title: Radiosensitivity of Patient-Derived Glioma Stem Cell 3-Dimensional Cultures to Photon, Proton, and Carbon Irradiation.
abstract: OBJECTIVE
  To investigate the radiosensitivity of primary glioma stem cell (GSC) cultures with different CD133 status in a 3-dimensional (3D) model after photon versus proton versus carbon irradiation.
  
  
  METHODS
  Human primary GSC spheroid cultures were established from tumor specimens of six consented glioblastoma patients. Human U87MG was used as a classical glioblastoma radioresistant cell line. Cell suspensions were generated by mechanical dissociation of GSC spheroids and embedded in a semi-solid 3D matrix before irradiation. Spheroid-like colonies were manually counted by microscopy. Cells were also recovered and quantified by fluorescence. CD133 expression and DNA damage were evaluated by flow cytometry.
  
  
  RESULTS
  The fraction of CD133(+) cells varied between 0.014% and 96% in the six GSC cultures and showed a nonsignificant correlation with plating efficiency and survival fractions. The 4 most photon-radioresistant GSC cultures were NCH644, NCH421k, NCH441, and NCH636. Clonogenic survival for proton irradiation revealed relative biologic effectiveness (RBE) in the range of 0.7-1.20. However, carbon irradiation rendered the photon-resistant GSC cultures sensitive, with average RBE of 1.87-3.44. This effect was partly attributed to impaired capability of GSC to repair carbon ion-induced DNA double-strand breaks as determined by residual DNA repair foci. Interestingly, radiosensitivity of U87 cells was comparable to GSC cultures using clonogenic survival as the standard readout.
  
  
  CONCLUSIONS
  Carbon irradiation is effective in GSC eradication with similar RBE ranges approximately 2-3 as compared with non-stem GSC cultures (U87). Our data strongly suggest further exploration of GSC using classic radiobiology endpoints such as the here-used 3D clonogenic survival assay and integration of additional GSC-specific markers.
authors.affiliation: German Cancer Consortium, Heidelberg, Germany; Molecular and Translational Radiation Oncology, Heidelberg Ion Therapy Center, Heidelberg Institute of Radiation Oncology, University of Heidelberg Medical School and National Center for Tumor Diseases, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Chiblak
authors.affiliation: German Cancer Consortium, Heidelberg, Germany; Molecular and Translational Radiation Oncology, Heidelberg Ion Therapy Center, Heidelberg Institute of Radiation Oncology, University of Heidelberg Medical School and National Center for Tumor Diseases, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Zili
authors.initials: Z
authors.lastname: Tang
authors.affiliation: Division of Neurological Research, Department of Neurosurgery, University of Heidelberg Medical School, Heidelberg, Germany.
authors.forename: Benito
authors.initials: B
authors.lastname: Campos
authors.affiliation: Division of Neurological Research, Department of Neurosurgery, University of Heidelberg Medical School, Heidelberg, Germany.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Gal
authors.affiliation: Division of Neurological Research, Department of Neurosurgery, University of Heidelberg Medical School, Heidelberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Unterberg
authors.affiliation: German Cancer Consortium, Heidelberg, Germany; Molecular and Translational Radiation Oncology, Heidelberg Ion Therapy Center, Heidelberg Institute of Radiation Oncology, University of Heidelberg Medical School and National Center for Tumor Diseases, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Debus
authors.affiliation: Division of Neurological Research, Department of Neurosurgery, University of Heidelberg Medical School, Heidelberg, Germany.
authors.forename: Christel
authors.initials: C
authors.lastname: Herold-Mende
authors.affiliation: German Cancer Consortium, Heidelberg, Germany; Molecular and Translational Radiation Oncology, Heidelberg Ion Therapy Center, Heidelberg Institute of Radiation Oncology, University of Heidelberg Medical School and National Center for Tumor Diseases, German Cancer Research Center, Heidelberg, Germany. Electronic address: a.amir@dkfz.de.
authors.forename: Amir
authors.initials: A
authors.lastname: Abdollahi
mesh_terms: D000071916:AC133 Antigen; D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000032:analysis; D000951:Antigens, Neoplasm / Q000032:analysis; D002244:Carbon; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000528:radiation effects; D004260:DNA Repair; D005909:Glioblastoma / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy*; D005910:Glioma / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy*; D006023:Glycoproteins / Q000032:analysis; D006657:Histones / Q000032:analysis; D006801:Humans; D014411:Neoplastic Stem Cells / Q000276:immunology / Q000528:radiation effects*; D010455:Peptides / Q000032:analysis; D017785:Photons; D011522:Protons; D011836:Radiation Tolerance / Q000528:radiation effects*; D012062:Relative Biological Effectiveness; D018874:Spheroids, Cellular / Q000276:immunology / Q000473:pathology / Q000528:radiation effects; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay / Q000379:methods
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D006023:Glycoproteins; C468783:H2AX protein, human; D006657:Histones; C000606023:PROM1 protein, human; D010455:Peptides; D011522:Protons; D002244:Carbon