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Tumour-associated macrophages (TAMs) are crucial components of the tumour microenvironment and play a significant role in tumour development and drug resistance by creating an immunosuppressive microenvironment. Macrophages are essential components of both the innate and adaptive immune systems and contribute to pathogen resistance and the regulation of organism homeostasis. Macrophage function and polarization are closely linked to altered metabolism. Generally, M1 macrophages rely primarily on aerobic glycolysis, whereas M2 macrophages depend on oxidative metabolism. Metabolic studies have revealed that the metabolic signature of TAMs and metabolites in the tumour microenvironment regulate the function and polarization of TAMs. However, the precise effects of metabolic reprogramming on tumours and TAMs remain incompletely understood. In this review, we discuss the impact of metabolic pathways on macrophage function and polarization as well as potential strategies for reprogramming macrophage metabolism in cancer treatment., (© 2023. The Author(s).)

Background: Tumour-associated macrophages (TAMs) play an important role in promoting the progression of pancreatic ductal adenocarcinoma (PDAC). Here, we aimed to study the epigenetic mechanisms in regulating pro-tumour M2-polarised TAMs in the PDAC tumour microenvironment., Methods: This study was conducted based on ex vivo TAMs isolated from PDAC tissues and in vitro THP1-derived TAM model. RNA-sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing and chromatin immunoprecipitation sequencing were performed to investigate gene expression, chromatin accessibility, transcription factor binding sites and histone modifications. Gene knockdown in THP1-derived TAMs was performed with lentivirus, and the impact of THP1-derived TAMs on invasion and metastasis ability of PDAC cells were investigated with in vitro and in vivo functional assays. RNA-chromatin interaction was analysed by chromatin isolation through RNA purification with sequencing. RNA-protein interaction was studied by RNA immunoprecipitation and RNA pull-down., Results: Our data showed that the transcription factor CTCF (CCCTC-binding factor) was highly expressed in TAMs and predicted to be significantly enriched in hyper-accessible chromatin regions when compared to monocytes. High infiltration of CTCF + TAMs was significantly associated with poor prognosis in PDAC patients. Knockdown of CTCF in THP1-derived TAMs led to the down-regulation of specific markers for M2-polarised TAMs, including CD206 and CD163. When THP1-derived TAMs with CTCF knockdown, they showed a decreased ability of invasion and metastasis. Further integrative analysis of multi-omics data revealed that prostaglandin-endoperoxide synthase 2 (PTGS2) and PTGS2 antisense NF-κB1 complex-mediated expression regulator RNA (PACERR) were critical downstream targets of CTCF and positively correlated with each other, which are closely situated on a chromosome. Knockdown of PACERR exhibited a similar phenotype as observed in CTCF knockdown THP1-derived TAMs. Moreover, PACERR could directly bind to CTCF and recruit histone acetyltransferase E1A binding protein p300 to the promoter regions of PACERR and PTGS2, thereby enhancing histone acetylation and gene transcription, promoting the M2 polarization of TAMs in PDAC., Conclusions: Our study demonstrated a novel epigenetic regulation mechanism of promoting pro-tumour M2-polarised TAMs in the PDAC tumour microenvironment., (© 2022 The Authors. Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.)

Background: Gliomas are the most common malignant primary brain tumours with a highly immunosuppressive tumour microenvironment (TME) and poor prognosis. Circular RNAs (circRNA), a newly found type of endogenous noncoding RNA, characterized by high stability, abundance, conservation, have been shown to play an important role in the pathophysiological processes and TME remodelling of various tumours., Methods: CircRNA sequencing analysis was performed to explore circRNA expression profiles in normal and glioma tissues. The biological function of a novel circRNA, namely, circNEIL3, in glioma development was confirmed both in vitro and in vivo. Mechanistically, RNA pull-down, mass spectrum, RNA immunoprecipitation (RIP), luciferase reporter, and co-immunoprecipitation assays were conducted., Results: We identified circNEIL3, which could be cyclized by EWS RNA-binding protein 1(EWSR1), to be upregulated in glioma tissues and to correlate positively with glioma malignant progression. Functionally, we confirmed that circNEIL3 promotes tumorigenesis and carcinogenic progression of glioma in vitro and in vivo. Mechanistically, circNEIL3 stabilizes IGF2BP3 (insulin-like growth factor 2 mRNA binding protein 3) protein, a known oncogenic protein, by preventing HECTD4-mediated ubiquitination. Moreover, circNEIL3 overexpression glioma cells drives macrophage infiltration into the tumour microenvironment (TME). Finally, circNEIL3 is packaged into exosomes by hnRNPA2B1 and transmitted to infiltrated tumour associated macrophages (TAMs), enabling them to acquire immunosuppressive properties by stabilizing IGF2BP3 and in turn promoting glioma progression., Conclusions: This work reveals that circNEIL3 plays a nonnegligible multifaceted role in promoting gliomagenesis, malignant progression and macrophage tumour-promoting phenotypes polarization, highlighting that circNEIL3 is a potential prognostic biomarker and therapeutic target in glioma., (© 2022. The Author(s).)

Bacillus Calmette‑Guérin (BCG) immunotherapy increases macrophage polarization toward M1‑type macrophages. In the present study, to identify the M1/M2 marker genes in the carcinogenesis and progression of cervical cancer, the microarray datasets GSE9750 and GSE7803 were downloaded from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and the University of California Santa Cruz (UCSC) Xena browser. Survival analysis revealed that M1 markers (IL‑12) were involved in anti‑tumour progression, and M2 markers (IL‑10) were involved in the carcinogenesis and invasion of cervical cancer. The expression of M1 markers (IL‑12, inducible nitric oxide synthase and CD80) and M2 markers (IL‑10 and arginase) was examined to determine whether BCG affects the polarization of macrophages and to elucidate the underlying mechanisms. The results revealed that BCG promoted macrophage polarization towards the M1 phenotype and enhanced the transition of M2 to M1 macrophages. The results also revealed that polarized M1 macrophages induced by BCG decreased the protein expression of phosphorylated (p‑)retinoblastoma (Rb)/E2F transcription factor 1 (E2F1), inhibited the proliferation and promoted the apoptosis of HeLa cells. On the whole, these results demonstrated that BCG promoted the anti‑tumour progression of M1 macrophages and inhibited the pro‑tumour activation of M2 macrophages via the Rb/E2F1 signalling pathway in HeLa cells. This suggests the possibility of a direct translation of this combination strategy to clinical practice for the treatment of cervical cancer.

One of the cancer hallmarks is immune evasion mediated by the tumour microenvironment (TME). Oncolytic virotherapy is a form of immunotherapy based on the application of oncolytic viruses (OVs) that selectively replicate in and induce the death of tumour cells. Virotherapy confers reciprocal interaction with the host's immune system. The aim of this review is to explore the role of macrophage-mediated responses in oncolytic virotherapy efficacy. The approach was to study current scientific literature in this field in order to give a comprehensive overview of the interactions of OVs and macrophages and their effects on the TME. The innate immune system has a central influence on the TME; tumour-associated macrophages (TAMs) generally have immunosuppressive, tumour-supportive properties. In the context of oncolytic virotherapy, macrophages were initially thought to predominantly contribute to anti-viral responses, impeding viral spread. However, macrophages have now also been found to mediate transport of OV particles and, after TME infiltration, to be subjected to a phenotypic shift that renders them pro-inflammatory and tumour-suppressive. These TAMs can present tumour antigens leading to a systemic, durable, adaptive anti-tumour immune response. After phagocytosis, they can recirculate carrying tissue-derived proteins, which potentially enables the monitoring of OV replication in the TME. Their role in therapeutic efficacy is therefore multifaceted, but based on research applying relevant, immunocompetent tumour models, macrophages are considered to have a central function in anti-cancer activity. These novel insights hold important clinical implications. When optimised, oncolytic virotherapy, mediating multifactorial inhibition of cancer immune evasion, could contribute to improved patient survival.

Background: The immunosuppressive tumour microenvironment is a critical factor in the initiation and progression of glioblastoma (GBM), which is characterized by an abundance of tumour-associated macrophages (TAMs) but a paucity of infiltrating T cells. In this research, we studied whether epithelial membrane protein 3 (EMP3) plays a crucial role in immune modulation in GBM., Methods: TCGA and CGGA transcriptomic profiles of wild-type IDH1 GBM were used for bioinformatic analysis. The role of EMP3 in GBM was validated through in vivo and in vitro experiments. Human GBM specimens were collected and evaluated using immunofluorescence analysis., Results: EMP3 was associated with immunosuppression in GBM. Elevated EMP3 in GBM areas was accompanied by high expression of PD-L1 and abundant M2 TAM recruitment but a lake of T cell infiltration. We found that EMP3 was a potent protein in M2 TAM polarization and recruitment that impaired the ability of GBM cells to secrete CCL2 and TGF-β1. Furthermore, EMP3 suppressed T cell infiltration into GBM tumours by inhibiting the secretion of CXCL9 and CXCL10 by macrophages and led to an effective response to anti-PD1 therapy., Conclusions: EMP3 is thus a critical immunosuppressive factor for recruiting TAMs in GBM and suppressing intratumoural T cell infiltration to facilitate tumour progression and is a potential therapeutic target.

The immune microenvironment of breast cancer (BC) is composed by high macrophage infiltrates, correlated with the most aggressive subtypes. Tumour-associated macrophages (TAM) within the BC microenvironment are key regulators of immune suppression and BC progression. Nevertheless, several key questions regarding TAM polarisation by BC are still not fully understood. Recently, the modulation of the immune microenvironment has been described via the recognition of abnormal glycosylation patterns at BC cell surface. These patterns rise as a resource to identify potential targets on TAM in the BC context, leading to the development of novel immunotherapies. Herein, we will summarize recent studies describing advances in identifying altered glycan structures in BC cells. We will focus on BC-specific glycosylation patterns known to modulate the phenotype and function of macrophages recruited to the tumour site, such as structures with sialylated or N-acetylgalactosamine epitopes. Moreover, the lectins present at the surface of macrophages reported to bind to such antigens, inducing tumour-prone TAM phenotypes, will also be highlighted. Finally, we will discuss and give our view on the potential and current challenges of targeting these glycan-lectin interactions to reshape the immunosuppressive landscape of BC.

Background: Tumour-associated macrophages (TAMs) in the tumour microenvironment (TME) can promote the progression of hepatocellular carcinoma (HCC). Some tumours can be suppressed by targeting Wnt2b in tumour cells. However, the role of Wnt2b in HCC is still unknown. In particular, the role of Wnt2b-mediated signal activation in macrophage polarization in the HCC microenvironment, and the regulatory effect between Wnt and glycolysis in TAMs has not been described., Methods: The expression of Wnt2b in TAMs was detected by qPCR and immunofluorescence. Wnt2b/β-catenin interference in HCC-TAMs was performed by lentivirus carrying targeted shRNA or TLR9 agonist. Markers related to macrophage polarization and the changes of key glycolytic enzymes expression were detected by flow cytometry and qPCR. ECAR was analysed by Seahorse analyser. MTT assay, wound healing assay, western blotting were used to evaluate the promoting effect of different HCC-TAMs on the proliferation, migration and EMT of HCC in vitro. Tumour cells and different HCC-TAMs were injected via subcutaneously into immunodeficient mice to assess the effects of CpG ODN, Wnt2b, or β-catenin on HCC-TAMs in tumour growth in vivo., Results: Polarization-promoting factors derived from HCC cells upregulated the expression of Wnt2b in macrophages, which promoted the polarization of TAMs to M2-like macrophages by activating Wnt2b/β-catenin/c-Myc signalling. Furthermore, this process was associated with the activation of glycolysis in HCC-TAMs. These HCC-TAMs could promote the development of EMT, proliferation, and migration of HCC. In addition to silencing Wnt2b or β-catenin expression, TLR9 agonist CpG ODN downregulated the level of glycolysis and inhibited the M2 polarization of HCC-TAMs, reversing the tumour-promoting effects of TAMs in vitro and vivo., Conclusions: As a potential target for HCC therapy, Wnt2b may play an important regulatory role for the functions of TAMs in the TME. Moreover, the TLR9 agonist CpG ODN might act as a Wnt2b signal inhibitor and can potentially be employed for HCC therapy by disturbing Wnt2b/β-catenin/c-Myc and inhibiting glycolysis in HCC-TAMs.

Tumour-associated macrophages (TAMs) inhibit the killing effect of T lymphocytes on tumour cells through the immunocheckpoint programmed death ligand-1 (PD-L1)/programmed death-1 (PD-1) axis. TAMs-targeted therapy is a promising approach that could be used to reverse the immunosuppressive tumour microenvironment. Here, we further report CMPB90-1, a novel natural polysaccharide from Cordyceps militaris, could function as an anti-tumour modulator that resets TAMs from a tumour-promoting M2 phenotype to a tumour-killing M1 phenotype. This process involves reversing the functional inhibition of T lymphocytes by inhibiting the PD-L1/PD-1 axis between TAMs and T lymphocytes. Mechanistically, the membrane receptor of CMPB90-1 binding to M2 macrophages was identified by tandem mass spectrometry. CMPB90-1 converts immunosuppressive TAMs via binding to toll-like receptor 2 (TLR2), which causes the release of Ca 2+ and the activation of p38, Akt and NF-κB, or ERK. This process then leads to the polarization of TAMs from M2 phenotype to the M1 phenotype. In vivo experiment shows that CMPB90-1 is able to polarize TAMs into the M1 phenotype and has anti-tumour effects with improved safety. Additionally, the anti-tumour effects of CMPB90-1 in vivo depend on the phenotypic conversion of TAMs. The results demonstrated that CMPB90-1 could be developed as a potential immune-oncology treatment reagent., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Aim: Tumour-associated macrophages (TAMs) are prominent immune cells infiltrating in solid tumours with phenotypic and functional heterogeneity. However, the clinical significance of heterogeneous subtypes of TAMs in gastric cancer still remains obscure. Here, we aimed to explore the clinical significance of TAMs expressing dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) and its relevance with immune contexture in gastric cancer., Methods: We selected 453 formalin-fixed and paraffin-embedded samples and 51 fresh tissue specimens of patients with gastric cancer from Zhongshan Hospital. The association of DC-SIGN + macrophages with clinicopathological parameters, overall survival (OS) and responsiveness to fluorouracil-based adjuvant chemotherapy (ACT) was inspected. Immunohistochemistry (IHC) and flow cytometry (FCM) were applied to characterize immune cells in gastric cancer., Results: We demonstrated that high intratumoral DC-SIGN + macrophages infiltration predicted poor OS and inferior therapeutic responsiveness to fluorouracil-based ACT in patients with gastric cancer. Furthermore, higher infiltration of DC-SIGN + macrophages indicated an increased number of Foxp3 + regulatory T cells (Tregs), CD8 + T cells and a higher ratio of Foxp3 + /CD8 + within the tumour microenvironment (TME). In addition, CD8 + T cells in DC-SIGN + macrophages high subgroup were functionally impaired, showing decreased interferon-γ (IFN-γ), granzyme B (GZMB) and perforin production yet elevated programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expression., Conclusions: DC-SIGN + macrophages were associated with immunoinvasive TME and indicated poor prognosis and inferior therapeutic responsiveness to fluorouracil-based ACT. DC-SIGN + macrophages might be an independent prognosticator and a potential immunotherapeutic target for gastric cancer., Competing Interests: Conflict of interest statement The authors declare no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Tumour-associated macrophages (TAMs) comprise an important part of the tumour microenvironment and play a key role in malignant tumours progression. Tumour-derived extracellular vesicles (EVs) modulated TAMs polarization and reprogrammed TAMs to influence the progression of various tumours. Here, we hypothesized that diffuse large B cell lymphoma (DLBCL)-derived EVs can regulate macrophages polarization and thus contribute to tumour progression. Our results demonstrated that EVs, released from DLBCL, augment the M2 polarization effects of macrophages. Moreover, conditional medium derived from macrophages by DLBCL-derived EVs stimulation revealed the superior effects of promoting tumour proliferation, migration and invasion. Further analysis demonstrated that DLBCL-derived EVs regulated the metabolism of macrophages by increasing the expression of PGC-1β protein, thereby reprogramming the macrophage phenotype of promoting tumour progression. In conclusion, our findings signify that the DLBCL-derived EVs mediated the increasing of functional PGC-1β protein in macrophages to promote the tumour progression., (© 2019 The Scandinavian Foundation for Immunology.)

High-fat diet (HFD) is a well-known risk factor for gut microbiota dysbiosis and colorectal cancer (CRC). However, evidence relating HFD, gut microbiota and carcinogenesis is limited. Our study aimed to demonstrate that HFD-induced gut dysbiosis promoted intestinal adenoma-adenocarcinoma sequence. In clinical study, we found that HFD increased the incidence of advanced colorectal neoplasia (AN). The expression of monocyte chemoattractant protein 1 (MCP-1), CC chemokine receptor 2 (CCR2) and CD163 in CRC patients with HFD was significantly higher than that in CRC patients with normal diet. When it comes to the Apc min/+ mice, HFD consumption could induce gut dysbiosis and promote intestinal carcinogenesis, accompanying with activation of MCP-1/CCR2 axis that recruited and polarized M2 tumour-associated macrophages. Interestingly, transfer of faecal microbiota from HFD-fed mice to another batch of Apc min/+ mice in the absence of HFD could also enhance carcinogenesis without significant body weight gain and induced MCP-1/CCR2 axis activation. HFD-induced dysbiosis could also be transmitted. Meanwhile, antibiotics cocktail treatment was sufficient to inhibit HFD-induced carcinogenesis, indicating the vital role of dysbiosis in cancer development. Conclusively, these data indicated that HFD-induced dysbiosis accelerated intestinal adenoma-adenocarcinoma sequence through activation of MCP-1/CCR2 axis, which would provide new insight into better understanding of the mechanisms and prevention for HFD-related CRC., (© 2020 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley.)

Tumour-associated macrophages (TAMs) play an important role in the tumour environment and were reported to be associated with poor prognosis in several tumours. However, the prognostic significance of TAMs in Non-Hodgkin's Lymphoma (NHL) remains controversial. Consequently, we aimed to evaluate the relationship between subpopulations of TAMs and clinical outcomes in NHL patients. We did a comprehensive search of the PubMed, elsevier ScienceDirect, and Cochrane databases and extracted hazard ratio (HR) and their corresponding 95% confidence intervals (95% CIs) from eligible studies. Pooling total effect value by the stata statistical software and analysing correlation of TAMs with overall survival (OS) and progression-free survival (PFS). Furthermore, subgroup analysis and sensitivity analysis were also conducted. We deemed eleven studies, including 1211 NHL patients. Our study demonstrated that high-density CD68 + TAMs are associated with poor OS (HR: 1.17; 95% CI, 0.81-1.54; P = .000) and poor PFS (HR: 1.15; 95% CI, 0.63-1.67; P = .000) compared with low-density CD68 + TAMs in the tumour microenvironment. Similarly, high-density CD163 + TAMs can also predict poor OS (HR: 1.52; 95% CI, 1.11-1.92; P = .000) and shorter PFS (HR: 1.52; 95% CI, 0.73-2.30; P = .000). In addition, the high CD163 + /CD68 + TAMs ratio is significantly correlated with poor OS (HR: 3.59; 95% CI, 0.77-6.40; P = .013). However, in our subgroup analysis, high-density CD68 + TAMs in the tumour microenvironment is associated with better OS (HR: 0.75; 95% CI, 0.41-1.09; P = .000) in NHL patients treated with rituximab chemotherapy. Our results suggest that TAMs are a robust predictor of outcomes in NHL., (© 2019 The Scandinavian Foundation for Immunology.)

Background: The role of tumour-associated macrophages (TAMs) in predicting the prognosis of colorectal cancer (CRC) remains controversial. This is especially so because the prognostic significance and clinicopathological relevance of different subtypes of TAMs in the immune microenvironment of CRC have not yet been established., Objective: To assess the clinicopathological and prognostic value of pan-macrophages, M1-macrophages or M2-macrophages in patients with CRC., Methods: Comprehensive searched on the Medline/PubMed, Web of Science (WoS) and Google Scholar databases was conducted to identify relevant studies published up to April 2019. The association between overall survival (OS), cancer-specific survival (CSS) or disease-free survival (DFS) and TAMs was analysed by meta-analysis., Results: A total of 3749 patients from 17 studies were included. The pooled hazard ratios (HRs) indicated that high-density pan-macrophages improved OS (HR 0.67, P = 0.02). The pooled HR for M2-macrophages showed that high M2-macrophages infiltration was significantly associated with shorter OS (HR 2.93, P < 0.0001) and DFS (HR 2.04, P = 0.02). The pooled odds ratios (ORs) revealed that high-density TAMs was associated with high CD8+ T cell infiltration (OR 2.04, P = 0.007), no distant metastasis (NDM) (OR 0.38, P < 0.0001), microsatellite instability-high (MSI-H) (OR 0.38, P = 0.001), no lymph node metastasis (NLNM) (OR 0.54, P = 0.0002) and non-mucinous cancer (OR 0.39, P < 0.00001)., Conclusions: Unlike other solid tumours, high-density CD68+ macrophage infiltration can be a good prognostic marker for CRC. However, when macrophages act as targets of combination therapy in CRC treatment, this might be more effective for CRC patients with high CD8+ T cell infiltrate, NDM, MSI-H, NLNM and non-mucinous cancer.

Background: Tumour-associated macrophages (TAMs) are often implicated in cancer progression but can also exert anti-tumour activities. Selective eradication of cancer-promoting (M2-like) TAM subsets is a highly sought-after goal. Here, we have devised a novel strategy to achieve selective TAM depletion, involving the use of T cell engagers to direct endogenous T cell cytotoxicity towards specific M2-like TAMs. To avoid "on-target off-tumour" toxicities, we have explored localising expression of the T cell engagers to the tumour with enadenotucirev (EnAd), an oncolytic adenovirus in Phase I/II clinical trials., Method: A panel of bi- and tri-valent T cell engagers (BiTEs/TriTEs) was constructed, recognising CD3ε on T cells and CD206 or folate receptor β (FRβ) on M2-like macrophages. Initial characterisation of BiTE/TriTE activity and specificity was performed with M1- and M2-polarised monocyte-derived macrophages and autologous lymphocytes from healthy human peripheral blood donors. T cell engagers were inserted into the genome of EnAd, and oncolytic activity and BiTE secretion assessed with DLD-1 tumour cells. Clinically-relevant ex vivo models (whole malignant ascites from cancer patients) were employed to assess the efficacies of the free- and virally-encoded T cell engagers., Results: T cells activated by the CD206- and FRβ-targeting BiTEs/TriTEs preferentially killed M2- over M1-polarised autologous macrophages, with EC 50 values in the nanomolar range. A TriTE with bivalent CD3ε binding - the first of its kind - demonstrated enhanced potency whilst retaining target cell selectivity, whereas a CD28-containing TriTE elicited non-specific T cell activation. In immunosuppressive malignant ascites, both free and EnAd-encoded T cell engagers triggered endogenous T cell activation and IFN-γ production, leading to increased T cell numbers and depletion of CD11b + CD64 + ascites macrophages. Strikingly, surviving macrophages exhibited a general increase in M1 marker expression, suggesting microenvironmental repolarisation towards a pro-inflammatory state., Conclusions: This study is the first to achieve selective depletion of specific M2-like macrophage subsets, opening the possibility of eradicating cancer-supporting TAMs whilst sparing those with anti-tumour potential. Targeted TAM depletion with T cell engager-armed EnAd offers a powerful therapeutic approach combining direct cancer cell cytotoxicity with reversal of immune suppression.

Background: The activation of tumour-associated macrophages (TAMs) contributes to the progression of hepatocellular carcinoma (HCC). SIRT4 acts as a tumour suppressor of tumour growth by regulating cell metabolism, inflammation, and anti-tumourigenesis. However, the involvement of SIRT4 in the activation of TAMs is unknown. Based on previous findings, the expression of SIRT4 in distinct groups of TAMs as well as the effect of SIRT4 silencing on macrophage polarization was investigated., Methods: The expression of SIRT4 in HCC tissues and peritumour tissues was tested by qRT-PCR, western blotting and histological analysis. A Kaplan-Meier survival curve was generated based on the expression of SIRT4 in the HCC samples. Next, immunofluorescence staining was used to evaluate distinct groups of TAMs in human HCC samples, and the expression of SIRT4 in M1 and M2 TAMs was examined by flow cytometry. A homograft mouse model was used to assess the effect of SIRT4 silencing in TAMs on the development of HCC cells., Results: SIRT4 was significantly downregulated in HCC tumour tissues, and the expression of SIRT4 in peritumour tissues was positively associated with survival in patients. We further found that downregulation of SIRT4 was associated with increased macrophage infiltration and a high ratio of M2/M1 macrophages in HCC peritumour tissues. Using gene interference, we found that SIRT4 silencing in TAMs significantly modulated the alternative activation of macrophages and promoted in vitro and in vivo HCC cell growth. Mechanistically, we revealed that HCM restricted the expression of SIRT4 in macrophages and promoted alternative activation of macrophages via the FAO-PPARδ-STAT3 axis. Furthermore, we also revealed that elevated MCP-1 expression induced by SIRT4 downregulation was responsible for increased TAM infiltration in peritumour tissues., Conclusions: Overall, our results demonstrate that downregulation of SIRT4 in TAMs modulates the alternative activation of macrophages and promotes HCC development via the FAO-PPARδ-STAT3 axis. These results could provide a new therapeutic target for the treatment of HCC.

The aim of the present study was to investigate the correlation between the density of infiltrating T cells and macrophages in the parental colorectal cancer (CRC) and the growth rate of tumoroids (i.e. a patient-derived in vitro 3D model). Tumoroids were established from fresh specimens of primary and metastatic CRC from 29 patients. The in vitro growth rate of tumoroids was monitored by automated imaging. The density of infiltrating T cells and macrophages was determined in the centre of the tumour (CT) and at the invasive margin (IM) of the parental tumours. This was performed by digital image analysis on the whole-slide scanned images using Visiopharm ® software. Tumoroids with higher density of infiltrating CD3+ lymphocytes in the IM of their parental tumour showed a higher growth rate (P < .0005). The average relative growth rate (log10) during the period from day 1 to day 11 was 0.364 ± 0.006 (mean ± SD) for the CD3+ (IM)-high group and 0.273 ± 0.008 (mean ± SD) for the CD3+ (IM)-low group. In contrast, the density of CD68+ infiltrating macrophages in the parental tumours showed significant inverse effect on the growth rate of the tumoroids (P < .0005). The present study showed that the density of immune cells in the parental CRC correlates with the growth rate of the tumoroids. The future perspective for such a 3D model could be in vitro investigations of the tumour-associated inflammatory microenvironment as well as personalized cancer immunotherapy., (© 2020 The Authors. International Journal of Experimental Pathology © 2020 International Journal of Experimental Pathology.)

The tumor microenvironment is an important determinant of glioblastoma (GBM) progression and response to treatment. How oncogenic signaling in GBM cells modulates the composition of the tumor microenvironment and its activation is unclear. We aimed to explore the potential local immunoregulatory function of ERK1/2 signaling in GBM. Using proteomic and transcriptomic data (RNA seq) available for GBM tumors from The Cancer Genome Atlas (TCGA), we show that GBM with high levels of phosphorylated ERK1/2 have increased infiltration of tumor-associated macrophages (TAM) with a non-inflammatory M2 polarization. Using three human GBM cell lines in culture, we confirmed the existence of ERK1/2-dependent regulation of the production of the macrophage chemoattractant CCL2/MCP1. In contrast with this positive regulation of TAM recruitment, we found no evidence of a direct effect of ERK1/2 signaling on two other important aspects of TAM regulation by GBM cells: (1) the expression of the immune checkpoint ligands PD-L1 and PD-L2, expressed at high mRNA levels in GBM compared with other solid tumors; (2) the production of the tumor metabolite lactate recently reported to dampen tumor immunity by interacting with the receptor GPR65 present on the surface of TAM. Taken together, our observations suggest that ERK1/2 signaling regulates the recruitment of TAM in the GBM microenvironment. These findings highlight some potentially important particularities of the immune microenvironment in GBM and could provide an explanation for the recent observation that GBM with activated ERK1/2 signaling may respond better to anti-PD1 therapeutics., (© 2019 The Author(s).)

Background: Tumour-associated macrophages (TAMs) play an important role in the growth, progression, and metastasis of tumours. Epithelial-mesenchymal transition (EMT) is a mechanism for tumour invasion and metastasis. In this study, we aimed to determine whether TAMs can induce EMT for the invasion and metastasis of Kazakh oesophageal squamous cell cancer (ESCC)., Methods: CD163 was used as a marker for TAMs, and the density of TAMs in tumour nest and surrounding stroma was quantified using immunohistochemistry (IHC). IHC staining was used to evaluate the expression of E-cadherin (epithelial marker) and vimentin (mesenchymal marker) in Kazakh ESCC and cancer-adjacent normal tissues (CANs). Additionally, 6-well transwell plates (0.4 μm) were used to establish the co-culture system of ESCC (EC109 or EC9706) cells and macrophages. Real-time quantitative polymerase chain reaction (qPCR) and western blot experiments were used to determine whether ESCC cells undergo EMT transformation after co-culture with macrophages. Transwell assays were used to detect the migration and invasion of the ESCC cells., Results: The distribution of CD163-positive TAMs in cancer tissues was closely related to EMT in Kazakh ESCC. The expression of vimentin in the ESCC cells was significantly upregulated, the expression of E-cadherin was significantly downregulated, and the invasion and migration of the ESCC cells were significantly enhanced after tumour-associated macrophages were added to the co-culture., Conclusions: Tumour-associated macrophages promote EMT in ESCC, which may be one of the important factors involved in the invasion and progression of Kazakh ESCC.

A new and diverse range of somatic mutation signatures are observed in late-stage cancers, but the underlying reasons are not fully understood. We advance a "combinatorial association model" for deaminase binding domain (DBD) diversification to explain the generation of previously observed cancer-progression associated mutation signatures. We also propose that changes in the polarization of tumour-associated macrophages (TAMs) are accompanied by the expression of deaminases with a new and diverse range of DBDs, and thus accounting for the generation of new somatic mutation signatures. The mechanism proposed is molecularly reminiscent of combinatorial association of heavy (H) and light (L) protein chains following V(D)J recombination of immunoglobulin molecules (and similarly for protein chains in heterodimers α/β and γ/δ of V(D)Js of T Cell Receptors) required for pathogen antigen recognition by B cells and T cells, respectively. We also discuss whether extracellular vesicles (EVs) emanating from tumour enhancing M2-polarized macrophages represent a likely source of the de novo deaminase DBDs. We conclude that M2-polarized macrophages extruding EVs loaded with deaminase proteins or deaminase-specific transcription/translation regulatory factors and like information may directly trigger deaminase diversification within cancer cells, and thus account for the many new somatic mutation signatures that are indicative of cancer progression. This hypothesis now has a plausible evidentiary base, and it is worth direct testing in future investigations. A long-term objective would be to identify molecular biomarkers predicting cancer progression (or metastatic disease) and to support the development of new drug targets before metastatic pathways are activated., (© 2019 The Authors. Scandinavian Journal of Immunology published by John Wiley & Sons Ltd on behalf of The Foundation for the Scandinavian Journal of Immunology.)

Tumour hypoxia has long presented a challenge for cancer therapy: Poor vascularisation in hypoxic regions hinders both the delivery of chemotherapeutic agents and the response to radiotherapy, and hypoxic cancer cells that survive treatment can trigger tumour regrowth after treatment has ended. Tumour-associated macrophages are attractive vehicles for drug delivery because they localise in hypoxic areas of the tumour. In this paper, we derive a mathematical model for the infiltration of an in vitro tumour spheroid by macrophages that have been engineered to release an oncolytic adenovirus under hypoxic conditions. We use this model to predict the efficacy of treatment schedules in which radiotherapy and the engineered macrophages are given in combination. Our work suggests that engineered macrophages should be introduced immediately after radiotherapy for maximum treatment efficacy. Our model provides a framework that may guide future experiments to determine how multiple rounds of radiotherapy and macrophage virotherapy should be coordinated to maximise therapeutic responses., (Copyright © 2018. Published by Elsevier Ltd.)

The tumour microenvironment (TME) is composed of extracellular matrix and non-mutated cells supporting tumour growth and development. Tumour-associated macrophages (TAMs) are among the most abundant immune cells in the TME and are responsible for the onset of a smouldering inflammation. TAMs play a pivotal role in oncogenic processes as tumour proliferation, angiogenesis and metastasis, and they provide a barrier against the cytotoxic effector function of T lymphocytes and natural killer (NK) cells. However, TAMs are highly plastic cells that can adopt either pro- or anti-inflammatory roles in response to environmental cues. Consequently, TAMs represent an attractive target to recalibrate immune responses in the TME. Initial TAM-targeted strategies, such as macrophage depletion or disruption of TAM recruitment, have shown beneficial effects in preclinical models and clinical trials. Alternatively, reprogramming TAMs towards a proinflammatory and tumouricidal phenotype has become an attractive strategy in immunotherapy. This work summarises the molecular wheelwork of macrophage biology and presents an overview of molecular strategies to repolarise TAMs in immunotherapy.

The tumour microenvironment (TME) shapes disease progression and influences therapeutic response. Most aggressive solid tumours have high levels of myeloid cell infiltration, namely tumour associated macrophages (TAM). Recapitulation of the interaction between the different cellular players of the TME, along with the extracellular matrix (ECM), is critical for understanding the mechanisms underlying disease progression. This particularly holds true for prediction of therapeutic response(s) to standard therapies and interrogation of efficacy of TME-targeting agents. In this work, we explored a culture platform based on alginate microencapsulation and stirred culture systems to develop the 3D-3-culture, which entails the co-culture of tumour cell spheroids of non-small cell lung carcinoma (NSCLC), cancer associated fibroblasts (CAF) and monocytes. We demonstrate that the 3D-3-culture recreates an invasive and immunosuppressive TME, with accumulation of cytokines/chemokines (IL4, IL10, IL13, CCL22, CCL24, CXCL1), ECM elements (collagen type I, IV and fibronectin) and matrix metalloproteinases (MMP1/9), supporting cell migration and promoting cell-cell interactions within the alginate microcapsules. Importantly, we show that both the monocytic cell line THP-1 and peripheral blood-derived monocytes infiltrate the tumour tissue and transpolarize into an M2-like macrophage phenotype expressing CD68, CD163 and CD206, resembling the TAM phenotype in NSCLC. The 3D-3-culture was challenged with chemo- and immunotherapeutic agents and the response to therapy was assessed in each cellular component. Specifically, the macrophage phenotype was modulated upon treatment with the CSF1R inhibitor BLZ945, resulting in a decrease of the M2-like macrophages. In conclusion, the crosstalk between the ECM and tumour, stromal and immune cells in microencapsulated 3D-3-culture promotes the activation of monocytes into TAM, mimicking aggressive tumour stages. The 3D-3-culture constitutes a novel tool to study tumour-immune interaction and macrophage plasticity in response to external stimuli, such as chemotherapeutic and immunomodulatory drugs., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Macrophages represent a major component of the overall leucocyte population within neoplasms and are important for tumour behaviour in several cancers in human beings. However, little information regarding their role in canine mammary tumours (CMTs) is available. The aim of this study was to address the potential role of tumour-associated macrophages (TAMs) in CMTs. TAMs in CMTs excised from 82 female dogs were quantified at high power (400× magnification) and categorised as low (≤50) or high (>50) TAM counts. Higher TAM counts were associated with clinical stage (P<0.001), tumour type (P=0.016), tumour size (P=0.013), vascular invasion (P=0.031), lymph node metastasis (P=0.003), high proliferation rates (P=0.009), vascular microdensity (P=0.008), invasive tumour profile (P=0.002) and worse prognosis (P=0.018; hazard ratio=0.283). Almost all macrophages infiltrating malignant tumours with high TAM counts expressed CD206 (macrophage mannose receptor 1), while all benign tumours were infiltrated by macrophages expressing inducible nitric oxide synthase (NOS2), suggesting a phenotypic shift from classically activated macrophage (M1) subpopulations towards alternatively activated macrophage (M2) subpopulations in malignant tumours. A triple staining pattern revealed mixed M1/M2 profiles in some tumours, thus characterising an intermediate state. The results indicate that TAMs are associated with more aggressive types of mammary cancer in dogs., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: To assess the relationships between CD163 expression, localization of CD163 + macrophages, clinicopathological features and prognosis of NPC., Methods: A total of 110 cases of NPC specimens and 80 cases of nasopharyngitis specimens were analysed for CD163 expression by immunohistochemistry and EBERs expression in situ hybridization., Results: CD163 + macrophages in the tumour stroma were positively correlated with the tumour and nodal stage. Higher expression of Epstein-Barr virus-encoded RNAs (EBERs) in the nuclei of tumour cells was associated with higher density of CD163 + macrophages in the tumour stroma. More importantly, greater infiltration of CD163 + macrophages in the tumour stroma was associated with poor overall survival (OS) and poor progression-free survival (PFS). Multivariate analysis revealed that the density of CD163 +  macrophages in the tumour stroma may be an independent risk factor for NPC prognosis., Conclusions: Increased infiltration of CD163 +  macrophages in the tumour stroma correlates with worse outcomes and with Epstein-Barr virus (EBV) infection status of tumour cells in nasopharyngeal carcinoma (NPC).

Tumour-associated macrophages (TAMs) represent pivotal components of tumour microenvironment promoting angiogenesis, tumour progression and invasion. In colorectal cancer (CRC), there are no conclusive data about the role of TAMs in angiogenesis-mediated tumour progression. In this study, we aimed to evaluate a correlation between TAMs, TAM immunostained area (TAMIA) microvascular density (MVD), endothelial area (EA) and cancer cells positive to VEGF-A (CCP-VEGF-A) in primary tumour tissue of locally advanced CRC patients undergone to radical surgery. A series of 76 patients with CRC were selected and evaluated by immunohistochemistry and image analysis. An anti-CD68 antibody was employed to assess TAMs and TAMIA expression, an anti-CD34 antibody was utilized to detect MVD and EA expression, whereas an anti-VEGF-A antibody was used to detect CCP-VEGF-A; then, tumour sections were evaluated by image analysis methods. The mean ± S.D. of TAMs, MVD and CCP-VEGF-A was 65.58 ± 21.14, 28.53 ± 7.75 and 63% ± 37%, respectively; the mean ± S.D. of TAMIA and EA was 438.37 ± 124.14μ(2) and 186.73 ± 67.22μ(2) , respectively. A significant correlation was found between TAMs, TAMIA, MVD and EA each other (r ranging from 0.69 to 0.84; P ranging from 0.000 to 0.004). The high level of expression of TAMs and TAMIA in tumour tissue and the significant correlation with both MVD and EA illustrate that TAMs could represent a marker that plays an important role in promoting angiogenesis-mediated CRC. In this context, novel agents killing TAMs might be evaluated in clinical trials as a new anti-angiogenic approach., (© 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

As the most predominant tumour-infiltrating immune cells, tumour-associated macrophages (TAMs) are significant for fostering tumour growth, progression and metastasis. CD68-positive TAMs display dissimilarly polarized programmes comprising CD11c-positive pro-inflammatory macrophages (M1) and CD206-positive immunosuppressive macrophages (M2). The aim of this study is to determine the prognostic significance of diametrically polarized TAMs in hepatocellular carcinoma (HCC) and their application to risk stratification of patients according to their specific prognostic values. This study included 80 consecutive patients with HCC, and we evaluated diametrically polarized functional status of macrophages by immunohistochemical staining of CD68, CD11c and CD206. Prognostic values and clinicopathologic features were assessed in these patients. High versus low CD11c-positive TAM density (P = 0.005) and low versus high CD206-positive TAM density (P = 0.002) were associated with better overall survival, whereas CD68-positive TAM density had no prognostic significance (low versus high, P = 0.065). Furthermore, the presence of these positive staining macrophages did not show any prognostic significance for recurrence-free survival (all P > 0.05). Multivariate Cox regression analysis identified CD11c-positive and CD206-positive TAMs as an independent prognostic factor (P < 0.001, P = 0.031, respectively). Intratumoural infiltration of diametrically polarized TAMs, a novel identified independent prognostic factor for survival in patients with HCC, could be combined with the TNM stage and the Barcelona Clinic Liver Cancer stage to improve a risk stratification system., (© 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

To confirm our hypothesis that macrophages recruited to fight against oral squamous cell carcinoma (SCC) invasion are functionally differentiated within neoplastic stromata, we analysed arrangements of macrophage subtypes and cancer-associated fibroblasts (CAFs) in their association with blood vasculatures in the neoplastic stroma. Surgical specimens of oral SCC were immunohistochemically examined for macrophage phenotypes (CD68, CD163, and CD204) and stromal environments (perlecan, connexin 43, and CD31). Human monocytes were co-cultured with ZK-1 cells of oral SCC origin in different culture conditions. SCC stromata were divided into two types: fascicular (fibroblast-rich) and reticular (perlecan-rich). Regardless of stromal types, CD68 positive (+)/CD163+/CD204+ macrophages were recruited when blood vessels were abundant. Connexin 43+ fibroblasts were enriched in the fascicular stroma, where blood vessels were depleted. In co-culture experiments, monocytes, in the presence of ZK-1 cells, showed TNF-α(low)/IL-12(low) and IL-10(high)/VEGF(high)/MMP-9(high) with increased expression levels for fibronectin and perlecan. With direct contact with monocytes, SCC cells also expressed CD68 and CD163. SCC stromata were characterised by CD163+/CD204+ tumour-associated macrophages (TAMs) and connexin 43+ CAFs. TAMs are differentiated from monocytes by the physical contact with oral SCC cells in the perlecan-rich neoplastic stroma, which is also induced by the cross-talk between SCC cells and stromal cells including TAMs., (Copyright © 2016 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.)

Tumour-associated macrophages (TAMs) have been implicated in carcinogenesis including an important role in angiogenesis. In this study, we describe the relationship between TAMs and angiogenesis in canine mammary tumours (CMT). Formalin-fixed paraffin-embedded CMT samples [(n = 128: malignant (n = 97) and benign (n = 31)] were submitted to immunohistochemical staining to detect MAC387, vascular endothelial growth factor VEGF and CD31 expression. A statistical analysis was carried out to assess possible associations with clinicopathological variables and biological markers of tumour angiogenesis. TAMs, detected by MAC387 expression, were significantly associated with malignant CMT (P < 0.001) and VEGF positive tumours (P = 0.002) and also associated with VEGF expression within malignant CMT (P = 0.043). Associations with clinicopathological variables were found between TAMs and the presence of infiltrative growth (P = 0.031), low tubule formation (P = 0.040) and lymph node metastasis (P = 0.016). The results support the hypothesis that TAMs influence angiogenesis in CMT suggesting TAMs may represent a therapeutic target in this disease., (© 2013 John Wiley & Sons Ltd.)

Tumour-associated macrophages (TAMs) are a set of macrophages residing in the tumour microenvironment. They play essential roles in mediating tumour angiogenesis, metastasis and immune evasion. Delivery of therapeutic agents to eliminate TAMs can be a promising strategy for cancer immunotherapy but an efficient vehicle to target these cells is still in pressing need. In this study, we developed a bisphosphonate-glucomannan conjugate that could efficiently target and specifically eliminate TAMs in the tumour microenvironment. We employed the polysaccharide from Bletilla striata (BSP), a glucomannan affinitive for macrophages that express abundant mannose receptors, to conjugate alendronate (ALN), a bisphosphonate compound with in vitro macrophage-inhibiting activities. In both in vitro and in vivo tests, the prepared ALN-BSP conjugate could preferentially accumulate in macrophages and induced them into apoptosis. In the subcutaneous S180 tumour-bearing mice model, the treatment using ALN-BSP effectively eliminated TAMs, remarkably inhibited angiogenesis, recovered local immune surveillance, and eventually suppressed tumour progression, without eliciting any unwanted effect such as systematic immune response. Interestingly, ALN alone failed to exhibit any anti-TAM activity in vivo, probably because this compound was susceptible to the mildly acidic tumour microenvironment. Taken together, these results demonstrate the potential of ALN-BSP as a safe and efficient tool targeted at direct depletion of TAMs for cancer immunotherapy., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Tumour-associated macrophages (TAMs) have already been associated in human breast cancer to a poor prognosis. As a part of a tumoural microenvironment, TAMs have an important contribution influencing neoplastic progression. Hitherto, in canine mammary tumours (CMT) the prognostic value of TAMs has not been reported. In this study, MAC387 immunohistochemical expression was evaluated in 59 CMTs (20 benign and 39 malignant). The TAM value was significantly higher in malignant than benign CMT (P = 0.011). In malignant CMT, TAMs were associated with skin ulceration (P = 0.022), histological type (P = 0.044), nuclear grade (P = 0.031) and tubular differentiation (P = 0.042). The survival analysis revealed a significant association between tumours with higher levels of TAMs and the decrease in overall survival (P = 0.030). TAMs have proven to have a prognostic value. These findings suggest the future possibility of using TAMs as a novel therapeutic target in CMT., (© 2012 John Wiley & Sons Ltd.)

Introduction: More effective therapies are required to improve survival of pancreatic cancer. Possible immunologic targets include tumour associated macrophages (TAMs), generally consisting of M1- and M2-macrophages. We have analysed the impact of TAMS on pancreatic cancer in a syngeneic orthotopic murine model., Methods: 6606PDA murine pancreatic cancer cells were orthotopically injected into C57BL6 mice. Tumour growth was monitored using MRI. Macrophages were depleted by clodronate liposomes. Tumours including microvessel density were evaluated using immunohistochemistry, immunofluorescence and/or cytometric beads assays. Naïve macrophages were generated employing peritoneal macrophages. In vitro experiments included culturing of macrophages in tumour supernatants as well as tumour cells cultured in macrophage supernatants using arginase as well as Griess assays., Results: Clodronate treatment depleted macrophages by 80% in livers (p = 0.0051) and by 60% in pancreatic tumours (p = 0.0169). MRI revealed tumour growth inhibition from 221.8 mm(3) to 92.3 mm(3) (p = 0.0216). Micro vessel densities were decreased by 44% (p = 0.0315). Yet, MCP-1-, IL-4- and IL-10-levels within pancreatic tumours were unchanged. 6606PDA culture supernatants led to a shift from naïve macrophages towards an M2-phenotype after a 36 h treatment (p < 0.0001), reducing M1-macrophages at the same time (p < 0.037). In vivo, M2-macrophages represented 85% of all TAMs (p < 0.0001). Finally, culture supernatants of M2-macrophages induced tumour growth in vitro by 63.2% (p = 0.0034)., Conclusions: This quid pro quo of tumour cells and M2-macrophages could serve as a new target for future immunotherapies that interrupt tumour promoting activities of TAMs and change the iNOS-arginase balance towards their tumoricidal capacities., (Copyright © 2013 IAP and EPC. Published by Elsevier B.V. All rights reserved.)

Macrophages infiltrating tumour tissues or residing in the microenvironment of solid tumours are known as tumour-associated macrophages (TAMs). These specialized immune cells play crucial roles in tumour growth, angiogenesis, immune regulation, metastasis, and chemoresistance. TAMs encompass various subpopulations, primarily classified into M1 and M2 subtypes based on their differentiation and activities. M1 macrophages, characterized by a pro-inflammatory phenotype, exert anti-tumoural effects, while M2 macrophages, with an anti-inflammatory phenotype, function as protumoural regulators. These highly versatile cells respond to stimuli from tumour cells and other constituents within the tumour microenvironment (TME), such as growth factors, cytokines, chemokines, and enzymes. These stimuli induce their polarization towards one phenotype or another, leading to complex interactions with TME components and influencing both pro-tumour and anti-tumour processes. This review comprehensively and deeply covers the literature on macrophages, their origin and function as well as the intricate interplay between macrophages and the TME, influencing the dual nature of TAMs in promoting both pro- and anti-tumour processes. Moreover, the review delves into the primary pathways implicated in macrophage polarization, examining the diverse stimuli that regulate this process. These stimuli play a crucial role in shaping the phenotype and functions of macrophages. In addition, the advantages and limitations of current macrophage based clinical interventions are reviewed, including enhancing TAM phagocytosis, inducing TAM exhaustion, inhibiting TAM recruitment, and polarizing TAMs towards an M1-like phenotype. In conclusion, while the treatment strategies targeting macrophages in precision medicine show promise, overcoming several obstacles is still necessary to achieve an accessible and efficient immunotherapy. [ABSTRACT FROM AUTHOR]

Immunotherapy is a promising and safer alternative to conventional cancer therapies. It involves adaptive T-cell therapy, cancer vaccines, monoclonal antibodies, immune checkpoint blockade (ICB), and chimeric antigen receptor (CAR) based therapies. However, most of these modalities encounter restrictions in solid tumours owing to a dense, highly hypoxic and immune-suppressive microenvironment as well as the heterogeneity of tumour antigens. The elevated intra-tumoural pressure and mutational rates within fast-growing solid tumours present challenges in efficient drug targeting and delivery. The tumour microenvironment is a dynamic niche infiltrated by a variety of immune cells, most of which are macrophages. Since they form a part of the innate immune system, targeting macrophages has become a plausible immunotherapeutic approach. In this review, we discuss several versatile approaches (both at pre-clinical and clinical stages) such as the direct killing of tumour-associated macrophages, reprogramming pro-tumour macrophages to anti-tumour phenotypes, inhibition of macrophage recruitment into the tumour microenvironment, novel CAR macrophages, and genetically engineered macrophages that have been devised thus far. These strategies comprise a strong and adaptable macrophage-toolkit in the ongoing fight against cancer and by understanding their significance, we may unlock the full potential of these immune cells in cancer therapy. [ABSTRACT FROM AUTHOR]

Tumour immune microenvironment (TIME) plays an indispensable role in tumour progression, and tumour‐associated macrophages (TAMs) are the most abundant immune cells in TIME. Non‐apoptotic regulated cell death (RCD) can avoid the influence of tumour apoptosis resistance on anti‐tumour immune response. Specifically, autophagy, ferroptosis, pyroptosis and necroptosis mediate the crosstalk between TAMs and tumour cells in TIME, thus reprogram TIME and affect the progress of tumour. In addition, although some achievements have been made in immune checkpoint inhibitors (ICIs), there is still defect that ICIs are only effective for some people because non‐apoptotic RCD can bypass the apoptosis resistance of tumour. As a result, ICIs combined with targeting non‐apoptotic RCD may be a promising solution. In this paper, the basic molecular mechanism of non‐apoptotic RCD, the way in which non‐apoptotic RCD mediates crosstalk between TAMs and tumour cells to reprogram TIME, and the latest research progress in targeting non‐apoptotic RCD and ICIs are reviewed. [ABSTRACT FROM AUTHOR]

Background and aims: In gastric cancer, the response rate of programmed cell death protein‐1 (PD‐1) inhibitor is far from satisfactory, indicating additional nonredundant pathways might hamper antitumour immunity. V‐domain immunoglobulin suppressor of T‐cell activation (VISTA) has been reported in several malignancies as a novel immune‐checkpoint. Nevertheless, the role of VISTA in gastric cancer still remains obscure. Our purpose is to explore the clinical significance and potential mechanism of VISTA in affecting gastric cancer patients' survival and immunotherapeutic responsiveness. Methods: Our study recruited eight independent cohorts with a total of 1403 gastric cancer patients. Immunohistochemistry, multiplex immunofluorescence, flow cytometry or intracellular flow cytometry, quantitative polymerase chain reaction, western blotting, fluorescence‐activated cell sorting, magnetic‐activated cell sorting, smart‐seq2, in vitro cell co‐culture and ex vivo tumour inhibition assays were applied to investigate the clinical significance and potential mechanism of VISTA in gastric cancer. Results: VISTA was predominantly expressed on tumour‐associated macrophages (TAMs), and indicated poor clinical outcomes and inferior immunotherapeutic responsiveness. VISTA+ TAMs showed a mixed phenotype. Co‐culture of TAMs and CD8+ T cells indicated that VISTA+ TAMs attenuated effective function of CD8+ T cells. Blockade of VISTA reprogrammed TAMs to a proinflammatory phenotype, reactivated CD8+ T cells and promoted apoptosis of tumour cells. Moreover, blockade of VISTA could also enhance the efficacy of PD‐1 inhibitor, suggesting that blockade of VISTA might synergise with PD‐1 inhibitor in gastric cancer. Conclusions: Our data revealed that VISTA was an immune‐checkpoint associated with immunotherapeutic resistance. Blockade of VISTA reprogrammed TAMs, promoted T‐cell‐mediated antitumour immunity, and enhanced efficacy of PD‐1 inhibitor, which might have implications in the treatment of gastric cancer. [ABSTRACT FROM AUTHOR]

As one of the deadliest cancers of the gastrointestinal tract, there has been limited improvement in long-term survival rates for gastric cancer (GC) in recent decades. The poor prognosis is attributed to difficulties in early detection, minimal opportunity for radical resection and resistance to chemotherapy and radiation. Macrophages are among the most abundant infiltrating immune cells in the GC stroma. These cells engage in crosstalk with cancer cells, adipocytes and other stromal cells to regulate metabolic, inflammatory and immune status, generating an immunosuppressive tumour microenvironment (TME) and ultimately promoting tumour initiation and progression. In this review, we summarise recent advances in our understanding of the origin of macrophages and their types and polarisation in cancer and provide an overview of the role of macrophages in GC carcinogenesis and development and their interaction with the GC immune microenvironment and flora. In addition, we explore the role of macrophages in preclinical and clinical trials on drug resistance and in treatment of GC to assess their potential therapeutic value in this disease. [ABSTRACT FROM AUTHOR]

Single cell transcriptomics and spatial profiling have revealed that tumor-associated macrophages comprise multiple subtypes (molecularly), and harbor different functions within the tumor microenvironment. This can depend on their spatial localization, tumor type, and disease stage. Six major macrophage clusters might exist in tumors including: inflammatory macrophages, angiogenic macrophages, immunoregulatory macrophages, interferon-mediated regulatory macrophages, immunostimulatory macrophages, and a CD169+ macrophage cluster whose distinct function remains an active area of investigation. Putative therapies aiming to specifically target these functional classes of macrophages are actively being tested preclinically and might begin to show clinical impact. The aim is to block the immunosuppressive, inflammatory, or angiogenic activities of these macrophages. A deeper understanding of the molecular, spatial, and functional heterogeneity of tumor-associated macrophages, within the local TME has driven the development of a new class of therapies directed against such diverse functional subsets. This is leading to impressive antitumor responses in preclinical models and is now being tested in patients when given as monotherapies or in combination with targeted and T cell-based immunotherapies. Macrophages represent a key component of the tumor microenvironment (TME) and are largely associated with poor prognosis. Therapeutic targeting of macrophages has historically focused on inhibiting their recruitment or reprogramming their phenotype from a protumor (M2-like) to an antitumor (M1-like) one. Unfortunately, this approach has not provided clinical breakthroughs that have changed practice. Emerging studies utilizing single-cell RNA-sequencing (scRNA-seq) and spatial transcriptomics have improved our understanding of the ontogeny, phenotype, and functional plasticity of macrophages. Overlaying the wealth of current information regarding macrophage molecular subtypes and functions has also identified novel therapeutic vulnerabilities that might drive better control of tumor-associated macrophages (TAMs). Here, we discuss the functional profiling of macrophages and provide an update of novel macrophage-targeted therapies in development. [ABSTRACT FROM AUTHOR]

Simple Summary: Approximately one in seven patients with classical Hodgkin lymphoma have refractory disease or relapse after standard front line chemotherapy. Prognostic biomarkers could help determine candidates for more effective treatment. The latest advances in research techniques have contributed to new insights in understanding the tumour microenvironment of Hodgkin lymphoma and the crucial role it plays in the disease course and response to treatment. Many new potential biomarkers are being explored in this setting and the results of these studies, as well as diagnostic methodologies, are presented in this review. Classical Hodgkin lymphoma (cHL) accounts for 0.4% of all new cancer cases globally. Despite high cure rates with standard treatment, approximately 15% of patients still experience relapsed or refractory (RR) disease, and many of these eventually die from lymphoma-related causes. Exciting new targeted agents such as anti-PD-1 agents and brentuximab vedotin have changed the therapeutic paradigm beyond chemotherapy and radiotherapy alone. Advances in understanding of the molecular biology are providing insights in the context of novel therapies. The signature histology of cHL requires the presence of scant malignant Hodgkin Reed–Sternberg cells (HRSCs) surrounded by a complex immune-rich tumour microenvironment (TME). The TME cellular composition strongly influences outcomes, yet knowledge of the precise characteristics of TME cells and their interactions with HRSCs is evolving. Novel high-throughput technologies and single-cell sequencing allow deeper analyses of the TME and mechanisms elicited by HRSCs to propagate growth and avoid immune response. In this review, we explore the evolution of knowledge on the prognostic role of immune cells within the TME and provide an up-to-date overview of emerging prognostic data on cHL from new technologies that are starting to unwind the complexity of the cHL TME and provide translational insights into how to improve therapy in the clinic. [ABSTRACT FROM AUTHOR]

Simple Summary: Hepatocellular carcinoma (HCC) is a highly lethal disease with an increasing incidence. Despite the advancements in diagnosis and recent therapeutic options, improving the prognosis of HCC patients remains challenging. One of the reasons of the unsatisfactory outcome of patients with HCC is the complex tumour microenvironment (TME), which is composed of immune and stromal cells, limiting effective treatments. Recent research has highlighted the importance of macrophages in the development and progression of HCC, opening new possibilities for therapy. This review focuses on the heterogeneity of tumour-associated macrophages (TAMs) in HCC, the mechanisms through which HCC tumour cells polarize macrophages, and the therapeutic targets that are currently being tested to explore novel therapies that can improve the prognosis and quality of life of HCC patients. Hepatocellular carcinoma (HCC) is a prevalent and aggressive cancer that comprises a complex tumour microenvironment (TME). Tumour-associated macrophages (TAMs) are one of the most abundant immune cells present in the TME, and play a key role both in the development and in the progression of HCC. Thus, TAM-based immunotherapy has been presented as a promising strategy to complement the currently available therapies for HCC treatment. Among the novel approaches focusing on TAMs, reprogramming their functional state has emerged as a promising option for targeting TAMs as an immunotherapy in combination with the currently available treatment options. Nevertheless, a further understanding of the immunobiology of TAMs is still required. This review synthesizes current insights into the heterogeneous nature of TAMs in HCC and describes the mechanisms behind their pro-tumoural polarization focusing the attention on their interaction with HCC cells. Furthermore, this review underscores the potential involvement of TAMs' reprogramming in HCC therapy and highlights the urgency of advancing our understanding of these cells within the dynamic landscape of HCC. [ABSTRACT FROM AUTHOR]

Numerous studies have shown the positive correlation between high levels of Pi and tumour progression. A critical goal of macrophage‐based cancer therapeutics is to reduce anti‐inflammatory macrophages (M2) and increase proinflammatory antitumour macrophages (M1). This study aimed to investigate the relationship between macrophage polarization and low‐Pi stress. First, the spatial populations of M2 and M1 macrophages in 22 HCC patient specimens were quantified and correlated with the local Pi concentration. The levels of M2 and M1 macrophage markers expressed in the peritumour area were higher than the intratumour levels, and the expression of M2 markers was positively correlated with Pi concentration. Next, monocytes differentiated from THP‐1 cells were polarized against different Pi concentrations to investigate the activation or silencing of the expression of p65, IκB‐α and STAT3 as well as their phosphorylation. Results showed that low‐Pi stress irreversibly repolarizes tumour‐associated macrophages (TAMs) towards the M1 phenotype by silencing stat6 and activating p65. Moreover, HepG‐2 and SMCC‐7721 cells were cultured in conditioned medium to investigate the innate anticancer immune effects on tumour progression. Both cancer cell lines showed reduced proliferation, migration and invasion, as epithelial–mesenchymal transition (EMT) was inactivated. In vivo therapeutic effect on the innate and adaptive immune processes was validated in a subcutaneous liver cancer model by the intratumoural injection of sevelamer. Tumour growth was significantly inhibited by the partial deprivation of intratumoural Pi as the tumour microenvironment under low‐Pi stress is more immunostimulatory. The anticancer immune response, activated by low‐Pi stress, suggests a new macrophage‐based immunotherapeutic modality. [ABSTRACT FROM AUTHOR]

M2 macrophages contribute to the progression of oesophageal squamous cell carcinoma (ESCC); however, the roles of M2 macrophages in early ESCC remain unclear. To clarify the biological mechanisms underlying the interaction between M2 macrophages and oesophageal epithelial cells in early‐stage ESCC, in vitro co‐culture assays between the immortalised oesophageal epithelial cell line Het‐1A and cytokine‐defined M2 macrophages were established. Co‐culture with M2 macrophages promoted the proliferation and migration of Het‐1A cells via the mTOR–p70S6K signalling pathway activated by YKL‐40, also known as chitinase 3‐like 1, and osteopontin (OPN) that were hypersecreted in the co‐culture supernatants. YKL‐40 and OPN promoted the above phenotypes of Het‐1A by making a complex with integrin β4 (β4). Furthermore, YKL‐40 and OPN promoted M2 polarisation, proliferation, and migration of macrophages. To validate the pathological and clinical significances of in vitro experimental results, immunohistochemistry of human early ESCC tissues obtained by endoscopic submucosal dissection (ESD) was performed, confirming the activation of the YKL‐40/OPN–β4–p70S6K axis in the tumour area. Moreover, epithelial expression of β4 and the number of epithelial and stromal infiltrating YKL‐40‐ and OPN‐positive cells correlated with the Lugol‐voiding lesions (LVLs), a well‐known predictor of the incidence of metachronous ESCC. Furthermore, the combination of high expression of β4 and LVLs or high numbers of epithelial and stromal infiltrating YKL‐40‐ and OPN‐positive immune cells could more clearly detect the incidence of metachronous ESCC than each of the parameters alone. Our results demonstrated that the YKL‐40/OPN–β4–p70S6K axis played important roles in early‐stage ESCC, and the high expression levels of β4 and high numbers of infiltrating YKL‐40‐ and OPN‐positive immune cells could be useful predictive parameters for the incidence of metachronous ESCC after ESD. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Tumour‐associated macrophages (TAMs) are highly plastic and are broadly grouped into two major functional states, namely the pro‐inflammatory M1‐type and the pro‐tumoural M2‐type. Conversion of the functional states of TAMs is regulated by various cytokines, chemokines growth factors and other secreted factors in the microenvironment. Dysregulated metabolism is a hallmark of cancer. Emerging evidence suggests that metabolism governs the TAM differentiation and functional conversation in support of tumour growth and metastasis. Aside from the altered metabolism reprogramming in TAMs, extracellular metabolites secreted by cancer, stromal and/or other cells within the tumour microenvironment have been found to regulate TAMs through passive competition for metabolite availability and direct regulation via receptor/transporter‐mediated signalling reaction. In this review, we focus on the regulatory roles of different metabolites and metabolic pathways in TAM conversion and function. We also discuss if the dysregulated metabolism in TAMs can be exploited for the development of new therapeutic strategies against cancer. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) initiated by hepatitis B virus (HBV) infection is a complicated process. MiR‐155 can alter the immune microenvironment to affect the host's anti‐infective ability. This study investigated the mechanism by which miR‐155 affects tumour‐associated macrophage (TAM) polarization at a molecular level, thus affecting the malignant progression of HBV+HCC. MiR‐155 and TAM‐related cytokine expression were analysed by qRT‐PCR. The distribution of TAMs was detected by immunohistochemistry. The effect of the aberrant miR‐155 expression on macrophage polarization was examined by flow cytometry. The targeted relationship was verified by dual‐luciferase assay, and the protein level of src homology 2 domain‐containing inositol polyphosphate 5‐phosphatase 1 (SHIP1) was detected by western blot. The proliferation of HCC cells was examined by CCK‐8 and colony formation assays. Invasion and migration of HCC cells were detected by transwell assay. In HBV+HCC tissues, miR‐155 was significantly highly expressed and the number of CD206‐positive TAM (CD206+ TAM) and CD68‐positive TAM (CD68+ TAM) were higher than those in HBV−HCC tissues. In addition, miR‐155 overexpression significantly promoted M2‐type macrophage polarization, whilst miR‐155 silencing expression significantly promoted M1‐type macrophage polarization. Besides, the miR‐155/SHIP1 axis accelerated HCC cell invasion, proliferation and migration by inducing M2‐type macrophage polarization. MiR‐155 accelerates HCC cell proliferation, migration and invasion by targeting SHIP1 expression and inducing macrophage M2 polarization. This finding provides new insights into the development of novel therapeutic strategies for combatting HBV+HCC and a new reference for exploring anti‐tumour immunotherapy. [ABSTRACT FROM AUTHOR]

Background: DNMT1 has been shown to be highly expressed in a variety of cancers, including breast cancer. However, the mechanism is not very clear. Therefore, we aim to reveal the mechanism of DNMT1 highly express in breast cancer. And we also want to explore the role of DNMT1 in tumour microenvironment promoting breast cancer progression. Results: In this study, we demonstrate that DNMT1 is overexpressed in breast cancer and that DNMT1 promotes breast cancer tumorigenesis and metastasis. We discovered that ZEB1 activates DNMT1 expression in breast cancer cells by recruiting P300 binding to the DNMT1 promoter and increasing its acetylation. Moreover, we revealed that tumour-associated macrophages (TAMs) increase DNMT1 expression in breast cancer cells via the IL-6-pSTAT3-ZEB1-DNMT1 axis in the tumour microenvironment. DNMT1 is required for TAM-mediated breast cancer cell migration. In addition, we confirmed that there were positive correlations among CD163 (TAM marker) expression, ZEB1 expression and DNMT1 expression in breast cancer patient tissues. Conclusions: Our study indicates that DNMT1 is necessary for TAM-mediated breast cancer metastasis. Decitabine (DAC), as a specific DNA methylation inhibitor and FDA-approved drug, is a bona fide drug for breast cancer treatment. [ABSTRACT FROM AUTHOR]

Background: The roles of different subtypes of tumour‐associated macrophages (TAMs) in predicting the prognosis of colorectal cancer (CRC) remain controversial. In this study, different subtypes of TAMs were investigated as prognostic and predictive biomarkers for CRC. Methods: Expressions of CD68, CD86 and CD163 were investigated by immunohistochemistry (IHC) and immunofluorescence (IF), and the correlation between the expression of CD86 and CD163 was calculated in colorectal cancer tissues from 64 CRC patients. Results: The results showed that high expressions of CD86+ and CD68+CD86+ TAMs as well as low expression of CD163+ and CD68+CD163+ TAMs were significantly associated with favourable overall survival (OS). The level of CD86 protein expression showed a negative correlation with CD163 protein expression. In addition, CD86 protein expression remarkably negatively correlated with tumour differentiation and tumour node metastasis (TNM) stage, while CD163 protein expression significantly positively correlated with tumour differentiation and tumour size. As an independent risk factor, high expression of CD86 TAMs had prominently favourable prognostic efficacy, while high expression of CD68+CD163+ TAMs had significantly poor prognostic efficacy. Conclusions: These results indicate that CD86+ and CD68+CD163+ TAMs as prognostic and predictive biomarkers for CRC. [ABSTRACT FROM AUTHOR]

Though circulating monocytes are the main source of tumour-associated macrophages (TAMs), the regulatory mechanisms of their recruitment to tumours and further differentiation remain unclear. In the present study, we observed a significant decrease in CXCR2 expression in classical circulating monocytes of patients with colorectal cancer (CRC), particularly those in the late TNM stage. The percentage of CXCR2+ monocytes was negatively associated with systemic inflammatory markers and positively associated with intratumoural immunocyte infiltration. The pro-inflammatory cytokine IFN-γ, which was overexpressed in patients with CRC, down-regulated CXCR2 expression of monocytes/TAMs by promoting GRK-2 expression. In vitro, inhibition of CXCR2 signalling in monocytes led to impaired chemotaxis to the tumour cell line supernatant and lower responsiveness to lipopolysaccharide (LPS) stimulation. Finally, monocytes from patients with CRC with decreased CXCR2 expression showed distinct phenotypes and functions after differentiating into CRC cell line-educated TAMs, including expression of co-stimulatory factors and secretion profile, than those from healthy controls. GRK-2 inhibitor altered the functional characteristics of TAMs. In summary, our findings suggest that CXCR2 expression on circulating monocytes reflects CRC stages and is an important factor determining TAM composition in the tumour microenvironment. [ABSTRACT FROM AUTHOR]

Tumour-associated macrophages (TAMs) constitute a plastic and heterogeneous cell population of the tumour microenvironment (TME) that can account for up to 50% of solid tumours. TAMs heterogeneous are associated with different cancer types and stages, different stimulation of bioactive molecules and different TME, which are crucial drivers of tumour progression, metastasis and resistance to therapy. In this context, understanding the sources and regulatory mechanisms of TAM heterogeneity and searching for novel therapies targeting TAM subpopulations are essential for future studies. In this review, we discuss emerging evidence highlighting the redefinition of TAM heterogeneity from three different directions: origins, phenotypes and functions. We notably focus on the causes and consequences of TAM heterogeneity which have implications for the evolution of therapeutic strategies that targeted the subpopulations of TAMs. [ABSTRACT FROM AUTHOR]

Nucleotide‐binding and oligomerization domain‐containing protein 2 (NOD2) was a member of the NOD‐like receptor family and played an important role in the innate immune response. Dysregulated NOD2 had been reported to contribute to tumorigenesis and progression. Here, we investigated that decreased NOD2 expressions could affect the phenotypic polarization of tumour‐associated macrophages and thus lead to the poor prognosis of lung adenocarcinoma patients. We clustered the patients by the single‐sample gene set enrichment analysis of tumour microenvironment and 13 prognostic differentially expressed immune‐related genes (PDEIRGs) were obtained based on prognostic analyses. After multiple assessments on the 13 PDEIRGs, NOD2 was considered to be the central immune gene and had a strong effect on suppressing tumour progression. Decreased NOD2 expression could be induced by cancer cells and lead to the phenotypic polarization of macrophages from protective M1 phenotype to pro‐tumorigenic M2 subtype which might be attributed to the down‐regulating of NF‐κB signalling pathway. This study draw attention to the role of inhibited innate immune function mediated by depletion of NOD2 in the TME. Our work also points to a potential strategy of NOD2‐mediated TAM‐targeted immunotherapy. [ABSTRACT FROM AUTHOR]

Glioblastomas (GBMs), a type of highly malignant brain tumour, contain various macrophages/microglia that are known as tumour-associated macrophages (TAMs). These TAMs have various roles in tumour biology. Histopathological aspects of TAMs and associations with tumour growth assessed by magnetic resonance imaging (MRI) are poorly described. In the present study, 16 patients that had sufficient tumour tissue and histological hallmarks were examined. The tumours were classified as either slow- (n=7) or fast-growing (n=9) based on the segmented tumour volumes from MRI scans taken at diagnosis and preoperatively. Using cluster of differentiation (CD)68 and ionized calcium-binding adaptor molecule 1 (Iba1) antibodies, the number, morphology, localization and distribution of TAMs in the GBM tissue were studied. TAMs were significantly more immunoreactive for anti-Iba1 (TAMsIba1) compared with anti-CD68 (TAMsCD68; P<0.001). In central tumour areas and around vessels in the infiltration zone there were more TAMsCD68 in slow-growing tumours (P=0.003 and P=0.025, respectively). Central tumour areas contained more TAMs compared with the infiltration zone (P=0.001 for TAMsCD68 and P<0.001 for TAMsIba1). The majority of TAMs exhibited a ramified phenotype in the infiltration zone, whereas central TAMs were mostly amoeboid. TAMs were present in high numbers in most regions of the tumour, whereas there were few in necrotic areas. In conclusion, the present study demonstrated and confirmed that the high numbers of TAMs in GBMs assume a range of morphologies consistent with various activation states, and that slow-growing GBMs seem to contain a TAM-population different to their fast-growing counterparts. [ABSTRACT FROM AUTHOR]