The macrophage growth factor CSF-1 in mammary gland development and tumor progression

MYC regulates CSF1 expression via microRNA 17/20a to modulate tumor-associated macrophages in osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor of childhood. Approximately 20%-30% of OSs carry amplification of chromosome 8q24, which harbors the oncogene c-MYC and correlates with a poor prognosis. To understand the mechanisms that underlie the ability of MYC to alter both the tumor and its surrounding tumor microenvironment (TME), we generated and molecularly characterized an osteoblast-specific Cre-Lox-Stop-Lox-c-MycT58A p53fl/+ knockin genetically engineered mouse model (GEMM). Phenotypically, the Myc-knockin GEMM had rapid tumor development with a high incidence of metastasis. MYC-dependent gene signatures in our murine model demonstrated significant homology to the human hyperactivated MYC OS. We established that hyperactivation of MYC led to an immune-depleted TME in OS demonstrated by the reduced number of leukocytes, particularly macrophages. MYC hyperactivation led to the downregulation of macrophage colony-stimulating factor 1, through increased microRNA 17/20a expression, causing a reduction of macrophage population in the TME of OS. Furthermore, we developed cell lines from the GEMM tumors, including a degradation tag-MYC model system, which validated our MYC-dependent findings both in vitro and in vivo. Our studies utilized innovative and clinically relevant models to identify a potentially novel molecular mechanism through which MYC regulates the profile and function of the OS immune landscape.

Dual CSF1R inhibition and CD40 activation demonstrates anti-tumor activity in a 3D macrophage- HER2+ breast cancer spheroid model

The complex interaction between tumor-associated macrophages (TAMs) and tumor cells through soluble factors provides essential cues for breast cancer progression. TAMs-targeted therapies have shown promising clinical therapeutical potential against cancer progression. The molecular mechanisms underlying the response to TAMs-targeted therapies depends on complex dynamics of immune cross-talk and its understanding is still incomplete. In vitro models are helpful to decipher complex responses to combined immunotherapies. In this study, we established and characterized a 3D human macrophage-ER⁺ PR⁺ HER2⁺ breast cancer model, referred to as macrophage-tumor spheroid (MTS). Macrophages integrated within the MTS had a mixed M2/M1 phenotype, abrogated the anti-proliferative effect of trastuzumab on tumor cells, and responded to IFNγ with increased M1-like polarization. The targeted treatment of MTS with a combined CSF1R kinase inhibitor and an activating anti-CD40 antibody increased M2 over M1 phenotype (CD163⁺/CD86⁺ and CD206⁺/CD86⁺ ratio) in time, abrogated G2/M cell cycle phase transition of cancer cells, promoted the secretion of TNF-α and reduced cancer cell viability. In comparison, combined treatment in a 2D macrophage-cancer cell co-culture model reduced M2 over M1 phenotype and decreased cancer cell viability. Our work shows that this MTS model is responsive to TAMs-targeted therapies, and may be used to study the response of ER⁺ PR⁺ HER2⁺ breast cancer lines to novel TAM-targeting therapies.

The generation, activation, and polarization of monocyte-derived macrophages in human malignancies

Macrophages are immune cells that originate from embryogenesis or from the differentiation of monocytes. They can adopt numerous phenotypes depending on their origin, tissue distribution and in response to different stimuli and tissue environment. Thus, in vivo, macrophages are endowed with a continuum of phenotypes that are rarely strictly pro-inflammatory or anti-inflammatory and exhibit a broad expression profile that sweeps over the whole polarization spectrum. Schematically, three main macrophage subpopulations coexist in human tissues: naïve macrophages also called M0, pro-inflammatory macrophages referred as M1 macrophages, and anti-inflammatory macrophages also known as M2 macrophages. Naïve macrophages display phagocytic functions, recognize pathogenic agents, and rapidly undergo polarization towards pro or anti-inflammatory macrophages to acquire their full panel of functions. Pro-inflammatory macrophages are widely involved in inflammatory response, during which they exert anti-microbial and anti-tumoral functions. By contrast, anti-inflammatory macrophages are implicated in the resolution of inflammation, the phagocytosis of cell debris and tissue reparation following injuries. Macrophages also play important deleterious or beneficial roles in the initiation and progression of different pathophysiological settings including solid and hematopoietic cancers. A better understanding of the molecular mechanisms involved in the generation, activation and polarization of macrophages is a prerequisite for the development of new therapeutic strategies to modulate macrophages functions in pathological situations.

Crosstalk between extracellular vesicles and tumor-associated macrophage in the tumor microenvironment

In concert with hijacking key genes to drive tumor progression, cancer cells also have the unique ability to dynamically interact with host microenvironment and discreetly manipulate the surrounding stroma, also known as the tumor microenvironment (TME), to provide optimal conditions for tumor cells to thrive and evade host immunity. Complex cellular crosstalk and molecular signaling between cancer cells, surrounding non-malignant cells, and non-cellular components are involved in this process. While intercellular communication traditionally centers around chemokines, cytokines, inflammatory mediators, and growth factors, emerging pathways involving extracellular vesicles (EVs) are gaining increasing attention. The immunosuppressive TME is created and maintained in part by the large abundance of tumor-associated macrophages (TMAs), which are associated with drug resistance, poor prognosis, and have emerged as potential targets for cancer immunotherapy. TMAs are highly dynamic, and can be polarized into either M1 or M2-like macrophages. EVs are efficient cell-cell communication molecules that have been catapulted to the center of TMA polarization. In this article, we provide detailed examination of the determinative role of EVs in sustaining the TME through mediating crosstalk between tumor cells and tumor-associated macrophages.

Immunomodulatory role of metalloproteinase ADAM17 in tumor development

ADAM17 is a member of the a disintegrin and metalloproteinase (ADAM) family of transmembrane proteases involved in the shedding of some cell membrane proteins and regulating various signaling pathways. More than 90 substrates are regulated by ADAM17, some of which are closely relevant to tumor formation and development. Besides, ADAM17 is also responsible for immune regulation and its substrate-mediated signal transduction. Recently, ADAM17 has been considered as a major target for the treatment of tumors and yet its immunomodulatory roles and mechanisms remain unclear. In this paper, we summarized the recent understanding of structure and several regulatory roles of ADAM17. Importantly, we highlighted the immunomodulatory roles of ADAM17 in tumor development, as well as small molecule inhibitors and monoclonal antibodies targeting ADAM17.

Macrophage-Secreted CSF1 Transmits a Calorie Restriction-Induced Self-Renewal Signal to Mammary Epithelial Stem Cells

Calorie restriction enhances stem cell self-renewal in various tissues, including the mammary gland. We hypothesized that similar to their intestinal counterparts, mammary epithelial stem cells are insulated from sensing changes in energy supply, depending instead on niche signaling. The latter was investigated by subjecting cultures of mammary epithelial stem cells for 8 days to in vivo paracrine calorie-restriction signals collected from a 4-day-conditioned medium of individual mammary cell populations. Conditioned medium from calorie-restricted non-epithelial cells induced latent cell propagation and mammosphere formation—established markers of stem cell self-renewal. Combined RNA-Seq, immunohistochemistry and immunofluorescence analyses of the non-epithelial population identified macrophages and secreted CSF1 as the energy sensor and paracrine signal, respectively. Calorie restriction-induced pStat6 expression in macrophages suggested that skewing to the M2 phenotype contributes to the sensing mechanism. Enhancing CSF1 signaling with recombinant protein and interrupting the interaction with its highly expressed receptor in the epithelial stem cells by neutralizing antibodies were both affected stem cell self-renewal. In conclusion, combined in vivo, in vitro and in silico studies identified macrophages and secreted CSF1 as the energy sensor and paracrine transmitter, respectively, of the calorie restriction-induced effect on mammary stem cell self-renewal.

ADAM17-mediated EGFR ligand shedding directs macrophage promoted cancer cell invasion

Macrophages in the tumor microenvironment have a significant impact on tumor progression. Depending on the signaling environment in the tumor, macrophages can either support or constrain tumor progression. It is therefore of therapeutic interest to identify the tumor-derived factors that control macrophage education. With this aim, we correlated the expression of ADAM proteases, which are key mediators of cell-cell signaling, to the expression of pro-tumorigenic macrophage markers in human cancer cohorts. We identified ADAM17, a sheddase upregulated in many cancer types, as a protein of interest. Depletion of ADAM17 in cancer cell lines reduced the expression of several pro-tumorigenic markers in neighboring macrophages in vitro as well as in mouse models. Moreover, ADAM17-/- educated macrophages demonstrated a reduced ability to induce cancer cell invasion. Using mass spectrometry-based proteomics and ELISA, we identified HB-EGF and AREG, shed by ADAM17 in the cancer cells, as the implicated molecular mediators of macrophage education. Additionally, RNA-seq and ELISA experiments revealed that ADAM17-dependent HB-EGF-ligand release induces the expression and secretion of CXCL chemokines in macrophages, which in turn stimulates cancer cell invasion.In conclusion, we provide evidence that ADAM17 mediates a paracrine EGFR-ligand-chemokine feedback loop, whereby cancer cells hijack macrophages to promote tumor progression.

Identification of pyroptosis-related subtypes, development of a prognostic model, and characterization of tumour microenvironment infiltration in gastric cancer

As a new programmed death mode, pyroptosis plays an indispensable role in gastric cancer (GC) and has strong immunotherapy potential, but the specific pathogenic mechanism and antitumor function remain unclear. We comprehensively analysed the overall changes of pyroptosis-related genes (PRGs) at the genomic and epigenetic levels in 886 GC patients. We identified two molecular subtypes by consensus unsupervised clustering analysis. Then, we calculated the risk score and constructed the risk model for predicting prognostic and selected nine PRGs related genes (IL18RAP, CTLA4, SLC2A3, IL1A, KRT7,PEG10, IGFBP2, GPA33, and DES) through LASSO and COX regression analyses in the training cohorts and were verified in the test cohorts. Consequently, a highly accurate nomogram for improving the clinical applicability of the risk score was constructed. Besides, we found that multi-layer PRGs alterations were correlated with patient clinicopathological features, prognosis, immune infiltration and TME characteristics. The low risk group mainly characterized by increased microsatellite hyperinstability, tumour mutational burden and immune infiltration. The group had lower stromal cell content, higher immune cell content and lower tumour purity. Moreover, risk score was positively correlated with T regulatory cells, M1 and M2 macrophages. In addition, the risk score was significantly associated with the cancer stem cell index and chemotherapeutic drug sensitivity. This study revealed the genomic, transcriptional and TME multiomics features of PRGs and deeply explored the potential role of pyroptosis in the TME, clinicopathological features and prognosis in GC. This study provides a new immune strategy and prediction model for clinical treatment and prognosis evaluation.

Monocytes secrete CXCL7 to promote breast cancer progression

Certain immune cells and inflammatory cytokines are essential components in the tumor microenvironment to promote breast cancer progression. To identify key immune players in the tumor microenvironment, we applied highly invasive MDA-MB-231 breast cancer cell lines to co-culture with human monocyte THP-1 cells and identified CXCL7 by cytokine array as one of the increasingly secreted cytokines by THP-1 cells. Further investigations indicated that upon co-culturing, breast cancer cells secreted CSF1 to induce expression and release of CXCL7 from monocytes, which in turn acted on cancer cells to promote FAK activation, MMP13 expression, migration, and invasion. In a xenograft mouse model, administration of CXCL7 antibodies significantly reduced abundance of M2 macrophages in tumor microenvironment, as well as decreased tumor growth and distant metastasis. Clinical investigation further suggested that high CXCL7 expression is correlated with breast cancer progression and poor overall survival of patients. Overall, our study unveils an important immune cytokine, CXCL7, which is secreted by tumor infiltrating monocytes, to stimulate cancer cell migration, invasion, and metastasis, contributing to the promotion of breast cancer progression.

Tumor-Derived Extracellular Vesicles: A Means of Co-opting Macrophage Polarization in the Tumor Microenvironment

Extracellular vesicles (EVs) are a heterogeneous population of membrane-bound parcels of bioactive proteins, nucleic acids, and lipids released from almost all cell types. The diversity of cargo packaged into EVs proffer the induction of an array of effects on recipient cells. EVs released from tumor cells have emerged as a vital means of communication and immune modulation within the tumor microenvironment (TME). Macrophages are an important contributor to the TME with seemingly paradoxical roles promoting either pro- or anti-tumoral immune function depending on their activated phenotypes. Here, we discuss the influence of tumor-derived extracellular vesicles on the functional plasticity of macrophages in tumor progression.

CAFs Interacting With TAMs in Tumor Microenvironment to Enhance Tumorigenesis and Immune Evasion

Cancer associated fibroblasts (CAFs) and tumor associated macrophages (TAMs) are among the most important and abundant players of the tumor microenvironment. CAFs as well as TAMs are known to play pivotal supportive roles in tumor growth and progression. The number of CAF or TAM cells is mostly correlated with poor prognosis. Both CAFs and TAMs are in a reciprocal communication with the tumor cells in the tumor milieu. In addition to such interactions, CAFs and TAMs are also involved in a dynamic and reciprocal interrelationship with each other. Both CAFs and TAMs are capable of altering each other's functions. Here, the current understanding of the distinct mechanisms about the complex interplay between CAFs and TAMs are summarized. In addition, the consequences of such a mutual relationship especially for tumor progression and tumor immune evasion are highlighted, focusing on the synergistic pleiotropic effects. CAFs and TAMs are crucial components of the tumor microenvironment; thus, they may prove to be potential therapeutic targets. A better understanding of the tri-directional interactions of CAFs, TAMs and cancer cells in terms of tumor progression will pave the way for the identification of novel theranostic cues in order to better target the crucial mechanisms of carcinogenesis.

Macrophage Biology and Mechanisms of Immune Suppression in Breast Cancer

Macrophages are crucial innate immune cells that maintain tissue homeostasis and defend against pathogens; however, their infiltration into tumors has been associated with adverse outcomes. Tumor-associated macrophages (TAMs) represent a significant component of the inflammatory infiltrate in breast tumors, and extensive infiltration of TAMs has been linked to poor prognosis in breast cancer. Here, we detail how TAMs impede a productive tumor immunity cycle by limiting antigen presentation and reducing activation of cytotoxic T lymphocytes (CTLs) while simultaneously supporting tumor cell survival, angiogenesis, and metastasis. There is an urgent need to overcome TAM-mediated immune suppression for durable anti-tumor immunity in breast cancer. To date, failure to fully characterize TAM biology and classify multiple subsets has hindered advancement in therapeutic targeting. In this regard, the complexity of TAMs has recently taken center stage owing to their subset diversity and tightly regulated molecular and metabolic phenotypes. In this review, we reveal major gaps in our knowledge of the functional and phenotypic characterization of TAM subsets associated with breast cancer, before and after treatment. Future work to characterize TAM subsets, location, and crosstalk with neighboring cells will be critical to counteract TAM pro-tumor functions and to identify novel TAM-modulating strategies and combinations that are likely to enhance current therapies and overcome chemo- and immuno-therapy resistance.

Immune Checkpoints in Pediatric Solid Tumors: Targetable Pathways for Advanced Therapeutic Purposes

The tumor microenvironment (TME) represents a complex network between tumor cells and a variety of components including immune, stromal and vascular endothelial cells as well as the extracellular matrix. A wide panel of signals and interactions here take place, resulting in a bi-directional modulation of cellular functions. Many stimuli, on one hand, induce tumor growth and the spread of metastatic cells and, on the other hand, contribute to the establishment of an immunosuppressive environment. The latter feature is achieved by soothing immune effector cells, mainly cytotoxic T lymphocytes and B and NK cells, and/or through expansion of regulatory cell populations, including regulatory T and B cells, tumor-associated macrophages and myeloid-derived suppressor cells. In this context, immune checkpoints (IC) are key players in the control of T cell activation and anti-cancer activities, leading to the inhibition of tumor cell lysis and of pro-inflammatory cytokine production. Thus, these pathways represent promising targets for the development of effective and innovative therapies both in adults and children. Here, we address the role of different cell populations homing the TME and of well-known and recently characterized IC in the context of pediatric solid tumors. We also discuss preclinical and clinical data available using IC inhibitors alone, in combination with each other or administered with standard therapies.

Early Events Triggering the Initiation of a Type 2 Immune Response

Type 2 immune responses are typically associated with protection against helminth infections and also with harmful inflammation in response to allergens. Recent advances have revealed that type 2 immunity also contributes to sterile inflammation, cancer, and microbial infections. However, the early events that initiate type 2 immune responses remain poorly defined. New insights reveal major contributions from danger-associated molecular patterns (DAMPs) in the initiation of type 2 immune responses. In this review, we examine the molecules released by the host and pathogens and the role they play in mediating the initiation of mammalian innate type 2 immune responses under a variety of conditions.

Immune microenvironment in different molecular subtypes of ductal breast carcinoma

PURPOSE

Ductal breast carcinoma as a heterogeneous disease has different molecular subtypes associated with clinical prognosis and patients' survival. The role of immune system as a consistent part of the tumor microenvironment (TME) has been documented in progression of ductal breast carcinoma. Here, we aimed to describe the important immune cells and the immune system-associated molecules in Ductal Carcinoma In situ (DCIS) and Invasive Ductal Carcinoma (IDC) with special emphasis on their associations with different molecular subtypes and patients' prognosis.

RESULTS

The immune cells have a dual role in breast cancer (BC) microenvironment depending on the molecular subtype or tumor grade. These cells with different frequencies are present in the TME of DCIS and IDC. The presence of regulatory cells including Tregs, MDSC, Th2, Th17, M2 macrophages, HLADR^- T cells, and Tγδ cells is related to more immunosuppressive microenvironment, especially in ER^- and TN subtypes. In contrast, NK cells, CTL, Th, and Tfh cells are associated to the anti-tumor activity. These cells are higher in ER⁺ BC, although in other subtypes such as TN or HER2⁺ are associated with a favorable prognosis.

CONCLUSION

Determining the specific immune response in each subtype could be helpful in estimating the possible behavior of the tumor cells in TME. It is important to realize that different frequencies of immune cells in BC environment likely determine the patients' prognosis and their survival in each subtype. Therefore, elucidation of the distinct immune players in TME would be helpful toward developing targeted therapies in each subtype.

Metabolism in tumour-associated macrophages: a quid pro quo with the tumour microenvironment

Lung cancer is the leading cause of death from cancer worldwide. Recent studies demonstrated that the tumour microenvironment (TME) is pivotal for tumour progression, providing multiple targeting opportunities for therapeutic strategies. As one of the most abundant stromal cell types in the TME, tumour-associated macrophages (TAMs) exhibit high plasticity. Malignant cells alter their metabolic profiles to adapt to the limited availability of oxygen and nutrients in the TME, resulting in functional alteration of TAMs. The metabolic features of TAMs are strongly associated with their functional plasticity, which further impacts metabolic profiling in the TME and contributes to tumourigenesis and progression. Here, we review the functional determination of the TME by TAM metabolic alterations, including glycolysis as well as fatty acid and amino acid metabolism, which in turn are influenced by environmental changes. Additionally, we discuss metabolic reprogramming of TAMs to a tumouricidal phenotype as a potential antitumoural therapeutic strategy.

Tumour-associated macrophages (TAMs) display a high level of functional plasticity and altered metabolism symbolised by high sensitivity to the surrounding tumour microenvironment. The metabolism of TAMs provides novel therapeutic opportunities to treat cancer.https://bit.ly/31OqHhe

Delicate Balances in Cancer Chemotherapy: Modeling Immune Recruitment and Emergence of Systemic Drug Resistance

Metronomic chemotherapy can drastically enhance immunogenic tumor cell death. However, the mechanisms responsible are still incompletely understood. Here, we develop a mathematical model to elucidate the underlying complex interactions between tumor growth, immune system activation, and therapy-mediated immunogenic cell death. Our model is conceptually simple, yet it provides a surprisingly excellent fit to empirical data obtained from a GL261 SCID mouse glioma model treated with cyclophosphamide on a metronomic schedule. The model includes terms representing immune recruitment as well as the emergence of drug resistance during prolonged metronomic treatments. Strikingly, a single fixed set of parameters, adjusted neither for individuals nor for drug schedule, recapitulates experimental data across various drug regimens remarkably well, including treatments administered at intervals ranging from 6 to 12 days. Additionally, the model predicts peak immune activation times, rediscovering experimental data that had not been used in parameter fitting or in model construction. Notably, the validated model suggests that immunostimulatory and immunosuppressive intermediates are responsible for the observed phenomena of resistance and immune cell recruitment, and thus for variation of responses with respect to different schedules of drug administration.

Macrophages Interaction and MicroRNA Interplay in the Modulation of Cancer Development and Metastasis

Advancement in cancer research has shown that the tumor microenvironment plays a crucial role in the installation, progression, and dissemination of cancer cells. Among the heterogeneous panel of cells within the malignant microenvironment are tumor-associated macrophages that are sustaining the malignant cells through strict feedback mechanisms and spatial distribution. Considering that the presence of metastasis is one of the main feature associated with decreased survival rates among patients, in the present article we briefly present the involvement of tumor-associated macrophages in the hallmarks of metastasis and their microRNA-related regulation with a focus on lung cancer in order to coordinate the vast information under one pathology. As shown, these cells have emerged as coordinators of immunosuppression, angiogenesis and lymphangiogenesis, vessel intravasation and extravasation of cancer cells, and premetastatic niche formation, transforming the macrophages in potential therapeutic targets and also prognostic markers according to their density within the tumor and polarization phenotype. An indirect therapeutic approach on tumor-associated macrophages can be also represented by regulation of microRNAs involved in their polarization and implicit oncogenic features. Examples of these microRNAs consist in the highly studied miR-21 and miR-155, but also other microRNA with less feedback in the literature: miR-1207-5p, miR-193b, miR-320a, and others.

The role of tumor-associated macrophages in gastric cancer development and their potential as a therapeutic target

Gastric cancer (GC) represents the fifth cause of cancer-related death worldwide. Molecular biology has become a central area of research in GC and there are currently at least three major classifications available to elucidate the mechanisms that drive GC oncogenesis. Further, tumor microenvironment seems to play a crucial role, and tumor-associated macrophages (TAMs) are emerging as key players in GC development. TAMs are cells derived from circulating chemokine- receptor-type 2 (CCR2) inflammatory monocytes in blood and can be divided into two main types, M1 and M2 TAMs. M2 TAMs play an important role in tumor progression, promoting a pro-angiogenic and immunosuppressive signal in the tumor. The diffuse GC subtype, in particular, seems to be strongly characterized by an immuno-suppressive and pro-angiogenic phenotype. No molecular targets in this subgroup have yet been identified. There is an urgent need to understand the molecular pathways and tumor microenvironment features in the GC molecular subtypes. The role of anti-angiogenics and checkpoint inhibitors has recently been clinically validated in GC. Both ramucirumab, a fully humanized IgG1 monoclonal anti-vascular endothelial growth factor receptor 2 (VEGFR2) antibody, and checkpoint inhibitors in Epstein Bar Virus (EBV) and Microsatellite Instable (MSI) subtypes, have proved beneficial in advanced GC. Nevertheless, there is a need to identify predictive markers of response to anti-angiogenics and immunotherapy in clinical practice for a personalized treatment approach. The importance of M2 TAMs in development of solid tumors is currently gaining increasing interest. In this literature review we analyze immune microenvironment composition and signaling related to M1 and M2 TAMs in GC as well as its potential role as a therapeutic target.

miR-149 Suppresses Breast Cancer Metastasis by Blocking Paracrine Interactions with Macrophages

Paracrine activation of cells contained in the tumor microenvironment promotes tumor progression and metastasis. In breast cancer, malignant cells recruit and educate macrophages into a M2 tumor-promoting phenotype that supports the metastatic spread of cancer cells. Here, we show that miR-149 functions as a metastasis-suppressing microRNA in breast cancer cells by limiting colony-stimulating factor-1 (CSF1)-dependent recruitment and M2 polarization of macrophages. In lymph node-positive, triple-negative breast cancer (TNBC) tissues, low miR-149 expression correlated with macrophage infiltration and reduced patient survival. By directly targeting CSF1, miR-149 expression in TNBC cell lines (MDA-MB-231 and BT-549) inhibited the recruitment of human monocytic THP-1 cells and primary human macrophages. Furthermore, in macrophages cocultured with MDA-MB-231 cells expressing miR-149, epidermal growth factor (EGF) and amphiregulin expression levels were strongly reduced, resulting in reduced EGF receptor activation in the cancer cells. In vivo, lung metastases developing from orthotopic MDA-MB-231 tumors were reduced by 75% by miR-149 expression, and this was associated with impaired M2 macrophage infiltration of the primary tumors. These data suggest that miR-149 downregulation functionally contributes to breast tumor progression by recruiting macrophages to the tumor and facilitating CSF1 and EGF receptor cross-talk between cancer cells and macrophages. SIGNIFICANCE: These findings contribute to the understanding of tumor-stroma interactions by showing that miR-149 downregulation in TNBC enhances reciprocal growth factor signaling between macrophages and cancer cells, which promotes tumor progression and metastasis. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/6/1330/F1.large.jpg.

Monocytes and Macrophages in Cancer: Unsuspected Roles

The behavior of cancer is undoubtedly affected by stroma. Macrophages belong to this microenvironment and their presence correlates with reduced survival in most cancers. After a tumor-induced "immunoediting", these monocytes/macrophages, originally the first line of defense against tumor cells, undergo a phenotypic switch and become tumor-supportive and immunosuppressive.The influence of these tumor-associated macrophages (TAMs) on cancer is present in all traits of carcinogenesis. These cells participate in tumor initiation and growth, migration, vascularization, invasion and metastasis. Although metastasis is extremely clinically relevant, this step is always reliant on the angiogenic ability of tumors. Therefore, the formation of new blood vessels in tumors assumes particular importance as a limiting step for disease progression.Herein, the once unsuspected roles of macrophages in cancer will be discussed and their importance as a promising strategy to treat this group of diseases will be reminded.

Intravasation as a Key Step in Cancer Metastasis

Intravasation is a key step in cancer metastasis during which tumor cells penetrate the vessel wall and enter circulation, thereby becoming circulating tumor cells and potential metastatic seeds. Understanding the molecular mechanisms of intravasation is critically important for the development of therapeutic strategies to prevent metastasis. In this article, we review current data on the mechanisms of cancer cell intravasation into the blood and lymphatic vessels. The entry of mature thymocytes into the circulation and of dendritic cells into the regional lymph nodes is considered as example of intravasation under physiologically normal conditions. Intravasation in a pathophysiological state is illustrated by the reverse transendothelial migration of leukocytes into the bloodstream from the sites of inflammation mediated by the sphingosine 1-phosphate interaction with its receptors. Intravasation involves both invasion-dependent and independent mechanisms. In particular, mesenchymal and amoeboid cell invasion, as well as neoangiogenesis and vascular remodeling, are discussed to play a significant role in the entry of tumor cells to the circulation. Special attention is given to the contribution of macrophages to the intravasation via the CSF1/EGF (colony stimulating factor 1/epidermal growth factor) paracrine signaling pathway and the TMEM (tumor microenvironment of metastasis)-mediated mechanisms. Other mechanisms including intravasation of tumor cell clusters surrounded by the vessel wall elements, cooperative intravasation (entry of non-invasive tumor cells to the circulation following invasive tumor cells), and intravasation associated with the vasculogenic mimicry (formation of vascular channels by tumor cells) are also discussed. Novel intravasation-specific mechanisms that have not yet been described in the literature are suggested. The importance of targeted therapeutic strategies to prevent cancer intravasation is emphasized.

Bordetella Adenylate Cyclase Toxin Inhibits Monocyte-to-Macrophage Transition and Dedifferentiates Human Alveolar Macrophages into Monocyte-like Cells

Monocytes arriving at the site of infection differentiate into functional effector macrophages to replenish the resident sentinel cells. Bordetella pertussis, the pertussis agent, secretes an adenylate cyclase toxin-hemolysin (CyaA) that binds myeloid phagocytes through complement receptor 3 (CD11b/CD18) and swiftly delivers its adenylyl cyclase enzyme domain into phagocytes. This ablates the bactericidal capacities of phagocytes through massive and unregulated conversion of cytosolic ATP into the key signaling molecule cAMP. We show that exposure of primary human monocytes to as low a concentration as 22.5 pM CyaA, or a low (2:1) multiplicity of infection by CyaA-producing B. pertussis bacteria, blocks macrophage colony-stimulating factor (M-CSF)-driven differentiation of monocytes. CyaA-induced cAMP signaling mediated through the activity of protein kinase A (PKA) efficiently blocked expression of macrophage markers, and the monocytes exposed to 22.5 pM CyaA failed to acquire the characteristic intracellular complexity of mature macrophage cells. Neither M-CSF-induced endoplasmic reticulum (ER) expansion nor accumulation of Golgi bodies, mitochondria, or lysosomes was observed in toxin-exposed monocytes, which remained small and poorly phagocytic and lacked pseudopodia. Exposure to 22.5 pM CyaA toxin provoked loss of macrophage marker expression on in vitro differentiated macrophages, as well as on primary human alveolar macrophages, which appeared to dedifferentiate into monocyte-like cells with upregulated CD14 levels. This is the first report that terminally differentiated tissue-resident macrophage cells can be dedifferentiated in vitro The results suggest that blocking of monocyte-to-macrophage transition and/or dedifferentiation of the sentinel cells of innate immunity through cAMP-elevating toxin action may represent a novel immune evasion strategy of bacterial pathogens.IMPORTANCE Macrophages are key sentinel cells of the immune system, and, as such, they are targeted by the toxins produced by the pertussis agent Bordetella pertussis The adenylate cyclase toxin (CyaA) mediates immune evasion of B. pertussis by suspending the bactericidal activities of myeloid phagocytes. We reveal a novel mechanism of potential subversion of host immunity, where CyaA at very low (22 pM) concentrations could inhibit maturation of human monocyte precursors into the more phagocytic macrophage cells. Furthermore, exposure to low CyaA amounts has been shown to trigger dedifferentiation of mature primary human alveolar macrophages back into monocyte-like cells. This unprecedented capacity is likely to promote survival of the pathogen in the airways, both by preventing maturation of monocytes attracted to the site of infection into phagocytic macrophages and by dedifferentiation of the already airway-resident sentinel cells.

Myeloid-Derived Lymphatic Endothelial Cell Progenitors Significantly Contribute to Lymphatic Metastasis in Clinical Breast Cancer

Lymphatic metastasis is a high-impact prognostic factor for mortality of breast cancer (BC) patients, and it directly depends on tumor-associated lymphatic vessels. We previously reported that lipopolysaccharide-induced inflammatory lymphangiogenesis is strongly promoted by myeloid-derived lymphatic endothelial cell progenitors (M-LECPs) derived from the bone marrow (BM). As BC recruits massive numbers of provascular myeloid cells, we hypothesized that M-LECPs, within this recruited population, are specifically programmed to promote tumor lymphatics that increase lymph node metastasis. In support of this hypothesis, high levels of M-LECPs were found in peripheral blood and tumor tissues of BC patients. Moreover, the density of M-LECPs and lymphatic vessels positive for myeloid marker proteins strongly correlated with patient node status. It was also established that tumor M-LECPs coexpress lymphatic-specific, stem/progenitor and M2-type macrophage markers that indicate their BM hematopoietic-myeloid origin and distinguish them from mature lymphatic endothelial cells, tumor-infiltrating lymphoid cells, and tissue-resident macrophages. Using four orthotopic BC models, we show that mouse M-LECPs are similarly recruited to tumors and integrate into preexisting lymphatics. Finally, we demonstrate that adoptive transfer of in vitro differentiated M-LECPs, but not naïve or nondifferentiated BM cells, significantly increased metastatic burden in ipsilateral lymph nodes. These data support a causative role of BC-induced lymphatic progenitors in tumor lymphangiogenesis and suggest molecular targets for their inhibition.

A simultaneous blow-up problem arising in tumor modeling

Although macrophages are part of the human immune system, it has been remarkably observed in laboratory experiments that decreasing its number can slow down the tumor progression. We analyze through a recently mathematical model proposed in the literature, necessary conditions for aggregation of tumor cells and macrophages. In order to do so, we prove the possibility of having blow-up in finite time. Next, we study if the aggregation of macrophages can occur when having a low density of tumor cells, and vice versa. With this purpose, we consider the problem of analyzing the existence or not of a simultaneous blow-up. We achieve this goal thanks to a novel process that allows us to compare the entropy functional associated with the density of each population, which turns out to be also a method to find enough conditions for having a simultaneous blow-up.

Specific targeting of PKCδ suppresses osteoclast differentiation by accelerating proteolysis of membrane-bound macrophage colony-stimulating factor receptor

c-Fms is the macrophage colony-stimulating factor (M-CSF) receptor, and intracellular signalling via the M-CSF/c-Fms axis mediates both innate immunity and bone remodelling. M-CSF-induced transient proteolytic degradation of c-Fms modulates various biological functions, and protein kinase C (PKC) signalling is activated during this proteolytic process via an unknown mechanism. Notably, the role of specific PKC isoforms involved in c-Fms degradation during osteoclast differentiation is not known. Here, we observed that inactivation of PKCδ by the biochemical inhibitor rottlerin, a cell permeable peptide inhibitor, and short hairpin (sh) RNA suppresses osteoclast differentiation triggered by treatment with M-CSF and receptor activator of NF-κB ligand. Interestingly, inhibition of PKCδ by either inhibitor or gene silencing of PKCδ accelerated M-CSF-induced proteolytic degradation of membrane-bound c-Fms via both the lysosomal pathway and regulated intramembrane proteolysis (RIPping), but did not affect c-fms expression at the mRNA level. Degradation of c-Fms induced by PKCδ inactivation subsequently inhibited M-CSF-induced osteoclastogenic signals, such as extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK), p38, and Akt. Furthermore, mice administered PKCδ inhibitors into the calvaria periosteum exhibited a decrease in both osteoclast formation on the calvarial bone surface and the calvarial bone marrow cavity, which reflects osteoclastic bone resorption activity. These data suggest that M-CSF-induced PKCδ activation maintains membrane-anchored c-Fms and allows the sequential cellular events of osteoclastogenic signalling, osteoclast formation, and osteoclastic bone resorption.

Cancer associated fibroblasts sculpt tumour microenvironment by recruiting monocytes and inducing immunosuppressive PD-1+ TAMs

Fibroblasts turn into cancer associated fibroblasts (CAFs) in the tumour microenvironment. CAFs have recently attracted attention for their function as a regulator of immune cell recruitment and function in addition to their tumour-promoting roles. In this study, we aimed to determine the role of CAFs on monocyte recruitment and macrophage polarization in breast cancer. CAFs, which were α-SMA expressing fibroblasts in contrast to normal fibroblasts (NFs), effectively recruited monocytes. Recruitment of monocytes by CAFs might be mediated by monocyte chemotactic protein-1 (MCP-1) as well as stromal cell-derived factor-1 (SDF-1) cytokines. CAFs differentiated the recruited monocytes into M2-like macrophages which are capable of exerting their immunosuppressive roles via the PD-1 axis. CAF-educated monocytes exhibited strong immune suppression unlike NF-educated monocytes and enhanced the motility/invasion of breast cancer cells in addition to increasing the expressions of epithelial–mesenchymal transition (EMT)-related genes and vimentin protein in cancer cells. CAF-educated M1 macrophages displayed increased expression of M2 markers and production of anti-inflammatory cytokine IL-10 in contrast to decreased production of pro-inflammatory cytokine IL-12 compared with control M1 macrophages; suggesting that CAFs were also able to induce the trans-differentiation of M1 macrophages to M2 macrophages. We then investigated the relationship between the infiltration of CAFs and tumour associated macrophages (TAMs) using tissue samples obtained from breast cancer patients. High grade of CAFs significantly correlated with the number of TAMs in human breast cancer tissue samples. It was also associated with higher Ki-67 proliferation index, and higher tumour volume. This result is in line with our finding of increased breast cancer cell proliferation due to the effects of CAF-educated monocytes in vitro. Our results concluded that CAFs play pivotal roles in sculpturing the tumour microenvironment in breast cancer, and therapeutic strategies to reverse the CAF-mediated immunosuppressive microenvironment should be taken into consideration.

Hypoxia and the Metastatic Niche

Metastasis is considered the latest stage of cancer development; however, metastasis occurs earlier than it can be detected. Metastatic sites are actively remodeled by secretory factors including growth factors, chemokines and cytokines, extracellular matrix (ECM) enzymes, and exosomes produced by the primary cancer tissues. Many of the associated-secretory factors are abundantly induced by inflammation and hypoxia. These secretory factors modify the ECM, immune composition, and blood vessel permeability of the future metastatic sites, a process termed 'metastatic niche formation.' In general, ECM is modified to enhance the attachment of other cell types or cancer cells to establish a growth-factor rich metastatic niche. Immune-suppressive cells such as tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) dominate the metastatic niche to allow metastatic cancer cells to bypass immune surveillance and propagate. Endothelial cell-to-cell junctions of blood vessels are loosened to enhance the penetrance of metastatic cancer cells to the metastatic sites. Different metastatic tissues have unique ECM constituents, resident immune cells, and anatomical positions linked with the circulatory system; therefore, many cancer types have their own metastatic pattern, and they favor metastasis to specific organs. Some of the remodeling events represent the earliest step of metastasis, even preceding the detachment of cancer cells from the primary tumor site. Understanding how the metastatic niche is formed is important for the development of drugs to prevent the earliest step of metastasis and advance our understanding of organotrophic metastasis. This review summarizes the major findings in the field of metastatic niche highlighting the role of hypoxia.

Turn Back the TIMe: Targeting Tumor Infiltrating Myeloid Cells to Revert Cancer Progression

Tumor cells frequently produce soluble factors that favor myelopoiesis and recruitment of myeloid cells to the tumor microenvironment (TME). Consequently, the TME of many cancer types is characterized by high infiltration of monocytes, macrophages, dendritic cells and granulocytes. Experimental and clinical studies show that most myeloid cells are kept in an immature state in the TME. These studies further show that tumor-derived factors mold these myeloid cells into cells that support cancer initiation and progression, amongst others by enabling immune evasion, tumor cell survival, proliferation, migration and metastasis. The key role of myeloid cells in cancer is further evidenced by the fact that they negatively impact on virtually all types of cancer therapy. Therefore, tumor-associated myeloid cells have been designated as the culprits in cancer. We review myeloid cells in the TME with a focus on the mechanisms they exploit to support cancer cells. In addition, we provide an overview of approaches that are under investigation to deplete myeloid cells or redirect their function, as these hold promise to overcome resistance to current cancer therapies.

Immune Evasion in Pancreatic Cancer: From Mechanisms to Therapy

Pancreatic ductal adenocarcinoma (PDA), the most frequent type of pancreatic cancer, remains one of the most challenging problems for the biomedical and clinical fields, with abysmal survival rates and poor therapy efficiency. Desmoplasia, which is abundant in PDA, can be blamed for much of the mechanisms behind poor drug performance, as it is the main source of the cytokines and chemokines that orchestrate rapid and silent tumor progression to allow tumor cells to be isolated into an extensive fibrotic reaction, which results in inefficient drug delivery. However, since immunotherapy was proclaimed as the breakthrough of the year in 2013, the focus on the stroma of pancreatic cancer has interestingly moved from activated fibroblasts to the immune compartment, trying to understand the immunosuppressive factors that play a part in the strong immune evasion that characterizes PDA. The PDA microenvironment is highly immunosuppressive and is basically composed of T regulatory cells (Tregs), tumor-associated macrophages (TAMs), and myeloid-derived suppressive cells (MDSCs), which block CD8⁺ T-cell duties in tumor recognition and clearance. Interestingly, preclinical data have highlighted the importance of this immune evasion as the source of resistance to single checkpoint immunotherapies and cancer vaccines and point at pathways that inhibit the immune attack as a key to solve the therapy puzzle. Here, we will discuss the molecular mechanisms involved in PDA immune escape as well as the state of the art of the PDA immunotherapy.

Fluorine-19 Magnetic Resonance Imaging and Positron Emission Tomography of Tumor-Associated Macrophages and Tumor Metabolism

The presence of tumor-associated macrophages (TAMs) is significantly associated with poor prognosis of tumors. Currently, magnetic resonance imaging- (MRI-) based TAM imaging methods that use nanoparticles such as superparamagnetic iron oxide and perfluorocarbon nanoemulsions are available for quantitative monitoring of TAM burden in tumors. However, whether MRI-based measurements of TAMs can be used as prognostic markers has not been evaluated yet. In this study, we used positron emission tomography (PET) with ¹⁸F-2-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) as a radioactive tracer and fluorine-19- (¹⁹F-) MRI for imaging mouse breast cancer models to determine any association between TAM infiltration and tumor metabolism. Perfluorocarbon nanoemulsions were intravenously administered to track and quantify TAM infiltration using a 7T MR scanner. To analyze glucose uptake in tumors, ¹⁸F-FDG-PET images were acquired immediately after ¹⁹F-MRI. Coregistered ¹⁸F-FDG-PET and ¹⁹F-MR images enabled comparison of spatial patterns of glucose uptake and TAM distribution in tumors. ¹⁹F-MR signal intensities from tumors exhibited a strong inverse correlation with ¹⁸F-FDG uptake while having a significant positive correlation with tumor growth from days 2 to 7. These results show that combination of ¹⁹F-MRI and ¹⁸F-FDG-PET can improve our understanding of the relationship between TAM and tumor microenvironment.

Deciphering Epithelial-Mesenchymal Transition Regulatory Networks in Cancer through Computational Approaches

Epithelial–mesenchymal transition (EMT), the process by which epithelial cells can convert into motile mesenchymal cells, plays an important role in development and wound healing but is also involved in cancer progression. It is increasingly recognized that EMT is a dynamic process involving multiple intermediate or “hybrid” phenotypes rather than an “all-or-none” process. However, the role of EMT in various cancer hallmarks, including metastasis, is debated. Given the complexity of EMT regulation, computational modeling has proven to be an invaluable tool for cancer research, i.e., to resolve apparent conflicts in experimental data and to guide experiments by generating testable hypotheses. In this review, we provide an overview of computational modeling efforts that have been applied to regulation of EMT in the context of cancer progression and its associated tumor characteristics. Moreover, we identify possibilities to bridge different modeling approaches and point out outstanding questions in which computational modeling can contribute to advance our understanding of pathological EMT.

Tumor-Induced Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous, immune-suppressive leukocyte population that develops systemically and infiltrates tumors. MDSCs can restrain the immune response through different mechanisms including essential metabolite consumption, reactive oxygen and nitrogen species production, as well as display of inhibitory surface molecules that alter T-cell trafficking and viability. Moreover, MDSCs play a role in tumor progression, acting directly on tumor cells and promoting cancer stemness, angiogenesis, stroma deposition, epithelial-to-mesenchymal transition, and metastasis formation. Many biological and pharmaceutical drugs affect MDSC expansion and functions in preclinical tumor models and patients, often reversing host immune dysfunctions and allowing a more effective tumor immunotherapy.

Nanoparticle-Based Magnetic Resonance Imaging on Tumor-Associated Macrophages and Inflammation

The inflammatory response, mediated by tissue-resident or newly recruited macrophages, is an underlying pathophysiological condition for many diseases, including diabetes, obesity, neurodegeneration, atherosclerosis, and cancer. Paradoxically, inflammation is a double-edged sword in oncology. Macrophages are, generally speaking, the major drivers of inflammatory insult. For many solid tumors, high density of cells expressing macrophage-associated markers have generally been found in association with a poor clinical outcome, characterized by inflamed microenvironment, a high level of dissemination and resistance to conventional chemotherapies. On another hand, radiation treatment also triggers an inflammatory response in tumors (often referred to as pseudoprogression), which can be associated with a positive treatment response. As such, non-invasive imaging of cancer inflammation and tumor-associated macrophages (TAMs) provides a revolutionary diagnostic tool and monitoring strategy for anti-inflammatory, immuno- and radiotherapies. Recently, quantitative T2-weighted magnetic resonance imaging (qT2wMRI), using injection of superparamagnetic iron oxide nanoparticles (SPIONs), has been reported for the assessment of TAMs non-invasively in animal models and in human trials. The SPIONs are magnetic resonance imaging (MRI) contrast agents that significantly decrease T2 MR relaxation times in inflamed tissues due to the macrophage-specific uptake and retention. It has been shown that macrophage-populated tumors and metastases will accumulate iron oxide nanoparticles and decrease T2-relaxation time that will result in a negative (dark) contrast in qT2wMRI. Non-invasive imaging of TAMs using SPION holds a great promise for staging the inflammatory microenvironment of primary and metastatic tumors as well monitoring the treatment response of cancer patients treated with radiation and immunotherapy.

Assessment of the Cancer Risk of the Fat-Grafted Breast in a Murine Model

Background

The results of experimental studies indicate that grafting of autologous adipose tissue may induce tumorigenesis at the recipient site, but clinical results do not support a carcinogenic effect of fat grafting to the breast.

Objectives

The authors assessed cancer risk following transplantation of autologous fat into murine mammary tissue.

Methods

In this animal study, mammary tissues from 54 breasts of 9 female rats were either grafted with autologous subcutaneous fat, grafted with autologous omental fat, or unmanipulated. Tissues were harvested and processed for histologic and immunohistochemical analyses, and the mRNA expression levels of specific genes were determined.

Results

No atypia or changes in lobular structures were observed in lipofilled breasts compared with controls. The numbers of ductal cell layers and terminal ductal units were similar for lipofilled and control breasts. Macrophage concentrations also were similar for the 3 groups. The localization and magnitude of plasminogen activator inhibitor 1 were similar for lipofilled and unmanipulated breast tissue. The percentages of cells expressing Ki67 or estrogen receptor (ER) and the ER/Ki67 balance were similar for the 3 groups. Gene expression was not altered in lipofilled breasts, compared with controls.

Conclusions

No theoretical risk of cancer was detected in the microenvironment of the lipofilled rat breast.

Targeting oncogenic vulnerabilities in triple negative breast cancer: biological bases and ongoing clinical studies

Triple negative breast cancer (TNBC) is still an incurable disease despite the great scientific effort performed during the last years. The huge heterogeneity of this disease has motivated the evaluation of a great number of therapies against different molecular alterations. In this article, we review the biological bases of this entity and how the known molecular evidence supports the current preclinical and clinical development of new therapies. Special attention will be given to ongoing clinical studies and potential options for future drug combinations.

Barriers to Radiation-Induced In Situ Tumor Vaccination

The immunostimulatory properties of radiation therapy (RT) have recently generated widespread interest due to preclinical and clinical evidence that tumor-localized RT can sometimes induce antitumor immune responses mediating regression of non-irradiated metastases (abscopal effect). The ability of RT to activate antitumor T cells explains the synergy of RT with immune checkpoint inhibitors, which has been well documented in mouse tumor models and is supported by observations of more frequent abscopal responses in patients refractory to immunotherapy who receive RT during immunotherapy. However, abscopal responses following RT remain relatively rare in the clinic, and antitumor immune responses are not effectively induced by RT against poorly immunogenic mouse tumors. This suggests that in order to improve the pro-immunogenic effects of RT, it is necessary to identify and overcome the barriers that pre-exist and/or are induced by RT in the tumor microenvironment. On the one hand, RT induces an immunogenic death of cancer cells associated with release of powerful danger signals that are essential to recruit and activate dendritic cells (DCs) and initiate antitumor immune responses. On the other hand, RT can promote the generation of immunosuppressive mediators that hinder DCs activation and impair the function of effector T cells. In this review, we discuss current evidence that several inhibitory pathways are induced and modulated in irradiated tumors. In particular, we will focus on factors that regulate and limit radiation-induced immunogenicity and emphasize current research on actionable targets that could increase the effectiveness of radiation-induced in situ tumor vaccination.

Plasma Levels and Diagnostic Utility of Macrophage Colony-Stimulating Factor, Matrix Metalloproteinase-9, and Tissue Inhibitor of Metalloproteinases-1 as New Biomarkers of Breast Cancer

Background

Macrophage colony-stimulating factor (M-CSF), matrix metalloproteinase-9 (MMP-9), and its specific tissue inhibitor - tissue inhibitor of metalloproteinases-1 (TIMP-1) may play an important role in the pathogenesis and spread of cancer. We investigated the plasma levels of M-CSF, MMP-9, and TIMP-1 in comparison with a commonly accepted tumor marker CA 15-3 in breast cancer patients and in control groups.

Methods

The cohort included 110 breast cancer patients in groups at stages I-IV. The control group consisted of 50 healthy volunteers and 50 benign tumor patients. Plasma levels of M-CSF, MMP-9, and TIMP-1 were determined by using ELISA, while CA 15-3 concentrations were determined by using chemiluminescent microparticle immunoassay (CMIA).

Results

The results showed significant differences in concentrations of the analyzed parameters and in levels of CA 15-3 between the groups of breast cancer patients and the two control groups. Diagnosis using these markers was equal to that using CA 15-3 in terms of sensitivity, predictive values of positive and negativetest results (PPV, NPV) and area under the ROC curve (AUC) in the studied groups. The diagnostic specificities of MMP-9, TIMP-1, M-CSF, and CA 15-3 showed equally high values (95%). The combined use of all tested parameters with CA 15-3 resulted in increased sensitivity, NPV, and AUC, especially in the combination of M-CSF with tumor markers (76%, 64%, and 0.8653).

Conclusions

These findings suggest the tested parameters are useful in the diagnosis of breast cancer patients (except stage I), when combined with CA 15-3.

The Fate of the Tumor in the Hands of Microenvironment: Role of TAMs and mTOR Pathway

Since 2000, written with elegance and accuracy, Hanahan and Weinberg have proposed six major hallmarks of cancer and, together, they provide great advances to the understanding of tumoral biology. Our knowledge about tumor behavior has improved and the investigators have now recognized that inflammatory microenvironment may be a new feature for the tumor entities. Macrophages are considered as an important component of tumoral microenvironment. Biologically, two forms of activated macrophages can be observed: classically activated macrophages (M1) and alternative activated macrophages (M2). Despite the canonical pathways that control this puzzle of macrophages polarization, recently, mTOR signaling pathway has been implicated as an important piece in determining the metabolic and functional differentiation of M1 and M2 profiles. Currently, it is believed that macrophages related to tumoral microenvironment present an “M2-like” feature promoting an immunosuppressive microenvironment enhancing tumoral angiogenesis, growth, and metastasis. In the present review we discuss the role of macrophages in the tumor microenvironment and the role of mTOR pathway in M1 and M2 differentiation. We also discuss the recent findings in M1 and M2 polarization as a possible target in the cancer therapy.

Modeling synovial sarcoma metastasis in the mouse: PI3'-lipid signaling and inflammation

Solid tumor metastasis is a complex biology, impinged upon by a variety of dysregulated signaling pathways. PI3'-lipid signaling has been associated with metastasis and inflammation in many cancers, but the relationship between tumor cell-intrinsic PI3'-lipid signaling and inflammatory cell recruitment has remained enigmatic. Elevated PI3'-lipid signaling associates with progression of synovial sarcoma, a deadly soft tissue malignancy initiated by a t(X;18) chromosomal translocation that generates an SS18-SSX fusion oncoprotein. Here, we show in genetically engineered mouse models of locally induced expression of SS18-SSX1 or SS18-SSX2 that Pten silencing dramatically accelerated and enhanced sarcomagenesis without compromising synovial sarcoma characteristics. PTEN deficiency increased tumor angiogenesis, promoted inflammatory gene expression, and enabled highly penetrant spontaneous pulmonary metastasis. PTEN-deficient sarcomas revealed infiltrating myeloid-derived hematopoietic cells, particularly macrophages and neutrophils, recruited via PI3'-lipid-induced CSF1 expression in tumor cells. Moreover, in a large panel of human synovial sarcomas, enhanced PI3'-lipid signaling also correlated with increased inflammatory cell recruitment and CSF1R signal transduction in both macrophages and endothelial cells. Thus, both in the mouse model and in human synovial sarcomas, PI3'-lipid signaling drives CSF1 expression and associates with increased infiltration of the monocyte/macrophage lineage as well as neutrophils.

Tumor-derived factors modulating dendritic cell function

Dendritic cells (DC) play unique and diverse roles in the tumor occurrence, development, progression and response to therapy. First of all, DC can actively uptake tumor-associated antigens, process them and present antigenic peptides to T cells inducing and maintaining tumor-specific T cell responses. DC interaction with different immune effector cells may also support innate antitumor immunity, as well as humoral responses also known to inhibit tumor development in certain cases. On the other hand, DC are recruited to the tumor site by specific tumor-derived and stroma-derived factors, which may also impair DC maturation, differentiation and function, thus resulting in the deficient formation of antitumor immune response or development of DC-mediated tolerance and immune suppression. Identification of DC-stimulating and DC-suppressing/polarizing factors in the tumor environment and the mechanism of DC modulation are important for designing effective DC-based vaccines and for recovery of immunodeficient resident DC responsible for maintenance of clinically relevant antitumor immunity in patients with cancer. DC-targeting tumor-derived factors and their effects on resident and administered DC in the tumor milieu are described and discussed in this review.

Macrophages, Inflammation, and Lung Cancer

Lung cancer is the leading cause of cancer mortality worldwide, and at only 18%, it has one of the lowest 5-year survival rates of all malignancies. With its highly complex mutational landscape, treatment strategies against lung cancer have proved largely ineffective. However with the recent success of immunotherapy trials in lung cancer, there is renewed enthusiasm in targeting the immune component of tumors. Macrophages make up the majority of the immune infiltrate in tumors and are a key cell type linking inflammation and cancer. Although the mechanisms through which inflammation promotes cancer are not fully understood, two connected hypotheses have emerged: an intrinsic pathway, driven by genetic alterations that lead to neoplasia and inflammation, and an extrinsic pathway, driven by inflammatory conditions that increase cancer risk. Here, we discuss the contribution of macrophages to these pathways and subsequently their roles in established tumors. We highlight studies investigating the association of macrophages with lung cancer prognosis and discuss emerging therapeutic strategies for targeting macrophages in the tumor microenvironment.

Tumor-associated macrophages in skin: How to treat their heterogeneity and plasticity

Immunosuppressive tumor-associated macrophages (TAMs) promote an immunosuppressive environment in the tumor-bearing host, together with regulatory T cells (Tregs). TAMs compose cancer stroma in skin cancers including melanomas and non-melanomas. The majority of tumor-associated macrophages (TAMs) are alternatively activated M2 macrophages that favor tumor development, and they comprise one of the main populations of inflammatory cells in skin cancers. On the other hand, TAMs could be modulated into M1-type macrophages that suppress tumor growth by stimulating and recruiting Th1 and effector cells in the tumor sites. Therefore, TAMs are a target for immunotherapy in various cancers. In this review, we discuss the definition and suppressive mechanisms of TAMs, as well as their biological activities in tumor-bearing hosts to assess potential therapeutic strategies.

The Role of Stroma in Tumor Development

The tumor microenvironment plays an essential role in various stages of cancer development. This environment, composed of the extracellular matrix, fibroblasts, endothelial cells, and cells of the immune system regulates the behavior of and co-evolve with tumor cells. Many of the components, including the innate and adaptive immune cells, play multifaceted roles during cancer progression and can promote or inhibit tumor development, depending on local and systemic conditions. Interestingly, a strategy by which tumor cells gain drug resistance is by modifying the tumor microenvironment. Together, understanding the mechanisms by which the tumor microenvironment functions should greatly facilitate the development of new therapeutic interventions by targeting the tumor niche.

Follicular thyroid carcinoma but not adenoma recruits tumor-associated macrophages by releasing CCL15

BACKGROUND

The differential diagnosis of follicular thyroid carcinoma (FTC) and follicular adenoma (FA) before surgery is a clinical challenge. Many efforts have been made but most focusing on tumor cells, while the roles of tumor associated macrophages (TAMs) remained unclear in FTC. Here we analyzed the differences between TAMs in FTC and those in FA.

METHODS

We first analyzed the density of TAMs by CD68 immunostaining in 59 histologically confirmed FTCs and 47 FAs. Cytokines produced by FTC and FA were profiled using antibody array, and validated by quantitative PCR. Chemotaxis of monocyte THP-1 was induced by condition medium of FTC cell lines (FTC133 and WRO82-1) with and without anti-CCL15 neutralizing antibody. Finally, we analyzed CCL15 protein level in FTC and FA by immunohistochemistry.

RESULTS

The average density of CD68(+) cells was 9.5 ± 5.4/field in FTC, significantly higher than that in FA (4.9 ± 3.4/field, p < 0.001). Subsequently profiling showed that CCL15 was the most abundant chemokine in FTC compared with FA. CCL15 mRNA in FTC was 51.4-folds of that in FA. CM of FTC cell lines induced THP-1 cell chemotaxis by 33 ~ 77%, and anti-CCL15 neutralizing antibody reduced THP-1 cell migration in a dose-dependent manner. Moreover, we observed positive CCL15 immunostaining in 67.8% of FTCs compared with 23.4% of FAs.

CONCLUSION

Our study suggested FTC might induce TAMs infiltration by producing CCL15. Measurement of TAMs and CCL15 in follicular thyroid lesions may be applied clinically to differentiate FTC from FA pre-operation.

Prognostic significance of the pre-chemotherapy lymphocyte-to-monocyte ratio in patients with previously untreated metastatic colorectal cancer receiving FOLFOX chemotherapy

Background

As a surrogate marker of systemic inflammation, the lymphocyte-to-monocyte ratio (LMR) is an independent prognostic factor for various malignancies. This study investigated the prognostic significance of the pre-chemotherapy LMR in patients with previously untreated metastatic colorectal cancer (mCRC) receiving chemotherapy.

Methods

The present study included newly diagnosed mCRC patients treated between January 2005 and December 2013 with FOLFOX chemotherapy, specifically oxaliplatin 180 mg/m² on day 1, with leucovorin 400 mg/m² administered as a 2-hour infusion before the administration of 5-fluorouracil 400 mg/m² as an intravenous bolus injection, and 5-fluorouracil 2400 mg/m² as a 46-h infusion immediately after 5-fluorouracil bolus injection. The LMR was calculated as the absolute count of lymphocytes divided by the absolute count of monocytes. COX proportional hazards analysis was performed to evaluate the association of LMR with survival outcomes.

Results

A total of 488 patients were included. Patients with high pre-chemotherapy LMR experienced significant improvements in progression-free survival (PFS, 9.2 vs. 7.6 months, P < 0.001) and overall survival (OS, 19.4 vs. 16.6 months, P < 0.001) compared with patients with low pre-chemotherapy LMR. Subsequent COX multivariate analysis showed that high pre-chemotherapy LMR (≥3.11) was an independent favorable prognostic factor for PFS and OS. Additionally, patients whose LMR remained high (high–high subgroup), increased (low–high subgroup), or decreased (high–low subgroup) following chemotherapy showed better results in terms of PFS and OS than patients whose LMR remained low (low–low subgroup) after chemotherapy.

Conclusions

For patients with previously untreated mCRC receiving FOLFOX chemotherapy, an elevated pre-chemotherapy LMR is an independent favorable prognostic factor for PFS and OS, and changes in the LMR before and after chemotherapy seem to predict the benefit of chemotherapy.

Interactions between colon cancer cells and tumor-infiltrated macrophages depending on cancer cell-derived colony stimulating factor 1

Tumor-infiltrated macrophages were potential targets of the immune therapy for patients with colon cancer. Colony stimulating factor 1 (CSF1) is a primary chemoattractant and functional regulator for macrophages, and therefore would be a feasible intervention for the macrophage-targeting therapeutics. However, the expression of CSF1 in colon cancer microenvironment and its roles in cancer development is largely unknown. In the present study, we found that CSF1 was over-expressed exclusively in colon cancer cells and was correlated with macrophages infiltration. The high CSF1 expression and macrophages infiltration were related to the tumor-node-metastasis (TNM) stage of colon cancer, and suggested to be positively associated with survival of colon cancer patients. In the in vitro studies based on an indirect Transwell system, we found that co-culture with macrophage promoted CSF1 production in colon cancer cells. Further investigation on regulatory mechanisms suggested that CSF1 production in colon cancer cells was dependent on PKC pathway, which was activated by IL-8, mainly produced by macrophages. Moreover, colon cancer cell-derived CSF1 drove the recruitment of macrophages and re-educated their secretion profile, including the augment of IL-8 production. The mice tumor xenografts study also found that over-expression of CSF1 in colon cancer cells promoted intratumoral infiltration of macrophages, and partially suppressed tumor growth. In all, our results demonstrated that CSF1 was an important factor in the colon cancer microenvironment, involving in the interactions between colon cancer cells and tumor-infiltrated macrophages.

The Macrophage Inhibitor CNI-1493 Blocks Metastasis in a Mouse Model of Ewing Sarcoma through Inhibition of Extravasation

Metastatic Ewing Sarcoma carries a poor prognosis, and novel therapeutics to prevent and treat metastatic disease are greatly needed. Recent evidence demonstrates that tumor-associated macrophages in Ewing Sarcoma are associated with more advanced disease. While some macrophage phenotypes (M1) exhibit anti-tumor activity, distinct phenotypes (M2) may contribute to malignant progression and metastasis. In this study, we show that M2 macrophages promote Ewing Sarcoma invasion and extravasation, pointing to a potential target of anti-metastatic therapy. CNI-1493 is a selective inhibitor of macrophage function and has shown to be safe in clinical trials as an anti-inflammatory agent. In a xenograft mouse model of metastatic Ewing Sarcoma, CNI-1493 treatment dramatically reduces metastatic tumor burden. Furthermore, metastases in treated animals have a less invasive morphology. We show in vitro that CNI-1493 decreases M2-stimulated Ewing Sarcoma tumor cell invasion and extravasation, offering a functional mechanism through which CNI-1493 attenuates metastasis. These data indicate that CNI-1493 may be a safe and effective adjuvant agent for the prevention and treatment of metastatic Ewing Sarcoma.

3-D individual cell based computational modeling of tumor cell-macrophage paracrine signaling mediated by EGF and CSF-1 gradients

High density of macrophages in mammary tumors has been associated with a higher risk of metastasis and thus increased mortality in women. The EGF/CSF-1 paracrine signaling increases the number of invasive tumor cells by both recruiting tumor cells further away and manipulating the macrophages' innate ability to open up a passage into blood vessels thus promoting intravasation and finally metastasis. A 3-D individual-cell-based model is introduced, to better understand the tumor cell-macrophage interactions, and to explore how changing parameters of the paracrine signaling system affects the number of invasive tumor cells. The simulation data and videos of the cell movements correlated well with findings from both in vitro and in vivo experimental results. The model demonstrated how paracrine signaling is necessary to achieve co-migration of tumor cells and macrophages towards a specific signaling source. We showed how the paracrine signaling enhances the number of both invasive tumor cells and macrophages. The simulations revealed that for the in vitro experiments the imposed no-flux boundary condition might be affecting the results, and that changing the setup might lead to different experimental findings. In our simulations, the 3 : 1 tumor cell/macrophage ratio, observed in vivo, was robust for many parameters but sensitive to EGF signal strength and fraction of macrophages in the tumor. The model can be used to identify new agents for targeted therapy and we suggest that a successful strategy to prevent or limit invasion of tumor cells would be to block the tumor cell-macrophage paracrine signaling. This can be achieved by either blocking the EGF or CSF-1 receptors or supressing the EGF or CSF-1 signal.