Abstract 387: Ionizing radiation induces lipid metabolism-associated vulnerabilities in glioblastoma multiforme
Authors: Izawa-Ishiguro Arianna Richelle , Nandakumar Subhiksha , Carbone Nicholas , Ferrotta Annalisa V. , Raziuddin Raashed , Vogt Kristen C. , Heller Daniel A. , Mellinghoff Ingo K. 
Published: March 2024

Abstract
Introduction: Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults. It is highly resistant to its current standard-of-care regimen, which includes surgical resection followed by adjuvant ionizing radiation and temozolomide. Therapy resistance can be attributed to the abundance of genomic alterations in GBM tumors that evolve over time, which contribute to intra-and inter-tumoral heterogeneities that render targeted therapies as inadequate treatment options. Thus, there is an urgent unmet need for effective therapies targeting primary and recurrent GBM. Here, we investigated the impact of ionizing radiation on the transcriptome of patient derived GBM tumor spheres to identify key alterations and biological pathways involved in therapy resistance.
Materials and methods: We acquired four independent human GBM tumor sphere cell lines, which were derived from patients and cultured in serum-free media. Tumor spheres were treated with either a sham radiation or a single dose of 10Gy. Using poly-A enrichment whole transcriptome sequencing, we evaluated transcriptional alterations occurring in GBM tumors spheres at 96h post-radiation. To do so, we performed differential expression analysis and gene set enrichment analysis (GSEA) to identify top differentially expressed genes and significant changes in biological phenomena. Additionally, we evaluated the cell viability response of these GBM tumor spheres to radiation.
Results and discussion: PCA analysis of the four human GBM tumor sphere cell lines demonstrates that cell type has a substantial impact on variation among samples compared to non-irradiated and irradiated treatment conditions. Upon analysis of genes in common that are either upregulated or downregulated followed by GSEA, we identified enrichment of genes associated with inflammatory responses and ferroptosis repression (e.g., NUPR1, PTGS1, AOX1), and depletion of genes involved in fatty acid metabolism (e.g., INSIG1, PLA2G3, ACAT2). Furthermore, the GBM tumor sphere cell viability responses allowed us to stratify our models into radiosensitive and radioresistant subgroups.
Conclusion: Radiosensitive human GBM tumor spheres exhibit transcriptional alterations in genes linked to inflammation and fatty acid metabolism to a greater extent compared to radioresistant tumor spheres. Our study characterizes the radiation response of patient derived GBM models, which is to be leveraged for combating therapeutic resistance.
Citation Format: Arianna Richelle Izawa-Ishiguro, Subhiksha Nandakumar, Nicholas Carbone, Annalisa V. Ferrotta, Raashed Raziuddin, Kristen C. Vogt, Daniel A. Heller, Ingo K. Mellinghoff. Ionizing radiation induces lipid metabolism-associated vulnerabilities in glioblastoma multiforme [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 387.