Abstract PR-004: Targeting EPHB2/ABL1 restores anti-tumor immunity in a preclinical model of ependymoma

Abstract Purpose: Ependymoma (EPN) is a common type of brain tumor in children and is often resistant to available cytotoxic therapies. Molecular profiling studies have led to a better understanding of unique EPN subtypes and revealed a critical role of EPHB2. However, the immune system's role in tumor progression and treatment response remains poorly understood. New treatments for EPN are desperately needed and should be developed in a molecular subtype-specific fashion. Experimental Design: We developed a syngeneic mouse model using subtype-specific EPHB2-driven genetically engineered EPN tumor cells. Druggable targets were identified by matching transcriptomic signatures with the target spectrum of FDA-approved drugs. After identifying dasatinib as a potentially effective agent, we measured the changes in the immune microenvironment during EPN growth and after dasatinib treatment. Results: Transcriptomic profiling of EPHB2-driven EPN and analysis of a human EPN dataset revealed multiple protein kinases as potential druggable targets. We found that the multikinase inhibitor dasatinib potently inhibited the growth of EPN both in vitro and in vivo, mainly through blocking EPHB2 and ABL1 signaling. We found an increased frequency of immunosuppressive M2-like tumor-associated macrophages (TAMs), which proportionally increased with tumor size during tumor progression. However, treatment with dasatinib reprogrammed the EPN immune microenvironment by polarizing the TAMs toward an anti-tumor M1-like phenotype and increasing CD8 T cell activation. Furthermore, dasatinib treatment induced complete regression of established EPN tumors in 78% of the animals and protected survivors against tumor recurrence. Depletion of CD8 T cells compromised the durability of EPN responses and reduced overall survival. Conclusions: These data indicate that dasatinib may be an effective therapy for EPHB2-driven molecular subgroup of EPNs by activating the anti-tumor immune response and support further investigations of dasatinib in clinical trials. Citation Format: Taylor P. Uccello, Jun Ren, Zohreh Amoozgar, Yuhui Zhao, Pin-Ji Lei, William W. Ho, Sylvie Roberge, Peigen Huang, Dan G. Duda, Lei Xu, Rakesh K. Jain. Targeting EPHB2/ABL1 restores anti-tumor immunity in a preclinical model of ependymoma abstract. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₁): Abstract nr PR-004.