The tumor microenvironment underlies acquired resistance to CSF-1R inhibition in gliomas

Structural and material basis of neuron-glioma interactions

The intricate interplay between neurons and gliomas has emerged as an important area of investigation in glioma biology. Accumulating evidence underscores that structural and material alterations constitute the fundamental basis of neuron‒glioma interactions and their pathological consequences. This review comprehensively examines the mechanisms underlying these interactions, with a particular emphasis on specialized structures that facilitate neuron‒glioma communication, including synapses, cell surface ion channels, and tumor microtubules (TMs). In addition to classical neurotransmitters, we highlight the exchange of cytokines, proteins, and extracellular vesicles (EVs) between these cell types. By synthesizing current research findings, this review establishes a conceptual framework for developing innovative therapeutic strategies targeting neuron‒glioma interfaces, offering new perspectives for glioma treatment approaches.

Emerging therapeutics targeting tumor-associated macrophages for the treatment of solid organ cancers

INTRODUCTION

Over the last decade, immune checkpoint inhibitors (ICIs) like PD-1/PD-L1 or CTLA-4, which reinvigorate T cells for tumor control have become standard-of-care treatment options. In response to the increasingly recognized mechanisms of resistance to T cell activation in immunologically cold tumors, immuno-oncology drug development has started to shift beyond T cell approaches. These include tumor-associated macrophages (TAMs), a major pro-tumor immune cell population in the tumor microenvironment known to silence immune responses.

AREAS COVERED

Here we outline anti-TAM therapies in current development, either as monotherapy or in combination with other treatment modalities. We describe emerging drugs targeting TAMs under investigation in phase II and III testing with a focus on their distinguishing mechanism of action which include (1) reprogramming of TAMs toward anti-tumor function and immune surveillance, (2) blockade of recruitment, and (3) reduction and ablation of TAMs.

EXPERT OPINION

Several new immuno-oncology agents are under investigation to harness anti-tumor functions of TAMs. While robust anti-tumor efficacy of anti-TAM therapies across advanced solid organ cancers remains elusive to-date, TAM reprogramming therapies have yielded benefits in select cancers. The inherent heterogeneity of the diverse TAM population will require enhanced investments into biomarker-driven approaches to fully leverage its therapeutic potential.

Emerging strategies for targeting tumor-associated macrophages in glioblastoma: A focus on chemotaxis blockade

Glioblastoma (GBM) remains one of the most aggressive and treatment-resistant brain tumors, with poor prognosis for affected patients. A key player in the GBM tumor microenvironment is the tumor-associated macrophage (TAM), which promotes tumor progression, immune evasion, and therapeutic resistance. The recruitment of TAMs to the tumor site is driven by specific chemotactic signals, including CSF-1/CSF-1R, CXCR4/CXCL12, and HGF/MET pathways. This review explores the current understanding of these chemotaxis mechanisms and their role in GBM progression. It highlights the potential therapeutic benefits of targeting TAM chemotaxis pathways to disrupt TAM infiltration, reduce immunosuppression, and enhance the efficacy of conventional treatments. Additionally, we discuss the preclinical and clinical evidence surrounding key inhibitors, such as PLX3397, AMD3100, and Crizotinib, which have shown promise in reprogramming TAMs and improving treatment outcomes in GBM. While these strategies offer hope for overcoming some of the challenges of GBM therapy, the review also addresses the limitations and obstacles in clinical translation, emphasizing the need for further research and the development of combination therapies to achieve sustained therapeutic benefit.

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.

Glioblastoma: molecular features, emerging molecular targets and novel therapeutic strategies

Glioblastomas (GBMs) constitute the most common malignant tumors of the Central Nervous System (CNS) with a complex molecular, genetic and histological profile and extensive heterogenicity. GBMs are notoriously difficult to treat, with morbidity and mortality rate that remain high and practically unchanged, despite the aggressive and multimodal treatment strategies. Keeping up with current research and emerging scientific data is of primary importance for the detection of new molecular targets, enabling the design of novel therapeutic strategies. Herein, we discuss current data on the cellular and molecular features that contribute to GBM pathophysiological mechanisms in an effort to reveal emerging molecular targets with therapeutic potential as well as effective immunotherapeutic approaches, including chimeric antigen receptor (CAR) T-cell therapy and adaptive immune modulation with immune checkpoint inhibitors. Enhanced drug delivery strategies such as ultrasound-assisted technologies to overcome drug resistance are also discussed, aiming to provide an overall translational perspective that bridges molecular insights with practical therapeutic implications.

The Basis for Targeting the Tumor Macrophage Compartment in Glioblastoma Immunotherapy

Background: Glioblastoma (GBM) remains the most aggressive primary brain tumor with limited treatment options. The immunosuppressive tumor microenvironment (TME), largely shaped by tumor-associated macrophages (TAMs), represents a significant barrier to effective immunotherapy. Objective: This review aims to explore the role of TAMs within the TME, highlighting the phenotypic plasticity, interactions with tumor cells, and potential therapeutic targets to enhance anti-tumor immunity. Findings: TAMs constitute a substantial portion of the TME, displaying functional plasticity between immunosuppressive and pro-inflammatory phenotypes. Strategies targeting TAMs include depletion, reprogramming, and inhibition of pro-tumor signaling pathways. Preclinical studies show that modifying TAM behavior can shift the TME towards a pro-inflammatory state, enhancing antitumor immune responses. Clinical trials investigating inhibitors of TAM recruitment, polarization, and downstream signaling pathways reveal promising yet limited results, necessitating further research to optimize approaches. Conclusions: Therapeutic strategics targeting TAM plasticity through selective depletion, phenotypic reprogramming, or modulation of downstream immunosuppressive signals represent promising avenues to overcome GBM-associated immunosuppression. Early clinical trials underscore their safety and feasibility, yet achieving meaningful clinical efficacy requires deeper mechanistic understanding and combinatorial approaches integrating macrophage-direct therapies with existing immunotherapeutic modalities.

MS CETSA deep functional proteomics uncovers DNA repair programs leading to gemcitabine resistance

Mechanisms for resistance to cytotoxic cancer drugs are dependent on dynamic changes in the biochemistry of cellular pathways, information which is hard to obtain at the systems level. Here we use a deep functional proteomics implementation of the Cellular Thermal Shift Assay to reveal a range of induced biochemical responses to gemcitabine in resistant and sensitive diffuse large B cell lymphoma cell lines. Initial responses in both, gemcitabine resistant and sensitive cells, reflect known targeted effects by gemcitabine on ribonucleotide reductase and DNA damage responses. However, later responses diverge dramatically where sensitive cells show induction of characteristic CETSA signals for early apoptosis, while resistant cells reveal biochemical modulations reflecting transition through a distinct DNA-damage signaling state, including opening of cell cycle checkpoints and induction of translesion DNA synthesis programs, allowing bypass of damaged DNA-adducts. The results also show the induction of a protein ensemble, labeled the Auxiliary DNA Damage Repair, likely supporting DNA replication at damaged sites that can be attenuated in resistant cells by an ATR inhibitor, thus re-establishing gemcitabine sensitivity and demonstrating ATR as a key signaling node of this response.

A zinc transporter drives glioblastoma progression via extracellular vesicles-reprogrammed microglial plasticity

Glioblastoma (GBM) is the most aggressive form of brain cancer, with limited therapeutic options. While microglia contribute to GBM progression, the mechanisms by which they foster a protumorigenic immune environment remain poorly understood. We identify the zinc transporter Zrt- And Irt-Like Protein 4 (ZIP4) as a pivotal regulator of the GBM immune landscape. In orthotopic mouse models, ZIP4 drives tumor growth and behavioral changes. Mechanistically, ZIP4 modulates microglial plasticity through tumor-derived extracellular vesicles carrying triggering receptor expressed on myeloid cells-1 (TREM1), a process regulated by the zinc-dependent transcription factor Zinc Finger E-box Binding Homeobox 1 in GBM cells. TREM1 enhances microglial plasticity through the spleen associated tyrosine kinase-Pyruvate dehydrogenase kinase-signal transducer and activator of transcription 3 (SYK-PDK-STAT3) signaling axis, ultimately promoting an immune environment favorable to tumor progression. ZIP4 depletion or TREM1 inhibition attenuates tumor growth and behavioral effects in vivo by disrupting the tumor-microglia interaction. These findings establish ZIP4 as a key modulator of the GBM immune landscape and suggest a promising therapeutic target to counteract microglia-mediated tumor progression.

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.

The multilayered transcriptional architecture of glioblastoma ecosystems

In isocitrate dehydrogenase wildtype glioblastoma (GBM), cellular heterogeneity across and within tumors may drive therapeutic resistance. Here we analyzed 121 primary and recurrent GBM samples from 59 patients using single-nucleus RNA sequencing and bulk tumor DNA sequencing to characterize GBM transcriptional heterogeneity. First, GBMs can be classified by their broad cellular composition, encompassing malignant and nonmalignant cell types. Second, in each cell type we describe the diversity of cellular states and their pathway activation, particularly an expanded set of malignant cell states, including glial progenitor cell-like, neuronal-like and cilia-like. Third, the remaining variation between GBMs highlights three baseline gene expression programs. These three layers of heterogeneity are interrelated and partially associated with specific genetic aberrations, thereby defining three stereotypic GBM ecosystems. This work provides an unparalleled view of the multilayered transcriptional architecture of GBM. How this architecture evolves during disease progression is addressed in the companion manuscript by Spitzer et al.

The therapeutic effect of mRNA vaccines in glioma: a comprehensive review

INTRODUCTION

Glioma is the most common primary brain tumor, with glioblastoma being the most lethal type due to its heterogeneous and invasive nature of the cancer. Current therapies have low curative success and are limited to surgery, radiotherapy, and chemotherapy. More than 50% of patients become resistant to chemotherapy, and tumor recurrence occurs in most patients following an initial course of therapy. Therefore, developing novel, effective strategies for glioma treatment is essential. Cancer vaccines are novel therapies that demonstrate advantages over conventional methods and, therefore, may be promising options for treating glioma.

AREAS COVERED

This article provided a critical review of pre-clinical and clinical studies that explored appropriate tumor antigen candidates for developing mRNA vaccines and discussed their clinical application in glioma patients. Medline database, PubMed, and ClinicalTrials.gov were searched for glioma vaccine studies published before 2025 using related keywords.

EXPERT OPINION

mRNA vaccines are promising strategies for treating glioma because they are efficient, cost-beneficial, and have lower side effects than other types such as peptide or DNA-based vaccines.

TAMing Gliomas: Unraveling the Roles of Iba1 and CD163 in Glioblastoma

Gliomas, the most common type of primary brain tumor, are a significant cause of morbidity and mortality worldwide. Glioblastoma, a highly malignant subtype, is particularly common, aggressive, and resistant to treatment. The tumor microenvironment (TME) of gliomas, especially glioblastomas, is characterized by a distinct presence of tumor-associated macrophages (TAMs), which densely infiltrate glioblastomas, a hallmark of these tumors. This macrophage population comprises both tissue-resident microglia as well as macrophages derived from the walls of blood vessels and the blood stream. Ionized calcium-binding adapter molecule 1 (Iba1) and CD163 are established cellular markers that enable the identification and functional characterization of these cells within the TME. This review provides an in-depth examination of the roles of Iba1 and CD163 in malignant gliomas, with a focus on TAM activation, migration, and immunomodulatory functions. Additionally, we will discuss how recent advances in AI-enhanced cell identification and visualization techniques have begun to transform the analysis of TAMs, promising unprecedented precision in their characterization and providing new insights into their roles within the TME. Iba1 and CD163 appear to have both unique and shared roles in glioma pathobiology, and both have the potential to be targeted through different molecular and cellular mechanisms. We discuss the therapeutic potential of Iba1 and CD163 based on available preclinical (experimental) and clinical (human tissue-based) evidence.

Genetically Engineered IL12/CSF1R-Macrophage Membrane-Liposome Hybrid Nanovesicles for NIR-II Fluorescence Imaging-Guided and Membrane-Targeted Mild Photothermal-Immunotherapy of Glioblastoma

It is a big challenge for precision therapy of glioblastoma, mainly due to the existence of blood-brain barrier (BBB), tumor immunosuppressive microenvironment (TIM), and lack of efficient treatment paradigms. Herein, a theranostic nanoplatform for the second near-infrared window (NIR-II) fluorescence imaging-guided membrane-targeted mild photothermal-immunotherapy of glioblastoma using genetically engineered CSF1R/IL12-macrophage membrane (MM)-liposome hybrid nanovesicles, is reported. By mimicking lipophilic membrane probe (Dil) with octadecyl chains, a NIR-II emissive photothermal dye (IRC18), which realizes labeling of nanovesicle lipid bilayers for biodistribution tracing, glioblastoma diagnosis, and molecular imaging of tumoral microenvironment, is synthesized. Importantly, MM and c-RGD-decorated liposome together offer BBB crossing, tumor targeting, and long-term circulation; while, the genetically overexpressed CSF1R and IL12 on MM surface contribute to effective modulation of M2-to-M1 macrophage repolarization and local promotion of T cell cytotoxicity in glioblastoma microenvironment, respectively. Notably, through membrane fusion, IRC18 dyes translocate from nanovesicle lipid bilayers to glioblastoma membranes, which achieve membrane-targeted mild photothermal therapy to ablate primary tumor and induce immunogenic cell death to promote antigen presentation. More importantly, the combined blockade of the CSF1-CSF1R axis and IL-12 enrichment not only reprograms the tumor microenvironment through macrophage M1 repolarization but also activates cytotoxic T cells, ultimately achieving complete glioblastoma eradication. This research provides an efficient theranostic paradigm for glioblastoma treatment.

Coordinated regulation of IGF1R by HIF1α and HIF2α enhances chemoresistance in glioblastoma

Background

This study investigates whether Hypoxia-Inducible Factor 1 alpha (HIF1α) and Hypoxia-Inducible Factor 2 alpha (HIF2α) coordinately regulate insulin-like growth factor 1 receptor (IGF1R) expression, thereby influencing chemosensitivity in glioblastoma multiforme (GBM).

Methods

We analyzed the expression and correlation of HIF1α, HIF2α, and IGF1R in glioma using The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) databases. Immunohistochemistry (IHC) was performed to detect the expression of HIF1α, HIF2α, and IGF1R in GBM tissues and cells, as well as oxygen tension. Cell cycle analysis, apoptosis assays, lactate dehydrogenase (LDH) release measurements, Western blotting, and xenograft tumor models were employed to explore the synergistic regulation of IGF1R by HIF1α and HIF2α, focusing on activation of the PI3K/AKT signaling pathway and its contribution to GBM drug resistance. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) and dual-luciferase reporter assays were used to investigate the binding sites of HIF1α and HIF2α involved in regulating IGF1R.

Results

Our study demonstrated that HIF1α and HIF2α were highly expressed in GBM tissues and hypoxia-cultured cells, and their expression positively correlated with IGF1R expression. Simultaneous knockout of HIF1α and HIF2α in GBM cells resulted in the highest LDH release and apoptosis rates under hypoxic conditions, accompanied by the most significant decrease in IGF1R, p-PDK1, and p-AKT levels. Knockout of IGF1R in tumor cells under hypoxia led to an increas of LDH release and apoptosis rates, and reduced phosphorylation of PDK1 and AKT. In addition, we demonstrated that HIF1α and HIF2α promoted IGF1R expression by binding to a specific hypoxia response element (HRE) sequence (5'-GAACGTGCCT-3') within the IGF1R promoter using dual-luciferase reporter system.

Conclusion

Glioblastoma cells, residing within a hypoxic microenvironment, exhibit high expression of HIF1α and HIF2α. These transcription factors promote the upregulation of IGF1R, which subsequently activates the PI3K/AKT signaling pathway. This activation, in turn, promotes cell proliferation and chemoresistance, ultimately contributing to tumor malignancy.

Phototherapy in cancer treatment: strategies and challenges

Phototherapy has emerged as a promising modality in cancer treatment, garnering considerable attention for its minimal side effects, exceptional spatial selectivity, and optimal preservation of normal tissue function. This innovative approach primarily encompasses three distinct paradigms: Photodynamic Therapy (PDT), Photothermal Therapy (PTT), and Photoimmunotherapy (PIT). Each of these modalities exerts its antitumor effects through unique mechanisms-specifically, the generation of reactive oxygen species (ROS), heat, and immune responses, respectively. However, significant challenges impede the advancement and clinical application of phototherapy. These include inadequate ROS production rates, subpar photothermal conversion efficiency, difficulties in tumor targeting, and unfavorable physicochemical properties inherent to traditional phototherapeutic agents (PTs). Additionally, the hypoxic microenvironment typical of tumors complicates therapeutic efficacy due to limited agent penetration in deep-seated lesions. To address these limitations, ongoing research is fervently exploring innovative solutions. The unique advantages offered by nano-PTs and nanocarrier systems aim to enhance traditional approaches' effectiveness. Strategies such as generating oxygen in situ within tumors or inhibiting mitochondrial respiration while targeting the HIF-1α pathway may alleviate tumor hypoxia. Moreover, utilizing self-luminescent materials, near-infrared excitation sources, non-photoactivated sensitizers, and wireless light delivery systems can improve light penetration. Furthermore, integrating immunoadjuvants and modulating immunosuppressive cell populations while deploying immune checkpoint inhibitors holds promise for enhancing immunogenic cell death through PIT. This review seeks to elucidate the fundamental principles and biological implications of phototherapy while discussing dominant mechanisms and advanced strategies designed to overcome existing challenges-ultimately illuminating pathways for future research aimed at amplifying this intervention's therapeutic efficacy.

Abnormal Vessels Potentially Accelerate Glioblastoma Proliferation by Inducing the Protumor Activation of Macrophages

Glioblastoma (GBM) involves disruptions in the blood-brain barrier (BBB) and alterations in the immune microenvironment, including the activation of glioma-associated macrophages (GAMs). Vascular endothelial growth factor inhibitors, commonly used in recurrent GBM treatment, can influence these processes. This study investigates the relationship between BBB disruption and GAM activation, focusing on plasmalemma vesicle-associated protein (PLVAP), a marker of BBB disruption, and α1-acid glycoprotein (AGP), an inflammatory protein implicated in tumor progression. PLVAP expression was analyzed by immunohistochemistry (IHC) in human GBM samples to determine correlations with tumor grade, proliferation, and GAM activation. Pre- and post-bevacizumab treatment GBM samples were compared to assess changes in BBB integrity and macrophage activity. AGP's role in GAM activation was studied through in vitro assays and glioma implantation in AGP knockout mice, with assessments of tumor growth and angiogenesis. Results showed elevated PLVAP expression in higher-grade gliomas, correlating with increased tumor proliferation and GAM activation, particularly around PLVAP-positive vessels. Bevacizumab treatment reduced PLVAP expression and macrophage activity. AGP localized to regions of BBB disruption, promoting macrophage-mediated tumor growth in vitro. AGP knockout mice demonstrated reduced angiogenesis and prolonged survival. Spatial analysis revealed increased expression of macrophage-inducing molecules near PLVAP-positive vessels. These findings suggest PLVAP as a marker of BBB disruption and glioma malignancy. AGP, associated with BBB leakage, contributes to GAM activation and tumor progression, highlighting its potential as a therapeutic target for GBM.

Predicting Prognosis and Immunotherapy Response in Glioblastoma (GBM) With a 5-Gene CAF-Risk Signature

BACKGROUND

Cancer-associated fibroblasts (CAF) represent significant constituents within the extracellular matrix (ECM) across a range of cancers. Nevertheless, there exists a scarcity of direct proof concerning the function of CAF in glioblastoma (GBM).

AIMS

This study endeavors to probe the participation of CAF in GBM by developing and validating a CAF-risk signature and exploring its correlation with immune infiltration and immunotherapy responsiveness.

METHODS AND RESULTS

To fulfill these objectives, mRNA expression profiles of GBM samples and their corresponding clinical data were retrieved from two databases. First, stromal CAF-associated genes were identified by weighted gene co-expression network analysis (WGCNA). This method constructs co-expression networks and pinpoints gene modules with similar expression patterns to detect relevant genes. Subsequently, a CAF-risk signature was established via univariate and LASSO Cox regression analyses. Thereafter, gene set enrichment analysis (GSEA) and single-sample gene set enrichment analysis (ssGSEA) were carried out to investigate the underlying molecular mechanisms. The immune status was evaluated with several R packages, and the Tumor Immune Dysfunction and Exclusion (TIDE) algorithm was utilized to assess the response to immunotherapy. Validation was performed using single-cell RNA sequencing (scRNA) datasets, the Cancer Cell Line Encyclopedia (CCLE), and the Human Protein Atlas (HPA). Eventually, a 5-gene (ITGA5, MMP14, FN1, COL5A1, and COL6A1) prognostic CAF model was constructed. Notably, immune infiltration analysis demonstrated a significant correlation between Treg, Macrophage, and CAF risk scores. Moreover, TIDE analysis suggested a decreased responsiveness to immunotherapy in high CAF-risk patients. In addition, GSEA showed significant enrichment of the transforming growth factor alpha (TGF-α), inflammatory response, and epithelial-mesenchymal transition (EMT) pathways in this subgroup. Finally, the validation through scRNA, CCLE, and HPA datasets confirmed these findings.

CONCLUSION

The 5-gene CAF-risk signature exhibited accurate prognostic predictions and efficiently evaluated clinical immunotherapy responses among GBM patients. These results offer robust evidence regarding the implication of CAF in GBM and underscore the potential clinical value of personalized anti-CAF therapies in conjunction with immunotherapy.

Emerging immunologic approaches as cancer anti-angiogenic therapies

Targeting tumor angiogenesis, the formation of new blood vessels supporting cancer growth and spread, has been an intense focus for therapy development. However, benefits from anti-angiogenic drugs like bevacizumab have been limited by resistance stemming from activation of compensatory pathways. Recent immunotherapy advances have sparked interest in novel immunologic approaches that can induce more durable vascular pruning and overcome limitations of existing angiogenesis inhibitors. This review comprehensively examines these emerging strategies, including modulating tumor-associated macrophages, therapeutic cancer vaccines, engineered nanobodies and T cells, anti-angiogenic cytokines/chemokines, and immunomodulatory drugs like thalidomide analogs. For each approach, the molecular mechanisms, preclinical/clinical data, and potential advantages over conventional drugs are discussed. Innovative therapeutic platforms like nanoparticle delivery systems are explored. Moreover, the importance of combining agents with distinct mechanisms to prevent resistance is evaluated. As tumors hijack angiogenesis for growth, harnessing the immune system's specificity to disrupt this process represents a promising anti-cancer strategy covered by this review.

Overcoming immunotherapy resistance in glioblastoma: challenges and emerging strategies

Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults, characterized by rapid proliferation, extensive infiltration, and significant intratumoral heterogeneity. Despite advancements in conventional treatments, including surgery, radiotherapy, and chemotherapy, the prognosis for GBM patients remains poor, with a median survival of approximately 15 months. Immunotherapy has emerged as a promising alternative; however, the unique biological and immunological features, including its immunosuppressive tumor microenvironment (TME) and low mutational burden, render it resistant to many immunotherapeutic strategies. This review explores the key challenges in GBM immunotherapy, focusing on immune evasion mechanisms, the blood-brain barrier (BBB), and the TME. Immune checkpoint inhibitors and CAR-T cells have shown promise in preclinical models but have limited clinical success due to antigen heterogeneity, immune cell exhaustion, and impaired trafficking across the BBB. Emerging strategies, including dual-targeting CAR-T cells, engineered immune cells secreting therapeutic molecules, and advanced delivery systems to overcome the BBB, show potential for enhancing treatment efficacy. Addressing these challenges is crucial for improving GBM immunotherapy outcomes.

The local microenvironment suppresses the synergy between irradiation and anti-PD1 therapy in breast-to-brain metastasis

The brain environment is uniquely specialized to protect its neuronal tissue from excessive inflammation by tightly regulating adaptive immunity. However, in the context of brain cancer progression, this regulation can lead to a conflict between T cell activation and suppression. Here, we show that, while CD8+ T cells can infiltrate breast cancer-brain metastases, their anti-tumor cytotoxicity is locally suppressed in the brain. Conversely, CD8+ T cells exhibited tumoricidal activity in extracranial mammary lesions originating from the same cancer cells. Consequently, combined high-dose irradiation and anti-programmed cell death protein 1 (PD1) therapy was effective in extracranial tumors but not intracranial lesions. Transcriptional analyses and functional studies identified neutrophils and Trem2-expressing macrophages as key sources for local T cell suppression within the brain, providing rational targets for future therapeutic strategies.

Reactive Astrocytes in Glioma: Emerging Opportunities and Challenges

Gliomas are the most prevalent malignant tumors in the adult central nervous system (CNS). Glioblastoma (GBM) accounts for approximately 60-70% of primary gliomas. It is a great challenge to human health because of its high degree of malignancy, rapid progression, short survival time, and susceptibility to recurrence. Owing to the specificity of the CNS, the glioma microenvironment often contains numerous glial cells. Astrocytes are most widely distributed in the human brain and form reactive astrocyte proliferation regions around glioma tissue. In addition, astrocytes are activated under pathological conditions and regulate tumor and microenvironmental cells through cell-to-cell contact or the secretion of active substances. Therefore, astrocytes have attracted attention as important components of the glioma microenvironment. Here, we focus on the mechanisms of reactive astrocyte activation under glioma conditions, their contribution to the mechanisms of glioma genesis and progression, and their potential value as targets for clinical intervention in gliomas.

Cross-Talk Between Cancer and Its Cellular Environment-A Role in Cancer Progression

The tumor microenvironment is a dynamic and complex three-dimensional network comprising the extracellular matrix and diverse non-cancerous cells, including fibroblasts, adipocytes, endothelial cells and various immune cells (lymphocytes T and B, NK cells, dendritic cells, monocytes/macrophages, myeloid-derived suppressor cells, and innate lymphoid cells). A constantly and rapidly growing number of studies highlight the critical role of these cells in shaping cancer survival, metastatic potential and therapy resistance. This review provides a synthesis of current knowledge on the modulating role of the cellular microenvironment in cancer progression and response to treatment.

Glioblastoma Tumor Microenvironment and Purinergic Signaling: Implications for Novel Therapies

Glial-origin brain tumors, particularly glioblastomas (GBMs), are known for their devastating prognosis and are characterized by rapid progression and fatal outcomes. Despite advances in surgical resection, complete removal of the tumor remains unattainable, with residual cells driving recurrence that is resistant to conventional therapies. The GBM tumor microenviroment (TME) significantly impacts tumor progression and treatment response. In this review, we explore the emerging role of purinergic signaling, especially the P2X7 receptor (P2X7R). Due to its unique characteristics, it plays a key role in tumor progression and offers a potential therapeutic strategy for GBM through TME modulation. We discuss also the emerging role of the P2X4 receptor (P2X4R) as a promising therapeutic target. Overall, targeting purinergic signaling offers a potential approach to overcoming current GBM treatment limitations.

The roles of glioma-associated macrophages/microglia and potential targets for anti-glioma therapy

Glioblastoma (GBM) is the central nervous system tumor with the most aggressive behavior, and no definitive therapy has yet been found. The tumor microenvironment of GBM is immunosuppressive and is considered a 'cold tumor' with low lymphocytic infiltration, but is characterized by a high proportion of glioma-associated macrophages/microglia (GAMs). GAMs promote tumor growth and also affect treatment resistance in GBM. In this review, we describe the origin and classification of GAMs in humans and describe the mechanisms of their activation and the cell-cell interactions between tumor cells and GAMs. We also describe the history of GAM detection methods, especially immunohistochemistry, and discusses the merits and limitations of these techniques. In addition, we summarized chemotactic factors for GAMs and the therapies targeting these factors. Recent single-cell RNA analysis and spatial analysis add new insights to our previous knowledge of GAMs. Based on these studies, GBM therapies targeting GAMs are expected to be further developed.

Multicellular Network-Informed Survival Model for Identification of Drug Targets of Gliomas

Increasing evidence suggests that communication between tumor cells (TCs) and tumor-associated macrophages (TAMs) plays a substantial role in promoting progression of low-grade gliomas (LGG). Hence, it is becoming critical to model TAM-TC interplay and interrogate how the crosstalk affects prognosis of LGG patients. This article proposed a translational research pipeline to construct the multicellular interaction gene network (MIGN) for identification of druggable targets to develop novel therapeutic strategies. Firstly, we selected immunotherapy-related feature genes (IFGs) for TAMs and TCs using RNA-seq data of glioma mice from preclinical trials. After translating the IFGs to human genome, we constructed TAM- and TC- associated networks separately, using a training set of 524 human LGGs. Subsequently, clustering analysis was performed within each network, and the concordance measure K-index was adopted to correlate gene clusters with patient survival. The MIGN was built by combining the clusters highly associated with survival in TAM- and TC-associated networks. We then developed a MIGN-based survival model to identify prognostic signatures comprised of ligands, receptors and hub genes. An independent cohort of 172 human LGG samples was leveraged to validate predictive accuracy of the signature. The areas under time-dependent ROC curves were 0.881, 0.867, and 0.839 with respect to 1-year, 3-year, and 5-year survival rates respectively in the validation set. Furthermore, literature survey was conducted on the signature genes, and potential clinical responses to targeted drugs were evaluated for LGG patients, further highlighting potential utilities of the MIGN signature to develop novel immunotherapies to extend survival of LGG patients.

Extracellular vesicles derived from Lactobacillus johnsonii promote gut barrier homeostasis by enhancing M2 macrophage polarization

INTRODUCTION

Diarrheic disease is a common intestinal health problem worldwide, causing great suffering to humans and animals. Precise manipulation strategies based on probiotics to combat diarrheic diseases have not been fully developed.

OBJECTIVES

The aim of this study was to investigate the molecular mechanisms by which probiotics manipulate macrophage against diarrheic disease.

METHODS

Metagenome reveals gut microbiome profiles of healthy and diarrheic piglets. Fecal microbial transplantation (FMT) was employed to explore the causal relationship between gut microbes and diarrhea. The protective role of probiotics and their derived extracellular vesicles (EVs) was investigated in ETEC K88-infected mice. Macrophage depletion was performed to assess the role of macrophages in EVs against diarrhea. Execution of in vitro cell co-culture and transcriptome analyses elucidated the molecular mechanisms by which EVs modulate the macrophage and intestinal epithelial barrier.

RESULTS

Escherichia coli was enriched in weaned diarrheic piglets, while Lactobacillus johnsonii (L. john) showed a negative correlation with Escherichia coli. The transmission of diarrheic illness symptoms was achieved by transferring fecal microbiota, but not metabolites, from diarrheic pigs to germ-free (GF) mice. L. john's intervention prevented the transmission of disease phenotypes from diarrheic piglets to GF mice. L. john also reduces the gut inflammation induced by ETEC K88. The EVs secreted by L. john demonstrated enhanced efficacy in mitigating the adverse impacts induced by ETEC K88 through the modulation of macrophage phenotype. In vitro experiments have revealed that EVs activate M2 macrophages in a manner that shuts down ERK, thereby inhibiting NLRP3 activation in intestinal epithelial cells.

CONCLUSION

Our results reveal that intestinal microbiota drives the onset of diarrheic disease and that probiotic-derived EVs ameliorate diarrheic disease symptoms by modulating macrophage phenotypes. These findings can enhance the advancement of innovative therapeutic approaches for diarrheic conditions based on probiotic-derived EVs.

Proguanil inhibits proliferation and migration in glioblastoma development through targeting CSF1R receptor

Glioblastoma (GBM) is the most common and aggressive malignant tumor of the central nervous system, characterized by high morbidity and invasive potential, necessitating urgent development of novel therapeutic strategies. Studies have shown that colony stimulating factor-1 receptor (CSF1R) is abnormally expressed in a variety of solid tumors, which is closely related to the development of tumor cells. In this study, the CSF1R/cell membrane Chromatographic model was successfully constructed, and was used to screen active compounds targeting CSF1R from more than 60 compounds. Among these, Proguanil exhibited the strongest affinity with retention time of 69 min, and a KD value of (6.73 ± 0.05) × 10-7 M. Proguanil effectively inhibited the growth of U87MG cells in vitro and in vivo by inducing G0/G1 phase cell cycle arrest and suppressing U87MG cells migration. More importantly, we found that Proguanil's inhibitory effect on U87MG cell growth and migration was positively correlated with CSF1R expression, and this effect diminished following CSF1R knockdown and Proguanil demonstrated synergistic effects with CSF1R-targeting positive drugs (BLZ945 and GW2580). Furthermore, Proguanil was found to inhibit CSF1R phosphorylation along with downstream signaling pathways such as PTEN/AKT/mTOR and Ras/MEK1/2/ERK1/2, thereby regulating cell cycle-related molecules (p21, CDK4, and CyclinD1) and cell migration-related molecule MMP3. Meanwhile, Proguanil targeted CSF1R to inhibit M2-type polarization of tumor-associated macrophages (TAMs) and their proliferation, thus altering the tumor microenvironment while indirectly suppressing the proliferation and migration of U87MG cells. Taken together, these findings suggest that Proguanil may serve as a promising CSF1R antagonist for GBM treatment.

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.

Opportunities and challenges for patient-derived models of brain tumors in functional precision medicine

Here, we review a growing paradigm shift from genomics-based precision medicine toward functional precision medicine, which evaluates therapeutic efficacy by directly treating living patient tumors ex vivo to better predict patient-specific responses to treatment. We discuss several classes of patient-derived models of central nervous system tumors, highlighting unique features of each. Each class of models holds promise to improve treatment selection, prolong survival, and enhance patient outcomes.

Unraveling MCL biology to understand resistance and identify vulnerabilities

ABSTRACT

Mantle cell lymphoma (MCL) is a rare (5%-7%), aggressive B-cell non-Hodgkin lymphoma with well-defined hallmarks (eg, cyclin D1, SOX11), and its expansion is highly dependent on the tumor microenvironment (TME). Parallel drastic progress in the understanding of lymphomagenesis and improved treatments led to a paradigm shift in this B-cell malignancy with now prolonged disease-free survival after intensive chemotherapy and anti-CD20-based maintenance. However, this toxic strategy is not applicable in frail or older patients, and a small but significant part of the cases present a refractory disease representing unmet medical needs. Importantly, the field has recently seen the rapid emergence of targeted and immune-based strategies with effective combinations relying on biological rationales to overcome malignant plasticity and intratumor heterogeneity. In this review, we expose how unraveling the biology of MCL allows to better understand the therapeutic resistances and to identify neo-vulnerabilities in tumors, which are essential to offer efficient novel strategies for high-risk patients. We first highlight the tumor intrinsic resistance mechanisms and associated Achilles heels within various pathways, such as NF-κB, mitochondrial apoptosis, DNA repair, and epigenetic regulators. We then place the tumor in its complex ecosystem to decipher the dialog with the multiple TME components and show how the resulting protumoral signals could be disrupted with innovative therapeutic strategies. Finally, we discuss how these progresses could be integrated into a personalized approach in MCL.

Multifunctional biosynthesized magnetosome for multimodal imaging and combined therapy of tumor

The large recruitment of tumor-associated macrophages and low exposure of tumor-associated antigens in tumor microenvironment have severely suppress the efficacy of anti-tumor immunotherapy. Herein, biosynthesized magnetosome (Mag) from bacteria was loaded with photothermal/photodynamic agent/near infrared (NIR) fluorescence dye (IR780) and further modified with lipid-PEG-c(RGDyK) through biomembrane, forming IMagRGD for fluorescence imaging, magnetic resonance imaging, immunotherapy and photodynamic/photothermal therapy. After intravenous injection into B16F10 tumor-bearing mice, IMagRGD could efficiently accumulate in tumor tissues based on near infrared (NIR) fluorescence and magnetic resonance dual-modality imaging, and repolarize tumor-associated macrophages (TAMs) from M2 phenotype to M1 phenotype, significantly improving the effect of tumor immunotherapy. Moreover, photothermal and photodynamic effect of IR780 could kill tumor cells and elicit immunogenic cell death to mediate anti-tumor immunity, promoting dendritic cells (DCs) maturation and then activating specific effector T cells to further eliminate tumor cells. This study provides a new approach for reversing the activity of tumor immunosuppressive microenvironment and strengthening the efficiency of tumor photoimmunotherapy.

Splicing dysregulation in glioblastoma alters the function of cell migration-related genes

Glioblastoma (GBM) has a poor prognosis with a high recurrence and low survival rate. Previous RNA-seq analyses have revealed that alternative splicing (AS) plays a role in GBM progression. Here, we present a novel AS analysis method (Semi-Q) and describe its use to identify GBM-specific AS events. We analyzed RNA-seq data from normal brain (NB), normal human astrocytes (NHAs) and GBM samples, and found that comparison between NHA and GBM was especially informative. Importantly, this analysis revealed that genes encoding cell migration-related proteins, including filamins (FLNs) and actinins (ACTNs), were among those most affected by differential AS. Functional assays revealed that dysregulated AS of FLNA, B and C transcripts produced protein isoforms that not only altered transcription of cell proliferation-related genes but also led to enhanced cell migration, resistance to cell death and/or mitochondrial respiratory function, while a dysregulated AS isoform of ACTN4 enhanced cell migration. Together, our results indicate that cell migration and actin cytoskeleton-related genes are differentially regulated by AS in GBM, supporting a role for AS in facilitating tumor growth and invasiveness.

Harnessing the tumor microenvironment: targeted cancer therapies through modulation of epithelial-mesenchymal transition

The tumor microenvironment (TME) is integral to cancer progression, impacting metastasis and treatment response. It consists of diverse cell types, extracellular matrix components, and signaling molecules that interact to promote tumor growth and therapeutic resistance. Elucidating the intricate interactions between cancer cells and the TME is crucial in understanding cancer progression and therapeutic challenges. A critical process induced by TME signaling is the epithelial-mesenchymal transition (EMT), wherein epithelial cells acquire mesenchymal traits, which enhance their motility and invasiveness and promote metastasis and cancer progression. By targeting various components of the TME, novel investigational strategies aim to disrupt the TME's contribution to the EMT, thereby improving treatment efficacy, addressing therapeutic resistance, and offering a nuanced approach to cancer therapy. This review scrutinizes the key players in the TME and the TME's contribution to the EMT, emphasizing avenues to therapeutically disrupt the interactions between the various TME components. Moreover, the article discusses the TME's implications for resistance mechanisms and highlights the current therapeutic strategies toward TME modulation along with potential caveats.

Infiltrating plasma cells maintain glioblastoma stem cells through IgG-Tumor binding

Glioblastoma is a highly aggressive primary brain tumor with glioblastoma stem cells (GSCs) enforcing the intra-tumoral hierarchy. Plasma cells (PCs) are critical effectors of the B-lineage immune system, but their roles in glioblastoma remain largely unexplored. Here, we leverage single-cell RNA and B cell receptor sequencing of tumor-infiltrating B-lineage cells and reveal that PCs are aberrantly enriched in the glioblastoma-infiltrating B-lineage population, experience low level of somatic hypermutation, and are associated with poor prognosis. PCs secrete immunoglobulin G (IgG), which stimulates GSC proliferation via the IgG-FcγRIIA-AKT-mTOR axis. Disruption of IgG-FcγRIIA paracrine communication inhibits GSC proliferation and self-renewal. Glioblastoma-infiltrating PCs are recruited to GSC niches via CCL2-CCR2 chemokine program. GSCs further derive pro-proliferative signals from broadly utilized monoclonal antibody-based immune checkpoint inhibitors via FcγRIIA signaling. Our data generate an atlas of B-lineage cells in glioblastoma with a framework for combinatorial targeting of both tumor cell-intrinsic and microenvironmental dependencies.

Protocol for studying macrophage lipid crosstalk with murine tumor cells

Lipid accumulation has recently emerged as a key feature underlying the pro-tumorigenic role of macrophages. Here, we present a workflow to study macrophage lipid crosstalk with tumor cells. We describe steps for the identification, purification, and multi-omics characterization of lipid-laden macrophages (LLMs) from murine tumors and outline protocols to assess the functional significance of LLMs in cancer malignancy. This approach has the potential to uncover the source of lipids that drives LLM formation and its pro-tumorigenic potential in multiple cancer types. For complete details on the use and execution of this protocol, please refer to Kloosterman, Erbani, et al.1.

Glioblastoma-associated macrophages: A key target in overcoming glioblastoma therapeutic resistance

Glioblastoma multiforme (GBM) is recognized as the most aggressive and malignant form of brain cancer, characterized by a highly heterogeneous phenotype, poor prognosis, and a median survival time of less than 16 months. Recent studies have highlighted the critical role of glioblastoma-associated macrophages (GAMs) in promoting tumor progression and resistance not only to immunotherapy but also to radiotherapy and chemotherapy. GAMs actively suppress immune responses, promote angiogenesis, facilitate tumor metastasis, and induce therapy resistance, through various mechanisms such as cytokines production, signaling pathways regulation, and angiogenesis. In this context, understanding these regulatory mechanisms is essential for developing efficient therapies. Preclinical studies have investigated diverse approaches to target these cells, both as monotherapies or in combination with other treatments. While these approaches have shown promise in strengthening antitumor immune responses in animal models, their clinical success remains to be fully determined. Herein, we provide a comprehensive overview of GAMs's role in GBM therapeutic resistance and summarizes existing approaches to target GAMs in overcoming tumor resistance.

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.

Macrophage diversity in cancer dissemination and metastasis

Invasion and metastasis are hallmarks of cancer. In addition to the well-recognized hematogenous and lymphatic pathways of metastasis, cancer cell dissemination can occur via the transcoelomic and perineural routes, which are typical of ovarian and pancreatic cancer, respectively. Macrophages are a universal major component of the tumor microenvironment and, in established tumors, promote growth and dissemination to secondary sites. Here, we review the role of tumor-associated macrophages (TAMs) in cancer cell dissemination and metastasis, emphasizing the diversity of myeloid cells in different tissue contexts (lungs, liver, brain, bone, peritoneal cavity, nerves). The generally used models of lung metastasis fail to capture the diversity of pathways and tissue microenvironments. A better understanding of TAM diversity in different tissue contexts may pave the way for tailored diagnostic and therapeutic approaches.

Role of T Lymphocytes in Glioma Immune Microenvironment: Two Sides of a Coin

Glioma is known for its immunosuppressive microenvironment, which makes it challenging to target through immunotherapies. Immune cells like macrophages, microglia, myeloid-derived suppressor cells, and T lymphocytes are known to infiltrate the glioma tumor microenvironment and regulate immune response distinctively. Among the variety of immune cells, T lymphocytes have highly complex and multifaceted roles in the glioma immune landscape. T lymphocytes, which include CD4+ helper and CD8+ cytotoxic T cells, are known for their pivotal roles in anti-tumor responses. However, these cells may behave differently in the highly dynamic glioma microenvironment, for example, via an immune invasion mechanism enforced by tumor cells. Therefore, T lymphocytes play dual roles in glioma immunity, firstly by their anti-tumor responses, and secondly by exploiting gliomas to promote immune invasion. As an immunosuppression strategy, glioma induces T-cell exhaustion and suppression of effector T cells by regulatory T cells (Tregs) or by altering their signaling pathways. Further, the expression of immune checkpoint inhibitors on the glioma cell surface leads to T cell anergy and dysfunction. Overall, this dynamic interplay between T lymphocytes and glioma is crucial for designing more effective immunotherapies. The current review provides detailed knowledge on the roles of T lymphocytes in the glioma immune microenvironment and helps to explore novel therapeutic approaches to reinvigorate T lymphocytes.

Insights into CSF-1R Expression in the Tumor Microenvironment

The colony-stimulating factor 1 receptor (CSF-1R) plays a pivotal role in orchestrating cellular interactions within the tumor microenvironment (TME). Although the CSF-1R has been extensively studied in myeloid cells, the expression of this receptor and its emerging role in other cell types in the TME need to be further analyzed. This review explores the multifaceted functions of the CSF-1R across various TME cellular populations, including tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), dendritic cells (DCs), cancer-associated fibroblasts (CAFs), endothelial cells (ECs), and cancer stem cells (CSCs). The activation of the CSF-1R by its ligands, colony-stimulating factor 1 (CSF-1) and Interleukin-34 (IL-34), regulates TAM polarization towards an immunosuppressive M2 phenotype, promoting tumor progression and immune evasion. Similarly, CSF-1R signaling influences MDSCs to exert immunosuppressive functions, hindering anti-tumor immunity. In DCs, the CSF-1R alters antigen-presenting capabilities, compromising immune surveillance against cancer cells. CSF-1R expression in CAFs and ECs regulates immune modulation, angiogenesis, and immune cell trafficking within the TME, fostering a pro-tumorigenic milieu. Notably, the CSF-1R in CSCs contributes to tumor aggressiveness and therapeutic resistance through interactions with TAMs and the modulation of stemness features. Understanding the diverse roles of the CSF-1R in the TME underscores its potential as a therapeutic target for cancer treatment, aiming at disrupting pro-tumorigenic cellular crosstalk and enhancing anti-tumor immune responses.

Dual targeting macrophages and microglia is a therapeutic vulnerability in models of PTEN-deficient glioblastoma

Tumor-associated macrophages and microglia (TAMs) are critical for tumor progression and therapy resistance in glioblastoma (GBM), a type of incurable brain cancer. We previously identified lysyl oxidase (LOX) and olfactomedin like-3 (OLFML3) as essential macrophage and microglia chemokines, respectively, in GBM. Here, single-cell transcriptomics and multiplex sequential immunofluorescence followed by functional studies demonstrate that macrophages negatively correlate with microglia in the GBM tumor microenvironment. LOX inhibition in PTEN-deficient GBM cells upregulates OLFML3 expression via the NF-κB-PATZ1 signaling pathway, inducing a compensatory increase of microglia infiltration. Dual targeting macrophages and microglia via inhibition of LOX and the CLOCK-OLFML3 axis generates potent antitumor effects and offers a complete tumor regression in more than 60% of animals when combined with anti-PD1 therapy in PTEN-deficient GBM mouse models. Thus, our findings provide a translational triple therapeutic strategy for this lethal disease.

Tumor-associated macrophages: A sentinel of innate immune system in tumor microenvironment gone haywire

The tumor microenvironment (TME) is a critical determinant in the initiation, progression, and treatment outcomes of various cancers. Comprising of cancer-associated fibroblasts (CAF), immune cells, blood vessels, and signaling molecules, the TME is often likened to the soil supporting the seed (tumor). Among its constituents, tumor-associated macrophages (TAMs) play a pivotal role, exhibiting a dual nature as both promoters and inhibitors of tumor growth. This review explores the intricate relationship between TAMs and the TME, emphasizing their diverse functions, from phagocytosis and tissue repair to modulating immune responses. The plasticity of TAMs is highlighted, showcasing their ability to adopt either protumorigenic or anti-tumorigenic phenotypes based on environmental cues. In the context of cancer, TAMs' pro-tumorigenic activities include promoting angiogenesis, inhibiting immune responses, and fostering metastasis. The manuscript delves into therapeutic strategies targeting TAMs, emphasizing the challenges faced in depleting or inhibiting TAMs due to their multifaceted roles. The focus shifts towards reprogramming TAMs to an anti-tumorigenic M1-like phenotype, exploring interventions such as interferons, immune checkpoint inhibitors, and small molecule modulators. Noteworthy advancements include the use of CSF1R inhibitors, CD40 agonists, and CD47 blockade, demonstrating promising results in preclinical and clinical settings. A significant section is dedicated to Chimeric Antigen Receptor (CAR) technology in macrophages (CAR-M cells). While CAR-T cells have shown success in hematological malignancies, their efficacy in solid tumors has been limited. CAR-M cells, engineered to infiltrate solid tumors, are presented as a potential breakthrough, with a focus on their development, challenges, and promising outcomes. The manuscript concludes with the exploration of third-generation CAR-M technology, offering insight into in-vivo reprogramming and nonviral vector approaches. In conclusion, understanding the complex and dynamic role of TAMs in cancer is crucial for developing effective therapeutic strategies. While early-stage TAM-targeted therapies show promise, further extensive research and larger clinical trials are warranted to optimize their targeting and improve overall cancer treatment outcomes.

Tumor‑associated macrophages activated in the tumor environment of hepatocellular carcinoma: Characterization and treatment (Review)

Hepatocellular carcinoma (HCC) tissue is rich in dendritic cells, T cells, B cells, macrophages, natural killer cells and cellular stroma. Together they form the tumor microenvironment (TME), which is also rich in numerous cytokines. Tumor‑associated macrophages (TAMs) are involved in the regulation of tumor development. TAMs in HCC receive stimuli in different directions, polarize in different directions and release different cytokines to regulate the development of HCC. TAMs are mostly divided into two cell phenotypes: M1 and M2. M1 TAMs secrete pro‑inflammatory mediators, and M2 TAMs secrete a variety of anti‑inflammatory and pro‑tumorigenic substances. The TAM polarization in HCC tumors is M2. Both direct and indirect methods for TAMs to regulate the development of HCC are discussed. TAMs indirectly support HCC development by promoting peripheral angiogenesis and regulating the immune microenvironment of the TME. In terms of the direct regulation between TAMs and HCC cells, the present review mainly focuses on the molecular mechanism. TAMs are involved in both the proliferation and apoptosis of HCC cells to regulate the quantitative changes of HCC, and stimulate the related invasive migratory ability and cell stemness of HCC cells. The present review aims to identify immunotherapeutic options based on the mechanisms of TAMs in the TME of HCC.

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.

Fibrotic response to anti-CSF-1R therapy potentiates glioblastoma recurrence

Glioblastoma recurrence is currently inevitable despite extensive standard-of-care treatment. In preclinical studies, an alternative strategy of targeting tumor-associated macrophages and microglia through CSF-1R inhibition was previously found to regress established tumors and significantly increase overall survival. However, recurrences developed in ∼50% of mice in long-term studies, which were consistently associated with fibrotic scars. This fibrotic response is observed following multiple anti-glioma therapies in different preclinical models herein and in patient recurrence samples. Multi-omics analyses of the post-treatment tumor microenvironment identified fibrotic areas as pro-tumor survival niches that encapsulated surviving glioma cells, promoted dormancy, and inhibited immune surveillance. The fibrotic treatment response was mediated by perivascular-derived fibroblast-like cells via activation by transforming growth factor β (TGF-β) signaling and neuroinflammation. Concordantly, combinatorial inhibition of these pathways inhibited treatment-associated fibrosis, and significantly improved survival in preclinical trials of anti-colony-stimulating factor-1 receptor (CSF-1R) therapy.

The critical roles of IGFs in immune modulation and inflammation

Insulin-like growth factors (IGFs) are crucial for embryonic and postnatal growth and development, influencing cell survival, metabolism, myogenesis, and cancer progression. Many studies have demonstrated that IGFs also play prominent roles in the modulation of both innate and adaptive immune systems during inflammation. Strikingly, IGFs dictate the phenotype and functional properties of macrophages and T cells. Furthermore, the interplay between IGFs and inflammatory cytokines may generate tissue-protective properties during inflammation. Herein, we review the recent advances on the dialogue between immune cells and IGFs, especially zooming in on the significance of immunomodulatory properties in inflammatory conditions, cancer and autoimmune diseases. The investigation of IGFs may have broad clinical implications.

Immune landscape of oncohistone-mutant gliomas reveals diverse myeloid populations and tumor-promoting function

Histone H3-mutant gliomas are deadly brain tumors characterized by a dysregulated epigenome and stalled differentiation. In contrast to the extensive datasets available on tumor cells, limited information exists on their tumor microenvironment (TME), particularly the immune infiltrate. Here, we characterize the immune TME of H3.3K27M and G34R/V-mutant gliomas, and multiple H3.3K27M mouse models, using transcriptomic, proteomic and spatial single-cell approaches. Resolution of immune lineages indicates high infiltration of H3-mutant gliomas with diverse myeloid populations, high-level expression of immune checkpoint markers, and scarce lymphoid cells, findings uniformly reproduced in all H3.3K27M mouse models tested. We show these myeloid populations communicate with H3-mutant cells, mediating immunosuppression and sustaining tumor formation and maintenance. Dual inhibition of myeloid cells and immune checkpoint pathways show significant therapeutic benefits in pre-clinical syngeneic mouse models. Our findings provide a valuable characterization of the TME of oncohistone-mutant gliomas, and insight into the means for modulating the myeloid infiltrate for the benefit of patients.

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

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

Clinical landscape of macrophage-reprogramming cancer immunotherapies

Tumour-associated macrophages (TAMs) sustain a tumour-supporting and immunosuppressive milieu and therefore aggravate cancer prognosis. To modify TAM behaviour and unlock their anti-tumoural potential, novel TAM-reprogramming immunotherapies are being developed at an accelerating rate. At the same time, scientific discoveries have highlighted more sophisticated TAM phenotypes with complex biological functions and contradictory prognostic associations. To understand the evolving clinical landscape, we reviewed current and past clinically evaluated TAM-reprogramming cancer therapeutics and summarised almost 200 TAM-reprogramming agents investigated in more than 700 clinical trials. Observable overall trends include a high frequency of overlapping strategies against the same therapeutic targets, development of more complex strategies to improve previously ineffective approaches and reliance on combinatory strategies for efficacy. However, strong anti-tumour efficacy is uncommon, which encourages re-directing efforts on identifying biomarkers for eligible patient populations and comparing similar treatments earlier. Future endeavours will benefit from considering the shortcomings of past treatment strategies and accommodating the emerging complexity of TAM biology.