Identification of radiation induced miRNA biomarkers using the CGL1 cell model system

Abstract

The overall aim of this study was to identify novel radiation induced miRNA biomarkers for low dose radiation (LDR) exposures. MicroRNAs (miRNAs) have emerged as a potential class of biomolecules for diagnostic biomarker applications. miRNAs are small non-coding RNA molecules produced and released by cells in response to various stimuli. miRNAs also demonstrate remarkable stability in a wide range of biological fluids, in extreme pH fluctuations, and after multiple freeze-thaw cycles. Given these advantages, identification of microRNA-based biomarkers for radiation exposures can contribute to the development of reliable biological dosimetry methods, especially for LDR exposures. In this study, an miRNAome next-generation sequencing (NGS) approach was utilized to identify novel radiation induced miRNA gene changes within the CGL1 human cell line. Here, irradiations of 10, 100, and 1000 mGy were performed and samples collected 1, 6 and 24 h post-irradiation. Corroboration of the NGS results with RT-qPCR verification confirmed the identification of numerous radiation-induced miRNA expression changes at all doses assessed. Further evaluation of select radiation induced miRNAs including miR-1228-3p and miR-758-5p, as well as their downstream mRNA targets UBE2D2, PPP2R2D and ID2 demonstrated significantly dysregulated reciprocal expression patterns. In order to explore the miRNA profile in a sub-background ultra-low dose radiation (ULDR) environment, the CGL1 cells were grown in the underground SNOLAB laboratory in a specialized tissue culture incubator (STCI) designed to lower natural background radiation by a 27-fold difference relative to surface. Here, the cells were grown in the ULDR environment and natural background radiation (NBR) controls for a period of three months. Total RNA was periodically extracted to assess miRNA expression levels. Here, miR-502-3p was significantly upregulated in CGL1 cells cultured in the ULDR environment compared to the NBR control cells. Taken together, this study has identified novel radiation induced miRNA biomarkers at various radiation dose ranges, spanning from ULDR, LDR (10 and 100 mGy) and high dose (1 Gy) radiation exposures. Further evaluation is needed to determine whether the candidate miRNA biomarkers identified from this study can serve as suitable targets for radiation biodosimetry applications.