Topoisomerase I (TOP1) dynamics: conformational transition from open to closed states

Eukaryotic topoisomerases I (TOP1) are ubiquitous enzymes removing DNA torsional stress. However, there is little data concerning the three-dimensional structure of TOP1 in the absence of DNA, nor how the DNA molecule can enter/exit its closed conformation. Here, we solved the structure of thermostable archaeal Caldiarchaeum subterraneum CsTOP1 in an apo-form. The enzyme displays an open conformation resulting from one substantial rotation between the capping (CAP) and the catalytic (CAT) modules. The junction between these two modules is a five-residue loop, the hinge, whose flexibility permits the opening/closing of the enzyme and the entry of DNA. We identified a highly conserved tyrosine near the hinge as mediating the transition from the open to closed conformation upon DNA binding. Directed mutagenesis confirmed the importance of the hinge flexibility, and linked the enzyme dynamics with sensitivity to camptothecin, a TOP1 inhibitor targeting the TOP1 enzyme catalytic site in the closed conformation.

Copper(II) and silver(I)-1,10-phenanthroline-5,6-dione complexes interact with double-stranded DNA: further evidence of their apparent multi-modal activity towards Pseudomonas aeruginosa

Tackling microbial resistance requires continuous efforts for the development of new molecules with novel mechanisms of action and potent antimicrobial activity. Our group has previously identified metal-based compounds, [Ag(1,10-phenanthroline-5,6-dione)2]ClO4 (Ag-phendione) and [Cu(1,10-phenanthroline-5,6-dione)3](ClO4)2.4H2O (Cu-phendione), with efficient antimicrobial action against multidrug-resistant species. Herein, we investigated the ability of Ag-phendione and Cu-phendione to bind with double-stranded DNA using a combination of in silico and in vitro approaches. Molecular docking revealed that both phendione derivatives can interact with the DNA by hydrogen bonding, hydrophobic and electrostatic interactions. Cu-phendione exhibited the highest binding affinity to either major (− 7.9 kcal/mol) or minor (− 7.2 kcal/mol) DNA grooves. In vitro competitive quenching assays involving duplex DNA with Hoechst 33258 or ethidium bromide demonstrated that Ag-phendione and Cu-phendione preferentially bind DNA in the minor grooves. The competitive ethidium bromide displacement technique revealed Cu-phendione has a higher binding affinity to DNA (Kapp = 2.55 × 106 M−1) than Ag-phendione (Kapp = 2.79 × 105 M−1) and phendione (Kapp = 1.33 × 105 M−1). Cu-phendione induced topoisomerase I-mediated DNA relaxation of supercoiled plasmid DNA. Moreover, Cu-phendione was able to induce oxidative DNA injuries with the addition of free radical scavengers inhibiting DNA damage. Ag-phendione and Cu-phendione avidly displaced propidium iodide bound to DNA in permeabilized Pseudomonas aeruginosa cells in a dose-dependent manner as judged by flow cytometry. The treatment of P. aeruginosa with bactericidal concentrations of Cu-phendione (15 µM) induced DNA fragmentation as visualized by either agarose gel or TUNEL assays. Altogether, these results highlight a possible novel DNA-targeted mechanism by which phendione-containing complexes, in part, elicit toxicity toward the multidrug-resistant pathogen P. aeruginosa. Graphical abstract

Análise da eficácia da combinação do bevacizumabe e irinotecano para o tratamento de tumores gliais

Os tumores gliais, ou gliomas, são o tipo mais comum de tumor cerebral e de alta incidência, sendo a maioria difusos e propensos à infiltração extensa no parênquima cerebral, causando recorrência do tumor. Os gliomas de alto grau, como os glioblastomas, são altamente angiogênicos e possuem altos níveis de fatores proangiogênicos, como o fator de crescimento endotelial vascular (VEGF), essencial para a neovascularização tumoral. O alvo para inibir o VEGF é o bevacizumabe, um anticorpo monoclonal humanizado, com associação do irinotecano, um inibidor da topoisomerase I. Dessa forma, o objetivo da seguinte revisão é analisar a eficácia da combinação do bevacizumabe e irinotecano para o tratamento de tumores gliais. Trata-se de uma revisão bibliográfica sistemática que utilizou as plataformas PubMed, SciELO e Google Scholar como base de dados para pesquisa de artigos científicos, com recorte temporal entre 2016 e 2021, na língua inglesa. De acordo com o mecanismo de busca, 3 resultados foram encontrados após os critérios de exclusão nas bases de dados PubMed e Google Scholar. Constatou-se, portanto, que a quimioterapia combinada de bevacizumabe e irinotecano é eficaz no tratamento de tumores gliais, ademais, a combinação de ambas as drogas possui maior taxa de sobrevida global do que apenas a terapia isolada do antiangiogênico bevacizumabe.

Combined Fluorescence and Optoacoustic Imaging for Monitoring Treatments against CT26 Tumors with Photoactivatable Liposomes

The newly developed multimodal imaging system combining raster-scan optoacoustic (OA) microscopy and fluorescence (FL) wide-field imaging was used for characterizing the tumor vascular structure with 38/50 μm axial/transverse resolution and assessment of photosensitizer fluorescence kinetics during treatment with novel theranostic agents. A multifunctional photoactivatable multi-inhibitor liposomal (PMILs) nano platform was engineered here, containing a clinically approved photosensitizer, Benzoporphyrin derivative (BPD) in the bilayer, and topoisomerase I inhibitor, Irinotecan (IRI) in its inner core, for a synergetic therapeutic impact. The optimized PMIL was anionic, with the hydrodynamic diameter of 131.6 ± 2.1 nm and polydispersity index (PDI) of 0.05 ± 0.01, and the zeta potential between −14.9 ± 1.04 to −16.9 ± 0.92 mV. In the in vivo studies on BALB/c mice with CT26 tumors were performed to evaluate PMILs’ therapeutic efficacy. PMILs demonstrated the best inhibitory effect of 97% on tumor growth compared to the treatment with BPD-PC containing liposomes (PALs), 81%, or IRI containing liposomes (L-[IRI]) alone, 50%. This confirms the release of IRI within the tumor cells upon PMILs triggering by NIR light, which is additionally illustrated by FL monitoring demonstrating enhancement of drug accumulation in tumor initiated by PDT in 24 h after the treatment. OA monitoring revealed the largest alterations of the tumor vascular structure in the PMILs treated mice as compared to BPD-PC or IRI treated mice. The results were further corroborated with histological data that also showed a 5-fold higher percentage of hemorrhages in PMIL treated mice compared to the control groups. Overall, these results suggest that multifunctional PMILs simultaneously delivering PDT and chemotherapy agents along with OA and FL multi-modal imaging offers an efficient and personalized image-guided platform to improve cancer treatment outcomes.

Divergent Actions of Pyruvate and ATP in Glucose-mediated Irinotecan Chemoresistance in Colorectal Cancer

Background: Altered glucose metabolism is associated with chemoresistance in colorectal cancer (CRC). The aim of this study was to illustrate the molecular mechanisms of glucose-mediated chemoresistance against irinotecan, a topoisomerase I inhibitor, focusing on the distinct roles of metabolites such as pyruvate and ATP in modulating cell death and proliferation. Methods: Four human CRC cell lines, tumorspheres, and mouse xenograft models were treated with various doses of irinotecan in the presence of high concentrations of glucose, pyruvate or ATP-encapsulated liposomes. Cell apoptosis was measured by DNA fragmentation and caspase activities, and necroptosis was evaluated by immunoprecipitation of receptor-interacting protein kinase (RIP) 1/3 complex. Cell cycles were assessed by flow cytometric analysis.Results: Human CRC cell lines treated with irinotecan in the presence of high glucose displayed increased cell viability and larger xenograft tumor sizes in mouse models compared to those treated in the presence of normal glucose. Irinotecan induced apoptosis and necroptosis, both of which were mitigated by high glucose. Liposomal ATP prevented irinotecan-induced apoptosis, while it had no effect on necroptosis. In contrast, pyruvate attenuated the RIP1/3-dependent necroptosis via free radical scavenging, without modulating apoptotic levels. Regarding the cell cycle, liposomal ATP aggravated irinotecan-induced G0/G1 shift whereas pyruvate diminished the G0/G1 shift, showing opposite effects on proliferation. Last, tumorsphere structural damage, an index of solid tumor responsiveness to chemotherapy, was determined. Liposomal ATP increased tumorsphere sizes while pyruvate prevented the deformation of spheroid mass. Conclusions: Glucose metabolites confer tumor chemoresistance via multiple modes of action. Glycolytic pyruvate attenuated irinotecan-induced necroptosis and potentiated drug insensitivity by shifting cells from a proliferative to quiescent state. On the other hand, ATP decreased irinotecan-induced apoptosis and promoted active cell proliferation, which might contribute to tumor recurrence.

High Antitumor Activity of the Dual Topoisomerase Inhibitor P8-D6 in Breast Cancer

Breast cancer constitutes the leading cause of cancer deaths among females. However, numerous shortcomings, including low bioavailability, resistance and significant side effects, are responsible for insufficient treatment. The ultimate goal, therefore, is to improve the success rates and, thus, the range available treatment options for breast cancer. Consequently, the identification, development and evaluation of potential novel drugs such as P8-D6 with seminal antitumor capacities have a high clinical need. P8-D6 effectively induces apoptosis by acting as a dual topoisomerase I/II inhibitor. This study provides an overview of the effectiveness of P8-D6 in breast cancer with both 2D monolayers and 3D spheroids compared to standard therapeutic agents. For this drug effectiveness review, cell lines and ex vivo primary cells were used and cytotoxicity, apoptosis rates and membrane integrity were examined. This study provides evidence for a significant P8-D6-induced increase in apoptosis and cytotoxicity in breast cancer cells compared to the efficacy of standard therapeutic drugs. To sum up, P8-D6 is a fast and powerful inductor of apoptosis and might become a new and suitable therapeutic option for breast cancer in the future.

Toosendanin, A Novel Late-Stage Autophagy Inhibitor Sensitizes Triple-Negative Breast Cancer to Irinotecan cChemotherapy In Vitro and In Vivo

Background: Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer that develops resistance to chemotherapy frequently. Autophagy has been regarded as a pro-survival response to chemotherapeutic drugs in TNBC, and suppression of autophagy can be a therapeutic strategy to overcome drug resistance. Methods: We verified the efficacy of TSN in blocking autophagy flux. The co-localization of autophagosomes and lysosomes was analyzed. Then, lysosome function was determined by pH value and the activity of hydrolytic proteases. For preclinical research, human triple-negative breast cancer MDA-MB-231 and MDA-MB-436 were used for evaluating the anti-proliferative effect in vitro. In vivo, the nude mice were intraperitoneal injection of irinotecan (10 mg/kg), TSN (0.5 mg/kg) or a combination. Autophagy activity and cell apoptosis were determined in tumor tissue. The degree of pathological injury of tissue was evaluated by liver index.Results: Here we reported the natural autophagy inhibitor toosendanin, a triterpenoid extracted from Melia toosenda Sieb. et Zucc, potently inhibited late-stage autophagy in TNBC cells. This effect was achieved via elevating lysosome pH rather than blocking the fusion of autophagosomes and lysosomes. We further investigated the effects of toosendanin on the in vitro and in vivo TNBC models, in combination with chemotherapeutic drug irinotecan (or its active metabolite SN-38), a topoisomerase I (TOP1) inhibitor showing therapeutic potential for TNBC. The data showed that toosendanin blocked SN-38/irinotecan-induced protective autophagy, and significantly induced apoptosis in TNBC cells and tumor xenograft models when compared to SN-38/irinotecan or TSN treatment alone group.

Functionally Active Antibodies to the Angiotensin II Type 1-Receptor Measured by a Luminometric Bioassay Do Not Correlate With Clinical Manifestations in Systemic Sclerosis: A Comparison With Antibodies to Vascular Receptors and Topoisomerase I Detected by ELISA

Objectives1) To detect functionally active antibodies(abs) to the angiotensin II type-1-receptor (AT1R) by a novel luminometric assay. 2) To assess their prevalence in systemic sclerosis (SSc), other collagen disorders, as well as in further chronic inflammatory disorders including autoimmune, toxic and chronic viral diseases. 3) To compare these abs with anti-AT1R antibodies by ELISA as well as with antibodies to endothelin-type-A receptors (ETA1) and to topoisomerase I (topo-I) with respect to their specificity and clinical relevance.MethodsSera from 98 SSc-patients, 110 patients with other chronic inflammatory rheumatic disorders, 97 patients with autoimmune liver diseases, 57 patients with toxic or chronic viral liver diseases and 36 healthy controls were analyzed. A luminometric bioassay was established with Huh-7-cells constitutively expressing the AT1R. Patients’ sera were also tested by commercially available ELISA for anti-AT1R, -ETA1- and by an in-house ELISA for anti–topo-I-abs.ResultsFifty-two percent of the SSc-patients had functionally active anti-AT1R-abs with stimulatory (34%) or inhibitory capacity (18%). They were present also in up to 59% of patients with other rheumatic diseases but only 22% of healthy individuals (sensitivity 52%, specificity 53%). The functionally active antibodies detected by the luminometric assay did not correlate with anti-AT1R-, -ETA1- or -topo-I-abs measured by ELISA, but there was a strong correlation between anti-topo-I-, AT1R-, and -ETA1-ab reactivity measured by ELISA. Sensitivities of 55%, 28% and 47% and specificities of 66%, 87%, and 99% were calculated for these anti-AT1R-, -ETA1-, and anti-topo-I-abs, respectively. Functionally active abs did not correlate with disease severity or any organ manifestation. In contrast, abs to topo-I, AT1R, and ETA1 were associated with digital ulcers, pulmonary- and esophageal manifestation.ConclusionsFunctionally active anti-AT1R-abs can be detected in SSc-patients but do not correlate with disease activity. They are not specific for this disease and occur also in other autoimmune disorders and even viral or toxic diseases. Also, the vascular antibodies detected by ELISA are not SSc-specific but correlated with disease manifestations. In contrast, anti-topo-I-abs were confirmed to be a highly specific biomarker for both, diagnosis and organ manifestations of SSc.