Inhibition of human DNA topoisomerase IIα by two novel ellipticine derivatives

Bioactivities and Action Mechanisms of Ellipticine Derivatives Reported Prior to 2023

Currently, natural products are one of the priceless options for finding novel chemical pharmaceutical entities. Ellipticine is a naturally occurring alkaloid isolated from the leaves of Ochrosia elliptica Labill. Ellipticine and its derivatives are characterized by multiple biological activities. The purpose of this review was to provide a critical and systematic assessment of ellipticine and its derivatives as bioactive molecules over the last 60 years. Publications focused mainly on the total synthesis of alkaloids of this type without any evaluation of bioactivity have been excluded. We have reviewed papers dealing with the synthesis, bioactivity evaluation and mechanism of action of ellipticine and its derivatives. It was found that ellipticine and its derivatives showed cytotoxicity, antimicrobial ability, and anti-inflammatory activity, among which cytotoxicity toward cancer cell lines was the most investigated aspect. The inhibition of DNA topoisomerase II was the most relevant mechanism for cytotoxicity. The PI3K/AKT pathway, p53 pathway, and MAPK pathway were also closely related to the antiproliferative ability of these compounds. In addition, the structure-activity relationship was deduced, and future prospects were outlined. We are confident that these findings will lay a scientific foundation for ellipticine-based drug development, especially for anticancer agents.

Synthesis and evaluation of 7-(3-aminopropyloxy)-substituted flavone analogue as a topoisomerase IIα catalytic inhibitor and its sensitizing effect to enzalutamide in castration-resistant prostate cancer cells

Prostate cancer patients primarily receive androgen receptor (AR)-targeted drugs as a primary treatment option because prostate cancer is associated with highly activated AR signaling. AR amplification made prostate cancer cells viable under treatment of AR-targeted therapy, leading to castration resistance. AR amplification was more common in enzalutamide-resistant patients. As a strategy to overcome castration resistance and to improve the efficacy of enzalutamide, second-generation nonsteroidal antiandrogen drugs for castration-resistant prostate cancer (CRPC) including topoisomerase II (topo II) poisons such as etoposide and mitoxantrone, have been administered in combination with enzalutamide. In the present study, it was confirmed that amplification of topo IIα, but not I and IIβ, was directly and proportionally associated with poor clinical outcome of Prostate cancer. Among a novel series of newly designed and synthesized 7-(3-aminopropyloxy)-substituted flavone analogues, compound 6, the most potent derivative, was further characterized and identified as a topo IIα catalytic inhibitor that intercalates into DNA and binds to the DNA minor groove with better efficacy and less genotoxicity than etoposide, a topo II poison. Compound 6 showed remarkable efficacy in inhibiting AR-negative CRPC cell growth and sensitizing activity to enzalutamide in AR-positive CRPC cells, thus confirming the potential of topo IIα catalytic inhibitor to overcome resistance to androgen deprivation therapy.

The Chemotherapeutic Potentials of Compounds Isolated from the Plant, Marine, Fungus, and Microorganism: Their Mechanism of Action and Prospects

Research on natural products mainly focuses on developing a suitable drug to treat human disease. There has been a sharp increase in the development of drugs from natural products. Most of the drugs that are available are from the terrestrial origin. Marine natural products are less explored. Oceans are considered as a vast ecosystem with a wide variety of living organisms and natural products that are unexplored. Large numbers of antitumor drugs are from natural sources such as plants, marine, and microorganisms. 80% new chemical entities that were launched over the past 60 decades were from a natural source. In this article, the anticancer potential from the natural source such as plants, fungi, microorganisms, marine, and endophytes has been reviewed. Emphasis is given on the compound from the marine, plant, and of bacterial origin. Finally, we consider the future and how we might achieve better sustainability to alleviate human cancer suffering while having fewer side effects, more efficacies, and causing less harm than the present treatments.

Acridine Based N-Acylhydrazone Derivatives as Potential Anticancer Agents: Synthesis, Characterization and ctDNA/HSA Spectroscopic Binding Properties

A series of novel acridine N-acylhydrazone derivatives have been synthesized as potential topoisomerase I/II inhibitors, and their binding (calf thymus DNA—ctDNA and human serum albumin—HSA) and biological activities as potential anticancer agents on proliferation of A549 and CCD-18Co have been evaluated. The acridine-DNA complex 3b (-F) displayed the highest Kb value (Kb = 3.18 × 103 M−1). The HSA-derivatives interactions were studied by fluorescence quenching spectra. This method was used for the calculation of characteristic binding parameters. In the presence of warfarin, the binding constant values were found to decrease (KSV = 2.26 M−1, Kb = 2.54 M−1), suggesting that derivative 3a could bind to HSA at Sudlow site I. The effect of tested derivatives on metabolic activity of A549 cells evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide or MTT assay decreased as follows 3b(-F) > 3a(-H) > 3c(-Cl) > 3d(-Br). The derivatives 3c and 3d in vitro act as potential dual inhibitors of hTopo I and II with a partial effect on the metabolic activity of cancer cells A594. The acridine-benzohydrazides 3a and 3c reduced the clonogenic ability of A549 cells by 72% or 74%, respectively. The general results of the study suggest that the novel compounds show potential for future development as anticancer agents.

Platinum Complexes as Inhibitors of DNA Repair Protein Ku70 and Topoisomerase IIα in Cancer Cells

Ku70 protein and topoisomerase IIα (Topo IIα) are promising targets of anticancer drugs, which play critical roles in DNA repair and replication processes. Three platinum(II) complexes, [PtCl(NH3)2(9-(pyridin-2-ylmethyl)-9H-carbazole)]NO3 (OPPC), [PtCl(NH3)2(9-(pyridin-3-ylmethyl)-9H-carbazole)]NO3 (MPPC),...

DNA topoisomerases as molecular targets for anticancer drugs

The significant role of topoisomerases in the control of DNA chain topology has been confirmed in numerous research conducted worldwide. The prevalence of these enzymes, as well as the key importance of topoisomerase in the proper functioning of cells, have made them the target of many scientific studies conducted all over the world. This article is a comprehensive review of knowledge about topoisomerases and their inhibitors collected over the years. Studies on the structure-activity relationship and molecular docking are one of the key elements driving drug development. In addition to information on molecular targets, this article contains details on the structure-activity relationship of described classes of compounds. Moreover, the work also includes details about the structure of the compounds that drive the mode of action of topoisomerase inhibitors. Finally, selected topoisomerases inhibitors at the stage of clinical trials and their potential application in the chemotherapy of various cancers are described.

Repurposing Ellipticine Hydrochloride to Combat Colistin-Resistant Extraintestinal Pathogenic E. coli (ExPEC)

Extraintestinal pathogenic Escherichia coli (ExPEC) strains are the cause of a majority of human extraintestinal infections globally, resulting in enormous direct economic and medical costs. The plasmid-mediated, colistin-resistant gene mcr-1 has broken through the ultimate defense line against MDR Gram-negative pathogens. There is an urgent need to discover the new compound intended for colistin-resistant E. coli. In this study, antibacterial targets of ellipticine hydrochloride (EH) were confirmed by localized surface plasmon resonance (LSPR) and decatenation assay. The LSPR analysis exhibited good binding between EH and E. coli topoisomerase IV. In this study, a synergistic effect is obvious in the combination of EH and colistin, to which eight of ten strains showed synergy, while two isolates (20%) showed no difference. The bacteria enumeration analysis of EH treatment group suggested that the decreased bacterial titer can be observed in various tissues of infected mice. EH treatment significantly decreased the levels of a variety of pro-inflammatory factors, such as TNF-α and IL-6. Moreover, other related lesions, such as inflammatory cell infiltration, alveolar interstitial congestion, and edema were observed to be relieved to different extents. This study reveals the anti-E. coli potential activities and molecular mechanism of EH and the therapeutical effectiveness of EH application to animals. It provides us with a new option for fighting against multidrug-resistant ExPEC infections in the future.

Selected ellipticine derivatives, known to target topoisomerase II, suppress the alternative lengthening of telomere (ALT) pathway in telomerase-negative cells

BACKGROUND

DNA topoisomerase and telomerase enzymes are popular targets of several anti-tumor drugs. Smooth proceeding of telomeric recombination requires Topoisomerase II (Top2), which is involved in telomere-telomere recombination through functioning in relaxation of positive supercoils among the cells adopting telomerase-independent Alternative lengthening of telomere (ALT) pathway. Most of the inhibitors reported so far have been designed to targetsolely telomerase-positive cells, which can potentially lead to therapeutic failure because tumor cells treated with telomerase inhibitors can activate the ALT pathway for telomere maintenance. Knowing that ALT cells are more sensitive against a Top2 inhibitor, ICRF-93 agent, compared to telomerase-positive cells, we analyzed two selected ellipticine derivatives that we recently reported as TopII-targeting compounds, to assess their effects on the formation of DNA breaks and suppression of ALT pathway.

METHODS

Cell viability, Comet, C-Circle assays, dot blot, immunofluorescence staining, and telomere fluorescence in situ hybridization (FISH) staining were used for determining the effect of the compounds on ALT status of tumor cells.

RESULTS AND CONCLUSIONS

Treatment of ALT cells with ellipticine derivatives resulted in the formation of DNA breaks and suppression of ALT-associated phenotypes in vitro. Our results will contribute to the development of therapeutic strategies combining telomerase and ALT pathway inhibitors.

Modeling the Antileukemia Activity of Ellipticine-Related Compounds: QSAR and Molecular Docking Study

The antileukemia cancer activity of organic compounds analogous to ellipticine representes a critical endpoint in the understanding of this dramatic disease. A molecular modeling simulation on a dataset of 23 compounds, all of which comply with Lipinski's rules and have a structure analogous to ellipticine, was performed using the quantitative structure activity relationship (QSAR) technique, followed by a detailed docking study on three different proteins significantly involved in this disease (PDB IDs: SYK, PI3K and BTK). As a result, a model with only four descriptors (HOMO, softness, AC1RABAMBID, and TS1KFABMID) was found to be robust enough for prediction of the antileukemia activity of the compounds studied in this work, with an R² of 0.899 and Q² of 0.730. A favorable interaction between the compounds and their target proteins was found in all cases; in particular, compounds 9 and 22 showed high activity and binding free energy values of around -10 kcal/mol. Theses compounds were evaluated in detail based on their molecular structure, and some modifications are suggested herein to enhance their biological activity. In particular, compounds 22_1, 22_2, 9_1, and 9_2 are indicated as possible new, potent ellipticine derivatives to be synthesized and biologically tested.

Synthetic Optimization of Ellipticine and Antitumor Activity of Novel Hexacyclic Derivatives of Ellipticine

Background:

For decades, a great deal of research work has been done to synthesize ellipticine and its derivatives because of their potential antitumor properties and anti-HIV activities. However, the resonance structures in different media, a low level of solubility at physiological pH and systemic toxicity have prevented the use of ellipticine as a therapeutic agent. Besides, the low yield and complex steps of ellipticine synthesis limit its application.

Methods:

A high-yield synthetic procedure of ellipticine has been optimized, and the total yield was up to 50% without silica gel column chromatography. Novel hexacyclic ellipticine derivatives were synthesized by coupling ellipticine with o-aminobenzoic acid. Their cytotoxicities against HCT116, MGC803, HT29 and MCF-7 tumor cells were evaluated.

Results:

The synthesis process of ellipticine was optimized, and the total yield of the synthetic route was increased to 50% through several operation steps optimization. Fourteen ellipticine hexacyclic derivatives were synthesized. The synthetic compounds were screened for anti-tumor activity in vivo and in vitro, and some of the derivatives had good anti-tumor activity.

Conclusion:

Compared with ellipticine, the compound 1l showed higher antitumor activity and better tolerance to tumor models. The compound 1l treatment increased the percentage of late apoptotic cells from 3.1% (DMSO) to 21.6% (20.0 μM) in NCI-H460 cells. It also was observed the effect of 1l on G2 phase arrest was similar as that of ellipticine. The mechanism of action indicated compound 1l could be a topoisomerase IIα poison. These studies provided the basis for the pharmacodynamics and toxicology of ellipticine, and further clarifies the structureactivity relationship of antitumor activity of ellipticine.

D-Ring-Modified Analogues of Luotonin A with Reduced Planarity: Design, Synthesis, and Evaluation of Their Topoisomerase Inhibition-Associated Cytotoxicity

A- and D-ring-modified luotonin-inspired heterocycles have been synthesized and were evaluated for their activity against the viability of four cancer cell lines in vitro, namely, MCF7, HCT116, JURKAT, and NCI-H460. The analysis of results indicated that two of the synthesized derivatives displayed good inhibition against the growth of the human colon cancer HCT116 cell line, with potencies lower than but in the same order of magnitude as camptothecin (CPT). These two luotonin analogues also showed an activity similar to that of the highly potent alkaloid CPT as inhibitors of topoisomerase I and also inhibited topoisomerase II. These results show that complete planarity is not a strict requirement for topoisomerase inhibition by luotonin-related compounds, paving the way to the design of analogues with improved solubility.

Smoothed Potential MD Simulations for Dissociation Kinetics of Etoposide To Unravel Isoform Specificity in Targeting Human Topoisomerase II

Human type II topoisomerases (TopoII) are essential for controlling DNA topology within the cell. For this reason, there are a number of TopoII-targeted anticancer drugs that act by inducing DNA cleavage mediated by both TopoII isoforms (TopoIIα and TopoIIβ) in cells. However, recent studies suggest that specific poisoning of TopoIIα may be a safer strategy for treating cancer. This is because poisoning of TopoIIβ appears to be linked to the generation of secondary leukemia in patients. We recently reported that enzyme-mediated DNA cleavage complexes (in which TopoII is covalently linked to the cleaved DNA during catalysis) formed in the presence of the anticancer drug etoposide persisted approximately 3-fold longer with TopoIIα than TopoIIβ. Notably, enhanced drug-target residence time may reduce the adverse effects of specific TopoIIα poisons. However, it is still not clear how to design drugs that are specific for the α isoform. In this study, we report the results of classical molecular dynamics (MD) simulations to comparatively analyze the molecular interactions formed within the TopoII/DNA/etoposide complex with both isoforms. We also used smoothed potential MD to estimate etoposide dissociation kinetics from the two isoform complexes. These extensive classical and enhanced sampling simulations revealed stabilizing interactions of etoposide with two serine residues (Ser763 and Ser800) in TopoIIα. These interactions are missing in TopoIIβ, where both amino acids are alanine residues. This may explain the greater persistence of etoposide-stabilized cleavage complexes formed with Topo TopoIIα. These findings could be useful for the rational design of specific TopoIIα poisons.

Application of hepatic cytochrome b5/P450 reductase null (HBRN) mice to study the role of cytochrome b5 in the cytochrome P450-mediated bioactivation of the anticancer drug ellipticine

The anticancer drug ellipticine exerts its genotoxic effects after metabolic activation by cytochrome P450 (CYP) enzymes. The present study has examined the role of cytochrome P450 oxidoreductase (POR) and cytochrome b5 (Cyb5), electron donors to P450 enzymes, in the CYP-mediated metabolism and disposition of ellipticine in vivo. We used Hepatic Reductase Null (HRN) and Hepatic Cytochrome b5/P450 Reductase Null (HBRN) mice. HRN mice have POR deleted specifically in hepatocytes; HBRN mice also have Cyb5 deleted in the liver. Mice were treated once with 10 mg/kg body weight ellipticine (n = 4/group) for 24 h. Ellipticine-DNA adduct levels measured by 32P-postlabelling were significantly lower in HRN and HBRN livers than in wild-type (WT) livers; however no significant difference was observed between HRN and HBRN livers. Ellipticine-DNA adduct formation in WT, HRN and HBRN livers correlated with Cyp1a and Cyp3a enzyme activities measured in hepatic microsomes in the presence of NADPH confirming the importance of P450 enzymes in the bioactivation of ellipticine in vivo. Hepatic microsomal fractions were also utilised in incubations with ellipticine and DNA in the presence of NADPH, cofactor for POR, and NADH, cofactor for Cyb5 reductase (Cyb5R), to examine ellipticine-DNA adduct formation. With NADPH adduct formation decreased as electron donors were lost which correlated with the formation of the reactive metabolites 12- and 13-hydroxy-ellipticine in hepatic microsomes. No difference in adduct formation was observed in the presence of NADH. Our study demonstrates that Cyb5 contributes to the P450-mediated bioactivation of ellipticine in vitro, but not in vivo.

N-thioalkylcarbazoles derivatives as new anti-proliferative agents: synthesis, characterisation and molecular mechanism evaluation

Synthetic or natural carbazole derivatives constitute an interesting class of heterocycles, which showed several pharmaceutical properties and occupied a promising place as antitumour tools in preclinical studies. They target several cellular key-points, e.g. DNA and Topoisomerases I and II. The most studied representative, i.e. Ellipticine, was introduced in the treatment of metastatic breast cancer. However, because of the onset of dramatic side effects, its use was almost dismissed. Many efforts were made in order to design and synthesise new carbazole derivatives with good activity and reduced side effects. The major goal of the present study was to synthesise a series of new N-thioalkylcarbazole derivatives with anti-proliferative effects. Two compounds, 5a and 5c, possess an interesting anti-proliferative activity against breast and uterine cancer cell lines without affecting non-tumoural cell lines viability. The most active compound (5c) induces cancer cells death triggering the intrinsic apoptotic pathway by inhibition of Topoisomerase II.

Inhibition of Human Topoisomerase II by N,N,N-Trimethylethanammonium Iodide Alkylcarbazole Derivatives

Chemotherapy is used for the treatment of all stages of breast cancer, including the metastatic stage of the disease. Treatment regimens are generally tailored for each patient's particular situation. However, chemotherapeutic agents are the leading cause of serious drug-related adverse effects; moreover, drug resistance often occurs. In this study, we designed and synthesized a new series of N-alkylcarbazoles derived from ellipticine, an alkaloid with a carbazole skeleton initially used in the treatment of metastatic breast cancer and later dismissed because of poor aqueous solubility and severe side effects. After evaluating the binding modes of our class of newly synthesized compounds with human topoisomerase II (hTopo II), we performed hTopo II decatenation assays, identifying compound 4 f (2-(4-((3-chloro-9H-carbazol-9-yl)pentyl)piperazin-1-yl)-N,N,N-trimethylethanammonium iodide) as a good inhibitor. Moreover, 4 f and 4 g (2-(4-((3-chloro-9H-carbazol-9-yl)hexyl)piperazin-1-yl)-N,N,N-trimethylethanammonium iodide) showed a good anti-proliferative activity toward breast cancer cells, causing apoptosis by activation of the caspase pathway. Interestingly, the activity of these two compounds on triple-negative MDA-MB-231 cells, which tend to be highly metastatic and aggressive, is strictly connected to the observed inhibition of hTopo II.

Increasing the distance between two monomers of topoisomerase IIβ under the action of antitumor agent 4β-sulfur-(benzimidazole) 4'-demethylepipodophyllotoxin

Topoisomerases II (Top2s) are a group of essential enzymes involved in replication, transcription, chromosome condensation, and segregation via altering DNA topology. The mechanism of the Top2s poisons such as etoposide (VP-16) was reported as stabilizing the Top2-DNA complex and engendering permanent DNA breakage. As the structurally similar compound of VP-16, a novel 4β-sulfur-substituted 4′-demethylepipodophyllotoxin (DMEP) derivative (compound C-Bi) with superior antitumor activity was developed in our previous study. To understand the structural basis of the compound action, the crystal structure (2.54 Å) of human Top2 β-isoform (hTop2β) cleavage complexes stabilized by compound C-Bi was determined. However, compound C-Bi was not visible in the crystal structure. Through the comparison of the structures of hTop2β-DNA-etoposide ternary complex and hTop2β-DNA binary complex, it could be observed that the distance between drug-binding sites Arg503 of the two monomers was 26.62 Å in hTop2β-DNA-etoposide ternary complex and 34.54 Å in hTop2β-DNA binary complex, respectively. Significant twist were observed in the DNA chains of binary complex. It suggested that compound C-Bi played antitumor roles through increasing spacing of hTop2β monomers. The changes in hTop2β structure further caused double changes in the torsional direction and migration distance of the DNA chains, resulting in impeding religation of DNA.

Molecular modeling of cationic porphyrin-anthraquinone hybrids as DNA topoisomerase IIβ inhibitors

Human DNA Topoisomerase II has been regarded as a promising target in anticancer drug discovery. In the present study, we designed six porphyrin-anthraquinone hybrids bearing pyrazole or pyridine group as meso substituents and evaluated their potentials as DNA Topoisomerase IIβ inhibitor. First, we investigated the binding orientation of porphyrin hybrids into DNA topoisomerase IIβ employing AutoDock 4.2 and then performed 20-ns molecular dynamics simulations to see the dynamic stability of each porphyrin-Topo IIβ complex using Amber 14. We found that the binding of porphyrin hybrids occured through intercalation and groove binding mode in addition interaction with the amino acid residues constituting the active cavity of Topo IIβ. Each porphyrin-Topo IIβ complex was stabilized during 20-ns dynamics simulations. The MM-PBSA free energy calculation shows that the binding affinities of porphyrin hybrids were modified with the number of meso substituent. Interestingly, the affinity of all porphyrin hybrids to Topo IIβ was stronger than that of native ligand (EVP), indicating the potential of the designed porphyrin to be considered in experimental research.

Over-expression of Topoisomerase II Enhances Salt Stress Tolerance in Tobacco

Topoisomerases are unique enzymes having an ability to remove or add DNA supercoils and untangle the snarled DNA. They can cut, shuffle, and religate DNA strands and remove the torsional stress during DNA replication, transcription or recombination events. In the present study, we over-expressed topoisomerase II (TopoII) in tobacco (Nicotiana tabaccum) and examined its role in growth and development as well as salt (NaCl) stress tolerance. Several putative transgenic plants were generated and the transgene integration and expression was confirmed by PCR and Southern blot analyses, and RT-PCR analysis respectively. Percent seed germination, shoot growth, and chlorophyll content revealed that transgenic lines over-expressing the NtTopoIIα-1 gene exhibited enhanced tolerance to salt (150 and 200 mM NaCl) stress. Moreover, over-expression of TopoII lead to the elevation in proline and glycine betaine levels in response to both concentrations of NaCl as compared to wild-type. In response to NaCl stress, TopoII over-expressing lines showed reduced lipid peroxidation derived malondialdehyde (MDA) generation. These results suggest that TopoII plays a pivotal role in salt stress tolerance in plants.