Inhibition of breast cancer cell adhesion and bone metastasis by the extracellular adherence protein of Staphylococcus aureus

Abstract

Bone metastasis is a common sequelae of breast cancer and the interaction of αvβ3-integrin with osteopontin (OPN) found in the extracellular matrix of mineralized tissues is implicated in this process. The integrin-dependent proadhesive and promigratory functions of OPN are particularly attributed to the 40kD N-terminal fragment that derives upon matrix metalloproteinase (MMP) cleavage. Based on the broad repertoire of interactions between Staphylococcus aureus extracellular adherence protein (Eap) and host components, we here characterized Eap to specifically interact with recombinant full-length OPN and the 40kD N-terminal MMP cleavage fragment, but not with the 32kD or the 25kD C-terminal fragments of OPN. Eap thereby prevented the OPN/αvβ3-integrin interaction, as well as the αvβ3-integrin-dependent adhesion of MDA-MB-231 breast cancer cells to full-length OPN or to the 40kD fragment and the migration of these cells towards OPN. Furthermore, Eap treatment markedly impaired the development of osseous metastasis of human MDA-MB-231 cells in vivo. Taken together, Eap may represent an attractive novel treatment for the prevention of breast cancer bone metastasis.