Abstract
BACKGROUND: Lysine-specific demethylase 1 (LSD1) is overexpressed in glioblastoma, contributing to tumor growth and treatment resistance. LSD1 inhibitors have shown preclinical promise but have had limited clinical development for glioblastoma. Given the frequent kinase pathway alterations seen in glioblastoma, the interplay between LSD1 inhibition and kinase signaling pathways was investigated. METHODS: Glioblastoma stem cell (GSC) lines and normal human astrocytes (NHAs) were treated with catalytic LSD1 inhibitors, NCD38 and bomedemstat, and the LSD1 scaffolding inhibitor, seclidemstat alone and in combination with kinase inhibitors, including osimertinib, afatinib, and ulixertinib. The effect on cell viability, proliferation, and neurosphere formation was assessed, and synergy scores were calculated using Bliss synergy models. Kinase signaling was analyzed and in vivo efficacy was evaluated in orthotopic xenograft models. RESULTS: LSD1 knockdown and seclidemstat reduced kinase signaling, while catalytic LSD1 inhibitors increased kinase activity or had no effect. Catalytic LSD1 inhibitors combined with kinase inhibitors, synergistically reduced GSC viability and proliferation while sparing NHAs. Combination treatment consistently reduced phospho-S6 ribosomal protein levels in three different GSC lines, and basal phospho-S6 ribosomal protein levels across the GSCs and the NHAs were negatively correlated with a synergistic response. The generation of an NCD38-resistant GSC showed increased kinase activity and was associated with enhanced osimertinib sensitivity. Combined treatment with NCD38 and osimertinib in glioblastoma-bearing mice delayed tumor growth and improved survival outcomes. DISCUSSION: These findings provide a rationale for further investigation of combination therapies of catalytic inhibitors of LSD1 and EGFR and dual-targeted inhibitors to overcome resistance and improve outcomes.