We describe the landscape of somatic genomic alterations based on multi-dimensional and comprehensive characterization of more than 500 glioblastoma tumors (GBMs). We identify several novel mutated genes as well as complex rearrangements of signature receptors including EGFR and PDGFRA. TERT promoter mutations are shown to correlate with elevated mRNA expression, supporting a role in telomerase reactivation. Correlative analyses confirm that the survival advantage of the proneural subtype is conferred by the G-CIMP phenotype, and MGMT DNA methylation may be a predictive biomarker for treatment response only in classical subtype GBM. Integrative analysis of genomic and proteomic profiles challenges the notion of therapeutic inhibition of a pathway as an alternative to inhibition of the target itself. These data will facilitate the discovery of therapeutic and diagnostic target candidates, the validation of research and clinical observations and the generation of unanticipated hypotheses that can advance our molecular understanding of this lethal cancer.

SUMMARY The dynamic and reversible N6-methyladenosine (m6A) RNA modification installed and erased by N6-methyltransferases and demethylases regulates gene expression and cell fate. We show that the m6A demethylase ALKBH5 is highly expressed in glioblastoma stem-like cells (GSCs). Silencing ALKBH5 suppresses the proliferation of patient-derived GSCs. Integrated transcriptome and m6A-seq analyses revealed altered expression of certain ALKBH5 target genes, including the transcription factor FOXM1. ALKBH5 demethylates FOXM1 nascent transcripts, leading to enhanced FOXM1 expression. Further, a long noncoding RNA antisense to FOXM1 (FOXM1-AS) promotes the interaction of ALKBH5 with FOXM1 nascent transcripts. Depleting ALKBH5 and FOXM1-AS disrupted GSC tumorigenesis through the FOXM1 axis. Our work uncovers a critical function for ALKBH5 and provides insight into critical roles of m6A methylation in glioblastoma.

Bipotential oligodendrocyte-type-2 astrocyte (0-2A) progenitor cells, which give rise to oligodendrocytes and type-2 astrocytes in cultures of rat optic nerve, are one of the few cell types in which most aspects of proliferation and differentiation can be manipulated in a defmed in vitro environment. Previous studies have shown that 0-2A progenitors exposed to platelet-derived growth factor (PDGF) divide as migratory bipolar cells a limited number of times, with a cell cycle time of 18 hr, before clonally related progenitors differentiate into nondividing oligodendrocytes with a timing similar to that seen in vivo. In contrast, 0-2A progenitors grown in the absence of mitogen do not divide but instead differentiate prematurely into oligodendrocytes, and progenitors exposed to appropriate inducing factors differentiate into type-2 astrocytes. We now have found that 0-2A progenitors can be induced to undergo continuous self-renewal in the absence of oligodendrocytic differentiation by exposure to a combination of PDGF and basic fibroblast growth factor (bFGF). With the exception of the inhibition of differentiation, the 0-2A progenitors exposed to PDGF and bFGF behaved similarly to those exposed to PDGF alone. In contrast, progenitors exposed to basic bFGF alone were multipolar, had a cell-cycle length of 45 hr, showed little migratory behavior, underwent premature oligodendrocytic differentiation, and did not cease division upon expression of oligodendrocyte marker antigens. Thus, inhibition of differentiation required the presence of both mitogens. Our results demonstrate that PDGF and bFGF act on 0-2A progenitors as both inducers of division and as regulators of differentiation that modulate multiple aspects of 0-2A progenitor development and, additionally, reveal a previously unrecognized means of regulating self-renewal processes, wherein cooperation between growth factors promotes continuous division in the absence of differentiation.To better understand the cellular and molecular interactions that regulate the development of multipotential precursor cells, we have been studying the control of division and differentiation in oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells of the rat optic nerve (1). These glial precursors represent one of the few cell types in which most aspects of differentiation and proliferation can be manipulated in a defined in vitro environment. For example, 0-2A progenitors grown in chemically defined medium in the absence of mitogen do not divide but instead differentiate rapidly into oligodendrocytes (1-3), while progenitors exposed to appropriate inducing factors differentiate into type-2 astrocytes (1, 4, 5).Several studies have demonstrated that the induction of cell division in 0-2A progenitors is associated with the expression of several characteristics that are quite distinct from the events of mitosis (see Fig. 1 for a summary). 0-2A progenitors induced to divide by platelet-derived growth factor (PDGF) or by growth in the presence of type-1 astrocytes (wh...