Transformed stem cells have been isolated from some human cancers. We report that, unlike other brain cancers, the lethal glioblastoma multiforme contains neural precursors endowed with all of the critical features expected from neural stem cells. Similar, yet not identical, to their normal neural stem cell counterpart, these precursors emerge as unipotent (astroglial) in vivo and multipotent (neuronal-astroglial-oligodendroglial) in culture. More importantly, these cells can act as tumor-founding cells down to the clonal level and can establish tumors that closely resemble the main histologic, cytologic, and architectural features of the human disease, even when challenged through serial transplantation. Thus, cells possessing all of the characteristics expected from tumor neural stem cells seem to be involved in the growth and recurrence of adult human glioblastomas multiforme.

Recent observations have suggested that extensive culturing of adult neural stem cells (ANSCs) by exploiting the NeuroSphere assay might select for aggressive cell clones, endowed with neoplastic potential, that overgrow the rest of the native stem cells. However, a detailed study of the propensity of ANSCs to transform has never been thoroughly undertaken. Here, we report the first demonstration that ANSCs can be propagated in vitro for over a year, maintaining a strikingly stable profile with regard to self-renewal, differentiation, growth factor dependence, karyotype, and molecular profiling. Most importantly, the long-term culturing of ANSCs did not result in the formation of tumors in vivo, even when ANSCs were transduced with Myc and Ras oncogenes. The cancer resistance could depend on specific mechanisms aimed at protecting ANSCs and preserved by optimal nonstressful culture conditions. In conclusion, besides a plentiful and safe source of cells for therapeutic applications, ANSCs provide an ideal model to study aging and cancer in the context of stemness. [Cancer Res 2007;67(8):3725-33]

Medulloblastoma arises from mutations occurring in stem/progenitor cells located in restricted hindbrain territories. Here we report that the mouse postnatal ventricular zone lining the IV ventricle also harbors bona fide stem cells that, remarkably, share the same molecular profile with cerebellar white matter–derived neural stem cells (NSC). To identify novel molecular mediators involved in medulloblastomagenesis, we compared these distinct postnatal hindbrain-derived NSC populations, which are potentially tumor initiating, with murine compound Ptch/p53 mutant medulloblastoma cancer stem cells (CSC) that faithfully phenocopy the different variants of human medulloblastoma in vivo. Transcriptome analysis of both hindbrain NSCs and medulloblastoma CSCs resulted in the generation of well-defined gene signatures, each reminiscent of a specific human medulloblastoma molecular subclass. Most interestingly, medulloblastoma CSCs upregulated developmentally related genes, such as Ebfs, that were shown to be highly expressed in human medulloblastomas and play a pivotal role in experimental medullo-blastomagenesis. These data indicate that gene expression analysis of medulloblastoma CSCs holds great promise not only for understanding functional differences between distinct CSC populations but also for identifying meaningful signatures that might stratify medulloblastoma patients beyond histopathologic staging. Significance: The functional and molecular comparison between the cell progenitor lineages from which medulloblastoma is thought to arise and medulloblastoma CSCs might lead to the identification of novel, potentially relevant mediators of medulloblastomagenesis. Our findings provide a rationale for the exploitation of mouse CSCs as a valuable preclinical model for human medulloblastoma, both for the definition of CSC-associated gene signatures with predictive mean and for the identification of therapeutically targetable genes. Cancer Discov; 2(6); 554–68. © 2012 AACR. This article is highlighted in the In This Issue feature, p. 473

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Dr. Francesco M. No e is a researcher with experience in EEG and animal models of epilepsy. SUMMARYObjective: Systemic administration of kainic acid (KA) is a widely used procedure utilized to develop a model of temporal lobe epilepsy (TLE). Despite its ability to induce status epilepticus (SE) in vivo, KA applied to in vitro preparations induces only interictal-like activity and/or isolated ictal discharges. The possibility that extravasation of the serum protein albumin from the vascular compartment enhances KA-induced brain excitability is investigated here. Methods: Epileptiform activity was induced by arterial perfusion of 6 lM KA in the in vitro isolated guinea pig brain preparation. Simultaneous field potential recordings were carried out bilaterally from limbic (CA1, dentate gyrus [DG], and entorhinal cortex) and extralimbic regions (piriform cortex and neocortex). Blood-brain barrier (BBB) breakdown associated with KA-induced epileptiform activity was assessed by parenchymal leakage of intravascular fluorescein-isothiocyanate albumin. Seizureinduced brain inflammation was evaluated by western blot analysis of interleukin (IL)-1b expression in brain tissue. Results: KA infusion caused synchronized activity at 15-30 Hz in limbic (but not extralimbic) cortical areas, associated with a brief, single seizure-like event. A second bolus of KA, 60 min after the induction of the first ictal event, did not further enhance excitability. Perfusion of serum albumin between the two administrations of KA enhanced epileptiform discharges and allowed a recurrent ictal event during the second KA infusion. Significance: Our data show that arterial KA administration selectively alters the synchronization of limbic networks. However, KA is not sufficient to generate recurrent seizures unless serum albumin is co-perfused during KA administration. These findings suggest a role of serum albumin in facilitating acute seizure generation. KEY WORDS: In vitro guinea pig brain preparation, Status epilepticus, Beta-gamma activity, Neuronal network synchronization, IL-1 beta.Pathologic features mimicking mesial temporal lobe epilepsy (mTLE) can be reproduced in experimental animals by systemic and intracerebral application of kainic acid (KA).1 Intrahippocampal administration of KA at high doses (≥5 mM) is effective in inducing convulsive 2 and nonconvulsive 3 status epilepticus (SE), eventually followed by recurrent spontaneous limbic seizures, between 5 days and 1 month after SE. 3,4 In this in vivo model of TLE, altered patterns of rhythmic activity in the gamma frequency range (30-80 Hz) occur during the acute SE and before the onset