title: Tumor blood vessels formation in osteosarcoma: vasculogenesis mimicry.
abstract: BACKGROUND
  Osteosarcoma is characterized by high neovascularization and a high propensity for metastasis through bloodstream. This study was to examine whether there is evidence for vasculogenic mimicry in osteosarcoma and to illustrate mechanism of tumor blood vessels formation in osteosarcoma.
  
  
  METHODS
  Osteosarcoma cell lines (U-2OS) were tested for their ability to form tubular networks in three-dimensional culture containing type I collagen. The structures of the tubular networks were observed with phase contrast microscope and transmission electron microscope (TEM). Morphometric studies using hematoxylin and eosin (HE) stain and CD31 immunohistochemical stain to show tumor-lined channels in human osteosarcoma were also performed.
  
  
  RESULTS
  Observation with light microscope and TEM showed that highly aggressive osteosarcoma cell lines (U-2OS) formed networks containing channels when grown in three-dimensional culture containing type I collagen, in the absence of endothelial cells or fibroblasts. Morphometric observation using HE stain and CD31 immunohistochemical stain showed that tumor cell-lined channels were also detected in vivo in osteosarcoma; by comparison, all vascular areas in the pedicle of osteochondroma or outside osteochondroma were endothelial-lined.
  
  
  CONCLUSIONS
  These observations strongly suggest that aggressive osteosarcoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis and have the ability of vasculogenic mimicry.
authors.affiliation: Department of Orthopedics, Tongji Hospital, Tongji University, Shanghai 200065, China. caixuansong@hotmail.com
authors.forename: Xuan-song
authors.initials: XS
authors.lastname: Cai
authors.forename: Yong-wei
authors.initials: YW
authors.lastname: Jia
authors.forename: Jiong
authors.initials: J
authors.lastname: Mei
authors.forename: Ru-yong
authors.initials: RY
authors.lastname: Tang
mesh_terms: D001859:Bone Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D045744:Cell Line, Tumor; D003094:Collagen / Q000096:biosynthesis; D006801:Humans; D007150:Immunohistochemistry; D009389:Neovascularization, Pathologic / Q000473:pathology*; D012516:Osteosarcoma / Q000473:pathology*
chemical_list: D003094:Collagen