title: Akt3 controls vascular endothelial growth factor secretion and angiogenesis in ovarian cancer cells.
abstract: The PI3 kinase/Akt pathway is commonly deregulated in human cancers, functioning in such processes as proliferation, glucose metabolism, survival and motility. We have previously described a novel function for one of the Akt isoforms (Akt3) in primary endothelial cells: the control of VEGF-induced mitochondrial biogenesis. We sought to determine if Akt3 played a similar role in carcinoma cells. Because the PI3 kinase/Akt pathway has been strongly implicated as a key regulator in ovarian carcinoma, we tested the role of Akt3 in this tumor type. Silencing of Akt3 by shRNA did not cause an overt reduction in mitochondrial gene expression in a series of PTEN positive ovarian cancer cells. Rather, we find that blockade of Akt3, results in smaller, less vascularized tumors in a xenograft mouse model that is correlated with a reduction in VEGF expression. We find that blockade of Akt3, but not Akt1, results in a reduction in VEGF secretion and retention of VEGF protein in the endoplasmic reticulum (ER). The reduction in secretion under conditions of Akt3 blockade is, at least in part, due to the down regulation of the resident golgi protein and reported tumor cell marker, RCAS1. Conversely, over-expression of Akt3 results in an increase in RCAS1 expression and in VEGF secretion. Silencing of RCAS1 using siRNA inhibits VEGF secretion. These findings suggest an important role for Akt3 in the regulation of RCAS1 and VEGF secretion in ovarian cancer cells.
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Tiera A
authors.initials: TA
authors.lastname: Liby
authors.forename: Perry
authors.initials: P
authors.lastname: Spyropoulos
authors.forename: Haley
authors.initials: H
authors.lastname: Buff Lindner
authors.forename: Juanita
authors.initials: J
authors.lastname: Eldridge
authors.forename: Craig
authors.initials: C
authors.lastname: Beeson
authors.forename: Tien
authors.initials: T
authors.lastname: Hsu
authors.forename: Robin C
authors.initials: RC
authors.lastname: Muise-Helmericks
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000235:genetics; D010051:Ovarian Neoplasms / Q000098:blood supply / Q000201:enzymology* / Q000235:genetics; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D047368:Tumor Burden / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C120762:EBAG9 protein, human; D042461:Vascular Endothelial Growth Factor A; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase