title: Suppression of tumor angiogenesis by metformin treatment via a mechanism linked to targeting of HER2/HIF-1α/VEGF secretion axis.
abstract: Anti-angiogenesis is currently considered as one of the major antitumor strategies for its protective effects against tumor emergency and later progression. The anti-diabetic drug metformin has been demonstrated to significantly inhibit tumor angiogenesis based on recent studies. However, the mechanism underlying this anti-angiogenic effect still remains an enigma. In this study, we investigated metformin-induced inhibitory effect on tumor angiogenesis in vitro and in vivo. Metformin pretreatment significantly suppressed tumor paracrine signaling-induced angiogenic promotion even in the presence of heregulin (HRG)-β1 (a co-activator of HER2) pretreatment of HER2+ tumor cells. Similar to that of AG825, a specific inhibitor of HER2 phosphorylation, metformin treatment decreased both total and phosphorylation (Tyr 1221/1222) levels of HER2 protein and significantly reduced microvessel density and the amount of Fitc-conjugated Dextran leaking outside the vessel. Furthermore, our results of VEGF-neutralizing and -rescuing tests showed that metformin markedly abrogated HER2 signaling-induced tumor angiogenesis by inhibiting VEGF secretion. Inhibition of HIF-1α signaling by using RNAi or YC-1, a specific inhibitor of HIF-1α synthesis, both completely diminished mRNA level of VEGF and greatly inhibited endothelial cell proliferation promoted by HER2+ tumor cell-conditioned medium in both the absence and presence of HRG-β1 pretreatment. Importantly, metformin treatment decreased the number of HIF-1α nucleus positive cells in 4T1 tumors, accompanied by decreased microvessel density. Our data thus provides novel insight into the mechanism underlying the metformin-induced inhibition of tumor angiogenesis and indicates possibilities of HIF-1α-VEGF signaling axis in mediating HER2-induced tumor angiogenesis.
authors.affiliation: Department of Neurosurgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.|Department of Vascular Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Jichang
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Science and Technology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Guangyue
authors.initials: G
authors.lastname: Li
authors.affiliation: Center for Translational Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Yaochun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Breast Cancer Program and Interdisciplinary Translational Research Team, Georgia Regents University Cancer Center, Augusta, Georgia, 30912, United States of America.|Tianjin Medical University Cancer Institute and Hospital, Tianjin, 300060, China.
authors.forename: Shouching
authors.initials: S
authors.lastname: Tang
authors.affiliation: Department of Thoracic Surgery and Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.affiliation: Center for Translational Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Feng
authors.affiliation: Department of Vascular Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Neurosurgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Gang
authors.initials: G
authors.lastname: Bao
authors.affiliation: Center for Translational Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Pingping
authors.initials: P
authors.lastname: Li
authors.affiliation: Center for Translational Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Xiaona
authors.initials: X
authors.lastname: Mao
authors.affiliation: Department of Neurosurgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Maode
authors.initials: M
authors.lastname: Wang
authors.affiliation: Center for Translational Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710061, P.R.China.
authors.forename: Peijun
authors.initials: P
authors.lastname: Liu
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D001943:Breast Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002196:Capillaries / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018920:Coculture Techniques; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D061986:MCF-7 Cells; D008687:Metformin / Q000494:pharmacology*; D008807:Mice, Inbred BALB C; D009389:Neovascularization, Pathologic; D019899:Paracrine Communication / Q000187:drug effects; D010766:Phosphorylation; D034622:RNA Interference; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D020533:Angiogenesis Inhibitors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008687:Metformin; D018719:Erb-b2 Receptor Tyrosine Kinases; D042461:Vascular Endothelial Growth Factor A; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; C467484:VEGFA protein, human; C467480:vascular endothelial growth factor A, mouse; C508053:ERBB2 protein, human; C524056:Erbb2 protein, mouse
keywords: HER2; HIF-1α-VEGF signaling; anti-angiogenesis; heregulin-β1; metformin