(Data were not shown). These data confirmed that Ad-PEDF-mediated PEDF gene transfer and expression is responsible for the inhibition of tumor angiogenesis in the studied tumor model. Figure 6 Alginate-encapsulated tumor cell assay for the inhibition of angiogenesis. Mice bearing

alginate beads containing CT26 tumor cells were treated with NS, Ad-Null, or Ad-PEDF twice on day 1 and 8, respectively. On day 11, all mice received an injection of FITC-dextran and were sacrificed 20 min later. A. Photographs show surface of alginate beads from different groups. B. FITC-dextran uptake in the tumor tissue was significantly decreased in mice treated with Ad-PEDF compared to mice treated with NS (a) or Ad-Null (b) group

(p < 0.05). n = 2; 4 beads/mouse. Discussion Angiogenesis is required for a variety of physiological and pathological processes. It is a GDC-0449 molecular weight complex biological process under precise regulation of multiple factors in multiple steps [19]. There are two groups of reciprocally antagonizing factors, proangiogenitors and antiangiogenitors. The former includes vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (b-FGF) and fibroblast growth factor (FGF), check details and the latter includes angiostatin, endostatin, thrombospondin and PEDF. PEDF is notable for its inhibitory function responsible for the avascularity of ocular compartments by opposing the angiogenic effect of VEGF in eye. It has been shown that PEDF is the most potent endogenous inhibitor of angiogenesis; its potency is twice that of angiostatin and seven times of endostatin [5, 20]. Recently, data showed that PEDF also plays important roles in regulating normal development and tumor growth. For example, a recent study showed

that the expression of PEDF is inversely proportional to the expression of VEGF at the growth plate of cartilage and is involved in the control of osteosarcoma [21]. In addition, it has been reported that PEDF could significantly inhibit neuroblastoma and Wilms’ tumor [22, 23]. A decrease of PEDF results in a tumor-permissive environment and promotes Phospholipase D1 tumor growth and metastasis [9]. It is generally thought that PEDF’s anti-tumor activity is the extended function of its antiangiogenic effect, decreasing microvascularity and blood supplying. In the past decade, researchers have prepared various forms of PEDF and demonstrated its beneficial effects in several tumor models. Doll et al reported that exogenous recombinant PEDF protein induced tumor epithelial apoptosis in mouse prostate and pancreas [24]. Liu et al showed that a short peptide derived from the parent PEDF molecule was able to inhibit osteosarcoma growth [25]. Streck et al reported that adeno-associated virus (AAV) delivering PEDF gene treatment successfully restricted human neuroblastoma engraftment in a dose-dependent fashion [22].