αvβ3 integrin mediates mammary tumor cell adhesion to vitronectin but not to endothelial cells. (a) Short-term adhesion to different matrices. (b) Effect of neutralizing antibodies against β3 integrin on short-term adhesion to vitronectin. (c) Adhesion of 66cl4pBabe and 66cl4beta3 cells to a monolayer of bEnd.3 endothelial cells in the absence of serum. The experiments were repeated at least twice and the results represent the mean ± standard deviation of a representative experiment performed in triplicate wells. *P < 0.001.