8
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Variation of 4 MV X-ray dose rate strongly impacts biological response both in vitro and in vivo

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Whereas an RBE > 1 is described for very low-energy X-ray beams (in the range of 25–50 kV), there is a consensus that the RBE of X-rays (from 0.1 to 3 MeV) is equal to 1, whatever the energy or dose rate of the beam. Comparisons of X-ray beam dose rates are scarce even though these beams are widely used in medical diagnosis or radiotherapy. By using two dose rates (0.63 and 2.5 Gy.min −1) of high-energy X-rays on normal endothelial cells (HUVECs), we have studied the clonogenic assay, but also viability/mortality, cell cycle analysis and measured cellular senescence by flow cytometry, and have performed gene analysis on custom arrays. In order to consolidate these data, we performed localized irradiation of exteriorized small intestine at 0.63 and 2.5 Gy.min −1. Interestingly, in vivo validation has shown a significantly higher loss of weight at the higher dose when irradiating to 19 Gy a small fragment of exteriorized small intestine of C57Bl6J mice. Nevertheless, no significant differences were observed in lesioned scores between the two dose rates, while bordering epithelium staining indicated twofold greater severe damage at 2.5 Gy.min −1 compared to 0.63 Gy.min −1 at one week post-irradiation. Taken together, these experiments systematically show that the relative biological effectiveness of photons is different from 1 when varying the dose rate of high-energy X-rays. Moreover, these results strongly suggest that, in support of clonogenic assay, multiparametric analysis should be considered to provide an accurate evaluation of the outcome of irradiated cells.

          Related collections

          Most cited references 43

          • Record: found
          • Abstract: found
          • Article: not found

          Relative biological effectiveness (RBE) values for proton beam therapy. Variations as a function of biological endpoint, dose, and linear energy transfer.

          Proton therapy treatments are based on a proton RBE (relative biological effectiveness) relative to high-energy photons of 1.1. The use of this generic, spatially invariant RBE within tumors and normal tissues disregards the evidence that proton RBE varies with linear energy transfer (LET), physiological and biological factors, and clinical endpoint. Based on the available experimental data from published literature, this review analyzes relationships of RBE with dose, biological endpoint and physical properties of proton beams. The review distinguishes between endpoints relevant for tumor control probability and those potentially relevant for normal tissue complication. Numerous endpoints and experiments on sub-cellular damage and repair effects are discussed. Despite the large amount of data, considerable uncertainties in proton RBE values remain. As an average RBE for cell survival in the center of a typical spread-out Bragg peak (SOBP), the data support a value of ~1.15 at 2 Gy/fraction. The proton RBE increases with increasing LETd and thus with depth in an SOBP from ~1.1 in the entrance region, to ~1.15 in the center, ~1.35 at the distal edge and ~1.7 in the distal fall-off (when averaged over all cell lines, which may not be clinically representative). For small modulation widths the values could be increased. Furthermore, there is a trend of an increase in RBE as (α/β)x decreases. In most cases the RBE also increases with decreasing dose, specifically for systems with low (α/β)x. Data on RBE for endpoints other than clonogenic cell survival are too diverse to allow general statements other than that the RBE is, on average, in line with a value of ~1.1. This review can serve as a source for defining input parameters for applying or refining biophysical models and to identify endpoints where additional radiobiological data are needed in order to reduce the uncertainties to clinically acceptable levels.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            ACTION OF X-RAYS ON MAMMALIAN CELLS

            The effects of x-irradiation have been quantitatively studied on single cells of a human cervical carcinoma (HeLa) under conditions such that 100 per cent of the unirradiated cells reproduce in isolation to form macroscopic colonies. This technique eliminates complexities due to interactions of members of large cell populations. Survival of single cells (defined as the ability to form a macroscopic colony within 15 days) yields a typical 2 hit curve when plotted against x-ray dose. The initial shoulder extends to about 75 r, after which a linear logarithmic survival rate is obtained, in which the dose needed to reduce survivors to 37 per cent is 96 r. This radiation sensitivity is tens to hundreds of times greater than that of any microorganism for which the equivalent function bas been studied. Evidence, though not proof, is presented that the lethal effect is due to a radiation-induced genetic defect which, however, cannot be a simple single gene inactivation. The locus of the action could be chromosomal. Beginning at doses of 100 r, or possibly earlier, growth-delaying effects of radiation are visible. Cells in which the ability to reproduce has been destroyed by doses below 800 r, can still multiply several times. At higher doses even a single cell division is precluded. A large proportion of the cells killed by radiation at any dose gives rise to one or more giant cells. These metabolize actively, grow to huge proportions but never reproduce under the experimental conditions employed. Methods of preparing large populations of giant cells are described. These giants are particularly susceptible to virus action. Some of the irradiated cells disappear from the plate, presumably by disintegration. This action of radiation is by far the least efficient, since even after 10,000 r, 5 to 10 per cent of the original cell inoculum is recoverable as giants.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Methods to detect biomarkers of cellular senescence: the senescence-associated beta-galactosidase assay.

              Most normal human cells undergo cellular senescence after accruing a fixed number of cell divisions, or are challenged by a variety of potentially oncogenic stimuli, in culture and most likely in vivo. Cellular senescence is characterized by an irreversible growth arrest and certain altered functions. Senescent cells in culture are identified by their inability to undergo DNA synthesis, a property also shared by quiescent cells. Several years ago, we described a biomarker associated with the senescent phenotype, a senescence associated beta-galactosidase (SA-beta-gal), which is detected by histochemical staining of cells using the artificial substrate X-gal. The presence of the SA-beta-gal biomarker is independent of DNA synthesis and generally distinguishes senescent cells from quiescent cells. The method to detect SA-beta-gal is a convenient, single cell-based assay, which can identify senescent cells even in heterogeneous cell populations and aging tissues, such as skin biopsies from older individuals. Because it is easy to detect, SA-beta-gal is currently a widely used biomarker of senescence. Here we describe a method to detect SA-beta-gal in detail, including some recent modifications.
                Bookmark

                Author and article information

                Contributors
                vincent.paget@irsn.fr
                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group UK (London )
                2045-2322
                27 April 2020
                27 April 2020
                2020
                : 10
                Affiliations
                [1 ]ISNI 0000 0001 1414 6236, GRID grid.418735.c, Institute for Radiological Protection and Nuclear Safety (IRSN), Department of RAdiobiology and Regenerative Medicine (SERAMED), Laboratory of Medical Radiobiology (LRMed), ; Fontenay-aux-Roses, 92260 France
                [2 ]ISNI 0000 0001 1414 6236, GRID grid.418735.c, Institute for Radiological Protection and Nuclear Safety (IRSN), Department of Radiobiology and Regenerative Medicine (SERAMED), ; Fontenay-aux-Roses, France
                [3 ]ISNI 0000 0001 1414 6236, GRID grid.418735.c, Institute for Radiological Protection and Nuclear Safety (IRSN), Department of Radiobiology and Regenerative Medicine (SERAMED), Laboratory of Radiobiology of Accidental Exposures (LRAcc), ; Fontenay-aux-Roses, France
                [4 ]ISNI 0000 0001 2298 5443, GRID grid.410455.1, Electricité de France, Cap Ampère, ; Saint-Denis, France
                Article
                64067
                10.1038/s41598-020-64067-4
                7184727
                32341396
                78fbf3b8-03fe-420f-9854-9c8a4ee5cb61
                © The Author(s) 2020

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

                Categories
                Article
                Custom metadata
                © The Author(s) 2020

                Uncategorized

                senescence, cell-cycle exit

                Comments

                Comment on this article