Given what is known about the complexity of CXCR4 regulation, from transcriptional to post-transcriptional mechanisms, translational to post-translational modifications, and the active process of sub-cellular trafficking [39, 40], it is highly likely that multiple mechanisms contribute to dynamic regulation of CXCR4 in Ewing sarcoma. Here, CXCR4 is linked to Ewing sarcoma.