ITGAM and neoplasm: To examine the direct contribution of the Tu-Gr1+CD11b+ cells in promoting the enrichment of the SCA1+ population, we MACS isolated Gr1+ cells from PTs, bone marrow, and spleen of 4T1 tumor–bearing BALB/c mice and cocultured them in vitro with parental 4T1 or sorted 4T1-SCA1– cells (Figure 2B).