Design,synthesis and anticancer evaluation of acridine hydroxamic acid derivatives as dual Topo and HDAC inhibitors

Multitarget inhibitors design has generated great interest in cancer treatment. Based on the synergistic effects of topoisomerase and histone deacetylase inhibitors, we designed and synthesized a new series of acridine hydroxamic acid derivatives as potential novel dual Topo and HDAC inhibitors. MTT assays indicated that all the hybrid compounds displayed good antiproliferative activities with IC₅₀ values in low micromolar range, among which compound 8c displayed potent activity against U937 (IC₅₀?=?0.90?μM). In addition, compound 8c also displayed the best HDAC inhibitory activity, which was several times more potent than HDAC inhibitor SAHA. Subsequent studies indicated that all the compounds displayed Topo II inhibition activity at 50?μM. Moreover, compound 8c could interact with DNA and induce U937 apoptosis. This study provides a suite of compounds for further exploration of dual Topo and HDAC inhibitors, and compound 8c can be a new dual Topo and HDAC inhibitory anticancer agent.     

Synthesis and biological evaluation of histone deacetylase and DNA topoisomerase II-Targeted inhibitors

HDAC inhibitors enable histones to maintain a high degree of acetylation. The resulting looser state of chromatin DNA may increase the accessibility of DNA drug targets and consequently improve the efficiency of anticancer drugs targeting DNA, such as Topo II inhibitors. A novel class of nucleoside-SAHA derivatives has been designed and synthesized based on the synergistic antitumor effects of topoisomerase II and histone deacetylase inhibitors. Their inhibitory activities toward histone deacetylases and Topo II, and their cytotoxicities in cancer cell lines, were evaluated. Among the synthesized hybrid compounds, compound 16b showed the potent HDAC inhibitory activity at a low nanomolar level and exhibited antiproliferative activity toward cancer cell lines including MCF-7 (breast), HCT-116 (colon), and DU-145 (prostate) cancer cells at a low micromolar level. Moreover, compound 16a showed HDAC6-selectivity 20-fold over HDAC1.     

Design,synthesis and preliminary bioactivity studies of 1,2-dihydrobenzo[d]isothiazol-3-one-1,1-dioxide hydroxamic acid derivatives as novel histone deacetylase inhibitors

Histone deacetylase (HDAC) is a clinically validated target for antitumor therapy. In order to increase HDAC inhibition and efficiency, we developed a novel series of saccharin hydroxamic acids as potent HDAC inhibitors. Among them, compounds 11e, 11m, 11p exhibited similar or better HDACs inhibitory activity compared with the approved drug SAHA. Further biological evaluation indicated that compound 11m had potent antiproliferative activities against MDA-MB-231 and PC-3.     

Inhibition of histone deacetylase activity is a novel function of the antifolate drug methotrexate

Methotrexate (MTX) is a dihydrofolate reductase (DHFR) inhibitor widely used for treating human cancers, and overexpression of histone deacetylase (HDAC) is usually found in tumors. HDAC inhibitors (HDACi) can reactivate tumor suppressor genes and serve as potential anti-cancer drugs. In this study, we found that MTX shared structural similarity with some HDACi and molecular modeling showed that MTX indeed docks into the active site of HDLP, a bacterial homologue of HDAC. Subsequent in vitro assay demonstrated MTX’s inhibition on HDAC activity in human cancer cells. The global acetylation of histone H3 was also induced by MTX. Moreover, MTX inhibited immunoprecipitated HDAC1/2 activity but not their protein levels. This study provides evidence that MTX inhibits HDAC activity.     

组蛋白去乙酰化酶抑制剂诱导肿瘤细胞凋亡的机制

组蛋白去乙酰化酶抑制剂（HDACi）是一类新的化疗药物,能够有效抑制组蛋白去乙酰化酶的活性,促进组蛋白及非组蛋白的乙酰化修饰,在转录和翻译后修饰水平调控肿瘤靶蛋白及凋亡相关蛋白的表达和降解,活化凋亡信号通路,诱导肿瘤细胞凋亡。HDACi抑制抗氧化蛋白的表达,提高细胞内活性氧的水平,引起细胞的氧化损伤。因此,氧化损伤诱导的细胞凋亡也是HDACi杀伤肿瘤细胞的重要机制。HDACi诱导细胞凋亡机制的发现将进一步促进HDACi在临床治疗中的应用。     

Application of p21 and klf2 reporter gene assays to identify selective histone deacetylase inhibitors for cancer therapy

Novel 2-aminoanilide histone deacetylase (HDAC) inhibitors were designed to increase their contact with surface residues surrounding the HDAC active site compared to the contacts made by existing clinical 2-aminoanilides such as SNDX-275, MGCD0103, and Chidamide. Their HDAC selectivity was assessed using p21 and klf2 reporter gene assays in HeLa and A204 cells, respectively, which provide a cell-based readout for the inhibition of HDACs associated either with the p21 or klf2 promoter. A subset of the designed compounds selectively induced p21 over klf2 relative to the clinical reference compound SNDX-275. A representative lead compound from this subset had antiproliferative effects in cancer cells associated with induction of acetylated histone H4, endogenous p21, cell cycle arrest, and apoptosis. The p21- versus klf2-selective compounds described herein may provide a chemical starting point for developing clinically-differentiated HDAC inhibitors for cancer therapy.     

Design and synthesis of novel and highly-active pan-histone deacetylase (pan-HDAC) inhibitors

Histone deacetylase (HDAC) inhibitions are known to elicit anticancer effects. We designed and synthesized several HDAC inhibitors. Among these compounds, compound 40 exhibited a more than 10-fold stronger inhibitory activity compared with that of suberoylanilide hydroxamic acid (SAHA) against each human HDAC isozyme in vitro (IC₅₀ values of 40: HDAC1, 0.0038 μM; HDAC2, 0.0082 μM; HDAC3, 0.015 μM; HDAC8, 0.0060 μM; HDAC4, 0.058 μM; HDAC9, 0.0052 μM; HDAC6, 0.058 μM). The dose of the administered HDAC inhibitors that contain hydroxamic acid as the zinc-binding group may be reduced by 40. Because the carbostyril subunit is a time-tested structural component of drugs and biologically active compounds, 40 most likely exhibits good absorption, distribution, metabolism, excretion, and toxicity (ADMET). Thus, compound 40 is expected to be a promising therapeutic agent or chemical tool for the investigation of life process.     

Novel alkoxyamide-based histone deacetylase inhibitors reverse cisplatin resistance in chemoresistant cancer cells

Although histone deacetylase inhibitors (HDACi) have shown promising antitumor effects in specific types of blood cancer, their effects on solid tumors are limited. Previously, we developed LMK235 (5), a class I and class IIb preferential HDACi with chemosensitizing effects on breast cancer, ovarian cancer and HNSCC. Based on its promising effects on solid tumor cells, we modified the cap group of 5 to improve its anticancer activity. The tri- and dimethoxy-phenyl substituted compounds 13a and 13d turned out to be the most potent HDAC inhibitors of this study. The isoform profiling revealed a dual HDAC2/HDAC6 inhibition profile, which was confirmed by the acetylation of α-tubulin and histone H3 in Cal27 and Cal27CisR. In combination with cisplatin, both compounds enhanced the cisplatin-induced cytotoxicity via caspase-3/7 activation. The effect was more pronounced in the cisplatin resistant subline Cal27CisR. The pretreatment with 13d resulted in a complete resensitisation of Cal27CisR with IC₅₀ values in the range of the parental cell line. Therefore, 13d may serve as an epigenetic tool to analyze and modulate the cisplatin resistance of solid tumors.     

Histone deacetylase inhibitors: Potential in cancer therapy

The role of histone deacetylases (HDAC) and the potential of these enzymes as therapeutic targets for cancer, neurodegenerative diseases and a number of other disorders is an area of rapidly expanding investigation. There are 18 HDACs in humans. These enzymes are not redundant in function. Eleven of the HDACs are zinc dependent, classified on the basis of homology to yeast HDACs: Class I includes HDACs 1, 2, 3, and 8; Class IIA includes HDACs 4, 5, 7, and 9; Class IIB, HDACs 6 and 10; and Class IV, HDAC 11. Class III HDACs, sirtuins 1–7, have an absolute requirement for NAD⁺, are not zinc dependent and generally not inhibited by compounds that inhibit zinc dependent deacetylases. In addition to histones, HDACs have many nonhistone protein substrates which have a role in regulation of gene expression, cell proliferation, cell migration, cell death, and angiogenesis. HDAC inhibitors (HDACi) have been discovered of different chemical structure. HDACi cause accumulation of acetylated forms of proteins which can alter their structure and function. HDACi can induce different phenotypes in various transformed cells, including growth arrest, apoptosis, reactive oxygen species facilitated cell death and mitotic cell death. Normal cells are relatively resistant to HDACi induced cell death. Several HDACi are in various stages of development, including clinical trials as monotherapy and in combination with other anti‐cancer drugs and radiation. The first HDACi approved by the FDA for cancer therapy is suberoylanilide hydroxamic acid (SAHA, vorinostat, Zolinza), approved for treatment of cutaneous T‐cell lymphoma. J. Cell. Biochem. 107: 600–608, 2009. © 2009 Wiley‐Liss, Inc.     

Synthesis and biological evaluation of 2-quinolineacrylamides

A series of C6-substituted N-hydroxy-2-quinolineacrylamides (3–15), with four types of bridging groups have been synthesized. Most of these compounds exhibit antiproliferative activity against A549 and HCT116 cells and Western blot analysis revealed that they are able to inhibit HDAC. Measurement of the HDAC isoform activity of ether-containing compounds showed that compound 9 has distinct HDAC6 selectivity, more than 300-fold over other isoforms. This paper describes the development of 6-aryloxy-N-hydroxy-2-quinolineacrylamides as potential HDAC6 inhibitors.     

Fluorescent analogs of peptoid-based HDAC inhibitors: Synthesis,biological activity and cellular uptake kinetics

Fluorescent tagging of bioactive molecules is a powerful tool to study cellular uptake kinetics and is considered as an attractive alternative to radioligands. In this study, we developed fluorescent histone deacetylase (HDAC) inhibitors and investigated their biological activity and cellular uptake kinetics. Our approach was to introduce a dansyl group as a fluorophore in the solvent-exposed cap region of the HDAC inhibitor pharmacophore model. Three novel fluorescent HDAC inhibitors were synthesized utilizing efficient submonomer protocols followed by the introduction of a hydroxamic acid or 2-aminoanilide moiety as zinc-binding group. All compounds were tested for their inhibition of selected HDAC isoforms, and docking studies were subsequently performed to rationalize the observed selectivity profiles. All HDAC inhibitors were further screened in proliferation assays in the esophageal adenocarcinoma cell lines OE33 and OE19. Compound 2, 6-((N-(2-(benzylamino)-2-oxoethyl)-5-(dimethylamino)naphthalene)-1-sulfonamido)-N-hydroxyhexanamide, displayed the highest HDAC inhibitory capacity as well as the strongest anti-proliferative activity. Fluorescence microscopy studies revealed that compound 2 showed the fastest uptake kinetic and reached the highest absolute fluorescence intensity of all compounds. Hence, the rapid and increased cellular uptake of 2 might contribute to its potent anti-proliferative properties.     

Discovery of a series of hydroximic acid derivatives as potent histone deacetylase inhibitors

Abstract

To develop potent histone deacetylase inhibitors as antitumor agents, structural modification was performed. The synthesized molecules were tested by enzymatic inhibition assay and anti-proliferation assay. Several molecules show improved activities in the enzymatic inhibition assay. However, in the MTT assays, all these derived molecules have limited performance compared with SAHA. The IC50 values of molecule ((S)-N-(6-(hydroxyamino)-6-oxohexyl)-4-(3-(2-oxo-1-phenyl-2-((3-(trifluoromethyl)phenyl)amino)ethyl)ureido)benzamide, L8) which has the best enzymatic inhibition activity (with an IC50 value of 11.7?nm and 967?nm against Hela nucleus extract and HDAC8, respectively) were calculated compared with SAHA. Molecular docking was performed to predict the binding mode of molecule L8 in the active site of HDAC2 and HDAC8. Hydrophobic interaction, chelate binding, electrostatic attraction and H-bond interaction in combination make contribution to the ligand–receptor interactions.     

Downregulation of HDAC2 and HDAC3 via oleuropein as a potent prevention and therapeutic agent in MCF-7 breast cancer cells

Breast cancer is the most common malignancy in the world with the highest rate of morbidity and mortality. Due to the several side effects of chemotherapy and radiotherapy, recent studies have focused on the use of herbal medicines. Epidemiological reports have shown the inverse relationship between breast cancer risk and intake of olive. Oleuropein (OLE) is a polyphenolic compound in virgin olive oil with antineoplastic properties and it is well tolerated by humans. Recent reports have shown that OLE has effects on the control of cancer by modulating epigenetics, such as histone deacetylase (HDAC) inhibition. However, the epigenetic mechanisms of OLE anticancer properties are yet to be properly investigated. Therefore, this study aimed to determine the therapeutic effects of OLE through the modulation of histone deacetylase 2 (HDAC2) and histone deacetylase 3 (HDAC3) expression in breast cancer cell line. MCF-7 cells were tested with and without OLE, and also the cell viability, apoptosis, and migration were examined. HDAC2 and HDAC3 expression genes were assessed by quantitative real-time polymerase chain reaction. It was found that OLE decreased the expression of both HDAC2 and HDAC3 (P < 0.05), induced apoptosis and retarded cell migration and cell invasion in a dose-dependent manner (P < 0.05). These results showed that OLE is a potential therapeutic and preventive agent for breast cancer.     

The discovery and optimization of novel dual inhibitors of topoisomerase ii and histone deacetylase

A novel class of podophyllotoxin derivatives have been designed and synthesized based on the synergistic antitumor effects of topoisomerase II and histone deacetylase inhibitors. Their inhibitory activities towards histone deacetylases and Topo II and their cytotoxicities in cancer cell lines were evaluated. The aromatic capping group connection, linker length and zinc-binding group were systematically varied and preliminary conclusions regarding structure–activity relationships are discussed. Among all of the synthesized hybrid compounds, compound 24d showed the most potent HDAC inhibitory activity at a low nanomolar level and exhibited powerful antiproliferative activity towards HCT116 colon carcinoma cells at a low micromolar level. Further exploration of this series led to the discovery of potent dual inhibitor 32, which exhibited the strongest in vitro cytotoxic activity.     

Histone deacetylase inhibitors with a primary amide zinc binding group display antitumor activity in xenograft model

Histone deacetylase (HDAC) inhibition causes hyperacetylation of histones leading to differentiation, growth arrest and apoptosis of malignant cells, representing a new strategy in cancer therapy. Many of the known HDAC inhibitors (HDACi) that are in clinical trials possess a hydroxamic acid, that is a strong Zn²⁺ binding group, thereby inhibiting some of the class I and class II isoforms. Herein we describe the identification of a selective class I HDAC inhibitor bearing a primary carboxamide moiety as zinc binding group. This HDACi displays good antiproliferative activity against multiple cancer cell lines, and demonstrates efficacy in a xenograft model comparable to vorinostat.     

组蛋白去乙酰化酶4与人类疾病

组蛋白去乙酰化酶4（histone deacetylase 4,HDAC4）是一类依赖锌的去乙酰化酶,属于Ⅱ类组蛋白去乙酰化酶（histone deacetylases,HDACs）,主要具有去乙酰化酶的活性。HDAC4由去乙酰化酶结构域发挥去乙酰化酶的作用,还具有核定位序列和核输出序列,通过转录后与翻译后水平的修饰可在细胞核和细胞质之间穿梭,进而参与多种调节过程。近年来的研究发现,HDAC4可参与基因的转录调控、细胞凋亡、代谢等诸多生物进程,在多种疾病的发生发展中发挥重要作用。本文主要从HDAC4的结构、去乙酰作用、自身的修饰及其在核浆中的穿梭作用对其进行概述,同时对其在骨关节炎、心血管疾病、肌萎缩性侧索硬化症等不同疾病中的作用、相关的分子机制及组蛋白抑制剂在肿瘤中的应用等方面的研究进展进行综述。     

Design and synthesis of novel histone deacetylase inhibitor derived from nuclear localization signal peptide

We describe herein the synthesis and characterization of a new class of histone deacetylase (HDAC) inhibitors derived from conjugation of a suberoylanilide hydroxamic acid-like aliphatic-hydroxamate pharmacophore to a nuclear localization signal peptide. We found that these conjugates inhibited the histone deacetylase activities of HDACs 1, 2, 6, and 8 in a manner similar to suberoylanilide hydroxamic acid (SAHA). Notably, compound 7b showed a threefold improvement in HDAC 1/2 inhibition, a threefold increase in HDAC 6 selectivity and a twofold increase in HDAC 8 selectivity when compared to SAHA.     

Utilization of tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidinone as a cap moiety in design of novel histone deacetylase inhibitors

A series of novel 5,6,7,8-Tetrahydro[1]benzothieno[2,3-d]pyrimidin-4(3H)-one derivatives bearing a hydroxamic acid, 2-aminoanilide and hydrazide moieties as zinc-binding group (ZBG) were designed, synthesized and evaluated for the HDAC inhibition activity and antiproliferative activity. Most of the tested compounds displayed strong to moderate HDAC inhibitory activity. Some of these compounds showed potent anti-proliferative activity against human HepG2, MCF-7 and HCT-116 cell lines. In particular, compounds IVa, IVb, IXa and IXb exhibited significant anti-proliferative activity against the three cell lines tested compared to SAHA as a reference. Compound IVb is equipotent inhibitor for HDAC1 and HDAC2 as SAHA. It is evident that the presence of free hydroxamic acid group is essential for Zn binding affinity with maximal activity with a linker of aliphatic 6 carbons. Docking study results revealed that compound IVb could occupy the HDAC2 binding site and had the potential to exhibit antitumor activity through HDAC inhibition, which merits further investigation.