IMMU-30. DISSECTING THE DYNAMIC RESPONSES OF GLIOBLASTOMA TO CAR T CELL THERAPY USING PATIENT-DERIVED TUMOR ORGANOIDS AND SINGLE-CELL MULTI-OMICS ANALYSES

Abstract

Abstract Immunotherapy, including chimeric antigen receptor (CAR) T cell therapy, has yielded major advancements for a number of hard-to-treat cancers; however, its transformative potential has yet to be realized in glioblastoma (GBM). Clinical studies of EGFRvIII targeted CAR T cell therapy have indicated that tumor heterogeneity, immune microenvironment, and adaptive responses to treatment may play important roles in limiting overall efficacy. We sought to examine comprehensively the dynamic molecular landscape of CAR T cell therapy in GBM using patient-derived GBM organoids (GBOs), a newly established laboratory model of inter- and intra- tumoral heterogeneity. Especially advantageous in these studies, GBOs preserve the intrinsic composition of somatic mutations, transcriptomic states, and non-neoplastic cells that contribute to the tumor microenvironment. Complementing the complexity of this biological system, we constructed an integrated single-cell multi-omics platform to interrogate gene expression, cell surface protein expression, somatic variants, and TCR sequences all from the same cell. Co-culture of GBOs and EGFRvIII targeted CAR T cells led to rapid T cell activation with concomitant upregulation of cytokine response gene programs in both antigen-positive and antigen-negative tumor cells. The adaptive tumor response also included expression of immune checkpoint receptor (ICR) ligands, such as PD-L1. At later time points, T cells transitioned into a dysfunctional or exhausted state, as characterized by increased cell surface expression of inhibitory receptors, such as PD-1, and decreased markers of effector activity despite the presence of antigen. Interestingly, CAR T cell therapy not only led to changes in immune-related pathways and tumor microenvironment, but it also induced shifts in tumor cell states with the depletion of an oligodendrocyte precursor cell-like state and corresponding enrichment in an astrocyte-like state. This finding suggests that EGFRvIII targeted CAR T cell therapy may leverage intrinsic cellular plasticity to induce differentiation-like effects in the surviving tumor cells.