title: Side population cells have the characteristics of cancer stem-like cells/cancer-initiating cells in bone sarcomas.
abstract: BACKGROUND
  Several human cancers have been found to contain cancer stem-like cells (CSCs) having cancer-initiating ability. However, only a few reports have shown the existence of CSCs in bone and soft tissue sarcomas. In this study, we identified and characterised side population (SP) cells that showed drug-resistant features in human bone sarcoma cell lines.
  
  
  METHODS
  In seven osteosarcoma cell lines (OS2000, KIKU, NY, Huo9, HOS, U2OS and Saos2) and in one bone malignant fibrous histiocytoma (MFH) cell line (MFH2003), the frequency of SP cells was analysed. Tumourigenicity of SP cells was assessed in vitro and in vivo. Gene profiles of SP cells and other populations (main population; MP) of cells were characterised using cDNA microarrays.
  
  
  RESULTS
  SP cells were found in NY (0.31%) and MFH2003 (5.28%). SP cells of MFH2003 formed spherical colonies and re-populated into SP and MP cells. In an NOD/SCID mice xenograft model, 1 x 10(3) sorted SP cell-induced tumourigenesis. cDNA microarray analysis showed that 23 genes were upregulated in SP cells.
  
  
  CONCLUSIONS
  We showed that SP cells existed in bone sarcoma cell lines. SP cells of MFH2003 had cancer-initiating ability in vitro and in vivo. The gene profiles of SP cells could serve as candidate markers for CSCs in bone sarcomas.
authors.affiliation: Department of Orthopaedic Surgery, Sapporo Medical University School of Medicine, Chuo-ku, Sapporo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Murase
authors.forename: M
authors.initials: M
authors.lastname: Kano
authors.forename: T
authors.initials: T
authors.lastname: Tsukahara
authors.forename: A
authors.initials: A
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Torigoe
authors.forename: S
authors.initials: S
authors.lastname: Kawaguchi
authors.forename: S
authors.initials: S
authors.lastname: Kimura
authors.forename: T
authors.initials: T
authors.lastname: Wada
authors.forename: Y
authors.initials: Y
authors.lastname: Uchihashi
authors.forename: T
authors.initials: T
authors.lastname: Kondo
authors.forename: T
authors.initials: T
authors.lastname: Yamashita
authors.forename: N
authors.initials: N
authors.lastname: Sato
mesh_terms: D000818:Animals; D001859:Bone Neoplasms / Q000473:pathology*; D045744:Cell Line, Tumor; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D014411:Neoplastic Stem Cells / Q000473:pathology*; D012516:Osteosarcoma / Q000473:pathology*