title: BMI1 confers radioresistance to normal and cancerous neural stem cells through recruitment of the DNA damage response machinery.
abstract: Glioblastoma multiforme (GBM) is an aggressive brain tumor that is resistant to all known therapies. Within these tumors, a CD133-positive cancer-initiating neural stem cell (NSC) population was shown to be resistant to gamma radiation through preferential activation of the DNA double-strand break (DSB) response machinery, including the ataxia-telangiectasia-mutated (ATM) kinase. The polycomb group protein BMI1 is enriched in CD133-positive GBM cells and required for their self-renewal in an INK4A/ARF-independent manner through transcriptional repression of alternate tumor suppressor pathways. We report here that BMI1 copurifies with DNA DSB response and nonhomologous end joining (NHEJ) repair proteins in GBM cells. BMI1 was enriched at the chromatin after irradiation and colocalized and copurified with ATM and the histone gammaH2AX. BMI1 also preferentially copurified with NHEJ proteins DNA-PK, PARP-1, hnRNP U, and histone H1 in CD133-positive GBM cells. BMI1 deficiency in GBM cells severely impaired DNA DSB response, resulting in increased sensitivity to radiation. In turn, BMI1 overexpression in normal NSCs enhanced ATM recruitment to the chromatin, the rate of gammaH2AX foci resolution, and resistance to radiation. BMI1 thus displays a previously uncharacterized function in controlling DNA DSB response and repair. Pharmacological inhibition of BMI1 combined with radiation therapy may provide an effective mean to target GBM stem cells.
authors.affiliation: Developmental Biology Laboratory, Maisonneuve-Rosemont Hospital, Montréal, Québec, Canada.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Facchino
authors.forename: Mohamed
authors.initials: M
authors.lastname: Abdouh
authors.forename: Wassim
authors.initials: W
authors.lastname: Chatoo
authors.forename: Gilbert
authors.initials: G
authors.lastname: Bernier
mesh_terms: D000071916:AC133 Antigen; D015703:Antigens, CD / Q000378:metabolism; D001932:Brain Neoplasms / Q000473:pathology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000473:pathology / Q000528:radiation effects; D064447:Checkpoint Kinase 2; D002853:Chromatography, Liquid / Q000379:methods; D020552:Comet Assay / Q000379:methods; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004249:DNA Damage / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000502:physiology / Q000528:radiation effects*; D005333:Fetus; D005434:Flow Cytometry / Q000379:methods; D005909:Glioblastoma / Q000473:pathology; D006023:Glycoproteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D014411:Neoplastic Stem Cells / Q000502:physiology / Q000528:radiation effects*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation / Q000235:genetics; D063150:Polycomb Repressive Complex 1; D063146:Polycomb-Group Proteins; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011836:Radiation Tolerance; D017382:Reactive Oxygen Species / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D053719:Tandem Mass Spectrometry / Q000379:methods; D014162:Transfection / Q000379:methods
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; C069077:BMI1 protein, human; D004268:DNA-Binding Proteins; D006023:Glycoproteins; D009687:Nuclear Proteins; C000606023:PROM1 protein, human; D010455:Peptides; D063146:Polycomb-Group Proteins; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D012097:Repressor Proteins; D049452:Green Fluorescent Proteins; D063150:Polycomb Repressive Complex 1; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases