Human glioblastomas harbour a subpopulation of glioblastoma stem cells that drive tumorigenesis. However, the origin of intratumoural functional heterogeneity between glioblastoma cells remains poorly understood. Here we study the clonal evolution of barcoded glioblastoma cells in an unbiased way following serial xenotransplantation to define their individual fate behaviours. Independent of an evolving mutational signature, we show that the growth of glioblastoma clones in vivo is consistent with a remarkably neutral process involving a conserved proliferative hierarchy rooted in glioblastoma stem cells. In this model, slow-cycling stem-like cells give rise to a more rapidly cycling progenitor population with extensive self-maintenance capacity, which in turn generates non-proliferative cells. We also identify rare ‘outlier’ clones that deviate from these dynamics, and further show that chemotherapy facilitates the expansion of pre-existing drug-resistant glioblastoma stem cells. Finally, we show that functionally distinct glioblastoma stem cells can be separately targeted using epigenetic compounds, suggesting new avenues for glioblastoma-targeted therapy. Using unique barcodes for tumour cells, the authors explore the dynamics of human glioblastoma subpopulations, and suggest that clonal heterogeneity emerges through stochastic fate decisions of a neutral proliferative hierarchy. Cancers are heterogeneous between patients and between tumour cells. It is still difficult to identify the subpopulations of cells that most contribute to tumour growth and those that are targeted by therapy. Xiaoyang Lan et al. now explore the dynamics of human glioblastoma (GBM) subpopulations using barcodes for tumour cells. They suggest that a proliferative hierarchy emerges through stochastic cell fate decision. In this model, slow-cycling stem cells give rise to rapidly proliferative progenitors that fuel tumour growth and which in turn generate cells that are short-lived and do not proliferate. This is in contrast to a clonal evolution model based on the different fitness of cells that are selected for. The authors also identify a rare subpopulation of GBM cells that is resistant to TMZ treatment (the common treatment for GBM) but can be targeted by drug combinations.

Fate mapping of human glioblastoma reveals an invariant stem cell hierarchy