Inhibition of glioma invasion by overexpression of pigment epithelium-derived factor

Abstract

Pigment epithelium-derived factor (PEDF) is a potent inhibitor of angiogenesis and an inducer of neural differentiation. We previously reported the loss of PEDF expression in glioma progression. In this study, we investigated whether PEDF overexpression could suppress glioma growth and invasion. Glioma cell line U251 was stably transfected with a full-length human PEDF expression vector. The expression and release of various cytokines and angiogenic factors into the medium were analyzed by realtime reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and gelatin zymography. Apoptosis was checked by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. Growth inhibition was evaluated by using the in vitro Matrigel invasion. Tumorigenicity was examined in vivo by subcutaneous xenotransplantation into severe combined immunodeficient mice. In U251 cells overexpressing PEDF, thrombospondin-1 protein was upregulated (5.3-fold more), but the production of vascular endothelial growth factor (VEGF) (1.8-fold less) and basic fibroblast growth factor (2.5-fold less) was lower than in cells transfected with the vector only. PEDF also downregulated the production of matrix metalloproteinase-9. Conditioned medium collected from the PEDF-transfected U251 cells showed a significant reduction of VEGF expression. In vitro invasiveness was reduced by approximately 40%. PEDF expression prevented the growth of transfected cells and caused a significant increase in the percentage of cells undergoing apoptosis (50.4% in PEDF-transfected cells). Furthermore, the size of xenotransplants was significantly smaller. In conclusion, PEDF overexpression decreased malignancy, and this might be attributed to the promotion of apoptosis and the regulation of expression of angiogenic effectors. Thus, treatment with PEDF may be useful in patients with malignant gliomas. However, the mechanism of apoptosis induction needs to be investigated.

Pigment Epithelium-Derived Factor Regulates Early Pancreatic Fibrotic Responses and Suppresses the Profibrotic Cytokine Thrombospondin-1

“…Unlike our findings in the PEDF-null mice, previous reports 34,35 had indicated that PEDF and TSP-1 are coordinately regulated. To investigate a potential suppressive effect of PEDF on TSP-1, PEDF was overexpressed in Panc-1 cells (a pancreatic cancer cell line with relatively low PEDF levels).…”

“…35 PEDF overexpression in tumor cells similarly increased TSP-1 expression, with transcription factors implicated in this coordinated regulation. 34,37 However, the results from this study suggest that their respective roles in mediating tissue repair are unique. This is suggested by protein structure interactions with the tissue matrix and the phenotype of transgenic mice.…”

Pigment epithelium-derived factor overexpression inhibits orthotopic osteosarcoma growth, angiogenesis and metastasis

“…The complete inhibition of metastases with PEDF overexpression strongly indicates that it plays a key antimetastatic role, possibly through regulation of the microenvironment or direct changes in tumor cell phenotype. In a study by Guan et al, 37 decreased cellular invasion of malignant U251 cells was also seen in cells overexpressing PEDF. They showed that this was associated with a significant downregulation in matrix metalloproteinase-9 (MMP-9) activity, which plays an important role in extracellular matrix degradation.…”

Endogenous Inhibitors of Angiogenesis

“…In addition, PEDF may serve as a multifunctional antitumor agent in neuroblastomas, inhibiting angiogenesis while promoting the numbers of Schwann cells and differentiated tumor cells that in turn produce PEDF (172). The loss of PEDF expression was also detected in glioma progression (173). In PEDF-deficient mice, stromal vessels were increased and associated with epithelial cell hyperplasia (174).…”