Immuno-oncological interactions between meningeal lymphatics and glioblastoma: from mechanisms to therapies

Abstract

The recent discovery of meningeal lymphatic vessels (MLVs) has revolutionized our understanding of immune regulation within the central nervous system (CNS), overturning the long-standing view of the brain as an immune-privileged organ. Glioblastoma (GBM), the most aggressive primary brain tumor, remains therapeutically intractable due to its highly immunosuppressive microenvironment and poor response to conventional and immune-based therapies. Emerging evidence suggests that MLVs play a crucial role in CNS immune surveillance, cerebrospinal fluid drainage, and solute clearance, all of which are directly linked to GBM pathophysiology. This review is motivated by the urgent need to explore novel therapeutic strategies that address GBM's immune escape and therapeutic resistance. We comprehensively analyze the bidirectional interactions between MLVs and GBM, including their role in antigen transport, T cell activation, and tumor dissemination. Furthermore, we evaluate the therapeutic potential of targeting MLVs through lymphangiogenic stimulation or as alternative routes for immune modulation and drug delivery. These approaches offer promising avenues to enhance anti-tumor immunity and may pave the way for next-generation treatment paradigms in GBM.

Keywords: central nervous system; glioblastoma; glymphatic system; immune modulation; meningeal lymphatic vessels; tumor therapy.

Figure 1

Key factors contributing to the poor prognosis of GBM. Cranial hypertension, tumor heterogeneity, and immune escape are three interconnected factors that significantly contribute to the poor prognosis and therapeutic resistance of GBM. Cranial hypertension arises from tumor-induced space occupation and peritumoral edema, compounded by impaired cerebrospinal fluid outflow, which exacerbates intracranial pressure and disrupts normal brain function. Tumor heterogeneity, driven by glioblastoma stem cells and the tumor microenvironment, promotes invasive growth, metastasis, and treatment resistance through diverse cellular phenotypes and genetic variations. Immune escape mechanisms, including limited antigen presentation, T-cell infiltration barriers, and tumor-associated macrophage polarization toward the immunosuppressive M2 phenotype, further reduce the efficacy of immune-based therapies. Together, these interlinked factors disrupt immune regulation, impair waste clearance, and synergistically drive GBM progression and hinder therapeutic success.

Figure 2

Tumor stem cells can confer multiple heterogeneities to tumor cells. (A) As stem cells, GSCs act with the ability to self-renew and differentiate. It can also give other heterogeneous characteristics to other tumor cells, thus increasing the invasiveness of GBM, promoting proliferation and metastasis, and even developing immunosuppressive properties. (B) Heatmap of mass spectrometric analysis of secreted metabolites of 4 GSC cells versus paired non-stem tumor cells (NSTCs). Red indicates upregulated metabolites and blue indicates downregulated ones. (C) Immunofluorescence analysis of histamine and SOX2 in 6 GBM samples. Left: representative image; Scale bar, 20 μm. Right: percentage of histamine-positive cells in SOX2-positive cells compared to SOX2-negative cells by t-test in five randomly selected microscopic fields of view for each tumor. (D) Metabolic pathway of histamine. Metabolic enzymes are blue. HDC: histidine decarboxylase; HNMT: histamine N-methyltransferase. (E) Immunofluorescence analysis of HDC, SOX2, and CD133 in 6 GBM samples; Left: representative images; Scale bars, 20 μm. Right: comparison of the percentage of HDC-positive cells in SOX2- or CD133-positive versus SOX2- or CD133-negative cells by t-test in five randomly selected microscopic fields of view for each tumor. Reproduced with permission from Ref. . Copyright 2022, Elsevier Cell Stem Cell.

Figure 3

Inhibition of M2-type TAM activation suppresses GBM progression. (A) TAMs consist of two main sources: microglia and bone marrow-derived macrophages (BMDMs), the latter constituting over 90% of TAMs in GBM. TAMs can differentiate into either M1 or M2 phenotypes upon activation, with M1 TAMs exhibiting anti-tumor properties and M2 TAMs promoting immunosuppression and tumor progression. (B) Co-culture of U373MG GBM cells and microglia with miRNA EVs showed that miR-124 EV treatment significantly inhibited cell migration compared to miR-NC EV treatment. Immunostaining for F-actin (green) and nuclei (blue) revealed shorter maximum migration distances of both GBM and microglial cells toward the gel in the miR-124-treated group, indicating reduced migratory capacity. (C) In a microfluidic device, U373MG and microglia (embedded in collagen gels at a 2:1 ratio) were co-cultured for 2 days prior to the introduction of NK cells. Representative images of NK cells immunostained with PE-coupled CD45 (red) on day 2 and day 4 showed increased NK cell infiltration in the miR-124 EV-treated system compared to the miR-NC control. Reproduced with permission from Ref. . Available under a CC-BY 4.0 license. Copyright 2021, The author(s).

Figure 4

The discovery process of meningeal lymphatic vessels. The timeline traces key discoveries in MLVs research. Early hints emerged in the 1940s-1980s, including lymphatic-like structures in the rat dura mater (1966) and unique features of carotid artery epithelium (1987). The 1990s-2000s revealed meningeal mesothelial cell properties. Breakthroughs from 2004-2020 confirmed functional MLVs in mice and humans via MRI/confocal microscopy, with findings extending to the human optic nerve and potential glymphatic system connections. These milestones established MLVs as critical players in brain waste clearance and neuroimmunology, reshaping understanding of neurological diseases.

Figure 5

Anatomy and location of basal and dorsal MLVs. (A) Photoacoustic imaging reveals the stereoscopic morphology of mouse MLVs, demonstrating depth layering within a range of approximately 3.75 mm (scale bar: 1 mm). LYVE-1 staining further confirms the structural characteristics of MLVs in vitro. (B) Magnetic resonance imaging of coronal views of cerebral vessels and lymphatic vessels supports the presence of MLVs surrounding the transverse sinus and superior sagittal sinus. Fluorescence imaging further confirms their anatomical localization in the dura mater. Reproduced with permission from Ref. . Available under a CC-BY 4.0 license. Copyright 2024, Nature light: science & applications. (C) Schematic illustration of mouse meningeal lymphatic vessels and their anatomical course. These vessels accompany major veins, including those along the sigmoid sinus and transverse sinus, and extend toward the cervical lymph nodes.

Figure 6

Immunological potential of meningeal lymphatics under GBM states. This schematic illustrates the dual role of meningeal lymphatics in GBM pathology. In the tumor state, reduced CSF outflow and exacerbated cranial hypertension impair the immunological functions of meningeal lymphatics. These vessels, while serving as pathways for CSF drainage, also facilitate antigen presentation and immune activation by transporting tumor-derived antigens to deep cervical lymph nodes. However, the pathological state compromises their capacity for immune surveillance, potentially allowing immune evasion.

Figure 7

Current treatment strategies in GBM. Current glioma treatment presents a diversified and integrated model. Surgical operation remains the core approach, with intraoperative navigation and electrophysiological monitoring being utilized to expand the resection range while protecting functional areas. Postoperative standardized chemotherapy mainly uses temozolomide, combined with conformal intensity-modulated radiotherapy. However, issues such as drug resistance and long-term cognitive impairment remain prominent. Among the emerging new strategies in recent years, immunotherapy, such as immune checkpoint inhibitors and CAR-T therapy, is undergoing clinical trials, and targeted drugs for specific gene mutations (such as IDH1 inhibitors) have entered the application stage. Tumor treatment fields (TTFields) demonstrate unique advantages by interfering with cell division through low-frequency alternating electric fields. In the frontier field, nanoparticle drug delivery systems can cross the blood-brain barrier to deliver drugs specifically, while regulating the function of MLVs provides treatment from the aspects of metabolic clearance and immune microenvironment regulation.

Figure 8

Current exploration of MLVs in the treatment of GBM. (A) Left: representative meningeal LYVE-1 staining 1 week after subdural injection of GL261 or B16 cells into WT mice. Right: quantification of the diameter (n = 12) and percentage area (n = 10) of LYVE-1⁺ MLVs around the TS. Scale bars, 500 µm in wide-fields; 100 µm in insets. (B) Left: heat map of differentially expressed genes (Up, 219; Down, 100; power > 0.4). Right: gene sets involved in lymphatic remodeling, fluid drainage, as well as inflammatory and immunological responses as shown by the representative upregulated pathways in GL261 tumor-associated and B16 tumor-associated MLECs compared to control MLECs. Reproduced with permission from Ref. . Available under a CC-BY 4.0 license. Copyright 2020, Center for Excellence in Molecular Cell Science, CAS. (C) Distribution of bare ICG and NP-1 in the brain of glioblastoma-bearing mice 24 h post-s.c. or i.v. injection. Dotted white circles outline tumor sites. Reproduced with permission from Ref. . Copyright 2020, American Chemical Society.