Galectin-1 sensitizes carcinoma cells to anoikis via the fibronectin receptor α5β1-integrin

Anoikis resistance is a hallmark of transformed epithelial cells. Here, we show that treatment of anoikis-resistant carcinoma cell lines with the endogenous lectin galectin-1 (Gal-1) promoted apoptosis via interaction with the unligated fibronectin receptor alpha(5)beta(1)-integrin. Gal-1 efficiency correlated with expression of alpha(5)beta(1)-integrin, and transfection of the alpha(5)-subunit into deficient cell lines conferred Gal-1 binding and anoikis stimulation. Furthermore, Gal-1 and the alpha(5)- and beta(1)-integrin subunits co-precipitated in Gal-1-stimulated cells undergoing anoikis. Other members of the galectin family failed to be active. The functional interaction between Gal-1 and alpha(5)beta(1)-integrin was glycan dependent with alpha 2,6-sialylation representing a switch-off signal. Desialylation of cell surface glycans resulted in increased electrophoretic mobility of alpha(5)beta(1)-integrin and facilitated Gal-1 binding and anoikis stimulation. On the level of signaling, Gal-1-stimulated anoikis was prevented by filipin, which impaired the internalization of alpha(5)beta(1)-integrin via cholesterol-enriched microdomains, and by pretreatment with a caspase-8 inhibitor. We propose that Gal-1/alpha(5)beta(1)-integrin interaction participates in the control of epithelial integrity and integrin sialylation may enable carcinoma cells to evade this Gal-1-dependent control mechanism. Cell Death and Differentiation (2011) 18, 806-816; doi:10.1038/cdd.2010.148; published online 26 November 2010