Galectin-1 Influences Breast Cancer Cell Adhesion to E-selectin Via Ligand Intermediaries.

INTRODUCTION: Invasion of other tissues during bloodborne metastasis in part requires adhesion of cancer cells to vascular endothelium by specific fluid shear-dependent receptor-ligand interactions. This study investigates the hypothesis that the adhesion is mediated by ligands shared between endothelial E-selectin and Galectin-1 (Gal-1), both of which are upregulated during inflammation and cancer. METHODS: Flow chamber adhesion and dynamic biochemical tissue analysis (DBTA) assays were used to evaluate whether Gal-1 modulates E-selectin adhesive interactions of breast cancer cells and tissues under dynamic flow conditions, while immunocytochemistry, immunohistochemistry, western blotting, and fluorescence anisotropy were used to study molecular interactions under static conditions. RESULTS: Dynamic adhesion assays revealed a shear-dependent binding interaction between Gal-1hFc treated breast cancer cells and tissues and E-selectin-coated beads, causing ~ 300% binding increase of the beads compared to negative controls. Immunocyto- and immunohistochemical analyses showed that Gal-1 and E-selectin fluorescent signals colocalized on cells and tissues at ~ 75% for each assay. Immunoprecipitation and Western blotting of Mac-2BP from breast cancer cell lysates revealed that Gal-1 and E-selectin share Mac-2BP as a ligand, while fluorescence anisotropy and circulating tumor cell model systems exhibited competitive or antagonistic binding between Gal-1 and E-selectin for shared ligands, including Mac-2BP. Furthermore, Mac-2BP functional blockade inhibited the effects of Gal-1 on E-selectin binding. CONCLUSIONS: In summary, this investigation reveals a shear-dependent interaction between E-selectin and Gal-1 that may be due to intermediation by a similar or shared ligand(s), including Mac-2BP, which may provide a rational basis for development of novel diagnostics or therapeutics for breast cancer.