A long-term organotypic slice culture model of patient high-grade glioma preserving tumor heterogeneity and architecture, and specificity of CAR T cell targeting

ABSTRACT Background: High grade glioma (HGG), encompassing IDH-wildtype glioblastoma (CNS WHO grade 4), diffuse midline glioma (CNS WHO grade 4), oligodendroglioma (IDH-mutant and 1p/19q-codeleted) CNS WHO grade 3, together with IDH-mutant astrocytoma of CNS grade 3 and grade 4, represents the most lethal group of adult diffuse gliomas. Despite significant efforts, obtaining improvements in patient survival has been limited, in part, by difficulties in comprehensive ex vivo modeling of the complexities of HGG. Although organotypic slice cultures and other platforms have shown promise, existing models often fail to capture the intrinsic cellular heterogeneity, microenvironment, and architecture of HGG, restricting investigations into their fundamental biology as well as design of novel therapeutics. Methods: We developed a patient-derived HGG organotypic slice culture (GOSC) platform demonstrating long-term preservation of intrinsic tumor characteristics. Vibratome-sectioned slices were cultured in defined medium under conditions approximating those in situ: reduced oxygen (4%), low glucose (2.5 mM), and no added growth factors. The characteristics of GOSCs after 28 days in culture, including expression of immunotherapy targets, were compared to parental tumors using histological staining, immunofluorescence, multiplexed PhenoCycler (CODEX) imaging, bulk RNA-seq expression profiling, and CAR T cell killing assays. Results: GOSCs preserved the histopathology, cell heterogeneity, tumor microenvironment, and tissue architecture of their parental tumors throughout at least 28 days in culture. Importantly, GOSCs retained parental patterns of immunotherapy target expression, and CAR T cells co-cultured with GOSCs demonstrated target-specific killing consistent with parental tumors. Conclusions: This ex vivo GOSC platform offers long-term preservation of the cellular and structural properties of parental HGG tumors, thereby providing a robust tool for extended preclinical studies, and facilitating development and evaluation of advanced tumor-targeting strategies.