MicroRNAs (miRNAs) are short single-stranded RNA molecules that regulate the stability or translational efficiency of target messenger RNAs. Specific miRNAs are required for strict tissue- and developmental stage-specific expression. These miRNAs have roles in many human tumor malignancies and their expression is specifically regulated on each stage of oncogenic process. Therefore, miRNA expression profiling can be used as a new class of biomarker that indicates the development of cancer. Many recent studies indicated that cell exposure to ionizing radiation also induces various physiological responses including DNA repair, cell cycle arrest, cell death and differentiation. In addition, some studies suggest that exposure to low dose radiation induces a favorable effect on cells. However, the functions of miRNAs related to the response of irradiated cells have not been well studied, especially after low dose radiation. In this study, expression profiles of miRNAs isolated from irradiated cells at low and high dose radiation were analyzed with microarrays, and these data were validated using quantitative RT-PCR. Here, we describe specific miRNAs that are expressed in a dose-dependent manner that serve as new markers of irradiated immune cells.

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