Sunitinib treatment affected tumor physiology. A-B, representative immunohistochemical preparations stained with anti-CD31 antibody to visualize microvessels (A) or anti-pimonidazole antibody to visualize hypoxic regions (B). The images show an untreated A-07 tumor (vehicle; left) and a sunitinib-treated A-07 tumor (sunitinib; right). C-F, microvascular density (MVD), hypoxic fraction, necrotic fraction, and IFP in untreated and sunitinib-treated A-07 tumors. Columns, means of 11-15 tumors; bars, SEM.