Summary Glioblastomas display hierarchies with self-renewing cancer stem-like cells (CSCs). RNA sequencing and enhancer mapping revealed regulatory programs unique to CSCs causing upregulation of the iron transporter transferrin, the top differentially expressed gene compared to tissue-specific progenitors. Direct interrogation of iron uptake demonstrated CSCs potently extract iron from the microenvironment more effectively than other tumor cells. Systematic interrogation of iron flux determined that CSCs preferentially require transferrin receptor and ferritin - two core iron regulators - to propagate and form tumors in vivo. Depleting ferritin disrupted CSC mitotic progression, through the STAT3-FoxM1 regulatory axis, revealing an iron-regulated CSC pathway. Iron is a unique, primordial metal fundamental for earliest life forms, and on which CSCs have an epigenetically programmed, targetable dependence.

Autocrine VEGFR2 signaling in glioma stem-like cells evades VEGF neutralization.

Glioblastoma (World Health Organization grade IV glioma) represents the most common primary, intrinsic brain tumor with inevitable recurrence, limiting the median survival of patients to little more than a year ( 1, 2 ). Glioblastomas display cellular hierarchies with self-renewing glioblastoma stem cells (GSC) at the apex, with contributions of GSCs to therapeutic resistance and tumor recurrence ( 3-5 ). Standard-of-care therapy includes surgical resection followed by combined radiotherapy and chemotherapy, and then adjuvant chemotherapy, but treatment remains palliative ( 6 ). Given the roles of GSCs in therapeutic resistance, angiogenesis, immune escape, and invasion, clinical and preclinical observations suggest that targeting GSCs may improve tumor outcome ( 7 ). SIGNIFICANCE:Epitranscriptomics promotes cellular heterogeneity in cancer. RNA m6A landscapes of cancer and NSCs identifi ed cell type-specifi c dependencies and therapeutic vulnerabilities. The m6A reader YTHDF2 stabilized MYC mRNA specifi cally in cancer stem cells. Given the challenge of targeting MYC, YTHDF2 presents a therapeutic target to perturb MYC signaling in glioblastoma.Research.

Malignant gliomas, the deadliest of brain neoplasms, show rampant genetic instability and resistance to genotoxic therapies, implicating potentially aberrant DNA damage response (DDR) in glioma pathogenesis and treatment failure. Here, we report on gross, aberrant constitutive activation of DNA damage signalling in low-and highgrade human gliomas, and analyze the sources of such endogenous genotoxic stress. Based on analyses of human glioblastoma multiforme (GBM) cell lines, normal astrocytes and clinical specimens from grade II astrocytomas (n ¼ 41) and grade IV GBM (n ¼ 60), we conclude that the DDR machinery is constitutively activated in gliomas, as documented by phosphorylated histone H2AX (cH2AX), activation of the ATM-Chk2-p53 pathway, 53BP1 foci and other markers. Oxidative DNA damage (8-oxoguanine) was high in some GBM cell lines and many GBM tumors, while it was low in normal brain and grade II astrocytomas, despite the degree of DDR activation was higher in grade II tumors. Markers indicative of ongoing DNA replication stress (Chk1 activation, Rad17 phosphorylation, replication protein A foci and single-stranded DNA) were present in GBM cells under high-or lowoxygen culture conditions and in clinical specimens of both low-and high-grade tumors. The observed global checkpoint signaling, in contrast to only focal areas of overabundant p53 (indicative of p53 mutation) in grade II astrocytomas, are consistent with DDR activation being an early event in gliomagenesis, initially limiting cell proliferation (low Ki-67 index) and selecting for mutations of p53 and likely other genes that allow escape (higher Ki-67 index) from the checkpoint and facilitate tumor progression. Overall, these results support the potential role of the DDR machinery as a barrier to gliomagenesis and indicate that replication stress, rather than oxidative stress, fuels the DNA damage signalling in early stages of astrocytoma development.