BMP signaling induces astrocytic differentiation of clinically derived oligodendroglioma propagating cells.

UNLABELLED: Oligodendrogliomas are a type of glioma that lack detailed investigation because of an inability to cultivate oligodendroglioma cells that faithfully recapitulate their salient qualities. We have successfully isolated and propagated glioma stem-like cells from multiple clinical oligodendroglioma specimens. These oligodendroglioma-propagating cells (OligPC) are multipotent and form xenografts with oligodendroglioma features. Bone morphogenetic proteins (BMP) are considered potent inhibitors of oligodendrogliogenesis during development; therefore, the effects of BMP signaling in OligPCs were characterized. BMP pathway components are expressed by OligPCs and canonical signaling via Smad proteins is intact. This signaling potently depletes CD133-positive OligPCs, decreasing proliferation, and inducing astrocytic differentiation. Furthermore, analyses revealed that cytoplasmic sequestration of the oligodendrocyte differentiation factors OLIG1/2 by the BMP signaling effectors ID2 and ID4 is a plausible underlying mechanism. These findings elucidate the molecular pathways that underlie the effects of BMP signaling on oligodendroglioma stem-like cells. IMPLICATIONS: Stem-like cells are capable of propagating oligodendrogliomas, and BMP signaling potently diminishes their stemness by inducing astrocytic differentiation, suggesting that BMP activation may be effective as a cancer stem cell-targeted therapy.

Cadherin-11 regulates motility in normal cortical neural precursors and glioblastoma.

Metastasizing tumor cells undergo a transformation that resembles a process in normal development when non-migratory epithelial cells modulate the expression of cytoskeletal and adhesion proteins to promote cell motility. Here we find a mesenchymal cadherin, Cadherin-11 (CDH11), is increased in cells exiting the ventricular zone (VZ) neuroepithelium during normal cerebral cortical development. When overexpressed in cortical progenitors in vivo, CDH11 causes premature exit from the neuroepithelium and increased cell migration. CDH11 expression is elevated in human brain tumors, correlating with higher tumor grade and decreased patient survival. In glioblastoma, CDH11-expressing tumor cells can be found localized near tumor vasculature. Endothelial cells stimulate TGFß signaling and CDH11 expression in glioblastoma cells. TGFß promotes glioblastoma cell motility, and knockdown of CDH11 expression in primary human glioblastoma cells inhibits TGFß-stimulated migration. Together, these findings show that Cadherin-11 can promote cell migration in neural precursors and glioblastoma cells and suggest that endothelial cells increase tumor aggressiveness by co-opting mechanisms that regulate normal neural development.

The emerging roles of microRNAs in CNS injuries.

The consequences of injuries to the CNS are profound and persistent, resulting in substantial burden to both the individual patient and society. Existing treatments for CNS injuries such as stroke, traumatic brain injury and spinal cord injury have proved inadequate, partly owing to an incomplete understanding of post-injury cellular and molecular changes. MicroRNAs (miRNAs) are RNA molecules composed of 20-24 nucleotides that function to inhibit mRNA translation and have key roles in normal CNS development and function, as well as in disease. However, a role for miRNAs as effectors of CNS injury has recently emerged. Use of bioinformatics to assess the mRNA targets of miRNAs enables high-order analysis of interconnected networks, and can reveal affected pathways that may not be identifiable with the use of traditional techniques such as gene knock-in or knockout approaches, or mRNA microarrays. In this Review, we discuss the findings of miRNA microarray studies of spinal cord injury, traumatic brain injury and stroke, as well as the use of gene ontological algorithms to discern global patterns of molecular and cellular changes following such injuries. Furthermore, we examine the current state of miRNA-based therapies and their potential to improve functional outcomes in patients with CNS injuries.

Nanofiber-mediated inhibition of focal adhesion kinase sensitizes glioma stemlike cells to epidermal growth factor receptor inhibition.

BACKGROUND: Glioblastoma multiforme is the most common glioma in adults and carries a poor prognosis, due to tumor recurrence despite aggressive treatment. Such relapse has been attributed to the persistence of glioma stemlike cells (GSCs), a subpopulation of glioma cells with stem cell properties. Thus, targeting these cells will be critical to achieving meaningful improvement in glioblastoma multiforme survival. We investigated the role of ß1-integrin signaling as one such potential target. METHODS: We used GSCs isolated from primary human gliomas and maintained in stem cell conditions. We manipulated ß1-integrin signaling using a self-assembling peptide amphiphile (PA) displaying the IKVAV (isoleucine-lysine-valine-alanine-valine) epitope as well as lentiviral overexpression, and we assayed the effects on downstream effectors and apoptosis using immunofluorescence. RESULTS: We show that ß1-integrin expression correlates with decreased survival in glioma patients and that ß1-integrin is highly expressed by GSCs. The IKVAV PA potently increases immobilized ß1-integrin at the GSC membrane, activating integrin-linked kinase while inhibiting focal adhesion kinase (FAK). The IKVAV PA induces striking apoptosis in GSCs via this FAK inhibition, which is enhanced in combination with inhibition of epidermal growth factor receptor (EGFR). Conversely, lentiviral overexpression of ß1-integrin renders GSCs resistant to EGFR inhibition, which was overcome by FAK inhibition. CONCLUSIONS: These observations reveal a role for ß1-integrin signaling through FAK in GSC treatment resistance and introduce self-assembling PAs as a novel new therapeutic approach for overcoming this resistance.

Nanotechnology-novel therapeutics for CNS disorders.

Research into treatments for diseases of the CNS has made impressive strides in the past few decades, but therapeutic options are limited for many patients with CNS disorders. Nanotechnology has emerged as an exciting and promising new means of treating neurological disease, with the potential to fundamentally change the way we approach CNS-targeted therapeutics. Molecules can be nanoengineered to cross the blood-brain barrier, target specific cell or signalling systems, respond to endogenous stimuli, or act as vehicles for gene delivery, or as a matrix to promote axon elongation and support cell survival. The wide variety of available nanotechnologies allows the selection of a nanoscale material with the characteristics best suited to the therapeutic challenges posed by an individual CNS disorder. In this Review, we describe recent advances in the development of nanotechnology for the treatment of neurological disorders-in particular, neurodegenerative disease and malignant brain tumours-and for the promotion of neuroregeneration.

Cancer stem cells and glioma.

Despite continued advances in surgical and medical therapies, the outcomes for patients diagnosed with glioblastoma multiforme remain dismal. Recent data suggest that progression of these brain tumors is driven by a small subpopulation of tumor cells, which are termed cancer stem cells (CSCs) because of their capability to self-renew, proliferate and give rise to progeny of multiple neuroepithelial lineages. According to the CSC hypothesis, current therapies that are extremely cytotoxic to the bulk of highly proliferative tumor cells fail to obliterate the relatively quiescent and resistant CSC compartment, thereby allowing these cells to survive and drive tumor recurrence. This Review summarizes current knowledge regarding neural stem cells in the normal adult brain and CSCs in glial tumors and discusses the implications of the CSC hypothesis for the development of future therapies for brain tumors.

Regulatory effects of mammalian target of rapamycin-activated pathways in type I and II interferon signaling.

The mechanisms regulating initiation of mRNA translation for the generation of protein products that mediate interferon (IFN) responses are largely unknown. We have previously shown that both Type I and II IFNs engage the mammalian target of rapamycin (mTOR), resulting in downstream phosphorylation and deactivation of the translational repressor 4E-BP1 (eIF4E-binding protein 1). In the current study, we provide direct evidence that such regulation of 4E-BP1 by IFNalpha or IFNgamma results in sequential dissociation of 4E-BP1 from eukaryotic initiation factor-4E and subsequent formation of a functional complex between eukaryotic initiation factor-4E and eukaryotic initiation factor-4G, to allow initiation of mRNA translation. We also demonstrate that the induction of key IFNalpha- or IFNgamma-inducible proteins (ISG15 (interferon-stimulated gene 15) and CXCL10) that mediate IFN responses are enhanced in 4E-BP1 (4E-BP1(-/-)) knockout MEFs, as compared with wild-type 4E-BP1(+/+) MEFs. On the other hand, IFN-dependent transcriptional regulation of the Isg15 and Cxcl10 genes is intact in the absence of 4E-BP1, as determined by real time reverse transcriptase-PCR assays and promoter assays for ISRE and GAS, establishing that 4E-BP1 plays a selective negative regulatory role in IFN-induced mRNA translation. Interestingly, the induction of expression of ISG15 and CXCL10 proteins by IFNs was also strongly enhanced in cells lacking expression of the tuberin (TSC2(-/-)) or hamartin (TSC1(-/-)) genes, consistent with the known negative regulatory effect of the TSC1-TSC2 complex on mTOR activation. In other work, we demonstrate that the induction of an IFN-dependent antiviral response is strongly enhanced in cells lacking expression of 4E-BP1 and TSC2, demonstrating that these elements of the IFN-activated mTOR pathway exhibit important regulatory effects in the generation of IFN responses. Taken altogether, our data suggest an important role for mTOR-dependent pathways in IFN signaling and identify 4E-BP1 and TSC1-TSC2 as key components in the generation of IFN-dependent biological responses.

Prostaglandin E(2) metabolism is activated in Schwann cell lines derived from human NF1 malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNSTs) are characteristic of Neurofibromatosis type 1 (NF1), a human genetic disorder affecting approximately 1 in 3000 individuals. The absence of neurofibromin in Schwann cells results in hyperactivation of Ras, which contributes to Schwann cell hyperplasia. However, additional intracellular abnormalities in Schwann cells might contribute to the malignancy. We now report that cell lines derived from MPNSTs secrete elevated levels of prostaglandin E(2) (PGE(2)), express higher levels of phosphorylated mitogen-activated protein kinase (MAPK), phosphorylated cytosolic phospholipaseA(2) (cPLA(2)) and cyclooxygenase 2 (COX-2) when compared to normal adult human Schwann cells (nhSCs). PCR analysis reveals that NF1 MPNST cell lines express mRNA for both EP2 and EP4 prostaglandin E2 receptors, whereas nhSCs express only the EP4 receptor. COX-2 inhibitors and PGE(2) receptor antagonists decrease the proliferation of MPNST cell lines. These results indicate that prostaglandin metabolism is activated in MPNSTs and might contribute to tumor growth in NF1.