title: Abrogation of radioresistance in glioblastoma stem-like cells by inhibition of ATM kinase.
abstract: Resistance to radiotherapy in glioblastoma (GBM) is an important clinical problem and several authors have attributed this to a subpopulation of GBM cancer stem cells (CSCs) which may be responsible for tumour recurrence following treatment. It is hypothesised that GBM CSCs exhibit upregulated DNA damage responses and are resistant to radiation but the current literature is conflicting. We investigated radioresistance of primary GBM cells grown in stem cell conditions (CSC) compared to paired differentiated tumour cell populations and explored the radiosensitising effects of the ATM inhibitor KU-55933. We report that GBM CSCs are radioresistant compared to paired differentiated tumour cells as measured by clonogenic assay. GBM CSC's display upregulated phosphorylated DNA damage response proteins and enhanced activation of the G2/M checkpoint following irradiation and repair DNA double strand breaks (DSBs) more efficiently than their differentiated tumour cell counterparts following radiation. Inhibition of ATM kinase by KU-55933 produced potent radiosensitisation of GBM CSCs (sensitiser enhancement ratios 2.6-3.5) and effectively abrogated the enhanced DSB repair proficiency observed in GBM CSCs at 24 h post irradiation. G2/M checkpoint activation was reduced but not abolished by KU-55933 in GBM CSCs. ATM kinase inhibition overcomes radioresistance of GBM CSCs and, in combination with conventional therapy, has potential to improve outcomes for patients with GBM.
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, UK. Electronic address: ross.carruthers@glasgow.ac.uk.
authors.forename: Ross
authors.initials: R
authors.lastname: Carruthers
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, UK. Electronic address: Shafiq.Ahmed@glasgow.ac.uk.
authors.forename: Shafiq U
authors.initials: SU
authors.lastname: Ahmed
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, UK. Electronic address: Karen.Strathdee@glasgow.ac.uk.
authors.forename: Karen
authors.initials: K
authors.lastname: Strathdee
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, UK. Electronic address: n.gomez-roman@beatson.gla.ac.uk.
authors.forename: Natividad
authors.initials: N
authors.lastname: Gomez-Roman
authors.affiliation: University of Ghana Medical School, University of Ghana, Ghana. Electronic address: evelynbuahin@yahoo.co.uk.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Amoah-Buahin
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, UK. Electronic address: cw209@cam.ac.uk.
authors.forename: Colin
authors.initials: C
authors.lastname: Watts
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, UK. Electronic address: Anthony.chalmers@glasgow.ac.uk.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Chalmers
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005260:Female; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000528:radiation effects; D005720:Gamma Rays; D005909:Glioblastoma / Q000201:enzymology / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000528:radiation effects; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000201:enzymology* / Q000473:pathology; D011753:Pyrones / Q000494:pharmacology*; D011836:Radiation Tolerance / Q000187:drug effects* / Q000528:radiation effects; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; D009025:Morpholines; D009363:Neoplasm Proteins; D011753:Pyrones; D011838:Radiation-Sensitizing Agents; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins
keywords: ATM; Cancer stem cells; DNA damage response; Glioblastoma; Radiotherapy