Upregulation of tumor suppressor protein neurofibromin in normal human wound healing and in vitro evidence for platelet derived growth factor (PDGF) and transforming growth factor-beta1 (TGF-beta1) elicited increase in neurofibromin mRNA steady-state levels in dermal fibroblasts

Clinical Findings and Outcome in 30 Dogs with Presumptive or Confirmed Nerve Sheath Tumors

Nerve sheath tumors (NSTs) are well-recognized primary nervous system tumors, but there is relatively limited information in dogs including comparison of NSTs in different anatomical locations. This retrospective study describes the clinical features and outcomes in a group of dogs with NSTs affecting the cranial nerves or spinal nerves. Thirty dogs were included, 25 with a presumptive diagnosis and five confirmed by histopathologic analysis. Seven dogs also had cytology of tumor samples, which were supportive of the NST diagnosis in four. Eight dogs had cranial nerve-associated NSTs, with six involving the trigeminal nerve. Twenty-two dogs had spinal nerve-associated NSTs including 13 invading the spinal canal and nine peripheral to the spinal canal, with the majority affecting nerves or nerve roots of the brachial plexus. The prognosis was poor, with dogs being euthanized eventually because of disease progression. Among dogs alive 1 week after diagnosis, the median survival time was 4 months but ranged from 2 weeks to >2 years. While there was a broad overlap between NST locations, survival was generally longer for dogs without spinal canal or intracranial involvement. The results expand available information on NSTs in dogs but should be interpreted with caution given the small number of dogs with a definitive diagnosis. Further investigation is warranted to determine how tumor location, invasiveness, and treatments pursued impact outcome.

Altered actin dynamics is possibly implicated in the inhibition of mechanical stimulation-induced dermal fibroblast differentiation into myofibroblasts

The formation of hypertrophic scars and keloids is strongly associated with mechanical stimulation, and myofibroblasts are known to play a major role in abnormal scar formation. Wounds in patients with neurofibromatosis type 1 (NF1) become inconspicuous and lack the tendency to form abnormal scars. We hypothesized that there would be a unique response to mechanical stimulation and subsequent scar formation in NF1. To test this hypothesis, we investigated the molecular mechanisms of differentiation into myofibroblasts in NF1-derived fibroblasts and neurofibromin-depleted fibroblasts and examined actin dynamics, which is involved in fibroblast differentiation, with a focus on the pathway linking LIMK2/cofilin to actin dynamics. In normal fibroblasts, expression of α-smooth muscle actin (α-SMA), a marker of myofibroblasts, significantly increased after mechanical stimulation, whereas in NF1-derived and neurofibromin-depleted fibroblasts, α-SMA expression did not change. Phosphorylation of cofilin and subsequent actin polymerization did not increase in NF1-derived and neurofibromin-depleted fibroblasts after mechanical stimulation. Finally, in normal fibroblasts treated with Jasplakinolide, an actin stabilizer, α-SMA expression did not change after mechanical stimulation. Therefore, when neurofibromin was dysfunctional or depleted, subsequent actin polymerization did not occur in response to mechanical stimulation, which may have led to the unchanged expression of α-SMA. We believe this molecular pathway can be a potential therapeutic target for the treatment of abnormal scars.

Transcriptomic Profiling of Human Limbus-Derived Stromal/Mesenchymal Stem Cells-Novel Mechanistic Insights into the Pathways Involved in Corneal Wound Healing

Limbus-derived stromal/mesenchymal stem cells (LMSCs) are vital for corneal homeostasis and wound healing. However, despite multiple pre-clinical and clinical studies reporting the potency of LMSCs in avoiding inflammation and scarring during corneal wound healing, the molecular basis for the ability of LMSCs remains unknown. This study aimed to uncover the factors and pathways involved in LMSC-mediated corneal wound healing by employing RNA-Sequencing (RNA-Seq) in human LMSCs for the first time. We characterized the cultured LMSCs at the stages of initiation (LMSC−P0) and pure population (LMSC−P3) and subjected them to RNA-Seq to identify the differentially expressed genes (DEGs) in comparison to native limbus and cornea, and scleral tissues. Of the 28,000 genes detected, 7800 DEGs were subjected to pathway-specific enrichment Gene Ontology (GO) analysis. These DEGs were involved in Wnt, TGF-β signaling pathways, and 16 other biological processes, including apoptosis, cell motility, tissue remodeling, and stem cell maintenance, etc. Two hundred fifty-four genes were related to wound healing pathways. COL5A1 (11.81 ± 0.48) and TIMP1 (20.44 ± 0.94) genes were exclusively up-regulated in LMSC−P3. Our findings provide new insights involved in LMSC-mediated corneal wound healing.

Trabecular Bone Score (TBS) and Bone Metabolism in Patients Affected with Type 1 Neurofibromatosis (NF1)

In patients with neurofibromatosis type 1 (NF1), decreased bone mineral density (BMD) and low levels of 25-hydroxy vitamin D3 (25OHD) have been reported. Recently, the trabecular bone score (TBS) measurement has been proposed as index of bone microarchitecture and fracture risk. In 74 NF1 patients (48 females, 26 males, age 41 ± 12), we measured TBS and investigated clinical stage, lifestyle, vitamin D, serum bone turnover markers, vertebral and femoral BMD. A homogenous cohort of 61 healthy subjects was used as control group. TBS was lower in NF1 patients (1.266 ± 0.113 vs. 1.346 ± 0.105) without differences between sexes. No correlations with 25OHD, low exercise, low calcium intake, reduced sun exposure, and number of skin neurofibromas were observed. As expected, hypovitaminosis D was common (98.6%), as well as BMD reduction in hip and spine sites: In NF1 patients, bone texture evaluated by TBS was low in both sexes without any correlation with clinical or metabolic parameters, suggesting a direct role of the fibromin mutation.

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.

Peripheral neural sheath tumors (PNST)--what a radiologist should know

Peripheral neural sheath tumors (PNST) are rare and the common goal of management focuses on eliminating pain and maximizing function of the affected nerve. Therefore preoperative assessment of the specific morphological behaviour of such tumors regarding the nerves internal architecture is of utmost importance. PNSTs may affect one or more fascicles of a peripheral nerve resulting in a significant functional loss after resection and the necessity of functional reconstruction in one step. Enhancement of preoperative information should also address the biological behaviour of the tumor regarding its dignity and the resulting implications on amount of radical resection, additional treatment and prognosis. Since high-resolution techniques promise more and more detail resolution in many fields of imaging, delineation of intra- and extraneural processes as well as biological informations shall lead towards a well prepared and foreseeable image-guided treatment of PNSTs.

Clinico-pathological and biomolecular findings in Italian patients with multiple cutaneous neurofibromas

Background

Neurofibroma occurs as isolated or multiple lesions frequently associated with neurofibromatosis type 1 (NF1), a common autosomal dominant disorder affecting 1 in 3500 individuals. It is caused by mutations in the NF1 gene, which comprises 60 exons and is located on chromosome 17q11.2. NF1 is a fully penetrant gene exhibiting a mutation rate some 10-fold higher compared with most other disease genes. As a consequence, a high number of cases (up to 50%) are sporadic. Mutation detection is complex due to the large size of the NF1 gene, the presence of pseudogenes and the great variety of lesions.

Methods

110 patients with at least two neurofibroma lesions recorded in the files of the Pathology Department of the University of Modena during the period 1999-2010, were included in this study. Through interviews and examination of clinical charts, pedigrees were drawn for all patients who were affected by at least two neurofibromas. We attempted to delineate the clinical features of NF1 and the mutational spectrum in the cohort of 11 NF1 families identified. For each proband, the whole coding sequence and all splice sites were studied for mutations, either by the protein truncation test (PTT), or, more frequently, by denaturing high performance liquid chromatography (DHPLC). Two GIST tumors of NF1 patients were tested for somatic NF1 mutations.

Results

NF1 germline mutations were identified in 7 (68%) patients. A novel mutation, c.3457_3460delCTCA in exon 20, was detected in two unrelated patients and was associated with different clinical features. No NF1 somatic mutations were detected in the GIST tumors. A wide phenotypic and genotypic variability was registered, both in the spectrum of skin lesions and visceral neoplasms, even among members of the same family who had different clinical manifestations. A proclivity to multiple tumors arising in the same subject, and a higher tumor burden per family were the most relevant findings observed in patients affected with the NF1 mutation.

Conclusions

We report a novel NF1 mutation and we contribute data for the refinement of the NF1 genotype-phenotype spectrum.

The pathoetiology of neurofibromatosis 1

Although a mutation in the NF1 gene is the only factor required to initiate the neurocutaneous-skeletal neurofibromatosis 1 (NF1) syndrome, the pathoetiology of the multiple manifestations of this disease in different organ systems seems increasingly complex. The wide spectrum of different clinical phenotypes and their development, severity, and prognosis seem to result from the cross talk between numerous cell types, cell signaling networks, and cell-extracellular matrix interactions. The bi-allelic inactivation of the NF1 gene through a "second hit" seems to be of crucial importance to the development of certain manifestations, such as neurofibromas, café-au-lait macules, and glomus tumors. In each case, the second hit involves only one cell type, which is subsequently clonally expanded in a discrete lesion. Neurofibromas, which are emphasized in this review, and cutaneous neurofibromas in particular, are known to contain a subpopulation of NF1-diploinsufficient Schwann cells and a variety of NF1-haploinsufficient cell types. A recent study identified a multipotent precursor cell population with an NF1(+/-) genotype that resides in human cutaneous neurofibromas and that has been suggested to play a role in their pathogenesis.

Significance of expression of metastasis-related factors uPA, MMP-2, MMP-9 and TGF-β1 in gastrointestinal stromal tumors

AIM: To investigate the significance of expression of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and transforming growth factor-β1 (TGF-β1) in gastrointestinal stromal tumors (GISTs).

METHODS: The expression of uPA, MMP-2, MMP-9 and TGF-β1 mRNAs and proteins in 124 GISTs specimens was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively.

RESULTS: In gastrointestinal stromal tumors, the mRNA expression of uPA, MMP-2, MMP-9 and TGF-β1 is closely correlated with tumor stage (NIH classification), mucosal invasion and lymphatic metastasis. The mRNA expression levels of uPA, MMP-2, MMP-9 and TGF-β1 were up-regulated with increasing tumor stage, showing significant differences among low-, moderate- and high-risk GISTs. The positive rates of uPA, MMP-2, MMP-9 and TGF-β1 mRNA expression was not correlated with age, sex and histological type. Similar results were obtained for the expression of uPA, MMP-2, MMP-9 and TGF-β1 proteins in GISTs. The expression of uPA protein is positively correlated with that of TGF-β1, MMP-2 and MMP-9 (r = 0.356, 0.323 and 0.346, respectively).

CONCLUSION: The positive activation of TGF-β1 in GISTs possibly up-regulates uPA expression which in turn activates MMP-2 and MMP-9. The activation of MMP-2 and MMP-9 may lead to the degradation of extracellular matrix degradation and promote tumor invasion and metastasis.

Role of integrins and focal adhesion kinase in the orientation of dermal fibroblasts exposed to cyclic strain

Stretch is applied to skin under normal physiological conditions, for example pregnancy, or artificially using soft tissue expanders. Because cells are known to orient in response to the application of mechanical forces, the current studies were carried out to assess the effects of stretch on dermal fibroblast orientation and cell signalling. Dermal fibroblasts were seeded onto collagen-coated flexible membranes and grown to 70-80% confluence. Membranes were then deformed at 10 cycles per minute by the application of 135 mmHg subatmospheric pressure. This corresponded to strain levels of 0-24% from the centre to extremity of the flexible membrane. We show that a minimum of 15% cell stretch is required to significantly stimulate the fibroblast orientation response. focal adhesion kinase (FAK), p38 and Rho were activated in fibroblasts exposed to cyclic stretch and incubation of cells with anti-integrin beta1 before the application of stretch abrogated fibroblast orientation, as well as FAK, p38 and Rho activation. Fibroblast orientation in response to cyclic stretch is mediated at least in part by integrin beta1 through phosphorylation of FAK, p38 and activation of Rho.

Class III beta-tubulin is a component of the mitotic spindle in multiple cell types

The findings of this study show that Class III beta-tubulin is a component of the mitotic spindle in multiple cell types. Class III beta-tubulin has been widely used as a neuron-specific marker, but it has been detected also in association with breast and pancreatic cancers. In this study, we describe a novel finding of Class III beta-tubulin in a subpopulation of cells in malignant peripheral nerve sheath tumor. The findings of this study also show that Class III beta-tubulin is expressed by normal mesenchymal and epithelial cells (fibroblasts and keratinocytes), two transitional cell carcinoma cell lines, and neurofibroma Schwann cells, as shown by immunolabeling and Western transfer analysis using two different Tuj-1 antibodies that are specific for Class III beta-tubulin. The corresponding mRNA was detected using RT-PCR and whole human genome microarrays. Both antibodies localized Class III beta-tubulin to the mitotic spindle and showed a colocalization with alpha-tubulin. The immunoreaction became visible in early prophase, and the most intense immunoreaction was detected during metaphase and anaphase when microtubules were connected to the kinetochores on chromosomes. Class III beta-tubulin-specific immunoreaction lasted to the point when the midbody of cytokinesis became detectable.

Evidence of increased bone resorption in neurofibromatosis type 1 using urinary pyridinium crosslink analysis

Although neurofibromatosis type 1 (NF1) is a neurocutaneous disorder, skeletal abnormalities such as long-bone dysplasia, scoliosis, sphenoid wing dysplasia, and osteopenia are observed. To investigate the role of bone resorption as a mechanism for the bony abnormalities, we selected urinary pyridinium crosslinks (collagen degradation products excreted in urine) as a measure of bone resorption in NF1. Bone resorption was evaluated by quantitative assessment of the urinary excretion of pyridinium crosslinks [pyridinoline (Pyd) and deoxypyridinoline (Dpd)]. Total (free plus peptide-bound) pyridinium crosslinks from the first morning urines from 59 NF1 children (ages 5-19) were extracted and analyzed (17 children with a localized skeletal dysplasia, and 42 without). The data were compared with a healthy reference population without NF1 (n = 99). Multivariate analyses, controlling for age showed statistically significant increases for Dpd (p < 0.001) and the Dpd/Pyd ratio (p < 0.001) in NF1 individuals with and without a skeletal dysplasia. NF1 children have an increase in the urinary excretion of pyridinium crosslinks, reflecting increased bone resorption. The effects of NF1 haploinsufficiency likely contribute to abnormal bone remodeling, either directly or indirectly by aberrant Ras signaling, potentially predisposing NF1 individuals to localized skeletal defects.

RasGAPs: a crucial regulator of extracellular stimuli for homeostasis of cellular functions

Ras and its GTPase activating proteins (GAPs) are among the crucial regulators of extracelluar ligands. Information about these regulators has been elucidated during the course of studies in signal transduction over the last two decades. RasGAPs such as p120GAP and neurofibromin have been studied extensively for their roles as either "negative" regulators or effectors of Ras. Accumulating evidence suggests that these molecules are crucial regulators of extracellular stimuli that serve to maintain the homeostasis of cellular functions. This compendium highlights cellular functions of RasGAPs and their signaling characteristics from the viewpoint of homeostasis, including our recent finding of the phenotype of R-RasGAP mutant mice whose GAP activity is down-regulated.

Radiation-induced gene expression in human subcutaneous fibroblasts is predictive of radiation-induced fibrosis

BACKGROUND AND PURPOSE

Breast cancer patients show a large variation in normal tissue reactions after ionizing radiation (IR) therapy. One of the most common long-term adverse effects of ionizing radiotherapy is radiation-induced fibrosis (RIF), and several attempts have been made over the last years to develop predictive assays for RIF. Our aim was to identify basal and radiation-induced transcriptional profiles in fibroblasts from breast cancer patients that might be related to the individual risk of RIF in these patients.

MATERIALS AND METHODS

Fibroblast cell lines from 31 individuals with variable risk of RIF (grouped into five classes from low to high risk) were irradiated with two different schemes: 1 x 3.5 Gy with RNA isolated 2 and 24h after irradiation, and a fractionated scheme with 3 x 3.5 Gy in intervals of 24h with RNA isolated 2h after the last dose. RNA was also isolated from non-treated fibroblasts. Transcriptional differences in basal and radiation-induced gene expression profiles were investigated using 15K cDNA microarrays, and results analyzed by both SAM and PAM.

RESULTS

Sixty differentially expressed genes were identified by applying SAM on 10 patients with the highest risk of RIF and the four patients with the lowest risk of RIF after the fractionated scheme. The genes were associated with known functions in processes like apoptosis, extracellular matrix remodelling/cell adhesion, proliferation and ROS scavenging. A minimum set of 18 genes were identified that could differentiate high risk from low risk-patients after the fractionated scheme.

CONCLUSIONS

The classifier of 18 genes may provide basis for a predictive assay for normal tissue reactions after radiotherapy, and provide new insight into the molecular mechanisms of RIF.

Hereditary neuroendocrine tumors of the gastroenteropancreatic system

Approximately 5-10% of neuroendocrine tumors (NETs) of the gastroenteropancreatic system (GEP) have a hereditary background. The known inherited syndromes include multiple endocrine neoplasia type 1, neurofibromatosis type 1, von Hippel-Lindau disease, and the tuberous sclerosis complex. This review discusses for each of these syndromes the: (1) involved genes and specific types of mutations, (2) disease prevalence and penetrance, (3) affected neuroendocrine tissues and related clinical syndromes, (4) special morphological features of NETs and their putative precursor lesions. In addition, GEP-NETs clustering in individual families or associated with other malignancies without known genetic background are discussed.

Neurofibromin: a general outlook

Neurofibromin is a cytoplasmic protein that is predominantly expressed in neurons, Schwann cells, oligodendrocytes, astrocytes and leukocytes. It is encoded by the gene NF1, located on chromosome 17, at q11.2, and has different biochemical functions, including association to microtubules and participation in several signaling pathways. Alterations in this protein are responsible for a phacomatosis named neurofibromatosis type 1.

NF1 gene expression in mouse fracture healing and in experimental rat pseudarthrosis

Neurofibromatosis type 1 (NF1) is an inherited disease with an incidence of about 1:3000 worldwide. Approximately half of all patients with NF1 present osseous manifestations, which can vary from mild to severely debilitating changes such as congenital pseudarthrosis. In the present study, fracture healing of mouse tibia was followed and specimens were collected 5, 9, 14, and 22 days postoperatively. Experimental pseudarthrosis of rat was followed up to 15 weeks postoperatively. In situ hybridization and immunohistochemistry were used to demonstrate expression of NF1 tumor suppressor and phosphorylated p44/42 mitogen-activated protein kinase (MAPK), an indicator of the Ras-MAPK pathway. The results showed that ossified callus was formed in mouse fracture 22 days after the operation. The final outcome of rat pseudarthrosis was detected 9 weeks after the operation, presenting abundant cartilaginous callus at the pseudarthrosis. NF1 gene expression was noted in the maturing and in the hypertrophic cartilages during normal mouse fracture healing, and in rat pseudarthrosis. Phosphorylated p44/42 MAPK was detected in a subpopulation of the hypertrophic chondrocytes in both models. Furthermore, positive labeling for NF1 mRNA and protein was detected in endothelium in both the pseudarthrosis and in the fracture. In conclusion, NF1 gene expression and function are needed for normal fracture healing, possibly restraining excessive Ras-MAPK pathway activation.

Distinctive clinical presentation of a NF-1 patient with loss of heterozygosity of PTCH in his epithelial tumors

Although patients with neurofibromatosis (NF) have an increased incidence of tumors, there is only one study that suggests that NF1 patients may have an increased risk for epithelial malignancies. We present a patient with known NF1 who had developed multiple epithelial tumors since early in his life. All but one of these tumors were morphologically most consistent with trichoepitheliomas. Loss of heterozygosity (LOH) for Patched 1 gene (PTCH) was demonstrated within two of the trichoepitheloma-like tumors and one tumor diagnosed as basal cell carcinoma, and the patient was show to have a PTCH gene deletion. To our knowledge, a patient presenting with both NF1 and multiple trichoepitheliomas (MTE) has not previously been reported. The dysregulation in cellular proliferation and signaling induced by decreased NF1 along with the PTCH gene mutation may explain the pattern of immunohistochemical staining within these tumors, and the rare association of NF1 with epithelial neoplasms.

NF1 tumor suppressor in epidermal wound healing with special focus on wound healing in patients with type 1 neurofibromatosis

Type 1 neurofibromatosis syndrome (NF1) has been linked with mutations of the NF1 gene which encodes tumor suppressor neurofibromin, a regulator of Ras-MAPK signaling. In human epidermis, keratinocytes express NF1 tumor suppressor and it may have a distinctive function in these cells during wound healing, such as regulating Ras activity. NF1 expression was first studied during the epidermal wound healing using suction blister method. NF1 gene expression increased both in hypertrophic and migrating zones of the healing epidermis, and also in dermal fibroblasts underneath the injury. This prompted us to study epidermal wound healing in NF1 patients. Wound healing efficiency was evaluated 4 days after blister induction by clinical, physiological and histological methods. Epidermal wound healing was equally effective in NF1 patients and healthy controls. In addition, dermal wound healing appears to function normally in NF1 patients based on retrospective and follow-up study of biopsy scars. Furthermore, the healing wounds were analyzed immunohistochemically for cell proliferation rate and Ras-MAPK activity. Neither epidermal keratinocytes nor dermal fibroblasts showed difference in the cell proliferation rate or Ras-MAPK activity between NF1 patients and controls. Interestingly, NF1 patients displayed increased cell proliferation rate and Ras-MAPK activity in periarteriolar tissue underneath the wound. The results of the study suggest that epidermal wound healing is not markedly altered in NF1 patients. Furthermore, NF1 protein seems not to have an important function as a Ras-MAPK regulator in epidermal keratinocytes or dermal fibroblasts but instead appears to be regulator of Ras-MAPK signaling in vascular tissues.

A series of 397 peripheral neural sheath tumors: 30-year experience at Louisiana State University Health Sciences Center

OBJECT

This is a retrospective review of 397 benign and malignant peripheral neural sheath tumors (PNSTs) that were surgically treated between 1969 and 1999 at the Louisiana State University Health Sciences Center (LSUHSC). The surgical techniques and adjunctive treatments are presented, the tumors are classified with respect to type and prevalence at each neuroanatomical location, and the management of malignant PNSTs is reviewed.

METHODS

There were 361 benign PNSTs (91%). One hundred forty-one benign lesions were brachial plexus tumors: 54 schwannomas (38%) and 87 neurofibromas (62%), of which 55 (63%) were solitary neurofibromas and 32 (37%) were neurofibromatosis Type 1 (NF1)-associated neurofibromas. Among the brachial plexus lesions supraclavicular tumors predominated with 37 (69%) of 54 schwannomas; 34 (62%) of 55 solitary neurofibromas; and 19 (59%) of 32 NF1-associated neurofibromas. One hundred ten upper-extremity benign PNSTs consisted of 32 schwannomas (29%) and 78 neurofibromas (71%), of which 45 (58%) were sporadic neurofibromas and 33 (42%) were NF1-associated neurofibromas. Twenty-five benign PNSTs were removed from the pelvic plexus. Lower-extremity PNSTs included 32 schwannomas (38%) and 53 neurofibromas (62%), of which 31 were solitary neurofibromas and 22 were NF1-associated neurofibromas. There were 36 malignant PNSTs: 28 neurogenic sarcomas and eight other sarcomas (fibro-, spindle cell, synovial, and perineurial sarcomas).

CONCLUSIONS

The majority of tumors were benign PNSTs from the brachial plexus region. Most of the benign PNSTs in all locations were neurofibromas, with sporadic neurofibromas predominating. Similar numbers of schwannomas were found in the upper and lower extremities, whereas neurofibromas were more prevalent in the upper extremities. Despite aggressive limb-ablation or limb-sparing surgery plus adjunctive therapy, malignant PNSTs continue to be associated with high morbidity and mortality rates.

The effect of extracellular calcium concentration on calcium-mediated cell signaling in NF1 tumor suppressor-deficient keratinocytes

Capacitative calcium entry and calcium wave propagation were studied in keratinocytes from healthy volunteers and patients with type 1 neurofibromatosis (NF1) in calcium-depleted and in low calcium culture medium. In previous studies, we found evidence that mutations of the NF1 tumor suppressor gene can lead to altered calcium-mediated cell signaling in keratinocytes cultured in the presence of a high extracellular calcium concentration. The present study demonstrated that the differences between normal and NF1 keratinocytes were dependent on extracellular calcium concentration. Specifically, when keratinocytes were exposed to thapsigargin under calcium-depleted culture conditions the subsequent increase in free intracellular calcium concentration was moderate in NF1 keratinocytes compared to controls. The finding indicates lowered endoplasmic calcium stores in NF1 which may also in part explain the reduced activation signal for capacitative calcium influx and the wound-induced intracellular Ca2+ transient observed in NF1 keratinocytes maintained in culture medium containing 0.05 mM calcium. The differences between control and NF1 keratinocytes were most pronounced when the cells were cultured in the presence of a high (1.8 mM) calcium concentration. Since elevated extracellular calcium levels induce keratinocytes to form cellular contacts and lead to terminal differentiation, markedly aberrant responses of NF1 keratinocytes in the presence of a high calcium concentration may help to explain previous findings on impaired formation of cellular junctions and differentiation in NF1 deficient cells.

Neurofibromatosis type 1 tumour suppressor gene expression is deficient in psoriatic skin in vivo and in vitro: a potential link to increased Ras activity

BACKGROUND

Neurofibromatosis type 1 (NF1) protein (neurofibromin) accelerates the inactivation of Ras-GTP in various cell types. Somatic mutations of the NF1 gene may lead to malignant transformation and uncontrolled proliferation. We have previously shown that NF1 protein expression is downregulated in psoriasis in vivo.

OBJECTIVES

To study the functional expression and distribution of NF1 mRNA and protein in vivo and in psoriatic and normal keratinocyte cultures.

METHODS

Immunohistochemistry and in situ hybridization were used to study NF1 gene and protein expression in psoriasis in vivo. Furthermore, Northern and in situ hybridizations, immunoblot and localization analyses were utilized to study NF1 mRNA and protein in vitro in keratinocyte cultures.

RESULTS

NF1 tumour suppressor gene expression was reduced in lesional psoriatic skin compared with perilesional and normal skin in vivo. The in vitro results showed that the levels of NF1 mRNA and protein were reduced in cultured psoriatic keratinocytes during cellular differentiation even after multiple passaging of the cells. Moreover, cultured nonlesional psoriatic keratinocytes were almost equally defective as lesional cells with respect to NF1 expression.

CONCLUSIONS

Our findings demonstrate that psoriatic keratinocytes maintain an altered phenotype and gene expression profile even when isolated from interaction with lymphocytes and fibroblasts, which are known to increase proliferation of keratinocytes. As NF1 protein is regarded as a Ras proto-oncogene regulator, the aberrant expression and distribution of NF1 protein and mRNA found in the present study may be causative to the previously described increased activation of Ras in psoriatic lesions, and relate to altered cellular behaviour.

NF1 modulates the effects of ras oncogenes: Evidence of other NF1 function besides its GAP activity

Neurofibromin (NF1) (the product of Nf1 gene) is a large cytosolic protein known as a negative regulator of Ras. A fragment of some 400 residues located at the center of the NF1 GAP-Related Domain (NF1-GRD) has strong identity with other molecules of the GAP family, which comprises, among others, the mammalian proteins NF1 and p120GAP, and the yeast proteins IRA1 and IRA2. GAP family members are known by their ability to promote the GTPase activity of Ras proteins, facilitating the transit of those proteins to their inactive state. Recent findings (Tong et al., 2002, Nat Neurosci 5:95-96) indicate that NF1 may be involved in the regulation of adenyl cyclase activity. Our results show that NF1-GRD cooperates with Ras in the anchorage-independent growth capacity of Ras-expressing fibroblasts, without affecting: (i) their ability to grow in low serum, (ii) their cellular adhesion capability, or (iii) the expression of key proteins involved in cell-cell and cell-matrix interactions. On the other hand, NF1 overexpression induces an increase in the expression levels of the focal adhesion kinase (FAK), and specific changes in the activation status of the mitogen-activated protein kinases (MAPKs). These results suggest the existence of a Ras-independent NF1-dependent pathway able to modify the levels of expression of FAK and the levels of activation of MAPKs. Because FAK and many proteins recently found to bind NF1 have a role in the cytoskeleton, this pathway may involve rearrangement of cytoskeletal components that facilitate anchorage independence.

Bone development in neurofibromatosis 1

Bony abnormalities are common findings in cases of neurofibromatosis 1. We might hypothesize that neurofibromin, the protein encoded by the neurofibromatosis 1 gene, plays important roles in bone development. Loss of function of oligodendrocyte-myelin glycoprotein gene and increased activity of ras p21 might increase the level of c-fos proto-oncogene in bones with formation of fibrous dysplasia-like tissue. Also, increased ras p21 might disturb collagen I synthesis by osteoblasts. Moreover, increased ras activity might increase the mitogenic signals to the nucleus through mitogen-activated protein kinase (MAPK) and disturb the level of the transcription factor core-binding factor alpha(1) (Cbfa1). Abnormal fibrous tissue and neurofibromas formed at the site of pseudarthrosis might represent abnormal response of periosteal fibroblasts for injury, an effect simulating the response of skin fibroblasts in neurofibromatosis 1 to injury.

Wound healing effects of porcine placental extracts on rats with thermal injury

BACKGROUND

Placental extracts have been used as Chinese folk medicines to accelerate wound healing. However, the molecular mechanism of placental extracts on wound healing has not been identified. It is known that fibroblast growth factors (FGF) and transforming growth factors (TGF) are two key factors involved in wound healing.

OBJECTIVES

To determine the molecular mechanism of placental extracts on wound healing.

METHODS

The protein levels of both growth factors in rat skins with thermal injury were therefore studied to explore the molecular mechanism of placental extracts on wound healing. As cell proliferation is essential for wound healing, effects of placental extracts on fibroblast proliferation were also determined.

RESULTS

As compared with the controls, the S phase of fibroblasts was significantly increased by 1.5-, 1.7- and 4.7-fold for 1, 10 and 30 mg mL(-1) of placental extracts, respectively. The increase of the S phase was not due to the minute amount of sex hormones in the placental extracts as the addition of equivalent amounts of hormones showed no increase of the S phase. In addition, a 2.5-fold increase of TGF-beta1 in wound skin biopsy was noticed with 30 mg mL(-1) of porcine placental extracts. The FGF levels in the wound skin receiving 30 mg mL(-1) of porcine placental extracts were also significantly increased compared with the controls.

CONCLUSIONS

These ex vivo data support the observation that the application of 30 mg mL(-1) of placental extracts reduced the wound healing time by about 50%. To the best of our knowledge, this is the first report to explore the molecular mechanisms of porcine placental extracts on wound healing. These results may provide the insight into the potential use of porcine placental extracts as an alternative medicine for accelerating wound healing.

Pathogenesis of hereditary tumors: beyond the "two-hit" hypothesis

Knudson's 'two-hit' hypothesis has provided extremely important insights into the pathogenesis of tumors in autosomal dominant tumor predisposition syndromes, but recent evidence suggests that some such tumors may occur without a 'second hit' or require more than two mutations. Inactivation of both RB1 alleles appears to be insufficient by itself to cause malignancy in the tumors that develop in patients with hereditary retinoblastoma. On the other hand, certain tumors in patients with tuberous sclerosis complex appear to develop in haploinsufficient tissues that do not have 'second hit' mutations of a tuberous sclerosis gene. The molecular pathogenesis of certain other tumors in patients with tuberous sclerosis complex or neurofibromatosis 1 may not be fully explained by the 'two-hit' hypothesis either. Hereditary tumors, like non-hereditary tumors, may arise by a variety of molecular mechanisms, with loss of both alleles of a particular tumor suppressor gene being a frequent, but not invariably necessary or sufficient, event. Four models are presented to explain how various tumors may arise in patients with inherited tumor predisposition syndromes such as hereditary retinoblastoma, tuberous sclerosis complex or neurofibromatosis 1. Even tumors of one particular type may develop by more than one mechanism.

A long-term coculture model for the study of mast cell-keratinocyte interactions

Physiologic and pathologic events associated with cutaneous differentiation and repair are the result of a concerted action of various types of resident tissue cells. In vitro models simulating this complex in vivo situation are therefore needed to clarify the specific contribution and relevant interaction of, for example, dermal mast cells with other major cutaneous cells. The aim of this study was to establish a long-term coculture model that includes dermal mast cells, dermal fibroblasts, and keratinocytes in a human skin equivalent organotypic setting. Normal dermal mast cells and fibroblasts (1:4) were enclosed in collagen gel and normal keratinocytes were grown on top with exposure to the air interface. Under these conditions, mast cell integrity and functionality was preserved even after 4 wk of culture, as shown by electron microscopy and immunohistochemistry using antibodies against the mast-cell-specific granule enzyme tryptase and the receptors for stem cell factor and IgE. Mast cells also released histamine on stimulation with anti-IgE, and on ultrastructure were found to degranulate, with decrease of granule matrix density and formation of cell-cell contacts with fibroblasts. After 2 wk of culture, keratinocytes had formed an epidermis-like multilayer and were able to proliferate and differentiate, as shown by bromodeoxyuridine incorporation of basal cells and immunohistochemical staining for transglutaminase and cytokeratins 1 and 10. The model presented here thus provides a potentially relevant tool to further clarify the interaction of dermal mast cells with major other skin cells and their contribution to cutaneous physiology, repair processes, and pathology.

Altered calcium-mediated cell signaling in keratinocytes cultured from patients with neurofibromatosis type 1

Capacitative calcium entry and calcium wave propagation were studied in keratinocytes cultured from control persons and patients with type 1 neurofibromatosis. The cells were stimulated mechanically in the presence of inhibitors of gap-junctional or ATP-mediated communication to determine which pathways are operative in Ca(2+) signaling between these cells. Keratinocytes cultured from patients with type 1 neurofibromatosis (NF1) had a tendency to form cultures with markedly altered calcium-related signaling characteristics. Specifically, the resting Ca(2+) levels, intracellular Ca(2+) stores, capacitative calcium influx, and gap-junctional signal transduction were defective in NF1 keratinocytes. Western transfer analysis revealed apparently equal connexin 43 protein levels in normal control and in NF1 keratinocytes. Indirect immunofluorescence, however, demonstrated that connexin 43 was relatively evenly distributed in NF1 cells and did not form typical gap-junctional plaques between keratinocytes. Furthermore, the speed of the calcium wave was reduced in NF1 cells compared to normal keratinocytes. The results demonstrate that keratinocytes cultured from patients with NF1 display altered calcium-mediated signaling between cells.

The role of neurofibromin and melatonin in pathogenesis of pseudarthrosis after spinal fusion for neurofibromatous scoliosis

We might hypothesize that the high rate of pseudarthrosis after spinal fusion for neurofibromatous scoliosis is related to two factors: the absence of neurofibromin and melatonin deficiency. Loss of the up-regulation of neurofibromin during the healing process might abolish the bone-forming effects mediated through platelet-derived growth factor (PDGF) and transforming growth factor (TGF) beta1. The absence of neurofibromin might cause an increase in the Ras activity that increases the mitogen-activated protein kinase (MAPK) with resultant disturbance of the regulatory mechanism of core binding transcription factor (Cbfa 1) and increase of osteocalcin. These effects might inhibit bone formation. Melatonin deficiency might cause defective bone formation and favour excess fibrous tissue formation.

NF1 tumor suppressor mRNA is targeted to the cell-cell contact zone in Ca(2+)-induced keratinocyte differentiation

SUMMARY

We have previously shown that NF1 (type 1 neurofibromatosis) p21ras GTPase-activating tumor suppressor protein undergoes major relocalization during the formation of cell-cell junctions in differentiating keratinocytes in vitro. This prompted us to study the distribution of NF1 mRNA under the same conditions by in situ hybridization. In differentiating keratinocytes, the NF1 mRNA signal intensified within the cell cytoplasm within the first 0.5 to 2 hours after induction of cellular differentiation. First, the hybridization signal was evenly distributed throughout the cytoplasm. Subsequently, NF1 mRNA was gradually polarized to the cellular periphery at the side of cell-cell junctions and finally disappeared. Reappearance of NF1 mRNA was found in migrating keratinocytes forming a bilayered culture. Disruption of microfibrillar cytoskeleton, but not microtubules, caused a marked change in the subcellular distribution of NF1 mRNA. This data may suggest that intact actin microfilaments are essential for transport of NF1 mRNA to the cell periphery. This is the first study demonstrating that NF1, or any tumor suppressor mRNA, belongs to a rare group of mRNAs not targeted to free polysomes or ribosomes of the rough endoplasmic reticulum. This finding recognizes a potential way for post-transcriptional modification of NF1 expression.

Mast cell-fibroblast interactions: human mast cells as source and inducers of fibroblast and epithelial growth factors

As mast cells have been implicated in cutaneous repair processes, we have examined the ability of human mast cells to produce important epithelial and fibroblast growth factors or to stimulate the production of such factors in dermal fibroblasts. Isolated, highly purified human dermal mast cells and human leukemic mast cells were examined for mRNA and partly also for protein expression of these molecules as such or after preincubation with interleukin-4, stem cell factor, or with phorbol myristate acetate. In addition, mast cells were studied for their ability to induce fibroblast growth factor 2 and fibroblast growth factor 7 secretion from dermal fibroblasts. Both dermal and leukemic mast cells expressed fibroblast growth factor 2, fibroblast growth factor 7, and heparin-binding epidermal growth factor, but not hepatocyte growth factor at mRNA level, and dermal mast cells expressed fibroblast growth factor 10 in addition. At protein level, spontaneous fibroblast growth factor 2 secretion was noted that was markedly enhanced by phorbol myristate acetate, whereas no fibroblast growth factor 7 protein was detected under these conditions. Instead, human mast cell-1 supernatants induced enhanced fibroblast growth factor 7 secretion from dermal fibroblasts, with phorbol-myristate-acetate-stimulated supernatants being more effective. This effect could be reproduced with histamine and was H1-receptor mediated. Tryptase was ineffective but stimulated instead fibroblast growth factor 2 secretion from fibroblasts. These data demonstrate for the first time the ability of mast cells to express and/or secrete several growth factors of the fibroblast growth factor family as well as heparin-binding epidermal growth factor directly or indirectly via stimulation of fibroblasts, underlining the potentially pivotal role of these cells during human tissue repair and homeostasis.

Cardiac findings in an individual with neurofibromatosis 1 and sudden death

Vascular lesions in neurofibromatosis 1 (NF1) are infrequently recognised as manifestations of the disease, yet they can produce serious complications. Most individuals with NF1 vasculopathy are asymptomatic, which may contribute to underestimation of its frequency. A recent study indicates that vascular changes in individuals with NF1 contribute to mortality at younger ages. We report the sudden death of a young man with NF1. On autopsy examination there was evidence of an intramyocardial vasculopathy characteristic of the vascular pathology previously described in NF1. Other cardiac findings included non-specific cardiomyopathic changes, myocardial fibrosis, and a "floppy" mitral valve.

Insights into the pathogenesis of neurofibromatosis 1 vasculopathy

Intrinsic lesions of arterial walls are an important manifestation of neurofibromatosis 1 (NF1). Neurofibromin is expressed in blood vessel endothelial and smooth muscle cells, and NF1 vasculopathy may result from an alteration of neurofibromin function in these cells. Elucidation of the role of neurofibromin in the maintenance and repair of blood vessels may lead to novel approaches to the treatment of NF1 vasculopathy and vascular disease in general.

The neurofibromatosis type 1 (Nf1) tumor suppressor is a modifier of carcinogen-induced pigmentation and papilloma formation in C57BL/6 mice

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.

The Nf1 tumor suppressor regulates mouse skin wound healing, fibroblast proliferation, and collagen deposited by fibroblasts

Neurofibromatosis type 1 patients develop peripheral nerve tumors (neurofibromas) composed mainly of Schwann cells and fibroblasts, in an abundant collagen matrix produced by fibroblasts. Trauma has been proposed to trigger neurofibroma formation. To test if loss of the neurofibromatosis type 1 gene (Nf1) compromises fibroblast function in vivo following trauma, skin wounding was performed in Nf1 knockout mice. The pattern and amount of collagen-rich granulation bed tissue, manufactured by fibroblasts, was grossly abnormal in 60% of Nf1+/- wounds. Nf1 mutant fibroblasts showed cell autonomous abnormalities in collagen deposition in vitro that were not mimicked by Ras activation in fibroblasts, even though some Nf1 effects are mediated through Ras. Nf1+/- skin wound fibroblasts also proliferated past the normal wound maturation phase; this in vivo effect was potentiated by muscle injury. In vitro, Nf1+/- fibroblasts showed higher proliferation in 10% serum than Nf1+/+ fibroblasts. Macrophage-conditioned media or epidermal growth factor potentiated Nf1+/- fibroblast proliferation in vitro, demonstrating abnormal response of mutant fibroblasts to wound cytokines. Thus Nf1 is a key regulator of fibroblast responses to injury, and Nf1 mutation in mouse fibroblasts causes abnormalities characteristic of human neurofibromas.

Urinary bladder transitional cell carcinogenesis is associated with down-regulation of NF1 tumor suppressor gene in vivo and in vitro

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.