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Biomedical subjects

Paul A Marks

Publications and source records attributed to Paul A Marks.

At least 19 recordsLinked to original sources
PubMed2007

Suberoylanilide hydroxamic acid (vorinostat) represses androgen receptor expression and acts synergistically with an androgen receptor antagonist to inhibit prostate cancer cell proliferation.

Growth of prostate cancer cells is initially dependent on androgens, and androgen ablation therapy is used to control tumor growth. Unfortunately, resistance to androgen ablation therapy inevitably occurs, and there is an urgent need for better treatments for advanced prostate cancer. Histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid (SAHA; vorinostat), are promising agents for the treatment of a range of malignancies, including prostate cancer. SAHA inhibited growth of the androgen-responsive LNCaP prostate cancer cell line at low micromolar concentrations and induced caspase-dependent apoptosis associated with chromatin condensation, DNA fragmentation, and mitochondrial membrane depolarization at higher concentrations (>/=5 mumol/L). Gene profiling and immunoblot analyses showed a decrease in androgen receptor (AR) mRNA and protein in LNCaP cells cultured with SAHA compared with control cells, with a corresponding decrease in levels of the AR-regulated gene, prostate-specific antigen. Culture of LNCaP cells in steroid-free medium markedly sensitized the cells to SAHA. Moreover, a combination of low, subeffective doses of SAHA and the AR antagonist bicalutamide resulted in a synergistic reduction in cell proliferation and increase in caspase-dependent cell death. Addition of exogenous androgen prevented the induction of cell death, indicating that suppression of androgen signaling was required for synergy. At the subeffective concentrations, these agents had no effect, alone or in combination, on proliferation or death of AR-negative PC-3 prostate cancer cells. Our findings indicate that SAHA is effective in targeting the AR signaling axis and that androgen deprivation sensitizes prostate cancer cells to SAHA. Consequently, combinatorial treatments that target different components of the AR pathway may afford a more effective strategy to control the growth of prostate cancer cells.

Androgen Receptor Antagonists↗
PubMed2007

Dimethyl sulfoxide to vorinostat: development of this histone deacetylase inhibitor as an anticancer drug.

In our quest to understand why dimethyl sulfoxide (DMSO) can cause growth arrest and terminal differentiation of transformed cells, we followed a path that led us to discover suberoylanilide hydroxamic acid (SAHA; vorinostat (Zolinza)), which is a histone deacetylase inhibitor. SAHA reacts with and blocks the catalytic site of these enzymes. Extensive structure-activity studies were done along the path from DMSO to SAHA. SAHA can cause growth arrest and death of a broad variety of transformed cells both in vitro and in tumor-bearing animals at concentrations not toxic to normal cells. SAHA has many protein targets whose structure and function are altered by acetylation, including chromatin-associated histones, nonhistone gene transcription factors and proteins involved in regulation of cell proliferation, migration and death. In clinical trials, SAHA has shown significant anticancer activity against both hematologic and solid tumors at doses well tolerated by patients. A new drug application was approved by the US Food and Drug Administration for vorinostat for treatment of cutaneous T-cell lymphoma. More potent analogs of SAHA have shown unacceptable toxicity.

Animals↗
PubMed2006

Intrinsic apoptotic and thioredoxin pathways in human prostate cancer cell response to histone deacetylase inhibitor.

There is a great need to develop better mechanism-based therapies for prostate cancer. In this investigation, we studied four human prostate cancer cell lines, LNCaP, DU145, LAPC4, and PC3, which differ in response to the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (vorinostat), a new anticancer drug. Examining the role of intrinsic mitochondrial caspase-dependent apoptosis and caspase-independent, reactive oxygen species (ROS) facilitated cell death, has provided an understanding of mechanisms that may determine the varied response to the histone deacetylase inhibitor. We found striking differences among these cancer cells in constitutive expression and response to suberoylanilide hydroxamic acid in levels of antiapoptotic and proapoptotic proteins, mitochondria membrane integrity, activation of caspases, ROS accumulation, and expression of thioredoxin, the major scavenger of ROS. Identifying these differences can have predictive value in assessing therapeutic response and identifying targets to enhance therapeutic efficacy.

Antineoplastic Agents↗
PubMed2006

Thioredoxin in cancer--role of histone deacetylase inhibitors.

Increased levels of thioredoxin (Trx) occur in a number of human cancers, which may contribute to the resistance of cancers to therapy by scavenging reactive oxygen species (ROS) which are generated by various anti-cancer agents. Many human cancers have low levels of thioredoxin-binding protein (TBP-2). TBP-2 binds to Trx and blocks its reducing activity. Histone deacetylase inhibitors (HDACi) up-regulate TBP-2 in various transformed cells, associated with a decrease in Trx levels. Up-regulation of TBP-2 and decrease of Trx may contribute to the sensitivity of many hematologic and solid tumors to anti-cancer activity of HDACi.

Enzyme Inhibitors↗
PubMed2005

Prospects: histone deacetylase inhibitors.

Histone deacetylase (HDAC), inhibitors represent a new class of targeted anti-cancer agents. Several of these compounds are in clinical trials with significant activity against a spectrum of both hematologic and solid tumors at doses that are well tolerated by the patients. The HDAC inhibitors are a structurally diverse group of molecules that can induce growth arrest, differentiation, apoptosis, and autophagocytic cell death of cancer cells. While the base sequence of DNA provides the genetic code for proteins, the expression of genes is regulated, in large part, by the structure of the chromatin proteins around which the DNA is wrapped (epigenetic gene regulation). The acetylation and deacetylation of the lysines in the tails of the core histones, among the most extensively studied aspects of chromatin structure, is controlled by the action of two families of enzymes, histone deacetylases (HDACs) and histone acetyltransferases (HATs). Protein components of transcription factor complexes and many other non-histone proteins are also substrates for HDACs and HATs. The structure and activity of these non-histone proteins may be altered by acetylation/deacetylation with consequent effects on various cell functions including gene expression, cell cycle progression, and cell death pathways. This review focuses on several key questions with respect to the mechanism of action of HDACi, including, what are the different cell phenotypes induced by HDACi, why are normal cells compared to transformed cells relatively resistant to HDACi induced cell death, why are certain tumors more responsive to HDACi than others, and what is the basis of the selectivity of HDACi in altering gene expression. The answers to these questions will have therapeutic importance since we will identify targets for enhancing the efficacy and safety of HDACi.

Animals↗
PubMed2005

Induction of polyploidy by histone deacetylase inhibitor: a pathway for antitumor effects.

Histone deacetylase (HDAC) inhibitors can induce various transformed cells to undergo growth arrest and/or death. Suberoylanilide hydroxamic acid (SAHA) is an HDAC inhibitor which is in phase I/II clinical trials and has shown antitumor activity in hematologic and solid tumors at doses well tolerated by patients. HDAC is the target for SAHA, but the mechanisms of the consequent induced death of transformed cells are not completely understood. In this study, we report that SAHA induced polyploidy in human colon cancer cell line HCT116 and human breast cancer cell lines, MCF-7, MDA-MB-231, and MBA-MD-468, but not in normal human embryonic fibroblast SW-38 and normal mouse embryonic fibroblasts. The polyploid cells lost the capacity for proliferation and committed to senescence. The induction of polyploidy was more marked in HCT116 p21WAF1-/- or HCT116 p53-/- cells than in wild-type HCT116. The development of senescence of SAHA-induced polyploidy cells was similar in all colon cell lines. The present findings indicate that the HDAC inhibitor could exert antitumor effects by inducing polyploidy, and this effect is more marked in transformed cells with nonfunctioning p21WAF1 or p53 genes.

Antineoplastic Agents↗
PubMed2005

Phase I study of an oral histone deacetylase inhibitor, suberoylanilide hydroxamic acid, in patients with advanced cancer.

PURPOSE: To determine the safety, dosing schedules, pharmacokinetic profile, and biologic effect of orally administered histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in patients with advanced cancer. PATIENTS AND METHODS: Patients with solid and hematologic malignancies were treated with oral SAHA administered once or twice a day on a continuous basis or twice daily for 3 consecutive days per week. Pharmacokinetic profile and bioavailibity of oral SAHA were determined. Western blots and enzyme-linked immunosorbent assays of histones isolated from peripheral-blood mononuclear cells (PBMNCs) pre and post-therapy were performed to evaluate target inhibition. RESULTS: Seventy-three patients were treated with oral SAHA and major dose-limiting toxicities were anorexia, dehydration, diarrhea, and fatigue. The maximum tolerated dose was 400 mg qd and 200 mg bid for continuous daily dosing and 300 mg bid for 3 consecutive days per week dosing. Oral SAHA had linear pharmacokinetics from 200 to 600 mg, with an apparent half-life ranging from 91 to 127 minutes and 43% oral bioavailability. Histones isolated from PBMNCs showed consistent accumulation of acetylated histones post-therapy, and enzyme-linked immunosorbent assay demonstrated a trend towards a dose-dependent accumulation of acetylated histones from 200 to 600 mg of oral SAHA. There was one complete response, three partial responses, two unconfirmed partial responses, and 22 (30%) patients remained on study for 4 to 37+ months. CONCLUSIONS: Oral SAHA has linear pharmacokinetics and good bioavailability, inhibits histone deacetylase activity in PBMNCs, can be safely administered chronically, and has a broad range of antitumor activity.

Administration, Oral↗
PubMed2005

Novel histone deacetylase inhibitors in the treatment of thyroid cancer.

Histone deacetylases (HDAC) and histone acetyltransferases exert opposing enzymatic activities that modulate the degree of acetylation of histones and other intracellular molecular targets, thereby regulating gene expression, cellular differentiation, and survival. HDAC inhibition results in accumulation of acetylated histones and induces differentiation and/or apoptosis in transformed cells. In this study, we characterized the effect of two HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and m-carboxycinnamic acid bis-hydroxamide, on thyroid carcinoma cell lines, including lines originating from anaplastic and medullary carcinomas. In these models, both SAHA and m-carboxycinnamic acid bis-hydroxamide induced growth arrest and caspase-mediated apoptosis and increased p21 protein levels, retinoblastoma hypophosphorylation, BH3-interacting domain death agonist cleavage, Bax up-regulation, down-regulation of Bcl-2, A1, and Bcl-x(L) expression, and cleavage of poly(ADP-ribose) polymerase and caspase-8, -9, -3, -7, and -2. Transfection of Bcl-2 cDNA partially suppressed SAHA-induced cell death. SAHA down-regulated the expression of the apoptosis inhibitors FLIP and cIAP-2 and sensitized tumor cells to cytotoxic chemotherapy and death receptor activation. Our studies provide insight into the tumor type-specific mechanisms of antitumor effects of HDAC inhibitors and a framework for future clinical applications of HDAC inhibitors in patients with thyroid cancer, including histologic subtypes (e.g., anaplastic and medullary thyroid carcinomas) for which limited, if any, therapeutic options are available.

Antineoplastic Agents↗
PubMed2005

Histone deacetylase inhibitors in programmed cell death and cancer therapy.

Histone deacetylase (HDAC) inhibitors, such as suberoylanilide hydroxamic acid (SAHA), are targeted anticancer agents that have significant anticancer activity at doses well tolerated by patients. Recently, we found that HDAC inhibitors can trigger both mitochondria-mediated apoptosis and caspase-independent autophagic cell death, indicating potential benefit of HDAC inhibitors in treating cancers with apoptotic defects. We also found that thioredoxin (TRX) might play a significant role in HDAC inhibitor-induced cell death, and HDAC inhibitors increase TRX levels in normal cells but not transformed cells, which is likely to be one of the reasons why HDAC inhibitors preferentially kill cancer cells. In this review, we discuss the study of HDAC inhibitors in cell death and cancer research, the implications of our recent findings, and some outstanding questions that need to be addressed.

Antineoplastic Agents↗
PubMed2005

Identification and functional significance of genes regulated by structurally different histone deacetylase inhibitors.

Histone deacetylase inhibitors (HDACis) inhibit tumor cell growth and survival, possibly through their ability to regulate the expression of specific proliferative and/or apoptotic genes. However, the HDACi-regulated genes necessary and/or sufficient for their biological effects remain undefined. We demonstrate that the HDACis suberoylanilide hydroxamic acid (SAHA) and depsipeptide regulate a highly overlapping gene set with at least 22% of genes showing altered expression over a 16-h culture period. SAHA and depsipeptide coordinately regulated the expression of several genes within distinct apoptosis and cell cycle pathways. Multiple genes within the Myc, type beta TGF, cyclin/cyclin-dependent kinase, TNF, Bcl-2, and caspase pathways were regulated in a manner that favored induction of apoptosis and decreased cellular proliferation. APAF-1, a gene central to the intrinsic apoptotic pathway, was induced by SAHA and depsipeptide and shown to be important, but not essential, for HDACi-induced cell death. Overexpression of p16(INK4A) and arrest of cells in G(1) can suppress HDACi-mediated apoptosis. Although p16(INK4A) did not affect the genome-wide transcription changes mediated by SAHA, a small number of apoptotic genes, including BCLXL and B-MYB, were differentially regulated in a manner consistent with attenuated HDACi-mediated apoptosis in arrested cells. We demonstrate that different HDACi alter transcription of a large and common set of genes that control diverse molecular pathways important for cell survival and proliferation. The ability of HDACi to target multiple apoptotic and cell proliferation pathways may provide a competitive advantage over other chemotherapeutic agents because suppression/loss of a single pathway may not confer resistance to these agents.

Apoptosis↗
PubMed2005

Drug insight: Histone deacetylase inhibitors--development of the new targeted anticancer agent suberoylanilide hydroxamic acid.

This review focuses on the discovery and development of the histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA). Post-translational modifications of the histones of chromatin are important factors in regulating gene expression--so-called epigenetic gene regulation. Acetylation and deacetylation of lysine residues in histone tails, controlled by the activities of HDACs and histone acetyltransferases, are among the most studied post-translational modification of histones. In addition to chromatin protein, transcription factors, cell-signaling regulatory proteins, and proteins regulating cell death are substrates of HDACs and may be altered in function by HDAC inhibitors. HDAC inhibitors have several remarkable aspects. For instance, despite HDACs being ubiquitously distributed through chromatin, SAHA selectively alters the transcription of relatively few genes, and normal cells are at least 10-fold more resistant than transformed cells to SAHA and related HDAC inhibitor-induced cell death. HDAC inhibitors represent a relatively new group of targeted anticancer compounds, which are showing significant promise as agents with activity against a broad spectrum of neoplasms, at doses that are well tolerated by cancer patients. SAHA is one of the HDAC inhibitors most advanced in development. It is in phase I and II clinical trials for patients with both hematologic and solid tumors.

Cell Death↗
PubMed2005

Histone deacetylase inhibitors: discovery and development as anticancer agents.

Histone deacetylase (HDAC) inhibitors are a new class of targeted anticancer agents. Several HDAC inhibitors are in clinical trials and have shown significant activity against a spectrum of both haematological and solid tumours at doses that are well tolerated by patients. HDACs and histone acetyltransferases can, by reversible acetylation, modify the structure and function of histones and proteins in transcription factor complexes, which are involved in the regulation of gene expression, as well as many non-histone proteins that are involved in regulating cell proliferation and cell death. HDAC inhibitors are a structurally diverse group of molecules; these agents selectively alter the expression of genes. HDAC inhibitors can induce cancer cell death, whereas normal cells are relatively resistant to HDAC inhibitor-induced cell death.

Animals↗
PubMed2004

Apoptotic and autophagic cell death induced by histone deacetylase inhibitors.

Histone deacetylase (HDAC) inhibitors can induce programmed cell death in cancer cells, although the underlying mechanism is obscure. In this study, we show that two distinct HDAC inhibitors, butyrate and suberoylanilide hydroxamic acid (SAHA), induced caspase-3 activation and cell death in multiple human cancer cell lines. The activation of caspase-3 was via the mitochondria/cytochrome c-mediated apoptotic pathway because it was abrogated in mouse embryonic fibroblasts with knockout of Apaf-1, the essential mediator of the pathway. Overexpression of Bcl-XL in HeLa cells also blocked caspase activation by the HDAC inhibitors. Nevertheless, Apaf-1 knockout, overexpression of Bcl-XL, and pharmacological inhibition of caspase activity did not prevent SAHA and butyrate-induced cell death. The cells undergoing such caspase-independent death had unambiguous morphological features of autophagic cell death. Therefore, HDAC inhibitors can induce both mitochondria-mediated apoptosis and caspase-independent autophagic cell death. Induction of autophagic cell death by HDAC inhibitors has clear clinical implications in treating cancers with apoptotic defects.

Animals↗
PubMed2004

Modulation of renal disease in MRL/lpr mice by suberoylanilide hydroxamic acid.

Epigenetic regulation of gene expression is involved in the development of many diseases. Histone acetylation is a posttranslational modification of the nucleosomal histone tails that is regulated by the balance of histone deacetylases and histone acetyltransferases. Alterations in the balance of histone acetylation have been shown to cause aberrant expression of genes that are a hallmark of many diseases, including systemic lupus erythematosus. In this study, we determined whether suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor: 1) inhibits inflammatory mediator production in vitro and 2) modulates lupus progression in vivo. Mesangial cells isolated from 10-wk-old MRL/lpr mice were stimulated with LPS/IFN-gamma and incubated with SAHA. TNF-alpha, IL-6, NO, and inducible NO synthase expression were inhibited by SAHA. We then treated MRL/lpr mice with daily injections of SAHA from age 10 to 20 wk. The animals treated with SAHA had decreased spleen size and a concomitant decrease in CD4-CD8- (double-negative) T cells compared with controls. Serum autoantibody levels and glomerular IgG and C3 deposition in SAHA-treated mice were similar to controls. In contrast, proteinuria and pathologic renal disease were significantly inhibited in the mice receiving SAHA. These data indicate that SAHA blocks mesangial cell inflammatory mediator production in vitro and disease progression in vivo in MRL/lpr mice.

Adjuvants, Immunologic↗
PubMed2004

The mechanism of the anti-tumor activity of the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA).

Histone deacetylases (HDAC) are ubiquitously distributed through chromatin. Nevertheless HDAC inhibitors (HDACi), such as SAHA, selectively alter the transcription of as few as 2-5% of expressed genes in various transformed cells. p21(WAF1) is one of the most commonly induced genes in cells cultured with SAHA. Understanding the mechanism of the selective effects of the HDACi is a challenging problem. Gui et al. have identified effects of SAHA on p21(WAF1) promotor associated proteins that explain, at least in part, the selective effects of HDAC in altering gene expression.

Antineoplastic Agents↗
PubMed2004

Histone deacetylase inhibitors.

The base sequence of DNA provides the genetic code for proteins. The regulation of expression or suppression of gene transcription is largely determined by the structure of the chromatin--referred to as epigenetic gene regulation (Agalioti et al., 2002; Jenuwein and Allis, 2001; Richards and Elgin, 2002; Spotswood and Turner, 2002; Zhang and Reinberg, 2001). Posttranslational modifications of the histones of chromatin play an important role in regulating gene expression. Some of the most extensively studied epigenetic modifications involve acetylation/deacetylation of lysines in the tails of the core histones, which is controlled by the action of histone deacetylases (HDACs) and histone acetyltransferases (HATs). A controlled balance between histone acetylation and deacetylation appears to be essential for normal cell growth (Waterborg, 2002). Alterations in the structure or expression of HATs and HDACs occur in many cancers (Jones and Baylin, 2002; Marks et al., 2001, 2003; Timmermann et al., 2001; Wang et al., 2001). A structurally diverse group of molecules has been developed that can inhibit HDACs (HDACi) (Arts et al., 2003; Bouchain and Delorme, 2003; Curtin and Glaser, 2003; Johnstone and Licht, 2003; Marks et al., 2003; Remiszewski, 2003; Richon et al., 1998; Yoshida et al., 2003). These inhibitors induce growth arrest, differentiation, and?or apoptosis of cancer cells in vitro and in in vivo tumor-bearing animal models. Clinical trials with several of these agents have shown that certain HDACi have antitumor activity against various cancers at doses that are well tolerated by patients (Gottlicher et al., 2001; Kelly et al., 2002a,b; Piekarz et al., 2001; Wozniak et al., 1999).

Acetylation↗