1
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Wang S, Mautner VF, Buchert R, Flibotte S, Suppa P, Friedman JM, Heran MKS. Alterations in brain morphology by MRI in adults with neurofibromatosis 1. Orphanet J Rare Dis 2021; 16:462. [PMID: 34727946 PMCID: PMC8561988 DOI: 10.1186/s13023-021-02097-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 10/24/2021] [Indexed: 12/05/2022] Open
Abstract
OBJECTIVE Neurofibromatosis 1 (NF1) is a rare autosomal dominant disease that causes the dysregulated growth of Schwann cells. Most reported studies of brain morphology in NF1 patients have included only children, and clinical implications of the observed changes later in life remain unclear. In this study, we used MRI to characterize brain morphology in adults with NF1. METHODS Planar (2D) MRI measurements of 29 intracranial structures were compared in 389 adults with NF1 and 112 age- and sex-matched unaffected control subjects. The 2D measurements were correlated with volumetric (3D) brain measurements in 99 of the adults with NF1 to help interpret the 2D findings. A subset (n = 70) of these NF1 patients also received psychometric testing for attention deficits and IQ and was assessed for clinical severity of NF1 features and neurological problems. Correlation analysis was performed between the MRI measurements and clinical and psychometric features of these patients. RESULTS Four of nine corpus callosum measurements were significantly greater in adults with NF1 than in sex- and age-matched controls. All seven brainstem measurements were significantly greater in adults with NF1 than in controls. Increased corpus callosum and brainstem 2D morphology were correlated with increased total white matter volume among the NF1 patients. No robust correlations were observed between the 2D size of these structures and clinical or neuropsychometric assessments. CONCLUSION Our findings are consistent with the hypothesis that dysregulation of brain myelin production is an important manifestation of NF1 in adults.
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Affiliation(s)
- Su Wang
- Department of Medical Genetics, University of British Columbia, Children's and Women's Hospital, 4500 Oak Street, Vancouver, BC, V6H 3N1, Canada
| | - Victor-Felix Mautner
- Department of Neurology, University Hospital Hamburg-Eppendorf, Hamburg, Germany
| | - Ralph Buchert
- Department of Nuclear Medicine, University Hospital Hamburg-Eppendorf, Hamburg, Germany
| | - Stephane Flibotte
- UBC/LSI Bioinformatics Facility, University of British Columbia, Vancouver, BC, Canada
| | - Per Suppa
- Department of Nuclear Medicine, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität Zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Jan M Friedman
- Department of Medical Genetics, University of British Columbia, Children's and Women's Hospital, 4500 Oak Street, Vancouver, BC, V6H 3N1, Canada.
| | - Manraj K S Heran
- Diagnostic and Therapeutic Neuroradiology, University of British Columbia, Vancouver, Canada
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2
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Wojtas B, Gielniewski B, Wojnicki K, Maleszewska M, Mondal SS, Nauman P, Grajkowska W, Glass R, Schüller U, Herold-Mende C, Kaminska B. Gliosarcoma Is Driven by Alterations in PI3K/Akt, RAS/MAPK Pathways and Characterized by Collagen Gene Expression Signature. Cancers (Basel) 2019; 11:cancers11030284. [PMID: 30818875 PMCID: PMC6468745 DOI: 10.3390/cancers11030284] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 02/18/2019] [Accepted: 02/19/2019] [Indexed: 01/15/2023] Open
Abstract
Gliosarcoma is a very rare brain tumor reported to be a variant of glioblastoma (GBM), IDH-wildtype. While differences in molecular and histological features between gliosarcoma and GBM were reported, detailed information on the genetic background of this tumor is lacking. We intend to fill in this knowledge gap by the complex analysis of somatic mutations, indels, copy number variations, translocations and gene expression patterns in gliosarcomas. Using next generation sequencing, we determined somatic mutations, copy number variations (CNVs) and translocations in 10 gliosarcomas. Six tumors have been further subjected to RNA sequencing analysis and gene expression patterns have been compared to those of GBMs. We demonstrate that gliosarcoma bears somatic alterations in gene coding for PI3K/Akt (PTEN, PI3K) and RAS/MAPK (NF1, BRAF) signaling pathways that are crucial for tumor growth. Interestingly, the frequency of PTEN alterations in gliosarcomas was much higher than in GBMs. Aberrations of PTEN were the most frequent and occurred in 70% of samples. We identified genes differentially expressed in gliosarcoma compared to GBM (including collagen signature) and confirmed a difference in the protein level by immunohistochemistry. We found several novel translocations (including translocations in the RABGEF1 gene) creating potentially unfavorable combinations. Collected results on genetic alterations and transcriptomic profiles offer new insights into gliosarcoma pathobiology, highlight differences in gliosarcoma and GBM genetic backgrounds and point out to distinct molecular cues for targeted treatment.
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Affiliation(s)
- Bartosz Wojtas
- Laboratory of Molecular Neurobiology, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
| | - Bartlomiej Gielniewski
- Laboratory of Molecular Neurobiology, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
| | - Kamil Wojnicki
- Laboratory of Molecular Neurobiology, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
| | - Marta Maleszewska
- Laboratory of Molecular Neurobiology, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
| | - Shamba S Mondal
- Laboratory of Bioinformatics, Nencki Institute of Experimental Biology, Warsaw 02-093, Poland.
| | - Pawel Nauman
- Department of Neurosurgery, Institute of Psychiatry and Neurology, Warsaw 02-957, Poland.
| | - Wieslawa Grajkowska
- Department of Pathology, The Children's Memorial Health Institute, Warsaw 04-730, Poland.
| | - Rainer Glass
- Neurosurgical Research, University Clinics, LMU Munich 80539, Germany.
| | - Ulrich Schüller
- Institute of Neuropathology, University Medical Center, Hamburg-Eppendorf 20251, Germany.
- Research Institute Children's Cancer Center Hamburg, Hamburg 20251, Germany.
- Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg 20251, Germany.
| | - Christel Herold-Mende
- Division of Experimental Neurosurgery, Department of Neurosurgery, University of Heidelberg, Heidelberg 69120, Germany.
| | - Bozena Kaminska
- Laboratory of Molecular Neurobiology, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
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3
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Que Y, Liang Y, Zhao J, Ding Y, Peng R, Guan Y, Zhang X. Treatment-related adverse effects with pazopanib, sorafenib and sunitinib in patients with advanced soft tissue sarcoma: a pooled analysis. Cancer Manag Res 2018; 10:2141-2150. [PMID: 30050324 PMCID: PMC6055834 DOI: 10.2147/cmar.s164535] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Objective Research efforts have investigated therapies targeting tyrosine kinase signaling pathways. We performed a pooled analysis to determine the frequency of severe adverse effects in patients with soft tissue sarcoma treated with pazopanib, sorafenib and sunitinib. Materials and methods We performed a comprehensive search of PubMed, Web of Science, Ovid, the Cochrane Library and Embase databases from the drugs’ inception to May 2017 to identify clinical trials. All-grade and severe adverse events (AEs; grade≥3) were analyzed. Results A total of 10 trials published between 2009 and 2016, including 843 patients, were eligible for analysis. We included 424 patients (three studies) who received pazopanib 800 mg daily, 353 patients (five studies) who received sorafenib 400 mg twice daily and 66 patients (two studies) who received sunitinib 37.5 mg daily. The incidence of AEs is different among the three VEGFR-tyrosine kinase inhibitors (TKIs). Pazopanib showed higher incidence of all-grade nausea, diarrhea and hypertension compared with sorafenib and sunitinib. However, patients in the sorafenib group experienced a significantly higher frequency of all-grade rash (26.1%), hand–foot syndrome (33.4%) and mucositis (38.5%). The difference was highly significant for sorafenib vs. pazopanib in the incidence of all-grade rash (odds ratio [OR] 1.649, 95% CI 1.086–2.505, P=0.023), hand–foot syndrome (OR 3.096, 95% CI 1.271–7.544, P=0.009) and mucositis (OR 4.562, 95% CI 2.132–9.609, P<0.001). Moreover, the frequency of grade ≥3 mucositis was significantly higher in the sunitinib group compared with the pazopanib or sorafenib group (7.6% vs. 1.3%, OR 6.448, 95% CI 1.499–27.731, P=0.013). Conclusion Statistically significant differences in certain common adverse effects, such as all-grade and severe AEs, were detected among pazopanib, sorafenib and sunitinib in the current study. Early and prompt management is critically needed to avoid unnecessary dose reductions and treatment-related discontinuations.
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Affiliation(s)
- Yi Que
- Department of Medical Melanoma and Sarcoma, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
| | - Yao Liang
- Department of Gastric and Pancreatic Surgery, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
| | - Jingjing Zhao
- Department of Medical Melanoma and Sarcoma, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
| | - Ya Ding
- Department of Medical Melanoma and Sarcoma, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
| | - Ruiqing Peng
- Department of Medical Melanoma and Sarcoma, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
| | - Yuanxiang Guan
- Department of Gastric and Pancreatic Surgery, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
| | - Xing Zhang
- Department of Medical Melanoma and Sarcoma, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, People's Republic of China,
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Doll S, Urisman A, Oses-Prieto JA, Arnott D, Burlingame AL. Quantitative Proteomics Reveals Fundamental Regulatory Differences in Oncogenic HRAS and Isocitrate Dehydrogenase (IDH1) Driven Astrocytoma. Mol Cell Proteomics 2017; 16:39-56. [PMID: 27834733 PMCID: PMC5217781 DOI: 10.1074/mcp.m116.063883] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 11/04/2016] [Indexed: 12/18/2022] Open
Abstract
Glioblastoma multiformes (GBMs) are high-grade astrocytomas and the most common brain malignancies. Primary GBMs are often associated with disturbed RAS signaling, and expression of oncogenic HRAS results in a malignant phenotype in glioma cell lines. Secondary GBMs arise from lower-grade astrocytomas, have slower progression than primary tumors, and contain IDH1 mutations in over 70% of cases. Despite significant amount of accumulating genomic and transcriptomic data, the fundamental mechanistic differences of gliomagenesis in these two types of high-grade astrocytoma remain poorly understood. Only a few studies have attempted to investigate the proteome, phosphorylation signaling, and epigenetic regulation in astrocytoma. In the present study, we applied quantitative phosphoproteomics to identify the main signaling differences between oncogenic HRAS and mutant IDH1-driven glioma cells as models of primary and secondary GBM, respectively. Our analysis confirms the driving roles of the MAPK and PI3K/mTOR signaling pathways in HRAS driven cells and additionally uncovers dysregulation of other signaling pathways. Although a subset of the signaling changes mediated by HRAS could be reversed by a MEK inhibitor, dual inhibition of MEK and PI3K resulted in more complete reversal of the phosphorylation patterns produced by HRAS expression. In contrast, cells expressing mutant IDH1 did not show significant activation of MAPK or PI3K/mTOR pathways. Instead, global downregulation of protein expression was observed. Targeted proteomic analysis of histone modifications identified significant histone methylation, acetylation, and butyrylation changes in the mutant IDH1 expressing cells, consistent with a global transcriptional repressive state. Our findings offer novel mechanistic insight linking mutant IDH1 associated inhibition of histone demethylases with specific histone modification changes to produce global transcriptional repression in secondary glioblastoma. Our proteomic datasets are available for download and provide a comprehensive catalogue of alterations in protein abundance, phosphorylation, and histone modifications in oncogenic HRAS and IDH1 driven astrocytoma cells beyond the transcriptomic level.
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Affiliation(s)
- Sophia Doll
- From the ‡Department of Pharmaceutical Chemistry, University of California, San Francisco, 94158-2517 California
| | - Anatoly Urisman
- From the ‡Department of Pharmaceutical Chemistry, University of California, San Francisco, 94158-2517 California
| | - Juan A Oses-Prieto
- From the ‡Department of Pharmaceutical Chemistry, University of California, San Francisco, 94158-2517 California
| | - David Arnott
- §Department of Protein Chemistry, Genentech Inc, South San Francisco, 94158-2517 California
| | - Alma L Burlingame
- From the ‡Department of Pharmaceutical Chemistry, University of California, San Francisco, 94158-2517 California;
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5
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Kamar FG, Kairouz VF, Sabri AN. Dermatofibrosarcoma protuberans (DFSP) successfully treated with sorafenib: case report. Clin Sarcoma Res 2013; 3:5. [PMID: 23557478 PMCID: PMC3637545 DOI: 10.1186/2045-3329-3-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2013] [Accepted: 03/21/2013] [Indexed: 02/07/2023] Open
Abstract
DFSP is a locally invasive, slow-growing tumor of the subcutaneous tissue that rarely metastasizes but recurs frequently after surgical excision. We report herein a case of highly recurrent, locally invasive DFSP that failed both postoperative radiation therapy and complete trial of Imatinib, but was successfully treated with Sorafenib, which showed unprecedented response.
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Affiliation(s)
- Francois G Kamar
- Division of Hematology & Oncology, Clemenceau Medical Center, City Center Building, Suite 3 A, Avenue Nouvelle, P,O, Box 1076, Beirut, Jounieh, Lebanon.
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6
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Lenarduzzi M, Hui ABY, Alajez NM, Shi W, Williams J, Yue S, O’Sullivan B, Liu FF. MicroRNA-193b enhances tumor progression via down regulation of neurofibromin 1. PLoS One 2013; 8:e53765. [PMID: 23335975 PMCID: PMC3546079 DOI: 10.1371/journal.pone.0053765] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 12/05/2012] [Indexed: 01/01/2023] Open
Abstract
Despite improvements in therapeutic approaches for head and neck squamous cell carcinomas (HNSCC), clinical outcome has remained disappointing, with 5-year overall survival rates hovering around 40-50%, underscoring an urgent need to better understand the biological bases of this disease. We chose to address this challenge by studying the role of micro-RNAs (miRNAs) in HNSCC. MiR-193b was identified as an over-expressed miRNA from global miRNA profiling studies previously conducted in our lab, and confirmed in HNSCC cell lines. In vitro knockdown of miR-193b in FaDu cancer cells substantially reduced cell proliferation, migration and invasion, along with suppressed tumour formation in vivo. By integrating in silico prediction algorithms with in vitro experimental mRNA profilings, plus mRNA expression data of clinical specimens, neurofibromin 1 (NF1) was identified to be a target of miR-193b. Concordantly, miR-193b knockdown decreased NF1 transcript and protein levels significantly. Luciferase reporter assays confirmed the direct interaction of miR-193b with NF1. Moreover, p-ERK, a downstream target of NF1 was also suppressed after miR-193b knockdown. FaDu cells treated with a p-ERK inhibitor (U0126) phenocopied the reduced cell proliferation, migration and invasion observed with miR-193b knockdown. Finally, HNSCC patients whose tumours expressed high levels of miR-193b experienced a lower disease-free survival compared to patients with low miR-193b expression. Our findings identified miR-193b as a potentially novel prognostic marker in HNSCC that drives tumour progression via down-regulating NF1, in turn leading to activation of ERK, resulting in proliferation, migration, invasion, and tumour formation.
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Affiliation(s)
- Michelle Lenarduzzi
- Ontario Cancer Institute, University Health Network, Toronto, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Angela B. Y. Hui
- Ontario Cancer Institute, University Health Network, Toronto, Canada
| | - Nehad M. Alajez
- Stem Cell Unit, Department of Anatomy, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Wei Shi
- Ontario Cancer Institute, University Health Network, Toronto, Canada
| | - Justin Williams
- Ontario Cancer Institute, University Health Network, Toronto, Canada
| | - Shijun Yue
- Ontario Cancer Institute, University Health Network, Toronto, Canada
| | - Brian O’Sullivan
- Radiation Medicine Program University Health Network, Toronto, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Ontario
| | - Fei-Fei Liu
- Ontario Cancer Institute, University Health Network, Toronto, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Canada
- Radiation Medicine Program University Health Network, Toronto, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, Ontario
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7
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Maki RG, D'Adamo DR, Keohan ML, Saulle M, Schuetze SM, Undevia SD, Livingston MB, Cooney MM, Hensley ML, Mita MM, Takimoto CH, Kraft AS, Elias AD, Brockstein B, Blachère NE, Edgar MA, Schwartz LH, Qin LX, Antonescu CR, Schwartz GK. Phase II study of sorafenib in patients with metastatic or recurrent sarcomas. J Clin Oncol 2009; 27:3133-40. [PMID: 19451436 PMCID: PMC2716936 DOI: 10.1200/jco.2008.20.4495] [Citation(s) in RCA: 405] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 01/27/2009] [Indexed: 12/14/2022] Open
Abstract
PURPOSE Since activity of sorafenib was observed in sarcoma patients in a phase I study, we performed a multicenter phase II study of daily oral sorafenib in patients with recurrent or metastatic sarcoma. PATIENTS AND METHODS We employed a multiarm study design, each representing a sarcoma subtype with its own Simon optimal two-stage design. In each arm, 12 patients who received 0 to 1 prior lines of therapy were treated (0 to 3 for angiosarcoma and malignant peripheral-nerve sheath tumor). If at least one Response Evaluation Criteria in Solid Tumors (RECIST) was observed, 25 further patients with that sarcoma subtype were accrued. Results Between October 2005 and November 2007, 145 patients were treated; 144 were eligible for toxicity and 122 for response. Median age was 55 years; female-male ratio was 1.8:1. The median number of cycles was 3. Five of 37 patients with angiosarcoma had a partial response (response rate, 14%). This was the only arm to meet the RECIST response rate primary end point. Median progression-free survival was 3.2 months; median overall survival was 14.3 months. Adverse events (typically dermatological) necessitated dose reduction for 61% of patients. Statistical modeling in this limited patient cohort indicated sorafenib toxicity was correlated inversely to patient height. There was no correlation between phosphorylated extracellular signal regulated kinase expression and response in six patients with angiosarcoma with paired pre- and post-therapy biopsies. CONCLUSION As a single agent, sorafenib has activity against angiosarcoma and minimal activity against other sarcomas. Further evaluation of sorafenib in these and possibly other sarcoma subtypes appears warranted, presumably in combination with cytotoxic or kinase-specific agents.
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Affiliation(s)
- Robert G Maki
- Melanoma-Sarcoma Program, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, Howard 909, New York, NY 10065, USA.
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8
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Morgan KJ, Rowley MA, Wiesner SM, Hasz DE, Van Ness B, Largaespada DA. The GAP-related domain of neurofibromin attenuates proliferation and downregulates N- and K-Ras activation in Nf1-negative AML cells. Leuk Res 2007; 31:1107-13. [PMID: 17222906 PMCID: PMC2788398 DOI: 10.1016/j.leukres.2006.11.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Revised: 10/09/2006] [Accepted: 11/26/2006] [Indexed: 11/26/2022]
Abstract
Inactivation of the NF1 tumor suppressor causes myeloproliferative diseases. NF1 encodes a GTPase activating protein (GAP) for Ras. Myeloid cells with loss of NF1 have high levels of Ras-GTP, functionally equivalent to the effects of RAS oncogenes. We investigated the effects of the NF1 GAP-related domain (GRD) in proliferation, apoptosis and Ras-GTP levels in Nf1-negative acute myeloid leukemia (AML) cells. In AML cells, with cooperating mutations, the expression of the neurofibromin GRD causes significant reductions of N- and K-Ras-GTP levels, which is not incompatible with AML cell survival, but which is strongly selected against due to suppression of proliferation.
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Affiliation(s)
- Kelly J. Morgan
- University of Minnesota, Department of Genetics, Cell Biology and Development, University of Minnesota Cancer Center; Minneapolis, MN
| | - Matthew A. Rowley
- University of Minnesota, Department of Genetics, Cell Biology and Development, University of Minnesota Cancer Center; Minneapolis, MN
| | - Stephen M. Wiesner
- University of Minnesota, Department of Genetics, Cell Biology and Development, University of Minnesota Cancer Center; Minneapolis, MN
| | - Diane E. Hasz
- University of Minnesota, Department of Genetics, Cell Biology and Development, University of Minnesota Cancer Center; Minneapolis, MN
| | - Brian Van Ness
- University of Minnesota, Department of Genetics, Cell Biology and Development, University of Minnesota Cancer Center; Minneapolis, MN
| | - David A. Largaespada
- University of Minnesota, Department of Genetics, Cell Biology and Development, University of Minnesota Cancer Center; Minneapolis, MN
- To whom correspondence should be addressed 6-160 Jackson Hall, 321 Church Street, S.E., Minneapolis, MN 55455, Tel: 612-626-4979, Fax: 612-625-4648,
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9
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Abstract
Neurofibromatosis type 1 (NF1) patients are predisposed to learning disabilities, macrocephaly, and brain tumors as well as abnormalities on magnetic resonance imaging that are postulated to result from abnormal myelination. Here we show that Nf1+/- spinal cords in adult mice have more than twofold-increased numbers of NG2+ progenitor cells. Nf1-/- embryonic spinal cords have increased numbers of Olig2+ progenitors. Also, cultures from Nf1 mutant embryos with hemizygous and biallelic Nf1 mutations have dramatically increased numbers of CNS oligodendrocyte progenitor cells. In medium that allows growth of neuroepithelial cells and glial progenitors, mutant cells hyper-respond to FGF2, have increased basal and FGF-stimulated Ras-GTP, and fail to accumulate when treated with a farnesyltransferase inhibitor. Cell accumulation results in part from increased proliferation and decreased cell death. In contrast to wild-type cells, Nf1-/- progenitors express the glial differentiation marker O4 while retaining expression of the progenitor marker nestin. Nf1 mutant progenitors also abnormally coexpress the glial differentiation markers O4 and GFAP. Importantly, Nf1-/- spinal cord-derived oligodendrocyte progenitors, which are amplified 12-fold, retain the ability to form oligodendrocytes after in vivo transplantation. The data reveal a key role for neurofibromin and Ras signaling in the maintenance of CNS progenitor cell pools and also suggest a potential role for progenitor cell defects in the CNS abnormalities of NF1 patients.
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10
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Zhu Y, Romero MI, Ghosh P, Ye Z, Charnay P, Rushing EJ, Marth JD, Parada LF. Ablation of NF1 function in neurons induces abnormal development of cerebral cortex and reactive gliosis in the brain. Genes Dev 2001; 15:859-76. [PMID: 11297510 PMCID: PMC312666 DOI: 10.1101/gad.862101] [Citation(s) in RCA: 447] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Neurofibromatosis type 1 (NF1) is a prevalent genetic disorder that affects growth properties of neural-crest-derived cell populations. In addition, approximately one-half of NF1 patients exhibit learning disabilities. To characterize NF1 function both in vitro and in vivo, we circumvent the embryonic lethality of NF1 null mouse embryos by generating a conditional mutation in the NF1 gene using Cre/loxP technology. Introduction of a Synapsin I promoter driven Cre transgenic mouse strain into the conditional NF1 background has ablated NF1 function in most differentiated neuronal populations. These mice have abnormal development of the cerebral cortex, which suggests that NF1 has an indispensable role in this aspect of CNS development. Furthermore, although they are tumor free, these mice display extensive astrogliosis in the absence of conspicuous neurodegeneration or microgliosis. These results indicate that NF1-deficient neurons are capable of inducing reactive astrogliosis via a non-cell autonomous mechanism.
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MESH Headings
- Alleles
- Animals
- Cell Transformation, Neoplastic/genetics
- Cells, Cultured
- Cerebral Cortex/abnormalities
- Cerebral Cortex/embryology
- Disease Models, Animal
- Ganglia, Spinal/pathology
- Gene Expression Regulation, Developmental
- Genes, Neurofibromatosis 1
- Genes, Reporter
- Genes, Synthetic
- Genetic Vectors/genetics
- Gliosis/metabolism
- Integrases/genetics
- Integrases/physiology
- Lac Operon
- Learning Disabilities/genetics
- MAP Kinase Signaling System/genetics
- Mice
- Mice, Knockout
- Mice, Neurologic Mutants
- Mice, Transgenic
- Nerve Tissue Proteins/deficiency
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Neurofibromin 1
- Neurons/metabolism
- Promoter Regions, Genetic
- Proto-Oncogene Proteins p21(ras)/physiology
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/physiology
- Signal Transduction
- Synapsins/genetics
- Viral Proteins
- p120 GTPase Activating Protein/genetics
- p120 GTPase Activating Protein/physiology
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Affiliation(s)
- Y Zhu
- Center for Developmental Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133, USA
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11
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Benvenuto G, Li S, Brown SJ, Braverman R, Vass WC, Cheadle JP, Halley DJ, Sampson JR, Wienecke R, DeClue JE. The tuberous sclerosis-1 (TSC1) gene product hamartin suppresses cell growth and augments the expression of the TSC2 product tuberin by inhibiting its ubiquitination. Oncogene 2000; 19:6306-16. [PMID: 11175345 DOI: 10.1038/sj.onc.1204009] [Citation(s) in RCA: 196] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We report here that overexpression of the tuberous sclerosis-1 (TSC1) gene product hamartin results in the inhibition of growth, as well as changes in cell morphology. Growth inhibition was associated with an increase in the endogenous level of the product of the tuberous sclerosis-2 (TSC2) gene, tuberin. As overexpression of tuberin inhibits cell growth, and hamartin is known to bind tuberin, these results suggested that hamartin stabilizes tuberin and this contributes to the inhibition of cell growth. Indeed, transient transfection of TSC1 increased the endogenous level of tuberin, and transient co-transfection of TSC1 with TSC2 resulted in higher tuberin levels. The stabilization was explained by the finding that tuberin is highly ubiquitinated in cells, while the fraction of tuberin that is bound to hamartin is not ubiquitinated. Co-expression of tuberin stabilized hamartin, which is weakly ubiquitinated, in transiently transfected cells. The amino-terminal two-thirds of tuberin was responsible for its ubiquitination and for stabilization of hamartin. A mutant of tuberin from a patient missense mutation of TSC2 was also highly ubiquitinated, and was unable to stabilize hamartin. We conclude that hamartin is a growth inhibitory protein whose biological effect is likely dependent on its interaction with tuberin.
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Affiliation(s)
- G Benvenuto
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland, MD 20892, USA
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Sherman LS, Atit R, Rosenbaum T, Cox AD, Ratner N. Single cell Ras-GTP analysis reveals altered Ras activity in a subpopulation of neurofibroma Schwann cells but not fibroblasts. J Biol Chem 2000; 275:30740-5. [PMID: 10900196 PMCID: PMC3066458 DOI: 10.1074/jbc.m001702200] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by multiple neurofibromas, peripheral nerve tumors containing mainly Schwann cells and fibroblasts. The NF1 gene encodes neurofibromin, a tumor suppressor postulated to function in part as a Ras GTPase-activating protein. The roles of different cell types and of elevated Ras-GTP in neurofibroma formation are unclear. To determine which neurofibroma cell type has altered Ras-GTP regulation, we developed an immunocytochemical assay for active, GTP-bound Ras. In NIH 3T3 cells, the assay detected overexpressed, constitutively activated K-, N-, and Ha-Ras and insulin-induced endogenous Ras-GTP. In dissociated neurofibroma cells from NF1 patients, Ras-GTP was elevated in Schwann cells but not fibroblasts. Twelve to 62% of tumor Schwann cells showed elevated Ras-GTP, unexpectedly revealing neurofibroma Schwann cell heterogeneity. Increased basal Ras-GTP did not correlate with increased cell proliferation. Normal human Schwann cells, however, did not demonstrate elevated basal Ras activity. Furthermore, compared with cells from wild type littermates, Ras-GTP was elevated in all mouse Nf1(-/-) Schwann cells but never in Nf1(-/-) mouse fibroblasts. Our results indicate that Ras activity is detectably increased in only some neurofibroma Schwann cells and suggest that neurofibromin is not an essential regulator of Ras activity in fibroblasts.
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Affiliation(s)
- Larry S. Sherman
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521
| | - Radhika Atit
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521
| | - Thorsten Rosenbaum
- Department of Neuropediatrics, Children’s Hospital, Heinrich-Heine-University, Dusseldorf, Germany
| | - Adrienne D. Cox
- Departments of Radiation Oncology and Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599-7512
| | - Nancy Ratner
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521
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Atit RP, Mitchell K, Nguyen L, Warshawsky D, Ratner N. The neurofibromatosis type 1 (Nf1) tumor suppressor is a modifier of carcinogen-induced pigmentation and papilloma formation in C57BL/6 mice. J Invest Dermatol 2000; 114:1093-100. [PMID: 10844550 PMCID: PMC2862652 DOI: 10.1046/j.1523-1747.2000.00994.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is increasing evidence implicating the human NF1 gene in epithelial carcinogenesis. To test if NF1 can play a part in skin tumor formation, we analyzed effects of the skin cancer initiator dimethylbenz-anthracene and/or the tumor promoter 12-O-tetradecanoyl-13-acetylphorbol on mice heterozygous for null mutations in Nf1 (Nf1+/-). Mice were on the C57BL/6 background, noted for resistance to chemical carcinogens. Nf1+/- mice (18 of 24) developed papillomas after treatment with dimethylbenzanthracene and 12-O-tetradecanoyl-13-acetylphorbol; papillomas did not develop in wild-type C57BL/6 mice nor Nf1+/- mice treated with 12-O-tetradecanoyl-13-acetylphorbol alone. All papillomas analyzed (six of six) had mutations in codon 61 of H-ras, demonstrating strong cooperation between the Nf1 GTPase activating protein for Ras, neurofibromin, and Ras-GTP. After exposure to 12-O-tetradecanoyl-13-acetylphorbol, Nf1+/- keratinocytes showed significant, sustained, increases in proliferation, implicating Nf1 in phorbol ester responsive pathways. Thus, Nf1 levels regulate the response of keratinocytes to 12-O-tetradecanoyl-13-acetylphorbol. Nf1+/- mice also showed a 2-fold increase in the development of pigmented skin patches stimulated by dimethylbenzanthracene; patches were characterized by hair follicles in anagen phase, implicating keratinocytes in the aberrant hyperpigmentation. Our results show that mutation in the Nf1 gene causes abnormal keratinocyte proliferation that can be revealed by environmental assaults such as carcinogen exposure. The data support a plausible role for NF1 mutation in human epithelial carcinogenesis.
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Affiliation(s)
- Radhika P. Atit
- Division of Molecular and Developmental Biology, Children’s Hospital Research Foundation, Cincinnati, Ohio, U.S.A
| | - Kent Mitchell
- Department of Environmental Health, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
| | - Lam Nguyen
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
| | - David Warshawsky
- Department of Environmental Health, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
| | - Nancy Ratner
- Division of Molecular and Developmental Biology, Children’s Hospital Research Foundation, Cincinnati, Ohio, U.S.A
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
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14
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Aaltonen V, Boström PJ, Söderström KO, Hirvonen O, Tuukkanen J, Nurmi M, Laato M, Peltonen J. Urinary bladder transitional cell carcinogenesis is associated with down-regulation of NF1 tumor suppressor gene in vivo and in vitro. THE AMERICAN JOURNAL OF PATHOLOGY 1999; 154:755-65. [PMID: 10079253 PMCID: PMC1866425 DOI: 10.1016/s0002-9440(10)65322-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The NF1 gene product (neurofibromin) is known to act as a tumor suppressor protein by inactivating ras. The best documented factors involved in urinary bladder transitional cell carcinoma (TCC) are ras proto-oncogene activation and p53 suppressor gene mutations. This is the first study reporting alterations in NF1 gene expression in TCC. We examined NF1 gene expression in a total of 29 surgical urinary bladder TCC specimens representing grades 1 to 3 and in three cell lines, RT4, 5637, and T24 (representing grades 1 to 3, respectively). Decreased NF1 gene expression was observed in 23 of 29 (83%) TCC specimens as estimated by immunohistochemistry, the decrease being more pronounced in high-grade tumors. NF1 mRNA levels were markedly lower in TCC tissue compared with adjacent non-neoplastic urothelium, as studied by in situ hybridization for grade 3 TCC. Immunohistochemistry and Western blotting demonstrated that TCC cell lines expressed NF1 protein at different levels, expression being almost undetectable in T24 (grade 3) cells. Northern blotting for cell lines demonstrated reduced NF1 mRNA levels in grade 3 TCC cells. Reverse transcription polymerase chain reaction for cell lines and selected grade 2 and grade 3 tissue samples demonstrated NF1 type II mRNA isoform predominance in all samples studied. Our results show that both NF1 mRNA and protein levels are decreased in high-grade TCC, suggesting that alterations of NF1 gene expression may be involved in bladder TCC carcinogenesis.
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Affiliation(s)
- V Aaltonen
- Department of Surgery, Turku University Central Hospital, Turku, Finland
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15
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p21 ras and phosphatidylinositol-3 kinase are required for survival of wild-type and NF1 mutant sensory neurons. J Neurosci 1999. [PMID: 9852579 DOI: 10.1523/jneurosci.18-24-10420.1998] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nerve growth factor (NGF) is a required differentiation and survival factor for sympathetic and a majority of neural crest-derived sensory neurons in the developing vertebrate peripheral nervous system. Although much is known about the function of NGF, the intracellular signaling cascade that it uses continues to be a subject of intense study. p21 ras signaling is considered necessary for sensory neuron survival. How additional intermediates downstream or in parallel may function has not been fully understood yet. Two intracellular signaling cascades, extra cellular regulated kinase (erk) and phosphatidylinositol-3 (PI 3) kinase, transduce NGF signaling in the pheochromocytoma cell line PC12. To elucidate the role these cascades play in survival and differentiation, we used a combination of recombinant adenoviruses and chemical inhibitors to perturb these pathways in sensory neurons from wild-type mice and mice deficient for neurofibromin in which the survival and differentiation pathway is constitutively active. We demonstrate that ras activity is both necessary and sufficient for the survival of embryonic sensory neurons. Downstream of ras, however, the erk cascade is neither required nor sufficient for neuron survival or overall differentiation. Instead, the activity of PI 3 kinase is necessary for the survival of the wild-type and neurofibromin-deficient neurons. Therefore, we conclude that in sensory neurons, NGF acts via a signaling pathway, which includes both ras and PI 3 kinase.
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16
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Scheffzek K, Ahmadian MR, Wiesmüller L, Kabsch W, Stege P, Schmitz F, Wittinghofer A. Structural analysis of the GAP-related domain from neurofibromin and its implications. EMBO J 1998; 17:4313-27. [PMID: 9687500 PMCID: PMC1170765 DOI: 10.1093/emboj/17.15.4313] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Neurofibromin is the product of the NF1 gene, whose alteration is responsible for the pathogenesis of neurofibromatosis type 1 (NF1), one of the most frequent genetic disorders in man. It acts as a GTPase activating protein (GAP) on Ras; based on homology to p120GAP, a segment spanning 250-400 aa and termed GAP-related domain (NF1GRD; 25-40 kDa) has been shown to be responsible for GAP activity and represents the only functionally defined segment of neurofibromin. Missense mutations found in NF1 patients map to NF1GRD, underscoring its importance for pathogenesis. X-ray crystallographic analysis of a proteolytically treated catalytic fragment of NF1GRD comprising residues 1198-1530 (NF1-333) of human neurofibromin reveals NF1GRD as a helical protein that resembles the corresponding fragment derived from p120GAP (GAP-334). A central domain (NF1c) containing all residues conserved among RasGAPs is coupled to an extra domain (NF1ex), which despite very limited sequence homology is surprisingly similar to the corresponding part of GAP-334. Numerous point mutations found in NF1 patients or derived from genetic screening protocols can be analysed on the basis of the three-dimensional structural model, which also allows identification of the site where structural changes in a differentially spliced isoform are to be expected. Based on the structure of the complex between Ras and GAP-334 described earlier, a model of the NF1GRD-Ras complex is proposed which is used to discuss the strikingly different properties of the Ras-p120GAP and Ras-neurofibromin interactions.
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Affiliation(s)
- K Scheffzek
- Max-Planck-Institut für molekulare Physiologie, Dortmund, Germany.
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17
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Denhardt DT. Signal-transducing protein phosphorylation cascades mediated by Ras/Rho proteins in the mammalian cell: the potential for multiplex signalling. Biochem J 1996; 318 ( Pt 3):729-47. [PMID: 8836113 PMCID: PMC1217680 DOI: 10.1042/bj3180729] [Citation(s) in RCA: 366] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The features of three distinct protein phosphorylation cascades in mammalian cells are becoming clear. These signalling pathways link receptor-mediated events at the cell surface or intracellular perturbations such as DNA damage to changes in cytoskeletal structure, vesicle transport and altered transcription factor activity. The best known pathway, the Ras-->Raf-->MEK-->ERK cascade [where ERK is extracellular-signal-regulated kinase and MEK is mitogen-activated protein (MAP) kinase/ERK kinase], is typically stimulated strongly by mitogens and growth factors. The other two pathways, stimulated primarily by assorted cytokines, hormones and various forms of stress, predominantly utilize p21 proteins of the Rho family (Rho, Rac and CDC42), although Ras can also participate. Diagnostic of each pathway is the MAP kinase component, which is phosphorylated by a unique dual-specificity kinase on both tyrosine and threonine in one of three motifs (Thr-Glu-Tyr, Thr-Phe-Tyr or Thr-Gly-Tyr), depending upon the pathway. In addition to activating one or more protein phosphorylation cascades, the initiating stimulus may also mobilize a variety of other signalling molecules (e.g. protein kinase C isoforms, phospholipid kinases, G-protein alpha and beta gamma subunits, phospholipases, intracellular Ca2+). These various signals impact to a greater or lesser extent on multiple downstream effectors. Important concepts are that signal transmission often entails the targeted relocation of specific proteins in the cell, and the reversible formation of protein complexes by means of regulated protein phosphorylation. The signalling circuits may be completed by the phosphorylation of upstream effectors by downstream kinases, resulting in a modulation of the signal. Signalling is terminated and the components returned to the ground state largely by dephosphorylation. There is an indeterminant amount of cross-talk among the pathways, and many of the proteins in the pathways belong to families of closely related proteins. The potential for more than one signal to be conveyed down a pathway simultaneously (multiplex signalling) is discussed. The net effect of a given stimulus on the cell is the result of a complex intracellular integration of the intensity and duration of activation of the individual pathways. The specific outcome depends on the particular signalling molecules expressed by the target cells and on the dynamic balance among the pathways.
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Affiliation(s)
- D T Denhardt
- Department of Biological Sciences, Rutgers University, Piscataway, NJ 08855, USA
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18
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Jin F, Wienecke R, Xiao GH, Maize JC, DeClue JE, Yeung RS. Suppression of tumorigenicity by the wild-type tuberous sclerosis 2 (Tsc2) gene and its C-terminal region. Proc Natl Acad Sci U S A 1996; 93:9154-9. [PMID: 8799170 PMCID: PMC38611 DOI: 10.1073/pnas.93.17.9154] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The Tsc2 gene, which is mutationally inactivated in the germ line of some families with tuberous sclerosis, encodes a large, membrane-associated GTPase activating protein (GAP) designated tuberin. Studies of the Eker rat model of hereditary cancer strongly support the role of Tsc2 as a tumor suppressor gene. In this study, the biological activity of tuberin was assessed by expressing the wild-type Tsc2 gene in tumor cell lines lacking functional tuberin and also in rat fibroblasts with normal levels of endogenous tuberin. The colony forming efficiency of Eker rat-derived renal carcinoma cells was significantly reduced following reintroduction of wild-type Tsc2. Tumor cells expressing the transfected Tsc2 gene became more anchorage-dependent and lost their ability to form tumors in severe combined immunodeficient mice. At the cellular level, restoration of tuberin expression caused morphological changes characterized by enlargement of the cells and increased contact inhibition. As with the full-length Tsc2 gene, a clone encoding only the C terminus of tuberin (amino acids 1049-1809, including the GAP domain) was capable of reducing both colony formation and in vivo tumorigenicity when transfected into the Eker rat tumor cells. In normal Rat1 fibroblasts, conditional overexpression of tuberin also suppressed colony formation and cell growth in vitro. These results provide direct experimental evidence for the tumor suppressor function of Tsc2 and suggest that the tuberin C terminus plays an important role in this activity.
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Affiliation(s)
- F Jin
- Division of Medical Science, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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19
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Abstract
The genes involved in the genesis and progression of adult astrocytic tumors have been an area of considerable investigation. The tumor suppressor gene, p53, has been implicated, as has the epidermal growth factor receptor gene. Additional currently unidentified genes lie on chromosomes 10 and 19. Interestingly, work on pediatric astrocytomas suggests that the genes involved are different. p53 is rarely mutated in pediatric tumors, the epidermal growth factor receptor gene is rarely amplified or mutated, and chromosome 10 deletions are rare. The only pediatric tumor that seems to mimic the findings in adult tumors is brainstem glioma, perhaps explaining the uniformly grim prognosis in this type of tumor. In the pilocytic astrocytoma of childhood, mutations in the neurofibromatosis type I gene have been implicated in tumor development. In this review, the oncogenesis of pediatric gliomas is discussed and compared and contrasted to what is known about tumors.
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Affiliation(s)
- C Raffel
- Department of Neurological Surgery, Mayo Clinic and Foundation, Rochester, MN, USA
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20
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Morcos P, Thapar N, Tusneem N, Stacey D, Tamanoi F. Identification of neurofibromin mutants that exhibit allele specificity or increased Ras affinity resulting in suppression of activated ras alleles. Mol Cell Biol 1996; 16:2496-503. [PMID: 8628317 PMCID: PMC231238 DOI: 10.1128/mcb.16.5.2496] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Neurofibromin plays a critical role in the downregulation of Ras proteins in neurons and Schwann cells. Thus, the ability of neurofibromin to interact with Ras is crucial for its function, as mutations in NF1 that abolish this interaction fail to maintain function. To investigate the neurofibromin-Ras interaction in a systematic manner, we have carried out a yeast two-hybrid screen using a mutant of H-ras, H-rasD92K, defective for interaction with the GTPase-activated protein-related domain (GRD) of NF1. Two screens of a randomly mutagenized NF1-GRD library led to the identification of seven novel NF1 mutants. Characterization of the NF1-GRD mutants revealed that one class of mutants are allele specific for H-raSD92K. These mutants exhibit increased affinity for H-raSD92K and significantly reduced affinity for wild-type H-ras protein. Furthermore, they do not interact with another H-ras mutant defective for interaction with GTPase-activating proteins. Another class of mutants are high-affinity mutants which exhibit dramatically increased affinity for both wild-type and mutant forms of Ras. They also exhibit a striking ability to suppress the heat shock sensitive traits of activated RAS2G19v in yeast cells. Five mutations cluster within a region encompassing residues 1391 to 1436 (region II). Three NF1 patient mutations have previously been identified in this region. Two mutations that we identified occur in a region encompassing residues 1262 to 1276 (region I). Combining high-affinity mutations from both regions results in even greater affinity for Ras. These results demonstrate that two distinct regions of NF1-GRD are involved in the Ras interaction and that single amino acid changes can affect NF1's affinity for Ras.
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Affiliation(s)
- P Morcos
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095-1489, USA
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21
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Abstract
Neurofibromatosis type 1 (NF1), also called von Recklinghausen disease or peripheral neurofibromatosis, is a common autosomal dominant disorder characterised by multiple neurofibromas, café au lait spots, and Lisch nodules of the iris, with a variable clinical expression. The gene responsible for this condition, NF1, has been isolated by positional cloning. It spans over 350 kb of genomic DNA in chromosomal region 17q11.2 and encodes an mRNA of 11-13 kb containing at least 59 exons. NF1 is widely expressed in a variety of human and rat tissues. Four alternatively spliced NF1 transcripts have been identified. Three of these transcript isoforms (each with an extra exon: 9br, 23a, and 48a, respectively) show differential expression to some extent in various tissues, while the fourth isoform (2.9 kb in length) remains to be examined. The protein encoded by NF1, neurofibromin, has a domain homologous to the GTPase activating protein (GAP) family, and downregulates ras activity. The identification of somatic mutations in NF1 from tumour tissues strongly supports the speculation that NF1 is a member of the tumour suppressor gene family. Although the search for mutations in the gene has proved difficult, germline mutation analysis has shown that around 82% of all the fully characterised NF1 specific mutations so far predict severe truncation of neurofibromin. Further extensive studies are required to elucidate the gene function and the mutation spectrum. This should then facilitate the molecular diagnosis and the development of new therapy for the disease.
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Affiliation(s)
- M H Shen
- Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK
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22
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Largaespada DA, Shaughnessy JD, Jenkins NA, Copeland NG. Retroviral integration at the Evi-2 locus in BXH-2 myeloid leukemia cell lines disrupts Nf1 expression without changes in steady-state Ras-GTP levels. J Virol 1995; 69:5095-102. [PMID: 7609078 PMCID: PMC189327 DOI: 10.1128/jvi.69.8.5095-5102.1995] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Approximately 15% of BXH-2 myeloid leukemias harbor proviral integrations at the Evi-2 common viral integration site. Evi-2 is located within a large intron of the Nf1 tumor suppressor gene, raising the possibility that proviral integration at Evi-2 predisposes mice to myeloid tumor development by disrupting Nf1 expression. This hypothesis is supported by data suggesting that mutations in the human NF1 gene are causally associated with the development of juvenile chronic myelogenous leukemia (K. M. Shannon, P. O'Connell, G. A. Martin, D. Paderanga, K. Olson, P. Dinndorf, and F. McCormick, N. Engl. J. Med. 330:597-601, 1994) and mouse studies showing that aged mice, heterozygous for a germ line Nf1 mutation, develop myeloid leukemia with loss of the wild-type Nf1 allele (T. Jacks, T. S. Shih, E. M. Schmitt, R. T. Bronson, A. Bernards, and R. A. Weinberg, Nat. Genet. 7:353-361, 1994). To determine if viral integration at Evi-2 disrupts Nf1 expression, we derived a series of BXH-2 myeloid leukemia cell lines with or without viral integrations at Evi-2. In all cell lines examined, viral integration at Evi-2 resulted in the production of only truncated Nf1 transcripts and no stable, full-length neurofibromin. Although neurofibromin is a GTPase-activating protein (GAP) for p21ras proteins, its loss in the BXH-2 leukemic cell lines was not correlated with an increased steady-state level of p21ras bound to GTP. These data suggest that neurofibromin is not the sole mediator of Ras-GAP activity in myeloid cells and may have a GAP-independent function in myeloid cells.
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Affiliation(s)
- D A Largaespada
- Mammalian Genetics Laboratory, NCI-Frederick Cancer Research and Development Center, Maryland 21702, USA
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23
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Clark GJ, Der CJ. Aberrant function of the Ras signal transduction pathway in human breast cancer. Breast Cancer Res Treat 1995; 35:133-44. [PMID: 7612899 DOI: 10.1007/bf00694753] [Citation(s) in RCA: 160] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Although ras mutations are infrequent (approximately 5%) in breast cancers, there is considerable evidence that suggests that the pathways which Ras services may still be deregulated in breast cancer cells. The recent identification of many of the components of the Ras signal transduction pathway has defined a network of proto-oncogene proteins controlling diverse signaling events that regulate cell growth and differentiation. Consequently, mutations that perturb the function of any one component of this signal pathway may trigger the same oncogenic events as mutation of ras itself. Moreover, several Ras-related proteins have recently been demonstrated to possess the ability to trigger malignant transformation via signaling pathways shared with Ras proteins. Thus, it is possible that the aberrant function of Ras-related proteins may contribute to breast cancer development. Consequently, it is important not to dismiss the Ras pathway in the development of breast cancer merely because of the infrequent detection of mutations in ras itself, but rather to consider the influence of aberrations upstream or downstream of Ras and of certain Ras-related proteins in the development of breast cancer. Finally, the critical importance of components upstream and downstream of Ras provides additional targets for rational drug design approaches to block the aberrant function of Ras signaling in human tumors.
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Affiliation(s)
- G J Clark
- Department of Pharmacology, University of North Carolina at Chapel Hill 27599, USA
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24
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Baffa R, Negrini M, Schichman SA, Huebner K, Croce CM. Involvement of the ALL-1 gene in a solid tumor. Proc Natl Acad Sci U S A 1995; 92:4922-6. [PMID: 7761425 PMCID: PMC41819 DOI: 10.1073/pnas.92.11.4922] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Translocations involving chromosome band 11q23, found in 5-10% of human acute leukemias, disrupt the ALL-1 gene. This gene is fused by reciprocal translocation with a variety of other genes in acute lymphoblastic and myelogenous leukemias, and it undergoes self-fusion in acute myeloid leukemias with normal karyotype or trisomy 11. Here we report an alteration of the ALL-1 gene in a gastric carcinoma cell line (Mgc80-3). Characterization of this rearrangement revealed a three-way complex translocation, involving chromosomes 1 and 11, resulting in a partial duplication of the ALL-1 gene. Sequencing of reverse transcription-PCR products and Northern blot analysis showed that only the partially duplicated ALL-1 gene was transcribed, producing an mRNA with exon 8 fused to exon 2. This report of ALL-1 gene rearrangement in a solid tumor suggests that ALL-1 plays a role in the pathogenesis of some solid malignancies. The absence of the normal transcript in this cell line, in association with the loss-of-heterozygosity studies on chromosome 11q23 seen in solid tumors, suggests that ALL-1 is involved in tumorigenesis by a loss-of-function mechanism.
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Affiliation(s)
- R Baffa
- Jefferson Cancer Institute, Jefferson Cancer Center, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
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