title: Radiation-induced micro-RNA expression changes in peripheral blood cells of radiotherapy patients.
abstract: OBJECTIVE
  MicroRNAs (miRNAs), a class of noncoding small RNAs that regulate gene expression, are involved in numerous physiologic processes in normal and malignant cells. Our in vivo study measured miRNA and gene expression changes in human blood cells in response to ionizing radiation, to develop miRNA signatures that can be used as biomarkers for radiation exposure.
  
  
  METHODS
  Blood from 8 radiotherapy patients in complete remission 1 or 2 was collected immediately before and 4 hours after total body irradiation with 1.25 Gy x-rays. Both miRNA and gene expression changes were measured by means of quantitative polymerase chain reaction and microarray hybridization, respectively. Hierarchic clustering, multidimensional scaling, class prediction, and gene ontology analysis were performed to investigate the potential of miRNAs to serve as radiation biomarkers and to elucidate their likely physiologic roles in the radiation response.
  
  
  RESULTS
  The expression levels of 45 miRNAs were statistically significantly upregulated 4 hours after irradiation with 1.25 Gy x-rays, 27 of them in every patient. Nonirradiated and irradiated samples form separate clusters in hierarchic clustering and multidimensional scaling. Out of 223 differentially expressed genes, 37 were both downregulated and predicted targets of the upregulated miRNAs. Paired and unpaired miRNA-based classifiers that we developed can predict the class membership of a sample with unknown irradiation status, with accuracies of 100% when all 45 upregulated miRNAs are included. Both miRNA control of and gene involvement in biologic processes such as hemopoiesis and the immune response are increased after irradiation, whereas metabolic processes are underrepresented among all differentially expressed genes and the genes controlled by miRNAs.
  
  
  CONCLUSIONS
  Exposure to ionizing radiation leads to the upregulation of the expression of a considerable proportion of the human miRNAome of peripheral blood cells. These miRNA expression signatures can be used as biomarkers of radiation exposure.
authors.affiliation: Center for Radiological Research, Department of Radiation Oncology, Columbia University Medical Center, New York, NY 10032, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Templin
authors.forename: Sunirmal
authors.initials: S
authors.lastname: Paul
authors.forename: Sally A
authors.initials: SA
authors.lastname: Amundson
authors.forename: Erik F
authors.initials: EF
authors.lastname: Young
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Barker
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: Wolden
authors.forename: Lubomir B
authors.initials: LB
authors.lastname: Smilenov
mesh_terms: D000328:Adult; D015415:Biomarkers; D001773:Blood Cells / Q000378:metabolism / Q000528:radiation effects*; D015536:Down-Regulation; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods*; D006801:Humans; D007938:Leukemia / Q000097:blood; D008223:Lymphoma / Q000097:blood; D008297:Male; D035683:MicroRNAs / Q000378:metabolism / Q000528:radiation effects*; D046228:Microarray Analysis / Q000379:methods; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D014916:Whole-Body Irradiation; D055815:Young Adult
chemical_list: D015415:Biomarkers; D035683:MicroRNAs