Integrin alphavbeta3 binding to human alpha5-laminins facilitates FGF-2- and VEGF-induced proliferation of human ECV304 carcinoma cells.

Human ECV304 cells respond reproducibly by tube formation to complex basement membrane matrices. Laminins are major glycoproteins of basement membranes. We therefore studied the ability of ECV304 cells to attach to defined laminin isoforms and to fibronectin, and identified the involved laminin receptors. The cells bound poorly to fibronectin, to some extent to laminin-1, whereas laminin-2/4 and -10/11 were strong adhesive substrates. Antibody perturbation assays showed that adhesion to laminin-1 was mediated by integrin α6β1, and adhesion to laminin-2/4 by cooperative activity of integrins α3β1 and α6β1. Adhesion of ECV 304 cells to laminin-10/11 was mainly mediated by integrins α3β1, with minor involvement of α6β1/4 and αvβ3. Solid-phase binding assays confirmed that integrin αvβ3 binds human laminin-10/11 and -10, in an RGD-dependent fashion. Although integrin αvβ3 played a very minor role in cell adhesion to laminin-10/11, this interaction facilitated growth factor-induced proliferation of ECV304 cells. In response to FGF-2 or VEGF, the cells proliferated better when attached on laminin-10/11 than on laminin-1, -2/4, or gelatin. The proliferation induced by the joint application of laminin-10/11 and either one of the growth factors could be blocked by antibodies against integrin αvβ3. Fragments of several other basement membrane components are known to interact with αvβ3. The current data show that that integrin αvβ3 can bind intact α5-containing laminin trimers. Since the laminin α5 chain is broadly expressed in adult basement membranes, this interaction could be physiologically important. Our data suggest that this interaction is involved in the regulation of cellular responses to growth factors known to be involved in epithelial and endothelial development. (Less)