MiRNAs differentially expressed in MLL-AF9-transduced versus HOXA9/MEIS1-transduced LSK cells
ABSTRACT: HOXA9 and MEIS1 are essential downstream effectors of the MLL-AF9 oncoprotein during leukemia induction. Leukemia derived from MLL-AF9-transduced LSK cells has a more aggressive phenotype than that derived from HOXA9/MEIS1-transduced LSK cells. To determine differential miRNA expression that contributes to increased aggressiveness in MLL-AF9-induced leukemia, miRCURY LNA microRNA Array was performed on LSK cells transduced with MLL-AF9 versus HOXA/MEIS1 oncogenes.
Project description:HOXA9 and MEIS1 are essential downstream effectors of the MLL-AF9 oncoprotein during leukaemia induction. Leukaemia derived from MLL-AF9-transduced LSK cells has a more aggressive phenotype than that derived from HOXA9/MEIS1-transduced LSK cells. To determine differential gene expression that contributes to increased aggressiveness in MLL-AF9-induced leukaemia, microarray was performed on LSK cells transduced with MLL-AF9 versus HOXA/MEIS1 oncogenes.
Project description:To investigate whether co-expression of PBX3/MEIS1 can mimic that of MLL-AF9, HOXA9/MEIS1 or HOXA9/PBX3 in inducing leukemogenesis, we conducted in vivo mouse bone marrow transplantation (BMT) assays. Briefly, normal mouse bone marrow (BM) progenitor (i.e., lineage negative; Lin-) cells collected from B6.SJL (CD45.1) donor mice (CD45.1) were retrovirally co-transduced with MSCVneo-MLL-AF9+MSCV-PIG (MLL-AF9), MSCVneo-HOXA9+MSCV-PIG (HOXA9), MSCVneo-HOXA9+MSCV-PIG-MEIS1 (HOXA9+MEIS1), MSCVneo-HOXA9+MSCV-PIG-PBX3 (HOXA9+PBX3), MSCV-PIG-PBX3+MSCVneo-MEIS1 (PBX3+MEIS1), MSCVneo+MSCV-PIG-PBX3 (PBX3) , MSCVneo+MSCV-PIG-MEIS1 (MEIS1), or MSCVneo+MSCV-PIG (normal control; NC). Retrovirally transduced cells then were cultured with cytokines as well as puromycin and G418. Seven days later, the donor cells were transplanted into lethally irradiated (960 rads) 8- to 10-week-old C57BL/6 (CD45.2) recipient mice. The transplanted mice were watched for leukemogenesis. Then, gene expression profiling was conducted with bone marrow samples collected from leukemia groups and control group. Overall design: A total of 20 mouse BM samples including 15 mouse AML samples with 3 each of the MLL-AF9, HOXA9+MEIS1, HOXA9+PBX3, HOXA9, and PBX3+MEIS1 groups, along with 5 samples from the normal control (NC) group, were analyzed by use of Affymetrix GeneChip Mouse Gene 2.0 ST Array (Affymetirx, Santa Clara, CA). For each sample, the CD45.1+ cells (i.e., transplanted donor cells) were sorted with flow cytometry from whole BM cells collected from BMT recipient mice at the end stage. Then total RNA was isolated by use of miRNeasy extraction kit (Qiagen, Valencia, CA).
Project description:Leukemias with MLL-rearrangements are characterized by high expression of the homeo box gene MEIS1. In these studies, we knocked down Meis1 expression by shRNA lentivirus transduction in murine Mll-AF9 leukemia cells. Meis1 knockdown resulted in decreased proliferation and survival of murine Mll-AF9 leukemia cells. We also observed reduced clonogenic capacity and increased monocytic differentiation. The establishment of leukemia in transplant recipients was significantly delayed by Meis1 knockdown. Gene expression profiling of cells transduced with Meis1 shRNA showed reduced expression of genes associated with cell cycle entry and progression. shRNA mediated knockdown of MEIS1 in human MLL-fusion gene leukemia cell lines resulted in reduced cell growth. These results show that MEIS1 expression is important for MLL-rearranged leukemias and suggest that MEIS1 promotes cell cycle entry. Targeting MEIS1 may have therapeutic potential for treating leukemias expressing this transcription factor. Keywords: Gene expression Overall design: Murine Mll-AF9 leukemia (4166) cells were transduced with lentivirus expressing shRNA against Meis1 or control lentivirus (empty vector). Gene expression profiles were compared at 48 hours post transduction, using Puromycin as selection agent for transduced cells.
Project description:miR-101 has been reported as a tumor suppressor in several types of cancer. However, its role in AML is still unknown. In this study, we restored the expression of miR-101 in MLL-AF9 transduced LSK cells by introducing a retroviral miR-101 expression vector. To identify miR-101-regulated gene expression, we performed genome-wide gene expression analysis on GFP+ MLL-AF9-transduced LSK cells overexpressing miR-101 versus control vector. Our gene expression analysis and subsequent functional studies demonstrate that enforced expression of miR-101 has antitumor effects on the development of MLL-rearranged AML. Each group has 3 samples.
Project description:These data include the genome wide occupancy of H2AUbq by ChIP sequencing in Cdkn2a-/- Lin- HSC cells non-transduced or transduced with MLL-AF9, HOXA9 and PML-RARa. Immuno-precipitation of formaldehyde cross-linked chromatin prepared from Cdkn2a-/- Lin- HSC cells non-transduced or transduced with MLL-AF9, HOXA9 and PML-RARa using H2AK119Ubq antibody.
Project description:These data include RNA Seq data generated from Ring1b wild type and Ring1b KO Ring1a-/- Cdkn2a-/- Lin- HSC cells non-transduced or transduced with MLL-AF9, HOXA9 and PML-RARa. Total RNA extracted from Ring1b wild type and Ring1b KO Ring1a-/- Cdkn2a-/- Lin- HSC cells non-transduced or transduced with MLL-AF9, HOXA9 and PML-RARa.
Project description:MLL-fusions are potent oncogenes that initiate aggressive forms of acute leukemia. As aberrant transcriptional regulators, MLL-fusion proteins alter gene expression in hematopoietic cells through interactions with the histone H3 lysine 79 (H3K79) methyltransferase DOT1L. Notably, interference with MLL-fusion cofactors like DOT1L is an emerging therapeutic strategy in this disease. Here we identify the histone H2B E3 ubiquitin ligase RNF20 as an additional requirement for MLL-fusion-mediated leukemogenesis. Suppressing the expression of Rnf20 in diverse models of MLL-rearranged leukemia leads to inhibition of cell proliferation; under tissue culture conditions as well as in vivo. Rnf20 knockdown leads to reduced expression of MLL-fusion target genes, including Hoxa9 and Meis1; effects that resemble Dot1l-inhibition. Using ChIP-seq, we found that H2B ubiquitination (H2Bub) is enriched in the body of MLL-fusion target genes, correlating with sites of H3K79 methylation and transcription elongation. Furthermore, we found that Rnf20 is required to maintain local levels of H3K79 di-methylation by Dot1l at Hoxa9 and Meis1. These findings support a model whereby co-transcriptional recruitment of Rnf20 at MLL-fusion target genes leads to amplification of Dot1l-mediated H3K79 methylation, thereby rendering leukemia cells dependent on Rnf20 to maintain their oncogenic transcriptional program. Examination of gene expression profiles upon RNF20 RNAi in MLL-AF9 acute myeloid leukemia cells
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. Overall design: We GFP-sorted MLL-AF9 transformed cells transduced with pMIG or pMIG-TGIF1
Project description:The transcription factor Meis1 drives myeloid leukemogenesis in the context of Hox gene overexpression but is currently considered undruggable. We therefore investigated whether myeloid progenitor cells transformed by Hoxa9 and Meis1 become addicted to targetable signaling pathways. A comprehensive (phospho)proteomic analysis revealed that Meis1 increased Syk protein expression and activity. Syk upregulation occurs through a Meis1-dependent feed-forward loop. By dissecting this loop, we show that Syk is a direct target of miR-146a, whose expression is indirectly regulated by Meis1 through the transcription factor PU.1. In the context of Hoxa9 overexpression, Syk induces Meis1, recapitulating several leukemogenic features of Hoxa9/Meis1-driven leukemia. Finally, we show that Syk inhibition disrupts the identified regulatory loop, prolonging survival of mice with Hoxa9/Meis1-driven leukemia.
Project description:Aberrant Hox gene activation is a recurrent feature in several different types of human leukemia, including leukemias with rearrangements of the mixed lineage leukemia (MLL) gene. In this study, we demonstrate that Hox gene expression is controlled by higher degree H3K79 methylation in acute myeloid leukemia (AML). We show that the deposition of progressive H3K79 methylation states at the genomic loci of critical Hox genes is dependent on the interaction of the H3K79 methyltransferase Dot1l with Af10, a protein that is found in the Dot1l complex isolated from diverse cell types. Furthermore, abrogation of the Dot1l-Af10 interaction reverses aberrant epigenetic profiles found in the leukemia epigenome and impairs the transforming ability of mechanistically distinct AML oncogenes. Primary MLL-AF9 leukemias in the AF10 floxed background (homozygous) were transduced with MSCV-IRES-tdTomato (MIT) or the Cre recombinase expressing MIT vector, cells were sorted and injected into secondary recipient mice to generate Af10 floxed (MIT) or deleted (CRE) leukemias. BM cells fresly harvested from these leukemias were sorted for tdTomato expression and used for microarrays. BM cells from Hoxa9-Meis1 transduced primary leukemias were used for comparison.