Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients prese... more Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients present with a variety of clinical manifestations and are predisposed to cancer development. Many NF1 animal models have been developed, yet none display the spectrum of disease seen in patients and the translational impact of these models has been limited. We describe a minipig model that exhibits clinical hallmarks of NF1, including café au lait macules, neurofibromas, and optic pathway glioma. Spontaneous loss of heterozygosity is observed in this model, a phenomenon also described in NF1 patients. Oral administration of a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor suppresses Ras signaling. To our knowledge, this model provides an unprecedented opportunity to study the complex biology and natural history of NF1 and could prove indispensable for development of imaging methods, biomarkers, and evaluation of safety and efficacy of NF1-targeted therapies.
Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma for which th... more Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma for which the only effective therapy is surgery. In 2016, an international meeting entitled "MPNST State of the Science: Outlining a Research Agenda for the Future" was convened to establish short-and long-term research priorities. Key recommendations included the: 1) development of standardized, cost-efficient fluorodeoxyglucose positron emission tomography and whole-body magnetic resonance imaging guidelines to evaluate masses concerning for MPNST; 2) development of better understanding and histologic criteria for the transformation of a plexiform neurofibroma to MPNST; 3) establishment of a centralized database to collect genetic, genomic, histologic, immunohistochemical, molecular, radiographic, treatment, and related clinical data from MPNST subspecialty centers in a standardized manner; 4) creation of accurate mouse models to study the plexiform neurofibroma-to-MPNST transition, MPNST metastasis, and drug resistance; 5) use of trial designs that minimize regulatory requirements, maximize availability to patients, consider novel secondary end points, and study patients with newly diagnosed disease. Lastly, in order to minimize delays in developing novel therapies and promote the most efficient use of research resources and patient samples, data sharing should be incentivized. Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma associated with dismal clinical outcomes. The risk of MPNST is dramatically increased in individuals with neurofibromatosis type 1 (NF1). In 2002, an international consensus meeting on NF1-associated MPNSTs (1) emphasized the importance of a multidisciplinary approach, molecular genetic studies to identify patients at high risk, development of an international database and tumor bank, new imaging methods, and the need for targeted therapies. Although the clinical outcome for MPNST has not changed substantially in the past 15 years, there has been progress in our understanding of the natural history, biology, and pathogenesis COMMENTARY
inactivation of the gene (U L 39) encoding viral ribonucleotide reductase. Quantitative western b... more inactivation of the gene (U L 39) encoding viral ribonucleotide reductase. Quantitative western blot analysis demonstrated superior expression of endostatin in-vitro using HSV-endo at low multiplicity of infection (MOI) when compared to an equivalent cell number of AB12pEndo. Intra-tumoral treatment with HSV-endo displayed a marked anti-tumor effect compared to PBS treatment in a flank model of murine mesothelioma, but was virtually identical to a control Herpes virus harboring a lacZ transgene in lieu of endostatin. In conclusion, murine mesothelioma (AB12) appears quite sensitive to the oncolytic effect of this Herpes vector, but may be too sensitive to effectively evaluate the relative contribution of angiogenesis inhibition. Cell lines relatively resistant to Herpes oncolysis should be considered to adequately evaluate this novel reagent.
Neurofibromatosis type 2 (NF2) is a genetic disorder characterized by bilateral schwannomas of th... more Neurofibromatosis type 2 (NF2) is a genetic disorder characterized by bilateral schwannomas of the eighth cranial nerve. The NF2 tumor sup- pressor protein, merlin, is related to the ERM (ezrin, radixin, and moesin) family of membrane/F-actin linkers. Merlin resists solubilization by the detergent Triton X-100 (TX-100), a property commonly attributed to association with the cytoskeleton. Accordingly, NF2 patient mutations that
2014 Titus-Mitchell, HE, Rizvi, TA, Mayes, DA, Ciraolo, G, Ratner, N, (2014). Identification of S... more 2014 Titus-Mitchell, HE, Rizvi, TA, Mayes, DA, Ciraolo, G, Ratner, N, (2014). Identification of Signaling Pathways Controlling CNS Myelin Compaction in Neurofibromatosis Type I. - American Society of Neurochemistry Meeting, Long Beach, CA (3/9/14). - Ohio Miami Valley, Society for Neuroscience, Annual Meeting, Wright State University, Fairborn, OH (5/16/14).
2013 Titus-Mitchell, HE, Mayes, DA, Rizvi, TA, Ciraolo, G, Cancelas, JA, Ratner, N, (2013). Unrav... more 2013 Titus-Mitchell, HE, Mayes, DA, Rizvi, TA, Ciraolo, G, Cancelas, JA, Ratner, N, (2013). Unraveled: Molecular Mechanisms Behind Disrupted CNS White Matter Ultrastructure in Neurofibromatosis Type I. - Academic Health Center Poster Session, University of Cincinnati College of Medicine, Cincinnati, OH (10/24/13). - Graduate Student Research Forum, University of Cincinnati College of Medicine, Cincinnati, OH (10/15/13). - Great Lakes Glia Meeting, Traverse City, MI (10/5-10/8/13). - Ohio River Valley Cytometry Association, 3rd Annual Imaging & Cytometry Research Day, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH (9/18/13).
Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas with minimal therapeut... more Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas with minimal therapeutic opportunities. We observed that lipid droplets (LDs) accumulate in human MPNST cell lines and in primary human tumor samples. The goal of this study was to investigate the relevance of lipid metabolism to MPNST survival and as a possible therapeutic target. Based on preliminary findings that MPNSTs accumulate LDs, we hypothesized that a deregulated lipid metabolism supports MPNST cell survival/proliferation rate. To test this, we examined respiration, role of fatty acid oxidation (FAO), and the enzyme fatty acid synthase involved in de novo fatty acid synthesis in MPNSTs using both genetic and pharmacological tools. We demonstrate that LDs accumulate in MPNST cell lines, primary human and mouse MPNST tumors, and neural crest cells. LDs from MPNST cells disappear on lipid deprivation, indicating that LDs can be oxidized as a source of energy. Inhibition of FAO decreased oxygen consumpt...
International Journal of Developmental Neuroscience, 2006
that readily progresses to malignancy. Neurofibromin, the tumor suppressor protein encoded by NF1... more that readily progresses to malignancy. Neurofibromin, the tumor suppressor protein encoded by NF1 has rasGap activity thus, implicating constitutive activation of the ras pathway as a major consequence of NF1 loss of function. Patients with NF1 also have increased incidence of glioblastoma formation. We have sought to model these tumors for which no effective therapies have been developed. The prognosis remains unchanged over the past three decades. According to the WHO classification, four grades of astrocytoma exist. Grade 1 is benign and also referred to as pilocytic astrocytoma. Grade II or low grade astrocytoma is characterized by infiltrative cells that home on neuronal bodies (perineural satellosis). Grade III or anaplastic astrocytoma is cell dense and highly proliferative. Grade IV or glioblastoma multiforme is characterized by pseudopalisading, necrotic foci, and intense microvascularization. All forms of astrocytoma express primitive cell markers such as nestin. In addition, all forms of astrocytoma appear throughout the brain but do not leave the CNS. These observations have led to the suggestion that the CNS provides a niche that is required for tumor growth and that spontaneous tumorigenesis occurs throughout. Historically, the prevalent model for astrocytoma formation invoked mechanisms of dedifferentiation of glial cells, followed by genetic and epigenetic signals that drive neoplastic transformation. The more recent appreciation of the existence of stem cells in the lateral ventricles and dentate gyrus has raised the question of a potential role for stem cells in tumor formation.
International Journal of Developmental Neuroscience, 2008
Associations were found for four SNPs within intron 1 of the Tiam1 gene. These SNPs are rs7280029... more Associations were found for four SNPs within intron 1 of the Tiam1 gene. These SNPs are rs7280029, rs8131958, rs2833423, and rs8133912 and had p-values of 0.03, 0.04, 0.03, and 0.05 respectively, corrected for multiple testing. Haplotype analysis within Cdc42 showed suggestive results for three overtransmitted two-SNP haplotypes: CT (rs2056974-rs10917145), CT (rs2056975-rs2056974), and GT (rs10917145-rs2268177) with nominal pvalues of 0.003, 0.002, and 0.002 respectively.
Neurofibromatosis type 1 (NF1) is a genetic disorder that predisposes affected individuals to for... more Neurofibromatosis type 1 (NF1) is a genetic disorder that predisposes affected individuals to formation of benign neurofibromas, peripheral nerve tumors that can be associated with significant morbidity. Loss of the NF1 Ras-GAP protein causes increased Ras-GTP, and we previously found that inhibiting MEK signaling downstream of Ras can shrink established neurofibromas in a genetically engineered murine model. We studied effects of MEK inhibition using 1.5 mg/kg/day PD-0325901 prior to neurofibroma onset in the Nf1 (flox/flox) ; Dhh-Cre mouse model. We also treated mice with established tumors at 0.5 and 1.5 mg/kg/day doses of PD-0325901. We monitored tumor volumes using MRI and volumetric measurements, and measured pharmacokinetic and pharmacodynamic endpoints. Early administration significantly delayed neurofibroma development as compared to vehicle controls. When treatment was discontinued neurofibromas grew, but no rebound effect was observed and neurofibromas remained significan...
Neurofibromatosis type 1 (NF1) is a common genetic disorder that predisposes affected individuals... more Neurofibromatosis type 1 (NF1) is a common genetic disorder that predisposes affected individuals to tumours. The NF1 gene encodes a RAS GTPase-activating protein called neurofibromin and is one of several genes that (when mutant) affect RAS-MAPK signalling, causing related diseases collectively known as RASopathies. Several RASopathies, beyond NF1, are cancer predisposition syndromes. Somatic NF1 mutations also occur in 5-10% of human sporadic cancers and may contribute to resistance to therapy. To highlight areas for investigation in RASopathies and sporadic tumours with NF1 mutations, we summarize current knowledge of NF1 disease, the NF1 gene and neurofibromin, neurofibromin signalling pathways and recent developments in NF1 therapeutics.
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2002
The neural crest gives rise to numerous cell types, including Schwann cells, neurons, and melanoc... more The neural crest gives rise to numerous cell types, including Schwann cells, neurons, and melanocytes. The extent to which adult neural crest-derived cells retain plasticity has not been tested previously. We report that cutting adult mouse sciatic nerve induces pigmentation around nerve fascicles, among muscle bundles, and in the hypodermis. Pigmented cells are derived from adult nerve, because pigmentation occurs even when nerve fragments are grafted into tyrosinase null albino mice. Pigmentation defects are pervasive in patients with neurofibromatosis type 1 (NF1). Mice hemizygous for Nf1 mutations show enhanced pigmentation after nerve lesion and occasionally form pigmented and unpigmented tumors. The Nf1 nerve and the Nf1 host environment both contribute to enhanced pigmentation. Grafted purified Nf1 mutant glial cells [S100(+)-p75NGFR(+)-GFAP(+)-EGFR(+) or S100(+)-p75NGFR(+)-GFAP(+)-EGFR(-)] mimic nerve-derived pigmentation. The NF1 protein, neurofibromin, is a Ras-GAP that ac...
Journal of speech, language, and hearing research : JSLHR, 2000
There has been clinical speculation that parents of young stuttering children have expectations o... more There has been clinical speculation that parents of young stuttering children have expectations of their children's communication abilities that are not well-matched to the children's actual skills. We appraised the language abilities of 15 children close to the onset of stuttering symptoms and 15 age-, sex-, and SES-matched fluent children using an array of standardized tests and spontaneous language sample measures. Parents concurrently completed two parent-report measures of the children's communicative development. Results indicated generally depressed performance on all child speech and language measures by the children who stutter. Parent report was closely attuned to child performance for the stuttering children; parents of nonstuttering children were less accurate in their predictions of children's communicative performance. Implications for clinical advisement to parents of stuttering children are discussed.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1998
Proteins that interact with both cytoskeletal and membrane components are candidates to modulate ... more Proteins that interact with both cytoskeletal and membrane components are candidates to modulate membrane trafficking. The tumor suppressor proteins neurofibromin (NF1) and adenomatous polyposis coli (APC) both bind to microtubules and interact with membrane-associated proteins. The effects of recombinant NF1 and APC fragments on vesicle motility were evaluated by measuring fast axonal transport along microtubules in axoplasm from squid giant axons. APC4 (amino acids 1034-2844) reduced only anterograde movements, whereas APC2 (aa 1034-2130) or APC3 (aa 2130-2844) reduced both anterograde and retrograde transport. NF1 had no effect on organelle movement in either direction. Because APC contains multiple cyclin-dependent kinase (CDK) consensus phosphorylation motifs, the kinase inhibitor olomoucine was examined. At concentrations in which olomoucine is specific for cyclin-dependent kinases (5 microM), it reduced only anterograde transport, whereas anterograde and retrograde movement w...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1993
NF1 patients display CNS abnormalities including learning disabilities, clumsiness, astrocytomas,... more NF1 patients display CNS abnormalities including learning disabilities, clumsiness, astrocytomas, and abnormalities on magnetic resonance imaging exams. To determine whether the cellular and neuroanatomical distribution of neurofibromin reveals possible function for neurofibromin in the brain, we stained rat brain tissue sections with anti-neurofibromin antibodies. Neurofibromin is highly enriched in large projection neurons, such as cortical and hippocampal pyramidal cells and cerebellar Purkinje cells. Neurofibromin is present in cell bodies and in axons, but is highly enriched in dendrites. Immunoelectron microscopic analysis demonstrates that NF1 is associated with smooth vesiculotubular elements and cisternal stacks and with multivesicular bodies in the cell body and dendrites, but not with the plasma membrane, nucleus, nuclear envelope, Golgi apparatus, mitochondria, or rough endoplasmic reticulum. The preferential localization of neurofibromin to the smooth endoplasmic reticu...
The neural crest gives rise to a variety of cell types including Schwann cells of the peripheral ... more The neural crest gives rise to a variety of cell types including Schwann cells of the peripheral nervous system. Schwann cell precursors begin to differentiate early and migrate along specific pathways in the embryo before associating with nerve trunks. To determine whether motor axons direct the migration of Schwann cell precursors along specific pathways, we tested the effect of ablating the ventral half of the neural tube, which contains motor neuron cell bodies. The ventral neural tube was removed unilaterally from lumbar regions of chicken embryos at stage 17, when neural crest cells are just beginning to migrate and before motor axons have extended out of the neural tube. At several stages after ventral tube ablation, sections of the lumbar region of these embryos were stained with anti-acetylated tubulin to label developing axons, HNK-1 to label migrating neural crest cells and 1E8 to label Schwann cell precursors. In many embryos the ablation of motor neurons was incomplete....
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2002
Mutations in the neurofibromatosis type 1 gene predispose patients to develop benign peripheral n... more Mutations in the neurofibromatosis type 1 gene predispose patients to develop benign peripheral nerve tumors (neurofibromas) containing Schwann cells (SCs). SCs from neurofibromatosis type-1 gene (Nf1) null mutant mice showed increased levels of Ras-GTP and cAMP. The proliferation and differentiation of SCs are regulated by Ras-GTP and cAMP-mediated signaling, which have been linked to expression of K+ channels. We investigated the differential expression of K+ currents in Nf1 null mutant SCs (Nf1-/-) and their wild-type (Nf1+/+) counterparts and determined the mechanisms underlying the differences. The current densities of the sustained component of K+ currents were similar in the two genotypes. However, Nf1-/- SCs showed a significant increase (approximately 1.5-fold) in a 4-aminopyridine-sensitive transient outward K+ current (I(A)). Nonstationary fluctuation analysis revealed a significant increase in the number of functional channels in the null mutant cells. When the involveme...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2001
In most mammalian cells, the cAMP-dependent protein kinase A pathway promotes growth arrest and c... more In most mammalian cells, the cAMP-dependent protein kinase A pathway promotes growth arrest and cell differentiation. However in Schwann cells, the reverse is true. Elevated levels of cAMP function as the cofactor to a broad range of mitogenic cues in culture and in animals. Previous studies have suggested that cAMP acts at an early point in the Schwann cell mitogenic response, perhaps by stimulating the expression of growth factor receptors. We show here that cAMP acts downstream rather than upstream of growth factor receptor expression. The essential function(s) of cAMP is exerted as Schwann cells progress through the G(1) phase of the cell cycle. Ectopic expression studies using an inducible retroviral vector show that the G(1) phase requirement for cAMP can be alleviated by a single protein, cyclin D1. We show, in addition, that at least one function of the Nf1 tumor suppressor is to antagonize the accumulation of cAMP and the expression of cyclin D1 in Schwann cells. Thus a G(1...
Malignant peripheral nerve sheath tumors (MPNSTs) are genetically diverse, aggressive sarcomas th... more Malignant peripheral nerve sheath tumors (MPNSTs) are genetically diverse, aggressive sarcomas that occur sporadically or in association with neurofibromatosis type 1 syndrome. Reduced TP53 gene expression and amplification/overexpression of the epidermal growth factor receptor (EGFR) gene occur in MPNST formation. We focused on determining the cooperativity between reduced TP53 expression and EGFR overexpression for Schwann cell transformation in vitro (immortalized human Schwann cells) and MPNST formation in vivo (transgenic mice). Human gene copy number alteration data, microarray expression data, and TMA analysis indicate that TP53 haploinsufficiency and increased EGFR expression co-occur in human MPNST samples. Concurrent modulation of EGFR and TP53 expression in HSC1λ cells significantly increased proliferation and anchorage-independent growth in vitro. Transgenic mice heterozygous for a Trp53-null allele and overexpressing EGFR in Schwann cells had a significant increase in neurofibroma and grade 3 PNST (MPNST) formation compared with single transgenic controls. Histological analysis of tumors identified a significant increase in pAkt expression in grade 3 PNSTs compared with neurofibromas. Array comparative genome hybridization analysis of grade 3 PNSTs identified recurrent focal regions of chromosomal gains with significant enrichment in genes involved in extracellular signal-regulated kinase 5 signaling. Collectively, altered p53 expression cooperates with overexpression of EGFR in Schwann cells to enhance in vitro oncogenic properties and tumorigenesis and progression in vivo.
Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients prese... more Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients present with a variety of clinical manifestations and are predisposed to cancer development. Many NF1 animal models have been developed, yet none display the spectrum of disease seen in patients and the translational impact of these models has been limited. We describe a minipig model that exhibits clinical hallmarks of NF1, including café au lait macules, neurofibromas, and optic pathway glioma. Spontaneous loss of heterozygosity is observed in this model, a phenomenon also described in NF1 patients. Oral administration of a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor suppresses Ras signaling. To our knowledge, this model provides an unprecedented opportunity to study the complex biology and natural history of NF1 and could prove indispensable for development of imaging methods, biomarkers, and evaluation of safety and efficacy of NF1-targeted therapies.
Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma for which th... more Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma for which the only effective therapy is surgery. In 2016, an international meeting entitled "MPNST State of the Science: Outlining a Research Agenda for the Future" was convened to establish short-and long-term research priorities. Key recommendations included the: 1) development of standardized, cost-efficient fluorodeoxyglucose positron emission tomography and whole-body magnetic resonance imaging guidelines to evaluate masses concerning for MPNST; 2) development of better understanding and histologic criteria for the transformation of a plexiform neurofibroma to MPNST; 3) establishment of a centralized database to collect genetic, genomic, histologic, immunohistochemical, molecular, radiographic, treatment, and related clinical data from MPNST subspecialty centers in a standardized manner; 4) creation of accurate mouse models to study the plexiform neurofibroma-to-MPNST transition, MPNST metastasis, and drug resistance; 5) use of trial designs that minimize regulatory requirements, maximize availability to patients, consider novel secondary end points, and study patients with newly diagnosed disease. Lastly, in order to minimize delays in developing novel therapies and promote the most efficient use of research resources and patient samples, data sharing should be incentivized. Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma associated with dismal clinical outcomes. The risk of MPNST is dramatically increased in individuals with neurofibromatosis type 1 (NF1). In 2002, an international consensus meeting on NF1-associated MPNSTs (1) emphasized the importance of a multidisciplinary approach, molecular genetic studies to identify patients at high risk, development of an international database and tumor bank, new imaging methods, and the need for targeted therapies. Although the clinical outcome for MPNST has not changed substantially in the past 15 years, there has been progress in our understanding of the natural history, biology, and pathogenesis COMMENTARY
inactivation of the gene (U L 39) encoding viral ribonucleotide reductase. Quantitative western b... more inactivation of the gene (U L 39) encoding viral ribonucleotide reductase. Quantitative western blot analysis demonstrated superior expression of endostatin in-vitro using HSV-endo at low multiplicity of infection (MOI) when compared to an equivalent cell number of AB12pEndo. Intra-tumoral treatment with HSV-endo displayed a marked anti-tumor effect compared to PBS treatment in a flank model of murine mesothelioma, but was virtually identical to a control Herpes virus harboring a lacZ transgene in lieu of endostatin. In conclusion, murine mesothelioma (AB12) appears quite sensitive to the oncolytic effect of this Herpes vector, but may be too sensitive to effectively evaluate the relative contribution of angiogenesis inhibition. Cell lines relatively resistant to Herpes oncolysis should be considered to adequately evaluate this novel reagent.
Neurofibromatosis type 2 (NF2) is a genetic disorder characterized by bilateral schwannomas of th... more Neurofibromatosis type 2 (NF2) is a genetic disorder characterized by bilateral schwannomas of the eighth cranial nerve. The NF2 tumor sup- pressor protein, merlin, is related to the ERM (ezrin, radixin, and moesin) family of membrane/F-actin linkers. Merlin resists solubilization by the detergent Triton X-100 (TX-100), a property commonly attributed to association with the cytoskeleton. Accordingly, NF2 patient mutations that
2014 Titus-Mitchell, HE, Rizvi, TA, Mayes, DA, Ciraolo, G, Ratner, N, (2014). Identification of S... more 2014 Titus-Mitchell, HE, Rizvi, TA, Mayes, DA, Ciraolo, G, Ratner, N, (2014). Identification of Signaling Pathways Controlling CNS Myelin Compaction in Neurofibromatosis Type I. - American Society of Neurochemistry Meeting, Long Beach, CA (3/9/14). - Ohio Miami Valley, Society for Neuroscience, Annual Meeting, Wright State University, Fairborn, OH (5/16/14).
2013 Titus-Mitchell, HE, Mayes, DA, Rizvi, TA, Ciraolo, G, Cancelas, JA, Ratner, N, (2013). Unrav... more 2013 Titus-Mitchell, HE, Mayes, DA, Rizvi, TA, Ciraolo, G, Cancelas, JA, Ratner, N, (2013). Unraveled: Molecular Mechanisms Behind Disrupted CNS White Matter Ultrastructure in Neurofibromatosis Type I. - Academic Health Center Poster Session, University of Cincinnati College of Medicine, Cincinnati, OH (10/24/13). - Graduate Student Research Forum, University of Cincinnati College of Medicine, Cincinnati, OH (10/15/13). - Great Lakes Glia Meeting, Traverse City, MI (10/5-10/8/13). - Ohio River Valley Cytometry Association, 3rd Annual Imaging & Cytometry Research Day, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH (9/18/13).
Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas with minimal therapeut... more Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas with minimal therapeutic opportunities. We observed that lipid droplets (LDs) accumulate in human MPNST cell lines and in primary human tumor samples. The goal of this study was to investigate the relevance of lipid metabolism to MPNST survival and as a possible therapeutic target. Based on preliminary findings that MPNSTs accumulate LDs, we hypothesized that a deregulated lipid metabolism supports MPNST cell survival/proliferation rate. To test this, we examined respiration, role of fatty acid oxidation (FAO), and the enzyme fatty acid synthase involved in de novo fatty acid synthesis in MPNSTs using both genetic and pharmacological tools. We demonstrate that LDs accumulate in MPNST cell lines, primary human and mouse MPNST tumors, and neural crest cells. LDs from MPNST cells disappear on lipid deprivation, indicating that LDs can be oxidized as a source of energy. Inhibition of FAO decreased oxygen consumpt...
International Journal of Developmental Neuroscience, 2006
that readily progresses to malignancy. Neurofibromin, the tumor suppressor protein encoded by NF1... more that readily progresses to malignancy. Neurofibromin, the tumor suppressor protein encoded by NF1 has rasGap activity thus, implicating constitutive activation of the ras pathway as a major consequence of NF1 loss of function. Patients with NF1 also have increased incidence of glioblastoma formation. We have sought to model these tumors for which no effective therapies have been developed. The prognosis remains unchanged over the past three decades. According to the WHO classification, four grades of astrocytoma exist. Grade 1 is benign and also referred to as pilocytic astrocytoma. Grade II or low grade astrocytoma is characterized by infiltrative cells that home on neuronal bodies (perineural satellosis). Grade III or anaplastic astrocytoma is cell dense and highly proliferative. Grade IV or glioblastoma multiforme is characterized by pseudopalisading, necrotic foci, and intense microvascularization. All forms of astrocytoma express primitive cell markers such as nestin. In addition, all forms of astrocytoma appear throughout the brain but do not leave the CNS. These observations have led to the suggestion that the CNS provides a niche that is required for tumor growth and that spontaneous tumorigenesis occurs throughout. Historically, the prevalent model for astrocytoma formation invoked mechanisms of dedifferentiation of glial cells, followed by genetic and epigenetic signals that drive neoplastic transformation. The more recent appreciation of the existence of stem cells in the lateral ventricles and dentate gyrus has raised the question of a potential role for stem cells in tumor formation.
International Journal of Developmental Neuroscience, 2008
Associations were found for four SNPs within intron 1 of the Tiam1 gene. These SNPs are rs7280029... more Associations were found for four SNPs within intron 1 of the Tiam1 gene. These SNPs are rs7280029, rs8131958, rs2833423, and rs8133912 and had p-values of 0.03, 0.04, 0.03, and 0.05 respectively, corrected for multiple testing. Haplotype analysis within Cdc42 showed suggestive results for three overtransmitted two-SNP haplotypes: CT (rs2056974-rs10917145), CT (rs2056975-rs2056974), and GT (rs10917145-rs2268177) with nominal pvalues of 0.003, 0.002, and 0.002 respectively.
Neurofibromatosis type 1 (NF1) is a genetic disorder that predisposes affected individuals to for... more Neurofibromatosis type 1 (NF1) is a genetic disorder that predisposes affected individuals to formation of benign neurofibromas, peripheral nerve tumors that can be associated with significant morbidity. Loss of the NF1 Ras-GAP protein causes increased Ras-GTP, and we previously found that inhibiting MEK signaling downstream of Ras can shrink established neurofibromas in a genetically engineered murine model. We studied effects of MEK inhibition using 1.5 mg/kg/day PD-0325901 prior to neurofibroma onset in the Nf1 (flox/flox) ; Dhh-Cre mouse model. We also treated mice with established tumors at 0.5 and 1.5 mg/kg/day doses of PD-0325901. We monitored tumor volumes using MRI and volumetric measurements, and measured pharmacokinetic and pharmacodynamic endpoints. Early administration significantly delayed neurofibroma development as compared to vehicle controls. When treatment was discontinued neurofibromas grew, but no rebound effect was observed and neurofibromas remained significan...
Neurofibromatosis type 1 (NF1) is a common genetic disorder that predisposes affected individuals... more Neurofibromatosis type 1 (NF1) is a common genetic disorder that predisposes affected individuals to tumours. The NF1 gene encodes a RAS GTPase-activating protein called neurofibromin and is one of several genes that (when mutant) affect RAS-MAPK signalling, causing related diseases collectively known as RASopathies. Several RASopathies, beyond NF1, are cancer predisposition syndromes. Somatic NF1 mutations also occur in 5-10% of human sporadic cancers and may contribute to resistance to therapy. To highlight areas for investigation in RASopathies and sporadic tumours with NF1 mutations, we summarize current knowledge of NF1 disease, the NF1 gene and neurofibromin, neurofibromin signalling pathways and recent developments in NF1 therapeutics.
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2002
The neural crest gives rise to numerous cell types, including Schwann cells, neurons, and melanoc... more The neural crest gives rise to numerous cell types, including Schwann cells, neurons, and melanocytes. The extent to which adult neural crest-derived cells retain plasticity has not been tested previously. We report that cutting adult mouse sciatic nerve induces pigmentation around nerve fascicles, among muscle bundles, and in the hypodermis. Pigmented cells are derived from adult nerve, because pigmentation occurs even when nerve fragments are grafted into tyrosinase null albino mice. Pigmentation defects are pervasive in patients with neurofibromatosis type 1 (NF1). Mice hemizygous for Nf1 mutations show enhanced pigmentation after nerve lesion and occasionally form pigmented and unpigmented tumors. The Nf1 nerve and the Nf1 host environment both contribute to enhanced pigmentation. Grafted purified Nf1 mutant glial cells [S100(+)-p75NGFR(+)-GFAP(+)-EGFR(+) or S100(+)-p75NGFR(+)-GFAP(+)-EGFR(-)] mimic nerve-derived pigmentation. The NF1 protein, neurofibromin, is a Ras-GAP that ac...
Journal of speech, language, and hearing research : JSLHR, 2000
There has been clinical speculation that parents of young stuttering children have expectations o... more There has been clinical speculation that parents of young stuttering children have expectations of their children's communication abilities that are not well-matched to the children's actual skills. We appraised the language abilities of 15 children close to the onset of stuttering symptoms and 15 age-, sex-, and SES-matched fluent children using an array of standardized tests and spontaneous language sample measures. Parents concurrently completed two parent-report measures of the children's communicative development. Results indicated generally depressed performance on all child speech and language measures by the children who stutter. Parent report was closely attuned to child performance for the stuttering children; parents of nonstuttering children were less accurate in their predictions of children's communicative performance. Implications for clinical advisement to parents of stuttering children are discussed.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1998
Proteins that interact with both cytoskeletal and membrane components are candidates to modulate ... more Proteins that interact with both cytoskeletal and membrane components are candidates to modulate membrane trafficking. The tumor suppressor proteins neurofibromin (NF1) and adenomatous polyposis coli (APC) both bind to microtubules and interact with membrane-associated proteins. The effects of recombinant NF1 and APC fragments on vesicle motility were evaluated by measuring fast axonal transport along microtubules in axoplasm from squid giant axons. APC4 (amino acids 1034-2844) reduced only anterograde movements, whereas APC2 (aa 1034-2130) or APC3 (aa 2130-2844) reduced both anterograde and retrograde transport. NF1 had no effect on organelle movement in either direction. Because APC contains multiple cyclin-dependent kinase (CDK) consensus phosphorylation motifs, the kinase inhibitor olomoucine was examined. At concentrations in which olomoucine is specific for cyclin-dependent kinases (5 microM), it reduced only anterograde transport, whereas anterograde and retrograde movement w...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1993
NF1 patients display CNS abnormalities including learning disabilities, clumsiness, astrocytomas,... more NF1 patients display CNS abnormalities including learning disabilities, clumsiness, astrocytomas, and abnormalities on magnetic resonance imaging exams. To determine whether the cellular and neuroanatomical distribution of neurofibromin reveals possible function for neurofibromin in the brain, we stained rat brain tissue sections with anti-neurofibromin antibodies. Neurofibromin is highly enriched in large projection neurons, such as cortical and hippocampal pyramidal cells and cerebellar Purkinje cells. Neurofibromin is present in cell bodies and in axons, but is highly enriched in dendrites. Immunoelectron microscopic analysis demonstrates that NF1 is associated with smooth vesiculotubular elements and cisternal stacks and with multivesicular bodies in the cell body and dendrites, but not with the plasma membrane, nucleus, nuclear envelope, Golgi apparatus, mitochondria, or rough endoplasmic reticulum. The preferential localization of neurofibromin to the smooth endoplasmic reticu...
The neural crest gives rise to a variety of cell types including Schwann cells of the peripheral ... more The neural crest gives rise to a variety of cell types including Schwann cells of the peripheral nervous system. Schwann cell precursors begin to differentiate early and migrate along specific pathways in the embryo before associating with nerve trunks. To determine whether motor axons direct the migration of Schwann cell precursors along specific pathways, we tested the effect of ablating the ventral half of the neural tube, which contains motor neuron cell bodies. The ventral neural tube was removed unilaterally from lumbar regions of chicken embryos at stage 17, when neural crest cells are just beginning to migrate and before motor axons have extended out of the neural tube. At several stages after ventral tube ablation, sections of the lumbar region of these embryos were stained with anti-acetylated tubulin to label developing axons, HNK-1 to label migrating neural crest cells and 1E8 to label Schwann cell precursors. In many embryos the ablation of motor neurons was incomplete....
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2002
Mutations in the neurofibromatosis type 1 gene predispose patients to develop benign peripheral n... more Mutations in the neurofibromatosis type 1 gene predispose patients to develop benign peripheral nerve tumors (neurofibromas) containing Schwann cells (SCs). SCs from neurofibromatosis type-1 gene (Nf1) null mutant mice showed increased levels of Ras-GTP and cAMP. The proliferation and differentiation of SCs are regulated by Ras-GTP and cAMP-mediated signaling, which have been linked to expression of K+ channels. We investigated the differential expression of K+ currents in Nf1 null mutant SCs (Nf1-/-) and their wild-type (Nf1+/+) counterparts and determined the mechanisms underlying the differences. The current densities of the sustained component of K+ currents were similar in the two genotypes. However, Nf1-/- SCs showed a significant increase (approximately 1.5-fold) in a 4-aminopyridine-sensitive transient outward K+ current (I(A)). Nonstationary fluctuation analysis revealed a significant increase in the number of functional channels in the null mutant cells. When the involveme...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2001
In most mammalian cells, the cAMP-dependent protein kinase A pathway promotes growth arrest and c... more In most mammalian cells, the cAMP-dependent protein kinase A pathway promotes growth arrest and cell differentiation. However in Schwann cells, the reverse is true. Elevated levels of cAMP function as the cofactor to a broad range of mitogenic cues in culture and in animals. Previous studies have suggested that cAMP acts at an early point in the Schwann cell mitogenic response, perhaps by stimulating the expression of growth factor receptors. We show here that cAMP acts downstream rather than upstream of growth factor receptor expression. The essential function(s) of cAMP is exerted as Schwann cells progress through the G(1) phase of the cell cycle. Ectopic expression studies using an inducible retroviral vector show that the G(1) phase requirement for cAMP can be alleviated by a single protein, cyclin D1. We show, in addition, that at least one function of the Nf1 tumor suppressor is to antagonize the accumulation of cAMP and the expression of cyclin D1 in Schwann cells. Thus a G(1...
Malignant peripheral nerve sheath tumors (MPNSTs) are genetically diverse, aggressive sarcomas th... more Malignant peripheral nerve sheath tumors (MPNSTs) are genetically diverse, aggressive sarcomas that occur sporadically or in association with neurofibromatosis type 1 syndrome. Reduced TP53 gene expression and amplification/overexpression of the epidermal growth factor receptor (EGFR) gene occur in MPNST formation. We focused on determining the cooperativity between reduced TP53 expression and EGFR overexpression for Schwann cell transformation in vitro (immortalized human Schwann cells) and MPNST formation in vivo (transgenic mice). Human gene copy number alteration data, microarray expression data, and TMA analysis indicate that TP53 haploinsufficiency and increased EGFR expression co-occur in human MPNST samples. Concurrent modulation of EGFR and TP53 expression in HSC1λ cells significantly increased proliferation and anchorage-independent growth in vitro. Transgenic mice heterozygous for a Trp53-null allele and overexpressing EGFR in Schwann cells had a significant increase in neurofibroma and grade 3 PNST (MPNST) formation compared with single transgenic controls. Histological analysis of tumors identified a significant increase in pAkt expression in grade 3 PNSTs compared with neurofibromas. Array comparative genome hybridization analysis of grade 3 PNSTs identified recurrent focal regions of chromosomal gains with significant enrichment in genes involved in extracellular signal-regulated kinase 5 signaling. Collectively, altered p53 expression cooperates with overexpression of EGFR in Schwann cells to enhance in vitro oncogenic properties and tumorigenesis and progression in vivo.
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Papers by Nancy Ratner