Edwige Nicolle

Antimitotic and antiproliferative activities of chalcones: forward structure-activity relationship

A series of 59 chalcones was prepared and evaluated for the antimitotic effect against K562 leukemia cells. The most active chalcones were evaluated for their antiproliferative activity against a panel of 11 human and murine cell cancer lines. We found that three chalcones were of great interest as potential antimitotic drugs. In vivo safety studies conducted on one of the most active chalcones revealed that the compound was safe, allowing further in vivo antitumor evaluation.

Discovery of Naturally Occurring Aurones That Are Potent Allosteric Inhibitors of Hepatitis C Virus RNA-Dependent RNA Polymerase

We have identified naturally occurring 2-benzylidenebenzofuran-3-ones (aurones) as new templates for non-nucleoside hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) inhibitors. The aurone target site, identified by site-directed mutagenesis, is located in thumb pocket I of HCV RdRp. The RdRp inhibitory activity of 42 aurones was rationally explored in an enzyme assay. Molecular docking studies were used to determine how aurones bind to HCV RdRp and to predict their range of inhibitory activity. Seven aurone derivatives were found to have potent inhibitory effects on HCV RdRp, with IC(50) below 5 μM and excellent selectivity index (inhibition activity versus cellular cytotoxicity). The most active aurone analogue was (Z)-2-((1-butyl-1H-indol-3-yl)methylene)-4,6-dihydroxybenzofuran-3(2H)-one (compound 51), with an IC(50) of 2.2 μM. Their potent RdRp inhibitory activity and their low toxicity make these molecules attractive candidates as direct-acting anti-HCV agents.

QSAR analysis and molecular modeling of ABCG2-specific inhibitors ☆

In addition to its critical role is controlling drug availability and protecting sensitive organs and stem cells through cellular detoxification, breast cancer resistance protein (BCRP/ABCG2) plays an important role in cancer cell resistance to chemotherapy, together with P-glycoprotein/ABCB1. A main approach to abolish multidrug resistance is to find out specific inhibitors of the drug-efflux activity, able to chemosensitize cancer cell proliferation. Many efforts have been primarily focused on ABCB1, discovered thirty years ago, whereas very few studies have concerned ABCG2, identified much more recently. This review describes the main types of inhibitors presently known for ABCG2, and how quantitative structure-activity relationship analysis among series of compounds may lead to build up molecular models and pharmacophores allowing to design lead inhibitors as future candidates for clinical trials. A special attention is drawn on flavonoids which constitute a structurally-diverse class of compounds, well suited to identify potent ABCG2-specific inhibitors.

Breast cancer resistance protein (BCRP/ABCG2): new inhibitors and QSAR studies by a 3D linear solvation energy approach.

A series of compounds derived from naturally occurring flavonoids and synthetic analogs have been evaluated on cell lines overexpressing the wild-type breast cancer resistance protein (BCRP/ABCG2) half-transporter. Human ABCG2-transfected cells were used for screening their inhibitory activity. Five new natural compounds obtained from Morus mesozygia Stapf and one synthetic chromone, comprising a flavonoidic scaffold, were also evaluated. Based on the results obtained with a total of 34 compounds, a 3D linear solvation energy QSAR was investigated by VolSurf descriptors of molecular-interaction fields (MIFs) related to hydrophobic-interaction forces, polarisability and hydrogen-bonding capacity. Accuracy of the constructed 3D-QSAR model was attested by a correlation coefficient r(2) of 0.77. Shape parameters and hydrophobicity were revealed to be major physicochemical parameters responsible for the inhibition activity of flavonoid derivatives and synthetic analogs towards ABCG2, whereas hydrogen-bond donor capacity appeared highly unfavorable.

A 3D linear solvation energy model to quantify the affinity of flavonoid derivatives toward P-glycoprotein

P-glycoprotein (Pgp/ABCB1) both accounts for multidrug resistance (MDR) in chemotherapy and contributes to reduce oral bioavailability and brain distribution of drugs. Flavonoids, reported as potent Pgp inhibitors, are able to bind to the cytosolic ATP-binding site and a vicinal hydrophobic pocket. In order to explore the interaction forces governing the affinity of flavonoids towards Pgp, the 3D quantitative structure-activity relationship (QSAR) approach was used to analyze a set of flavonoid derivatives. The variation of affinity towards Pgp was investigated by VolSurf descriptors of Molecular Interaction Fields (MIFs) related to hydrophobic interaction forces, polarizability, and hydrogen-bonding capacity. The 3D linear solvation energy VolSurf model developed here identifies shape parameters and hydrophobicity as the major physicochemical parameters responsible for the affinity of flavonoid derivatives towards Pgp and hydrogen-bonding capacities as minor modulators of this activity. Furthermore, this predictive model (q(2) of 0.71) was also validated by use of an external set of 10 flavones.

Targeting the Multidrug ABCG2 Transporter with Flavonoidic Inhibitors: In Vitro Optimization and In Vivo Validation

This review describes the breast cancer resistance protein ABCG2 through its structure, functional roles and involvement in cell multidrug resistance, especially in cancer cells resistance to chemotherapeutics. The different types of known inhibitors are described, some being non-selective, since they also bind to other targets, and others being quite specific such as flavonoids. The different classes of active flavonoids and other polyphenols are described, some as plant natural compounds, but most of them being prepared and derivatized through medicinal chemistry. Quantitative structure-activity relationships of the ability of flavones, chalcones, xanthones, acridones and various benzopyrane/benzofurane derivatives to inhibit ABCG2-mediated drug efflux have led to pharmacophores and molecular models allowing to optimize the available hit compounds and to design new-generation lead compounds. Interestingly, inhibitory flavonoids are quite specific for ABCG2 versus ABCB1 and ABCC1, and appear either non-competitive or partially competitive towards mitoxantrone efflux. Most compounds do not inhibit ATPase activity, and are assumed not to be transported themselves by the transporter. Some acridones, firstly optimized in vitro as potent inhibitors, are indeed efficient in vivo, against human xenografts in SCID mice, more efficiently than gefitinib taken as a control. Future developments should open the way to more efficient/targeted modulators including (i) the potential interest of bimodulation by combining two different inhibitors, (ii) computer-assisted ligand-based drug design for getting more potent and more specific inhibitors, (iii) structure-based drug design from ABCG2 molecular models allowing in silico screening and docking of new inhibitors.

Identification of xanthones as selective killers of cancer cells overexpressing the ABC transporter MRP1.

Multidrug‐resistance protein 1 (MRP1) belongs to the ATP‐binding cassette (ABC) transporter family. MRP1 mediates MDR (multidrug resistance) by causing drug efflux either by conjugation to glutathione (GSH) or by co‐transport with free GSH (without covalent bonding between the drug and GSH). We recently reported that the calcium channel blocker verapamil can activate massive GSH efflux in MRP1‐overexpressing cells, leading to cell death through apoptosis. However, clinical use of verapamil is hampered by its cardiotoxicity. Then, in the search for compounds that act similarly to verapamil, but without major side effects, we investigated xanthones. Herein we show that xanthones induce apoptosis among resistant cells overexpressing MRP1 similarly to the verapamil effect. Among the xanthones studied, 1,3‐dihydroxy‐6‐methoxyxanthone was identified as the most active derivative, able to specifically kill cells transfected with human MRP1 with even greater potency than verapamil. Under the same conditions, the active xanthones have no toxic effect on control (sensitive) cells. Xanthones could therefore be considered as new potential anticancer agents for the selective treatment of MRP1‐positive tumors.

New series of aryloxypropanolamines with both human β3-adrenoceptor agonistic activity and free radical scavenging properties

A series of 13 novel hybrid molecules designed to possess both free radical scavenging activity and to stimulate the beta(3)-adrenoceptors in order to improve antidiabetic effect and to restore insulin sensitivity was synthesized and evaluated. Compounds were of quinolyl-, isoquinolyl-, pyridoindolyl- or carbazolyloxypropanolamine structure with a terminal amino group of benzopyranolyl-, di-tert-butylphenolyl- or methoxyindolyl-type. Some of the products possessed both the expected activities.

The PAMPA technique as a HTS tool for partition coefficients determination in different solvent/water systems

1,2-dichloroethane (DCE) and o-nitrophenyl octyl ether (o-NPOE), were tested for their ability to form artificial membranes immobilized on polycarbonate (PC) and polyvinylidene fluoride (PVDF) supporting filters using the PAMPA (parallel artificial membrane permeability assays) technique. These detailed studies provided important information on the application domain of the artificial membranes investigated. According to the nature of the organic solvent and the composition of the filter, different permeation behaviours were noted. A double permeation pathway was observed for DCE-coated with PVDF filters since hydrophilic compounds permeated the membrane through aqueous pores created by the interaction of DCE and PVDF filters, while the more lipophilic compounds were trapped in the DCE present on filters. On the other hand, the permeation through PVDF and PC filters coated with o-NPOE did not follow the same mechanisms. An interesting application emerged from these mechanistic studies, namely the use of PC filters for a first high throughput assay designed to measure o-NPOE/water partition coefficients.

Syntheses and molecular structures of 3-N,N-di-n-Propylamino-2-chromanones as new analogues of dopamine

A series of 3-N,N-di-n-propylamino-2-chromanones were synthesized as dopamine analogues. The lactone ring was introduced as a means to reduce their propensity to cross the blood-brain barrier and to avoid central side effects, rendering these compounds potentially useful for the treatment of glaucoma. Pharmacological activities were determined in vitro on rat striatum, by examining their capacity to displace the specific binding of the labeled dopaminergic ligand 3H sulpiride or 3H spiperone and 3H SCH 23390 for D2 and D1 sites, respectively. Compound 6a showed a weak dopaminergic activity on D2-receptors and no affinity for D1-receptors, which can be explained, at least in part, by a weak pKa and the presence of an internal hydrogen bonding. Furthermore, computer molecular modelling studies showed that the aromatic ring of 6a was negatively charged in contrast to the classical D2-agonists aminotetralin derivatives, hampering a possible interaction with a negatively charged area of the D2-receptor. These results, taken together, can account for the moderate dopaminergic activities exhibited by these lactone derivatives.