CXCL12 and cancer: Especially, CXC chemokine and their receptor signaling introduced by CXCL12 (same as SDF1, stromal cell-derived factor-1) and its receptor CXCR4, are known to promote the migration of neural stem cells [67], primordial germ cells [65], cancer stem cells [68] and neural crest cells [69], and are involved in the homing and maintenance of hematopoietic stem cells (HSCs) [70,71,72].