Double immunofluorescence staining (A) and quantitative analysis (B) of proliferating tumor cells (Ki67+, arrowheads) and tumor-induced endothelial cells (CD31, arrows) in pulmonary metastases with different diameters (n > 20 metastases for each group are counted, error bars show SEM). (C) SU5416 treatment impaired both ECs penetration and initial pulmonary metastases expansion. Images show 10 dpi mouse lungs with B16 metastases (black spots in bright-field or red spots in fluorescent panel. H&E staining shows the pulmonary metastases in mice lungs, CD31 and Ki67 double immunofluorescence staining shows the ECs (arrows) and proliferating tumor cells (arrowheads). Yellow dotted line is based on DAPI staining to indicate the outline of the main tumor clones. White dotted line is based on Ki67 and DAPI staining to indicate the range of proliferating tumor cells. (D–F) Quantitative analysis of the tumor-induced ECs, size and density of pulmonary metastases of 10d mouse lungs treated with or without SU5416. (G,H) Quantitative analysis of the density and size of pulmonary metastases under stereomicroscope of 15d mouse lungs treated with either SU5416 or Sunitinib. (n > 20 selected areas in each group, n = 5 individual mice lung are counted).( *p < 0.05, **p < 0.01, error bars show SEM). (I,J) Representative image and quantitative analysis of apoptosis in pulmonary metastases in mice treated by SU5416. **p < 0.01.