The role of adhesion molecules, αvβ3, αvβ5 and their ligands in the tumor cell and endothelial cell adhesion

Abstract

Tumor metastasis is a complex process involving the interaction between tumor cells and endothelial cells in which some adhesion molecules play an important role. It was our aim to investigate the role of the adhesion molecules, alpha v beta 3 and alpha v beta 5 and their ligands, developmental endothelial locus-1 (Del-1) and L1, in tumor cell adhesion to endothelial cells in vitro. In this study, the expression and regulation of alpha v beta 3, alpha v beta 5 and intercellular adhesion molecule -1 on liver sinusoidal endothelial cells and liver cancer endothelial cells (T3A) were analyzed by real-time PCR and fluorescent-activated cell sorter. The expression and regulation of the integrin ligands, Del-1 and L1, in six tumor cell lines were analyzed by real-time PCR and western blot. We found the expressions of alpha v beta 3 and alpha v beta 5 were higher on T3A than that on liver sinusoidal endothelial cells, whereas expression of intercellular adhesion molecule-1 was lower on T3A than that on liver sinusoidal endothelial cells. After 24 h hypoxia, the expressions of alpha v beta 3 and alpha v beta 5 were upregulated on T3A and liver sinusoidal endothelial cells; the expression of intercellular adhesion molecule-1 was increased on liver sinusoidal endothelial cells, but remained unchanged on T3A. Del-1 and L1 expression levels were obviously diverse in various tumor cell lines and differentially modulated after 12 h hypoxia. The adhesion of tumor cells with Del-1 and L1 expression was higher in T3A than that in liver sinusoidal endothelial cells, and was significantly increased under hypoxic conditions. Interestingly, the tumor cell adherence could be inhibited by antibodies against alpha v beta 5 and alpha v beta 5, but not by an antibody against intercellular adhesion molecule-1. The adhesion of tumor cells without Del-1 and L1 expression was also higher on T3A than that on liver sinusoidal endothelial cells, but the adhesion could not be inhibited by antibodies against alpha v beta 5, alpha v beta 5 or intercellular adhesion molecule-1, suggesting that other receptors are involved. In conclusion, alpha v beta 5, alpha v beta 5 and their ligands Del-1 and L1 play an important role in the process of tumor cells moving from the original place.