In vivo efficacy of Ad5/3-9HIF-Δ24-VEGFR-1-Ig in a subcutaneous model. Subcutaneous 786-O renal cancer tumors were injected intratumorally. Tumor size was followed and plotted relative to size on the day before virus injection, which was performed on day 1 (a). Blood samples were analyzed for VEGFR-1-Ig expression by ELISA (b). At the end of the experiment, tumors were collected, sections were made and stained with polyclonal von Willebrand Factor antibody for blood vessels (red) and pictures were taken at × 20 magnification (c). Quantification of the blood vessel density revealed significantly inhibited vascularization (d). Tumor sections were also stained for adenovirus hexon protein (brown) (e). Bars, standard error; *significant difference (P<0.05).