Blocking Triggering Receptor Expressed on Myeloid Cells-1-Positive Tumor-Associated Macrophages Induced by Hypoxia Reverses Immunosuppression and Anti-Programmed Cell Death Ligand 1 Resistance in Liver Cancer

A nanodrug provokes antitumor immune responses via synchronous multicellular regulation for enhanced cancer immunotherapy

Hepatocellular carcinoma (HCC) exhibits a low response to immunotherapy due to the dense extracellular matrix (ECM) filled with immunosuppressive cells including dendritic cells (DCs) of blocked maturation. Herein, we develop a nanoprodrug self-assembled from polyethylene glycol-poly-4-borono-l-phenylalanine (mPEG-PBPA) conjugating with quercetin (QUE) via boronic ester bonds. In addition, an immune adjuvant of imiquimod (R837) is incorporated. The nanodrug (denoted as Q&R@NPs) is prepared from a simple mixing means with a high loading content of QUE reaching more than 30%. Owing to the acid and reactive oxygen species (ROS) sensitivities of boronic ester bonds, Q&R@NPs can respond to the tumor microenvironment (TME) and release QUE and R837 to synchronously exert multicellular regulation functions. Specifically, QUE inhibits the activation state of hepatic stellate cells and reduces highly expressed programmed death receptor ligand 1 (PD-L1) on tumor cells, meanwhile R837 exposes calreticulin on tumor cell surface as an "eat me" signal and leads to a large number of DCs maturing for enhanced antigen presentation. Consequently, the cooperative immune regulation results in a remodeled TME with high infiltration of cytotoxic T lymphocytes for enhanced HCC immunotherapy, which demonstrates an effective immunotherapy paradigm for dense ECM characterized solid tumors with high PD-L1 expression.

Immunotherapy resistance in solid tumors: mechanisms and potential solutions

While the emergence of immunotherapies has fundamentally altered the management of solid tumors, cancers exploit many complex biological mechanisms that result in resistance to these agents. These encompass a broad range of cellular activities - from modification of traditional paradigms of immunity via antigen presentation and immunoregulation to metabolic modifications and manipulation of the tumor microenvironment. Intervening on these intricate processes may provide clinical benefit in patients with solid tumors by overcoming resistance to immunotherapies, which is why it has become an area of tremendous research interest with practice-changing implications. This review details the major ways cancers avoid both natural immunity and immunotherapies through primary (innate) and secondary (acquired) mechanisms of resistance, and it considers available and emerging therapeutic approaches to overcoming immunotherapy resistance.

NK cell-based immunotherapy in hepatocellular carcinoma: An attractive therapeutic option for the next decade

Hepatocellular carcinoma (HCC), a major subtype of liver cancer, poses significant therapeutic challenges due to its late diagnosis and rapid progression. The evolving landscape of immunotherapy offers a beacon of hope, with natural killer (NK) cells emerging as pivotal players in combating HCC. NK cells are unique cytotoxic lymphocytes that are essential in the fight against infections and malignancies. Phenotypic and functional NK cell abnormalities have been shown in HCC patients, indicating their significance as a component of the innate immune system against cancer. This review elucidates the critical role of NK cells in combating HCC, focusing on their interaction with the tumor microenvironment, the development of NK cell-based therapies, and the innovative strategies to enhance their efficacy in the immunosuppressive milieu of HCC. The review delves into the various therapeutic strategies, including autologous and allogeneic NK cell therapies, genetic engineering to improve NK cell resilience and targeting, and the integration of NK cells with other immunotherapeutic approaches like checkpoint inhibitors and oncolytic virotherapy. By highlighting recent advancements and the ongoing challenges in the field, this review sets the stage for future research directions that could unlock the full potential of NK cell-based immunotherapy for HCC, offering a beacon of hope for patients battling this formidable cancer.

Hypoxic tumour-derived exosomal miR-1290 exacerbates the suppression of CD8+ T cells by promoting M2 macrophage polarization

Hypoxia plays an important role in the metastasis of hepatocellular carcinoma (HCC). Exosomes have been widely studied as mediators of communication between tumours and immune cells. However, the specific mechanism by which hypoxic HCC cell-derived exosomes suppress antitumor immunity is unclear. Hypoxia scores were determined for The Cancer Genome-Liver Hepatocellular Carcinoma (TCGA-LIHC) dataset patients, and HCC patients in the hyperhypoxic group had a higher degree of M2 macrophage infiltration. Patients in the M2 high-invasion group had a lower probability of survival than those in the low-invasion group. In vivo and in vitro experiments demonstrated that exosomes secreted by hypoxic HCC cells promote M2 macrophage polarization. This polarization induces apoptosis in CD8+ T cells. Additionally, it encourages epithelial-mesenchymal transition (EMT), which increases HCC migration. Exosomal miRNA sequencing revealed that miR-1290 was highly expressed in exosomes secreted by hypoxic HCC cells. Mechanistically, miR-1290 in macrophages inhibited Akt2 while upregulating PD-L1 to promote M2 polarization, induce apoptosis in CD8+ T cells, and enhance EMT in HCC. Animal studies found that the miR-1290 antagomir in combination with the immune checkpoint inhibitor produced better antitumor effects than the monotherapies. In conclusion, the secretion of exosome-derived miR-1290 from HCC cells in a hypoxic environment supported immune escape by HCC cells by promoting M2 macrophage polarization to induce apoptosis in CD8+ T cells and enhance EMT that promoted HCC metastasis. Therefore, miR-1290 is an important molecule in antitumor immunity in HCC, and inhibition of miR-1290 could provide a novel immunotherapeutic approach for HCC treatment.

Blocking CX3CR1+ Tumor-Associated Macrophages Enhances the Efficacy of Anti-PD1 Therapy in Hepatocellular Carcinoma

The efficacy of immune checkpoint inhibitors in the treatment of hepatocellular carcinoma (HCC) remains limited, highlighting the need for further investigation into the mechanisms underlying treatment resistance. Accumulating evidence indicates that tumor-associated macrophages (TAM) within the tumor microenvironment demonstrate a key role in immune evasion and treatment resistance. This study explored the role of TAMs in the HCC tumor microenvironment. Our findings reveal that TAMs expressing CX3C motif chemokine receptor 1 (CX3CR1) induced T-cell exhaustion through IL27 secretion in orthotopic models of HCC following treatment with anti-PD1. Moreover, we identified prostaglandin E2 (PGE2), released by immune-attacked tumor cells, as a key regulator of TAM transition to a CX3CR1+ phenotype. To augment the therapeutic response to anti-PD1 therapy, we propose targeting CX3CR1+ TAMs in addition to anti-PD1 therapy. Our study contributes to the understanding of the role of TAMs in cancer immunotherapy and highlights potential clinical implications for HCC treatment. The combination of targeting CX3CR1+ TAMs with anti-PD1 therapy holds promise for enhancing the efficacy of immunotherapeutic interventions in patients with HCC.

The influence of biophysical niche on tumor-associated macrophages in liver cancer

HCC, the most common type of primary liver cancer, is a leading cause of cancer-related mortality worldwide. Although the advancement of immunotherapies by immune checkpoint inhibitors (ICIs) that target programmed cell death 1 or programmed cell death 1-ligand 1 has revolutionized the treatment for HCC, the majority is still not beneficial. Accumulating evidence has pointed out that the potent immunosuppressive tumor microenvironment in HCC poses a great challenge to ICI therapeutic efficacy. As a key component in tumor microenvironment, tumor-associated macrophages (TAMs) play vital roles in HCC development, progression, and ICI low responsiveness. Mechanistically, TAM can promote cancer invasion and metastasis, angiogenesis, epithelial-mesenchymal transition, maintenance of stemness, and most importantly, immunosuppression. Targeting TAMs, therefore, represents an opportunity to enhance the ICI therapeutic efficacy in patients with HCC. While previous research has primarily focused on biochemical cues influencing macrophages, emerging evidence highlights the critical role of biophysical signals, such as substrate stiffness, topography, and external forces. In this review, we summarize the influence of biophysical characteristics within the tumor microenvironment that regulate the phenotype and function of TAMs in HCC pathogenesis and progression. We also explore the possible mechanisms and discuss the potential of manipulating biophysical cues in regulating TAM for HCC therapy. By gaining a deeper understanding of how macrophages sense and respond to mechanical forces, we may potentially usher in a path toward a curative approach for combinatory cancer immunotherapies.

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.

Novel insights into immune cells modulation of tumor resistance

Tumor resistance poses a significant challenge to effective cancer treatment, making it imperative to explore new therapeutic strategies. Recent studies have highlighted the profound involvement of immune cells in the development of tumor resistance. Within the tumor microenvironment, macrophages undergo polarization into the M2 phenotype, thus promoting the emergence of drug-resistant tumors. Neutrophils contribute to tumor resistance by forming extracellular traps. While T cells and natural killer (NK) cells exert their impact through direct cytotoxicity against tumor cells. Additionally, dendritic cells (DCs) have been implicated in preventing tumor drug resistance by stimulating T cell activation. In this review, we provide a comprehensive summary of the current knowledge regarding immune cell-mediated modulation of tumor resistance at the molecular level, with a particular focus on macrophages, neutrophils, DCs, T cells, and NK cells. The targeting of immune cell modulation exhibits considerable potential for addressing drug resistance, and an in-depth understanding of the molecular interactions between immune cells and tumor cells holds promise for the development of innovative therapies. Furthermore, we explore the clinical implications of these immune cells in the treatment of drug-resistant tumors. This review emphasizes the exploration of novel approaches that harness the functional capabilities of immune cells to effectively overcome drug-resistant tumors.

Recent Progress on Nanomedicine-Mediated Repolarization of Tumor-Associated Macrophages for Cancer Immunotherapy

Tumor-associated macrophages (TAMs) constitute the largest number of immune cells in the tumor microenvironment (TME). They play an essential role in promoting tumor progression and metastasis, which makes them a potential therapeutic target for cancer treatment. TAMs are usually divided into two categories: pro-tumoral M2-like TAMs and antitumoral M1 phenotypes at either extreme. The reprogramming of M2-like TAMs toward a tumoricidal M1 phenotype is of particular interest for the restoration of antitumor immunity in cancer immunotherapy. Notably, nanomedicines have shown great potential for cancer therapy due to their unique structures and properties. This review will briefly describe the biological features and roles of TAMs in tumor, and then discuss recent advances in nanomedicine-mediated repolarization of TAMs for cancer immunotherapy. Finally, perspectives on nanomedicine-mediated repolarization of TAMs for effective cancer immunotherapy are also presented.

Dissection of pro-tumoral macrophage subtypes and immunosuppressive cells participating in M2 polarization

Alternatively activated macrophage (M2) polarization can result in one of four subtypes based on cytokines and signaling pathways associated with macrophage activation: M2a, M2b, M2c, and M2d macrophages. The majority of M2 subtypes are anti-inflammatory and pro-angiogenic, secreting growth factors (VEGF, PDGF) and matrix metalloproteinases (MMP2, MMP9) which boost tumor growth, metastasis, and invasion. M2-polarized macrophages are associated with immune suppressor cells harboring Myeloid derived suppressor cells, Regulatory T cells (Tregs), Regulatory B cells as well as alternatively activated (N2) neutrophils. Treg cells selectively support the metabolic stability, mitochondrial integrity, and survival rate of M2-like TAMs in an indirect environment. Also, the contribution of Breg cells influences macrophage polarization towards the M2 direction. TAM is activated when TAN levels in the tumor microenvironment are insufficient or vice versa, suggesting that macrophage and its polarization are fine-tuned. Understanding the functions of immune suppressive cells, mediators, and signaling pathways involved with M2 polarization will allow us to identify potential strategies for targeting the TAM repolarization phenotype for innovative immunotherapy approaches. In this review, we have highlighted the critical factors for M2 macrophage polarization, differential cytokine/chemokine profiles of M1 and M2 macrophage subtypes, and other immune cells' impact on the polarization within the immunosuppressive niche.

Engineering Versatile Bacteria-Derived Outer Membrane Vesicles: An Adaptable Platform for Advancing Cancer Immunotherapy

In recent years, cancer immunotherapy has undergone a transformative shift toward personalized and targeted therapeutic strategies. Bacteria-derived outer membrane vesicles (OMVs) have emerged as a promising and adaptable platform for cancer immunotherapy due to their unique properties, including natural immunogenicity and the ability to be engineered for specific therapeutic purposes. In this review, a comprehensive overview is provided of state-of-the-art techniques and methodologies employed in the engineering of versatile OMVs for cancer immunotherapy. Beginning by exploring the biogenesis and composition of OMVs, unveiling their intrinsic immunogenic properties for therapeutic appeal. Subsequently, innovative approaches employed to engineer OMVs are delved into, ranging from the genetic engineering of parent bacteria to the incorporation of functional molecules. The importance of rational design strategies is highlighted to enhance the immunogenicity and specificity of OMVs, allowing tailoring for diverse cancer types. Furthermore, insights into clinical studies and potential challenges utilizing OMVs as cancer vaccines or adjuvants are also provided, offering a comprehensive assessment of the current landscape and future prospects. Overall, this review provides valuable insights for researchers involved in the rapidly evolving field of cancer immunotherapy, offering a roadmap for harnessing the full potential of OMVs as a versatile and adaptable platform for cancer treatment.

Hypoxia as a Target for Combination with Transarterial Chemoembolization in Hepatocellular Carcinoma

Hypoxia is a hallmark of solid tumors, including hepatocellular carcinoma (HCC). Hypoxia has proven to be involved in multiple tumor biological processes and associated with malignant progression and resistance to therapy. Transarterial chemoembolization (TACE) is a well-established locoregional therapy for patients with unresectable HCC. However, TACE-induced hypoxia regulates tumor angiogenesis, energy metabolism, epithelial-mesenchymal transition (EMT), and immune processes through hypoxia-inducible factor 1 (HIF-1), which may have adverse effects on the therapeutic efficacy of TACE. Hypoxia has emerged as a promising target for combination with TACE in the treatment of HCC. This review summarizes the impact of hypoxia on HCC tumor biology and the adverse effects of TACE-induced hypoxia on its therapeutic efficacy, highlighting the therapeutic potential of hypoxia-targeted therapy in combination with TACE for HCC.

Hemoglobin nanoclusters-mediated regulation of KPNA4 in hypoxic tumor microenvironment enhances photodynamic therapy in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly malignant tumor known for its hypoxic environment, which contributes to resistance against the anticancer drug Sorafenib (SF). Addressing SF resistance in HCC requires innovative strategies to improve tumor oxygenation and effectively deliver therapeutics.

RESULTS

In our study, we explored the role of KPNA4 in mediating hypoxia-induced SF resistance in HCC. We developed hemoglobin nanoclusters (Hb-NCs) capable of carrying oxygen, loaded with indocyanine green (ICG) and SF, named HPRG@SF. In vitro, HPRG@SF targeted HCC cells, alleviated hypoxia, suppressed KPNA4 expression, and enhanced the cytotoxicity of PDT against hypoxic, SF-resistant HCC cells. In vivo experiments supported these findings, showing that HPRG@SF effectively improved the oxygenation within the tumor microenvironment and countered SF resistance through combined photodynamic therapy (PDT).

CONCLUSION

The combination of Hb-NCs with ICG and SF, forming HPRG@SF, presents a potent strategy to overcome drug resistance in hepatocellular carcinoma by improving hypoxia and employing PDT. This approach not only targets the hypoxic conditions that underlie resistance but also provides a synergistic anticancer effect, highlighting its potential for clinical applications in treating resistant HCC.

Role of tumor-associated macrophages in hepatocellular carcinoma: impact, mechanism, and therapy

Hepatocellular carcinoma (HCC) is a highly frequent malignancy worldwide. The occurrence and progression of HCC is a complex process closely related to the polarization of tumor-associated macrophages (TAMs) in the tumor microenvironment (TME). The polarization of TAMs is affected by a variety of signaling pathways and surrounding cells. Evidence has shown that TAMs play a crucial role in HCC, through its interaction with other immune cells in the TME. This review summarizes the origin and phenotypic polarization of TAMs, their potential impacts on HCC, and their mechanisms and potential targets for HCC immunotherapy.

Hybrid Cellular Nanovesicles Block PD-L1 Signal and Repolarize M2 Macrophages for Cancer Immunotherapy

The PD1/PD-L1 immune checkpoint blocking is a promising therapy, while immunosuppressive tumor microenvironment (TME) and poor tumor penetration of therapeutic antibodies limit its efficacy. Repolarization of tumor-associated macrophages (TAMs) offers a potential method to ameliorate immunosuppression of TME and further boost T cell antitumor immunity. Herein, hybrid cell membrane biomimetic nanovesicles (hNVs) are developed by fusing M1 macrophage-derived nanovesicles (M1-NVs) and PD1-overexpressed tumor cell-derived nanovesicles (PD1-NVs) to improve cancer immunotherapy. The M1-NVs promote the transformation of M2-like TAMs to M1-like phenotype and further increase the release of pro-inflammatory cytokines, resulting in improved immunosuppressive TME. Concurrently, the PD1-NVs block PD1/PD-L1 pathway, which boosts cancer immunotherapy when combined with M1-NVs. In a breast cancer mouse model, the hNVs efficiently accumulate at the tumor site after intravenous injection and significantly inhibit the tumor growth. Mechanically, the M1 macrophages and CD8+ T lymphocytes in TME increase by twofold after the treatment, indicating effective immune activation. These results suggest the hNVs as a promising strategy to integrate TME improvement with PD1/PD-L1 blockade for cancer immunotherapy.

Melatonin enhances the efficacy of anti-PD-L1 by improving hypoxia in residual tumors after insufficient radiofrequency ablation

The hypoxic microenvironment and inflammatory state of residual tumors caused by insufficient radiofrequency ablation (iRFA) are major reasons for rapid tumor progression and pose challenges for immunotherapy. We retrospectively analyzed the clinical data of patients with hepatocellular carcinoma (HCC) treated with RFA and observed that iRFA was associated with poor survival outcomes and progression-free survival. Using an orthotopic HCC mouse model and a colorectal liver metastasis model, we observed that treatment with melatonin after iRFA reduced tumor growth and metastasis and achieved the best outcomes when combined with anti-programmed death-ligand 1 (anti-PD-L1) therapy. In mechanism, melatonin inhibited the expression of epithelial-mesenchymal transitions, hypoxia-inducible factor (HIF)-1α, and PD-L1 in tumor cells after iRFA. Flow cytometry revealed that melatonin reduced the proportion of myeloid-derived suppressor cells and increased the proportion of CD8+ T cells. Transcriptomic analysis revealed an upregulation of immune-activated function-related genes in residual tumors. These findings demonstrated that melatonin can reverse hypoxia and iRFA-induced inflammation, thereby overcoming the immunosuppressive tumor microenvironment (TME) and enhancing the efficacy of immunotherapy.

Tumor-associated macrophages derived exosomes; from pathogenesis to therapeutic opportunities

Tumor-associated macrophages (TAMs) exert profound influences on cancer progression, orchestrating a dynamic interplay within the tumor microenvironment. Recent attention has focused on the role of TAM-derived exosomes, small extracellular vesicles containing bioactive molecules, in mediating this intricate communication. This review comprehensively synthesizes current knowledge, emphasizing the diverse functions of TAM-derived exosomes across various cancer types. The review delves into the impact of TAM-derived exosomes on fundamental cancer hallmarks, elucidating their involvement in promoting cancer cell proliferation, migration, invasion, and apoptosis evasion. By dissecting the molecular cargo encapsulated within these exosomes, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and proteins, the review uncovers key regulatory mechanisms governing these effects. Noteworthy miRNAs, such as miR-155, miR-196a-5p, and miR-221-3p, are highlighted for their pivotal roles in mediating TAM-derived exosomal communication and influencing downstream targets. Moreover, the review explores the impact of TAM-derived exosomes on the immune microenvironment, particularly their ability to modulate immune cell function and foster immune evasion. The discussion encompasses the regulation of programmed cell death ligand 1 (PD-L1) expression and subsequent impairment of CD8 + T cell activity, unraveling the immunosuppressive effects of TAM-derived exosomes. With an eye toward clinical implications, the review underscores the potential of TAM-derived exosomes as diagnostic markers and therapeutic targets. Their involvement in cancer progression, metastasis, and therapy resistance positions TAM-derived exosomes as key players in reshaping treatment strategies. Finally, the review outlines future directions, proposing avenues for targeted therapies aimed at disrupting TAM-derived exosomal functions and redefining the tumor microenvironment.

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.

Role of triggering receptor expressed on myeloid cells-1 in kidney diseases: A biomarker and potential therapeutic target

ABSTRACT

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a member of the immunoglobulin superfamily. As an amplifier of the inflammatory response, TREM-1 is mainly involved in the production of inflammatory mediators and the regulation of cell survival. TREM-1 has been studied in infectious diseases and more recently in non-infectious disorders. More and more studies have shown that TREM-1 plays an important pathogenic role in kidney diseases. There is evidence that TREM-1 can not only be used as a biomarker for diagnosis of disease but also as a potential therapeutic target to guide the development of novel therapeutic agents for kidney disease. This review summarized molecular biology of TREM-1 and its signaling pathways as well as immune response in the progress of acute kidney injury, renal fibrosis, diabetic nephropathy, immune nephropathy, and renal cell carcinoma.

Complex Role of Regulatory T Cells (Tregs) in the Tumor Microenvironment: Their Molecular Mechanisms and Bidirectional Effects on Cancer Progression

Regulatory T cells (Tregs) possess unique immunosuppressive activity among CD4-positive T cells. Tregs are ubiquitously present in mammals and function to calm excessive immune responses, thereby suppressing allergies or autoimmune diseases. On the other hand, due to their immunosuppressive function, Tregs are thought to promote cancer progression. The tumor microenvironment (TME) is a multicellular system composed of many cell types, including tumor cells, infiltrating immune cells, and cancer-associated fibroblasts (CAFs). Within this environment, Tregs are recruited by chemokines and metabolic factors and impede effective anti-tumor responses. However, in some cases, their presence can also improve patient's survival rates. Their functional consequences may vary across tumor types, locations, and stages. An in-depth understanding of the precise roles and mechanisms of actions of Treg is crucial for developing effective treatments, emphasizing the need for further investigation and validation. This review aims to provide a comprehensive overview of the complex and multifaceted roles of Tregs within the TME, elucidating cellular communications, signaling pathways, and their impacts on tumor progression and highlighting their potential anti-tumor mechanisms through interactions with functional molecules.

Who is who within the universe of TREM-like transcripts (TREML)?

The Triggering Receptor Expressed on Myeloid Cells (TREM) family of receptors plays a crucial role in the immune response across various species. Particularly, TREM-1 and TREM-2 have been extensively studied, both in terms of their applications and their expression sites and signaling pathways. However, the same is not observed for the other family members collectively known as TREM-like-transcripts (TREML). The TREML family consists of eight receptors, with TREML1-5 identified in humans and mice, TREML-6 exclusive found in mice, TREML-7 in dogs and horses, and TREML-8 in rabbits and opossums. Despite the limited data available on the TREML members, they have been implicated in different immune and non-immune activities, which have been proposed to display both pro and anti-inflammatory activities, and to influence fundamental biological processes such as coagulation, bone and neurological development. In this review, we have compiled available information regarding the already discovered members of the family and provided foundational framework for understanding the function, localization, and therapeutic potential of all TREML members. Additionally, we hope that this review may shed light on this family of receptors, whose underlying mechanisms are still awaiting elucidation, while emphasizing the need for future studies to explore their functions and potential therapeutic application.

Harnessing CD8+ T cell dynamics in hepatitis B virus-associated liver diseases: Insights, therapies and future directions

Hepatitis B virus (HBV) infection playsa significant role in the etiology and progression of liver-relatedpathologies, encompassing chronic hepatitis, fibrosis, cirrhosis, and eventual hepatocellularcarcinoma (HCC). Notably, HBV infection stands as the primary etiologicalfactor driving the development of HCC. Given the significant contribution ofHBV infection to liver diseases, a comprehensive understanding of immunedynamics in the liver microenvironment, spanning chronic HBV infection,fibrosis, cirrhosis, and HCC, is essential. In this review, we focused on thefunctional alterations of CD8+ T cells within the pathogenic livermicroenvironment from HBV infection to HCC. We thoroughly reviewed the roles ofhypoxia, acidic pH, metabolic reprogramming, amino acid deficiency, inhibitory checkpointmolecules, immunosuppressive cytokines, and the gut-liver communication in shapingthe dysfunction of CD8+ T cells in the liver microenvironment. Thesefactors significantly impact the clinical prognosis. Furthermore, we comprehensivelyreviewed CD8+ T cell-based therapy strategies for liver diseases,encompassing HBV infection, fibrosis, cirrhosis, and HCC. Strategies includeimmune checkpoint blockades, metabolic T-cell targeting therapy, therapeuticT-cell vaccination, and adoptive transfer of genetically engineered CD8+ T cells, along with the combined usage of programmed cell death protein-1/programmeddeath ligand-1 (PD-1/PD-L1) inhibitors with mitochondria-targeted antioxidants.Given that targeting CD8+ T cells at various stages of hepatitis Bvirus-induced hepatocellular carcinoma (HBV + HCC) shows promise, we reviewedthe ongoing need for research to elucidate the complex interplay between CD8+ T cells and the liver microenvironment in the progression of HBV infection toHCC. We also discussed personalized treatment regimens, combining therapeuticstrategies and harnessing gut microbiota modulation, which holds potential forenhanced clinical benefits. In conclusion, this review delves into the immunedynamics of CD8+ T cells, microenvironment changes, and therapeuticstrategies within the liver during chronic HBV infection, HCC progression, andrelated liver diseases.

Tumor-associated macrophages in anti-PD-1/PD-L1 immunotherapy for hepatocellular carcinoma: recent research progress

Hepatocellular carcinoma (HCC) is one of the cancers that seriously threaten human health. Immunotherapy serves as the mainstay of treatment for HCC patients by targeting the programmed cell death protein 1/programmed cell death 1 ligand 1 (PD-1/PD-L1) axis. However, the effectiveness of anti-PD-1/PD-L1 treatment is limited when HCC becomes drug-resistant. Tumor-associated macrophages (TAMs) are an important factor in the negative regulation of PD-1 antibody targeted therapy in the tumor microenvironment (TME). Therefore, as an emerging direction in cancer immunotherapy research for the treatment of HCC, it is crucial to elucidate the correlations and mechanisms between TAMs and PD-1/PD-L1-mediated immune tolerance. This paper summarizes the effects of TAMs on the pathogenesis and progression of HCC and their impact on HCC anti-PD-1/PD-L1 immunotherapy, and further explores current potential therapeutic strategies that target TAMs in HCC, including eliminating TAMs in the TME, inhibiting TAMs recruitment to tumors and functionally repolarizing M2-TAMs (tumor-supportive) to M1-TAMs (antitumor type).

S100A16 is a potential target for reshaping the tumor microenvironment in the hypoxic context of liver cancer

BACKGROUND

The research on the S100 family has garnered significant attention; however, there remains a dearth of understanding regarding the precise role of S100A16 in the tumor microenvironment of liver cancer.

METHOD

Comprehensive analysis was conducted on the expression of S100A16 in tumor tissues and its correlation with hypoxia genes. Furthermore, an investigation was carried out to examine the association between S100A16 and infiltration of immune cells in tumors as well as immunotherapy. Relevant findings were derived from the analysis of single cell sequencing data, focusing on the involvement of S100A16 in both cellular differentiation and intercellular communication. Finally, we validated the expression of S100A16 in liver cancer by Wuhan cohort and multiplexed immunofluorescence to investigate the correlation between S100A16 and hypoxia.

RESULT

Tumor tissues displayed a notable increase in the expression of S100A16. A significant correlation was observed between S100A16 and genes associated with hypoxic genes. Examination of immune cell infiltration revealed an inverse association between T cell infiltration and the level of S100A16 expression. The high expression group of S100A16 exhibited a decrease in the expression of genes related to immune cell function. Single-cell sequencing data analysis revealed that non-immune cells predominantly expressed S100A16, and its expression levels increased along with the trajectory of cell differentiation. Additionally, there were significant variations observed in hypoxia genes as cells underwent differentiation. Cellular communication identified non-immune cells interacting with immune cells through multiple signaling pathways. The Wuhan cohort verified that S100A16 expression was increased in liver cancer. The expression of S100A16 and HIF was simultaneously elevated in endothelial cells.

CONCLUSION

The strong association between S100A16 and immune cell infiltration is observed in the context of hypoxia, indicating its regulatory role in shaping the hypoxic tumor microenvironment in liver cancer.

Allicin regulates Sestrin2 ubiquitination to affect macrophage autophagy and senescence, thus inhibiting the growth of hepatoma cells

BACKGROUND

Allicin regulates macrophage autophagy and senescence, and inhibits hepatoma cell growth. This study investigated the mechanism by which allicin inhibits the growth of hepatoma cells.

METHODS

Hepa1-6 mouse hepatoma cells were subcutaneously injected into C57BL/6 J mice to construct a tumor transplantation model. Macrophages were cultured with the supernatant of hepatoma cells to construct a cell model. The levels of mRNA and proteins and the level of Sestrin2 ubiquitination were measured by RTqPCR, immunofluorescence and Western blotting. The levels of autophagy-related factors and the activity of senescence-associated β-galactosidase were determined by kits, and protein stability was detected by cycloheximide (CHX) tracking.

RESULTS

Data analysis of clinical samples revealed that RBX1 was highly expressed in tumor tissues, while Sestrin2 was expressed at low levels in tumor tissues. Allicin can promote the expression of the autophagy-related proteins LC3 and Beclin-1 in tumor macrophages and inhibit the expression of the aging-related proteins p16 and p21, thus promoting autophagy in macrophages and inhibiting cell senescence. Moreover, allicin can inhibit the expression of RBX1, thereby reducing the ubiquitination of Sestrin2, enhancing the stability of Sestrin2, activating autophagy in tumor macrophages and inhibiting senescence. In addition, allicin treatment inhibited the proliferation and migration of hepatoma carcinoma cells cocultured with macrophages and significantly improved the development of liver cancer in mice.

CONCLUSION

Allicin can affect the autophagy of macrophages and restrain the growth of hepatoma cells by regulating the ubiquitination of Sestrin2.

TREM1: Activation, signaling, cancer and therapy

Triggering receptor expressed on myeloid cells 1 (TREM1) is a cell surface receptor expressed on neutrophils, monocytes and some tissue macrophages, where it functions as an immunoregulator that controls myeloid cell responses. The activation of TREM1 is suggested to be an upregulation-based, ligands-induced and structural multimerization-mediated process, in which damage- and pathogen-associated molecular patterns play important roles. Activated TREM1 initiates an array of downstream signaling pathways that ultimately result in the production of pro-inflammatory cytokines and chemokines, whereby it functions as an amplifier of inflammation and is implicated in the pathogenesis of many inflammation-associated diseases. Over the past decade, there has been growing evidence for the involvement of TREM1 overactivation in tumor stroma inflammation and cancer progression. Indeed, it was shown that TREM1 promotes tumor progression, immunosuppression, and resistance to therapy by activating tumor-infiltrating myeloid cells. TREM1-deficiency or blockade provide protection against tumors and reverse the resistance to anti-PD-1/PD-L1 therapy and arginine-deprivation therapy in preclinical models. Here, we first review the structure, activation modes and signaling pathways of TREM1 and emphasize the role of soluble TREM1 as a biomarker of infection and cancer. We then focus on the role of TREM1 in cancer and systematically summarize its expression patterns, upregulation mechanisms and functions in tumor development and progression. Lastly, we discuss the therapeutic prospects of TREM1 inhibition, via effective pharmacological inhibitors, in treating cancer and other diseases.

Hypoxia-induced TREM1 promotes mesenchymal-like states of glioma stem cells via alternatively activating tumor-associated macrophages

The mesenchymal subtype of glioblastoma (GBM) cells characterized by aggressive invasion and therapeutic resistance is thought to be dependent on cell-intrinsic alteration and extrinsic cellular crosstalk. Tumor-associated macrophages (TAMs) are pivotal in tumor progression, chemo-resistance, angiogenesis, and stemness maintenance. However, the impact of TAMs on the shifts in glioma stem cells (GSCs) states remains largely uncovered. Herein, we showed that the triggering receptor expressed on myeloid cells-1 (TREM1) preferentially expressed by M2-like TAMs and induced GSCs into mesenchymal-like states by modulating the secretion of TGFβ2, which activated the TGFβR/SMAD2/3 signaling in GSCs. Furthermore, we demonstrated that TREM1 was transcriptionally regulated by HIF1a under the hypoxic environment and thus promoted an immunosuppressive type of TAMs via activating the TLR2/AKT/mTOR/c-MYC axis. Collectively, this study reveals that cellular communication between TAMs and GSCs through the TREM1-mediated TGFβ2/TGFβR axis is involved in the mesenchymal-like transitions of GSCs. Our study provides valuable insights into the regulatory mechanisms between the tumor immune microenvironment and the malignant characteristics of GBM, which can lead to potential novel strategies targeting TAMs for tumor control.

Τ cell-mediated adaptive immunity in the transition from metabolic dysfunction-associated steatohepatitis to hepatocellular carcinoma

Metabolic dysfunction-associated steatohepatitis (MASH) is the progressed version of metabolic dysfunction-associated steatotic liver disease (MASLD) characterized by inflammation and fibrosis, but also a pathophysiological "hub" that favors the emergence of liver malignancies. Current research efforts aim to identify risk factors, discover disease biomarkers, and aid patient stratification in the context of MASH-induced hepatocellular carcinoma (HCC), the most prevalent cancer among MASLD patients. To investigate the tumorigenic transition in MASH-induced HCC, researchers predominantly exploit preclinical animal-based MASH models and studies based on archived human biopsies and clinical trials. Recapitulating the immune response during tumor development and progression is vital to obtain mechanistic insights into MASH-induced HCC. Notably, the advanced complexity behind MASLD and MASH pathogenesis shifted the research focus towards innate immunity, a fundamental element of the hepatic immune niche that is usually altered robustly in the course of liver disease. During the last few years, however, there has been an increasing interest for deciphering the role of adaptive immunity in MASH-induced HCC, particularly regarding the functions of the various T cell populations. To effectively understand the specific role of T cells in MASH-induced HCC development, scientists should urgently fill the current knowledge gaps in this field. Pinpointing the metabolic signature, sketching the immune landscape, and characterizing the cellular interactions and dynamics of the specific T cells within the MASH-HCC liver are essential to unravel the mechanisms that adaptive immunity exploits to enable the emergence and progression of this cancer. To this end, our review aims to summarize the current state of research regarding the T cell functions linked to MASH-induced HCC.

Macrophages Orchestrate the Liver Tumor Microenvironment

Liver cancer is one of the leading causes of cancer-related mortality. Hepatocellular carcinoma and cholangiocarcinoma are the most common types, and despite numerous advances, therapeutic options still remain poor for these cancer patients. Tumor development and progression strictly depend on a supportive tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are the most abundant immune cells population within a tumorigenic liver; they sustain cancer cells' growth and invasiveness, and their presence is correlated with a poor prognosis. Furthermore, TAM cross-talk with cells and components of the TME promotes immunosuppression, a desmoplastic response, and angiogenesis. In this review, we summarize the latest advances in understanding TAM heterogeneity and function, with a particular focus on TAM modulation of the TME. We also discuss the potential of targeting macrophage subpopulations and how this is now being exploited in current clinical trials for the treatment of liver cancer.

Triggering receptor expressed in myeloid cells 1 (TREM1) as a potential prognostic biomarker and association with immune infiltration in oral squamous cell carcinoma

OBJECTIVE

The objective of this study is to investigate the significance and impact of Triggering Receptor Expression on Myeloid Cells-1 (TREM-1) in the context of oral squamous cell carcinoma (OSCC).

METHODS

This study involved 51 OSCC patients, 21 oral epithelial dysplasia patients (OED), and the TCGA-HNSCC dataset. TREM1 expression was analyzed using quantitative reverse transcription PCR (RT-qPCR), and Western blot. Furthermore, we assessed TREM1 expression for clinicopathological, prognosis, and immune infiltration correlations utilizing publicly available TCGA-HNSCC datasets through UALCAN, Protein Atlas, Kaplan-Meier plot, TIMER2.0, and TISIDB. We also conducted bioinformatic analyses for functional enrichment employing publicly accessible datasets.

RESULTS

TREM1 was significantly upregulated in OSCC and OED when compared to normal tissues, confirmed through multiple methods. Analysis of clinicopathological features showed associations with disease stage, grade, nodal metastasis, HPV status, and TP53 mutation. High TREM1 expression correlated with poorer patient survival. TREM1 was linked to immune cell infiltration and immune-related pathways.

CONCLUSION

TREM1 is significantly upregulated in OSCC and is associated with poor clinicopathological features and survival. It may hold promise as a therapeutic target and prognostic marker in OSCC. Further research is needed to understand its functional role in OSCC.

Lactic acid in macrophage polarization: A factor in carcinogenesis and a promising target for cancer therapy

Cancer remains a formidable challenge, continually revealing its intricate nature and demanding novel treatment approaches. Within this intricate landscape, the tumor microenvironment and its dynamic components have gained prominence, particularly macrophages that can adopt diverse polarization states, exerting a profound influence on cancer progression. Recent revelations have spotlighted lactic acid as a pivotal player in this complex interplay. This review systematically explores lactic acid's multifaceted role in macrophage polarization, focusing on its implications in carcinogenesis. We commence by cultivating a comprehensive understanding of the tumor microenvironment and the pivotal roles played by macrophages. The dynamic landscape of macrophage polarization, typified by M1 and M2 phenotypes, is dissected to reveal its substantial impact on tumor progression. Lactic acid, a metabolic byproduct, emerges as a key protagonist, and we meticulously unravel the mechanisms underpinning its generation within cancer cells, shedding light on its intimate association with glycolysis and its transformative effects on the tumor microenvironment. Furthermore, we decipher the intricate molecular framework that underlies lactic acid's pivotal role in facilitating macrophage polarization. Our review underscores lactic acid's dual role in carcinogenesis, orchestrating tumor growth and immune modulation within the tumor microenvironment, thereby profoundly influencing the balance between pro-tumor and anti-tumor immune responses. This duality highlights the therapeutic potential of selectively manipulating lactic acid metabolism for cancer treatment. Exploring strategies to inhibit lactic acid production by tumor cells, novel approaches to impede lactic acid transport in the tumor microenvironment, and the burgeoning field of immunotherapeutic cancer therapies utilizing lactic acid-induced macrophage polarization form the core of our investigation.

The dual role of regulatory T cells in hepatitis B virus infection and related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major contributor to cancer-related deaths worldwide. Hepatitis B virus (HBV) infection is a major etiologic factor leading to HCC. While there have been significant advancements in controlling HBV replication, achieving a complete cure for HBV-related HCC (HBV-HCC) remains an intricate challenge. HBV persistence is attributed to a myriad of mechanisms, encompassing both innate and adaptive immune responses. Regulatory T cells (Tregs) are pivotal in upholding immune tolerance and modulating excessive immune activation. During HBV infection, Tregs mediate specific T cell suppression, thereby contributing to both persistent infection and the mitigation of liver inflammatory responses. Studies have demonstrated an augmented expression of circulating and intrahepatic Tregs in HBV-HCC, which correlates with impaired CD8+ T cell function. Consequently, Tregs play a dual role in the context of HBV infection and the progression of HBV-HCC. In this comprehensive review, we discuss pertinent studies concerning Tregs in HBV infection, HBV-related cirrhosis and HCC. Furthermore, we summarize Treg responses to antiviral therapy and provide Treg-targeted therapies specific to HBV and HCC.

Macrophage: Hidden Criminal in Therapy Resistance

BACKGROUND

Although substantial efforts have been made by researchers to develop drugs, a disappointing reality is that the emergence of drug resistance is an unavoidable reality for the majority of patients. In recent years, emerging evidence suggests a connection between drug resistance and immune dysregulation.

SUMMARY

As a ubiquitously distributed, versatile innate immune cell, macrophages play essential roles in maintaining tissue homeostasis in a steady state. Nevertheless, it is becoming aware that macrophages undermine the action of therapeutic drugs across various disease types. Reprogramming macrophage function has been proven to be effective in restoring patient responsiveness to treatment. Herein, we comprehensively reviewed how macrophages respond to drugs and the mechanisms by which they contribute to treatment unresponsiveness in cancer, inflammatory diseases, and metabolic diseases. In addition, future prospects in macrophage-based combination therapy were discussed.

KEY MESSAGES

Targeting macrophages is a promising strategy for overcoming drug resistance in immune disorders.

Identification of SLC2A1 as a predictive biomarker for survival and response to immunotherapy in lung squamous cell carcinoma

BACKGROUND

As one of the common subtypes of non-small lung cancer, lung squamous cell carcinoma (LUSC) patients with advanced stage have few choices of treatment strategies. Therefore, it is urgent to discover genes that are associated with the survival and efficacy of immunotherapies.

METHOD

Differential gene expression analyses were conducted using TCGA LUSC bulk-sequencing and single-cell RNA-sequencing data. Prognostic genes were identified from the TCGA LUSC cohort. Protein expression validation and survival analyses were performed. Experiments were conducted to explore the underlying mechanisms. In addition, the correlation between gene expression and pathological response to adjuvant immunochemotherapy was also investigated.

RESULTS

After a series of bioinformatic analyses, solute carrier family 2 member 1(SLC2A1), encoding glucose transporter-1 (GLUT1), was found to be differentially expressed between tumor and normal tissues. GLUT1 was subsequently identified as an independent prognostic factor for LUSC. GSEA analysis revealed the glycolysis metabolism pathway of KEGG enriched in SLC2A1high tumor tissues. LASSO analyses revealed that tumor tissues with high expression of SLC2A1 were associated with high levels of protein lactylation. We found that SLC2A1 was preferentially expressed by SPP1+ macrophages in the tumor microenvironment, and the expression of SLC2A1 was associated with the abundance of SPP1+ macrophages. Immunofluorescence demonstrated GLUT1 and HIF1α colocalization in tumor-infiltrating macrophages. In vitro experiments showed HIF-1α-induced macrophage polarization under hypoxia, and GLUT1 inhibition blocked this polarization. In addition, SLC2A1 was negatively associated with the common immune checkpoint molecules, such as programmed cell death 1(PD-1), T cell immunoreceptor with Ig and ITIM domains (TIGIT), cytotoxic T-lymphocyte associated protein 4 (CTLA4) and lymphocyte activating 3 (LAG3), while showed a positive association with CD44. Finally, we observed that there was a significant correlation between pre-adjuvant-treatment GLUT1 expression and the pathological response.

CONCLUSION

SLC2A1 expression was differentially upregulated in tumor tissues, and elevated GLUT1 expression was associated with worse survival and poor pathological response to adjuvant immunochemotherapy. Upregulation of GLUT1 promoted macrophage polarization into the M2 phenotype. The findings will contribute to guiding the treatment selection for LUSC patients and providing personalized immunotherapy strategies.

Regulatory T cell: a double-edged sword from metabolic-dysfunction-associated steatohepatitis to hepatocellular carcinoma

Metabolic-dysfunction-associated steatotic liver disease (MASLD) is becoming a leading cause of end-stage liver disease globally. Metabolic-dysfunction-associated steatohepatitis (MASH) represents a progressive inflammatory manifestation of MASLD. MASH underlies a versatile and dynamic inflammatory microenvironment, accompanied by aberrant metabolism and ongoing liver regeneration, establishing itself as a significant risk factor for hepatocellular carcinoma (HCC). The mechanisms underlying the escape and survival of malignant cells within the extensive inflammatory microenvironment of MASH remain elusive. Regulatory T cells (Tregs) play a crucial role in maintaining homeostasis and preventing excessive immune responses in the liver. Paradoxically, Tregs have been implicated in inhibiting tumour-promoting inflammation and facilitating the evasion of cancer cells. Recent studies have unveiled distinct behaviours of Tregs at different stages of MASLD, suggesting a dual role in the pathogenesis. In this review, we explore the fate of Tregs from MASLD to HCC, offering recent insights into potential targets for clinical intervention.

Dawn era for revisited cancer therapy by innate immune system and immune checkpoint inhibitors

Immunotherapy is a promising therapeutic strategy for cancer. However, it shows limited efficacy against certain tumor types. The activation of innate immunity can suppress tumors by mitigating inflammatory and malignant behaviors through immune surveillance. The tumor microenvironment, which is composed of immune cells and cancer cells, plays a crucial role in determining the outcomes of immunotherapy. Relying solely on immune checkpoint inhibitors is not an optimal approach. Instead, there is a need to consider the use of a combination of immune checkpoint inhibitors with other modulators of the innate immune system to improve the tumor microenvironment. This can be achieved through methods such as immune cell antigen presentation and recognition. In this review, we delve into the significance of innate immune cells in tumor regression, as well as the role of the interaction of tumor cells with innate immune cells in evading host immune surveillance. These findings pave the way for the next chapter in the field of immunotherapy.

Oleuropein-driven reprogramming of the myeloid cell compartment to sensitise tumours to PD-1/PD-L1 blockade strategies

BACKGROUND

Previous studies have shown that functional systemic immunity is required for the efficacy of PD-1/PD-L1 blockade immunotherapies in cancer. Hence, systemic reprogramming of immunosuppressive dysfunctional myeloid cells could overcome resistance to cancer immunotherapy.

METHODS

Reprogramming of tumour-associated myeloid cells with oleuropein was studied by quantitative differential proteomics, phenotypic and functional assays in mice and lung cancer patients. Combinations of oleuropein and two different delivery methods of anti-PD-1 antibodies were tested in colorectal cancer tumour models and in immunotherapy-resistant lung cancer models.

RESULTS

Oleuropein treatment reprogrammed monocytic and granulocytic myeloid-derived suppressor cells, and tumour-associated macrophages towards differentiation of immunostimulatory subsets. Oleuropein regulated major differentiation programmes associated to immune modulation in myeloid cells, which potentiated T cell responses and PD-1 blockade. PD-1 antibodies were delivered by two different strategies, either systemically or expressed within tumours using a self-amplifying RNA vector. Combination anti-PD-1 therapies with oleuropein increased tumour infiltration by immunostimulatory dendritic cells in draining lymph nodes, leading to systemic antitumour T cell responses. Potent therapeutic activities were achieved in colon cancer and lung cancer models resistant to immunotherapies, even leading to complete tumour regression.

DISCUSSION

Oleuropein significantly improves the outcome of PD-1/PD-L1 blockade immunotherapy strategies by reprogramming myeloid cells.

THBS1+ myeloid cells expand in SLD hepatocellular carcinoma and contribute to immunosuppression and unfavorable prognosis through TREM1

Hepatocellular carcinoma (HCC) is an inflammation-associated cancer arising from viral or non-viral etiologies including steatotic liver diseases (SLDs). Expansion of immunosuppressive myeloid cells is a hallmark of inflammation and cancer, but their heterogeneity in HCC is not fully resolved and might underlie immunotherapy resistance. Here, we present a high-resolution atlas of innate immune cells from patients with HCC that unravels an SLD-associated contexture characterized by influx of inflammatory and immunosuppressive myeloid cells, including a discrete population of THBS1+ regulatory myeloid (Mreg) cells expressing monocyte- and neutrophil-affiliated genes. THBS1+ Mreg cells expand in SLD-associated HCC, populate fibrotic lesions, and are associated with poor prognosis. THBS1+ Mreg cells are CD163+ but distinguished from macrophages by high expression of triggering receptor expressed on myeloid cells 1 (TREM1), which contributes to their immunosuppressive activity and promotes HCC tumor growth in vivo. Our data support myeloid subset-targeted immunotherapies to treat HCC.

Predictive indicators of immune therapy efficacy in hepatocellular carcinoma based on neutrophil-to-lymphocyte ratio

Hepatocellular carcinoma (HCC) exhibits high incidence and mortality rates in China. Most cases are often diagnosed at late stages and require multi-strategy therapies. In recent years, immune checkpoint inhibitors (ICIs), particularly programmed cell death protein 1 (PD-1) antibodies, have demonstrated effectiveness in comprehensive HCC treatment. However, the efficacy and prognosis vary greatly among patients. Screening suitable patients and predicting outcomes are crucial for improving the efficacy of ICIs. Although PD-L1 expression levels in tumor cells have been used as predictors of PD-1/PD-L1 antibody therapy, they may not consistently correlate with clinical response in some studies; thus, exploring new biomarkers is necessary. The neutrophil-to-lymphocyte ratio (NLR) emerged as a new predictor of ICI immunotherapy efficacy, and its application in HCC is worth exploring. This study utilizes the Cancer Genome Atlas Liver Hepatocellular Carcinoma Collection (TCGA-LIHC) project in the Genomic Data Commons (GDC) database for methylation and transcriptome data analysis. The correlation between NLR and ICI immunotherapy efficacy for HCC was evaluated, identifying differentially expressed genes. Analysis revealed 74 up-regulated and 445 down-regulated genes in the high-NLR group compared to the low-NLR group. NLR-related differential methylation analysis identified 68 hypermethylated and 65 hypomethylated probes in the NLR high group. Furthermore, a machine learning model using 27 intersecting genes predicted PD-1 antibody therapy efficacy, achieving an AUC value of 0.813. In summary, we established a predictive model for HCC immunotherapy based on 27 genes related to differential expressions and NLR-associated methylation, showing significant potential for clinical research potential in this field.

Molecular and immunological features of TREM1 and its emergence as a prognostic indicator in glioma

Triggering receptor expressed on myeloid cells 1 (TREM1), which belongs to the Ig-like superfamily expressed on myeloid cells, is reportedly involved in various diseases but has rarely been studied in glioma. In this study, the prognostic value and functional roles of TREM2 in glioma were analyzed. TERM1 was observed to be significantly upregulated in GBM compared to in other grade gliomas and was associated with poor prognosis. Increased TREM1 accompanied distinct mutation and amplification of driver oncogenes. Moreover, gene ontology and KEGG analyses showed that TREM1 might play a role in immunologic biological processes in glioma. TREM1 was also found to be tightly correlated with immune checkpoint molecules. xCell research revealed a link between TREM1 expression and multiple immune cell types, especially monocytes and macrophages. Single-cell analysis and immunofluorescence results showed that macrophages expressed TREM1. In vitro, inhibition of TREM1 signaling could result in a decrease in tumor-promoting effects of monocytes/TAMs. In summary, TREM1 may be a potential independent prognostic factor and immune target, which might provide new avenues to improve the efficacy of immunotherapy in glioma patients.

Blocking MARCO+ tumor-associated macrophages improves anti-PD-L1 therapy of hepatocellular carcinoma by promoting the activation of STING-IFN type I pathway

The PD-L1/PD-1 axis is a classic immunotherapy target. However, anti-PD-L1/PD-1 therapy alone can not achieve satisfactory results in solid tumors, especially liver cancer. Among the several factors involved in tumor anti-PD-L1/PD-1 treatment resistance, tumor-associated macrophages (TAMs) have attracted attention because of their immunosuppressive ability. TAMs with a macrophage receptor with a collagenous structure (MARCO) are a macrophage subset group with strong immunosuppressive abilities. Clinical specimens and animal experiments revealed a negative correlation between MARCO + TAMs and patient prognosis with liver cancer. Transcriptional data and in vitro and in vivo experiments revealed that MARCO + TAM immunosuppressive ability was related to secretion. MARCO suppressed IFN-β secretion from TAMs, reducing antigen presentation molecule expression, infiltration, and CD8+T cell dysfunction, thus producing an immunosuppressive microenvironment in liver cancer. MARCO can promote dying tumor cell clearance by macrophages, reducing tumor-derived cGAMP and ATP accumulation in the tumor microenvironment and inhibiting sting-IFN-β pathway activation mediated by P2X7R in MARCO+TAMs. Animal experiments revealed that the MARCO and PD-L1 monoclonal antibody combination could significantly inhibit liver cancer growth. Conclusively, targeting MARCO+TAMs can significantly improve anti-PD-L1 resistance in liver cancer, making it a potential novel immune target for liver cancer therapy.

Hypoxia-Induced Signaling in Gut and Liver Pathobiology

Oxygen (O2) is essential for cellular metabolism and biochemical reactions. When the demand for O2 exceeds the supply, hypoxia occurs. Hypoxia-inducible factors (HIFs) are essential to activate adaptive and survival responses following hypoxic stress. In the gut (intestines) and liver, the presence of oxygen gradients or physiologic hypoxia is necessary to maintain normal homeostasis. While physiologic hypoxia is beneficial and aids in normal functions, pathological hypoxia is harmful as it exacerbates inflammatory responses and tissue dysfunction and is a hallmark of many cancers. In this review, we discuss the role of gut and liver hypoxia-induced signaling, primarily focusing on HIFs, in the physiology and pathobiology of gut and liver diseases. Additionally, we examine the function of HIFs in various cell types during gut and liver diseases, beyond intestinal epithelial and hepatocyte HIFs. This review highlights the importance of understanding hypoxia-induced signaling in the pathogenesis of gut and liver diseases and emphasizes the potential of HIFs as therapeutic targets.

Targeting tumor-associated macrophages: Novel insights into immunotherapy of skin cancer

BACKGROUND

The incidence of skin cancer is currently increasing, and conventional treatment options inadequately address the demands of disease management. Fortunately, the recent rapid advancement of immunotherapy, particularly immune checkpoint inhibitors (ICIs), has ushered in a new era for numerous cancer patients. However, the efficacy of immunotherapy remains suboptimal due to the impact of the tumor microenvironment (TME). Tumor-associated macrophages (TAMs), a major component of the TME, play crucial roles in tumor invasion, metastasis, angiogenesis, and immune evasion, significantly impacting tumor development. Consequently, TAMs have gained considerable attention in recent years, and their roles have been extensively studied in various tumors. However, the specific roles of TAMs and their regulatory mechanisms in skin cancer remain unclear.

AIM OF REVIEW

This paper aims to elucidate the origin and classification of TAMs, investigate the interactions between TAMs and various immune cells, comprehensively understand the precise mechanisms by which TAMs contribute to the pathogenesis of different types of skin cancer, and finally discuss current strategies for targeting TAMs in the treatment of skin cancer.

KEY SCIENTIFIC CONCEPTS OF OVERVIEW

With a specific emphasis on the interrelationship between TAMs and skin cancer, this paper posits that therapeutic modalities centered on TAMs hold promise in augmenting and harmonizing with prevailing clinical interventions for skin cancer, thereby charting a novel trajectory for advancing the landscape of immunotherapeutic approaches for skin cancer.

The BCL-2 inhibitor APG-2575 resets tumor-associated macrophages toward the M1 phenotype, promoting a favorable response to anti-PD-1 therapy via NLRP3 activation

The main challenges in the use of immune checkpoint inhibitors (ICIs) are ascribed to the immunosuppressive tumor microenvironment and the lack of sufficient infiltration of activated CD8+ T cells. Transforming the tumor microenvironment (TME) from "cold" to "hot" and thus more likely to potentiate the effects of ICIs is a promising strategy for cancer treatment. We found that the selective BCL-2 inhibitor APG-2575 can enhance the antitumor efficacy of anti-PD-1 therapy in syngeneic and humanized CD34+ mouse models. Using single-cell RNA sequencing, we found that APG-2575 polarized M2-like immunosuppressive macrophages toward the M1-like immunostimulatory phenotype with increased CCL5 and CXCL10 secretion, restoring T-cell function and promoting a favorable immunotherapy response. Mechanistically, we demonstrated that APG-2575 directly binds to NF-κB p65 to activate NLRP3 signaling, thereby mediating macrophage repolarization and the activation of proinflammatory caspases and subsequently increasing CCL5 and CXCL10 chemokine production. As a result, APG-2575-induced macrophage repolarization could remodel the tumor immune microenvironment, thus improving tumor immunosuppression and further enhancing antitumor T-cell immunity. Multiplex immunohistochemistry confirmed that patients with better immunotherapeutic efficacy had higher CD86, p-NF-κB p65 and NLRP3 levels, accompanied by lower CD206 expression on macrophages. Collectively, these data provide evidence that further study on APG-2575 in combination with immunotherapy for tumor treatment is required.

Tumor-Associated Macrophage Targeting of Nanomedicines in Cancer Therapy

The tumor microenvironment (TME) is pivotal in tumor growth and metastasis, aligning with the "Seed and Soil" theory. Within the TME, tumor-associated macrophages (TAMs) play a central role, profoundly influencing tumor progression. Strategies targeting TAMs have surfaced as potential therapeutic avenues, encompassing interventions to block TAM recruitment, eliminate TAMs, reprogram M2 TAMs, or bolster their phagocytic capabilities via specific pathways. Nanomaterials including inorganic materials, organic materials for small molecules and large molecules stand at the forefront, presenting significant opportunities for precise targeting and modulation of TAMs to enhance therapeutic efficacy in cancer treatment. This review provides an overview of the progress in designing nanoparticles for interacting with and influencing the TAMs as a significant strategy in cancer therapy. This comprehensive review presents the role of TAMs in the TME and various targeting strategies as a promising frontier in the ever-evolving field of cancer therapy. The current trends and challenges associated with TAM-based therapy in cancer are presented.

Translocated HMGB3 is involved in papillary thyroid cancer progression by activating cytoplasmic TLR3 and transmembrane TREM1

The family of high mobility group box (HMGB) proteins participates in various biological processes including immunity, inflammation, as well as cancer formation and progression. However, its role in thyroid cancer remains to be clarified. We performed quantitative RT-PCR (qRT-PCR), western blot, enzyme-linked immunosorbent, immunohistochemistry, and immunofluorescence assays to evaluate the expression level and subcellular location of HMGB3. The effects of HMGB3 knockdown on malignant biological behaviors of thyroid cancer were determined by cell proliferation assays, cell cycle and apoptosis assays, and transwell chamber migration and invasion assays. Differential expression genes (DEGs) altered by HMGB3 were analyzed using the Ingenuity Pathway Analysis (IPA) and TRRUST v2 database. HMGB3 correlated pathways predicted by bioinformatic analysis were then confirmed using western blot, co-immunoprecipitation, dual-luciferase reporter assay, and flow cytometry. We found that HMGB3 is overexpressed and its downregulation inhibits cell viability, promotes cell apoptosis and cell cycle arrest, and suppresses cell migration and invasion in thyroid cancer. In PTC, both tissue and serum levels of HMGB3 are elevated and are correlated with lymph node metastasis and advanced tumor stage. Mechanistically, we observed the translocation of HMGB3 in PTC, induced at least partially by hypoxia. Cytoplasmic HMGB3 activates nucleic-acid-mediated TLR3/NF-κB signaling and extracellular HMGB3 interacts with the transmembrane TREM1 receptor in PTC. This study demonstrates the oncogenic role of HMGB3 cytoplasmic and extracellular translocation in papillary thyroid cancers; we recommend its future use as a potential circulating biomarker and therapeutic target for PTC.

The role of tumor-associated macrophages in hepatocellular carcinoma progression: A narrative review

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world, with complex etiology and mechanism, and a high mortality rate. Tumor-associated macrophages (TAMs) are an important part of the HCC tumor microenvironment. Studies in recent years have shown that TAMs are involved in multiple stages of HCC and are related to treatment and prognosis in HCC. The specific mechanisms between TAMs and HCC are gradually being revealed. This paper reviews recent advances in the mechanisms associated with TAMs in HCC, concentrating on an overview of effects of TAMs on drug resistance in HCC and the signaling pathways linked with HCC, providing clues for the treatment and prognosis determination of HCC.

Nanomedicine Strategies in Conquering and Utilizing the Cancer Hypoxia Environment

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

Mechanisms of Resistance to Immunotherapy in Hepatocellular Carcinoma

Systemic treatment for advanced hepatocellular carcinoma (HCC) has been revolutionized over the last few years following the approval of immune checkpoint inhibitors (ICI). Despite the promising survival extension seen with ICI combination regimens, responses are not universally seen and the optimal partner for programmed cell death 1 pathway inhibitors remains to be identified. Even fewer encouraging results have been demonstrated with ICI used for monotherapy. Several mechanisms of resistance have been described so far, involving characteristics of cancer cells (intrinsic mechanisms) and of the surrounding tumor microenvironment (extrinsic mechanisms). Factors related to therapy may also contribute to the development of resistance. Increasing research efforts are being dedicated to the discovery of novel approaches and targets to overcome resistance, some of which may be introduced into clinic in the future. Herein we describe a selection of resistance mechanisms that have been involved in impairing response to ICI and propose potential therapeutic approaches to overcome resistance.

Targeting TREM1 augments antitumor T cell immunity by inhibiting myeloid-derived suppressor cells and restraining anti-PD-1 resistance

The triggering receptor expressed on myeloid cell 1 (TREM1) plays a critical role in development of chronic inflammatory disorders and the inflamed tumor microenvironment (TME) associated with most solid tumors. We examined whether loss of TREM1 signaling can abrogate the immunosuppressive TME and enhance cancer immunity. To investigate the therapeutic potential of TREM1 in cancer, we used mice deficient in Trem1 and developed a novel small molecule TREM1 inhibitor, VJDT. We demonstrated that genetic or pharmacological TREM1 silencing significantly delayed tumor growth in murine melanoma (B16F10) and fibrosarcoma (MCA205) models. Single-cell RNA-Seq combined with functional assays during TREM1 deficiency revealed decreased immunosuppressive capacity of myeloid-derived suppressor cells (MDSCs) accompanied by expansion in cytotoxic CD8+ T cells and increased PD-1 expression. Furthermore, TREM1 inhibition enhanced the antitumorigenic effect of anti-PD-1 treatment, in part, by limiting MDSC frequency and abrogating T cell exhaustion. In patient-derived melanoma xenograft tumors, treatment with VJDT downregulated key oncogenic signaling pathways involved in cell proliferation, migration, and survival. Our work highlights the role of TREM1 in cancer progression, both intrinsically expressed in cancer cells and extrinsically in the TME. Thus, targeting TREM1 to modify an immunosuppressive TME and improve efficacy of immune checkpoint therapy represents what we believe to be a promising therapeutic approach to cancer.