Interaction of platelet-derived autotaxin with tumor integrin a_Vb₃ controls metastasis of breast cancer cells to bone

Autotaxin (ATX), through its lysophospholipase D activity controls physiological levels of lysophosphatidic acid (LPA) in blood. ATX is overexpressed in multiple types of cancers, and together with LPA generated during platelet activation promotes skeletal metastasis of breast cancer. However, the pathophysiological sequelae of regulated interactions between circulating LPA, ATX, and platelets remain undefined in cancer. In this study, we show that ATX is stored in α-granules of resting human platelets and released upon tumor cell-induced platelet aggregation, leadingto the productionofLPA. Our in vitro and in vivo experiments using human breast cancer cells that do not express ATX (MDA-MB-231 and MDA-B02) demonstrate that nontumoral ATX controls the early stage of bone colonization by tumor cells. Moreover, expression of a dominant negative integrin α_vβ₃-Δ744 or treatment with the anti-human α_vβ₃ monoclonal antibody LM609, completely abolished binding of ATX to tumor cells, demonstrating the requirement of afully active integrin α_vβ₃inthisprocess.The present results establishanewmechanism for platelet contribution to LPA-dependent metastasis of breast cancer cells, and demonstrate the therapeutic potential of disrupting the binding of nontumor-derived ATX with the tumor cells for the prevention of metastasis.