Biodosimetry of Low Dose Ionizing Radiation Using DNA Repair Foci in Human Lymphocytes

Abstract

Purpose: Ionizing radiation induced foci (IRIF) known also as DNA repair foci represent most sensitive endpoint for assessing DNA double strand breaks (DSB). IRIF are usually visualized and enumerated with the aid of fluorescence microscopy using antibodies to γH2AX and 53BP1. This study analyzed effect of low dose ionizing radiation on residual IRIF in human lymphocytes to the aim of potential biodosimetry and possible extrapolation of high-dose γH2AX/53BP1 effects to low doses and compared kinetics of DSB and IRIF. We also analyzed whether DNaseI, which is used for reducing of clumps, affects the IRIF level. Materials and Methods: The cryopreserved human lymphocytes from umbilical cord blood (UCB) were thawed with/without DNaseI, γ-irradiated at doses of 0, 5, 10, and 50 cGy and γH2AX/53BP1 foci were analyzed 30 min, 2 h, and 22 h post-irradiation using appropriate antibodies. We also analyzed kinetics of DSB using PFGE. Results: No significant difference was observed between data obtained by γH2AX foci evaluation in cells that were irradiated by low doses and data obtained by extrapolation from higher doses. Residual 53BP1 foci induced by low doses significantly outreached the data extrapolated from irradiation by higher doses. 53BP1 foci induced by low dose-radiation remain longer at DSB loci than foci induced by higher doses. There was no significant effect of DNaseI on DNA repair foci. Conclusions: Primary γH2AX, 53BP1 foci and their co-localization represent valuable markers for biodosimetry of low doses, but their usefulness is limited by short time window. Residual γH2AX and 53BP1 foci are more useful markers for biodosimetry in vitro. Effects of low doses can be extrapolated from high dose using γH2AX residual foci while γH2AX/53BP1 foci are valuable markers for evaluation of initial DSB induced by ionizing radiation. Residual IRIF induced by low doses persist longer time than those induced by higher doses.

Assessment of γ-H2AX and 53BP1 Foci in Peripheral Blood Lymphocytes to Predict Subclinical Hematotoxicity and Response in Somatostatin Receptor-Targeted Radionuclide Therapy for Advanced Gastroenteropancreatic Neuroendocrine Tumors

“…Finally, dosimetry based on lymphocytes is still under investigation. One recent study on human lymphocytes showed that residual γ-H2AX and 53BP1 foci are very useful markers for biodosimetry [ 37 ]. We were interested in the characterization of the DDR in patients receiving PRRT with ( 177 Lu)Lu-DOTA-TATE beyond mere biodosimetry and its exploitation for a better understanding of the biology of the response to PRRT.…”

Low Repair Capacity of DNA Double-Strand Breaks Induced by Laser-Driven Ultrashort Electron Beams in Cancer Cells

“…H2AX phosphorylation, mediated by ATM, ATR and DNA-PK sensor kinases, arises in response to DSBs formation and presents the evidence of their recognition [ 19 ]. 53BP1 is a p53 binding protein, which is a well known promoter of the DSB repair [ 20 ].…”

Comparison of inexperienced operators and experts in γH2A.X and 53BP1 foci assay for high-throughput biodosimetry approaches in a mass casualty incident

“…The dose dependent formation of RIF of cH2A.X and 53BP1 in respect to foci numbers and intensity enables the quantification of signals. Therefore, both are commonly used biomarkers for evaluation of DSBs in radiation biology and are potentially suitable as a biodosimetric assay in accidental exposure (Jakl et al 2020).…”