NF2-related schwannomatosis (NF2-SWN) is associated with multiple benign tumors in the nervous system. NF2-SWN, caused by mutations in the NF2 gene, has developed into intracranial and spinal schwannomas. Because of the high surgical risk and frequent recurrence of multiple tumors, targeted therapy is necessary. However, there are no approved drugs.

We examined the action mechanism of PRG-N-01, a candidate molecule for NF2-SWN, through the direct binding assay and mass spectrometry. For in vitro anti-proliferative experiments, primary cells derived from the NF2 mouse model and patient tumors were treated with PRG-N-01. The in vivo therapeutic and preventive efficacy was validated via intraperitoneal and oral administration in the NF2 mouse model (Postn-Cre; Nf2f/f). Gene expression profile in the DRG of the mouse model was explored by RNA sequencing. The pharmacological properties of PRG-N-01 were analyzed through the preclinical study.

PRG-N-01 binds to the N-terminal extremity of TGFβR1 (TβR1) kinase domain, where TβR1 and RKIP interact, inhibiting the binding and preventing degradation of RKIP. In vivo administration in the mouse model suppressed schwannoma progression in the DRG. Early oral administration of the PRG-N-01 also demonstrated preventive effects on NF2-SWN. PRG-N-01 treatment suppressed tumor growth genes while upregulating genes related to for normal cell metabolism and Schwann cell differentiation in DRG. PRG-N-01 showed druggable properties through the preclinical study, including ADME, pharmacodynamics, pharmacokinetics, and toxicology.

Together, our study provides the rationale and critical data for a prospective clinical trial of PRG-N-01 in NF2-SWN patients indicating PRG-N-01 as a promising candidate for the treatment.

NF2-related schwannomatosis (NF2-SWN) is a rare genetic disorder characterized by bilateral vestibular schwannomas. NF2-SWN represents a difficult management problem with most patients facing substantial morbidity and reduced life expectancy. Gene therapy involves replacing a faulty gene or adding a new gene in an attempt to cure disease or improve the patient's condition. Several studies of gene therapy for NF2-SWN have utilized adeno-associated viral vector serotype-1 (AAV1) to deliver apoptosis-inducing enzyme, the pore-forming protein gasdermin-D, apoptosis-associated speck-like protein containing a caspase recruitment domain, and functional merlin causing schwannoma regression in a xenograft mouse model. These studies support the potential therapeutic efficacy of gene therapy against NF2-SWN. Currently, gene therapy approaches primarily include bystander-killing effect by inducing immune responses, gene replacement or augmentation therapy, and gene knockdown and replacement combination approach through genome-editing technology. Although these gene therapeutic strategies have shown potential in preclinical animal model studies, they still face many specific challenges apart from the traditional challenges in gene therapy, such as immunogenicity, delivery vector, manufacturing, and long-term effects of treatments. In this article, we discuss the current understanding and future directions of gene therapy and genome-editing for schwannoma in NF2-SWN.

This article focuses on the phosphatidylethanolamine-binding protein (PEBP) family proteins, detailing PEBP1 and PEBP4 due to limited information on PEBP2 and PEBP3, in cellular signaling pathways and research in a spectrum of pathologies, including diverse cancers, metabolic disorders, immunological diseases and a subset of organ-specific diseases. It outlines the mechanisms through which PEBP1 and PEBP4 regulate essential signaling pathways that are critical for cellular processes such as proliferation, apoptosis, and metastasis. Recent advancements have shown further understanding of these proteins' roles in pathophysiology and their potential as future therapeutic targets. The findings suggest that the impact of PEBP1 and PEBP4 on the course of different diseases has underscored their potential for more in-depth medical research and novel clinically targeted therapies.

Malignant peripheral nerve sheath tumors (MPNSTs) primarily originate from the neurofibromatosis 1 (NF1)- associated and/or sporadic neurofibromas. Reports of malignant transformation from a sporadic soft tissue schwannoma are rare. In most tumors documented in this context so far, the malignant component is an epithelioid MPNST with a strong and diffuse S100 positivity. We present a patient diagnosed with a sporadic soft tissue schwannoma on core biopsy, which underwent rapid malignant transformation to a spindle cell type MPNST. Somatic tumor profiling of the excision specimen revealed NF2 loss, TP53, NRAS, and subclonal RICTOR gene mutations. A retrospective immunohistochemical stain for p53 on the core biopsy demonstrated an aberrant staining pattern, indicating an early effect of TP53 in the process of malignant transformation.

The extension of lamellipodia, which are thin, fanlike projections at the cell periphery, requires the assembly of branched actin networks under the control of the small GTPase Rac1. In melanoma, a hyperactive P29S Rac1 mutant is associated with resistance to inhibitors that target the kinases BRAF and MAPK and with more aggressive disease because it sequesters and inactivates the tumor suppressor merlin (encoded by NF2) inside abnormally large lamellipodia. Here, we investigated how these merlin-inactivating lamellipodia are maintained using quantitative, live cell imaging of cell morphology and signaling dynamics. We showed that Rac1 and merlin activity were regulated in spatially confined regions or microdomains within the lamellipodium. The role of merlin as a proliferation-limiting tumor suppressor required its ability to inhibit lamellipodial extension and to locally inhibit Rac1 signaling. Conversely, local inactivation of merlin in lamellipodia released these restraints on morphology and signaling, leading to enhanced proliferation. Merlin and Rac1 are thus in a morphologically and dynamically regulated double-negative feedback loop, a signaling motif that can amplify and stabilize modest stimuli of lamellipodia extensions that enable melanoma to sustain mitogenic signaling under growth challenge. This represents an example of how acute oncogenicity is promoted by collaborations between cell morphological programs and biochemical signaling.

Vertebrate embryogenesis requires the precisely timed specification of 3 germ cell layers- ectoderm, mesoderm, and endoderm- which give rise to tissues and organs in the developing organism. The tumor suppressor gene NF2, moesin-ezrin-radixin like (MERLIN) tumor suppressor (Nf2) is expressed in all 3 germ layers during mouse development and its homozygous deletion causes embryonic lethality. People with heterozygous NF2 mutations typically develop Schwann cell tumors, especially vestibular schwannoma, but the specific role of NF2 in human embryonic development is unclear. Here, human induced pluripotent stem cells (hiPSCs) are used to demonstrate that NF2 is essential for endoderm specification and formation in humans. Although endoderm differentiation is not impaired in hiPSCs with heterozygous NF2 mutation, NF2 knockout (NF2-/-) abolished the capacity to form endoderm in vitro, confirmed by loss of expression of endoderm-related genes and proteins, or teratomas in vivo. This defect is mediated by the nuclear translocation of yes-associated protein 1 (YAP1), a transcription co-activator regulating lineage fate via the Hippo pathway and subsequent YAP1-mediated shutdown of Activin/Nodal signaling. Endoderm formation can be rescued via YAP1 knockdown or forced re-expression of NF2 in NF2-/- cells. Taken together, the essential role of NF2 during endoderm specification in human embryogenesis as a regulator of YAP1 is reported.

Meningioma, a tumor arising from the meninges of the central nervous system, is generally considered benign. Familial meningiomas are extremely rare, and the genetic basis of this condition remains largely elusive, especially in under-represented populations. This study investigates a family from Kashan, Isfahan province, Iran-an under-explored region in genetic research-with the goal of identifying novel germline variants contributing to meningioma development.

Whole Exome Sequencing (WES) was performed on a family with multiple meningioma cases (n = 3). Bioinformatic analyses identified candidate variants, which were further validated in additional family members and a cohort of 23 idiopathic, sporadic meningioma patients.

A novel heterozygous missense mutation in the IQCA1 gene (NM_001270584: c.C787T; p.R263W) was found to segregate with the disease, supporting an autosomal dominant inheritance pattern. In silico analysis suggests that this mutation may disrupt IQCA1's ATP hydrolysis activity, potentially contributing to tumorigenesis. This is the first report linking IQCA1 to familial meningioma, providing new insights into its pathogenesis.

Our findings reveal a novel IQCA1 p.R263W mutation in a familial meningioma case, with implications for genetic counseling and surveillance in at-risk populations. This study highlights the importance of studying under-represented populations and contributes new insights into meningioma genetics and oncogenesis.

Pleural mesothelioma (PM) is a rare and highly aggressive malignancy originating from the pleural lining, with a median overall survival of merely 1 year. This cancer primarily arises from mesothelial cells following exposure to carcinogenic, biopersistent mineral fibers, particularly asbestos. The histological subtypes of mesothelioma are epithelioid (approximately 60%), sarcomatoid (20%), and biphasic (20%), exhibiting epithelioid and sarcomatoid characteristics. Classification is important for prognosis and guides the therapeutic strategy. Due to the typical late presentation, most patients with PM are ineligible for localized treatments such as surgery or radiotherapy. Systemic therapy, including cytotoxic chemotherapy, targeted therapies, and immunotherapy, is thus critical for managing advanced PM. For unresectable PM, decisions regarding systemic treatment are guided by patient suitability and histological characteristics. First-line therapies for advanced PM currently include the cisplatin-pemetrexed combination and the nivolumab-ipilimumab regimen. Historically, cisplatin-pemetrexed has been administered as first-line treatment, though recent advancements have introduced new therapies that significantly prolong patient survival. Innovative approaches combining immunotherapy and chemotherapy offer promising avenues for further improvement. Future treatment strategies should incorporate novel paradigms, such as combination chemo-immunotherapy, targeted agents, and potential cellular therapies, alongside companion biomarkers tailored to the histologic and molecular diversity of mesothelioma. This review explores the latest advancements in drug therapy for PM and provides an overview of current systemic treatment options.

The Hippo signaling pathway is a pivotal regulator of tissue homeostasis, organ size, and cell proliferation. Its dysregulation is profoundly implicated in various forms of cancer, making it a highly promising target for therapeutic intervention. This review extensively evaluates the mechanisms underlying the dysregulation of the Hippo pathway in cancer cells and the molecular processes linking these alterations to tumorigenesis. Under normal physiological conditions, the Hippo pathway is a guardian, ensuring controlled cellular proliferation and programmed cell death. However, numerous mutations and epigenetic modifications can disrupt this equilibrium in cancer cells, leading to unchecked cell proliferation, enhanced survival, and metastatic capabilities. The pathway's interaction with other critical signaling networks, including Wnt/β-catenin, PI3K/Akt, TGF-β/SMAD, and EGFR pathways, further amplifies its oncogenic potential. Central to these disruptions is the activation of YAP and TAZ transcriptional coactivators, which drive the expression of genes that promote oncogenesis. This review delves into the molecular mechanisms responsible for the dysregulation of the Hippo pathway in cancer, elucidating how these disruptions contribute to tumorigenesis. We also explore potential therapeutic strategies, including inhibitors targeting YAP/TAZ activity and modulators of upstream signaling components. Despite significant advancements in understanding the Hippo pathway's role in cancer, numerous questions remain unresolved. Continued research is imperative to unravel the complex interactions within this pathway and to develop innovative and effective therapies for clinical application. In conclusion, the comprehensive understanding of the Hippo pathway's regulatory mechanisms offers significant potential for advancing cancer therapies, regenerative medicine, and treatments for chronic diseases. The translation of these insights into clinical practice will necessitate collaborative efforts from researchers, clinicians, and pharmaceutical developers to bring novel and effective therapies to patients, ultimately improving clinical outcomes and advancing the field of oncology.

The mutation in NF2 is the most common alteration associated with meningioma oncogenesis, and it is related to the loss of a suppressing protein called merlin. At the same time, alterations in energy production are visible in cancer cells, where increased demands for energy are observed. Fatty acid oxidation could be one of the ways cancer cells obtain energy. This metabolic pathway uses the acylcarnitine shuttle system, which is responsible for the acylation of fatty acids and their transport through the mitochondria. Therefore, this study aimed to profile acylcarnitines with short, medium, and long acyl chain lengths in meningiomas to assess their changes in tumors with different NF2 mutation statuses. For the analysis, solid-phase microextraction (SPME) coupled with liquid chromatography-high-resolution mass spectrometry (LC-HRMS) was used. The presented sampling method enabled less invasive and easy collection of the analytes from the studied lesions, which can be crucial for future analysis of potential biomarkers in the surgery room. It was observed that higher levels of these analytes characterized meningiomas with NF2 mutations. Moreover, the increased energy consumption and elevated levels of acylcarnitines show that these analytes can be considered markers of increased fatty acid oxidation in NF2 mutated cells.

Schwannomas are tumors that originate from myelinating Schwann cells and can occur in cranial, spinal, and peripheral nerves. Although our understanding of the molecular biology underlying schwannomas remains incomplete, numerous studies have identified various molecular findings and biomarkers associated with schwannomas of the central nervous system (CNS). The development of these tumors is primarily linked to mutations in the NF2 gene. Merlin, the protein encoded by NF2, is integral to several signaling pathways, including Ras/Raf/MEK/ERK, PI3K/Akt/mTORC1, Wnt/β-catenin, and the Hippo pathway.

Recent research has also uncovered novel genetic alterations, such as the SH3PXD2A::HTRA1 fusion gene, VGLL-fusions in intraparenchymal CNS schwannomas, and the SOX10 mutation particularly in non-vestibular cranial nerve schwannomas. In addition to genetic alterations, research is also being conducted on gene expression and epigenetic regulation, with a focus on NF2 methylation and post-transcriptional silencing by micro RNA. Furthermore, the advent of advanced techniques like single-cell sequencing and multi-omics analysis has facilitated rapid discoveries related to the tumor microenvironment and tumor heterogeneity in schwannomas.

A deeper exploration of these molecular findings could clarify the mechanisms of schwannoma tumorigenesis and progression, ultimately guiding the development of new therapeutic targets. This review offers a comprehensive overview of the current molecular understanding of CNS schwannomas, emphasizing the insights gained from previous research, while addressing existing controversies and outlining future research and treatment perspectives.

It is important to systematically identify tumor suppressor genes (TSGs) to improve our understanding of tumorigenesis and develop strategies for early diagnosis and mitigating disease progression. In the present study, we used an in vivo genome-wide clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) screen and identified FPS/FES-related (FER) as a TSG. Single-cell RNA sequencing (scRNA-seq) revealed that normal cells with low FER expression exhibited elevated malignant transformation potential and stemness properties. FER knockout promoted the tumorigenic transformation, characterized by high colony-forming efficiency and suspension growth ability, acquired tumorigenicity in vivo, increased metabolic activity, dedifferentiation properties, and immune evasion. Moreover, analysis revealed that low FER expression tumors share molecular phenotypes with FER knockout cells, suggesting the consistent role of FER in tumor initiation and progression. Taken together, our findings not only provide insights into the essential role of FER as a tumor suppressor in tumor initiation and progression but also highlight its potential as a target for future clinical diagnosis. © 2024 The Pathological Society of Great Britain and Ireland.

Background: Charcot-Marie-Tooth (CMT) disease is an inherited peripheral neuropathy primarily involving motor and sensory neurons. Mutations in INF2, an actin assembly factor, cause two diseases: peripheral neuropathy CMT-DIE (MIM614455) and/or focal segmental glomerulosclerosis (FSGS). These two phenotypes arise from the progressive degeneration affecting podocytes and Schwann cells. In general, nerve enlargement has been reported in 25% of the demyelinating CMT subtype (CMT1), while little is known about the CMT-DIE caused by INF2 variants. Methods: To characterize the peripheral nerve phenotype of INF2-related CMT, we studied the clinical course, imaging, histology, and germline genetic variants in two unrelated CMT-DIE patients. Results: Patient 1 (INF2 p.Gly73Asp) and patient 2 (p.Val108Asp) first noticed walking difficulties at 10 to 12 years old. Both of them were electrophysiologically diagnosed with demyelinating neuropathy. In patient 2, the sural nerve biopsy revealed an onion bulb formation. Both patients developed nephrotic syndrome almost simultaneously with CMT and progressed into renal failure at the age of 16 to 17 years. Around the age of 30 years, both patients manifested multiple hypertrophy of the trunk, plexus, and root in the cervical, brachial, lumbosacral nerves, and cauda equina. The histology of the cervical mass in patient 2 revealed Schwannoma. Exome analysis showed that patient 2 harbors a germline LZTR1 p.Arg68Gly variant, while patient 1 has no schwannomatosis-related mutations. Conclusions: Peripheral neuropathy caused by INF2 variants may lead to the development of multifocal hypertrophy with age, likely due to the initial demyelination and subsequent Schwann cell proliferation. Schwannoma could co-occur when the tissues attain additional hits in schwannomatosis-related genes (e.g., LZTR1).

Alternative splicing is a crucial cellular process in eukaryotes, enabling the generation of multiple protein isoforms with diverse functions from a single gene. To better understand the impact of alternative splicing on protein structures, protein-protein interaction and human diseases, we developed ASpdb (https://biodataai.uth.edu/ASpdb/), a comprehensive database integrating experimentally determined structures and AlphaFold 2-predicted models for human protein isoforms. ASpdb includes over 3400 canonical isoforms, each represented by both experimentally resolved and predicted structures, and >7200 alternative isoforms with AlphaFold 2 predictions. In addition to detailed splicing events, 3D structures, sequence variations and functional annotations, ASpdb uniquely offers comparative analyses and visualization of structural alterations among isoforms. This resource is invaluable for advancing research in alternative splicing, structural biology and disease mechanisms.

Lead is a persistent inorganic environmental pollutant with global implication for human health. Among the diseases associated with lead exposure, the damage to the central nervous system has received considerable attention. It has been reported that long-term lead exposure increases the risk of meningioma; however, the underlying mechanism remains poorly understood. Clinical studies have indicated that loss-of-function and mutations in the neurofibromin-2 (NF2) gene play a crucial role in promoting meningioma formation.

The effect of Pb on meningioma were tested in-vitro and in-vivo. Two human meningioma cell lines were used in this study, including NF2-wildtype IOMM-Lee cell and NF2-null CH157-MN cell. Cell viability, cell cycle and cell size were examined after Pb exposure. The expression of Merlin, mammalian sterile 20-like kinases 1 and 2 (MST1/2) and Yes-associated protein (YAP) from these two meningioma cells were analyzed by Western blot. A xenograft mouse model was constructed by subcutaneous injection of IOMM-Lee meningioma cells.

This study demonstrated that treatment with lead induce dose-dependent proliferation in IOMM-Lee cell (with an EC50 value of 19.6 µM). Moreover, IOMM-Lee cell exhibited augmented cell size in conjunction with elevated levels of phosphorylated histone H3, indicative of altered cell cycle progression resulting from lead exposure. However, no significant change was observed in the CH157-MN cell. Additionally, the Merlin-Hippo signaling pathway was inactivated with decreased Merlin and phosphorylation levels of MST1/2 and YAP, leading to increased YAP nuclear translocation in IOMM-Lee cells. However, there was no change in the Merlin-Hippo signaling pathway in CH157-MN cells after lead treatment. The administration of Pb resulted in an acceleration of the subcutaneous IOMM-Lee meningioma xenograft growth in mice.

Overall, the current study elucidates the potential mechanism by which lead exposure promotes the proliferation of meningioma with NF2 expression for the first time.

Meningioma is the most prevalent primary intracranial tumor, with approximately half of patients harboring NF2 alteration. The rationale behind the presence of NF2 alteration in meningiomas and its absence in non-nerve system tumors remains elusive. Therefore, meningiomas and several non-nerve system tumor types were analyzed using KEGG analysis and CRISPR/Cas 9 technology to determine the role of NF2 in regulating tissue specificity. Moreover, the different regulatory patterns of Ca2+ and calcium/calmodulin-dependent protein kinase II alpha (CAMK2A) that play a decisive role in NF2 tissue-specific regulation were deciphered. Our results revealed that NF2 has a positive correlation in CAMK2A expression in both meningiomas and normal nervous system tissues but not in non-nervous system tumors and tissues, implying NF2 tissue-specificity is mediated by CAMK2A-related pathways. Thus, targeting CAMK2A may represent a promising strategy for drug screening and the development of therapeutics for NF2-associated meningiomas and other nervous system tumors.

Background/Objectives: With the rise in prevalence of diagnostic genetic techniques like RNA sequencing and whole exome sequencing (WES), as well as biological treatment regiments for cancer therapy, several genes have been implicated in carcinogenesis. This review aims to update our understanding of the Neurofibromatosis 2 (NF2) gene and its role in the pathogenesis of various cancers. Methods: A comprehensive search of five online databases yielded 43 studies that highlighted the effect of sporadic NF2 mutations on several cancers, including sporadic meningioma, ependymoma, schwannoma, mesothelioma, breast cancer, hepatocellular carcinoma, prostate cancer, glioblastoma, thyroid cancer, and melanoma. Of note were key biological pathways implicated in cancer formation resulting from sporadic NF2 mutations. Results: NF2 gene mutations are implicated in over 11 different cancers, including several CNS tumors, soli-organ tumors, and skin cancer. NF2 acts as a driver mutation in some cancers, as a non-driver mutation in some cancers, and has simple associated mutations with other cancers. In terms of biological pathway involvement, 8 of the 11 cancers with NF2 mutations show evidence of Hippo signaling cascade involvement. Conclusions: Several cancers characterized by mutations in the NF2 gene have associations with the Hippo signaling pathway. However, future studies remain to be done to further elucidate the role of the Hippo signaling pathway in the carcinogenesis of human NF2-mutant tumors. The findings of this review provide insights into the role of NF2 mutations in cancers, Hippo signaling in NF2-mutant cancers, and current gaps in our knowledge regarding the two.

Decades of research into the Hippo signaling pathway have greatly advanced our understanding of its roles in organ growth, tissue regeneration, and tumorigenesis. The Hippo pathway is frequently dysregulated in human cancers and is recognized as a prominent cancer signaling pathway. Hence, the Hippo pathway represents an ideal molecular target for cancer therapies. This review will highlight recent advancements in targeting the Hippo pathway for cancer treatment and discuss the potential opportunities for developing new therapeutic modalities.

Meningiomas are the most common primary central nervous system (CNS) tumor in adults, comprising one-third of all primary adult CNS tumors. Although several recent publications have identified molecular alterations in meningioma including characteristic mutations, copy number alterations, and gene expression signatures, our understanding of the drivers of meningioma recurrence is limited.

To identify gene expression signatures of 1p-22q-NF2- meningioma recurrence, with concurrent biallelic inactivation of NF2 and loss of chr1p that are heterogenous but enriched for recurrent meningiomas.

Transcriptomic alterations present in recurrent versus primary 1p-22q-NF2- meningiomas were identified using RNA sequencing (RNA-seq) data in a clinically annotated cohort.

Recurrent 1p-22q-NF2- meningiomas were enriched for a newly identified GSTM1 null genotype compared to primary meningiomas that showed variable GSTM1 expression and independent external validation was performed.

The GSTM1 null genotype is a novel biomarker of 1p-22q-NF2- meningioma recurrence that resolves heterogeneity in existing meningioma subtypes and may be used to guide future clinical management decisions on extent of treatment to improve patient outcomes.

Traumatic brain injury (TBI) is a critical condition associated with cognitive impairments, including dementia. This study is aimed to construct a long noncoding RNA (lncRNA)-microRNA (miRNA)-messenger RNA (mRNA) network based on bioinformatics analysis and explore molecular mechanisms underlying post-TBI dementia.

GSE104687 and GSE205661 datasets were downloaded from Gene Expression Omnibus database. Molecular Signatures Database (MSigDB) was used to search oxidative stress-, metabolism- and immune-related genes as the target gene datasets. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes were carried out for functional annotation and enrichment analysis. A TBI mouse model was built to validate the expression of NF2, PLXNA2, NCBP2 and U2SURP in brain tissues.

A total of 7 differentially expressed lncRNAs (DElncRNAs) and 191 DEmRNAs were obtained. Subsequent to differential expression (DE) analysis, a lncRNA-miRNA-mRNA network was established. Notably, 13 key DEmRNAs were identified, potentially playing pivotal roles in the pathogenesis of TBI-induced dementia. By comparing the target gene datasets with 13 DEmRNAs, we identified 4 target genes that overlap with the 13 DEGmRNAs, namely NF2, PLXNA2, NCBP2 and U2SURP. Functional enrichment analysis highlighted the involvement of neuronal projections in the dementia-enriched cluster, while the protective cluster showed associations with protein synthesis and ubiquitination pathways. Importantly, we explored potential drug interventions based on interactions with the above 4 target genes. Additionally, drug interaction prediction showed that NF2 could interact with SELUMETINIB, EVEROLIMUS and TEMSIROLIMUS.

Our study provides insights into the complex regulatory networks underlying post-TBI dementia and suggests a potential role for three classes of drugs in managing dementia symptoms in TBI-induced dementia.

The Hippo signaling governs the expression of genes critically important for cell proliferation and survival. The components of this pathway are considered antitumor drug targets. However, the design of Hippo inhibitors is a challenge given the complexity of the network and redundancy of its elements.

We review the current state-of-the-art in the structure of the Hippo pathway, the microenvironment-induced extracellular cues, the strategies to design pharmacological instruments for inactivation of the Hippo signaling using small molecular weight modulators, as well as the results of initial clinical trials.

One special characteristic of the Hippo signaling is the adverse role of phosphorylation: opposite to classical kinase cascades that activate the transcription factors, the Hippo kinases retain their partners in a transcriptionally inactive state. Therefore, approaches for pharmacological or genetic inhibition of Hippo protein kinases are counterproductive. The developing alternatives such as disruption of protein-protein interactions or PROTAC techniques are straightforward for preventing the Hippo signaling in cancer therapy.

Protein kinase A (PKA) is a basophilic kinase implicated in the modulation of many cell-signaling and physiological processes. PKA also contributes to cancer-relevant events such as growth factor action, cell cycle control, cell migration and tumor metabolism. Germline and somatic mutations in PKA, gene amplifications, and chromosome rearrangements that encode kinase fusions, are linked to a growing number of malignant neoplasms. Mislocalization of PKA by exclusion from A-Kinase Anchoring Protein (AKAP) signaling islands further underlies cancer progression. This article highlights the influence of AKAP signaling and local kinase action in selected hallmarks of cancer. We also feature the utility of kinase inhibitor drugs as frontline and future anti-cancer therapies.

The Hippo signaling pathway is recognized for its significant role in cell differentiation, proliferation, survival, and tissue regeneration. Recently, the Hippo signaling pathway was also found to be associated with oxidative stress and reactive oxygen species (ROS) regulation, which are important in the regulation of cell survival. Studies indicate a correlation between components of the Hippo signaling pathway, including MST1, YAP, and TAZ, and the generation of ROS. On the other hand, ROS and oxidative stress can activate key components of the Hippo signaling pathway. For example, ROS production activates MST1, which subsequently phosphorylates FOXO3, leading to apoptotic cell death. ROS was also found to regulate YAP, in addition to MST1/2. Oxidative stress and ROS formation can impair lipids, proteins, and DNA, leading to many disorders, including aging, neurodegeneration, atherosclerosis, and diabetes. Consequently, understanding the interplay between the Hippo signaling pathway, ROS, and oxidative stress is crucial for developing future disease management strategies. This paper aimed to review the association between the Hippo signaling pathway, regulation of ROS production, and oxidative stress to provide beneficial information in understanding cell function and pathological processes.

Mesothelioma is an uncommon tumor that can be difficult to diagnose.

To provide updated, practical guidelines for the pathologic diagnosis of mesothelioma.

Pathologists involved in the International Mesothelioma Interest Group and others with expertise in mesothelioma contributed to this update. Reference material includes peer-reviewed publications and textbooks.

There was consensus opinion regarding guidelines for (1) histomorphologic diagnosis of mesothelial tumors, including distinction of epithelioid, biphasic, and sarcomatoid mesothelioma; recognition of morphologic variants and patterns; and recognition of common morphologic pitfalls; (2) molecular pathogenesis of mesothelioma; (3) application of immunohistochemical markers to establish mesothelial lineage and distinguish mesothelioma from common morphologic differentials; (4) application of ancillary studies to distinguish benign from malignant mesothelial proliferations, including BAP1 and MTAP immunostains; novel immunomarkers such as Merlin and p53; fluorescence in situ hybridization (FISH) for homozygous deletion of CDKN2A; and novel molecular assays; (5) practical recommendations for routine reporting of mesothelioma, including grading epithelioid mesothelioma and other prognostic parameters; (6) diagnosis of mesothelioma in situ; (7) cytologic diagnosis of mesothelioma, including use of immunostains and molecular assays; and (8) features of nonmalignant peritoneal mesothelial lesions.

Eosinophilic solid and cystic renal cell carcinoma is now defined in the 5th edition of the 2022 World Health Organization classification of urogenital tumors.

To perform morphologic, immunohistochemical, and preliminary genetic studies about this new entity in China for the purpose of understanding it better.

The study includes 18 patients from a regional tertiary oncology center in northern China (Tianjin, China). We investigated the clinical and immunohistochemical features of these cases.

The mean age of patients was 49.6 years, and the male to female ratio was 11:7. Macroscopically, 1 case had the classic cystic and solid appearance, whereas the others appeared purely solid. Microscopically, all 18 tumors shared a similar solid and focal macrocystic or microcystic growth pattern, and the cells were characterized by voluminous and eosinophilic cytoplasm, along with coarse amphophilic stippling. Immunohistochemically, most of the tumors had a predominant cytokeratin (CK) 20-positive feature, ranging from focal cytoplasmic staining to diffuse membranous accentuation. Initially, we separated these cases into different immunohistochemical phenotypes. Group 1 (7 of 18; 38.5%) was characterized by positive phospho-4EBP1 and phospho-S6, which can imply hyperactive mechanistic target of rapamycin complex 1 (mTORC1) signaling. Group 2 (4 of 18; 23%) was negative for NF2, probably implying a germline mutation of NF2. Group 3 (7 of 18; 38.5%) consisted of the remaining cases. One case had metastatic spread and exhibited an aggressive clinical course, and we detected cyclin-dependent kinase inhibitor 2A (CDKN2A) mutation in this case; other patients were alive and without disease progression.

Our research proposes that eosinophilic solid and cystic renal cell carcinoma exhibits prototypical pathologic features with CK20 positivity and has aggressive potential.

Tumors develop in an oxidative environment characterized by peroxynitrite production and downstream protein tyrosine (Y) nitration. We showed that tyrosine nitration supports schwannoma cell proliferation and regulates cell metabolism in the inheritable tumor disorder NF2-related Schwannomatosis (NF2-SWN). Here, we identified the chaperone Heat shock protein 90 (Hsp90) as the first nitrated protein that acts as a metabolic switch to promote schwannoma cell proliferation. Doubling the endogenous levels of nitrated Hsp90 in schwannoma cells or supplementing nitrated Hsp90 into normal Schwann cells increased their proliferation. Metabolically, nitration on either Y33 or Y56 conferred Hsp90 distinct functions; nitration at Y33 (Hsp90NY33) down-regulated mitochondrial oxidative phosphorylation, while nitration at Y56 (Hsp90NY56) increased glycolysis by activating the purinergic receptor P2X7 in both schwannoma and normal Schwann cells. Hsp90NY33 and Hsp90NY56 showed differential subcellular and spatial distribution corresponding with their metabolic and proliferative functions in schwannoma three-dimensional cell culture models. Collectively, these results underscore the role of tyrosine nitration as a post-translational modification regulating critical cellular processes. Nitrated proteins, particularly nitrated Hsp90, emerge as a novel category of tumor-directed therapeutic targets.

In the central nervous system, the formation of myelin by oligodendrocytes (OLs) relies on the switch from the polymerization of the actin cytoskeleton to its depolymerization. The molecular mechanisms that trigger this switch have yet to be elucidated. Here, we identified P21-activated kinase 1 (PAK1) as a major regulator of actin depolymerization in OLs. Our results demonstrate that PAK1 accumulates in OLs in a kinase-inhibited form, triggering actin disassembly and, consequently, myelin membrane expansion. Remarkably, proteomic analysis of PAK1 binding partners enabled the identification of NF2/Merlin as its endogenous inhibitor. Our findings indicate that Nf2 knockdown in OLs results in PAK1 activation, actin polymerization, and a reduction in OL myelin membrane expansion. This effect is rescued by treatment with a PAK1 inhibitor. We also provide evidence that the specific Pak1 loss-of-function in oligodendroglia stimulates the thickening of myelin sheaths in vivo. Overall, our data indicate that the antagonistic actions of PAK1 and NF2/Merlin on the actin cytoskeleton of the OLs are critical for proper myelin formation. These findings have broad mechanistic and therapeutic implications in demyelinating diseases and neurodevelopmental disorders.

Meningiomas are the most prevalent primary central nervous system tumors. Although low-grade meningiomas are considered benign tumors, a subset of these can behave aggressively, showing progression and recurrence. In such cases, functional assays could influence treatment decisions and improve patient outcomes.

A 78-year-old female presented with a long-standing history of a supratentorial meningioma that was initially resected and treated with Gamma Knife radiosurgery. Surveillance revealed progression. She began systemic therapy with everolimus and octreotide but was lost to follow-up and did not continue the treatment. She returned because of a rapid decline in her neurological status. Biopsy with advanced molecular characterization by next-generation sequencing revealed NF2 and CREBBP mutations, and a commercial functional assay was done. This assay successfully isolated cancer stem cells (CSCs) from biopsy cores and identified potential drugs based on cellular sensitivity profiles. This is the first reported case in which a commercial functional drug screen was used for a meningioma.

In cases in which meningiomas exhibit specific genetic alterations and characteristics of aggressiveness, functional assays can be a useful tool for isolating CSCs. The authors report success in obtaining drug-screen profiling for a World Health Organization grade 1 meningioma. Multimodal approaches utilizing multi-omics analyses with functional assays can improve patient outcomes. https://thejns.org/doi/10.3171/CASE24242.

The neurofibromatosis type 2 (NF2) gene, known for encoding the tumor suppressor protein Merlin, is central to the study of tumorigenesis and associated cellular processes. This review comprehensively examines the multifaceted role of NF2/Merlin, detailing its structural characteristics, functional diversity, and involvement in various signaling pathways such as Wnt/β-catenin, Hippo, TGF-β, RTKs, mTOR, Notch, and Hedgehog. These pathways are crucial for cellular growth, proliferation, and differentiation. NF2 mutations are specifically linked to the development of schwannomas, meningiomas, and ependymomas, although the precise mechanisms of tumor formation in these specific cell types remain unclear. Additionally, the review explores Merlin's role in embryogenesis, highlighting the severe developmental defects and embryonic lethality caused by NF2 deficiency. The potential therapeutic strategies targeting these genetic aberrations are also discussed, emphasizing inhibitors of mTOR, HDAC, and VEGF as promising avenues for treatment. This synthesis of current knowledge underscores the necessity for ongoing research to elucidate the detailed mechanisms of NF2/Merlin and develop effective therapeutic strategies, ultimately aiming to improve the prognosis and quality of life for individuals with NF2 mutations.

Meningiomas are the most common primary intracranial tumors and account for nearly 30% of all nervous system tumors. Approximately half of meningioma patients exhibit neurofibromin 2 (NF2) gene inactivation. Here, NF2 was shown to interact with the endoplasmic reticulum (ER) calcium (Ca2+) channel inositol 1,4,5-trisphosphate receptor 1 (IP3R1) in IOMM-Lee, a high-grade malignant meningioma cell line, and the F1 subdomain of NF2 plays a critical role in this interaction. Functional assays indicated that NF2 promotes the phosphorylation of IP3R (Ser 1756) and IP3R-mediated endoplasmic reticulum (ER) Ca2+ release by binding to IP3R1, which results in Ca2+-dependent apoptosis. Knockout of NF2 decreased Ca2+ release and promoted resistance to apoptosis, which was rescued by wild-type NF2 overexpression but not by F1 subdomain deletion truncation overexpression. The effects of NF2 defects on the development of tumors were further studied in mouse models. The decreased expression level of NF2 caused by NF2 gene knockout or mutation affects the activity of the IP3R channel, which reduces Ca2+-dependent apoptosis, thereby promoting the development of tumors. We elucidated the interaction patterns of NF2 and IP3R1, revealed the molecular mechanism through which NF2 regulates IP3R1-mediated Ca2+ release, and elucidated the new pathogenic mechanism of meningioma-related NF2 variants. Our study broadens the current understanding of the biological function of NF2 and provides ideas for drug screening of NF2-associated meningioma.

MPM stands as a rare malignancy necessitating improved therapeutic strategies due to its limited treatment choices and unfavorable prognosis. The advent of immune checkpoint inhibitors has heralded a paradigm shift in the therapeutic landscape of MPM, offering promising avenues across diverse clinical scenarios. In the context of advanced stages of the disease, Immune check-point inhibitors targeting programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-as-sociated protein 4 (CTLA-4), have exhibited encouraging potential in clinical trials, particularly manifesting efficacy among patients exhibiting disease progression following chemotherapy regimens. Innovative combination regimens, exemplified by the concurrent administration of nivolumab and ipilimumab, have demonstrated marked improvement in survival and patient's benefits. A deeper comprehension of the intricate genetic underpinnings of MPM, encompassing key mutations such as cyclin-dependent kinase inhibitor 2A (CDKN2A), neurofibromin 2 (NF2), and BRCA1-associated protein 1 (BAP1) mutations, has elucidated novel avenues for targeted therapeutic interventions. This review accentuates the transformative capacity of immunotherapy in revolutionizing the therapeutic outlook for MPM, thereby potentially translating into augmented survival rates and offering glimpses of new approaches on the horizon. Despite the persisting challenges, the synergistic crossroads of interdisciplinary research and collaborative clinical endeavors portend a hopeful landscape for MPM treatment.

The YAP-TEAD protein-protein interaction mediates YAP oncogenic functions downstream of the Hippo pathway. To date, available YAP-TEAD pharmacologic agents bind into the lipid pocket of TEAD, targeting the interaction indirectly via allosteric changes. However, the consequences of a direct pharmacological disruption of the interface between YAP and TEADs remain largely unexplored. Here, we present IAG933 and its analogs as potent first-in-class and selective disruptors of the YAP-TEAD protein-protein interaction with suitable properties to enter clinical trials. Pharmacologic abrogation of the interaction with all four TEAD paralogs resulted in YAP eviction from chromatin and reduced Hippo-mediated transcription and induction of cell death. In vivo, deep tumor regression was observed in Hippo-driven mesothelioma xenografts at tolerated doses in animal models as well as in Hippo-altered cancer models outside mesothelioma. Importantly this also extended to larger tumor indications, such as lung, pancreatic and colorectal cancer, in combination with RTK, KRAS-mutant selective and MAPK inhibitors, leading to more efficacious and durable responses. Clinical evaluation of IAG933 is underway.

Neurofibromatosis Type II (NFII) is a genetic condition caused by loss of the NF2 gene, resulting in activation of the YAP/TAZ pathway and recurrent Schwann cell tumors, as well as meningiomas and ependymomas. Unfortunately, few pharmacological options are available for NFII. Here, we undertake a genome-wide CRISPR/Cas9 screen to search for synthetic-lethal genes that, when inhibited, cause death of NF2 mutant Schwann cells but not NF2 wildtype cells. We identify ACSL3 and G6PD as two synthetic-lethal partners for NF2, both involved in lipid biogenesis and cellular redox. We find that NF2 mutant Schwann cells are more oxidized than control cells, in part due to reduced expression of genes involved in NADPH generation such as ME1. Since G6PD and ME1 redundantly generate cytosolic NADPH, lack of either one is compatible with cell viability, but not down-regulation of both. Since genetic deficiency for G6PD is tolerated in the human population, G6PD could be a good pharmacological target for NFII.