Single-Cell Atlas Reveals Complexity of the Immunosuppressive Microenvironment of Initial and Recurrent Glioblastoma

Deciphering the tumor immune microenvironment from a multidimensional omics perspective: insight into next-generation CAR-T cell immunotherapy and beyond

Tumor immune microenvironment (TIME) consists of intra-tumor immunological components and plays a significant role in tumor initiation, progression, metastasis, and response to therapy. Chimeric antigen receptor (CAR)-T cell immunotherapy has revolutionized the cancer treatment paradigm. Although CAR-T cell immunotherapy has emerged as a successful treatment for hematologic malignancies, it remains a conundrum for solid tumors. The heterogeneity of TIME is responsible for poor outcomes in CAR-T cell immunotherapy against solid tumors. The advancement of highly sophisticated technology enhances our exploration in TIME from a multi-omics perspective. In the era of machine learning, multi-omics studies could reveal the characteristics of TIME and its immune resistance mechanism. Therefore, the clinical efficacy of CAR-T cell immunotherapy in solid tumors could be further improved with strategies that target unfavorable conditions in TIME. Herein, this review seeks to investigate the factors influencing TIME formation and propose strategies for improving the effectiveness of CAR-T cell immunotherapy through a multi-omics perspective, with the ultimate goal of developing personalized therapeutic approaches.

Recurrent Glioblastoma-Molecular Underpinnings and Evolving Treatment Paradigms

Glioblastoma is the most common and lethal central nervous system malignancy with a median survival after progression of only 6-9 months. Major biochemical mechanisms implicated in glioblastoma recurrence include aberrant molecular pathways, a recurrence-inducing tumor microenvironment, and epigenetic modifications. Contemporary standard-of-care (surgery, radiation, chemotherapy, and tumor treating fields) helps to control the primary tumor but rarely prevents relapse. Cytoreductive treatment such as surgery has shown benefits in recurrent glioblastoma; however, its use remains controversial. Several innovative treatments are emerging for recurrent glioblastoma, including checkpoint inhibitors, chimeric antigen receptor T cell therapy, oncolytic virotherapy, nanoparticle delivery, laser interstitial thermal therapy, and photodynamic therapy. This review seeks to provide readers with an overview of (1) recent discoveries in the molecular basis of recurrence; (2) the role of surgery in treating recurrence; and (3) novel treatment paradigms emerging for recurrent glioblastoma.

Upregulation of HLA-II related to LAG-3+CD4+ T cell infiltration is associated with patient outcome in human glioblastoma

Glioblastoma (GBM) is the most common malignant diffuse glioma of the brain. Although immunotherapy with immune checkpoint inhibitors (ICIs), such as programmed cell death protein (PD)-1/PD ligand-1 inhibitors, has revolutionized the treatment of several cancers, the clinical benefit in GBM patients has been limited. Lymphocyte-activation gene 3 (LAG-3) binding to human leukocyte antigen-II (HLA-II) plays an essential role in triggering CD4+ T cell exhaustion and could interfere with the efficiency of anti-PD-1 treatment; however, the value of LAG-3-HLA-II interactions in ICI immunotherapy for GBM patients has not yet been analyzed. Therefore, we aimed to investigate the expression and regulation of HLA-II in human GBM samples and the correlation with LAG-3+CD4+ T cell infiltration. Human leukocyte antigen-II was highly expressed in GBM and correlated with increased LAG-3+CD4+ T cell infiltration in the stroma. Additionally, HLA-IIHighLAG-3High was associated with worse patient survival. Increased interleukin-10 (IL-10) expression was observed in GBM, which was correlated with high levels of HLA-II and LAG-3+ T cell infiltration in stroma. HLA-IIHighIL-10High GBM associated with LAG-3+ T cells infiltration synergistically showed shorter overall survival in patients. Combined anti-LAG-3 and anti-IL-10 treatment inhibited tumor growth in a mouse brain GL261 tumor model. In vitro, CD68+ macrophages upregulated HLA-II expression in GBM cells through tumor necrosis factor-α (TNF-α). Blocking TNF-α-dependent inflammation inhibited tumor growth in a mouse GBM model. In summary, T cell-tumor cell interactions, such as LAG-3-HLA-II, could confer an immunosuppressive environment in human GBM, leading to poor prognosis in patients. Therefore, targeting the LAG-3-HLA-II interaction could be beneficial in ICI immunotherapy to improve the clinical outcome of GBM patients.

Deciphering Glioblastoma: Fundamental and Novel Insights into the Biology and Therapeutic Strategies of Gliomas

Gliomas constitute a diverse and complex array of tumors within the central nervous system (CNS), characterized by a wide range of prognostic outcomes and responses to therapeutic interventions. This literature review endeavors to conduct a thorough investigation of gliomas, with a particular emphasis on glioblastoma (GBM), beginning with their classification and epidemiological characteristics, evaluating their relative importance within the CNS tumor spectrum. We examine the immunological context of gliomas, unveiling the intricate immune environment and its ramifications for disease progression and therapeutic strategies. Moreover, we accentuate critical developments in understanding tumor behavior, focusing on recent research breakthroughs in treatment responses and the elucidation of cellular signaling pathways. Analyzing the most novel transcriptomic studies, we investigate the variations in gene expression patterns in glioma cells, assessing the prognostic and therapeutic implications of these genetic alterations. Furthermore, the role of epigenetic modifications in the pathogenesis of gliomas is underscored, suggesting that such changes are fundamental to tumor evolution and possible therapeutic advancements. In the end, this comparative oncological analysis situates GBM within the wider context of neoplasms, delineating both distinct and shared characteristics with other types of tumors.

Antitumor Effects of Intravenous Natural Killer Cell Infusion in an Orthotopic Glioblastoma Xenograft Murine Model and Gene Expression Profile Analysis

Despite standard multimodality treatment, containing maximum safety resection, temozolomide, radiotherapy, and a tumor-treating field, patients with glioblastoma (GBM) present with a dismal prognosis. Natural killer cell (NKC)-based immunotherapy would play a critical role in GBM treatment. We have previously reported highly activated and ex vivo expanded NK cells derived from human peripheral blood, which exhibited anti-tumor effect against GBM cells. Here, we performed preclinical evaluation of the NK cells using an in vivo orthotopic xenograft model, the U87MG cell-derived brain tumor in NOD/Shi-scid, IL-2RɤKO (NOG) mouse. In the orthotopic xenograft model, the retro-orbital venous injection of NK cells prolonged overall survival of the NOG mouse, indirectly indicating the growth-inhibition effect of NK cells. In addition, we comprehensively summarized the differentially expressed genes, especially focusing on the expression of the NKC-activating receptors' ligands, inhibitory receptors' ligands, chemokines, and chemokine receptors, between murine brain tumor treated with NKCs and with no agents, by using microarray. Furthermore, we also performed differentially expressed gene analysis between an internal and external brain tumor in the orthotopic xenograft model. Our findings could provide pivotal information for the NK-cell-based immunotherapy for patients with GBM.

The need for paradigm shift: prognostic significance and implications of standard therapy-related systemic immunosuppression in glioblastoma for immunotherapy and oncolytic virotherapy

Despite significant advances in our knowledge regarding the genetics and molecular biology of gliomas over the past two decades and hundreds of clinical trials, no effective therapeutic approach has been identified for adult patients with newly diagnosed glioblastoma, and overall survival remains dismal. Great hopes are now placed on combination immunotherapy. In clinical trials, immunotherapeutics are generally tested after standard therapy (radiation, temozolomide, and steroid dexamethasone) or concurrently with temozolomide and/or steroids. Only a minor subset of patients with progressive/recurrent glioblastoma have benefited from immunotherapies. In this review, we comprehensively discuss standard therapy-related systemic immunosuppression and lymphopenia, their prognostic significance, and the implications for immunotherapy/oncolytic virotherapy. The effectiveness of immunotherapy and oncolytic virotherapy (viro-immunotherapy) critically depends on the activity of the host immune cells. The absolute counts, ratios, and functional states of different circulating and tumor-infiltrating immune cell subsets determine the net immune fitness of patients with cancer and may have various effects on tumor progression, therapeutic response, and survival outcomes. Although different immunosuppressive mechanisms operate in patients with glioblastoma/gliomas at presentation, the immunological competence of patients may be significantly compromised by standard therapy, exacerbating tumor-related systemic immunosuppression. Standard therapy affects diverse immune cell subsets, including dendritic, CD4+, CD8+, natural killer (NK), NKT, macrophage, neutrophil, and myeloid-derived suppressor cell (MDSC). Systemic immunosuppression and lymphopenia limit the immune system's ability to target glioblastoma. Changes in the standard therapy are required to increase the success of immunotherapies. Steroid use, high neutrophil-to-lymphocyte ratio (NLR), and low post-treatment total lymphocyte count (TLC) are significant prognostic factors for shorter survival in patients with glioblastoma in retrospective studies; however, these clinically relevant variables are rarely reported and correlated with response and survival in immunotherapy studies (e.g., immune checkpoint inhibitors, vaccines, and oncolytic viruses). Our analysis should help in the development of a more rational clinical trial design and decision-making regarding the treatment to potentially improve the efficacy of immunotherapy or oncolytic virotherapy.

The landscape of PBMCs in AQP4-IgG seropositive NMOSD and MOGAD, assessed by high dimensional mass cytometry

OBJECTIVES

Data on peripheral blood mononuclear cells (PBMCs) characteristics of aquaporin-4 (AQP4)-IgG seropositive neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) are lacking. In this study, we describe the whole PBMCs landscape of the above diseases using cytometry by time-of-flight mass spectrometry (CyTOF).

METHODS

The immune cell populations were phenotyped and clustered using CyTOF isolated from 27 AQP4-IgG seropositive NMOSD, 11 MOGAD patients, and 15 healthy individuals. RNA sequencing was employed to identify critical genes. Fluorescence cytometry and qPCR analysis were applied to further validate the algorithm-based results that were obtained.

RESULTS

We identified an increased population of CD11b+ mononuclear phagocytes (MNPs) in patients with high expression of CCR2, whose abundance may correlate with brain inflammatory infiltration. Using fluorescence cytometry, we confirmed the CCR2+ monocyte subsets in a second cohort of patients. Moreover, there was a wavering of B, CD4+ T, and NKT cells between AQP4-IgG seropositive NMOSD and MOGAD.

CONCLUSIONS

Our findings describe the whole landscape of PBMCs in two similar demyelinated diseases and suggest that, besides MNPs, T, NK and B, cells were all involved in the pathogenesis. The identified cell population may be used as a predictor for monitoring disease development or treatment responses.

Current state of immune checkpoints therapy for glioblastoma

Glioblastoma (GBM), one of the most aggressive forms of brain cancer, has limited treatment options. Recent years have witnessed the remarkable success of checkpoint inhibitor immunotherapy across various cancer types. Against this backdrop, several clinical trials investigating checkpoint inhibitors for GBM are underway in multiple countries. Furthermore, the integration of immunotherapy with traditional treatment approaches is now emerging as a highly promising strategy. This review summarizes the latest advancements in checkpoint inhibitor immunotherapy for GBM treatment. We provide a concise yet comprehensive overview of current GBM immunotherapy options. Additionally, this review underscores combination strategies and potential biomarkers for predicting response and resistance in GBM immunotherapies.

Glioblastoma may evade immune surveillance through primary cilia-dependent signaling in an IL-6 dependent manner

Glioblastoma is the most common, malignant primary brain tumor in adults and remains universally fatal. While immunotherapy has vastly improved the treatment of several solid cancers, efficacy in glioblastoma is limited. These challenges are due in part to the propensity of glioblastoma to recruit tumor-suppressive immune cells, which act in conjunction with tumor cells to create a pro-tumor immune microenvironment through secretion of several soluble factors. Glioblastoma-derived EVs induce myeloid-derived suppressor cells (MDSCs) and non-classical monocytes (NCMs) from myeloid precursors leading to systemic and local immunosuppression. This process is mediated by IL-6 which contributes to the recruitment of tumor-associated macrophages of the M2 immunosuppressive subtype, which in turn, upregulates anti-inflammatory cytokines including IL-10 and TGF-β. Primary cilia are highly conserved organelles involved in signal transduction and play critical roles in glioblastoma proliferation, invasion, angiogenesis, and chemoradiation resistance. In this perspectives article, we provide preliminary evidence that primary cilia regulate intracellular release of IL-6. This ties primary cilia mechanistically to tumor-mediated immunosuppression in glioblastomas and potentially, in additional neoplasms which have a shared mechanism for cancer-mediated immunosuppression. We propose potentially testable hypotheses of the cellular mechanisms behind this finding.

Integrative analysis of multi-omics data reveals a pseudouridine-related lncRNA signature for prediction of glioma prognosis and chemoradiotherapy sensitivity

BACKGROUND

Glioblastoma is the most common type of glioma with a high incidence and poor prognosis, and effective medical treatment remains challenging. Pseudouridine (Ψ) is the first post-transcriptional modification discovered and one of the most abundant modifications to RNA. However, the prognostic value of Ψ-related lncRNAs (ΨrLs) for glioma patients has never been systematically evaluated. This study aims to construct a risk model based on ΨrLs signature and to validate the predictive efficiency of the model.

METHOD

Transcriptomic data, genomic data, and relevant clinical data of glioma patients were extracted from the Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA). ΨrLs with significant correlation with Ψ-related genes were identified, and univariate Cox regression, least absolute shrinkage and selection operator (LASSO) regression, and multivariate Cox regression were used to further select biomarkers and construct a ΨrLs signature risk model. Then, the expression of lncRNAs of ΨrLs signature in multiple glioma cell lines was detected by qPCR. Further, ROC analysis, stratification analysis, correlation analysis, survival analysis, nomogram, enrichment analysis, immune infiltration analysis, chemoradiotherapy sensitivity analysis, somatic mutation, and recurrent copy number variation (CNV) analysis were used to validate the predictive efficiency of ΨrLs signature in TCGA and CGGA datasets.

RESULTS

A four-lncRNA ΨrLs signature (DNAJC27-AS1, GDNF-AS1, ZBTB20-AS4, and DNMBP-AS1) risk model was constructed. By ROC analysis, stratified analysis, correlation analysis, survival analysis, and nomogram, the signature showed satisfactory predictive efficiency. Functional enrichment analysis revealed the differences in immune-related biological processes between high- and low-risk groups. Immune infiltration analysis showed that the high-risk group had lower tumor purity and higher stromal, immune and ESTIMATE scores. Mitoxantrone was identified as effective drug for low-risk group of glioma patients. Key genes in glioma development, including IDH1, EGFR, PTEN, etc., were differentially mutated between risk groups. The main recurrent CNVs in low-risk groups were 19q13.42 deletion and 7q34 amplification; 10q23.31 deletion and 12q14.1 in the high-risk group.

CONCLUSIONS

Our study identified a four-lncRNA ΨrLs signature that effectively predicts the prognosis of glioma patients and may serve as a diagnostic tool. Risk scores of glioma patients generated by the signature is associated with immune-related biological processes and chemoradiotherapy sensitivity. These findings may inform the development of more targeted and effective therapies for glioma patients.

Spatial transcriptomics in glioblastoma: is knowing the right zip code the key to the next therapeutic breakthrough?

Spatial transcriptomics, the technology of visualizing cellular gene expression landscape in a cells native tissue location, has emerged as a powerful tool that allows us to address scientific questions that were elusive just a few years ago. This technological advance is a decisive jump in the technological evolution that is revolutionizing studies of tissue structure and function in health and disease through the introduction of an entirely new dimension of data, spatial context. Perhaps the organ within the body that relies most on spatial organization is the brain. The central nervous system's complex microenvironmental and spatial architecture is tightly regulated during development, is maintained in health, and is detrimental when disturbed by pathologies. This inherent spatial complexity of the central nervous system makes it an exciting organ to study using spatial transcriptomics for pathologies primarily affecting the brain, of which Glioblastoma is one of the worst. Glioblastoma is a hyper-aggressive, incurable, neoplasm and has been hypothesized to not only integrate into the spatial architecture of the surrounding brain, but also possess an architecture of its own that might be actively remodeling the surrounding brain. In this review we will examine the current landscape of spatial transcriptomics in glioblastoma, outline novel findings emerging from the rising use of spatial transcriptomics, and discuss future directions and ultimate clinical/translational avenues.

Drug resistance in glioblastoma: from chemo- to immunotherapy

As the most common and aggressive type of primary brain tumor in adults, glioblastoma is estimated to end over 10,000 lives each year in the United States alone. Stand treatment for glioblastoma, including surgery followed by radiotherapy and chemotherapy (i.e., Temozolomide), has been largely unchanged since early 2000. Cancer immunotherapy has significantly shifted the paradigm of cancer management in the past decade with various degrees of success in treating many hematopoietic cancers and some solid tumors, such as melanoma and non-small cell lung cancer (NSCLC). However, little progress has been made in the field of neuro-oncology, especially in the application of immunotherapy to glioblastoma treatment. In this review, we attempted to summarize the common drug resistance mechanisms in glioblastoma from Temozolomide to immunotherapy. Our intent is not to repeat the well-known difficulty in the area of neuro-oncology, such as the blood-brain barrier, but to provide some fresh insights into the molecular mechanisms responsible for resistance by summarizing some of the most recent literature. Through this review, we also hope to share some new ideas for improving the immunotherapy outcome of glioblastoma treatment.

Dysregulation of inflammasome activation in glioma

Gliomas are the most common brain tumors characterized by complicated heterogeneity. The genetic, molecular, and histological pathology of gliomas is characterized by high neuro-inflammation. The inflammatory microenvironment in the central nervous system (CNS) has been closely linked with inflammasomes that control the inflammatory response and coordinate innate host defenses. Dysregulation of the inflammasome causes an abnormal inflammatory response, leading to carcinogenesis in glioma. Because of the clinical importance of the various physiological properties of the inflammasome in glioma, the inflammasome has been suggested as a promising treatment target for glioma management. Here, we summarize the current knowledge on the contribution of the inflammasomes in glioma and therapeutic insights. Video Abstract.

Untangling the web of glioblastoma treatment resistance using a multi-omic and multidisciplinary approach

Glioblastoma (GBM), the most common human brain tumor, has been notoriously resistant to treatment. As a result, the dismal overall survival of GBM patients has not changed over the past three decades. GBM has been stubbornly resistant to checkpoint inhibitor immunotherapies, which have been remarkably effective in the treatment of other tumors. It is clear that GBM resistance to therapy is multifactorial. Although therapeutic transport into brain tumors is inhibited by the blood brain barrier, there is evolving evidence that overcoming this barrier is not the predominant factor. GBMs generally have a low mutation burden, exist in an immunosuppressed environment and they are inherently resistant to immune stimulation, all of which contribute to treatment resistance. In this review, we evaluate the contribution of multi-omic approaches (genomic and metabolomic) along with analyzing immune cell populations and tumor biophysical characteristics to better understand and overcome GBM multifactorial resistance to treatment.

The Development of Immunotherapy for the Treatment of Recurrent Glioblastoma

Recurrent glioblastoma (rGBM) is a highly aggressive form of brain cancer that poses a significant challenge for treatment in neuro-oncology, and the survival status of patients after relapse usually means rapid deterioration, thus becoming the leading cause of death among patients. In recent years, immunotherapy has emerged as a promising strategy for the treatment of recurrent glioblastoma by stimulating the body's immune system to recognize and attack cancer cells, which could be used in combination with other treatments such as surgery, radiation, and chemotherapy to improve outcomes for patients with recurrent glioblastoma. This therapy combines several key methods such as the use of monoclonal antibodies, chimeric antigen receptor T cell (CAR-T) therapy, checkpoint inhibitors, oncolytic viral therapy cancer vaccines, and combination strategies. In this review, we mainly document the latest immunotherapies for the treatment of glioblastoma and especially focus on rGBM.

Clinical Applications of Immunotherapy for Recurrent Glioblastoma in Adults

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. Despite standard therapies, including resection and chemoradiation, recurrence is virtually inevitable. Current treatment for recurrent glioblastoma (rGBM) is rapidly evolving, and emerging therapies aimed at targeting primary GBM are often first tested in rGBM to demonstrate safety and feasibility, which, in recent years, has primarily been in the form of immunotherapy. The purpose of this review is to highlight progress in clinical trials of immunotherapy for rGBM, including immune checkpoint blockade, oncolytic virotherapy, chimeric antigen receptor (CAR) T-cell therapy, cancer vaccine and immunotoxins. Three independent reviewers covered literature, published between the years 2000 and 2022, in various online databases. In general, the efficacy of immunotherapy in rGBM remains uncertain, and is limited to subsets/small cohorts of patients, despite demonstrating feasibility in early-stage clinical trials. However, considerable progress has been made in understanding the mechanisms that may preclude rGBM patients from responding to immunotherapy, as well as in developing new approaches/combination strategies that may inspire optimism for the utility of immunotherapy in this devastating disease. Continued trials are necessary to further assess the best therapeutic avenues and ascertain which treatments might benefit each patient individually.

Macrophage's role in solid tumors: two edges of a sword

The tumor microenvironment is overwhelmingly dictated by macrophages, intimately affiliated with tumors, exercising pivotal roles in multiple processes, including angiogenesis, extracellular matrix reconfiguration, cellular proliferation, metastasis, and immunosuppression. They further exhibit resilience to chemotherapy and immunotherapy via meticulous checkpoint blockades. When appropriately stimulated, macrophages can morph into a potent bidirectional component of the immune system, engulfing malignant cells and annihilating them with cytotoxic substances, thus rendering them intriguing candidates for therapeutic targets. As myelomonocytic cells relentlessly amass within tumor tissues, macrophages rise as prime contenders for cell therapy upon the development of chimeric antigen receptor effector cells. Given the significant incidence of macrophage infiltration correlated with an unfavorable prognosis and heightened resistance to chemotherapy in solid tumors, we delve into the intricate role of macrophages in cancer propagation and their promising potential in confronting four formidable cancer variants-namely, melanoma, colon, glioma, and breast cancers.

NR2F6, a new immune checkpoint that acts as a potential biomarker of immunosuppression and contributes to poor clinical outcome in human glioma

Intoroduction

Nuclear receptor subfamily 2 group F member 6 (NR2F6) is a promising checkpoint target for cancer immunotherapy. However, there has been no investigation of NR2F6 in glioma. Our study systematically explored the clinical characteristics and biological functions of NR2F6 in gliomas.

Methods

We extracted RNA sequencing (RNA-seq) data of 663 glioma samples from The Cancer Genome Atlas (TCGA) as the training cohort and 325 samples from the Chinese Glioma Genome Atlas (CGGA) as the validation cohort. We also confirmed the NR2F6 gene expression feature in our own cohort of 60 glioma patients. R language and GraphPad Prism softwares were mainly used for statistical analysis and graphical work.

Results

We found that NR2F6 was significantly related to high tumor aggressiveness and poor outcomes for glioma patients. Functional enrichment analysis demonstrated that NR2F6 was associated with many biological processes that are related to glioma progression, such as angiogenesis, and with multiple immune-related functions. Moreover, NR2F6 was found to be significantly correlated with stromal and immune infiltration in gliomas. Subsequent analysis based on Gliomas single-cell sequencing datasets showed that NR2F6 was expressed in immune cells, tumor cells, and stromal cells. Mechanistically, results suggested that NR2F6 might act as a potential immunosuppression-mediated molecule in the glioma microenvironment through multiple ways, such as the recruitment of immunosuppressive cells, secretion of immunosuppressive cytokines, M2 polarization of macrophages, in addition to combining with other immune checkpoint inhibitors.

Conclusion

Our findings indicated that intracellular targeting of NR2F6 in both immune cells and tumor cells, as well as stromal cells, may represent a promising immunotherapeutic strategy for glioma. Stromal cells, may represent a promising immunotherapeutic strategy for glioma.

MiR-146a-5p deficiency in extracellular vesicles of glioma-associated macrophages promotes epithelial-mesenchymal transition through the NF-κB signaling pathway

Glioma-associated macrophages (GAMs) are pivotal chains in the tumor immune microenvironment (TIME). GAMs mostly display M2-like phenotypes with anti-inflammatory features related to the malignancy and progression of cancers. Extracellular vesicles derived from immunosuppressive GAMs (M2-EVs), the essential components of the TIME, greatly impact the malignant behavior of GBM cells. M1- or M2-EVs were isolated in vitro, and human GBM cell invasion and migration were reinforced under M2-EV treatment. Signatures of the epithelial-mesenchymal transition (EMT) were also enhanced by M2-EVs. Compared with M1-EVs, miR-146a-5p, considered the key factor in TIME regulation, was deficient in M2-EVs according to miRNA-sequencing. When the miR-146a-5p mimic was added, EMT signatures and the invasive and migratory abilities of GBM cells were correspondingly weakened. Public databases predicted the miRNA binding targets and interleukin 1 receptor-associated kinase 1 (IRAK1) and tumor necrosis factor receptor-associated factor 6 (TRAF6) were screened as miR-146a-5p binding genes. Bimolecular fluorescent complementation and coimmunoprecipitation confirmed interactions between TRAF6 and IRAK1. The correlation between TRAF6 and IRAK1 was evaluated with immunofluorescence (IF)-stained clinical glioma samples. The TRAF6-IRAK1 complex is the switch and the brake that modulates IKK complex phosphorylation and NF-κB pathway activation, as well as the EMT behaviors of GBM cells. Furthermore, a homograft nude mouse model was explored and mice transplanted with TRAF6/IRAK1-overexpressing glioma cells had shorter survival times while mice transplanted with glioma cells with miR-146a-5p overexpression or TRAF6/IRAK1 knockdown lived longer. This work indicated that in the TIME of GBM, the deficiency of miR-146a-5p in M2-EVs enhances tumor EMT through disinhibition of the TRAF6-IRAK1 complex and IKK-dependent NF-κB signaling pathway providing a novel therapeutic strategy targeting the TIME of GBM.

Immunotherapy for Recurrent Glioma-From Bench to Bedside

Glioma is the most aggressive malignant tumor of the central nervous system, and most patients suffer from a recurrence. Unfortunately, recurrent glioma often becomes resistant to established chemotherapy and radiotherapy treatments. Immunotherapy, a rapidly developing anti-tumor therapy, has shown a potential value in treating recurrent glioma. Multiple immune strategies have been explored. The most-used ones are immune checkpoint blockade (ICB) antibodies, which are barely effective in monotherapy. However, when combined with other immunotherapy, especially with anti-angiogenesis antibodies, ICB has shown encouraging efficacy and enhanced anti-tumor immune response. Oncolytic viruses and CAR-T therapies have shown promising results in recurrent glioma through multiple mechanisms. Vaccination strategies and immune-cell-based immunotherapies are promising in some subgroups of patients, and multiple new tumor antigenic targets have been discovered. In this review, we discuss current applicable immunotherapies and related mechanisms for recurrent glioma, focusing on multiple preclinical models and clinical trials in the last 5 years. Through reviewing the current combination of immune strategies, we would like to provide substantive thoughts for further novel therapeutic regimes treating recurrent glioma.

Bi-Specific Killer Cell Engager Enhances NK Cell Activity against Interleukin-13 Receptor Alpha-2 Positive Gliomas

Glioblastoma (GBM) is a lethal brain tumor with limited therapeutic options. Bi-specific killer cell engagers (BiKEs) are novel immunotherapies designed to engage natural killer (NK) cells against cancer. We designed a BiKE molecule consisting of a single-domain CD16 antibody, an interleukin-15 linker, and a single-chain variable antibody against the glioma-associated antigen interleukin 13 receptor alpha 2 (IL13Rα2). Recombinant BiKE protein was expressed in HEK cells and purified. Flow cytometric analysis of co-cultures of peripheral blood-derived NK cells with GBM6 and GBM39 patient-derived xenograft lines revealed significantly increased activation of NK cells (CD25+CD69+) and increased glioma cell killing following BiKE treatment compared to controls (n = 4, p < 0.01). Glioma cell killing was also confirmed via immunofluorescence staining for cleaved caspase-3 (p < 0.05). In vivo, intracranial delivery of NK cells with BiKE extended median survival in mice bearing GBM6 (p < 0.01) and GBM12 (p < 0.01) tumors compared to controls. Finally, histological analysis of brain tissues revealed a higher frequency of peritumoral NK cells in mice treated with BiKE than with NK cells alone (p < 0.05). In conclusion, we demonstrate that a BiKE generated in a mammalian expression system is functional in augmenting NK cell targeting of IL13Rα2-positive gliomas.

CAR-NK cell therapy for glioblastoma: what to do next?

Glioblastoma is a malignant tumor with the highest morbidity and mortality in the central nervous system. Conventional surgical resection combined with radiotherapy or chemotherapy has a high recurrence rate and poor prognosis. The 5-year survival rate of patients is less than 10%. In tumor immunotherapy, CAR-T cell therapy represented by chimeric antigen receptor-modified T cells has achieved great success in hematological tumors. However, the application of CAR-T cells in solid tumors such as glioblastoma still faces many challenges. CAR-NK cells are another potential adoptive cell therapy strategy after CAR-T cells. Compared with CAR-T cell therapy, CAR-NK cells have similar anti-tumor effects. CAR-NK cells can also avoid some deficiencies in CAR-T cell therapy, a research hotspot in tumor immunity. This article summarizes the preclinical research status of CAR-NK cells in glioblastoma and the problems and challenges faced by CAR-NK in glioblastoma.

IGFBP3 induced by the TGF-β/EGFRvIII transactivation contributes to the malignant phenotype of glioblastoma

Dual or multi-targets therapy targeting epidermal growth factor receptor variant III (EGFRvIII) and other molecular may relax the constraint for glioblastoma (GBM), putting forward the urgent requirement of finding candidate molecules. Here, the insulin-like growth factor binding protein-3 (IGFBP3) was considered a candidate, whereas the mechanisms of IGFBP3 production remain unclear. We treated GBM cells with exogenous transforming growth factor β (TGF-β) to simulate the microenvironment. We found that TGF-β and EGFRvIII transactivation induced the activation of transcription factor c-Jun, which specifically bound to the promoter region of IGFBP3 through Smad2/3 and ERK1/2 pathways and promoted the production and secretion of IGFBP3. IGFBP3 knockdown inhibited the activation of TGF-β and EGFRvIII signals and the malignant behaviors triggered by them in vitro and in vivo. Collectively, our results indicated a positive feedback loop of p-EGFRvIII/IGFBP3 under administration of TGF-β, blocking IGFBP3 may be an additional target in EGFRvIII-expressing GBM-selective therapeutic strategy.

DKK3 expression is associated with immunosuppression and poor prognosis in glioblastoma, in contrast to lower-grade gliomas

PURPOSE

We previously reported that expression of dickkopf-3 (DKK3), which is involved in the Wnt/β-catenin pathway, is significantly associated with prognosis in patients with glioblastoma multiforme (GBM). The aim of this study was to compare the association of DKK3 with other Wnt/β-catenin pathway-related genes and immune responses between lower grade glioma (LGG) and GBM.

METHODS

We obtained the clinicopathological data of 515 patients with LGG (World Health Organization [WHO] grade II and III glioma) and 525 patients with GBM from the Cancer Genome Atlas (TCGA) database. We performed Pearson's correlation analysis to investigate the relationships between Wnt/β-catenin-related gene expression in LGG and GBM. Linear regression analysis was performed to identify the association between DKK3 expression and immune cell fractions in all grade II to IV gliomas.

RESULTS

A total of 1,040 patients with WHO grade II to IV gliomas were included in the study. As the grade of glioma increased, DKK3 showed a tendency to be more strongly positively correlated with the expression of other Wnt/β-catenin pathway-related genes. DKK3 was not associated with immunosuppression in LGG but was associated with downregulation of immune responses in GBM. We hypothesized that the role of DKK3 in the Wnt/β-catenin pathway might be different between LGG and GBM.

CONCLUSION

According to our findings, DKK3 expression had a weak effect on LGG but a significant effect on immunosuppression and poor prognosis in GBM. Therefore, DKK3 expression seems to play different roles, through the Wnt/β-catenin pathway, between LGG and GBM.

Re-convolving the compositional landscape of primary and recurrent glioblastoma reveals prognostic and targetable tissue states

Glioblastoma (GBM) diffusely infiltrates the brain and intermingles with non-neoplastic brain cells, including astrocytes, neurons and microglia/myeloid cells. This complex mixture of cell types forms the biological context for therapeutic response and tumor recurrence. We used single-nucleus RNA sequencing and spatial transcriptomics to determine the cellular composition and transcriptional states in primary and recurrent glioma and identified three compositional 'tissue-states' defined by cohabitation patterns between specific subpopulations of neoplastic and non-neoplastic brain cells. These tissue-states correlated with radiographic, histopathologic, and prognostic features and were enriched in distinct metabolic pathways. Fatty acid biosynthesis was enriched in the tissue-state defined by the cohabitation of astrocyte-like/mesenchymal glioma cells, reactive astrocytes, and macrophages, and was associated with recurrent GBM and shorter survival. Treating acute slices of GBM with a fatty acid synthesis inhibitor depleted the transcriptional signature of this pernicious tissue-state. These findings point to therapies that target interdependencies in the GBM microenvironment.

Macrophages in Recurrent Glioblastoma as a Prognostic Factor in the Synergistic System of the Tumor Microenvironment

Glioblastoma (GBM) is a common and highly malignant primary tumor of the central nervous system in adults. Ever more recent papers are focusing on understanding the role of the tumor microenvironment (TME) in affecting tumorigenesis and the subsequent prognosis. We assessed the impact of macrophages in the TME on the prognosis in patients with recurrent GBM. A PubMed, MEDLINE and Scopus review was conducted to identify all studies dealing with macrophages in the GBM microenvironment from January 2016 to December 2022. Glioma-associated macrophages (GAMs) act critically in enhancing tumor progression and can alter drug resistance, promoting resistance to radiotherapy and establishing an immunosuppressive environment. M1 macrophages are characterized by increased secretion of proinflammatory cytokines, such as IL-1ß, tumor necrosis factor (TNF), IL-27, matrix metalloproteinase (MMPs), CCL2, and VEGF (vascular endothelial growth factor), IGF1, that can lead to the destruction of the tissue. In contrast, M2 is supposed to participate in immunosuppression and tumor progression, which is formed after being exposed to the macrophage M-CSF, IL-10, IL-35 and the transforming growth factor-ß (TGF-β). Because there is currently no standard of care in recurrent GBM, novel identified targeted therapies based on the complex signaling and interactions between the glioma stem cells (GSCs) and the TME, especially resident microglia and bone-marrow-derived macrophages, may be helpful in improving the overall survival of these patients in the near future.

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.

Recent advances and future challenges of tumor vaccination therapy for recurrent glioblastoma

Glioblastoma (GBM) is the most malignant CNS tumor with a highest incidence rate, and most patients would undergo a recurrence. Recurrent GBM (rGBM) shows an increasing resistance to chemotherapy and radiotherapy, leading to a significantly poorer prognosis and the urgent need for novel treatments. Immunotherapy, a rapidly developing anti-tumor therapy in recent years, has shown its potential value in rGBM. Recent studies on PD-1 immunotherapy and CAR-T therapy have shown some efficacy, but the outcome was not as expected. Tumor vaccination is the oldest approach of immunotherapies, which has returned to the research focus because of the failure of other strategies and subversive understanding of CNS. The isolation effect of blood brain barrier and the immunosuppressive cell infiltration could lead to resistance existing in all phases of the anti-tumor immune response, where novel tumor vaccines have been designed to overcome these problems through new tumor antigenic targets and regulatory of the systematic immune response. In this review, the immunological characteristics of CNS and GBM would be discussed and summarized, as well as the mechanism of each novel tumor vaccine for rGBM. And through the review of completed early-phase studies and ongoing large-scale phase III clinical trials, evaluation could be conducted for potential immune response, biosecurity and initial clinical outcome, which further draw a panorama of this vital research field and provide some deep thoughts for the prospective tendency of vaccination strategy. Video Abstract.

Modeling glioblastoma complexity with organoids for personalized treatments

Glioblastoma (GBM) remains a fatal diagnosis despite the current standard of care of maximal surgical resection, radiation, and temozolomide (TMZ) therapy. One aspect that impedes drug development is the lack of an appropriate model representative of the complexity of patient tumors. Brain organoids derived from cell culture techniques provide a robust, easily manipulatable, and high-throughput model for GBM. In this review, we highlight recent progress in developing GBM organoids (GBOs) with a focus on generating the GBM microenvironment (i.e., stem cells, vasculature, and immune cells) recapitulating human disease. Finally, we also discuss the use of organoids as a screening tool in drug development for GBM.

Kynureninase Promotes Immunosuppression and Predicts Survival in Glioma Patients: In Silico Data Analyses of the Chinese Glioma Genome Atlas (CGGA) and of the Cancer Genome Atlas (TCGA)

Kynureninase (KYNU) is a kynurenine pathway (KP) enzyme that produces metabolites with immunomodulatory properties. In recent years, overactivation of KP has been associated with poor prognosis of several types of cancer, in particular by promoting the invasion, metastasis, and chemoresistance of cancer cells. However, the role of KYNU in gliomas remains to be explored. In this study, we used the available data from TCGA, CGGA and GTEx projects to analyze KYNU expression in gliomas and healthy tissue, as well as the potential contribution of KYNU in the tumor immune infiltrate. In addition, immune-related genes were screened with KYNU expression. KYNU expression correlated with the increased malignancy of astrocytic tumors. Survival analysis in primary astrocytomas showed that KYNU expression correlated with poor prognosis. Additionally, KYNU expression correlated positively with several genes related to an immunosuppressive microenvironment and with the characteristic immune tumor infiltrate. These findings indicate that KYNU could be a potential therapeutic target for modulating the tumor microenvironment and enhancing an effective antitumor immune response.

Single-cell RNA sequencing reveals tumor heterogeneity, microenvironment, and drug-resistance mechanisms of recurrent glioblastoma

Glioblastomas are highly heterogeneous brain tumors. Despite the availability of standard treatment for glioblastoma multiforme (GBM), i.e., Stupp protocol, which involves surgical resection followed by radiotherapy and chemotherapy, glioblastoma remains refractory to treatment and recurrence is inevitable. Moreover, the biology of recurrent glioblastoma remains unclear. Increasing evidence has shown that intratumoral heterogeneity and the tumor microenvironment contribute to therapeutic resistance. However, the interaction between intracellular heterogeneity and drug resistance in recurrent GBMs remains controversial. The aim of this study was to map the transcriptome landscape of cancer cells and the tumor heterogeneity and tumor microenvironment in recurrent and drug-resistant GBMs at a single-cell resolution and further explore the mechanism of drug resistance of GBMs. We analyzed six tumor tissue samples from three patients with primary GBM and three patients with recurrent GBM in which recurrence and drug resistance developed after treatment with the standard Stupp protocol using single-cell RNA sequencing. Using unbiased clustering, nine major cell clusters were identified. Upregulation of the expression of stemness-related and cell-cycle-related genes was observed in recurrent GBM cells. Compared with the initial GBM tissues, recurrent GBM tissues showed a decreased proportion of microglia, consistent with previous reports. Finally, vascular endothelial growth factor A expression and the blood-brain barrier permeability were high, and the O⁶ -methylguanine DNA methyltransferase-related signaling pathway was activated in recurrent GBM. Our results delineate the single-cell map of recurrent glioblastoma, tumor heterogeneity, tumor microenvironment, and drug-resistance mechanisms, providing new insights into treatment strategies for recurrent glioblastomas.

Advances in NK cell therapy for brain tumors

Despite advances in treatment regimens that comprise surgery, chemotherapy, and radiation, outcome of many brain tumors remains dismal, more so when they recur. The proximity of brain tumors to delicate neural structures often precludes complete surgical resection. Toxicity and long-term side effects of systemic therapy remain a concern. Novel therapies are warranted. The field of NK cell-based cancer therapy has grown exponentially and currently constitutes a major area of immunotherapy innovation. This provides a new avenue for the treatment of cancerous lesions in the brain. In this review, we explore the mechanisms by which the brain tumor microenvironment suppresses NK cell mediated tumor control, and the methods being used to create NK cell products that subvert immune suppression. We discuss the pre-clinical studies evaluating NK cell-based immunotherapies that target several neuro-malignancies and highlight advances in molecular imaging of NK cells that allow monitoring of NK cell-based therapeutics. We review current and ongoing NK cell based clinical trials in neuro-oncology.

Development of a novel angiogenesis-related lncRNA signature to predict the prognosis and immunotherapy of glioblastoma multiforme

Background

Long noncoding RNA (lncRNA) can regulate tumorigenesis, angiogenesis, proliferation, and other tumor biological behaviors, and is closely related to the growth and progression of glioma. The purpose of this research was to investigate the role of angiogenesis-related lncRNA in the prognosis and immunotherapy of glioblastoma multiforme (GBM).

Methods

Differential analysis was carried out to acquire angiogenesis-related differentially expressed lncRNAs (AR-DElncRNAs). The AR-DElncRNAs were then subjected to univariate Cox and least absolute shrinkage and selection operator (LASSO) analyses to construct a prognostic model. Based on the median risk score, patients were classified into high-risk and low-risk groups. Kaplan-Meier survival analysis was conducted to estimate the prognostic value of the prognostic model. In addition, a nomogram was built to predict individual survival probabilities by combining clinicopathological characteristics and a prognostic model. Furthermore, immune infiltration, immunotherapy, and drug sensitivity analyses were administered to investigate the differences between the high- and low-risk groups.

Results

We identified 3 lncRNAs (DGCR5, PRKAG2-AS1, and ACAP2-IT1) that were significantly associated with the survival of GBM patients from the 255 AR-DElncRNAs based on univariate Cox and LASSO analyses. Then, a prognostic model was structured according to these 3 lncRNAs, from which we found that high-risk GBM patients had a worse prognosis than that of low-risk patients. Moreover, the risk score was determined to be an independent prognostic factor [hazard ratio (HR) =1.444; 95% confidence interval (CI): 1.014-2.057; P<0.05]. The immune microenvironment analysis revealed that the immune score, stromal score, and Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE) score were significantly higher in the high-risk group than in the low-risk group. Neutrophils, macrophages, immature dendritic cells (iDCs), natural killer (NK) CD56dim cells, activated DCs (aDCs), and uncharacterized cells were different in the high- and low-risk groups. In addition, the high-risk group had a stronger sensitivity to immunotherapy. Furthermore, the sensitivity of 28 potential chemotherapeutic drugs differed significantly between the high- and low-risk groups.

Conclusions

A novel angiogenesis-related lncRNA signature could be used to predict the prognosis and treatment of GBM.

Natural Killer Cell-Based Immunotherapy against Glioblastoma

Glioblastoma (GBM) is the most aggressive and malignant primary brain tumor in adults. Despite multimodality treatment involving surgical resection, radiation therapy, chemotherapy, and tumor-treating fields, the median overall survival (OS) after diagnosis is approximately 2 years and the 5-year OS is poor. Considering the poor prognosis, novel treatment strategies are needed, such as immunotherapies, which include chimeric antigen receptor T-cell therapy, immune checkpoint inhibitors, vaccine therapy, and oncolytic virus therapy. However, these therapies have not achieved satisfactory outcomes. One reason for this is that these therapies are mainly based on activating T cells and controlling GBM progression. Natural killer (NK) cell-based immunotherapy involves the new feature of recognizing GBM via differing mechanisms from that of T cell-based immunotherapy. In this review, we focused on NK cell-based immunotherapy as a novel GBM treatment strategy.

Myeloidcells in the immunosuppressive microenvironment in glioblastoma: The characteristics and therapeutic strategies

Glioblastoma (GBM) is the most common and lethal malignant tumor of the central nervous system in adults. Conventional therapies, including surgery, radiotherapy, and chemotherapy, have limited success in ameliorating patient survival. The immunosuppressive tumor microenvironment, which is infiltrated by a variety of myeloid cells, has been considered a crucial obstacle to current treatment. Recently, immunotherapy, which has achieved great success in hematological malignancies and some solid cancers, has garnered extensive attention for the treatment of GBM. In this review, we will present evidence on the features and functions of different populations of myeloid cells, and on current clinical advances in immunotherapies for glioblastoma.

The Heterogeneity of Tumour-Associated Macrophages Contributes to the Recurrence and Outcomes of Glioblastoma Patients

Cellular heterogeneity and immune cell molecular phenotypes may be involved in the malignant progression of glioblastoma (GBM). In this study, we aimed to know whether the heterogeneity of tumour-associated macrophages contributes to the recurrence and outcomes of glioblastoma patients. Single-cell RNA sequencing (scRNA-Seq) data were used to assess the heterogeneity of CD45 + immune cells in recurrent GBM and analyse differentially expressed genes (DEGs) in master cells. Then, a prognostic signature based on the identified DEGs was established and validated, the correlation between risk score and tumour microenvironment (TME) was explored. The correlation between immune infiltration and LGMN, an important DEG in GBM tumour-associated macrophages (TAMs) was illuminated, using integrated bioinformatics analyses. Finally, immunohistochemistry and multiplex immunohistochemistry (mIHC) were used to analyse the expression of LGMN in GBM tissues from our hospital. scRNA-Seq analysis showed that the heterogeneity of recurrent GBM mainly comes from TAMs, which can be divided into 8 cell subclusters. Among these subclusters, TAM1 (markers: CXCL10, ADORA3), TAM3 (markers: MRC1, CFP), TAM4 (markers: GPNMB, PLTP), and TAM5 (markers: CCL4, IRAK2) were specifically present in recurrent GBM. After 342 DEGs in TAMs were identified, a prognostic signature was established based on 13 TAM-associated DEGs, and this signature could serve as an excellent prognostic predictor for patients with GBM. LGMN, one of 13 TAM-associated DEGs, was an important gene in lysosome pathway, we found that macrophage infiltration levels were higher after LGMN upregulation. GBM tissues from our hospital were collected for histopathologic validation, then LGMN was co-expressed with CD68, which is associated with the immune regulation of GBM. In conclusion, cell heterogeneity of TAMs is important for recurrent GBM, a prognostic signature based on 13 TAM-related DEGs can predict the survival outcome of GBM patients. An important DEG, LGMN may regulate the immune cell infiltration of GBM.

Comprehensive Assessment of Secreted Immuno-Modulatory Cytokines by Serum-Differentiated and Stem-like Glioblastoma Cells Reveals Distinct Differences between Glioblastoma Phenotypes

Glioblastoma is refractory to therapy and presents a significant oncological challenge. Promising immunotherapies have not shown the promise observed in other aggressive cancers. The reasons for this include the highly immuno-suppressive tumour microenvironment controlled by the glioblastoma cells and heterogeneous phenotype of the glioblastoma cells. Here, we wanted to better understand which glioblastoma phenotypes produced the regulatory cytokines, particularly those that are implicated in shaping the immune microenvironment. In this study, we employed nanoString analysis of the glioblastoma transcriptome, and proteomic analysis (proteome profiler arrays and cytokine profiling) of secreted cytokines by different glioblastoma phenotypes. These phenotypes were cultured to reflect a spectrum of glioblastoma cells present in tumours, by culturing an enhanced stem-like phenotype of glioblastoma cells or a more differentiated phenotype following culture with serum. Extensive secretome profiling reveals that there is considerable heterogeneity in secretion patterns between serum-derived and glioblastoma stem-like cells, as well as between individuals. Generally, however, the serum-derived phenotypes appear to be the primary producers of cytokines associated with immune cell recruitment into the tumour microenvironment. Therefore, these glioblastoma cells have considerable importance in shaping the immune landscape in glioblastoma and represent a valuable therapeutic target that should not be ignored.

Bioinformatic Analysis of Kynurenine Pathway Enzymes and Their Relationship with Glioma Hallmarks

Indoleamine dioxygenase (IDO), a rate limiting enzyme of the tryptophan catabolism through the kynurenine pathway (KP), has been related with a lower survival and a poor patient prognosis on several solid tumors, including gliomas. However, the use of IDO inhibitors as a therapeutic strategy for tumor treatment remains controversial in clinical trials and the role of other KP enzymes on tumor progression has remained poorly understood so far. Recently, different studies on different types of cancer have pointed out the importance of KP enzymes downstream IDO. Because of this, we conducted a bioinformatic analysis of the expression of different KP enzymes and their correlation with the gene expression of molecules related to the hallmarks of cancer in transcriptomic datasets from patients with different types of brain tumors including low grade gliomas, glioblastoma multiforme, neuroblastoma, and paraganglioma and pheochromocytoma. We found that KP enzymes that drive to NAD+ synthesis are overexpressed on different brain tumors compared to brain cortex data. Moreover, these enzymes presented positive correlations with the expression of genes related to immune response modulation, angiogenesis, Signal Transducer and Activator of Transcription (STAT) signaling, and Rho GTPase expression. These correlations suggest the relevance of the expression of the KP enzymes in brain tumor pathogenesis.

H2B gene family: A prognostic biomarker and correlates with immune infiltration in glioma

The current prognosis of glioma is unfavorable and effective treatments remain limited. However, bioinformatics has created new opportunities for improving glioma treatment. Research indicates that H2B is involved in the pathological process of cancer. Thus, this study conducted bioinformatic analyses of the H2B gene family to evaluate whether these genes can play a role in predicting prognosis and are associated with immune infiltration. High expression of H2B genes was observed in cholangiocarcinoma, esophageal carcinoma, glioblastoma multiforme (GBM), head and neck squamous cell carcinoma, and other cancers. In addition, a rise in H2B gene expression was correlated with an increase in glioma grade. In the Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA) database and multiple datasets from the Gene Expression Omnibus (GEO), high expression of H2B gene family members predicted poor prognosis of a variety of tumors including glioma. In particular, high H2BC5, H2BC9, H2BC11, and H2BC21 expression was associated with poor glioma prognosis. H2BC9, H2BC11, and H2BC12 expression were also positively correlated with both immune and stromal scores. Enrichment analysis indicated that H2B family genes may be involved in the pathological process of glioma using various pathways including the cell cycle and immune response. H2B-specific siRNAs were used to verify the role of H2BC5, H2BC9, H2BC11, and H2BC21 expression on cell cycle distribution. In summary, H2BC5, H2BC9, H2BC11, and H2BC21 were independent prognostic indicators of glioma, and H2BC9 and H2BC11 may correlate with tumor immunity.

Exploring glioblastoma stem cell heterogeneity: Immune microenvironment modulation and therapeutic opportunities

Despite its growing use in cancer treatment, immunotherapy has been virtually ineffective in clinical trials for gliomas. The inherently cold tumor immune microenvironment (TIME) in gliomas, characterized by a high ratio of pro-tumor to anti-tumor immune cell infiltrates, acts as a seemingly insurmountable barrier to immunotherapy. Glioma stem cells (GSCs) within these tumors are key contributors to this cold TIME, often functioning indirectly through activation and recruitment of pro-tumor immune cell types. Furthermore, drivers of GSC plasticity and heterogeneity (e.g., reprogramming transcription factors, epigenetic modifications) are associated with induction of immunosuppressive cell states. Recent studies have identified GSC-intrinsic mechanisms, including functional mimicry of immune suppressive cell types, as key determinants of anti-tumor immune escape. In this review, we cover recent advancements in our understanding of GSC-intrinsic mechanisms that modulate GSC-TIME interactions and discuss cutting-edge techniques and bioinformatics platforms available to study immune modulation at high cellular resolution with exploration of both malignant (i.e., GSC) and non-malignant (i.e., immune) cell fractions. Finally, we provide insight into the therapeutic opportunities for targeting immunomodulatory GSC-intrinsic mechanisms to potentiate immunotherapy response in gliomas.

Construction of immune cell infiltration protein network based on clinical low grade glioma cases

Many researchers have studied low-grade glioma and the immune microenvironment have been studied by many researchers. Recent studies suggest that macrophages and dendritic cells trigger part of the local immune dysregulation in the tumor microenvironment, and they have been polarized into a mixed pro-inflammatory and immunosuppressive phenotype. It is suggested that the degree of immune infiltration is related to the survival, therapeutic effect, and prognosis of patients. This opens up new avenues for cancer treatment. On the basis of immune infiltration degree, a protein interaction network (PIN) and a prognosis model were established, and we chose the top 20 pathways from enrichment analysis to provide potential targets for glioma clinical treatment.

Peroxidase is a novel potential marker in glioblastoma through bioinformatics method and experimental validation

Peroxidase (PXDN), a specific extracellular matrix (ECM)-associated protein, has been determined as a tumor indicator and therapeutic target in various tumors. However, the effects of PXDN in prognostic performance and clinical implications in glioblastoma multiforme (GBM) remains unknown. Here, we assessed PXDN expression pattern and its performance on prognosis among GBM cases from TCGA and CGGA databases. PXDN was up-regulated within GBM samples in comparison with normal control. High PXDN expression was a dismal prognostic indicator in GBM. Single cell RNA analysis was conducted to detect the cell localization of PXDN. We also set up a PPI network to explore the interacting protein associated with PXDN, including TSKU, COL4A1 and COL5A1. Consistently, functional enrichment analysis revealed that several cancer hallmarks were enriched in the GBM cases with high PXDN expression, such as epithelial-mesenchymal transition (EMT), fatty acid metabolism, glycolysis, hypoxia, inflammatory response, and Wnt/beta-catenin signaling pathway. Next, this study analyzed the association of PXDN expression and immunocyte infiltration. PXDN expression was in direct proportion to the infiltrating degrees of NK cells resting, T cells regulatory, M0 macrophage, monocytes and eosinophils. The roles of PXDN on immunity were further estimated by PXDN-associated immunomodulators. In addition, four prognosis-related lncRNAs co-expressed with PXDN were identified. Finally, we observed that PXDN depletion inhibits GBM cell proliferation and migration by in vitro experiments. Our data suggested that PXDN has the potential to be a powerful prognostic biomarker, which might offer a basis for developing therapeutic targets for GBM.

Emerging role of ferroptosis in glioblastoma: Therapeutic opportunities and challenges

Glioblastoma (GBM) is the most common malignant craniocerebral tumor. The treatment of this cancer is difficult due to its high heterogeneity and immunosuppressive microenvironment. Ferroptosis is a newly found non-apoptotic regulatory cell death process that plays a vital role in a variety of brain diseases, including cerebral hemorrhage, neurodegenerative diseases, and primary or metastatic brain tumors. Recent studies have shown that targeting ferroptosis can be an effective strategy to overcome resistance to tumor therapy and immune escape mechanisms. This suggests that combining ferroptosis-based therapies with other treatments may be an effective strategy to improve the treatment of GBM. Here, we critically reviewed existing studies on the effect of ferroptosis on GBM therapies such as chemotherapy, radiotherapy, immunotherapy, and targeted therapy. In particular, this review discussed the potential of ferroptosis inducers to reverse drug resistance and enhance the sensitivity of conventional cancer therapy in combination with ferroptosis. Finally, we highlighted the therapeutic opportunities and challenges facing the clinical application of ferroptosis-based therapies in GBM. The data generated here provide new insights and directions for future research on the significance of ferroptosis-based therapies in GBM.

Macrophages in Glioblastoma Development and Therapy: A Double-Edged Sword

Glioblastoma (GBM) is one of the leading lethal tumors, featuring aggressive malignancy and poor outcome to current standard temozolomide (TMZ) or radio-based therapy. Developing immunotherapies, especially immune checkpoint inhibitors, have improved patient outcomes in other solid tumors but remain fatigued in GBM patients. Emerging evidence has shown that GBM-associated macrophages (GAMs), comprising brain-resident microglia and bone marrow-derived macrophages, act critically in boosting tumor progression, altering drug resistance, and establishing an immunosuppressive environment. Based on its crucial role, evaluations of the safety and efficacy of GAM-targeted therapy are ongoing, with promising (pre)clinical evidence updated. In this review, we summarized updated literature related to GAM nature, the interplay between GAMs and GBM cells, and GAM-targeted therapeutic strategies.

Proteomics approaches to characterize the immune responses in cancer

Despite the dynamic development of cancer research, annually millions of people die of cancer. The human immune system is the major 'guard' against tumor development. Unfortunately, cancer cells have the ability to evade the immune system and continue to grow. The proper understanding of the intricate immune response in tumorigenesis remains the holy grail of cancer immunology and designing effective immunotherapy. To decode the immune responses in cancer, in recent years, proteomics studies have received considerable attention. Proteomics studies focus on the detection and quantification of proteins, which are the effectors of biological functions, and as such, are proven to reflect the cell state more accurately, in comparison to genomic or transcriptomic studies. In this review, we discuss the proteomics studies applied to characterize the immune responses in cancer and tumor immune microenvironment heterogeneity. Further, we describe emerging single-cell proteomics approaches that have the potential to be applied in cancer immunity studies.

CBLRR: a cauchy-based bounded constraint low-rank representation method to cluster single-cell RNA-seq data

The rapid development of single-cel+l RNA sequencing (scRNA-seq) technology provides unprecedented opportunities for exploring biological phenomena at the single-cell level. The discovery of cell types is one of the major applications for researchers to explore the heterogeneity of cells. Some computational methods have been proposed to solve the problem of scRNA-seq data clustering. However, the unavoidable technical noise and notorious dropouts also reduce the accuracy of clustering methods. Here, we propose the cauchy-based bounded constraint low-rank representation (CBLRR), which is a low-rank representation-based method by introducing cauchy loss function (CLF) and bounded nuclear norm regulation, aiming to alleviate the above issue. Specifically, as an effective loss function, the CLF is proven to enhance the robustness of the identification of cell types. Then, we adopt the bounded constraint to ensure the entry values of single-cell data within the restricted interval. Finally, the performance of CBLRR is evaluated on 15 scRNA-seq datasets, and compared with other state-of-the-art methods. The experimental results demonstrate that CBLRR performs accurately and robustly on clustering scRNA-seq data. Furthermore, CBLRR is an effective tool to cluster cells, and provides great potential for downstream analysis of single-cell data. The source code of CBLRR is available online at https://github.com/Ginnay/CBLRR.

Natural killer cell awakening: unleash cancer-immunity cycle against glioblastoma

Due to the negligence of the complex tumor immune microenvironment, traditional treatment for glioblastoma has reached its limitation and cannot achieve a satisfying outcome in the past decade. The emergence of immunotherapy based on the theory of cancer-immunity cycle has brought a new dawn to glioblastoma patients. However, the results of most phase II and phase III clinical trials are not optimistic due to the simple focus on T cells activation rather than other immune cells involved in anti-tumor immunity. NK cells play a critical role in both innate and adaptive immunity, having the ability to coordinate immune response in inflammation, autoimmune disease and cancer. They are expected to cooperate with T cells to maximize the anti-tumor immune effect and have great potential in treating glioblastoma. Here, we describe the traditional treatment methods and current immunotherapy strategies for glioblastoma. Then, we list a microenvironment map and discuss the reasons for glioblastoma inhibitory immunity from multiple perspectives. More importantly, we focus on the advantages of NK cells as potential immune regulatory cells and the ways to maximize their anti-tumor immune effect. Finally, our outlook on the directions and potential applications of NK cell-based therapy combining with the advance technologies is presented. This review depicts NK cell awakening as the precondition to unleash the cancer-immunity cycle against glioblastoma and elaborate this idea from biology to clinical treatment.

Immunologic Features in De Novo and Recurrent Glioblastoma Are Associated with Survival Outcomes

Glioblastoma (GBM) is an immunologically "cold" tumor characterized by poor responsiveness to immunotherapy. Standard of care for GBM is surgical resection followed by chemoradiotherapy and maintenance chemotherapy. However, tumor recurrence is the norm, and recurring tumors are found frequently to have acquired molecular changes (e.g., mutations) that may influence their immunobiology. Here, we compared the immune contexture of de novo GBM and recurrent GBM (rGBM) using high-dimensional cytometry and multiplex IHC. Although myeloid and T cells were similarly abundant in de novo and rGBM, their spatial organization within tumors differed and was linked to outcomes. In rGBM, T cells were enriched and activated in perivascular regions and clustered with activated macrophages and fewer regulatory T cells. Moreover, a higher expression of phosphorylated STAT1 by T cells in these regions at recurrence was associated with a favorable prognosis. Together, our data identify differences in the immunobiology of de novo GBM and rGBM and identify perivascular T cells as potential therapeutic targets. See related Spotlight by Bayik et al., p. 787.

Cancer Stem Cell-Associated Immune Microenvironment in Recurrent Glioblastomas

Glioblastoma multiforme (GBM) is the most incurable tumor (due to the difficulty in complete surgical resection and the resistance to conventional chemo/radiotherapies) that displays a high relapse frequency. Cancer stem cells (CSCs) have been considered as a promising target responsible for therapy resistance and cancer recurrence. CSCs are known to organize a self-advantageous microenvironment (niche) for their maintenance and expansion. Therefore, understanding how the microenvironment is reconstructed by the remaining CSCs after conventional treatments and how it eventually causes recurrence should be essential to inhibit cancer recurrence. However, the number of studies focusing on recurrence is limited, particularly those related to tumor immune microenvironment, while numerous data have been obtained from primary resected samples. Here, we summarize recent investigations on the immune microenvironment from the viewpoint of recurrent GBM (rGBM). Based on the recurrence-associated immune cell composition reported so far, we will discuss how CSCs manipulate host immunity and create the special microenvironment for themselves to regrow. An integrated understanding of the interactions between CSCs and host immune cells at the recurrent phase will lead us to develop innovative therapies and diagnoses to achieve GBM eradication.

Comparison of tumor immune environment between newly diagnosed and recurrent glioblastoma including matched patients

PURPOSE

Glioblastoma (GBM) is the most lethal primary brain tumor in adult patients. The disease progression, response to chemotherapy and radiotherapy at initial diagnosis, and prognosis are profoundly associated with the tumor microenvironment, especially the features of tumor-infiltrating immune cells (TII). Recurrent GBM is even more challenging to manage. Differences in the immune environment between newly diagnosed and recurrent GBM and an association with tumor prognosis are not well defined.

METHODS

To address this knowledge gap, we analyzed the clinical data and tissue specimens from 24 GBM patients (13 at initial diagnosis and 11 at recurrence). The expression levels of multiple immunobiological markers in patients' GBM at initial diagnosis versus at recurrence were compared, including five patients with both specimens available (paired). The distribution patterns of TII were evaluated in both the intratumoral and perivascular regions.

RESULTS

We found that tumors from recurrent GBM have significantly more tumor-infiltrating lymphocytes (TILs) and macrophages and higher PD-L1 and PD-1 expression than tumors at primary diagnosis and benign brain specimens from epilepsy surgery. The pattern changes of the TILs and macrophages of the five paired specimens were consistent with the unpaired patients, while the CD8 to CD4 ratio remained constant from diagnosis to recurrence in the paired tissues. The levels of TILs, macrophages, PD-1 or PD-L1+ cells at initial diagnosis did not correlate with OS. TILs, macrophages, and PD-1+ cells were increased in recurrent tumors both in intratumoral and perivascular areas, with higher distribution levels in intratumoral than perivascular regions. Higher CD4 or CD8 infiltration at recurrence was associated with a worse prognosis, respectively.

CONCLUSIONS

Our study elucidated that TIL and TAM tend to accumulate in perivascular region and are more abundant in recurrent GBM than newly diagnosed GBM.