RENEB Inter-Laboratory Comparison 2021: Inter-Assay Comparison of Eight Dosimetry Assays.

Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.

Genotoxic risk of ethyl-paraben could be related to telomere shortening.

The ability of parabens to promote the appearance of multiple cancer hallmarks in breast epithelium cells provides grounds for regulatory review of the implication of the presence of parabens in human breast tissue. It is well documented that telomere dysfunction plays a significant role in the initiation of genomic instability during carcinogenesis in human breast cancer. In the present study, we evaluated the genotoxic effect of ethyl 4-hydroxybenzoate (ethyl-paraben), with and without metabolic activation (S9), in studies following OECD guidelines. We observed a significant increase in genotoxic damage using the Mouse Lymphoma Assay and in vitro micronucleus (MN) tests in the L5178Y cell line in the presence of S9 only after a short exposure. A high frequency of MN was observed in the TK6 cells after a short exposure (3 h) in the presence of S9 and a long exposure (26 h) without S9. We found significant increases in the MN frequency and induced chromosomal aberrations in the lymphocytes of only one donor after ethyl-paraben exposure in the presence of S9 after a short exposure. Cytogenetic characterization of the paraben-treated cells demonstrated telomere shortening associated with telomere loss and telomere deletions in L5178Y and TK6 cells and lymphocytes of the paraben sensitive-donor. In a control cohort of 68 human lymphocytes, telomere length and telomere aberrations were age-dependent and showed high inter-individual variation. This study is the first to link telomere shortening and the genotoxic effect of ethyl paraben in the presence of S9 and raises the possibility that telomere shortening may be a proxy for underlying inter-individual sensitivity to ethyl-paraben. Copyright © 2016 John Wiley & Sons, Ltd.

Telomere shortening: a new prognostic factor for cardiovascular disease post-radiation exposure.

Telomere length has been proposed as a marker of mitotic cell age and as a general index of human organism aging. Telomere shortening in peripheral blood lymphocytes has been linked to cardiovascular-related morbidity and mortality. The authors investigated the potential correlation of conventional risk factors, radiation dose and telomere shortening with the development of coronary artery disease (CAD) following radiation therapy in a large cohort of Hodgkin lymphoma (HL) patients. Multivariate analysis demonstrated that hypertension and telomere length were the only independent risk factors. This is the first study in a large cohort of patients that demonstrates significant telomere shortening in patients treated by radiation therapy who developed cardiovascular disease. Telomere length appears to be an independent prognostic factor that could help determine patients at high risk of developing CAD after exposure in order to implement early detection and prevention.