Single-Cell RNA-Seq Reveals the Invasive Trajectory and Molecular Cascades Underlying Glioblastoma Progression

Background: Glioblastoma (GBM) is the most common and aggressive primary brain tumor, in which glioblastoma stem cells (GSCs) were identified to contribute to aggressive phenotypes and poor prognosis. However, the mechanism of GBM invasion remains largely unexplored. Methods: We investigated the various status and constructed a branched trajectory of GBM cells utilizing single-cell RNA-seq data. Then the molecular cascades and key factors underlying the trajectory were comprehensively analyzed. Findings: We revealed the existence of cells with high invasive potential in heterogeneous primary GBM tumors. We reconstructed a branched trajectory by pseudotemporal ordering of single tumor cells, in which the root showed GSC-like phenotype while the end displayed high invasive activity. We further determined a path reflecting glioblastoma progression, called the "stem-to-invasion path". Along this path, cells showed incremental expressions of GBM invasion-associated signatures and diminishing expressions of glioblastoma stem cell markers. These findings were validated in an independent single-cell data set of GBM with 3589 cells. Through analyzing the molecular cascades underlying the path, we identify crucial factors controlling the achievement of invasive potential of tumor cells, including transcription factors and lncRNAs. Interpretation: Our work provides novel insights into GBM progression, especially the achievement of invasive potential in primary tumor cells, and support the cancer stem cell model, with valuable implications for GBM therapy. Funding: the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, the Heilongjiang Postdoctoral Foundation, the Health Department Science Foundation of Heilongjiang Province and the Fundamental Research Funds for the Provincial Universities. Declaration of Interest: The authors declare that they have no competing interests.