title: Response of human hematopoietic stem and progenitor cells to energetic carbon ions.
abstract: OBJECTIVE
  To characterise the radiation response of human hematopoietic stem and progenitor cells (HSPC) with respect to X and carbon ion irradiation.
  
  
  METHODS
  HSPC from peripheral blood of healthy donors treated with granulocyte-colony stimulating factor (G-CSF) were enriched for the transmembrane glycoprotein CD34 (cluster of differentiation) and irradiated with X rays or carbon ions (29 keV/microm monoenergetic beam and 60-85 keV/microm spread-out Bragg peak), mimicking radiotherapy conditions. Apoptotic cell death, cell cycle progression and the frequency of chromosomal aberrations were determined.
  
  
  RESULTS
  After radiation exposure no inhibition in the progression of the cell cycle was detected. However, an enhanced frequency of apoptotic cells and an increase in aberrant cells were observed, both effects being more pronounced for carbon ions than X rays, resulting in a relative biological effectiveness (RBE) of 1.4-1.7. The fraction of complex-type aberrations was higher following carbon ion exposure.
  
  
  CONCLUSIONS
  RBE values of carbon ions are low, as expected for radiosensitive cells. The observed frequencies of apoptotic cells and chromosome aberrations in HSPC are similar to those reported for human peripheral blood lymphocytes suggesting that at least with respect to apoptosis and chromosomal aberrations mature lymphocytes reflect the respective radiation responses of their proliferating progenitors.
authors.affiliation: GSI, Biophysics, Darmstadt, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Becker
authors.forename: Thilo
authors.initials: T
authors.lastname: Elsässer
authors.forename: Torsten
authors.initials: T
authors.lastname: Tonn
authors.forename: Erhard
authors.initials: E
authors.lastname: Seifried
authors.forename: Marco
authors.initials: M
authors.lastname: Durante
authors.forename: Sylvia
authors.initials: S
authors.lastname: Ritter
authors.forename: Claudia
authors.initials: C
authors.lastname: Fournier
mesh_terms: D017209:Apoptosis / Q000528:radiation effects; D002244:Carbon; D002453:Cell Cycle / Q000528:radiation effects; D002869:Chromosome Aberrations / Q000528:radiation effects; D006412:Hematopoietic Stem Cells / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D066298:In Vitro Techniques; D011836:Radiation Tolerance; D012062:Relative Biological Effectiveness
chemical_list: D002244:Carbon