Lactate supports a metabolic-epigenetic link in macrophage polarization

Moonlighting functions of glucose metabolic enzymes and metabolites in cancer

Glucose metabolic enzymes and their metabolites not only provide energy and building blocks for synthesizing macromolecules but also possess non-canonical or moonlighting functions in response to extracellular and intracellular signalling. These moonlighting functions modulate various cellular activities, including gene expression, cell cycle progression, DNA repair, autophagy, senescence and apoptosis, cell proliferation, remodelling of the tumour microenvironment and immune responses. These functions integrate glucose metabolism with other essential cellular activities, driving cancer progression. Targeting these moonlighting functions could open new therapeutic avenues and lead to cancer-specific treatments.

Tumor-stromal metabolic crosstalk in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a dire prognosis. Standard-of-care chemotherapy regimens offer marginal survival benefit and carry risk of severe toxicity, while immunotherapy approaches have uniformly failed in clinical trials. Extensive desmoplasia in the PDAC tumor microenvironment (TME) disrupts blood flow to and from the tumor, thereby creating a nutrient-depleted, hypoxic, and acidic milieu that suppresses the function of antitumor immune cells and imparts chemotherapy resistance. Additionally, recent seminal studies have demonstrated crucial roles for metabolic crosstalk - the exchange of metabolites between PDAC cells and stromal cell populations in the TME - in establishing and maintaining core malignant behaviors of PDAC: tumor growth, metastasis, immune evasion, and therapy resistance. In this review, we provide a conceptual overview of metabolic crosstalk and how it evolves under various selection pressures in the TME, analyze the landscape of proposed tumorigenic metabolic crosstalk pathways, and highlight potentially druggable nodes.

Lactate-mediated metabolic reprogramming of tumor-associated macrophages: implications for tumor progression and therapeutic potential

The tumor microenvironment (TME) is characterized by distinct metabolic adaptations that not only drive tumor progression but also profoundly influence immune responses. Among these adaptations, lactate, a key metabolic byproduct of aerobic glycolysis, accumulates in the TME and plays a pivotal role in regulating cellular metabolism and immune cell function. Tumor-associated macrophages (TAMs), known for their remarkable functional plasticity, serve as critical regulators of the immune microenvironment and tumor progression. Lactate modulates TAM polarization by influencing the M1/M2 phenotypic balance through diverse signaling pathways, while simultaneously driving metabolic reprogramming. Furthermore, lactate-mediated histone and protein lactylation reshapes TAM gene expression, reinforcing their immunosuppressive properties. From a therapeutic perspective, targeting lactate metabolism has shown promise in reprogramming TAMs and enhancing anti-tumor immunity. Combining these metabolic interventions with immunotherapies may further augment treatment efficacy. This review underscores the crucial role of lactate in TAM regulation and tumor progression, highlighting its potential as a promising therapeutic target in cancer treatment.

Lactate Facilitates Pancreatic Repair Following Acute Pancreatitis by Promoting Reparative Macrophage Polarization

BACKGROUND & AIMS

During acute pancreatitis (AP), glycolysis is enhanced. The upregulation of glycolysis increases the level of metabolite lactate. Lactate has been shown to facilitate tissue repair across various pathologic conditions. However, its role in the recovery following AP remains unclear. This study aims to explore the role of lactate in the regenerative processes following AP and to elucidate its underlying molecular mechanisms.

METHODS

The caerulein-induced recovery AP model was established using wild-type and 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 3 (Pfkfb3) heterozygous mice. Pancreatic repair was evaluated histologically, whereas lactate levels and inflammatory markers were measured serologically. Macrophages were isolated from pancreatic tissue using fluorescence-activated cell sorting for mRNA sequencing to identify phenotypes. In ex vivo, macrophages were indirectly co-cultured with inflammatory acinar, and the effect of lactate on macrophage phenotype were investigated through immunoprecipitation, fluorescence analysis, and Western blotting.

RESULTS

We first found that exogenous lactate administration promoted pancreatic repair, whereas Pfkfb3 deficiency lowered lactate levels and ultimately delayed pancreatic repair. Mechanistically, lactate altered macrophage phenotype during recovery after AP, by reducing the proportion of pro-inflammatory macrophages and increasing the percentage of reparative macrophages. In the indirectly co-cultured macrophage, lactate increased lactylation levels and enhanced repair gene expression. Treatment with AZD3965, a chemical inhibitor of lactate transportation, blocked the effects on lactylation and gene expression. Besides, lactate repressed the JAK2-STAT1 pathway via GPR132 receptor, thereby suppressing the expression of pro-inflammatory genes.

CONCLUSIONS

Lactate facilitates pancreatic repair by promoting reparative macrophage polarization, achieved through promoting lactylation and inhibiting JAK2-STAT1 signaling. This phenotypic shift alleviates inflammation and facilitates tissue recovery, highlighting a potential therapeutic approach for AP.

Targeting Metabolic Reprogramming in Bladder Cancer Immunotherapy: A Precision Medicine Approach

Bladder cancer, as a highly heterogeneous malignant tumor of the urinary system, is significantly affected by tumor metabolic reprogramming in its response to immunotherapy. This review systematically elaborates on the molecular mechanisms of abnormal glucose and lipid metabolism in the bladder cancer microenvironment and immune escape, and discusses precision treatment strategies based on metabolic regulation. In the future, it will be necessary to combine spatiotemporal omics and artificial intelligence technologies to construct a multi-target intervention system for the metabolic-immune interaction network, promoting a paradigm shift in precision treatment for bladder cancer.

Foxp3 confers long-term efficacy of chimeric antigen receptor-T cells via metabolic reprogramming

The tumor microenvironment, characterized by low oxygen tension and scarce nutrients, impairs chimeric antigen receptor (CAR)-T cell metabolism, leading to T cell exhaustion and dysfunction. Notably, Foxp3 confers a metabolic advantage to regulatory T cells under such restrictive conditions. Exploiting this property, we generated CAR-TFoxp3 cells by co-expressing Foxp3 with a third-generation CAR construct. The CAR-TFoxp3 cells exhibited distinct metabolic reprogramming, marked by downregulated aerobic glycolysis and oxidative phosphorylation coupled with upregulated lipid metabolism. This metabolic shift was driven by Foxp3's interaction with dynamin-related protein 1. Crucially, CAR-TFoxp3 cells did not acquire regulatory T cell immunosuppressive functions but instead demonstrated enhanced antitumor potency and reduced expression of exhaustion markers via Foxp3-mediated adaptation. The potent antitumor effect and absence of immunosuppression were confirmed in a humanized immune system mouse model. Our findings establish a metabolic reprogramming-based strategy to enhance CAR-T cell adaptability within the hostile tumor microenvironment while preserving therapeutic efficacy.

Identification of molecular clusters and a risk prognosis model for diffuse large B-cell lymphoma based on lactate metabolism-related genes

Diffuse large B-cell lymphoma (DLBCL) is a leading cause of morbidity and mortality among lymphomas in adults, with tumor cells undergoing metabolic reprogramming linked to the immune microenvironment. This study explored the relationship between lactate metabolism-related genes (LMRGs), DLBCL prognosis, and immune microenvironment interactions. Publicly available datasets (GSE10846 and GSE87371) were analyzed, with LMRGs identified using Cox regression and LASSO regression. A risk prognosis model comprising five LMRGs was developed, showing that high-risk patients had worse outcomes due to adverse clinical features, aggressive immune microenvironments, and poor treatment responses. A nomogram combining the model with clinical data predicted 1-, 3-, and 5-year survival. Single-cell RNA sequencing indicated that high LMRG risk scores in B cells may promote immunosuppression via the MIF-CD74/CXCR4 pathway. Functional validation revealed that SDHA knockdown reduced DLBCL cell proliferation in U2932 and KIS-1 cell lines. This LMRG-based model serves as a valuable tool for predicting survival, immune landscape, and clinical risk stratification in DLBCL patients, while also highlighting the crucial role of lactate metabolism in DLBCL pathogenesis. Furthermore, these findings underscore the potential of LMRGs risk scores to guide personalized therapies and improve treatment outcomes.

Lactylation in Glioblastoma: A Novel Epigenetic Modifier Bridging Epigenetic Plasticity and Metabolic Reprogramming

Glioblastoma, the most common and aggressive primary malignant brain tumor, is characterized by a high rate of recurrence, disability, and lethality. Therefore, there is a pressing need to develop more effective prognostic biomarkers and treatment approaches for glioblastoma. Lactylation, an emerging form of protein post-translational modification, has been closely associated with lactate, a metabolite of glycolysis. Since the initial identification of lactylation sites in core histones in 2019, accumulating evidence has shown the critical role that lactylation plays in glioblastoma development, assessment of poor clinical prognosis, and immunosuppression, which provides a fresh angle for investigating the connection between metabolic reprogramming and epigenetic plasticity in glioblastoma cells. The objective of this paper is to present an overview of the metabolic and epigenetic roles of lactylation in the expanding field of glioblastoma research and explore the practical value of developing novel treatment plans combining targeted therapy and immunotherapy.

The role of protein lactylation: A kaleidoscopic post-translational modification in cancer

The recently discovered lysine lactylation represents a critical post-translational modification with widespread implications in epigenetics and cancer biology. Initially identified on histones, lysine lactylation has been also described on non-histone proteins, playing a pivotal role in transcriptional activation, protein function, and cellular processes. Two major sources of the lactyl moiety have been currently distinguished: L-lactyl-CoA (precursor of the L-lactyl moiety) and S-D-lactylglutathione (precursor of the D-lactyl moiety), which enable enzymatic and non-enzymatic mechanisms of lysine lactylation, respectively. Although the specific writers, erasers, and readers of this modification are still unclear, acetyltransferases and deacetylases have been proposed as crucial mediators of lysine lactylation. Remarkably, lactylation exerts significant influence on critical cancer-related pathways, thereby shaping cellular behavior during malignant transformation and the metastatic cascade. Hence, as recent insights into lysine lactylation underscore its growing potential in tumor biology, targeting this modification is emerging as a significant opportunity for cancer treatment.

Monitoring Acidification Preceding Aβ Deposition in Alzheimer's Disease

Amyloid beta (Aβ) is the primary early biomarker of Alzheimer's disease (AD), and since an acidic environment promotes Aβ aggregation, acidification plays a crucial role in AD progression. In this study, a novel acid-responsive near-infrared (NIR) fluorescent probe alongside multiple molecular biology techniques to investigate the temporal relationship between acidification and Aβ deposition, as well as the underlying mechanisms of acidification is employed. By monitoring 2- to 11-month-old APP/PS1 mice and wild-type (WT) mice, it is detected significant fluorescence signal in APP/PS1 mice beginning at 3 months preceding Aβ deposition at 5 months, and peaking at 5 months, followed by cognitive deficits at 8 months. Additionally, elevated monocarboxylate transporter 4 (MCT4) protein expression in 3-month-old APP/PS1 mice indicated disruption of astrocyte-neuron lactate shuttle (ANLS) homeostasis. Overall, this findings first demonstrate that acidification precedes Aβ deposition, peaks at the onset of Aβ deposition, and diminishes thereafter, with early acidification likely driven by the disruption of ANLS.

Metabolic Dialogue Shapes Immune Response in the Tumor Microenvironment

The fate of immune cells is fundamentally linked to their metabolic program, which is also influenced by the metabolic landscape of their environment. The tumor microenvironment represents a unique system for intercellular metabolic interactions, where tumor-derived metabolites suppress effector CD8+ T cells and promote tumor-promoting macrophages, reinforcing an immune-suppressive niche. This review will discuss recent advancements in metabolism research, exploring the interplay between various metabolites and their effects on immune cells within the tumor microenvironment.

Cancer Biology and the Perioperative Period: Opportunities for Disease Evolution and Challenges for Perioperative Care

Efforts to deconvolve the complex interactions of cancer cells with other components of the tumor micro- and macro-environment have exposed a common tendency for cancers to subvert systems physiology and exploit endogenous programs involved in homeostatic control of metabolism, immunity, regeneration, and repair. Many such programs are engaged in the healing response to surgery which, together with other abrupt biochemical changes in the perioperative period, provide an opportunity for the macroevolution of residual disease. This review relates contemporary perspectives of cancer as a systemic disease with the overlapping biology of host responses to surgery and events within the perioperative period. With a particular focus on examples of cancer cell plasticity and changes within the host, we explore how perioperative inflammation and acute metabolic, neuroendocrine, and immune dyshomeostasis might contribute to cancer evolution within this contextually short, yet crucially influential timeframe, and highlight potential therapeutic opportunities within to further optimize surgical cancer care and its long-term oncological outcomes.

Metabolic reprogramming shapes post-translational modification in macrophages

Polarized macrophages undergo metabolic reprogramming, as well as extensive epigenetic and post-translational modifications (PTMs) switch. Metabolic remodeling and dynamic changes of PTMs lead to timely macrophage response to infection or antigenic stimulation, as well as its transition from a pro-inflammatory to a reparative phenotype. The transformation of metabolites in the microenvironment also determines the PTMs of macrophages. Here we reviewed the current understanding of the altered metabolites of glucose, lipids and amino acids in macrophages shape signaling and metabolism pathway during macrophage polarization via PTMs, and how these metabolites in some macrophage-associated diseases affect disease progression by shaping macrophage PTMs.

Crosstalk between metabolism and epigenetics during macrophage polarization

Macrophage polarization is a dynamic process driven by a complex interplay of cytokine signaling, metabolism, and epigenetic modifications mediated by pathogens. Upon encountering specific environmental cues, monocytes differentiate into macrophages, adopting either a pro-inflammatory (M1) or anti-inflammatory (M2) phenotype, depending on the cytokines present. M1 macrophages are induced by interferon-gamma (IFN-γ) and are characterized by their reliance on glycolysis and their role in host defense. In contrast, M2 macrophages, stimulated by interleukin-4 (IL-4) and interleukin-13 (IL-13), favor oxidative phosphorylation and participate in tissue repair and anti-inflammatory responses. Metabolism is tightly linked to epigenetic regulation, because key metabolic intermediates such as acetyl-coenzyme A (CoA), α-ketoglutarate (α-KG), S-adenosylmethionine (SAM), and nicotinamide adenine dinucleotide (NAD+) serve as cofactors for chromatin-modifying enzymes, which in turn, directly influences histone acetylation, methylation, RNA/DNA methylation, and protein arginine methylation. These epigenetic modifications control gene expression by regulating chromatin accessibility, thereby modulating macrophage function and polarization. Histone acetylation generally promotes a more open chromatin structure conducive to gene activation, while histone methylation can either activate or repress gene expression depending on the specific residue and its methylation state. Crosstalk between histone modifications, such as acetylation and methylation, further fine-tunes macrophage phenotypes by regulating transcriptional networks in response to metabolic cues. While arginine methylation primarily functions in epigenetics by regulating gene expression through protein modifications, the degradation of methylated proteins releases arginine derivatives like asymmetric dimethylarginine (ADMA), which contribute directly to arginine metabolism-a key factor in macrophage polarization. This review explores the intricate relationships between metabolism and epigenetic regulation during macrophage polarization. A better understanding of this crosstalk will likely generate novel therapeutic insights for manipulating macrophage phenotypes during infections like tuberculosis and inflammatory diseases such as diabetes.

Impact of lactate on immune cell function in the tumor microenvironment: mechanisms and therapeutic perspectives

Lactate has emerged as a key regulator in the tumor microenvironment (TME), influencing both tumor progression and immune dynamics. As a byproduct of aerobic glycolysis, lactate satisfies the metabolic needs of proliferating tumor cells while reshaping the TME to facilitate immune evasion. Elevated lactate levels inhibit effector immune cells such as CD8+ T and natural killer cells, while supporting immunosuppressive cells, such as regulatory T cells and myeloid-derived suppressor cells, thus fostering an immunosuppressive environment. Lactate promotes epigenetic reprogramming, stabilizes hypoxia-inducible factor-1α, and activates nuclear factor kappa B, leading to further immunological dysfunction. In this review, we examined the role of lactate in metabolic reprogramming, immune suppression, and treatment resistance. We also discuss promising therapeutic strategies targeting lactate metabolism, including lactate dehydrogenase inhibitors, monocarboxylate transporter inhibitors, and TME neutralization methods, all of which can restore immune function and enhance immunotherapy outcomes. By highlighting recent advances, this review provides a theoretical foundation for integrating lactate-targeted therapies into clinical practice. We also highlight the potential synergy between these therapies and current immunotherapeutic strategies, providing new avenues for addressing TME-related challenges and improving outcomes for patients with cancer.

Burning lactic acid: a road to revitalizing antitumor immunity

Lactic acid (LA) accumulation in tumor microenvironments (TME) has been implicated in immune suppression and tumor progress. Diverse roles of LA have been elucidated, including microenvironmental pH regulation, signal transduction, post-translational modification, and metabolic remodeling. This review summarizes LA functions within TME, focusing on the effects on tumor cells, immune cells, and stromal cells. Reducing LA levels is a potential strategy to attack cancer, which inevitably affects the physiological functions of normal tissues. Alternatively, transporting LA into the mitochondria as an energy source for immune cells is intriguing. We underscore the significance of LA in both tumor biology and immunology, proposing the burning of LA as a potential therapeutic approach to enhance antitumor immune responses.

Bridging epigenomics and tumor immunometabolism: molecular mechanisms and therapeutic implications

Epigenomic modifications-such as DNA methylation, histone acetylation, and histone methylation-and their implications in tumorigenesis, progression, and treatment have emerged as a pivotal field in cancer research. Tumors undergo metabolic reprogramming to sustain proliferation and metastasis in nutrient-deficient conditions, while suppressing anti-tumor immunity in the tumor microenvironment (TME). Concurrently, immune cells within the immunosuppressive TME undergo metabolic adaptations, leading to alterations in their immune function. The complicated interplay between metabolites and epigenomic modulation has spotlighted the significance of epigenomic regulation in tumor immunometabolism. In this review, characteristics of the epigenomic modification associated with tumors are systematically summarized alongside with their regulatory roles in tumor metabolic reprogramming and immunometabolism. Classical and emerging approaches are delineated to broaden the boundaries of research on the crosstalk research on the crosstalk between tumor immunometabolism and epigenomics. Furthermore, we discuss potential therapeutic strategies that target tumor immunometabolism to modulate epigenomic modifications, highlighting the burgeoning synergy between metabolic therapies and immunotherapy as a promising avenue for cancer treatment.

The lactate receptor HCAR1 drives the recruitment of immunosuppressive PMN-MDSCs in colorectal cancer

Most patients with colorectal cancer do not achieve durable clinical benefits from immunotherapy, underscoring the existence of alternative immunosuppressive mechanisms. Here we found that activation of the lactate receptor HCAR1 signaling pathway induced the expression of chemokines CCL2 and CCL7 in colorectal tumor cells, leading to the recruitment of immunosuppressive CCR2+ polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) to the tumor microenvironment. Ablation of Hcar1 in mice with colorectal tumors significantly decreased the abundance of tumor-infiltrating CCR2+ PMN-MDSCs, enhanced the activation of CD8+ T cells and, consequently, reduced tumor burden. We detected immunosuppressive CCR2+ PMN-MDSCs in tumor specimens from individuals with colorectal and other cancers. The US Food and Drug Administration-approved drug reserpine suppressed lactate-mediated HCAR1 activation, impaired the recruitment of CCR2+ PMN-MDSCs, boosted CD8+ T cell-dependent antitumor immunity and sensitized immunotherapy-resistant tumors to programmed cell death protein 1 antibody therapy in mice with colorectal tumors. Altogether, we described HCAR1-driven recruitment of CCR2+ PMN-MDSCs as a mechanism of immunosuppression.

Acetyl-CoA synthesis in the skin is a key determinant of systemic lipid homeostasis

ATP-citrate lyase (ACLY) generates cytosolic acetyl-coenzyme A (acetyl-CoA) for lipid synthesis and is a promising therapeutic target in diseases with altered lipid metabolism. Here, we developed inducible whole-body Acly-knockout mice to determine the requirement for ACLY in normal tissue functions, uncovering its crucial role in skin homeostasis. ACLY-deficient skin upregulates the acetyl-CoA synthetase ACSS2; deletion of both Acly and Acss2 from the skin exacerbates skin abnormalities, with differential effects on two major lipid-producing skin compartments. While the epidermis is depleted of barrier lipids, the sebaceous glands increase production of sebum, supplied at least in part by circulating fatty acids and coinciding with adipose lipolysis and fat depletion. Dietary fat supplementation further boosts sebum production and partially rescues both the lipoatrophy and the aberrant skin phenotypes. The data establish a critical role for cytosolic acetyl-CoA synthesis in maintaining skin barrier integrity and highlight the skin as a key organ in systemic lipid regulation.

From silent partners to potential therapeutic targets: macrophages in colorectal cancer

Cancer cells grow and survive in the tumor microenvironment, which is a complicated process. As a key part of how colorectal cancer (CRC) progresses, tumor-associated macrophages (TAMs) exhibit a double role. Through angiogenesis, this TAM can promote the growth of cancers. Although being able to modify and adjust immune cells is a great advantage, these cells can also exhibit anti-cancer properties including direct killing of cancer cells, presenting antigens, and aiding T cell-mediated responses. The delicate regulatory mechanisms between the immune system and tumors are composed of a complex network of pathways regulated by several factors including hypoxia, metabolic reprogramming, cytokine/chemokine signaling, and cell interactions. Decoding and figuring out these complex systems become significant in building targeted treatment programs. Targeting TAMs in CRC involves disrupting chemokine signaling or adhesion molecules, reprogramming them to an anti-tumor phenotype using TLR agonists, CD40 agonists, or metabolic modulation, and selectively removing TAM subsets that promote tumor growth. Multi-drug resistance, the absence of an accurate biomarker, and drug non-specificity are also major problems. Combining macrophage-targeted therapies with chemotherapy and immunotherapy may revolutionize treatment. Macrophage studies will advance with new technology and multi-omics methodologies to help us understand CRC and build specific and efficient treatments.

A375 melanoma-derived lactate controls A375 melanoma phenotypes by inducing macrophage M2 polarization via TCA cycle and TGF-β signaling

Introduction

Macrophage phenotypes have been linked to progression and prognosis of cutaneous melanoma. However, the association between Warburg effect in A375 melanoma and macrophages polarization, as well as the underlying mechanisms, remains less well documented.

Objective

The present study aimed to investigate the effect of lactate derived from A375 melanoma on macrophage polarization, melanoma phenotype responses and the underlying mechanisms.

Methods

Flow cytometry was performed to evaluate the expression of M1 and M2 markers, cell cycle and apoptosis. Levels of transforming growth factor β (TGF-β) and tumor necrosis factor α (TNF-α) were determined with enzyme-linked immunosorbent assay (ELISA) kit. Proliferation and invasion were assessed by CCK8 and transwell assays, respectively. The extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) were analyzed using an XF96 extracellular flux analyzer. Protein expressions were determined by Western blotting.

Results

Our results revealed that melanoma A375 conditioned medium (A375-CM) induced peripheral blood mononuclear cells (PBMCs) to polarize toward anti-inflammatory M2 macrophages. M2 markers CD206 and ARG1 expression increased, as did TGF-β secretion. Conversely, M1 marker CD68 expression decreased. Furthermore, hypoxia promoted macrophage M2 polarization induced by A375-CM. Elevated lactate level in PIG1-conditioned medium (PIG1-CM) induced M2 polarization, whereas the lactate transport inhibitor AZD3965 suppressed this effect in PBMCs cultured with A375-CM. Additionally, lactate derived from melanoma regulated M1/M2 polarization by the tricarboxylic acid (TCA) cycle instead of glycolysis. Significantly, polarized macrophages altered melanoma phenotypes including proliferation, clone formation, cell cycle, apoptosis, migration and invasion via TCA cycle and TGF-β.

Conclusion

Our data collectively demonstrate that lactate derived from melanoma facilitates polarization of M2 macrophages, which subsequently leads to modifications in melanoma phenotypes via TCA cycle and TGF-β signaling.

Lactate and lactylation in cancer

Accumulated evidence has implicated the diverse and substantial influence of lactate on cellular differentiation and fate regulation in physiological and pathological settings, particularly in intricate conditions such as cancer. Specifically, lactate has been demonstrated to be pivotal in molding the tumor microenvironment (TME) through its effects on different cell populations. Within tumor cells, lactate impacts cell signaling pathways, augments the lactate shuttle process, boosts resistance to oxidative stress, and contributes to lactylation. In various cellular populations, the interplay between lactate and immune cells governs processes such as cell differentiation, immune response, immune surveillance, and treatment effectiveness. Furthermore, communication between lactate and stromal/endothelial cells supports basal membrane (BM) remodeling, epithelial-mesenchymal transitions (EMT), metabolic reprogramming, angiogenesis, and drug resistance. Focusing on lactate production and transport, specifically through lactate dehydrogenase (LDH) and monocarboxylate transporters (MCT), has shown promise in the treatment of cancer. Inhibitors targeting LDH and MCT act as both tumor suppressors and enhancers of immunotherapy, leading to a synergistic therapeutic effect when combined with immunotherapy. The review underscores the importance of lactate in tumor progression and provides valuable perspectives on potential therapeutic approaches that target the vulnerability of lactate metabolism, highlighting the Heel of Achilles for cancer treatment.

MAZ-mediated tumor progression and immune evasion in hormone receptor-positive breast cancer: Targeting tumor microenvironment and PCLAF+ subtype-specific therapy

BACKGROUND

Breast cancer had been the most frequently diagnosed cancer among women, making up nearly one-third of all female cancers. Hormone receptor-positive breast cancer (HR+BC) was the most prevalent subtype of breast cancer and exhibited significant heterogeneity. Despite advancements in endocrine therapies, patients with advanced HR+BC often faced poor outcomes due to the development of resistance to treatment. Understanding the molecular mechanisms behind this resistance, including tumor heterogeneity and changes in the tumor microenvironment, was crucial for overcoming resistance, identifying new therapeutic targets, and developing more effective personalized treatments.

METHODS

The study utilized single-cell RNA sequencing (scRNA-seq) data sourced from the Gene Expression Omnibus database and The Cancer Genome Atlas to analyze HR+BC and identify key cellular characteristics. Cell type identification was achieved through Seurat's analytical tools, and subtype differentiation trajectories were inferred using Slingshot. Cellular communication dynamics between tumor cell subtypes and other cells were analyzed with the CellChat. The pySCENIC package was utilized to analyze transcription factors regulatory networks in the identified tumor cell subtypes. The results were verified by in vitro experiments. A risk scoring model was developed to assess patient outcomes.

RESULTS

This study employed scRNA-seq to conduct a comprehensive analysis of HR+BC tumor subtypes, identifying the C3 PCLAF+ tumor cells subtype, which demonstrated high proliferation and differentiation potential. C3 PCLAF+ tumor cells subtype was found to be closely associated with cancer-associated fibroblasts through the MK signaling pathway, facilitating tumor progression. Additionally, we discovered that MAZ was significantly expressed in C3 PCLAF+ tumor cells subtype, and in vitro experiments confirmed that MAZ knockdown inhibited tumor growth, accentuating its underlying ability as a therapeutic target. Furthermore, we developed a novel prognostic model based on the expression profile of key prognostic genes within the PCLAF+/MAZ regulatory network. This model linked high PCLAF+ tumor risk scores with poor survival outcomes and specific immune microenvironment characteristics.

CONCLUSION

This study utilized scRNA-seq to reveal the role of the C3 PCLAF+ tumor cells subtype in HR+BC, emphasizing its association with poor prognosis and resistance to endocrine therapies. MAZ, identified as a key regulator, contributed to tumor progression, while the tumor microenvironment had a pivotal identity in immune evasion. The findings underscored the importance of overcoming drug resistance, recognizing novel treatment targets, and crafting tailored diagnosis regimens.

Metabolic and epigenetic regulation of macrophage polarization in atherosclerosis: Molecular mechanisms and targeted therapies

Atherosclerosis, a multifactorial progressive inflammatory disease, is the common pathology underlying cardiovascular and cerebrovascular diseases. The macrophage plasticity is involved in the pathogenesis of atherosclerosis. With the advance of metabolomics and epigenetics, metabolites/metabolic and epigenetic modification such as DNA methylation, histone modification and noncoding RNA, play a crucial role in macrophage polarization and the progression of atherosclerosis. Herein, we provide a comprehensive review of the essential role of metabolic and epigenetic regulation, as well as the crosstalk between the two in regulating macrophage polarization in atherosclerosis. We also highlight the potential therapeutic strategies of regulating macrophage polarization via epigenetic and metabolic modifications for atherosclerosis, and offer recommendations to advance our knowledge of the roles of metabolic-epigenetic crosstalk in macrophage polarization in the context of atherosclerosis. Fundamental studies that elucidate the mechanisms by which metabolic and epigenetic regulation of macrophage polarization influence atherosclerosis will pave the way for novel therapeutic approaches.

Linking macrophage metabolism to function in the tumor microenvironment

Macrophages are present at high frequency in most solid tumor types, and their relative abundance negatively correlates with therapy responses and survival outcomes. Tissue-resident macrophages are highly tuned to integrate tissue niche signals, and multiple factors within the idiosyncratic tumor microenvironment (TME) drive macrophages to polarization states that favor immune suppression, tumor growth and metastasis. These diverse functional states are underpinned by extensive and complex rewiring of tumor-associated macrophage (TAM) metabolism. In this Review, we link distinct and specific macrophage functional states within the TME to major, phenotype-sustaining metabolic programs and discuss the metabolic impact of macrophage-modulating therapeutic interventions.

Sex-related changes in lactate dehydrogenase A expression differently impact the immune response in melanoma

Melanoma is more aggressive in male patients than female ones and this is associated with sexual dimorphism in immune responses. Taking into consideration the impact tumour metabolic alterations in affecting the immune landscape, we aimed to investigate the effect of the sex-dependent metabolic profile of melanoma in re-shaping immune composition. Melanoma is characterised by Warburg metabolism, and secreted lactate has emerged as a key driver in the establishment of an immunosuppressive environment. Here, we identified lactate dehydrogenase A (LDH-A) as a crucial player in modulating sex-related differences in melanoma immune responses, both in vitro and in patient-derived specimens. LDH-A is associated with higher lactate secretion in male melanoma cells, which leads to a significant enrichment in pro-tumoural regulatory T cells (Treg) with a concurrent decrease in the number and activity of anti-tumour CD8+ T cells. Remarkably, pharmacological and genetic impairment of LDH-A in male melanoma cells normalises Treg and CD8+ infiltration. In keeping with this, in vivo pharmacological targeting of LDH-A in melanoma-bearing male mice impairs tumour growth and lung colonisation, with a concomitant modulation of Treg and CD8+ T cells infiltration. Taken together, our findings highlight the sex-related differences promoted by LDH-A in immune reshaping in melanoma, and suggest that therapeutic targeting of LDH-A could be leveraged as an effective strategy to abolish the sex-gap in melanoma progression.

Nanomaterial-enabled metabolic reprogramming strategies for boosting antitumor immunity

Immunotherapy has become a crucial strategy in cancer treatment, but its effectiveness is often constrained. Most cancer immunotherapies focus on stimulating T-cell-mediated immunity by driving the cancer-immunity cycle, which includes tumor antigen release, antigen presentation, T cell activation, infiltration, and tumor cell killing. However, metabolism reprogramming in the tumor microenvironment (TME) supports the viability of cancer cells and inhibits the function of immune cells within this cycle, presenting clinical challenges. The distinct metabolic needs of tumor cells and immune cells require precise and selective metabolic interventions to maximize therapeutic outcomes while minimizing adverse effects. Recent advances in nanotherapeutics offer a promising approach to target tumor metabolism reprogramming and enhance the cancer-immunity cycle through tailored metabolic modulation. In this review, we explore cutting-edge nanomaterial strategies for modulating tumor metabolism to improve therapeutic outcomes. We review the design principles of nanoplatforms for immunometabolic modulation, key metabolic pathways and their regulation, recent advances in targeting these pathways for the cancer-immunity cycle enhancement, and future prospects for next-generation metabolic nanomodulators in cancer immunotherapy. We expect that emerging immunometabolic modulatory nanotechnology will establish a new frontier in cancer immunotherapy in the near future.

Targeting glycolysis: exploring a new frontier in glioblastoma therapy

Glioblastoma(GBM) is a highly malignant primary central nervous system tumor that poses a significant threat to patient survival due to its treatment resistance and rapid recurrence.Current treatment options, including maximal safe surgical resection, radiotherapy, and temozolomide (TMZ) chemotherapy, have limited efficacy.In recent years, the role of glycolytic metabolic reprogramming in GBM has garnered increasing attention. This review delves into the pivotal role of glycolytic metabolic reprogramming in GBM, with a particular focus on the multifaceted roles of lactate, a key metabolic product, within the tumor microenvironment (TME). Lactate has been implicated in promoting tumor cell proliferation, invasion, and immune evasion. Additionally, this review systematically analyzes potential therapeutic strategies targeting key molecules within the glycolytic pathway, such as Glucose Transporters (GLUTs), Monocarboxylate Transporters(MCTs), Hexokinase 2 (HK2), 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 3 (PFKFB3), Pyruvate Kinase Isozyme Type M2 (PKM2), and the Lactate Dehydrogenase A (LDHA). These studies provide a novel perspective for GBM treatment. Despite progress made in existing research, challenges remain, including drug penetration across the blood-brain barrier, side effects, and resistance. Future research will aim to address these challenges by improving drug delivery, minimizing side effects, and exploring combination therapies with radiotherapy, chemotherapy, and immunotherapy to develop more precise and effective personalized treatment strategies for GBM.

Resveratrol-driven macrophage polarization: unveiling mechanisms and therapeutic potential

Resveratrol, a polyphenolic compound known for its diverse biological activities, has demonstrated multiple pharmacological effects, including anti-inflammatory, anti-aging, anti-diabetic, anti-cancer, and cardiovascular protective properties. Recent studies suggest that these effects are partly mediated through the regulation of macrophage polarization, wherein macrophages differentiate into pro-inflammatory M1 or anti-inflammatory M2 phenotypes. Our review highlights how resveratrol modulates macrophage polarization through various signaling pathways to achieve therapeutic effects. For example, resveratrol can activate the senescence-associated secretory phenotype (SASP) pathway and inhibit the signal transducer and activator of transcription (STAT3) and sphingosine-1-phosphate (S1P)-YAP signaling axes, promoting M1 polarization or suppressing M2 polarization, thereby inhibiting tumor growth. Conversely, it can promote M2 polarization or suppress M1 polarization by inhibiting the NF-κB signaling pathway or activating the PI3K/Akt and AMP-activated protein kinase (AMPK) pathways, thus alleviating inflammatory responses. Notably, the effect of resveratrol on macrophage polarization is concentration-dependent; moderate concentrations tend to promote M1 polarization, while higher concentrations may favor M2 polarization. This concentration dependence offers new perspectives for clinical treatment but also underscores the necessity for precise dosage control when using resveratrol. In summary, resveratrol exhibits significant potential in regulating macrophage polarization and treating related diseases.

Epigenetic Regulation of Stromal and Immune Cells and Therapeutic Targets in the Tumor Microenvironment

The tumor microenvironment (TME) plays a pivotal role in neoplastic initiation and progression. Epigenetic machinery, governing the expression of core oncogenes and tumor suppressor genes in transformed cells, significantly contributes to tumor development at both primary and distant sites. Recent studies have illuminated how epigenetic mechanisms integrate external cues and downstream signals, altering the phenotype of stromal cells and immune cells. This remolds the area surrounding tumor cells, ultimately fostering an immunosuppressive microenvironment. Therefore, correcting the TME by targeting the epigenetic modifications holds substantial promise for cancer treatment. This review synthesizes recent research that elucidates the impact of specific epigenetic regulations-ranging from DNA methylation to histone modifications and chromatin remodeling-on stromal and immune cells within the TME. Notably, we highlight their functional roles in either promoting or restricting tumor progression. We also discuss the potential applications of epigenetic agents for cancer treatment, envisaging their ability to normalize the ecosystem. This review aims to assist researchers in understanding the dynamic interplay between epigenetics and the TME, paving the way for better epigenetic therapy.

Metabolic reprogramming, sensing, and cancer therapy

The metabolic reprogramming of tumor cells is a crucial strategy for their survival and proliferation, involving tissue- and condition-dependent remodeling of certain metabolic pathways. While it has become increasingly clear that tumor cells integrate extracellular and intracellular signals to adapt and proliferate, nutrient and metabolite sensing also exert direct or indirect influences, although the underlying mechanisms remain incompletely understood. Furthermore, metabolic changes not only support the rapid growth and dissemination of tumor cells but also promote immune evasion by metabolically "educating" immune cells in the tumor microenvironment (TME). Recent studies have highlighted the profound impact of metabolic reprogramming on the TME and the potential of targeting metabolic pathways as a therapeutic strategy, with several enzyme inhibitors showing promising results in clinical trials. Thus, understanding how tumor cells alter their metabolic pathways and metabolically remodel the TME to support their survival and proliferation may offer new strategies for metabolic therapy and immunotherapy.

Multiomics analyses reveal adipose-derived stem cells inhibit the inflammatory response of M1-like macrophages through secreting lactate

BACKGROUND

Adipose-derived stem cells (ADSCs) are widely used in the field of regenerative medicine because of their various functions, including anti-inflammatory effects. ADSCs are considered to exert their anti-inflammatory effects by secreting anti-inflammatory cytokines and extracellular vesicles. Although recent studies have reported that metabolites have a variety of physiological activities, whether those secreted by ADSCs have anti-inflammatory properties remains unclear. Here, we performed multiomics analyses to examine the effect of ADSC-derived metabolites on M1-like macrophages, which play an important role in inflammatory responses.

METHODS

The concentration of metabolites in the culture supernatant of ADSCs was quantified using capillary electrophoresis time-of-flight mass spectrometry. To evaluate their effects on inflammatory responses, M1-like macrophages were exposed to the conditioned ADSC medium or their metabolites, and RNA sequencing was used to detect gene expression changes. Immunoblotting was performed to examine how the metabolite suppresses inflammatory processes. To clarify the contribution of the metabolite in the conditioned medium to its anti-inflammatory effects, metabolite uptake was pharmacologically inhibited, and gene expression and the tumor necrosis factor-α concentration were measured by quantitative PCR and enzyme-linked immunosorbent assay, respectively.

RESULTS

Metabolomic analysis showed large amounts of lactate in the culture supernatant. The conditioned medium and lactate significantly suppressed or increased the pro-inflammatory and anti-inflammatory gene expressions. However, sequencing and immunoblotting analysis revealed that lactate did not induce polarization from M1- to M2-like macrophages. Based on a recent report that the immunosuppressive effect of lactate depends on epigenetic reprogramming, histone acetylation was investigated, and H3K27ac expression was upregulated. In addition, 7ACC2, which specifically inhibits the monocarboxylate transporter 1, significantly inhibited the anti-inflammatory effect of the conditioned ADSC medium on M1-like macrophages.

CONCLUSIONS

Our results showed that ADSCs suppress pro-inflammatory effects of M1-like macrophages by secreting lactate. This study adds to our understanding of the importance of metabolites and is also expected to elucidate new mechanisms of ADSC treatments.

The Role of Macrophages in Hepatocellular Carcinoma and Their Therapeutic Potential

Hepatocellular carcinoma (HCC) represents a significant clinical burden globally and is predicted to continue to increase in incidence for the foreseeable future. The treatment of HCC is complicated by the fact that, in the majority of cases, it develops on a background of advanced chronic inflammatory liver disease. Chronic inflammation can foster an immunosuppressive microenvironment that promotes tumour progression and metastasis. In this setting, macrophages make up a major immune component of the HCC tumour microenvironment, and in this review, we focus on their contribution to HCC development and progression. Tumour-associated macrophages (TAMs) are largely derived from infiltrating monocytes and their potent anti-inflammatory phenotype can be induced by factors that are found within the tumour microenvironment, such as growth factors, cytokines, hypoxia, and extracellular matrix (ECM) proteins. In general, experimental evidence suggest that TAMs can exhibit a variety of functions that aid HCC tumour progression, including the promotion of angiogenesis, resistance to drug therapy, and releasing factors that support tumour cell proliferation and metastasis. Despite their tumour-promoting profile, there is evidence that the underlying plasticity of these cells can be targeted to help reprogramme TAMs to drive tumour-specific immune responses. We discuss the potential for targeting TAMs therapeutically either by altering their phenotype within the HCC microenvironment or by cell therapy approaches by taking advantage of their infiltrative properties from the circulation into tumour tissue.

Antitumoral Activity and Metabolic Signatures of Dichloroacetate, 6-Aminonicotinamide and Etomoxir in Breast-Tumor-Educated Macrophages

Pharmacological targeting of metabolic pathways represents an appealing strategy to selectively kill cancer cells while promoting antitumor functions of stromal cells. In this study, we assessed the effectiveness of 13 metabolic drugs (MDs) in steering in vitro generated breast tumor-educated macrophages (TEMs) toward an antitumoral phenotype. For that, the production of vascular endothelial growth factor (VEGF) and tumor necrosis factor α (TNF-α), two important regulators of tumor progression, was evaluated. Notably, dichloroacetate (DCA), 6-aminonicotinamide (6-AN), and etomoxir decreased VEGF production and enhanced TNF-α release. Hence, we further clarified their impact on TEM metabolism using an untargeted NMR-based metabolomics approach. DCA downregulated glycolysis and enhanced the utilization of extracellular substrates like lactate while reconfiguring lipid metabolism. Several DCA-induced changes significantly correlated with heightened TNF-α production in response to pro-inflammatory stimulation. The inhibition of the pentose phosphate pathway by 6-AN was accompanied by enhanced glutaminolysis, which correlated with a decreased level of VEGF production. In etomoxir-treated TEM, inhibition of fatty acid oxidation was compensated through upregulation of glycolysis, catabolism of intracellular amino acids, and consumption of extracellular branched chain alpha-ketoacids (BCKA) and citrate. Overall, our results offer a comprehensive view of the metabolic signature of each MD in breast TEM and highlight putative correlations with phenotypic effects.

A low level of tumor necrosis factor α in tumor microenvironment maintains the self-renewal of glioma stem cells by Vasorin-mediated glycolysis

BACKGROUND

Self-renewal of glioma stem cells (GSCs) is responsible for glioblastoma (GBM) therapy resistance and recurrence. Tumor necrosis factor α (TNFα) and TNF signaling pathway display an antitumor activity in preclinical models and in tumor patients. However, TNFα exhibits no significance for glioma clinical prognosis based on the Glioma Genome Atlas database. This study aimed to explore whether TNFα of tumor microenvironment maintains self-renewal of GSCs and promotes worse prognosis in glioma patients.

METHODS

Spatial transcriptomics, immunoblotting, sphere formation assay, extreme limiting dilution, and gene expression analysis were used to determine the role of TNFα on GSC's self-renewal. Mass spectrometry, RNA-sequencing detection, bioinformatic analyses, qRT-RNA, immunofluorescence, immunohistochemistry, single-cell RNA sequencing, in vitro and in vivo models were used to uncover the mechanism of TNFα-induced GSC self-renewal.

RESULTS

A low level of TNFα displays a promoting effect on GSC self-renewal and worse glioma prognosis. Mechanistically, Vasorin (VASN) mediated TNFα-induced self-renewal by potentiating glycolysis. Lactate produced by glycolysis inhibits the TNFα secretion of tumor-associated macrophages (TAMs) and maintains TNFα at a low level.

CONCLUSIONS

TNFα-induced GSC self-renewal mediated by VASN provides a possible explanation for the failures of endogenous TNFα effect on GBM. A combination of targeting VASN and TNFα antitumor effect may be an effective approach for treating GBM.

Metabolism and macrophages in the tumor microenvironment

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

Lactate reprograms glioblastoma immunity through CBX3-regulated histone lactylation

Glioblastoma (GBM), an aggressive brain malignancy with a cellular hierarchy dominated by GBM stem cells (GSCs), evades antitumor immunity through mechanisms that remain incompletely understood. Like most cancers, GBMs undergo metabolic reprogramming toward glycolysis to generate lactate. Here, we show that lactate production by patient-derived GSCs and microglia/macrophages induces tumor cell epigenetic reprogramming through histone lactylation, an activating modification that leads to immunosuppressive transcriptional programs and suppression of phagocytosis via transcriptional upregulation of CD47, a "don't eat me" signal, in GBM cells. Leveraging these findings, pharmacologic targeting of lactate production augments efficacy of anti-CD47 therapy. Mechanistically, lactylated histone interacts with the heterochromatin component chromobox protein homolog 3 (CBX3). Although CBX3 does not possess direct lactyltransferase activity, CBX3 binds histone acetyltransferase (HAT) EP300 to induce increased EP300 substrate specificity toward lactyl-CoA and a transcriptional shift toward an immunosuppressive cytokine profile. Targeting CBX3 inhibits tumor growth by both tumor cell-intrinsic mechanisms and increased tumor cell phagocytosis. Collectively, these results suggest that lactate mediates metabolism-induced epigenetic reprogramming in GBM that contributes to CD47-dependent immune evasion, which can be leveraged to augment efficacy of immuno-oncology therapies.

Acid affairs in anti-tumour immunity

Metabolic rewiring of cancer cells is one of the hallmarks of cancer. As a consequence, the metabolic landscape of the tumour microenvironment (TME) differs compared to correspondent healthy tissues. Indeed, due to the accumulation of acid metabolites, such as lactate, the pH of the TME is generally acidic with a pH drop that can be as low as 5.6. Disruptions in the acid-base balance and elevated lactate levels can drive malignant progression not only through cell-intrinsic mechanisms but also by impacting the immune response. Generally, acidity and lactate dampen the anti-tumour response of both innate and adaptive immune cells favouring tumour progression and reducing the response to immunotherapy. In this review, we summarize the current knowledge on the functional, metabolic and epigenetic effects of acidity and lactate on the cells of the immune system. In particular, we focus on the role of monocarboxylate transporters (MCTs) and other solute carrier transporters (SLCs) that, by mediating the exchange of lactate (among other metabolites) and bicarbonate, participate in pH regulation and lactate transport in the cancer context. Finally, we discuss advanced approaches to target pH or lactate in the TME to enhance the anti-tumour immune response.

A new perspective on the therapeutic potential of tumor metastasis: targeting the metabolic interactions between TAMs and tumor cells

Tumor-associated macrophages (TAMs) undergo metabolic reprogramming, encompassing glucose, amino acid, fatty acid metabolism, tricarboxylic acid (TCA) cycle, purine metabolism, and autophagy, within the tumor microenvironment (TME). The metabolic interdependencies between TAMs and tumor cells critically influence macrophage recruitment, differentiation, M2 polarization, and secretion of epithelial-mesenchymal transition (EMT)-related factors, thereby activating intratumoral EMT pathways and enhancing tumor cell invasion and metastasis. Tumor cell metabolic alterations, including hypoxia, metabolite secretion, aerobic metabolism, and autophagy, affect the TME's metabolic landscape, driving macrophage recruitment, differentiation, M2 polarization, and metabolic reprogramming, ultimately facilitating EMT, invasion, and metastasis. Additionally, macrophages can induce tumor cell EMT by reprogramming their aerobic glycolysis. Recent experimental and clinical studies have focused on the metabolic interactions between macrophages and tumor cells to control metastasis and inhibit tumor progression. This review highlights the regulatory role of TAM-tumor cell metabolic codependencies in EMT, offering valuable insights for TAM-targeted therapies in highly metastatic tumors. Modulating the metabolic interplay between tumors and TAMs represents a promising therapeutic strategy for treating patients with metastatic cancers.

Lactate's impact on immune cells in sepsis: unraveling the complex interplay

Lactate significantly impacts immune cell function in sepsis and septic shock, transcending its traditional view as just a metabolic byproduct. This review summarizes the role of lactate as a biomarker and its influence on immune cell dynamics, emphasizing its critical role in modulating immune responses during sepsis. Mechanistically, key lactate transporters like MCT1, MCT4, and the receptor GPR81 are crucial in mediating these effects. HIF-1α also plays a significant role in lactate-driven immune modulation. Additionally, lactate affects immune cell function through post-translational modifications such as lactylation, acetylation, and phosphorylation, which alter enzyme activities and protein functions. These interactions between lactate and immune cells are central to understanding sepsis-associated immune dysregulation, offering insights that can guide future research and improve therapeutic strategies to enhance patient outcomes.

Macrophage fate: to kill or not to kill?

Macrophages are dynamic innate immune cells that either reside in tissue, serving as sentinels, or recruited as monocytes from bone marrow into inflamed and infected tissue. In response to cues in the tissue microenvironment (TME), macrophages polarize on a continuum toward M1 or M2 with diverse roles in progression and resolution of disease. M1-like macrophages exhibit proinflammatory functions with antimicrobial and anti-tumorigenic activities, while M2-like macrophages have anti-inflammatory functions that generally resolve inflammatory responses and orchestrate a tissue healing process. Given these opposite phenotypes, proper spatiotemporal coordination of macrophage polarization in response to cues within the TME is critical to effectively resolve infectious disease and regulate wound healing. However, if this spatiotemporal coordination becomes disrupted due to persistent infection or dysregulated coagulation, macrophages' inappropriate response to these cues will result in the development of diseases with clinically unfavorable outcomes. Since plasticity and heterogeneity are hallmarks of macrophages, they are attractive targets for therapies to reprogram toward specific phenotypes that could resolve disease and favor clinical prognosis. In this review, we discuss how basic science studies have elucidated macrophage polarization mechanisms in TMEs during infections and inflammation, particularly coagulation. Therefore, understanding the dynamics of macrophage polarization within TMEs in diseases is important in further development of targeted therapies.

The prognostic value and its relationship with immune infiltration of ACLY in clear cell renal cell carcinoma

ATP citrate lyase (ACLY) is activated in various cancers, but its role in clear cell renal cell carcinoma (ccRCC) remains poorly understood. Herein, we investigated the prognostic role and potential mechanism of ACLY in ccRCC. The expression profile of ACLY in ccRCC was explored using Gene Expression Profiling Interactive Analysis 2 (GEPIA2), Gene Expression Omnibus (GEO), UALCAN and western blotting assays. The prognosis was investigated using immunohistochemistry (IHC) and Kaplan-Meier plotter assays. The relationship with immune infiltration was further evaluated using Tumor Immune Estimation Resource 2 (TIMER2) and Tumor Immune System Interactions and DrugBank (TISIDB) databases, respectively. Further biological function of ACLY in ccRCC pathogenesis was explored using in vitro experiments. ACLY level was higher in ccRCC than adjacent kidney tissues, and Kaplan-Meier survival analysis showed ACLY mRNA or protein were predictors of poor prognosis in ccRCC patients. Importantly, we reported for the first time that ACLY gene expression was significantly correlated with numerous immune cells and immune inhibitors in ccRCC. ACLY inhibition significantly impaired cell proliferation, induced cell apoptosis, attenuated cell migration, decreased lipid droplets formation, and suppressed epithelial-mesenchymal transition (EMT) of ccRCC. Moreover, these effects might be acted through mammalian target of rapamycin complex 1 (mTORC1) pathway. Collectively, ACLY was not only implicated in ccRCC tumorigenesis and progression, but also potentially interacted with immune infiltration and mTORC1 pathway. Our findings may provide a novel therapeutic strategy by targeting ACLY for ccRCC treatment.

Two-pronged anti-cancer nanovaccines enpowered by exogenous/endogenous tumor-associated antigens

Cancer vaccines based on single-source (exogenous or endogenous) tumor-associated antigens (TAAs) are often challenged by the insufficient T cell response and the immunosuppressive tumor microenvironment (TME). Herein, a dual TAAs-boosted nanovaccine based on cancer cell (4T1) membrane-cloaked, CO-immobilized Prussian blue nanoparticles (4T1-PB-CO NPs) is developed and coupled with anti-interleukin (IL)-10 therapy to maximize the efficacy of antitumor immunotherapy. 4T1 cell membrane not only endows NPs with tumor targeting ability, but also serves as exogenous TAAs to trigger CD4+ T cell response and M1-phenotype polarization of tumor-associated macrophages. Under near-infrared light irradiation, 4T1-PB-CO NPs release CO to induce immunogenic cell death (ICD) of tumor cells, thus generating endogenous TAAs to activate CD8+ T cell response. Meanwhile, ICD triggers release of damage-associated molecular patterns, which can promote DC maturation to amplify the antitumor T cell response. When combined with anti-IL-10 that reverses the immunosuppressive TME, 4T1-PB-CO NPs efficiently suppress the primary tumors and produce an abscopal effect to inhibit distant tumors in a breast tumor-bearing mouse model. Such a two-pronged cancer vaccine represents a promising paradigm for robust antitumor immunotherapy.

The Effects of Hypoxia on the Immune-Metabolic Interplay in Liver Cancer

M2-like macrophages promote tumor growth and cancer immune evasion. This study used an in vitro model to investigate how hypoxia and tumor metabolism affect macrophage polarization. Liver cancer cells (HepG2 and VX2) and macrophages (THP1) were cultured under hypoxic (0.1% O2) and normoxic (21% O2) conditions with varying glucose levels (2 g/L or 4.5 g/L). Viability assays and extracellular pH (pHe) measurements were conducted over 96 hours. Macrophages were exposed to the tumor-conditioned medium (TCM) from the cancer cells, and polarization was assessed using arginase and nitrite assays. GC-MS-based metabolic profiling quantified TCM meta-bolites and correlated them with M2 polarization. The results showed that pHe in TCMs decreased more under hypoxia than normoxia (p < 0.0001), independent of glucose levels. The arginase assay showed hypoxia significantly induced the M2 polarization of macrophages (control group: p = 0.0120,0.1%VX2-TCM group: p = 0.0149, 0.1%HepG2-TCM group: p < 0.0001, 0.1%VX2-TCMHG group: p = 0.0001, and 0.1%HepG2-TCMHG group: p < 0.0001). TCMs also induced M2 polarization under normoxic conditions, but the strongest M2 polarization occurred when both tumor cells and macrophages were incubated under hypoxia with high glucose levels. Metabolomics revealed that several metabolites, particularly lactate, were correlated with hypoxia and M2 polarization. Under normoxia, elevated 2-amino-butanoic acid (2A-BA) strongly correlated with M2 polarization. These findings suggest that targeting tumor hypoxia could mitigate immune evasion in liver tumors. Lactate drives acidity in hypoxic tumors, while 2A-BA could be a therapeutic target for overcoming immunosuppression in normoxic conditions.

Epigenetic regulation of macrophage activation in chronic obstructive pulmonary disease

Macrophages in the innate immune system play a vital role in various lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), acute lung injury and pulmonary fibrosis. Macrophages involved in the process of immunity need to go through a process of activation, including changes in gene expression and cell metabolism. Epigenetic modifications are key factors of macrophage activation including DNA methylation, histone modification and non-coding RNA regulation. Understanding the role and mechanisms of epigenetic regulation of macrophage activation can provide insights into the function of macrophages in lung diseases and help identification of potential therapeutic targets. This review summarizes the latest progress in the epigenetic changes and regulation of macrophages in their development process and in normal physiological states, and the epigenetic regulation of macrophages in COPD as well as the influence of macrophage activation on COPD development.

Lactate supports cell-autonomous ECM production to sustain metastatic behavior in prostate cancer

Extracellular matrix (ECM) is a major component of the tumor environment, promoting the establishment of a pro-invasive behavior. Such environment is supported by both tumor- and stromal-derived metabolites, particularly lactate. In prostate cancer (PCa), cancer-associated fibroblasts (CAFs) are major contributors of secreted lactate, able to impact on metabolic and transcriptional regulation in cancer cells. Here, we describe a mechanism by which CAF-secreted lactate promotes in PCa cells the expression of genes coding for the collagen family. Lactate-exploiting PCa cells rely on increased α-ketoglutarate (α-KG) which activates the α-KG-dependent collagen prolyl-4-hydroxylase (P4HA1) to support collagen hydroxylation. De novo synthetized collagen plays a signaling role by activating discoidin domain receptor 1 (DDR1), supporting stem-like and invasive features of PCa cells. Inhibition of lactate-induced collagen hydroxylation and DDR1 activation reduces the metastatic colonization of PCa cells. Overall, these results provide a new understanding of the link between collagen remodeling/signaling and the nutrient environment exploited by PCa.

Regulation of macrophage polarization by targeted metabolic reprogramming for the treatment of lupus nephritis

Lupus nephritis (LN) is a severe and common manifestation of systemic lupus erythematosus (SLE) that is frequently identified with a poor prognosis. Macrophages play an important role in its pathogenesis. Different macrophage subtypes have different effects on lupus-affected kidneys. Based on their origin, macrophages can be divided into monocyte-derived macrophages (MoMacs) and tissue-resident macrophages (TrMacs). During nephritis, TrMacs develop a hybrid pro-inflammatory and anti-inflammatory functional phenotype, as they do not secrete arginase or nitric oxide (NO) when stimulated by cytokines. The infiltration of these mixed-phenotype macrophages is related to the continuous damage caused by immune complexes and exposure to circulating inflammatory mediators, which is an indication of the failure to resolve inflammation. On the other hand, MoMacs differentiate into M1 or M2 cells under cytokine stimulation. M1 macrophages are pro-inflammatory and secrete pro-inflammatory cytokines, while the M2 main phenotype is essentially anti-inflammatory and promotes tissue repair. Conversely, MoMacs undergo differentiation into M1 or M2 cells in response to cytokine stimulation. M1 macrophages are considered pro-inflammatory cells and secrete pro-inflammatory mediators, whereas the M2 main phenotype is primarily anti-inflammatory and promotes tissue repair. Moreover, based on cytokine expression, M2 macrophages can be further divided into M2a, M2b, and M2c phenotypes. M2a and M2c have anti-inflammatory effects and participate in tissue repair, while M2b cells have immunoregulatory and pro-inflammatory properties. Further, memory macrophages also have a role in the advancement of LN. Studies have demonstrated that the polarization of macrophages is controlled by multiple metabolic pathways, such as glycolysis, the pentose phosphate pathway, fatty acid oxidation, sphingolipid metabolism, the tricarboxylic acid cycle, and arginine metabolism. The changes in these metabolic pathways can be regulated by substances such as fish oil, polyenylphosphatidylcholine, taurine, fumaric acid, metformin, and salbutamol, which inhibit M1 polarization of macrophages and promote M2 polarization, thereby alleviating LN.

Metabolic flexibility ensures proper neuronal network function in moderate neuroinflammation

Microglia, brain-resident macrophages, can acquire distinct functional phenotypes, which are supported by differential reprogramming of cell metabolism. These adaptations include remodeling in glycolytic and mitochondrial metabolic fluxes, potentially altering energy substrate availability at the tissue level. This phenomenon may be highly relevant in the brain, where metabolism must be precisely regulated to maintain appropriate neuronal excitability and synaptic transmission. Direct evidence that microglia can impact on neuronal energy metabolism has been widely lacking, however. Combining molecular profiling, electrophysiology, oxygen microsensor recordings and mathematical modeling, we investigated microglia-mediated disturbances in brain energetics during neuroinflammation. Our results suggest that proinflammatory microglia showing enhanced nitric oxide release and decreased CX3CR1 expression transiently increase the tissue lactate/glucose ratio that depends on transcriptional reprogramming in microglia, not in neurons. In this condition, neuronal network activity such as gamma oscillations (30-70 Hz) can be fueled by increased ATP production in mitochondria, which is reflected by elevated oxygen consumption. During dysregulated inflammation, high energy demand and low glucose availability can be boundary conditions for neuronal metabolic fitness as revealed by kinetic modeling of single neuron energetics. Collectively, these findings indicate that metabolic flexibility protects neuronal network function against alterations in local substrate availability during moderate neuroinflammation.

Epigenetic regulation of tumor immunity

Although cancer has long been considered a genetic disease, increasing evidence shows that epigenetic aberrations play a crucial role in affecting tumor biology and therapeutic response. The dysregulated epigenome in cancer cells reprograms the immune landscape within the tumor microenvironment, thereby hindering antitumor immunity, promoting tumor progression, and inducing immunotherapy resistance. Targeting epigenetically mediated tumor-immune crosstalk is an emerging strategy to inhibit tumor progression and circumvent the limitations of current immunotherapies, including immune checkpoint inhibitors. In this Review, we discuss the mechanisms by which epigenetic aberrations regulate tumor-immune interactions and how epigenetically targeted therapies inhibit tumor progression and synergize with immunotherapy.