Figure 4

Differential VEGF expression and angiogenesis in NIH3T3 cells overexpressing of distinct ErbB receptor combinations. Transduced NIH3T3 cells, expressing single ErbB receptors (A) or paired ErbB receptor combinations (B), were injected subcutaneously into BALB/c nude mice and resulting tumor xenografts were analyzed immunohistochemically. Paraffin sections from NIH3T3-ErbB tumors were stained with hematoxylin and eosin to analyze the tumor morphology or immunolabeled with anti-VEGF antibody. Cryostat sections were immunolabeled with anti-CD31 antibody. The primary antibody was omitted for negative control staining (−). Bar, 400 μm. (C) Quantitation of vascularization in NIH3T3-ErbB tumors. NIH3T3-ErbB tumors were quantitated for vessel staining as described in MATERIALS AND METHODS. Results were obtained from three independent tumor sections. Values represent the mean ± SD. *p < 0.05, compared with EGFR or ErbB-2; **p < 0.05, compared with ErbB-2 or ErbB-3.