OP14
GENETIC AND FUNCTIONAL DIVERSITY OF PROPAGATING CELLS IN GLIOBLASTOMA Free

INTRODUCTION: Glioblastoma (GBM) is a lethal malignancy whose clinical intransigence has been linked to extensive intraclonal genetic and phenotypic diversity and the common emergence of therapeutic resistance. This interpretation embodies the implicit assumption that cancer stem cells or tumour-propagating cells are themselves genetically and functionally diverse. METHOD: We screened primary GBM by SNP array to identify copy number alterations (a minimum of three) that could be visualized in single cells by multicolor fluorescence in situ hybridization. Interrogation of neurosphere-derived cells (from four patients) and cells derived from secondary transplants of these same cells in NOD-SCID mice allowed us to infer the clonal and phylogenetic architectures. Whole-exome sequencing and single-cell genetic analysis in one case were used to further dissect the complex clonal structure. RESULTS: All together our results show that: (i) GBM can be propagated by multiple stem cell-like clonal populations, (ii) Tumour-propagating clones display genetic and functional diversity, (iii) Clonal phylogenetic analysis reveals the temporal evolution of a fitness advantage, (iv) Competitive propagating ability is associated with TP53 mutation/EGFR amplification. CONCLUSION: This proof-of-principle experiment revealed that subclones in each GBM had variable regenerative or stem cell activity, and highlighted genetic alterations associated with more competitive propagating activity in vivo.