Abstract PO-022: Inhibition of the citrate carrier SLC25A1 affects repair of radiation-induced DNA damage, increases radiosensitivity, and enhances lethality of IR in combination with DNA repair defects or DSB inhibitors

Administration of exogenous keratinocyte growth factor (KGF) prevents or attenuates several forms of oxidant-mediated lung injury. Because DNA damage in epithelial cells is a component of radiation pneumotoxicity, we determined whether KGF ameliorated DNA strand breaks in irradiated A549 cells. Cells were exposed to 137Cs gamma rays, and DNA damage was measured by alkaline unwinding and ethidium bromide fluorescence after a 30-min recovery period. Radiation induced a dose-dependent increase in DNA strand breaks. The percentage of double-stranded DNA after exposure to 30 Gy increased from 44.6 +/- 3.5% in untreated control cells to 61.6 +/- 5.0% in cells cultured with 100 ng/ml KGF for 24 h (P < 0.05). No reduction in DNA damage occurred when the cells were cultured with KGF but maintained at 0 degree C during and after irradiation. The sparing effect of KGF on radiation-induced DNA damage was blocked by aphidicolin, an inhibitor of DNA polymerases-alpha, -delta, and -epsilon and by butylphenyl dGTP, which blocks DNA polymerase-alpha strongly and polymerases-delta and -epsilon less effectively. However, dideoxythymidine triphosphate, a specific inhibitor of DNA polymerase-beta, did not abrogate the KGF effect. Thus KGF increases DNA repair capacity in irradiated pulmonary epithelial cells, an effect mediated at least in part by DNA polymerases-alpha, -delta, and -epsilon. Enhancement of DNA repair capability after cell damage may be one mechanism by which KGF is able to ameliorate oxidant-mediated alveolar epithelial injury.

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Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.633344 ◽

2021 ◽

Vol 8 ◽

Author(s):

Jessica Buck ◽

Patrick J. C. Dyer ◽

Hilary Hii ◽

Brooke Carline ◽

Mani Kuchibhotla ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Combination Therapy ◽

Cellular Response ◽

Molecular Subtype ◽

Parp Inhibitor ◽

Single Agent ◽

Parp Inhibition ◽

Preclinical Model ◽

Radiation Induced

Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan–Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.

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Influence of Acute Exercise on DNA Repair and PARP Activity before and after Irradiation in Lymphocytes from Trained and Untrained Individuals

International Journal of Molecular Sciences ◽

10.3390/ijms20122999 ◽

2019 ◽

Vol 20 (12) ◽

pp. 2999 ◽

Cited By ~ 5

Author(s):

Maria Moreno-Villanueva ◽

Andreas Kramer ◽

Tabea Hammes ◽

Maria Venegas-Carro ◽

Patrick Thumm ◽

...

Keyword(s):

Physical Activity ◽

Dna Damage ◽

Dna Repair ◽

Immune Cells ◽

Acute Exercise ◽

Dna Strand Breaks ◽

Strand Breaks ◽

Before And After ◽

Radiation Induced ◽

Dna Strand

Several studies indicate that acute exercise induces DNA damage, whereas regular exercise increases DNA repair kinetics. Although the molecular mechanisms are not completely understood, the induction of endogenous reactive oxygen species (ROS) during acute exhaustive exercise due to metabolic processes might be responsible for the observed DNA damage, while an adaptive increase in antioxidant capacity due to regular physical activity seems to play an important protective role. However, the protective effect of physical activity on exogenously induced DNA damage in human immune cells has been poorly investigated. We asked the question whether individuals with a high aerobic capacity would have an enhanced response to radiation-induced DNA damage. Immune cells are highly sensitive to radiation and exercise affects lymphocyte dynamics and immune function. Therefore, we measured endogenous and radiation-induced DNA strand breaks and poly (ADP-ribose) polymerase-1 (PARP1) activity in peripheral blood mononuclear cells (PBMCs) from endurance-trained (maximum rate of oxygen consumption measured during incremental exercise V’O2max > 55 mL/min/kg) and untrained (V’O2max < 45 mL/min/kg) young healthy male volunteers before and after exhaustive exercise. Our results indicate that: (i) acute exercise induces DNA strand breaks in lymphocytes only in untrained individuals, (ii) following acute exercise, trained individuals repaired radiation-induced DNA strand breaks faster than untrained individuals, and (iii) trained subjects retained a higher level of radiation-induced PARP1 activity after acute exercise. The results of the present study indicate that increased aerobic fitness can protect immune cells against radiation-induced DNA strand breaks.

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Radiation-induced cytotoxicity, DNA damage and DNA repair: Implications for cell survival theory

Radiation and Environmental Biophysics ◽

10.1007/bf01210553 ◽

1990 ◽

Vol 29 (2) ◽

pp. 93-102 ◽

Cited By ~ 6

Author(s):

S. G. Swarts ◽

G. B. Nelson ◽

C. A. Wallen ◽

K. T. Wheeler

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Cell Survival ◽

Radiation Induced

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Akt/PKB suppresses DNA damage processing and checkpoint activation in late G2

The Journal of Cell Biology ◽

10.1083/jcb.201003004 ◽

2010 ◽

Vol 190 (3) ◽

pp. 297-305 ◽

Cited By ~ 53

Author(s):

Naihan Xu ◽

Nadia Hegarat ◽

Elizabeth J. Black ◽

Mary T. Scott ◽

Helfrid Hochegger ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Protein A ◽

Strand Break ◽

Checkpoint Activation ◽

Interacting Protein ◽

Dna Double Strand Break ◽

Radiation Induced ◽

G2 Cells ◽

Tumor Types

Using chemical genetics to reversibly inhibit Cdk1, we find that cells arrested in late G2 are unable to delay mitotic entry after irradiation. Late G2 cells detect DNA damage lesions and form γ-H2AX foci but fail to activate Chk1. This reflects a lack of DNA double-strand break processing because late G2 cells fail to recruit RPA (replication protein A), ATR (ataxia telangiectasia and Rad3 related), Rad51, or CtIP (C-terminal interacting protein) to sites of radiation-induced damage, events essential for both checkpoint activation and initiation of DNA repair by homologous recombination. Remarkably, inhibition of Akt/PKB (protein kinase B) restores DNA damage processing and Chk1 activation after irradiation in late G2. These data demonstrate a previously unrecognized role for Akt in cell cycle regulation of DNA repair and checkpoint activation. Because Akt/PKB is frequently activated in many tumor types, these findings have important implications for the evolution and therapy of such cancers.

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Irradiation-Induced Upregulation of miR-711 Inhibits DNA Repair and Promotes Neurodegeneration Pathways

International Journal of Molecular Sciences ◽

10.3390/ijms21155239 ◽

2020 ◽

Vol 21 (15) ◽

pp. 5239 ◽

Cited By ~ 1

Author(s):

Boris Sabirzhanov ◽

Oleg Makarevich ◽

James P. Barrett ◽

Isabel L. Jackson ◽

Ethan P. Glaser ◽

...

Keyword(s):

Dna Damage ◽

Cell Death ◽

Dna Repair ◽

Neuronal Cell Death ◽

Neuronal Cell ◽

Intrinsic Apoptosis ◽

In Vivo Models ◽

Neuroprotective Strategy ◽

Radiation Induced

Radiotherapy for brain tumors induces neuronal DNA damage and may lead to neurodegeneration and cognitive deficits. We investigated the mechanisms of radiation-induced neuronal cell death and the role of miR-711 in the regulation of these pathways. We used in vitro and in vivo models of radiation-induced neuronal cell death. We showed that X-ray exposure in primary cortical neurons induced activation of p53-mediated mechanisms including intrinsic apoptotic pathways with sequential upregulation of BH3-only molecules, mitochondrial release of cytochrome c and AIF-1, as well as senescence pathways including upregulation of p21WAF1/Cip1. These pathways of irradiation-induced neuronal apoptosis may involve miR-711-dependent downregulation of pro-survival genes Akt and Ang-1. Accordingly, we demonstrated that inhibition of miR-711 attenuated degradation of Akt and Ang-1 mRNAs and reduced intrinsic apoptosis after neuronal irradiation; likewise, administration of Ang-1 was neuroprotective. Importantly, irradiation also downregulated two novel miR-711 targets, DNA-repair genes Rad50 and Rad54l2, which may impair DNA damage responses, amplifying the stimulation of apoptotic and senescence pathways and contributing to neurodegeneration. Inhibition of miR-711 rescued Rad50 and Rad54l2 expression after neuronal irradiation, enhancing DNA repair and reducing p53-dependent apoptotic and senescence pathways. Significantly, we showed that brain irradiation in vivo persistently elevated miR-711, downregulated its targets, including pro-survival and DNA-repair molecules, and is associated with markers of neurodegeneration, not only across the cortex and hippocampus but also specifically in neurons isolated from the irradiated brain. Our data suggest that irradiation-induced miR-711 negatively modulates multiple pro-survival and DNA-repair mechanisms that converge to activate neuronal intrinsic apoptosis and senescence. Using miR-711 inhibitors to block the development of these regulated neurodegenerative pathways, thus increasing neuronal survival, may be an effective neuroprotective strategy.

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Primary Vestibular Schwannoma Cells Activate p21 and RAD51-Associated DNA Repair Following Radiation-Induced DNA Damage

Otology & Neurotology ◽

10.1097/mao.0000000000003322 ◽

2021 ◽

Vol Publish Ahead of Print ◽

Author(s):

Torin P. Thielhelm ◽

Stefania Goncalves ◽

Scott Welford ◽

Eric A. Mellon ◽

Olena Bracho ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Vestibular Schwannoma ◽

Radiation Induced

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Live Cell Imaging to Study Real-Time ATM-Mediated Recruitment of DNA Repair Complexes to Sites of Ionizing Radiation-Induced DNA Damage

Methods in Molecular Biology - ATM Kinase ◽

10.1007/978-1-4939-6955-5_21 ◽

2017 ◽

pp. 287-302 ◽

Cited By ~ 2

Author(s):

Burkhard Jakob ◽

Gisela Taucher-Scholz

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Ionizing Radiation ◽

Real Time ◽

Live Cell Imaging ◽

Cell Imaging ◽

Live Cell ◽

Radiation Induced

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Inhibition of Karyopherin-α2 Augments Radiation-Induced Cell Death by Perturbing BRCA1-Mediated DNA Repair

International Journal of Molecular Sciences ◽

10.3390/ijms20112843 ◽

2019 ◽

Vol 20 (11) ◽

pp. 2843 ◽

Cited By ~ 4

Author(s):

Kyung-Hee Song ◽

Seung-Youn Jung ◽

Jeong-In Park ◽

Jiyeon Ahn ◽

Jong Kuk Park ◽

...

Keyword(s):

Dna Damage ◽

Cell Death ◽

Dna Repair ◽

Apoptotic Cell ◽

Nucleocytoplasmic Transport ◽

Repair Protein ◽

Damage Response ◽

Dna Repair Protein ◽

Radiation Induced ◽

Early Local Recurrence

Ionizing radiation (IR) has been widely used in the treatment of cancer. Radiation-induced DNA damage triggers the DNA damage response (DDR), which can confer radioresistance and early local recurrence by activating DNA repair pathways. Since karyopherin-α2 (KPNA2), playing an important role in nucleocytoplasmic transport, was significantly increased by IR in our previous study, we aimed to determine the function of KPNA2 with regard to DDR. Exposure to radiation upregulated KPNA2 expression in human colorectal cancer HT29 and HCT116 cells and breast carcinoma MDA-MB-231 cells together with the increased expression of DNA repair protein BRCA1. The knockdown of KPNA2 effectively increased apoptotic cell death via inhibition of BRCA1 nuclear import following IR. Therefore, we propose that KPNA2 is a potential target for overcoming radioresistance via interruption to DDR.

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