QSAR Studies on the Inhibitory Activityof Levofloxacin-thiadiazole HDACi Conjugates to Histone Deacetylases

A molecular electronegativity distance vector(M)based on 13 atomic types has been used to describe the structures of 19 conjugates(LHCc)of levofloxacin-thiadiazole HDAC inhibitor(HDACi)and related inhibitory activities(pH,i=1,2,6)of LHCc against histone deacetylases(HDACs,such as HDAC1,HDAC2 and HDAC6).The quantitative structure-activity relationships(QSAR)were established by using leaps-and-bounds regression analysis for the inhibitory activities(pH)of 19 above compounds to HDAC1,HDAC2 and HDAC6 along with M.The correlation coefficients(R~2)and the leave-one-out(LOO)cross validation Rfor the pH,pHand pHmodels were 0.976 and 0.949;0.985 and 0.977;0.976 and 0.932,respectively.The QSAR models had favorable correlations,as well as robustness and good prediction capability by R~2,F,R~2,A,Fand Vtests.Validated by using 3876 training sets,the models have good external prediction ability.The results indicate that the molecular structural units:–CH–(g=1,2),–NH,–OH,=O,–O–and–S–are the main factors which can affect the inhibitory activity of pH,pHas well as pHbioactivities of these compounds directly.Accordingly,the main interactions between HDACs inhibitor and HDACs are hydrophobic interaction,hydrogen bond,and coordination with Znto form compounds,which is consistent with the results in reports.

Histone deacetylase inhibitor pracinostat suppresses colorectal cancer by inducing CDK5-Drp1 signaling-mediated peripheral mitofission

Divisions at the periphery and midzone of mitochondria are two fission signatures that determine the fate of mitochondria and cells.Pharmacological induction of excessively asymmetric mitofissionassociated cell death(MFAD)by switching the scission position from the mitochondrial midzone to the periphery represents a promising strategy for anticancer therapy.By screening a series of paninhibitors,we identified pracinostat,a pan-histone deacetylase(HDAC)inhibitor,as a novel MFAD inducer,that exhibited a significant anticancer effect on colorectal cancer(CRC)in vivo and in vitro.Pracinostat increased the expression of cyclin-dependent kinase 5(CDK5)and induced its acetylation at residue lysine 33,accelerating the formation of complex CDK5/CDK5 regulatory subunit 1 and dynaminrelated protein 1(Drp1)-mediated mitochondrial peripheral fission.CRC cells with high level of CDK5(CDK5-high)displayed midzone mitochondrial division that was associated with oncogenic phenotype,but treatment with pracinostat led to a lethal increase in the already-elevated level of CDK5 in the CRC cells.Mechanistically,pracinostat switched the scission position from the mitochondrial midzone to the periphery by improving the binding of Drp1 from mitochondrial fission factor(MFF)to mitochondrial fission 1 protein(FIS1).Thus,our results revealed the anticancer mechanism of HDACi pracinostat in CRC via activating CDK5-Drp1 signaling to cause selective MFAD of those CDK5-high tumor cells,which implicates a new paradigm to develop potential therapeutic strategies for CRC treatment.

HDAC抑制剂西达本胺在血液恶性肿瘤中的研究进展

表观遗传调控失调是血液恶性肿瘤发生发展的机制之一。组蛋白去乙酰化酶(histone deacetylase, HDAC)对于调节基因表达和各种信号通路至关重要,是最具代表性的表观遗传修饰物之一。靶向HDAC的抑制剂已成为血液系统恶性肿瘤的一种新的治疗选择。西达本胺是一种新型的亚型选择性HDAC抑制剂,可抑制I类HDAC1、HDAC2、HDAC3以及II_(b)类HDAC10。2014年,西达本胺单药或与现有疗法联合使用被中国食品药品监督管理局批准为复发/难治性(relapsed or refractory, R/R)外周T细胞淋巴瘤(peripheral T-cell lymphoma, PTCL)的二线治疗方案。近年来,体外研究表明,西达本胺影响信号通路、细胞增殖、细胞凋亡和细胞周期的调控。在临床研究中,西达本胺在急性白血病、多发性骨髓瘤等血液恶性肿瘤的治疗中也取得了较大进展。该文就西达本胺在血液恶性肿瘤中的多种应用进行综述,包括西达本胺单药或联合其他治疗在各种血液系统恶性肿瘤的实验室和临床数据,为继续探索西达本胺提供理论依据。

HDAC3:动脉粥样硬化治疗的新靶点

组蛋白去乙酰化酶3(HDAC3)是一种表观遗传修饰酶,参与动脉粥样硬化(As)的发生发展,寻找有效的HDAC3抑制剂对治疗As具有重要意义。本文综述了HDAC3与As的关系、HDAC3抑制剂最新的研究进展以及一些中药通过抑制HDAC3治疗心血管疾病的作用机制,旨在为研发以HDAC3为靶点的抗As药物提供新的思路。

组蛋白去乙酰化酶HDAC5调控乳腺癌的研究进展

乳腺癌是世界范围内最常见的恶性肿瘤之一,在女性群体中发病率较高。作为IIa组蛋白去乙酰化酶(HDACs),组蛋白去乙酰化酶5(HDAC5)在乳腺癌患者和健康人群中的表达存在巨大的差异,从而成为在乳腺癌乃至其他癌症中具有潜在价值的生物标志物之一,被认为是抗癌药物的可靠分子治疗靶点。本文将对HDAC5的结构表征和其在乳腺癌发生发展中的作用,以及HDAC5抑制剂的应用作一简要总结,并为早期乳腺癌HDACs的检测、HDACs抑制剂(HDACi)的设计以及与HDACi联用的相关药物作用靶点等方面提供可行性建议,以期为乳腺癌肿瘤治疗提供理论策略参考。

Progress in clinical trial of histone deacetylase(HDAC) inhibitors for non-small cell lung cancers

Histone deacetylase(HDAC) inhibitors, which represent a structurally diverse group of molecules, have emerged as a novel therapeutic class of molecules with significant anticancer potential. Vorinostat and romidepsin, known as the first generation of HDAC inhibitors, were approved in the United States for the treatment of T-cell lymphomas. Preliminary activity of HDAC inhibitors has also been observed in non-small cell lung cancer(NSCLC) in combination with the existing treatment regimens, of which is the focus of the current review.

LSD1、HDAC及其双靶点抑制剂在抗肿瘤应用中的研究进展

表观遗传学调控因其可逆性及在疾病进程中的关键作用,已成为肿瘤治疗的重要靶点。组蛋白赖氨酸特异性去甲基化酶(LSD1)与组蛋白去乙酰化酶(HDAC)是调控癌细胞基因表达的重要靶点,抑制这两种蛋白可以显示出显著的肿瘤治疗效果。本综述聚焦于LSD1和HDAC的单靶点及双靶点抑制剂的研究进展,探讨了这些抑制剂在抗肿瘤治疗中的应用。双靶点抑制剂通过同时抑制LSD1和HDAC活性,提供了超越单一抑制剂的抗癌效果,展示了改善治疗效果的潜力。文章细致回顾了这些抑制剂在临床前研究和临床试验中的表现,指出其优势与挑战,并对未来研究方向进行了展望。

白藜芦醇衍生物作为新型LSD1/HDAC双靶点抑制剂的计算模拟研究

本研究选择前期设计出来的6个白藜芦醇衍生物LSD1抑制剂R1~R6,通过分子对接、分子动力学模拟、分子力学/广义玻恩表面积(MM/GBSA)等计算模拟方法探索了这些衍生物与HDAC8的相互作用模式以及结合自由能。以HDAC8的共晶配体CRA-A作为参考,结果显示,白藜芦醇衍生物R1~R6均能以双齿配位的形式与Zn^(2+)结合,与HDAC8有效结合。在分子动力学模拟的过程中,小分子的羟肟酸基团的两个氧原子始终与Zn^(2+)双齿配位,且6个白藜芦醇衍生物始终在HDAC8的疏水腔内。R1~R6与HDAC8的结合自由能计算结果表明,R1和R3与HDAC8的结合能力最强(分别为-200.00 kcal·mol^(-1)和-202.62 kcal·mol^(-1)),和其与LSD1的结合能力一致。其中,静电相互作用是主要的稳定因素。能量分解结果揭示ASP164、ASP253和HIS166是小分子与HDAC8结合过程中的关键氨基酸。

Current evidence for histone deacetylase inhibitors in pancreatic cancer

Pancreatic cancer is one of the most aggressive human cancers,with more than 200 000 deaths worldwide every year.Despite recent efforts,conventional treatment approaches,such as surgery and classic chemotherapy,have only slightly improved patient outcomes.More effective and well-tolerated therapies are required to reverse the current poor prognosis of this type of neoplasm.Among new agents,histone deacetylase inhibitors (HDACIs) are now being tested.HDACIs have multiple biological effects related to acetylation of histones and many non-histone proteins that are involved in regulation of gene expression,apoptosis,cell cycle progression and angiogenesis.HDACIs induce cell cycle arrest and can activate the extrinsic and intrinsic pathways of apoptosis in different cancer cell lines.In the present review,the main mechanisms by which HDACIs act in pancreatic cancer cells in vitro,as well as their antiproliferative effects in animal models are presented.HDACIs constitute a promising treatment for pancreatic cancer with encouraging anti-tumor ef-fects,at well-tolerated doses.

Deacetylase inhibitors-focus on non-histone targets and effects

Inhibitors of protein deacetylases have recently been established as a novel therapeutic principle for several human diseases,including cancer.The original notion of the mechanism of action of these compounds focused on the epigenetic control of transcriptional processes, especially of tumor suppressor genes,by interfering with the acetylation status of nuclear histone proteins,hence the name histone deacetylase inhibitors was coined.Yet,this view could not explain the high specificity for tumor cells and recent evidence now suggests that non-histone proteins represent major targets for protein deacetylase inhibitors and that the post-translational modification of the acetylome is involved in various cellular processes of differentiation,survival and cell death induction.

Inhibition of autophagy significantly enhances combination therapy with sorafenib and HDAC inhibitors for human hepatoma cells

AIM: To clarify whether histone deacetylase inhibitors histone deacetylase inhibitors (HDACIs) can sensitize hepatocellular carcinoma (HCC) cells to sorafenib treatment. METHODS: Bax, Bcl-2, ATG5-ATG12, p21, and p27 protein levels in Hep3B, HepG2, and PLC/PRF/5 cells were examined by Western blot. CCK8 and a fluoro-metric caspase-3 assay were used to examine cellular viability and apoptosis levels. The effect of Beclin-1 on sensitization of HCC cells to sorafenib was examined by transfecting Beclin-1 siRNA into Hep3B, HepG2, and PLC/PRF/5 cells. RESULTS: Autophagy inhibition enhances the inhibitory effects of vorinostat and sorafenib alone or in combination on HCC cell growth. Vorinostat and sorafenib synergistically induced apoptosis and cell cycle alterations. Western blot data indicated that HDACIs and Beclin- 1 knockdown increased the p53 acetylation level. The knockdown of Beclin-1 enhanced the synergistic effect of the combination of vorinostat with sorafenib. CONCLUSION: HDACIs can sensitize HCC cells to sorafenib treatment by regulating the acetylation level of Beclin-1. (C) 2014 Baishideng Publishing Group Co., Limited. All rights reserved.

A phaseⅠtrial of an oral subtype-selective histone deacetylase inhibitor,chidamide,in combination with paclitaxel and carboplatin in patients with advanced non-small cell lung cancer

Objective： This phase I study was to evaluate safety, maximum tolerated dose, pharmacokinetics and preliminary antitumor activity of chidamide, a novel subtype-selective histone deacetylase （HDAC） inhibitor, in combination with paclitaxel and carboplatin in patients with advanced non-small cell lung cancer （NSCLC）. Methods： Ten patients received oral chidamide 20, 25, or 30 mg twice per week continuously with paclitaxel （175 mg/m2） and carboplatin [area under the curve （AUC） 5 mg/mL/min] administered in a 3-week cycle. Patients with response and stable disease after four cycles maintained chidamide monotherapy until disease progression or unacceptable toxicity. Blood samples were collected for pharmacoldnetic analysis after the first single oral of chidamide and first combination treatment in cycle 1 from all patients. Results： Two dose-limiting toxicities were recorded in the 30 mg cohort, including thrombocytopenia and prolonged neutropenia in the first cycle. Grade 3/4 neutropenia in any cycle was observed in all patients, but was not associated with significant complications. Other grade 3/4 hematologic toxicities included thrombocytopenia and leucopenia. No significant changes were observed in pharmacokinetic parameters for both chidamide and paclitaxel. One patient in the 20 mg cohort had confirmed partial response （PR）. Two out of 5 patients with brain metastases had intracranial complete remission after 4-cycle treatment. Conclusions： Chidamide combined with paclitaxel and carboplatin was generally tolerated without unanticipated toxicities or clinically relevant pharmacokinetic interactions. The recommended dose for chidamide in this combination was established at 20 mg, and a phase II trial is ongoing with this regimen in patients with advanced NSCLC.

Histone deacetylase inhibitor MS-275 alone or combined with bortezomib or sorafenib exhibits strong antiproliferative action in human cholangiocarcinoma cells

AIM: To investigate the antiproliferative effect of the histone deacetylase (HDAC) inhibitor MS-275 on cholangiocarcinoma cells alone and in combination with conventional cytostatic drugs (gemcitabine or doxorubicin) or the novel anticancer agents sorafenib or bortezomib. METHODS: Two human bile duct adenocarcinoma cell lines (EGI-1 and TFK-1) were studied. Crystal violet staining was used for detection of cell number changes. Cytotoxicity was determined by measuring the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). Apoptosis was determined by measuring the enzyme activity of caspase-3. Cell cycle status reflected by the DNA content was detected by flow cytometry.RESULTS: MS-275 treatment potently inhibited the proliferation of EGI-1 and TFK-1 cholangiocarcinoma cells by inducing apoptosis and cell cycle arrest. MS-275-induced apoptosis was characterized by activation of caspase-3, up-regulation of Bax and down-regulation of Bcl-2. Cell cycle was predominantly arrested at the G1/S checkpoint, which was associated with induction of the cyclin-dependent kinase inhibitor p21Waf/CIP1. Furthermore, additive anti-neoplastic effects were observed when MS-275 treatment was combined with gemcitabine or doxorubicin, while combination with the multi-kinase inhibitor sorafenib or the proteasome inhibitor bortezomib resulted in overadditive anti-neoplastic effects.CONCLUSION: The growth of human cholangiocarcinoma cells can be potently inhibited by MS-275 alone or in combination with conventional cytostatic drugs or new, targeted anticancer agents.

Neuroprotective mechanism of TMP269, a selective class ⅡA histone deacetylase inhibitor, after cerebral ischemia/reperfusion injury

TMP269 is a selective class ⅡA histone deacetylase inhibitor that has a protective effect on the central nervous system, whose specific mechanism of action is unclear. We aimed to reveal the optimal concentration of TMP269 for protecting against cerebral ischemia/reperfusion injury and its neuroprotective mechanism. Male Sprague-Dawley rats were randomly divided into sham, ischemia/reperfusion, and 1, 4, 10 and 16 mg/kg TMP269 groups. Cerebral ischemia/reperfusion injury was induced by middle cerebral artery occlusion. TMP269 was intraperitoneally administered at different doses 0.5 hours before ischemia induction. Western blot assay and immunohistochemistry were used to detect effects of TMP269 on histone 2 acetylation. The results showed that the level of histone 2 acetylation was increased 24 hours after TMP269 injection. 2,3,5-Triphenyltetrazolium chloride staining was utilized to examine effect of TMP269 on infarct volume. The results found that different doses of TMP269 could reduce the infarct volume. Western blot assay, immunohistochemistry and Evans blue staining were employed to measure the effect of TMP269 on blood-brain barrier. The results showed that TMP269 counteracted the abnormal endothelial cell permeability changes caused by cerebral ischemia/reperfusion. Western blot assay and immunohistochemistry were used to determine the effect of TMP269 on tissue kallikrein. The results found that TMP269 up-regulated the expression of tissue kallikrein. Western blot assay further determined the optimal concentration to be 4 mg/kg. In conclusion, TMP269 plays a neuroprotective role by up-regulating the level of histone 2 acetylation, alleviating endothelial cell injury after cerebral ischemia/reperfusion, and up-regulating the expression of tissue kallikrein. The experimental protocol was approved in 2014 by the Department of Laboratory Animal Science, Fudan University, China(approval No. 20140143 C001).

Histone deacetylase inhibitors and pancreatic cancer:Are there any promising clinical trials?

Pancreatic cancer,although not very frequent,has an exceptionally high mortality rate,making it one of the most common causes of cancer mortality in developed countries.Pancreatic cancer is difficult to diagnose,allowing few patients to have the necessary treatment at a relatively early stage.Despite a marginal benefit in survival,the overall response of pancreatic cancer to current systemic therapy continues to be poor,and new therapies are desperately needed.Histone deacetylase(HDAC) enzymes play an important role in the development and progression of cancer and HDAC inhibitors(HDACIs) have been shown to induce differentiation and cell cycle arrest,activate the extrinsic or intrinsic pathways of apoptosis,and inhibit invasion,migration and angiogenesis in different cancer cell lines.As a result of promising preclinical data,various HDACIs are being tested as either monotherapeutic agents or in combination regimens for both solid and hematological malignancies.Vorinostat was the first HDACI approved by the Food and Drug Administration for patients with cutaneous T-cell lymphoma.The use of HDACIs in clinical trials,in pretreated and relapsed patients suffering from advanced pancreatic cancer is discussed.Unfortunately,clinical data for HDACIs in patients with pancreatic cancer are inadequate,because only a few studies have included patients suffering from this type of neoplasm and the number of pancreatic cancer patients that entered HDACIs phase Ⅱ/Ⅲ trials,among others with advanced solid tumors,is very limited.More studies recruiting patients with pancreatic cancer remain to determine the efficiency of these therapies.

The HDAC inhibitor GCJ-490A suppresses c-Met expression through IKKα and overcomes gefitinib resistance in non-small cell lung cancer

Objective:The novel compound GCJ-490A has been discovered as a pan-histone deacetylase(HDAC)inhibitor that exerts potent inhibitory activity against HDAC1,HDAC3,and HDAC6.Because of the important roles of HDACs in lung cancer development and the high distribution of GCJ-490A in lung tissue,we explored the anti-tumor potency of GCJ-490A against non-small cell lung cancer(NSCLC)in vitro and in vivo in this study.Methods:The in vitro effects of GCJ-490A alone or combined with the EGFR inhibitor gefitinib against NSCLC were measured with proliferation,apoptosis,and colony formation assays.NSCLC xenograft models were used to investigate the efficacy of GCJ-490A combined with gefitinib for the treatment of NSCLC in vivo.Western blot assays,luciferase reporter assays,chromatin immunoprecipitation assays,quantitative real time-PCR,immunohistochemistry,and transcription factor activity assays were used to elucidate possible mechanisms.Results:GCJ-490A effectively inhibited NSCLC cell proliferation and induced apoptosis in vitro and in vivo.Interestingly,inhibition of HDAC1 and HDAC6 by GCJ-490A increased histone acetylation at the IKKαpromoter and enhanced IKKαtranscription,thus decreasing c-Met.Moreover,this c-Met downregulation was found to be essential for the synergistic anti-tumor activity of GCJ-490A and gefitinib.Conclusions:These findings highlight the promising potential of HDAC inhibitors in NSCLC treatment and provide a rational basis for the application of HDAC inhibitors in combination with EGFR inhibitors in clinical trials.

Histone deacetylase inhibitor pre-treatment enhances the efficacy of DNA-interacting chemotherapeutic drugs in gastric cancer

BACKGROUND The prognosis of gastric cancer continues to remain poor,and epigenetic drugs like histone deacetylase inhibitors(HDACi)have been envisaged as potential therapeutic agents.Nevertheless,clinical trials are facing issues with toxicity and efficacy against solid tumors,which may be partly due to the lack of patient stratification for effective treatments.To study the need of patient stratification before HDACi treatment,and the efficacy of pre-treatment of HDACi as a chemotherapeutic drug sensitizer.METHODS The expression activity of class 1 HDACs and histone acetylation was examined in human gastric cancer cells and tissues.The potential combinatorial regime of HDACi and chemotherapy drugs was defined on the basis of observed drug binding assays,chromatin remodeling and cell death.RESULTS In the present study,the data suggest that the differential increase in HDAC activity and the expression of class 1 HDACs are associated with hypoacetylation of histone proteins in tumors compared to normal adjacent mucosa tissue samples of gastric cancer.The data highlights for the first time that pretreatment of HDACi results in an increased amount of DNA-bound drugs associated with enhanced histone acetylation,chromatin relaxation and cell cycle arrest.Fraction-affected plots and combination index-based analysis show that pre-HDACi chemo drug combinatorial regimes,including valproic acid with cisplatin or oxaliplatin and trichostatin A with epirubicin,exhibit synergism with maximum cytotoxic potential due to higher cell death at low combined doses in gastric cancer cell lines.CONCLUSION Expression or activity of class 1 HDACs among gastric cancer patients present an effective approach for patient stratification.Furthermore,HDACi therapy in pretreatment regimes is more effective with chemotherapy drugs,and may aid in predicting individual patient prognosis.

Drug repurposing of histone deacetylase inhibitors that alleviate neutrophilic inflammation in acute lung injury and idiopathic pulmonary fibrosis via inhibiting leukotriene a4 hydrolase and blocking LTB4 biosynthesis

OBJECTIVE Leukotriene B4(LTB4)biosynthesis and subsequently neutrophilic inflammation may provide a potential strategy for the treatment of acute lung injury(ALI)or idiopathic pulmonary fibrosis(IPF).To provide a potential strategy for the treatment of ALI or IPF,we identified potent inhibitors of Leukotriene A4 hydrolase(LTA4H),a key enzyme in the biosynthesis of LTB4.METHODS In this study,we identified two known histone deacetylase(HDAC)inhibitors,suberanilohydroxamic acid(SAHA)and its analogue 4-(dimethylamino)-N-[7-(hydroxyamino)-7-oxoheptyl]benzamide(M344),as effective inhibitors of LTA4H using enzymatic assay,thermofluor assay,and X-ray crystallographic investigation.We next tested the effect of SAHA and M344 on endogenous LTB4 biosynthesis in neutrophils by ELISA and neutrophil migration by transwell migration assay.A murine experimental model of ALI was induced by lipopolysaccharide(LPS)inhalation.Histopathological analysis of lung tissue using H&E staining revealed the serious pulmonary damage caused by LPS treatment and the effect of the SAHA.We next examined m RNA and protein levels of pro-inflammatory cytokines in lung tissue and bronchoalveolar lavage fluid using q RT-PCR and ELISA to further investigate the underlying mechanisms of anti-inflammatory activities by SAHA.We also investigated the effects of SAHA and M344 on a murine experimental model of bleomycin(BLM)-induced IPF model.RESULTS The results of enzymatic assay and X-ray crystallography showed that both SAHA and M344 bind to LTA4H,significantly decrease LTB4 levels in neutrophil,and markedly diminish early neutrophilic inflammation in mouse models of ALI and IPF under a clinical safety dose.CONCLUSION Collectively,SAHA and M344 would provide promising agents with well-known clinical safety for potential treatment in patients with ALI and IPF via pharmacologically inhibiting LAT4H and blocking LTB4 biosynthesis.

HDACs及其抑制剂对急性肺损伤调控作用的研究进展

急性肺损伤(acute lung injury,ALI)和其最极端的形式急性呼吸窘迫(acute respiratory distress syndrome,ARDS)是一种高发病率和死亡率的肺部疾病。因其病理生理过程及调节机制非常复杂,目前尚无有效的治疗药物。组蛋白去乙酰化酶(HDACs)是一类具有去乙酰化酶活性的家族蛋白,研究表明,HDACs参与调控ALI/ARDS的病理生理过程,包括对炎症反应、内皮细胞通透性、氧化应激、肺泡液清除和肺组织修复等过程有调节作用,同时,使用HDACs抑制剂(HDACIs)能对ALI/ARDS产生干预作用。该文就HDACs及HDACIs调控ALI/ARDS病理生理过程及其机制进行详细阐述,以期为HDACs靶向药物的临床应用提供依据和参考,并为后续研究HDACs调控ALI/ARDS提供方向。

Experimental treatment of pancreatic cancer with two novel histone deacetylase inhibitors

AIM:To investigate in vitro and in vivo treatment with histone deacetylase inhibitors NVP-LAQ824 and NVP-LBH589 in pancreatic cancer. METHODS:Cell-growth inhibition by NVP-LAQ824 and NVP-LBH589 was studied in vitro in 8 human pancreatic cancer cell lines using the 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide(MTT) assay. In addition,the anti-tumoral effect of NVP-LBH589 was studied in a chimeric mouse model. Anti-tumoral activity of the drugs was assessed by immunoblotting for p21WAF-1,acH4,cell cycle analysis,TUNEL assay,and immunohistochemistry for MIB-1. RESULTS:In vitro treatment with both compounds significantly suppressed the growth of all cancer cell lines and was associated with hyperacetylation of nucleosomal histone H4,increased expression of p21WAF-1,cell cycle arrest at G2/M-checkpoint,and increased apoptosis. In vivo,NVP-LBH589 alone significantly reduced tumor mass and potentiated the efficacy of gemcitabine. Further analysis of the tumor specimens revealed slightly increased apoptosis and no significant reduction of cell proliferation.CONCLUSION:Our findings suggest that NVP-LBH589 and NVP-LAQ824 are active against human pancreatic cancer,although the precise mechanism of in vivo drug action is not yet completely understood. Therefore,further preclinical and clinical studies for the treatment of pancreatic cancer are recommended.