Search Results (16)

Plexiform neurofibromas (hereafter called pNF1) are often diagnosed in early childhood and occur in about 30% of neurofibromatosis type 1 (NF1) patients. pNF1 exhibits aggressive growth along a nerve in the body and has substantial potential for progression to malignant peripheral nerve sheath tumors that are rarely curable. There are two recently FDA-approved drugs, selumetinib and mirdametinib, for pNF1 patients who have symptomatic and inoperable plexiform neurofibromas; however, these treatments achieve only approximately 30% tumor shrinkage. Fibroblasts, the most abundant cell types within the pNF1 tumor microenvironment, are implicated in pNF1 growth and invasion; however, how fibroblasts affect a drug response of pNF1 remains poorly understood. In the present study, we focused on contributions of fibroblasts to the drug resistance in pNF1 via their secretome. We employed our established three-dimensional (3D) culture system incorporating human pNF1 tumor cells (Nf1^−/−) and primary fibroblasts (Nf1^+/−) grown in our patented microfluidic culture chips for monocultures and parallel cocultures in which 3D pNF1 structures and fibroblasts share their secretome without direct cell-to-cell contact. Three-dimensional pNF1 structures in 3D parallel cocultures with fibroblasts exhibited greater drug resistance than ones in monocultures. We found that pNF1 tumor cells showed increased P-glycoprotein expression when incubated with fibroblast-derived conditioned media or parallel cocultured with fibroblasts, compared to control conditions. Pharmacological inhibition of P-glycoprotein partially restored drug sensitivity. Additionally, fibroblasts showed higher resistance to selumetinib and mirdametinib than pNF1 tumor structures, likely due to elevated P-glycoprotein levels. This study is the first to define precise roles of fibroblasts in pNF1 drug resistance, emphasizing the potential of fibroblast-targeted therapies as a promising approach to improve pNF1 treatment outcomes. Full article

Background/Objectives: Plexiform neurofibromas (pNFs) are one of the cardinal presentations of NF1 patients, often arising during early childhood. Since selumetinib was approved by the FDA in 2020, the long-term side effects and various responses of mitogen-activated protein kinase inhibitors (MEKi) in pediatric patients necessitate a new strategy. We propose that combining selumetinib with heat shock protein 90 inhibitors (HSP90i) can enhance the inhibitory effects as well as reduce the dosage of selumetinib in combination. We validated the synergistic effects and the significantly improved treatment effects of the combination of selumetinib and HSP90i in pNFs. Methods: We used drug screen data mining to predict the combination of selumetinib and HSP90i. Using cell lines and in vivo mouse models for pNFs, we tested a series of combinations with different concentrations. We validated the in vivo inhibitory effects using the transplanted tumors from DhhCreNf1^f/f mouse models. Results: We demonstrated that combining selumetinib and SNX-2112 or retaspimycin can achieve better tumor inhibition with synergistic effects. The combination significantly delays the progression of mouse pNFs. Conclusions: The combination of selumetinib and HSP90i has significant synergistic effects, provides therapeutic inhibitor effects, and reduces the selumetinib dosage in combination. Full article

Background/Objectives: Neurofibromatosis type 1 (NF1) is a prevalent inherited disorder, with approximately 50% of affected individuals developing plexiform neurofibromas (PNFs), which can progress to highly aggressive malignant peripheral nerve sheath tumors (MPNSTs). While selumetinib is FDA-approved for PNFs, its efficacy in MPNSTs is limited and associated with dose-limiting toxicities. NF1 deficiency drives tumorigenesis and alters immune dynamics via RAS hyperactivation. Given the substantial macrophage infiltration in NF1 lesions and its association with disease progression, we hypothesized that targeting tumor-promoting immune cells with the retinoid X receptor (RXR) agonist MSU-42011 could be an alternative therapeutic strategy, as it has shown promise in KRAS-driven cancers by decreasing pERK levels and reducing tumor-promoting immune cells. Methods: We examined the effects of MSU-42011 and selumetinib, alone and in combination, on NF1-deficient cells and in a syngeneic MPNST model. Results: In vivo, the combination of MSU-42011 and selumetinib significantly reduced tumor growth, pERK levels, and tumor-promoting macrophages and increased activated CD8⁺ T cells in syngeneic MPNST models. In NF1-deficient cells, MSU-42011 or selumetinib reduced pERK levels, with combination treatment achieving greater reductions. Conditioned media (CM) from NF1-deficient cells increased the protein and mRNA levels of several cytokines and chemokines in human THP1 cells and bone marrow-derived macrophages (BMDMs). MSU-42011 and selumetinib, alone or in combination, partially reversed this induction. Conclusions: These findings suggest RXR agonists may have therapeutic potential against NF1, and their combination with MEK inhibitors could represent a promising strategy for NF1-associated tumors. Further studies are needed to validate these results and assess their translational relevance. Full article

Plexiform neurofibroma (PNF) is an immune cell-rich peripheral nerve sheath tumor that develops primarily in individuals with Neurofibromatosis Type 1 (NF1). Granulocyte-macrophage colony stimulating factor receptor-β (GM-CSFR-β^c) is a shared component of receptors for the cytokines GM-CSF, IL-3, and IL-5, ligands with immunomodulatory and tumor promoting roles. In the present study, we use genetically engineered mouse model of neurofibroma. We identified the expression of GM-CSFR-β^c and GM-CSFR-α on PNF cells and on macrophages and dendritic cells in the PNF, using the Nf1^f/f; DhhCre mouse model of neurofibroma formation. Genetic deletion of GM-CSFR-β^c in this model reduced the number of PNFs, which was associated with decreased numbers of tumor-associated Iba1+ macrophages and CD11c+ dendritic cells (DC), while loss of GM-CSFR-α had no effect. Deletion of GM-CSFR-α or GM-CSFR-β^c did not improve mouse survival or the structure of Remak bundles in peripheral nerves. Proteome analysis of tumor lysates showed altered levels of numerous cytokines after receptor loss, suggesting that the compensatory effects of other cyto/chemokines maintain a proinflammatory environment promoting neurofibroma. Thus, GM-CSFR-β^c signaling contributes modestly to neurofibroma formation, apparently independently of its ligand GM-CSF. Full article

Due to the complex anatomy of the pelvis, various tumors may arise in this region. Some of these tumors are well known and have distinctive features that allow them to be identified by magnetic resonance imaging (MRI). These include sacrococcygeal teratoma (SCT), the most prevalent congenital tumor in children, often diagnosed prenatally and most frequently occurring in this anatomical location, and ovarian teratoma, which in its mature form is the most common ovarian neoplasm in children and adolescents. Additionally, rhabdomyosarcoma (RMS), commonly found in the bladder in both genders and in the prostate in males, and Ewing sarcoma (ES), affecting the flat bones of the pelvis, are relatively common tumors. In this study, selected atypical pelvic tumors in children are presented. Most of them are tumors of the reproductive system, such as cervical cancer, small cell neuroendocrine carcinoma of the ovary, ES/primitive neuroectodermal tumor (PNET) of the ovary, diffuse large B-cell lymphoma (DLBCL) of the ovaries and ovarian Sertoli–Leydig cell tumor (SLCT) with RMS due to DICER1 syndrome. Additionally, tumors originating from the nervous system, including neuroblastoma (NBL) and plexiform neurofibroma (pNF), associated and not associated with neurofibromatosis type 1 (NF1), are discussed. Furthermore, Rosai–Dorfman disease involving the pelvic and inguinal lymph nodes is presented. By reviewing the literature and presenting our cases, we tried to find radiological features of individual tumors that would bring the radiologist closer to the correct diagnosis, ensuring the implementation of appropriate treatment. However, the MR images cannot be considered in isolation. Additional patient data, such as the clinical picture, comorbidities/syndromes, and laboratory test results, are necessary. Full article

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. Full article

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

Background: Plexiform neurofibromas (pNFs) are benign neoplasms, primarily originating from Schwann cells, posing challenges in patients with type 1 neurofibromatosis (NF1) due to pain, disfigurement, compression of vital structures and potential for malignancy. Selumetinib, a MEK1/2 inhibitor, has shown promising results in treating inoperable pNFs, with clinical trials demonstrating tumor volume reduction and improved patient-reported outcomes. Despite its efficacy, dermatologic toxicities may impact the quality of life and treatment adherence. Evaluating the frequency and spectrum of such effects is crucial for effective management. Methods: In a four-year retrospective and prospective study, pediatric NF1 patients with symptomatic, inoperable plexiform neurofibromas (pNFs) were treated with selumetinib. Eligibility criteria included significant morbidity, pNF size exceeding 3 cm or surgical inoperability, and performance status >70%. Hematological, liver, lung and cardiac assessments established baseline health. Selumetinib, orally administered at 25 mg/m² twice, was administered for two years unless a response warranting extension occurred. Cutaneous AEs were documented and graded by severity according to CTCAE v5.0, with evaluations every three to six months. The impact on symptoms and pNF size was systematically recorded, and biopsies characterized histopathological features in those patients requiring surgery. Results: Twenty patients were enrolled, with an average age at therapy initiation of 11.6 years. Cutaneous side effects were common, with all patients experiencing at least one and a median of two per patient. Xerosis, paronychia and acneiform rash were prevalent. Notably, pre-pubertal individuals were more susceptible to xerosis. Acneiform rash had a higher incidence in older patients and those with skin phototypes II and III. Successful management involved tailored approaches, such as clindamycin for acneiform rash and topical agents for paronychia. Hair abnormalities, including color changes and thinning, occurred, with female patients at higher risk for the latter. Paronychia presented challenges, necessitating various interventions, including surgical approaches. AEs led to treatment suspension in 20% of patients, with tumor rebound observed in 75%. Conclusions: According to our experience, successful management of selumetinib-induced cutaneous AEs requires tailored strategies including surgery. AEs might indirectly determine pNF regrowth due to therapy suspension. We thus emphasize the pivotal role of addressing cutaneous reactions for effective selumetinib management in pediatric patients. Full article

Neurofibromatosis Type 1 (NF1) is a common neurogenic condition characterized by heterozygous loss of function mutations in the neurofibromin gene. NF1 patients are susceptible to the development of neurofibromas, including plexiform neurofibromas (pNFs), which occurs in about half of all cases. Plexiform neurofibroma are benign peripheral nerve sheath tumors originating from Schwann cells after complete loss of neurofibromin; they can be debilitating and also transform into deadly malignant peripheral nerve sheath tumors (MPNSTs). Here, our data indicates that silver nanoparticles (AgNPs) may be useful in the treatment of pNFs. We assessed the cytotoxicity of AgNPs using pNF cells and Schwann cells derived from the same NF1 patient. We found that AgNPs are selectively cytotoxic to pNF cells relative to isogenic Schwann cells. We then examined the role of neurofibromin expression on AgNP-mediated cytotoxicity; restoration of neurofibromin expression in pNF cells decreased sensitivity to AgNP, and knockdown of neurofibromin in isogenic Schwann cells increased sensitivity to AgNP, outlining a correlation between neurofibromin expression and AgNP-mediated cytotoxicity. AgNP was able to selectively remove pNF cells from a co-culture with patient-matched Schwann cells. Therefore, AgNPs represent a new approach for clinical management of NF1-associated pNF to address significant clinical need. Full article

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

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

Malignant peripheral nerve sheath tumors (MPNSTs) are deadly sarcomas, which desperately need effective therapies. Half of all MPNSTs arise in patients with neurofibromatosis type I (NF1), a common inherited disease. NF1 patients can develop benign lesions called plexiform neurofibromas (PNFs), often in adolescence, and over time, some PNFs, but not all, will transform into MPNSTs. A deeper understanding of the molecular and genetic alterations driving PNF–MPNST transformation will guide development of more targeted and effective treatments for these patients. This review focuses on an oncogenic transcription factor, FOXM1, which is a powerful oncogene in other cancers but little studied in MPNSTs. Elevated expression of FOXM1 was seen in patient MPNSTs and correlated with poor survival, but otherwise, its role in the disease is unknown. We discuss what is known about FOXM1 in MPNSTs relative to other cancers and how FOXM1 may be regulated by and/or regulate the most commonly altered players in MPNSTs, particularly in the MEK and CDK4/6 kinase pathways. We conclude by considering FOXM1, MEK, and CDK4/6 as new, clinically relevant targets for MPNST therapy. Full article

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. Full article

Plexiform neurofibromas (Pnfs) are benign peripheral nerve sheath tumors that are major features of the human genetic syndrome, neurofibromatosis type 1 (NF1). Pnfs are derived from Schwann cells (SCs) undergoing loss of heterozygosity (LOH) at the NF1 locus in an NF1^+/− milieu and thus are variably lacking in the key Ras-controlling protein, neurofibromin (Nfn). As these SCs are embedded in a dense desmoplastic milieu of stromal cells and abnormal extracellular matrix (ECM), cell–cell cooperativity (CCC) and the molecular microenvironment play essential roles in Pnf progression towards a malignant peripheral nerve sheath tumor (MPNST). The complexity of Pnf biology makes treatment challenging. The only approved drug, the MEK inhibitor Selumetinib, displays a variable and partial therapeutic response. Here, we explored ECM contributions to the growth of cells lacking Nfn. In a 3D in vitro culture, NF1 loss sensitizes cells to signals from a Pnf-mimicking ECM through focal adhesion kinase (FAK) hyperactivation. This hyperactivation correlated with phosphorylation of the downstream effectors, Src, ERK, and AKT, and with colony formation. Expression of the GAP-related domain of Nfn only partially decreased activation of this signaling pathway and only slowed down 3D colony growth of cells lacking Nfn. However, combinatorial treatment with both the FAK inhibitor Defactinib (VS-6063) and Selumetinib (AZD6244) fully suppressed colony growth. These observations pave the way for a new combined therapeutic strategy simultaneously interfering with both intracellular signals and the interplay between the various tumor cells and the ECM. Full article

Neurofibromatosis type 1 (NF1) is a monogenic syndrome that gives rise to numerous symptoms including cognitive impairment, skeletal abnormalities, and growth of benign nerve sheath tumors. Nearly all NF1 patients develop cutaneous neurofibromas (cNFs), which occur on the skin surface, whereas 40–60% of patients develop plexiform neurofibromas (pNFs), which are deeply embedded in the peripheral nerves. Patients with pNFs have a ~10% lifetime chance of these tumors becoming malignant peripheral nerve sheath tumors (MPNSTs). These tumors have a severe prognosis and few treatment options other than surgery. Given the lack of therapeutic options available to patients with these tumors, identification of druggable pathways or other key molecular features could aid ongoing therapeutic discovery studies. In this work, we used statistical and machine learning methods to analyze 77 NF1 tumors with genomic data to characterize key signaling pathways that distinguish these tumors and identify candidates for drug development. We identified subsets of latent gene expression variables that may be important in the identification and etiology of cNFs, pNFs, other neurofibromas, and MPNSTs. Furthermore, we characterized the association between these latent variables and genetic variants, immune deconvolution predictions, and protein activity predictions. Full article