Tumour-associated carbohydrate antigens in breast cancer

Glycosylation changes that occur in cancer often lead to the expression of tumour-associated carbohydrate antigens. In breast cancer, these antigens are usually associated with a poor prognosis and a reduced overall survival. Cellular models have shown the implication of these antigens in cell adhesion, migration, proliferation and tumour growth. The present review summarizes our current knowledge of glycosylation changes (structures, biosynthesis and occurrence) in breast cancer cell lines and primary tumours, and the consequences on disease progression and aggressiveness. The therapeutic strategies attempted to target tumour-associated carbohydrate antigens in breast cancer are also discussed

Effet de l'expression de la GD3 synthétase sur la progression et l'agressivité du cancer du sein

Les gangliosides représentent une classe de glycosphingolipides porteurs d un ou plusieurs résidus d acide sialique. Alors que les tissus sains adultes expriment principalement des gangliosides de la série-a, l expression des gangliosides complexes des séries b- et c- est limitée au système nerveux central. Une augmentation d expression de ces gangliosides complexes est cependant observée sous certaines conditions physiopathologiques, notamment dans les cancers d origine neuro-ectodermique. Ainsi, le GD3 et le GD2 sont des marqueurs oncofœtaux du mélanome et du neuroblastome où ils favorisent la prolifération, la migration et la différenciation cellulaires, ainsi que l angiogenèse. L objectif de ma thèse a été de déterminer l influence des gangliosides complexes dans la progression et l agressivité du cancer du sein. A cet effet, nous avons établi un modèle dérivant des cellules de cancer du sein MDA-MB-231 qui expriment la GD3 synthétase. Ces cellules expriment des gangliosides des séries b- et c- à leur surface, principalement le GD2, et se caractérisent par une augmentation de la migration et des capacités de prolifération en absence de facteurs de croissance. Ce phénotype prolifératif a été confirmé in vivo par des expériences de xénogreffes chez des souris immunodéficientes. Nous avons pu démontrer que l expression de la GD3 synthétase renforce l agressivité des cellules MDA-MB-231 par un mécanisme d activation spécifique du récepteur c-Met et des voies de signalisation cellulaire MEK/ERK et PI3K/Akt. Les derniers résultats indiquent que le disialoganglioside GD2 joue un rôle essentiel dans la spécificité d activation du récepteur c-Met dans les cellules MDA-MB-231.Gangliosides define a class of glycosphingolipids with one or more sialic acid residues. Whereas normal human tissues mainly express a-series gangliosides deriving from GM3, the expression of complex gangliosides from b- and c-series is limited to the central nervous system and developing tissues during embryogenesis. However, an increase of complex gangliosides expression is observed in several pathological conditions including neuro-ectoderm-derived cancers. Thus, GD3 and GD2 are oncofetal markers of melanoma and neuroblastoma where they promote tumor progression by mediating cell proliferation, migration, adhesion and angiogenesis. The goal of my thesis was to determine the effect of complex gangliosides on breast cancer progression and aggressiveness. For that propose, we have established a cellular model deriving from MDA-MB-231 breast cancer cells expressing the GD3 synthase. The GD3 synthase expression induces the accumulation of b- and c-series gangliosides (mainly GD2) at the cell surface together with an increased migration and the acquisition of a proliferative phenotype in absence of growth factors. GD3 synthase expression also induces an increased tumor growth of MDA-MB-231 cells in severe combined immunodeficiency mice. We have clearly demonstrated that GD3 synthase expression induces the specific and constitutive activation of c-Met receptor and subsequent activation of MEK/ERK and PI3K/Akt transduction pathways. Altogether, these results clearly demonstrate the involvement of the disialoganglioside GD2 in MDA-MB-231 cell proliferation via the constitutive activation of c-Met.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Mannose phosphate isomerase regulates fibroblast growth factor receptor family signaling and glioma radiosensitivity.

Asparagine-linked glycosylation is an endoplasmic reticulum co- and post-translational modification that enables the transit and function of receptor tyrosine kinase (RTK) glycoproteins. To gain insight into the regulatory role of glycosylation enzymes on RTK function, we investigated shRNA and siRNA knockdown of mannose phosphate isomerase (MPI), an enzyme required for mature glycan precursor biosynthesis. Loss of MPI activity reduced phosphorylation of FGFR family receptors in U-251 and SKMG-3 malignant glioma cell lines and also resulted in significant decreases in FRS2, Akt, and MAPK signaling. However, MPI knockdown did not affect ligand-induced activation or signaling of EGFR or MET RTKs, suggesting that FGFRs are more susceptible to MPI inhibition. The reductions in FGFR signaling were not caused by loss of FGF ligands or receptors, but instead were caused by interference with receptor dimerization. Investigations into the cellular consequences of MPI knockdown showed that cellular programs driven by FGFR signaling, and integral to the clinical progression of malignant glioma, were impaired. In addition to a blockade of cellular migration, MPI knockdown also significantly reduced glioma cell clonogenic survival following ionizing radiation. Therefore our results suggest that targeted inhibition of enzymes required for cell surface receptor glycosylation can be manipulated to produce discrete and limited consequences for critical client glycoproteins expressed by tumor cells. Furthermore, this work identifies MPI as a potential enzymatic target for disrupting cell surface receptor-dependent survival signaling and as a novel approach for therapeutic radiosensitization

Copper-free click chemistry for highly luminescent quantum dot conjugates: application to in vivo metabolic imaging.

International audienceQuantum dots (QD) are inorganic nanocrystals with outstanding optical properties, specially suited for biological imaging applications. Their attachment to biomolecules in mild aqueous conditions for the design of bioconjugates is therefore highly desirable. 1,3-dipolar [3 + 2] cycloaddition between azides and terminal alkynes ("click chemistry") could represent an attractive QD functionalization method. Unfortunately, the use of the popular Cu(I)-catalyzed version of this reaction is not applicable for achieving this goal, since the presence of copper dramatically alters the luminescence properties of QD dispersions. We demonstrate here that copper-free click chemistry, between strained cyclooctyne functionalized QD and azido-biomolecules, leads to highly luminescent conjugates. In addition, we show that QD-cyclooctyne can be used at previously unreported low concentration (250 nM) for imaging the incorporation of azido-modified sialic acid in cell membrane glycoproteins

Carbohydrate-to-carbohydrate interactions between α2,3-linked sialic acids on α2 integrin subunits and asialo-GM1 underlie the bone metastatic behaviour of LNCAP-derivative C4-2B prostate cancer cells

Complex interplays among proteins, lipids and carbohydrates can alter the phenotype and are suggested to have a crucial role in tumour metastasis. Our previous studies indicated that a complex of the GSLs (glycosphingolipids), AsGM1 (asialo-GM1), which lacks α2,3-linked sialic acid, and α2β1 integrin receptors is responsible for the metastatic behaviour of C4-2B prostate cancer cells. Herein, we identified and addressed the functional significance of changes in sialylation during prostate cancer progression. We observed an increase in α2,3-linked sialic acid residues on α2 subunits of α2β1 integrin receptors, correlating with increased gene expression of α2,3-STs (sialyltransferases), particularly ST3GAL3. Cell surface α2,3-sialylation of α2 subunits was required for the integrin α2β1-dependent cell adhesion to collagen type I and the same α2,3-linked sialic acid residues on the integrin receptor were responsible for the interaction with the carbohydrate moiety of AsGM1, explaining the complex formation between AsGM1 and α2β1 integrin receptors. These results provide novel insights into the role of sialic acids in the organization and function of important membrane components in invasion and metastatic processes

Accumulation of Unusual Gangliosides GQ3 and GP3 in Breast Cancer Cells Expressing the GD3 Synthase

molecule