Tumor-derived adhesion factor/
angiomodulin (AGM) is accumulated in
tumor blood vessels and on the endothelial cell surface (Akaogi, K., Okabe, Y., Sato, J., Nagashima, Y., Yasumitsu, H., Sugahara, K., and Miyazaki, K. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 8384-8389). In cell culture, it promotes cell adhesion and morphological changes to form cord-like structures of the human bladder
carcinoma cell line ECV-304. The cord formation is prevented by
heparin, which inhibits the binding of AGM to ECV-304 cells. This observation suggests that AGM interacts with cell surface
heparan sulfate (HS)
proteoglycans. In this study, HS
glycosaminoglycans and core
proteins of integral transmembrane
proteoglycans,
syndecan-1 and -4, were identified by immunocytochemistry on ECV-304 cells, and the structural requirements for the interaction of HS with AGM were characterized. Inhibition experiments with sulfated
polysaccharides and chemically modified
heparin derivatives indicated that
sulfate groups were essential for both AGM-HS binding and cord-like structure formation and that the rank order of the different
sulfate groups in terms of their contribution was N-
sulfate > 6-O-sulfate > 2-O-sulfate. The minimum size of
heparin, a chemical analog of HS, required for the binding to AGM was a dodecasaccharide as determined by competition experiments using size-defined
heparin oligosaccharides. Thus, a specific sulfation pattern in the HS of cell surface
syndecans of ECV-304 cells is required for AGM binding and the morphological changes.