Macrophages at the interface of the co-evolving cancer ecosystem

CIMT 2024: Report on the 21st Annual Meeting of the Association for Cancer Immunotherapy

The 21st Association for Cancer Immunotherapy (CIMT) Annual Meeting took place from May 15th to May 17th in Mainz, Germany, and was attended by a total of 855 academic and clinical professionals hailing from 33 different countries. The conference served as a platform for these experts to convene and discuss the latest breakthroughs in cancer immunology and immunotherapy research. Dedicated sessions covering advancements in artificial intelligence tools for cancer immunotherapy research, as well as the landscape of cancer care and cancer immunotherapy trials on the African continent, prompted lively and informative discussions among the attendees. This report aims to provide an overview of the most noteworthy highlights and key takeaways from CIMT2024.

NOX2 Enzyme Mimicking Nano-Networks Regulate Tumor-Associated Macrophages to Initiate Both Innate and Adaptive Immune Effects

Macrophages, capable of both direct killing and antigen presentation, are crucial for the interplay between innate and adaptive immunity. However, strategies mainly focus on polarizing tumor-associated macrophages (TAMs) to M1 phenotype, while overlooking the inefficient antigen cross-presentation due to hyperactive hydrolytic protease within lysosomes which leads to antigen degradation. In light of the significant influence of reactive oxygen species (ROS) on TAMs' polarization and the inhibition of phagosomal proteolysis, a novel nanosystem termed OVA-Fe-GA (OFG) is engineered, drawing inspiration from the NOX2 enzyme's role. OFG integrates ovalbumin (OVA) and a network composed of Fe-gallic acid (GA), emulating the NOX2 enzyme's sequential ROS generation process ("O2 to O2 •- to H2O2/•OH"). Furthermore, it elucidates a biological mechanism that augments antigen cross-presentation by suppressing the expression of cysteine proteases. OFG restores the innate anti-tumor functionality of TAMs and significantly amplifies their antigen cross-presentation (4.5-fold compared to the PBS control group) in B16-OVA tumor-bearing mice. Notably, the infiltration and activity of intratumoral CD8+ T cells are enhanced, indicating an adaptive immune response. Moreover, OFG exhibits excellent photothermal properties, thereby fostering a system antitumor immune response. This study provides a promising strategy for initiating both innate and adaptive immunity via TAMs activation.

Tumor Microenvironment-Responsive Macrophage-Mediated Immunotherapeutic Drug Delivery

Immunotherapy, as a promising treatment strategy for cancer, has been widely employed in clinics, while its efficiency is limited by the immunosuppression of tumor microenvironment (TME). Tumor-associate macrophages (TAMs) are the most abundant immune cells infiltrating the TME and play a crucial role in immune regulation. Herein, a M0-type macrophage-mediated drug delivery system (PR-M) was designed for carrying Toll-like receptors (TLRs) agonist-loaded nanoparticles. When TLR agonist R848 was released by responding to the TME, the PR-Ms were polarized from M0-type to M1-type and TAMs were also stimulated from M2-type to M1-type, which eventually reversed the immunosuppressive states of TME. By synergizing with the released R848 agonists, the PR-M significantly activated CD4+ and CD8+ T cells in the TME and turned the 'cold' tumor into 'hot' tumor by regulating the secretion of cytokines including IFN-γ, TNF-α, IL-10, and IL-12, thus ultimately promoting the activation of antitumor immunity. In a colorectal cancer mouse model, the PR-M treatment effectively accumulated at the tumor site, with a 5.47-fold increase in M1-type and a 2.85-fold decrease in M2-type, resulting in an 85.25% inhibition of tumor growth and a 732.49% reduction of tumor volume compared with the non-treatment group. Our work suggests that immune cell-mediated drug delivery systems can effectively increase drug accumulation at the tumor site and reduce toxic side effects, resulting in a strong immune system for tumor immunotherapy. STATEMENT OF SIGNIFICANCE: The formation of tumor microenvironment (TME) and the activation of tumor-associated macrophages (TAMs) create an immunosuppressive network that allows tumor to escape the immune system and promotes its growth and spread. In this study, we designed an M0-type macrophage-mediated drug delivery system (PR-M). It leverages the synergistic effect of macrophages and agonists to improve the tumor immunosuppressive micro-environment by increasing M1-type macrophages and decreasing M2-type macrophages. As part of the treatment, the drug-loaded macrophages endowed the system with excellent tumor targeting. Furthermore, loading R848 into TME-responsive nanoparticles could protect macrophages and reduce the potential toxicity of agonists. Further investigations demonstrated that the designed PR-M could be a feasible strategy with high efficacy in tumor targeting, drug loading, autoimmunity activation, and lower side effects.

Decoding the spatiotemporal heterogeneity of tumor-associated macrophages

Tumor-associated macrophages (TAMs) are pivotal in cancer progression, influencing tumor growth, angiogenesis, and immune evasion. This review explores the spatial and temporal heterogeneity of TAMs within the tumor microenvironment (TME), highlighting their diverse subtypes, origins, and functions. Advanced technologies such as single-cell sequencing and spatial multi-omics have elucidated the intricate interactions between TAMs and other TME components, revealing the mechanisms behind their recruitment, polarization, and distribution. Key findings demonstrate that TAMs support tumor vascularization, promote epithelial-mesenchymal transition (EMT), and modulate extracellular matrix (ECM) remodeling, etc., thereby enhancing tumor invasiveness and metastasis. Understanding these complex dynamics offers new therapeutic targets for disrupting TAM-mediated pathways and overcoming drug resistance. This review underscores the potential of targeting TAMs to develop innovative cancer therapies, emphasizing the need for further research into their spatial characteristics and functional roles within the TME.

SHISA3 Reprograms Tumor-Associated Macrophages Toward an Antitumoral Phenotype and Enhances Cancer Immunotherapy

The main challenge for immune checkpoint blockade (ICB) therapy lies in immunosuppressive tumor microenvironment (TME). Repolarizing M2-like tumor-associated macrophages (TAMs) into inflammatory M1 phenotype is a promising strategy for cancer immunotherapy. Here, this study shows that the tumor suppressive protein SHISA3 regulates the antitumor functions of TAMs. Local delivery of mRNA encoding Shisa3 enables cancer immunotherapy by reprogramming TAMs toward an antitumoral phenotype, thus enhancing the efficacy of programmed cell death 1 (PD-1) antibody. Enforced expression of Shisa3 in TAMs increases their phagocytosis and antigen presentation abilities and promotes CD8+ T cell-mediated antitumor immunity. The expression of SHISA3 is induced by damage/pathogen-associated molecular patterns (DAMPs/PAMPs) in macrophages via nuclear factor-κB (NF-κB) transcription factors. Reciprocally, SHISA3 forms a complex with heat shock protein family A member 8 (HSPA8) to activate NF-κB signaling thus maintaining M1 polarization of macrophages. Knockout Shisa3 largely abolishes the antitumor efficacy of combination immunotherapy with Toll-like receptor 4 (TLR4) agonist monophosphoryl lipid A (MPLA) and PD-1 antibody. It further found that higher expression of SHISA3 in antitumoral TAMs is associated with better overall survival in lung cancer patients. Taken together, the findings describe the role of SHISA3 in reprogramming TAMs that ameliorate cancer immunotherapy.

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.

Antibody-Decorated Nanoplatform to Reprogram Macrophage and Block Immune Checkpoint LSECtin for Effective Cancer Immunotherapy

Repolarizing tumor-associated macrophages (TAMs) into tumor-inhibiting M1 macrophages has been considered a promising strategy for enhanced cancer immunotherapy. However, several immunosuppressive ligands (e.g., LSECtin) can still be highly expressed on M1 macrophages, inducing unsatisfactory therapeutic outcomes. We herein developed an antibody-decorated nanoplatform composed of PEGylated iron oxide nanoparticles (IONPs) and LSECtin antibody conjugated onto the surface of IONPs via the hydrazone bond for enhanced cancer immunotherapy. After intravenous administration, the tumor microenvironment (TME) pH could trigger the hydrazone bond breakage and induce the disassociation of the nanoplatform into free LSECtin antibodies and IONPs. Consequently, the IONPs could repolarize TAMs into M1 macrophages to remodel immunosuppressive TME and provide an additional anticancer effect via secreting tumoricidal factors (e.g., interlukin-12). Meanwhile, the LSECtin antibody could further block the activity of LSECtin expressed on M1 macrophages and relieve its immunosuppressive effect on CD8+ T cells, ultimately leading to significant inhibition of tumor growth.

Rational design of ROS generation nanosystems to regulate innate immunity of macrophages, dendrtical and natural killing cells for immunotherapy

Innate immunity serves as the first line of host defense in the body against pathogenic infections or malignant diseases. Reactive oxygen species (ROS), as vital signaling mediators, can efficiently elicit innate immune responses to oxidative-related stress or damage. In the era of nanomedicine, various immunostimulatory nanosystems have been extensively designed and synthesized to elicit immune responses for the immunotherapy of cancer or infectious diseases. In this review, we emphasize that ROS derived from nanosystems regulates innate immune cells to potentiate immunotherapeutic efficacy, such as primarily dendritic cells, macrophages, or natural killer cells. Meanwhile, we also summarize the pathway of ROS generation triggered by exogenous nanosystems in innate immune cells of DCs, macrophages, and NK cells.

Recent Advances in Nanoimmunotherapy by Modulating Tumor-Associated Macrophages for Cancer Therapy

Cancer immunotherapy has yielded remarkable results across a variety of tumor types. Nevertheless, the complex and immunosuppressive microenvironment within solid tumors poses significant challenges to established therapies such as immune checkpoint blockade (ICB) and chimeric antigen receptor T-cell (CAR-T) therapy. Within the milieu, tumor-associated macrophages (TAMs) play a significant role by directly suppressing T-cell functionality and fostering an immunosuppressive environment. Effective regulation of TAMs is, therefore, crucial to enhancing the efficacy of immunotherapies. Various therapeutic strategies targeting TAM modulation have emerged, including blocking TAM recruitment, direct elimination, promoting repolarization toward the M1 phenotype, and enhancing phagocytic capacity against tumor cells. The recently introduced CAR macrophage (CAR-M) therapy opens new possibilities for macrophage-based immunotherapy. Compared with CAR-T, CAR-M may demonstrate superior targeting and infiltration capabilities toward solid tumors. This review predominantly delves into the origin and development process of TAMs, their role in promoting tumor growth, and provides a comprehensive overview of immunotherapies targeting TAMs. It underscores the significance of regulating TAMs in bolstering antitumor therapies while discussing the potential and challenges of developing TAMs as targets for immunotherapy.

Context-dependent roles for autophagy in myeloid cells in tumor progression

Autophagy is known to suppress tumor initiation by removing genotoxic stresses in normal cells. Conversely, autophagy is also known to support tumor progression by alleviating metabolic stresses in neoplastic cells. Centered on this pro-tumor role of autophagy, there have been many clinical trials to treat cancers through systemic blocking of autophagy. Such systemic inhibition affects both tumor cells and non-tumor cells, and the consequence of blocked autophagy in non-tumor cells in the context of tumor microenvironment is relatively understudied. Here, we examined the effect of autophagy-deficient myeloid cells on the progression of autophagy-competent tumors. We found that blocking autophagy only in myeloid cells modulated tumor progression markedly but such effects were context dependent. In a tumor implantation model, the growth of implanted tumor cells was substantially reduced in mice with autophagy-deficient myeloid cells; T cells infiltrated deeper into the tumors and were responsible for the reduced growth of the implanted tumor cells. In an oncogene-driven tumor induction model, however, tumors grew faster and metastasized more in mice with autophagy-deficient myeloid cells. These data demonstrate that the autophagy status of myeloid cells plays a critical role in tumor progression, promoting or suppressing tumor growth depending on the context of tumor-myeloid cell interactions. This study indicates that systemic use of autophagy inhibitors in cancer therapy may have differential effects on rates of tumor progression in patients due to effects on myeloid cells and that this warrants more targeted use of selective autophagy inhibitors in a cancer therapy in a clinical setting.

Deciphering the roles of the HMGB family in cancer: Insights from subcellular localization dynamics

The high-mobility group box (HMGB) family consists of four DNA-binding proteins that regulate chromatin structure and function. In addition to their intracellular functions, recent studies have revealed their involvement as extracellular damage-associated molecular patterns (DAMPs), contributing to immune responses and tumor development. The HMGB family promotes tumorigenesis by modulating multiple processes including proliferation, metabolic reprogramming, metastasis, immune evasion, and drug resistance. Due to the predominant focus on HMGB1 in the literature, little is known about the remaining members of this family. This review summarizes the structural, distributional, as well as functional similarities and distinctions among members of the HMGB family, followed by a comprehensive exploration of their roles in tumor development. We emphasize the distributional and functional hierarchy of the HMGB family at both the organizational and subcellular levels, with a focus on their relationship with the tumor immune microenvironment (TIME), aiming to prospect potential strategies for anticancer therapy.

Unbiasedly decoding the tumor microenvironment with single-cell multiomics analysis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a poor prognosis and limited therapeutic options. Research on the tumor microenvironment (TME) of PDAC has propelled the development of immunotherapeutic and targeted therapeutic strategies with a promising future. The emergence of single-cell sequencing and mass spectrometry technologies, coupled with spatial omics, has collectively revealed the heterogeneity of the TME from a multiomics perspective, outlined the development trajectories of cell lineages, and revealed important functions of previously underrated myeloid cells and tumor stroma cells. Concurrently, these findings necessitated more refined annotations of biological functions at the cell cluster or single-cell level. Precise identification of all cell clusters is urgently needed to determine whether they have been investigated adequately and to identify target cell clusters with antitumor potential, design compatible treatment strategies, and determine treatment resistance. Here, we summarize recent research on the PDAC TME at the single-cell multiomics level, with an unbiased focus on the functions and potential classification bases of every cellular component within the TME, and look forward to the prospects of integrating single-cell multiomics data and retrospectively reusing bulk sequencing data, hoping to provide new insights into the PDAC TME.

Radiotherapy and immunology

The majority of cancer patients receive radiotherapy during the course of treatment, delivered with curative intent for local tumor control or as part of a multimodality regimen aimed at eliminating distant metastasis. A major focus of research has been DNA damage; however, in the past two decades, emphasis has shifted to the important role the immune system plays in radiotherapy-induced anti-tumor effects. Radiotherapy reprograms the tumor microenvironment, triggering DNA and RNA sensing cascades that activate innate immunity and ultimately enhance adaptive immunity. In opposition, radiotherapy also induces suppression of anti-tumor immunity, including recruitment of regulatory T cells, myeloid-derived suppressor cells, and suppressive macrophages. The balance of pro- and anti-tumor immunity is regulated in part by radiotherapy-induced chemokines and cytokines. Microbiota can also influence radiotherapy outcomes and is under clinical investigation. Blockade of the PD-1/PD-L1 axis and CTLA-4 has been extensively investigated in combination with radiotherapy; we include a review of clinical trials involving inhibition of these immune checkpoints and radiotherapy.

Emerging Innate Immune Cells in Cancer Immunotherapy: Promises and Challenges

Immune checkpoint inhibitor (ICI)-based therapy has made an unprecedented impact on survival benefit for a subset of cancer patients; however, only a subset of cancer patients is benefiting from ICI therapy if all cancer types are considered. With the advanced understanding of interactions of immune effector cell types and tumors, cell-based therapies are emerging as alternatives to patients who could not benefit from ICI therapy. Pioneering work of chimeric antigen receptor T (CAR-T) therapy for hematological malignancies has brought encouragement to a broad range of development for cellular-based cancer immunotherapy, both innate immune cell-based therapies and T-cell-based therapies. Innate immune cells are important cell types due to their rapid response, versatile function, superior safety profiles being demonstrated in early clinical development, and being able to utilize multiple allogeneic cell sources. Efforts on engineering innate immune cells and exploring their therapeutic potential are rapidly emerging. Some of the therapies, such as CD19 CAR natural killer (CAR-NK) cell-based therapy, have demonstrated comparable early efficacy with CD19 CAR-T cells. These studies underscore the significance of developing innate immune cells for cancer therapy. In this review, we focus on the current development of emerging NK cells, γδ T cells, and macrophages. We also present our views on potential challenges and perspectives to overcome these challenges.

Promotion and Detection of Cell-Cell Interactions through a Bioorthogonal Approach

Manipulation of cell-cell interactions via cell surface modification is crucial in tissue engineering and cell-based therapy. To be able to monitor intercellular interactions, it can also provide useful information for understanding how the cells interact and communicate. We report herein a facile bioorthogonal strategy to promote and monitor cell-cell interactions. It involves the use of a maleimide-appended tetrazine-caged boron dipyrromethene (BODIPY)-based fluorescent probe and a maleimide-substituted bicyclo[6.1.0]non-4-yne (BCN) to modify the membrane of macrophage (RAW 264.7) and cancer (HT29, HeLa, and A431) cells, respectively, via maleimide-thiol conjugation. After modification, the two kinds of cells interact strongly through inverse electron-demand Diels-Alder reaction of the surface tetrazine and BCN moieties. The coupling also disrupts the tetrazine quenching unit, restoring the fluorescence emission of the BODIPY core on the cell-cell interface, and promotes phagocytosis. Hence, this approach can promote and facilitate the detection of intercellular interactions, rendering it potentially useful for macrophage-based immunotherapy.

Cancer plasticity in therapy resistance: Mechanisms and novel strategies

Therapy resistance poses a significant obstacle to effective cancer treatment. Recent insights into cell plasticity as a new paradigm for understanding resistance to treatment: as cancer progresses, cancer cells experience phenotypic and molecular alterations, corporately known as cell plasticity. These alterations are caused by microenvironment factors, stochastic genetic and epigenetic changes, and/or selective pressure engendered by treatment, resulting in tumor heterogeneity and therapy resistance. Increasing evidence suggests that cancer cells display remarkable intrinsic plasticity and reversibly adapt to dynamic microenvironment conditions. Dynamic interactions between cell states and with the surrounding microenvironment form a flexible tumor ecosystem, which is able to quickly adapt to external pressure, especially treatment. Here, this review delineates the formation of cancer cell plasticity (CCP) as well as its manipulation of cancer escape from treatment. Furthermore, the intrinsic and extrinsic mechanisms driving CCP that promote the development of therapy resistance is summarized. Novel treatment strategies, e.g., inhibiting or reversing CCP is also proposed. Moreover, the review discusses the multiple lines of ongoing clinical trials globally aimed at ameliorating therapy resistance. Such advances provide directions for the development of new treatment modalities and combination therapies against CCP in the context of therapy resistance.

Tumor initiation and early tumorigenesis: molecular mechanisms and interventional targets

Tumorigenesis is a multistep process, with oncogenic mutations in a normal cell conferring clonal advantage as the initial event. However, despite pervasive somatic mutations and clonal expansion in normal tissues, their transformation into cancer remains a rare event, indicating the presence of additional driver events for progression to an irreversible, highly heterogeneous, and invasive lesion. Recently, researchers are emphasizing the mechanisms of environmental tumor risk factors and epigenetic alterations that are profoundly influencing early clonal expansion and malignant evolution, independently of inducing mutations. Additionally, clonal evolution in tumorigenesis reflects a multifaceted interplay between cell-intrinsic identities and various cell-extrinsic factors that exert selective pressures to either restrain uncontrolled proliferation or allow specific clones to progress into tumors. However, the mechanisms by which driver events induce both intrinsic cellular competency and remodel environmental stress to facilitate malignant transformation are not fully understood. In this review, we summarize the genetic, epigenetic, and external driver events, and their effects on the co-evolution of the transformed cells and their ecosystem during tumor initiation and early malignant evolution. A deeper understanding of the earliest molecular events holds promise for translational applications, predicting individuals at high-risk of tumor and developing strategies to intercept malignant transformation.

The cellular-centered view of hypoxia tumor microenvironment: Molecular mechanisms and therapeutic interventions

Cancer is a profoundly dynamic, heterogeneous and aggressive systemic ailment, with a coordinated evolution of various types of tumor niches. Hypoxia plays an indispensable role in the tumor micro-ecosystem, drastically enhancing the plasticity of cancer cells, fibroblasts and immune cells and orchestrating intercellular communication. Hypoxia-induced signals, particularly hypoxia-inducible factor-1α (HIF-1α), drive the reprogramming of genetic, transcriptional, and proteomic profiles. This leads to a spectrum of interconnected processes, including augmented survival of cancer cells, evasion of immune surveillance, metabolic reprogramming, remodeling of the extracellular matrix, and the development of resistance to conventional therapeutic modalities like radiotherapy and chemotherapy. Here, we summarize the latest research on the multifaceted effects of hypoxia, where a multitude of cellular and non-cellular elements crosstalk with each other and co-evolve in a synergistic manner. Additionally, we investigate therapeutic approaches targeting hypoxic niche, encompassing hypoxia-activated prodrugs, HIF inhibitors, nanomedicines, and combination therapies. Finally, we discuss some of the issues to be addressed and highlight the potential of emerging technologies in the treatment of cancer.

Prognostic Significance of CD163+ and/or CD206+ Tumor-Associated Macrophages Is Linked to Their Spatial Distribution and Tumor-Infiltrating Lymphocytes in Breast Cancer

Tumor-associated macrophages (TAMs) is a key element in the breast tumor microenvironment. CD163 and CD206 have been utilized for TAM identification, but the clinical implications of TAMs identified by these markers have not been thoroughly explored. This study conducted a comparative analysis of CD163 and CD206 TAMs using digital image analysis, focusing on their spatial distribution and prognostic significance in relation to tumor-infiltrating lymphocytes (TILs). Distinct clinico-pathological and prognostic characteristics were noted between the two types of TAMs. CD163 TAMs were linked to high-grade tumors (p = 0.006), whereas CD206 TAMs were associated with a higher incidence of nodal metastasis (p = 0.033). CD206 TAMs were predominantly found in the stroma, with more cases being stromal CD206-high (sCD206-high) than tumoral CD206-high (tCD206-high) (p = 0.024). Regarding prognostication, patients stratified according to stromal and tumoral densities of CD163 showed different disease-free survival (DFS) time. Specifically, those that were sCD163-low but tCD163-high exhibited the poorest DFS (chi-square = 10.853, p = 0.013). Furthermore, a high sCD163-to-stromal-TILs ratio was identified as an independent predictor of unfavorable survival outcomes (DFS: HR = 3.477, p = 0.018). The spatial distribution and interactions with TILs enhanced the prognostic value of CD163 TAMs, while CD206 TAMs appeared to have limited prognostic utility in breast cancer cases.

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.

Engineered CD47 protects T cells for enhanced antitumour immunity

Adoptively transferred T cells and agents designed to block the CD47-SIRPα axis are promising cancer therapeutics that activate distinct arms of the immune system1,2. Here we administered anti-CD47 antibodies in combination with adoptively transferred T cells with the goal of enhancing antitumour efficacy but observed abrogated therapeutic benefit due to rapid macrophage-mediated clearance of T cells expressing chimeric antigen receptors (CARs) or engineered T cell receptors. Anti-CD47-antibody-mediated CAR T cell clearance was potent and rapid enough to serve as an effective safety switch. To overcome this challenge, we engineered the CD47 variant CD47(Q31P) (47E), which engages SIRPα and provides a 'don't eat me' signal that is not blocked by anti-CD47 antibodies. TCR or CAR T cells expressing 47E are resistant to clearance by macrophages after treatment with anti-CD47 antibodies, and mediate substantial, sustained macrophage recruitment to the tumour microenvironment. Although many of the recruited macrophages manifested an M2-like profile3, the combined therapy synergistically enhanced antitumour efficacy. Our study identifies macrophages as major regulators of T cell persistence and illustrates the fundamental challenge of combining T-cell-directed therapeutics with those designed to activate macrophages. It delivers a therapeutic approach that is capable of simultaneously harnessing the antitumour effects of T cells and macrophages, offering enhanced potency against solid tumours.

A new era of cancer immunotherapy: combining revolutionary technologies for enhanced CAR-M therapy

Significant advancements have been made in the application of chimeric antigen receptor (CAR)-T treatment for blood cancers during the previous ten years. However, its effectiveness in treating solid tumors is still lacking, necessitating the exploration of alternative immunotherapies that can overcome the significant challenges faced by current CAR-T cells. CAR-based immunotherapy against solid tumors shows promise with the emergence of macrophages, which possess robust phagocytic abilities, antigen-presenting functions, and the ability to modify the tumor microenvironment and stimulate adaptive responses. This paper presents a thorough examination of the latest progress in CAR-M therapy, covering both basic scientific studies and clinical trials. This study examines the primary obstacles hindering the realization of the complete potential of CAR-M therapy, as well as the potential strategies that can be employed to overcome these hurdles. With the emergence of revolutionary technologies like in situ genetic modification, synthetic biology techniques, and biomaterial-supported gene transfer, which provide a wider array of resources for manipulating tumor-associated macrophages, we suggest that combining these advanced methods will result in the creation of a new era of CAR-M therapy that demonstrates improved efficacy, safety, and availability.

The role of tumor-associated macrophages in the radioresistance of esophageal cancer cells via regulation of the VEGF-mediated angiogenic pathway

Tumor-associated macrophages (TAMs) are known to promote tumor growth, invasion, metastasis, and protumor angiogenesis, but the role of TAMs in evading radiotherapy in esophagus cancer remains unclear. In this study, we first induced TAMs from human monocytes (THP-1) and identified using immunofluorescence and Western blotting assays. We then co-cultured them with human esophageal cancer cell lines. CCK-8, colony formation, Transwell, scratch test, and TUNEL assays showed that TAMs could promote proliferation, survival rate, invasion, migration, and radioresistance and could inhibit apoptosis of the esophageal squamous carcinoma cell lines KYSE-150 and TE-1 before and after radiotherapy both in vivo and in vitro. Using LV-VEGFA-RNAi lentiviral vectors, we also found that TAMs could increase the expression of VEGFA and that inhibition of VEGFA could inhibit the biological function caused by TAMs. Finally, a Western blotting assay was used to evaluate the expression of various factors underlying the mechanism of TAMs. VEGFA, MAPK, P-MAPK, BCL-2, and Snail proteins were found to be overexpressed in co-cultured groups, whereas after VEGFA inhibition, MAPK, P-MAPK, BCL-2, and Snail proteins were found to be significantly downregulated in the radiotherapy group. These study results offer important information regarding the mechanism of radioresistance in esophageal cancer.

Identification of hypoxic macrophages in glioblastoma with therapeutic potential for vasculature normalization

Monocyte-derived tumor-associated macrophages (Mo-TAMs) intensively infiltrate diffuse gliomas with remarkable heterogeneity. Using single-cell transcriptomics, we chart a spatially resolved transcriptional landscape of Mo-TAMs across 51 patients with isocitrate dehydrogenase (IDH)-wild-type glioblastomas or IDH-mutant gliomas. We characterize a Mo-TAM subset that is localized to the peri-necrotic niche and skewed by hypoxic niche cues to acquire a hypoxia response signature. Hypoxia-TAM destabilizes endothelial adherens junctions by activating adrenomedullin paracrine signaling, thereby stimulating a hyperpermeable neovasculature that hampers drug delivery in glioblastoma xenografts. Accordingly, genetic ablation or pharmacological blockade of adrenomedullin produced by Hypoxia-TAM restores vascular integrity, improves intratumoral concentration of the anti-tumor agent dabrafenib, and achieves combinatorial therapeutic benefits. Increased proportion of Hypoxia-TAM or adrenomedullin expression is predictive of tumor vessel hyperpermeability and a worse prognosis of glioblastoma. Our findings highlight Mo-TAM diversity and spatial niche-steered Mo-TAM reprogramming in diffuse gliomas and indicate potential therapeutics targeting Hypoxia-TAM to normalize tumor vasculature.

A temporal perspective for tumor-associated macrophage identities and functions

Cancer is a progressive disease that can develop and evolve over decades, with inflammation playing a central role at each of its stages, from tumor initiation to metastasis. In this context, macrophages represent well-established bridges reciprocally linking inflammation and cancer via an array of diverse functions that have spurred efforts to classify them into subtypes. Here, we discuss the intertwines between macrophages, inflammation, and cancer with an emphasis on temporal dynamics of macrophage diversity and functions in pre-malignancy and cancer. By instilling temporal dynamism into the more static classic view of tumor-associated macrophage biology, we propose a new framework to better contextualize their significance in the inflammatory processes that precede and result from the onset of cancer and shape its evolution.

Mesenchymal stem cells-macrophages crosstalk and myeloid malignancy

As major components of the tumor microenvironment, both mesenchymal stem cells (MSCs) and macrophages can be remodelled and exhibit different phenotypes and functions during tumor initiation and progression. In recent years, increasing evidence has shown that tumor-associated macrophages (TAMs) play a crucial role in the growth, metastasis, and chemotherapy resistance of hematological malignancies, and are associated with poor prognosis. Consequently, TAMs have emerged as promising therapeutic targets. Notably, MSCs exert a profound influence on modulating immune cell functions such as macrophages and granulocytes, thereby playing a crucial role in shaping the immunosuppressive microenvironment surrounding tumors. However, in hematological malignancies, the cellular and molecular mechanisms underlying the interaction between MSCs and macrophages have not been clearly elucidated. In this review, we provide an overview of the role of TAMs in various common hematological malignancies, and discuss the latest advances in understanding the interaction between MSCs and macrophages in disease progression. Additionally, potential therapeutic approaches targeting this relationship are outlined.

Targeting PHGDH reverses the immunosuppressive phenotype of tumor-associated macrophages through α-ketoglutarate and mTORC1 signaling

Phosphoglycerate dehydrogenase (PHGDH) has emerged as a crucial factor in macromolecule synthesis, neutralizing oxidative stress, and regulating methylation reactions in cancer cells, lymphocytes, and endothelial cells. However, the role of PHGDH in tumor-associated macrophages (TAMs) is poorly understood. Here, we found that the T helper 2 (Th2) cytokine interleukin-4 and tumor-conditioned media upregulate the expression of PHGDH in macrophages and promote immunosuppressive M2 macrophage activation and proliferation. Loss of PHGDH disrupts cellular metabolism and mitochondrial respiration, which are essential for immunosuppressive macrophages. Mechanistically, PHGDH-mediated serine biosynthesis promotes α-ketoglutarate production, which activates mTORC1 signaling and contributes to the maintenance of an M2-like macrophage phenotype in the tumor microenvironment. Genetic ablation of PHGDH in macrophages from tumor-bearing mice results in attenuated tumor growth, reduced TAM infiltration, a phenotypic shift of M2-like TAMs toward an M1-like phenotype, downregulated PD-L1 expression and enhanced antitumor T-cell immunity. Our study provides a strong basis for further exploration of PHGDH as a potential target to counteract TAM-mediated immunosuppression and hinder tumor progression.

IFNα-induced BST2+ tumor-associated macrophages facilitate immunosuppression and tumor growth in pancreatic cancer by ERK-CXCL7 signaling

Pancreatic ductal adenocarcinoma (PDAC) features an immunosuppressive tumor microenvironment (TME) that resists immunotherapy. Tumor-associated macrophages, abundant in the TME, modulate T cell responses. Bone marrow stromal antigen 2-positive (BST2+) macrophages increase in KrasG12D/+; Trp53R172H/+; Pdx1-Cre mouse models during PDAC progression. However, their role in PDAC remains elusive. Our findings reveal a negative correlation between BST2+ macrophage levels and PDAC patient prognosis. Moreover, an increased ratio of exhausted CD8+ T cells is observed in tumors with up-regulated BST2+ macrophages. Mechanistically, BST2+ macrophages secrete CXCL7 through the ERK pathway and bind with CXCR2 to activate the AKT/mTOR pathway, promoting CD8+ T cell exhaustion. The combined blockade of CXCL7 and programmed death-ligand 1 successfully decelerates tumor growth. Additionally, cGAS-STING pathway activation in macrophages induces interferon (IFN)α synthesis leading to BST2 overexpression in the PDAC TME. This study provides insights into IFNα-induced BST2+ macrophages driving an immune-suppressive TME through ERK-CXCL7 signaling to regulate CD8+ T cell exhaustion in PDAC.

Taurine Inhibits Lung Metastasis in Triple-Negative Breast Cancer by Modulating Macrophage Polarization Through PTEN-PI3K/Akt/mTOR Pathway

SUMMARY

Taurine (Tau) has been found to inhibit triple-negative breast cancer (TNBC) invasion and metastasis. However, its effect on tumor-promoting macrophages and tumor suppressor macrophages in breast cancer progression remains unknown. In this study, we investigated the effects of Tau on macrophage polarization and its role in TNBC cell growth, invasion, and metastasis. We induced human THP-1 monocytes to differentiate into M2 macrophages through exogenous addition of interleukin-4. We used the TNBC cell lines MDA-MB-231 and BT-549 cultured in a conditioned medium from M2 macrophages to investigate the effect of Tau on tumor growth and invasion. We analyzed macrophage subset distribution, M1 and M2 macrophage-associated markers, and mRNA expression by quantitative polymerase chain reaction. We also detected the PTEN-PI3K/Akt/mTOR signaling pathway that mediates M1 macrophage to suppress tumor invasion using western blotting. Our results showed that Tau inhibits breast cancer metastasis to the lungs in vivo and cell invasion by altering the polarization of tumor-associated macrophage in vitro. In addition, Tau can up-regulate PTEN expression, suppress the PI3K-Akt signaling pathway, and promote the M1 polarization of macrophages, which ultimately inhibits the metastasis of TNBC cells. Our findings suggest that Tau inhibits the activation of the PI3K-Akt-mTOR signaling pathway by up-regulating PTEN, promotes the proportion of M1 macrophages in tumor-associated macrophage, and suppresses the invasion and metastasis of TNBC. This provides a potential therapeutic approach to influence cancer progression and metastasis.

Understanding Macrophage-Tumor Interactions: Insights from Single-Cell Behavior Monitoring in a Sessile Microdroplet System

Interaction between tumor-associated macrophages and tumor cells is crucial for tumor development, metastasis, and the related immune process. However, the macrophages are highly heterogeneous spanning from anti-tumorigenic to pro-tumorigenic, which needs to be understood at the single-cell level. Herein, a sessile microdroplet system designed for monitoring cellular behavior and analyzing intercellular interaction, demonstrated with macrophage-tumor cell pairs is presented. An automatic procedure based on the inkjet printing method is utilized for the precise pairing and co-encapsulation of heterotypic cells within picoliter droplets. The sessile nature of microdroplets ensures controlled fusion and provides stable environments conducive to adherent cell culture. The nitric oxide generation and morphological changes over incubation are explored to reveal the complicated interactions from a single-cell perspective. The immune response of macrophages under distinct cellular microenvironments is recorded. The results demonstrate that the tumor microenvironment displays a modulating role in polarizing macrophages from anti-tumorigenic into pro-tumorigenic phenotype. The approach provides a versatile and compatible platform to investigate intercellular interaction at the single-cell level, showing promising potential for advancing single-cell behavior studies.

Macrophage polarization in adenomyosis: A review

Adenomyosis (AM) is a common gynecological disorder characterized by the presence of endometrial glands and stroma within the uterine myometrium. It is associated with abnormal uterine bleeding (AUB), dysmenorrhea, and infertility. Although several mechanisms have been proposed to elucidate AM, the exact cause and development of the condition remain unclear. Recent studies have highlighted the significance of macrophage polarization in the microenvironment, which plays a crucial role in AM initiation and progression. However, a comprehensive review regarding the role and regulatory mechanism of macrophage polarization in AM is currently lacking. Therefore, this review aims to summarize the phenotype and function of macrophage polarization and the phenomenon of the polarization of adenomyosis-associated macrophages (AAMs). It also elaborates on the role and regulatory mechanism of AAM polarization in invasion/migration, fibrosis, angiogenesis, dysmenorrhea, and infertility. Furthermore, this review explores the underlying molecular mechanisms of AAM polarization and suggests future research directions. In conclusion, this review provides a new perspective on understanding the pathogenesis of AM and provides a theoretical foundation for developing targeted drugs through the regulation of AAM polarization.

Prognostic Significance of the Microenvironment in Human Papillomavirus Oropharyngeal Carcinoma: A Systematic Review

OBJECTIVE

The immune microenvironment of HPV-associated (HPV+) oropharyngeal squamous cell carcinomas (OPSCCs) (HPV+OPSCCs) differs from that of HPV-independent oropharyngeal cancers (HPV-independent OPSCCs). The literature on the subject is very abundant, demanding an organized synthesis of this wealth of information to evaluate the hypothesis associating the favorable prognosis of HPV+OPSCC patients with a different immune microenvironment. A systematic review of the literature was conducted regarding the microenvironment of HPV+OPSCCs.

DATA SOURCE

MEDLINE/PubMed, Embase, and Cochrane Library databases.

REVIEW METHODS

A literature search was performed following PRISMA guidelines (Moher D. PLoS Med. 2009). The PEO (Population, Exposure, and Outcome) framework is detailed as follows: P: patients with oropharyngeal squamous cell carcinomas, E: human papillomavirus (HPV), and O: histological and immunological composition of the tumoral microenvironment (TME). No meta-analysis was performed.

RESULTS

From 1,202 studies that were screened, 58 studies were included (n = 6,474 patients; n = 3,581 (55%) HPV+OPSCCs and n = 2,861(45%) HPV-independent OPSCCs). The presence of tumor-infiltrating lymphocytes (TIL), CD3+ in 1,733 patients, CD4+ in 520 patients, and CD8+ (cytotoxic T lymphocytes (CTL)) in 3,104 patients, and high levels of PD-L1 expression in 1,222 patients is strongly correlated with an improved clinical outcome in HPV+OPSCCs.

CONCLUSION

This systematic review provides the most comprehensive information on the immune microenvironment of HPV+OPSCCs to date. Tumor-infiltrating lymphocytes and PD-L1 expression are associated with a favorable prognosis. B, CD8+ and resident memory cells densities are higher in HPV+OPSCCs. The importance of myeloid lineages is still a matter of debate and research.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1507-1516, 2024.

New insights into the role of macrophages in cancer immunotherapy

Macrophages are the main component of the tumor microenvironment, which are differentiated from monocytes in the blood and play an important role in cancer development. Tumor-associated macrophages (TAMs) can promote tumor growth, invasion, metastasis, and resistance to anti-programmed death receptor 1 therapy by regulating programmed cell death ligand 1 expression and interacting with other immune cells in the tumor microenvironment. However, when activated properly, macrophages can also play an anti-tumor role by enhancing the phagocytosis and cytotoxicity of tumor cells. TAM is associated with poor prognosis and drug resistance in patients treated with immunotherapy, indicating that macrophages are attractive targets for combined therapy in cancer treatment. Combination of targeting TAMs and immunotherapy overcomes the drug resistance and achieved excellent results in some cancers, which may be a promising strategy for cancer treatment in the future. Herein, we review the recent findings on the role of macrophages in tumor development, metastasis, and immunotherapy. We focus mainly on macrophage≥centered therapy, including strategies to deplete and reprogram TAMs, which represent the potential targets for improving tumor immunotherapy efficacy.

Immune Specific and Tumor-Dependent mRNA Vaccines for Cancer Immunotherapy: Reprogramming Clinical Translation into Tumor Editing Therapy

Extensive research into mRNA vaccines for cancer therapy in preclinical and clinical trials has prepared the ground for the quick development of immune-specific mRNA vaccines during the COVID-19 pandemic. Therapeutic cancer vaccines based on mRNA are well tolerated, and are an attractive choice for future cancer immunotherapy. Ideal personalized tumor-dependent mRNA vaccines could stimulate both humoral and cellular immunity by overcoming cancer-induced immune suppression and tumor relapse. The stability, structure, and distribution strategies of mRNA-based vaccines have been improved by technological innovations, and patients with diverse tumor types are now being enrolled in numerous clinical trials investigating mRNA vaccine therapy. Despite the fact that therapeutic mRNA-based cancer vaccines have not yet received clinical approval, early clinical trials with mRNA vaccines as monotherapy and in conjunction with checkpoint inhibitors have shown promising results. In this review, we analyze the most recent clinical developments in mRNA-based cancer vaccines and discuss the optimal platforms for the creation of mRNA vaccines. We also discuss the development of the cancer vaccines' clinical research, paying particular attention to their clinical use and therapeutic efficacy, which could facilitate the design of mRNA-based vaccines in the near future.

Chemotherapy induces myeloid-driven spatial T-cell exhaustion in ovarian cancer

To uncover the intricate, chemotherapy-induced spatiotemporal remodeling of the tumor microenvironment, we conducted integrative spatial and molecular characterization of 97 high-grade serous ovarian cancer (HGSC) samples collected before and after chemotherapy. Using single-cell and spatial analyses, we identify increasingly versatile immune cell states, which form spatiotemporally dynamic microcommunities at the tumor-stroma interface. We demonstrate that chemotherapy triggers spatial redistribution and exhaustion of CD8+ T cells due to prolonged antigen presentation by macrophages, both within interconnected myeloid networks termed "Myelonets" and at the tumor stroma interface. Single-cell and spatial transcriptomics identifies prominent TIGIT-NECTIN2 ligand-receptor interactions induced by chemotherapy. Using a functional patient-derived immuno-oncology platform, we show that CD8+T-cell activity can be boosted by combining immune checkpoint blockade with chemotherapy. Our discovery of chemotherapy-induced myeloid-driven spatial T-cell exhaustion paves the way for novel immunotherapeutic strategies to unleash CD8+ T-cell-mediated anti-tumor immunity in HGSC.

Macrophage-derived exosomal microRNAs promote metastasis in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly invasive disease that can metastasize to distant organs such as the lung and liver. However, the exact mechanisms underlying PDAC metastasis remain unclear. Tumor-associated macrophages (TAMs) have been shown to play a critical role in cancer initiation, progression, outgrowth, and metastasis, likely through their interaction with cancer cells via extracellular vesicles known as exosomes. However, the precise mechanisms of this interaction are not fully understood.

METHODS

In this study, we obtained TAMs from PDAC patients and isolated exosomes from their culture medium. We characterized these exosomes and analyzed their miRNA expression profiles using Multiplex miRNA assays with FirePlex particle technology. Additionally, we conducted in vitro co-culture experiments between PDAC cells and conditioned media or exosomes from TAMs to investigate the crosstalk between these cells via exosomes. Furthermore, we evaluated the in vivo lung metastasis of PDAC cells treated with TAM-derived exosomes in athymic nude mice.

RESULTS

TAMs from PDAC patients promoted the invasiveness and migratory potential of PDAC cells, partially through the effects of TAM-derived exosomes. Specifically, we identified two microRNAs, miR-202-5p and miR-142-5p, which were transferred from TAM-derived exosomes to PDAC cells, resulting in the suppression of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and promoting their invasiveness and migratory potential. We also found that distal metastasis was increased in PDAC cells treated with TAM-derived exosomes, partially through miR-202-5p and miR-142-5p.

CONCLUSIONS

Exosomal transfer of miR-202-5p and miR-142-5p plays a significant role in conferring invasiveness and migratory potential to PDAC cells. Targeting exosome communication may represent a promising new therapeutic strategy for reducing cancer metastasis of PDACs.

NF-κB in biology and targeted therapy: new insights and translational implications

NF-κB signaling has been discovered for nearly 40 years. Initially, NF-κB signaling was identified as a pivotal pathway in mediating inflammatory responses. However, with extensive and in-depth investigations, researchers have discovered that its role can be expanded to a variety of signaling mechanisms, biological processes, human diseases, and treatment options. In this review, we first scrutinize the research process of NF-κB signaling, and summarize the composition, activation, and regulatory mechanism of NF-κB signaling. We investigate the interaction of NF-κB signaling with other important pathways, including PI3K/AKT, MAPK, JAK-STAT, TGF-β, Wnt, Notch, Hedgehog, and TLR signaling. The physiological and pathological states of NF-κB signaling, as well as its intricate involvement in inflammation, immune regulation, and tumor microenvironment, are also explicated. Additionally, we illustrate how NF-κB signaling is involved in a variety of human diseases, including cancers, inflammatory and autoimmune diseases, cardiovascular diseases, metabolic diseases, neurological diseases, and COVID-19. Further, we discuss the therapeutic approaches targeting NF-κB signaling, including IKK inhibitors, monoclonal antibodies, proteasome inhibitors, nuclear translocation inhibitors, DNA binding inhibitors, TKIs, non-coding RNAs, immunotherapy, and CAR-T. Finally, we provide an outlook for research in the field of NF-κB signaling. We hope to present a stereoscopic, comprehensive NF-κB signaling that will inform future research and clinical practice.

Metabolic interplay: tumor macrophages and regulatory T cells

The tumor microenvironment (TME) contains a complex cellular ecosystem where cancer, stromal, vascular, and immune cells interact. Macrophages and regulatory T cells (Tregs) are critical not only for maintaining immunological homeostasis and tumor growth but also for monitoring the functional states of other immune cells. Emerging evidence reveals that metabolic changes in macrophages and Tregs significantly influence their pro-/antitumor functions through the regulation of signaling cascades and epigenetic reprogramming. Hence, they are increasingly recognized as therapeutic targets in cancer immunotherapy. Specific metabolites in the TME may also affect their pro-/antitumor functions by intervening with the metabolic machinery. We discuss how metabolites influence the immunosuppressive phenotypes of tumor-associated macrophages (TAMs) and Tregs. We then describe how TAMs and Tregs, independently or collaboratively, utilize metabolic mechanisms to suppress the activity of CD8+ T cells. Finally, we highlight promising metabolic interventions that can improve the outcome of current cancer therapies.

The promising role of tumor-associated macrophages in the treatment of cancer

Macrophages are important components of the immune system. Mature macrophages can be recruited to tumor microenvironment that affect tumor cell proliferation, invasion and metastasis, extracellular matrix remodeling, immune suppression, as well as chemotherapy resistance. Classically activated type I macrophages (M1) exhibited marked tumor killing and phagocytosis. Therefore, using macrophages for adoptive cell therapy has attracted attention and become one of the most effective strategies for cancer treatment. Through cytokines and/or chemokines, macrophage can inhibit myeloid cells recruitment, and activate anti-tumor and immune killing functions. Applying macrophages for anti-tumor delivery is one of the most promising approaches for cancer therapy. This review article introduces the role of macrophages in tumor development and drug resistance, and the possible clinical application of targeting macrophages for overcoming drug resistance and enhancing cancer therapeutics, as well as its challenges.

Pumilio RNA binding family member 1 deficiency activates anti-tumor immunity in hepatocellular carcinoma via restraining M2 macrophage polarization

Pumilio RNA-binding family member 1 (PUM1) has been implicated in both the progression of colorectal cancer and the regulation of inflammation. The role of PUM1 in the polarization of tumor-associated macrophages (TAMs) into the M2 phenotype has not yet been reported in hepatocellular carcinoma. Using the PUM1-knockout mice model, flow cytometry, and IHC, we validated the role of PUM1 in hepatocellular carcinoma (HCC) TAMs. One-way analysis of variance (ANOVA) or student's t-tests was used to compare the experimental groups. We found that PUM1 inhibited anti-tumor immunity in HCC through TAM-mediated inhibition of CD8+ T cells. We also showed that PUM1 promotes the transformation of TAMs into pro-tumorigenic M2-like phenotypes by activating cAMP signaling pathway. This study emphasized the potential of PUM1 as a target for immunotherapy in HCC through TAMs. The present study revealed the molecular mechanism underlying the pro-tumor role of PUM1 in HCC.

PD-L1-expressing tumor-associated macrophages are immunostimulatory and associate with good clinical outcome in human breast cancer

Tumor-associated macrophages (TAMs) are the predominant cells that express programmed cell death ligand 1 (PD-L1) within human tumors in addition to cancer cells, and PD-L1+ TAMs are generally thought to be immunosuppressive within the tumor immune microenvironment (TIME). Using single-cell transcriptomic and spatial multiplex immunofluorescence analyses, we show that PD-L1+ TAMs are mature and immunostimulatory with spatial preference to T cells. In contrast, PD-L1- TAMs are immunosuppressive and spatially co-localize with cancer cells. Either higher density of PD-L1+ TAMs alone or ratio of PD-L1+/PD-L1- TAMs correlate with favorable clinical outcome in two independent cohorts of patients with breast cancer. Mechanistically, we show that PD-L1 is upregulated during the monocyte-to-macrophage maturation and differentiation process and does not require external IFN-γ stimulus. Functionally, PD-L1+ TAMs are more mature/activated and promote CD8+ T cells proliferation and cytotoxic capacity. Together, our findings reveal insights into the immunological significance of PD-L1 within the TIME.

Androgen deprivation triggers a cytokine signaling switch to induce immune suppression and prostate cancer recurrence

Androgen deprivation therapy (ADT) is an effective but not curative treatment for advanced and recurrent prostate cancer (PC). We investigated the mechanisms controlling the response to androgen-deprivation by surgical castration in genetically-engineered mouse models (GEMM) of PC, using high frequency ultrasound imaging to rigorously measure tumor volume. Castration initially causes almost all tumors to shrink in volume, but many tumors subsequently recur within 5-10 weeks. Blockade of tumor necrosis factor (TNF) signaling a few days in advance of castration surgery, using a TNFR2 ligand trap, prevents regression in a PTEN-deficient GEMM. Following tumor regression, a basal stem cell-like population within the tumor increases along with TNF protein levels. Tumor cell lines in culture recapitulate these in vivo observations, suggesting that basal stem cells are the source of TNF. When TNF signaling blockade is administered immediately prior to castration, tumors regress but recurrence is prevented, implying that a late wave of TNF secretion within the tumor, which coincides with the expression of NFkB regulated genes, drives recurrence. The inhibition of signaling downstream of one NFkB-regulated protein, chemokine C-C motif ligand 2 (CCL2), prevents post-castration tumor recurrence, phenocopying post-castration (late) TNF signaling blockade. CCL2 was originally identified as a macrophage chemoattractant and indeed at late times after castration gene sets related to chemotaxis and migration are up-regulated. Importantly, enhanced CCL2 signaling during the tumor recurrence phase coincides with an increase in pro-tumorigenic macrophages and a decrease in CD8 T cells, suggesting that recurrence is driven at least in part by tumor immunosuppression. In summary, we demonstrate that a therapy-induced switch in TNF signaling, a consequence of the increased stem cell-like character of the residual tumor cells surviving ADT, induces an immunosuppressive tumor microenvironment and concomitant tumor recurrence.

Immune cell networking in solid tumors: focus on macrophages and neutrophils

The tumor microenvironment is composed of tumor cells, stromal cells and leukocytes, including innate and adaptive immune cells, and represents an ecological niche that regulates tumor development and progression. In general, inflammatory cells are considered to contribute to tumor progression through various mechanisms, including the formation of an immunosuppressive microenvironment. Macrophages and neutrophils are important components of the tumor microenvironment and can act as a double-edged sword, promoting or inhibiting the development of the tumor. Targeting of the immune system is emerging as an important therapeutic strategy for cancer patients. However, the efficacy of the various immunotherapies available is still limited. Given the crucial importance of the crosstalk between macrophages and neutrophils and other immune cells in the formation of the anti-tumor immune response, targeting these interactions may represent a promising therapeutic approach against cancer. Here we will review the current knowledge of the role played by macrophages and neutrophils in cancer, focusing on their interaction with other immune cells.

Immunotherapy Innovations in the Fight against Osteosarcoma: Emerging Strategies and Promising Progress

Immunosuppressive elements within the tumor microenvironment are the primary drivers of tumorigenesis and malignant advancement. The presence, as well as the crosstalk between myeloid-derived suppressor cells (MDSCs), osteosarcoma-associated macrophages (OS-Ms), regulatory T cells (Tregs), and endothelial cells (ECs) with osteosarcoma cells cause the poor prognosis of OS. In addition, the consequent immunosuppressive factors favor the loss of treatment potential. Nanoparticles offer a means to dynamically and locally manipulate immuno-nanoparticles, which present a promising strategy for transforming OS-TME. Additionally, chimeric antigen receptor (CAR) technology is effective in combating OS. This review summarizes the essential mechanisms of immunosuppressive cells in the OS-TME and the current immune-associated strategies. The last part highlights the limitations of existing therapies and offers insights into future research directions.

Comprehensive Proteomics Analysis Reveals Dynamic Phenotypes of Tumor-Associated Macrophages and Their Precursor Cells in Tumor Progression

Tumor-associated macrophages (TAMs) are key regulators in tumor progression, but the precise role of bone marrow-derived monocytes (Mons) as TAM precursors and their dynamic phenotypes regulated by the tumor microenvironment (TME) remain unclear. Here, we developed an optimized microproteomics workflow to analyze low-cell-number mouse myeloid cells. We sorted TAMs and their corresponding Mons (1 × 105 per sample) from individual melanoma mouse models at both the early and late stages. We established the protein expression profiles for these cells by mass spectrometry. Subsequently, we analyzed the dynamics phenotypes of TAMs and identified a characteristic protein expression profile characterized by upregulated cholesterol metabolism and downregulated immune responses during tumor progression. Moreover, we found the downregulation of both STAT5 and PYCARD expression not only in late-stage TAMs but also in late-stage Mons, indicating a loss of the ability to induce inflammatory responses prior to Mons infiltration into TME. Taken together, our study provides valuable insights into the progression-dependent transitions between TAMs and their precursor cells, as well as the cross-organ communications of tumor and bone marrow.

JAM2 is a prognostic biomarker and inhibits proliferation, metastasis and epithelial-mesenchymal transition in lung adenocarcinoma

BACKGROUND

Junctional adhesion molecule 2 (JAM2) plays a pivotal role in various biological processes, including proliferation, metastasis and angiogenesis, contributing to tumor progression. While previous studies have highlighted the polarizing functions of JAM2 in different cancer types, its specific role in lung adenocarcinoma (LUAD) remains unclear.

METHODS

In this study, we harnessed multiple public databases to analyze the expression and prognostic significance of JAM2 in LUAD. Using the Linkedomics database, Matescape database and R package, we explored the associated genes, the potential biological functions and the impact of JAM2 on the tumor microenvironment. Our findings from public databases were further validated using real-time quantitative PCR, western blot and immunohistochemistry. Additionally, in vitro experiments were conducted to assess the influence of JAM2 on LUAD cell proliferation, invasion, migration, apoptosis and epithelial-mesenchymal transition. Furthermore, we established a xenograft model to investigate the in vivo effects of JAM2 on tumorigenesis.

RESULTS

Our results revealed a significant downregulation of JAM2 in LUAD, and patients with low JAM2 expression exhibited unfavorable overall survival outcomes. Functional enrichment analysis indicated that JAM2 may be associated with processes such as cell adhesion, extracellular matrix, cell junctions and regulation of proliferation. Notably, increased JAM2 expression correlated with higher tumor microenvironment scores and reduced immune cell abundance. Furthermore, overexpression of JAM2 induced apoptosis, suppressed tumor proliferation and exhibited potential inhibitory effects on tumor invasion and migration through the modulation of epithelial-mesenchymal transition. Additionally, in vivo experiments confirmed that JAM2 overexpression led to a reduction in tumor growth.

CONCLUSION

Overall, our study highlights the clinical significance of low JAM2 expression as a predictor of poor prognosis in LUAD patients. Moreover, JAM2 was found to exert inhibitory effects on various aspects of tumor progression. Consequently, JAM2 emerges as a promising prognostic biomarker and a potential therapeutic target for LUAD patients.

Oncometabolite 2-hydroxyglutarate regulates anti-tumor immunity

"Oncometabolite" 2-hydroxyglutarate (2-HG) is an aberrant metabolite found in tumor cells, exerting a pivotal influence on tumor progression. Recent studies have unveiled its impact on the proliferation, activation, and differentiation of anti-tumor T cells. Moreover, 2-HG regulates the function of innate immune components, including macrophages, dendritic cells, natural killer cells, and the complement system. Elevated levels of 2-HG hinder α-KG-dependent dioxygenases (α-KGDDs), contributing to tumorigenesis by disrupting epigenetic regulation, genome integrity, hypoxia-inducible factors (HIF) signaling, and cellular metabolism. The chiral molecular structure of 2-HG produces two enantiomers: D-2-HG and L-2-HG, each with distinct origins and biological functions. Efforts to inhibit D-2-HG and leverage the potential of L-2-HG have demonstrated efficacy in cancer immunotherapy. This review delves into the metabolism, biological functions, and impacts on the tumor immune microenvironment (TIME) of 2-HG, providing a comprehensive exploration of the intricate relationship between 2-HG and antitumor immunity. Additionally, we examine the potential clinical applications of targeted therapy for 2-HG, highlighting recent breakthroughs as well as the existing challenges.

Tumor-Microenvironment-Activatable Nanoparticle Mediating Immunogene Therapy and M2 Macrophage-Targeted Inhibitor for Synergistic Cancer Immunotherapy

Immunotherapy has achieved prominent clinical efficacy in combating cancer and has recently become a mainstream treatment strategy. However, achieving broad efficacy with a single modality is challenging, and the heterogeneity of the tumor microenvironment (TME) restricts the accuracy and effectiveness of immunotherapy strategies for tumors. Herein, a TME-responsive targeted nanoparticle to enhance antitumor immunity and reverse immune escape by codelivering interleukin-12 (IL-12) expressing gene and colony-stimulating factor-1 receptor (CSF-1R) inhibitor PLX3397 (PLX) is presented. The introduction of disulfide bonds and cyclo(Arg-Gly-Asp-d-Phe-Lys) (cRGD) peptides conferred reduction reactivity and tumor targeting to the nanoparticles, respectively. It is hypothesized that activating host immunity by the local expression of IL-12, while modulating the tumor-associated macrophages (TAM) function through blocking CSF-1/CSF-1R signaling, could constitute a feasible approach for cancer immunotherapy. The fabricated functional nanoparticle successfully ameliorated the TME by stimulating the proliferation and activation of T lymphocytes, promoting the repolarization of TAMs, reducing myeloid-derived suppressor cells (MDSCs), and promoting the maturation of dendritic cells (DC) as well as the secretion of antitumor cytokines, which efficiently suppressed tumor growth and metastasis. Finally, substantial changes in the TME were deciphered by single-cell analysis including infiltration of different cells, transcriptional states, secretory signaling and cell-cell communications. These findings provide a promising combinatorial immunotherapy strategy through immunomodulatory nanoparticles.

Targeting TAM-secreted S100A9 effectively enhances the tumor-suppressive effect of metformin in treating lung adenocarcinoma

Metformin's effect on tumor treatment was complex, because it significantly reduced cancer cell proliferation in vitro, but made no difference in prognosis in several clinical cohorts. Our transcriptome sequencing results revealed that tumor-associated macrophage (TAM) infiltration significantly increased in active lung adenocarcinoma (LUAD) patients with long-term metformin use. We further identified that the tumor suppressive effect of metformin was more significant in mice after the depletion of macrophages, suggesting that TAMs might play an important role in metformin's effects in LUAD. Combining 10X Genomics single-cell sequencing of tumor samples, transcriptome sequencing of metformin-treated TAMs, and the ChIP-Seq data of the Encode database, we identified and validated that metformin significantly increased the expression and secretion of S100A9 of TAMs through AMPK-CEBP/β pathway. For the downstream, S100A9 binds to RAGE receptors on the surface of LUAD cells, and then activates the NF-κB pathway to promote EMT and progression of LUAD, counteracting the inhibitory effect of metformin on LUAD cells. In cell-derived xenograft models (CDX) and patient-derived xenograft models (PDX) models, our results showed that neutralizing antibodies targeting TAM-secreted S100A9 effectively enhanced the tumor suppressive effect of metformin in treating LUAD. Our results will enable us to better comprehend the complex role of metformin in LUAD, and advance its clinical application in cancer treatment.

Ribosome profiling: a powerful tool in oncological research

Neoplastic cells need to adapt their gene expression pattern to survive in an ever-changing or unfavorable tumor microenvironment. Protein synthesis (or mRNA translation), an essential part of gene expression, is dysregulated in cancer. The emergence of distinct translatomic technologies has revolutionized oncological studies to elucidate translational regulatory mechanisms. Ribosome profiling can provide adequate information on diverse aspects of translation by aiding in quantitatively analyzing the intensity of translating ribosome-protected fragments. Here, we review the primary currently used translatomics techniques and highlight their advantages and disadvantages as tools for translatomics studies. Subsequently, we clarified the areas in which ribosome profiling could be applied to better understand translational control. Finally, we summarized the latest advances in cancer studies using ribosome profiling to highlight the extensive application of this powerful and promising translatomic tool.