Topo IIα Research Articles

Human Topoisomerase IIα Promotes Chromatin Condensation Via a Phase Transition.

Topoisomerase II (topo II) enzymes are essential enzymes known to resolve topological entanglements during DNA processing. Curiously, while yeast expresses a single topo II, humans express two topo II isozymes, topo IIα and topo IIβ, which share a similar catalytic domain but differ in their intrinsically disordered C-terminal domains (CTDs). During mitosis, topo IIα and condensin I constitute the most abundant chromosome scaffolding proteins essential for chromosome condensation. However, how topo IIα enables this function is poorly understood. Here, we discovered a new and functionally distinct role for human topo IIα - it condenses DNA and chromatin at a low topo IIα concentration (100 pM or less) during a polymer-collapse phase transition. The removal of the topo IIα CTDs effectively abolishes its condensation ability, indicating that the condensation is mediated by the CTDs. Although topo IIβ can also perform condensation, it is about 4-fold less effective. During the condensation, topo IIα-DNA condensates form along DNA, working against a DNA tension of up to 1.5 pN, greater than that previously reported for yeast condensin. In addition, this condensation does not require ATP and thus is independent of topo IIα's catalytic activity. We also found that condensation and catalysis can concurrently proceed with minimal mutual interference. Our findings suggest topo IIα may directly participate in chromosome condensation during mitosis.

Unveiling the potential of germinated black bean extracts: Targeting topoisomerase IIα through in silico and in vitro approaches

This study investigates the potential of germinated black bean extracts (GBBE) to modulate the activity of topoisomerase IIα (topo IIα), a key enzyme involved in DNA replication and repair, particularly in triple-negative breast cancer (TNBC). Germination significantly elevated the polyphenolic content of black beans, thereby enhancing their antioxidant properties. Molecular docking studies demonstrated a strong interaction between GBBE and the active site of topo IIα, suggesting a possible mechanism for its inhibitory action. In vitro experiments revealed a significant inhibitory effect of GBBE on topo IIα ATPase activity, which was further confirmed by the decatenation assay, with bean extracts germinated for three days showing the highest effect. The study underscores the significance of GBBE as a promising natural source of bioactive compounds with the capacity to inhibit topo IIα activity, offering a potential novel therapeutic strategy against TNBC. Warranting further investigation to clarify the molecular mechanisms underlying these effects.

Development of β‐Carboline‐Coumarin Based Hybrids as Potential Cytotoxic and Topoisomerase IIα Inhibitors

AbstractCancer remains a global health concern, prompting extensive efforts to develop novel inhibitors targeting the enzyme topoisomerase IIα as potential anti‐cancer agents. Herein, we strategically combined the pharmacophores from natural (β‐carboline) and (coumarin) sources, diversifying them at two distinct points. The in vitro evaluation of cytotoxic properties were estimated on human cancer cell lines, reveals that among the tested compounds, 13 r (isopropyl‐substituted β‐carboline) exhibited remarkable potency with IC50 value of 4.37 μM in the HCT116 cell line. Its selectivity for cancer cells was validated against normal keratinocyte cells, establishing a favourable selectivity index. Further, SAR studies indicate that no substitution (13 r) at C‐6 and C‐7 of β‐carboline, enhance anticancer activity. Assays confirmed its ability to intercalate with DNA, inhibit topoisomerase IIα, induce apoptosis, and disrupt mitochondrial membrane potential in HCT116 cells. Flow cytometric assays gauged the induction of apoptosis using Annexin‐V/PI dual staining and the disruption of mitochondrial membrane potential through JC staining. Results demonstrated that compound 13 r induced apoptosis and dose‐dependent depolarization of the mitochondrial membrane in HCT116 cells. Molecular docking studies further validated that compound 13 r binds within the active site of DNA when complexed with topo IIα, and this binding was stabilized through interactions with DNA base pairs and amino acid residues.

Investigating the potent TOPO IIα inhibitors in breast cancer through the study of computational drug discovery research approaches.

Breast cancer (BC) is the second-leading cause of cancer after lung cancer. The disease has affected millions of people and resulted in many deaths. In the metastasis of breast cancer cells, Topoisomerase IIα plays a vital role. Therefore, this investigation aims to identify potential flavonoid compounds against BC by inhibiting this enzyme at an early stage. Based on previous studies, we selected and screened several plant-derived flavonoid compounds with potential anti-breast cancer activity using PyRx 0.8 and Schrodinger applications for preliminary molecular docking: the highest docking scores of Myricetin (-11.6kcal/mol) and Quercetin (-10.0kcal/mol). Next, we evaluated the top four compounds on the Way2Drug server to complete the cytotoxicity evaluation, which demonstrated anti-cancer and anti-breast cancer activity in various cell lines. According to pharmacokinetics studies, four compounds exhibited outstanding values and functioned similar to drug-like molecules. Moreover, Myricetin, Quercetin, and Morin displayed the highest number of hydrogen bonds, with the corresponding receptor forming residues asn120, thr147, and lys168. The protein-ligand complexes were validated using the Desmond simulator, and their data were compared to the anti-breast cancer drug Doxorubicin. In the simulation analysis, various parameters were evaluated, including RMSD, RMSF, Rg, SASA, MolSA, PSA, and hydrogen bond interaction. Finally, validated our dynamic simulation result with MM-GBSA operation, and Myricetin and Quercetin had the greatest score of -72.74344651, -66.66771823kcal/mol, which is outstanding than the control drug. Hence, the computational research approach determined that Myricetin, Quercetin, and Morin could be industrially developed for the alternative treatment of breast cancer following additional confirmation from animal and cell line studies.

Molecular choreography: Unveiling the dynamic landscape of type IIA DNA topoisomerases before T-segment passage through all-atom simulations

Type IIA DNA topoisomerases are molecular nanomachines responsible for controlling topological states of DNA molecules. Here, we explore the dynamic landscape of yeast topoisomerase IIA during key stages of its catalytic cycle, focusing in particular on the events preceding the passage of the T-segment. To this end, we generated six configurations of fully catalytic yeast topo IIA, strategically inserted a T-segment into the N-gate in relevant configurations, and performed all-atom simulations.The essential motion of topo IIA protein dimer was characterized by rotational gyrating-like movement together with sliding motion within the DNA-gate. Both appear to be inherent properties of the enzyme and an inbuilt feature that allows passage of the T-segment through the cleaved G-segment. Coupled dynamics of the N-gate and DNA-gate residues may be particularly important for controlled and smooth passage of the T-segment and consequently the prevention of DNA double-strand breaks. QTK loop residue Lys367, which interacts with ATP and ADP molecules, is involved in regulating the size and stability of the N-gate. The unveiled features of the simulated configurations provide insights into the catalytic cycle of type IIA topoisomerases and elucidate the molecular choreography governing their ability to modulate the topological states of DNA topology.

Molecular Docking and QSAR Study of 5-O-acylpinostrobin Derivatives as Topoisomerase IIα Inhibitors

Background: Cancer is one of the top causes of death worldwide. A wide range of illnesses known as cancer can start in almost any organ or tissue in the body when abnormal cells multiply uncontrollably. Cancer patients have higher levels of the Topo IIα protein in their cells, this protein has been proposed as a relevant target for anticancer treatment development. Objective: This study aims to predict the anticancer activity of pinostrobin and 5-O-acylpinostrobin derivatives against topoisomerase IIα by docking molecular and QSAR study. Methods: In silico analysis was performed using the structure of the topoisomerase IIα (PDB: 5GWK)) as templates. Molecular docking analysis was performed with AutoDock Vina. Result: All 5-O-acyl pinostrobin derivatives, showed lower ΔG values than the parent pinostrobin. The 5-O-acetyl pinostrobin compound showed the highest score, namely -9.14 kcal/mol. 5-O-acetyl pinostrobin is predicted as the most powerful inhibitor that can cause inhibition of topoisomerase IIα. Conclution: The results of the best QSAR equation obtained can be used as a reference for predicting the activity of the new pinostrobin derivatives to be synthesized by inserting the electronic (Etot) parameter values of the compounds into the equation.

Abstract 1732: Linker histone h1 inhibits topoisomerase IIa in vitro and in vivo

Abstract H1 linker histones play a crucial role in organizing chromatin into higher-order structures and regulating gene expression, contributing significantly to various cellular processes. Topoisomerase IIa (TopoIIa) is essential for multiple cellular functions via regulating DNA topology. Here, we report a direct interaction between H1 linker histones and TopoIIa through both N- and C-terminal domains of H1 variants. H1 suppresses the decatenation enzymatic activity of TopoIIa in vitro in a dose-dependent manner. Overexpressing specific H1 variants in HeLa cells results in a marked decrease in cell proliferation and a dramatic increase in the occurrence of cells displaying abnormal mitotic chromosomes. Additionally, we find that the inhibitory effect of the specific H1 variant on TopoIIa activity occurs prior to the formation of DNA-TopoIIa complexes. These results reveal a novel mechanistic link between histone H1 and Topo IIa in the regulation of chromatin function. Citation Format: Samantha Lasater, Hiba Hamdan, Po-Yi Ho, Ting Wu, Kaixiang Cao, Ruiqiao Yang, Yunzhe Zhang, Yuhong Fan. Linker histone h1 inhibits topoisomerase IIa in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1732.

Abstract 4756: Targeting DNA topoisomerase II to manage acquired resistance to third generation EGFR tyrosine kinase inhibitors in the treatment of EGFR mutant NSCLC

Abstract Development of effective strategies to manage the inevitable acquired resistance to osimertinib, a 3rd generation EGFR inhibitor with proven clinical efficacy in prolonging survival of patients with EGFR mutant (EGFRm) non-small cell lung cancer (NSCLC), is an urgent and critical area of unmet need in the clinic. Effort toward this direction led us to find that the DNA topoisomerase II (Topo II) inhibitors, doxorubicin and etoposide (VP-16), but not other chemotherapeutic agents, synergistically decreased the survival of osimertinib-resistant cell lines when combined with osimertinib. The combination of osimertinib with either doxorubcin or VP-16 effectively induced DNA damage and apoptosis in osimertinib-resistant cells, suppressed the growth of osimertinib-resistant tumors, and delayed the emergence of acquired resistance to osimertinib. Mechanistic studies found that osimertinib as well other EGFR-TKIs effectively decreased Topo IIα levels in EGFRm NSCLC cells by facilitating its proteasomal degradation and induced DNA damage; these effects were lost in cell lines with osimertinib acquired resistance that possessed elevated basal levels of Topo IIα. In the majority of EGFRm NSCLC tissues relapsed from EGFR-TKI treatment, Topo IIα levels were substantially increased. Enforced expression of ectopic TOP2A genes in sensitive EGFRm NSCLC cells conferred resistance to osimertinib in inducing DNA damage and apoptosis, whereas knockdown of TOP2A in osimertinib-resistant cell lines restored their responses to undergo osimertinib-induced DNA damage and apoptosis. Together, these results reveal a previously undiscovered essential role of Topo IIα modulation in regulating the responses of EGFRm NSCLC cells to osimertinib, providing scientific rationale for targeting Topo II to manage acquired resistance to osimertinib and possibly other third generation EGFR-TKIs, thus warranting clinical validation of this strategy. (This study was supported by NIH/NCI R01 CA223220 and UG1 CA233259 and Emory Winship Cancer Institute lung cancer research pilot funds). Citation Format: Zhen Chen, Karin A. Vallega, Dongsheng Wang, Zihan Quan, Songqing Fan, Qiming Wang, Ticiana A. Leal, Suresh S. Ramalingam, Shi-Yong Sun. Targeting DNA topoisomerase II to manage acquired resistance to third generation EGFR tyrosine kinase inhibitors in the treatment of EGFR mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4756.

DNA topoisomerase II inhibition potentiates osimertinib's therapeutic efficacy in EGFR-mutant non-small cell lung cancer models.

Development of effective strategies to manage the inevitable acquired resistance to osimertinib, a third-generation EGFR inhibitor for the treatment of EGFR-mutant (EGFRm) non-small cell lung cancer (NSCLC), is urgently needed. This study reports that DNA topoisomerase II (Topo II) inhibitors, doxorubicin and etoposide, synergistically decreased cell survival, with enhanced induction of DNA damage and apoptosis in osimertinib-resistant cells; suppressed the growth of osimertinib-resistant tumors; and delayed the emergence of osimertinib-acquired resistance. Mechanistically, osimertinib decreased Topo IIα levels in EGFRm NSCLC cells by facilitating FBXW7-mediated proteasomal degradation, resulting in induction of DNA damage; these effects were lost in osimertinib-resistant cell lines that possess elevated levels of Topo IIα. Increased Topo IIα levels were also detected in the majority of tissue samples from patients with NSCLC after relapse from EGFR tyrosine kinase inhibitor treatment. Enforced expression of an ectopic TOP2A gene in sensitive EGFRm NSCLC cells conferred resistance to osimertinib, whereas knockdown of TOP2A in osimertinib-resistant cell lines restored their susceptibility to osimertinib-induced DNA damage and apoptosis. Together, these results reveal an essential role of Topo IIα inhibition in mediating the therapeutic efficacy of osimertinib against EGFRm NSCLC, providing scientific rationale for targeting Topo II to manage acquired resistance to osimertinib.

Palindromic carbazole derivatives: unveiling their antiproliferative effect via topoisomerase II catalytic inhibition and apoptosis induction

Human DNA topoisomerases are essential for crucial cellular processes, including DNA replication, transcription, chromatin condensation, and maintenance of its structure. One of the significant strategies employed in cancer treatment involves the inhibition of a specific type of topoisomerase, known as topoisomerase II (Topo II). Carbazole derivatives, recognised for their varied biological activities, have recently become a significant focus in oncological research. This study assesses the efficacy of three symmetrically substituted carbazole derivatives: 2,7-Di(2-furyl)-9H-carbazole (27a), 3,6-Di(2-furyl)-9H-carbazole (36a), and 3,6-Di(2-thienyl)-9H-carbazole (36b) – as anticancer agents. Among investigated carbazole derivatives, compound 3,6-di(2-furyl)-9H-carbazole bearing two furan moieties emerged as a novel catalytic inhibitor of Topo II. Notably, 3,6-di(2-furyl)-9H-carbazole effectively selectively inhibited the relaxation and decatenation activities of Topo IIα, with minimal effects on the IIβ isoform. These findings underscore the potential of compound 3,6-Di(2-furyl)-9H-carbazole as a promising lead candidate warranting further investigation in the realm of anticancer drug development.

Regulation of condensin II by self-suppression and release mechanisms.

In vertebrates, two distinct condensin complexes, condensin I and condensin II, cooperate to drive mitotic chromosome assembly. It remains largely unknown how the two complexes differentially contribute to this process at a mechanistic level. We have previously dissected the role of individual subunits of condensin II by introducing recombinant complexes into Xenopus egg extracts. Here we extend these efforts by introducing a modified functional assay using extracts depleted of topoisomerase IIα (topo IIα), which allows us to further elucidate the functional similarities and differences between condensin I and condensin II. The intrinsically disordered C-terminal region of the CAP-D3 subunit (the D3 C-tail) is a major target of Cdk1 phosphorylation, and phosphorylation-deficient mutations in this region impair condensin II functions. We also identify a unique helical structure in CAP-D3 (the D3 HEAT docker) that is predicted to directly interact with CAP-G2. Deletion of the D3 HEAT docker, along with the D3 C-tail, enhances the ability of condensin II to assemble mitotic chromosomes. Taken together, we propose a self-suppression mechanism unique to condensin II that is released by mitotic phosphorylation. Evolutionary implications of our findings are also discussed.

Cell cycle responses to Topoisomerase II inhibition: Molecular mechanisms and clinical implications.

DNA Topoisomerase IIA (Topo IIA) is an enzyme that alters the topological state of DNA and is essential for the separation of replicated sister chromatids and the integrity of cell division. Topo IIA dysfunction activates cell cycle checkpoints, resulting in arrest in either the G2-phase or metaphase of mitosis, ultimately triggering the abscission checkpoint if non-disjunction persists. These events, which directly or indirectly monitor the activity of Topo IIA, have become of major interest as many cancers have deficiencies in Topoisomerase checkpoints, leading to genome instability. Recent studies into how cells sense Topo IIA dysfunction and respond by regulating cell cycle progression demonstrate that the Topo IIA G2 checkpoint is distinct from the G2-DNA damage checkpoint. Likewise, in mitosis, the metaphase Topo IIA checkpoint is separate from the spindle assembly checkpoint. Here, we integrate mechanistic knowledge of Topo IIA checkpoints with the current understanding of how cells regulate progression through the cell cycle to accomplish faithful genome transmission and discuss the opportunities this offers for therapy.

Ligand Based Multi-Targeted Molecular Docking Analysis o f Terpenoid Phytoconstituents as Potential Chemotherapeutic Agents Against Breast Cancer: An In Silico Approach

Breast cancer is one of the most common cancers in women all around the world and is a dominant cause of deaths occurring all around the globe. The available potent drugs for breast cancer show adverse effects and resistance and are found to be ineffective in patients. The high cost of currently available cancer therapy and certain limitations of current treatment make it necessary to search for novel, cost-effective and efficient methods of cancer treatment. Phytochemicals are directly involved in treatment or precursors to synthesize useful drugs. Therefore, in the current investigation, 500 terpenoid phytoconstituents and five proteins associated with breast cancer including EGFR, ERα, HER2, NF-κB and Topo IIa were selected from various databases. Selected compounds were screened for their molecular properties based on Lipinski's rule of five resulting in 235 compounds exclusion. Drug-likeness and PAINS alert properties were predicted using pkCSM and SwissADME web servers which led to the omission of 43 compounds. The remaining 222 compounds were screened to predict their ADMET properties and based on these results, 117 compounds were selected to predict the anti-breast cancer potential. Finally, 73 compounds, which showed anti-breast cancer activity prediction, were virtually screened and the top four best-scoring compounds were selected as lead-like molecules and docked with the five respective breast cancer targets. The results showed that the top four lead-like molecules exhibited greater binding affinity and lesser toxicity than the standard drugs namely 4–Hydroxytamoxifen, Daunorubicin, Erlotinib and Lapatinib. Keywords: ADMET, Breast cancer, Chemotherapeutic agents, In silico analysis, Molecular docking, Terpenoids

In Silico Study of a Small Bioactive Molecule Targeting Topoisomerase II and P53-MDM2 Complex in Triple-Negative Breast Cancer.

Treatment of triple-negative breast cancer (TNBC) is very challenging as only few therapeutic options are available, including chemotherapy. Thus, a constant search for new and effective approaches of therapy that could potentially fight against TNBC and mitigate side effects is "turn-on". Recently, multitarget therapy has come up with huge possibilities, and it may possibly be useful to overcome several concurrent challenges in cancer therapy. Herein, we proposed the inhibition of both Topoisomerase II enzyme and p53-MDM2 (p53 cavity in MDM2) protein complex by the same bioactive molecules for multitarget therapy. RNA-seq analysis was performed to get a network of essential proteins involved in the apoptosis pathway by considering the triple-negative breast cancer cell line (MDA-MB-231). All of the untreated duplicate sample data were retrieved from NCBI (GSC149768). Further, via in silico screening, potent bioactive molecules were screened out to target both Topo II and the p53-MDM2 complex. The results of ligand-based screening involving docking, MMGBSA, ADME/T, MD simulation, and PCA suggested that resveratrol, a plant bioactive molecule, showed more potential binding in the same cavity of target proteins compared with doxorubicin for Topo IIα (5GWK) and etoposide for the second protein target (p53-MDM2 complex; 4OQ3) as the control drug. This is also evident from the in vitro validation in case of triple-negative breast cancer cell lines (MDA-MB-231) and Western blotting analysis. Thus, it paves the scope of multitargeting against triple-negative breast cancer.

Topoisomerase IIα immunoexpression in feline mammary carcinomas: A correlation with Ki67 immunoexpression and the mitotic count

The aim of the study was to compare the immunohistochemical expression of topoisomerase IIα protein (Topo IIα) with Ki67 expression and mitotic count in feline mammary carcinomas (FMCs). Topo IIα is considered as a proliferation indicator as well as a molecular target of anthracycline chemotherapy. The studied material included 70 FMCs from female cats treated with mastectomy. Primary mouse monoclonal antibodies directed against Topo IIα and Ki67 were used in immunohistochemical reactions. The number of mitotic figures was counted at 400× magnification in a field of 2.37 mm2. Immunohistochemical reaction for Topo IIα occurred in cell nuclei. The Topo IIα index ranged from 6.12% to 54.60% and was positively correlated with the values of the Ki67 index (r = 0.7193) and the mitotic count (r = 0. 2858). This indicates the potential possibility of use of the immunohistochemical expression of Topo IIα to assess the rate of proliferation in FMCs. The wide range of expression of Topo IIα in individual tumorus found in the conducted studies allows us to hypothesize that its assessment could be used as a predictive marker in chemotherapy of FMCs with the use of anthracyclines. However, this requires confirmation in clinical trials.

Di-indenopyridines as topoisomerase II-selective anticancer agents: Design, synthesis, and structure–activity relationships

Topoisomerases are key molecular enzymes responsible for altering DNA topology, thus they have long been considered as attractive targets for novel chemotherapeutic agents. Topoisomerase type II (Topo II) catalytic inhibitors embrace a fresh perspective meant to get beyond drawbacks caused by topo II poisons, such as cardiotoxicity and secondary malignancies. Based on previously reported 5H-indeno[1,2-b]pyridines, here we presented new twenty-three hybrid di-indenopyridines along with their topo I/IIα inhibitory and antiproliferative activity. Most of the prepared 11-phenyl-diindenopyridines showed negligible topo I inhibitory activity, showing selectivity over topo II. Among the series, we finally selected compound 17, which displayed 100 % topo IIα inhibition at 20 μM concentration and comparable antiproliferative activity against the tested cell lines. Through competitive EtBr displacement assay, cleavable complex assay, and comet assay, compound 17 was finally determined as a non-intercalative catalytic topo IIα inhibitor. The findings in this study highlight the significance of phenolic, halophenyl, thienyl, and furyl groups at the 4-position of the indane ring in the design and synthesis of di-indenopyridines as potent catalytic topo IIα inhibitors with remarkable anticancer effects.

Topoisomerase IIalpha (TopoIIa) A New Promising Marker for Early Detection of Laryngeal Squamous Cell Carcinoma: An Immunohistochemical Study.

the aim of this study is evaluation of Topo IIa expression in laryngeal squamous cell carcinomas and correlation of this expression with various clinicopathological parameters. ninety cases of laryngeal squamous cell carcinoma archived paraffin blocks were collected in the form of total laryngectomies. Each paraffin block was re-cut by rotatory microtome at 4 μm thickness and stained by hematoxylin and eosin for routine histopathological examination and on charged slides for immunohistochemistry using an automated staining system with antibodies against Topo IIa. Mainly nuclear and slightly cytoplasmic staining was considered positive. Percentage of positive Topo IIa cells was graded then grouped into low expression and overexpression. Topo IIa overexpression was seen in 91.1% of cases, while low expression was noticed in the remaining 8.9% of cases. There were statistically significant correlations between Topo IIa expression and tumor histological grade, lymph node metastasis and T stage as well as statistically significant positive correlation between Topo IIa expression as we progress from normal to dysplastic/in situ up to malignant transformation. High expression of Topo IIa may indicate more aggressive tumor and may play a role in tumorogenesis in laryngeal squamous cell carcinoma.

Imidazopyridine chalcones as potent anticancer agents: Synthesis, single-crystal X-ray, docking, DFT and SAR studies.

New imidazopyridine-chalcone analogs were synthesized through the Claisen-Schmidt condensation reaction. The newly synthesized imidazopyridine-chalcones (S1-S12) were characterized using spectroscopic and elemental analysis. The structures of compounds S2 and S5 were confirmed by X-ray crystallography. The global chemical reactivity descriptor parameter was calculated using theoretically (DFT-B3LYP-3-211, G) estimated highest occupied molecular orbital and lowest unoccupied molecular orbital values and the results are discussed. Compounds S1-S12 were screened on A-549 (lung carcinoma epithelial cells) and MDA-MB-231 (M.D. Anderson-Metastatic Breast 231) cancer cell lines. Compounds S6 and S12 displayed exceptional antiproliferative activity against lung A-549 cancer cells with IC50 values of 4.22 and 6.89 µM, respectively, compared to the standard drug doxorubicin (IC50 = 3.79 μM). In the case of the MDA-MB-231 cell line, S1 and S6 exhibited exceptionally superior antiproliferative activity with IC50 of 5.22 and 6.50 μM, respectively, compared to doxorubicin (IC50 = 5.48 μM). S1 was found to be more active than doxorubicin. Compounds S1-S12 were tested for their cytotoxicity on human embryonic kidney 293 cells, which confirmed the nontoxic nature of the active compounds. Further molecular docking studies verified that compounds S1-S12 have a higher docking score and interacted well with the target protein. The most active compound S1 interacted well with the target protein carbonic anhydrase II in complex with pyrimidine-based inhibitor, and S6 with human Topo IIα ATPase/AMP-PNP. The results suggest that imidazopyridine-chalcone analogs may serve as new leads as anticancer agents.

Novel topoisomerase II/EGFR dual inhibitors: design, synthesis and docking studies of naphtho[2′,3′:4,5]thiazolo[3,2-a]pyrimidine hybrids as potential anticancer agents with apoptosis inducing activity

Topoisomerases II are ubiquitous enzymes with significant genotoxic effects in many critical DNA processes. Additionally, epidermal growth factor receptor (EGFR) plays pivotal role in tumour growth and angiogenesis. A novel series of naphtho[2',3':4,5]thiazolo[3,2- a ]pyrimidine hybrids have been designed, synthesised and evaluated for their topo IIα/EGFR inhibitory and apoptotic inducer activities. Cytotoxicity of the synthesised hybrids was evaluated against MCF-7, A549 and HCT-116 cell lines. Of the synthesised hybrids, 6i, 6a and 6c experienced superior cytotoxic activity compared to doxorubicin and erlotinib against the tested cancer cells. The molecular mechanism of these hybrids revealed their ability to successfully inhibit topo IIα and EGFR activities in micromolar concentration and may serve as topo II catalytic inhibitor. Moreover, these hybrids significantly arrested cell cycle at G2/M phase together with increased p53, caspae-7, caspase-9 levels and Bax/Bcl-2 ratio. The synthesised hybrids showed efficient binding pattern in molecular docking study and have acceptable drug likeness characters.

Acridine/Acridone-Carborane Conjugates as Strong DNA-Binding Agents with Anticancer Potential.

Synthesis of acridine derivatives that act as DNA-targeting anticancer agents is an evolving field and has resulted in the introduction of several drugs into clinical trials. Carboranes can be of importance in designing biologically active compounds due to their specific properties. Therefore, a series of novel acridine analogs modified with carborane clusters were synthesized. The DNA-binding ability of these analogs was evaluated on calf thymus DNA (ct-DNA). Results of these analyses showed that 9-[(1,7-dicarba-closo-dodecaborane-1-yl)propylamino]acridine (30) interacted strongly with ct-DNA, indicating its ability to intercalate into DNA, whereas 9-[(1,7-dicarba-closo-dodecaborane-1-yl)propanamido]acridine (29) changed the B-form of ct-DNA to the Z form. Compound 30 demonstrated cytotoxicity, was able to inhibit cell proliferation, arrest the cell cycle in the S phase in the HeLa cancer cell line, and induced the production of reactive oxygen species (ROS). In addition, it was specifically localized in lysosomes and was a weak inhibitor of Topo IIα.