Effect of Mdivi-1 Mediated DRP-1 Inhibition on Mitochondrial Fission and Mitophagy in Glioblastoma Multiform (GBM) Cancer Stem Cells

It has been reported that the presence of glioblastoma stem cells (GSC) in GBM causes drug resistance and tumor recurrence. Studies show that SSCs differ from neural stem cells (NKC) and differentiated GBM cells in terms of their different molecular, genetic and metabolic properties. Therefore, it is important to fully understand the mechanisms that maintain the stem cell properties of SSCs in order to develop new therapeutic strategies targeting SSCs. As a result of investigating the effects of Mdivi-1-mediated pharmacological inhibition of Drp1, which plays a role in fission, on fission and mitophagy mechanisms for the first time, important and original results have been obtained to support our hypothesis, specifically in SSCs that express CD133 and CD24 lentivirally, which are among the SSC markers. The efficacy of mitochondrial fission inhibitor alone or in combination with TMZ as an alternative treatment protocol in the treatment of GBM was investigated for the first time in vitro at the GCC level. Within the scope of this thesis, the expression of apoptosis and mitophagy-related genes at the mRNA level was examined. Simultaneous polymerase chain reaction and mRNA expression analyzes of DRP-1, Fis1, Bax, Bcl-2, Mcl-1 for apoptosis, and Pink1 as a mitophagy marker, Parkin genes for Fission were performed. . Activating phosphorylation and inhibitory phosphorylation levels of Drp1, which is controlled at the post-translational level, were investigated at protein level by western blot analysis. It was determined for the first time that Mdivi-1 applied bulk tumor cells and two different GKH cell lines were affected by this inhibition according to dose and time and caused a decrease in their viability more effectively than TMZ. It was determined that this death observed in cells was mediated by apoptosis. It has been shown for the first time that Mdivi-1 inhibitor can be used as an alternative therapeutic agent that stimulates TMZ-independent apoptosis in Glioblastoma and can also target cancer stem cells. It was determined for the first time that Drp1 expression and fission mechanism were more active in CD24high cells and Mdivi-1 was shown to cause the most effective fission suppression in these cells. The fact that the effects of Mdivi-1 alone or in combination with TMZ at low doses on cell viability and apoptosis in bulk tumor cells and SSCs were determined for the first time in this thesis study will contribute to the production of alternative approaches that can be used in GBM treatment. Keywords: Glioblastoma Stem Cell, CD133, CD24, Mitochondrial Quality Control, Mitochondrial Metabolism