STEM-09. EXPLORING THE ROLE OF TP53 IN REDOX REGULATION AND RESPONSE OF GLIOBLASTOMA STEM CELLS TO ROS-INDUCING AGENTS

Abstract Glioblastoma, the most malignant primary tumor of the central nervous system in adults presents a major therapeutic challenge due to the presence of chemo-radioresistant glioblastoma stem cells (GSCs). These GSCs adapt the thioredoxin (Trx) and glutathione (GSH) antioxidant systems to counteract treatment-induced reactive oxygen species (ROS) and promote their survival. The tumor suppressor gene wild-type (wt)TP53 regulates the expression of pro-oxidant or antioxidant genes in response to chemoradiotherapy based on p53 DNA-binding activity in a reducing microenvironment. Given the importance of p53 as a redox-sensitive protein, we hypothesized that p53 might protect GSCs against ROS-inducing agents. Auranofin (Au), a FDA-approved gold(I)-containing compound inhibits thioredoxin reductase 1 (TrxR1), a key antioxidant protein. We investigated the effects of Au on different GSCs including wtp53 GSC line and its counterpart p53-knockdown. We assessed viability, neurosphere formation, ROS levels and expression of p53 and TrXR1 to evaluate the cytotoxicity of Au, alone and in combination with L-buthionine sulfoximine (L-BSO), a GSH-depleting agent. We conducted TCGA analysis to explore the correlation between TrxR1 and p53. Our findings revealed a positive significant correlation between p53 and TrxR1 expression, consistent with lower levels of TrxR1 in p53-knockdown GSCs compared to their wt-p53 counterparts. P53-knockdown GSCs displayed a higher basal level of ROS, which further increased upon treatment with Au. P53-knockdown significantly increased the sensitivity of cells to Au, with pronounced effects for Au/L-BSO combination. Our findings reveal that expression levels of wtp53 affect the role of p53 in TrxR1-redox regulation and sensitivity to ROS-inducing agents in GSCs.