Neoadjuvant PD-1 blockade induces T cell and cDC1 activation but fails to overcome the immunosuppressive tumor associated macrophages in recurrent glioblastoma

Unraveling UPR-mediated intercellular crosstalk: Implications for immunotherapy resistance mechanisms

Endoplasmic reticulum (ER) is the critical organelle that regulates essential cellular processes, including protein synthesis, folding, and post-translational modification, as well as lipid metabolism and calcium homeostasis. Disruption in ER homeostasis leads to a condition known as ER stress, characterized by the accumulation of misfolded or unfolded proteins. This triggers the unfolded protein response (UPR), an adaptive pathway mediated by three ER-resident sensors: inositol-requiring enzyme 1α (IRE1α), protein kinase R-like ER kinase (PERK), and activating transcription factor 6 (ATF6). Increasing evidence highlights sustained UPR activation in malignant and immune cells within the tumor microenvironment (TME), which promotes tumor progression and metastasis while simultaneously impairing antitumor immunity. This review explores how UPR-driven intercellular signaling influences immunotherapy resistance, focusing on the alterations occurring in tumor cells as well as in the surrounding immune environment. By providing insights into these mechanisms, we aim to highlight the therapeutic potential of targeting the UPR pathways in modulating cancer immunity.

Improved overall survival in an anti-PD-L1 treated cohort of newly diagnosed glioblastoma patients is associated with distinct immune, mutation, and gut microbiome features: a single arm prospective phase I/II trial

This phase I/II trial aims to evaluate the efficacy of concurrent atezolizumab with radiation therapy and temozolomide (TMZ) followed by adjuvant atezolizumab and TMZ in newly diagnosed glioblastoma (GBM) patients and to identify pre-treatment correlates with outcome (N = 60). Trial number: NCT03174197. The primary outcome was overall survival (OS) whereas secondary outcomes were retrospective global-omics analyses to identify pre-treatment immune and genetic tumor features that correlated with survival. Concurrent use of atezolizumab with radiation and TMZ demonstrated OS in line with published trials for newly diagnosed GBM. Tumor genomic (WES and/or targeted NGS panel), transcriptomic (RNAseq) and tissue microenvironment imaging, as well as fecal metagenomic sequencing were conducted. Gene set enrichment analysis of tumors identified multiple immune-based transcriptomic programs to distinguish patients with longer versus shorter survival (p ≤ 0.01). GBM immune enrichment was highly associated with the pre-treatment tumor mesenchymal subtype and patient gastrointestinal bacterial taxa profile.

7aaRGD - a novel SPP1/integrin signaling-blocking peptide reverses immunosuppression and improves anti-PD-1 immunotherapy outcomes in experimental gliomas

BACKGROUND

Immune checkpoint inhibitors (ICIs) present clinical benefits in many cancer patients but invariably fail in glioblastoma (GBM), the most common and deadly primary brain tumor. The lack of ICIs efficacy in GBM is attributed to the accumulation of tumor-reprogrammed glioma-associated myeloid cells (GAMs) that create a "cold" immunosuppressive tumor microenvironment (TME), impeding the infiltration and activation of effector T cells. GBM-derived αvβ3/αvβ5-integrin ligands, including SPP1, were shown to mediate the emergence of GAMs. We hypothesized that a combination strategy aiming to block the reprogramming of GAMs using a synthetic 7aaRGD peptide that targets SPP1/integrin signaling might overcome resistance to ICIs and reinvigorate anti-tumor immunity.

METHODS

Matrigel invasion assay was used to test the efficacy of 7aaRGD in glioma-microglia co-cultures. We determined the impact of 7aaRGD, administered as a monotherapy or combined with PD-1 blockade, on tumor growth, GAMs accumulation and phenotypes, arginase-1 levels and neovasculature in experimental gliomas. The effects of treatments on the tumor immune landscape were dissected using multiparameter flow cytometry, immunocytochemistry, cytokine profiling and RNA-seq analysis of sorted GAMs followed by CITE-seq based data deconvolution.

RESULTS

7aaRGD efficiently blocked microglia-dependent invasion of human and mouse glioma cells in vitro. Intratumorally delivered 7aaRGD alone did not reduce tumor growth in orthotopic gliomas but prevented the emergence of immunosuppressive GAMs and led to normalization of peritumoral blood vessels. Combining 7aaRGD with anti-PD-1 antibody resulted in reduced tumor growth, with an increase in the number of proliferating, interferon-ɣ producing CD8+T cells and depletion of regulatory T cells. Transcriptomic profiles of myeloid cells were altered by the combined treatment, reflecting the restored "hot" inflammatory TME and boosted immunotherapy responses. Intratumoral administration of 7aaRGD similarly modified the phenotypes of GAMs in human U87-MG gliomas in immunocompromised mice. Exploration of transcriptomic datasets revealed that high expression of integrin receptor coding genes in pre-treatment biopsies was associated with a poorer response to immune check-point blockade in patients with several types of cancers.

CONCLUSIONS

We demonstrate that combining the blockade of SPP1/integrin signaling with ICIs modifies innate immunity and reinvigorates adaptive antitumor responses, which paves the way to improve immunotherapy outcomes in GBM.

Glioblastoma Cell Lysate and Adjuvant Nanovaccines via Strategic Vaccination Completely Regress Established Murine Tumors

Tumor vaccines have shown great promise for treating various malignancies; however, glioblastoma (GBM), characterized by its immunosuppressive tumor microenvironment, high heterogeneity, and limited accessibility, has achieved only modest clinical benefits. Here, it is reported that GBM cell lysate nanovaccines boosted with TLR9 agonist CpG ODN (GlioVac) via a strategic vaccination regimen achieve complete regression of malignant murine GBM tumors. Subcutaneous administration of GlioVac promotes uptake by cervical lymph nodes and antigen presentation cells, bolstering antigen cross-presentation and infiltration of GBM-specific CD8+ T cells into the tumor. Notably, a regimen involving two subcutaneous and three intravenous vaccinations not only activates systemic anti-GBM immunity but also further enhances the tumor infiltration of cytotoxic T lymphocytes, effectively reshaping the "cold" GBM tumor into a "hot" tumor. This approach led to a state of tumor-free survival in 5 out of 7 mice bearing the established GL261 GBM model with complete protection from tumor rechallenge. In an orthotopic hRas-GBM model induced by a lentiviral plasmid, GlioVac resulted in ≈100% complete tumor regression. These findings suggest that GlioVac provides a personalized therapeutic vaccine strategy for glioblastoma.

Transcript-targeted antigen mapping reveals the potential of POSTN splicing junction epitopes in glioblastoma immunotherapy

Tumor antigens are crucial for T-cell mediated immunotherapy, but identified antigens for gliomas remain limited. Aberrant splicing variants are commonly expressed in tumors, resulting in unique tumor isoforms with potential antigenic properties. Herein, we analyzed multi-omics data from 587 glioma patients and assembled a library of putative tumor-enriched isoform antigens (TIA) and corresponding peptides presented on each HLA-I allele. We constructed an individual-specific TIA peptide candidate repertoire for each patient based on their TIA expression and HLA-I haplotypes. TIAs were highly expressed, enriched with glioma malignancy, and demonstrated strong HLA-binding affinity. We focused on periostin isoform-203 (POSTN-203), which was associated with poor survival of patients and contained multiple predicted HLA-restricted peptide epitopes. A selected HLA-A11-restricted peptide from POSTN-203 (POSTN-203A11) induced antigen-specific T-cell responses against both peptide-pulsed and POSTN-203-expressing glioma cells in an HLA-specific manner. Our findings highlight TIAs as a promising source of immunogenic antigens and POSTN-203 as a potential promising target for glioma immunotherapy.

Programs, origins and immunomodulatory functions of myeloid cells in glioma

Gliomas are incurable malignancies notable for having an immunosuppressive microenvironment with abundant myeloid cells, the immunomodulatory phenotypes of which remain poorly defined1. Here we systematically investigate these phenotypes by integrating single-cell RNA sequencing, chromatin accessibility, spatial transcriptomics and glioma organoid explant systems. We discovered four immunomodulatory expression programs: microglial inflammatory and scavenger immunosuppressive programs, which are both unique to primary brain tumours, and systemic inflammatory and complement immunosuppressive programs, which are also expressed by non-brain tumours. The programs are not contingent on myeloid cell type, developmental origin or tumour mutational state, but instead are driven by microenvironmental cues, including tumour hypoxia, interleukin-1β, TGFβ and standard-of-care dexamethasone treatment. Their relative expression can predict immunotherapy response and overall survival. By associating the respective programs with mediating genomic elements, transcription factors and signalling pathways, we uncover strategies for manipulating myeloid-cell phenotypes. Our study provides a framework to understand immunomodulation by myeloid cells in glioma and a foundation for the development of more-effective immunotherapies.

Dendritic cell maturation in cancer

Dendritic cells (DCs) are specialized antigen-presenting cells that are present at low abundance in the circulation and tissues; they serve as crucial immune sentinels by continually sampling their environment, migrating to secondary lymphoid organs and shaping adaptive immune responses through antigen presentation. Owing to their ability to orchestrate tolerogenic or immunogenic responses to a specific antigen, DCs have a pivotal role in antitumour immunity and the response to immune checkpoint blockade and other immunotherapeutic approaches. The multifaceted functions of DCs are acquired through a complex, multistage process called maturation. Although the role of inflammatory triggers in driving DC maturation was established decades ago, less is known about DC maturation in non-inflammatory contexts, such as during homeostasis and in cancer. The advent of single-cell technologies has enabled an unbiased, high-dimensional characterization of various DC states, including mature DCs. This approach has clarified the molecular programmes associated with DC maturation and also revealed how cancers exploit these pathways to subvert immune surveillance. In this Review, we discuss the mechanisms by which cancer disrupts DC maturation and highlight emerging therapeutic opportunities to modulate DC states. These insights could inform the development of DC-centric immunotherapies, expanding the arsenal of strategies to enhance antitumour immunity.

Injectable hydrogel-assisted local lipopolysaccharide delivery improves immune checkpoint blockade therapy

Tumor-associated macrophages (TAMs) significantly influence the clinical outcomes of immune checkpoint blockade (ICB) therapy. Strategies aimed at reprogramming TAMs from the immunosuppressive M2 phenotype to the pro-inflammatory M1 phenotype hold promise for enhancing ICB efficacy. Lipopolysaccharide (LPS), a potent Toll-like receptor 4 (TLR4) ligand, can reprogram TAMs toward an M1 phenotype. However, the systemic application of LPS is restricted due to its pronounced pro-inflammatory properties, which limit safe dosing in cancer treatment. To address this, thermosensitive hydrogels offer a viable solution by optimizing drug bioavailability and reducing systemic dissemination. In our study, carboxymethyl chitosan (CS) was incorporated into Pluronic F127 to extend the hydrogel's degradation period, facilitating the localized delivery and accumulation of LPS within tumor sites. Peritumoral injection of this hydrogel enhanced the tumor-inhibitory effects of anti-PD-1 antibodies, significantly improving the survival of 4T1 tumor-bearing mice. The GelF127CS-LPS hydrogel also increased the expression of the activation marker on tumor-infiltrating dendritic cells, promoted a higher M1/M2 TAM ratio, and enhanced CD8+ T cell infiltration into tumors-key indicators of T-cell-mediated anti-tumor immunity. Notably, no significant liver or hematological toxicity was observed with GelF127CS-LPS treatment, underscoring its favorable safety profile. These findings demonstrate the potential of GelF127CS-LPS as a TAMs-modulating agent and a promising combinatorial strategy to boost ICB therapy effectiveness. STATEMENT OF SIGNIFICANCE: LPS, a potent TLR4 ligand, can reprogram tumor-associated macrophages (TAMs) toward an M1 phenotype, thereby contributing to tumor inhibition. However, its anti-tumor application is constrained by the contradiction between high-dose toxicity and insufficient efficacy at low doses. To address this issue, we developed a thermosensitive hydrogel encapsulating LPS, GelF127CS-LPS, which allows localized LPS release within the tumor area. This hydrogel reprograms TAMs at a picogram level of LPS to achieve a favorable M1/M2 ratio and promotes the activation of T cell-mediated antitumor immunity without observable toxicity. Consequently, when combined with immune checkpoint blockade (ICB), the hydrogel can inhibit tumor growth and improve overall survival. This study provides an effective method for tumor-targeted therapeutic LPS delivery to enhance the efficacy of ICB.

Pathological diagnosis of central nervous system tumours in adults: what's new?

In the course of the last decade, the pathological diagnosis of many tumours of the central nervous system (CNS) has transitioned from a purely histological to a combined histological and molecular approach, resulting in a more precise 'histomolecular diagnosis'. Unfortunately, translation of this refinement in CNS tumour diagnostics into more effective treatment strategies is lagging behind. There is hope though that incorporating the assessment of predictive markers in the pathological evaluation of CNS tumours will help to improve this situation. The present review discusses some novel aspects with regard to the pathological diagnosis of the most common CNS tumours in adults. After a brief update on recognition of clinically meaningful subgroups in adult-type diffuse gliomas and the value of assessing predictive markers in these tumours, more detailed information is provided on predictive markers of (potential) relevance for immunotherapy especially for glioblastomas, IDH-wildtype. Furthermore, recommendations for improved grading of meningiomas by using molecular markers are briefly summarised, and an overview is given on (predictive) markers of interest in metastatic CNS tumours. In the last part of this review, some 'emerging new CNS tumour types' that may occur especially in adults are presented in a table. Hopefully, this review provides useful information on 'what's new' for practising pathologists diagnosing CNS tumours in adults.

Neoadjuvant triplet immune checkpoint blockade in newly diagnosed glioblastoma

Glioblastoma (GBM) is an aggressive primary adult brain tumor that rapidly recurs after standard-of-care treatments, including surgery, chemotherapy and radiotherapy. While immune checkpoint inhibitor therapies have transformed outcomes in many tumor types, particularly when used neoadjuvantly or as a first-line treatment, including in melanoma brain metastases, they have shown limited efficacy in patients with resected or recurrent GBM. The lack of efficacy has been attributed to the scarcity of tumor-infiltrating lymphocytes (TILs), an immunosuppressive tumor microenvironment and low tumor mutation burden typical of GBM tumors, plus exclusion of large molecules from the brain parenchyma. We hypothesized that upfront neoadjuvant combination immunotherapy, administered with disease in situ, could induce a stronger immune response than treatment given after resection or after recurrence. Here, we present a case of newly diagnosed IDH-wild-type, MGMT promoter unmethylated GBM, treated with a single dose of neoadjuvant triplet immunotherapy (anti-programmed cell death protein 1 plus anti-cytotoxic T-lymphocyte protein 4 plus anti-lymphocyte-activation gene 3) followed by maximal safe resection 12 days later. The anti-programmed cell death protein 1 drug was bound to TILs in the resected GBM and there was marked TIL infiltration and activation compared with the baseline biopsy. After 17 months, there is no definitive sign of recurrence. If used first line, before safe maximal resection, checkpoint inhibitors are capable of immune activation in GBM and may induce a response. A clinical trial of first-line neoadjuvant combination checkpoint inhibitor therapy in newly diagnosed GBM is planned (GIANT; trial registration no. NCT06816927 ).

Identification of Prognostic Genes Related to Cell Senescence and Lipid Metabolism in Glioblastoma Based on Transcriptome and Single-Cell RNA-Seq Data

Glioblastoma (GBM) is the most aggressive primary brain cancer, with poor prognosis due to its aggressive behavior and high heterogeneity. This study aimed to identify cellular senescence (CS) and lipid metabolism (LM)-related prognostic genes to improve GBM prognosis and treatment. Transcriptome and scRNA-seq data, CS-associated genes (CSAGs), and LM-related genes (LMRGs) were acquired from public databases. Prognostic genes were identified by intersecting CSAGs, LMRGs, and differentially expressed genes (DEGs), followed by WGCNA and univariate Cox regression. A risk model and nomogram were constructed. Analyses covered clinicopathological features, immune microenvironment, somatic mutations, and drug sensitivity. GBM scRNA-seq data identified key cells and prognostic gene expression. SOCS1 and PHB2 were identified as prognostic markers, contributing to the construction of a robust risk model with excellent predictive ability. High-risk group (HRG) patients had poorer survival, higher immune and stromal scores, and distinct somatic mutation profiles. Drug sensitivity analysis revealed significant differences in IC50 values. In microglia differentiation, SOCS1 and PHB2 showed dynamic expression patterns. These findings provide new strategies for GBM prognosis and treatment.

Imaging PD-L1 in the brain-Journey from the lab to the clinic

BACKGROUND

Immune checkpoint inhibitors (ICPIs) have proven to restore adaptive anti-tumor immunity in many cancers; however, no noteworthy therapeutic schedule has been established for patients with glioblastoma (GBM). High programmed death-ligand 1 (PD-L1) expression is associated with immunosuppressive and aggressive phenotypes in GBM. Presently, there is no standardized protocol for assessing PD-L1 expression levels to select patients and monitor their response to ICPI therapy. The aim of this study was to investigate the use of 89Zr-DFO-Atezolizumab to image the spatio-temporal distribution of PD-L1 in preclinical mouse models and in patients with newly diagnosed GBM treated with/without neoadjuvant Pembrolizumab.

METHODS

The immunoreactivity, binding affinity, and specificity of 89Zr-DFO-Atezolizumab were confirmed in vitro. Mice-bearing orthotopic GBM tumors or patients with newly diagnosed GBM treated with/without Pembrolizumab were intravenously injected with 89Zr-DFO-Atezolizumab, and PET/CT images were acquired 24, 48, and 72 hours in mice and at 48 and 72 post-injection in patients. Radioconjugate uptake was quantified in the tumor and healthy tissues. Ex vivo immunohistochemistry (IHC) and immunophenotyping were performed on mouse tumor samples or resected human tumors.

RESULTS

89Zr-DFO-Atezolizumab was prepared with high radiochemical purity (RCP > 99%). In vitro cell-associated radioactivity of 89Zr-DFO-Atezolizumab corroborated cell line PD-L1 expression. PD-L1 in mouse GBM tumors was detected with high specificity using 89Zr-DFO-Atezolizumab and radioconjugate uptake correlated with IHC. Patients experienced no 89Zr-DFO-Atezolizumab-related side effects. High 89Zr-DFO-Atezolizumab uptake was observed in patient tumors at 48 hours post-injection, however, the uptake varied between patients treated with/without Pembrolizumab.

CONCLUSIONS

89Zr-DFO-Atezolizumab can visualize distinct PD-L1 expression levels with high specificity in preclinical mouse models and in patients with GBM, whilst complementing ex vivo analysis.

Single-cell data-driven design of armed oncolytic virus to boost cooperative innate-adaptive immunity against cancer

Oncolytic viruses have been considered promising cancer immunotherapies. However, oncovirotherapy agents impart durable responses in only a subset of cancer patients. Thus, exploring the cellular and molecular mechanisms underlying the heterogeneous responses in patients can provide guidance to develop more effective oncolytic virus therapies. Single-cell RNA sequencing (scRNA-seq) analysis of tumors responsive and non-responsive to oncovirotherapy revealed signatures of the tumor immune microenvironment associated with immune response. Thus, we designed and constructed an armed oncolytic virus, OV-5A, that expressed five genes with non-redundant functions. OV-5A treatment exhibits robust immune response against various tumors in multiple mouse models, peripheral blood mononuclear cell -patient-derived xenograft models, organoid-immune cell co-culture systems, and patient tissue sections by activating a cooperative innate-adaptive immune response against tumor cells. scRNA-seq analysis of complete responders and partial responders to OV-5A treatment guided the design of combination therapy of OV-5A. This data-driven approach paves an innovative way to rationalize the design of oncolytic virus and multi-agent combination therapies.

Dysfunction of Endothelial Cell-Mediated Intercellular Communication and Metabolic Pathways in Age-Related Macular Degeneration

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly, but the therapies are not satisfactory. This study aimed to find AMD specific features through the analysis of high-throughput sequencing.

METHODS

In this study, we integrated six projects containing single-cell RNA sequencing (scRNA-seq) data to perform a comprehensive analysis for AMD samples in the tissues of retina and retinal pigment epithelium/choroid, and in the positions of macula and periphery. Differentially expressed genes (DEGs) were analyzed and crucial signaling pathways were identified across cell types and between the macula and periphery. The intercellular signaling transduction among cell types were inferred by "CellChat" to build cell-cell communication network under normal and AMD conditions, and verified at the transcriptional level. The CD31+ endothelial cells were obtained to evaluate the enrichment of KEGG pathways in atrophic and neovascular AMD, and GSVA was adopted to discover differential metabolic signals in each AMD type.

RESULTS

Thirteen major cell types were identified in the integrated scRNA-seq data. Although no disease-specific cell type or differential cell proportion was found, DEGs and enriched pathways were shown in cell-type- and position-dependent manners. Severe impairment of endothelial cell-mediated cell interactions was found in the signaling transduction network of the macula, and compromised cell interactions were observed in the periphery. Furthermore, distinct signaling pathways and metabolic states were uncovered in atrophic and neovascular AMD. Striking reduction in energy metabolism, lipid metabolism, and oxidative stress was indicated in the atrophic AMD.

CONCLUSION

Conclusively, we discover aberrant signals and metabolic pathways in AMD samples, providing insight into mechanisms and potential therapeutic targets for the AMD treatment.

Overcoming immune evasion with innovative multi-target approaches for glioblastoma

Glioblastoma (GBM) cells leverage complex endogenous and environmental regulatory mechanisms to drive proliferation, invasion, and metastasis. Tumor immune evasion, facilitated by a multifactorial network, poses a significant challenge to effective therapy, as evidenced by the limited clinical benefits of monotherapies, highlighting the adaptive nature of immune evasion. This review explores glioblastoma's immune evasion mechanisms, the role of ICIs in the tumor microenvironment, and recent clinical advancements, offering theoretical insights and directions for monotherapy and combination therapy in glioblastoma management.

Is modulation of immune checkpoints on glioblastoma-infiltrating myeloid cells a viable therapeutic strategy?

The field of immunology has traditionally focused on immune checkpoint modulation of adaptive immune cells. However, many malignancies such as glioblastoma are mostly devoid of T cells and rather are enriched with immunosuppressive myeloid cells of the innate immune system. While some immune checkpoint targets are shared between adaptive and innate immunity, myeloid-specific checkpoints could also serve as potential therapeutics. To better understand the impact of immune checkpoint blockade on myeloid cells, we systematically summarize the current literature focusing on the direct immunological effects of PD-L1/PD-1, CD24/Siglec-10, collagen/LAIR-1, CX3CL1/CX3CR1, and CXCL10/CXCR3. By synthesizing the molecular mechanisms and the translational implications, we aim to prioritize agents in this category of therapeutics for glioblastoma.

Role of T cell metabolism in brain tumor development: a genetic and metabolic approach

BACKGROUND

Malignant brain tumors are among the most lethal cancers. Recent studies emphasized the crucial involvement of the immune system, especially T cells, in driving tumor progression and influencing patient outcomes. The emerging field of immunometabolism has shown that metabolic pathways play a pivotal role in regulating immune responses within the tumor microenvironment. This study aims to clarify the relationships between specific T cell phenotypes, circulating metabolites, and malignant brain tumors.

METHODS

We utilized a multiple mendelian randomization approach to investigate the associations between T cell phenotypes and malignant brain tumors, as well as the role of plasma metabolites in mediating these interactions. Instrumental variables were selected based on stringent criteria, and multiple mendelian randomization methods were utilized to identify causal pathways and metabolites potentially mediating these effects.

RESULTS

Our analysis identified significant associations between seven distinct T cell phenotypes, including various CD8 + and regulatory T cell subsets, and the presence of malignant brain tumors. We also identified 87 plasma metabolites correlated with these tumors. Notably, metabolites such as octadecanedioylcarnitine (C18-DC) and eicosanedioate (C20-DC) were implicated in modulating the risk of developing malignant brain tumors. Furthermore, metabolites such as 5-dodecenoate (12:1n7) and arachidonate (20:4n6) were found to influence tumor risk, particularly in relation to CD28 - CD8 + T cells.

CONCLUSION

The study identifies key T cell phenotypes and plasma metabolites involved in the pathogenesis of malignant brain tumors, offering potential biomarkers and therapeutic targets for future interventions.

Neoadjuvant anti-PD1 immunotherapy for surgically accessible recurrent glioblastoma: clinical and molecular outcomes of a stage 2 single-arm expansion cohort

Glioblastoma is immunologically "cold" and resistant to single-agent immune-checkpoint inhibitors (ICI). Our previous study of neoadjuvant pembrolizumab in surgically-accessible recurrent glioblastoma identified a molecular signature of response to ICI and suggested that neoadjuvant pembrolizumab may improve survival. To increase the power of this observation, we enrolled an additional 25 patients with a primary endpoint of evaluating the cell cycle gene signature associated with neoadjuvant pembrolizumab and performed bulk-RNA seq on resected tumor tissue (NCT02852655). Neoadjuvant pembrolizumab was associated with suppression of cell cycle/cancer proliferation genes and upregulation of T-cell/interferon-related gene expression. This signature was unique to patients treated with neoadjuvant pembrolizumab and was an independent positive risk factor for survival. Our results demonstrate a clear pharmacodynamic effect of anti-PD1 therapy in glioblastoma and identify pathways that may mediate resistance. However, we did not confirm a survival benefit to neoadjuvant pembrolizumab in recurrent glioblastoma and our secondary endpoint of PFS-6 was 19.5% (95% CI: 9.29-41.2%) for the pooled neoadjuvant cohorts. Our new data suggests some patients may exhibit innate resistance to pre-surgical ICI and require other concomitant therapies to sensitize effectively.

Immune landscape of isocitrate dehydrogenase-stratified primary and recurrent human gliomas

BACKGROUND

Human gliomas are classified using isocitrate dehydrogenase (IDH) status as a prognosticator; however, the influence of genetic differences and treatment effects on ensuing immunity remains unclear.

METHODS

In this study, we used sequential single-cell transcriptomics on 144 678 and spectral cytometry on over 2 million immune cells encompassing 48 human gliomas to decipher their immune landscape.

RESULTS

We identified 22 distinct immune cell types that contribute to glioma immunity. Specifically, brain-resident microglia (MG) were reduced with a concomitant increase in CD8+ T lymphocytes during glioma recurrence independent of IDH status. In contrast, IDH-wild type-associated patterns, such as an abundance of antigen-presenting cell-like MG and cytotoxic CD8+ T cells, were observed. Beyond elucidating the differences in IDH, relapse, and treatment-associated immunity, we discovered novel inflammatory MG subpopulations expressing granulysin, a cytotoxic peptide that is otherwise expressed in lymphocytes only. Furthermore, we provide a robust genomic framework for defining macrophage polarization beyond M1/M2 paradigm and reference signatures of glioma-specific tumor immune microenvironment (termed GlioTIME-36) for deconvoluting transcriptomic datasets.

CONCLUSIONS

This study provides advanced optics of the human pan-glioma immune contexture as a valuable guide for translational and clinical applications.

Clinical research framework proposal for ketogenic metabolic therapy in glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with a universally lethal prognosis despite maximal standard therapies. Here, we present a consensus treatment protocol based on the metabolic requirements of GBM cells for the two major fermentable fuels: glucose and glutamine. Glucose is a source of carbon and ATP synthesis for tumor growth through glycolysis, while glutamine provides nitrogen, carbon, and ATP synthesis through glutaminolysis. As no tumor can grow without anabolic substrates or energy, the simultaneous targeting of glycolysis and glutaminolysis is expected to reduce the proliferation of most if not all GBM cells. Ketogenic metabolic therapy (KMT) leverages diet-drug combinations that inhibit glycolysis, glutaminolysis, and growth signaling while shifting energy metabolism to therapeutic ketosis. The glucose-ketone index (GKI) is a standardized biomarker for assessing biological compliance, ideally via real-time monitoring. KMT aims to increase substrate competition and normalize the tumor microenvironment through GKI-adjusted ketogenic diets, calorie restriction, and fasting, while also targeting glycolytic and glutaminolytic flux using specific metabolic inhibitors. Non-fermentable fuels, such as ketone bodies, fatty acids, or lactate, are comparatively less efficient in supporting the long-term bioenergetic and biosynthetic demands of cancer cell proliferation. The proposed strategy may be implemented as a synergistic metabolic priming baseline in GBM as well as other tumors driven by glycolysis and glutaminolysis, regardless of their residual mitochondrial function. Suggested best practices are provided to guide future KMT research in metabolic oncology, offering a shared, evidence-driven framework for observational and interventional studies.

Immunotherapy for glioblastoma: current state, challenges, and future perspectives

Glioblastoma (GBM) is an aggressive and lethal type of brain tumor in human adults. The standard of care offers minimal clinical benefit, and most GBM patients experience tumor recurrence after treatment. In recent years, significant advancements have been made in the development of novel immunotherapies or other therapeutic strategies that can overcome immunotherapy resistance in many advanced cancers. However, the benefit of immune-based treatments in GBM is limited because of the unique brain immune profiles, GBM cell heterogeneity, and immunosuppressive tumor microenvironment. In this review, we present a detailed overview of current immunotherapeutic strategies and discuss the challenges and potential molecular mechanisms underlying immunotherapy resistance in GBM. Furthermore, we provide an in-depth discussion regarding the strategies that can overcome immunotherapy resistance in GBM, which will likely require combination therapies.

Vagus nerve stimulation: Novel concept for the treatment of glioblastoma and solid cancers by cytokine (interleukin-6) reduction, attenuating the SASP, enhancing tumor immunity

Immuno-oncology, specifically immune checkpoint inhibitors (ICIs), has revolutionized cancer care with dramatic, long-term responses and increased survival, including patients with metastatic cancer to the brain. Glioblastomas, and other primary brain tumors, are refractory to ICIs as monotherapy or in combination with standard therapy. The tumor microenvironment (TME) poses multiple biological hurdles: blood-brain barrier, immune suppression, heterogeneity, and tumor infiltration. Genomic analysis of the senescence-associated secretory phenotype (SASP) and preclinical models of glioma suggest that an exciting approach would entail reprogramming of the glioma microenvironment, attenuating the pro-inflammatory, pro-tumorigenic cytokines of the SASP, especially interleukin-6 (IL-6). A testable hypothesis now proposed is to modulate the immune system by harnessing the body's 'inflammatory reflex' to reduce cytokines. Vagus nerve stimulation can activate T cell immunity by the cholinergic, α7nicotinic acetylcholine receptor agonist (α7nAchR), and suppress IL-6 systemically, as well as other pro-inflammatory cytokines of the SASP, interleukin -1β (IL-1β) and tumor necrosis factor-alpha (TNF-α). The hypothesis predicts that electrical activation of the vagus nerve, with cytokine reduction, in combination with ICIs, would convert an immune resistant ("cold") tumor to an immune responsive ("hot") tumor, and halt glioma progression. The hypothesis also envisions cancer as an immune "dysautonomia" whereby a therapeutic intervention, vagus nerve stimulation (VNS), resets the systemic and local cytokine levels. A prospective, randomized, phase II clinical trial, to confirm the hypothesis, is a logical, exigent, next step. Cytokine reduction by VNS could also be useful for other forms of human cancer, e.g., breast, colorectal, head and neck, lung, melanoma, ovarian, pancreatic, and prostate cancer, as the emerging field of "cancer neuroscience" shows a role for neural regulation of multiple tumor types. Because IL-6, and companion pro-inflammatory cytokines, participate in the initiation, progression, spread and recurrence of cancer, minimally invasive VNS could be employed to suppress glioma or cancer progression, while also mitigating depression and/or seizures, thereby enhancing quality of life. The current hypothesis reimagines glioma pathophysiology as a dysautonomia with the therapeutic objective to reset the autonomic nervous system and form an immune responsive state to halt tumor progression and prevent recurrence. VNS, as a novel method to control cancer, can be administered with ICIs, standard therapy, or in clinical trials, combined with emerging immunotherapy: dendritic cell, mRNA, or chimeric antigen receptor (CAR) T cell vaccines.

Spatially organized tumor-stroma boundary determines the efficacy of immunotherapy in colorectal cancer patients

Colorectal cancer (CRC) patients with mismatch repair (MMR)-deficient (dMMR) but not MMR-proficient (pMMR) tend to benefit from immune checkpoint blockade (ICB) therapy. To profile the tumor microenvironments (TME) underlying these varied therapeutic responses, we integrate spatial enhanced resolution omics-sequencing (Stereo-seq), single-cell RNA sequencing, and multiplexed imaging analysis to create high-definition spatial maps of tumors from treatment-naïve and ICB-treated CRC patients. Our results identify the spatial organization and immune status of the tumor-stroma boundary as a distinctive feature of dMMR and pMMR CRCs, which associates with ICB response. The physical interactions and abundance of LAMP3+DCs and CXCL13+T cells may shape the ICB-responsive tumor-stroma boundary, whereas CXCL14+cancer-associated fibroblasts tend to remodel extracellular matrix to form a structural barrier in non-responders. Our work therefore points out the importance of the molecular and cellular spatial structures of tumors in ICB response, raising the possibility of reprogramming tumor-stroma boundary for sensitizing immunotherapies in the majority of CRCs.

The mechanisms of B-cell acute lymphoblastic leukemia relapsing following chimeric antigen receptor-T cell therapy; the plausible future strategies

Research has demonstrated the high mortality and morbidity associated with B-Acute lymphoblastic lymphoma (B-ALL). Researchers have developed several therapeutic approaches to combat the disorder. Recently, researchers developed chimeric antigen receptors (CARs)-T cells, which recognize antigens independently of major histocompatibility complexes (MHCs) and activate at a higher level with additional persistence. However, relapsing B-ALL has been reported in several cases. This review article was aimed to collecting recent information regarding the mechanisms used by B-ALL-related lymphocytes to escape from CAR-T cells and the plausible resolution projects.

Degradation fragments of Tau and type IV collagen as serum biomarkers in patients with recurrent glioblastoma treated with nivolumab and bevacizumab

PURPOSE

There is an unmet need for new treatment options and biomarkers for patients with glioblastoma (GBM). Here we investigated three non-invasive biomarkers: type VI collagen degraded by granzyme B (C4G) and matrix metalloproteases (C4M), respectively, and ADAM10-degraded Tau (Tau-A).

METHODS

Biomarker levels in pre- and on-treatment serum samples from patients with recurrent GBM (n = 39) treated with nivolumab and bevacizumab (NCT03890952) were compared to healthy levels (n = 22) and associated with overall survival (OS) outcome (median cutpoint). Longitudinal changes in biomarkers were investigated by a Mixed-effects analysis.

RESULTS

Tau-A (p < 0.0001) and C4G (p = 0.005), but not C4M (p = 0.106), were increased in patients. High Tau-A and C4G associated with improved OS (Tau-A: HR = 0.41, 95%CI = 0.20-0.86, C4G: HR = 0.47, 95%CI = 0.24-0.94). Only C4G increased with treatment (p = 0.024-0.005).

CONCLUSIONS

Tau-A and C4G are elevated in serum from patients with recurrent GBM and prognostic for OS. If validated, these biomarkers could be applied to clinical trials.

PSF-lncRNA interaction as a target for novel targeted anticancer therapies

The Polypyrimidine Tract-Binding Protein-Associated Splicing Factor (PSF), a component of the Drosophila Behavior/Human Splicing (DBHS) complex, plays a pivotal role in cancer pathogenesis. The epigenetic regulation mediated by PSF and long noncoding RNA (lncRNA), along with PSF's alternative splicing activity, has been implicated in promoting cancer cell proliferation, migration, invasion, metastasis, and drug resistance in various human cancers. Recent research highlights the therapeutic promise of targeting the PSF-lncRNA interaction to combat aggressive malignancies, making it a compelling target for cancer therapy. This review offers a detailed synthesis of the current understanding of PSF's role in oncogenic pathways and recent progress in identifying inhibitors of PSF-lncRNA interactions. Furthermore, it discusses the potential of using these inhibitors in cancer treatment strategies, especially as adjuncts to immune checkpoint blockade therapies to improve the efficacy of anti-PD-(L)1 treatments in Glioblastoma Multiforme (GBM). By outlining the interaction patterns of existing PSF-lncRNA inhibitors, this article aims to guide the development and refinement of future pharmacological interventions.

T-cell Responses to Individualized Neoantigen Therapy mRNA-4157 (V940) Alone or in Combination with Pembrolizumab in the Phase 1 KEYNOTE-603 Study

mRNA-4157 (V940) is an individualized neoantigen therapy targeting up to 34 patient-specific tumor neoantigens to induce T-cell responses and potentiate antitumor activity. We report mechanistic insights into the immunogenicity of mRNA-4157 via characterization of T-cell responses to neoantigens from the first-in-human, phase 1, KEYNOTE-603 study (NCT03313778) in patients with resected non-small cell lung cancer (Part A: 1-mg mRNA-4157, n = 4) or resected cutaneous melanoma (Part D: 1-mg mRNA-4157 + 200-mg pembrolizumab, n = 12). Safety, tolerability, and immunogenicity were assessed. All patients experienced ≥1 treatment-emergent adverse event; there were no grade 4/5 adverse events or dose-limiting toxicities. mRNA-4157 alone induced consistent de novo and strengthened preexisting T-cell responses to targeted neoantigens. Following combination therapy, sustained mRNA-4157-induced neoantigen-specific T-cell responses and expansion of cytotoxic CD8 and CD4 T cells were observed. These findings show the potential of a novel mRNA individualized neoantigen therapy approach in oncology. Significance: The safety and immunogenicity results from this phase 1 study of mRNA-4157 as adjuvant monotherapy or combination therapy with pembrolizumab show generation of de novo and enhancement of existing neoantigen-specific T-cell responses and provide mechanistic proof of concept to support further development of mRNA-4157 for patients with resected solid tumors. See related commentary by Berraondo et al., p. 2021.

Alterations in intratumoral and peripheral immune status in recurrent gliomas and their prognostic implications for patients underwent reoperation

BACKGROUND

Reoperation is a treatment option for recurrent gliomas, yet factors impacting survival following reoperation remain poorly defined. Tumor immunity is profoundly associated with disease progression. Here, we analyze the immune status characteristics and their prognostic implications in recurrent gliomas.

METHODS

Intratumoral and peripheral immune characteristics between primary and recurrent gliomas were compared by conducting immunohistological staining and hematological examination with our in-house samples, and analyzing bulk and single-cell sequencing data from publicly available sources. Survival analysis was conducted to identify immunological markers with prognostic significances.

RESULTS

We observed a significant reduction in peripheral lymphocyte count, while an elevation in neutrophil-to-lymphocyte ratio (NLR) and red cell distribution width-to-platelet ratio (RPR) in patients with recurrent gliomas than in newly-diagnosed patients. Higher NLR and RPR indicated worse survival following reoperation in recurrent patients. Transcriptomic and immunohistological analysis showed an increased infiltration of tumor-associated macrophages (TAMs) and CD8+ T cell in recurrent gliomas compared to primary gliomas in both IDH-wildtype and mutant subtypes. Moreover, the abundance of TAMs emerged as an independent indicator for an inferior prognosis in recurrent gliomas. Single-cell profiling revealed a significant heterogeneity in the phenotypes of TAMs between primary and recurrent gliomas. Notably, TAMs enriched in recurrent gliomas exhibited elevated expression of interferon-γ-induced genes, multiple immunosuppressive molecules (TGFB1, CD276), and increased activity in glycose and lipid metabolism, indicating metabolic reprogramming.

CONCLUSION

Recurrent gliomas demonstrate augmented immune cell infiltration, but they fail to overcome TAMs-induced immunosuppression. Immunosuppressive indices, including TAM abundance, peripheral NLR and RPR, have prognostic implications for recurrent gliomas.

IL-13Rα2/TGF-β bispecific CAR-T cells counter TGF-β-mediated immune suppression and potentiate anti-tumor responses in glioblastoma

BACKGROUND

Chimeric antigen receptor (CAR)-T cell therapies targeting glioblastoma (GBM)-associated antigens such as interleukin-13 receptor subunit alpha-2 (IL-13Rα2) have achieved limited clinical efficacy to date, in part due to an immunosuppressive tumor microenvironment (TME) characterized by inhibitory molecules such as transforming growth factor-beta (TGF-β). The aim of this study was to engineer more potent GBM-targeting CAR-T cells by countering TGF-β-mediated immune suppression in the TME.

METHODS

We engineered a single-chain, bispecific CAR targeting IL-13Rα2 and TGF-β, which programs tumor-specific T cells to convert TGF-β from an immunosuppressant to an immunostimulant. Bispecific IL-13Rα2/TGF-β CAR-T cells were evaluated for efficacy and safety against both patient-derived GBM xenografts and syngeneic models of murine glioma.

RESULTS

Treatment with IL-13Rα2/TGF-β CAR-T cells leads to greater T-cell infiltration and reduced suppressive myeloid cell presence in the tumor-bearing brain compared to treatment with conventional IL-13Rα2 CAR-T cells, resulting in improved survival in both patient-derived GBM xenografts and syngeneic models of murine glioma.

CONCLUSIONS

Our findings demonstrate that by reprogramming tumor-specific T-cell responses to TGF-β, bispecific IL-13Rα2/TGF-β CAR-T cells resist and remodel the immunosuppressive TME to drive potent anti-tumor responses in GBM.

Feeding the wrath with myelin

Kloosterman and colleagues studied molecular and cellular changes during radiation therapy and disease recurrence across molecular subtypes of glioblastoma. They uncovered a distinct immune-cancer cell metabolic crosstalk during proneural/oligodendrocyte progenitor cell-like to mesenchymal-like transition, wherein macrophages feed on cholesterol-rich myelin debris to provide lipids to mesenchymal tumor cells, thereby fueling glioblastoma growth.

LTBR acts as a novel immune checkpoint of tumor-associated macrophages for cancer immunotherapy

Tumor-associated macrophages (TAMs) greatly contribute to immune checkpoint inhibitor (ICI) resistance of cancer. However, its underlying mechanisms and whether TAMs can be promising targets to overcome ICI resistance remain to be unveiled. Through integrative analysis of immune multiomics data and single-cell RNA-seq data (iMOS) in lung adenocarcinoma (LUAD), lymphotoxin β receptor (LTBR) is identified as a potential immune checkpoint of TAMs, whose high expression, duplication, and low methylation are correlated with unfavorable prognosis. Immunofluorescence staining shows that the infiltration of LTBR+ TAMs is associated with LUAD stages, immunotherapy failure, and poor prognosis. Mechanistically, LTΒR maintains immunosuppressive activity and M2 phenotype of TAMs by noncanonical nuclear factor kappa B and Wnt/β-catenin signaling pathways. Macrophage-specific knockout of LTBR hinders tumor growth and prolongs survival time via blocking TAM immunosuppressive activity and M2 phenotype. Moreover, TAM-targeted delivery of LTΒR small interfering RNA improves the therapeutic effect of ICI via reversing TAM-mediated immunosuppression, such as boosting cytotoxic CD8+ T cells and inhibiting granulocytic myeloid-derived suppressor cells infiltration. Taken together, we bring forth an immune checkpoint discovery pipeline iMOS, identify LTBR as a novel immune checkpoint of TAMs, and propose a new immunotherapy strategy by targeting LTBR+ TAMs.

A brave new framework for glioma drug development

Patients with brain tumours are motivated to participate in clinical trials involving repeat tissue sampling. Normalising the use of neoadjuvant and staged surgical trials necessitates collaboration among patients, regulatory agencies, and researchers. Initial and repetitive tissue sampling plays a crucial role in enhancing our understanding of resistance mechanisms and vulnerabilities in brain tumour therapy. Standardising biopsy techniques and ensuring technical uniformity across institutions are vital for effective interinstitutional collaboration. Although liquid biopsy technologies hold promise, they are not yet ready to replace tissue analysis. Clear communication about the risks and benefits of biopsies is essential, particularly regarding potential postoperative deficits. Changes in mindset and neurosurgical culture are imperative to achieve much needed breakthroughs in the development of new, effective therapies for brain tumours.

Allogeneic stem cells engineered to release interferon β and scFv-PD1 target glioblastoma and alter the tumor microenvironment

Highly malignant brain tumors, glioblastomas (GBM), are immunosuppressive, thereby limiting current promising immunotherapeutic approaches. In this study, we created interferon receptor 1 knockout allogeneic mesenchymal stem cells (MSC) to secrete dual-function pro-apoptotic and immunomodulatory interferon (IFN) β (MSCKO-IFNβ) using a single lentiviral vector CRISPR/Cas9 system. We show that MSCKO-IFNβ induces apoptosis in GBM cells and upregulates the cell surface expression of programmed death ligand-1 in tumor cells. Next, we engineered MSCKO to release a secretable single-chain variable fragment (scFv) to block programmed death (PD)-1 and show the ability of MSCKO-scFv-PD1 to enhance T-cell activation and T-cell-mediated tumor cell killing. To simultaneously express both immune modulators, we engineered MSCKO-IFNβ to co-express scFv-PD1 (MSCKO-IFNβ-scFv-PD1) and show the expression of both IFNβ and scFv-PD1 in vitro leads to T-cell activation and lowers the viability of tumor cells. Furthermore, to mimic the clinical scenario of GBM tumor resection and subsequent treatment, we show that synthetic extracellular matrix (sECM) encapsulated MSCKO-IFNβ-scFv-PD1 treatment of resected tumors results in the increase of CD4+ and CD8+ T cells, mature conventional dendritic cells type II and activation of microglia as compared to the control treatment group. Overall, these results reveal the ability of MSCKO-IFNβ-scFv-PD1 to shape the tumor microenvironment and enhance therapeutic outcomes in GBM.

Macrophage-mediated myelin recycling fuels brain cancer malignancy

Tumors growing in metabolically challenged environments, such as glioblastoma in the brain, are particularly reliant on crosstalk with their tumor microenvironment (TME) to satisfy their high energetic needs. To study the intricacies of this metabolic interplay, we interrogated the heterogeneity of the glioblastoma TME using single-cell and multi-omics analyses and identified metabolically rewired tumor-associated macrophage (TAM) subpopulations with pro-tumorigenic properties. These TAM subsets, termed lipid-laden macrophages (LLMs) to reflect their cholesterol accumulation, are epigenetically rewired, display immunosuppressive features, and are enriched in the aggressive mesenchymal glioblastoma subtype. Engulfment of cholesterol-rich myelin debris endows subsets of TAMs to acquire an LLM phenotype. Subsequently, LLMs directly transfer myelin-derived lipids to cancer cells in an LXR/Abca1-dependent manner, thereby fueling the heightened metabolic demands of mesenchymal glioblastoma. Our work provides an in-depth understanding of the immune-metabolic interplay during glioblastoma progression, thereby laying a framework to unveil targetable metabolic vulnerabilities in glioblastoma.

The dual role of POSTN in maintaining glioblastoma stem cells and the immunosuppressive phenotype of microglia in glioblastoma

BACKGROUND

Glioblastoma (GBM) is an immunosuppressive, universally lethal cancer driven by glioblastoma stem cells (GSCs). The interplay between GSCs and immunosuppressive microglia plays crucial roles in promoting the malignant growth of GBM; however, the molecular mechanisms underlying this crosstalk are unclear. This study aimed to investigate the role of POSTN in maintaining GSCs and the immunosuppressive phenotype of microglia.

METHODS

The expression of POSTN in GBM was identified via immunohistochemistry, quantitative real-time PCR, and immunoblotting. Tumorsphere formation assay, Cell Counting Kit-8 assay and immunofluorescence were used to determine the key role of POSTN in GSC maintenance. ChIP-seq and ChIP-PCR were conducted to confirm the binding sequences of β-catenin in the promoter region of FOSL1. Transwell migration assays, developmental and functional analyses of CD4+ T cells, CFSE staining and analysis, enzyme-linked immunosorbent assays and apoptosis detection tests were used to determine the key role of POSTN in maintaining the immunosuppressive phenotype of microglia and thereby promoting the immunosuppressive tumor microenvironment. Furthermore, the effects of POSTN on GSC maintenance and the immunosuppressive phenotype of microglia were investigated in a patient-derived xenograft model and orthotopic glioma mouse model, respectively.

RESULTS

Our findings revealed that POSTN secreted from GSCs promotes GSC self-renewal and tumor growth via activation of the αVβ3/PI3K/AKT/β-catenin/FOSL1 pathway. In addition to its intrinsic effects on GSCs, POSTN can recruit microglia and upregulate CD70 expression in microglia through the αVβ3/PI3K/AKT/NFκB pathway, which in turn promotes Treg development and functionality and supports the formation of an immunosuppressive tumor microenvironment. In both in vitro models and orthotopic mouse models of GBM, POSTN depletion disrupted GSC maintenance, decreased the recruitment of immunosuppressive microglia and suppressed GBM growth.

CONCLUSION

Our findings reveal that POSTN plays critical roles in maintaining GSCs and the immunosuppressive phenotype of microglia and provide a new therapeutic target for treating GBM.

Nivolumab Reaches Brain Lesions in Patients with Recurrent Glioblastoma and Induces T-cell Activity and Upregulation of Checkpoint Pathways

Glioblastoma (GBM) is an aggressive brain tumor with poor prognosis. Although immunotherapy is being explored as a potential treatment option for patients with GBM, it is unclear whether systemic immunotherapy can reach and modify the tumor microenvironment in the brain. We evaluated immune characteristics in patients receiving the anti-PD-1 immune checkpoint inhibitor nivolumab 1 week prior to surgery, compared with control patients receiving salvage resection without prior nivolumab treatment. We observed saturating levels of nivolumab bound to intratumorally and tissue-resident T cells in the brain, implicating saturating levels of nivolumab reaching brain tumors. Following nivolumab treatment, significant changes in T-cell activation and proliferation were observed in the tumor-resident T-cell population, and peripheral T cells upregulated chemokine receptors related to brain homing. A strong nivolumab-driven upregulation in compensatory checkpoint inhibition molecules, i.e., TIGIT, LAG-3, TIM-3, and CTLA-4, was observed, potentially counteracting the treatment effect. Finally, tumor-reactive tumor-infiltrating lymphocytes (TIL) were found in a subset of nivolumab-treated patients with prolonged survival, and neoantigen-reactive T cells were identified in both TILs and blood. This indicates a systemic response toward GBM in a subset of patients, which was further boosted by nivolumab, with T-cell responses toward tumor-derived neoantigens. Our study demonstrates that nivolumab does reach the GBM tumor lesion and enhances antitumor T-cell responses both intratumorally and systemically. However, various anti-inflammatory mechanisms mitigate the clinical efficacy of the anti-PD-1 treatment.

Proteomics mining of cancer hallmarks on a single-cell resolution

Dysregulated proteome is an essential contributor in carcinogenesis. Protein fluctuations fuel the progression of malignant transformation, such as uncontrolled proliferation, metastasis, and chemo/radiotherapy resistance, which severely impair therapeutic effectiveness and cause disease recurrence and eventually mortality among cancer patients. Cellular heterogeneity is widely observed in cancer and numerous cell subtypes have been characterized that greatly influence cancer progression. Population-averaged research may not fully reveal the heterogeneity, leading to inaccurate conclusions. Thus, deep mining of the multiplex proteome at the single-cell resolution will provide new insights into cancer biology, to develop prognostic biomarkers and treatments. Considering the recent advances in single-cell proteomics, herein we review several novel technologies with particular focus on single-cell mass spectrometry analysis, and summarize their advantages and practical applications in the diagnosis and treatment for cancer. Technological development in single-cell proteomics will bring a paradigm shift in cancer detection, intervention, and therapy.

Brain macrophage senescence in glioma

Gliomas are a diverse group of primary central nervous system neoplasms with no curative therapies available. Brain macrophages comprise microglia in the brain parenchyma, border-associated macrophages in the meningeal-choroid plexus-perivascular space and monocyte-derived macrophages infiltrating the brain. With the great improvement of our recognition of brain macrophages, diverse macrophage populations have been found in the context of glioma, which exhibit functional and phenotypic heterogeneity. We have long thought that brain macrophage senescence is detrimental, manifested by specialized forms of persistent cell cycle arrest and chronic low-grade inflammation. Persistent senescence of macrophages may result in immune dysfunction, potentially contributing to glioma initiation and development. Given the crucial roles played by brain macrophages in glioma, we unravel how brain macrophages undergo reprogramming and their contribution to glioma. We outline general molecular alterations and specific biomarkers in senescent brain macrophages, as well as functional changes (such as metabolism, autophagy, phagocytosis, antigen presentation, and infiltration and recruitment). In addition, recent advances in genetic regulation and mechanisms linked to senescent brain macrophages are discussed. In particular, this review emphasizes the contribution of senescent brain macrophages to glioma, which may drive translational efforts to utilize brain macrophages as a prognostic marker or/and treatment target in glioma. An in-depth comprehending of how brain macrophage senescence functionally influences the tumor microenvironment will be key to our development of innovative therapeutics for glioma.

Integrated bioinformatics analysis and experimental validation reveal the relationship between ALOX5AP and the prognosis and immune microenvironment in glioma

BACKGROUND

Treatment of gliomas, the most prevalent primary malignant neoplasm of the central nervous system, is challenging. Arachidonate 5-lipoxygenase activating protein (ALOX5AP) is crucial for converting arachidonic acid into leukotrienes and is associated with poor prognosis in multiple cancers. Nevertheless, its relationship with the prognosis and the immune microenvironment of gliomas remains incompletely understood.

METHODS

The differential expression of ALOX5AP was evaluated based on public Databases. Kaplan-Meier, multivariate Cox proportional hazards regression analysis, time-dependent receiver operating characteristic, and nomogram were used to estimate the prognostic value of ALOX5AP. The relationship between ALOX5AP and immune infiltration was calculated using ESTIMATE and CIBERSORT algorithms. Relationships between ALOX5AP and human leukocyte antigen molecules, immune checkpoints, tumor mutation burden, TIDE score, and immunophenoscore were calculated to evaluate glioma immunotherapy response. Single gene GSEA and co-expression network-based GO and KEGG enrichment analysis were performed to explore the potential function of ALOX5AP. ALOX5AP expression was verified using multiplex immunofluorescence staining and its prognostic effects were confirmed using a glioma tissue microarray.

RESULT

ALOX5AP was highly expressed in gliomas, and the expression level was related to World Health Organization (WHO) grade, age, sex, IDH mutation status, 1p19q co-deletion status, MGMTp methylation status, and poor prognosis. Single-cell RNA sequencing showed that ALOX5AP was expressed in macrophages, monocytes, and T cells but not in tumor cells. ALOX5AP expression positively correlated with M2 macrophage infiltration and poor immunotherapy response. Immunofluorescence staining demonstrated that ALOX5AP was upregulated in WHO higher-grade gliomas, localizing to M2 macrophages. Glioma tissue microarray confirmed the adverse effect of ALOX5AP in the prognosis of glioma.

CONCLUSION

ALOX5AP is highly expressed in M2 macrophages and may act as a potential biomarker for predicting prognosis and immunotherapy response in patients with glioma.

Immunotherapy drives mesenchymal tumor cell state shift and TME immune response in glioblastoma patients

BACKGROUND

Glioblastoma is a highly aggressive type of brain tumor for which there is no curative treatment available. Immunotherapies have shown limited responses in unselected patients, and there is an urgent need to identify mechanisms of treatment resistance to design novel therapy strategies.

METHODS

Here we investigated the phenotypic and transcriptional dynamics at single-cell resolution during nivolumab immune checkpoint treatment of glioblastoma patients.

RESULTS

We present the integrative paired single-cell RNA-seq analysis of 76 tumor samples from patients in a clinical trial of the PD-1 inhibitor nivolumab and untreated patients. We identify a distinct aggressive phenotypic signature in both tumor cells and the tumor microenvironment in response to nivolumab. Moreover, nivolumab-treatment was associated with an increased transition to mesenchymal stem-like tumor cells, and an increase in TAMs and exhausted and proliferative T cells. We verify and extend our findings in large external glioblastoma dataset (n = 298), develop a latent immune signature and find 18% of primary glioblastoma samples to be latent immune, associated with mesenchymal tumor cell state and TME immune response. Finally, we show that latent immune glioblastoma patients are associated with shorter overall survival following immune checkpoint treatment (P = .0041).

CONCLUSIONS

We find a resistance mechanism signature in one fifth of glioblastoma patients associated with a tumor-cell transition to a more aggressive mesenchymal-like state, increase in TAMs and proliferative and exhausted T cells in response to immunotherapy. These patients may instead benefit from neuro-oncology therapies targeting mesenchymal tumor cells.

EZH2-STAT3 signaling pathway regulates GSDMD-mediated pyroptosis in glioblastoma

Glioblastoma multiforme (GBM) is the most therapeutically challenging primary brain tumor owing to the unique physiological structure of the blood-brain barrier. Lately, research on targeted therapy for gliomas has shifted focus toward the tumor microenvironment and local immune responses. Pyroptosis is a newly identified cellular demise characterized by the release of numerous inflammatory factors. While pyroptosis shows promise in impeding the occurrence and progression of GBM, the regulatory mechanisms governing this process in gliomas still require further investigation. The function of the Enhancer of zeste homolog 2 (EZH2) in pyroptosis remains unexplored. In this study, we discovered that 3-Deazaneplanocin A (DZNep), an inhibitor of EZH2, can induce pyroptosis in GBM in vitro experiments. Moreover, our investigation unveiled that the signal transducer and activator of transcription (STAT3) could serve as a downstream regulator influenced by EZH2, impacting pyroptosis in GBM. Following treatment with DZNep and the STAT3 inhibitor (SH-4-54), there was an elevation in the levels of pyroptosis-related factors, namely NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) and Gasdermin D (GSDMD). Moreover, simultaneous inhibition of both EZH2 and STAT3 led to the expression of inflammatory factors such as IL-1β and IL-18. In summary, we have identified that EZH2 regulates pyroptosis in GBM through STAT3, and pyroptosis could potentially be targeted for immunotherapy in GBM.

Modeling glioblastoma

Establishing a zebrafish model of a deadly type of brain tumor highlights the role of the immune system in the early stages of the disease.

TCF1-positive and TCF1-negative TRM CD8 T cell subsets and cDC1s orchestrate melanoma protection and immunotherapy response

BACKGROUND

Melanoma, the most lethal form of skin cancer, has undergone a transformative treatment shift with the advent of checkpoint blockade immunotherapy (CBI). Understanding the intricate network of immune cells infiltrating the tumor and orchestrating the control of melanoma cells and the response to CBI is currently of utmost importance. There is evidence underscoring the significance of tissue-resident memory (TRM) CD8 T cells and classic dendritic cell type 1 (cDC1) in cancer protection. Transcriptomic studies also support the existence of a TCF7+ (encoding TCF1) T cell as the most important for immunotherapy response, although uncertainty exists about whether there is a TCF1+TRM T cell due to evidence indicating TCF1 downregulation for tissue residency activation.

METHODS

We used multiplexed immunofluorescence and spectral flow cytometry to evaluate TRM CD8 T cells and cDC1 in two melanoma patient cohorts: one immunotherapy-naive and the other receiving immunotherapy. The first cohort was divided between patients free of disease or with metastasis 2 years postdiagnosis while the second between CBI responders and non-responders.

RESULTS

Our study identifies two CD8+TRM subsets, TCF1+ and TCF1-, correlating with melanoma protection. TCF1+TRM cells show heightened expression of IFN-γ and Ki67 while TCF1- TRM cells exhibit increased expression of cytotoxic molecules. In metastatic patients, TRM subsets undergo a shift in marker expression, with the TCF1- subset displaying increased expression of exhaustion markers. We observed a close spatial correlation between cDC1s and TRMs, with TCF1+TRM/cDC1 pairs enriched in the stroma and TCF1- TRM/cDC1 pairs in tumor areas. Notably, these TCF1- TRMs express cytotoxic molecules and are associated with apoptotic melanoma cells. Both TCF1+ and TCF1- TRM subsets, alongside cDC1, prove relevant to CBI response.

CONCLUSIONS

Our study supports the importance of TRM CD8 T cells and cDC1 in melanoma protection while also highlighting the existence of functionally distinctive TCF1+ and TCF1- TRM subsets, both crucial for melanoma control and CBI response.

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.

Targeting MS4A4A: A novel pathway to improve immunotherapy responses in glioblastoma

INTRODUCTION

Glioblastoma (GBM) remains a challenging brain tumor to treat, with limited response to PD-1 immunotherapy due to tumor-associated macrophages (TAMs), specifically the M2 phenotype. This study explores the potential of MS4A4A (membrane spanning four domains, subfamily A, member 4A) inhibition in driving M2 macrophage polarization toward the M1 phenotype via the ferroptosis pathway to enhance the effectiveness of immunotherapy in GBM.

METHODS

Single-cell RNA sequencing and spatial transcriptomic analyses were employed to characterize M2 macrophages and MS4A4A expression in GBM. In vitro studies utilizing TAM cultures, flow cytometry, and western blot validations were conducted to assess the impact of MS4A4A on the tumor immune microenvironment and M2 macrophage polarization. In vivo models, including subcutaneous and orthotopic transplantation in mice, were utilized to evaluate the effects of MS4A4A knockout and combined immune checkpoint blockade (ICB) therapy on tumor growth and response to PD-1 immunotherapy.

RESULTS

Distinct subsets of GBM-associated macrophages were identified, with spatial distribution in tumor tissue elucidated. In vivo experiments demonstrated that inhibiting MS4A4A and combining ICB therapy effectively inhibited tumor growth, reshaped the tumor immune microenvironment by reducing M2 TAM infiltration and enhancing CD8+ T-cell infiltration, ultimately leading to complete tumor eradication.

CONCLUSION

MS4A4A inhibition shows promise in converting M2 macrophages to M1 phenotype via ferroptosis, decreasing M2-TAM infiltration, and enhancing GBM response to PD-1 immunotherapy. These findings offer a novel approach to developing more effective immunotherapeutic strategies for GBM.

Recurrent Glioblastoma-Molecular Underpinnings and Evolving Treatment Paradigms

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

Programmed cell death disrupts inflammatory tumor microenvironment (TME) and promotes glioblastoma evolution

Glioblastoma (GBM) is the most common malignant brain tumor and has a dismal prognosis even under the current first-line treatment, with a 5-year survival rate less than 7%. Therefore, it is important to understand the mechanism of treatment resistance and develop new anti-tumor strategies. Induction of programmed cell death (PCD) has become a promising anti-tumor strategy, but its effectiveness in treating GBM remains controversial. On the one hand, PCD triggers tumor cell death and then release mediators to draw in immune cells, creating a pro-inflammatory tumor microenvironment (TME). One the other hand, mounting evidence suggests that PCD and inflammatory TME will force tumor cells to evolve under survival stress, leading to tumor recurrence. The purpose of this review is to summarize the role of PCD and inflammatory TME in the tumor evolution of GBM and promising methods to overcome tumor evolution.

Glioblastoma Vaccines as Promising Immune-Therapeutics: Challenges and Current Status

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor. Standard treatments including surgical resection, radiotherapy, and chemotherapy, have failed to significantly improve the prognosis of glioblastoma patients. Currently, immunotherapeutic approaches based on vaccines, chimeric antigen-receptor T-cells, checkpoint inhibitors, and oncolytic virotherapy are showing promising results in clinical trials. The combination of different immunotherapeutic approaches is proving satisfactory and promising. In view of the challenges of immunotherapy and the resistance of glioblastomas, the treatment of these tumors requires further efforts. In this review, we explore the obstacles that potentially influence the efficacy of the response to immunotherapy and that should be taken into account in clinical trials. This article provides a comprehensive review of vaccine therapy for glioblastoma. In addition, we identify the main biomarkers, including isocitrate dehydrogenase, epidermal growth factor receptor, and telomerase reverse transcriptase, known as potential immunotherapeutic targets in glioblastoma, as well as the current status of clinical trials. This paper also lists proposed solutions to overcome the obstacles facing immunotherapy in glioblastomas.

Dendritic cell subsets and implications for cancer immunotherapy

Dendritic cells (DCs) play a central role in the orchestration of effective T cell responses against tumors. However, their functional behavior is context-dependent. DC type, transcriptional program, location, intratumoral factors, and inflammatory milieu all impact DCs with regard to promoting or inhibiting tumor immunity. The following review introduces important facets of DC function, and how subset and phenotype can affect the interplay of DCs with other factors in the tumor microenvironment. It will also discuss how current cancer treatment relies on DC function, and survey the myriad ways with which immune therapy can more directly harness DCs to enact antitumor cytotoxicity.

Glioblastoma-Infiltrating CD8+ T Cells Are Predominantly a Clonally Expanded GZMK+ Effector Population

Recent clinical trials have highlighted the limited efficacy of T cell-based immunotherapy in patients with glioblastoma (GBM). To better understand the characteristics of tumor-infiltrating lymphocytes (TIL) in GBM, we performed cellular indexing of transcriptomes and epitopes by sequencing and single-cell RNA sequencing with paired V(D)J sequencing, respectively, on TILs from two cohorts of patients totaling 15 patients with high-grade glioma, including GBM or astrocytoma, IDH-mutant, grade 4 (G4A). Analysis of the CD8+ TIL landscape reveals an enrichment of clonally expanded GZMK+ effector T cells in the tumor compared with matched blood, which was validated at the protein level. Furthermore, integration with other cancer types highlights the lack of a canonically exhausted CD8+ T-cell population in GBM TIL. These data suggest that GZMK+ effector T cells represent an important T-cell subset within the GBM microenvironment and may harbor potential therapeutic implications.

SIGNIFICANCE

To understand the limited efficacy of immune-checkpoint blockade in GBM, we applied a multiomics approach to understand the TIL landscape. By highlighting the enrichment of GZMK+ effector T cells and the lack of exhausted T cells, we provide a new potential mechanism of resistance to immunotherapy in GBM. This article is featured in Selected Articles from This Issue, p. 897.