Neurofibromatosis type 1. I. General overview

A Fibroblast-Derived Secretome Stimulates the Growth and Invasiveness of 3D Plexiform Neurofibroma Spheroids

Plexiform neurofibromas (PNs) occur in about a half of neurofibromatosis type 1 (NF1) patients and have garnered significant research attention due to their capacity for growth and potential for malignant transformation. NF1 plexiform neurofibroma (pNF1) is a complex tumor composed of Schwann cell-derived tumor cells (Nf1-/-) and the tumor microenvironment (TME). Although it has been widely demonstrated that the TME is involved in the formation of neurofibromas, little is known about the effects of the TME on the subsequent progression of human pNF1. Elucidating the molecular interactions between tumor cells and the TME may provide new therapeutic targets to reduce the progression of pNF1. In the present study, we focused on the contributions of fibroblasts, the most abundant cell types in the TME, to the growth of pNF1. To simulate the TME, we used a three-dimensional (3D) coculture model of immortalized pNF1 tumor cells (Nf1-/-) and primary fibroblasts (Nf1+/-) derived from pNF1 patients. We performed live-cell imaging of 3D/4D (3D in real-time) cultures through confocal microscopy followed by 3D quantitative analyses using advanced imaging software. The growth of pNF1 spheroids in 3D cocultures with fibroblasts was significantly greater than that of pNF1 spheroids in 3D monocultures. An increase in the growth of pNF1 spheroids also occurred when they were cultured with conditioned media (CM) from fibroblasts. Moreover, fibroblast-derived CM increased the invasive outgrowth and further local invasion of pNF1 spheroids. Interestingly, when small extracellular vesicles (sEVs) were depleted from the fibroblast-derived CM, the stimulation of the growth of pNF1 spheroids was lost. Our results suggest that fibroblast-derived sEVs are a therapeutic target for reducing the growth of pNF1.

Ophthalmic manifestations of endocrine disorders-endocrinology and the eye

Disorders of the endocrine system usually manifest in a multi-organ fashion. More specifically, many endocrinopathies become apparent in the eye first through a variety of distinct pathophysiologic disturbances. The eye provides physicians with valuable clues for the recognition and management of numerous systemic diseases, including many disorders of the endocrine pathway. Recognizing ophthalmic manifestations of endocrine disorders is critical not only for rapid diagnosis and treatment, but also to prevent significant morbidity and mortality. In this review, we discuss relevant ophthalmic findings associated with key disorders of the pancreas, thyroid gland, and hypothalamic-pituitary axis, as well as with multiple hereditary endocrine syndromes. We have chosen to focus on diabetes mellitus (DM), Graves' ophthalmopathy, pituitary tumors, and some less common disorders that underscore the unique relationship between the eye and the endocrine system.

Medium throughput biochemical compound screening identifies novel agents for pharmacotherapy of neurofibromatosis type 1

The variable manifestation of phenotypes that occur in patients with neurofibromatosis type 1 (NF1) includes benign and malignant neurocutaneous tumors for which no adequate treatment exists. Cell-based screening of known bioactive compounds library identified the protein phosphatase 2A (PP2A) inhibitor Cantharidin and the L-type calcium channel blocker Nifedipine as potential candidates for NF1 pharmacotherapy. Validation of screening results using human NF1-associated malignant peripheral nerve sheath tumor (MPNST) cells showed that Cantharidin effectively impeded MPNST cell growth, while Nifedipine treatment significantly decreased local tumor growth in an MPNST xenograft animal model. These data suggest that inhibitors of PP2A, as well as calcium channel blockers, might be used in broader MPNST preclinical studies as single agents or in combinatorial therapeutic strategies.

Giant neurofibroma in the right lower limb of a 26-year-old woman: report of a case

Neurofibromatosis (NF) is a genetically inherited, autosomal-dominant disease with an incidence of 1 in 3000 live births. There are two types of NF, NF 1 and NF 2, and NF 1 is the most common. This study reports on the diagnosis, treatment, and related family medical history of a rare case with NF-1 in the right lower limb.

Heat hyperalgesia and mechanical hypersensitivity induced by calcitonin gene-related peptide in a mouse model of neurofibromatosis

This study examined whether mice with a deficiency of neurofibromin, a Ras GTPase activating protein, exhibit a nociceptive phenotype and probed a possible contribution by calcitonin gene-related peptide. In the absence of inflammation, Nf1^+/− mice (B6.129S6 Nf1<tm1Fcr>/J) and wild type littermates responded comparably to heat or mechanical stimuli, except for a subtle enhanced mechanical sensitivity in female Nf1^+/− mice. Nociceptive phenotype was also examined after inflammation induced by capsaicin and formalin, which release endogenous calcitonin gene-related peptide. Intraplantar injection of capsaicin evoked comparable heat hyperalgesia and mechanical hypersensitivity in Nf1^+/− and wild type mice of both genders. Formalin injection caused a similar duration of licking in male Nf1^+/− and wild type mice. Female Nf1^+/− mice licked less than wild type mice, but displayed other nociceptive behaviors. In contrast, intraplantar injection of CGRP caused greater heat hyperalgesia in Nf1^+/− mice of both genders compared to wild type mice. Male Nf1^+/− mice also exhibited greater mechanical hypersensitivity; however, female Nf1^+/− mice exhibited less mechanical hypersensitivity than their wild type littermates. Transcripts for calcitonin gene-related peptide were similar in the dorsal root ganglia of both genotypes and genders. Transcripts for receptor activity-modifying protein-1, which is rate-limiting for the calcitonin gene-related peptide receptor, in the spinal cord were comparable for both genotypes and genders. The increased responsiveness to intraplantar calcitonin gene-related peptide suggests that the peripheral actions of calcitonin gene-related peptide are enhanced as a result of the neurofibromin deficit. The analgesic efficacy of calcitonin gene-related peptide receptor antagonists may therefore merit investigation in neurofibromatosis patients.

Spinal cord ependymoma associated with neurofibromatosis 1 : case report and review of the literature

Patients with neurofibromatosis 1 (NF1) are predisposed to develop central nervous system tumors, due to the loss of neurofibromin, an inactivator of proto-oncogene Ras. However, to our knowledge, only three cases of ependymomas with NF1 have been reported in the literature. The authors present a case of NF1 patient with a spinal cord ependymoma. She was referred for about half a year history of increasing numbness that progressed from her fingers to her entire body above the bellybutton. Magnetic resonance imaging revealed a relative-demarcated, heterogeneously enhanced mass lesion accompanied by perifocal edema in C5-7 level, a left-sided T11 spinous process heterogeneously enhanced mass in soft tissue, intervertebral disk hernia in L2-5 level, and widespread punctum enhancing lesion in her scalp and in T11-L5 level. The patient underwent C5-7 laminectomies and total excision of the tumor under operative microscope, and intraoperative ultrasonography and physiological monitoring were used during the surgery. Histopathologically, her tumor was found to be a ependymoma without malignant features (grade II in the World Health Organization classification). Therefore, no adjuvant therapy was applied. Following the operation, the patient showed an uneventful clinical recovery with no evidence of tumor recurrence after one year of follow-up.

Malignant uveal schwannoma with peripheral nerve extension in a 12-week-old color-dilute Labrador Retriever

The formalin-fixed, amber-colored right globe from a 12-week-old female silver Labrador Retriever dog was submitted to the Comparative Ocular Pathology Laboratory of Wisconsin for light microscopic evaluation. The clinical history described a collapsed anterior chamber and multifocal nodular lesions in the peripheral iris. Histologically, immunohistochemically, and ultrastructurally, the uveal mass was consistent with a malignant schwannoma; there was extension along peripheral nerves within the sclera. The signalment and behavior of the neoplasm distinguish it from the uveal schwannoma of blue-eyed dogs and bear some resemblance to the ocular lesions in human neurofibromatosis. The dilute color mutation may contribute to the cause. Six weeks later, the dog did not develop any additional masses.

Intramedullary and retroperitoneal melanocytic tumor associated with congenital blue nevus and nevus flammeus: an uncommon combination of neurocutaneous melanosis and phacomatosis pigmentovascularis--case report

Neurocutaneous melanosis (NCM) is a rare condition characterized by central nervous system melanocytic tumors associated with congenital melanocytic nevi. Phacomatosis pigmentovascularis (PPV) is an association of vascular nevus with pigmentary nevus. Aberrant maturation of neural crest-derived cells is considered to be related to pathogenesis in both conditions. However, association of NCM and PPV has not been reported to the best of our knowledge. Melanocytoma, which usually involves the leptomeninges or spinal cord, is extremely rare in the retroperitoneum. We present here a case of a patient with NCM, PPV, and melanocytic tumors in the spinal cord and retroperitoneum, which were treated surgically. A 40-year-old woman had a 2-year history of dysesthesia and weakness in the left leg. History included congenital giant blue nevus-like lesion in the trunk, a port-wine stain in the sacral area, and Caesarean section performed 8 years before, when diffuse pigmentation in the peritoneum was noted. Magnetic resonance (MR) imaging of the spine revealed an intramedullary tumor at T10 level with paramagnetic signal characteristics. The spinal cord tumor was totally removed, and the histological diagnosis was melanocytoma. Three months later, a left retroperitoneal mass with histological features of melanocytic tumor was removed. Neither tumors recurred and the patient stays ambulatory 4 years after the surgery. Multiple subtypes of melanocytic tumors with distinctive features of NCM and PPV can develop simultaneously, mimicking malignant melanoma. Gross total resection of each tumor, when indicated, is beneficial.

Skin-derived precursor cells as an in vitro modelling tool for the study of type 1 neurofibromatosis

The most characteristic feature of neurofibromatosis type 1 (NF1) is the development of neurofibromas. It has been suggested that these tumors are caused by somatic inactivation of the wild-type NF1 allele, but the cell that originally suffers this mutation remains controversial. Several lines of evidence support the clonal origin of these tumors, and it has been recently suggested that skin-derived precursor cells (SKPs) could be the cell of origin of dermal neurofibromas. Nullizygous (NF1(-/-)) SKPs do give rise to neurofibromas when transplanted to heterozygous mice. Moreover, a nullizygous population of cells that is S100β negative is present in human neurofibromas, and NF1(+/-) multipotent progenitor cells are seemingly recruited to the tumor. This evidence supports the neurofibroma stem cell hypothesis and a putative involvement of SKPs in the aetiopathogenesis of the disease, suggesting that SKPs could become a valuable tool for the in vitro study of NF1.

Susceptible stages in Schwann cells for NF1-associated plexiform neurofibroma development

Stem cells are under strict regulation by both intrinsic factors and the microenvironment. There is increasing evidence that many cancers initiate through acquisition of genetic mutations (loss of intrinsic control) in stem cells or their progenitors, followed by alterations of the surrounding microenvironment (loss of extrinsic control). In neurofibromatosis type 1 (NF1), deregulation of Ras signaling results in development of multiple neurofibromas, complex tumors of the peripheral nerves. Neurofibromas arise from the Schwann cell lineage following loss of function at the NF1 locus, which initiates a cascade of interactions with other cell types in the microenvironment and additional cell autonomous modifications. In this study, we sought to identify whether a temporal "window of opportunity" exists during which cells of the Schwann cell lineage can give rise to neurofibromas following loss of NF1. We showed that acute loss of NF1 in both embryonic and adult Schwann cells can lead to neurofibroma formation. However, the embryonic period when Schwann cell precursors and immature Schwann cells are most abundant coincides with enhanced susceptibility to plexiform neurofibroma tumorigenesis. This model has important implications for understanding early cellular events that dictate neurofibroma development, as well as for the development of novel therapies targeting these tumors.

Clinical features and pedigree report of a patient with giant neurofibroma

Neurofibromatosis (NF) is a genetically inherited, autosomal-dominant disease with an incidence of 1/3,000 in live births. There are two types of NF, NF 1 and NF 2, and NF 1 is the most common type. This study reports on the diagnosis, treatment, and related family medical history of a rare case with NF-1 in the right lower leg.

Totally Laparoscopic Gastrectomy for Gastric Cancer Associated with Recklinghausen's Disease

This paper documents the first case of gastric cancer associated with Recklinghausen's disease, which was successfully treated by a totally laparoscopic operation. A 67-year-old woman with Recklinghausen's disease was referred to this department to undergo surgical treatment for early gastric cancer. The physical examination showed multiple cutaneous neurofibromas throughout the body surface, which made an upper abdominal incision impossible. Laparoscopic surgery requiring only small incisions was well indicated, and a totally laparoscopic distal gastrectomy with lymph node dissection was performed. Billroth I reconstruction was done intra-abdominally using a delta-shaped anastomosis. The patient followed a satisfactory postoperative course with no complications. Since the totally laparoscopic gastrectomy has many advantages over open surgery, it should therefore be preferentially used as a less invasive treatment in the field of gastric cancer.

Cell of origin and microenvironment contribution for NF1-associated dermal neurofibromas

The tumor predisposition disorder neurofibromatosis type I (NF1) is one of the most common genetic disorders of the nervous system. It is caused by mutations in the Nf1 tumor-suppressor gene, which encodes a GTPase-activating protein (GAP) that negatively regulates p21-RAS. Development of malignant nerve tumors and neurofibromas occurs frequently in NF1. However, little is known about the molecular mechanisms mediating the initiation and progression of these complex tumors, or the identity of the specific cell type that gives rise to dermal or cutaneous neurofibromas. In this study, we identify a population of stem/progenitor cells residing in the dermis termed skin-derived precursors (SKPs) that, through loss of Nf1, form neurofibromas. We propose that SKPs, or their derivatives, are the cell of origin of dermal neurofibroma. We also provide evidence that additional signals from nonneoplastic cells in the tumor microenvironment play essential roles in neurofibromagenesis.

Ral overactivation in malignant peripheral nerve sheath tumors

Ras leads an important signaling pathway that is deregulated in neurofibromatosis type 1 and malignant peripheral nerve sheath tumor (MPNST). In this study, we show that overactivation of Ras and many of its downstream effectors occurred in only a fraction of MPNST cell lines. RalA, however, was overactivated in all MPNST cells and tumor samples compared to nontransformed Schwann cells. Silencing Ral or inhibiting it with a dominant-negative Ral (Ral S28N) caused a significant reduction in proliferation, invasiveness, and in vivo tumorigenicity of MPNST cells. Silencing Ral also reduced the expression of epithelial mesenchymal transition markers. Expression of the NF1-GTPase-related domain (NF1-GRD) diminished the levels of Ral activation, implicating a role for neurofibromin in regulating RalA activation. NF1-GRD treatment caused a significant decrease in proliferation, invasiveness, and cell cycle progression, but cell death increased. We propose Ral overactivation as a novel cell signaling abnormality in MPNST that leads to important biological outcomes with translational ramifications.

The Neurofibromatosis type 1:A dominantly inherited tumors-predisposing disorder

Neurofibromatosis type I (NF1) is a hereditary multisystem disease involving the skin and nervous system. It is the most common form of autosomal dominant phakomatoses with 100% penetrance but wide phenotypic variability. The NF1 gene is located on chromosome 17q11.2 and encodes for a tumour suppressor protein. Because affected individuals have an increased risk of tumor formation, this disorder is classified as inherited cancer syndrome. The risk of malignancies in NF1 affected patients is estimated to be 5–15% higher than in the general population. We reviewed clinical aspects and genetic mechanisms of tumorigenesis in NF1 affected patients.

Multipotent skin-derived precursors: adult neural crest-related precursors with therapeutic potential

We previously made the surprising finding that cultures of multipotent precursors can be grown from the dermis of neonatal and adult mammalian skin. These skin-derived precursors (SKPs) display multi-lineage differentiation potential, producing both neural and mesodermal progeny in vitro, and are an apparently novel precursor cell type that is distinct from other known precursors within the skin. In this review, we begin by placing these findings within the context of the rapidly evolving stem cell field. We then describe our recent efforts focused on understanding the developmental biology of SKPs, discussing the idea that SKPs are neural crest-related precursors that (i) migrate into the skin during embryogenesis, (ii) persist within a specific dermal niche, and (iii) play a key role in the normal physiology, and potentially pathology, of the skin. We conclude by highlighting some of the therapeutic implications and unresolved questions raised by these studies.

Detection of novel NF1 mutations and rapid mutation prescreening with Pyrosequencing

Neurofibromatosis type 1 (NF1) is caused by mutations in the neurofibromin (NF1) gene. Mutation analysis of NF1 is complicated by its large size, the lack of mutation hotspots, pseudogenes and frequent de novo mutations. Additionally, the search for NF1 mutations on the mRNA level is often hampered by nonsense-mediated mRNA decay (NMD) of the mutant allele. In this study we searched for mutations in a cohort of 38 patients and investigated the relationship between mutation type and allele-specific transcription from the wild-type versus mutant alleles. Quantification of relative mRNA transcript numbers was done by Pyrosequencing, a novel real-time sequencing method whose signals can be quantified very accurately. We identified 21 novel mutations comprising various mutation types. Pyrosequencing detected a definite relationship between allelic NF1 transcript imbalance due to NMD and mutation type in 24 of 29 patients who all carried frame-shift or nonsense mutations. NMD was absent in 5 patients with missense and silent mutations, as well as in 4 patients with splice-site mutations that did not disrupt the reading frame. Pyrosequencing was capable of detecting NMD even when the effects were only moderate. Diagnostic laboratories could thus exploit this effect for rapid prescreening for NF1 mutations as more than 60% of the mutations in this gene disrupt the reading frame and are prone to NMD.

Tumor microenvironment and neurofibromatosis type I: connecting the GAPs

The human disease von Recklinghausen's neurofibromatosis (Nf1) is one of the most common genetic disorders. It is caused by mutations in the NF1 tumor suppressor gene, which encodes a GTPase activating protein (GAP) that negatively regulates p21-RAS signaling. Dermal and plexiform neurofibromas as well as malignant peripheral nerve sheath tumors and other malignant tumors, are significant complications in Nf1. Neurofibromas are complex tumors and composed mainly of abnormal local cells including Schwann cells, endothelial cells, fibroblasts and additionally a large number of infiltrating inflammatory mast cells. Recent work has indicated a role for the microenvironment in plexiform neurofibroma genesis. The emerging evidence points to mast cells as crucial contributors to neurofibroma tumorigenesis. Therefore, further understanding of the molecular interactions between Schwann cells and their environment will provide tools to develop new therapies aimed at delaying or preventing tumor formation in Nf1 patients.

Stephen L. Gans Distinguished Overseas Lecture. The neural crest in pediatric surgery

AIM

This review highlights the relevance of the neural crest (NC) as a developmental control mechanism involved in several pediatric surgical conditions and the investigative interest of following some of its known signaling pathways.

METHODS

The participation of the NC in facial clefts, ear defects, branchial fistulae and cysts, heart outflow tract and aortic arch anomalies, pigmentary disorders, abnormal enteric innervation, neural tumors, hemangiomas, and vascular anomalies is briefly reviewed. Then, the literature on clinical and experimental esophageal atresia-tracheoesophageal fistula (EA-TEF) and congenital diaphragmatic hernia (CDH) is reviewed for the presence of associated NC defects. Finally, some of the molecular signaling pathways involved in both conditions (sonic hedgehog, Hox genes, and retinoids) are summarized.

RESULTS

The association of facial, cardiovascular, thymic, parathyroid, and C-cell defects together with anomalies of extrinsic and intrinsic esophageal innervation in babies and/or animals with both EA-TEF and CDH strongly supports the hypothesis that NC is involved in the pathogenesis of these malformative clusters. On the other hand, both EA-TEF and CDH are observed in mice mutant for genes involved in the previously mentioned signaling pathways.

CONCLUSIONS

The investigation of NC-related molecular pathogenic pathways involved in malformative associations like EA-TEF and CDH that are induced by chromosomal anomalies, chemical teratogens, and engineered mutations is a promising way of clarifying why and how some pediatric surgical conditions occur. Pediatric surgeons should be actively involved in these investigations.

Clinicopathologic and genetic analysis of siblings with NF1 and adult-onset gliomas

BACKGROUND

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant neurogenetic disorder characterized by neoplasms involving the nervous system which typically present in children. The development of intracranial tumors in adults with NF1 is uncommon and to our knowledge, siblings with adult onset gliomas have not been previously reported.

OBJECTIVE

To perform pathological, clinical and genetic analysis of an unusual family with NF1 and adult onset intracranial gliomas.

RESULTS

A 39-year-old woman presented with seizures and aphasia and was diagnosed with an intracerebral tumor. Although there was no family history, she met the accepted clinical criteria for NF1. A biopsy was performed and pathological examination revealed an anaplastic pleomorphic xanthoastrocytoma (PXA). In spite of therapy, she died from complications of tumor recurrence. Her 32-year-old sister developed headaches and was diagnosed with a glioma. Although she did not meet the accepted clinical criteria for NF1, given that she has a sibling with NF1 and a malignancy observed in this disorder, we hypothesize that she also has NF1. Our genetic analysis indicated a shared haplotype in these siblings who developed brain tumors but not in an unaffected sister suggesting that both carry the NF1 disease-producing allele. This haplotype was inherited from their unaffected father indicating a paternal origin of the spontaneous putative mutation in the NF1 gene in this family.

CONCLUSION

NF1 should be a diagnostic consideration when siblings develop intracranial brain tumors even when they develop in adults. Our study supports and extends other reports that broaden the clinical and pathological spectrum of manifestations that can occur in NF1 to include not only adult-onset gliomas but uncommon histological subtypes such as PXA.

Stimulus-evoked release of neuropeptides is enhanced in sensory neurons from mice with a heterozygous mutation of the Nf1 gene

Neurofibromatosis type I is a common autosomal dominant disease characterized by formation of multiple benign and malignant tumors. People with this disorder also experience chronic pain, which can be disabling. Neurofibrinomin, the protein product of the NF1 gene (neurofibromin gene (human)), is a guanosine triphosphate activating protein for p21(ras). Loss of NF1 results in an increase in activity of the p21(ras) transduction cascade. Because of the growing evidence suggesting involvement of downstream components of the p21(ras) transduction cascade in the sensitization of nociceptive sensory neurons, we examined the stimulus-evoked release of the neuropeptides, substance P and calcitonin gene-related peptide, from primary sensory neurons of mice with a mutation of the Nf1 gene (neurofibromin gene (mouse)) (Nf1+/-). Measuring immunoreactive substance P and immunoreactive calcitonin gene-related peptide by radioimmunoassay, we demonstrated that capsaicin-stimulated release of neuropeptides is three to five-fold higher in spinal cord slices from Nf1+/- mice than from wildtype mouse tissue. In addition, the potassium and capsaicin-stimulated release of immunoreactive calcitonin gene-related peptide from cultures of sensory neurons isolated from Nf1+/- mice was more than double that from cultures of wildtype neurons. Treatment of wildtype sensory neurons with nerve growth factor for 5-7 days mimicked the enhanced stimulus-evoked release observed from the Nf1+/- neurons. When nerve growth factor was removed 48 h before conducting release experiments, nerve growth factor-induced augmentation of immunoreactive calcitonin gene-related peptide release from Nf1+/- neurons was more pronounced than in Nf1+/- sensory neurons that were treated with nerve growth factor continuously for 5-7 days. Thus, sensory neurons from mice with a heterozygous mutation of the Nf1 gene that is analogous to the human disease neurofibromatosis type I, exhibit increased sensitivity to chemical stimulation. This augmented responsiveness may explain the abnormal pain sensations experienced by people with neurofibromatosis type I and suggests an important role for guanosine triphosphate activating proteins, in the regulation of nociceptive sensory neuron sensitization.

Activation of the neuregulin-1/ErbB signaling pathway promotes the proliferation of neoplastic Schwann cells in human malignant peripheral nerve sheath tumors

Patients with neurofibromatosis type 1 develop aggressive Schwann cell neoplasms known as malignant peripheral nerve sheath tumors (MPNSTs). Although tumor suppressor gene mutations play an important role in MPNST pathogenesis, it is likely that dysregulated signaling by as yet unidentified growth factors also contributes to the formation of these sarcomas. To test the hypothesis that neuregulin-1 (NRG-1) growth factors promote mitogenesis in MPNSTs, we examined the expression and action of NRG-1 in human MPNSTs and neurofibromas, the benign precursor lesions from which MPNSTs arise. Multiple alpha and beta transmembrane precursors from the class II and III NRG-1 subfamilies are present in both tumor types. Neoplastic Schwann cells within these neoplasms variably express the erbB kinases mediating NRG-1 responses (erbB2, erbB3 and/or erbB4). Human MPNST cell lines (Mash-1, YST-1, NMS-2 and NMS-2PC cells) similarly coexpress multiple NRG-1 isoforms and erbB receptors. These MPNST lines are NRG-1 responsive and demonstrate constitutive erbB phosphorylation. Treatment with PD168393 and PD158780, two structurally and mechanistically distinct erbB inhibitors, abolishes erbB phosphorylation and reduces DNA synthesis in these lines. These findings suggest that autocrine and/or paracrine NRG-1/erbB signaling promotes neoplastic Schwann cell proliferation and may be an important therapeutic target in neurofibromas and MPNSTs.

Sensory neurons from Nf1 haploinsufficient mice exhibit increased excitability

Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by tumor formation. People with NF1 also can experience more intense painful responses to stimuli, such as minor trauma, than normal. NF1 results from a heterozygous mutation of the NF1 gene, leading to decreased levels of neurofibromin, the protein product of the NF1 gene. Neurofibromin is a guanosine triphosphatase activating protein (GAP) for Ras and accelerates the conversion of active Ras-GTP to inactive Ras-GDP; therefore mutation of the NF1 gene frequently results in an increase in activity of the Ras transduction cascade. Using patch-clamp electrophysiological techniques, we examined the excitability of capsaicin-sensitive sensory neurons isolated from the dorsal root ganglia of adult mice with a heterozygous mutation of the Nf1 gene (Nf1+/-), analogous to the human mutation, in comparison to wildtype sensory neurons. Sensory neurons from adult Nf1+/- mice generated a more than twofold higher number of action potentials in response to a ramp of depolarizing current as wild-type neurons. Consistent with the greater number of action potentials, Nf1+/- neurons had lower firing thresholds, lower rheobase currents, and shorter firing latencies than wild-type neurons. Interestingly, nerve growth factor augmented the excitability of wild-type neurons in a concentration-related manner but did not further alter the excitability of the Nf1+/- sensory neurons. These data clearly suggest that GAPs, such as neurofibromin, can play a key role in the excitability of nociceptive sensory neurons. This increased excitability may explain the painful conditions experienced by people with NF1.

Pigment cell-related manifestations in neurofibromatosis type 1: an overview

Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disorder, affecting approximately 1 in 3500 individuals. The most commonly seen tumors in NF1 patients are the (sub)cutaneous neurofibromas. However, individuals with NF1 typically present in childhood with well-defined pigmentary defects, including cafe-au-lait macules (CALMs), intertriginous freckling and iris Lisch nodules. NF1 is considered a neurocristopathy, primarily affecting tissues derived from the neural crest. Since the pigment producing melanocyte originates in the neural crest, the presence of (hyper)pigmentary lesions in the NF1 phenotype because of changes in melanocyte cell growth and differentiation is to be expected. We want to discuss the pigmentary cutaneous manifestations of NF1 represented by CALMs and intertriginous freckles and the pigmentary non-cutaneous manifestations represented by iris Lisch nodules. Several hypotheses have been suggested in explaining the poorly understood etiopathogenesis of CALMs. Whether other pigmentary manifestations might share similar etiopathogenic mechanisms remains obscure. Additional attention will be drawn to a readily seen phenomenon in NF1: hyperpigmentation overlying (plexiform) neurofibromas, which could suggest common etiopathogenetic-environmental cues or mechanisms underlying CALMs and neurofibromas. Finally, we want to address the relationship between malignant melanoma and NF1.

Hypersensitive carotid sinus syndrome due to neurofibromatosis-1 and manifested by repeated episodes of syncope

A 28-year-old patient with neurofibromatosis-1 presented with syncope. The exam demonstrated a mass adjacent and inferior to the right occiput that extended to the posterior lateral right-sided neck. Initial invasive and noninvasive testing was negative. Imaging of her head and neck demonstrated a large neurofibroma enveloping her right carotid sinus without vessel occlusion or evidence of malignancy. An event recorder documented asystole. A pacemaker was implanted to avoid the surgical morbidity of removing the neck mass. The patient has since been free of syncope. We believe neurofibromatosis-1 should be included in the differential of syncope.

Tumor suppressor mutations and growth factor signaling in the pathogenesis of NF1-associated peripheral nerve sheath tumors. I. The role of tumor suppressor mutations

Patients with neurofibromatosis type 1 (NF1), a common autosomal dominant tumor predisposition syndrome, develop benign cutaneous, intraneural, and plexiform neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs), an aggressive form of Schwann cell neoplasm that frequently arises from plexiform neurofibromas. Impressive advances have been made in defining the molecular mechanisms responsible for neurofibroma and MPNST tumorigenesis, including the identification of key tumor suppressor gene mutations, an improved understanding of the functions of these tumor suppressors, and the production of transgenic mouse models in which tumor suppressor gene mutations predispose animals to the development of neurofibromas and MPNSTs. It has also become apparent that dysregulated growth factor signaling cooperates with tumor suppressor mutations to promote neurofibroma and MPNST tumorigenesis. In Part I of this two-part review, we consider findings demonstrating that Schwann cells are the primary neoplastic cell type in neurofibromas and MPNSTs and that specific tumor suppressor gene mutations promote the development of these tumors. In Part II, which will be published in a later issue, we will review evidence indicating that inappropriate growth factor signaling contributes to this process by stimulating the proliferation, survival, and migration of Schwann cells whose regulatory mechanisms have been crippled by a loss of tumor suppressor function.

Peripheral nerve tumors: management strategies and molecular insights

Because of its relative rarity and a wide variety of clinical manifestations, peripheral nerve tumors (PNTs) often present to specialists from widely different disciplines, thus often resulting in delayed diagnosis and a non-cohesive pattern of management. Critical appraisal of the history and physical examination followed by radiological investigations, by experienced medical personnel, ultimately suggests that the extremity mass is perhaps a PNT, rather than the wide variety and more common soft tissue tumors. Included in this appraisal is a search for a pre-disposition syndrome, the most common of which are neurofibromatosis-1 and -2 (NF1, NF2) and schwannomatosis, which may require life-long careful follow up. Intra-operative and post-operative management decisions in a multidisciplinary manner with knowledge of the biological, pathological and clinical behavior of the PNT, is of utmost importance. In the context of pre-disposition syndromes, where multiple tumors may exist along with other nervous system lesions, molecular biological insights and hopefully the biological therapies that stem from this knowledge are of interest. In this article the spectrum of PNTs and their management protocols, including the algorithm for treatment of malignant PNTs advocated by our institute, are presented and currently available genetic insights and probable role of experimental therapies are briefly reviewed.

Glioneuronal tumours in neurofibromatosis type 1: MRI-pathological study

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

Correction of intraoperative coagulopathy in a patient with neurofibromatosis type I with intravenous desmopressin (DDAVP)

A patient with the genetic condition neurofibromatosis type I and no known coagulopathy undergoing cesarean delivery, had diffuse uterine and surgical site bleeding that was not correctable by oxytocin, methylergonovine and PGF2 alpha. Despite good uterine tone, hemorrhage continued from the uterus and the surrounding tissues, persisting even after surgical ligation of the uterine arteries. With no change in her condition, which was behaving clinically as a coagulopathy, an infusion of desmopressin acetate (DDAVP) was begun. The patient's bleeding promptly resolved shortly after infusion of this agent. A review of relevant literature suggests that platelet reactivity of patients with neurofibromatosis type 1 is attenuated in some in vitro conditions. Thus, there may be some theoretical basis for using DDAVP in patients with neurofibromatosis type 1 who have bleeding problems with no other known source, such as in the case presented here.

Genetics of Neurofibromatosis 1-Associated Peripheral Nerve Sheath Tumors

Neurofibromatosis 1, an inherited disorder that affects 1/3500 individuals worldwide, predisposes to the development of benign and malignant peripheral nerve sheath tumors. The disorder results from inactivation of one of the NFI genes. The second NFI gene is typically inactivated in Schwann cells during tumor formation. This article reviews the different types of genetic alterations in NFI in both constitutional and tumor tissues and genetic alterations of other genes that may affect tumorigenesis. These studies have provided insight into the genetic basis of both the variable expression of the disorder and of benign and malignant peripheral nerve sheath tumorigenesis.

Neurofibromatosis--Noonan's syndrome with associated rhabdomyosarcoma of the urinary bladder in an infant: case report

Neurofibromatosis 1 is an autosomal dominant disorder. Noonan's syndrome is known to be associated with neurofibromatoses. Patients with neurofibromatosis are predisposed to developing malignant tumors. The relationship between the genetic changes in the neurofibromin gene and mechanisms associated with tumor development in neurofibromatosis has been investigated. A non-sense mutation C2446T --> R816X of the neurofibromin gene has been detected in some patients with the neurofibromatosis 1-Noonan's syndrome phenotype. We describe a case of an infant with the overlapping features of neurofibromatosis 1 and Noonan's syndrome who presented with rhabdomyosarcoma of the urinary bladder. The genetic analysis of our patient revealed neither mutation in the neurofibromatosis 1-guanosine triphosphatase-activating protein-related domain nor the R816X nonsense mutation. The phenotypic and genotypic features of neurofibromatosis, Noonan's syndrome, and cases with the overlapping features of both syndromes have been reviewed. The presentation of our case underlines the importance of careful examination for the clinical features of neurofibromatosis and phenotypic traits of associated diseases, especially in patients with malignant tumors.

Genetic insights into familial cancers-- update and recent discoveries

While the vast majority of cancers are believed to occur sporadically, most forms of cancer, both adult and paediatric, have a hereditary equivalent. In the case of adult malignancies, these include hereditary breast and ovarian cancer and syndromes such as the multiple endocrine neoplasias types 1 and 2 characterised by specific tumours of the endocrine gland system. In the case of paediatric malignancies, these include syndromes such as retinoblastoma and Wilms tumour. In a little over a single decade, we have seen a tremendous increase in the knowledge of the primary genetic basis of many of the familial cancer syndromes. The majority of familial syndromes are inherited as autosomal dominant traits including hereditary colon cancer and familial malignant melanoma, however, the genetics behind autosomal recessive disorders such as Bloom syndrome and Fanconi anaemia are also being elucidated. A third mode of inheritance less well understood in the setting of familial cancer is that of imprinting recently observed in a subset of families with inherited paraganglioma. In this review, we discuss 31 genes inherited in an autosomal dominant manner associated with 20 familial cancer syndromes. Genes inherited in an autosomal recessive manner linked to familial cancer syndromes are also discussed. The identification of genes associated with familial cancer syndromes has in some families enabled a 'molecular diagnosis' that complements clinical assessment and allows directed cancer surveillance for those individuals determined to be at-risk of disease.