Comparative study of the effects of different radiation qualities on normal human breast cells

Abstract

BackgroundAs there is a growing number of long-term cancer survivors, the incidence of carcinogenesis as a late effect of radiotherapy is getting more and more into the focus. The risk for the development of secondary malignant neoplasms might be significantly increased due to exposure of healthy tissue outside of the target field to secondary neutrons, in particular in proton therapy. Thus far, the radiobiological effects of these neutrons and a comparison with photons on normal breast cells have not been sufficiently characterised.MethodsMCF10A cells were irradiated with doses of up to 2 Gy with neutrons of different energy spectra and X-rays for comparison. The biological effects of neutrons with a broad energy distribution (<E n > = 5.8 MeV), monoenergetic neutrons (1.2 MeV, 0.56 MeV) and of the mixed field of gamma’s and secondary neutrons (<E n > = 70.5 MeV) produced by 190 MeV protons impinging on a water phantom, were analysed. The clonogenic survival and the DNA repair capacity were determined and values of relative biological effectiveness were compared. Furthermore, the influence of radiation on the sphere formation was observed to examine the radiation response of the potential fraction of stem like cells within the MCF10A cell population.ResultsX-rays and neutrons caused dose-dependent decreases of survival fractions after irradiations with up to 2 Gy. Monoenergetic neutrons with an energy of 0.56 MeV had a higher effectiveness on the survival fraction with respect to neutrons with higher energies and to the mixed gamma - secondary neutron field induced by proton interactions in water. Similar effects were observed for the DNA repair capacity after exposure to ionising radiation (IR). Both experimental endpoints provided comparable values of the relative biological effectiveness. Significant changes in the sphere formation were notable following the various radiation qualities.ConclusionThe present study compared the radiation response of MCF10A cells after IR with neutrons and photons. For the first time it was shown that monoenergetic neutrons with energies around 1 MeV have stronger radiobiological effects on normal human breast cells with respect to X rays, to neutrons with a broad energy distribution (<E n > = 5.8 MeV), and to the mixed gamma - secondary neutron field given by interactions of 190 MeV protons in water. The results of the present study are highly relevant for further investigations of radiation-induced carcinogenesis and are very important in perspective for a better risk assessment after secondary neutron exposure in the field of conventional and proton radiotherapy.Electronic supplementary materialThe online version of this article (10.1186/s13014-017-0895-8) contains supplementary material, which is available to authorized users.

A microdosimetric analysis of the interactions of mono-energetic neutrons with human tissue

“…A similar approach was recently taken by the ANDANTE project [81], a multidisciplinary research collaboration who investigated the risk of neutron carcinogenesis through radiobiological experiments [82], numerical studies [63], and epidemiological models [83]. Building on previous work done by Satoh et al [12] on the depth and energy dependence of secondary charged-particle dose contributions, Baiocco et al [63] studied the depth dependence of single event microdosimetric distributions for external, mono-energetic neutron sources.…”

Development of zebrafish embryo model, an alternative in vivo vertebrate system for radiation biology research

“…We have observed that the 1 MeV mean energy mixed neutron-photon beam proved to be 4 times more effective biologically than the 18 MeV mean energy mixed neutron-photon radiation. The result of the calculated RBE values was well supported by the experiments performed using broad energy spectra, mixed neutron-photon and monoenergetic neutron beams (Juerß et al, 2017). The high reliability of the zebrafish embryo survival assay was revealed during the repeated neutron irradiation experiments, therefore, survival analysis is considered as reliable tool for RBE measurements.…”

A novel vertebrate system for the examination and direct comparison of the relative biological effectiveness for different radiation qualities and sources

“…Recent calculations on neutron transport with track structures up to DNA damage induction at different neutron energy levels have provided a better understanding on the physical and biochemical mechanism and have resulted in strong correlation of the RBE to neutron energy (Baiocco et al 2016). The result of the calculated values were well supported by the experiments performed using broad energy spectra, mixed neutron-photon and monoenergetic neutron beams (Juerß et al 2017).…”