Tumour-associated macrophages as a prototypic type II polarised phagocyte population: role in tumour progression

Clinical significance of the induction of macrophage differentiation by the costimulatory molecule B7-H3 in human non-small cell lung cancer

B7-H3, a member of the B7 family of molecules, is expressed in certain types of human cancer and is important in tumor development and progression. Although several studies have reported that the expression of B7-H3 is correlated with poor outcomes in patients with cancer, its exact role in cancer remains unknown. In the present study, the expression levels of B7-H3 in the pathological specimens of 105 patients treated for non-small cell lung cancer (NSCLC) were examined by immunohistochemistry. A high expression level of B7-H3 was observed in 46.9% of the 105 NSCLC tissue specimens. These patients demonstrated a more advanced tumor grade and a shorter survival time. In addition, we also examined the levels of tumor-associated macrophages (TAMs) in NSCLC tissues and observed that the levels were positively correlated with the expression of B7-H3, and that higher levels of macrophages were associated with lower levels of infiltrating T cells and a shorter survival time. These results demonstrated that TAMs are important in the evasion of tumor immune surveillance in NSCLC. Furthermore, through knockdown of B7-H3 by RNA interference, we observed that soluble B7-H3 was capable of inducing macrophages to express higher levels of macrophage mannose receptor (MMR) and lower levels of human leukocyte antigen (HLA)-DR, as well as higher levels of interleukin-10 (IL-10) and lower levels of IL-1β in vitro. These observations are characteristic of an anti-inflammatory/reparatory (alternative/M2) phenotype. Therefore, our data suggests that B7-H3 proteins are involved in the progression of NSCLC by inducing the development of monocytes into anti-inflammatory cells.

The irradiated tumor microenvironment: role of tumor-associated macrophages in vascular recovery

Radiotherapy is an important modality used in the treatment of more than 50% of cancer patients in the US. However, despite sophisticated techniques for radiation delivery as well as the combination of radiation with chemotherapy, tumors can recur. Thus, any method of improving the local control of the primary tumor by radiotherapy would produce a major improvement in the curability of cancer patients. One of the challenges in the field is to understand how the tumor vasculature can regrow after radiation in order to support tumor recurrence, as it is unlikely that any of the endothelial cells within the tumor could survive the doses given in a typical radiotherapy regimen. There is now considerable evidence from both preclinical and clinical studies that the tumor vasculature can be restored following radiotherapy from an influx of circulating cells consisting primarily of bone marrow derived monocytes and macrophages. The radiation-induced influx of bone marrow derived cells (BMDCs) into tumors can be prevented through the blockade of various cytokine pathways and such strategies can inhibit tumor recurrence. However, the post-radiation interactions between surviving tumor cells, recruited immune cells, and the remaining stroma remain poorly defined. While prior studies have described the monocyte/macrophage inflammatory response within normal tissues and in the tumor microenvironment, less is known about this response with respect to a tumor after radiation therapy. The goal of this review is to summarize existing research studies to provide an understanding of how the myelomonocytic lineage may influence vascular recovery within the irradiated tumor microenvironment.

Tumor cell-macrophage interactions increase angiogenesis through secretion of EMMPRIN

Tumor macrophages are generally considered to be alternatively/M2 activated to induce secretion of pro-angiogenic factors such as VEGF and MMPs. EMMPRIN (CD147, basigin) is overexpressed in many tumor types, and has been shown to induce fibroblasts and endothelial cell expression of MMPs and VEGF. We first show that tumor cell interactions with macrophages resulted in increased expression of EMMPRIN and induction of MMP-9 and VEGF. Human A498 renal carcinoma or MCF-7 breast carcinoma cell lines were co-cultured with the U937 monocytic-like cell line in the presence of TNFα (1 ng/ml). Membranal EMMPRIN expression was increased in the co-cultures (by 3-4-folds, p < 0.01), as was the secretion of MMP-9 and VEGF (by 2-5-folds for both MMP-9 and VEGF, p < 0.01), relative to the single cultures with TNFα. Investigating the regulatory mechanisms, we show that EMMPRIN was post-translationally regulated by miR-146a, as no change was observed in the tumoral expression of EMMPRIN mRNA during co-culture, expression of miR-146a was increased and its neutralization by its antagomir inhibited EMMPRIN expression. The secretion of EMMPRIN was also enhanced (by 2-3-folds, p < 0.05, only in the A498 co-culture) via shedding off of the membranal protein by a serine protease that is yet to be identified, as demonstrated by the use of wide range protease inhibitors. Finally, soluble EMMPRIN enhanced monocytic secretion of MMP-9 and VEGF, as inhibition of its expression levels by neutralizing anti-EMMPRIN or siRNA in the tumor cells lead to subsequent decreased induction of these two pro-angiogenic proteins. These results reveal a mechanism whereby tumor cell-macrophage interactions promote angiogenesis via an EMMPRIN-mediated pathway.

Induction of M2-macrophages by tumour cells and tumour growth promotion by M2-macrophages: a quid pro quo in pancreatic cancer

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.

Altered protein prenylation in Sertoli cells is associated with adult infertility resulting from childhood mumps infection

Loss of GGPPS from childhood mumps infection or deletion in mice results in constitutively activated MAPK and NF-kB signaling that induces spermatogonium apoptosis, macrophage invasion into seminiferous tubules, and sterility.

Mumps commonly affects children 5–9 yr of age, and can lead to permanent adult sterility in certain cases. However, the etiology of this long-term effect remains unclear. Mumps infection results in progressive degeneration of the seminiferous epithelium and, occasionally, Sertoli cell–only syndrome. Thus, the remaining Sertoli cells may be critical to spermatogenesis recovery after orchitis healing. Here, we report that the protein farnesylation/geranylgeranylation balance is critical for patients’ fertility. The expression of geranylgeranyl diphosphate synthase 1 (GGPPS) was decreased due to elevated promoter methylation in the testes of infertile patients with mumps infection history. When we deleted GGPPS in mouse Sertoli cells, these cells remained intact, whereas the adjacent spermatogonia significantly decreased after the fifth postnatal day. The proinflammatory MAPK and NF-κB signaling pathways were constitutively activated in GGPPS^−/− Sertoli cells due to the enhanced farnesylation of H-Ras. GGPPS^−/− Sertoli cells secreted an array of cytokines to stimulate spermatogonia apoptosis, and chemokines to induce macrophage invasion into the seminiferous tubules. Invaded macrophages further blocked spermatogonia development, resulting in a long-term effect through to adulthood. Notably, this defect could be rescued by GGPP administration in EMCV-challenged mice. Our results suggest a novel mechanism by which mumps infection during childhood results in adult sterility.

Macrophages in T cell/histiocyte rich large B cell lymphoma strongly express metal-binding proteins and show a bi-activated phenotype

Abundant macrophage infiltration in tumors often correlates with a poor prognosis. T cell/histiocyte rich large B cell lymphoma (THRLBCL) is a distinct aggressive B cell lymphoma entity showing a high macrophage content. To further elucidate the role of tumor-associated macrophages in THRLBCL, we performed gene expression profiling of microdissected histiocyte subsets of THRLBCL, nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), Piringer lymphadenitis, sarcoidosis, nonspecific lymphadenitis and monocytes from peripheral blood. In a supervised principal component analysis, histiocytes from THRLBCL were most closely related to epithelioid cells from NLPHL, with both types of cells expressing genes related to proinflammatory and regulatory macrophage activity. Moreover, histiocytes from THRLBCL strongly expressed metal-binding proteins like MT2A, by which histiocytes of THRLBCL can be distinguished from the other histiocyte subsets investigated. Interestingly, the validation at the protein level showed a strong expression of TXN, CXCL9, MT2A and SOD2 not only in macrophages of THRLBCL but also in the tumor cells of NLPHL and classical Hodgkin lymphoma (cHL). Overall, the present findings indicate that macrophages in the microenvironment of THRLBCL have acquired a distinct gene expression pattern that is characterized by a mixed M1/M2 phenotype and a strong expression of several metal binding proteins. The microenvironments in NLPHL and THRLBCL appear to have a similar influence on the macrophage phenotype. The high expression of metal binding proteins in histiocytes of THRLBCL may be diagnostically useful, but a potential pathophysiological role remains to be identified.

Hydrazinocurcumin Encapsuled nanoparticles "re-educate" tumor-associated macrophages and exhibit anti-tumor effects on breast cancer following STAT3 suppression

Tumor-associated macrophages (TAMs) are essential cellular components within tumor microenvironment (TME). TAMs are educated by TME to transform to M2 polarized population, showing a M2-like phenotype, IL-10(high), IL-12(low), TGF-β(high). STAT3 signaling triggers crosstalk between tumor cells and TAMs, and is crucial for the regulation of malignant progression. In our study, legumain-targeting liposomal nanoparticles (NPs) encapsulating HC were employed to suppress STAT3 activity and "re-educate" TAMs, and to investigate the effects of suppression of tumor progression in vivo. The results showed that TAMs treated by HC encapsuled NPs could switch to M1-like phenotype, IL-10(low), IL-12(high), TGF-β(low), and the "re-educated" macrophages (M1-like macrophages) considerably demonstrated opposite effect of M2-like macrophages, especially the induction of 4T1 cells migration and invasion in vitro, and suppression of tumor growth, angiogenesis and metastasis in vivo. These data indicated that inhibition of STAT3 activity of TAMs by HC-NPs was able to reverse their phenotype and could regulate their crosstalk between tumor cells and TAMs in order to suppress tumor progression.

Spindle-shaped CD163+ rosetting macrophages replace CD4+ T-cells in HIV-related classical Hodgkin lymphoma

Combination antiretroviral therapy is highly effective in HIV infection, leading to decreased incidences of AIDS-defining neoplasms. However, HIV patients still have a 10-fold increased risk of developing classical Hodgkin lymphoma compared with the general population. As Hodgkin- and Reed-Sternberg cells represent only a minority in the tumor infiltrate, the aim of the present study was to characterize the microenvironment of HIV-related classical Hodgkin lymphoma and compare it with classical Hodgkin lymphoma cases of immunocompetent individuals. The major morphologic differences were the presence of necrotic foci and the absence of epithelioid cell formation in HIV-related Hodgkin lymphoma. We observed a significantly decreased number of CD4+ T-cells and a significantly increased number of CD163+ macrophages in HIV-related Hodgkin lymphoma. Cases exhibiting a 'sarcomatoid' pattern of the reactive infiltrate exhibited significantly greater numbers of macrophages, associating the 'sarcomatoid' pattern to the presence of spindle-shaped macrophages. Whereas, rosetting of CD4+ T-cells around Hodgkin- and Reed-Sternberg cells was frequently observed in classical Hodgkin lymphoma in immunocompetent persons; rosetting in a subset of HIV-related Hodgkin lymphoma cases appeared to involve cytoplasmic protrusions of spindle-shaped macrophages. HIV-related Hodgkin lymphoma, therefore, is characterized by unique morphologic features, which should be recognized by pathologists.

Osteopontin splice variants expressed by breast tumors regulate monocyte activation via MCP-1 and TGF-β1

Osteopontin (OPN), a multifunctional glycoprotein, has three transcripts that have distinct roles in tumors in vitro. Whether OPN transcripts have different functions in tumor processes in vivo is unclear. It has been reported that immune cell-derived OPN can promote tumor formation. We propose a hypothesis that tumor-derived OPN may facilitate tumor immune escape by affecting immune cell differentiation and function. In this study, we constructed lentiviral expression vectors of OPN transcripts and transfected them into the MCF-7 cell line. MCF-7 cells transfected with OPN transcripts were injected into the armpit of nude mice, and tumor growth was monitored. The results showed that all OPN transcripts promoted local tumor formation, but that there was no significant difference among transcripts. We also investigated the effect of the OPN expressed by tumor cells on monocyte differentiation by coculturing monocytes with tumor supernatant. We found OPN-c upregulated CD163 levels compared with OPN-a and OPN-b; however, none of the transcripts affected HLA-DR and CD206 levels. All OPN transcripts significantly inhibited TNF-α and enhanced IL-10 production by monocytes. Furthermore, we found that the overexpression of OPN transcripts significantly upregulated TGF-β1 and MCP-1 production by tumor cells. Using neutralizing antibody and recombinant cytokines, we found that OPN overexpressed by tumor cells regulates the production of TNF-α and IL-10 by monocytes partly via MCP-1 and TGF-β1, respectively. Collectively, our results show that OPN transcripts have no distinct role in breast cancer formation in vivo. We also demonstrate that OPN regulates the alternative activation of monocytes via TGF-β1 and MCP-1, which may represent an additional mechanism for tumor immune escape.

Multiple myeloma macrophages: pivotal players in the tumor microenvironment

Tumor microenvironment is essential for multiple myeloma (MM) growth, progression, and drug resistance through provision of survival signals and secretion of growth and proangiogenic factors. This paper examines the importance of macrophages within MM bone marrow (BM) microenvironment, referred to as MM-associated macrophages, as a potential niche component that supports tumor plasma cells. These macrophages are derived from peripheral blood monocytes recruited into the tumor. Upon activation by MM plasma cells and mesenchymal stromal cells, macrophages can release growth factors, proteolytic enzymes, cytokines, and inflammatory mediators that promote plasma cell growth and survival. Macrophages promote tumor progression through several mechanisms including angiogenesis, growth, and drug resistance. Indeed, these macrophages are essential for the induction of an angiogenic response through vasculogenic mimicry, and this ability proceeds in step with progression of the plasma cell tumors. Data suggest that macrophages play an important role in the biology and survival of patients with MM, and they may be a target for the MM antivascular management.

Role of macrophage polarization in tumor angiogenesis and vessel normalization: implications for new anticancer therapies

Angiogenesis, the formation of new capillary blood vessels from preexisting vasculature, is one of the hallmarks of cancer that is pivotal for tumor growth and metastasis. Tumor vessels are known to be abnormal, with typically aberrant, leaky and disordered vessels. Thus, the combination of angiogenesis inhibition and vessel normalization is a potential strategy for anticancer therapy. The solid tumor is composed of not only cancer cells, but also the nonmalignant resident stromal cells, such as bone-marrow-derived cells (BMDCs) and cancer-associated fibroblasts (CAFs). Tumor-associated macrophages (TAMs) are the most abundant cell components of BMDCs, which play a significant role in promoting tumor progression. Accumulating evidences from both patient biopsies and experimental animal models have shown that TAMs function in tumor angiogenesis and vessel abnormalization in a density- and phenotype-dependent manner. This chapter will discuss the evidence for the factors and signaling pathways that are involved in macrophage recruitment and polarization in the tumor microenvironment, and it summarizes the role and underlying molecular mechanisms of macrophage polarization in tumor angiogenesis and vessel normalization. In addition, an overview of the potential of targeting TAM polarization for anticancer therapy will be provided.

T-cell-independent antitumor effects of CD40 ligation

CD40 ligation has been shown to induce antitumor effects in mice and cancer patients. Most of the studies have focused on the ability of an agonistic anti-CD40 mAb to either directly kill CD40-positive tumor cells or activate T-cell immune responses. In this review the authors focus on the ability of CD40 ligation to activate antitumor effector mechanisms of the cells of innate immunity such as macrophages and NK cells.

Importance of chemokine (CC-motif) ligand 2 in breast cancer

Breast cancer is the leading cause of cancer-related death in women in the United States. Chemokine (CC-motif) ligand 2 (CCL2), an inflammatory cytokine and chemokine, is highly expressed within the tumor and stromal cell populations and has been associated with enhanced tumorigenesis. In breast cancer patients, CCL2 has been correlated with high tumor grade and has been shown to have significant prognostic value for relapse-free survival. CCL2 likely exerts its pro-tumorigenic effects through recruitment of tumor-associated macrophages (TAMs); TAMs promote a tumorigenic microenvironment through the induction of growth enhancers, angiogenic factors and inflammatory mediators. CCL2 may also stimulate angiogenesis independently of TAM recruitment as it is closely associated with several endothelial cell growth factors. Additionally, CCL2 has been implicated in several processes leading to metastatic establishment including the development of bone metastasis. It has also been reported to directly upregulate pro-tumorigenic inflammatory mediators, including regulated upon activation, normal T cell expressed and secreted (RANTES) and tumor necrosis factor-alpha (TNF-α). While there is emerging support for a tumor promoting role of CCL2 in breast cancer, additional research is required before CCL2 can be decisively established as a prognostic factor and/or treatment target in breast cancer.

IL-33/ST2 axis in inflammation and immunopathology

Interleukin-33 (IL-33), a member of the IL-1 family of cytokines, binds to its plasma membrane receptor, heterodimeric complex consisted of membrane-bound ST2L and IL-1R accessory protein, inducing NFkB and MAPK activation. IL-33 exists as a nuclear precursor and may act as an alarmin, when it is released after cell damage or as negative regulator of NFκB gene transcription, when acts in an intracrine manner. ST2L is expressed on several immune cells: Th2 lymphocytes, NK, NKT and mast cells and on cells of myeloid lineage: monocytes, dendritic cells and granulocytes. IL-33/ST2 axis can promote both Th1 and Th2 immune responses depending on the type of activated cell and microenvironment and cytokine network in damaged tissue. We previously described and discuss here the important role of IL-33/ST2 axis in experimental models of type 1 diabetes, experimental autoimmune encephalomyelitis, fulminant hepatitis and breast cancer. We found that ST2 deletion enhance the development of T cell-mediated autoimmune disorders, EAE and diabetes mellitus type I. Disease development was accompanied by dominantly Th1/Th17 immune response but also higher IL-33 production, which suggest that IL-33 in receptor independent manner could promote the development of inflammatory autoreactive T cells. IL-33/ST2 axis has protective role in Con A hepatitis. ST2-deficient mice had more severe hepatitis with higher influx of inflammatory cells in liver and dominant Th1/Th17 systemic response. Pretreatment of mice with IL-33 prevented Con A-induced liver damage through prevention of apoptosis of hepatocytes and Th2 amplification. Deletion of IL-33/ST2 axis enhances cytotoxicity of NK cells, production of IFN-γ in these cells and systemic production of IFN-γ, IL-17 and TNF-α, which leads to attenuated tumor growth. IL-33 treatment of tumor-bearing mice suppresses activity of NK cells, dendritic cell maturation and enhances alternative activation of macrophages. In conclusion, we observed that IL-33 has attenuated anti-inflammatory effects in T cell-mediated responses and that both IL-33 and ST2 could be further explored as potential therapeutic targets in treatment of immune-mediated diseases.

Role of immune escape mechanisms in Hodgkin's lymphoma development and progression: a whole new world with therapeutic implications

Hodgkin's lymphoma represents one of the most frequent lymphoproliferative syndromes, especially in young population. Although HL is considered one of the most curable tumors, a sizeable fraction of patients recur after successful upfront treatment or, less commonly, are primarily resistant. This work tries to summarize the data on clinical, histological, pathological, and biological factors in HL, with special emphasis on the improvement of prognosis and their impact on therapeutical strategies. The recent advances in our understanding of HL biology and immunology show that infiltrated immune cells and cytokines in the tumoral microenvironment may play different functions that seem tightly related with clinical outcomes. Strategies aimed at interfering with the crosstalk between tumoral Reed-Sternberg cells and their cellular partners have been taken into account in the development of new immunotherapies that target different cell components of HL microenvironment. This new knowledge will probably translate into a change in the antineoplastic treatments in HL in the next future and hopefully will increase the curability rates of this disease.

Modulatory effects of the acid polysaccharide fraction from one of anamorph of Cordyceps sinensis on Ana-1 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps sinensis has been used as a precious herbal medicine for thousands of years in China. Its polysaccharide fraction has been confirmed possessing immunomodulatory function and we have reported the acid polysaccharide fraction (APSF), from an anamorph of C. sinensis, has stimulating activity on macrophages. The mechanism still needs to be further elucidated.

MATERIALS AND METHODS

In order to investigate the effects of APSF on macrophage's phenotypes, Ana-1 mouse macrophages were polarized to M2 phenotype by culturing the cells with culture supernatant of H22 cells. M2 phenotype was determined by measuring the expression of TNF-α and checking cell surface markers mannose receptor (MR) and scavenger receptor (SR). After cultured with H22 supernatant for 72 h, the TNF-α level of Ana-1 cells was decreased while the SR and MR expressions were up-regulated, suggesting that Ana-1 cells were polarized towards M2 macrophages. Then the effects of APSF on M2 macrophages were investigated by measuring mRNA levels of TNF-α, inducible nitric oxide synthase (iNOS), IL-12 and IL-10. Nuclear NF-κB was detected by Western blotting.

RESULTS

APSF treatment increased the expressions of TNF-α, IL-12 and iNOS, and reduced the expression of IL-10 of Ana-1 cells. Besides, the expressions of SR and MR were down-regulated by APSF. And the result of Western blotting showed NF-κB level was decreased in M2 macrophages and up-regulated after APSF treatment.

CONCLUSIONS

APSF may convert M2 macrophages to M1 phenotype by activating NF-κB pathway.

M2-polarized macrophages promote metastatic behavior of Lewis lung carcinoma cells by inducing vascular endothelial growth factor-C expression

OBJECTIVES

Tumor-associated macrophages that generally exhibit an alternatively activated (M2) phenotype have been linked to tumor progression and metastasis. However, the role of M2-polarized macrophages in the growth and metastasis of lung adenocarcinoma remains enigmatic. The aim of this study was to explore the effect of M2 macrophages on the proliferation and migration of mouse Lewis lung carcinoma cells and tumor-induced lymphangiogenesis.

METHODS

Trypan blue staining and the Transwell migration assay were performed to evaluate the effects of activated (M1 or M2) macrophages on the proliferation and migration of Lewis cells. Furthermore, vascular endothelial growth factor-C expression in Lewis cells and nitric oxide secretion from activated macrophages were detected during the co-culture assay. Following treatment with activated macrophages, lymphatic endothelial cells differentiated into capillary-like structures, and the induction of Lewis cell migration was assessed using a two-dimensional Matrigel-based assay.

RESULTS

In the co-culture Transwell system, the proliferation and migration of Lewis cells were promoted by M2 macrophages. Moreover, the co-culture significantly increased the expression of vascular endothelial growth factor-C by Lewis cells and reduced the secretion of nitric oxide from M2 macrophages, which subsequently led to the capillary morphogenesis of lymphatic endothelial cells. Interestingly, following co-culture with Lewis cells, the function of RAW264.7 cells was polarized toward that of the M2 macrophage phenotype.

CONCLUSION

M2-polarized macrophages promoted the metastatic behavior of Lewis cells by inducing vascular endothelial growth factor-C expression. Thus, the interruption of signaling between M2 macrophages and Lewis cells may be considered to be a new therapeutic strategy.

Claudin-1, claudin-2 and claudin-11 genes differentially associate with distinct types of anti-inflammatory macrophages in vitro and with parasite- and tumour-elicited macrophages in vivo

Macrophages altered by various Th2-associated and anti-inflammatory mediators--including IL-4 and IL-13 [inducing alternatively activated macrophages (AAMs)], IL-10 and TGF-β--were generically termed M2. However, markers that discriminate between AAMs and other M2 remain scarce. We previously described E-cadherin as a marker for AAMs, permitting these macrophages to fuse upon IL-4 stimulation. To identify novel potential contributors to macrophage fusion, we assessed the effect of IL-4 on other adherens and tight junction-associated components. We observed an induction of claudin-1 (Cldn1), Cldn2 and Cldn11 genes by IL-4 in different mouse macrophage populations. Extending our findings to other stimuli revealed Cldn1 as a mainly TGF-β-induced gene and showed that Cldn11 is predominantly associated with IL-4-induced AAMs. Cldn2 is upregulated by diverse stimuli and is not associated with a specific macrophage activation state in vitro. Interestingly, different claudin genes preferentially associate with M2 from distinct diseases. While Cldn11 is predominantly expressed in AAMs from helminth-infected mice, Cldn1 is the major macrophage claudin during chronic trypanosomiasis and Cldn2 dominates in tumour-associated macrophages. Overall, we identified Cldn1, Cldn2 and Cldn11 as genes that discriminate between diverse types of M2.

A multifunctional mesothelin antibody-tagged microparticle targets human mesotheliomas

Pleural and peritoneal mesotheliomas (MMs) are chemoresistant tumors with no effective therapeutic strategies. The authors first injected multifunctional, acid-prepared mesoporous spheres (APMS), microparticles functionalized with tetraethylene glycol oligomers, intraperitoneally into rodents. Biodistribution of APMS was observed in major organs, peritoneal lavage fluid (PLF), and urine of normal mice and rats. After verification of increased mesothelin in human mesotheliomas injected into severe combined immunodeficient (SCID) mice, APMS were then functionalized with an antibody to mesothelin (APMS-MB) or bovine serum albumin (BSA), a nonspecific protein control, and tumor targeting was evaluated by inductively coupled plasma mass spectrometry and multifluorescence confocal microscopy. Some APMS were initially cleared via the urine over a 24 hr period, and small amounts were observed in liver, spleen, and kidneys at 24 hr and 6 days. Targeting with APMS-MB increased APMS uptake in mesenteric tumors at 6 days. Approximately 10% to 12% of the initially injected amount was observed in both spheroid and mesenteric MM at this time point. The data suggest that localized delivery of APMS-MB into the peritoneal cavity after encapsulation of drugs, DNA, or macromolecules is a novel therapeutic approach for MM and other tumors (ovarian and pancreatic) that overexpress mesothelin.

Tumor-associated myeloid cells can be activated in vitro and in vivo to mediate antitumor effects

Tumor growth is often accompanied by the accumulation of myeloid cells in the tumors and lymphoid organs. These cells can suppress T cell immunity, thereby posing an obstacle to T cell-targeted cancer immunotherapy. In this study, we tested the possibility of activating tumor-associated myeloid cells to mediate antitumor effects. Using the peritoneal model of B16 melanoma, we show that peritoneal cells (PEC) in tumor-bearing mice (TBM) had reduced ability to secrete nitric oxide (NO) following in vitro stimulation with interferon gamma and lipopolysaccharide, as compared to PEC from control mice. This reduced function of PEC was accompanied by the influx of CD11b(+) Gr-1(+) myeloid cells to the peritoneal cavity. Nonadherent PEC were responsible for most of the NO production in TBM, whereas in naïve mice NO was mainly secreted by adherent CD11b(+) F4/80(+) macrophages. Sorted CD11b(+) Gr-1(-) monocytic and CD11b(+) Gr-1(+) granulocytic PEC from TBM had a reduced ability to secrete NO following in vitro stimulation (compared to naïve PEC), but effectively suppressed proliferation of tumor cells in vitro. In vivo, treatment of mice bearing established peritoneal B16 tumors with anti-CD40 and CpG resulted in activation of tumor-associated PEC, reduction in local tumor burden and prolongation of mouse survival. Inhibition of NO did not abrogate the antitumor effects of stimulated myeloid cells. Taken together, the results indicate that in tumor-bearing hosts, tumor-associated myeloid cells can be activated to mediate antitumor effects.

Immunology in the clinic review series; focus on cancer: tumour-associated macrophages: undisputed stars of the inflammatory tumour microenvironment

Mononuclear phagocytes are cells of the innate immunity that defend the host against harmful pathogens and heal tissues after injury. Contrary to expectations, in malignancies, tumour-associated macrophages (TAM) promote disease progression by supporting cancer cell survival, proliferation and invasion. TAM and related myeloid cells [Tie2(+) monocytes and myeloid-derived suppressor cells (MDSC)] also promote tumour angiogenesis and suppress adaptive immune responses. These divergent biological activities are mediated by macrophages/myeloid cells with distinct functional polarization, which are ultimately dictated by microenvironmental cues. Clinical and experimental evidence has shown that cancer tissues with high infiltration of TAM are associated with poor patient prognosis and resistance to therapies. Targeting of macrophages in tumours is considered a promising therapeutic strategy: depletion of TAM or their 're-education' as anti-tumour effectors is under clinical investigation and will hopefully contribute to the success of conventional anti-cancer treatments.

Decoy receptor 3 enhances tumor progression via induction of tumor-associated macrophages

Tumor-associated macrophages (TAMs) are the major component of tumor-infiltrating leukocytes. TAMs are heterogeneous, with distinct phenotypes influenced by the microenvironment surrounding tumor tissues. Decoy receptor 3 (DcR3), a member of the TNFR superfamily, is overexpressed in tumor cells and is capable of modulating host immunity as either a neutralizing decoy receptor or an effector molecule. Upregulation of DcR3 has been observed to correlate with a poor prognosis in various cancers. However, the mechanisms underlying the DcR3-mediated tumor-promoting effect remain unclear. We previously demonstrated that DcR3 modulates macrophage activation toward an M2-like phenotype in vitro and that DcR3 downregulates MHC class II expression in TAMs via epigenetic control. To investigate whether DcR3 promotes tumor growth, CT26-DcR3 stable transfectants were established. Compared with the vector control clone, DcR3-transfectants grew faster and resulted in TAM infiltration. We further generated CD68 promoter-driven DcR3 transgenic (Tg) mice to investigate tumor growth in vivo. Compared with wild-type mice, macrophages isolated from DcR3-Tg mice displayed higher levels of IL-10, IL-1ra, Ym1, and arginase activity, whereas the expression of IL-12, TNF-α, IL-6, NO, and MHC class II was downregulated. Significantly enhanced tumor growth and spreading were observed in DcR3-Tg mice, and the enhanced tumor growth was abolished by arginase inhibitor N-ω-hydroxy-l-norarginine and histone deacetylase inhibitor sodium valproate. These results indicated that induction of TAMs is an important mechanism for DcR3-mediated tumor progression. Our findings also suggest that targeting DcR3 might help in the development of novel treatment strategies for tumors with high DcR3 expression.

Targeting of the innate immunity/inflammation as complementary anti-tumor therapies

Different types of cancer take advantage of inflammatory components to improve their life-span in the organs. A sustenance of growth factors and cytokines (e.g. interleukin (IL)-1, tumor necrosis factor, IL-6, vascular endothelial growth factor) supports malignant cell progression and contributes to suppress the body immune defense. Strategies to modulate the host micro-environment offer new approaches for anti-cancer therapies. For these reasons new molecules with anti-tumor and anti-inflammatory features (e.g. trabectedin) are looked at with new eyes in the light of the crucial link between inflammation and cancer.

What can ecology teach us about cancer?

In 2008, Pienta et al. (Transl Oncol. 2008;1:158-164) introduced the term ecological therapy for cancer treatment and, in particular, emphasized that destruction of the tumor microenvironment would be more effective than just killing the cells that inhabit it. Proposed here is an expansion on the idea of ecological therapy of cancer, incorporating 1) literature on species invasion, i.e., a right cancerous clone needs to be at the right place at the right time to actually invade its environment, and 2) the literature on niche construction, that is, the idea that once a tumor is formed, cancer cells they modify their microenvironment (niche construction) by changing pH through glycolysis, secreting growth factors and recruiting tumor-associated macrophages to promote cell growth, activating fibroblasts, evading predation from immune system, making the cancer that much more difficult to eradicate. Paleontological literature suggests that the largestmass extinctions occurred when environmental stress that would weaken the population was coupled with some pulse destructive event that caused extensive mortality. To have the same effect on cells in the tumor, rather than, or at least in addition to, killing the cells, one would also need to target the niche that they created for themselves.

Origin and Functions of Tumor-Associated Myeloid Cells (TAMCs)

The construction of an inflammatory microenvironment provides the fuel for cancer development and progression. Hence, solid tumors promote the expansion and the recruitment of leukocyte populations, among which tumor-associated myeloid cells (TAMCs) represent a paradigm for cancer-promoting inflammation. TAMCs group heterogeneous phagocytic populations stemming from a common myeloid progenitor (CMP), that orchestrate various aspects of cancer, including: diversion and skewing of adaptive responses; immunosuppression; cell growth; angiogenesis; matrix deposition and remodelling; construction of a metastatic niche and actual metastasis. Several evidence indicate that TAMCs show plasticity and/or functional heterogeneity, suggesting that tumour-derived factors promote their functional "reprogramming" towards protumoral activities. While recent studies have attempted to address the role of microenvironment signals, the interplay between cancer cells, innate and adaptive immunity is now emerging as a crucial step of the TAMCs reprogramming. Here we discuss the evidence for the differentiation of TAMCs during the course of tumor progression and the molecular mechanisms that regulate such event.

TLR signaling-mediated differential histone modification at IL-10 and IL-12 promoter region leads to functional impairments in tumor-associated macrophages

Tumor-associated macrophages (TAM) are severely compromised for the induction of proinflammatory mediators following toll-like receptor (TLR) activation. Here, we reported that the defective TLR response in TAM was due to the malfunctioning of the myeloid differentiation primary response gene 88 (MyD88)-dependent signaling cascade in concert with downregulation of tumor necrosis factor receptor-associated factor (TRAF) 6 and interleukin-1 receptor-associated kinase (IRAK) 1. However, the expression of toll-interleukin1 receptor domain-containing adapter-inducing interferon beta (TRIF) and TRAF 3, which act via the TRIF-dependent pathway of TLR signaling, were found to be unaffected in TAM. Although, TRIF-mediated signal inducers, lipopolysaccharide or poly (I:C), induced high level of extracellular signal-regulated kinase (ERK)-1/2 mitogen-activated protein kinase (MAPK) phosphorylation, but they were failed to induce significant p38MAPK phosphorylation in TAM. Consequently, ERK-1/2-dependent histone phosphorylation at the IL-10 promoter elicited enhanced interleukin (IL)-10 production by TAM. Whereas, the lack of transcription favorable histone phosphorylation at the IL-12 promoter was accompanied with a very low amount of IL-12 expression in TAM. Moreover, ERK-1/2 MAPK activation resulted in enhanced IRAK M induction in TAM, a specific inhibitor of MyD88 pathway. Therefore, for the first time, we decipher an unexplored TLR signaling in TAM where ERK-1/2 activation in a MyD88-independent pathway results in transcription favorable histone modification at the IL-10 promoter region to enhance IL-10-mediated immunosuppression. Additionally, by enhancing IRAK M induction, it also polarizes TAM toward a more immunosuppressive form.

IL-6 and leukemia-inhibitory factor are involved in the generation of tumor-associated macrophage: regulation by IFN-γ

Tumor-associated macrophages (TAMs), the most abundant immunosuppressive myeloid cells in the tumor microenvironment, exhibit an IL-10(high)IL-12(low) profile called M2, opposite to the immunostimulatory M1. We reported that ovarian cancer ascites switched monocyte differentiation into TAM-like cells that exhibit most phenotypic and functional characteristics of TAMs, suggesting that soluble mediators are involved in the differentiation of monocytes into TAM-like cells. We observed that leukemia-inhibitory factor and IL-6, present at high concentrations in ovarian cancer ascites, skew monocyte differentiation into TAM-like cells by increasing macrophage colony-stimulating factor consumption. Moreover, we observed that IFN-γ switches established TAMs into immunostimulatory M1 cells and skews monocyte differentiation from TAM-like cells to M1s. In addition to revealing a new tumor-escape mechanism associated with TAM generation via leukemia-inhibitory factor and IL-6, these findings offer novel therapeutic perspectives to subvert TAM-induced immunosuppression and to improve antitumor immunotherapy efficacy.

Chemokines: key players in cancer progression and metastasis

Instructed cell migration is a fundamental component of various biological systems and is critical to the pathogenesis of many diseases including cancer. Role of chemokines in providing navigational cues to migrating cancer cells bearing specific receptors is well established. However, functional mechanisms of chemokine are not well implicit, which is crucial for designing new therapeutics to control tumor growth and metastasis. Multiple functions and mode of actions have been advocated for chemokines and their receptors in the progression of primary and secondary tumors. In this review, we have discussed current advances in understanding the role of the chemokines and their corresponding receptor in tumor progression and metastasis.

T cells contribute to tumor progression by favoring pro-tumoral properties of intra-tumoral myeloid cells in a mouse model for spontaneous melanoma

Tumors affect myelopoeisis and induce the expansion of myeloid cells with immunosuppressive activity. In the MT/ret model of spontaneous metastatic melanoma, myeloid cells are the most abundant tumor infiltrating hematopoietic population and their proportion is highest in the most aggressive cutaneous metastasis. Our data suggest that the tumor microenvironment favors polarization of myeloid cells into type 2 cells characterized by F4/80 expression, a weak capacity to secrete IL-12 and a high production of arginase. Myeloid cells from tumor and spleen of MT/ret mice inhibit T cell proliferation and IFNγ secretion. Interestingly, T cells play a role in type 2 polarization of myeloid cells. Indeed, intra-tumoral myeloid cells from MT/ret mice lacking T cells are not only less suppressive towards T cells than corresponding cells from wild-type MT/ret mice, but they also inhibit more efficiently melanoma cell proliferation. Thus, our data support the existence of a vicious circle, in which T cells may favor cancer development by establishing an environment that is likely to skew myeloid cell immunity toward a tumor promoting response that, in turn, suppresses immune effector cell functions.

Tumor-associated macrophages in breast cancer as potential biomarkers for new treatments and diagnostics

While several inflammatory cell types participate in cancer development, macrophages specifically play a key role in breast cancer, where they appear to be part of the pathogenesis of high-grade tumors. Tumor-associated macrophages (TAMs) produce factors that promote angiogenesis, remodel tissue and dampen the immune response to tumors. Specific macrophage types contribute to increased metastases in animal models, while human studies show an association between TAMs and tumors with poor prognostic features. Macrophages display a spectrum of phenotypic states, with the tumor microenvironment skewing TAMs towards a 'nonclassical' activation state, known as the M2, or wound healing/regulatory state. These TAMs are found in high-risk breast cancers, making them an important therapeutic target to explore. Improved techniques for identifying TAMs should translate into clinical applications for prognosis and treatment.

Nuclear expression of N-myc downstream regulated gene 1/Ca(2+)-associated protein 43 is closely correlated with tumor angiogenesis and poor survival in patients with gastric cancer

Expression of N-myc downstream regulated gene 1 (NDRG1)/Ca(2+)-associated protein 43 (Cap43) in cancer cells is a predictive marker of good or poor prognosis depending on tumor type. In this study, we examined whether NDRG1/Cap43 is a marker of good or poor prognosis in gastric cancer patients, and whether it is associated with tumor stromal responses, including angiogenesis and macrophage infiltration. The expression levels of NDRG1/Cap43, the number of CD68-positive macrophages and the CD34-positive microvessel density were analyzed by immunohistochemistry in 129 gastric cancer patients, including 65 with the intestinal type and 64 with the diffuse type. The expression of NDRG1/Cap43 in the nucleus and the membrane was evaluated. Nuclear NDRG1/Cap43 expression was found in 20/65 (30.8%) patients with the intestinal type and in 9/64 (14.1%) patients with the diffuse type of gastric cancer. Nuclear NDRG1/Cap43 expression was significantly associated with pathological stage in the intestinal type (P=0.002), but not in the diffuse type (P=0.039). Nuclear NDRG1/Cap43 expression was also closely associated with infiltrating macrophages (P=0.001) and tumor angiogenesis (P=0.001) in the intestinal type. Furthermore, nuclear NDRG1/Cap43 expression was associated with poor prognosis in both the intestinal (P=0.001) and the diffuse types of gastric cancer (P=0.047). By contrast, membranous NDRG1/Cap43 expression was not associated with the overall survival of gastric cancer patients with either the intestinal or diffuse type of gastric cancer. The expression of NDRG1/Cap43 in the nucleus may be a predictive biomarker for malignant progression in the intestinal type of gastric cancer, preferable to the expression of NDRG1/Cap43 in the membrane.

Tumor-associated macrophages as targets for tumor immunotherapy

Restoration of one of the major physiological functions of the body's immune response, the rejection of malignant cells, is a promising yet challenging task for cancer therapy. Prinicipally, immunotherapeutic approaches make use of cells of the adaptive immune system, since antigen-based tumor rejection might be the most specific approach. However, other immune cell populations, such as tumor-associated macrophages (TAMs), contribute significantly to protumor mechanisms elicited by a distorted immune response. In this review, we summarize the current knowledge about the pathology of TAMs and discuss potential therapeutic approaches to overcome TAM-mediated tumor promotion. Hereby, we focus on TAM phenotypes that were observed in the clinically relevant stages of cancer progression. The function of macrophages and other inflammatory cells in the onset of cancer has been discussed elsewhere.

Circulating CD14(+) CD16(+) monocyte levels predict tissue invasive character of cholangiocarcinoma

Chronic inflammation as a risk factor for cancer development is driven in part by monocyte/macrophages, which in many cancers exhibit pro-tumorigenic activity. In this study we identified elevation in CD14(+) CD16(+) , a minor blood monocyte subpopulation in cholangiocarcinoma (CCA) patients, compared to normal and biliary disease patient specimens. Tumour association was suggested by the observation that this elevated level decreased to normal after tumour resection. Moreover, the elevated level of CD14(+) CD16(+) monocytes in CCA patient blood correlated with degree of MAC387-positive (recent blood-derived macrophage migrant-specific marker) tumour-associated macrophage infiltration as determined by immunohistochemistry. These CD14(+) CD16(+) monocytes were suggested to enhance tumour progression as this subpopulation possesses (i) high expression of adhesion molecules (CD11c, CD49d, and CD54) and scavenger receptor (CD163), which enable them to adhere strongly to endothelial cells, and (ii) that peripheral blood monocytes from CCA patients express high levels of growth and angiogenic factor-related genes (epiregulin, VEGF-A and CXCL3). Elevation of peripheral CD14(+) CD16(+) monocyte levels was associated with features associated with poor prognosis CCA parameters (non-papillary type and high number of tissue macrophages). These data indicate that the CD14(+) CD16(+) monocytes from CCA patients with pro-tumorigenic characteristics may associate with rapid tumour progression and poor patient outcome. If confirmed in subsequent studies, the level of CD14(+) CD16(+) monocytes may serve as a marker for disease activity in CCA patients and serve as a target for pathogenic macrophage specific drug development.

M2-polarized tumor-associated macrophages are associated with poor prognoses resulting from accelerated lymphangiogenesis in lung adenocarcinoma

OBJECTIVES

Tumor-associated macrophages have been implicated in promoting tumor growth, progression and metastasis. However, the activated phenotype (M1 or M2) of tumor-associated macrophages remains unknown in solid tumors. Therefore, this study examined the density and prognostic significance of M2-polarized tumor-associated macrophages in lung adenocarcinoma.

METHODS

Tumor specimens from 65 lung adenocarcinoma patients were assessed by ELISA for Th1/Th2 cytokine concentrations. The activated phenotype (M1 or M2) of tumor-associated macrophages was determined utilizing immunofluorescence staining. Additionally, to evaluate lymphangiogenesis, peritumoral lymphatic microvessel density was measured using D2-40. The correlation between tumor-associated macrophage subtype and overall patient survival was analyzed using the Kaplan-Meier method and compared using the log-rank test.

RESULTS

A shift toward Th2 cytokine expression was detected within lung adenocarcinoma microenvironments. Approximately 79.71±16.27% of tumor-associated macrophages were M2 polarized; the remaining 20.35±5.31% were M1 polarized. The infiltration of M2-polarized macrophages was significantly associated with P-TNM staging and lymph node metastasis. The peritumoral lymphatic microvessel density was significantly higher in the high M2-polarized tumor-associated macrophage group than in the low M2-polarized tumor-associated macrophage group. A significant difference in overall patient survival was detected not only between patients with tumors with high and low macrophage counts but also between patients with tumors with high and low counts of M2-polarized macrophages.

CONCLUSION

Tumor-associated macrophages in lung adenocarcinoma have an M2-polarized subtype and are associated with poor prognoses, perhaps resulting from accelerated lymphangiogenesis and lymph node metastasis.

The tumor-immune microenvironment and response to radiation therapy

Chemotherapy and radiation therapy (RT) are standard therapeutic modalities for patients with cancer, including breast cancer. Historic studies examining tissue and cellular responses to RT have predominantly focused on damage caused to proliferating malignant cells leading to their death. However, there is increasing evidence that RT also leads to significant alterations in the tumor microenvironment, particularly with respect to effects on immune cells infiltrating tumors. This review focuses on tumor-associated immune cell responses following RT and discusses how immune responses may be modified to enhance durability and efficacy of RT.

Tumor infiltration by FcγRIII (CD16)+ myeloid cells is associated with improved survival in patients with colorectal carcinoma

The prognostic significance of macrophage and natural killer (NK) cell infiltration in colorectal carcinoma (CRC) microenvironment is unclear. We investigated the CRC innate inflammatory infiltrate in over 1,600 CRC using two independent tissue microarrays and immunohistochemistry. Survival time was assessed using the Kaplan-Meier method and Cox proportional hazards regression analysis in a multivariable setting. Spearman's rank correlation tested the association between macrophage and lymphocyte infiltration. The Basel study included over 1,400 CRCs. The level of CD16+ cell infiltration correlated with that of CD3+ and CD8+ lymphocytes but not with NK cell infiltration. Patients with high CD16+ cell infiltration (score 2) survived longer than patients with low (score 1) infiltration (p = 0.008), while no survival difference between patients with score 1 or 2 for CD56+ (p = 0.264) or CD57+ cell (p = 0.583) infiltration was detected. CD16+ infiltrate was associated with improved survival even after adjusting for known prognostic factors including pT, pN, grade, vascular invasion, tumor growth and age [(p = 0.001: HR (95% CI) = 0.71 (0.6-0.9)]. These effects were independent from CD8+ lymphocyte infiltration [(p = 0.036: HR (95% CI) = 0.81 (0.7-0.9)] and presence of metastases [(p = 0.002: HR (95% CI) = 0.43 (0.3-0.7)]. Phenotypic studies identified CD16+ as CD45+CD33+CD11b+CD11c+ but CD64- HLA-DR-myeloid cells. Beneficial effects of CD16+ cell infiltration were independently validated by a study carried out at the University of Athens confirming that patients with CD16 score 2 survived longer than patients with score 1 CRCs (p = 0.011). Thus, CD16+ cell infiltration represents a novel favorable prognostic factor in CRC.

Alternatively activated macrophage possess antitumor cytotoxicity that is induced by IL-4 and mediated by arginase-1

Earlier studies have shown that the adoptive transfer of Th2-polarized CD4 T cells can clear established tumors from mice in an antigen-specific manner. Although eosinophils were implicated in this process, the exact mechanism of tumor clearance and which immune effector cells were involved, remain to be defined. Consequently, experiments were undertaken to elucidate the mechanism of Th2-mediated destruction of B16-F1 melanoma cells by examining the in vitro antitumor activity of leukocytes within a type-2 inflammatory infiltrate. The experimental data show that activation of alternatively activated macrophages (aaMacs) within type-2 infiltrates by IL-4 or IL-13 can inhibit B16-F1 melanoma cell proliferation through a mechanism that is dependent on arginase-1 depletion of L-arginine within the tumor cell microenvironment. Interestingly, whilst at higher E:T ratios aaMac exhibited antitumor activity, at lower E:T ratios aaMacs were observed to enhance rather than inhibit B16-F1 melanoma cell growth. This highlights the fine balance between stimulating the antitumorigenic and protumorigenic properties of aaMacs in tumor immunotherapy protocols.

Immune cell location and function during post-natal mammary gland development

Post-natal mammary gland development requires complex interactions between the epithelial cells and various cell types within the stroma. Recent studies have illustrated the importance of immune cells and their mediators during the various stages of mammary gland development. However, the mechanisms by which these immune cells functionally contribute to mammary gland development are only beginning to be understood. This review provides an overview of the localization of immune cells within the mammary gland during the various stages of post-natal mammary gland development. Furthermore, recent studies are summarized that illustrate the mechanisms by which these cells are recruited to the mammary gland and their functional roles in mammary gland development.

Alternatively activated alveolar macrophages in pulmonary fibrosis-mediator production and intracellular signal transduction

Activated macrophages have been characterized as M1 and M2 according to their inflammatory response pattern. Here we analyzed the M2 marker expression and intracellular signal transduction in the course of cytokine-driven differentiation. We found elevated spontaneous production of the chemokines CCL17, CCL18 and CCL22 and increased expression of CD206 by alveolar macrophages from patients with lung fibrosis. Stimulation of normal human AM with Th2 cytokines IL-4 and/or IL-10 in vitro revealed IL-4 as the most powerful inducer of M2-phenotype in AM and monocytes. Importantly, IL-10 enhanced IL-4-induced expression of CCL18 and IL-1RA in a synergistic fashion. IL-4/IL-10 stimulation induces a strong activation of STAT3 in AM from fibrosis patients. These results suggest an important role for M2 polarized AM in the pathogenesis of pulmonary fibrosis and indicate that both IL-4 and IL-10 account for human AM phenotype shift to M2, as seen in patients with fibrotic interstitial lung diseases.

Obesity and gastrointestinal cancer

BACKGROUND

There is emerging evidence of a strong association between obesity and gastrointestinal cancer. This review summarizes the evidence from an epidemiological and pathophysiological perspective.

METHODS

Relevant medical literature was identified from searches of PubMed and references cited in appropriate articles were identified. Selection of articles was based on peer review, journal and relevance.

RESULTS

Numerous epidemiological studies consistently identified an increased risk of developing oesophageal adenocarcinoma and colorectal carcinoma in the obese. The association between obesity and other gastrointestinal malignancies was less robust. Sex seems important with respect to cancer risk. Adipose tissue, particularly viscerally located fat, is metabolically active and exerts systemic endocrine effects. Putative pathophysiological mechanisms linking obesity and carcinogenesis include the insulin-like growth factor axis, adipocytokines and sex steroids.

CONCLUSION

A better understanding of the mechanisms that link obesity and cancer may uncover targets for intervention. Tackling obesity may result in a reduction in the incidence in addition to mortality of certain cancers in future.

Fra-1 protooncogene regulates IL-6 expression in macrophages and promotes the generation of M2d macrophages

The tumor microenvironment (TME) plays a prominent role in the growth of tumor cells. As the major inflammatory component of the TME, M2d macrophages are educated by the TME such that they adopt an immunosuppressive role that promotes tumor metastasis and progression. Fra-1 forms activator protein-1 heterodimers with Jun partners and drives gene transcription. Fra-1 is thought to drastically induce tumorigenesis and progression. However, the functional role of Fra-1 in the generation of M2d macrophages is poorly understood to date. Here, we demonstrate that 4T1 mammary carcinoma cells, when co-cultured with RAW264.7 macrophage cells, skew the RAW264.7 macrophage cell differentiation into M2d macrophages. The 4T1 cells stimulate de novo overexpression of Fra-1 in RAW264.7 cells, and then Fra-1 binds to the interleukin 6 (IL-6) promoter to increase the production of the cytokine IL-6 in RAW264.7 cells. IL-6 acts in an autocrine fashion to skew RAW264.7 macrophage cell differentiation into M2d macrophages. These findings open new insights into how to reverse M2d macrophage-induced immune tolerance to improve the efficacy of immunotherapeutic approaches.

Macrophages in Langerhans cell histiocytosis are differentiated toward M2 phenotype: their possible involvement in pathological processes

Although numerous macrophages are found in the lesions of Langerhans cell histiocytosis (LCH), their activation phenotypes and their roles in the disease process have not been clarified. Paraffin-embedded LCH samples were examined on immunohistochemistry and it was found that CD163 can be used to distinguish infiltrated macrophages from neoplastic Langerhans cells (LC). The number of CD163-positve macrophages was positively correlated with the number of multinucleated giant cells (MGC), indicating that most MGC are derived from infiltrated macrophages. A significant number of CD163-positive macrophages were positive for interleukin (IL)-10 and phospho-signal transducer and activator of transcription-3 (pSTAT3), an IL-10-induced signal transduction molecule. This indicates that these macrophages are polarized to anti-inflammatory macrophages of M2 phenotype. Tumor-derived macrophage-colony-stimulating factor (M-CSF) was considered to responsible for inducing M2 differentiation of infiltrated macrophages. The number of CD163-positive macrophages in different cases of LCH varied, and interestingly the density of CD163-positive macrophages was inversely correlated with the Ki-67-positivity of LC. Although the underlying mechanism is not fully elucidated, macrophage-derived IL-10 was considered to be involved in the suppression of tumor cell proliferation via activation of STAT3.