A New 1,2-Naphthoquinone Derivative with Anti-lung Cancer Activity.

1,2-Naphthoquinone (2-NQ) is a nucleophile acceptor that non-selectively makes covalent bonds with cysteine residues in various cellular proteins, and is also found in diesel exhaust, an air pollutant. This molecule has rarely been considered as a pharmacophore of bioactive compounds, in contrast to 1,4-naphthoquinone. We herein designed and synthesized a compound named N-(7,8-dioxo-7,8-dihydronaphthalen-1-yl)-2-methoxybenzamide (MBNQ), in which 2-NQ was hybridized with the nuclear factor-κB (NF-κB) inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) as a nucleophile acceptor. Although 50 µM MBNQ did not inhibit NF-κB signaling, 10 µM MBNQ induced cell death in the lung cancer cell line A549, which was insensitive to 2-NQ (10 µM). In contrast, MBNQ was less toxic in normal lung cells than 2-NQ. A mechanistic study showed that MBNQ mainly induced apoptosis, presumably via the activation of p38 mitogen-activated protein kinase (MAPK). Collectively, the present results demonstrate that the introduction of an appropriate substituent into 2-NQ constitutes a new biologically active entity, which will lead to the development of 2-NQ-based drugs.

Development of chimeric receptor activator of nuclear factor-kappa B with glutathione S-transferase in the extracellular domain: Artificial switch in a membrane receptor.

Various chimeric receptors have been developed and used for biological experiments. In the present study, we constructed three types of chimeric receptor activator of nuclear factor-kappa B (RANK) with the glutathione S-transferase (GST) protein in the extracellular domain, and stimulated them using newly synthesized chemical trimerizers with three glutathiones. Although this stimulation did not activate these proteins, we unexpectedly found that the chimera named RANK-GST-SC, in which GST replaced a major part of the RANK extracellular domain, activated nuclear factor-kappa B (NF-κB) signaling approximately sixfold more strongly than wild-type RANK without the ligand. The dimerization of extracellular GST is considered to function as a switch outside the cell, and signal transduction then occurs. GST has been widely employed as a tag for protein purification; GST-fusion protein can be conveniently captured by glutathione-conjugated beads and easily purified from impurity. The present study is a pioneering example of the novel utility of GST and provides information for the development of new chemical biology systems.

Interruption of Vif/Elongin C interaction: In silico and experimental elucidation of the underlying molecular mechanism of benzimidazole-based APOBEC3G stabilizers.

In 2014, two novel and promising benzimidazole-based APOBEC3G stabilizers MM-1 and MM-2 (MMs) were uncovered with an elusive mechanism of action. Vif-APOBEC3G axis has been recognized as a novel therapeutic target for anti HIV-1 drug development. The unexplored mechanism of MMs hindered their further development into lead compounds. To recognize their underlying mechanism we adopted an exhaustive in silico workflow by which we tested their ability to interrupt Vif complex network formation. The preliminary outcome guided us to a high likelihood of MMs interaction within Elongin C binding site, which in turn, perturbs Vif/Elongin C binding and ultimately undermines Vif action. To validate our estimation, we synthesized only MM-1 as a model to complement our study by in vitro assay for a real-time understanding. An immunoprecipitation experiment confirmed the capacity of MM-1 to interrupt Vif/Elongin C interaction. This is an integral study that lies at the interface between theoretical and experimental approaches showing the potential of molecular modelling to address issues related to drug development.

HSP70 induction by bleomycin metal core analogs.

Induction of heat shock protein 70 (HSP70) is known to be effective against various diseases. We are interested in HSP70 induction capability of an antitumor antibiotic bleomycin which produces oxidative stress by iron chelate formation and oxygen activation in a cell. The HSP70 induction activity of bleomycin and its six metal core analogs was examined, and a compound HPH-1Trt of 10 µM was found to induce this protein in a pheochromocytoma cell line and some T cell and monocytic cell lines. Its mechanism is increase of HSP70 mRNA, but higher concentration of this compound showed toxicity. Two new derivatives were then synthesized, and one of them named DHPH-1Trt was shown to have less toxicity and higher HSP70 induction activity. This study would lead to a clue for new HSP70 inducer clinically used in near future.

Novel metal chelating molecules with anticancer activity. Striking effect of the imidazole substitution of the histidine-pyridine-histidine system.

Previously we have reported a metal chelating histidine-pyridine-histidine system possessing a trityl group on the histidine imidazole, namely HPH-2Trt, which induces apoptosis in human pancreatic adenocarcinoma AsPC-1 cells. Herein the influence of the imidazole substitution of HPH-2Trt was examined. Five related compounds, HPH-1Trt, HPH-2Bzl, HPH-1Bzl, HPH-2Me, and HPH-1Me were newly synthesized and screened for their activity against AsPC-1 and brain tumor cells U87 and U251. HPH-1Trt and HPH-2Trt were highly active among the tested HPH compounds. In vitro DNA cleavage assay showed both HPH-1Trt and HPH-2Trt completely disintegrate pUC19 DNA. The introduction of trityl group decisively potentiated the activity.

l-Histidyl-glycyl-glycyl-l-histidine. Amino-acid structuring of the bleomycin-type pentadentate metal-binding environment capable of efficient double-strand cleavage of plasmid DNA.

A tetrapeptide, l-histidyl-glycyl-glycyl-l-histidine (HGGH), was synthesized and the pUC19 plasmid DNA cleaving activity by copper(II) complex of HGGH (Cu(II)-HGGH) was investigated. Cu(II)-HGGH showed bleomycin-like DNA cleaving activity and, at 50nM, converted a supercoiled DNA efficiently to a linear DNA in the presence of 500µM H2O2/sodium ascorbate through an oxidative pathway.