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Heim D, Gil-Ibanez I, Herden J, Parplys AC, Borgmann K, Schmidt-Arras D, Lohse AW, Rose-John S, Wege H. Constitutive gp130 activation rapidly accelerates the transformation of human hepatocytes via an impaired oxidative stress response. Oncotarget 2018; 7:55639-55648. [PMID: 27489351 PMCID: PMC5342442 DOI: 10.18632/oncotarget.10956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 07/09/2016] [Indexed: 01/29/2023] Open
Abstract
Pro-inflammatory signaling pathways, especially interleukin 6 (IL-6), and reactive oxygen species (ROS) promote carcinogenesis in the liver. In order to elucidate the underlying oncogenic mechanism, we activated the IL-6 signal transducer glycoprotein 130 (gp130) via stable expression of a constitutively active gp130 construct (L-gp130) in untransformed telomerase-immortalized human fetal hepatocytes (FH-hTERT). As known from hepatocellular adenomas, forced gp130 activation alone was not sufficient to induce malignant transformation. However, additional challenge of FH-hTERT L-gp130 clones with oxidative stress resulted in 2- to 3-fold higher ROS levels and up to 6-fold more DNA-double strand breaks (DSB). Despite increased DNA damage, ROS-challenged FH-hTERT L-gp130 clones displayed an enhanced proliferation and rapidly developed colony growth capabilities in soft agar. As driving gp130-mediated oncogenic mechanism, we detected a decreased expression of antioxidant genes, in particular glutathione peroxidase 3 and apolipoprotein E, and an absence of P21 upregulation following ROS-conferred induction of DSB. In summary, an impaired oxidative stress response in hepatocytes with gp130 gain-of-function mutations, as detected in dysplastic intrahepatic nodules and hepatocellular adenomas, is one of the central oncogenic mechanisms in chronic liver inflammation.
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Affiliation(s)
- Denise Heim
- Department of Gastroenterology and Hepatology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Ines Gil-Ibanez
- Department of Gastroenterology and Hepatology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Johannes Herden
- Department of Gastroenterology and Hepatology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Ann Christin Parplys
- Laboratory of Radiobiology and Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Kerstin Borgmann
- Laboratory of Radiobiology and Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Dirk Schmidt-Arras
- Institute of Biochemistry, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Ansgar W Lohse
- Department of Gastroenterology and Hepatology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Stefan Rose-John
- Institute of Biochemistry, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Henning Wege
- Department of Gastroenterology and Hepatology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
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Parplys AC, Seelbach JI, Becker S, Behr M, Wrona A, Jend C, Mansour WY, Joosse SA, Stuerzbecher HW, Pospiech H, Petersen C, Dikomey E, Borgmann K. High levels of RAD51 perturb DNA replication elongation and cause unscheduled origin firing due to impaired CHK1 activation. Cell Cycle 2016; 14:3190-202. [PMID: 26317153 DOI: 10.1080/15384101.2015.1055996] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In response to replication stress ATR signaling through CHK1 controls the intra-S checkpoint and is required for the maintenance of genomic integrity. Homologous recombination (HR) comprises a series of interrelated pathways that function in the repair of DNA double strand breaks and interstrand crosslinks. In addition, HR, with its key player RAD51, provides critical support for the recovery of stalled forks during replication. High levels of RAD51 are regularly found in various cancers, yet little is known about the effect of the increased RAD51 expression on intra-S checkpoint signaling. Here, we describe a role for RAD51 in driving genomic instability caused by impaired replication and intra-S mediated CHK1 signaling by studying an inducible RAD51 overexpression model as well as 10 breast cancer cell lines. We demonstrate that an excess of RAD51 decreases I-Sce-I mediated HR despite formation of more RAD51 foci. Cells with high RAD51 levels display reduced elongation rates and excessive dormant origin firing during undisturbed growth and after damage, likely caused by impaired CHK1 activation. In consequence, the inability of cells with a surplus of RAD51 to properly repair complex DNA damage and to resolve replication stress leads to higher genomic instability and thus drives tumorigenesis.
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Affiliation(s)
- Ann Christin Parplys
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Jasna Irena Seelbach
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Saskia Becker
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Matthias Behr
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Agnieszka Wrona
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Camilla Jend
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Wael Yassin Mansour
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany.,b Tumor Biology Department; National Cancer Institute; Cairo University ; Cairo , Egypt
| | - Simon Andreas Joosse
- d Department of Tumor Biology ; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | | | - Helmut Pospiech
- f Leibniz Institute for Age Research - Fritz Lipmann Institute ; Jena , Germany.,g Faculty of Biochemistry and Molecular Medicine; University of Oulu ; Oulu , Finland
| | - Cordula Petersen
- c Department of Radiotherapy and Radiooncology ; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Ekkehard Dikomey
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
| | - Kerstin Borgmann
- a Laboratory of Radiobiology & Experimental Radiooncology; University Medical Center Hamburg-Eppendorf ; Hamburg , Germany
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Fontana AO, Augsburger MA, Grosse N, Guckenberger M, Lomax AJ, Sartori AA, Pruschy MN. Differential DNA repair pathway choice in cancer cells after proton- and photon-irradiation. Radiother Oncol 2015; 116:374-80. [DOI: 10.1016/j.radonc.2015.08.014] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 08/12/2015] [Accepted: 08/15/2015] [Indexed: 01/23/2023]
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4
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Magwood AC, Malysewich MJ, Cealic I, Mundia MM, Knapp J, Baker MD. Endogenous levels of Rad51 and Brca2 are required for homologous recombination and regulated by homeostatic re-balancing. DNA Repair (Amst) 2013; 12:1122-33. [PMID: 24210700 DOI: 10.1016/j.dnarep.2013.10.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 10/15/2013] [Indexed: 12/17/2022]
Abstract
Stable expression of Rad51 siRNA was used to generate mouse hybridoma cell lines in which endogenous Rad51 levels were depleted by as much as 60%. Stable Rad51 knockdowns feature reduced homologous recombination responses. The relative ease with which stable Rad51 knockdowns were recovered was surprising, given the embryonic lethality of Rad51 ablation. Interestingly, Rad51-depleted hybridoma cell lines are characterized by reduced levels of p53 protein. Completely unexpected, was the finding that Rad51-depleted hybridoma cell lines are also reduced for the breast cancer susceptibility 2 (Brca2) protein. Additionally, hybridoma cell lines that are siRNA depleted for mouse Brca2 show a corresponding reduction in Rad51 and p53 proteins. Furthermore, cellular levels of Rad51, Brca2 and p53 can be elevated in these cell lines by ectopic expression of wild-type human Rad51 and wild-type human BRCA2. In marked contrast, hybridoma cell lines that are siRNA depleted for mouse p53 feature relatively normal Rad51 and Brca2 levels. These results suggest that cellular levels of Brca2 and Rad51 are mutually dependent on each other, and that low levels of these proteins provide selective pressure for reduction of p53, which permits cell growth.
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Affiliation(s)
- Alissa C Magwood
- Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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5
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Tennstedt P, Fresow R, Simon R, Marx A, Terracciano L, Petersen C, Sauter G, Dikomey E, Borgmann K. RAD51 overexpression is a negative prognostic marker for colorectal adenocarcinoma. Int J Cancer 2012; 132:2118-26. [PMID: 23065657 DOI: 10.1002/ijc.27907] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 09/13/2012] [Indexed: 12/31/2022]
Abstract
RAD51 is the central protein in the homologous recombination pathway and is therefore of great relevance in terms of both therapy resistance as well as genomic stability. By using a tissue microarray analysis of 1,213 biopsies taken from colorectal adenocarcinomas (CRCs), we investigated whether RAD51 expression can be used as a prognostic marker as well as potential associations between this and the expression of other proteins known to be related to CRC. Strong RAD51 expression was observed in 1% of CRC, moderate in 11%, weak in 34% and no expression in 44%. No correlation was found between RAD51 expression and clinicopathological parameters. RAD51 expression correlated significantly (p = 0.001) with overall survival, with a median survival of 11 months for patients with strong, 46 with moderate, 76 with weak and 68 with negative expression. Multivariate analyses revealed that in addition to tumor stage (p < 0.0001) and nodal status (p < 0.0001), RAD51 expression is also an independent prognostic parameter (p = 0.011). Strong RAD51 expression was found to be associated with the loss of the two DNA mismatch repair proteins MSH (p = 0.0003), MLH (p = 0.002) and β-catenin (p = 0.012) as well as with elevated p21 (p = 0.003) and EGFR expression (p = 0.0001). However, a correlation with overall survival could only be found for EGFR expression (p = 0.008), although no added benefit in risk stratification could be determined when evaluated together with RAD51. Overexpression of RAD51 is a predictor of poor outcome in CRC. This finding indicated the promise of future studies using RAD51 as a prognostic marker and therapeutic target.
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Affiliation(s)
- Pierre Tennstedt
- Institute of Pathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Platelet-derived endothelial cell growth factor/thymidine phosphorylase inhibitor augments radiotherapeutic efficacy in experimental colorectal cancer. Cancer Lett 2011; 318:199-205. [PMID: 22178656 DOI: 10.1016/j.canlet.2011.12.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 12/04/2011] [Accepted: 12/07/2011] [Indexed: 11/21/2022]
Abstract
PURPOSES A lot of radiosensitizers have been developed. However, there are few to be available in the clinical setting. Thymidine phosphorylase inhibitor (TPI) regulates the phosphorolysis of thymidine to thymine and 2-deoxy-d-ribose-1-phosphate which is essential for tumor angiogenesis. The aim of this study is to evaluate whether TPI augments the radiotherapy for colorectal cancer in vitro and in vivo studies. MATERIALS AND METHODS The cytotoxicity of TPI with irradiation on HT29 and HCT116 cells was examined using MTT- and colony formation assay. At 10days post-inoculation, HT29 bearing orthotopic model mice (n=28) were divided into four groups and orally treated with TPI- (50mg/kg/day for 2weeks), radiation (RT, 2Gy×4: Total 8Gy), their combination or the vehicle. The mechanisms underlying the efficacy were assessed genomically and immunohistochemically. RESULTS Compared to each single treatment, the combination of TPI and RT synergistically inhibited the cell viability in a time- and dose-dependent manner. In the HT-29 bearing mice, the combination of TPI and RT reduced the tumor growth compared with RT alone. Notably, the mRNA levels of VEGF, TGF-β and, Rad51 and the protein expressions of VEGF and CD34 were significantly lower in the combination than the others. Furthermore, the combination markedly increased the TUNEL-positive cells, suggesting that TPI augments the cancer cell death through inhibition of angiogenesis and DNA repair system in the radiotherapy. CONCLUSIONS Our study first demonstrated that the combination of TPI and irradiation was effective in colon cancer. TPI would provide a promising therapeutic strategy as a radiosensitizer.
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7
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Rodemann HP, Wouters BG. Frontiers in molecular radiation biology/oncology. Radiother Oncol 2011; 101:1-6. [DOI: 10.1016/j.radonc.2011.09.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 09/30/2011] [Indexed: 12/15/2022]
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8
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Wennemers M, Bussink J, Grebenchtchikov N, Sweep FC, Span PN. TRIB3 protein denotes a good prognosis in breast cancer patients and is associated with hypoxia sensitivity. Radiother Oncol 2011; 101:198-202. [DOI: 10.1016/j.radonc.2011.05.057] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 05/25/2011] [Accepted: 05/26/2011] [Indexed: 11/27/2022]
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A standardized G2-assay for the prediction of individual radiosensitivity. Radiother Oncol 2011; 101:28-34. [DOI: 10.1016/j.radonc.2011.09.021] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 09/16/2011] [Accepted: 09/29/2011] [Indexed: 11/21/2022]
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Nagathihalli NS, Nagaraju G. RAD51 as a potential biomarker and therapeutic target for pancreatic cancer. Biochim Biophys Acta Rev Cancer 2011; 1816:209-18. [PMID: 21807066 DOI: 10.1016/j.bbcan.2011.07.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2011] [Revised: 07/14/2011] [Accepted: 07/16/2011] [Indexed: 11/30/2022]
Abstract
Chemotherapy is a very important therapeutic strategy for cancer treatment. The failure of conventional and molecularly targeted chemotherapeutic regimes for the treatment of pancreatic cancer highlights a desperate need for novel therapeutic interventions. Chemotherapy often fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Overexpression of RAD51 protein, a key player in DNA repair/recombination has been observed in many cancer cells and its hyperexpression is implicated in drug resistance. Recent studies suggest that RAD51 overexpression contributes to the development, progression and drug resistance of pancreatic cancer cells. Here we provide a brief overview of the available pieces of evidence in support of the role of RAD51 in pancreatic tumorigenesis and drug resistance, and hypothesize that RAD51 could serve as a potential biomarker for diagnosis of pancreatic cancer. We discuss the possible involvement of RAD51 in the drug resistance associated with epithelial to mesenchymal transition and with cancer stem cells. Finally, we speculate that targeting RAD51 in pancreatic cancer cells may be a novel approach for the treatment of pancreatic cancer.
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Affiliation(s)
- Nagaraj S Nagathihalli
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, TN 37232-6860, USA.
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11
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The role of homologous recombination in radiation-induced double-strand break repair. Radiother Oncol 2011; 101:7-12. [PMID: 21737170 DOI: 10.1016/j.radonc.2011.06.019] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 06/08/2011] [Accepted: 06/08/2011] [Indexed: 11/23/2022]
Abstract
DNA double-strand breaks (DSBs) represent the most biologically significant lesions induced by ionizing radiation (IR). HR is the predominant pathway for repairing one-ended DSBs arising in S-phase when the replication fork encounters single-stranded breaks or base damages. Here, we discuss recent findings that two-ended DSBs directly induced by X- or γ-rays in late S- or G2-phase are repaired predominantly by NHEJ, with HR only repairing a sub-fraction of such DSBs. This sub-fraction represents DSBs which localize to heterochromatic DNA regions and, which in control cells, are repaired with slow kinetics over many hours post irradiation. The observation that defined DSB populations are repaired by either NHEJ or HR suggests an assignment of specific tasks for each of the two processes. Furthermore, heavy ion induced complex DSBs, which are in general more slowly repaired than X- or γ-ray induced breaks, are nearly always repaired by HR independent of chromatin localization suggesting that the speed of repair is an important factor determining the DSB repair pathway usage. Finally, NHEJ and HR can, under certain conditions, also compensate for each other such that DSBs normally repaired by one pathway can undergo repair by the other if genetic failures necessitate the pathway switch.
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12
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Menegakis A, Eicheler W, Yaromina A, Thames HD, Krause M, Baumann M. Residual DNA double strand breaks in perfused but not in unperfused areas determine different radiosensitivity of tumours. Radiother Oncol 2011; 100:137-44. [DOI: 10.1016/j.radonc.2011.07.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 06/30/2011] [Accepted: 07/02/2011] [Indexed: 12/26/2022]
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Martin NT, Nahas SA, Tunuguntla R, Fike F, Gatti RA. Assessing 'radiosensitivity' with kinetic profiles of γ-H2AX, 53BP1 and BRCA1 foci. Radiother Oncol 2011; 101:35-8. [PMID: 21722985 DOI: 10.1016/j.radonc.2011.05.065] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 05/24/2011] [Accepted: 05/26/2011] [Indexed: 01/09/2023]
Abstract
BACKGROUND AND PURPOSE DNA repair assays to identify radiosensitive patients have had limited clinical implementation due to long turn-around times or limited specificity. This study evaluates γ-H2AX-Irradiation Induced Foci (IRIF) kinetics as a more rapid surrogate for the 'gold standard' colony survival assay (CSA) using several known DNA repair disorders as reference models. MATERIALS AND METHODS Radiosensitive cells of known and unknown etiology were studied. γ-H2AX-IRIFs were quantified over 24 h, and the curves were fitted by combining logarithmic growth and exponential decay functions. Fitted values that differed from radionormal controls were considered aberrant and compared to CSA results. RESULTS We observed 87% agreement of IRIF data with the CSA for the 14 samples tested. Analysis of γ-H2AX-IRIF kinetics for known repair disorders indicated similarities between an RNF168(-/-) cell line and an RS cell of unknown etiology. These cell lines were further characterized by a reduction in BRCA1-IRIF formation and G2/M checkpoint activation. CONCLUSIONS γ-H2AX-IRIF kinetics showed high concordance with the CSA in RS populations demonstrating its potential as a more rapid surrogate assay. This method provides a means to globally identify defective DNA repair pathways in RS cells of unknown etiology through comparison with known DNA repair defects.
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Affiliation(s)
- Nathan T Martin
- UCLA School of Medicine, Department of Pathology and Laboratory Medicine, Los Angeles, CA 90095-1732, USA.
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14
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The amount of DNA damage needed to activate the radiation-induced G2 checkpoint varies between single cells. Radiother Oncol 2011; 101:24-7. [PMID: 21722983 DOI: 10.1016/j.radonc.2011.05.060] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 05/24/2011] [Accepted: 05/26/2011] [Indexed: 11/21/2022]
Abstract
BACKGROUND AND PURPOSE The radiation-induced G2 checkpoint helps facilitate DNA repair before cell division. However, recent work has revealed that human cells often escape the G2 checkpoint with unrepaired DNA breaks. The purpose was to explore whether G2 checkpoint activation occurs according to a threshold level of DNA damage. MATERIALS AND METHODS G2 checkpoint activation was assayed at 75-90 min and 24-48 h after X-ray irradiation of BJ diploid fibroblasts and U2OS osteosarcoma cells. Multiparameter flow cytometry with pacific blue barcoding, and flow cytometry-based sorting of phospho-H3 positive cells to microscope slides, were used to examine the DNA damage marker γ-H2AX in individual mitotic cells that had escaped the G2 checkpoint. RESULTS For all radiation doses and times tested, the number of γ-H2AX foci varied between individual mitotic cells. At 75 min the median levels of γ-H2AX in mitotic cells increased with higher radiation doses. At 24-48 h, following a prolonged G2 checkpoint, cells were more resistant to checkpoint re-activation by a second dose of radiation. CONCLUSION Our results suggest that different amounts of DNA damage are needed to activate the G2 checkpoint in individual cells. Such single cell variation in checkpoint activation may potentially contribute to radiation-induced genomic instability.
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Beucher A, Deckbar D, Schumann E, Krempler A, Frankenberg-Schwager M, Löbrich M. Elevated radiation-induced γH2AX foci in G2 phase heterozygous BRCA2 fibroblasts. Radiother Oncol 2011; 101:46-50. [PMID: 21665305 DOI: 10.1016/j.radonc.2011.05.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 05/18/2011] [Accepted: 05/18/2011] [Indexed: 12/26/2022]
Abstract
BACKGROUND AND PURPOSE About 5-10% of all breast cancer cases are associated with heterozygous germ-line mutations in the genes encoding BRCA1 and BRCA2. Carriers of such mutations are highly predisposed for developing breast or ovarian cancer and, thus, are advised to undergo regular radio-diagnostic examinations. BRCA1 and BRCA2 are involved in multiple cellular processes including the repair of ionizing radiation (IR)-induced DNA double-strand breaks (DSBs) and different studies addressing the DSB repair capacity of BRCA1+/- or BRCA2+/- cells led to contradictory results. MATERIALS AND METHODS Using the sensitive method of γH2AX foci analysis in combination with cell cycle markers, we specifically measured DSB repair in confluent G0 as well as in exponentially growing G1 and G2 phase primary WT, BRCA1+/- and BRCA2+/- fibroblasts. RESULTS Both BRCA1+/- and BRCA2+/- cells displayed normal DSB repair in G0 and in G1. In contrast, in G2, BRCA2+/- but not BRCA1+/- cells exhibited a decreased DSB repair capacity which was in between that of WT and that of a hypomorphic BRCA2-/- cell line. CONCLUSIONS The residual amount of normal BRCA1 seems to be sufficient for efficient DSB repair in all cell cycle phases, while the decreased DSB repair capacity of heterozygous BRCA2 mutations suggests gene dosage effects in G2.
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Affiliation(s)
- Andrea Beucher
- Radiation Biology and DNA Repair, Darmstadt University of Technology, Germany
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16
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Harding SM, Coackley C, Bristow RG. ATM-dependent phosphorylation of 53BP1 in response to genomic stress in oxic and hypoxic cells. Radiother Oncol 2011; 99:307-12. [DOI: 10.1016/j.radonc.2011.05.039] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 05/17/2011] [Accepted: 05/17/2011] [Indexed: 10/18/2022]
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17
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Molecular and translational radiation biology/oncology: What’s up? Radiother Oncol 2011; 99:257-61. [DOI: 10.1016/j.radonc.2011.06.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 06/14/2011] [Indexed: 01/02/2023]
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18
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D’Andrea FP, Safwat A, Kassem M, Gautier L, Overgaard J, Horsman MR. Cancer stem cell overexpression of nicotinamide N-methyltransferase enhances cellular radiation resistance. Radiother Oncol 2011; 99:373-8. [DOI: 10.1016/j.radonc.2011.05.086] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 05/26/2011] [Accepted: 05/27/2011] [Indexed: 12/29/2022]
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19
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Brassat U, Balabanov S, Bali D, Dierlamm J, Braig M, Hartmann U, Sirma H, Günes C, Wege H, Fehse B, Gontarewicz A, Dikomey E, Borgmann K, Brümmendorf TH. Functional p53 is required for effective execution of telomerase inhibition in BCR-ABL-positive CML cells. Exp Hematol 2010; 39:66-76.e1-2. [PMID: 20940029 DOI: 10.1016/j.exphem.2010.10.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 09/16/2010] [Accepted: 10/04/2010] [Indexed: 02/08/2023]
Abstract
OBJECTIVE In chronic myeloid leukemia (CML), increased cellular turnover of hematopoietic cells driven by the oncogene BCR-ABL leads to accelerated telomere shortening despite increased telomerase activity. It has been postulated that shortened telomeres, particularly in the context of increased telomerase activity, might facilitate accumulation of genetic aberrations and, consequently, disease progression from chronic phase to accelerated phase and blast crisis. Therefore, inhibition of telomerase might be a promising approach in CML therapy. MATERIAL AND METHODS To investigate the therapeutic potential of telomerase inhibition in this model disorder, we used a small molecule telomerase inhibitor, BIBR1532 as well as expression of a dominant-negative mutant of hTERT (DNhTERT-IRES-GFP) in the p53-negative CML blast crisis cell line K562 and characterized the effects in long-term culture. Furthermore, we expressed an inducible p53 construct (vector pBabe-p53ER(tam)) via retroviral transduction in cells with critically short telomeres and in cells with a normal telomere length to explain the role of the tumor suppressor in response to critical telomere shortening in BCR-ABL-positive cells. RESULTS BIBR1532-treated bulk cultures did not show altered growth kinetics despite significant telomere shortening to a critical length of approximately 5 kb. In comparison, DNhTERT-expressing clones either lost telomere length, leading to a significant but transient slow down in proliferation but eventually all escaped senescence/crisis (group I) or, alternatively, remained virtually unaffected despite measurable telomerase inhibition (group II). Further analyses of group I clones revealed impaired DNA damage response and an accumulation of dicentric chromosomes. However, upon restoration of p53 in telomerase-negative K562 clones with critically short telomeres, immediate reinduction of apoptosis and complete eradication of cells was observed, whereas vector control cells continued to escape from crisis. CONCLUSIONS These results suggest that the success of strategies aimed at telomerase inhibition in CML is highly dependent on the presence of functional p53 and should be explored preferentially in chronic phase CML.
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Affiliation(s)
- Ute Brassat
- Department of Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Kriegs M, Kasten-Pisula U, Rieckmann T, Holst K, Saker J, Dahm-Daphi J, Dikomey E. The epidermal growth factor receptor modulates DNA double-strand break repair by regulating non-homologous end-joining. DNA Repair (Amst) 2010; 9:889-97. [DOI: 10.1016/j.dnarep.2010.05.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 04/28/2010] [Accepted: 05/24/2010] [Indexed: 10/19/2022]
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Ionizing radiation or mitomycin-induced micronuclei in lymphocytes of BRCA1 or BRCA2 mutation carriers. Breast Cancer Res Treat 2010; 127:611-22. [PMID: 20625817 DOI: 10.1007/s10549-010-1017-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 06/23/2010] [Indexed: 01/18/2023]
Abstract
BRCA1 and BRCA2 genes are essential in preserving the integrity of genome, and it is not unambiguously clear whether the heterozygosity status may affect BRCA1 or BRCA2 functions. This may have implications for the clinical management of BRCA1 and BRCA2 mutation carriers both in breast cancer (BC) screening modality and in cancer treatment based on DNA-damaging or DNA-repair-inhibiting drugs. We investigated whether lymphocytes carrying BRCA1 or BRCA2 mutations displayed an increased sensitivity to radiation or mitomycin C (MMC) in vitro treatments. Peripheral blood from 21 BRCA1 mutation carriers (12 with BC and 9 healthy), 24 BRCA2 carriers (13 with BC and 11 healthy), 15 familial BC patients without detected mutation in BRCA1 or BRCA2 and 16 controls without familial history of cancer (5 with BC and 11 healthy) were irradiated or treated with MMC. Chromosomal damage was measured using the cytokinesis-block micronucleus assay. We evaluated micronuclei (MN) and nucleoplasmic bridges (NPBs). The BRCA2 mutation carriers and familial BC patients without detected mutation in BRCA1 or BRCA2 showed less basal NPB than BRCA1 carriers and controls. The BRCA1 (+/-) or BRCA2 (+/-) lymphocytes did not have increased frequencies of MN or NPB after irradiation. In contrast, BRCA2 (+/-) lymphocytes presented higher levels of MN after MMC exposure than BRCA1 carriers and controls. The monoallelic BRCA1 or BRCA2 pathogenic mutations seem not to be associated with an enhanced radiosensitivity. The mutation of one BRCA2 allele conferred an increased sensitivity to MMC, presumably because of the role of this gene in the repair of MMC-induced DNA damage. This finding indicates that the MMC-induced MN analysis could be useful in identifying functional deficiencies of BRCA2 or genes related to BRCA2. Since MMC can be used as an anti-cancer drug, these data may be relevant for the management and follow-up of BRCA2 mutation carriers.
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Wilson PF, Nagasawa H, Fitzek MM, Little JB, Bedford JS. G2-phase chromosomal radiosensitivity of primary fibroblasts from hereditary retinoblastoma family members and some apparently normal controls. Radiat Res 2010; 173:62-70. [PMID: 20041760 DOI: 10.1667/rr1943.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We previously described an enhanced sensitivity for cell killing and gamma-H2AX focus induction after both high-dose-rate and continuous low-dose-rate gamma irradiation in 14 primary fibroblast strains derived from hereditary-type retinoblastoma family members (both affected RB1(+/-) probands and unaffected RB1(+/+) parents). Here we present G(2)-phase chromosomal radiosensitivity assay data for primary fibroblasts derived from these RB family members and five Coriell cell bank controls (four apparently normal individuals and one bilateral RB patient). The RB family members and two normal Coriell strains had significantly higher ( approximately 1.5-fold, P < 0.05) chromatid-type aberration frequencies in the first postirradiation mitosis after doses of 50 cGy and 1 Gy of (137)Cs gamma radiation compared to the remaining Coriell strains. The induction of chromatid-type aberrations by high-dose-rate G(2)-phase gamma irradiation is significantly correlated to the proliferative ability of these cells exposed to continuous low-dose-rate gamma irradiation (reported in Wilson et al., Radiat. Res. 169, 483-494, 2008). Our results suggest that these moderately radiosensitive individuals may harbor hypomorphic genetic variants in genomic maintenance and/or DNA repair genes or may carry epigenetic changes involving genes that more broadly modulate such systems, including G(2)-phase-specific DNA damage responses.
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Affiliation(s)
- Paul F Wilson
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado 80523, USA.
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Banáth JP, Klokov D, MacPhail SH, Banuelos CA, Olive PL. Residual gammaH2AX foci as an indication of lethal DNA lesions. BMC Cancer 2010; 10:4. [PMID: 20051134 PMCID: PMC2819996 DOI: 10.1186/1471-2407-10-4] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Accepted: 01/05/2010] [Indexed: 01/02/2023] Open
Abstract
Background Evidence suggests that tumor cells exposed to some DNA damaging agents are more likely to die if they retain microscopically visible γH2AX foci that are known to mark sites of double-strand breaks. This appears to be true even after exposure to the alkylating agent MNNG that does not cause direct double-strand breaks but does produce γH2AX foci when damaged DNA undergoes replication. Methods To examine this predictive ability further, SiHa human cervical carcinoma cells were exposed to 8 DNA damaging drugs (camptothecin, cisplatin, doxorubicin, etoposide, hydrogen peroxide, MNNG, temozolomide, and tirapazamine) and the fraction of cells that retained γH2AX foci 24 hours after a 30 or 60 min treatment was compared with the fraction of cells that lost clonogenicity. To determine if cells with residual repair foci are the cells that die, SiHa cervical cancer cells were stably transfected with a RAD51-GFP construct and live cell analysis was used to follow the fate of irradiated cells with RAD51-GFP foci. Results For all drugs regardless of their mechanism of interaction with DNA, close to a 1:1 correlation was observed between clonogenic surviving fraction and the fraction of cells that retained γH2AX foci 24 hours after treatment. Initial studies established that the fraction of cells that retained RAD51 foci after irradiation was similar to the fraction of cells that retained γH2AX foci and subsequently lost clonogenicity. Tracking individual irradiated live cells confirmed that SiHa cells with RAD51-GFP foci 24 hours after irradiation were more likely to die. Conclusion Retention of DNA damage-induced γH2AX foci appears to be indicative of lethal DNA damage so that it may be possible to predict tumor cell killing by a wide variety of DNA damaging agents simply by scoring the fraction of cells that retain γH2AX foci.
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Affiliation(s)
- Judit P Banáth
- Medical Biophysics Department, BC Cancer Agency Research Centre, 675 W, 10th Ave, Vancouver, BC V5Z 1L3, Canada
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Rodemann HP. Molecular radiation biology: Perspectives for radiation oncology. Radiother Oncol 2009; 92:293-8. [PMID: 19726094 DOI: 10.1016/j.radonc.2009.08.023] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 08/15/2009] [Indexed: 12/27/2022]
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