CXCR2 and neoplasm: The results showed that normal myelopoiesis was not affected in CXCR2−/− mice (Fig. S1A–D), however, the number of mo-MDSCs were all significantly reduced in CXCR2−/− mice bearing tumors after 3 weeks (Fig. 1d), indicating that CXCR2 was required for mo-MDSCs expansion under tumor conditions.