Improved ATM kinase inhibitor KU-60019 radiosensitizes glioma cells, compromises insulin, AKT and ERK prosurvival signaling, and inhibits migration and invasion.
Ataxia telangiectasia (A-T) mutated (ATM) is critical for cell cycle checkpoints and DNA repair. Thus, specific small molecule inhibitors targeting ATM could perhaps be developed into efficient radiosensitizers. Recently, a specific inhibitor of the ATM kinase, KU-55933, was shown to radiosensitize human cancer cells. Herein, we report on an improved analogue of KU-55933 (KU-60019) with K(i) and IC(50) values half of those of KU-55933. KU-60019 is 10-fold more effective than KU-55933 at blocking radiation-induced phosphorylation of key ATM targets in human glioma cells. As expected, KU-60019 is a highly effective radiosensitizer of human glioma cells. A-T fibroblasts were not radiosensitized by KU-60019, strongly suggesting that the ATM kinase is specifically targeted. Furthermore, KU-60019 reduced basal S473 AKT phosphorylation, suggesting that the ATM kinase might regulate a protein phosphatase acting on AKT. In line with this finding, the effect of KU-60019 on AKT phosphorylation was countered by low levels of okadaic acid, a phosphatase inhibitor, and A-T cells were impaired in S473 AKT phosphorylation in response to radiation and insulin and unresponsive to KU-60019. We also show that KU-60019 inhibits glioma cell migration and invasion in vitro, suggesting that glioma growth and motility might be controlled by ATM via AKT. Inhibitors of MEK and AKT did not further radiosensitize cells treated with KU-60019, supporting the idea that KU-60019 interferes with prosurvival signaling separate from its radiosensitizing properties. Altogether, KU-60019 inhibits the DNA damage response, reduces AKT phosphorylation and prosurvival signaling, inhibits migration and invasion, and effectively radiosensitizes human glioma cells.
Golding
Sarah E
SE
Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA 23298-0058, USA.
Rosenberg
Elizabeth
E
Valerie
Nicholas
N
Hussaini
Isa
I
Frigerio
Mark
M
Cockcroft
Xiaoling F
XF
Chong
Wei Yee
WY
Hummersone
Marc
M
Rigoreau
Laurent
L
Menear
Keith A
KA
O'Connor
Mark J
MJ
Povirk
Lawrence F
LF
van Meter
Timothy
T
Valerie
Kristoffer
K
D001260:Ataxia Telangiectasia / Q000201:enzymology / Q000473:pathology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D005720:Gamma Rays; D005910:Glioma / Q000188:drug therapy* / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000528:radiation effects; D009025:Morpholines / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D009361:Neoplasm Invasiveness; D010768:Phosphoserine / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011753:Pyrones / Q000737:chemistry / Q000494:pharmacology; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology / Q000627:therapeutic use; D013892:Thioxanthenes / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
C546193:2-(2,6-dimethylmorpholin-4-yl)-N-(5-(6-morpholin-4-yl-4-oxo-4H-pyran-2-yl)-9H-thioxanthen-2-yl)acetamide; C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D007328:Insulin; D009025:Morpholines; D047428:Protein Kinase Inhibitors; D011753:Pyrones; D011838:Radiation-Sensitizing Agents; D013892:Thioxanthenes; D025521:Tumor Suppressor Proteins; D010768:Phosphoserine; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases