title: Side population cells from HXO-Rb44 retinoblastoma cell line have cancer-initiating property.
abstract: OBJECTIVE
  To ascertain whether side population (SP) cells in HXO-Rb44 retinoblastoma cell line have cancer stem cell-like property in vitro and in vivo.
  
  
  METHODS
  We analyzed and sorted SP from HXO-Rb44 retinoblastoma cell line by Hoechst 33342 staining on flow cytometry. SP and NSP cells were determined their ability of proliferation and self-renewal by SP reanalysis, soft agar assay and tumor sphere assay in vitro. Clone formation was detected by seeding HXO-Rb44 and HXO-Rb44 -RFP cells into soft agar. The expression of ABCG2, MDRI, Bmi-1 and Oct-4 was determined by RT-PCR between SP and non-SP (NSP) cells. Moreover, they were injected into nude mice to determine their tumorigency in vivo.
  
  
  RESULTS
  SP from HXO-Rb44 retinoblastoma cell line could grow clonally in soft agar assays and form tumor spheres from single cells in conditioned media. The expressions of ABCG2, MDRI, Bmi-1 and Oct-4 were significantly higher in SP than NSP cells. As few as SP cells resulted in tumor formation in 6 of 12 injected sites, however, the injection of NSP cells failed to form new tumor.
  
  
  CONCLUSIONS
  SP cells isolated by Hoechst 33342 from the HXO-Rb44 retinoblastoma cell line had property of high tumorigency in vivo and in vitro. Therefore, SP might be a target while developing retinoblastoma therapies.
authors.affiliation: Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China.
authors.forename: Jun-Jun
authors.initials: JJ
authors.lastname: She
authors.forename: Peng-Ge
authors.initials: PG
authors.lastname: Zhang
authors.forename: Xiang-Ming
authors.initials: XM
authors.lastname: Che
authors.forename: Xuan
authors.initials: X
authors.lastname: Wang
authors.forename: Zi-Ming
authors.initials: ZM
authors.lastname: Wang