Abstract 5725: Epigenetic and transcriptional profiling reveal endosomal protein sorting as a glioblastoma cancer stem cell dependency

Abstract

Abstract Glioblastoma is a highly lethal primary intrinsic brain tumor for which current standard-of-care therapies are merely palliative. Functionally defined glioblastoma stem cells (GSCs) contribute to this poor prognosis by driving therapeutic resistance, maintenance of cellular heterogeneity, and disease recurrence. A deeper appreciation for the specific features that distinguish normal from neoplastic stem cells may inform selective therapeutic targeting. To further understand the molecular processes essential for maintaining cancer stem cell populations, we interrogated the active enhancer landscapes and transcriptional output of GSCs and normal neural stem cells (NSCs) through H3K27ac ChIP-seq and RNA-seq respectively. GSC-specific targets that held prognostic significance in patient datasets and which were essential in whole genome CRISPR screening data implicated endosomal protein sorting as a key feature in GSC biology. Targeting endosomal sorting impaired GSC viability and proliferation and contributed to apoptosis, while NSCs displayed a reduced cell proliferation deficit. Impaired endosomal protein sorting led to a reduction in the mRNA and protein levels of the stem and neuro-developmental transcription factors SOX2 and OLIG2 and reduced self-renewal capacity of GSCs, suggesting a role in the maintenance of stemness. Mechanistically, regulation of endosomal sorting may impact localization and stability of receptor tyrosine kinases and WNT signaling elements to control GSC maintenance. High expression of this endosomal sorting factor is associated with poor glioblastoma patient prognosis, suggesting its clinical importance. Thus, targeting the endosomal sorting pathway may represent a novel therapeutic approach for glioblastoma treatment. Citation Format: Ryan C. Gimple, Guoxin Zhang, Jeremy N. Rich. Epigenetic and transcriptional profiling reveal endosomal protein sorting as a glioblastoma cancer stem cell dependency [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5725.