Role of c-Met/β1 integrin complex in the metastatic cascade

Metastases cause 90% of human cancer deaths. The metastatic cascade involves local invasion, intravasation, extravasation, metastatic site colonization, and proliferation. While individual mediators of these processes have been investigated, interactions between these mediators remain less well defined. We previously identified a structural complex between receptor tyrosine kinase c-Met and β1 integrin in metastases. Using novel cell culture and assays, we found that c-Met/β1 complex induction promotes breast cancer intravasation and adhesion to the vessel wall, but does not increase extravasation. These effects may be driven by the ability of the c-Met/β1 complex to increase mesenchymal and stem cell characteristics. Multiplex transcriptomic analysis revealed upregulated Wnt and hedgehog pathways after c-Met/β1 complex induction. A β1 integrin point mutation that prevented binding to c-Met reduced intravasation. OS2966, a therapeutic antibody disrupting c-Met/β1 binding, decreased invasion and mesenchymal gene expression and morphology of breast cancer cells. Bone-seeking breast cancer cells exhibited higher c-Met/β1 complex levels than parental controls and preferentially adhere to tissue-specific matrix. Patient bone metastases demonstrated higher c-Met/β1 levels than brain metastases. Thus, the c-Met/β1 complex drives breast cancer cell intravasation and preferential affinity for bone tissue-specific matrix. Pharmacological targeting of the complex may prevent metastases, particularly osseous metastases.