Notably, CXCL12/CXCR4 appears to be important for site-specific metastasis of several cancers; CXCR4-positive cancer cells invade along CXCL12 gradients thus promoting metastasis to CXCL12-expressing organs such as lymph nodes, lung, livers and bone [95,96]. The gene discussed is CXCL12; the disease is cancer.