Abstract 4619: Spatial analysis of the immunosuppressive tumor microenvironment in brain cancer applying a novel multiplex immunofluorescence panel

Abstract Glioblastoma (GBM) and brain metastases (BM) account for >70% of all brain cancers. The annual incidence averages to 10-17 cases per 100.000 person (~ 3 cases for GBM and 7-14 for BM), resulting in 45.000-77.000 new cases in the European Union alone. The standard of care for GBM includes maximal surgical resection followed by radiation and chemotherapy with temozolomide, whilst whole brain irradiation or surgical removal with or without chemotherapy are used for BM. In spite of therapy, the median overall survival remains < 6 months for BM, and 16 months for GBM, suggesting brain cancers as one of the most therapy-resistant tumors. Despite the emergence of novel therapeutic strategies, such as anti-angiogenic therapy, targeting myeloid cells or checkpoint immunotherapy, no significant improvement in overall survival of brain cancer patients was observed. Several studies have suggested the resistance to therapy in brain cancers is largely attributed by the presence of an immunosuppressive brain tumor microenvironment. To investigate the spatial architecture of the tumor microenvironment in BM derived from lung and breast cancers, we employed the Lunaphore 13-plex immune-oncology (IO) Core Panel, consisting of clinically relevant IO biomarkers (CD3, CD4, CD8, CD45, FoxP3, PD1, PD-L1, CD11c, CD20, CD56, CD68, aSMA and Ki-67) for multiplex immunofluorescence (mIF) assays. These findings were then compared to isocitrate dehydrogenase-wildtype glioblastoma, which is a T-cell-poor cancer that is also characterized by an immunosuppressive tumor microenvironment. Further, the IO Core Panel was expanded with previously established antibodies targeting myeloid, blood-brain barrier and tumor cell markers in a proteomic workflow on COMET™, a fully automated, sequential immunofluorescence (seqIF™) platform. Comprehensive mapping of the GBM microenvironment and BM confirmed previous observations obtained by bulk and single cell RNA sequencing analysis that described profound differences in the tumor microenvironment of BM versus GBM. In contrast to GBM, anti-tumor immunity in BM was increased, whereas immunosuppressive cells remained unchanged between the two. Of note, T- and B-cells were not evenly distributed within the tumor tissue, providing an additional level of spatial information that would have been missed by bulk RNA or proteomic analyses. Our study is the first to demonstrate a successful application of Lunaphore’s IO core panel on GBM and BM samples. This highlights potential future use in the development of tools for personalized medicine for GBM and other tumor types. Citation Format: Yvonne Reiss, Jadranka Macas, François Rivest, Victor de Gautard, Saska Brajkovic, Bastian Nicolai, Tatjana Starzetz, Kathleen Sommer, Pinar Cakmak, Jonathan Schup, Jennifer H. Lun, Karl H. Plate. Spatial analysis of the immunosuppressive tumor microenvironment in brain cancer applying a novel multiplex immunofluorescence panel. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4619.