title: Daoy medulloblastoma cells that express CD133 are radioresistant relative to CD133- cells, and the CD133+ sector is enlarged by hypoxia.
abstract: OBJECTIVE
  Primary medulloblastoma and glioblastoma multiforme tumor cells that express the surface marker CD133 are believed to be enriched for brain tumor stem cells because of their unique ability to initiate or reconstitute tumors in immunodeficient mice. This study sought to characterize the radiobiological properties and marker expression changes of CD133+ vs. CD133- cells of an established medulloblastoma cell line.
  
  
  METHODS
  Daoy and D283 Med cell lines were stained with fluorescently labeled anti-CD133 antibody and sorted into CD133+ and CD133- populations. The effect of oxygen (2% vs. 20%) on CD133 expression was measured. Both populations were analyzed for marker stability, cell cycle distribution, and radiosensitivity.
  
  
  RESULTS
  CD133+ Daoy cells restored nearly native CD133+ and CD133- populations within 18 days, whereas CD133- cells remained overwhelmingly CD133-. Culturing Daoy cells in 2% oxygen rather than the standard 20% oxygen increased their CD133 expression 1.6-fold. CD133+ Daoy cells were radioresistant via the beta-parameter of the linear-quadratic model relative to CD133- Daoy cells, although their alpha-parameters and cell cycle distributions were identical.
  
  
  CONCLUSIONS
  Restoration of the original CD133+ and CD133- populations from CD133+ Daoy cells in serum is further evidence that CD133+ cells are functionally distinct from CD133- cells. The radioresistance of CD133+ compared with CD133- Daoy cells is consistent with better repair of sublethal damage. Enlargement of the CD133+ sector is a new feature of the hypoxic response.
authors.affiliation: Radiation Oncology Department, Division of Hematology/Oncology, Rush University Medical Center, Chicago, IL 60612, USA. Ed_R_Blazek@rush.edu
authors.forename: Ed R
authors.initials: ER
authors.lastname: Blazek
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Foutch
authors.forename: Guitta
authors.initials: G
authors.lastname: Maki
mesh_terms: D000071916:AC133 Antigen; D015703:Antigens, CD / Q000378:metabolism*; D002453:Cell Cycle; D015687:Cell Hypoxia / Q000502:physiology*; D002528:Cerebellar Neoplasms / Q000378:metabolism / Q000473:pathology; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D008527:Medulloblastoma / Q000378:metabolism / Q000473:pathology; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D011836:Radiation Tolerance / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D010100:Oxygen