CARCINOEMBRYONIC ANTIGEN AND OTHER GLYCOCONJUGATES ACT AS LIGANDS FORGALECTIN-3 IN HUMAN COLON-CARCINOMA CELLS

Galectin-1 and galectin-3, galactoside-binding lectins with molecular weights of M(r) 14,500 and 31,000, respectively, are expressed in norm al and malignant cells and have been implicated in regulation of cell growth, adhesion, and metastasis. We analyzed the expression of galect ins in 21 cultured human colon carcinoma cell lines by immunoblotting. Galectin-1 was detected in only 7, whereas galectin-3 was found in 20 of the cell lines. KM12 cells, which express only galectin-3, were us ed to isolate this lectin by affinity chromatography, and the purified lectin was used to identify complementary glycoconjugates by blotting . Galectin-3 was shown to bind to human laminin, carcinoembryonic anti gen, and lysosome-associated membrane glycoproteins, which are involve d in cell adhesion. Galectin-3 was localized on the KM12 cell surface and colocalized with carcinoembryonic antigen. Several endogenous glyc oproteins and cell surface proteins of molecular weights in the range M(r) 58,000 to >200,000, including carcinoembryonic antigen and lysoso me-associated membrane glycoproteins, were identified as galectin-3 li gands by coimmunoprecipitation with and affinity chromatography on imm obilized galectin-3. These data demonstrate that galectin-3 interacts with several adhesion molecules and suggest that this lectin may have a role in human colon carcinoma cell adhesion.