title: Dynamic inhibition of ATM kinase provides a strategy for glioblastoma multiforme radiosensitization and growth control.
abstract: Glioblastoma multiforme (GBM) is notoriously resistant to treatment. Therefore, new treatment strategies are urgently needed. ATM elicits the DNA damage response (DDR), which confers cellular radioresistance; thus, targeting the DDR with an ATM inhibitior (ATMi) is very attractive. Herein, we show that dynamic ATM kinase inhibition in the nanomolar range results in potent radiosensitization of human glioma cells, inhibits growth and does not conflict with temozolomide (TMZ) treatment. The second generation ATMi analog KU-60019 provided quick, reversible and complete inhibition of the DDR at sub-micromolar concentrations in human glioblastoma cells. KU-60019 inhibited the phosphorylation of the major DNA damage effectors p53, H2AX and KAP1 as well as AKT. Colony-forming radiosurvival showed that continuous exposure to nanomolar concentrations of KU-60019 effectively radiosensitized glioblastoma cell lines. When cells were co-treated with KU-60019 and TMZ, a slight increase in radiation-induced cell killing was noted, although TMZ alone was unable to radiosensitize these cells. In addition, without radiation, KU-60019 with or without TMZ reduced glioma cell growth but had no significant effect on the survival of human embryonic stem cell (hESC)-derived astrocytes. Altogether, transient inhibition of the ATM kinase provides a promising strategy for radiosensitizing GBM in combination with standard treatment. In addition, without radiation, KU-60019 limits growth of glioma cells in co-culture with human astrocytes that seem unaffected by the same treatment. Thus, inter-fraction growth inhibition could perhaps be achieved in vivo with minor adverse effects to the brain.
authors.affiliation: Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Golding
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rosenberg
authors.forename: Bret R
authors.initials: BR
authors.lastname: Adams
authors.forename: Shayalini
authors.initials: S
authors.lastname: Wignarajah
authors.forename: Jason M
authors.initials: JM
authors.lastname: Beckta
authors.forename: Mark J
authors.initials: MJ
authors.lastname: O'Connor
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Valerie
mesh_terms: D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045744:Cell Line, Tumor / Q000187:drug effects; D002470:Cell Survival; D018920:Coculture Techniques; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D005909:Glioblastoma / Q000201:enzymology / Q000473:pathology* / Q000532:radiotherapy; D006657:Histones / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000077204:Temozolomide; D013892:Thioxanthenes / Q000494:pharmacology; D000076183:Tripartite Motif-Containing Protein 28; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: C546193:2-(2,6-dimethylmorpholin-4-yl)-N-(5-(6-morpholin-4-yl-4-oxo-4H-pyran-2-yl)-9H-thioxanthen-2-yl)acetamide; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D009025:Morpholines; D047428:Protein Kinase Inhibitors; D011838:Radiation-Sensitizing Agents; D012097:Repressor Proteins; D013892:Thioxanthenes; D025521:Tumor Suppressor Proteins; D003606:Dacarbazine; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D000077204:Temozolomide