Joëlle Dubois

Glycopeptide dendrimer colchicine conjugates targeting cancer cells

Screening of a 65,536-member one-bead-one-compound (OBOC) combinatorial library of glycopeptide dendrimers of structure ((betaGal)(n)(+1)X(8)X(7)X(6)X(5))(2)DapX(4)X(3)X(2)X(1)(beta-Gal)(m) (betaGal=beta-galactosyl-thiopropionic acid, X(8-1)=variable amino acids, Dap=l-2,3-diaminopropionic acid, n, m=0, or 1 if X(8)=Lys resp. X(1)=Lys) for binding of Jurkat cells to the library beads in cell culture, resynthesis and testing lead to the identification of dendrimer J1 (betaGal-Gly-Arg-His-Ala)(2)Dap-Thr-Arg-His-Asp-CysNH(2) and related analogues as delivery vehicles. Cell targeting is evidenced by FACS with fluorescein conjugates such as J1F. The colchicine conjugate J1C is cytotoxic with LD(50)=1.5 microM. The beta-galactoside groups are necessary for activity, as evidenced by the absence of cell-binding and cytotoxicity in the non-galactosylated, acetylated analogue AcJ1F and AcJ1C, respectively. The pentagalactosylated dendrimer J4 betaGal(4)(Lys-Arg-His-Leu)(2)Dap-Thr-Tyr-His-Lys(betaGal)-Cys) selectively labels Jurkat cell as the fluorescein derivative J4F, but its colchicine conjugate J4C lacks cytotoxicity. Tubulin binding assays show that the colchicine dendrimer conjugates do not bind to tubulin, implying intracellular degradation of the dendrimers releasing the active drug.

A Phenotypic Assay to Identify Chikungunya Virus Inhibitors Targeting the Nonstructural Protein nsP2

Chikungunya virus (CHIKV) is a mosquito-transmitted pathogen responsible for an acute infection of abrupt onset, characterized by high fever, polyarthralgia, myalgia, headaches, chills, and rash. In 2006, CHIKV was responsible for an epidemic outbreak of unprecedented magnitude in the Indian Ocean, stressing the need for therapeutic approaches. Since then, we have acquired a better understanding of CHIKV biology, but we are still missing active molecules against this reemerging pathogen. We recently reported that the nonstructural nsP2 protein of CHIKV induces a transcriptional shutoff that allows the virus to block cellular antiviral response. This was demonstrated using various luciferase-based reporter gene assays, including a trans-reporter system where Gal4 DNA binding domain is fused to Fos transcription factor. Here, we turned this assay into a high-throughput screening system to identify small molecules targeting nsP2-mediated shutoff. Among 3040 molecules tested, we identified one natural compound that partially blocks nsP2 activity and inhibits CHIKV replication in vitro. This proof of concept suggests that similar functional assays could be developed to target other viral proteins mediating a cellular shutoff and identify innovative therapeutic molecules.

Synthesis and biological evaluation of cis-locked vinylogous combretastatin-A4 analogues: Derivatives with a cyclopropyl-vinyl or a cyclopropyl-amide bridge

A series of novel combretastatin A4 analogues, in which the cis-olefinic bridge is replaced by a cyclopropyl-vinyl or a cyclopropyl-amide moiety, were synthesized and evaluated for inhibition of tubulin polymerization and antiproliferative activity. The derivative 9a with a (cis,E)-cyclopropyl-vinyl unit is the most promising compound. As expected, molecular docking of 9a has shown that only one of the cis-cyclopropyl enantiomers is a good ligand for tubulin.

Synthesis of 5,5′-dihydroxyleucine and 4-fluoro 5,5′-dihydroxyleucine, the reduction products of 4-carboxyglutamic and 4-carboxy-4-fluoroglutamic acids

Abstract Schemes for the synthesis of 5-5′-dihydroxyleucine 3 and its 4-fluoro analog 7 involving the condensation of a suitable “aminoacid moiety” with 2,2-dimethyl-5-iodomethyl-1,3-dioxane 15D or its fluoro analog 27A were tested. The anion of the ethyl N-diphenylmethylene-glycinate 25 gave better yields of 3 than the classical anion of diethyl acetamidomalonate. This strategy could not be successfully applied to the synthesis of 7 , which could be prepared by reduction of a suitably protected 4-fluoro-4-carboxyglutamate with BMS.

Potent Antiproliferative Cembrenoids Accumulate in Tobacco upon Infection with Rhodococcus fascians and Trigger Unusual Microtubule Dynamics in Human Glioblastoma Cells

Aims Though plant metabolic changes are known to occur during interactions with bacteria, these were rarely challenged for pharmacologically active compounds suitable for further drug development. Here, the occurrence of specific chemicals with antiproliferative activity against human cancer cell lines was evidenced in hyperplasia (leafy galls) induced when plants interact with particular phytopathogens, such as the Actinomycete Rhodococcus fascians. Methods We examined leafy galls fraction F3.1.1 on cell proliferation, cell division and cytoskeletal disorganization of human cancer cell lines using time-lapse videomicroscopy imaging, combined with flow cytometry and immunofluorescence analysis. We determined the F3.1.1-fraction composition by gas chromatography coupled to mass spectrometry. Results The leafy galls induced on tobacco by R. fascians yielded fraction F3.1.1 which inhibited proliferation of glioblastoma U373 cells with an IC50 of 4.5 µg/mL, F.3.1.1 was shown to increase cell division duration, cause nuclear morphological deformations and cell enlargement, and, at higher concentrations, karyokinesis defects leading to polyploidization and apoptosis. F3.1.1 consisted of a mixture of isomers belonging to the cembrenoids. The cellular defects induced by F3.1.1 were caused by a peculiar cytoskeletal disorganization, with the occurrence of fragmented tubulin and strongly organized microtubule aggregates within the same cell. Colchicine, paclitaxel, and cembrene also affected U373 cell proliferation and karyokinesis, but the induced microtubule rearrangement was very different from that provoked by F3.1.1. Altogether our data indicate that the cembrenoid isomers in F3.1.1 have a unique mode of action and are able to simultaneously modulate microtubule polymerization and stability.

Resolution of γ-methyl and γ-fluoroglutamic acids. Lack of stereospecificity of leucine aminopeptidase with L-leucyl-L-erthro-γ-substituted glutamates

The hydrolysis of L-leucyl-γ-substituted D,L-glutamates by leucine aminopeptidase, from porcine kidney, is stereospecific with erythro-γ-methyl and erytho-γ-fluoroglutamate containing dipeptides whereas there is a lack of stereospecificity with the erytho-isomers. The optical purities of L-threo- and L-erythro-glutamate isomers thus obtained have been monitored by gas chromatography, high pressure liquid chromatography, or nuclear magnetic resonance. The optical rotations of optically pure L-isomers have been measured and the discrepancies with former publications are discussed.

Taxoids: 11,12-dihydro-4-deacetyldocetaxel

Abstract 11,12-dihydro-4-deacetyldocetaxel was prepared from 10-deacetylbaccatin III via its reduced derivative at C11, C12. The title compound is not active on microtubules disassembly.

Synthesis and biological evaluation of a new class of triazin–triazoles as potential inhibitors of human farnesyltransferase

A new synthesis of ethynyldimethoxytriazine 1, an important platform-compound for developing new chemical entities for anticancer research and for other biological applications, is described. Compound 1 was further reacted with azides 5a–i to provide triazin–triazoles 2a–i, which were tested on human farnesyltransferase and on the NCI-60 human tumor cell lines. Synthesis of other dimethoxytriazine derivatives 15 and 16, linked to a sp2 or a sp3 carbon atom were also studied.Graphical Abstract

Semisynthesis of α-methyl-γ-lactones and in vitro evaluation of their activity on protein farnesyltransferase

The semisynthesis of xanthanolide derivatives is reported from xanthinin and 4-epi-isoxanthanol, two sesquiterpene lactones isolated from the crude chloroformic extract of the leaves of Xanthium macrocarpum DC. (Asteraceae) by liquid/liquid chromatography. In vitro evaluation of their protein farnesyltransferase (PFTase) inhibitory activity has been investigated. In contrast to other biological activities of xanthanolides, PFTase inhibition is not associated with the presence of the potentially toxic α-methylene-γ-lactone function.