(A). Balb/C mice were challenged with Renca tumor cells then treated with sunitinib 7 days later. On indicated days after first sunitinib treatment, mice were given retroorbital injections of FITC-labeled Annexin V (green, to detect apoptotic cells), Dextran-rhodamine (red, to stain vessels) and Hoechst 33342 (blue, to stain nuclei). Intravital multi-photon microscopy analysis was performed, 15 min after injection, on tumors grown in mice treated with vehicle or sunitinib. Western blot analysis of Renca tumor tissues harvested 1 day after sunitinib treatment shows its effects on p-Stat3 and other indicated molecules. (B). Frozen tumor sections of vehicle and sunitinib-treated tumors (same as in A) were stained for pY-Stat3 (green), CD31/PECAM-1 (red), and Hoechst 33342 (blue) and analyzed by confocal laser scanning microscopy; scale bar, 10 μm.