With research suggesting that both CXCR4 and CXCR7 alone can enhance metastasis, we set out to dissect the roles of CXCR4 and CXCR7 in the different steps of metastasis (invasion, intravasation, and metastasis formation) by overexpressing CXCR4, CXCR7, or both receptors in the rat mammary adenocarcinoma cell line MTLn3. The gene discussed is CXCR4; the disease is breast adenocarcinoma.