Radiotherapy-Associated Long-term Modification of Expression of the Inflammatory Biomarker Genes ARG1, BCL2L1, and MYC

Abstract

Ionizing radiation (IR) exposure of cells in vitro and in vivo triggers a complex cellular response among which modifications of gene expression have been consistently reported. Nevertheless, little is currently known about the transcriptionally responsive genes which play a role in the inflammation response. In order to improve our understanding of such transcriptional response to radiation in vivo, we simultaneously monitored the expression of 249 genes associated with the inflammation response over the course of the radiotherapy treatment in blood of patients treated for endometrial or head and neck cancer. We have identified genes whose transcriptional expression is either upregulated (ARG1, BCL2L1) or downregulated (MYC) several fold in vivo. These modifications were consistently detected across patients and further confirmed by quantitative real-time polymerase chain reaction (QRT-PCR); they were specifically significant toward the end of the radiotherapy treatment, 5 weeks following the first radiation fraction and more pronounced in endometrial patients (respectively, 2.9, 4.1, and 1.8 times). Importantly, in an attempt to correlate expression levels with normal tissue reaction to IR, we also identified three other genes CD40, OAS2, and CXCR1 whose expression level fluctuations during radiotherapy were more pronounced in patients developing late normal tissue responses to curative radiotherapy after the end of the radiotherapy treatment. Overall, we identified inflammation-associated genes which are promising biomarkers of IR exposure and susceptibility to radiation-induced toxicity.

Generation of a Transcriptional Radiation Exposure Signature in Human Blood Using Long-Read Nanopore Sequencing

“…This is not surprising, since P53 is the master regulator of the cellular radiation response and many of the genes identified are p53 dependent (56). The cytokine-cytokine receptor interaction pathway was also enriched, suggesting a radiation-induced inflammatory response as has been previously observed ex vivo (57) and in vivo in humans (58). Not surprisingly, apoptosis was also highly represented by the DEGS, as the programmed cell death, the most important cell death pathway after radiation exposure, is mainly regulated by radiation-induced double-strand breaks (59).…”

The first in vivo multiparametric comparison of different radiation exposure biomarkers in human blood

“…We evaluated late toxicity grading as the worst grade of symptoms persisting more than 3 months after the end of the treatment as described in Manning et al [ 19 ]. Here we correlated our data with incidence of MN ( Fig 3B ).…”

Dicentric Dose Estimates for Patients Undergoing Radiotherapy in the RTGene Study to Assess Blood Dosimetric Models and the New Bayesian Method for Gradient Exposure

“…RTGene was a feasibility study to develop and further validate the gene expression assay for biodosimetry with human blood samples exposed in vivo (Manning et al, 2017;O'Brien et al 2018) and included conventional biomarkers for additional validation. This has allowed dose estimates based on the dicentric assay to be calculated.…”

“…Linearity of the transcriptional dose-response for specific radiation-responsive genes in ex vivo exposed human blood samples has recently been demonstrated for the first time, and inter-individual variability in the response after low doses and high doses exposures has been newly assessed (Kabacik et al 2011a;Manning et al 2013). The logical next stage for biological development of the gene expression assay was to further validate these new techniques with human blood samples exposed to radiation in vivo (Manning et al 2017, O'Brien et al 2018. The RTGene Project was a feasibility study to develop existing knowledge on coding and non-coding transcriptional responses to IR into a useable radiation specific biomarker of exposure and response using blood samples from RT patients.…”