CXCR4 and neoplasm: In addition to its critical role in tumor cell growth, survival and angiogenesis in multiple cancers, the CXCR4/SDF-1α pair has been shown to mediate homing and metastatic secondary growth in SDF-1α-producing organs, such as liver and bone marrow (21–23) and a study indicates that neuroblastoma cells are equipped with a bone marrow homing system that may mediate the establishment of bone marrow metastasis by neuroblastoma cells (24).