Unique ability of integrin αvβ3 to support tumor cell arrest under dynamic flow conditions

Shear-resistant arrest of circulating tumor cells is required for metastasis from the blood stream. Arrest during blood flow can be supported by tumor cell interaction with attached, activated platelets. This is mediated by tumor cell integrin alpha(v)beta(3) and cross-linking plasma protein ligands. To analyze the mechanism of tumor cell ligand interactions under dynamic flow conditions, we used real-time video microscopy and tested human melanoma cell binding to fibrinogen, von Willebrand Factor, or fibronectin matrices in a buffer perfusion system. When perfused at venous flow, melanoma cells arrested abruptly and began to spread immediately. This was uniquely mediated by integrin alpha(v)beta(3) on all tested ligands, and required alpha(v)beta(3) activation and actin polymerization. Under static conditions, alpha(v)beta(3) cooperated with alpha(v)beta(1) and alpha(5)beta(1), in supporting melanoma cell adhesion to fibronectin. But even when activated, beta(1), integrins did not contribute to melanoma cell arrest during flow. Soluble ligand served as a cross-linker between attached and circulating tumor cells and enhanced melanoma cell arrest. Cohesion of activated melanoma cells was restricted to the matrix surface and did not occur in suspension. We conclude that the presence of alpha(v)beta(3) in a functionally activated state provides a unique advantage for circulating tumor cells by promoting tumor cell arrest in the presence of flow-dependent shear forces.