CXCR4 and breast cancer: The SDF-1/CXCR4 signaling axis has been shown to be a major player in the dissemination and metastasis of tumor cells, e.g., in breast cancer metastasis to the bone marrow [43], VEGF-induced neovascularization and retention of myeloid cells in normal and cancerous tissues [44], recruitment of vascular progenitors to glioma [38], and glioma invasion and growth [45], [46].