Using a xenograft model in which human breast cancer cell lines with different tumorigenic potential were injected contralaterally into the same mouse, pro-angiogenic cytokines secreted by human luminal breast cancer cells have been shown to mobilize pro-angiogenic vascular endothelial growth factor receptor 2 (VEGFR2)+ bone marrow-derived cells into distal tumors to promote angiogenesis (Kuznetsov et al., 2012). The gene discussed is KDR; the disease is breast cancer.