Relapse pathway of glioblastoma revealed by single-cell molecular analysis.

Glioblastoma multiforme (GBM) remains an incurable brain tumor. The highly malignant behavior of GBM may, in part, be attributed to its intraclonal genetic and phenotypic diversity (subclonal evolution). Identifying the molecular pathways driving GBM relapse may provide novel, actionable targets for personalized diagnosis, characterization of prognosis and improvement of precision therapy. We screened single-cell transcriptomes, namely RNA-seq data of primary and relapsed GBM tumors from a patient, to define the molecular profile of relapse. Characterization of hundreds of individual tumor cells identified three mutated genes within single cells, involved in the RAS/GEF GTP-dependent signaling pathway. The identified molecular pathway was further verified by meta-analysis of RNA-seq data from more than 3000 patients. This study showed that single-cell molecular analysis overcomes the inherent heterogeneity of bulk tumors with respect to defining tumor subclonal evolution relevant to GBM relapse.

Cancer stem cells from a rare form of glioblastoma multiforme involving the neurogenic ventricular wall.

BACKGROUND: The cancer stem cell (CSC) hypothesis posits that deregulated neural stem cells (NSCs) form the basis of brain tumors such as glioblastoma multiforme (GBM). GBM, however, usually forms in the cerebral white matter while normal NSCs reside in subventricular and hippocampal regions. We attempted to characterize CSCs from a rare form of glioblastoma multiforme involving the neurogenic ventricular wall. METHODS: We described isolating CSCs from a GBM involving the lateral ventricles and characterized these cells with in vitro molecular biomarker profiling, cellular behavior, ex vivo and in vivo techniques. RESULTS: The patient's MRI revealed a heterogeneous mass with associated edema, involving the left subventricular zone. Histological examination of the tumor established it as being a high-grade glial neoplasm, characterized by polygonal and fusiform cells with marked nuclear atypia, amphophilic cytoplasm, prominent nucleoli, frequent mitotic figures, irregular zones of necrosis and vascular hyperplasia. Recurrence of the tumor occurred shortly after the surgical resection. CD133-positive cells, isolated from the tumor, expressed stem cell markers including nestin, CD133, Ki67, Sox2, EFNB1, EFNB2, EFNB3, Cav-1, Musashi, Nucleostemin, Notch 2, Notch 4, and Pax6. Biomarkers expressed in differentiated cells included Cathepsin L, Cathepsin B, Mucin18, Mucin24, c-Myc, NSE, and TIMP1. Expression of unique cancer-related transcripts in these CD133-positive cells, such as caveolin-1 and -2, do not appear to have been previously reported in the literature. Ex vivo organotypic brain slice co-culture showed that the CD133+ cells behaved like tumor cells. The CD133-positive cells also induced tumor formation when they were stereotactically transplanted into the brains of the immune-deficient NOD/SCID mice. CONCLUSIONS: This brain tumor involving the neurogenic lateral ventricular wall was comprised of tumor-forming, CD133-positive cancer stem cells, which are likely the driving force for the rapid recurrence of the tumor in the patient.