Radioresistant MTp53-expressing rat embryo cell transformants exhibit increased DNA-dsb rejoining during exposure to ionizing radiation

Bristow, Robert G.; Hu, Qiyue; Jang, Anne; Chung, Stephen W.; Peacock, James W.; Benchimol, Samuel; Hill, Richard P.

doi:10.1038/sj.onc.1201935

Cited by 42 publications

(33 citation statements)

References 43 publications

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“…Six hours later the calcium phosphate-DNA co-precipitates were removed and the cells were washed and incubated in fresh medium. At various times after transfection, the cells were harvested and lysed on ice in 250 ml of Laemmli sample bu er (62 mM Tris HCl pH 6.8, 10% glycerol, 2% sodium dodecyl sulfate (SDS), 5% b-mercaptoethanol, 0.003% bromophenol blue, 0.4 mM phenylmethylsulfonyl¯uoride) and the DNA was sheared by passage through a 27 gauge needle (Bristow et al, 1994). After boiling for 10 min and centrifugation, the supernatant proteins were assayed (Bradford, 1976) and samples were loaded onto a 10% polyacrylamide gel containing SDS and subjected to electrophoresis (Laemmli, 1970).…”

Section: Western Blot Analysismentioning

confidence: 99%

The p53 tumor suppressor protein reduces point mutation frequency of a shuttle vector modified by the chemical mutagens (±)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, aflatoxin B1 and meta-chloroperoxybenzoic acid

Courtemanche

Anderson

1999

Oncogene

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The p53 tumor suppressor protein reduces point mutation frequency of a shuttle vector modi®ed by the chemical mutagens (+)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, a¯atoxin B 1 and meta-chloroperoxybenzoic acid Chantal Courtemanche 1,2 and Alan Anderson* ,1,2 1 Centre de recherche en canceÂrologie de l'UniversiteÂ Laval, Pavillon L'HoÃtel-Dieu de QueÂbec, Centre hospitalier universitaire de QueÂbec, QueÂbec G1R 2J6 Canada; and 2 DeÂpartement de biologie, UniversiteÂ Laval, QueÂbec G1K 7P4 Canada p53 has been postulated to be the guardian of the genome. However, results supporting the prediction that point mutation frequencies are elevated in p53-de®cient cells either have not been forthcoming or have been equivocal. To analyse the e ect of p53 on point mutation frequency, we used the supF gene of the pYZ289 shuttle vector as a mutagenic target. pYZ289 was treated in vitro by ultraviolet irradiation, a¯atoxin B 1 , (+)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and meta-chloroperoxybenzoic acid and then transfected into p53-de®cient cells with or without a p53 expression vector. p53 reduced the mutant frequency up to ®vefold when pYZ289 was treated with a¯atoxin B 1 , (+)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene or meta-chloroperoxybenzoic acid but not when it was ultraviolet-irradiated. The p53-dependent mutation frequency reduction was higher at a higher level of premutational lesions for a¯atoxin B 1 and (+)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and at a lower level of lesions for meta-chloroperoxybenzoic acid. This suggests that the chemical mutagens produce, in a dose-dependent fashion, two kinds of DNA damage, one subject to p53-dependent mutation frequency reduction and the other not. These results indicate that p53 can reduce the point mutation frequency in a shuttle vector treated by chemical mutagens and suggest that p53 can act as guardian of the genome for at least some kinds of point mutations.

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Section: Western Blot Analysismentioning

confidence: 99%

The p53 tumor suppressor protein reduces point mutation frequency of a shuttle vector modified by the chemical mutagens (±)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, aflatoxin B1 and meta-chloroperoxybenzoic acid

Courtemanche

Anderson

1999

Oncogene

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“…Cells were stained with anti-BrdUrd FITC (BD Bioscience) and propidium iodide and analyzed using a FACSCalibre flow cytometer (BD Biosciences) and CellQuest software (BD Biosciences; ref. 33).…”

Section: Methodsmentioning

confidence: 99%

“…The cell cycle distribution of cells grown under the varying O 2 conditions was quantified using dual-variable flow cytometry (33). Briefly, gas-treated cells were incubated with 10 Amol/L bromodeoxyuridine (BrdUrd) for 30 min before collection without reoxygenation.…”

Section: Methodsmentioning

confidence: 99%

Chronic Hypoxia Decreases Synthesis of Homologous Recombination Proteins to Offset Chemoresistance and Radioresistance

et al. 2008

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Hypoxic and/or anoxic tumor cells can have increased rates of mutagenesis and altered DNA repair protein expression. Yet very little is known regarding the functional consequences of any hypoxia-induced changes in the expression of proteins involved in DNA double-strand break repair. We have developed a unique hypoxic model system using H1299 cells expressing an integrated direct repeat green fluorescent protein (DR-GFP) homologous recombination (HR) reporter system to study HR under prolonged chronic hypoxia (up to 72 h under 0.2% O 2 ) without bias from altered proliferation, cell cycle checkpoint activation, or severe cell toxicity. We observed decreased expression of HR proteins due to a novel mechanism involving decreased HR protein synthesis. Error-free HR was suppressed 3-fold under 0.2% O 2 as measured by the DR-GFP reporter system. This decrease in functional HR resulted in increased sensitivity to the DNA cross-linking agents mitomycin C and cisplatin but not to the microtubule-interfering agent, paclitaxel. Chronically hypoxic H1299 cells that had decreased functional HR were relatively radiosensitive [oxygen enhancement ratio (OER), 1.37] when compared with acutely hypoxic or anoxic cells (OER, 1.96-2.61). Using CAPAN1 cells isogenic for BRCA2 and siRNA to RAD51, we confirmed that the hypoxia-induced radiosensitivity was due to decreased HR capacity. Persistent down-regulation of HR function by the tumor microenvironment could result in low-fidelity DNA repair and have significant implications for response to therapy and genetic instability in human cancers. [Cancer Res 2008;68(2):605-14]

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“…Although some cell lines with WT P53 show radiosensitivity (Servomaa et al, 1996), much evidence has indicated that WT P53 plays a crucial role in mediating radiosensitivity. In vitro cell line studies have showed that P53 mutations are associated with increased radioresistance (Bristow et al, 1994;McIlwrath et al, 1994;Yount et al, 1996). In vivo WT P53 has proven to be essential in determining the radiosensitivity in a variety of tissues (Lowe et al, 1993;Merritt et al, 1994;MacCallum et al, 1996;Komarova et al, 1997;Merritt et al, 1997;Herzog et al, 1998;Bouvard et al, 2000;Burns et al, 2001).…”

Section: P53-mediated Apoptosis In Irmentioning

confidence: 99%

P53 and radiation responses

2003

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Cells have evolved elaborate mechanisms (checkpoints) to monitor genomic integrity in order to ensure the highfidelity transmission of genetic information. Cells harboring defects in checkpoint pathways respond to DNA damage improperly, which in turn may enhance the rate of cancer development. Ionizing radiation (IR) primarily leads to double-strand DNA breaks (DSBs), which activate DNA damage checkpoints to initiate signals ultimately leading to a binary decision between cell death and cell survival. TP53 has been recognized as an important checkpoint protein, functioning mainly through transcriptional control of target genes that influence multiple response pathways and leading to the diversity of responses to IR in mammalian cells. We review how the tumor suppressor P53 is involved in the complex response to IR to enforce the cell's fate to live by inducing the growth arrest coupled to DNA damage repair or to die by inducing irreversible growth arrest or apoptosis. Moreover, recent insights have emerged in our understanding of how P53 modulates radiosensitivity in tissues following IR as well as its role in sensitizing cells to chemo-and radiotherapy. The P53 pathway remains an attractive target for exploitation in the war on cancer.

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Radioresistant MTp53-expressing rat embryo cell transformants exhibit increased DNA-dsb rejoining during exposure to ionizing radiation

Cited by 42 publications

References 43 publications

The p53 tumor suppressor protein reduces point mutation frequency of a shuttle vector modified by the chemical mutagens (±)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, aflatoxin B1 and meta-chloroperoxybenzoic acid

The p53 tumor suppressor protein reduces point mutation frequency of a shuttle vector modified by the chemical mutagens (±)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, aflatoxin B1 and meta-chloroperoxybenzoic acid

Chronic Hypoxia Decreases Synthesis of Homologous Recombination Proteins to Offset Chemoresistance and Radioresistance

P53 and radiation responses

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