Analysis of differentially expressed genes after ex vivo X-rays irradiation of human peripheral white blood cells

Abstract

The understanding and characterization of the radio-induced response at molecular level is pivotal for developing new approaches on practices that employ Ionizing Radiation (IR). Currently, gene expression signatures are being developed for radiation biodosimetry and as predictive biomarkers for personalizing radiotherapy. In order to detect potential radiation-exposure biomarkers, we performed a bioinformatic meta-analysis of public microarrays of ex vivo X-rays-irradiated human peripheral white blood cells and a validation of the resulting differentially expressed genes (DEGs) by qPCR. Gene expression of five datasets from Gene Expression Omnibus were analyzed with R software and Bioconductor packages. DEGs functional enrichment was performed with Over Representation and Gene Set Enrichment Analysis while iRegulon was used to detect master regulators transcription factors (TF) from DEGs. Human peripheral blood samples from six healthy human donors were X-rays-irradiated at 1-4Gy or left unirradiated. Dicentric Chromosome Assay was performed as biodosimetry control while mRNA from samples was obtained 24 h after exposure for qPCR validations with GAPDH as a reference gene (p-values<0.05 were considered significant). Bioinformatic analysis identified a total of 452 DEGs after X-rays exposure (parameters: lfc=0.7, p-value<0.05). While some of them are well known to be involved in radiation response, others resulted as novel. The DGEs showed enrichment in biological processes such as regulation after IR-exposure, DNA damage checkpoint, signal transduction by p53 and mitotic cell cycle checkpoint. PCNA, TIGAR, DRAM, PLK2 and NUDT15 expressions levels significantly increased at 1-4 Gy vs controls, demonstrated by qPCR. Meanwhile, TCF4 exhibited a significant decrease post-irradiation. This gene was previously detected as a master regulator TF by the bioinformatic analysis.Therefore, the detection and validation of this six DEGs can provide potential candidates as radiation-exposure biomarkers. These findings could also reveal novel insights about molecular networks involved in radio-induce response.