Armengol, G. | Search bioRxiv

bioRxiv2024

Correlation between DNA double strand breaks and cell death in peripheral blood lymphocytes from breast cancer patients

Radiotherapy is an effective treatment to fight cancer. However, it not only affects cancer cells but also healthy tissues, causing side effects. Different factors can influence the appearance of radiotoxicity, like total dose administered or patient individual characteristics, such as genetic variability. Several biomarkers have been proposed to predict radiotoxicity, especially those based on apoptosis or DNA damage, for example {gamma}-H2AX, which correlates with DNA double strand breaks. Our purpose is to analyze how apoptosis and {gamma}-H2AX correlate to each other and to link these results with selected SNPs associated with apoptosis. Blood samples from 60 breast cancer patients in remission were recruited. After mononucleated cells isolation, samples were irradiated. Then, we assessed induction and kinetics of disappearance of {gamma}-H2AX at different times after 2-Gy irradiation and apoptosis induced 24 and 48 h after 8-Gy irradiation. A negative correlation was observed between basal and residual {gamma}-H2AX and apoptosis at 48 h post-irradiation. This result supports previous studies with cancer patients showing a negative correlation between these two biomarkers. Considering the high variability of radio-induced apoptosis, we performed a genotyping study. Two SNPs located at TP53 and FAS genes were associated with apoptosis. Overall, our results indicate that individuals with less efficiency in removing damaged cells, probably due to genetic polymorphisms, presented more basal and residual levels of DNA damage.

cell biology↗

bioRxiv2024

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

PurposeExposure 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 MethodsSeveral 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. ResultsAfter 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. ConclusionsA 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.

molecular biology↗