To gain insight into the role of the CXCR4-CXCL12 axis in EWS biology, CXCR4 expression and functionality (in the presence of CXCL12 and/or CXCR4-antagonist AMD3100) were evaluated in a large panel of therapy-naïve and metastatic tumors and cell lines, respectively. The gene discussed is CXCL12; the disease is metastatic neoplasm.