Search

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.

Lymphatic remodelling in the hypoxic tumour microenvironment (TME) is critically involved in the metastasis of cervical squamous cell carcinoma (CSCC); however, its underlying mechanisms remain unclear. Here, we uncovered a novel lymphatic pattern in the hypoxic TME, wherein lymphatic vessels (LVs) are encapsulated by tumour-associated macrophages (TAMs) to form an interconnected network. We describe these aggregates as LVEM (LVs encapsulated by TAMs) considering their advantageous metastatic capacity and active involvement in early lymph node metastasis (LNM). Mechanistic investigations revealed that interleukin-10 (IL-10) derived from hypoxic TAMs adjacent to LVs was a prerequisite for lymphangiogenesis and LVEM formation through its induction of Sp1 upregulation in lymphatic endothelial cells (LECs). Interestingly, Sp1high LECs promoted the transactivation of C–C motif chemokine ligand 1 (CCL1) to facilitate TAM and tumour cell recruitment, thereby forming a positive feedback loop to strengthen the LVEM formation. Knockdown of Sp1 or blockage of CCL1 abrogated LVEM and consequently attenuated LNM. Notably, CSCCnon-LNM is largely devoid of hypoxic TAMs and the resultant LVEM, which might explain its metastatic delay. These findings identify a novel and efficient metastasis-promoting lymphatic pattern in the hypoxic TME, which might provide new targets for anti-metastasis therapy and prognostic assessment. Supplementary Information The online version contains supplementary material available at 10.1007/s10456-020-09766-2.

Radiation therapy is an essential component of cancer care, contributing up to 40% of curative cancer treatment regimens. It creates DNA double-strand breaks causing cell death in highly replicating tumour cells. However, tumours can develop acquired resistance to therapy. The efficiency of radiation treatment has been increased by means of combining it with other approaches such as chemotherapy, molecule-targeted therapies and, in recent years, immunotherapy (IT). Cancer-cell apoptosis after radiation treatment causes an immunological reaction that contributes to eradicating the tumour via antigen presentation and subsequent T-cell activation. By contrast, radiotherapy also contributes to the formation of an immunosuppressive environment that hinders the efficacy of the therapy. Innate immune cells from myeloid and lymphoid origin show a very active role in both acquired resistance and antitumourigenic mechanisms. Therefore, many efforts are being made in order to reach a better understanding of the innate immunity reactions after radiation therapy (RT) and the design of new combinatorial IT strategies focused in these particular populations.

Since the theory of seed and soil was put forward, people have increasingly recognized that the tumour microenvironment is an important regulator of tumour progression and therapeutic response. Among them, M2-type macrophages (M2, as the major macrophage subtype in the tumour foci) have important promoting effects on various biological behaviours. Secreted protein acidic and rich in cysteine (SPARC) is an important anti-tumour component in the microenvironment of gastric cancer. This study shows that macrophages are an important source of the SPARC and that SPARC overexpression in M2 can reduce M2-mediated promoting proliferation, migration and anti-apoptotic effects in gastric cancer. Additionally, the AKT/mTOR signalling pathways may participate in the malignant process.

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.

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 Apcmin/+ 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 Apcmin/+ 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.

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.

SARI (suppressor of AP‐1, regulated by IFN) impaired tumour growth by promoting apoptosis and inhibiting cell proliferation and tumour angiogenesis in various cancers. However, the role of SARI in regulating tumour‐associated inflammation microenvironment is still elusive. In our study, the colitis‐dependent and ‐independent primary model were established in SARI deficiency mice and immuno‐reconstructive mice to investigate the functional role of SARI in regulating tumour‐associated inflammation microenvironment and primary colon cancer formation. The results have shown that SARI deficiency promotes colitis‐associated cancer (CAC) development only in the presence of colon inflammation. SARI inhibited tumour‐associated macrophages (TAM) infiltration in colon tissues, and SARI deficiency in bone marrow cells has no observed role in the promotion of intestinal tumorigenesis. Mechanism investigations indicated that SARI down‐regulates p‐STAT1 and STAT1 expression in colon cancer cells, following inhibition of MCP‐1/CCR2 axis activation during CAC development. Inverse correlations between SARI expression and macrophage infiltration, MCP‐1 expression and p‐STAT1 expression were also demonstrated in colon malignant tissues. Collectively, our results prove the inhibition role of SARI in colon cancer formation through regulating TAM infiltration.

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.

Simple Summary Colorectal cancer that has become metastatic continues to have a poor outlook. Many patients will undergo intensive chemotherapy, often with limited effects but many side effects. In other types of cancer, immunotherapy has shown to be effective by targeting the immune cells of the patient and restoring their function to fight off cancer. This review explores the up-to-date evidence for immunotherapy in metastatic colorectal cancer. We have discussed in which patients this treatment is effective, but also why this has not been effective in a large number of patients. By summarizing the key components of the immune cells within the proximity to the tumour and its areas of spread, we discuss how these components can be targeted. Areas of future research are also highlighted, which includes combining immunotherapy with current treatments, such as surgery, radiotherapy and chemotherapy as well as some recent advances from basic and translational studies that promises to improve outcomes in these patients. Abstract Metastatic colorectal cancer carries poor prognosis, and current therapeutic regimes convey limited improvements in survival and high rates of detrimental side effects in patients that may not stand to benefit. Immunotherapy has revolutionised cancer treatment by restoring antitumoural mechanisms. However, the efficacy in metastatic colorectal cancer, is limited. A literature search was performed using Pubmed (Medline), Web of Knowledge, and Embase. Search terms included combinations of immunotherapy and metastatic colorectal cancer, primarily focusing on clinical trials in humans. Analysis of these studies included status of MMR/MSS, presence of combination strategies, and disease control rate and median overall survival. Evidence shows that immune checkpoint inhibitors, such as anti-PD1 and anti-PD-L1, show efficacy in less than 10% of patients with microsatellite stable, MMR proficient colorectal cancer. In the small subset of patients with microsatellite unstable, MMR deficient cancers, response rates were 40–50%. Combination strategies with immunotherapy are under investigation but have not yet restored antitumoural mechanisms to permit durable disease regression. Immunotherapy provides the potential to offer additional strategies to established chemotherapeutic regimes in metastatic colorectal cancer. Further research needs to establish which adjuncts to immune checkpoint inhibition can unpick resistance, and better predict which patients are likely to respond to individualised therapies to not just improve response rates but to temper unwarranted side effects.

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.

Simple Summary Preclinical studies suggest that interactions between granulocyte colony-stimulating factor (G-CSF) and hypoxia-induced carbonic anhydrase IX regulate the trafficking and function of immune cells in the tumour microenvironment. We investigated the clinical significance of this crosstalk by analyzing the protein expression of G-CSF and macrophage markers by immunohistochemistry on a well-characterized tissue microarray series of invasive breast cancers. We report that high expression of G-CSF on breast carcinoma cells is linked with significantly improved survival in an important group of breast cancers that do not respond to hormonal therapy. These tumours were infiltrated by immune cells expressing biomarkers that can be targeted with immune checkpoint inhibitor drugs. In contrast, carbonic anhydrase IX expression was associated with unfavourable outcomes. Abstract Purpose: Granulocyte colony-stimulating factor (G-CSF) and hypoxia modulate the tumour immune microenvironment. In model systems, hypoxia-induced carbonic anhydrase IX (CAIX) has been associated with G-CSF and immune responses, including M2 polarization of macrophages. We investigated whether these associations exist in human breast cancer specimens, their relation to breast cancer subtypes, and clinical outcome. Methods: Using validated protocols and prespecified scoring methodology, G-CSF expression on carcinoma cells and CD163 expression on tumour-associated macrophages were assayed by immunohistochemistry and applied to a tissue microarray series of 2960 primary excision specimens linked to clinicopathologic, biomarker, and outcome data. Results: G-CSFhigh expression showed a significant positive association with ER negativity, HER2 positivity, presence of CD163+ M2 macrophages, and CAIX expression. In univariate analysis, G-CSFhigh phenotype was associated with improved survival in non-luminal cases, although the CAIX+ subset had a significantly adverse prognosis. A significant positive association was observed between immune checkpoint biomarkers on tumour-infiltrating lymphocytes and both G-CSF- and CAIX-expressing carcinoma cells. Immune checkpoint biomarkers correlated significantly with favourable prognosis in G-CSFhigh/non-luminal cases independent of standard clinicopathological features. Conclusions: The prognostic associations linking G-CSF to immune biomarkers and CAIX strongly support their immunomodulatory roles in the tumour microenvironment.

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.

Prostate cancer is a multifocal disease, but if and how individual prostate tumours influence each other is largely unknown. We therefore explored signs of direct or indirect tumour–tumour interactions in experimental models and patient samples. Low‐metastatic AT1 and high‐metastatic MatLyLu (MLL) Dunning rat prostate cancer cells were injected into separate lobes of the ventral prostate of immunocompetent rats. AT1 tumours growing in the same prostate as MLL tumours had increased tumour size and proliferation compared to AT1 tumours growing alone. In addition, the vasculature and macrophage density surrounding the AT1 tumours were increased by MLL tumour closeness. In patient prostatectomy samples, selected to contain an index tumour [tumour with the highest grade, International Society of Urological Pathology (ISUP) grade 1, 2, 3 or 4] and a low‐grade satellite tumour (ISUP grade 1), cell proliferation in low‐grade satellite tumours gradually increased with increasing histological grade of the index tumour. The density of blood vessels and CD68+ macrophages also increased around the low‐grade satellite tumour if a high‐grade index tumour was present. This suggests that high‐grade tumours, by changing the prostate microenvironment, may increase the aggressiveness of low‐grade lesions in the organ. Future studies are needed to explore the mechanisms behind tumour–tumour interactions and their clinical importance. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Bacillus Calmette-Guerin (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 {"type":"entrez-geo","attrs":{"text":"GSE9750","term_id":"9750"}}GSE9750 and {"type":"entrez-geo","attrs":{"text":"GSE7803","term_id":"7803"}}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.

Tumour-associated macrophages (TAMs) can be divided into M1 and M2 TAMs. M2 TAMs play an important role in tumor progression, promoting a pro-angiogenic and immunosuppressive signal in the tumor. Previous studies have shown a correlation between schistosomiasis and colorectal cancer (CRC), but the specific mechanism has not been clarified. The differences between schistosomal CRC and non-schistosomal CRC were explored by analysing the clinicopathological data and survival time prognosis of schistosomal CRC and non-schistosomal CRC patients. The underlying mechanisms leading to the differences were investigated via tissue pathology experiments. Here, we investigated whether TAMs play a role in schistosomal CRC, leading to different clinicopathological features and prognoses in schistosomal CRC and non-schistosomal CRC patients and whether TAMs have a regulatory effect on the development and prognosis of schistosomal CRC. We found that schistosomal CRC and non-schistosomal CRC patients differ in age, sex, TNM staging and prognosis survival. Applying a logistic regression analysis model, the results showed that age, sex, pathological T stage and combined schistosomiasis were independent risk factors for CRC. Prognostic analysis of follow-up patients with schistosomal CRC found that the T stage, M stage and M2 TAMs numbers were independent prognostic factors for overall survival (OS). TAMs are significantly higher in tissues of schistosomal CRC than in non-schistosomal CRC patients, especially M2 TAMs. Studies on schistosomal colorectal tissue found that the expression of M2 TAMs increased with the malignant process of intestinal tissue. In summary, schistosomal CRC and non-schistosomal CRC patients have different clinicopathological features and prognosis, schistosomiasis is a risk factor for CRC and M2 TAMs are independent prognostic factors for OS.

Pancreatic ductal adenocarcinoma (PDAC) is an incurable cancer resistant to traditional treatments, although a limited number of early-stage patients can undergo radical resection. Immunotherapies for the treatment of haematological malignancies as well as solid tumours have been substantially improved over the past decades, and impressive results have been obtained in recent preclinical and clinical trials. However, PDAC is likely the exception because of its unique tumour microenvironment (TME). In this review, we summarize the characteristics of the PDAC TME and focus on the network of various tumour-infiltrating immune cells, outlining the current advances in PDAC immunotherapy and addressing the effect of the PDAC TME on immunotherapy. This review further explores the combinations of different therapies used to enhance antitumour efficacy or reverse immunodeficiencies and describes optimizable immunotherapeutic strategies for PDAC. The concordant combination of various treatments, such as targeting cancer cells and the stroma, reversing suppressive immune reactions and enhancing antitumour reactivity, may be the most promising approach for the treatment of PDAC. Traditional treatments, especially chemotherapy, may also be optimized for individual patients to remodel the immunosuppressive microenvironment for enhanced therapy.

Beneficial effects of metformin on cancer risk and mortality have been proved by epidemiological and clinical studies, thus attracting research interest in elucidating the underlying mechanisms. Recently, tumour‐associated macrophages (TAMs) appeared to be implicated in metformin‐induced antitumour activities. However, how metformin inhibits TAMs‐induced tumour progression remains ill‐defined. Here, we report that metformin‐induced antitumour and anti‐angiogenic activities were not or only partially contributed by its direct inhibition of functions of tumour and endothelial cells. By skewing TAM polarization from M2‐ to M1‐like phenotype, metformin inhibited both tumour growth and angiogenesis. Depletion of TAMs by clodronate liposomes eliminated M2‐TAMs‐induced angiogenic promotion, while also abrogating M1‐TAMs‐mediated anti‐angiogenesis, thus promoting angiogenesis in tumours from metformin treatment mice. Further in vitro experiments using TAMs‐conditioned medium and a coculture system were performed, which demonstrated an inhibitory effect of metformin on endothelial sprouting and tumour cell proliferation promoted by M2‐polarized RAW264.7 macrophages. Based on these results, metformin‐induced inhibition of tumour growth and angiogenesis is greatly contributed by skewing of TAMs polarization in microenvironment, thus offering therapeutic opportunities for metformin in cancer treatment.

Background: Lurbinectedin is a novel anticancer agent currently undergoing late-stage (Phase II /III) clinical evaluation in platinum-resistant ovarian, BRCA1/2-mutated breast and small-cell lung cancer. Lurbinectedin is structurally related to trabectedin and it inhibits active transcription and the DNA repair machinery in tumour cells. Methods: In this study we investigated whether lurbinectedin has the ability to modulate the inflammatory microenvironment and the viability of myeloid cells in tumour-bearing mice. Results: Administration of lurbinectedin significantly and selectively decreased the number of circulating monocytes and, in tumour tissues, that of macrophages and vessels. Similar findings were observed when a lurbinectedin-resistant tumour variant was used, indicating a direct effect of lurbinectedin on the tumour microenviroment. In vitro, lurbinectedin induced caspase-8-dependent apoptosis of human purified monocytes, whereas at low doses it significantly inhibited the production of inflammatory/growth factors (CCL2, CXCL8 and VEGF) and dramatically impaired monocyte adhesion and migration ability. These findings were supported by the strong inhibition of genes of the Rho-GTPase family in lurbinectedin-treated monocytes. Conclusions: The results illustrate that lurbinectedin affects at multiple levels the inflammatory microenvironment by acting on the viability and functional activity of mononuclear phagocytes. These peculiar effects, combined with its intrinsic activity against cancer cells, make lurbinectedin a compound of particular interest in oncology.

Immature myeloid cells including myeloid‐derived suppressor cells (MDSCs) and tumour‐associated macrophages (TAMs) promote tumour growth and metastasis by facilitating tumour transformation and angiogenesis, as well as by suppressing antitumour effector immune responses. Therefore, strategies designed to reduce MDSCs and TAMs accumulation and their activities are potentially valuable therapeutic goals. In this study, we show that negative immune checkpoint molecule B7‐H3 is significantly overexpressed in human head and neck squamous cell carcinoma (HNSCC) specimen as compared with normal oral mucosa. Using immunocompetent transgenic HNSCC models, we observed that targeting inhibition of B7‐H3 reduced tumour size. Flow cytometry analysis revealed that targeting inhibition of B7‐H3 increases antitumour immune response by decreasing immunosuppressive cells and promoting cytotoxic T cell activation in both tumour microenvironment and macroenvironment. Our study provides direct in vivo evidence for a rationale for B7‐H3 blockade as a future therapeutic strategy to treat patients with HNSCC.

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 EC50 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.

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 ± 124.14μ2 and 186.73 ± 67.22μ2, 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.

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.

International audience; no abstract

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

SummaryAlternatively activated M2 macrophages play an important role in maintenance of tissue homeostasis by scavenging dead cells, cell debris and lipoprotein aggregates via phagocytosis. Using proteomics, we investigated how alternative activation, driven by IL-4, modulated the phagosomal proteome to control macrophage function. Our data indicate that alternative activation enhances homeostatic functions such as proteolysis, lipolysis and nutrient transport. Intriguingly, we identified the enhanced recruitment of the TAK1/MKK7/JNK signalling complex to phagosomes of IL-4 activated macrophages. The recruitment of this signalling complex was mediated through K63-polyubiquitylation of the macrophage scavenger receptor 1 (MSR1). Triggering of MSR1 in IL-4 activated macrophages leads to enhanced JNK activation, thereby promoting a phenotypic switch from an anti-inflammatory to a pro-inflammatory state, which was abolished upon MSR1 deletion or JNK inhibition. Moreover, MSR1 K63-polyubiquitylation correlated with the activation of JNK signalling in ovarian cancer tissue from human patients, suggesting that it may be relevant for macrophage phenotypic shift in vivo. Altogether, we identified that MSR1 signals through JNK via K63-polyubiquitylation and provide evidence for the receptor’s involvement in macrophage polarization.

Background: Myxoid liposarcoma (MLS) is the second most common subtype of liposarcoma, and metastasis occurs in up to one-third of cases. However, the mechanisms of invasion and metastasis remain unclear. Tumour-associated macrophages (TAMs) have important roles in tumour invasion, metastasis, and/or poor prognosis. The aim of this study was to investigate the relationship between TAMs and MLS. Methods: Using 78 primary MLS samples, the association between clinical prognosis and macrophage infiltration was evaluated by immunochemistry. The effects of macrophages on cell growth, cell motility, and invasion of MLS cell lines were investigated in vitro. In addition, clinicopathological factors were analysed to assess their prognostic implications in MLS. Results: Higher levels of CD68-positive macrophages were associated with poorer overall survival in MLS samples. Macrophage-conditioned medium enhanced MLS cell motility and invasion by activating epidermal growth factor receptor (EGFR), with the key ligand suggested to be heparin-binding EGF-like growth factor (HB-EGF). The phosphoinositide 3-kinase/Akt pathway was mostly involved in HB-EGF-induced cell motility and invasion of MLS. The expression of phosphorylated EGFR in MLS clinical samples was associated with macrophage infiltration. In addition, more significant macrophage infiltration was associated with poor prognosis even in multivariate analysis. Conclusions: Macrophage infiltration in MLS predicts poor prognosis, and the relationship between TAMs and MLS may be a new candidate for therapeutic targets of MLS.

Macrophages are conventionally classified into M1 and M2 subtypes according to their differentiation status and functional role in the immune system. However, accumulating evidence suggests that this binary classification system is insufficient to account for the remarkable plasticity of macrophages that gives rise to an immense diversity of subtypes. This diverse spectrum of macrophage subtypes play critical roles in various homeostatic and immune functions, but remain far from being fully characterised. In addition to their roles in normal physiological conditions, macrophages also play crucial roles in disease conditions such as cancer. In this review, we discuss the roles tumour-associated macrophages (TAMs) play in regulating different steps of tumour progression and metastasis, and the opportunities to target them in the quest for cancer prevention and treatment.

Background: The mechanisms of brain metastasis in renal cell cancer (RCC) patients are poorly understood. Chemokine and chemokine receptor expression may contribute to the predilection of RCC for brain metastasis by recruitment of monocytes/macrophages and by control or induction of vascular permeability of the blood–brain barrier. Methods: Frequency and patterns of brain metastasis were determined in 246 patients with metastatic RCC at autopsy. Expression of CXCR4, CCL7 (MCP-3), CCR2 and CD68+ tumour-associated macrophages (TAMs) were analysed in a separate series of 333 primary RCC and in 48 brain metastases using immunohistochemistry. Results: Fifteen percent of 246 patients with metastasising RCC had brain metastasis. High CXCR4 expression levels were found in primary RCC and brain metastases (85.7% and 91.7%, respectively). CCR2 (52.1%) and CCL7 expression (75%) in cancer cells of brain metastases was more frequent compared with primary tumours (15.5% and 16.7%, respectively; P

The skeleton is one of the most common sites of metastatic disease, affecting a large number of patients with advanced cancer. Although an increasing number of therapies are available for treatment of bone metastasis, this remains incurable, highlighting the need for better understanding of the underlying biology. Metastatic tumour spread to distant organs is a multistage process, involving not only cancer cells but also those of the surrounding host microenvironment. Tumour associated macrophages are multifunctional cells that contribute both to tumour development and response to treatment by regulating adaptive immunity, remodelling of stroma, mediating basement membrane breakdown and angiogenesis. Although direct evidence for a specific role of macrophages in bone metastasis is limited, their involvement in metastasis in general is well documented. In this review we provide an overview of role of macrophages in tumour progression, with particular emphasis on their potential role in bone metastasis.

Background: Successful immunotherapy will require alteration of the tumour microenvironment and/or decreased immune suppression. Tumour-associated macrophages (TAMs) are one major factor affecting tumour microenvironment. We hypothesised that altering TAM phenotype would augment the efficacy of immunotherapy. Methods: We and others have reported that 5,6-Dimethylxanthenone-4-acetic-acid (DMXAA, Vadimezan) has the ability to change TAM phenotypes, inducing a tumour microenvironment conducive to antitumour immune responses. We therefore combined DMXAA with active immunotherapies, and evaluated anti-tumour efficacy, immune cell phenotypes (flow cytometry), and tumour microenvironment (RT–PCR). Results: In several different murine models of immunotherapy for lung cancer, DMXAA-induced macrophage activation significantly augmented the therapeutic effects of immunotherapy. By increasing influx of neutrophils and anti-tumour (M1) macrophages to the tumour, DMXAA altered myeloid cell phenotypes, thus changing the intratumoural M2/non-M2 TAM immunoinhibitory ratio. It also altered the tumour microenvironment to be more pro-inflammatory. Modulating macrophages during immunotherapy resulted in increased numbers, activity, and antigen-specificity of intratumoural CD8+ T cells. Macrophage depletion reduced the effect of combining immunotherapy with macrophage activation, supporting the importance of TAMs in the combined effect. Conclusion: Modulating intratumoural macrophages dramatically augmented the effect of immunotherapy. Our observations suggest that addition of agents that activate TAMs to immunotherapy should be considered in future trials.

Thymidine phosphorylase is an angiogenic factor primarily expressed by cancer cells, stromal cells and tumour-associated macrophages in many human malignancies. These different types of thymidine phosphorylase-expressing cells, however, may have a distinct place in the angiogenic process, and this question was addressed in the present study. A series of 20 normal/hyperplastic prostate glands and 60 prostate carcinomas was investigated by immunohistochemistry, using specific antibodies for thymidine phosphorylase (P-GF.44C), tumour-associated macrophages (CD68), endothelium (CD31) and prostate specific antigen (ER-PR8). Thymidine phosphorylase expression by normal and hyperplastic epithelial or stromal cells occurred almost exclusively in the context of an intense lymphocytic infiltrate. High thymidine phosphorylase cancer cells and thymidine phosphorylase stromal cells expression was associated with high angiogenesis in prostate carcinomas, and this significant association was extended to include both tumour-associated macrophages and tumour-infiltrating lymphocytes. Thymidine phosphorylase expression and tumour-infiltrating lymphocytes were related inversely with prostate specific antigen reactivity. In conclusion, thymidine phosphorylase is a major angiogenic factor in prostate carcinomas and its up-regulation is likely to occur in the context of a host immune response. British Journal of Cancer (2002) 86, 1465–1471. DOI: 10.1038/sj/bjc/6600281 www.bjcancer.com © 2002 Cancer Research UK

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.

International audience; We previously reported a strong IL4I1 gene expression in primary mediastinal B-cell lymphoma (PMBL) and recently identified the protein as a secreted L-phenylalanine oxidase, physiologically expressed by myeloid cells, which inhibits T-cell proliferation in vitro. Here, we analyzed the pattern of IL4I1 protein expression in 315 human lymphoid and non-lymphoid malignancies. Besides PMBL, IL4I1 expression in tumors was very frequent. IL4I1 was detected in tumor-associated macrophages from most of the tumors and in neoplastic cells from follicular lymphoma, classic and nodular lymphocyte predominant Hodgkin lymphomas and small lymphocytic lymphoma, three of which are germinal center derived. IL4I1-positive tumor cells were also detected in rare cases of solid cancers, mainly mesothelioma. The enzymatic activity paralleled protein expression, suggesting that IL4I1 is functional in vivo. Depending on the tumor type, IL4I1 may impact on different infiltrating lymphocyte populations with consequences on tumor evolution. In the particular case of follicular lymphoma cells, which are susceptible to antitumor cytotoxic T cells killing but depend on interactions with local T helper cells for survival, a high level of IL4I1 expression seems associated with the absence of bone marrow involvement and a better outcome. These findings plead for an evaluation of IL4I1 as a prognosis factor.

Background: We aimed to characterize the localization and prognostic significance of tumour-associated macrophages (tams) in pancreatic ductal adenocarcinoma (pdac). Methods: Tumour specimens from 70 patients with pdac and inflammatory specimens from 13 patients with chronic pancreatitis were collected and analyzed for tam and M2 macrophage counts by immunohistochemistry. Correlations between tam distributions and clinicopathologic features were determined. Results: Immunohistochemical analysis showed that tam and M2 macrophage counts were higher in tissues from pdac than from chronic pancreatitis. The tams and M2 macrophages both infiltrated more into peritumour. Both macrophage types were positively associated with lymph node metastasis (p = 0.041 for tams in peritumour, p = 0.013 for M2 macrophages in introtumour, p = 0.006 for M2 macrophage in peritumour). In addition, abdominal pain was significantly more frequent in pdac patients with a greater tams count. The survival rate was much lower in patients having high infiltration by M2 macrophages than in those having low infiltration. Conclusions: The tam count might be associated with neural invasion in pdac, and M2 macrophages might play an important role in lymph node metastasis. Higher counts of either macrophage type were associated with increased risk of lymph node metastasis, and the M2 macrophage count could potentially be a marker for evaluating prognosis.

European journal of nuclear medicine and molecular imaging 42(9), 1430-1438 (2015). doi:10.1007/s00259-015-3084-8, Published by Springer-Verl., Heidelberg [u.a.]

Background:The prognostic impact of tumour-promoting immune cells in cervical cancer is unclear.Methods:Federation of Gynaecology and Obstetrics (FIGO) stage IB and IIA cervical cancer patients (N=101) were assessed for tumour-associated CD66b + neutrophils and CD163 + macrophages by immunohistochemistry in whole tissue sections using stereology. Results were correlated with previous results on tumour-infiltrating CD3 +, CD4 +, and CD8 + lymphocytes in the same cohort with recurrence-free survival (RFS) as end point.Results:The highest densities of CD66b + neutrophils and CD163 + macrophages were observed in the peritumoural compartment (median 53.1 cells mm-2 and 1.3% area fraction, respectively). Above median peritumoural and stromal CD66b + neutrophils and peritumoural CD163 + macrophages were significantly associated with short RFS. Multivariate analysis identified high peritumoural neutrophils (HR 2.27; 95% CI 1.09-4.75; P=0.03), low peritumoural CD8 + lymphocytes (HR 3.67; 95% CI 1.63-8.25; P=0.002), and lymph node metastases (HR 2.70; 95% CI 1.26-5.76; P=0.01) as independent prognostic factors for short RFS, whereas CD163 + macrophages were not significant. An index of combined intratumoral and peritumoral CD66b + neutrophils to CD8 + lymphocytes had good discriminatory power for each quartile with 5-year RFS of 92%, 80%, 62%, and 44% (P=0.001).Conclusion:Tumour-associated neutrophil count is an independent prognostic factor for short RFS in localised cervical cancer. Combining CD66b and CD8 may further improve prognostic stratification. These findings require prospective validation.

Tumour cells communicate with the cells of their microenvironment via a series of molecular and cellular interactions to aid their progression to a malignant state and ultimately their metastatic spread. Of the cells in the microenvironment with a key role in cancer development, tumour associated macrophages (TAMs) are among the most notable. Tumour cells release a range of chemokines, cytokines and growth factors to attract macrophages, and these in turn release numerous factors (e.g. VEGF, MMP-9 and EGF) that are implicated in invasion-promoting processes such as tumour cell growth, flicking of the angiogenic switch and immunosuppression. TAM density has been shown to correlate with poor prognosis in breast cancer, suggesting that these cells may represent a potential therapeutic target. However, there are currently no agents that specifically target TAM's available for clinical use. Bisphosphonates (BPs), such as zoledronic acid, are anti-resorptive agents approved for treatment of skeletal complication associated with metastatic breast cancer and prostate cancer. These agents act on osteoclasts, key cells in the bone microenvironment, to inhibit bone resorption. Over the past 30 years this has led to a great reduction in skeletal-related events (SRE's) in patients with advanced cancer and improved the morbidity associated with cancer-induced bone disease. However, there is now a growing body of evidence, both from in vitro and in vivo models, showing that zoledronic acid can also target tumour cells to increase apoptotic cell death and decrease proliferation, migration and invasion, and that this effect is significantly enhanced in combination with chemotherapy agents. Whether macrophages in the peripheral tumour microenvironment are exposed to sufficient levels of bisphosphonate to be affected is currently unknown. Macrophages belong to the same cell lineage as osteoclasts, the major target of BPs, and are highly phagocytic cells shown to be sensitive to bisphosphonates in model studies; In vitro, zoledronic acid causes increased apoptotic cell death; in vivo the drug has been shown to inhibit the production of pro-angiogenic factor MMP-9, as well as most recent evidence showing it can trigger the reversal of the TAMs phenotype from pro-tumoral M2 to tumoricidal M1. There is thus accumulating evidence supporting the hypothesis that effects on TAMs may contribute to the anti-tumour effect of bisphosphonates. This review will focus in detail on the role of tumour associated macrophages in breast cancer progression, the actions of bisphosphonates on macrophages in vitro and in tumour models in vivo and summarise the evidence supporting the potential for the targeting of tumour macrophages with bisphosphonates.

Interleukin (IL)-10 is expressed in many solid tumours and plays an ambiguous role in controlling cancer growth and metastasis. In order to determine whether IL-10 is involved in tumour progression and prognosis in nonsmall cell lung cancer (NSCLC), IL-10 expression in tumour cells and tumour-associated macrophages (TAMs) and its associations, if any, with clinicopathological features were investigated. Paraffin-embedded sections of surgical specimens obtained from 50 patients who had undergone surgery for NSCLC were immunostained with an antibody directed against IL-10. TAMs and tumour cells positive for IL-10 were subsequently quantified. IL-10-positive TAM percentage was higher in patients with stage II, III and IV NSCLC, and in those with lymph node metastases compared with patients with stage I NSCLC. High IL-10 expression by TAMs was a significant independent predictor of advanced tumour stage, and thus was associated with worse overall survival. Conversely, IL-10 expression by tumour cells did not differ between stages II, III and IV and stage I NSCLC. In conclusion, interleukin-10 expression by tumour-associated macrophages, but not by tumour cells, may play a role in the progression and prognosis of nonsmall cell lung cancer. These results may be useful in the development of novel approaches for anticancer treatments.

Tumour-associated macrophages, TAMs, play a pivotal role in tumour growth and metastasis by promoting tumour angiogenesis. Treatment with clodronate encapsulated in liposomes (clodrolip) efficiently depleted these phagocytic cells in the murine F9 teratocarcinoma and human A673 rhabdomyosarcoma mouse tumour models resulting in significant inhibition of tumour growth ranging from 75 to >92%, depending on therapy and schedule. Tumour inhibition was accompanied by a drastic reduction in blood vessel density in the tumour tissue. Vascular endothelial growth factor (VEGF) is one of the major inducers of tumour angiogenesis and is also required for macrophage recruitment. The strongest effects were observed with the combination therapy of clodrolip and a VEGF-neutralising antibody, whereas free clodronate was not significantly active. Immunohistologic evaluation of the tumours showed significant depletion of F4/80+ and MOMA-1+ and a less pronounced depletion of CD11b+ TAMs. Blood vessel staining (CD31) and quantification of the vessels as well as TAMs and tumour-associated dendritic cells (TADCs) in the A673 model showed reduction rates of 85 to >94%, even 9 days after the end of therapy. In addition, CD11c+ TADCs, which have been shown to potentially differentiate into endothelial-like cells upon stimulation by tumour released growth and differentiation factors, were similarly reduced by clodrolip or antibody treatment. These results validate clodrolip therapy in combination with angiogenesis inhibitors as a promising novel strategy for an indirect cancer therapy aimed at the haematopoietic precursor cells that stimulate tumour growth and dissemination and as a tool to study the role of macrophages and dendritic cells in tumorigenesis.

ResumenEl cáncer de próstata es la segunda causa de muerte por neoplasias en hombres. Así como en otros tumores sólidos, el microambiente tumoral está emergiendo como una pieza fundamental en la progresión de la enfermedad y como un potencial blanco terapéutico. Este microambiente contiene líneas celulares no malignas, entre ellas los macrófagos asociados a tumores (TAM), los cuales pueden controlar o favorecer el crecimiento tumoral. Por lo tanto, el conocimiento de la forma en que estas células interactúan con las células tumorales y el microambiente resulta fundamental en la comprensión del cáncer de próstata. La presente revisión se centra en el papel de los TAM en el microambiente del tumor prostático y en cómo estos pueden promover la progresión de dicha enfermedad.AbstractProstate cancer is the second leading cause of malignancy-associated death in males. As with other solid tumours, their microenvironment is emerging as a key player in the progression of the disease, and as a potential therapeutic target. This microenvironment contains non-malignant cell lines, among them tumour-associated macrophages (TAMs), which can control or promote tumour growth. Thus, knowledge on how these cells interact with tumour cells and with the microenvironment is central to the understanding of prostate cancer. This review focuses on the role of TAMs in tumour microenvironment of prostate cancer and how they can promote the progression of this disease.

Background Canine mammary carcinoma is the most common cancer in female dogs and is often fatal due to the development of distance metastasis. The microenvironment of a tumour often contains abundant infiltrates of macrophages called tumour-associated macrophages (TAMs). TAMs express an activated phenotype, termed M2, which sustains proliferation of cancer cells, and has been correlated with poor clinical outcomes in human cancer patients. Cancer cells themselves have been implicated in stimulating the conversion of macrophages to a TAM with an M2 phenotype. This process has yet to be fully elucidated. Here we investigate the interplay between cancer cells and macrophages in the context of canine mammary carcinoma. Results We show that cancer cells inhibit lipopolysaccharide (LPS)-induced macrophage activation. Further, we show that macrophage associated proteins, colony-stimulating factor (CSF)-1 and C-C motif ligand (CCL)-2, stimulate macrophages and are responsible for the effects of cancer cells on macrophages. We suggest the existence of a feedback loop between macrophages and cancer cells; while cancer cells influence the phenotype of the TAMs through CSF-1 and CCL2, the macrophages induce canine mammary cancer cells to upregulate their own expression of the receptors for CSF-1 and CCL2 and increase the cancer cellular metabolic activity. However, these cytokines in isolation induce a phenotypic state in macrophages that is between M1 and M2 phenotypes. Conclusions Overall, our results demonstrate the extent to which canine mammary carcinoma cells influence the macrophage phenotype and the relevance of a feedback loop between these cells, involving CSF-1 and CCL2 as important mediators. Electronic supplementary material The online version of this article (doi:10.1186/s12917-015-0473-y) contains supplementary material, which is available to authorized users.