trichostatin-a and Leukemia--Myeloid--Acute

To investigate the trichostain A (TSA)-induced expression of costinmulatory molecules CD80 and CD86 in HL-60, K562 and mononuclear cells (MNC) of bone marrow in AML patients and its clinical significance.. The TSA-induced expression of costimulatory molecules CD80, CD86 in HL-60, K562 and BMMNC, and the cell viability were detected by flow cytometry; the mRNA expression of CD80 and CD86 was detected by RT-PCR; after the TSA-induced HL-60 cells and K562 cells were irradiated with 75 Gy, the effect of these cells on proliferation of PBMNC from healthy volunteers was determined with CCK-8 method.. The HL-60 cells and BMMNC in AML patients expressed CD86, not expressed CD80, while the K562 cells not expressed CD86 and CD80. TSA could up-regulate the expression of CD86 in HL-60 cells and BMMNC of AML patients. The TSA-induced HL-60 cells expressing costimulatory molecule CD86 showed the proliferative effect on BMMNC from healthy volunteers.. The TSA can induce the expression of costimulatory molecule CD86 in HL-60 cells and BMMNC in AML patients, and can improve the proliferation of PBMNC in healthy volunteers.

Topics: B7-1 Antigen; B7-2 Antigen; Cell Line, Tumor; Cell Survival; Flow Cytometry; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute

An exciting recent approach to targeting transcription factors in cancer is to block formation of oncogenic complexes. We investigated whether interfering with the interaction of the transcription factor SALL4, which is critical for leukemic cell survival, and its epigenetic partner complex represents a novel therapeutic approach. The mechanism of SALL4 in promoting leukemogenesis is at least in part mediated by its repression of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) through its interaction with a histone deacetylase (HDAC) complex. In this study, we demonstrate that a peptide can compete with SALL4 in interacting with the HDAC complex and reverse its effect on PTEN repression. Treating SALL4-expressing malignant cells with this peptide leads to cell death that can be rescued by a PTEN inhibitor. The antileukemic effect of this peptide can be confirmed on primary human leukemia cells in culture and in vivo, and is identical to that of down-regulation of SALL4 in these cells using an RNAi approach. In summary, our results demonstrate a novel peptide that can block the specific interaction between SALL4 and its epigenetic HDAC complex in regulating its target gene, PTEN. Furthermore, targeting SALL4 with this approach could be an innovative approach in treating leukemia.

Topics: Animals; Carcinoma, Hepatocellular; Drug Design; Endometrial Neoplasms; Epigenesis, Genetic; Female; Gene Expression Regulation, Leukemic; Histone Deacetylase 1; Histone Deacetylase 2; Histone Deacetylase Inhibitors; HL-60 Cells; Humans; Hydroxamic Acids; Leukemia, Monocytic, Acute; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukemia, Myeloid, Acute; Liver Neoplasms; Male; Mice; Mice, Inbred NOD; Mice, SCID; Peptide Fragments; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Transcription Factors; Xenograft Model Antitumor Assays

SUV39H1 is a histone 3 lysine 9 (H3K9)-specific methyltransferase that is important for heterochromatin formation and the regulation of gene expression. Chaetocin specifically inhibits SUV39H1, resulted in H3K9 methylation reduction as well as reactivation of silenced genes in cancer cells. Histone deacetylase (HDAC) inhibitors inhibit deacetylases and accumulate high levels of acetylation lead to cell cycle arrest and apoptosis. In this study, we demonstrated that treatment with chaetocin enhanced apoptosis in human leukemia HL60, KG1, Kasumi, K562, and THP1 cells. In addition, chaetocin induced the expression of cyclin-dependent kinase inhibitor 2B (p15), E-cadherin (CDH1) and frizzled family receptor 9 (FZD9) through depletion of SUV39H1 and reduced H3K9 methylation in their promoters. Co-treatment with chaetocin and HDAC inhibitor trichostatin A (TSA) dramatically increased apoptosis and produced greater activation of genes. Furthermore, this combined treatment significantly increased loss of SUV39H1 and reduced histone H3K9 trimethylation responses accompanied by increased acetylation. Importantly, co-treatment with chaetocin and TSA produced potent antileukemic effects in leukemia cells derived from patients. These in vitro findings suggest that combination therapy with SUV39H1 and HDAC inhibitors may be of potential value in the treatment of leukemia.

Topics: Acetylation; Adolescent; Adult; Aged; Apoptosis; Cadherins; Cell Line, Tumor; Cyclin-Dependent Kinase Inhibitor p15; DNA Methylation; Enzyme Inhibitors; Frizzled Receptors; Gene Expression Regulation; Histone Deacetylase Inhibitors; Histone Methyltransferases; Histone-Lysine N-Methyltransferase; Histones; HL-60 Cells; Humans; Hydroxamic Acids; K562 Cells; Leukemia; Leukemia, Myeloid, Acute; Male; Middle Aged; Piperazines; Promoter Regions, Genetic; Young Adult

Cancer-testis antigens (CTA) represent attractive targets for tumor immunotherapy. However, a broad picture of CTA expression in acute myeloid leukemia (AML) is missing. CTA expression was analyzed in normal bone marrow (BM) as well as in AML cell lines before and after treatment with demethylating agents and/or histone acetylase inhibitors. Presence of selected CTA with a strictly tumor-restricted expression was then determined in samples of patients with AML before and after demethylating therapy. Screening AML cell lines for the expression of 20 CTA, we identified six genes (MAGE-A3, PRAME, ROPN1, SCP-1, SLLP1, and SPO11) with an AML-restricted expression. Analyzing the expression of these CTA in blast-containing samples from AML patients (N = 64), we found all samples to be negative for MAGE-A3 and SPO11 while a minority of patients expressed ROPN1 (1.6%), SCP-1 (3.1%), or SLLP1 (9.4%). The only CTA expressed in substantial proportion of patients (53.1%) was PRAME. Following demethylating treatment with 5'-aza-2'-deoxycytidine, we observed an increased or de novo expression of CTA, in particular of SSX-2, in AML cell lines. In AML patients, we detected increased expression of PRAME and induction of SSX-2 after demethylating therapy with 5-azacytidine. With the exception of PRAME, CTA are mostly absent from AML blasts. However, demethylating treatment induces strong expression of CTA, particularly of SSX-2, in vitro and in vivo. Therefore, we propose that CTA-specific immunotherapy for AML should preferentially target PRAME and/or should be combined with the application of demethylating agents opening the perspective for alternative targets like CTA SSX-2.

Topics: Aged; Antigens, Neoplasm; Antimetabolites, Antineoplastic; Azacitidine; Biomarkers; Bone Marrow Cells; Case-Control Studies; Cell Line, Tumor; Decitabine; DNA Methylation; Epigenomics; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Histone Deacetylase Inhibitors; Histone Deacetylases; Humans; Hydroxamic Acids; Immunotherapy; Leukemia, Myeloid, Acute; Male; Middle Aged; Molecular Targeted Therapy; Neoplasm Proteins; Repressor Proteins; Reverse Transcriptase Polymerase Chain Reaction; Up-Regulation

Translocations of the Mixed Lineage Leukemia (MLL) gene occur in a subset (5%) of acute myeloid leukemias (AML), and in mixed phenotype acute leukemias in infancy - a disease with extremely poor prognosis. Animal model systems show that MLL gain of function mutations may contribute to leukemogenesis. Wild-type (wt) MLL possesses histone methyltransferase activity and functions at the level of chromatin organization by affecting the expression of specific target genes. While numerous MLL fusion proteins exert a diverse array of functions, they ultimately serve to induce transcription of specific genes. Hence, acute lymphoblastic leukemias (ALL) with MLL mutations (MLLmu) exhibit characteristic gene expression profiles including high-level expression of HOXA cluster genes. Here, we aimed to relate MLL mutational status and tumor suppressor gene (TSG) methylation/expression in acute leukemia cell lines.. Using MS-MLPA (methylation-specific multiplex ligation-dependent probe amplification assay), methylation of 24 different TSG was analyzed in 28 MLLmu and MLLwt acute leukemia cell lines. On average, 1.8/24 TSG were methylated in MLLmu AML cells, while 6.2/24 TSG were methylated in MLLwt AML cells. Hypomethylation and expression of the TSG BEX2, IGSF4 and TIMP3 turned out to be characteristic of MLLmu AML cell lines. MLLwt AML cell lines displayed hypermethylated TSG promoters resulting in transcriptional silencing. Demethylating agents and inhibitors of histone deacetylases restored expression of BEX2, IGSF4 and TIMP3, confirming epigenetic silencing of these genes in MLLwt cells. The positive correlation between MLL translocation, TSG hypomethylation and expression suggested that MLL fusion proteins were responsible for dysregulation of TSG expression in MLLmu cells. This concept was supported by our observation that Bex2 mRNA levels in MLL-ENL transgenic mouse cell lines required expression of the MLL fusion gene.. These results suggest that the conspicuous expression of the TSG BEX2, IGSF4 and TIMP3 in MLLmu AML cell lines is the consequence of altered epigenetic properties of MLL fusion proteins.

Topics: Azacitidine; Cell Adhesion Molecule-1; Cell Adhesion Molecules; Cell Line, Tumor; DNA Methylation; Gene Expression Regulation, Leukemic; Histones; Humans; Hydroxamic Acids; Immunoglobulins; Leukemia, Myeloid, Acute; Membrane Proteins; Mutation; Myeloid-Lymphoid Leukemia Protein; Nerve Tissue Proteins; Oncogene Proteins, Fusion; Promoter Regions, Genetic; Receptors, Retinoic Acid; Sequence Analysis, DNA; Tissue Inhibitor of Metalloproteinase-3; Transcription, Genetic; Translocation, Genetic; Tumor Suppressor Proteins

Malignant myeloblasts arising in high-risk myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are characterized by the constitutive activation of the anti-apoptotic transcription factor NFkappaB. We found that DNA methyltransferase (DNMT) inhibitors (such as azacytidine and 5-aza-2'-deoxycytidine) and histone deacetylase (HDAC) inhibitors (such as trichostatin and valproic acid) efficiently induced apoptosis in the P39 MDS/AML cell line, correlating with an inhibition of NFkappaB (which translocated from the nucleus to the cytoplasm). This effect was obtained rapidly, within a few hours, suggesting that it was not due to epigenetic reprogramming. Indeed, DNMT and HDAC inhibitors reduced the phosphorylation of the NFkappaB-activating kinase IKKalpha/beta, and this effect was also observed in enucleated cells. Finally, circulating myeloblasts from AML patients treated with the DNMT inhibitor 5-aza-2'-deoxycytidine manifested a rapid (2 hours post-treatment) inhibition of NFkappaB and IKKalpha/beta. Altogether, these results indicate that DNMT and HDAC inhibitors can inhibit the constitutive activation of NFkappaB in malignant myeloblasts in vitro and in vivo through a novel mechanism.

Topics: Azacitidine; Cell Line, Tumor; DNA (Cytosine-5-)-Methyltransferases; Enzyme Inhibitors; Female; Granulocyte Precursor Cells; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; I-kappa B Kinase; Leukemia, Myeloid, Acute; Male; Middle Aged; NF-kappa B; Valproic Acid

AML1-ETO is one of the most common chromosomal translocation products associated with acute myelogenous leukemia (AML). Patients carrying the AML1-ETO fusion gene exhibit an accumulation of granulocyte precursors in the bone marrow and the blood. Here, we describe a transgenic zebrafish line that enables inducible expression of the human AML1-ETO oncogene. Induced AML1-ETO expression in embryonic zebrafish causes a phenotype that recapitulates some aspects of human AML. Using this highly tractable model, we show that AML1-ETO redirects myeloerythroid progenitor cells that are developmentally programmed to adopt the erythroid cell fate into the granulocytic cell fate. This fate change is characterized by a loss of gata1 expression and an increase in pu.1 expression in myeloerythroid progenitor cells. Moreover, we identify scl as an early and essential mediator of the effect of AML1-ETO on hematopoietic cell fate. AML1-ETO quickly shuts off scl expression, and restoration of scl expression rescues the effects of AML1-ETO on myeloerythroid progenitor cell fate. These results demonstrate that scl is an important mediator of the ability of AML1-ETO to reprogram hematopoietic cell fate decisions, suggesting that scl may be an important contributor to AML1-ETO-associated leukemia. In addition, treatment of AML1-ETO transgenic zebrafish embryos with a histone deacetylase inhibitor, Trichostatin A, restores scl and gata1 expression, and ameliorates the accumulation of granulocytic cells caused by AML1-ETO. Thus, this zebrafish model facilitates in vivo dissection of AML1-ETO-mediated signaling, and will enable large-scale chemical screens to identify suppressors of the in vivo effects of AML1-ETO.

Topics: Animals; Animals, Genetically Modified; Basic Helix-Loop-Helix Transcription Factors; Blood Cells; Cardiovascular System; Cell Lineage; Core Binding Factor Alpha 2 Subunit; Down-Regulation; Embryo, Nonmammalian; Erythroid Precursor Cells; Erythropoiesis; GATA1 Transcription Factor; Gene Expression Regulation, Developmental; Hematopoietic System; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Monocytes; Oncogene Proteins, Fusion; Proto-Oncogene Proteins; RUNX1 Translocation Partner 1 Protein; T-Cell Acute Lymphocytic Leukemia Protein 1; Transcription, Genetic; Zebrafish; Zebrafish Proteins

Acute myeloid leukemia (AML) is a heterogeneous group of disorders characterized by an abnormal proliferation of the myeloid precursors and a maturation block. The most common chromosomal lesions in AML are the t(8;21) and inv(16). To better understand the leukemogenic mechanism of these fusion proteins, we performed gene expression studies in samples from (8;21), AML1 mutated and inv(16) patients, as well as from the Kasumi-1 cell line and a U937 cell line expressing the AML1-ETO fusion gene. To assess the influence of associated epigenetic lesions, we performed gene expression studies in Kasumi-1 cells and cells extracted from an Inv(16) patient, both treated with demethylating and HDAC inhibitor agents. Shared deregulated genes in the different types of core-binding factor leukemias were identified. We found a tight link between Inv(16) and mutant AML1 samples. Furthermore, some of the genes deregulated by the leukemogenic process reverted to their normal expression with demethylating and HDAC inhibitor treatment, highlighting the role of chromatin remodeling processes in AML.

Topics: Adult; Azacitidine; Biomarkers, Tumor; Chromatin Assembly and Disassembly; Chromosome Inversion; Chromosomes, Human, Pair 16; Chromosomes, Human, Pair 21; Chromosomes, Human, Pair 8; Core Binding Factor Alpha 2 Subunit; Decitabine; DNA Methylation; DNA Modification Methylases; Enzyme Inhibitors; Epigenesis, Genetic; Gene Expression Profiling; Gene Expression Regulation, Leukemic; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Mutation; Oligonucleotide Array Sequence Analysis; Oncogene Proteins, Fusion; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RUNX1 Translocation Partner 1 Protein; Translocation, Genetic; Tumor Cells, Cultured; U937 Cells

ID1, founding member of the inhibitor of differentiation (ID) family, is involved in cell population growth, apoptosis and tumourigenesis.. We investigated mRNA levels of ID1 in human myeloid leukaemic cell lines and in specimens of patients with acute myeloid leukaemia (AML), using semiquantitative reverse transcription-polymerase chain reaction, and protein levels of ID1 in human myeloid leukaemic cell lines using Western blot analysis. Six of seven AML cell lines and 12 of 15 AML patient samples were found to have barely detectable ID1 mRNA. All of these cell lines showed the same levels of protein in proportion to levels of mRNA. Two of the AML cell lines with low ID1 expression, KG1 and KG-1a, were chosen for treatment with either the DNA demethylation reagent, 5-aza-2'-deoxycytidine (DAC), or the histone deacetylase (HDAC) inhibitor, trichostatin A (TSA). These treatments were alone or in combination, and ID1 expression was induced by both DAC and TSA. No hypermethylated ID1 gene promoter was detected in the majority of the cell lines and patient specimens, by methylation-specific polymerase chain reaction, suggesting that induction of ID1 in KG1 and KG-1a was not due to direct demethylation of the ID1 gene promoter. Chromatin immunoprecipitation showed that accumulation of acetyl-histone H3 and release of HDAC1 were correlated with ID1 induction by these drugs. Flow cytometric assay demonstrated more apoptosis induced by TSA or TSA in combination with DAC, in both KG-1 and KG-1a cell lines. Increase of intracellular reactive oxygen species was observed when treated with TSA.. Most AML cell lines and human AML samples have very low levels of expression of ID1. TSA or TSA in combination with DAC is able to restore ID1 expression in low ID1-expressing AML cell lines by re-activating the aberrantly deacetylated promoter, and this also results in more apoptotic cell death, in which ID1 and the redox pathway may be involved.

Topics: Apoptosis; Base Sequence; Chromatin Immunoprecipitation; DNA Methylation; DNA Primers; Enzyme Inhibitors; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Inhibitor of Differentiation Protein 1; Leukemia, Myeloid, Acute; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction

Modulation of gene expression through histone deacetylase (HDAC) inhibition is considered a possible therapeutic strategy in acute myeloid leukaemia (AML). In vitro effects and basal gene expression of structurally different HDAC inhibitors were examined. Primary human AML cells were derived from 59 consecutive patients. The HDAC inhibitors valproic acid, PXD101, trichostatin A and sodium butyrate inhibited leukaemic and clonogenic cell proliferation and increased apoptosis in a dose-dependent manner when tested at high concentrations. However, at lower concentrations proliferation increased for a subset of patients. This divergence was also observed in the presence of all-trans retinoic acid, theophylline and decitabine, and in cocultures with bone marrow stromal cells. Levels of IL-1beta, IL-6, GM-CSF and TNFalpha increased. Based on the basal expression of 100 genes the patients with growth enhancement at intermediate HDAC inhibitor concentrations and those without this response were clustered into two mutually exclusive groups. Functional characterization and gene expression analyses identify AML patient subsets that differ in their response to HDAC inhibitors. These observations may explain why HDAC inhibitor therapy affects only a subset of patients.

Topics: Adult; Aged; Cell Proliferation; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Gene Expression Profiling; Hematopoietic Stem Cells; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Male; Middle Aged; Stromal Cells; Sulfonamides; Valproic Acid

Decitabine is a potent demethylating agent that exhibits clinical activity against myeloid malignancies. Numerous genes silenced by hypermethylation are reactivated by decitabine through a mechanism involving promoter demethylation with subsequent release of histone deacetylases (HDACs) and accumulation of acetylated histones. Recent studies indicating that decitabine also induces regional chromatin remodeling of some unmethylated genes suggest additional mechanisms of action. Decitabine reactivates unmethylated p21WAF1 in some AML cell lines but the possible occurrence of p21WAF1 methylation in AML in vivo has not been studied in detail and decitabine effects on p21WAF1 chromatin remodeling have not been reported. We found that p21WAF1 mRNA was undetectable in 6 of 24 AML patient samples and 4 of 5 AML cell lines but there was no evidence of p21WAF1 promoter methylation. However, decitabine induced p21WAF1 in AML cell lines KG-1 and KG-1a in association with release of HDAC1 and increased acetylated histone H3 at the unmethylated p21WAF1 promoter. Decitabine effects on p21WAF1 histone acetylation and induction were enhanced by the HDAC inhibitor trichostatin A and were independent of wild type p53. Our findings indicate that decitabine can relieve p21WAF1 repression in AML by a mechanism that involves release of HDAC1 without requiring promoter demethylation. Furthermore, our study provides evidence that combined decitabine and HDAC inhibitor treatment can enhance chromatin remodeling and reactivation of an unmethylated tumor suppressor gene. This latter finding is of relevance to the clinical use of these agents in AML as we found the p21WAF1 promoter to be unmethylated in vivo.

Topics: Acylation; Azacitidine; Chromatin Assembly and Disassembly; Cyclin-Dependent Kinase Inhibitor p21; Decitabine; DNA Methylation; Enzyme Inhibitors; Histone Deacetylase 1; Histone Deacetylase Inhibitors; Histone Deacetylases; Histones; Humans; Hydroxamic Acids; K562 Cells; Leukemia, Myeloid, Acute; Neoplasm Proteins; Promoter Regions, Genetic; Protein Processing, Post-Translational; Tumor Suppressor Protein p53

The folate receptor (FR) type beta is a promising target for therapeutic intervention in acute myelogenous leukemia (AML), owing particularly to its selective up-regulation in the leukemic cells by all-trans retinoic acid (ATRA). Here we show, using KG-1 and MV4-11 AML cells and recombinant 293 cells, that the histone deacetylase (HDAC) inhibitors trichostatin A (TSA), valproic acid (VPA), and FK228 potentiated ATRA induction of FR-beta gene transcription and FR-beta mRNA/protein expression. ATRA and/or TSA did not induce de novo FR synthesis in any of a variety of FR-negative cell lines tested. TSA did not alter the effect of ATRA on the expression of retinoic acid receptor (RAR) alpha, beta, or gamma. Chromatin immunoprecipitation assays indicate that HDAC inhibitors act on the FR-beta gene by enhancing RAR-associated histone acetylation to increase the association of Sp1 with the basal FR-beta promoter. Under these conditions, the expression level of Sp1 is unaltered. A decreased availability of putative repressor AP-1 proteins may also indirectly contribute to the effect of HDAC inhibitors. Finally, FR-beta selectively mediated growth inhibition by (6S) dideazatetrahydrofolate in a manner that was greatly potentiated in AML cells by ATRA and HDAC inhibition. Therefore, the combination of ATRA and innocuous HDAC inhibitors may be expected to facilitate selective FR-beta-targeted therapies in AML.

Topics: Acetylation; Animals; Antineoplastic Combined Chemotherapy Protocols; Biomarkers, Tumor; Carrier Proteins; CHO Cells; Cricetinae; Drug Synergism; Enzyme Inhibitors; Folate Receptors, GPI-Anchored; Folic Acid Antagonists; Histone Deacetylase Inhibitors; Histones; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Promoter Regions, Genetic; Receptors, Cell Surface; Receptors, Immunologic; Receptors, Retinoic Acid; RNA, Messenger; Substrate Specificity; Tetrahydrofolates; Transcription Factor AP-1; Tretinoin; Up-Regulation; Valproic Acid

The t(8;21)(q22;q22) translocation, occurring in 40% of patients with acute myeloid leukemia (AML) of the FAB-M2 subtype (AML with maturation), results in expression of the RUNX1-CBF2T1 [AML1-ETO (AE)] fusion oncogene. AML/ETO may contribute to leukemogenesis by interacting with nuclear corepressor complexes that include histone deacetylases, which mediate the repression of target genes. However, expression of AE is not sufficient to transform primary hematopoietic cells or cause disease in animals, suggesting that additional mutations are required. Activating mutations in receptor tyrosine kinases (RTK) are present in at least 30% of patients with AML. To test the hypothesis that activating RTK mutations cooperate with AE to cause leukemia, we transplanted retrovirally transduced murine bone marrow coexpressing TEL-PDGFRB and AE into lethally irradiated syngeneic mice. These mice (19/19, 100%) developed AML resembling M2-AML that was transplantable in secondary recipients. In contrast, control mice coexpressing with TEL-PDGFRB and a DNA-binding-mutant of AE developed a nontransplantable myeloproliferative disease identical to that induced by TEL-PDGFRB alone. We used this unique model of AML to test the efficacy of pharmacological inhibition of histone deacetylase activity by using trichostatin A and suberoylanilide hydroxamic acid alone or in combination with the tyrosine kinase inhibitor, imatinib mesylate. We found that although imatinib prolonged the survival of treated mice, histone deacetylase inhibitors provided no additional survival benefit. These data demonstrate that an activated RTK can cooperate with AE to cause AML in mice, and that this system can be used to evaluate novel therapeutic strategies.

Topics: 3T3 Cells; Acetylation; Animals; Benzamides; Blotting, Southern; Bone Marrow Transplantation; Core Binding Factor Alpha 2 Subunit; DNA; Flow Cytometry; Histone Deacetylases; Histones; Humans; Hydroxamic Acids; Imatinib Mesylate; Leukemia, Myeloid, Acute; Mice; Mice, Inbred BALB C; Mice, Transgenic; Models, Genetic; Mutation; Oncogene Proteins, Fusion; Phenotype; Piperazines; Plasmids; Protein Binding; Protein Structure, Tertiary; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-kit; Pyrimidines; Retroviridae; RUNX1 Translocation Partner 1 Protein; Time Factors; Transcription Factors; Vorinostat

Histone deacetylase (HDAC)-dependent transcriptional repression of the retinoic acid (RA)-signaling pathway underlies the differentiation block of acute promyelocytic leukemia. RA treatment relieves transcriptional repression and triggers differentiation of acute promyelocytic leukemia blasts, leading to disease remission. We report that transcriptional repression of RA signaling is a common mechanism in acute myeloid leukemias (AMLs). HDAC inhibitors restored RA-dependent transcriptional activation and triggered terminal differentiation of primary blasts from 23 AML patients. Accordingly, we show that AML1/ETO, the commonest AML-associated fusion protein, is an HDAC-dependent repressor of RA signaling. These findings relate alteration of the RA pathway to myeloid leukemogenesis and underscore the potential of transcriptional/differentiation therapy in AML.

Topics: Acetylation; Antineoplastic Agents; Cell Differentiation; Core Binding Factor Alpha 2 Subunit; Enzyme Inhibitors; Gene Expression Regulation, Leukemic; Histone Deacetylase Inhibitors; Histone Deacetylases; Histones; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Leukemia, Myelomonocytic, Acute; Oncogene Proteins, Fusion; RUNX1 Translocation Partner 1 Protein; Signal Transduction; Transcription Factors; Transcriptional Activation; Tretinoin; Tumor Cells, Cultured