MLL Fusion Protein Driven AML Is Selectively Inhibited by Targeted Disruption of the MLL-PAFc Interaction

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 56-56 ◽  
Author(s):  
Andrew G. Muntean ◽  
Eric M Granowicz ◽  
Jay L. Hess
Keyword(s):  
Fusion Protein ◽  
Colony Formation ◽  
Fusion Proteins ◽  
Target Genes ◽  
Hox Genes ◽  
Conflicts Of Interest ◽  
Dominant Negative ◽  
Conditional Knockout ◽  
Transformed Cells ◽  
Mouse Bone Marrow

Abstract Abstract 56 Balanced chromosomal translocations of the MLL gene located on chromosome 11q23 result in the expression of a chimeric fusion proteins with enhanced transcriptional activity. The HOX genes and their co-factors, such as MEIS1 and PBX2, are critical downstream targets of MLL fusion proteins and essential for transformation. Previously we showed MLL fusion proteins are critically dependent on a direct interaction with the RNA Pol II Associated Factor complex (PAFc). PAFc is a protein complex important for the initiation, elongation and termination of transcription. It is also necessary for histone H2B K120 mono-ubiquitination through the direct recruitment of the BRE1/RAD6 E3 ubiquitin ligase complex. MLL fusion proteins make two direct contacts with the PAF1 and CTR9 subunits of the PAFc that are crucial for MLL fusion protein mediated transformation. Deletion of regions of MLL that interact with PAFc abrogates AML in mouse bone marrow transplantation assays. Here we tested the general requirement for PAFc in AML using a conditional knockout mouse model of one component of PAFc, Cdc73. These studies show that PAFc is necessary for growth of both E2A-HLF and MLL-AF9 transformed cells. Excision of Cdc73 leads to decreased expression of the MLL target genes Hoxa9 and Meis1, decreased colony formation and decreased proliferation of leukemic blasts and ultimately apoptosis. We then performed chromatin immunoprecipitation assays to assess the binding of PAFc and MLL to target loci with and without Cdc73. Excision of Cdc73 leads to a rapid decrease in association of PAFc as well as MLL fusion proteins and wild type MLL at target loci confirming that proper targeting of MLL fusion proteins requires PAFc. A decrease in H3K4me3 and H2Bub is also observed and consistent with a role of PAFc in the deposition of these epigenetic marks. We then sought to disrupt the MLL-PAFc interaction through expression of a small 40 amino acid fragment of MLL that interacts with the PAF1 subunit of PAFc. As the MLL-PAFc interaction involves interactions between MLL and both CTR9 and PAF1, it was unknown whether targeting one interaction site would be sufficient to disrupt transformation. Indeed, expression of the short fragment encompassing the pre-CxxC region of MLL acts as a dominant negative and disrupts the MLL-PAFc interaction, significantly decreasing Hox gene expression, colony formation and cell proliferation of MLL-AF9 transformed cells. Importantly, expression of the MLL fragment selectively inhibited MLL fusion mediated leukemic transformation and cell growth while the growth and proliferation of E2A-HLF cells is unaffected. Together these data show that targeting the MLL-PAFc interaction with a small MLL fragment can act as a dominant negative and selectively inhibit the growth of AML cells transformed with MLL fusion proteins. These data also suggest the MLL-PAF1 interaction surface is a promising region for therapeutic targeting. Disclosures: No relevant conflicts of interest to declare.

Interaction of MLL Amino Terminal Sequences with Menin Is Required for Transformation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 664-664
Author(s):  
Jay L. Hess ◽  
Zhaohai Yang ◽  
Haoren Wang ◽  
Ya-Xiong Chen ◽  
Thomas A. Milne ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Rna Polymerase Ii ◽  
Fusion Proteins ◽  
Target Genes ◽  
Hox Genes ◽  
Dominant Negative ◽  
Similar Distribution ◽  
Genetic Ablation ◽  
Amino Terminal ◽  
Coding Regions

Abstract Rearrangements of the mixed lineage leukemia gene MLL are associated with aggressive lymphoid and myeloid leukemias. The resulting MLL fusion proteins enforce high-level expression of HOX genes including HOX A7 and HOX A9 and the HOX cofactor MEIS1, which is pivotal for leukemogenesis. The mechanism by which this occurs and the relationship to normal MLL function is unknown. MLL and MLL fusion proteins bind with a similar distribution in hematopoietic cells at both promoters and coding sequences of target genes. Our studies suggest that a major mechanism of regulating MLL, which is expressed throughout hematopoiesis, is through modulating it’s binding to target promoters. MLL binds directly to the promoters and coding regions of HOX A7, HOX A9, and MEIS1 only in myeloblasts and not in neutrophils, indicating MLL is physically associated with genes only when they are actively transcribed. Expression of A cluster HOX loci and MEIS1 remains persistently elevated when MLL-ENL or dimerized MLL fusion proteins are expressed. Expression of either fusion protein is associated with increased binding of wild type MLL accompanied by increases in histone acetylation and histone H3 lysine 4, marks that are normally almost completely erased during myeloid differentiation. In addition MLL-ENL induces increased lysine 79 methylation. Both MLL and MLL fusion proteins interact with the tumor suppressor menin via sequences in the extreme amino terminus of MLL. In addition both proteins physically interact with RNA polymerase II, which shows abnormal pausing in the coding regions of HOX genes in Mll null cells. Genetic ablation of menin or expression of a dominant negative inhibitor of the MLL-menin interaction inhibits the growth of MLL fusion protein transformed cells. These findings suggest MLL fusion proteins act in concert with menin, MLL and other coactivators to deregulate HOX gene expression pivotal for transformation.

Targeting Menin-MLL Interaction to Inhibit MLL Fusion Oncoproteins in Leukemia

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2497-2497
Author(s):  
Jolanta Grembecka ◽  
Shihan He ◽  
Aibin Shi ◽  
Trupta Purohit ◽  
Andrew G. Muntean ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Acute Leukemia ◽  
Protein Interaction ◽  
Fusion Proteins ◽  
Target Genes ◽  
Hox Genes ◽  
Conflicts Of Interest ◽  
Acute Leukemias ◽  
In Vivo Models ◽  
Novel Therapeutic

Abstract Abstract 2497 Chromosomal translocations that affect the MLL (Mixed Lineage Leukemia) proto-oncogene occur in aggressive acute leukemias, both in children and adults. Fusion of MLL to one of more than 50 partner genes results in generation of the MLL fusion oncoprotein, which upregulates expression of HOX genes required for normal hematopoiesis, and ultimately leads to the development of acute leukemia. Patients harboring translocations of MLL gene suffer from very aggressive leukemias and respond poorly to available therapies, emphasizing the urgent need for novel therapeutic treatments. All oncogenic MLL fusion proteins have a preserved N-terminal fragment of MLL that interacts with menin, a tumor suppressor protein encoded by MEN1 (Multiple Endocrine Neoplasia 1) gene. Importantly, the menin-MLL fusion protein interaction is critical to the leukemogenic activity of MLL fusion proteins and misregulation of HOXA9 genes, and therefore it represents a valuable molecular target for therapeutic intervention. Selective targeting of the protein-protein interaction between menin and MLL fusion proteins with small molecules could block the oncogenic activity of MLL fusion proteins and inhibit development of acute leukemia. To identify small molecule inhibitors of the menin-MLL interaction we have performed a High Throughput Screen of 350,000 compounds using a collection of biochemical assays and biophysical methods. This resulted in several classes of compounds that specifically bind to menin and inhibit the menin-MLL interaction both in vitro and in human cells. We then applied medicinal chemistry approaches to develop analogues of selected lead candidates, resulting in very potent compounds that inhibit the menin-MLL interaction with nanomolar affinities. To evaluate potency, specificity and mechanism of action of these compounds we used a broad collection of cellular assays. These compounds selectively inhibit proliferation of the MLL leukemia cells, strongly induce apoptosis and differentiation of these cells. Importantly, these compounds substantially downregulate expression of HOXA9 and MEIS1 genes that are downstream targets of MLL fusion proteins required for their leukemogenicity, and they also deplete the menin-MLL fusion protein complex from the target genes. Furthermore, the compounds that we developed specifically inhibit the MLL fusion protein mediated oncogenic transformation. All these effects closely recapitulate the effects observed upon acute loss of menin or disruption of the menin-MLL fusion protein interaction using genetic manipulations, demonstrating highly specific mode of action for these compounds. Our current efforts are focused to assess the effect of these compounds in in vivo models of MLL leukemia and evaluate their utility as future drug candidates for acute leukemias. This may provide a novel therapeutic approach for the treatment of very aggressive leukemias with MLL translocations. Disclosures: No relevant conflicts of interest to declare.

The PAF Complex Synergizes with MLL Fusion Proteins at .Hox Loci to Promote Leukemogenesis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1277-1277 ◽  
Author(s):  
Andrew G. Muntean ◽  
Jiaying Tan ◽  
Venkatesha Basrur ◽  
Kojo S.J. Elenitoba-Johnson ◽  
Jay Hess
Keyword(s):  
Stem Cell ◽  
Fusion Protein ◽  
Fusion Proteins ◽  
Hox Genes ◽  
Conflicts Of Interest ◽  
Embryonic Stem ◽  
Cell Phenotype ◽  
Mouse Bone Marrow ◽  
Hematopoietic Stem ◽  
Paf Complex

Abstract Abstract 1277 Poster Board I-299 Mixed lineage leukemia (MLL) is a histone H3 lysine 4 methyltransferase that is required to maintain a normal hematopoietic stem cell compartment. MLL functions to maintain expression of HOX genes as well as the HOX co-factor MEIS1, which play significant roles in regulating hematopoiesis. MLL is involved in chromosomal translocations with up to sixty different partners in both acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL). HOXA9 and MEIS1, are directly regulated by MLL fusion proteins and are crucial for MLL fusion protein mediated transformation. The deregulated expression of target genes in AML is dependent on specific protein-protein interactions and functional domains of MLL. For example, the tumor suppressor Menin bridges LEDGF to the extreme N-terminus of MLL and both of these interactions are necessary for transformation. Furthermore, a DNA methyltransferase homology region (CxxC domain) of MLL is essential for binding to non-methylated CpG islands and MLL-fusion protein oncogenesis. We have found that sequences downstream of the CxxC domain, termed the RD2 region, that interact with the Polymerase Associated Factor (PAF) complex are also required for MLL fusion protein mediated transformation. The PAF complex interacts with RNA polymerase II and is required for H2B mono-ubiquitination and subsequent histone H3K4 and H3K79 methylation. Together the PAF complex has been shown to be involved in transcriptional initiation, elongation and termination. Interaction of MLL with the PAF complex is mediated through direct contacts with two subunits: Ctr9 and PAF1. The PAF complex synergizes with MLL-AF9 to augment transcriptional activation of the Hoxa9 promoter. Furthermore, MLL fusion proteins recruit high levels of the PAF complex to the Hoxa9 promoter. Importantly, deletions of the MLL RD2 region that abolish interactions with the PAF complex eliminate MLL-AF9 mediated transformation of mouse bone marrow cells. Transcription of PAF components is dramatically downregulated during differentiation of hematopoietic cells, consistent with recent data showing a requirement for the PAF complex to maintain an embryonic stem cell phenotype. Knock down and transplantation experiments are underway to further define how the PAF complex regulates normal MLL function and cooperates with MLL fusion proteins to promote leukemogenesis. Disclosures No relevant conflicts of interest to declare.

Analysis of Hoxd-13 and Hoxd-11 misexpression in chick limb buds reveals that Hox genes affect both bone condensation and growth

Development ◽  
1997 ◽  
Vol 124 (3) ◽  
pp. 627-636 ◽  
Author(s):  
D.J. Goff ◽  
C.J. Tabin
Keyword(s):  
Growth Phase ◽  
Target Genes ◽  
Hox Genes ◽  
Bone Development ◽  
Tritiated Thymidine ◽  
Retroviral Vectors ◽  
Dominant Negative ◽  
Thymidine Uptake ◽  
Growth Promoters ◽  
Proliferative Zone

Hox genes are important regulators of limb pattern in vertebrate development. Misexpression of Hox genes in chicks using retroviral vectors provides an opportunity to analyze gain-of-function phenotypes and to assess their modes of action. Here we report the misexpression phenotype for Hoxd-13 and compare it to the misexpression phenotype of Hoxd-11. Hoxd-13 misexpression in the hindlimb results in a shortening of the long bones, including the femur, the tibia, the fibula and the tarsometatarsals. Mutations in an alanine repeat region in the N-terminus of Hoxd-13 have recently been implicated in human synpolydactyly (Muragaki, Y., Mundlos, S., Upton, J. and Olsen, B. R. (1996) Science 272, 548–551). N-terminal truncations of Hoxd-13 which lack this repeat were constructed and were found to produce a similar, although slightly milder, misexpression phenotype than the full-length Hoxd-13. The stage of bone development regulated by Hox genes has not previously been examined. The changes in bone lengths caused by Hoxd-13 misexpression are late phenotypes that first become apparent during the growth phase of the bones. Analysis of tritiated thymidine uptake by the tibia and fibula demonstrates that Hox genes can pattern the limb skeleton by regulating the rates of cell division in the proliferative zone of growing cartilage. Hoxd-11, in contrast to Hoxd-13, acts both at the initial cartilage condensation phase in the foot and during the later growth phase in the lower leg. Ectopic Hoxd-13 appears to act in a dominant negative manner in regions where it is not normally expressed. We propose a model in which all Hox genes are growth promoters, regulating the expression of the same target genes, with some Hox genes being more effective promoters of growth than other Hox genes. According to this model, the overall rate of growth in a given region is the result of the combined action of all of the Hox genes expressed in that region competing for the same target genes.

AML-1/ETO fusion protein is a dominant negative inhibitor of transcriptional repression by the promyelocytic leukemia zinc finger protein

Blood ◽  
2000 ◽  
Vol 96 (12) ◽  
pp. 3939-3947 ◽  
Author(s):  
Ari Melnick ◽  
Graeme W. Carlile ◽  
Melanie J. McConnell ◽  
Adam Polinger ◽  
Scott W. Hiebert ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Zinc Finger ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Zinc Finger Protein ◽  
Promyelocytic Leukemia ◽  
Dominant Negative ◽  
Myelogenous Leukemia ◽  
Promyelocytic Leukemia Zinc Finger ◽  
Dominant Negative Inhibitor

Abstract The AML-1/ETO fusion protein, created by the (8;21) translocation in M2-type acute myelogenous leukemia (AML), is a dominant repressive form of AML-1. This effect is due to the ability of the ETO portion of the protein to recruit co-repressors to promoters of AML-1 target genes. The t(11;17)(q21;q23)-associated acute promyelocytic leukemia creates the promyelocytic leukemia zinc finger PLZFt/RARα fusion protein and, in a similar manner, inhibits RARα target gene expression and myeloid differentiation. PLZF is expressed in hematopoietic progenitors and functions as a growth suppressor by repressing cyclin A2 and other targets. ETO is a corepressor for PLZF and potentiates transcriptional repression by linking PLZF to a histone deacetylase-containing complex. In transiently transfected cells and in a cell line derived from a patient with t(8;21) leukemia, PLZF and AML-1/ETO formed a tight complex. In transient assays, AML-1/ETO blocked transcriptional repression by PLZF, even at substoichiometric levels relative to PLZF. This effect was dependent on the presence of the ETO zinc finger domain, which recruits corepressors, and could not be rescued by overexpression of co-repressors that normally enhance PLZF repression. AML-1/ETO also excluded PLZF from the nuclear matrix and reduced its ability to bind to its cognate DNA-binding site. Finally, ETO interacted with PLZF/RARα and enhanced its ability to repress through the RARE. These data show a link in the transcriptional pathways of M2 and M3 leukemia.

Mutation In Erythroid Specific Transcription Factor KLF1 Causes Hereditary Spherocytosis In the Nan (Neonatal Anemia) Hemolytic Anemia Mouse Model

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3217-3217
Author(s):  
Robert A White ◽  
Daniel P. Heruth ◽  
Troy Hawkins ◽  
Derek Logsdon ◽  
Margaret Gibson ◽  
...  
Keyword(s):  
Amino Acid ◽  
Hemolytic Anemia ◽  
Zinc Finger ◽  
Target Genes ◽  
Zinc Finger Protein ◽  
Hereditary Spherocytosis ◽  
Competitive Inhibition ◽  
Conflicts Of Interest ◽  
Dominant Negative ◽  
Zinc Finger Domain

Abstract Abstract 3217 The zinc finger protein Erythroid Krüuppel-like factor (EKLF, KLF1) regulates definitive erythropoiesis and terminal differentiation of red blood cells. KLF1 facilitates transcription through high affinity binding to CACCC elements within its erythroid-specific target genes which include genes encoding erythrocyte membrane skeleton (EMS) proteins. Deficiencies of EMS proteins lead to the hemolytic anemia Hereditary Spherocytosis (HS). We have identified a new HS gene by studying the hemolytic anemia mouse mutant Nan (Neonatal Anemia). Here we report that a mutation, E339D, in the second zinc finger domain of KLF1 is responsible for HS in Nan mice. The causative nature of the E339D mutation was verified with an allelic test cross between Nan/+ and heterozygous Klf1+/− knockout mice. Homology modeling predicted Nan KLF1 binds CACCC elements more tightly, suggesting that Nan KLF1 is a competitive inhibitor of wild type KLF1. Competitive inhibition may help explain the apparent disconnect between the finding that Nan/+ heterozygous mice are anemic, whereas Klf1+/− heterozygous mice are normal and haplo-sufficient. This is the first direct association of a KLF1mutation with a disease in adult mammals. After examining a small population of HS patients, we also discovered one HS patient with a KLF1 mutation, which resulted in a significant amino acid substitution (T251I) in the activator/repressor domain, 28 amino acid residues upstream of the first zinc finger domain. This HS subject had no known mutations in the exons or intron/exon boundaries of EMS genes (SPTA1, SPTB, ANK1, SLC4A1) which comprise 85% of HS mutations in humans. The lack of a known genetic mutation in EMS genes leaves this patient's KLF1 mutation as the leading candidate defect. The identification of the gene causing the Nan mutation is significant because the Nan mutant has allowed discovery of a new HS gene which may also cause this disease in humans. In addition, the putative dominant/negative competitive inhibition of the Nan mutation makes the Nan mouse an excellent model system to study the function of KLF1. Disclosures: No relevant conflicts of interest to declare.

C/ebpα and Pu.1 Are Members of a Critical Regulatory Network Required for Hoxa9-Mediated Immortalization

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 650-650
Author(s):  
Cailin Collins ◽  
Jingya Wang ◽  
Joel Bronstein ◽  
Jay L. Hess
Keyword(s):  
Transcription Factor ◽  
Binding Sites ◽  
Target Genes ◽  
De Novo ◽  
Conflicts Of Interest ◽  
Epigenetic Modifications ◽  
Conditional Knockout ◽  
Motif Analysis ◽  
Myeloid Leukemias

Abstract Abstract 650 HOXA9 is a homeodomain-containing transcription factor that plays important roles in both development and hematopoiesis. Deregulation of HOXA9 occurs in a variety of acute lymphoid and myeloid leukemias and plays a key role in their pathogenesis. More than 50% of acute myeloid leukemia (AML) cases show up-regulation of HOXA9, which correlates strongly with poor prognosis. Nearly all cases of AML with mixed lineage leukemia (MLL) translocations have increased HOXA9 expression, as well as cases with mutation of the nucleophosmin gene NPM1, overexpression of CDX2, and fusions of NUP98. Despite the crucial role that HOXA9 plays in development, hematopoiesis and leukemia, its transcriptional targets and mechanisms of action are poorly understood. Previously we identified Hoxa9 and Meis1 binding sites in myeloblastic cells, profiled their epigenetic modifications, and identified the target genes regulated by Hoxa9. Hoxa9 and Meis1 co-bind at hundreds of promoter distal, highly evolutionarily conserved sites showing high levels of histone H3K4 monomethylation and CBP/p300 binding characteristic of enhancers. Hoxa9 association at these sites correlates strongly with increases in histone H3K27 acetylation and activation of downstream target genes, including many proleukemic gene loci. De novo motif analysis of Hoxa9 binding sites shows a marked enrichment of motifs for the transcription factors in the C/EBP and ETS families, and C/ebpα and the ETS transcription factor Pu.1 were found to cobind at Hoxa9-regulated enhancers. Both C/ebpα and Pu.1 are known to play critical roles in the establishment of functional enhancers during normal myeloid development and are mutated or otherwise deregulated in various myeloid leukemias. To determine the importance of co-association of Hoxa9, C/ebpα and Pu.1 at myeloid enhancers, we generated cell lines from C/ebpα and Pu.1 conditional knockout mice (kindly provided by Dr. Daniel Tenen, Harvard University) by immortalization with Hoxa9 and Meis1. In addition we transformed bone marrow with a tamoxifen-regulated form of Hoxa9. Strikingly, loss of C/ebpα or Pu.1, or inactivation of Hoxa9, blocks proliferation and leads to myeloid differentiation. ChIP experiments show that both C/ebpα and Pu.1 remain bound to Hoxa9 binding sites in the absence of Hoxa9. After the loss of Pu.1, both Hoxa9 and C/ebpα dissociate from Hoxa9 binding sites with a corresponding decrease in target gene expression. In contrast, loss of C/ebpα does not lead to an immediate decrease in either Hoxa9 or Pu.1 binding, suggesting that C/ebpα may be playing a regulatory as opposed to a scaffolding role at enhancers. Current work focuses on performing ChIP-seq analysis to assess how C/ebpα and Pu.1 affect Hoxa9 and Meis1 binding and epigenetic modifications genome-wide, and in vivo leukemogenesis assays to confirm the requirement of both Pu.1 and C/ebpα in the establishment and maintenance of leukemias with high levels of Hoxa9. Collectively, our findings implicate C/ebpα and Pu.1 as members of a critical transcription factor network required for Hoxa9-mediated transcriptional regulation in leukemia. Disclosures: No relevant conflicts of interest to declare.

MiR-29a Maintains Hematopoietic Stem Cell Self-Renewal and Is Required For Myeloid Leukemogenesis

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1190-1190
Author(s):  
Wenhuo Hu ◽  
James Dooley ◽  
Stephen S. Chung ◽  
Safak Yalcin ◽  
Yu Sup Shin ◽  
...  
Keyword(s):  
Stem Cell ◽  
Colony Formation ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Ectopic Expression ◽  
Null Mouse ◽  
Cell Cycle Regulators ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract microRNAs (miRNAs) are important regulators of both embryonic and adult tissue stem cell self-renewal. We previously showed that ectopic expression of miR-29a, a miRNA highly expressed in HSCs as well as in human acute myeloid leukemia (AML) stem cells, in immature mouse hematopoietic cells is sufficient to induce a myeloproliferative disorder that progresses to AML. During the early phase of this disease, miR-29a induces aberrant self-renewal of committed myeloid progenitors, strongly suggesting a role for miR-29a in regulating HSC self-renewal. In order to determine the role of miR-29a in HSC function, we have evaluated our recently described miR-29a/b1 null mouse. Homozygous deletion of miR-29a/b1 resulted in reduced bone marrow cellularity and reduced colony forming capacity of hematopoietic stem and progenitor cells (HSPCs). The phenotype was mediated specifically by miR-29a since miR-29b expression was not significantly altered in HSCs and reconstitution of miR-29a/b1 null HSPCs with miR-29a, but not miR-29b, rescued in vitro colony formation defects. Self-renewal defects were observed in miR-29a deficient HSCs in both competitive and non-competitive transplantation assays, and these deficits were associated with increased HSC cell cycling and apoptosis. Gene expression studies of miR-29a deficient HSCs demonstrated widespread gene dysregulation including a number of up-regulated miR-29a target genes including DNA methylation enzymes (Dnmt3a, -3b) and cell cycle regulators (e.g. Cdk6, Tcl1, Hbp1, Pten). Knockdown of one of these targets, Dnmt3a, in miR-29a deficient HSCs resulted in partial restoration of colony formation, providing functional validation that Dnmt3a mediates part of miR-29a null HSPCs functional defects. miR-29a loss also abrogated leukemogenesis in the MLL-AF9 retroviral AML model. Together, our results demonstrate that miR-29a positively regulates HSC self-renewal and is required for myeloid leukemogenesis. Disclosures: No relevant conflicts of interest to declare.

Anti-CD138-IFNα Fusion Proteins Are Effective in Treating Multiple Myeloma

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 939-939
Author(s):  
Esther Yoo ◽  
Alex Vasuthasawat ◽  
Danh Tran ◽  
Alan Lichtenstein ◽  
Sherie Morrison
Keyword(s):  
Multiple Myeloma ◽  
Fusion Protein ◽  
Cell Lines ◽  
Dna Content ◽  
Fusion Proteins ◽  
Conflicts Of Interest ◽  
Myeloma Cell ◽  
Inhibition Of Proliferation ◽  
Discontinue Therapy

Abstract Abstract 939 Although IFNα has shown some efficacy in the treatment of multiple myeloma (MM), this efficacy has been limited in large part because systemic toxicity makes it difficult if not impossible to reach therapeutically effective doses at the site of the tumor. The short half-life of IFN also makes it difficult to sustain high levels during treatment, and because of the side effects, the patients often discontinue therapy. To address these issues, we have genetically fused IFNα2 to a chimeric IgG1 antibody specific for the antigen CD138 expressed on the surface of MM cells, yielding anti-CD138-IFNα. We have also produced a fusion protein (anti-CD138-mutIFNα) using a mutant IFNα that binds the IFN receptor (IFNAR) more tightly. The fusion proteins continued to bind CD138 and retained IFN activity and showed anti-proliferative activity against a broad panel of myeloma cell lines (HMCL) representing MM with different characteristic. To investigate the events responsible for the inhibition of proliferation, 8226/S, ANBL-6, MM1-144, H929, OCI-My5 and U266 cells were incubated with 500 pM anti-CD138-IFNα for 72 h and their DNA content analyzed by FLOW cytometry following permeabilization and staining with PI. The different cell lines exhibited different responses. All of the cell lines except OCI-My5 underwent apoptosis. For 8226/S, OCI-My5 and U266 there was little change in DNA content following treatment. ANBL-6 showed a slight increase in the number of cells in S. However, MM1-144 and H929 showed a marked accumulation in G2 with H929 also showing accumulation of cells with sub-G0content of DNA. Therefore, there is heterogeneity in the response of different HMCL to treatment with targeted IFNα2. For many but not all of the cell lines, anti-CD138-mutIFNα was more effective than anti-CD138-IFNα in inhibiting proliferation and causing DNA fragmentation. Anti-CD138-mutIFNα was more effective than anti-CD138-IFNα in inducing senescence-associated β-galactosidase and STAT1 activation in OCI-My5 cells. Treatment with anti-CD138-IFNα or anti-CD138-mutIFNα resulted in a decrease in the amount of IRF4 present in U266, suggesting that this may be responsible for the efficacy of the fusion proteins in this cell line. Treatment of the other cell lines did not alter the level of IRF4 present, but anti-CD138-IFNα and anti-CD138-mutIFNα treatment caused a decrease in the amount of ppRB present in 8226/S, OCI-My5 and MM1-144, and to a lesser extent in H929. To determine the in vivo efficacy of fusion protein treatment, SCID mice were injected subcutaneously with OCI-My5 cells and treated intravenously on days 14, 16 and 18 with 100 μg of the indicated proteins and monitored for tumor growth (Figure 1). Mice were sacrificed when tumors exceeded 1.5 cm in diameter. Treatment with anti-CD138-IFNα provided some protection (p ≤ 0.0001 compared to PBS). However, treatment with anti-CD138-mutIFNα was even more effective (p = 0.0004 compared to anti-CD138-IFNα). Anti-CD138-mutIFNα was also found to be more effective than anti-CD138-IFNα against primary MM cells. Patients with active myeloma were biopsied while off therapy and the marrow cells isolated by a negative antibody selection to >95% purity. After 72 h incubation with 25 nM of protein, anti-CD138 was found to have little effect. In contrast treatment with anti-CD138-IFNα caused a decrease in viability with anti-CD138-mutIFNα treatment leading to an even greater decrease in cell viability. Following 72 h of treatment, 25 nM of anti-CD138-mutIFNα was found to have more potent cytoreductive effects than 100 nM of anti-CD138-IFNα. Disclosures: No relevant conflicts of interest to declare.

Early Different Downstream Target of Glucocorticoid Receptor Contributing to Glucocorticoids Sensitivity in Kasumi-1 Cells

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5132-5132
Author(s):  
Wenbin Gu ◽  
Meng Li ◽  
Liang Liang ◽  
Jian Zhang ◽  
Chongye Guo ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Fusion Protein ◽  
Cell Line ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Critical Role ◽  
Leukemia Cell ◽  
Leukemia Cells ◽  
Non Coding Rnas

Abstract The t(8;21) chromosome translocation frequently occurs in acute myeloid leukemia (AML), resulting in an in-frame fusion between the DNA-binding domain of AML1 and almost the entire of ETO gene. The fusion AML1-ETO protein is thought to play a critical role in the abnormal proliferation and differentiation of myeloid leukemia cells, such as Kasumi-1 and SKNO-1 cells. Glucocorticoids (GC) can induce apoptosis in these cells at low concentrations, whereas most other myeloid leukemia cell lines are resistant to glucocorticoid-induced apoptosis. To experimentally address possible sensitive mechanisms in leukemia cells with AML1-ETO translocation, we generated aGC-resistant Kasumi-1 cell line by induction of 10-6 M dexamethasone (Dex) for three weeks. The IC50 of Dex to cells is increased from 2.5×10-8 M for original GC-sensitive Kasumi-1 cell line ( K-S cell line) to more than 1×10-5 M for induced GC-resistant Kasumi-1 cell line (K-R cell line). Since GC resistance often results from mutations in the glucocorticoid receptor (GR), all the exons of GR gene were sequenced and no mutation was found in K-R cells. Comparing to those in K-S cells, the GR protein level didn't decrease in K-R cells after 2h, 4h, 8h, 12h and 24h exposure to dexamethasone. Given that the difference of direct GR downstream genes between K-S and K-R cells may play a key role in the GC sensitivity, we systematically analyzed the changes of gene expression induced by Dex versus ethanol vehicle for 8h in K-S and K-R cells by high throughput RNA sequencing. The time point of 8h was selected according to the expression peaks of several foregone GR target genes after Dex induction. There were found 32 genes conversely regulated in K-S and K-R cells, including 14 mRNAs and 18 long non-coding RNAs. Pathway analysis indicated that the upregulated genes in K-S cells might promote the AML1-ETO fusion protein degradation by proteasomes, while the component genes of this pathway were downregulated in K-R cells. Further validation and function studies of these mRNAs and long non-coding RNAs are ongoing. Our data suggested that the downstream targets of GR among GC-sensitive and -resistant Kasumi-1 cells were significant different and they may contribute to the GC sensitivity and resistance by degradation or reservation of AML-ETO fusion protein and the regulation of apoptosis in t(8;21) leukemia cell subtype. Disclosures No relevant conflicts of interest to declare.

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