Moreover, many pediatric neuroblastoma, Ewing sarcoma (ES), osteosarcoma, and ALL, show altered expression of circulating cytokines/chemokines such as CCL2, CXCL4, CXCL6, CXCL10, and CXCL12 [40,41,42]. The gene discussed is CXCL12; the disease is Ewing sarcoma.