Heme catabolism by tumor-associated macrophages controls metastasis formation

A detailed insight into macrophages' role in shaping lung carcinogenesis

Despite significant advancements in cancer treatment in recent decades, the high mortality rate associated with lung cancer remains a significant concern. The development and proper execution of new targeted therapies needs more deep knowledge regarding the lung cancer associated tumour microenvironment. One of the key component of that tumour microenvironment is the lung resident macrophages. Although in normal physiological condition the lung resident macrophages are believed to maintain lung homeostasis, but they may also initiate a vicious inflammatory response in abnormal conditions which is linked to lung cancer development. Depending on the activation pathway, the lung resident macrophages are either of M1 or M2 sub-type. The M1 and M2 sub-types differ significantly in various prospectuses, from phenotypic markers to metabolic pathways. In addition to this generalized classification, the recent advancement of the multiomics technology is able to identify some other sub-types of lung resident macrophages. Researchers have also observed that these different sub-types can manipulate the pathogenesis of lung carcinogenesis in a context dependent manner and can either promote or inhibit the development of lung carcinogenesis upon receiving proper activation. As proper knowledge about the role played by the lung resident macrophages' in shaping the lung carcinogenesis is limited, so the main purpose of this review is to bring all the available information under the same roof. We also elaborated the different mechanisms involved in maintenance of the plasticity of M1/M2 sub-type, as this plasticity can be a good target for lung cancer treatment.

Mechanism insights and therapeutic intervention of tumor metastasis: latest developments and perspectives

Metastasis remains a pivotal characteristic of cancer and is the primary contributor to cancer-associated mortality. Despite its significance, the mechanisms governing metastasis are not fully elucidated. Contemporary findings in the domain of cancer biology have shed light on the molecular aspects of this intricate process. Tumor cells undergoing invasion engage with other cellular entities and proteins en route to their destination. Insights into these engagements have enhanced our comprehension of the principles directing the movement and adaptability of metastatic cells. The tumor microenvironment plays a pivotal role in facilitating the invasion and proliferation of cancer cells by enabling tumor cells to navigate through stromal barriers. Such attributes are influenced by genetic and epigenetic changes occurring in the tumor cells and their surrounding milieu. A profound understanding of the metastatic process's biological mechanisms is indispensable for devising efficacious therapeutic strategies. This review delves into recent developments concerning metastasis-associated genes, important signaling pathways, tumor microenvironment, metabolic processes, peripheral immunity, and mechanical forces and cancer metastasis. In addition, we combine recent advances with a particular emphasis on the prospect of developing effective interventions including the most popular cancer immunotherapies and nanotechnology to combat metastasis. We have also identified the limitations of current research on tumor metastasis, encompassing drug resistance, restricted animal models, inadequate biomarkers and early detection methods, as well as heterogeneity among others. It is anticipated that this comprehensive review will significantly contribute to the advancement of cancer metastasis research.

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.

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.

TFPI from erythroblasts drives heme production in central macrophages promoting erythropoiesis in polycythemia

Bleeding and thrombosis are known as common complications of polycythemia for a long time. However, the role of coagulation system in erythropoiesis is unclear. Here, we discover that an anticoagulant protein tissue factor pathway inhibitor (TFPI) plays an essential role in erythropoiesis via the control of heme biosynthesis in central macrophages. TFPI levels are elevated in erythroblasts of human erythroblastic islands with JAK2V617F mutation and hypoxia condition. Erythroid lineage-specific knockout TFPI results in impaired erythropoiesis through decreasing ferrochelatase expression and heme biosynthesis in central macrophages. Mechanistically, the TFPI interacts with thrombomodulin to promote the downstream ERK1/2-GATA1 signaling pathway to induce heme biosynthesis in central macrophages. Furthermore, TFPI blockade impairs human erythropoiesis in vitro, and normalizes the erythroid compartment in mice with polycythemia. These results show that erythroblast-derived TFPI plays an important role in the regulation of erythropoiesis and reveal an interplay between erythroblasts and central macrophages.

Ultrastructural and immunohistochemical evaluation of hyperplastic soft tissues surrounding dental implants in fibular jaws

In reconstructive surgery, complications post-fibula free flap (FFF) reconstruction, notably peri-implant hyperplasia, are significant yet understudied. This study analyzed peri-implant hyperplastic tissue surrounding FFF, alongside peri-implantitis and foreign body granulation (FBG) tissues from patients treated at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Using light microscopy, pseudoepitheliomatous hyperplasia, anucleate and pyknotic prickle cells, and excessive collagen deposition were observed in FFF hyperplastic tissue. Ultrastructural analyses revealed abnormal structures, including hemidesmosome dilation, bacterial invasion, and endoplasmic reticulum (ER) swelling. In immunohistochemical analysis, unfolded protein-response markers ATF6, PERK, XBP1, inflammatory marker NFκB, necroptosis marker MLKL, apoptosis marker GADD153, autophagy marker LC3, epithelial-mesenchymal transition, and angiogenesis markers were expressed variably in hyperplastic tissue surrounding FFF implants, peri-implantitis, and FBG tissues. NFκB expression was higher in peri-implantitis and FBG tissues compared to hyperplastic tissue surrounding FFF implants. PERK expression exceeded XBP1 significantly in FFF hyperplastic tissue, while expression levels of PERK, XBP1, and ATF6 were not significantly different in peri-implantitis and FBG tissues. These findings provide valuable insights into the interconnected roles of ER stress, necroptosis, apoptosis, and angiogenesis in the pathogenesis of oral pathologies, offering a foundation for innovative strategies in dental implant rehabilitation management and prevention.

The role of tumor-associated macrophages in tumor immune evasion

BACKGROUND

Tumor growth is closely linked to the activities of various cells in the tumor microenvironment (TME), particularly immune cells. During tumor progression, circulating monocytes and macrophages are recruited, altering the TME and accelerating growth. These macrophages adjust their functions in response to signals from tumor and stromal cells. Tumor-associated macrophages (TAMs), similar to M2 macrophages, are key regulators in the TME.

METHODS

We review the origins, characteristics, and functions of TAMs within the TME. This analysis includes the mechanisms through which TAMs facilitate immune evasion and promote tumor metastasis. Additionally, we explore potential therapeutic strategies that target TAMs.

RESULTS

TAMs are instrumental in mediating tumor immune evasion and malignant behaviors. They release cytokines that inhibit effector immune cells and attract additional immunosuppressive cells to the TME. TAMs primarily target effector T cells, inducing exhaustion directly, influencing activity indirectly through cellular interactions, or suppressing through immune checkpoints. Additionally, TAMs are directly involved in tumor proliferation, angiogenesis, invasion, and metastasis. Developing innovative tumor-targeted therapies and immunotherapeutic strategies is currently a promising focus in oncology. Given the pivotal role of TAMs in immune evasion, several therapeutic approaches have been devised to target them. These include leveraging epigenetics, metabolic reprogramming, and cellular engineering to repolarize TAMs, inhibiting their recruitment and activity, and using TAMs as drug delivery vehicles. Although some of these strategies remain distant from clinical application, we believe that future therapies targeting TAMs will offer significant benefits to cancer patients.

Multiomics Analysis Revealed Colorectal Cancer Pathogenesis

Gut microbiota-derived microbial compounds may link to the pathogenesis of colorectal cancer (CRC). However, the role of the host-microbiome in the incidence and progression of CRC remains elusive. We performed 16S rRNA sequencing, metabolomics, and proteomic studies on samples from 85 CRC patients who underwent colonoscopy examination and found two distinct changed patterns of microbiome in CRC patients. The relative abundances of Catabacter and Mogibacterium continuously increased from intramucosal carcinoma to advanced stages, whereas Clostridium, Anaerostipes, Vibrio, Flavonifractor, Holdemanella, and Hungatella were significantly altered only in intermediate lesions. Fecal metabolomics analysis exhibited consistent increases in bile acids, indoles, and urobilin as well as a decrease in heme. Serum metabolomics uncovered the highest levels of bilin, glycerides, and nucleosides together with the lowest levels of bile acids and amino acids in the stage of intermediate lesions. Three fecal and one serum dipeptides were elevated in the intermediate lesions. Proteomics analysis of colorectal tissues showed that oxidation and autophagy through the PI3K/Akt-mTOR signaling pathway contribute to the development of CRC. Diagnostic analysis showed multiomics features have good predictive capability, with AUC greater than 0.85. Our overall findings revealed new candidate biomarkers for CRC, with potentially significant diagnostic and prognostic capabilities.

METTL3/16-mediated m6A modification of ZNNT1 promotes hepatocellular carcinoma progression by activating ZNNT1/osteopontin/S100A9 positive feedback loop-mediated crosstalk between macrophages and tumour cells

Macrophages are the major components of tumour microenvironment, which play critical roles in tumour development. N6-methyladenosine (m6A) also contributes to tumour progression. However, the potential roles of m6A in modulating macrophages in hepatocellular carcinoma (HCC) are poorly understood. Here, we identified ZNNT1 as an HCC-related m6A modification target, which was upregulated and associated with poor prognosis of HCC. METTL3 and METTL16-mediated m6A modification contributed to ZNNT1 upregulation through stabilizing ZNNT1 transcript. ZNNT1 exerted oncogenic roles in HCC. Furthermore, ZNNT1 recruited and induced M2 polarization of macrophages via up-regulating osteopontin (OPN) expression and secretion. M2 Macrophages-recruited by ZNNT1-overexpressed HCC cells secreted S100A9, which further upregulated ZNNT1 expression in HCC cells via AGER/NF-κB signaling. Thus, this study demonstrates that m6A modification activated the ZNNT1/OPN/S100A9 positive feedback loop, which promoted macrophages recruitment and M2 polarization, and enhanced malignant features of HCC cells. m6A modification-triggered ZNNT1/OPN/S100A9 feedback loop represents potential therapeutic target for HCC.

Ferritin heavy chain supports stability and function of the regulatory T cell lineage

Regulatory T (TREG) cells develop via a program orchestrated by the transcription factor forkhead box protein P3 (FOXP3). Maintenance of the TREG cell lineage relies on sustained FOXP3 transcription via a mechanism involving demethylation of cytosine-phosphate-guanine (CpG)-rich elements at conserved non-coding sequences (CNS) in the FOXP3 locus. This cytosine demethylation is catalyzed by the ten-eleven translocation (TET) family of dioxygenases, and it involves a redox reaction that uses iron (Fe) as an essential cofactor. Here, we establish that human and mouse TREG cells express Fe-regulatory genes, including that encoding ferritin heavy chain (FTH), at relatively high levels compared to conventional T helper cells. We show that FTH expression in TREG cells is essential for immune homeostasis. Mechanistically, FTH supports TET-catalyzed demethylation of CpG-rich sequences CNS1 and 2 in the FOXP3 locus, thereby promoting FOXP3 transcription and TREG cell stability. This process, which is essential for TREG lineage stability and function, limits the severity of autoimmune neuroinflammation and infectious diseases, and favors tumor progression. These findings suggest that the regulation of intracellular iron by FTH is a stable property of TREG cells that supports immune homeostasis and limits the pathological outcomes of immune-mediated inflammation.

Downregulation of IRF8 in alveolar macrophages by G-CSF promotes metastatic tumor progression

Tissue-resident macrophages (TRMs) are abundant immune cells within pre-metastatic sites, yet their functional contributions to metastasis remain incompletely understood. Here, we show that alveolar macrophages (AMs), the main TRMs of the lung, are susceptible to downregulation of the immune stimulatory transcription factor IRF8, impairing anti-metastatic activity in models of metastatic breast cancer. G-CSF is a key tumor-associated factor (TAF) that acts upon AMs to reduce IRF8 levels and facilitate metastasis. Translational relevance of IRF8 downregulation was observed among macrophage precursors in breast cancer and a CD68hiIRF8loG-CSFhi gene signature suggests poorer prognosis in triple-negative breast cancer (TNBC), a G-CSF-expressing subtype. Our data highlight the underappreciated, pro-metastatic roles of AMs in response to G-CSF and identify the contribution of IRF8-deficient AMs to metastatic burden. AMs are an attractive target of local neoadjuvant G-CSF blockade to recover anti-metastatic activity.

Made to order: emergency myelopoiesis and demand-adapted innate immune cell production

Definitive haematopoiesis is the process by which haematopoietic stem cells, located in the bone marrow, generate all haematopoietic cell lineages in healthy adults. Although highly regulated to maintain a stable output of blood cells in health, the haematopoietic system is capable of extensive remodelling in response to external challenges, prioritizing the production of certain cell types at the expense of others. In this Review, we consider how acute insults, such as infections and cytotoxic drug-induced myeloablation, cause molecular, cellular and metabolic changes in haematopoietic stem and progenitor cells at multiple levels of the haematopoietic hierarchy to drive accelerated production of the mature myeloid cells needed to resolve the initiating insult. Moreover, we discuss how dysregulation or subversion of these emergency myelopoiesis mechanisms contributes to the progression of chronic inflammatory diseases and cancer.

Advanced insights on tumor-associated macrophages revealed by single-cell RNA sequencing: The intratumor heterogeneity, functional phenotypes, and cellular interactions

Single-cell RNA sequencing (scRNA-seq) is an emerging technology used for cellular transcriptome analysis. The application of scRNA-seq has led to profoundly advanced oncology research, continuously optimizing novel therapeutic strategies. Intratumor heterogeneity extensively consists of all tumor components, contributing to different tumor behaviors and treatment responses. Tumor-associated macrophages (TAMs), the core immune cells linking innate and adaptive immunity, play significant roles in tumor progression and resistance to therapies. Moreover, dynamic changes occur in TAM phenotypes and functions subject to the regulation of the tumor microenvironment. The heterogeneity of TAMs corresponding to the state of the tumor microenvironment has been comprehensively recognized using scRNA-seq. Herein, we reviewed recent research and summarized variations in TAM phenotypes and functions from a developmental perspective to better understand the significance of TAMs in the tumor microenvironment.

The Multifaceted Roles of NRF2 in Cancer: Friend or Foe?

Physiological concentrations of reactive oxygen species (ROS) play vital roles in various normal cellular processes, whereas excessive ROS generation is central to disease pathogenesis. The nuclear factor erythroid 2-related factor 2 (NRF2) is a critical transcription factor that regulates the cellular antioxidant systems in response to oxidative stress by governing the expression of genes encoding antioxidant enzymes that shield cells from diverse oxidative alterations. NRF2 and its negative regulator Kelch-like ECH-associated protein 1 (KEAP1) have been the focus of numerous investigations in elucidating whether NRF2 suppresses tumor promotion or conversely exerts pro-oncogenic effects. NRF2 has been found to participate in various pathological processes, including dysregulated cell proliferation, metabolic remodeling, and resistance to apoptosis. Herein, this review article will examine the intriguing role of phase separation in activating the NRF2 transcriptional activity and explore the NRF2 dual impacts on tumor immunology, cancer stem cells, metastasis, and long non-coding RNAs (LncRNAs). Taken together, this review aims to discuss the NRF2 multifaceted roles in both cancer prevention and promotion while also addressing the advantages, disadvantages, and limitations associated with modulating NRF2 therapeutically in cancer treatment.

Transcription Factor NRF2 in Shaping Myeloid Cell Differentiation and Function

NFE2-related factor 2 (NRF2) is a master transcription factor (TF) that coordinates key cellular homeostatic processes including antioxidative responses, autophagy, proteostasis, and metabolism. The emerging evidence underscores its significant role in modulating inflammatory and immune processes. This chapter delves into the role of NRF2 in myeloid cell differentiation and function and its implication in myeloid cell-driven diseases. In macrophages, NRF2 modulates cytokine production, phagocytosis, pathogen clearance, and metabolic adaptations. In dendritic cells (DCs), it affects maturation, cytokine production, and antigen presentation capabilities, while in neutrophils, NRF2 is involved in activation, migration, cytokine production, and NETosis. The discussion extends to how NRF2's regulatory actions pertain to a wide array of diseases, such as sepsis, various infectious diseases, cancer, wound healing, atherosclerosis, hemolytic conditions, pulmonary disorders, hemorrhagic events, and autoimmune diseases. The activation of NRF2 typically reduces inflammation, thereby modifying disease outcomes. This highlights the therapeutic potential of NRF2 modulation in treating myeloid cell-driven pathologies.

Emerging prognostic biomarkers in advanced cutaneous melanoma: a literature update

INTRODUCTION

Over the past two years, the scientific community has witnessed an exponential growth in research focused on identifying prognostic biomarkers for melanoma, both in pre-clinical and clinical settings. This surge in studies reflects the need of developing effective prognostic indicators in the field of melanoma.

AREAS COVERED

The aim of this work is to review the scientific literature on the most recent findings on the development or validation of prognostic biomarkers in melanoma, in the attempt of providing both clinicians and researchers with an updated broad synopsis of prognostic biomarkers in cutaneous melanoma.

EXPERT OPINION

While the field of prognostic biomarkers in melanoma appears promising, there are several complexities and limitations to address. The interdependence of clinical, histological, and molecular features requires accurate classification of different biomarker families. Correlation does not imply causation, and adjustments for confounding factors are often overlooked. In this scenario, large-scale studies based on high-quality clinical trial data can provide more reliable evidence. It is essential to avoid oversimplification by focusing on a single biomarker, as the interactions among multiple factors contribute to define the disease course and patient's outcome. Furthermore, implementing well-supported evidence in real-life settings can help advance prognostic biomarker research in melanoma.

Targeting vascular normalization: a promising strategy to improve immune-vascular crosstalk in cancer immunotherapy

Blood vessels are a key target for cancer therapy. Compared with the healthy vasculature, tumor blood vessels are extremely immature, highly permeable, and deficient in pericytes. The aberrantly vascularized tumor microenvironment is characterized by hypoxia, low pH, high interstitial pressure, and immunosuppression. The efficacy of chemotherapy, radiotherapy, and immunotherapy is affected by abnormal blood vessels. Some anti-angiogenic drugs show vascular normalization effects in addition to targeting angiogenesis. Reversing the abnormal state of blood vessels creates a normal microenvironment, essential for various cancer treatments, specifically immunotherapy. In addition, immune cells and molecules are involved in the regulation of angiogenesis. Therefore, combining vascular normalization with immunotherapy may increase the efficacy of immunotherapy and reduce the risk of adverse reactions. In this review, we discussed the structure, function, and formation of abnormal vessels. In addition, we elaborated on the role of the immunosuppressive microenvironment in the formation of abnormal vessels. Finally, we described the clinical challenges associated with the combination of immunotherapy with vascular normalization, and highlighted future research directions in this therapeutic area.

Hemorrhage-activated NRF2 in tumor-associated macrophages drives cancer growth, invasion, and immunotherapy resistance

Microscopic hemorrhage is a common aspect of cancers, yet its potential role as an independent factor influencing both cancer progression and therapeutic response is largely ignored. Recognizing the essential function of macrophages in red blood cell disposal, we explored a pathway that connects intratumoral hemorrhage with the formation of cancer-promoting tumor-associated macrophages (TAMs). Using spatial transcriptomics, we found that NRF2-activated myeloid cells possessing characteristics of procancerous TAMs tend to cluster in perinecrotic hemorrhagic tumor regions. These cells resembled antiinflammatory erythrophagocytic macrophages. We identified heme, a red blood cell metabolite, as a pivotal microenvironmental factor steering macrophages toward protumorigenic activities. Single-cell RNA-Seq and functional assays of TAMs in 3D cell culture spheroids revealed how elevated intracellular heme signals via the transcription factor NRF2 to induce cancer-promoting TAMs. These TAMs stabilized epithelial-mesenchymal transition, enhancing cancer invasiveness and metastatic potential. Additionally, NRF2-activated macrophages exhibited resistance to reprogramming by IFN-γ and anti-CD40 antibodies, reducing their tumoricidal capacity. Furthermore, MC38 colon adenocarcinoma-bearing mice with NRF2 constitutively activated in leukocytes were resistant to anti-CD40 immunotherapy. Overall, our findings emphasize hemorrhage-activated NRF2 in TAMs as a driver of cancer progression, suggesting that targeting this pathway could offer new strategies to enhance cancer immunity and overcome therapy resistance.

Targeting tumor-associated macrophage: an adjuvant strategy for lung cancer therapy

The emergence of immunotherapy has revolutionized the treatment landscape for various types of cancer. Nevertheless, lung cancer remains one of the leading causes of cancer-related mortality worldwide due to the development of resistance in most patients. As one of the most abundant groups of immune cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play crucial and complex roles in the development of lung cancer, including the regulation of immunosuppressive TME remodeling, metabolic reprogramming, neoangiogenesis, metastasis, and promotion of tumoral neurogenesis. Hence, relevant strategies for lung cancer therapy, such as inhibition of macrophage recruitment, TAM reprograming, depletion of TAMs, and engineering of TAMs for drug delivery, have been developed. Based on the satisfactory treatment effect of TAM-targeted therapy, recent studies also investigated its synergistic effect with current therapies for lung cancer, including immunotherapy, radiotherapy, chemotherapy, anti-epidermal growth factor receptor (anti-EGFR) treatment, or photodynamic therapy. Thus, in this article, we summarized the key mechanisms of TAMs contributing to lung cancer progression and elaborated on the novel therapeutic strategies against TAMs. We also discussed the therapeutic potential of TAM targeting as adjuvant therapy in the current treatment of lung cancer, particularly highlighting the TAM-centered strategies for improving the efficacy of anti-programmed cell death-1/programmed cell death-ligand 1 (anti-PD-1/PD-L1) treatment.

Roles of macrophages in tumor development: a spatiotemporal perspective

Macrophages are critical regulators of tissue homeostasis but are also abundant in the tumor microenvironment (TME). In both primary tumors and metastases, such tumor-associated macrophages (TAMs) seem to support tumor development. While we know that TAMs are the dominant immune cells in the TME, their vast heterogeneity and associated functions are only just being unraveled. In this review, we outline the various known TAM populations found thus far and delineate their specialized roles associated with the main stages of cancer progression. We discuss how macrophages may prime the premetastatic niche to enable the growth of a metastasis and then how subsequent metastasis-associated macrophages can support secondary tumor growth. Finally, we speculate on the challenges that remain to be overcome in TAM research.

Lactate-Responsive Gene Editing to Synergistically Enhance Macrophage-Mediated Cancer Immunotherapy

Combination therapies involving metabolic regulation and immune checkpoint blockade are considered an encouraging new strategy for cancer therapy. However, the effective utilization of combination therapies for activating tumor-associated macrophages (TAMs) remains challenging. Herein, a lactate-catalyzed chemodynamic approach to activate the therapeutic genome editing of signal-regulatory protein α (SIRPα) to reprogram TAMs and improve cancer immunotherapy is proposed. This system is constructed by encapsulating lactate oxidase (LOx) and clustered regularly interspaced short palindromic repeat-mediated SIRPα genome-editing plasmids in a metal-organic framework (MOF). The genome-editing system is released and activated by acidic pyruvate, which is produced by the LOx-catalyzed oxidation of lactate. The synergy between lactate exhaustion and SIRPα signal blockade can enhance the phagocytic ability of TAMs and promote the repolarization of TAMs to the antitumorigenic M1 phenotype. Lactate exhaustion-induced CD47-SIRPα blockade efficiently improves macrophage antitumor immune responses and effectively reverses the immunosuppressive tumor microenvironment to inhibit tumor growth, as demonstrated by in vitro and in vivo studies. This study provides a facile strategy for engineering TAMs in situ by combining CRISPR-mediated SIRPα knockout with lactate exhaustion for effective immunotherapy.

Deciphering the Role of the Anaphylatoxin C3a: A Key Function in Modulating the Tumor Microenvironment

The complement system plays a crucial role in cancer development. Our study investigated the role of C3a anaphylatoxin on the tumor microenvironment. Our models consisted of mesenchymal stem cells (MSC-like, 3T3-L1), macrophages (Raw 264.7 Blue, (RB)) and tumor cells (melanoma B16/F0). Recombinant mouse (Mo) C3a (rC3a) was produced in CHO cells transfected with a Mo-IL10-signal peptide-Mo C3a plasmid construct. The effects of rC3a, IFN-γ, TGF-β1, and LPS were tested on the expression of C3, C3aR, PI3K, cytokines, chemokines, transcription factors, antioxidant defense mechanisms, angiogenesis and macrophage polarization (M1/M2). 3T3-L1 expressed the highest levels of C3, while C3aR was expressed more by RB. Interestingly, expression of C3/3T3-L1 and C3aR/RB was markedly upregulated by IFN-γ. rC3a was found to upregulate the expression of anti-inflammatory cytokines (IL-10) on 3T3-L1 and TGF-β1 on RB. rC3a also upregulated the expression of pro-inflammatory cytokines in RB. The expression of CCL-5 increased in 3T3-L1 in response to rC3a. On RB, rC3a did not alter M1/M2 polarization but upregulated the expression of antioxidant defense genes, HO-1, and VEGF. C3/C3a produced mainly by MSC may play a critical role in TME remodeling by stimulating both anti-inflammatory and proangiogenic activities of tumor stromal cells.

Complement Activation and Up-Regulated Expression of Anaphylatoxin C3a/C3aR in Glioblastoma: Deciphering the Links with TGF-β and VEGF

The complement (C) innate immune system has been shown to be activated in the tumor microenvironment of various cancers. The C may support tumor growth by modulating the immune response and promoting angiogenesis through the actions of C anaphylatoxins (e.g., C5a, C3a). The C has important double-edged sword functions in the brain, but little is known about its role in brain tumors. Hence, we analyzed the distribution and the regulated expression of C3a and its receptor C3aR in various primary and secondary brain tumors. We found that C3aR was dramatically upregulated in Grade 4 diffuse gliomas, i.e., glioblastoma multiforme, IDH-wildtype (GBM) and astrocytoma, IDH-mutant, Grade 4, and was much less expressed in other brain tumors. C3aR was observed in tumor-associated macrophages (TAM) expressing CD68, CD18, CD163, and the proangiogenic VEGF. Robust levels of C3a were detected in the parenchyma of GBM as a possible result of Bb-dependent C activation of the alternative C pathway. Interestingly, in vitro models identified TGF-β1 as one of the most potent growth factors that upregulate VEGF, C3, and C3aR in TAM (PMA-differentiated THP1) cell lines. Further studies should help to delineate the functions of C3a/C3aR on TAMs that promote chemotaxis/angiogenesis in gliomas and to explore the therapeutic applications of C3aR antagonists for brain tumors.

The capture of extracellular vesicles endogenously released by xenotransplanted tumours induces an inflammatory reaction in the premetastatic niche

The capture of tumour-derived extracellular vesicles (TEVs) by cells in the tumour microenvironment (TME) contributes to metastasis and notably to the formation of the pre-metastatic niche (PMN). However, due to the challenges associated with modelling release of small EVs in vivo, the kinetics of PMN formation in response to endogenously released TEVs have not been examined. Here, we have studied the endogenous release of TEVs in mice orthotopically implanted with metastatic human melanoma (MEL) and neuroblastoma (NB) cells releasing GFP-tagged EVs (GFTEVs) and their capture by host cells to demonstrate the active contribution of TEVs to metastasis. Human GFTEVs captured by mouse macrophages in vitro resulted in transfer of GFP vesicles and the human exosomal miR-1246. Mice orthotopically implanted with MEL or NB cells showed the presence of TEVs in the blood between 5 and 28 days after implantation. Moreover, kinetic analysis of TEV capture by resident cells relative to the arrival and outgrowth of TEV-producing tumour cells in metastatic organs demonstrated that the capture of TEVs by lung and liver cells precedes the homing of metastatic tumour cells, consistent with the critical roles of TEVs in PMN formation. Importantly, TEV capture at future sites of metastasis was associated with the transfer of miR-1246 to lung macrophages, liver macrophages, and stellate cells. This is the first demonstration that the capture of endogenously released TEVs is organotropic as demonstrated by the presence of TEV-capturing cells only in metastatic organs and their absence in non-metastatic organs. The capture of TEVs in the PMN induced dynamic changes in inflammatory gene expression which evolved to a pro-tumorigenic reaction as the niche progressed to the metastatic state. Thus, our work describes a novel approach to TEV tracking in vivo that provides additional insights into their role in the earliest stages of metastatic progression.

Heme oxygenase 1 in erythropoiesis: an important regulator beyond catalyzing heme catabolism

Heme oxygenase 1 (HO-1), encoded by the HMOX-1 gene, is the main heme oxygenase that catalyzes the degradation of heme into iron, carbon monoxide, and biliverdin. HMOX-1 gene expression is stimulated by oxidative stress and regulated at transcriptional and post-transcriptional levels. After translation, subcellular location and protein stability of HO-1 are also altered by different extracellular and intracellular stimuli. HO-1 plays a key role in regulating iron homeostasis and cell protection and has become a new target for disease treatment. Erythropoiesis is a tightly controlled, iron-dependent process that begins with hematopoietic stem cells and maturates to red blood cells. HO-1 is expressed in hematopoietic stem/progenitor cells, hematopoietic niche cells, erythroblasts, and especially erythroblastic island and phagocytic macrophages. HO-1 functions importantly in the entire erythroid development process by influencing hematopoietic stem cell proliferation, erythroid lineage engagement, terminal erythroid differentiation, and even senescent RBC erythrophagocytosis. HO-1 is also related to stress erythropoiesis and certain red blood cell diseases. Elucidation of HO-1 regulation and function in erythropoiesis will be of great significance for the treatment of related diseases.

Nrf2 in TIME: The Emerging Role of Nuclear Factor Erythroid 2-Related Factor 2 in the Tumor Immune Microenvironment

Nuclear factor erythroid 2-related factor 2 (Nrf2) mediates the cellular antioxidant response, allowing adaptation and survival under conditions of oxidative, electrophilic and inflammatory stress, and has a role in metabolism, inflammation and immunity. Activation of Nrf2 provides broad and long-lasting cytoprotection, and is often hijacked by cancer cells, allowing their survival under unfavorable conditions. Moreover, Nrf2 activation in established human tumors is associated with resistance to chemo-, radio-, and immunotherapies. In addition to cancer cells, Nrf2 activation can also occur in tumor-associated macrophages (TAMs) and facilitate an anti-inflammatory, immunosuppressive tumor immune microenvironment (TIME). Several cancer cell-derived metabolites, such as itaconate, L-kynurenine, lactic acid and hyaluronic acid, play an important role in modulating the TIME and tumor-TAMs crosstalk, and have been shown to activate Nrf2. The effects of Nrf2 in TIME are context-depended, and involve multiple mechanisms, including suppression of pro-inflammatory cytokines, increased expression of programmed cell death ligand 1 (PD-L1), macrophage colony-stimulating factor (M-CSF) and kynureninase, accelerated catabolism of cytotoxic labile heme, and facilitating the metabolic adaptation of TAMs. This understanding presents both challenges and opportunities for strategic targeting of Nrf2 in cancer.

M2 tumor-associated macrophages resist to oxidative stress through heme oxygenase-1 in the colorectal cancer tumor microenvironment

M2 tumor-associated macrophages (M2-TAMs) promote cancer cell proliferation and metastasis in the TME. Our study aimed to elucidate the mechanism of increased frequency of M2-TAMs infiltration in the colorectal cancer (CRC)-TME, focusing on the resistance to oxidative stress through nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. In this study, we evaluated the correlation between M2-TAM signature and mRNA expression of antioxidant related genes using public datasets, and the expression level of antioxidants in M2-TAMs by flow cytometry and the prevalence of M2-TAMs expressing antioxidants by immunofluorescence staining using surgically resected specimens of CRC (n = 34). Moreover, we generated M0 and M2 macrophages from peripheral blood monocytes and evaluated their resistance to oxidative stress using the in vitro viability assay. Analysis of GSE33113, GSE39582, and The Cancer Genome Atlas (TCGA) datasets indicated that mRNA expression of HMOX1 (heme oxygenase-1 (HO-1)) was significantly positively correlated with M2-TAM signature (r = 0.5283, r = 0.5826, r = 0.5833, respectively). The expression level of both Nrf2 and HO-1 significantly increased in M2-TAMs compared to M1- and M1/M2-TAMs in the tumor margin, and the number of Nrf2⁺ or HO-1⁺M2-TAMs in the tumor stroma significantly increased more than those in the normal mucosa stroma. Finally, generated M2 macrophages expressing HO-1 significantly resisted to oxidative stress induced by H₂O₂ in comparison with generated M0 macrophages. Taken together, our results suggested that an increased frequency of M2-TAMs infiltration in the CRC-TME is related to Nrf2-HO-1 axis mediated resistance to oxidative stress.

LncRNA UCA1 promoted cisplatin resistance in lung adenocarcinoma with HO1 targets NRF2/HO1 pathway

PURPOSE

Our previous experiments have demonstrated that lncRNA UCA1 (UCA1) promoted cisplatin resistance in lung adenocarcinoma (LUAD). This study aimed to explore the potential downstream target genes regulated by UCA1 and how this downstream gene promotes cisplatin resistance in LUAD.

METHODS

Here, we measured the expression level of Heme oxygenase1 (HO1) in LUAD cell lines by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) based on UCA1 overexpression cell lines and UCA1 knockdown cell lines. HO1 was knocked down in the UCA1 overexpression cell line, and HO1 was overexpressed in the UCA1 knockdown cell line, and the half maximal inhibitory concentration (IC50) trends were observed by adding cisplatin containing a certain concentration gradient. Cell functional assays were performed to observe the changes in the biological behavior of HO1 after overexpression and knockdown, and the tumorigenic assay in nude mice was performed to verify the effect of UCA1 in regulating the growth and cisplatin resistance of HO1 on LUAD cells in vivo.

RESULTS

The results showed that HO1 and UCA1 expression were both upregulated in LUAD tissues and LUAD cisplatin-resistant cell lines, and there was a significant positive correlation between the expression of HO1 and UCA1. In vitro experiments showed that HO1 overexpression could reverse the reduced sensitivity to cisplatin caused by UCA1 knockdown in A549/DDP cells, and HO1 knockdown could reduce cisplatin resistance in A549 UCA1 overexpressing cells. Tumorigenic assays in nude mice further confirmed the role of HO1 in the regulation of UCA1 by activating the NRF2/HO1 pathway against LUAD cisplatin resistance.

CONCLUSION

Our findings suggested that UCA1 regulates HO1 targets the UCA1/NRF2-HO1 pathway to exert cisplatin resistance in LUAD.

Cell-cell communications shape tumor microenvironment and predict clinical outcomes in clear cell renal carcinoma

BACKGROUND

Cell-cell communications of various cell populations within tumor microenvironment play an essential role in primary tumor growth, metastasis evolution, and immune escape. Nevertheless, comprehensive investigation of cell-cell communications in the ccRCC (Clear cell renal carcinoma) microenvironment and how this interplay affects prognosis still remains limited.

METHODS

Intercellular communications were characterized by single-cell data. Firstly, we employed "CellChat" package to characterize intercellular communications across all types of cells in microenvironment in VHL mutated and non-mutated samples from 8 patients, respectively. And pseudotime trajectory analyses were performed with monocle analyses. Finally clinical prognosis and immunotherapy efficacy with different landscapes of intercellular interplay are evaluated by TCGA-KIRC and immunotherapy cohort.

RESULTS

Firstly, the VHL phenotype may be related to the intercellular communication landscape. And trajectory analysis reveals the potential relationship of cell-cell communication molecules with T cells and Myeloid cells differentiation. Furthermore, those molecules also correlate with the infiltration of T cells and Myeloid cells. A tumor cluster with highly expressed ligands was defined by quantitative analysis and transcription factor enrichment analysis, which was identified to be pivotal for intercellular communications in tumor microenvironment. Finally, bulk data indicates bulk that different clusters with different intercellular communications have significant predictive value for prognosis and distinguished immunotherapy efficiency.

CONCLUSIONS

The intercellular communication landscapes of VHL wild and VHL mutant ccRCC vary. Intercellular communications within the tumor microenvironment also influence T cell and myeloid cell development and infiltration, as well as predict clinical prognosis and immunotherapy efficacy in ccRCC.

A new method for predicting the prognosis of colorectal cancer patients through a combination of multiple tumor-associated macrophage markers at the invasive front

Tumor-associated macrophages (TAMs) are closely related to tumorigenesis and metastasis of multiple cancer types. The infiltration of TAMs is used for predicting the prognosis of cancers, including colorectal cancer (CRC). However, the density and prognostic significance of M1 and M2 TAM phenotypes in the intratumor versus the invasive front (IF) are largely unknown in CRC. In this study, CD68 was selected as a general marker of TAMs, CD11c, NOS2 and CXCL10 as markers for M1 phenotype and CD163, CD206, CD115 as markers for M2 phenotype. Firstly, immunohistochemistry staining and double-labeling immunofluorescence staining showed that M1 molecular markers (NOS2, CXCL10, CD11c) were lowly expressed at both IF and intratumor, while M2 molecular markers (CD163, CD206, CD115) were highly expressed mainly at IF. Moreover, we also demonstrated that three M1 molecular markers including NOS2, CXCL10 and CD11c were correlated to each other. Meanwhile, three M2 molecular markers including CD163, CD206, and CD115 were also correlated to each other. Patients with low expression of three M1 molecular markers (NOS2/CXCL10/CD11c) exhibited low overall survival (OS) rate, whereas patients with high expression of three M2 molecular markers (CD163/CD206/CD115) exhibited low OS rate. We also observed that the prognostic value of treble markers combination (NOS2/CXCL10/CD11c or CD163/CD206/CD115) was superior to that of single marker. Together, our results reveal the combination of treble TAMs markers (NOS2/CXCL10/CD11c or CD163/CD206/CD115) could better evaluate the prognosis of CRC patients, which might be used as a more comprehensive method for predicting the prognosis of CRC patients.

Research progress of bone metastases: From disease recognition to clinical practice

Bone metastases, as one of the common types of metastatic tumors, have a great impact on the survival period and quality of life of patients. Bone metastases are usually characterized by bone destruction. Skeletal related events caused by bone destruction often lead to pain, pathological fractures and even paralysis. In this review, we provide a detailed explanation of bone metastases from the epidemiology, clinical features, pathogenesis, and recently developed clinical treatment viewpoints. We concluded that the incidence of bone metastases is increasing gradually, with serious clinical symptoms, complex pathogenesis and diverse clinical treatment. Tumor cells, immune cells, osteoblasts/osteoclasts and other cells as well as cytokines and enzymes all play a key role in the pathogenesis of bone metastases. We believe that the future treatment of bone metastases will be diversified and comprehensive. Some advanced technologies, such as nanomedicine, could be used for treatment, but this depends on understanding how disease occurs. With the development of treatment, the survival time and quality of life of patients will be improved.

Control of tumor-associated macrophage responses by nutrient acquisition and metabolism

Metazoan tissue specification is associated with integration of macrophage lineage cells in sub-tissular niches to promote tissue development and homeostasis. Oncogenic transformation, most prevalently of epithelial cell lineages, results in maladaptation of resident tissue macrophage differentiation pathways to generate parenchymal and interstitial tumor-associated macrophages that largely foster cancer progression. In addition to growth factors, nutrients that can be consumed, stored, recycled, or converted to signaling molecules have emerged as crucial regulators of macrophage responses in tumor. Here, we review how nutrient acquisition through plasma membrane transporters and engulfment pathways control tumor-associated macrophage differentiation and function. We also discuss how nutrient metabolism regulates tumor-associated macrophages and how these processes may be targeted for cancer therapy.

The promise of targeting heme and mitochondrial respiration in normalizing tumor microenvironment and potentiating immunotherapy

Cancer immunotherapy shows durable treatment responses and therapeutic benefits compared to other cancer treatment modalities, but many cancer patients display primary and acquired resistance to immunotherapeutics. Immunosuppressive tumor microenvironment (TME) is a major barrier to cancer immunotherapy. Notably, cancer cells depend on high mitochondrial bioenergetics accompanied with the supply of heme for their growth, proliferation, progression, and metastasis. This excessive mitochondrial respiration increases tumor cells oxygen consumption, which triggers hypoxia and irregular blood vessels formation in various regions of TME, resulting in an immunosuppressive TME, evasion of anti-tumor immunity, and resistance to immunotherapeutic agents. In this review, we discuss the role of heme, heme catabolism, and mitochondrial respiration on mediating immunosuppressive TME by promoting hypoxia, angiogenesis, and leaky tumor vasculature. Moreover, we discuss the therapeutic prospects of targeting heme and mitochondrial respiration in alleviating tumor hypoxia, normalizing tumor vasculature, and TME to restore anti-tumor immunity and resensitize cancer cells to immunotherapy.

Screening and identifying a novel M-MDSCs-related gene signature for predicting prognostic risk and immunotherapeutic responses in patients with lung adenocarcinoma

Background: Lung adenocarcinoma (LUAD) shows intratumoral heterogeneity, a highly complex phenomenon that known to be a challenge during cancer therapy. Considering the key role of monocytic myeloid-derived suppressor cells (M-MDSCs) in the tumor microenvironment (TME), we aimed to build a prognostic risk model using M-MDSCs-related genes. Methods: M-MDSCs-related genes were extracted from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Utilized univariate survival analysis and random forest algorithm to screen candidate genes. A least absolute shrinkage and selection operator (LASSO) Cox regression analysis was selected to build the risk model. Patients were scored and classified into high- and low-risk groups based on the median risk scores. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis along with R packages "estimate" and "ssGSEA" were performed to reveal the mechanism of risk difference. Prognostic biomarkers and tumor mutation burden (TMB) were combined to predict the prognosis. Nomogram was carried out to predict the survival probability of patients in 1, 3, and 5 years. Results: 8 genes (VPREB3, TPBG, LRFN4, CD83, GIMAP6, PRMT8, WASF1, and F12) were identified as prognostic biomarkers. The GEO validation dataset demonstrated the risk model had good generalization effect. Significantly enrichment level of cell cycle-related pathway and lower content of CD8⁺ T cells infiltration in the high-risk group when compared to low-risk group. Morever, the patients were from the intersection of high-TMB and low-risk groups showed the best prognosis. The nomogram demonstrated good consistency with practical outcomes in predicting the survival rate over 1, 3, and 5 years. Conclusion: The risk model demonstrate good prognostic predictive ability. The patients from the intersection of low-risk and high-TMB groups are not only more sensitive response to but also more likely to benefit from immune-checkpoint-inhibitors (ICIs) treatment.

The dual role and mutual dependence of heme/HO-1/Bach1 axis in the carcinogenic and anti-carcinogenic intersection

INTRODUCTION

In physiological concentrations, heme is nontoxic to the cell and is essential for cell survival and proliferation. Increasing intracellular heme concentrations beyond normal levels, however, will lead to carcinogenesis and facilitate the survival of tumor cells. Simultaneously, heme in an abnormally high quantity is also a potent inducer of tumor cell death, contributing to its ability to generate oxidative stress on the cells by boosting oxidative phosphorylation and suppressing tumors through ferroptosis. During tumorigenesis and progression, therefore, heme works as a double-edged sword. Heme oxygenase 1 (HO-1) is the rate-limiting enzyme in heme catabolism, which converts heme into physiologically active catabolites of carbon monoxide (CO), biliverdin, and ferrous iron (Fe²⁺). HO-1 maintains redox equilibrium in healthy cells and functions as a carcinogenesis inhibitor. It is widely recognized that HO-1 is involved in the adaptive response to cellular stress and the anti-inflammation effect. Notably, its expression level in cancer cells corresponds with tumor growth, aggressiveness, metastasis, and angiogenesis. Besides, heme-binding transcription factor BTB and CNC homology 1 (Bach1) play a critical regulatory role in heme homeostasis, oxidative stress and senescence, cell cycle, angiogenesis, immune cell differentiation, and autoimmune disorders. Moreover, it was found that Bach1 influences cancer cells' metabolism and metastatic capacity. Bach1 controls heme level by adjusting HO-1 expression, establishing a negative feedback loop.

MATERIALS AND METHODS

Herein, the authors review recent studies on heme, HO-1, and Bach1 in cancer. Specifically, they cover the following areas: (1) the carcinogenic and anticarcinogenic aspects of heme; (2) the carcinogenic and anticarcinogenic aspects of HO-1; (3) the carcinogenic and anticarcinogenic aspects of Bach1; (4) the interactions of the heme/HO-1/Bach1 axis involved in tumor progression.

CONCLUSION

This review summarized the literature about the dual role of the heme/HO-1/Bach1 axis and their mutual dependence in the carcinogenesis and anti-carcinogenesis intersection.

Knockdown of membrane-bound complement regulatory proteins suppresses colon cancer growth in mice through inducing tumor cell apoptosis

CD46, CD55 and CD59 are membrane-bound complement regulatory proteins (mCRPs) and highly expressed in many tumor tissues. Our analysis by RNA sequencing and qRT-PCR revealed that the expression of mCRPs was significantly elevated in cancer tissues of 15 patients with colon cancer. To further investigate the role of mCRPs in the development of colon cancer, we suppressed the expression of mCRPs by CD46-shRNA, CD55-shRNA and CD59-shRNA in colon cancer cell lines, SW620 and HT-29 cells. The results indicated that CD46-shRNA, CD55-shRNA and CD59-shRNA effectively reduced the expression of mCRPs, accompanied with the increased LDH release and the percentage of Annexin V + 7-AAD- early phase of apoptotic cells. The similar cytotoxic effects were also observed in the cells treated with CD46 neutralizing antibody (aCD46), associated with the increased C5b-9 deposition, cleaved caspase-3 and Bax expression in the treated cells. The cytotoxic effects by mCRPs knock-down were potentiated in the cells co-treated with doxorubicin (Dox). In addition, STAT3, STAT6, and p38 MAPK inhibitors, including C188-9, AS1517499 and SB203580 effectively reduced the expression of CD46 in the treated colon cells, associated with increased cell apoptosis and LDH release. Further study with mouse model revealed that mCRPs knockdown by mCRPs-shRNA significantly reduced colon cancer growth, associated with increased expression of Bax, cleaved caspase-3 and C5b-9 deposition, but reduced expression of Bcl-2, IL-6 and IL-1beta in tumor tissues of nude mice transplanted with SW620 cells. Thereby, mCRPs expression in human colon cancer cells were upregulated by STAT3/STAT6/p38 MAPK signaling and mCRPs knockdown reduced colon cancer growth in mice through inducing tumor cell apoptosis.

Targeting macrophages: a novel treatment strategy in solid tumors

In the tumor microenvironment (TME), tumor-associated macrophages (TAMs) are the most abundant immune cells, which act as a key regulator in tumorigenesis and progression. Increasing evidence have demonstrated that the TME alters the nature of macrophages to maintain dynamic tissue homeostasis, allowing TAMs to acquire the ability to stimulate angiogenesis, promote tumor metastasis and recurrence, and suppress anti-tumor immune responses. Furthermore, tumors with high TAM infiltration have poor prognoses and are resistant to treatment. In the field of solid tumor, the exploration of tumor-promoting mechanisms of TAMs has attracted much attention and targeting TAMs has emerged as a promising immunotherapeutic strategy. Currently, the most common therapeutic options for targeting TAMs are as follows: the deletion of TAMs, the inhibition of TAMs recruitment, the release of phagocytosis by TAMs, and the reprogramming of macrophages to remodel their anti-tumor capacity. Promisingly, the study of chimeric antigen receptor macrophages (CAR-Ms) may provide even greater benefit for patients with solid tumors. In this review, we discuss how TAMs promote the progression of solid tumors as well as summarize emerging immunotherapeutic strategies that targeting macrophages.

Targeting oncogenic transcription factors in skin malignancies: An update on cancer stemness and therapeutic outcomes

The skin is the largest organ of the human body and prone to various diseases, including cancer; thus, provides the first line of defense against exogenous biological and non-biological agents. Skin cancer, a complex and heterogenic process, with steep incidence rate often metastasizes due to poor understanding of the underlying mechanisms of pathogenesis and clinical challenges. Indeed, accumulating evidence indicates that deregulation of transcription factors (TFs) due to genetic, epigenetic and signaling distortions plays essential role in the development of cutaneous malignancies and therapeutic challenges including cancer stemness features and reprogramming. This review highlights the recent developments exploring underlying mechanisms how deregulated TFs (e.g., NF-κB, AP-1, STAT etc.,) orchestrates cutaneous onco-pathogenesis, reprogramming, stemness and poor clinical outcomes. Along this line, bioactive drugs, and their derivatives from natural and or synthetic origin has gained attention due to their multitargeting potential, potentially safer and effective therapeutic outcome for human malignancies. We also discussed therapeutic importance of targeting aberrantly expressed TFs in skin cancers with bioactive natural products and or synthetic agents.

Comprehensive Analysis and Validation of Solute Carrier Family 25 (SLC25) and Its Correlation with Immune Infiltration in Pan-Cancer

As the largest gene family functioning in protein transport among human solute carriers, the SLC25 family (mitochondrial carrier family) can participate in development of cancer. However, a comprehensive exploration for the exactly roles of SLC family remains lacking. In the present study, a total of 15 functional SLC25 family genes were retrieved from all current publications. And multidimensional analyses were systematically performed based on the transcriptome and genome data of SLC25 family from a variety of online databases for their expression, immune cell infiltration, and cancer prognosis. Validation by qPCR and immunohistochemistry were further conducted for the expression of partial SLC25 family members in some tumor tissue. We found that the SLC25 family had strong correlation with immune cells, such as macrophages M2, CD8⁺ T cell, CD4⁺ T cell memory activated, and memory resting. Among them, SLC25A6 was most correlated with Macrophage M1 in uveal melanoma (r = −0.68, P = 1.9e − 0.5). Expression of mRNA level showed that SLC25A4 was downregulated in stomach adenocarcinoma and colon adenocarcinoma. SLC25A7 was highly expressed in stomach adenocarcinoma and colon adenocarcinoma. SLC25A23 was decreased in colon adenocarcinoma. qPCR and immunohistochemistry validation results were consistent with our bioinformatics prediction. SLC25A8 was associated with the prognosis of cancer. All these findings suggested that the SLC25 family might affects the immune microenvironment of the cancer and then had the potential to be predictive biomarkers for early diagnosis and prognosis as well as novel targets for individualized treatment of cancer.

Erythrophagocytes in hemolytic anemia, wound healing, and cancer

Hemolysis is a ubiquitous pathology defined as premature red blood cell destruction within the circulation or local tissues. One of the most archetypal functions of macrophages is phagocytosis of damaged or extravasated red blood cells, preventing the extracellular release of toxic hemoglobin and heme. Upon erythrophagocytosis, spiking intracellular heme concentrations drive macrophage transformation into erythrophagocytes, leveraging antioxidative and iron recycling capacities to defend against hemolytic stress. This unique phenotype transformation is coordinated by a regulatory network comprising the transcription factors BACH1, SPI-C, NRF2, and ATF1. Erythrophagocytes negatively regulate inflammation and immunity and may modulate disease-specific outcomes in hemolytic anemia, wound healing, atherosclerosis, and cancer. In this opinion article, we outline the known and presumed functions of erythrophagocytes and their implications for therapeutic innovation and research.

Heme oxygenase 1 overexpression induces immune evasion of acute myeloid leukemia against natural killer cells by inhibiting CD48

Background

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. Given the high relapse rate, more effective treatments are needed to improve clinical outcomes. We previously demonstrated that heme oxygenase 1 (HO1) is overexpressed in AML, while the functional roles of HO1 remain unclear.

Methods

Bioinformatics analysis and flow cytometry were conducted to assess the association between HO1 levels and immune cells or immune checkpoint/ligand molecules in AML patients. Primary natural killer (NK) cells were purified and subsequently co-cultured in vitro with transduced AML cells to determine the effects of HO1 expression on NK cell functions. AML mice models were established to investigate the effects of HO1 expression on cytotoxic effects of NK cells in vivo. The molecular mechanism was studied by flow cytometry, quantitative real-time PCR (qRT-PCR), western blotting, and immunoprecipitation.

Results

Bioinformatics analysis indicated a correlation between HO1 expression and the AML immune microenvironment. The present study findings indicated that HO1 specifically downregulates the expression of CD48, a ligand of the NK cell-activating receptor 2B4, thus decreasing the cytotoxic effect of NK cells. HO1 overexpression promoted tumor growth and inhibited the cytotoxic effect of NK cells in the AML mice model. Mechanistic investigations found that HO1 directly interacted with Sirt1 and increased its expression and deacetylase activity. With the overexpression of HO1, increased Sirt1 in AML cells enabled histone H3K27 deacetylation to suppress CD48 transcription and expression. Administration of Sirt1 inhibitor restored the expression of CD48.

Conclusions

Collectively, HO1 promotes NK cell dysfunction in AML. Therefore, restoring NK cell function by inhibiting HO1 activity is a potential immunotherapeutic approach against AML.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03589-z.

The different facets of heme-oxygenase 1 in innate and adaptive immunity

Heme oxygenase (HO) enzymes are responsible for the main oxidative step in heme degradation, generating equimolar amounts of free iron, biliverdin and carbon monoxide. HO-1 is induced as a crucial stress response protein, playing protective roles in physiologic and pathological conditions, due to its antioxidant, anti-apoptotic and anti-inflammatory effects. The mechanisms behind HO-1-mediated protection are being explored by different studies, affecting cell fate through multiple ways, such as reduction in intracellular levels of heme and ROS, transcriptional regulation, and through its byproducts generation. In this review we focus on the interplay between HO-1 and immune-related signaling pathways, which culminate in the activation of transcription factors important in immune responses and inflammation. We also discuss the dual interaction of HO-1 and inflammatory mediators that govern resolution and tissue damage. We highlight the dichotomy of HO-1 in innate and adaptive immune cells development and activation in different disease contexts. Finally, we address different known anti-inflammatory pharmaceuticals that are now being described to modulate HO-1, and the possible contribution of HO-1 in their anti-inflammatory effects.

Monocyte-derived macrophages aggravate pulmonary vasculitis via cGAS/STING/IFN-mediated nucleic acid sensing

Autoimmune vasculitis is a group of life-threatening diseases, whose underlying pathogenic mechanisms are incompletely understood, hampering development of targeted therapies. Here, we demonstrate that patients suffering from anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) showed increased levels of cGAMP and enhanced IFN-I signature. To identify disease mechanisms and potential therapeutic targets, we developed a mouse model for pulmonary AAV that mimics severe disease in patients. Immunogenic DNA accumulated during disease onset, triggering cGAS/STING/IRF3-dependent IFN-I release that promoted endothelial damage, pulmonary hemorrhages, and lung dysfunction. Macrophage subsets played dichotomic roles in disease. While recruited monocyte-derived macrophages were major disease drivers by producing most IFN-β, resident alveolar macrophages contributed to tissue homeostasis by clearing red blood cells and limiting infiltration of IFN-β-producing macrophages. Moreover, pharmacological inhibition of STING, IFNAR-I, or its downstream JAK/STAT signaling reduced disease severity and accelerated recovery. Our study unveils the importance of STING/IFN-I axis in promoting pulmonary AAV progression and identifies cellular and molecular targets to ameliorate disease outcomes.

Classical epithelial-mesenchymal transition (EMT) and alternative cell death process-driven blebbishield metastatic-witch (BMW) pathways to cancer metastasis

Metastasis is a pivotal event that accelerates the prognosis of cancer patients towards mortality. Therapies that aim to induce cell death in metastatic cells require a more detailed understanding of the metastasis for better mitigation. Towards this goal, we discuss the details of two distinct but overlapping pathways of metastasis: a classical reversible epithelial-to-mesenchymal transition (hybrid-EMT)-driven transport pathway and an alternative cell death process-driven blebbishield metastatic-witch (BMW) transport pathway involving reversible cell death process. The knowledge about the EMT and BMW pathways is important for the therapy of metastatic cancers as these pathways confer drug resistance coupled to immune evasion/suppression. We initially discuss the EMT pathway and compare it with the BMW pathway in the contexts of coordinated oncogenic, metabolic, immunologic, and cell biological events that drive metastasis. In particular, we discuss how the cell death environment involving apoptosis, ferroptosis, necroptosis, and NETosis in BMW or EMT pathways recruits immune cells, fuses with it, migrates, permeabilizes vasculature, and settles at distant sites to establish metastasis. Finally, we discuss the therapeutic targets that are common to both EMT and BMW pathways.

CRISPR/Cas9-mediated knockout of HO-1 decreased the proliferation and migration of T47D cells and increased cisplatin-induced apoptosis: an in vitro study

Breast cancer is the most common type of neoplasm and the second cause of cancer-related death in women. Despite the development of novel therapeutic strategies and improved the clinical outcomes, the mortality rate for breast cancer is still high. Therefore, development of a new modality, particularly based on knocking out key genes, is under focus of investigation. Heme oxygenase-1 (HO-1) deregulation has been associated with various neoplasms-related behaviors of many types of tumor cells including breast cancer. In the current study, in order to evaluate the role of the HO-1 gene in breast cancer, we utilized the CRISPR/Cas9 technology to knock out HO-1 gene in T47D breast cancer cell line and studied its potential therapeutic effects in vitro. The cell proliferation and their sensitivity to Cisplatin were determined by CCK-8 kit. In addition, the apoptosis and the migratory potential of the cells were evaluated using Hoechst staining, and Transwell/Scratch methods, respectively. Our findings revealed that HO-1 suppression significantly reduced the proliferation ability of T47D cells (P < 0.001). Moreover, sensitivity to Cisplatin-induced toxicity increased significantly in KO-T47D cells compared to the control T47D cells. Furthermore, our findings indicated that Cisplatin-induced apoptosis increased in the KO-T47D cells. Moreover, the migratory capability of KO-T47D cells was abolished significantly (P < 0.001) as determined by Transwell migration assay. In a nutshell, our findings strongly suggest that HO-1 involved in breast cancer progression and metastasis and chemotherapy resistance. However, further comprehensive studies are required to clarify the precise role of the HO-1 gene on breast cancer cells.

HMOX1 promotes lung adenocarcinoma metastasis by affecting macrophages and mitochondrion complexes

Background

Metastasis is the leading cause of lung adenocarcinoma (LUAD) patient death. However, the mechanism of metastasis is unclear. We performed bioinformatic analyses for HMOX1 (Heme oxygenase-1), aiming to explore its role in LUAD metastasis.

Methods

Pan-cancer analysis was first used to identify the metastasis-associated role of HMOX1 in LUAD. HMOX1-related genomic alterations were then investigated. Based on functional enrichment, we systematically correlated HMOX1 with immunological characteristics and mitochondrial activities. Furthermore, weighted gene co-expression network analysis (WGCNA) was applied to construct the HMOX1-mediated metastasis regulatory network, which was then validated at the proteomic level. Finally, we conducted the survival analysis and predicted the potential drugs to target the HMOX1 network.

Results

HMOX1 expression was significantly associated with epithelial-mesenchymal transition (EMT) and lymph and distant metastasis in LUAD. High HMOX1 levels exhibited higher macrophage infiltration and lower mitochondrial complex expression. WGCNA showed a group of module genes co-regulating the traits mentioned above. Subsequently, we constructed an HMOX1-mediated macrophage-mitochondrion-EMT metastasis regulatory network in LUAD. The network had a high inner correlation at the proteomic level and efficiently predicted prognosis. Finally, we predicted 9 potential drugs targeting HMOX1-mediated metastasis in LUAD, like chloroxine and isoliquiritigenin.

Conclusions

Our analysis elaborates on the role of HMOX1 in LUAD metastasis and identified a highly prognostic HMOX1-mediated metastasis regulatory network. Novel potential drugs targeting the HMOX1 network were also proposed, which should be tested for their activity against LUAD metastasis in future studies.

Macrophage diversity in cancer revisited in the era of single-cell omics

Tumor-associated macrophages (TAMs) have multiple potent functions in cancer and, thus, represent important therapeutic targets. These diverse functions highlight the heterogenous nature of TAMs. Recent single cell omics technologies have significantly advanced our understanding of the molecular diversity of TAMs. However, a unifying nomenclature of TAM diversity and annotation of their molecular signatures is lacking. Here, we review recent major studies of single cell transcriptome, epigenome, metabolome, and spatial omics of cancer with a specific focus on TAMs. We also propose a consensus model of TAM diversity and present avenues for future research.