(A,B) After 3, 6, and 9 days +/− sunitinib initiation to 4T1+ mice, mice were pulsed with BrdU (1 hour following sunitinib dosing) for 4 hours. Splenic and BM CD11b+Gr1+lo and CD11b+Gr1+hi cells were gated on and BrdU positivity determined by FACS. Cells from mice not given BrdU were used as staining controls. (C) 4T1+ splenocytes were stained for CD11b, Gr1, Ly6G, and F4/80 before and after MDSC subset isolation with magnetic beads. Representative FACS data and cytospins shown. n=2. (D) Mice were treated as above for (A) only splenocytes were stained for CD11b, Gr1, and annexinV and immediately ran for FACS.