Glioblastoma is the most aggressive brain tumour. Its resistance to standard therapy is due to glioblastoma stem cells (GSC) and their interaction with tumour microenvironment, part of which are also mesenchymal stem cells (MSC). Research on MSC effects on tumour growth and invasion shows seemingly contradictory results. Still, MSC have great potential as vectors for drug delivery to the tumour. Here, we studied how ionizing radiation affects GSC and MSC in monocultures and cocultures, both in tridimensional (3D) spheroid model. We used clonogenic assay, invasion assay, proliferation assay with antibodies for Ki-67 protein and we also analysed cell cycle with Hoechst dye. GSC were more clonogenic then MSC, when irradiated. When in coculture with MSC, GSC spheroid growth slowed down compared to GSC monocultures. When irradiated, MSC were more invasive in monoculture than in coculture. Irradiation and MSC didn't influence invasion of GSC. GSC were more proliferative then MSC in monoculture. Proliferation of MSC increased in coculture but decreased when they were exposed to radiation. Proliferation of GSC decreased in irradiated coculture with MSC compared to radiated monoculture of GSC. GSC and radiation didn't affect cell cycle of MSC. When we radiated GSC in monoculture cell cycle stopped in G2 phase, but not when they were irradiated in the presence of MSC. Our results contribute to understanding of effect of irradiation on GSC and effect of MMC on GSC radioresistance. Results of this study are useful for future research of mechanisms that are responsible for glioblastoma resistance to standard therapy.
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