Neurofibromatosis Research Articles

The Cardiofaciocutaneous Syndrome: From Genetics to Prognostic-Therapeutic Implications.

Cardiofaciocutaneous (CFC) syndrome is one of the rarest RASopathies characterized by multiple congenital ectodermal, cardiac and craniofacial abnormalities with a mild to severe ocular, gastrointestinal and neurological involvement. It is an autosomal dominant syndrome, with complete penetrance, caused by heterozygous pathogenic variants in the genes BRAF, MAP2K1/MEK1, MAP2K2/MEK2, KRAS or, rarely, YWHAZ, all part of the RAS-MAPK pathway. This pathway is a signal transduction cascade that plays a crucial role in normal cellular processes such as cell growth, proliferation, differentiation, survival, metabolism and migration. CFC syndrome overlaps with Noonan syndrome, Costello syndrome, neurofibromatosis type 1 and Legius syndrome, therefore making the diagnosis challenging. Neurological involvement in CFC is more severe than in other RASopathies. Phenotypic variability in CFC patients is related to the specific gene affected, without a recognized genotype-phenotype correlation for distinct pathogenic variants. Currently, there is no specific treatment for CFC syndrome. Encouraging zebrafish model system studies suggested that, in the future, MEK inhibitors could be a suitable treatment of progressive phenotypes of CFC in children. A multidisciplinary care is necessary for appropriate medical management.

A bimetallic dual-targeting nanoplatform for combinational ferroptosis activation/epigenetic regulation/photothermal therapy against breast cancer and tumor microenvironment remodeling

Restricted by the complex intracellular ferroptosis regulatory networks, single ferroptotic therapy against breast cancer (BC) yields limited therapeutic outcomes. Therefore, novel combination modes are being widely attempted; however, the interactions between different treatments are still less studied. Herein, we propose a combinational pattern by constructing a novel nanoplatform (T-FeCo/P) composed of Panobinostat (histone deacetylase inhibitor)-loaded iron (Fe)/cobalt (Co)-based metal-organic framework with surface modification of telmisartan for dual 4T1 cell/cancer-associated fibroblast (CAF) targeting. T-FeCo/P exhibits good photothermal performance and forcefully triggers cellular ferroptosis, and the dopant of Fe realizes stronger ferroptosis activation than the corresponding single-metal system. Interestingly, for the first time, Panobinostat is elucidated to promote ferroptosis by inhibiting SLC7A11 transcription and regulating thioredoxin binding protein 2 (TBP2)/thioredoxin (Trx) axis. For tumor microenvironment (TME) remodeling, T-FeCo/P specifically kills CAFs, thus destroying extracellular matrix and retarding C-X-C motif chemokine ligand 12 (CXCL12) secretion, which are beneficial to intratumoral drug penetration and cytotoxic T lymphocyte infiltration. Also, this CAF elimination probably sensibilizes ferroptosis by regulating neurofibromatosis type 2 (NF2)-yes associated protein (YAP) pathway and reducing myeloid-derived suppressor cell infiltration. Our experimental data support T-FeCo/P’s tumoricidal activity thanks to the combined ferroptosis activation, epigenetic regulation, photothermal therapy and TME re-education, providing a mighty pattern for BC treatment and constituting a substantial addition to ferroptosis sensitization.

Screening saves sight: An unusual case of type-1 neurofibromatosis

Neurofibromatosis (NF), described by von Recklinghausen in 1882, consists of at least two distinct disorders: NF1 (von Recklinghausen's or peripheral neurofibromatosis) and NF2, formerly known as 'central neurofibromatosis." The prevalence of NF is approximately 1 in 4,000, and of NF2, 1 in 50,000. Neurofibromatosis type 1 is a multisystemic neurocutaneous disorder with an autosomal dominant hereditary pattern. Ocular manifestations include plexiform neurofibroma of eyelid, Lisch nodules in iris, optic nerve glioma, glaucoma, sphenoid wing dysplasia. Retinal and choroidal involvement are encountered less frequently. Unusual ocular findings include multiple choroidal nevi, combined hamartoma, choroidal Schwannoma, choroidal melanoma and vaso proliferative retinal tumors.Here we report a case of an 18 year old girl diagnosed with neurofibromatosis type 1 who on routine ocular examination was found to have high myopia in both eyes and on fundus examination had a macula ‘on’ inferior retinal detachment with retinal hole in right eye. Inferior retinal detachment is rarely reported in neurofibromatosis type 1. This case emphasizes the importance of conducting ocular examination even in asymptomatic patients with neurofibromatosis, so that early detection and treatment can prevent vision loss secondary to retinal detachment.

Perspectives of adults with neurofibromatosis regarding the design of psychosocial trials: Results from an anonymous online survey.

Individuals with neurofibromatosis, including neurofibromatosis 1 (NF1), neurofibromatosis 2 (NF2)-related schwannomatosis (SWN), and other forms of SWN, often experience disease manifestations and mental health difficulties for which psychosocial interventions may help. An anonymous online survey of adults with neurofibromatosis assessed their physical, social, and emotional well-being and preferences about psychosocial interventions to inform clinical trial design. Neurofibromatosis clinical researchers and patient representatives from the Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration developed the survey. Eligibility criteria included age ≥ 18 years, self-reported diagnosis of NF1, NF2, or SWN, and ability to read and understand English. The online survey was distributed internationally by the Neurofibromatosis Registry and other neurofibromatosis foundations from June to August 2020. Surveys were completed by 630 adults (18-81 years of age; M = 45.5) with NF1 (78%), NF2 (14%), and SWN (8%) who were mostly White, not Hispanic/Latino, female, and from the United States. The majority (91%) reported that their neurofibromatosis symptoms had at least some impact on daily life. In the total sample, 51% endorsed a mental health diagnosis, and 27% without a diagnosis believed they had an undiagnosed mental health condition. Participants indicated that neurofibromatosis affected their emotional (44%), physical (38%), and social (35%) functioning to a high degree. Few reported ever having participated in a drug (6%) or psychosocial (7%) clinical trial, yet 68% reported they "probably" or "definitely" would want to participate in a psychosocial trial if it targeted a relevant concern. Top treatment targets were anxiety, healthier lifestyle, and daily stress. Top barriers to participating in psychosocial trials were distance to clinic, costs, and time commitment. Respondents preferred interventions delivered by clinicians via individual sessions or a combination of group and individual sessions, with limited in-person and mostly remote participation. There were no significant group differences by neurofibromatosis type in willingness to participate in psychosocial trials (p = 0.27). Regarding interest in intervention targets, adults with SWN were more likely to prefer psychosocial trials for pain support compared to those with NF1 (p < 0.001) and NF2 (p < 0.001). This study conducted the largest survey assessing physical symptoms, mental health needs, and preferences for psychosocial trials in adults with neurofibromatosis. Results indicate a high prevalence of disease manifestations, psychosocial difficulties, and untreated mental health problems in adults with neurofibromatosis and a high degree of willingness to participate in psychosocial clinical trials. Patient preferences should be considered when designing and implementing psychosocial interventions to develop the most feasible and meaningful studies.

Multidisciplinary neurofibromatosis conference in the management of patients with neurofibromatosis type 1 and schwannomatosis in a single tertiary care institution.

To evaluate the role of weekly neurofibromatosis (NF) multi-disciplinary conferences (MDC) on the diagnostic and therapeutic plan for patients with NF type 1 (NF1) and schwannomatosis (SWN). This retrospective study reviewed patients with confirmed or suspected NF1 and SWN discussed in weekly MDC from March to July 2021. Demographic data collected included patient age, sex, pre-conference and post-conference diagnosis, radiological studies reviewed, and provider specialties in attendance. Outcomes reported included changes in imaging interpretation and treatment plans, changes in post-conference diagnosis relative to pre-conference diagnosis, and time to completion of the recommended change in treatment. Data from 17 MDC "pre-conference" lists included 75 patients (38 female, 37 males, mean age (years): 38 (range: 6-80)) with NF1 (52%, 39/75) and SWN (36%, 27/75) discussed over a total of 91 case reviews. 18.7% (14/75) of all patients had NF2-related SWN, and 17.3% (13/75) of all patients had non-NF2 SWN. The MDC led to changes in imaging interpretation in 18.7% and changes in patient management in 74.7% (diagnostic testing (n = 52), surgical plan (n = 24), medical treatment (n = 9), clinical trial status (n = 4), and radiation treatment (n = 1)) of cases. Among patients for whom a change in management was recorded, 91% (62/68) completed at least one recommendation (mean time to completion (days): 41.4 (range: 0-278)). Weekly MDC changes the diagnostic and therapeutic management of the majority of patients discussed (74.7%) and promotes a high adherence rate to recommendations (91%).

MODL-07. NF1 MUTATION IN OLIGODENDROCYTE PRECURSOR CELLS INDUCES PRENEOPLASTIC LESIONS IN THE BRAIN

Abstract Oligodendrocyte precursor cells (OPCs) are progenitor cells that give rise to oligodendrocytes in the central nervous system throughout the lifespan. Transcriptomic and lineage tracing studies suggest that OPCs may be the putative cell of origin for many gliomas in children and adults. While children with the neurofibromatosis type 1 (NF1) cancer predisposition syndrome typically develop optic pathway and brainstem gliomas, as many as 50% of children develop gliomas in other brain regions using radiologic criteria. Relevant to these gliomas, discrete patches of hyperdense OPCs were found in the brains of Nf1+/- mice. The OPCs within the lesions display a transient increase in proliferation and hypercellularity. When the brains of mice carrying different heterozygous NF1 patient derived germline Nf1 gene mutations were examined, hyperdense OPC lesions were only seen in mice whose Nf1 mutations also predispose to optic gliomas. Mechanistically, monoallelic KRAS hyperactivation also results in similar OPC hyperdense lesions. Moreover, OPC-specific Nf1-heterozygous mice display similar lesions, while OPC-specific Nf1-knockout results in generalized OPC hyperdensity throughout the entire brain. Taken together, these data suggest the existence of a preneoplastic state conferred by Nf1 mutation in OPCs and establish a tractable model system to explore the transition to glioma in children with NF1.

TMIC-13. EXHAUSTED CD8+ T CELLS MAINTAIN LOW-GRADE GLIOMAS IN NF1-MUTANT MICE

Abstract T cells are minor cellular constituents of the brain tumor microenvironment, but have recently been shown to play critical roles in glioma pathobiology and treatment. Previous studies from our laboratory have shown that T cells are required for the formation and growth of low-grade gliomas (LGGs) in murine models of the Neurofibromatosis type 1 (NF1) tumor predisposition syndrome. To better characterize the immune landscape of these pediatric low-grade tumors, we leveraged single cell RNA sequencing of human pediatric pilocytic astrocytomas and genetically engineered mouse LGG (Nf1-optic glioma) models. First, we showed that both human and murine LGGs contain a CD8+ T cell population expressing PD-1 and TIGIT, similar to conventional exhausted T cell populations. Second, these PD-1+/TIGIT+ CD8+ T cells are actively recruited to the tumor site by Ccl2 where they dictate tumorigenesis through the elaboration of Ccl4, a cytokine necessary for microglia Ccl5-mediated support of Nf1-OPG growth. As such, Ccl4 expression was enriched in PD-1+/TIGIT+ CD8+ T cells relative to all other T cell populations within these tumors. Third, this “exhausted” CD8+ T cell population was exclusively present in the optic nerves, but not in the blood, dura, or deep cervical nodes of optic glioma-bearing mice. Fourth, targeting this PD1+/TIGIT+ exhausted CD8+ T cell population with immune checkpoint monoclonal antibody inhibitors reduced CD8+ T cell tumoral recruitment, Ccl4 production, and optic glioma growth. Collectively, these findings establish an obligate role for PD-1+/TIGIT+ CD8+ T cells in Nf1-optic glioma control and suggest that immune checkpoint modulation may be useful for the treatment of LGGs in children.

RADT-39. CYBERKNIFE: THE CURRENT STATE OF LINAC AS TREATMENT FOR VESTIBULAR SCHWANNOMAS

Abstract INTRODUCTION In the present study, we systematically review the extant literature describing CyberKnife radiosurgery (CKRS) as treatment for vestibular schwannoma (VS). We then perform pooled meta-analysis of long-term tumor control and hearing preservation rates reported across all retrospective observational series describing the efficacy of CKRS. METHODS We queried three databases to identify all primary retrospective studies reporting local tumor control and hearing preservation rates following CKRS for treatment of vestibular schwannoma. All studies returned across the three databases were subject to systematic screen according to pre-defined inclusion and exclusion criteria in a multi-step process performed by two investigators. RESULTS Following a comprehensive systematic search, a total of 15 studies comprising 2018 vestibular schwannoma patients were included. The proportion of females ranged from 30% to 60.3%, and the mean age of all 2,018 patients was 60.2 years. There were 64 patients who had neurofibromatosis type 2 (NF-2). Additionally, 309 patients had previously undergone surgical resection and/or radiosurgery for VS. In regard to CKRS treatment parameters, the marginal dose ranged from 1.9-25.78 Gy. The mean follow-up duration across the included studies was 40.0 months. Pooled rate of tumor control using the random effects model was 96% (95% CI: 95%-98%), and that of hearing preservation was 73% (95% CI: 66%-81%). The most common major complications following CKRS were trigeminal neuralgia, facial neuropathy, and hydrocephalus. CONCLUSIONS As studies on CyberKnife radiosurgery, one of the SRS modalities administered via LINAC, are far less common than studies on Gamma Knife radiosurgery for treatment of VS, more studies are needed in order to solidify the findings reported in the present meta-analysis. Although there are currently only 15 single-institution retrospective studies available in the neurosurgical literature, this study provides the most comprehensive and up-to-date analysis of highly relevant outcomes of interest in treatment of vestibular schwannoma via CyberKnife.

NCOG-03. SURGICAL MANAGEMENT OF CRANIOSPINAL AXIS MALIGNANT PERIPHERAL NERVE SHEATH TUMORS: A SINGLE-INSTITUTION EXPERIENCE AND LITERATURE REVIEW

Abstract Malignant peripheral nerve sheath tumors (MPNSTs) are exceedingly rare and aggressive tumors with an overall incidence rate of 0.001%. The craniospinal axis is a rare location for primary MPNSTs with very few cases reported in the literature to date. Here-in, we present one of the larger series of single-institutional primary craniospinal MPNSTs, analyze patient outcomes, and extensively review the associated literature. All primary craniospinal axis MPNSTs managed at our institution between January 2005 to May 2023 were retrospectively reviewed. Patient demographics, tumor characteristics and radiographic features, treatment, and clinical outcomes were collected and analyzed. Descriptive statistics and multivariate logistic regression were performed. A total of 8 patients satisfied inclusion criteria (4 male and 4 female patients). Median age at presentation was 40 years (range 34-80 years). Most of these tumors were localized to the spine (6, 75%) and 3 patients (37%) had neurofibromatosis type 1(NF-1). Most common presenting symptoms were paresthesia/numbness in 50% of cases, and vision changes in 13%. Median tumor size was 3 cm (range 1-20), and most tumors were oval-shaped (4, 50%), with well-defined borders (6, 75%). One spinal tumor (11%) had an intramedullary extension. Most tumors were high grade (6, 75%), and gross-total resection was achieved in 5 (63%) patients with subtotal resection performed in the remaining 3 (37%). Radiotherapy and chemotherapy after surgery were performed in 6 (75%) and 4 (50%) cases, respectively. Local recurrence was evidenced in 5 (63%) cases and distant metastatic disease in 2 (25%) cases. The median progression-free survival time was 26.0 months, and 5 (63%) patients died due to recurrent disease. Early diagnosis and initiation of treatment is key as these tumors are highly aggressive with increased local invasion and distant metastatic rates. Maximal safe gross total resection with negative margins with adjuvant radiation therapy is associated with improved survival.

Case report of selumetinib as a novel therapy in a neurofibromatosis type 2-associated ependymoma

We report partial response (PR) to novel therapy with selumetinib in a patient with Neurofibromatosis type 2 (NF2). A 25-year-old male presented with bilateral vestibular schwannomas, spinal cord intramedullary ependymomas, cranial and spinal meningiomas, spinal nerve root mixed schwannoma-neurofibromas, and peripheral nerve sheath tumors. He tested negative for germline NF2, SWItch/Sucrose Non-Fermentable-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 (SMARCB1), and leucine zipper like transcription regulator 1 (LZTR1) mutations. Molecular analysis of a resected cervical spine schwannoma-neurofibroma demonstrated an isolated somatic SMARCB1 mutation. Due to progression of all tumors, he was treated medically with both everolimus (10 mg/day) and selumetinib (25 mg/kg BID), but rapidly transitioned to selumetinib monotherapy due to everolimus toxicity. Three months of treatment resulted in PR in one spinal ependymoma and stable disease in other tumors. This partial response was quantified by the differences in units of intensity in pre- and post-treatment MR image. To the best of our knowledge, this is the first reported case for using selumetinib in NF2-associated tumors or ependymomas.

MODL-17. OBESOGENIC DIET INCREASES NF1-OPTIC PATHWAY GLIOMA FORMATION THROUGH EFFECTS ON THE TUMOR CELL OF ORIGIN

Abstract Rates of both pediatric low-grade glioma and obesity have been rising in the U.S., and children of obese mothers have increased rates of several tumor types, including brain tumors. Importantly, obesity in the U.S. is largely dietary-driven, given the prevalence of high fat and high sugar (HFHS) diets. High-fat diet exposure can promote proliferation of embryonic neuroglial progenitor cells (NPCs), which animal modeling suggests are potential cells of origin for low-grade glioma. Together, these data suggested that in utero exposure to an obesogenic diet might affect the formation of pediatric brain tumors. Using preclinical models of the Neurofibromatosis type 1 (NF1) cancer predisposition syndrome, in which optic pathway gliomas (Nf1-OPGs) arise from NPCs in the developing third ventricular zone (TVZ), we sought to determine whether maternal obesogenic exposure would increase glioma formation through intrinsic effects on the tumor cell of origin. We demonstrated that progeny from obese dams exposed to HFHS diet during and preceding gestation had increased proliferation and glial differentiation of WT and Nf1-mutant TVZ NPCs. Progeny of non-obese dams exposed to this diet during gestation demonstrate a similar phenotype, suggesting these effects are related to maternal diet rather than weight. Obesogenic diet exposure (Ob) also increased glioma penetrance in two low-penetrance murine models of Nf1-OPG. Moreover, we demonstrated that Ob mice developed earlier tumor onset with elevated Erk activity in a high-penetrance Nf1-OPG model. In contrast, when obesogenic diet was introduced postnatally, only 11% of mice showed accelerated tumor formation. Ob-exposed nerves also displayed elevated levels of activated Stat3, consistent with upregulation of the IL6/Jak/Stat3 pathway with HFHS diet exposure. These findings establish maternal obesogenic diet as a risk for pediatric glioma formation, in part through in utero effects on the tumor cell of origin, and identify the MAPK and IL6/Jak/Stat3 pathways as targets for further investigation.

EPCO-04. SPATIAL TRANSCRIPTOMIC ANALYSIS OF MALIGNANT PERIPHERAL NERVE SHEATH TUMORS REVEALS THERAPEUTICALLY TARGETABLE MOLECULAR SIGNATURES IN REGIONS UNDERGOING HISTOPATHOLOGIC TRANSFORMATION

Abstract Malignant peripheral nerve sheath tumors (MPNSTs) evolve from plexiform neurofibromas (pNF) in patients with neurofibromatosis type-1 (NF-1) yet the cellular and transcriptomic mechanisms underlying this transformation remain unclear. Here, we perform spatial gene expression profiling on fifteen MPNSTs to correlate histologic observations with transcriptomic programs and identify mechanisms underlying malignant transformation. METHODS: Fifteen MPNSTs, including tumors with a histopathologically defined transition zone between adjacent low-grade and high-grade areas (n=3), were retrospectively identified. Spatial transcriptomic profiling was performed using Visium followed by downstream processing with SpaceRanger, Seurat, Harmony, and monocle. RESULTS: 50,807 unique spatial transcriptomes were distributed across 17 unique clusters, of which 12 were enriched for tumor cells and 5 for non-tumor microenvironment cells based on histologic evaluation, unsupervised cell-type assignment, marker gene expression, and cell signature gene sets. Transcriptomic clusters in low-grade areas were enriched for genes regulating mononuclear cell migration and cell-cell adhesion, while high-grade regions were enriched for Ras/Raf/MEK/ERK target genes, anti-apoptotic programs, and extracellular matrix reorganization genes. Trajectory inference beginning in low grade regions revealed spatially organized molecular signatures of malignant transformation enriched for cell cycle progression within histopathologically homogeneous regions. Moreover, the intermediate transformation zone between low-grade neurofibromatous and high-grade MPNST histopathologic regions was marked by loss of cell differentiation genes and increased cell cycle progression. CONCLUSIONS: Spatial transcriptomic analysis elucidates the cellular and gene expression patterns underlying progression from pNF to MPNST. Distinct cell populations exist across low-grade, transformation zone, and high-grade regions in MPNSTs highlighted by alterations in Ras/Raf/MEK/ERK signaling, cell differentiation and cell cycle programs, shedding light on targets for combinatorial molecular therapy to decrease the risk of malignant transformation and serving as a biomarker of aggressive peripheral nerve tumors to complement conventional histopathology.

SURG-27. 17-YEAR EXPERIENCE OF SURGICAL MANAGEMENT OF INTRADURAL EXTRAMEDULLARY (IDEM) TUMORS: CLINICAL OUTCOMES FROM A LOW- AND MIDDLE-INCOME COUNTRY

Abstract INTRODUCTION Surgical outcomes of intradural extramedullary (IDEM) tumors have been well-reported in the literature from high-income countries. However, limited contemporaneous data from low- and middle-income countries (LMICs) exists. This study sought to analyze the clinical outcomes of all IDEM tumor cases operated during a 17-year period at a resource-limited setting in an LMIC. METHODS The present work was conducted and reported in accordance with Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. A retrospective cohort study was carried out to analyze all IDEM tumor cases, operated upon by a consultant neurosurgeon, during 2004-2021, at a resource-limited setting in Southern India. All patients underwent routine biochemical and radiological investigations, including contrast-enhanced MRI. Laminectomy and tumor resection under the microscope were done without using intraoperative neuro-monitoring. Nerve fibers running through the tumor were sacrificed. Bilateral facet joints were preserved to ensure integrity without spinal fusion. All cases received a dural closure with 5-0 Prolene, with postoperative MRI confirming complete resection. Patients received telephonic and/or in-person follow-up visits. RESULTS 50 patients with a mean age of 46.3 years (range 13-80) were included, with 31 males and 19 females. Their clinical presentation included radiculopathy (78%), radiculomyelopathy (12%), and radiculomyelopathy with bowel and bladder symptoms (10%). Histologically, schwannomas were the most common (52%), followed by neurofibromas (34%), meningiomas (12%), and ependymomas (2%). Two individuals were diagnosed with Neurofibromatosis Type 1. All meningiomas occurred in the thoracic region, with 83.3% of cases being in females. All patients had symptomatic relief postoperatively. No major adverse events occurred, including CSF leaks, permanent neurological deficits, or spinal instability. Recurrence occurred in two 'dumbbell' tumors (4%) at 5 and 7 years after primary excision during follow-up, managed with successful re-resection. CONCLUSION Microsurgical excision of IDEM tumors carries high safety and efficacy, including in resource-limited settings like LMICs.

EPCO-03. A COMPREHENSIVE SINGLE-CELL ATLAS OF SCHWANNOMA REVEALS CONSERVED CELLULAR STATES ACROSS DIFFERENT GENETIC BACKGROUNDS AND ANATOMIC LOCATIONS

Abstract BACKGROUND Despite being associated with molecular alterations in the NF2 gene, there is limited understanding of the gene expression programs that govern the behavior of schwannomas both in sporadic cases as well as in patients with schwannoma predisposition syndromes, and also with respect to their anatomic location. METHODS We characterized the transcriptional heterogeneity of schwannomas across different genetic backgrounds and anatomic locations at the single-cell level. Tumor samples from patients undergoing resection for symptomatic schwannoma were dissociated and single cells were processed for full-transcript whole transcriptome profiling via Smart-seq2. Our cohort of 22 schwannomas, includes 5 tumors from schwannomatosis patients, 11 tumors from neurofibromatosis type 2 patients, and 6 sporadic tumors – 3 of which had grown after radiation treatment. Anatomically, 12 tumors were excised from cranial nerves (11 vestibular, 1 accessory) and 10 from spinal and other peripheral nerves. RESULTS We profiled 11,373 cells, including 4725 neoplastic cells, 2425 fibroblasts, 1314 T cells, 1258 endothelial cells, 969 myeloid cells, 503 pericytes and 240 Schwann cells. Copy number alteration analyses reveal evidence of intratumoral polyclonality (supporting the hypothesis of multiple sites of origin for a tumor). Using non-negative matrix factorization, we identify 6 distinct transcriptional metaprograms, with gene signatures related to stress, myelin production, antigen presentation, interferon signaling, glycolysis and extracellular matrix. After comparison with a pan-cancer gene expression dataset, we note unique interferon and antigen presentation metaprograms in schwannoma, with the latter being mainly characterized by expression of MHC Class II genes. Overall, we observe conserved expression of these metaprograms across anatomic locations and genetic backgrounds, with the exception of decreased interferon signaling for vestibular tumors. CONCLUSION We provide a comprehensive single-cell characterization of schwannoma spanning diverse genetic and anatomic backgrounds. We describe unique transcriptional metaprograms for antigen presentation and interferon signaling, which might underlie mechanisms for immune evasion.

INNV-38. PREDICTING THE CLINICAL PHENOTYPE IN NF2 RELATED SCHWANNOMATOSIS PATIENTS

Abstract BACKGROUND Different genetic scores have been proposed to predict the phenotype of NF2 related Schwannomatosis (NF2 -SCHW MIM # 101000) , a rare autosomal dominant familial cancer syndromes caused by pathogenic variants of the NF2 gene. The UK NF2 Reference Group proposed the Genetic Severity Score (GSS) based on the type and location of NF2 germline variant observed. Catasus et al. suggested a new score based also on a functional assay of Merlin and its downstream pathways (FGSS). Recently Teranish et al. used targeted deep sequencing to predict functional prognosis in those patients. Material and METHODS 70 patients (median age 40) were identified by scanning the electronic NF2-SCHW patient database at Fondazione IRCCS C. Besta,. The median follow-up was 14 yrs. Clinical diagnosis was established following the Updated diagnostic criteria and nomenclature for neurofibromatosis type 2 and schwannomatosis”. All patients underwent NF2, SMARCB1 and LZTR1 mutational screening by NGS and MPLA analysis using blood DNA or the tissue of two different tumors when available. NF2 gene germline pathogenic were found in 45 subjects (64%), in most cases NF2 point mutations, but in 4 cases and whole gene deletions was observed and in 2 a ring NF2 chromosome was identified, in four cases a mosaic NF2-SCH was identified and in 21 (30%) patients no pathogenic variant was found. We assessed NF2 clinical phenotype in relation to the UK GSS and FGSS to validate their use. RESULTS The disease phenotype differed significantly depending both on clinical and genetic factors.. GSS and FGSS showed significant correlation with several measures, allowing stratification of patients with severe and mild disease but not with moderate phenotype. Furthermore, we provided evidence on correlation between whole NF2 deletion extent and phenotype severity. Large cohorts of NF2-SCHW patients are needed to identify more accurate scores.

Biallelic inactivation of the NF1 tumour suppressor gene in juvenile myelomonocytic leukaemia: Genetic evidence of driver function and implications for diagnostic workup.

Juvenile myelomonocytic leukaemia (JMML) is characterized by gene variants that deregulate the RAS signalling pathway. Children with neurofibromatosis type 1 (NF-1) carry a defective NF1 allele in the germline and are predisposed to JMML, which presumably requires somatic inactivation of the NF1 wild-type allele. Here we examined the two-hit concept in leukaemic cells of 25 patients with JMML and NF-1. Ten patients with JMML/NF-1 exhibited a NF1 loss-of-function variant in combination with uniparental disomy of the 17q arm. Five had NF1 microdeletions combined with a pathogenic NF1 variant and nine carried two compound-heterozygous NF1 variants. We also examined 16 patients without clinical signs of NF-1 and no variation in the JMML-associated driver genes PTPN11, KRAS, NRAS or CBL (JMML-5neg) and identified eight patients with NF1 variants. Three patients had microdeletions combined with hemizygous NF1 variants, three had compound-heterozygous NF1 variants and two had heterozygous NF1 variants. In addition, we found a high incidence of secondary ASXL1 and/or SETBP1 variants in both groups. We conclude that the clinical diagnosis of JMML/NF-1 reliably indicates a NF1-driven JMML subtype, and that careful NF1 analysis should be included in the genetic workup of JMML even in the absence of clinical evidence of NF-1.

Asymmetry of thalamic hypometabolism on FDG-PET/CT in neurofibromatosis type 1: Association with peripheral tumor burden.

Thalamic hypometabolism is a consistent finding in brain PET with F-18 fluorodeoxyglucose (FDG) in patients with neurofibromatosis type 1 (NF1). However, the pathophysiology of this metabolic alteration is unknown. We hypothesized that it might be secondary to disturbance of peripheral input to the thalamus by NF1-characteristic peripheral nerve sheath tumors (PNSTs). To test this hypothesis, we investigated the relationship between thalamic FDG uptake and the number, volume, and localization of PNSTs. This retrospective study included 22 adult NF1 patients (41% women, 36.2±13.0years) referred to whole-body FDG-PET/contrast-enhanced CT for suspected malignant transformation of PNSTs and 22 sex- and age-matched controls. Brain FDG uptake was scaled voxelwise to the individual median uptake in cerebellar gray matter. Bilateral mean and left-right asymmetry of thalamic FDG uptake were determined using a left-right symmetric anatomical thalamus mask. PNSTs were manually segmented in contrast-enhanced CT. Thalamic FDG uptake was reduced in NF1 patients by 2.0 standard deviations (p<.0005) compared to controls. Left-right asymmetry was increased by 1.3 standard deviations (p=.013). Thalamic hypometabolism was higher in NF1 patients with ≥3 PNSTs than in patients with ≤2 PNSTs (2.6 vs. 1.6 standard deviations, p=.032). The impact of the occurrence of paraspinal/paravertebral PNSTs and of the mean PNST volume on thalamic FDG uptake did not reach statistical significance (p=.098 and p=.189). Left-right asymmetry of thalamic FDG uptake was not associated with left-right asymmetry of PNST burden (p=.658). This study provides first evidence of left-right asymmetry of thalamic hypometabolism in NF1 and that it might be mediated by NF1-associated peripheral tumors.

Unveiling a Biomarker Signature of Meningioma: The Need for a Panel of Genomic, Epigenetic, Proteomic, and RNA Biomarkers to Advance Diagnosis and Prognosis.

Meningiomas are the most prevalent primary intracranial tumors. The majority are benign but can undergo dedifferentiation into advanced grades classified by World Health Organization (WHO) into Grades 1 to 3. Meningiomas' tremendous variability in tumor behavior and slow growth rates complicate their diagnosis and treatment. A deeper comprehension of the molecular pathways and cellular microenvironment factors implicated in meningioma survival and pathology is needed. This review summarizes the known genetic and epigenetic aberrations involved in meningiomas, with a focus on neurofibromatosis type 2 (NF2) and non-NF2 mutations. Novel potential biomarkers for meningioma diagnosis and prognosis are also discussed, including epigenetic-, RNA-, metabolomics-, and protein-based markers. Finally, the landscape of available meningioma-specific animal models is overviewed. Use of these animal models can enable planning of adjuvant treatment, potentially assisting in pre-operative and post-operative decision making. Discovery of novel biomarkers will allow, in combination with WHO grading, more precise meningioma grading, including meningioma identification, subtype determination, and prediction of metastasis, recurrence, and response to therapy. Moreover, these biomarkers may be exploited in the development of personalized targeted therapies that can distinguish between the 15 diverse meningioma subtypes.

Characterization of Immune Cell Populations of Cutaneous Neurofibromas in Neurofibromatosis 1

Cutaneous neurofibromas (cNFs) are characteristic of neurofibromatosis 1 (NF1), yet their immune microenvironment is incompletely known. A total of 61 cNFs from 10 patients with NF1 were immunolabeled for different types of T cells and macrophages, and the cell densities were correlated with clinical characteristics. Eight cNFs and their overlying skin were analyzed for T cell receptor CDR domain sequences, and mass spectrometry of 15 cNFs and the overlying skin was performed to study immune-related processes. Intratumoral T cells were detected in all cNFs. Tumors from individuals younger than the median age of the study participants (33 years), growing tumors, and tumors smaller than the data set median showed increased T cell density. Most samples displayed intratumoral or peritumoral aggregations of CD3-positive cells. T cell receptor sequencing demonstrated that the skin and cNFs host distinct T cell populations, whereas no dominant cNF-specific T cell clones were detected. Unique T cell clones were fewer in cNFs than in skin, and mass spectrometry suggested lower expression of proteins related to T cell-mediated immunity in cNFs than in skin. CD163-positive cells, suggestive of M2 macrophages, were abundant in cNFs. Human cNFs have substantial T cell and macrophage populations that may be tumor-specific.

Lived experiences of neurofibromatosis type 1 patients: Social life, stigma, and intervention strategies.

Neurofibromatosis type 1 (NF1) is a neurogenetic disorder associated with visual-spatial problems, executive dysfunction, and language deficits, making patients experience social isolation, stigma, anxiety, and depression. Here, we explored NF1 patients' lived experiences by conducting semi-structured, in-depth interviews with 21 NF1 patients and 16 care providers. The thematic analysis uncovered dimensions of NF1 patients' social lives at different ecological levels, including their relationships with family, friends, teachers, coworkers, providers, and society. Positive dimensions of NF1 patients' social life (e.g. familial support and sacrifice, responsibility, and self-sufficiency, supportive friends, and professors) counter negative dimensions (e.g. the vulnerability in sexual relationships, social interactions, discriminatory professors, misconceptions about abilities, appearance bias, internalized and social stigma, violence, and low self-esteem). Adaptive strategies used or suggested by NF1 patients at personal (e.g. supportive network, positive reframing, acceptance of their bodies) and social levels (e.g. psychological support, group therapy, public awareness, and governmental support) were identified.