ASSESSMENT OF RADIATION-INDUCED BYSTANDER EFFECT IN ASTROCYTE-GBM CELL LINES
Project no. 20105 · Status: Kapanmış · 2018
Summary
Glioblastoma (GBM) is an intra-cranial brain tumor originating from glial cells. The most effective treatment modality in GBM is radiotherapy (RT) and chemotherapy after surgical resection. RT aims to induce DNA damage in tumor cells and to induce DNA damage leading to apoptosis. However, cells which are not affected by radiation in RT are under the influence of signals at different levels from the cells exposed to radiation. The effect of radiation, known as the bystander effect, on normal cells has not been well understood. In this thesis, the efficacy of the bystander effect on reactive oxygen derivatives (ROS) and DNA damage in normal astrocytic cells was examined by a co-culture experiment mimicking the boundary between cancer and normal cells and modeling the GBM tumor. For this purpose, astrocytes and GBM cells were co-cultured in the current study. In tumor tissue, GBM cells invade into normal astrocytes. To mimic this construct, GBM cells and normal astrocyte cells were separately seeded into certain areas on the same plane of well-plate. Four Gy and 2Gy radiation were applied to the co-cultures and then allowed to incubation for 2, 4, 6 and 8 hours. The same conditions on which were used the cell lines was applied to normal culture. Furthermore, in order to determine a possible bystander effect of the cell culture medium interacted with the radiation, the medium of the co-culture obtained from 4Gy radiation was transferred into non-irradiated co-cultures. Radiation-dependent reactive oxygen derivatives in cell lines were determined by the ROS-defined assay. The damage by the radiation to DNA was identified by the TUNEL assay. Data were analyzed using SPSS statistics 17.0 and GraphPad Prism 6.0 software. Differences between cell groups were evaluated by Wilcoxon Signed Rank test. Correlation between groups was tested with Spearman's rank correlation coefficient. As a result, there were statistically significant differences in the amount of DNA double-stranded breaks (DSB) and reactive oxygen derivative (ROS) between some of the all cell groups that were directly irradiated by radiation and cell groups whose bystander effect of transferred media was measured. It was observed that the radiation-exposed medium could not induce itself a bystander effect on non-irradiated cells. In our co-cultured model of GB cell lines with astrocyte cell lines, considering the decreased cell death and ROS values, it is necessary to study the cellular radiation mechanism as a model to explain the possible radiation resistance.