Meningioma Cell Proliferation Research Articles

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.

The FGF6 amplification mutation plays an important role in the progression and treatment of malignant meningioma

Meningioma is a benign tumor with slow growth and long course. However, patients with recurrent malignant meningioma still face a lack of effective treatment. Here, we report a rare case of primary mediastinal malignant meningioma with lung and bone metastases, who benefited from the treatment of apatinib (≥33 months) and anlotinib (until the publication date). Retrospective molecular analysis revealed the frequent amplification of FGF6 in primary and metastatic lesions. Then we constructed the FGF6 over-expressed IOMM-LEE and CH157MN malignant meningioma cell lines, and in vitro and vivo experiments showed that overexpression of FGF6 can promote the proliferation, migration and invasion of malignant meningioma cells. Based on the Western analysis, we revealed that FGF6 can promote the phosphorylation of FGFR, AKT, and ERK1/2, which can be inhibited by anlotinib. Together, we were the first to verify that overexpression of FGF6 promotes the progression of malignant meningiomas by activating FGFR/AKT/ERK1/2 pathway and pointed out that anlotinib may effectively inhibit the disease progression of patients with FGF6 amplification.

302 Targeted Inhibition of the Epigenetically Activated miR-483-5p IGF-2 Pathway as a Novel Therapeutic Strategy for Meningioma

INTRODUCTION: Meningioma is the most common primary central nervous system tumor. These are usually treated by surgical resection with curative intent, however gross total resection is not always feasible and there are many cases of recurrent and refractory disease despite adjuvant radiotherapy. Presently, there is no effective pharmacotherapeutic options for these tumors. METHODS: Small RNA sequencing was performed on meningioma tumor samples to study grade-dependent changes in microRNA expression. Gene expression was analyzed by chromatin marks, qRT-PCR and western blot. miRNA modulation, anti-IGF-2 neutralizing antibodies, and inhibitors against IGF1R were evaluated in a tumor-derived primary cultures of meningioma cells. RESULTS: Meningioma tumor samples showed high, grade-dependent expression of miR-483-5p, associated with high mRNA and protein expression of its host gene IGF-2. Inhibition of miR-483-5p reduced the growth of cultured meningioma cells, whereas a miR-483 mimic increased cell proliferation. Similarly, inhibition of this pathway with anti-IGF-2 neutralizing antibodies reduced meningioma cell proliferation. Small molecule tyrosine kinase inhibitor blockade of the IGF-2 receptor (IGF1R) resulted in rapid loss of viability of cultured meningioma tumor-derived cells, suggesting that autocrine IGF-2 feedback is obligatory for meningioma tumor cell survival and growth. The observed IGF1R-inhibitory IC50 for GSK1838705A and Ceritinib in cell-based assays along with the available pharmacokinetics data predicted that effective drug concentration could be achieved in vivo as a new medical treatment of meningioma. CONCLUSIONS: Meningioma cell growth is critically dependent on autocrine miR-483/IGF-2 stimulation and the IGF-2 pathway provides a new feasible meningioma treatment target.

Hsa_circ_0004872 alleviates meningioma progression by sponging miR-190a-3p/PTEN signaling

BackgroundMeningioma, the most prevalent intracranial tumor, possesses a significant propensity for malignant transformation. Circular RNAs (circ-RNAs), a class of non-coding RNAs, have emerged as crucial players in tumorigenesis. This study explores the functional relevance of hsa_circ_0004872, a specific circ-RNA, in the context of meningioma.MethodsMolecular structure and stability of hsa_circ_0004872 were elucidated through PCR identification. Meningioma cell proliferation and apoptosis were assessed using the CCK-8 assay and flow cytometry, respectively. Gene and protein expression were analyzed via qRT-PCR and western blot. Molecular interactions were confirmed through dual-luciferase reporter gene and RIP assays.ResultsHsa_circ_0004872, derived from exons 2 to 4 of the host gene MAPK1, demonstrated enhanced stability compared to its host MAPK1. Clinical data described that hsa_circ_0004872 was reduced in meningioma tissues and cell lines, and negatively correlated to poor survival rate of meningioma patients. Overexpression of hsa_circ_0004872 exhibited inhibitory effects on cell proliferation and promotion of apoptosis in vitro. Subsequent investigations unveiled a direct interaction between hsa_circ_0004872 and miR-190a-3p, leading to the activation of the PI3K/AKT signaling pathway through targeting PTEN. Notably, miR-190a-3p silence accelerated the apoptosis and proliferation inhibition of meningioma cells by inactivating PTEN/PI3K/AKT signaling, while miR-190a-3p overexpression showed an opposite effect, which greatly reversed the anti-tumor effects of hsa_circ_0004872 overexpression.ConclusionIn summary, our findings highlighted the intricate role of hsa_circ_0004872 in meningioma, shedding light on the regulatory mechanisms involving circ-RNAs in tumor progression. This positions hsa_circ_0004872 as a potential key regulatory factor in meningioma with implications for future therapeutic interventions.

EXTH-57. THE IGF-2 SIGNALING PATHWAY IS A PROMISING MENINGIOMA TREATMENT TARGET

Abstract Meningioma is the most common primary central nervous system tumor often causing serious complications while there is no effective medical treatment. We developed a tumor-derived primary culture model featuring tumor cells with retained PDG2S lineage marker as well as non-arachnoid cells mimicking the tumor cell microenvironment. We used this model to test the relevance of miRNA differentially expressed in meningioma tumor samples identified by small RNA sequencing. We found that in all meningiomas studied, there was activation of the IGF2/miR-483 locus with high expression of both miR-483-5p and IGF2. Inhibition of miR-483-5p reduced the growth of cultured meningioma cells, whereas a miR-483 mimic increased cell proliferation. Anti-IGF2 neutralizing antibodies reduced meningioma cell proliferation. Small molecule tyrosine kinase inhibitor blockade of the IGF2 receptor (IGF1R) resulted in rapid loss of viability of cultured meningioma tumor-derived cells. Autocrine IGF2 feed-back appears to be obligatory for meningioma tumor cell survival and growth. Inhibition of this circuit with IGF1R small molecule tyrosine kinase inhibitors or receptor-binding antibodies as well as anti-IGF2 neutralizing antibodies may have therapeutic potential for meningioma.

CBX7 reprograms metabolic flux to protect against meningioma progression by modulating the USP44/c-MYC/LDHA axis.

Meningioma is one of the most common primary neoplasms in the central nervous system, but no specific molecularly targeted therapy has been approved for the clinical treatment of aggressive meningiomas. There is hence an urgent demand to decrypt the biological and molecular landscape of malignant meningioma. Here, through the in-silica prescreening and 10-year follow-up studies of 445 meningioma patients, we uncovered that CBX7 expression progressively decreases with malignancy grade and neoplasia stage in meningioma, and a high CBX7 expression level predicts a favorable prognosis in meningioma patients. CBX7 restoration significantly induces cell cycle arrest and inhibits meningioma cell proliferation. iTRAQ-based proteomics analysis indicated that CBX7 restoration triggers the metabolic shift from glycolysis to oxidative phosphorylation. The mechanistic study demonstrated that CBX7 promotes the proteasome-dependent degradation of c-MYC protein by transcriptionally inhibiting the expression of a c-MYC deubiquitinase, USP44, consequently attenuates c-MYC-mediated transactivation of LDHA transcripts, and further inhibits glycolysis and subsequent cell proliferation. More importantly, the functional role of CBX7 was further confirmed in subcutaneous and orthotopic meningioma xenograft mouse models and meningioma patients. Altogether, our results shed light on the critical role of CBX7 in meningioma malignancy progression and identify the CBX7/USP44/c-MYC/LDHA axis as a promising therapeutic target against meningioma progression.

Epigenetic Downregulation of Hsa-miR-193b-3p Increases Cyclin D1 Expression Level and Cell Proliferation in Human Meningiomas.

Meningiomas are common intracranial tumors in adults. Abnormal microRNA (miRNA) expression plays a role in their pathogenesis. Change in miRNA expression level can be caused by impaired epigenetic regulation of miRNA-encoding genes. We found the genomic region covering the MIR193B gene to be DNA hypermethylated in meningiomas based on analysis of genome-wide methylation (HumanMethylation450K Illumina arrays). Hypermethylation of MIR193B was also confirmed via bisulfite pyrosequencing. Both hsa-miR-193b-3p and hsa-miR-193b-5p are downregulated in meningiomas. Lower expression of hsa-miR-193b-3p and higher MIR193B methylation was observed in World Health Organization (WHO) grade (G) II/III tumors as compared to GI meningiomas. CCND1 mRNA was identified as a target of hsa-miR-193b-3p as further validated using luciferase reporter assay in IOMM-Lee meningioma cells. IOMM-Lee cells transfected with hsa-miR-193b-3p mimic showed a decreased cyclin D1 level and lower cell viability and proliferation, confirming the suppressive nature of this miRNA. Cyclin D1 protein expression (immunoreactivity) was higher in atypical than in benign meningiomas, accordingly to observations of lower hsa-miR-193b-3p levels in GII tumors. The commonly observed hypermethylation of MIR193B in meningiomas apparently contributes to the downregulation of hsa-miR-193b-3p. Since hsa-miR-193b-3p regulates proliferation of meningioma cells through negative regulation of cyclin D1 expression, it seems to be an important tumor suppressor in meningiomas.

MicroRNAs miR-16 and miR-519 control meningioma cell proliferation via overlapping transcriptomic programs shared with the RNA-binding protein HuR.

Meningiomas are the most common type of primary central nervous system tumors. In about 80% cases, these tumors are benign and grow very slowly, but the remainder 20% can unlock higher proliferation rates and become malignant. In this study we examined two miRs, miR-16 and miR-519, and evaluated their role in tumorigenesis and cell growth in human meningioma. A cohort of 60 intracranial grade 1 and grade 2 human meningioma plus 20 healthy meningeal tissues was used to quantify miR-16 and miR-519 expressions. Cell growth and dose-response assays were performed in two human meningioma cell lines, Ben-Men-1 (benign) and IOMM-Lee (aggressive). Transcriptomes of IOMM-lee cells were measured after both miR-mimics transfection, followed by integrative bioinformatics to expand on available data. In tumoral tissues, we detected decreased levels of miR-16 and miR-519 when compared with arachnoid cells of healthy patients (miR-16: P=8.7e-04; miR-519: P=3.5e-07). When individually overexpressing these miRs in Ben-Men-1 and IOMM-Lee, we observed that each showed reduced growth (P<0.001). In IOMM-Lee cell transcriptomes, downregulated genes, among which ELAVL1/HuR (miR-16: P=6.1e-06; miR-519:P=9.38e-03), were linked to biological processes such as mitotic cell cycle regulation, pre-replicative complex, and brain development (FDR<1e-05). Additionally, we uncovered a specific transcriptomic signature of miR-16/miR-519-dysregulated genes which was highly enriched in HuR targets (>6-fold; 79.6% of target genes). These results were confirmed on several public transcriptomic and microRNA datasets of human meningiomas, hinting that the putative tumor suppressor effect of these miRs is mediated, at least in part, via HuR direct or indirect inhibition.

Inhibition of the epigenetically activated miR-483-5p/IGF-2 pathway results in rapid loss of meningioma tumor cell viability

PurposeMeningioma is the most common primary central nervous system tumor often causing serious complications, and presently no medical treatment is available. The goal of this study was to discover miRNAs dysregulated in meningioma, and explore miRNA-associated pathways amenable for therapeutic interventions.MethodsSmall RNA sequencing was performed on meningioma tumor samples to study grade-dependent changes in microRNA expression. Gene expression was analyzed by chromatin marks, qRT-PCR and western blot. miRNA modulation, anti-IGF-2 neutralizing antibodies, and inhibitors against IGF1R were evaluated in a tumor-derived primary cultures of meningioma cells.ResultsMeningioma tumor samples showed high, grade-dependent expression of miR-483-5p, associated with high mRNA and protein expression of its host gene IGF-2. Inhibition of miR-483-5p reduced the growth of cultured meningioma cells, whereas a miR-483 mimic increased cell proliferation. Similarly, inhibition of this pathway with anti-IGF-2 neutralizing antibodies reduced meningioma cell proliferation. Small molecule tyrosine kinase inhibitor blockade of the IGF-2 receptor (IGF1R) resulted in rapid loss of viability of cultured meningioma tumor-derived cells, suggesting that autocrine IGF-2 feedback is obligatory for meningioma tumor cell survival and growth. The observed IGF1R-inhibitory IC50 for GSK1838705A and ceritinib in cell-based assays along with the available pharmacokinetics data predicted that effective drug concentration could be achieved in vivo as a new medical treatment of meningioma.ConclusionMeningioma cell growth is critically dependent on autocrine miR-483/IGF-2 stimulation and the IGF-2 pathway provides a feasible meningioma treatment target.

Male sex and presence of preoperative symptoms are associated with early recurrence of WHO grade I meningiomas after surgical resection: analysis from the nationwide Brain Tumor Registry of Japan.

This study aimed to assess the risk factors for the recurrence of WHO grade I intracranial meningiomas using the Brain Tumor Registry of Japan (BTRJ) database. We extracted the data of 4641 patients with intracranial WHO grade I meningiomas treated only by surgical resection between 2001 and 2008. We conducted complete data analysis (n = 3690) and multiple imputation analysis (n = 4641) to adjust for missing data on tumor size. The influence of factors including age, sex, size, extent of resection, location, and preoperative symptoms on PFS was assessed. Univariate analyses of the complete data set showed that age did not affect PFS; however, male sex (p < 0.001), tumor size ≥ 30mm (p < 0.001), low extent of resection, tumor location at the skull base (p < 0.001), and the presence of preoperative symptoms (p < 0.001) were risk factors for a significantly shorter PFS. Multivariate analysis demonstrated that male sex (p < 0.001) and presence of preoperative symptoms (p = 0.027) were independent risk factors for shorter PFS alongside large tumor size (p < 0.001) and non-gross total resection (p < 0.001). These results were confirmed for the imputed dataset. While most previous large nationwide studies of meningiomas have evaluated overall survival, progression-free survival has yet to be thoroughly examined. This study suggests that even histologically benign meningiomas may have a sex difference in postoperative behavior. This observation may provide clues to understanding the mechanism of meningioma cell proliferation.

ITF2357 induces cell cycle arrest and apoptosis of meningioma cells via the PI3K-Akt pathway.

As a type of central nervous system tumor, meningioma usually compresses the nerve center due to its local expansion, further causing neurological deficits. However, there are limited therapeutic approaches for meningiomas. ITF2357, a potent class I and II histone deacetylase inhibitor (HDACi), has been shown to inhibit cell proliferation, promote apoptosis, and block the cell cycle in various sarcoma cells, including glioblastoma and peripheral T-cell lymphoma. Here, we investigated the potential role of ITF2357 on meningioma cancer cells (IOMM-Lee cells). First, we demonstrated that the half-maximal inhibitory concentration (IC50) of ITF2357 was 1.842μM by MTT assay. In addition, ITF2357 effectively inhibited the proliferation and colonization ability of IOMM-Lee cells. Flow cytometry analysis showed that ITF2357 induced G0/G1 and G2/M phase cell cycle arrest and cell apoptosis. Mechanically, the RNA sequencing data revealed that ITF2357 could affect the PI3K-Akt signaling pathway and the cell cycle progression. Furthermore, the expression levels of Akt, PI3K, p-Akt, and p-PI3K were determined by western blotting. Collectively, our data revealed that ITF2357 induces G0 G1 and G2/M phase arrest and apoptosis by inhibiting hyperactivation of the PI3K-Akt pathway, ultimately inhibiting cell viability and proliferation of meningioma cells, which developed a new approach to the treatment of meningioma.

CSIG-37. MERLIN S13 DEPHOSPHORYLATION DRIVES MENINGIOMA WNT SIGNALLING AND CELL PROLIFERATION

Abstract How Merlin-intact meningiomas arise in the absence of NF2/Merlin inactivation is incompletely understood. Here, we integrate single-cell RNA sequencing of 86,000 cells from meningioma xenografts with APEX2 proteomic proximity-labelling mass spectrometry and functional biochemical approaches to discover Merlin Serine 13 (S13) dephosphorylation drives meningioma Wnt signalling and cell proliferation. Cell biology, molecular biology, and biochemical techniques were used to validate Merlin functions in meningioma cells or xenografts using wildtype Merlin constructs or Merlin constructs encoding S13A, phosphomimetic S13D, or cancer-associated missense substitutions (L46R, A211D). Single-cell RNA sequencing of meningioma xenografts showed Merlin rescue activated the Wnt pathway in Merlin-deficient meningiomas. Proteomic proximity-labelling mass spectrometry revealed b-catenin, PKC, and PP1A interactions with wildtype Merlin, but not with Merlin L46R or A211D. b-catenin does not interact with other FERM family members, and Merlin contains a unique N-terminal domain (NTD) with a PKC phosphorylation motif overlapping with a PP1A dephosphorylation motif at S13. Thus, we hypothesized the Merlin S13, PKC, and PP1A may be important for Wnt signalling in Merlin-intact meningiomas. In support of this hypothesis, over-expression of wildtype Merlin or Merlin S13A but not Merlin DNTD, S13D, L46R, A211D, or other FERM family members drove meningioma Wnt signalling and sustained meningioma cell proliferation in vivo. Moreover, b-catenin was detected in proximity to Merlin S13D but not Merlin S13A in meningioma cells. Meningioma cell fractionation and immunofluorescence showed Merlin S13D over-expression stabilized b-catenin at the plasma membrane and inhibited Wnt signalling. Phospho-proteomic mass spectrometry and custom phospho-specific antibodies integrated with shRNA or siRNA gene suppression demonstrated PKC phosphorylated Merlin S13, but meningioma Wnt pathway activation induced PP1A to dephosphorylate Merlin S13 and drive cell proliferation. In summary, Merlin S13 dephosphorylation drives meningioma Wnt signalling and cell proliferation. These data reveal a novel tumor-promoting function of NF2/Merlin in Merlin-intact meningiomas.

CSIG-36. NOTCH3 DRIVES MENINGIOMA TUMORIGENESIS AND RESISTANCE TO RADIOTHERAPY

Abstract There are no approved targeted therapies for meningiomas and the cell types underlying meningeal tumorigenesis are incompletely understood. To address these limitations, we performed single-cell RNA sequencing of 57,114 cells from 8 human meningiomas and 54,607 cells from 3 canine meningiomas. Pseudotime, gene ontology, and copy number variant analyses revealed a population of pericyte-like meningioma cells that were conserved across human and canine tumors and were enriched in expression of Notch3 and other cancer stem cell genes. Deconvolution of cell types from bulk RNA sequencing and DNA methylation profiling of 200 human meningiomas integrated with immunohistochemistry (IHC), immunofluorescence (IF), and RNAScope demonstrated Notch3+ pericytes and Notch3 expression were enriched in high grade or Immune-enriched meningiomas, which were distinguished from other meningioma DNA methylation groups by genes driving vasculature development. IHC and IF of human meninges integrated with lineage tracing approaches using Notch3-CreERT2 ROSAmT/mG alleles in mice demonstrated Notch3 expression was restricted to the perivascular stem cell niche during meningeal development and homeostasis. Mice harboring Notch3-CreERT2 Nf2fl/fl alleles developed meningeal hyperproliferation. Overexpression of constitutively activated Notch3 (Notch3AICD) in Immune-enriched human meningioma cells increased the expression of cancer stem cell genes, driving clonogenic growth in vitro, limiting dilution tumor-initiating capacity in vivo, and resistance to radiotherapy in vivo. A selective Notch3 neutralizing antibody (αNRR3) blocked meningioma cell proliferation and expression of Notch3 target genes, inhibiting meningioma xenograft growth and prolonging overall survival. Single-cell RNA sequencing of 187,366 cells from meningioma xenografts after αNRR3 or radiotherapy treatment ± Notch3AICD overexpression revealed distinct meningioma cell-intrinsic or cell-extrinsic mechanisms driving responses to radiotherapy or αNRR3, respectively. Combined treatment with αNRR3 and radiotherapy additively blocked meningioma xenograft growth and extended survival benefit. In sum, these data shed light on a novel cell type, molecular mechanism, and therapeutic vulnerability in the most common primary intracranial tumor.

MiR-127-5p Targets JAM3 to Regulate Ferroptosis, Proliferation, and Metastasis in Malignant Meningioma Cells.

Objective Meningiomas are one of the most common primary tumors of the central nervous system. Most of them are benign and can be cured by surgery, while a few meningiomas are malignant. Ferroptosis gene characteristics might be associated with drug therapy and survival in patients with clinically aggressive, unresectable meningiomas. This study explored the mechanism of differentially expressed miRNAs and ferroptosis in meningioma to provide a new reference to treat meningioma. Methods Bioinformatics analysis of differential miRNA profiles and functions in patients with meningioma was performed. The contents of lactate dehydrogenase (LDH), malondialdehyde (MDA), and Fe2+ were determined. Reactive oxygen species (ROS) values, as well as cell cycle changes, were analyzed by flow cytometry. The targets of miR-127-5p and JAM3 were detected by dual luciferase assays. Cell counting kit-8 (CCK8) and Transwell assays were used to analyze cell activity. Ki67 expression was analyzed by immunohistochemistry. Expression levels of miR-127-5p and JAM3 were analyzed by RT-qPCR. GPX4 expression was quantified by western blotting. Results miR-127-5p was expressed at low levels in IOMM-Lee cells, while JAM3 was highly expressed in IOMM-Lee cells. A dual luciferase assay demonstrated that miR-127-5p could target JAM3. Upregulation of miR-127-5p in IOMM-Lee cells resulted in cell cycle arrest and inhibition of cell activity. Upregulation of miR-127-5p increased LDH, MDA, and ROS levels and Fe2+ content and inhibited the expression of GPX4 protein. Upregulation of JAM3 reversed the results of miR-127-5p upregulation. Conclusion miR-127-5p regulated meningioma formation and ferroptosis through JAM3, providing insights for the development of new treatments for meningioma.

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.

AKT1E17K‐mutated meningioma cell lines respond to treatment with the AKT inhibitor AZD5363

AbstractAimsMeningiomas are the most frequent primary brain tumours. Recently, knowledge about the molecular drivers underlying aggressive meningiomas has been expanded. A hotspot mutation in the AKT1 gene (AKT1E17K), which is found in meningiomas at the convexity and especially at the skull base, has been associated with earlier tumour recurrence.MethodsHere, we analysed the effects of the AKT1E17K mutation and treatment response to the Akt inhibitor AZD5363 in transgenic meningioma cell clones and mouse xenografts modelling convexity or skull base meningiomas.ResultsWe show that the AKTE17K mutation significantly enhances meningioma cell proliferation and colony size in vitro, resulting in significantly shortened survival times of mice carrying convexity or skull base AKT1E17K xenografts. Treatment of mutant cells or xenografts (150 mg/kg/d) with AZD5363 revealed a significant decrease in cell proliferation and colony size and a prolongation of mouse survival. Western blots revealed activation of AKT1 kinase (phosphorylation at Ser273 and Thr308) by the E17K mutation in human meningioma samples and in our in vitro and in vivo models.ConclusionsOur data suggest that AKT1E17K mutated meningiomas are a promising selective target for AZD5363.

ET-7 Roles for hENT1 and dCK in gemcitabine sensitivity and malignancy of meningioma

Background: High-grade meningiomas are aggressive tumors with high morbidity and mortality rates that frequently recur even after surgery and adjuvant radiotherapy. However, limited information is currently available on the biology of these tumors, and no alternative adjuvant treatment options exist. Although we previously demonstrated that high-grade meningioma cells were highly sensitive to gemcitabine in vitro and in vivo, the underlying molecular mechanisms remain unknown. Methods: We examined the roles of hENT1 (human equilibrative nucleoside transporter 1) and dCK (deoxycytidine kinase) in the gemcitabine sensitivity and growth of meningioma cells in vitro. Tissue samples from meningiomas (26 WHO grade I and 21 WHO grade II/III meningiomas) were immunohistochemically analyzed for hENT1 and dCK as well as for Ki-67 as a marker of proliferative activity. Results: hENT1 and dCK, which play critical roles in the intracellular transport and activation of gemcitabine, respectively, were responsible for the high gemcitabine sensitivity of high-grade meningioma cells and were strongly expressed in high-grade meningiomas. hENT1 expression was required for the proliferation and survival of high-grade meningioma cells and dCK expression. Furthermore, high hENT1 and dCK expression levels correlated with stronger tumor cell proliferative activity and shorter survival in meningioma patients. Conclusions: The present results suggest that hENT1 is a key molecular factor influencing the growth capacity and gemcitabine sensitivity of meningioma cells and also that hENT1, together with dCK, may be a viable prognostic marker for meningioma patients as well as a predictive marker of their responses to gemcitabine.

Receptor-Tyrosine Kinase Inhibitor Ponatinib Inhibits Meningioma Growth In Vitro and In Vivo.

Simple SummaryThe clinical management for aggressive meningiomas remains challenging due to the lack of systemic treatment options. Receptor tyrosine kinases (RTKs) are frequently overexpressed in meningiomas and are associated with poor patient survival. In this study, we evaluated the clinically approved pan-RTK inhibitor ponatinib as a novel candidate for the treatment of aggressive meningiomas. Ponatinib decreased cell viability and proliferation of meningioma cells and subsequently induced programmed cell death. Furthermore, the drug demonstrated a considerable tumor growth inhibition without causing any adverse effects in mice. Mechanistically, this was presumably caused by blocking the PDGFR signaling pathway accompanied by induction of mitochondrial dysfunction. Altogether, the multi-RTKi ponatinib may serve as a promising candidate for targeted therapy for aggressive meningiomas.To date, there is no standard-of-care systemic therapy for the treatment of aggressive meningiomas. Receptor tyrosine kinases (RTK) are frequently expressed in aggressive meningiomas and are associated with poor survival. Ponatinib is a FDA- and EMA-approved RTK inhibitor and its efficacy in meningioma has not been studied so far. Therefore, we investigated ponatinib as a potential drug candidate against meningioma. Cell viability and cell proliferation of ponatinib-treated meningioma cells were assessed using crystal violet assay, manual counting and BrdU assay. Treated meningioma cell lines were subjected to flow cytometry to evaluate the effects on cell cycle and apoptosis. Meningioma-bearing mice were treated with ponatinib to examine antitumor effects in vivo. qPCR was performed to assess the mRNA levels of tyrosine kinase receptors after ponatinib treatment. Full-length cDNA sequencing was carried out to assess differential gene expression. IC50 values of ponatinib were between 171.2 and 341.9 nM in three meningioma cell lines. Ponatinib induced G0/G1 cell cycle arrest and subsequently led to an accumulation of cells in the subG1-phase. A significant induction of apoptosis was observed in vitro. In vivo, ponatinib inhibited meningioma growth by 72.6%. Mechanistically, this was associated with downregulation of PDGFRA/B and FLT3 mRNA levels, and mitochondrial dysfunction. Taken together, ponatinib is a promising candidate for targeted therapy in the treatment of aggressive meningioma.

NF2 Gene Participates in Regulation of the Cell Cycle of Meningiomas by Restoring Spindle Assembly Checkpoint Function and Inhibiting the Binding of Cdc20 Protein to Anaphase Promoting Complex/Cyclosome

The neurofibromatosis type 2 (NF2) gene mutation is the leading genetic event in meningiomas, usually accompanied by malignant features. Dysfunction of the spindle assembly checkpoint (SAC) induces tumorigenesis. However, the crosstalk between NF2 and SAC in meningiomas remains unclear. Cell proliferation, invasion, apoptosis, and cell cycle of meningiomas were determined by cell counting kit-8 assay, transwell assay, and flow cytometry, respectively. The expression of SAC in meningioma cells was detected by quantitative real-time polymerase chain reaction and Western blot. The interaction between anaphase promoting complex/cyclosome (APC/C) and cell division cycle 20 (Cdc20) protein in meningioma cells was further explored by co-immunoprecipitation. We found that the expression of NF2/merlin was low or absent in malignant meningiomas. Overexpression of NF2 suppressed the proliferation and invasion of meningioma cells, prolonged the G2/M phase, and elevated the expression of SAC proteins at posttranscription. Furthermore, the interaction between APC/C and Cdc20 was inhibited by NF2. Our findings suggested that NF2 might restore SAC function by impairing the binding of APC/C and Cdc20, thereby limiting the mitotic rate and inhibiting proliferation of meningiomas.

Glutamine anaplerosis is required for amino acid biosynthesis in human meningiomas.

We postulate that meningiomas undergo distinct metabolic reprogramming in tumorigenesis and unraveling their metabolic phenotypes provide new therapeutic insights. Glutamine catabolism is key to the growth and proliferation of tumors. Here, we investigated the metabolomics of freshly resected meningiomas and glutamine metabolism in patient-derived meningioma cells. 1H NMR spectroscopy of tumor tissues from meningioma patients was used to differentiate the metabolite profiles of grade-I and grade-II meningiomas. Glutamine metabolism was examined using 13C/15N glutamine tracer, in 5 patient-derived meningioma cells. Alanine, lactate, glutamate, glutamine, and glycine were predominantly elevated only in grade-II meningiomas by 74%, 76%, 35%, 75%, and 33%, respectively, with alanine and glutamine levels being statistically significant (P ≤ .02). 13C/15N glutamine tracer experiments revealed that both grade-I and -II meningiomas actively metabolize glutamine to generate various key carbon intermediates including alanine and proline that are necessary for the tumor growth. Also, it is shown that glutaminase (GLS1) inhibitor, CB-839 is highly effective in downregulating glutamine metabolism and decreasing proliferation in meningioma cells. Alanine and glutamine/glutamate are mainly elevated in grade-II meningiomas. Grade-I meningiomas possess relatively higher glutamine metabolism providing carbon/nitrogen for the biosynthesis of key nonessential amino acids. GLS1 inhibitor (CB-839) is very effective in downregulating glutamine metabolic pathways in grade-I meningiomas leading to decreased cellular proliferation.