Inhibition of tumor angiogenesis by Ad-PEDF systemic administration. Tumors were harvested from NS (a), Ad-Null/Liposome (b), Ad-PEDF (c), or Ad-PEDF/Liposome (d) treated mice. Frozen tissue sections were fixed and treated with anti-CD31 antibody. The stained sections were visualized. Significantly decreased micro-vessels were observed in the Ad-E/Lipo-treated group compared with other groups (e, *indicates P < 0.05).