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Abstract 4887: Mitochondrial SOD2 is the mainstay to protect the stemness-featured glioblastoma cells against drug-induced reactive oxygen stress

Glioblastoma (GBM) is a highly aggressive primary brain tumor with presence of stemness-featured cells that are prone to survive from cancer treatment. We reported Sp1-induced SOD2 was associated with the process to acquire temozolomide (TMZ) resistance that the significance remained to be elucidated. Resistant models were established through long-term coincubation with TMZ in GBM cell lines, which expressed significantly higher stemness properties in extreme limiting dilution analysis (ELDA) and serial transplantation. These cells also showed increased expression of SOD2. Enrichment of stemness-featured cells by spheroid culturing or by CD133-positive cells selection resulted in increased SOD2, suggesting their associations. The impact of the protein to glioma stem cells (GSCs) was then studied through SOD2 RNA interference (RNAi), displaying downregulated stemness features in the knockdown models. Functional studies of the resistant cells showed superior scavenging ability in TMZ- or H2O2-induced ROS that would be dysfunctioned in pretreatment with SOD2 RNAi. In addition, co-treatment with the reagents over the knockdown cells resulted in enhancement of apoptosis as well as inhibition in tumor spheroid culture and cell clonogenic formation, suggesting re-sensitization to the drug. By establishing in vivo model from patient derived xenograft implantation that was obtained from clinical resistant disease, the mouse receiving combination treatment with TMZ and SOD inhibitor had lower tumor proliferation comparing to those receiving TMZ alone. These data indicate that there was an association between SOD2 and the stemness features, suggesting the protein to play important roles in regulation of GSCs behavior. Down-regulation of SOD2 levels may thus be a potential therapeutic strategy for modulating stemness properties of GSCs, making these cells more susceptive to the chemo-therapeutic agent. Citation Format: Kwang-Yu Chang, Chia-Hung Chien, Jui-Mei Chu, Pei-Hsuan Chung, Ming-Sheng Liu, Jian-Ying Chuang. Mitochondrial SOD2 is the mainstay to protect the stemness-featured glioblastoma cells against drug-induced reactive oxygen stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4887.