As for the mechanism by which Ephrin A3 protein promotes a metastatic behavior, using a combination of breast cancer orthotopic xenotransplantation and co-culture models, we demonstrated that by imposing repulsive interactions between tumor and endothelial cells Ephrin-A3 enhances the ability of tumor cells to intravasate/extravasate into the tumor microvasculature (Figure). The gene discussed is EFNA3; the disease is breast carcinoma.