Abstract 6171: Evolution of the spatial myeloid-lymphoid engagement in glioblastoma under temozolomide treatment

Abstract The current standard of care for glioblastoma (GBM), encompassing surgery, chemotherapy, and radiation, fails to extend patient survival beyond ~12-15 months. Even advanced immunotherapies, such as checkpoint blockade and chimeric antigen receptor-armored T-cell therapies, are ineffective in GBM due to tissue-specific niche-dependent escape strategies employed by glioma cells. Immune effectiveness, a finely regulated spatial and context-dependent process, underpins such a dismal state of the present therapeutic options. Herein, we applied CO-Detection by indEXing (CODEX), a state-of-the-art multiplex imaging platform, to elucidate the immune cell networks of the tumor microenvironment. By harnessing computational tools on multiplexed regions of interest across whole-slide images, we characterize the immune repertoire of GBMs by studying intratumor heterogeneity across space-histological territories- and time, matching pre- and post-treatment tissue sections of GBMs from seven patients under treatment (Stupp protocol). We aimed to assess changes in the interactions between the two main compartments of the immune system, myeloid and lymphoid, pre- and post-treatment using spatial statistics. We designed a computational workflow for the georeferencing, classification, and phenotyping individual cells of CODEX images across 105 regions of interest, representative of a mosaic of histologically defined cellular tumor (CT) or infiltrating tumor. We defined six major immune phenotypes and evaluated their spatial association with Cd45-Nestin+Olig2+ glioma cells. We modeled the GBM ecosystem and the cells’ spatial coexistence as spatial point processes that allowed the projection of coexistence networks. After stringent quality control, we detected and phenotyped 2. 3M cells. Despite interpatient heterogeneity, some patients maintained an even immune composition, while others showed an enrichment in microglia, particularly in CT. Spatial network analyses revealed an increased coexistence between myeloid and lymphoid cells after treatments despite T cells being canonically considered moderately abundant. Quantitatively, the immune meta-network displayed higher edge density and lower modularity post-treatment compared with pre-treatment, reflecting increased lymphoid-myeloid engagement. In summary, we detected an increased spatial myeloid-lymphoid engagement in GBM undergoing chemo-radiation treatments. Spatiotemporal rearrangement of tumor-immune interactions indicates mechanisms implicated in disease recurrence and resistance to standard treatment, opening the frontiers for developing new targeted immunotherapies. Citation Format: Simon P. Castillo, Afrooz Jahedi, Pravesh Gupta, Jason T. Huse, Kasthuri Kannan, Yinyin Yuan, Krishna P. Bhat. Evolution of the spatial myeloid-lymphoid engagement in glioblastoma under temozolomide treatment 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 6171.