Genomic Biomarkers of Meningioma: A Focused Review

Molecular biomarkers in meningioma (Review)

Meningioma is the most common type of primary intracranial tumor. These tumors are typically slow-growing and benign [World Health Organization (WHO) grade 1]. However, 20% of meningiomas (WHO grade 2 and 3) can be difficult to treat owing to their aggressive characteristics and higher recurrence rate, which presents a significant therapeutic challenge. Histopathological grading can yield inconsistent results due to interexaminer variability, which calls for more reliable biomarkers. Genetic and epigenetic alterations may define biological behavior and predict the prognosis of meningioma. The present review highlights the relevant genetic mutations, DNA methylation status in meningioma and their associations with relevant histomorphology, location and prognosis. Mutations in TNF receptor-associated factor 7, Krüppel-like factor 4 (KLF4), v-Akt murine thymoma viral oncogene homolog (AKT1), Smoothened frizzled-class receptor (SMO), Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and RNA polymerase II subunit A (POLR2A) were associated with a good prognosis and a low recurrence rate. By contrast, mutations in NF2, TERT promoter, SMARCB1, SMARCE1, CDKN2A/B and BAP1 are associated with poor prognosis and higher recurrence rates. DNA methylation status plays a role in diagnosis, predicting tumor recurrence and prognosis. Combining the WHO grading and molecular biomarkers may lead to better diagnosis, prognosis, and targeted therapy for meningioma.

Cas9 Mouse Model of Skull Base Meningioma Driven by Combinational Gene Inactivation in Meningeal Cells

INTRODUCTION

Neurofibromatosis type 2 (Nf2) gene inactivation is common in sporadic and Nf2-related meningioma. There is currently scant literature describing the development of an intracranial meningioma model in animals. Given the role of Nf2 and other gene inactivation in meningeal cells, we used Cas9 mice here as the background host to establish a new animal model of skull base meningioma in this study.

AIMS

Cas9 transgenic mice were purchased from Jackson Laboratory and raised in our institution. Subsequently, meningeal cells were obtained from the Cas9 transgenic mice, cultured in medium, and passaged in vitro. We then prepared lentivirus vector pLentiCre/gRNA, which could express the elements blocking the function of four genes: Nf2, P15Ink4b, P16Ink4a, and P19Arf. We infected the meningeal cells with the lentivirus vector pLentiCre/gRNA and tested the expression of these four genes in those infected meningeal cells. Next, adeno-associated virus vector pAAVCre/gRNA was injected in vivo into the skull base meningeal cells of the neonate Cas9 transgenic mice. These mice were observed once a week and killed 10 months later for brain inspection and pathological analysis.

RESULTS

Twenty Cas9 transgenic mice were successfully bred. Five mice were killed so that meningeal cells could be extracted, cultured, and infected with the lentivirus vector pLentiCre/gRNA for 72 h in vitro. The gene function test showed that Nf2, P15Ink4b, P16Ink4a, and P19Arf were all blocked in the infected meningeal cells, which indicated that the lentivirus vector pLentiCre/gRNA could effectively block the expression of the four genes in targeted cells. Then pAAVCre/gRNA was injected into the skull base meningeal cells of 15 mice in vivo, and nine mice were observed for 10 months so that the intracranial tumor growth could be assessed. Among these nine mice, pathological analysis showed that six mice had benign meningioma subtypes similar to human meningioma, one mouse had atypical meningioma, one mouse had malignant meningioma, and one mouse had sarcoma.

CONCLUSIONS

The Cas9 mouse model of skull base meningioma generated with the Nf2 genetic defect and the combinational loss of P15Ink4b, P16Ink4a, and P19Arf could provide a new tool for investigating the pathogenesis of meningioma and the development of chemical interventions for this disease.

Protein expression of CD44 in patients with meningioma tumors: association with clinicopathological parameters and survival

OBJECTIVE

Meningiomas are a molecularly ill-defined heterogeneous group of indolent intracranial tumors. Though, WHO grade 1 tumors are histologically benign, sometimes they transform into malignant and may be recurrent which remains always challenging to clinicians. Therefore, the current study sought to discover the clinical relevance of CD44 in meningioma patients.

METHOD

Protein expression of CD44 was investigated using immunohistochemistry in a total of 70 meningioma patients. Immunoscore performed using modified H-score, CD44 expression correlated with clinicopathological parameters and progression-free survival (PFS) and overall survival (OS). Univariate and multivariate survival analysis was analyzed. The data was evaluated using SPSS statistical software and P-value ≤ 0.05 was considered as significant.

RESULTS

The membranous and cytoplasmic protein expression of CD44 was noted in meningioma tumors. Based on H-score, the weak (0-190 score) and strong (191-300 score) immunoreactivity was observed in 62.9% and 37.1% of patients, respectively. A statistically significant positive correlation was found between strong CD44 expression and WHO grade 2/3 tumors (χ2 = 33.551, r = + 0.692, P = 0.0001), and with the presence of brain invasion (χ2 = 19.521, r = + 0.528, P = 0.001). In Kaplan-Meier univariate survival analysis for PFS and OS, apart from WHO grade of tumors (PFS; log-rank = 12.309, P = 0.0001, OS; log-rank = 17.830, P = 0.0001) and brain invasion status (PFS; log-rank = 11.941, P = 0.001, OS; log-rank = 13.554, P = 0.0001) CD44 expression (PFS; log-rank = 14.942, P = 0.0001, OS; log-rank = 20.986, P = 0.0001) remained significant prognostic factor for PFS and OS. In multivariate survival analysis, at step 1, only CD44 remained independent prognosticator for PFS (HR = 11.014, 95% CI = 2.256-23.602, P = 0.001) and OS (HR = 8.553, 95% CI = 2.831-25.847, P = 0.0001). In relation to treatment offered, patients with strong CD44 expression and if treated with surgery followed by adjuvant radiotherapy showed a high incidence of death (log-rank = 13.402, P = 0.0001) as compared to patients treated with surgery only. Receiver operating characteristic (ROC) curves also confirmed a good efficacy of CD44 as a prognosticator for disease outcome (PFS; P = 0.0001, OS; P = 0001).

CONCLUSION

Our overall findings addressed that a study of CD44 protein expression would be beneficiated to meningioma patients from unnecessary overtreatment and drug-induced toxicity. Also, CD44 could be one of the promising biomarkers that might differentiate high-risk meningioma patients for better treatment management.

Surgery alone versus surgery plus adjuvant radiotherapy for WHO grade 2 meningioma: meta-analysis of reconstructed time-to-event data

INTRODUCTION

WHO Grade 2 meningiomas present diagnostic and management challenges. Surgery, particularly gross total resection (GTR), is crucial, often followed by adjuvant radiotherapy (RT); however, there are clinical equipoise and ongoing randomized trials of RT after GTR.

METHODS

This systematic review evaluates the efficacy of gross total resection (GTR) and GTR plus adjuvant radiotherapy (RT) for WHO grade 2 meningiomas, adhering to PRISMA guidelines. It excludes irrelevant studies, conducts a thorough search until January 2024, and specifically analyzes overall survival (OS) and progression-free survival (PFS) outcomes for WHO grade 2 meningiomas. Statistical analysis adopts a two-stage approach with the R package "IPDfromKM," and quality assessment is conducted using the ROBINS-I tool.

RESULTS

In our analysis of 23 studies involving 3822 WHO grade 2 meningioma patients, GTR + RT resulted in a significantly longer PFS (HR: 0.849, 95% CI: 0.730 to 0.988, p = 0.035) compared to GTR alone. Although OS trended better with GTR + RT (HR: 0.79, 95% CI: 0.57 to 1.11, p = 0.173), the difference was not statistically significant, suggesting the need for further investigation.

CONCLUSION

Our study reveals a benefit to adjuvant RT for improving PFS for WHO grade 2 meningiomas. Integrating molecular characteristics into treatment strategies will refine the management of these tumors in the future.

ADAM12 Silencing Mediated by FOXC2 Represses Meningioma Progression Through Inactivating the JAK1/STAT3/VEGFA Pathway

Meningioma is a prevalently intracranial tumor, and the malignant type is aggressive with high recurrence. A Disintegrin and Metalloprotease 12 (ADAM12) is a common oncogene and differentially expressed in meningioma. However, its roles and mechanisms in meningioma development remain obscure. The differentially expressed genes in meningioma were analyzed by GEO (GSE77259 and GSE43290) datasets and weighted gene co-expression network analysis (WGCNA) based on GSE16581. ADAM12 expression was measured via qRT-PCR and western blot. The correlation between ADAM12 and FOXC2 was predicted through JASPER tool and identified via luciferase reporter analysis. Cell proliferation, migration and invasion were investigated using CCK-8, EdU, transwell assays. The JAK1/STAT3/VEGFA signaling was activated by IL-6, and analyzed via western blot. The differentially expressed ADAM12 in meningioma was screened by WGCNA and GEO analyses. ADAM12 silencing repressed meningioma cell proliferation, and decreased migration and invasion. The transcription factor FOXC2 expression was enhanced in meningioma based on GSE77259 and GSE43290 datasets, and positively induced ADAM12 transcription. The JAK1/STAT3/VEGFA signaling was inactivated due to ADAM12 silencing and activated via IL-6. Upregulation of FOXC2 promoted cell proliferation, migration and invasion, and these effects were reversed by silencing ADAM12. ADAM12 knockdown mediated via FOXC2 silencing restrained proliferation, migration and invasion of meningioma cells through inactivating the JAK1/STAT3/VEGFA pathway.

Hsa_circ_0004872 mitigates proliferation, metastasis and immune escape of meningioma cells by suppressing PD-L1

Meningioma is a prevalent intracranial malignancy known for its aggressive growth. Circular RNAs (circRNAs) play a crucial role in the development of various cancers. However, their involvement in meningioma remains understudied. This study aimed to investigate the function and underlying mechanism of hsa_circ_0004872 in meningioma. The molecular expression of hsa_circ_0004872, PD-L1 and EIF4A3 was identified by RT-qPCR and/or western blot assays. Cell viability, migration, and invasion were assessed through CCK-8 and Transwell assays, respectively. Cytotoxicity was determined using an LDH assay, and cell apoptosis was monitored by flow cytometry. The RNA and protein interactions were assessed through RNA-protein immunoprecipitation (RIP) and RNA pull down analyses. Our findings revealed that hsa_circ_0004872 expression was significantly downregulated in both meningioma tissue samples and cells. Overexpression of hsa_circ_0004872 inhibited the proliferation, metastasis, and immune escape of meningioma cells, as well as enhanced the cytotoxicity of CD8+ T cells by suppressing PD-L1. Furthermore, hsa_circ_0004872 directly interacted with EIF4A3, leading to the degradation of PD-L1 mRNA. Finally, inhibiting EIF4A3 improved the proliferation, metastasis, and immune escape of meningioma cells, as well as the cytotoxicity of CD8+ T cells. Our study demonstrated that hsa_circ_0004872 mitigated the proliferation, metastasis,and immune escape of meningioma cells by targeting the EIF4A3/PD-L1 axis. These findings suggested that hsa_circ_0004872 and EIF4A3 might serve as promising biological markers and therapeutic targets for meningioma treatment.

Predictors of early and late postoperative seizures in meningioma patients: a systematic review and meta-analysis

Meningioma is the most common type of primary brain tumor which presents with a variety of neurological manifestations. Surgical resection tends to be the preferred treatment. The occurrence of seizures after resection is common, which occur either early, within seven days of operation, or late. Our meta-analysis investigated the possible predictors of early and late postoperative seizures. We assessed the relevant observational studies on predictors of postoperative seizures published in PubMed, Scopus, and Web of Science from January 2000 to September 2022, and those that met inclusion criteria were included. We calculated the association between potential predicting factors and postoperative seizures, odds ratios (ORs) with 95% confidence intervals (CIs) applying either random or fixed-effect models. The early and late postoperative seizures were evaluated individually. Thirteen observational studies involving 4176 patients were included. Seizures occurred in 250 (6%) and 584 (14%) patients, respectively, in the early and late postoperative phases. Shared predictors for early and late seizures included tumors involving the motor cortex (OR = 2.7; 95% CI: 1.67-4.38, OR = 2.46; 95% CI: 1.68-3.61), postoperative neurological deficit (OR = 4.68; 95% CI: 2.67-8.22, OR = 2.01; 95% CI: 1.39-2.92), and preoperative seizures (OR = 2.52; 95% CI: 1.82-3.49, OR = 4.35; 95% CI: 3.29-5.75). Peritumoral edema (OR = 1.99; 95% CI: 1.49-2.64) was a significant factor only among late postoperative seizure patients while surgical complications (OR = 3.77; 95% CI: 2.39-5.93) was a significant factor solely for early postoperative seizures. Meningioma patients commonly experience early and late postoperative seizures. Identifying predictors of postoperative seizures is essential to diagnose and manage them effectively.

Advances in Mass Spectrometry of Gangliosides Expressed in Brain Cancers

Gangliosides are highly abundant in the human brain where they are involved in major biological events. In brain cancers, alterations of ganglioside pattern occur, some of which being correlated with neoplastic transformation, while others with tumor proliferation. Of all techniques, mass spectrometry (MS) has proven to be one of the most effective in gangliosidomics, due to its ability to characterize heterogeneous mixtures and discover species with biomarker value. This review highlights the most significant achievements of MS in the analysis of gangliosides in human brain cancers. The first part presents the latest state of MS development in the discovery of ganglioside markers in primary brain tumors, with a particular emphasis on the ion mobility separation (IMS) MS and its contribution to the elucidation of the gangliosidome associated with aggressive tumors. The second part is focused on MS of gangliosides in brain metastases, highlighting the ability of matrix-assisted laser desorption/ionization (MALDI)-MS, microfluidics-MS and tandem MS to decipher and structurally characterize species involved in the metastatic process. In the end, several conclusions and perspectives are presented, among which the need for development of reliable software and a user-friendly structural database as a search platform in brain tumor diagnostics.

Liquid biopsy evaluation of circulating tumor DNA, miRNAs, and cytokines in meningioma patients

Introduction

Liquid biopsy is a non-invasive method used to detect cancer and monitor treatment responses by analyzing blood or other bodily fluids for cancer biomarkers. Meningiomas are the most common primary central nervous system tumors, and biomarkers play a crucial role in their diagnosis, prognosis, and treatment monitoring. The World Health Organization (WHO) classifies meningiomas based on tumor grades and molecular alterations in genes such as in NF2, AKT1, TRAF7, SMO, PIK3CA, KLF4, SMARCE1, BAP1, H3K27me3, TERT promoter, and CDKN2A/B. Liquid biopsy, specifically cell-free DNA (cfDNA) analysis, has shown potential for monitoring meningiomas as it can detect ctDNA release in the blood, unaffected by the blood-brain barrier. MicroRNAs (miRNAs) have also been found to be deregulated in various cancers, including meningiomas, presenting potential as diagnostic biomarkers. Additionally, studying cytokines in the tumor microenvironment may aid in establishing prognostic or diagnostic panels for meningiomas.

Methods

In the present study we analyzed the DNA coming from both the plasma and tumor samples, in addition to analyze miRNA-21 and cytokines in the plasma of 28 meningioma patients.

Discussion and Conclusion

Our findings indicate that the detection of ctDNA in the plasma of meningioma patients is feasible. However, it's important to note that certain challenges persist when comparing plasma DNA analysis to that of tumor tissues. In our study, we observed a paired identification of mutations in only one patient, highlighting the complexities involved. Furthermore, we successfully identified miR-21 and cytokines in the plasma samples. Notably, our analysis of Interleukin 6 (IL-6) unveiled higher expression in the clear cell subtype compared to the other types. Despite the ongoing research, the clinical implementation of liquid biopsy in meningiomas remains somewhat limited. Nevertheless, our promising results underscore the need for further investigation.

CDKN2A/B deletions are strongly associated with meningioma progression: a meta-analysis of individual patient data

Homozygous CDKN2A/B deletion has been associated with an increased risk of recurrence in meningiomas. However, the evidence is confined to a limited number of studies, and the importance of heterozygous CDKN2A/B deletions remains insufficiently investigated. Hence, the present meta-analysis reconstructs individual patient data (IPD) and reconstructs the probabilities of progression-free survival (PFS) stratified by CDKN2A/B status. IPD of PFS rates were extracted from published Kaplan-Meier plots using the R package IPDfromKM in R studio (RStudio, Boston, MA, USA). Reconstructed Kaplan-Meier Plots of the pooled IPD data were created. One-stage and two-stage meta-analyses were performed. Hazard ratios (HR) were used as effective measures. Of 181 records screened, four articles with 2521 participants were included. The prevalence of homozygous CDKN2A/B deletions in the included studies was 0.049 (95% CI 0.040-0.057), with higher tumor grades associated with a significantly greater proportion of CDKN2A/B deletions. The reconstructed PFS curves for the pooled cohort showed that the median PFS time of patients with a CDKN2A/B wild-type status, heterozygous or homozygous CDKN2A/B deletion was 180.0 (95% CI 145.7-214.3), 26.1 (95% CI 23.3-29.0), and 11.00 (95% CI 8.6-13.3) months, respectively (p < 0.0001). Both hetero- or homozygous CDKN2A/B deletions were significantly associated with shortened time to meningioma progression. One-stage meta-analysis showed that hetero- (HR: 5.5, 95% CI 4.0-7.6, p < 0.00001) and homozygous CDKN2A/B deletions (HR: 8.4, 95% CI 6.4-11.0, p < 0.00001) are significantly associated with shortened time to meningioma progression. Multivariable Cox regression analysis of progression in a subgroup with available covariates (age, sex, WHO grade, and TERT status) and also two-stage meta-analysis confirmed and validated the results of the one-stage analysis that both heterozygous and homozygous CDKN2A/B deletions are of prognostic importance. Further large-scale studies of WHO grade 2 and 3 meningiomas are needed to validate the importance of heterozygous CDKN2A/B deletions with consideration of established factors.

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

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

Clinical Management of Supratentorial Non-Skull Base Meningiomas

Supratentorial non-skull base meningiomas are the most common primary central nervous system tumor subtype. An understanding of their pathophysiology, imaging characteristics, and clinical management options will prove of substantial value to the multi-disciplinary team which may be involved in their care. Extensive review of the broad literature on the topic is conducted. Narrowing the scope to meningiomas located in the supratentorial non-skull base anatomic location highlights nuances specific to this tumor subtype. Advances in our understanding of the natural history of the disease and how findings from both molecular pathology and neuroimaging have impacted our understanding are discussed. Clinical management and the rationale underlying specific approaches including observation, surgery, radiation, and investigational systemic therapies is covered in detail. Future directions for probable advances in the near and intermediate term are reviewed.

Advances in Molecular Biological and Translational Studies in World Health Organization Grades 2 and 3 Meningiomas: A Literature Review

The treatment of World Health Organization (WHO) grades 2 and 3 meningiomas remains difficult and controversial. The pathogenesis of high-grade meningiomas was expected to be elucidated to improve treatment strategies. The molecular biology of meningiomas has been clarified in recent years. High-grade meningiomas have been linked to NF2 mutations and 22q deletion. CDKN2A/B homozygous deletion and TERT promoter mutations are independent prognostic factors for WHO grade 3 meningiomas. In addition to 22q loss, 1p, 14p, and 9q loss have been linked to high-grade meningiomas. Meningiomas enriched in copy number alterations may be biologically invasive. Furthermore, several new comprehensive classifications of meningiomas have been proposed based on these molecular biological features, including DNA methylation status. The new classifications may have implications for treatment strategies for refractory aggressive meningiomas because they provide a more accurate prognosis compared to the conventional WHO classification. Although several systemic therapies, including molecular targeted therapies, may be effective in treating refractory aggressive meningiomas, these drugs are being tested. Systemic drug therapy for meningioma is expected to be developed in the future. Thus, this review aims to discuss the distinct genomic alterations observed in WHO grade 2 and 3 meningiomas, as well as their diagnostic and therapeutic implications and systemic drug therapies for high-grade meningiomas.

Molecular determinants of outcomes in meningiomas

Meningiomas are the most common intracranial primary tumor in adults. Surgery is the predominant therapeutic modality for symptomatic meningiomas. Although the majority of meningiomas are benign, there exists a subset of meningiomas that are clinically aggressive. Recent advances in genetics and epigenetics have uncovered molecular alterations that drive tumor meningioma biology with prognostic and therapeutic implications. In this review, we will discuss the advances on molecular determinants of therapeutic response in meningiomas to date and discuss findings of targeted therapies in meningiomas.

Current knowledge on spinal meningiomas: a systematic review protocol

INTRODUCTION

Meningiomas are primary central nervous system tumours that arise from both cranial and spinal meninges. Spinal meningiomas occur less frequently than their cranial counterparts and are consequently given less attention in the literature. Therefore, systematic studies are needed to summarise the current knowledge on spinal meningiomas, providing a solid evidence base for treatment strategies. This systematic review of the literature will therefore assess studies describing spinal meningiomas, their epidemiology, diagnostics, treatment and outcomes.

METHODS AND ANALYSIS

Electronic databases, including PubMed, Web of Science and Embase, will be searched using the keywords "spinal" and "meningioma". The search will be set to provide only English studies published after 2000 to avoid any conflicts regarding terminology and classification, as well as to reflect the current status. Case reports, editorials, letters and reviews will also be excluded. Reference lists of relevant records will also be searched. Identified studies will be screened for inclusion, by one reviewer in a first step and then three in the next step to decrease the risk of bias. The results will be categorised to allow for a structured summary of the outcomes and their evidence grade conforming to the Grading of Recommendations, Assessment, Development and Evaluation approach. Categories may include: epidemiology, histopathology, radiological diagnostics, surgery, complications, non-surgical or adjuvant treatments, disease outcomes and predictors, and lastly recurrence. This review will summarise the current knowledge on spinal meningiomas to allow for a better understanding of the disease and contribute to improve its management. For clinicians, the systematic collection and grading of available evidence may aid in decision making and for those seeking to further the scientific field, this review may help to identify areas where knowledge is currently lacking.

ETHICS AND DISSEMINATION

Ethics approval was not required for our systematic review as it is based on existing publications. The results will be disseminated via submission for publication in a peer-reviewed journal.

M2-Macrophage-Derived Exosomes Promote Meningioma Progression through TGF-β Signaling Pathway

Tumor-associated macrophages (TAMs) have been shown to be an essential component of the tumor microenvironment and facilitate the proliferation and invasion of a variety of malignancies. However, the contribution of TAMs to meningioma progression has not been characterized in detail. In this study, we aimed to discover a novel regulatory pathway by which exosome-mediated M2-polarized macrophages participate in meningioma tumorigenesis and progression. Methods. First, the distribution and functional phenotype of macrophages in meningioma tissues were assessed by immunohistochemistry. Macrophage-derived exosomes (MDEs) were characterized, and further cell coculture experiments were performed to explore the effects of M2-MDEs on the proliferation, migration, and invasion of meningioma cells. RNA sequencing was used to analyze the transcriptomic signatures in meningioma cells treated with M2-MDEs. Three-dimensional tumorspheres and xenograft tumor models were used to evaluate the effects of M2-MDEs on meningioma tumorigenesis and development. Results. We found that M2 macrophages were enriched in meningioma tissue. Coculture with meningioma cells induced the M2 polarization of macrophages. We also found that M2-MDEs were able to significantly promote cell proliferation, cell migration, cell invasion, and tumorigenesis in meningiomas. Bioinformatic analysis suggested that the TGF-β pathway was activated in meningioma cells treated with M2-MDEs. Functional experiments demonstrated that blocking the TGF-β signaling pathway could effectively reverse the tumor-promotive effects mediated by M2-MDEs. Conclusions. Overall, our study showed that M2-MDEs promoted meningioma development and invasion by activating the TGF-β signaling pathway. Targeting exosome-mediated intercellular communication in the tumor microenvironment may be a novel therapeutic strategy for meningioma patients.