CXCL12 and cancer: Amongst the chemoattractant signaling molecules that are known to be involved in tumor cell chemotaxis, CXCR4 (which binds stromal derived growth factor (SDF-1α or CXCL12) and EGFR (epidermal growth factor receptor) are notable in their relevance to the metastasis in many different cancer types, particularly breast cancer [4].