Histone deacetylase inhibitors and paclitaxel cause synergistic effects on apoptosis and microtubule stabilization in papillary serous endometrial cancer cells

The use of histone deacetylase (HDAC) inhibitors has shown promise for a variety of malignancies. In this investigation, we define the activity of this class of inhibitors in combination with traditional cytotoxic chemotherapy in endometrial cancer cells. Significant reductions in growth were observed in Ark2 and KLE endometrial cancer cells following treatment with paclitaxel, doxorubicin, carboplatin, or the HDAC inhibitor trichostatin A (TSA). However, only combined treatment with TSA/paclitaxel caused synergistic inhibition of cell growth. This combination also resulted in significant changes in cell morphology. Using cell cycle analysis, nuclear staining, and Western blot analysis for poly(ADP-ribose) polymerase and caspase-9 degradation products, TSA/paclitaxel showed the most dramatic activation of the apoptotic cascade. These effects were also observed when the HDAC inhibitors HDAC inhibitor-1 or oxamflatin were substituted for TSA. The anticancer properties of paclitaxel are known to result in part from inhibition of microtubule depolymerization, which results in apoptosis. We show that TSA administration also stabilizes microtubules via alpha-tubulin acetylation. Furthermore, using Western blot and immunohistochemical analysis, treatment with TSA/paclitaxel led to a significant increase in acetylated tubulin and microtubule stabilization. These effects were confirmed in a mouse xenograft model. Moreover, TSA/paclitaxel resulted in a 50% reduction in tumor weight compared with either agent alone. This study provides in vivo evidence of nonhistone protein acetylation as one possible mechanism by which HDAC inhibitors reduce cancer growth. The TSA/paclitaxel combination seems to hold promise for the treatment of serous endometrial carcinoma and other malignancies with limited sensitivity to paclitaxel.     

Ability of plasma-activated acetated Ringer’s solution to induce A549 cell injury is enhanced by a pre-treatment with histone deacetylase inhibitors

Non-thermal plasma (NTP) is applicable to living cells and has emerged as a novel technology for cancer therapy. NTP affect cells not only by direct irradiation, but also by an indirect treatment with previously prepared plasma-activated liquid. Histone deacetylase (HDAC) inhibitors have the potential to enhance susceptibility to anticancer drugs and radiation because these reagents decondense the compact chromatin structure by neutralizing the positive charge of the histone tail. The aim of the present study was to demonstrate the advantage of the combined application of plasma-activated acetated Ringer’s solution (PAA) and HDAC inhibitors on A549 cancer cells. PAA maintained its ability for at least 1 week stored at any temperature tested. Cell death was enhanced more by combined regimens of PAA and HDAC inhibitors, such as trichostatin A (TSA) and valproic acid (VPA), than by a single PAA treatment and was accompanied by ROS production, DNA breaks, and mitochondria dysfunction through a caspase-independent pathway. These phenomena induced the depletion of ATP and elevations in intracellular calcium concentrations. The sensitivities of HaCaT cells as normal cells to PAA were less than that of A549 cells. These results suggest that HDAC inhibitors synergistically induce the sensitivity of cancer cells to PAA.     

Antimalarial activity of the anticancer histone deacetylase inhibitor SB939

Histone deacetylase (HDAC) enzymes posttranslationally modify lysines on histone and nonhistone proteins and play crucial roles in epigenetic regulation and other important cellular processes. HDAC inhibitors (e.g., suberoylanilide hydroxamic acid [SAHA; also known as vorinostat]) are used clinically to treat some cancers and are under investigation for use against many other diseases. Development of new HDAC inhibitors for noncancer indications has the potential to be accelerated by piggybacking onto cancer studies, as several HDAC inhibitors have undergone or are undergoing clinical trials. One such compound, SB939, is a new orally active hydroxamate-based HDAC inhibitor with an improved pharmacokinetic profile compared to that of SAHA. In this study, the in vitro and in vivo antiplasmodial activities of SB939 were investigated. SB939 was found to be a potent inhibitor of the growth of Plasmodium falciparum asexual-stage parasites in vitro (50% inhibitory concentration [IC(50)], 100 to 200 nM), causing hyperacetylation of parasite histone and nonhistone proteins. In combination with the aspartic protease inhibitor lopinavir, SB939 displayed additive activity. SB939 also potently inhibited the in vitro growth of exoerythrocytic-stage Plasmodium parasites in liver cells (IC(50), ~150 nM), suggesting that inhibitor targeting to multiple malaria parasite life cycle stages may be possible. In an experimental in vivo murine model of cerebral malaria, orally administered SB939 significantly inhibited P. berghei ANKA parasite growth, preventing development of cerebral malaria-like symptoms. These results identify SB939 as a potent new antimalarial HDAC inhibitor and underscore the potential of investigating next-generation anticancer HDAC inhibitors as prospective new drug leads for treatment of malaria.     

Cell cycle checkpoint signaling involved in histone deacetylase inhibition and radiation-induced cell death

In breast cancer, radiation has a central role in the treatment of brain metastasis, although tumor sensitivity might be limited. The tumor cell defense response to ionizing radiation involves activation of cell cycle checkpoint signaling. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby aberrations in the chromatin structure, may also override the DNA damage defense response and facilitate the radiation-induced mitotic cell death. In experimental metastasis models, the human breast carcinoma cell line MA-11 invariably disseminates to the central nervous system. We compared profiles of in vitro MA-11 cell cycle response to ionizing radiation and HDAC inhibition. After radiation exposure, the G2-M phase accumulation and the preceding repression of the G2 phase regulatory factors Polo-like kinase-1 and cyclin B1 required intact G2 checkpoint signaling through the checkpoint kinase CHK1, whereas the similar phenotypic changes observed with HDAC inhibition did not. MA-11 cells did not show radiation-induced expression of the G1 cell cycle inhibitor p21, indicative of a defective G1 checkpoint and consistent with a point mutation detected in the tumor suppressor TP53 gene. Increase in the p21 level, however, was observed with HDAC inhibition. Following pretreatment with the HDAC inhibitor, the efficiency of clonogenic regrowth after irradiation was reduced, which is in accordance with the concept of increased probability of mitotic cell death when the chromatin structure is disrupted. Among molecular cell cycle-targeted drugs currently in the pipeline for testing in early-phase clinical trials, HDAC inhibitors may have therapeutic potential as radiosensitizers.     

Antitumor activity of histone deacetylase inhibitors in non-small cell lung cancer cells: development of a molecular predictive model

To ascertain the potential for histone deacetylase (HDAC) inhibitor-based treatment in non-small cell lung cancer (NSCLC), we analyzed the antitumor effects of trichostatin A (TSA) and suberoylanilide hydroxamic acid (vorinostat) in a panel of 16 NSCLC cell lines via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. TSA and vorinostat both displayed strong antitumor activities in 50% of NSCLC cell lines, suggesting the need for the use of predictive markers to select patients receiving this treatment. There was a strong correlation between the responsiveness to TSA and vorinostat (P < 0.0001). To identify a molecular model of sensitivity to HDAC inhibitor treatment in NSCLC, we conducted a gene expression profiling study using cDNA arrays on the same set of cell lines and related the cytotoxic activity of TSA to corresponding gene expression pattern using a modified National Cancer Institute program. In addition, pathway analysis was done with Pathway Architect software. We used nine genes, which were identified by gene-drug sensitivity correlation and pathway analysis, to build a support vector machine algorithm model by which sensitive cell lines were distinguished from resistant cell lines. The prediction performance of the support vector machine model was validated by an additional nine cell lines, resulting in a prediction value of 100% with respect to determining response to TSA and vorinostat. Our results suggested that (a) HDAC inhibitors may be promising anticancer drugs to NSCLC and (b) the nine-gene classifier is useful in predicting drug sensitivity to HDAC inhibitors and may contribute to achieving individualized therapy for NSCLC patients.     

MGCD0103, a novel isotype-selective histone deacetylase inhibitor, has broad spectrum antitumor activity in vitro and in vivo

Nonselective inhibitors of human histone deacetylases (HDAC) are known to have antitumor activity in mice in vivo, and several of them are under clinical investigation. The first of these, Vorinostat (SAHA), has been approved for treatment of cutaneous T-cell lymphoma. Questions remain concerning which HDAC isotype(s) are the best to target for anticancer activity and whether increased efficacy and safety will result with an isotype-selective HDAC inhibitor. We have developed an isotype-selective HDAC inhibitor, MGCD0103, which potently targets human HDAC1 but also has inhibitory activity against HDAC2, HDAC3, and HDAC11 in vitro. In intact cells, MGCD0103 inhibited only a fraction of the total HDAC activity and showed long-lasting inhibitory activity even upon drug removal. MGCD0103 induced hyperacetylation of histones, selectively induced apoptosis, and caused cell cycle blockade in various human cancer cell lines in a dose-dependent manner. MGCD0103 exhibited potent and selective antiproliferative activities against a broad spectrum of human cancer cell lines in vitro, and HDAC inhibitory activity was required for these effects. In vivo, MGCD0103 significantly inhibited growth of human tumor xenografts in nude mice in a dose-dependent manner and the antitumor activity correlated with induction of histone acetylation in tumors. Our findings suggest that the isotype-selective HDAC inhibition by MGCD0103 is sufficient for antitumor activity in vivo and that further clinical investigation is warranted.     

CRA-024781: a novel synthetic inhibitor of histone deacetylase enzymes with antitumor activity in vitro and in vivo

CRA-024781 is a novel, broad spectrum hydroxamic acid-based inhibitor of histone deacetylase (HDAC) that shows antitumor activity in vitro and in vivo preclinically and is under evaluation in phase I clinical trials for cancer. CRA-024781 inhibited pure recombinant HDAC1 with a K(i) of 0.007 mumol/L, and also inhibited the other HDAC isozymes HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10 in the nanomolar range. Treatment of cultured tumor cell lines grown in vitro with CRA-024781 resulted in the accumulation of acetylated histone and acetylated tubulin, resulting in an inhibition of tumor cell growth and the induction of apoptosis. CRA-024781 parenterally administered to mice harboring HCT116 or DLD-1 colon tumor xenografts resulted in a statistically significant reduction in tumor growth at doses that were well tolerated as measured by body weight. Inhibition of tumor growth was accompanied by an increase in the acetylation of alpha-tubulin in peripheral blood mononuclear cells, and an alteration in the expression of many genes in the tumors, including several involved in apoptosis and cell growth. These results reveal CRA-024781 to be a novel HDAC inhibitor with potent antitumor activity.     

Histone deacetylase cytoplasmic trapping by a novel fluorescent HDAC inhibitor

Inhibitors of histone deacetylases (HDAC) are an important emerging class of drugs for the treatment of cancers. HDAC inhibitors are currently under evaluation in clinical trials as single agents and as sensitizers in combinations with chemotherapies and radiation therapy. Although these drugs have important effects on cancer cell growth and functions, the mechanisms underlying HDAC inhibitor activities remain to be fully defined. By using rational drug design, compound 2, a fluorescent class II HDAC targeting inhibitor, was synthesized and observed to accumulate in the cytoplasmic compartments of treated cells, but not in the nuclei. Furthermore, immunostaining of inhibitor exposed cells for HDAC4 showed accumulation of this enzyme in the cytoplasmic compartment with concomitant increased acetylation of tubulin and nuclear histones. These observations support a mechanism by which nuclear histone acetylation is increased as a result of HDAC4 trapping and sequestration in the cytoplasm after binding to compound 2. The HDAC inhibitor offers potential as a novel theranostic agent, combining diagnostic and therapeutic properties in the same molecule.     

EFFECTS OF p53 GENE THERAPY COMBINED WITH CYCLOOXYGENASE-2 INHIBITOR ON CYCLOOXYGENASE-2 GENE EXPRESSION AND GROWTH INHIBITION OF HUMAN LUNG CANCER CELLS

1 INTRODUCTIONCOXis the key enzyme involved in the synthesis of prostanoids,a collective termfor the PGs andthromboxanes.Of the two major isoforms of the COXenzyme,COX-1 is ubiquitous and constitutively ex-pressedin virtually all normal tissues.In contras…     

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.     

Histone tail modifications and noncanonical functions of histones: perspectives in cancer epigenetics

Over the past few years, the histone deacetylase (HDAC) inhibitors have occupied an important place in the effort to develop novel, but less toxic, anticancer therapy. HDAC inhibitors block HDACs, which are the enzymes responsible for histone deacetylation, and therefore they modulate gene expression. The cellular effects of HDAC inhibitors include growth arrest and the induction of differentiation. Early successes in cancer therapeutics obtained using these drugs alone or in combination with other anticancer drugs emphasize the important place of posttranslational modifications of histones in cancer therapy. Histone tail modifications along with DNA methylation are the most studied epigenetic events related to cancer progression. Moreover, extranuclear functions of histones have also been described. Because HDAC inhibitors block HDACs and thereby increase histone acetylation, we propose a model wherein exogenous acetylated histones or other related acetylated proteins that are introduced into the nucleus become HDAC substrates and thereby compete with endogenous histones for HDACs. This competition may lead to the increased acetylation of the endogenous histones, as in the case of HDAC inhibitor therapy. Moreover, other mechanisms of action, such as binding to chromatin and modulating gene expression, are also possible for exogenously introduced histones.     

Lipoxygenase inhibitors attenuate growth of human pancreatic cancer xenografts and induce apoptosis through the mitochondrial pathway

Several studies have suggested that high dietary fat intake, particularly essential fatty acids, is associated with pancreatic cancer development and growth. Our previous studies have demonstrated that blockade of either the 5-lipoxygenase (LOX) or 12-LOX pathway of arachidonic acid metabolism inhibited pancreatic cancer cell proliferation and induced apoptosis. This study investigated the underlying mechanisms for LOX inhibitor-induced apoptosis and the potential of LOX inhibitors as antipancreatic cancer agents using the athymic mice xenograft model. Apoptosis of pancreatic cancer cells induced by LOX inhibitors (including the nonselective LOX inhibitor nordihydroguaiaretic acid, the 5-LOX inhibitor Rev-5901, and the 12-LOX inhibitor baicalein) was confirmed by growth inhibition, annexin V binding, and terminal deoxynucleotidyl transferase-mediated nick end labeling assay in MiaPaCa-2 and AsPC-1 human pancreatic cancer cells. Expression of the antiapoptotic proteins Bcl-2 and Mcl-1 was significantly decreased after LOX inhibitor treatment while that of the proapoptotic protein bax was increased. LOX inhibitors also markedly induced the release of cytochrome c from mitochondria into the cytosol. Caspase-9, caspase-7, and caspase-3 but not caspase-8 were activated after treatment, concomitant with cleavage of the capase-3 substrate poly(ADP-ribose) polymerase. In vivo studies in the athymic mice xenograft model also confirmed the growth inhibitory effect and induction of apoptosis by these LOX inhibitors in pancreatic cancer. In conclusion, LOX inhibitors block pancreatic cancer cell proliferation and induce apoptosis through the mitochondrial pathway both in vivo and in vitro. LOX inhibitors are likely to be valuable for the treatment of human pancreatic cancer.     

地西他滨联合曲古抑菌素A对MDS细胞株SKM-1作用的体外研究

本研究探讨去甲基化制剂地西他滨（decitabine）和（或）组蛋白去乙酰化酶抑制剂曲古抑菌素A（TSA）对MDS—RAEB细胞株SKM—1的影响及作用机制．用台盼蓝拒染法研究药物对SKM—1细胞生长曲线的影响；用四氮唑蓝还原试验和流式细胞术观察药物对SKM—1细胞分化作用；用Annexin V—FITC标记药物作用后的细胞，了解其早期凋亡的情况；用RT—PCR研究药物作用前后细胞Fas，survivin和P15^INK4B。基因表达的变化。结果表明：decitabine和（或）TSA对SKM—1细胞生长有抑制作用，能促进SKM—1细胞分化，细胞表面CD14、CD11b表达增加，HLA—DR表达减少；decitabine和（或）TSA处理SKM—1细胞后，SKM—1细胞凋亡增加，细胞Fas和P15^INK4B mRNA表达增加，survivin mRNA表达减少。结论：decitabine和TSA均可以促进SKM—1细胞凋亡和分化，可能与Fas、P15^INK4B和survivin基因表达有关，二者联用有协同作用。     

Histone deacetylase inhibitors exhibit anti-inflammatory and neuroprotective effects in a rat permanent ischemic model of stroke: multiple mechanisms of action

The pathophysiology of cerebral ischemia involves multiple mechanisms including neuroinflammation mediated by activated microglia and infiltrating macrophages/monocytes. The present study employed a rat permanent middle cerebral artery occlusion (pMCAO) model to study effects of histone deacetylase (HDAC) inhibition on ischemia-induced brain infarction, neuroinflammation, gene expression, and neurological deficits. We found that post-pMCAO injections with HDAC inhibitors, valproic acid (VPA), sodium butyrate (SB), or trichostatin A (TSA), decreased brain infarct volume. Postinsult treatment with VPA or SB also suppressed microglial activation, reduced the number of microglia, and inhibited other inflammatory markers in the ischemic brain. The reduction in levels of acetylated histone H3 in the ischemic brain was prevented by treatment with VPA, SB, or TSA. Moreover, injections with HDAC inhibitors superinduced heat-shock protein 70 and blocked pMCAO-induced down-regulation of phospho-Akt, as well as ischemia-elicited up-regulation of p53, inducible nitric oxide synthase, and cyclooxygenase-2. The motor, sensory, and reflex performance of pMCAO rats was improved by VPA, SB, or TSA treatment. The beneficial effects of SB and VPA in reducing brain infarct volume and neurological deficits occurred when either drug was administrated at least 3 h after ischemic onset, and the behavioral improvement was long-lasting. Together, our results demonstrate robust neuroprotective effects of HDAC inhibitors against cerebral ischemia-induced brain injury. The neuroprotection probably involves multiple mechanisms including suppression of ischemia-induced cerebral inflammation. Given that there is no effective treatment for stroke, HDAC inhibitors, such as VPA, SB, and TSA, should be evaluated for their potential use for clinical trials in stroke patients.     

HDAC inhibitor M344 suppresses MCF-7 breast cancer cell proliferation

Histone deacetylase (HDAC) inhibitors represent a novel class of drugs that selectively induce cell cycle arrest and apoptosis in transformed cells. This study examined, for the first time, the effects of the relatively new HDAC inhibitor, M344 [4-dimethylamino-N-(6-hydroxycarbamoylhexyl)-benzamide], on the proliferation of MCF-7 breast cancer cells. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays revealed significant concentration- and time-dependent decreases in MCF-7 cell proliferation following treatment with M344 (1-100 μM). In contrast to the significant induction of p21^waf1/cip1 mRNA expression following treatment with M344 (10 μM) for 1 or 3 days, there was a significant decrease in p53 mRNA expression, although p53 protein levels were unchanged. Similar treatment with M344 also induced expression of the pro-apoptotic genes, Puma and Bax, together with the morphological features of apoptosis, in MCF-7 cells. The results of this study reinforce previous findings indicating that HDAC inhibitors are an important group of oncostatic drugs, and show that M344 is a potent suppressor of breast cancer cell proliferation.     

Inhibition of histone deacetylases by chlamydocin induces apoptosis and proteasome-mediated degradation of survivin

The naturally occurring cyclic tetrapeptide chlamydocin is a very potent inhibitor of cell proliferation. Here we show that chlamydocin is a highly potent histone deacetylase (HDAC) inhibitor, inhibiting HDAC activity in vitro with an IC(50) of 1.3 nM. Like other HDAC inhibitors, chlamydocin induces the accumulation of hyperacetylated histones H3 and H4 in A2780 ovarian cancer cells, increases the expression of p21(cip1/waf1), and causes an accumulation of cells in G(2)/M phase of the cell cycle. In addition, chlamydocin induces apoptosis by activating caspase-3, which in turn leads to the cleavage of p21(cip1/waf1) into a 15-kDa breakdown product and drives cells from growth arrest into apoptosis. Concomitant with the activation of caspase-3 and cleavage of p21(cip1/waf1), chlamydocin decreases the protein level of survivin, a member of the inhibitor of apoptosis protein family that is selectively expressed in tumors. Although our data indicate a potential link between degradation of survivin and activation of the apoptotic pathway induced by HDAC inhibitors, stable overexpression of survivin does not suppress the activation of caspase-3 or cleavage of p21(cip1/waf1) induced by chlamydocin treatment. The decrease of survivin protein level is mediated by degradation via proteasomes since it can be inhibited by specific proteasome inhibitors. Taken together, our results show that induction of apoptosis by chlamydocin involves caspase-dependent cleavage of p21(cip1/waf1), which is strikingly associated with proteasome-mediated degradation of survivin.