Rebeccamycin derivatives as dual DNA-damaging agents and potent checkpoint kinase 1 inhibitors

Kinases and their derived inhibitors from natural products

Protein kinase dysregulation is a hallmark of many cancers, yet their tumorigenic mechanisms remain elusive despite 60 years of study. Since learning that their mechanism includes catalyzing phosphorylation of amino acids in protein substrates, researchers began devising their inhibition strategies. Initially, protein kinase inhibitors (PKIs) derived from natural products were employed despite high cytotoxicity risks. While synthetic PKIs proved less toxic, they face significant drug resistance challenges. This review examines the progress in understanding protein kinases' role in cancer, their classification and modes of action since their discovery. To illuminate the path towards less toxic yet highly effective kinase inhibitors, this study analyzes the synthesis and modification of all FDA-approved natural product derived kinase inhibitors (NPDKIs) as well as those that failed clinical trials. By providing insights into successful and unsuccessful approaches, this review also aims to advance medicinal chemistry strategies for developing more effective and safer PKIs, potentially improving cancer treatment outcomes.

Unique Carbazole-Oxadiazole Derivatives as New Potential Antibiotics for Combating Gram-Positive and -Negative Bacteria

Novel carbazole-oxadiazoles were developed as new potential antibacterial agents to combat dreadful resistance. Some target compounds displayed predominant inhibitory effects on the tested Gram-positive and -negative bacteria, and carbazole-oxadiazoles 5g, 5i-k, 16a-c, and tetrazole analogues 23b-c were found to be efficient in impeding the growth of MRSA and Pseudomonas aeruginosa ATCC 27853 (MICs = 0.25-4 μg/mL). Furthermore, compounds 5g and 23b-c not only possessed rapid bactericidal ability and low tendency to develop resistance but also exhibited low cytotoxic effects toward Hek 293T, HeLa, and red blood cells (RBCs), especially molecule 5g also showed low toxicity in vivo, which showed the therapeutic potential of these compounds. Further exploration indicated that compounds 5g, 5i, and 23b-c could disintegrate the integrity of bacterial cell membranes to leak the cytoplasmic contents, thus exerting excellent antibacterial effects. These facts mean that carbazole-based antibacterial agents might have bright prospects in confronting bacterial infections.

Sensitization to oxidative stress and G2/M cell cycle arrest by histone deacetylase inhibition in hepatocellular carcinoma cells

Oxidative stress resistance in cancer cells has contributed to multi-drug resistance, which poses a serious challenge to cancer therapy. To surmount this, combinatorial treatment involving anticancer drugs and histone deacetylase inhibitors (HDACi) have emerged as a chemotherapeutic option. Yet, HDACi's role in redox states of cancer cells still requires elucidation. In the present study, we hypothesized that HDACi sensitizes cancer cells to oxidative stress and results in G2/M cell cycle arrest. Cell viability and cell cycle were analyzed using Cell Counting Kit 8 (CCK8) and fluorescent activated cell sorting (FACS), respectively. The transcriptomes of cells were investigated by massive analysis of cDNA end (MACE). Expression of mRNA and proteins were analyzed by quantitative real-time PCR (qPCR) and Western blot, respectively. Intracellular oxidative stress induced by tert-Butyl hydroperoxide (tBHP) reduced cell viability and resulted in G2/M cell cycle arrest in a dose-dependent manner in hepatocellular carcinoma (HCC) cells. The effects of sorafenib on cell cycle arrest and HCC viability were enhanced through HDACi treatment. MACE revealed that genes related to progression of G2/M cell cycle including Foxm1, Aurka, Plk1, and Ccnb1 were significantly down-regulated in tBHP and HDACi-treated HepG2 cells. Inhibition of FOXM1 with thiostrepton also resulted in reduced cell viability and expression of FOXM1 target genes such as Aurka, Plk1, and Ccnb1. These results indicate that HDACi sensitizes HepG2 cells to oxidative stress and results in G2/M cell cycle arrest via down-regulation of FOXM1, which plays a key role in progression of G2/M cell cycle.

In situ electrochemical evaluation of dsDNA interaction with the anticancer drug danusertib nitrenium radical product using the DNA-electrochemical biosensor

Danusertib is a kinase inhibitor and anti-cancer drug. The evaluation of the interaction between danusertib and dsDNA was investigated in bulk solution and using the dsDNA-electrochemical biosensor. The dsDNA-danusertib interaction occurs in two sequential steps. First, danusertib binds electrostatically todsDNA phosphate backbone through the positively charged piperazine moiety. The second step involved the pyrrolo-pyrazolemoiety and led to small morphological modifications in the dsDNA double helix which were electrochemically characterised through the changes of guanine and adenine residue oxidation peaks and confirmed by electrophoretic and spectrophotometric measurements. The nitrenium cation radical product of danusertib amino group oxidation was electrochemically generated in situ on the dsDNA-electrochemical biosensor surface. The danusertib nitrenium cation radical redox metabolite was covalently attached to the C8 of guanine residues preventing their oxidation. An interaction mechanism of dsDNA-danusertib is proposed and the formation of the danusertib redox nitrenium radical metabolite-guanine adduct explained.

The anticancer multi-kinase inhibitor dovitinib also targets topoisomerase I and topoisomerase II

Dovitinib (TKI258/CHIR258) is a multi-kinase inhibitor in phase III development for the treatment of several cancers. Dovitinib is a benzimidazole-quinolinone compound that structurally resembles the bisbenzimidazole minor groove binding dye Hoechst 33258. Dovitinib bound to DNA as shown by its ability to increase the DNA melting temperature and by increases in its fluorescence spectrum that occurred upon the addition of DNA. Molecular modeling studies of the docking of dovitinib into an X-ray structure of a Hoechst 33258-DNA complex showed that dovitinib could reasonably be accommodated in the DNA minor groove. Because DNA binders are often topoisomerase I (EC 5.99.1.2) and topoisomerase II (EC 5.99.1.3) inhibitors, the ability of dovitinib to inhibit these DNA processing enzymes was also investigated. Dovitinib inhibited the catalytic decatenation activity of topoisomerase IIα. It also inhibited the DNA-independent ATPase activity of yeast topoisomerase II which suggested that it interacted with the ATP binding site. Using isolated human topoisomerase IIα, dovitinib stabilized the enzyme-cleavage complex and acted as a topoisomerase IIα poison. Dovitinib was also found to be a cellular topoisomerase II poison in human leukemia K562 cells and induced double-strand DNA breaks in K562 cells as evidenced by increased phosphorylation of H2AX. Finally, dovitinib inhibited the topoisomerase I-catalyzed relaxation of plasmid DNA and acted as a cellular topoisomerase I poison. In conclusion, the cell growth inhibitory activity and the anticancer activity of dovitinib may result not only from its ability to inhibit multiple kinases, but also, in part, from its ability to target topoisomerase I and topoisomerase II.

Molecular modeling study of checkpoint kinase 1 inhibitors by multiple docking strategies and prime/MM-GBSA calculation

Developing chemicals that inhibit checkpoint kinase 1 (Chk1) is a promising adjuvant therapeutic to improve the efficacy and selectivity of DNA-targeting agents. Reliable prediction of binding-free energy and binding affinity of Chk1 inhibitors can provide a guide for rational drug design. In this study, multiple docking strategies and Prime/Molecular Mechanics Generalized Born Surface Area (Prime/MM-GBSA) calculation were applied to predict the binding mode and free energy for a series of benzoisoquinolinones as Chk1 inhibitors. Reliable docking results were obtained using induced-fit docking and quantum mechanics/molecular mechanics (QM/MM) docking, which showed superior performance on both ligand binding pose and docking score accuracy to the rigid-receptor docking. Then, the Prime/MM-GBSA method based on the docking complex was used to predict the binding-free energy. The combined use of QM/MM docking and Prime/MM-GBSA method could give a high correlation between the predicted binding-free energy and experimentally determined pIC(50) . The molecular docking combined with Prime/MM-GBSA simulation can not only be used to rapidly and accurately predict the binding-free energy of novel Chk1 inhibitors but also provide a novel strategy for lead discovery and optimization targeting Chk1.