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Determination of fast neutron RBE using a fully mechanistic computational model. Appl Radiat Isot 2020; 156:108952. [DOI: 10.1016/j.apradiso.2019.108952] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 10/11/2019] [Accepted: 10/21/2019] [Indexed: 11/19/2022]
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2
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Abstract
The Radiological Research Accelerator Facility (RARAF) is in its 50th year of operation. It was commissioned on April 1, 1967 as a collaboration between the Radiological Research Laboratory (RRL) of Columbia University, and members of the Medical Research Center of Brookhaven National Laboratory (BNL). It was initially funded as a user facility for radiobiology and radiological physics, concentrating on monoenergetic neutrons. Facilities for irradiation with MeV light charged particles were developed in the mid-1970s. In 1980 the facility was relocated to the Nevis Laboratories of Columbia University. RARAF now has seven beam lines, each having a dedicated irradiation facility: monoenergetic neutrons, charged particle track segments, two charged particle microbeams (one electrostatically focused to <1 μm, one magnetically focused), a 4.5 keV soft X-ray microbeam, a neutron microbeam, and a facility that produces a neutron spectrum similar to that of the atomic bomb dropped at Hiroshima. Biology facilities are available on site within close proximity to the irradiation facilities, making the RARAF very user friendly.
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Affiliation(s)
- Stephen A Marino
- Radiological Research Accelerator Facility, Columbia University, Irvington, New York 10533
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3
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Gerweck LE, Huang P, Lu HM, Paganetti H, Zhou Y. Lifetime increased cancer risk in mice following exposure to clinical proton beam-generated neutrons. Int J Radiat Oncol Biol Phys 2014; 89:161-6. [PMID: 24725699 DOI: 10.1016/j.ijrobp.2014.01.057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 01/29/2014] [Accepted: 01/30/2014] [Indexed: 11/26/2022]
Abstract
PURPOSE To evaluate the life span and risk of cancer following whole-body exposure of mice to neutrons generated by a passively scattered clinical spread-out Bragg peak (SOBP) proton beam. METHODS AND MATERIALS Three hundred young adult female FVB/N mice, 152 test and 148 control, were entered into the experiment. Mice were placed in an annular cassette around a cylindrical phantom, which was positioned lateral to the mid-SOBP of a 165-MeV, clinical proton beam. The average distance from the edge of the mid-SOBP to the conscious active mice was 21.5 cm. The phantom was irradiated with once-daily fractions of 25 Gy, 4 days per week, for 6 weeks. The age at death and cause of death (ie, cancer and type vs noncancer causes) were assessed over the life span of the mice. RESULTS Exposure of mice to a dose of 600 Gy of proton beam-generated neutrons, reduced the median life span of the mice by 4.2% (Kaplan-Meier cumulative survival, P=.053). The relative risk of death from cancer in neutron exposed versus control mice was 1.40 for cancer of all types (P=.0006) and 1.22 for solid cancers (P=.09). For a typical 60 Gy dose of clinical protons, the observed 22% increased risk of solid cancer would be expected to decrease by a factor of 10. CONCLUSIONS Exposure of mice to neutrons generated by a proton dose that exceeds a typical course of radiation therapy by a factor of 10, resulted in a statistically significant increase in the background incidence of leukemia and a marginally significant increase in solid cancer. The results indicate that the risk of out-of-field second solid cancers from SOBP proton-generated neutrons and typical treatment schedules, is 6 to 10 times less than is suggested by current neutron risk estimates.
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Affiliation(s)
- Leo E Gerweck
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
| | - Peigen Huang
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Hsiao-Ming Lu
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Yenong Zhou
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
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4
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Faria FP, Dickman R, Moreira CHC. Models of the radiation-induced bystander effect. Int J Radiat Biol 2012; 88:592-9. [DOI: 10.3109/09553002.2012.692568] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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5
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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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6
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Abstract
Radon is by far the most important contributor to the collective dose equivalent. Most of what is known about the hazards of radon daughters comes from epidemiological studies of miners. There are a few well defined areas in which in vitro research can complement such studies: First, more data on the relative effects of differing energy (LET) alpha-particles would help: (1) understand the significance of the depth of sensitive cells in the bronchial epithelium--which varies between individuals, as well as between smokers and non-smokers, and between miners and non-miners; (2) understand the relative hazards of radon and thoron daughters. Second, reliable methods for predicting high LET responses from low LET response, would enable Japanese A-bomb survivor data to be applied with confidence. Third, understanding the effects of single-particle traversals of cells relative to multiple traversals could allow reliable extrapolation of epidemiological miner data to low exposures. Fourth, a better understanding of the nature of the interaction between tobacco and radiation damage would help predict the effect of radon on non-smokers.
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Affiliation(s)
- D J Brenner
- Center for Radiological Research, Columbia University, New York, NY 10032
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7
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Yamaguchi H, Waker AJ. A model for the induction of DNA damages by fast neutrons and their evolution into cell clonogenic inactivation. JOURNAL OF RADIATION RESEARCH 2007; 48:289-303. [PMID: 17515661 DOI: 10.1269/jrr.06107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
It has been long stated that cellular inactivation through neutron irradiation is mainly caused by energy deposition in DNA molecules from recoiled secondary charged particles. Complexities associated with neutrons, such as the generally broad energy spectrum and the inherently wide energy spectrum of the induced charged particles, not to mention that the dependence of cellular inactivation by charged particles on radiation quality is yet to be fully understood, make it difficult to check this statement. Recently a molecular model has been proposed that improves the quantitative explanation of the dependence of cellular inactivation by charged particles on radiation quality. An attempt was made to apply this model for analysis of neutron cellular inactivation. As a preliminary result it is suggested that neutron cellular inactivation is caused not only by secondary charged particles but also by an "atomic deletion" effect, generated by a stripped atom recoiling from a DNA molecule. This effect seems to be of significant importance, the inactivation cross section of this effect for fission neutrons is as much as 15% (aerobic conditions) or 55% (hypoxic) of the total, and the severity of one occurrence of atomic deletion by a single neutron is estimated as much as 3.1 +/- 1.1 times (aerobic) or 6.8 +/- 1.2 times (hypoxic) higher than the severity of one event by a single track of a charged particle interacting with DNA.
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Affiliation(s)
- Hiroshi Yamaguchi
- Department of Technological Support and Development, National Institute of Radiological Sciences, Anagawa, Chiba.
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8
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Watanabe H, Kashimoto N, Kajimura J, Ishikawa M, Kamiya K. Tumor induction by monoenergetic neutrons in B6C3F1 mice. JOURNAL OF RADIATION RESEARCH 2007; 48:205-10. [PMID: 17443058 DOI: 10.1269/jrr.0614] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
This study was undertaken to investigate induction of tumors by monoenergetic neutrons in B6C3F1 mice. Individual groups of 6 week-old animals of both sexes (about 30 mice/group) were exposed to 0.5 Gy of various monoenergetic neutrons (dose rate 0.5 cGy/min) and then observed for 13 months. The incidences of tumors (mainly liver neoplasms) in non-irradiated male and female controls were 11% and 0%, respectively. In the irradiated animals, the incidences were 53%, 50%, 60% and 43% in males, and 75%, 81%, 71%, and 85% in females, after 0.18, 0.32, 0.6 and 1.0 MeV neutron exposure, respectively. There were no significant differences in the tumor induction rate among the different energy groups.
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Affiliation(s)
- Hiromitsu Watanabe
- Department of Experimental Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University.
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Suit H, Goldberg S, Niemierko A, Ancukiewicz M, Hall E, Goitein M, Wong W, Paganetti H. Secondary carcinogenesis in patients treated with radiation: a review of data on radiation-induced cancers in human, non-human primate, canine and rodent subjects. Radiat Res 2007; 167:12-42. [PMID: 17214511 DOI: 10.1667/rr0527.1] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2005] [Accepted: 09/19/2006] [Indexed: 11/03/2022]
Abstract
Concern for risk of radiation-induced cancer is growing with the increasing number of cancer patients surviving long term. This study examined data on radiation transformation of mammalian cells in vitro and on the risk of an increased cancer incidence after irradiation of mice, dogs, monkeys, atomic bomb survivors, occupationally exposed persons, and patients treated with radiation. Transformation of cells lines in vitro increased linearly with dose from approximately 1 to approximately 4-5 Gy. At <0.1 Gy, transformation was not increased in all studies. Dose-response relationships for cancer incidence varied with mouse strain, gender and tissue/organ. Risk of cancer in Macaca mulatta was not raised at 0.25-2.8 Gy. From the atomic bomb survivor study, risk is accepted as increasing linearly to 2 Sv for establishing exposure standards. In irradiated patients, risk of cancer increased significantly from 1 to 45 Gy (a low to a high dose level) for stomach and pancreas, but not for bladder and rectum (1-60 Gy) or kidney (1-15 Gy). Risk for several organs/tissues increased substantially at doses far above 2 Gy. There is great heterogeneity in risk of radiation-associated cancer between species, strains of a species, and organs within a species. At present, the heterogeneity between and within patient populations of virtually every parameter considered in risk estimation results in substantial uncertainty in quantification of a general risk factor. An implication of this review is that reduced risks of secondary cancer should be achieved by any technique that achieved a dose reduction down to approximately [corrected] 0.1 Gy, i.e. dose to tissues distant from the target. The proportionate gain should be greatest for dose decrement to less than 2 Gy.
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Affiliation(s)
- Herman Suit
- Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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10
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Nitta Y, Satoh K, Suga S, Endo S, Nitta K. Comparison of the effectiveness of high and low LET radiations for the proportion of survivals with liver tumors at every age in (C57BL/6N x C3H/HeN) F1 mice. J Vet Med Sci 2006; 68:647-53. [PMID: 16891775 DOI: 10.1292/jvms.68.647] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To investigate the late effects of neutrons at the energy below 1 MeV on the liver carcinogenesis as a function of age, one-week old mice were exposed to 1.0 Gy monoenergetic neutrons (0.317, 0.525 and 1.026 MeV) or 137Cs gamma rays. Survival and carcinogenesis were examined by 18 months of age. Following radiation, tumor incidences in liver, Harderian gland, lung, ovary and pituitary gland were compared. The proportion of the lifespan with liver tumors exposed to neutrons to that exposed to gamma rays was calculated as a function of age. Survival rates among the three groups exposed to neutrons of different energies were not significantly different from one another but shorter than those treated with gamma rays for both sexes. With regard to liver tumor incidence evaluated at 18 months of age, the effectiveness of neutrons to gamma rays was 2.54 for females, and 2.08 for males by the factor. Levels of estrogen in the serum were similar between mice bearing liver tumors and those devoid of tumors. In conclusion, all three energies of neutrons induced similar effectiveness with respect to liver carcinogenicity. Proportions of the lifespan with liver tumors of neutron-exposed to gamma-exposed were shorter in females than males along with ages over 12 months. To obtain this factor at every age contributed for the evaluation of the biological effectiveness of radiations with the parameter of tumor incidence and latency simultaneously.
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Affiliation(s)
- Yumiko Nitta
- International Radiation Information Center, Research Institute for Radiation Biology and Medicine, Hiroshima University
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11
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Kocher DC, Apostoaei AI, Hoffman FO. Radiation effectiveness factors for use in calculating probability of causation of radiogenic cancers. HEALTH PHYSICS 2005; 89:3-32. [PMID: 15951689 DOI: 10.1097/01.hp.0000154172.48895.45] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
This paper presents so-called radiation effectiveness factors that are intended to represent the biological effectiveness of different radiation types, relative to high-energy Co gamma rays, for the purpose of estimating cancer risks and probability of causation of radiogenic cancers in identified individuals. Radiation effectiveness factors are expressed as subjective probability distributions to represent uncertainty that arises from uncertainties in estimates of relative biological effectiveness obtained from radiobiological studies of stochastic endpoints, limited data on biological effectiveness obtained from human epidemiological studies, and other judgments involved in evaluating the applicability of available information to induction of cancers in humans. Primarily on the basis of reviews and evaluations of available data by experts, probability distributions of radiation effectiveness factors are developed for the following radiation types: neutrons of energy less than 10 keV, 10-100 keV, 0.1-2 MeV (including fission neutrons), 2-20 MeV, and greater than 20 MeV; alpha particles of any energy emitted by radionuclides; photons of energy 30-250 keV and less than 30 keV; and electrons of energy less than 15 keV. Photons of energy greater than 250 keV and electrons of energy greater than 15 keV are assumed to have the same biological effectiveness as reference Co gamma rays and are assigned a radiation effectiveness factor of unity, without uncertainty. For neutrons and alpha particles, separate probability distributions of radiation effectiveness factors are developed for solid tumors and leukemias, and small corrections to represent an inverse dose-rate effect are applied to those distributions in cases of chronic exposure. A radiation effectiveness factor different from unity for 15-60 keV electrons is discussed but is not adopted due to a lack of relevant radiobiological data. Radiation effectiveness factors presented in this paper are incorporated in the Interactive RadioEpidemiological Program and were developed for use by The National Institute for Occupational Safety and Health and U.S. Department of Labor in evaluating claims for compensation for radiogenic cancers by workers at U.S. Department of Energy facilities.
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Affiliation(s)
- D C Kocher
- SENES Oak Ridge, Inc., 102 Donner Drive, Oak Ridge, TN 37830, USA.
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12
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Takada M, Mihara E, Sasaki M, Nakamura T, Honma T, Kono K, Fujitaka K. Neutron field produced by 25 MeV deuteron on thick beryllium for radiobiological study; energy spectrum. RADIATION PROTECTION DOSIMETRY 2004; 110:601-606. [PMID: 15353715 DOI: 10.1093/rpd/nch142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Biological data is necessary for estimation of protection from neutrons, but there is a lack of data on biological effects of neutrons for radiation protection. Radiological study on fast neutrons has been done at the National Institute of Radiological Sciences. An intense neutron source has been produced by 25 MeV deuterons on a thick beryllium target. The neutron energy spectrum, which is essential for neutron energy deposition calculation, was measured from thermal to maximum energy range by using an organic liquid scintillator and multi-sphere moderated 3He proportional counters. The spectrum of the gamma rays accompanying the neutron beam was measured simultaneously with the neutron spectrum using the organic liquid scintillator. The transmission by the shield of the spurious neutrons originating from the target was measured to be less than 1% by using the organic liquid scintillator placed behind the collimator. The measured neutron energy spectrum is useful in dose calculations for radiobiology studies.
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Affiliation(s)
- Masashi Takada
- National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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13
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Zhang W, Fujikawa K, Endo S, Ishikawa M, Ohtaki M, Ikeda H, Hoshi M. Energy-dependent RBE of neutrons to induce micronuclei in root-tip cells of Allium cepa onion irradiated as dry dormant seeds and seedlings. JOURNAL OF RADIATION RESEARCH 2003; 44:171-177. [PMID: 13678347 DOI: 10.1269/jrr.44.171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The relative biological effectiveness (RBE) of various energy neutrons produced from a Schenkel-type accelerator at the Research Institute for Radiation Biology and Medicine, Hiroshima University (HIRRAC), compared with 60Co gamma-ray radiation was determined. The neutron radiations and gamma-ray radiation produced good linear changes in the frequency of micronuclei induced in the root-tip cells of Allium cepa onion irradiated as dry dormant seeds (seed assay) and seedlings (seedling assay) with varying radiation doses. Therefore the RBE for radiation-induced micronuclei can be calculated as the ratio of the slopes of the fitted linear dose response for the neutron radiations and the 60Co gamma-ray radiation. The RBE values by seed assay and seedling assay decreased to 174 +/- 7, from 216 +/- 9, and to 31.4 +/- 1.0, from 45.3 +/- 1.3 (one standard error), respectively, when neutron energies increased to 1.0 MeV, from 0.2 MeV, in the present study. Furthermore, the ratio of the micronucleus induction rates of seed assay to seedling assay by gamma-ray radiation was much lower than that by neutron radiations.
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Affiliation(s)
- Wenyi Zhang
- International Radiation Information Center, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan
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Schmid E. Is there reliable experimental evidence for a low-dose RBE of about 4 for mammography X rays relative to 200 kV X rays? Radiat Res 2002; 158:778-81. [PMID: 12452781 DOI: 10.1667/0033-7587(2002)158[0778:itreef]2.0.co;2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
recently reported, on the basis of observations of neoplastic transformation in human hybrid CGL1 cells, a low-dose relative biological effectiveness (RBE(M)) of 4.3 for mammography X rays (29 kV) relative to 200 kV X rays. With reference to data in the literature, they inferred a factor of about 8 relative to 60Co gamma rays and concluded that this result is relevant to risk estimation. However, the conclusions do not appear to be valid. The data from the transformation study exhibit uncertainties in the statistical analysis that preclude any generalization of the inferred RBE(M). The data selected or inferred from the literature are likewise insufficient to support the stated RBEs. Our own uniform data set for the yields of dicentrics was obtained for widely varying photon energies with blood samples from the same donor, and it avoids interindividual variations in sensitivity as well as the differences in methodology that are associated with interlaboratory comparisons. Our data provide RBE(M) values for 29 kV X rays of 1.64 +/- 0.27 relative to 220 kV X rays and 4.75 +/- 1.67 and 6.12 +/- 2.51 relative to 60Co gamma rays.
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Affiliation(s)
- Ernst Schmid
- GSF-National Research Center for Environment and Health, Institute of Radiobiology, Neuherberg, Germany.
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15
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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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Brenner DJ, Hall EJ. Commentary 2 to Cox and Little: radiation-induced oncogenic transformation: the interplay between dose, dose protraction, and radiation quality. ADVANCES IN RADIATION BIOLOGY 2001; 16:167-79. [PMID: 11537507 DOI: 10.1016/b978-0-12-035416-0.50012-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
There is now a substantial body of evidence for end points such as oncogenic transformation in vitro, and carcinogenesis and life shortening in vivo, suggesting that dose protraction leads to an increase in effectiveness relative to a single, acute exposure--at least for radiations of medium linear energy transfer (LET) such as neutrons. Table I contains a summary of the pertinent data from studies in which the effect is seen. [table: see text] This phenomenon has come to be known as the "inverse dose rate effect," because it is in marked contrast to the situation at low LET, where protraction in delivery of a dose of radiation, either by fractionation or low dose rate, results in a decreased biological effect; additionally, at medium and high LET, for radiobiological end points such as clonogenic survival, the biological effectiveness is independent of protraction. The quantity and quality of the published reports on the "inverse dose rate effect" leaves little doubt that the effect is real, but the available evidence indicates that the magnitude of the effect is due to a complex interplay between dose, dose rate, and radiation quality. Here, we first summarize the available data on the inverse dose rate effect and suggest that it follows a consistent pattern in regard to dose, dose rate, and radiation quality; second, we describe a model that predicts these features; and, finally, we describe the significance of the effect for radiation protection.
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Affiliation(s)
- D J Brenner
- Center for Radiological Research, Columbia University, New York 10032
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17
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Abstract
There is strong evidence that biological response to ionizing radiation has a contribution from unirradiated "bystander" cells that respond to signals emitted by irradiated cells. We discuss here an approach incorporating a radiobiological bystander response, superimposed on a direct response due to direct energy deposition in cell nuclei. A quantitative model based on this approach is described for alpha-particle-induced in vitro oncogenic transformation. The model postulates that the oncogenic bystander response is a binary "all or nothing" phenomenon in a small sensitive subpopulation of cells, and that cells from this sensitive subpopulation are also very sensitive to direct hits from alpha particles, generally resulting in a directly hit sensitive cell being inactivated. The model is applied to recent data on in vitro oncogenic transformation produced by broad-beam or microbeam alpha-particle irradiation. Two parameters are used in analyzing the data for transformation frequency. The analysis suggests that, at least for alpha-particle-induced oncogenic transformation, bystander effects are important only at small doses-here below about 0.2 Gy. At still lower doses, bystander effects may dominate the overall response, possibly leading to an underestimation of low-dose risks extrapolated from intermediate doses, where direct effects dominate.
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Affiliation(s)
- D J Brenner
- Center for Radiological Research, Columbia University, New York, New York 10032, USA
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18
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Abstract
The suitability of comet assay to identify DNA damage induced by neutrons of varying energy was tested. For this purpose, monoenergetic neutrons from Hiroshima University Radiobiological Research Accelerator (HIRRAC) were used to induce DNA damage in irradiated human peripheral blood lymphocytes. The level of damage was computed as tail moment for different doses (0.125-1 Gy) and compared with the effects resulting from irradiation with (60)Co gamma. The neutron-irradiated cells exhibited longer comet tails consisting of tiny pieces of broken DNA in contrast to the streaking tails generated by (60)Co gamma. The peak biological effectiveness occurred at 0.37 and 0.57 MeV; a further increase or decrease in neutron energy led to a reduced RBE value. The RBE values, as measured by the comet assay, were 6.3, 5.4, 4.7, 4.3, 2.6, and 1.7 for 0.37, 0.57, 0.79, 0.186, 1, and 2.3 MeV neutrons. The lower RBE value obtained by the comet assay when compared to that for other biological end points is discussed. This study reports the usefulness of the alkaline comet assay for identifying DNA damage induced by neutrons of the same radiation weighting factor. The comet assay is a potential tool for use in neutron therapy, as well as a method for the rapid screening of samples from individuals accidentally exposed to radiation.
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Affiliation(s)
- N Gajendiran
- Health and Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India.
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Miller RC, Marino SA, Martin SG, Komatsu K, Geard CR, Brenner DJ, Hall EJ. Neutron-energy-dependent cell survival and oncogenic transformation. JOURNAL OF RADIATION RESEARCH 1999; 40 Suppl:53-59. [PMID: 10804994 DOI: 10.1269/jrr.40.s53] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Both cell lethality and neoplastic transformation were assessed for C3H10T1/2 cells exposed to neutrons with energies from 0.040 to 13.7 MeV. Monoenergetic neutrons with energies from 0.23 to 13.7 MeV and two neutron energy spectra with average energies of 0.040 and 0.070 MeV were produced with a Van de Graaff accelerator at the Radiological Research Accelerator Facility (RARAF) in the Center for Radiological Research of Columbia University. For determination of relative biological effectiveness (RBE), cells were exposed to 250 kVp X rays. With exposures to 250 kVp X rays, both cell survival and radiation-induced oncogenic transformation were curvilinear. Irradiation of cells with neutrons at all energies resulted in linear responses as a function of dose for both biological endpoints. Results indicate a complex relationship between RBEm and neutron energy. For both survival and transformation, RBEm was greatest for cells exposed to 0.35 MeV neutrons. RBEm was significantly less at energies above or below 0.35 MeV. These results are consistent with microdosimetric expectation. These results are also compatible with current assessments of neutron radiation weighting factors for radiation protection purposes. Based on calculations of dose-averaged LET, 0.35 MeV neutrons have the greatest LET and therefore would be expected to be more biologically effective than neutrons of greater or lesser energies.
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Affiliation(s)
- R C Miller
- Center for Radiological Research, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA.
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Tanaka K, Gajendiran N, Endo S, Komatsu K, Hoshi M, Kamada N. Neutron energy-dependent initial DNA damage and chromosomal exchange. JOURNAL OF RADIATION RESEARCH 1999; 40 Suppl:36-44. [PMID: 10804992 DOI: 10.1269/jrr.40.s36] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This study was undertaken to investigate the biological effect of monoenergetic neutrons on human lymphocyte DNA and chromosomes. Monoenergetic neutrons of 2.3, 1.0, 0.79, 0.57, 0.37 and 0.186 MeV were generated, and 252Cf neutrons and 60Co gamma-rays were also used for comparison. Biological effect was evaluated two ways. The RBE values with the comet assay were estimated as 6.3 and 5.4 at 0.37 MeV and 0.57 MeV relative to that of 60Co gamma-rays, and chromosome aberration rates were also observed in these different levels of monoenergetic neutrons. The yield of chromosome aberrations per unit dose was high at lower neutron energies with a gradual decline with 0.186 MeV neutron energy. The RBE was increased to 10.7 at 0.57 MeV from 3.9 at 252Cf neutrons and reached 16.4 as the highest RBE at 0.37 MeV, but the value decreased to 11.2 at 0.186 MeV. The response patterns of initial DNA damage and chromosome exchange were quite similar to that of LET. These results show that the intensity of DNA damage and chromosomal exchange is LET dependent. RBE of low energy neutrons is higher than that of fission neutrons. Low energy neutrons containing Hiroshima atomic bomb radiation may have created a significantly higher incidence of biological effect in atomic bomb survivors.
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Affiliation(s)
- K Tanaka
- International Radiation Information Center, Hiroshima University, Japan.
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21
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Mill AJ, Frankenberg D, Bettega D, Hieber L, Saran A, Allen LA, Calzolari P, Frankenberg-Schwager M, Lehane MM, Morgan GR, Pariset L, Pazzaglia S, Roberts CJ, Tallone L. Transformation of C3H 10T1/2 cells by low doses of ionising radiation: a collaborative study by six European laboratories strongly supporting a linear dose-response relationship. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 1998; 18:79-100. [PMID: 9656189 DOI: 10.1088/0952-4746/18/2/004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
For the assessment of radiation risk at low doses, it is presumed that the shape of the low-dose-response curve in humans for cancer induction is linear. Epidemiological data alone are unlikely to ever have the statistical power needed to confirm this assumption. Another approach is to use oncogenic transformation in vitro as a surrogate for carcinogenesis in vivo. In mid-1990, six European laboratories initiated such an approach using C3H 10T1/2 mouse cells. Rigid standardisation procedures were established followed by collaborative measurements of transformation down to absorbed doses of 0.25 Gy of x-radiation resulting in a total of 759 transformed foci. The results clearly support a linear dose-response relationship for cell transformation in vitro with no evidence for a threshold dose or for an enhanced, supralinear response at doses approximately 200-300 mGy. For radiological protection this represents a large dose, and the limitations of this approach are apparent. Only by understanding the fundamental mechanisms involved in radiation carcinogenesis will further knowledge concerning the effects of low doses become available. These results will, however, help validate new biologically based models of radiation cancer risk thus providing increased confidence in the estimation of cancer risk at low doses.
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Affiliation(s)
- A J Mill
- Faculty of Applied Sciences, University of the West of England, Bristol, UK.
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22
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Freyer GA, Palmer DA, Yu Y, Miller RC, Pandita TK. Neoplastic transformation of mouse C3H10T1/2 cells following exposure to neutrons does not involve mutation of ras gene as analyzed by SSCP and cycle sequencing. Mutat Res 1996; 357:237-44. [PMID: 8876700 DOI: 10.1016/0027-5107(96)00130-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
About 25% of human tumors contain a mutated member of the ras gene family. Neutron exposure is an occupational risk in several work places and while we know that cells exposed to neutrons can become transformed, the molecular basis of this process is not understood. To determine whether neutron-induced cellular transformation involves ras mutation, C3H10T1/2 cells were exposed to a single dose of 5.9 MeV neutrons. Type II and type III foci were isolated and established as cell lines. A total of 34 foci were selected and expanded for analysis of tumorigenicity, chromosomal aberrations and mutations in members of the ras gene family. The presence of mutations in genomic DNA in N-ras or K-ras of each focus was examined by either single-strand conformational polymorphism (SSCP) analysis or by asymmetric PCR coupled cell cycle sequence analysis. Although chromosomal aberrations were detected at metaphase, no alterations in either ras gene were detected. We conclude that in vitro neutron-induced transformation must occur through a mechanism other than ras mutation.
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Affiliation(s)
- G A Freyer
- Center for Radiological Research, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Hall EJ. Neutrons and carcinogenesis: a cautionary tale. BULLETIN DU CANCER. RADIOTHERAPIE : JOURNAL DE LA SOCIETE FRANCAISE DU CANCER : ORGANE DE LA SOCIETE FRANCAISE DE RADIOTHERAPIE ONCOLOGIQUE 1996; 83 Suppl:43s-6s. [PMID: 8949750 DOI: 10.1016/0924-4212(96)84883-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The best estimates for radiation induced cancer and leukemia are based on the Japanese survivors of Hiroshima and Nagasaki. With the earlier dosimetry systems of the 1960s, it was possible to drive an RBE (relative biological effectiveness) for neutrons from the Japanese data, because it was thought that there was a significant neutron dose at Hiroshima compared with Nagasaki. The estimated RBE of about 20 was consistent with laboratory estimates for oncogenic transformation in vitro and tumors in animals. The revised dosimetry of the 1980s [DS 86] essentially eliminated the neutron component at Hiroshima, and consequently removed the only neutron RBE estimate based on human data. However, recent neutron activation measurements indicate that there may indeed have been thermal neutrons at Hiroshima, and measurements of the ratio of inter- to intra-chromosomal aberrations in peripheral lymphocytes of survivors also tend to indicate that the biologically effective dose was dominated by neutrons. Another area in which the large biological effectiveness of neutrons assumes importance is the production of photoneutrons in high energy medical linear accelerators (Linacs). An increasing number of accelerators operating in the 18 to 20 MV range are coming into routine clinical use and at this energy, photoneutrons generated largely in the collimators result in a total body dose to the patient. The increased risk of second malignancies must be balanced against the slight improvement in percentage depth doses compared with more conventional machines operating at 6 to 10 MV, below the threshold for photoneutron production.
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Affiliation(s)
- E J Hall
- Center for Radiological Research, Columbia University, New York, NY 10032, USA
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Tanaka K, Hoshi M, Sawada S, Kamada N. Effects of 252Cf neutrons, transmitted through an iron block on human lymphocyte chromosome. Int J Radiat Biol 1994; 66:391-7. [PMID: 7930842 DOI: 10.1080/09553009414551341] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chromosome aberration of human peripheral blood lymphocytes exposed to californium-252 (252Cf) neutrons transmitted through a 15 cm thick iron block was analysed. The spectrum of the filtered neutrons ranged from 0.1 to 2 MeV with a peak at 0.7 MeV, simulating the Hiroshima atomic bomb neutron spectrum as shown in the Dosimetry System 1986 (DS86). Chromosome aberration frequencies after exposure to filtered and unfiltered 252Cf radiation were compared. Acentric ring chromosomes were significantly increased (p < 0.05) in the filtered condition. However, yields of dicentrics and centric rings induced by the filtered neutrons were not statistically different from those induced by the unfiltered neutrons (p > 0.1). The relative biological effectiveness (RBE) of the neutrons with respect to the formation of dicentrics and centric rings was 10.9 and 12.3 in the filtered and unfiltered conditions respectively, but the difference was not statistically significant. These results provide useful information for the re-evaluation of the biological effect of the Hiroshima atomic bomb radiations.
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Affiliation(s)
- K Tanaka
- Department of Hematology, Hiroshima University, Japan
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Yang CH, Craise LM. Development of human epithelial cell systems for radiation risk assessment. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1994; 14:115-120. [PMID: 11538024 DOI: 10.1016/0273-1177(94)90459-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The most important health effect of space radiation for astronauts is cancer induction. For radiation risk assessment, an understanding of carcinogenic effect of heavy ions in human cells is most essential. In our laboratory, we have successfully developed a human mammary epithelial cell system for studying the neoplastic transformation in vitro. Growth variants were obtained from heavy ion irradiated immortal mammary cell line. These cloned growth variants can grow in regular tissue culture media and maintain anchorage dependent growth and density inhibition property. Upon further irradiation with high-LET radiation, transformed foci were found. Experimental results from these studies suggest that multiexposure of radiation is required to induce neoplastic transformation of human epithelial cells. This multihits requirement may be due to high genomic stability of human cells. These growth variants can be useful model systems for space flight experiments to determine the carcinogenic effect of space radiation in human epithelial cells.
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Affiliation(s)
- C H Yang
- NASA Johnson Space Center, Houston, TX 77058, USA
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26
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Edwards AA. Chromosomal data relevant for Q values. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1992; 12:421-430. [PMID: 11537040 DOI: 10.1016/0273-1177(92)90139-o] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It has been known for many years that relationships between absorbed dose and biological effect vary with the type of radiation. In particular, neutrons and alpha particles are more damaging than x or gamma radiations. This applies to a range of biological effects such as cell killing, chromosome aberrations, cell mutation, cell transformation as well as life shortening and cancer induction in animals. The application of this knowledge to devise a scheme for specifying the quality factor (Q) in radiological protection has been the subject of much debate. There are no tumour data in humans from which the quality factor may be derived. The problems of using animal and cell transformation data which are probably the next best choice are discussed. The extensive data base on chromosomal aberrations in human lymphocytes is described and discussed in terms of relevance to deducing quality factors. Particular emphasis is placed on data obtained at low doses and low dose rates.
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Affiliation(s)
- A A Edwards
- National Radiological Protection Board, Chilton, Oxon, U.K
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27
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Craise LM, Prioleau JC, Stampfer MR, Rhim JS. Chromosomal changes in cultured human epithelial cells transformed by low- and high-LET radiation. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1992; 12:127-136. [PMID: 11537000 DOI: 10.1016/0273-1177(92)90099-j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
For a better assessment of radiation risk in space, an understanding of the responses of human cells, especially the epithelial cells, to low- and high-LET radiation is essential. In our laboratory, we have successfully developed techniques to study the neoplastic transformation of two human epithelial cell systems by ionizing radiation. These cell systems are human mammary epithelial cells (H184B5) and human epidermal keratinocytes (HEK). Both cell lines are immortal, anchorage dependent for growth, and nontumorigenic in athymic nude mice. Neoplastic transformation was achieved by irradiating cells successively. Our results showed that radiogenic cell transformation is a multistep process and that a single exposure of ionizing radiation can cause only one step of transformation. It requires, therefore, multihits to make human epithelial cells fully tumorigenic. Using a simple karyotyping method, we did chromosome analysis with cells cloned at various stages of transformation. We found no consistent large terminal deletion of chromosomes in radiation-induced transformants. Some changes of total number of chromosomes, however, were observed in the transformed cells. These transformants provide an unique opportunity for further genetic studies at a molecular level.
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Balcer-Kubiczek EK, Harrison GH. Lack of dose rate modification (0.0049 vs. 0.12 Gy/min) of fission-neutron-induced neoplastic transformation in C3H/10T1/2 cells. Int J Radiat Biol 1991; 59:1017-26. [PMID: 1674268 DOI: 10.1080/09553009114550901] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Clonogenic survival and neoplastic transformation of asynchronous cultures of C3H/10T1/2 cells were used to assay the effect of dose protraction of reactor-produced fission neutrons. Cells were exposed to eight neutron doses ranging from 0.05 to 0.9 Gy delivered at 11.7 or at 0.49 cGy/min. For each dose level, high and low dose rate irradiations were performed on the same day. At each dose a similar effectiveness of fission neutron irradiation at high or low dose rates was measured for both cell survival and transformation. The combined high and low dose-rate data were analysed by two- or three-parameter models. Depending on the model used, values of the effectiveness per unit dose derived as parameters of linear terms of the respective dose-response curves were 0.9-1.2 Gy-1 for clonogenic survival and 5-8 x 10(-4) Gy-1 for neoplastic transformation. It is concluded that the modification of fission neutron dose-response curves by dose rate is negligible or absent in the range of doses and dose rates examined, in contrast to results with other sources of fission or fast neutrons.
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Affiliation(s)
- E K Balcer-Kubiczek
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore 21201
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Calkins J, Einspenner M, Azzam E, Kunhi M, Sigut D, Hannan M. Observations and an interpretation of dose-response relationships for cellular transformation in terms of induced (T) repair. Int J Radiat Biol 1991; 59:41-51. [PMID: 1671074 DOI: 10.1080/09553009114550041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Both radiation-induced lethality and transformation frequency have been observed to plateau or diminish abruptly at relatively low dose levels and then increase with increasing doses, but at a reduced incremental rate. Discontinuities in dose-response relationships are postulated to correspond to the induction of a repair system ('T' repair) not functional at lower doses, i.e. below the induction threshold dose (Tt). Anomalies (discontinuities) in dose-response relationships and effects of dose fractionation previously noted are qualitatively explained in terms of this model.
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Affiliation(s)
- J Calkins
- Department of Biomedical Physics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
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30
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Redpath JL, Hill CK, Jones CA, Sun C. Fission-neutron-induced expression of a tumour-associated antigen in human cell hybrids (HeLa x skin fibroblasts): evidence for increased expression at low dose rate. Int J Radiat Biol 1990; 58:673-80. [PMID: 1976727 DOI: 10.1080/09553009014552021] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The induction of a tumour-associated antigen in a human cell hybrid line (HeLa x skin fibroblast) following exposure to fission neutrons of average energy 0.85 MeV (Janus reactor, Argonne National Laboratory) at two dose rates, 0.086 and 10.3 cGy/min, has been examined. The dose-response data obtained indicate the lower dose rate to be 2.9-fold more effective than the higher in inducing expression of the tumour-associated antigen, while there was no significant dose-rate effect in terms of cell killing. These results are qualitatively in agreement with previous observations using neutrons from the Janus reactor for the neoplastic transformation of C3H10T1/2 cells and Syrian hamster embryo cells.
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Affiliation(s)
- J L Redpath
- Department of Radiological Sciences, University of California, Irvine 92715
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31
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Brenner DJ, Quan H. Confidence limits for low induced frequencies of oncogenic transformation in the presence of a background. Int J Radiat Biol 1990; 57:1031-45. [PMID: 1970991 DOI: 10.1080/09553009014551141] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The problem is addressed of assessing realistic confidence limits for oncogenic transformation rates when the incidence of transformation is small, and there is a background present. It is shown that the commonly used approximations for assessing the confidence interval on the radiation-induced transformation rate (t1) and the control rate (t2) are inadequate when only a small number of transformants are observed. Accurate techniques are described for these cases for the estimation of confidence limits of t1, t2 and also t1-t2.
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Affiliation(s)
- D J Brenner
- Center for Radiological Research, Columbia University, New York, NY 10032
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Abstract
Modern screen-film mammography with molybdenum-anode X rays results in tissue doses being delivered primarily by photons with an energy of less than 20 keV. Such photons interact with tissue predominantly through the photoelectric effect, producing low-energy electrons that have different patterns of energy deposition at the cellular level compared with those from higher-energy X rays. These differences result in low doses of typical molybdenum-based mammography X rays having an estimated radiobiological effectiveness of approximately 1.3 compared with 80 kVp or 250 kVp X rays, and approximately 2 compared with higher-energy gamma rays. Thus the risk from mammography could be higher, by such factors, than previously estimated. This would result in the optimal age for beginning mammographic screening, derived from risk-benefit ratios, being increased by at least 1-2 years and possibly by as many as 10 years.
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Affiliation(s)
- D J Brenner
- Radiological Research Laboratories, College of Physicians and Surgeon Columbia University, New York, NY 10032
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