Abstract Medulloblastoma (MB) is the most common paediatric malignant brain tumour, the ontogeny of which is closely linked to dysregulated cerebellar development. Extensive characterisation of these tumours has informed their molecular classification into four distinct subgroups (WNT, SHH, G3 and G4), whilst recent studies have shown the fundamental role of human-specific progenitor cells in the development of G3 and G4 MB, clearly exposing the limitations of mouse models for their study. Therefore, despite advances in dissecting MB heterogeneity, a lack of faithful preclinical human-specific models has hampered their translation towards patient treatment. Here we generate a novel expanded potential stem cell derived human cerebellar organoid (CbO) model. Epigenetic and single cell transcriptomic characterisation showed faithful recapitulation of human cerebellar development in CbOs, including cells enriched for cerebellar glutamatergic progenitor and Protogenin+ve stem cell rhombic lip signatures specific to spatiotemporally restricted G3 and G4 MB cells-of-origin. We further demonstrate these cells arise in CbOs at a matched developmental timepoint to when MB tumour onset is thought to occur in patients and can be specifically targeted for genetic engineering studies to dissect MB tumour biology. Upon co-culture with MB cells (CbO-MB), CbOs can sustain MB growth and proliferation, including MB cells previously maintained as xenografts only, to better phenocopy patient tumours and reveal potential tumour microenvironment mediators. Finally, CbO-MBs reproduced the pre-clinical efficacy of anti-tumour compounds from in vivo drug testing in xenograft models, whilst also providing insight into adverse effects on non-neoplastic CbO cells. Our results demonstrate the utility of CbOs as a novel, scalable tool upon co-culture for studies on MB microenvironment interactions and drug testing, whilst providing unprecedented access to human-specific G3 and G4 MB cells-of-origin to interrogate MB tumour onset and progression.
Willott et al. (Fri,) studied this question.