Are anatomic brain locations important in determining the clinical outcomes in acute ischemic stroke? --- An exploratory analysis of the NINDS Stroke Trial data

Background and purpose. Brain lesions in acute ischemic stroke measured by imaging tools provide important clinical information for diagnosis and final infarct volume has been considered as a potential surrogate marker for clinical outcomes. Strong correlations have been found between lesion volume and clinical outcomes in the NINDS t-PA Stroke Trial but little has been published about lesion location and clinical outcomes. Studies of the National Institute of Neurological Disorders and Stroke (NINDS) t-PA Stroke Trial data found the direction of the t-PA treatment effect on a decrease in CT lesion volume was consistent with the observed clinical effects at 3 months, but measure of t-PA treatment benefits using CT lesion volumes showed a diminished statistical significance, as compared to using clinical scales. ^ Methods. We used the global test to evaluate the hypothesis that lesion locations were strongly associated with clinical outcomes within each treatment group at 3 months after stroke. The anatomic locations of CT scans were used for analysis. We also assessed the effect of t-PA on lesion location using a global statistical test. ^ Results. In the t-PA group, patients with frontal lesions had larger infarct volumes and worse NIHSS score at 3 months after stroke. The clinical status of patients with frontal lesions in t-PA group was less likely to be affected by lesion volume, as compared to those who had no frontal lesions in at 3 months. For patients within the placebo group, both brain stem and internal capsule locations were significantly associated with a lower odd of having favorable outcomes at 3 months. Using a global test we could not detect a significant effect of t-PA treatment on lesion location although differences between two treatment groups in the proportion of lesion findings in each location were found. ^ Conclusions. Frontal, brain stem, and internal capsule locations were significantly related to clinical status at 3 months after stroke onset. We detect no significant t-PA effect on all 9 locations although proportion of lesion findings in differed among locations between the two treatment groups.^

Effects of hypoxic-ischemic encephalopathy and whole-body hypothermia on neonatal auditory function: a pilot study.

We assessed the effects of hypoxic-ischemic encephalopathy (HIE) and whole-body hypothermia therapy on auditory brain stem evoked responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We performed serial assessments of ABRs and DPOAEs in newborns with moderate or severe HIE, randomized to hypothermia ( N = 4) or usual care ( N = 5). Participants were five boys and four girls with mean gestational age (standard deviation) of 38.9 (1.8) weeks. During the first week of life, peripheral auditory function, as measured by the DPOAEs, was disrupted in all nine subjects. ABRs were delayed but central transmission was intact, suggesting a peripheral rather than a central neural insult. By 3 weeks of age, peripheral auditory function normalized. Hypothermia temporarily prolonged the ABR, more so for waves generated higher in the brain stem but the effects reversed quickly on rewarming. Neonatal audiometric testing is feasible, noninvasive, and capable of enhancing our understanding of the effects of HIE and hypothermia on auditory function.

Abnormal expression of REST/NRSF and Myc in neural stem/progenitor cells causes cerebellar tumors by blocking neuronal differentiation.

Medulloblastoma, one of the most malignant brain tumors in children, is thought to arise from undifferentiated neural stem/progenitor cells (NSCs) present in the external granule layer of the cerebellum. However, the mechanism of tumorigenesis remains unknown for the majority of medulloblastomas. In this study, we found that many human medulloblastomas express significantly elevated levels of both myc oncogenes, regulators of neural progenitor proliferation, and REST/NRSF, a transcriptional repressor of neuronal differentiation genes. Previous studies have shown that neither c-Myc nor REST/NRSF alone could cause tumor formation. To determine whether c-Myc and REST/NRSF act together to cause medulloblastomas, we used a previously established cell line derived from external granule layer stem cells transduced with activated c-myc (NSC-M). These immortalized NSCs were able to differentiate into neurons in vitro. In contrast, when the cells were engineered to express a doxycycline-regulated REST/NRSF transgene (NSC-M-R), they no longer underwent terminal neuronal differentiation in vitro. When injected into intracranial locations in mice, the NSC-M cells did not form tumors either in the cerebellum or in the cerebral cortex. In contrast, the NSC-M-R cells did produce tumors in the cerebellum, the site of human medulloblastoma formation, but not when injected into the cerebral cortex. Furthermore, the NSC-M-R tumors were blocked from terminal neuronal differentiation. In addition, countering REST/NRSF function blocked the tumorigenic potential of NSC-M-R cells. To our knowledge, this is the first study in which abnormal expression of a sequence-specific DNA-binding transcriptional repressor has been shown to contribute directly to brain tumor formation. Our findings indicate that abnormal expression of REST/NRSF and Myc in NSCs causes cerebellum-specific tumors by blocking neuronal differentiation and thus maintaining the "stemness" of these cells. Furthermore, these results suggest that such a mechanism plays a role in the formation of human medulloblastoma.

Intravenous mesenchymal stem cell therapy for traumatic brain injury.

OBJECT: Cell therapy has shown preclinical promise in the treatment of many diseases, and its application is being translated to the clinical arena. Intravenous mesenchymal stem cell (MSC) therapy has been shown to improve functional recovery after traumatic brain injury (TBI). Herein, the authors report on their attempts to reproduce such observations, including detailed characterizations of the MSC population, non-bromodeoxyuridine-based cell labeling, macroscopic and microscopic cell tracking, quantification of cells traversing the pulmonary microvasculature, and well-validated measurement of motor and cognitive function recovery. METHODS: Rat MSCs were isolated, expanded in vitro, immunophenotyped, and labeled. Four million MSCs were intravenously infused into Sprague-Dawley rats 24 hours after receiving a moderate, unilateral controlled cortical impact TBI. Infrared macroscopic cell tracking was used to identify cell distribution. Immunohistochemical analysis of brain and lung tissues 48 hours and 2 weeks postinfusion revealed transplanted cells in these locations, and these cells were quantified. Intraarterial blood sampling and flow cytometry were used to quantify the number of transplanted cells reaching the arterial circulation. Motor and cognitive behavioral testing was performed to evaluate functional recovery. RESULTS: At 48 hours post-MSC infusion, the majority of cells were localized to the lungs. Between 1.5 and 3.7% of the infused cells were estimated to traverse the lungs and reach the arterial circulation, 0.295% reached the carotid artery, and a very small percentage reached the cerebral parenchyma (0.0005%) and remained there. Almost no cells were identified in the brain tissue at 2 weeks postinfusion. No motor or cognitive functional improvements in recovery were identified. CONCLUSIONS: The intravenous infusion of MSCs appeared neither to result in significant acute or prolonged cerebral engraftment of cells nor to modify the recovery of motor or cognitive function. Less than 4% of the infused cells were likely to traverse the pulmonary microvasculature and reach the arterial circulation, a phenomenon termed the "pulmonary first-pass effect," which may limit the efficacy of this therapeutic approach. The data in this study contradict the findings of previous reports and highlight the potential shortcomings of acute, single-dose, intravenous MSC therapy for TBI.

Subacute neural stem cell therapy for traumatic brain injury.

INTRODUCTION: Traumatic brain injury (TBI) frequently results in devastating and prolonged morbidity. Cellular therapy is a burgeoning field of experimental treatment that has shown promise in the management of many diseases, including TBI. Previous work suggests that certain stem and progenitor cell populations migrate to sites of inflammation and improve functional outcome in rodents after neural injury. Unfortunately, recent study has revealed potential limitations of acute and intravenous stem cell therapy. We studied subacute, direct intracerebral neural stem and progenitor cell (NSC) therapy for TBI. MATERIALS AND METHODS: The NSCs were characterized by flow cytometry and placed (400,000 cells in 50 muL 1x phosphate-buffered saline) into and around the direct injury area, using stereotactic guidance, of female Sprague Dawley rats 1 wk after undergoing a controlled cortical impact injury. Immunohistochemistry was used to identify cells located in the brain at 48 h and 2 wk after administration. Motor function was assessed using the neurological severity score, foot fault, rotarod, and beam balance. Cognitive function was assessed using the Morris water maze learning paradigm. Repeated measures analysis of variance with post-hoc analysis were used to determine significance at P < 0.05. RESULTS: Immunohistochemistry analysis revealed that 1.4-1.9% of infused cells remained in the neural tissue at 48 h and 2 wk post placement. Nearly all cells were located along injection tracks at 48 h. At 2 wk some cell dispersion was apparent. Rotarod motor testing revealed significant increases in maximal speed among NSC-treated rats compared with saline controls at d 4 (36.4 versus 27.1 rpm, P < 0.05) and 5 (35.8 versus 28.9 rpm, P < 0.05). All other motor and cognitive evaluations were not significantly different compared to controls. CONCLUSIONS: Placement of NSCs led to the cells incorporating and remaining in the tissues 2 wk after placement. Motor function tests revealed improvements in the ability to run on a rotating rod; however, other motor and cognitive functions were not significantly improved by NSC therapy. Further examination of a dose response and optimization of placement strategy may improve long-term cell survival and maximize functional recovery.

Expression of the neural stem cell markers NG2 and L1 in human angiomyolipoma: are angiomyolipomas neoplasms of stem cells?

Angiomyolipomas are benign tumors of the kidney which express phenotypes of smooth muscle, fat, and melanocytes. These tumors appear with increased frequency in the autosomal dominant disorder tuberous sclerosis and are the leading cause of morbidity in adults with tuberous sclerosis. While benign, these tumors are capable of provoking life threatening hemorrhage and replacement of the kidney parenchyma, resulting in renal failure. The histogenesis of these tumors is currently unclear, although currently, we believe these tumors arise from "perivascular epithelioid cells" of which no normal counterpart has been convincingly demonstrated. Recently, stem cell precursors have been recognized that can give rise to smooth muscle and melanocytes. These precursors have been shown to express the neural stem cell marker NG2 and L1. In order to determine whether angiomyolipomas, which exhibit smooth muscle and melanocytic phenotypes, express NG2 and L1, we performed immunocytochemistry on a cell line derived from a human angiomyolipoma, and found that these cells are uniformly positive. Immunohistochemistry of human angiomyolipoma specimens revealed uniform staining of tumor cells, while renal cell carcinomas revealed positivity only of angiogenic vessels. These results support a novel histogenesis of angiomyolipoma as a defect in differentiation of stem cell precursors.

Modern approaches to pediatric brain injury therapy.

Each year, pediatric traumatic brain injury (TBI) accounts for 435,000 emergency department visits, 37,000 hospital admissions, and approximately 2,500 deaths in the United States. TBI results in immediate injury from direct mechanical force and shear. Secondary injury results from the release of biochemical or inflammatory factors that alter the loco-regional milieu in the acute, subacute, and delayed intervals after a mechanical insult. Preliminary preclinical and clinical research is underway to evaluate the benefit from progenitor cell therapeutics, hypertonic saline infusion, and controlled hypothermia. However, all phase III clinical trials investigating pharmacologic monotherapy for TBI have shown no benefit. A recent National Institutes of Health consensus statement recommends research into multimodality treatments for TBI. This article will review the complex pathophysiology of TBI as well as the possible therapeutic mechanisms of progenitor cell transplantation, hypertonic saline infusion, and controlled hypothermia for possible utilization in multimodality clinical trials.

Progenitor cell therapies for traumatic brain injury: barriers and opportunities in translation.

Traumatic brain injury (TBI) directly affects nearly 1.5 million new patients per year in the USA, adding to the almost 6 million cases in patients who are permanently affected by the irreversible physical, cognitive and psychosocial deficits from a prior injury. Adult stem cell therapy has shown preliminary promise as an option for treatment, much of which is limited currently to supportive care. Preclinical research focused on cell therapy has grown significantly over the last decade. One of the challenges in the translation of this burgeoning field is interpretation of the promising experimental results obtained from a variety of cell types, injury models and techniques. Although these variables can become barriers to a collective understanding and to evidence-based translation, they provide crucial information that, when correctly placed, offers the opportunity for discovery. Here, we review the preclinical evidence that is currently guiding the translation of adult stem cell therapy for TBI.

The biology and mechanism of chemoresistance of brain metastases

Primary brain neoplasms and metastases to the brain are generally resistant to systemic chemotherapy. The purpose of theses studies was to determine the mechanism(s) for this resistance. We have developed a model to study the biology of brain metastasis by injecting metastatic K1735 melanoma cells into the carotid artery of syngeneic C3H/HeN or nude mice. The resulting brain lesions are produced in the parenchyma of the brain. Mice with subcutaneous or brain melanoma lesions were treated intravenously with doxorubicin (DXR) (7 mg/kg). The s.c. lesions regressed in most of the mice whereas no therapeutic benefits were produced in mice with brain metastases. The intravenous injection of sodium fluorescine revealed that the blood-brain barrier (BBB) is intact in and around brain metastases smaller than 0.2 mm$\sp2$ but not in larger lesions, implying that the BBB is not a major obstacle for chemotherapy of brain metastases.^ Western blot and FACS analyses revealed that K1735 melanoma brain metastases expressed high levels of P-glycoprotein (P-gp) as compared to s.c. tumors or in vitro cultures. Similarly, K1735 cells from brain metastases expressed higher levels of mdrl mRNA. This increased expression of mdrl was due to adaptation to the local brain environment. We base this conclusion on the results of two studies. First, K1735 cells from brain metastases cultured for 7 days lost the high mdrl expression. Second, in crossover experiments K1735 cells from s.c. tumors (low mdrl expression) implanted into the brain exhibited high levels of mdrl expression whereas cells from brain metastases implanted s.c. lost the high level mdrl expression.^ To investigate the mechanism by which the brain environment upregulates mdrl expression of the K1735 cells we first studied the regulation of P-gp in brain endothelial cells. Since astrocytes are closely linked with the BBB we cocultured brain endothelial cells for 3 days with astrocytes. These endothelial cells expressed high levels of mdrl mRNA and protein whereas endothelial cells cocultured with endothelial cells or fibroblasts did not. We next cocultured K1735 melanoma cells with astrocytes. Here again, astrocytes (but not fibroblasts or tumor cells) uprelated the mdrl expression in K1735 tumor cells. This upregulation inversely correlated with intracellular drug accumulation and sensitivity to DXR.^ The data conclude that the resistance of melanoma brain metastases to chemotherapy is not due to an intact BBB but to the upregulation of the mdrl gene by the organ microenvironment, i.e., the astrocytes. This epigenetic mediated resistance to chemotherapy has wide implications for the therapy of brain metastases. ^

The role of deregulated E2F1 expression in brain tumors

Mutations disabling the retinoblastoma (Rb) pathway are among the most common in human cancers, including brain cancer. These mutations promote tumor development through deregulated control of the E2F family of transcription factors. E2F1 belongs to a class of E2F's identified as transcriptional activators and involved in the G1/S phase transition of the cell. However, E2F-1 presents with a paradox as it is considered to have membership in two gene classes, functioning as both an oncogene and a tumor suppressor. This unusual trait generates a degree of uncertainty on the role that E2F1 plays in the development or maintenance of any given tumor. Here we show that E2F1 functions as an oncogene in brain tumors through the generation of mice engineered to overexpress E2F1 specifically within glial cells and neuronal progenitors as directed by the GFAP promoter. Mice carrying the transgene develop with high penetrance a phenotype characterized by neurological deficits including paresia, ataxia, head tilt and seizures. MRI imagining of the tgE2F1 mice reveals a low incidence of mild hydrocephalus, and most notably, histological analysis demonstrates that 25% of tgE2F1 mice present with the spontaneous formation of malignant brain tumors. Overall these neoplasms show histological features from a wide range of aggressive brain cancers including medulloblastoma, choroid plexus carcinoma, primary neuroectodermic tumor and malignant gliomas. Isolation and characterization of astrocytes from the tgE2F1 animal reveals a highly proliferative population of cells with 55% ± 2.5 of the tgE2F1astrocytes, 35% ± 3.4 normal mouse astrocytes in S-phase and the acquired capacity to grow in anchorage independent conditions. Additionally tgE2F1 astrocytes show an aberrant phenotype with random chromosomal fusions and nearly all cells demonstrating polyploidy. Taken together, this model forces a comparison to human brain tumor formation. Mouse age as related to tumoral mimics the human scenario with juvenile tgE2F1 mice presenting embryonal tumors typically identified in children, and older tgE2F1 mice demonstrating gliomas. In this regard, this study suggests a global role for E2F1 in the formation and maintenance of multilineage brain tumors, irrefutably establishing E2F1 as an oncogene in the brain. ^

Current United States stem cell policy considerations and a recommendation for an alternative policy based on guidelines from existing international policies

Embryonic stem cell research is a widely debated topic in modern politics and religion. Differing views on the fetal rights conflict with the rights of an embryo. Those who believe an embryo has the same human qualities as a fetus accordingly believe embryonic stem cell research is unethical because it destroys a potential human life. However, scientists advocate the embryo does not have human qualities and should be used for valuable research in the stem cell field. Stem cell research may lead to vast developments in medical treatments, including cancer and brain conditions and injuries that are currently incurable. ^ The current stem cell policy introduced by President Bush in 2001 in an attempt to balance the moral issues with the need for scientific research has broad negative implications on the furthering of stem cell research. There is a limited diversity of available stem cell lines, there may be constitutional issues, there is an increasing disparity between the public and private research spheres, and the U.S. is struggling to maintain its scientific community. The U.S. must develop a new stem cell research policy that will balance the interest of science and public health with the moral issues that concern the public. ^ The United Kingdom allows researchers great liberty in conducting research, permitting the creation of embryos for the sole purpose of research, while Germany is equally conservative in their laws, as their policies support the philosophy that all embryos deserve the protection of full life. The United States should adopt a policy that takes the "middle ground" approach and permit research on excess embryos created for IVF purposes, rather than simply discarding those potentially valuable research tools. ^

INDUCED-PLURIPOTENT STEM-DERIVED NEURONAL PROGENITOR CELLS AS A NOVEL TREATMENT FOR NEURODEGENERATIVE DISEASES

Cellular therapies, as neuronal progenitor (NP) cells grafting, are promising therapies for patients affected with neurodegenerative diseases like Creutzfeldt-Jakob Disease (CJD). At this time there is no effective treatment or cure for CJD. The disease is inevitably fatal and affected people usually die within months of the appearance of the first clinical symptoms. Compelling evidence indicate that the hallmark event in the disease is the conversion of the normal prion protein (termed PrPC) into the disease-associated, misfolded form (called PrPSc). Thus, a reasonable therapeutic target would be to prevent PrP misfolding and prion replication. This strategy has been applied with poor results since at the time of clinical intervention substantial brain damage has been done. It seems that a more effective treatment aimed at patients with established symptoms of CJD would need to stop further brain degeneration or even recover some of the previously lost brain tissue. The most promising possibility to recover brain tissue is the use of NPs that have the potential to replenish the nerve cells lost during the early stages of the disease. Advanced cellular therapies, beside their potential for cell replacement, might be used as biomaterials for drug delivery in order to stimulate cell survival or the resolution the disease. Also, implanted cells can be genetically manipulated to correct abnormalities causing disease or to make them more resistant to the toxic microenvironments present in damaged tissue. In recent years cell engineering has been within the scope of the scientific and general community after the development of technologies able to “de-differentiate” somatic cells into induced-pluripotent stem (IPS) cells. This new tool permits the use of easy-to-reach cells like skin or blood cells as a primary material to obtain embryonic stem-like cells for cellular therapies, evading all ethical issues regarding the use of human embryos as a source of embryonic stem cells. The complete work proposes to implant IPS-derived NP cells into the brain of prion-infected animals to evaluate their therapeutic potential. Since it is well known that the expression of prion protein in the cell membrane is necessary for PrPSc mediated toxicity, we also want to determine if NPs lacking the prion protein have better survival rates once implanted into sick animals. The main objective of this work is to develop implantable neural precursor from IPS coming from animals lacking the prion protein. Specific aim 1: To develop and characterize cellular cultures of IPS cells from prp-/- mice. Fibroblasts from prp-/- animals will be reprogrammed using the four Yamanaka factors. IPS colonies will be selected and characterized by immunohistochemistry for markers of pluripotency. Their developmental capabilities will be evaluated by teratoma and embryoid body formation assays. Specific aim 2: To differentiate IPS cells to a neuronal lineage. IPS cells will be differentiated to a NP stage by the use of defined media culture conditions. NP cells will be characterized by their immunohistochemical profile as well as by their ability to differentiate into neuronal cells. Specific aim 3: Cellular labeling of neuronal progenitors cells for in vitro traceability. In order to track the cells once implanted in the host brain, they will be tagged with different methods such as lipophilic fluorescent tracers and transduction with GFP protein expression.

TAZ AS A REGULATOR OF MESENCHYMAL TRANSFORMATION AND CLINICAL AGGRESSIVENESS IN GLIOMAS

Glioblastoma multiforme (GBM) is an aggressive, high grade brain tumor. Microarray studies have shown a subset of GBMs with a mesenchymal gene signature. This subset is associated with poor clinical outcome and resistance to treatment. To establish the molecular drivers of this mesenchymal transition, we correlated transcription factor expression to the mesenchymal signature and identified transcriptional co-activator with PDZ-binding motif (TAZ) to be highly associated with the mesenchymal shift. High TAZ expression correlated with worse clinical outcome and higher grade. These data led to the hypothesis that TAZ is critical to the mesenchymal transition and aggressive clinical behavior seen in GBM. We investigated the expression of TAZ, its binding partner TEAD, and the mesenchymal marker FN1 in human gliomas. Western analyses demonstrated increased expression of TAZ, TEAD4, and FN1 in GBM relative to lower grade gliomas. We also identified CpG islands in the TAZ promoter that are methylated in most lower grade gliomas, but not in GBMs. TAZ-methylated glioma stem cell (GSC) lines treated with a demethylation agent showed an increase in mRNA and protein TAZ expression; therefore, methylation may be another novel way TAZ is regulated since TAZ is epigenetically silenced in tumors with a better clinical outcome. To further characterize the role of TAZ in gliomagenesis, we stably silenced or over-expressed TAZ in GSCs. Silencing of TAZ decreased invasion, self-renewal, mesenchymal protein expression, and tumor-initiating capacity. Over-expression of TAZ led to an increase in invasion, mesenchymal protein expression, mesenchymal differentiation, and tumor-initiating ability. These actions are dependent on TAZ interacting with TEAD since all these effects were abrogated with TAZ could not bind to TEAD. We also show that TAZ and TEAD directly bind to mesenchymal gene promoters. Thus, TAZ-TEAD interaction is critically important in the mesenchymal shift and in the aggressive clinical behavior of GBM. We identified TAZ as a regulator of the mesenchymal transition in gliomas. TAZ could be used as a biomarker to both estimate prognosis and stratify patients into clinically relevant subgroups. Since mesenchymal transition is correlated to tumor aggressiveness, strategies to target and inhibit TAZ-TEAD and the downstream gene targets may be warranted in alternative treatment.

LOW REACTIVE OXYGEN SPECIES AND HIGH GLYCOLYSIS IN GLIOBLASTOMA STEM CELLS:MECHANISMS AND THERAPEUTIC IMPLICATIONS

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor with poor prognosis due in part to drug resistance and high incidence of tumor recurrence. The drug resistant and cancer recurrence phenotype may be ascribed to the presence of glioblastoma stem cells (GSCs), which seem to reside in special stem-cell niches in vivo and require special culture conditions including certain growth factors and serum-free medium to maintain their stemness in vitro. Exposure of GSCs to fetal bovine serum (FBS) can cause their differentiation, the underlying mechanism of which remains unknown. Reactive oxygen species (ROS) play an important role in normal stem cell differentiation, but their role in affecting cancer stem cell fate remains unclear. Whether the metabolic characteristics of GSCs are different from other glioblastoma cells and can be targeted are also unknown. In this study, we used several stem-like glioblastoma cell lines derived from clinical tissues by typical neurosphere culture system or orthotopic xenografts, and showed that addition of fetal bovine serum to the medium induced an increase of ROS, leading to aberrant differentiation and decreases of stem cell markers such as CD133. We found that exposure of GSCs to serum induced their differentiation through activation of mitochondrial respiration, leading to an increase in superoxide (O2-) generation and a profound ROS stress response manifested by upregulation of oxidative stress response pathway. This increase in mitochondrial ROS led to a down-regulation of molecules including SOX2, and Olig2, and Notch1 that are important for stem cell function and an upregulation of mitochondrial superoxide dismutase SOD2 that converts O2- to H2O2. Neutralization of ROS by antioxidant N-acetyl-cysteine in the serum-treated GSCs suppressed the increase of superoxide and partially rescued the expression of SOX2, Olig2, and Notch1, and prevented the serum-induced differentiation phenotype. Additionally, GSCs showed high dependence on glycolysis for energy production. The combination of a glycolytic inhibitor 3-BrOP and a chemotherapeutic agent BCNU depleted cellular ATP and inhibited the repair of BCNU-induced DNA damage, achieving strikingly synergistic killing effects in drug resistant GSCs. This study uncovers the metabolic properties of glioblastoma stem cells and suggests that mitochondrial function and cellular redox status may profoundly affect the fates of glioblastoma stem cells via a ROS-mediated mechanism, and that the active glycolytic metabolism in cancer stem cells may provide a biochemical basis for developing novel therapeutic strategies to effectively eliminate GSCs.

Potential REST Targets in Neural Stem Cells and Glioblastoma-Derived Stem Cells

Glioblastoma multiforme (GBM) tumors are the most common malignant primary brain tumors in adults. The current theory is that these tumors are caused by self-renewing glioblastoma-derived stem cells (GSCs). At the current time, the mechanisms that regulate self-renewal and other oncogenic properties of GSCs remain unknown. Recently, we found transcriptional repressor REST maintains self-renewal in neural stem cells (NSCs) and in GSCs. REST also regulates other oncogenic properties, such as apoptosis, invasion and proliferation. However, the mechanisms by which REST regulates these oncogenic properties are unknown. In an attempt to determine these mechanisms, we performed loss and gain-of-function experiments and genome-wide mRNA expression analysis in GSCs, and we were able to identify REST-regulated genes in GSCs. This was accomplished, after screening concordantly regulated genes in NSCs and GSCs, utilizing two RE1 databases, and setting two-fold expression as filters on the resulting genes. These results received further validation by qRT-PCR. Ingenuity Pathway Analysis (IPA) analysis further revealed the top REST target genes in GSCs were downstream targets of REST and/or involved in other cancers in other cell lines. IPA also revealed that many of the differentially-regulated genes identified in this study are involved in oncogenic properties seen in GBM, and which we believe are related to REST expression.