title: Inhibition of in vivo tumor angiogenesis and growth via systemic delivery of an angiopoietin 2-specific RNA aptamer.
abstract: BACKGROUND
  Cellular events mediated by the Tie2 receptor are important to tumor neovascularization. Despite the complex interplay of the best-characterized Tie2 ligands, angiopoietins 1 and 2, Ang2 is purportedly "proangiogenic" in the presence of vascular endothelial growth factor. We examined whether in vivo administration of an RNA aptamer that specifically blocks Ang 2 would inhibit tumor angiogenesis and growth.
  
  
  METHODS
  Ang2-mediated Tie2 receptor phosphorylation was assessed in vitro in the absence and presence of aptamer coupled to polyethylene glycol. IN VIVO ANGIOGENESIS ASSAY: CT26 murine colon carcinoma cells expressing green fluorescent protein were delivered into mouse dorsal skinfold window chambers. Animals received daily intraperitoneal injections of phosphate-buffered saline, low-dose (Ang2 aptamer-LD; 1 mg/kg/d), or high-dose aptamer (Ang2 aptamer-HD; 10 mg/kg/d). Vascular length density was measured under fluorescence microscopy. PRIMARY TUMOR GROWTH: CT26 cells expressing luciferase were injected into flanks of BALB/c mice to allow tumor growth monitoring by bioluminescence imaging. Animals received continuous phosphate-buffered saline or aptamer (1 mg/kg/d) via ALZET pumps. Tumors were assessed for CD31/PECAM-1 immunostaining and Hoechst dye uptake.
  
  
  RESULTS
  Pegylated aptamer inhibited Tie2 phosphorylation. Systemic aptamer administration reduced vascular length density (P < or = 0.03) and decreased bioluminescence emission (P < 0.04), corresponding to 50% decrease in tumor volume (P = 0.04). Control tumors displayed abundant vascular marker staining, in contrast to tumors from aptamer-treated animals.
  
  
  CONCLUSIONS
  in vivo administration of a clinically relevant, pegylated RNA aptamer specifically designed against Ang2 inhibited tumor angiogenesis and growth. These findings support targeted Ang2 inhibition as a relevant anti-angiogenic, anti-neoplastic strategy.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Shiva
authors.initials: S
authors.lastname: Sarraf-Yazdi
authors.forename: Jing
authors.initials: J
authors.lastname: Mi
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Moeller
authors.forename: Xilin
authors.initials: X
authors.lastname: Niu
authors.forename: Rebekah R
authors.initials: RR
authors.lastname: White
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Kontos
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Sullenger
authors.forename: Mark W
authors.initials: MW
authors.lastname: Dewhirst
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Clary
mesh_terms: D042702:Angiopoietin-2 / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D052157:Aptamers, Nucleotide / Q000494:pharmacology / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000098:blood supply* / Q000473:pathology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D042787:Receptor, TIE-2 / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D042702:Angiopoietin-2; D052157:Aptamers, Nucleotide; D042787:Receptor, TIE-2