Glioblastoma Cell Line–Based Analysis of Post-Radiation Gene Expression Changes and the Radiosensitizing Effect of a Dual mTOR Inhibitor

Project no. 31886 · Status: Kapanmış (Yayın bekleniyor) · 2023

Summary

Objective:This study aimed to comparatively evaluate the effects of the dual mTORC1/2 inhibitor RES529 and ionizing radiation on the glioblastoma cell line (T98G) and human brain microvascular endothelial cells (HBMEC), and to investigate whether this combination could create a potential therapeutic window in terms of tumor–normal tissue selectivity. The study particularly focused on the role of treatment timing—before or after irradiation—in determining cellular and molecular responses.Materials and Methods:T98G and HBMEC cell lines were exposed to RES529 and/or 4 Gy ionizing radiation, either alone or in combination. The experimental design included radiation administered 24 hours before (Pre24) or 24–48 hours after the drug treatment (Post24, Post48). At the cellular level, clonogenic survival, cell cycle distribution, apoptosis, wound healing, and γH2AX foci analysis of DNA damage response were assessed; at the molecular level, targeted gene expression panels were used.Results:In T98G cells, the Pre24 group showed the strongest radiosensitizing effect by markedly reducing clonogenic survival and wound closure. This group exhibited a limited accumulation in the G2/M phase, an increase in ≥8N polyploid fractions, and elevated apoptosis rates. These findings reveal a radiosensitization pattern characterized by mitotic catastrophe and reproductive cell death. In HBMEC cells, G1 phase arrest and minimal apoptosis were observed following 4 Gy irradiation. At the molecular level, T98G cells showed downregulation of checkpoint/repair genes (RAD1, HUS1, CDKN1A) and upregulation of mTOR-translation and G2/M effectors (RICTOR, S6K2, EIF4EBP2, CCNB1). Conversely, HBMEC cells displayed enhanced DDR and PI3K–AKT–mTOR signaling, along with suppressed angiogenesis, reflecting a repair-oriented survival response.Conclusion:These findings demonstrate that dual mTORC1/2 inhibition, when combined with radiotherapy, induces marked radiosensitization in glioblastoma cells through mitotic catastrophe and defective DNA repair, whereas in normal endothelial cells, DNA repair capacity and tissue integrity are preserved. This divergence suggests the presence of a potential therapeutic window based on tumor–normal selectivity. Overall, the results highlight that treatment timing is critical, and that pre-irradiation administration of RES529 may represent the most effective strategy for therapeutic radiosensitization.

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