Figure 2. Vasculature in tumors generated from clone 4. A) Histological analysis of tumor vasculature was performed by immunostaining for CD31 and VEGF receptor. Top) CD31 staining (original magnification x40). Bottom) immunohistochemistry of VEGFR (original magnification x200). B) Quantification of CD31-positive area from tumors described in A. n = 5 for number of tumors collected at each time point. Compared to tumors collected at day 14 postinjection, there is a statistically significant decrease in microvessel density (MVD) compared to tumors collected at day 60 (P=0.00199). There is statistically significant (P<0.01) increase in MVD in tumors collected after the angiogenic switch (day 138 on average).