title: Role of protein kinase C isoforms in phorbol ester-induced vascular endothelial growth factor expression in human glioblastoma cells.
abstract: Aberrant expression of the potent angiogenic cytokine, vascular endothelial growth factor (VEGF), has been demonstrated to be associated with most human solid tumors. Both transcriptional and post-transcriptional mechanisms have been shown to modulate VEGF expression in a multitude of cell types. Here we report that when protein kinase C (PKC) pathways were activated in human glioblastoma U373 cells by phorbol 12-myristate 13-acetate (PMA), VEGF mRNA expression was up-regulated via a post-transcriptional mRNA stabilization mechanism. PMA treatment exhibited no increase in VEGF-specific transcriptional activation as determined by run-off transcription assays and VEGF promoter-luciferase reporter assays. However, PMA increased VEGF mRNA half-life from 0.8 to 3.6 h which was blocked by PKC inhibitors but not by protein kinase A or cyclic nucleotide-dependent protein kinase inhibitors. When U373 cells were transfected with antisense oligonucleotide sequences to the translation start sites of PKC-alpha, -beta, -gamma, -delta, -epsilon, or -zeta isoforms, both PKC-alpha and -zeta antisense oligonucleotides showed substantial inhibition of PMA-induced VEGF mRNA. In addition, overexpression of PKC-zeta resulted in a strong constitutive up-regulation of VEGF mRNA expression. This study demonstrates for the first time that specific PKC isoforms regulate VEGF mRNA expression through post-transcriptional mechanisms.
authors.affiliation: Departments of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Shih
authors.forename: A
authors.initials: A
authors.lastname: Mullen
authors.forename: K
authors.initials: K
authors.lastname: Abrams
authors.forename: D
authors.initials: D
authors.lastname: Mukhopadhyay
authors.forename: K P
authors.initials: KP
authors.lastname: Claffey
mesh_terms: D016228:Endothelial Growth Factors / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D005909:Glioblastoma / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008222:Lymphokines / Q000235:genetics*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008222:Lymphokines; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate