GBM heterogeneity as a function of variable epidermal growth factor receptor variant III activity.

Abnormal activation of the epidermal growth factor receptor (EGFR) due to a deletion of exons 2-7 of EGFR (EGFRvIII) is a common alteration in glioblastoma (GBM). While this alteration can drive gliomagenesis, tumors harboring EGFRvIII are heterogeneous. To investigate the role for EGFRvIII activation in tumor phenotype we used a neural progenitor cell-based murine model of GBM driven by EGFR signaling and generated tumor progenitor cells with high and low EGFRvIII activation, pEGFRHi and pEGFRLo. In vivo, ex vivo, and in vitro studies suggested a direct association between EGFRvIII activity and increased tumor cell proliferation, decreased tumor cell adhesion to the extracellular matrix, and altered progenitor cell phenotype. Time-lapse confocal imaging of tumor cells in brain slice cultures demonstrated blood vessel co-option by tumor cells and highlighted differences in invasive pattern. Inhibition of EGFR signaling in pEGFRHi promoted cell differentiation and increased cell-matrix adhesion. Conversely, increased EGFRvIII activation in pEGFRLo reduced cell-matrix adhesion. Our study using a murine model for GBM driven by a single genetic driver, suggests differences in EGFR activation contribute to tumor heterogeneity and aggressiveness

Olig2-Regulated Lineage-Restricted Pathway Controls Replication Competence in Neural Stem Cells and Malignant Glioma

Recent studies have identified stem cells in brain cancer. However, their relationship to normal CNS progenitors, including dependence on common lineage-restricted pathways, is unclear. We observe expression of the CNS-restricted transcription factor, OLIG2, in human glioma stem and progenitor cells reminiscent of type C transit-amplifying cells in germinal zones of the adult brain. Olig2 function is required for proliferation of neural progenitors and for glioma formation in a genetically relevant murine model. Moreover, we show p21^(WAF1/CIP1), a tumor suppressor and inhibitor of stem cell proliferation, is directly repressed by OLIG2 in neural progenitors and gliomas. Our findings identify an Olig2-regulated lineage-restricted pathway critical for proliferation of normal and tumorigenic CNS stem cells

Id4 promotes the elimination of the pro-activation factor ascl1 to maintain quiescence of adult hippocampal stem cells

Quiescence is essential for the long-term maintenance of adult stem cells but how stem cells maintain quiescence is poorly understood. Here we show that neural stem cells in the adult mouse hippocampus actively transcribe the pro-activation factor Ascl1 regardless of their activated or quiescent states. We found that the inhibitor of DNA binding protein Id4 is enriched in quiescent neural stem cells and that elimination of Id4 results in abnormal accumulation of Ascl1 protein and premature stem cell activation. Accordingly, Id4 and other Id proteins promote elimination of Ascl1 protein in neural stem cell cultures. Id4 sequesters Ascl1 heterodimerisation partner E47, promoting Ascl1 protein degradation and stem cell quiescence. Our results highlight the importance of non-transcriptional mechanisms for the maintenance of neural stem cell quiescence and reveal a role for Id4 as a quiescence-inducing factor, in contrast with its role of promoting the proliferation of embryonic neural progenitors

A Glial Signature and Wnt7 Signaling Regulate Glioma-Vascular Interactions and Tumor Microenvironment.

Gliomas comprise heterogeneous malignant glial and stromal cells. While blood vessel co-option is a potential mechanism to escape anti-angiogenic therapy, the relevance of glial phenotype in this process is unclear. We show that Olig2+ oligodendrocyte precursor-like glioma cells invade by single-cell vessel co-option and preserve the blood-brain barrier (BBB). Conversely, Olig2-negative glioma cells form dense perivascular collections and promote angiogenesis and BBB breakdown, leading to innate immune cell activation. Experimentally, Olig2 promotes Wnt7b expression, a finding that correlates in human glioma profiling. Targeted Wnt7a/7b deletion or pharmacologic Wnt inhibition blocks Olig2+ glioma single-cell vessel co-option and enhances responses to temozolomide. Finally, Olig2 and Wnt7 become upregulated after anti-VEGF treatment in preclinical models and patients. Thus, glial-encoded pathways regulate distinct glioma-vascular microenvironmental interactions

In vivo models of brain tumors: roles of genetically engineered mouse models in understanding tumor biology and use in preclinical studies

International audienceAlthough our knowledge of the biology of brain tumors has increased tremendously over the past decade, progress in treatment of these deadly diseases remains modest. Developing in vivo models that faithfully mirror human diseases is essential for the validation of new therapeutic approaches. Genetically engineered mouse models (GEMMs) provide elaborate temporally and genetically controlled systems to investigate the cellular origins of brain tumors and gene function in tumorigenesis. Furthermore, they can prove to be valuable tools for testing targeted therapies. In this review, we discuss GEMMs of brain tumors, focusing on gliomas and medulloblastomas. We describe how they provide critical insights into the molecular and cellular events involved in the initiation and maintenance of brain tumors, and illustrate their use in preclinical drug testing

ID4 Is Required for Normal Ependymal Cell Development

International audienceEpendymal cells are radial glia-derived multiciliated cells lining the lateral ventricles of the brain and spinal cord. Correct development and coordinated cilia beating is essential for proper cerebrospinal fluid (CSF) flow and neurogenesis modulation. Dysfunctions of ependymal cells were associated with transcription factor deregulation. Here we provide evidence that the transcriptional regulator ID4 is involved in ependymal cell development and maturation. We observed that Id4-deficient mice display altered ventricular cell cytoarchitecture, decreased ependymal cell number and enlarged ventricles. In addition, absence of ID4 during embryonic development resulted in decreased ependymal cell number and delayed maturation. Our findings open the way for a potential role of ID4 in ependymal cell development and motor cilia function

Disruption of CK2β in Embryonic Neural Stem Cells Compromises Proliferation and Oligodendrogenesis in the Mouse Telencephalon▿ †

Genetic programs that govern neural stem/progenitor cell (NSC) proliferation and differentiation are dependent on extracellular cues and a network of transcription factors, which can be regulated posttranslationally by phosphorylation. However, little is known about the kinase-dependent pathways regulating NSC maintenance and oligodendrocyte development. We used a conditional knockout approach to target the murine regulatory subunit (beta) of protein kinase casein kinase 2 (CK2β) in embryonic neural progenitors. Loss of CK2β leads to defects in proliferation and differentiation of embryonic NSCs. We establish CK2β as a key positive regulator for the development of oligodendrocyte precursor cells (OPCs), both in vivo and in vitro. We show that CK2β directly interacts with the basic helix-loop-helix (bHLH) transcription factor Olig2, a critical modulator of OPC development, and activates the CK2-dependent phosphorylation of its serine-threonine-rich (STR) domain. Finally, we reveal that the CK2-targeted STR domain is required for the oligodendroglial function of Olig2. These findings suggest that CK2 may control oligodendrogenesis, in part, by regulating the activity of the lineage-specific transcription factor Olig2. Thus, CK2β appears to play an essential and uncompensated role in central nervous system development

Etude biochimique et fonctionnelle de la protéine Drm/Gremlin (rôles au cours du développement embryonnaire aviaire)

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

PAK3 is a key signature gene of the glioma proneural subtype and affects its proliferation, differentiation and growth

International audiencePurpose Gliomas are the most lethal adult primary brain cancers. Recent advances in their molecular characterization have contributed to a better understanding of their pathophysiology, but there is still a need to identify key genes controlling glioma cell proliferation and differentiation. The p21-activated kinases PAK1 and PAK2 play essential roles in cell division and brain development and are well-known oncogenes. In contrast, the role of PAK3 in cancer is poorly understood. It is known, however that this gene is involved in brain ontogenesis and has been identified as a gene of the proneural subtype signature in glioblastomas. Methods To better understand the role of PAK kinases in the pathophysiology of gliomas, we conducted expression analyses by querying multiple gene expression databases and analyzing primary human glioma samples. We next studied PAK3 expression upon differentiation in patient-derived cell lines (PDCLs) and the effects of PAK3 inhibition by lentiviral-mediated shRNA on glioma cell proliferation, differentiation and tumor growth. Results We show that contrary to PAK1 and PAK2, high PAK3 expression positively correlates with a longer survival of glioma patients. We also found that PAK3 displays differential expression patterns between glioma subgroups with a higher expression in 1p/19q-codeleted oligodendrogliomas, and is highly expressed in tumors and PDCLs of the proneural subtype. In PDCLs, high PAK3 expression negatively correlated with proliferation and positively correlated with neuronal differentiation. Inhibition of PAK3 expression increased PDCL proliferation and glioma tumor growth in nude mice. Conclusions Our results indicate that PAK3 plays a unique role among PAKs in glioma development and may represent a potential therapeutic target

Cellular senescence in malignant cells promotes tumor progression in mouse and patient Glioblastoma

Abstract Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, yet it remains refractory to systemic therapy. Elimination of senescent cells has emerged as a promising new treatment approach against cancer. Here, we investigated the contribution of senescent cells to GBM progression. Senescent cells were identified in patient and mouse GBMs. Partial removal of p16 Ink4a -expressing malignant senescent cells, which make up less than 7 % of the tumor, modified the tumor ecosystem and improved the survival of GBM-bearing mice. By combining single cell and bulk RNA sequencing, immunohistochemistry and genetic knockdowns, we identified the NRF2 transcription factor as a determinant of the senescent phenotype. Remarkably, our mouse senescent transcriptional signature and underlying mechanisms of senescence are conserved in patient GBMs, in whom higher senescence scores correlate with shorter survival times. These findings suggest that senolytic drug therapy may be a beneficial adjuvant therapy for patients with GBM