EXPRESSION OF GALECTINS ON MICROVESSEL ENDOTHELIAL-CELLS AND THEIR INVOLVEMENT IN TUMOR-CELL ADHESION

Lactoside-binding lectins (galectins) with molecular weights of about 14.5 kDa (galectin-1) and 29-35 kDa (galectin-3) bind preferentially t o polylactosaminoglycan-containing glycoconjugates and have been found on the surface of tumour cells and implicated in cell-cell and cell-e xtracellular matrix adhesion and metastasis. We have demonstrated by i mmunoblotting that both galectin-1 and galectin-3 are present in extra cts of endothelial cells cultured from bovine aorta, rat lung, mouse l ung and mouse brain microvessels, whereas mouse hepatic sinusoidal end othelial cells expressed primarily galectin-1. These galectins were al so localized by indirect immunofluorescent labelling on the surface of the different endothelial cells in culture and by immunohistochemical staining in human tissues in vivo. Anti-galectin-1 antibodies inhibit ed the adhesion of liver-preferring murine RAW117-H10 large-cell lymph oma cells to hepatic sinusoidal endothelial cells or lung microvessel endothelial cells in vitro. The data indicate that galectin-1 is expre ssed on the extracellular surface of endothelial cells and can mediate in part the adhesion of RAW117-H10 cells to liver microvessel endothe lial cells.