Histone Deactylase Research Articles

Abstract 1711: Proteasomal alterations in a newly created model of FLT3-ITD positive AML with acquired pan-TKI resistance

Abstract Acute myeloid leukemia (AML) is an aggressive hematologic cancer. Thirty percent of AMLs express mutations in the FMS-like tyrosine kinase receptor-3 (FLT3) that render it constitutively active. The internal tandem duplication (ITD) mutation of FLT3 is associated with poor clinical prognosis as it results in aberrant signaling leading to proliferation and survival. As such, tyrosine kinase inhibitors (TKI) directed against FLT3 are being developed. However, as with most TKI therapies, de novo and acquired resistance occurs. We have developed an isogenic cell line model of acquired resistance to FLT3 TKIs by treating BaF3/FLT3-ITD cells (FLT3-ITD) with lestaurtinib over time (FLT3-ITDR cells). Challenge of FLT3-ITDR cells with lestaurtinib showed >3-fold resistance to this TKI as measured by proliferation and propidium iodide sub-diploid analysis. In addition, we tested FLT3-ITDR cells for sensitivity to quizartinib, a more potent and selective inhibitor of FLT3, and found that FLT3-ITDR cells were 7-fold more resistant, suggesting pan-FLT3-TKI resistance. To confirm this resistance was specific for TKI, FLT3-ITDR and FLT3-ITD cells were treated with the histone deactylase inhibitor vorinostat and the anthracycline doxorubicin. Similar sensitivities were noted between the two cell lines to both of these drugs suggesting that resistance of FLT3-ITDR cells to FLT3-directed TKI is specific. Combination therapy is often utilized as a mechanism to overcome clinical resistance. Recently, proteasome inhibitors have been explored as an option for combinatorial therapeutics in leukemia. To determine if the proteasome may be a good target for combination therapy in FLT3-ITDR cells, the proteasomal chymotrypsin-like activity was measured in FLT3-WT, FLT3-ITD, and FLT3-ITDR cells. Chymotrypsin-like proteasome activity was significantly reduced in both FLT3-ITD (41%) and FLT3-ITDR (59%) vs. FLT3-WT cells. This activity stems from activation of the β5 subunit of the proteasome; therefore we performed western blotting with antibodies directed against β5. As seen with chymotrypsin-like activity, FLT3-ITD cells had a significant decrease in β5 protein expression (58%) compared to FLT3-WT. However, despite decreased proteasome activity, FLT3-ITDR had no decrease in β5 protein compared to FLT3-WT cells. One potential explanation for this result is that FLT3-ITDR cells have increased levels of inactive free β5 subunits compared to FLT3-WT. Future studies will examine the implication of these alterations. Despite these changes in proteasome sub-unit regulation and activity, all three cell lines were sensitive to single agent treatment with the reversible FDA-approved proteasome inhibitor bortezomib and its irreversible counterpart marizomib. As such, we will continue to explore the efficacy of proteasome inhibitors in combination therapy for TKI resistant FLT3-ITD-positive AML. Citation Format: Katie Wilson, Mary E. Irwin, Joya Chandra. Proteasomal alterations in a newly created model of FLT3-ITD positive AML with acquired pan-TKI resistance. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1711. doi:10.1158/1538-7445.AM2014-1711

Molecular pathways: targeting ETS gene fusions in cancer.

Rearrangements, or gene fusions, involving the ETS family of transcription factors are common driving events in both prostate cancer and Ewing sarcoma. These rearrangements result in pathogenic expression of the ETS genes and trigger activation of transcriptional programs enriched for invasion and other oncogenic features. Although ETS gene fusions represent intriguing therapeutic targets, transcription factors, such as those comprising the ETS family, have been notoriously difficult to target. Recently, preclinical studies have demonstrated an association between ETS gene fusions and components of the DNA damage response pathway, such as PARP1, the catalytic subunit of DNA protein kinase (DNAPK), and histone deactylase 1 (HDAC1), and have suggested that ETS fusions may confer sensitivity to inhibitors of these DNA repair proteins. In this review, we discuss the role of ETS fusions in cancer, the preclinical rationale for targeting ETS fusions with inhibitors of PARP1, DNAPK, and HDAC1, as well as ongoing clinical trials targeting ETS gene fusions.

The use of protein-DNA, chromatin immunoprecipitation, and transcriptome arrays to describe transcriptional circuits in the dehydrated male rat hypothalamus.

The supraoptic nucleus (SON) of the hypothalamus is responsible for maintaining osmotic stability in mammals through its elaboration of the antidiuretic hormone arginine vasopressin. Upon dehydration, the SON undergoes a function-related plasticity, which includes remodeling of morphology, electrical properties, and biosynthetic activity. This process occurs alongside alterations in steady state transcript levels, which might be mediated by changes in the activity of transcription factors. In order to identify which transcription factors might be involved in changing patterns of gene expression, an Affymetrix protein-DNA array analysis was carried out. Nuclear extracts of SON from dehydrated and control male rats were analyzed for binding to the 345 consensus DNA transcription factor binding sequences of the array. Statistical analysis revealed significant changes in binding to 26 consensus elements, of which EMSA confirmed increased binding to signal transducer and activator of transcription (Stat) 1/Stat3, cellular Myelocytomatosis virus-like cellular proto-oncogene (c-Myc)-Myc-associated factor X (Max), and pre-B cell leukemia transcription factor 1 sequences after dehydration. Focusing on c-Myc and Max, we used quantitative PCR to confirm previous transcriptomic analysis that had suggested an increase in c-Myc, but not Max, mRNA levels in the SON after dehydration, and we demonstrated c-Myc- and Max-like immunoreactivities in SON arginine vasopressin-expressing cells. Finally, by comparing new data obtained from Roche-NimbleGen chromatin immunoprecipitation arrays with previously published transcriptomic data, we have identified putative c-Myc target genes whose expression changes in the SON after dehydration. These include known c-Myc targets, such as the Slc7a5 gene, which encodes the L-type amino acid transporter 1, ribosomal protein L24, histone deactylase 2, and the Rat sarcoma proto-oncogene (Ras)-related nuclear GTPase.

Antitumor Action of a Novel Histone Deacetylase Inhibitor, YF479, in Breast Cancer

Accumulating evidence demonstrates important roles for histone deacetylase in tumorigenesis (HDACs), highlighting them as attractive targets for antitumor drug development. Histone deactylase inhibitors (HDACIs), which have shown favorable anti-tumor activity with low toxicity in clinical investigations, are a promising class of anticancer therapeutics. Here, we screened our compound library to explore small molecules that possess anti-HDAC activity and identified a novel HDACI, YF479. Suberoylanilide hydroxamic acid (SAHA), which was the first approved HDAC inhibitor for clinical treatment by the FDA, was as positive control in our experiments. We further demonstrated YF479 abated cell viability, suppressed colony formation and tumor cell motility in vitro. To investigate YF479 with superior pharmacodynamic properties, we developed spontaneous and experimental breast cancer animal models. Our results showed YF479 significantly inhibited breast tumor growth and metastasis in vivo. Further study indicated YF479 suppressed both early and end stages of metastatic progression. Subsequent adjuvant chemotherapy animal experiment revealed the elimination of local-regional recurrence (LRR) and distant metastasis by YF479. More important, YF479 remarkably prolonged the survival of tumor-bearing mice. Intriguingly, YF479 displayed more potent anti-tumor activity in vitro and in vivo compared with SAHA. Together, our results suggest that YF479, a novel HDACI, inhibits breast tumor growth, metastasis and recurrence. In light of these results, YF479 may be an effective therapeutic option in clinical trials for patients burdened by breast cancer.

Potential adverse effects of histone deactylase inhibition in spinocerebellar ataxia type 1

Potential adverse effects of histone deactylase inhibition in spinocerebellar ataxia type 1

Epigenetics and pancreatic cancer: pathophysiology and novel treatment aspects.

An improvement in pancreatic cancer treatment represents an urgent medical goal. Late diagnosis and high intrinsic resistance to conventional chemotherapy has led to a dismal overall prognosis that has remained unchanged during the past decades. Increasing knowledge about the molecular pathogenesis of the disease has shown that genetic alterations, such as mutations of K-ras, and especially epigenetic dysregulation of tumor-associated genes, such as silencing of the tumor suppressor p16(ink4a), are hallmarks of pancreatic cancer. Here, we describe genes that are commonly affected by epigenetic dysregulation in pancreatic cancer via DNA methylation, histone acetylation or miRNA (microRNA) expression, and review the implications on pancreatic cancer biology such as epithelial-mesenchymal transition, morphological pattern formation, or cancer stem cell regulation during carcinogenesis from PanIN (pancreatic intraepithelial lesions) to invasive cancer and resistance development. Epigenetic drugs, such as DNA methyltransferases or histone deactylase inhibitors, have shown promising preclinical results in pancreatic cancer and are currently in early phases of clinical development. Combinations of epigenetic drugs with established cytotoxic drugs or targeted therapies are promising approaches to improve the poor response and survival rate of pancreatic cancer patients.

An HDAC in the Cytoplasm, not the Nucleus, Plays a Pathogenic Role in Huntington's Disease

​TheThe gene for Huntington's disease (HD) was discovered in 1993 and ever since has been puzzling researchers intent on understanding its effects. The mutation, an expanded CAG repeat, is translated into an extended polyglutamine tract in the huntingtin protein (HTT), which leads to protein misfolding, accumulation of sticky protein aggregates in both cytoplasm and nucleus, and degeneration of neurons, first in the brain's striatum and later in the cortex and elsewhere. There are no disease-altering treatments and no single hypothesis of disease pathogenesis. In a new study, Michal Mielcarek, Gillian Bates, and colleagues elucidate a key role for the transcription regulator histone deactylase 4 (HDAC4)—not within the nucleus as you might expect, but instead in the cytoplasm. HDAC4 acts in the cytoplasm of brain cells to exacerbate the Huntington's disease (HD) pathogenic process. Reduction of HDAC4 levels ameliorates cytoplasmic-related HD phenotypes and improves survival, but does not change gene transcription. One prominent feature of HD molecular pathology is a global transcriptional dysregulation, likely driven in part by reduced histone acetylation. To counterbalance that effect, researchers have investigated whether inhibiting HDACs might be therapeutic, and one HDAC inhibitor has produced promising results in preclinical trials in models of HD. There are 11 different mammalian HDACs, and in order to better characterize their individual contributions to HD, the authors examined the effects of partially or completely knocking out each one. They found that reducing HDAC4 by 50% in a mouse model of HD reduced neuronal dysfunction of striatal neurons and delayed loss of motor function of the mice, allowing them to perform a balancing task at 12 weeks of age as well as untreated mice who were a month younger. Treatment also extended lifespan by about 20%, a significant improvement in this aggressive disease model of HD. Antibodies against HDAC4 and either mutant or wild-type HTT indicated that HDAC4 bound to mutant HTT in either soluble or aggregated form, but not to normal protein. Like HTT, HDAC4 includes a polyglutamine region, and it is likely that its interaction with mutant HTT is through the reciprocal attractions between these regions. Reducing HDAC4 reduced the total burden of HTT aggregates throughout the brain while increasing the amount of soluble HTT, indicating that treatment delayed the aggregation process. The work thereby finds a novel route to modulating the toxicity of HTT. HDAC4 remains sequestered in the cytoplasm until it is called upon to shuttle into the nucleus to take part in regulating transcription. Co-labeling HDAC4 and mutant HTT indicated that they localized together in the cytoplasm, but not the nucleus, and that reducing HDAC4 reduced aggregation in the cytoplasm while leaving the number of nuclear aggregates unchanged. This ability of the work to separate cytoplasmic pathologies from nuclear ones is an important advance in this field. Surprisingly, reducing HDAC4 had no effect on the widespread transcriptional dysregulation that led HD researchers to consider HDAC inhibitors in the first place. It did, however, have one potentially important effect on gene expression: it largely restored the levels of brain-derived neurotrophic factor, a growth factor that neurons need for survival and that is known to be lost in HD. This effect is likely mediated through a cytoplasmic, not nuclear, mechanism, based on previous work on this pathway in HD; further work will be needed to understand it in detail. These results have several implications for understanding and treating HD. There is no shortage of hypotheses of pathogenic mechanisms in HD, and this new mechanism is unlikely to be the sole cause of neuronal damage. But the discovery of a strictly cytoplasmic pathogenic effect of mutant HTT is new and will likely bring more attention to the cytoplasm as a site for further research. The demonstration that shifting the balance of mutant protein from aggregated to soluble forms has a beneficial effect further informs a long-standing debate in disorders of protein misfolding, about whether aggregates are toxic or protective, and will likely accelerate exploration of therapies to promote disaggregation. As mentioned, there are currently no disease-modifying therapeutics available for HD. The discovery that reducing HDAC4 has therapeutic effects in the HD model tested here—which happens to be a gold standard model in which most therapeutics fail when tested—will spur efforts to mimic this effect with small molecules to obstruct the interaction of HDAC4 and mutant HTT, or antisense therapies designed to prevent production of HDAC4 protein. Mielcarek M, Landles C, Weiss A, Bradaia A, Seredenina T, et al (2013). HDAC4 Reduction: A Novel Therapeutic Strategy to Target Cytoplasmic Huntingtin and Ameliorate Neurodegeneration. doi:10.1371/journal.pbio.1001717

S128 Reduction of lung metastasis by engineered Mesenchymal stem cells expressing secreted soluble TRAIL

Bone marrow–derived mesenchymal stem cells (MSC) are promising tools for cancer therapy because they are able to home to and incorporate within tumour tissue. Tumour necrosis factor–related apoptosis-inducing ligand (TRAIL)...

Differential regulation of Bdnf expression in cortical neurons by class-selective histone deacetylase inhibitors

Histone deactylase (HDAC) inhibitors show promise as therapeutics for neurodegenerative and psychiatric diseases. Increased expression of brain-derived neurotrophic factor (BDNF) has been associated with memory-enhancing and neuroprotective properties of these drugs, but the mechanism of BDNF induction is not well understood. Here, we compared the effects of a class I/IIb selective HDAC inhibitor SAHA, a class I selective inhibitor MS-275, a class II selective inhibitor MC1568 and a HDAC6 selective inhibitor tubacin on Bdnf mRNA expression in rat primary neurons. We show that inhibition of class II HDACs resulted in rapid upregulation of Bdnf mRNA levels, whereas class I HDAC inhibition produced a markedly delayed Bdnf induction. In contrast to relatively slow upregulation of Bdnf transcripts, histone acetylation at BDNF promoters I and IV was rapidly induced by SAHA. Bdnf induction by SAHA and MS-275 at 24 h was sensitive to protein synthesis inhibition, suggesting that delayed Bdnf induction by HDAC inhibitors is secondary to changed expression of its regulators. HDAC4 and HDAC5 repressed Bdnf promoter IV activity, supporting the role of class II HDACs in regulation of Bdnf expression. In addition, we show a critical role for the cAMP/Ca2+ response element (CRE) in induction of Bdnf promoter IV by MS-275, MC1568, SAHA and sodium valproate. In contrast, MEF2-binding CaRE1 element was not necessary for promoter IV induction by HDAC inhibition. Finally, we show that similarly to Bdnf, the studied HDAC inhibitors differentially induced expression of neuronal activity-regulated genes c-fos and Arc. Together, our findings implicate class II HDACs in transcriptional regulation of Bdnf and indicate that class II selective HDAC inhibitors may have potential as therapeutics for nervous system disorders.

Histone Deactylase Inhibitors as Novel Target for Cancer, Diabetes, and Inflammation

Histone deacetylase (HDACs) is an enzyme family that deacetylates histones and non-histones protein. Availability of crystal structure of HDAC8 has been a boosting factor to generate target based inhibitors. Hydroxamic class is the most studied one to generate potent inhibitors. HDAC class I and class II enzymes are emerging as a therapeutic target for cancer, diabetes, inflammation and other diseases. DNA methylation and histone modification are epigenetic mechanism, is important for the regulation of cellular functions. HDACs enzymes play essential role in gene transcription to regulate cell proliferation, migration and death. The aim of this article is to provide a comprehensive overview about structure and function of HDACs enzymes, histone deacetylase inhibitors (HDACi) and HDACs enzymes as a therapeutic target for cancer, inflammation and diabetes.

Heterochromatinization induced by GAA-repeat hyperexpansion in Friedreich's ataxia can be reduced upon HDAC inhibition by vitamin B3

Large intronic expansions of the triplet-repeat sequence (GAA.TTC) cause transcriptional repression of the Frataxin gene (FXN) leading to Friedreich's ataxia (FRDA). We previously found that GAA-triplet expansions stimulate heterochromatinization in vivo in transgenic mice. We report here using chromosome conformation capture (3C) coupled with high-throughput sequencing that the GAA-repeat expansion in FRDA cells stimulates a higher-order structure as a fragment containing the GAA-repeat expansion showed an increased interaction frequency with genomic regions along the FXN locus. This is consistent with a more compacted chromatin and coincided with an increase in both constitutive H3K9me3 and facultative H3K27me3 heterochromatic marks in FRDA. Consistent with this, DNase I accessibility in regions flanking the GAA repeats in patients was decreased compared with healthy controls. Strikingly, this effect could be antagonized with the class III histone deactylase (HDAC) inhibitor vitamin B3 (nicotinamide) which activated the silenced FXN gene in several FRDA models. Examination of the FXN locus revealed a reduction of H3K9me3 and H3K27me3, an increased accessibility to DNase I and an induction of euchromatic H3 and H4 histone acetylations upon nicotinamide treatment. In addition, transcriptomic analysis of nicotinamide treated and untreated FRDA primary lymphocytes revealed that the expression of 67% of genes known to be dysregulated in FRDA was ameliorated by the treatment. These findings show that nictotinamide can up-regulate the FXN gene and reveal a potential mechanism of action for nicotinamide in reactivating the epigenetically silenced FXN gene and therefore support the further assessment of HDAC inhibitors (HDACi's) in FRDA and diseases caused by a similar mechanism.

Sustained inhibition of deacetylases is required for the antitumor activity of the histone deactylase inhibitors panobinostat and vorinostat in models of colorectal cancer

Despite compelling preclinical data in colorectal cancer (CRC), the efficacy of HDACIs has been disappointing in the clinic. The goal of this study was to evaluate the effectiveness of vorinostat and panobinostat in a dose- and exposure-dependent manner in order to better understand the dynamics of drug action and antitumor efficacy. In a standard 72 h drug exposure MTS assay, notable concentration-dependent antiproliferative effects were observed in the IC50 range of 1.2-2.8 μmol/L for vorinostat and 5.1-17.5 nmol/L for panobinostat. However, shorter clinically relevant exposures of 3 or 6 h failed to elicit any significant growth inhibition and in most cases a >24 h exposure to vorinostat or panobinostat was required to induce a sigmoidal dose-response. Similar results were observed in colony formation assays where ≥ 24 h of exposure was required to effectively reduce colony formation. Induction of acetyl-H3, acetyl-H4 and p21 by vorinostat were transient and rapidly reversed within 12 h of drug removal. In contrast, panobinostat-induced acetyl-H3, acetyl-H4, and p21 persisted for 48 h after an initial 3 h exposure. Treatment of HCT116 xenografts with panobinostat induced significant increases in acetyl-H3 and downregulation of thymidylate synthase after treatment. Although HDACIs exert both potent growth inhibition and cytotoxic effects when CRC cells were exposed to drug for ≥ 24 h, these cells demonstrate an inherent ability to survive HDACI concentrations and exposure times that exceed those clinically achievable. Continued efforts to develop novel HDACIs with improved pharmacokinetics/phamacodynamics, enhanced intratumoral delivery and class/isoform-specificity are needed to improve the therapeutic potential of HDACIs and HDACI-based combination regimens in solid tumors.

The development and potential clinical utility of biomarkers for HDAC inhibitors

Drug discovery has always been a complex process including many phases from target validation to clinical development. Data from the Food and Drug Administration (FDA) has estimated that the elimination rate for investigational new drugs entering clinical trials is up to 80%. In recent years, many kinds of biomarkers have been used to predict response in cancer treatment and for evaluation of new drugs. By increasing the understanding of histone deactylase (HDAC) inhibitors cellular mechanism of action, we have elucidated how HDAC inhibitors exert their effect by the use of proper biomarkers. In this paper, we mainly focus on the development and potential clinical utility of HDAC inhibitor biomarkers.

Histone Deactylase Inhibitor SAHA Induces a Synergistic HIV-1 Reactivation by 12-O-Tetradecanoylphorbol-13-Acetate in Latently Infected Cells

Objectives: Recent studies have reported that human immunodeficiency virus type 1 (HIV-1) proviruses are strongly suppressed in the unique epigenetic environments caused by chromatin modifications such as acetylation and methylation. Therefore, optimized therapeutic strategies directed against the virus reservoir using these epigenetic modifying agents (EMAs) should cure HIV infection. Methods: Cytotoxicity and HIV-1 reactivation were determined using the PrestoBlue™ Cell Viability Reagent and p24 HIV ELISA, respectively. Results: EMAs, including histone deacetylase inhibitors (VPA and SAHA), DNA methyltransferase inhibitor (5′-Aza-CdR), histone methyltransferase inhibitor (ADOX) and 12-O-tetradecanoylphorbol-13-acetate (TPA), were used to reactivate proviruses in HIV-1 latently infected cells. The effect of monotreatment with these EMAs on HIV-1 reactivation was VPA or SAHA > 5′-Aza-CdR > ADOX. Even though cotreatment with these potential HIV-1 reactivating agents did not show any significant reactivation effects in HIV-1 latently infected cells, employing SAHA under TPA treatment demonstrated a dramatic synergistic effect on purging HIV-1 proviruses in all HIV-1 latently infected cells via the ERK and AP-1 pathways. Conclusions: These results suggest that the combined approaches of EMAs, cotreatment of SAHA and TPA, could provide an effective way to lead a decline of HIV-1 reservoirs in patients.

The gene for the transcription factor BHLHE40/DEC1/stra13 is a dynamically regulated primary target of the vitamin D receptor

The basic helix-loop-helix protein BHLHE40 functions as a transcriptional repressor and is involved in the control of cellular growth, development and circadian rhythms. By the use of genome-wide data on vitamin D receptor (VDR) location, open chromatin and histone modification backed-up by gene-specific mRNA expression studies we show that the human BHLHE40 gene is dynamically up-regulated by the VDR ligand 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) and down-regulated by the histone deactylase inhibitor trichostatin A. The VDR binding site is located 1.7kb upstream of the transcription start site of the BHLHE40 gene and the chromatin at this genomic site is significantly opened by treatment with 1α,25(OH)2D3. The stair case style fluctuations in the BHLHE40 mRNA accumulation relate to the short half-life of the gene's mRNA of 0.9h. The identification of the widely expressed BHLHE40 gene as a primary VDR target may explain secondary effects of 1α,25(OH)2D3 on BHLHE40 responding genes.This article is part of a Special Issue entitled ‘Vitamin D Workshop’.

Vorinostat (SAHA), Cladribine, and Rituximab in Previously Untreated Mantle Cell Lymphoma: Updated Results From a Phase I/II Trial

AbstractAbstract 3675 Background:Mantle cell lymphoma (MCL) remains incurable and little consensus exists on the best standard initial therapy. However, improved understanding of disease biology has the potential to lead to novel treatment approaches including new perspectives on older drugs. For example, epigenetic modifications including altered DNA methylation and histone acetylation previously identified in MCL has provided the rationale for using the combination of a hypomethylating agent and a histone deactylase inhibitor. Here we show that agents with differing mechanisms have significant activity in previously untreated MCL.In addition to its cytotoxic effects in lymphoid malignancies, cladribine has hypomethylating properties. Vorinostat (SAHA) is a histone deacetylase inhibitor (HDACi) FDA approved in cutaneous T cell lymphoma with modest single agent activity in MCL. Preclinically, the combination of these agents has been shown to activate silenced genes. Since cladribine inhibits DNA methylation via a unique mechanism, it could also potentially inhibit histone methylation.We previously reported initial results of our Phase I/II trial combining SAHA, cladribine, and rituximab (SCR) for the treatment of B-cell non-Hodgkin's Lymphoma (NHL) [Spurgeon et al, ASH, 2012]. Here we present the updated results from the Phase II portion of the trial in the untreated MCL cohort including response rate, overall and progression free survival, and correlative studies. Methods:The achieved phase II starting dose was vorinostat 400 mg po (days 1–14) combined with cladribine 5mg/m2 IV (days 1–5), and Rituximab 375 mg/m2 IV (weekly × 4 for cycle 1 and 1x/month) every 28 days for up to 6 cycles. Response evaluation occurs after 2 cycles and at the completion of therapy. Responding patients are eligible to receive maintenance rituximab. Phase II eligibility includes relapsed NHL as well as previously untreated MCL. The primary outcome is response rate (ORR); secondary endpoints include progression-free survival (PFS) and overall survival (OS). Scientific correlatives include analysis of CD20 expression, histone acetylation, gene microarray, qRT-PCR and HELP methylation analysis. To evaluate the possible effects of SAHA metabolism on toxicity and response, UDP-glucuronosyltransferase 2B17 (UGT2B17) genotyping is also performed. This study continues to enroll patients. Results:28 previously untreated MCL patients have been enrolled on the phase II portion of the study. 7 have not yet completed the planned 6 cycles; however, 26 patients have completed ≥ 2 cycles and are evaluable for response. The majority of responding patients have received maintenance rituximab. The overall response rate (ORR) is 100% (26/26) with 69% (18/26) achieving CR. Of those patients not attaining CR, 2 had blastic MCL and died, 3 have not yet completed active treatment, and 1 withdrew consent after two cycles. At a median follow up of 14.7 months (.07 – 25 months) 4 patients have relapsed and 3 have died. Of the relapsing patients, two had blastic MCL. None of the patients achieving a CR has relapsed. The estimated PFS curve (shown in the Kaplan-Meier curve below) did not reach the 0.5 level and therefore, median PFS could not be estimated. Toxicities were defined using CTCAE 4 and primarily include neutropenia, thrombocytopenia, fatigue, anorexia, and dehydration. [Display omitted] We found that cladribine hypomethylates DNA in vivo (8/8 pts) and inhibits histone methylation in vitro. There were no upregulated genes common to untreated leukemic MCL patients; however, a number of changes in gene expression were observed. For example, upregulated genes after treatment included DUSP2 (3 patients), FOXO3 (2 patients), NOXA1 (2 patients), CEBPb (2 patients) and p53 (3 patients). Conclusions:The SCR regimen has significant activity and shows epigenetic activity in previously untreated MCL. Initial follow up results are promising, especially in patients without blastic MCL who continue with maintenance rituximab. The SCR regimen should be studied further in NHL. Disclosures:Spurgeon:Merck : Research Funding. Off Label Use: vorinostat: off label use mantle cell lymphoma. Epner:Merck: Research Funding, Speakers Bureau.

Selective Histone Deacetylase 6 Inhibitors Bearing Substituted Urea Linkers Inhibit Melanoma Cell Growth

The incidence of malignant melanoma has dramatically increased in recent years thus requiring the need for improved therapeutic strategies. In our efforts to design selective histone deactylase inhibitors (HDACI), we discovered that the aryl urea 1 is a modestly potent yet nonselective inhibitor. Structure-activity relationship studies revealed that adding substituents to the nitrogen atom of the urea so as to generate compounds bearing a branched linker group results in increased potency and selectivity for HDAC6. Compound 5 g shows low nanomolar inhibitory potency against HDAC6 and a selectivity of ∼600-fold relative to the inhibition of HDAC1. These HDACIs were evaluated for their ability to inhibit the growth of B16 melanoma cells with the most potent and selective HDAC6I being found to decrease tumor cell growth. To the best of our knowledge, this work constitutes the first report of HDAC6-selective inhibitors that possess antiproliferative effects against melanoma cells.

Functional rescue of mutant ABCA1 proteins by sodium 4-phenylbutyrate

Mutations in the ATP-binding cassette transporter A1 (ABCA1) are a major cause of decreased HDL cholesterol (HDL-C), which infers an increased risk of cardiovascular disease (CVD). Many ABCA1 mutants show impaired localization to the plasma membrane. The aim of this study was to investigate whether the chemical chaperone, sodium 4-phenylbutyrate (4-PBA) could improve cellular localization and function of ABCA1 mutants. Nine different ABCA1 mutants (p.A594T, p.I659V, p.R1068H, p.T1512M, p.Y1767D, p.N1800H, p.R2004K, p.A2028V, p.Q2239N) expressed in HEK293 cells, displaying different degrees of mislocalization to the plasma membrane and discrete impacts on cholesterol efflux, were subject to treatment with 4-PBA. Treatment restored localization to the plasma membrane and increased cholesterol efflux function for the majority of mutants. Treatment with 4-PBA also increased ABCA1 protein expression in all transfected cell lines. In fibroblast cells obtained from low HDL-C subjects expressing two of the ABCA1 mutants (p.R1068H and p.N1800H), 4-PBA increased cholesterol efflux without any increase in ABCA1 expression. Our study is the first to investigate the effect of the chemical chaperone, 4-PBA on ABCA1 and shows that it is capable of restoring plasma membrane localization and enhancing the cholesterol efflux function of mutant ABCA1s both in vitro and ex vivo. These results suggest 4-PBA may warrant further investigation as a potential therapy for increasing cholesterol efflux and HDL-C levels.

Activation of tachykinin, neurokinin 3 receptors affects chromatin structure and gene expression by means of histone acetylation

The tachykinin, neurokinin 3 receptor (NK3R) is a g-protein coupled receptor that is broadly distributed in the nervous system and exerts its diverse physiological actions through multiple signaling pathways. Despite the role of the receptor system in a range of biological functions, the effects of NK3R activation on chromatin dynamics and gene expression have received limited attention. The present work determined the effects of senktide, a selective NK3R agonist, on chromatin organization, acetylation, and gene expression, using qRT-PCR, in a hypothalamic cell line (CLU 209) that expresses the NK3R. Senktide (1nM, 10nM) caused a relaxation of chromatin, an increase in global acetylation of histone H3 and H4, and an increase in the expression of a common set of genes involved in cell signaling, cell growth, and synaptic plasticity. Pretreatment with histone acetyltransferase (HAT) inhibitor (garcinol and 2-methylene y-butylactone), that inhibits p300, p300/CREB binding protein (CBP) associated factor (PCAF), and GCN 5, prevented the senktide-induced increase in expression of most, but not all, of the genes upregulated in response to 1nM and 10nM senktide. Treatment with 100nM had the opposite effect: a reduction in chromatin relaxation and decreased acetylation. The expression of four genes was significantly decreased and the HAT inhibitor had a limited effect in blocking the upregulation of genes in response to 100nM senktide. Activation of the NK3R appears to recruit multiple pathways, including acetylation, and possibly histone deactylases, histone methylases, or DNA methylases to affect chromatin structure and gene expression.

Differential Sirtuin Expression Patterns in Amyotrophic Lateral Sclerosis (ALS) Postmortem Tissue: Neuroprotective or Neurotoxic Properties of Sirtuins in ALS?

Background/Aims: Sirtuins (SIRT1–7; class III histone deactylases) modulate fundamental mechanisms in age-related neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). We assessed the expression levels of sirtuins in human postmortem ALS and control brain and spinal cord. Methods and Results: By quantitative real-time PCR, a significant reduction of SIRT1 and SIRT2 was detected in homogenates of the primary motor cortex (white and gray matter), while there were no differences in spinal cord homogenates. When specifically analyzing mRNA and protein expression in the gray matter (cortical layers I–VI of the precentral gyrus, ventral/dorsal horn of the spinal cord) by in situ hybridization histochemistry and immunohistochemistry, we found increased levels of SIRT1, SIRT2 and SIRT5 in ALS which were significant for SIRT1 and SIRT5 mRNA in the spinal cord. Conclusion: Our results indicate a general reduction of SIRT1 and SIRT2 in ALS primary motor cortex, while in situ hybridization histochemistry and immunohistochemistry showed neuron-specific upregulation of SIRT1, SIRT2 and SIRT5, particularly in the spinal cord. Opposed effects have been described for SIRT1 and SIRT2: while SIRT1 activation is mainly associated with neuroprotection, SIRT2 upregulation is toxic to neuronal cells. Novel therapeutic approaches in ALS could therefore target SIRT1 activation or SIRT2 inhibition.