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Purpose: To identify sensitive genes for space radiation, we integrated the transcriptomic samples of spaceflight mice from GeneLab and predicted the radiation doses absorbed by individuals in space., Methods and Materials: A single-sample network (SSN) for each individual sample was constructed. Then, using machine learning and genetic algorithms, we built the regression models to predict the absorbed dose equivalent based on the topological structure of SSNs. Moreover, we analyzed the SSNs from each tissue and compared the similarities and differences among them., Results: Our model exhibited excellent performance with the following metrics: R 2 = 0.980 , MSE = 6.74 e - 04 , and the Pearson correlation coefficient of 0.990 ( p value <.0001) between predicted and actual values. We identified 20 key genes, the majority of which had been proven to be associated with radiation. However, we uniquely established them as space radiation sensitive genes for the first time. Through further analysis of the SSNs, we discovered that the different tissues exhibited distinct mechanisms in response to space stressors., Conclusions: The topology structures of SSNs effectively predicted radiation doses under spaceflight conditions, and the SSNs revealed the gene regulatory patterns within the organisms under space stressors.

Purpose: People are exposed to low-dose radiation in medical diagnosis, occupational, or life circumstances, but the effect of low-dose radiation on human health is still controversial. The biological effects of radiation below 100 mGy are still unproven. In this study, we observed the effects of low-dose radiation (100 mGy) on gene expression in human coronary artery endothelial cells (HCAECs) and its effect on molecular signaling., Materials and Methods: HCAECs were exposed to 100 mGy ionizing radiation at 6 mGy/h (low-dose-rate) or 288 mGy/h (high-dose-rate). After 72 h, total RNA was extracted from sham or irradiated cells for Quant-Seq 3'mRNA-Seq, and bioinformatic analyses were performed using Metascape. Gene profiling was validated using qPCR., Results: Compared to the non-irradiated control group, 100 mGy of ionizing radiation at 6 mGy/h altered the expression of 194 genes involved in signaling pathways related to heart contraction, blood circulation, and cardiac myofibril assembly differentially. However, 100 mGy at 288 mGy/h altered expression of 450 genes involved in cell cycle-related signaling pathways, including cell division, nuclear division, and mitosis differentially. Additionally, gene signatures responding to low-dose radiation, including radiation dose-specific gene profiles (HIST1H2AI, RAVER1, and POTEI) and dose-rate-specific gene profiles (MYL2 for the low-dose-rate and DHRS9 and CA14 for the high-dose-rate) were also identified., Conclusions: We demonstrated that 100 mGy low-dose radiation could alter gene expression and molecular signaling pathways at the low-dose-rate and the high-dose-rate differently. Our findings provide evidence for further research on the potential impact of low-dose radiation on cardiovascular function.

Purpose: Ionizing radiation has very complex biological effects, such as inducing damage to DNA and proteins, ionizing water molecules to produce toxic free radicals, and triggering genetic and somatic effects. Understanding the biomolecular response mechanism of radiation is very important for the prevention and treatment of radiation diseases. However, function information of these radiation-associated genes is hidden in numbers of scientific papers and databases, making it difficult to understand the response mechanism of ionizing radiation. Materials and methods: We collected radiation-associated genes by literature and database mining. Literature and database mining was performed on the basis of biomedical literature from PubMed and gene expression datasets from GEO respectively. Results: We built an ionizing radiation related knowledgebase RadAtlas 1.0 (http://biokb.ncpsb.org/radatlas), which contains 598 radiation-associated genes compiled from literature mining, and 611 potential radiation-associated genes collected from gene expression datasets by differential gene expression analysis. We also provide a user-friendly web interface that offers multiple search methods. Conclusions: RadAtlas collected a large amount of information about genes, biological processes, and pathways related to ionizing radiation. It is the first attempt to provide a comprehensive catalog of radiation-associated genes with literature evidence and potential radiation-associated genes with differential expression evidence. We believe that RadAtlas would be a helpful tool to understand the response mechanism to ionizing radiation.

Purpose: Design and characterization of a radiation biodosimetry device are complicated by the fact that the requisite data are not available in the intended use population, namely humans exposed to a single, whole-body radiation dose. Instead, one must turn to model systems. We discuss our studies utilizing healthy, unexposed humans, human bone marrow transplant patients undergoing total body irradiation (TBI), non-human primates subjected to the same irradiation regimen received by the human TBI patients and NHPs given a single, whole-body dose of ionizing radiation. Materials and Methods: We use Bayesian linear mixed models to characterize the association between NHP and human expression patterns in radiation response genes when exposed to a common exposure regimen and across exposure regimens within the same species. Results: We show that population average differences in expression of our radiation response genes from one to another model system are comparable to typical differences between two randomly sampled members of a given model system and that these differences are smaller, on average, for linear combinations of the probe data and for the model-based combinations employed for dose prediction as part of a radiation biodosimetry device. Conclusions: Our analysis suggests that dose estimates based on our gene list will be accurate when applied to humans who have received a single, whole-body exposure to ionizing radiation.

Purpose: To examine the effects of low-dose exposure to uranium with a systems biology approach, a multiscale high-throughput multi-omics analysis was applied with a protocol for chronic exposure to the rat kidney. Methods: Male and female rats were contaminated for nine months through their drinking water with a nontoxic solution of uranyl nitrate. A multiscale approach enabled clinical monitoring associated with metabolomic and transcriptomic (mRNA and microRNA) analyses. Results: A sex-interaction effect was observed in the kidney, urine, and plasma metabolomes of contaminated rats. Moreover, urine and kidney metabolic profiles correlated and confirmed that the primary dysregulated metabolisms are those of nicotinate-nicotinamide and of unsaturated fatty acid biosynthesis. Upstream of the metabolic pathways, transcriptomic profiles of the kidney reveal gene activity focused on gene regulation mechanisms, cell signaling, cell structure, developmental processes, and cell proliferation. Examination of epigenetic post-transcriptional gene regulation processes showed significant dysregulation of 70 micro-RNAs. The multi-omics approach highlighted the activities of the cells' biological processes on multiple scales through analysis of gene expression, confirmed by changes observed in the metabolome. Conclusion: Our results showed changes in multi-omic profiles of rats exposed to low doses of uranium contamination, compared with controls. These changes involved gene expression as well as modifications in the transcriptome and the metabolome. The metabolomic profile confirmed that the main molecular targets of uranium in kidney cells are the metabolism of nicotinate-nicotinamide and the biosynthesis of unsaturated fatty acids. Additionally, gene expression analysis showed that the metabolism of fatty acids is targeted by processes associated with cell function. These results demonstrate that multiscale systems biology is useful in elucidating the most discriminative pathways from genomic to metabolomic levels for assessing the biological impact of this low-level environmental exposure, i.e. the exposome.

Purpose: The application of radiation therapy (RT) is not only used to treat cancer, in Germany, it is also an accepted and empirically established treatment of patients with benign diseases at low doses. The immune modulatory response generated by low-dose RT has a supporting anti-inflammatory effect within the treatment of inflammation-related diseases. The aim of this study was to investigate the effect of ionizing radiation (IR) on the expression and secretion of inflammatory mediators by endothelial cells (ECs) exposed to low and moderate doses., Methods: Non-activated and activated EC were irradiated with doses between 0.01 Gy and 2 Gy with X-rays. Using a multiplex-assay, protein values of interleukin-8 (IL-8), granulocyte macrophage colony-stimulating factor (G-CSF) and platelet-derived growth factor (PDGF-BB) were measured in the supernatant at different time-points. To investigate possible differences between mRNA expression and protein secretion after IR, the mRNA expression of IL-8, G-CSF and PDGF-BB was determined by real-time quantitative PCR., Results: Radiation treatment caused non-linear dose dependent effects on pro-inflammatory cytokine secretion of IL-8; G-CSF and PDGF-BB. The mRNA-expression levels of those cytokines were non-linear dose-dependent and differed from protein level in the culture supernatant., Conclusions: This study provides deeper insights into the radiobiological effects of radiation doses below 0.3 Gy, in particular 0.05 Gy, and their significant immunomodulatory properties on EC, which is very important in order to assess the effect of LD-IR on EC.

Purpose: To unravel the role of the vasculature in radiation-induced brain tissue damage., Materials and Methods: Postnatal day 14 mice received a single dose of 10 Gy cranial irradiation and were sacrificed 6 h, 24 h or 7 days post-irradiation. Endothelial cells were isolated from the hippocampus and cerebellum using fluorescence-activated cell sorting, followed by cell cycle analysis and gene expression profiling., Results: Flow cytometric analysis revealed that irradiation increased the percentage of endothelial cells, relative to the whole cell population in both the hippocampus and the cerebellum. This change in cell distribution indicates that other cell types are more susceptible to irradiation-induced cell death, compared to endothelial cells. This was supported by data showing that genes involved in endothelial cell-specific apoptosis (e.g. Smpd1) were not induced at any time point investigated but that genes involved in cell-cycle arrest (e.g. Cdkn1a) were upregulated at all investigated time points, indicating endothelial cell repair. Inflammation-related genes, on the other hand, were strongly induced, such as Ccl2, Ccl11 and Il6., Conclusions: We conclude that endothelial cells are relatively resistant to ionizing radiation but that they play an active, hitherto unknown, role in the inflammatory response after irradiation. In the current study, this was shown in both the hippocampus, where neurogenesis and extensive cell death after irradiation occurs, and in the cerebellum, where neurogenesis no longer occurs at this developmental age.

Purpose: Leptin (LEP) is a peptide hormone with multiple physiological functions. Besides its systemic actions, it has important peripheral roles such as a mitogen action on keratinocytes following skin lesions. We previously showed that LEP mRNA is significantly induced in response to neutron irradiation in mouse skin and that the protein increases in the irradiated epidermis and in the related subcutaneous adipose tissue. In this work, we investigated the post-transcriptional regulation of LEP by miRNAs and the conservation of LEP's role in radiation response in human cells., Methods: We used microarray analysis and real-time polymerase chain reaction (RT-PCR) to analyze modulation of miRNAs potentially targeting LEP in mouse skin following irradiation and bioinformatic analysis of transcriptome of irradiated human cell lines and cancer tissues from radiotherapy-treated patients to evaluate LEP expression., Results and Conclusions: We show that a network of miRNAs potentially targeting LEP mRNA is modulated in irradiated mouse skin and that LEP itself is significantly modulated by irradiation in human epithelial cell lines and in breast cancer tissues from radiotherapy-treated patients. These results confirm and extend the previous evidence that LEP has a general and important role in the response of mammalian cells to irradiation.

Purpose: 5-Aminolevulinic acid (ALA) is a precursor of the photosensitizer protoporphyrin (PpIX) used in photodynamic therapy. In our previous work, PpIX enhanced the generation of reactive oxygen species by X-ray irradiation. In this study, we evaluated the potential of ALA as an endogenous sensitizer to X-ray irradiation., Methodology: Tumor-bearing C57BL/6J mice implanted with B16-BL6 melanoma cells were subsequently treated with irradiation (3 Gy/day for 10 days; total, 30 Gy) plus local administration of 50 mg/kg ALA 24 hours prior to each irradiation (ALA-XT). Tumor-bearing mice without treatment (NT), those treated with ALA only (ALAT), and those treated with X-ray irradiation only (XT) were used as controls., Results: ALA potentiated tumor suppression by X-ray irradiation. In microarray analyses using tumor tissue collected after 10 sessions of fractional irradiation, functional analysis revealed that the majority of dysregulated genes in the XT and ALA-XT groups were related to cell-cycle arrest. Finally, the XT and ALA-XT groups differed in the strength of expression, but not in the pattern of expression., Conclusions: mRNA analysis revealed that the combined use of ALA and X-ray irradiation sensitized tumors to X-ray treatment. Furthermore, the present results were consistent with ALA's tumor suppressive effects in vivo.

Purpose: Gamma rays (GR) induce significant changes in the structure and expression of genes involved in the regulation of diverse biochemical and physiological processes. Arabidopsis plants exhibit different growth and development patterns in response to exposure to GR. The effects on gene expression of different radiation doses of GR (100 and 800 Gy) administered to Arabidopsis plants were examined at the reproductive stage., Materials and Methods: We irradiated 26-day-old plants with three replications [developmental stages 5.1-6.0, according to Boyes et al. ( 2001 )] using a GR irradiator (60 Co, ca. 150 TBq capacity, Atomic Energy of Canada Limited, Ontario, Canada) at the Korea Atomic Energy Research Institute. Plants were treated with 100, 200, 300, 400, 800, 1200, 1600, or 2000 Gy, and the doses were made from varying the distance to the source., Results: We conducted a high-throughput screening analysis and detected 883 GR-responsive genes that showed significant changes; these were involved in several putative metabolic pathways related to biotic stress. Additionally, five overrepresented cis-regulatory elements were identified in the 1-kb upstream regions of GR-responsive genes by using motif enrichment analysis. We also detected three GR-responsive genes associated with stamen development and confirmed their co-regulation with functionally interacting genes., Conclusions: This finding suggests that a network-based analysis is a viable approach to identify significant GR-responsive genes associated with the reproductive stage of Arabidopsis. Our results provide further insights into the complex biological systems involved in the response to different doses of GR in plants.

Purpose: MicroRNAs (miRNA) play a paramount role in growth, differentiation, proliferation and cell death by suppressing one or more target genes. However, their interaction with radiofrequencies is still unknown. The aim of this study was to investigate the long-term effects of radiofrequency radiation emitted from a Wireless Fidelity (Wi-Fi) system on some of the miRNA in brain tissue., Materials and Methods: The study was carried out on 16 Wistar Albino adult male rats by dividing them into two groups such as sham (n = 8) and exposure (n = 8). Rats in the exposure group were exposed to 2.4 GHz radiofrequency (RF) radiation for 24 hours a day for 12 months (one year). The same procedure was applied to the rats in the sham group except the Wi-Fi system was turned off. Immediately after the last exposure, rats were sacrificed and their brains were removed. miR-9-5p, miR-29a-3p, miR-106b-5p, miR-107, miR-125a-3p in brain were investigated in detail., Results: The results revealed that long-term exposure of 2.4 GHz Wi-Fi radiation can alter expression of some of the miRNAs such as miR-106b-5p (adj p* = 0.010) and miR-107 (adj p* = 0.005). We observed that mir 107 expression is 3.3 times and miR- 106b-5p expression is 3.65 times lower in the exposure group than in the control group. However, miR-9-5p, miR-29a-3p and miR-125a-3p levels in brain were not altered., Conclusion: Long-term exposure of 2.4 GHz RF may lead to adverse effects such as neurodegenerative diseases originated from the alteration of some miRNA expression and more studies should be devoted to the effects of RF radiation on miRNA expression levels.

Purpose: Ionizing radiation has been recognized to increase the risk of cardiovascular diseases (CVD). However, there is no consensus concerning the dose-risk relationship for low radiation doses and a mechanistic understanding of low dose effects is needed., Material and Methods: Previously, human umbilical vein endothelial cells (HUVEC) were exposed to chronic low dose rate radiation (1.4 and 4.1 mGy/h) during one, three and six weeks which resulted in premature senescence in cells exposed to 4.1 mGy/h. To gain more insight into the underlying signaling pathways, we analyzed gene expression changes in these cells using microarray technology. The obtained data were analyzed in a dual approach, combining single gene expression analysis and Gene Set Enrichment Analysis., Results: An early stress response was observed after one week of exposure to 4.1 mGy/h which was replaced by a more inflammation-related expression profile after three weeks and onwards. This early stress response may trigger the radiation-induced premature senescence previously observed in HUVEC irradiated with 4.1 mGy/h. A dedicated analysis pointed to the involvement of insulin-like growth factor binding protein 5 (IGFBP5) signaling in radiation-induced premature senescence., Conclusion: Our findings motivate further research on the shape of the dose-response and the dose rate effect for radiation-induced vascular senescence.

Purpose: Some members of the organic anion transporting polypeptide (OATP) family may play critical roles in determining the concentration of anticancer drugs in targeted organs/cells. The purpose of the present study was to investigate whether radiation can alter the expression of OATP in cancer cells so that OATP can be used as a specific drug target for anti-tumor treatment in combination with radiotherapy., Materials and Methods: Two cancer cell lines (HepG2 and MCF7) were irradiated with three doses of X-ray and the expression levels of six OATP were assessed., Results: Expressions of several OATP were altered after irradiation. OATP1A2, an OATP that was found to transport anti-tumor drugs and was undetectable in untreated cells, showed dramatically elevated level of expression after irradiation in MCF7 cells. The combined treatment of X-rays and the OATP1A2 substrate methotrexate exerted a more significant effect on growth rate and cell death compared with radiation or methotrexate treatment alone. At certain time points, X-rays increased OATP1A2 level while suppressing the expression of efflux transporters., Conclusions: Radiation may simultaneously increase the expression of uptake transporters and decrease the level of efflux transporters, suggesting OATP may be considered a novel target for delivery of anti-neoplastic agents in combination with radiotherapy.

Purpose: Health risks from exposure to low doses of ionizing radiation (IR) are becoming a concern due to the rapidly growing medical applications of X-rays. Using microarray techniques, this study aims for a better understanding of whole blood response to low and high doses of IR., Materials and Methods: Aliquots of peripheral blood samples were irradiated with 0, 0.05, and 1 Gy X-rays. RNA was isolated and prepared for microarray gene expression experiments. Bioinformatic approaches, i.e., univariate statistics and Gene Set Enrichment Analysis (GSEA) were used for analyzing the data generated. Seven differentially expressed genes were selected for further confirmation using quantitative real-time PCR (RT-PCR)., Results: Functional analysis of genes differentially expressed at 0.05 Gy showed the enrichment of chemokine and cytokine signaling. However, responsive genes to 1 Gy were mainly involved in tumor suppressor protein 53 (p53) pathways. In a second approach, GSEA showed a higher statistical ranking of inflammatory and immune-related gene sets that are involved in both responding and/or secretion of growth factors, chemokines, and cytokines. This indicates the activation of the immune response. Whereas, gene sets enriched at 1 Gy were 'classical' radiation pathways like p53 signaling, apoptosis, DNA damage and repair. Comparative RT-PCR studies showed the significant induction of chemokine-related genes (PF4, GNG11 and CCR4) at 0.05 Gy and DNA damage and repair genes at 1 Gy (DDB2, AEN and CDKN1A)., Conclusions: This study moves a step forward in understanding the different cellular responses to low and high doses of X-rays. In addition to that, and in a broader context, it addresses the need for more attention to the risk assessment of health effects resulting from the exposure to low doses of IR.

Purpose: To study the oxidative stress-induced changes by sublethal doses of cadmium chloride (CdCl2) and gamma irradiation, two redox-inducing agents, on metallothionein (MT) gene and protein expression in Plantago ovata Forsk (P. ovata)., Materials and Methods: Chlorophyll content was estimated to study the stress response in P. ovata seedlings following exposure to gamma irradiation and CdCl2. Lipid peroxidation and proline content, two oxidative stress markers, were also studied. The level of metallothionein gene and protein expression was further investigated using polymerase chain reaction (PCR), reverse transcription-PCR (RT-PCR), immunocytochemistry and flow cytometry., Results: Three MT genes of P. ovata namely PoMT 1, PoMT 2 and PoMT 3 were isolated, sequenced and characterized and their expressions were found to be altered in the case of both oxidative stresses in a dose-dependent and tissue-specific manner. The results were in agreement with the observations from immunocytochemistry and FACS analysis., Conclusions: The results suggest that both gamma irradiation and CdCl2 alter redox balance in P. ovata. The metallothionein gene may play an important role in metal tolerance and stress balance. It is conjectured that the stress-mediated imbalance is maintained by altered MT gene and protein expression.

Purpose: The aim of this study was to identify gene expression profiles distinguishing alpha-particle (211)At and (60)Co irradiation., Materials and Methods: Gene expression microarray profiling was performed using total RNA from confluent human fibroblasts 5 hours after exposure to (211)At labeled trastuzumab monoclonal antibody (0.25, 0.5, and 1 Gy) and (60)Co (1, 2, and 3 Gy)., Results: We report gene expression profiles that distinguish the effect different radiation qualities and absorbed doses have on cellular functions in human fibroblasts. In addition, we identified commonly expressed transcripts between (211)At and (60)Co irradiation. A greater number of transcripts were modulated by (211)At than (60)Co irradiation. In addition, down-regulation was more prevalent than up-regulation following (211)At irradiation. Several biological processes were enriched for both irradiation qualities such as transcription, cell cycle regulation, and cell cycle arrest, whereas mitosis, spindle assembly checkpoint, and apoptotic chromosome condensation were uniquely enriched for alpha particle irradiation., Conclusions: LET-dependent transcriptional modulations were observed in human fibroblasts 5 hours after irradiation exposure. These findings suggest that in comparison with (60)Co, (211)At has the clearest influence on both tumor protein p53-activated and repressed genes, which impose a greater overall burden to the cell following alpha particle irradiation.

Purpose: We studied the response of human embryonic stem cells (hESC) to the β-emitter (131)I, which affects the entire cell and to the Auger electron emitter (125)I-deoxyuridine ((125)I-dU), primarily affecting the deoxyribonuleic acid (DNA). The effects were also studied in keratinocytes as a prototype for somatic cells., Methods: HESC (H1) and human keratinocytes (HaCaT, human) were exposed to (125)I-dU (5 × 10(-5) - 5 MBq/ml) and (131)I-iodide (5 × 10(-5) - 12.5 MBq/ml) and apoptosis was measured by DNA-fragmentation. Cell morphology was studied by light microscopy and electron microscopy. Transcriptional profiling was done on the Agilent oligonucleotide microarray platform., Results: Auger-process induced no apoptosis but a strong transcriptional response in hESC. In contrast, HaCaT cells showed a pronounced induction of apoptosis but only a moderate transcriptional response. Transcriptional response of hESC was similar after (125)I-dU and (131)I treatments, whereas HaCaT cells expressed a much more pronounced response to (125)I-dU than to (131)I. A striking radiation-induced down-regulation of pluripotency genes was observed in hESC whereas in keratinocytes the enriched gene annotations were related primarily to apoptosis, cell division and proliferation., Conclusions: Human embryonic stem cells respond to ionizing radiation by (125)I-dU and (131)I in a different way compared to keratinocytes. Transcriptional response and gene expression appear to facilitate an escape from programmed cell death by striking a new path which probably leads to cell differentiation.

Purpose: Triplex-forming oligonucleotides (TFO) bind to the DNA double helix in a sequence-specific manner. Therefore, TFO seem to be a suitable carrier for Auger electron emitters to damage exclusively targeted DNA sequences, e.g., in tumor cells. We studied the influence of I-125 labeled TFO with regard to cell survival and induction of DNA double-strand breaks (DSB) using TFO with different genomic targets and target numbers. Furthermore, the ability of TFO to alter the gene expression of targeted genes was examined., Materials and Methods: TFO were labeled with I-125 using the primer extension method. DNA triplex formation and sequence-specific DSB were demonstrated in vitro. Cell survival was analyzed by colony-forming assay and DNA damage was assessed by microscopic quantification of protein 53 binding protein 1 (53BP1) foci in the human squamous carcinoma cell line II (SCL-II). Quantitative real-time polymerase-chain-reaction (qRT-PCR) was performed to analyze gene expression alterations., Results: The sequence-specific induction of a single DSB in a 1695 bp long DNA double stranded fragment was demonstrated in vitro. I-125-labeled TFO binding to single and multiple targets were shown to induce a pronounced decrease in cell survival and an increase of DSB. TFO targeting multiple sites differing in the total target number showed a significant different cell killing per decay that is also in good accordance with the observed induction of DSB. Single gene targeting I-125-labeled TFO significantly decreased cell survival and altered gene expression in the targeted gene., Conclusions: I-125-labeled TFO enable specific targeting of DNA in vitro as well as in a cellular environment and thus induce sequence-specific complex DNA lesions. Therefore I-125-labeled TFO might be a very useful tool for basic DNA repair research.

Purpose: The objective of this study was to demonstrate the radiation-induced bystander effect (RIBE) in human F11 fibroblasts using micronucleus (MN) formation as an end-point and to investigate transcriptional responses towards low doses of α-particle radiation in irradiated and bystander fibroblasts employing genome-wide microarray analysis., Materials and Methods: The MN frequency was investigated in unirradiated bystander cells recipient of growth medium from α-particle irradiated (0, 0.1, 0.5 and 2 Gy) immortalized human F11 fibroblasts. The irradiated conditioned medium (ICM) was transferred from irradiated to bystander fibroblasts 2 h after irradiation. Microarray analysis was performed in 0.1 Gy α-particle irradiated cells, unirradiated bystander cells and appropriate controls at different time points after ICM transfer. Microarray data analysis was performed at the single-gene level and gene-set level., Results: MN were induced in unirradiated fibroblasts recipient of ICM harvested from 0.1 Gy α-particle irradiated cultures, but not from cultures irradiated with 0.5 or 2 Gy. Fibroblasts irradiated with 0.1 Gy showed repression of 26 genes 4 h after being irradiated. However, no significantly altered genes were found in bystander fibroblasts at any of the time points used in this study. Gene-set enrichment analysis showed that pathways such as ribosome, protein export, proteasome and protein 53 (p53) signaling were enriched in irradiated cells. However, bystander cells were enriched only in the lysosome pathway 24 h after receiving ICM, indicating persistence of the signals received from the irradiated cells., Conclusion: MN formation was induced in bystander fibroblast receiving medium from 0.1 Gy α-particle irradiated fibroblasts, but this was accompanied with only minor transcriptional responses.