Neurofibromin physically interacts with the N-terminal domain of focal adhesion kinase

[Gene therapy strategies and prospects for neurofibromatosis type 1]

Objective

To summarize the gene therapy strategies for neurofibromatosis type 1 (NF1) and related research progress.

Methods

The recent literature on gene therapy for NF1 at home and abroad was reviewed. The structure and function of the NF1 gene and its mutations were analyzed, and the current status as well as future prospects of the transgenic therapy and gene editing strategies were summarized.

Results

NF1 is an autosomal dominantly inherited tumor predisposition syndrome caused by mutations in the NF1 tumor suppressor gene, which impair the function of the neurofibromin and lead to the disease. It has complex clinical manifestations and is not yet curable. Gene therapy strategies for NF1 are still in the research and development stage. Existing studies on the transgenic therapy for NF1 have mainly focused on the construction and expression of the GTPase-activating protein-related domain in cells that lack of functional neurofibromin, confirming the feasibility of the transgenic therapy for NF1. Future research may focus on split adeno-associated virus (AAV) gene delivery, oversized AAV gene delivery, and the development of new vectors for targeted delivery of full-length NF1 cDNA. In addition, the gene editing tools of the new generation have great potential to treat monogenic genetic diseases such as NF1, but need to be further validated in terms of efficiency and safety.

Conclusion

Gene therapy, including both the transgenic therapy and gene editing, is expected to become an important new therapeutic approach for NF1 patients.

Drug Responses in Plexiform Neurofibroma Type I (PNF1) Cell Lines Using High-Throughput Data and Combined Effectiveness and Potency

Background: Neurofibromatosis type 1 (NF1) is a genetic disorder characterized by heterozygous germline NF1 gene mutations that predispose patients to developing plexiform neurofibromas, which are benign but often disfiguring tumors of the peripheral nerve sheath induced by loss of heterozygosity at the NF1 locus. These can progress to malignant peripheral nerve sheath tumors (MPNSTs). There are no approved drug treatments for adults with NF1-related inoperable plexiform neurofibromas, and only one drug (selumetinib), which is an FDA-approved targeted therapy for the treatment of symptomatic pediatric plexiform neurofibromas, highlighting the need for additional drug screening and development. In high-throughput screening, the effectiveness of drugs against cell lines is often assessed by measuring in vitro potency (AC50) or the area under the curve (AUC). However, the variability of dose-response curves across drugs and cell lines and the frequency of partial effectiveness suggest that these measures alone fail to provide a full picture of overall efficacy. Methods: Using concentration-response data, we combined response effectiveness (EFF) and potency (AC50) into (a) a score characterizing the effect of a compound on a single cell line, S = log[EFF/AC50], and (b) a relative score, ΔS, characterizing the relative difference between a reference (e.g., non-tumor) and test (tumor) cell line. ΔS was applied to data from high-throughput screening (HTS) of a drug panel tested on NF1-/- tumor cells, using immortalized non-tumor NF1+/- cells as a reference. Results: We identified drugs with sensitivity, targeting expected pathways, such as MAPK-ERK and PI3K-AKT, as well as serotonin-related targets, among others. The ΔS technique used here, in tandem with a supplemental ΔS web tool, simplifies HTS analysis and may provide a springboard for further investigations into drug response in NF1-related cancers. The tool may also prove useful for drug development in a variety of other cancers.

The Contribution of Oxidative Stress to NF1-Altered Tumors

The neurofibromatosis-1 gene (NF1) was initially characterized because its germline mutation is responsible for an inherited syndromic disease predisposing tumor development, in particular neurofibromas but also various malignancies. Recently, large-scale tumor sequencing efforts have demonstrated NF1 as one of the most frequently mutated genes in human cancer, being mutated in approximately 5-10% of all tumors, especially in malignant peripheral nerve sheath tumors and different skin tumors. NF1 acts as a tumor suppressor gene that encodes neurofibromin, a large protein that controls neoplastic transformation through several molecular mechanisms. On the other hand, neurofibromin loss due to NF1 biallelic inactivation induces tumorigenic hyperactivation of Ras and mTOR signaling pathways. Moreover, neurofibromin controls actin cytoskeleton structure and the metaphase-anaphase transition. Consequently, neurofibromin deficiency favors cell mobility and proliferation as well as chromosomal instability and aneuploidy, respectively. Growing evidence supports the role of oxidative stress in NF1-related tumorigenesis. Neurofibromin loss induces oxidative stress both directly and through Ras and mTOR signaling activation. Notably, innovative therapeutic approaches explore drug combinations that further increase reactive oxygen species to boost the oxidative unbalance of NF1-altered cancer cells. In our paper, we review NF1-related tumors and their pathogenesis, highlighting the twofold contribution of oxidative stress, both tumorigenic and therapeutic.

RAS Signaling Gone Awry in the Skin: The Complex Role of RAS in Cutaneous Neurofibroma Pathogenesis, Emerging Biological Insights

Cutaneous neurofibromas (cNFs) are the most common tumor in people with the rasopathy neurofibromatosis type 1. They number in hundreds or even thousands throughout the body, and currently, there are no effective interventions to prevent or treat these skin tumors. To facilitate the identification of novel and effective therapies, essential studies including a more refined understanding of cNF biology and the role of RAS signaling and downstream effector pathways responsible for cNF initiation, growth, and maintenance are needed. This review highlights the current state of knowledge of RAS signaling in cNF pathogenesis and therapeutic development for cNF treatment.

The therapeutic potential of neurofibromin signaling pathways and binding partners

Neurofibromin controls many cell processes, such as growth, learning, and memory. If neurofibromin is not working properly, it can lead to health problems, including issues with the nervous, skeletal, and cardiovascular systems and cancer. This review examines neurofibromin's binding partners, signaling pathways and potential therapeutic targets. In addition, it summarizes the different post-translational modifications that can affect neurofibromin's interactions with other molecules. It is essential to investigate the molecular mechanisms that underlie neurofibromin variants in order to provide with functional connections between neurofibromin and its associated proteins for possible therapeutic targets based on its biological function.

Domain landscapes of somatic NF1 mutations in pheochromocytoma and paraganglioma

Pheochromocytoma and paraganglioma (PPGL), are rare neuroendocrine tumors arising from the adrenal medulla and extra-adrenal paraganglia, respectively. Up to about 60% are explained by germline or somatic mutations in one of the major known susceptibility genes e.g., inNF1,RET,VHL, SDHx,MAXandHRAS. Targeted Next Generation Sequencing was performed in 14 sporadic tumors using a panel including 26 susceptibility genes to characterize the mutation profile. A total of 6 germline and 8 somatic variants were identified. The most frequent somatic mutations were found in NF1(36%), four have not been reported earlier in PCC or PGL. Gene expression profile analysis showed that NF1 mutated tumors are classified into RTK3 subtype, cluster 2, with a high expression of genes associated with chromaffin cell differentiation, and into a RTK2 subtype, cluster 2, as well with overexpression of genes associated with cortisol biosynthesis. On the other hand, by analyzing the entire probe set on the array and TCGA data, ALDOC was found as the most significantly down regulated gene in NF1-mutated tumors compared to NF1-wild-type. Differential gene expression analysis showed a significant difference between Nt - and Ct-NF1 domains in mutated tumors probably engaging different cellular pathways. Notably, we had a metastatic PCC with a Ct-NF1 frameshift mutation and when performing protein docking analysis, Ct-NF1 showed an interaction with Nt-FAK suggesting their involvement in cell adhesion and cell growth. These results show that depending on the location of the NF1-mutation different pathways are activated in PPGLs. Further studies are required to clarify their clinical significance.

The PYK2 inhibitor PF-562271 enhances the effect of temozolomide on tumor growth in a C57Bl/6-Gl261 mouse glioma model

BACKGROUND

The development of resistance to temozolomide (TMZ), a standard chemotherapeutic, limits the effective treatment of glioblastoma (GBM). Focal adhesion kinase (FAK) and proline rich tyrosine kinase 2 (Pyk2) regulate proliferation and invasion of GBM cells. We found that TMZ activates FAK and Pyk2 signaling in GBM. We hypothesized that pharmacological inhibitors of Pyk2/FAK together with TMZ can enhance the inhibitory effect of TMZ on tumor growth and dispersal and improve the treatment outcome.

METHODS

Primary human GBM cell cultures and a C57Bl/6-GL261 mouse glioma implantation model were used. Pyk2 (Tyr579/580) and FAK (Tyr925) phosphorylation was analyzed by western blotting. Viability, cell cycle, migration, invasion and invadopodia formation were investigated in vitro. Animal survival, tumor size and invasion, TUNEL apoptotic cell death and the Ki67 proliferation index were evaluated in vivo upon treatment with TMZ (50 mg/kg, once/day, orally) and the Pyk2/FAK inhibitor PF-562271 (once/daily, 50 mg/kg, orally) vs. TMZ monotherapy.

RESULTS

In vitro studies revealed significantly reduced viability, cell cycle progression, invasion and invadopodia with TMZ (100 µM) + PF-562271 (16 nM) compared with TMZ alone. In vivo studies demonstrated that combinatorial treatment led to prominent reductions in tumor size and invasive margins, extensive signs of apoptosis and a reduced proliferation index, together with a 15% increase in the survival rate in animals, compared with TMZ monotherapy.

CONCLUSION

TMZ + PF-562271 eliminates TMZ-related Pyk2/FAK activation in GBM and improves the treatment efficacy.

Role of nerves in neurofibromatosis type 1-related nervous system tumors

BACKGROUND

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that affects nearly 1 in 3000 infants. Neurofibromin inactivation and NF1 gene mutations are involved in various aspects of neuronal function regulation, including neuronal development induction, electrophysiological activity elevation, growth factor expression, and neurotransmitter release. NF1 patients often exhibit a predisposition to tumor development, especially in the nervous system, resulting in the frequent occurrence of peripheral nerve sheath tumors and gliomas. Recent evidence suggests that nerves play a role in the development of multiple tumor types, prompting researchers to investigate the nerve as a vital component in and regulator of the initiation and progression of NF1-related nervous system tumors.

CONCLUSION

In this review, we summarize existing evidence about the specific effects of NF1 mutation on neurons and emerging research on the role of nerves in neurological tumor development, promising a new set of selective and targeted therapies for NF1-related tumors.

Mechanistic insights from animal models of neurofibromatosis type 1 cognitive impairment

Neurofibromatosis type 1 (NF1) is an autosomal-dominant neurogenetic disorder caused by mutations in the gene neurofibromin 1 (NF1). NF1 predisposes individuals to a variety of symptoms, including peripheral nerve tumors, brain tumors and cognitive dysfunction. Cognitive deficits can negatively impact patient quality of life, especially the social and academic development of children. The neurofibromin protein influences neural circuits via diverse cellular signaling pathways, including through RAS, cAMP and dopamine signaling. Although animal models have been useful in identifying cellular and molecular mechanisms that regulate NF1-dependent behaviors, translating these discoveries into effective treatments has proven difficult. Clinical trials measuring cognitive outcomes in patients with NF1 have mainly targeted RAS signaling but, unfortunately, resulted in limited success. In this Review, we provide an overview of the structure and function of neurofibromin, and evaluate several cellular and molecular mechanisms underlying neurofibromin-dependent cognitive function, which have recently been delineated in animal models. A better understanding of neurofibromin roles in the development and function of the nervous system will be crucial for identifying new therapeutic targets for the various cognitive domains affected by NF1.

Summary: Neurofibromin influences neural circuits through RAS, cAMP and dopamine signaling. Exploring the mechanisms underlying neurofibromin-dependent behaviors in animal models might enable future treatment of the various cognitive deficits that are associated with neurofibromatosis type 1.

Neurofibromatosis Type 1 Gene Alterations Define Specific Features of a Subset of Glioblastomas

Neurofibromatosis type 1 (NF1) gene mutations or alterations occur within neurofibromatosis type 1 as well as in many different malignant tumours on the somatic level. In glioblastoma, NF1 loss of function plays a major role in inducing the mesenchymal (MES) subtype and, therefore defining the most aggressive glioblastoma. This is associated with an immune signature and mediated via the NF1–MAPK–FOSL1 axis. Specifically, increased invasion seems to be regulated via mutations in the leucine-rich domain (LRD) of the NF1 gene product neurofibromin. Novel targets for therapy may arise from neurofibromin deficiency-associated cellular mechanisms that are summarised in this review.

NF1-Dependent Transcriptome Regulation in the Melanocyte Lineage and in Melanoma

The precise role played by the tumor suppressor gene NF1 in melanocyte biology and during the transformation into melanoma is not completely understood. In particular, understanding the interaction during melanocyte development between NF1 and key signaling pathways, which are known to be reactivated in advanced melanoma, is still under investigation. Here, we used RNAseq datasets from either situation to better understand the transcriptomic regulation mediated by an NF1 partial loss of function. We found that NF1 mutations had a differential impact on pluripotency and on melanoblast differentiation. In addition, major signaling pathways such as VEGF, senescence/secretome, endothelin, and cAMP/PKA are likely to be upregulated upon NF1 loss of function in both melanoblasts and metastatic melanoma. In sum, these data bring new light on the transcriptome regulation of the NF1-mutated melanoma subgroup and will help improve the possibilities for specific treatment.

The Crossroads between RAS and RHO Signaling Pathways in Cellular Transformation, Motility and Contraction

Ras and Rho proteins are GTP-regulated molecular switches that control multiple signaling pathways in eukaryotic cells. Ras was among the first identified oncogenes, and it appears mutated in many forms of human cancer. It mainly promotes proliferation and survival through the MAPK pathway and the PI3K/AKT pathways, respectively. However, the myriad proteins close to the plasma membrane that activate or inhibit Ras make it a major regulator of many apparently unrelated pathways. On the other hand, Rho is weakly oncogenic by itself, but it critically regulates microfilament dynamics; that is, actin polymerization, disassembly and contraction. Polymerization is driven mainly by the Arp2/3 complex and formins, whereas contraction depends on myosin mini-filament assembly and activity. These two pathways intersect at numerous points: from Ras-dependent triggering of Rho activators, some of which act through PI3K, to mechanical feedback driven by actomyosin action. Here, we describe the main points of connection between the Ras and Rho pathways as they coordinately drive oncogenic transformation. We emphasize the biochemical crosstalk that drives actomyosin contraction driven by Ras in a Rho-dependent manner. We also describe possible routes of mechanical feedback through which myosin II activation may control Ras/Rho activation.

Splicing Patterns in SF3B1-Mutated Uveal Melanoma Generate Shared Immunogenic Tumor-Specific Neoepitopes

Disruption of splicing patterns due to mutations of genes coding splicing factors in tumors represents a potential source of tumor neoantigens, which would be both public (shared between patients) and tumor-specific (not expressed in normal tissues). In this study, we show that mutations of the splicing factor SF3B1 in uveal melanoma generate such immunogenic neoantigens. Memory CD8⁺ T cells specific for these neoantigens are preferentially found in 20% of patients with uveal melanoma bearing SF3B1-mutated tumors. Single-cell analyses of neoepitope-specific T cells from the blood identified large clonal T-cell expansions, with distinct effector transcription patterns. Some of these expanded T-cell receptors are also present in the corresponding tumors. CD8⁺ T-cell clones specific for the neoepitopes specifically recognize and kill SF3B1-mutated tumor cells, supporting the use of this new family of neoantigens as therapeutic targets. SIGNIFICANCE: Mutations of the splicing factor SF3B1 in uveal melanoma generate shared neoantigens that are uniquely expressed by tumor cells, leading to recognition and killing by specific CD8 T cells. Mutations in splicing factors can be sources of new therapeutic strategies applicable to diverse tumors.This article is highlighted in the In This Issue feature, p. 1861.

Neurofibromin Structure, Functions and Regulation

Neurofibromin is a large and multifunctional protein encoded by the tumor suppressor gene NF1, mutations of which cause the tumor predisposition syndrome neurofibromatosis type 1 (NF1). Over the last three decades, studies of neurofibromin structure, interacting partners, and functions have shown that it is involved in several cell signaling pathways, including the Ras/MAPK, Akt/mTOR, ROCK/LIMK/cofilin, and cAMP/PKA pathways, and regulates many fundamental cellular processes, such as proliferation and migration, cytoskeletal dynamics, neurite outgrowth, dendritic-spine density, and dopamine levels. The crystallographic structure has been resolved for two of its functional domains, GRD (GAP-related (GTPase-activating protein) domain) and SecPH, and its post-translational modifications studied, showing it to be localized to several cell compartments. These findings have been of particular interest in the identification of many therapeutic targets and in the proposal of various therapeutic strategies to treat the symptoms of NF1. In this review, we provide an overview of the literature on neurofibromin structure, function, interactions, and regulation and highlight the relationships between them.

Nuclear Isoforms of Neurofibromin Are Required for Proper Spindle Organization and Chromosome Segregation

Mitotic spindles are highly organized, microtubule (MT)-based, transient structures that serve the fundamental function of unerring chromosome segregation during cell division and thus of genomic stability during tissue morphogenesis and homeostasis. Hence, a multitude of MT-associated proteins (MAPs) regulates the dynamic assembly of MTs in preparation for mitosis. Some tumor suppressors, normally functioning to prevent tumor development, have now emerged as significant MAPs. Among those, neurofibromin, the product of the Neurofibromatosis-1 gene (NF1), a major Ras GTPase activating protein (RasGAP) in neural cells, controls also the critical function of chromosome congression in astrocytic cellular contexts. Cell type- and development-regulated splicings may lead to the inclusion or exclusion of NF1exon51, which bears a nuclear localization sequence (NLS) for nuclear import at G2; yet the functions of the produced NLS and ΔNLS neurofibromin isoforms have not been previously addressed. By using a lentiviral shRNA system, we have generated glioblastoma SF268 cell lines with conditional knockdown of NLS or ΔNLS transcripts. In dissecting the roles of NLS or ΔNLS neurofibromins, we found that NLS-neurofibromin knockdown led to increased density of cytosolic MTs but loss of MT intersections, anastral spindles featuring large hollows and abnormal chromosome positioning, and finally abnormal chromosome segregation and increased micronuclei frequency. Therefore, we propose that NLS neurofibromin isoforms exert prominent mitotic functions.

NF1-RAC1 axis regulates migration of the melanocytic lineage

Metastases's spreading is the main cause of mortality for advanced stage cancer patients, including melanoma. The formation of metastases is favored by enhanced migratory and invasive capacities of tumor cells. Tumor suppressor gene NF1 is a negative regulator of RAS and its deregulation plays an important role in several aspects of melanoma transformation and progression. However, very little is described about the role of NF1 in cellular migration and invasion. In this study, our results show on the one hand, that the loss of NF1 expression delays migration of human melanoblasts via a RAC1-dependent mechanism. On the other hand, our data indicate that NF1 loss in melanoma cells is enhancing migration, intravasation and metastases formation in vivo. Moreover, not only this phenotype is associated with an upregulation of PREX1 but also patient-derived melanoma samples with low NF1 expression present increased levels of PREX1. In sum, our study brings new elements on the mechanism controlling cellular migration in the context of NF1 loss. These data are of prime interest to improve treatment strategies against all NF1-mutated tumors, including this subtype of melanoma.

NF1, Neurofibromin and Gene Therapy: Prospects of Next-Generation Therapy

Neurofibromatosis type 1 [NF1] is an autosomal dominant genetic disorder affecting multiple organs. NF1 is well known for its various clinical manifestations, including café-au-late macules, Lisch nodules, bone deformity and neurofibromas. However, there is no effective therapy for NF1. Current therapies are aimed at alleviating NF1 clinical symptoms but not curing the disease. By altering pathogenic genes, gene therapy regulates cell activities at the nucleotide level. In this review, we described the structure and functions of neurofibromin domains, including GAP-related domain [GRD], cysteine-serine rich domain [CSRD], leucine-rich domain [LRD] and C-terminal domain [CTD], which respectively alter downstream pathways. By transfecting isolated sequences of these domains, researchers can partially restore normal cell functions in neurofibroma cell lines. Furthermore, recombinant transgene sequences may be designed to encode truncated proteins, which is functional and easy to be packaged into viral vectors. In addition, the treatment effect of gene therapy is also determined by various factors such as the vectors selection, transgene packaging strategies and drug administration. We summarized multiple NF1 gene therapy strategies and discussed their feasibility from multiple angles. Different protein domains alter the function and downstream pathways of neurofibromin.

Nf1 loss promotes Kras-driven lung adenocarcinoma and results in Psat1-mediated glutamate dependence

Mutations to KRAS are recurrent in lung adenocarcinomas (LUAD) and are daunting to treat due to the difficulties in KRAS oncoprotein inhibition. A possible resolution to this problem may lie with co-mutations to other genes that also occur in KRAS-driven LUAD that may provide alternative therapeutic vulnerabilities. Approximately 3% of KRAS-mutant LUADs carry functional mutations in NF1 gene encoding neurofibromin-1, a negative regulator of focal adhesion kinase 1 (FAK1). We evaluated the impact of Nf1 loss on LUAD development using a CRISPR/Cas9 platform in a murine model of Kras-mutant LUAD We discovered that Nf1 deactivation is associated with Fak1 hyperactivation and phosphoserine aminotransferase 1 (Psat1) upregulation in mice. Nf1 loss also accelerates murine Kras-driven LUAD tumorigenesis. Analysis of the transcriptome and metabolome reveals that LUAD cells with mutation to Nf1 are addicted to glutamine metabolism. We also reveal that this metabolic vulnerability can be leveraged as a treatment option by pharmacologically inhibiting glutaminase and/or Psat1. Lastly, the findings advocate that tumor stratification by co-mutations to KRAS/NF1 highlights the LAUD patient population expected to be susceptible to inhibiting PSAT1.

Neurofibromin Is an Estrogen Receptor-α Transcriptional Co-repressor in Breast Cancer

We report that neurofibromin, a tumor suppressor and Ras-GAP (GTPase-activating protein), is also an estrogen receptor-α (ER) transcriptional co-repressor through leucine/isoleucine-rich motifs that are functionally independent of GAP activity. GAP activity, in turn, does not affect ER binding. Consequently, neurofibromin depletion causes estradiol hypersensitivity and tamoxifen agonism, explaining the poor prognosis associated with neurofibromin loss in endocrine therapy-treated ER⁺ breast cancer. Neurofibromin-deficient ER⁺ breast cancer cells initially retain sensitivity to selective ER degraders (SERDs). However, Ras activation does play a role in acquired SERD resistance, which can be reversed upon MEK inhibitor addition, and SERD/MEK inhibitor combinations induce tumor regression. Thus, neurofibromin is a dual repressor for both Ras and ER signaling, and co-targeting may treat neurofibromin-deficient ER⁺ breast tumors.

Pumping the brakes on RAS - negative regulators and death effectors of RAS

Mutations that activate the RAS oncoproteins are common in cancer. However, aberrant upregulation of RAS activity often occurs in the absence of activating mutations in the RAS genes due to defects in RAS regulators. It is now clear that loss of function of Ras GTPase-activating proteins (RasGAPs) is common in tumors, and germline mutations in certain RasGAP genes are responsible for some clinical syndromes. Although regulation of RAS is central to their activity, RasGAPs exhibit great diversity in their binding partners and therefore affect signaling by multiple mechanisms that are independent of RAS. The RASSF family of tumor suppressors are essential to RAS-induced apoptosis and senescence, and constitute a barrier to RAS-mediated transformation. Suppression of RASSF protein expression can also promote the development of excessive RAS signaling by uncoupling RAS from growth inhibitory pathways. Here, we will examine how these effectors of RAS contribute to tumor suppression, through both RAS-dependent and RAS-independent mechanisms.

Antiatherogenic Effect of Resveratrol Attributed to Decreased Expression of ICAM-1 (Intercellular Adhesion Molecule-1)

Objective- Increasing evidence shows that resveratrol has antiatherogenic effects, but its underlying mechanisms are unknown. Thus, we evaluated the molecular mechanisms underlying the antiatherogenic effect of resveratrol. Approach and Results- Using the previously established mouse atherosclerosis model of partial ligation of the left carotid artery, we evaluated the role of resveratrol in antiatherosclerosis. We attempted to determine the mechanisms associated with focal adhesions using vascular endothelial cells. The results showed that resveratrol stimulated focal adhesion kinase cleavage via resveratrol-increased expression of lactoferrin in endothelial cells. Furthermore, we found that an N-terminal focal adhesion kinase fragment cleaved by resveratrol contained the FERM (band 4.1, ezrin, radixin, and moesin)-kinase domain. Furthermore, resveratrol inhibited lipopolysaccharide-stimulated adhesion of THP-1 human monocytes by decreased expression of ICAM-1 (intercellular adhesion molecule-1). A decreased ICAM-1 level was also observed in the left carotid artery of mice treated with resveratrol. To understand the relationship between resveratrol-induced antiinflammation and focal adhesion disruption, endothelial cells were transfected with FERM-kinase. Ectopically expressed FERM-kinase, the resveratrol-cleaved focal adhesion kinase fragment, was found in the nuclear fraction and inhibited the transcription level of icam-1 via the Nrf2 (nuclear factor erythroid 2-related factor 2)-antioxidant response element complex. Finally, ectopically expressed FERM-kinase blocked tumor necrosis factor-α- or IL- (interleukin) stimulated monocytic binding to endothelial cells. Conclusions- Our results show that resveratrol inhibits the expression of ICAM-1 via transcriptional regulation of the FERM-kinase and Nrf2 interaction, thereby blocking monocyte adhesion. These suppressive effects on the inflammatory mechanism suggest that resveratrol delayed the onset of atherosclerosis.

Joint Transcriptomic Analysis of Lung Cancer and Other Lung Diseases

Background: Epidemiological and clinical evidence points cancer comorbidity with pulmonary chronic disease. The acquisition of some hallmarks of cancer by cells affected with lung pathologies as a cell adaptive mechanism to a shear stress, suggests that could be associated with the establishment of tumoral processes. Objective: To propose a bioinformatic pipeline for the identification of all deregulated genes and the transcriptional regulators (TFs) that are coexpressed during lung cancer establishment, and therefore could be important for the acquisition of the hallmarks of cancer. Methods: Ten microarray datasets (six of lung cancer, four of lung diseases) comparing normal and diseases-related lung tissue were selected to identify hub differentiated expressed genes (DEGs) in common between lung pathologies and lung cancer, along with transcriptional regulators through the utilization of specialized libraries from R language. DAVID bioinformatics tool for gene enrichment analyses was used to identify genes with experimental evidence associated to tumoral processes and signaling pathways. Coexpression networks of DEGs and TFs in lung cancer establishment were created with Coexnet library, and a survival analysis of the main hub genes was made. Results: Two hundred ten DEGs were identified in common between lung cancer and other lung diseases related to the acquisition of tumoral characteristics, which are coexpressed in a lung cancer network with TFs, suggesting that could be related to the establishment of the tumoral pathology in lung. The comparison of the coexpression networks of lung cancer and other lung diseases allowed the identification of common connectivity patterns (CCPs) with DEGs and TFs correlated to important tumoral processes and signaling pathways, that haven´t been studied to experimentally validate their role in the early stages of lung cancer. Some of the TFs identified showed a correlation between its expression levels and the survival of lung cancer patients. Conclusion: Our findings indicate that lung diseases share genes with lung cancer which are coexpressed in lung cancer, and might be able to explain the epidemiological observations that point to direct and inverse comorbid associations between some chronic lung diseases and lung cancer and represent a complex transcriptomic scenario.

Pathogenic mutations in neurofibromin identifies a leucine-rich domain regulating glioma cell invasiveness

Glioblastoma (GBM) is the most aggressive tumor of the brain. NF1, a tumor suppressor gene and RAS-GTPase, is one of the highly mutated genes in GBM. Dysregulated NF1 expression promotes cell invasion, proliferation, and tumorigenesis. Loss of NF1 expression in glioblastoma is associated with increased aggressiveness of the tumor. Here, we show that NF1-loss in patient-derived glioma cells using shRNA increases self-renewal, heightens cell invasion, and promotes mesenchymal subtype and epithelial mesenchymal transition-specific gene expression that enhances tumorigenesis. The neurofibromin protein contains at least four major domains, with the GAP-related domain being the most well-studied. In this study, we report that the leucine-rich domain (LRD) of neurofibromin inhibits invasion of human glioblastoma cells without affecting their proliferation. Moreover, under conditions tested, the NF1-LRD fails to hydrolyze Ras-GTP to Ras-GDP, suggesting that its suppressive function is independent of Ras signaling. We further demonstrate that rare variants within the NF1-LRD domain found in a subset of the patients are pathogenic and reduce NF1-LRD’s invasion suppressive function. Taken together, our results show, for the first time, that NF1-LRD inhibits glioma invasion, and provides evidence of a previously unrecognized function of NF1-LRD in glioma biology.

Ras-Specific GTPase-Activating Proteins-Structures, Mechanisms, and Interactions

Ras-specific GTPase-activating proteins (RasGAPs) down-regulate the biological activity of Ras proteins by accelerating their intrinsic rate of GTP hydrolysis, basically by a transition state stabilizing mechanism. Oncogenic Ras is commonly not sensitive to RasGAPs caused by interference of mutants with the electronic or steric requirements of the transition state, resulting in up-regulation of activated Ras in respective cells. RasGAPs are modular proteins containing a helical catalytic RasGAP module surrounded by smaller domains that are frequently involved in the subcellular localization or contributing to regulatory features of their host proteins. In this review, we summarize current knowledge about RasGAP structure, mechanism, regulation, and dual-substrate specificity and discuss in some detail neurofibromin, one of the most important negative Ras regulators in cellular growth control and neuronal function.

Recent Advances in the Diagnosis and Pathogenesis of Neurofibromatosis Type 1 (NF1)-associated Peripheral Nervous System Neoplasms

The diagnosis of a neurofibroma or a malignant peripheral nerve sheath tumor (MPNST) often raises the question of whether the patient has the genetic disorder neurofibromatosis type 1 (NF1) as well as how this will impact the patient's outcome, what their risk is for developing additional neoplasms and whether treatment options differ for NF1-associated and sporadic peripheral nerve sheath tumors. Establishing a diagnosis of NF1 is challenging as this disorder has numerous neoplastic and non-neoplastic manifestations which are variably present in individual patients. Further, other genetic diseases affecting the Ras signaling cascade (RASopathies) mimic many of the clinical features of NF1. Here, we review the clinical manifestations of NF1 and compare and contrast them with those of the RASopathies. We also consider current approaches to genetic testing for germline NF1 mutations. We then focus on NF1-associated neurofibromas, considering first the complicated clinical behavior and pathology of these neoplasms and then discussing our current understanding of the genomic abnormalities that drive their pathogenesis, including the mutations encountered in atypical neurofibromas. As several neurofibroma subtypes are capable of undergoing malignant transformation to become MPNSTs, we compare and contrast patient outcomes in sporadic, NF1-associated and radiation-induced MPNSTs, and review the challenging pathology of these lesions. The mutations involved in neurofibroma-MPNST progression, including the recent identification of mutations affecting epigenetic regulators, are then considered. Finally, we explore how our current understanding of neurofibroma and MPNST pathogenesis is informing the design of new therapies for these neoplasms.

Neurofibromin level directs RAS pathway signaling and mediates sensitivity to targeted agents in malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumor (MPNST) is a type of soft-tissue sarcoma strongly associated with dysfunction in neurofibromin; an inhibitor of the RAS pathway. We performed high-throughput screening of an array of FDA approved and promising agents in clinical development both alone and in combination at physiologically achievable concentrations against a panel of established MPNST cell line models. We found that drugs targeting a variety of factors in the RAS pathway can effectively lead to cell death in vitro with considerable drug combination synergy in regimens that target MEK or mTOR. We observed that the degree of relative sensitivity to chemotherapeutic agents was associated with the status of neurofibromin in these cell line models. Using a combination of agents that target MEK and mTORC1/2, we effectively silenced RAS/PI3K/MEK/mTOR signaling in vitro. Moreover, we employed RNAi against NF1 to establish that MPNST drug sensitivity is directly proportional to relative level of intracellular neurofibromin. Thus, two-drug combinations that target MEK and mTORC1/2 are most effective in halting the RAS signaling cascade, and the relative success of this and related small molecule interventions in MPNSTs may be predicated upon the molecular status of neurofibromin.

Clinical and Molecular Characteristics of NF1-Mutant Lung Cancer

PURPOSE

NF1 is a tumor suppressor that negatively regulates Ras signaling. NF1 mutations occur in lung cancer, but their clinical significance is unknown. We evaluated clinical and molecular characteristics of NF1 mutant lung cancers with comparison to tumors with KRAS mutations.

EXPERIMENTAL DESIGN

Between July 2013 and October 2014, 591 non-small cell lung cancer (NSCLC) tumors underwent targeted next-generation sequencing in a 275 gene panel that evaluates gene mutations and genomic rearrangements. NF1 and KRAS cohorts were identified, with subsequent clinical and genomic analysis.

RESULTS

Among 591 patients, 60 had NF1 mutations (10%) and 141 (24%) had KRAS mutations. 15 NF1 mutations (25%) occurred with other oncogenic mutations [BRAF (2); ERBB2 (2); KRAS (9); HRAS (1); NRAS (1)]. There were 72 unique NF1 variants. NF1 tumor pathology was diverse, including both adenocarcinoma (36, 60%) and squamous cell carcinoma (10, 17%). In contrast, KRAS mutations occurred predominantly in adenocarcinoma (136, 96%). Both mutations were common in former/current smokers. Among NF1 tumors without concurrent oncogenic alterations, TP53 mutations/2-copy deletions occurred more often (33, 65%) than with KRAS mutation (46, 35%; P < 0.001). No difference between cohorts was seen with other tumor suppressors.

CONCLUSIONS

NF1 mutations define a unique population of NSCLC. NF1 and KRAS mutations present in similar patient populations, but NF1 mutations occur more often with other oncogenic alterations and TP53 mutations. Therapeutic strategies targeting KRAS activation, including inhibitors of MAP kinase signaling, may warrant investigation in NF1 mutant tumors. Tumor-suppressor inactivation patterns may help further define novel treatment strategies. Clin Cancer Res; 22(13); 3148-56. ©2016 AACR.

Neurofibromatosis type 1: Fundamental insights into cell signalling and cancer

Neurofibromatosis type 1 (NF1) is an autosomal dominant tumour predisposition syndrome that is caused through loss of function mutations of a tumour suppressor gene called Neurofibromin 1. Therapeutic options are currently limited for NF1-associated tumours, where treatment is often restricted to complete surgical resection with clear margins. Herein, we discuss the multifunctional tumour suppressive role of neurofibromin, which is classically known as a GTPase activating protein (GAP) towards the RAS small GTPase. While neurofibromin inhibits proliferative growth through blockade of RAS-mediated signal transduction, neurofibromin should also be considered as a modulator of cell motility and cell adhesion. Through interfacing with the cytoskeleton and membrane structures, neurofibromin acts as a negative regulator of RHO/ROCK signalling pathways involved in cytoskeletal dynamics that are instrumental in proper neuronal development. In the context of cancer, the loss of normal function of neurofibromin via genetic mutation results in heightened cell proliferation and migration, predisposing NF1 patients to cancer. Malignant Peripheral Nerve Sheath Tumours (MPNSTs) can develop from benign neurofibromas and are the main cause of death amongst NF1 patients. Through recent research on MPNSTs, we have gained insight into the key molecular events that drive their malignancy. Advances regarding malignant drivers involved in cell migration, cell invasion and angiogenic signalling are discussed in this review, where these findings will likely influence future therapies for both NF1 and related sporadic cancers.

The NF1 gene revisited - from bench to bedside

Neurofibromatosis type 1 (NF1) is a relatively common tumour predisposition syndrome related to germline aberrations of NF1, a tumour suppressor gene. The gene product neurofibromin is a negative regulator of the Ras cellular proliferation pathway, and also exerts tumour suppression via other mechanisms.

Recent next-generation sequencing projects have revealed somatic NF1 aberrations in various sporadic tumours. NF1 plays a critical role in a wide range of tumours. NF1 alterations appear to be associated with resistance to therapy and adverse outcomes in several tumour types.

Identification of a patient's germline or somatic NF1 aberrations can be challenging, as NF1 is one of the largest human genes, with a myriad of possible mutations. Epigenetic factors may also contribute to inadequate levels of neurofibromin in cancer cells.

Clinical trials of NF1-based therapeutic approaches are currently limited. Preclinical studies on neurofibromin-deficient malignancies have mainly been on malignant peripheral nerve sheath tumour cell lines or xenografts derived from NF1 patients. However, the emerging recognition of the role of NF1 in sporadic cancers may lead to the development of NF1-based treatments for other tumour types. Improved understanding of the implications of NF1 aberrations is critical for the development of novel therapeutic strategies.

Focal adhesion kinase and p53 synergistically decrease neuroblastoma cell survival

Neuroblastoma is the most common extracranial solid tumor of childhood and is responsible for over 15% of pediatric cancer deaths. Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase that is important in many facets of neuroblastoma tumor development and progression. The p53 oncogene, although wild type in most neuroblastomas, lacks significant function as a tumor suppressor in these tumors. Recent reports have found that FAK and p53 interact in some tumor types. We have hypothesized FAK and p53 coordinately control each other's expression and also interact in neuroblastoma. In the present study, we showed that not only do FAK and p53 interact but each one controls the expression of the other. In addition, we also examined the effects of FAK inhibition combined with p53 activation in neuroblastoma and showed that these two, in combination, had a synergistic effect on neuroblastoma cell survival. The findings from this present study help to further our understanding of the regulation of neuroblastoma tumorigenesis and may provide novel therapeutic strategies and targets for neuroblastoma and other pediatric solid tumors.

Targeting FAK scaffold functions inhibits human renal cell carcinoma growth

Human conventional renal cell carcinoma (CCC) remains resistant to current therapies. Focal Adhesion Kinase (FAK) is upregulated in many epithelial tumors and clearly implicated in nearly all facets of cancer. However, only few reports have assessed whether FAK may be associated with renal tumorigenesis. In this study, we investigated the potential role of FAK in the growth of human CCC using a panel of CCC cell lines expressing or not the von Hippel-Lindau (VHL) tumor suppressor gene as well as normal/tumoral renal tissue pairs. FAK was found constitutively expressed in human CCC both in culture cells and freshly harvested tumors obtained from patients. We showed that CCC cell growth was dramatically reduced in FAK-depleted cells or after FAK inhibition with various inhibitors and this effect was obtained through inhibition of cell proliferation and induction of cell apoptosis. Additionally, our results indicated that FAK knockdown decreased CCC cell migration and invasion. More importantly, depletion or pharmacological inhibition of FAK substantially inhibited tumor growth in vivo. Interestingly, investigations of the molecular mechanism revealed loss of FAK phosphorylation during renal tumorigenesis impacting multiple signaling pathways. Taken together, our findings reveal a previously uncharacterized role of FAK in CCC whereby FAK exerts oncogenic properties through a non canonical signaling pathway involving its scaffolding kinase-independent properties. Therefore, targeting the FAK scaffold may represent a promising approach for developing innovative and highly specific therapies in human CCC.

Neuregulin-1 overexpression and Trp53 haploinsufficiency cooperatively promote de novo malignant peripheral nerve sheath tumor pathogenesis

Malignant peripheral nerve sheath tumors (MPNSTs) are Schwann cell-derived malignancies that arise from plexiform neurofibromas in patients with mutation of the neurofibromin 1 (NF1) gene. We have shown that the growth factor neuregulin-1 (NRG1) also contributes to human neurofibroma and MPNST pathogenesis and that outbred C57BL/6J × SJL/J transgenic mice overexpressing NRG1 in Schwann cells (P0-GGFβ3 mice) recapitulate the process of neurofibroma-MPNST progression. However, it is unclear whether NRG1 acts predominantly within NF1-regulated signaling cascades or instead activates other essential cascades that cooperate with NF1 loss to promote tumorigenesis. We now report that tumorigenesis is suppressed in inbred P0-GGFβ3 mice on a C57BL/6J background. To determine whether NRG1 overexpression interacts with reduced Nf1 or Trp53 gene dosage to "unmask" tumorigenesis in these animals, we followed cohorts of inbred P0-GGFβ3;Nf1+/−, P0-GGFβ3;Trp53+/− and control (P0-GGFβ3, Nf1+/− and Trp53+/−) mice for 1 year. We found no reduction in survival or tumors in control and P0-GGFβ3;Nf1+/− mice. In contrast, P0-GGFβ3;Trp53+/− mice died on average at 226 days, with MPNSTs present in 95 % of these mice. MPNSTs in inbred P0-GGFβ3;Trp53+/− mice arose de novo from micro-MPNSTs that uniformly develop intraganglionically. These micro-MPNSTs are of lower grade (WHO grade II-III) than the major MPNSTs (WHO grade III-IV); array comparative genomic hybridization showed that lower grade MPNSTs also had fewer genomic abnormalities. Thus, P0-GGFβ3;Trp53+/− mice represent a novel model of low- to high-grade MPNST progression. We further conclude that NRG1 promotes peripheral nervous system neoplasia predominantly via its effects on the signaling cascades affected by Nf1 loss.

Disruption of focal adhesion kinase and p53 interaction with small molecule compound R2 reactivated p53 and blocked tumor growth

BACKGROUND

Focal Adhesion Kinase (FAK) is a 125 kDa non-receptor kinase that plays a major role in cancer cell survival and metastasis.

METHODS

We performed computer modeling of the p53 peptide containing the site of interaction with FAK, predicted the peptide structure and docked it into the three-dimensional structure of the N-terminal domain of FAK involved in the complex with p53. We screened small molecule compounds that targeted the site of the FAK-p53 interaction and identified compounds (called Roslins, or R compounds) docked in silico to this site.

RESULTS

By different assays in isogenic HCT116p53+/+ and HCT116 p53-/- cells we identified a small molecule compound called Roslin 2 (R2) that bound FAK, disrupted the binding of FAK and p53 and decreased cancer cell viability and clonogenicity in a p53-dependent manner. In addition, dual-luciferase assays demonstrated that the R2 compound increased p53 transcriptional activity that was inhibited by FAK using p21, Mdm-2, and Bax-promoter targets. R2 also caused increased expression of p53 targets: p21, Mdm-2 and Bax proteins. Furthermore, R2 significantly decreased tumor growth, disrupted the complex of FAK and p53, and up-regulated p21 in HCT116 p53+/+ but not in HCT116 p53-/- xenografts in vivo. In addition, R2 sensitized HCT116p53+/+ cells to doxorubicin and 5-fluorouracil.

CONCLUSIONS

Thus, disruption of the FAK and p53 interaction with a novel small molecule reactivated p53 in cancer cells in vitro and in vivo and can be effectively used for development of FAK-p53 targeted cancer therapy approaches.

Disrupting the scaffold to improve focal adhesion kinase-targeted cancer therapeutics

Focal adhesion kinase (FAK) is emerging as a promising cancer target because it is highly expressed at both the transcriptional and translational level in cancer and is involved in many aspects of tumor growth, invasion, and metastasis. Existing FAK-based therapeutics focus on inhibiting the kinase's catalytic function and not the large scaffold it creates that includes many oncogenic receptor tyrosine kinases and tumor suppressor proteins. Targeting the FAK scaffold is a feasible and promising approach for developing highly specific therapeutics that disrupt FAK signaling pathways in cancer.

Partial Blindness to Submicron Topography in NF1 Haploinsufficient Cultured Fibroblasts Indicates a New Function of Neurofibromin in Regulation of Mechanosensoric

Cells sense physical properties of their extracellular environment and translate them into biochemical signals. In this study, cell responses to surfaces with submicron topographies were investigated in cultured human NF1 haploinsufficient fibroblasts. Age-matched fibroblasts from 8 patients with neurofibromatosis type 1 (NF1(+/-)) and 9 controls (NF1(+/+)) were cultured on surfaces with grooves of 200 nm height and lateral distance of 2 μm. As cellular response indicator, the mean cell orientation along microstructured grooves was systematically examined. The tested NF1 haploinsufficient fibroblasts were significantly less affected by the topography than those from healthy donors. Incubation of the NF1(+/-) fibroblasts with the farnesyltransferase inhibitor FTI-277 and other inhibitors of the neurofibromin pathway ameliorates significantly the cell orientation. These data indicate that NF1 haploinsufficiency results in an altered response to specific surface topography in fibroblasts. We suggest a new function of neurofibromin in the sensoric mechanism to topographies and a partial mechanosensoric blindness by NF1 haploinsufficiency.

Alterations in white matter microstructure in neurofibromatosis-1

Neurofibromatosis (NF1) represents the most common single gene cause of learning disabilities. NF1 patients have impairments in frontal lobe based cognitive functions such as attention, working memory, and inhibition. Due to its well-characterized genetic etiology, investigations of NF1 may shed light on neural mechanisms underlying such difficulties in the general population or other patient groups. Prior neuroimaging findings indicate global brain volume increases, consistent with neural over-proliferation. However, little is known about alterations in white matter microstructure in NF1. We performed diffusion tensor imaging (DTI) analyses using tract-based spatial statistics (TBSS) in 14 young adult NF1 patients and 12 healthy controls. We also examined brain volumetric measures in the same subjects. Consistent with prior studies, we found significantly increased overall gray and white matter volume in NF1 patients. Relative to healthy controls, NF1 patients showed widespread reductions in white matter integrity across the entire brain as reflected by decreased fractional anisotropy (FA) and significantly increased absolute diffusion (ADC). When radial and axial diffusion were examined we found pronounced differences in radial diffusion in NF1 patients, indicative of either decreased myelination or increased space between axons. Secondary analyses revealed that FA and radial diffusion effects were of greatest magnitude in the frontal lobe. Such alterations of white matter tracts connecting frontal regions could contribute to the observed cognitive deficits. Furthermore, although the cellular basis of these white matter microstructural alterations remains to be determined, our findings of disproportionately increased radial diffusion against a background of increased white matter volume suggest the novel hypothesis that one potential alteration contributing to increased cortical white matter in NF1 may be looser packing of axons, with or without myelination changes. Further, this indicates that axial and radial diffusivity can uniquely contribute as markers of NF1-associated brain pathology in conjunction with the typically investigated measures.

Nf1 RasGAP inhibition of LIMK2 mediates a new cross-talk between Ras and Rho pathways

BACKGROUND

Ras GTPases mediate numerous biological processes through their ability to cycle between an inactive GDP-bound form and an active GTP-bound form. Guanine nucleotide exchange factors (GEFs) favor the formation of the active Ras-GTP, whereas GTPase activating proteins (GAPs) promote the formation of inactive Ras-GDP. Numerous studies have established complex signaling cross-talks between Ras GTPases and other members of the superfamily of small GTPases. GEFs were thought to play a major role in these cross-talks. However, recently GAPs were also shown to play crucial roles in these processes. Among RasGAPs, Nf1 is of special interest. Nf1 is responsible for the genetic disease Neurofibromatosis type I, and recent data strongly suggest that this RasGAP connects different signaling pathways.

METHODOLOGY/PRINCIPAL FINDINGS

In order to know if the RasGAP Nf1 might play a role in connecting Ras GTPases to other small GTPase pathways, we systematically looked for new partners of Nf1, by performing a yeast two-hybrid screening on its SecPH domain. LIMK2, a major kinase of the Rho/ROCK/LIMK2/cofilin pathway, was identified in this screening. We confirmed this interaction by co-immunoprecipitation experiments, and further characterized it. We also demonstrated its specificity: the close related homolog of LIMK2, LIMK1, does not interact with the SecPH domain of Nf1. We then showed that SecPH partially inhibits the kinase activity of LIMK2 on cofilin. Our results furthermore suggest a precise mechanism for this inhibition: in fact, SecPH would specifically prevent LIMK2 activation by ROCK, its upstream regulator.

CONCLUSIONS/SIGNIFICANCE

Although previous data had already connected Nf1 to actin cytoskeleton dynamics, our study provides for the first time possible detailed molecular requirements of this involvement. Nf1/LIMK2 interaction and inhibition allows to directly connect neurofibromatosis type I to actin cytoskeleton remodeling, and provides evidence that the RasGAP Nf1 mediates a new cross-talk between Ras and Rho signaling pathways within the superfamily of small GTPases.

Comparative oncogenomics implicates the neurofibromin 1 gene (NF1) as a breast cancer driver

Identifying genomic alterations driving breast cancer is complicated by tumor diversity and genetic heterogeneity. Relevant mouse models are powerful for untangling this problem because such heterogeneity can be controlled. Inbred Chaos3 mice exhibit high levels of genomic instability leading to mammary tumors that have tumor gene expression profiles closely resembling mature human mammary luminal cell signatures. We genomically characterized mammary adenocarcinomas from these mice to identify cancer-causing genomic events that overlap common alterations in human breast cancer. Chaos3 tumors underwent recurrent copy number alterations (CNAs), particularly deletion of the RAS inhibitor Neurofibromin 1 (Nf1) in nearly all cases. These overlap with human CNAs including NF1, which is deleted or mutated in 27.7% of all breast carcinomas. Chaos3 mammary tumor cells exhibit RAS hyperactivation and increased sensitivity to RAS pathway inhibitors. These results indicate that spontaneous NF1 loss can drive breast cancer. This should be informative for treatment of the significant fraction of patients whose tumors bear NF1 mutations.

Nanog increases focal adhesion kinase (FAK) promoter activity and expression and directly binds to FAK protein to be phosphorylated

Nanog and FAK were shown to be overexpressed in cancer cells. In this report, the Nanog overexpression increased FAK expression in 293, SW480, and SW620 cancer cells. Nanog binds the FAK promoter and up-regulates its activity, whereas Nanog siRNA decreases FAK promoter activity and FAK mRNA. The FAK promoter contains four Nanog-binding sites. The site-directed mutagenesis of these sites significantly decreased up-regulation of FAK promoter activity by Nanog. EMSA showed the specific binding of Nanog to each of the four sites, and binding was confirmed by ChIP assay. Nanog directly binds the FAK protein by pulldown and immunoprecipitation assays, and proteins co-localize by confocal microscopy. Nanog binds the N-terminal domain of FAK. In addition, FAK directly phosphorylates Nanog in a dose-dependent manner by in vitro kinase assay and in cancer cells in vivo. The site-directed mutagenesis of Nanog tyrosines, Y35F and Y174F, blocked phosphorylation and binding by FAK. Moreover, overexpression of wild type Nanog increased filopodia/lamellipodia formation, whereas mutant Y35F and Y174F Nanog did not. The wild type Nanog increased cell invasion that was inhibited by the FAK inhibitor and increased by FAK more significantly than with the mutants Y35F and Y174F Nanog. Down-regulation of Nanog with siRNA decreased cell growth reversed by FAK overexpression. Thus, these data demonstrate the regulation of the FAK promoter by Nanog, the direct binding of the proteins, the phosphorylation of Nanog by FAK, and the effect of FAK and Nanog cross-regulation on cancer cell morphology, invasion, and growth that plays a significant role in carcinogenesis.

From neurodevelopment to neurodegeneration: the interaction of neurofibromin and valosin-containing protein/p97 in regulation of dendritic spine formation

Both Neurofibromatosis type I (NF1) and inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) are autosomal dominant genetic disorders. These two diseases are fully penetrant but with high heterogeneity in phenotypes, suggesting the involvement of genetic modifiers in modulating patients' phenotypes. Although NF1 is recognized as a developmental disorder and IBMPFD is associated with degeneration of multiple tissues, a recent study discovered the direct protein interaction between neurofibromin, the protein product of the NF1 gene, and VCP/p97, encoded by the causative gene of IBMPFD. Both NF1 and VCP/p97 are critical for dendritic spine formation, which provides the cellular mechanism explaining the cognitive deficits and dementia found in patients. Moreover, disruption of the interaction between neurofibromin and VCP impairs dendritic spinogenesis. Neurofibromin likely influences multiple downstream pathways to control dendritic spinogenesis. One is to activate the protein kinase A pathway to initiate dendritic spine formation; another is to regulate the synaptic distribution of VCP and control the activity of VCP in dendritic spinogenesis. Since neurofibromin and VCP/p97 also regulate cell growth and bone metabolism, the understanding of neurofibromin and VCP/p97 in neurons may be applied to study of cancer and bone. Statin treatment rescues the spine defects caused by VCP deficiency, suggesting the potential role of statin in clinical treatment for these two diseases.

Molecular mechanisms promoting the pathogenesis of Schwann cell neoplasms

Neurofibromas, schwannomas and malignant peripheral nerve sheath tumors (MPNSTs) all arise from the Schwann cell lineage. Despite their common origin, these tumor types have distinct pathologies and clinical behaviors; a growing body of evidence indicates that they also arise via distinct pathogenic mechanisms. Identification of the genes that are mutated in genetic diseases characterized by the development of either neurofibromas and MPNSTs [neurofibromatosis type 1 (NF1)] or schwannomas [neurofibromatosis type 2 (NF2), schwannomatosis and Carney complex type 1] has greatly advanced our understanding of these mechanisms. The development of genetically engineered mice with ablation of NF1, NF2, SMARCB1/INI1 or PRKAR1A has confirmed the key role these genes play in peripheral nerve sheath tumorigenesis. Establishing the functions of the NF1, NF2, SMARCB1/INI1 and PRKAR1A gene products has led to the identification of key cytoplasmic signaling pathways promoting Schwann cell neoplasia and identified new therapeutic targets. Analyses of human neoplasms and genetically engineered mouse models have established that interactions with other tumor suppressors such as TP53 and CDKN2A promote neurofibroma-MPNST progression and indicate that intratumoral interactions between neoplastic and non-neoplastic cell types play an essential role in peripheral nerve sheath tumorigenesis. Recent advances have also provided new insights into the identity of the neural crest-derived populations that give rise to different types of peripheral nerve sheath tumors. Based on these findings, we now have an initial outline of the molecular mechanisms driving the pathogenesis of neurofibromas, MPNSTs and schwannomas. However, this improved understanding in turn raises a host of intriguing new questions.

Valosin-containing protein and neurofibromin interact to regulate dendritic spine density

Inclusion body myopathy with Paget disease of bone and frontotemporal dementia (IBMPFD) is an autosomal dominant disorder characterized by progressive myopathy that is often accompanied by bone weakening and/or frontotemporal dementia. Although it is known to be caused by mutations in the gene encoding valosin-containing protein (VCP), the underlying disease mechanism remains elusive. Like IBMPFD, neurofibromatosis type 1 (NF1) is an autosomal dominant disorder. Neurofibromin, the protein encoded by the NF1 gene, has been shown to regulate synaptogenesis. Here, we show that neurofibromin and VCP interact and work together to control the density of dendritic spines. Certain mutations identified in IBMPFD and NF1 patients reduced the interaction between VCP and neurofibromin and impaired spinogenesis. The functions of neurofibromin and VCP in spinogenesis were shown to correlate with the learning disability and dementia phenotypes seen in patients with IBMPFD. Consistent with the previous finding that treatment with a statin rescues behavioral defects in Nf1(+/-) mice and providing further support for our hypothesis that there is crosstalk between neurofibromin and VCP, statin exposure neutralized the effect of VCP knockdown on spinogenesis in cultured hippocampal neurons. The data presented here demonstrate that there is a link between IBMPFD and NF1 and indicate a role for VCP in synapse formation.

Genetically engineered mouse models shed new light on the pathogenesis of neurofibromatosis type I-related neoplasms of the peripheral nervous system

Neurofibromatosis type 1 (NF1), the most common genetic disorder affecting the human nervous system, is characterized by the development of multiple benign Schwann cell tumors in skin and large peripheral nerves. These neoplasms, which are termed dermal and plexiform neurofibromas respectively, have distinct clinical courses; of particular note, plexiform, but not dermal, neurofibromas often undergo malignant progression to form malignant peripheral nerve sheath tumors (MPNSTs), the most common malignancy occurring in NF1 patients. In recent years, a number of genetically engineered mouse models have been created to investigate the molecular mechanisms driving the pathogenesis of these tumors. These models have been designed to address key questions including: (1) whether NF1 loss in the Schwann cell lineage is essential for tumorigenesis; (2) what cell type(s) in the Schwann cell lineage gives rise to dermal neurofibromas, plexiform neurofibromas and MPNSTs; (3) how the tumor microenvironment contributes to neoplasia; (4) what additional mutations contribute to neurofibroma-MPNST progression; (5) what role different neurofibromin-regulated Ras proteins play in this process and (6) how dysregulated growth factor signaling facilitates PNS tumorigenesis. In this review, we summarize the major findings from each of these models and their limitations as well as how discrepancies between these models may be reconciled. We also discuss how information gleaned from these models can be synthesized to into a comprehensive model of tumor formation in peripheral nervous system and consider several of the major questions that remain unanswered about this process.

Focal adhesion kinase regulation of mechanotransduction and its impact on endothelial cell functions

Vascular endothelial cells lining the blood vessels form the interface between the bloodstream and the vessel wall and as such they are continuously subjected to shear and cyclic stress from the flowing blood in the lumen. Additional mechanical stimuli are also imposed on these cells in the form of substrate stiffness transmitted from the extracellular matrix components in the basement membrane, and additional mechanical loads imposed on the lung endothelium as the result of respiration or mechanical ventilation in clinical settings. Focal adhesions (FAs) are complex structures assembled at the abluminal endothelial plasma membrane which connect the extracellular filamentous meshwork to the intracellular cytoskeleton and hence constitute the ideal checkpoint capable of controlling or mediating transduction of bidirectional mechanical signals. In this review we focus on focal adhesion kinase (FAK), a component of FAs, which has been studied for a number of years with regards to its involvement in mechanotransduction. We analyzed the recent advances in the understanding of the role of FAK in the signaling cascade(s) initiated by various mechanical stimuli with particular emphasis on potential implications on endothelial cell functions.

Analysis of steroid hormone effects on xenografted human NF1 tumor schwann cells

The neurofibroma, a common feature of neurofibromatosis type 1 (NF1), is a benign peripheral nerve sheath tumor that contains predominantly Schwann cells (SC). There are reports that neurofibroma growth may be affected by hormonal changes, particularly in puberty and pregnancy, suggesting an influence by steroid hormones. This study examined the effects of estrogen and progesterone on proliferation and apoptosis in a panel of NF1 tumor xenografts. SC-enriched cultures derived from three human NF1 tumor types (dermal neurofibroma, plexiform neurofibroma, and malignant peripheral nerve sheath tumor (MPNST)) were xenografted in sciatic nerves of ovariectomized scid /Nf1-/+ mice. At the same time, mice were implanted with time-release pellets for systemic delivery of progesterone, estrogen or placebo. Proliferation and apoptosis by the xenografted SC were examined two months after implantation, by Ki67 immunolabeling and TUNEL. Estrogen was found to increase the growth of all three MPNST xenografts. Progesterone was associated with increased growth in two of the three MPNSTs, yet decreased growth of the other. Of the four dermal neurofibroma xenografts tested, estrogen caused a statistically significant growth increase in one, and progesterone did in another. Of the four plexiform neurofibroma SC xenografts, estrogen and progesterone significantly decreased growth in one of the xenografts, but not the other three. No relationship of patient age or gender to steroid response was observed. These findings indicate that human NF1 Schwann cells derived from some tumors show increased proliferation or decreased apoptosis in response to particular steroid hormones in a mouse xenograft model. This suggests that anti-estrogen or anti-progesterone therapies may be worth considering for specific NF1 neurofibromas and MPNSTs.