Macrophages impede CD8 T cells from reaching tumor cells and limit the efficacy of anti-PD-1 treatment

Advances in nanoplatform-based multimodal combination therapy activating STING pathway for enhanced anti-tumor immunotherapy

Activation of the cyclic GMP-AMP synthase(cGAS)-stimulator of interferon genes (STING) has great potential to promote antitumor immunity. As a major effector of the cell to sense and respond to the aberrant presence of cytoplasmic double-stranded DNA (dsDNA), inducing the expression and secretion of type I interferons (IFN) and STING, cGAS-STING signaling pathway establishes an effective natural immune response, which is one of the fundamental mechanisms of host defense in organisms. In addition to the release of heterologous DNA due to pathogen invasion and replication, mitochondrial damage and massive cell death can also cause abnormal leakage of the body's own dsDNA, which is then recognized by the DNA receptor cGAS and activates the cGAS-STING signaling pathway. However, small molecule STING agonists suffer from rapid excretion, low bioavailability, non-specificity and adverse effects, which limits their therapeutic efficacy and in vivo application. Various types of nano-delivery systems, on the other hand, make use of the different unique structures and surface modifications of nanoparticles to circumvent the defects of small molecule STING agonists such as fast metabolism and low bioavailability. Also, the nanoparticles are precisely directed to the focal site, with their own appropriate particle size combined with the characteristics of passive or active targeting. Herein, combined with the cGAS-STING pathway to activate the immune system and kill tumor tissues directly or indirectly, which help maximize the use of the functions of chemotherapy, photothermal therapy(PTT), chemodynamic therapy(CDT), and radiotherapy(RT). In this review, we will discuss the mechanism of action of the cGAS-STING pathway and introduce nanoparticle-mediated tumor combination therapy based on the STING pathway. Collectively, the effective multimodal nanoplatform, which can activate cGAS-STING pathway for enhanced anti-tumor immunotherapy, has promising avenue clinical applications for cancer treatment.

Single-cell transcriptomics reveal the effects of chemoimmunotherapy on hypopharyngeal cancer and its tumor microenvironment

Induction chemoimmunotherapy (ICIT) has emerged as a potential treatment option for resectable hypopharyngeal cancer (HPC), while its effectiveness remains limited to a significant portion of HPC cases, and a major challenge behind lies in the lack of reliable molecular markers to identify treatment-resistant patients. In this study, we analyzed biopsy samples of HPC patients collected before and after ICIT, classifying them based on treatment response. By investigating the tumor microenvironment (TME) at the single-cell level, we demonstrated that the heterogeneity within the TME is closely linked to different treatment outcomes. Specially, a strong treatment response correlated with a subpopulation of cancer-associated fibroblasts (CAFs). Additionally, we identified that the S100A2 gene is highly expressed in tumor cells and appears to influence ICIT efficacy. Using bulk RNA sequencing, we estimated cell composition and validated these observations at the protein level. Our research provides a novel approach for identifying genes and cell populations that predict treatment responses in HPC, potentially enabling the timely identification of treatment-resistant patients. This could increase the likelihood of preserving laryngeal function and optimizing treatment strategies.

Nano co-inducer of immunogenic cell death and ferroptosis for anti-tumor immunotherapy

Due to population aging and lifestyle changes, the global tumor burden has increased, making tumor disease a significant challenge in public health. Recently, immunotherapy emerged as an effective approach for tumor treatment by activating and enhancing the body's immune system to precisely identify and attack tumor cells. However, its efficacy was limited by the "cold" immunosuppressive tumor microenvironment (ITME) and the tissue repair capabilities of tumors. To address this issue, we developed a dual-target ferroptosis immune-inducer, FTB@CC, which releases photosensitizer (PS), calcium (Ca2+), and Fe2+ under weakly acidic conditions. Upon near-infrared (NIR) laser irradiation, PSs induced endoplasmic reticulum (ER) stress, producing large amounts of reactive oxygen species (ROS) and releasing significant quantities of damage-associated molecular patterns (DAMPs), which mediated immunogenic cell death (ICD). Simultaneously, Ca2+ overload activates the inflammasome and amplifies cellular cytotoxicity for DAMPs release, eventually activating the ICD pathway. The supplementation of Fe2+ increased iron storage within tumor cells and downregulated the expression of glutathione peroxidase 4 (GPX4), leading to the accumulation of lipid peroxides (LPO) and ultimately resulting in ferroptosis. This multi-level interaction strategy restructured the ITME and induced ICD, overcoming the limitations of single-agent therapies, and significantly enhancing the efficacy of anti-PD-L1 antibody (α-PD-L1) in suppressing tumor cell immune evasion. As a result, it promoted the infiltration of immune cells and inhibited both distal and proximal tumors. This nano-integrated ICD-ferroptosis co-inducer offers an intelligent strategy for effectively overcoming ITME, thereby providing a promising avenue for advanced immunotherapeutic interventions.

Tumor-Associated Macrophages: Polarization, Immunoregulation, and Immunotherapy

Tumor-associated macrophages' (TAMs) origin, polarization, and dynamic interaction in the tumor microenvironment (TME) influence cancer development. They are essential for homeostasis, monitoring, and immune protection. Cells from bone marrow or embryonic progenitors dynamically polarize into pro- or anti-tumor M2 or M1 phenotypes based on cytokines and metabolic signals. Recent advances in TAM heterogeneity, polarization, characterization, immunological responses, and therapy are described here. The manuscript details TAM functions and their role in resistance to PD-1/PD-L1 blockade. Similarly, TAM-targeted approaches, such as CSF-1R inhibition or PI3Kγ-driven reprogramming, are discussed to address anti-tumor immunity suppression. Furthermore, innovative biomarkers and combination therapy may enhance TAM-centric cancer therapies. It also stresses the relevance of this distinct immune cell in human health and disease, which could impact future research and therapies.

A machine learning-based glycolysis and fatty acid metabolism-related prognostic signature is constructed and identified ACSL5 as a novel marker inhibiting the proliferation of breast cancer

INTRODUCTION

A new perspective on cancer metabolism suggests that it varies by context and is diverse. Cancer metabolism reprogramming can create a heterogeneous microenvironment that affects immune cell infiltration and function, complicating the selection of treatment methods. However, the specifics of this relationship remain unclear in breast cancer. This research aims to explore how glycolysis and fatty acid metabolism (GF) influence the immune microenvironment and their predictive capabilities for immunotherapy responses and overall survival.

METHODS

We at first time identified 602 GF-related genes. Utilizing multiple datasets from various centers and employing 10 different machine learning algorithms, we developed a GF-related signature called GFSscore, driven by artificial intelligence.

RESULTS

The GFSscore served as an independent prognostic indicator and demonstrated greater robustness than other models. Its validity was validated through multiple databases. Our study found that breast cancer patients with a high GFSscore, indicative of a greater tendency towards glycolytic activity, experienced poorer prognosis due to immunosuppression from distinct immune evasion mechanisms. Conversely, those with a low GFSscore, more inclined towards fatty acid metabolism, had better outcomes. Additionally, the GFSscore has the potential to forecast how well a patient might respond to immunotherapy and their susceptibility to chemotherapy medications. Moreover, we found that the overexpressed ACSL5 gene inhibits the proliferation of BRCA through experiments.

CONCLUSIONS

The GFSscore may offer patients personalized therapy by identifying new therapeutic targets for tumors. By understanding the relationship between cancer metabolism and the immune microenvironment, we can better tailor treatments to individual patients.

Vascularized tumor-on-a-chip to investigate immunosuppression of CAR-T cells

Chimeric antigen receptor (CAR)-T cell immunotherapy, effective in blood cancers, shows limited success in solid tumors, such as prostate, pancreatic, and brain cancers due, in part, to an immunosuppressive tumor microenvironment (TME). Immunosuppression affects various cell types, including tumor cells, macrophages, and endothelial cells. Conventional murine-based models offer limited concordance with human immunology and cancer biology. Therefore, we have developed a human "tumor-on-a-chip" (TOC) platform to model elements of immunosuppression at high spatiotemporal resolution. Our TOC features an endothelial cell-lined channel that mimics features of an in vivo capillary, such as cell attachment and extravasation across the endothelium and into the TME. Using 70 kDa dextran and fluorescence-recovery-after-photobleaching (FRAP), we confirmed physiologic interstitial flow velocities (0.1-1 μm s-1). Our device demonstrates that tumor-derived factors can diffuse in the opposite direction of interstitial flow to reach the endothelium up to 200 μm away, and at concentrations as high as 20% of those at the tumor margin. M2-like immunosuppressive macrophages and endothelial cells affect prostate tumor cell growth, clustering, and migration. M2-like macrophages also induce PD-L1 and inhibit ICAM-1 gene expression on the adjacent endothelium in a pattern that limits CAR-T cell extravasation and effector function. This observation is abrogated in the presence of the anti-PD-L1 drug atezolizumab. These results provide mechanistic insight for in vivo observations showing limited CAR-T cell extravasation and effector function in solid tumors. Furthermore, they point to a specific role of M2 macrophages in driving CAR-T cell migration into and within the TME and could prove useful in the development of novel therapies to improve solid tumor CAR-T cell therapies.

Translating genetics into tissue: inflammatory cytokine-producing TAMs and PD-L1 tumor expression as poor prognosis factors in cutaneous melanoma

Myeloid cells within tumor microenvironments exhibit significant heterogeneity and play a critical role in influencing clinical outcomes. In this study, we investigated the infiltration of various myeloid cell subtypes in a cohort of cutaneous melanomas, revealing no significant correlation between myeloid cell densities and the occurrence of distant metastasis. We further examined the phenotypic characteristics of primary melanoma tumor-associated macrophages (TAMs) utilizing the seven-phenotype classification recently proposed by Ma et al., derived from extensive pan-cancer single-cell RNA-sequencing studies. First, we analyzed the transcriptomic profile of TAMs isolated from stage IV metastasizing primary melanomas, alongside melanoma-conditioned monocytes cultured in vitro, both supporting the inflammatory cytokine-producing macrophage phenotype. Next, we employed multicolor fluorescence confocal microscopy, to assess the expression of TAM phenotype markers at the protein level in a cohort of primary melanoma samples. Notably, markers indicative of the inflammatory TAM phenotype, quantified at single-cell level, were significantly enriched in metastasizing tumors, demonstrating an independent correlation with shorter disease-free and overall survival (log-rank test, p< 0.0002). Additionally, our screening of phenotype markers expression revealed that PD-L1 positivity in tumor cells, rather than in TAMs, was associated with poor prognosis, highlighting a novel aspect of the immune landscape in cutaneous melanoma.

AXL promotes inflammatory breast cancer progression by regulating immunosuppressive macrophage polarization

BACKGROUND

Tumor-associated macrophages (TAMs) are key promoters of inflammatory breast cancer (IBC), the most aggressive form of breast cancer. The receptor tyrosine kinase AXL is highly expressed in various cancer types, including IBC, but its role in TAMs remains unexplored.

METHODS

We examined the effects of AXL inhibitor TP-0903 on tumor growth and tumor microenvironment (TME) component M2 macrophages (CD206+) in IBC and triple-negative breast cancer mouse models using flow cytometry and immunohistochemical staining. Additionally, we knocked out AXL expression in human THP-1 monocytes and evaluated the effect of AXL signaling on immunosuppressive M2 macrophage polarization and IBC cell growth and migration. We then investigated the underlying mechanisms through RNA sequencing analysis. Last, we performed CIBERSORT deconvolution to analyze the association between AXL expression and tumor-infiltrating immune cell types in tumor samples from the Inflammatory Breast Cancer International Consortium.

RESULTS

We found that inhibiting the AXL pathway significantly reduced IBC tumor growth and decreased CD206+ macrophage populations within tumors. Mechanistically, our in vitro data showed that AXL promoted M2 macrophage polarization and enhanced the secretion of immunosuppressive chemokines, including CCL20, CCL26, and epiregulin, via the transcription factor STAT6 and thereby accelerated IBC cell growth and migration. RNA sequencing analysis further indicated that AXL signaling in immunosuppressive M2 macrophages regulated the expression of molecules and cytokines, contributing to an immunosuppressive TME in IBC. Moreover, high AXL expression was correlated with larger populations of immunosuppressive immune cells but smaller populations of immunoactive immune cells in tissues from patients with IBC.

CONCLUSIONS

AXL signaling promotes IBC growth by inducing M2 macrophage polarization and driving the secretion of immunosuppressive molecules and cytokines via STAT6 signaling, thereby contributing to an immunosuppressive TME. Collectively, these findings highlight the potential of targeting AXL signaling as a novel therapeutic approach for IBC that warrants further investigation in clinical trials.

GPR65 Inactivation in Tumor Cells Drives Antigen-Independent CAR T-cell Resistance via Macrophage Remodeling

SIGNIFICANCE

The study identifies GPR65 as an important determinant of B-cell acute lymphoblastic leukemia response to CAR T-cell therapy. Notably, GPR65 absence signals CAR T resistance. By emphasizing the therapeutic potential of targeting VEGFA or host macrophages, our study identifies routes to optimize CAR T-cell therapy outcomes in hematologic malignancies via tumor microenvironment manipulation.

Immune profiling of gastric adenocarcinomas in EU and LATAM countries identifies global differences in immune subgroups and microbiome influence

BACKGROUND

Gastric cancer (GC) patients from European (EU) and especially Latin American (LATAM) countries are underrepresented in previous large-scale multi-omic studies that have identified clinically relevant subgroups. The LEGACY study aimed to profile the molecular and immunological features of GCs from EU and LATAM countries.

METHODS

Tumor biopsies from 95 EU and 56 LATAM GCs were profiled with immunohistochemistry (CD3, CD8, FOXP3, PD-L1, MSI and HER2), Nanostring mRNA expression analyses, and microbiome sequencing.

RESULTS

Immune profiling identified four distinct immune clusters: a T cell dominant cluster with enriched activation pathways, a macrophage dominant cluster and an immune excluded microenvironment which were equally distributed among the countries. A fourth cluster of mostly Mexican patients consisted of excessive T cell numbers accompanied by enhanced cytokine signaling in absence of enhanced antigen presentation and cytotoxicity signatures and a strong association with H. pylori infection.

DISCUSSION

Both EU and LATAM countries have GCs with a T cell inflamed microenvironment that might benefit from checkpoint inhibition. We identified a highly inflamed GC subgroup that lacked antigen presentation and cytotoxicity associated with H. pylori CagA-positive strains, suggesting their contribution to tumor immune tolerance. Future studies are needed to unravel whether these cancers benefit from immunotherapy as well.

Boosting antitumor immunity in breast cancers: Potential of adjuvants, drugs, and nanocarriers

Despite advancements in breast cancer treatment, therapeutic resistance, and tumor recurrence continue to pose formidable challenges. Therefore, a deep knowledge of the intricate interplay between the tumor and the immune system is necessary. In the pursuit of combating breast cancer, the awakening of antitumor immunity has been proposed as a compelling avenue. Tumor stroma in breast cancers contains multiple stromal and immune cells that impact the resistance to therapy and also the expansion of malignant cells. Activating or repressing these stromal and immune cells, as well as their secretions can be proposed for exhausting resistance mechanisms and repressing tumor growth. NK cells and T lymphocytes are the prominent components of breast tumor immunity that can be triggered by adjuvants for eradicating malignant cells. However, stromal cells like endothelial and fibroblast cells, as well as some immune suppressive cells, consisting of premature myeloid cells, and some subsets of macrophages and CD4+ T lymphocytes, can dampen antitumor immunity in favor of breast tumor growth and therapy resistance. This review article aims to research the prospect of harnessing the power of drugs, adjuvants, and nanoparticles in awakening the immune reactions against breast malignant cells. By investigating the immunomodulatory properties of pharmacological agents and the synergistic effects of adjuvants, this review seeks to uncover the mechanisms through which antitumor immunity can be triggered. Moreover, the current review delineates the challenges and opportunities in the translational journey from bench to bedside.

The Prognostic Impact of the Tumor Immune Microenvironment in Synovial Sarcoma: An Immunohistochemical Analysis Using Digital Pathology and Conventional Interpretation

BACKGROUND AND OBJECTIVES

Innate and adaptive immune responses serve a crucial role in neoplasms. The interaction of immune cells with the neoplastic tissue influences tumor behavior, resulting in either pro-tumorigenic or anti-tumorigenic effects. However, the prognostic significance of the tumor immune microenvironment (TIME) in synovial sarcoma (SS) remains poorly studied. This study aimed to analyze the TIME of SS to determine its impact on the prognosis by examining the intratumoral lymphocytic and macrophagic infiltrate and its potential correlation with survival and recurrence.

METHODS

We conducted a retrospective observational study of 49 fusion-confirmed SS cases collected from two different institutions. We obtained clinical and follow-up data, and SSs were histologically classified according to WHO criteria. Immunohistochemical analysis, including of CD163, CD68, CD3, CD8, and CD20, was conducted in tissue microarrays using an analog scale. We examined the whole-slide tissue for the 23 cases with sufficient material available and then assessed the positive area by scanning the slides and analyzing the images using QuPath (0.4.4, Belfast, Northern Ireland) to calculate the positive area in an immune hotspot. We correlated the expression of these markers with clinical outcomes. A log-rank test and Kaplan-Meyer curves were used as appropriate (significance: p ≤ 0.05).

RESULTS

The most frequent morphological subtype was monophasic (59.6%), followed by biphasic (26.9%) and undifferentiated (7%). The mean disease specific survival (DSS) was 55.3 months, with a median of 33 months. The median overall survival (OS) was 50 months (range: 2-336 months). Both evaluation methods showed a good correlation for all antibodies, with Chi-square values of p < 0.05. All cases showed variable amounts of CD163-positive macrophages. The cases that showed a higher density of CD163-positive macrophages in whole-slide images subjected to digital analysis demonstrated an improved OS and DSS on Kaplan-Meier curves. Cases with lower CD8 and CD3 positivity showed a tendency toward faster progression and a slightly worse prognosis.

CONCLUSIONS

The tumor immune microenvironment in sarcomas is a complex system that requires further investigation to fully understand its impact on tumorigenesis and patient clinical outcomes. Our results demonstrate that a higher amount of intratumoral CD163-positive macrophage infiltrate is associated with an increased OS and DSS. Our findings show that digital pathology is more precise than subjective quantitative analysis.

Role of Tumor-Associated Macrophages in Breast Cancer Immunotherapy

Breast cancer (BC) is the second leading cause of death among women worldwide. Immunotherapy has become an effective treatment for BC patients due to the rapid development of medical technology. Considerable breakthroughs have been made in research, marking the beginning of a new era in cancer treatment. Among them, various cancer immunotherapies such as immune checkpoint inhibitors (ICIs), cancer vaccines, and adoptive cell transfer are effective and have good prospects. The tumor microenvironment (TME) plays a crucial role in determining the outcomes of tumor immunotherapy. Tumor-associated macrophages (TAMs) are a key component of the TME, with an immunomodulatory effect closely related to the immune evasion of tumor cells, thereby affecting malignant progression. TAMs also significantly affect the therapeutic effect of ICIs (such as programmed death 1/programmed death ligand 1 (PD-1/PD-L1) inhibitors). TAMs are composed of multiple heterogeneous subpopulations, including M1 phenotypes macrophages (M1) and M2 phenotypes macrophages (M2). Furthermore, they mainly play an M2-like role and moderate a variety of harmful consequences such as angiogenesis, immunosuppression, and metastasis. Therefore, TAMs have become a key area of focus in the development of tumor therapies. However, several tumor immunotherapy studies demonstrated that ICIs are effective only in a small number of solid cancers, and tumor immunotherapy still faces relevant challenges in the treatment of solid tumors. This review explores the role of TAMs in BC immunotherapy, summarizing their involvement in BC development. It also explains the classification and functions of TAMs, outlines current tumor immunotherapy approaches and combination therapies, and discusses the challenges and potential strategies for TAMs in immuno-oncology treatments.

Peritoneal resident macrophages constitute an immunosuppressive environment in peritoneal metastasized colorectal cancer

Patients with peritoneal metastasized colorectal cancer (PM-CRC) have a dismal prognosis. We hypothesized that an immunosuppressive environment in the peritoneal cavity underlies poor prognosis. We define the composition of the human peritoneal immune system (PerIS) using single-cell technologies in 18 patients with- and without PM-CRC, as well as in matched peritoneal metastases (n = 8). Here we show that the PerIS contains abundant immunosuppressive C1Q+VSIG4+ and SPP1+VSIG4+ peritoneal-resident macrophages (PRMs), as well as monocyte-like cavity macrophages (mono-CMs), which share features with tumor-associated macrophages, even in homeostasis. In PM-CRC, expression of immunosuppressive cytokines IL10 and VEGF increases, while simultaneously expression of antigen-presenting molecules decreases in PRMs. These intratumoral suppressive PRMs originate from the PerIS, and intraperitoneal depletion of PRMs in vivo using anti-CSF1R combined with anti-PD1 significantly reduces tumor burden and improves survival. Thus, PRMs define a metastatic site-specific immunosuppressive niche, and targeting PRMs is a promising treatment strategy for PM-CRC.

Multimodal sequencing of neoadjuvant nivolumab treatment in hepatocellular carcinoma reveals cellular and molecular immune landscape for drug response

A striking characteristic of liver cancer is its extensive heterogeneity, particularly with regard to its varied response to immunotherapy. In this study, we employed multimodal sequencing approaches to explore the various aspects of neoadjuvant nivolumab treatment in liver cancer patients. We used spatially-resolved transcriptomics, single- and bulk-cell transcriptomics, and TCR clonotype analyses to examine the spatiotemporal dynamics of the effects of nivolumab. We observed a significantly higher clonal expansion of T cells in the tumors of patients who responded to the treatment, while lipid accumulation was detected in those of non-responders, likely due to inherent differences in lipid metabolic processes. Furthermore, we found a preferential enrichment of T cells, which was associated with a better drug response. Our results also indicate a functional antagonism between tumor-associated macrophages (TAMs) and CD8 cells and their spatial separation. Notably, we identified a UBASH3B/NR1I2/CEACAM1/HAVCR2 signaling axis, highlighting the intense communication among TAMs, tumor cells, and T-cells that leads to pro-tumorigenic outcomes resulting in poorer nivolumab response. In summary, using integrative multimodal sequencing investigations, combined with the multi-faceted exploration of pre- and post-treatment samples of neoadjuvant nivolumab-treated HCC patients, we identified useful mechanistic determinants of therapeutic response. We also reconstructed the spatiotemporal model that recapitulates the physiological restoration of T cell cytotoxicity by anti-PD1 blockade. Our findings could provide important biomarkers and explain the mechanistic basis differentiating the responders and non-responders.

Induction of macrophage efferocytosis in pancreatic cancer via PI3Kγ inhibition and radiotherapy promotes tumour control

BACKGROUND

The immune suppression mechanisms in pancreatic ductal adenocarcinoma (PDAC) remain unknown, but preclinical studies have implicated macrophage-mediated immune tolerance. Hence, pathways that regulate macrophage phenotype are of strategic interest, with reprogramming strategies focusing on inhibitors of phosphoinositide 3-kinase-gamma (PI3Kγ) due to restricted immune cell expression. Inhibition of PI3Kγ alone is ineffective in PDAC, despite increased infiltration of CD8+ T cells.

OBJECTIVE

We hypothesised that the immune stimulatory effects of radiation, and its ability to boost tumour antigen availability could synergise with PI3Kγ inhibition to augment antitumour immunity.

DESIGN

We used orthoptic and genetically engineered mouse models of pancreatic cancer (LSL-KrasG12D/+;Trp53R172H/+;Pdx1-Cre). Stereotactic radiotherapy was delivered using contrast CT imaging, and PI3Kγ inhibitors by oral administration. Changes in the tumour microenvironment were quantified by flow cytometry, multiplex immunohistochemistry and RNA sequencing. Tumour-educated macrophages were used to investigate efferocytosis, antigen presentation and CD8+ T cell activation. Single-cell RNA sequencing data and fresh tumour samples with autologous macrophages to validate our findings.

RESULTS

Tumour-associated macrophages that employ efferocytosis to eradicate apoptotic cells can be redirected to present tumour antigens, stimulate CD8+ T cell responses and increase local tumour control. Specifically, we demonstrate how PI3Kγ signalling restricts inflammatory macrophages and that inhibition supports MERTK-dependent efferocytosis. We further find that the combination of PI3Kγ inhibition with targeted radiotherapy stimulates inflammatory macrophages to invoke a pathogen-induced like efferocytosis that switches from immune tolerant to antigen presenting.

CONCLUSIONS

Our data supports a new immunotherapeutic approach and a translational rationale to improve survival in PDAC.

Deciphering T-cell exhaustion in the tumor microenvironment: paving the way for innovative solid tumor therapies

In solid tumors, the tumor microenvironment (TME) is a complex mix of tumor, immune, stromal cells, fibroblasts, and the extracellular matrix. Cytotoxic T lymphocytes (CTLs) constitute a fraction of immune cells that may infiltrate into the TME. The primary function of these T-cells is to detect and eliminate tumor cells. However, due to the immunosuppressive factors present in the TME primarily mediated by Myeloid-Derived Suppressor Cells (MDSCs), Tumor associated macrophages (TAMs), Cancer Associated Fibroblasts (CAFs) as well as the tumor cells themselves, T-cells fail to differentiate into effector cells or become dysfunctional and are unable to eliminate the tumor. In addition, chronic antigen stimulation within the TME also leads to a phenomenon, first identified in chronic lymphocytic choriomeningitis virus (LCMV) infection in mice, where the T-cells become exhausted and lose their effector functions. Exhausted T-cells (Tex) are characterized by the presence of remarkably conserved inhibitory receptors, transcription and signaling factors and the downregulation of key effector molecules. Tex cells have been identified in various malignancies, including melanoma, colorectal and hepatocellular cancers. Recent studies have indicated novel strategies to reverse T-cell exhaustion. These include checkpoint inhibitor blockade targeting programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin-domain containing-3 (Tim-3), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), or combinations of different immune checkpoint therapies (ICTs) or combination of ICTs with cytokine co-stimulation. In this review, we discuss aspects of T-cell dysfunction within the TME with a focus on T-cell exhaustion. We believe that gaining insight into the mechanisms of T-cell exhaustion within the TME of human solid tumors will pave the way for developing therapeutic strategies to target and potentially re-invigorate exhausted T-cells in cancer.

Key immune cells and their crosstalk in the tumor microenvironment of bladder cancer: insights for innovative therapies

Bladder cancer (BC) is a heterogeneous disease associated with high mortality if not diagnosed early. BC is classified into non-muscle-invasive BC (NMIBC) and muscle-invasive BC (MIBC), with MIBC linked to poor systemic therapy response and high recurrence rates. Current treatments include transurethral resection with Bacillus Calmette-Guérin (BCG) therapy for NMIBC and radical cystectomy with chemotherapy and/or immunotherapy for MIBC. The tumor microenvironment (TME) plays a critical role in cancer progression, metastasis, and therapeutic efficacy. A comprehensive understanding of the TME's complex interactions holds substantial translational significance for developing innovative treatments. The TME can contribute to therapeutic resistance, particularly in immune checkpoint inhibitor (ICI) therapies, where resistance arises from tumor-intrinsic changes or extrinsic TME factors. Recent advancements in immunotherapy highlight the importance of translational research to address these challenges. Strategies to overcome resistance focus on remodeling the TME to transform immunologically "cold" tumors, which lack immune cell infiltration, into "hot" tumors that respond better to immunotherapy. These strategies involve disrupting cancer-microenvironment interactions, inhibiting angiogenesis, and modulating immune components to enhance anti-tumor responses. Key mechanisms include cytokine involvement [e.g., interleukin-6 (IL-6)], phenotypic alterations in macrophages and natural killer (NK) cells, and the plasticity of cancer-associated fibroblasts (CAFs). Identifying potential therapeutic targets within the TME can improve outcomes for MIBC patients. This review emphasizes the TME's complexity and its impact on guiding novel therapeutic approaches, offering hope for better survival in MIBC.

Spatial mapping of immune cell environments in NF2-related schwannomatosis vestibular schwannoma

NF2-related Schwannomatosis (NF2 SWN) is a rare disease characterised by the growth of multiple nervous system neoplasms, including bilateral vestibular schwannoma (VS). VS tumours are characterised by extensive leucocyte infiltration. However, the immunological landscape in VS and the spatial determinants within the tumour microenvironment that shape the trajectory of disease are presently unknown. In this study, to elucidate the complex immunological networks across VS, we performed imaging mass cytometry (IMC) on clinically annotated VS samples from NF2 SWN patients. We reveal the heterogeneity in neoplastic cell, myeloid cell and T cell populations that co-exist within VS, and that distinct myeloid cell and Schwann cell populations reside within varied spatial contextures across characteristic Antoni A and B histomorphic niches. Interestingly, T-cell populations co-localise with tumour-associated macrophages (TAMs) in Antoni A regions, seemingly limiting their ability to interact with tumorigenic Schwann cells. This spatial landscape is altered in Antoni B regions, where T-cell populations appear to interact with PD-L1+ Schwann cells. We also demonstrate that prior bevacizumab treatment (VEGF-A antagonist) preferentially reduces alternatively activated-like TAMs, whilst enhancing CD44 expression, in bevacizumab-treated tumours. Together, we describe niche-dependent modes of T-cell regulation in NF2 SWN VS, indicating the potential for microenvironment-altering therapies for VS.

Tebentafusp, a T cell engager, promotes macrophage reprogramming and in combination with IL-2 overcomes macrophage immunosuppression in cancer

Uveal melanoma (UM) is the most common intraocular cancer in adults, with metastatic disease (mUM) occurring in approximately half of the patients. Tebentafusp, an immune-mobilizing monoclonal T cell receptor against cancer (ImmTAC), is a therapeutic shown to improve overall survival (OS) in HLA-A*02:01+ adult patients with mUM. Here we investigate the impact of tumor-associated macrophages (TAM) on ImmTAC activity. In vitro, M2 macrophages inhibit ImmTAC-mediated tumor-killing in a dose-dependent and contact-dependent manner. Accordingly, high baseline intratumoral TAM-to-T cell ratios correlate with shorter OS (HR = 2.09, 95% CI, 1.31-3.33, p = 0.002) in tebentafusp-treated mUM patients from a phase 2 trial. By contrast, IL-2 conditioning of T cells overcomes M2 macrophage-mediated suppression in vitro, while ImmTAC treatment leads to M2-to-M1 macrophage reprogramming both in vitro and in tebentafusp-treated mUM patients. Overall, we show that tebentafusp reshapes the tumor microenvironment to enhance anti-tumor T cell activity, whilst combining tebentafusp with IL-2 may enhance benefit in patients with high levels of TAM.

Feature gene selection and functional validation of SH3KBP1 in infantile hemangioma using machine learning

BACKGROUND

Infantile hemangioma (IH) is a prevalent vascular tumor in infancy with a complex pathogenesis that remains unclear. This study aimed to investigate the underlying mechanisms of IH using comprehensive bioinformatics analyses and in vitro experiments.

METHODS

Using GSE127487, we identified differentially expressed genes (DEGs) in IH patients across three age groups (6, 12, and 24 months). GO and KEGG enrichment analyses were performed to identify biological processes and pathways. Immune cell infiltration, transcription factor target genes, miRNA expression, and metabolic pathways were analyzed. WGCNA classified IH patients into clusters, and machine learning algorithms identified key genes. The role of SH3KBP1, the most abundantly expressed gene in the skin, was investigated using shRNA knockdown and functional assays.

RESULTS

Gene expression in IH patients exhibited dynamic changes with age. Cellular processes and signaling pathways were consistent in the early proliferative phase, with gradual resolution in the late phase. Immune infiltration analysis revealed reduced immune cells in patients, while Pericytes were increased. NR5A1 was downregulated, while ZNF112, HSF4, and multiple miRNAs were upregulated with age. Metabolic pathways confirmed differences between proliferative and involution phases. WGCNA identified two clusters: Cluster 1 (angiogenesis and signal transduction) and Cluster 2 (metabolic and synthetic processes). Key genes, including SH3KBP1, were identified using machine learning algorithms. In vitro experiments demonstrated SH3KBP1's crucial role in cell migration and invasion.

CONCLUSION

This study unravels the gene expression and regulatory mechanisms of IH at different stages, providing new insights into its pathophysiology. SH3KBP1 offers a potential biomarker for future diagnostic and therapeutic strategies.

Macrophage-derived lncRNAs in cancer: regulators of tumor progression and therapeutic targets

Macrophages are key tumor microenvironment (TME) regulators, exhibiting remarkable plasticity that enables them to either suppress or promote cancer progression. Emerging evidence highlights the critical role of macrophage-derived long non-coding RNAs (lncRNAs) in shaping tumor immunity, influencing macrophage polarization, immune evasion, angiogenesis, metastasis, and therapy resistance. This review comprehensively elucidates the functional roles of M1- and M2-associated lncRNAs, detailing their molecular mechanisms and impact on cancer pathogenesis. In summary, elucidating the roles of lncRNAs derived from macrophages in cancer progression offers new avenues for therapeutic strategies, significantly improving patient outcomes in the fight against the disease. Further research into the functional significance of these lncRNAs and the development of targeted therapies is essential to harness their potential fully in clinical applications. We further explore their potential as biomarkers for cancer prognosis and therapeutic targets for modulating macrophage activity to enhance anti-cancer immunity. Targeting macrophage-derived lncRNAs represents a promising avenue for precision oncology, offering novel strategies to reshape the TME and improve cancer treatment outcomes.

The contribution of the monocyte-macrophage lineage to immunotherapy outcomes

ABSTRACT

Macrophages execute core functions in maintaining tissue homeostasis, in which their extensive plasticity permits a spectrum of functions from tissue remodeling to immune defense. However, perturbations to tissue-resident macrophages during disease, and the subsequent emergence of monocyte-derived macrophages, can hinder tissue recovery and promote further damage through inflammatory and fibrotic programs. Gaining a fundamental understanding of the critical pathways defining pathogenic macrophage populations enables the development of targeted therapeutic approaches to improve disease outcomes. In the setting of chronic graft-versus-host disease (cGVHD), which remains the major complication of allogeneic hematopoietic stem cell transplantation, colony-stimulating factor 1 (CSF1)-dependent donor-derived macrophages have been identified as key pathogenic mediators of fibrotic skin and lung disease. Antibody blockade of the CSF1 receptor (CSF1R) to induce macrophage depletion showed remarkable capacity to prevent fibrosis in preclinical models and has subsequently demonstrated impressive efficacy for improving cGVHD in ongoing clinical trials. Similarly, macrophage depletion approaches are currently under investigation for their potential to augment responses to immune checkpoint inhibition. Moreover, both monocyte and tissue-resident macrophage populations have recently been implicated as mediators of the numerous toxicities associated with chimeric antigen receptor T-cell therapy, further highlighting potential avenues of macrophage-based interventions to improve clinical outcomes. Herein, we examine the current literature on basic macrophage biology and contextualize this in the setting of cellular and immunotherapy. Additionally, we highlight mechanisms by which macrophages can be targeted, largely by interfering with the CSF1/CSF1R signaling axis, for therapeutic benefit in the context of both cellular and immunotherapy.

Deciphering functional tumor-immune crosstalk through highly multiplexed imaging and deep visual proteomics

Deciphering the intricate tumor-immune interactions within the microenvironment is crucial for advancing cancer immunotherapy. Here, we introduce mipDVP, an advanced approach integrating highly multiplexed imaging, single-cell laser microdissection, and sensitive mass spectrometry to spatially profile the proteomes of distinct cell populations in a human colorectal and tonsil cancer with high sensitivity. In a colorectal tumor-a representative cold tumor-we uncovered spatial compartmentalization of an immunosuppressive macrophage barrier that potentially impedes T cell infiltration. Spatial proteomic analysis revealed distinct functional states of T cells in different tumor compartments. In a tonsil cancer sample-a hot tumor-we identified significant proteomic heterogeneity among cells influenced by proximity to cytotoxic T cell subtypes. T cells in the tumor parenchyma exhibit metabolic adaptations to hypoxic regions. Our spatially resolved, highly multiplexed strategy deciphers the complex cellular interplay within the tumor microenvironment, offering valuable insights for identifying immunotherapy targets and predictive signatures.

Stratification of the immunotypes of tongue squamous cell carcinoma to improve prognosis and the response to immune checkpoint inhibitors

OBJECTIVES

An understanding of the tumor immune microenvironment is required to improve treatment, especially the selection of immune checkpoint inhibitors (ICIs). In this study, we stratified the immunotypes of tongue squamous cell carcinoma (TSCC) based on the results of comprehensive immune profiling.

METHODS

We enrolled 87 therapy-naïve TSCC and 17 ICI-treated TSCC patients who underwent glossectomy without any other prior therapy. Comprehensive immune profile analyses employed multiplex immunofluorescence and tissue imaging.

RESULTS

Based on the hierarchies of 58 immune parameters and the spatial distances between cytotoxic T lymphocytes (CTL) and tumor cells, we stratified five immunotypes: Immunoactive type I, border type II, immunosuppressed type III, immunoisolating type IV, and immunodesert type V. The type I frequency was only 16%. Most TSCCs (~ 70%) were of types III-V. The CTL density (CTL-D) was closely correlated with the PD-L1+ pan-macrophages (panM)-D, and the panM-D closely correlated with the PD-1+ CTL-D. This indicated that PD-1 and PD-L1 expression required macrophages and CTL recruitment in the tumor microenvironment. No ICI-treated TSCC patients, all of whom were recurrent/metastatic cases, were of the type I immunotype, and almost half (47.0%) were of the immunodesert type V. Most cases exhibited an imbalance between T-cell PD-1 and macrophage PD-L1 expression.

CONCLUSION

We defined five TSCC-specific immunotypes based on the results of comprehensive immune profiling analyses. Immunoactive type, which would be sensitive to ICI monotherapy, was rare, and most TSCC cases exhibited immune-regulated immunotypes. Immunotype-based personalized treatments are required to improve clinical outcomes.

The role of tumor-associated macrophages in lung cancer

Lung cancer remains a leading cause of cancer-related deaths worldwide, necessitating innovative treatments. Tumor-associated macrophages (TAMs) are primary immunosuppressive effectors that foster tumor proliferation, angiogenesis, metastasis, and resistance to therapy. They are broadly categorized into proinflammatory M1 and tumor-promoting M2 phenotypes, with elevated M2 infiltration correlating with poor prognosis. Strategies aimed at inhibiting TAM recruitment, depleting TAMs, or reprogramming M2 to M1 are therefore highly promising. Key signaling pathways, such as CSF-1/CSF-1R, IL-4/IL-13-STAT6, TLRs, and CD47-SIRPα, regulate TAM polarization. Additionally, macrophage-based drug delivery systems permit targeted agent transport to hypoxic regions, enhancing therapy. Preclinical studies combining TAM-targeted therapies with chemotherapy or immune checkpoint inhibitors have yielded improved responses and prolonged survival. Several clinical trials have also reported benefits in previously unresponsive patients. Future work should clarify the roles of macrophage-derived exosomes, cytokines, and additional mediators in shaping the immunosuppressive tumor microenvironment. These insights will inform the design of next-generation drug carriers and optimize combination immunotherapies within precision medicine frameworks. Elucidating TAM phenotypes and their regulatory molecules remains central to developing novel strategies that curb tumor progression and ultimately improve outcomes in lung cancer. Importantly, macrophage-based immunomodulation may offer expanded treatment avenues.

Utilizing Nanoparticles to Overcome Anti-PD-1/PD-L1 Immunotherapy Resistance in Non-Small Cell Lung cancer: A Potential Strategy

Lung cancer is the leading cause of cancer-related mortality globally, with non-small cell lung cancer (NSCLC) constituting 85% of cases. Immune checkpoint inhibitors (ICIs) represented by anti-programmed cell death protein 1 (PD-1)/ programmed cell death ligand 1 (PD-L1) have emerged as a promising frontier in cancer treatment, effectively extending the survival of patients with NSCLC. However, the efficacy of ICIs exhibits significant variability across diverse patient populations, with a substantial proportion showing poor responsiveness and acquired resistance in those initially responsive to ICIs treatments. With the advancement of nanotechnology, nanoparticles offer unique advantages in tumor immunotherapy, including high permeability and prolonged retention(EPR) effects, enhanced drug delivery and stability, and modulation of the inflammatory tumor microenvironment(TME). This review summarizes the mechanisms of resistance to ICIs in NSCLC, focusing on tumor antigens loss and defective antigen processing and presentation, failure T cell priming, impaired T cell migration and infiltration, immunosuppressive TME, and genetic mutations. Furthermore, we discuss how nanoparticles, through their intrinsic properties such as the EPR effect, active targeting effect, shielding effect, self-regulatory effect, and synergistic effect, can potentiate the efficacy of ICIs and reverse resistance. In conclusion, nanoparticles serve as a robust platform for ICIs-based NSCLC therapy, aiding in overcoming resistance challenges.

Advancing Immunotherapy in Pancreatic Cancer: A Brief Review of Emerging Adoptive Cell Therapies

Pancreatic cancer has the lowest 5-year survival rate (13%) among major cancers and is the third leading cause of cancer-related deaths in the United States. The high lethality of this cancer is attributed to its insidious onset, late-stage diagnosis, rapid progression, and limited treatment options. Addressing these challenges requires a deeper understanding of the complex tumor microenvironment to identify novel therapeutic targets. Newer approaches like adoptive cell therapy have shown remarkable success in treating hematological malignancies, but their application in solid tumors, particularly pancreatic cancer, is still in the early stages of development. ACT broadly involves isolating immune cells (T lymphocytes, Natural Killer cells, and macrophages) from the patient, followed by genetic engineering to enhance and mount a specific anti-tumor response. Various ACT modalities are under investigation for pancreatic cancer, including chimeric antigen receptor T cells (CAR-T), chimeric antigen receptor NK cells (CAR-NK), tumor-infiltrating lymphocytes (TIL), T-cell receptor (TCR)-engineered T cells, and cytokine-induced killer cells (CIK). Major hurdles have been identifying actionable tumor antigens and delivering focused cellular therapies to overcome the immunosuppressive and dense fibrotic stroma surrounding the pancreatic cancer. Further studies are needed to explore the limitations faced by cellular therapy in pancreatic cancer and identify novel combination treatment approaches in order to improve clinical outcomes.

The cardio-oncologic burden of breast cancer: molecular mechanisms and importance of preclinical models

Breast cancer, the most prevalent cancer affecting women worldwide, poses a significant cardio-oncological burden. Despite advancements in novel therapeutic strategies, anthracyclines, HER2 antagonists, and radiation remain the cornerstones of oncological treatment. However, each carries a risk of cardiotoxicity, though the molecular mechanisms underlying these adverse effects differ. Common mechanisms include DNA damage response, increased reactive oxygen species, and mitochondrial dysfunction, which are key areas of ongoing research for potential cardioprotective strategies. Since these mechanisms are also essential for effective tumor cytotoxicity, we explore tumor-specific effects, particularly in hereditary breast cancer linked to BRCA1 and BRCA2 mutations. These genetic variants impair DNA repair mechanisms, increase the risk of tumorigenesis and possibly for cardiotoxicity from treatments such as anthracyclines and HER2 antagonists. Novel therapies, including immune checkpoint inhibitors, are used in the clinic for triple-negative breast cancer and improve the oncological outcomes of breast cancer patients. This review discusses the molecular mechanisms underlying BRCA dysfunction and the associated pathological pathways. It gives an overview of preclinical models of breast cancer, such as genetically engineered mouse models, syngeneic murine models, humanized mouse models, and various in vitro and ex vivo systems and models to study cardiovascular side effects of breast cancer therapies. Understanding the underlying mechanism of cardiotoxicity and developing cardioprotective strategies in preclinical models are essential for improving treatment outcomes and reducing long-term cardiovascular risks in breast cancer patients.

Changes in tumor and cardiac metabolism upon immune checkpoint

Cardiovascular disease and cancer are the leading causes of death in the Western world. The associated risk factors are increased by smoking, hypertension, diabetes, sedentary lifestyle, aging, unbalanced diet, and alcohol consumption. Therefore, the study of cellular metabolism has become of increasing importance, with current research focusing on the alterations and adjustments of the metabolism of cancer patients. This may also affect the efficacy and tolerability of anti-cancer therapies such as immune-checkpoint inhibition (ICI). This review will focus on metabolic adaptations and their consequences for various cell types, including cancer cells, cardiac myocytes, and immune cells. Focusing on ICI, we illustrate how anti-cancer therapies interact with metabolism. In addition to the desired tumor response, we highlight that ICI can also lead to a variety of side effects that may impact metabolism or vice versa. With regard to the cardiovascular system, ICI-induced cardiotoxicity is increasingly recognized as one of the most life-threatening adverse events with a mortality of up to 50%. As such, significant efforts are being made to assess the specific interactions and associated metabolic changes associated with ICIs to improve both efficacy and management of side effects.

Tumor-associated-fibrosis and active collagen-CD44 axis characterize a poor-prognosis subtype of gastric cancer and contribute to tumor immunosuppression

BACKGROUND

Tumor-associated fibrosis modifies the tumor microenvironment (TME), hinders the infiltration and activity of cytotoxic immune cells, and is a critical pathological process leading to the ineffectiveness of tumor immunotherapy in gastric cancer (GC). However, the specific mechanisms and interventions are yet to be fully explored.

METHODS

Our study included 375 gastric cancer samples from TCGA, 1 single-cell RNA sequencing (scRNA-seq) dataset comprising of 15 gastric cancer samples from GEO, 19 cohorts of immunotherapy and 2 GWAS datasets. Consensus clustering identified a gastric cancer subtype characterized primarily by fibrosis, and various methods such as pseudotime analysis, CellChat analysis and Colocalization analysis were used to explore its mechanisms.

RESULTS

A subtype of gastric cancer was identified with poor prognosis, characterized by higher malignancy, drug resistance, and poor immune infiltration, associated with elevated expression of genes related with Extracellular matrix (ECM). Single-cell transcriptome analysis showed active Collagen-CD44 signaling axis between cancer-associated fibroblasts (CAFs) and immune cells in gastric cancer, with ECM-related genes upregulated during tumor progression. The expression of CD44 was significantly elevated in the subtype, associated with poor prognosis and tumor immune suppression in gastric cancer, potentially involved in the recruitment of immunosuppressive cells such as M2 macrophages and regulatory T cells (Tregs) and the upregulation of multiple immune checkpoints including PD-1/PD-L1.

CONCLUSION

Our study identified a new subtype of gastric cancer, revealing that fibrosis is a critical mechanism driving immune suppression in gastric cancer and emphasizing the central role of the Collagen-CD44 signaling axis. The Collagen-CD44 signaling axis has the potential to serve as a novel therapeutic target for gastric cancer by enhancing immune cell-mediated tumor suppression. By combining it with immune checkpoint inhibitors (ICIs), it may improve the efficacy of immunotherapy for gastric cancer and offer new hope for treatment.

Phase I study of BMS-986299, an NLRP3 agonist, as monotherapy and in combination with nivolumab and ipilimumab in patients with advanced solid tumors

PURPOSE

BMS-986299 is a first-in-class, NOD-, LRR-, and pyrin-domain containing-3 (NLRP3) inflammasome agonist enhancing adaptive immune and T-cell memory responses.

MATERIALS AND METHODS

This was a phase-I (NCT03444753) study that assessed the safety and tolerability of intra-tumoral BMS-986299 monotherapy (part 1A) and in combination (part 1B) with nivolumab, and ipilimumab in advanced solid tumors. Reported here are single-center results.

RESULTS

36 patients were enrolled, with breast (31%), colorectal (17%), and head and neck (14%) being the more commonly enrolled cancers. Most patients (58%) had received prior immunotherapy. Therapy was well-tolerated, with G1-G2 fever (70%), neutrophilia (36%), and leukocytosis (33%) being the most common treatment-related adverse events with one case of G4 interstitial nephritis and one case of G3 hepatotoxicity and G3 colitis. Intratumoral BMS-986299 monotherapy resulted in dose-dependent increases in systemic exposure with increase in tumor CTLs (67%), CD4+ TILs (63%), along with notable above twofold increases in serum IL-1B, G-CSF and IL-6 at doses above 2000 µg. Systemic BMS-986299 exposure was positively associated with systemic cytokine elevation for G-CSF and IL-6. No antitumor activity was noted in BMS-986299 monotherapy cohort. However, in the combination therapy cohort (BMS-986299+nivolumab+ipilimumab), overall objective response rate was 10%, with confirmed PRs observed in TNBC, hormone receptor-positive, human epidermal growth factor receptor 2 negative breast cancer, and cutaneous squamous cell carcinoma.

CONCLUSION

BMS-986299 in combination with immune checkpoint inhibitors demonstrated manageable toxicities, good tolerability, and promising antitumor activity in certain cancer types.

TRIAL REGISTRATION NUMBER

NCT03444753.

Resistance mechanisms to immune checkpoint inhibitors: updated insights

The last decade has witnessed unprecedented succusses with the use of immune checkpoint inhibitors in treating cancer. Nevertheless, the proportion of patients who respond favorably to the treatment remained rather modest, partially due to treatment resistance. This has fueled a wave of research into potential mechanisms of resistance to immune checkpoint inhibitors which can be classified into primary resistance or acquired resistance after an initial response. In the current review, we summarize what is known so far about the mechanisms of resistance in terms of being tumor-intrinsic or tumor-extrinsic taking into account the multimodal crosstalk between the tumor, immune system compartment and other host-related factors.

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.

Targeting CD206+ macrophages disrupts the establishment of a key antitumor immune axis

CD206 is a common marker of a putative immunosuppressive "M2" state in tumor-associated macrophages (TAMs). We made a novel conditional CD206 (Mrc1) knock-in mouse to specifically visualize and/or deplete CD206+ TAMs. Early depletion of CD206+ macrophages and monocytes (Mono/Macs) led to the indirect loss of conventional type I dendritic cells (cDC1), CD8 T cells, and NK cells in tumors. CD206+ TAMs robustly expressed CXCL9, contrasting with stress-responsive Spp1-expressing TAMs and immature monocytes, which became prominent with early depletion. CD206+ TAMs differentially attracted activated CD8 T cells, and the NK and CD8 T cells in CD206-depleted tumors were deficient in Cxcr3 and cDC1-supportive Xcl1 and Flt3l expressions. Disrupting this key antitumor axis decreased tumor control by antigen-specific T cells in mice. In human cancers, a CD206Replete, but not a CD206Depleted Mono/Mac gene signature correlated robustly with CD8 T cell, cDC1, and NK signatures and was associated with better survival. These findings negate the unqualified classification of CD206+ "M2-like" macrophages as immunosuppressive.

Gastric cancer-derived exosomal let-7 g-5p mediated by SERPINE1 promotes macrophage M2 polarization and gastric cancer progression

BACKGROUND

Tumor-associated macrophages (TAMs), particularly M2-polarized TAMs, are significant contributors to tumor progression, immune evasion, and therapy resistance in gastric cancer (GC). Despite efforts to target TAM recruitment or depletion, clinical efficacy remains limited. Consequently, the identification of targets that specifically inhibit or reprogram M2-polarized TAMs presents a promising therapeutic strategy.

OBJECTIVE

This study aims to identify a dual-function target in GC cells that drives both malignant phenotypes and M2 macrophage polarization, revealing its molecular mechanisms to provide novel therapeutic targets for selectivly targeting M2-polarized TAMs in GC.

METHODS

Transcriptomic and clinical data from GC and adjacent tissues were utilized to identify mRNAs associated with high M2 macrophage infiltration and poor prognosis. Single-cell sequencing elucidated cell types expressing the target gene. Transwell co-culture and exosome intervention experiments demonstrated its role in M2 polarization. Small RNA sequencing of exosomes, western blotting, and CoIP assays revealed the molecular mechanisms underlying exosome-mediated M2 polarization. Protein array, ChIP and dual-luciferase reporter assays clarified the molecular mechanisms by which the target gene regulated exosomal miRNA. In vivo validation was performed using xenograft tumor models.

RESULTS

SERPINE1 was identified as a highly expressed mRNA in GC tissues and cells, significantly associated with advanced clinical stages, worse prognosis, and higher M2 macrophage infiltration in patients with GC. SERPINE1 overexpression in GC cells promoted tumor growth and M2 macrophage polarization. SERPINE1 facilitated the transfer of let-7 g-5p to macrophages via cancer-derived exosomes, inducing M2 polarization. Exosomal let-7 g-5p internalized by macrophages downregulated SOCS7 protein levels, disrupting its interaction with STAT3 and relieving the inhibition of STAT3 phosphorylation, thereby leading to STAT3 hyperactivation, which consequently drove M2 polarization. Additionally, in GC cells, elevated SERPINE1 expression activated JAK2, enhancing STAT3 binding to the let-7 g-5p promoter and promoting its transcription, thereby increasing let-7 g-5p levels in exosomes.

CONCLUSION

GC cell-derived SERPINE1, functioning as a primary driver of GC growth and TAM M2 polarization, promotes M2 polarization through the regulation of exosomal let-7 g-5p transfer via autocrine activation of the JAK2/STAT3 signaling pathway. These findings elucidate a novel mechanism of SERPINE1-induced M2 polarization and highlight SERPINE1 as a promising target for advancing immunotherapy and targeted treatments in GC.

NADPH Oxidases-Inspired Reactive Oxygen Biocatalysts with Electron-Rich Pt Sites to Potently Amplify Immune Checkpoint Blockade Therapy

Clinical immune checkpoint blockade (ICB)-based immunotherapy of malignant tumors only elicits durable responses in a minority of patients, primarily due to the highly immunosuppressive tumor microenvironment. Although inducing immunogenic cell death (ICD) through reactive oxygen biocatalyst represents an attractive therapeutic strategy to amplify ICB, currently reported biocatalysts encounter insurmountable challenges in achieving high ROS-generating activity to induce potent ICD. Here, inspired by the natural catalytic characteristics of NADPH oxidases, the design of efficient, robust, and electron-rich Pt-based redox centers on the non-stoichiometric W18O49 substrates (Pt─WOx) to serve as bioinspired reactive oxygen biocatalysts to potently activate the ICD, which eventually enhance cancer immune responses and amplifies the ICB-based immunotherapy is reported. These studies demonstrate that the Pt─WOx exhibits rapid electron transfer capability and can promote the formation of electron-rich and low oxophilic Pt redox centers for superior reactive oxygen biocatalysis, which enables the Pt─WOx-based inducers to trigger endoplasmic reticulum stress directly and stimulate immune responses potently for amplifying the anti-PD-L1-based ICB therapy. This bioinspired design provides a straightforward strategy to engineer efficient, robust, and electron-rich reactive oxygen biocatalysts and also opens up a new avenue to create efficient ICD inducers for primary/metastatic tumor treatments.

Macrophage Polarisation in the Tumour Microenvironment: Recent Research Advances and Therapeutic Potential of Different Macrophage Reprogramming

BACKGROUND

Macrophages are a critical component of the innate immune system, derived from monocytes, with significant roles in anti-inflammatory and anti-tumour activities. In the tumour microenvironment, however, macrophages are often reprogrammed into tumour-associated macrophages (TAMs), which promote tumour growth, metastasis, and therapeutic resistance.

PURPOSE

To review recent advancements in the understanding of macrophage polarisation and reprogramming, highlighting their role in tumour progression and potential as therapeutic targets.

RESEARCH DESIGN

This is a review article synthesising findings from recent studies on macrophage polarisation and reprogramming in tumour biology.

STUDY SAMPLE

Not applicable (review of existing literature).

DATA COLLECTION AND/OR ANALYSIS

Key studies were identified and summarised to explore mechanisms of macrophage polarisation and reprogramming, focusing on M1/M2 polarisation, metabolic and epigenetic changes, and pathway regulation.

RESULTS

Macrophage reprogramming in the tumour microenvironment involves complex mechanisms, including phenotypic and functional alterations. These processes are influenced by M1/M2 polarisation, metabolic and epigenetic reprogramming, and various signalling pathways. TAMs play a pivotal role in tumour progression, metastasis, and therapy resistance, making them prime targets for combination therapies.

CONCLUSIONS

Understanding the mechanisms underlying macrophage polarisation and reprogramming offers promising avenues for developing therapies to counteract tumour progression. Future research should focus on translating these insights into clinical applications for effective cancer treatment.

Immune regulation and the tumor microenvironment in anti-PD-1/PDL-1 and anti-CTLA-4 therapies for cancer immune evasion: A bibliometric analysis

This study aims to conduct a bibliometric analysis, employing visualization tools to examine literature pertaining to tumor immune evasion related to anti-CTLA-4 and anti-PD-1/PD-L1 therapy from 1999 to 2022. A special emphasis is placed on the interplay between tumor microenvironment, signaling pathways, immune cells and immune evasion, with data sourced from the Web of Science core collection (WoSCC). Advanced tools, including VOSviewer, Citespace, and Scimago Graphica, were utilized to analyze various parameters, such as co-authorship/co-citation patterns, regional contributions, journal preferences, keyword co-occurrences, and significant citation bursts. Out of 4778 publications reviewed, there was a marked increase in research focusing on immune evasion, with bladder cancer being notably prominent. Geographically, China, the USA, and Japan were the leading contributors. Prestigious institutions like MD Anderson Cancer Center, Harvard Medical School, Fudan University, and Sun Yat Sen University emerged as major players. Renowned journals in this domain included Frontiers in Immunology, Cancers, and Frontiers in Oncology. Ehen LP and Wang W were identified as prolific authors on this topic, while Topalian SL stood out as one of the most cited. Research current situation is notably pivoting toward challenges like immunotherapy resistance and the intricate signaling pathways driving drug resistance. This bibliometric study seeks to provide a comprehensive overview of past and current research trends, emphasizing the potential role of tumor microenvironment, signaling pathways and immune cells in the context of immune checkpoint inhibitors (ICIs) and tumor immune evasion.

Targeting OAS3 for reversing M2d infiltration and restoring anti-tumor immunity in pancreatic cancer

Abundant infiltration of tumor-associated macrophages (TAMs) within the tumor stroma plays a pivotal role in inducing immune escape in pancreatic cancer (PC). Lactate serves as a direct regulator of macrophage polarization and functions, although the precise regulation mechanism remains inadequately understood. Our study revealed that PC cells (PCs) promote macrophage polarization toward M2d through high lactate secretion. M2d is characterized by elevated secretion of IL-10 and VEGF-A, which diminish CD8+T cells cytotoxicity and promote tumor neoangiogenesis simultaneously. Additionally, we identify 2,5'-oligoadenylate synthase 3 (OAS3) as an essential regulator of M2d polarization, upregulated by PCs via lactate/METTL3/OAS3 axis. Increased OAS3 expression in TAMs correlates with m6A modification mediated by METTL3 on OAS3 mRNA and is associated with poorer prognosis in PC patients. OAS3 deficiency in macrophages substantially impairs IL-10highVEGF-AhighM2d polarization and their pro-tumor functions while enhancing the therapeutic efficacy of gemcitabine and anti-PD-L1 mAb in humanized mouse models. In conclusion, OAS3 presents as a promising immune therapeutic target for reversing IL-10highVEGF-AhighM2d infiltration and restoring CD8+T cell-mediated anti-tumor immunity in pancreatic cancer.

Optimized Spheroid Model of Pancreatic Cancer Demonstrates Influence of Macrophage-T Cell Interaction for Intratumoral T Cell Motility

BACKGROUND

Most spheroid models use size measurements as a primary readout parameter; some models extend analysis to T cell infiltration or perform caspase activation assays. However, to our knowledge, T cell motility analysis is not regularly included as an endpoint in imaging studies on cancer spheroids.

METHODS

Here, we intend to demonstrate that motility analysis of macrophages and T cells is a valuable functional endpoint for studies on molecular interventions in the tumor microenvironment. In particular, T cell migration analysis represents the final step of effector function, as T cells engage with targets cells upon cytotoxic interaction, which is represented by an arrest within the spheroid volume. Therefore, T cell arrest is a novel readout parameter of T cell effector function in spheroids.

RESULTS

Here, we demonstrate that incubation of macrophages with nigericin for NLRP3 activation increases T cell velocity, but results in decreased T cellular arrest. This is paralleled by reduced rejection kinetics of pancreatic cancer spheroids in the presence of antigen-dependent T cells and nigericin-treated macrophages. Our model demonstrates consistent changes in T cell motility upon coculturing of T cells and tumors cells with macrophages, including influences of molecular interventions such as NLRP3 activation.

CONCLUSIONS

Motility analysis using a spheroid model of pancreatic cancer is a more sophisticated alternative to in vitro cytotoxicity assays measuring spheroid size. Ultimately, an optimized spheroid model might replace at least some aspects of animal experiments investigating T cell effector function.

Manganese improves CD8+ T cell recruitment via cGAS-STING in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer-related deaths worldwide. Chemotherapy using cisplatin, a drug that damages deoxyribonucleic acid (DNA), is not very effective in treating HCC due to its side effects and drug resistance. Manganese (Mn2+), a trace element, has been shown to enhance immune responses, but its ability to improve cisplatin-induced antitumor immunity in HCC remains unclear. The present study found that treatment with Mn2+ in combination with cisplatin promoted cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling activation and C-X-C motif chemokine ligand 10 (CXCL10) production in tumor and dendritic cells. CXCL10 is associated with CD8A levels, and its high expression is linked to better prognosis in patients with HCC. In addition, Mn2+ and cisplatin co-treatment enhanced the recruitment of CD8+ T cells through the CXCL10/CXCR3 axis. Similarly, in an orthotopic transplantation tumor model, STING activation, CD8+ T cell infiltration, and tumor cell killing levels were higher in the combined treatment group. The above findings suggest that utilizing Mn2+ in combination with cisplatin could be a potential treatment option for HCC.

Colorectal cancer cell-derived exosomal miRNA-372-5p induces immune escape from colorectal cancer via PTEN/AKT/NF-κB/PD-L1 pathway

Tumor cells can escape immune surveillance by changing their own escape or expressing abnormal genes and proteins, resulting in unlimited proliferation and invasive growth of cells. These changes are related to microRNAs (miRNAs), which reduce the killing effect of immune cells, devastate the immune response, and interfere with apoptosis through the aberrant expression of relevant miRNAs. In the preliminary phase of this study, miRNAs in clinical plasma exosomes of colorectal cancer patients were differentially analyzed by RNA sequencing technology, and miR-372-5p derived from extracellular vesicles (sEVs) was found to be a key signaling molecule mediating the regulation of macrophages by colorectal cancer (CRC). miRNA-372-5p is upregulated in colorectal cancer patient tissues and serum, as well as colorectal cancer cell lines and their exosomes. Subsequently, we found that macrophages could take up sEV secreted by colorectal cancer cells HCT116, affecting the expression of the immune checkpoint PD-L1, resulting in the generation of a tumor-immunosuppressive microenvironment and suppression of T cell activation in CRC. Gene enrichment mapping and database revealed that miR-372-5p regulates PD-L1 expression in colorectal cancer through the homologous phosphatase-tensin (PTEN)-phosphatidylinositol 3-kinase-protein kinase B (AKT)-nuclear factor-κB (NF-κB) pathway. Further studies confirmed that miRNA-372-5p-treated macrophages co-cultured with T cells affected the regulation of PD-L1 expression through the PTEN/AKT/NF-κB signaling pathway, resulting in decreased CD3+CD8+ T cell activity, decreased cytokine IL-2 and increased IFN-γ. And miRNA-372-5p could down-regulate the expression of PD-L1 in HCT116 through the PTEN/AKT/NF-κB pathway, inhibit tumor cell proliferation and promote apoptosis. Conclusion: Colorectal cancer cell-derived exosome miR-372-5p can be phagocytosed by colorectal cancer and macrophage cells, regulate the expression of PD-L1 in colorectal cancer cells and macrophages by targeting the PTEN/AKT/NF-κB pathway, and induce the immunosuppressive microenvironment of CRC to promote CRC development. This suggests that inhibiting the secretion of HCT116-specific sEV-miR-372-5p or targeting PD-L1 in tumor-associated macrophages could be a novel approach for CRC treatment and possibly a sensitizing approach for CRC anti-PD-L1 therapy.

Imaging of tumor-associated macrophage dynamics during immunotherapy using a CD163-specific nanobody-based immunotracer

Immunotherapies have emerged as an effective treatment option for immune-related diseases, such as cancer and inflammatory diseases. However, variations in patient responsiveness limit the broad applicability and success of these immunotherapies. Noninvasive whole-body imaging of the immune status of individual patients during immunotherapy could enable the prediction and monitoring of the patient's response, resulting in more personalized treatments. In this study, we developed a nanobody-based immunotracer targeting CD163, a receptor specifically expressed on macrophages. This anti-CD163 immunotracer bound to human and mouse CD163 with high affinity and specificity without competing for ligand binding. Furthermore, the tracer showed no unwanted immune cell activation and was nonimmunogenic. Upon radiolabeling of the anti-CD163 immunotracer, specific imaging of CD163+ macrophages using micro-single-photon emission computerized tomography/computed tomography or micro-positron emission tomography/CT was performed. The anti-CD163 immunotracer was able to stratify immunotherapy responders from nonresponders (NR) by visualizing differences in the intratumoral CD163+ TAM distribution in Lewis lung carcinoma-ovalbumin tumor-bearing mice receiving an anti-programmed cell death protein-1 (PD-1)/CSF1R combination treatment. Immunotherapy-responding mice showed a more homogeneous distribution of the PET signal in the middle of the tumor, while CD163+ TAMs were located at the tumor periphery in NR. As such, visualization of CD163+ TAM distribution in the tumor microenvironment could allow a prediction or follow-up of therapy response. Altogether, this study describes an immunotracer, specific for CD163+ macrophages, that allows same-day imaging and follow-up of these immune cells in the tumor microenvironment, providing a good basis for the prediction and follow-up of immunotherapy responses in cancer patients.

Cardamonin anticancer effects through the modulation of the tumor immune microenvironment in triple-negative breast cancer cells

The tumor immune microenvironment (TIME) plays a critical role in cancer development and response to immunotherapy. Immune checkpoint inhibitors aim to reverse the immunosuppressive effects of the TIME, but their success has been limited. Immunotherapy directed at PD-1/PD-L1 has been widely employed, yielding positive results. Unfortunately, the gradual emergence of resistance to PD-1/PD-L1 inhibition has diminished the effectiveness of this immunotherapy in cancer patients, emphasizing the need for new compounds that will be more effective in managing immunotherapy. This study investigated the effect of the natural compound cardamonin on PD-L1 expression and its ability to modulate the TIME, which could overcome immunotherapy resistance in triple-negative breast cancer (TNBC). This investigation used two genetically distinct triple-negative breast cancer cell lines, MDA-MB-231 (MDA-231) and MDA-MB-468 (MDA-468). The results show that TNBC cell treatment with cardamonin inhibited PD-L1 expression and reduced JAK1 and STAT3 levels in MDA-231 cells, while it increased JAK1 expression in MDA-468 cells. Also, cardamonin increased the expression of Nrf2 in both cell lines. In addition, cardamonin decreased MUC1, NF-κB1, and NF-κB2 expression in MDA-MB-231 cells and selectively reduced NF-κB1 expression in MDA-468 cells. Furthermore, cardamonin very potently reduced the inflammatory cytokine CCL2 levels. The decrease in CCL2 release reduces the chemoattraction of macrophages in the tumor microenvironment, which may increase the effectiveness of PD-1/PD-L1 inhibition and allow T-cell infiltration. These findings suggest that the cardamonin modulation of TIME holds promise in reversing resistance of PD-1/PD-L1 inhibition when it is used along with immunotherapy in TNBC treatment.

Chemotherapy induces myeloid-driven spatially confined T cell exhaustion in ovarian cancer

Anti-tumor immunity is crucial for high-grade serous ovarian cancer (HGSC) prognosis, yet its adaptation upon standard chemotherapy remains poorly understood. Here, we conduct spatial and molecular characterization of 117 HGSC samples collected before and after chemotherapy. Our single-cell and spatial analyses reveal increasingly versatile immune cell states forming spatiotemporally dynamic microcommunities. We describe Myelonets, networks of interconnected myeloid cells that contribute to CD8+ T cell exhaustion post-chemotherapy and show that M1/M2 polarization at the tumor-stroma interface is associated with CD8+ T cell exhaustion and exclusion, correlating with poor chemoresponse. Single-cell and spatial transcriptomics reveal prominent myeloid-T cell interactions via NECTIN2-TIGIT induced by chemotherapy. Targeting these interactions using a functional patient-derived immuno-oncology platform demonstrates that high NECTIN2-TIGIT signaling in matched tumors predicts responses to immune checkpoint blockade. Our discovery of clinically relevant myeloid-driven spatial T cell exhaustion unlocks immunotherapeutic strategies to unleash CD8+ T cell-mediated anti-tumor immunity in HGSC.

A novel small molecule Enpp1 inhibitor improves tumor control following radiation therapy by targeting stromal Enpp1 expression

The uniqueness in each person's cancer cells and variation in immune infiltrates means that each tumor represents a unique problem, but therapeutic targets can be found among their shared features. Radiation therapy alters the interaction between the cancer cells and the stroma through release of innate adjuvants. The extranuclear DNA that can result from radiation damage of cells can result in production of the second messenger cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) by cyclic GMP-AMP synthase (cGAS). In turn, cGAMP can activate the innate sensor stimulator of interferon genes (STING), resulting in innate immune activation. Ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1) is a phosphodiesterase that can be expressed by cancer cells that can degrade cGAMP, thus can decrease or block STING activation following radiation therapy, impairing the innate immunity that is critical to support adaptive immune control of tumors. We observed that many human and murine cancer cells lack Enpp1 expression, but that Enpp1 is expressed in cells of the tumor stroma where it limits tumor control by radiation therapy. We demonstrate in preclinical models the efficacy of a novel Enpp1 inhibitor and show that this inhibitor improves tumor control by radiation even where the cancer cells lack Enpp1. This mechanism requires STING and type I interferon (IFN) receptor expression by non-cancer cells and is dependent on CD8 T cells as a final effector mechanism of tumor control. This suggests that Enpp1 inhibition may be an effective partner for radiation therapy regardless of whether cancer cells express Enpp1. This broadens the potential patient base for whom Enpp1 inhibitors can be applied to improve innate immune responses following radiation therapy.

Impact of bone marrow fibrosis on outcomes of allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia

Bone marrow fibrosis (BMF) of unknown etiology was common in hematological malignancies, but its prognostic value for acute myeloid leukemia (AML) is unclear. We interrogated data from 532 newly diagnosed subjects with AML receiving allogeneic hematological stem cell transplantation to evaluate the prognostic impact of BMF on transplant outcomes. Using the European consensus on the grading of BMF at diagnosis, 255 (48%) subjects were BMF-0, 209 (39%), BMF-1 and 68 (13%), BMF-2-3. Subjects with BMF-2-3 had poor overall survival (P < 0.001), disease-free survival (P < 0.001) and a higher incidence of relapse (CIR, P < 0.001). Multi-variable analyses in subjects achieving pre-transplant complete remission showed BMF-2-3 was an independent risk factor for CIR (Hazard Ratio [HR] = 2.17, (95% CI, 1.11, 4,24); P = 0.02). Furthermore, BMF-2-3 group showed delayed neutrophil and platelet engraftment and delayed B cell recovery post-transplantation. These findings demonstrate the significance of BMF in transplant outcomes and attract more attention to AML with BMF.

PTGR1-mediated immune evasion mechanisms in late-stage triple-negative breast cancer: mechanisms of M2 macrophage infiltration and CD8+ T cell suppression

Triple-negative breast cancer (TNBC) is a heterogeneous disease characterized by metabolic dysregulation. Tumor cell immune escape plays an indispensable role in the development of TNBC tumors. Furthermore, in the abstract, we explicitly mention the techniques used and enhance the clarity and impact of our findings. "Based on bioinformatics analysis results, we utilized CRISPR/Cas9 technology to knockout the target gene and established a mouse model of breast cancer. Through experiments such as CCK8, scratch assay, and Transwell assay, we further investigated the impact of target gene knockout on the malignant behavior of tumor cells. Subsequently, we conducted immunohistochemistry and Western Blot experiments to study the expression of macrophage polarization and infiltration-related markers and evaluate the effect of the target gene on macrophage polarization. Next, through co-culture experiments, we simulated the tumor microenvironment and used immunohistochemistry staining to observe and analyze the distribution and activation status of M2 macrophages and CD8+ T cells in the co-culture system. We validated in vivo experiments the molecular mechanism by which the target gene regulates immune cell impact on TNBC progression.

Current status of research on the mechanisms of tumor-associated macrophages in esophageal cancer progression

Esophageal carcinoma (EC) is one of the most common tumors in China and seriously affects patient survival and quality of life. In recent years, increasing studies have shown that the tumor microenvironment is crucial in promoting tumor progression and metastasis. Tumor-associated macrophages (TAM) are key components of the tumor immune microenvironment and promote both tumor growth and antitumor immunity. Much evidence suggests that TAMs are closely associated with esophageal tumors. However, understanding of the clinical value and mechanism of action of TAM in esophageal cancer remains limited. Therefore, we reviewed the status of research on the role and mechanism of action of TAM in EC progression and summarized its potential clinical application value to provide a theoretical basis for the clinical treatment of EC.