STRUCTURE AND BIOSYNTHESIS OF SELECTIN LIGANDS

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The primary objective of this proposal is to elucidate the structures and biosynthesis of selectin ligands, and the roles of selectin-carbohydrate interaction in tumor cell adhesion and metastasis. In the past few years, we have made critical progress in this field. First, we found that highly metastatic colonic carcinoma cells adhere more strongly to E-selectin than low metastatic counterparts. Second, such tumor cell adhesion can be inhibited by sialyl LeX-containing recombinant glycoproteins. Third, we demonstrated that en bloc transfer sialyl LeX oligosaccharide transferred on the cell surface results in adhesion to E-selectin. In addition, we have cloned the core 2 and I beta-16-N-acetylglucosaminyltransferases and polysialyltransferase, gaining significant expertise in expression cloning. Based on these findings, three major areas are proposed as follows: 1. Elucidation of selectin ligands in mice and modulation of selectin ligand by gene transfer. We will elucidate the mouse neutrophil oligosaccharides, thus mouse selectin ligands. In addition, modulation of sialyl LeX and sialyl Lea formation by glycosyltransferase gene transfer is correlated with adhesion to E- and P-selectin. 2. Molecular Identification of L-selectin ligands. We will determine if sulfo sialyl LeX achieves L-selectin-mediated adhesion. We will also clone cDNA encoding a sulfotransferase that forms sulfo sialyl LeX, a putative L- selectin ligand. 3. Roles of carbohydrates in tumor metastasis. We will determne if sialyl LeX (and sialyl Lea plays a major role in blood-borne tumor metastasis. The studies will also be extended to determine if oligosaccharide structures play a critical role in tumor metastasis. These studies will allow us to understand the structure and biosynthesis of selectin ligands and the roles selectin-mediated adhesion in tumor metastasis.