Gene Expression Signatures of Radiation Response Are Specific, Durable and Accurate in Mice and Humans Sarah K. Meadows1., Holly K. Dressman2,3., Garrett G. Muramoto1, Heather Himburg1, Alice Salter1, ZhengZheng Wei2, Geoff Ginsburg3, Nelson J. Chao1, Joseph R. Nevins2,3, John P. Chute1,3* 1 Division of Cellular Therapy, Duke University Medical Center, Durham, North Carolina, United States of America, 2 Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America, 3 Institute for Genome Sciences and Policy, Duke University Medical Center, Durham, North Carolina, United States of America Abstract Background: Previous work has demonstrated the potential for peripheral blood (PB) gene expression profiling for the detection of disease or environmental exposures. Methods and Findings: We have sought to determine the impact of several variables on the PB gene expression profile of an environmental exposure, ionizing radiation, and to determine the specificity of the PB signature of radiation versus other genotoxic stresses. Neither genotype differences nor the time of PB sampling caused any lessening of the accuracy of PB signatures to predict radiation exposure, but sex difference did influence the accuracy of the prediction of radiation exposure at the lowest level (50 cGy). A PB signature of sepsis was also generated and both the PB signature of radiation and the PB signature of sepsis were found to be 100% specific at distinguishing irradiated from septic animals. We also identified human PB signatures of radiation exposure and chemotherapy treatment which distinguished irradiated patients and chemotherapy-treated individuals within a heterogeneous population with accuracies of 90% and 81%, respectively. Conclusions: We conclude that PB gene expression profiles can be identified in mice and humans that are accurate in predicting medical conditions, are specific to each condition and remain highly accurate over time. Citation: Meadows SK, Dressman HK, Muramoto GG, Himburg H, Salter A, et al. (2008) Gene Expression Signatures of Radiation Response Are Specific, Durable and Accurate in Mice and Humans. PLoS ONE 3(4): e1912. doi:10.1371/journal.pone.0001912 Editor: Jo¨ rg Hoheisel, Deutsches Krebsforschungszentrum, Germany Received October 30, 2007; Accepted February 28, 2008; Published April 2, 2008 Copyright: 2008 Meadows et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was funded, in part, by grant AI-067798-01 from the National Institutes of Allergy and Infectious Diseases (JRN and JPC). Competing Interests: The authors have declared that no competing interests exist. * E-mail: john.chute@duke.edu . These authors contributed equally to this work. Introduction Invasive procedures are often required for accurate screening and diagnosis of common medical conditions [1]. Examination of the peripheral blood often suffices to establish certain diagnoses, such as chronic lymphocytic leukemia [2], which afflicts the circulating lymphocyte directly. Measurement of total white blood cell counts and the WBC differential (e.g. neutrophils, lympho- cytes, monocytes) is routinely performed in medical practice and can facilitate many diagnoses (e.g. bacterial or viral infection). Recently, it has been suggested that gene expression profiling of peripheral blood cells, particularly lymphocytes, can serve as sensitive tool to assess for the presence of certain diseases, such as systemic lupus erythematosus, rheumatoid arthritis, neurologic disease, viral and bacterial infections, breast cancer, atherosclerosis and environmental exposures, including tobacco smoke [3–11]. Results from these studies suggest that patterns of gene expression within circulating PB cells can distinguish individuals afflicted by these conditions from those who are not [3–11]. It has therefore been suggested that PB gene expression profiling has potential utility in the screening for diseases and environmental exposures. However, any consideration of applying PB gene expression profiles for the detection of disease or environmental exposures requires a determination of the impact of PB cellular composition, time, gender, and genotype on PB gene expression [10–13]. Additionally, it is unclear whether PB gene expression profiles that have been associated with various medical conditions are specific for that phenotype, or rather reflect a generalized response to genotoxic stress. Examination of the specificity of PB gene expression profiles in response to different stimuli and the durability of these signatures over time will be critical to allow the translation of this strategy into clinical practice. Ionizing radiation represents a particularly important environ- mental hazard, which, at lowest dose exposures, causes little acute health effects [14] and, at higher dose exposures, can cause acute radiation syndrome and death [15–17]. Numerous studies have been performed to attempt to understand the biologic effects of ionizing radiation in humans and specific mutations in p53 and HPRT have been identified in somatic cells from survivors of the Hiroshima and Nagasaki atomic bombings [18–21]. Gene expression analyses have also been performed on human tumor cells, cell lines, and peripheral blood from small numbers of irradiated patients in order to identify specific genes that are involved in the response to radiation injury [22–26]. Recently, public health focus has centered on the development of capabilities to accurately screen large numbers of people for radiation PLoS ONE | www.plosone.org 1 April 2008 | Volume 3 | Issue 4 | e1912