Sequential fate-switches in stem-like cells drive the tumorigenic trajectory from human neural stem cells to malignant glioma.

Glioblastoma (GBM) is an incurable and highly heterogeneous brain tumor, originating from human neural stem/progenitor cells (hNSCs/hNPCs) years ahead of diagnosis. Despite extensive efforts to characterize hNSCs and end-stage GBM at bulk and single-cell levels, the de novo gliomagenic path from hNSCs is largely unknown due to technical difficulties in early-stage sampling and preclinical modeling. Here, we established two highly penetrant hNSC-derived malignant glioma models, which resemble the histopathology and transcriptional heterogeneity of human GBM. Integrating time-series analyses of whole-exome sequencing, bulk and single-cell RNA-seq, we reconstructed gliomagenic trajectories, and identified a persistent NSC-like population at all stages of tumorigenesis. Through trajectory analyses and lineage tracing, we showed that tumor progression is primarily driven by multi-step transcriptional reprogramming and fate-switches in the NSC-like cells, which sequentially generate malignant heterogeneity and induce tumor phenotype transitions. We further uncovered stage-specific oncogenic cascades, and among the candidate genes we functionally validated C1QL1 as a new glioma-promoting factor. Importantly, the neurogenic-to-gliogenic switch in NSC-like cells marks an early stage characterized by a burst of oncogenic alterations, during which transient AP-1 inhibition is sufficient to inhibit gliomagenesis. Together, our results reveal previously undercharacterized molecular dynamics and fate choices driving de novo gliomagenesis from hNSCs, and provide a blueprint for potential early-stage treatment/diagnosis for GBM.

A reignited debate over the cell(s) of origin for glioblastoma and its clinical implications.

Glioblastoma (GBM) is the most common and lethal primary neoplasm in the central nervous system. Despite intensive treatment, the prognosis for patients with GBM remains poor, with a median survival of 14-16 months. 90% of GBMs are primary GBMs that are full-blown at diagnosis without evidences of a pre-existing less-malignant precursor lesion. Therefore, identification of the cell(s) of origin for GBM-the normal cell or cell type that acquires the initial GBM-promoting genetic hit(s)-is the key to the understanding of the disease etiology and the development of novel therapies. Neural stem cells and oligodendrocyte precursor cells are the two major candidates for the cell(s) of origin for GBM. Latest data from human samples have reignited the longstanding debate over which cells are the clinically more relevant origin for GBMs. By critically analyzing evidences for or against the candidacy of each cell type, we highlight the most recent progress and debate in the field, explore the clinical implications, and propose future directions toward early diagnosis and preventive treatment of GBMs.