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1.  Asparagine Depletion Potentiates the Cytotoxic Effect of Chemotherapy Against Brain Tumors 
Molecular cancer research : MCR  2014;12(5):694-702.
Targeting amino acid metabolism has therapeutic implications for aggressive brain tumors. Asparagine is an amino acid that is synthesized by normal cells. However, some cancer cells lack asparagine synthetase (ASNS), the key enzyme for asparagine synthesis. Asparaginase (ASNase) contributes to eradication of acute leukemia by decreasing asparagine levels in serum and cerebrospinal fluid. However, leukemic cells may become ASNase-resistant by up-regulating ASNS. High expression of ASNS has also been associated with biological aggressiveness of other cancers, including gliomas. Here, the impact of enzymatic depletion of asparagine on proliferation of brain tumor cells was determined. ASNase was used as monotherapy or in combination with conventional chemotherapeutic agents. Viability assays for ASNase-treated cells demonstrated significant growth reduction in multiple cell lines. This effect was reversed by glutamine in a dose-dependent manner -- as expected, because glutamine is the main amino group donor for asparagine synthesis. ASNase treatment also reduced sphere formation by medulloblastoma and primary glioblastoma cells. ASNase-resistant glioblastoma cells exhibited elevated levels of ASNS mRNA. ASNase co-treatment significantly enhanced gemcitabine or etoposide cytotoxicity against glioblastoma cells. Xenograft tumors in vivo showed no significant response to ASNase monotherapy and little response to temozolomide (TMZ) alone. However, combinatorial therapy with ASNase and TMZ resulted in significant growth suppression for an extended duration of time. Taken together, these findings indicate that amino acid depletion warrants further investigation as adjunctive therapy for brain tumors.
PMCID: PMC4020976  PMID: 24505127
Asparaginase; deamination; glutamine; glioblastoma; medulloblastoma; temozolomide
2.  Maternal Inflammation Contributes to Brain Overgrowth and Autism-Associated Behaviors through Altered Redox Signaling in Stem and Progenitor Cells 
Stem Cell Reports  2014;3(5):725-734.
A period of mild brain overgrowth with an unknown etiology has been identified as one of the most common phenotypes in autism. Here, we test the hypothesis that maternal inflammation during critical periods of embryonic development can cause brain overgrowth and autism-associated behaviors as a result of altered neural stem cell function. Pregnant mice treated with low-dose lipopolysaccharide at embryonic day 9 had offspring with brain overgrowth, with a more pronounced effect in PTEN heterozygotes. Exposure to maternal inflammation also enhanced NADPH oxidase (NOX)-PI3K pathway signaling, stimulated the hyperproliferation of neural stem and progenitor cells, increased forebrain microglia, and produced abnormal autism-associated behaviors in affected pups. Our evidence supports the idea that a prenatal neuroinflammatory dysregulation in neural stem cell redox signaling can act in concert with underlying genetic susceptibilities to affect cellular responses to environmentally altered cellular levels of reactive oxygen species.
Graphical Abstract
•Mild maternal inflammation produces brain overgrowth and autistic behaviors in pups•Maternal inflammation increases stem cell division, ROS levels, and PI3K activation•Genetic susceptibility produces even greater brain overgrowth when combined with MIR•Overgrowth and some associated abnormal behaviors can be rescued by inhibition of NOX
In this article, Kornblum and colleagues show that exposure to maternal inflammation and an altered cellular redox balance during critical periods of embryonic development can promote brain overgrowth and autism-associated behaviors as a result of altered neural stem cell function. Additionally, they demonstrate that PTEN heterozygosity can act as a genetic susceptibility to produce a more pronounced brain overgrowth phenotype.
PMCID: PMC4235743  PMID: 25418720
3.  Clinical Outcome in Pediatric Glial and Embryonal Brain Tumors Correlates With In Vitro Multi-Passageable Neurosphere Formation 
Pediatric blood & cancer  2010;55(4):644-651.
Cultured brain tumors can form neurospheres harboring tumorigenic cells with self renewal and differentiation capacities. Renewable neurosphere formation has clinical predictive value in adult malignant gliomas, yet its prognostic role for pediatric brain tumors is unknown.
Established neurosphere conditions were used for culturing samples from glial, embryonal and mixed glioneuronal tumors from 56 pediatric patients. Potential associations between neurosphere formation and clinical outcome were analyzed retrospectively.
Thirty-seven percent of all samples formed renewable neurospheres. Analysis of available clinical outcome data from 51 patients demonstrated significantly increased hazard ratios (HR) for both disease progression (HR=9.9, P < 0.001) and death (HR=16.6, P < 0.01) in the neurosphere forming group. Furthermore, neurosphere formation correlated with adverse progression free survival (PFS) in glial and embryonal tumors, but not in mixed glioneuronal tumors. Overall survival (OS) was significantly worse for neurosphere-forming patients with embryonal tumors, as a group and amongst the subgroup with medulloblastoma, but not in the glial group. Multivariate analysis showed that neurosphere formation was associated with diminished PFS and OS independent of age, gender, or treatment. Neurosphere formation was an independent predictor of diminished PFS of glial tumors after adjusting for grade. Multivariate analysis, adjusting for both Ki67 staining and neurosphere formation, demonstrated that neurosphere formation remained predictive of progression whereas Ki67 did not.
Neurosphere formation is more predictive of pediatric brain tumor progression than semi-quantitative Ki67 staining. Pediatric brain tumor derived neurospheres may provide a predictive model for preclinical explorations.
PMCID: PMC4017922  PMID: 20589659
brain; brain tumors; cancer biology; CNS tumors; neuro-oncology; outcomes research; tumors
4.  Siomycin A targets brain tumor stem cells partially through a MELK-mediated pathway 
Neuro-Oncology  2011;13(6):622-634.
Glioblastoma multiforme (GBM) is a devastating disease, and the current therapies have only palliative effect. Evidence is mounting to indicate that brain tumor stem cells (BTSCs) are a minority of tumor cells that are responsible for cancer initiation, propagation, and maintenance. Therapies that fail to eradicate BTSCs may ultimately lead to regrowth of residual BTSCs. However, BTSCs are relatively resistant to the current treatments. Development of novel therapeutic strategies that effectively eradicate BTSC are, therefore, essential. In a previous study, we used patient-derived GBM sphere cells (stemlike GBM cells) to enrich for BTSC and identified maternal embryonic leucine-zipper kinase (MELK) as a key regulator of survival of stemlike GBM cells in vitro. Here, we demonstrate that a thiazole antibiotic, siomycin A, potently reduced MELK expression and inhibited tumor growth in vivo. Treatment of stemlike GBM cells with siomycin A resulted in arrested self-renewal, decreased invasion, and induced apoptosis but had little effect on growth of the nonstem cells of matched tumors or normal neural stem/progenitor cells. MELK overexpression partially rescued the phenotype of siomycin A–treated stemlike GBM cells. In vivo, siomycin A pretreatment abraded the sizes of stemlike GBM cell–derived tumors in immunodeficient mice. Treatment with siomycin A of mice harboring intracranial tumors significantly prolonged their survival period compared with the control mice. Together, this study may be the first model to partially target stemlike GBM cells through a MELK-mediated pathway with siomycin A to pave the way for effective treatment of GBM.
PMCID: PMC3107094  PMID: 21558073
cancer stem cell; glioblastoma; glioma; maternal embryonic leucine-zipper kinase; therapy
5.  Neurosphere formation is an independent predictor of clinical outcome in malignant glioma 
Stem cells (Dayton, Ohio)  2009;27(4):980-987.
Renewable neurosphere formation in culture is a defining characteristic of certain brain tumor initiating cells. This retrospective study was designed to assess the relationship between neurosphere formation in cultured human glioma, tumorigenic capacity, and patient clinical outcome. Tumor samples were cultured in neurosphere conditions from 32 patients with glioma, including a subpopulation of 15 patients with primary glioblastoma. A subsample of renewable neurosphere cultures was xenografted into mouse brain to determine if they were tumorigenic. Our study shows that both renewable neurosphere formation and tumorigenic capacity are significantly associated with clinical outcome measures. Renewable neurosphere formation in cultured human glioma significantly predicted an increased hazard of patient death and more rapid tumor progression. These results pertained to both the full population of glioma and the subpopulation of primary glioblastoma. Similarly, there was a significant hazard of progression for patients whose glioma had tumorigenic capacity. Multivariate analysis demonstrated that neurosphere formation remained a significant predictor of clinical outcome independent of Ki67 proliferation index. In addition, multivariate analysis of neurosphere formation, tumor grade and patient age, demonstrated that neurosphere formation was a robust, independent predictor of glioma tumor progression. While the lengthy duration of this assay may preclude direct clinical application, these results exemplify how neurosphere culture serves as a clinically relevant model for the study of malignant glioma. Furthermore, this study suggests that the ability to propagate brain tumor stem cells in vitro is associated with clinical outcome.
PMCID: PMC3177534  PMID: 19353526
Brain tumor stem cell; human glioma; glioblastoma (GBM); neurosphere; progression free survival; cancer
6.  A microfluidic platform for systems pathology: multiparameter single-cell signaling measurements of clinical brain tumor specimens 
Cancer research  2010;70(15):6128-6138.
The clinical practice of oncology is being transformed by molecular diagnostics that will enable predictive and personalized medicine. Current technologies for quantitation of the cancer proteome are either qualitative (e.g., immunohistochemistry) or require large sample sizes (e.g., flow cytometry). Here, we report a microfluidic platform, Microfluidic Image Cytometry (MIC), capable of quantitative, single-cell proteomic analysis of multiple signaling molecules using only 1,000-2,800 cells. Using cultured cell lines, we demonstrate simultaneous measurement of four critical signaling proteins (EGFR, PTEN, phospho-Akt and phospho-S6) within the oncogenic PI3K/Akt/mTOR signaling pathway. To demonstrate the clinical application of the MIC platform to solid tumors, we analyzed a panel of 19 human brain tumor biopsies, including glioblastomas. Our MIC measurements were validated by clinical immunohistochemistry and confirmed the striking inter- and intra-tumoral heterogeneity characteristic of glioblastoma. To interpret the multiparameter, single-cell MIC measurements, we adapted bioinformatic methods including self-organizing maps that stratify patients into clusters which predict tumor progression and patient survival. Together with bioinformatic analysis, the MIC platform represents a robust, enabling in vitro molecular diagnostic technology for systems pathology analysis and personalized medicine.
PMCID: PMC3163840  PMID: 20631065
molecular diagnostics; microfluidics; systems biology; glioblastoma; PI3K
7.  High-Dose Chemotherapy with Autologous Hematopoietic Stem-Cell Rescue for Pediatric Brain Tumor Patients: A Single Institution Experience from UCLA 
Journal of Transplantation  2011;2011:740673.
Background. Dose-dependent response makes certain pediatric brain tumors appropriate targets for high-dose chemotherapy with autologous hematopoietic stem-cell rescue (HDCT-AHSCR). Methods. The clinical outcomes and toxicities were analyzed retrospectively for 18 consecutive patients ≤19 y/o treated with HDCT-AHSCR at UCLA (1999–2009). Results. Patients' median age was 2.3 years. Fourteen had primary and 4 recurrent tumors: 12 neural/embryonal (7 medulloblastomas, 4 primitive neuroectodermal tumors, and a pineoblastoma), 3 glial/mixed, and 3 germ cell tumors. Eight patients had initial gross-total and seven subtotal resections. HDCT mostly consisted of carboplatin and/or thiotepa ± etoposide (n = 16). Nine patients underwent a single AHSCR and nine ≥3 tandems. Three-year progression-free and overall survival probabilities were 60.5% ± 16 and 69.3% ± 11.5. Ten patients with pre-AHSCR complete remissions were alive/disease-free, whereas 5 of 8 with measurable disease were deceased (median followup: 2.3 yrs). Nine of 13 survivors avoided radiation. Single AHSCR regimens had greater toxicity than ≥3 AHSCR (P < .01). Conclusion. HDCT-AHSCR has a definitive, though limited role for selected pediatric brain tumors with poor prognosis and pretransplant complete/partial remissions.
PMCID: PMC3087896  PMID: 21559259

Results 1-7 (7)