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Publications
Year of publication 2017
Targeting Conformational Activation of CDK2 Kinase.
Biotechnology journal : 12 : 1600531 : DOI : 10.1002/biot.201600531 Learn moreSummary
Cyclin-dependent kinases constitute attractive pharmacological targets for cancer therapeutics, yet inhibitors in clinical trials target the ATP-binding pocket of the CDK and therefore suffer from limited selectivity and emergence of resistance. The more recent development of allosteric inhibitors targeting conformational plasticity of protein kinases offers promising perspectives for therapeutics. In particular tampering with T-loop dynamics of CDK2 kinase would provide a selective means of inhibiting this kinase, by preventing its conformational activation. To this aim we engineered a fluorescent biosensor that specifically reports on conformational changes of CDK2 activation loop and is insensitive to ATP or ATP-competitive inhibitors, which constitutes a highly sensitive probe for identification of selective T-loop modulators. This biosensor was successfully applied to screen a library of small chemical compounds leading to discovery of a family of quinacridine analogs, which potently inhibit cancer cell proliferation, and promote accumulation of cells in S phase and G2. These compounds bind CDK2/ Cyclin A, inhibit its kinase activity, compete with substrate binding, but not with ATP, and dock onto the T-loop of CDK2. The best compound also binds CDK4 and CDK4/Cyclin D1, but not CDK1. The strategy we describe opens new doors for the discovery of a new class of allosteric CDK inhibitors for cancer therapeutics.
Fold upExploring the mechanism of inhibition of human telomerase by cysteine-reactive compounds.
FEBS letters : 591 : 863-874 : DOI : 10.1002/1873-3468.12589 Learn moreSummary
Telomerase is an almost universal cancer target that consists minimally of a core protein (hTERT) and an RNA (hTR). Some inhibitors of this enzyme are thought to function by the covalent binding to one or several cystein residues; however, this inhibition mechanism has never been investigated because of the difficulty in producing telomerase. In the present study, we use a recent method to produce recombinant hTERT to analyse the effect of cysteine reactive inhibitors on telomerase. Using mass-spectrometry (MS) and mutagenesis analysis, we identify several targeted residues in separated domains of the hTERT protein and show that cysteine-reactive reagents abolish the interaction with the CR4/5 region of hTR. This article is protected by copyright. All rights reserved.
Fold upYear of publication 2016
CD45 phosphatase is crucial for human and murine acute myeloid leukemia maintenance through its localization in lipid rafts.
Oncotarget : 7 : 64785-64797 : DOI : 10.18632/oncotarget.11622 Learn moreSummary
CD45 is a pan-leukocyte protein with tyrosine phosphatase activity involved in the regulation of signal transduction in hematopoiesis. Exploiting CD45 KO mice and lentiviral shRNA, we prove the crucial role that CD45 plays in acute myeloid leukemia (AML) development and maintenance. We discovered that CD45 does not colocalize with lipid rafts on murine and human non-transformed hematopoietic cells. Using a mouse model, we proved that CD45 positioning within lipid rafts is modified during their oncogenic transformation to AML. CD45 colocalized with lipid rafts on AML cells, which contributes to elevated GM-CSF signal intensity involved in proliferation of leukemic cells. We furthermore proved that the GM-CSF/Lyn/Stat3 pathway that contributes to growth of leukemic cells could be profoundly affected, by using a new plasma membrane disrupting agent, which rapidly delocalized CD45 away from lipid rafts. We provide evidence that this mechanism is also effective on human primary AML samples and xenograft transplantation. In conclusion, this study highlights the emerging evidence of the involvement of lipid rafts in oncogenic development of AML and the targeting of CD45 positioning among lipid rafts as a new strategy in the treatment of AML.
Fold upRespiratory syncytial virus infection in macaques is not suppressed by intranasal sprays of pyrimidine biosynthesis inhibitors.
Antiviral research : 58-62 : DOI : 10.1016/j.antiviral.2015.11.006 Learn moreSummary
There is imperious need for efficient therapies against ubiquitous and life-threatening respiratory viruses, foremost among them being the human respiratory syncytial virus (hRSV). Several research groups who performed functional screens for broad-spectrum antivirals identified compounds targeting the de novo pyrimidine biosynthesis pathway. Despite their strong antiviral activity in vitro, whether such antimetabolites are effective in vivo remains highly controversial. Here, we evaluated two potent pyrimidine biosynthesis inhibitors developed in our laboratory, IPPA17-A04 and GAC50, in a model of mild hRSV-infection in cynomolgus macaques. In this model, hRSV replication is restricted to the epithelium of the upper respiratory tract, and is compatible with a topical treatment by intranasal sprays. The local administration of palivizumab, a neutralizing anti-hRSV antibody used in clinics, significantly reduced virus replication. In contrast, pyrimidine biosynthesis inhibitors did not show any inhibitory effect on hRSV growth when delivered topically as experimented in our model. Our results should help to better define the potential applications of this class of antimetabolites in the treatment of viral infections.
Fold upYear of publication 2015
Discovery of benzo[e]pyridoindolones as kinase inhibitors that disrupt mitosis exit while erasing AMPK-Thr172 phosphorylation on the spindle.
Oncotarget : 6 : 22152-22166 : DOI : 10.18632/oncotarget.4158 Learn moreSummary
Aurora kinases play an essential role in mitotic progression and are attractive targets in cancer therapy. The first generation of benzo[e]pyridoindole exhibited powerful aurora kinase inhibition but their low solubility limited further development. Grafting a pyperidine-ethoxy group gives rise to a hydrosoluble inhibitor: compound C5M.C5M could efficiently inhibit the proliferation of cells from different origins. C5M prevented cell cycling, induced a strong mitotic arrest then, cells became polyploid and finally died. C5M did not impair the spindle checkpoint, the separation of the sister chromatids and the transfer of aurora B on the mid-zone. C5M prevented histone H3 phosphorylation at mitotic entry and erased AMPK-Thr172 phosphorylation in late mitosis. With this unique profile of inhibition, C5M could be useful for understanding the role of phospho-Thr172-AMPK in abscission and the relationship between the chromosomal complex and the energy sensing machinery.C5M is a multikinase inhibitor with interesting preclinical characteristics: high hydro-solubility and a good stability in plasma. A single dose prevents the expansion of multicellular spheroids. C5M can safely be injected to mice and reduces significantly the development of xenograft. The next step will be to define the protocol of treatment and the cancer therapeutic field of this new anti-proliferative drug.
Fold upThe French National Compound Library: advances and future prospects.
Médecine sciences : M/S : 31 : 417-22 : DOI : 10.1051/medsci/20153104016 Learn moreSummary
The French National Compound Library (Chimiothèque Nationale) has been created in 2003 and is the federation of local collections. It contains more than 56 000 small molecules and natural compounds synthesised or isolated in different laboratories over the past years. This explains the diversity of the collection. The strength of this initiative is the ability to connect chemists and biologists for the development of hits. This development involves the synthesis of analogues or/and chemical tools to find new targets. These collaborations lead to the identification of new chemical probes. These probes able to modulate a biological function are essential to study biological pathways. They can also be useful for therapeutic applications. This article will describe the major achievements and perspectives of the French Chemical Library.
Fold upIdentification of human telomerase assembly inhibitors enabled by a novel method to produce hTERT.
Nucleic acids research : 43 : e99 : DOI : 10.1093/nar/gkv425 Learn moreSummary
Telomerase is the enzyme that maintains the length of telomeres. It is minimally constituted of two components: a core reverse transcriptase protein (hTERT) and an RNA (hTR). Despite its significance as an almost universal cancer target, the understanding of the structure of telomerase and the optimization of specific inhibitors have been hampered by the limited amount of enzyme available. Here, we present a breakthrough method to produce unprecedented amounts of recombinant hTERT and to reconstitute human telomerase with purified components. This system provides a decisive tool to identify regulators of the assembly of this ribonucleoprotein complex. It also enables the large-scale screening of small-molecules capable to interfere with telomerase assembly. Indeed, it has allowed us to identify a compound that inhibits telomerase activity when added prior to the assembly of the enzyme, while it has no effect on an already assembled telomerase. Therefore, the novel system presented here may accelerate the understanding of human telomerase assembly and facilitate the discovery of potent and mechanistically unique inhibitors.
Fold upYear of publication 2013
Inhibition of pyrimidine biosynthesis pathway suppresses viral growth through innate immunity.
PLoS pathogens : e1003678 : DOI : 10.1371/journal.ppat.1003678 Learn moreSummary
Searching for stimulators of the innate antiviral response is an appealing approach to develop novel therapeutics against viral infections. Here, we established a cell-based reporter assay to identify compounds stimulating expression of interferon-inducible antiviral genes. DD264 was selected out of 41,353 compounds for both its immuno-stimulatory and antiviral properties. While searching for its mode of action, we identified DD264 as an inhibitor of pyrimidine biosynthesis pathway. This metabolic pathway was recently identified as a prime target of broad-spectrum antiviral molecules, but our data unraveled a yet unsuspected link with innate immunity. Indeed, we showed that DD264 or brequinar, a well-known inhibitor of pyrimidine biosynthesis pathway, both enhanced the expression of antiviral genes in human cells. Furthermore, antiviral activity of DD264 or brequinar was found strictly dependent on cellular gene transcription, nuclear export machinery, and required IRF1 transcription factor. In conclusion, the antiviral property of pyrimidine biosynthesis inhibitors is not a direct consequence of pyrimidine deprivation on the virus machinery, but rather involves the induction of cellular immune response.
Fold upHydrosoluble benzo[e]pyridoindolones as potent inhibitors of aurora kinases.
ChemMedChem : 8 : 289-96 : DOI : 10.1002/cmdc.201200479 Learn moreSummary
Aurora kinases play an essential role in mitotic progression and are potentially druggable targets in cancer therapy. We identified benzo[e]pyridoindoles (BePI) as powerful aurora kinase inhibitors. Their efficiency was demonstrated both in enzymatic inhibition studies and in cell culture assays. New BePI molecules were synthesized, and a structure-activity relationship study was conducted with the aim of improving the activity and solubility of the lead compound. Tetracyclic BePI derivatives are characterized by a particular curved shape, and the presence of an oxo group on the pyridine ring was found to be required for aurora kinase B inhibition. New hydrosoluble benzo[e]pyridoindolones were subsequently designed, and their efficacy was tested by a combination of cell-cycle analysis and time-lapse experiments in live cells. The most active BePI derivative, 13 b, inhibited the cell cycle, drove cells to polyploidy, and eventually induced apoptosis. It exhibited high antiproliferative activity in HeLa cells with an IC(50) value of 63 nM. Relative to compounds tested in clinical trials, this antiproliferative potency places 13 b among the top 10 aurora kinase inhibitors. Our results justify further in vivo evaluation in preclinical animal models of cancer.
Fold upYear of publication 2012
Extensive characterization of sphere models established from colorectal cancer cell lines.
Cellular and molecular life sciences : CMLS : 2 : 729-42 : DOI : 10.1007/s00018-012-1160-9 Learn moreSummary
Links between cancer and stem cells have been proposed for many years. As the cancer stem cell (CSC) theory became widely studied, new methods were developed to culture and expand cancer cells with conserved determinants of “stemness”. These cells show increased ability to grow in suspension as spheres in serum-free medium supplemented with growth factors and chemicals. The physiological relevance of this phenomenon in established cancer cell lines remains unclear. Cell lines have traditionally been used to explore tumor biology and serve as preclinical models for the screening of potential therapeutic agents. Here, we grew cell-forming spheres (CFS) from 25 established colorectal cancer cell lines. The molecular and cellular characteristics of CFS were compared to the bulk of tumor cells. CFS could be isolated from 72 % of the cell lines. Both CFS and their parental CRC cell lines were highly tumorigenic. Compared to their parental cells, they showed similar expression of putative CSC markers. The ability of CRC cells to grow as CFS was greatly enhanced by prior treatment with 5-fluorouracil. At the molecular level, CFS and parental CRC cells showed identical gene mutations and very similar genomic profiles, although microarray analysis revealed changes in CFS gene expression that were independent of DNA copy-number. We identified a CFS gene expression signature common to CFS from all CRC cell lines, which was predictive of disease relapse in CRC patients. In conclusion, CFS models derived from CRC cell lines possess interesting phenotypic features that may have clinical relevance for drug resistance and disease relapse.
Fold upAzaindole derivatives are inhibitors of microtubule dynamics, with anti-cancer and anti-angiogenic activities.
British journal of pharmacology : 673-85 : DOI : 10.1111/j.1476-5381.2012.02230.x Learn moreSummary
Drugs targeting microtubules are commonly used for cancer treatment. However, the potency of microtubule inhibitors used clinically is limited by the emergence of resistance. We thus designed a strategy to find new cell-permeable microtubule-targeting agents.
Fold upPharmacological inhibition of LIM kinase stabilizes microtubules and inhibits neoplastic growth.
Cancer research : 4429-39 Learn moreSummary
The emergence of tumor resistance to conventional microtubule-targeting drugs restricts their clinical use. Using a cell-based assay that recognizes microtubule polymerization status to screen for chemicals that interact with regulators of microtubule dynamics, we identified Pyr1, a cell permeable inhibitor of LIM kinase, which is the enzyme that phosphorylates and inactivates the actin-depolymerizing factor cofilin. Pyr1 reversibly stabilized microtubules, blocked actin microfilament dynamics, inhibited cell motility in vitro and showed anticancer properties in vivo, in the absence of major side effects. Pyr1 inhibition of LIM kinase caused a microtubule-stabilizing effect, which was independent of any direct effects on the actin cytoskeleton. In addition, Pyr1 retained its activity in multidrug-resistant cancer cells that were resistant to conventional microtubule-targeting agents. Our findings suggest that LIM kinase functions as a signaling node that controls both actin and microtubule dynamics. LIM kinase may therefore represent a targetable enzyme for cancer treatment.
Fold upYear of publication 2011
C5-DNA methyltransferase inhibitors: from screening to effects on zebrafish embryo development.
Chembiochem : a European journal of chemical biology : 12 : 1337-45 : DOI : 10.1002/cbic.201100130 Learn moreSummary
DNA methylation is involved in the regulation of gene expression and plays an important role in normal developmental processes and diseases, such as cancer. DNA methyltransferases are the enzymes responsible for DNA methylation on the position 5 of cytidine in a CpG context. In order to identify and characterize novel inhibitors of these enzymes, we developed a fluorescence-based throughput screening by using a short DNA duplex immobilized on 96-well plates. We have screened 114 flavones and flavanones for the inhibition of the murine catalytic Dnmt3a/3L complex and found 36 hits with IC(50) values in the lower micromolar and high nanomolar ranges. The assay, together with inhibition tests on two other methyltransferases, structure-activity relationships and docking studies, gave insights on the mechanism of inhibition. Finally, two derivatives effected zebrafish embryo development, and induced a global demethylation of the genome, at doses lower than the control drug, 5-azacytidine.
Fold upYear of publication 2010
Antitumor activity of pyridocarbazole and benzopyridoindole derivatives that inhibit protein kinase CK2.
Cancer research : 9865-74 : DOI : 10.1158/0008-5472.CAN-10-0917 Learn moreSummary
The alkyloid compound ellipticine derived from the berrywood tree is a topoisomerase II poison that is used in ovarian and breast cancer treatment. In this study, we report the identification of ellipticine derivatives and their tetracyclic angular benzopyridoindole analogues as novel ATP-competitive inhibitors of the protein kinase CK2. In vitro and in vivo assays showed that these compounds have a good pharmacologic profile, causing a marked inhibition of CK2 activity associated with cell cycle arrest and apoptosis in human cancer cells. Further, in vivo assays demonstrate antitumor activity in a mouse xenograft model of human glioblastoma. Finally, crystal structures of CK2-inhibitor complex provide structural insights on the molecular basis of CK2 inhibition. Our work lays the foundation for development of clinically useful CK2 inhibitors derived from a well-studied scaffold with suitable pharmacokinetics parameters.
Fold upNew potent dual inhibitors of CK2 and Pim kinases: discovery and structural insights.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology : 3171-85 : DOI : 10.1096/fj.09-143743 Learn moreSummary
Protein kinase casein kinase 2 (CK2) is a serine/threonine kinase with evidence of implication in growth dysregulation and apoptosis resistance, making it a relevant target for cancer therapy. Several CK2 inhibitors have been developed showing variable efficiency, emphasizing the need to expand the chemical diversity of those inhibitors. We report the identification and characterization of 2,8-difurandicarboxylic acid derivatives as a new class of nanomolar ATP-competitive inhibitors. Selectivity profiling pointed out proviral insertion Moloney virus kinases (Pim kinases) as the only other kinases that are significantly inhibited. By combining structure-activity relationship analysis with structural determination, we were able to determine the binding mode of these inhibitors for both kinases and to explain their strong inhibitory potency. Essential chemical features necessary for activity on both kinases were then identified. The described compounds are not cell permeable: however, they could provide a lead for developing novel inhibitors usable also in vivo. Given the similar but not redundant pathophysiological functions of CK2 and Pim family members, such inhibitors would provide new attractive leads for targeted cancer therapy. This work highlights that 2 functionally related kinases from different kinome branches display exquisite sensitivity to a common inhibitor.
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