CXCR4, the receptor of the chemokine CXCL12/SDF-1, is expressed in many tumours of multiple types including mammary (Muller et al, 2001), colon (Zeelenberg et al, 2003) and pancreatic (Saur et al, 2005) carcinoma, melanoma (Scala et al, 2005) and brain tumours (Rubin et al, 2003). The gene discussed is CXCL12; the disease is melanoma.