CXCR4 and breast carcinoma: Most particularly, the protein complex CXCR4/stromal cell-derived factor-1α (SDF-1α) is considered to play a central role in breast carcinoma metastasis (20), and might be involved in regulation of the metastatic behavior of tumor cells (21), as well as in metastasis of CXCR4+ tumor cells into the bone marrow and lymph nodes (22).