Transient Inhibition of ATM Kinase Is Sufficient to Enhance Cellular Sensitivity to Ionizing Radiation

Rainey, Michael D.; Charlton, Maura E.; Stanton, Robert V.; Kastan, Michael B.

doi:10.1158/0008-5472.can-08-0763

Cited by 227 publications

(162 citation statements)

References 47 publications

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“…To that end, we tested the autophagy interfering capacity of two other compounds known to inhibit ATM kinase, i.e. caffeine (27) and CP466722, a recently introduced highly specific and potent ATM inhibitor with a structure distinct from that of KU55933 (28). As analyzed by their ability to inhibit ionizing radiation (IR)-induced phosphorylation (Ser-15) and subsequent stabilization of a well-described ATM target, tumor protein 53 (TP53) in MCF7 cells, 4 mM caffeine and 5 M CP466722 were as effective in inhibiting ATM activity as 2 M KU55933 ( Fig.…”

Section: Identification Of Small Molecule Inhibitors Of Autophagy-mentioning

confidence: 99%

Identification of Small Molecule Inhibitors of Phosphatidylinositol 3-Kinase and Autophagy

Farkas

Daugaard

Jäättelä

2011

Journal of Biological Chemistry

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Macroautophagy (hereafter autophagy) is a lysosomal catabolic pathway that controls cellular homeostasis and survival. It has recently emerged as an attractive target for the treatment of a variety of degenerative diseases and cancer. The targeting of autophagy has, however, been hampered by the lack of specific small molecule inhibitors. Thus, we screened two small molecule kinase inhibitor libraries for inhibitors of rapamycin-induced autophagic flux. The three most potent inhibitors identified conferred profound inhibition of autophagic flux by inhibiting the formation of autophagosomes. Notably, the autophagy inhibitory effects of all three compounds were independent of their established kinase targets, i.e. ataxia telangiectasia mutated for KU55933, protein kinase C for Gö6976, and Janus kinase 3 for Jak3 inhibitor VI. Instead, we identified phosphatidylinositol 3-kinase (PtdIns3K) as a direct target of KU55933 and Gö6976. Importantly, and in contrast to the currently available inhibitors of autophagosome formation (e.g. 3-methyladenine), none of the three compounds inhibited the cell survival promoting class I phosphoinositide 3-kinase-Akt signaling at the concentrations required for effective autophagy inhibition. Accordingly, they proved to be valuable tools for investigations of autophagy-associated cell death and survival. Employing KU55399, we demonstrated that autophagy protects amino acid-starved cells against both apoptosis and necroptosis. Taken together, our data introduce new possibilities for the experimental study of autophagy and can form a basis for the development of clinically relevant autophagy inhibitors.Autophagy is an intracellular degradative process by which cells recycle macromolecules and organelles (1-4). In this process, cellular material is sequestered in double membrane vesicles termed autophagosomes that fuse with lysosomes to form autolysosomes, in which the cargo is exposed to acidic hydrolases. Autophagy is essential for energy homeostasis and removal of damaged organelles and protein complexes during various kinds of stresses, such as starvation, growth factor deprivation, hypoxia, and DNA damage. It is also involved in physiological processes like development, immunity, and aging as well as in various diseases including neurodegenerative disorders and cancer. Whereas autophagy clearly has a beneficial effect in preventing many degenerative disorders, its role in cancer is more complex. It can function as a tumor suppressor mechanism, and yet it can also promote tumor growth by protecting cancer cells against the hostile tumor environment and antineoplastic drugs (5, 6).The mammalian target of rapamycin complex 1 (mTORC1) 3 serine/threonine kinase integrates information on cell metabolic, growth, and stress status to regulate biosynthetic pathways and autophagy (7,8). It activates biosynthetic pathways and inhibits autophagy in response to various growth factors via MAPK/ERK and class I phosphoinositide 3-kinase (PI3K)/Aktdependent pathways. On the other hand, when the ene...

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Section: Identification Of Small Molecule Inhibitors Of Autophagy-mentioning

confidence: 99%

Identification of Small Molecule Inhibitors of Phosphatidylinositol 3-Kinase and Autophagy

Farkas

Daugaard

Jäättelä

2011

Journal of Biological Chemistry

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“…To date, three selective inhibitors of ATM kinase activity have been identified: KU55933, 16 CP466722, 17 and KU60019. 18 As expected, ATM kinase inhibition using KU55933, CP466722 or KU60019 is sufficient to enhance cellular sensitivity to IR.…”

Section: Atm Kinase Inhibitorsmentioning

confidence: 99%

“…18 As expected, ATM kinase inhibition using KU55933, CP466722 or KU60019 is sufficient to enhance cellular sensitivity to IR. [16][17][18] We showed that the competitive ATP inhibitors KU55933 and KU60019 can be used as "molecular switches" to selectively and transiently inhibit ATM kinase activity in cells. ATM kinase activity is inhibited in irradiated cells within 15 min of the addition of KU55933 or KU60019 and is restored within 15 min following the removal of either inhibitor.…”

Section: Atm Kinase Inhibitorsmentioning

confidence: 99%

Inhibition of ATM kinase activity does not phenocopy ATM protein disruption

et al. 2010

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Biallelic mutations in ataxiatelangiectasia mutated (ATM), which encodes for a protein kinase, cause ataxia telangiectasia (A-T). A-T is a pleiotropic disease, with a characteristic hypersensitivity to ionizing radiation (IR). A-T patients typically lack both detectable ATM protein and ATM kinase activity, and small molecule inhibitors of ATM kinase activity have been developed as strategies to improve radiotherapy for the treatment of cancers. As predicted, inhibition of ATM kinase activity is sufficient to radiosensitize cells. However, we recently showed that inhibition of ATM kinase activity disrupts DNA damage-induced sister chromatid exchange (SCE). This result was unanticipated since SCE is normal in A-T cells that lack detectable ATM protein. In these studies, we showed, for the first time, that the consequences of inhibition of ATM kinase activity and adaptation to ATM protein disruption are distinct. Here, we discuss the mechanistic implications of this finding for the function of ATM at the replication fork and the clinical utility of ATM kinase inhibitors.

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“…It is well established that ATM is essential in maintaining G 2 checkpoint function (Terzoudi et al, 2005;Deckbar et al, 2007) through inhibition of cyclin B1/cdc2 (Abraham, 2001). We, therefore, examined the effect of a specific and potent ATM inhibitor, KU55933 (Rainey et al, 2008), which is known as a 'molecular switch' because of its rapid and reversible inactivation of ATM (White et al, 2008), on centromeric instability. Being aware that ATM also has G 1 /S checkpoint functions (Abraham, 2001), we particularly designed experiments to examine the effect of KU55933 treatment without the confounding factor of G 1 /S checkpoint inactivation.…”

Section: Resultsmentioning

confidence: 99%

Impact of G2 checkpoint defect on centromeric instability

et al. 2010

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Centromeric instability is characterized by dynamic formation of centromeric breaks, deletions, isochromosomes and translocations, which are commonly observed in cancer. So far, however, the mechanisms of centromeric instability in cancer cells are still poorly understood. In this study, we tested the hypothesis that G 2 checkpoint defect promotes centromeric instability. Our observations from multiple approaches consistently support this hypothesis. We found that overexpression of cyclin B1, one of the pivotal genes driving G 2 to M phase transition, impaired G 2 checkpoint and promoted the formation of centromeric aberrations in telomerase-immortalized cell lines. Conversely, centromeric instability in cancer cells was ameliorated through reinforcement of G 2 checkpoint by cyclin B1 knockdown. Remarkably, treatment with KU55933 for only 2.5 h, which abrogated G 2 checkpoint, was sufficient to produce centromeric aberrations. Moreover, centromeric aberrations constituted the major form of structural abnormalities in G 2 checkpoint-defective ataxia telangiectasia cells. Statistical analysis showed that the frequencies of centromeric aberrations in G 2 checkpoint-defective cells were always significantly overrepresented compared with random assumption. As there are multiple pathways leading to G 2 checkpoint defect, our finding offers a broad explanation for the common occurrence of centromeric aberrations in cancer cells.

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Transient Inhibition of ATM Kinase Is Sufficient to Enhance Cellular Sensitivity to Ionizing Radiation

Cited by 227 publications

References 47 publications

Identification of Small Molecule Inhibitors of Phosphatidylinositol 3-Kinase and Autophagy

Identification of Small Molecule Inhibitors of Phosphatidylinositol 3-Kinase and Autophagy

Inhibition of ATM kinase activity does not phenocopy ATM protein disruption

Impact of G2 checkpoint defect on centromeric instability

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