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McMahon SJ. The linear quadratic model: usage, interpretation and challenges. ACTA ACUST UNITED AC 2018; 64:01TR01. [DOI: 10.1088/1361-6560/aaf26a] [Citation(s) in RCA: 125] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Seltzsam S, Ziemann F, Dreffke K, Preising S, Arenz A, Schötz U, Engenhart-Cabillic R, Dikomey E, Wittig A. In HPV-Positive HNSCC Cells, Functional Restoration of the p53/p21 Pathway by Proteasome Inhibitor Bortezomib Does Not Affect Radio- or Chemosensitivity. Transl Oncol 2018; 12:417-425. [PMID: 30554133 PMCID: PMC6370941 DOI: 10.1016/j.tranon.2018.11.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 11/20/2018] [Accepted: 11/26/2018] [Indexed: 12/16/2022] Open
Abstract
Human papillomavirus (HPV) associated squamous cell carcinomas of the head and neck region (HPV+ HNSCCs) harbor diverging biological features as compared to classical noxa-induced (HPV−) HNSCC. One striking difference between subtypes is that the tumor suppressor gene TP53 is usually not mutated in HPV+ HNSCCs. However, p53 is inhibited by viral oncoprotein E6, leading to premature proteasomal degradation. We asked whether bortezomib (BZM), a clinically approved inhibitor of the proteasome, can functionally restore p53 and investigated in how far this will result in an enhanced radio- or chemosensitivity of HPV+ HNSCC cell lines. For all four HPV+ cell lines tested, BZM led to functional restoration of p53 and transactivation of downstream protein p21. In HPV+ cells, BZM also restored the radiation-induced p53/p21 transactivation. Consistently, in HPV+ cells, a restored G1 arrest as well as enhanced apoptosis were seen when BZM was given prior to irradiation (IR) or cisplatin (CDDP). BZM alone reduced the clonogenic survival of both HPV− and HPV+ cells. However, if BZM was combined with IR or CDDP, BZM did not significantly enhance radio- or chemosensitivity of HPV+ or HPV− HNSCC cell lines.
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Affiliation(s)
- Steve Seltzsam
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Frank Ziemann
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Kristin Dreffke
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Stefanie Preising
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Andrea Arenz
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Ulrike Schötz
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Rita Engenhart-Cabillic
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany.
| | - Ekkehard Dikomey
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany; Laboratory for Radiobiology & Experimental Radiooncology, University Medical Center Hamburg Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
| | - Andrea Wittig
- Department of Radiotherapy and Radiation Oncology, Philipps University of Marburg, University Hospital Gießen and Marburg, Baldingerstrasse, 35043 Marburg, Germany; Department of Radiotherapy and Radiation Oncology, University Hospital Jena, Bachstrasse 18, 07743 Jena, Germany.
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Buontempo F, Orsini E, Zironi I, Isolan L, Cappellini A, Rapino S, Tartari A, Mostacci D, Cucchi G, Martelli AM, Sumini M, Castellani G. Enhancing radiosensitivity of melanoma cells through very high dose rate pulses released by a plasma focus device. PLoS One 2018; 13:e0199312. [PMID: 29958291 PMCID: PMC6025851 DOI: 10.1371/journal.pone.0199312] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 06/05/2018] [Indexed: 12/19/2022] Open
Abstract
Radiation therapy is a useful and standard tumor treatment strategy. Despite recent advances in delivery of ionizing radiation, survival rates for some cancer patients are still low because of recurrence and radioresistance. This is why many novel approaches have been explored to improve radiotherapy outcome. Some strategies are focused on enhancement of accuracy in ionizing radiation delivery and on the generation of greater radiation beams, for example with a higher dose rate. In the present study we proposed an in vitro research of the biological effects of very high dose rate beam on SK-Mel28 and A375, two radioresistant human melanoma cell lines. The beam was delivered by a pulsed plasma device, a "Mather type" Plasma Focus for medical applications. We hypothesized that this pulsed X-rays generator is significantly more effective to impair melanoma cells survival compared to conventional X-ray tube. Very high dose rate treatments were able to reduce clonogenic efficiency of SK-Mel28 and A375 more than the X-ray tube and to induce a greater, less easy-to-repair DNA double-strand breaks. Very little is known about biological consequences of such dose rate. Our characterization is preliminary but is the first step toward future clinical considerations.
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Affiliation(s)
- Francesca Buontempo
- University of Bologna, Department of Biomedical and Neuromotor Sciences, Bologna, Italy
| | - Ester Orsini
- University of Bologna, Department of Biomedical and Neuromotor Sciences, Bologna, Italy
| | - Isabella Zironi
- University of Bologna, Department of Physics and Astronomy, Bologna, Italy
- University of Bologna, Department of Chemistry “G. Ciamician”, Bologna, Italy
- Interdepartmental Centre “L. Galvani” (CIG) for integrated studies of bioinformatics, biophysics and biocomplexity, Bologna, Italy
| | - Lorenzo Isolan
- European Institute of Oncology and Monzino Cardiac Center Foundation (IEO-CCM), Milano, Italy
- University of Bologna, Department of Industrial Engineering, Bologna, Italy
| | - Alessandra Cappellini
- University of Cassino and Southern Lazio, Department of Human Social and Health Sciences, Cassino, Italy
| | - Stefania Rapino
- Interdepartmental Centre “L. Galvani” (CIG) for integrated studies of bioinformatics, biophysics and biocomplexity, Bologna, Italy
- National Institute for Nuclear Physics (INFN), Bologna, Italy
| | - Agostino Tartari
- European Institute of Oncology and Monzino Cardiac Center Foundation (IEO-CCM), Milano, Italy
| | - Domiziano Mostacci
- European Institute of Oncology and Monzino Cardiac Center Foundation (IEO-CCM), Milano, Italy
| | - Giorgio Cucchi
- European Institute of Oncology and Monzino Cardiac Center Foundation (IEO-CCM), Milano, Italy
| | | | - Marco Sumini
- University of Bologna, Department of Chemistry “G. Ciamician”, Bologna, Italy
- European Institute of Oncology and Monzino Cardiac Center Foundation (IEO-CCM), Milano, Italy
| | - Gastone Castellani
- University of Bologna, Department of Physics and Astronomy, Bologna, Italy
- University of Bologna, Department of Chemistry “G. Ciamician”, Bologna, Italy
- Interdepartmental Centre “L. Galvani” (CIG) for integrated studies of bioinformatics, biophysics and biocomplexity, Bologna, Italy
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4
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Targeting CREB-binding protein overrides LPS induced radioresistance in non-small cell lung cancer cell lines. Oncotarget 2018; 9:28976-28988. [PMID: 29989005 PMCID: PMC6034744 DOI: 10.18632/oncotarget.25665] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/04/2018] [Indexed: 12/12/2022] Open
Abstract
Non-small cell lung cancer (NSCLC) has a very poor prognosis even when treated with the best therapies available today often including radiation. NSCLC is frequently complicated by pulmonary infections which appear to impair prognosis as well as therapy, whereby the underlying mechanisms are still not known. It was investigated here, whether the bacterial lipopolysaccharides (LPS) might alter the tumor cell radiosensitivity. LPS were found to induce a radioresistance but solely in cells with an active TLR-4 pathway. Proteome profiling array revealed that LPS combined with irradiation resulted in a strong phosphorylation of cAMP response element-binding protein (CREB). Inhibition of CREB binding protein (CBP) by the specific inhibitor ICG-001 not only abrogated the LPS-induced radioresistance but even led to an increase in radiosensitivity. The sensitization caused by ICG-001 could be attributed to a reduction of DNA double-strand break (DSB) repair. It is shown that in NSCLC cells LPS leads to a CREB dependent radioresistance which is, however, reversible through CBP inhibition by the specific inhibitor ICG-001. These findings indicate that the combined treatment with radiation and CBP inhibition may improve survival of NSCLC patients suffering from pulmonary infections.
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Wu S, Zhu L, Tu L, Chen S, Huang H, Zhang J, Ma S, Zhang S. AZD9291 Increases Sensitivity to Radiation in PC-9-IR Cells by Delaying DNA Damage Repair after Irradiation and Inducing Apoptosis. Radiat Res 2018; 189:283-291. [PMID: 29332537 DOI: 10.1667/rr14682.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AZD9291 is a novel, irreversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), which is administered orally. It has been proven effective in non-small cell lung cancer (NSCLC) patients, with both EGFR-sensitizing and EGFR T790M mutations in preclinical models. However, the potential therapeutic effects of AZD9291 combined with other modalities, including ionizing radiation, are not well understood. The presence of AZD9291 significantly increases the cell-killing effects of radiation in PC-9-IR cells with a secondary EGFR mutation (T790M), which was developed from NSCLC PC-9 cells (human lung adenocarcinoma cell with EGFR 19 exon 15 bp deletion) after chronic exposure to increasing doses of gefitinib, and in H1975 cells (human lung adenocarcinoma cell with EGFR exon 20 T790M mutation de novo), but not in PC-9 cells or in H460 cells (human lung adenocarcinoma cell with wild-type EGFR). In PC-9-IR cells, AZD9291 remarkably decreases phosphorylation levels of EGFR, extracellular regulated protein kinase (ERK), and protein kinase B (AKT). AZD9291 increases sensitivity to radiation in PC-9-IR cells by delaying deoxyribonucleic acid (DNA) damage repair after irradiation and inducing apoptosis, and enhances tumor growth inhibition when combined with radiation in PC-9-IR xenografts. Our findings suggest a potential therapeutic effect of AZD9291 as a radiation sensitizer in lung cancer cells with an acquired EGFR T790M mutation, providing a rationale for a clinical trial using the combination of AZD9291 and radiation in NSCLCs harboring acquired T790M mutation.
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Affiliation(s)
- Shenghai Wu
- a Department of Laboratory, Hangzhou First People's Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Lucheng Zhu
- b Department of Oncology, Hangzhou First People's Hospital of Nanjing Medical University, Hangzhou, China
| | - Linglan Tu
- c Centre of Molecular Medicine, Zhejiang Academy of Medical Sciences, Hangzhou, China
| | - Sumei Chen
- d Department of Oncology, Hangzhou Cancer Hospital, Hangzhou, China; and
| | - Haixiu Huang
- b Department of Oncology, Hangzhou First People's Hospital of Nanjing Medical University, Hangzhou, China
| | - Jingjing Zhang
- b Department of Oncology, Hangzhou First People's Hospital of Nanjing Medical University, Hangzhou, China
| | - Shenglin Ma
- e Department of Oncology, Hangzhou First People's Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Shirong Zhang
- b Department of Oncology, Hangzhou First People's Hospital of Nanjing Medical University, Hangzhou, China
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Dickreuter E, Eke I, Krause M, Borgmann K, van Vugt MA, Cordes N. Targeting of β1 integrins impairs DNA repair for radiosensitization of head and neck cancer cells. Oncogene 2016; 35:1353-62. [PMID: 26073085 DOI: 10.1038/onc.2015.212] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 04/08/2015] [Accepted: 04/12/2015] [Indexed: 11/09/2022]
Abstract
β1 Integrin-mediated cell-extracellular matrix interactions allow cancer cell survival and confer therapy resistance. It was shown that inhibition of β1 integrins sensitizes cells to radiotherapy. Here, we examined the impact of β1 integrin targeting on the repair of radiation-induced DNA double-strand breaks (DSBs). β1 Integrin inhibition was accomplished using the monoclonal antibody AIIB2 and experiments were performed in three-dimensional cell cultures and tumor xenografts of human head and neck squamous cell carcinoma (HNSCC) cell lines. AIIB2, X-ray irradiation, small interfering RNA-mediated knockdown and Olaparib treatment were performed and residual DSB number, protein and gene expression, non-homologous end joining (NHEJ) activity as well as clonogenic survival were determined. β1 Integrin targeting impaired repair of radiogenic DSB (γH2AX/53BP1, pDNA-PKcs T2609 foci) in vitro and in vivo and reduced the protein expression of Ku70, Rad50 and Nbs1. Further, we identified Ku70, Ku80 and DNA-PKcs but not poly(ADP-ribose) polymerase (PARP)-1 to reside in the β1 integrin pathway. Intriguingly, combined inhibition of β1 integrin and PARP using Olaparib was significantly more effective than either treatment alone in non-irradiated and irradiated HNSCC cells. Here, we support β1 integrins as potential cancer targets and highlight a regulatory role for β1 integrins in the repair of radiogenic DNA damage via classical NHEJ. Further, the data suggest combined targeting of β1 integrin and PARP as promising approach for radiosensitization of HNSCC.
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Affiliation(s)
- E Dickreuter
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - I Eke
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - M Krause
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany
- German Cancer Consortium (DKTK), 01307 Dresden, Germany, and German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - K Borgmann
- Laboratory of Radiobiology and Experimental Radiooncology, Clinic of Radiotherapy and Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - M A van Vugt
- Department of Medical Oncology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands
| | - N Cordes
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany
- German Cancer Consortium (DKTK), 01307 Dresden, Germany, and German Cancer Research Center (DKFZ), Heidelberg, Germany
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7
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Zhang S, Zheng X, Huang H, Wu K, Wang B, Chen X, Ma S. Afatinib increases sensitivity to radiation in non-small cell lung cancer cells with acquired EGFR T790M mutation. Oncotarget 2016; 6:5832-45. [PMID: 25714021 PMCID: PMC4467405 DOI: 10.18632/oncotarget.3332] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 01/03/2015] [Indexed: 01/12/2023] Open
Abstract
Afatinib is a second-generation of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor and has shown a significant clinical benefit in non-small cell lung cancer (NSCLC) patients with EGFR-activating mutations. However, the potential therapeutic effects of afatinib combining with other modalities, including ionizing radiation (IR), are not well understood. In this study, we developed a gefitinib-resistant cell subline (PC-9-GR) with a secondary EGFR mutation (T790M) from NSCLC PC-9 cells after chronic exposures to increasing doses of gefitinib. The presence of afatinib significantly increases the cell killing effect of radiation in PC-9-GR cells harboring acquired T790M, but not in H1975 cells with de novo T790M or in H460 cells that express wild-type EGFR. In PC-9-GR cells, afatinib remarkable blocks baseline of EGFR and ERK phosphorylations, and causes delay of IR-induced AKT phosphorylation. Afatinib treatment also leads to increased apoptosis and suppressed DNA damage repair in irradiated PC-9-GR cells, and enhanced tumor growth inhibition when combined with IR in PC-9-GR xenografts. Our findings suggest a potential therapeutic impact of afatinib as a radiation sensitizer in lung cancer cells harboring acquired T790M mutation, providing a rationale for a clinical trial with combination of afatinib and radiation in NSCLCs with EGFR T790M mutation.
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Affiliation(s)
- Shirong Zhang
- Department of Radiation Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, Zhejiang, China
| | - Xiaoliang Zheng
- Centre of Molecular Medicine, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China
| | - Haixiu Huang
- Department of Radiation Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, Zhejiang, China
| | - Kan Wu
- Department of Radiation Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, Zhejiang, China
| | - Bing Wang
- Department of Radiation Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, Zhejiang, China
| | - Xufeng Chen
- Department of Pathology and Laboratory Medicine, University of California at Los Angeles, Los Angeles, CA, USA
| | - Shenglin Ma
- Department of Radiation Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, Zhejiang, China
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Feng J, Zhang S, Wu K, Wang B, Wong JYC, Jiang H, Xu R, Ying L, Huang H, Zheng X, Chen X, Ma S. Combined Effects of Suberoylanilide Hydroxamic Acid and Cisplatin on Radiation Sensitivity and Cancer Cell Invasion in Non-Small Cell Lung Cancer. Mol Cancer Ther 2016; 15:842-53. [PMID: 26839308 DOI: 10.1158/1535-7163.mct-15-0445] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 01/19/2016] [Indexed: 11/16/2022]
Abstract
Lung cancer is a leading cause of cancer-related mortality worldwide, and concurrent chemoradiotherapy has been explored as a therapeutic option. However, the chemotherapeutic agents cannot be administered for most patients at full doses safely with radical doses of thoracic radiation, and further optimizations of the chemotherapy regimen to be given with radiation are needed. In this study, we examined the effects of suberoylanilide hydroxamic acid (SAHA) and cisplatin on DNA damage repairs, and determined the combination effects of SAHA and cisplatin on human non-small cell lung cancer (NSCLC) cells in response to treatment of ionizing radiation (IR), and on tumor growth of lung cancer H460 xenografts receiving radiotherapy. We also investigated the potential differentiation effect of SAHA and its consequences on cancer cell invasion. Our results showed that SAHA and cisplatin compromise distinct DNA damage repair pathways, and treatment with SAHA enhanced synergistic radiosensitization effects of cisplatin in established NSCLC cell lines in a p53-independent manner, and decreased the DNA damage repair capability in cisplatin-treated primary NSCLC tumor tissues in response to IR. SAHA combined with cisplatin also significantly increased inhibitory effect of radiotherapy on tumor growth in the mouse xenograft model. In addition, SAHA can induce differentiation in stem cell-like cancer cell population, reduce tumorigenicity, and decrease invasiveness of human lung cancer cells. In conclusion, our data suggest a potential clinical impact for SAHA as a radiosensitizer and as a part of a chemoradiotherapy regimen for NSCLC. Mol Cancer Ther; 15(5); 842-53. ©2016 AACR.
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Affiliation(s)
- Jianguo Feng
- Cancer Research Institute and Key Laboratory Diagnoses and Treatment Technology on Thoracic Oncology, Zhejiang Cancer Hospital, Hangzhou, China
| | - Shirong Zhang
- Department of Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, China. Affiliated Hangzhou First People's Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Kan Wu
- Affiliated Hangzhou First People's Hospital of Zhejiang Chinese Medical University, Hangzhou, China. Department of Radiation Oncology, Hangzhou Cancer Hospital, Hangzhou, China
| | - Bing Wang
- Affiliated Hangzhou First People's Hospital of Zhejiang Chinese Medical University, Hangzhou, China. Department of Radiation Oncology, Hangzhou Cancer Hospital, Hangzhou, China
| | - Jeffrey Y C Wong
- Department of Radiation Oncology, City of Hope Cancer Center, Duarte, California
| | - Hong Jiang
- Department of Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, China
| | - Rujun Xu
- Department of Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, China
| | - Lisha Ying
- Cancer Research Institute and Key Laboratory Diagnoses and Treatment Technology on Thoracic Oncology, Zhejiang Cancer Hospital, Hangzhou, China
| | - Haixiu Huang
- Department of Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, China
| | - Xiaoliang Zheng
- Centre of Molecular Medicine, Zhejiang Academy of Medical Sciences, Hangzhou, China
| | - Xufeng Chen
- Department of Pathology and Laboratory Medicine, University of California at Los Angeles, Los Angeles, California
| | - Shenglin Ma
- Department of Oncology, Affiliated Hangzhou Hospital of Nanjing Medical University, Hangzhou, China. Affiliated Hangzhou First People's Hospital of Zhejiang Chinese Medical University, Hangzhou, China.
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Cellular Pathways in Response to Ionizing Radiation and Their Targetability for Tumor Radiosensitization. Int J Mol Sci 2016; 17:ijms17010102. [PMID: 26784176 PMCID: PMC4730344 DOI: 10.3390/ijms17010102] [Citation(s) in RCA: 268] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 12/22/2015] [Accepted: 12/25/2015] [Indexed: 12/20/2022] Open
Abstract
During the last few decades, improvements in the planning and application of radiotherapy in combination with surgery and chemotherapy resulted in increased survival rates of tumor patients. However, the success of radiotherapy is impaired by two reasons: firstly, the radioresistance of tumor cells and, secondly, the radiation-induced damage of normal tissue cells located in the field of ionizing radiation. These limitations demand the development of drugs for either radiosensitization of tumor cells or radioprotection of normal tissue cells. In order to identify potential targets, a detailed understanding of the cellular pathways involved in radiation response is an absolute requirement. This review describes the most important pathways of radioresponse and several key target proteins for radiosensitization.
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Kriegs M, Gurtner K, Can Y, Brammer I, Rieckmann T, Oertel R, Wysocki M, Dorniok F, Gal A, Grob TJ, Laban S, Kasten-Pisula U, Petersen C, Baumann M, Krause M, Dikomey E. Radiosensitization of NSCLC cells by EGFR inhibition is the result of an enhanced p53-dependent G1 arrest. Radiother Oncol 2015; 115:120-7. [DOI: 10.1016/j.radonc.2015.02.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/16/2015] [Accepted: 02/21/2015] [Indexed: 11/30/2022]
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Reuther S, Reiter M, Raabe A, Dikomey E. Effect of irradiation on the expression of DNA repair genes studied in human fibroblasts by real-time qPCR using three methods of reference gene validation. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2013; 52:463-469. [PMID: 23884658 DOI: 10.1007/s00411-013-0482-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 07/09/2013] [Indexed: 06/02/2023]
Abstract
The aim of this study was to determine the effects of ionizing radiation on gene expression by using for a first time a qPCR platform specifically established for the detection of 94 DNA repair genes but also to test the robustness of these results by using three analytical methods (global pattern recognition, ΔΔCq/Normfinder and ΔΔCq/Genorm). Study was focused on these genes because DNA repair is known primarily to determine the radiation response. Six strains of normal human fibroblasts were exposed to 2 Gy, and changes in gene expression were analyzed 24 h thereafter. A significant change in gene expression was found for only few genes, but the genes detected were mostly different for the three analytical methods used. For GPR, a significant change was found for four genes, in contrast to the eight or nine genes when applying ΔΔCq/Genorm or ΔΔCq/Normfinder, respectively. When using all three methods, a significant change in expression was only seen for GADD45A and PCNA. These data demonstrate that (1) the genes identified to show an altered expression upon irradiation strongly depend on the analytical method applied, and that (2) overall GADD45A and PCNA appear to play a central role in this response, while no significant change is induced for any of the other DNA repair genes tested.
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Affiliation(s)
- Sebastian Reuther
- Laboratory of Radiobiology & Experimental Radiooncology, Center of Oncology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
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12
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Liu C, Kawata T, Zhou G, Furusawa Y, Kota R, Kumabe A, Sutani S, Fukada J, Mishima M, Shigematsu N, George K, Cucinotta F. Comparison of the repair of potentially lethal damage after low- and high-LET radiation exposure, assessed from the kinetics and fidelity of chromosome rejoining in normal human fibroblasts. JOURNAL OF RADIATION RESEARCH 2013; 54:989-997. [PMID: 23674607 PMCID: PMC3823769 DOI: 10.1093/jrr/rrt031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 03/09/2013] [Accepted: 03/12/2013] [Indexed: 06/02/2023]
Abstract
Potentially lethal damage (PLD) and its repair (PLDR) were studied in confluent human fibroblasts by analyzing the kinetics of chromosome break rejoining after X-ray or heavy-ion exposures. Cells were either held in the non-cycling G0 phase of the cell cycle for 12 h, or forced to proliferate immediately after irradiation. Fusion premature chromosome condensation (PCC) was combined with fluorescence in situ hybridization (FISH) to study chromosomal aberrations in interphase. The culture condition had no impact on the rejoining kinetics of PCC breaks during the 12 h after X-ray or heavy-ion irradiation. However, 12 h after X-ray and silicon irradiation, cycling cells had more chromosome exchanges than non-cycling cells. After 6 Gy X-rays, the yield of exchanges in cycling cells was 2.8 times higher than that in non-cycling cells, and after 2 Gy of 55 keV/μm silicon ions the yield of exchanges in cycling cells was twice that of non-cycling cells. In contrast, after exposure to 2 Gy 200-keV/μm or 440-keV/μm iron ions the yield of exchanges was similar in non-cycling and cycling cells. Since the majority of repair in G0/G1 occurs via the non-homologous end joining process (NHEJ), increased PLDR in X-ray and silicon-ion irradiated cells may result from improved cell cycle-specific rejoining fidelity through the NHEJ pathway, which is not the case in high-LET iron-ion irradiated cells.
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Affiliation(s)
- Cuihua Liu
- Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Tetsuya Kawata
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Guangming Zhou
- Department of Space Radiobiology, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730-000, China
| | - Yoshiya Furusawa
- Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Ryuichi Kota
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Atsuhiro Kumabe
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Shinya Sutani
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Junichi Fukada
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Masayo Mishima
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Naoyuki Shigematsu
- Department of Radiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Kerry George
- Wyle Integrated Science and Engineering Group, Houston, Texas, USA
| | - Francis Cucinotta
- NASA Johnson Space Center, Radiation Biophysics, Houston, Texas, USA
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13
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Reuther S, Metzke E, Bonin M, Petersen C, Dikomey E, Raabe A. No Effect of the Transforming Growth Factor β1 Promoter Polymorphism C-509T on TGFB1 Gene Expression, Protein Secretion, or Cellular Radiosensitivity. Int J Radiat Oncol Biol Phys 2013; 85:460-5. [DOI: 10.1016/j.ijrobp.2012.01.090] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 01/12/2012] [Accepted: 01/31/2012] [Indexed: 12/14/2022]
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14
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Chen X, Wong P, Radany EH, Stark JM, Laulier C, Wong JYC. Suberoylanilide hydroxamic acid as a radiosensitizer through modulation of RAD51 protein and inhibition of homology-directed repair in multiple myeloma. Mol Cancer Res 2012; 10:1052-64. [PMID: 22729783 DOI: 10.1158/1541-7786.mcr-11-0587] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Histone deacetylase inhibitors (HDI) have shown promise as candidate radiosensitizers for many types of cancers. However, the mechanisms of action are not well understood, and whether they could sensitize multiple myeloma (MM) to radiation therapy is unclear. In this study, we show that suberoylanilide hydroxamic acid (SAHA) at low concentrations has minimal cytotoxic effects, yet can significantly increase radiosensitivity of MM cells. SAHA seems to block RAD51 protein response to ionizing radiation, consistent with an inhibitory effect on the formation of RAD51 focus in irradiated MM cells. These effects of SAHA on RAD51 focus are independent of cell-cycle distribution changes. Furthermore, we show that SAHA selectively inhibits the homology-directed repair (HDR) pathway. The results of this study suggest that SAHA, a recently approved HDI in clinical trials for malignancies, at lower concentrations may act as a radiosensitizer via disruption of the RAD51-dependent HDR pathway.
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Affiliation(s)
- Xufeng Chen
- Department of Radiation Oncology, City of Hope Cancer Center, Duarte, CA 91010, USA
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15
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Wang M, Morsbach F, Sander D, Gheorghiu L, Nanda A, Benes C, Kriegs M, Krause M, Dikomey E, Baumann M, Dahm-Daphi J, Settleman J, Willers H. EGF receptor inhibition radiosensitizes NSCLC cells by inducing senescence in cells sustaining DNA double-strand breaks. Cancer Res 2011; 71:6261-9. [PMID: 21852385 DOI: 10.1158/0008-5472.can-11-0213] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mechanisms by which inhibition of the epidermal growth factor receptor (EGFR) sensitizes non-small cell lung cancer (NSCLC) cells to ionizing radiation remain poorly understood. We set out to characterize the radiosensitizing effects of the tyrosine kinase inhibitor erlotinib and the monoclonal antibody cetuximab in NSCLC cells that contain wild-type p53. Unexpectedly, EGFR inhibition led to pronounced cellular senescence but not apoptosis of irradiated cells, both in vitro and in vivo. Senescence was completely dependent on wild-type p53 and associated with a reduction in cell number as well as impaired clonogenic radiation survival. Study of ten additional NSCLC cell lines revealed that senescence is a prominent mechanism of radiosensitization in 45% of cell lines and occurs not only in cells with wild-type p53 but also in cells with mutant p53, where it is associated with an induction of p16. Interestingly, senescence and radiosensitization were linked to an increase in residual radiation-induced DNA double-strand breaks irrespective of p53/p16 status. This effect of EGFR inhibition was at least partially mediated by disruption of the MEK-ERK pathway. Thus, our data indicate a common mechanism of radiosensitization by erlotinib or cetuximab across diverse genetic backgrounds. Our findings also suggest that assays that are able to capture the initial proliferative delay that is associated with senescence should be useful for screening large cell line panels to identify genomic biomarkers of EGFR inhibitor-mediated radiosensitization.
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Affiliation(s)
- Meng Wang
- Laboratory of Cellular & Molecular Radiation Oncology, Massachusetts General Hospital Cancer Center, Charlestown, Massachusetts, USA
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16
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Wilson PF, Hinz JM, Urbin SS, Nham PB, Thompson LH. Influence of homologous recombinational repair on cell survival and chromosomal aberration induction during the cell cycle in gamma-irradiated CHO cells. DNA Repair (Amst) 2010; 9:737-44. [PMID: 20434408 DOI: 10.1016/j.dnarep.2010.03.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/23/2010] [Accepted: 03/26/2010] [Indexed: 11/29/2022]
Abstract
The repair of DNA double-strand breaks (DSBs) by homologous recombinational repair (HRR) underlies the high radioresistance and low mutability observed in S-phase mammalian cells. To evaluate the contributions of HRR and non-homologous end-joining (NHEJ) to overall DSB repair capacity throughout the cell cycle after gamma-irradiation, we compared HRR-deficient RAD51D-knockout 51D1 to CgRAD51D-complemented 51D1 (51D1.3) CHO cells for survival and chromosomal aberrations (CAs). Asynchronous cultures were irradiated with 150 or 300cGy and separated by cell size using centrifugal elutriation. Cell survival of each synchronous fraction ( approximately 20 fractions total from early G1 to late G2/M) was measured by colony formation. 51D1.3 cells were most resistant in S, while 51D1 cells were most resistant in early G1 (with survival and chromosome-type CA levels similar to 51D1.3) and became progressively more sensitive throughout S and G2. Both cell lines experienced significantly reduced survival from late S into G2. Metaphases were collected from every third elutriation fraction at the first post-irradiation mitosis and scored for CAs. 51D1 cells irradiated in S and G2 had approximately 2-fold higher chromatid-type CAs and a remarkable approximately 25-fold higher level of complex chromatid-type exchanges compared to 51D1.3 cells. Complex exchanges in 51D1.3 cells were only observed in G2. These results show an essential role for HRR in preventing gross chromosomal rearrangements in proliferating cells and, with our previous report of reduced survival of G2-phase NHEJ-deficient prkdc CHO cells [Hinz et al., DNA Repair 4, 782-792, 2005], imply reduced activity/efficiency of both HRR and NHEJ as cells transition from S to G2.
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Affiliation(s)
- Paul F Wilson
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551-0808, USA
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17
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Borgmann K, Raabe A, Reuther S, Szymczak S, Schlomm T, Isbarn H, Gomolka M, Busjahn A, Bonin M, Ziegler A, Dikomey E. The potential role of G2- but not of G0-radiosensitivity for predisposition of prostate cancer. Radiother Oncol 2010; 96:19-24. [DOI: 10.1016/j.radonc.2010.04.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 04/09/2010] [Accepted: 04/12/2010] [Indexed: 11/30/2022]
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18
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Storch K, Eke I, Borgmann K, Krause M, Richter C, Becker K, Schröck E, Cordes N. Three-dimensional cell growth confers radioresistance by chromatin density modification. Cancer Res 2010; 70:3925-34. [PMID: 20442295 DOI: 10.1158/0008-5472.can-09-3848] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cell shape and architecture are determined by cell-extracellular matrix interactions and have profound effects on cellular behavior, chromatin condensation, and tumor cell resistance to radiotherapy and chemotherapy. To evaluate the role of chromatin condensation for radiation cell survival, tumor cells grown in three-dimensional (3D) cell cultures as xenografts and monolayer cell cultures were compared. Here, we show that increased levels of heterochromatin in 3D cell cultures characterized by histone H3 deacetylation and induced heterochromatin protein 1alpha expression result in increased radiation survival and reduced numbers of DNA double strand breaks (DSB) and lethal chromosome aberrations. Intriguingly, euchromatin to heterochromatin-associated DSBs were equally distributed in irradiated 3D cell cultures and xenograft tumors, whereas irradiated monolayer cultures showed a 2:1 euchromatin to heterochromatin DSB distribution. Depletion of histone deacetylase (HDAC) 1/2/4 or application of the class I/II pharmacologic HDAC inhibitor LBH589 induced moderate or strong chromatin decondensation, respectively, which was translated into cell line-dependent radiosensitization and, in case of LBH589, into an increased number of DSBs. Neither growth conditions nor HDAC modifications significantly affected the radiation-induced phosphorylation of the important DNA repair protein ataxia telangiectasia mutated. Our data show an interrelation between cell morphology and cellular radiosensitivity essentially based on chromatin organization. Understanding the molecular mechanisms by which chromatin structure influences the processing of radiation-induced DNA lesions is of high relevance for normal tissue protection and optimization of cancer therapy.
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Affiliation(s)
- Katja Storch
- OncoRay-Center for Radiation Research in Oncology, Department of Radiation Oncology, Medical Faculty Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
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19
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El-Awady RA, Mahmoud M, Saleh EM, El-Baky HA, Lotayef M, Dahm-Daphi J, Dikomey E. No correlation between radiosensitivity or double-strand break repair capacity of normal fibroblasts and acute normal tissue reaction after radiotherapy of breast cancer patients. Int J Radiat Biol 2009; 81:501-8. [PMID: 16263653 DOI: 10.1080/09553000500280500] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The aim was to study the relationship between cellular radiosensitivity or double-strand break (dsb) repair capacity of skin fibroblasts and the extent of acute reaction after radiotherapy for breast cancer. The study was performed with 25 breast cancer patients submitted to the radiotherapy unit of the Egyptian National Cancer Institute after conserving surgery. Dermal fibroblasts, established from skin biopsies, were used to determine the cellular radiosensitivity via colony assay and the capacity of dsb repair by constant-field gel electrophoresis. Acute reactions were scored using the Radiation Therapy Oncology Group (RTOG) classification. The spectrum of acute reactions varied from grade 1 to 4, whereby most patients developed a grade 1 reaction after total doses ranging between 46 and 70 Gy. Skin fibroblasts showed a pronounced variation in both cellular radiosensitivity expressed as the mean inactivation dose (Dbar) (coefficient of variation, CV=25%) as well as in the number of residual dsb (CV=33%) with no significant correlation between these two endpoints (r2=0.20, p=0.14). Both parameters did not correlate with the extent of acute reaction of the respective patient. The data obtained indicate that the sensitivity of fibroblasts measured either by colony assay or by dsb repair capacity is not a major parameter determining the extent of acute reaction after radiotherapy of breast cancer patients.
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Affiliation(s)
- R A El-Awady
- Tumour Biology Department, National Cancer Institute, Cairo University, Cairo, Egypt, and Department of Radiotherapy and Radiation Oncology, University-Hospital Hamburg-Eppendorf, Hamburg, Germany
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20
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Dikomey E, Borgmann K, Hoeller U. In Reply to Dr. Azria. Int J Radiat Oncol Biol Phys 2009. [DOI: 10.1016/j.ijrobp.2009.01.072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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21
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Koch K, Wrona A, Dikomey E, Borgmann K. Impact of homologous recombination on individual cellular radiosensitivity. Radiother Oncol 2009; 90:265-72. [DOI: 10.1016/j.radonc.2008.07.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 06/26/2008] [Accepted: 07/25/2008] [Indexed: 12/24/2022]
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22
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Kasten-Pisula U, Menegakis A, Brammer I, Borgmann K, Mansour WY, Degenhardt S, Krause M, Schreiber A, Dahm-Daphi J, Petersen C, Dikomey E, Baumann M. The extreme radiosensitivity of the squamous cell carcinoma SKX is due to a defect in double-strand break repair. Radiother Oncol 2008; 90:257-64. [PMID: 19038467 DOI: 10.1016/j.radonc.2008.10.019] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 10/15/2008] [Accepted: 10/22/2008] [Indexed: 11/17/2022]
Abstract
PURPOSE Squamous cell carcinomas (SCCs) are characterized by moderate radiosensitivity. We have established the human head & neck SCC cell line SKX, which shows an exceptionally high radiosensitivity. It was the aim of this study to understand the underlying mechanisms. MATERIALS & METHODS Experiments were performed with SKX and FaDu, the latter taken as a control of moderate radiosensitivity. Cell lines were grown as xenografts as well as cell cultures. For xenografts, radiosensitivity was determined via local tumour control assay, and for cell cultures using colony assay. For cell cultures, apoptosis was determined by Annexin V staining and G1-arrest by BrdU labelling. Double-strand breaks (DSBs) were detected by both constant-field gel electrophoresis (CFGE) and gammaH2AX-foci technique; DSB rejoining was also assessed by in vitro rejoining assay; chromosomal damage was determined by G01-assay. RESULTS Compared to FaDu, SKX cells are extremely radiosensitive as found for both xenografts (TCD(50) for 10 fractions 46.0Gy [95% C.I.: 39; 54 Gy] vs. 18.9 Gy [95% C.I.: 13; 25Gy]) and cell cultures (D(0.01); 7.1 vs. 3.5Gy). Both cell lines showed neither radiation-induced apoptosis nor radiation-induced permanent G1-arrest. For DSBs, there was no difference in the induction but for repair with SKX cells showing a higher level of both, slowly repaired DSBs and residual DSBs. The in vitro DSB repair assay revealed that SKX cells are defective in nonhomologous endjoining (NHEJ), and that more than 40% of DSBs are rejoined by single-strand annealing (SSA). SKX cells also depicted a two-fold higher number of lethal chromosomal aberrations when compared to FaDu cells. CONCLUSIONS The extreme radiosensitivity of the SCC SKX seen both in vivo and in vitro can be ascribed to a reduced DNA double-strand break repair, resulting from a defect in NHEJ. This defect might be due to preferred usage of other pathways, such as SSA, which prevents efficient endjoining.
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Affiliation(s)
- Ulla Kasten-Pisula
- Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg - Eppendorf, Hamburg, Germany
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23
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Kasten-Pisula U, Vronskaja S, Overgaard J, Dikomey E. In normal human fibroblasts variation in DSB repair capacity cannot be ascribed to radiation-induced changes in the localisation, expression or activity of major NHEJ proteins. Radiother Oncol 2008; 86:321-8. [PMID: 18158193 DOI: 10.1016/j.radonc.2007.11.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Accepted: 11/30/2007] [Indexed: 10/22/2022]
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24
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Dikomey E, Borgmann K, Brammer I, Kasten-Pisula U. Molecular mechanisms of individual radiosensitivity studied in normal diploid human fibroblasts. Toxicology 2003; 193:125-35. [PMID: 14599772 DOI: 10.1016/s0300-483x(03)00293-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The molecular mechanisms of individual radiosensitivity were studied in normal diploid human fibroblasts. For fibroblasts irradiated with X-rays in G1-phase the individual radiosensitivity was shown to be correlated with the extent of double-strand break (dsb) repair. The number of residual dsbs (including both non- and mis-rejoined dsbs) varied between 2 and 5% of the initial number induced and was low for resistant and high for sensitive strains. In the G1-phase dsbs are considered to be mostly repaired via the non-homologous end-joining pathway (NHEJ). However, so far none of the parameters tested for this pathway was found to be correlated with the number of residual dsbs. The parameters tested were mRNA expression, protein level and localisation and activity of the DNA-PK, which is the central complex of NHEJ. The dsb-repair capacity is also not regulated by the differentiation status, which varies substantially among fibroblast strains, whereas there is some indication that dsb repair might depend on the chromatin structure, with more efficient repair in cells with condensed DNA. Residual dsbs are converted into lethal chromosome aberrations finally leading to the loss of clonogenic activity, when cells pass through mitosis. Beside this so-called mitotic death, X-irradiated human fibroblasts are also inactivated via the TP53-dependent permanent G1-arrest, while apoptosis appears to be not important. On average, mitotic death and G1-arrest are equally effective, but there is a broad variation from one strain to the other, with a negative correlation between these two pathways. Fibroblast strains exhibiting only a moderate G1-arrest showed a high number of lethal aberrations and vice versa. This result points to a common regulator of both G1-arrest and dsb repair, which is presently under investigation.
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Affiliation(s)
- Ekkehard Dikomey
- Institute of Biophysics and Radiobiology, University-Hospital Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.
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