A novel tetrazole analogue of resveratrol is a potent anticancer agent

A series of novel tetrazole analogues of resveratrol were synthesized and evaluated for their anti-leukemic activity against an extensive panel of human cancer cell lines and against the MV4-11 AML cell line. These molecules were designed as drug-like derivatives of the resveratrol analogue DMU-212 and its cyano derivatives. Four compounds 8g, 8h, 10a and 10b exhibited LD₅₀ values of 4.60?µM, 0.02?µM, 1.46?µM, and 1.08?µM, respectively, against MV4-11 leukemia cells. The most potent compounds, 8h and 10b, were also found to be active against an extensive panel of human hematological and solid tumor cell lines; compound 8h was the most potent compound with GI₅₀ values <10?nM against more than 90% of the human cancer cell lines in the 60-cell panel. Analogues 8g, 8h, 10a and 10b were also tested for their ability to inhibit the polymerization of tubulin, and compound 8h was found to be the most potent analogue. Molecular modeling studies demonstrated that 8h binds to the colchicine binding site on tubulin. Thus, compound 8h is considered to be a lead druglike molecule from this tetrazole series of compounds.     

Barminomycin functions as a potent pre-activated analogue of Adriamycin.

The anthracycline Adriamycin is known to form adducts with DNA, but requires prior activation by formaldehyde. In contrast, the anthracycline barminomycin is also able to form adducts with DNA, but does not require activation by formaldehyde. Barminomycin, therefore, appears to function as a pre-activated form of Adriamycin. The DNA adducts formed by both anthracyclines are bound covalently to only one strand of DNA, but both also stabilise duplex DNA sufficiently that they can be detected as virtual interstrand crosslinks in heat denaturation electrophoretic crosslinking assays. The barminomycin-DNA adducts form extremely rapidly with DNA, and at exceedingly low concentrations (approximately 50-fold lower than with Adriamycin in the presence of excess formaldehyde), both characteristics consistent with barminomycin being in a pre-activated state, hence, undergoing a bimolecular reaction with DNA compared with the trimolecular reaction (drug, formaldehyde and DNA) required with Adriamycin. Surprisingly, barminomycin-DNA adducts are substantially more stable (essentially irreversible) than Adriamycin-DNA adducts (half life of approximately 25 h at 37 degrees C). Due to this understanding of the reactivity of barminomycin and its exceptional cytotoxicity (1000-fold more cytotoxic than Adriamycin), detailed structural studies of barminomycin-DNA adducts are now warranted, both in vitro and in tumour cells.     

Structures of potent anticancer compounds bound to tubulin

Small molecules that bind to tubulin exert powerful effects on cell division and apoptosis (programmed cell death). Cell‐based high‐throughput screening combined with chemo/bioinformatic and biochemical analyses recently revealed a novel compound MI‐181 as a potent mitotic inhibitor with heightened activity towards melanomas. MI‐181 causes tubulin depolymerization, activates the spindle assembly checkpoint arresting cells in mitosis, and induces apoptotic cell death. C2 is an unrelated compound previously shown to have lethal effects on microtubules in tumorigenic cell lines. We report 2.60 Å and 3.75 Å resolution structures of MI‐181 and C2, respectively, bound to a ternary complex of αβ‐tubulin, the tubulin‐binding protein stathmin, and tubulin tyrosine ligase. In the first of these structures, our crystallographic results reveal a unique binding mode for MI‐181 extending unusually deep into the well‐studied colchicine‐binding site on β‐tubulin. In the second structure the C2 compound occupies the colchicine‐binding site on β‐tubulin with two chemical moieties recapitulating contacts made by colchicine, in combination with another system of atomic contacts. These insights reveal the source of the observed effects of MI‐181 and C2 on microtubules, mitosis, and cultured cancer cell lines. The structural details of the interaction between tubulin and the described compounds may guide the development of improved derivative compounds as therapeutic candidates or molecular probes to study cancer cell division.     

Optimization of gefitinib analogues with potent anticancer activity

The interactions of gefitinib (Iressa) in EGFR are hydrogen bonding and van der Waals forces through quinazoline and aniline rings. However the morpholino group of gefitinib is poorly ordered due to its weak electron density. A series of novel piperazino analogues of gefitinib where morpholino group substituted with various piperazino groups were designed and synthesized. Most of them indicated significant anti-cancer activities against human cancer cell lines. In particular, compounds 52–54 showed excellent potency against cancer cells. Convergent synthetic approach has been developed for the synthesis of gefitinib intermediate which can lead to gefitinib as well as numerous analogues.     

Oxidant-based anticancer activity of a novel synthetic analogue of capsaicin,capsaicin epoxide

Abstract

Objectives

Plant-derived natural substances, such as capsaicin, with potent antiproliferative activity against cancer cells in vitro are considered to be promising nutraceuticals in anticancer therapy. Nevertheless, the limited systemic bioavailability of phytochemicals may raise questions regarding the physiological relevance of their phytochemical effects in vivo. Thus, the search for novel phytochemical-based substances with more efficient anticancer action is needed.

Methods

In the present study, a capsaicin analogue, namely, capsaicin epoxide, was synthesized, and its cytotoxic potential against cancer cells was evaluated and compared to that of capsaicin through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and multi-caspase assays. The abilities of capsaicin and capsaicin epoxide to induce oxidative stress were estimated using redox-sensitive fluorogenic probes: 2′,7′-dichlorodihydrofluorescein diacetate (H₂DCF-DA) and dihydroethidium.

Results

The structure and purity of the synthesized product were confirmed by nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and gas chromatography. Normal human dermal fibroblasts were not susceptible to treatment with the agent, whereas a cancer cell type-specific response was observed. Human breast carcinoma cells were found to be the most sensitive to capsaicin epoxide treatment compared with capsaicin treatment, and the action of capsaicin epoxide was oxidant based.

Discussion

Our data indicate that the antiproliferative activity of capsaicin epoxide is potentiated in vitro, when used at much lower concentrations compared with capsaicin at similar concentrations. Thus, the findings of this study may have implications for phytochemical-based anticancer drug development.     

Synthesis and characterization of a small analogue of the anticancer natural product leinamycin

Leinamycin (1) is a Streptomyces-derived natural product that displays nanomolar IC₅₀ values against human cancer cell lines. In the work described here, we report the synthesis and characterization of a small leinamycin analogue 19 that closely resembles the ‘upper-right quadrant’ of the natural product, consisting of an alicyclic 1,2-dithiolan-3-one 1-oxide heterocycle connected to an alkene by a two-carbon linker. The results indicate that this small analogue contains the core set of functional groups required to enable thiol-triggered generation of both redox active polysulfides and an episulfonium ion intermediate via the complex reaction cascade first seen in the natural product leinamycin. The small leinamycin analogue 19 caused thiol-triggered oxidative DNA strand cleavage in a manner similar to the natural product, but did not alkyate duplex DNA effectively. This highlights the central role of the 18-membered macrocycle of leinamycin in driving efficient DNA alkylation by the natural product.     

Sangivamycin, a nucleoside analogue, is a potent inhibitor of protein kinase C

Protein kinase C functions prominently in cell regulation via its pleiotropic role in signal transduction processes. Certain oncogene products resemble elements involved in transmembrane signaling, elevate cellular sn-1,2-diacylglycerol second messenger levels, and activate protein kinase C. Sangivamycin was unique among the nucleoside compounds tested in its ability to potently inhibit protein kinase C activity. Inhibition was competitive with respect to ATP for both protein kinase C and the catalytic fragment of protein kinase C prepared by trypsin digestion. Sangivamycin was a noncompetitive inhibitor with respect to histone and lipid cofactors (phosphatidylserine and diacylglycerol). Sangivamycin inhibited native protein kinase C and the catalytic fragment identically, with apparent Ki values of 11 and 15 microM, respectively. Sangivamycin was an effective an inhibitor of protein kinase C as H-7, an isoquinolinsulfonamide. Sangivamycin did not inhibit [3H]phorbol-12,13-dibutyrate binding to protein kinase C. Sangivamycin did not exert its action through the lipid binding/regulatory domain; inhibition was not affected by the presence of lipid or detergent. Unlike H-7, sangivamycin selectively inhibited protein kinase C compared to cAMP-dependent protein kinase. The discovery that protein kinase C is inhibited by sangivamycin and other antitumor agents suggests that protein kinase C may be a target for rational design of antitumor compounds.     

Synthesis of dual-action parthenolide prodrugs as potent anticancer agents

Cancer stem cells are responsible for the failure of a large number of cancer treatments and the re-emergence of cancer in patients. Parthenolide is a potent anticancer sesquiterpene lactone that is also able to kill cancer stem cells. The main problem with this compound is its poor solubility in water. To solve this problem, medicinal chemists have tried to prepare amino-derivatives of parthenolide, however, most amino-derivatives have less potency than that of parthenolide. In this paper, we proposed a new approach to synthesize parthenolide derivatives with better solubility and higher potency. We prepared novel parthenolide derivatives through the aza-Michael addition of nitrogen-containing anticancer drug molecules (cytarabine and melphalan) to the α-methylene-γ-lactone group of parthenolide. Different types of catalysts were used to catalyze the aza-Michael addition. Among all the used catalysts, 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) was found to have the highest catalytic activity. In addition, we examined the effects of parthenolide-anticancer drug hybrids on the growth and proliferation of three cancer cell lines (MCF-7, LNcaP, Hep G2) and CHO. The parthenolide prodrugs showed potent cytotoxic property with IC₅₀ values ranging from 0.2 to 5.2 μM, higher than those of parthenolide and anticancer drugs (cytarabine and melphalan).     

EB1627: a soluble prodrug of the potent anticancer cyanoguanidine CHS828

To overcome pharmacokinetic and solubility problems observed in early clinical trials with the potent anticancer compound CHS828, we synthesised a series of prodrugs with improved properties. The best compound obtained was EB1627, with a tetraethyleneglycol moiety attached to the parent drug via a carbonate linkage. This compound was found soluble enough to be given i.v. and the drug was rapidly released in vivo exerting a very potent inhibitory activity alone and in combination with known cytostatics (etoposide) in animal models in vivo.     

Identification of potent and broad-spectrum antibiotics from SAR studies of a synthetic vancomycin analogue

Dimeric vancomycin analogues based on a lead compound identified from a library of synthetic analogues of vancomycin have up to 60-fold greater activity than vancomycin against vancomycin-resistant Enterococcus faecium (VRE, VanA phenotype). Simplified analogues have also been prepared and found to maintain activity against VRE and have broad-spectrum antibiotic activity.     

Multi-chaperone-peptide-rich mixture from colo-carcinoma cells elicits potent anticancer immunity

Background: Chaperones play an important role in inducing anti-cancer immunity. To explore the probability of using chaperone-peptide-rich complexes extracted from colo-carcinoma cells as anti-cancer vaccine, we extracted and prepared chaperone-peptide-rich complexes from CT26 cells, which were subsequently investigated on anti-cancer efficacy. Methods: The crude extracts of the CT26 cells treated with heat and Trichosanthin were precipitated with salt and dialyzed to remove proteins below 50 kDa and above 300 kDa in molecular weight; the proteins with the molecular weights in 70 kDa, 90 kDa, 95 kDa, 110 kDa and 170 kDa were collected through gel filtration and SDS-PAGE. After confirmation, the purified proteins were used to determine their effects on lymphocyte proliferation, the activities of NK and CTL, tumor suppression and the tumor-bearing mouse survival. Results: The majority of the chaperone-peptides of anti-cancer immunity in CT26 cells, including HSP70-antigen peptide, HSP90-antigen peptide, gp96-antigen peptide, HSP-110 antigen peptide, HSP170-antigen peptide, was satisfactorily extracted that the multi-chaperone-peptide-rich mixtures were obtained. All the mixtures prepared could elicit lymphocyte proliferation, enhance the activities of CTL and NK, reinforce the tumor suppression and prolong the mouse survival. Conclusions: The multi-chaperone-peptide-rich mixtures could be prepared via dialysis and gel filtration combining with SDS-PAGE. Both the heat stress and Trichosanthin could induce and increase the mixtures, of which that treated by 42 °C heat and Trichosanthin was found to possess the strongest anti-cancer efficacy.     

Design of a potent anticancer lead inspired by natural products from traditional Indian medicine

Abstract

Among the plant constituents of Clerodendrum colebrookianum Walp., acteoside, martinoside, and osmanthuside β6 interact with ROCK, a drug target for cancer. In this study, aglycone fragments of these plant constituents (caffeic acid, ferulic acid, and p-coumaric acid) along with the homopiperazine ring of fasudil (standard ROCK inhibitor) were used to design hybrid molecules. The designed molecules interact with the key hinge region residue Met156/Met157 of ROCK I/II in a stable manner according to our docking and molecular dynamics simulations. These compounds were synthesized and tested in vitro in SW480, MDA-MB-231, and A-549 cancer cell lines. The most promising compound was chemically optimized to obtain a thiourea analog, 6a (IC₅₀ = 25?µM), which has >3-fold higher antiproliferative activity than fasudil (IC₅₀ = 87?µM) in SW480 cells. Treatment with this molecule also inhibits the migration of colon cancer cells and induces cell apoptosis. Further, SPR experiments suggests that the binding affinity of 6a with ROCK I protein is better than that of fasudil. Hence, the drug-like natural product analog 6a constitutes a highly promising new anticancer lead.

Communicated by Ramaswamy H. Sarma     

Development of a novel,multifunctional, membrane-interactive pyridinium salt with potent anticancer activity

The synthesis and biological evaluation of a novel pyridinium salt is reported. Initial membrane interaction with isolated phospholipid monolayers was obtained with the pyridinium salt, and two neutral analogues for comparison, and the anticancer effects of the best compound established using a cytotoxicity screening assay against glioma cells using both an established cell line and three short-term cell cultures—one of which has been largely resistant to all chemotherapeutic drugs tested to date. The results indicate that the pyridinium salt exhibits potent anticancer activity (EC₅₀s = 9.8–312.5 μM) on all cell types, including the resistant one, for a continuous treatment of 72 h. Microscopic examination of the treated cells using a trypan blue exclusion assay showed membrane lysis had occurred. Therefore, this letter highlights the potential for a new class of pyridinium salt to be developed as a much needed alternative treatment for glioma chemotherapy.     

Induction of potent antitumor CTL responses by recombinant vaccinia encoding a melan-A peptide analogue

There is considerable interest in the development of vaccination strategies that would elicit strong tumor-specific CTL responses in cancer patients. One strategy consists of using recombinant viruses encoding amino acid sequences corresponding to natural CTL-defined peptide from tumor Ags as immunogens. However, studies with synthetic tumor antigenic peptides have demonstrated that introduction of single amino acid substitutions may dramatically increase their immunogenicity. In this study we have used a well-defined human melanoma tumor Ag system to test the possibility of translating the immunological potency of synthetic tumor antigenic peptide analogues into recombinant vaccinia viruses carrying constructs with the appropriate nucleotide substitutions. Our results indicate that the use of a mutated minigene construct directing the expression of a modified melanoma tumor Ag leads to improved Ag recognition and, more importantly, to enhanced immunogenicity. Thus, recombinant vaccinia viruses containing mutated minigene sequences may lead to new strategies for the induction of strong tumor-specific CTL responses in cancer patients.     

Ethaselen: a potent mammalian thioredoxin reductase 1 inhibitor and novel organoselenium anticancer agent

Mammalian thioredoxin reductase 1 (TrxR1) is considered to be an important anticancer drug target and to be involved in both carcinogenesis and cancer progression. Here, we report that ethaselen, a novel organoselenium compound with anticancer activity, specifically binds to the unique selenocysteine-cysteine redox pair in the C-terminal active site of mammalian TrxR1. Ethaselen was found to be a potent inhibitor rather than an efficient substrate of mammalian TrxR1. It effectively inhibits wild-type mammalian TrxR1 at submicromolar concentrations with an initial mixed-type inhibition pattern. By using recombinant human TrxR1 variants and human glutathione reductase, we prove that ethaselen specifically targets the C-terminal but not the N-terminal active site of mammalian TrxR1. In A549 human lung cancer cells, ethaselen significantly suppresses cell viability in parallel with direct inhibition of TrxR1 activity. It does not, however, alter either the disulfide-reduction capability of thioredoxin or the activity of glutathione reductase. As a downstream effect of TrxR1 inactivation, ethaselen causes a dose-dependent thioredoxin oxidation and enhances the levels of cellular reactive oxygen species in A549 cells. Thus, we propose ethaselen as the first selenium-containing inhibitor of mammalian TrxR1 and provide evidence that selenium compounds can act as anticancer agents based on mammalian TrxR1 inhibition.