CXCR4 and neuroblastoma: Later, in vitro studies suggested that NB cells use the same CXCR4/CXCL12 axis for metastasis as HSPCs do for homing after stem cell transplantation [108] and that this process is supported by MSCs (Fig. 1D): Upon incubation with MSC-conditioned medium, NB cells showed increased migration and invasiveness, which was dependent on the CXCR4/CXCL12 axis [68,100,109].