Figure 2. ADI-PEG20 induces significant reduction in ASS1-positive tumor edema and angiogenic vessels and in combination with ionizing radiation drastically reduces GL261-GFP tumor growth.

(A) H&E-stained fresh-frozen brain sections from saline-treated animals (green box) and cryoblocks from all treatment groups. Vasogenic edema (blue box) (Ed) and intratumor vasculature (black box) (TV) in saline control animals (green box). (B) Representative brains from each treatment group were cryosectioned and stained with H&E. (C) The percentage tumor volume was measured using the formula V = (L × W²)/2, where L represents the largest tumor diameter and W represents the perpendicular tumor diameter. (D) Immunohistochemical analysis of free-floating sections for tumor vasculature using anti-CD31 and –α_vβ₃ integrin antibodies. Scale bar: 50 μm. (E) Percentage of angiogenic vessels in tumor sections as assessed by colocalization of CD31 and α_vβ₃ staining. Results are representative of 3 animals per group. Note in the combined treatment group only 1 animal had evidence of tumor. ***P < 0.001; ****P < 0.0001. Data were analyzed using 1-way ANOVA.