Lal, Bachchu

Background/Objectives: CSCs are critical drivers of the tumor and stem cell phenotypes of glioblastoma (GBM) cells. Chromatin modifications play a fundamental role in driving a GBM CSC phenotype. The goal of this study is to further our understanding of how stem cell-driving events control changes in chromatin architecture that contribute to the tumor-propagating phenotype of GBM. Methods: We utilized computational analyses to identify a subset of clinically relevant genes that were predicted to be repressed in a Polycomb repressive complex 2 (PRC2)-dependent manner in GBM upon induction of stem cell-driving events. These associations were validated in patient-derived GBM neurosphere models using state-of-the-art molecular techniques to express, silence, and measure microRNA (miRNA) and gene expression changes. Advanced Poly(β-amino ester) nanoparticle formulations (PBAEs) were used to deliver miRNAs in vivo to orthotopic human GBM tumor models. Results: We show that glioma stem cell (GSC) formation and tumor propagation involve the crosstalk between multiple epigenetic mechanisms, resulting in the repression of the miRNAs that regulate PRC2 function and histone H3 lysine 27 tri-methylation (H3K27me3). We also identified miR-217-5p as an EZH2 regulator repressed in GSCs and showed that miR-217-5p reconstitution using advanced nanoparticle formulations re-activates the PRC2-repressed genes, inhibits GSC formation, impairs tumor growth, and enhances the effects of ionizing radiation in an orthotopic model of GBM. Conclusions: These findings suggest that inhibiting PRC2 function by targeting EZH2 with miR-217-5p advanced nanoparticle formulations could have a therapeutic benefit in GBM.

Abstract Despite aggressive therapy consisting of surgery followed by radio/chemotherapy Glioblastoma (GBM) recurs in almost all patients and, currently, there are no proven therapies to treat recurrent GBM (rGBM). Recent developments in nanomedicine provide new and promising opportunities to develop new targeted therapeutics to treat brain tumors. In this study we combine bioinformatics, forward-thinking understanding of miRNA biology and cutting-edge nucleic acid delivery vehicles to advance targeted therapeutics for rGBM. Bioinformatic analysis of RNA sequencing from GSCs and clinical rGBM specimens identified TGF-beta receptor II (TGFBR2) signaling as a targetable pathway in rGBM. Mechanistically, we show that alterations in chromatin state driven by stem-cell driving events are conducive to a therapy-resistant state induced by TGFBR2. We show that blocking TGFBR2 via molecular and pharmacological approaches decreases the stem cell capacity, cell viability and re-sensitizes clinical rGBM isolates to temozolomide (TMZ) in vitro. Network analysis of SMAD2/3 targets enriched in rGBM predicted a subset of miRNAs that can target multiple genes within this set. Notably, miR-590-3p was predicted to inhibit 37 SMAD 2/3 gene targets that are also enriched in rGBMs. Bioinformatics analysis also showed that expression of 24 of those 37 miR-590-3p targets are positively correlated with TGFBR2 expression in rGBM clinical specimens. Consistent with these predictions, miR-590-3p inhibited expression of 25 of the 37 targets across 3 distinct therapy-resistant GSC isolates. To translate these in vitro finding, we developed novel bioreducible Lipophilic poly(β-amino ester) nanoparticles (LiPBAEs) for in vivo miRNA delivery. Following direct intratumoral infusion, these nanomiRs efficiently distribute through the tumors and spatial transcriptomic analysis (STA) found a decrease in 34 out of the 37 miR- 590-3p targets in animals that received the active nanomiR compared to control miRNA. Furthermore, STA identified 3 cell populations with distinct transcriptomic profiles reflecting a gradient pharmacodynamic response within tumors that received miR-590-3p nanomiRs with decreasing target expression towards the core of the tumor closest to catheter tip placement. To test the effect of 590-3p nanomiR therapy on survival, animals bearing pre-established intracranial rGBM xenografts received three infusions of either control or miR-590-3p nanomiRs every other day beginning on post-implantation day 7. All 10 animals treated with control nanomiRs were either dead or premorbid requiring euthanasia by post-implantation day 23. In contrast, 3 of 10 animals treated with miR-590-3p nanomiRs remained alive and healthy by post-implantation day 45, at which time the experiment was terminated. These results show that miRNA-based targeted therapeutics provide new opportunities to treat rGBM and bypass the resistance that is developed to standard of care. Citation Format: Hernando Lopez-Bertoni, Jack Korleski, Sophie Sall, Kathryn Luly, Maya K Johnson, Amanda L Johnson, Harmon Khela, Bachchu Lal, TC Taylor, Jean Micheal Ashby, Hector Alonso, Alice Li, Stephany Tzeng, John Laterra, Jordan J Green. Multipronged SMAD Pathway Targeting by LiPBAE miR-590-3p NanomiRs Inhibits Recurrent Glioblastoma Growth and Prolongs Survival [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr PR011.