Genetic and Functional Diversity of Propagating Cells in Glioblastoma

Abstract

Summary: 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 tumor-propagating cells are themselves genetically and functionally diverse. To test this, we screened primary GBM tumors 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 revealed a more complex clonal structure. 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. : In this article, Greaves and colleagues show that tumor-propagating cells in glioblastoma are genetically and functionally heterogeneous. When used in in vivo experiments, these cells show a variable competitive capacity for tumor propagation and further genetic diversification, suggesting that glioblastoma evolves through complex dynamics of subclonal fitness advantage and acquisition of mutations and copy number alterations.