Abstract 3463: Exploiting mechanisms of glioblastoma invasion to induce vulnerabilities that promote synergistic lethality

Abstract Glioblastoma (GBM) is the most common and aggressive form of adult brain cancer. Diffuse infiltration of tumor cells into surrounding vital brain tissue prevents complete surgical removal and poses a significant challenge to treatment. Therefore, a better understanding of the molecular programs that drive GBM invasion is crucial to designing more effective therapies. We hypothesized that GBM invasion is mediated by generalizable molecular mechanisms and that disrupting these programs induced vulnerabilities that could be exploited by combination therapies. In this study, we used a clinically diverse cohort of 17 patient-derived GBM cell lines and advanced experimental conditions to develop more controlled models of GBM invasion. Since hypoxia is a known driver of tumor invasion, we cultured GBM cells under 20%, 1%, and 0.2% oxygen concentrations and performed mass spectrometry-based profiling to investigate the invasive signaling pathways promoted by hypoxia. Additionally, we also performed mass spectrometry-based profiling of GBM cells cultured in the glioma cerebral organoid (GLICO) model of brain infiltration to investigate hypoxia-independent invasion mechanisms. These analyses identified the enrichment of several integrin-related signaling signatures as a general mediator of GBM invasion across cell lines, in both hypoxia-induced invasion conditions and in brain infiltration. To identify downstream targets of the integrin signaling pathway that could impair tumor cell migration, we performed a chemical screen using a MAPK compound library (n=802 compounds), which identified MAP4K4 as a top invasion-specific kinase. Pharmacological inhibition of MAP4K4 significantly impaired migration across multiple cell lines in live imaging experiments and reduced tumor infiltration in GLICOs, supporting its broad generalizability as a target to disrupt GBM invasion. By performing phospho-proteomic profiling, we then mechanistically determined that MAP4K4 inhibition led to the dysregulation of focal adhesion dynamics and cytoskeletal remodeling, which was validated through live fluorescent imaging experiments. Lastly, to explore if MAP4K4 inhibition induced vulnerabilities that could be exploited by sequential treatment with a second compound, we performed a combination screen using an FDA approved drug library (n=3196 compounds). We identified three compounds with a synergistic effect dependent on MAP4K4 inhibition that reduced tumor cell viability by 35-40% compared to single agent treatment. As the therapeutic strategies to treat GBM have remained unchanged for decades, the administration of synergistic drug combinations that exploit the characteristic infiltrative nature of GBM may therefore represent a promising treatment avenue for this devastating disease. Citation Format: Rifat S. Sajid, Lennart J. van Winden, Okty Abbasi Borhani, Evelyn R. Kamski-Hennekam, Ameesha Paliwal, Nakita E. Gopal, Lauren Omoto, Olaf van Tellingen, Phedias Diamandis. Exploiting mechanisms of glioblastoma invasion to induce vulnerabilities that promote synergistic lethality abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3463.