Shu-Chuan Jao

Inhibition of glutathione S-Transferase M1 by new gabosine analogues is essential for overcoming cisplatin resistance in lung cancer cells

A new class of human GST inhibitors has been identified via rational design approach; we report their discovery, synthesis, inhibitory activity, and synergetic effect in combination with cisplatin against A549 lung cancer cell line. The results of this effort show that the lead 4-O-decyl-gabosine D (24) has optimum synergetic effect in A549 human lung adenocarcinoma epithelial cell and that this activity involves inhibition of glutathione S-transferase M1, apparently consistent with siRNA-mediated knockdown of GSTM1 gene.

Aminopeptidase P Mediated Detoxification of Organophosphonate Analogues of Sarin: Mechanistic and Stereochemical Study at the Phosphorus Atom of the Substrate

The activity of the aminopeptidase P from Escherichia coli in hydrolyzing a series of organophosphonate sarin analogues (1–6) was evaluated. The enzymatic rates of hydrolysis for methylphosphonate 1 with a methoxy group attached to the phosphorus center were 7‐ to 15‐fold higher than those for the corresponding analogues 2–6. Double mutant R153W/R370L was able to hydrolyze the Sp enantiomer of racemic 1 at a considerable rate. This mutant allowed the preparation of the Rp isomer of the sarin analogue 1. All the mutants, R370L, R153A, W88L, R153L/R370L, and R153W/R370L, preferred the formation of (Sp)‐8 to that of the corresponding (Rp)‐8 enantiomer and displayed a better enantiomeric excess of products, by 1.4‐ to 2‐fold as compared to the wild‐type enzyme. Enzymatic hydrolysis of O,O‐diisopropyl‐p‐nitrophenyl phosphate (9) in H218O led to the formation of the 18O‐labeled O,O‐diisopropyl phosphate product and confirmed that the catalytic reaction starts with cleavage of the PO bond. From chemical and kinetic studies, the utilization of an optically pure Sp enantiomer of O‐methyl‐p‐nitrophenyl methylphosphonothioate ((Sp)‐MNMPT, 7) has demonstrated that the enzymatic reaction proceeds through a displacement mechanism and generates a chiral product in situ with an inversion of stereochemical configuration at the phosphorus atom. The results also lead to the conclusion that alteration of the active site through site‐directed mutagenesis can result in a preference for (Sp)‐MNMPT (7) rather than the Rp isomer.

Polyfluorinated bipyridine cisplatins manipulate cytotoxicity through the induction of S-G2/M arrest and partial intercalation mechanism.

A series of polyfluorinated bipyridine cisplatins 2-6 were prepared, characterized, and evaluated for their in vitro cytotoxicities against a panel of human cancer cell lines, MCF7 (breast adenocarcinoma), MDA-MB-231 (breast adenocarcinoma) and A549 (lung adenocarcinoma). The results show that a correlation between the relative order of lipophilicity of complexes 2-4 and their cytotoxicity is established by following the trend: 4>2>3. Complex 4, which is the most active compound in the series, was found to be a more effective and selective anticancer agent than cisplatin. Complex 4 inhibited cancer cell proliferation by partial intercalation to DNA, which subsequently resulted in induction of S-G2/M arrest and apoptosis.

Overcoming the drug resistance in breast cancer cells by rational design of efficient glutathione S-transferase inhibitors.

A new type of competitive human GST inhibitors has been developed via the bioisostere and structure activity profile strategies; we report their discovery, preparation, inhibitory activity, and synergetic effect in combination with chemotherapy drugs against breast cancer cells.

Synthesis and Evaluation of the Cytotoxicities of Tetraindoles: Observation that the 5-Hydroxy Tetraindole (SK228) Induces G2 Arrest and Apoptosis in Human Breast Cancer Cells

Current chemical and biological interest in indole-3-carbinol (I3C) and its metabolites has resulted in the discovery of new biologically active indoles. As part of a program aimed at the development of indole analogues, tetraindoles 1-15 were prepared and their antiproliferative effects on human breast cancer cells were evaluated. The results show that the 5-hydroxy-tetraindole 8 (SK228) has optimum antiproliferative activity against breast adenocarcinoma (MCF 7 and MDA-MB-231) cells and that this activity involves G(2)-phase arrest of the cell cycle with a distinctive increase in the expression of cyclin B1 and phospho-cdc2. Further observations suggest that 5-hydroxy-tetraindole 8 induces apoptosis through externalization of membrane phosphatidylserine, DNA fragmentation, and activation of caspase-3. Given the fact that I3C and its metabolites have been shown to improve therapeutic efficacy and to have a broad range of antitumor activities in human cancer cells, the current findings have important pharmacological relevance as they open a promising route to the development of a potential chemotherapeutic application of tetraindoles as agents for the treatment of breast cancer.

The Calcium‐Chelating Capability of Tetrahydrofuranic Moieties Modulates the Cytotoxicity of Annonaceous Acetogenins

Annonaceous acetogenins (AGEs) are potential phytochemicals of herbal medicines and exhibit a wide variety of biological activities. Recent work has demonstrated that AGEs have a cytotoxic potency comparable to that of Taxol. AGEs belong to a unique class of polyketides with a C35 or C37 aliphatic chain terminated by an a,b-unsaturated g-lactone group on one end and interrupted mid-chain by one or two tetrahydrofuran (THF) rings with hydroxy groups (Scheme 1). Both structural groups have been recognized as the pharmacophores that block electron transport in mitochondrial complex I. Efforts to clarify the targeting and mechanism of AGEs include altering the space between two moieties, removing either one of two critical moieties (DLac acetogenins or muricatacin), mimicking the THF moieties by ether linkage, connecting a fluorescent group at the end of the aliphatic chain or with a hydroxy group, or replacing the g-lactone moiety by a fluorescent group. Hemisynthetic and proteomic techniques to clarify the mechanism underlying the action of AGEs have suggested some cytosolic and reticulum-

Synthesis and structure-activity relationships of novel furazan-3,4-diamide analogs as potent anti-cancer agents

This study describes the synthesis and structure-activity relationships of a series of furazan-3,4-diamide analogs. 1,2,5-Oxadiazole ring and electron-withdrawing substituent on the phenyl ring are proposed to be the important elements which contribute to a significant extent maximal potency of anti-proliferation effect.

Evaluation of organophosphorus chemicals-degrading enzymes: a comparison of Escherichia coli and human cytosolic aminopeptidase P.

An enzyme capable of hydrolyzing organophosphate compounds is of biological as well as environmental significance. We evaluated the possibility of human cytosolic aminopeptidase P (hcAMPP) as an attractive bioscavenger candidate by measuring the enzymatic rates of hydrolysis for a wide variety of organophosphorus compounds. The comparison of substrate specificity exhibited by hcAMPP and E. coli aminopeptidase P (E. coli AMPP) was studied.

Investigation of the proton relay system operative in human cystosolic aminopeptidase P

Aminopeptidase P, a metalloprotease, targets Xaa-Proline peptides for cleavage [1–4]. There are two forms of human AMPP, a membrane-bound form (hmAMPP) and a soluble cytosolic form (hcAMPP)[5]. Similar to the angiotensin-I-converting enzyme, AMPP plays an important role in the catabolism of inflammatory and vasoactive peptides, known as kinins. The plasma kinin, bradykinin, was used as the substrate to conduct enzymatic activity analyses and to determine the Michaelis constant (Km) of 174 μM and the catalytic rate constant (kcat) of 10.8 s-1 for hcAMPP. Significant differences were observed in the activities of Y527F and R535A hcAMPP mutants, which displayed a 6-fold and 13.5-fold for decrease in turnover rate, respectively. Guanidine hydrochloride restored the activity of R535A hcAMPP, increasing the kcat/Km 20-fold, yet it had no impact on the activities of the wild-type or Y527F mutant hcAMPPs. Activity restoration by guanidine derivatives followed the order guanidine hydrochloride >> methyl-guanidine > amino-guanidine > N-ethyl-guanidine. Overall, the results indicate the participation of R535 in the hydrogen bond network that forms a proton relay system. The quaternary structure of hcAMPP was determined by using analytical ultracentrifugation (AUC). The results show that alanine replacement of Arg535 destabilizes the hcAMPP dimer and that guanidine hydrochloride restores the native monomer-dimer equilibrium. It is proposed that Arg535 plays an important role in hcAMMP catalysis and in stabilization of the catalytically active dimeric state.