Orphan nuclear receptor TLX promotes immunosuppression via its transcriptional activation of PD-L1 in glioma

Recent advances in biomimetic strategies for the immunotherapy of glioblastoma

Immunotherapy is regarded as one of the most promising approaches for treating tumors, with a multitude of immunotherapeutic thoughts currently under consideration for the lethal glioblastoma (GBM). However, issues with immunotherapeutic agents, such as limited in vivo stability, poor blood-brain barrier (BBB) penetration, insufficient GBM targeting, and represented monotherapy, have hindered the success of immunotherapeutic interventions. Moreover, even with the aid of conventional drug delivery systems, outcomes remain suboptimal. Biomimetic strategies seek to overcome these formidable drug delivery challenges by emulating nature's intelligent structures and functions. Leveraging the variety of biological structures and functions, biomimetic drug delivery systems afford a versatile platform with enhanced biocompatibility for the co-delivery of diverse immunotherapeutic agents. Moreover, their inherent capacity to traverse the BBB and home in on GBM holds promise for augmenting the efficacy of GBM immunotherapy. Thus, this review begins by revisiting the various thoughts and agents on immunotherapy for GBM. Then, the barriers to successful GBM immunotherapy are analyzed, and the corresponding biomimetic strategies are explored from the perspective of function and structure. Finally, the clinical translation's current state and prospects of biomimetic strategy are addressed. This review aspires to provide fresh perspectives on the advancement of immunotherapy for GBM.

Exploring the prognostic value of BRMS1 + microglia based on single-cell anoikis regulator patterns in the immunologic microenvironment of GBM

BACKGROUND

Anoikis is a specialized form of programmed cell death induced by the loss of cell adhesion to the extracellular matrix (ECM). Acquisition of anoikis resistance is a significant marker for cancer cell invasion, metastasis, therapy resistance, and recurrence. Although current research has identified multiple factors that regulate anoikis resistance, the pathological mechanisms of anoikis-mediated tumor microenvironment (TME) in glioblastoma (GBM) remain largely unexplored.

METHODS

Utilizing single-cell RNA sequencing (scRNA-seq) data and employing non-negative matrix factorization (NMF), we identified and characterized TME cell clusters with distinct anoikis-associated gene signatures. Prognostic and therapeutic response analyses were conducted using TCGA and CGGA datasets to assess the clinical significance of different TME cell clusters. The spatial relationship between BRMS1 + microglia and tumor cells was inferred from spatial transcriptome RNA sequencing (stRNA-seq) data. To simulate the tumor immune microenvironment, co-culture experiments were performed with microglia (HMC3) and GBM cells (U118/U251), and microglia were transfected with a BRMS1 overexpression lentivirus. Western blot or ELISA were used to detect BRMS1, M2 macrophage-specific markers, PI3K/AKT signaling proteins, and apoptosis-related proteins. The proliferation and apoptosis capabilities of tumor cells were evaluated using CCK-8, colony formation, and apoptosis assays, while the invasive and migratory abilities of tumor cells were assessed using Transwell assays.

RESULTS

NMF-based analysis successfully identified CD8 + T cell and microglia cell clusters with distinct gene signature characteristics. Trajectory analysis, cell communication, and gene regulatory network analyses collectively indicated that anoikis-mediated TME cell clusters can influence tumor cell development through various mechanisms. Notably, BRMS1 + AP-Mic exhibited an M2 macrophage phenotype and had significant cell communication with malignant cells. Moreover, high expression of BRMS1 + AP-Mic in TCGA and CGGA datasets was associated with poorer survival outcomes, indicating its detrimental impact on immunotherapy. Upregulation of BRMS1 in microglia may lead to M2 macrophage polarization, activate the PI3K/AKT signaling pathway through SPP1/CD44-mediated cell interactions, inhibit tumor cell apoptosis, and promote tumor proliferation and invasion.

CONCLUSION

This pioneering study used NMF-based analysis to reveal the important predictive value of anoikis-regulated TME in GBM for prognosis and immunotherapeutic response. BRMS1 + microglial cells provide a new perspective for a deeper understanding of the immunosuppressive microenvironment of GBM and could serve as a potential therapeutic target in the future.

ALOX5 contributes to glioma progression by promoting 5-HETE-mediated immunosuppressive M2 polarization and PD-L1 expression of glioma-associated microglia/macrophages

BACKGROUND

Oxylipin metabolism plays an essential role in glioma progression and immune modulation in the tumor microenvironment. Lipid metabolic reprogramming has been linked to macrophage remodeling, while the understanding of oxylipins and their catalyzed enzymes lipoxygenases in the regulation of glioma-associated microglia/macrophages (GAMs) remains largely unexplored.

METHODS

To explore the pathophysiological relevance of oxylipin in human glioma, we performed Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) analysis in human glioma and non-tumor brain tissues. To comprehensively investigate the role of arachidonate lipoxygenase 5 (ALOX5) in glioma, we performed in vivo bioluminescent imaging, immunofluorescence staining and flow cytometry analysis on tumors from orthotopic glioma-bearing mice. We developed an ALOX5-targeted nanobody, and tested its anti-glioma efficacy of combination therapy with α-programmed cell death protein-1 (PD-1).

RESULTS

In this study, we found that ALOX5 and its oxylipin 5-hydroxyeicosatetraenoic acid (5-HETE) are upregulated in glioma, accumulating programmed death-ligand 1 (PD-L1)+ M2-GAMs and orchestrating an immunosuppressive tumor microenvironment. Mechanistically, 5-HETE derived from ALOX5-overexpressing glioma cells, promotes GAMs migration, PD-L1 expression, and M2 polarization by facilitating nuclear translocation of nuclear factor erythroid 2-related factor 2. Additionally, a nanobody targeting ALOX5 is developed that markedly suppresses 5-HETE efflux from glioma cells, attenuates M2 polarization of GAMs, and consequently ameliorates glioma progression. Furthermore, the combination therapy of the ALOX5-targeted nanobody plus α-PD-1 exhibits superior anti-glioma efficacy.

CONCLUSIONS

Our findings reveal a pivotal role of the ALOX5/5-HETE axis in regulating GAMs and highlight the ALOX5-targeted nanobody as a potential therapeutic agent, which could potentiate immune checkpoint therapy for glioma.

IGFBP3 induces PD-L1 expression to promote glioblastoma immune evasion

BACKGROUND

Glioblastoma (GBM) characterized by immune escape is the most malignant primary brain tumors, which has strong immunosuppressive effect. Programmed death ligand-1 (PD-L1) is a recognized immunosuppressive member on the surface of tumor cells, and plays a crucial role in immune evasion of tumors. Actually, little is known about the regulation of PD-L1 expression in GBM. Insulin-like growth factor binding protein 3 (IGFBP3) is upregulated in GBM and is related to poor patient prognosis. However, it remains unclear whether IGFBP3 plays a role in the regulation of PD-L1 expression in GBM.

METHODS

The role of IGFBP3 in the glioma immune microenvironment was investigated using the CIBERSORT algorithm. The correlation between IGFBP3 and PD-L1 expression was analyzed using TCGA and CGGA databases. QRT-PCR, immunoblotting and RNA-seq were used to examine the regulatory effect of IGFBP3 on PD-L1 expression. Co-culture assay, cell counting kit (CCK-8), qRT-PCR, ELISA and flow cytometry were performed to explore the function of IGFBP3 in inducing immunosuppression. The biological role of IGFBP3 was verified using immunohistochemical, immunofluorescence and mice orthotopic tumor model.

RESULTS

In this study, we analyzed immune cells infiltration in gliomas and found that IGFBP3 may be associated with an immunosuppressive microenvironment. Then, by analyzing TCGA and CGGA databases, our results showed that IGFBP3 and PD-L1 expression were positively correlated in GBM patients, but not in LGG patients. In vitro experiments conducted on different GBM cell lines revealed that the overexpression of IGFBP3 led to an increase in PD-L1 expression, which was reversible upon knockdown IGFBP3. Mechanistically, IGFBP3 activated the JAK2/STAT3 signaling pathway, leading to an increase in PD-L1 expression. Additionally, co-culture experiments results showed IGFBP3 overexpression induced upregulation of PD-L1 expression promoted apoptosis in Jurkat cells, and this effect was blocked by IGFBP3 antibody and PDL-1 inhibitors. Importantly, in vivo experiments targeting IGFBP3 suppressed tumor growth and significantly prolonged the survival of mice.

CONCLUSIONS

This research demonstrated IGFBP3 is a novel regulator for PD-L1 expression in GBM, and identified a new mechanism by which IGFBP3 regulates immune evasion through PD-L1, suggesting that IGFBP3 may be a potential novel target for GBM therapy.

Interaction, immune infiltration characteristics and prognostic modeling of efferocytosis-related subtypes in glioblastoma

BACKGROUND

Efferocytosis is a biological process in which phagocytes remove apoptotic cells and vesicles from tissues. This process is initiated by the release of inflammatory mediators from apoptotic cells and plays a crucial role in resolving inflammation. The signals associated with efferocytosis have been found to regulate the inflammatory response and the tumor microenvironment (TME), which promotes the immune escape of tumor cells. However, the role of efferocytosis in glioblastoma multiforme (GBM) is not well understood and requires further investigation.

METHODS

In this study, we conducted a comprehensive analysis of 22 efferocytosis-related genes (ERGs) by searching for studies related to efferocytosis. Using bulk RNA-Seq and single-cell sequencing data, we analyzed the expression and mutational characteristics of these ERGs. By using an unsupervised clustering algorithm, we obtained ERG clusters from 549 GBM patients and evaluated the immune infiltration characteristics of each cluster. We then identified differential genes (DEGs) in the two ERG clusters and classified GBM patients into different gene clusters using univariate cox analysis and unsupervised clustering algorithms. Finally, we utilized the Boruta algorithm to screen for prognostic genes and reduce dimensionality, and the PCA algorithm was applied to create a novel efferocytosis-related scoring system.

RESULTS

Differential expression of ERGs in glioma cell lines and normal cells was analyzed by rt-PCR. Cell function experiments, on the other hand, validated TIMD4 as a tumor risk factor in GBM. We found that different ERG clusters and gene clusters have distinct prognostic and immune infiltration profiles. The ERG signature we developed provides insight into the tumor microenvironment of GBM. Patients with lower ERG scores have a better survival rate and a higher likelihood of benefiting from immunotherapy.

CONCLUSIONS

Our novel efferocytosis-related signature has the potential to be used in clinical practice for risk stratification of GBM patients and for selecting individuals who are likely to respond to immunotherapy. This can help clinicians design appropriate targeted therapies before initiating clinical treatment.

Combining single-cell sequencing and spatial transcriptome sequencing to identify exosome-related features of glioblastoma and constructing a prognostic model to identify BARD1 as a potential therapeutic target for GBM patients

Background

Glioblastoma (GBM) is a malignant primary brain tumor. This study focused on exploring the exosome-related features of glioblastoma to better understand its cellular composition and molecular characteristics.

Methods

Single-cell RNA sequencing (scRNA-seq) and spatial transcriptome RNA sequencing (stRNA-seq) were used to analyze the heterogeneity of glioblastomas. After data integration, cell clustering, and annotation, five algorithms were used to calculate scores for exosome-related genes(ERGs). Cell trajectory analysis and intercellular communication analysis were performed to explore exosome-related communication patterns. Spatial transcriptome sequencing data were analyzed to validate the findings. To further utilize exosome-related features to aid in clinical decision-making, a prognostic model was constructed using GBM's bulk RNA-seq.

Results

Different cell subpopulations were observed in GBM, with Monocytes/macrophages and malignant cells in tumor samples showing higher exosome-related scores. After identifying differentially expressed ERGs in malignant cells, pseudotime analysis revealed the cellular status of malignant cells during development. Intercellular communication analysis highlighted signaling pathways and ligand-receptor interactions. Spatial transcriptome sequencing confirmed the high expression of exosome-related gene features in the tumor core region. A prognostic model based on six ERGs was shown to be predictive of overall survival and immunotherapy outcome in GBM patients. Finally, based on the results of scRNA-seq and prognostic modeling as well as a series of cell function experiments, BARD1 was identified as a novel target for the treatment of GBM.

Conclusion

This study provides a comprehensive understanding of the exosome-related features of GBM in both scRNA-seq and stRNA-seq, with malignant cells with higher exosome-related scores exhibiting stronger communication with Monocytes/macrophages. In terms of spatial data, highly scored malignant cells were also concentrated in the tumor core region. In bulk RNA-seq, patients with a high exosome-related index exhibited an immunosuppressive microenvironment, which was accompanied by a worse prognosis as well as immunotherapy outcomes. Prognostic models constructed using ERGs are expected to be independent prognostic indicators for GBM patients, with potential implications for personalized treatment strategies for GBM. Knockdown of BARD1 in GBM cell lines reduces the invasive and value-added capacity of tumor cells, and thus BARD1-positively expressing malignant cells are a risk factor for GBM patients.

Regulation of PD-L1 Expression by Nuclear Receptors

The suppression of excessive immune responses is necessary to prevent injury to the body, but it also allows cancer cells to escape immune responses and proliferate. Programmed cell death 1 (PD-1) is a co-inhibitory molecule that is present on T cells and is the receptor for programmed cell death ligand 1 (PD-L1). The binding of PD-1 to PD-L1 leads to the inhibition of the T cell receptor signaling cascade. PD-L1 has been found to be expressed in many types of cancers, such as lung, ovarian, and breast cancer, as well as glioblastoma. Furthermore, PD-L1 mRNA is widely expressed in normal peripheral tissues including the heart, skeletal muscle, placenta, lungs, thymus, spleen, kidney, and liver. The expression of PD-L1 is upregulated by proinflammatory cytokines and growth factors via a number of transcription factors. In addition, various nuclear receptors, such as androgen receptor, estrogen receptor, peroxisome-proliferator-activated receptor γ, and retinoic-acid-related orphan receptor γ, also regulate the expression of PD-L1. This review will focus on the current knowledge of the regulation of PD-L1 expression by nuclear receptors.

Crosstalk between microglia and neural stem cells influences the relapse of glioblastoma in GBM immunological microenvironment

Interactions between immunocytes and Neural Stem Cells (NSCs) in glioblastoma multiforme still remains unclear. Here, microglial cells and NSCs in peri-tumoral tissue were analyzed via single-cell whole-transcriptome sequencing. Results showed that two clusters of putative NSCs (the EGFR⁺BCAN⁺ cell cluster, and the FABPT⁺H19⁺ cell cluster) exhibited immune-related functions. Two clusters of putative microglia (the XIST⁺PDK4⁺ and APOC1⁺CCL3⁺ cell clusters) exhibited the function of glial cell activation. The results of ligand receptor network analysis disclosed significant interactions between the APOC1⁺CCL3⁺ microglia and the NSCs. Correlation analysis on the overall survival (OS) and relapse-free survival (RFS) with 102 potential molecular targets in the TCGA database showed that a much larger number of molecules were correlated with RFS than with OS (34.31% vs. 8.82%), nine of them were validated in clinical specimens. In conclusion, crosstalk between APOC1⁺CCL3⁺ microglia and multiple molecule-labeled NSCs distal to the tumor core play certain roles on the recurrence of GBM.

A Novel Tumor-Promoting Role for Nuclear Factor IX in Glioblastoma Is Mediated through Transcriptional Activation of GINS1

Our previous study illustrated that nuclear factor IX (NFIX) promotes glioblastoma (GBM) progression by inducing migration and proliferation of GBM cells. However, the underlying mechanism of how NFIX regulates GBM cell proliferation remains obscure. In this study, we uncovered that Go-Ichi-Ni-San 1 (GINS1) is upregulated and positively correlated with NFIX in human GBM specimen. NFIX silencing downregulates the expression of GINS1, which is pivotal for cell-cycle progression and proliferation of GBM cells. Replenishment of GINS1 largely rescues the NFIX-null effect on GBM cell proliferation. Mechanistic investigation revealed that NFIX transcriptionally actives GINS1 expression by directly binding to promoter region (-1779 to -1793bp) of the GINS1 gene. Furthermore, knockdown of NFIX sensitizes GBM cells to DNA damage-inducing agents including doxorubicin and temozolomide, in a GINS1-dependent manner.

IMPLICATIONS

Our study highlights that targeting NFIX-GINS1 axis could be a novel and potential therapeutic approach for GBM treatment.

Safety and antitumor activity of GD2-Specific 4SCAR-T cells in patients with glioblastoma

BACKGROUND

This study aimed to validate whether infusion of GD2-specific fourth-generation safety-designed chimeric antigen receptor (4SCAR)-T cells is safe and whether CAR-T cells exert anti-glioblastoma (GBM) activity.

METHODS

A total of eight patients with GD2-positive GBM were enrolled and infused with autologous GD2-specific 4SCAR-T cells, either through intravenous administration alone or intravenous combined with intracavitary administration.

RESULTS

4SCAR-T cells expanded for 1-3 weeks and persisted at a low frequency in peripheral blood. Of the eight evaluable patients, four showed a partial response for 3 to 24 months, three had progressive disease for 6 to 23 months, and one had stable disease for 4 months after infusion. For the entire cohort, the median overall survival was 10 months from the infusion. GD2 antigen loss and infiltrated T cells were observed in the tumor resected after infusion.

CONCLUSION

Both single and combined infusions of GD2-specific 4SCAR-T cells in targeting GBM were safe and well tolerated, with no severe adverse events. In addition, GD2-specific 4SCAR-T cells partially mediate antigen loss and activate immune responses in the tumor microenvironment. Validation of our findings in a larger prospective trial is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03170141 . Registered 30 May 2017.

INPP4B inhibits glioma cell proliferation and immune escape via inhibition of the PI3K/AKT signaling pathway

INPP4B (Inositol polyphosphate 4-phosphatase type II) has been regarded as a suppressor of several human tumors, but its biological function, expression, and clinical significance in glioma tissues and cell lines are unclear. Notably, whether INPP4B participates in immune escape of glioma deserves urgent attention. Here, we confirmed that INPP4B expression is often downregulated in low- and high-grade human glioma tissues, in tissues from an orthotopic mouse model of brain glioma and in glioma cells. We found that INPP4B overexpression restrained the proliferation, migration, apoptosis resistance, PD-L1 expression, and T cell suppression by glioma cells, whereas INPP4B silencing had the opposite effects. Moreover, we showed that INPP4B inhibited glioma cell proliferation, migration, and PD-L1 expression by downregulating PI3K/AKT signaling. Collectively, these data support that INPP4B may inhibit glioma progression, and particularly, glioma’s immune escape. Thus, INPP4B may constitute a valuable target for glioma treatment.

Tripartite motif-containing 25 facilitates immunosuppression and inhibits apoptosis of glioma via activating NF-κB

As a crucial tumor type of the central nervous system, gliomas are characterized by a dismal prognosis. Tripartite motif-containing 25 (TRIM25), an essential E3 ubiquitin ligase, participates in various biological processes. This study sought to demonstrate its functional role in gliomas. Data obtained from publicly available databases - including The Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA), and the Repository for Molecular Brain Neoplasia Data (REMBRANDT) - were employed. TRIM25 expression pattern and its association with different clinical characteristics were analyzed. Kaplan-Meier analysis was utilized to compare different TRIM25 expressions with glioma patients' survival. Subsequently, we performed bioinformatic analyses to investigate the biological functions of TRIM25, which were further validated by in vitro experiments, CIBERSORT algorithm, and ESTIMATE evaluation. TRIM25 expression was upregulated in glioma patients and can predict an unfavorable prognosis. Bioinformatic results indicated the involvement of TRIM25 in apoptosis and immune regulation. TRIM25 was associated with programmed death-ligand 1 (PD-L1) related and macrophage-induced immune suppression in gliomas. Meanwhile, silencing TRIM25 promoted apoptosis in glioma cells, which is attributed to its regulation of NF-κB. Therefore, TRIM25 contributed to the glioma malignant progression and suppressive immune microenvironments via NF-κB activation, which may play a therapeutic role in gliomas.

IFN-γ induces PD-L1 through p38/JNK/ERK signaling pathways and counteracts the tumor promoting effect mediated by PD-L1 in Glioblastoma

Glioblastoma is the most malignant primary glioma. Conventional treatment methods that include surgery, radiotherapy, and chemotherapy have a limited curative effect on the tumor. With the deepening of molecular biology research, molecular targeted therapy has opened a new era of tumor therapy. Programmed death ligand 1 (PD-L1) has been proved to play a pivotal role in the tumor immune evasion process. Previous studies have confirmed the specific expression of PD-L1 in glioblastoma tissues and cells, but there are few studies on inflammation regulating PD-L1 in glioblastoma. In this study, real-time PCR, flow cytometry, and western blot were applied to detect PD-L1 in glioblastoma cells. Short hairpin RNA was used to knock down PD-L1 in glioblastoma cells. Cell counting kit-8 experiment and wound-healing assay were used to detect the proliferation and migration of glioblastoma cells. Here we demonstrated that PD-L1 was overexpressed in glioblastoma cells, and interferon-gamma (IFN-γ) induces PD-L1 in glioblastoma cells via activating p38/JNK/ERK signaling pathways. To summarize, PD-L1 promotes the occurrence and development of glioblastoma. IFN-γ counteracts the tumor-promoting effects mediated by PD-L1 in glioblastoma. IFN-γ regulates PD-L1 through multiple signaling pathways, but the total effect of IFN-γ-mediated inflammatory signals still need to be further explored in glioblastoma. PD-L1 enhances the proliferation and migration of glioblastoma cells by regulating CDK4, CDK6, MMP-2, and vimentin molecules. Most importantly, targeting PD-L1 can be applied in the treatment of glioblastoma. We speculate that IFN-γ may affect glioblastoma through other pathways, and we will continue to further explore the mechanisms in the future.

Large-Scale Single-Cell and Bulk Sequencing Analyses Reveal the Prognostic Value and Immune Aspects of CD147 in Pan-Cancer

CD147 plays an important role in promoting tumor proliferation and inhibiting cancer cell apoptosis in the tumor microenvironment. However, the mechanisms by which CD147 is involved in tumorigenesis remains unclear. This study systematically analyzed the prognostic value and immune characteristics of CD147 in 31 cancer types. The expression levels and mutant landscapes of CD147 in pan-cancer were explored. The Kaplan-Meier (KM) analysis was applied to analyze the prognostic value of CD147. The immune characteristics of CD147 in the tumor microenvironment were evaluated via TIMER 2.0 and R package (immunedeconv). We also explored the expression of CD147 on tumor cells and stromal cells through Gene Set Variation Analysis and single-cell sequencing analysis. The co-expression of CD147 and macrophage markers CD68 and CD163 in pan-cancer was detected using multiplex immunofluorescence staining on tissue microarrays. CD147 was found to be overexpressed in almost all cancer types, which was related to poor outcome. CD147 expression exhibited a strong association with immune infiltrates, immune checkpoint molecules, and neoantigen levels in the tumor microenvironment. In addition, CD147 was expressed on various cell types in the tumor microenvironment, including tumor cells, macrophages, T cells, monocytes, fibroblasts, etc. Furthermore, multiplex immunofluorescence revealed the co-expression pattern of CD147 and macrophage markers CD68 and CD163 in many tumor types. Finally, the immunotherapy response and sensitive small molecule drugs based on CD147 expression were predicted. In sum, CD147 has a significant relationship with the clinical outcome and immune infiltrates in multiple cancer types. Inhibiting the CD147-dependent signaling pathways might be a promising therapeutic strategy for tumor immunotherapy.

TLX, an Orphan Nuclear Receptor With Emerging Roles in Physiology and Disease

TLX (NR2E1), an orphan member of the nuclear receptor superfamily, is a transcription factor that has been described to be generally repressive in nature. It has been implicated in several aspects of physiology and disease. TLX is best known for its ability to regulate the proliferation of neural stem cells and retinal progenitor cells. Dysregulation, overexpression, or loss of TLX expression has been characterized in numerous studies focused on a diverse range of pathological conditions, including abnormal brain development, psychiatric disorders, retinopathies, metabolic disease, and malignant neoplasm. Despite the lack of an identified endogenous ligand, several studies have described putative synthetic and natural TLX ligands, suggesting that this receptor may serve as a therapeutic target. Therefore, this article aims to briefly review what is known about TLX structure and function in normal physiology, and provide an overview of TLX in regard to pathological conditions. Particular emphasis is placed on TLX and cancer, and the potential utility of this receptor as a therapeutic target.