Quantitative analysis of γ-H2AX foci kinetics: differential DNA damage response between primary PBMCs and HEp-2 tumor cells following gamma-irradiation

The aims of this study was to establish a robust and quantitative methodological basis for the in vitro γ-H2AX assay, validating its dose–response and repair kinetics in both primary peripheral blood mononuclear cells (PBMCs) and human epithelial type 2 laryngcal carcinoma cells (HEp-2), following exposure to γ radiation doses ranging of 1 to 6 Gy. The mean γ-H2AX foci per cell in both PBMCs and HEp-2 tumor cells increased sharply reaching 52.43 ± 0.61 and 43.96 ± 3.53 foci respectively compared to the control (3,47 ± 0.18) at 6Gy after 30 min post irradiation, reflecting a clear dose-dependent response. However, HEp-2 exhibits a slower overall repair rate than the PBMCs. After 24 h, γ-H2AX phosphorylation levels decreased, indicating substantial DNA repair, though residual foci persisted in PBMCs (11.3 ± 0.26) and HEp-2 cells (13.64 ± 0.33) at 6Gy. The findings suggest that further translational research is warranted to assess its role in clinical biodosimetry and radiotherapy individualization.