Abstract 1441: Establishing a novel clinically relevant disease model of glioblastoma
Authors: Connor Kate , White Kieron , Clerkin James , Sweeney Kieron , Shiels Liam , van Brussel Thomas , Arijs Ingrid , Lambrechts Diether , Shankar Gautam , de Smet Frederik , Maher Stephen G. , Marignol Laure , Dicker Patrick , Prehn Jochen , O'Brien David , Byrne Annette T. 
Published: March 2024

Abstract
Introduction: GBM is the most common primary malignancy of the CNS. Historically pre-clinical models have failed to predict response in humans, despite promising preclinical data. Moreover, current models seldom incorporate surgical resection and/or standard of care chemotherapy treatment. These models also commonly employ young animals exclusively, whose immune contexture differs from older patients. We therefore sought to establish an improved, orthotopic, preclinical GBM model, which better recapitulates patient response to standard-of-care and targeted treatments.
Methods: NFpp10a-Luc2 GBM cells were orthotopically implanted into C57BL/6-mice (aged[&gt;18months] and young[6-8weeks]) and weekly bioluminescence imaging performed to monitor tumor growth. Overall survival (OS) and tumor growth were assessed in response to (1) Surgical Resection, (2) Temozolomide (TMZ) (3) anti-PD1 (4) neoadjuvant anti-PD1 and (5) Regorafenib (REGO) therapy. Tissue collected post-mortem underwent bulk RNA sequencing followed by analysis via microenvironment cell population counter (MCP) and gene set enrichment (GSEA) to determine changes in the GBM-TME following treatment.
Results: We demonstrated OS advantage in aged mice undergoing surgical resection (Resection:33.5 days vs Non-Resection: 18 days; p=0.0166) and observed age to be a significant prognostic factor (Young:62 days vs Aged: 22 days; p=0.0002). Subsequently, we observed that TMZ and anti-PD1 monotherapies had no impact on NFpp10-Luc2 growth (p=0.9001, p=0.7933) or survival (p=0.3035, p=0.6328). Neoadjuvant anti-PD1 treated mice demonstrated no significant survival advantage compared to IgG control (33 days vs 35 days; p=0.9429). Lastly, REGO treatment demonstrated a trend towards improved OS vs Vehicle (p=0.096). MCP analysis revealed both neoadjuvant anti-PD1 and REGO treatment induced influx of CD8+ T cells, B cells and monocytes into the TME, with neoadjuvant anti-PD1 associated with an upregulation of CXCR3 (p=0.0045).
Conclusions: We have, for the first time, established and characterized response of the NFpp10a-C57BL/6 model to surgical resection, TMZ, anti-PD1 and REGO therapy in both young and aged mice. We have shown the model is markedly insensitive to intervention with chemotherapy and immune checkpoint therapy, mirroring what is seen clinically in patients. The model may therefore be employed in future pre-clinical studies to guide clinical trials in the setting of mesenchymal GBM.
Citation Format: Kate Connor, Kieron White, James Clerkin, Kieron Sweeney, Liam Shiels, Thomas van Brussel, Ingrid Arijs, Diether Lambrechts, Gautam Shankar, Frederik de Smet, Stephen G. Maher, Laure Marignol, Patrick Dicker, Jochen Prehn, David O'Brien, Annette T. Byrne. Establishing a novel clinically relevant disease model of glioblastoma [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(6_Suppl):Abstract nr 1441.