CXC chemokine receptor type 4 (CXCR4) is a 7-transmembrane G-protein-coupled receptor [27], which is widely expressed in peripheral blood and other organ tissues, including hematopoietic stem cells, endothelial cells, lymphocytes, and cancer cells [28], and mainly participates in chemotaxis in the immune and hematopoietic systems [29]. The gene discussed is CXCR4; the disease is cancer.