The molecular impact of pigment epithelium-derived factor, PEDF, on lung cancer cells and the clinical significance

Pigment epithelium-derived factor (PEDF) is an endogenous protein factor that has been shown to act as anti-angiognesis factor. The present study aimed to determine the direct biological effects of PEDF on lung cancer cells and deduce a clinical relevance in patients with lung cancer, major cause of death worldwide in which the knowledge of PEDF remains poor. We constructed a mammalian expression system for human PEDF produced recombinant PEDF (rhPEDF) protein from 3T3 cells. The expression of PEDF was examined using SDS-PAGE and Western blot analysis. Using the rhPEDF protein, we investigated the biological function of PEDF in the lung cancer cells as well as endothelial cells. PEDF expression levels were assessed in a cohort of human lung cancer specimen (77 pairs of matched normal and tumour tissues), in association with patient clinical variables and survival, using quantitative analysis of PEDF. In vitro, we found that administration of rhPEDF on two lung cancer cell lines (A549 and SK-MES1) significantly reduced tumour cell growth (P<0.05) with no significant effect on the growth of vascular cell line (HECV). We also found that rhPEDF significantly decreased lung cancer motility and adhesion to extracellular matrix (Matrigel) when compared with the control cells (P<0.05). We showed that reduced PEDF levels in lung cancer tissues significantly correlated with lymph node metastasis and an overall poor prognosis in the lung cancer patients. PEDF suppresses the growth and motility of lung cancer cells and has a significant correlation with the clinical outcome of the patients. These results contribute to our understanding of the molecular mechanisms of PEDF and indicates a potential prognostic and therapeutic impact of PEDF in lung cancer.