Immunosuppression in Glioblastoma: Current Understanding and Therapeutic Implications

Transcriptional regulation of CYR61 and CTGF by LM98: a synthetic YAP-TEAD inhibitor that targets in-vitro vasculogenic mimicry in glioblastoma cells

Glioblastoma (GBM) is a highly angiogenic malignancy of the central nervous system that resists standard antiangiogenic therapy, in part because of an alternative process to angiogenesis termed vasculogenic mimicry. Intricately linked to GBM, dysregulation of the Hippo signaling pathway leads to overexpression of YAP/TEAD and several downstream effectors involved in therapy resistance. Little is known about whether vasculogenic mimicry and the Hippo pathway intersect in the GBM chemoresistance phenotype. This study seeks to investigate the expression patterns of Hippo pathway regulators within clinically annotated GBM samples, examining their involvement in vitro regarding vasculogenic mimicry. In addition, it aims to assess the potential for pharmacological targeting of this pathway. In-silico analysis of the Hippo signaling members YAP1 , TEAD1 , AXL , NF2 , CTGF , and CYR61 transcript levels in low-grade GBM and GBM tumor tissues was done by Gene Expression Profiling Interactive Analysis. Gene expression was analyzed by real-time quantitative PCR from human U87, U118, U138, and U251 brain cancer cell lines and in clinically annotated brain tumor cDNA arrays. Transient gene silencing was performed with specific small interfering RNA. Vasculogenic mimicry was assessed using a Cultrex matrix, and three-dimensional capillary-like structures were analyzed with Wimasis. CYR61 and CTGF transcript levels were elevated in GBM tissues and were further induced when in-vitro vasculogenic mimicry was assessed. Silencing of CYR61 and CTGF , or treatment with a small-molecule TEAD inhibitor LM98 derived from flufenamic acid, inhibited vasculogenic mimicry. Silencing of SNAI1 and FOXC2 also altered vasculogenic mimicry and reduced CYR61 / CTGF levels. Pharmacological targeting of the Hippo pathway inhibits in-vitro vasculogenic mimicry. Unraveling the connections between the Hippo pathway and vasculogenic mimicry may pave the way for innovative therapeutic strategies.

CSF1R Ligands Expressed by Murine Gliomas Promote M-MDSCs to Suppress CD8+ T Cells in a NOS-Dependent Manner

Glioblastoma (GBM) is the most common malignant primary brain tumor, resulting in poor survival despite aggressive therapies. GBM is characterized by a highly heterogeneous and immunosuppressive tumor microenvironment (TME) made up predominantly of infiltrating peripheral immune cells. One significant immune cell type that contributes to glioma immune evasion is a population of immunosuppressive cells, termed myeloid-derived suppressor cells (MDSCs). Previous studies suggest that a subset of myeloid cells, expressing monocytic (M)-MDSC markers and dual expression of chemokine receptors CCR2 and CX3CR1, utilize CCR2 to infiltrate the TME. This study evaluated the mechanism of CCR2+/CX3CR1+ M-MDSC differentiation and T cell suppressive function in murine glioma models. We determined that bone marrow-derived CCR2+/CX3CR1+ cells adopt an immune suppressive cell phenotype when cultured with glioma-derived factors. Glioma-secreted CSF1R ligands M-CSF and IL-34 were identified as key drivers of M-MDSC differentiation while adenosine and iNOS pathways were implicated in the M-MDSC suppression of T cells. Mining a human GBM spatial RNAseq database revealed a variety of different pathways that M-MDSCs utilize to exert their suppressive function that is driven by complex niches within the microenvironment. These data provide a more comprehensive understanding of the mechanism of M-MDSCs in glioblastoma.

Immunotherapeutic advances in glioma management: The rise of vaccine-based approaches

BACKGROUND

Gliomas, particularly glioblastoma multiforme (GBM), are highly aggressive brain tumors that present significant challenges in oncology due to their rapid progression and resistance to conventional therapies. Despite advancements in treatment, the prognosis for patients with GBM remains poor, necessitating the exploration of novel therapeutic approaches. One such emerging strategy is the development of glioma vaccines, which aim to stimulate the immune system to target and destroy tumor cells.

AIMS

This review aims to provide a comprehensive evaluation of the current landscape of glioma vaccine development, analyzing the types of vaccines under investigation, the outcomes of clinical trials, and the challenges and opportunities associated with their implementation. The goal is to highlight the potential of glioma vaccines in advancing more effective and personalized treatments for glioma patients.

MATERIALS AND METHODS

This narrative review systematically assessed the role of glioma vaccines by including full-text articles published between 2000 and 2024 in English. Databases such as PubMed/MEDLINE, EMBASE, the Cochrane Library, and Scopus were searched using key terms like "glioma," "brain tumor," "glioblastoma," "vaccine," and "immunotherapy." The review incorporated both pre-clinical and clinical studies, including descriptive studies, animal-model studies, cohort studies, and observational studies. Exclusion criteria were applied to omit abstracts, case reports, posters, and non-peer-reviewed studies, ensuring the inclusion of high-quality evidence.

RESULTS

Clinical trials investigating various glioma vaccines, including peptide-based, DNA/RNA-based, whole-cell, and dendritic-cell vaccines, have shown promising results. These vaccines demonstrated potential in extending survival rates and managing adverse events in glioma patients. However, significant challenges remain, such as therapeutic resistance due to tumor heterogeneity and immune evasion mechanisms. Moreover, the lack of standardized guidelines for evaluating vaccine responses and issues related to ethical considerations, regulatory hurdles, and vaccine acceptance among patients further complicate the implementation of glioma vaccines.

DISCUSSION

Addressing the challenges associated with glioma vaccines involves exploring combination therapies, targeted approaches, and personalized medicine. Combining vaccines with traditional therapies like radiotherapy or chemotherapy may enhance efficacy by boosting the immune system's ability to fight tumor cells. Personalized vaccines tailored to individual patient profiles present an opportunity for improved outcomes. Furthermore, global collaboration and equitable distribution are critical for ensuring access to glioma vaccines, especially in low- and middle-income countries with limited healthcare resources CONCLUSION: Glioma vaccines represent a promising avenue in the fight against gliomas, offering hope for improving patient outcomes in a disease that is notoriously difficult to treat. Despite the challenges, continued research and the development of innovative strategies, including combination therapies and personalized approaches, are essential for overcoming current barriers and transforming the treatment landscape for glioma patients.

Dendritic cell vaccine for glioblastoma: an updated meta-analysis and trial sequential analysis

BACKGROUND

Dendritic cell (DC) vaccine is an emerging immunotherapy that could potentially improve glioblastoma survival. The first phase III clinical trial of DC vaccine was recently published. This meta-analysis aims to update and reappraise existing evidence on the efficacy of DC vaccine in patients with glioblastoma.

METHODS

We searched PubMed, Embase, and Cochrane Library for clinical trials of DC vaccine for glioblastoma. The quality of the studies was assessed using the RoB 2.0 and ROBINS-I tools. The results of overall survival (OS) and progression-free survival (PFS) were pooled using hazard ratios (HRs) with corresponding 95% confidence intervals (CI). Summary effects were evaluated using random effects models. Trial sequential analysis (TSA) was performed.

RESULTS

Seven clinical trials involving 3,619 patients were included. DC vaccine plus standard care was associated with significantly improved OS (HR = 0.71; 95% CI, 0.57 - 0.88) and PFS (HR = 0.65; 95% CI, 0.43 - 0.98). In the subgroup of newly diagnosed glioblastoma, DC vaccine was associated with improved PFS (HR = 0.59; 95% CI, 0.39 - 0.90). TSA of OS showed that the cumulative z-score line for the DC vaccine crossed the benefit boundary and reached the required sample size. TSA of PFS and subgroup analysis of newly diagnosed glioblastoma showed that the required sample size was not reached.

CONCLUSIONS

This updated meta-analysis, which included the first phase III trial of a DC vaccine for glioblastoma, demonstrated that the DC vaccine was associated with improved OS. Moreover, TSA showed that the required sample size was reached, indicating a true-positive result. Future studies are required for patient subgroups with newly diagnosed and recurrent glioblastoma.

From bench to bedside: the application of cannabidiol in glioma

Glioma is the most common malignant tumor in central nervous system, with significant health burdens to patients. Due to the intrinsic characteristics of glioma and the lack of breakthroughs in treatment modalities, the prognosis for most patients remains poor. This results in a heavy psychological and financial load worldwide. In recent years, cannabidiol (CBD) has garnered widespread attention and research due to its anti-tumoral, anti-inflammatory, and neuroprotective properties. This review comprehensively summarizes the preclinical and clinical research on the use of CBD in glioma therapy, as well as the current status of nanomedicine formulations of CBD, and discusses the potential and challenges of CBD in glioma therapy in the future.

An Update on the Clinical Status, Challenges, and Future Directions of Oncolytic Virotherapy for Malignant Gliomas

OPINION STATEMENT

Malignant gliomas are common central nervous system tumors that pose a significant clinical challenge due to the lack of effective treatments. Glioblastoma (GBM), a grade 4 malignant glioma, is the most prevalent primary malignant brain tumor and is associated with poor prognosis. Current clinical trials are exploring various strategies to combat GBM, with oncolytic viruses (OVs) appearing particularly promising. In addition to ongoing and recently completed clinical trials, one OV (Teserpaturev, Delytact®) received provisional approval for GBM treatment in Japan. OVs are designed to selectively target and eliminate cancer cells while promoting changes in the tumor microenvironment that can trigger and support long-lasting anti-tumor immunity. OVs offer the potential to remodel the tumor microenvironment and reverse systemic immune exhaustion. Additionally, an increasing number of OVs are armed with immunomodulatory payloads or combined with immunotherapy approaches in an effort to promote anti-tumor responses in a tumor-targeted manner. Recently completed oncolytic virotherapy trials can guide the way for future treatment individualization through patient preselection, enhancing the likelihood of achieving the highest possible clinical success. These trials also offer valuable insight into the numerous challenges inherent in malignant glioma treatment, some of which OVs can help overcome.

Role of renin angiotensin system inhibitors and metformin in Glioblastoma Therapy: a review

Glioblastoma multiforme (GBM) is a highly aggressive and incurable disease accounting for about 10,000 deaths in the USA each year. Despite the current treatment approach which includes surgery with chemotherapy and radiation therapy, there remains a high prevalence of recurrence. Notable improvements have been observed in persons receiving concurrent antihypertensive drugs such as renin angiotensin inhibitors (RAS) or the antidiabetic drug metformin with standard therapy. Anti-tumoral effects of RAS inhibitors and metformin have been observed in in vitro and in vivo studies. Although clinical trials have shown mixed results, the potential for the use of RAS inhibitors and metformin as adjuvant GBM therapy remains promising. Nevertheless, evidence suggest that these drugs exert multimodal antitumor actions; by particularly targeting several cancer hallmarks. In this review, we highlight the results of clinical studies using multidrug cocktails containing RAS inhibitors and or metformin added to standard therapy for GBM. In addition, we highlight the possible molecular mechanisms by which these repurposed drugs with an excellent safety profile might elicit their anti-tumoral effects. RAS inhibition elicits anti-inflammatory, anti-angiogenic, and immune sensitivity effects in GBM. However, metformin promotes anti-migratory, anti-proliferative and pro-apoptotic effects mainly through the activation of AMP-activated protein kinase. Also, we discussed metformin's potential in targeting both GBM cells as well as GBM associated-stem cells. Finally, we summarize a few drug interactions that may cause an additive or antagonistic effect that may lead to adverse effects and influence treatment outcome.

GBM Immunotherapy: Macrophage Impacts

BACKGROUND

Glioblastoma (GBM) is an extremely aggressive form of brain tumor with low survival rates. Current treatments such as chemotherapy, radiation, and surgery are problematic due to tumor growth, invasion, and tumor microenvironment. GBM cells are resistant to these standard treatments, and the heterogeneity of the tumor makes it difficult to find a universal approach. Progression of GBM and acquisition of resistance to therapy are due to the complex interplay between tumor cells and the TME. A significant portion of the TME consists of an inflammatory infiltrate, with microglia and macrophages being the predominant cells.

METHODS

Analysis of the literature data over a course of 5 years suggest that the tumor-associated macrophages (TAMs) are capable of releasing cytokines and growth factors that promote tumor proliferation, survival, and metastasis while inhibiting immune cell function at the same time.

RESULTS

Thus, immunosuppressive state, provided with this intensively studied kind of TME cells, is supposed to promote GBM development through TAMs modulation of tumor treatment-resistance and aggressiveness. Therefore, TAMs are an attractive therapeutic target in the treatment of glioblastoma.

CONCLUSION

This review provides a comprehensive overview of the latest research on the nature of TAMs and the development of therapeutic strategies targeting TAMs, focusing on the variety of macrophage properties, being modulated, as well as molecular targets.

Hypoxia within the glioblastoma tumor microenvironment: a master saboteur of novel treatments

Glioblastoma (GBM) tumors are the most aggressive primary brain tumors in adults that, despite maximum treatment, carry a dismal prognosis. GBM tumors exhibit tissue hypoxia, which promotes tumor aggressiveness and maintenance of glioma stem cells and creates an overall immunosuppressive landscape. This article reviews how hypoxic conditions overlap with inflammatory responses, favoring the proliferation of immunosuppressive cells and inhibiting cytotoxic T cell development. Immunotherapies, including vaccines, immune checkpoint inhibitors, and CAR-T cell therapy, represent promising avenues for GBM treatment. However, challenges such as tumor heterogeneity, immunosuppressive TME, and BBB restrictiveness hinder their effectiveness. Strategies to address these challenges, including combination therapies and targeting hypoxia, are actively being explored to improve outcomes for GBM patients. Targeting hypoxia in combination with immunotherapy represents a potential strategy to enhance treatment efficacy.

Endocannabinoid Receptor 2 Function is Associated with Tumor-Associated Macrophage Accumulation and Increases in T Cell Number to Initiate a Potent Antitumor Response in a Syngeneic Murine Model of Glioblastoma

Introduction: Glioblastoma patients have a highly immunosuppressive tumor microenvironment and systemic immunosuppression that comprise a major barrier to immune checkpoint therapy. Based on the production of endocannabinoids by glioblastomas, we explored involvement of endocannabinoid receptor 2 (CB2R), encoded by the CNR2 gene, which is predominantly expressed by immune cells, in glioblastoma-related immunosuppression. Materials & Methods: Bioinformatics of human glioblastoma databases was used to correlate enzymes involved in the synthesis and degradation of endocannabinoids, as well as CB2Rs, with patient overall survival. Intrastriatal administration of luciferase-expressing, murine GL261 glioblastoma cells was used to establish in in vivo glioblastoma model for characterization of tumor growth and intratumoral immune cell infiltration, as well as provide immune cells for in vitro co-culture experiments. Involvement of CB2Rs was determined by treatment with CB2R agonist (GW405833) or CB2R antagonist (AM630). ELISA, FACS, and immunocytochemistry were used to determine perforin, granzyme B, and surface marker levels. Results: Bioinformatics of human glioblastoma databases showed high expression of CB2R and elevated endocannabinoid production correlated with poorer prognosis, and involved immune-associated pathways. AM630treatment of GL261 glioblastoma-bearing mice induced a potent antitumor response, with survival plateauing at 50% on Day 40, when all control mice (median survival 28 days) and mice treated with GW405833 (median survival 21 days) had died. Luciferase tumor imaging revealed accelerated tumor growth by GW405833 treatment, but stable or regressing tumors in AM630-treated mice. Notably, in spleens, AM630 treatment caused an 83% decrease in monocytes/macrophages, and 1.8- and 1.6-fold increases in CD8+ and CD4+ cells, respectively. Within tumors, there was a corresponding decrease in tumor-associated macrophages (TAMs) and increase in CD8+ T cells. In vitro, lymphocytes from AM630-treated mice showed greater cytotoxic function (increased percentage of perforin- and granzyme B-positive CD8+ T cells). Discussion: These results suggest that inhibition of CB2R enhances both immunosuppressive TAM infiltration and systemic T-cell suppression through CB2R activation, and that inhibition of CB2Rs can potently counter both the immunosuppressive tumor microenvironment, as well as systemic immunosuppression in glioblastoma.

Pathway analysis of peripheral blood CD8+ T cell transcriptome shows differential regulation of sphingolipid signaling in multiple sclerosis and glioblastoma

Multiple sclerosis (MS) and glioblastoma (GBM) are CNS diseases in whose development and progression immune privilege is intimately important, but in a relatively opposite manner. Maintenance and strengthening of immune privilege have been shown to be an important mechanism in glioblastoma immune evasion, while the breakdown of immune privilege leads to MS initiation and exacerbation. We hypothesize that molecular signaling pathways can be oppositely regulated in peripheral blood CD8+ T cells of MS and glioblastoma patients at a transcriptional level. We analyzed publicly available data of the peripheral blood CD8+ T cell MS vs. control (MSvsCTRL) and GBM vs. control (GBMvsCTRL) differentially expressed gene (DEG) contrasts with Qiagen's Ingenuity pathway analysis software (IPA). We have identified sphingolipid signaling pathway which was significantly downregulated in the GBMvsCTRL and upregulated in the MSvsCTRL. As the pathway is important for the CD8+ T lymphocytes CNS infiltration, this result is in line with our previously stated hypothesis. Comparing publicly available lists of differentially expressed serum exosomal miRNAs from MSvsCTRL and GBMvsCTRL contrasts, we have identified that hsa-miR-182-5p has the greatest potential effect on sphingolipid signaling regarding the number of regulated DEGs in the GBMvsCTRL contrast, while not being able to find any relevant potential sphingolipid signaling target transcripts in the MSvsCTRL contrast. We conclude that the sphingolipid signaling pathway is a top oppositely regulated pathway in peripheral blood CD8+ T cells from GBM and MS, and might be crucial for the differences in CNS immune privilege maintenance of investigated diseases, but further experimental research is necessary.

Glioma-derived M-CSF and IL-34 license M-MDSCs to suppress CD8+ T cells in a NOS-dependent manner

Glioblastoma (GBM) is the most common malignant primary brain tumor, resulting in poor survival despite aggressive therapies. GBM is characterized by a highly heterogeneous and immunosuppressive tumor microenvironment (TME) made up predominantly of infiltrating peripheral immune cells. One significant immune cell type that contributes to glioma immune evasion is a population of immunosuppressive cells, termed myeloid-derived suppressor cells (MDSCs). Previous studies suggest that a subset of myeloid cells, expressing monocytic (M)-MDSC markers and dual expression of chemokine receptors CCR2 and CX3CR1, utilize CCR2 to infiltrate the TME. This study evaluated the mechanism of CCR2+/CX3CR1+ M-MDSC differentiation and T cell suppressive function in murine glioma models. We determined that bone marrow-derived CCR2+/CX3CR1+ cells adopt an immune suppressive cell phenotype when cultured with glioma-derived factors. Glioma secreted CSF1R ligands M-CSF and IL-34 were identified as key drivers of M-MDSC differentiation while adenosine and iNOS pathways were implicated in M-MDSC suppression of T cells. Mining a human GBM spatial RNAseq database revealed a variety of different pathways that M-MDSCs utilize to exert their suppressive function that are driven by complex niches within the microenvironment. These data provide a more comprehensive understanding of the mechanism of M-MDSCs in glioblastoma.

BCL6 is a context-dependent mediator of the glioblastoma response to irradiation therapy

Glioblastoma is a rapidly fatal brain cancer that does not respond to therapy. Previous research showed that the transcriptional repressor protein BCL6 is upregulated by chemo and radiotherapy in glioblastoma, and inhibition of BCL6 enhances the effectiveness of these therapies. Therefore, BCL6 is a promising target to improve the efficacy of current glioblastoma treatment. BCL6 acts as a transcriptional repressor in germinal centre B cells and as an oncogene in lymphoma and other cancers. However, in glioblastoma, BCL6 induced by therapy may not be able to repress transcription. Using a BCL6 inhibitor, the whole proteome response to irradiation was compared with and without BCL6 activity. Acute high dose irradiation caused BCL6 to switch from repressing the DNA damage response to promoting stress response signalling. Rapid immunoprecipitation mass spectrometry of endogenous proteins (RIME) enabled comparison of BCL6 partner proteins between untreated and irradiated glioblastoma cells. BCL6 was associated with transcriptional coregulators in untreated glioblastoma including the known partner NCOR2. However, this association was lost in response to acute irradiation, where BCL6 unexpectedly associated with synaptic and plasma membrane proteins. These results reveal the activity of BCL6 under therapy-induced stress is context-dependent, and potentially altered by the intensity of that stress.

Therapeutic Implications of Targeting YY1 in Glioblastoma

The transcription factor Yin Yang 1 (YY1) plays a pivotal role in the pathogenesis of glioblastoma multiforme (GBM), an aggressive form of brain tumor. This review systematically explores the diverse roles of YY1 overexpression and activities in GBM, including its impact on the tumor microenvironment (TME) and immune evasion mechanisms. Due to the poor response of GBM to current therapies, various findings of YY1-associated pathways in the literature provide valuable insights into novel potential targeted therapeutic strategies. Moreover, YY1 acts as a significant regulator of immune checkpoint molecules and, thus, is a candidate therapeutic target in combination with immune checkpoint inhibitors. Different therapeutic implications targeting YY1 in GBM and its inherent associated challenges encompass the use of nanoparticles, YY1 inhibitors, targeted gene therapy, and exosome-based delivery systems. Despite the inherent complexities of such methods, the successful targeting of YY1 emerges as a promising avenue for reshaping GBM treatment strategies, presenting opportunities for innovative therapeutic approaches and enhanced patient outcomes.

Targeting inflammation in glioblastoma: An updated review from pathophysiology to novel therapeutic approaches

Glioblastoma (GBM) is a highly aggressive primary malignant brain tumor with a dismal prognosis despite current treatment strategies. Inflammation plays an essential role in GBM pathophysiology, contributing to tumor growth, invasion, immunosuppression, and angiogenesis. As a result, pharmacological intervention with anti-inflammatory drugs has been used as a potential approach for the management of GBM. To provide an overview of the current understanding of GBM pathophysiology, potential therapeutic applications of anti-inflammatory drugs in GBM, conventional treatments of glioblastoma and emerging therapeutic approaches currently under investigation. A narrative review was carried out, scanning publications from 2000 to 2023 on PubMed and Google Scholar. The search was not guided by a set research question or a specific search method but rather focused on the area of interest. Conventional treatments such as surgery, radiotherapy, and chemotherapy have shown some benefits, but their effectiveness is limited by various factors such as tumor heterogeneity and resistance.

From lymphopenia to restoration: IL-7 immunotherapy for lymphocyte recovery in glioblastoma

Glioblastoma, the most prevalent malignant primary brain tumor, presents substantial treatment challenges because of its inherent aggressiveness and limited therapeutic options. Lymphopenia, defined as reduced peripheral blood lymphocyte count, commonly occurs as a consequence of the disease and its treatment. Recent studies have associated lymphopenia with a poor prognosis. Factors that contribute to lymphopenia include radiotherapy, chemotherapy, and the tumor itself. Patients who are female, older, using dexamethasone, or receiving higher doses of radiation therapy are particularly vulnerable to this condition. Several preclinical studies have explored the use of interleukin-7, a crucial cytokine for lymphocyte homeostasis, to restore lymphocyte counts and potentially rebuild the immune system to combat glioblastoma cells. With the development of recombinant interleukin-7 for prolonged activity in the body, various clinical trials are underway to explore this treatment in patients with glioblastoma. Our study provides a comprehensive summary of the incidence of lymphopenia, its potential biological background, and the associated clinical risk factors. Furthermore, we reviewed several clinical trials using IL-7 cytokine therapy in glioblastoma patients. We propose IL-7 as a promising immunotherapeutic strategy for glioblastoma treatment. We are optimistic that our study will enhance understanding of the complex interplay between lymphopenia and glioblastoma and will pave the way for the development of more effective treatment modalities.

Pentraxin 3: A Main Driver of Inflammation and Immune System Dysfunction in the Tumor Microenvironment of Glioblastoma

Brain tumors are a heterogeneous group of brain neoplasms that are highly prevalent in individuals of all ages worldwide. Within this pathological framework, the most prevalent and aggressive type of primary brain tumor is glioblastoma (GB), a subtype of glioma that falls within the IV-grade astrocytoma group. The death rate for patients with GB remains high, occurring within a few months after diagnosis, even with the gold-standard therapies now available, such as surgery, radiation, or a pharmaceutical approach with Temozolomide. For this reason, it is crucial to continue looking for cutting-edge therapeutic options to raise patients' survival chances. Pentraxin 3 (PTX3) is a multifunctional protein that has a variety of regulatory roles in inflammatory processes related to extracellular matrix (ECM). An increase in PTX3 blood levels is considered a trustworthy factor associated with the beginning of inflammation. Moreover, scientific evidence suggested that PTX3 is a sensitive and earlier inflammation-related marker compared to the short pentraxin C-reactive protein (CRP). In several tumoral subtypes, via regulating complement-dependent and macrophage-associated tumor-promoting inflammation, it has been demonstrated that PTX3 may function as a promoter of cancer metastasis, invasion, and stemness. Our review aims to deeply evaluate the function of PTX3 in the pathological context of GB, considering its pivotal biological activities and its possible role as a molecular target for future therapies.

Principles in the Management of Glioblastoma

Glioblastoma, the most aggressive and common malignant primary brain tumour, is characterized by infiltrative growth, abundant vascularization, and aggressive clinical evolution. Patients with glioblastoma often face poor prognoses, with a median survival of approximately 15 months. Technological progress and the subsequent improvement in understanding the pathophysiology of these tumours have not translated into significant achievements in therapies or survival outcomes for patients. Progress in molecular profiling has yielded new omics data for a more refined classification of glioblastoma. Several typical genetic and epigenetic alterations in glioblastoma include mutations in genes regulating receptor tyrosine kinase (RTK)/rat sarcoma (RAS)/phosphoinositide 3-kinase (PI3K), p53, and retinoblastoma protein (RB) signalling, as well as mutation of isocitrate dehydrogenase (IDH), methylation of O6-methylguanine-DNA methyltransferase (MGMT), amplification of epidermal growth factor receptor vIII, and codeletion of 1p/19q. Certain microRNAs, such as miR-10b and miR-21, have also been identified as prognostic biomarkers. Effective treatment options for glioblastoma are limited. Surgery, radiotherapy, and alkylating agent chemotherapy remain the primary pillars of treatment. Only promoter methylation of the gene MGMT predicts the benefit from alkylating chemotherapy with temozolomide and it guides the choice of first-line treatment in elderly patients. Several targeted strategies based on tumour-intrinsic dominant signalling pathways and antigenic tumour profiles are under investigation in clinical trials. This review explores the potential genetic and epigenetic biomarkers that could be deployed as analytical tools in the diagnosis and prognostication of glioblastoma. Recent clinical advancements in treating glioblastoma are also discussed, along with the potential of liquid biopsies to advance personalized medicine in the field of glioblastoma, highlighting the challenges and promises for the future.

ImmunoPET imaging of TIGIT in the glioma microenvironment

Glioblastoma (GBM) is the most common primary malignant brain tumor. Currently, there are few effective treatment options for GBM beyond surgery and chemo-radiation, and even with these interventions, median patient survival remains poor. While immune checkpoint inhibitors (ICIs) have demonstrated therapeutic efficacy against non-central nervous system cancers, ICI trials for GBM have typically had poor outcomes. TIGIT is an immune checkpoint receptor that is expressed on activated T-cells and has a role in the suppression of T-cell and Natural Killer (NK) cell function. As TIGIT expression is reported as both prognostic and a biomarker for anti-TIGIT therapy, we constructed a molecular imaging agent, [89Zr]Zr-DFO-anti-TIGIT (89Zr-αTIGIT), to visualize TIGIT in preclinical GBM by immunoPET imaging. PET imaging and biodistribution analysis of 89Zr-αTIGIT demonstrated uptake in the tumor microenvironment of GBM-bearing mice. Blocking antibody and irrelevant antibody tracer studies demonstrated specificity of 89Zr-αTIGIT with significance at a late time point post-tracer injection. However, the magnitude of 89Zr-αTIGIT uptake in tumor, relative to the IgG tracer was minimal. These findings highlight the features and limitations of using 89Zr-αTIGIT to visualize TIGIT in the GBM microenvironment.

PTEN loss in glioma cell lines leads to increased extracellular vesicles biogenesis and PD-L1 cargo in a PI3K-dependent manner

Phosphatase and Tensin Homologue (PTEN) is one of the most frequently lost tumor suppressors in cancer and the predominant negative regulator of the PI3K/AKT signaling axis. A growing body of evidence has highlighted the loss of PTEN with immuno-modulatory functions including the upregulation of the programmed death ligand-1 (PD-L1), an altered tumor derived secretome that drives an immunosuppressive tumor immune microenvironment (TIME), and resistance to certain immunotherapies. Given their roles in immunosuppression and tumor growth, we examined whether the loss of PTEN would impact the biogenesis, cargo, and function of extracellular vesicles (EVs) in the context of the anti-tumor associated cytokine interferon-γ (IFN-γ). Through genetic and pharmacological approaches, we show that PD-L1 expression is regulated by JAK/STAT signaling, not PI3K signaling. Instead, we observe that PTEN loss positively upregulates cell surface levels of PD-L1 and enhances the biogenesis of EVs enriched with PD-L1 in a PI3K-dependent manner. We demonstrate that because of these changes, EVs derived from glioma cells lacking PTEN have a greater ability to suppress T cell receptor (TCR) signaling. Taken together, these findings provide important new insights into how the loss of PTEN can contribute to an immunosuppressive TIME, facilitate immune evasion, and highlight a novel role for PI3K signaling in the regulation of EV biogenesis and the cargo they contain.

Systemic and local immunosuppression in glioblastoma and its prognostic significance

The effectiveness of tumor therapy, especially immunotherapy and oncolytic virotherapy, critically depends on the activity of the host immune cells. However, various local and systemic mechanisms of immunosuppression operate in cancer patients. Tumor-associated immunosuppression involves deregulation of many components of immunity, including a decrease in the number of T lymphocytes (lymphopenia), an increase in the levels or ratios of circulating and tumor-infiltrating immunosuppressive subsets [e.g., macrophages, microglia, myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs)], as well as defective functions of subsets of antigen-presenting, helper and effector immune cell due to altered expression of various soluble and membrane proteins (receptors, costimulatory molecules, and cytokines). In this review, we specifically focus on data from patients with glioblastoma/glioma before standard chemoradiotherapy. We discuss glioblastoma-related immunosuppression at baseline and the prognostic significance of different subsets of circulating and tumor-infiltrating immune cells (lymphocytes, CD4+ and CD8+ T cells, Tregs, natural killer (NK) cells, neutrophils, macrophages, MDSCs, and dendritic cells), including neutrophil-to-lymphocyte ratio (NLR), focus on the immune landscape and prognostic significance of isocitrate dehydrogenase (IDH)-mutant gliomas, proneural, classical and mesenchymal molecular subtypes, and highlight the features of immune surveillance in the brain. All attempts to identify a reliable prognostic immune marker in glioblastoma tissue have led to contradictory results, which can be explained, among other things, by the unprecedented level of spatial heterogeneity of the immune infiltrate and the significant phenotypic diversity and (dys)functional states of immune subpopulations. High NLR is one of the most repeatedly confirmed independent prognostic factors for shorter overall survival in patients with glioblastoma and carcinoma, and its combination with other markers of the immune response or systemic inflammation significantly improves the accuracy of prediction; however, more prospective studies are needed to confirm the prognostic/predictive power of NLR. We call for the inclusion of dynamic assessment of NLR and other blood inflammatory markers (e.g., absolute/total lymphocyte count, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, and systemic immune response index) in all neuro-oncology studies for rigorous evaluation and comparison of their individual and combinatorial prognostic/predictive significance and relative superiority.

Small Molecule Immunomodulators as Next-Generation Therapeutics for Glioblastoma

Glioblastoma (GBM), the most aggressive astrocytic glioma, remains a therapeutic challenge despite multimodal approaches. Immunotherapy holds promise, but its efficacy is hindered by the highly immunosuppressive GBM microenvironment. This review underscores the urgent need to comprehend the intricate interactions between glioma and immune cells, shaping the immunosuppressive tumor microenvironment (TME) in GBM. Immunotherapeutic advancements have shown limited success, prompting exploration of immunomodulatory approaches targeting tumor-associated macrophages (TAMs) and microglia, constituting a substantial portion of the GBM TME. Converting protumor M2-like TAMs to antitumor M1-like phenotypes emerges as a potential therapeutic strategy for GBM. The blood-brain barrier (BBB) poses an additional challenge to successful immunotherapy, restricting drug delivery to GBM TME. Research efforts to enhance BBB permeability have mainly focused on small molecules, which can traverse the BBB more effectively than biologics. Despite over 200 clinical trials for GBM, studies on small molecule immunomodulators within the GBM TME are scarce. Developing small molecules with optimal brain penetration and selectivity against immunomodulatory pathways presents a promising avenue for combination therapies in GBM. This comprehensive review discusses various immunomodulatory pathways in GBM progression with a focus on immune checkpoints and TAM-related targets. The exploration of such molecules, with the capacity to selectively target key immunomodulatory pathways and penetrate the BBB, holds the key to unlocking new combination therapy approaches for GBM.

Blocking TGF-β- and Epithelial-to-Mesenchymal Transition (EMT)-mediated activation of vessel-associated mural cells in glioblastoma impacts tumor angiogenesis

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. GBM displays excessive and unfunctional vascularization which may, among others, be a reason for its devastating prognosis. Pericytes have been identified as the major component of the irregular vessel structure in GBM. In vitro data suggest an epithelial-to-mesenchymal transition (EMT)-like activation of glioma-associated pericytes, stimulated by GBM-secreted TGF-β, to be involved in the formation of a chaotic and dysfunctional tumor vasculature. This study investigated whether TGF-β impacts the function of vessel associated mural cells (VAMCs) in vivo via the induction of the EMT transcription factor SLUG and whether this is associated with the development of GBM-associated vascular abnormalities. Upon preventing the TGF-β-/SLUG-mediated EMT induction in VAMCs, the number of PDGFRβ and αSMA positive cells was significantly reduced, regardless of whether TGF-β secretion by GBM cells was blocked or whether SLUG was specifically knocked out in VAMCs. The reduced amount of PDGFRβ+ or αSMA+ cells observed under those conditions correlated with a lower vessel density and fewer vascular abnormalities. Our data provide evidence that the SLUG-mediated modulation of VAMC activity is induced by GBM-secreted TGF-β¬ and that activated VAMCs are key contributors in neo-angiogenic processes. We suggest that a pathologically altered activation of GA-Peris in the tumor microenvironment is responsible for the unstructured tumor vasculature. There is emerging evidence that vessel normalization alleviates tumor hypoxia, reduces tumor-associated edema and improves drug delivery. Therefore, avoiding the generation of an unstructured and non-functional tumor vasculature during tumor recurrence might be a promising treatment approach for GBM and identifies pericytes as a potential novel therapeutic target.

Enrichment of a neutrophil-like monocyte transcriptional state in glioblastoma myeloid suppressor cells

Glioblastomas (GBM) are lethal central nervous system cancers associated with tumor and systemic immunosuppression. Heterogeneous monocyte myeloid-derived suppressor cells (M-MDSC) are implicated in the altered immune response in GBM, but M-MDSC ontogeny and definitive phenotypic markers are unknown. Using single-cell transcriptomics, we revealed heterogeneity in blood M-MDSC from GBM subjects and an enrichment in a transcriptional state reminiscent of neutrophil-like monocytes (NeuMo), a newly described pathway of monopoiesis in mice. Human NeuMo gene expression and Neu-like deconvolution fraction algorithms were created to quantitate the enrichment of this transcriptional state in GBM subjects. NeuMo populations were also observed in M-MDSCs from lung and head and neck cancer subjects. Dexamethasone (DEX) and prednisone exposures increased the usage of Neu-like states, which were inversely associated with tumor purity and survival in isocitrate dehydrogenase wildtype (IDH WT) gliomas. Anti-inflammatory ZC3HA12/Regnase-1 transcripts were highly correlated with NeuMo expression in tumors and in blood M-MDSC from GBM, lung, and head and neck cancer subjects. Additional novel transcripts of immune-modulating proteins were identified. Collectively, these findings provide a framework for understanding the heterogeneity of M-MDSCs in GBM as cells with different clonal histories and may reshape approaches to study and therapeutically target these cells.

Correlation of MR-Based Metabolomics and Molecular Profiling in the Tumor Microenvironment of Temozolomide-Treated Orthotopic GL261 Glioblastoma in Mice

The tumor microenvironment in glioblastoma (GB) is considered to be "cold", i.e., the fraction of cytotoxic T cells, for instance, is low. Instead, macrophages are the major immune cell population in GB, which stem either from tissue response (resident microglia) or recruitment of macrophages from the periphery, thereby undergoing tumor-dependent "imprinting" mechanisms by which macrophages can adapt a tumor-supportive phenotype. In this regard, it is important to describe the nature of macrophages associated with GB, in particular under therapy conditions using the gold standard chemotherapy drug temozolomide (TMZ). Here, we explored the suitability of combining information from in vivo magnetic resonance spectroscopic (MRS) approaches (metabolomics) with in vitro molecular analyses to assess therapy response and characterize macrophage populations in mouse GB using an isogenic GL261 model. For macrophage profiling, expression levels of matrix metalloproteinases (MMPs) and A disintegrin and metalloproteinases (ADAMs) were determined, since their gene products affect macrophage-tumor cell communication by extensive cleavage of immunomodulatory membrane proteins, such as PD-L1. In tumor mice with an overall therapy response, expression of genes encoding the proteases ADAM8, ADAM10, and ADAM17 was increased and might contribute to the immunosuppressive phenotype of GB and immune cells. In tumors responding to therapy, expression levels of ADAM8 were upregulated by TMZ, and higher levels of PD-L1 were correlated significantly. Using a CRISPR/Cas9 knockout of ADAM8 in GL261 cells, we demonstrated that soluble PD-L1 (sPD-L1) is only generated in the presence of ADAM8. Moreover, primary macrophages from WT and ADAM8-deficient mice showed ADAM8-dependent release of sPD-L1, independent of the macrophage polarization state. Since ADAM8 expression is induced in responding tumors and PD-L1 shedding is likely to decrease the anti-tumor activities of T-cells, we conclude that immunotherapy resistance is caused, at least in part, by the increased presence of proteases, such as ADAM8.

Immune Escape in Glioblastoma: Mechanisms of Action and Implications for Immune Checkpoint Inhibitors and CAR T-Cell Therapy

Glioblastoma, the most common primary brain cancer in adults, is characterized by a poor prognosis and resistance to standard treatments. The advent of immunotherapy has revolutionized the treatment of several cancers in recent years but has failed to demonstrate benefit in patients with glioblastoma. Understanding the mechanisms by which glioblastoma exerts tumor-mediated immune suppression in both the tumor microenvironment and the systemic immune landscape is a critical step towards developing effective immunotherapeutic strategies. In this review, we discuss the current understanding of immune escape mechanisms in glioblastoma that compromise the efficacy of immunotherapies, with an emphasis on immune checkpoint inhibitors and chimeric antigen receptor T-cell therapy. In parallel, we review data from preclinical studies that have identified additional therapeutic targets that may enhance overall treatment efficacy in glioblastoma when administered alongside existing immunotherapies.

Revealing the biology behind MRI signatures in high grade glioma

Magnetic resonance imaging (MRI) measurements are routinely collected during the treatment of high-grade gliomas (HGGs) to characterize tumor boundaries and guide surgical tumor resection. Using spatially matched MRI and transcriptomics we discovered HGG tumor biology captured by MRI measurements. We strategically overlaid the spatially matched omics characterizations onto a pre-existing transcriptional map of glioblastoma multiforme (GBM) to enhance the robustness of our analyses. We discovered that T1+C measurements, designed to capture vasculature and blood brain barrier (BBB) breakdown and subsequent contrast extravasation, also indirectly reveal immune cell infiltration. The disruption of the vasculature and BBB within the tumor creates a permissive infiltrative environment that enables the transmigration of anti-inflammatory macrophages into tumors. These relationships were validated through histology and enrichment of genes associated with immune cell transmigration and proliferation. Additionally, T2-weighted (T2W) and mean diffusivity (MD) measurements were associated with angiogenesis and validated using histology and enrichment of genes involved in neovascularization. Furthermore, we establish an unbiased approach for identifying additional linkages between MRI measurements and tumor biology in future studies, particularly with the integration of novel MRI techniques. Lastly, we illustrated how noninvasive MRI can be used to map HGG biology spatially across a tumor, and this provides a platform to develop diagnostics, prognostics, or treatment efficacy biomarkers to improve patient outcomes.

A closer look at the role of iron in glioblastoma

Glioblastoma (GBM) is among the deadliest malignancies facing modern oncology. While our understanding of certain aspects of GBM biology has significantly increased over the last decade, other aspects, such as the role of bioactive metals in GBM progression, remain understudied. Iron is the most abundant transition metal found within the earth's crust and plays an intricate role in human physiology owing to its ability to participate in oxidation-reduction reactions. The importance of iron homeostasis in human physiology is apparent when examining the clinical consequences of iron deficiency or iron overload. Despite this, the role of iron in GBM progression has not been well described. Here, we review and synthesize the existing literature examining iron's role in GBM progression and patient outcomes, as well as provide a survey of iron's effects on the major cell types found within the GBM microenvironment at the molecular and cellular level. Iron represents an accessible target given the availability of already approved iron supplements and chelators. Improving our understanding of iron's role in GBM biology may pave the way for iron-modulating approaches to improve patient outcomes.

Biomarkers in Adult-Type Diffuse Gliomas: Elevated Levels of Circulating Vesicular Heat Shock Protein 70 Serve as a Biomarker in Grade 4 Glioblastoma and Increase NK Cell Frequencies in Grade 3 Glioma

The presence of circulating Hsp70 levels and their influence on the immunophenotype of circulating lymphocyte subsets were examined as diagnostic/prognostic biomarkers for the overall survival (OS) in patients with IDH-mutant WHO grade 3 oligodendroglioma, astrocytoma, and IDH-wildtype grade 4 glioblastoma (GBM). Vesicular and free Hsp70 in the plasma/serum was measured using the Hsp70-exo and R&D Systems DuoSet® Hsp70 ELISAs. The immunophenotype and membrane Hsp70 status was determined by multiparameter flow cytometry on peripheral blood lymphocytes and single-cell suspensions of tumor specimens and cultured cells. Compared to healthy controls, circulating vesicular Hsp70 levels were significantly increased in patients with GBM, concomitant with a significant decrease in the proportion of CD3+/CD4+ helper T cells, whereas the frequency of NK cells was most prominently increased in patients with grade 3 gliomas. Elevated circulating Hsp70 levels and a higher prevalence of activated CD3-/CD56+/CD94+/CD69+ NK cells were associated with an improved OS in grade 3 gliomas, whereas high Hsp70 levels and low CD3+/CD4+ frequencies were associated with an adverse OS in GBM. It is assumed that a reduced membrane Hsp70 density on grade 4 versus grade 3 primary glioma cells and reduced CD3+/CD4+ T cell counts in GBM might drive an immunosuppressive tumor microenvironment.

The genes significantly associated with an improved prognosis and long-term survival of glioblastoma

BACKGROUND AND PURPOSE

Glioblastoma multiforme (GBM) is the most devastating brain tumor with less than 5% of patients surviving 5 years following diagnosis. Many studies have focused on the genetics of GBM with the aim of improving the prognosis of GBM patients. We investigated specific genes whose expressions are significantly related to both the length of the overall survival and the progression-free survival in patients with GBM.

METHODS

We obtained data for 12,042 gene mRNA expressions in 525 GBM tissues from the Cancer Genome Atlas (TCGA) database. Among those genes, we identified independent genes significantly associated with the prognosis of GBM. Receiver operating characteristic (ROC) curve analysis was performed to determine the genes significant for predicting the long-term survival of patients with GBM. Bioinformatics analysis was also performed for the significant genes.

RESULTS

We identified 33 independent genes whose expressions were significantly associated with the prognosis of 525 patients with GBM. Among them, the expressions of five genes were independently associated with an improved prognosis of GBM, and the expressions of 28 genes were independently related to a poorer prognosis of GBM. The expressions of the ADAM22, ATP5C1, RAC3, SHANK1, AEBP1, C1RL, CHL1, CHST2, EFEMP2, and PGCP genes were either positively or negatively related to the long-term survival of GBM patients.

CONCLUSIONS

Using a large-scale and open database, we found genes significantly associated with both the prognosis and long-term survival of patients with GBM. We believe that our findings may contribute to improving the understanding of the mechanisms underlying GBM.

The Role of Antibody-Based Therapies in Neuro-Oncology

This review explores the evolving landscape of antibody-based therapies in neuro-oncology, in particular, immune checkpoint inhibitors and immunomodulatory antibodies. We discuss their mechanisms of action, blood-brain barrier (BBB) penetration, and experience in neuro-oncological conditions. Evidence from recent trials indicates that while these therapies can modulate the tumor immune microenvironment, their clinical benefits remain uncertain, largely due to challenges with BBB penetration and tumor-derived immunosuppression. This review also examines emerging targets such as TIGIT and LAG3, the potential of antibodies in modulating the myeloid compartment, and tumor-specific targets for monoclonal antibody therapy. We further delve into advanced strategies such as antibody-drug conjugates and bispecific T cell engagers. Lastly, we explore innovative techniques being investigated to enhance antibody delivery, including CAR T cell therapy. Despite current limitations, these therapies hold significant therapeutic potential for neuro-oncology. Future research should focus on optimizing antibody delivery to the CNS, identifying novel biological targets, and discovering combination therapies to address the hostile tumor microenvironment.

Tumor Niches: Perspectives for Targeted Therapies in Glioblastoma

Significance: Glioblastoma (GBM), the most common and lethal primary brain tumor with a median survival rate of only 15 months and a 5-year survival rate of only 6.8%, remains largely incurable despite the intensive multimodal treatment of surgical resection and radiochemotherapy. Developing effective new therapies is an unmet need for patients with GBM. Recent Advances: Targeted therapies, such as antiangiogenesis therapy and immunotherapy, show great promise in treating GBM based upon increasing knowledge about brain tumor biology. Single-cell transcriptomics reveals the plasticity, heterogeneity, and dynamics of tumor cells during GBM development and progression. Critical Issues: While antiangiogenesis therapy and immunotherapy have been highly effective in some types of cancer, the disappointing results from clinical trials represent continued challenges in applying these treatments to GBM. Molecular and cellular heterogeneity of GBM is developed temporally and spatially, which profoundly contributes to therapeutic resistance and tumor recurrence. Future Directions: Deciphering mechanisms of tumor heterogeneity and mapping tumor niche trajectories and functions will provide a foundation for the development of more effective therapies for GBM patients. In this review, we discuss five different tumor niches and the intercellular and intracellular communications among these niches, including the perivascular, hypoxic, invasive, immunosuppressive, and glioma-stem cell niches. We also highlight the cellular and molecular biology of these niches and discuss potential strategies to target these tumor niches for GBM therapy. Antioxid. Redox Signal. 39, 904-922.

Methods behind oncolytic virus-based DC vaccines in cancer: Toward a multiphase combined treatment strategy for Glioblastoma (GBM) patients

Glioblastoma (GBM) remains an orphan cancer disease with poor outcome. Novel treatment strategies are needed. Immunotherapy has several modes of action. The addition of active specific immunotherapy with dendritic cell vaccines resulted in improved overall survival of patients. Integration of DC vaccination within the first-line combined treatment became a challenge, and immunogenic cell death immunotherapy during chemotherapy was introduced. We used a retrospective analysis using real world data to evaluate the complex combined treatment, which included individualized multimodal immunotherapy during and after standard of care, and which required adaptations during treatment, and found a further improvement of overall survival. We also discuss the use of real world data as evidence. Novel strategies to move the field of individualized multimodal immunotherapy forward for GBM patients are reviewed.

Unveiling Novel Avenues in mTOR-Targeted Therapeutics: Advancements in Glioblastoma Treatment

The mTOR signaling pathway plays a pivotal and intricate role in the pathogenesis of glioblastoma, driving tumorigenesis and proliferation. Mutations or deletions in the PTEN gene constitutively activate the mTOR pathway by expressing growth factors EGF and PDGF, which activate their respective receptor pathways (e.g., EGFR and PDGFR). The convergence of signaling pathways, such as the PI3K-AKT pathway, intensifies the effect of mTOR activity. The inhibition of mTOR has the potential to disrupt diverse oncogenic processes and improve patient outcomes. However, the complexity of the mTOR signaling, off-target effects, cytotoxicity, suboptimal pharmacokinetics, and drug resistance of the mTOR inhibitors pose ongoing challenges in effectively targeting glioblastoma. Identifying innovative treatment strategies to address these challenges is vital for advancing the field of glioblastoma therapeutics. This review discusses the potential targets of mTOR signaling and the strategies of target-specific mTOR inhibitor development, optimized drug delivery system, and the implementation of personalized treatment approaches to mitigate the complications of mTOR inhibitors. The exploration of precise mTOR-targeted therapies ultimately offers elevated therapeutic outcomes and the development of more effective strategies to combat the deadliest form of adult brain cancer and transform the landscape of glioblastoma therapy.

Agent-Based Modelling Reveals the Role of the Tumor Microenvironment on the Short-Term Success of Combination Temozolomide/Immune Checkpoint Blockade to Treat Glioblastoma

Glioblastoma is the most common and deadly primary brain tumor in adults. All glioblastoma patients receiving standard-of-care surgery-radiotherapy-chemotherapy (i.e., temozolomide (TMZ)) recur, with an average survival time of only 15 months. New approaches to the treatment of glioblastoma, including immune checkpoint blockade and oncolytic viruses, offer the possibility of improving glioblastoma outcomes and have as such been under intense study. Unfortunately, these treatment modalities have thus far failed to achieve approval. Recently, in an attempt to bolster efficacy and improve patient outcomes, regimens combining chemotherapy and immune checkpoint inhibitors have been tested in trials. Unfortunately, these efforts have not resulted in significant increases to patient survival. To better understand the various factors impacting treatment outcomes of combined TMZ and immune checkpoint blockade, we developed a systems-level, computational model that describes the interplay between glioblastoma, immune, and stromal cells with this combination treatment. Initializing our model to spatial resection patient samples labeled using imaging mass cytometry, our model's predictions show how the localization of glioblastoma cells, influence therapeutic success. We further validated these predictions in samples of brain metastases from patients given they generally respond better to checkpoint blockade compared with primary glioblastoma. Ultimately, our model provides novel insights into the mechanisms of therapeutic success of immune checkpoint inhibitors in brain tumors and delineates strategies to translate combination immunotherapy regimens more effectively into the clinic. SIGNIFICANCE STATEMENT: Extending survival times for glioblastoma patients remains a critical challenge. Although immunotherapies in combination with chemotherapy hold promise, clinical trials have not shown much success. Here, systems models calibrated to and validated against patient samples can improve preclinical and clinical studies by shedding light on the factors distinguishing responses/failures. By initializing our model with imaging mass cytometry visualization of patient samples, we elucidate how factors such as localization of glioblastoma cells and CD8+ T cell infiltration impact treatment outcomes.

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.

Advances in computational and translational approaches for malignant glioma

Gliomas are the most common primary brain tumors in adults and carry a dismal prognosis for patients. Current standard-of-care for gliomas is comprised of maximal safe surgical resection following by a combination of chemotherapy and radiation therapy depending on the grade and type of tumor. Despite decades of research efforts directed towards identifying effective therapies, curative treatments have been largely elusive in the majority of cases. The development and refinement of novel methodologies over recent years that integrate computational techniques with translational paradigms have begun to shed light on features of glioma, previously difficult to study. These methodologies have enabled a number of point-of-care approaches that can provide real-time, patient-specific and tumor-specific diagnostics that may guide the selection and development of therapies including decision-making surrounding surgical resection. Novel methodologies have also demonstrated utility in characterizing glioma-brain network dynamics and in turn early investigations into glioma plasticity and influence on surgical planning at a systems level. Similarly, application of such techniques in the laboratory setting have enhanced the ability to accurately model glioma disease processes and interrogate mechanisms of resistance to therapy. In this review, we highlight representative trends in the integration of computational methodologies including artificial intelligence and modeling with translational approaches in the study and treatment of malignant gliomas both at the point-of-care and outside the operative theater in silico as well as in the laboratory setting.

Evaluation of Radiosensitization and Cytokine Modulation by Differentially PEGylated Gold Nanoparticles in Glioblastoma Cells

Glioblastoma (GBM) is known as the most aggressive type of malignant brain tumour, with an extremely poor prognosis of approximately 12 months following standard-of-care treatment with surgical resection, radiotherapy (RT), and temozolomide treatment. Novel RT-drug combinations are urgently needed to improve patient outcomes. Gold nanoparticles (GNPs) have demonstrated significant preclinical potential as radiosensitizers due to their unique physicochemical properties and their ability to pass the blood-brain barrier. The modification of GNP surface coatings with poly(ethylene) glycol (PEG) confers several therapeutic advantages including immune avoidance and improved cellular localisation. This study aimed to characterise both the radiosensitizing and immunomodulatory properties of differentially PEGylated GNPs in GBM cells in vitro. Two GBM cell lines were used, U-87 MG and U-251 MG. The radiobiological response was evaluated by clonogenic assay, immunofluorescent staining of 53BP1 foci, and flow cytometry. Changes in the cytokine expression levels were quantified by cytokine arrays. PEGylation improved the radiobiological efficacy, with double-strand break induction being identified as an underlying mechanism. PEGylated GNPs also caused the greatest boost in RT immunogenicity, with radiosensitization correlating with a greater upregulation of inflammatory cytokines. These findings demonstrate the radiosensitizing and immunostimulatory potential of ID11 and ID12 as candidates for RT-drug combination in future GBM preclinical investigations.

Oncolytic herpes simplex viruses for the treatment of glioma and targeting glioblastoma stem-like cells

Glioblastoma (GBM) is one of the most lethal cancers, having a poor prognosis and a median survival of only about 15 months with standard treatment (surgery, radiation, and chemotherapy), which has not been significantly extended in decades. GBM demonstrates remarkable cellular heterogeneity, with glioblastoma stem-like cells (GSCs) at the apex. GSCs are a subpopulation of GBM cells that possess the ability to self-renew, differentiate, initiate tumor formation, and manipulate the tumor microenvironment (TME). GSCs are no longer considered a static population of cells with specific markers but are quite flexible phenotypically and in driving tumor heterogeneity and therapeutic resistance. In light of these features, they are a critical target for successful GBM therapy. Oncolytic viruses, in particular oncolytic herpes simplex viruses (oHSVs), have many attributes for therapy and are promising agents to target GSCs. oHSVs are genetically-engineered to selectively replicate in and kill cancer cells, including GSCs, but not normal cells. Moreover, oHSV can induce anti-tumor immune responses and synergize with other therapies, such as chemotherapy, DNA repair inhibitors, and immune checkpoint inhibitors, to potentiate treatment effects and reduce GSC populations that are partly responsible for chemo- and radio-resistance. Herein, we present an overview of GSCs, activity of different oHSVs, clinical trial results, and combination strategies to enhance efficacy, including therapeutic arming of oHSV. Throughout, the therapeutic focus will be on GSCs and studies specifically targeting these cells. Recent clinical trials and approval of oHSV G47Δ in Japan for patients with recurrent glioma demonstrate the efficacy and promise of oHSV therapy.

Ready for Prime Time? Dendritic Cells in High-Grade Gliomas

High-grade gliomas are malignant brain tumors, and patient outcomes remain dismal despite the emergence of immunotherapies aimed at promoting tumor elimination by the immune system. A robust antitumor immune response requires the presentation of tumor antigens by dendritic cells (DC) to prime cytolytic T cells. However, there is a paucity of research on dendritic cell activity in the context of high-grade gliomas. As such, this review covers what is known about the role of DC in the CNS, DC infiltration of high-grade gliomas, tumor antigen drainage, the immunogenicity of DC activity, and DC subsets involved in the antitumor immune response. Finally, we consider the implications of suboptimal DC function in the context of immunotherapies and identify opportunities to optimize immunotherapies to treat high-grade gliomas.

Long-Acting Therapeutic Delivery Systems for the Treatment of Gliomas

Despite the emergence of cutting-edge therapeutic strategies and tremendous progress in research, a complete cure of glioma remains elusive. The heterogenous nature of tumor, immunosuppressive state and presence of blood brain barrier are few of the major obstacles in this regard. Long-acting depot formulations such as injectables and implantables are gaining attention for drug delivery to brain owing to their ease in administration and ability to elute drug locally for extended durations in a controlled manner with minimal toxicity. Hybrid matrices fabricated by incorporating nanoparticulates within such systems help to enhance pharmaceutical advantages. Utilization of long-acting depots as monotherapy or in conjunction with existing strategies rendered significant survival benefits in many preclinical studies and some clinical trials. The discovery of novel targets, immunotherapeutic strategies and alternative drug administration routes are now coupled with several long-acting systems with an ultimate aim to enhance patient survival and prevent glioma recurrences.

The Interplay between T Cells and Cancer: The Basis of Immunotherapy

Over the past decade, immunotherapy has emerged as one of the most promising approaches to cancer treatment. The use of immune checkpoint inhibitors has resulted in impressive and durable clinical responses in the treatment of various cancers. Additionally, immunotherapy utilizing chimeric antigen receptor (CAR)-engineered T cells has produced robust responses in blood cancers, and T cell receptor (TCR)-engineered T cells are showing promising results in the treatment of solid cancers. Despite these noteworthy advancements in cancer immunotherapy, numerous challenges remain. Some patient populations are unresponsive to immune checkpoint inhibitor therapy, and CAR T cell therapy has yet to show efficacy against solid cancers. In this review, we first discuss the significant role that T cells play in the body's defense against cancer. We then delve into the mechanisms behind the current challenges facing immunotherapy, starting with T cell exhaustion due to immune checkpoint upregulation and changes in the transcriptional and epigenetic landscapes of dysfunctional T cells. We then discuss cancer-cell-intrinsic characteristics, including molecular alterations in cancer cells and the immunosuppressive nature of the tumor microenvironment (TME), which collectively facilitate tumor cell proliferation, survival, metastasis, and immune evasion. Finally, we examine recent advancements in cancer immunotherapy, with a specific emphasis on T-cell-based treatments.

Immunotherapy in glioblastoma treatment: Current state and future prospects

Glioblastoma remains as the most common and aggressive malignant brain tumor, standing with a poor prognosis and treatment prospective. Despite the aggressive standard care, such as surgical resection and chemoradiation, median survival rates are low. In this regard, immunotherapeutic strategies aim to become more attractive for glioblastoma, considering its recent advances and approaches. In this review, we provide an overview of the current status and progress in immunotherapy for glioblastoma, going through the fundamental knowledge on immune targeting to promising strategies, such as Chimeric antigen receptor T-Cell therapy, immune checkpoint inhibitors, cytokine-based treatment, oncolytic virus and vaccine-based techniques. At last, it is discussed innovative methods to overcome diverse challenges, and future perspectives in this area.

The Current Status, Challenges, and Future Potential of Therapeutic Vaccination in Glioblastoma

Glioblastoma (GBM) is the most common malignant primary brain tumor and confers a dismal prognosis. With only two FDA-approved therapeutics showing modest survival gains since 2005, there is a great need for the development of other disease-targeted therapies. Due, in part, to the profound immunosuppressive microenvironment seen in GBMs, there has been a broad interest in immunotherapy. In both GBMs and other cancers, therapeutic vaccines have generally yielded limited efficacy, despite their theoretical basis. However, recent results from the DCVax-L trial provide some promise for vaccine therapy in GBMs. There is also the potential that future combination therapies with vaccines and adjuvant immunomodulating agents may greatly enhance antitumor immune responses. Clinicians must remain open to novel therapeutic strategies, such as vaccinations, and carefully await the results of ongoing and future trials. In this review of GBM management, the promise and challenges of immunotherapy with a focus on therapeutic vaccinations are discussed. Additionally, adjuvant therapies, logistical considerations, and future directions are discussed.

T cell exhaustion in malignant gliomas

Despite advances in understanding tumor biology, malignant gliomas remain incurable. While immunotherapy has improved outcomes in other cancer types, comparable efficacy has not yet been demonstrated for primary cancers of the central nervous system (CNS). T cell exhaustion, defined as a progressive decrease in effector function, sustained expression of inhibitory receptors, metabolic dysfunction, and distinct epigenetic and transcriptional alterations, contributes to the failure of immunotherapy in the CNS. Herein, we describe recent advances in understanding the drivers of T cell exhaustion in the glioma microenvironment. We discuss the extrinsic and intrinsic factors that contribute to exhaustion and highlight potential avenues for reversing this phenotype. Our ability to directly target specific immunosuppressive drivers in brain cancers would be a major advance in immunotherapy.

Transcription Factor-Forced Astrocytic Differentiation Impairs Human Glioblastoma Growth In Vitro and In Vivo

Direct cellular reprogramming has recently gained attention of cancer researchers for the possibility to convert undifferentiated cancer cells into more differentiated, postmitotic cell types. While a few studies have attempted reprogramming of glioblastoma (GBM) cells toward a neuronal fate, this approach has not yet been used to induce differentiation into other lineages and in vivo data on reduction in tumorigenicity are limited. Here, we employ cellular reprogramming to induce astrocytic differentiation as a therapeutic approach in GBM. To this end, we overexpressed key transcriptional regulators of astroglial development in human GBM and GBM stem cell lines. Treated cells undergo a remarkable shift in structure, acquiring an astrocyte-like morphology with star-shaped bodies and radial branched processes. Differentiated cells express typical glial markers and show a marked decrease in their proliferative state. In addition, forced differentiation induces astrocytic functions such as induced calcium transients and ability to respond to inflammatory stimuli. Most importantly, forced differentiation substantially reduces tumorigenicity of GBM cells in an in vivo xenotransplantation model. The current study capitalizes on cellular plasticity with a novel application in cancer. We take advantage of the similarity between neural developmental processes and cancer hierarchy to mitigate, if not completely abolish, the malignant nature of tumor cells and pave the way for new intervention strategies.

Reprogramming systemic and local immune function to empower immunotherapy against glioblastoma

The limited benefits of immunotherapy against glioblastoma (GBM) is closely related to the paucity of T cells in brain tumor bed. Both systemic and local immunosuppression contribute to the deficiency of tumor-infiltrating T cells. However, the current studies focus heavily on the local immunosuppressive tumor microenvironment but not on the co-existence of systemic immunosuppression. Here, we develop a nanostructure named Nano-reshaper to co-encapsulate lymphopenia alleviating agent cannabidiol and lymphocyte recruiting cytokine LIGHT. The results show that Nano-reshaper increases the number of systemic T cells and improves local T-cell recruitment condition, thus greatly increasing T-cell infiltration. When combined with immune checkpoint inhibitor, this therapeutic modality achieves 83.3% long-term survivors without recurrence in GBM models in male mice. Collectively, this work unveils that simultaneous reprogramming of systemic and local immune function is critical for T-cell based immunotherapy and provides a clinically translatable option for combating brain tumors.

Investigating the Effects of Olaparib on the Susceptibility of Glioblastoma Multiforme Tumour Cells to Natural Killer Cell-Mediated Responses

Glioblastoma multiforme (GBM) is the most common adult primary brain malignancy, with dismal survival rates of ~14.6 months. The current standard-of-care consists of surgical resection and chemoradiotherapy, however the treatment response is limited by factors such as tumour heterogeneity, treatment resistance, the blood-brain barrier, and immunosuppression. Several immunotherapies have undergone clinical development for GBM but demonstrated inadequate efficacy, yet future combinatorial approaches are likely to hold more promise. Olaparib is FDA-approved for BRCA-mutated advanced ovarian and breast cancer, and clinical studies have revealed its utility as a safe and efficacious radio- and chemo-sensitiser in GBM. The ability of Olaparib to enhance natural killer (NK) cell-mediated responses has been reported in prostate, breast, and lung cancer. This study examined its potential combination with NK cell therapies in GBM by firstly investigating the susceptibility of the GBM cell line T98G to NK cells and, secondly, examining whether Olaparib can sensitise T98G cells to NK cell-mediated responses. Here, we characterise the NK receptor ligand profile of T98G cells and demonstrate that Olaparib does not dampen T98G susceptibility to NK cells or elicit immunomodulatory effects on the function of NK cells. This study provides novel insights into the potential combination of Olaparib with NK cell therapies for GBM.

The Tumor Immune Microenvironment in Primary CNS Neoplasms: A Review of Current Knowledge and Therapeutic Approaches

Primary CNS neoplasms are responsible for considerable mortality and morbidity, and many therapies directed at primary brain tumors have proven unsuccessful despite their success in preclinical studies. Recently, the tumor immune microenvironment has emerged as a critical aspect of primary CNS neoplasms that may affect their malignancy, prognosis, and response to therapy across patients and tumor grades. This review covers the tumor microenvironment of various primary CNS neoplasms, with a focus on glioblastoma and meningioma. Additionally, current therapeutic strategies based on elements of the tumor microenvironment, including checkpoint inhibitor therapy and immunotherapeutic vaccines, are discussed.