Glial Cell Line-Derived Neurotrophic Factor (GDNF) Promotes Angiogenesis through the Demethylation of the Fibromodulin (FMOD) Promoter in Glioblastoma

BACKGROUND: Angiogenesis plays an important role in the progression of glioblastoma, with a high degree of malignancy. Previous studies have proved that glial cell line-derived neurotrophic factor (GDNF) and fibromodulin (FMOD) are strongly expressed in human glioblastoma. The purpose of this study was to explore the roles of GDNF and FMOD in angiogenesis and the molecular mechanisms underlying these roles in human glioblastoma. MATERIAL/METHODS: The effects of GDNF on the expression and secretion of vascular endothelial growth factor (VEGF) in human glioblastoma cell line U251 and angiogenesis in human umbilical vein endothelial cells (HUVECs) were investigated. The molecular mechanism of GDNF-induced expression of FMOD was explored. The roles of FMOD in GDNF-induced expression and secretion of VEGF and angiogenesis were also examined. RESULTS: In the present study, we showed that GDNF promoted the expression and secretion of VEGF in U251 cells. VEGF mediated GDNF-induced angiogenesis in human glioblastoma. In addition, GDNF significantly upregulated the expression of FMOD in U251 cells. Mechanistically, the results of luciferase reporter assay and methylation-specific PCR (MSP) demonstrated that GDNF facilitated the demethylation of the FMOD promoter. More importantly, we found that FMOD acted as an important mediator in VEGF expression and angiogenesis induced by GDNF in human glioblastoma. CONCLUSIONS: Collectively, our data show that GDNF promotes angiogenesis through demethylation of the FMOD promoter in human glioblastoma, indicating that GDNF and FMOD may be potential therapeutic targets for glioblastoma.