Differential biological effect of low doses of ionizing radiation depending on the radiosensitivity in a cell line model

Abstract

Purpose Exposure to low doses (LD) of ionizing radiation (IR), such as the ones employed in computed tomography (CT) examination, can be associated with cancer risk. However, not all individuals respond the same to IR, and cancer development could depend on the individual radiosensitivity. Notably, inter-individual differences in the response to IR have been very well studied for high and medium doses, but not for LD. In the present study, we wanted to evaluate the differences in the response to a CT-scan radiation dose of 20 mGy in two lymphoblastoid cell lines with different radiosensitivity. Materials and Methods Several parameters were studied: gene expression, DNA damage, and its repair (by analyzing gamma-H2AX foci, chromosome breaks, and sister chromatid exchange), as well as cell viability, proliferation, and death. Results After 20 mGy of IR, the radiosensitive (RS) cell line showed an increase in DNA damage, and higher cell proliferation and apoptosis, whereas the radioresistant (RR) cell line was insensitive to this LD. Interestingly, gene expression analysis showed a higher expression of an antioxidant gene in the RR cell line, which could be used by the cells as a protective mechanism. After a dose of 500 mGy, both cell lines were affected by IR but with significant differences. The RS cells presented an increase in DNA damage and apoptosis, but a decrease in cell proliferation and cell viability, as well as less antioxidant response. Conclusions A differential biological effect was observed between two cell lines with different radiosensitivity, and these differences are especially interesting after a CT scan dose. If this is confirmed by further studies, one could think that individuals with radiosensitivity-related genetic variants may be more vulnerable to long-term effects of IR, potentially increasing cancer risk after LD exposure.