The effect of this mechanism on metastatic behaviour was demonstrated early in breast cancer: e.g., breast cancer cells express high levels of CXCR4 and CCR7, which are responsible for metastasis settlement in LN, lung, liver and bone marrow, as these organs are rich in corresponding ligands CXCL12 and CCL21 [182,183];. The gene discussed is CCL21; the disease is breast carcinoma.