Biomedical subjects

David H Gutmann

Publications and source records attributed to David H Gutmann.

88 records · Page 5Linked to original sources

PubMed2002

Nf2 gene inactivation in arachnoidal cells is rate-limiting for meningioma development in the mouse.

Biallelic NF2 gene inactivation is common in sporadic and in neurofibromatosis type 2 (NF2)-related meningiomas. We show that, beginning at four months of age, thirty percent of mice with arachnoidal cell Cre-mediated excision of Nf2 exon 2 developed a range of meningioma subtypes histologically similar to the human tumors. Additional hemizygosity for p53 did not modify meningioma frequency or progression suggesting that Nf2 and p53 mutations do not synergize in meningeal tumorigenesis. This first mouse model initiated with a genetic lesion found in human meningiomas provides a powerful tool for investigating tumor progression and for the preclinical evaluation of therapeutic interventions.

Adenoviridae↗

PubMed2002

Comparative gene expression profile analysis of neurofibromatosis 1-associated and sporadic pilocytic astrocytomas.

Pilocytic astrocytomas (PAs) are WHO grade I brain tumors that do not typically progress to more malignant grades of astrocytoma. Whereas there have been significant advances in the molecular genetics of high-grade astrocytomas, relatively little is known about the genetic changes associated with PA formation. In an effort to better characterize these low-grade neoplasms, we compared the gene expression profiles of six sporadic and two neurofibromatosis 1-associated PAs with other tissues and cell lines of both astrocytic and oligodendroglial origin. Hierarchical cluster analysis of gene expression data clearly delineated PAs from low-grade oligodendrogliomas and normal white matter. The two NF1-associated tumors and one of the sporadic PAs displayed expression profiles that were more closely related to those of cultured normal human fetal astrocytes. However, PAs also expressed individual genes typically associated with oligodendroglial lineage (e.g., proteolipid protein and PMP-22). The expression patterns of specific genes (e.g., ApoD) were unique to PA tumors, whereas genetic changes characteristic of high-grade astrocytomas were not encountered. Differential expression of two transcripts, neural cellular adhesion molecule and connexin-43, was confirmed at the protein level, suggesting that these cell adhesion molecules might be particularly important in the molecular pathogenesis of these tumors. We conclude that PAs are genetically unique gliomas with gene expression profiles that resemble those of fetal astrocytes and, to a lesser extent, oligodendroglial precursors.

Astrocytoma↗

PubMed2002

International consensus statement on malignant peripheral nerve sheath tumors in neurofibromatosis.

Neurofibromatosis 1 (NF1) is an autosomal dominant tumor predisposition syndrome in which affected individuals have a greatly increased risk of developing malignant peripheral nerve sheath tumors (MPNSTs). These cancers are difficult to detect and have a poor prognosis. Because patients may present to specialists from widely differing disciplines, the association with NF1 is often not appreciated, and there is no cohesive pattern of care. A multidisciplinary group of 33 clinicians and scientists with specialist knowledge in MPNST and NF1 reviewed the current published and unpublished data in this field, and distilled their collective experience to produce a consensus summary on MPNST in NF1. The known clinical, pathological, and genetic information on MPNST in NF1was collated, and a database was established to record information in a uniform manner. Subgroups with a higher risk of developing MPNSTwere identified within the NF1 population. The consortium formulated proposals and guidelines for clinical and pathological diagnosis, surgical management, and medical treatment of MPNST in individuals with NF1.A multidisciplinary team approach to the management of this complex disorder is advocated. Progress can be made by adopting the guidelines proposed by this consortium and by widespread dissemination of standardized information. Collaborative research should be promoted with the aim of harnessing advances in molecular genetics to develop targeted therapies for MPNST in people with NF1.

Adolescent↗

PubMed2002

Astrocyte-specific expression of CDK4 is not sufficient for tumor formation, but cooperates with p53 heterozygosity to provide a growth advantage for astrocytes in vivo.

The development of malignant gliomas (astrocytomas) involves the accumulation of multiple genetic changes, including mutations in the p53 and retinoblastoma (Rb) cell cycle regulatory pathways. One Rb pathway alteration seen in high-grade astrocytomas is amplification of cyclin dependent kinase-4 (CDK4). To define the function of CDK4 amplification/overexpression in astrocytoma pathogenesis, we generated three transgenic mouse lines that overexpress human CDK4 (hCDK4) in astrocytes using the human glial fibrillary acidic protein (GFAP) promoter. GFAP-hCDK4 mice do not develop brain tumors, but exhibit a small increase in astrocyte number. Cultured astrocytes from these mice do not demonstrate a cell-autonomous growth advantage in vitro and lack properties of transformed cells. To determine whether cdk4 overexpression provides a cooperative growth advantage in vitro, CDK4-overexpressing C6 glioma cell lines were generated and found to exhibit increased cell growth. In addition, GFAP-hCDK4; p53+/- as well as p53+/-; Rb+/- mice exhibited increased numbers of astrocytes compared to GFAP-hCDK4, p53+/-, or Rb+/- mice in vivo. No cooperative effect was observed with GFAP-hCDK4; Rb+/- mice. These results support the hypothesis that cdk4 overexpression alone is not sufficient for astrocytoma formation, but can provide a cooperative growth advantage in concert with genetic alterations in the p53 pathway.

Animals↗

PubMed2002

Mouse glioma gene expression profiling identifies novel human glioma-associated genes.

Based on previous studies demonstrating increased RAS activity in human astrocytomas, we developed a transgenic mouse model (B8) that targets an activated RAS molecule to astrocytes. Within 3 to 4 months after birth, these mice develop high-grade astrocytomas that are histologically identical to human astrocytomas. To characterize genetic events associated with B8 mouse astrocytoma formation, we employed comparative gene expression profiling of wild-type cultured mouse astrocytes, non-neoplastic B8 astrocytes, B8 astrocytoma cultures, and two other astrocytoma cultures from independently derived RAS transgenic mouse lines. We identified several classes of gene expression changes, including those associated with the non-neoplastic state in the B8 transgenic mouse, those associated with astrocytoma formation, and those specifically associated with only one of the three independently derived transgenic mouse astrocytomas. Differential expression of several unique genes was confirmed at the protein level in both the RAS transgenic mouse astrocytomas and two human glioblastoma multiforme cell lines. Furthermore, reexpression of one of these downregulated astrocytoma-associated proteins, GAP43, resulted in C6 glioma cell growth suppression. The use of this transgenic mouse model to identify novel genetic changes that might underlie the pathogenesis of human high-grade astrocytomas provides a unique opportunity to discover future targets for brain tumor therapy.

Animals↗

PubMed2002

Astrocyte-specific TSC1 conditional knockout mice exhibit abnormal neuronal organization and seizures.

Persons affected with tuberous sclerosis complex (TSC) develop a wide range of neurological abnormalities including aberrant neuronal migration and seizures. In an effort to model TSC-associated central nervous system abnormalities in mice, we generated two independent lines of astrocyte-specific Tsc1 conditional knockout mice by using the Cre-LoxP system. Astrocyte-specific Tsc1-null mice exhibit electroencephalographically proven seizures after the first month of age and begin to die at 3 to 4 months. Tsc1-null mice show significant increases in astrocyte numbers throughout the brain by 3 weeks of age and abnormal neuronal organization in the hippocampus between 3 and 5 weeks. Moreover, cultured Tsc1-null astrocytes behave similar to wild-type astrocytes during log phase growth but demonstrate increased saturation density associated with reduced p27(Kip1) expression. Collectively, our results demonstrate that astrocyte-specific disruption of Tsc1 in mice provides a context-dependent growth advantage for astrocytes that results in abnormalities in neuronal organization and epilepsy.

Animals↗

PubMed2002

Loss of heterozygosity for the NF2 gene in retinal and optic nerve lesions of patients with neurofibromatosis 2.

Individuals affected with the neurofibromatosis 2 (NF2) cancer predisposition syndrome develop specific ocular lesions. To determine whether these lesions result from altered NF2 gene expression, microdissection and PCR were used to investigate 40 ocular lesions from seven eyes of four NF2 patients for LOH, with markers that flank the NF2 gene on chromosome 22q. NF2 protein (merlin) expression was also evaluated in these lesions, using immunohistochemistry. Retinal hamartoma was observed in all seven eyes, including one with combined pigment epithelial and retinal hamartoma (CPERH). Retinal tufts were present in four eyes (three patients), retinal dysplasia in two eyes (two patients), optic nerve neurofibroma in one eye, iris naevoid hyperplasia in two eyes (two patients) and pseudophakia in all eyes. Markers were informative in three patients (six eyes from three unrelated families). One patient was non-informative due to prolonged decalcification. All retinal and optic nerve, but not iris lesions, demonstrated consistent LOH for the NF2 gene. Merlin was not expressed in the retina, optic nerve, or iris lesions. These results suggest that inactivation of the NF2 gene is associated with the formation of a variety of retinal and optic nerve lesions in NF2 patients.

Adolescent↗

PubMed2002

Molecular characterization of human meningiomas by gene expression profiling using high-density oligonucleotide microarrays.

Meningiomas are common central nervous system neoplasms that exhibit remarkably diverse histopathology and biological behavior. Compared to astrocytomas, the most common central nervous system tumor, little is known about the molecular pathways critical for meningioma tumor formation and malignant progression. As an initial step toward characterizing the genetic basis of meningioma pathogenesis, we assessed cancer-related gene expression profiles of nonneoplastic leptomeningeal specimens and human meningiomas of varying World Health Organization (WHO) grade using high-density oligonucleotide microarrays. Although expression profile differences between nonneoplastic and meningioma specimens were readily discernible, the expression profile of a subset of genes could also distinguish WHO grade I from WHO grades II and III tumors. Altered expression levels of several genes identified in this study have been previously noted in meningiomas (eg, growth hormone receptor, IGFBP-7, endothelin receptor A, IGF2). However, we also identified a number of novel genes whose expression was associated with WHO grade and was confirmed by reverse transcriptase-polymerase chain reaction in a larger, independent set of meningeal tumors (n = 47). This report represents the first gene expression profiling studies of meningiomas and identifies some initial candidate genes that may provide further insights into the genetic basis for meningioma pathogenesis.

Carrier Proteins↗

PubMed2002

Neurofibromatosis 1.

Neurofibromatosis 1 is one of the most common genetic conditions affecting the nervous system. Individuals with NF1 are predisposed to the development of peripheral nerve sheath tumors (neurofibromas and MPNSTs), astrocytomas (optic pathway gliomas), learning disabilities, seizures, strokes, macrocephaly, and vascular abnormalities. The NF1 tumor suppressor gene encodes a large protein (neurofibromin) that functions primarily as a RAS negative regulator, suggesting that targeted therapy for NF1 might derive from inhibition of the RAS signaling pathway.

Adult↗

PubMed2002

Differential involvement of protein 4.1 family members DAL-1 and NF2 in intracranial and intraspinal ependymomas.

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 tumori-genesis.

Adolescent↗

PubMed2002

Differential NF1, p16, and EGFR patterns by interphase cytogenetics (FISH) in malignant peripheral nerve sheath tumor (MPNST) and morphologically similar spindle cell neoplasms.

Malignant peripheral nerve sheath tumors (MPNSTs) are diagnostically challenging neoplasms for which sensitive and specific immunohistochemical markers are lacking. Although limited to date, previous studies have suggested that NF1 (17q), NF2 (22q), p16 (9p), and EGFR (7p) alterations may be involved in MPNST tumorigenesis. To determine whether specific genetic changes differentiate between MPNST and morphologically similar neoplasms, we assessed these chromosomal regions in 22 MPNSTs (9 NF1-associated, 13 sporadic), 13 plexiform neurofibromas, 5 cellular schwannomas, 8 synovial sarcomas, 6 fibrosarcomas, and 13 hemangiopericytomas by 2-color FISH. NF1 deletions, often in the form of monosomy 17, were found in MPNSTs (76%). neurofibromas (31%), hemangiopericytomas (17%), and fibrosarcomas (17%), but not in synovial sarcomas or cellular schwannomas. NF1 losses were encountered more frequently in MPNSTs versus other sarcomas (p < 0.001), as were p16 homozygous deletions (45% vs 0%; p < 0.001), EGFR amplifications (26% vs 0%; p = 0.006), and polysomies for either chromosomes 7 (53% vs 12%; p = 0.003) or 22 (50% vs 4%; p < 0.001). Hemizygous or homozygous p16 deletions were detected in 75% of MPNSTs, but not in benign nerve sheath tumors (p < 0.001). Thus, FISH analysis identifies relatively specific genetic patterns that may be useful in selected cases, for which the differential diagnosis includes low- or high-grade MPNST.

Cytogenetic Analysis↗

PubMed2002

Astrocyte-specific inactivation of the neurofibromatosis 1 gene (NF1) is insufficient for astrocytoma formation.

Individuals with the neurofibromatosis 1 (NF1) inherited tumor syndrome develop low-grade gliomas (astrocytomas) at an increased frequency, suggesting that the NF1 gene is a critical growth regulator for astrocytes. In an effort to determine the contribution of the NF1 gene product, neurofibromin, to astrocyte growth regulation and NF1-associated astrocytoma formation, we generated astrocyte-specific Nf1 conditional knockout mice (Nf1(GFAP)CKO) by using Cre/LoxP technology. Transgenic mice were developed in which Cre recombinase was specifically expressed in astrocytes by embryonic day 14.5. Successive intercrossing with mice bearing a conditional Nf1 allele (Nf1flox) resulted in GFAP-Cre Nf1flox/flox (Nf1(GFAP)CKO) animals. No astrocytoma formation or neurological impairment was observed in Nf1(GFAP)CKO mice after 20 months, but increased numbers of proliferating astrocytes were observed in several brain regions. To determine the consequence of Nf1 inactivation at different developmental times, the growth properties of embryonic day 12.5 and postnatal day 2 Nf1 null astrocytes were analyzed. Nf1 null astrocytes exhibited increased proliferation but lacked tumorigenic properties in vitro and did not form tumors when injected into immunocompromised mouse brains in vivo. Collectively, our results suggest that loss of neurofibromin is not sufficient for astrocytoma formation in mice and that other genetic or environmental factors might influence NF1-associated glioma tumorigenesis.

Animals↗

PubMed2002

Neurofibromin in the brain.

Neurofibromatosis 1 is one of the most common autosomal dominant disorders affecting the nervous system. Individuals with neurofibromatosis 1 present with abnormalities of both astrocytes and neurons that result from reduced or absent expression of the NF1 gene product neurofibromin. Impaired neurofibromin function in these nervous system cells contributes to the development of astrocytomas, learning disabilities, and radiographic abnormalities of the brain. With the identification of NF1, significant advances have begun to unlock some of the mysteries that surround the molecular pathogenesis of neurofibromatosis 1-associated brain abnormalities. With continued advances in our basic understanding of NF1 function, future targeted therapies for neurofibromatosis 1-associated central nervous system abnormalities can be developed.

Astrocytoma↗

PubMed2002

Aberrant G protein signaling in nervous system tumors.

OBJECT: Guanosine triphosphate (GTP)-binding proteins, also known as G proteins, play important roles in the regulation of cell growth and differentiation by transmitting intracellular signals from cell surface receptors. In this paper, the authors review G protein signaling in general and its aberrations in four human nervous system tumors. METHODS: In the nervous system, four tumor types have been associated with aberrant G protein signaling. The first tumor type includes astrocytomas, which have increased levels of the activated form of the small G protein, p21-ras, without primary oncogenic p21-ras mutations. The likely source for increased p21-ras activity in sporadically occurring astrocytomas is overexpressed or constitutively activated growth factor receptors, whereas in neurofibromatosis Type 1 (NF1)-associated astrocytomas, the source is a loss of expression of neurofibromin, a major inactivator of p21-ras (ras-GTPase activating protein [GAP]). The second type of tumor associated with aberrant G protein signaling includes sporadic and NF1-associated neurofibromas and malignant peripheral nerve sheath tumors, which also have increased p21-ras activity due to a loss of neurofibromin expression. The third tumor type includes subependymal giant cell astrocytomas as part of the tuberous sclerosis complex (TSC). These tumors display a loss of tuberin expression due to germline mutations in the TSC2 gene. Tuberin functions as an inactivator of the small G protein rap1B (rap1-GAP) and, hence, loss of its expression could lead to increased rap1B activity. In addition to TSC-associated tumors, the authors demonstrate that the majority of sporadically occurring astrocytomas display either loss of tuberin or overexpression of rap1B. This suggests that increased rap1B activity, which can augment p21-ras-mediated signals, also contributes to G protein-mediated aberrant signaling in sporadically occurring astrocytomas. The fourth tumor type includes a significant subset of pituitary adenomas that show constitutive activation of the G alpha subunit of the large heterotrimeric G s protein, which is involved in hormone receptor signaling. The net result of this aberrant activation is increased cyclic adenosine monophosphate and mitogenic tumor-promoting signals. CONCLUSIONS: The authors' review of G protein signaling and aberrations in this process is made with the long-term view that increased understanding of relevant signaling pathways will eventually lead to novel biological targeted therapies against these tumors.

Adenoma↗

PubMedDate not supplied

Mouse models of neurofibromatosis 1 and 2.

The neurofibromatoses represent two of the most common inherited tumor predisposition syndromes affecting the nervous system. Individuals with neurofibromatosis 1 (NF1) are prone to the development of astrocytomas and peripheral nerve sheath tumors whereas those affected with neurofibromatosis 2 (NF2) develop schwannomas and meningiomas. The development of traditional homozygous knockout mice has provided insights into the roles of the NF1 and NF2 genes during development and in differentiation, but has been less instructive regarding the contribution of NF1 and NF2 dysfunction to the pathogenesis of specific benign and malignant tumors. Recent progress employing novel mouse targeting strategies has begun to illuminate the roles of the NF1 and NF2 gene products in the molecular pathogenesis of NF-associated tumors.

Animals↗

PubMedDate not supplied

Cardiovascular disease in neurofibromatosis 1: report of the NF1 Cardiovascular Task Force.

PURPOSE: Patients with neurofibromatosis 1 (NF1) are at increased risk for a variety of cardiovascular disorders, but the natural history and pathogenesis of these abnormalities are poorly understood. METHODS: The National Neurofibromatosis Foundation convened an expert task force to review current knowledge about cardiovascular manifestations of NF1 and to make recommendations regarding clinical management and research priorities related to these features of the disease. RESULTS: This report summarizes the NF1 Cardiovascular Task Force's current understanding of vasculopathy, hypertension, and congenital heart defects that occur in association with NF1. Recommendations are made regarding routine surveillance for cardiovascular disease and diagnostic evaluation and management of cardiovascular disorders in individuals with NF1. CONCLUSION: Our understanding of the natural history and pathogenesis of cardiovascular disease in NF1 has improved substantially in the past few years, but many clinically important questions remain unanswered.

Advisory Committees↗