David Gutmann - Academia.edu (original) (raw)

Papers by David Gutmann

Stem cells (Dayton, Ohio), Jan 18, 2015

Neural stem cells (NSCs) give rise to all the major cell types in the brain, including neurons, o... more Neural stem cells (NSCs) give rise to all the major cell types in the brain, including neurons, oligodendrocytes, and astrocytes. However, the intracellular signaling pathways that govern brain NSC proliferation and differentiation have been incompletely characterized to date. Since some neurodevelopmental brain disorders (Costello syndrome, Noonan syndrome) are caused by germline activating mutations in the RAS genes, Ras small GTPases are likely critical regulators of brain NSC function. In the mammalian brain, Ras exists as three distinct molecules (H-Ras, K-Ras, and N-Ras), each with different subcellular localizations, downstream signaling effectors, and biological effects. Leveraging a novel series of conditional activated Ras molecule-expressing genetically-engineered mouse strains, we demonstrate that activated K-Ras, but not H-Ras or N-Ras, expression increases brain NSC growth in a Raf-dependent, but Mek-independent, manner. Moreover, we show that activated K-Ras regulatio...

Neuro-oncology, 2015

Inhibition of the mammalian target of rapamycin (mTOR) signaling pathway has become an attractive... more Inhibition of the mammalian target of rapamycin (mTOR) signaling pathway has become an attractive target for human cancer therapy. Hyperactivation of mTOR has been reported in both sporadic and syndromic (hereditary) brain tumors. In contrast to the large number of successful clinical trials employing mTOR inhibitors in different types of epithelial neoplasms, their use to treat intracranial neoplasms is more limited. In this review, we summarize the role of mTOR activation in brain tumor pathogenesis and growth relevant to new human brain tumor trials currently under way using mTOR inhibitors.

Modern Pathology, 2014

Cellular schwannoma is an uncommon, but well-recognized, benign peripheral nerve sheath tumor, wh... more Cellular schwannoma is an uncommon, but well-recognized, benign peripheral nerve sheath tumor, which can be misdiagnosed as malignant peripheral nerve sheath tumor. To develop consensus diagnostic criteria for cellular schwannoma, we reviewed 115 malignant peripheral nerve sheath tumor and 26 cellular schwannoma cases from two institutions. Clinical data were retrieved from the electronic medical records, and morphologic features, maximal mitotic counts, Ki67 labeling indices, and immunohistochemical profiles (SOX10, SOX2, p75NTR, p16, p53, EGFR, and neurofibromin) were assessed. Several features distinguish cellular schwannoma from malignant peripheral nerve sheath tumor. First, in contrast to patients with malignant peripheral nerve sheath tumor, no metastases or disease-specific deaths were found in patients with cellular schwannoma. More specifically, 5-year progression-free survival rates were 100 and 18%, and 5-year disease-specific survival rates were 100 and 32% for cellular schwannoma and malignant peripheral nerve sheath tumor, respectively. Second, the presence of Schwannian whorls, a peritumoral capsule, subcapsular lymphocytes, macrophage-rich infiltrates, and the absence of fascicles favored the diagnosis of cellular schwannoma, while the presence of perivascular hypercellularity, tumor herniation into vascular lumens, and necrosis favor malignant peripheral nerve sheath tumor. Third, complete loss of SOX10, neurofibromin or p16 expression, or the presence of EGFR immunoreactivity was specific for malignant peripheral nerve sheath tumor (Po0.001 for each). Expression of p75NTR was observed in 80% of malignant peripheral nerve sheath tumors compared with 31% of cellular schwannomas (Po0.001). Fourth, Ki-67 labeling indices Z20% were highly predictive of malignant peripheral nerve sheath tumor (87% sensitivity and 96% specificity). Taken together, the combinations of these histopathological and immunohistochemical features provide useful criteria to distinguish between malignant peripheral nerve sheath tumor and cellular schwannoma with high sensitivity and specificity. Additional retrospective and prospective multicenter studies with larger data sets will be required to validate these findings.

PloS one, 2014

Most meningiomas are benign, but some clinical-aggressive tumors exhibit brain invasion and canno... more Most meningiomas are benign, but some clinical-aggressive tumors exhibit brain invasion and cannot be resected without significant complications. To identify molecular markers for these clinically-aggressive meningiomas, we performed microarray analyses on 24 primary cultures from 21 meningiomas and 3 arachnoid membranes. Using this approach, increased transglutaminase 2 (TGM2) expression was observed, which was subsequently validated in an independent set of 82 meningiomas by immunohistochemistry. Importantly, the TGM2 expression level was associated with increasing WHO malignancy grade as well as meningioma recurrence. Inhibition of TGM2 function by siRNA or cystamine induced meningioma cell death, which was associated with reduced AKT phosphorylation and caspase-3 activation. Collectively, these findings suggest that TGM2 expression increases as a function of malignancy grade and tumor recurrence and that inhibition of TGM2 reduces meningioma cell growth.

Cancer research, Jan 15, 2003

Whereas biallelic neurofibromatosis 1 (NF1) inactivation is observed in NF1-associated gliomas, a... more Whereas biallelic neurofibromatosis 1 (NF1) inactivation is observed in NF1-associated gliomas, astrocyte-restricted Nf1 conditional knockout mice do not develop gliomas. These observations suggest that NF1 glioma formation requires additional cellular or genetic conditions. To determine the effect of an Nf1 heterozygous brain environment on NF1 glioma formation, we generated Nf1+/- mice lacking Nf1 expression in astrocytes. In contrast to astrocyte-restricted Nf1 conditional knockout mice, Nf1+/- mice lacking Nf1 in astrocytes develop optic nerve gliomas. This mouse model demonstrates that Nf1+/- cells contribute to the pathogenesis of gliomas in NF1 and provides a tool for the preclinical evaluation of potential therapeutic interventions for these tumors.

One of the major limitations to preclinical mouse therapeutic evaluation is the inherent difficul... more One of the major limitations to preclinical mouse therapeutic evaluation is the inherent difficulty in imaging small tumors in vivo. We present a rapid and reliable method to detect optic glioma (OPG) in a mouse neurofibromatosis-1 model (Nf1 flox/mut GFAP-Cre mice) in vivo using Manganese-Enhanced Magnetic Resonance Imaging (MEMRI). In a blinded study, twenty-three mice were chosen randomly from a cohort of Nf1 flox/mut GFAP-Cre mice and two sets of age-matched controls. In all cases, OPG presence or absence was correctly identified. In addition, the OPG size and shape was accurately measured in vivo, facilitating the use of this model for preclinical drug studies. Over the past several years, we have developed a robust mouse model of NF1-asscociated optic glioma resulting from Nf1 gene inactivation in glial cells (Nf1 flox/mut GFAP-Cre mice). Nf1 flox/mut GFAP-Cre mice are born healthy, but develop gliomas restricted to the prechiasmatic optic nerves and optic chiasm by 2-3 months of age (Bajenaru et al. 2005; Bajenaru et al. 2003). These optic gliomas can be visualized by small-animal magnetic

Neuro-oncology, Jan 14, 2014

Plexiform neurofibromas (PNs) are benign peripheral nerve sheath tumors that arise in one-third o... more Plexiform neurofibromas (PNs) are benign peripheral nerve sheath tumors that arise in one-third of individuals with neurofibromatosis type 1 (NF1). They may cause significant disfigurement, compression of vital structures, neurologic dysfunction, and/or pain. Currently, the only effective management strategy is surgical resection. Converging evidence has demonstrated that the NF1 tumor suppressor protein, neurofibromin, negatively regulates activity in the mammalian Target of Rapamycin pathway. We employed a 2-strata clinical trial design. Stratum 1 included subjects with inoperable, NF1-associated progressive PN and sought to determine whether sirolimus safely and tolerably increases time to progression (TTP). Volumetric MRI analysis conducted at regular intervals was used to determine TTP relative to baseline imaging. The estimated median TTP of subjects receiving sirolimus was 15.4 months (95% CI: 14.3-23.7 mo), which was significantly longer than 11.9 months (P < .001), the m...

SUMMARY Individuals with neurofibromatosis type 1 (NF1) develop abnormalities of both neuronal an... more SUMMARY Individuals with neurofibromatosis type 1 (NF1) develop abnormalities of both neuronal and glial cell lineages, suggesting that the NF1 pro- tein neurofibromin is an essential regulator of neuroglial progenitor function. In this regard, Nf1-deficient embryonic telencephalic neuro- spheres exhibit increased self-renewal and pro- longed survival as explants in vivo. Using a newly developed brain lipid binding protein (BLBP)-Cre mouse

American Journal of Pathology, 2001

Although plexiform neurofibroma (PN) is thought to represent a benign neoplasm with the potential... more Although plexiform neurofibroma (PN) is thought to represent a benign neoplasm with the potential for malignant transformation (malignant peripheral nerve sheath tumor; MPNST), its neoplastic nature has been difficult to prove due to cellular heterogeneity, which hampers standard molecular genetic analysis. Its mixed composition typically includes Schwann cells, fibroblasts, perineurial-like cells, and mast cells. Although NF1 loss of heterozygosity has been reported in subsets of PNs, it remains uncertain which cell type(s) harbor these alterations. Using a dual-color fluorescence in situ hybridization and immunohistochemistry technique, we studied NF1 gene status in S-100 protein-positive and-negative cell subpopulations in archival paraffin-embedded specimens from seven PNs, two atypical PNs, one cellular/ atypical PN, and eight MPNSTs derived from 13 patients, seven of which had neurofibromatosis type 1 (NF1). NF1 loss was detected in four of seven PNs and one atypical PN, with deletions entirely restricted to S-100 protein-immunoreactive Schwann cells. In contrast, all eight MPNSTs harbored NF1 deletions, regardless of S-100 protein expression or NF1 clinical status. Our results suggest that the Schwann cell is the primary neoplastic component in PNs and that S-100 protein-negative cells in MPNST represent dedifferentiated Schwann cells, which harbor NF1 deletions in both NF1-associated and sporadic tumors.

Neuropathology and Applied Neurobiology, 2000

The critical role of the neurofibromatosis 1 (NF1) gene as a tumour suppressor has been clearly d... more The critical role of the neurofibromatosis 1 (NF1) gene as a tumour suppressor has been clearly demonstrated for malignancies arising in NF1 patients. However, little is known about the more common benign tumours, such as the pilocytic astrocytoma. Most NF1‐associated astrocytomas are benign and clinically non‐progressive, though aggressive tumours are occasionally encountered. In this study, eight pilocytic astrocytomas from six individuals affected with NF1 were analysed for NF1 expression. All eight tumours demonstrated loss of neurofibromin expression by immunohistochemistry, which was confirmed in one case using Western blot analysis. Microsatellite analysis showed loss of a single NF1 allele (LOH) in two of four NF1‐associated tumours. These results demonstrate that, in contrast to sporadic astrocytomas, loss of NF1 expression is an important primary genetic event in the pathogenesis of NF1‐associated pilocytic astrocytomas.

PLoS ONE, 2010

Vascular endothelial growth factor (VEGF) plays a critical role in normal development as well as ... more Vascular endothelial growth factor (VEGF) plays a critical role in normal development as well as retinal vasculature disease. During retinal vascularization, VEGF is most strongly expressed by not yet vascularized retinal astrocytes, but also by retinal astrocytes within the developing vascular plexus, suggesting a role for retinal astrocyte-derived VEGF in angiogenesis and vessel network maturation. To test the role of astrocyte-derived VEGF, we used Cre-lox technology in mice to delete VEGF in retinal astrocytes during development. Surprisingly, this only had a minor impact on retinal vasculature development, with only small decreases in plexus spreading, endothelial cell proliferation and survival observed. In contrast, astrocyte VEGF deletion had more pronounced effects on hyperoxia-induced vaso-obliteration and led to the regression of smooth muscle cell-coated radial arteries and veins, which are usually resistant to the vessel-collapsing effects of hyperoxia. These results suggest that VEGF production from retinal astrocytes is relatively dispensable during development, but performs vessel stabilizing functions in the retinal vasculature and might be relevant for retinopathy of prematurity in humans.

PLoS ONE, 2014

The proper control of tissue growth is essential during normal development and an important probl... more The proper control of tissue growth is essential during normal development and an important problem in human disease. Merlin, the product of the Neurofibromatosis 2 tumor suppressor gene, has been extensively studied to understand its functions in growth control. Here we describe experiments in which we used Drosophila as an in vivo system to test the functions of the normal human NF2 gene products and patient-derived mutant alleles. Although the predominant NF2 gene isoform, isoform 1, could functionally replace the Drosophila Merlin gene, a second isoform with a distinct C-terminal tail could not. Immunofluorescence studies show that the two isoforms have distinct subcellular localizations when expressed in the polarized imaginal epithelium, and function in genetic rescue assays correlates with apical localization of the NF2 protein. Interestingly, we found that a patient-derived missense allele, NF2 L64P , appears to be temperature sensitive. These studies highlight the utility of Drosophila for in vivo functional analysis of highly conserved human disease genes.

Oncogene, 1999

Individuals aected with neuro®bromatosis 1 (NF1) harbor increased numbers of GFAP-immunoreactive ... more Individuals aected with neuro®bromatosis 1 (NF1) harbor increased numbers of GFAP-immunoreactive cerebral astrocytes and develop astrocytomas that can lead to blindness and death. Mice heterozygous for a targeted Nf1 mutation (Nf1+/7) were employed as a model for the human disease to evaluate the hypothesis that reduced NF1 protein (neuro®bromin) expression may confer a growth advantage for astrocytes, such that inactivation of only one NF1 allele is sucient for abnormal astrocyte proliferation. Here, we report that Nf1+/7 mice have increased numbers of cerebral astrocytes and increased astrocyte proliferation compared to wild-type littermates. Intriguingly, primary Nf1+/7 astrocyte cultures failed to demonstrate a cell-autonomous growth advantage unless they were cocultured with C17 neuronal cells. This C17 neuronal cellinduced Nf1+/7 increase in proliferation was blocked by MEK inhibition (PD98059), suggesting a p21-rasdependent eect. Furthermore, mice heterozygous for a targeted mutation in another GAP molecule, p120-GAP, demonstrated no increases in cerebral astrocyte number. These ®ndings suggest that reduced NF1 expression results in a cell context-dependent increase in astrocyte proliferation that may be sucient for the development of astrocytic growth abnormalities in patients with NF1.

Nature, 2010

Users may view, print, copy, download and text and data-mine the content in such documents, for t... more Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Modern Pathology, 2002

Ependymomas are malignant CNS neoplasms with highly variable biologic behavior, including a gener... more Ependymomas are malignant CNS neoplasms with highly variable biologic behavior, including a generally better prognosis for intraspinal tumors. Inactivation of the NF2 gene on 22q12 and loss of its protein product, merlin, have been well documented in subsets of meningiomas and ependymomas. DAL-1, a related tumor suppressor and protein 4.1 family member on 18p11.3, has also been recently implicated in meningioma pathogenesis, though its role in ependymoma remains unknown. Therefore, we evaluated 27 ependymomas (12 intracranial and 15 spinal) using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) to determine NF2/merlin and DAL-1/DAL-1 status at the DNA and protein levels. Demonstrable NF2 and DAL-1 gene deletions were each detected in 6 (22%) ependymomas. All 5 merlin losses by IHC occurred in spinal ependymomas (P ‫؍‬ .047), whereas 5 (71%) DAL-1-negative cases were intracranial (P ‫؍‬ .185). The former result is consistent with prior observations that NF2 mutations are generally limited to spinal ependymomas. In contrast to meningiomas, simultaneous merlin and DAL-1 losses were not encountered. Our findings suggest that (1) NF2 and DAL-1 losses are involved in the pathogenesis of spinal and intracranial ependymoma subsets, respectively and (2) given the number of cases with no demonstrable losses, other cellular perturbations must also be critical for tumorigenesis.

Modern Pathology, 2005

Ependymomas are common pediatric and adult CNS malignancies with a wide biologic spectrum that is... more Ependymomas are common pediatric and adult CNS malignancies with a wide biologic spectrum that is often hard to predict using classic prognostic variables. The molecular pathogenesis is also poorly understood and few reproducible genetic alterations have been identified. The most common genetic alteration has been the loss of the Protein 4.1 family member, NF2, predominantly in spinal ependymomas. In contrast, a pilot study suggested that 4.1B deletions might be more common in intracranial ependymomas. These findings prompted us to study Protein 4.1 family members (NF2, 4.1B, 4.1R, 4.1G) in a larger cohort of 84 ependymomas (51 intracranial and 33 spinal; 11 WHO grade I, 43 grade II, 30 grade III). Fluorescence in situ hybridization was performed using NF2, 4.1B, 4.1R and 4.1G probes and immunohistochemical staining was performed in a subset using merlin, Protein 4.1B and Protein 4.1R antibodies. Additionally, frozen tissue from nine ependymomas (four intracranial and five spinal) was obtained for Western blot analysis for merlin, 4.1B and 4.1R expression. The majority of cases harbored one or more detectable genetic alterations, but we found that 4.1B gene deletions and 4.1R loss of expression were statistically more common in the pediatric vs adult, intracranial vs spinal, and grade III vs grade I/II subsets (P-values of 0.038 to o0.001). Also, 4.1G deletions were seen in 11/27 (41%) patients who either died of disease or had residual/recurrent tumor vs 5/41 patients with no evidence of disease at last follow-up (P ¼ 0.009). We conclude that alterations of Protein 4.1 family members are common in ependymal tumors and that specific alterations are associated with distinct clinicopathologic subsets.

Journal of Neuro-Oncology, 2004

Meningiomas are common central nervous system tumors that originate from the meningeal coverings ... more Meningiomas are common central nervous system tumors that originate from the meningeal coverings of the brain and the spinal cord. Most meningiomas are slowly growing benign tumors that histologically correspond to World Health Organization (WHO) grade I. However, certain rare histological variants (clear cell, chordoid, papillary, and rhabdoid), as well as atypical (WHO grade II) and anaplastic (WHO grade III) meningiomas show a more aggressive biological behavior and are clinically associated with a high risk of local recurrence and a less favorable prognosis. This review summarizes the most important features of meningioma pathology and provides an up-to-date overview about the molecular mechanisms involved in meningioma initiation and progression. Current data indicate that meningioma initiation is closely linked to the inactivation of one or more members of the highly conserved protein 4.1 superfamily, including the neurofibromatosis type 2 gene product merlin/schwannomin, protein 4.IB (DAL-1) and protein 4.1R. The genetic alterations in atypical meningiomas are complex and involve losses on 1p, 6q, 10, 14q and 18q, as well as gains on multiple chromosomes. The relevant genes are still unknown. Anaplastic meningiomas show even more complex genetic alterations, including frequent alteration of the CDKN2A, p14 ARF , and CDKN2B tumor suppressor genes at 9p21, as well as gene amplification on 17q23. A better understanding of the molecular mechanisms involved in meningioma pathogenesis may not only lead to the identification of novel diagnostic and prognostic marker but will also facilitate the development of new pathogenesis-based therapeutic strategies.

Journal of Neurogenetics, 2000

J . h'eurogenelics. Vol. 14(2). pp. 63-106 Reprints available dimly from the publisher Photo... more J . h'eurogenelics. Vol. 14(2). pp. 63-106 Reprints available dimly from the publisher Photocopying permincd by license only 0 2000 OPA (Overseas Publishers Association) NV Published by license under the Hanvood Academic Publishers imprint, part of The Gordon and Breach ...

Journal of Clinical Neuroscience, 2004

Neurofibromatosis type 1 (NF1) is an inherited disorder in which affected individuals develop bot... more Neurofibromatosis type 1 (NF1) is an inherited disorder in which affected individuals develop both benign and malignant tumours at an increased frequency. Glioneuronal tumours, such as ganglioglioma and dysembryoplastic neuroepithelial tumour, have been previously reported in patients with NF1. We describe two patients with glioneuronal tumours and typical clinical features of NF1. Molecular analysis of these tumours did not demonstrate loss of the NF1 gene by fluorescence in situ hybridization (FISH) or immunohistochemistry analysis, suggesting they might not be causally associated with gross defects in NF1 expression. Because of the excellent prognosis following the resection of these tumours, it is important to distinguish them from other NF1-associated tumours.