Abstract 3170: Targeting tumor-associated astrocyte dependence in glioblastoma treatment

Abstract

Abstract Glioblastoma (GBM) is the most common malignant primary brain tumor and remains challenging to treat due to its aggressive nature with high rate of recurrence. Despite advances in therapy, prognosis is poor with median survival of 19 months with maximal therapy. The normal astrocytes within the GBM TME undergo a phenotypic shift, promoting alterations supportive of tumor growth. There is increasing attention on the role of tumor-associated astrocytes (TAA) in GBM progression and resistance to therapy. Previous studies assessing astrocyte support of GBM employ astrocytes derived from murine or fetal sources. We have isolated TAAs from patients with GBM as well as normal human astrocytes (NHA) from cancer-free patients undergoing surgical treatment of epilepsy. The cells are maintained at a low passage number (<10 passes). Our data emphasize the supportive role these cells in GBM progression and resistance to GBM therapy. Briefly, conditioned media (CM) from non-malignant, GFAP positive TAAs, demonstrate a propensity to induce invasion and migration of U87 GBM cells compared to the NHA CM. In addition, TAA CM significantly increased the IC50 dose of U87 cells treated with temozolomide from 536 μM to 1351 μM demonstrating treatment resistance (p<0.001). TAA CM induced temozolomide resistance of the GBM cells can be abolished with supra-therapeutic dosing. RNA sequencing (RNAseq) of two TAA and three NHA samples revealed 399 differentially expressed genes identified with 38 of those upregulated genes coding extracellular products. Expression data was verified by quantitative polymerase chain reaction (qPCR), thus validating the differential expression profile generated by RNAseq. The differential expression data was explored further using Ingenuity Pathway Analysis (IPA) and gene set enrichment analysis (GSEA). Attention was focused on genes with excreted factors as products or involved in the regulation of critical excreted products. We identified and validated high expression of IL1β in TAAs compared to NHAs. RNAseq data revealed multiple potential pathways for targeted therapies aimed at modulating the effect of TAAs in the tumor microenvironment. In ongoing studies, we will determine the efficacy of IL1β in attenuating the TAA-induced temozolomide resistance in GBM. These studies reveal for the first time a highly clinically relevant approach to attenuate TAA-facilitated GBM progression and therapy resistance. Citation Format: Joseph S. Domino, Anthony Alvarado, Levi Arnold, Sumedha Gunewardena, David Akhavan, Sufi M. Thomas. Targeting tumor-associated astrocyte dependence in glioblastoma treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3170.