In vitro study | KU-55933 is an improved water-soluble inhibitor of ATM kinase with an IC50 of 6.3 nM and a similar target-specific selectivity compared to an IC50 of 13 nM at KU-60019 ATM. KU-60019 had little activity at DNA-PKcs and ATR, with IC50 of 1.7 μm and> 10 μm, and no activity at 229 other protein kinases, such as PI3K, mTOR/fkbp12. Blocking radiation-induced phosphorylation of key ATM protein targets such as p53,γ-H2AX, and CHK2 in human glioma U87 and U1242 cells, KU-60019 was 3 to 10 times more potent than KU-55933, 1 M KU-60019 significantly induced p53(S15) phosphorylation decreased by more than 70%, and ~ 10 M KU-55933 to achieve the same degree of reduction. KU-60019 to effectively make human glioma cells radiosensitization, 1 μm and 10 μm treatment, dose enhancement ratio were 1.7 and 4.4, normal fibroblasts, but not A- T fibroblasts, were also radiosensitized. 3 μm KU-60019 inhibited basal and insulin-induced phosphorylation of AKT S473 by 70% and-50%, respectively, and completely reduced radiation-induced phosphorylation of AKT to below control levels. The effect of KU-60019 on AKT S473 phosphorylation was observed in glioma cell lines and normal fibroblasts but not in A- T(h-TERT) cells, and was effectively inhibited by the phosphatase inhibitor okadaic acid, the key role of ATM kinase in the regulation of AKT phosphorylation is illustrated. Consistent with inhibition of pro-survival AKT signaling, 3 μm KU-60019 significantly inhibited migration and invasion of human glioma U87 cells by> 70% and ~ 60%, respectively, and also inhibited migration and invasion of U1242 cells, inhibition was> 50% and-60%, respectively. |