title: Paradoxic effects of metformin on endothelial cells and angiogenesis.
abstract: The biguanide metformin is used in type 2 diabetes management and has gained significant attention as a potential cancer preventive agent. Angioprevention represents a mechanism of chemoprevention, yet conflicting data concerning the antiangiogenic action of metformin have emerged. Here, we clarify some of the contradictory effects of metformin on endothelial cells and angiogenesis, using in vitro and in vivo assays combined with transcriptomic and protein array approaches. Metformin inhibits formation of capillary-like networks by endothelial cells; this effect is partially dependent on the energy sensor adenosine-monophosphate-activated protein kinase (AMPK) as shown by small interfering RNA knockdown. Gene expression profiling of human umbilical vein endothelial cells revealed a paradoxical modulation of several angiogenesis-associated genes and proteins by metformin, with short-term induction of vascular endothelial growth factor (VEGF), cyclooxygenase 2 and CXC chemokine receptor 4 at the messenger RNA level and downregulation of ADAMTS1. Antibody array analysis shows an essentially opposite regulation of numerous angiogenesis-associated proteins in endothelial and breast cancer cells including interleukin-8, angiogenin and TIMP-1, as well as selective regulation of angiopioetin-1, -2, endoglin and others. Endothelial cell production of the cytochrome P450 member CYP1B1 is upregulated by tumor cell supernatants in an AMPK-dependent manner, metformin blocks this effect. Metformin inhibits VEGF-dependent activation of extracellular signal-regulated kinase 1/2, and the inhibition of AMPK activity abrogates this event. Metformin hinders angiogenesis in matrigel pellets in vivo, prevents the microvessel density increase observed in obese mice on a high-fat diet, downregulating the number of white adipose tissue endothelial precursor cells. Our data show that metformin has an antiangiogenic activity in vitro and in vivo associated with a contradictory short-term enhancement of pro-angiogenic mediators, as well as with a differential regulation in endothelial and breast cancer cells.
authors.affiliation: Department of Research and Statistics Infrastructure, IRCCS "Tecnologie Avanzate e Modelli Assistenziali in Oncologia"Arcispedale S. Maria Nuova, 42123 Reggio Emilia, Italy.
authors.forename: Katiuscia
authors.initials: K
authors.lastname: Dallaglio
authors.forename: Antonino
authors.initials: A
authors.lastname: Bruno
authors.forename: Anna R
authors.initials: AR
authors.lastname: Cantelmo
authors.forename: Alessia I
authors.initials: AI
authors.lastname: Esposito
authors.forename: Luca
authors.initials: L
authors.lastname: Ruggiero
authors.forename: Stefania
authors.initials: S
authors.lastname: Orecchioni
authors.forename: Angelica
authors.initials: A
authors.lastname: Calleri
authors.forename: Francesco
authors.initials: F
authors.lastname: Bertolini
authors.forename: Ulrich
authors.initials: U
authors.lastname: Pfeffer
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Noonan
authors.forename: Adriana
authors.initials: A
authors.lastname: Albini
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects; D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D016000:Cluster Analysis; D065633:Cytochrome P-450 CYP1B1; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000187:drug effects* / Q000235:genetics; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D042461:Vascular Endothelial Growth Factor A; D008687:Metformin; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585498:Cyp1b1 protein, mouse; D065633:Cytochrome P-450 CYP1B1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D055372:AMP-Activated Protein Kinases