Cancers present challenges due to their complexity, making them one of the leading causes of death worldwide. Radiation therapy, especially external beam radiation therapy using X-rays, is a widely used treatment as it concerns about 50–60 % of cancer patients. However, the appearance of radioresistance often leads to treatment failure. Hence, a deeper understanding of the mechanisms underlying cancer radioresistance is essential. While research has mainly focused on nuclear DNA (nDNA) to understand cell responses to radiation, mitochondria, and mitochondrial DNA (mtDNA) have received relatively less attention. These aims of this master thesis are: 1) to better understand the putative contribution of mitochondria (if any) to the cell sensitivity to X-rays and 2) to identify potential mitochondrial actors that contribute to cell responses upon radiation exposition. To do so, two Rho0 (ρ0) cell lines (cells depleted in mitochondrial DNA) derived from143B (osteosarcoma) or A549 (adenocarcinoma lung cancer) were used and exposed or not (0 Gy, control cells) to varying X-ray doses. First, qPCR analyses were performed to validate the mtDNA depletion in ρ0 cells. Then, the cells indicate that A549 " ρ0" were not clonal and only partially depleted in mitochondrial DNA (Rho-, ρ-). These cells were therefore treated with ethidium bromide to generate a true ρ0 clonal population. Concerning the clonogenicity assays, the results showed no significant difference in X-ray resistance for 143B ρ0 and wild-type cells, but A549 ρ0 exhibited increased resistance that correlated with sublethal radiation-induced damage when compared to wild-type cells. However, biases were detected, including contamination with PIV5. To assess the cytopathic effects of PIV5, uncontaminated cells were used, which revealed a loss of clonogenic potential in A549 ρ0 clones. Therefore, further investigations are now needed to draw conclusions on the first objective. For the second objective, focusing on the cGAS-STING pathway in A549 cells exposed to X-rays, the activation of TBK1 and NF-κB was investigated. NF-κB was activated in A549 cells 24 h after IR, whereas p65 translocation was reduced in ρ0 cells, suggesting a more prominent role of NF-κB in the radioresponse in WT cells.
Effects of irradiation on mitochondria in cancer cells: a comparative study between Rho0 and parental cancer cell lines
TOUSSAINT, E. (Author). 16 Jan 2024
Student thesis: Master types › Master in Biology