Triptolide induced DNA damage in A375.S2 human malignant melanoma cells is mediated via reduction of DNA repair genes
- Authors:
- Published online on: December 7, 2012 https://doi.org/10.3892/or.2012.2170
- Pages: 613-618
Abstract
Introduction
Of the skin cancers, melanoma is the leading cause of death and the mortality rate is increasing (1–3). Thus, for all ages, melanoma is the primary focus of early detection campaigns. Sun UV has been recognized to cause skin cancer (4–6). UV can cause DNA damage of skin cells (4–6). DNA damage is involved in neurodegeneration in age-related disease, cerebral ischemia, and brain trauma including DNA damage (7–9). It was reported that in anticancer therapy, irradiation and DNA-damaging chemotherapeutic drugs play an important key role based on their ability to induce DNA double-strand breaks leading to cancer cell death (10–12). Thus, if agents can block DNA repair proteins it may lead to increase in the sensitivity of DNA damaging chemotherapeutic agents (13–16).
Triptolide (diterpenoid triepoxide; PG490) extracted from Tripterygium wilfordii Hook F (TWHF) has been shown to present anti-fertility function (17), anti-neoplastic activity such as anti-leukemia (18–25), anti-human hepatocellular carcinoma cells (25), colon cancer cells (23,26,27) and cervical cancer cells (28). Furthermore, evidence has been shown that triptolide inhibited the growth and metastasis of various solid tumors and has been suggested capable of acting synergistically with conventional chemotherapeutic drugs (29,30).
Substantial evidence has been demonstrated that triptolide induced cytotoxic effects in many human cancer cell lines but no available information exists to show triptolide-induced DNA damage in human skin cancer cells. Therefore, we investigated the effects of triptolide on DNA damage associated DNA repair genes expression (mRNA) in A375.S2 human malignant melanoma cells in vitro. Our findings demonstrated that triptolide induced DNA damage and also inhibited the expression of DNA repair genes in A375.S2 cells.
Materials and methods
Chemicals and reagents
Triptolide, dimethyl sulfoxide (DMSO), ethidium bromide, propidium iodide (PI), Tris-HCl and Triton X-100 were purchased from Sigma-Aldrich. RPMI-1640 medium, fetal bovine serum (FBS), L-glutamine, penicillin-streptomycin and trypsin-EDTA were purchased from Gibco®/Invitrogen (Grand Island, NY, USA).
Cell culture and chemical treatment
The human malignant melanoma cell line (A375.S2) was purchased from the Food Industry Research and Development Institute (Hsinchu, Taiwan). Cells were cultured with minimum essential medium (MEM) supplemented with 10% fetal bovine serum, 100 U/ml of penicillin, 100 μg/ml of streptomycin, and 2 mmol/l of L-glutamine in 75 cm2 tissue culture flasks and grown in a humidified 5% CO2 and 95% air at 37°C (31,32).
Flow cytometric assay for percentage of viable cells
Equal numbers of cells (2×105 cells/well) were seeded in 12-well plates and allowed to attach overnight. The cells were treated with 0.1% DMSO or triptolide (0, 15, 20, 25 and 30 nM) diluted in MEM with 5% FBS for 24 h. Cells from each treatment were stained with PI (5 μg/ml) and were analyzed for percentage of viable cells by using flow cytometry (Becton-Dickinson, San Jose, CA, USA) and cell viability was calculated as previously described (33,34).
Comet assay and DAPI staining for DNA damage
A375.S2 cells at the density of 2×105 cells/well in 12-well plates were incubated with triptolide at final concentrations of 0, 15, 20, 25 and 30 nM, vehicle (1 μl DMSO) and 0.1% of H2O2 (positive control) for 24 h or the cells were treated with 20 nM triptolide for 0, 6, 12, 24 and 48 h in MEM medium grown at 37°C in 5% CO2 and 95% air. Cells were harvested for the measurement of DNA damage using the Comet assay as described previously (33,35,36). Comet tail length was calculated and quantified by using the TriTek CometScore™ software image analysis system (TriTek Corp., Sumerduck, VA, USA) as described previously (33,35,36). Harvested cells were stained by DAPI then examined and photographed by using fluorescence microscopy as described elsewhere (33,35,37).
DNA gel electrophoresis for DNA damage
A375.S2 cells at the density of 2×105 cells/well in 12-well plates were incubated with triptolide at final concentrations of 0, 15, 20, 25 and 30 nM for 48 h in MEM medium grown in 5% CO2 and 95% air at 37°C. Cells in each well were individually isolated by using DNA isolation kit. The isolated DNA (2 μg) from each treatment was examined for DNA damage by using DNA electrophoresis which was carried out in 0.5% agarose gel in Tris/acetate buffer at 15 V for 2 h. At the end of electrophoresis the DNA was stained with ethidium bromide then examined and photographed under a fluorescence microscope as previously described (38–40).
Real-time PCR assay for examining the expression of DNA repair genes
A375.S2 cells at the density of 1×106 cells/well in 6-well plates were incubated with or without 20 nM of triptolide for 24 h in MEM medium grown at 37°C in 5% CO2 and 95% air. The cells from each treatment were collected and total RNA was individually extracted by using the Qiagen RNeasy mini kit (Qiagen, Inc, Valencia, CA, USA) as previously described (41–43). Isolated RNA samples were individually reverse-transcribed for 30 min at 42°C with High Capacity cDNA Reverse Transcription kit according to the standard protocol of the supplier (Applied Biosystems, Carlsbad, CA, USA). Quantitative PCR from each sample was conducted as follows: 2 min at 50°C, 10 min at 95°C, and 40 cycles of 15 sec at 95°C, 1 min at 60°C using 1 μl of the cDNA reverse-transcribed as described above, 2X SYBR Green PCR Master Mix (Applied Biosystems) and 200 nM of forward and reverse primers as shown in Table I, and previously described (41,43,44). Each assay was run on an Applied Biosystems 7300 Real-time PCR system in triplicate. The expression fold-changes were performed by using the comparative CT method.
 | Table IThe DNA sequence was evaluated using the Primer Express software and each assay was run on an Applied Biosystems 7300 Real-time PCR system. |
Statistical analysis
All studies were performed in duplicate. Results are presented as mean ± standard deviation. One-tailed Student’s t-test was used to analyze the difference between control and triptolide treated groups. Significance was defined as p<0.05.
Results
Effect of triptolide on the percentage of viable A375.S2 cells
A375.S2 cells were incubated with 15, 20, 25 and 30 nM of triptolide for 24 h. At the end of incubation, all samples were collected for determining the percentage of viable cells and the results are presented in Fig. 1, which indicated that triptolide decreased the percentage of viable cells at the concentration of 15–30 nM.
Effects of triptolide on DNA in A375.S2 cells examined by Comet assay and DAPI staining
To confirm whether triptolide can induce DNA damage in A375.S2 cells, after cells were treated with triptolide DNA damage was examined by Comet assay and the results are presented in Fig. 2. Triptolide induced DNA damage in A375.S2 cells and these effects were dose-dependent (Fig. 2B) and time-dependent (Fig. 2D). The higher concentration of triptolide led to a longer DNA migration smear (Comet tail). H2O2 is known to be a highly reactive oxygen species, in the present studies, 0.1% H2O2 induced Comet tails. Fig. 3 shows DNA damage by DAPI stain and the effects based on the mean fluorescence intensity (Fig. 3A) are dose-dependent (Fig. 3B).
Effects of triptolide on DNA in A375.S2 cells examined by DNA gel electrophoresis
To confirm whether or not triptolide can induced DNA damage in A375.S2 cells, DNA gel electrophoresis was used and results are shown in Fig. 4. The results show that triptolide induced DNA damage and fragments in A375.S2 cells (Fig. 4). The higher dose of triptolide (30 nM) led to more DNA damage and fragments than that of low dose (15 nM) incubation in A375.S2 cells.
Effects of triptolide on DNA damage and of repair gene expression in A375.S2 cells measured by real-time PCR
Figs. 2 and 3 results show that triptolide induced DNA damage and fragments in A375.S2 cells. We investigated whether or not triptolide affects the gene expression of DNA damage and repair in A375.S2 cells. We used DNA agarose gel electrophoresis for examining the products from real-time PCR and results are shown in Fig. 5. The results indicated that all examined gene expression including ATM, ATR, BRCA-1, DNA-PK, MGMT and p53 mRNA were decreased in 24 h treatment with triptolide. ATM and BRCA-1 gene were more sensitive than the other genes (ATR, DNA-PK, MGMT and p53). P53 was the least sensitive compared to the other genes.
Discussion
Numerous experiments have shown that triptolide induces cell death via induction of apoptosis in human cancer cell lines (26,45,46), but no available information exists to demonstrate triptolide induced DNA damage and affected DNA repair gene expression in human skin cancer cells. We found that A375.S2 cells treated with various concentrations of triptolide led to decreased percentage of viable cells (Fig. 1) and it also induced DNA damage (Figs. 2 and 3) and inhibited gene expression of DNA repair genes (Fig. 5) in A375.S2 cells. These findings are based on the observations from i) flow cytometric assay showing the decrease of percentage of viable cells (Fig. 1); ii) Comet assay and DAPI staining, the longer comet tail means higher DNA damage (Fig. 2); the light of fluorescence means higher DNA condensation (Fig. 3); iii) DNA fragments in DNA gel electrophoresis indicate high dose of triptolide treatment led to high DNA damage and fragments (Fig. 4) and iv) RT-PCR showed that triptolide inhibited the gene expression (mRNA) of DNA associated repair genes (Fig. 5).
It is well documented that Comet assay is a highly sensitive technique for DNA damage examination (47,48) and trend-break formation during the process of excision repair of DNA in cells (49,50). Herein, our results showed triptolide-induced DNA damage, which was examined by Comet assay and DAPI staining. The DNA damage of A375.S2 cells from triptolide treatment was also confirmed by DNA gel electophoresis (Fig. 4).
It was reported that agent-induced DNA damage can be reduced in cells via the DNA repair system through eliminating DNA lesions (49,50). Thus, we further investigated whether or not triptolide can affect the DNA repair gene expression in A375.S2 cells and results indicated that triptolide inhibit the expression of mRNA such as ataxia telangiectasia mutated (ATM), ataxia-telangiectasia (ATR), breast cancer gene 1 (BRCA-1), p53, DNA-dependent protein kinase (DNA-PK) and O6-methylguanine DNA methyltransferase (MGMT) in the examined A375.S2 cells. The results in Fig. 5 indicate that p53 gene has the lowest sensitivity to triptolide when compared to the other examined genes.
It was reported that DNA damage responses of cells could lead to p53 activation and activated p53 regulates the cell cycle arrest, DNA repair and apoptosis (51,52). The role of p53 in skin cancer cell response to triptolide-induced DNA damage and repair is unclear. Our results show that triptolide inhibited p53 gene expression in A375.S2 cells. In response to DNA damage, DNA damage checkpoints associate with cell cycle for maintaining genomic integrity (53–55). It was reported that both ATM and ATR are master checkpoint kinases which can be activated by double-stranded DNA breaks (52,56). Our results also show that triptolide inhibited the ATM and ATR gene expression in A375.S2 cells.
DNA-PK plays an important role in DNA damage repair (52) and the deficiency in DNA-PK activity of human glioblastoma cells can lead to a slow, error prone repair process causing increased formation of chromosome aberrations (52). BRCA1 plays and important roles in DNA damage and repair response, homologous recombination, cell cycle regulation, protein ubiquitination and apoptosis (57,58) and loss of BRCA1 causes a defective DNA repair response and G2/M cell cycle checkpoint in breast cancer cells (57,59). MGMT reduces cytotoxicity of therapeutic or environmental alkylating agents (60,61). Our results showed that triptolide inhibited the gene expression (mRNA) of DNA-PK, MGMT and BRCA-1.
In conclusion, A375.S2 cells were exposed to various concentrations of triptolide and DNA damage occurred. Moreover, the proposed flow chart for triptolide effect on DNA in A375.S2 human malignant melanoma cells is summarized in Fig. 6. Triptolide induces DNA damage in a dose response followed by inhibition of DNA repair-associated gene expression including ATM, ATR, BRCA-1, p53, DNA-PK and MGMT, then leading to DNA damage (Fig. 6).
Acknowledgements
This study was supported by the grant CMU-100-ASIA-4 from China Medical University.
References
|
Pang J, Assaad D, Breen D, et al: Extramammary Paget disease: review of patients seen in a non-melanoma skin cancer clinic. Curr Oncol. 17:43–45. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Martinez JC and Otley CC: The management of melanoma and nonmelanoma skin cancer: a review for the primary care physician. Mayo Clin Proc. 76:1253–1265. 2001. View Article : Google Scholar : PubMed/NCBI | |
|
Rigel DS: Epidemiology of melanoma. Semin Cutan Med Surg. 29:204–209. 2010. View Article : Google Scholar | |
|
Berwick M: How do solar UV irradiance and smoking impact the diagnosis of second cancers after diagnosis of melanoma?: No answer yet. Dermatoendocrinology. 4:18–19. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Pfeifer GP and Besaratinia A: UV wavelength-dependent DNA damage and human non-melanoma and melanoma skin cancer. Photochem Photobiol Sci. 11:90–97. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Aceituno-Madera P, Buendia-Eisman A, Olmo FJ, Jimenez-Moleon JJ and Serrano-Ortega S: Melanoma, altitude, and UV-B radiation. Actas Dermosifiliogr. 102:199–205. 2011.(In Spanish). | |
|
Mathew A, Lindsley TA, Sheridan A, et al: Degraded mitochondrial DNA is a newly identified subtype of the damage associated molecular pattern (DAMP) family and possible trigger of neurodegeneration. J Alzheimers Dis. 30:617–627. 2012. | |
|
Baltanas FC, Casafont I, Weruaga E, Alonso JR, Berciano MT and Lafarga M: Nucleolar disruption and cajal body disassembly are nuclear hallmarks of DNA damage-induced neurodegeneration in purkinje cells. Brain Pathol. 21:374–388. 2011. View Article : Google Scholar : PubMed/NCBI | |
|
Barzilai A: DNA damage, neuronal and glial cell death and neurodegeneration. Apoptosis. 15:1371–1381. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Engelmann D and Putzer BM: Translating DNA damage into cancer cell death-A roadmap for E2F1 apoptotic signalling and opportunities for new drug combinations to overcome chemoresistance. Drug Resist Updat. 13:119–131. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Ye Y, Xiao Y, Wang W, et al: Inhibition of expression of the chromatin remodeling gene, SNF2L, selectively leads to DNA damage, growth inhibition, and cancer cell death. Mol Cancer Res. 7:1984–1999. 2009. View Article : Google Scholar : PubMed/NCBI | |
|
Suganuma M, Kawabe T, Hori H, Funabiki T and Okamoto T: Sensitization of cancer cells to DNA damage-induced cell death by specific cell cycle G2 checkpoint abrogation. Cancer Res. 59:5887–5891. 1999.PubMed/NCBI | |
|
Potter AJ and Rabinovitch PS: The cell cycle phases of DNA damage and repair initiated by topoisomerase II-targeting chemotherapeutic drugs. Mutat Res. 572:27–44. 2005. View Article : Google Scholar : PubMed/NCBI | |
|
Friedmann B, Caplin M, Hartley JA and Hochhauser D: Modulation of DNA repair in vitro after treatment with chemotherapeutic agents by the epidermal growth factor receptor inhibitor gefitinib (ZD1839). Clin Cancer Res. 10:6476–6486. 2004. View Article : Google Scholar : PubMed/NCBI | |
|
Kerklaan PR, Bouter S, van Elburg PE and Mohn GR: Evaluation of the DNA repair host-mediated assay. II Presence of genotoxic factors in various organs of mice treated with chemotherapeutic agents. Mutat Res. 164:19–29. 1986.PubMed/NCBI | |
|
Norin AJ and Goldschmidt EP: Effect of mutagens, chemotherapeutic agents and defects in DNA repair genes on recombination in F′ partial diploid Escherichia coli. Mutat Res. 59:15–26. 1979.PubMed/NCBI | |
|
Hikim AP, Lue YH, Wang C, Reutrakul V, Sangsuwan R and Swerdloff RS: Posttesticular antifertility action of triptolide in the male rat: Evidence for severe impairment of cauda epididymal sperm ultrastructure. J Androl. 21:431–437. 2000. | |
|
Zhou GS, Hu Z, Fang HT, et al: Biologic activity of triptolide in t(8;21) acute myeloid leukemia cells. Leuk Res. 35:214–218. 2011. View Article : Google Scholar : PubMed/NCBI | |
|
Mak DH, Schober WD, Chen W, et al: Triptolide induces cell death independent of cellular responses to imatinib in blast crisis chronic myelogenous leukemia cells including quiescent CD34+ primitive progenitor cells. Mol Cancer Ther. 8:2509–2516. 2009. View Article : Google Scholar | |
|
Shi X, Jin Y, Cheng C, et al: Triptolide inhibits Bcr-Abl transcription and induces apoptosis in STI571-resistant chronic myelogenous leukemia cells harboring T315I mutation. Clin Cancer Res. 15:1686–1697. 2009. View Article : Google Scholar : PubMed/NCBI | |
|
Pigneux A, Mahon FX, Uhalde M, et al: Triptolide cooperates with chemotherapy to induce apoptosis in acute myeloid leukemia cells. Exp Hematol. 36:1648–1659. 2008. View Article : Google Scholar : PubMed/NCBI | |
|
Yao GH, Luan JF, Ye D, et al: Effects of triptolide on proliferation and apoptosis of Jurkat cell line in acute T lymphocytic leukemia. Zhongguo Shi Yan Xue Ye Xue Za Zhi. 16:506–509. 2008.(In Chinese). | |
|
Tong X, Zheng S, Jin J, Zhu L, Lou Y and Yao H: Triptolide inhibits cyclooxygenase-2 and inducible nitric oxide synthase expression in human colon cancer and leukemia cells. Acta Biochim Biophys Sin. 39:89–95. 2007. View Article : Google Scholar : PubMed/NCBI | |
|
Lou YJ and Jin J: Triptolide down-regulates bcr-abl expression and induces apoptosis in chronic myelogenous leukemia cells. Leuk Lymphoma. 45:373–376. 2004. View Article : Google Scholar : PubMed/NCBI | |
|
Chan EW, Cheng SC, Sin FW and Xie Y: Triptolide induced cytotoxic effects on human promyelocytic leukemia, T cell lymphoma and human hepatocellular carcinoma cell lines. Toxicol Lett. 122:81–87. 2001. View Article : Google Scholar : PubMed/NCBI | |
|
Liu J, Shen M, Yue Z, et al: Triptolide inhibits colon-rectal cancer cells proliferation by induction of G1 phase arrest through upregulation of p21. Phytomedicine. 19:756–762. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Liu Y, Song F, Wu WK, et al: Triptolide inhibits colon cancer cell proliferation and induces cleavage and translocation of 14-3-3 epsilon. Cell Biochem Funct. 30:271–278. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Kim MJ, Lee TH, Kim SH, Choi YJ, Heo J and Kim YH: Triptolide inactivates Akt and induces caspase-dependent death in cervical cancer cells via the mitochondrial pathway. Int J Oncol. 37:1177–1185. 2010.PubMed/NCBI | |
|
Zhang C, Cui GH, Liu F, Wu QL and Chen Y: Inhibitory effect of triptolide on lymph node metastasis in patients with non-Hodgkin lymphoma by regulating SDF-1/CXCR4 axis in vitro. Acta Pharmacol Sin. 27:1438–1446. 2006. View Article : Google Scholar : PubMed/NCBI | |
|
Yang S, Chen J, Guo Z, et al: Triptolide inhibits the growth and metastasis of solid tumors. Mol Cancer Ther. 2:65–72. 2003.PubMed/NCBI | |
|
Hsiao YP, Yu CS, Yu CC, et al: Triggering apoptotic death of human malignant melanoma a375. S2 cells by bufalin: involvement of caspase cascade-dependent and independent mitochondrial signaling pathways. Evid Based Complement Alternat Med. 2012:5912412012. View Article : Google Scholar | |
|
Lo C, Lai TY, Yang JS, et al: Gallic acid inhibits the migration and invasion of A375. S2 human melanoma cells through the inhibition of matrix metalloproteinase-2 and Ras. Melanoma Res. 21:267–273. 2011. View Article : Google Scholar : PubMed/NCBI | |
|
Yu CS, Huang AC, Yang JS, et al: Safrole induces G0/G1 phase arrest via inhibition of cyclin E and provokes apoptosis through endoplasmic reticulum stress and mitochondrion-dependent pathways in human leukemia HL-60 cells. Anticancer Res. 32:1671–1679. 2012. | |
|
Liu KC, Ho HC, Huang AC, et al: Gallic acid provokes DNA damage and suppresses DNA repair gene expression in human prostate cancer PC-3 cells. Environ Toxicol. Sept 2–2011.(Epub ahead of print). | |
|
Ni CH, Yu CS, Lu HF, et al: Chrysophanol-induced cell death (necrosis) in human lung cancer A549 cells is mediated through increasing reactive oxygen species and decreasing the level of mitochondrial membrane potential. Environ Toxicol. Jul 30–2012.(Epub ahead of print). | |
|
Yu CC, Ko FY, Yu CS, et al: Norcantharidin triggers cell death and DNA damage through S-phase arrest and ROS-modulated apoptotic pathways in TSGH 8301 human urinary bladder carcinoma cells. Int J Oncol. 41:1050–1060. 2012. | |
|
Ni CH, Chen PY, Lu HF, et al: Chrysophanol-induced necrotic-like cell death through an impaired mitochondrial ATP synthesis in Hep3B human liver cancer cells. Arch Pharm Res. 35:887–895. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Tsai SC, Yang JS, Peng SF, et al: Bufalin increases sensitivity to AKT/mTOR-induced autophagic cell death in SK-HEP-1 human hepatocellular carcinoma cells. Int J Oncol. 41:1431–1442. 2012.PubMed/NCBI | |
|
Chen HY, Lu HF, Yang JS, et al: The novel quinolone CHM-1 induces DNA damage and inhibits DNA repair gene expressions in a human osterogenic sarcoma cell line. Anticancer Res. 30:4187–4192. 2010.PubMed/NCBI | |
|
Lin YT, Yang JS, Lin SY, et al: Diallyl disulfide (DADS) induces apoptosis in human cervical cancer Ca Ski cells via reactive oxygen species and Ca2+-dependent mitochondria-dependent pathway. Anticancer Res. 28:2791–2799. 2008.PubMed/NCBI | |
|
Chen YY, Chiang SY, Lin JG, et al: Emodin, aloe-emodin and rhein induced DNA damage and inhibited DNA repair gene expression in SCC-4 human tongue cancer cells. Anticancer Res. 30:945–951. 2010.PubMed/NCBI | |
|
Ho YT, Lu CC, Yang JS, et al: Berberine induced apoptosis via promoting the expression of caspase-8, -9 and -3, apoptosis-inducing factor and endonuclease G in SCC-4 human tongue squamous carcinoma cancer cells. Anticancer Res. 29:4063–4070. 2009. | |
|
Lu HF, Yang JS, Lai KC, et al: Curcumin-induced DNA damage and inhibited DNA repair genes expressions in mouse-rat hybrid retina ganglion cells (N18). Neurochem Res. 34:1491–1497. 2009. View Article : Google Scholar : PubMed/NCBI | |
|
Ji BC, Yu CC, Yang ST, et al: Induction of DNA damage by deguelin is mediated through reducing DNA repair genes in human non-small cell lung cancer NCI-H460 cells. Oncol Rep. 27:959–964. 2012.PubMed/NCBI | |
|
Wu PP, Liu KC, Huang WW, et al: Triptolide induces apoptosis in human adrenal cancer NCI-H295 cells through a mitochondrial-dependent pathway. Oncol Rep. 25:551–557. 2011.PubMed/NCBI | |
|
Huang W, He T, Chai C, et al: Triptolide inhibits the proliferation of prostate cancer cells and down-regulates SUMO-specific protease 1 expression. PLoS One. 7:e376932012. View Article : Google Scholar : PubMed/NCBI | |
|
Petriccione M and Ciniglia C: Comet assay to assess the genotoxicity of Persian walnut (Juglans regia L.) husks with statistical evaluation. Bull Environ Contam Toxicol. 89:166–171. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Kwasniewska J, Grabowska M, Kwasniewski M and Kolano B: Comet-FISH with rDNA probes for the analysis of mutagen-induced DNA damage in plant cells. Environ Mol Mutagen. 53:369–375. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Goutham HV, Mumbrekar KD, Vadhiraja BM, et al: DNA double-strand break analysis by γ-H2AX foci: A useful method for determining the overreactors to radiation-induced acute reactions among head-and-neck cancer patients. Int J Radiat Oncol Biol Phys. Jul 24–2012.(Epub ahead of print). | |
|
Savina NV, Smal MP, Kuzhir TD, Ershova-Pavlova AA and Goncharova RI: DNA-damage response associated with occupational exposure, age and chronic inflammation in workers in the automotive industry. Mutat Res. 748:21–28. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Pennington KP, Walsh T, Lee M, et al: BRCA1, TP53, and CHEK2 germline mutations in uterine serous carcinoma. Cancer. Jul 18–2012.(Epub ahead of print). | |
|
Serrano MA, Li Z, Dangeti M, et al: DNA-PK, ATM and ATR collaboratively regulate p53-RPA interaction to facilitate homologous recombination DNA repair. Oncogene. Jul 16–2012.(Epub ahead of print). | |
|
Fortini P, Ferretti C, Pascucci B, et al: DNA damage response by single-strand breaks in terminally differentiated muscle cells and the control of muscle integrity. Cell Death Differ. Jun 15–2012.(Epub ahead of print). | |
|
Jia YG, Yang YM, Zuo B, Guo LD and Lou JY: DNA damage response in ovarian clear cell adenocarcinoma. Sichuan Da Xue Xue Bao Yi Xue Ban. 43:331–334. 2012.(In Chinese). | |
|
Wong VC, Cash HL, Morse JL, Lu S and Zhitkovich A: S-phase sensing of DNA-protein crosslinks triggers TopBP1-independent ATR activation and p53-mediated cell death by formaldehyde. Cell Cycle. 11:2526–2537. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Boltz KA, Leehy K, Song X, Nelson AD and Shippen DE: ATR cooperates with CTC1 and STN1 to maintain telomeres and genome integrity in Arabidopsis. Mol Biol Cell. 23:1558–1568. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Tammaro C, Raponi M, Wilson DI and Baralle D: BRCA1 exon 11 alternative splicing, multiple functions and the association with cancer. Biochem Soc Trans. 40:768–772. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Pessetto ZY, Yan Y, Bessho T and Natarajan A: Inhibition of BRCT(BRCA1)-phosphoprotein interaction enhances the cytotoxic effect of olaparib in breast cancer cells: a proof of concept study for synthetic lethal therapeutic option. Breast Cancer Res Treat. 134:511–517. 2012. View Article : Google Scholar | |
|
Yarden RI, Metsuyanim S, Pickholtz I, Shabbeer S, Tellio H and Papa MZ: BRCA1-dependent Chk1 phosphorylation triggers partial chromatin disassociation of phosphorylated Chk1 and facilitates S-phase cell cycle arrest. Int J Biochem Cell Biol. 44:1761–1769. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Silber JR, Bobola MS, Blank A and Chamberlain MC: O(6)-Methylguanine-DNA methyltransferase in glioma therapy: Promise and problems. Biochim Biophys Acta. 1826:71–82. 2012.PubMed/NCBI | |
|
Fumagalli C, Pruneri G, Possanzini P, et al: Methylation of O6-methylguanine-DNA methyltransferase (MGMT) promoter gene in triple-negative breast cancer patients. Breast Cancer Res Treat. 134:131–137. 2012. View Article : Google Scholar : PubMed/NCBI |
