Abstract 3318: Phosphoproteomic profiling of glioblastoma stem cells to uncover mechanisms of radiation resistance

Abstract

Abstract Glioblastoma (GBM) is the most common and aggressive primary malignant brain tumor in adults. GBM tumors universally develop resistance to chemotherapy and radiation therapy; thus, there is an urgent need to develop novel treatment strategies. In this study, we identify signaling pathways altered specifically in radioresistant glioblastoma stem cells (GSCs) following radiation treatment, in order to identify mechanisms of radiation resistance. Protein phosphorylation is a highly regulated and dynamic post-translational modification that is the primary mechanism of signal transduction. We hypothesized that phosphoproteomic profiling of GSCs can be used to identify novel signaling pathways involved in GBM radioresistance. Phosphopeptides were isolated from three GSC lines and one differentiated GBM cell line before and after radiation treatment. Mass spectrometry-based global phosphoproteomic profiling was then utilized to quantify radiation-induced changes in protein phosphorylation. About 6,000 phosphopeptides mapping to about 2,300 phosphoproteins were quantified at two post-radiation timepoints (relative to untreated) across all four cell lines. Three biological replicates of each sample were analyzed by mass spectrometry to obtain statistical significance. Fold changes of phosphoproteins following radiation treatment were then mapped to canonical signaling pathways, and pathways altered specifically in radiation-resistant GSCs were identified. We conclude that different pathways are activated in GSCs compared to differentiated GBM cells following radiation treatment, and some of these pathways may mediate radioresistance. Future efforts will focus on validation of the mass spectrometry results in vivo, and cell-based assays to identify the role of specific phosphoproteins in radioresistance pathways. Results of this study will guide future efforts to develop radiosensitizing agents that, when used in combination with current treatments, may increase the survival of patients with this devastating disease. This study was supported by funds from The Ohio State University Comprehensive Cancer Center (to AC); NIH/NCI 1U10CA180850-01(to AC); NIH/NCI 1RC2CA148190 (to AC); NIH/NCI 2K12CA133250-06 (to AC); NIH/NCI/CTEP 1R01CA169368 (to AC); NIH/NCI 1R01CA11522358 (to AC), RTOG (to AC). Citation Format: Emily Bassett, Kamalakannan Palanichamy, Arnab Chakravarti. Phosphoproteomic profiling of glioblastoma stem cells to uncover mechanisms of radiation resistance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3318. doi:10.1158/1538-7445.AM2015-3318