Valproic acid as epigenetic cancer drug: preclinical, clinical and transcriptional effects on solid tumors

Histone deacetylation inhibition in pulmonary hypertension: therapeutic potential of valproic acid and suberoylanilide hydroxamic acid

BACKGROUND

Epigenetic programming, dynamically regulated by histone acetylation, is a key mechanism regulating cell proliferation and survival. Little is known about the contribution of histone deacetylase (HDAC) activity to the development of pulmonary arterial hypertension, a condition characterized by profound structural remodeling of pulmonary arteries and arterioles.

METHODS AND RESULTS

HDAC1 and HDAC5 protein levels were elevated in lungs from human idiopathic pulmonary arterial hypertension and in lungs and right ventricles from rats exposed to hypoxia. Immunohistochemistry localized increased expression to remodeled vessels in the lung. Both valproic acid, a class I HDAC inhibitor, and suberoylanilide hydroxamic acid (vorinostat), an inhibitor of class I, II, and IV HDACs, mitigated the development of and reduced established hypoxia-induced pulmonary hypertension in the rat. Both valproic acid and suberoylanilide hydroxamic acid inhibited the imprinted highly proliferative phenotype of fibroblasts and R-cells from pulmonary hypertensive bovine vessels and platelet-derived growth factor-stimulated growth of human vascular smooth muscle cells in culture. Exposure to valproic acid and suberoylanilide hydroxamic acid was associated with increased levels of p21 and FOXO3 and reduced expression of survivin. The significantly higher levels of expression of cKIT, monocyte chemoattractant protein-1, interleukin-6, stromal-derived factor-1, platelet-derived growth factor-b, and S100A4 in R-cells were downregulated by valproic acid and suberoylanilide hydroxamic acid treatment.

CONCLUSIONS

Increased HDAC activity contributes to the vascular pathology of pulmonary hypertension. The effectiveness of HDAC inhibitors, valproic acid, and suberoylanilide hydroxamic acid, in models of pulmonary arterial hypertension supports a therapeutic strategy based on HDAC inhibition in pulmonary arterial hypertension.

DNA methylation-based biomarkers in serum of patients with breast cancer

Alterations of genetic and epigenetic features can provide important insights into the natural history of breast cancer. Although DNA methylation analysis is a rapidly developing field, a reproducible epigenetic blood-based assay for diagnosis and follow-up of breast cancer has yet to be successfully developed into a routine clinical test. The aim of this study was to review multiple serum DNA methylation assays and to highlight the value of those novel biomarkers in diagnosis, prognosis and prediction of therapeutic outcome. Serum is readily accessible for molecular diagnosis in all individuals from a peripheral blood sample. The list of hypermethylated genes in breast cancer is heterogeneous and no single gene is methylated in all breast cancer types. There is increasing evidence that a panel of epigenetic markers is essential to achieve a higher sensitivity and specificity in breast cancer detection. However, the reported percentages of methylation are highly variable, which can be partly explained by the different sensitivities and the different intra-/inter-assay coefficients of variability of the analysis methods. Moreover, there is a striking lack of receiver operating characteristic (ROC) curves of the proposed biomarkers. Another point of criticism is the fact that 'normal' patterns of DNA methylation of some tumor suppressor and other cancer-related genes are influenced by several factors and are often poorly characterized. A relatively frequent methylation of those genes has been observed in high-risk asymptomatic women. Finally, there is a call for larger prospective cohort studies to determine methylation patterns during treatment and follow-up. Identification of patterns specific for a differential response to therapeutic interventions should be useful. Only in this way, it will be possible to evaluate the predictive and prognostic characteristics of those novel promising biomarkers.

Valproic acid downregulates the expression of MGMT and sensitizes temozolomide-resistant glioma cells

Temozolomide (TMZ) has become a key therapeutic agent in patients with malignant gliomas; however, its survival benefit remains unsatisfactory. Valproic acid (VPA) has emerged as an anticancer drug via inhibition of histone deacetylases (HDACs), but the therapeutic advantages of a combination with VPA and TMZ remain poorly understood. The main aim of the present study was to determine whether an antitumor effect could be potentiated by a combination of VPA and TMZ, especially in TMZ-resistant cell lines. A combination of VPA and TMZ had a significantly enhanced antitumor effect in TMZ-resistant malignant glioma cells (T98 and U138). This enhanced antitumor effect correlated with VPA-mediated reduced O6-methylguanine-DNA methyltransferase (MGMT) expression, which plays an important role in cellular resistance to alkylating agents. In vitro, the combination of these drugs enhanced the apoptotic and autophagic cell death, as well as suppressed the migratory activities in TMZ-resistant cell lines. Furthermore, in vivo efficacy experiment showed that treatment of combination of VPA and TMZ significantly inhibited tumor growth compared with the monotherapy groups of mice. These results suggest that the clinical efficacy of TMZ chemotherapy in TMZ-resistant malignant glioma may be improved by combination with VPA.

Valproic acid increases susceptibility to endotoxin shock through enhanced release of high-mobility group box 1

High-mobility group box 1 (HMGB1) is a nuclear factor and a secreted protein. During inflammation, HMGB1 is secreted into the extracellular space where it can interact with the receptor for advanced glycation end products and trigger proinflammatory signals. Extracellular HMGB1 plays a critical role in several inflammatory diseases such as sepsis and rheumatoid arthritis. Valproic acid (VPA) is one of the most frequently prescribed antiepileptic drugs. The present study was undertaken to investigate the effect of VPA on secretion of HMGB1 in systemic inflammatory responses induced by lipopolysaccharide. Pretreatment with VPA increased the susceptibility of mice to lipopolysaccharide in endotoxemia. Valproic acid induced HMGB1 release and nuclear factor κB activation in RAW-blue cells. Valproic acid promoted the phosphorylation of ERK1/2 but not that of p38 or JNK. The MEK1/2 inhibitor PD98059 also suppressed HMGB1 release and activation of nuclear factor κB induced by VPA. Valproic acid induced expression of γ-aminobutyric acid receptors in macrophages, and picrotoxin, a γ-aminobutyric acid A receptor antagonist, inhibited the VPA-activated phosphorylation of ERK and VPA-induced HMGB1 release. These results suggest that VPA may exacerbate innate immune responses to endotoxin through enhanced release of HMGB1.

Developmental plasticity and epigenetic mechanisms underpinning metabolic and cardiovascular diseases

The importance of developmental factors in influencing the risk of later-life disease has a strong evidence base derived from multiple epidemiological, clinical and experimental studies in animals and humans. During early life, an organism is able to adjust its phenotypic development in response to environmental cues. Such developmentally plastic responses evolved as a fitness-maximizing strategy to cope with variable environments. There are now increasing data that these responses are, at least partially, underpinned by epigenetic mechanisms. A mismatch between the early and later-life environments may lead to inappropriate early life-course epigenomic changes that manifest in later life as increased vulnerability to disease. There is also growing evidence for the transgenerational transmission of epigenetic marks. This article reviews the evidence that susceptibility to metabolic and cardiovascular disease in humans is linked to changes in epigenetic marks induced by early-life environmental cues, and discusses the clinical, public health and therapeutic implications that arise.

Valproic acid affected the survival and invasiveness of human glioma cells through diverse mechanisms

The effects of valproic acid (VPA) on the viability, apoptosis, and invasiveness of two glioma cells (A172 and T98G) and the underlying mechanisms were studied. VPA induced cytotoxicity and apoptosis, and suppressed the invasiveness of both cells. VPA increased the activity of matrix metalloproteinase-2 (MMP-2) and MMP-9 in A172 cells, but decreased it in T98G cells. siRNA blockade of reversion-inducing cysteine-rich protein with Kazal motifs (RECK) expression partially reversed VPA-mediated effects in T98G cells, but had no effect on A172 cells. VPA increased the expression of phospho-JNK1 and phospho-ERK1/2 in A172 cells, but decreased it in T98G cells. Inhibition of JNK1 and/or ERK1/2 partially reversed the VPA effects in A172 cells. In conclusion, the effects of VPA (loss of viability, increased apoptosis, and decreased invasiveness) are, at least partly, mediated through the RECK-MMPs pathway in T98G cells and the mitogen-activated protein kinase pathways in A172 cells. The action of VPA seems to be cell type-specific in glioma cells.

Valproic acid enhances anti-tumor effect of mesenchymal stem cell mediated HSV-TK gene therapy in intracranial glioma

Suicide gene therapy of glioma based on herpes simplex virus type I thymidine kinase (HSV-TK) and prodrug ganciclovir (GCV) suffers from the lack of efficacy in clinical trials, which is mostly due to low transduction efficacy and absence of bystander effect in tumor cells. Recently, stem cells as cellular delivery vehicles of prodrug converting gene has emerged as a new treatment strategy for malignant glioma. In this study, we evaluated the anti-glioma effect of suicide gene therapy using human bone marrow mesenchymal stem cells expressing HSV-TK (MSCs-TK) combined with valproic acid (VPA), which can upregulate the gap junction proteins and may enhance the bystander effect of suicide gene therapy. Expression of HSV-TK in MSCs was confirmed by RT-PCR analysis and the sensitivity of MSCs-TK to GCV was assessed. A bystander effect was observed in co-cultures of MSCs-TK and U87 glioma cells by GCV in a dose-dependent manner. VPA induced the expression of the gap junction proteins connexin (Cx) 43 and 26 in glioma cell and thereby enhanced the bystander effect in co-culture experiment. The enhanced bystander effect was inhibited by the gap junction inhibitor 18-β-glycyrrhetinic acid (18-GA). Moreover, the combined treatment with VPA and MSCs-TK synergistically enhanced apoptosis in glioma cells by caspase activation. In vivo efficacy experiments showed that combination treatment of MSCs-TK and VPA significantly inhibited tumor growth and prolonged the survival of glioma-bearing mice compared with single-treatment groups. In addition, TUNEL staining also demonstrated a significant increase in the number of apoptotic cells in the combination treated group compared with single-treatment groups. Taken together, these results provide the rational for designing novel experimental protocols to increase bystander killing effect against intracranial gliomas using MSCs-TK and VPA.

Epigenetic therapy with hydralazine and magnesium valproate reverses imatinib resistance in patients with chronic myeloid leukemia

The epigenetic drugs hydralazine and valproate were administered in a compassionate manner to 8 patients with chronic myeloid leukemia (CML) refractory to imatinib. Two patients had a complete hematologic response (25%),1 major cytogenetic response, 1 complete cytogenetic response (25% any cytogenetic response), and 3 (37.5%)stable disease. No grade 3 or 4 toxicity was observed. These results show the ability of epigenetic therapy to revert imatinib resistance.

BACKGROUND

Epigenetic alterations participate in the development of acquired resistance to imatinib, hence, the DNA methylation, and histone deacetylase inhibitors hydralazine and valproate, respectively, has the potential to overcome it.

PATIENT AND METHODS

A series of 8 patients with chronic myeloid leukemia (CML) refractory to imatinib mesylate with no access to second-generation tyrosine kinase inhibitors were treated with hydralazine and valproate in a compassionate manner. Clinical efficacy and safety of these drugs added to imatinib mesylate were evaluated.

RESULTS

Two patients were in the blast phase, 5 were in the accelerated phase, and 1 was in the chronic phase. All the patients continued with the same dose of imatinib that they had been receiving at the time of development of resistance, with a median dose of 600 mg daily (range, 400-800 mg). The median time from diagnosis of CML to the start of hydralazine and valproate was 53.6 months (range, 19-84 months). Two (25%) patients had a complete hematologic response, one (12.5%) had an major cytogenetic response, and one (12.5%) had a complete cytogenetic response. Three (37.5%) patients had stable disease, and only one (12.5%) patient failed to respond. At a median follow-up time of 18 months (range, 3-18 months), the median survival had not been reached, and the projected overall survival was 63%. All the patients had mild neurologic toxicity, including distal tremor and somnolence. No grade 3 or 4 toxicity was observed.

CONCLUSIONS

Our results suggest that the epigenetic drugs hydralazine and valproate revert the resistance to imatinib in patients with CML.

Sodium valproate inhibits MDA-MB-231 breast cancer cell migration by upregulating NM23H1 expression

Breast cancer is a common cancer in women, with a highly variable course, from inoffensive to lethal. To find a more effective strategy for its treatment, sodium valproate has been tested as an anti-cancer drug; it is the only clinically available histone deacetylase inhibitor. However, data about the effects of sodium valproate on breast cancer are insufficient in both animals and humans; studies have yielded conflicting conclusions. In particular, little is known about the association between expression of the metastasis suppressor Nm23H1 gene and breast cancer. We hypothesized that sodium valproate regulates NM23H1 expression, and affects migration and/or invasion. We found that sodium valproate at concentrations of 0.8-3.2 mM inhibits migration and modulates Nm23H1 gene expression in a concentration-dependent manner. Confluent MDA-MB-231 cells were scratched by a micropipette tip after VPA treatment for 24 h; 24 h later, the scratch was almostly closed in the 0 mM VPA-treated cells, while the 3.2 mM VPA-treated cells migrated the slowest. The cell migration ratio exposed to 0.8, 1.6 and 3.2 mM VPA was about 66.67, 30.67 and 26.67% (P < 0.05). We also found evidence that sodium valproate upregulates NM23H1 expression, which is a clue to its anti-cancer mode of action. The NM23H1 gene expression was relative fold increased determined by Western blotting at 3.2 mM VPA. Collectively, these observations indicate that sodium valproate has potential for use in breast cancer treatment.

Histone deacetylase inhibition redistributes topoisomerase IIβ from heterochromatin to euchromatin

The genome is organized into large scale structures in the interphase nucleus. Pericentromeric heterochromatin represents one such compartment characterized by histones H3 and H4 tri-methylated at K9 and K20 respectively and with a correspondingly low level of histone acetylation. HP1 proteins are concentrated in pericentric heterochromatin and histone deacetylase inhibitors such as trichostatin A (TSA) promote hyperacetylation of heterochromatic nucleosomes and the dispersal of HP1 proteins. We observed that in mouse cells, which contain prominent heterochromatin, DNA topoisomerase IIβ (topoIIβ) is also concentrated in heterochromatic regions. Similarly, a detergent-resistant fraction of topoIIβ is associated with heterochromatin in human cell lines. Treatment with TSA displaced topoIIβ from the heterochromatin with similar kinetics to the displacement of HP1β. Topoisomerase II is the cellular target for a number of clinically important cytotoxic anti-cancer agents known collectively as topoisomerase poisons, and it has been previously reported that histone deacetylase inhibitors can sensitize cells to these drugs. While topoIIα appears to be the major target for most topoisomerase poisons, histone deacetylase-mediated potentiation of these drugs is dependent on topoIIβ. We find that while prior treatment with TSA did not increase the quantity of etoposide-mediated topoIIβ-DNA covalent complexes, it did result in a shift in their distribution from a largely heterochromatin-associated to a pannuclear pattern. We suggest that this redistribution of topoIIβ converts this isoform of topoII to a effective relevant target for topoisomerase poisons.

Epigenetics modifications and therapeutic prospects in human thyroid cancer

At present no successful treatment is available for advanced thyroid cancer, which comprises poorly differentiated, anaplastic, and metastatic or recurrent differentiated thyroid cancer not responding to radioiodine. In the last few years, biologically targeted therapies for advanced thyroid carcinomas have been proposed on the basis of the recognition of key oncogenic mutations. Although the results of several phase II trials look promising, none of the patients treated had a complete response, and only a minority of them had a partial response, suggesting that the treatment is, at best, effective in stabilizing patients with progressive disease. "Epigenetic" refers to the study of heritable changes in gene expression that occur without any alteration in the primary DNA sequence. The epigenetic processes establish and maintain the global and local chromatin states that determine gene expression. Epigenetic abnormalities are present in almost all cancers and, together with genetic changes, drive tumor progression. Various genes involved in the control of cell proliferation and invasion (p16INK4A, RASSF1A, PTEN, Rap1GAP, TIMP3, DAPK, RARβ2, E-cadherin, and CITED1) as well as genes specific of thyroid differentiation (Na+/I- symport, TSH receptor, pendrin, SL5A8, and TTF-1) present aberrant methylation in thyroid cancer. This review deals with the most frequent epigenetic alterations in thyroid cancer and focuses on epigenetic therapy, whose goal is to target the chromatin in rapidly dividing tumor cells and potentially restore normal cell functions. Experimental data and clinical trials, especially using deacetylase inhibitors and demethylating agents, are discussed.

Chemotherapeutic properties of phospho-nonsteroidal anti-inflammatory drugs, a new class of anticancer compounds

Nonsteroidal anti-inflammatory drugs (NSAID) exhibit antineoplastic properties, but conventional NSAIDs do not fully meet safety and efficacy criteria for use as anticancer agents. In this study, we evaluated the chemotherapeutic efficacy of 5 novel phospho-NSAIDs, each of which includes in addition to the NSAID moiety a diethylphosphate linked through a butane moiety. All 5 compounds inhibited the growth of human breast, colon, and pancreatic cancer cell lines with micromolar potency. In vivo investigations confirmed the antitumor activity of phospho-aspirin (PA) and phospho-sulindac (PS) in inhibiting tumor growth in established human xenograft models, in which cell proliferation was suppressed and apoptosis enhanced in the absence of detectable animal toxicity. Notably, all of the phospho-NSAIDs tested induced reactive oxygen and nitrogen species in cultured cells, with PA and PS inducing detectable levels of oxidative stress in vivo that were associated positively with apoptosis and negatively with proliferation. Potentially explaining these effects, all of the phospho-NSAIDs tested also inhibited the thioredoxin system and the redox sensitive transcription factor NF-κB. Taken together, our findings show the strong anticancer efficacy and promising safety of phospho-NSAIDs in preclinical models of breast, colon, and pancreatic cancer, suggesting further evaluation as anticancer agents.

Epilepsy in patients with a brain tumour: focal epilepsy requires focused treatment

Brain tumours frequently cause epileptic seizures. Medical antiepileptic treatment is often met with limited success. Pharmacoresistance, drug interactions and adverse events are common problems during treatment with antiepileptic drugs. The unpredictability of epileptic seizures and the treatment-related problems deeply affect the quality of life of patients with a brain tumour. In this review, we focus on both clinical and basic aspects of possible mechanisms in epileptogenesis in patients with a brain tumour. We provide an overview of the factors that are involved in epileptogenesis, starting focally at the tumour and the peritumoral tissue and eventually extending to alterations in functional connectivity throughout the brain. We correlate this knowledge to the known mechanisms of antiepileptic drugs. We conclude that the underlying mechanisms of epileptogenesis in patients with a brain tumour are poorly understood. The currently available antiepileptic drugs have little to no influence on the known epileptogenic mechanisms that could contribute to the poor efficacy. Better understanding of focal changes that are involved in epileptogenesis may provide new tools for optimal treatment of both the seizures and the underlying tumour. In our opinion, therapy for every patient with a brain tumour suffering from epilepsy should first and foremost aim at eliminating the tumour as well as the epileptic focus through resection combined with postoperative treatment, and only if this strategy does not result in adequate seizure control should medical antiepileptic treatment be intensified. If this strategy, however, results in sustained seizure freedom, tapering of antiepileptic drugs should be considered in the long term.

Maternal-foetal epigenetic interactions in the beginning of cardiovascular damage

Several studies indicate that impaired foetal growth, and in utero exposure to risk factors, especially maternal hypercholesterolaemia, may be relevant for the early onset of cardiovascular damage. The exact molecular mechanisms of such foetal programming are still unclear. Epigenetics may represent one of the possible scientific explanations of the impact of such intrauterine risk factors for the subsequent development of cardiovascular disease (CVD) during adulthood. Translational studies support this hypothesis; however, a direct causality in humans has not been ascertained. This hypothesis could be investigated in primates and in human post-mortem foetal arteries. Importantly, some studies also suggest the transgenerational transmission of epigenetic risk. The recently launched International Human Epigenome Consortium and the NIH Roadmap Epigenomics Mapping Consortium will provide the rationale for a useful clinical scenario for primary prevention and therapy of CVD. Despite the heritable nature of epigenetic modification, the clinically relevant information shows that it could be reversible through therapeutic approaches, including histone deacetylase inhibitors, histone acetyltransferase inhibitors, and commonly used drugs such as statins.

Metformin may antagonize Lin28 and/or Lin28B activity, thereby boosting let-7 levels and antagonizing cancer progression

Cancer cells with stem cell characteristics are harbored by most tumors, and are characterized by epithelial-mesenchymal transition (EMT) - which promotes invasive growth and metastasis - chemoresistance, and the capacity to reconstitute new tumors. Hence, the control or destruction of cancer stem cells should be a major goal of cancer management. The let-7 family of microRNAs has cancer suppressor activity, and recent evidence suggests that markedly reduced levels of let-7 are not only a typical feature of cancer stem cells, but may be largely responsible for cancer stemness. It is therefore particularly intriguing that metformin, a diabetes drug thought to have potential in the prevention and treatment of cancer, has recently been found to oppose cancer cell stemness, to markedly potentiate chemotherapeutic control of cancer in mouse xenograft models, and to notably boost let-7a levels in cancer stem cells. It is proposed that this latter effect of metformin may reflect AMPK-mediated inhibition of the expression or activity of Lin28/Lin28A, proteins which act post-transcriptionally to decrease the levels of all let-7 family members. The transcription of Lin28B is promoted by NF-kappaB and by Myc; hence, practical measures which antagonize NF-kappaB or Myc activity may complement the utility of metformin for boosting let-7 expression and controlling cancer stemness; salsalate, antioxidants, tyrosine kinase and cox-2 inhibitors, ribavirin, vitamin D, gamma-secretase inhibitors (when available), and parenteral curcumin may have some utility in this regard. Although the impact of histone deacetylase inhibitors on let-7 expression has not been assessed, there is reason to suspect that these drugs might complement let-7's impact on chemoresistance, EMT, and stemness. Multifocal strategies centering on metformin may have considerable potential for reversing cancer stemness and rendering advanced cancers more susceptible to long term control.

Potential role for valproate in the treatment of high--risk brain tumors of childhood-results from a retrospective observational cohort study

Although substantial progress has been made in pediatric brain tumor management, patients with brainstem tumors and high-grade gliomas, as well as patients less than 3 years of age with high-risk malignant tumors, have a poorer prognosis. The authors have been treating these patients with radiotherapy and standard carboplatin and vincristine chemotherapy. Since January 2007 the authors have been using valproate as anticonvulsant for prophylaxis. The authors performed a retrospective cohort analysis of pediatric patients with high-risk brain tumors treated with chemotherapy, radiotherapy, and valproate prophylaxis, comparing this group with a historical control. The 2007-2008 group was comprised of 22 patients, 15 with brainstem tumors (7 diffuse intrinsic pontine glioma [DIPG], 3 focal, the remaining infiltrating with a solid portion), 4 with diencephalic tumors (2 thalamic), and 3 with supratentorial high-grade tumors (1 glioblastoma, 1 recurrent grade III ependymoma, 1 with gliomatosis). There were 15 patients alive (68%) after a mean follow-up time of 19 months. Survival function comparison by log rank test was highly significant (P = .004) with a hazard ratio of 0.31 (0.14-0.70). Radiological response showed 3 complete responses (14%), 8 partial responses (36%), 5 stable diseases (23%), and 5 progresssive diseases (23%). The authors hypothesize that valproate may have potentiated the antiangiogenic effect of vincristine, diminished expression of resistance to carboplatin, and sensitized tumor cells to radiotherapy. The authors suggest that clinical trials of carboplatin and vincristine associated with oral continuous low-dose valproate are indicated for pediatric patients with high-risk brain tumor.

Efficacy of novel histone deacetylase inhibitor, AR42, in a mouse model of, human T-lymphotropic virus type 1 adult T cell lymphoma

Human T-lymphotropic virus type 1 (HTLV-1) causes a variety of forms of adult T-cell leukemia/lymphoma (ATL), a refractory CD4+/CD25+ T-cell malignancy. Novel approaches to treat ATL patients are required due to the resistance of ATL to conventional chemotherapies. Histone deacetylase inhibitors (HDACi), which induce histone hyperacetylation leading to chromatin remodeling and reactivation of transcriptionally repressed genes have shown efficacy against a variety of cancers. Herein, we tested if valproic acid and the novel orally bioavailable HDACi, AR-42 reduced the proliferation of ATL cell lines by promoting apoptosis and histone hyperacetylation. Both compounds were cytotoxic and elicited a dose dependent increase in cytochrome C and cleaved Poly (ADP-ribose) polymerase (PARP) indicating the induction of cell death by apoptosis and promoted acetylation of histone H3 in both MT-2 and C8166 cell lines. We then evaluated the effects of AR-42, for survival in an ATL NOD/SCID mouse model. A dietary formulation of AR-42 prolonged survival of ATL engrafted mice compared to controls. Our data provide new directions for the treatment of ATL and support the further development of AR-42 against HTLV-1-associated lymphoid malignancies.

Histone deacetylase inhibition enhances self renewal and cardioprotection by human cord blood-derived CD34 cells

Background

Use of peripheral blood- or bone marrow-derived progenitors for ischemic heart repair is a feasible option to induce neo-vascularization in ischemic tissues. These cells, named Endothelial Progenitors Cells (EPCs), have been extensively characterized phenotypically and functionally. The clinical efficacy of cardiac repair by EPCs cells remains, however, limited, due to cell autonomous defects as a consequence of risk factors. The devise of “enhancement” strategies has been therefore sought to improve repair ability of these cells and increase the clinical benefit.

Principal Findings

Pharmacologic inhibition of histone deacetylases (HDACs) is known to enhance hematopoietic stem cells engraftment by improvement of self renewal and inhibition of differentiation in the presence of mitogenic stimuli in vitro. In the present study cord blood-derived CD34⁺ were pre-conditioned with the HDAC inhibitor Valproic Acid. This treatment affected stem cell growth and gene expression, and improved ischemic myocardium protection in an immunodeficient mouse model of myocardial infarction.

Conclusions

Our results show that HDAC blockade leads to phenotype changes in CD34⁺ cells with enhanced self renewal and cardioprotection.

Role of isovaleryl-CoA dehydrogenase and short branched-chain acyl-CoA dehydrogenase in the metabolism of valproic acid: implications for the branched-chain amino acid oxidation pathway

Many biological systems including the oxidative catabolic pathway for branched-chain amino acids (BCAAs) are affected in vivo by valproate therapy. In this study, we investigated the potential effect of valproic acid (VPA) and some of its metabolites on the metabolism of BCAAs. In vitro studies were performed using isovaleryl-CoA dehydrogenase (IVD), isobutyryl-CoA dehydrogenase (IBD), and short branched-chain acyl-CoA dehydrogenase (SBCAD), enzymes involved in the degradation pathway of leucine, valine, and isoleucine. The enzymatic activities of the three purified human enzymes were measured using optimized high-performance liquid chromatography procedures, and the respective kinetic parameters were determined in the absence and presence of VPA and the corresponding CoA and dephosphoCoA conjugates. Valproyl-CoA and valproyl-dephosphoCoA inhibited IVD activity significantly by a purely competitive mechanism with K(i) values of 74 ± 4 and 170 ± 12 μM, respectively. IBD activity was not affected by any of the tested VPA esters. However, valproyl-CoA did inhibit SBCAD activity by a purely competitive mechanism with a K(i) of 249 ± 29 μM. In addition, valproyl-dephosphoCoA inhibited SBCAD activity via a distinct mechanism (K(i) = 511 ± 96 μM) that appeared to be of the mixed type. Furthermore, we show that both SBCAD and IVD are active, using valproyl-CoA as a substrate. The catalytic efficiency of SBCAD turned out to be much higher than that of IVD, demonstrating that SBCAD is the most probable candidate for the first dehydrogenation step of VPA β-oxidation. Our data explain some of the effects of valproate on the branched-chain amino acid metabolism and shed new light on the biotransformation pathway of valproate.

Epigenetic aberrations during oncogenesis

The aberrant epigenetic landscape of a cancer cell is characterized by global genomic hypomethylation, CpG island promoter hypermethylation of tumor suppressor genes, and changes in histone modification patterns, as well as altered expression profiles of chromatin-modifying enzymes. Recent advances in the field of epigenetics have revealed that microRNAs' expression is also under epigenetic regulation and that certain microRNAs control elements of the epigenetic machinery. The reversibility of epigenetic marks catalyzed the development of epigenetic-altering drugs. However, a better understanding of the intertwined relationship between genetics, epigenetics and microRNAs is necessary in order to resolve how gene expression aberrations that contribute to tumorigenesis can be therapeutically corrected.

Epigenetic mechanisms in Alzheimer's disease

Epigenetic modifications help orchestrate sweeping developmental, aging, and disease-causing changes in phenotype by altering transcriptional activity in multiple genes spanning multiple biologic pathways. Although previous epigenetic research has focused primarily on dividing cells, particularly in cancer, recent studies have shown rapid, dynamic, and persistent epigenetic modifications in neurons that have significant neuroendocrine, neurophysiologic, and neurodegenerative consequences. Here, we provide a review of the major mechanisms for epigenetic modification and how they are reportedly altered in aging and Alzheimer's disease (AD). Because of their reach across the genome, epigenetic mechanisms may provide a unique integrative framework for the pathologic diversity and complexity of AD.

On target? Strategies and progress in the development of therapies for colorectal cancer targeted against WNT signalling

Chemotherapy is an integral part of treatment for colorectal cancer (CRC), especially in the context of metastatic cancer. Targeted therapies in the form of monoclonal antibodies directed against the endothelial growth factor receptor or the vascular endothelial growth factor have met with success, and have demonstrated the advantages of molecularly targeted therapy in colorectal cancer. Nevertheless, CRC remains a major cause of death, which demonstrates the urgent need for improved treatment strategies. The pathway activated by the Wingless-type mouse mammary tumour virus integration site (WNT) family members is constitutively active and promotes cancer growth in the majority of CRCs. As a result, there has been interest in developing therapeutics that circumvent it either by inhibiting WNT-mediated transcription or by inactivating the target genes. This review considers the current therapies approved for use in CRC and discusses the progress with therapies designed to target the WNT signalling pathway.

Next generation histone deacetylase inhibitors: the answer to the search for optimized epigenetic therapies?

INTRODUCTION

HDAC inhibitors have demonstrated potent anticancer activities in preclinical and clinical studies. Currently, two drugs (SAHA and romidepsin) have gained the FDA approval for the treatment of cutaneous T-cell lymphoma. Clinical efficacy of HDAC inhibitors has been observed in advanced hematological malignancies, while response in other cancers has been in most cases unpredictable and often rather limited. The search for new molecules with the potential to overcome the limitations of the first HDAC inhibitors has become a primary goal in the field of epigenetic drug discovery as well as drugs acting on other chromatin modifying enzymes.

AREAS COVERED

The article shortlists seven new HDAC inhibitors that have recently entered clinical studies as representative examples of next generation drugs. The most recently published preclinical profile is reviewed, together with the first clinical data for these compounds. The article then focuses on challenges faced during the progress of first generation HDAC inhibitors and analyzes whether these new compounds are likely to provide a solution to the existing issues and needs.

EXPERT OPINION

Next generation HDAC inhibitors have the 'best-in-class' potential, particularly regarding potency and in vivo exposure. However, several issues remain unresolved. For example, none of the presented compounds appears to have a significantly different selectivity profile towards various HDAC isoforms and, thus, none of them may provide a further elucidation between the toxicity seen in more advanced HDAC inhibitors and isoform selectivity. Additionally, a need for a continuous effort on target validation is seen as a necessary requirement for further progress in the field.

DNA hypermethylation as a chemotherapy target

Epigenetics refers to partially reversible, somatically inheritable, but DNA sequence-independent traits that modulate gene expression, chromatin structure, and cell functions such as cell cycle and apoptosis. DNA methylation is an example of a crucial epigenetic event; aberrant DNA methylation patterns are frequently found in human malignancies. DNA hypermethylation and the associated expression silencing of tumor suppressor genes represent a hallmark of neoplastic cells. The cancer methylome is highly disrupted, making DNA methylation an excellent target for anti-cancer therapies. Several small synthetic and natural molecules, are able to reverse the DNA hypermethylation through inhibition of DNA methyltransferase (DNMT). DNMT is the enzyme catalyzing the transfer of methyl groups to cytosines in genomic DNA. These reagents are studied intensively in cell cultures, animal models, and clinical trials for potential anti-cancer activities. It was found that accompanying DNA demethylation is a dramatic reactivation of the silenced genes and inhibition of cancer cell proliferation, promotion of cell apoptosis, or sensitization of cells to other chemotherapeutic reagents. During the last few decades, an increasing number of DNMT inhibitors (DNMTi) targeting DNA methylation have been developed to increase efficacy with reduced toxicity. This review provides an update on new findings on cancer epigenetic mechanisms, the development of new DNMTi, and their application in the clinical setting. Current challenges, potential solutions, and future directions concerning the development of DNMTi are also discussed in this review.

Epilepsy in the cancer patient

PURPOSE

Epileptic seizures in patients with malignancies usually occur as a consequence of brain metastases from systemic cancer or the presence of a primary brain tumor. Other less-frequent causes include metabolic disorders such as electrolyte abnormalities, hypoglycemia, hypoxia and liver failure, paraneoplastic encephalitis, leptomeningeal carcinomatosis, side effects of certain chemotherapeutic agents, central nervous system infections, and pre-existing epilepsy.

METHODS

We reviewed all published literature in the English language regarding the use of antiepileptic drugs in patients with cancer.

RESULTS

In patients with brain metastases or primary brain tumors that had never experienced seizures, prophylactic anticonvulsant treatment is justified only for a period up to 6 months postoperatively after surgical excision of a cerebral tumor, since approximately half of the patients will never develop seizures and the anti-epileptic drugs may cause toxicity and interactions with antineoplastic therapies. For brief prophylaxis, newer antiepileptic drugs such as levetiracetam and oxcarbazepine are superior to older agents like phenytoin. In patients with a malignancy and seizures, certain antiepileptic drugs that express tumor inhibitory properties should be used such as valproic acid and levetiracetam, followed by oxcarbazepine and topiramate that exhibit good tolerance, efficient seizure control and absence of significant interactions with the chemotherapy.

CONCLUSIONS

Future clinical trials in patients with cancer and epilepsy should focus on combinations of chemotherapeutic interventions with antiepileptic drugs that demonstrate antineoplastic activities.

Epigenomics in cancer management

The identification of all epigenetic modifications implicated in gene expression is the next step for a better understanding of human biology in both normal and pathological states. This field is referred to as epigenomics, and it is defined as epigenetic changes (ie, DNA methylation, histone modifications and regulation by noncoding RNAs such as microRNAs) on a genomic scale rather than a single gene. Epigenetics modulate the structure of the chromatin, thereby affecting the transcription of genes in the genome. Different studies have already identified changes in epigenetic modifications in a few genes in specific pathways in cancers. Based on these epigenetic changes, drugs against different types of tumors were developed, which mainly target epimutations in the genome. Examples include DNA methylation inhibitors, histone modification inhibitors, and small molecules that target chromatin-remodeling proteins. However, these drugs are not specific, and side effects are a major problem; therefore, new DNA sequencing technologies combined with epigenomic tools have the potential to identify novel biomarkers and better molecular targets to treat cancers. The purpose of this review is to discuss current and emerging epigenomic tools and to address how these new technologies may impact the future of cancer management.

Valproic acid inhibits proliferation of human coronary vascular cells (SI/MPL-ratio: 0.5): a novel candidate for systemic and local therapy of postinterventional restenosis

OBJECTIVES

The branched-chain fatty acid, valproic acid (VPA), is the most commonly used anti-epileptic drug for treating generalized epilepsy. Recently antiproliferative effects of VPA have been described in human cancer cells, and phase I trials for the treatment of solid tumors have been initiated. In cardiologic patients, increased cell proliferation and migration from the media into the subendothelial space are the key events causing restenosis after coronary angioplasty and stenting. This study investigates the effect of VPA on proliferation and migration in human coronary vascular cells.

METHODS AND RESULTS

The theoretical clinical relevance of the data is estimated with a SI/MPL-ratio, which is defined as the relationship between a significant effect in vitro (SI) and the maximal plasma level in vivo (MPL). Dilution of VPA: Aqua dest, MPL in vivo: 100 microg/ml. Cell culture: HUVEC, human umbilical endothelial cells; HCAEC, human coronary artery endothelial cells; HCMSMC, human coronary media smooth muscle cells. Proliferation assay: HUVEC, HCAEC, and HCMSMC were seeded as described. At day 1, after seeding the cell number was calculated in a cell counter. VPA was added in six different concentrations ranging between 50 and 300 microg/ml. At day 3, the medium and agent were renewed, and after another 2 days, the cell number was calculated in relation with the cell number at day 1. Cell toxicity: Cytotoxic effects of VPA were studied in concentrations ranging from 50 to 300 microg/ml. Migration assay: migration of HCMSMC after incubation with VPA in concentrations ranging from 50 to 300 microg/ml was studied for a period of 24 h. Proliferation assay: strong dose-dependent antiproliferative effects were detected after 5 days of incubation with all the three tested cell types. In HUVEC, significant antiproliferative effects were found with VPA in concentrations of 100 microg/ml (P<0.05, SI/MPL-ratio: 1.0) and more. In HCAEC and HCMSMC, significant antiproliferative effects were detected after incubation with VPA in the concentrations of 50 microg/ml (HCAEC: P<0.01, SI/MPL ratio: 0.5; HCMSMC: P<0.001, SI/MPL-ratio: 0.5). Migration assay: no effect on cell migration was detected after incubation of HCMSMC for a period of 48 h with VPA in concentrations ranging from 50 to 300 microg/ml. Cell toxicity: in HUVEC, HCAEC, and HCMSMC significant toxic effects were detected in all the VPA concentrations studied.

CONCLUSION

Significant dose-dependent antiproliferative effects of VPA with SI/MPL ratios of 0.5 identify the drug as a promising candidate for both systemic and local therapy of postinterventional restenosis. The partial cytotoxic effects, however, may restrict the use of VPA to local high-dose devices such as drug eluting stents.

A double-blind, placebo-controlled, randomized phase III trial of chemotherapy plus epigenetic therapy with hydralazine valproate for advanced cervical cancer. Preliminary results

The reversing of epigenetic aberrations using the inhibitors of DNA methylation and histone deacetylases may have therapeutic value in cervical cancer. This is a randomized phase III, placebo-controlled study of hydralazine and valproate (HV) added to cisplatin topotecan in advanced cervical cancer. Patients received hydralazine at 182 mg for rapid, or 83 mg for slow acetylators, and valproate at 30 mg/kg, beginning a week before chemotherapy and continued until disease progression. Response, toxicity, and PFS were evaluated, and 36 patients (17 CT + HV and 19 CT + PLA) were included. The median number of cycles was 6. There were four PRs to CT + HV and one in CT + PLA. Stable disease in five (29%) and six (32%) patients, respectively, whereas eight (47%) and 12 (63%) showed progression (P = 0.27). At a median follow-up time of 7 months (1-22), the median PFS is 6 months for CT + PLA and 10 months for CT + HV (P = 0.0384, two tailed). Although preliminary, this study represents the first randomized clinical trial to demonstrate a significant advantage in progression-free survival for epigenetic therapy over one of the current standard combination chemotherapy in cervical cancer. Molecular correlates with response and survival from this trial are pending to analyze.

Mechanisms of synergistic antileukemic interactions between valproic acid and cytarabine in pediatric acute myeloid leukemia

PURPOSE

To determine the possibility of synergistic antileukemic activity and the underlying molecular mechanisms associated with cytarabine combined with valproic acid (VPA; a histone deacetylase inhibitor and a Food and Drug Administration-licensed drug for treating both children and adults with epilepsy) in pediatric acute myeloid leukemia (AML).

EXPERIMENTAL DESIGN

The type and extent of antileukemic interactions between cytarabine and VPA in clinically relevant pediatric AML cell lines and diagnostic blasts from children with AML were determined by MTT assays and standard isobologram analyses. The effects of cytarabine and VPA on apoptosis and cell cycle distributions were determined by flow cytometry analysis and caspase enzymatic assays. The effects of the two agents on DNA damage and Bcl-2 family proteins were determined by Western blotting.

RESULTS

We showed synergistic antileukemic activities between cytarabine and VPA in four pediatric AML cell lines and nine diagnostic AML blast samples. t(8;21) AML blasts were significantly more sensitive to VPA and showed far greater sensitivities to combined cytarabine and VPA than non-t(8;21) AML cases. Cytarabine and VPA cooperatively induced DNA double-strand breaks, reflected in induction of γH2AX and apoptosis, accompanied by activation of caspase-9 and caspase-3. Further, VPA induced Bim expression and short hairpin RNA knockdown of Bim resulted in significantly decreased apoptosis induced by cytarabine and by cytarabine plus VPA.

CONCLUSIONS

Our results establish global synergistic antileukemic activity of combined VPA and cytarabine in pediatric AML and provide compelling evidence to support the use of VPA in the treatment of children with this deadly disease.

Recent advances in histone deacetylase targeted cancer therapy

Epigenetic regulators such as histone acetyltransferases (HATs) and histone deacetylases (HDACs) are known to play an important role in gene expression. Of these enzymes, HDACs have been shown to be commonly associated with many types of cancers and to affect cancer development. Consequently, HDACs have been considered as promising targets for cancer therapy. In addition, the inhibition of HDACs by histone deacetylase inhibitors (HDACIs) shifts the balance between the deacetylating activity of HDACs and the acetylating activity of HATs in the regulation of gene expression. Therefore, HDACIs are an exciting new addition in cancer therapies. Numerous HDACIs have been identified and some have recently been used in clinical trials for cancer treatment, although the mechanisms underlying the anticancer effects of HDACIs remain unclear. In this review, we examine the most recent developments in HDACIs and various aspects of HDAC-targeted cancer treatment.

Molecular and therapeutic potential and toxicity of valproic acid

Valproic acid (VPA), a branched short-chain fatty acid, is widely used as an antiepileptic drug and a mood stabilizer. Antiepileptic properties have been attributed to inhibition of Gamma Amino Butyrate (GABA) transaminobutyrate and of ion channels. VPA was recently classified among the Histone Deacetylase Inhibitors, acting directly at the level of gene transcription by inhibiting histone deacetylation and making transcription sites more accessible. VPA is a widely used drug, particularly for children suffering from epilepsy. Due to the increasing number of clinical trials involving VPA, and interesting results obtained, this molecule will be implicated in an increasing number of therapies. However side effects of VPA are substantially described in the literature whereas they are poorly discussed in articles focusing on its therapeutic use. This paper aims to give an overview of the different clinical-trials involving VPA and its side effects encountered during treatment as well as its molecular properties.

Characterization of valproic acid-initiated homologous recombination

BACKGROUND

Valproic acid (VPA) is a frequently used antiepileptic agent and known teratogen. Previous research suggests that inhibition of histone deacetylases (HDACs) may play a role in VPA-induced teratogenicity. We have also shown that VPA exposure leads to both an increase in reactive oxygen species (ROS) production and increased frequency of homologous recombination (HR).

METHODS

In the present study, we evaluated the role of HDAC inhibition in VPA-initiated HR to determine if HDAC inhibition could alter repair activity and/or cause DNA double-strand breaks (DSBs), which would then initiate repair. Histone acetylation status was assessed to determine if VPA exposure led to HDAC inhibition in CHO 33 cells.

RESULTS

Our results demonstrate that VPA (5 mM) exposure leads to increased acetylated histone H3 and H4 protein levels after 10 to 24 hr. Secondly, in our recombination assay where an artificial DNA DSB was induced in CHO 33 cells to assess repair activity, VPA exposure did not affect the repair activity of VPA-initiated HR. Subsequently, to determine if VPA could increase susceptibility to DNA DSBs, the number of gamma-H2AX foci was assessed using immunocytochemistry and results revealed an increase in gamma-H2AX foci after 10- to 24-hr exposure to VPA.

CONCLUSIONS

Although we demonstrated the protective effect of polyethylene glycol-catalase against VPA-induced HR and the generation of intracellular ROS within 24 hr, we did not observed an increase in DNA oxidation. These studies suggest that HDAC inhibition and ROS signaling may play roles in DNA maintenance and cell-cycle arrest in initiating DNA damage and repair.

Cell type-specific anti-cancer properties of valproic acid: independent effects on HDAC activity and Erk1/2 phosphorylation

Background

The anti-epileptic drug valproic acid (VPA) has attracted attention as an anti-cancer agent.

Methods

The present study investigated effects of VPA exposure on histone deacetylase (HDAC) inhibition, cell growth, cell speed, and the degree of Erk1/2 phosphorylation in 10 cell lines (BT4C, BT4Cn, U87MG, N2a, PC12-E2, CSML0, CSML100, HeLa, L929, Swiss 3T3).

Results

VPA induced significant histone deacetylase (HDAC) inhibition in most of the cell lines, but the degree of inhibition was highly cell type-specific. Moreover, cell growth, motility and the degree of Erk1/2 phosphorylation were inhibited, activated, or unaffected by VPA in a cell type-specific manner. Importantly, no relationship was found between the effects of VPA on HDAC inhibition and changes in the degree of Erk1/2 phosphorylation, cell growth, or motility. In contrast, VPA-induced modulation of the MAPK pathway downstream of Ras but upstream of MEK (i.e., at the level of Raf) was important for changes in cell speed.

Conclusions

These results suggest that VPA can modulate the degree of Erk1/2 phosphorylation in a manner unrelated to HDAC inhibition and emphasize that changes in the degree of Erk1/2 phosphorylation are also important for the anti-cancer properties of VPA.

Induction of hepatic differentiation of mouse bone marrow stromal stem cells by the histone deacetylase inhibitor VPA

Bone marrow stromal stem cells (BMSSCs) may have potential to differentiate in vitro and in vivo into hepatocytes. Here, we investigated the effects of valproic acid (VPA) involved in epigenetic modification, a direct inhibitor of histone deacetylase, on hepatic differentiation of mouse BMSSCs. Following the treatment of 2.5 mM VPA for 72 hrs, the in vitro expanded, highly purified and functionally active mouse BMSSCs from bone marrow were either exposed to some well-defined cytokines and growth factors in a sequential way (fibroblast growth factor-4 [FGF-4], followed by HGF, and HGF + OSM + ITS + dexamethasone, resembling the order of secretion during liver embryogenesis) or transplanted (caudal vein) in mice submitted to a protocol of chronic injury (chronic i.p. injection of CCl4). Additional exposure of the cells to VPA considerably improved the in vitro differentiation, as demonstrated by a more homogeneous cell population exhibited epithelial morphology, increasing expression of hepatic special genes and enhanced hepatic functions. Further more, in vivo results indicate that the pre-treatment of VPA significantly increased the homing efficiency of BMSSCs to the site of liver injury and, additionally, for supporting hepatic differentiation as well as in vitro. We have demonstrated the usefulness of VPA in the transdifferentiation of BMSSCs into hepatocytes both in vitro and in vivo, and regulation of fibroblast growth factor receptors (FGFRs) and c-Met gene expression through post-translational modification of core histones might be the primary initiating event for these effects. This mode could be helpful for liver engineering and clinical therapy.

Alterations of the gene expression profile in renal cell carcinoma after treatment with the histone deacetylase-inhibitor valproic acid and interferon-alpha

PURPOSE

Renal cell carcinoma (RCC) is highly resistant to chemotherapy and unresponsive to radio- and immunotherapy. Recently, we have documented that the histone deacetylase (HDAC)-inhibitor valproic acid (VPA) in combination with low-dosed interferon (IFN)-alpha significantly inhibits RCC proliferation and adhesion in vitro and in vivo. The current study investigated the effects of these compounds on gene transcription of metastatic RCC cell line Caki-1 after 3 and 5 days exposure.

METHODS

To evaluate the gene expression profiles of the RCC cells, we performed microarray analysis using Affymetrix GeneChip. Selected significant genes were further validated by Real Time PCR.

RESULTS

Microarray revealed that VPA altered genes that are involved in cell growth, cell survival, immune response, cell motility and cell adhesion. Combination of VPA with IFN-alpha not only enhanced the effects on gene transcription but also resulted in the expression of novel genes, which were not induced by either VPA or IFN-alpha alone. Among the up-regulated genes were chemokines (CXCL10, CXCL11, CXCL16) and integrins (ITGA2, ITGA4, ITGA5, ITGA6, ITGA7). Genes encoding for adhesion molecules (NCAM1, ICAM1, VCAM1) were also modulated. Real Time PCR approved these findings.

CONCLUSION

This data provides insight into the molecular mechanism of action of the combined treatment of VPA and IFN-alpha in RCC. Implications are that the combined application of VPA and IFN-alpha may represent a more efficient alternative to existing therapy options for RCC.

Preclinical evidence for a beneficial impact of valproate on the response of small cell lung cancer to first-line chemotherapy

Prognosis of small cell lung carcinoma (SCLC) is particularly poor, less than 5% of patients with extensive stage being alive after two years. We hypothesized that SCLC chemotherapy could be improved by using histone deacetylase (HDAC) inhibitors based on their ability to interfere with lysine acetylation and to alter gene expression. The goal of this study was to evaluate the anticancer efficacy of a HDAC inhibitor (valproate: VPA) on SCLC cells in combination with the standard chemotherapeutic first-line regimen (cisplatin+etoposide). We show that VPA induces apoptosis of small cell lung cancer cell lines and improves efficacy of cisplatin combined with etoposide. Both mitochondrial and death receptor pathways are involved in VPA-induced apoptosis. As expected for an HDAC inhibitor, VPA hyperacetylates histone H3. The mechanism of VPA pro-apoptotic activity involves induction of p21, inhibition of Bcl-xL, cleavage of Bid and phosphorylation of Erk and H2AX. In the presence of VPA, Bax is translocated from the cytoplasm to the mitochondria and cleaved in an 18kDa isoform. Cytochrome c is released from the mitochondria into the cytosol. Transcriptomic analyses by microarray show that VPA modulates transcription of genes (Na(+)/K(+) ATPase, Bcl-xL) involved in chemoresistance to cisplatin and etoposide. Finally, the efficacy of VPA combined with cisplatin and etoposide is supported by preclinical models of SCLC cells engrafted into SCID mice. Together, these data demonstrate that VPA augments anticancer activity of cisplatin and etoposide, two components of the standard first-line chemotherapy of small cell lung cancer.

Histone deacetylase inhibitor valproic acid inhibits cancer cell proliferation via down-regulation of the alzheimer amyloid precursor protein

The beta-amyloid precursor protein (APP) represents a type I transmembrane glycoprotein that is ubiquitously expressed. In the brain, it is a key player in the molecular pathogenesis of Alzheimer disease. Its physiological function is however less well understood. Previous studies showed that APP is up-regulated in prostate, colon, pancreatic tumor, and oral squamous cell carcinoma. In this study, we show that APP has an essential role in growth control of pancreatic and colon cancer. Abundant APP staining was found in human pancreatic adenocarcinoma and colon cancer tissue. Interestingly, treating pancreatic and colon cancer cells with valproic acid (VPA, 2-propylpentanoic acid), a known histone deacetylase (HDAC) inhibitor, leads to up-regulation of GRP78, an endoplasmic reticulum chaperone immunoglobulin-binding protein. GRP78 is involved in APP maturation and inhibition of tumor cell growth by down-regulation of APP and secreted soluble APPalpha. Trichostatin A, a pan-HDAC inhibitor, also lowered APP and increased GRP78 levels. In contrast, treating cells with valpromide, a VPA derivative lacking HDAC inhibitory properties, had no effect on APP levels. VPA did not modify the level of epidermal growth factor receptor, another type I transmembrane protein, and APLP2, a member of the APP family, demonstrating the specificity of the VPA effect on APP. Small interfering RNA-mediated knockdown of APP also resulted in significantly decreased cell growth. Based on these observations, the data suggest that APP down-regulation via HDAC inhibition provides a novel mechanism for pancreatic and colon cancer therapy.

Response to hydralazine-valproate in a patient with mycosis fungoides

Histone deacetylase (HDAC) inhibitors have shown significant activity in the treatment of cutaneous T-cell lymphomas (CTCL). The epigenetic alterations of CTCL not only are limited to altered histone acetylation but also include aberrant DNA gene methylation hence, the combination of an HDAC inhibitor with a DNA demethylating agent is a promising therapy to be tested. Here we report a mycosis fungoides patient having a dramatic response to hydralazine and valproate, two repositioned drugs as HDAC and DNA methylation inhibitors, respectively.

Epigenetics in atherosclerosis and inflammation

Atherosclerosis is a multifactorial disease with a severe burden on western society. Recent insights into the pathogenesis of atherosclerosis underscore the importance of chronic inflammation in both the initiation and progression of vascular remodelling. Expression of immunoregulatory molecules by vascular wall components within the atherosclerotic lesions is accordingly thought to contribute to the ongoing inflammatory process. Besides gene regulatory proteins (transcription factors), epigenetic mechanisms also play an essential and fundamental role in the transcriptional control of gene expression. These epigenetic mechanisms change the accessibility of chromatin by DNA methylation and histone modifications. Epigenetic modulators are thus critically involved in the regulation of vascular, immune and tissue-specific gene expression within the atherosclerotic lesion. Importantly, epigenetic processes are reversible and may provide an excellent therapeutic target. The concept of epigenetic regulation is gradually being recognized as an important factor in the pathogenesis of atherosclerosis. Recent research provides an essential link between inflammation and reprogramming of the epigenome. In this review we therefore discuss the basis of epigenetic regulation – and the contribution thereof in the regulation of inflammatory processes in general and during atherosclerosis in particular. Moreover we highlight potential therapeutic interventions based on epigenetic mechanisms.

Chemical modifier screen identifies HDAC inhibitors as suppressors of PKD models

Polycystic kidney disease (PKD) is a common human genetic disease with severe medical consequences. Although it is appreciated that the cilium plays a central role in PKD, the underlying mechanism for PKD remains poorly understood and no effective treatment is available. In zebrafish, kidney cyst formation is closely associated with laterality defects and body curvature. To discover potential drug candidates and dissect signaling pathways that interact with ciliary signals, we performed a chemical modifier screen for the two phenotypes using zebrafish pkd2(hi4166) and ift172(hi2211) models. pkd2 is a causal gene for autosomal dominant PKD and ift172 is essential for building and maintaining the cilium. We identified trichostatin A (TSA), a pan-HDAC (histone deacetylase) inhibitor, as a compound that affected both body curvature and laterality. Further analysis verified that TSA inhibited cyst formation in pkd2 knockdown animals. Moreover, we demonstrated that inhibiting class I HDACs, either by valproic acid (VPA), a class I specific HDAC inhibitor structurally unrelated to TSA, or by knocking down hdac1, suppressed kidney cyst formation and body curvature caused by pkd2 deficiency. Finally, we show that VPA was able to reduce the progression of cyst formation and slow the decline of kidney function in a mouse ADPKD model. Together, these data suggest body curvature may be used as a surrogate marker for kidney cyst formation in large-scale high-throughput screens in zebrafish. More importantly, our results also reveal a critical role for HDACs in PKD pathogenesis and point to HDAC inhibitors as drug candidates for PKD treatment.