MODL-23. PAIRED GLIOBLASTOMA CELL CULTURES OF THE FLUORESCENT BULK TUMOR AND NON-FLUORESCENT TUMOR MARGIN DISPLAY DIFFERENTIAL PHENOTYPES AND CELL STATES ACROSS PATIENTS

Abstract

Abstract Glioblastoma is a devastating disease with a median survival of 8 months after diagnosis. Over 90% of patients have a recurrence that is in contact with the resection cavity. To understand the potential relapse-causing cells of the local infiltrative tumor margin, which have rarely been studied, we have established and analyzed paired cell cultures from the fluorescent bulk tumor and non-fluorescent tumor margin. Tumor samples were resected using 5-ALA fluorescence-guided surgery and employing stringent procedures to separate margin samples from bulk tumor cells. All margin samples were resected at least 1cm beyond the fluorescent border in non eloquent areas as determined intraoperatively. Bulk and margin samples from 13 glioblastoma patients were explanted and 7 paired cultures that could be maintained to at least passage 7 were established. Analysis of self-renewal and orthotopic tumor formation of both acutely dissociated cells and established cultures showed that bulk tumor cells in all cases had a higher capacity than their paired margin cells. Conversely, margin cells always displayed a higher invasive capacity than their paired bulk tumor cells. Combined single nucleus RNA- and ATAC-sequencing was performed on three paired cultures. Analysis of snRNA-seq data showed that the margin cell phenotype was connected with transitions towards more differentiated (AC- and MES-like) cell states compared to paired bulk tumor cells that showed a higher rate of cells in progenitor cell-like states (NPC- and OPC-like). snATAC analysis uncovered that the margin cell phenotype was connected with transcription factor (TF) motifs known to be involved in cell invasion and differentiation, while paired bulk tumor cells were enriched for TF motifs involved in neural development and proliferation. We present a unique collection of margin cell cultures that we believe are more relevant models of the relapse-causing glioblastoma cells than those established from the bulk tumor.