL) 4,15-iso-atriplicolide tiglate (AT) is a novel potent inhibitor of MYB-dependent transcription. Further analysis revealed that C/EBPb, a transcription factor cooperating with MYB in myeloid cells, rather than MYB itself is inhibited by AT and related STLs. We show that these compounds induce apoptosis and differentiation in human acute myeloid leukemia (AML) cell lines and that ectopic expression of C/EBPbor of an activated version of MYB counteract these effects. Furthermore, gene expression profiling shows that AT as well as helenalin acetate, a compound previously shown to inhibit C/EBPb, affect the expression of a significant number of MYB-regulated genes although neither of these compounds targets MYB directly. Taken together these results suggest that C/EBPbp lays a key role in AML cells by cooperating with MYB and supporting its activity. Finally, we show that AT inhibits primary murine and human AML patient cells in colony formation assays significantly stronger than normal hematopoietic progenitor cells. In summary, our work identifies several related STLs as novel potential drugs targeting AML and highlights a novel role of C/EBPbas a pro-leukemogenic factor in AML cells. We hypothesize that MYB and C/EBPbact together in a transcriptional module to maintain an undifferentiated state of AML cells and that targeting of this module via MYB or C/EBPbmay have therapeutic potential against AML.
Project description:The transcription factor MYB plays a pivotal role in haematopoietic homeostasis and its aberrant expression is involved in the genesis and maintenance of acute myeloid leukaemia (AML). Our previous work on CEBPA mutants has demonstrated that not all AML types display the same dependency on MYB expression, rather this depends on the nature of the driving mutations. However, whether this difference in MYB expression dependency is a general trend in AML still remains to be further elucidated. In this study, we investigate the importance of MYB in human leukaemia by performing siRNA-mediated knock-down in cell lines modelling AML driven by different genetic lesions. We show that the reduction in proliferation and the concomitant induction of myeloid commitment observed in MLL-driven leukaemia upon suppression of MYB expression is not seen in AML cells with a complex karyotype. By performing transcriptome analysis, we demonstrate that reduction of MYB in the cell line that responds to its manipulation leads to a strong activation of MAFB expression. Correlating with these observations, stratification of publicly available patient data reveals a reciprocal relationship between the expression of MYB and MAFB, highlighting a novel connection between those two factors in such AML.
Project description:Primary leukemia stem cells (LSCs) reside in an in vivo microenvironment that supports the growth and survival of malignant cells. We used an in vivo short hairpin RNA (shRNA) screening approach to identify novel genes that are essential for primary murine MLL-AF9 acute myeloid leukemia (AML). We found that Integrin Beta 3 (Itgb3) is selectively essential for murine leukemia cells in vivo, and for human leukemia cells in xenotransplantation studies. In leukemia cells, Itgb3 knockdown impaired homing, downregulated LSC transcriptional programs, and induced differentiation. In contrast, loss of Itgb3 in normal HSPCs did not affect engraftment, reconstitution, or differentiation in long term transplantation assays. We explored the signaling pathways downstream of Itgb3 using an additional in vivo shRNA screen and identified Syk as a critical mediator of Itgb3 activity in leukemia. Finally, we confirmed that Itgb3 is dispensable for normal hematopoiesis and required for leukemogenesis using the Itgb3 knockout mouse model. Our results establish the significance of the Itgb3 signaling pathway as a potential therapeutic target in AML, and demonstrate the utility of in vivo RNA interference screens. We examined the effect of Itgb3 knockdown by gene expression profiling in primary leukemia cells.