PDGFRβ blockade abrogates the effects of FGF9 on tumor vessels and metastasis.
A, micrographs of zinc-fixed renal tumor sections harvested 10 days after orthotopic injection of Renca cell and immunostained for NG2 (red) and VE-cadherin (brown) or SM α-actin (red) and CD31 (brown). PDGFRβ-blocking antibody or isotype-matched IgG was applied on day 7. On the right are graphs depicting the percentage of microvessels invested with NG2-positive pericytes or SM α-actin-positive mural cells (top, *, p = 0.026 versus GFP + IgG; †, p = 0.006 versus FGF9 + IgG) (lower, *, p = 0.027 versus GFP + IgG; †, p = 0.038 versus FGF9 + IgG). B, data from FGF9-incubated tumors exposed to anti-PDGFRβ antibody or control IgG, depicting vascular lumen diameter (*, p < 0.001), branch point density (*, p = 0.003), length density (p = 0.094) or capillary density (*, p = 0.046). Data are derived from analysis of intravital microscopy videos. C, hematoxylin and eosin-sections of lungs, harvested 10 days after orthotopic injection of FGF9-Renca cells with subsequent exposure of primary tumors to anti-PDGFRβ antibody or control IgG. On the right are graphs depicting the density and size of intrapulmonary metastases (*, p = 0.002; *, p < 0.001, respectively).