Unique challenges for glioblastoma immunotherapy-discussions across neuro-oncology and non-neuro-oncology experts in cancer immunology. Meeting Report from the 2019 SNO Immuno-Oncology Think Tank

Glioma-neuronal circuit remodeling induces regional immunosuppression

Neuronal activity-driven mechanisms influence glioblastoma cell proliferation and invasion, while glioblastoma remodels neuronal circuits. Although a subpopulation of malignant cells enhances neuronal connectivity, their impact on the immune system remains unclear. Here, we show that glioblastoma regions with enhanced neuronal connectivity exhibit regional immunosuppression, characterized by distinct immune cell compositions and the enrichment of anti-inflammatory tumor-associated macrophages (TAMs). In preclinical models, knockout of Thrombospondin-1 (TSP1/Thbs1) in glioblastoma cells suppresses synaptogenesis and glutamatergic neuronal hyperexcitability. Furthermore, TSP1 knockout restores antigen presentation-related genes, promotes the infiltration of pro-inflammatory TAMs and CD8 + T-cells in the tumor, and alleviates TAM-mediated T-cell suppression. Pharmacological inhibition of glutamatergic signaling also shifts TAMs toward a less immunosuppressive state, prolongs survival in mice, and shows the potential to enhance the efficacy of immune cell-based therapy. These findings confirm that glioma-neuronal circuit remodeling is strongly linked with regional immunosuppression and suggest that targeting glioma-neuron-immune crosstalk could provide avenues for immunotherapy.

Immune checkpoint inhibitor (ICI) therapy in central nervous system cancers: State-of-the-art and future outlook

Invasive central nervous system (CNS) cancers are an area where the development of breakthrough therapies is urgently needed. For instance, conditions such as glioblastoma multiforme (GBM) are associated with poor clinical prognosis, with the majority of trials offering no improvement to marginally enhanced survival. Unleashing the potential of targeting the immune system in CNS cancers has gained attention in recent years. Inhibition of immune checkpoints such as CTLA-4, PD-1/PD-L1, TIM-3, and LAG-3 has been attempted in recent trials. While potentially offering a notable edge over other immunotherapies, multi-organ adverse events have been found with the administration of immune checkpoint inhibitors (ICIs). The present review captures the state-of-the-art evidence on ICI treatments in different CNS cancers. Also, we discuss the value of combinational therapies involving ICIs as well as next-generation therapeutics such as bispecific antibodies targeting PD-1/LAG-3/TIM-3 and CRISPR-Cas9-edited PD-1-knock-out checkpoint-resistant CAR T-cells.

Advancing glioblastoma therapy: Learning from the past and innovations for the future

Marred by a median survival of only around 12-15 months coupled with poor prognosis and effective therapeutic deprived drug armory, treatment/management of glioblastoma has proved to be a daunting task. Surgical resection, flanked by radiotherapy and chemotherapy with temozolomide, stands as the standard of care; however, this trimodal therapy often manifests limited efficacy due to the heterogeneous and highly infiltrative nature of GBM cells. In addition, the existence of the blood-brain barrier, tumor microenvironment, and the immunosuppressive nature of GBM, along with the encountered resistance of GBM cells towards conventional therapy, also hinders the therapeutic applications of chemotherapeutics in GBM. This review presents key insights into the molecular pathology of GBM, including genetic mutations, signaling pathways, and tumor microenvironment characteristics. Recent innovations such as immunotherapy, oncolytic viral therapies, vaccines, nanotechnology, electric field, and cancer neuroscience, as well as their clinical progress, have been covered. In addition, this compilation also encompasses a discussion on the role of personalized medicine in tailoring treatments based on individual tumor profiles, an approach that is gradually shifting the paradigm in GBM management. Endowed with the learnings imbibed from past failures coupled with the zeal to embrace novel/multidisciplinary approaches, researchers appear to be on the right track to pinpoint more effective and durable solutions in the context of GBM treatment.

Combination of Sodium Butyrate and Immunotherapy in Glioma: regulation of immunologically hot and cold tumors via gut microbiota and metabolites

Background

Recent studies have highlighted the importance of cross-talk along the gut-brain axis in regulating inflammatory nociception, inflammatory responses, and immune homeostasis. The gut microbiota, particularly its bacterial composition, plays a crucial role in the development and function of the immune system. Moreover, metabolites produced by the gut microbiota can significantly impact both systemic immune responses and central nervous system (CNS) immunity. Sodium butyrate is a key metabolite produced by the gut microbiota and, as a histone deacetylase inhibitor, can enhance the anti-tumor immunity of cytotoxic CD8+ T cells. However, it remains unclear whether sodium butyrate treatment can enhance the efficacy of PD-1 blockade in glioma therapy. In this research, the effect and underlying mechanism of combination of gut microbiota metabolites and anti-mouse PD-1 mAb on glioma has been investigated.

Methods

RNA-seq assay in glioma cell and biomedical databases, including ONCOMINE, GEPIA and TCGA were incorporated. Subsequently, the inhibitory effect of sodium butyrate on glioma cells and its related mechanisms were assessed through Counting Kit-8 (CCK-8), Flow Cytometry, Western blot (WB), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and other in vitro experiments. In vitro, an orthotopic mouse glioma model was established. MRI imaging, Immunohistochemistry, and Immune cell flow cytometry were used to investigate the therapeutic effects of combined sodium butyrate and PD-1 inhibitor treatment on glioma-bearing mice.

Results

We discovered that deacetylation-associated gene expression is significantly increased in glioma patients and affects patient survival time. Moreover, we found sodium butyrate promoted glioma cell apoptosis, disrupted the cell cycle, and inhibited tumor growth. Additionally, sodium butyrate may upregulate PD-L1 expression in glioma cells by modulating the PI3K/AKT pathway. The experimental results demonstrated that this combination therapy significantly reduced tumor volume and prolonged survival in an orthotopic murine glioma model. Moreover, combination therapy led to an increase in the proportion of probiotic bacteria in the mouse gut microbiota, resulting in elevated levels of antitumor metabolites and a decrease in metabolites that affect immune cell function.

A Radiologist's Guide to IDH-Wildtype Glioblastoma for Efficient Communication With Clinicians: Part II-Essential Information on Post-Treatment Imaging

Owing to recent advancements in various postoperative treatment modalities, such as radiation, chemotherapy, antiangiogenic treatment, and immunotherapy, the radiological and clinical assessment of patients with isocitrate dehydrogenase-wildtype glioblastoma using post-treatment imaging has become increasingly challenging. This review highlights the challenges in differentiating treatment-related changes such as pseudoprogression, radiation necrosis, and pseudoresponse from true tumor progression and aims to serve as a guideline for efficient communication with clinicians for optimal management of patients with post-treatment imaging.

Curative timed NK cell-based immunochemotherapy aborts brain tumour recurrence driven by mesenchymal glioma stem cells

High grade gliomas (HGG) are incurable brain cancers, where inevitable disease recurrence is driven by tumour-initiating glioma stem cells (GSCs). GSCs survive and expand in the brain after surgery, radiation and temozolomide (TMZ) chemotherapy, amidst weak immune and natural killer (NK) cell surveillance. The present study was designed to understand how to enhance the contribution of innate immunity to post TMZ disease control. Strikingly, molecular subtypes of HGG impacted the repertoire of NK cell sensitivity markers across human HGG transcriptomes, and in a panel of GSCs with either proneural (PN-GSC) or mesenchymal (MES-GSC) phenotypes. Indeed, only MES-GSCs (but not PN-GSCs) were enriched for NK cell ligands and sensitive to NK-mediated cytotoxicity in vitro. While NK cells alone had no effect on HGG progression in vivo, the post-chemotherapy (TMZ) recurrence of MES-GSC-driven xenografts was aborted by timed intracranial injection of live or irradiated NK (NK92MI) cells, resulting in long term survival of animals. This curative effect declined when NK cell administration was delayed relative to TMZ exposure pointing to limits of the immune control over resurging residual tumour stem cell populations that survived chemotherapy. Overall, these results suggest that chemotherapy-dependent tumour depopulation may create a unique window of opportunity for NK-mediated intervention with curative effects restricted to a subset of HGGs driven by mesenchymal brain tumour initiating cells.

CD47 Knock-Out Using CRISPR-Cas9 RNA Lipid Nanocarriers Results in Reduced Mesenchymal Glioblastoma Growth In Vivo

Immune checkpoint (ICP) blockade has shown limited effectiveness in glioblastoma (GBM), particularly in the mesenchymal subtype, where interactions between immune cells and glioblastoma cancer stem cells (GSCs) drive immunosuppression and therapy resistance. Tailoring ICPs specific to GSCs can enhance the antitumor immune response. This study proposes the use of lipid nanoparticles (LNPs) encapsulating CRISPR RNAs as an in vivo screening tool for ICPs in a syngeneic model of mesenchymal GSCs. Using PD-L1 and CD47 to validate the proof of concept, intratumoral administration of LNPs in orthotopic tumors achieved efficient editing of ICPs, leading to enhanced immune cell infiltration within the tumor microenvironment. Targeting CD47 reduced tumor growth, suggesting improved cancer cell sensitization to the immune system post-ICP editing. The study positions LNPs as a robust tool for in vivo validation of ICPs as therapeutic targets in clinically relevant GBM models. LNPs could serve as a screening tool in patient-derived xenografts to identify and optimize ICP combinations, potentially expediting ICP translation and enhancing personalized GBM immunotherapies.

Immune Resistance in Glioblastoma: Understanding the Barriers to ICI and CAR-T Cell Therapy

BACKGROUND

Glioblastoma (GBM) is the most common primary malignant brain tumor, with fewer than 5% of patients surviving five years after diagnosis. The introduction of immune checkpoint inhibitors (ICIs), followed by chimeric antigen receptor (CAR) T-cell therapy, marked major advancements in oncology. Despite demonstrating efficacy in other blood and solid cancers, these therapies have yielded limited success in clinical trials for both newly diagnosed and recurrent GBM. A deeper understanding of GBM's resistance to immunotherapy is essential for enhancing treatment responses and translating results seen in other cancer models.

OBJECTIVES

In this review, we examine clinical trial outcomes involving ICIs and CAR-T for GBM patients and explore the evasive mechanisms of GBM and the tumor microenvironment.

FINDINGS AND DISCUSSION

Multiple clinical trials investigating ICIs in GBM have shown poor outcomes, with no significant improvement in progression-free survival (PFS) or overall survival (OS). Results from smaller case studies with CAR-T therapy have warranted further investigation. However, no large-scale trials or robust studies have yet established these immunotherapeutic approaches as definitive treatment strategies. Future research should shift focus from addressing the scarcity of functional T cells to exploiting the abundant myeloid-derived cells within the tumor microenvironment.

CONCLUSIONS

Translating these therapies into effective treatments for glioblastoma in humans remains a significant challenge. The highly immunosuppressive nature of GBM and its tumor microenvironment continue to hinder the success of these innovative immunotherapeutic approaches. Targeting the myeloid-derived compartment may lead to more robust and sustained immune responses.

The PARPscore system using poly (ADP-ribose) polymerase (PARP) family features and tumor immune microenvironment in glioma

The immune response plays a pivotal role in tumor progression and therapy. However, the influence of protein PAR polymerases (PARPs) modifications on cell infiltration within the tumor microenvironment (TME) remains insufficiently understood. In this study, the Clinical and RNA sequencing data we performed a comprehensive analysis of PARPs modification patterns, exploring their associations with TME cell infiltration were acquired from the Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) database. To quantify PARPs modification in individual tumors, we developed a novel metric, the PARPscore, derived using principal component analysis. Our findings revealed three distinct PARPs modification patterns, each correlated with unique TME infiltration characteristics and tumor immunophenotypes. These patterns demonstrated predictive value for various clinical parameters, including inflammation stage, tumor subtypes, TME matrix activity, genetic variations, and patient prognosis. Notably, the high PARPscore subtype exhibited features of stromal activation and reduced immune infiltration, indicative of a non-inflamed, immune-excluded TME phenotype, and was associated with poorer survival outcomes. Conversely, lower PARPscore subtypes corresponded to substantial therapeutic benefits and improved outcomes in two independent immunotherapy cohorts. This study underscores the critical role of PARPs modification in shaping the diverse and dynamic TME. By delineating tumor-specific PARPs modification patterns, we provide valuable insights into TME complexity and its implications for immunotherapy.

Interferon regulatory factor 8-driven reprogramming of the immune microenvironment enhances antitumor adaptive immunity and reduces immunosuppression in murine glioblastoma

BACKGROUND

Glioblastoma (GBM) has a highly immunosuppressive tumor immune microenvironment (TIME), largely mediated by myeloid-derived suppressor cells (MDSCs). Here, we utilized a retroviral replicating vector (RRV) to deliver Interferon Regulatory Factor 8 (IRF8), a master regulator of type 1 conventional dendritic cell (cDC1) development, in a syngeneic murine GBM model. We hypothesized that RRV-mediated delivery of IRF8 could "reprogram" intratumoral MDSCs into antigen-presenting cells and thereby restore T-cell responses.

METHODS

Effects of RRV-IRF8 on survival and tumor growth kinetics were examined in the SB28 murine GBM model. The immunophenotype was analyzed by flow cytometry and gene expression assays. We assayed functional immunosuppression and antigen presentation by ex vivo T-cell-myeloid co-culture.

RESULTS

Intratumoral injection of RRV-IRF8 in mice bearing intracerebral SB28 glioma significantly suppressed tumor growth and prolonged survival. RRV-IRF8 treated tumors exhibited significant enrichment of cDC1s and CD8+ T-cells. Additionally, myeloid cells derived from RRV-IRF8 tumors showed decreased expression of the immunosuppressive markers Arg1 and IDO1 and demonstrated reduced suppression of naïve T-cell proliferation in ex vivo co-culture, compared to controls. Furthermore, DCs from RRV-IRF8 tumors showed increased antigen presentation compared to those from control tumors. In vivo treatment with azidothymidine (AZT), a viral replication inhibitor, showed that IRF8 transduction in both tumor and non-tumor cells is necessary for survival benefit, associated with a reprogrammed, cDC1- and CD8 T-cell-enriched TIME.

CONCLUSIONS

Our results indicate that reprogramming of glioma-infiltrating myeloid cells by in vivo expression of IRF8 may reduce immunosuppression and enhance antigen presentation, achieving improved tumor control.

Therapeutic approaches to modulate the immune microenvironment in gliomas

Immunomodulatory therapies, including immune checkpoint inhibitors, have drastically changed outcomes for certain cancer types over the last decade. Gliomas are among the cancers that have seem limited benefit from these agents, with most trials yielding negative results. The unique composition of the glioma immune microenvironment is among the culprits for this lack of efficacy. In recent years, several efforts have been made to improve understanding of the glioma immune microenvironment, aiming to pave the way for novel therapeutic interventions. In this review, we discuss some of the main components of the glioma immune microenvironment, including macrophages, myeloid-derived suppressor cells, neutrophils and microglial cells, as well as lymphocytes. We then provide a comprehensive overview of novel immunomodulatory agents that are currently in clinical development, namely oncolytic viruses, vaccines, cell-based therapies such as CAR-T cells and CAR-NK cells as well as antibodies and peptides.

Research progress on the role of PTEN deletion or mutation in the immune microenvironment of glioblastoma

Recent advances in immunotherapy represent a breakthrough in solid tumor treatment but the existing data indicate that immunotherapy is not effective in improving the survival time of patients with glioblastoma. The tumor microenvironment (TME) exerts a series of inhibitory effects on immune effector cells, which limits the clinical application of immunotherapy. Growing evidence shows that phosphate and tension homology deleted on chromosome ten (PTEN) plays an essential role in TME immunosuppression of glioblastoma. Emerging evidence also indicates that targeting PTEN can improve the anti-tumor immunity in TME and enhance the immunotherapy effect, highlighting the potential of PTEN as a promising therapeutic target. This review summarizes the function and specific upstream and downstream targets of PTEN-associated immune cells in glioblastoma TME, providing potential drug targets and therapeutic options for glioblastoma.

Lessons from Post-Immunotherapy Tumor Tissues in Clinical Trials: How Can We Fuel the Tumor Microenvironment in Gliomas?

Despite recent advancements in cancer immunotherapy, many patients with gliomas and glioblastomas have yet to experience substantial therapeutic benefits. Modulating the tumor microenvironment (TME) of gliomas, which is typically "cold", is crucial for improving treatment outcomes. Clinical tumor specimens obtained post-immunotherapy provide invaluable insights. However, access to such post-immunotherapy samples remains limited, even in clinical trials, as tumor tissues are often collected only at tumor relapse. Recent studies of neoadjuvant immunotherapy provided important insights by incorporating surgical resections of post-treatment tumors. Moreover, pre-surgical immunotherapies are increasingly integrated into clinical trial designs to evaluate treatment efficacy. These investigations reveal critical information, particularly regarding the delivery success of therapeutic agents, the expansion and persistence of immune products, and the cellular and molecular changes induced in the TME. In this review, we assess the findings on post-treatment tumor specimens obtained from recent immunotherapy clinical trials on gliomas, highlight the importance of these samples for understanding therapeutic impacts, and discuss proactive investigation approaches for future clinical trials.

TIM-3/CD68 double-high expression in Glioma: Prognostic characteristics and potential therapeutic approaches

BACKGROUND

Immunotherapy has revolutionized the treatment of various types of tumors, but there has been no breakthrough in the treatment of gliomas. The aim of this study is to discover valuable immunotherapy target in glioma, analyze its expression in glioma and the related microenvironment, explore potential immunotherapy strategies, and propose new possibilities for the treatment of gliomas.

METHODS

Immunohistochemistry (IHC) and multiplex fluorescence immunohistochemistry (mIHC) were used to analyze the expression of common immune markers and checkpoints in 187 glioma patients from Sun Yat-sen University Caner Center (SYSUCC). Bioinformatics analysis was used to examine the expression of TIM-3 in different macrophages using the Chinese Glioma Genome Atlas (CGGA) single-cell sequencing database. The Kaplan-Meier curve was used to predict the prognostic value of samples with high TIM-3 and CD68 expression. The R package was used to analyze the somatic mutation status and the sensitivity of small molecule inhibitors in TIM-3/CD68 double-high expression samples.

RESULTS

TIM-3 is a relatively highly expressed immune checkpoint in glioma. Unlike other tumors, TIM-3 is mainly expressed on macrophages in the glioma microenvironment. TIM-3/CD68 double-high expression suggests poor survival in glioma and may be a new upgrade marker in both IDH-mutant glioma and IDH-wildtype low-grade glioma (LGG) glioma (P < 0.01). Exploring the combination of TIM-3 inhibitors and p38 MAPK inhibitor may be a potential treatment direction for TIM-3/CD68 double high expression gliomas in the future.

CONCLUSIONS

The combination of TIM-3 and CD68 holds significant importance as a potential target for both prognosis and therapeutic intervention in glioma.

Tumor biomechanics as a novel imaging biomarker to assess response to immunotherapy in a murine glioma model

Glioblastoma is the most common and aggressive primary malignant brain tumor with poor prognosis. Novel immunotherapeutic approaches are currently under investigation. Even though magnetic resonance imaging (MRI) is the most important imaging tool for treatment monitoring, response assessment is often hampered by therapy-related tissue changes. As tumor and therapy-associated tissue reactions differ structurally, we hypothesize that biomechanics could be a pertinent imaging proxy for differentiation. Longitudinal MRI and magnetic resonance elastography (MRE) were performed to monitor response to immunotherapy with a toll-like receptor 7/8 agonist in orthotopic syngeneic experimental glioma. Imaging results were correlated to histology and light sheet microscopy data. Here, we identify MRE as a promising non-invasive imaging method for immunotherapy-monitoring by quantifying changes in response-related tumor mechanics. Specifically, we show that a relative softening of treated compared to untreated tumors is linked to the inflammatory processes following therapy-induced re-education of tumor-associated myeloid cells. Mechanistically, combined effects of myeloid influx and inflammation including extracellular matrix degradation following immunotherapy form the basis of treated tumors being softer than untreated glioma. This is a very early indicator of therapy response outperforming established imaging metrics such as tumor volume. The overall anti-tumor inflammatory processes likely have similar effects on human brain tissue biomechanics, making MRE a promising tool for gauging response to immunotherapy in glioma patients early, thereby strongly impacting patient pathway.

Glioblastoma microenvironment-from biology to therapy

Glioblastoma (GBM) is the most aggressive primary brain cancer. These tumors exhibit high intertumoral and intratumoral heterogeneity in neoplastic and nonneoplastic compartments, low lymphocyte infiltration, and high abundance of myeloid subsets that together create a highly protumorigenic immunosuppressive microenvironment. Moreover, heterogeneous GBM cells infiltrate adjacent brain tissue, remodeling the neural microenvironment to foster tumor electrochemical coupling with neurons and metabolic coupling with nonneoplastic astrocytes, thereby driving growth. Here, we review heterogeneity in the GBM microenvironment and its role in low-to-high-grade glioma transition, concluding with a discussion of the challenges of therapeutically targeting the tumor microenvironment and outlining future research opportunities.

The Role of Mesenchymal Reprogramming in Malignant Clonal Evolution and Intra-Tumoral Heterogeneity in Glioblastoma

Glioblastoma (GBM) is the most common yet uniformly fatal adult brain cancer. Intra-tumoral molecular and cellular heterogeneities are major contributory factors to therapeutic refractoriness and futility in GBM. Molecular heterogeneity is represented through molecular subtype clusters whereby the proneural (PN) subtype is associated with significantly increased long-term survival compared to the highly resistant mesenchymal (MES) subtype. Furthermore, it is universally recognized that a small subset of GBM cells known as GBM stem cells (GSCs) serve as reservoirs for tumor recurrence and progression. The clonal evolution of GSC molecular subtypes in response to therapy drives intra-tumoral heterogeneity and remains a critical determinant of GBM outcomes. In particular, the intra-tumoral MES reprogramming of GSCs using current GBM therapies has emerged as a leading hypothesis for therapeutic refractoriness. Preventing the intra-tumoral divergent evolution of GBM toward the MES subtype via new treatments would dramatically improve long-term survival for GBM patients and have a significant impact on GBM outcomes. In this review, we examine the challenges of the role of MES reprogramming in the malignant clonal evolution of glioblastoma and provide future perspectives for addressing the unmet therapeutic need to overcome resistance in GBM.

Hypoxia coordinates the spatial landscape of myeloid cells within glioblastoma to affect survival

Myeloid cells are highly prevalent in glioblastoma (GBM), existing in a spectrum of phenotypic and activation states. We now have limited knowledge of the tumor microenvironment (TME) determinants that influence the localization and the functions of the diverse myeloid cell populations in GBM. Here, we have utilized orthogonal imaging mass cytometry with single-cell and spatial transcriptomic approaches to identify and map the various myeloid populations in the human GBM tumor microenvironment (TME). Our results show that different myeloid populations have distinct and reproducible compartmentalization patterns in the GBM TME that is driven by tissue hypoxia, regional chemokine signaling, and varied homotypic and heterotypic cellular interactions. We subsequently identified specific tumor subregions in GBM, based on composition of identified myeloid cell populations, that were linked to patient survival. Our results provide insight into the spatial organization of myeloid cell subpopulations in GBM, and how this is predictive of clinical outcome.

Novel Clinical Trials and Approaches in the Management of Glioblastoma

PURPOSE OF REVIEW

The purpose of this review is to discuss a wide variety of novel therapies recently studied or actively undergoing study in patients with glioblastoma. This review also discusses current and future strategies for improving clinical trial design in patients with glioblastoma to maximize efficacy in discovering effective treatments.

RECENT FINDINGS

Over the years, there has been significant expansion in therapy modalities studied in patients with glioblastoma. These therapies include, but are not limited to, targeted molecular therapies, DNA repair pathway targeted therapies, immunotherapies, vaccine therapies, and surgically targeted radiotherapies. Glioblastoma is the most common malignant primary brain tumor in adults and unfortunately remains with poor overall survival following the current standard of care. Given the dismal prognosis, significant clinical and research efforts are ongoing with the goal of improving patient outcomes and enhancing quality and quantity of life utilizing a wide variety of novel therapies.

Enhancing CAR-T cell metabolism to overcome hypoxic conditions in the brain tumor microenvironment

The efficacy of chimeric antigen receptor T cell (CAR-T) therapy has been limited against brain tumors to date. CAR-T cells infiltrating syngeneic intracerebral SB28 EGFRvIII gliomas revealed impaired mitochondrial ATP production and a markedly hypoxic status compared with ones migrating to subcutaneous tumors. Drug screenings to improve metabolic states of T cells under hypoxic conditions led us to evaluate the combination of the AMPK activator metformin and the mTOR inhibitor rapamycin (Met+Rap). Met+Rap-pretreated mouse CAR-T cells showed activated PPAR-γ coactivator 1α (PGC-1α) through mTOR inhibition and AMPK activation, and a higher level of mitochondrial spare respiratory capacity than those pretreated with individual drugs or without pretreatment. Moreover, Met+Rap-pretreated CAR-T cells demonstrated persistent and effective antiglioma cytotoxic activities in the hypoxic condition. Furthermore, a single intravenous infusion of Met+Rap-pretreated CAR-T cells significantly extended the survival of mice bearing intracerebral SB28 EGFRvIII gliomas. Mass cytometric analyses highlighted increased glioma-infiltrating CAR-T cells in the Met+Rap group, with fewer Ly6c+CD11b+ monocytic myeloid-derived suppressor cells in the tumors. Finally, human CAR-T cells pretreated with Met+Rap recapitulated the observations with murine CAR-T cells, demonstrating improved functions under in vitro hypoxic conditions. These findings advocate for translational and clinical exploration of Met+Rap-pretreated CAR-T cells in human trials.

IRF8-driven reprogramming of the immune microenvironment enhances anti-tumor adaptive immunity and reduces immunosuppression in murine glioblastoma

Background

Glioblastoma (GBM) has a highly immunosuppressive tumor immune microenvironment (TIME), largely mediated by myeloid-derived suppressor cells (MDSCs). Here, we utilized a retroviral replicating vector (RRV) to deliver Interferon Regulatory Factor 8 (IRF8), a master regulator of type 1 conventional dendritic cell (cDC1) development, in a syngeneic murine GBM model. We hypothesized that RRV-mediated delivery of IRF8 could "reprogram" intratumoral MDSCs into antigen-presenting cells (APCs) and thereby restore T-cell responses.

Methods

Effects of RRV-IRF8 on survival and tumor growth kinetics were examined in the SB28 murine GBM model. Immunophenotype was analyzed by flow cytometry and gene expression assays. We assayed functional immunosuppression and antigen presentation by ex vivo T-cell-myeloid co-culture.

Results

Mice with RRV-IRF8 pre-transduced intracerebral tumors had significantly longer survival and slower tumor growth compared to controls. RRV-IRF8 treated tumors exhibited significant enrichment of cDC1s and CD8+ T-cells. Additionally, myeloid cells derived from RRV-IRF8 tumors showed decreased expression of the immunosuppressive markers Arg1 and IDO1 and demonstrated reduced suppression of naïve T-cell proliferation in ex vivo co-culture, compared to controls. Furthermore, DCs from RRV-IRF8 tumors showed increased antigen presentation compared to those from control tumors. In vivo treatment with azidothymidine (AZT), a viral replication inhibitor, showed that IRF8 transduction in both tumor and non-tumor cells is necessary for survival benefit, associated with a reprogrammed, cDC1- and CD8 T-cell-enriched TIME.

Conclusions

Our results indicate that reprogramming of glioma-infiltrating myeloid cells by in vivo expression of IRF8 may reduce immunosuppression and enhance antigen presentation, achieving improved tumor control.

IL4I1 in M2-like macrophage promotes glioma progression and is a promising target for immunotherapy

Background

Glioma is the prevailing malignant intracranial tumor, characterized by an abundance of macrophages. Specifically, the infiltrating macrophages often display the M2 subtype and are known as tumor-associated macrophages (TAMs). They have a critical role in promoting the oncogenic properties of tumor cells. Interleukin-4-induced-1 (IL4I1) functions as an L-phenylalanine oxidase, playing a key part in regulating immune responses and the progression of various tumors. However, there is limited understanding of the IL4I1-mediated cross-talk function between TAMs and glioma cell in the glioma microenvironment.

Methods

TCGA, GTEx, and HPA databases were applied to assess the IL4I1 expression, clinical characteristics, and prognostic value of pan-cancer. The link between IL4I1 levels and the prognosis, methylation, and immune checkpoints (ICs) in gliomas were explored through Kaplan-Meier curve, Cox regression, and Spearman correlation analyses. The IL4I1 levels and their distribution were investigated by single-cell analysis and the TIMER 2 database. Additionally, validation of IL4I1 expression was performed by WB, RT-qPCR, IHC, and IF. Co-culture models between glioma cells and M2-like macrophages were used to explore the IL4I1-mediated effects on tumor growth, invasion, and migration of glioma cells. Moreover, the function of IL4I1 on macrophage polarization was evaluated by ELISA, RT-qPCR, WB, and siRNA transfection.

Results

Both transcriptome and protein levels of IL4I1 were increased obviously in various tumor types, and correlated with a dismal prognosis. Specifically, IL4I1 was implicated in aggressive progression and a dismal prognosis for patients with glioma. A negative association was noticed between the glioma grade and DNA promoter methylation of IL4I1. Enrichment analyses in glioma patients suggested that IL4I1 was linked to cytokine and immune responses, and was positively correlated with ICs. Single-cell analysis, molecular experiments, and in vitro assays showed that IL4I1 was significantly expressed in TAMs. Importantly, co-culture models proved that IL4I1 significantly promoted the invasion and migration of glioma cells, and induced the polarization of M2-like macrophages.

Conclusion

IL4I1 could be a promising immunotherapy target for selective modulation of TAMs and stands as a novel macrophage-related prognostic biomarker in glioma.

Preclinical and early clinical studies of a novel compound SYHA1813 that efficiently crosses the blood-brain barrier and exhibits potent activity against glioblastoma

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor in adults and is poorly controlled. Previous studies have shown that both macrophages and angiogenesis play significant roles in GBM progression, and co-targeting of CSF1R and VEGFR is likely to be an effective strategy for GBM treatment. Therefore, this study developed a novel and selective inhibitor of CSF1R and VEGFR, SYHA1813, possessing potent antitumor activity against GBM. SYHA1813 inhibited VEGFR and CSF1R kinase activities with high potency and selectivity and thus blocked the cell viability of HUVECs and macrophages and exhibited anti-angiogenetic effects both in vitro and in vivo. SYHA1813 also displayed potent in vivo antitumor activity against GBM in immune-competent and immune-deficient mouse models, including temozolomide (TMZ) insensitive tumors. Notably, SYHA1813 could penetrate the blood-brain barrier (BBB) and prolong the survival time of mice bearing intracranial GBM xenografts. Moreover, SYHA1813 treatment resulted in a synergistic antitumor efficacy in combination with the PD-1 antibody. As a clinical proof of concept, SYHA1813 achieved confirmed responses in patients with recurrent GBM in an ongoing first-in-human phase I trial. The data of this study support the rationale for an ongoing phase I clinical study (ChiCTR2100045380).

Model incorporating multiple diffusion MRI features: development and validation of a radiomics-based model to predict adult-type diffuse gliomas grade

OBJECTIVES

To develop and validate a radiomics-based model (ADGGIP) for predicting adult-type diffuse gliomas (ADG) grade by combining multiple diffusion modalities and clinical and imaging morphologic features.

METHODS

In this prospective study, we recruited 103 participants diagnosed with ADG and collected their preoperative conventional MRI and multiple diffusion imaging (diffusion tensor imaging, diffusion kurtosis imaging, neurite orientation dispersion and density imaging, and mean apparent propagator diffusion-MRI) data in our hospital, as well as clinical information. Radiomic features of the diffusion images and clinical information and morphological data from the radiological reports were extracted, and multiple pipelines were used to construct the optimal model. Model validation was performed through a time-independent validation cohort. ROC curves were used to evaluate model performance. The clinical benefit was determined by decision curve analysis.

RESULTS

From June 2018 to May 2021, 72 participants were recruited for the training cohort. Between June 2021 and February 2022, 31 participants were enrolled in the prospective validation cohort. In the training cohort (AUC 0.958), internal validation cohort (0.942), and prospective validation cohort (0.880), ADGGIP had good accuracy in predicting ADG grade. ADGGIP was also significantly better than the single-modality prediction model (AUC 0.860) and clinical imaging morphology model (0.841) (all p < .01) in the prospective validation cohort. When the threshold probability was greater than 5%, ADGGIP provided the greatest net benefit.

CONCLUSION

ADGGIP, which is based on advanced diffusion modalities, can predict the grade of ADG with high accuracy and robustness and can help improve clinical decision-making.

CLINICAL RELEVANCE STATEMENT

Integrated multi-modal predictive modeling is beneficial for early detection and treatment planning of adult-type diffuse gliomas, as well as for investigating the genuine clinical significance of biomarkers.

KEY POINTS

• Integrated model exhibits the highest performance and stability. • When the threshold is greater than 5%, the integrated model has the greatest net benefit. • The advanced diffusion models do not demonstrate better performance than the simple technology.

Enhancing CAR-T Cell Metabolism to Overcome Hypoxic Conditions in the Brain Tumor Microenvironment

The efficacy of chimeric antigen receptor (CAR)-T therapy has been limited against brain tumors to date. CAR-T cells infiltrating syngeneic intracerebral SB28-EGFRvIII glioma revealed impaired mitochondrial ATP production and a markedly hypoxic status compared to ones migrating to subcutaneous tumors. Drug screenings to improve metabolic states of T cells under hypoxic conditions led us to evaluate the combination of AMPK activator Metformin and the mTOR inhibitor Rapamycin (Met+Rap). Met+Rap-pretreated mouse CAR-T cells showed activated PPAR-gamma coactivator 1α (PGC-1α) through mTOR inhibition and AMPK activation, and a higher level of mitochondrial spare respiratory capacity than those pretreated with individual drugs or without pretreatment. Moreover, Met+Rap-pretreated CAR-T cells demonstrated persistent and effective anti-glioma cytotoxic activities in the hypoxic condition. Furthermore, a single intravenous infusion of Met+Rap-pretreated CAR-T cells significantly extended the survival of mice bearing intracerebral SB28-EGFRvIII gliomas. Mass cytometric analyses highlighted increased glioma-infiltrating CAR-T cells in the Met+Rap group with fewer Ly6c+ CD11b+ monocytic myeloid-derived suppressor cells in the tumors. Finally, human CAR-T cells pretreated with Met+Rap recapitulated the observations with murine CAR-T cells, demonstrating improved functions in vitro hypoxic conditions. These findings advocate for translational and clinical exploration of Met+Rap-pretreated CAR-T cells in human trials.

Clinical trial links oncolytic immunoactivation to survival in glioblastoma

Immunotherapy failures can result from the highly suppressive tumour microenvironment that characterizes aggressive forms of cancer such as recurrent glioblastoma (rGBM)1,2. Here we report the results of a first-in-human phase I trial in 41 patients with rGBM who were injected with CAN-3110-an oncolytic herpes virus (oHSV)3. In contrast to other clinical oHSVs, CAN-3110 retains the viral neurovirulence ICP34.5 gene transcribed by a nestin promoter; nestin is overexpressed in GBM and other invasive tumours, but not in the adult brain or healthy differentiated tissue4. These modifications confer CAN-3110 with preferential tumour replication. No dose-limiting toxicities were encountered. Positive HSV1 serology was significantly associated with both improved survival and clearance of CAN-3110 from injected tumours. Survival after treatment, particularly in individuals seropositive for HSV1, was significantly associated with (1) changes in tumour/PBMC T cell counts and clonal diversity, (2) peripheral expansion/contraction of specific T cell clonotypes; and (3) tumour transcriptomic signatures of immune activation. These results provide human validation that intralesional oHSV treatment enhances anticancer immune responses even in immunosuppressive tumour microenvironments, particularly in individuals with cognate serology to the injected virus. This provides a biological rationale for use of this oncolytic modality in cancers that are otherwise unresponsive to immunotherapy (ClinicalTrials.gov: NCT03152318 ).

Combined cytotoxic and immune-stimulatory gene therapy using Ad-TK and Ad-Flt3L: Translational developments from rodents to glioma patients

Gliomas are the most prevalent and devastating primary malignant brain tumors in adults. Despite substantial advances in understanding glioma biology, there have been no regulatory drug approvals in the US since bevacizumab in 2009 and tumor treating fields in 2011. Recent phase III clinical trials have failed to meet their prespecified therapeutic primary endpoints, highlighting the need for novel therapies. The poor prognosis of glioma patients, resistance to chemo-radiotherapy, and the immunosuppressive tumor microenvironment underscore the need for the development of novel therapies. Gene therapy-based immunotherapeutic strategies that couple the ability of the host immune system to specifically kill glioma cells and develop immunological memory have shown remarkable progress. Two adenoviral vectors expressing Ad-HSV1-TK/GCV and Ad-Flt3L have shown promising preclinical data, leading to FDA approval of a non-randomized, phase I open-label, first in human trial to test safety, cytotoxicity, and immune-stimulatory efficiency in high-grade glioma patients (NCT01811992). This review provides a thorough overview of immune-stimulatory gene therapy highlighting recent advancements, potential drawbacks, future directions, and recommendations for future implementation of clinical trials.

Dendritic cell vaccine trials in gliomas: Untangling the lines

Glioblastoma is a deadly brain tumor without any significantly successful treatments to date. Tumor antigen-targeted immunotherapy platforms including peptide and dendritic cell (DC) vaccines, have extended survival in hematologic malignancies. The relatively "cold" tumor immune microenvironment and heterogenous nature of glioblastoma have proven to be major limitations to translational application and efficacy of DC vaccines. Furthermore, many DC vaccine trials in glioblastoma are difficult to interpret due to a lack of contemporaneous controls, absence of any control comparison, or inconsistent patient populations. Here we review glioblastoma immunobiology aspects that are relevant to DC vaccines, review the clinical experience with DC vaccines targeting glioblastoma, discuss challenges in clinical trial design, and summarize conclusions and directions for future research for the development of effective DC vaccines for patients.

Bispecific T-Cell Engagers and Chimeric Antigen Receptor T-Cell Therapies in Glioblastoma: An Update

Glioblastoma is the most common malignant primary brain tumor in adults. The prognosis is extremely poor even with standard treatment of maximal safe resection, radiotherapy, and chemotherapy. Recurrence is inevitable within months, and treatment options are very limited. Chimeric antigen receptor T-cell therapy (CART) and bispecific T-cell engagers (TCEs) are two emerging immunotherapies that can redirect T-cells for tumor-specific killing and have shown remarkable success in hematological malignancies and been under extensive study for application in glioblastoma. While there have been multiple clinical trials showing preliminary evidence of safety and efficacy for CART, bispecific TCEs are still in the early stages of clinical testing, with preclinical studies showing very promising results. However, there are multiple shared challenges that need to be addressed in the future, including the route of delivery, antigen escape, the immunosuppressive tumor microenvironment, and toxicity resulting from the limited choice of tumor-specific antigens. Efforts are underway to optimize the design of both these treatments and find the ideal combination therapy to overcome these challenges. In this review, we describe the work that has been performed as well as novel approaches in glioblastoma and in other solid tumors that may be applicable in the future.

Tumor-associated macrophage-related strategies for glioma immunotherapy

High-grade glioma is one of the deadliest primary tumors of the central nervous system. Despite the many novel immunotherapies currently in development, it has been difficult to achieve breakthrough results in clinical studies. The reason may be due to the suppressive tumor microenvironment of gliomas that limits the function of specific immune cells (e.g., T cells) which are currently the primary targets of immunotherapy. However, tumor-associated macrophage, which are enriched in tumors, plays an important role in the development of GBM and is becoming a research hotspot for immunotherapy. This review focuses on current research advances in the use of macrophages as therapeutic targets or therapeutic tools for gliomas, and provides some potential research directions.

Glioma-neuronal circuit remodeling induces regional immunosuppression

Neuronal activity-driven mechanisms impact glioblastoma cell proliferation and invasion 1-7 , and glioblastoma remodels neuronal circuits 8,9 . Distinct intratumoral regions maintain functional connectivity via a subpopulation of malignant cells that mediate tumor-intrinsic neuronal connectivity and synaptogenesis through their transcriptional programs 8 . However, the effects of tumor-intrinsic neuronal activity on other cells, such as immune cells, remain unknown. Here we show that regions within glioblastomas with elevated connectivity are characterized by regional immunosuppression. This was accompanied by different cell compositions and inflammatory status of tumor-associated macrophages (TAMs) in the tumor microenvironment. In preclinical intracerebral syngeneic glioblastoma models, CRISPR/Cas9 gene knockout of Thrombospondin-1 (TSP-1/ Thbs1 ), a synaptogenic factor critical for glioma-induced neuronal circuit remodeling, in glioblastoma cells suppressed synaptogenesis and glutamatergic neuronal hyperexcitability, while simultaneously restoring antigen-presentation and pro-inflammatory responses. Moreover, TSP-1 knockout prolonged survival of immunocompetent mice harboring intracerebral syngeneic glioblastoma, but not of immunocompromised mice, and promoted infiltrations of pro-inflammatory TAMs and CD8+ T-cells in the tumor microenvironment. Notably, pharmacological inhibition of glutamatergic excitatory signals redirected tumor-associated macrophages toward a less immunosuppressive phenotype, resulting in prolonged survival. Altogether, our results demonstrate previously unrecognized immunosuppression mechanisms resulting from glioma-neuronal circuit remodeling and suggest future strategies targeting glioma-neuron-immune crosstalk may open up new avenues for immunotherapy.

Novel Immunotherapeutic Approaches for the Treatment of Glioblastoma

Glioblastoma is highly aggressive and remains difficult to treat despite being the most common malignant primary brain tumor in adults. Current standard-of-care treatment calls for maximum resection of the tumor mass followed by concurrent chemotherapy and radiotherapy and further adjuvant chemotherapy if necessary. Despite this regimen, prognosis remains grim. Immunotherapy has shown promising success in a variety of solid tumor types, but efficacy in glioblastoma is yet to be demonstrated. Barriers to the success of immunotherapy in glioblastoma include: a heterogeneous tumor cell population, a highly immunosuppressive microenvironment, and the blood-brain barrier, to name a few. Several immunotherapeutic approaches are actively being investigated and developed to overcome these limitations. In this review, we present different classes of immunotherapy targeting glioblastoma, their most recent results, and potential future directions.

Personalized Treatment of Glioblastoma: Current State and Future Perspective

Glioblastoma (GBM) is the most aggressive glial tumor of the central nervous system. Despite intense scientific efforts, patients diagnosed with GBM and treated with the current standard of care have a median survival of only 15 months. Patients are initially treated by a neurosurgeon with the goal of maximal safe resection of the tumor. Obtaining tissue samples during surgery is indispensable for the diagnosis of GBM. Technological improvements, such as navigation systems and intraoperative monitoring, significantly advanced the possibility of safe gross tumor resection. Usually within six weeks after the surgery, concomitant radiotherapy and chemotherapy with temozolomide are initiated. However, current radiotherapy regimens are based on population-level studies and could also be improved. Implementing artificial intelligence in radiotherapy planning might be used to individualize treatment plans. Furthermore, detailed genetic and molecular markers of the tumor could provide patient-tailored immunochemotherapy. In this article, we review current standard of care and possibilities of personalizing these treatments. Additionally, we discuss novel individualized therapeutic options with encouraging results. Due to inherent heterogeneity of GBM, applying patient-tailored treatment could significantly prolong survival of these patients.

Barriers to overcoming immunotherapy resistance in glioblastoma

Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor, known for its poor prognosis and high recurrence rate. Current standard of care includes surgical resection followed by combined radiotherapy and chemotherapy. Although immunotherapies have yielded promising results in hematological malignancies, their successful application in GBM remains limited due to a host of immunosuppressive factors unique to GBM. As a result of these roadblocks, research efforts have focused on utilizing combinatorial immunotherapies that target networks of immune processes in GBM with promising results in both preclinical and clinical trials, although limitations in overcoming the immunosuppressive factors within GBM remain. In this review, we aim to discuss the intrinsic and adaptive immune resistance unique to GBM and to summarize the current evidence and outcomes of engineered and non-engineered treatments targeted at overcoming GBM resistance to immunotherapy. Additionally, we aim to highlight the most promising strategies of targeted GBM immunotherapy combinatorial treatments and the insights that may directly improve the current patient prognosis and clinical care.

The Blood-Brain Barrier: Implications for Experimental Cancer Therapeutics

The blood-brain barrier is critically important for the treatment of both primary and metastatic cancers of the central nervous system (CNS). Clinical outcomes for patients with primary CNS tumors are poor and have not significantly improved in decades. As treatments for patients with extracranial solid tumors improve, the incidence of CNS metastases is on the rise due to suboptimal CNS exposure of otherwise systemically active agents. Despite state-of-the art surgical care and increasingly precise radiation therapy, clinical progress is limited by the ability to deliver an effective dose of a therapeutic agent to all cancerous cells. Given the tremendous heterogeneity of CNS cancers, both across cancer subtypes and within a single tumor, and the range of diverse therapies under investigation, a nuanced examination of CNS drug exposure is needed. With a shared goal, common vocabulary, and interdisciplinary collaboration, the field is poised for renewed progress in the treatment of CNS cancers.

Reversing T Cell Dysfunction to Boost Glioblastoma Immunotherapy by Paroxetine-Mediated GRK2 Inhibition and Blockade of Multiple Checkpoints through Biomimetic Nanoparticles

T cell dysfunction-induced tumor immune escape is particularly severe in glioblastoma (GBM), and significantly affects the efficacy of immunotherapy. It is crucial to innovatively reverse the T cell dysfunction for improving GBM immunotherapy. Herein, T cell dysfunction is remarkably reversed and immunotherapy of GBM is boosted by repurposing the U. S. Food and Drug Administration-approved antidepressant paroxetine (PX) with biomimetic nanoparticles (CS-J@CM/6 NPs). The PX is successfully applied to abrogate T cell sequestration in the bone marrow of GBM-bearing mice and increase their infiltration in tumor. The biomimetic NPs are composed of ultrasmall Cu_{2- x} Se NPs, JQ1, and tumor cell membrane modified with CD6, and are efficiently delivered into tumor through the specific interactions between CD6 and activated leukocyte cell adhesion molecule. They ameliorate the T cell dysfunction through the double roles of loaded JQ1, which simultaneously decreases the expression of PD-1 and TIM-3 on T cells, and the expression of PD-L1 on tumor cells. The NP also induces the immunogenic cell death of tumor cells to activate immune response. The synergistic roles of PX and biomimetic CS-J@CM/6 NPs notably enhance the survival of GBM-bearing mice. This work provides new insights into tumor immunotherapy by repurposing "old drugs" with advanced NPs.

Recent Developments in Glioblastoma Therapy: Oncolytic Viruses and Emerging Future Strategies

Glioblastoma is the most aggressive form of malignant brain tumor. Standard treatment protocols and traditional immunotherapy are poorly effective as they do not significantly increase the long-term survival of glioblastoma patients. Oncolytic viruses (OVs) may be an effective alternative approach. Combining OVs with some modern treatment options may also provide significant benefits for glioblastoma patients. Here we review virotherapy for glioblastomas and describe several OVs and their combination with other therapies. The personalized use of OVs and their combination with other treatment options would become a significant area of research aiming to develop the most effective treatment regimens for glioblastomas.

T cell-independent eradication of experimental glioma by intravenous TLR7/8-agonist-loaded nanoparticles

Glioblastoma, the most common and aggressive primary brain tumor type, is considered an immunologically "cold" tumor with sparse infiltration by adaptive immune cells. Immunosuppressive tumor-associated myeloid cells are drivers of tumor progression. Therefore, targeting and reprogramming intratumoral myeloid cells is an appealing therapeutic strategy. Here, we investigate a β-cyclodextrin nanoparticle (CDNP) formulation encapsulating the Toll-like receptor 7 and 8 (TLR7/8) agonist R848 (CDNP-R848) to reprogram myeloid cells in the glioma microenvironment. We show that intravenous monotherapy with CDNP-R848 induces regression of established syngeneic experimental glioma, resulting in increased survival rates compared with unloaded CDNP controls. Mechanistically, CDNP-R848 treatment reshapes the immunosuppressive tumor microenvironment and orchestrates tumor clearing by pro-inflammatory tumor-associated myeloid cells, independently of T cells and NK cells. Using serial magnetic resonance imaging, we identify a radiomic signature in response to CDNP-R848 treatment and ultrasmall superparamagnetic iron oxide (USPIO) imaging reveals that immunosuppressive macrophage recruitment is reduced by CDNP-R848. In conclusion, CDNP-R848 induces tumor regression in experimental glioma by targeting blood-borne macrophages without requiring adaptive immunity.

Immunotoxin-αCD40 therapy activates innate and adaptive immunity and generates a durable antitumor response in glioblastoma models

D2C7-immunotoxin (IT), a dual-specific IT targeting wild-type epidermal growth factor receptor (EGFR) and mutant EGFR variant III (EGFRvIII) proteins, demonstrates encouraging survival outcomes in a subset of patients with glioblastoma. We hypothesized that immunosuppression in glioblastoma limits D2C7-IT efficacy. To improve the response rate and reverse immunosuppression, we combined D2C7-IT tumor cell killing with αCD40 costimulation of antigen-presenting cells. In murine glioma models, a single intratumoral injection of D2C7-IT+αCD40 treatment activated a proinflammatory phenotype in microglia and macrophages, promoted long-term tumor-specific CD8+ T cell immunity, and generated cures. D2C7-IT+αCD40 treatment increased intratumoral Slamf6+CD8+ T cells with a progenitor phenotype and decreased terminally exhausted CD8+ T cells. D2C7-IT+αCD40 treatment stimulated intratumoral CD8+ T cell proliferation and generated cures in glioma-bearing mice despite FTY720-induced peripheral T cell sequestration. Tumor transcriptome profiling established CD40 up-regulation, pattern recognition receptor, cell senescence, and immune response pathway activation as the drivers of D2C7-IT+αCD40 antitumor responses. To determine potential translation, immunohistochemistry staining confirmed CD40 expression in human GBM tissue sections. These promising preclinical data allowed us to initiate a phase 1 study with D2C7-IT+αhCD40 in patients with malignant glioma (NCT04547777) to further evaluate this treatment in humans.

Dual Immunostimulatory Pathway Agonism through a Synthetic Nanocarrier Triggers Robust Anti-Tumor Immunity in Murine Glioblastoma

Myeloid cells are abundant, create a highly immunosuppressive environment in glioblastoma (GBM), and thus contribute to poor immunotherapy responses. Based on the hypothesis that small molecules can be used to stimulate myeloid cells to elicit anti-tumor effector functions, a synthetic nanoparticle approach is developed to deliver dual NF-kB pathway-inducing agents into these cells via systemic administration. Synthetic, cyclodextrin-adjuvant nanoconstructs (CANDI) with high affinity for tumor-associated myeloid cells are dually loaded with a TLR7 and 8 (Toll-like receptor, 7 and 8) agonist (R848) and a cIAP (cellular inhibitor of apoptosis protein) inhibitor (LCL-161) to dually activate these myeloid cells. Here CANDI is shown to: i) readily enter the GBM tumor microenvironment (TME) and accumulate at high concentrations, ii) is taken up by tumor-associated myeloid cells, iii) potently synergize payloads compared to monotherapy, iv) activate myeloid cells, v) fosters a "hot" TME with high levels of T effector cells, and vi) controls the growth of murine GBM as mono- and combination therapies with anti-PD1. Multi-pathway targeted myeloid stimulation via the CANDI platform can efficiently drive anti-tumor immunity in GBM.

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.

Analysis of PD-L1 and CD3 Expression in Glioblastoma Patients and Correlation with Outcome: A Single Center Report

With the advent of immunotherapies, the field of cancer therapy has been revived with new hope, especially for cancers with dismal prognoses, such as the glioblastoma multiforme (GBM). Currently, immunotherapies should potentiate the host's own antitumor immune response against cancer cells, but it has been documented that they are effective only in small subsets of patients. Therefore, accurate predictors of response are urgently needed to identify who will benefit from immune-modulatory therapies. Brain tumors are challenging in terms of treatments. The immune response in the brain is highly regulated, and the immune microenvironment in brain metastases is active with a high density of tumor-infiltrating lymphocytes (TILs, CD3+ T cells) in certain patients and, therefore, may serve as a potential treatment target. In our study, we performed immunohistochemistry for CD3 and PD-L1 along the routine assessment of the O6-methylguanine-methyltransferase (MGMT) promoter methylation status and the IDH1 and 2 status in a single center cohort of 69 patients with GBM (58 primary tumors and 11 recurrences) who underwent standard multimodal therapies (surgery/radiotherapy/adjuvant temozolamide). We analyzed the association of PD-L1 tumor expression and TILs with overall survival (OS). The PD-L1 expression was observed in 25 of 58 (43%) newly diagnosed primary glioblastoma specimens. The sparse-to-moderate density of TILs, identified with CD3+ expression, was found in 48 of 58 (83%) specimens. Neither PD-L1 expression nor TILs were associated with overall survival. In conclusion, TILs and/or PD-L1 expression are detectable in the majority of glioblastoma samples, and even if they slightly relate to the outcome, they do not show a statistically significant correlation.

Evaluating hematologic parameters in newly diagnosed and recurrent glioblastoma: Prognostic utility and clinical trial implications of myelosuppression

BACKGROUND

Glioblastoma (GBM) patients are treated with radiation therapy, chemotherapy, and corticosteroids, which can cause myelosuppression. To understand the relative prognostic utility of blood-based biomarkers in GBM and its implications for clinical trial design, we examined the incidence, predictors, and prognostic value of lymphopenia, neutrophil-to-lymphocyte ratio (NLR), and platelet count during chemoradiation (CRT) and recurrence.

METHODS

This cohort study included 764 newly diagnosed glioblastoma patients treated from 2005 to 2019 with blood counts prior to surgery, within 6 weeks of CRT, and at first recurrence available for automatic extraction from the medical record. Logistic regression was used to evaluate exposures and Kaplan-Meier was used to evaluate outcomes.

RESULTS

Among the cohort, median age was 60.3 years; 87% had Karnofsky performance status ≥ 70, 37.5% had gross total resection, and 90% received temozolomide (TMZ). During CRT, 37.8% (248/656) of patients developed grade 3 or higher lymphopenia. On multivariable analysis (MVA), high NLR during CRT remained an independent predictor for inferior survival (Adjusted Hazard Ratio [AHR] = 1.57, 95% CI = 1.14-2.15) and shorter progression-free survival (AHR = 1.42, 95% CI = 1.05-1.90). Steroid use was associated with lymphopenia (OR = 2.66,1.20-6.00) and high NLR (OR = 3.54,2.08-6.11). Female sex was associated with lymphopenia (OR = 2.33,1.03-5.33). At first recurrence, 28% of patients exhibited grade 3 or higher lymphopenia. High NLR at recurrence was associated with worse subsequent survival on MVA (AHR = 1.69, 95% CI = 1.25-2.27).

CONCLUSIONS

High NLR is associated with worse outcomes in newly diagnosed and recurrent glioblastoma. Appropriate eligibility criteria and accounting and reporting of blood-based biomarkers are important in the design and interpretation of newly diagnosed and recurrent glioblastoma trials.

Determining the Research Priorities for Adult Primary Brain Tumours in Australia and New Zealand: A Delphi Study with Consumers, Health Professionals, and Researchers

The aim of this project was to determine research priorities, barriers, and enablers for adult primary brain tumour research in Australia and New Zealand. Consumers, health professionals, and researchers were invited to participate in a two-phase modified Delphi study. Phase 1 comprised an initial online survey (n = 91) and then focus groups (n = 29) which identified 60 key research topics, 26 barriers, and 32 enablers. Phase 2 comprised two online surveys to (1) reduce the list to 37 research priorities which achieved consensus (>75% 2-point agreement) and had high mean importance ratings (n = 116 participants) and (2) determine the most important priorities, barriers, and enablers (n = 90 participants). The top ten ranked research priorities for the overall sample and sub-groups (consumers, health professionals, and researchers) were identified. Priorities focused on: tumour biology, pre-clinical research, clinical and translational research, and supportive care. Variations were seen between sub-groups. The top ten barriers to conducting brain tumour research related to funding and resources, accessibility and awareness of research, collaboration, and process. The top ten research enablers were funding and resources, collaboration, and workforce. The broad list of research priorities identified by this Delphi study, together with how consumers, health professionals, and researchers prioritised items differently, and provides an evidence-based research agenda for brain tumour research that is needed across a wide range of areas.

Immunotherapy approaches for adult glioma: knowledge gained from recent clinical trials

PURPOSE OF REVIEW

Summarize principles behind various immunotherapy approaches for high and low-grade glioma in the context of recently completed clinical trials and the new insights they provide.

RECENT FINDINGS

Despite the widespread success of therapies targeting the T-cell checkpoints programmed-death 1 and cytotoxic T lymphocyte antigen 4 in other malignancies, recent phase III trials in glioblastoma confirm the lack of efficacy of anti-programmed-death 1 monotherapy in more than 90% of patients. Vaccination approaches remain under investigation for high-grade glioma and have shown activity in some low-grade glioma patients. Chimeric antigen receptor T cells now feature a new generation of products engineered to potentially withstand glucocorticoid therapy. Oncolytic viral therapies have similarly advanced in sophistication, with drug-sensitive gene expression and tumor-selective modifications. Combinations of therapies hold promise for overcoming the numerous mechanisms of immune suppression in glioma.

SUMMARY

Although immunotherapies have yet to show rates of efficacy compared with other malignancies, new knowledge of immunology and combination therapies brings hope for improved efficacy in the future.

Advances in molecular biomarkers and liquid biopsy in gliomas

There have been significant strides toward understanding the molecular landscape of brain cancer. These advances have been focused on analyses of the tumor microenvironment and have recently expanded to include liquid biopsies to identify molecular biomarkers noninvasively. Moving from tissue to liquid-based analyses of molecular biomarkers has been challenging and currently, there are no approved noninvasive tests that are clinically useful. However, the emerging field of molecular liquid biopsy assay development in the neuro-oncology space has great potential to revolutionize the detection and monitoring of patients with brain cancer.

DNA methylation regulator-mediated modification patterns and tumor microenvironment characterization in glioma

Growing evidences indicate DNA methylation plays a crucial regulatory role in inflammation, innate immunity, and immunotherapy. However, the overall landscape of various DNA methylation regulatory genes and their relationship with the infiltration of immune cells into the tumor microenvironment (TME) as well as the response to immunotherapy in gliomas is still not clear. Therefore, we comprehensively analyzed the correlation between DNA methylation regulator patterns, infiltration of immune cell-types, and tumor immune response status in gather glioma cohorts. Furthermore, we calculated the DNA methylation score (DMS) for individual glioma samples, then evaluated the relationship between DMS, clinicopathological characteristics, and overall survival (OS) in patients with gliomas. Our results showed three distinct DNA methylation regulator patterns among the glioma patients which correlated with three distinct tumor immune response phenotypes, namely, immune-inflamed, immune-excluded, and immune desert. We then calculated DMS for individual glioma samples based on the expression of DNA methylation-related gene clusters. Furthermore, DMS, tumor mutation burden (TMB), programmed death 1 (PD-1) expression, immune cell infiltration status in the TME, and Tumor Immune Dysfunction and Exclusion (TIDE) scores were associated with survival outcomes and clinical responses to immune checkpoint blockade therapy. We also validated the predictive value of DMS in two independent immunotherapy cohorts. In conclusion, our results demonstrated that three DNA methylation regulator patterns that correlated with three tumor immune response phenotypes. Moreover, we demonstrated that DMS was an independent predictive biomarker that correlated with survival outcomes of glioma patients and their responses to immunotherapy therapeutic regimens.