Inhibition of DNA-dependent protein kinase induces accelerated senescence in irradiated human cancer cells

Arun Azad, Susan Jackson, Carleen M Cullinane, Anthony L Natoli, Paul M Neilsen, David Frederick Callen, Sauveur-Michel Maira, Wolfgang Hackl, Grant A McArthur, Benjamin J Solomon

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Abstract

DNA-dependent protein kinase (DNA-PK) plays a pivotal role in the repair of DNA double-strand breaks (DSB) and is centrally involved in regulating cellular radiosensitivity. Here, we identify DNA-PK as a key therapeutic target for augmenting accelerated senescence in irradiated human cancer cells. We find that BEZ235, a novel inhibitor of DNA-PK and phosphoinositide 3-kinase (PI3K)/mTOR, abrogates radiation-induced DSB repair resulting in cellular radiosensitization and growth delay of irradiated tumor xenografts. Importantly, radiation enhancement by BEZ235 coincides with a prominent p53-dependent accelerated senescence phenotype characterized by positive ?-galactosidase staining, G(2)-M cell-cycle arrest, enlarged and flattened cellular morphology, and increased p21 expression and senescence-associated cytokine secretion. Because this senescence response to BEZ235 is accompanied by unrepaired DNA DSBs, we examined whether selective targeting of DNA-PK also induces accelerated senescence in irradiated cells. Significantly, we show that specific pharmacologic inhibition of DNA-PK, but not PI3K or mTORC1, delays DSB repair leading to accelerated senescence after radiation. We additionally show that PRKDC knockdown using siRNA promotes a striking accelerated senescence phenotype in irradiated cells comparable with that of BEZ235. Thus, in the context of radiation treatment, our data indicate that inhibition of DNA-PK is sufficient for the induction of accelerated senescence. These results validate DNA-PK as an important therapeutic target in irradiated cancer cells and establish accelerated senescence as a novel mechanism of radiosensitization induced by DNA-PK blockade.
Original languageEnglish
Pages (from-to)1696 - 1707
Number of pages12
JournalMolecular Cancer Research
Volume9
Issue number12
DOIs
Publication statusPublished - 2011
Externally publishedYes

Cite this

Azad, A., Jackson, S., Cullinane, C. M., Natoli, A. L., Neilsen, P. M., Callen, D. F., ... Solomon, B. J. (2011). Inhibition of DNA-dependent protein kinase induces accelerated senescence in irradiated human cancer cells. Molecular Cancer Research, 9(12), 1696 - 1707. https://doi.org/10.1158/1541-7786.MCR-11-0312
Azad, Arun ; Jackson, Susan ; Cullinane, Carleen M ; Natoli, Anthony L ; Neilsen, Paul M ; Callen, David Frederick ; Maira, Sauveur-Michel ; Hackl, Wolfgang ; McArthur, Grant A ; Solomon, Benjamin J. / Inhibition of DNA-dependent protein kinase induces accelerated senescence in irradiated human cancer cells. In: Molecular Cancer Research. 2011 ; Vol. 9, No. 12. pp. 1696 - 1707.
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abstract = "DNA-dependent protein kinase (DNA-PK) plays a pivotal role in the repair of DNA double-strand breaks (DSB) and is centrally involved in regulating cellular radiosensitivity. Here, we identify DNA-PK as a key therapeutic target for augmenting accelerated senescence in irradiated human cancer cells. We find that BEZ235, a novel inhibitor of DNA-PK and phosphoinositide 3-kinase (PI3K)/mTOR, abrogates radiation-induced DSB repair resulting in cellular radiosensitization and growth delay of irradiated tumor xenografts. Importantly, radiation enhancement by BEZ235 coincides with a prominent p53-dependent accelerated senescence phenotype characterized by positive ?-galactosidase staining, G(2)-M cell-cycle arrest, enlarged and flattened cellular morphology, and increased p21 expression and senescence-associated cytokine secretion. Because this senescence response to BEZ235 is accompanied by unrepaired DNA DSBs, we examined whether selective targeting of DNA-PK also induces accelerated senescence in irradiated cells. Significantly, we show that specific pharmacologic inhibition of DNA-PK, but not PI3K or mTORC1, delays DSB repair leading to accelerated senescence after radiation. We additionally show that PRKDC knockdown using siRNA promotes a striking accelerated senescence phenotype in irradiated cells comparable with that of BEZ235. Thus, in the context of radiation treatment, our data indicate that inhibition of DNA-PK is sufficient for the induction of accelerated senescence. These results validate DNA-PK as an important therapeutic target in irradiated cancer cells and establish accelerated senescence as a novel mechanism of radiosensitization induced by DNA-PK blockade.",
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Azad, A, Jackson, S, Cullinane, CM, Natoli, AL, Neilsen, PM, Callen, DF, Maira, S-M, Hackl, W, McArthur, GA & Solomon, BJ 2011, 'Inhibition of DNA-dependent protein kinase induces accelerated senescence in irradiated human cancer cells', Molecular Cancer Research, vol. 9, no. 12, pp. 1696 - 1707. https://doi.org/10.1158/1541-7786.MCR-11-0312

Inhibition of DNA-dependent protein kinase induces accelerated senescence in irradiated human cancer cells. / Azad, Arun; Jackson, Susan; Cullinane, Carleen M; Natoli, Anthony L; Neilsen, Paul M; Callen, David Frederick; Maira, Sauveur-Michel; Hackl, Wolfgang; McArthur, Grant A; Solomon, Benjamin J.

In: Molecular Cancer Research, Vol. 9, No. 12, 2011, p. 1696 - 1707.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Inhibition of DNA-dependent protein kinase induces accelerated senescence in irradiated human cancer cells

AU - Azad, Arun

AU - Jackson, Susan

AU - Cullinane, Carleen M

AU - Natoli, Anthony L

AU - Neilsen, Paul M

AU - Callen, David Frederick

AU - Maira, Sauveur-Michel

AU - Hackl, Wolfgang

AU - McArthur, Grant A

AU - Solomon, Benjamin J

PY - 2011

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N2 - DNA-dependent protein kinase (DNA-PK) plays a pivotal role in the repair of DNA double-strand breaks (DSB) and is centrally involved in regulating cellular radiosensitivity. Here, we identify DNA-PK as a key therapeutic target for augmenting accelerated senescence in irradiated human cancer cells. We find that BEZ235, a novel inhibitor of DNA-PK and phosphoinositide 3-kinase (PI3K)/mTOR, abrogates radiation-induced DSB repair resulting in cellular radiosensitization and growth delay of irradiated tumor xenografts. Importantly, radiation enhancement by BEZ235 coincides with a prominent p53-dependent accelerated senescence phenotype characterized by positive ?-galactosidase staining, G(2)-M cell-cycle arrest, enlarged and flattened cellular morphology, and increased p21 expression and senescence-associated cytokine secretion. Because this senescence response to BEZ235 is accompanied by unrepaired DNA DSBs, we examined whether selective targeting of DNA-PK also induces accelerated senescence in irradiated cells. Significantly, we show that specific pharmacologic inhibition of DNA-PK, but not PI3K or mTORC1, delays DSB repair leading to accelerated senescence after radiation. We additionally show that PRKDC knockdown using siRNA promotes a striking accelerated senescence phenotype in irradiated cells comparable with that of BEZ235. Thus, in the context of radiation treatment, our data indicate that inhibition of DNA-PK is sufficient for the induction of accelerated senescence. These results validate DNA-PK as an important therapeutic target in irradiated cancer cells and establish accelerated senescence as a novel mechanism of radiosensitization induced by DNA-PK blockade.

AB - DNA-dependent protein kinase (DNA-PK) plays a pivotal role in the repair of DNA double-strand breaks (DSB) and is centrally involved in regulating cellular radiosensitivity. Here, we identify DNA-PK as a key therapeutic target for augmenting accelerated senescence in irradiated human cancer cells. We find that BEZ235, a novel inhibitor of DNA-PK and phosphoinositide 3-kinase (PI3K)/mTOR, abrogates radiation-induced DSB repair resulting in cellular radiosensitization and growth delay of irradiated tumor xenografts. Importantly, radiation enhancement by BEZ235 coincides with a prominent p53-dependent accelerated senescence phenotype characterized by positive ?-galactosidase staining, G(2)-M cell-cycle arrest, enlarged and flattened cellular morphology, and increased p21 expression and senescence-associated cytokine secretion. Because this senescence response to BEZ235 is accompanied by unrepaired DNA DSBs, we examined whether selective targeting of DNA-PK also induces accelerated senescence in irradiated cells. Significantly, we show that specific pharmacologic inhibition of DNA-PK, but not PI3K or mTORC1, delays DSB repair leading to accelerated senescence after radiation. We additionally show that PRKDC knockdown using siRNA promotes a striking accelerated senescence phenotype in irradiated cells comparable with that of BEZ235. Thus, in the context of radiation treatment, our data indicate that inhibition of DNA-PK is sufficient for the induction of accelerated senescence. These results validate DNA-PK as an important therapeutic target in irradiated cancer cells and establish accelerated senescence as a novel mechanism of radiosensitization induced by DNA-PK blockade.

UR - http://mcr.aacrjournals.org/content/9/12/1696.full.pdf+html

U2 - 10.1158/1541-7786.MCR-11-0312

DO - 10.1158/1541-7786.MCR-11-0312

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JF - Molecular Cancer Research

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