Chemokine receptor CXCR4 is involved only in some partially clarified steps of carcinoma (breast, prostate) metastatic process (Balkwill, 2004; Darash-Yahana et al, 2004), and silencing CXCR4 blocks breast cancer metastasis (Liang et al, 2005). The gene discussed is CXCR4; the disease is breast carcinoma.