Histone Deacetylase Inhibitor Valproic Acid Research Articles

Reversal of increased mammary tumorigenesis by valproic acid and hydralazine in offspring of dams fed high fat diet during pregnancy

Maternal or paternal high fat (HF) diet can modify the epigenome in germ cells and fetal somatic cells leading to an increased susceptibility among female offspring of multiple generations to develop breast cancer. We determined if combined treatment with broad spectrum DNA methyltransferase (DNMT) inhibitor hydralazine and histone deacetylase (HDAC) inhibitor valproic acid (VPA) will reverse this increased risk. C57BL/6 mouse dams were fed either a corn oil-based HF or control diet during pregnancy. Starting at age 7 weeks, female offspring were administered 3 doses of 7,12-dimethylbenz[a]anthracene (DMBA) to initiate mammary cancer. After last dose, offspring started receiving VPA/hydralazine administered via drinking water: no adverse health effects were detected. VPA/hydralazine reduced mammary tumor multiplicity and lengthened tumor latency in HF offspring when compared with non-treated HF offspring. The drug combination inhibited DNMT3a protein levels and increased expression of the tumor suppressor gene Cdkn2a/p16 in mammary tumors of HF offspring. In control mice not exposed to HF diet in utero, VPA/hydralazine increased mammary tumor incidence and burden, and elevated expression of the unfolded protein response and autophagy genes, including HIF-1α, NFkB, PERK, and SQSTM1/p62. Expression of these genes was already upregulated in HF offspring prior to VPA/hydralazine treatment. These findings suggest that breast cancer prevention strategies with HDAC/DNMT inhibitors need to be individually tailored.

Comparative analysis of isoform-specific and non-selective histone deacetylase inhibitors in attenuating the intestinal damage after hemorrhagic shock

BackgroundIsoform-specific histone deacetylase inhibitors (HDACIs) MC1568 and ACY1083 are comparable to the non-selective HDACI valproic acid (VPA) in improving survival in rodents undergoing lethal hemorrhage. However, the organ-specific properties of...

Oestrogen and androgen receptor activation contribute to the masculinisation of oxytocin receptors in the bed nucleus of the stria terminalis of rats.

Oxytocin (OT) often regulates social behaviours in sex-specific ways, and this may be a result of sex differences in the brain OT system. Adult male rats show higher OT receptor (OTR) binding in the posterior bed nucleus of the stria terminalis (pBNST) than adult female rats. In the present study, we investigated the mechanisms that lead to this sex difference. First, we found that male rats have higher OTR mRNA expression in the pBNST than females at postnatal day (P)35 and P60, which demonstrates the presence of the sex difference in OTR binding density at message level. Second, the sex difference in OTR binding density in the pBNST was absent at P0 and P3, but was present by P5. Third, systemic administration of the oestrogen receptor (ER) antagonist fulvestrant at P0 and P1 dose-dependently reduced OTR binding density in the pBNST of 5-week-old male rats, but did not eliminate the sex difference in OTR binding density. Fourth, pBNST-OTR binding density was lower in androgen receptor (AR) deficient genetic male rats compared to wild-type males, but higher compared to wild-type females. Finally, systemic administration of the histone deacetylase inhibitor valproic acid at P0 and P1 did not alter pBNST-OTR binding density in 5-week-old male and female rats. Interestingly, neonatal ER antagonism, AR deficiency, and neonatal valproic acid treatment each eliminated the sex difference in pBNST size. Overall, we demonstrate a role for neonatal ER and AR activation in setting up the sex difference in OTR binding density in the pBNST, which may underlie sexual differentiation of the pBNST and social behaviour.

Abstract 1603: Valproic acid and hydralazine reverse increased mammary cancer risk and upregulate Cdkn2a/p16 in mice exposed to a high fat diet in utero

Abstract Maternal or paternal high fat (HF) diet that modifies the epigenome in germ cells and fetal somatic cells can program increased susceptibility to breast cancer among offspring. Resulting epigenetic changes include transgenerational upregulation of DNA methyltransferases (DNMTs). We studied here if this increased breast cancer risk can be reversed by treating HF offspring with a well-tolerated drug that inhibits DNA methyl transferase (DNMT; hydralazine), combined with a histone deacetylase (HDAC) inhibitor valproic acid (VPA). Adult C57BL/6NTac mouse offspring of dams fed either corn oil -based HF or control diet during pregnancy were treated with 5 g/kg/day VPA and 5 mg/kg/day hydralazine in drinking water, starting after mice received 7,12-dimethylbenz[a]anthracene (DMBA) to initiate mammary cancer. Treatment with VPA/hydralazine prevented the increase in mammary cancer risk associated with in utero HF diet exposure: it reduced mammary tumor multiplicity and lengthened tumor latency, compared with non-treated HF offspring. These drugs downregulated DNMT3a protein levels, and reversed down-regulation of Cdkn2a/p16 mRNA in the mammary tumors of HF offspring. p16 is a tumor suppressor that is often epigenetically silenced in human breast cancers. However, in control offspring not exposed to HF diet in utero, VPA/hydralazine increased mammary tumor incidence and burden. Further, this treatment upregulated genes involved in the unfolded protein response pathway in in utero control diet exposed animals that were already upregulated in non-VPA/hydralazine treated mammary tumors from in utero HF diet exposed animals, including HIF-1α, NFkB, PERK and SQSTM1 p62. Thus, VPA and hydralazine had opposing effects on breast cancer risk in HF and control offspring, suggesting the importance of individually tailoring breast cancer prevention strategies. Citation Format: Leena A. Hilakivi-Clarke, Fabia de Oliveira Andrade, Nguyen Nguyen, Kerrie Bouker. Valproic acid and hydralazine reverse increased mammary cancer risk and upregulate Cdkn2a/p16 in mice exposed to a high fat diet in utero [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1603.

Chinese‐German Cooperation Group Tumor Immunology: Another inspiring Meeting in Deidesheim

Chinese‐German Cooperation Group Tumor Immunology: Another inspiring Meeting in Deidesheim

Potentiating Oncolytic Virus-Induced Immune-Mediated Tumor Cell Killing Using Histone Deacetylase Inhibition.

A clinical oncolytic herpes simplex virus (HSV) encoding granulocyte-macrophage colony-stimulating factor (GM-CSF), talimogene laherparepvec, causes regression of injected and non-injected melanoma lesions in patients and is now licensed for clinical use in advanced melanoma. To date, limited data are available regarding the mechanisms of human anti-tumor immune priming, an improved understanding of which could inform the development of future combination strategies with improved efficacy. This study addressed direct oncolysis and innate and adaptive human immune-mediated effects of a closely related HSV encoding GM-CSF (HSVGM-CSF) alone and in combination with histone deacetylase inhibition. We found that HSVGM-CSF supported activation of anti-melanoma immunity via monocyte-mediated type I interferon production, which activates NK cells, and viral maturation of immature dendritic cells (iDCs) into potent antigen-presenting cells for cytotoxic T lymphocyte (CTL) priming. Addition of the histone deacetylase inhibitor valproic acid (VPA) to HSVGM-CSF treatment of tumor cells increased viral replication, viral GM-CSF production, and oncolysis and augmented the development of anti-tumor immunity. Mechanistically, VPA increased expression of activating ligands for NK cell recognition and induced expression of tumor-associated antigens, supporting innate NK cell killing and CTL priming. These data support the clinical combination of talimogene laherparepvec with histone deacetylase inhibition to enhance oncolysis and anti-tumor immunity.

A novel imaging flow cytometry method for the detection of histone H4 acetylation in myeloid cells

The histone deacetylase inhibitor (HDACI) valproic acid has been shown to inhibit the growth of multiple paediatric tumour types and is well tolerated in a childhood cancer setting. The current study was designed to develop a novel imaging flow cytometry method for the detection of histone H4 acetylation in white blood cells obtained from childhood cancer patients treated with valproic acid. HL-60 cells and whole blood samples from healthy volunteers were incubated with valproic acid (0-8mM) for 0-24hours, with additional blood samples collected from ependymoma patients receiving valproic acid on the SIOP Ependymoma II clinical trial. An imaging flow cytometry method was developed using an ImageStream®χ flow cytometer, collecting 100000 images per sample following excitation of PE tagged acH4 antibody and DAPI. The mean percentage of acH4-positive cells increased to a greater extent than increases in mean and median fluorescence intensity following incubation with valproic acid. Comparable results were observed for in vitro and ex vivo experiments, and the assay was shown to be appropriate for clinical sample analysis. Myeloid cells exhibited a smaller proportion of acH4-positive cells than the lymphoid population, but a greater fold increase above basal levels. The percentage of acH4-positive myeloid cells has the potential to be used as a robust pharmacodynamic biomarker for the measurement of acH4 for HDACIs. The developed assay is now being utilised in a clinical trial involving the treatment of childhood ependymoma patients with valproic acid.

Histone Deacetylase Inhibitor Modulates NKG2D Receptor Expression and Memory Phenotype of Human Gamma/Delta T Cells Upon Interaction With Tumor Cells.

The functional plasticity and anti-tumor potential of human γδ T cells have been widely studied. However, the epigenetic regulation of γδ T-cell/tumor cell interactions has been poorly investigated. In the present study, we show that treatment with the histone deacetylase inhibitor Valproic acid (VPA) significantly enhanced the expression and/or release of the NKG2D ligands MICA, MICB and ULBP-2, but not ULBP-1 in the pancreatic carcinoma cell line Panc89 and the prostate carcinoma cell line PC-3. Under in vitro tumor co-culture conditions, the expression of full length and the truncated form of the NKG2D receptor in γδ T cells was significantly downregulated. Furthermore, using a newly established flow cytometry-based method to analyze histone acetylation (H3K9ac) in γδ T cells, we showed constitutive H3K9aclow and inducible H3K9achigh expression in Vδ2 T cells. The detailed analysis of H3K9aclow Vδ2 T cells revealed a significant reversion of TEMRA to TEM phenotype during in vitro co-culture with pancreatic ductal adenocarcinoma cells. Our study uncovers novel mechanisms of how epigenetic modifiers modulate γδ T-cell differentiation during interaction with tumor cells. This information is important when considering combination therapy of VPA with the γδ T-cell-based immunotherapy for the treatment of certain types of cancer.

Histone deacetylase inhibitors valproic acid and vorinostat enhance trastuzumab-mediated antibody-dependent cell-mediated phagocytosis

Histone deacetylase inhibitors valproic acid and vorinostat enhance trastuzumab-mediated antibody-dependent cell-mediated phagocytosis

HDAC (Histone Deacetylase) Inhibitor Valproic Acid Attenuates Atrial Remodeling and Delays the Onset of Atrial Fibrillation in Mice.

A structural, electrical and metabolic atrial remodeling is central in the development of atrial fibrillation (AF) contributing to its initiation and perpetuation. In the heart, HDACs (histone deacetylases) control remodeling associated processes like hypertrophy, fibrosis, and energy metabolism. Here, we analyzed, whether the HDAC class I/IIa inhibitor valproic acid (VPA) is able to attenuate atrial remodeling in CREM-IbΔC-X (cAMP responsive element modulator isoform IbΔC-X) transgenic mice, a mouse model of extensive atrial remodeling with age-dependent progression from spontaneous atrial ectopy to paroxysmal and finally long-lasting AF. VPA was administered for 7 or 25 weeks to transgenic and control mice. Atria were analyzed macroscopically and using widefield and electron microscopy. Action potentials were recorded from atrial cardiomyocytes using patch-clamp technique. ECG recordings documented the onset of AF. A proteome analysis with consecutive pathway mapping identified VPA-mediated proteomic changes and related pathways. VPA attenuated many components of atrial remodeling that are present in transgenic mice, animal AF models, and human AF. VPA significantly ( P<0.05) reduced atrial dilatation, cardiomyocyte enlargement, atrial fibrosis, and the disorganization of myocyte's ultrastructure. It significantly reduced the occurrence of atrial thrombi, reversed action potential alterations, and finally delayed the onset of AF by 4 to 8 weeks. Increased histone H4-acetylation in atria from VPA-treated transgenic mice verified effective in vivo HDAC inhibition. Cardiomyocyte-specific genetic inactivation of HDAC2 in transgenic mice attenuated the ultrastructural disorganization of myocytes comparable to VPA. Finally, VPA restrained dysregulation of proteins in transgenic mice that are involved in a multitude of AF relevant pathways like oxidative phosphorylation or RhoA (Ras homolog gene family, member A) signaling and disease functions like cardiac fibrosis and apoptosis of muscle cells. Our results suggest that VPA, clinically available, well-tolerated, and prescribed to many patients for years, has the therapeutic potential to delay the development of atrial remodeling and the onset of AF in patients at risk.

HDAC inhibitors and cardioprotection: Homing in on a mechanism of action.

HDAC inhibitors and cardioprotection: Homing in on a mechanism of action.

HDAC inhibitor valproic acid protects heart function through Foxm1 pathway after acute myocardial infarction.

BackgroundEpigenetic histone acetylation is a major event controlling cell functions, such as metabolism, differentiation and repair. Here, we aim to determine whether Valproic acid (VPA), a FDA approved inhibitor of histone deacetylation for bipolar disease, could protect heart against myocardial infarction (MI) injury and elucidate key molecular pathways.MethodsVPA was administrated to MI rats at different time points, onset and after MI injury. Echocardiography, histology, serum biology assays, and gene expression, inhibition, and over-expression were performed to characterize the systolic function, infarct size, gene and signaling pathways.FindingsVPA treatment reduced the infarct size by ~50% and preserved the systolic function of heart after acute MI in rats. Even 60 min after infarction, VPA treatment significantly decreased infarct size. Furthermore, long-term treatment of VPA markedly improved myocardial performance. VPA regulated gene expression essential for cell survival and anti-inflammatory response. Consequently, oxidative stress and cell death were notably reduced after VPA treatment. Moreover, Foxm1 was identified as a potential key target of VPA. Overexpression of Foxm1 provided similar heart protective effect to VPA treatment. Particularly, both VPA treatment and Foxm1 over-expression repressed inflammatory response after MI for heart protection. In contrast, inhibition of Foxm1 activity abolished the cardiac protective effect of VPA. VPA mediated CM protection through Foxm1 upregulation was also identified in a human ESC derived CM hypoxia/reperfusion system.InterpretationVPA treatments significantly reduce cardiac damage after MI and the cardioprotective effect of VPA is likely mediated via Foxm1 pathway.FundThis work was mainly supported by 1R01HL109054.

HDAC2 depletion promotes osteosarcoma\u2019s stemness both in vitro and in vivo: a study on a putative new target for CSCs directed therapy

BackgroundCancer stem cells (CSCs) play a key role in cancer initiation, progression and chemoresistance. Epigenetic alterations have been identified as prominent factors that contribute to the CSCs phenotype. Here, we investigated the effects of the HDAC inhibitor valproic acid (VPA) and the demethylating agent, 5’azacytidine (DAC) on the stem phenotype of MG63 and Saos2 osteosarcoma cell lines.MethodsSaos2 and MG63 cells were treated with DAC and VPA, alone and in combination. Untreated and treated cells were examined for stemness phenotype by cytometry and real-time PCR. Sarcospheres and colonies formation were also evaluated. Moreover, histone modification and methylation were tested by flow cytomery and western blotting. HDAC2 depleted cells were examined for stemness phenotype and their ability to generate tumors in NOD/SCID IL2R-gamma-0 (NSG) mice. HDAC2 expression on human osteosarcoma tissues was evaluated.ResultsWe found that DAC and VPA induce an increased expression of stem markers including CD133, OCT4, SOX2 and NANOG, and an increased ability in sarcospheres and colonies formation efficiency. Interestingly, we showed that DAC and VPA treatment decreased repressive histone markers, while increased the active ones. These histone modifications were also associated with an increase of acetylation of histones H3, a decrease of DNA global methylation, HDAC2 and DNMT3a. Furthermore, HDAC2 silenced-MG63 and Saos2 cells acquired a stem phenotype, and promoted in vivo tumorigenesis. In human osteosarcoma tissues, HDAC2 was strongly expressed in nucleus.ConclusionsCollectively, our results suggest that VPA and DAC induce an expansion of osteosarcoma CSCs, and we report for the first time that HDAC2 is a key factor regulating both CSCs phenotype and in vivo cancer growth. In conclusion, we have identified HDAC2 as a potential therapeutic target in human osteosarcoma treatment.

HDAC Inhibition Counteracts Metastatic Re-Activation of Prostate Cancer Cells Induced by Chronic mTOR Suppression.

This study was designed to investigate whether epigenetic modulation by histone deacetylase (HDAC) inhibition might circumvent resistance towards the mechanistic target of rapamycin (mTOR) inhibitor temsirolimus in a prostate cancer cell model. Parental (par) and temsirolimus-resistant (res) PC3 prostate cancer cells were exposed to the HDAC inhibitor valproic acid (VPA), and tumor cell adhesion, chemotaxis, migration, and invasion were evaluated. Temsirolimus resistance was characterized by reduced binding of PC3res cells to endothelium, immobilized collagen, and fibronectin, but increased adhesion to laminin, as compared to the parental cells. Chemotaxis, migration, and invasion of PC3res cells were enhanced following temsirolimus re-treatment. Integrin α and β receptors were significantly altered in PC3res compared to PC3par cells. VPA significantly counteracted temsirolimus resistance by down-regulating tumor cell–matrix interaction, chemotaxis, and migration. Evaluation of integrin expression in the presence of VPA revealed a significant down-regulation of integrin α5 in PC3res cells. Blocking studies demonstrated a close association between α5 expression on PC3res and chemotaxis. In this in vitro model, temsirolimus resistance drove prostate cancer cells to become highly motile, while HDAC inhibition reversed the metastatic activity. The VPA-induced inhibition of metastatic activity was accompanied by a lowered integrin α5 surface level on the tumor cells.

Abstract 2583: Imaging flow cytometry assay development and validation for the detection of histone H4 acetylation in white blood cells

Abstract Introduction: Histone deacetylases have been identified as oncogenes in several cancer types, providing an attractive target for anticancer treatment. In this respect, the histone deacetylase inhibitor valproic acid has been shown to inhibit the growth of multiple paediatric tumor types and is well tolerated in children with refractory solid or CNS tumors. Objective: The aim of the current study was to develop and validate a novel imaging flow cytometry method for the detection of histone H4 acetylation in lymphoid and myeloid cell populations, and to assess the applicability of the method to a clinical trial setting. Method: HL-60 cells and whole blood samples from healthy volunteers were incubated with valproic acid (0.5-8 mM) for 0.5-24 hours, followed by RBC lysis for the whole blood samples and fixed with cold methanol. Additional blood samples were collected from patients with ependymoma who were receiving valproic acid as part of the SIOP Ependymoma II clinical trial. An imaging flow cytometry method was developed using an ImageStreamχ flow cytometer, collecting WBCs with excitation of PE conjugated acH4 antibody and DAPI. Data were collected using Inspire™ software and further analysed by Ideas™ software 6.2. Both in vitro and ex vivo experiments were repeated on at least 3 occasions. Result: In the HL-60 cell line the mean percentage of acH4 positive cells was 1.98% in the vehicle control sample, increasing to 10.9-77.9% when treated with 0.5-8 mM valproic acid for 6 hours, with percentages of 8.7-49.0% observed following incubation with 4 mM valproic acid for 0.5-24 hours. Comparable data were generated in lymphoid and myeloid WBC populations following ex vivo incubation of whole blood samples with valproic acid. Increases in the percentage of acH4 positive cells were observed in samples collected at 4 hours post-administration in patients receiving valproic acid as compared to pre-treatment samples. Myeloid cells appeared to have a smaller proportion of acH4 positive cells than observed in the lymphoid population but a greater fold increase above basal levels. Conclusion: A new assay for detection of histone H4 acetylation in WBCs by imaging flow cytometry has been developed and optimised. The assay showed increases in acH4 positivity in both in vitro and ex vivo experiments following exposure to valproic acid. The method can be used for the measurement of acH4 as a pharmacodynamic biomarker for histone deacetylase inhibitors in drug development and monitoring of drug efficacy in clinical trials. Citation Format: Suriyon Uitrakul, Gareth James Veal, Claire Hutton, David Jamieson. Imaging flow cytometry assay development and validation for the detection of histone H4 acetylation in white blood cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2583.

Evaluation of the efficacy of valproic acid and suberoylanilide hydroxamic acid (vorinostat) in enhancing the effects of first-line tuberculosis drugs against intracellular Mycobacterium tuberculosis

BackgroundNew tuberculosis (TB) drug treatment regimens are urgently needed. This study evaluated the potential of the histone deacetylase inhibitors (HDIs) valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA) to enhance the effects of first-line anti-TB drugs against intracellular Mycobacterium tuberculosis. MethodsM. tuberculosis H37Rv cultures were exposed to VPA or SAHA over 6 days, in the presence or absence of isoniazid (INH) and rifampicin (RIF). The efficacy of VPA and SAHA against intracellular M. tuberculosis with and without INH or RIF was tested by treating infected macrophages. Bactericidal activity was assessed by counting mycobacterial colony-forming units (CFU). ResultsVPA treatment exhibited superior bactericidal activity to SAHA (2-log CFU reduction), while both HDIs moderately improved the activity of RIF against extracellular M. tuberculosis. The bactericidal effect of VPA against intracellular M. tuberculosis was greater than that of SAHA (1-log CFU reduction) and equalled that of INH (1.5-log CFU reduction). INH/RIF and VPA/SAHA combination treatment inhibited intracellular M. tuberculosis survival in a shorter time span than monotherapy (3days vs. 6 days). ConclusionsVPA and SAHA have adjunctive potential to World Health Organization-recommended TB treatment regimens. Clinical evaluation of the two drugs with regard to reducing the treatment duration and improving treatment outcomes in TB is warranted.

A Phase I/II Study Targeting Angiogenesis Using Bevacizumab Combined with Chemotherapy and a Histone Deacetylase Inhibitor (Valproic Acid) in Advanced Sarcomas.

Epigenetic events and genetic alterations under the control of the tumor microenvironment potentially mediate tumor induced angiogenesis involved in soft tissue sarcoma (STS) metastasis. Addition of antiangiogenic agent, such as bevacizumab, to standard chemotherapy in treatment of sarcoma has been studied in clinical trials, but most of the findings have not supported its use. We hypothesized the existence of an epigenetically mediated “angiogenic switch”, and the tumor microenvironment, prevents bevacizumab from truly blocking angiogenesis. The addition of valproic acid (VPA), a weak histone deacetylase inhibitor, and bevacizumab, a monoclonal antibody against vascular endothelial growth factor, together with the cytotoxic effects of gemcitabine and docetaxel, may enhance responses and alter chemoresistance. This was designed as a phase I/II trial with primary endpoints including safety of the treatment combination and tumor response. Unresectable or metastatic sarcoma patients >18 years of age, irrespective of number of prior treatments, received VPA 40 mg/kg orally for 5 days prior to day 1, bevacizumab at 15 mg/kg IV on day 1, gemcitabine 900 mg/m2 (day 1, day 8), and docetaxel 75 mg/m2 (day 8). Cycles were of 28 day duration. Bevacizumab and VPA were continued as maintenance after 6 cycles, until disease progression. A standard 3 + 3 phase I dose de-escalation design was utilized to evaluate safety. Gain of function p53 gene mutation testing was performed on available archival tissue specimens. A total of 46 patients (30 female, 16 male) with median age of 60 (range 24–81) years were enrolled; 34 (73.9%) patients received prior chemotherapy, 14 (30%) of which received prior gemcitabine and docetaxel. Patients received a median of 5.5 cycles (range 0–24 of treatment (min 0, one patient died prior to completing the first cycle; max: 24, one patient received 6 cycles and 18 maintenance cycles before progressing). Seventeen patients underwent dose reduction, of which VPA was reduced in 6 patients. Forty-one patients were evaluable for response. There was a confirmed complete response in 1 (epithelioid sarcoma), and a partial response (PR) in 6 (1 carcinosarcoma, 2 extrauterine leiomyosarcoma (LMS), 2 undifferentiated pleomorphic sarcoma, and 1 uterine LMS) patients. Stable disease (SD) was seen in 21 patients for at least 2 months. One subject with prior gemcitabine and docetaxel had PR, and 7 had SD. Median progression-free survival (PFS) was 5.7 months (95% CI: 2.1–8.0), and overall survival (OS) was 12.9 months (95% CI: 8.3–14.5). Three patients died due to tumor progression while on the study. The combination of VPA, bevacizumab, gemcitabine, and docetaxel appears to be moderately safe and well tolerated. Given that there are very limited options for patients with relapsed refractory STS, this drug combination may be an important therapy to consider. This combination treatment deserves further investigation in epithelioid and carcinosarcoma subtypes.

The Histone Deacetylase Inhibitor Valproic Acid Exerts a Synergistic Cytotoxicity with the DNA-Damaging Drug Ellipticine in Neuroblastoma Cells.

Neuroblastoma (NBL) originates from undifferentiated cells of the sympathetic nervous system. Chemotherapy is judged to be suitable for successful treatment of this disease. Here, the influence of histone deacetylase (HDAC) inhibitor valproate (VPA) combined with DNA-damaging chemotherapeutic, ellipticine, on UKF-NB-4 and SH-SY5Y neuroblastoma cells was investigated. Treatment of these cells with ellipticine in combination with VPA led to the synergism of their anticancer efficacy. The effect is more pronounced in the UKF-NB-4 cell line, the line with N-myc amplification, than in SH-SY5Y cells. This was associated with caspase-3-dependent induction of apoptosis in UKF-NB-4 cells. The increase in cytotoxicity of ellipticine in UKF-NB-4 by VPA is dictated by the sequence of drug administration; the increased cytotoxicity was seen only after either simultaneous exposure to these drugs or after pretreatment of cells with ellipticine before their treatment with VPA. The synergism of treatment of cells with VPA and ellipticine seems to be connected with increased acetylation of histones H3 and H4. Further, co-treatment of cells with ellipticine and VPA increased the formation of ellipticine-derived DNA adducts, which indicates an easier accessibility of ellipticine to DNA in cells by its co-treatment with VPA and also resulted in higher ellipticine cytotoxicity. The results are promising for in vivo studies and perhaps later for clinical studies of combined treatment of children suffering from high-risk NBL.

In Vitro Effect of the Histone Deacetylase Inhibitor Valproic Acid on Viability and Apoptosis of the PLC/PRF5 Human Hepatocellular Carcinoma Cell Line

The nucleosome is the fundamental building block of eukaryotic chromatin formed by DNA and histone proteins. Chromatin modifications such as acetylation, methylation, and phosphorylation are necessary for protection, replication, and gene transcription. Histone deacetylases (HDACs) are a group of enzymes that remove acetyl groups to re-establish positive charges on histones and aberrant deacetylation may lead to tumorigenesis in different tissues. Histone deacetylase inhibitors (HDACIs) are a class of chemotherapeutic agent that can reactivate gene expression and inhibit the growth of tumor cells by histone deacetylase inhibition. HDACI valproic acid (VPA) has shown potent anticancer effects in vitro and in vivo. Previously, we reported that VAP can inhibit the growth and induce apoptosis of human colon carcinoma HT 29 and hepatocellular carcinoma HepG 2 cells. The aim of the present study was to access the effect of VPA on proliferation and apoptosis of the human hepatocellular carcinoma (HCC) PLC/PRF5 cell line.Materials and Methods:PLC/PRF5 cells were treated with VPA and then MTT and flow cytometry assays were used to determine the effects on viability and apoptosis, respectively.Results:VPA inhibited cell growth and induced apoptosis in PLC/PRF5 cells significantly.Discussion:Our results clearly demonstrated that VPA has inhibitory and apoptotic effects.Conclusion:VPA can significantly inhibit the growth of HCC cells and play a significant role in apoptosis induction.

HDAC inhibition as a treatment concept to combat temsirolimus-resistant bladder cancer cells.

IntroductionAlthough the mechanistic target of rapamycin (mTOR) might be a promising molecular target to treat advanced bladder cancer, resistance develops under chronic exposure to an mTOR inhibitor (everolimus, temsirolimus). Based on earlier studies, we proposed that histone deacetylase (HDAC) blockade might circumvent resistance and investigated whether HDAC inhibition has an impact on growth of bladder cancer cells with acquired resistance towards temsirolimus.ResultsThe HDAC inhibitor valproic acid (VPA) significantly inhibited growth, proliferation and caused G0/G1 phase arrest in RT112res and UMUC-3res. cdk1, cyclin B, cdk2, cyclin A and Skp1 p19 were down-regulated, p27 was elevated. Akt-mTOR signaling was deactivated, whereas acetylation of histone H3 and H4 in RT112res and UMUC-3res increased in the presence of VPA. Knocking down cdk2 or cyclin A resulted in a significant growth blockade of RT112res and UMUC-3res.Materials And MethodsParental (par) and resistant (res) RT112 and UMUC-3 cells were exposed to the HDAC inhibitor VPA. Tumor cell growth, proliferation, cell cycling and expression of cell cycle regulating proteins were then evaluated. siRNA blockade was used to investigate the functional impact of the proteins.ConclusionsHDAC inhibition induced a strong response of temsirolimus-resistant bladder cancer cells. Therefore, the temsirolimus-VPA-combination might be an innovative strategy for bladder cancer treatment.