Selective inhibition of PDGFRβ impairs vascular function and increases vessel apoptosis in tumors with high PDGF-BB expression. (A) Tumor blood vessel perfusion was assessed by injection of FITC-lectin in LLC tumor-bearing ASKA mice treated with vehicle, 1-NaPP1 or imatinib daily for 10 consecutive days. Tumor sections were then stained for CD31 and vessel perfusion was examined in more than 20 field 200x magnification images for each mouse (n=6 or more animals); FITC-lectin, green; CD31, red; DAPI, blue. Scale bar, 50 µM. Quantification of vessel perfusion is shown where each data point corresponds to one individual mouse. ***p<0.001. (B) Endothelial cell apoptosis was analyzed by co-immunostaining of cleaved caspase 3 and CD31; cleaved caspase 3, red; CD31, green; DAPI, blue. Quantification of the vessels positive for the apoptosis marker is depicted. *p<0.05; each data point corresponds to one individual mouse (n=6 or more animals).