title: P70S6K 1 regulation of angiogenesis through VEGF and HIF-1alpha expression.
abstract: The 70kDa ribosomal S6 kinase 1 (p70S6K1), a downstream target of phosphoinositide 3-kinase (PI3K) and ERK mitogen-activated protein kinase (MAPK), is an important regulator of cell cycle progression, and cell proliferation. Recent studies indicated an important role of p70S6K1 in PTEN-negative and AKT-overexpressing tumors. However, the mechanism of p70S6K1 in tumor angiogenesis remains to be elucidated. In this study, we specifically inhibited p70S6K1 activity in ovarian cancer cells using vector-based small interfering RNA (siRNA) against p70S6K1. We found that knockdown of p70S6K1 significantly decreased VEGF protein expression and VEGF transcriptional activation through the HIF-1alpha binding site at its enhancer region. The expression of p70S6K1 siRNA specifically inhibited HIF-1alpha, but not HIF-1beta protein expression. We also found that p70S6K1 down-regulation inhibited ovarian tumor growth and angiogenesis, and decreased cell proliferation and levels of VEGF and HIF-1alpha expression in tumor tissues. Our results suggest that p70S6K1 is required for tumor growth and angiogenesis through HIF-1alpha and VEGF expression, providing a molecular mechanism of human ovarian cancer mediated by p70S6K1 signaling.
authors.affiliation: Department of Pathology, Cancer Center, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Chuan-Xiu
authors.initials: CX
authors.lastname: Bian
authors.forename: Zhumei
authors.initials: Z
authors.lastname: Shi
authors.forename: Qiao
authors.initials: Q
authors.lastname: Meng
authors.forename: Yue
authors.initials: Y
authors.lastname: Jiang
authors.forename: Ling-Zhi
authors.initials: LZ
authors.lastname: Liu
authors.forename: Bing-Hua
authors.initials: BH
authors.lastname: Jiang
mesh_terms: D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000098:blood supply* / Q000235:genetics / Q000473:pathology*; D034741:RNA, Small Interfering / Q000235:genetics; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000096:biosynthesis*
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D038762:Ribosomal Protein S6 Kinases, 70-kDa