High affinity E-Selectin ligands as mediators of the tumor-endothelium interaction during hematogenous metastasis of human gastrointestinal cancer

• Applicants: Professor Dr. Falk Büttner; Professor Tobias Lange, Ph.D.
• Subject Area: Hematology, Oncology
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325043972

In the project applied for extension, we have developed a novel pharmacotherapeutic approach to reduce the E-selectin-mediated endothelial adhesion of tumor cells and thus the metastasis of solid human tumors. The approach is based on an incomplete pharmacological reduction of E-selectin expression by treating the endothelial cells with the approved proteasome inhibitor bortezomib (BZM). This approach was only successful in tumors lacking the canonical, high-affinity E-selectin ligands sialyl-Lewis A and X (sLeA/X). However, gastrointestinal (GI) adenocarcinoma cells, which utilize sLeA/X for E-selectin binding and adhesion, were not targetable by BZM. The molecular determinants of endothelial adhesion capacity of these cells were largely independent of glycoproteins, which raised our interest in studying glycosphingolipids (GSLs) known to carry sLeA/X epitopes. In addition, the sLeA/X-positive tumor cells were characterized by consistent expression of the fucosyltransferase FUT3. The aim of the continuation application is to decipher the role of GSLs and FUT3 products for E-selectin binding, endothelial adhesion and thus metastasis of human GI adenocarcinoma cells. To achieve these goals, we will deplete selected glycosyltransferases (GTfs) involved in GSL synthesis and FUT3 in tumor cell lines and determine the resulting changes in (I) the overall tumor cell glycome, (II) sLeA/X levels, (III) E-selectin binding and (IV) endothelial adhesion in vitro as well as hematogenous metastasis in vivo. For the latter, we will expand our long-standing xenograft expertise by using mice with humanized E-selectin for the first time to account for species-specific differences in the E-selectin ligand repertoire. We discovered these differences in the previous project. Finally, we will address the question whether depletion of GSL-synthesizing GTfs and/or FUT3 turns tumor cells that were previously not targetable with BZM due to their high sLeA/X levels into BZM-sensitive cells. Encouraged by recent findings of other groups on the importance of GSLs for the plasma membrane protein composition, we will finally investigate how the deletion of (selected) GSL-synthesizing GTfs and/or FUT3 affects the plasma membrane proteome of GI tumor cells. By integrating the expected results, we aim to develop a novel co-targeting approach to inhibit metastasis of sLeA+/X+ GI adenocarcinomas by reducing endothelial E-selectin levels on the one hand and impairing sLeA/X synthesis by targeting GSL synthesis and/or FUT3 activity on the other.

• DFG Programme: Research Grants