Inhibition of phosphoinositide 3-kinase related kinases by the radiosensitizing agent wortmannin.
Members of the phosphatidylinositol-3 kinase related kinase (PIKK) family function in both cell cycle progression and DNA damage-induced cell cycle checkpoints. The fungal metabolite, wortmannin, is an effective radiosensitizer that irreversibly inhibits certain members of the PIKK family. Based on their roles in DNA damage responses, several PIKKs, DNA-dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM) and the ataxia- and Rad3-related protein (ATR), are potential targets for the radiosensitizing effect of wortmannin. In this report, we demonstrate that wortmannin is a relatively potent inhibitor of DNA-PK (IC50, 16 nM) and ATM (IC50, 150 nM) activities, whereas ATR activity is significantly less sensitive to this drug (IC50, 1.8 microM). In intact A549 lung adenocarcinoma cells, wortmannin inhibited both DNA-PK and ATM at concentrations that correlated closely with those required for radiosensitization. Furthermore, pretreatment of A549 cells with wortmannin resulted in radioresistant DNA synthesis, a characteristic abnormality of ATM-deficient cells. These results identify wortmannin as an inhibitor of ATM activity and suggest that ATM and DNA-PK are relevant targets for the radiosensitizing effect of this drug in cancer cells.
Sarkaria
J N
JN
Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA.
Tibbetts
R S
RS
Busby
E C
EC
Kennedy
A P
AP
Hill
D E
DE
Abraham
R T
RT
D000230:Adenocarcinoma; D000730:Androstadienes / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm / Q000096:biosynthesis / Q000187:drug effects; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016195:G2 Phase; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms; D009687:Nuclear Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011506:Proteins / Q000037:antagonists & inhibitors*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D016196:S Phase; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D000077191:Wortmannin
D000730:Androstadienes; D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011506:Proteins; D011838:Radiation-Sensitizing Agents; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D000077191:Wortmannin