Tumor cell proliferation, apoptosis, and microvessel density in response to PTK787 and IR. Mice with NF9006-derived allografts or spontaneous mammary carcinomas were treated with PTK787 (100 mg/kg × 4), IR (4 Gy × 3), or in combination. At day 4 of treatment, mice were sacrificed, and tumors were harvested, formalin fixed, and stained for the Ki-67 (A), TUNEL (B), and CD31 (C) as marker of tumor cell proliferation, apoptosis, and microvessel density, respectively. Percentage CD31-positive cells and Ki-67- and TUNEL-positive nuclei per high-powered fields (hpf) was determined in 4-10 randomly chosen visual fields in each of at least two similarly treated vital tumor tissues of allografts and orthotopic tumors. For the allograft tumor tissue sections 3 mice/group and for the spontaneous tumor model tissue sections 2-4 mice/group were used. Each bar represents the mean value per group ± SD (*<0.05; **<0.01; ***<0.005).