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Histone deacetylase inhibitors (HDACi) have been reported to have potent chemopreventive activity because of their effects on the inhibition of cell growth and apoptosis in human cancer cell lines. In the present study, we investigated the apoptotic effect of a novel HDACi, Ky2, and its molecular mechanism in MDA-MB-231 human breast cancer cells in vitro. The chemopreventive effects of Ky2 in MDA-MB-231 cells were evaluated using the MTS assay, anchorage-independent cell transformation assay, DAPI staining, western blot analysis, reverse transcriptase-PCR, and small interfering RNA. Ky2 enhanced histone acetylation and decreased cell viability. Ky2 induced apoptosis evidenced by nuclear condensation and fragmentation, the accumulation of sub-G1 phase, and caspase-dependent PARP cleavage. In addition, Ky2 released cytochrome c from mitochondria to cytosol through the regulation of mitochondria-related proteins (Bid, Bim, and Bcl-xL). Ky2 markedly decreased the level of Sp1 protein expression through both the decrease of Sp1 mRNA level and proteasome-dependent protein degradation. Interestingly, the apoptotic effect of Ky2 is more potent than SAHA, a well-known HDACi. Furthermore, the knockdown of Sp1 protein by Sp1-specific inhibitor, mithramycin A, and siRNA resulted in the alteration of truncated Bid and Bim to induce apoptosis. Furthermore, Ky2 significantly decreased TPA-induced or EGF-induced neoplastic cell transformation in JB6 cells. Our results suggest that Ky2 may be a potential chemopreventive and chemotherapeutic agent by modulating Sp1 in human breast cancer cells.

Expression and stability of the tumor suppressor runt-related transcription factor 3 (RUNX3) are regulated by histone deacetylase (HDAC). HDAC inhibition alters epigenetic and posttranslational stability of RUNX3, leading to tumor suppression. However, HDAC inhibitors can nonselectively alter global gene expression through chromatin remodeling. Thus, lactam-based HDAC inhibitors were screened to identify potent protein stabilizers that maintain RUNX3 stability by acetylation. RUNX activity and HDAC inhibition were determined for 111 lactam-based analogues through a cell-based RUNX activation and HDAC inhibition assay. 3-[1-(4-Bromobenzyl)-2-oxo-2,5-dihydro-1H-pyrrol-3-yl]-N-hydroxypropanamide (11-8) significantly increased RUNX3 acetylation and stability with relatively low RUNX3 mRNA expression and HDAC inhibitory activity. This compound showed significant antitumor effects, which were stronger than SAHA, in an MKN28 xenograft model. Thus, we propose a novel strategy, in which HDAC inhibitors serve as antitumor chemotherapeutic agents that selectively target epigenetic regulation and protein stability of RUNX3., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Histone deacetylase (HDAC) inhibitors are emerging as potent anticancer agents due to their ability to induce apoptosis in various cancer cells, including prostate cancer cells. In the present study, we synthesized a novel HDAC inhibitor, A248, and investigated its apoptotic activity and molecular target in the DU145 and PC3 human prostate cancer cell lines. A248 inhibited the growth of DU145 and PC3 cells and induced apoptosis, as demonstrated by nuclear fragmentation and the accumulation of cells at subG1 phase of cell cycle. The treatment of DU145 and PC3 prostate cancer cells with A248 resulted in the downregulation of specificity protein 1 (Sp1) expression. Since the expression levels of survivin and Mcl-1 depend on Sp1, we also investigated the effects of A248 on survivin and Mcl-1 expression using western blot analysis and immunocytochemistry. The results showed that A248 markedly decreased the expression of survivin and Mcl-1. These data suggest that A248 has apoptotic activity in human prostate cancer cells and that Sp1 may be the molecular target of A248 treatment for inducing apoptosis in prostate cancer cells.

Histone deacetylases (HDACs) are important enzymes in epigenetic regulation and are therapeutic targets for cancer. Most zinc-dependent HDACs induce proliferation, dedifferentiation, and anti-apoptotic effects in cancer cells. We designed and synthesized a new series of pyridone-based HDAC inhibitors that have a pyridone ring in the core structure and a conjugated system with an olefin connecting the hydroxamic acid moiety. Consequently, most of the selected pyridone-based HDAC inhibitors showed similar or higher inhibition profiles in addition to remarkable metabolic stability against hydrolysis relative to the corresponding lactam-based HDAC inhibitors. Furthermore, the selectivity of the novel pyridine-based compounds was evaluated across all of the HDAC isoforms. One of these compounds, (E)-N-hydroxy-3-{1-[3-(naphthalen-2-yl)propyl]-2-oxo-1,2-dihydropyridin-3-yl}acrylamide, exhibited the highest level of HDAC inhibition (IC(50) =0.07 μM), highly selective inhibition of class I HDAC1 and class II HDAC6 enzymes, metabolic stability in mouse liver microsomal studies, and effective growth inhibition of various cancer cell lines. Docking studies indicated that a long alkyl linker and bulky hydrophobic cap groups affect in vitro activities. Overall, the findings reported herein regarding pyridone-based HDAC inhibitors can be used to guide future research efforts to develop new and effective anticancer therapeutics., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hydroxamate-based HDAC inhibitors have promising anticancer activities but metabolic instability and poor pharmacokinetics leading to poor in vivo results. QSAR and PK studies of HDAC inhibitors showed that a γ-lactam core and a modified cap group, including halo, alkyl, and alkoxy groups with various carbon chain linkers, improved HDAC inhibition and metabolic stability. The biological properties of the γ-lactam HDAC inhibitors were evaluated; the compound designated 8f had potent anticancer activity and high oral bioavailability.

Histone deacetylases (HDACs) are involved in post-translational modification and epi-genetic expression, and have been the intriguing targets for treatment of cancer. In previous study, we reported synthesis and the biological preliminary results of γ-lactam based HDAC inhibitors. Based on the previous results, smaller γ-lactam core HDAC inhibitors are more active than the corresponding series of larger δ-lactam based analogues and the hydrophobic and bulky cap groups are required for better potency which decreased microsomal stability. Thus, γ-lactam analogues with methoxy, trifluoromethyl groups of ortho-, meta-, para-positions of cap group were prepared and evaluated their biological potency. Among them, trifluoromethyl analogues, which have larger lipophilicity, showed better HDAC inhibitory activity than other analogues. In overall, lipophilicity leads to increase hydrophobic interaction between surface of HDAC active site and HDAC inhibitor, improves HDAC inhibitory activity., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Histone deacetylases (HDACs) are involved in post-translational modification and gene expression. Cancer cells recruited amounts of HDACs for their survival by epi-genetic down regulation of tumor suppressor genes. HDACs have been the promising targets for treatment of cancer, and many HDAC inhibitors have been investigated nowadays. In previous study, we synthesized δ-lactam core HDAC inhibitors which showed potent HDAC inhibitory activities as well as cancer cell growth inhibitory activities. Through QSAR study of the δ-lactam based inhibitors, the smaller core is suggested as more active than larger one because it fits better in narrow hydrophobic tunnel of the active pocket of HDAC enzyme. The smaller γ-lactam core HDAC inhibitors were designed and synthesized for biological and property optimization. Phenyl, naphthyl and thiophenyl groups were introduced as the cap groups. Hydrophobic and bulky cap groups increase potency of HDAC inhibition because of hydrophobic interaction between HDAC and inhibitors. In overall, γ-lactam based HDAC inhibitors showed more potent than δ-lactam analogues., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The novel δ-lactam based HDAC inhibitor, KBH-A118 (3) shows a good HDAC enzyme and cancer cell growth inhibitory activities but has undesirable pharmacokinetics profiles because of instability in mouse liver microsome. To improve metabolic stability, various analogues were prepared with substituents on aromatic ring of cap group and various chain lengths between the cap group and δ-lactam core. The newly prepared analogues showed moderate to potent in vitro activities. Among them six compounds (8a, 8e, 8j, 8n, 8t, and 8v) were evaluated on mouse liver microsome assay and it turned out that the microsomal stabilities were dependent on lipophilicity and the number of the rotatable bonds. Finally, the animal pharmacokinetic profiles of 8e displayed improving oral exposure and oral bioavailability., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Multidrug resistance mediated by the drug efflux protein, P-glycoprotein (P-gp), is one of the principal mechanisms by which tumor cells escape the cell death induced by chemotherapeutic agents. In our previous study, we demonstrated that KBH-A42 [N-hydroxy-3-(2-oxo-1-(3-phenylpropyl)-1,2,5,6-tetrahydropyridin-3-yl)propanamide], a synthetic histone deacetylase inhibitor, effectively inhibited the growth of several human cancer cell lines. In this study, we attempted to determine whether KBH-A42 was also capable of inhibiting the growth of multidrug-resistant cells. Doxorubicin dose-dependently inhibited the growth of P-gp-negative K562 human leukemia cells, but did not show substantial inhibition on the growth of P-gp-positive K562/ADR cells even at 10 microM, the highest concentration of KBH-A42 used, which increased the acetylation of histones in these leukemia cells, dose-dependently and effectively inhibited the cell growth, regardless of the presence of P-gp in the cells. KBH-A42 mediated G0/G1 cell cycle arrest, probably as the result of the down-regulation of CDK2, CDK4 and CDK6 and the up-regulation of p21WAF1. When the expression of p21WAF1 was ablated by a specific siRNA, the inhibition of cell growth by KBH-A42 was partly reduced in both cell lines. In addition to the cell cycle arrest, KBH-A42 also induced apoptosis in these cells, which was accompanied by the activation of caspases, including caspase-9, caspase-8 and caspase-3. The pan-caspase inhibitor, Z-VAD-fmk, partially blocked the cell death induced by KBH-A42. These results indicate that KBH-A42 induces cell cycle arrest and apoptosis via the up-regulation of p21WAF1 and caspase activation, respectively, regardless of the presence of P-gp in the leukemia cells.

We evaluated the novel gamma-lactam-based analogue, KBH-A145, for its anticancer activities. KBH-A145 markedly inhibited histone deacetylase (HDAC) activity in vitro and in vivo to an extent comparable to suberoyl-anilide hydroxamic acid (SAHA). The proliferation of various types of cancers was significantly suppressed by KBH-A145, among which MDA-MB-231 and MCF, human breast cancer cells and ACHN human renal cancer cells, were most sensitive. This was accompanied by induction of p21(WAF1/Cip1) through compromised recruitment of HDAC1, which leads to hyperacetylation of its promoter region and thus arrested both cells in the G(2)/M phase. Interestingly, this compound induced apoptosis of MDA-MB-231 cells, but not ACHN cells, through cleavage of poly(ADP-ribose) polymerase (PARP). Taken together, these results show that this novel gamma-lactam-based HDAC inhibitor potently inhibits the growth of human breast and renal cancer cells. Thus KBH-A145 is a potential therapeutic agent for the treatment of these types of cancer.

In this study, we investigated the anti-tumor activity of KBH-A42 [N-hydroxy-3-(2-oxo-1-(3-phenylpropyl)-1,2,5,6-tetrahydropyridin-3-yl)propanamide], a novel synthetic histone deacetylase (HDAC) inhibitor. KBH-A42 inhibited a variety of HDAC isoforms in enzyme assays and suppressed growth of various cancer cell lines. Among the cell lines examined, colon cancer cells, including SW620, SW480 and HCT-15, were the cell types most sensitive to KBH-A42. KBH-A42 inhibition of cancer cell growth was comparable to or stronger than that of suberoylanilide hydroxamic acid (SAHA), a well-known HDAC inhibitor approved by the FDA to treat cutaneous T cell lymphomas. In SW620 cells, KBH-A42 increased the acetylation of histones, mediated cell cycle arrest (G1 arrest at low doses and G2 arrest at high doses), and induced apoptosis. The cell cycle arrest and apoptosis induced by KBH-A42 might be mediated through up-regulation of p21(Waf1) and activation of caspases, respectively. In addition, KBH-A42 inhibited SW620 tumor growth in a human tumor xenograft model. Taken together, our results indicate that KBH-A42 exerts an anti-tumor activity in vitro and in vivo and is a promising therapeutic candidate to treat human cancers.

In light of the anti-inflammatory properties of histone deacetylase (HDAC) inhibitors, such as suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA), we examined a new HDAC inhibitor KBH-A42 for its anti-inflammatory activities. KBH-A42 showed noteworthy anti-inflammatory properties in vitro via suppression of the production of TNF-alpha, a proinflammatory cytokine, and nitric oxide (NO), a proinflammatory effector molecule, in LPS-stimulated RAW264.7 cells and peritoneal macrophages. It also inhibited TNF-alpha production in vivo as demonstrated in a LPS-induced mouse endotoxemia model. The levels of TNF-alpha, IL-1beta, IL-6 and iNOS mRNAs determined by RT-PCR propose that the inhibition of these pro-inflammatory mediators by KBH-A42 resulted from inhibiting expression of these genes. However, the EMSA study to see the effect of KBH-A42 on the binding of NF-kappaB, a transcription factor, to a specific DNA sequence showed that the binding of NF-kappaB to DNA was not changed regardless of increasing the concentration of KBH-A42 in the presence and absence of LPS stimulation. Interestingly, DNA binding of another transcription factor AP-1 dose-dependently increased by KBH-A42. KBH-A42 differentially regulated the phosphorylation of MAP kinases. While the phosphorylation of ERK1/2 and SAPK/JNK was not affected by KBH-A42, the phosphorylation of p38 decreased by KBH-A42. These results showed that KBH-A42 inhibits production of proinflammatory cytokines in macrophages by decreasing their mRNA levels, and p38 kinase is involved in the KBH-A42-mediated inhibition.

Novel delta-lactam-based HDAC inhibitors which have various substituted benzyl, bi-aromatic cap groups were prepared using ring closure metathesis reaction, and evaluated their HDAC inhibitory activities and anti-proliferative effects. Among prepared analogues, 11m and 11o have very strong HDAC enzymatic inhibition and showed the most potent growth inhibitory activity to five human tumor cell lines including PC-3, ACHN, NUGC-3, HCT-15, and MBA-MB-231 tumor cell lines. Compounds 11m and 11o also showed good tumor growth inhibition of MDA-MB-231 cells in in vivo xenograft model. Structure-activity relationship study using docking model explained the significance of hydrophobic aromatic cap groups for their in vitro activities.

We synthesized a series of delta-lactam-based HDAC inhibitors that were identified with various degrees of anti-inflammatory and cell growth inhibitory activities. Compounds possessing significant HDAC inhibitory activity exhibited both anti-inflammatory and cell growth inhibitory activities as well as significant tumor growth inhibition in the in vivo tumor xenograft experiments. Besides, these compounds demonstrated anti-inflammatory properties in vitro via suppression of the production of the proinflammatory cytokine TNF-alpha and nitric oxide by LPS-stimulated RAW264.7 cells.

delta-Lactam-based hydroxamic acids, inhibitors of histone deacetylase (HDAC), have been synthesized via ring closure metathesis of key diene intermediates followed by conversion to hydroxamic acid analogues. The hydroxamic acids 12a, 12b, and 17c showed potent inhibitory activity in HDAC enzyme assay. The hydroxamic acid 12b exhibited growth inhibitory activity on five human tumor cell lines, showing good sensitivity on the MDA-MB-231 breast tumor cell.