Neurofibromatosis 2 Mutations Research Articles

Responses to immune checkpoint inhibitor therapy in NF1 mutated cutaneous melanoma.

e21535 Background: NF1 mutations occur in 14% of cutaneous melanoma. Less than 20% of advanced melanoma patients on Immune Checkpoint Inhibitor (ICI) therapy achieve radiographic Complete Response (CR). We present data on radiographic responses to ICI therapy in advanced melanoma patients with tumors harboring NF1 (Neurofibromatosis 1) mutations. Methods: Patients with metastatic or unresectable NF1 mutated melanoma were included in the analysis. Mutation status was identified via NGS and mutation pathogenic status was determined using Genome Oncology Software. All patients received ICI therapy. RECIST 1.1 was used to assess treatment responses with CT scans. CR on PET was defined as disappearance of all metabolically active lesions. Results: 26 metastatic or unresectable melanoma patients met criteria for inclusion. Of these, eight (30.8%) had CNS metastasis. ICI therapy included Ipilimumab-Nivolumab, Pembrolizumab, Nivolumab, or Relatlimab-Nivolumab (24/26 in front-line setting). The 12- and 24-month estimated cumulative incidence of CR were 43.9% and 60.6%, respectively. Altogether, 16 patients achieved CR as their best overall response. Four patients that achieved CR subsequently progressed. Four patients progressed without achieving CR. Six patients achieved a partial response by last follow-up without achieving CR or disease progression. Of the 8 patients with CNS metastasis, five (62.5%) had intra-cranial radiographic responses to ICI therapy, including 1 (12.5%) complete response. Five (62.5%) had multifocal ( > 2 sites of intracranial metastasis) intracranial disease. Five (62.5%) of these patients with intracranial disease received radiation, 2/8 (25.0%) received radiation and surgical resection, and one (12.5%) received neither radiation nor surgery. Three (37.5%) patients with CNS metastasis experienced disease progression while on ICI therapy. Conclusions: NF1 mutated melanoma appears to have high rates of radiographic responses to ICI therapy. Prospective validation of this finding, particularly in patients with CNS metastasis, is warranted.

Abstract CT006: First-in-class, first-in-human phase 1 trial of VT3989, an inhibitor of yes-associated protein (YAP)/transcriptional enhancer activator domain (TEAD), in patients (pts) with advanced solid tumors enriched for malignant mesothelioma and other tumors with neurofibromatosis 2 (NF2) mutations

Abstract Background: Inactivation of the Hippo pathway is a common finding in MM and other cancers, leading to constitutive YAP activation, but has thus far been undruggable. NF2 encodes Merlin that activates Hippo kinase resulting in inactivation of YAP, which is the major effector of Hippo signaling. NF2-deficient tumors, often due to inactivating NF2 mutations (NF2m), are dependent on YAP for growth. VT3989 is an oral, highly potent and selective inhibitor of TEAD palmitoylation, which blocks YAP function and has shown promising preclinical activity. Materials and Methods: This FIH trial used a 3 + 3 dose escalation design and evaluated VT3989 from 25 to 200 mg QD continuously and 50 to 200 mg intermittently. Pts with refractory solid tumors, ECOG PS 0-1, serum albumin > 2.5, urinary protein creatinine ratio ≤ 0.5 mg/mg and albumin creatinine ratio ≤ 100 mg/g were enrolled. Objectives were to determine the safety, tolerability and recommended Phase 2 dose (RP2D) of VT3989; to evaluate antitumor activity, pharmacokinetics (PK) and correlate NF2m and other alterations in tumor and ctDNA with response. Results: 67 pts have been enrolled. Median age 63.5y (21-83y), ECOG PS 0:1 13:54 pts. Median prior therapies 3 (range 0-8). Tumor types: 42 MM (29 pleural and 13 non-pleural) and 25 solid tumors including 9 meningioma and 4 sarcoma pts. 34 pts had NF2m (29 somatic and 5 germline). All MM pts had progressed on prior platinum/pemetrexed; all but 2 had prior immune checkpoint inhibitors. VT3989 is safe and well tolerated with no dose limiting toxicities. No MTD was defined up to 200 mg QD. The most common AEs are proteinuria, albuminuria and peripheral edema, mainly observed with the continuous schedule. There were 7 possibly related G3 AEs (fatigue, ALT, AST, dehydration, dyspnea, hypotension and peripheral edema) and 1 G4 cardiomyopathy. No pt developed decreased renal function or nephrotic syndrome. VT3989 has a 12-15 day half-life, dose proportional PK and reaches steady state within 2 weeks. Seven pts (6 refractory MM and 1 NF2m sarcoma) achieved RECIST v1.1 partial responses (PRs) with 4 confirmed, 3 unconfirmed (1 pending). 3 PRs in MM pts are ongoing up to 18+ months. The clinical benefit response rate (PR + SD > 8 weeks, per protocol) in MM pts is 57%. Of the 6 MM pts (1 pericardial, 1 pleural/peritoneal and 4 peritoneal) with PR, 2 have NF2m, 3 are wildtype, and 1 is unknown. Conclusions: VT3989 is safe and well tolerated with durable RECIST v1.1 antitumor responses in pts with advanced MM and NF2m cancers, providing the first early clinical proof-of-concept for effectively drugging the Hippo-YAP-TEAD pathway. RP2D optimization including further schedule evaluation and expansion are ongoing in pts with MM and NF2m tumors. Citation Format: Timothy A. Yap, David J. Kwiatkowski, Jayesh Desai, Ibiayi Dagogo-Jack, Michael Millward, Hedy L. Kindler, Anthony W. Tolcher, Sophia Frentzas, Archie W. Thurston, Len Post, F Andrew Dorr. First-in-class, first-in-human phase 1 trial of VT3989, an inhibitor of yes-associated protein (YAP)/transcriptional enhancer activator domain (TEAD), in patients (pts) with advanced solid tumors enriched for malignant mesothelioma and other tumors with neurofibromatosis 2 (NF2) mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT006.

A Translational Approach to Spinal Neurofibromatosis: Clinical and Molecular Insights from a Wide Italian Cohort.

Spinal neurofibromatosis (SNF), a phenotypic subclass of neurofibromatosis 1 (NF1), is characterized by bilateral neurofibromas involving all spinal roots. In order to deepen the understanding of SNF’s clinical and genetic features, we identified 81 patients with SNF, 55 from unrelated families, and 26 belonging to 19 families with at least 1 member affected by SNF, and 106 NF1 patients aged >30 years without spinal tumors. A comprehensive NF1 mutation screening was performed using NGS panels, including NF1 and several RAS pathway genes. The main features of the SNF subjects were a higher number of internal neurofibromas (p < 0.001), nerve root swelling (p < 0.001), and subcutaneous neurofibromas (p = 0.03), while hyperpigmentation signs were significantly less frequent compared with the classical NF1-affected cohorts (p = 0.012). Fifteen patients underwent neurosurgical intervention. The histological findings revealed neurofibromas in 13 patients and ganglioneuromas in 2 patients. Phenotypic variability within SNF families was observed. The proportion of missense mutations was higher in the SNF cases than in the classical NF1 group (21.40% vs. 7.5%, p = 0.007), conferring an odds ratio (OR) of 3.34 (CI = 1.33−10.78). Two unrelated familial SNF cases harbored in trans double NF1 mutations that seemed to have a subclinical worsening effect on the clinical phenotype. Our study, with the largest series of SNF patients reported to date, better defines the clinical and genetic features of SNF, which could improve the management and genetic counseling of NF1.

Neuronal hyperexcitability drives central and peripheral nervous system tumor progression in models of neurofibromatosis-1

Neuronal activity is emerging as a driver of central and peripheral nervous system cancers. Here, we examined neuronal physiology in mouse models of the tumor predisposition syndrome Neurofibromatosis-1 (NF1), with different propensities to develop nervous system cancers. We show that central and peripheral nervous system neurons from mice with tumor-causing Nf1 gene mutations exhibit hyperexcitability and increased secretion of activity-dependent tumor-promoting paracrine factors. We discovered a neurofibroma mitogen (COL1A2) produced by peripheral neurons in an activity-regulated manner, which increases NF1-deficient Schwann cell proliferation, establishing that neurofibromas are regulated by neuronal activity. In contrast, mice with the Arg1809Cys Nf1 mutation, found in NF1 patients lacking neurofibromas or optic gliomas, do not exhibit neuronal hyperexcitability or develop these NF1-associated tumors. The hyperexcitability of tumor-prone Nf1-mutant neurons results from reduced NF1-regulated hyperpolarization-activated cyclic nucleotide-gated (HCN) channel function, such that neuronal excitability, activity-regulated paracrine factor production, and tumor progression are attenuated by HCN channel activation. Collectively, these findings reveal that NF1 mutations act at the level of neurons to modify tumor predisposition by increasing neuronal excitability and activity-regulated paracrine factor production.

Identification of three clinical neurofibromatosis 1 subtypes: Latent class analysis of a series of 1351 patients.

Neurofibromatosis 1 (NF1) is one of the most common inherited disorders characterized by mutations in the tumour suppressor gene NF1. Its clinical manifestations are highly variable and unpredictable. A specific NF1 mutation does not predict the severity or complications of the disease. The objective of this study was to build an empirical classification scheme without any a priori hypotheses to identify the underlying NF1 subtypes that best explain the observed heterogeneity. We performed latent class analysis (LCA) of 1351 consecutive NF1 patients aged >17 years seen between 2002 and 2014. Data and phenotypic features were collected prospectively on a standardized form. The median age was 36.8 (17-81) years. A three-class model showed the best fit: 706 (52%) belonged to the LC1 'Cutaneous neurofibromas' class having preferentially cutaneous neurofibromas (99%), plexiform neurofibromas (63%) and blue-red macules (29%); 593 (44%) belonged to the LC2 'Subcutaneous neurofibromas' class characterized by the presence of at least 10 subcutaneous neurofibromas (21%) and a familial form (77%) and 52 (4%) belonged to the LC3 'Dysmorphic phenotype' class characterized by dysmorphic features (78%) and learning difficulties (87%). Patients in LC1 had a higher likelihood of developing scoliosis (RR = 1.7, 95% confidence interval (CI) [1.2-2.4]). Patients in LC2 were more likely to be men (RR = 1.4, 95% CI [1.1-1.7]). Patients in LC3 were at higher risk of having an optic pathway glioma (RR = 4.8, 95% CI [1.9-11.8]) and epilepsy (RR = 4.5, 95% CI [1.8-11.6]). Our findings invite the performance of a larger cohort study to test whether the various latent classes reflect different underlying genetic modifiers of these phenotypic traits.

Abstract P5-13-04: NF1 mutations render HER2+ breast cancer highly sensitive to T-DM1 by altering microtubule dynamics

Abstract Background: Despite major technological and conceptual advancements, treatment decisions in HER2+ metastatic breast cancer (mBC) remain largely based on clinical evidence, with no established predictive biomarkers to direct treatment for individual patients. The tumour suppressor Neurofibromatosis 1 (NF1) has been implicated in endocrine resistance but its role remains incompletely characterized in mBC. NF1 is best known as a GTPase-activating protein (GAP) that attenuates RAS signalling. However, the GAP function is likely not limited to RAS, and NF1 has been involved in other GTP-dependent processes including cytoskeletal dynamics. Data mining and analysis of public mutational registries revealed NF1 mutations as particularly enriched in HER2+ mBC compared to other molecular subtypes. Methods: To investigate the biological consequences of NF1 loss, we generated NF1 KO HER2+ mBC cell lines (BT474 and SKBR3) by CRISPR-Cas9 and both 2D and 3D proliferations assays were used for drug sensitivity profiling; live-cell imaging, high-resolution confocal microscopy and an ad-hoc computational algorithm were employed to study cell fate and microtubule conformational changes. Patient data were obtained from the Northwestern University through a prospective observational study in mBC patients. Results: Screening of several compounds approved for HER2+ mBC showed that response was generally equal or reduced in NF1 KO vs WT cells. However, response to trastuzumab-emtansine (T-DM1) was significantly increased in NF1 KO cells (IC50 ~0,3 vs 1,6 μg/mL in NF1WT). This sensitization was not observed with other antibody drug conjugates (ADCs) like DS-8201 and was reproducible with maytansine alone, suggesting a pharmacologically relevant NF1 activity on microtubules. Using the FUCCI(Ca) reporter, which tracks cell cycle progression at single-cell level, we saw a more prominent G2/M phase arrest and cell death upon T-DM1 treatment in NF1 KO compared to WT cells. Notably, NF1 KO cells exhibited a higher frequency of aberrant mitotic figures (chromosome alignment defects and multipolar spindle formation) and stronger β-galactosidase activity, an established marker of senescence. Collectively, these results suggest that NF1 KO cells become particularly subject to T-DM1-triggered mitotic catastrophe. Dephosphorylation of GTP-bound tubulin is required for appropriate microtubular dynamics; so-called “GTP islands” within the inner microtubule region are prone to rapid repolymerization and are normally kept at low levels. We hypothesize that expanded GTP-tubulin islands generated by the loss of NF1 GAP activity is a major cause of microtubular instability in NF1 KO cells. Preliminary evidence in support of this model was obtained by quantification of GTP-tubulin with a specific antibody. Finally, we assessed the predictive role of NF1 as a biomarker for T-DM1 response in a cohort of 300 mBC patients with mutational data in circulating tumour DNA (Guardant 360); we identified 13 heavily pretreated patients (&amp;gt;4 prior lines) who received T-DM1, of which 3 had loss-of-function NF1 mutations and 10 were NF1 WT. Median progression-free survival was higher in NF1-mutated than WT patients (334 vs 80 days); given the small sample size, these results cannot yet be considered significant (p=0.14). Conclusions: These results provide preliminary mechanistic and clinical evidence supporting the use of NF1 loss to guide treatment in HER2+ mBC. As novel HER2-specific agents are being rapidly added to the therapeutic arsenal, we propose biology-driven criteria to identify patients that may benefit specifically from T-DM1. In addition, NF1 dependence for correct microtubular dynamics may be exploited by other inhibitors of microtubular polymerization in use as ADC payloads, further extending the potential usefulness of NF1 determination. Citation Format: Bruno A Duso, Elena Gavilán Dorronzoro, Giulia Tini, Maria R de Filippo, Emanuele Bonetti, Maria R Ippolito, Chiara Soriani, Paolo D'Amico, Simona Rodighiero, Giuseppe Curigliano, Stefano Santaguida, Massimo Cristofanilli, Pier Giuseppe Pelicci, Luca Mazzarella. NF1 mutations render HER2+ breast cancer highly sensitive to T-DM1 by altering microtubule dynamics [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-04.

175 Concomitant LZTR1 and NF1 mutations contribute to the diversity of the Neurofibromatosis 1 phenotypic spectrum

Neurofibromatosis 1 (NF1) is a genetic disorder caused by germline mutations in the NF1 gene, manifested by various tissues proliferation, including plexiform neurofibromas. Even though somatic loss of NF1 is a common molecular mechanism, plexiform neurofibroma phenotype, varies from indolent to locally aggressive, suggesting contribution of additional modifiers. We investigated the development of a life-threatening, rapidly progressive plexiform neurofibroma in a 9-month-old female infant with NF1. Germline and somatic genetic analysis was conducted through whole exome sequencing and chromosomal microarray analysis. Site-directed mutagenesis, Lentiviral transduction, cell culture and western blot were used for functional studies. In addition to a de-novo pathogenic variant in the NF1 gene, the proband harbored a known pathogenic variant in another Rasopathy gene, LZTR1 which was inherited from the patient’s mother. Further somatic analysis revealed NF1 loss of heterozygosity and a variant in the gene encoding a G Protein Coupled Receptor, GNAZ. Cells expressing the mutant GNAZ exhibited increased ERK activation compared to those expressing the wild type GNAZ. We suggest that variants in NF1, LZRT1, and GNAZ act synergistically in our patient, leading to activation of the MAPK pathway and contributing to the severity of her plexiform neurofibromatosis. This case study demonstrates the power of next generation sequencing in understanding the patho-mechanisms of complex cases, and contributes to the knowledge of germline and somatic non-NF1 variants affecting the clinical phenotype.

Genetic diagnosis and follow-up study in pediatric neurofibromatosis 1 patients

Objective: Based on the genetic diagnosis and follow-up study on pediatric neurofibromatosis 1 (NF1) patients, interrogating the genotype-phenotype correlations of patients with NF1 mutations. Methods: 32 Patients from age of 2 months to 5 years old (17 male and 15 female) suspected for neurofibromatosis 1 were recruited during September 2016 to January 2018 in Shanghai Children's Medical Center retrospectively. Genetic diagnosis was applied to detect pathogenic variants. Long-term follow-up study were conducted to reveal progress of the disease and genotype-phenotype correlations. Results: 27 patients were detected with pathogenic NF1 variants, among them three were not reported. 3 patients inherited pathogenic variants from their NF1 diagnosed parents, all the other variants were de novo. Progressive development of phenotypes wasn't observed in most patients during the follow-up (14/27). Some patients were diagnosed with short stature, pulmonary artery stenosis and developmental delay during the follow-up(7/27). Short stature and pulmonary artery stenosis may be associated with missense mutation and severe truncation mutation of NF1 gene, respectively. Conclusions: Genetic diagnosis is required in young patients of NF1.Follow-up plan of pediatric patients should be adjusted based on genetic findings. Early follow-up of cardiovascular abnormalities should be noted in patients with missense mutation. Height development in patients with severe truncating variants are needed.

A phase 2 study of defactinib (VS-6063) in patients with NF2 altered tumors: Results from NCI-match (EAY131) subprotocol U.

3087 Background: The NCI-MATCH trial assigns patients (pts) with solid tumors, lymphomas, or multiple myeloma to targeted therapies based on genetic alterations identified in tumor biopsies. Neurofibromatosis 2 (NF2)-inactivated tumors demonstrate increased sensitivity to FAK inhibition in preclinical models. Arm U evaluated the FAK inhibitor defactinib in pts with NF2 altered tumors. Methods: Patients found to harbor an inactivating NF2 mutation on NGS were assigned to the ARM U substudy MATCH. Defactinib 400 mg was given by mouth twice daily until progression or intolerable toxicity. The primary endpoint was objective response rate (ORR). Secondary endpoints included toxicity, progression-free survival (PFS), and 6-month PFS. Results: Of 5,548 cases with sufficient tissue for genomic analysis, 51 pts were found to have NF2 alterations (&lt; 1% of the total analyzed). While NF2 alterations are known to occur more commonly in meningiomas and mesotheliomas, alterations were also detected in an array of other tumor types, including renal cell carcinomas and ovarian cancers. Thirty-five pts were ultimately enrolled; 33 patients were started on therapy, with 2 of those determined to be ineligible for outcome analysis. All pts had received at least one prior therapy, with 52% (16/31) having received 3 or more prior lines of therapy. Median follow-up was 35.9 months. ORR [90% CI] was 3% (1/31, [0.16, 14.86]), with the one partial response in a pt with choroid meningioma. Of the twelve pts whose best response was stable disease (39%, 12/31), 8 demonstrated some degree of tumor shrinkage (Table) with a disease control rate of 42% (13/31). Median PFS was 1.9 months for the 31 eligible pts who received study treatment, with median PFS of 9.3 months for the 9 patients who had a best response of stable disease or better. Six pts achieved a PFS of greater than 5.5 months. Among all treated pts (n=33), the most common treatment-related toxicities were fatigue (36%), nausea (33%), and hyperbilirubinemia (27%). There were no grade 4 or 5 toxicities; 27% of pts had grade 3 toxicities. No correlation could be made between clinical outcomes and tumor histology or specific NF2 genotype. Conclusions: Defactinib monotherapy had limited clinical activity in this cohort of previously treated patients with solid tumors exhibiting NF2 loss. Clinical trial information: NCT04439331. [Table: see text]

Biochemical and structural analyses reveal that the tumor suppressor neurofibromin (NF1) forms a high-affinity dimer

Biochemical and structural analyses reveal that the tumor suppressor neurofibromin (NF1) forms a high-affinity dimer

Genetic Profile of Indian Pheochromocytoma and Paraganglioma Patients - A Single Institutional Study.

Background and Aims:Pheochromocytomas (PCCs) and Paragangliomas (PGL) are rare catecholamine producing tumors that may present in sporadic or familial settings. Despite vast strides in understanding of PCC/PGL genetics in the last two decades, there is a dearth of information from India. The aim here is to study the prevalence of genetic mutations in Indian PCC/PGL patients.Settings and Design:Tertiary care academic hospital; prospective study.Methods:50 histopathologically diagnosed PCC/PGL patients formed the study group. Clinical, biochemical, pathological attributes and outcomes were documented and the phenotype was compared to the genotype. Succinyl dehydrogenase (SDH), Re-Arranged during Transfection (RET), Von-Hippel-Lindau (VHL) and NeuroFibromatosis-1 (NF1) mutations were studied. Additionally, immunohistochemisty for SDHB was also done, and the results compared to mutational analysis of SDH by MLPA (Multiplex Ligation-dependent Probe Activation).Statistical Analysis:Independent samples t-test and Fisher's exact test were used as appropriate. P values ≤0.05 were considered statistically significant.Results:The mean age was 34.3 years. Of the 50 patients, 27 were males and 23 females. 10 patients (20%) in all were detected to have a genetic mutation. 6 patients possessed a RET mutation, while two had VHL mutations. No patient presented with a NF1 mutation. 2 patients had a SDH mutation, and Immunohistochemistry for SDHB correlated with mutational analysis for these patients.Conclusions:The proportion of patients with a familial variant of PCC/PGL is more than what the historic “Rule of Ten” suggests. Our study found that one in five patients have a genetic mutation. PCC/PGL patients with genetic mutations not only require more stringent follow-up, but also screening of family members.

Phenotypic and molecular dissection of metaplastic breast cancer and the prognostic implications.

Metaplastic breast carcinoma (MBC) is relatively rare but accounts for a significant proportion of global breast cancer mortality. This group is extremely heterogeneous and by definition exhibits metaplastic change to squamous and/or mesenchymal elements, including spindle, squamous, chondroid, osseous, and rhabdomyoid features. Clinically, patients are more likely to present with large primary tumours (higher stage), distant metastases, and overall, have shorter 5-year survival compared to invasive carcinomas of no special type. The current World Health Organisation (WHO) diagnostic classification for this cancer type is based purely on morphology-the biological basis and clinical relevance of its seven sub-categories are currently unclear. By establishing the Asia-Pacific MBC (AP-MBC) Consortium, we amassed a large series of MBCs (n = 347) and analysed the mutation profile of a subset, expression of 14 breast cancer biomarkers, and clinicopathological correlates, contextualising our findings within the WHO guidelines. The most significant indicators of poor prognosis were large tumour size (T3; p = 0.004), loss of cytokeratin expression (lack of staining with pan-cytokeratin AE1/3 antibody; p = 0.007), EGFR overexpression (p = 0.01), and for 'mixed' MBC, the presence of more than three distinct morphological entities (p = 0.007). Conversely, fewer morphological components and EGFR negativity were favourable indicators. Exome sequencing of 30 cases confirmed enrichment of TP53 and PTEN mutations, and intriguingly, concurrent mutations of TP53, PTEN, and PIK3CA. Mutations in neurofibromatosis-1 (NF1) were also overrepresented [16.7% MBCs compared to ∼5% of breast cancers overall; enrichment p = 0.028; mutation significance p = 0.006 (OncodriveFM)], consistent with published case reports implicating germline NF1 mutations in MBC risk. Taken together, we propose a practically minor but clinically significant modification to the guidelines: all WHO_1 mixed-type tumours should have the number of morphologies present recorded, as a mechanism for refining prognosis, and that EGFR and pan-cytokeratin expression are important prognostic markers. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Neurofibromatosis type 1 (NF1) gene: Beyond café au lait spots and dermal neurofibromas.

Neurofibromatosis 1 (NF1) occurs in 1:2000 births. The main diagnostic signs are visible on the skin, and this opens several interesting aspects for dermatological point of view. The NF1 syndrome is caused by mutations in the NF1 gene which encodes the tumor suppressor protein neurofibromin. Neurofibromin functions as a Ras-GTPase-activating protein (RasGAP), and NF1 mutations lead to overactivation of the Ras signalling pathway. The NF1 gene and neurofibromin have intriguing functions in keratinocytes and melanocytes. Neurofibromin regulates melanin synthesis and keratinocyte differentiation in a currently unknown manner. The NF1 gene has also an important but poorly understood role in tumorigenesis and cancer. Compared to the general population, NF1 patients have a fivefold risk for cancer and a more than 2000-fold risk for neurogenic malignancies. Mutations of the NF1 gene are common in numerous cancer types in patients without NF1, and this suggests a more general role for the NF1 gene in oncogenesis. In melanoma, NF1 mutations seem to drive tumorigenesis and contribute to drug resistance. In this article, we review the literature on neurofibromin with special attention to keratinocytes, melanocytes, NF1-related tumors and melanoma.

Breast cancer in neurofibromatosis type 1: overrepresentation of unfavourable prognostic factors

Background:An increased breast cancer incidence and poor survival have been reported for women with neurofibromatosis 1 (NF1). To explain the poor survival, we aimed to link the histopathology and clinical characteristics of NF1-associated breast cancers.Methods:The Finnish Cancer Registry and the Finnish NF Registry were cross-referenced to identify the NF1 patients with breast cancer. Archival NF1 breast cancer specimens were retrieved for histopathological typing and compared with matched controls.Results:A total of 32 breast cancers were diagnosed in 1404 NF1 patients during the follow-up. Women with NF1 had an estimated lifetime risk of 18.0% for breast cancer, and this is nearly two-fold compared with that of the general Finnish female population (9.74%). The 26 successfully retrieved archival NF1 breast tumours were more often associated with unfavourable prognostic factors, such as oestrogen and progesterone receptor negativity and HER2 amplification. However, survival was worse in the NF1 group (P=0.053) even when compared with the control group matched for age, diagnosis year, gender and oestrogen receptor status. Scrutiny of The Cancer Genome Atlas data set showed that NF1 mutations and deletions were associated with similar characteristics in the breast cancers of the general population.Conclusions:These results emphasise the role of the NF1 gene in the pathogenesis of breast cancer and a need for active follow-up for breast cancer in women with NF1.

Immortalization of human normal and NF1 neurofibroma Schwann cells

Neurofibromas, which are benign Schwann cell tumors, are the hallmark feature in the autosomal dominant condition neurofibromatosis 1 (NF1) and are associated with biallelic loss of NF1 gene function. There is a need for effective therapies for neurofibromas, particularly the larger, plexiform neurofibromas. Tissue culture is an important tool for research. However, it is difficult to derive enriched human Schwann cell cultures, and most enter replicative senescence after 6–10 passages, impeding cell-based research in NF1. Through exogenous expression of human telomerase reverse transcriptase and murine cyclin-dependent kinase (mCdk4), normal (NF1 wild-type), neurofibroma-derived Schwann cells heterozygous for NF1 mutation, and neurofibroma-derived Schwann cells homozygous for NF1 mutation were immortalized, including some matched samples from the same NF1 patient. Initial experiments employed retroviral vectors, while subsequent work utilized lentiviral vectors carrying these genes because of improved efficiency. Expression of both transgenes was required for immortalization. Molecular and immunohistochemical analysis indicated that these cell lines are of Schwann cell lineage and have a range of phenotypes, many of which are consistent with their primary cultures. This is the first report of immortalization and detailed characterization of multiple human NF1 normal nerve and neurofibroma-derived Schwann cell lines, which will be highly useful research tools to study NF1 and other Schwann tumor biology and conditions.

Segmental Neurofibromatosis with Visceral Neurofibromas.

Dear Editor: Segmental neurofibromatosis 1 (NF1) is generally accepted to be the result of somatic mosaicism for a NF1 mutation that occurs early in embryogenesis. Segmental NF1 is roughly 10 times less frequent than NF1. This condition is characterized by the typical features of NF1 that are limited to a specific body segment1. The distribution is usually unilateral; however, bilateral occurrences have been reported2. Although deep-seated neurofibromas have been occasionally reported in generalized NF1, extracutaneous manifestations in segmental NF1 have rarely been reported3. A 45-year-old Korean man visited the emergency department in our medical center with signs of an acute abdomen. The history and physical examination revealed a 35-year history of multiple, soft-to-firm, asymptomatic, flesh colored plaques and nodules on the left side of neck, shoulder and upper back (Fig. 1A, B). The plaques had gradually increased in size over time. He had several cafe-au-lait macules, but no skin-fold freckling. His medical history and family history were non-contributory. The ophthalmologic examination revealed Lisch nodules on both the irises. Fig. 1 A 35-year history of multiple, soft-to-firm, flesh colored plaques and nodules on the left side of neck, shoulder (A), and upper back (B). Computed tomography scan. Low attenuated masses in porta hepatis and small bowel mesentery (C, arrows). A contrast-enhanced computed tomography (CT) was performed of the chest and abdomen and revealed diffuse, infiltrative skin and subcutaneous masses. Furthermore, low attenuated masses were also seen in the retroperitoneal space, porta hepatis and small bowel mesentery, and mediastinum (Fig. 1C). The diagnostic laparoscopy revealed multiple nodules in the intraperitoneal space. A resection of the visible nodules in the mesentery of the small bowel was performed for biopsy. The brain CT revealed normal findings. The patient did not undergo any other additional therapy. The histological analysis of the nodules from the skin and the mesentery of the small bowel revealed nodular infiltration of fusiform cells and the presence of oval and fusiform shaped nuclei that formed strands crossing each other. The immunohistochemical examination showed positive staining with S-100 protein. In 1987, Roth et al.4 suggested that segmental neurofibromatosis should be separated into four different subtypes. Roth's classification type II was defined as non-familial and segmental neurofibromatosis with deep systemic involvement as in our case. The frequency of deep-seated neurofibromas in NF1 has been reported to be 44% in abdomen/pelvis and 20% in thorax, respectively1. In contrast to NF1, systemic involvement in segmental NF1 is uncommon3 and the incidence of visceral neurofibromas in segmental NF1 is unknown. Since gastrointestinal neurofibromas are rare, a high degree of suspicion is needed for timely diagnosis. Generally, delay and difficulty arises in the diagnosis of gastrointestinal neurofibromas, due to the presence of non-specific symptoms as well as the predominantly small bowel location5. In our case, the patient reported abdominal pain, but during the laparoscopy the physicians did not observe any other specific findings except for the intra-peritoneal neurofibromas. Consequently, we suspected that the patient had symptomatic intra-abdominal neurofibromas. Surgical excision is the treatment of choice for all symptomatic tumors occurring in patients with NF1, and it may be the same in segmental NF1. However, surgical excision of benign asymptomatic tumors is still controversial. In conclusion, we report a rare case of segmental NF1 with intra-thoracic and intra-abdominal neurofibromas. To our knowledge, this is the first such case report in Korea. If patient with segmental NF1 complains of non-specific abdominal pain, visceral neurofibromas should be considered.

Correlation of Unilateral Sporadic Vestibular Schwannoma Growth Rates with Genetic and Immunohistochemical Abnormalities

Background: Unilateral sporadic vestibular schwannomas (USVS) are caused by inactivating somatic mutations of both alleles of the neurofibromatosis 2 (NF2) tumor suppressor gene. Unilateral sporadic vestibular schwannomas have a widely-varying growth patterns whose causes are poorly understood. Objective: We examined the relationships between an index of USVS growth, and genetic abnormalities and pathological growth indices. Subjects and Methods: Single-strand conformational polymorphism analysis and heteroduplex methods were used to screen for mutations in all 17 exons of the NF2 gene in USVS from 63 patients. Loss of heterozygosity (LOH) analyses were also carried out. An index of USVS growth (clinical growth index, CGI) was calculated as maximum tumor diameter divided by duration of symptoms. The immunohistochemical growthindices were based on monoclonal antibodies to Ki-67 and another tumor cell proliferation marker (platelet-derived growth factor (PDGF)). Results: CGI was highly variable and did not significantly decrease with increasing age at diagnosis. Either somatic NF2 mutations or LOH was found in 88% of tumors. PDGF and Ki-67 increased significantly with increasing age at diagnosis, and PDGF was lower in tumors with LOH than in those without LOH. In multiple linear regression analysis, CGI was significantly higher in people with higher PDGF, after accounting for age at diagnosis and LOH. Conclusion: An index of USVS growth increases with increasing PDGF, after accounting for age and LOH.

Outcomes of preimplantation genetic diagnosis in neurofibromatosis type 1

To examine the effect of patient and facility level factors on the success of preimplantation genetic diagnosis (PGD) in patients with neurofibromatosis 1 (NF1). Retrospective review. Large PGD reference laboratory. All patients with NF1 referred from June 2004 to May 2013. None. Embryos' NF1 mutation status and live birth rates. Seventy-seven couples underwent 156 PGD cycles during the study period. The average maternal age at the time of embryo biopsy was 33.2 years. The majority of embryos had a day 3 single blastomere biopsy without aneuploidy screening. A diagnosis was obtained for 80% of biopsied embryos; 20% of biopsies were nondiagnostic due to technical failures. Diagnosis was more often obtained for embryos of parents with familial disease and for embryos biopsied at centers that referred multiple NF1 cases. Among diagnosed embryos, 483/1,060 (46%) were unaffected by the parental NF1 mutation. Twenty-two (14%) of the 156 cycles had a confirmed live birth; if the observed success rate is applied to cycles with unknown outcomes, 33/156 (21%) cycles are expected to have resulted in live birth. In multivariate logistic regression, having a live birth was significantly associated with having more unaffected embryos available for transfer (odds ratio 1.33 per additional embryo, 95% confidence interval 1.02-1.72). Advances in biopsy and diagnostic techniques which increase the number of unaffected embryos identified may improve live birth rates for patients with NF1. Clinicians should counsel patients about their fertility and reproductive options early, with the use of disease-specific data, to set appropriate expectations for the PGD process.

Lymphangiopathy in neurofibromatosis 1 manifesting with chylothorax, pericardial effusion, and leg edema

BackgroundThis case report documents the affliction of the lymph vessels as a phenotypic feature of neurofibromatosis-1 (NF-1).MethodologyRoutine transthoracic echocardiography, computed tomography scan of the thorax, magnetic resonance angiography of the renal arteries, and conventional digital subtraction angiography were applied. Comprehensive NF-1 mutation analysis was carried out by fluorescence in situ hybridization analysis, long-range reverse transcriptase polymerase chain reaction, and multiple-ligation probe assay. All other investigations were performed using routine, well-established techniques.ResultsThe subject is a 34-year-old, half-Chinese male; NF-1 was suspected at age 15 years for the first time. His medical history included preterm birth, mild facial dysmorphism, “café au lait” spots, subcutaneous and paravertebral fibromas, multifocal tachycardia, atrial fibrillation, and heart failure in early infancy. Noncalcified bone fibromas in the femur and tibia were detected at age 8 years. Surgical right leg lengthening was carried out at age 11 years. Bilateral renal artery stenosis, stenosis and aneurysm of the superior mesenteric artery, and an infrarenal aortic stenosis were detected at age 15 years. Leg edema and ectasia of the basilar artery were diagnosed at age 18 years. After an episode with an erysipela at age 34 years, he developed pericardial and pleural effusion during a 4-month period. Stenosis of the left subclavian vein at the level of thoracic duct insertion was detected. After repeated pleural punctures, pleural effusion was interpreted as chylothorax. Reduction of lymph fluid production by diet and injection of talcum into the pleural cavity had a long-term beneficial effect on the chylothorax. Leg edema and chylothorax were attributed to affliction of the lymph vessels by the NF-1.DiscussionLymphangiopathy resulting in impaired lymph fluid flow and sequestration of lymph fluid into the pleural sinus and the legs may be a rare phenotypic feature of NF-1.

Genomic characterization of meningiomas.

2020 Background: Understanding the genetic alterations in cancer has lead to groundbreaking discoveries in targeted therapies. Meningiomas are among the most common primary brain tumors, with approximately 18,000 new cases diagnosed annually. Though certain genes have been associated with the development of meningiomas, most notably the tumor suppressor gene neurofibromatosis 2 (NF2), the genetic changes that drive meningiomas remain poorly understood. Our objective was to comprehensively characterize the somatic genetic alterations of meningiomas to gain insight into the molecular pathways that drive this disease. Methods: Fresh frozen specimens and paired blood were collected from 16 consented patients. DNA was extracted from regions of high tumor purity determined by evaluation of H&amp;E slides. Whole-genome sequencing from 10 tumor-normal pairs and whole-exome sequencing from 6 tumor-normal pairs was carried out. We performed an unbiased screen for point mutations, insertions-deletions, rearrangements and copy-number changes across the exomes and genomes. Recurrent (potential driver) events were then analyzed with additional algorithms for statistical significance. Results: Alterations in the NF2 gene were present in 9 of 16 patients. Multiple novel rearrangements and recurrent non-NF2 mutations were also identified in the cohort. Massive genomic rearrangement termed chromothripsis was observed in chromosome 1 in one sample, which has never previously been described in meningiomas, and represents a potentially new mechanism of malignant transformation in this tumor type. Conclusions: While NF2 mutations appear to drive a majority of these tumors, our analysis has uncovered additional potential driver genes in meningiomas, particularly in those tumors negative for NF2 alterations. To our knowledge, this is the first study to comprehensively characterize the totality of somatic genetic alterations in meningiomas, and brings us closer to the development of new therapeutic targets for this disease.