Neurofibromatosis Type 1 Tumor Research Articles

Inhibition of autophagy as a novel treatment for neurofibromatosis type 1 tumors.

Neurofibromatosis type 1 (NF1) is a genetic disorder caused by mutation of the NF1 gene that is associated with various symptoms, including the formation of benign tumors, called neurofibromas, within nerves. Drug treatments are currently limited. The mitogen-activated protein kinase kinase (MEK) inhibitor selumetinib is used for a subset of plexiform neurofibromas (PNs) but is not always effective and can cause side effects. Therefore, there is a clear need to discover new drugs to target NF1-deficient tumor cells. Using a Drosophila cell model of NF1, we performed synthetic lethal screens to identify novel drug targets. We identified 54 gene candidates, which were validated with variable dose analysis as a secondary screen. Pathways associated with five candidates could be targeted using existing drugs. Among these, chloroquine (CQ) and bafilomycin A1, known to target the autophagy pathway, showed the greatest potential for selectively killing NF1-deficient Drosophila cells. When further investigating autophagy-related genes, we found that 14 out of 30 genes tested had a synthetic lethal interaction with NF1. These 14 genes are involved in multiple aspects of the autophagy pathway and can be targeted with additional drugs that mediate the autophagy pathway, although CQ was the most effective. The lethal effect of autophagy inhibitors was conserved in a panel of human NF1-deficient Schwann cell lines, highlighting their translational potential. The effect of CQ was also conserved in a Drosophila NF1 in vivo model and in a xenografted NF1-deficient tumor cell line grown in mice, with CQ treatment resulting in a more significant reduction in tumor growth than selumetinib treatment. Furthermore, combined treatment with CQ and selumetinib resulted in a further reduction in NF1-deficient cell viability. In conclusion, NF1-deficient cells are vulnerable to disruption of the autophagy pathway. This pathway represents a promising target for the treatment of NF1-associated tumors, and we identified CQ as a candidate drug for the treatment of NF1 tumors.

NFS-20. DECIPHERING CELLULAR CROSSTALK IN PERIPHERAL NERVOUS SYSTEM TUMORS ASSOCIATED WITH NEUROFIBROMATOSIS TYPE 1 THROUGH SINGLE-CELL RNA SEQUENCING

Abstract BACKGROUND Neurofibromatosis Type 1 (NF1) is a genetic disorder characterized by mutations and dysfunctional expression of neurofibromin 1 gene, a critical tumor-suppressor gene. NF1’s complex pathophysiology involves dysregulation of the RAS-MAPK signaling pathway, resulting in sustained MAPK signaling. Among others, the spectrum of clinical features includes low-grade tumors (e.g. plexiform neurofibromas (pNFs)) and malignant peripheral nerve sheath tumors (MPNST). While surgical removal of peripheral nerve tumors is common, total resection is often unattainable. Additionally, approved therapies comprising MEK inhibitors fail to prevent malignization, highlighting the urgent need for novel targets for effective therapies. METHODS To explore novel potential targets across a broad spectrum, we analyzed published scRNA-seq datasets (Kershner et al. 2021, Wu et al. 2022) from human patients, including pNFs and MPNSTs. We further investigated key pathways in vitro with patient-derived cell culture models. RESULTS ScRNA-seq provides insight into complex networks of cell-to-cell interactions that drive the malignant phenotype of cancerous tissues. Due to the rich presence of ECM in NF1 tumors we aimed to investigate cell types contributing to key extracellular matrix (ECM) components and associated signaling pathways. Analysis of 19 NF1 tumor samples revealed consistent presence of Schwann cells (SCs), fibroblasts, endothelial cells, and immune cells. Proliferating cells were found in MPNSTs, while pericytes were exclusive to pNFs. We compared secreted and ECM signaling between the cell types of both tumors. Our analysis discovered, among other findings, collagen signaling, highlighting fibroblasts as emitters and SCs as receivers. We further confirmed these findings through culturing of NF1-derived cells in vitro with and without collagen, observing increased cell proliferation in the presence of collagen. Further experiments and analyses are ongoing. CONCLUSIONS The emphasis on ECM and signaling adds depth to our understanding of NF1 pathogenesis and suggests potential therapeutic targets.

PD-L1 regulates tumor proliferation and T-cell function in NF2-associated meningiomas.

Programmed death-ligand 1 (PD-L1) expression is an immune evasion mechanism that has been demonstrated in many tumors and is commonly associated with a poor prognosis. Over the years, anti-PD-L1 agents have gained attention as novel anticancer therapeutics that induce durable tumor regression in numerous malignancies. They may be a new treatment choice for neurofibromatosis type 2 (NF2) patients. The aims of this study were to detect the expression of PD-L1 in NF2-associated meningiomas, explore the effect of PD-L1 downregulation on tumor cell characteristics and T-cell functions, and investigate the possible pathways that regulate PD-L1 expression to further dissect the possible mechanism of immune suppression in NF2 tumors and to provide new treatment options for NF2 patients. PD-L1 is heterogeneously expressed in NF2-associated meningiomas. After PD-L1 knockdown in NF2-associated meningioma cells, tumor cell proliferation was significantly inhibited, and the apoptosis rate was elevated. When T cells were cocultured with siPD-L1-transfected NF2-associated meningioma cells, the expression of CD69 on both CD4+ and CD8+ T cells was partly reversed, and the capacity of CD8+ T cells to kill siPD-L1-transfected tumor cells was partly restored. Results also showed that the PI3K-AKT-mTOR pathway regulates PD-L1 expression, and the mTOR inhibitor rapamycin rapidly and persistently suppresses PD-L1 expression. Invivo experimental results suggested that anti-PD-L1 antibody may have a synergetic effect with the mTOR inhibitor in reducing tumor cell proliferation and that reduced PD-L1 expression could contribute to antitumor efficacy. Targeting PD-L1 could be helpful for restoring the function of tumor-infiltrating lymphocytes and inducing apoptosis to inhibit tumor proliferation in NF2-associated meningiomas. Dissecting the mechanisms of the PD-L1-driven tumorigenesis of NF2-associated meningioma will help to improve our understanding of the mechanisms underlying tumor progression and could facilitate further refinement of current therapies to improve the treatment of NF2 patients.

PET Imaging of Neurofibromatosis Type 1 with a Fluorine-18 Labeled Tryptophan Radiotracer.

Neurofibromatosis type 1 (NF1) is a neurocutaneous disorder. Plexiform neurofibromas (PNFs) are benign tumors commonly formed in patients with NF1. PNFs have a high incidence of developing into malignant peripheral nerve sheath tumors (MPNSTs) with a 5-year survival rate of only 30%. Therefore, the accurate diagnosis and differentiation of MPNSTs from benign PNFs are critical to patient management. We studied a fluorine-18 labeled tryptophan positron emission tomography (PET) radiotracer, 1-(2-[18F]fluoroethyl)-L-tryptophan (L-[18F]FETrp), to detect NF1-associated tumors in an animal model. An ex vivo biodistribution study of L-[18F]FETrp showed a similar tracer distribution and kinetics between the wild-type and triple mutant mice with the highest uptake in the pancreas. Bone uptake was stable. Brain uptake was low during the 90-min uptake period. Static PET imaging at 60 min post-injection showed L-[18F]FETrp had a comparable tumor uptake with [1⁸F]fluorodeoxyglucose (FDG). However, L-[18F]FETrp showed a significantly higher tumor-to-brain ratio than FDG (n = 4, p < 0.05). Sixty-minute-long dynamic PET scans using the two radiotracers showed similar kidney, liver, and lung kinetics. A dysregulated tryptophan metabolism in NF1 mice was further confirmed using immunohistostaining. L-[18F]FETrp is warranted to further investigate differentiating malignant NF1 tumors from benign PNFs. The study may reveal the tryptophan-kynurenine pathway as a therapeutic target for treating NF1.

The NF1+/- Immune Microenvironment: Dueling Roles in Neurofibroma Development and Malignant Transformation.

Neurofibromatosis type 1 (NF1) is a common genetic disorder resulting in the development of both benign and malignant tumors of the peripheral nervous system. NF1 is caused by germline pathogenic variants or deletions of the NF1 tumor suppressor gene, which encodes the protein neurofibromin that functions as negative regulator of p21 RAS. Loss of NF1 heterozygosity in Schwann cells (SCs), the cells of origin for these nerve sheath-derived tumors, leads to the formation of plexiform neurofibromas (PNF)-benign yet complex neoplasms involving multiple nerve fascicles and comprised of a myriad of infiltrating stromal and immune cells. PNF development and progression are shaped by dynamic interactions between SCs and immune cells, including mast cells, macrophages, and T cells. In this review, we explore the current state of the field and critical knowledge gaps regarding the role of NF1(Nf1) haploinsufficiency on immune cell function, as well as the putative impact of Schwann cell lineage states on immune cell recruitment and function within the tumor field. Furthermore, we review emerging evidence suggesting a dueling role of Nf1+/- immune cells along the neurofibroma to MPNST continuum, on one hand propitiating PNF initiation, while on the other, potentially impeding the malignant transformation of plexiform and atypical neurofibroma precursor lesions. Finally, we underscore the potential implications of these discoveries and advocate for further research directed at illuminating the contributions of various immune cells subsets in discrete stages of tumor initiation, progression, and malignant transformation to facilitate the discovery and translation of innovative diagnostic and therapeutic approaches to transform risk-adapted care.

Gene therapy strategies and prospects for neurofibromatosis type 1

To summarize the gene therapy strategies for neurofibromatosis type 1 (NF1) and related research progress. 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. 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. Gene therapy, including both the transgenic therapy and gene editing, is expected to become an important new therapeutic approach for NF1 patients.

Dental Developmental Stages and Decayed, Missing, and Restored Teeth in Neurofibromatosis Type 1-affected Children and Adolescents.

Neurofibromatosis type 1 (NF1) is an autosomal dominant inherited tumor predisposition disease with a highly variable phenotype. The influence of the characteristic NF1 tumors (neurofibromas) on dentition has not yet been examined in detail. The aim of the study was to assess the dentition of NF1 children and adolescents, considering the symmetry of tooth development. The panoramic radiographs of 59 patients with a confirmed NF1 diagnosis were compared with 59 age-and-sex-matched controls. The stages of tooth development on the sides of the jaw, added to a score, were assessed. In addition, the number of filled or decayed teeth, and the number of retained or missing teeth were assessed. The tooth development of both study groups is symmetrical for almost all parameters and in the same developmental stage according to the sum score of the tooth development stages. Discrete developmental delays of teeth, in particular in the oral area of facial plexiform neurofibroma (PNF) are noticeable. NF1 patients' teeth showed less decay and more restorations than that of the control group. The facial PNF (FPNF) does not impair emergence of deciduous teeth. Development of dentition of NF1 patients does not differ from the general population. However, FPNF with oral tumor components often prevent mesial movement of permanent molars and premolars, so these teeth do not develop contact (spacing), hardly emerge or may stay retained in bone. Oral PNF may have a low-retarding effect on some tooth root development (e.g., wisdom teeth). This effect is negligible when comparing the affected and unaffected sides of the jaw and is probably non-specific. Key words:Neurofibromatosis type 1, plexiform neurofibroma, dentition, mixed dentition, symmetry, oral health, tooth development.

Is vestibular schwannoma really a benign tumor? Case report and review

Introduction: Vestibular schwannoma (VS) is a benign tumor that develops from Schwann cells of the eighth cranial pair, mainly in the cerebellopontine angle. Case Presentation: We report the case of a 30-year-old female patient who developed left otalgia associated with neglected tinnitus, the evolution of which was marked by the development of a static cerebellar syndrome and a behavioral disorder, whose brain MRI revealed a locally advanced process in the cerebellopontine angle at the expense of the vestibulocochlear nerve, in favor of a VS, complicated by involvement of the tonsils, which unfortunately led to the patient’s death. Discussion: VS, formerly known as acoustic neuroma, is an extra-axial intracranial tumor that accounts for over 80% of pontocerebellar angle tumors, and is secondary in the majority of cases to inactivation of the neurofibromatosis type 2 (NF2) tumor suppressor gene, either by mutation of the NF2 gene or loss of chromosome 22q. In the majority of cases, it is unilateral and solitary, but in almost 8% of cases, it is associated with NF2. Cerebral MRI is the examination of choice for the detection, characterization, and diagnosis of VS without the need for biopsy, mainly with T1-weighted sequences before and after gadolinium injection. Treatment is based essentially on surgery or radiosurgery, depending on the size, impact, and expertise of the treatment team. Conclusion: VS remains an important intracranial tumor entity, which can be life-threatening in cases of advanced local invasion.

Development of a novel treatment by inhibition of mast cell-associated proteins in neurofibroma tumours

Neurofibromatosis type 1 (NF1), also known as von Recklinghausen's disease, is an inherited disorder that will (with high probability) lead to multiple benign tumors in the future. There are several types of NF1 tumors and there is no way to control their incidence other than surgical resection. Associate Professor Misa Yamamoto, an expert in regenerative medicine, is currently conducting a project to elucidate the tumor growth mechanism in NF1 patients. This will lead to the development of innovative treatments for this disease. The researchers are affiliated with the Department of Clinical Laboratory Sciences, Graduate School of Medicine, Yamaguchi University, Japan. Currently, we have worked on analyzing the function of mast cells in cutaneous neurofibroma and aim to develop a new treatment method that suppresses the function of mast cells involved in tumor growth. There are still many gaps in knowledge regarding NF1. Neurofibroma tumors are known to contain a considerable number of mast cells though Professor Yamamoto found with the research has shown that each cell has an abnormally high concentration of an inflammatory substance called tryptase. This means that neurofibromas are constantly exposed to a strong inflammatory state, suggesting that it is difficult to stop tumor growth unless inflammation is stopped. Professor Yamamoto investigated the differences in the properties of disease-specific mast cells with NF1 gene mutations and mast cells derived from healthy subjects, and clarified differences in the production of tryptase, TGF-β1, and Stem Cell Factor. These findings suggest that tumor growth is driven by the overexpression of these proteins, and researchers believe that blocking the pathways that suppress the expression of these proteins can reduce inflammation and tumor growth.

Unilateral gingival enlargement in a patient with neurofibromatosis type 1 - Case report

Neurofibromatosis type 1 (NF1), also known as von Recklinghausen disease, is an autosomal disease caused by mutations in the NF1 tumor suppressor gene. NF1 affects bones, nerves, soft tissues and skin. Oral manifestations of NF1 consist of soft tissue tumors, bone defects, periodontal and dental changes, and altered salivary flow. We report one such case, a 26-year-old man with Gingival enlargement, Café au lait spots, axillary freckling, and multiple nodules on his body.

Assessment of Ecotropic Viral Integration Site 2B (EVI2B) Gene in Juvenile Myelomonocytic Leukemia and Neurofibromatosis Type 1 NF1 Tumors.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease that affects the development and growth of various tissues. NF1 is a major risk factor for the development of malignancies, particularly malignant peripheral nerve sheath tumors, optic gliomas, and leukemia. NF1 encodes a neurofibromin. Three genes, EVI2A, EVI2B, and OMGP, are embedded within intron 27b of NF1. However, the function of these genes remains unclear. EVI2A and EVI2B encode for putative transmembrane proteins. Mouse homologs are associated with viral insertions involved in leukemia in mice. Mouse Evi2b has been identified as a direct target gene of C/EBPα, a transcription factor critical for myeloid differentiation. Also possible is that these genes are related to the leukemia observed in patients with NF1. These genes might act as modifiers of NF1 phenotypic variations. Therefore, we investigated the EVI2B gene in leukemia and NF1 tumors. We analyzed DNA from 10, 20, and 3 patients with NF1, leukemia, and NF1-leukemia, respectively, and six NF1 tumor tissues. DNA sequencing analysis was used to identify the viral integration sequence, and the protein amounts and EVI2B gene expression were analyzed by flow cytometry and quantitative real-time PCR techniques. The EVI2B gene expression was increased in cutaneous neurofibroma compared with the control both at the level of protein and mRNA. However, its expression in plexiform neurofibroma was decreased significantly at protein level and increased at mRNA level compare to control. Moreover, integration of 455 bases near the 3' end of the exon was detected. When this integrated sequence was blasted into the NCBI retroviral genome database, an 87% match with the HIV-1 virus envelope gene was obtained. These preliminary results show that EVI2B might be important in NF1 tumorigenesis and leukemia.

Cellular mechanisms of heterogeneity in NF2-mutant schwannoma

Schwannomas are common sporadic tumors and hallmarks of familial neurofibromatosis type 2 (NF2) that develop predominantly on cranial and spinal nerves. Virtually all schwannomas result from inactivation of the NF2 tumor suppressor gene with few, if any, cooperating mutations. Despite their genetic uniformity schwannomas exhibit remarkable clinical and therapeutic heterogeneity, which has impeded successful treatment. How heterogeneity develops in NF2-mutant schwannomas is unknown. We have found that loss of the membrane:cytoskeleton-associated NF2 tumor suppressor, merlin, yields unstable intrinsic polarity and enables Nf2−/− Schwann cells to adopt distinct programs of ErbB ligand production and polarized signaling, suggesting a self-generated model of schwannoma heterogeneity. We validated the heterogeneous distribution of biomarkers of these programs in human schwannoma and exploited the synchronous development of lesions in a mouse model to establish a quantitative pipeline for studying how schwannoma heterogeneity evolves. Our studies highlight the importance of intrinsic mechanisms of heterogeneity across human cancers.

Advances in Targeted Therapy for Neurofibromatosis Type 2 (NF2)-Associated Vestibular Schwannomas.

Neurofibromatosis 2 (NF2) is an autosomal-dominant genetic disorder characterized by bilateral vestibular schwannomas (VS), meningiomas, ependymomas, spinal and peripheral schwannomas, optic gliomas, and juvenile cataracts. Ongoing studies provide new insight into the role of the NF2 gene and merlin in VS tumorigenesis. As NF2 tumor biology becomes increasingly understood, therapeutics targeting specific molecular pathways have been developed and evaluated in preclinical and clinical studies. NF2-associated VS are a source of significant morbidity with current treatments including surgery, radiation, and observation. Currently, there are no FDA-approved medical therapies for VS, and the development of selective therapeutics is a high priority. This manuscript reviews NF2 tumor biology and current therapeutics undergoing investigation for treatment of patients with VS.

Pilot study for the treatment of cutaneous neurofibromas in neurofibromatosis type 1 patients using topical sirolimus gel

To the Editor: Neurofibromatosis type 1 (NF1) is a genetic disorder involving plexiform and cutaneous neurofibromas (cNFs) in which the constitutive activation of MAPK (mitogen-activated protein kinase) and mechanistic target of rapamycin complex 1 (mTORC1) promote tumorigenesis.1 Unlike the case for plexiform neurofibromas,2 no clinical trials have been conducted on cNFs that impair quality of life. mTORC1 is involved in the tumor microenvironment in addition to cell proliferation. Therefore, mTORC1 inhibitors appear extremely effective against NF1 tumors, where the microenvironment is essential for tumorigenesis.

Long-term follow-up of surgical intervention pattern in pediatric low-grade gliomas: report from the German SIOP-LGG 2004 cohort.

Neurosurgical treatment is an integral part of the treatment algorithms for pediatric low-grade glioma (LGG), yet patterns of surgical procedures are rarely challenged. The objective of this study was to evaluate surgical treatment patterns in pediatric LGG. The German Societé Internationale d'Oncologie Pédiatrique (SIOP)-LGG 2004 cohort was analyzed to identify relevant patient and tumor characteristics associated with time to death, next surgery, number of resections, and radiological outcome. A total of 1271 patients underwent 1713 neurosurgical interventions (1 intervention in 947, 2 in 230, 3 in 70, and 4-6 in 24). The median age of the study population was 8.57 years at first surgery, and 46.1% were female. Neurofibromatosis type 1 (NF1) was found in 4.4%, and 5.4% had tumor dissemination. Three hundred fifty-four patients (27.9%) had chemotherapy and/or radiotherapy. The cumulative incidence of second surgery at 10 years was 26%, and was higher for infants, those with spinal and supratentorial midline (SML) tumors, and those with pilomyxoid astrocytomas. The hazard ratio for subsequent surgery was higher given dissemination and noncomplete initial resection, and lower for caudal brainstem and SML tumors. Among 1225 patients with fully documented surgical records and radiological outcome, 613 reached complete remission during the observation period, and 50 patients died. Patients with pilocytic astrocytoma had higher chances for a final complete remission, whereas patients with initial partial or subtotal tumor resection, dissemination, NF1, or primary tumor sites in the spinal cord and SML had lower chances. Neurosurgery is a key element of pediatric LGG treatment. In almost 50% of the patients, however, at least some tumor burden will remain during long-term follow-up. This study found that most of these patients reached a stable disease status without further surgeries. Multidisciplinary team decisions must balance the goal of complete resection, risk factors, repeated surgeries, and possible treatment alternatives in a wide range of heterogeneous entities. Procedural details and neurological outcome should be recorded to better assess their impact on long-term outcome.

Neurofibromatosis Type 2: Multiple Meningiomatosis and Vestibular Schwannomas on 68 Ga-DOTATATE PET/CT.

Neurofibromatosis type 2 (NF2) is an autosomal-dominant tumor predisposing syndrome that results from mutations in the NF2 tumor suppressor gene on chromosome 22. The development of bilateral vestibular schwannomas is the characteristic feature of the disease. However, other nervous system tumors, including meningiomas, ependymomas, and schwannomas, can be seen frequently. Herein, we present 68 Ga-DOTATATE PET/CT findings of 2 siblings with NF2.

Neurofibromatosis from Head to Toe: What the Radiologist Needs to Know.

Neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) are autosomal dominant inherited neurocutaneous disorders or phakomatoses secondary to mutations in the NF1 and NF2 tumor suppressor genes, respectively. Although they share a common name, NF1 and NF2 are distinct disorders with a wide range of multisystem manifestations that include benign and malignant tumors. Imaging plays an essential role in diagnosis, surveillance, and management of individuals with NF1 and NF2. Therefore, it is crucial for radiologists to be familiar with the imaging features of NF1 and NF2 to allow prompt diagnosis and appropriate management. Key manifestations of NF1 include café-au-lait macules, axillary or inguinal freckling, neurofibromas or plexiform neurofibromas, optic pathway gliomas, Lisch nodules, and osseous lesions such as sphenoid dysplasia, all of which are considered diagnostic features of NF1. Other manifestations include focal areas of signal intensity in the brain, low-grade gliomas, interstitial lung disease, various abdominopelvic neoplasms, scoliosis, and vascular dysplasia. The various NF1-associated abdominopelvic neoplasms can be categorized by their cellular origin: neurogenic neoplasms, interstitial cells of Cajal neoplasms, neuroendocrine neoplasms, and embryonal neoplasms. Malignant peripheral nerve sheath tumors and intracranial tumors are the leading contributors to mortality in NF1. Classic manifestations of NF2 include schwannomas, meningiomas, and ependymomas. However, NF2 may have shared cutaneous manifestations with NF1. Lifelong multidisciplinary management is critical for patients with either disease. The authors highlight the genetics and molecular pathogenesis, clinical and pathologic features, imaging manifestations, and multidisciplinary management and surveillance of NF1 and NF2. Online supplemental material is available for this article. ©RSNA, 2022.

Adolescents and young adults with neurofibromatosis type 1: A descriptive study of adaptive functioning.

Neurofibromatosis type 1 (NF1) is a genetic syndrome affecting about 1 in 3500 individuals; many of those affected have plexiform neurofibroma (pNF) tumors and associated symptoms and complications. Furthermore, learning and attention problems, as well as deficits in adaptive functioning, are common, often beginning in early childhood. This study aimed to describe adaptive functioning and to examine relationships between adaptive functioning and cognitive and academic variables and level of independence among adolescents and young adults (AYA) with NF1 and pNF tumors. Fifty-five AYA aged 16-31 years participated in a series of neuropsychological evaluations while parents completed the Vineland Adaptive Behavior Scales (VABS-II) as part of a larger natural history study. Over one-third (35%) of AYA were neither in school nor employed. Mean VABS-II daily living and socialization scores were low average while mean Verbal and Performance IQ scores were average. VABS-II scores were positively correlated with processing speed, executive functioning, and working memory scores. Verbal IQ was the only significant predictor of work/school status. Identification of the correlates and predictors of adaptive functioning and life achievement can help guide healthcare providers with the early identification of risk factors and possible areas for intervention.

The structure of neurofibromin isoform 2 reveals different functional states

The autosomal dominant monogenetic disease neurofibromatosis type 1 (NF1) affects approximately one in 3,000 individuals and is caused by mutations in the NF1 tumour suppressor gene, leading to dysfunction in the protein neurofibromin (Nf1)1,2. As a GTPase-activating protein, a key function of Nf1 is repression of the Ras oncogene signalling cascade. We determined the human Nf1 dimer structure at an overall resolution of 3.3 Å. The cryo-electron microscopy structure reveals domain organization and structural details of the Nf1 exon 23a splicing3 isoform 2 in a closed, self-inhibited, Zn-stabilized state and an open state. In the closed conformation, HEAT/ARM core domains shield the GTPase-activating protein-related domain (GRD) so that Ras binding is sterically inhibited. In a distinctly different, open conformation of one protomer, a large-scale movement of the GRD occurs, which is necessary to access Ras, whereas Sec14-PH reorients to allow interaction with the cellular membrane4. Zn incubation of Nf1 leads to reduced Ras-GAP activity with both protomers in the self-inhibited, closed conformation stabilized by a Zn binding site between the N-HEAT/ARM domain and the GRD–Sec14-PH linker. The transition between closed, self-inhibited states of Nf1 and open states provides guidance for targeted studies deciphering the complex molecular mechanism behind the widespread neurofibromatosis syndrome and Nf1 dysfunction in carcinogenesis.

Multiplatform Genomic Profiling and Immunohistochemistry Identify Prognostic and Predictive Signatures in Malignant Peripheral Nerve Sheath Tumors (MPNSTs)

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive neoplasms arising either sporadically or in patients with neurofibromatosis type 1 (NF1). To elucidate markers of prognosis and treatment response, we retrospectively identified MPNST tumor resection specimens at a single institution and performed histopathologic evaluation, immunohistochemistry (IHC), DNA methylation profiling, and whole exome sequencing (WES).We identified a total of 54 consecutive patients treated at one institution between 1990 and 2019 with tumors meeting diagnostic criteria for MPNST and had sufficient tissue available for comprehensive histopathological evaluation (n = 54), DNA methylation profiling (n = 45) and whole exome sequencing (n = 35, n = 15 with paired normal). Overall survival (OS), metastasis free survival (MFS), and locoregional failure free rate (LFFR), were estimated using the Kaplan-Meier method. Log-rank test, Cox Proportional Hazards regression, and hierarchical clustering were performed in R.The median follow up was 22 months with no significant differences in LFFR, MFS, or OS between NF1 associated (n = 32) and sporadic MPNSTs (n = 22). Radiotherapy significantly improved LFFR (P = 0.05) but not OS. With regard to histopathologic and IHC analyses, increasing tumor grade using a two-tiered system (P = 0.01) and Ki-67 index (P = 0.01) were associated with worse OS. Unsupervised hierarchical clustering of DNA methylation profiles identified two groups with significant differences in chromosome instability and tumor purity but not clinical outcome. Recurrently identified copy number variants (CNVs) included chromosome 22q loss, 11q loss, 10 loss, 9p loss, 8q gain, and 1q loss. Chromosome 9p loss (P = 0.02) and 8q gain (P = 0.04) were significantly associated with worse OS. On WES analysis, recurrently mutated genes included NF1, EED, SUZ12, TP53, and CDKNA2A. Of these alterations, only CKND2A loss (on Chr9p) was associated with worse OS (P = 0.01). With regard to treatment response, MPNSTs exhibiting NF1 and H3K27 trimethylation loss demonstrated greater LFFR benefit from radiation therapy (P = 0.004) compared to NF1 and H3K27 trimethylation intact tumors (P = 0.83) with clinical NF1 diagnosis as the only significantly different baseline parameter between these two subgroups.MPNSTs are a common cause of death in adult patients with NF1. Radiotherapy improves LFFR in all patients, and integrated IHC and genomic analysis further identifies putative prognostic and predictive markers, including the identification of a patient subset in whom the benefit of radiotherapy is most pronounced. Taken together, these data support radiation therapy in management of MPNSTs and suggest molecular characterization may be important for counseling patients with MPNST or potentially informing clinical trial design. Prospective and multi-institutional analyses are needed to validate these findings.