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Al-khayyat W, Pirkkanen J, Dougherty J, Laframboise T, Dickinson N, Khaper N, Lees SJ, Mendonca MS, Boreham DR, Tai TC, Thome C, Tharmalingam S. Overexpression of FRA1 ( FOSL1) Leads to Global Transcriptional Perturbations, Reduced Cellular Adhesion and Altered Cell Cycle Progression. Cells 2023; 12:2344. [PMID: 37830558 PMCID: PMC10571788 DOI: 10.3390/cells12192344] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 09/18/2023] [Accepted: 09/21/2023] [Indexed: 10/14/2023] Open
Abstract
FRA1 (FOSL1) is a transcription factor and a member of the activator protein-1 superfamily. FRA1 is expressed in most tissues at low levels, and its expression is robustly induced in response to extracellular signals, leading to downstream cellular processes. However, abnormal FRA1 overexpression has been reported in various pathological states, including tumor progression and inflammation. To date, the molecular effects of FRA1 overexpression are still not understood. Therefore, the aim of this study was to investigate the transcriptional and functional effects of FRA1 overexpression using the CGL1 human hybrid cell line. FRA1-overexpressing CGL1 cells were generated using stably integrated CRISPR-mediated transcriptional activation, resulting in a 2-3 fold increase in FRA1 mRNA and protein levels. RNA-sequencing identified 298 differentially expressed genes with FRA1 overexpression. Gene ontology analysis showed numerous molecular networks enriched with FRA1 overexpression, including transcription-factor binding, regulation of the extracellular matrix and adhesion, and a variety of signaling processes, including protein kinase activity and chemokine signaling. In addition, cell functional assays demonstrated reduced cell adherence to fibronectin and collagen with FRA1 overexpression and altered cell cycle progression. Taken together, this study unravels the transcriptional response mediated by FRA1 overexpression and establishes the role of FRA1 in adhesion and cell cycle progression.
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Affiliation(s)
- Wuroud Al-khayyat
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada; (W.A.-k.); (N.D.); (D.R.B.); (T.C.T.); (C.T.)
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
| | - Jake Pirkkanen
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
| | - Jessica Dougherty
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
| | - Taylor Laframboise
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
| | - Noah Dickinson
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada; (W.A.-k.); (N.D.); (D.R.B.); (T.C.T.); (C.T.)
| | - Neelam Khaper
- Medical Sciences Division, NOSM University, 955 Oliver Rd., Thunder Bay, ON P7B 5E1, Canada; (N.K.); (S.J.L.)
- Department of Biology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada
| | - Simon J. Lees
- Medical Sciences Division, NOSM University, 955 Oliver Rd., Thunder Bay, ON P7B 5E1, Canada; (N.K.); (S.J.L.)
- Department of Biology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada
| | - Marc S. Mendonca
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Douglas R. Boreham
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada; (W.A.-k.); (N.D.); (D.R.B.); (T.C.T.); (C.T.)
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
| | - Tze Chun Tai
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada; (W.A.-k.); (N.D.); (D.R.B.); (T.C.T.); (C.T.)
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada
| | - Christopher Thome
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada; (W.A.-k.); (N.D.); (D.R.B.); (T.C.T.); (C.T.)
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada
| | - Sujeenthar Tharmalingam
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada; (W.A.-k.); (N.D.); (D.R.B.); (T.C.T.); (C.T.)
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (J.P.); (J.D.); (T.L.)
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada
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Pirkkanen J, Tharmalingam S, Thome C, Sinex HC, Benjamin LV, Losch AC, Borgmann AJ, Dhaemers RM, Gordon C, Boreham DR, Mendonca MS. Genomic Loss and Epigenetic Silencing of the FOSL1 Tumor Suppressor Gene in Radiation-induced Neoplastic Transformation of Human CGL1 Cells Alters the Tumorigenic Phenotype In Vitro and In Vivo. Radiat Res 2023; 200:48-64. [PMID: 37141110 PMCID: PMC10409446 DOI: 10.1667/rade-22-00216.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 03/24/2023] [Indexed: 05/05/2023]
Abstract
The CGL1 human hybrid cell system has been utilized for many decades as an excellent cellular tool for investigating neoplastic transformation. Substantial work has been done previously implicating genetic factors related to chromosome 11 to the alteration of tumorigenic phenotype in CGL1 cells. This includes candidate tumor suppressor gene FOSL1, a member of the AP-1 transcription factor complex which encodes for protein FRA1. Here we present novel evidence supporting the role of FOSL1 in the suppression of tumorigenicity in segregants of the CGL1 system. Gamma-induced mutant (GIM) and control (CON) cells were isolated from 7 Gy gamma-irradiated CGL1s. Western, Southern and Northern blot analysis were utilized to assess FOSL1/FRA1 expression as well as methylation studies. GIMs were transfected to re-express FRA1 and in vivo tumorigenicity studies were conducted. Global transcriptomic microarray and RT-qPCR analysis were used to further characterize these unique cell segregants. GIMs were found to be tumorigenic in vivo when injected into nude mice whereas CON cells were not. GIMs show loss of Fosl/FRA1 expression as confirmed by Western blot. Southern and Northern blot analysis further reveals that FRA1 reduction in tumorigenic CGL1 segregants is likely due to transcriptional suppression. Results suggest that radiation-induced neoplastic transformation of CGL1 is in part due to silencing of the FOSL1 tumor suppressor gene promoter by methylation. The radiation-induced tumorigenic GIMs transfected to re-express FRA1 resulted in suppression of subcutaneous tumor growth in nude mice in vivo. Global microarray analysis and RT-qPCR validation elucidated several hundred differentially expressed genes. Downstream analysis reveals a significant number of altered pathways and enriched Gene Ontology terms genes related to cellular adhesion, proliferation, and migration. Together these findings provide strong evidence that FRA1 is a tumor suppressor gene deleted and epigenetically silenced after ionizing radiation-induced neoplastic transformation in the CGL1 human hybrid cell system.
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Affiliation(s)
- Jake Pirkkanen
- Department of Biology, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
- Biomolecular Sciences Program, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
| | - Sujeenthar Tharmalingam
- Department of Biology, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
- Biomolecular Sciences Program, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
- Medical Sciences Division, NOSM University, Sudbury, Ontario, P3E 2C6, Canada
| | - Christopher Thome
- Department of Biology, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
- Biomolecular Sciences Program, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
- Medical Sciences Division, NOSM University, Sudbury, Ontario, P3E 2C6, Canada
| | - Helen Chin Sinex
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Laura V. Benjamin
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Adam C. Losch
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Anthony J. Borgmann
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Ryan M. Dhaemers
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Christopher Gordon
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Douglas R. Boreham
- Biomolecular Sciences Program, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Bruce Power, PO Box 1540, 177 Tie Rd, R.R. 2, Tiverton, Ontario, N0G 2T0, Canada
- Nuclear Innovation Institute, Port Elgin, Ontario, N0H 2C0, Canada
| | - Marc S. Mendonca
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
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Pirkkanen J, Tharmalingam S, Morais IH, Lam-Sidun D, Thome C, Zarnke AM, Benjamin LV, Losch AC, Borgmann AJ, Sinex HC, Mendonca MS, Boreham DR. Transcriptomic profiling of gamma ray induced mutants from the CGL1 human hybrid cell system reveals novel insights into the mechanisms of radiation-induced carcinogenesis. Free Radic Biol Med 2019; 145:300-311. [PMID: 31580949 DOI: 10.1016/j.freeradbiomed.2019.09.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 08/22/2019] [Accepted: 09/29/2019] [Indexed: 01/26/2023]
Abstract
BACKGROUND Somatic cell hybrid systems generated by combining cancerous with non-cancerous cells provide useful model systems to study neoplastic transformation. Combined with recent advances in omics-based technologies, novel molecular signatures that drive radiation-induced carcinogenesis can be analyzed at an exceptional global level. METHODS Here, we present a complete whole-transcriptome analysis of gamma-induced mutants (GIM) and gamma irradiated control (CON) segregants isolated from the CGL1 (HeLa x normal fibroblast) human hybrid cell-system exposed to high doses of radiation. Using the Human Transcriptome Array 2.0 microarray technology and conservative discrimination parameters, we have elucidated 1067 differentially expressed genes (DEGs) between tumorigenic and non-tumorigenic cells. RESULTS Gene ontology enrichment analysis revealed that tumorigenic cells demonstrated shifts in extracellular matrix (ECM) and cellular adhesion profiles, dysregulation of cyclic AMP (cAMP) signaling, and alterations in nutrient transport and cellular energetics. Furthermore, putative upstream master regulator analysis demonstrated that loss of TGFβ1 signaling due to reduced SMAD3 expression is involved in radiation-induced carcinogenesis. CONCLUSIONS Taken together, this study presents novel insights into specific gene expression and pathway level differences that contribute to radiation-induced carcinogenesis in a human cell-based model. This global transcriptomic analysis and our published tumor suppressor gene deletion loci analyses will allow us to identify and functionally test candidate nexus upstream tumor suppressor genes that are deleted or silenced after exposure to radiation.
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Affiliation(s)
- Jake Pirkkanen
- Laurentian University, 935 Ramsey Lake Rd, Sudbury, Ontario, P3E 2C6, Canada.
| | | | - Igor H Morais
- Laurentian University, 935 Ramsey Lake Rd, Sudbury, Ontario, P3E 2C6, Canada.
| | - Daniel Lam-Sidun
- Northern Ontario School of Medicine, 935 Ramsey Lake Rd, Sudbury, Ontario, P3E 2C6, Canada.
| | - Christopher Thome
- Northern Ontario School of Medicine, 935 Ramsey Lake Rd, Sudbury, Ontario, P3E 2C6, Canada.
| | - Andrew M Zarnke
- Laurentian University, 935 Ramsey Lake Rd, Sudbury, Ontario, P3E 2C6, Canada.
| | - Laura V Benjamin
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
| | - Adam C Losch
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
| | - Anthony J Borgmann
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
| | - Helen Chin Sinex
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
| | - Marc S Mendonca
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
| | - Douglas R Boreham
- Northern Ontario School of Medicine, 935 Ramsey Lake Rd, Sudbury, Ontario, P3E 2C6, Canada; Bruce Power, PO Box 1540, 177 Tie Rd, R.R. 2, Tiverton, Ontario, N0G 2T0, Canada.
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Pirkkanen JS, Boreham DR, Mendonca MS. The CGL1 (HeLa × Normal Skin Fibroblast) Human Hybrid Cell Line: A History of Ionizing Radiation Induced Effects on Neoplastic Transformation and Novel Future Directions in SNOLAB. Radiat Res 2017; 188:512-524. [PMID: 28873027 DOI: 10.1667/rr14911.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Cellular transformation assays have been utilized for many years as powerful in vitro methods for examining neoplastic transformation potential/frequency and mechanisms of carcinogenesis for both chemical and radiological carcinogens. These mouse and human cell based assays are labor intensive but do provide quantitative information on the numbers of neoplastically transformed foci produced after carcinogenic exposure and potential molecular mechanisms involved. Several mouse and human cell systems have been generated to undertake these studies, and they vary in experimental length and endpoint assessment. The CGL1 human cell hybrid neoplastic model is a non-tumorigenic pre-neoplastic cell that was derived from the fusion of HeLa cervical cancer cells and a normal human skin fibroblast. It has been utilized for the several decades to study the carcinogenic/neoplastic transformation potential of a variety of ionizing radiation doses, dose rates and radiation types, including UV, X ray, gamma ray, neutrons, protons and alpha particles. It is unique in that the CGL1 assay has a relatively short assay time of 18-21 days, and rather than relying on morphological endpoints to detect neoplastic transformation utilizes a simple staining method that detects the tumorigenic marker alkaline phosphatase on the neoplastically transformed cells cell surface. In addition to being of human origin, the CGL1 assay is able to detect and quantify the carcinogenic potential of very low doses of ionizing radiation (in the mGy range), and utilizes a neoplastic endpoint (re-expression of alkaline phosphatase) that can be detected on both viable and paraformaldehyde fixed cells. In this article, we review the history of the CGL1 neoplastic transformation model system from its initial development through the wide variety of studies examining the effects of all types of ionizing radiation on neoplastic transformation. In addition, we discuss the potential of the CGL1 model system to investigate the effects of near zero background radiation levels available within the radiation biology lab we have established in SNOLAB.
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Affiliation(s)
- Jake S Pirkkanen
- a Department of Biology, Laurentian University, Sudbury, Ontario, Canada, P3E 2C6
| | - Douglas R Boreham
- a Department of Biology, Laurentian University, Sudbury, Ontario, Canada, P3E 2C6.,b Northern Ontario School of Medicine, Sudbury, Ontario, Canada, P3E 2C6.,c Bruce Power, Tiverton, Ontario, Canada, N0G 2T0
| | - Marc S Mendonca
- d Department of Radiation Oncology, Radiation and Cancer Biology Laboratories, and Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202
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Frankenberg-Schwager M, Spieren S, Pralle E, Giesen U, Brede HJ, Thiemig M, Frankenberg D. The RBE of 3.4 MeV alpha-particles and 0.565 MeV neutrons relative to 60Co gamma-rays for neoplastic transformation of human hybrid cells and the impact of culture conditions. RADIATION PROTECTION DOSIMETRY 2010; 138:29-39. [PMID: 19828717 DOI: 10.1093/rpd/ncp201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The neoplastic transformation of human hybrid CGL1 cells is affected by perturbations from external influences such as serum batch and concentration, the number of medium changes during the 21-day expression period and cell seeding density. Nevertheless, for doses up to 1.5 Gy, published transformation frequencies for low linear energy transfer (LET) radiations (gamma-rays, MeV electrons or photons) are in good agreement, whereas for higher doses larger variations are reported. The (60)Co gamma-ray data here for doses up to 1.5 Gy, using a low-yield serum batch and only one medium change, are in agreement with published frequencies of neoplastic transformation of human hybrid cells. For 3.4 MeV alpha-particles (LET = 124 keV/mum) and 0.565 MeV monoenergetic neutrons relative to low doses of (60)Co gamma-rays, a maximum relative biological effectiveness (RBE(M)) of 2.8 +/- 0.2 and 1.5 +/- 0.2, respectively, was calculated. Surprisingly, at higher doses of (60)Co gamma-rays lower frequencies of neoplastic transformation were observed. This non-monotonic dose relationship for neoplastic transformation by (60)Co gamma-rays is likely due to the lack of a G2/M arrest observed at low doses resulting in higher transformation frequencies per dose, whereas the lower frequencies per dose observed for higher doses are likely related to the induction of a G2/M arrest.
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Affiliation(s)
- M Frankenberg-Schwager
- Abteilung Nuklearmedizin im Zentrum Radiologie, Universität Göttingen, Von-Siebold-Str. 3, 37075 Göttingen, Germany
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Mendonca MS, Mayhugh BM, McDowell B, Chin-Sinex H, Smith ML, Dynlacht JR, Spandau DF, Lewis DA. A Radiation-Induced Acute Apoptosis Involving TP53 and BAX Precedes the Delayed Apoptosis and Neoplastic Transformation of CGL1 Human Hybrid Cells. Radiat Res 2005; 163:614-22. [PMID: 15913393 DOI: 10.1667/rr3387] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Exposing CGL1 (HeLa x fibroblast) hybrid cells to 7 Gy of X rays results in the onset of a delayed apoptosis in the progeny of the cells 10 to 12 cell divisions postirradiation that correlates with the emergence of neoplastically transformed foci. The delayed apoptosis begins around day 8 postirradiation and lasts for 11 days. We now demonstrate that the delayed apoptosis is also characterized by the appearance of approximately 50-kb apoptotic DNA fragments and caspase 3 activation postirradiation. In addition, we confirm that stabilization of TP53 and transactivation of pro-apoptosis BAX also occurs during the delayed apoptosis and show that anti-apoptosis BCL-X(L) is down-regulated. To test whether the delayed apoptosis was due to a nonfunctional acute TP53 damage response in CGL1 cells, studies of acute apoptosis were completed. After irradiation, CGL1 cells underwent an acute wave of apoptosis that involves TP53 stabilization, transactivation of BAX gene expression, and a rapid caspase activation that ends by 96 h postirradiation. In addition, the acute onset of apoptosis correlates with transactivation of a standard wild-type TP53-responsive reporter (pG13-CAT) in CGL1 cells after radiation exposure. We propose that the onset of the delayed apoptosis is not the result of a nonfunctional acute TP53 damage response pathway but rather is a consequence of X-ray-induced genomic instability arising in the distant progeny of the irradiated cells.
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Affiliation(s)
- Marc S Mendonca
- Department of Radiation Oncology, Radiation and Cancer Biology Laboratory, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Frankenberg D, Frankenberg-Schwager M, Garg I, Pralle E, Uthe D, Greve B, Severin E, Göhde W. Mutation induction and neoplastic transformation in human and human-hamster hybrid cells: dependence on photon energy and modulation in the low-dose range. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2002; 22:A17-A20. [PMID: 12400941 DOI: 10.1088/0952-4746/22/3a/303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Mutation induction in the HPRT gene of human fibroblasts after irradiation with mammography-like 29 kVp or 200 kVp x-rays shows radiohypersensitivity for doses smaller than approximately 0.5 Gy. Similarly, mutation induction in the CD 59 gene on human chromosome 11 in A(L) cells shows radiohypersensitivity for doses smaller than approximately 0.5 Gy after exposure to 200 kVp x-rays, but not after irradiation with low-filtered 30 kVp x-rays. The RBE values of 29 and 30 kVp x-rays relative to 200 kVp x-rays are strongly dose dependent. For neoplastic transformation of human hybrid (CGL1) cells after irradiation with 29 or 200 kVp x-rays or 60Co gamma rays a linear-quadratic dose relationship was observed with RBE values of approximately four and eight for mammography relative to 200 kVp x-rays and 60Co gamma rays, respectively.
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Affiliation(s)
- D Frankenberg
- Abt. Klin. Strahlenbiologie und Klin. Strahlenphysik, Universität Göttingen, Germany
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Frankenberg D, Kelnhofer K, Bär K, Frankenberg-Schwager M. Enhanced neoplastic transformation by mammography X rays relative to 200 kVp X rays: indication for a strong dependence on photon energy of the RBE(M) for various end points. Radiat Res 2002; 157:99-105. [PMID: 11754647 DOI: 10.1667/0033-7587(2002)157[0099:entbmx]2.0.co;2] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The fundamental assumption implicit in the use of the atomic bomb survivor data to derive risk estimates is that the gamma rays of Hiroshima and Nagasaki are considered to have biological efficiencies equal to those of other low-LET radiations up to 10 keV/microm, including mammography X rays. Microdosimetric and radiobiological data contradict this assumption. It is therefore of scientific and public interest to evaluate the efficiency of mammography X rays (25-30 kVp) to induce cancer. In this study, the efficiency of mammography X rays relative to 200 kVp X rays to induce neoplastic cell transformation was evaluated using cells of a human hybrid cell line (CGL1). For both radiations, a linear-quadratic dose-effect relationship was observed for neoplastic transformation of CGL1 cells; there was a strong linear component for the 29 kVp X rays. The RBE(M) of mammography X rays relative to 200 kVp X rays was determined to be about 4 for doses < or = 0.5 Gy. A comparison of the electron fluences for both X rays provides strong evidence that electrons with energies of < or = 15 keV can induce neoplastic transformation of CGL1 cells. Both the data available in the literature and the results of the present study strongly suggest an increase of RBE(M) for carcinogenesis in animals, neoplastic cell transformation, and clastogenic effects with decreasing photon energy or increasing LET to an RBE(M) approximately 8 for mammography X rays relative to 60Co gamma rays.
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Affiliation(s)
- D Frankenberg
- Department for Clinical Radiobiology and Clinical Radiation Physics, University of Göttingen, von-Siebold-Strasse 3, D-37075 Göttingen, Germany.
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Lewis DA, Mayhugh BM, Qin Y, Trott K, Mendonca MS. Production of delayed death and neoplastic transformation in CGL1 cells by radiation-induced bystander effects. Radiat Res 2001; 156:251-8. [PMID: 11500134 DOI: 10.1667/0033-7587(2001)156[0251:poddan]2.0.co;2] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Other investigators have demonstrated by transfer of medium from irradiated cells and by irradiation with low-fluence alpha particles or microbeams that cells do not have to be directly exposed to ionizing radiation to be detrimentally affected, i.e. bystander effects. In this study, we demonstrate by transfer of medium from X-irradiated human CGL1 hybrid cells that the killing of bystander cells reduces the plating efficiency of the nonirradiated CGL1 cells by 33 +/- 6%. In addition, we show that the amount of cell death induced by bystander effects is not dependent on X-ray dose, and that the induction of apoptosis does not appear to be responsible for the cell death. Furthermore, we found that the reduction in plating efficiency in bystander cells is evident for over 18 days, or 22 cell population doublings, after medium transfer, despite repeated refeeding of the cell cultures. Finally, we report the novel observation that bystander effects induced by the transfer of medium from irradiated cells can induce neoplastic transformation. Exposing unirradiated CGL1 cells to medium from cells irradiated with 5 or 7 Gy increased the frequency of neoplastic transformation significantly from 6.3 x 10(-6) in unirradiated controls to 2.3 x 10(-5) (a factor of nearly four). We conclude that the bystander effect induces persistent, long-term, transmissible changes in the progeny of CGL1 cells that result in delayed death and neoplastic transformation. The data suggest that neoplastic transformation in bystander cells may play a significant role in radiation-induced neoplastic transformation at lower doses of X rays.
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Affiliation(s)
- D A Lewis
- Radiation and Cancer Biology Laboratory, Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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