Abstract 307: Generation and characterization of a glioblastoma stem cell model with acquired resistance to LSD1 inhibition

Abstract Epigenetic modifications play an important role in the initiation of various cancer types, including glioblastoma (GBM), and in the development of therapeutic resistance. Patients with GBM, a common malignant brain tumor, have an average survival of 12-15 months after first-line therapy. Lysine-specific demethylase 1 (LSD1) is a histone demethylase that is overexpressed in glioblastoma stem cells (GSCs) and functions to promote proliferation, inhibit differentiation, and enhance motility. Previous work from our group has investigated LSD1 as a therapeutic target in glioblastoma and identified genes that may predict resistance to pharmacological LSD1 inhibitors using RNA-seq. Five upregulated genes, HKDC1, RAB3IL1, RAB39B, FTH1, and FAM213A, were associated with LSD1 inhibitor (LSD1i) resistance and were validated in brain tissue of a GBM model treated with GSK-LSD1 after succumbing to tumor burden. In order to determine whether selection pressure from LSD1 inhibitor treatment caused upregulation of these genes, we created a model of acquired resistance in GSC lines in vitro. Isogenic resistant lines were generated by treating MDA-GSC17 cells with increasing concentrations of LSD1i or diluent (DMSO), as tolerated starting at 50 uM (which was five fold below the IC50 for these lines). In parallel, MDA-GSC17 controls were exposed to DMSO. The resistant line was created over 4 weeks and monitored by cell number and viability to reach 90%. To assess the change in gene expression, we conducted quantitative PCR for the five genes in the parental and resistant MDA-GSC17 line and saw upregulation in 3 of the 5 genes. Two genes, HKDC1 and RAB3IL1, were unable to be assessed due to low basal expression. However, 3 genes were upregulated which are RAB39B, FTH1, and FAM213A. RAB39B is a Ras-analog in brain (RAB) small GTPase and a member of the RAS oncogene family, involved in vesicular trafficking. High expression of ferritin heavy chain 1 (FTH1) is correlated with high-grade gliomas and poor prognosis in glioblastoma. Lastly, the redox regulatory protein, FAM213A, can activate antioxidant proteins and elevated expression is associated with worse outcomes for AML patients. This suggests that modulating the RAS signaling pathways and specific redox pathways may overcome LSD1 resistance. Understanding the changes in gene expression as the cells acquire resistance to LSD1 inhibitors will help us understand the mechanism of resistance to LSD1 inhibitors in glioblastoma and to design new treatment strategies. Citation Format: Kareena H. Patel, Lea Stitzlein, Deokhwa Nam, Frederick Lang, Joy Gumin, Joya Chandra. Generation and characterization of a glioblastoma stem cell model with acquired resistance to LSD1 inhibition 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 (6Suppl): Abstract nr 307.