Antiproliferative action of valproate is associated with aberrant expression and nuclear translocation of cyclin D3 during the C6 glioma G1 phase

Exploring the therapeutic potential of Potentilla fragarioides var. major (Rosaceae) extract in Alzheimer's disease using in vitro and in vivo models: A multi-faceted approach

Alzheimer's disease (AD) is the most common cause of dementia and is caused by various factors including amyloid-beta (Aβ) aggregation. We investigated the pharmacological effects of the ethanol extract of Potentilla fragarioides var. major (Rosaceae) (EEPF) on AD-related pathogenesis, which remain elusive. We observed the effects of EEPF on Aβ disaggregation and free-radical scavenging activities for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) using in vitro assays, evaluated the effects of EEPF on memory loss in two animal models, and examined the molecular regulatory mechanisms of EEPF using an antibody-protein microarray in EEPF-treated neuronal cell lines. EEPF inhibited Aβ aggregation in a concentration-dependent manner and enhanced free-radical scavenging activities for ABTS and DPPH. EEPF significantly inhibited memory impairment in the passive avoidance task, Y-maze test, and Morris water maze test in scopolamine-induced short-term memory loss mice and Aβ-injected AD-like mice. Nissl staining and immunohistochemistry for NeuN and Iba-1 confirmed the neuroprotective and anti-inflammatory effects of EEPF in both animal models. In H2O2-treated HT22 hippocampal cells, EEPF significantly prevented cell damage, enhanced CaMK2, and reduced ferric reductase. In lipopolysaccharide (LPS)-stimulated BV-2 microglia, EEPF significantly inhibited LPS-induced production of inflammatory factors, such as nitric oxide, prostaglandin E2, tumor necrosis factor-α, and interleukin-6, and decreased the phosphorylation of Smad3 and cyclin D3. High-performance liquid chromatography confirmed that EEPF has five major components: neochlorogenic acid, chlorogenic acid, polydatin, isochlorogenic acid A, and buddleoside, with amounts ranging across 1.91-9.41 mg/g. EEPF may be a promising drug for treatment of AD and AD-related brain disorders.

Valproate and lithium: Old drugs for new pharmacological approaches in brain tumors?

Beyond its use as an antiepileptic drug, over time valproate has been increasingly used for several other therapeutic applications. Among these, the antineoplastic effects of valproate have been assessed in several in vitro and in vivo preclinical studies, suggesting that this agent significantly inhibits cancer cell proliferation by modulating multiple signaling pathways. During the last years various clinical trials have tried to find out if valproate co-administration could enhance the antineoplastic activity of chemotherapy in glioblastoma patients and in patients suffering from brain metastases, demonstrating that the inclusion of valproate in the therapeutic schedule causes an improved median overall survival in some studies, but not in others. Thus, the effects of the use of concomitant valproate in brain cancer patients are still controversial. Similarly, lithium has been tested as an anticancer drug in several preclinical studies mainly using the unregistered formulation of lithium chloride salts. Although, there are no data showing that the anticancer effects of lithium chloride are superimposable to the registered lithium carbonate, this formulation has shown preclinical activity in glioblastoma and hepatocellular cancers. However, few but interesting clinical trials have been performed with lithium carbonate on a very small number of cancer patients. Based on published data, valproate could represent a potential complementary therapeutic approach to enhance the anticancer activity of brain cancer standard chemotherapy. Same advantageous characteristics are less convincing for lithium carbonate. Therefore, the planning of specific phase III studies is necessary to validate the repositioning of these drugs in present and future oncological research.

Drug repositioning: Using psychotropic drugs for the treatment of glioma

Psychotropic drugs can penetrate the blood-brain barrier and regulate the levels of neurotransmitters and neuromodulators such as γ-aminobutyric acid, glutamate, serotonin, dopamine, and norepinephrine in the brain, and thus influence neuronal activity. Neuronal activity in the tumor microenvironment can promote the growth and expansion of glioma. There is increasing evidence that in addition to their use in the treatment of mental disorders, antipsychotic, antidepressant, and mood-stabilizing drugs have clinical potential for cancer therapy. These drugs have been shown to inhibit the malignant progression of glioma by targeting signaling pathways related to cell proliferation, apoptosis, or invasion/migration or by increasing the sensitivity of glioma cells to conventional chemotherapy or radiotherapy. In this review, we summarize findings from preclinical and clinical studies investigating the use of antipsychotics, antidepressants, and mood stabilizers in the treatment of various types of cancer, with a focus on glioma; and discuss their presumed antitumor mechanisms. The existing evidence indicates that psychotropic drugs with established pharmacologic and safety profiles can be repurposed as anticancer agents, thus providing new options for the treatment of glioma.

The therapeutic and neuroprotective effects of an antiepileptic drug valproic acid in glioma patients

Glioma is the most common primary malignant brain tumor in adults and the patients have poor prognosis despite treatment with surgery, radiotherapy and chemotherapy. The anti-epileptic drug, valproic acid (VPA) as a HDAC inhibitors is often used in glioma patients even if the patients don't have brain tumors associated epilepsy (BAE). Some previous studies have found that VPA not only has anti-epileptic effect, but also has anti-glioma growth effect through enhance radiotherapy sensitivity or other mechanism. Then VPA is reported to improve the survival of glioma patients receiving chemoradiation therapy. In addition, there are limited researches have shown that VPA has a neuroprotective effect in protect normal cells and tissues from the deleterious effects of treatment of glioma, especially radiotherapy. We'll give a brief overview of these effects of VPA in glioma patients.

Emerging therapeutic potential of anti-psychotic drugs in the management of human glioma: A comprehensive review

Despite numerous advancements in the last decade, human gliomas such as astrocytoma and glioblastoma multiforme have the worst prognoses among all cancers. Anti-psychotic drugs are commonly prescribed to treat mental disorders among cancer patients, and growing empirical evidence has revealed their antitumor, anti-metastatic, anti-angiogenic, anti-proliferative, chemo-preventive, and neo-adjuvant efficacies in various in vitro, in vivo, and clinical glioma models. Anti-psychotic drugs have drawn the attention of physicians and researchers owing to their beneficial effects in the prevention and treatment of gliomas. This review highlights data on the therapeutic potential of various anti-psychotic drugs as anti-proliferative, chemopreventive, and anti-angiogenic agents in various glioma models via the modulation of upstream and downstream molecular targets involved in apoptosis, autophagy, oxidative stress, inflammation, and the cell cycle in in vitro and in vivo preclinical and clinical stages among glioma patients. The ability of anti-psychotic drugs to modulate various signaling pathways and multidrug resistance-conferring proteins that enhance the efficacy of chemotherapeutic drugs with low side-effects exemplifies their great potential as neo-adjuvants and potential chemotherapeutics in single or multimodal treatment approach. Moreover, anti-psychotic drugs confer the ability to induce glioma into oligodendrocyte-like cells and neuronal-like phenotype cells with reversal of epigenetic alterations through inhibition of histone deacetylase further rationalize their use in glioma treatment. The improved understanding of anti-psychotic drugs as potential chemotherapeutic drugs or as neo-adjuvants will provide better information for their use globally as affordable, well-tolerated, and effective anticancer agents for human glioma.

An in vitro analysis of the rat C6 glioma cells to elucidate the linear alkylbenzene sulfonate induced oxidative stress and consequent G2/M phase cell cycle arrest and cellular apoptosis

Linear alkylbenzene Sulphonate (LAS) is the anionic surfactant component of globally consumed detergents. Exposure of sub-inhibitory fractions viz., 1/10th (T1), 1/5th (T2), and 1/2.5th (T3) of IC₅₀ for 48 h, of LAS (5 μM, 10 μM, and 20 μM, respectively) to viable C6 glioma cells of rat, besides imparting morphological alterations leads to gross cytotoxicity. Expression of the damaged DNA coupled with cleaved PARP (p < 0.05; p < 0.01 and p < 0.001) were recorded for T1, T2 and T3, respectively. Subsequently, the cell cycle at G2/M check point was significantly arrested (p < 0.05 for T1 and T2; p < 0.01 for T3). The flow cytometric analysis reveals the initiation of apoptosis in C6 cells as is evident by a significant increase (p < 0.01 for T1, p < 0.001 for T2, and T3) in the intake of annexin-V, the calcium dependent apoptotic phospholipid binding protein. Moreover, significantly increased reactive oxygen species (ROS) (p < 0.05; p < 0.01 and p < 0.001) after 6 h of exposure for all the three sets, registered a declining trend (P < 0.001) when T3 cells were co-treated with N-acetyl cysteine (NAC). Furthermore, the significant attenuation (p < 0.01) of expression of the cleaved PARP and a consequent decrease (p < 0.05) in the cell cycle arrest at G2/M phase after scavenging ROS induced oxidative stress by treating C6 cells with NAC clearly evinces that LAS induced apoptosis is mediated by intracellular ROS. Thus, these findings provide a tangible basis for further investigations including in vivo studies, to unravel the molecular mechanism involved in ROS mediated and LAS induced cytotoxic manifestations.

The role and possible molecular mechanism of valproic acid in the growth of MCF-7 breast cancer cells

Aim

To investigate the role of valproic acid (VPA), a class I selective histone deacetylase inhibitor, on Michigan Cancer Foundation (MCF)-7 breast cancer cells, named and explore its possible molecular mechanism.

Methods

MCF-7 cells were cultured with sodium valproate (0. 5-4.0 mmol/L) for 24 h, 48 h, and 72 h in vitro, respectively. The cell viability, apoptosis, and cell cycle were examined. The activities and protein expressions of caspase-3, caspase-8, and caspase-9 were subsequently assayed. Finally, mRNA and protein expressions of cyclin A, cyclin D1, cyclin E, and p21 were analyzed.

Results

Sodium valproate suppressed MCF-7 cell growth, induced cell apoptosis, and arrested G1 phase in a time- and concentration- dependent manner, with the relative cell viabilities decreased, cell apoptosis ratios increased, and percentage of G1 phase enhanced (P < 0.05). Increased activity of caspase-3 and caspase-9, but not caspase-8, and increased protein levels were found under sodium valproate (2.0 mmol/L, 48h). P21 was up-regulated and cyclin D1 was down-regulated at both mRNA and protein levels under sodium valproate (2.0 mmol/L, 48h)(P < 0.05), although cyclin E and cyclin A remained changed.

Conclusion

These results indicate that VPA can suppress the growth of breast cancer MCF-7 cells by inducing apoptosis and arresting G1 phase. Intrinsic apoptotic pathway is dominant for VPA-induced apoptosis. For G1 phase arrest, p21 up-regulation and down-regulation of cyclin D1 may be the main molecular mechanism.

Valproate inhibits MAP kinase signalling and cell cycle progression in S. cerevisiae

The mechanism of action of valproate (VPA), a widely prescribed short chain fatty acid with anticonvulsant and anticancer properties, remains poorly understood. Here, the yeast Saccharomyces cerevisiae was used as model to investigate the biological consequences of VPA exposure. We found that low pH strongly potentiates VPA-induced growth inhibition. Transcriptional profiling revealed that under these conditions, VPA modulates the expression of genes involved in diverse cellular processes including protein folding, cell wall organisation, sexual reproduction, and cell cycle progression. We further investigated the impact of VPA on selected processes and found that this drug: i) activates markers of the unfolded protein stress response such as Hac1 mRNA splicing; ii) modulates the cell wall integrity pathway by inhibiting the activation of the Slt2 MAP kinase, and synergizes with cell wall stressors such as micafungin and calcofluor white in preventing yeast growth; iii) prevents activation of the Kss1 and Fus3 MAP kinases of the mating pheromone pathway, which in turn abolishes cellular responses to alpha factor; and iv) blocks cell cycle progression and DNA replication. Overall, our data identify heretofore unknown biological responses to VPA in budding yeast, and highlight the broad spectrum of cellular pathways influenced by this chemical in eukaryotes.

Valproic acid enhances the efficacy of radiation therapy by protecting normal hippocampal neurons and sensitizing malignant glioblastoma cells

Neurocognitive deficits are serious sequelae that follow cranial irradiation used to treat patients with medulloblastoma and other brain neoplasms. Cranial irradiation causes apoptosis in the subgranular zone of the hippocampus leading to cognitive deficits. Valproic acid (VPA) treatment protected hippocampal neurons from radiation-induced damage in both cell culture and animal models. Radioprotection was observed in VPA-treated neuronal cells compared to cells treated with radiation alone. This protection is specific to normal neuronal cells and did not extend to cancer cells. In fact, VPA acted as a radiosensitizer in brain cancer cells. VPA treatment induced cell cycle arrest in cancer cells but not in normal neuronal cells. The level of anti-apoptotic protein Bcl-2 was increased and the pro-apoptotic protein Bax was reduced in VPA treated normal cells. VPA inhibited the activities of histone deacetylase (HDAC) and glycogen synthase kinase-3β (GSK3β), the latter of which is only inhibited in normal cells. The combination of VPA and radiation was most effective in inhibiting tumor growth in heterotopic brain tumor models. An intracranial orthotopic glioma tumor model was used to evaluate tumor growth by using dynamic contrast-enhanced magnetic resonance (DCE MRI) and mouse survival following treatment with VPA and radiation. VPA, in combination with radiation, significantly delayed tumor growth and improved mouse survival. Overall, VPA protects normal hippocampal neurons and not cancer cells from radiation-induced cytotoxicity both in vitro and in vivo. VPA treatment has the potential for attenuating neurocognitive deficits associated with cranial irradiation while enhancing the efficiency of glioma radiotherapy.

Antiepileptic drugs in patients with malignant brain tumor: beyond seizures and pharmacokinetics

In neurological malignancies, antiepileptic drugs (AEDs) are frequently used to control the seizure activity that accompanies the disorder. There is a growing body of evidence on the importance of AED selection for reasons other than pharmacokinetics (PK) properties. Epigenetic modifications may occur in glioblastomas, such as changes in gene methylation and histone acetylation states. Secondary mechanisms of AED drug action which impact these epigenetic modifications could play a significant role in patient survival outcomes. Both valproic acid (VPA) and carbamazepine have histone deacetylase (HDAC) inhibitory activities, and levetiracetam and VPA reduce the activity of O6-methylguanine-DNA methyltransferase (MGMT), a DNA-repair molecule implicated in resistance to alkylating agents used for chemotherapy. The use of AEDs for purposes other than seizure prophylaxis and their selection based on non-PK properties present a potential paradigm shift in the field of neuro-oncology.

Valproic acid sensitizes human glioma cells to gefitinib-induced autophagy

Autophagy and apoptosis represent important cellular processes involved in cancer cell killing mechanisms. Epidermal growth factor receptor inhibitor gefitinib and valproic acid have been implicated in the treatment of malignancies including glioma involving autophagic and apoptotic mechanisms. Therefore, it is interesting to investigate whether a combination of gefitinib and valproic acid shows better cancer cell killing effect on human glioma cells. We found that a nontoxic concentration of valproic acid sensitized U87 and T98G glioma cells to gefitinib cytotoxicity by inhibiting cell growth and long-term clonogenic survival. The augmented consequences were accompanied by the formation of autophagic vacuoles, conversion of microtubule-associated protein-1 light chain 3-II (LC3-II), and degradation of p62. Autophagy inhibitor 3-methyladenosine and chloroquine and genetic silencing of LC3 but not broad-spectrum caspase inhibitor attenuated gefitinib/valproic acid-induced growth inhibition. Gefitinib/valproic acid-induced autophagy was accompanied by the activation of liver kinase-B1 (LKB1)/AMP-activated protein kinase (AMPK)/ULK1. Silencing of AMPK and ULK1 suppressed gefitinib/valproic acid-induced autophagy and growth inhibition. Mechanistic studies showed that gefitinib/valproic acid increased intracellular reactive oxygen species generation and N-acetyl cysteine attenuated gefitinib/valproic acid-caused autophagy and growth inhibition. In addition to demonstrating the autophagic mechanisms of gefitinib/valproic acid, the results of this study further suggest that intracellular oxidative stress and the LKB1/AMPK signaling might be a potential target for the development of therapeutic strategy against glioma.

Histone deacetylase inhibitor valproic acid sensitizes B16F10 melanoma cells to cucurbitacin B treatment

Cucurbitacin B (CuB) is reported to have anti-proliferation effects on a variety of tumors including melanoma, and more effective regimens by combination of this agent with others are under investigation. In this study, the anti-melanoma effect of CuB as a single agent and in combination with valproic acid (VPA), an inhibitor of histone deacetylase (HDAC), was evaluated in B16F10, a mouse melanoma cell line. The results demonstrated that CuB inhibited the proliferation of the cell line in a dose-dependent manner. However, it was likely that a pro-survival compensatory response, involving the induction of autophagy and upregulation of anti-apoptotic Bcl-2 protein, was induced by CuB treatment, which might greatly decrease the cytotoxicity of this agent. Supporting this, the melanoma cells were found to be more sensitive to the combination of CuB with chloroquine, a well-known autophagy inhibitor. And CuB-induced autophagy was associated with c-Jun N-terminal kinase (JNK) activation, at least partly, since inhibition of JNK activity by SP600125 could alleviate the autophagy. When CuB was combined with VPA, the two drugs showed synergistic cytotoxicity by induction of cell apoptosis. Moreover, the multiploidization effect of CuB was also suppressed in the presence of VPA. In contrast to the transient activation of JNKs by CuB, the combination of CuB and VPA resulted in prolonged JNK activation, although at low level after 4 h. Our results demonstrated that HDAC inhibitor VPA can sensitize B16F10 cells to CuB treatment through induction of apoptotic pathway.

Interpreting clinical assays for histone deacetylase inhibitors

As opposed to genetics, dealing with gene expressions by direct DNA sequence modifications, the term epigenetics applies to all the external influences that target the chromatin structure of cells with impact on gene expression unrelated to the sequence coding of DNA itself. In normal cells, epigenetics modulates gene expression through all development steps. When "imprinted" early by the environment, epigenetic changes influence the organism at an early stage and can be transmitted to the progeny. Together with DNA sequence alterations, DNA aberrant cytosine methylation and microRNA deregulation, epigenetic modifications participate in the malignant transformation of cells. Their reversible nature has led to the emergence of the promising field of epigenetic therapy. The efforts made to inhibit in particular the epigenetic enzyme family called histone deacetylases (HDACs) are described. HDAC inhibitors (HDACi) have been proposed as a viable clinical therapeutic approach for the treatment of leukemia and solid tumors, but also to a lesser degree for noncancerous diseases. Three epigenetic drugs are already arriving at the patient's bedside, and more than 100 clinical assays for HDACi are registered on the National Cancer Institute website. They explore the eventual additive benefits of combined therapies. In the context of the pleiotropic effects of HDAC isoforms, more specific HDACi and more informative screening tests are being developed for the benefit of the patients.

Histone modification therapy of cancer

The state of modification of histone tails plays an important role in defining the accessibility of DNA for the transcription machinery and other regulatory factors. It has been extensively demonstrated that the posttranslational modifications of the histone tails, as well as modifications within the nucleosome domain, regulate the level of chromatin condensation and are therefore important in regulating gene expression and other nuclear events. Together with DNA methylation, they constitute the most relevant level of epigenetic regulation of cell functions. Histone modifications are carried out by a multipart network of macromolecular complexes endowed with enzymatic, regulatory, and recognition domains. Not surprisingly, epigenetic alterations caused by aberrant activity of these enzymes are linked to the establishment and maintenance of the cancer phenotype and, importantly, are potentially reversible, since they do not involve genetic mutations in the underlying DNA sequence. Histone modification therapy of cancer is based on the generation of drugs able to interfere with the activity of enzymes involved in histone modifications: new drugs have recently been approved for use in cancer patients, clinically validating this strategy. Unfortunately, however, clinical responses are not always consistent and do not parallel closely the results observed in preclinical models. Here, we present a brief overview of the deregulation of chromatin-associated enzymatic activities in cancer cells and of the main results achieved by histone modification therapeutic approaches.

Beta1,4-galactosyltransferase V A growth regulator in glioma

One of the most prominent transformation-associated changes in the sugar chains of glycoproteins is an increase in the large N-glycans of cell surface glycoprotein. beta1,4-galactosyltransferase V (beta1,4GalT V) could effectively galactosylate the GlcNAcbeta1-->6 branch which is a marker of glioma. The expression of beta1,4GalT V is increased in the process of glioma development. beta1,4GalT V regulates the invasion, growth in vivo and in vitro of glioma cells. Downregulation of beta1,4GalT V expression increases the sensitivity of malignant glioma cells to DNA damage drugs. Furthermore, beta1,4GalT V regulates Ras and AKT signaling involving in glioma behaviors. Meanwhile, Ras/MAPK and PI3K/AKT signaling pathways are involved in the transcription regulation of beta1,4GalT V gene. E1AF transcription factor, a downstream target of Ras/MAPK and PI3K/AKT signaling pathways, regulates the transcription of beta1,4GalT V in cooperation with Sp1 transcription factor. The contribution of beta1,4GalT V in glioma development is further confirmed in glioma-initiation cells. beta1,4GalT V regulates the self-renewal of glioma-initiation cells. We now present evidence that beta1,4GalT V functions as a positive growth regulator in glioma and might represent a novel target in glioma therapy.

Epigenetic therapy of leukemia: An update

Carcinogenesis is classically thought to result from genetic alterations in DNA sequence such as deletions, mutations, or chromosomal translocations. These in turn may lead to the activation of oncogenes, inactivation of tumor suppressor genes or formation of chimeric oncoproteins. Epigenetics, in contrast, refers to a number of biochemical modifications of chromatin, either to DNA directly or to its associated protein complexes that affect gene expression without altering the primary sequence of DNA [Robertson KD, Wolffe AP. DNA methylation in health and disease. Nat Rev Genet 2000;1:11-9; Jones PA, Baylin SB. The epigenomics of cancer. Cell. 2007;128:683-92]. A fundamental difference between genetic and epigenetic alterations is the irreversible nature of genetic lesions whereas epigenetic ones are potentially reversible, allowing for therapeutic intervention. In the last decade, it has become apparent that epigenetic changes play an important role in cancer, particularly in leukemia. Significant advances have been made in the elucidation of these processes as well as in translating this knowledge to the clinic, as in the development of new prognostic biomarkers or targeted therapies. In this review, we will focus on recent advances in epigenetic therapy in leukemia.

Valproic acid induces differentiation and inhibition of proliferation in neural progenitor cells via the beta-catenin-Ras-ERK-p21Cip/WAF1 pathway

Background

Valproic acid (VPA), a commonly used mood stabilizer that promotes neuronal differentiation, regulates multiple signaling pathways involving extracellular signal-regulated kinase (ERK) and glycogen synthase kinase3β (GSK3β). However, the mechanism by which VPA promotes differentiation is not understood.

Results

We report here that 1 mM VPA simultaneously induces differentiation and reduces proliferation of basic fibroblast growth factor (bFGF)-treated embryonic day 14 (E14) rat cerebral cortex neural progenitor cells (NPCs). The effects of VPA on the regulation of differentiation and inhibition of proliferation occur via the ERK-p21^Cip/WAF1 pathway. These effects, however, are not mediated by the pathway involving the epidermal growth factor receptor (EGFR) but via the pathway which stabilizes Ras through β-catenin signaling. Stimulation of differentiation and inhibition of proliferation in NPCs by VPA occur independently and the β-catenin-Ras-ERK-p21^Cip/WAF1 pathway is involved in both processes. The independent regulation of differentiation and proliferation in NPCs by VPA was also demonstrated in vivo in the cerebral cortex of developing rat embryos.

Conclusion

We propose that this mechanism of VPA action may contribute to an explanation of its anti-tumor and neuroprotective effects, as well as elucidate its role in the independent regulation of differentiation and inhibition of proliferation in the cerebral cortex of developing rat embryos.

The histone deacetylase inhibitor valproic acid alters growth properties of renal cell carcinoma in vitro and in vivo

Histone deacetylase (HDAC) inhibitors represent a promising class of antineoplastic agents which affect tumour growth, differentiation and invasion. The effects of the HDAC inhibitor valproic acid (VPA) were tested in vitro and in vivo on pre-clinical renal cell carcinoma (RCC) models. Caki-1, KTC-26 or A498 cells were treated with various concentrations of VPA during in vitro cell proliferation 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and to evaluate cell cycle manipulation. In vivo tumour growth was conducted in subcutaneous xenograft mouse models. The anti-tumoural potential of VPA combined with low-dosed interferon-alpha (IFN-alpha) was also investigated. VPA significantly and dose-dependently up-regulated histones H3 and H4 acetylation and caused growth arrest in RCC cells. VPA altered cell cycle regulating proteins, in particular CDK2, cyclin B, cyclin D3, p21 and Rb. In vivo, VPA significantly inhibited the growth of Caki-1 in subcutaneous xenografts, accompanied by a strong accumulation of p21 and bax in tissue specimens of VPA-treated animals. VPA-IFN-alpha combination markedly enhanced the effects of VPA monotherapy on RCC proliferation in vitro, but did not further enhance the anti-tumoural potential of VPA in vivo. VPA was found to have profound effects on RCC cell growth, lending support to the initiation of clinical testing of VPA for treating advanced RCC.

Valproic acid for the treatment of myeloid malignancies

Valproic acid (VPA) has been used as an anticonvulsant for decades. Recently, it was demonstrated that VPA also acts as a histone deacetylase inhibitor and induces differentiation and apoptosis in a variety of malignant cells in vitro. The effect of VPA on tumor cells differs according to cell type, degree of differentiation, and underlying genetic alterations. Clinical trials with VPA have focused on acute myeloid leukemia and the myelodysplastic syndromes. When it was used as monotherapy or in combination with all-trans retinoic acid, which synergizes in vitro, VPA achieved hematologic improvement in a subset of patients. Similar to other inhibitors of histone deacetylases, complete or partial remissions rarely were observed. In this report, the authors reviewed the in vitro and in vivo data obtained with VPA, and they considered possible combination regimens aimed at improving therapeutic efficacy.

O6-methylguanine-DNA methyltransferase is downregulated in transformed astrocyte cells: implications for anti-glioma therapies

Background

A novel alkylating agent, temozolomide, has proven efficacious in the treatment of malignant gliomas. However, expression of O⁶-methylguanine-DNA methyltransferase (MGMT) renders glioma cells resistant to the treatment, indicating that identification of mechanisms underlying the gene regulation of MGMT is highly required. Although glioma-derived cell lines have been widely employed to understand such mechanisms, those models harbor numerous unidentified genetic lesions specific for individual cell lines, which complicates the study of specific molecules and pathways.

Results

We established glioma models by transforming normal human astrocyte cells via retroviral-mediated gene transfer of defined genetic elements and found that MGMT was downregulated in the transformed cells. Interestingly, inhibitors of DNA methylation and histone deacetylation failed to increase MGMT protein levels in the transformed astrocyte cells as well as cultured glioblastoma cell lines, whereas the treatment partially restored mRNA levels. These observations suggest that downregulation of MGMT may depend largely on cellular factors other than promoter-hypermethylation of MGMT genes, which is being used in the clinic to nominate patients for temozolomide treatment. Furthermore, we discovered that Valproic acid, one of histone deacetylase inhibitors, suppressed growth of the transformed astrocyte cells without increasing MGMT protein, suggesting that such epigenetic compounds may be used to some types of gliomas in combination with alkylating agents.

Conclusion

Normal human astrocyte cells allow us to generate experimental models of human gliomas by direct manipulation with defined genetic elements, in contrast to tumor-derived cell lines which harbor numerous unknown genetic abnormalities. Thus, we propose that the study using the transformed astrocyte cells would be useful for identifying the mechanisms underlying MGMT regulation in tumor and for the development of rational drug combination in glioma therapies.

Histone deacetylase inhibitors trichostatin A and valproic acid induce cell cycle arrest and p21 expression in immortalized human endometrial stromal cells

OBJECTIVE

Following our observation that histone deacetylase inhibitors (HDACIs) trichostatin A (TSA) and valproic acid (VPA) can suppress proliferation of endometrial stromal cells, we sought to determine whether TSA and VPA do so by inducing cell cycle arrest and p21 expression.

STUDY DESIGN

A recently established immortalized endometrial stromal cell line was treated with TSA, VPA, and/or all-trans retinoic acid (ATRA) and the consequent cell cycle progression was measured by flow cytometry and p21 protein expression by Western blot analysis.

RESULTS

Both TSA and VPA induced cell cycle arrest and p21 expression in a concentration-dependent manner. Treatment with ATRA alone also induced cell cycle arrest and moderate increase in p21 expression but joint treatment of ATRA and TSA/VPA did not further enhance cell cycle arrest as compared with TSA/VPA treatment alone.

CONCLUSIONS

HDACIs suppress proliferation of endometrial stromal cells through induction of cell cycle arrest and possibly also through apoptosis as well. RA also induces cell cycle arrest but it does not synergize with HDACIs in inducing cell cycle arrest. HDACIs may be promising compounds for treating endometriosis.

The histone deacetylase (HDAC) inhibitor valproic acid as monotherapy or in combination with all-trans retinoic acid in patients with acute myeloid leukemia

BACKGROUND

Valproic acid (VPA) inhibits histone deacetylase activity and, synergizing with all-trans retinoic acid (ATRA), achieves differentiation induction of myeloid blast cells in vitro.

METHODS

We used VPA in 58 patients with acute myeloid leukemia (AML) who were too old and/or medically unfit to receive intensive chemotherapy (32 AML secondary to myelodysplastic syndrome [MDS], 22 de novo AML, 4 AML secondary to myeloproliferative syndrome). VPA serum concentrations were 50-100 mug/mL. Thirty-one patients received VPA monotherapy. ATRA was added later in 13 patients who did not respond or who relapsed. Another 27 patients received VPA plus ATRA from the start. Median treatment duration was 93 days for VPA and 88 days for ATRA.

RESULTS

The response rate was only 5% according to International Working Group (IWG) criteria for AML but was 16% when IWG response criteria for MDS were used, which capture hematologic improvement and stabilization of the disease. These endpoints, which are not necessarily correlated with diminishing blast counts, are relevant for the patients' quality of life. Among 23 patients with a peripheral blast count > 5%, 6 (26%) showed a diminishing blast count, and 5 of these had a complete peripheral blast clearance.

CONCLUSIONS

Future trials should combine VPA with chemotherapy or demethylating agents.

Valproic acid induces growth arrest, apoptosis, and senescence in medulloblastomas by increasing histone hyperacetylation and regulating expression of p21Cip1, CDK4, and CMYC

Valproic acid is a well-tolerated anticonvulsant that has been identified recently as a histone deacetylase inhibitor. To evaluate the antitumor efficacy and mechanisms of action of valproic acid in medulloblastoma and supratentorial primitive neuroectodermal tumor (sPNET), which are among the most common malignant brain tumors in children with poor prognosis, two medulloblastoma (DAOY and D283-MED) and one sPNET (PFSK) cell lines were treated with valproic acid and evaluated with a panel of in vitro and in vivo assays. Our results showed that valproic acid, at clinically safe concentrations (0.6 and 1 mmol/L), induced potent growth inhibition, cell cycle arrest, apoptosis, senescence, and differentiation and suppressed colony-forming efficiency and tumorigenicity in a time- and dose-dependent manner. The medulloblastoma cell lines were more responsive than the sPNET cell line and can be induced to irreversible suppression of proliferation and significantly reduced tumorigenicity by 0.6 and 1 mmol/L valproic acid. Daily i.p. injection of valproic acid (400 mg/kg) for 28 days significantly inhibited the in vivo growth of DAOY and D283-MED s.c. xenografts in severe combined immunodeficient mice. With Western hybridization and real-time reverse transcription-PCR, we further showed that the antitumor activities of valproic acid correlated with induction of histone (H3 and H4) hyperacetylation, activation of p21, and suppression of TP53, CDK4, and CMYC expression. In conclusion, valproic acid possesses potent in vitro and in vivo antimedulloblastoma activities that correlated with induction of histone hyperacetylation and regulation of pathways critical for maintaining growth inhibition and cell cycle arrest. Therefore, valproic acid may represent a novel therapeutic option in medulloblastoma treatment.

Beta1,4-galactosyltransferase V functions as a positive growth regulator in glioma

beta1,4-galactosyltransferase V (GalT V; EC 2.4.1.38) can effectively galactosylate the GlcNAcbeta1-->6Man arm of the highly branched N-glycans that are characteristic of glioma. Previously, we have reported that the expression of GalT V is increased in the process of glioma. However, currently little is known about the role of GalT V in this process. In this study, the ectopic expression of GalT V could promote the invasion and survival of glioma cells and transformed astrocytes. Furthermore, decreasing the expression of GalT V in glioma cells promoted apoptosis, inhibited the invasion and migration and the ability of tumor formation in vivo, and reduced the activation of AKT. In addition, the activity of GalT V promoter could be induced by epidermal growth factor, dominant active Ras, ERK1, JNK1, and constitutively active AKT. Taken together, our results suggest that GalT V functioned as a novel glioma growth activator and might represent a novel target in glioma therapy.

Valproate activates bovine leukemia virus gene expression, triggers apoptosis, and induces leukemia/lymphoma regression in vivo

Leukemogenic viruses like human T-lymphotropic virus and bovine leukemia virus (BLV) presumably persist in the host partly by latent integration of the provirus in a fraction of infected cells, leading to accumulative increase in the outgrowth of transformed cells. Furthermore, viral infection also correlates with a blockade of the apoptotic mechanisms concomitant with an apparent latency of the host cell. Conceptually, induction of viral or cellular gene expression could thus also be used as a therapeutic strategy against retroviral-associated leukemia. Here, we provide evidence that valproate, an inhibitor of deacetylases, activates BLV gene expression in transient transfection experiments and in short-term cultures of primary B-lymphocytes. In vivo, valproate injection into newly BLV-inoculated sheep did not abrogate primary infection. However, valproate treatment, in the absence of any other cytotoxic drug, was efficient for leukemia/lymphoma therapy in the sheep model leading to decreased lymphocyte numbers (respectively from 25.6, 35.7, and 46.5 x 10(3) cells per mm3 to 1.0, 10.6, and 24.3 x 10(3) cells per mm3 in three leukemic sheep) and tumor regression (from >700 cm3 to undetectable). The concept of a therapy that targets the expression of viral and cellular genes might be a promising treatment of adult T cell leukemia or tropical spastic paraparesis/human T-lymphotropic virus-associated myelopathy, diseases for which no satisfactory treatment exists so far.

Valproic acid, in combination with all-trans retinoic acid and 5-aza-2'-deoxycytidine, restores expression of silenced RARbeta2 in breast cancer cells

Epigenetic silencing of tumor suppressor genes has been established as an important process of carcinogenesis. The retinoic acid (RA) receptor beta2 (RARbeta2) gene is one such tumor suppressor gene often silenced during carcinogenesis. The combined use of histone deacetylase and DNA methyltransferase inhibitors has been shown to reverse the epigenetic silencing of numerous growth regulatory genes. Valproic acid (VPA), which has long been used in the treatment of epilepsy, was shown recently to be an effective histone deacetylase inhibitor that can induce differentiation of neoplastically transformed cells. In this study, we show for the first time that VPA, in combination with RA and the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (Aza-dC), can overcome the epigenetic barriers to transcription of a prototypical silenced tumor suppressor gene, RARbeta2, in human breast cancer cells. Chromatin immunoprecipitation assays show that the combination of VPA, RA, and Aza-dC increases histone acetylation at the silenced RARbeta2 promoter of MCF-7 breast cancer cells. Furthermore, reverse transcription-PCR analyses reveal cell type-specific effects in the actions of VPA on RARbeta2 expression in cultured human breast cancer cells. Finally, we show that VPA, in combination with RA and Aza-dC, inhibits the proliferation of both estrogen receptor alpha-positive (MCF-7) and estrogen receptor alpha-negative (MDA-MB-231) breast cancer cell lines. These data suggest that VPA may ultimately be useful in combination therapies in the treatment of human breast cancers.

Expression of Rb2/p130 protein correlates with the degree of malignancy in gliomas

It has been reported that there is an inverse correlation between the immunohistochemical expression of Rb2/p130, a member of the retinoblastoma gene family, and the degree of malignancy in at least some histological types. In order to investigate the expression of this protein in gliomas, we evaluated 58 samples from patients with resected gliomas. We focused on the relationship between the degree of malignancy of the glioma and the immunohistochemical detection of Rb2/p130. Expression of Rb2/p130 was observed in 38 glioma specimens (65.5%), including a high expression level in low-grade glioma specimens (> 30% positive cells in 84% of tumors) and a low expression level in high-grade glioma specimens (> 30% positive cells in 12% of tumors). The most aggressive of the gliomas exhibited very low to undetectable levels of Rb2/p130. Moreover, we observed an inverse correlation between Rb2/p130 expression and the degree of malignancy. These findings suggest that the differentiation of gliomas might be partially mediated by the Rb2/p130 gene, and that Rb2/ p130 expression can additionally be an indicator of a better prognosis in patients with gliomas.

Valproate activates phosphodiesterase-mediated cAMP degradation: relevance to C6 glioma G1 phase progression

Forskolin, a diterpene activator of adenylate cyclase, stimulates the production of cyclic adenosine monophosphate (cAMP) in a wide variety of cell types. In C6 glioma, used in this study, the anticonvulsant agent valproic acid (VPA) inhibited forskolin-stimulated cAMP accumulation in intact cells in a concentration-dependent manner. Kinetic studies indicated this valproate effect not to be mediated by direct inhibition of adenylate cyclase activity. The valproate-induced inhibition of cAMP accumulation was partially reversed by the phosphodiesterase (PDE) inhibitor isobutylmethyl xanthine (IBMX). Degradation of cAMP over time was more rapid in valproate-treated cells than in controls, and this effect was also reversed by IBMX. In synchronised C6 glioma, phosphodiesterase type IV (PDE4A1) expression was selectively upregulated during the G1 phase, in tandem with temporal biphasic peaks of cAMP. However, the expression of PDE4 isoforms was not affected by a 48-h exposure to valproate. These findings suggest inhibition of forskolin-stimulated cAMP levels in C6 glioma by valproate to be mediated by increased activation of PDE in the G1 phase. Since the degree of cell cycle arrest induced by valproate is intimately associated with its teratogenic potency, it appears that PDE-mediated inhibition of cAMP may contribute to the molecular mechanisms of valproate-induced teratogenicity.

Structural Effects and Neurofunctional Sequelae of Developmental Exposure to Psychotherapeutic Drugs: Experimental and Clinical Aspects

The advent of psychotherapeutic drugs has enabled management of mental illness and other neurological problems such as epilepsy in the general population, without requiring hospitalization. The success of these drugs in controlling symptoms has led to their widespread use in the vulnerable population of pregnant women as well, where the potential embryotoxicity of the drugs has to be weighed against the potential problems of the maternal neurological state. This review focuses on the developmental toxicity and neurotoxicity of five broad categories of widely available psychotherapeutic drugs: the neuroleptics, the antiepileptics, the antidepressants, the anxiolytics and mood stabilizers, and a newly emerging class of nonprescription drugs, the herbal remedies. A brief review of nervous system development during gestation and following parturition in mammals is provided, with a description of the development of neurochemical pathways that may be involved in the action of the psychotherapeutic agents. A thorough discussion of animal research and human clinical studies is used to determine the risk associated with the use of each drug category. The potential risks to the fetus, as demonstrated in well described neurotoxicity studies in animals, are contrasted with the often negative findings in the still limited human studies. The potential risk fo the human fetus in the continued use of these chemicals without more adequate research is also addressed. The direction of future research using psychotherapeutic drugs should more closely parallel the methodology developed in the animal laboratories, especially since these models have already been used extremely successfully in specific instances in the investigation of neurotoxic agents.

Differential enantioselective effects of pentyl-4-yn-valproate on spatial learning in the rat, and neurite outgrowth and cyclin D3 expression in vitro

Previously, we demonstrated the racemic form of the valproate (VPA) analogue, 2-n-pentyl-4-pentynoic acid ([+/-]pentyl-4-yn-VPA), to be neuritogenic in vitro and to enhance cognition in vivo. To determine the enantioselectivity of these effects, the racemate and purified enantiomers of [+/-]pentyl-4-yn-VPA (84 mg/kg, i.p.) were administered to rodents 20 min prior to multi-session water maze training. The racemate and R-enantiomer significantly reduced escape latencies during water maze learning and enhanced its recall in a probe trial 3 days later. In contrast, S-pentyl-4-yn-VPA did not influence these behavioural parameters. The enantiomer-specific effects of [+/-]pentyl-4-yn-VPA were further discriminated in vitro using neuro 2A neuroblastoma and C6 glioma cell lines. In neuro 2A, the S-enantiomer induced profound neurite outgrowth at concentrations up to 0.5 mm, with the R-enantiomer and racemate being less neuritogenic. Immunoblot analysis of cyclin D3 expression in C6 glioma indicated the racemate and S-pentyl-4-yn-VPA to induce dose-dependent up-regulation of this protein, similar to that associated with G1-phase cell cycle arrest mediated by VPA, whereas R-pentyl-4-yn-VPA was without effect. These results indicate that the cognition-enhancing effects of pentyl-4-yn-VPA are due to the actions of the R-enantiomer, and that cyclin D3 up-regulation and associated anti-proliferative and pro-differentiative actions are predominantly associated with the S-enantiomer.

Antiproliferative action of neomycin is associated with inhibition of cyclin D1 activation in glioma cells

The progression of mammalian cells through G1 phase of the cell cycle is governed by the D-type cyclins (D1, D2, D3). These proteins are induced at the beginning of the G1 phase and associate with serine/threonine cyclin-dependent kinases to form holoenzymes. Overexpression of cyclin D1 in human cancers as well as in several cancer cell lines has been reported. Here, we employed mitotic selection to synchronize the C6 glioma cell cycle at the start of the G1 phase and assessed the effects of neomycin on cyclin D1 protein detection by immunocytochemical analysis. Cyclin D1 activation as well as cell proliferation were already significantly reduced after 3 h of incubation of the cells with neomycin. These findings suggested that the antiproliferative effects of neomycin in gliomas could be mediated by inhibition of the expression of cyclin D1 gene and support further consideration of therapeutic use of neomycin in a Phase I clinical study for patients with recurrent glioblastoma.

Valproic acid inhibits substance P-induced activation of protein kinase C epsilon and expression of the substance P receptor

The neuropeptide substance P (SP) has been hypothesized to be involved in the etiopathology of affective disorders. This hypothesis is based on the findings that neurokinin-1-receptor antagonists have antidepressant effects in depressed patients and that SP may worsen mood. In this study, we investigated the effect of the mood-stabilizing agents valproic acid (VPA), carbamazepine, and lithium on SP-induced gene expression. As a model system, we used primary rat astrocytes and human astrocytoma cells, which both express functional SP-receptors and, upon stimulation with SP, synthesize interleukin-6 (IL-6), a cytokine which has been shown to be elevated during the acute depressive state. We found that VPA dose-dependently inhibited SP-induced IL-6 synthesis which was seen with pre-incubation periods of 30 min, 3, 7 and 14 days, whereas carbamazepine and lithium showed no inhibitory effect. The inhibitory effect of VPA was not mediated by inhibition of the stress-regulated kinases p38 and p42/44 (Erk1/2) but by inhibition of protein kinase C epsilon activation. Furthermore, VPA down-regulated the expression of the substance P receptor (neurokinin(NK)-1-receptor) as assessed by real-time PCR. Whether both mechanisms contribute to the mood-stabilizing properties of VPA has to be evaluated in further studies.