title: Changes in the response of MCF-7 cells to ionizing radiation after the combination of ATM and DNA-PK inhibition.
abstract: The aim of the present study is to evaluate the role of ATM (KU55933) and DNA-PK (NU7441) inhibitors in the repair of double-strand breaks and downstream signaling of DNA damage introduced by ionizing radiation. The irradiation of MCF-7 cells alone increased the proportion of cells in the G1 phase in comparison with mock-treated cells. After ATM inhibitor pretreatment, the cells were more accumulated in the G2 phase, whereas DNA-PK inhibitor application increased the percentage of cells in the G1 phase. ATM and DNA-PK inhibitor application alone increased the sensitivity of MCF-7 cells to ionizing radiation; however, combining both inhibitors together resulted in a further enhancement of cell death. Unexpectedly, combining both inhibitors decreased the percentage of senescent cells and increased G2 cell cycle arrest 3 days after treatment. After irradiation, the p21 protein was increased and Chk1 and Chk2 were activated. These proteins were not increased in cells pretreated with the ATM inhibitor prior to ionizing radiation exposure, albeit DNA-PK inhibitor application did not affect the amount of proteins detected. Formation of γH2AX was found to be ATM and DNA-PK dependent, application of the ATM inhibitor suppressed incidence of γH2AX, whereas DNA-PK caused persistence of γH2AX. Our results suggest that the further investigation of the ATM inhibitor in combination with the DNA-PK inhibitor as sensitizers preventing cell senescence and promoting cell death in breast carcinoma MCF-7 cells is warranted.
authors: Department of Medical Biochemistry, Faculty of Medicine in Hradec Kralove, Charles University in Prague, Simkova 870, 500 38, Hradec Kralove, Czech Republic.
authors: Jana
authors: J
authors: Ćmielová
authors: Radim
authors: R
authors: Havelek
authors: Jiřina
authors: J
authors: Vávrová
authors: Martina
authors: M
authors: Řezáčová
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2 / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair / Q000187:drug effects; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D016193:G1 Phase / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D006657:Histones; D006801:Humans; D061986:MCF-7 Cells; D009025:Morpholines / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism; D011753:Pyrones / Q000494:pharmacology*; D011839:Radiation, Ionizing
chemical_list: C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; C499693:8-dibenzothiophen-4-yl-2-morpholin-4-yl-chromen-4-one; C493956:CDKN1A protein, human; D002867:Chromones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D009025:Morpholines; D011753:Pyrones; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D051747:DNA-Activated Protein Kinase