The foundation forour appreciation of the role that CXCR4 and CXCL12 may play in cancermetastasis was set in 2001, when a landmark study by Albert Zlotnik'sgroup demonstrated the importance of the CXCL12/CXCR4 axis in site-specificmetastasis of breast cancer [25]. This evidence concerns the gene CXCL12 and breast carcinoma.