Mutagenesis Advance Access published online on February 10, 2008
Mutagenesis, doi:10.1093/mutage/gen001
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
p53-dependent global nucleotide excision repair of cisplatin-induced intrastrand cross links in human cells
1Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK 2Section of Molecular Carcinogenesis, Institute of Cancer Research, Sutton, Surrey SM2 5NG, UK
Cisplatin is an extremely effective chemotherapeutic agent used for the treatment of testicular and other solid tumours. It induces a variety of structural modifications in DNA, the most abundant being the GpG- and ApG-1,2-intrastrand cross links formed between adjacent purine bases. These cross links account for 
90% of cisplatin-induced DNA damage and are thought to be responsible for the cytotoxic activity of the drug. In human cells, the nucleotide excision repair (NER) process removes the intrastrand cross links from the genome, the efficiency of which is likely to be an important determinant of cisplatin cytotoxicity. We have investigated whether the p53 tumour suppressor status affects global NER of cisplatin-induced intrastrand cross links in human cells. We have used a 32P-postlabelling method to monitor the removal of GpG- and ApG-intrastrand cross links from two human cell models (the 041TR system, in which p53 is regulated by a tetracycline-inducible promoter, together with WI38 fibroblasts and the SV40-transformed derivative VA13) that each differ in p53 status. We demonstrate that the absence of functional p53 leads to persistence of both cisplatin-induced intrastrand cross links in the genome, suggesting that p53 regulates NER of these DNA lesions. This observation extends the role of p53 in NER beyond enhancing the removal of environmentally induced DNA lesions to include those of clinical origin. Given the frequency of p53 mutations in human tumours, these results may have implications for the use of cisplatin in cancer chemotherapy.
 |
Introduction |
|---|
 Top Introduction Materials and methodsResultsDiscussionFundingReferences |
|---|
Cisplatin is one of the most successful and widely used chemotherapeutic agents. Discovered in the late 1960s, it revolutionized the treatment of testicular cancer in the late 1970s. Previously a disease with poor prognosis, the treatment of testicular cancer with cisplatin-based chemotherapy has become a paradigm for cancer chemotherapy. In total, 90–95% of patients with early stage testicular cancer are now cured, with good prognosis also for patients with metastatic disease (reviewed in ref. 1
).
Cisplatin acts by forming a variety of adducts with DNA that hinder normal cellular processes and ultimately result in cell death. Of the adducts induced, the most abundant are the 1,2-intrastrand cross links formed between adjacent purine bases on the same strand of DNA. These cross links account for 90% of the total DNA damage induced by cisplatin and are thought to be a major contributing factor to the cytotoxic effects of the drug (2,3). The intrastrand cross links cause significant bending and unwinding of the DNA double helix, ultimately resulting in the disruption of a variety of essential cellular processes. Thus, the cross links halt progression through the cell cycle, block transcription and attract a variety of proteins such as transcription factors to sequester them from their normal, essential cellular functions (4,5). Proteins involved in the mismatch repair pathway in humans also bind to cisplatin-induced intrastrand cross links, initiating futile cycles of mismatch repair and the introduction of toxic double-strand breaks (6). All these mechanisms are thought to co-ordinate in order to elicit the cytotoxic effects of cisplatin in tumour cells.
Cisplatin-induced cross links are recognized and removed from the genome by nucleotide excision repair (NER) (7,8). The removal of cross links from the genome of tumour cells, and consequent reduction in the frequency of the downstream cytotoxic pathways initiated in the presence of cross links, would clearly reduce the sensitivity of those cells to cisplatin. Thus, the efficiency of NER in tumour cells is likely to be an important factor in the success of cisplatin therapy. Previous work has established that the efficiency of NER of certain types of DNA damage is regulated by the p53 tumour suppressor protein. However, unlike the well-characterized role for p53 in apoptosis and regulation of the cell cycle (9,10), the precise role of p53 in DNA repair remains to be fully elucidated, in part, due to the wide variety of DNA damage induced in human cells and the number of mechanisms involved in their removal from the genome. For instance, it is known that p53 is required for the efficient global removal from the genome of UV-induced cyclobutane pyrimidine dimers (CPDs) (11–14) and adducts formed by diol-epoxide metabolites of the potent chemical carcinogens benzo[a]pyrene and benzo[g]chrysene (15–17). Global NER of UV-induced 6-4 photoproducts is, however, much less dependent upon p53 (12,13), and it is not required for transcription-coupled repair of CPDs (11–13).
Given that the p53 gene is mutated in >50% of human tumours, it is important to establish whether p53 status affects the ability of cells to remove the cytotoxic lesions induced by chemotherapeutic drugs such as cisplatin. Differences in the efficiency of NER between p53-proficient and p53-deficient cells would suggest that therapeutic outcome of DNA damage-based chemotherapy is influenced in some way by the tumour's p53 status. Host cell reactivation analysis of cisplatin-treated plasmids has indicated that p53 affects the ability of cells to repair cisplatin-induced DNA damage (18), although this type of analysis does not distinguish between global and transcription-coupled NER, nor the different types of DNA damage induced by cisplatin. In the present study, we have sought to determine whether p53 regulates the repair of the cytotoxic cisplatin-induced 1,2-intrastrand cross links. We have modified existing 32P-postlabelling protocols, developed for the analysis of in vitro-induced cisplatin cross links, to determine the requirement of p53 for the removal of the major GpG and ApG cross links from the genome in human cells. The results demonstrate that p53 is required for the efficient removal of both cross links in human cells and that these cytotoxic cross links persist in p53-deficient cells. This may have implications for the use of DNA-damaging chemotherapeutic agents such as cisplatin in the treatment of tumours with differing p53 status.
|
Materials and methods |
|---|
|
TopIntroductionMaterials and methodsResultsDiscussionFundingReferences |
|---|
Materials
Antibodies used in western blotting procedures were from DakoCytomation (Denmark), Santa Cruz Biotechnologies (Santa Cruz, CA, USA) or Sigma Chemical Co. (Poole, Dorset, UK), as indicated below. Tissue culture additives and Proteinase K were obtained from Invitrogen/GIBCO (Paisley, UK). Cisplatin and all other reagents and enzymes were from Sigma Chemical Co. (Poole), except where stated.
Cell culture
041TR cells were grown as monolayers in DMEM supplemented with 10% foetal bovine serum (Bio Whittaker Europe, Belgium) at 37°C in a humidified atmosphere of 5% CO2. These cells, originally obtained from Dr G. Stark (Cleveland Clinic Foundation, Cleveland, OH, USA), were derived from spontaneously immortalized Li–Fraumeni syndrome skin fibroblasts and stably transfected with a tetracycline-regulated system for the expression of wild-type p53 (19). They were grown in the continuous presence of G418 (600 µg/ml) and hygromycin (50 µg/ml) to maintain selection pressure for transfected cells. Tetracycline (2 µg/ml) was added when suppression of wild-type p53 was required. WI38 human Caucasian foetal lung fibroblast and isogenic SV40-transformed VA13 cells, both obtained from European Collection of Cell Cultures (90020107 and 85062512, respectively), were grown as monolayers in DMEM supplemented with 10% foetal bovine serum and non-essential amino acids at 37°C in a humidified atmosphere of 5% CO2.
To induce DNA damage, cisplatin was diluted from a 2 mM stock in 0.9% sodium chloride to the required concentration (20–100 µM) in serum-free medium. Treatment was for 2 h at 37°C, after which cells were washed twice in PBS and harvested for DNA isolation.
DNA isolation
Cells were lysed in 10 mM EDTA and 50 mM Tris–HCl (pH 8.0, 0.5 ml) containing SDS (1%) and Proteinase K (0.5 mg/ml) and incubated for 3 h at 37°C. DNA was purified from the lysates by phenol extraction and RNAse treatment (20), resuspended in 1/100 sodium chloride citrate buffer (1.5 mM sodium chloride and 0.15 mM sodium citrate) and stored at –20°C prior to analysis.
Western blotting
Total cellular protein was isolated by lysing cells in 100 µl of a stock buffer consisting of Triton X-100 (1%), Tris–HCl (50 mM, pH 7.4), sodium chloride (150 mM), EDTA (5 mM), together with Sigma Protease Inhibitor Cocktail used according to the manufacturer's instructions. Whole-cell extracts were prepared, protein concentration was determined by the Bradford method and equal amounts of protein (75 µg) were resolved by 12% SDS–PAGE and electroblotted to a nitrocellulose membrane. Membranes were then subjected to immunoblotting with mouse monoclonal antibodies to human p53 (DO-7, DakoCytomation), rabbit polyclonal antibodies to human p21 (C19, Santa Cruz Biotechnology) and mouse monoclonal antibodies to β-actin (AC-15, Sigma Chemical Co.) diluted 1:1000, 1:1000 and 1:5000, respectively, in 1% non-fat milk in PBS. This was followed by incubation with appropriate horseradish peroxidase-conjugated secondary antibodies (goat anti-mouse from DakoCytomation, goat anti-rabbit from Santa Cruz Biotechnology, both diluted 1:5000 in 1% non-fat milk and PBS). Proteins were detected by enhanced chemiluminescence (SuperSignal West Pico Chemiluminescence, Pierce Biotechnology) and transparency film.
32P-Postlabelling
DNA samples were subjected to a 32P-postlabelling method, based largely on previously published methods (21,22) with minor modifications. DNA was digested by dissolving 20 µg DNA in 50 mM ammonium acetate/1 mM zinc chloride (pH 5.0, 50 µl) to which nuclease P1 (3 U) was added and incubated for 2 h at 60°C. One micromolar Tris–HCl/10 mM magnesium chloride (pH 8.2, 10 µl) and DNase I (50 U) were then added and incubation continued for a further 2 h at 37°C. Finally, alkaline phosphatase (20 U) and 0.5 M Tris (5 µl) were added with incubation for a further 18 h. Unmodified nucleotides and nucleosides were removed by cation-exchange chromatography, with Lichrolut 200 mg strong cation exchange solid-phase extraction cartridges (Select Sciences Ltd, Bath, UK) and a vacuum manifold. Platinated adducts were subsequently eluted with 250 mM ammonium hydroxide. Platinum was removed during a 2 h incubation at 65°C by the addition of NaCN (0.1 M, 30 µl). Samples were then dried in a Speedvac vacuum centrifuge and redissolved in distilled water to a final volume of 200 µl. The deplatinated nucleotides were then desalted using C18 Sep-Pak light 100 mg cartridges (Biotage AB, supplied by Kinesis Ltd, St Neots, UK) previously washed with methanol and deionized water. Inorganic compounds were eluted with distilled water (2 ml). Dinucleoside monophosphates and nucleosides were then eluted with methanol (400 µl). The samples were evaporated to dryness in a Speedvac and redissolved in deionized water (10 µl). To each sample, 10 µCi [
-32P]ATP, 2 µl 10x kinase buffer (200 mM bicine, pH 9.0, 100 mM MgCl2, 100 mM DTT and 10 mM spermidine) and 3'-phosphatase-free T4 polynucleotide kinase (0.5 µl) were added. The resulting mixture was incubated for 40 min at 37°C.
Separation of the radioactively labelled products was achieved through a combination of thin layer chromatography (TLC) and HPLC. Compounds of interest were separated from excess ATP by spotting the reaction mixture on Polygram 300 PEI TLC sheets 20 x 20 cm (Macherey-Nagel, supplied by Camlab Ltd, Cambridge, UK) and run for 2–3 h in 1.5 M ammonium formate (pH 4.0). In order to improve separation and quantification of individual cross links beyond that possible with one-dimensional TLC, samples were further separated and analysed by HPLC. Radioactive spots of interest identified by autoradiography were excised and extracted with 4 M pyridinium formate (pH 4.5) by shaking for 3 h. After centrifugation, the supernatant was dried in a Speedvac and the residue redissolved in distilled water and injected onto a Waters Alliance HPLC linked to B150 Packard Radioactivity Detector. A gradient elution was utilized, in which an initial elution of 100% 100 mM KH2PO4 (pH 4)/methanol 97.5/2.5 (v/v) (Solvent A) was maintained for up to 25 min. The concentration was then decreased to 80% Solvent A over the next 5 min with 20% Solvent B (pure methanol). Solvent A was then increased to 100% over the following 10 min, while Solvent B was reduced to 0%. Flow was diverted away from the detector for first 10 min to avoid overload. Separation was performed on a Jupiter C18, 5 µm 250 x 4.6 mm column (Phenomenex, Torrance, CA, USA).
|
Results |
|---|
|
TopIntroductionMaterials and methodsResultsDiscussionFundingReferences |
|---|
p53 Levels in whole-cell extracts
In order to confirm that 041TR, WI38 and VA13 cells were suitable for the analysis of the role of p53 in the repair of cisplatin-induced DNA damage, western blotting was used to monitor p53 levels in whole extracts at several time points after cisplatin treatment. In order to evaluate p53-dependent transcriptional activity, levels of the downstream transactivation target p21 were also analysed, while β-actin levels were measured as a loading and transfer control. 041TR cells, homozygous p53 mutants stably transfected with a tetracycline-regulated system for the expression of wild-type p53 (19
), were grown in tetracycline (2 µg/ml) when suppression of wild-type p53 was required. In the absence of tetracycline, 041TR cells showed increasing p53 levels up to 24 h after treatment with 20 µM cisplatin, with p21 levels also being expressed at high levels after 24 h (Figure 1A). 041TR cells grown in the presence of tetracycline and treated with cisplatin showed no detectable p53 or p21 at any time after treatment (Figure 1A), confirming that tetracycline suppressed the expression of transcriptionally active p53 in 041TR cells. WI38 cells treated with 20 µM cisplatin showed increasing levels of both p53 and p21 up to 24 h after treatment (Figure 1B). VA13 cells, SV40-transformed derivatives of WI38 in which p53 function is abrogated, exhibited constitutively high levels of p53 up to 24 h after treatment, but very low and almost undetectable levels of p21 (Figure 1B); this is consistent with the loss of p53 function due to its binding to the SV40 large T-antigen and inhibition of p53-dependent transcription (23–25). These experiments confirmed that 041TR, WI38 and VA13 cells were suitable models to investigate the role of p53 in the removal of cisplatin-induced DNA damage.
|
32P-postlabelling analysis of cisplatin-induced intrastrand cross links
Analysis of DNA isolated from cisplatin-treated cells revealed the presence of several radioactive products (Figure 2A). The results from this one-dimensional TLC analysis were consistent with those obtained by Blommaert and Saris (21
), with two products observed in DNA samples isolated from cisplatin-treated cells that were not present in untreated control samples beyond background levels. These products exhibited an intermediate chromatographic mobility and were located between unidentified radioactive spots on the TLC plate that were also present in control samples. In order to improve separation and quantitation of the products of interest and confirm that these products corresponded with the GpG- and ApG-intrastrand cross links, 32P-postlabelled DNA samples were subjected to further analysis by HPLC. 32P-labelled material, which was excised from the spots identified after TLC and autoradiography, was subjected to high-resolution HPLC analysis, alongside 32P-labelled GpG and ApG dinucleotides. The combination of one-dimensional TLC and high-resolution HPLC confirmed that the radioactive spots identified by TLC analysis, and the peaks obtained on HPLC profiles at retention times of 5.0 and 11.5 min, correspond with the major cisplatin-induced GpG- and ApG-intrastrand cross links (Figure 2B). These radiolabelled products were not found in control samples containing the labelling mix and deionized water. This 32P-postlabelling method was used subsequently in the DNA repair time-course experiments to measure the formation and repair of cisplatin-induced cross links.
|
Formation and repair of cisplatin-induced intrastrand cross-linked adducts
041TR cells were grown to confluence, either in the presence of tetracycline or in its absence, and then treated with 100 µM cisplatin. Cells were incubated for various times up to 24 h after this treatment prior to isolation of DNA and detection of intrastrand cross links by 32P-postlabelling. In the absence of p53, levels of both ApG and GpG cross links increased substantially within the first 2 h after cisplatin treatment, reaching maximal levels after 8 h (Figure 3). After 24 h, the levels of each adduct had decreased only slightly. GpG cross links were
2.5 times the level of ApG cross links, in line with previous estimations of the proportion of each cross link formed in vitro (2). In an isogenic but p53-proficient cellular background (i.e. in the absence of tetracycline), maximal levels of ApG and GpG cross links were observed at lower levels than in the corresponding p53-deficient cells and at an earlier time point (between 0 and 2 h after treatment). After reaching this maximum, removal of both cross links proceeded rapidly with only low levels remaining after 8 h.
|
Identical experiments were performed in a second pair of cell lines: WI38 cells and their derivative cell line VA13 in which p53 is abrogated. ApG- and GpG-intrastrand cross links in p53-deficient VA13 cells reached maximum levels 2 h after cisplatin treatment, decreasing rapidly after 4 h. However, after this point, the remaining cross links persisted up to 24 h after treatment. In contrast, p53-proficient WI38 cells exhibited much lower maximum levels of both GpG and ApG cross links than the p53-deficient VA13 cells, decreasing by approximately half after 24 h.
|
Discussion |
|---|
|
TopIntroductionMaterials and methodsResultsDiscussionFundingReferences |
|---|
Previous work on the role of p53 in excision repair has principally focused on DNA damage induced by environmental agents such as UV, cigarette smoke and industrial waste (11
–17). The implication from these studies has been that the loss of p53 increases genetic instability and reduces the ability of cells to process carcinogenic DNA lesions, thus increasing the risk of cancer. This study has focused instead on the use of a chemotherapeutic agent whose mode of action is dependent upon the persistence of the cytotoxic intrastrand cross links it induces.
We have established in this study that p53 is required for the global NER of the two major cisplatin-induced intrastrand cross links. Consistent with the studies of the repair of DNA damage induced by chemical carcinogens (15,17), removal of cisplatin-induced intrastrand cross links was offset by continued formation as a result of cisplatin remaining in the cells after treatment. Thus, p53-dependent NER is evident from reduced maximum levels of DNA damage in the first 2–4 h after treatment as well as a greater reduction in levels of DNA damage at later time points. p53-dependent removal of the cisplatin-induced intrastrand cross links was observed in two pairs of cell lines that differ in p53 status. In keeping with similar studies, in which the same cells were used to investigate the role of p53 in DNA damage-dependent cytotoxicity (26), the effect of p53 status on removal of the cross links was greatest in the 041TR cells and least evident for the ApG cross link in WI38 and VA13 cells. This is likely to result from the different mechanisms involved in altering p53 status in these cells and is consistent with other studies in which the use of viruses to abrogate p53 function in human cells elicited a limited impairment of p53-dependent NER in comparison to other model systems (13,14). Since the 32P-postlabelling approach allowed detection of individual DNA lesions formed by cisplatin rather than an assessment of total DNA damage, these results also extend host cell reactivation and atomic absorption-based studies which have revealed that the removal of platinum-induced DNA damage was more efficient in p53-proficient cells than p53-deficient cells (18,27) by monitoring the removal of the two major cisplatin-induced intrastrand cross links independently.
The 32P-postlabelling assay used in this study was based on the existing methods (21,22) for detection of cisplatin-induced DNA damage in in vitro-modified DNA, and adapted for the detection of cross links formed in human cell cultures. Further development of the assay will be needed in order to allow the accurate quantitation in cisplatin-treated cell cultures due to the large number of stages and low adduct recovery often observed in 32P-postlabelling procedures. However, in its current form the assay remains very useful for the determination of DNA repair profiles, even in the absence of absolute numbers of cross links, and was sufficiently sensitive to detect persistence and removal of cisplatin-induced cross links in different cellular backgrounds. Furthermore, it complements existing studies that have exploited the sensitivity and versatility of 32P-postlabelling to monitor the repair of distinct types of DNA damage at biologically relevant levels (15,17). These studies collectively demonstrate that 32P-postlabelling has the potential to be a very powerful tool in the study of DNA repair.
Despite the persistence of cytotoxic cisplatin-induced intrastrand cross links in p53-deficient human cells observed in this study, we have also found, using the same cell models, that cells retaining p53 function are more sensitive to cisplatin and other DNA-damaging agents (26). This is supported by studies with similar findings (12,13,18,28,29) and in keeping with in silico prediction that p53 sensitizes cells to platinum-based DNA-damaging agents (30). Clinically, cisplatin has found the most success in the treatment of testicular germ cell tumours, which rarely exhibit mutations in the p53 gene (31), and less success in the treatment of ovarian cancer, for example, which exhibits a more balanced proportion of p53-defective versus p53-proficient tumours among a range of histological subtypes (32). This collectively suggests that the role of p53 in DNA-damage-induced cytotoxicity is more significant to human cells than its role in repairing cytotoxic DNA damage. Thus, while p53-dependent NER is likely to be an important factor that affects the efficacy of cancer chemotherapy using DNA-damaging agents such as cisplatin, it needs to be considered in the context of other p53-dependent pathways such as apoptosis. Since specific p53 mutations affect some pathways more than others (33), the biological and therapeutic response to cisplatin-induced DNA damage is also likely to be dependent upon the nature of the resulting functional p53 deficiency. Our own studies are continuing to evaluate the effect of specific p53 mutations on the cellular response to DNA damage, and which of these mutations are likely to have the greatest influence on the efficacy of DNA-damage-based chemotherapy.
|
Funding |
|---|
|
TopIntroductionMaterials and methodsResultsDiscussionFundingReferences |
|---|
BBSRC to (S.B.); EB Hutchinson Trust, Royal Society to (D.R.L.); Cancer Research UK to (D.H.P.).
|
Acknowledgments |
|---|
Conflict of interest statement: None declared.
|
Notes |
|---|
* To whom correspondence should be addressed. Tel: +44 1227 827357; Fax: +44 1227 763912; Email: D.Lloyd{at}kent.ac.uk
|
References |
|---|
|
TopIntroductionMaterials and methodsResultsDiscussionFundingReferences |
|---|
-
1. Shelley MD, Burgon K, Mason MD. Treatment of testicular germ-cell cancer: a Cochrane evidence-based systematic review. Cancer Treat. Rev. (2002) 28:237–253.[CrossRef][Web of Science][Medline]
2. Baik M-H, Friesner RA, Lippard SJ. Theoretical study of cisplatin binding to purine bases: why does cisplatin prefer guanine over adenine? J. Am. Chem. Soc. (2003) 125:14082–14092.[CrossRef][Web of Science][Medline]
3. Fichtinger-Schepman AJ, van der Veer JL, den Hartog JHJ, Lohman PHM, Reedijk J. Adducts of the antitumor drug cis-diamminedichloroplatinum(II) with DNA: formation, identification, and quantitation. Biochemistry (1985) 24:707–713.[CrossRef][Web of Science][Medline]
4. Kartalou M, Essigmann JM. Recognition of cisplatin adducts by cellular proteins. Mutat. Res. (2001) 478:1–21.[Web of Science][Medline]
5. Tornaletti S, Patrick SM, Turchi JJ, Hanawalt PC. Behavior of T7 RNA polymerase and mammalian RNA polymerase II at site-specific cisplatin adducts in the template DNA. J. Biol. Chem. (2003) 278:35791–35797.
6. Mello JA, Acharya S, Fishel R, Essigmann JM. The mismatch repair protein hMSH2 binds selectively to DNA adducts of the anti-cancer drug cisplatin. Chem. Biol. (1996) 3:579–589.[CrossRef][Web of Science][Medline]
7. Zamble DB, Mu D, Reardon JT, Sancar A, Lippard SJ. Repair of cisplatin-DNA adducts by the mammalian excision nuclease. Biochemistry (1996) 35:10004–10013.[CrossRef][Web of Science][Medline]
8. Wang D, Hara R, Singh G, Sancar A, Lippard SJ. Nucleotide excision repair from site-specifically platinum-modified nucleosomes. Biochemistry (2003) 42:6747–6753.[CrossRef][Web of Science][Medline]
9. Kastan MB, Onyekwere O, Sidransky D, Vogelstein B, Craig RW. Participation of p53 in the cellular response to DNA damage. Cancer Res. (1991) 51:6304–6311.
10. Lowe SW, Lin AW. Apoptosis in cancer. Carcinogenesis (2001) 21:485–495.[CrossRef][Web of Science]
11. Ford JM, Hanawalt PC. Li-Fraumeni syndrome fibroblasts homozygous for p53 mutations are deficient in global DNA repair but exhibit normal transcription-coupled repair and enhanced UV-resistance. Proc. Natl Acad. Sci. USA. (1995) 92:8876–8880.
12. Ford JM, Hanawalt PC. Expression of wild type p53 is required for efficient global nucleotide excision repair in UV-irradiated human fibroblasts. J. Biol. Chem. (1997) 272:28073–28080.
13. Ford JM, Baron EL, Hanawalt PC. Human fibroblasts expressing the human papilloma virus E6 gene are deficient in global genomic nucleotide excision repair and sensitive to ultraviolet irradiation. Cancer Res. (1998) 58:599–603.
14. Bowman KK, Sicard DM, Ford JM, Hanawalt PC. Reduced global genomic repair of ultraviolet light-induced cyclobutane pyrimidine dimers in simian virus 40-transformed cells. Mol. Carcinog. (2000) 29:17–24.[CrossRef][Web of Science][Medline]
15. Lloyd DR, Hanawalt PC. p53-dependent global genomic repair of benzo(a)pyrene-7,8-diol-9,10-epoxide adducts in human cells. Cancer Res. (2000) 60:517–521.
16. Wani MA, Zhu Q, El-Mahdy M, Venkatachalam S, Wani AA. Enhanced sensitivity to anti-benzo(a)pyrene-diol-epoxide DNA damage correlates with decreased global genomic repair attributable to abrogated p53 function in human cells. Cancer Res. (2000) 60:2273–2280.
17. Lloyd DR, Hanawalt PC. p53 controls global nucleotide excision repair of structurally diverse benzo(g)chrysene adducts in human fibroblasts. Cancer Res. (2002) 62:5288–5294.
18. Fan J, Bertino JR. Modulation of cisplatinum cytotoxicity by p53: effect of p53-mediated apoptosis and DNA repair. Mol. Pharmacol. (1999) 56:966–972.
19. Agarwal ML, Agarwal A, Taylor WR, Stark GR. p53 controls both the G2/M and the G1 cell cycle checkpoints and mediated reversible growth arrest in human fibroblasts. Proc. Natl Acad. Sci. USA. (1995) 92:8493–8497.
20. Gupta RC. Non-random binding of the carcinogen N-hydroxy-2-acetylaminofluorene to repetitive sequences of rat liver DNA in vivo. Proc. Natl Acad. Sci. USA. (1984) 81:6943–6947.
21. Welters MJP, Maliepaard M, Jacobs-Bergmans AJ, Baan RA, Schellens JHJ, Ma WJ. Improved 32P-postlabeling assay for the quantitation of the major platinum-DNA adducts. Carcinogenesis (1997) 18:1767–1774.
22. Blommaert FA, Saris CP. Detection of platinum-DNA adducts by 32P-postlabeling. Nucleic Acids Res. (1995) 23:1300–1306.
23. Bargonetti J, Reynisdottir I, Friedman PN, Prives C. Site-specific binding of wild-type p53 to cellular DNA is inhibited by SV40 T antigen and mutant p53. Genes Dev. (1992) 6:1886–1898.
24. Sheppard HM, Corneillie SI, Espiritu C, Gatti A, Liu X. New insights into the mechanism of inhibition of p53 by simian virus 40 large T antigen. Mol. Cell. Biol. (1999) 19:2746–2753.
25. Xing J, Sheppard HM, Corneillie SI, Liu X. p53 stimulated TFIID-TFIIA-promoter complex assembly, and p53-T antigen complex inhibits TATA binding protein-TATA interaction. Mol. Cell. Biol. (2001) 21:3652–3661.
26. Bhana S, Lloyd DR. The role of p53 in DNA damage-mediated cytotoxicity overrides its ability to regulate nucleotide excision repair in human fibroblasts. Mutagenesis (2008) 23:43–50.
27. Pestell KE, Hobbs SM, Titley JC, Kelland LR, Walton MR. Effect of p53 status on sensitivity to platinum complexes in a human ovarian cell line. Mol. Pharmacol. (2000) 57:503–511.
28. Park CM, Park MJ, Kwak HJ, Moon SI, Yoo DH, Lee HC, Park IC, Rhee CH, Hong SI. Induction of p53-mediated apoptosis and recovery of chemosensitivity through p53 transduction in human glioblastoma cells by cisplatin. Int. J. Oncol. (2006) 28:119–125.[Web of Science][Medline]
29. Mandic R, Schamberger CJ, Muller JF, Geyer M, Zhu L, Carey TE, Grenman R, Dunne AA, Werner JA. Reduced cisplatin sensitivity of head and neck squamous cell carcinoma cell lines correlates with mutations affecting the COOH-terminal nuclear localisation signal of p53. Clin. Cancer Res. (2005) 11:6845–6852.
30. Vekris A, Meynard D, Haaz M-C, Bayssas M, Bonnet J, Robert J. Molecular determinants of the cytotoxicity of platinum compounds: the contribution of in silico research. Cancer Res. (2004) 64:356–362.
31. Spierings DC, de Vries EG, Vellenga E, de Jong S. The attractive Achilles heel of germ cell tumours: and inherent sensitivity to apoptosis-inducing stimuli. J. Pathol. (2003) 200:137–148.[CrossRef][Web of Science][Medline]
32. Schuijer M, Berns EMJJ. TP53 and ovarian cancer. Hum. Mutat. (2003) 21:285–291.[CrossRef][Web of Science][Medline]
33. Meek D. The p53 response to DNA damage. DNA Repair (2004) 3:1049–1056.[CrossRef][Medline]
Received on August 21, 2007; revised on December 20, 2007; accepted on January 2, 2008.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  Y. Auclair, R. Rouget, E. B. Affar, and E. A. Drobetsky ATR kinase is required for global genomic nucleotide excision repair exclusively during S phase in human cells PNAS, November 18, 2008; 105(46): 17896 - 17901. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||