Integrin dependence of Calu-1 cell motility on endothelial extracellular matrix proteins

We recently showed that the motility of the malignant Calu-1 human epidermoid lung carcinoma cells correlates to their expression levels of alpha 2, alpha 3, alpha 6, and beta 1 integrin subunits. To determine a causative relationship underlying this correlation, here we measured Calu-1 cell adhesion to and migration on laminin, collagen IV, human umbilical vein endothelial cell monolayers, and endothelial cell extracellular matrix in the presence of function-blocking antibodies against the suspect integrin subunits. Blocking individual alpha subunits did not affect adhesion to or motility on laminin, but when used in pair-wise combinations, monoclonal antibody treatments significantly decreased tumor cell motility on, without diminishing adhesion to, laminin and the other substrates. Blocking all three alpha subunits at once or the beta 1 subunit alone abolished migration on laminin; however, the latter treatment also abolished adhesion, whereas the former treatment did not. By contrast, blocking the beta 1 subunit significantly reduced motility on collagen IV, endothelial cell monolayers, and endothelial cell extracellular matrix, but always without affecting adhesion. These results suggest a separation of roles and mechanisms of different integrins in adhesion and motility.