Cancer Research Cell Death Mechanisms and Cancer Therapy Sign up for Cancer Research eTOC's
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bajenaru, M. L.
Right arrow Articles by Gutmann, D. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bajenaru, M. L.
Right arrow Articles by Gutmann, D. H.
[Cancer Research 63, 8573-8577, December 15, 2003]
© 2003 American Association for Cancer Research

Advances in Brief

Optic Nerve Glioma in Mice Requires Astrocyte Nf1 Gene Inactivation and Nf1 Brain Heterozygosity

M. Livia Bajenaru1, M. Rosario Hernandez2, Arie Perry3, Yuan Zhu6, Luis F. Parada6, Joel R. Garbow45 and David H. Gutmann1

1 Departments of Neurology,
2 Ophthalmology,
3 Pathology,
4 Radiology, and
5 Chemistry, Washington University School of Medicine, St. Louis, Missouri, and
6 Center for Developmental Biology and Kent Waldrep Foundation Center for Basic Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas


   ABSTRACT
Top
 ABSTRACT
Introduction
 Materials and Methods
 Results and Discussion
 REFERENCES
 
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.


   Introduction
Top
 ABSTRACT
 Introduction
Materials and Methods
 Results and Discussion
 REFERENCES
 
Low-grade astrocytomas (gliomas) are common central nervous system tumors affecting children (1) . Children with the inherited tumor predisposition syndrome neurofibromatosis 1 (NF1) are prone to the development of WHO grade I pilocytic astrocytomas (PAs), which predominantly involve the optic nerve and chiasm (2) . Although these tumors are low-grade neoplasms, they can demonstrate aggressive biological features, diffusely infiltrate the optic pathway and neighboring hypothalamus, and culminate in visual loss and precocious puberty (2) . Previous studies have shown that NF1-associated optic pathway gliomas involve biallelic inactivation of the NF1 gene, whereas histologically similar sporadic PAs do not exhibit NF1 loss (3, 4, 5, 6) . In addition, PAs do not harbor genetic changes typical of diffuse fibrillary astrocytomas, such as inactivation of CDKN2A, TP53, or PTEN/MMAC1 or amplification of CDK4 or the epidermal growth factor receptor gene (7) .

Current animal models of astrocytoma have focused on oncogenic events (e.g., constitutive RAS activation) or on combinatorial inactivating events involving p53 (reviewed in Ref. 8 ). These mice develop high-grade gliomas, which are histologically and biologically distinct from those observed in NF1 patients. Using an alternate approach, heterozygous Nf1 mutant mice are cancer prone but do not develop gliomas (9) . Because mice lacking Nf1 expression do not survive embryonic development (9 , 10) , we developed a conditional knockout mouse in which the Nf1 gene was inactivated in astrocytes by embryonic day 14 using Cre/LoxP technology (11) . Glial fibrillary acidic protein (GFAP) Cre; Nf1flox/flox mice are viable and fertile and exhibit increased numbers of brain and optic nerve astrocytes, but they do not develop gliomas. The absence of glioma formation in these mice, even after 20 months of age, suggests that additional cellular or genetic events are necessary for glioma tumorigenesis in the setting of NF1. Because patients with NF1 are heterozygous for a germ-line inactivating NF1 mutation, and Nf1 mutant mice develop neurofibroma, another NF1-associated nervous system tumor, only in the setting of constitutional Nf1 heterozygosity (12) , we generated Nf1+/- mice lacking Nf1 expression in astrocytes. In this report, we describe this unique model of NF1-associated optic nerve glioma, in which Nf1+/- mice with conditional Nf1 inactivation in astrocytes develop low-grade optic nerve and chiasm astrocytomas.


   Materials and Methods
Top
 ABSTRACT
 Introduction
 Materials and Methods
Results and Discussion
 REFERENCES
 
Transgenic Mice.
Nf1+/- mice (10) were bred with Nf1flox/flox mice (13) to produce Nf1flox/mut mice, which were subsequently crossed with GFAPCre; Nf1flox/flox mice (11) to generate GFAPCre; Nf1flox/mut mice. Optic nerves and brains from 8–12-month-old GFAPCre; Nf1flox/mut mice (n = 12) and 8–18-month-old GFAPCre; Nf1flox/flox mice (n = 20) were analyzed. We used control mice of genotypes Nf1flox/flox, Nf1flox/mut, and Nf1+/- at 8–12 months of age (n = 10).

Histopathology and Immunohistochemistry.
Control and mutant mice were perfused transcardially with 4% paraformaldehyde in 0.1 M sodium phosphate buffer (pH 7.4). Eyes, optic nerves, optic chiasms, and brains were dissected and postfixed in 4% paraformaldehyde overnight at 4°C before examination for gross anatomical changes and photography with a digital camera (Optronics) attached to a dissection microscope (Nikon). All specimens were then processed for paraffin embedding and sectioning in the Pharmacology Histology Core or Ophthalmology Histology Core at Washington University School of Medicine.

Serial 4-µm paraffin sections of the eyes and optic nerve heads, optic nerves and chiasms, and brains were stained with H&E and examined under the microscope for the presence of tumors or abnormal collections of cells by an experienced neuropathologist (A. P.).

Immunohistochemistry was performed on adjacent paraffin sections with rat anti-GFAP (1:100; Zymed) and rabbit anti-Ki67 (1:1000; Novocastra) antibodies. We used microwave antigen retrieval and detected the primary antibodies with biotinylated secondary antibodies, followed by amplification with peroxidase-conjugated avidin (Vectastain Elite ABC Kit; Vector Laboratories) and treatment with 3,3'-diaminobenzidine or Vector VIP substrate kits (Vector Laboratories), followed by counterstaining with hematoxylin or methyl green (Vector Laboratories). Representative sections were photographed with a digital camera (Optronics) attached to an inverted microscope (Nikon).

Microglia cells were identified in optic nerve and chiasm sections by lectin histochemistry (14) using FITC-conjugated Bandeiraea (Griffonia) simplicifolia agglutinin isolectin-B4 (BSI-B4; Sigma). Briefly, optic nerve and chiasm sections were deparaffinized and washed in PBS, followed by overnight incubation at 4°C with FITC-conjugated BSI-B4 (10 µg/ml) in PBS containing 0.5% Triton X-100. After subsequent washes in PBS, fluorescence images were recorded by digital photomicrography (Spot Advanced; Diagnostic Instruments, Sterling Heights, MI).

Proliferative indices were determined by counting the number of Ki67-labeled nuclei per 100 cell nuclei within the prechiasmatic optic nerves (areas 1 and 2) and the optic chiasm (area 3), using a 10-mm ocular grid at x400 magnification.

Magnetic Resonance Imaging.
Images were collected in an Oxford Instruments 4.7-Tesla magnet (33 cm, clear bore) equipped with 15-cm inner diameter, actively shielded gradient coils (maximum gradient, 18 G/cm; rise time, 100 µs). The magnet/gradients are interfaced with a Varian (Palo Alto, CA) INOVA console, and data were collected using a 1.5-cm outer diameter surface coil (receive) and a 9-cm inner diameter Helmholtz coil (transmit). Before the imaging experiments, the mice were anesthetized with isoflurane/O2 [4% (v/v)], and they were maintained on isoflurane/O2 [1.5% (v/v)] throughout the experiments. Diffusion tensor imaging data were acquired using a conventional spin-echo imaging sequence, modified by the addition of a Stejskal-Tanner diffusion-sensitizing gradient pair. Six images with different gradient directions were acquired with a b value of 785 s/mm2, together with a reference spin-echo (b = 0) image. Other experimental parameters were 16 signal averages, time between scans (TR) = 0.75 s, echo time (TE) = 0.05 s, slice thickness = 0.5 mm, field of view (FOV) = 1.5 cm.

The diffusion tensor matrix was generated from a series of diffusion-weighted images, in which the primary diffusion parameters (three eigenvalues or diffusivities, {lambda}1, {lambda}2, and {lambda}3) were calculated by matrix diagonalization. These primary parameters were combined into two secondary parameters useful for describing water diffusion (15) : (a) apparent diffusion constant (the mean of the three directional diffusivities); and (b) relative anisotropy (the normalized standard deviation of the three diffusivities). These parameter maps, together with conventional T2-weighted spin-echo images, were used to visualize the mouse optic nerves.


   Results and Discussion
Top
 ABSTRACT
 Introduction
 Materials and Methods
 Results and Discussion
REFERENCES
 
Nf1 Inactivation in Astrocytes Alone Is Insufficient for Astrocytoma Formation.
Whereas both Nf1+/- and GFAPCre; Nf1flox/flox mice exhibit increased numbers of brain astrocytes (11 , 16 , 17) , neither strain develops astrocytoma in vivo. Similarly, Nf1-/- astrocytes have an incremental increase in cell-autonomous growth in vitro compared with Nf1+/- astrocytes, but they lack tumorigenic properties (11) . Because our GFAPCre mice (both lines 1 and 8) exhibit robust Cre expression in astrocytes throughout the optic nerve and chiasm (data not shown), in addition to the brain and spinal cord (11) , we sought to determine whether Nf1 inactivation in optic nerve astrocytes was sufficient for optic nerve/chiasm tumor formation. Compared with Nf1+/- mice, GFAPCre; Nf1flox/flox mice demonstrate complete loss of neurofibromin expression in astrocytes (11) , increased astrocyte numbers in the optic nerve, and minor increases in astrocyte proliferation. However, examination of the optic nerves from both Nf1+/- and GFAPCre; Nf1flox/flox mice failed to demonstrate any gross or microscopic evidence for optic nerve glioma. These results demonstrate that Nf1 inactivation in astrocytes, beginning on embryonic day 14, confers a growth advantage in vitro and in vivo that is not sufficient for astrocytoma formation in the optic nerve and raise the possibility that constitutional Nf1 heterozygosity in the supporting nonneoplastic cells is required for tumorigenesis.

Nf1 Inactivation in Astrocytes Results in Optic Nerve/Chiasm Glioma Formation in the Context of Nf1 Heterozygosity.
In an effort to model the human condition, where patients are heterozygous for an inactivating germ-line NF1 mutation, we first injected Nf1-null postnatal day 2 neocortical astrocytes, generated by Cre adenovirus-mediated Nf1flox inactivation, into the brains of syngeneic Nf1+/- mice. None of the 22 mice that received the injection exhibited any evidence of glioma formation after 1 year (data not shown).

Second, we generated Nf1+/- mice lacking Nf1 expression in astrocytes (GFAPCre; Nf1flox/mut mice). These mice are viable and healthy at 12 months of age, without obvious neurological abnormalities. Pathological examination of their brains failed to demonstrate astrocytoma (data not shown). These results suggest that Nf1 inactivation, either alone or in combination with Nf1 heterozygosity, does not result in parenchymal brain tumor formation.

Because gliomas in NF1 most typically involve the optic nerve, chiasm, and hypothalamus, we examined the optic nerves and chiasm in GFAPCre; Nf1flox/mut mice. All mice examined (n = 12) demonstrated areas of gross optic nerve and/or chiasm enlargement, which were not seen in either Nf1+/- or GFAPCre; Nf1flox/flox mice. These gross abnormalities were seen in mice as early as 8 months of age, although younger mice have not been systematically examined to date. We observed multiple patterns of gross pathology, including unilateral as well as bilateral optic nerve enlargement, with and without chiasmal involvement (Fig. 1)Citation . These patterns are highly reminiscent of those found in children with NF1.



View larger version (49K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 1. GFAPCre; Nf1flox/mut mice manifest swollen optic nerves and chiasms. The arrows denote two representative examples of enlarged optic nerves and chiasms in GFAPCre; Nf1flox/mut mice (A and C), not seen in GFAPCre; Nf1flox/flox mice (B) or Nf1+/- and Nf1flox/flox mice (D and E). Scale bar, 1 mm.

 
Microscopic examination of these optic nerve masses demonstrated increased cellularity (Fig. 2Citation , top panel, A–G) with collections of GFAP-immunoreactive astrocytes (Fig. 2Citation , top panel, I–K). In addition to exhibiting elevated Ki67 proliferative indices (Fig. 3ACitation , a–c), these proliferating individual or clustered cells exhibited enlarged, mildly to moderately atypical, hyperchromatic nuclei with small nucleoli, similar to their human counterparts (Ref. 1 ; Fig. 2Citation , top panel, D, H, and L). As is typical for low-grade gliomas, there was no evidence of endothelial hyperplasia or necrosis. However, unlike human optic pathway PAs, these mouse gliomas lacked microcystic spaces, Rosenthal fibers, or eosinophilic granular bodies and shared some histological features with WHO grade II fibrillary astrocytomas. It should be noted that even within human NF1-associated PAs, portions of the tumor may be infiltrative, lack Rosenthal fibers, eosinophilic granular bodies, and protein droplets; and can be confused with low-grade WHO II fibrillary astrocytoma (18) . In this respect, human pilocytic optic nerve gliomas most often appear as glial tumors with alternating dense-spindled and loose microcystic areas (Fig. 2Citation , bottom panel, A) with Rosenthal fibers and granular bodies (Fig. 2Citation , bottom panel, B), but they may exhibit nuclear pleiomorphism (Fig. 2Citation , bottom panel, C) with clustered atypical tumor nuclei (Fig. 2Citation , bottom panel, D), reminiscent of the Nf1 mouse model. Therefore, it is difficult to determine with certainty whether the optic gliomas in our mouse model represent low-grade fibrillary astrocytomas, an otherwise rare subtype in NF1 patients, or an earlier stage of PA, lacking some of the more characteristic findings seen in human examples that had grown for several years before resection. Nevertheless, we have classified these collections of GFAP-immunoreactive astrocytes as neoplastic, based on their formation of grossly and radiologically (see below) recognizable tumor masses, the presence of nuclear clustering/atypia, and demonstrable cellular proliferation.



View larger version (134K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 2. Histological analysis of optic pathway glioma in the GFAPCre; Nf1flox/mut mice (top panels). H&E staining (H&E) demonstrates enlarged optic nerves with areas of increased celullarity (C and G) in GFAPCre; Nf1flox/mut mice, compared with Nf1flox/flox (A and E) or GFAPCre; Nf1flox/flox mice (B and F). The areas of increased cellularity in the optic nerves of GFAPCre; Nf1flox/mut mice are highly enriched in GFAP-immunoreactive astrocytes (K), compared with control mice (I). GFAPCre; Nf1flox/flox mice exhibit moderate increases in astrocyte numbers in the chiasm and optic nerve (J). Many atypical nuclei were found clustered within the hypercellular optic nerve masses of GFAPCre; Nf1flox/mut mice. These atypical nuclei (arrows) are significantly larger than nonneoplastic cell nuclei (arrowheads), have an irregular contour, and are hyperchromatic (D and H). Mildly atypical nuclei (arrows) appear rarely in association with normal cell nuclei (arrowheads) in optic nerves from GFAPCre; Nf1flox/flox mice (L), and may represent reactive or hyperplastic astrocytes. Scale bar, 100 µm. Bottom panels: human pilocytic optic nerve gliomas typically appear as astrocytic tumors with alternating dense spindled and loose microcystic areas (A) with scattered brightly eosinophilic rod-shaped Rosenthal fibers and mulberry-shaped eosinophilic granular bodies (B), but may exhibit mild hypercellularity and nuclear pleiomorphism (C) with scattered individual and clustered atypical tumor nuclei (D) at the infiltrative edge of the same tumor, reminiscent of the Nf1 mouse model. Magnification, x200 (A) and x400 (B-D).

 


View larger version (75K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 3. Optic gliomas in GFAPCre; Nf1flox/mut mice contain proliferating astrocytes. A, Ki67 immunoreactivity was detected in clusters of cells corresponding to areas of increased cellularity, in prechiasmatic regions as well as along the optic nerves and in the chiasm of GFAPCre; Nf1flox/mut mice. The arrow points to a representative mitotic figure (b). The Ki67-labeled cells are GFAP-immunoreactive astrocytes as demonstrated by Ki67/GFAP double immunohistochemistry (c). No Ki67-labeled nuclei were identified in the Nf1flox/flox control mice (a). Scale bar, 400 µm. B, the Ki67 proliferative indices are tabulated for each optic nerve and chiasm from GFAPCre; Nf1flox/mut, GFAPCre; Nf1flox/flox, Nf1+/-, and Nf1flox/flox mice. C, Ki67 proliferative indices were determined in the prechiasmatic optic nerves (areas 1 and 2) and in the chiasm (area 3), denoted by the blue squares. D, microglia cells infiltrate the low-grade gliomas in GFAPCre; Nf1flox/mut mice. B. simplicifolia isolectin (BSI-B4) histochemistry identifies microglial cells (arrowheads) in the optic nerve areas (primarily optic nerve and chiasm), corresponding to the gliomas in GFAPCre; Nf1flox/mut mice. In contrast, there were few, if any, microglia in the optic nerves of control mice: Nf1flox/flox and GFAPCre; Nf1flox/flox. V, vessel. Scale bar, 100 µm.

 
Because these tumors grow asymmetrically within the optic nerves in these mice, we determined the proliferative index for the prechiasmatic optic nerves (areas 1 and 2) and chiasm (area 3; Fig. 3CCitation ) for each of eight tumors. As shown in Fig. 3BCitation , there was a spectrum of increased proliferative indices in GFAPCre; Nf1flox/mut mouse optic pathway tumors, ranging from 1% to 10%, using Ki67 as a proliferation marker, as has been reported for human low-grade astrocytomas (18) . The highest proliferation rates were consistently observed in older GFAPCre; Nf1flox/mut mice (>10 months old). Lower proliferative indices were observed in GFAPCre; Nf1flox/flox and Nf1+/- mice (1–2%), even after 18 months of age. No Ki67 labeling was observed in the optic nerve or chiasm of control Nf1flox/flox mice.

Previous studies on another nervous system tumor in NF1, the peripheral nerve-associated neurofibroma, demonstrated that Nf1+/- mast cells infiltrate tumors composed of neoplastic Nf1-/- Schwann cells and likely contribute to the genesis of these benign tumors (12) . In human optic nerve glioma, microglia are often observed at the periphery and within the tumor (19) . To determine whether infiltrating Nf1+/- microglia were found in GFAPCre; Nf1flox/mut mouse optic nerve tumors, we performed lectin histochemistry using B. (Griffonia) simplicifolia agglutinin isolectin-B4 (BSI-B4) to identify microglia. BSI-B4 labels D-galactose residues that are expressed on both resting and activated microglia cells, cells of the monocyte-macrophage lineage, and vascular endothelial cells. We observed increased numbers of microglia in the GFAPCre; Nf1flox/mut mouse optic nerve tumors compared with nonneoplastic optic nerve areas in these same mice or GFAPCre; Nf1flox/flox, Nf1+/-, or Nf1flox/flox mouse optic nerves. As reported for human low-grade gliomas (20) , the microglia infiltration was variable from one optic nerve glioma to another in GFAPCre; Nf1flox/mut mice (Fig. 3D)Citation . Whereas microglia are associated with these mouse optic nerve gliomas, it remains to be determined whether Nf1+/- microglia, oligodendrocytes, or neurons directly contribute to the pathogenesis of Nf1-null astrocyte transformation.

Relevance of Nf1 Heterozygosity to NF1 Tumorigenesis.
Recent studies by Zhu et al. (12) have demonstrated a role for Nf1+/- cells in the molecular pathogenesis of a related NF1-associated tumor, the plexiform neurofibroma. In this model, Nf1+/- mast cells are hypothesized to elaborate factors that promote Nf1-/- Schwann cell transformation and neurofibroma formation. Studies on Nf1+/- mast cells (21) , oligodendrocytes (22) , and astrocytes (16 , 17) have demonstrated that Nf1 heterozygosity results in abnormalities in cell migration, proliferation, and survival. These observations strongly support the emerging concept that Nf1+/- cells have unique properties, which might be important in the cellular pathogenesis of NF1-associated tumors.

Development of a Preclinical Model for NF1-Associated Optic Nerve Glioma.
All mice examined to date have gross and histopathological evidence of optic nerve glioma by 8 months of age, suggesting that this mouse might represent a preclinical model for NF1-associated optic pathway tumors. Because these tumors are routinely detected and followed by magnetic resonance imaging in children with NF1, we sought to determine whether small animal magnetic resonance imaging could detect abnormal optic nerve pathology in the living mouse. Diffusion tensor imaging was used to delineate tissue morphology and pathology (23) , as has been used for human NF1-associated optic nerve gliomas (24) . Using diffusion tensor imaging, we determined the location and size of the optic nerves in C57Bl/6 control, Nf1flox/flox (data not shown), GFAPCre; Nf1flox/flox, and GFAPCre; Nf1flox/mut mice, and we demonstrated the presence of abnormal tissue between the optic nerves only in GFAPCre; Nf1flox/mut mice (four of four mice imaged; age, 10–12 months; Fig. 4Citation ). Studies are in progress to determine the earliest time point when these tumors can be detected by magnetic resonance imaging.



View larger version (117K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 4. Magnetic resonance images of transaxial slices of mouse brains. A, T2-weighted spin-echo image of one representative control C57Bl/6 mouse; the yellow box shows the expanded region displayed in all subsequent images; (B) relative anisotropy (RA) and (C) apparent diffusion constant (ADC) maps of this same control mouse. Optic nerves, regions of high diffusion anisotropy that appear as bright spots in the RA map, are circled in red. The remaining images in this figure are T2-weighted spin-echo images collected from one representative C57Bl/6 control (D), one representative GFAPCre; Nf1flox/flox mouse (E), and two different GFAPCre; Nf1flox/mut mice (F and G). In each of these images, the optic nerves, as determined from RA and ADC maps are shown as red circles. The regions between the red circles in the bottom panels, highlighted by blue arrows, demonstrate the development of optic nerve gliomas only in GFAPCre; Nf1flox/mut mice, evidenced by the separation of the optic nerves by abnormal growth of tissue.

 
In this report, we describe a mouse model of optic nerve glioma, the most common brain tumor seen in individuals affected with NF1. Whereas astrocyte Nf1 inactivation is insufficient by itself for glioma formation, in the context of an Nf1 heterozygous environment, optic nerve gliomas develop. These observations extend previous results on Nf1 mouse modeling of nervous system tumors and strongly implicate Nf1+/- cells in the cellular pathogenesis of NF1 brain tumor formation. Future studies aimed at defining the contributing Nf1+/- or Nf1-/- cells to glioma formation as well as characterizing the factors that promote Nf1-/- astrocyte transformation will lead to an improved understanding of the cellular and molecular events involved in the development of this benign tumor in patients with NF1.


   ACKNOWLEDGMENTS
 
We thank Drs. Mercedes Salvador-Silva, Shu-Wei Sun, and David Louis for valuable technical advice and helpful scientific discussions. We thank Belinda K. McMahan, Zelma Jones, Erin Winkeler, and Nicole Hedrick for expert technical assistance.


   FOOTNOTES
 
Grant support: NIH Grants NS36996 (to D. H. G.), F32-NS42428 (to M. L. B.), and 1 R24 CA83060; a grant from the Small Animal Imaging Resource Program (to J. R. G.); a grant from National Institutes of Neurological Disorders and Stroke (to L. F. P.); The United States Army Medical Research and Materiel Command’s Office of Congressionally Directed Medical Research Programs Grant DAMD17-03-1-0215 (to D. H. G.), and a grant from The National Neurofibromatosis Foundation (to Y. Z.).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Requests for reprints: David H. Gutmann, Department of Neurology, Box 8111, 660 South Euclid Avenue, St. Louis, Missouri 63110. Phone: (314) 362-7379; Fax: (314) 362-2388; E-mail: gutmannd{at}neuro.wustl.edu

Received 8/31/03. Revised 10/10/03. Accepted 10/17/03.


   REFERENCES
Top
 ABSTRACT
 Introduction
 Materials and Methods
 Results and Discussion
 REFERENCES
 

  1. Kleihues P., Cavenee W. K. . Tumors of the Nervous System, IARC Press Lyon, France 2000.
  2. Listernick R., Louis D. N., Packer R. J., Gutmann D. H. Optic pathway gliomas in children with neurofibromatosis 1: consensus statement from the NF1 Optic Pathway Glioma Task Force. Ann. Neurol., 41: 143-149, 1997.[Medline]
  3. Platten M., Giordano M. J., Dirven C. M., Gutmann D. H., Louis D. N. Up-regulation of specific NF1 gene transcripts in sporadic pilocytic astrocytomas. Am. J. Pathol., 149: 621-627, 1996.[Abstract]
  4. Gutmann D. H., Donahoe J., Brown T., James C. D., Perry A. Loss of neurofibromatosis 1 (NF1) gene expression in NF1-associated pilocytic astrocytomas. Neuropathol. Appl. Neurobiol., 26: 361-367, 2000.[Medline]
  5. Kluwe L., Hagel C., Tatagiba M., Thomas S., Stavrou D., Ostertag H., von Deimling A., Mautner V. F. Loss of NF1 alleles distinguish sporadic from NF1-associated pilocytic astrocytomas. J. Neuropathol. Exp. Neurol., 60: 917-920, 2001.[Medline]
  6. Wimmer K., Eckart M., Meyer-Puttlitz B., Fonatsch C., Pietsch T. Mutational and expression analysis of the NF1 gene argues against a role as tumor suppressor in sporadic pilocytic astrocytomas. J. Neuropathol. Exp. Neurol., 61: 896-902, 2002.[Medline]
  7. Li J., Perry A., James C. D., Gutmann D. H. Cancer-related gene expression profiles in NF1-associated pilocytic astrocytomas. Neurology, 56: 885-890, 2001.[Abstract/Free Full Text]
  8. Gutmann D. H., Baker S. J., Giovannini M., Garbow J., Weiss W. Mouse models of human cancer consortium symposium on nervous system tumors. Cancer Res., 63: 3001-3004, 2003.[Abstract/Free Full Text]
  9. Jacks T., Shih T. S., Schmitt E. M., Bronson R. T., Bernards A., Weinberg R. A. Tumour predisposition in mice heterozygous for a targeted mutation in Nf1. Nat. Genet., 7: 353-361, 1994.[Medline]
  10. Brannan C. I., Perkins A. S., Vogel K. S., Ratner N., Nordlund M. L., Reid S. W., Buchberg A. M., Jenkins N. A., Parada L. F., Copeland N. G. Targeted disruption of the neurofibromatosis type-1 gene leads to developmental abnormalities in heart and various neural crest-derived tissues. Genes Dev., 8: 1019-1029, 1994.[Abstract/Free Full Text]
  11. Bajenaru M. L., Zhu Y., Hedrick N. M., Donahoe J., Parada L. F., Gutmann D. H. Astrocyte-specific inactivation of the neurofibromatosis 1 gene (NF1) is insufficient for astrocytoma formation. Mol. Cell. Biol., 22: 5100-5113, 2002.[Abstract/Free Full Text]
  12. Zhu Y., Ghosh P., Charnay P., Burns D. K., Parada L. F. Neurofibromas in NF1: Schwann cell origin and role of tumor environment. Science (Wash. DC), 296: 920-922, 2002.[Abstract/Free Full Text]
  13. Zhu Y., Romero M. I., Ghosh P., Ye Z., Charnay P., Rushing E. J., Marth J. D., Parada L. F. Ablation of NF1 function in neurons induces abnormal development of cerebral cortex and reactive gliosis in the brain. Genes Dev., 15: 859-876, 2001.[Abstract/Free Full Text]
  14. Ohmi K., Greenberg D. S., Rajavel K. S., Ryazantsev S., Li H. H., Neufeld E. F. Activated microglia in cortex of mouse models of mucopolysaccharidoses I and IIIB. Proc. Natl. Acad. Sci. USA, 100: 1902-1907, 2003.[Abstract/Free Full Text]
  15. Pierpaoli C., Basser P. J. Toward a quantitative assessment of diffusion anisotropy. Magn. Reson. Med., 36: 893-906, 1996.[Medline]
  16. Bajenaru M. L., Donahoe J., Corral T., Reilly K. M., Brophy S., Pellicer A., Gutmann D. H. Neurofibromatosis 1 (NF1) heterozygosity results in a cell-autonomous growth advantage for astrocytes. Glia, 33: 314-323, 2001.[Medline]
  17. Gutmann D. H., Loehr A., Zhang Y., Kim J., Henkemeyer M., Cashen A. Haploinsufficiency for the neurofibromatosis 1 (NF1) tumor suppressor results in increased astrocyte proliferation. Oncogene, 18: 4450-4459, 1999.[Medline]
  18. Cummings T. J., Provenzale J. M., Hunter S. B., Friedman A. H., Klintworth G. K., Bigner S. H., McLendon R. E. Gliomas of the optic nerve: histologic, immunohistochemical (MIB-1 and p53), and MRI analysis. Acta Neuropathol. (Berl.), 99: 563-570, 2000.[Medline]
  19. Klein R., Roggendorf W. Increased microglia proliferation separates pilocytic astrocytomas from diffuse astrocytomas: a double labeling study. Acta Neuropathol. (Berl.), 101: 245-248, 2001.[Medline]
  20. Roggendorf W., Strupp S., Paulus W. Distribution and characterization of microglia/macrophages in human brain tumors. Acta Neuropathol., 92: 288-293, 1996.[Medline]
  21. Ingram D. A., Yang F-C., Travers J. B., Wenning M. J., Hiatt K., New S., Hood A., Shannon K., Williams D. A., Clapp D. A. Genetic and biochemical evidence that haploinsufficiency of the Nf1 tumor suppressor gene modulates melanocytes and mast cell fates in vivo. J. Exp. Med., 191: 181-187, 2000.[Abstract/Free Full Text]
  22. Bennett M. R., Rizvi T. A., Karyala S., McKinnon R. D., Ratner N. Aberrant growth and differentiation of oligodendrocyte progenitors in neurofibromatosis type 1 mutants. J. Neurosci., 23: 7207-7217, 2003.[Abstract/Free Full Text]
  23. Basser P. J., Mattiello J., Le Bihan D. MR diffusion tensor spectroscopy and imaging. Biophys. J., 66: 259-267, 1994.[Medline]
  24. Sener R. N. Diffusion MRI in neurofibromatosis type 1: ADC evaluations of the optic pathways, and a comparison with normal individuals. Comput. Med. Imaging Graph., 26: 59-64, 2002.[Medline]



This article has been cited by other articles:


Home page
 Proc. Natl. Acad. Sci. USAHome page
C. Gregorian, J. Nakashima, S. M. Dry, P. L. Nghiemphu, K. B. Smith, Y. Ao, J. Dang, G. Lawson, I. K. Mellinghoff, P. S. Mischel, et al.
PTEN dosage is essential for neurofibroma development and malignant transformation
PNAS, November 17, 2009; 106(46): 19479 - 19484.
[Abstract] [Full Text] [PDF]

Home page
 Mol. Cell. Biol.Home page
V. Bodempudi, F. Yamoutpoor, W. Pan, A. Z. Dudek, T. Esfandyari, M. Piedra, D. Babovick-Vuksanovic, R. A. Woo, V. F. Mautner, L. Kluwe, et al.
Ral Overactivation in Malignant Peripheral Nerve Sheath Tumors
Mol. Cell. Biol., July 15, 2009; 29(14): 3964 - 3974.
[Abstract] [Full Text] [PDF]

Home page
 Mol. Cell. Biol.Home page
S. S. Houshmandi, R. J. Emnett, M. Giovannini, and D. H. Gutmann
The Neurofibromatosis 2 Protein, Merlin, Regulates Glial Cell Growth in an ErbB2- and Src-Dependent Manner
Mol. Cell. Biol., March 15, 2009; 29(6): 1472 - 1486.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
G. C. Daginakatte, S. M. Gianino, N. W. Zhao, A. S. Parsadanian, and D. H. Gutmann
Increased c-Jun-NH2-Kinase Signaling in Neurofibromatosis-1 Heterozygous Microglia Drives Microglia Activation and Promotes Optic Glioma Proliferation
Cancer Res., December 15, 2008; 68(24): 10358 - 10366.
[Abstract] [Full Text] [PDF]

Home page
 J Child NeurolHome page
D. H. Gutmann
Using Neurofibromatosis-1 to Better Understand and Treat Pediatric Low-Grade Glioma
J Child Neurol, October 1, 2008; 23(10): 1186 - 1194.
[Abstract] [PDF]

Home page
 Hum Mol GenetHome page
B. Hegedus, T.-H. Yeh, D. Y. Lee, R. J. Emnett, J. Li, and D. H. Gutmann
Neurofibromin regulates somatic growth through the hypothalamic-pituitary axis
Hum. Mol. Genet., October 1, 2008; 17(19): 2956 - 2966.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
N. de la Iglesia, G. Konopka, K.-L. Lim, C. L. Nutt, J. F. Bromberg, D. A. Frank, P. S. Mischel, D. N. Louis, and A. Bonni
Deregulation of a STAT3-Interleukin 8 Signaling Pathway Promotes Human Glioblastoma Cell Proliferation and Invasiveness
J. Neurosci., June 4, 2008; 28(23): 5870 - 5878.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
B. Hegedus, D. Banerjee, T.-H. Yeh, S. Rothermich, A. Perry, J. B. Rubin, J. R. Garbow, and D. H. Gutmann
Preclinical Cancer Therapy in a Mouse Model of Neurofibromatosis-1 Optic Glioma
Cancer Res., March 1, 2008; 68(5): 1520 - 1528.
[Abstract] [Full Text] [PDF]

Home page
 Genes Dev.Home page
N. de la Iglesia, G. Konopka, S. V. Puram, J. A. Chan, R. M. Bachoo, M. J. You, D. E. Levy, R. A. DePinho, and A. Bonni
Identification of a PTEN-regulated STAT3 brain tumor suppressor pathway
Genes & Dev., February 15, 2008; 22(4): 449 - 462.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
N. M. Warrington, B. M. Woerner, G. C. Daginakatte, B. Dasgupta, A. Perry, D. H. Gutmann, and J. B. Rubin
Spatiotemporal Differences in CXCL12 Expression and Cyclic AMP Underlie the Unique Pattern of Optic Glioma Growth in Neurofibromatosis Type 1
Cancer Res., September 15, 2007; 67(18): 8588 - 8595.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
D. K. Sandsmark, H. Zhang, B. Hegedus, C. L. Pelletier, J. D. Weber, and D. H. Gutmann
Nucleophosmin Mediates Mammalian Target of Rapamycin-Dependent Actin Cytoskeleton Dynamics and Proliferation in Neurofibromin-Deficient Astrocytes
Cancer Res., May 15, 2007; 67(10): 4790 - 4799.
[Abstract] [Full Text] [PDF]

Home page
 Hum Mol GenetHome page
G. C. Daginakatte and D. H. Gutmann
Neurofibromatosis-1 (Nf1) heterozygous brain microglia elaborate paracrine factors that promote Nf1-deficient astrocyte and glioma growth
Hum. Mol. Genet., May 1, 2007; 16(9): 1098 - 1112.
[Abstract] [Full Text] [PDF]

Home page
 Hum Mol GenetHome page
X. Wu, S. A. Estwick, S. Chen, M. Yu, W. Ming, T. D. Nebesio, Y. Li, J. Yuan, R. Kapur, D. Ingram, et al.
Neurofibromin plays a critical role in modulating osteoblast differentiation of mesenchymal stem/progenitor cells
Hum. Mol. Genet., October 1, 2006; 15(19): 2837 - 2845.
[Abstract] [Full Text] [PDF]

Home page
 ANN INTERN MEDHome page
A. Theos and B. R. Korf
Pathophysiology of neurofibromatosis type 1.
Ann Intern Med, June 6, 2006; 144(11): 842 - 849.
[Full Text] [PDF]

Home page
 DevelopmentHome page
Y. Zhu, T. Harada, L. Liu, M. E. Lush, F. Guignard, C. Harada, D. K. Burns, M. L. Bajenaru, D. H. Gutmann, and L. F. Parada
Inactivation of NF1 in CNS causes increased glial progenitor proliferation and optic glioma formation
Development, December 15, 2005; 132(24): 5577 - 5588.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
B. Dasgupta, Y. Yi, B. Hegedus, J. D. Weber, and D. H. Gutmann
Cerebrospinal Fluid Proteomic Analysis Reveals Dysregulation of Methionine Aminopeptidase-2 Expression in Human and Mouse Neurofibromatosis 1-Associated Glioma
Cancer Res., November 1, 2005; 65(21): 9843 - 9850.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
B. Dasgupta and D. H. Gutmann
Neurofibromin Regulates Neural Stem Cell Proliferation, Survival, and Astroglial Differentiation In Vitro and In Vivo
J. Neurosci., June 8, 2005; 25(23): 5584 - 5594.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
B. Dasgupta, Y. Yi, D. Y. Chen, J. D. Weber, and D. H. Gutmann
Proteomic Analysis Reveals Hyperactivation of the Mammalian Target of Rapamycin Pathway in Neurofibromatosis 1-Associated Human and Mouse Brain Tumors
Cancer Res., April 1, 2005; 65(7): 2755 - 2760.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
B. Dasgupta, W. Li, A. Perry, and D. H. Gutmann
Glioma Formation in Neurofibromatosis 1 Reflects Preferential Activation of K-RAS in Astrocytes
Cancer Res., January 1, 2005; 65(1): 236 - 245.
[Abstract] [Full Text] [PDF]

Home page
 J Child NeurolHome page
D. K. Scheidenhelm and D. H. Gutmann
Mouse Models of Tuberous Sclerosis Complex
J Child Neurol, September 1, 2004; 19(9): 726 - 733.
[Abstract] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bajenaru, M. L.
Right arrow Articles by Gutmann, D. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bajenaru, M. L.
Right arrow Articles by Gutmann, D. H.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online