ku-60019 and Ataxia-Telangiectasia

Ataxia-telangiectasia mutated (ATM) kinase is a serine/threonine protein kinase and plays a key role in DNA double-strand breaks repair. Thus, ATM is considered a promising target for radiotherapy and chemotherapy sensitizing. Herein, we report the discovery of ATM agonist A22 and inhibitor A41 by computational methods and further biological evaluation. Among them, A22 exhibited low cytotoxicity in vitro and might serve as a useful tool for ATM research. Moreover, we firstly proved that ATM inhibitors could sensitize Irinotecan and Etoposide in a time-dependent manner on MCF-7 and SW480 cells, antagonism in a short period treatment while synergy at a long-term treatment and ATM agonist worked in an opposite way of ATM inhibitors. Further mechanism study demonstrated that the antagonism effect of ATM inhibitors with chemotherapeutic agents in a short period was resulting from inhibiting the p53/p21 axis to accelerate G1/S phase cell-cycle transition and promote cell survival. Additionally, A41 displayed antitumor effects combined with a chemotherapeutic drug in the SW480 xenograft model, indicating that A41 is a promising ATM inhibitor, which could increase the antitumor effect of chemotherapeutic drugs in vivo. All in all, these findings will guide the combination of ATM inhibitors with chemotherapeutic agents in further preclinical and clinical studies.

Topics: Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Cell Line, Tumor; DNA-Binding Proteins; Humans; Neoplasms; Phosphorylation; Protein Serine-Threonine Kinases

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.

Topics: Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Cell Movement; Cell Survival; DNA-Binding Proteins; Extracellular Signal-Regulated MAP Kinases; Fibroblasts; Gamma Rays; Glioma; Humans; Insulin; MAP Kinase Signaling System; Morpholines; Neoplasm Invasiveness; Phosphoserine; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Pyrones; Radiation-Sensitizing Agents; Thioxanthenes; Tumor Suppressor Proteins