CEBPA and neoplasm: To determine if MDSCs were responsible for increased tumor angiogenesis and accelerated tumor growth observed in CebpaΔ/Δ mice in which C/EBPα was deleted in myeloid lineage cells, we sorted Gr1+ CD11b+ cells from the spleens of CebpaΔ/Δ and control mice bearing 3LL and B16 tumors by FACS.