Diazapyrenes: interaction with nucleic acids and biological activity

The review summarizes data on the practical aspects of the interaction of nucleic acids with diazapyrene derivatives. The information on biological activity is given and the probable mechanisms underlying the action of diazapyrenes are analyzed. It contains 119 references.

Main trends in the design of semi-synthetic antibiotics of a new generation

This review summarizes main advances achieved by Russian researchers in the synthesis and characterization of semi-synthetic antibiotics of a new generation in the period from 2004 to 2019. The following classes of compounds are considered as the basis for modification: polycyclic antibacterial glycopeptides of the vancomycin group, classical macrolides, antifungal polyene macrolides, the antitumour antibiotic olivomycin A, antitumour anthracyclines and broad-spectrum antibiotics, in particular, oligomycin A, heliomycin and some other. Main trends in the design of modern anti-infective and antitumour agents over this period are considered in relation to original natural antibiotics, which have been independently discovered by Russian researchers. It is shown that a new type of hybrid structures can, in principle, be synthesized based on glycopeptides, macrolides and other antibiotics, including heterodimers containing a new benzoxaborole pharmacophore. The review addresses the influence of the length of the spacer between two antibiotic molecules on the biological activity of hybrid structures. A combination of genetic engineering techniques and methods of organic synthesis is shown to be useful for the design of new potent antifungal antibiotics based on polyenes of the amphotericin B group. Many new semi-synthetic analogues exhibit important biological properties, such as a broad spectrum of activity and low toxicity. Emphasis is given to certain aspects related to investigation of a broad range of biological activity and mechanisms of action of new derivatives.

The bibliography includes 101 references.

Effects of folic acid on the antiproliferative efficiency of doxorubicin, camptothecin and methyl methanesulfonate in MCF-7 cells by mRNA endpoints

There is a lack of consensus on whether the role of folate in cancer cells is protective or harmful. The use of folates in combination with cancer-targeting therapeutic regimens requires detailed information to ensure their safe and proper use. Therefore, we evaluated the effects of folic acid (FA) in combination with the chemotherapeutic compounds doxorubicin (DXR), camptothecin (CPT) and methyl methanesulfonate (MMS) on the growth of MCF-7 cells. The data generated from the RTCA assays demonstrated that FA did not affect proliferation in MCF-7 cells treated with DXR and CPT; however, FA reduced the efficacy of MMS treatment. RTCA data also confirmed that DXR and CPT exert their cytotoxic effects in a time-dependent manner and that CPT induced a significantly greater decrease in MCF-7 cell proliferation compared with DXR. The MTT assay failed to detect a reduction in cell proliferation in cells treated with MMS. We quantified the mRNA expression levels of genes associated with cellular stress response, cell cycle and apoptosis pathways using RT-qPCR. The addition of FA to DXR or CPT promoted a similar shift in the gene expression profile of MCF-7 cells compared with cells treated with DXR or CPT without FA; however, this shift did not alter the bioactivity of these drugs. Rather, it indicated that these drugs promoted cell death by alternative mechanisms. In contrast, the addition of FA to MMS reduced the efficacy of the drug without changing the gene expression profile. None of the genes encoding folate receptors that were analyzed were differentially expressed in cells treated with or without FA. In conclusion, supplementation with 450 μM FA was not cytotoxic to MCF-7 cells. However, the addition of FA to anti-cancer drugs must be performed cautiously as the properties of FA might lead to a reduction in drug efficacy.

Computational Study of Anticancer Drug Resistance Caused by 10 Topisomerase I Mutations, Including 7 Camptothecin Analogs and Lucanthone

Although Camptothecin and its analogs as Topoisomerase I poisons can effectively treat cancers, serious drug resistance has been identified for this class of drugs. Recent computational studies have indicated that the mutations near the active binding site of the drug can significantly weaken the drug binding and cause drug resistance. However, only Topotecan and three mutations have been previously analyzed. Here we present a comprehensive binding study of 10 Topoisomerase I mutants (N722S, N722A, D533G, D533N, G503S, G717V, T729A, F361S, G363C, and R364H) and 8 poisons including 7 Camptothecin analogs as well as a new generation Topoisomerase I drug, Lucanthone. Utilizing Glide docking followed by MMGBSA calculations, we determined the binding energy for each complex. We examine the relative binding energy changes with reference to the wild type, which are linked to the degree of drug resistance. On this set of mutant complexes, Topotecan and Camptothecin showed much smaller binding energies than a set of new Camptothecin derivatives (Lurtotecan, SN38, Gimatecan, Exatecan, and Belotecan) currently under clinical trials. We observed that Lucanthone exhibited comparable results to Topotecan and Camptothecin, indicating that it may serve as a promising candidate for future studies as a Topoisomerase I poison. Our docked results on Topotecan were also validated by a set of molecular dynamics simulations. In addition to a good agreement on the MMGBSA binding energy change, our simulation data also shows there is larger conformation fluctuation upon the mutations. These results may be utilized to further advancements of Topoisomerase I drugs that are resistant to mutations.

An In Silico Approach of Coumarin-Derived Inhibitors for Human DNA Topoisomerase I

Human topoisomerase I (Htopo I) is a vital target for anti-cancer agents; however, available anti-cancer agents are linked with several limitations. Therefore, designing novel inhibitors for Htopo I is significant. The rationale behind the current study is to identify novel coumarin inhibitors for Htopo I using in silico approaches and predict drug leads for in vitro studies. Using molecular docking and molecular dynamics, the binding affinities of 75 coumarins were compared with a known Htopo I inhibitor, topotecan. Docking studies predict three coumarins T1L25, T2L25, and T3L25 as most potent inhibitors for Htopo I. T2L25 gives the best grid score (–295 kJ mol–1), which is very comparable with that of topotecan (–302 kJ mol–1). The binding of these coumarins occurs preferentially via a planar geometry, and ligands bind at the binding site parallel to the axis of base pairing. NHCOCH3-substituted ligands are more favourable for binding when compared with the other substitute groups considered. The binding free energies calculated from molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) method imply that T3L25 possesses the highest binding affinity when compared with the other two ligands. However, T1L25 and T2L25 have comparable binding free energies according to MM-PBSA calculations. Additionally, other calculated properties also support the suitability of these three derivatives as inhibitors for Htopo I. Therefore, the current study theoretically predicts three coumarin derivatives T1L25, T2L25, and T3L25 as potent inhibitors for Htopo I. These findings could lead to exploring novel non-camptothecin inhibitors for Htopo I.

Real-Time Label-Free Direct Electronic Monitoring of Topoisomerase Enzyme Binding Kinetics on Graphene

Monolayer graphene field-effect sensors operating in liquid have been widely deployed for detecting a range of analyte species often under equilibrium conditions. Here we report on the real-time detection of the binding kinetics of the essential human enzyme, topoisomerase I interacting with substrate molecules (DNA probes) that are immobilized electrochemically on to monolayer graphene strips. By monitoring the field-effect characteristics of the graphene biosensor in real-time during the enzyme-substrate interactions, we are able to decipher the surface binding constant for the cleavage reaction step of topoisomerase I activity in a label-free manner. Moreover, an appropriate design of the capture probes allows us to distinctly follow the cleavage step of topoisomerase I functioning in real-time down to picomolar concentrations. The presented results are promising for future rapid screening of drugs that are being evaluated for regulating enzyme activity.

Catalytic cyclometallation in steroid chemistry III: Synthesis of steroidal derivatives of 5Z,9Z-dienoic acid and investigation of its human topoisomerase I inhibitory activity

Two approaches to stereoselective synthesis of steroid 5Z,9Z-dienoic acids were developed, the first one being based on the cross-cyclomagnesiation of 2-(hepta-5,6-dien-1-yloxy)tetrahydro-2H-pyran and 1,2-diene cholesterol derivatives on treatment with EtMgBr catalyzed by Cp2TiCl2, while the other involving the synthesis of esters of hydroxy steroids with (5Z,9Z)-tetradeca-5,9-dienedioic acid, prepared in two steps using homo-cyclomagnesiation of 2-(hepta-5,6-dien-1-yloxy)tetrahydro-2H-pyran as the key step. High inhibitory activity of the synthesized acids against human topoisomerase I (hTop1) was found.