PO-340 Tumour heterogeneity in patient-derived glioblastoma organoids

Abstract

IntroductionGlioblastoma (GBM) is the most malignant primary brain tumour with a median survival of 15 months despite intensive multimodal treatment including surgery, chemoradiation and adjuvant chemotherapy. A major obstacle in the improvement of patient survival is intratumoral heterogeneity, responsible for differences in treatment sensitivity and a spatial and temporally dynamic process that drives tumour resistance mechanisms. New clinically relevant predictive models are needed that encompass this heterogeneity to discover improved tumor-tailored treatments.Cancer organoids are 3D cancer stem-cell cultures that can self-maintain a hierarchy of pluripotent cancer stem cells and differentiated tumour cells. At present, cancer organoid models for GBM are still understudied. Our goal is to demonstrate whether GBM organoids maintain genetic and phenotypic heterogeneity with respect to the patient biopsy and if standard treatment is predictive for resistance mechanisms. If so, GBM organoids may be used as co-clinical avatars to predict treatment response and guide adaptations to the treatment plan.Material and methodsIn this project, fresh GBM biopsies from 30 patients will be used to establish GBM organoids. Organoids are formed by suspending tumour cells in Matrigel plugs and cultured in stem cell medium. At set time points, GBM organoids have been harvested and embedded using paraffin- and cryopreservation. Sections are stained for hypoxia, proliferation, apoptosis and glioma stem cell markers. GBM organoids will be exposed to current standard treatment options (i.e. radiotherapy and temozolomide) and phenotypic changes will be determined. RNA expression analysis will be used to assess tumor-driving signal transduction pathways before and after treatment.Results and discussionsGBM organoids have been derived from five patients with different clinical subtypes and have been maintained in culture for several months. Our results show that GBM organoids develop a hypoxic core and an outer rim that has abundant proliferation. Data on the hypoxia, proliferation and presence of glioma stem cells will be presented before and after treatment. Future studies will include next-generation sequencing of glioma driver genes during tumour evolution in culture before and after treatment.ConclusionOur results demonstrate the feasibility of maintaining primary GBM organoids in culture for phenotypic and genotypic analysis. Future studies will demonstrate the genetic stability of the GBM organoids and their response to treatment.