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Amsterdam-Zuidoost, Netherlands

Van Zanten S.E.M.V.,VU University Amsterdam | Jansen M.H.,VU University Amsterdam | Sanchez Aliaga E.,VU University Amsterdam | Van Vuurden D.G.,VU University Amsterdam | And 2 more authors.
Expert Review of Anticancer Therapy | Year: 2015

Introduction: Children with diffuse intrinsic pontine glioma (DIPG) face a dismal prognosis, with a median overall survival of 9 months. Our aims are to determine the incidence of DIPG in the Netherlands and to identify points for improvement in clinical research, a prerequisite for increasing the chance to find a cure. Methods: We performed a population-based retrospective cohort study by evaluating all children diagnosed with DIPG in the Netherlands between 1990 and 2010. Results: The incidence of DIPG in the Netherlands corresponds with international literature. Between 1990 and 2010, a large heterogeneity of treatment schedules was applied and only a minority of patients was included in clinical trials. Discussion: Given the rarity of DIPG, we emphasize the need for (inter-)national trials to facilitate the identification of potentially effective therapeutics in the future. This can be supported by the recent development of a European DIPG registry enabling international study collaborations. © 2014 Informa UK, Ltd. Source

Smits M.,Cancer Center Amsterdam | Wurdinger T.,Cancer Center Amsterdam | Wurdinger T.,Harvard University | Van Het Hof B.,Blood Brain Barrier Research Group | And 9 more authors.
FASEB Journal | Year: 2012

In patients with glioblastomas, vascular endothelial growth factor (VEGF) is a key mediator of tumor-associated angiogenesis. Glioblastomas are notorious for their capacity to induce neovascularization, driving continued tumor growth. Here we report that miR-125b is down-regulated in glioblastoma-associated endothelial cells, resulting in increased expression of its target, myc-associated zinc finger protein (MAZ), a transcription factor that regulates VEGF. The down-regulation of miR-125b was also observed on exposure of endothelial cells to glioblastoma-conditioned medium or VEGF, resulting in increased MAZ expression. Further analysis revealed that inhibition of MAZ accumulation by miR-125b, or by MAZ-specific shRNAs, attenuated primary human brain endothelial cell migration and tubule formation in vitro, phenomena considered to mimick angiogenic processes in vitro. Moreover, MAZ expression was elevated in brain blood vessels of glioblastoma patients. Altogether these results demonstrate a functional feed-forward loop in glioblastomarelated angiogenesis, in which VEGF inhibits the expression of miR-125b, resulting in increased expression of MAZ, which in its turn causes transcriptional activation of VEGF. This loop is functionally impeded by the VEGF receptor inhibitor vandetanib, and our results may contribute to the further development of inhibitors of tumor-angiogenesis. © FASEB. Source

Germans M.R.,Neurosurgical Center Amsterdam | Post R.,Neurosurgical Center Amsterdam | Coert B.A.,Neurosurgical Center Amsterdam | Rinkel G.J.E.,University Utrecht | And 2 more authors.
Trials | Year: 2013

Background: A frequent complication in patients with subarachnoid hemorrhage (SAH) is recurrent bleeding from the aneurysm. The risk is highest within the first 6 hours after the initial hemorrhage. Securing the aneurysm within this timeframe is difficult owing to logistical delays. The rate of recurrent bleeding can also be reduced by ultra-early administration of antifibrinolytics, which probably improves functional outcome. The aim of this study is to investigate whether ultra-early and short-term administration of the antifibrinolytic agent tranexamic acid (TXA), as add-on to standard SAH management, leads to better functional outcome.Methods/Design: This is a multicenter, prospective, randomized, open-label trial with blinded endpoint (PROBE) assessment. Adult patients with the diagnosis of non-traumatic SAH, as proven by computed tomography (CT) within 24 hours after the onset of headache, will be randomly assigned to the treatment group or the control group. Patients in the treatment group will receive standard treatment with the addition of a bolus of TXA (1 g intravenously) immediately after randomization, followed by continuous infusion of 1 g per 8 hours until the start of aneurysm treatment, or a maximum of 24 hours after the start of medication. Patients in the control group will receive standard treatment without TXA. The primary outcome measure is favorable functional outcome, defined as a score of 0 to 3 on the modified Rankin Scale (mRS), at 6 months after SAH. Primary outcome will be determined by a trial nurse blinded for treatment allocation. We aim to include 950 patients in 3 years.Discussion: The strengths of this study are: 1. the ultra-early and short-term administration of TXA, resulting in a lower dose as compared to previous studies, which should reduce the risk for delayed cerebral ischemia (DCI), an important risk factor in the long-term treatment with antifibrinolytics; 2. the power calculation is based on functional outcome and calculated with use of recent study results of our own population, supported by data from prominent studies; and 3. the participation of several specialized SAH centers, and their referring hospitals, in the Netherlands with comparative treatment protocols.Trial registration: Nederlands Trial Register (Dutch Trial Registry) number NTR3272. © 2013 Germans et al.; licensee BioMed Central Ltd. Source

Bleeker F.E.,Neurosurgical Center Amsterdam | Molenaar R.J.,University of Amsterdam | Leenstra S.,Erasmus Medical Center
Journal of Neuro-Oncology | Year: 2012

Glioblastoma is the most common and most aggressive primary brain tumor. Despite maximum treatment, patients only have a median survival time of 15 months, because of the tumor's resistance to current therapeutic approaches. Thus far, methylation of the O 6-methylguanine-DNA methyltransferase (MGMT) promoter has been the only confirmed molecular predictive factor in glioblastoma. Novel "genome-wide" techniques have identified additional important molecular alterations as mutations in isocitrate dehydrogenase 1 (IDH1) and its prognostic importance. This review summarizes findings and techniques of genetic, epigenetic, transcriptional, and proteomic studies of glioblastoma. It provides the clinician with an up-to-date overview of current identified molecular alterations that should ultimately lead to new therapeutic targets and more individualized treatment approaches in glioblastoma. © 2012 The Author(s). Source

Smits M.,VU University Amsterdam | Van Rijn S.,VU University Amsterdam | Hulleman E.,VU University Amsterdam | Biesmans D.,VU University Amsterdam | And 9 more authors.
Clinical Cancer Research | Year: 2012

Purpose: Medulloblastoma is the most common malignant brain tumor in children. Despite recent improvements, the molecular mechanisms driving medulloblastoma are not fully understood and further elucidation could provide cues to improve outcome prediction and therapeutic approaches. Experimental Design: Here, we conducted a meta-analysis of mouse and human medulloblastoma gene expression data sets, to identify potential medulloblastoma tumor suppressor genes. Results: We identified DAB2IP, a member of the RAS-GTPase-activating protein family (RAS GAP), and showed that DAB2IP expression is repressed in medulloblastoma by EZH2-induced trimethylation. Moreover, we observed that reduced DAB2IP expression correlates significantly with a poor overall survival of patients with medulloblastoma, independent of metastatic stage. Finally, we showed that ectopic DAB2IP expression enhances stress-induced apoptosis in medulloblastoma cells and that reduced expression of DAB2IP in medulloblastoma cells conveys resistance to irradiation-induced cell death. Conclusion: These results suggest that repression of DAB2IP may at least partly protect medulloblastoma cells from apoptotic cell death. Moreover, DAB2IP may represent a molecular marker to distinguish patients with medulloblastoma at high risk from those with a longer survival prognosis. ©2012 AACR. Source

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