Inhibition de l'adhérence syndécan-1 dépendante – CHEMISPIKE

Cancer is the second mortality cause in developed countries with colorectal and breast cancers causing high rate of mortality. Approximately 90% of all cancer deaths arise from the metastatic spread of primary tumours. Of all the processes involved in carcinogenesis, local invasion and the formation of metastases are clinically the most relevant, but they are poorly understood at the molecular level. During progression from tumour growth to metastasis, cellular invasive and migratory behaviour is governed at both extracellular and intracellular levels and depends on the carefully balanced dynamic interaction of the cell with its extracellular matrix. The cell surface receptors syndecans and integrins are thought to play key roles in regulating tumour growth, metastasis and tumour angiogenesis. Laminin 332 (also named laminin 5) is a major adhesion substrate for epithelial cells. It is known for its role in promoting carcinoma cell migration, notably those with malignant characteristics, and may act as a ligand for invasiveness. We have recently identified a region in laminin 332 (the LG4/5 domain), which, by interacting with syndecan-1, may strongly influence epithelial cell behaviour. Indeed, we have shown that the syndecan-1 interaction with the LG4/5 domain in laminin 332 is essential for epithelial cell migration and we are currently studying the triggered intracellular signalling cascade. The fact that syndecan-1 is predominantly expressed by different carcinomas and plays multiple roles in the regulation of cell-matrix interactions reinforces the notion that the interaction between syndecan-1 and LG4/5 participates in the malignant process. In order to develop inhibitors of the LG4/5 domain that specifically block the syndecan-1 mediated interaction with this domain in laminin 332, we have developed a specific syndecan-1 mediated cell adhesion assay successfully used for the screening of a large library of chemical agents at the 'Plateforme de Criblage de Molécules Bio-Actives' CEA Grenoble. Among the 12 160 molecules tested, we have identified 243 hits, from the UMR 176 CNRS-Institut Curie chemical library, conferring a 50 to 100 % inhibition of cell adhesion to LG4/5 but not to the rest of the laminin 332 molecule. Further work needs to be done to sharpen the specificity of action of these inhibitors and identify new targets in the LG4/5-syndecan-1 cascade inhibited by the selected small molecules. Our research project, which relies on the cooperation between 3 groups, Patricia Rousselle at the Institut de Biologie et Chimie des Protéines in Lyon (UMR 5086), Emmanuel Bertounesque at the Institut Curie in Paris (UMR 176) and Isabel Garcia-Saez at the Institut de Biologie Structurale in Grenoble (UMR 5075), will be dedicated to the characterization of these specialized LG4/5 contacts found in migratory situations as well as to their inhibition. Using different and complementary methodological approaches, the proposal CHEMISPIKE aims (1) to dissect the molecular mechanism underlying the LG4/5-syndecan-1 interaction and the associated signaling cascade, (2) to identify, among the hits derived from the screening of a chemical library, the most specific inhibitors and determine their respective targets, (3) to test the anti-tumoral potential of the identified LG4/5 inhibitors in a pre-clinical model of colon carcinoma and (4) to solve the structure of the a3 LG4/5 fragment with the most relevant identified inhibitors using X-ray crystallography.