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PubMed1973

Altered mitochondrial respiration in a chromosomal mutant of Neurospora crassa.

A mutant of Neurospora crassa (cni-1) has been isolated that has two pathways of mitochondrial respiration. One pathway is sensitive to cyanide and antimycin A, the other is sensitive only to salicyl hydroxamic acid. Respiration can proceed through either pathway and both pathways together in this mutant account for greater than 90% of all mitochondrial respiration. The cni-1 mutation segregates as a nuclear gene in crosses to other strains of Neurospora. Absorption spectra of isolated mitochondria from cni-1 show typical b- and c-type cytochromes but the absorption peaks corresponding to cytochrome aa(3) are not detectable. Extraction of soluble cytochrome c-546 from these mitochondria followed by reduction with ascorbate reveals a new absorption peak at 426 nm that is not present in wild-type mitochondria. This peak may be due to an altered cytochrome oxidase with abnormal spectral properties. Mitochondria from cni-1 have elevated levels of succinate-cytochrome c reductase but reduced levels of nicotinamide adenine dinucleotide reduced form cytochrome c reductase and of cyanide- and azide-sensitive cytochrome c oxidase. These studies suggest that the cni-1 mutation results in the abnormal assembly of cytochrome c oxidase so that the typical cytochrome aa(3) spectrum is lost and the enzyme activity is reduced. As a consequence of this alteration, a cyanide-insensitive respiratory pathway is elaborated by these mitochondria which may serve to stimulate adenosine 5'-triphosphate production via substrate level phosphorylation by glycolysis and the Krebs cycle.

Antimycin A↗
PubMed2006

Histone deacetylase inhibitors stimulate cell migration in human endometrial adenocarcinoma cells through up-regulation of glycodelin.

Histone deacetylase inhibitors (HDACIs) have recently emerged as promising anticancer drugs to induce cell cycle arrest, cytodifferentiation, and apoptosis. It is suggested, however, that HDACIs promote cell migration and invasion depending on the cell type. We have reported previously that treatment with HDACIs, including trichostatin A and suberoylanilide hydroxamic acid (SAHA) or progesterone in combination with estrogen, can induce cytodifferentiation of endometrial adenocarcinoma Ishikawa cells through up-regulation of glycodelin, a progesterone-induced endometrial glycoprotein. Given the reported role of glycodelin in cell motility and the migration-modulating potential of HDACIs, we investigated using wound healing assay and transwell migration assay whether ovarian steroid hormones, trichostatin A, or SAHA affects cell migration in endometrial cancer cell lines, Ishikawa and RL95-2. Treatment with ovarian steroid hormones, trichostatin A, and SAHA enhanced cell migration together with up-regulation of glycodelin. SAHA-augmented cell migration was almost completely blocked by gene silencing of glycodelin. Furthermore, overexpression of gycodelin alone resulted in increased cell motility in Ishikawa cells. Our results collectively indicate that glycodelin positively regulates cell motility acting as a mediator of HDACI-enhanced endometrial cell migration, suggesting the involvement of glycodelin in the dynamic endometrial gland morphogenesis during menstrual cycle. Our results raise a possibility that the use of HDACIs in the therapy for glycodelin-inducible endometrial and presumably other gynecological cancers may enhance invasion in cases in which the HDACIs fail to exert differentiation-inducing and/or antiproliferative effects.

Adenocarcinoma↗
PubMed2002

Inhibition of alveolar bone loss by matrix metalloproteinase inhibitors in experimental periodontal disease.

Periodontal disease is characterized by excessive host collagenase resulting in loss of gingival and periodontal ligament collagen and adjacent alveolar bone. Intragingival endotoxin injection induces a model of periodontal disease characterized by rapid bone loss with biochemical features similar to that of naturally occurring adult periodontitis. CH1766, a peptide with a zinc binding moeity which fits into the active site of the enzyme, and CH6631, a hydroxamic acid derivative with aryl-substituted sulphonamide residues, are inhibitors of matrix metalloproteinases (MMPIs) with differing inhibitory profiles as characterized by in vitro assays. In this study, endotoxin was injected into the gingivae of rats which were then treated orally with either 3 mg/kg or 30 mg/kg of one of the two inhibitory compounds. The gingival tissues were assessed for collagenase and gelatinase activity, plus three different pro-inflammatory cytokines. In addition, alveolar bone height in defleshed jaws was studied by computerized morphometric analysis and scanning electron microscopy. Both drugs reduced active and/or total MMP activity, in many cases to normal, and also partially normalized cytokine levels as well. A dose-response effect was seen with regard to amelioration of lipopolysaccharide-induced alveolar bone loss with both drugs. Other than studies with tetracyclines, this is the first report of beneficial effects of MMPIs in a model of periodontal disease, strongly suggesting that this class of agents could bring therapeutic benefit to patients with this disorder, and that periodontal disease can be used as a model to demonstrate in vivo efficacy of this class of drugs.

ADAM Proteins↗
PubMed2007

A metabolic screening study of trichostatin A (TSA) and TSA-like histone deacetylase inhibitors in rat and human primary hepatocyte cultures.

Hydroxamic acid (HA)-based histone deacetylase (HDAC) inhibitors, with trichostatin A (TSA) as the reference compound, are potential antitumoral drugs and show promise in the creation of long-term primary cell cultures. However, their metabolic properties have barely been investigated. TSA is rapidly inactivated in rodents both in vitro and in vivo. We previously found that 5-(4-dimethylaminobenzoyl)aminovaleric acid hydroxyamide or 4-Me2N-BAVAH (compound 1) is metabolically more stable upon incubation with rat hepatocyte suspensions. In this study, we show that human hepatocytes also metabolize TSA more rapidly than compound 1 and that similar pathways are involved. Furthermore, structural analogs of compound 1 (compounds 2-9) are reported to have the same favorable metabolic properties. Removal of the dimethylamino substituent of compound 1 creates a very stable but 50% less potent inhibitor. Chain lengthening (4 to 5 carbon spacer) slightly improves both potency and metabolic stability, favoring HA reduction to hydrolysis. On the other hand, Calpha-unsaturation and spacer methylation not only reduce HDAC inhibition but also increase the rate of metabolic inactivation approximately 2-fold, mainly through HA reduction. However, in rat hepatocyte monolayer cultures, compound 1 is shown to be extensively metabolized by phase II conjugation. In conclusion, this study suggests that simple structural modifications of amide-linked TSA analogs can improve their phase I metabolic stability in both rat and human hepatocyte suspensions. Phase II glucuronidation, however, can compensate for their lower phase I metabolism in rat hepatocyte monolayers and could play a yet unidentified role in the determination of their in vivo clearance.

Animals↗
PubMed2006

Antileukemia activity of the combination of an anthracycline with a histone deacetylase inhibitor.

We studied the cellular and molecular effects of the combination of an anthracycline with 2 different histone deacetylase inhibitors (HDACIs): vorinostat (suberoylanilide hydroxamic acid) and valproic acid (VPA). The 10% inhibitory concentration (IC(10)) of idarubicin was 0.5 nM in MOLT4 and 1.5 nM in HL60 cells. Concentrations above 0.675 microM of vorinostat resulted in at least 80% loss of cell viability in both cell lines. Concentrations of 1.5 to 3 mM of VPA induced 50% to 60% loss in viability in HL60 and 80% in MOLT4 cells. The combination of idarubicin with vorinostat at 0.075 microM or VPA at 0.25 mM resulted in at least an additive loss of cell viability in both lines. Vorinostat (0.35 microM) and VPA (0.25 mM) in combination with idarubicin (0.5 nM) resulted in a significant increase in apoptotic cells in MOLT4 cells. The combination resulted in an increase in histone H3 and H4 acetylation at 24 hours, phosphorylated H2AX, as well as in the induction of p21(CIP1) mRNA. No effect on cell cycle transition was observed. Of importance, the cellular and molecular effects observed were independent of the sequence used. In summary, the combination of an anthracycline with an HDACI should have significant clinical activity in patients with leukemia.

Acetylation↗
PubMed2005

The histone-deacetylase inhibitor SAHA potentiates proapoptotic effects of 5-fluorouracil and irinotecan in hepatoma cells.

Treatment for advanced stages of hepatocellular carcinoma (HCC) remains unsatisfactory. While 5-fluorouracil (5-FU) and irinotecan are first-line treatment options for other gastrointestinal tumors, their effect on HCCs is low. Histone-deacetylase inhibitors such as suberoylanilide hydroxamic acid (SAHA) have shown antitumoral activity at micromolar concentrations in a variety of human cancers in vitro and in vivo. Here, we investigated the effects of a combination of 5-FU, irinotecan and SAHA on growth inhibition and apoptosis induction in HCC cell lines. HepG2, Hep1B and MH-7777A hepatoma cell lines and human foreskin fibroblasts as non-transformed controls were incubated with 5-FU, irinotecan and SAHA either alone or in combination. While the single agents did not show any effects on growth of the cell lines, the combination of 5-FU and irinotecan (both 10 microM) led to a moderate increase in apoptosis and proliferation inhibition. Adding 1 microM SAHA increased the apoptosis rate in hepatoma cell lines up to 92% after 72 h, while fibroblasts showed no response (5.5% apoptosis). Induction of apoptosis was paralleled by loss of the mitochondrial transmembrane potential, downregulation of bcl-2 expression and activation of caspase 3 but not caspase 8. In summary, SAHA sensitized HCC cell lines for treatment with an otherwise ineffective combination of 5-FU and irinotecan and led to mitochondrial apoptosis induction. The use of the triple combination could optimize treatment results in vivo and needs further evaluation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Selective growth inhibition of tumor cells by a novel histone deacetylase inhibitor, NVP-LAQ824.

We have synthesized a histone deacetylase inhibitor, NVP-LAQ824, a cinnamic hydroxamic acid, that inhibited in vitro enzymatic activities and transcriptionally activated the p21 promoter in reporter gene assays. NVP-LAQ824 selectively inhibited growth of cancer cell lines at submicromolar levels after 48-72 h of exposure, whereas higher concentrations and longer exposure times were required to retard the growth of normal dermal human fibroblasts. Flow cytometry studies revealed that both tumor and normal cells arrested in the G(2)-M phase of the cell cycle after compound treatment. However, an increased sub-G(1) population at 48 h (reminiscent of apoptotic cells) was observed only in the cancer cell line. Annexin V staining data supported our hypothesis that NVP-LAQ824 induced apoptosis in tumor and transformed cells but not in normal cells. Western blotting experiments showed an increased histone H3 and H4 acetylation level in NVP-LAQ824-treated cancer cells, suggesting that the likely in vivo target of NVP-LAQ824 was histone deacetylase(s). Finally, NVP-LAQ824 exhibited antitumor effects in a xenograft animal model. Together, our data indicated that the activity of NVP-LAQ824 was consistent with its intended mechanism of action. This novel histone deacetylase inhibitor is currently in clinical trials as an anticancer agent.

Animals↗
PubMed2000

Inhibition of gelatinolytic activity in tumor tissues by synthetic matrix metalloproteinase inhibitor: application of film in situ zymography.

Inhibition of gelatinolytic activity in implanted tumor tissues by oral administration of N-biphenyl sulfonyl-phenylalanine hydroxamic acid (BPHA), a selective matrix metalloproteinase (MMP) inhibitor, was demonstrated by means of film in situ zymography (FIZ). Active-MMP-2 but not pro-MMP-2 showed gelatinolytic activity in FIZ, whereas both forms of MMP-2 were found to be active in conventional zymography. A mixture of either tissue inhibitors of metalloproteinase-2 or BPHA with active-MMP-2 resulted in inhibition of gelatinolytic activity in FIZ but not in zymography. Thus, FIZ, but not zymography, could detect net MMP activity in tumor tissues. When a specimen from Ma44 human lung cancer xenograft was subjected to FIZ, gelatinolytic activity was markedly detected with precise localization in the tumor tissues. The gelatinolytic activity detected in Ma44 tumor tissues was found to be mainly derived from MMPs because the gelatin-degrading activity was inhibited by pretreatment of the tumor specimen with MMP inhibitors. Oral administration of BPHA but not (-)BPHA, an enantiomer of BPHA lacking MMP inhibitory activity, successfully inhibited the MMP activity localized in Ma44 tumor tissues in both a dose-dependent and time-dependent manner. The data presented in this report showed for the first time that oral administration of synthetic MMP inhibitor could inhibit the net activity of MMP activity in tumor tissues, suggesting the usefulness of the FIZ technique for determining the effective dose of MMP inhibitor in clinical studies.

Animals↗
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↗
PubMed2003

Reduction of experimental laser-induced choroidal neovascularization by orally administered BPHA, a selective metalloproteinase inhibitor.

BACKGROUND: N-Biphenyl sulfonyl-phenylalanine hydroxamic acid (BPHA), a synthetic, selective matrix metalloproteinase (MMP)-2, -9, -14 inhibitor, has been reported to show significant antiangiogenic activity without unpleasant adverse effects. After film in situ zymography (FIZ) and conventional zymography were performed to detect MMP in experimental choroidal neovascularizations (CNVs), we studied the reducible effect of BPHA on CNVs. METHODS: Using FIZ, the gelatinolytic activity of MMPand BPHA-reduction on gelatinolysis were examined in diode-laser-induced CNV lesions in a total of 22 male Brown Norway rats. The MMP subtypes were studied in the CNV lesions of three rats using conventional zymography. Vehicle solution only or 25-, 50-, or 100 mg/kg-body-weight of BPHA was administered orally twice daily for 14 days after the laser photocoagulation in 18 rats, respectively. Fluorescein angiograms were taken, and the late hyperfluorescence of CNVs was given scores by three researchers using four grades. The thickness of CNV lesions was studied histologically. RESULTS: In laser-induced CNVs, the gelatinolytic activity of MMP and reduction of gelatinolysis by BPHA were observed on FIZ, and MMP-2 and proMMP-2 were identified by conventional zymography. The scores given to the late dye leakage and staining on angiograms were lower in the BPHA-treated groups ( p<0.01) than in the controls, and the effect appeared to be dose-dependent. Similarly, the CNV lesions in the BPHA-treated groups were less thick than in the controls ( p<0.01). CONCLUSIONS: MMP-2 played a role in laser-induced CNV development, and administration of BPHA reduced the experimental CNVs.

Administration, Oral↗
PubMed2005

Histone deacetylase inhibitors suppress the induction of c-Jun and its target genes including COX-2.

Cyclooxygenase-2 (COX-2) is considered to be a target for anticancer therapy. Histone deacetylase (HDAC) inhibitors exhibit antitumor activity, but the mechanisms of action are incompletely understood. We investigated whether HDAC inhibitors blocked AP-1-mediated activation of COX-2 transcription. Trichostatin A and suberoylanilide hydroxamic acid, two structurally related inhibitors of HDAC activity, blocked AP-1-mediated induction of COX-2 expression and prostaglandin E2 biosynthesis. Chromatin immunoprecipitation assays indicated that HDAC inhibitors suppressed c-Jun binding to the COX-2 promoter and thereby blocked transcription. The observed reduction in binding reflected reduced levels of c-Jun. HDAC inhibitors suppressed the induction of c-jun transcription by blocking the recruitment of the preinitiation complex (RNA polymerase II and TFIIB) to the c-jun promoter. HDAC3 but not HDAC1 or HDAC2 was required for AP-1-mediated stimulation of c-jun expression. Because HDAC inhibitors suppressed the induction of c-jun gene expression, resulting in reduced COX-2 transcription, it was important to determine whether other known AP-1 target genes were also modulated. Cyclin D1 and collagenase-1 are AP-1-dependent genes that have been implicated in carcinogenesis. HDAC inhibitors suppressed the induction of both cyclin D1 and collagenase-1 transcription by inhibiting the binding of c-Jun to the respective promoters. Taken together, these results suggest that HDAC inhibitors block the induction of c-jun transcription by inhibiting the recruitment of the preinitiation complex to the c-jun promoter. This led, in turn, to reduced expression of several activator protein-1-dependent genes (COX-2, cyclin D1, collagenase-1). These findings provide new insights into the mechanisms underlying the antitumor activity of HDAC inhibitors.

Blotting, Northern↗
PubMed2006

Histone deacetylase inhibitors reduce VEGF production and induce growth suppression and apoptosis in human mantle cell lymphoma.

OBJECTIVES: Mantle cell lymphoma (MCL) is an incurable disease with an aggressive course and novel treatment strategies are urgently needed. The purpose of this study was to evaluate the effects of histone deacetylase (HDAC) inhibitors, a new group of antiproliferative agents, on human MCL cells. METHODS: Three MCL cell lines (JeKo-1, Hbl-2 and Granta-519) were exposed to different concentrations of the HDAC inhibitors sodium butyrate (NaB) and suberoylanilide hydroxamic acid (SAHA) for 8-72 h. Their effects on cell viability, apoptosis induction and cell cycle proliferation were studied. Moreover, the influence of SAHA on the expression of cyclin D1, the cell cycle regulators p21 and p27 and the production of vascular endothelial growth factor (VEGF) were analyzed. RESULTS: The HDAC inhibitors induced accumulation of acetylated histones in MCL cells. MTT assays and Annexin-V staining showed that they potently inhibited viability in a dose-dependent manner and induced apoptosis in all cell lines tested. Cell cycle analysis indicated that their exposure to SAHA or NaB decreased the proportion of cells in S phase and increased the proportion of cells in the G0/G1 and/or G2/M phases. Incubation with the two HDAC inhibitors resulted in downregulation of cyclin D1. SAHA lead to an upregulation of p21 in all cell lines and an upregulation of p27 in JeKo-1 and Granta-519 cells, while expression of p27 in Hbl-2 was not altered. In addition, SAHA inhibited the production of the angiogenic cytokine VEGF. Treatment with NaB increased the expression of p21 in JeKo-1 and Hbl-2 cells, while in Granta 519 cells no effect was noted. The expression of p27 remained constant in all three cell lines after exposure to NaB. CONCLUSION: Based on these findings, we provide evidence that HDAC inhibitors have antiproliferative effects in MCL and may represent a promising therapeutic approach.

Apoptosis↗
PubMed2006

Histone deacetylase inhibitors suppress the inducibility of nuclear factor-kappaB by tumor necrosis factor-alpha receptor-1 down-regulation.

Recently, the inhibition of histone deacetylase (HDAC) enzymes has attracted attention in the oncologic community as a new therapeutic opportunity for hematologic and solid tumors including non-small cell lung cancer (NSCLC). In hematologic malignancies, such as diffuse large B-cell lymphoma, the HDAC inhibitor (HDI), suberoylanilide hydroxamic acid (SAHA), has recently entered phase II and III clinical trials. To further advance our understanding of their action on tumor cells, we investigated the possible effect of HDI treatment on the functionality of the nuclear factor-kappaB (NF-kappaB) pathway in NSCLC. We found that in the NSCLC cell lines, A549 and NCI-H460, the NF-kappaB pathway was strongly inducible, for example, by stimulation with tumor necrosis factor-alpha (TNF-alpha). Incubation of several NSCLC cell lines with HDIs resulted in greatly reduced gene expression of TNF-alpha receptor-1. HDI-treated A549 and NCI-H460 cells down-regulated TNF-alpha receptor-1 mRNA and protein levels as well as surface exposure, and consequently responded to TNF-alpha treatment with reduced IKK phosphorylation and activation, delayed IkappaB-alpha phosphorylation, and attenuated NF-kappaB nuclear translocation and DNA binding. Accordingly, stimulation of NF-kappaB target gene expression by TNF-alpha was strongly decreased. In addition, we observed that SAHA displayed antitumor efficacy in vivo against A549 xenografts grown on nude mice. HDIs, therefore, might beneficially contribute to tumor treatment, possibly by reducing the responsiveness of tumor cells to the TNF-alpha-mediated activation of the NF-kappaB pathway. These findings also hint at a possible use of HDIs in inflammatory diseases, which are associated with the overproduction of TNF-alpha, such as rheumatoid arthritis or Crohn's disease.

Animals↗
PubMed2004

Contribution of disruption of the nuclear factor-kappaB pathway to induction of apoptosis in human leukemia cells by histone deacetylase inhibitors and flavopiridol.

Interactions between the cyclin-dependent kinase inhibitor flavopiridol and the histone deacetylase inhibitors (HDACIs) sodium butyrate (NaB) and suberoylanilide hydroxamic acid (SAHA) have been examined in human leukemia cells in relation to effects on nuclear factor kappaB (NF-kappaB) activation. Exposure (24 h) of U937 human leukemia cells to NaB (1 mM) or SAHA (1.5 microM) resulted in a marked increase in NF-kappaB DNA binding, effects that were essentially abrogated by coadministration of flavopiridol (100 nM). These events were accompanied by a marked increase in mitochondrial injury, caspase activation, and apoptosis. Mutant cells expressing an IkappaBalpha super-repressor exhibited impairment of NF-kappaB DNA binding in response to HDACIs and a significant although modest increase in apoptosis. However, disruption of the NF-kappaB pathway also increased mitochondrial injury and caspase activation in response to flavopiridol and to an even greater extent to the combination of flavopiridol and HDACIs. Coadministration of flavopiridol with HDACIs down-regulated the X-linked inhibitor of apoptosis (XIAP), Mcl-1, and p21CIP1/WAF1 and activated c-Jun NH2-terminal kinase; moreover, these effects were considerably more pronounced in IkappaBalpha mutants. Similar responses were observed in U937 mutant cells stably expressing RelA/p65 small interfering RNA. In all cases, flavopiridol was significantly more potent than genetic interruption of the NF-kappaB cascade in promoting HDACI-mediated lethality. Together, these findings are consistent with the notion that although inhibition of NF-kappaB activation by flavopiridol contributes to antileukemic interactions with HDACIs, other NF-kappaB-independent flavopiridol actions (e.g., down-regulation of Mcl-1, XIAP, and p21CIP1/WAF1) play particularly critical roles in this phenomenon.

Antineoplastic Agents↗
PubMed2005

Selective induction of apoptosis by histone deacetylase inhibitor SAHA in cutaneous T-cell lymphoma cells: relevance to mechanism of therapeutic action.

Suberoylanilide hydroxamic acid (SAHA), an orally administered inhibitor of histone deacetylases, is currently in phase II clinical trials for cutaneous T cell lymphomas (CTCL), but the mechanism of SAHA action is unknown. In this study, we investigated the anti-tumor effects of SAHA in CTCL cell lines and freshly isolated peripheral blood lymphocytes (PBL) from CTCL patients with high percentage of circulating malignant T cells. Three cell lines (MJ, Hut78, and HH) and PBL from 11 patients and three healthy donors were treated with SAHA (1, 2.5, and 5 microM) for 24 and/or 48 h. Apoptosis was determined by flow cytometry analysis of sub-G1 hypodiploid nuclei and/or annexin V binding populations. Acetylated histones and apoptosis-associated proteins were detected by Western blotting. SAHA at 1-5 microM for 24 and 48 h induced apoptosis in a concentration- and time-dependent manner in three cell lines: MJ (0%-7% and 1%-32%), Hut78 (4%-36% and 5%-54%), and HH (4%-67% and 8%-81%). SAHA at 1-5 muM for 48 h also induced more apoptosis of patients' PBL than healthy donors' (15%-32%versus 6%-13%, p < 0.05). SAHA treatment caused an accumulation of acetylated histones (H2B, H3, and H4), an increase of p21(WAF1) and bax proteins, a decrease of Stat6 and phospho-Stat6 proteins, and activation of caspase-3 in CTCL cells. Our data suggest that selective induction of malignant T cell apoptosis and modulation of acetylated histones, p21(WAF1), bax, Stat6, and caspase-3 may underlie the therapeutic action of SAHA in CTCL patients.

Acetylation↗
PubMed2001

Inhibition of transformed cell growth and induction of cellular differentiation by pyroxamide, an inhibitor of histone deacetylase.

PURPOSE: We have synthesized a series of hybrid polar compounds that induce differentiation and/or apoptosis of various transformed cells. These agents are also potent inhibitors of histone deacetylases (HDACs). Pyroxamide (suberoyl-3-aminopyridineamide hydroxamic acid) is a new member of this class of compounds that is currently under development as an anticancer agent. We investigated the activity of pyroxamide as an inducer of differentiation and/or apoptosis in transformed cells. EXPERIMENTAL DESIGN AND RESULTS: Pyroxamide, at micromolar concentrations, induced terminal differentiation in murine erythroleukemia (MEL) cells and caused growth inhibition by cell cycle arrest and/or apoptosis in MEL, prostate carcinoma, bladder carcinoma, and neuroblastoma cells. Administration of pyroxamide (100 or 200 mg/kg/day) to nude mice at doses that caused little evident toxicity significantly suppressed the growth of s.c. CWR22 prostate cancer xenografts. Despite the potent growth-inhibitory effects of pyroxamide in this tumor model, serum prostate-specific antigen levels in control versus pyroxamide-treated mice were not significantly different. Pyroxamide is a potent inhibitor of affinity-purified HDAC1 (ID(50) = 100 nM) and causes the accumulation of acetylated core histones in MEL cells cultured with the agent. Human CWR22 prostate tumor xenografts from mice treated with pyroxamide (100 or 200 mg/kg/day) showed increased levels of histone acetylation and increased expression of the cell cycle regulator p21/WAF1, compared with tumors from vehicle-treated control animals. CONCLUSIONS: The findings suggest that pyroxamide may be a useful agent for the treatment of malignancy and that induction of p21/WAF1 in transformed cells by pyroxamide may contribute to the antitumor effects of this agent.

Acetylation↗
PubMed2004

Combination of the histone deacetylase inhibitor LBH589 and the hsp90 inhibitor 17-AAG is highly active against human CML-BC cells and AML cells with activating mutation of FLT-3.

Present studies show that LBH589, a novel cinnamic hydroxamic acid analog histone deacetylase inhibitor, induces acetylation of histone H3 and H4 and of heat shock protein 90 (hsp90), increases p21 levels, as well as induces cell-cycle G(1) phase accumulation and apoptosis of the human chronic myeloid leukemia blast crisis (CML-BC) K562 cells and acute leukemia MV4-11 cells with the activating length mutation of FLT-3. In MV4-11 cells, this was associated with marked attenuation of the protein levels of p-FLT-3, FLT-3, p-AKT, and p-ERK1/2. In K562 cells, exposure to LBH589 attenuated Bcr-Abl, p-AKT, and p-ERK1/2. Treatment with LBH589 inhibited the DNA binding activity of signal transducers and activators of transcription 5 (STAT5) in both K562 and MV4-11 cells. The hsp90 inhibitor 17-allyl-amino-demethoxy geldanamycin (17-AAG) also induced polyubiquitylation and proteasomal degradation of FLT-3 and Bcr-Abl by reducing their chaperone association with hsp90. Cotreatment with LBH589 and 17-AAG exerted synergistic apoptosis of MV4-11 and K562 cells. In the imatinib mesylate (IM)-refractory leukemia cells expressing Bcr-Abl with the T315I mutation, treatment with the combination attenuated the levels of the mutant Bcr-Abl and induced apoptosis. Finally, cotreatment with LBH589 and 17-AAG also induced more apoptosis of IM-resistant primary CML-BC and acute myeloid leukemia (AML) cells (with activating mutation of FLT-3) than treatment with either agent alone.

Acute Disease↗
PubMed2005

Inhibition of histone deacetylase 6 acetylates and disrupts the chaperone function of heat shock protein 90: a novel basis for antileukemia activity of histone deacetylase inhibitors.

The hydroxamic acid (HAA) analogue pan-histone deacetylase (HDAC) inhibitors (HDIs) LAQ824 and LBH589 have been shown to induce acetylation and inhibit the ATP binding and chaperone function of heat shock protein (HSP) 90. This promotes the polyubiquitylation and degradation of the pro-growth and pro-survival client proteins Bcr-Abl, mutant FLT-3, c-Raf, and AKT in human leukemia cells. HDAC6 is a member of the class IIB HDACs. It is predominantly cytosolic, microtubule-associated alpha-tubulin deacetylase that is also known to promote aggresome inclusion of the misfolded polyubiquitylated proteins. Here we demonstrate that in the Bcr-abl oncogene expressing human leukemia K562 cells, HDAC6 can be co-immunoprecipitated with HSP90, and the knock-down of HDAC6 by its siRNA induced the acetylation of HSP90 and alpha-tubulin. Depletion of HDAC6 levels also inhibited the binding of HSP90 to ATP, reduced the chaperone association of HSP90 with its client proteins, e.g. Bcr-Abl, and induced polyubiquitylation and partial depletion of Bcr-Abl. Conversely, the ectopic overexpression of HDAC6 inhibited LAQ824-induced acetylation of HSP90 and alpha-tubulin and reduced LAQ824-mediated depletion of Bcr-Abl, AKT, and c-Raf. Collectively, these findings indicate that HDAC6 is also an HSP90 deacetylase. Targeted inhibition of HDAC6 leads to acetylation of HSP90 and disruption of its chaperone function, resulting in polyubiquitylation and depletion of pro-growth and pro-survival HSP90 client proteins including Bcr-Abl. Depletion of HDAC6 sensitized human leukemia cells to HAA-HDIs and proteasome inhibitors.

Acetylation↗