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The cell signaling pathways involved in the antiproliferative activities of T. rosea inner bark remain unexplored. This study evaluated the apoptotic effects of two iridoids from the inner bark of T. rosea and apicidin on THP-1 cells. The cytotoxic effects of the extract and the pure compounds on THP-1 and Jurkat cells were also evaluated using the MTT assay. The apoptotic effect was determined by measuring the mitochondrial membrane potential. The expression of mRNA and MAPK kinase, Bax, and Bcl-2 proteins was detected by Western blotting and RT–qPCR, respectively. The extract and the compounds evaluated increased the percentage of apoptotic cells. Depolarization of the mitochondrial membrane was observed, and the number of cells in the G0/G1 phase increased. Catalposide and specioside significantly increased p38 protein expression, mostly in cells pretreated with apicidin. The p38 MAPK signaling pathway is at least one of the pathways by which the n-butanol extract obtained from Tabebuia rosea, catalposide, and specioside exerts its apoptotic effect on THP-1 cells, and this effect generates a response in the G0/G1 phase and subsequent cell death. In addition, there was depolarization of the mitochondrial membrane, an effect that was related to the participation of the proapoptotic protein Bax. [ABSTRACT FROM AUTHOR]

The cell signaling pathways involved in the antiproliferative activities of T. rosea inner bark remain unexplored. This study evaluated the apoptotic effects of two iridoids from the inner bark of T. rosea and apicidin on THP-1 cells. The cytotoxic effects of the extract and the pure compounds on THP-1 and Jurkat cells were also evaluated using the MTT assay. The apoptotic effect was determined by measuring the mitochondrial membrane potential. The expression of mRNA and MAPK kinase, Bax, and Bcl-2 proteins was detected by Western blotting and RT–qPCR, respectively. The extract and the compounds evaluated increased the percentage of apoptotic cells. Depolarization of the mitochondrial membrane was observed, and the number of cells in the G0/G1 phase increased. Catalposide and specioside significantly increased p38 protein expression, mostly in cells pretreated with apicidin. The p38 MAPK signaling pathway is at least one of the pathways by which the n-butanol extract obtained from Tabebuia rosea, catalposide, and specioside exerts its apoptotic effect on THP-1 cells, and this effect generates a response in the G0/G1 phase and subsequent cell death. In addition, there was depolarization of the mitochondrial membrane, an effect that was related to the participation of the proapoptotic protein Bax.

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by abnormal cell proliferation, apoptosis repression and myeloid differentiation blockade of hematopoietic stem/progenitor cells. Developing and identifying novel therapeutic agents to reverse the pathological processes of AML are of great significance. Here in this study, we found that a fungus-derived histone deacetylase inhibitor, Apicidin, presents promising therapeutic effect on AML by inhibiting cell proliferation, facilitating apoptosis and inducing myeloid differentiation of AML cells. Mechanistic investigation revealed that QPCT is identified as a potential downstream target of Apicidin, which exhibits significantly decreased expression in AML samples compared with the normal controls and is remarkably up-regulated in AML cells upon Apicidin management. Functional study and rescue assay demonstrated that QPCT depletion further promotes cell proliferation, inhibits apoptosis and impairs myeloid differentiation of AML cells, alleviating the anti-leukemic effect of Apicidin on AML. Our findings not only provide novel therapeutic target for AML, but also lay theoretical and experimental foundation for the clinical application of Apicidin in AML patients.

Aims: Amyloid beta (Aβ) is an important pathological feature of Alzheimer's disease (AD). A disintegrin and metalloproteinase 10 (ADAM10) can reduce the production of toxic Aβ by activating the nonamyloidogenic pathway of amyloid precursor protein (APP). We previously found that apicidin, which is a histone deacetylase (HDAC) inhibitor, can promote the expression of ADAM10 and reduce the production of Aβ in vitro. This study was designed to determine the potential of apicidin treatment to reverse learning and memory impairments in an AD mouse model and the possible correlation of these effects with ADAM10. Methods: Nine‐month‐old APP/PS1 mice and C57 mice received intraperitoneal injections of apicidin or vehicle for 2 months. At 11 months of age, we evaluated the memory performance of mice with Morris water maze (MWM) and context fear conditioning tests. The Aβ levels were assessed in mouse brain using the immunohistochemical method and ELISA. The expression of corresponding protein involved in proteolytic processing of APP and the phosphorylation of tau were assessed by Western blotting. Results: Apicidin reversed the deficits of spatial reference memory and contextual fear memory, attenuated the formation of Aβ‐enriched plaques, and decreased the levels of soluble and insoluble Aβ40/42 in APP/PS1 mice. Moreover, apicidin significantly increased the expression of ADAM10, improved the level of sAPPα, and reduced the production of sAPPβ, but did not affect the levels of phosphorylated tau in APP/PS1 mice. Conclusion: Apicidin significantly improves the AD symptoms of APP/PS1 mice by regulating the expression of ADAM10, which may contribute to decreasing the levels of Aβ rather than decreasing the phosphorylation of tau. [ABSTRACT FROM AUTHOR]

Abstract Background Fusarium head blight is a disease of global concern that reduces crop yields and renders grains unfit for consumption due to mycotoxin contamination. Fusarium poae is frequently associated with cereal crops showing symptoms of Fusarium head blight. While previous studies have shown F. poae isolates produce a range of known mycotoxins, including type A and B trichothecenes, fusarins and beauvericin, genomic analysis suggests that this species may have lineage-specific accessory chromosomes with secondary metabolite biosynthetic gene clusters awaiting description. Methods We examined the biosynthetic potential of 38 F. poae isolates from Eastern Canada using a combination of long-read and short-read genome sequencing and untargeted, high resolution mass spectrometry metabolome analysis of extracts from isolates cultured in multiple media conditions. Results A high-quality assembly of isolate DAOMC 252244 (Fp157) contained four core chromosomes as well as seven additional contigs with traits associated with accessory chromosomes. One of the predicted accessory contigs harbours a functional biosynthetic gene cluster containing homologs of all genes associated with the production of apicidins. Metabolomic and genomic analyses confirm apicidins are produced in 4 of the 38 isolates investigated and genomic PCR screening detected the apicidin synthetase gene APS1 in approximately 7% of Eastern Canadian isolates surveyed. Conclusions Apicidin biosynthesis is linked to isolate-specific putative accessory chromosomes in F. poae. The data produced here are an important resource for furthering our understanding of accessory chromosome evolution and the biosynthetic potential of F. poae.

Objective: The mitigation of abdominal aortic aneurysm (AAA) growth through pharmaceutical intervention offers the potential to avert the perils associated with AAA rupture and the subsequent need for surgical intervention. Nevertheless, the existing effective drugs for AAA treatment are limited, necessitating a pressing exploration for novel therapeutic medications., Methods: AAA-related transcriptome data were downloaded from GEO, and differentially expressed genes (DEGs) in AAA tissue were screened for GO and KEGG enrichment analyses. Small molecule compounds and their target proteins with negative connectivity to the AAA expression profile were predicted in the Connectivity Map (CMap) database. Molecular docking and molecular dynamics simulation were performed to predict the binding of the target protein to the small molecule compound, and the MM/GBSA method was used to calculate the binding free energy. Cluster analysis was performed using the cluster tool in the GROMACS package. An AAA cell-free model was built, and CETSA experiments were used to demonstrate the binding ability of small molecules to the target protein in cells., Results: A total of 2244 DEGs in AAA were obtained through differential analysis, and the DEGs were mainly enriched in the tubulin binding biological function and cell cycle pathway. The CMap results showed that Apicidin had a potential therapeutic effect on AAA with a connectivity score of -97.74, and HDAC4 was the target protein of Apicidin. Based on literature, HDAC4-Apicidin was selected as the subsequent research object. The lowest affinity of Apicidin-HDAC4 molecular docking was -8.218 kcal/mol. Molecular dynamics simulation results indicated that Apicidin-HDAC4 could form a stable complex. MM/GBSA analysis showed a total binding free energy of -55.40 ± 0.79 kcal/mol, and cluster analysis showed that there were two main conformational clusters during the binding process, accounting for 22.4% and 57.8%, respectively. Apicidin could form hydrogen bonds with surrounding residues for stable binding. CETSA experiment proved the stable binding ability of Apicidin and HDAC4., Conclusion: Apicidin inhibited HDAC4 in AAA and exhibited favorable protein-ligand interactions and stability, making it a potential candidate drug for treating AAA., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Fusarium head blight is a disease of global concern that reduces crop yields and renders grains unfit for consumption due to mycotoxin contamination. Fusarium poae is frequently associated with cereal crops showing symptoms of Fusarium head blight. While previous studies have shown F. poae isolates produce a range of known mycotoxins, including type A and B trichothecenes, fusarins and beauvericin, genomic analysis suggests that this species may have lineage-specific accessory chromosomes with secondary metabolite biosynthetic gene clusters awaiting description. Methods: We examined the biosynthetic potential of 38 F. poae isolates from Eastern Canada using a combination of long-read and short-read genome sequencing and untargeted, high resolution mass spectrometry metabolome analysis of extracts from isolates cultured in multiple media conditions. Results: A high-quality assembly of isolate DAOMC 252244 (Fp157) contained four core chromosomes as well as seven additional contigs with traits associated with accessory chromosomes. One of the predicted accessory contigs harbours a functional biosynthetic gene cluster containing homologs of all genes associated with the production of apicidins. Metabolomic and genomic analyses confirm apicidins are produced in 4 of the 38 isolates investigated and genomic PCR screening detected the apicidin synthetase gene APS1 in approximately 7% of Eastern Canadian isolates surveyed. Conclusions: Apicidin biosynthesis is linked to isolate-specific putative accessory chromosomes in F. poae. The data produced here are an important resource for furthering our understanding of accessory chromosome evolution and the biosynthetic potential of F. poae. [ABSTRACT FROM AUTHOR]

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by abnormal cell proliferation, apoptosis repression and myeloid differentiation blockade of hematopoietic stem/progenitor cells. Developing and identifying novel therapeutic agents to reverse the pathological processes of AML are of great significance. Here in this study, we found that a fungus-derived histone deacetylase inhibitor, Apicidin, presents promising therapeutic effect on AML by inhibiting cell proliferation, facilitating apoptosis and inducing myeloid differentiation of AML cells. Mechanistic investigation revealed that QPCT is identified as a potential downstream target of Apicidin, which exhibits significantly decreased expression in AML samples compared with the normal controls and is remarkably up-regulated in AML cells upon Apicidin management. Functional study and rescue assay demonstrated that QPCT depletion further promotes cell proliferation, inhibits apoptosis and impairs myeloid differentiation of AML cells, alleviating the anti-leukemic effect of Apicidin on AML. Our findings not only provide novel therapeutic target for AML, but also lay theoretical and experimental foundation for the clinical application of Apicidin in AML patients.

Apicidin, a cyclic peptide histone deacetylase (HDAC) inhibitor, has been demonstrated to exhibit antitumor activity in a number of human cancer types. The present study examined the antitumor activity of apicidin in murine oral squamous cell carcinoma (OSCC) cells. Inhibition of cell proliferation and the expression of selective HDACs were determined in apicidin-treated AT-84 murine OSCC cells. A C3H mouse model with subcutaneous injection of AT-84 cells was used to assess the in vivo effect of apicidin on tumor growth. Apicidin-induced cell growth inhibition and selectively reduced HDAC8 expression in AT-84 cells. Induction of apoptosis and autophagy was observed in apicidin-treated AT-84 cells. Apicidin notably inhibited tumor growth by up to 46% relative to the control group at the end of a 14-day period in a murine tumor model. The immunohistochemistry results in tumor tissues indicated that apicidin inhibited cell proliferation and induced apoptosis and autophagy in AT-84 cell-derived tumor tissues. Overexpression of HDAC8 was observed in the nucleus and cytoplasm in tumor tissues and apicidin significantly inhibited the level of HDAC8 expression, compared with the vehicle group. These results indicated that apicidin inhibited cell proliferation through HDAC8 inhibition in murine OSCC cells in vitro and in vivo. The present study indicated that apicidin may be an effective therapeutic agent for OSCC. [ABSTRACT FROM AUTHOR]

Apicidin is a potent histone deacetylase inhibitor (HDACI) that selectively binds to histone deacetylases (HDACs) class I and interferes with the deacetylation process, which results in modification of acetylation level of cellular proteins. The aim of the study was to investigate the potential time and dose dependent cytotoxicity of the test compound, Apicidin, in pancreatic cancer cells Capan-1 and Panc-1 as well as estimate maximal tolerable dose (MTD) of the test agent and determine EC 50 using four complementary colorimetric cytotoxicity or viability assays. The cells were treated with increasing concentrations of Apicidin (0–5000 nM) for 2, 4 and 6 h (short term exposure) or 24, 48 and 72 h (long term exposure) before conducting cytotoxic analyses with lactate dehydrogenase assay or viability analyses with sulforhodamine B (SRB), methyl tetrazolium (MTT) and crystal violet (CV) assays. In order to investigate whether Apicidin irreversibly affects the cells already during the short term exposure, the medium containing Apicidin was removed and replaced with fresh culturing medium after 6 h of treatment. The cells were then incubated for additional 24, 48 or 72 h before carrying out the analysis. The results obtained from cytotoxicity and viability assays indicated, that Apicidin was well tolerated by both cell lines at concentrations below 100 nM at any given time point and at all applied concentrations during the short term (6 h or less) treatment. Continuous prolonged term exposures (48 h or greater) of the cells to Apicidin with concentration exceeding 100 nM resulted in significantly increasing cytotoxicity and sustained significant loss of cell viability. Moreover, long term exposure of pancreatic cancer cells Capan-1 and Panc-1 to Apicidin concentrations exceeding 100 nM showed an initial anti-proliferative effect before cytotoxicity onset. In summary, MTD was exposure time dependent and estimated to 100 nM for long term treatment and to at least 5000 nM for treatment not greater than 6 h. EC 50 concentration of Apicidin was established after long term treatment, however with some variation when comparing the different assays and cell lines. Results from this study may encourage reinvestigating the capacity of potent HDACI Apicidin as an attractive agent for interfering with the deacetylation process catalyzed by HDACs for potential pancreatic cancer intervention. [ABSTRACT FROM AUTHOR]

The article discusses the role of Apicidin-resistant HA22T hepatocellular carcinoma cells in activation of the Wnt/β- catenin signaling pathway and matrix metalloproteinase-2 (MMP-2) expression to enhance cell metastatic effect. Topics discussed include β- catenin nuclear localization, cancer metastasis and breakdown of the extracellular matrix (ECM). It also discusses role of matrix metalloproteinases (MMP) in malignant progression.

Abstract: This study examined the molecular mechanisms of apicidin in the modulation of human ovarian cancer SKOV-3 cells invasion and migration. Apicidin markedly decreased histone deacetylase 4 (HDAC4) expression and blocked cell migration and invasion. Cell migration was inhibited via down-regulation of matrix metalloproteinase-2 (MMP-2) and up-regulation of RECK in the HDAC4-blocked SKOV-3 cells. Apicidin significantly suppressed the binding of HDAC4 to Sp1 binding elements of the RECK promoter via repression of HDAC4. In an in vivo model, apicidin suppressed the growth of transplanted SKOV-3 cells by down-regulating HDAC4 and MMP-2. Apicidin may potentially be used as an anti-cancer agent for inhibition of cancer cell migration and invasion through the repression of MMP-2 which is related to the reduction of HDAC4. [Copyright &y& Elsevier]

Abstract: The effect of inhibitors of histone deacetylase (HDAC) on Apicomplexa has been previously reported with the discovery of apicidin, a cyclic tetrapeptide having broad-spectrum antiparasitic activity. In the current study, we expressed Babesia bovis (B. bovis) recombinant-HDAC 3 (rBbHDAC3) as a GST-fusion protein in Escherichia coli (E. coli) and found that it was antigenic. An antiserum against the recombinant protein was generated in mice. The mice serum demonstrated the presence of HDAC in B. bovis by a Western blot assay. The murine anti-rBbHDAC3 reacted with B. bovis, Babesia bigemina (B. bigemina), Theileria equi (T. equi), and Babeisa caballi (B. caballi) merozoites in the indirect fluorescent antibody test (IFAT). Furthermore, the HDAC-enzymatic activity of the rBbHDAC3 protein was evaluated by a colorimetric assay. The enzymatic activity of rBbHDAC3 was inhibited by 100ng/ml of apicidin, and the inhibitory effect of apicidin was dose-dependent. The inhibition of BbHDAC3 by apicidin was confirmed by Western blot, IFAT, and reverse transcription-polymerase chain reaction (RT-PCR). Finally, apicidin potentially inhibited the in vitro growth of Babesia parasites. The lower IC50 values of apicidin against apicomplexan parasites than those of mammalian cells point to HDAC as an excellent drug target. The findings of the present study indicate that BbHDAC3 is a potential target for apicidin and might be a promising target for the development of novel anti-babesial drugs. [Copyright &y& Elsevier]

Apicidin, a fungal metabolite that functions as a histone deacetylase inhibitor, induces apoptosis in cancer cells. We investigated the molecular mechanisms of the anti-cancer effects of apicidin in mouse Neuro-2a neuroblastoma cells. Apicidin induced apoptotic cell death and activation of caspase-12, -9, and -3. Apicidin induced expression of endoplasmic reticulum (ER) stress-associated proteins, including CCAAT/enhancer binding protein homologous protein (CHOP), cleavage of activating transcription factor 6α, and phosphorylation of eukaryotic initiation factor 2α. Inhibition of ER stress by CHOP knockdown or using the ER stress inhibitors, salubrinal and 4-phenylbutyric acid, reduced apicidin-induced cell death. Apicidin induced reactive oxygen species accumulation and mitochondrial membrane potential loss. An antioxidant, N-acetyl cysteine, reduced apicidin-induced cell death, CHOP expression, and mitochondrial dysfunction. In addition, apicidin increased cytosolic Ca, which was blocked by 2-aminoethoxydiphenyl borate, an antagonist of inositol 1,4,5-trisphosphate receptor, and BAPTA-AM, an intracellular Ca chelator. 2-Aminoethoxydiphenyl borate and BAPTA-AM inhibited apicidin-induced cell death and ER stress. Interestingly, apicidin induced phosphorylation of phospholipase Cγ1 (PLCγ1) and epidermal growth factor receptor (EGFR), and inhibition of PLCγ1 and EGFR reduced cell death and ER stress. Finally, apicidin-induced histone H3 hyperacetylation and reduction of histone deacetylase 2 mRNA expression were not affected by either a PLCγ1 inhibitor, U73122, or the antioxidant, N-acetyl cysteine. Taken together, the results suggest that apicidin induces apoptosis by ER stress and mitochondrial dysfunction via PLCγ1 activation, Ca release, and reactive oxygen species accumulation in Neuro-2a neuroblastoma cells. [ABSTRACT FROM AUTHOR]

Summary: Apicidin acts as a potent histone deacetylases (HDAC) inhibitor and the precise mechanism for its anti-tumor activity in human oral squamous cell carcinoma (OSCC) cells has not been examined. The aim of this study was to evaluate the anti-tumor efficacy of apicidin through apoptosis and autophagy in OSCC cells. Cells were treated with apicidin and cell death was quantified. Cell cycle and apoptosis were measured using flow cytometry assay, immunoblot. Autophagy was characterized by the increase of LC3B-II and the formation of acidic vesicular organelles (AVOs). Apicidin significantly inhibited the proliferation of OSCC cells in a dose-dependent manner. Apicidin markedly up-regulated p21WAF1 led to G2/M phase arrest. Apicidin significantly increased the number of apoptotic cells compared to untreated control. Apicidin induced not only apoptosis but also autophagy in OSCC cells. Apicidin dramatically increased the levels of LC3 type II expression, ATG5 protein expression and the accumulation of AVOs. Inhibition of autophagy enhanced apicidin-mediated cytotoxicity through an increase in apoptosis. These results suggest that apicidin exerts anti-tumor effects by inducing apoptosis and autophagy and provide novel evidence of apicidin-induced autophagy and autophagy inhibition enhances apicidin-mediated apoptosis in OSCC cells. [Copyright &y& Elsevier]

Purpose: The objectives of this study were to develop physiologically based models for the pharmacokinetics (PK) and organ distribution of apicidin in rats and mice and to predict human PK in blood and organs. Methods: The PK of apicidin was characterized in rats and mice after i.v. bolus injection, and distribution to various tissues was determined in rats following i.v. infusions at steady state. The developed models were prospectively validated within rat and within mouse and by scaling from rat to mouse using data after multiple i.v. injections. Human PK was predicted by the physiologically based modeling using intrinsic clearance data for humans from in vitro experiments. Results: The Cl predicted for human (9.8 ml/min/kg) was lower than those found in mice (116.9 ml/min/kg) and rats (61.6 ml/min/kg), and the V predicted for human (1.9 l/kg) was less than in mice (2.0 l/kg) and rats (2.5 l/kg). Consequently, the predicted t was longer in human (2.3 h) than in mice and rats (0.4 and 0.9 h, respectively). The highest concentrations of apicidin were predicted in liver followed by adipose tissue, kidney, lung, spleen, heart, arterial blood, venous blood, small intestine, stomach, muscle, testis, and brain. Conclusions: The developed models adequately described the PK of apicidin in rats and mice and were applied to predict human PK. These models may be useful in predicting human blood and tissue concentrations of apicidin under different exposure conditions. [ABSTRACT FROM AUTHOR]

Background: This study assessed the population pharmacokinetics and metabolic conversion of a novel histone deacetylase (HDAC) inhibitor, SD-2007, into its active metabolite, apicidin, in rats. Methods: SD-2007 was given to rats by intravenous injection (4 mg/kg) and oral administration (40 mg/kg). Serum concentrations of SD-2007 and apicidin were determined by LC-MS/MS. All concentrations were analyzed using a population pharmacokinetic model with 9 compartments in S-ADAPT. Results: The area under the curve for apicidin was 96 ± 16 mg·h/ml after 4 mg/kg administered intravenously and 2,455 ± 1,211 mg·h/ml after 40 mg/kg given orally. The population pharmacokinetic model described all profiles well. After oral administration of SD-2007, the median absolute bioavailability of SD-2007 was 6.67% (range 3.83-9.89) and the median apparent bioavailability was 22.3% (range 15.7-35.8) for apicidin, whereas only a median of 8.85% (range 7.57-9.34) of an intravenous SD-2007 dose was converted to apicidin. Conclusions: Oral SD-2007 displayed a substantial presystemic metabolism to active apicidin. The high serum concentrations of apicidin after oral administration of SD-2007 may cause significant HDAC inhibition. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

It has recently been reported that endometrial cancer cells are able to convert estron (E1) to 17β estradiol (E2). We observed the presence of 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) transcript and protein in receptor positive ER and negative ER Ishikawa endometrial adenocarcinoma (ISH) cells. ER ISH, but not ER02 ISH, cells were significantly susceptible to apicidin induced death, and we further used ERISH cells to study the effect of apicidin on cellular levels of HSD17B1 transcript and protein. We showed that apicidin significantly lowered HSD17B1 transcript and protein levels in ISH cells. There was no significant effect on HSD17B1 transcript stability. However, chromatin immunoprecipitation analysis revealed that apicidin significantly decreased occupation of the first exon of the HSD17B1 gene by Polymerase II. Since intratumoral E1 to E2 conversion is a significant contributor to the progression of estrogen dependent cancers, and HDAC inhibitors are being tested in anticancer clinical trials, our observations may have clinical value. [ABSTRACT FROM AUTHOR]

Abstract: Phospholipase C gamma-1 (PLCγ1) phosphorylation is a key step in intracellular signal transduction in T cells. We used Hut-78 T lymphoma cells to demonstrate the effect of apicidin on cellular levels of the PLCγ1 molecule. Using reverse-transcription, real-time quantitative PCR and Western blot analysis, we observed that apicidin reduced the PLCγ1 transcript and protein contents in Hut-78 T lymphoma cells. Our results indicate that protein synthesis appears to be crucial in the apicidin decrease of PLCγ1 mRNA steadiness. Moreover, we determined that apicidin reduces the half-life of PLCγ1 mRNAs from approximately 2 to 4h. Since PLCγ1 is considered a key molecule in signal transduction in T cells, apicidin may be useful in the treatment of some autoimmune diseases in which autoreactive T cells occur. [Copyright &y& Elsevier]

Abstract: TNF-related apoptosis-inducing ligand (TRAIL) is a pro-apoptotic cytokine that is capable of inducing apoptosis in a wide variety of cancer cells but not in normal cells. Although many cancer cells are sensitive to TRAIL-induced apoptosis, chronic myeloid leukemia (CML) develops resistance to TRAIL. In this study, we investigated whether apicidin, a novel histone deacetylase inhibitor, could overcome the TRAIL resistance in CML-derived K562 cells. Compared to treatment with apicidin or TRAIL alone, cotreatment with apicidin and TRAIL-induced apoptosis synergistically in K562 cells. This combination led to activation of caspase-8 and Bcl-2 interacting domain (Bid), resulting in the cytosolic accumulation of cytochrome c from mitochondria as well as an activation of caspase-3. Treatment with apicidin resulted in down-regulation of Bcr-Abl and inhibition of its downstream target, PI3K/AKT-NF-κB pathway. In addition, apicidin decreased the level of NF-κB-dependent Bcl-xL, leading to caspase activation and Bid cleavage. These results suggest that apicidin may sensitize K562 cells to TRAIL-induced apoptosis through caspase-dependent mitochondrial pathway by regulating expression of Bcr-Abl and its related anti-apoptotic proteins. Therefore, the present study suggests that combination of apicidin and TRAIL may be an effective strategy for treating TRAIL-resistant Bcr-Abl expressing CML cells. [Copyright &y& Elsevier]

Abstract: Histone deacetylase (HDAC) inhibitors are a promising new class of anticancer agents that act by inhibiting cell proliferation and inducing apoptosis in a variety of cancer cells. Although apicidin acts as a potent HDAC inhibitor, the precise mechanism for its anti-tumor activity in human endometrial cancer cells is not completely understood. This study examined the anti-tumor effects of apicidin in Ishikawa cancer cells. The level of cell proliferation, the stage of the cell cycle, and apoptosis were measured after the apicidin treatment. Apicidin significantly inhibited the proliferation of Ishikawa cells in a dose-dependent manner. In addition, apicidin markedly up-regulated the p21WAF1 and down-regulated the expression of cyclins (A, B1, D1, or E), and CDKs (2 or 4), which leading to cell cycle arrest. Cell cycle analysis showed that the apicidin treatment increased the proportion of cells in the G1 phase, and decreased the ratio of cells in the S phase in a dose-dependent manner. Apicidin significantly increased the sub-G1 population and the number of TUNEL positive apoptotic cells compared with the untreated control. These results were confirmed by poly-ADP ribose polymerase (PARP), an 85-kDa fragment resulting from PARP cleavage, where apicidin increased the level of PARP cleavage and caspase-3 activity in 1.0μM apicidin-treated cells. Apicidin-induced apoptosis through caspase-3 activation was confirmed by the increase in the release of cytochrome c and the decrease in the Bax/Bcl-2 ratio. These results suggest that apicidin has anti-tumor properties on endometrial cancer cells by inducing selectively the genes related to cell cycle arrest and apoptosis. [Copyright &y& Elsevier]

SD-2007 is a new derivative of apicidin, an anti-parasitic agent and a histone deacetylase (HDAC) inhibitor. A subacute toxicological evaluation of SD-2007 was investigated for 2 weeks in ICR mice. After oral administration of SD-2007 (0, 0.2, 1, 5 or 25 mg/mouse), the clinical signs, mortalities, body weight changes, blood biochemical parameters, absolute and relative organ weights were examined. One day after the administration of SD-2007, excretion of soft feces in 1 and 5 mg/head groups, and one male in 25 mg/mouse group developed diarrhea, but theses complications were disappeared two days after administration. No mortalities were observed in animals up to 25 mg/mouse (LD50, >25 mg/kg), but absolute and relative weights of testes were significantly lower at the highest dose group (25 mg/mouse) and serum LDH and glucose levels were elevated in male mice. In addition, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) activities were reduced in female mice at all dosages. These data suggest that SD- 2007 may be sex specific and be toxic to the male reproductive organ, and thus our findings require further investigation and in particular chronic toxicological investigations should be investigated. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of various histone deacetylase (HDAC) inhibitors on adipocyte differentiation. Treatment of 3T3-L1 cells with HDAC inhibitors such as apicidin, trichostatin A, or suberoylanilide hydroxamic acid, under conditions that normally promote differentiation led to a dramatic attenuation of adipocyte differentiation. In contrast, sodium butyrate (NaB) treatment increased adipocyte differentiation. Accordingly, the expression of adipogenic marker genes such as FAS, aP2, PPARγ, resistin, C/EBPα, ADD1/SREBP1c, and adiponectin were inhibited by apicidin treatment but not NaB, indicating that the adipocyte differentiation process could be differentially regulated depending on the type of HDAC inhibitor utilized. In addition, this differential effect seemed not to be due to disruption of the insulin- signaling pathway. Interestingly, our data showed that apicidin treatment could induce dedifferentiation of fully differentiated adipocytes, as evident by the fact that apicidin treatment led to a decrease of Oil Red O-stained adipocytes with a concomitant reduction in the expression levels of adipogenic marker genes. Collectively, our results suggest that adipocyte differentiation and dedifferentiation may be regulated by HDAC inhibitors. [ABSTRACT FROM AUTHOR]

Abstract: Virtually all cervical cancer morbidities are associated with genital skin or mucosa cell infection with human papillomavirus (HPV). The HPV oncogenic proteins E6 and E7 are able to inactivate p53 and Rb proteins, which results in malignant transformation. Employing quantitative real-time PCR and Western blot analysis, we observed that apicidin histone deacetylase (HDAC) inhibitor significantly reduced HPV16-E6 and -E7 transcripts and protein levels in SiHa cervical cancer cells. Moreover, we found that apicidin lowered HPV16-E6 and -E7 transcript stability and significantly decreased these transcripts’ half-life from approximately 5h to 2h and from 6h to 3h, respectively. Our results from experiments with protein biosynthesis inhibitor suggest the involvement of an RNase and/or mRNA stabilization protein in HPV16-E6 and -E7 transcript stabilization. Since the HPV type 16 is associated with most cervical cancer incidence and HDAC inhibitors are being tested in anti-cancer clinical trials, our observations may have clinical significance. [Copyright &y& Elsevier]

Abstract: Multidrug resistance (MDR), which is a significant impediment to the success of cancer chemotherapy, is attributable to the overexpression of membrane transport proteins, such as P-glycoprotein (P-gp), resulting in an increased drug efflux. In this study, we show that the histone deacetylase (HDAC) inhibitor apicidin leads to resistance of HeLa cells to paclitaxel through the induction of P-gp expression. Furthermore, apicidin dramatically increases the release of a fluorescent P-gp substrate, rhodamine 123, from cells. In parallel, apicidin resistance to the apoptotic potential of paclitaxel is associated with induction of P-gp expression in HeLa cells, as evidenced by specific inhibition of P-gp function using either the pharmacological inhibitor verapamil or RNA silencing. We also demonstrate the contribution of apicidin-induced functional P-gp expression to drug resistance using KB cells. Failure of P-gp induction by apicidin does not reverse paclitaxel-induced cytotoxicity in the cells. Although HDAC inhibitors are widely appreciated as a new class of anti-tumor agent, our findings clearly demonstrate that apicidin treatment may lead to P-gp-mediated resistance to other anti-tumor agents, suggesting a need for careful design of clinical applications using HDAC inhibitors. [Copyright &y& Elsevier]

Dysregulation of DNA methyltransferase (DNMT)1 expression is associated with cellular transformation, and inhibition of DNMT1 exerts antitumorigenic effects. Here, we report that DNMT1 abnormally expressed in HeLa cells is downregulated by a histone deacetylase (HDAC) inhibitor apicidin, which is correlated with induction of repressive histone modifications on the promoter site. Apicidin selectively represses the expression of DNMT1 among DNMTs in HeLa cells, independent of cell cycle arrest at G0/G1. Furthermore, apicidin causes a significant reduction in the recruitment of RNA polymerase II into the promoter. Chromatin immunoprecipitation analysis shows that even though apicidin causes global hyperacetylation of histone H3 and H4, localized deacetylation of histone H3 and H4 occurs at the E2F binding site, which is accompanied by the recruitment of pRB and the replacement of P/CAF with HDAC1 into the sites. In addition, K4-trimethylated H3 on nucleosomes associated with the transcriptional start site is depleted following apicidin treatment, whereas repressive markers, K9- and K27-trimethylation of H3 are enriched on the site. The downregulation of DNMT1 expression seems to require de novo protein synthesis, because the apicidin effect is antagonized by cycloheximide treatment. Moreover, knock down of DNMT1 with siRNA induces the apoptosis of HeLa cells, indicating that downregulation of DNMT1 might be a good strategy for therapeutics of human cervix cancer. Collectively, our findings will provide a mechanistic rationale for the use of HDAC inhibitors in cancer therapeutics.Oncogene (2008) 27, 1376–1386; doi:10.1038/sj.onc.1210776; published online 10 September 2007 [ABSTRACT FROM AUTHOR]

Abstract: Down-regulation of gelsolin expression is associated with cellular transformation and induction of gelsolin exerts antitumorigenic effects. In this study, we show that protein kinase C (PKC) signaling pathway is required for the induction of gelsolin by the histone deacetylase inhibitor apicidin in HeLa cells. Apicidin induces gelsolin mRNA independently of the de novo protein synthesis. Inhibitor study has revealed that the PKC signaling pathway is involved in the gelsolin expression. Furthermore, inhibition of PKCε by either siRNA or dominant-negative mutant completely abrogates the expression of gelsolin by apicidin, indicating that PKCε is the major isoform for this process. In parallel, apicidin induction of gelsolin is antagonized by the inhibition of Sp1 using dominant-negative Sp1 or specific Sp1 inhibitor mithramycin, and inhibition of PKC leads to suppression of Sp1 promoter activity. Our results provide mechanistic insights into molecular mechanisms of gelsolin induction by apicidin. [Copyright &y& Elsevier]

Histone deacetylase (HDAC) inhibitors are promising anti-cancer drugs, but these exert differential responses depending on the cell types. Here, we demonstrate a new mechanism for activation of nuclear factor-κB (NF-κB) by HDAC inhibitor apicidin and the role of NF-κB signaling pathway for mediating differential cellular responses, especially, apoptosis. Treatment of HeLa cells with apicidin increases transcriptional activity of NF-κB and its target gene IL-8 and cIAP-1 induction, which involves the activation of IKK–IκBα signaling pathway through Sp1-dependent de novo protein synthesis. In parallel, apicidin treatment leads to histone hyperacetylation in the IL-8 promoter region independent of NF-κB signaling pathway, which is not sufficient for full transcription of IL-8 gene. This NF-κB activation contributes to resistance of HeLa cells to apoptotic potential of apicidin. Collectively, our results suggest that activation of NF-κB signaling cascade functions as a critical modulator to determine cell fate on apoptosis in response to HDAC inhibitors.Cell Death and Differentiation (2006) 13, 2033–2041. doi:10.1038/sj.cdd.4401915; published online 21 April 2006 [ABSTRACT FROM AUTHOR]

Abstract: Histone deacetylase (HDAC) inhibitors are appreciated as one of promising anticancer drugs, but they exert differential responses depending on the cell type. We recently reported the critical role of NF-κB as a modulator in determining cell fate for apoptosis in response to an HDAC inhibitor. In this study, we investigate a possible signaling pathway required for NF-κB activation in response to the HDAC inhibitor apicidin. Treatment of HeLa cells with apicidin leads to an increase in transcriptional activity of NF-κB and the expression of its target genes, IL-8 and TNF-α. TNF-α expression by apicidin is induced at earlier time points than NF-κB activation or IL-8 expression. In addition, our data show that the early expression of TNF-α does not lead to activation of NF-κB, because disruption of TNF-α activity by a neutralizing antibody does not affect nuclear translocation of NF-κB, IκBα degradation or reporter gene activation by apicidin. However, this activation of NF-κB requires the PI3K and PKC signaling pathways, but not ERK or JNK. Furthermore, apicidin activation of NF-κB seems to result from HDAC1 inhibition, as evidenced by the observation that overexpression of HDAC1, but not HDAC2, 3 or 4, dramatically inhibits NF-κB reporter gene activity. Collectively, our results suggest that activation of NF-κB signaling by apicidin requires both the PI3K/PKC signaling pathways and HDAC1, and functions as a critical modulator in determining the cellular effect of apicidin. [Copyright &y& Elsevier]

Abstract: We show that a histone deacetylase (HDAC) inhibitor apicidin increases the transcriptional activity of cyclin E gene, which results in accumulation of cyclin E mRNA and protein in a time- and dose-dependent manner. Interestingly, apicidin induction of cyclin E gene is found to be mediated by Sp1- rather than E2F-binding sites in the cyclin E promoter, as evidenced by the fact that specific inhibition of Sp1 leads to a decrease in apicidin activation of cyclin E promoter activity and protein expression, but mutation of E2F-binding sites of cyclin E promoter region fails to inhibit the ability of apicidin to activate cyclin E transcription. In addition, this transcriptional activation of cyclin E by apicidin is associated with histone hyperacetylation of cyclin E promoter region containing Sp1-binding sites. Our results demonstrate that regulation of histone modification by an HDAC inhibitor apicidin contributes to induction of cyclin E expression and this effect is Sp1-dependent. [Copyright &y& Elsevier]

n-Butyrate is one of the most powerful chemical inducers of the differentiation of human eosinophilic leukemia HL-60 clone 15 cells into mature eosinophils. We have recently reported that the mechanism by which HL-60 clone 15 cells differentiate into eosinophils by n-butyrate is that n-butyrate continuously inhibits histone deacetylase activity as a histone deacetylase inhibitor, resulting in continuous acetylation of histones. In this review, we discuss roles of histone acetyltransferase, histone deacetylase and histone deacetylase inhibitors in the differentiation of HL-60 clone 15 cells into eosinophils. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

1. We have examined the effect of the histone deacetylase inhibitors apicidin, trichostatin A (TSA) and n-butyrate on the histone acetylation and the differentiation of human cosinophilic leukemia HL-60 clone 15 cells into eosinophils. 2. Viability of the cells incubated with apicidin (100 nM). TSA (30 nM) or n-butyrate (500 μM) did not change significantly, but higher concentrations of apicidin (⩾ 300 nM) or TSA (⩾ 100nM) decreased the viability when examined at day 1. 3. Apicidin (100 nM) as well as n-butyrate (500 μM) induced continuous acetylations of histone H4 and lysine14 residue on histone H3, while TSA (30 nM) induced transient acetylations. 4. After 6 days incubation, eosinophilic cells stained by Luxol-fast-blue were generated by apicidin (100 nM) and n-butyrate (500 μM) but not by TSA (30 nM). Other markers for differentiation into eosinophils such as changes in intracellular structure, and expressions of integrin β7 and major basic protein, and the inhibition of cell proliferation were also induced by apicidin and n-butyrate but not by TSA. 5. Continuous acetylation of histone H4 achieved by repeated treatment with TSA (30 nM) at an interval of 12 h tor more than three times induced such changes when examined on day 6. In addition, the induction was impaired by shortening the period of incubation with apicidin (100 nM) or n-butyrate (500 μM). 6 CCAAT/enhancer binding protein was continuously activated by apieidin (100 nM) and n-butyrate (500 μM), but was transiently activated by TSA (30 nM). 7. These findings suggest that the continuous acetylation of histones H3 and H4 is necessary for the differentiation of HL-60 clone 15 cells into eosinophils. [ABSTRACT FROM AUTHOR]

Apicidin has been identified as a histone deacetylase (HDAC) inhibitor. Since HDAC inhibitors are emerging as an exciting new class of potential anti-cancer agents, in the present study, we have examined the inhibitory effect of apicidin on cancer invasion and angiogenesis. Apicidin induced di- and tri-acetylated forms of histone H4 and the morphological alteration in v-ras-transformed mouse fibroblast NIH3T3 cells. Apicidin dramatically inhibited the invasion of v-ras-NIH3T3 and human melanoma A2058 cells and it could be associated with its ability to regulate the activities of matrix metalloproteinases. Interestingly, apicidin strongly inhibited the formation of new vessels on chorioallantoic membrane and the tube formation of ECV304 human vascular endothelial cells. This is the first report to show the anti-angiogenic potential of apicidin and it could be developed as a new type of anti-cancer drug. [Copyright &y& Elsevier]