CXCR2 and rhabdomyosarcoma: Elevated serum levels of the CXCR2 ligands CXCL1 and CXCL2 correlated with increased intra-tumoral MDSC infiltration and reduced overall survival in a cohort of ovarian cancer patients [44], while elevated serum CXCL8 was associated with metastasis and reduced overall survival in pediatric patients with rhabdomyosarcoma [45].