Single-cell profiling of human gliomas reveals macrophage ontogeny as a basis for regional differences in macrophage activation in the tumor microenvironment

Redefining macrophage phenotypes after spinal cord injury: An open data approach

Spinal cord injury (SCI) triggers intraspinal inflammation through an influx of blood-derived inflammatory cells such as neutrophils and monocyte-derived macrophages. Macrophages play a complex role in SCI pathophysiology ranging from potentiating secondary injury to facilitating recovery and wound healing. In vitro, macrophages have been classified as having a pro-inflammatory, M1 phenotype, or a regenerative, M2 phenotype. In vivo, however, studies suggest that macrophages exist in a spectrum of phenotypes and can shift from one phenotype to another. Single-cell RNA sequencing (scRNA-seq) allows us to assess immune cell heterogeneity in the spinal cord after injury, and several groups have created publicly available datasets containing valuable data for further exploration. In this study, we compared three different scRNA-seq datasets and analyzed macrophage heterogeneity after SCI based on cell clustering according to gene expression profiles. We analyzed data from 7 days post injury (dpi) in young female mice that received a mid-thoracic SCI contusion. Using the Seurat pipeline, we clustered cells, subsetted macrophages from microglia and other myeloid cells, and identified different macrophage populations. Using SingleR as a cross-dataset cluster comparison tool, we identified similarities in macrophage populations across datasets. To confirm and refine this analysis, we analyzed the top 10 differentially expressed genes for each population in each dataset. Most clusters identified in the SingleR analysis were confirmed to have a unique genetic signature and were consistently present in all datasets analyzed. Taken together, four distinct macrophage populations were consistently identified after SCI at 7 dpi in three datasets from independent research teams. Our identification of biologically conserved macrophage populations after SCI using an unbiased approach highlights the power of data sharing and open data in redefining macrophage heterogeneity.

Tumor-infiltrating myeloid cells; mechanisms, functional significance, and targeting in cancer therapy

Tumor-infiltrating myeloid cells (TIMs), which encompass tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), and tumor-associated dendritic cells (TADCs), are of great importance in tumor microenvironment (TME) and are integral to both pro- and anti-tumor immunity. Nevertheless, the phenotypic heterogeneity and functional plasticity of TIMs have posed challenges in fully understanding their complexity roles within the TME. Emerging evidence suggested that the presence of TIMs is frequently linked to prevention of cancer treatment and improvement of patient outcomes and survival. Given their pivotal function in the TME, TIMs have recently been recognized as critical targets for therapeutic approaches aimed at augmenting immunostimulatory myeloid cell populations while depleting or modifying those that are immunosuppressive. This review will explore the important properties of TIMs related to immunity, angiogenesis, and metastasis. We will also document the latest therapeutic strategies targeting TIMs in preclinical and clinical settings. Our objective is to illustrate the potential of TIMs as immunological targets that may improve the outcomes of existing cancer treatments.

Immunotherapy for High-Grade Gliomas

Background: High-grade gliomas (HGGs), particularly glioblastoma (GBM), are associated with exceptionally high mortality and inevitable recurrence. In considering novel treatment options for these devastating diseases, immunotherapies represent promising candidates. Immunotherapies have demonstrated efficacy for several advanced tumors outside the central nervous system, highlighting a potential role for these agents in treating HGGs. However, multiple challenges to immunotherapy efficacy have tempered therapeutic benefit in practice, including local and systemic immunosuppression, intratumoral heterogeneity, and various mechanisms of intrinsic and acquired resistance. In the past 30 years, diverse immunotherapeutic subclasses have been assessed for benefit against HGGs. Methods: We performed a PubMed search for randomized clinical trials performed within the last 30 years evaluating the following immunotherapy agents for high-grade gliomas: immune checkpoint inhibitors, vaccines, oncologic viruses, cytokines, and CAR T-cells. The present review offers a critical analysis of key pre-clinical and clinical trials that have shaped the immunotherapy landscape for high-grade gliomas over the past two decades. Results/Conclusions: Across the different immunotherapeutic methods and modalities explored thus far, a recurring theme emerges: while therapeutic strategies with a compelling conceptual basis are continually under development and even demonstrate a benefit in preclinical and early-phase trials, larger and later-phase trials consistently fail to produce concordantly significant outcomes. To date, no large-scale clinical trial has demonstrated a benefit of sufficient consequence to change practice. Continued critical appraisal of the strengths and pitfalls of prior investigative work, optimization of treatment development and delivery, and innovative approaches to combination therapy design will collectively be integral to future therapeutic advancement.

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.

A dynamic and multimodal framework to define microglial states

The widespread use of single-cell RNA sequencing has generated numerous purportedly distinct and novel subsets of microglia. Here, we challenge this fragmented paradigm by proposing that microglia exist along a continuum rather than as discrete entities. We identify a methodological over-reliance on computational clustering algorithms as the fundamental issue, with arbitrary cluster numbers being interpreted as biological reality. Evidence suggests that the observed transcriptional diversity stems from a combination of microglial plasticity and technical noise, resulting in terminology describing largely overlapping cellular states. We introduce a continuous model of microglial states, where cell positioning along the continuum is determined by biological aging and cell-specific molecular contexts. The model accommodates the dynamic nature of microglia. We advocate for a parsimonious approach toward classification and terminology that acknowledges the continuous spectrum of microglial states, toward a robust framework for understanding these essential immune cells of the CNS.

Targeting legumain-mediated cell-cell interaction sensitizes glioblastoma to immunotherapy in preclinical models

Tumor-associated macrophages (TAMs) are the most prominent immune cell population in the glioblastoma (GBM) tumor microenvironment and play critical roles in promoting tumor progression and immunosuppression. Here we identified that TAM-derived legumain (LGMN) exhibited a dual role in regulating the biology of TAMs and GBM cells. LGMN promoted macrophage infiltration in a cell-autonomous manner by activating the GSK3β/STAT3 pathway. Moreover, TAM-derived LGMN activated integrin αv/AKT/p65 signaling to drive GBM cell proliferation and survival. Targeting of LGMN-directed macrophage (inhibiting GSK3β and STAT3) and GBM cell (inhibiting integrin αv) mechanisms resulted in an antitumor effect in immunocompetent GBM mouse models that was further enhanced by combination with anti-PD-1 therapy. Our study reveals a paracrine and autocrine mechanism of TAM-derived LGMN that promotes GBM progression and immunosuppression, providing effective therapeutic targets to improve immunotherapy in GBM.

Complex neural-immune interactions shape glioma immunotherapy

Rich neural-immune interactions in the central nervous system (CNS) shape its function and create a unique immunological microenvironment for immunotherapy in CNS malignancies. Far from the now-debunked concept of CNS "immune privilege," it is now understood that unique immunological niches and constant immune surveillance of the brain contribute in multifaceted ways to brain health and robustly influence immunotherapy approaches for CNS cancers. Challenges include immune-suppressive and neurotoxicity-promoting crosstalk between brain, immune, and tumor cells. Developing effective immunotherapies for cancers of the nervous system will require a deeper understanding of these neural-immune-malignant cell interactions. Here, we review progress and challenges in immunotherapy for gliomas of the brain and spinal cord in light of these unique neural-immune interactions and highlight future work needed to optimize promising immunotherapies for gliomas.

Reduced HLA-I Transcript Levels and Increased Abundance of a CD56dim NK Cell Signature Are Associated with Improved Survival in Lower-Grade Gliomas

BACKGROUND

Human leukocyte antigen class I (HLA-I) plays a pivotal role in shaping anti-tumour immunity by influencing the functionality of T cells and natural killer (NK) cells within the tumour microenvironment.

METHODS

Here, we explored the transcriptional landscape of HLA-I molecules across various solid cancer transcriptomes from The Cancer Genome Atlas (TCGA) database and assessed the impact of HLA-I expression on the clinical significance of tumour-infiltrating CD56dim and CD56bright NK cells.

RESULTS

Our analysis revealed that high HLA-I expression correlated with reduced patient survival in the TCGA lower-grade glioma (LGG) cohort, with this association varying by histopathological subtype. We then estimated the relative abundance of 23 immune and stromal cell signatures in LGG transcriptomes using a cellular deconvolution approach, which revealed that LGG patients with low HLA-I expression and high CD56dim NK cell abundance had better survival outcomes compared to those with high HLA-I expression and low CD56dim NK cell abundance. Furthermore, HLA-I expression was positively correlated with various inhibitory NK cell receptors and negatively correlated with activating NK cell receptors, particularly those within the killer cell lectin-like receptor (KLR) gene family. High co-expression of HLA-E and NKG2A predicted poor survival outcomes in LGG patients, whereas low HLA-E and high NKG2C/E abundance predicted more favourable outcomes, suggesting a potential modulatory role of HLA-I on the tumour-infiltrating cytotoxic CD56dim NK cell subset.

CONCLUSIONS

Overall, our study unveils a potential role for deregulated HLA-I expression in modulating the clinical impact of glioma-infiltrating CD56dim NK cells. These findings lay the foundation for future in-depth experimental studies to investigate the underlying mechanisms.

Exploring tumor-associated macrophages in glioblastoma: from diversity to therapy

Glioblastoma is the most aggressive and lethal cancer of the central nervous system, presenting substantial treatment challenges. The current standard treatment, which includes surgical resection followed by temozolomide and radiation, offers limited success. While immunotherapies, such as immune checkpoint inhibitors, have proven effective in other cancers, they have not demonstrated significant efficacy in GBM. Emerging research highlights the pivotal role of tumor-associated macrophages (TAMs) in supporting tumor growth, fostering treatment resistance, and shaping an immunosuppressive microenvironment. Preclinical studies show promising results for therapies targeting TAMs, suggesting potential in overcoming these barriers. TAMs consist of brain-resident microglia and bone marrow-derived macrophages, both exhibiting diverse phenotypes and functions within the tumor microenvironment. This review delves into the origin, heterogeneity, and functional roles of TAMs in GBM, underscoring their dual roles in tumor promotion and suppression. It also summarizes recent progress in TAM-targeted therapies, which may, in combination with other treatments like immunotherapy, pave the way for more effective and personalized strategies against this aggressive malignancy.

Microglial ApoD-induced NLRC4 inflammasome activation promotes Alzheimer's disease progression

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease with no effective therapies. It is well known that chronic neuroinflammation plays a critical role in the onset and progression of AD. Well-balanced neuronal-microglial interactions are essential for brain functions. However, determining the role of microglia-the primary immune cells in the brain-in neuroinflammation in AD and the associated molecular basis has been challenging.

METHODS

Inflammatory factors in the sera of AD patients were detected and their association with microglia activation was analyzed. The mechanism for microglial inflammation was investigated. IL6 and TNF-α were found to be significantly increased in the AD stage.

RESULTS

Our analysis revealed that microglia were extensively activated in AD cerebra, releasing sufficient amounts of cytokines to impair the neural stem cells (NSCs) function. Moreover, the ApoD-induced NLRC4 inflammasome was activated in microglia, which gave rise to the proinflammatory phenotype. Targeting the microglial ApoD promoted NSC self-renewal and inhibited neuron apoptosis. These findings demonstrate the critical role of ApoD in microglial inflammasome activation, and for the first time reveal that microglia-induced inflammation suppresses neuronal proliferation.

CONCLUSION

Our studies establish the cellular basis for microglia activation in AD progression and shed light on cellular interactions important for AD treatment.

N-acetylcysteine remodels the tumor microenvironment of primary and recurrent mouse glioblastoma

PURPOSE

Glioblastoma (GBM) exhibits a high ROS character, giving rise to an immunosuppressive microenvironment and tumor vascular abnormality. This study investigated the potential effect of N-acetylcysteine (NAC), an antioxidant, on primary and recurrent mouse brain tumors.

METHODS

We measured reactive oxygen species (ROS)/ glutathione (GSH) levels in human GBM. Additionally, we conducted NAC trials on primary mouse brain tumor models (GL261-Luc, CT2A-Luc) and a recurrent mouse GBM model (GL261-iCasp9-Luc). After brain tumor inoculation, mice received a daily 100 mg/kg NAC treatment, and the tumor volume was monitored via IVIS imaging. The efficacy of NAC was evaluated through survival time, tumor volume, ROS/GSH levels, M1/M2 macrophages, immune cells infiltration, and tumor vascularization.

RESULTS

Human GBM suffered from significant oxidative stress. With NAC treatment, mouse brain tumors exhibited a lower ROS level, more M1-like tumor-associated macrophages/microglia (TAMs), more CD8 + T cell infiltration, and a normalized vascular character. NAC inhibited tumor growth and suppressed recurrence in mouse brain tumor models.

CONCLUSION

NAC is a promising adjunctive drug to remodel the brain tumors microenvironment.

Single-nucleus RNA sequencing reveals a preclinical model for the most common subtype of glioblastoma

Different glioblastoma (GBM) subtypes have been identified based on the tumor microenvironment (TME). The discovery of new therapies for these hard-to-treat tumors requires a thorough characterization of preclinical models, including their TME, to apply preclinical results to the most similar GBM subtype. Using single-nucleus RNA sequencing (snRNA-seq), we characterized the tumor and TME in an immunocompetent mouse model with intracranially implanted GBM stem cells at different stages and treatments. Visium spatial transcriptomics confirmed the location of annotated cells. This model exhibits GBM targets related to integration into neural circuits - Grik2, Nlgn3, Gap43 or Kcnn4-, immunoevasion - Nt5e, Cd274 or Irf8- and immunosuppression - Csf1r, Arg1, Mrc1 and Tgfb1. The landscape of cytokines, checkpoint ligands and receptors uncovered Mrc1, PD-L1, TIM-3 or B7-H3, among the immunotherapy targets that can be addressed in this model. The comparison with human GBMs unveiled crucial similarities with TMEMed GBM, the most frequent subtype.

Macrophage-derived exosomes in cancer: a double-edged sword with therapeutic potential

Solid cancer contains a complicated communication network between cancer cells and components in the tumor microenvironment (TME), significantly influencing the progression of cancer. Exosomes function as key carriers of signaling molecules in these communications, including the intricate signalings of tumor-associated macrophages (TAMs) on cancer cells and the TME. With their natural lipid bilayer structures and biological activity that relates to their original cell, exosomes have emerged as efficient carriers in studies on cancer therapy. Intrigued by the heterogeneity and plasticity of both macrophages and exosomes, we regard macrophage-derived exosomes in cancer as a double-edged sword. For instance, TAM-derived exosomes, educated by the TME, can promote resistance to cancer therapies, while macrophage-derived exosomes generated in vitro have shown favorable potential in cancer therapy. Here, we depict the reasons for the heterogeneity of TAM-derived exosomes, as well as the manifold roles of TAM-derived exosomes in cancer progression, metastasis, and resistance to cancer therapy. In particular, we emphasize the recent advancements of modified macrophage-derived exosomes in diverse cancer therapies, arguing that these modified exosomes are endowed with unique advantages by their macrophage origin. We outline the challenges in translating these scientific discoveries into clinical cancer therapy, aiming to provide patients with safe and effective treatments.

Ribosomal RNA Biosynthesis Functionally Programs Tumor-Associated Macrophages to Support Breast Cancer Progression

Macrophages are important cellular components of the innate immune system, serving as the first line of immune defense. They are also among the first immune cells to be reprogrammed by the evolving tumor milieu into tumor-supportive macrophages that facilitate tumor progression and promote therapeutic evasion. In this study, we uncovered that macrophages from preneoplastic breast lesions were enriched for ribosome biosynthesis genes, indicating that this is an early event that is maintained in the tumor tissue. Furthermore, following treatment with irradiation or chemotherapy, breast tumors featured an abundance of tumor-supporting macrophages that displayed an enrichment of signatures of rRNA expression and ribosome biosynthesis. Consistently, rRNA synthesis was increased in tumor-supportive macrophages. In preclinical models of mammary cancer, a low dose of the RNA biogenesis inhibitor BMH-21 converted protumor macrophages to tumor-suppressive macrophages and supported an inflammatory tumor microenvironment. Inhibition of rRNA transcription stimulated a nucleolar stress response that activated the p53 and NF-κB pathways, which orchestrated impaired ribosome biogenesis checkpoint signaling that induced an inflammatory program in macrophages. Finally, inhibiting ribosome biogenesis augmented the effectiveness of neoadjuvant therapy. Together, these findings provide evidence that ribosome biogenesis is a targetable dependency to reprogram the tumor immune microenvironment. Significance: Increased ribosome biogenesis is an integral attribute of protumor macrophages that occurs early during breast tumorigenesis and represents a therapeutically actionable process to reactivate the tumor-suppressive functions of macrophages.

Effective design of therapeutic nanovaccines based on tumor neoantigens

Neoantigen vaccines are among the most potent immunotherapies for personalized cancer treatment. Therapeutic vaccines containing tumor-specific neoantigens that elicit specific T cell responses offer the potential for long-term clinical benefits to cancer patients. Unlike immune-checkpoint inhibitors (ICIs), which rely on pre-existing specific T cell responses, personalized neoantigen vaccines not only promote existing specific T cell responses but importantly stimulate the generation of neoantigen-specific T cells, leading to the establishment of a persistent specific memory T cell pool. The review discusses the current state of clinical research on neoantigen nanovaccines, focusing on the application of vectors, adjuvants, and combinational strategies to address a range of challenges and optimize therapeutic outcomes.

Single-cell transcriptomics reveals immunosuppressive microenvironment and highlights tumor-promoting macrophage cells in Glioblastoma

Glioblastoma (GBM) is the most prevalent and aggressive primary brain malignancy in adults. Nevertheless, the cellular heterogeneity and complexity within the GBM microenvironment (TME) are still not fully understood, posing a significant obstacle in the advancement of more efficient immunotherapies for GBM. In this study, we conducted an integrated analysis of 48 tumor fragments from 24 GBM patients at the single-cell level, uncovering substantial molecular diversity within immune infiltrates. We characterized molecular signatures for five distinct tumor-associated macrophages (TAMs) subtypes. Notably, the TAM_MRC1 subtype displayed a pronounced M2 polarization signature. Additionally, we identified a subtype of natural killer (NK) cells, designated CD56dim_DNAJB1. This subtype is characterized by an exhausted phenotype, evidenced by an elevated stress signature and enrichment in the PD-L1/PD-1 checkpoint pathway. Our findings also highlight significant cell-cell interactions among malignant glioma cells, TAM, and NK cells within the TME. Overall, this research sheds light on the functional heterogeneity of glioma and immune cells in the TME, providing potential targets for therapeutic intervention in this immunologically cold cancer.

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.

Targeting HIF-2α in glioblastoma reshapes the immune infiltrate and enhances response to immune checkpoint blockade

Glioblastoma (GBM) is an aggressive primary brain tumor with dismal clinical prognosis and resistance to current therapies. GBM progression is facilitated by the tumor microenvironment (TME), with an immune infiltrate dominated by tumor-associated microglia/macrophages (TAMs) and regulatory T cells (Tregs). The TME is also characterized by hypoxia and the expression of hypoxia-inducible factors (HIFs), with HIF-2α emerging as a potential regulator of tumor progression. However, its role in GBM immunosuppression remains unknown. Here, we investigate HIF-2α and the use of the HIF-2α inhibitor PT2385 to modulate the TME in the immunocompetent GL261 mouse GBM model. PT2385 administration in vivo decreased tumor volume and prolonged survival of tumor-bearing mice, without affecting GL261 viability in vitro. Notably, HIF-2α inhibition alleviated the immunosuppressive TME and synergized with immune checkpoint blockade (ICB) using αPD-1 and αTIM-3 antibodies to promote long-term survival. Comprehensive analysis of the immune infiltrate through single-cell RNA sequencing and flow cytometry revealed that combining PT2385 with ICB reduced numbers of pro-tumoral macrophages and Tregs while increasing numbers of microglia, with a corresponding transcriptional modulation towards an anti-tumoral profile of these TAMs. In vitro, deletion of HIF-2α in microglia impeded their polarization towards a pro-tumoral M2-like profile, and its inhibition impaired Treg migration. Our results show that targeting HIF-2α can switch an immunosuppressive TME towards one that favors a robust and sustained response to ICB based immunotherapy. These findings establish that clinically relevant HIF-2α inhibitors should be explored not only in malignancies with defects in the HIF-2α axis, but also in those exhibiting an immunosuppressive TME that limits immunotherapy responsiveness.

Current Applications of Single-Cell RNA Sequencing in Glioblastoma: A Scoping Review

Background and Objective: The discovery of novel molecular biomarkers via next-generation sequencing technologies has revolutionized how glioblastomas (GBMs) are classified nowadays. This has resulted in more precise diagnostic, prognostic, and therapeutic approaches to address this malignancy. The present work examines the applications of single-cell RNA sequencing (scRNA-seq) in GBM, focusing on its potential to address tumor complexity and therapeutic resistance and improve patient outcomes. Methods: A scoping review of original studies published between 2009 and 2024 was conducted using the PUBMED and EMBASE databases. Studies in English or Spanish related to single-cell analysis and GBM were included. Key Findings: The database search yielded 453 publications. Themes related to scRNA-seq applied for the diagnosis, prognosis, treatment, and understanding of the cancer biology of GBM were used as criteria for article selection. Of the 24 studies that were included in the review, 11 focused on the tumor microenvironment and cell subpopulations in GBM samples, 5 investigated the use of sequencing to elucidate the GBM cancer biology, 3 examined disease prognosis using sequencing models, 3 applied translational research through scRNA-seq, and 2 addressed treatment-related problems in GBM elucidated by scRNA-seq. Conclusions: This scoping review explored the various clinical applications of scRNA-seq technologies in approaching GBM. The findings highlight the utility of this technology in unraveling the complex cellular and immune landscapes of GBM, paving the way for improved diagnosis and personalized treatments. This cutting-edge approach might strengthen treatment strategies against tumor progression and recurrence, setting the stage for multi-targeted interventions that could significantly improve outcomes for patients with aggressive, treatment-resistant GBMs.

Targeting cGAS-STING pathway for reprogramming tumor-associated macrophages to enhance anti-tumor immunotherapy

The cyclic GMP-AMP synthase (cGAS)-stimulator interferon genes (STING) signaling pathway plays a crucial role in activating innate and specific immunity in anti-tumor immunotherapy. As the major infiltrating cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) could be polarized into either anti-tumor M1 or pro-tumor M2 types based on various stimuli. Accordingly, targeted reprogramming TAMs to restore immune balance shows promise as an effective anti-tumor strategy. In this review, we aim to target cGAS-STING pathway for reprogramming TAMs to enhance anti-tumor immunotherapy. We investigated the double-edged sword effects of cGAS-STING in regulating TME. The regulative roles of cGAS-STING pathway in TAMs and its impact on the TME were further revealed. More importantly, several strategies of targeting cGAS-STING for reprogramming TAMs were designed for enhancing anti-tumor immunotherapy. Taken together, targeting cGAS-STING pathway for reprogramming TAMs in TME might be a promising strategy to enhance anti-tumor immunotherapy.

Tissue macrophages: origin, heterogenity, biological functions, diseases and therapeutic targets

Macrophages are immune cells belonging to the mononuclear phagocyte system. They play crucial roles in immune defense, surveillance, and homeostasis. This review systematically discusses the types of hematopoietic progenitors that give rise to macrophages, including primitive hematopoietic progenitors, erythro-myeloid progenitors, and hematopoietic stem cells. These progenitors have distinct genetic backgrounds and developmental processes. Accordingly, macrophages exhibit complex and diverse functions in the body, including phagocytosis and clearance of cellular debris, antigen presentation, and immune response, regulation of inflammation and cytokine production, tissue remodeling and repair, and multi-level regulatory signaling pathways/crosstalk involved in homeostasis and physiology. Besides, tumor-associated macrophages are a key component of the TME, exhibiting both anti-tumor and pro-tumor properties. Furthermore, the functional status of macrophages is closely linked to the development of various diseases, including cancer, autoimmune disorders, cardiovascular disease, neurodegenerative diseases, metabolic conditions, and trauma. Targeting macrophages has emerged as a promising therapeutic strategy in these contexts. Clinical trials of macrophage-based targeted drugs, macrophage-based immunotherapies, and nanoparticle-based therapy were comprehensively summarized. Potential challenges and future directions in targeting macrophages have also been discussed. Overall, our review highlights the significance of this versatile immune cell in human health and disease, which is expected to inform future research and clinical practice.

Society for Immunotherapy of Cancer (SITC) consensus statement on essential biomarkers for immunotherapy clinical protocols

Immunotherapy of cancer is now an essential pillar of treatment for patients with many individual tumor types. Novel immune targets and technical advances are driving a rapid exploration of new treatment strategies incorporating immune agents in cancer clinical practice. Immunotherapies perturb a complex system of interactions among genomically unstable tumor cells, diverse cells within the tumor microenvironment including the systemic adaptive and innate immune cells. The drive to develop increasingly effective immunotherapy regimens is tempered by the risk of immune-related adverse events. Evidence-based biomarkers that measure the potential for therapeutic response and/or toxicity are critical to guide optimal patient care and contextualize the results of immunotherapy clinical trials. Responding to the lack of guidance on biomarker testing in early-phase immunotherapy clinical trials, we propose a definition and listing of essential biomarkers recommended for inclusion in all such protocols. These recommendations are based on consensus provided by the Society for Immunotherapy of Cancer (SITC) Clinical Immuno-Oncology Network (SCION) faculty with input from the SITC Pathology and Biomarker Committees and the Journal for ImmunoTherapy of Cancer readership. A consensus-based selection of essential biomarkers was conducted using a Delphi survey of SCION faculty. Regular updates to these recommendations are planned. The inaugural list of essential biomarkers includes complete blood count with differential to generate a neutrophil-to-lymphocyte ratio or systemic immune-inflammation index, serum lactate dehydrogenase and albumin, programmed death-ligand 1 immunohistochemistry, microsatellite stability assessment, and tumor mutational burden. Inclusion of these biomarkers across early-phase immunotherapy clinical trials will capture variation among trials, provide deeper insight into the novel and established therapies, and support improved patient selection and stratification for later-phase clinical trials.

The C/EBPβ antagonist peptide lucicebtide (ST101) induces macrophage polarization toward a pro-inflammatory phenotype and enhances anti-tumor immune responses

Immune-checkpoint inhibitors (ICIs) have shown unprecedented success in a subset of immunogenic tumors, however a host of patients with advanced solid tumors fail to respond well or at all to immunotherapy. Refractory tumors commonly display a tumor microenvironment (TME) rich in immunosuppressive macrophages (M2-like) that suppress adaptive immunity and promote tumor progression. The ability to reprogram macrophages in the TME into an immune-active state holds great promise for enhancing responses to ICIs. Lucicebtide (previously referred to as ST101) is a peptide antagonist of the transcription factor C/EBPβ, a key activator of the transcriptional program in immunosuppressive macrophages. Here we show that lucicebtide exposure reprograms human immunosuppressive M2-like macrophages to a pro-inflammatory M1-like phenotype, restores cytotoxic T cell activation in immunosuppressed co-culture assays in vitro, and further increases T-cell activity in M1-like/T cell co-cultures. In immunocompetent, macrophage-rich triple-negative breast and colorectal cancer models, lucicebtide induces repolarization of tumor-associated macrophages (TAMs) to a pro-inflammatory M1-like phenotype and suppresses tumor growth. Lucicebtide synergizes with anti-PD-1 therapy and overcomes resistance to checkpoint inhibition in anti-PD-1-refractory tumors, but in vivo responses are impaired by systemic macrophage depletion, indicating that macrophage reprogramming is integral to lucicebtide activity. These results identify lucicebtide as a novel immunomodulator that reprograms immunosuppressive macrophage populations to enhance anti-tumor activity and suggests its utility for combination strategies in cancers with poor response to ICIs.

Sweet regulation - The emerging immunoregulatory roles of hexoses

BACKGROUND

It is widely acknowledged that dietary habits have profound impacts on human health and diseases. As the most important sweeteners and energy sources in human diets, hexoses take part in a broad range of physiopathological processes. In recent years, emerging evidence has uncovered the crucial roles of hexoses, such as glucose, fructose, mannose, and galactose, in controlling the differentiation or function of immune cells.

AIM OF REVIEW

Herein, we reviewed the latest research progresses in the hexose-mediated modulation of immune responses, provided in-depth analyses of the underlying mechanisms, and discussed the unresolved issues in this field.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Owing to their immunoregulatory effects, hexoses affect the onset and progression of various types of immune disorders, including inflammatory diseases, autoimmune diseases, and tumor immune evasion. Thus, targeting hexose metabolism is becoming a promising strategy for reversing immune abnormalities in diseases.

A subtype specific probe for targeted magnetic resonance imaging of M2 tumor-associated macrophages in brain tumors

Pro-tumoral M2 tumor-associated macrophages (TAMs) play a critical role in the tumor immune microenvironment (TIME), making them an important therapeutic target for cancer treatment. Approaches for imaging and monitoring M2 TAMs, as well as tracking their changes in response to tumor progression or treatment are highly sought-after but remain underdeveloped. Here, we report an M2-targeted magnetic resonance imaging (MRI) probe based on sub-5 nm ultrafine iron oxide nanoparticles (uIONP), featuring an anti-biofouling coating to prevent non-specific macrophage uptake and an M2-specific peptide ligand (M2pep) for active targeting of M2 TAMs. The targeting specificity of M2pep-uIONP was validated in vitro, using M0, M1, and M2 macrophages, and in vivo, using an orthotopic patient-tissue-derived xenograft (PDX) mouse model of glioblastoma (GBM). MRI of the mice revealed hypointense contrast in T2-weighted images of intracranial tumors 24 h after receiving intravenous (i.v.) injection of M2pep-uIONP. In contrast, no noticeable contrast change was observed in mice receiving scrambled-sequence M2pep-conjugated uIONP (scM2pep-uIONP) or the commercially available iron oxide nanoparticle formulation, Ferumoxytol. Measurement of nanoparticle-induced T2 value changes in tumors showed 38 %, 9 %, and 2 % decrease for M2pep-uIONP, scM2pep-uIONP, and Ferumoxytol, respectively. Moreover, M2pep-uIONP exhibited 88.7-fold higher intra-tumoral accumulation compared to co-injected Ferumoxytol at 24 h post-injection. Immunofluorescence-stained tumor sections showed that CD68+/CD163+ M2 TAMs were highly co-localized with Cy7-M2pep-uIONP, but not with Cy7-scM2pep-uIONP and Cy7-Ferumoxytol. Flow cytometry analysis revealed 26 ± 10 % of M2 TAMs were targeted by M2pep-uIONP, which was significantly higher than Ferumoxytol (16 ± 1 %) and scM2pep-uIONP (13 ± 4 %) with the same dosage (20 mg Fe/kg). These findings demonstrate that M2pep-uIONP functions as a ligand-mediated MRI probe for targeted imaging of M2 TAMs in GBM, with potential applications for imaging of M2 TAM in other cancer types. STATEMENT OF SIGNIFICANCE: Targeting the pro-tumoral M2 subtype of tumor-associated macrophages (TAMs) to modulate the tumor immune microenvironment (TIME) is an emerging strategy for developing novel cancer therapies and enhancing the efficacy of existing treatments. In this study, we have developed a magnetic resonance imaging (MRI) probe using sub-5 nm ultrafine iron oxide nanoparticles (uIONP), which are coated with an anti-biofouling polymer and conjugated to an M2-specific peptide ligand (M2pep). Our results demonstrate that M2pep-uIONP exhibits an 88.7-fold higher accumulation in intracranial tumors in an orthotopic patient-derived xenograft (PDX) model of glioblastoma compared to the commercial iron oxide nanoparticle, Ferumoxytol. This enhanced accumulation enables M2pep-uIONP to induce significant MRI contrast, providing a non-invasive imaging tool to visualize M2 TAMs and monitor changes in the TIME of brain tumors and potentially other cancers.

Microenvironmental Drivers of Glioma Progression

Gliomas, particularly glioblastoma (GBM), are among the most challenging brain tumors due to their complex and dynamic tumor microenvironment (TME). The TME plays a pivotal role in tumor progression, immune evasion, and resistance to therapy through intricate interactions among glioma cells, immune components, neurons, astrocytes, the extracellular matrix, and the blood-brain barrier. Targeting the TME has demonstrated potential, with immunotherapies such as checkpoint inhibitors and neoadjuvant therapies enhancing immune responses. Nonetheless, overcoming the immunosuppressive landscape and metabolic adaptations continues to pose significant challenges. This review explores the diverse cellular and molecular mechanisms that shape the glioma TME. A deeper understanding of these mechanisms holds promise for providing novel therapeutic opportunities to improve glioma treatment outcomes.

H3.3-G34R Mutation-Mediated Epigenetic Reprogramming Leads to Enhanced Efficacy of Immune Stimulatory Gene Therapy in Diffuse Hemispheric Gliomas

Diffuse hemispheric glioma (DHG), H3 G34-mutant, representing 9-15% of cases, are aggressive Central Nervous System (CNS) tumors with poor prognosis. This study examines the role of epigenetic reprogramming of the immune microenvironment and the response to immune-mediated therapies in G34-mutant DHG. To this end, we utilized human G34-mutant DHG biopsies, primary G34-mutant DHG cultures, and genetically engineered G34-mutant mouse models (GEMMs). Our findings show that the G34 mutation alters histone marks' deposition at promoter and enhancer regions, leading to the activation of the JAK/STAT pathway, which in turn results in an immune-permissive tumor microenvironment. The implementation of Ad-TK/Ad-Flt3L immunostimulatory gene therapy significantly improved median survival, and lead to over 50% long term survivors. Upon tumor rechallenge in the contralateral hemisphere without any additional treatment, the long-term survivors exhibited robust anti-tumor immunity and immunological memory. These results indicate that immune-mediated therapies hold significant potential for clinical translation in treating patients harboring H3.3-G34 mutant DHGs, offering a promising strategy for improving outcomes in this challenging cancer subtype affecting adolescents and young adults (AYA).

STATEMENT OF SIGNIFICANCE

This study uncovers the role of the H3.3-G34 mutation in reprogramming the tumor immune microenvironment in diffuse hemispheric gliomas. Our findings support the implementation of precision medicine informed immunotherapies, aiming at improving enhanced therapeutic outcomes in adolescents and young adults harboring H3.3-G34 mutant DHGs.

Sphingosine kinase 1 promotes M2 macrophage infiltration and enhances glioma cell migration via the JAK2/STAT3 pathway

Sphingosine kinase 1 (SPHK1) is a member of the SPHK family, enzymes essential for the phosphorylation of sphingosine to sphingosine-1-phosphate (S1P). Previous studies have revealed important roles of SPHK1 in inflammatory, anti-apoptotic, immune processes, and cancer. Although the predictive significance and possible roles of SPHK1 in gliomas have recently been examined, the precise molecular mechanisms remain unclear. We comprehensively examined SPHK1 and investigated its correlation with glioma survival time using different datasets. The correlation between SPHK1 and various cancer pathways was analyzed using the Kyoto encyclopedia of genes and genomes (KEGG) analysis. The SPHK1 influence on glioma migration was examined using transwell and wound healing experiments. M2 macrophage infiltration experiments investigated SPHK1's role in the glioma immune microenvironment. We identified SPHK1 downstream pathways and further elucidated their regulatory relationship. Survival analysis illustrated that patients with high-SPHK1 expression, particularly glioblastoma and IDH-wildtype, tended to have a shorter survival time. The Cox regression model (COX) results demonstrated that SPHK1 was an independent prognostic factor affecting the survival of patients with glioma. Functional experiments illustrated that SPHK1 suppression led to a reduction in the migration capacity of glioma cells. Enrichment analysis and Western blotting revealed that SPHK1 functions as a JAK2/STAT3 pathway controller. The SPHK1 overexpression-induced migration was suppressed by the JAK2/STAT3 pathway suppressor (AG490). We found that SPHK1 promotes M2 macrophage infiltration. Further study indicated that SPHK1 could serve as a prognostic indicator of glioma and promote cell migration, providing new insights for glioma therapy.

Gemistocytic tumor cells programmed for glial scarring characterize T cell confinement in IDH-mutant astrocytoma

Isocitrate dehydrogenase 1/2 mutant (IDHmt) astrocytoma is considered a T cell-deprived tumor, yet little is known regarding the phenotypes underlying T cell exclusion. Using bulk, single nucleus and spatial RNA and protein profiling, we demonstrate that a distinct spatial organization underlies T cell confinement to the perivascular space (T cell cuff) in IDHmt astrocytoma. T cell cuffs are uniquely characterized by a high abundance of gemistocytic tumor cells (GTC) in the surrounding stroma. Integrative analysis shows that GTC-high tumors are enriched for lymphocytes and tumor associated macrophages (TAM) and express immune cell migration and activation programs. Specifically, GTCs constitute a distinct sub-cluster of the astrocyte-like tumor cell state that co-localizes with immune reactive TAMs. Neighboring GTCs and TAMs express receptor-ligand pairs characteristic of reactive astrogliosis and glial scarring, such as SPP1/CD44 and IL-1β/IL1R1. Collectively, we reveal that T cell confinement in IDHmt astrocytomas associates with GTC-TAM networks that mimic glial scarring mechanisms.

Single-nucleus and spatial landscape of the sub-ventricular zone in human glioblastoma

The sub-ventricular zone (SVZ) is the most well-characterized neurogenic area in the mammalian brain. We previously showed that in 65% of patients with glioblastoma (GBM), the SVZ is a reservoir of cancer stem-like cells that contribute to treatment resistance and the emergence of recurrence. Here, we build a single-nucleus RNA-sequencing-based microenvironment landscape of the tumor mass and the SVZ of 15 patients and two histologically normal SVZ samples as controls. We identify a ZEB1-centered mesenchymal signature in the tumor cells of the SVZ. Moreover, the SVZ microenvironment is characterized by tumor-supportive microglia, which spatially coexist and establish crosstalks with tumor cells. Last, differential gene expression analyses, predictions of ligand-receptor and incoming/outgoing interactions, and functional assays reveal that the interleukin (IL)-1β/IL-1RAcP and Wnt-5a/Frizzled-3 pathways represent potential therapeutic targets in the SVZ. Our data provide insights into the biology of the SVZ in patients with GBM and identify potential targets of this microenvironment.

Single-cell analysis reveals Mycobacterium tuberculosis ESX-1-mediated accumulation of permissive macrophages in infected mouse lungs

Mycobacterium tuberculosis (MTB) ESX-1, a type VII secretion system, is a key virulence determinant contributing to MTB's survival within lung mononuclear phagocytes (MNPs), but its effect on MNP recruitment and differentiation remains unknown. Here, using multiple single-cell RNA sequencing techniques, we studied the role of ESX-1 in MNP heterogeneity and response in mice and murine bone marrow-derived macrophages (BMDM). We found that ESX-1 is required for MTB to recruit diverse MNP subsets with high MTB burden. Further, MTB induces a transcriptional signature of immune evasion in lung macrophages and BMDM in an ESX-1-dependent manner. Spatial transcriptomics revealed an up-regulation of permissive features within MTB lesions, where monocyte-derived macrophages concentrate near MTB-infected cells. Together, our findings suggest that MTB ESX-1 facilitates the recruitment and differentiation of MNPs, which MTB can infect and manipulate for survival. Our dataset across various models and methods could contribute to the broader understanding of recruited cell heterogeneity during MTB lung infection.

Distinct myeloid-derived suppressor cell populations in human glioblastoma

The role of glioma-associated myeloid cells in tumor growth and immune evasion remains poorly understood. We performed single-cell RNA sequencing of immune and tumor cells from 33 gliomas, identifying two distinct myeloid-derived suppressor cell (MDSC) populations in isocitrate dehydrogenase-wild-type (IDT-WT) glioblastoma: an early progenitor MDSC (E-MDSC) population with up-regulation of metabolic and hypoxia pathways and a monocytic MDSC (M-MDSC) population. Spatial transcriptomics demonstrated that E-MDSCs geographically colocalize with metabolic stem-like tumor cells in the pseudopalisading region. Ligand-receptor analysis revealed cross-talk between these cells, where glioma stem-like cells produce chemokines attracting E-MDSCs, which in turn produce growth factors for the tumor cells. This interaction is absent in IDH-mutant gliomas, associated with hypermethylation and repressed gene expression of MDSC-attracting chemokines. Our study elucidates specific MDSCs that may facilitate glioblastoma progression and mediate tumor immunosuppression.

Immunometabolic Effect of Nitric Oxide on Human Macrophages Challenged With the SARS-CoV2-Induced Cytokine Storm. A Fluxomic Approach

The cytokine storm associated with SARS-CoV-2 infection is one of the most distinctive pathological signatures in COVID-19 patients. Macrophages respond to this pro-inflammatory challenge by reprogramming their functional and metabolic phenotypes. Interestingly, human macrophages fail to express the inducible form of the NO synthase (NOS2) in response to pro-inflammatory activation and, therefore, NO is not synthesized by these cells. The contribution of exogenously added NO, via a chemical NO-donor, on the immunometabolic changes associated with the cytokine storm is investigated. By using metabolic, transcriptomic, and functional assays the effect of NO in human macrophages is evaluated and found specific responses. Moreover, through integrative fluxomic analysis, pathways modified by NO that contribute to the expression of a particular phenotype in human macrophages are identified, which includes a decrease in mitochondrial respiration and TCA with a slight increase in the glycolytic flux. A significant ROS increase and preserved cell viability are observed in the presence of NO, which may ease the inflammatory response and host defense. Also, NO reverses the cytokine storm-induced itaconate accumulation. These changes offer additional clues to understanding the potential crosstalk between NO and the COVID-19 cytokine storm-dependent signaling pathways.

Macrophage subtypes inhibit breast cancer proliferation in culture

Macrophages are a highly plastic cell type that adopt distinct subtypes and functional states depending on environmental cues. These functional states can vary widely, with distinct macrophages capable of displaying opposing functions. We sought to understand how macrophage subtypes that exist on two ends of a spectrum influence the function of other cells. We used a coculture system with primary human macrophages to probe the effects of macrophage subtypes on breast cancer cell proliferation. Our studies revealed a surprising phenotype in which both macrophage subtypes inhibited cancer cell proliferation compared with cancer cells alone. Of particular interest, using two different proliferation assays with two different breast cancer cell lines, we showed that differentiating macrophages into a "protumor" subtype inhibited breast cancer cell proliferation. These findings are inconsistent with the prevailing interpretation that "protumor" macrophages promote cancer cell proliferation and suggest a re-evaluation of how these interpretations are made.

Markers of tumor-associated macrophages and microglia exhibit high intratumoral heterogeneity in human glioblastoma tissue

BACKGROUND

Human glioblastoma multiforme (GBM) is a highly aggressive tumor with insufficient therapies available. Especially, novel concepts of immune therapies fail due to a complex immunosuppressive microenvironment, high mutational rates, and inter-patient variations. The intratumoral heterogeneity is currently not sufficiently investigated.

METHODS

Biopsies from six different locations were taken in a cohort of 16 GBM patients who underwent surgery. The tissue slides were analyzed utilizing high-content imaging microscopy and algorithm-based image quantification. Several immune markers for macrophage and microglia subpopulations were investigated. Flow cytometry was used to validate key results. Besides the surface marker, cytokines were measured and categorized based on their heterogenicity and overall expression.

RESULTS

M2-like antigens, including CD204, CD163, Arg1, and CSF1R, showed comparatively higher expression, with GFAP displaying the least intratumoral heterogeneity. In contrast, anti-tumor-macrophage-like antigens, such as PSGL-1, CD16, CD68, and MHC-II, exhibited low overall expression and concurrent high intratumoral heterogeneity. CD16 and PSGL-1 were the most heterogeneous antigens. High expression levels were observed for cytokines IL-6, VEGF, and CCL-2. VILIP-a was revealed to differentiate most in principle component analysis. Cytokines with the lowest overall expression, such as TGF-β1, β-NGF, TNF-α, and TREM1, showed low intratumoral heterogeneity, in contrast to βNGF, TNF-α, and IL-18, which displayed high heterogeneity despite low expression.

CONCLUSION

The study showed high intratumoral heterogeneity in GBM, emphasizing the need for a more detailed understanding of the tumor microenvironment. The described findings could be essential for future personalized treatment strategies and the implementation of reliable diagnostics in GBM.

Harnessing Antitumor Immunity in Ovarian Cancer

Despite progress in other tumor types, immunotherapy is not yet part of the standard of care treatment for high-grade serous ovarian cancer patients. Although tumor infiltration by T cells is frequently observed in patients with ovarian cancer, clinical responses to immunotherapy remain low. Mechanisms for immune resistance in ovarian cancer have been explored and may provide insight into future approaches to improve response to immunotherapy agents. In this review, we discuss what is known about the immune landscape in ovarian cancer, review the available data for immunotherapy-based strategies in these patients, and provide possible future directions.

Metabolism and macrophages in the tumor microenvironment

Tumor-associated macrophages (TAMs) constitute the primary subset of immune cells within the tumor microenvironment (TME). Exhibiting both phenotypic and functional heterogeneity, TAMs play distinct roles in tumor initiation, progression, and responses to therapy in patients with cancer. In response to various immune and metabolic cues within the TME, TAMs dynamically alter their metabolic profiles to adapt. Changes in glucose, amino acid, and lipid metabolism in TAMs, as well as their interaction with oncometabolites, not only sustain their energy demands but also influence their impact on tumor immune responses. Understanding the molecular mechanisms underlying the metabolic reprogramming of TAMs and their orchestration of metabolic processes can offer insights for the development of novel cancer immunotherapies targeting TAMs. Here, we discuss how metabolism reprograms macrophages in the TME and review clinical trials aiming to normalize metabolic alterations in TAMs and alleviate TAM-mediated immune suppression and protumor activity.

Co-expression of immune checkpoints in glioblastoma revealed by single-nucleus RNA sequencing and spatial transcriptomics

Glioblastoma (GBM) is one of the most malignant tumors of the central nervous system. The pattern of immune checkpoint expression in GBM remains largely unknown. We performed snRNA-Seq and spatial transcriptomic (ST) analyses on untreated GBM samples. 8 major cell types were found in both tumor and adjacent normal tissues, with variations in infiltration grade. Neoplastic cells_6 was identified in malignant cells with high expression of invasion and proliferator-related genes, and analyzed its interactions with microglia, MDM cells and T cells. Significant alterations in ligand-receptor interactions were observed, particularly between Neoplastic cells_6 and microglia, and found prominent expression of VISTA/VSIG3, suggesting a potential mechanism for evading immune system attacks. High expression of TIM-3, VISTA, PSGL-1 and VSIG-3 with similar expression patterns in GBM, may have potential as therapeutic targets. The prognostic value of VISTA expression was cross-validated in 180 glioma patients, and it was observed that patients with high VISTA expression had a poorer prognosis. In addition, multimodal cross analysis integrated SnRNA-seq and ST, revealing complex intracellular communication and mapping the GBM tumor microenvironment. This study reveals novel molecular characteristics of GBM, co-expression of immune checkpoints, and potential therapeutic targets, contributing to improving the understanding and treatment of GBM.

Microglia and macrophages in glioblastoma: landscapes and treatment directions

Glioblastoma is the most common primary malignant tumour of the central nervous system and remains uniformly and rapidly fatal. The tumour-associated macrophage (TAM) compartment comprises brain-resident microglia and bone marrow-derived macrophages (BMDMs) recruited from the periphery. Immune-suppressive and tumour-supportive TAM cell states predominate in glioblastoma, and immunotherapies, which have achieved striking success in other solid tumours have consistently failed to improve survival in this 'immune-cold' niche context. Hypoxic and necrotic regions in the tumour core are found to enrich, especially in anti-inflammatory and immune-suppressive TAM cell states. Microglia predominate at the invasive tumour margin and express pro-inflammatory and interferon TAM cell signatures. Depletion of TAMs, or repolarisation towards a pro-inflammatory state, are appealing therapeutic strategies and will depend on effective understanding and classification of TAM cell ontogeny and state based on new single-cell and spatial multi-omic in situ profiling. Here, we explore the application of these datasets to expand and refine TAM characterisation, to inform improved modelling approaches, and ultimately underpin the effective manipulation of function.

How to Use Macrophages Against Cancer

Numerous studies have demonstrated the significant influence of immune cells on cancer development and treatment. This study specifically examines tumor-associated macrophages (TAMs), detailing their characteristics and roles in tumorigenesis and analyzing the impact of the ratio of TAM subtypes on patient survival and prognosis. It is established that TAMs interact with immunotherapy, radiotherapy, and chemotherapy, thereby influencing the efficacy of these treatments. Emerging therapies are explored, such as the use of nanoparticles (NPs) for drug delivery to target TAMs and modify the tumor microenvironment (TME). Additionally, novel anticancer strategies like the use of chimeric antigen receptor macrophages (CAR-Ms) show promising results. Investigations into the training of macrophages using magnetic fields, plasma stimulation, and electroporation are also discussed. Finally, this study presents prospects for the combination of TAM-based therapies for enhanced cancer treatment outcomes.

Sentinels of neuroinflammation: the crucial role of myeloid cells in the pathogenesis of gliomas and neurodegenerative diseases

The inflammatory processes that drive pathologies of the central nervous system (CNS) are complex and involve significant contributions from the immune system, particularly myeloid cells. Understanding the shared and distinct pathways of myeloid cell regulation in different CNS diseases may offer critical insights into therapeutic development. This review aims to elucidate the mechanisms underlying myeloid cell dysfunction and neuroinflammation in two groups of neurological pathologies with significant social impact and a limited efficacy of their treatments: the most common primary brain tumors -gliomas-, and the most prevalent neurodegenerative disorders -Alzheimer's and Parkinson's disease. Despite their distinct clinical manifestations, these diseases share key pathological features, including chronic inflammation and immune dysregulation. The role of myeloid cells in neuroinflammation has garnered special interest in recent years in both groups, as evidenced by the growing focus on therapeutic research centred on myeloid cells. By examining the cellular and molecular dynamics that govern these conditions, we hope to identify common and unique therapeutic targets that can inform the development of more effective treatments. Recent advances in single-cell technologies have revolutionized our understanding of myeloid cell heterogeneity, revealing diverse phenotypes and molecular profiles across different disease stages and microenvironments. Here, we present a comprehensive analysis of myeloid cell involvement in gliomas, Alzheimer's and Parkinson's disease, with a focus on phenotypic acquisition, molecular alterations, and therapeutic strategies targeting myeloid cells. This integrated approach not only addresses the limitations of current treatments but also suggests new avenues for therapeutic intervention, aimed at modulating the immune landscape to improve patient outcomes.

Immunological responses to brain metastasis stereotactic radiosurgery in patient-matched longitudinal blood and tumour samples

Background

Stereotactic radiosurgery (SRS) is highly effective as focal treatment for brain metastases (BrMs), but whether it can promote anti-tumour immune responses that synergise with immunotherapy remains unclear. We investigated this by examining blood samples from a clinical trial for HER2-amplified breast cancer (HER2-BC) BrMs, matched with longitudinal HER2-BC BrM samples resected from the same location in the same patient.

Methods

Blood samples from 10 patients taken pre- and 7-14 days post-SRS were analysed by mass and flow cytometry. One patient received pre-operative SRS for a BrM that recurred 7 months after resection, followed by planned re-resection 8 days post-SRS. Pre- and post-SRS tumours from this patient were analysed by bulk RNAseq, multiplex immunohistochemistry (mIHC), and TCR sequencing.

Results

Monocytes, central memory CD8+ T and regulatory T cells were enriched in blood post-SRS, together with increased MHC-II expression on monocytes, conventional DCs, and monocytic MDSCs. In tumour, SRS upregulated antigen presentation, T cell proliferation and T cell co-stimulation signatures, alongside an influx of tumour-associated macrophages (TAMs) and CD4+ T cells. Specifically, TAMs and CD4+ T cells, but not CD8+ T cells, demonstrated spatial co-localisation post-SRS. These TAMs were lowly PD-L1 expressing, but CD4+ T cells showed increased PD-1 expression. A sizeable proportion of T cell clonotypes were retained post-SRS, and four clones demonstrated significant, non-stochastic expansion.

Conclusion

Systemic and local immunological changes in this homogenous patient cohort suggest that SRS may facilitate MHC-II-restricted T cell priming responses involving the monocyte-macrophage lineage and CD4+ T cells, which should be further explored.

Lipid metabolic rewiring in glioma‑associated microglia/macrophages (Review)

Gliomas are the most prevailing brain malignancy in both children and adults. Microglia, which are resident in the central nervous system (CNS), are distributed throughout the brain and serve an important role in the immunity of the CNS. Microglial cells exhibit varying phenotypic and metabolic properties during different stages of glioma development, making them a highly dynamic cell population. In particular, glioma‑associated microglia/macrophages (GAMs) can alter their metabolic characteristics and influence malignancies in response to the signals they receive. The significance of macrophage metabolic reprogramming in tumor growth is becoming increasingly acknowledged in recent years. However, to the best of our knowledge, there is currently a scarcity of data from investigations into the lipid metabolic profiles of microglia/macrophages in the glioma setting. Therefore, the present review aims to provide a thorough review of the role that lipid metabolism serves in tumor‑associated macrophages. In addition, it outlines potential targets for therapy based on lipid metabolism. The present review aims to serve as a reference source for future investigations into GAMs.

Glioma immune microenvironment composition calculator (GIMiCC): a method of estimating the proportions of eighteen cell types from DNA methylation microarray data

A scalable platform for cell typing in the glioma microenvironment can improve tumor subtyping and immune landscape detection as successful immunotherapy strategies continue to be sought and evaluated. DNA methylation (DNAm) biomarkers for molecular classification of tumor subtypes have been developed for clinical use. However, tools that predict the cellular landscape of the tumor are not well-defined or readily available. We developed the Glioma Immune Microenvironment Composition Calculator (GIMiCC), an approach for deconvolution of cell types in gliomas using DNAm data. Using data from 17 isolated cell types, we describe the derivation of the deconvolution libraries in the biological context of selected genomic regions and validate deconvolution results using independent datasets. We utilize GIMiCC to illustrate that DNAm-based estimates of immune composition are clinically relevant and scalable for potential clinical implementation. In addition, we utilize GIMiCC to identify composition-independent DNAm alterations that are associated with high immune infiltration. Our future work aims to optimize GIMiCC and advance the clinical evaluation of glioma.

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.

The Three Pillars of Glioblastoma: A Systematic Review and Novel Analysis of Multi-Omics and Clinical Data

Glioblastoma is the most fatal and common malignant brain tumor, excluding metastasis and with a median survival of approximately one year. While solid tumors benefit from newly approved drugs, immunotherapy, and prevention, none of these scenarios are opening for glioblastoma. The key to unlocking the peculiar features of glioblastoma is observing its molecular and anatomical features tightly entangled with the host's central nervous system (CNS). In June 2024, we searched the PUBMED electronic database. Data collection and analysis were conducted independently by two reviewers. Results: A total of 215 articles were identified, and 192 were excluded based on inclusion and exclusion criteria. The remaining 23 were used for collecting divergent molecular pathways and anatomical features of glioblastoma. The analysis of the selected papers revealed a multifaced tumor with extreme variability and cellular reprogramming that are observable within the same patient. All the variability of glioblastoma could be clustered into three pillars to dissect the physiology of the tumor: 1. necrotic core; 2. vascular proliferation; 3. CNS infiltration. These three pillars support glioblastoma survival, with a pivotal role of the neurovascular unit, as supported by the most recent paper published by experts in the field.

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.

Lipid-Conjugated Reduced Haloperidol in Association with Glucose-Based Nanospheres: A Strategy for Glioma Treatment

Aggressive glioma exhibits a poor survival rate. Increased tumor aggression is linked to both tumor cells and tumor-associated macrophages (TAMs), which induce pro-aggression, invasion, and metastasis. Imperatively, for effective treatment, it is important to target both glioma cells and TAMs. Haloperidol, a neuropsychotic drug, avidly targets the sigma receptor (SR), which is expressed in higher levels in both the cell types. Herein, we present the development of a novel cationic lipid-conjugated reduced haloperidol (±RHPC8), which aims to mediate the SR-targeted antiglioma effect. Hypothetically, ±RHPC8 would act simultaneously as an SR-targeting ligand and anticancer agent. As the blood-brain barrier (BBB) obstructs direct targeting of in situ glioma, we used BBB-crossing glucose-based carbon nanospheres (CSPs) to deliver ±RHPC8 within the glioma tumor-bearing mouse brain. The resultant ±RHPC8-CSP nanoconjugate targeted SR-expressing glioma cells. In both orthotopic and subcutaneous mouse tumor models, ±RHPC8-CSP prolonged survival and regressed tumors compared to other treated groups. Notably, ±RHPC8-CSP was significantly taken up by SR-expressing TAMs thus resulting in macrophage polarization from M2 to M1, as exhibited by markedly reduced expression of immunosuppressive cytokines released by TAMs, including TGF-β, IL-10, and VEGF. In conclusion, the designed ±RHPC8-CSP nanoconjugate presented an effective nanodrug delivery system for brain cancer treatment.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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