Constitutive Notch2 signaling in neural stem cells promotes tumorigenic features and astroglial lineage entry

Recent studies identified a highly tumorigenic subpopulation of glioma stem cells (GSCs) within malignant gliomas. GSCs are proposed to originate from transformed neural stem cells (NSCs). Several pathways active in NSCs, including the Notch pathway, were shown to promote proliferation and tumorigenesis in GSCs. Notch2 is highly expressed in glioblastoma multiforme (GBM), a highly malignant astrocytoma. It is therefore conceivable that increased Notch2 signaling in NSCs contributes to the formation of GBM. Here, we demonstrate that mice constitutively expressing the activated intracellular domain of Notch2 in NSCs display a hyperplasia of the neurogenic niche and reduced neuronal lineage entry. Neurospheres derived from these mice show increased proliferation, survival and resistance to apoptosis. Moreover, they preferentially differentiate into astrocytes, which are the characteristic cellular population of astrocytoma. Likewise, we show that Notch2 signaling increases proliferation and resistance to apoptosis in human GBM cell lines. Gene expression profiling of GBM patient tumor samples reveals a positive correlation of Notch2 transcripts with gene transcripts controlling anti-apoptotic processes, stemness and astrocyte fate, and a negative correlation with gene transcripts controlling proapoptotic processes and oligodendrocyte fate. Our data show that Notch2 signaling in NSCs produces features of GSCs and induces astrocytic lineage entry, consistent with a possible role in astrocytoma formation

GSK3β Regulates Differentiation and Growth Arrest in Glioblastoma

Cancers are driven by a population of cells with the stem cell properties of self-renewal and unlimited growth. As a subpopulation within the tumor mass, these cells are believed to constitute a tumor cell reservoir. Pathways controlling the renewal of normal stem cells are deregulated in cancer. The polycomb group gene Bmi1, which is required for neural stem cell self-renewal and also controls anti-oxidant defense in neurons, is upregulated in several cancers, including medulloblastoma. We have found that Bmi1 is consistently and highly expressed in GBM. Downregulation of Bmi1 by shRNAs induced a differentiation phenotype and reduced expression of the stem cell markers Sox2 and Nestin. Interestingly, expression of glycogen synthase kinase 3 beta (GSK3β), which was found to be consistently expressed in primary GBM, also declined. This suggests a functional link between Bmi1 and GSK3β. Interference with GSK3β activity by siRNA, the specific inhibitor SB216763, or lithium chloride (LiCl) induced tumor cell differentiation. In addition, tumor cell apoptosis was enhanced, the formation of neurospheres was impaired, and clonogenicity reduced in a dose-dependent manner. GBM cell lines consist mainly of CD133-negative (CD133-) cells. Interestingly, ex vivo cells from primary tumor biopsies allowed the identification of a CD133- subpopulation of cells that express stem cell markers and are depleted by inactivation of GSK3β. Drugs that inhibit GSK3, including the psychiatric drug LiCl, may deplete the GBM stem cell reservoir independently of CD133 status

East Mediterranean region sickle cell disease mortality trial: retrospective multicenter cohort analysis of 735 patients

PubMedID: 27068408Sickle cell disease (SCD), one of the most common genetic disorders worldwide, is characterized by hemolytic anemia and tissue damage from the rigid red blood cells. Although hydroxyurea and transfusion therapy are administered to treat the accompanying tissue injury, whether either one prolongs the lifespan of patients with SCD is unknown. SCD-related mortality data are available, but there are few studies on mortality-related factors based on evaluations of surviving patients. In addition, ethnic variability in patient registries has complicated detailed analyses. The aim of this study was to investigate mortality and mortality-related factors among an ethnically homogeneous population of patients with SCD. The 735 patients (102 children and 633 adults) included in this retrospective cohort study were of Eti-Turk origin and selected from 1367 patients seen at 5 regional hospitals. A central population management system was used to control for records of patient mortality. Data reliability was checked by a data supervision group. Mortality-related factors and predictors were identified in univariate and multivariate analyses using a Cox regression model with stepwise forward selection. The study group included patients with homozygous hemoglobin S (Hgb S) disease (67 %), Hb S-ß0 thalassemia (17 %), Hgb S-ß+ thalassemia (15 %), and Hb S-? thalassemia (1 %). They were followed for a median of 66 ± 44 (3–148) months. Overall mortality at 5 years was 6.1 %. Of the 45 patients who died, 44 (6 %) were adults and 1 (0.1 %) was a child. The mean age at death was 34.1 ± 10 (18–54) years for males, 40.1 ± 15 (17–64) years for females, and 36.6 ± 13 (17–64) years overall. Hydroxyurea was found to have a notable positive effect on mortality (p = 0.009). Mortality was also significantly related to hypertension and renal damage in a univariate analysis (p = 0.015 and p = 0.000, respectively). Acute chest syndrome, splenic sequestration, and prolonged painful-crisis-related multiorgan failure were the most common causes of mortality. In a multivariate analysis of laboratory values, only an elevated white blood cell count was related to mortality (p = 0.009). These data show that despite recent progress in the treatment of SCD, disease-related factors continue to result in mortality in young adult patients. Our results highlight the importance of evaluating curative treatment options for patients who have an appropriate stem cell donor in addition to improving patient care and patient education. © 2016, Springer-Verlag Berlin Heidelberg