Showing papers by "David Zagzag published in 2014"

Genomic analysis of diffuse intrinsic pontine gliomas identifies three molecular subgroups and recurrent activating ACVR1 mutations

Abstract: Diffuse intrinsic pontine glioma (DIPG) is a fatal brain cancer that arises in the brainstem of children, with no effective treatment and near 100% fatality. The failure of most therapies can be attributed to the delicate location of these tumors and to the selection of therapies on the basis of assumptions that DIPGs are molecularly similar to adult disease. Recent studies have unraveled the unique genetic makeup of this brain cancer, with nearly 80% found to harbor a p.Lys27Met histone H3.3 or p.Lys27Met histone H3.1 alteration. However, DIPGs are still thought of as one disease, with limited understanding of the genetic drivers of these tumors. To understand what drives DIPGs, we integrated whole-genome sequencing with methylation, expression and copy number profiling, discovering that DIPGs comprise three molecularly distinct subgroups (H3-K27M, silent and MYCN) and uncovering a new recurrent activating mutation affecting the activin receptor gene ACVR1 in 20% of DIPGs. Mutations in ACVR1 were constitutively activating, leading to SMAD phosphorylation and increased expression of the downstream activin signaling targets ID1 and ID2. Our results highlight distinct molecular subgroups and novel therapeutic targets for this incurable pediatric cancer.

Phase II study of sorafenib in children with recurrent or progressive low-grade astrocytomas.

Abstract: Recurrent pediatric low-grade astrocytoma (PLGA) represents a major clinical problem in neuro-oncology, and novel, less toxic and more effective therapies are needed.1 Recently, our increased understanding of the key molecular pathways driving PLGA growth and the increasing availability of targeted therapies for those pathways have led to great interest in exploring molecular targeted therapies for PLGA. Pilocytic astrocytoma (PA) is the most common histological subtype of PLGA. Patients with neurofibromatosis type 1 (NF1) are predisposed to developing PAs, predominantly in the optic tract (ie, optic pathway gliomas [OPGs]).2 NF1 is characterized by the loss of the NF1 gene product neurofibromin, resulting in activation of the RAS/RAF/MEK/ERK signaling pathway.3 The majority of sporadic PAs harbor a unique tandem duplication at chromosome 7q34, which produces a fusion gene between KIAA1549 and the kinase domain of BRAF that result in constitutive BRAF and ultimately MAPK activation. In recent genomic studies, almost all PAs that do not harbor KIAA-BRAF have been shown to harbor other genetic lesions that also result in constitutive MAPK pathway activation, such as activating genetic hits in FGFR1, NTRK2, and RAF1.4,5 PLGAs express pro-angiogenic factors (vascular endothelial growth factor [VEGF], platelet derived growth factor [PDGF]), and their receptors (VEGFR and PDGFR).6–8 Bevacizumab, a VEGF inhibitor, has recently shown very encouraging activity in PLGA.9,10 Sorafenib is an oral, small-molecule multikinase inhibitor with potent in vitro activity against both wild-type and mutant (V600E) BRAF.11 Recent preclinical data showed that overexpression of activated BRAF led to increased proliferation of primary mouse astrocytes that could be inhibited by treatment with sorafenib.12 Sorafenib also exerts anti-angiogenic activity via inhibition of VEGFR-1/2/3, PDGFRβ, Flt-3, and c-kit, which has been studied in a variety of preclinical models13,14 as well as in clinical studies using dynamic, contrast-enhanced MRI.15 Because sorafenib is a potent inhibitor of several key molecular pathways that are relevant in PLGAs and encouraging preclinical data,12 we conducted this prospective phase II clinical trial to assess the objective response rate to sorafenib in patients with PLGA.

Developmental brain abnormalities in tuberous sclerosis complex: A comparative tissue analysis of cortical tubers and perituberal cortex

Abstract: Summary Objective Genetic loss of Tsc1/Tsc2 function in tuberous sclerosis complex (TSC) results in altered mammalian target of rapamycin (mTOR) signaling and abnormal brain development. Although earlier studies have focused on characterization of cortical tubers, in this study we sought to examine the unique cellular and molecular features of the perituberal cortex in order to better understand its contribution to epileptogenesis, cognitive dysfunction, and autism. Methods Standard histologic and immunohistochemical labeling was used to assess structural abnormalities and cell-specific pattern of mTORC1 activation in surgically resected cortical tubers and perituberal cortex. Western blotting was performed to quantify the expression of the mTORC1 and mTORC2 biomarkers phospho-S6 (Ser235/236), phospho-S6 (Ser240/244), and phospho-Akt (Ser473), in addition to evaluating the differential expression levels of several neuronal and glial-specific proteins in tubers and peritubers, as compared to non-TSC epilepsy specimens. Results Tubers demonstrated mild to severe disruption of cortical lamination, the presence of pS6-positive dysplastic neurons and giant cells, an overall increase in mTORC1 and a decrease in mTORC2 activity, increased axonal connectivity and growth, and hypomyelination. Perituberal cortex presented similar histologic, immunohistochemical, and molecular features; however, they were overall milder. Axonal growth was specific for TSC and was negatively correlated with deficient myelination. Significance Our results show an extension of cellular dysplasia and dysregulated mTOR signaling in the perituberal tissue, and demonstrate for the first time aberrant connectivity in human TSC brain. This study provides new insights into the pathophysiology of neurologic dysfunction associated with TSC and supports the intrinsic epileptogenicity of normal-appearing perituberal cortex. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.

Decreased Expression of Cystathionine β-Synthase Promotes Glioma Tumorigenesis

Abstract: Cystathionine β-synthase (CBS) catalyzes metabolic reactions that convert homocysteine to cystathionine. To assess the role of CBS in human glioma, cells were stably transfected with lentiviral vectors encoding shRNA targeting CBS or a nontargeting control shRNA, and subclones were injected into immunodeficient mice. Interestingly, decreased CBS expression did not affect proliferation in vitro but decreased the latency period before rapid tumor xenograft growth after subcutaneous injection and increased tumor incidence and volume following orthotopic implantation into the caudate–putamen. In soft-agar colony formation assays, CBS knockdown subclones displayed increased anchorage-independent growth. Molecular analysis revealed that CBS knockdown subclones expressed higher basal levels of the transcriptional activator hypoxia-inducible factor 2α (HIF2α/EPAS1). HIF2α knockdown counteracted the effect of CBS knockdown on anchorage-independent growth. Bioinformatic analysis of mRNA expression data from human glioma specimens revealed a significant association between low expression of CBS mRNA and high expression of angiopoietin-like 4 (ANGPTL4) and VEGF transcripts, which are HIF2 target gene products that were also increased in CBS knockdown subclones. These results suggest that decreased CBS expression in glioma increases HIF2α protein levels and HIF2 target gene expression, which promotes glioma tumor formation. Implications: CBS loss-of-function promotes glioma growth. Mol Cancer Res; 12(10); 1398–406. ©2014 AACR .

Clinical response to bevacizumab in schwannomatosis.

Abstract: Schwannomatosis is a neurogenetic syndrome characterized by schwannomas throughout the peripheral nervous system without bilateral vestibular schwannomas (VS) or germline neurofibromatosis 2 (NF2) mutation.1 Management is difficult due to large tumor burden and treatment-resistant pain. Patients require multiple surgical procedures (average of 3.4 per decade) for pain, focal neurologic deficits, or myelopathy.1 There are no known effective drug therapies.

Selective lentiviral gene delivery to CD133-expressing human glioblastoma stem cells.

Abstract: Glioblastoma multiforme (GBM) is a deadly primary brain malignancy. Glioblastoma stem cells (GSC), which have the ability to self-renew and differentiate into tumor lineages, are believed to cause tumor recurrence due to their resistance to current therapies. A subset of GSCs is marked by cell surface expression of CD133, a glycosylated pentaspan transmembrane protein. The study of CD133-expressing GSCs has been limited by the relative paucity of genetic tools that specifically target them. Here, we present CD133-LV, a lentiviral vector presenting a single chain antibody against CD133 on its envelope, as a vehicle for the selective transduction of CD133-expressing GSCs. We show that CD133-LV selectively transduces CD133+ human GSCs in dose-dependent manner and that transduced cells maintain their stem-like properties. The transduction efficiency of CD133-LV is reduced by an antibody that recognizes the same epitope on CD133 as the viral envelope and by shRNA-mediated knockdown of CD133. Conversely, the rate of transduction by CD133-LV is augmented by overexpression of CD133 in primary human GBM cultures. CD133-LV selectively transduces CD133-expressing cells in intracranial human GBM xenografts in NOD.SCID mice, but spares normal mouse brain tissue, neurons derived from human embryonic stem cells and primary human astrocytes. Our findings indicate that CD133-LV represents a novel tool for the selective genetic manipulation of CD133-expressing GSCs, and can be used to answer important questions about how these cells contribute to tumor biology and therapy resistance.

Noninvasive diagnosis and management of spontaneous intracranial hypotension in patients with marfan syndrome: Case Report and Review of the Literature.

Abstract: Background Spontaneous intracranial hypotension is an uncommon clinical entity. Heritable connective tissue disorders (HCTD), such as Marfan syndrome, are frequently implicated as an underlying cause, due to dural structural weaknesses that predispose patients to spontaneous cerebrospinal fluid (CSF) leak. Due to the high prevalence of multi-system disease in HCTD, diagnosis and treatment are often complicated. Case description We present a 58-year-old female with Marfan syndrome on anticoagulation for a mechanical aortic valve replacement who came to medical attention with severe, acute-onset headache following a straining episode. Noninvasive magnetic resonance (MR) myelography confirmed thoracic CSF extravasations and multiple lumbar diverticula. The patient was treated conservatively and her symptoms resolved. Conclusion We discuss the common presentation, diagnostic tools, and treatment options for spontaneous CSF leaks in patients with Marfan syndrome or related HCTD with an emphasis on noninvasive modalities and a review of the major radiographic criteria used to diagnose dural abnormalities, such as dural ectasia.

Next-generation neuropathology - improving diagnostic accuracy for brain tumors using dna methylation array-based molecular profiling

Abstract: BACKGROUND: The current World Health Organisation (WHO) classification of central nervous system tumors comprises over 100 entities. Most of these are defined by purely histological criteria, with varying and sometimes overlapping spectra. Histological diagnosis is often challenging, however, especially in cases with limited or non-representative biopsy material. Thus, molecular technologies that can complement standard pathology testing have the potential to greatly enhance diagnostic precision and improve clinical decision-making. DNA methylation profiling, acting as a 'fingerprint' of cellular origin and molecular alterations, is one such promising technology. METHODS: We have assembled a reference dataset of more than 2,000 methylation profiles using the Illumina HumanMethylation450 (450k) array, currently representing over 50 brain tumor entities or subgroups. The array platform is suitable for both frozen and paraffin-embedded material, with minimal DNA input required. Each new diagnostic case receives an entity prediction with an associated probability score as a confidence measure. Genome-wide copy number profiles (e.g. for scoring 1p/19q loss or gene amplifications) and target gene methylation data (e.g. MGMT) generated from the array provide important additional information. RESULTS: In addition to the reference cohort, more than 500 diagnostic samples from Heidelberg University Hospital and external institutions have been processed. Approximately 5-10% of cases displayed a discrepancy between histological and molecular diagnoses. Careful re-examination of these often resulted in refinement of the original diagnosis, and improved patient care.Furthermore, samples collected for the reference cohort have led to significant improvements in our understanding of the biology of several tumor types, including the identification of further subgroups for several entities and associations with recurrent copy number changes and/or mutations. CONCLUSIONS: Our understanding of the molecular alterations underlying brain tumors has grown enormously in recent years, and it is crucial that this is translated into the clinic promptly. DNA methylation profiling is one tool with the potential to become an important part of the diagnostic armoury of neuropathologists. This relatively inexpensive and robust method is well suited to complement standard histopathologic techniques and improve diagnostic accuracy, thereby optimising patient management. We are currently expanding our pipeline to include additional diagnostic centres, allowing for further refinement and validation as well as broader international access. SECONDARY CATEGORY: Tumor Biology.