Project description:Chromosomal translocations of the mixed-lineage leukemia (MLL) gene with various partner genes result in aggressive leukemia with dismal outcomes. Despite similar expression at the mRNA level from the wild-type and chimeric MLL alleles, the chimeric protein is more stable. We report that UBE2O functions in regulating the stability of wild-type MLL in response to interleukin-1 signaling. Targeting wild-type MLL degradation impedes MLL leukemia cell proliferation, and it downregulates a specific group of target genes of the MLL chimeras and their oncogenic cofactor, the super elongation complex. Pharmacologically inhibiting this pathway substantially delays progression, and it improves survival of murine leukemia through stabilizing wild-type MLL protein, which displaces the MLL chimera from some of its target genes and, therefore, relieves the cellular oncogenic addiction to MLL chimeras. Stabilization of MLL provides us with a paradigm in the development of therapies for aggressive MLL leukemia and perhaps for other cancers caused by translocations.
Project description:TET1, the founding member of the TET family of enzymes (TET1/2/3) that convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), was first identified as a partner gene in MLL-rearranged leukemia, but its definitive pathological role in leukemia is unclear. The down-regulation of all three TET genes and loss-of-function mutations of TET2 have been frequently observed in various cancers, and it was thought that they all play tumor-suppressor roles in tumorigenesis. Here we show that TET1 is likely a direct target of MLL and significantly up-regulated in MLL-rearranged leukemia, associated with an increased level of 5hmC. Our further in vitro and in vivo studies demonstrate that Tet1 plays an indispensable oncogenic role in MLL-rearranged leukemia, through cooperating with MLL fusion proteins in regulating their co-targets including the Hoxa/Meis1/Pbx3/Flt3 genes. Our data delineate a MLL-fusion/Tet1/Hoxa/Meis1/Pbx3/Flt3 signaling axis in MLL-rearranged leukemia, and highlight TET1 as a potential therapeutic target in treating this presently therapy-resistant disease. We report genome-wide 5hmC enrichment profiles and RNA-Seq gene expression in MLL-AF9 transformed and control mouse bone marrow mononuclear cells. These 5hmC profiles are derived from selctive chemical labeling and enrichment of 5hmC containing genomic DNA fragments, while the RNA-Seq expression profiles are generated from polyA enriched RNA
Project description:Leukemias that harbor translocations involving the mixed lineage leukemia gene (MLL) possess unique biological characteristics and often have an unfavorable prognosis. Gene expression analyses demonstrate a distinct profile for MLL-rearranged leukemias with consistent high-level expression of select Homeobox genes including HOXA9. Here, we investigated the effects of HOXA9 suppression in MLL-rearranged and MLL-germline leukemias utilizing RNAi. Gene expression profiling after HOXA9 suppression demonstrated co-downregulation of a program highly expressed in human MLL-AML (this study) and murine MLL-leukemia (Krivtsov et al. 2006) stem cells including HOXA10, MEIS1, PBX3 and MEF2C. Our data indicates an important role for HOXA9 in human MLL-rearranged leukemias, and suggests targeting HOXA9 or downstream programs may be a novel therapeutic option. Experiment Overall Design: RNA was purified from t(9;11) MOLM-14 AML cells 44h after transduction in triplicates with 2 of the two most effective HOXA9shRNA constructs (3 x 1F3-HOXA9shRNA; 3 x 2A5-HOXA9shRNA) or GFP-controlshRNA (6x).
Project description:Leukemias that harbor translocations involving the mixed lineage leukemia gene (MLL) possess unique biological characteristics and often have an unfavorable prognosis. Gene expression analyses demonstrate a distinct profile for MLL-rearranged leukemias with consistent high-level expression of select Homeobox genes including HOXA9. Here, we investigated the effects of HOXA9 suppression in MLL-rearranged and MLL-germline leukemias utilizing RNAi. Gene expression profiling after HOXA9 suppression demonstrated co-downregulation of a program highly expressed in human MLL-AML (this study) and murine MLL-leukemia (Krivtsov et al. 2006) stem cells including HOXA10, MEIS1, PBX3 and MEF2C. Our data indicates an important role for HOXA9 in human MLL-rearranged leukemias, and suggests targeting HOXA9 or downstream programs may be a novel therapeutic option.
Project description:TET1, the founding member of the TET family of enzymes (TET1/2/3) that convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), was first identified as a partner gene in MLL-rearranged leukemia, but its definitive pathological role in leukemia is unclear. The down-regulation of all three TET genes and loss-of-function mutations of TET2 have been frequently observed in various cancers, and it was thought that they all play tumor-suppressor roles in tumorigenesis. Here we show that TET1 is likely a direct target of MLL and significantly up-regulated in MLL-rearranged leukemia, associated with an increased level of 5hmC. Our further in vitro and in vivo studies demonstrate that Tet1 plays an indispensable oncogenic role in MLL-rearranged leukemia, through cooperating with MLL fusion proteins in regulating their co-targets including the Hoxa/Meis1/Pbx3/Flt3 genes. Our data delineate a MLL-fusion/Tet1/Hoxa/Meis1/Pbx3/Flt3 signaling axis in MLL-rearranged leukemia, and highlight TET1 as a potential therapeutic target in treating this presently therapy-resistant disease.
Project description:MLL-rearranged acute myeloid leukemia (AML) remains a fatal disease with a high rate of relapse and therapeutic failure due to chemotherapy resistance. In analysis of our Affymetrix microarray profiling of human AML and normal control samples, we found that ALOX5 is especially down-regulated in MLL-rearranged AML. Our colony forming/replating and bone marrow transplantation (BMT) assays showed that Alox5 exhibited a moderate anti-tumor effect both in vitro and in vivo. Strikingly, leukemic cells with Alox5 overexpression showed a significantly higher sensitivity to the standard chemotherapeutic agents, i.e., doxorubicin (DOX) and cytarabine (Ara-C). The drug-sensitizing role of Alox5 was further confirmed in human and murine MLL-rearranged AML cell models in vitro, as well as in the in vivo MLL-rearranged AML BMT model coupled with treatment of “5+3” (i.e. DOX plus Ara-C) regimen. Our RNA-seq analysis showed that Stat and K-Ras signaling pathways were negatively correlated with Alox5 overexpression in MLL-AF9-leukemic blast cells, implying targeting those pathways likely contributes to Alox5’s functions. Collectively, our work shows that ALOX5 plays a moderate anti-tumor role and functions as a drug sensitizer, with a therapeutic potential, in MLL-rearranged AML.
Project description:WIN Site inhibitors bind the WIN Site of WDR5 resulting in decreased transcription of WDR5 target genes, many of which encode components of the protein synthesis machinery. In this study, we determined proteome alterations in an MLL-rearranged leukemia cell line treated for either 24 or 72 hours with a WIN Site inhibitor. The data from these studies, along with Ribo-Seq, RNA-Seq, and CRISPR screen experiments, guided us in assembling a collection of compounds that, when combined with WIN Site inhibitor, synergistically inhibit growth of MLL-rearranged leukemia cells.
Project description:Infant and adult MLL-rearranged (MLLr) leukemia represents a disease with few treatment options and a dismal prognosis. Here, we present an in-depth proteomic characterization of in utero-initiated and adult-onset MLLr leukemia in a mouse model of MLL-ENL-mediated leukemogenesis. We characterize early proteomic events of MLL-ENL-mediated transformation in fetal and adult progenitors.
Project description:In this study, we identify MBNL1 as a unique molecular vulnerability across MLL-rearranged leukemias. Through transcriptomic profiling and novel splicing analyses of MLL-rearranged leukemia cell lines following shRNA knockdown of MBNL1, we show that MBNL1 regulates alternative splicing (predominantly intron retention) of genes essential to MLL-rearranged leukemogenesis, such as DOT1L and SETD1A.