The CXCR4-CXCL12 signaling pathway, however, is not only involved in the migration of cancer cells, but also in the trafficking of stem cells and immune cells, such as CXCR4-expressing hematopoietic stem cells, progenitor cells, pre-B lymphocytes, and T lymphocytes [12, 13]. The gene discussed is CXCR4; the disease is cancer.