Fig. 3

Vascular response upon skin chemical tumorigenesis in D4BE and D4OE mice. a Tumor endothelium was visualized by section PECAM immunostaining of skin tumors collected from DMBA/TPA-treated mice 20 weeks after the DMBA-initiation. Endothelial Dll4 over-expression was found to reduce endothelial system density by reducing its ramification (b), although branch diameters were observed increased in D4OE vs. D4BE mice (c). d Mural cell recruitment was assessed by PECAM/SMA co-immunostaining (above). e Endothelial Dll4 over-expression promoted vessel wall assembly which contributed to the normalization of tumor vasculature. f To evaluate tumor vessel competence, sub-groups of both D4BE and D4OE mice were perfused before being sacrificed with i.v. injected lectin as presented in “Materials and Methods”. Simultaneous immunostaining to PECAM and biotinylated lectin visualization with Streptavidin-Alexa 488 demonstrate increased fraction of competent vessels in D4OE vs. D4BE skin tumors (f). Percentage of PECAM-positive area co-localized with lectin (Alexa 488 signal) was measured to quantify the portion of functional vessels within skin tumors (g). The images presented in panels a-g were captured and processed as described in Fig. 1. Error bars represent SEM. *, P < 0.05 and **, P < 0.01 were considered statistically significant and highly significant, respectively. Results are representative of n = 10 per mice group