Histone Deacetylase Inhibitor Valproic Acid Research Articles

Disease-stabilizing treatment based on all-trans retinoic acid and valproic acid in acute myeloid leukemia \u2013 identification of responders by gene expression profiling of pretreatment leukemic cells

BackgroundAcute myeloid leukemia (AML) is an aggressive malignancy only cured by intensive therapy. However, many elderly and unfit patients cannot receive such treatment due to an unacceptable risk of treatment-related morbidity and mortality. Disease-stabilizing therapy is then the only possible strategy, one alternative being treatment based on all-trans retinoic acid (ATRA) combined with the histone deacetylase inhibitor valproic acid and possibly low-toxicity conventional chemotherapy.MethodsPrimary AML cells were derived from 43 patients included in two clinical studies of treatment based on ATRA, valproic acid and theophyllamine; low toxicity chemotherapy (low-dose cytarabine, hydroxyurea, 6-mercaptopurin) was also allowed. Pretreatment leukemic cells were analyzed by mutation profiling of 54 genes frequently mutated in myeloid malignancies and by global gene expression profiling before and during in vivo treatment.ResultsPatients were classified as responders and non-responders to the treatment, however response to treatment showed no significant associations with karyotype or mutational profiles. Significance analysis of microarray (SAM) showed that responders and non-responders significantly differed with regard to the expression of 179 different genes. The differentially expressed genes encoding proteins with a known function were further classified based on the PANTHER (protein annotation through evolutionary relationship) classification system. The identified genes encoded proteins that are involved in several important biological functions, but a main subset of the genes were important for transcriptional regulation. These pretherapy differences in gene expression were largely maintained during treatment. Our analyses of primary AML cells during in vivo treatment suggest that ATRA modulates HOX activity (i.e. decreased expression of HOXA3, HOXA4 and HOXA5 and their regulator PBX3), but altered function of DNA methyl transferase 3A (DNMT3A) and G-protein coupled receptor signaling may also contribute to the effect of the overall treatment.ConclusionsResponders and non-responders to AML stabilizing treatment based on ATRA and valproic acid differ in the pretreatment transcriptional regulation of their leukemic cells, and these differences may be important for the clinical effect of this treatment.Trial registrationsClinicalTrials.gov no. NCT00175812; EudraCT no. 2004–001663-22, registered September 9, 2005 and ClinicalTrials.gov no. NCT00995332; EudraCT no. 2007–2007–001995-36, registered October 14, 2009.

Gestational Age-Dependent Increase of Survival Motor Neuron Protein in Umbilical Cord-Derived Mesenchymal Stem Cells.

Spinal muscular atrophy (SMA) is the most common genetic neurological disease leading to infant death. It is caused by loss of survival motor neuron (SMN) 1 gene and subsequent reduction of SMN protein in motor neurons. Because SMN is ubiquitously expressed and functionally linked to general RNA metabolism pathway, fibroblasts (FBs) are most widely used for the assessment of SMN expression in SMA patients but usually isolated from skin biopsy samples after the onset of overt symptoms. Although recent translational studies of SMN-targeted therapies have revealed the very limited time window for effective SMA therapies during perinatal period, the exact time point when SMN shortage became evident is unknown in human samples. In this study, we analyzed SMN mRNA and protein expression during perinatal period by using umbilical cord-derived mesenchymal stem cells (UC-MSCs) obtained from preterm and term infants. UC-MSCs were isolated from 16 control infants delivered at 22-40 weeks of gestation and SMA fetus aborted at 19 weeks of gestation (UC-MSC-Control and UC-MSC-SMA). FBs were isolated from control volunteer and SMA patient (FB-Control and FB-SMA). SMN mRNA and protein expression in UC-MSCs and FBs was determined by RT-qPCR and Western blot. UC-MSC-Control and UC-MSC-SMA expressed the comparable level of MSC markers on their cell surface and were able to differentiate into adipocytes, osteocytes, and chondrocytes. At steady state, SMN mRNA and protein expression was decreased in UC-MSC-SMA compared to UC-MSC-Control, as observed in FB-SMA and FB-Control. In response to histone deacetylase inhibitor valproic acid, SMN mRNA and protein expression in UC-MSC-SMA and FB-SMA was increased. During perinatal development from 22 to 40 weeks of gestation, SMN mRNA and protein expression in UC-MSC-Control was positively correlated with gestational age. UC-MSCs isolated from 17 fetus/infant of 19-40 weeks of gestation are expressed functional SMN mRNA and protein. SMN mRNA and protein expression in UC-MSCs is increased with gestational age during perinatal development.

Role of the histone deacetylase inhibitor valproic acid in high-fat diet-induced hypertension via inhibition of HDAC1/angiotensin II axis.

Obesity is known as an epidemic worldwide because of consumption of westernized high-fat diets and one of the major risk factors of hypertension. Histone deacetylases (HDACs) control gene expression by regulating histone/non-histone protein deacetylation. HDAC inhibitors exert anti-cancer and anti-inflammatory effects and play a protective role in cardiovascular diseases. In the present study, we tested the effect of an FDA-approved pan-HDAC inhibitor valproic acid (VPA) on high-fat diet (HFD)-induced hypertension in mice. Furthermore, we examined the mechanism of VPA-induced prevention of hypertension. Nine-week-old male C57BL/6 mice were fed either a normal diet (ND) or HFD. When the HFD group reached a pre-hypertensive phase (130-140 mm Hg systolic blood pressure), VPA was administered for 6 days (300 mg kg-1 per day). Body weights and blood pressure (BP), expression of renin-angiotensin system (RAS) components and HDAC1 were determined. The direct role of HDAC1 in the expression of RAS components was investigated using gene silencing. HFD accelerated the increase in body weight from 22.4±1.3 to 31.9±3.0 compared to in the ND group from 22.7±0.9 to 26.0±1.7 (P=0.0134 ND vs HFD), systolic BP from 118.5±5.7 to 145.0±3.0 (P<0.001), and diastolic BP from 91.0±13.6 to 121.0±5.0 (P=0.006); BP was not altered in the ND group. HFD increased RAS components and HDAC1 in the kidneys as well as leptin in the plasma. VPA administration prevented the progression of hypertension and inhibited the increase in expression of HDAC1 and RAS components. VPA did not affect plasma leptin level. Knockdown of HDAC1 in MDCK cells decreased the expression of angiotensinogen and type 1 angiotensin II receptor. VPA prevented HFD-induced hypertension by downregulating angiotensin II and its receptor via inhibition of HDAC1, offering a novel therapeutic option for HFD-induced hypertension.

Thymic Epithelial Tumors phenotype relies on miR-145-5p epigenetic regulation

BackgroundThymoma and thymic carcinoma are the most frequent subtypes of thymic epithelial tumors (TETs). A relevant advance in TET management could derive from a deeper molecular characterization of these neoplasms. We previously identified a set of microRNA (miRNAs) differentially expressed in TETs and normal thymic tissues and among the most significantly deregulated we described the down-regulation of miR-145-5p in TET. Here we describe the mRNAs diversely regulated in TETs and analyze the correlation between these and the miRNAs previously identified, focusing in particular on miR-145-5p. Then, we examine the functional role of miR-145-5p in TETs and its epigenetic transcriptional regulation.MethodsmRNAs expression profiling of a cohort of fresh frozen TETs and normal tissues was performed by microarray analysis. MiR-145-5p role in TETs was evaluated in vitro, modulating its expression in a Thymic Carcinoma (TC1889) cell line. Epigenetic transcriptional regulation of miR-145-5p was examined by treating the TC1889 cell line with the HDAC inhibitor Valproic Acid (VPA).ResultsStarting from the identification of a 69-gene signature of miR-145-5p putative target mRNAs, whose expression was inversely correlated to that of miR-145-5p, we followed the expression of some of them in vitro upon overexpression of miR-145-5p; we observed that this resulted in the down-regulation of the target genes, impacting on TETs cancerous phenotype. We also found that VPA treatment of TC1889 cells led to miR-145-5p up-regulation and concomitant down-regulation of miR-145-5p target genes and exhibited antitumor effects, as indicated by the induction of cell cycle arrest and by the reduction of cell viability, colony forming ability and migration capability. The importance of miR-145-5p up-regulation mediated by VPA is evidenced by the fact that hampering miR-145-5p activity by a LNA inhibitor reduced the impact of VPA treatment on cell viability and colony forming ability of TET cells. Finally, we observed that VPA was also able to enhance the response of TET cells to cisplatin and erlotinib.ConclusionsAltogether our results suggest that the epigenetic regulation of miR-145-5p expression, as well as the modulation of its functional targets, could be relevant players in tumor progression and treatment response in TETs.

Histone deacetylase inhibitors reverse age-related increases in side effects of haloperidol in mice.

Older patients can be especially susceptible to antipsychotic-induced side effects, and the pharmacodynamic mechanism underlying this phenomenon remains unclear. We hypothesized that age-related epigenetic alterations lead to decreased expression and functionality of the dopamine D2 receptor (D2R), contributing to this susceptibility. In this study, we treated young (2-3months old) and aged (22-24months old) C57BL/6 mice with the D2R antagonist haloperidol (HAL) once a day for 14days to evaluate HAL-induced motor side effects. In addition, we pretreated separate groups of young and aged mice with histone deacetylase (HDAC) inhibitors valproic acid (VPA) or entinostat (MS-275) and then administered HAL. Our results show that the motor side effects of HAL are exaggerated in aged mice as compared to young mice and that HDAC inhibitors are able to reverse the severity of these deficits. HAL-induced motor deficits in aged mice are associated with an age- and drug-dependent decrease in striatal D2R protein levels and functionality. Further, histone acetylation was reduced while histone tri-methylation was increased at specific lysine residues of H3 and H4 within the Drd2 promoter in the striatum of aged mice. HDAC inhibitors, particularly VPA, restored striatal D2R protein levels and functionality and reversed age- and drug-related histone modifications at the Drd2 promoter. These results suggest that epigenetic changes at the striatal Drd2 promoter drive age-related increases in antipsychotic side effect susceptibility, and HDAC inhibitors may be an effective adjunct treatment strategy to reduce side effects in aged populations.

Valproic acid mitigates the inflammatory response and prevents acute respiratory distress syndrome in a murine model of Escherichia coli pneumonia at the expense of bacterial clearance.

Histone deacetylase inhibitors (HDACI) are members of a family of epigenetic modifying agents with broad anti-inflammatory properties. These anti-inflammatory properties may have important therapeutic implications in acute respiratory distress syndrome (ARDS). However, administration of HDACI may create an immunosuppressive environment conducive to bacterial growth. Accordingly, the aim of the current study is to investigate the effect of HDACI valproic acid (VPA) on host inflammatory response and bacterial burden in a murine model of Escherichia coli pneumonia-induced ARDS. ARDS was induced in male C57BL6 mice (n = 24) by endotracheal instillation of 3 × 10 E. coli. VPA (250 mg/kg) was administered 30 minutes after E. coli instillation in the intervention group. Blood samples were collected at 3 and 6 hours, and animals were sacrificed at 6 hours. Bronchoalveolar lavage (BAL) was performed, and tissue specimens were harvested. Cytokine levels were measured in blood and BAL, and so was transalveolar protein transit. Cell counts and colony forming units were quantified in BAL fluid. VPA reduced neutrophil influx into the lungs and local tissue destruction through decreased myeloperoxidase activity. It also ameliorated the pulmonary and systemic inflammatory response. This led to greater bacterial proliferation in the pulmonary parenchyma. Administration of VPA in a clinically relevant bacterial model of murine ARDS mitigates the host inflammatory response, essentially preventing ARDS, but creates an immunosuppressive environment that favors bacterial overgrowth.

HDAC inhibitors show differential epigenetic regulation and cell survival strategies on p53 mutant colon cancer cells

Besides inactivating tumour suppressor activity in cells, mutations in p53 confer significant oncogenic functions and promote metastasis and resistance to anticancer therapy. A variety of therapies involving genetic and epigenetic signalling events regulate tumorogenesis and progression in such cases. Pharmacological interventions with HDAC inhibitors have shown promise in therapy. This work explores the changes in efficacy of the four HDAC inhibitors SAHA, MS-275, valproic acid and sodium butyrate on a panel of colon cancer cell lines – HCT116 (p53 wt), HCT116 p53-/-, HT29 and SW480 (with mutations in p53). Clonogenic assays, gene profiling and epigenetic expression done on these cells point to p53 dependent differential activity of the 4 HDAC inhibitors which also elevate methylation levels in p53 mutant cell lines. In silico modelling establishes the alterations in interactions that lead to such differential activity of valproic acid, one of the inhibitors considered for the work. Molecular Dynamic simulations carried out on the valproic acid complex ensure stability of the complex. This work establishes a p53 dependent epigenetic signalling mechanism triggered by HDAC inhibition expanding the scope of HDAC inhibitors in adjuvant therapy for p53 mutant tumours.

The histone deacetylase inhibitor valproic acid inhibits NKG2D expression in natural killer cells through suppression of STAT3 and HDAC3

NKG2D is a major activating receptor of NK cells and plays a critical role in tumor immunosurveillance. NKG2D expression in NK cells is inhibited by the histone deacetylase (HDAC) inhibitor valproic acid (VPA) and enhanced by the narrow-spectrum HDAC inhibitor entinostat. We previously demonstrated that entinostat enhanced NKG2D transcription by increasing acetylation of Histones H3 and H4. However, the mechanism by which VPA reduces NKG2D expression in NK cells is not known. We have also shown that NKG2D transcription is regulated by STAT3 phosphorylation. In this study, we investigated regulation of NKG2D expression in NK cells by VPA and entinostat by assessing protein expression, phosphorylation, and interaction of HDACs and STAT3. We find that VPA selectively inhibits STAT3 tyrosine705 phosphorylation, but entinostat does not. STAT3 complexes with HDAC3, and HDAC3 inhibition represses STAT3 phosphorylation and therefore NKG2D expression. NK cells from STAT3 wild-type mice downregulate NKG2D in response to VPA, but not NK cells from STAT3 knockout mice. These results show that VPA is a potent inhibitor of STAT3 phosphorylation and demonstrate that histone acetylation and STAT3 tyrosine705 phosphorylation cooperate in regulating NKG2D expression in NK cells.

Histone deacetylase inhibitors VPA and TSA induce apoptosis and autophagy in pancreatic cancer cells.

Histone deacetylase inhibitors (HDACi) are anti-neoplastic agents that are known to affect the growth of different cancer types, but their underlying mechanisms are still incompletely understood. Here, we compared the effects of two HDACi, i.e., Trichostatin A (TSA) and Valproic Acid (VPA), on the induction of cell death and autophagy in pancreatic cancer-derived cells that exhibit a high metastatic capacity and carry KRAS/p53 double mutations. Cell viability and proliferation tests were carried out using Trypan blue dye exclusion, MTT and BrdU assays. FACS analyses were carried out to assess cell cycle progression, apoptosis, reactive oxygen species (ROS) production and mitochondrial depolarization, while Western blot and immunoprecipitation analyses were employed to detect proteins involved in apoptosis and autophagy. We found that both VPA and TSA can induce apoptosis in Panc1 and PaCa44 pancreatic cancer-derived cells by triggering mitochondrial membrane depolarization, Cytochrome c release and Caspase 3 activation, although VPA was more effective than TSA, especially in Panc1 cells. As underlying molecular events, we found that ERK1/2 was de-phosphorylated and that the c-Myc and mutant p53 protein levels were reduced after VPA and, to a lesser extent, after TSA treatment. Up-regulation of p21 and Puma was also observed, concomitantly with mutant p53 degradation. In addition, we found that in both cell lines VPA increased the pro-apoptotic Bim level, reduced the anti-apoptotic Mcl-1 level and increased ROS production and autophagy, while TSA was able to induce these effects only in PaCA44 cells. From our results we conclude that both VPA and TSA can induce pancreatic cancer cell apoptosis and autophagy. VPA appears have a stronger and broader cytotoxic effect than TSA and, thus, may represent a better choice for anti-pancreatic cancer therapy.

Valproic acid assisted reprogramming of fibroblasts for generation of pluripotent stem cells in buffalo (Bubalus bubalis).

Generation of pluripotent stem cells by reprogramming somatic cells of quality animals has numerous potential applications in agricultural and biomedical sciences. Unfortunately, till now, reprogramming of buffalo fetal fibroblast cells (bFFs) has been very ineffient despite intensive efforts. Here, we attempted to enhance reprogramming efficiency by using the HDAC inhibitor valproic acid (VPA) in bFFs transfected with pLentG-KOSM pseudo virus carrying mouse specific pluripotent genes. FACS analysis revealed that VPA treatment significantly increased (p < 0.05) GFP+ cells in comparison to VPA untreated control. Further, among different concentrations, 1.5 mM VPA was found to be optimal, increasing about 5 fold GFP+ cells and 2.5-fold GFP+ colonies with significantly (P < 0.05) larger size as compared to control. These colonies were further propagated and characterised. The colonies displayed embryonic stem cell (ESC)-like morphology, normal karyotype, and were positive for alkaline phosphatase staining as well as immune-positive for the ESC specific markers Oct4, Nanog, SSEA1, TRA-1-60 and TRA-1-81. The primary colonies revealed significantly higher (P < 0.05) expression of pluripotent genes than control, which declined gradually on subsequent passages. The reprogrammed cells readily formed embryoid bodies in vitro and cells of all three germ layers. These results indicated that VPA treatment of viral transducted cells can improve the generation of induced pluripotent stem cells and help their long term maintenance in buffalo.

Effects of Histone Deacetylase Inhibitor (Valproic Acid) on the Expression of Hypoxia-inducible Factor-1 Alpha in Human Retinal Müller Cells.

PurposeTo evaluate the effects of valproic acid (VPA), a histone deacetylase inhibitor (HDACI), on the expression of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in human retinal Müller cells under hypoxic conditions.MethodsChemical hypoxia was induced in human retinal Müller cells (MIO-M1) by treatment with increasing concentrations of cobalt(II) chloride (CoCl2). Müller cells were also treated with a set concentration of CoCl2, along with various concentrations of VPA. The expression of HIF-1α and VEGF in the treated Müller cells was determined by enzyme-linked immunosorbent assay.ResultsExposure of human retinal Müller cells to increasing concentrations of CoCl2 produced a dose-dependent increase in HIF-1α expression. The addition of increasing concentrations of VPA lead to a dose-dependent decrease in expression of HIF-1α and VEGF in Müller cells exposed to a set concentration of CoCl2.ConclusionsHDACI VPA downregulated the expressions of HIF-1α and VEGF in human retinal Müller cells under hypoxic conditions. Using HDACI to target HIF-1α expression in Müller cells could be a new therapeutic strategy for the treatment of retinal vascular diseases.

Strategic Perspectives on Improved Anti-Tumor Drug Effects in Combination with Clinically Equivalent or Lower Concentrations of Epigenetic Modifiers, DNA Methyltransferase Inhibitors, and Histone Deacetylase Inhibitors

The aim of this research is to facilitate the pursuit of improved chemotherapeutic drugs in combination with epigenetic modifiers. Both in vitro studies and a clinical study have described the combinations of DNA methyltransferase inhibitors with irinotecan and histone deacetylase inhibitors with 5-fluorouracil or gemcitabine to enhance their anti-cancer activities. The molecular mechanisms involved in the potentiation of anti-tumor activities were apoptosis regulation, cellular metabolism, DNA topoisomerase-I upregulation, cell-cell adhesion, regulation of transcription (DNA-templated), DNA repair, and the PI3K/AKT signaling pathway. More importantly, the priming effects and long-lasting effects induced by DNA methyltransferase inhibitors, when applied as a pretreatment, sensitized cancer cells to subsequent anti-cancer drug treatments. The combinations of 5-fluorouracil and gemcitabine with histone deacetylase inhibitors (depsipeptide and valproic acid, respectively), increased the expression of major histocompatibility complex class II, which may warrant further investigation for possible accurate biomarkers and therapeutic targets. As valproic acid downregulated histone deacetylase in patients recruited in a clinical phase I/II study, the activity of valproic acid may be associated with the enhanced anti-tumor activity in combination with 5-fluorouracil. This research provides a positive perspective on the combination therapy of anticancer drugs with epigenetic modifiers.

HDAC Inhibitor Conjugated Polymeric Prodrug Micelles for Doxorubicin Delivery.

Amphiphilic diblock copolymers bearing histone deacetylase inhibitors (HDACi) (4-phenyl butyric acid and valproic acid) were synthesized by the ring-opening polymerization of γ-4-phenylbutyrate-ε-caprolactone (PBACL), γ-valproate-ε-caprolactone (VPACL), and ε-caprolactone (CL) from a poly(ethylene glycol) macroinitiator (PEG). These amphiphilic diblock copolymers self-assembled into stable pro-drug micelles and demonstrated excellent biocompatibility. High loading of doxorubicin (DOX) up to 5.1 wt% was achieved. Optimized micelles enabled sustained drug release in a concentration-dependent manner over time to expand the therapeutic window of cytotoxic small molecule drugs.

Histone deacetylase inhibitors in plasma cell leukemia treatment: effect of bone marrow microenvironment.

In the presented study we analysed the effect of histone deacetylase inhibitors (HDACi) suberoylanilide hydroxamic acid (SAHA) and valproic acid (VPA) on human plasma cell leukemia (PCL) cell line UHKT-944 in the presence of bone marrow microenvironment (BMM). For the analysis, the cells were cultured alone, with bone marrow stromal cells (BMSCs), with extracellular matrix (ECM) components or with interleukin-6, and treated with varied concentrations of SAHA and VPA for 24/48 hours. To study the effect of HDACi, we investigated cell proliferation, apoptosis, cell cycle and changes in selected signalling pathways. We found that both SAHA and VPA induced apoptosis, but had no effect on the cell cycle distribution of UHKT-944 cells. Investigation of the antiproliferative effect of SAHA and VPA revealed that BMSCs and high concentration of interleukin-6 had partial protective effect against SAHA or both inhibitors, respectively. No effect of ECM components on the efficiency of HDACi was observed. We further revealed that VPA down-regulated STAT3 phosphorylation while both inhibitors decreased Akt phosphorylation. In conclusion, VPA and SAHA might represent an additional therapeutic strategy in the PCL treatment. Protective effect of BMM should be taken into account when investigating prospective therapeutic agents against plasma cell disorders.

Identification of the Oncogene SKI As a New Target Gene of the Myeloid Transcription Factor c-MYB in AML

Background:Acute myeloid leukemia (AML) accounts for 80% of acute leukemias and arises through clonal expansion and arrest of differentiation of hematopoietic progenitor cells in the bone marrow. Depending on the AML subtype and age of the patient, AML patients have a 5-year survival rate of about 25%. AML is a genetically heterogenous disease, where chromosomal aberrations, point mutations in critical oncogenes as well as aberrant expression of key regulatory factors of hematopoiesis collude during transformation. c-MYB is an important hematopoietic transcription factor involved in proliferation and differentiation of progenitor cells of the myeloid and lymphoid lineages. It was first described as a viral oncogene of avian leukemia viruses and is upregulated or mutated in many leukemic subtypes as well as solid tumors. c-MYB interacts with other transcription factors or co-factors, which are essential for its transcriptional activity. In this regard, c-MYB transactivation ability is inhibited by a histone deacetylases recruiting corepressor complex containing SKI, TIF1BETA, NCOR and mSIN3A. c-SKI is a proto-oncogene and an inhibitor of TGFβ signalling. However, it acts not only as a transcriptional co-repressor but also as a transcriptional co-activator. Like c-MYB, c-SKI is upregulated in different solid tumors and leukemias. Though SKI activity is well described, transcriptional regulation of the SKI gene itself still remains unknown. Here, we deliver insight into the transcriptional regulation of the human SKI gene via the transcription factor c-MYB.Methods:In silico analyses were performed to identify potential MYB binding sites in the SKI regulatory region. Chromatin immunoprecipitation (ChIP) assays were used to validate the interaction between MYB and the potential SKI regulatory regions. Reporter gene assays were engaged to analyze MYB regulatory potential regarding SKI expression. RNAi experiments were performed to further examine transcriptional regulation of SKI by MYB. Since MYB is known to be downregulated by the histone deacetylase inhibitor (HDACi) valproic acid (VPA), MYB and SKI protein levels were analyzed in AML cell lines treated with VPA via Western Blot. Correlated protein levels of MYB and SKI were examined in the myeloid leukemia cell lines HL60, U937, THP1, NB4 and K562 as well as in primary cells of AML patients (n=27). Correlation of MYB and SKI transcript levels were performed in three different data sets of primary AML samples. The first cohort (n=7) was analyzed via RT-qPCR. Cohort 2 consists of cDNA microarray data of AML patients (n=17). Furthermore, principal component analysis (PCA) of the gene expression profile of MYB and SKI of AML patients (n=542) were performed with the leukemia gene atlas (LGA).Results:In silico analyses revealed four putative MYB binding sites (MBS1-4) in the SKI regulatory region. Direct binding of MYB to the regulatory sites MBS2-4 of the SKI gene could be confirmed via ChIP experiments. Dual luciferase reporter gene assays comprising c-MYB binding sites present in the SKI gene locus further show c-MYB-dependent transcriptional activation of the reporter. RNAi experiments depleting c-MYB in leukemic cell lines resulted in the decrease of SKI protein levels and thereby reveal that c-MYB is essential for the induction of SKI gene expression. Accordingly, treatment of the AML cell lines with the HDACi VPA led to a decrease of MYB and consequently SKI protein levels. Consistently, we observed a positive correlation of MYB and SKI protein expression in leukemic cell lines and in samples of AML patients. Moreover, a highly positive correlation of MYB and SKI transcript levels could be observed in three different cohorts of AML patients, further confirming regulation of SKI expression by the transcription factor MYB.Conclusion:Our findings provide new insights in the transcriptional regulation of the proto-oncogene c-SKI by the oncogenic transcription factor c-MYB during leukemogenesis. c-MYB and c-SKI expression and functions are highly positively correlated in human AML suggesting that c-SKI is a mediator of c-MYB oncogenic potential. So far, various therapeutic approaches targeting MYB failed to be transferred to patients. In this regard, c-MYB and c-SKI represent promising marker and target proteins for novel HDACi-based therapeutic approaches in AML. DisclosuresNo relevant conflicts of interest to declare.

Histone Deacetylase Inhibitors As Enhancers of Human Hematopoietic Stem Cell Activity

IntroductionThe identification of compounds which increase the number but also keep or enhance the activity of hematopoietic stem and progenitor cells (HSPCs) could improve the clinical outcome after autologous and allogeneic hematopoietic stem cell transplantation (HSCT). So far, most attempts to increase HSPC numbers ex vivo have been unsuccessful because of either inadequate cell numbers and/or loss of engraftment capacity and HSPC quality during expansion. Executing drug discovery screens in vertebrate systems is generally expensive, technically challenging and time consuming. Therefore, the zebrafish represents a versatile vertebrate model allowing HSPC regulation and development studies during embryogenesis and adulthood.MethodsWe used a semi-automated chemical screen to identify modulators of HSPC activity by transgenic (cmyb:EGFP) zebrafish embryos. Verification of identified histone deacetylase (HDAC) inhibitor candidates was carried out in vitro using human CD34+ HSPCs which were isolated from apharesis samples of healthy donors after mobilization with G-CSF by anti-CD34 coupled magnetic beads. The influence of HDAC inhibitors on HSPC phenotype, gene expression pattern as well as adhesion and migration capacity was analyzed after 5 days of treatment either in single or in co-culture with bone marrow-derived mesenchymal stromal cells (MSCs).ResultsThe HDAC inhibitors valproic acid (VPA), resminostat and entinostat were shown to significantly amplify the number of hematopoietic precursors in a chemical in vivo zebrafish embryo screen (Arulmozhivarman et al. 2016). Treatment of human CD34+ HSPCs with these compounds in vitro resulted in a significantly increased percentage of CD34+CD90+ cells up to 60% compared to controls which showed only 2% of double positive cells as well as in 3-fold higher CD34+ and about 12-fold higher CD34+CD90+ absolute cell numbers. CD34 is a well-known surface marker for human immature HSPCs and in combination with CD90 it defines a potentially pluripotent subpopulation. In a co-culture setting, we found that VPA treated cells showed 2 to 3-fold higher attachment capacity on MSCs compared to the control cells. This finding led us to quantify the adhesive capacity of cells using static adhesion assay and atomic force microscopy based single-cell force spectroscopy (AFM-SCFS). Interestingly, detachment forces of VPA treated HSPCs were 3 times increased on MSCs compared to control cells and a similar phenotype was observed by static adhesion assay. Accordingly, the chemokine-mediated migration of VPA treated HSPCs towards SDF-1/CXCL12 was inhibited. To reveal underlying downstream molecules and mechanisms mediating the modified cellular characteristics, a whole genome expression array was carried out for HSPCs treated with VPA in comparison to untreated controls. Amongst a panel of regulated genes, the melanoma cell adhesion molecule (MCAM/CD146), Notch 3 and its downstream effector Hes-1 as well as the SDF-1 receptor CXCR-4 were found to be significantly changed. Whereas the decreased expression of CXCR4 correlates with the inhibited migration potential of VPA-treated HSPCs and Notch-3/Hes-1 have a known role in normal and malignant hematopoiesis (Gu et al. 2016), the induced expression of MCAM on HSPCs was not described so far. The result was confirmed by flow cytometry which revealed a 40% MCAM-positive cell population when treated with VPA, whereas the control showed only negative cells. Additionally, significant higher transcript levels were detected for MCAM by quantitative real-time PCR in VPA expanded cells. Recently, we described a role of MCAM in MSCs for the hematopoietic support (Stopp et al. 2013). The inducible expression in HSPCs may reflect homotypic interactions which preserve a more immature subpopulation with high stem cell activity.ConclusionWe describe for the first time the ability of the HDAC inhibitors VPA, resminostat and entinostat to efficiently expand CD34+ HSPCs ex vivo especially supporting a CD34+CD90+ subpopulation with potentially high stem cell activity. Moreover, a potential role of MCAM in this context may offer new perspectives of the HSPC expansion ex vivo for the improvement of HSCT. DisclosuresNo relevant conflicts of interest to declare.

Valproic acid selectively increases vascular endothelial tissue‐type plasminogen activator production and reduces thrombus formation in the mouse

Background The endogenous fibrinolytic system has rarely been considered as a target to prevent thrombotic disease. Tissue-type plasminogen activator (t-PA) production is potently increased by histone deacetylase (HDAC) inhibitors in endothelial cells in vitro, but whether this translates into increased vascular t-PA production and an enhanced fibrinolytic capacity in vivo is unknown. Objectives To determine whether the HDAC inhibitor valproic acid (VPA) stimulates production of t-PA in the vasculature of mice, and whether VPA pretreatment affects fibrin deposition and clot formation after mechanical vessel injury. Methods Mice were injected with VPA twice daily for up to 5 days. t-PA mRNA, and antigen expression in the mouse aorta and the circulating levels of t-PA were determined. Fibrin and thrombus dynamics after mechanical vessel injury were monitored with intravital confocal microscopy. Potential effects of VPA on platelets and coagulation were investigated. Results and Conclusions We found that VPA treatment increased vascular t-PA production in vivo and, importantly, that VPA administration was associated with reduced fibrin accumulation and smaller thrombi in response to vascular injury, but still was not associated with an increased risk of bleeding. Furthermore, we observed that higher concentrations of VPA were required to stimulate t-PA production in the brain than in the vasculature. Thus, this study shows that VPA can be dosed to selectively manipulate the fibrinolytic system in the vascular compartment and reduce thrombus formation in vivo.

Pharmacogenomics and histone deacetylase inhibitors.

The histone deacetylase inhibitor valproic acid (VPA) has been used for many decades in neurology and psychiatry. The more recent introduction of the histone deacetylase inhibitors (HDIs) belinostat, romidepsin and vorinostat for treatment of hematological malignancies indicates the increasing popularity of these agents. Belinostat, romidepsin and vorinostat are metabolized or transported by polymorphic enzymes or drug transporters. Thus, genotype-directed dosing could improve pharmacotherapy by reducing the risk of toxicities or preventing suboptimal treatment. This review provides an overview of clinical studies on the effects of polymorphisms on the pharmacokinetics, efficacy or toxicities of HDIs including belinostat, romidepsin, vorinostat, panobinostat, VPA and a number of novel compounds currently being tested in Phase I and II trials. Although pharmacogenomic studies for HDIs are scarce, available data indicate that therapy with belinostat (UGT1A1), romidepsin (ABCB1), vorinostat (UGT2B17) or VPA (UGT1A6) could be optimized by upfront genotyping.

Valproic acid inhibits irradiation-induced epithelial-mesenchymal transition and stem cell-like characteristics in esophageal squamous cell carcinoma.

Esophageal carcinoma is one of the most aggressive malignancies, and is characterized by poor response to current therapy and a dismal survival rate. In this study we investigated whether irradiation induces epithelial-mesenchymal transition (EMT) in esophageal squamous cell carcinoma (ESCC) TE9 cells and whether the classic histone deacetylase (HDAC) inhibitor valproic acid (VPA) suppresses these changes. First, we showed that 2 Gy irradiation induced spindle cell-like morphologic changes, decreased expression of membranous E-cadherin, upregulated vimentin expression, and altered the localization of β-catenin from its usual membrane-bound location to cytoplasm in TE9 cells. Irradiation induced upregulation of transcription factors including Slug, Snail, and Twist, which regulate EMT. Stimulation by irradiation resulted in increased TGF-β1 and HIF-1α expression and induced Smad2 and Smad3 phosphorylation. Furthermore, irradiation enhanced CD44 expression, indicating acquisition of cancer stem-like cell properties. In addition, irradiation enhanced invasion and migration ability with upregulation of matrix metalloproteinases. These findings indicate that single-dose irradiation can induce EMT in ESCC cells. Second, we found that treatment with 1 mM VPA induced reversal of EMT caused by irradiation in TE9 cells, resulting in attenuated cell invasion and migration abilities. These results suggest that VPA might have clinical value to suppress irradiation-induced EMT. The reversal of EMT by HDAC inhibitors may be a new therapeutic strategy to improve the effectiveness of radiotherapy in ESCC by inhibiting the enhancement of invasion and metastasis.

Overexpression screens identify conserved dosage chromosome instability genes in yeast and human cancer

Somatic copy number amplification and gene overexpression are common features of many cancers. To determine the role of gene overexpression on chromosome instability (CIN), we performed genome-wide screens in the budding yeast for yeast genes that cause CIN when overexpressed, a phenotype we refer to as dosage CIN (dCIN), and identified 245 dCIN genes. This catalog of genes reveals human orthologs known to be recurrently overexpressed and/or amplified in tumors. We show that two genes, TDP1, a tyrosyl-DNA-phosphdiesterase, and TAF12, an RNA polymerase II TATA-box binding factor, cause CIN when overexpressed in human cells. Rhabdomyosarcoma lines with elevated human Tdp1 levels also exhibit CIN that can be partially rescued by siRNA-mediated knockdown of TDP1 Overexpression of dCIN genes represents a genetic vulnerability that could be leveraged for selective killing of cancer cells through targeting of an unlinked synthetic dosage lethal (SDL) partner. Using SDL screens in yeast, we identified a set of genes that when deleted specifically kill cells with high levels of Tdp1. One gene was the histone deacetylase RPD3, for which there are known inhibitors. Both HT1080 cells overexpressing hTDP1 and rhabdomyosarcoma cells with elevated levels of hTdp1 were more sensitive to histone deacetylase inhibitors valproic acid (VPA) and trichostatin A (TSA), recapitulating the SDL interaction in human cells and suggesting VPA and TSA as potential therapeutic agents for tumors with elevated levels of hTdp1. The catalog of dCIN genes presented here provides a candidate list to identify genes that cause CIN when overexpressed in cancer, which can then be leveraged through SDL to selectively target tumors.