Reconstructing and Reprogramming the Tumor-Propagating Potential of Glioblastoma Stem-like Cells

Abstract

Summary Developmental fate decisions are dictated by master transcription factors (TFs) that interact with cis-regulatory elements to direct transcriptional programs. Certain malignant tumors may also depend on cellular hierarchies reminiscent of normal development but superimposed on underlying genetic aberrations. In glioblastoma (GBM), a subset of stem-like tumor-propagating cells (TPCs) appears to drive tumor progression and underlie therapeutic resistance, yet remain poorly understood. Here, we identify a core set of neurodevelopmental TFs (POU3F2, SOX2, SALL2, OLIG2) essential for GBM propagation. These TFs coordinately bind and activate TPC-specific regulatory elements, and are sufficient to fully reprogram differentiated GBM cells to ‘induced’ TPCs, recapitulating the epigenetic landscape and phenotype of native TPCs. We reconstruct a network model that highlights critical interactions and identifies novel therapeutic targets for eliminating TPCs. Our study establishes the epigenetic basis of a developmental hierarchy in GBM, provides detailed insight into underlying gene regulatory programs, and suggests attendant therapeutic strategies.

An NAD + -dependent transcriptional program governs self-renewal and radiation resistance in glioblastoma

“…S2 A-C). Using a specific pharmacological inhibitor of NAMPT, FK866, we examined the biological role of NAMPT in GSC self-renewal, a defining characteristic of GSCs, which often parallels tumorinitiating potential (18). Treatment of GSC lines B18 and B36 with FK866 in vitro decreased NAD + levels in a dose-dependent fashion (Fig.…”

“…5A) (18,(23)(24)(25). Among these genes, E2F2 RNAi consistently decreased the levels of helixloop-helix gene inhibitor of differentiation 1 (ID1) (Fig.…”

Multiplexed RNAi therapy against brain tumor-initiating cells via lipopolymeric nanoparticle infusion delays glioblastoma progression

“…S3). The biological impact of these four TF knockdowns has been studied through the shRNA strategy (24) in in vitro and in vivo models, but the impact of transient siRNA knockdown, the only clinically translatable approach, has yet to be investigated in formed tumors in situ (39). BTICs treated with combo siRNAs (50 nM for each TF siRNA) for 48 h demonstrated significantly reduced tumor sphere formation and stem cell frequency for MGG8 at cell densities greater than 25 cells per well in 96-well plates (Fig.…”

“…To establish a suitable therapeutic target model using patient-derived GBM BTICs, we cultured GBM cell lines in serum-free Neurobasal medium supplemented for tumorsphere growth conditions (24,25,36). Cells then were collected for Western blotting and qRT-PCR analysis of the expression levels of four core TFs (for primer sequences see SI Appendix, Table S1).…”

“…A core set of four transcription factors (TFs), namely SOX2, OLIG2, SALL2, and POU3F2, was recently proposed to drive proneural BTICs (24). These TFs show high expression levels in the bulk of patient tumor tissue (SI Appendix, Fig.…”