Gene-Expression Biomarkers for Application to High-Throughput Radiation Biodosimetry

Molecular biodosimetry tools are a valuable asset for life-saving medical triage and patient management following a radiological or nuclear disaster. Even with the delayed onset of symptoms, sometimes several days after exposure, gene-expression biomarkers can identify these exposed individuals very early after exposure, allowing for prompt medical intervention. This early assessment of a radiation dose after exposure would enhance the operational commander’s situational awareness of the radiation exposure status of deployed units and increase the prospect of reduced morbidity and mortality through early medical intervention. Candidate gene targets were selected from microarray studies of ex vivo-irradiated human peripheral blood lymphocytes and measured using a quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) assay in a human whole blood model at 24 and 48 hr post-irradiation (0.2 to 5.0 Gy 60Co-gamma rays at 0.1 Gy/minute). A multi-target QRT-PCR technique was optimized, an inter-individual variation study of an ex vivo response was expanded to include a larger cohort of healthy donors, and a collaborative study was conducted involving the in vivo response of cancer patients undergoing total body irradiation treatment. These validation studies illustrated that gamma radiation causes quantifiable and reproducible gene-expression changes in the radiation biomarker targets CDKN1A, BAX, GADD45A, and DDB2 over several days across a broad dose range in both in vivo and ex vivo models. However, further validation studies are required before these gene targets can be used as molecular biodosimeters. Once validated, the gene-expression signatures of several sentinel biomarkers would provide an early dose estimate that would then be used when making decisions involving personnel operational capabilities and/or clinical therapy. In addition, we are implementing validated protocols for automation to create high-throughput clinical and deployable PCR-based diagnostic platforms. With the increased throughput, the use of the Armed Forces Radiobiology Research Institute’s Biodosimetry Assessment Tool (BAT), and a multi-parameter biodosimetry diagnostic approach, we can determine an individual’s exposure dose in a mass-casualty scenario, which would aid decision-making for medical triage (greater than 10 cGy).