Inhibition of ATR kinase with the selective inhibitor VE-821 results in radiosensitization of cells of promyelocytic leukaemia (HL-60).
We compared the effects of inhibitors of kinases ATM (KU55933) and ATR (VE-821) (incubated for 30 min before irradiation) on the radiosensitization of human promyelocyte leukaemia cells (HL-60), lacking functional protein p53. VE-821 reduces phosphorylation of check-point kinase 1 at serine 345, and KU55933 reduces phosphorylation of check-point kinase 2 on threonine 68 as assayed 4 h after irradiation by the dose of 6 Gy. Within 24 h after gamma-irradiation with a dose of 3 Gy, the cells accumulated in the G2 phase (67 %) and the number of cells in S phase decreased. KU55933 (10 μM) did not affect the accumulation of cells in G2 phase and did not affect the decrease in the number of cells in S phase after irradiation. VE-821 (2 and 10 μM) reduced the number of irradiated cells in the G2 phase to the level of non-irradiated cells and increased the number of irradiated cells in S phase, compared to irradiated cells not treated with inhibitors. In the 144 h interval after irradiation with 3 Gy, there was a considerable induction of apoptosis in the VE-821 group (10 μM). The repair of the radiation damage, as observed 72 h after irradiation, was more rapid in the group exposed solely to irradiation and in the group treated with KU55933 (80 and 77 % of cells, respectively, were free of DSBs), whereas in the group incubated with 10 μM VE-821, there were only 61 % of cells free of DSBs. The inhibition of kinase ATR with its specific inhibitor VE-821 resulted in a more pronounced radiosensitizing effect in HL-60 cells as compared to the inhibition of kinase ATM with the inhibitor KU55933. In contrast to KU55933, the VE-821 treatment prevented HL-60 cells from undergoing G2 cell cycle arrest. Taken together, we conclude that the ATR kinase inhibition offers a new possibility of radiosensitization of tumour cells lacking functional protein p53.
Department of Radiobiology, Faculty of Health Sciences, University of Defence, Hradec Králové, Brno, Czech Republic, vavrova@pmfhk.cz.
Jiřina
J
Vávrová
Lenka
L
Zárybnická
Emilie
E
Lukášová
Martina
M
Řezáčová
Eva
E
Novotná
Zuzana
Z
Sinkorová
Aleš
A
Tichý
Jaroslav
J
Pejchal
Kamila
K
Durišová
D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors*; D004260:DNA Repair / Q000187:drug effects; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D009025:Morpholines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology*; D011753:Pyrones / Q000494:pharmacology; D011836:Radiation Tolerance / Q000187:drug effects*; D013450:Sulfones / Q000494:pharmacology*
C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; C560580:3-amino-6-(4-(methylsulfonyl)phenyl)-N-phenylpyrazine-2-carboxamide; D009025:Morpholines; D047428:Protein Kinase Inhibitors; D011719:Pyrazines; D011753:Pyrones; D013450:Sulfones; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins