Abstract 4718: Reclaiming a dirty drug: What is the context of vulnerability to arsenic trioxide in glioblastoma

Abstract

Abstract Glioblastoma (GBM) is the most prevalent type of malignant tumor within the central nervous system. There is a growing demand to develop and adapt new therapeutic options in order to combat the five-year survival rate of 6.8% and improve patient quality of life. Arsenic trioxide (ATO) is the standard of care for myelodysplasia and relapsed or refractory acute promyelocytic leukemia. While currently being classified to have an idiopathic mechanism of action, two specific cytotoxic consequences of ATO have emerged: MNK1 activity and oxidative stress. Across six GBM PDX models a 20-fold difference in sensitivity manifests, indicative of underlying innate sensitivity or resistance to ATO. To correlate this to the proposed mechanisms of action, we observed ATO’s effect on MNK1 activity through eIF4E phosphorylation and glutathione (GSH) levels following treatment. A subset of GBM models exhibited a marked upregulation of eIF4E phosphorylation following treatment with 2 uM ATO. Of the six models, three were chosen to undergo further testing to observe whether this upregulation showed a consistent dose-dependent relationship across the models and correlated with vulnerability to ATO. Combination therapy with the MNK1 inhibitor, ETC-206, displayed mild to moderate synergy on overall cell viability and strong synergy when observing its effects on the glioma stem cell population. This preferential effect on the GSC populations suggests that MNK1i based combination strategies may show greater effectiveness in vivo than indicated by our previous in vitro studies. Nutraceuticals targeting GSH synthesis, Chrysin and Silibinin, displayed a 0.95 to 1.4-fold decrease in ATO IC50 values across all 6 models. To observe whether each nutraceutical impacted GSH levels consistently across all of the tested models, we measured GSH levels following treatment for each individual compound and their combination treatments. These findings further implicate MNK1 activity and cellular response to oxidative stress as markers of ATO sensitivity, however they are not the sole determinates of response. Understanding of the mechanism of action for idiopathic compounds may allow for the discovery of molecular signatures of sensitivity, improving patient selection for clinical trials and the development of new combination approaches to combat resistance in other tumor types. Citation Format: Charles Shaffer, Nanyun Tang, Yue Hao, Karen Fink, George Snipes, Bruce Mickey, Michael Berens. Reclaiming a dirty drug: What is the context of vulnerability to arsenic trioxide in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4718.