Bifunctional conjugates with potent inhibitory activity towards cyclooxygenase and histone deacetylase

A potent dual inhibitor targeting COX-2 and HDAC of acute myeloid leukemia cells

Acute myeloid leukemia (AML) is an aggressive cancer with complex issues of drug resistance and a poor prognosis; thus, effective therapeutics is urgently needed for AML. In this study, we designed and synthesized dual cyclooxygenase-2 (COX-2) and histone deacetylase (HDAC) inhibitors, IMC-HA and IMC-OPD, and applied them for the treatment of AML. IMC-HA comprised a COX-2 inhibitor skeleton of indomethacin (IMC) and an HDAC inhibitor moiety of the hydroxamic group and was found to exhibit potent antiproliferative activity against AML cells (THP-1 and U937) and low cytotoxicity toward normal cells. Molecular docking simulations suggested that IMC-HA had a high binding affinity for HDAC and COX-2, with binding energies of -6.8 and -9.0 kcal/mol, respectively. Mechanistic studies revealed that IMC-HA induced apoptosis and G0/G1 phase arrest in AML cells, which were characterized by alterations in the expression of apoptotic and cell cycle-related proteins. Further study demonstrated that IMC-HA also inhibited the MEK/ERK signaling pathway in AML cells. Overall, we believe that IMC-HA could serve as a potent COX-2/HDAC dual inhibitor and improve the treatment of AML.

Design, synthesis and antitumor activity evaluation of novel IMPDH II and HDAC1 dual inhibitor

The development of multi-target inhibitors has garnered considerable attention in the field of cancer therapy. We have designed and synthesized a total of 80 derivatives, categorized into A, B, and C series. Among these compounds, C12 (hIMPDH II, IC50 = 84.69 ± 0.83 nM; HDAC1, IC50 = 81.75 ± 0.82 nM) and C18 (hIMPDH II, IC50 = 820.50 ± 1.41 nM; HDAC1, IC50 = 131.90 ± 1.02 nM) exhibited promising inhibitory activity against hIMPDH II and HDAC1. Compared to the IMPDH-positive compound MPA (IC50 = 403.23 ± 2.92 nM) and the HDAC-positive compound SAHA (IC50 = 1165.72 ± 1.22 nM), compound C12 (IC50 value of 305.31 ± 0.67 nM) demonstrated superior anti-proliferative activity against K-562 cells in vitro. Compound C12 exhibited good liver microsomal stability with a moderate half-life (T 1/2). Furthermore, compound C12 exhibited acceptable in vivo pharmacokinetics of properties. In conclusion, compound C12 represents a potential new dual inhibitor targeting both hIMPDH II and HDAC1.

Carborane-Based Analogs of Celecoxib and Flurbiprofen, their COX Inhibition Potential, and COX Selectivity Index

The cylcooxygenase isoforms COX-1 and COX-2 are involved in the production of prostaglandins in physiological and pathological processes. The overexpression of COX-2 under inflammatory conditions, its role in cancer and neurodegenerative diseases necessitates the need to develop and improve nonsteroidal anti-inflammatory drugs. These mainly unselective COX inhibitors, e.g. aspirin, are used to reduce the symptoms of inflammation. To reduce unwanted side effects connected with unselective inhibition, the development of novel COX-2 selective inhibitors is a major goal. Herein, the synthesis, characterization and in vitro biological evaluation of eight flurbiprofen- and celecoxib-based carborane analogs are described. Carboranes as hydrophobic surrogates are suitable substituents that can contribute to a selectivity increase toward COX-2 due to size exclusion. The inhibitory efficacy for COX-1 and COX-2 of the four ortho- and four nido-carborane derivatives has been tested. The nido compounds are much more potent than their closo-carborane analogs. The celecoxib-based nido-carborane compound 10 shows an IC50(COX-2) value in the sub-μM range and slight selectivity for COX-2. This is in contrast to its ortho-carborane counterpart 9, which shows an inhibition preference for COX-1. While none of these carborane derivatives outperforms their organic analogs, the flurbiprofen-based nido-carborane derivatives 14a and 14b surpass the known carborane-based flurbiprofen analogs.

A review of progress in o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities for cancer therapy

Histone deacetylases, as a new class of anticancer targets, could maintain homeostasis by catalyzing histone deacetylation and play important roles in regulating the expression of target genes. Due to the fact that simultaneous intervention with dual tumor related targets could improve treatment effects, researches on innovative design of dual-target drugs are underway. HDAC is known as a "sensitizer" for the synergistic effects with other anticancer-target drugs because of its flexible structure design. The synergistic effects of HDAC inhibitor and other target inhibitors usually show enhanced inhibitory effects on tumor cells, and also provide new strategies to overcome multidrug resistance. Many research groups have reported that simultaneously inhibiting HDAC and other targets, such as tubulin, EGFR, could enhance the therapeutic effects. The o-aminobenzamide group is often used as a ZBG group in the design of HDAC inhibitors with potent antitumor effects. Given the prolonged inhibitory effects and reduced toxic side effects of HDAC inhibitors using o-aminobenzamide as the ZBG group, the o-aminobenzamide group is expected to become a more promising alternative to hydroxamic acid. In fact, o-aminobenzamide-based dual inhibitors of HDAC with different chemical structures have been extensively prepared and reported with synergistic and enhanced anti-tumor effects. In this work, we first time reviewed the rational design, molecular docking, inhibitory activities and potential application of o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities in cancer therapy, which might provide a reference for developing new and more effective anticancer drugs.

Solid-Phase Parallel Synthesis of Dual Histone Deacetylase-Cyclooxygenase Inhibitors

Multi-target drugs (MTDs) are emerging alternatives to combination therapies. Since both histone deacetylases (HDACs) and cyclooxygenase-2 (COX-2) are known to be overexpressed in several cancer types, we herein report the design, synthesis, and biological evaluation of a library of dual HDAC-COX inhibitors. The designed compounds were synthesized via an efficient parallel synthesis approach using preloaded solid-phase resins. Biological in vitro assays demonstrated that several of the synthesized compounds possess pronounced inhibitory activities against HDAC and COX isoforms. The membrane permeability and inhibition of cellular HDAC activity of selected compounds were confirmed by whole-cell HDAC inhibition assays and immunoblot experiments. The most promising dual inhibitors, C3 and C4, evoked antiproliferative effects in the low micromolar concentration range and caused a significant increase in apoptotic cells. In contrast to previous reports, the simultaneous inhibition of HDAC and COX activity by dual HDAC-COX inhibitors or combination treatments with vorinostat and celecoxib did not result in additive or synergistic anticancer activities.

Apigeninidin-rich Sorghum bicolor (L. Moench) extracts suppress A549 cells proliferation and ameliorate toxicity of aflatoxin B1-mediated liver and kidney derangement in rats

Sorghum bicolor plant has a high abundance of 3-deoxyanthocyanins, flavonoids and other polyphenol compounds that have been shown to offer numerous health benefits. Epidemiological studies have linked increased intake of S. bicolor to reduced risk of certain cancer types, including lung adenocarcinoma. S. bicolor extracts have shown beneficial effects in managing hepatorenal injuries. This study investigated the cytotoxic potential of three apigeninidin-rich extracts of S. bicolor (SBE-05, SBE-06 and SBE-07) against selected cancer cell lines and their ameliorative effect on aflatoxin B₁ (AFB₁)-mediated hepatorenal derangements in rats. We observed that, among the three potent extracts, SBE-06 more potently and selectively suppressed the growth of lung adenocarcinoma cell line (A549) (IC₅₀ = 6.5 μg/mL). SBE-06 suppressed the expression of STAT3 but increased the expression of caspase 3. In addition, SBE-05, SBE-06 and SBE-07 inhibited oxidative and nitrosative stress, inflammation, and apoptosis and preserved the histoarchitectural networks of the liver and kidney of rats treated with AFB₁. These in vitro and in vivo studies indicate the potential of these cheap and readily accessible extracts for cancer therapy and as chemo-preventive agents in preventing aflatoxin-related health issues.

Fluoxetine-induced hepatic lipid accumulation is mediated by prostaglandin endoperoxide synthase 1 and is linked to elevated 15-deoxy-Δ12,14 PGJ2

Major depressive disorder and other neuropsychiatric disorders are often managed with long-term use of antidepressant medication. Fluoxetine, an SSRI antidepressant, is widely used as a first-line treatment for neuropsychiatric disorders. However, fluoxetine has also been shown to increase the risk of metabolic diseases such as non-alcoholic fatty liver disease. Fluoxetine has been shown to increase hepatic lipid accumulation in vivo and in vitro. In addition, fluoxetine has been shown to alter the production of prostaglandins which have also been implicated in the development of non-alcoholic fatty liver disease. The goal of this study was to assess the effect of fluoxetine exposure on the prostaglandin biosynthetic pathway and lipid accumulation in a hepatic cell line (H4-II-E-C3 cells). Fluoxetine treatment increased mRNA expression of prostaglandin biosynthetic enzymes (Ptgs1, Ptgs2, and Ptgds), PPAR gamma (Pparg), and PPAR gamma downstream targets involved in fatty acid uptake (Cd36, Fatp2, and Fatp5) as well as production of 15-deoxy-Δ^12,14 PGJ₂ a PPAR gamma ligand. The effects of fluoxetine to induce lipid accumulation were attenuated with a PTGS1 specific inhibitor (SC-560), whereas inhibition of PTGS2 had no effect. Moreover, SC-560 attenuated 15-deoxy-Δ^12,14 PGJ₂ production and expression of PPAR gamma downstream target genes. Taken together these results suggest that fluoxetine-induced lipid abnormalities appear to be mediated via PTGS1 and its downstream product 15d-PGJ₂ and suggest a novel therapeutic target to prevent some of the adverse effects of fluoxetine treatment.

Active constituents of Zanthoxylum nitidium from Yunnan Province against leukaemia cells in vitro

Zanthoxylum nitidium (Roxb.) DC (Rutaceae) is well known for inhibiting the proliferation of human gastric, liver, kidney and lung cancer cells, though research on its potential use in treating leukaemia is relatively rare. Twenty-six compounds were isolated from the chloroform and petroleum ether extracts of the roots and leaves of Z. nitidium (Zanthoxylum nitidium). They were ( +)-9′-O-transferuloyl-5, 5′-dimethoxylaricriresinol (1), 8-(3′-oxobut-1′-en-1′-yl)-5, 7-dimethoxy-coumarin (2), 5, 7, 8-trimethoxy-coumarin (3), 5-(3′, 3′-dimethyl-2′-butenyloxy)-7, 8-dimethoxy-coumarin (4), 2-(5-methoxy-2-methyl-1H-indol-3-yl) methyl acetate (5), 2′-(5, 6-dihydrochleletrythrine-6-yl) ethyl acetate (6), 6-acetonyldi-hydrochelerythrine (7), 6β-hydroxymethyldihydronitidine (8), bocconoline (9), zanthoxyline (10), O-methylzanthoxyline (11), rhoifoline B (12), N-nornitidine (13), nitidine (14), chelerythrine (15), 4-hydroxyl-7,8-dimethoxy-furoquinoline (16), dictamnine (17), γ-fagarine (18), skimmianine (19), robustine (20), R-( +)-platydesmine (21), 4-methoxyl-1-methyl-2-quinoline (22), 4-methoxy-2-quinolone (23), liriodenine (24), aurantiamide acetate (25), 10-O-demethyl-12-O-methylarnottianamide (26). Four among them, compounds 4 – 6 and 16, were first confirmed in this study by UV, IR, 1D, 2D NMR and HR-ESI–MS spectra. Compounds 1 – 2 and 11 were isolated from Z. nitidium for the first time. Of the assayed compounds, 1, 2, 9, 10, 14, 15 and 24, exhibited good inhibitory activities in the leukaemia cell line HEL, whereas compound 14 (IC₅₀: 3.59 µM) and compound 24 (IC₅₀: 15.95 µM) exhibited potent inhibitory activities. So, to further investigate the possible mechanisms, cell cycle and apoptosis assays were performed, which indicated that compound 14 causes obvious S-phase arrest in HEL cells and induced apoptosis, whereas compound 24 only induced apoptosis. The present results suggested both compounds 14 and 24 are promising potential anti-leukaemia drug candidates.

Discovery of novel STAT3 DNA binding domain inhibitors

Background: STAT3 is a pro-oncogenic transcription factor. Pyrimethamine (PYM) is a STAT3 inhibitor that suppresses the proliferation of some cancer cells through downregulation of STAT3 target proteins. Methodology & Results: We have used structure-based tools to design novel PYM-based compounds. Intracellular target validation studies revealed that representative compounds 11b-d and 15a downregulate STAT3 downstream proteins and inhibit STAT3 DNA binding domain (DBD). Relative to PYM, a cohort of these compounds are >100-fold more cytotoxic to cancer cells with constitutively active (high pSTAT3) and basal (low pSTAT3) STAT3 signaling, suggesting that STAT3 DBD inhibition is deleterious to the proliferation of cancer cells with low and high pSTAT3 levels. Conclusion: These are promising leads for further preclinical evaluation as therapeutic agents for STAT3-dependent cancers.

Phenanthrotriazine Derivatives Containing Arylidine Hydrazone Moieties as Novel Potential c-Met Inhibitors with Anticancer Effect

Cancer is the second cause of death in the world and the discovery of novel anticancer agents is of vital importance to provide better therapeutic options for cancer patients. In this study, a new series of 12 arylidene hydrazone phenanthrotriazine derivatives were designed, synthesized, and tested in-vitro for antiproliferative activity against three cancer cell lines including colorectal cancer (HT-29), breast cancer (MCF-7) and leukemia (MOLT-4) cells and also against Vero normal cells. The effect of derivatives on cell cycle and apoptosis induction were studied by flow cytometric propidium iodide/RNase assay and Hoechst 33258 staining, respectively, while docking analysis was used to investigate the interactions of synthesized derivatives with the c-Met receptor kinase domain. Some compounds showed considerable antiproliferative activity against tested cancer cells. The most potent derivative was 9k bearing pyrrole moiety with IC₅₀ values of 14.3, 4.7 and 1.7 µM against HT-29, MCF-7 and MOLT-4 cells, respectively, while it showed negligible activity against Vero normal cells (IC₅₀: 95.4 µM). Derivatives bearing 2-nitrophenyl (9g), 4-cyanophenyl (9j), pyrrole (9k), and thiophene (9l) moieties induced G0/G1 cell cycle arrest and also apoptosis at higher doses in MCF-7 cells. Docking study showed that the phenanthrotriazine backbone form H-bond interactions with Asn1209, while phenyl moieties of the pendants generate different hydrophobic interactions with the Asp1164 and Asp1231 residues of c-Met. In conclusion, phenanthrene 1,2,4-triazines, especially the ones with less influence on normal cells, may constitute promising compounds for the discovery of antiproliferative agents with potential c-Met inhibitory capacity.

Liver-Targeting Class I Selective Histone Deacetylase Inhibitors Potently Suppress Hepatocellular Tumor Growth as Standalone Agents

Dysfunctions in epigenetic regulation play critical roles in tumor development and progression. Histone deacetylases (HDACs) and histone acetyl transferase (HAT) are functionally opposing epigenetic regulators, which control the expression status of tumor suppressor genes. Upregulation of HDAC activities, which results in silencing of tumor suppressor genes and uncontrolled proliferation, predominates in malignant tumors. Inhibition of the deacetylase activity of HDACs is a clinically validated cancer therapy strategy. However, current HDAC inhibitors (HDACi) have elicited limited therapeutic benefit against solid tumors. Here, we disclosed a class of HDACi that are selective for sub-class I HDACs and preferentially accumulate within the normal liver tissue and orthotopically implanted liver tumors. We observed that these compounds possess exquisite on-target effects evidenced by their induction of dose-dependent histone H4 hyperacetylation without perturbation of tubulin acetylation status and G0/G1 cell cycle arrest. Representative compounds 2 and 3a are relatively non-toxic to mice and robustly suppressed tumor growths in an orthotopic model of HCC as standalone agents. Collectively, our results suggest that these compounds may have therapeutic advantage against HCC relative to the current systemic HDACi. This prospect merits further comprehensive preclinical investigations.

Paradigm shift of "classical" HDAC inhibitors to "hybrid" HDAC inhibitors in therapeutic interventions

'Epigenetic' regulation of genes via post-translational modulation of proteins is the current mainstay approach for the disease therapies, particularly explored in the Histone Deacetylase (HDAC) class of enzymes. Mainly sight saw in cancer chemotherapeutics, HDAC inhibitors have also found a promising role in other diseases (neurodegenerative disorders, cardiovascular diseases, and viral infections) and successfully entered in various combination therapies (pre-clinical/clinical stages). The prevalent flexibility in the structural design of HDAC inhibitors makes them easily tuneable to merge with other pharmacophore modules for generating multi-targeted single hybrids as a novel tactic to overcome drawbacks of polypharmacy. Herein, we reviewed the putative role of prevalent HDAC hybrids inhibitors in the current and prospective stage as a translational approach to overcome the limitations of the existing conventional drug candidates (parent molecule) when used either alone (drug resistance, solubility issues, adverse side effects, selectivity profile) or in combination (pharmacokinetic interactions, patient compliance) for treating various diseases.

Small Molecule Inhibitors Targeting Gαi2 Protein Attenuate Migration of Cancer Cells

Heterotrimeric G-proteins are ubiquitously expressed in several cancers, and they transduce signals from activated G-protein coupled receptors. These proteins have numerous biological functions, and they are becoming interesting target molecules in cancer therapy. Previously, we have shown that heterotrimeric G-protein subunit alphai2 (Gαi2) has an essential role in the migration and invasion of prostate cancer cells. Using a structure-based approach, we have synthesized optimized small molecule inhibitors that are able to prevent specifically the activation of the Gαi2 subunit, keeping the protein in its inactive GDP-bound state. We observed that two of the compounds (13 and 14) at 10 μΜ significantly inhibited the migratory behavior of the PC3 and DU145 prostate cancer cell lines. Additionally, compound 14 at 10 μΜ blocked the activation of Gαi2 in oxytocin-stimulated prostate cancer PC3 cells, and inhibited the migratory capability of DU145 cells overexpressing the constitutively active form of Gαi2, under basal and EGF-stimulated conditions. We also observed that the knockdown or inhibition of Gαi2 negatively regulated migration of renal and ovarian cancer cell lines. Our results suggest that small molecule inhibitors of Gαi2 have potential as leads for discovering novel anti-metastatic agents for attenuating the capability of cancer cells to spread and invade to distant sites.

Zinc Dependent Histone Deacetylase Inhibitors in Cancer Therapeutics: Recent Update

BACKGROUND

Histone deacetylases (HDAC) are an important class of enzymes that play a pivotal role in epigenetic regulation of gene expression that modifies the terminal of core histones leading to remodelling of chromatin topology and thereby controlling gene expression. HDAC inhibitors (HDACi) counter this action and can result in hyperacetylation of histones, thereby inducing an array of cellular consequences such as activation of apoptotic pathways, generation of reactive oxygen species (ROS), cell cycle arrest and autophagy. Hence, there is a growing interest in the potential clinical use of HDAC inhibitors as a new class of targeted cancer therapeutics. Methodology and Result: Several research articles spanning between 2016 and 2017 were reviewed in this article and presently offer critical insights into the important strategies such as structure-based rational drug design, multi-parameter lead optimization methodologies, relevant SAR studies and biology of various class of HDAC inhibitors, such as hydroxamic acids, benzamides, cyclic peptides, aliphatic acids, summarising the clinical trials and results of various combination drug therapy till date.

CONCLUSION

This review will provide a platform to the synthetic chemists and biologists to cater the needs of both molecular targeted therapy and combination drug therapy to design and synthesize safe and selective HDAC inhibitors in cancer therapeutics.

HDAC3 Activity is Essential for Human Leukemic Cell Growth and the Expression of β-catenin, MYC, and WT1

Therapy of acute myeloid leukemia (AML) is unsatisfactory. Histone deacetylase inhibitors (HDACi) are active against leukemic cells in vitro and in vivo. Clinical data suggest further testing of such epigenetic drugs and to identify mechanisms and markers for their efficacy. Primary and permanent AML cells were screened for viability, replication stress/DNA damage, and regrowth capacities after single exposures to the clinically used pan-HDACi panobinostat (LBH589), the class I HDACi entinostat/romidepsin (MS-275/FK228), the HDAC3 inhibitor RGFP966, the HDAC6 inhibitor marbostat-100, the non-steroidal anti-inflammatory drug (NSAID) indomethacin, and the replication stress inducer hydroxyurea (HU). Immunoblotting was used to test if HDACi modulate the leukemia-associated transcription factors β-catenin, Wilms tumor (WT1), and myelocytomatosis oncogene (MYC). RNAi was used to delineate how these factors interact. We show that LBH589, MS-275, FK228, RGFP966, and HU induce apoptosis, replication stress/DNA damage, and apoptotic fragmentation of β-catenin. Indomethacin destabilizes β-catenin and potentiates anti-proliferative effects of HDACi. HDACi attenuate WT1 and MYC caspase-dependently and -independently. Genetic experiments reveal a cross-regulation between MYC and WT1 and a regulation of β-catenin by WT1. In conclusion, reduced levels of β-catenin, MYC, and WT1 are molecular markers for the efficacy of HDACi. HDAC3 inhibition induces apoptosis and disrupts tumor-associated protein expression.

Classification of Cyclooxygenase-2 Inhibitors Using Support Vector Machine and Random Forest Methods

This work reports the classification study conducted on the biggest COX-2 inhibitor data set so far. Using 2925 diverse COX-2 inhibitors collected from 168 pieces of literature, we applied machine learning methods, support vector machine (SVM) and random forest (RF), to develop 12 classification models. The best SVM and RF models resulted in MCC values of 0.73 and 0.72, respectively. The 2925 COX-2 inhibitors were reduced to a data set of 1630 molecules by removing intermediately active inhibitors, and 12 new classification models were constructed, yielding MCC values above 0.72. The best MCC value of the external test set was predicted to be 0.68 by the RF model using ECFP_4 fingerprints. Moreover, the 2925 COX-2 inhibitors were clustered into eight subsets, and the structural features of each subset were investigated. We identified substructures important for activity including halogen, carboxyl, sulfonamide, and methanesulfonyl groups, as well as the aromatic nitrogen atoms. The models developed in this study could serve as useful tools for compound screening prior to lab tests.

Aza-BODIPY probe for selective visualization of cyclooxygenase-2 in cancer cells

AZB-IMC₂ was developed as a COX-2 specific probe that exhibited a brighter fluorescence signal in cancer cells that overexpress COX-2 compared to normal cells. Oxidative stress agent-treated inflamed cell lines inducing high COX-2 levels revealed an enhanced fluorescence signal. Inhibitory studies showed a markedly reduced fluorescence intensity in cancer cells. The results suggested that AZB-IMC₂ could be developed as a promising molecular tool for imaging guiding during surgery.

A bivalent indomethacin/Aza-BODIPY conjugate can selectively visualize the COX-2 enzyme in cancer and inflamed cells confirming its potential as a COX-2-specific biomarker in clinical applications.

Designing multi-targeted agents: An emerging anticancer drug discovery paradigm

The dominant paradigm in drug discovery is to design ligands with maximum selectivity to act on individual drug targets. With the target-based approach, many new chemical entities have been discovered, developed, and further approved as drugs. However, there are a large number of complex diseases such as cancer that cannot be effectively treated or cured only with one medicine to modulate the biological function of a single target. As simultaneous intervention of two (or multiple) cancer progression relevant targets has shown improved therapeutic efficacy, the innovation of multi-targeted drugs has become a promising and prevailing research topic and numerous multi-targeted anticancer agents are currently at various developmental stages. However, most multi-pharmacophore scaffolds are usually discovered by serendipity or screening, while rational design by combining existing pharmacophore scaffolds remains an enormous challenge. In this review, four types of multi-pharmacophore modes are discussed, and the examples from literature will be used to introduce attractive lead compounds with the capability of simultaneously interfering with different enzyme or signaling pathway of cancer progression, which will reveal the trends and insights to help the design of the next generation multi-targeted anticancer agents.