Chemokine receptor CXCR4 is a highly conserved G-coupled protein receptor (GCPR) first discovered in 1996 as being required for HIV entry into CD4+ T cells [6] and later identified as being expressed in various cell types including hemopoietic stem cells, stromal fibroblast cells, and cancer cells [7,8]. The gene discussed is CXCR4; the disease is cancer.