Pathogenesis of plexiform neurofibroma: tumor-stromal/hematopoietic interactions in tumor progression

The Role of CXCR3 in Nervous System-Related Diseases

Inflammatory chemokines are a group of G-protein receptor ligands characterized by conserved cysteine residues, which can be divided into four main subfamilies: CC, CXC, XC, and CX3C. The C-X-C chemokine receptor (CXCR) 3 and its ligands, C-X-C chemokine ligands (CXCLs), are widely expressed in both the peripheral nervous system (PNS) and central nervous system (CNS). This comprehensive literature review aims to examine the functions and pathways of CXCR3 and its ligands in nervous system-related diseases. In summary, while the related pathways and the expression levels of CXCR3 and its ligands are varied among different cells in PNS and CNS, the MPAK pathway is the core via which CXCR3 exerts physiological functions. It is not only the core pathway of CXCR3 after activation but also participates in the expression of CXCR3 ligands in the nervous system. In addition, despite CXCR3 being a common inflammatory chemokine receptor, there is no consensus on its precise roles in various diseases. This uncertainty may be attributable to distinct inflammatory characteristics, that inflammation simultaneously possesses the dual properties of damage induction and repair facilitation.

Left distal sciatic giant solitary myxoid neurofibroma: a case report & literature review

Introduction

Neurofibroma, a rare benign tumor of the peripheral nervous system, can manifest anywhere along a nerve from the dorsal ganglion to its terminal branches. Myxoid neurofibroma can present as a solitary non-tender nodule and is often confirmed by positive immunohistochemical staining for S-100 protein. However, in 50% of cases, neurofibromas are associated with neurofibromatosis.

Case presentation

We present a case of a 34-year-old male with mild pain in the posterior part of his left thigh, accompanied by a slowly-growing swelling particularly noticeable when flexing his knee. It had gradually increased in size over several months, which the patient observed as a decrease in the degree of knee extension. Initial biopsy indicated schwannoma with no evidence of malignancy. Four years later, the swelling increased in size and necessitated resection surgery, revealing an irregular giant tumor measuring 8 *6 *4.5 cm, adherent to adjacent structures, including the femur, muscles, popliteal artery and vein, and a branch of the sciatic nerve. Pathological analysis reclassified the diagnosis to low-grade myxoid neurofibroma. Follow-up MRI three months later showed gross total resection without residual or recurrence of the tumor.

Discussion

Solitary neurofibromas are often small in size, ranging from 1 to 2 cm in the greatest dimension. Alternatively, tumors that occur as a part of genetic neurofibromatosis tend to be multiple and often grow to large sizes. In our case, the patient didn't have neurofibromatosis as he didn't meet its diagnostic criteria despite having a giant tumor measuring approximately 8*6*4.5 cm. To our knowledge, this is the first report of giant myxoid solitary neurofibroma of the thigh apart from neurofibromatosis. Thus, this type of tumor should be considered in the differential diagnosis of tumors at this location.

A Fibroblast-Derived Secretome Stimulates the Growth and Invasiveness of 3D Plexiform Neurofibroma Spheroids

Plexiform neurofibromas (PNs) occur in about a half of neurofibromatosis type 1 (NF1) patients and have garnered significant research attention due to their capacity for growth and potential for malignant transformation. NF1 plexiform neurofibroma (pNF1) is a complex tumor composed of Schwann cell-derived tumor cells (Nf1-/-) and the tumor microenvironment (TME). Although it has been widely demonstrated that the TME is involved in the formation of neurofibromas, little is known about the effects of the TME on the subsequent progression of human pNF1. Elucidating the molecular interactions between tumor cells and the TME may provide new therapeutic targets to reduce the progression of pNF1. In the present study, we focused on the contributions of fibroblasts, the most abundant cell types in the TME, to the growth of pNF1. To simulate the TME, we used a three-dimensional (3D) coculture model of immortalized pNF1 tumor cells (Nf1-/-) and primary fibroblasts (Nf1+/-) derived from pNF1 patients. We performed live-cell imaging of 3D/4D (3D in real-time) cultures through confocal microscopy followed by 3D quantitative analyses using advanced imaging software. The growth of pNF1 spheroids in 3D cocultures with fibroblasts was significantly greater than that of pNF1 spheroids in 3D monocultures. An increase in the growth of pNF1 spheroids also occurred when they were cultured with conditioned media (CM) from fibroblasts. Moreover, fibroblast-derived CM increased the invasive outgrowth and further local invasion of pNF1 spheroids. Interestingly, when small extracellular vesicles (sEVs) were depleted from the fibroblast-derived CM, the stimulation of the growth of pNF1 spheroids was lost. Our results suggest that fibroblast-derived sEVs are a therapeutic target for reducing the growth of pNF1.

C5aR plus MEK inhibition durably targets the tumor milieu and reveals tumor cell phagocytosis

Plexiform neurofibromas (PNFs) are nerve tumors caused by loss of NF1 and dysregulation of RAS-MAPK signaling in Schwann cells. Most PNFs shrink in response to MEK inhibition, but targets with increased and durable effects are needed. We identified the anaphylatoxin C5a as increased in PNFs and expressed largely by PNF m acrophages. We defined pharmacokinetic and immunomodulatory properties of a C5aR1/2 antagonist and tested if peptide antagonists augment the effects of MEK inhibition. MEK inhibition recruited C5AR1 to the macrophage surface; short-term inhibition of C5aR elevated macrophage apoptosis and Schwann cell death, without affecting MEK-induced tumor shrinkage. PNF macrophages lacking C5aR1 increased the engulfment of dying Schwann cells, allowing their visualization. Halting combination therapy resulted in altered T-cell distribution, elevated Iba1+ and CD169+ immunoreactivity, and profoundly altered cytokine expression, but not sustained trumor shrinkage. Thus, C5aRA inhibition independently induces macrophage cell death and causes sustained and durable effects on the PNF microenvironment.

Nf1 in heart development: a potential causative gene for congenital heart disease: a narrative review

Congenital heart disease is the most frequent congenital disorder, affecting a significant number of live births. Gaining insights into its genetic etiology could lead to a deeper understanding of this condition. Although the Nf1 gene has been identified as a potential causative gene, its role in congenital heart disease has not been thoroughly clarified. We searched and summarized evidence from cohort-based and experimental studies on the issue of Nf1 and heart development in congenital heart diseases from various databases. Available evidence demonstrates a correlation between Nf1 and congenital heart diseases, mainly pulmonary valvar stenosis. The mechanism underlying this correlation may involve dysregulation of epithelial-mesenchymal transition (EMT). The Nf1 gene affects the EMT process via multiple pathways, including directly regulating the expression of EMT-related transcription factors and indirectly regulating the EMT process by regulating the MAPK pathway. This narrative review provides a comprehensive account of the Nf1 involvement in heart development and congenital cardiovascular diseases in terms of epidemiology and potential mechanisms. RAS signaling may contribute to congenital heart disease independently or in cooperation with other signaling pathways. Efficient management of both NF1 and cardiovascular disease patients would benefit from further research into these issues.

Integration of single-nuclei RNA-sequencing, spatial transcriptomics and histochemistry defines the complex microenvironment of NF1-associated plexiform neurofibromas

Plexiform neurofibroma (PN) is a leading cause of morbidity in children with the genetic condition Neurofibromatosis Type 1 (NF1), often disfiguring or threatening vital structures. During formation of PN, a complex tumor microenvironment (TME) develops, with recruitment of neoplastic and non-neoplastic cell types being critical for growth and progression. Due to the cohesive cellularity of PN, single-cell RNA-sequencing is difficult and may result in a loss of detection of critical cellular subpopulations. To bypass this barrier, we performed single-nuclei RNA-sequencing (snRNA-seq) on 8 frozen PN samples, and integrated this with spatial transcriptomics (ST) in 4 PN samples and immunohistochemistry to provide morphological context to transcriptomic data. SnRNA-seq analysis definitively charted the heterogeneous cellular subpopulations in the PN TME, with the predominant fraction being fibroblast subtypes. PN showed a remarkable amount of inter-sample homogeneity regarding cellular subpopulation proportions despite being resected from a variety of anatomical locations. ST analysis identified distinct cellular subpopulations which were annotated using snRNA-seq data and correlated with histological features. Schwann cell/fibroblast interactions were identified by receptor/ligand interaction analysis demonstrating a high probability of Neurexin 1/Neuroligin 1 (NRXN1/NLGN1) receptor-ligand cross-talk predicted between fibroblasts and non-myelinated Schwann cells (NM-SC) and subtypes, respectively. We observed aberrant expression of NRXN1 and NLGN1 in our PN snRNA-seq data compared to a normal mouse sciatic nerve single-cell RNA-seq dataset. This pathway has never been described in PN and may indicate a clear and direct communication pathway between putative NM-SC cells of origin and surrounding fibroblasts, potentially driving disease progression. SnRNA-seq integrated with spatial transcriptomics advances our understanding of the complex cellular heterogeneity of PN TME and identify potential novel communication pathways that may drive disease progression, a finding that could provide translational therapy options for patients with these devastating tumors of childhood and early adulthood.

Combining SOS1 and MEK Inhibitors in a Murine Model of Plexiform Neurofibroma Results in Tumor Shrinkage

Individuals with neurofibromatosis type 1 develop rat sarcoma virus (RAS)-mitogen-activated protein kinase-mitogen-activated and extracellular signal-regulated kinase (RAS-MAPK-MEK)-driven nerve tumors called neurofibromas. Although MEK inhibitors transiently reduce volumes of most plexiform neurofibromas in mouse models and in neurofibromatosis type 1 (NF1) patients, therapies that increase the efficacy of MEK inhibitors are needed. BI-3406 is a small molecule that prevents Son of Sevenless (SOS)1 interaction with Kirsten rat sarcoma viral oncoprotein (KRAS)-GDP, interfering with the RAS-MAPK cascade upstream of MEK. Single agent SOS1 inhibition had no significant effect in the DhhCre;Nf1 fl/fl mouse model of plexiform neurofibroma, but pharmacokinetics (PK)-driven combination of selumetinib with BI-3406 significantly improved tumor parameters. Tumor volumes and neurofibroma cell proliferation, reduced by MEK inhibition, were further reduced by the combination. Neurofibromas are rich in ionized calcium binding adaptor molecule 1 (Iba1)+ macrophages; combination treatment resulted in small and round macrophages, with altered cytokine expression indicative of altered activation. The significant effects of MEK inhibitor plus SOS1 inhibition in this preclinical study suggest potential clinical benefit of dual targeting of the RAS-MAPK pathway in neurofibromas. SIGNIFICANCE STATEMENT: Interfering with the RAS-mitogen-activated protein kinase (RAS-MAPK) cascade upstream of mitogen activated protein kinase kinase (MEK), together with MEK inhibition, augment effects of MEK inhibition on neurofibroma volume and tumor macrophages in a preclinical model system. This study emphasizes the critical role of the RAS-MAPK pathway in controlling tumor cell proliferation and the tumor microenvironment in benign neurofibromas.

Abnormal peripheral blood cell counts in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1), also known as von Recklinghausen disease, is an autosomal dominant disease characterized by neurofibromas with infiltration of mast cells. Neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), platelet-to-lymphocyte ratio (PLR) and basophil-to-lymphocyte ratio (BLR) are examined as markers for various diseases. However, these parameters have not yet been assessed for NF1. This study therefore examined these parameters in NF1 patients. We recruited 153 NF patients (78 males, 75 females) and 51 control patients (31 males, 20 females). Complete blood counts were performed, then NLR, LMR, PLR and BLR were calculated. Neutrophil count was significantly higher in male NF1 patients than in male controls. Lymphocyte count was significantly lower in NF1 patients than in controls for both sexes. Monocyte count was significantly higher in male NF1 patients than in male controls. Basophil count was significantly higher in male NF1 patients than in male controls. NLR, PLR and BLR were significantly higher in NF1 patients than in controls for both sexes. LMR was significantly lower in NF1 patients than in controls for both sexes. NF1 shows high NLR, PLR and BLR and low lymphocyte count and LMR.

Management of neurofibromatosis type 1-associated plexiform neurofibromas

Plexiform Neurofibromas (PN) are a common manifestation of the genetic disorder neurofibromatosis type 1 (NF1). These benign nerve sheath tumors often cause significant morbidity, with treatment options limited historically to surgery. There have been tremendous advances over the past two decades in our understanding of PN, and the recent regulatory approvals of the MEK inhibitor selumetinib are reshaping the landscape for PN management. At present, there is no agreed upon PN definition, diagnostic evaluation, surveillance strategy, or clear indications for when to initiate treatment and selection of treatment modality. In this review, we address these questions via consensus recommendations from a panel of multidisciplinary NF1 experts.

Efficacy of Csaba stain to demonstrate mature and immature mast cells in oral inflammatory lesions: An in-vitro study

Background

Mast cells (MCs) are immune cells of the myeloid lineage and are present in connective tissues throughout the body. Mastocytosis regulates many physiologic processes and affects the pathogenesis of allergic conditions, anaphylactic reactions, autoimmune disorders and leukemias. Toluidine blue is commonly employed as a special stain for MCs that uniformly imparts blue color to both immature and mature cells. Csaba stain that distinguishes mature from immature MCs has not been widely explored. However, its use in differentiating mature and immature cells has not been reported in the literature. The identification of mature and immature MCs may provide a major clue for the diagnosis of any unrecognized systemic pathologies.

Objectives

To evaluate the staining efficacy of Csaba stain, toluidine blue and Leishman's stains in the identification of MCsTo compare the effectiveness of Csaba stain, toluidine blue and Leishman's stains to identify MCs in inflammatory pathologic lesions.

Materials and Methods

Fifty sections of inflammatory lesions were subjected to Csaba stain, toluidine blue and Leishman's stains each for studying MCs. The staining efficacy of the three stains was compared for parameters such as homogeneity, specificity, staining intensity, granular staining property and differentiation between mature and immature cells.

Results

The Csaba, toluidine blue and Leishman's stains showed statistically insignificant P = 0.50, 0.95, 0.29, 0.48 for homogeneity, specificity, staining intensity and granular staining property respectively, but Csaba stain showed statistically significant P = 0.0001* in differentiating mature from immature cells.

Conclusion

Csaba stain is more effective in differentiating mature from immature MCs compared to the other special stains.

Orbital Tumors-Clinical, Radiologic and Histopathologic Correlation

Orbital masses include a broad spectrum of benign and malignant entities. Often these masses are asymptomatic or show a slow growth rate, so that emergence of clinical symptoms is prolonged. In this context, cross-sectional imaging plays an elementary role in the characterization of these lesions. Aside from the characterization of the underlying entity, an evaluation of the involved compartments is possible by sufficient imaging, which also facilitates optimal treatment and surgery planning. The purpose of this review is to explore different benign and malignant orbital tumors and their typical appearance in imaging together with histopathologic findings.

Surgical Treatment and Complications of Deep-Seated Nodular Plexiform Neurofibromas Associated with Neurofibromatosis Type 1

Background: Nodular plexiform neurofibromas in individuals with neurofibromatosis type 1 often cause significant symptoms and are treated with surgical excision despite the potential risk of complications. This study aimed to clarify the surgical outcomes of deep-seated nodular plexiform neurofibromas and identify the factors associated with postoperative complications. Methods: We retrospectively reviewed patients with neurofibromatosis type 1 who underwent surgical excision for deep-seated nodular plexiform neurofibromas in our hospital from 2015 to 2021. Enucleation while preserving the nerve fascicles was attempted first, and en bloc resection, ligating the nerve origin in cases in which the parent nerve was entrapped by the tumor, making the tumor difficult to dissect, was performed. Results: In 15 patients, 24 nodular plexiform neurofibromas received surgical excision. Sixteen tumors were enucleated, and eight were en bloc resected. The symptoms of all 10 patients with preoperative symptoms resolved after surgery. Four patients developed new neurological deficits immediately after surgery, two of whom had retained neurological symptoms at the last visit, but these symptoms were mild. Conclusions: The present study demonstrates that surgical treatment of nodular plexiform neurofibromas, even deep-seated neurofibromas, is safe with a low risk of severe complications and improvement in preoperative symptoms.

Multiple Nf1 Schwann cell populations reprogram the plexiform neurofibroma tumor microenvironment

To define alterations early in tumor formation, we studied nerve tumors in neurofibromatosis 1 (NF1), a tumor predisposition syndrome. Affected individuals develop neurofibromas, benign tumors driven by NF1 loss in Schwann cells (SCs). By comparing normal nerve cells to plexiform neurofibroma (PN) cells using single-cell and bulk RNA sequencing, we identified changes in 5 SC populations, including a de novo SC progenitor-like (SCP-like) population. Long after Nf1 loss, SC populations developed PN-specific expression of Dcn, Postn, and Cd74, with sustained expression of the injury response gene Postn and showed dramatic expansion of immune and stromal cell populations; in corresponding human PNs, the immune and stromal cells comprised 90% of cells. Comparisons between injury-related and tumor monocytes/macrophages support early monocyte recruitment and aberrant macrophage differentiation. Cross-species analysis verified each SC population and unique conserved patterns of predicted cell-cell communication in each SC population. This analysis identified PROS1-AXL, FGF-FGFR, and MIF-CD74 and its effector pathway NF-κB as deregulated in NF1 SC populations, including SCP-like cells predicted to influence other types of SCs, stromal cells, and/or immune cells in mouse and human. These findings highlight remarkable changes in multiple types of SCs and identify therapeutic targets for PN.

Neurofibroma Development in Neurofibromatosis Type 1: Insights from Cellular Origin and Schwann Cell Lineage Development

BACKGROUND

Neurofibromatosis type 1 (NF1), a genetic tumor predisposition syndrome that affects about 1 in 3000 newborns, is caused by mutations in the NF1 gene and subsequent inactivation of its encoded neurofibromin. Neurofibromin is a tumor suppressor protein involved in the downregulation of Ras signaling. Despite a diverse clinical spectrum, one of several hallmarks of NF1 is a peripheral nerve sheath tumor (PNST), which comprises mixed nervous and fibrous components. The distinct spatiotemporal characteristics of plexiform and cutaneous neurofibromas have prompted hypotheses about the origin and developmental features of these tumors, involving various cellular transition processes.

METHODS

We retrieved published literature from PubMed, EMBASE, and Web of Science up to 21 June 2022 and searched references cited in the selected studies to identify other relevant papers. Original articles reporting the pathogenesis of PNSTs during development were included in this review. We highlighted the Schwann cell (SC) lineage shift to better present the evolution of its corresponding cellular origin hypothesis and its important effects on the progression and malignant transformation of neurofibromas.

CONCLUSIONS

In this review, we summarized the vast array of evidence obtained on the full range of neurofibroma development based on cellular and molecular pathogenesis. By integrating findings relating to tumor formation, growth, and malignancy, we hope to reveal the role of SC lineage shift as well as the combined impact of additional determinants in the natural history of PNSTs.

Epidemiological profile and clinical characteristics of 491 Brazilian patients with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a chronic and progressive autosomal dominant genetic and sporadic disease characterized by cutaneous and neurological abnormalities. Plexiform neurofibroma (PN), a significant cause of clinical complications in NF-1, is a benign tumor of the peripheral nerve sheath that involves multiple nerve fascicles. Although there is an important number of patients who are affected by NF1 in Brazil, there is little data on the behavior of the disease in the national literature as well as in other low- and middle-income countries.

METHODS

We performed a retrospective analysis of 491 patients with NF1 followed at two reference centers in Brazil.

RESULTS

Approximately 38% of patients had PNs, resulting in reduced life quality. The median patient age with PNs was 30 years (range: 6 to 83 years). Head and neck, and extremity were the main affected locations with 35.8 and 30.6%, respectively. PNs were classified as asymptomatic in 25.1% of patients, while 52.5% presented symptomatic and inoperable tumors. The most common manifestations related to PNs were disfigurement and orthopedic involvement. Twenty patients developed neoplasms and ten (50%) presented with malignant peripheral nerve sheath tumors (MPNST). The prevalence of MPNST in our study was 2.9%.

CONCLUSIONS

Patients with NF1 experience clinically significant morbidity, especially when it is associated with PN. Though there are many patients affected by NF1 in Brazil and other low- and middle-income countries, there is little data available in the corresponding literature. Our results are comparable to the previous results reported from higher-income countries and international registries.

Modeling iPSC-derived human neurofibroma-like tumors in mice uncovers the heterogeneity of Schwann cells within plexiform neurofibromas

Plexiform neurofibromas (pNFs) are developmental tumors that appear in neurofibromatosis type 1 individuals, constituting a major source of morbidity and potentially transforming into a highly metastatic sarcoma (MPNST). pNFs arise after NF1 inactivation in a cell of the neural crest (NC)-Schwann cell (SC) lineage. Here, we develop an iPSC-based NC-SC in vitro differentiation system and construct a lineage expression roadmap for the analysis of different 2D and 3D NF models. The best model consists of generating heterotypic spheroids (neurofibromaspheres) composed of iPSC-derived differentiating NF1(-/-) SCs and NF1(+/-) pNF-derived fibroblasts (Fbs). Neurofibromaspheres form by maintaining highly proliferative NF1(-/-) cells committed to the NC-SC axis due to SC-SC and SC-Fb interactions, resulting in SC linage cells at different maturation points. Upon engraftment on the mouse sciatic nerve, neurofibromaspheres consistently generate human NF-like tumors. Analysis of expression roadmap genes in human pNF single-cell RNA-seq data uncovers the presence of SC subpopulations at distinct differentiation states.

Clinical and humanistic burden among pediatric patients with neurofibromatosis type 1 and plexiform neurofibroma in the USA

PURPOSE

To assess clinical and humanistic burden among pediatric patients with neurofibromatosis type 1 (NF1) and plexiform neurofibroma (PN) in the USA.

METHODS

NF1-PN patients aged 8-18 years (treatment-naïve or ≤ 1 month of selumetinib treatment) and their caregivers and caregivers of similar patients aged 2-7 years were recruited through the Children's Tumor Foundation to participate in an online cross-sectional survey (December 2020-January 2021). Caregivers provided data on patients' demographic and clinical characteristics and burden of debulking surgeries. Patients and caregivers provided self-reported or proxy responses to health-related quality of life (HRQoL) questions using validated instruments.

RESULTS

Sixty-one patients and 82 caregivers responded to the survey. Median (range) age of patients was 11.5 (3-18) years, and 53.7% were female. Most were treatment-naïve (97.6%), with NF1-PN diagnosis for > 5 years (68.3%). Most patients (59.8%) had > 1 PN and 11.0% reporting > 5 PNs. Common NF1-PN symptoms included pain (64.6%), disfigurement (32.9%), and motor dysfunction (28.0%). Patients and caregiver proxies reported low overall HRQoL and reduced physical, emotional, social, and school functioning. Patients also reported considerable pain severity, interference, daily activity impairments, and movement difficulty. Few patients had received complete resections of their tumors (12.2%). 39.0% reported ≥ 1 debulking surgery, among whom, 15.6% had complications, and debulking surgery-related hospitalizations were common (53.1%).

CONCLUSIONS

The clinical and humanistic burden among pediatric NF1-PN patients is substantial. While debulking surgeries are used for symptom management, they are associated with considerable clinical sequelae. Results highlight a need for improved disease management strategies.

Plexiform neurofibroma: shedding light on the investigational agents in clinical trials

INTRODUCTION

Neurofibromatosis Type 1 (NF1) is an autosomal dominant genetic condition, which predisposes individuals to the development of plexiform neurofibromas (PN), benign nerve sheath tumors seen in 30-50% of patients with NF1. These tumors may cause significant pain and disfigurement or may compromise organ function. Given the morbidity associated with these tumors, therapeutic options for patients with NF1-related PN are necessary.

AREAS COVERED

We searched the www.clinicaltrials.gov database for 'plexiform neurofibroma.' This article summarizes completed and ongoing trials involving systemic therapies for PN.

EXPERT OPINION

Surgery is the mainstay treatment; however, complete resection is not possible in many cases. Numerous systemic therapies have been evaluated in patients with NF1, with MEK inhibitors (MEKi) showing the greatest efficacy for volumetric reduction and improvement in functional and patient-reported outcomes. The MEKi selumetinib is now FDA approved for the treatment of inoperable, symptomatic PN in pediatric NF1 patients. Questions remain regarding the use of this drug class in terms of when to initiate therapy, overall duration, reduced dosing schedules, and side effect management. Future studies are needed to fully understand the clinical application of MEKi and to evaluate other potential therapies through appropriate trial designs for this potentially devastating, manifestation in NF1.

The Lipid Asset Is Unbalanced in Peripheral Nerve Sheath Tumors

Peripheral nerve sheath tumors (PNSTs) include schwannomas, neurofibromas (NFs), and plexiform neurofibromas (PNFs), among others. While they are benign tumors, according to their biological behavior, some have the potential for malignant degeneration, mainly PNFs. The specific factors contributing to the more aggressive behavior of some PNSTs compared to others are not precisely known. Considering that lipid homeostasis plays a crucial role in fibrotic/inflammatory processes and in several cancers, we hypothesized that the lipid asset was also unbalanced in this group of nerve tumors. Through untargeted lipidomics, NFs presented a significant increase in ceramide, phosphatidylcholine, and Vitamin A ester. PNFs displayed a marked decrease in 34 out of 50 lipid class analyzed. An increased level of ether- and oxidized-triacylglycerols was observed; phosphatidylcholines were reduced. After sphingolipidomic analysis, we observed six sphingolipid classes. Ceramide and dihydroceramides were statistically increased in NFs. All the glycosylated species appeared reduced in NFs, but increased in PNFs. Our findings suggested that different subtypes of PNSTs presented a specific modulation in the lipidic profile. The untargeted and targeted lipidomic approaches, which were not applied until now, contribute to better clarifying bioactive lipid roles in PNS natural history to highlight disease molecular features and pathogenesis.

The clinico-pathologic profile of primary and recurrent orbital/periorbital plexiform neurofibromas (OPPN)

To evaluate and compare the clinical and histopathological profile of primary and recurrent orbital-periorbital plexiform neurofibromas (OPPN) in patients with neurofibromatosis type 1. We retrospectively evaluated 43 primary or recurrent neurofibroma (NF) specimens from 26 patients (2002 to 2018) at the King Khaled Eye Specialist Hospital, Saudi Arabia. Demographics, clinical presentation, and surgical intervention data were collected. Histopathological specimens were studied with hematoxylin-eosin, Alcian blue, and immunohistochemical markers; S-100, CD44, CD117, smooth muscle actin (SMA), neurofilament, and Ki-67. Of the 43 NFs specimens, 20 were primary and 23 recurrent tumors. For primary NF, the ratio of plexiform to the diffuse type was 13:7, however in recurrent tumors was 3:8 after the first recurrence, and 1:5 after multiple recurrences. Of the 17 patients with primary tumors that had paired recurrent tumors, 12/17 (70.6%) primary NFs were plexiform and 5/17 (29.4%) were diffuse. However, when tumors recurred, 13/17 tumors (76.5%) were diffuse and only 4/17 tumors (23.5%) had a plexiform pattern. The odds of a tumor having a diffuse pattern in recurrent NF was significantly higher than the plexiform pattern [OR = 7.8 (95% confidence interval 1.69:36.1) P = 0.008]. Primary plexiform NFs underwent an excision at a significantly younger age than the diffuse type. Recurrent NFs had significantly higher CD44, CD117, and neurofilament labeling (P = 0.02, P = 0.01 and P<0.001 respectively) but had significantly decreased Alcian blue, and S-100 labeling (P = 0.03, and P = 0.02 respectively) compared to primary tumors. SMA and Ki-67 proliferation index were not different between primary and recurrent NFs (P = 0.86, and P = 0.3 respectively). There appears to be a high risk for primary plexiform NFs to develop a diffuse histologic pattern when they recur. Immunohistochemical staining suggests a role of mast cells (CD117) and expression of infiltration makers (CD44) in the transformation of plexiform tumors to the diffuse phenotype.

Pharmacological Approaches in Neurofibromatosis Type 1-Associated Nervous System Tumors

Simple Summary

Neurofibromatosis type 1 (NF1) is a common cancer predisposition genetic disease that is associated with significant morbidity and mortality. In this literature review, we discuss the major pathways in the nervous system that are affected by NF1, tumors that are associated with NF1, drugs that target these pathways, and genetic models of NF1. We also summarize the latest updates from clinical trials that are evaluating pharmacological agents to treat these tumors and discuss the efforts that are being made to cure the disease in the future

Abstract

Neurofibromatosis type 1 is an autosomal dominant genetic disease and a common tumor predisposition syndrome that affects 1 in 3000 to 4000 patients in the USA. Although studies have been conducted to better understand and manage this disease, the underlying pathogenesis of neurofibromatosis type 1 has not been completely elucidated, and this disease is still associated with significant morbidity and mortality. Treatment options are limited to surgery with chemotherapy for tumors in cases of malignant transformation. In this review, we summarize the advances in the development of targeted pharmacological interventions for neurofibromatosis type 1 and related conditions.

Implications of new understandings of gliomas in children and adults with NF1: report of a consensus conference

Gliomas are the most common primary central nervous system tumors occurring in children and adults with neurofibromatosis type 1 (NF1). Over the past decade, discoveries of the molecular basis of low-grade gliomas (LGGs) have led to new approaches for diagnosis and treatments. However, these new understandings have not been fully applied to the management of NF1-associated gliomas. A consensus panel consisting of experts in NF1 and gliomas was convened to review the current molecular knowledge of NF1-associated low-grade “transformed” and high-grade gliomas; insights gained from mouse models of NF1-LGGs; challenges in diagnosing and treating older patients with NF1-associated gliomas; and advances in molecularly targeted treatment and potential immunologic treatment of these tumors. Next steps are recommended to advance the management and outcomes for NF1-associated gliomas.

Cabozantinib for neurofibromatosis type 1-related plexiform neurofibromas: a phase 2 trial

Neurofibromatosis type 1 (NF1) plexiform neurofibromas (PNs) are progressive, multicellular neoplasms that cause morbidity and may transform to sarcoma. Treatment of Nf1^fl/fl;Postn-Cre mice with cabozantinib, an inhibitor of multiple tyrosine kinases, caused a reduction in PN size and number and differential modulation of kinases in cell lineages that drive PN growth. Based on these findings, the Neurofibromatosis Clinical Trials Consortium conducted a phase II, open-label, nonrandomized Simon two-stage study to assess the safety, efficacy and biologic activity of cabozantinib in patients ≥16 years of age with NF1 and progressive or symptomatic, inoperable PN ( NCT02101736 ). The trial met its primary outcome, defined as ≥25% of patients achieving a partial response (PR, defined as ≥20% reduction in target lesion volume as assessed by magnetic resonance imaging (MRI)) after 12 cycles of therapy. Secondary outcomes included adverse events (AEs), patient-reported outcomes (PROs) assessing pain and quality of life (QOL), pharmacokinetics (PK) and the levels of circulating endothelial cells and cytokines. Eight of 19 evaluable (42%) trial participants achieved a PR. The median change in tumor volume was 15.2% (range, +2.2% to -36.9%), and no patients had disease progression while on treatment. Nine patients required dose reduction or discontinuation of therapy due to AEs; common AEs included gastrointestinal toxicity, hypothyroidism, fatigue and palmar plantar erythrodysesthesia. A total of 11 grade 3 AEs occurred in eight patients. Patients with PR had a significant reduction in tumor pain intensity and pain interference in daily life but no change in global QOL scores. These data indicate that cabozantinib is active in NF1-associated PN, resulting in tumor volume reduction and pain improvement.

Genetic disruption of the small GTPase RAC1 prevents plexiform neurofibroma formation in mice with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a common cancer predisposition syndrome caused by mutations in the NF1 tumor suppressor gene. NF1 encodes neurofibromin, a GTPase-activating protein for RAS proto-oncogene GTPase (RAS). Plexiform neurofibromas are a hallmark of NF1 and result from loss of heterozygosity of NF1 in Schwann cells, leading to constitutively activated p21RAS. Given the inability to target p21RAS directly, here we performed an shRNA library screen of all human kinases and Rho-GTPases in a patient-derived NF1-/- Schwann cell line to identify novel therapeutic targets to disrupt PN formation and progression. Rho family members, including Rac family small GTPase 1 (RAC1), were identified as candidates. Corroborating these findings, we observed that shRNA-mediated knockdown of RAC1 reduces cell proliferation and phosphorylation of extracellular signal-regulated kinase (ERK) in NF1-/- Schwann cells. Genetically engineered Nf1flox/flox;PostnCre+ mice, which develop multiple PNs, also exhibited increased RAC1-GTP and phospho-ERK levels compared with Nf1flox/flox;PostnCre- littermates. Notably, mice in which both Nf1 and Rac1 loci were disrupted (Nf1flox/floxRac1flox/flox;PostnCre+) were completely free of tumors and had normal phospho-ERK activity compared with Nf1flox/flox ;PostnCre+ mice. We conclude that the RAC1-GTPase is a key downstream node of RAS and that genetic disruption of the Rac1 allele completely prevents PN tumor formation in vivo in mice.

NF1 patient missense variants predict a role for ATM in modifying neurofibroma initiation

In Neurofibromatosis type 1, NF1 gene mutations in Schwann cells (SC) drive benign plexiform neurofibroma (PNF), and no additional SC changes explain patient-to-patient variability in tumor number. Evidence from twin studies suggests that variable expressivity might be caused by unidentified modifier genes. Whole exome sequencing of SC and fibroblast DNA from the same resected PNFs confirmed biallelic SC NF1 mutations; non-NF1 somatic SC variants were variable and present at low read number. We identified frequent germline variants as possible neurofibroma modifier genes. Genes harboring variants were validated in two additional cohorts of NF1 patients and by variant burden test. Genes including CUBN, CELSR2, COL14A1, ATR and ATM also showed decreased gene expression in some neurofibromas. ATM-relevant DNA repair defects were also present in a subset of neurofibromas with ATM variants, and in some neurofibroma SC. Heterozygous ATM G2023R or homozygous S707P variants reduced ATM protein expression in heterologous cells. In mice, genetic Atm heterozygosity promoted Schwann cell precursor self-renewal and increased tumor formation in vivo, suggesting that ATM variants contribute to neurofibroma initiation. We identify germline variants, rare in the general population, overrepresented in NF1 patients with neurofibromas. ATM and other identified genes are candidate modifiers of PNF pathogenesis.

Paradigm Shifts in Mast Cell and Basophil Biology and Function: An Emerging View of Immune Regulation in Health and Disease

The physiological role of the mast cell and basophil has for many years remained enigmatic. In this chapter, we briefly summarize some of the more recent studies that shed new light on the role of mast cells and basophils in health and disease. What we gain from these studies is a new appreciation for mast cells and basophils as sentinels in host defense and a further understanding that dysregulation of mast cell and basophil function can be a component of various diseases other than allergies. Perhaps the most important insight reaped from this work is the increasing awareness that mast cells and basophils can function as immunoregulatory cells that modulate the immune response in health and disease. Collectively, the recent knowledge provides new challenges and opportunities toward the development of novel therapeutic strategies to augment host protection and modify disease through manipulation of mast cell and basophil function.

Ketotifen Modulates Mast Cell Chemotaxis to Kit-Ligand, but Does Not Impact Mast Cell Numbers, Degranulation, or Tumor Behavior in Neurofibromas of Nf1-Deficient Mice

Neurofibromatosis Type 1 (NF1) is one of the most common genetic tumor predisposition syndromes in humans. Mutant NF1 results in dysregulated RAS allowing neoplasms throughout the neuroaxis. Plexiform neurofibromas (pNF) afflict up to 50% of patients with NF1. They are complex tumors of the peripheral nerve that cause major morbidity via nerve dysregulation and mortality via conversion to malignant sarcoma. Genetically engineered mouse models (GEMM) of NF1 provide valuable insights for the identification of therapies that have utility in people with pNF. Preclinical studies in GEMMs implicate mast cells and the c-Kit/Kit ligand pathway in pNF tumorigenesis. Kit ligand is a potent chemokine secreted by tumorigenic, Nf1-deficient Schwann cells. Ketotifen is an FDA-approved drug for the treatment of allergic conjunctivitis and asthma that promotes mast cell stabilization and has been used in prior case studies to treat or prevent pNFs. This study investigated the effect of ketotifen on mast cell infiltration and degranulation in the presence and absence of Kit ligand provocation and the effect of ketotifen on shrinking or preventing pNF formation in the Nf1^flox/flox ;PostnCre ⁺ GEMM. Ketotifen decreased mast cell infiltration in response to exogenous Kit ligand administration, but did not affect mast cell degranulation. Importantly, ketotifen did not reduce mast cells numbers or activity in pNF and did not prevent pNF formation or decrease the volume of established pNF despite administration of pharmacologically active doses. These findings suggest that ketotifen has limited use as monotherapy to prevent or reduce pNF burden in the setting of Nf1 mutations.

The role of collagen in cancer: from bench to bedside

Collagen is the major component of the tumor microenvironment and participates in cancer fibrosis. Collagen biosynthesis can be regulated by cancer cells through mutated genes, transcription factors, signaling pathways and receptors; furthermore, collagen can influence tumor cell behavior through integrins, discoidin domain receptors, tyrosine kinase receptors, and some signaling pathways. Exosomes and microRNAs are closely associated with collagen in cancer. Hypoxia, which is common in collagen-rich conditions, intensifies cancer progression, and other substances in the extracellular matrix, such as fibronectin, hyaluronic acid, laminin, and matrix metalloproteinases, interact with collagen to influence cancer cell activity. Macrophages, lymphocytes, and fibroblasts play a role with collagen in cancer immunity and progression. Microscopic changes in collagen content within cancer cells and matrix cells and in other molecules ultimately contribute to the mutual feedback loop that influences prognosis, recurrence, and resistance in cancer. Nanoparticles, nanoplatforms, and nanoenzymes exhibit the expected gratifying properties. The pathophysiological functions of collagen in diverse cancers illustrate the dual roles of collagen and provide promising therapeutic options that can be readily translated from bench to bedside. The emerging understanding of the structural properties and functions of collagen in cancer will guide the development of new strategies for anticancer therapy.

Activated androgen receptor accelerates angiogenesis in cutaneous neurofibroma by regulating VEGFA transcription

Accumulating evidence has demonstrated the significant progression of cutaneous neurofibroma (cNF) without necrosis during puberty. However, the molecular events involved in this process remain unclear. The alteration of the steroid hormone levels during puberty has led to the investigation of the expression levels of the androgen receptor (AR). A positive correlation between AR expression and microvessel density has been reported in human cNF tissues in combination with enhanced endothelial cell tube formation in vitro. In addition, activated AR signaling can promote neurofibroma cell growth in vivo and in vitro and tube formation in vitro. In the present study, AR was shown to bind directly to the promoter of vascular endothelial growth factor A (VEGFA), a key factor involved in angiogenesis, and to sequentially induce its expression. Furthermore, the AR inhibitor, MDV3100, downregulated VEGFA expression and abolished endothelial cell recruitment and tube formation. Taken collectively, the findings of this study revealed that AR signaling enhanced tumor growth and angiogenesis in cNF by regulating VEGFA transcription. However, whether AR can be regarded a therapeutic target for cNF requires further investigation.

Novel Three-Dimensional Morphometry to Reassess Orbit Deformities Associated With Orbital-Periorbital Plexiform Neurofibroma

BACKGROUND

Orbit deformities are usually found in neurofibromatosis type 1 patients, especially those with orbital-periorbital plexiform neurofibroma (OPPN). Unfortunately, current morphometry is complicated and, in some cases, cannot be performed on the deformed orbit due to the destruction of landmarks. Herein, we present a novel 3-dimensional (3D) morphometry for these orbital measurements.

METHODS

We retrospectively reviewed 29 patients with OPPN, and another 29 disseminated cutaneous neurofibroma patients served as controls. All patients had undergone craniofacial computed tomography and 3D reconstruction. New morphometry was used to measure the area of the orbital rim (OR) and superior orbital fissure (SOF).

RESULTS

For the 29 patients with OPPN, the area of the OR at the affected side was 14.18 ± 3.50 cm, while the OR at the nonaffected side was 12.32 ± 1.38 cm. In addition, the area of the SOF at the affected side was 5.37 ± 5.75 cm, while that at the nonaffected side was 1.27 ± 1.03 cm. The OR and SOF at the affected side are more likely to become enlarged compared with those at the nonaffected side. Among the 29 patients with OPPN, the novel morphometry could be performed in 19 cases (65.5%) that cannot be measured by previous morphometry.

CONCLUSION

The novel morphometry is convenient and reproducible, which optimizes its application in pathologic cases, especially those involving deformed orbits.

Analysis of intratumor heterogeneity in Neurofibromatosis type 1 plexiform neurofibromas and neurofibromas with atypical features: Correlating histological and genomic findings

Plexiform neurofibromas (PNFs) are benign peripheral nerve sheath tumors involving large nerves present in 30%-50% Neurofibromatosis type 1 (NF1) patients. Atypical neurofibromas (ANF) are distinct nodular lesions with atypical features on histology that arise from PNFs. The risk and timeline of malignant transformation in ANF is difficult to assess. A recent NIH workshop has stratified ANFs and separated a subgroup with multiple atypical features and higher risk of malignant transformation termed atypical neurofibromatous neoplasms with uncertain biological potential (ANNUBP). We performed an analysis of intratumor heterogeneity on eight PNFs to link histological and genomic findings. Tumors were homogeneous although histological and molecular heterogeneity was identified. All tumors were 2n, almost mutation-free and had a clonal NF1(-/-) origin. Two ANFs from the same patient showed atypical features on histology and deletions of CDKN2A/B. One of the ANFs exhibited different areas in which the degree of histological atypia correlated with the heterozygous or homozygous loss of the CDKN2A/B loci. CDKN2A/B deletions in different areas originated independently. Results may indicate that loss of a single CDKN2A/B copy in NF1(-/-) cells is sufficient to start ANF development and that total inactivation of both copies of CDKN2A/B is necessary to form an ANNUBP.

Contributions of inflammation and tumor microenvironment to neurofibroma tumorigenesis

Neurofibromatosis type 1 associates with multiple neoplasms, and the Schwann cell tumor neurofibroma is the most prevalent. A hallmark feature of neurofibroma is mast cell infiltration, which is recruited by chemoattractant stem cell factor (SCF) and has been suggested to sustain neurofibroma tumorigenesis. In the present study, we use new, genetically engineered Scf mice to decipher the contributions of tumor-derived SCF and mast cells to neurofibroma development. We demonstrate that mast cell infiltration is dependent on SCF from tumor Schwann cells. However, removal of mast cells by depleting the main SCF source only slightly affects neurofibroma progression. Other inflammation signatures show that all neurofibromas are associated with high levels of macrophages regardless of Scf status. These findings suggest an active inflammation in neurofibromas and partly explain why mast cell removal alone is not sufficient to relieve tumor burden in this experimental neurofibroma model. Furthermore, we show that plexiform neurofibromas are highly associated with injury-prone spinal nerves that are close to flexible vertebras. In summary, our study details the role of inflammation in neurofibromagenesis. Our data indicate that prevention of inflammation and possibly also nerve injury at the observed tumor locations are therapeutic approaches for neurofibroma prophylaxis and that such treatment should be explored.

Emerging therapeutic targets for neurofibromatosis type 1

INTRODUCTION

Neurofibromatosis type 1 (NF1) is an autosomal dominantly inherited tumor predisposition syndrome with an incidence of one in 3000-4000 individuals with no currently effective therapies. The NF1 gene encodes neurofibromin, which functions as a negative regulator of RAS. NF1 is a chronic multisystem disorder affecting many different tissues. Due to cell-specific complexities of RAS signaling, therapeutic approaches for NF1 will likely have to focus on a particular tissue and manifestation of the disease. Areas covered: We discuss the multisystem nature of NF1 and the signaling pathways affected due to neurofibromin deficiency. We explore the cell-/tissue-specific molecular and cellular consequences of aberrant RAS signaling in NF1 and speculate on their potential as therapeutic targets for the disease. We discuss recent genomic, transcriptomic, and proteomic studies combined with molecular, cellular, and biochemical analyses which have identified several targets for specific NF1 manifestations. We also consider the possibility of patient-specific gene therapy approaches for NF1. Expert opinion: The emergence of NF1 genotype-phenotype correlations, characterization of cell-specific signaling pathways affected in NF1, identification of novel biomarkers, and the development of sophisticated animal models accurately reflecting human pathology will continue to provide opportunities to develop therapeutic approaches to combat this multisystem disorder.

Large penile plexiform neurofibroma in an 11-year old boy

Background

Neurofibromatosis is a genetically inherited disorder of the nervous system (brain and spinal cord) which mainly affects the development of nerve (neural) cell tissues, causing tumors (neurofibromas) to develop on nerves. It is the most common single gene disorder of the nervous system and inheritance is through autosomal dominance. They are usually classified into types 1 and 2, the type 1 is the commoner type and also known as superficial neurofibroma. Plexiform neurofibromas are the next most common type of tumor in individuals with type 1 neurofibroma. Plexiform neurofibromas are histologically benign tumors that are made up of a variety of cell types including neuronal axons, Schwann cells, fibroblasts, mast cells, macrophages, perineural cells and extracellular matrix materials such as collagen. They can occur in any part of the body and can grow throughout the person's lifetime, often becoming disfiguring, disabling or deadly via compression of vital structures or conversion to a malignant sarcoma or malignant peripheral nerve sheath turmor. The aim of this report is to present a large penile plexiform neurofibroma which required extensive dissection for complete excision and reconstruction of the phallus and glans penis.

Objectives

To present a huge penile plexiform neurofibroma and the mode of surgical treatment.

Methods

The huge penile plexiform neurofibroma was completely excised and the penile defect resulting from the excision was repaired.

Conclusion

Plexiform neurofibromas are congenital tumors of peripheral nerve sheaths which may also develop near nerve roots deep within the body. They are usually benign but carry a malignant potential in 5-10% of patients. Plexiform neurofibromas are commoner in the face, chest and limbs but the index case occurred on the penile shaft.

The role of nerve microenvironment for neurofibroma development

Deregulation of RAS signaling in Neurofibromatosis type 1 (NF1) results in the development of multiple neurofibromas, complex tumor of the peripheral nerves with no effective medical treatment. There is increasing evidences that neurofibroma initiates through loss of NF1 function in the Schwann cell lineage, followed by a cascade of interactions with other cell types in the surrounding tumor microenvironment. In NF1 patients, neurofibromas always develop along peripheral nerves and do not migrate to distant organs, including the central nervous system. In this study, we sought to identify the contributions of these peripheral nerves in neurofibroma formation. Using in vivo and in vitro three-dimensional (3D) culturing system, we show that peripheral nerves are absolutely required for neurofibroma tumorigenesis and report a novel 3D skin raft culture system for neurofibroma formation in vitro to decipher tumor pathogenesis. This interaction between neoplastic Schwann cells and their surrounding neural microenvironment has important implications for understanding early cellular events that dictate tumorigenesis. It also provides fertile ground for the elucidation of intrinsic and extrinsic factors within the nerve microenvironment that likely play essential roles in neurofibroma development and, therefore, viable therapeutic targets in neurofibroma therapy.

Receptor of ghrelin is expressed in cutaneous neurofibromas of individuals with neurofibromatosis 1

BACKGROUND

Multiple cutaneous neurofibromas are a hallmark of neurofibromatosis 1 (NF1). They begin to appear during puberty and increase in number and volume during pregnancy, suggesting a hormonal influence. Ghrelin is a hormone that acts via growth hormone secretagogue receptor (GHS-R), which is overexpressed in many neoplasms and is involved in tumorigenesis. We aimed to investigate GHS-R expression in NF1 cutaneous neurofibromas and its relationship with tumors volume, and patient's age and gender.

RESULTS

Sample comprised 108 cutaneous neurofibromas (55 large and 53 small tumors) from 55 NF1 individuals. GHS-R expression was investigated by immunohistochemistry in tissue micro and macroarrays and quantified using a digital computer-assisted method. All neurofibromas expressed GHS-R, with a percentage of positive cells ranging from 4.9% to 76.1%. Large neurofibromas expressed more GHS-R than the small ones. The percentage of GHS-R-positive cells and intensity of GHS-R expression were positively correlated with neurofibromas volume. GHS-R expression was more common in female gender.

CONCLUSIONS

GHS-R is expressed in cutaneous neurofibromas. Larger neurofibromas have a higher percentage of positive cells and higher GHS-R intensity. Based on our results we speculate that ghrelin may have an action on the tumorigenesis of cutaneous neurofibromas. Future studies are required to understand the role of ghrelin in the pathogenesis of NF1-associated cutaneous neurofibroma.

Multiphoton fluorescence lifetime imaging of chemotherapy distribution in solid tumors

Doxorubicin is a commonly used chemotherapeutic employed to treat multiple human cancers, including numerous sarcomas and carcinomas. Furthermore, doxorubicin possesses strong fluorescent properties that make it an ideal reagent for modeling drug delivery by examining its distribution in cells and tissues. However, while doxorubicin fluorescence and lifetime have been imaged in live tissue, its behavior in archival samples that frequently result from drug and treatment studies in human and animal patients, and murine models of human cancer, has to date been largely unexplored. Here, we demonstrate imaging of doxorubicin intensity and lifetimes in archival formalin-fixed paraffin-embedded sections from mouse models of human cancer with multiphoton excitation and multiphoton fluorescence lifetime imaging microscopy (FLIM). Multiphoton excitation imaging reveals robust doxorubicin emission in tissue sections and captures spatial heterogeneity in cells and tissues. However, quantifying the amount of doxorubicin signal in distinct cell compartments, particularly the nucleus, often remains challenging due to strong signals in multiple compartments. The addition of FLIM analysis to display the spatial distribution of excited state lifetimes clearly distinguishes between signals in distinct compartments such as the cell nuclei versus cytoplasm and allows for quantification of doxorubicin signal in each compartment. Furthermore, we observed a shift in lifetime values in the nuclei of transformed cells versus nontransformed cells, suggesting a possible diagnostic role for doxorubicin lifetime imaging to distinguish normal versus transformed cells. Thus, data here demonstrate that multiphoton FLIM is a highly sensitive platform for imaging doxorubicin distribution in normal and diseased archival tissues.

NF1+/- Hematopoietic Cells Accelerate Malignant Peripheral Nerve Sheath Tumor Development without Altering Chemotherapy Response

Haploinsufficiency in the tumor suppressor NF1 contributes to the pathobiology of neurofibromatosis type 1, but a related role has not been established in malignant peripheral nerve sheath tumors (MPNST) where NF1 mutations also occur. Patients with NF1-associated MPNST appear to have worse outcomes than patients with sporadic MPNST, but the mechanism underlying this correlation is not understood. To define the impact of stromal genetics on the biology of this malignancy, we developed unique mouse models that reflect the genetics of patient-associated MPNST. Specifically, we used adenovirus-Cre injections to generate MPNST in Nf1Flox/Flox; Ink4a/ArfFlox/Flox and Nf1Flox/-; Ink4a/ArfFlox/Flox paired littermate mice to model tumors from NF1-wild-type and NF1-associated patients, respectively. In these models, Nf1 haploinsufficiency in hematopoietic cells accelerated tumor onset and increased levels of tumor-infiltrating immune cells comprised of CD11b+ cells, monocytes, and mast cells. We observed that mast cells were also enriched in human NF1-associated MPNST. In a coclinical trial to examine how the tumor microenvironment influences the response to multiagent chemotherapy, we found that stromal Nf1 status had no effect. Taken together, our results clarify the role of the NF1-haploinsufficient tumor microenvironment in MPNST. Cancer Res; 77(16); 4486-97. ©2017 AACR.

Immune profiling of NF1-associated tumors reveals histologic subtype distinctions and heterogeneity: implications for immunotherapy

Successful treatment of neurofibromatosis type 1 (NF1)-associated tumors poses a significant clinical challenge. While the primary underlying genetic defect driving RAS signaling is well described, recent evidence suggests immune dysfunction contributes to tumor pathogenesis and malignant transformation. As immunologic characterizations, prognostic and predictive of immunotherapeutic clinical response in other cancers, are not fully described for benign and malignant NF1-related tumors, we sought to define their immunologic profiles. We determined the expression of human leukocyte antigen (HLA)-A/-B/-C, β-2-microglobulin (B2M), and T cell inhibitory ligands PD-L1 and CTLA-4 by microarray gene analysis and flow cytometry. We examined HLA-A/-B/-C, B2M, and PD-L1 expression on thirty-six NF1-associated tumor samples by immunohistochemistry, and correlated these with tumoral CD4⁺, CD8⁺, FOXP3⁺, CD56⁺, and CD45RO⁺ lymphocytic infiltrates. We evaluated several tumors from a single patient, observing trends of increasing immunogenicity over time, even with disease progression. We observed similarly immunogenic profiles for malignant peripheral nerve sheath tumors (MPNST) and nodular and plexiform neurofibromas, contrasting with diffuse neurofibromas. These studies suggest that while immunotherapies may offer some benefit for MPNST and nodular and plexiform neurofibromas, tumor heterogeneity might pose a significant clinical challenge to this novel therapeutic approach.

Extensive Peculiar Cutaneous Form of Neurofibromatosis Type I as a New Mutation - a Case Report

Neurofibromatosis-1 (NF1) is one of the most common hereditary multisystemic disorders. The disease manifests a variety of characteristic features that include: hyperpigmentary abnormalities of the skin (café-au-lait macules, freckles in the axillae, and iris Lisch nodules) and growth of benign peripheral nerve sheath tumors (neurofibromas) in the skin. Associated extracutaneous clinical features include: skeletal abnormalities, neurological, cardiovascular, endocrine and other malformations. NF1 is caused by mutation in the neurofibromatosis-1 gene, which codes for the protein neurofibromin. The inheritance of NF1 follows an autosomal dominant trait, although about 50% of patients present with new („de novo“) mutations, and represent the first member of their family. No difference in the severity of the disease can be found in patients with familial mutations versus those with new mutations. We present a 78-year-old female patient with an extreme cutaneous form of neurofibromatosis who reported no affected family member. Apart from skin problems, she had no major health issues in childhood and adolescence, but in recent decades she had frequent headaches, occasional abdominal pain, and vision and hearing impairment. About 10 to 14 days before admission, she developed a severe cough, shortness of breath, and chest and abdominal pain. On examination, the patient of short stature (hight: 152 cm, weight: 49 kg) presented with thousands of soft nodules dispersed over the whole body, except on extensor sides of thighs and lower legs; the nodules varied in color from skin-colored, livid erythematous, to brown-grey; the nodules on the abdomen were moist, partly bleeding from the base, and accompanied by an unpleasant odor. Her feet were also densely covered by dark purple lumps, with dystrophic changes of the toe nails that were thickened, frayed, and yellowish. The skeletal abnormalities included: short stature, severe osteoporosis and osteosclerosis of the head bone structure; degenerative arthropathc-spondylotic changes of the thoracolumbar spine segment with signs of diffuse skeletal hyperostosis; pronounced degenerative changes of the lumbar spine. CT scans of the head, chest and abdomen showed the following abnormalities: flattening of the paraventricular gyri and reduction of brain parenchyma with hypodensity of the white matter in terms of cortical atrophy; periventricular bilateral small post-ischemic microvascular brain lesions of varying chronicity; in the parenchyma of the upper left lung lobe the apical presence of small areas of pleural effusion with consequent subatelectic region; distended stomach and a small inner wall herniation; hypotrophic right kidney; atherosclerotic lesions of the abdominal aorta; low grade infrarenal kinking of the abdominal aorta. Pathohistological analysis of biopsy specimen taken from the nodule corresponded with cutaneous neurofibroma. Consultative examinations of various specialists pointed to the existence of the following comorbidities: obstructive respiratory syndrome and right lobe pneumonia that were treated by antibiotics, aminophylline and dexamethasone infusions; psycho-organic syndrome without focal neurological deficit; Lisch nodules in each eye, and senile cataract. Considering the age and medical presentation of the patient, no other treatment was considered. In conclusion, this is a sporadic case of cutaneous neurofibromatosis 1 in a 78-year-old female patient who presented with extremely severe cutaneous neurofibromas, making this case at least rather peculiar.

The role of stem cells in benign tumors

As stem cells contribute to the development and homeostasis of normal adult tissues, malfunction of stem cells in self-renewal and differentiation has been associated with tumorigenesis. A growing number of evidences indicating that tumor initiating cells play a crucial role, not only in malignancies, but also in generation and development of benign tumors. Here we offer an overview of the identification and functional characterization of benign tumor initiating cells in several tissues and organs, which typically show capacities of uncontrolled self-renewal to fuel the tumor growth and abnormal differentiation to give rise to tumor heterogeneity. They may originate from alteration of normal stem cells, which confer the benign tumor initiating cells with different repertoire of "stemness". The plastic functions of benign tumor initiating cells are determined by niche regulation mediated via several signaling and epigenetic cues. Therefore, targeting stem cell function represents an important strategy for understanding the biology and management of benign tumors.

Therapeutic advances for the tumors associated with neurofibromatosis type 1, type 2, and schwannomatosis

Neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis (SWN) are tumor-suppressor syndromes. Each syndrome is an orphan disease; however, the tumors that arise within them represent the most common tumors of the nervous system worldwide. Systematic investigation of the pathways impacted by the loss of function of neurofibromin (encoded byNF1) and merlin (encoded byNF2) have led to therapeutic advances for patients with NF1 and NF2. In the syndrome of SWN, the genetic landscape is more complex, with 2 known causative genes (SMARCB1andLZTR1) accounting for up to 50% of familial SWN patients. The understanding of the molecular underpinnings of these syndromes is developing rapidly and offers more therapeutic options for the patients. In addition, common sporadic cancers harbor somatic alterations inNF1(ie, glioblastoma, breast cancer, melanoma),NF2(ie, meningioma, mesothelioma) andSMARCB1(ie, atypical teratoid/rhabdoid tumors) such that advances in management of syndromic tumors may benefit patients both with and without germline mutations. In this review, we discuss the clinical and genetic features of NF1, NF2 and SWN, the therapeutic advances for the tumors that arise within these syndromes and the interaction between these rare tumor syndromes and the common tumors that share these mutations.

Inflammation-Induced Plasticity in Melanoma Therapy and Metastasis

Phenotype switching contributes to nongenomic heterogeneity in melanoma and other cancers. These dynamic and in part reversible phenotype changes impose diagnostic and therapeutic challenges. Understanding the reciprocal coevolution of melanoma and immune cell phenotypes during disease progression and in response to therapy is a prerequisite to improve current treatment strategies. Here we discuss how proinflammatory signals promote melanoma cell plasticity and govern interactions of melanoma and immune cells in the tumor microenvironment. We examine phenotypic plasticity and heterogeneity in different melanoma mouse models with respect to their utility for translational research and emphasize the interplay between melanoma cells and neutrophils as a critical driver of metastasis.

Neurofibromatosis as a gateway to better treatment for a variety of malignancies

The neurofibromatoses (NF) are a group of rare genetic disorders that can affect all races equally at an incidence from 1:3000 (NF1) to a log unit lower for NF2 and schwannomatosis. Since the research community is reporting an increasing number of malignant cancers that carry mutations in the NF genes, the general interest of both the research and pharma community is increasing and the authors saw an opportunity to present a novel, fresh approach to drug discovery in NF. The aim of the paper is to challenge the current drug discovery approach to NF, whereby existing targeted therapies that are either in the clinic or on the market for other disease indications are repurposed for NF. We offer a suggestion for an alternative drug discovery approach. In the new approach, selective and tolerable targeted therapies would be developed for NF and later expanded to patients with more complex diseases such as malignant cancer in which the NF downstream pathways are deregulated. The Children's Tumor Foundation, together with some other major NF funders, is playing a key role in funding critical initiatives that will accelerate the development of better targeted therapies for NF patients, while these novel, innovative treatments could potentially be beneficial to molecularly characterized cancer patients in which NF mutations have been identified.

Preclinical Evidence for the Use of Sunitinib Malate in the Treatment of Plexiform Neurofibromas

PURPOSE

Plexiform neurofibromas (pNF) are pathognomonic nerve and soft tissue tumors of neurofibromatosis type I (NF1), which are highly resistant to conventional chemotherapy and associated with significant morbidity/mortality. Disruption of aberrant SCF/c-Kit signaling emanating from the pNF microenvironment induced the first ever objective therapeutic responses in a recent phase 2 trial. Sunitinib malate is a potent, highly selective RTK inhibitor with activity against c-Kit, PDGFR, and VEGFR, which have also been implicated in the pathogenesis of these lesions. Here, we evaluate the efficacy of sunitinib malate in a preclinical Krox20;Nf1(flox/-) pNF murine model.

EXPERIMENTAL DESIGN

Proliferation, β-hexosaminidase release (degranulation), and Erk1/2 phosphorylation were assessed in sunitinib treated Nf1(+/-) mast cells and fibroblasts, respectively. Krox20;Nf1(flox/-) mice with established pNF were treated sunitinib or PBS-vehicle control for a duration of 12 weeks. pNF metabolic activity was monitored by serial [(18)F]DG-PET/CT imaging.

RESULTS

Sunitinib suppressed multiple in vitro gain-in-functions of Nf1(+/-) mast cells and fibroblasts and attenuated Erk1/2 phosphorylation. Sunitinib treated Krox20;Nf1(flox/-) mice exhibited significant reductions in pNF size, tumor number, and FDG uptake compared to control mice. Histopathology revealed reduced tumor cellularity and infiltrating mast cells, markedly diminished collagen deposition, and increased cellular apoptosis in sunitinib treated pNF.

CONCLUSIONS

Collectively, these results demonstrate the efficacy of sunitinib in reducing tumor burden in Krox20;Nf1(flox/-) mice. These preclinical findings demonstrate the utility of inhibiting multiple RTKs in pNF and provide insights into the design of future clinical trials.