Abstract 3222: Acute and long-term responses to treatment with the HDAC inhibitor quisinostat in preclinical models of glioblastoma

Abstract

Abstract Introduction: High expression of histone deacetylases (HDACs), particularly HDAC1, is strongly associated with poor prognosis for glioblastoma (GBM) patients. Quisinostat is a second-generation, class I-II selective HDAC inhibitor with high specificity for HDAC1 and potent anti-tumor activity. Here, we evaluated GBM PDX tissues and glioma stem cells (GSCs) for cellular, transcriptomic and phenotypic changes after acute and long-term treatment with quisinostat. Methods: Multiple GBM PDX models and PDX-derived GSCs were treated with quisinostat, radiation, or a combination of quisinostat and radiation. Tissue and cells were processed for RNA-seq, qRT-PCR, and immunofluorescence assays to examine alterations in neuronal signaling, cell fate, DNA damage, and markers of stemness and differentiation. Results: Bulk RNA sequencing of tumor tissue revealed that chronic co-treatment with quisinostat and radiation led to increased cellular expression of neuronal signaling and neuronal development pathways compared to the untreated control group. Increase in expression of neuronal signaling genes was also observed upon in vitro treatment of GSCs with quisinostat. Immunocytochemistry and immunofluorescence staining confirmed changes in neuronal signaling and neuronal cell fate proteins after quisinostat treatment. Conclusions: Quisinostat treatment induces a shift in tumor cells towards a neuronal-like cell fate. Considering that GSCs have been shown to establish synaptic junctions with healthy neurons to evoke enhanced excitatory currents within glioma cells and contribute to treatment resistance, further investigation of this shift upon HDAC inhibition is crucial. Ongoing studies are aimed at evaluating the significance of these cellular and molecular changes resulting from quisinostat treatment and whether the quisinostat-induced cell fate changes can be exploited for future combination therapy for GBM. Citation Format: Keely Orndorff, James McNamara, Mariya Stavnichuk, Costanza Lo Cascio, Connor White, Ernesto Luna Melendez, Gozde Uzunalli, Nader Sanai, Shwetal Mehta. Acute and long-term responses to treatment with the HDAC inhibitor quisinostat in preclinical models of 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 3222.