In vivo gene expression changes in human blood cells in response to radiation therapy.

Our in vivo study measures miRNA and gene expression changes in human blood cells in response to ionizing radiation in order to develop miRNA signatures that can be used as biomarkers for radiation exposure. Blood was collected from 8 radiotherapy patients immediately prior to and at 4 h after total body irradiation with 1.25 Gy X-rays. Both miRNA and gene expression changes were measured by means of quantitative PCR and microarray hybridization, respectively. Patients were in complete remission at the time of blood collection. Out of 223 differentially expressed genes, 37 were both downregulated and predicted targets of the upregulated miRNAs. Both miRNA and gene control of biological processes such as hemopoiesis and the immune response is increased after irradiation, whereas metabolic processes are underrepresented among all differentially expressed genes and the genes controlled by miRNAs. Sixteen human whole-blood samples were included in this study. Eight samples were collected shortly before total body irradiation. The other 8 samples were collected at 4 h after total body irradiation with 1.25 Gy X-rays.