title: PTEN mutation and epidermal growth factor receptor activation regulate vascular endothelial growth factor (VEGF) mRNA expression in human glioblastoma cells by transactivating the proximal VEGF promoter.
abstract: Our previous work showed that, compared with parental U87MG human glioblastoma cells, vascular endothelial growth factor (VEGF) mRNA levels are decreased in U87/T691, a derivative line in which epidermal growth factor receptor (EGFR) signaling is inhibited by introduction of a truncated p185(Neu) protein (A. Maity et al., Cancer Res., 60: 5879-5886, 2000). The effect of EGFR activation on VEGF was mediated at the level of transcription via a phosphatidylinositol 3'-kinase (PI3K)-dependent pathway. In the current study we investigated the effect of PTEN, a negative regulator of PI3K signaling commonly mutated in glioblastoma cells, on VEGF expression. Several glioblastoma cell lines containing mutant PTEN, including U87MG, U87/T691, and U251MG, were infected with adenovirus expressing wild-type PTEN. This led to a decrease in the levels of both VEGF mRNA and phosphorylated Akt, a marker for PI3K activation. Treatment of U87MG cells with LY294002, a PI3K inhibitor, or cotransfection with a vector expressing wild-type PTEN decreased VEGF promoter activity using reporters containing either 1.5 kb of the promoter or a fragment extending from -88 to +54 bp. Activity of the -88/+54 VEGF promoter was down-regulated by dominant negative Akt and up-regulated by constitutively active myristoylated Akt. Introduction of wild-type PTEN and pharmacological inhibition of EGFR decreased VEGF mRNA expression and VEGF promoter activity in U87MG cells to a greater extent that did either manipulation by itself. Therefore, in human glioblastoma cells, PTEN mutation can cooperate with EGFR activation to increase VEGF mRNA levels by transcriptionally up-regulating the proximal VEGF promoter via the PI3K/Akt pathway.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Nabendu
authors.initials: N
authors.lastname: Pore
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.forename: Daphne A
authors.initials: DA
authors.lastname: Haas-Kogan
authors.forename: Donald M
authors.initials: DM
authors.lastname: O'Rourke
authors.forename: Amit
authors.initials: A
authors.lastname: Maity
mesh_terms: D016228:Endothelial Growth Factors / Q000235:genetics*; D066246:ErbB Receptors / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D005909:Glioblastoma / Q000235:genetics; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D008222:Lymphokines / Q000235:genetics*; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D012333:RNA, Messenger; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human