CXCR4 and neuroblastoma: In vivo studies performed by implantation of transduced NB cell lines expressing CXCR7, CXCR4, or a combination of both receptors, either subcutaneously or directly in adrenal gland (AG), showed that in contrast to CXCR4, CXCR7 elicited anti-tumorigenic properties, particularly in presence of CXCR4 [35].