Thus, Ewing sarcoma cell lines consistently grouped into CXCR4-high (TC-32 and CADO-ES1) and CXCR4-low (A673, TC-71, VH-64, DC-ES-6) surface expression; indicating that substantial CXCR4 surface expression was not essential for proliferative and migratory responses to plerixafor that were observed in both groups. Here, CXCR4 is linked to Ewing sarcoma.