Inhibition of VEGF or bFGF-induced angiogenesis. a, C57BL/6J mice (n = 8) were vaccinated with either attenuated S. typhimurium harboring the empty vector pcDNA3.1 (left panels) or the vector pcDNA3.1-FLK1 (right panels). Vascularization was induced either by VEGF (upper panels) or bFGF (lower panels). Arrows indicate borders of Matrigel plugs. b, Quantification of vessel growth after in vivo staining of endothelium with FITC-labeled Isolectin B4 and evaluation by fluorimetry. The average fluorescence of Matrigels is depicted. Vaccination with pcDNA3.1-FLK1 (_) or pcDNA3.1 (_) (P < 0.05). c, Immunhistochemical analysis of CD31 (top panels) and FLK-1 (bottom panels) in pulmonary metastases of a CT-26 colon carcinoma 4 wk after immunization (right panels) compared with a tissue specimen after control immunization (left panels). d, Quantification of vessel density by counting CD31+ and FLK-1+ cells in high-power fields in tumor tissue after vaccination with pcDNA3.1-FLK1 (_) or pcDNA3.1 (_) (P < 0.05). Error bars indicate s.d.