TOP2A Research Articles

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.

Tumor growth-arrest effect of tetrahydroquinazoline-derivative human topoisomerase II-alpha inhibitor in HPV-negative head and neck squamous cell carcinoma

Oral malignancies continue to have severe morbidity with less than 50% long-term survival despite the advancement in the available therapies. There is a persisting demand for new approaches to establish more efficient strategies for their treatment. In this regard, the human topoisomerase II (topoII) enzyme is a validated chemotherapeutics target, as topoII regulates vital cellular processes such as DNA replication, transcription, recombination, and chromosome segregation in cells. TopoII inhibitors are currently used to treat some neoplasms such as breast and small cells lung carcinomas. Additionally, topoII inhibitors are under investigation for the treatment of other cancer types, including oral cancer. Here, we report the therapeutic effect of a tetrahydroquinazoline derivative (named ARN21934) that preferentially inhibits the alpha isoform of human topoII. The treatment efficacy of ARN21934 has been evaluated in 2D cell cultures, 3D in vitro systems, and in chick chorioallantoic membrane cancer models. Overall, this work paves the way for further preclinical developments of ARN21934 and possibly other topoII alpha inhibitors of this promising chemical class as a new chemotherapeutic approach for the treatment of oral neoplasms.

Prediction model for pheochromocytoma/paraganglioma using nCounter assay.

World Health Organization defined pheochromocytomas/paragangliomas (PPGL) as malignant tumors in 2017 because the existing classification system could not reflect locally aggressive behavior sufficiently. However, predicting the likelihood of metastasis remains a crucial part of the treatment strategy. From one tertiary care hospital and onesecondary hospital, 97 PPGL cases were selected. Medical records of PPGL cases with the presence of formalin-fixed and paraffin-embedded (FFPE) tissue of primary lesion were reviewed. For FFPE tissues, a nCounter assay was conducted to determine differently expressed genes between metastatic and non-metastatic PPGL groups. Performances of prediction models for the likelihood of metastasis were calculated. Of a total of 97 PPGL cases, 39, 20, and 38 were classified as benign, malignant, and validation, respectively. In the nCounter assay, CDK1, TYMS, and TOP2A genes showed significant differences in expression. Tumor size was positively correlated with CDK1 expression level. The Lasso regression model showed supreme performance of sensitivity 91.7% and specificity 95.5% when those significant factors were considered. Machine learning of multi-modal classifiers can be used to create a prediction model for metastasis of PPGL with high sensitivity and specificity using nCounter assay. Moreover, CDK1 inhibitors could be considered for developing drug treatment.

Indisulam synergizes with melphalan to inhibit Multiple Myeloma malignancy via targeting TOP2A.

Multiple myeloma (MM) is the second most prevalent hematologic malignancy which remains uncurable. Numerous drugs have been discovered to inhibit MM cells. Indisulam, an aryl sulfonamide, has a potent anti-myeloma activity in vitro and in vivo. This study aims to explore the new mechanism of indisulam and investigate its potential use in combination with melphalan. We examined DNA damage in MM cells through various methods such as western blotting (WB), immunofluorescence, and comet assay. We also identified the role of topoisomerase IIα (TOP2A) using bioinformatic analyses. The impact of indisulam on the RNA and protein levels of TOP2A was investigated through qPCR and WB. Cell proliferation and apoptosis were assessed using CCK-8 assays, Annexin V/PI assays and WB. We predicted the synergistic effect of the combination treatment based on calculations performed on a website, and further explored the effect of indisulam in combination with melphalan on MM cell lines and xenografts. RNA sequencing data and basic experiments indicated that indisulam caused DNA damage and inhibited TOP2A expression by decreasing transcription and promoting degradation via the proteasome pathway. Functional experiments revealed that silencing TOP2A inhibited cell proliferation and induced apoptosis and DNA damage. Finally, Indisulam/melphalan combination treatment demonstrated a strong synergistic anti-tumor effect compared to single-agent treatments in vitro and in vivo. These findings suggest that combination therapies incorporating indisulam and melphalan have the potential to enhance treatment outcomes for MM.

Phytochemical Composition and Cytotoxic Activity of Senecio asirensis Hexane Fraction Using In Vitro and In Silico Approaches

Objective Senecio asirensis, an endemic species of Saudi Arabia, has been traditionally used to treat various ailments. The present study aimed to investigate the phytochemical composition, antimicrobial activity, and cytotoxic potential of Senecio asirensis fractions, and to identify the main compounds in the extract that are the most active. Methods The antimicrobial activity was evaluated using disc diffusion assay. Moreover, the cytotoxic activity evaluated using the MTT assay in various cancer cell lines (MCF-7, HepG2, and A549) and validated by molecular docking for the major compound of the most active fraction. Finally, gas chromatography and a mass spectrometer (GC-MS) analysis was carried out to identify the chemical compounds in hexane extract of Senecio asirensis. Results The hexane fraction exhibited significant antimicrobial activity against Gram-positive bacteria ( S. aureus) and yeast organisms ( C. albicans and C. tropicalis), while chloroform and butanol fractions showed no activity against the tested microbial strains. Moreover, in the cytotoxic activity assay, notably, the hexane fraction showed a significantly higher cytotoxic effect on MCF-7. The GC-MS analysis of the hexane fraction revealed the presence of 26 phytoconstituents, with nonacosane being the most abundant compound. Therefore, the molecular docking was employed to validate the cytotoxic activity for the major compound of the most active fraction (nonacosane) against human DNA topoisomerase IIa. Conclusion These findings provide a scientific basis for the traditional use of S. asirensis in medicine and suggest that its bioactive compounds have potential therapeutic applications in anticancer treatments. Further research is needed to isolate and characterize other active compounds and to explore potential synergistic effects among them.

The correlation study between TOP2A gene expression in circulating tumor cells and chemotherapeutic drug resistance of patients with breast cancer

BackgroundPatients with breast cancer (BC) at advanced stages have poor outcomes because of high rate of recurrence and metastasis. Biomarkers for predicting prognosis remain to be explored. This study aimed to evaluate the relationships between circulating tumor cells (CTCs) and outcomes of BC patients.Patients and methodsA total of 50 female were enrolled in this study. Their diagnoses were determined by clinical characteristics, image data, and clinical pathology. CTC subtypes and TOP2A gene expression on CTCs were detected by CanPatrol™ technology and triple color in situ RNA hybridization (RNA-ISH), which divided into epithelial CTCs (eCTCs), mesenchymal CTCs (MCTCs), and hybrid CTCs (HCTCs) based on their surface markers. Hormone receptor, including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) expression, was measured by immunohistochemistry (IHC) method before treatment. The risk factors for predicting recurrence and metastasis were calculated by COX risk regression model. The progression-free survival (PFS) of patients was determined using Kaplan–Meier survival curve.ResultsThe patients with a large tumor size (≥ 3 cm) and advanced tumor node metastasis (TNM) stages had high total CTCs (TCTCs) (P < 0.05). These patients also had high TOP2A expression level. COX risk regression analysis indicated that TOP2A expression levels in TCTCs, ER + , HER-2 + , and TNM stages were critical risk factors for recurrence and metastasis of patients (P < 0.05). The PFS of patients with ≥ 5 TCTCs, ≥ 3 HCTCs, and positive TOP2A expression in ≥ 3 TCTCs was significantly longer than that in patient with < 5 TCTCs, < 3 HCTCs, and TOP2A expression in < 3 TCTCs (P < 0.05). In contrast, the PFS of patients with positive hormone receptors (ER + , PR + , HER-2 +) also was dramatically lived longer than that in patients with negative hormone receptor expression.ConclusionsHigh TCTC, HCTCs, and positive TOP2A gene expression on CTCs were critical biomarkers for predicting outcomes of BC patients. Positive hormone receptor expression in BC patients has significant favor PFS.

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.

Investigation of Genes and Their Interactions in Liver Diseases Using Bioinformatics Algorithms

In this study, we considered progression of liver diseases. Particularly we considered Hepatocellular Carcinoma Cancer, HCC, whose patients have low survival rates. For this purpose, we researched molecular structures and protein interactions involved in the initiation and progression of HCC. We exploited microarray data samples and their gene expression profiles from literature. During analysis, we implemented statistical data analysis techniques and looked for Differentially Expressed Genes during the initiation and progression of HCC. As a result of this analysis we found 12 hub genes, where 3 of them (ANLN, TOP2A, ASPM and SPINK1) were upregulated and the others (CXCL14, LINC01093, OIT3, CLEC4G, THRSP, APOF, CLTRN and FCN3) were downregulated. By performing Gene Ontology Analysis, we classified genes with increased or decreased expressions in terms of cellular component, biological process, and molecular function. Subsequently, we executed protein-protein interaction network analysis and found important interactions between the hub genes. Results of data analysis concluded that these 12 genes and their interactions play a key role in the initiation and progression of significant liver diseases and can be used as a potential biomarker for disease progression. Furthermore, gene feature analysis showed that it is becoming more difficult to compensate functional deficiencies of the proteins encoded by these genes during biological processes. In particular, Gene Ontology Analysis denoted that TOP2A gene associates with many of the biological pathways and a change in the expression of this gene can cause decent problems in many cellular functions.

Activating the abscission checkpoint: Top2α senses chromatin bridges in cytokinesis: Top2α binds to DNA knots on chromatin bridges to activate the abscission checkpoint in human cells.

How chromatin bridges are detected by the abscission checkpoint during mammalian cell division is unknown. Here, we discuss recent findings from our lab showing that the DNA topoisomerase IIα (Top2α) enzyme binds to catenated ("knotted") DNA next to the midbody and forms abortive Top2-DNA cleavage complexes (Top2ccs) on chromatin bridges. Top2ccs are then processed by the proteasome to promote localization of the DNA damage sensor protein Rad17 to Top2-generated double-strand DNA ends on DNA knots. In turn, Rad17 promotes local recruitment of the MRN protein complex and downstream ATM-Chk2-INCENP signaling to delay abscission and prevent chromatin bridge breakage in cytokinesis.

The high expression of TOP2A and MELK induces the occurrence of psoriasis.

Psoriasis is a chronic inflammatory skin disease. However, the influence of the TOP2A and MELK genes on psoriasis remains unclear. Psoriasis datasets GSE166388 and GSE181318 were downloaded from the Gene Expression Omnibus (GEO) database generated from GPL570 and GPL22120. Differential gene expression (DEGs) was identified. Functional enrichment analysis, gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), and immune infiltration analysis were conducted. The protein-protein interaction (PPI) network was constructed and analyzed. Gene expression heat map was generated. The most relevant diseases associated with core genes were determined through comparison with the Comparative Toxicogenomics Database (CTD) website. TargetScan was used to select miRNAs regulating central DEGs. A total of 773 DEGs were identified. According to Gene Ontology (GO) analysis, they were mainly enriched in mitochondrial gene expression, oxidative phosphorylation, mitochondrial envelope, mitochondria and ribosome. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that target cells were mainly enriched in metabolic pathways, proteasome, and oxidative phosphorylation. Seven core genes (TOP2A, NUF2, MELK, ASPM, DLGAP5, CCNA2, DEPDC1B) were obtained. The gene expression heatmap showed high expression of core genes (TOP2A, MELK) in psoriasis samples, while DEPDC1B, CCNA2, DLGAP5, NUF2, ASPM were lowly expressed in psoriasis samples. CTD analysis found that TOP2A and MELK were related to skin neoplasms, skin diseases, psoriasis, erythema, dermatitis, and infections. TOP2A and MELK genes are highly expressed in psoriasis, and higher expression of TOP2A and MELK genes is associated with poorer prognosis.

Hellebrigenin triggers death of promyelocytic leukemia cells by non-genotoxic ways

Bufadienolides are digitalis-like aglycones mainly found in skin secretions of toads. Among their biological properties, the mechanisms of antiproliferative action on tumor cells remain unclear for many compounds, including against leukemia cells. Herein, it was evaluated the mechanisms involved in the antiproliferative and genotoxic actions of hellebrigenin on tumor cell lines and in silico capacity to inhibit the human topoisomerase IIa enzyme. Firstly, its cytotoxic action was investigated by colorimetric assays in human tumor and peripheral blood mononuclear cells (PBMC). Next, biochemical and morphological studies were detailed by light microscopy (trypan blue dye exclusion), immunocytochemistry (BrdU uptake), flow cytometry and DNA/chromosomal damages (Cometa and aberrations). Finally, computational modelling was used to search for topoisomerase inhibition. Hellebrigenin reduced proliferation, BrdU incorporation, viability, and membrane integrity of HL-60 leukemia cells. Additionally, it increased G2/M arrest, internucleosomal DNA fragmentation, mitochondrial depolarization, and phosphatidylserine externalization in a concentration-dependent manner. In contrast to doxorubicin, hellebrigenin did not cause DNA strand breaks in HL-60 cell line and lymphocytes, and it interacts with ATPase domain residues of human topoisomerase IIa, generating a complex of hydrophobic and van der Waals interactions and hydrogen bonds. So, hellebrigenin presented potent anti-leukemic activity at concentrations as low as 0.06 μM, a value comparable to the clinical anticancer agent doxorubicin, and caused biochemical changes suggestive of apoptosis without genotoxic/clastogenic-related action, but it probably triggers catalytic inhibition of topoisomerase II. These findings also emphasize toad steroid toxins as promising lead antineoplasic compounds with relatively low cytotoxic action on human normal cells.

Effects of Topoisomerase II alpha Inhibition on Oral Cancer Cell Metabolism and Cancer Stem Cell Function.

Topoisomerase IIα (TOP2A), is an enzyme involved in DNA replication, transcription, recombination, and chromatin remodeling and is found in a variety of cancers. However, the role of TOP2A regulation in oral cancer progression is not fully explained. We investigated the effect of TOP2A inhibition on cell survival, metabolism, and cancer stem cell self-renewal function in oral cancer cells. Oral carcinoma cell line SCC25 was cultured in complete DMEM/F12 media and treated with 5μM of Etoposide (Topoisomerase II inhibitor) for 48h. The critical parameters of cellular metabolism, including extracellular acidification rate (ECAR) and mitochondrial oxidative phosphorylation based on the oxygen consumption rate of cancer cells were assessed using Seahorse assay. Western blotting was performed to assess the proteins that are associated with proliferation (Survivin, IL-6) and cancer stem cell function (Oct4, Sox2) in cell lysates prepared from control and etoposide treated groups. Statistical analysis was performed using One-way ANOVA with Dunnett's multiple comparisons test. The protein expression of TOP2A was significantly (P<0.05) inhibited by etoposide. Additionally, TOP2A inhibition decreased the mitochondrial respiratory parameters including basal respiration, maximal respiration and ATP production. However, TOP2A inhibition has no impact on glycolytic function. Moreover, the proliferative marker survivin and IL-6 showed a significant (P<0.05) decrease after TOP2A inhibition. Conversely, the protein expression of cancer stem cell markers Oct-4 and Sox 2 were not altered. These results indicate that inhibition of TOP2A is more efficacious by decreasing the mitochondrial metabolic reprogramming and thereby downregulating the key anti-apoptotic and pro-survival mediators. Thus, TOP2A represents an ideal therapeutic target and offers a potential treatment strategy for OSCC.

Exploring substituted 3,4-dihydropyrimidinone and thione derivatives as anti-prostate cancer agents: Computational screening, synthesis, characterization, and in vitro efficacy assessment

Despite decades of research, anticancer medication therapy is still largely constrained to prevent growth and limit the spread of tumour cells. To speed up the process of finding anticancer drugs, exploring novel therapeutic macromolecules and identifying the right small molecules using an integration of computational and experimental approaches is a recent tactic adopted by investigators. In the present study, we designed and created a library of 200 ligands with 3,4-dihydropyrimidinones or their thiones linked with imidazolidinones through amide linkage and explored the extent of their in vitro anticancer activity towards human topoisomerase IIalpha (TOP2α or TOP2A) using DU-145 and PC-3 prostate cancer cell lines using the SRB assay method. This was accomplished by the molecular docking and synthesis of the titled compounds using a series of organic nucleophilic addition reactions, including the Biginelli one-pot condensation reaction. The preliminary physical character evaluation was employed for the synthesized compounds, and the structural parameters were analyzed using FTIR, proton NMR, 13C NMR, and LC-MS/MS. The anti-prostate cancer activity of the prepared Biginelli analogues was evaluated against cancer cell lines and mild-to-moderate reduction in the viability of cell lines was observed with compounds 5, 6, 9, 14, 15, 16, 17, and 19. Among them, compounds 5, 14, 15, and 16 exhibited significant potent activity against TOP2α or TOP2A. This result indicated that the derivatives of Biginelli (3,4-dihydropyrimidinones/thiones) could be promising anti-prostate cancer drug candidates.

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.

Study of nitrogen heterocycles as DNA/HSA binder, topoisomerase inhibitors and toxicological safety

Four new nitrogen-containing heterocyclic derivatives (acridine, quinoline, indole, pyridine) were synthesized and their biological properties were evaluated. The compounds showed affinity for DNA and HSA, with CAIC and CAAC displaying higher binding constants (Kb) of 9.54 × 104 and 1.06 × 106, respectively. The fluorescence quenching assay (Ksv) revealed suppression values ranging from 0.34 to 0.64 × 103 M−1 for ethidium bromide (EB) and 0.1 to 0.34 × 103 M−1 for acridine orange (AO). Molecular docking confirmed the competition of the derivatives with intercalation probes at the same binding site. At 10 μM concentrations, the derivatives inhibited topoisomerase IIα activity. In the antiproliferative assays, the compounds demonstrated activity against MCF-7 and T47-D tumor cells and nonhemolytic profile. Regarding toxicity, no acute effects were observed in the embryos. However, some compounds caused enzymatic and cardiac changes, particularly the CAIC, which increased SOD activity and altered heart rate compared to the control. These findings suggest potential antitumor action of the derivatives and indicate that substituting the acridine core with different cores does not interfere with their interaction and topoisomerase inhibition. Further investigations are required to assess possible toxicological effects, including reactive oxygen species generation.

Inverse Modulation of Aurora Kinase A and Topoisomerase IIα in Normal and Tumor Breast Cells upon Knockdown of Mitochondrial ASncmtRNA.

Breast cancer is currently the most diagnosed form of cancer and the leading cause of death by cancer among females worldwide. We described the family of long non-coding mitochondrial RNAs (ncmtRNAs), comprised of sense (SncmtRNA) and antisense (ASncmtRNA) members. Knockdown of ASncmtRNAs using antisense oligonucleotides (ASOs) induces proliferative arrest and apoptotic death of tumor cells, but not normal cells, from various tissue origins. In order to study the mechanisms underlying this selectivity, in this study we performed RNAseq in MDA-MB-231 breast cancer cells transfected with ASncmtRNA-specific ASO or control-ASO, or left untransfected. Bioinformatic analysis yielded several differentially expressed cell-cycle-related genes, from which we selected Aurora kinase A (AURKA) and topoisomerase IIα (TOP2A) for RT-qPCR and western blot validation in MDA-MB-231 and MCF7 breast cancer cells, as well as normal breast epithelial cells (HMEC). We observed no clear differences regarding mRNA levels but both proteins were downregulated in tumor cells and upregulated in normal cells. Since these proteins play a role in genomic integrity, this inverse effect of ASncmtRNA knockdown could account for tumor cell downfall whilst protecting normal cells, suggesting this approach could be used for genomic protection under cancer treatment regimens or other scenarios.

In Silico and In Vitro Studies of Novel Azomethines on DNA Repair Genes in Gastric Cell Lines.

We herein report the determination of the cytotoxic activity and expression profiles of some DNA repair genes of newly synthesized azomethines in the gastric cancer cell line (AGS). The studied novel compounds were synthesized by a condensation reaction and received compounds were characterized by 1H and 13C NMR spectroscopy methods. Furthermore, they were applied to the AGS cell line at eight different concentrations (0.1-50 µg/mL). Anticancer activities were determined using the MTT method. Expression levels of ATR, ERCC1, TOP2A, and ABCB1 genes were determined by the RT-PCR method. Biochemical parameters were also examined. The interaction of proteins with other proteins was investigated with the String v11 program. The IC50 values of compounds 1, 2, and 3 obtained after 72 h were 23.10, 8.93, and 1.58 µg/mL, respectively. The results demonstrate that the cytotoxic activity of compound 3 on AGS cancer cells is higher in comparison with other molecules. It was determined that the expression levels of ATR, TOP2A, and ABCB1 genes in compounds 1, 2, and 3 were decreased compared to the control group. In addition, it was determined that ERCC1 gene expression increased in compound 3, decreased in compound 2, and remained unchanged in compound 1 (p < 0.001). In AGS gastric cancer cells, a 64% decrease was detected for GST levels in compound 1, while a 38% decrease in GSH levels in compound 2. In addition, compounds 1-3 were examined at the molecular level with computational techniques and the docking studies revealed 4LN0 as a target protein.