Improved ATM kinase inhibitor KU-60019 radiosensitizes glioma cells, compromises insulin, AKT and ERK prosurvival signaling, and inhibits migration and invasion

Abstract

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. [Mol Cancer Ther 2009;8(10):2894-902]

ATM Inhibition Potentiates Death of Androgen Receptor-inactivated Prostate Cancer Cells with Telomere Dysfunction

“…As failure to repair DNA damage can lead to cell death, activation of ATM/ATR may thereby promote cell survival (7). Conversely, inhibition of ATM/ATR can block this process and promote cell death (27,49). In the present study we show that co-treatment of LNCaP cells with AR antagonist Casodex plus ATM inhibitor KU-60019 decreased cell survival to a much greater extent than did treatment with Casodex alone (Figs.…”

“…Exponentially growing cells (0.5-1.0 ϫ 10 4 cells/well of a 6-well plate) were treated with 0, 10, 25, or 50 M Casodex in the presence or absence of 2 M KU-60019 for 24 h, then washed to remove drugs and allowed to grow for 10 -14 days, then fixed and stained with 0.01% crystal violet (27). The areas of stained surviving cells in each plate were photographed and measured using the ImageJ program (26).…”

“…Since ATM/ATR inhibition or knockdown has been shown to inhibit the repair of telomere DNA damage caused by the disruption of shelterin components (16), we tested the effect of ATM inhibition in AR-inactivated LNCaP cells by using the ATM-kinase-specific inhibitor KU-60019 (27). Casodex alone induced ATM phosphorylation, but co-treatment with KU-60019 blocked this effect of Casodex (Fig.…”

DNA damage response during mouse oocyte maturation

“…S2A, C). The lack of an effect of inhibiting ATM on gH2AX phosphorylation in MI was confirmed by using the more potent ATM inhibitor KU 60019 28 (Fig. S2 D, E).…”

Differential response of normal and malignant urothelial cells to CHK1 and ATM inhibitors

“…KU60019: KU60019 is an improved inhibitor of ATM kinase from KU55933, which is reported 10-fold more effective than previous one in human glioma cells (Golding et al, 2009).…”