A G-quadruplex-binding compound shows potent activity in human gemcitabine-resistant pancreatic cancer cells.

Gemcitabine is a drug of choice in the treatment of human pancreatic cancer. Chemo-resistance to this drug is common and has been attributed to a variety of distinct mechanisms, involving > 100 genes. A recently developed small-molecule G-quadruplex ligand, the trisubstituted naphthalene diimide compound CM03, has previously been shown to have equivalent potency to gemcitabine in the pancreatic cancer cell line MIA PaCa-2.

Substituted Naphthalenediimide Compounds Bind Selectively to Two Human Quadruplex Structures with Parallel Topology.

Interactions are reported of three representative naphthalenediimide derivatives with three quadruplex targets, from the promoter region of the telomerase (hTERT) gene, a human telomeric DNA quadruplex, and a telomeric RNA quadruplex (TERRA). Thermal melting studies showed that these compounds strongly stabilize the quadruplexes, with weak stabilization of a duplex DNA. Binding studies by surface plasmon resonance and fluorescence spectroscopy found that the compounds bind to the quadruplexes with nanomolar equilibrium dissociation constants.

Targeting Multiple Effector Pathways in Pancreatic Ductal Adenocarcinoma with a G-Quadruplex-Binding Small Molecule.

Human pancreatic ductal adenocarcinoma (PDAC) involves the dysregulation of multiple signaling pathways. A novel approach to the treatment of PDAC is described, involving the targeting of cancer genes in PDAC pathways having over-representation of G-quadruplexes, using the trisubstituted naphthalene diimide quadruplex-binding compound 2,7-bis(3-morpholinopropyl)-4-((2-(pyrrolidin-1-yl)ethyl)amino)benzo[ lmn][3,8]phenanthroline-1,3,6,8(2 H,7 H)-tetraone (CM03). This compound has been designed by computer modeling, is a potent inhibitor of cell growth in PDAC cell lines, and has anticancer activity in PDAC models, with a superior profile compared to gemcitabine, a commonly used therapy.

Toward the Development of Specific G-Quadruplex Binders: Synthesis, Biophysical, and Biological Studies of New Hydrazone Derivatives.

G-Quadruplex-binding compounds are currently perceived as possible anticancer therapeutics. Here, starting from a promising lead, a small series of novel hydrazone-based compounds were synthesized and evaluated as G-quadruplex binders. The in vitro G-quadruplex-binding properties of the synthesized compounds were investigated employing both human telomeric and oncogene promoter G-quadruplexes with different folding topologies as targets.

A G-quadruplex-binding compound showing anti-tumour activity in an in vivo model for pancreatic cancer.

We report here that a tetra-substituted naphthalene-diimide derivative (MM41) has significant in vivo anti-tumour activity against the MIA PaCa-2 pancreatic cancer xenograft model. IV administration with a twice-weekly 15 mg/kg dose produces ca 80% tumour growth decrease in a group of tumour-bearing animals. Two animals survived tumour-free after 279 days.

Targeting KRAS Oncogene in Colon Cancer Cells with 7-Carboxylate Indolo[3,2-b]quinoline Tri-Alkylamine Derivatives.

Background: A guanine-rich strand within the promoter of the KRAS gene can fold into an intra-molecular G-quadruplex structure (G4), which has an important role in the regulation of KRAS transcription. We have previously identified indolo[3,2-b]quinolines with a 7-carboxylate group and three alkylamine side chains (IQ3A) as effective G4 stabilizers and promising selective anticancer leads. Herein we investigated the anticancer mechanism of action of these compounds, which we hypothesized due to stabilization of the G4 sequence in the KRAS promoter and subsequent down-regulation of gene expression.

Synthesis and Initial in Vivo Studies with [(11)C]SB-216763: The First Radiolabeled Brain Penetrative Inhibitor of GSK-3.

Quantifying glycogen synthase kinase-3 (GSK-3) activity in vivo using positron emission tomography (PET) imaging is of interest because dysregulation of GSK-3 is implicated in numerous diseases and neurological disorders for which GSK-3 inhibitors are being considered as therapeutic strategies. Previous PET radiotracers for GSK-3 have been reported, but none of the published examples cross the blood-brain barrier. Therefore, we have an ongoing interest in developing a brain penetrating radiotracer for GSK-3.

Macrocyclic naphthalene diimides as G-quadruplex binders.

The synthesis, biological and molecular modeling evaluation of a series of macrocyclic naphthalene diimides is reported. The present investigation expands on the study of structure-activity relationships of prototype compound 2 by constraining the molecule into a macrocyclic structure with the aim of improving its G-quadruplex binding activity and selectivity. The new derivatives, compounds 4-7 carry spermidine- and spermine-like linkers while in compound 8 the inner basic nitrogen atoms of spermine have been replaced with oxygen atoms.

KRAS oncogene repression in colon cancer cell lines by G-quadruplex binding indolo[3,2-c]quinolines.

KRAS is one of the most frequently mutated oncogenes in human cancer, yet remaining undruggable. To explore a new therapeutic strategy, a library of 5-methyl-indolo[3,2-c]quinoline derivatives (IQc) with a range of alkyldiamine side chains was designed to target DNA and RNA G-quadruplexes (G4) in the promoter and 5'-UTR mRNA of the KRAS gene. Biophysical experiments showed that di-substituted IQc compounds are potent and selective KRAS G4 stabilizers.

Indolo[3,2-c]quinoline G-quadruplex stabilizers: a structural analysis of binding to the human telomeric G-quadruplex.

A library of 5-methylindolo[3,2-c]quinolones (IQc) with various substitution patterns of alkyldiamine side chains were evaluated for G-quadruplex (G4) binding mode and efficiency. Fluorescence resonance energy transfer melting assays showed that IQcs with a positive charge in the heteroaromatic nucleus and two weakly basic side chains are potent and selective human telomeric (HT) and gene promoter G4 stabilizers. Spectroscopic studies with HT G4 as a model showed that an IQc stabilizing complex involves the binding of two IQc molecules (2,9-bis{[3-(diethylamino)propyl]amino}-5-methyl-11H-indolo[3,2-c]quinolin-5-ium chloride, 3 d) per G4 unit, in two non-independent but equivalent binding sites.

Small-molecule quadruplex-targeted drug discovery.

Repeated guanine tracts in human and other genomes can form higher-order four stranded structures, termed quadruplexes. In the human genome they have particular prevalence in telomeric and promoter regions and also in 5'-UTRs and introns. These structures, if unresolved and stabilised by small molecules, can form impediments to transcription and translation, and thus can be considered as a form of gene targeting.

Discovery of new G-quadruplex binding chemotypes.

We report here on the discovery and preliminary evaluation of a novel non-macrocyclic low molecular weight quadruplex-stabilizing chemotype. The lead compounds, based on a furan core, show high G-quadruplex stabilisation and selectivity as well as potent in vitro anti-proliferative activity.

Xanthene and xanthone derivatives as G-quadruplex stabilizing ligands.

Following previous studies on anthraquinone and acridine-based G-quadruplex ligands, here we present a study of similar aromatic cores, with the specific aim of increasing G-quadruplex binding and selectivity with respect to duplex DNA. Synthesized compounds include two and three-side chain xanthone and xanthene derivatives, as well as a dimeric "bridged" form. ESI and FRET measurements suggest that all the studied molecules are good G-quadruplex ligands, both at telomeres and on G-quadruplex forming sequences of oncogene promoters.

Optimization of anti-proliferative activity using a screening approach with a series of bis-heterocyclic G-quadruplex ligands.

Using a phenotypic screening and SAR optimization approach, a phenyl-bis-oxazole derivative has been identified with anti-proliferative activity, optimized with the use of a panel of cancer cell lines. The lead compound was synthesized by means of a short and effective two-step synthesis using Pd-catalyzed direct arylation. The compound stabilizes several quadruplex DNA sequences including a human telomeric DNA and one from the promoter of the HSP90 gene, although the structure-activity relationships of the series are not obviously related to the quadruplex binding.

Synthesis, G-quadruplex stabilisation, docking studies, and effect on cancer cells of indolo[3,2-b]quinolines with one, two, or three basic side chains.

G-quadruplex (G4) DNA structures in telomeres and oncogenic promoter regions are potential targets for cancer therapy, and G4 ligands have been shown to modulate telomerase activity and oncogene transcription. Herein we report the synthesis and G4 thermal stabilisation effects, determined by FRET melting assays, of 20 indolo[3,2-b]quinolines mono-, di-, and trisubstituted with basic side chains. Molecular modelling studies were also performed in an attempt to rationalise the ligands' binding poses with G4.

The influence of positional isomerism on G-quadruplex binding and anti-proliferative activity of tetra-substituted naphthalene diimide compounds.

The synthesis together with biophysical and biological evaluation of a series of tetra-substituted naphthalene diimide (ND) compounds, are presented. These compounds are positional isomers of a recently-described series of quadruplex-binding ND derivatives, in which the two N-methyl-piperidine-alkyl side-chains have now been interchanged with the positions of side-chains bearing a range of end-groups. Molecular dynamics simulations of a pair of positional isomers are in accord with the quadruplex stabilization and biological data for these compounds.

Structure-based design and evaluation of naphthalene diimide G-quadruplex ligands as telomere targeting agents in pancreatic cancer cells.

Tetra-substituted naphthalene diimide (ND) derivatives with positively charged termini are potent stabilizers of human telomeric and gene promoter DNA quadruplexes and inhibit the growth of human cancer cells in vitro and in vivo. The present study reports the enhancement of the pharmacological properties of earlier ND compounds using structure-based design. Crystal structures of three complexes with human telomeric intramolecular quadruplexes demonstrate that two of the four strongly basic N-methyl-piperazine groups can be replaced by less basic morpholine groups with no loss of intermolecular interactions in the grooves of the quadruplex.

Downregulation of androgen receptor transcription by promoter g-quadruplex stabilization as a potential alternative treatment for castrate-resistant prostate cancer.

Androgen receptor (AR) signaling remains an important regulatory pathway in castrate-resistant prostate cancer, and its transcriptional downregulation could provide a new line of therapy. A number of small-molecule ligands have previously demonstrated the ability to stabilize G-quadruplex structures and affect gene transcription for those genes whose promoters contain a quadruplex-forming sequence. Herein, we report the probable formation of new G-quadruplex structure present in the AR promoter in a transcriptionally important location.

Sequences in the HSP90 promoter form G-quadruplex structures with selectivity for disubstituted phenyl bis-oxazole derivatives.

The HSP90 protein is an important target in cancer. We report here that stable quadruplex DNAs can be formed from a promoter sequence in the HSP90 gene, on the basis of melting, circular and NMR studies, and show that these can be selectively targeted by non-macrocyclic quadruplex-stabilizing phenyl bis-oxazole derivatives. These do not bind significantly to duplex DNA and show low stabilization of the human telomeric quadruplex.

Direct arylations of 2H-indazoles on water.

The efficient palladium-catalyzed synthesis of a range of substituted 2H-Indazoles via C-H arylation is reported. Reactions are performed on water and provide a direct and mild route toward 2,3-diaryl indazoles of widespread biological significance.

Inhibition of oxidative metabolism of tocopherols with omega-N-heterocyclic derivatives of vitamin E.

The oxidative metabolism of tocopherols and tocotrienols by monooxygenases is a key factor in the plasma and tissue clearance of forms of vitamin E other than alpha-tocopherol. It is well known that a commonly ingested form of vitamin E, gamma-tocopherol, has greatly reduced plasma half-life (faster clearance) than alpha-tocopherol. The tocotrienols are metabolized even faster than gamma-tocopherol.

Direct arylations on water: synthesis of 2,5-disubstituted oxazoles balsoxin and texaline.

An efficient two-step palladium catalysed synthesis of 2,5-disubstituted oxazoles is reported.

Assignment of the 1H and 13C NMR of tocotrienols.

Vitamin E is a family of chromanols that vary by the degree of methylation of the chroman ring as well as the nature of the hydrophobic side chain at C2 that serves to anchor these lipids in biological membranes. The tocopherols contain saturated side chains, whereas the tocotrienols contain three sites of unsaturation and are derived from geranylgeranyl diphosphate. A growing interest in the unique biological activities of the tocotrienols has led us to begin syntheses of isotopically substituted forms and other derivatives that will be useful for probing the metabolism and membrane behavior of the tocotrienols.

Examining the correlations between GSK-3 inhibitory properties and anti-convulsant efficacy of valproate and valproate-related compounds.

A family of compounds based upon the chemical structure of valproate were synthesized and assayed for their ability to inhibit glycogen synthase kinase (GSK)-3 alpha and beta activity in vitro. This data is correlated to the known anti-convulsant properties of these compounds in order to determine the potential role of GSK-3 inhibition in the therapeutic efficacy of these drugs.