Human DNA Topoisomerase Research Articles

Design and synthesis of 3,5-substituted 1,2,4-oxadiazoles as catalytic inhibitors of human DNA topoisomerase IIα.

Cancer constitutes a group of diseases linked to abnormal cell growth that can potentially spread to other parts of the body and is one of the most common causes of death. The molecular motors - DNA topoisomerases - that enable topological changes of the DNA molecule are one of the most established targets of cancer therapies. Due to known limitations of established topo II poisons such as cardiotoxicity, induction of secondary malignancies and recognized cancer cell resistance, an emerging group of catalytic topo II inhibitors attempts to circumvent these challenges. Currently, this approach comprises several subgroups of mechanistically diverse inhibitors, one of which are compounds that act by binding to their ATPase domain. In this study we have designed, synthesized and characterized a new series of 3,5-substituted 1,2,4-oxadiazoles that act as catalytic inhibitors of human topo IIα. The introduction of the substituted rigid substitutions on the oxadiazole backbone was intended to enhance the interactions with the ATP binding site. In the inhibition assays selected compounds revealed a new class of catalytic inhibitors targeting this molecular motor and showed binding to the isolated topo IIα ATPase domain. The predicted inhibitor binding geometries were evaluated in molecular dynamics simulations and subsequently dynophore models were derived, which provided a deeper insight into molecular recognition with its macromolecular target. Selected compounds also displayed in vitro cytotoxicity on the investigated MCF-7 cancer cell line and did not induce double-strand breaks (DSB), thus displaying a mechanism of action diverse from the topo II poisons also on the cellular level. The substituted oxadiazoles thus comprise a chemical class of interesting compounds that are synthetically fully amenable for further optimization to anticancer drugs.

Molecular Docking Based Analysis to Elucidate the DNA Topoisomerase IIβ as the Potential Target for the Ganoderic Acid; A Natural Therapeutic Agent in Cancer Therapy.

Intermediate covalent complex of DNA-Topoisomerase II enzyme is the most promising target of the anticancer drugs to induce apoptosis in cancer cells. Currently, anticancer drug and chemotherapy are facing major challenges i.e., drug resistance, chemical instability and, dose-limiting side effect. Therefore, in this study, natural therapeutic agents (series of Ganoderic acids) were used for the molecular docking simulation against Human DNATopoisomerase II beta complex (PDB ID:3QX3). Molecular docking studies were performed on a 50 series of ganoderic acids reported in the NCBI-PubChem database and FDA approved anti-cancer drugs, to find out binding energy, an interacting residue at the active site of Human DNA-Topoisomerase II beta and compare with the molecular arrangements of the interacting residue of etoposide with the Human DNA topoisomerase II beta. The autodock 4.2 was used for the molecular docking and pharmacokinetic and toxicity studies were performed for the analysis of physicochemical properties and to check the toxicity effects. Discovery studio software was used for the visualization and analysis of docked pose. Ganoderic acids (GS-1, A and DM) were found to be a more suitable competitor inhibitor among the ganoderic acid series with appropriate binding energy, pharmacokinetic profile and no toxicity effects. The interacting residue (Met782, DC-8, DC-11 and DA-12) shared a chemical resemblance with the interacting residue of etoposide present at the active site of human topoisomerase II beta receptor.

Benzoxazines as new human topoisomerase I inhibitors and potential poisons.

The numbers of topoisomerase I targeted drugs on the market are very limited although they are used clinically for treatment of solid tumors. Hence, studies about finding new chemical structures which specifically target topoisomerase I are still remarkable. In this present study, we tested previously synthesized 3,4-dihydro-2H-1,4-benzoxazin-3-one derivatives to reveal their human DNA topoisomerase I inhibitory potentials. We investigated inhibitory activities of 3,4-dihydro-2H-1,4-benzoxazin-3-one derivatives on human topoisomerase I by relaxation assay to clarify inhibition mechanisms of effective derivatives with EMSA and T4 DNA ligase based intercalation assay. With SAR study, it was tried to find out effective groups in the ring system. While 10 compounds showed catalytic inhibitory activity, 8 compounds were found to be potential topoisomerase poisons. 4 of them also exhibited both activities. 2-hydroxy-3,4-dihydro-2H-1,4-benzoxazin-3-one (BONC-001) was the most effective catalytic inhibitor (IC50:8.34mM) and ethyl 6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-acetate (BONC-013) was the strongest potential poison (IC50:0.0006mM). BONC-013 was much more poisonous than camptothecin (IC50:0.034mM). Intercalation assay showed that BONC-013 was not an intercalator and BONC-001 most probably prevented enzyme-substrate binding in an unknown way. Another important result of this study was that OH group instead of ethoxycarbonylmethyl group at R position of benzoxazine ring was important for hTopo I catalytic inhibition while the attachment of a methyl group of R1 position at R2 position were play a role for increasing of its poisonous effect. As a result, we presented new DNA topoisomerase I inhibitors which might serve novel constructs for future anticancer agent designs. Graphical abstract.

Structural modification of ellipticine derivatives with alkyl groups of varying length is influential on their effects on human DNA topoisomerase II: a combined experimental and computational study

The compounds reducing tumor cell viability and disrupting DNA topoisomerase reactions have been widely used in anticancer drug development. Ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole) is a potent intercalating agent that interferes with nucleic acid processing through interaction with DNA topoisomerase II. Although ellipticine is a well-characterized compound, it is not a widely-accepted drug due to the adverse effects detected upon administration. We have previously reported two novel ellipticine derivatives, N-methyl-5-demethyl ellipticine (ET-1) and 2-methyl-N-methyl-5-demethyl ellipticinium iodide (ET-2) as potent compounds targeting DNA topoisomerase II. This study covers an extended synthesis, characterization, and activity data for five new salts of N-methyl 5-demetyl ellipticine (Z-1, Z-2, Z-4, Z-5 and Z-6) having several organic halides and their effects on human topoisomerase II enzymes. Moreover, combined in silico studies were conducted for better understanding of modes of action of studied molecules at the binding pocket of target. Our results showed that three of the derivatives (Z-1, Z-2, and Z-6) have considerable effect on the catalytic activity of human topoisomerase II implying the influence of alkyl groups added to the parental structure of ellipticine.

Anticancer, antimicrobial activities of quinoline based hydrazone analogues: Synthesis, characterization and molecular docking.

Based on the biologically active heterocycle quinoline, a series (18a-p) of quinoline hydrazone analogues were prepared, starting from 6-bromo/6-chloro-2-methyl-quinolin-4-yl-hydrazines. For all the newly synthesized compounds cytotoxic activities were carried out at the National Cancer Institute (NCI), USA, against full NCI 60 human cancer cell lines. Amongst all the tested compounds, nine compounds (18b, 18d, 18e, 18f, 18g, 18h, 18i, 18j, 18l) exhibited important anti-proliferative activity at 10 µM concentration and were further screened at 10-fold dilutions of five different concentrations (0.01, 0.1, 1, 10 and 100 µM) with GI50 values ranging from 0.33 to 4.87 µM and LC50 values ranging from 4.67 µM to >100j µM. Further, the mean values of GI50, TGI and LC50 of the most potent compound 18j were compared with the clinically used anticancer agents bendamustine and chlorambucil, revealed that the quinolyl hydrazones holds promise as a potential anticancer agents. Further all the newly prepared compounds were screened for their antimicrobial activity. All the quinolyl hydrazones displayed good to excellent antimicrobial activity with MIC values ranging from 6.25 to 100 µg/mL against the tested pathogenic strains. Molecular docking of the synthesized compounds into the active binding site of human DNA topoisomerase I (htopoI) was carried out to predict the binding mode to the DNA topoisomerase I inhibitors. Hopefully in future, compounds based on quinoline core could be used as a lead compounds for designing new anticancer agents.

Kinetic Study of DNA Topoisomerases by Supercoiling-Dependent Fluorescence Quenching.

DNA topoisomerases are essential enzymes for all living organisms and important targets for anticancer drugs and antibiotics. Although DNA topoisomerases have been studied extensively, steady-state kinetics has not been systematically investigated because of the lack of an appropriate assay. Previously, we demonstrated that newly synthesized, fluorescently labeled plasmids pAB1_FL905 and pAB1_FL924 can be used to study DNA topoisomerase-catalyzed reactions by fluorescence resonance energy transfer (FRET) or supercoiling-dependent fluorescence quenching (SDFQ). With the FRET or SDFQ method, we performed steady-state kinetic studies for six different DNA topoisomerases including two type IA enzymes (Escherichia coli and Mycobacterium smegmatis DNA topoisomerase I), two type IB enzymes (human and variola DNA topoisomerase I), and two type IIA enzymes (E. coli DNA gyrase and human DNA topoisomerase IIα). Our results show that all DNA topoisomerases follow the classical Michaelis–Menten kinetics and have unique steady-state kinetic parameters, KM, Vmax, and kcat. We found that kcat for all topoisomerases are rather low and that such low values may stem from the tight binding of topoisomerases to DNA. Additionally, we confirmed that novobiocin is a competitive inhibitor for adenosine 5′-triphosphate binding to E. coli DNA gyrase, demonstrating the utility of our assay for studying topoisomerase inhibitors.

Dual Inhibitors of Human DNA Topoisomerase II and Other Cancer-Related Targets.

Human DNA topoisomerase II is an important target in anticancer therapy. Despite the clinical success of drugs that target topoisomerase II, the development of resistant cancer cells can limit their clinical efficacy. To maximize the therapeutic potential of anticancer drugs, combination therapies and multitarget drugs have been suggested in many studies, where the use of multitarget drugs is advantageous from a pharmacokinetic point of view. There are various different options for the preparation of dual-target or multiple-target inhibitors, as topoisomerase II is both structurally (e.g., topoisomerase I, Hsp90, and kinases) and functionally (e.g., histone deacetylases and proteasome) connected to many validated anticancer targets. In this Perspective, we discuss the scientific background behind targeting topoisomerase II together with a number of other targets important in cancer therapy, review the present status, and discuss further options in the field.

Synthesis, in vitro cytotoxicity activity against the human cervix carcinoma cell line and in silico computational predictions of new 4-arylamino-3-nitrocoumarin analogues

A new series of 4-arylamino-3-nitrocoumarin analogues (4–18) have been synthesized and characterized by sophisticated spectroscopic techniques (1H NMR, 13C NMR) and mass spectrometry. All the new synthesized compounds were evaluated for their in vitro cytotoxic activity against the human cervix carcinoma cell line (KB-3-1) using resazurin assay with (+)-griseofulvin as the positive control (IC50 = 19 μM). Among them, thiazolidinylidene derivative 17a that bearing malononitrile unit displayed the best cytotoxic potency with IC50 value of 21 μM. Also, in silico docking simulation studies were conducted on human DNA topoisomerase 1 (Top1) (PDB: 1T8I) to explore and interpret the interaction pattern between the selected compounds and target enzyme as well confirm the acquired cytotoxicity results. In addition to the above, in silico predictions of physicochemical properties, ADME (absorption, distribution, metabolism and excretion) parameters, oral toxicity and indication of toxicity targets were implemented for some title compounds.

The influence of variations of furanosesquiterpenoids content of commercial samples of myrrh on their biological properties

Myrrh is an oleo-gum-resin produced in the stem of Commiphora myrrha (Burseraceae) and used for centuries for different medicinal purposes. The present work was designed to evaluate the cytotoxic and antioxidant properties of seventeen myrrh samples (S1–S17) obtained from different retail markets of Saudi Arabia and Yemen regions, along with two furanosesquiterpenoids (CM-1 and CM-2). The cytotoxicity assay was carried out on HepG2, MCF-7 and HUVEC cell lines. S2, S5, S10, S12, CM-1, CM-2 exhibited significant cytotoxicity against HepG2/MCF-7 cell lines [IC50 (μg/mL): 13.8/10, 14/10, 14.5/11.3, 18/13.2, 9.5/12.5, 10/15.8, respectively) compare to vinblastin (IC50 (μg/mL): 2/2.5) whereas the remaining samples were found as mild active or inactive. The antioxidant properties of the samples were tested by β-carotene-bleaching and DPPH free radical scavenging methods where the samples S8 (1000 μg/mL) exhibited the highest β-carotene bleaching (76.2%) and free radical scavenging activity (79.8%). The HPTLC analysis was performed on NP-HPTLC plate using toluene, chloroform and glacial acetic acid as mobile phase in ratio of 7:2.9:0.1 (V/V/V). The validated HPTLC method furnished sharp, intense and compact peaks of CM-1 and CM-2 at Rf = 0.39 and 0.44, respectively. The highest/lowest content of CM-1 and CM-2 were found in S12/S5 and S5/S17, respectively. The molecular docking studies of CM-1 and CM-2 with human DNA topoisomerase IIα have shown that both the compounds were bound the active sites of the respective enzymes. Molecular dynamics simulation studies further confirmed that the interactions of CM-1 and CM-2 with topoisomerase were stable in nature. This study will help us in selection of appropriate myrrh sample for the greater benefits of the population in the Middle East region.

Acalypha wilkesiana flowers: Phenolic profiling, cytotoxic activity of their biosynthesized silver nanoparticles and molecular docking study for its constituents as Topoisomerase-I inhibitors

The bio potential behavior of green silver nanoparticles (AgNPs) using Acalypha wilkesiana flowers extract weas evaluated. The AgNPs formed were confirmed using surface plasmon resonance band showed in UV–vis spectrophotometer that characterized with spherical shape in size range from 5 to 45 nm depending on Transmission electron microscopy (TEM) and with good stability (−50.75 mV) depending on Zeta-potential measurements. In order to identify the capping agents responsible for the reduction of silver ion and the stabilization of nanoparticles prepared, Fourier transform-infrared spectroscopy (FTIR) and HPLC-ESI-MS analysis were used. Our AgNPs exhibited cytotoxic activity against MCF-7 (Breast carcinoma), PC-3 (Prostate carcinoma) and BJ-1 (skin normal human) cell lines with IC50 values 4.00, 3.6 and 4.1 μg/mL, respectively (i.e. the higher selectivity of AgNPs toward prostate than breast cancer cell lines was observed). These highly cytotoxic activity may be back to the presence of the bi-apigenin derivatives; amentoflavone and Cupressuflavone that displayed unique binding docking score towards the active site of human DNA topoisomerase enzyme. The present study is a distinctive application for the biosynthesis of silver nanoparticles in a fast, simple, easy, eco-friendly, inexpensive and effective way.

Towards anticancer fluoroquinolones: A review article.

Different studies about the anticancer potential of several medically used antibacterial fluoroquinolones have been established. Fluoroquinolone derivatives, like some anti-cancer drugs, such as doxorubicin, can achieve antitumor activity via poisoning of type II human DNA topoisomerases. Interestingly, structural features required for the anticancer activity of quinolones have been determined. Most of the chemical modifications required to convert antibacterially acting fluoroquinolones into their anticancer analogs were at position 7 and the carboxylic group at position 3. This review highlights the antitumor potential of fluoroquinolones in general and summarizes the chemical modifications carried out on fluoroquinolones to become anticancer agents. Moreover, the review gives a quick recap on metal ion chelates with fluoroquinolones and their substantial role in topoisomerase poisoning and antitumor potential improvement. Hence, it should be highly interesting for researchers attempting to design and synthesize novel anticancer fluoroquinolone candidates.

Carboxylate-functionalized foldamer inhibitors of HIV-1 integrase and Topoisomerase 1: artificial analogues of DNA mimic proteins.

Inspired by DNA mimic proteins, we have introduced aromatic foldamers bearing phosphonate groups as synthetic mimics of the charge surface of B-DNA and competitive inhibitors of some therapeutically relevant DNA-binding enzymes: the human DNA Topoisomerase 1 (Top1) and the human HIV-1 integrase (HIV-1 IN). We now report on variants of these anionic foldamers bearing carboxylates instead of phosphonates. Several new monomers have been synthesized with protecting groups suitable for solid phase synthesis (SPS). Six hexadecaamides have been prepared using SPS. Proof of their resemblance to B-DNA was brought by the first crystal structure of one of these DNA-mimic foldamers in its polyanionic form. While some of the foldamers were found to be as active as, or even more active than, the original phosphonate oligomers, others had no activity at all or could even stimulate enzyme activity in vitro. Some foldamers were found to have differential inhibitory effects on the two enzymes. These results demonstrate a strong dependence of inhibitory activity on foldamer structure and charge distribution. They open broad avenues for the development of new classes of derivatives that could inhibit the interaction of specific proteins with their DNA target thereby influencing the cellular pathways in which they are involved.

Structure-guided optimization of 4,6-substituted-1,3,5-triazin-2(1H)-ones as catalytic inhibitors of human DNA topoisomerase IIα

Human DNA topoisomerases represent one of the key targets of modern chemotherapy. An emerging group of catalytic inhibitors of human DNA topoisomerase IIα comprises a new paradigm directed to circumvent the known limitations of topoisomerase II poisons such as cardiotoxicity and induction of secondary tumors. In our previous studies, 4,6-substituted-1,3,5-triazin-2(1H)-ones were discovered as catalytic inhibitors of topo IIα. Here, we report the results of our efforts to optimize several properties of the initial chemical series that did not exhibit cytotoxicity on cancer cell lines. Using an optimized synthetic route, a focused chemical library was designed aimed at further functionalizing substituents at the position 4 of the 1,3,5-triazin-2(1H)-one scaffold to enable additional interactions with the topo IIα ATP binding site. After virtual screening, selected 36 analogues were synthesized and experimentally evaluated for human topo IIα inhibition. The optimized series displayed improved inhibition of topo IIα over the initial series and the catalytic mode of inhibition was confirmed for the selected active compounds. The optimized series also showed cytotoxicity against HepG2 and MCF-7 cell lines and did not induce double-strand breaks, thus displaying a mechanism of action that differs from the topo II poisons on the cellular level. The new series represents a new step in the development of the 4,6-substituted-1,3,5-triazin-2(1H)-one class towards novel efficient anticancer therapies utilizing the catalytic topo IIα inhibition paradigm.

Synthesis and Biological Evaluation of 4β-N-Acetylamino Substituted Podophyllotoxin Derivatives as Novel Anticancer Agents.

A series of novel podophyllotoxin derivatives obtained by 4β-N-acetylamino substitution at C-4 position was designed, synthesized, and evaluated for in vitro cytotoxicity against four human cancer cell lines (EC-9706, HeLA, T-24 and H460) and a normal human epidermal cell line (HaCaT). The cytotoxicity test indicated that most of the derivatives displayed potent anticancer activities. In particular, compound 12h showed high activity with IC50 values ranging from 1.2 to 22.8 μM, with much better cytotoxic activity than the control drug etoposide (IC50: 8.4 to 78.2 μM). Compound 12j exhibited a promising cytotoxicity and selectivity profile against T24 and HaCaT cell lines with IC50 values of 2.7 and 49.1 μM, respectively. Compound 12g displayed potent cytotoxicity against HeLA and T24 cells with low activity against HaCaT cells. According to the results of fluorescence-activated cell sorting (FACS) analysis, 12g induced cell cycle arrest in the G2/M phase accompanied by apoptosis in T24 and HeLA cells. Furthermore, the docking studies showed possible interactions between human DNA topoisomerase IIα and 12g. These results suggest that 12g merits further optimization and development as a new podophyllotoxin-derived lead compound.

Examining the Impact of Antimicrobial Fluoroquinolones on Human DNA Topoisomerase IIα and IIβ

Fluoroquinolones are a class of widely prescribed antibiotics with a broad range of activity against Gram-positive, Gram-negative, and some atypical microbes. Unfortunately, these drugs are associated with significant adverse events including neuropathy, tendinopathy, cardiac rhythm abnormalities, and mental health side effects. The mechanism by which fluoroquinolones cause many of these toxicities is unknown. The antibacterial mechanism of action involves disruption of the catalytic mechanism of type-II topoisomerases in bacteria, namely topoisomerase IV and DNA gyrase. Fluoroquinolones inhibit the ability of the enzymes to ligate cleaved DNA and result in single- and double-stranded DNA breaks. Thus, there is an interest in investigating whether human topoisomerase II is involved in mediating the adverse events associated with quinolones. Previous studies demonstrate some response of human topoisomerase IIα and IIβ to high levels of ciprofloxacin. However, it is not clear whether the concentration of ciprofloxacin utilized in those studies corresponds to concentrations that would be routinely achievable in patients. Therefore, this study set out to examine three clinically relevant fluoroquinolones along with two older agents to determine whether these compounds display activity against topoisomerase IIα and IIβ at drug concentrations that more closely approximate typical patient plasma values. On the basis of our evidence, none of the quinolones studied were able to poison DNA cleavage by either human enzyme. Ciprofloxacin, desethylene-ciprofloxacin, and the recently removed from market gemifloxacin were able to inhibit topoisomerase II-mediated DNA relaxation at concentrations of 200–300 μM. On the basis of these data, we propose that human topoisomerase II is not likely to be the main cause of these adverse events and that additional targets need to be identified to clarify the mechanisms underlying quinolone toxicities.

Evaluation of DNA/BSA Binding and Chemical Nuclease Activity of L-Tyrosine-Based Mn(III) and Fe(III) Metallo-Intercalators

A novel class of Mn(III) and Fe(III) complexes of L-tyrosine-based ligand has been synthesized and characterized through various analytical and spectroscopic techniques. These complexes were found to exhibit efficient binding properties with the biomolecules viz. calf thymus DNA and BSA. The ability of complexes to bind with such biomolecules has been explored through absorption, emission and viscosity measurements. Based on spectroscopic techniques we can conclude that the complexes could bind to DNA via intercalation. It was observed that these complexes can cleave pBR322 DNA in gel-electrophoresis technique through oxidative mechanism. The BSA was quenched by the complexes around 340 nm adopting a mechanism of static mode. The binding constants, thermodynamic parameters and the donor to acceptor distance were calculated. Besides, molecular docking simulations were carried out for the complexes with human DNA topoisomerase and BSA protein. The docked poses are visualized to provide supportive evidence to the interaction of the synthesized complexes with DNA/BSA.

Antitumor Effect of Pomolic Acid in Acute Myeloid Leukemia Cells Involves Cell Death, Decreased Cell Growth and Topoisomerases Inhibition.

Acute myeloid leukemia (AML) represents the largest number of annual deaths from hematologic malignancy. In the United States, it was estimated that 21.380 individuals would be diagnosed with AML and 49.5% of patients would die in 2017. Therefore, the search for novel compounds capable of increasing the overall survival rate to the treatment of AML cells is urgent. To investigate the cytotoxicity effect of the natural compound pomolic acid (PA) and to explore the mechanism of action of PA in AML cell lines with different phenotypes. Three different AML cell lines, HL60, U937 and Kasumi-1 cells with different mechanisms of resistance were used to analyze the effect of PA on the cell cycle progression, on DNA intercalation and on human DNA topoisomerases (hTopo I and IIα) in vitro studies. Theoretical experiments of the inhibition of hTopo I and IIα were done to explore the binding modes of PA. PA reduced cell viability, induced cell death, increased sub-G0/G1 accumulation and activated caspases pathway in all cell lines, altered the cell cycle distribution and inhibited the catalytic activity of both human DNA topoisomerases. Finally, this study showed that PA has powerful antitumor activity against AML cells, suggesting that this natural compound might be a potent antineoplastic agent to improve the treatment scheme of this neoplasm.

The human DNA topoisomerase I mutant Gly717Asp: Higher religation rate is not always associated with camptothecin resistance

DNA topoisomerases are key enzyme responsible for modulating the topological state of the DNA by breaking and rejoining of DNA strand. Characterization of a Gly717Asp mutation in the human topoisomerase was performed using several catalytic assays. The mutant enzyme was shown to have comparable cleavage and fast religation rate as compared to the wild-type protein. Addition of the anticancer drug camptothecin significantly reduced the religation step. The simulative approaches and analysis of the cleavage/religation equilibrium indicate that the mutation is able to modify the architecture of the drug binding site, increasing the persistence of the drug for the enzyme–DNA covalent complex. Taken together these results indicate that the structure modification of the drug binding site is the key reason for the increasing CPT persistence and furthermore provide the possibility for new anti-cancer drug discovery.

Synthesis, human topoisomerase IIα inhibitory properties and molecular modeling studies of anti-proliferative curcumin mimics.

3,5-Bis(arylidene)-N-substituted-4-oxo-piperidine-1-carboxamides 24–51 were synthesized as curcumin mimics in a facile pathway through reaction of 3,5-bis(arylidene)-4-piperidones with the appropriate isocyanate in the presence of triethylamine. The 3E,5E′-stereochemical configuration was conclusively supported by single crystal X-ray studies of compounds 25 and 34. Most of the synthesized piperidinecarboxamides showed high anti-proliferative properties with potency higher than that of 5-fluorouracil (clinically approved drug against colon, breast and skin cancers) through in vitro MTT bio-assay. Some of them revealed anti-proliferative properties at sub-micromolar values (IC50 = 0.56–0.70 μM for compounds 29, 30 and 34–38 against HCT116; and IC50 = 0.64 μM for compound 30 against A431 cell lines) with promising inhibitory properties against human DNA topoisomerase IIα. The safe profile of the anti-proliferative active agents against the RPE1 normal cell line may prove their selectivity towards carcinoma cells. Robust molecular models (2D-QSAR, 3D-pharmacophore) supported the SAR and validated the observed bio-properties.

The synthesis and anticancer activities of chiral epoxy-substituted chromone analogs

Human DNA topoisomerases (topos) have been recognized as a good target molecule for the development of anticancer drugs because they play an important role in solving DNA topological problems caused by DNA strand separation during replication and transcription. In this study, we designed and synthesized 11 novel chromone backbone compounds possessing epoxy and halohydrin substituents with chirality. In the topos inhibition test, compounds 2, 9, 10, and 11 showed comparable topo I inhibitory activity at concentration of 100 μM compared to camptothecin, and all of the synthesized compounds showed moderate topo IIα inhibitory activity. Among them, compounds 9, 10 and 11 were more potent than the others in both topo I and IIα inhibitory activity. Compound 11 showed the most potent cell antiproliferative activity against all tested cancer cell lines with particularly strong inhibition (an IC50 of 0.04 µM) of K562 myelogenous leukemia cancer cell proliferation. In the brief structure-activity relationship analysis, there was no clear correlation between stereochemistry and topos inhibitory and cytotoxic activity. 5(R),7(S)-bisepoxy-substituted compound 11 was the most potent DNA cross-linker and induced G2/M arrest in a cell cycle assay in a dose- and time-dependent manner. After the treatment time period induced apoptosis in K562 cells without increasing G2/M-phase cells. Overall, compound 11 showed good consistent inhibitory biological activity related to cancer cell proliferation.