title: Sustained angiopoietin-2 expression disrupts vessel formation and inhibits glioma growth.
abstract: Systematic analyses of the expression of angiogenic regulators in cancer models should yield useful information for the development of novel therapies for malignant gliomas. In this study, we analyzed tumor growth, vascularization, and angiopoietin-2 (Ang2) expression during the development of U-87 MG xenografts. We found that tumoral angiogenesis in this model follows a multistage process characterized by avascular, prolific peripheral angiogenesis, and late vascular phases. On day 4, we observed an area of central necrosis, a peripheral ring of Ang2-positive glioma cells, and reactive Ang2-positive vascular structures in the tumor/brain interface. When the tumor had developed a vascular network, Ang2 was expressed only in peripheral vascular structures. Because Ang2 expression was downmodulated in the late stages of development, probably to maintain a stable tumoral vasculature, we next studied whether sustained Ang2 expression might impair vascular development and, ultimately, tumor growth. Ang2 prevented the formation of capillary-like structures by and impaired angiogenesis in a chorioallantoic membrane chicken model. Finally, we tested the effect of sustained Ang2 expression on U-87 MG xenograft development. Ang2 significantly prolonged the survival of intracranial U-87 MG tumor-bearing animals. Examination of Ang2-treated xenografts revealed areas of tumor necrosis and vascular damage. We therefore conclude that deregulated Ang2 expression during gliomagenesis hindered successful angiogenesis and that therapies that sustain Ang2 expression might be effective against malignant gliomas.
authors.affiliation: Department of Neuro-Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Ok-Hee
authors.initials: OH
authors.lastname: Lee
authors.forename: Juan
authors.initials: J
authors.lastname: Fueyo
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: W K Alfred
authors.initials: WK
authors.lastname: Yung
authors.forename: Michael G
authors.initials: MG
authors.lastname: Lemoine
authors.forename: Frederick F
authors.initials: FF
authors.lastname: Lang
authors.forename: B Nebiyou
authors.initials: BN
authors.lastname: Bekele
authors.forename: Xian
authors.initials: X
authors.lastname: Zhou
authors.forename: Marta A
authors.initials: MA
authors.lastname: Alonso
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Aldape
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Fuller
authors.forename: Candelaria
authors.initials: C
authors.lastname: Gomez-Manzano
mesh_terms: D042702:Angiopoietin-2 / Q000096:biosynthesis*; D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D004730:Endothelium, Vascular / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D008833:Microcirculation; D009368:Neoplasm Transplantation
chemical_list: D042702:Angiopoietin-2