Analysis of the survival and migration of ECs into tumor tissues after injection of anti–c-Kit mAb in tumor-bearing mice. Colon26 tumor cells (A-C) or PC3 tumor cells (D-F) were subcutaneously inoculated into mice. Then, anti-B220 control mAb (A,D), anti–c-Kit mAb (B,E), or CPM (C,F) was injected into the mice. Anti-B220 mAb or anti–c-Kit mAb (1 mg/d per mouse) was injected daily from day 2 to day 5 after inoculation of tumor cells, and CPM (170 mg/kg per single injection) was injected on day 0 and day 6. Tumors were dissected on day 7. Sections were stained with anti–PECAM-1 mAb (red) and were subsequently analyzed for the presence of apoptotic cells by the TUNEL assay (dark blue). Arrowheads in panels B,E indicate round, apoptotic cells, and arrows in panels C,F indicate ECs. The inset in each panel shows a high-power view of the area indicated by the box. Bar in panel A indicates 40 μm in panels A-C and 60 μm in panels D-F.