The German Thorotrast Cohort Study: a review and how to get access to the data

Incidence risk of hepatobiliary malignant neoplasms in the cohort of workers chronically exposed to ionizing radiation

The increased risk of liver malignancies was found in workers of the first Russian nuclear production facility, Mayak Production Association, who had been chronically exposed to gamma rays externally and to alpha particles internally due to plutonium inhalation. In the present study, we updated the radiogenic risk estimates of the hepatobiliary malignancies using the extended follow-up period (1948-2018) of the Mayak worker cohort and the improved «Mayak worker dosimetry system-2013». The cohort comprised 22,377 workers hired at the Mayak PA between 1948 and 1982. The analysis considered 62 liver malignancies (32 hepatocellular carcinomas, 13 intrahepatic cholangiocarcinomas, 16 angiosarcomas, and 1 anaplastic cancer) and 33 gallbladder adenocarcinomas. The analysis proved the positive significant association of the liver malignancy risk (the total of histological types, hepatocellular carcinoma) with the liver absorbed alpha dose from internal exposure. The excess relative risk per Gy (95% confidence interval) of alpha dose (the linear model) was 7.56 (3.44; 17.63) for the total of histological types and 3.85 (0.95; 13.30) for hepatocellular carcinoma. Indications of non-linearity were observed in the dose-response for internal exposure to alpha radiation. No impact of external gamma-ray exposure on the liver malignancy incidence was found. In the study cohort, the number of angiosarcomas among various types of liver malignancies was very high (25.8%), and most of these tumors (73.3%) were registered in individuals internally exposed to alpha radiation at doses ranging between 6.0 and 21.0 Gy. No association with chronic occupational radiation exposure was observed for the incidence of gallbladder malignancies.

Mechanistic insights into Thorium-232 induced liver carcinogenesis: The driving role of Wnt/β-catenin signaling pathway

Thorium-232 (Th-232), a naturally-occurring radioactive element with high potential of nuclear fuel is now being utilized in advanced nuclear reactors for CO2-free energy generation. To achieve all-round capability in Th-fuel cycle for health and environment, understanding the biological effects of Th-232 at cellular and molecular level are extremely important. The present study investigated long-term effects (6 and 12 months) of Th-232 (4, 10 and 20 mg/kg) on gene expression in mice liver (major target organ). Analysis of differentially expressed genes (DEGs, ≥2.0 folds, p < 0.05) showed that with the increase of Th dose (4 to 20 mg/kg), the number of upregulated DEGs increased and the number of downregulated DEGs decreased significantly. A significant number of upregulated DEGs (10 genes in 6 months and 14 genes in 12 months) were found common between 4 and 20 mg/kg. Gene Ontology analysis revealed significant (Padj ~ 10-6-10-28) enrichment of upregulated DEGs for metabolic process, signal transduction, cell death, cell cycle and cell proliferation. KEGG pathway analysis showed DEGs significantly enriched in several cancer-related pathways including hepatocellular carcinoma (HCC). Protein-protein interaction analysis further revealed statistically significant functional interaction (p-value ~10-6-10-10) among the proteins of HCC, which identified β-catenin as one of the most significant signaling nodes in association with myc, an oncogene and p53, a tumor suppressor. Importantly, these results were corroborated by quantitative real time-polymerase chain reaction and western blotting in liver tissues of animals exposed to Th-232. This study insights Wnt/β-catenin signaling network attributable to drive Th-induced liver carcinogenesis, which may have significant implications for management of long-term effects of Th-232.

Role of calcium ion channels and cytoskeletal proteins in Thorium-232 induced toxicity in normal human liver cells (WRL 68) and its validation in swiss mice

Hepatic disorders reported in humans exposed to Thorium-232 (Th-232) rationalizes the present study investigating the toxicological response of normal human liver cells (WRL 68) and its validation in Swiss mice. Cell count analysis of WRL 68 cells-treated with Th-nitrate (1-200 μM) estimated IC50 of ∼24 μM (at 24 h) and 35 μM (at 48 h). Analysis of cell viability (trypan blue assay) showed the IC50 of ∼172 μM. Phase contrast bright-field microscopy revealed Th-induced morphological changes and cell-released microvesicle-like structures in extracellular space. Th-estimation by ICP-MS (Inductively-coupled plasma mass-spectrometry) showed uptake of Th by cells as a function of concentration and incubation time. Employing DTPA as a chelating agent in cell harvesting solution, cell-internalized/strongly-bound Th was estimated to be ∼42% of total incubated Th. Th-uptake studies in the presence of ion-channel specific inhibitors (e.g. nifedipine, thapsigargin) revealed the role of plasma membrane calcium channels and cytoplasmic calcium in modulating the Th-uptake. Transmission electron microscopy of Th-treated cells showed cell-derived extracellular vesicles, alterations in the shape and size of nucleus and mitochondria as well as cytoplasmic inclusions. The order of Th accumulation in various sub-cellular protein fractions was found to be as cytoskeleton (43%) > cytoplasmic (15%) > chromatin (7%) > nuclear (5%) & membrane (5%). Immunofluorescence analysis of WRL 68 cells showed that Th significantly altered the expression of cytoskeleton proteins (F-actin and keratin), which was further validated in liver tissues of Swiss mice administered with Th-232. Findings herein highlight the role of calcium channels and cytoskeleton in Th-induced toxicity. Keywords: Thorium toxicity; Liver cells; Calcium channels; Sub-cellular targets, Cytoskeleton; Swiss Mice.

Radiation databases and archives - examples and comparisons

Studies of ionizing radiation effects through the archiving of data began with standardizing medical treatments in the early 1900s shortly after the discovery of X-rays. Once the breadth of the delayed effects of ionizing radiation was recognized, the need for long-term follow up became apparent. There are now many human archives of data from nuclear disasters and accidents, occupational exposures, and medical procedures. Planned animal irradiation experiments began around the time of the Cold War and included a variety of doses, fractions, dose rates, and types of ionizing radiation. The goal of most of these studies was to supplement information coming from human data through carefully planned experimental conditions and immediate and uninterrupted data collection. This review aims to highlight major archives and databases that have shaped the field of radiation biology and provide a broad range of the types of datasets currently available. By preserving all of these data and tissue sets, radiation biologists can combine databases and conduct large-scale analyses of detailed existing data and perform new assays with cutting edge scientific approaches.