Gene expression analysis of macrophages that facilitate tumor invasion supports a role for Wnt-signaling in mediating their activity in primary mammary tumors

Angiogenic activity of breast cancer patients' monocytes reverted by combined use of systems modeling and experimental approaches

Angiogenesis plays a key role in tumor growth and cancer progression. TIE-2-expressing monocytes (TEM) have been reported to critically account for tumor vascularization and growth in mouse tumor experimental models, but the molecular basis of their pro-angiogenic activity are largely unknown. Moreover, differences in the pro-angiogenic activity between blood circulating and tumor infiltrated TEM in human patients has not been established to date, hindering the identification of specific targets for therapeutic intervention. In this work, we investigated these differences and the phenotypic reversal of breast tumor pro-angiogenic TEM to a weak pro-angiogenic phenotype by combining Boolean modelling and experimental approaches. Firstly, we show that in breast cancer patients the pro-angiogenic activity of TEM increased drastically from blood to tumor, suggesting that the tumor microenvironment shapes the highly pro-angiogenic phenotype of TEM. Secondly, we predicted in silico all minimal perturbations transitioning the highly pro-angiogenic phenotype of tumor TEM to the weak pro-angiogenic phenotype of blood TEM and vice versa. In silico predicted perturbations were validated experimentally using patient TEM. In addition, gene expression profiling of TEM transitioned to a weak pro-angiogenic phenotype confirmed that TEM are plastic cells and can be reverted to immunological potent monocytes. Finally, the relapse-free survival analysis showed a statistically significant difference between patients with tumors with high and low expression values for genes encoding transitioning proteins detected in silico and validated on patient TEM. In conclusion, the inferred TEM regulatory network accurately captured experimental TEM behavior and highlighted crosstalk between specific angiogenic and inflammatory signaling pathways of outstanding importance to control their pro-angiogenic activity. Results showed the successful in vitro reversion of such an activity by perturbation of in silico predicted target genes in tumor derived TEM, and indicated that targeting tumor TEM plasticity may constitute a novel valid therapeutic strategy in breast cancer.

Microenvironmental regulation of therapeutic response in cancer

The tumor microenvironment (TME) not only plays a pivotal role during cancer progression and metastasis but also has profound effects on therapeutic efficacy. In the case of microenvironment-mediated resistance this can involve an intrinsic response, including the co-option of pre-existing structural elements and signaling networks, or an acquired response of the tumor stroma following the therapeutic insult. Alternatively, in other contexts, the TME has a multifaceted ability to enhance therapeutic efficacy. This review examines recent advances in our understanding of the contribution of the TME during cancer therapy and discusses key concepts that may be amenable to therapeutic intervention.

Targeting cell-intrinsic and cell-extrinsic mechanisms of intravasation in invasive breast cancer

The survival of breast cancer patients with metastatic disease has not markedly improved over recent decades, highlighting the need to better understand this process. In this issue of Science Signaling, Pignatelli et al. used freshly obtained invasive ductal carcinoma cells from patients to demonstrate the need for high abundance of the invasive isoform of the Mena protein (Mena(INV)) in cancer cells and colony-stimulating factor 1 (CSF-1)-mediated paracrine signaling in macrophages for efficient transendothelial migration and metastasis formation in all clinical breast cancer subtypes. Furthermore, the triple negative and HER2(+) subtypes, but not the ERPR(+)/HER2(-) subtype, had high CSF-1 receptor (CSF-1R) abundance and also partially used autocrine CSF-1/CSF-1R signaling for invasion. These data establish Mena(INV), CSF-1/CSF-1R, and macrophages as potential therapeutic targets for most human breast cancers.

Tumor-induced senescent T cells promote the secretion of pro-inflammatory cytokines and angiogenic factors by human monocytes/macrophages through a mechanism that involves Tim-3 and CD40L

Solid tumors are infiltrated by immune cells where macrophages and senescent T cells are highly represented. Within the tumor microenvironment, a cross-talk between the infiltrating cells may occur conditioning the characteristic of the in situ immune response. Our previous work showed that tumors induce senescence of T cells, which are powerful suppressors of lympho-proliferation. In this study, we report that Tumor-Induced Senescent (TIS)-T cells may also modulate monocyte activation. To gain insight into this interaction, CD4+ or CD8+TIS-T or control-T cells were co-incubated with autologous monocytes under inflammatory conditions. After co-culture with CD4+ or CD8+TIS-T cells, CD14+ monocytes/macrophages (Mo/Ma) exhibit a higher expression of CD16+ cells and a reduced expression of CD206. These Mo/Ma produce nitric oxide and reactive oxygen species; however, TIS-T cells do not modify phagocyte capacity of Mo/Ma. TIS-T modulated-Mo/Ma show a higher production of pro-inflammatory cytokines (TNF, IL-1β and IL-6) and angiogenic factors (MMP-9, VEGF-A and IL-8) and a lower IL-10 and IP-10 secretion than monocytes co-cultured with controls. The mediator(s) present in the supernatant of TIS-T cell/monocyte-macrophage co-cultures promote(s) tubulogenesis and tumor-cell survival. Monocyte-modulation induced by TIS-T cells requires cell-to-cell contact. Although CD4+ shows different behavior from CD8+TIS-T cells, blocking mAbs against T-cell immunoglobulin and mucin protein 3 and CD40 ligand reduce pro-inflammatory cytokines and angiogenic factors production, indicating that these molecules are involved in monocyte/macrophage modulation by TIS-T cells. Our results revealed a novel role for TIS-T cells in human monocyte/macrophage modulation, which may have deleterious consequences for tumor progression. This modulation should be considered to best tailor the immunotherapy against cancer.

Functional Relationship between Tumor-Associated Macrophages and Macrophage Colony-Stimulating Factor as Contributors to Cancer Progression

The current review article describes the functional relationship between tumor-associated macrophages (TAM) as key cellular contributors to cancer malignancy on the one hand and macrophage-colony-stimulating factor (M-CSF or CSF-1) as an important molecular contributor on the other. We recapitulate the available data on expression of M-CSF and the M-CSF receptor (M-CSFR) in human tumor tissue as constituents of a stromal macrophage signature and on the limits of the predictive and prognostic value of plasma M-CSF levels. After providing an update on current insights into the nature of TAM heterogeneity at the level of M1/M2 phenotype and TAM subsets, we give an overview of experimental evidence, based on genetic, antibody-mediated, and pharmacological disruption of M-CSF/M-CSFR signaling, for the extent to which M-CSFR signaling can not only determine the TAM quantity, but can also contribute to shaping the phenotype and heterogeneity of TAM and other related tumor-infiltrating myeloid cells (TIM). Finally, we review the accumulating information on the – sometimes conflicting – effects blocking M-CSFR signaling may have on various aspects of cancer progression such as tumor growth, invasion, angiogenesis, metastasis, and resistance to therapy and we thereby discuss in how far these different effects actually reflect a contribution of TAM.

Tumour Microenvironment: Overview with an Emphasis on the Colorectal Liver Metastasis Pathway

The tumour microenvironment (TME) represents a dynamic network that plays an important role in tumour initiation, proliferation, growth, and metastasis. Cell behaviour may be regulated by interplay of molecular interactions involving positive and negative reinforcement as well as a high level of cross-talk, which determines this system. Additionally, cancer involves cell proliferation, its malignancy defined by the tumour's ability to break down normal tissue architecture and by a dynamic process of invasion and metastasis. The metastatic cascade is regulated by a chain of molecular steps which triggers the progression of the developing cancer cell in the primary tumour into a number of transformations, leading to invasion and proceeding to metastases. Tumour-associated macrophages (TAMs) play a key-role in the progression from inflammatory conditions to cancer; TAMs are also capable of infiltrating the tumour microenvironment. Furthermore, myeloid-derived suppressor cells (MDSCs), a population of inhibitory immune cells, have been reported to increase in various cancer types, although characterising human MDSCs remains difficult, as their phenotype is quite variable. The future of cancer treatment is likely to involve creating more drugs that target these elements as well as others. An overview of the tumour's microenvironment is, therefore, presented in this paper, focusing on the metastatic pathways of primary colorectal cancer to the liver.

Macrophage iron homeostasis and polarization in the context of cancer

Macrophages are central in regulating iron homeostasis, which is tightly linked to their versatile role during innate immunity. They sequester iron by phagocytosis of senescent erythrocytes and represent a major source of available iron in the body. Macrophage iron homeostasis is coupled to the functional heterogeneity and plasticity of these cells, with their extreme roles during inflammation, immune modulation, and resolution of inflammation. It is now appreciated that the macrophage polarization process dictates expression profiles of genes involved in iron metabolism. Therefore, macrophages have evolved a multitude of mechanisms to sequester, transport, store, and release iron. A new, enigmatic protein entering the iron scene and affecting the macrophage phenotype is lipocalin-2. Iron sequestration in macrophages depletes the microenvironment, thereby limiting extracellular pathogen or tumor growth, while fostering inflammation. In contrast, iron release from macrophages contributes to bystander cell proliferation, which is important for tissue regeneration and repair. This dichotomy is also reflected by the dual role of lipocalin-2 in macrophages. Unfortunately, the iron release macrophage phenotype is also a characteristic of tumor-associated macrophages and stimulates tumor cell survival and growth. Iron sequestration versus its release is now appreciated to be associated with the macrophage polarization program and can be used to explain a number of biological functions attributed to distinct macrophage phenotypes. Here we discuss macrophage iron homeostasis with a special focus on lipocalin-2 related to the formation and function of tumor-associated macrophages.

Integrated miRNA and mRNA profiling of tumor-educated macrophages identifies prognostic subgroups in estrogen receptor-positive breast cancer

Introduction

Various studies have identified aberrantly expressed miRNAs in breast cancer and demonstrated an association between distinct miRNAs and malignant progression as well as metastasis. Even though tumor‐associated macrophages (TAM) are known mediators of these processes, little is known regarding their miRNA expression upon education by malignant cells in vivo.

Methods

We profiled miRNA and mRNA expression of in vitro tumor‐educated macrophages (TEM) by indirectly co‐culturing with estrogen‐receptor‐positive (ER+) MCF‐7 breast cancer cells. The prognostic power of the resulting miRNA list was investigated in primary breast cancer datasets and compared to other signatures. Furthermore, miRNA expression levels were correlated to mRNA expression of macrophage markers and the impact on prognosis was assessed.

Results

Through the evaluation of the group effects between differentially‐expressed miRNAs and their target mRNAs in TEM, the power of detecting regulated miRNAs was greatly increased. The resulting list of 96 miRNAs predicts disease‐free survival (DFS) in external datasets of ER+ breast cancer patients and performs well in comparison with other miRNA signatures. Clustering with the predefined miRNA list revealed a significant difference in survival between the two resulting patient groups. Furthermore, an optimized miRNA list, based on correlations with macrophages markers, proved even more capable at identifying patient clusters significantly differing in DFS.

Conclusions

In vitro profiling of TEM and subsequent bioinformatic verification identified miRNAs with a high prognostic power for DFS when transferred into the clinical setting of primary breast cancer. The resulting miRNAs not only verify previously established findings but also lead to new prognostic markers. Furthermore, our data suggest that TAM contribute to the total miRNA expression profile of ER + breast cancers.

miRNA and mRNA were measured in macrophages exposed to ER + breast cancer cells.

Regulated miRNAs were detected by analyzing group effects of mRNA targets.

The resulting miRNA list has good prognostic value for DFS in ER + breast cancer.

Correlation of miRNAs to macrophage markers improved identification of clusters differing in DFS.

Analysis of tumour- and stroma-supplied proteolytic networks reveals a brain-metastasis-promoting role for cathepsin S

Metastasis remains the most common cause of death in most cancers, with limited therapies for combating disseminated disease. While the primary tumor microenvironment is an important regulator of cancer progression, it is less well understood how different tissue environments influence metastasis. We analyzed tumor-stroma interactions that modulate organ tropism of brain, bone and lung metastasis in xenograft models. We identified a number of potential modulators of site-specific metastasis, including cathepsin S as a regulator of breast-to-brain metastasis. High cathepsin S expression at the primary site correlated with decreased brain metastasis-free survival in breast cancer patients. Both macrophages and tumor cells produce cathepsin S, and only the combined depletion significantly reduced brain metastasis in vivo. Cathepsin S specifically mediates blood-brain barrier transmigration via proteolytic processing of the junctional adhesion molecule (JAM)-B. Pharmacological inhibition of cathepsin S significantly reduced experimental brain metastasis, supporting its consideration as a therapeutic target for this disease.

Macrophage immunomodulation by breast cancer-derived exosomes requires Toll-like receptor 2-mediated activation of NF-κB

Growing evidence links tumor progression with chronic inflammatory processes and dysregulated activity of various immune cells. In this study, we demonstrate that various types of macrophages internalize microvesicles, called exosomes, secreted by breast cancer and non-cancerous cell lines. Although both types of exosomes targeted macrophages, only cancer-derived exosomes stimulated NF-κB activation in macrophages resulting in secretion of pro-inflammatory cytokines such as IL-6, TNFα, GCSF, and CCL2. In vivo mouse experiments confirmed that intravenously injected exosomes are efficiently internalized by macrophages in the lung and brain, which correlated with upregulation of inflammatory cytokines. In mice bearing xenografted human breast cancers, tumor-derived exosomes were internalized by macrophages in axillary lymph nodes thereby triggering expression of IL-6. Genetic ablation of Toll-like receptor 2 (TLR2) or MyD88, a critical signaling adaptor in the NF-κB pathway, completely abolished the effect of tumor-derived exosomes. In contrast, inhibition of TLR4 or endosomal TLRs (TLR3/7/8/9) failed to abrogate NF-κB activation by exosomes. We further found that palmitoylated proteins present on the surface of tumor-secreted exosomes contributed to NF-κB activation. Thus, our results highlight a novel mechanism used by breast cancer cells to induce pro-inflammatory activity of distant macrophages through circulating exosomal vesicles secreted during cancer progression.

CSF-1R signaling in health and disease: a focus on the mammary gland

Colony-stimulating factor-1 (CSF-1), also known as macrophage-colony stimulating factor (M-CSF), is the primary growth factor regulating survival, proliferation and differentiation of macrophages. It is also a potent chemokine for macrophages and monocytes. Signaling via the CSF-1 receptor (CSF-1R) is necessary for the production of almost all tissue resident macrophage populations and these macrophages participate, via trophic mechanisms, in the normal development and homeostasis of tissues and organs in which they reside, including the mammary gland. The drawback of this close interaction between macrophages and parenchymal cells is that dysregulation of macrophage trophic functions assists in the development and progression of many cancers, including breast cancer. Furthermore, tumour cells secrete CSF-1 to attract more macrophages to the tumour microenvironment where CSF-1R signaling frequently drives the behaviour of these tumour-associated macrophages (TAMs) to promote tumour progression and metastasis. Evidence is mounting that treated tumours secrete more CSF-1 and the increased recruitment of TAMs limits treatment efficacy. Thus, therapeutic targeting of the CSF-1R to inhibit TAM function is likely to enhance tumour response and improve patient outcomes in the treatment of cancer, including breast cancer.

Tumor-associated macrophages contribute to tumor progression in ovarian cancer

Ovarian cancer is the leading cause of death in women with gynecological malignancy and improvements in current treatments are needed. As with many other solid cancers, the ovarian tumor microenvironment is emerging as a key player in tumor progression and a potential therapeutic target. The tumor microenvironment contains several non-malignant cell types that are known to contribute to tumor progression and metastasis. Included in this population of non-malignant cells are several different types of immune cells, of which tumor-associated macrophages (TAMs) are the most abundant. An increasing amount of evidence is emerging to suggest that TAMs display a unique activation profile in ovarian tumors and are able to create an immunosuppressive microenvironment, allowing tumors to evade immune detection and promoting tumor progression. Therefore, an increased understanding of how these immune cells interact with tumor cells and the microenvironment will greatly benefit the development of more effective immunotherapies to treat ovarian cancer. This review focuses on the role of TAMs in the ovarian tumor microenvironment and how they promote tumor progression.

Progastrin represses the alternative activation of human macrophages and modulates their influence on colon cancer epithelial cells

Macrophage infiltration is a negative prognostic factor for most cancers but gastrointestinal tumors seem to be an exception. The effect of macrophages on cancer progression depends on their phenotype, which may vary between M1 (pro-inflammatory, defensive) to M2 (tolerogenic, pro-tumoral). Gastrointestinal cancers often become an ectopic source of gastrins and macrophages present receptors for these peptides. The aim of the present study is to analyze whether gastrins can affect the pattern of macrophage infiltration in colorectal tumors. We have evaluated the relationship between gastrin expression and the pattern of macrophage infiltration in samples from colorectal cancer and the influence of these peptides on the phenotype of macrophages differentiated from human peripheral monocytes in vitro. The total number of macrophages (CD68+ cells) was similar in tumoral and normal surrounding tissue, but the number of M2 macrophages (CD206+ cells) was significantly higher in the tumor. However, the number of these tumor-associated M2 macrophages correlated negatively with the immunoreactivity for gastrin peptides in tumor epithelial cells. Macrophages differentiated from human peripheral monocytes in the presence of progastrin showed lower levels of M2-markers (CD206, IL10) with normal amounts of M1-markers (CD86, IL12). Progastrin induced similar effects in mature macrophages treated with IL4 to obtain a M2-phenotype or with LPS plus IFNγ to generate M1-macrophages. Macrophages differentiated in the presence of progastrin presented a reduced expression of Wnt ligands and decreased the number and increased cell death of co-cultured colorectal cancer epithelial cells. Our results suggest that progastrin inhibits the acquisition of a M2-phenotype in human macrophages. This effect exerted on tumor associated macrophages may modulate cancer progression and should be taken into account when analyzing the therapeutic value of gastrin immunoneutralization.

Myeloid WNT7b mediates the angiogenic switch and metastasis in breast cancer

Oncogenic targets acting in both tumor cells and tumor stromal cells may offer special therapeutic appeal. Interrogation of the Oncomine database revealed that 52 of 53 human breast carcinomas showed substantial upregulation of WNT family ligand WNT7B. Immunolabeling of human mammary carcinoma showed that WNT7B immunoreactivity was associated with both tumor cells and with tumor-associated macrophages. In the MMTV-PymT mouse model of mammary carcinoma, we found tumor progression relied upon WNT7B produced by myeloid cells in the microenvironment. Wnt7b deletion in myeloid cells reduced the mass and volume of tumors due to a failure in the angiogenic switch. In the tumor overall, there was no change in expression of Wnt/β-catenin pathway target genes, but in vascular endothelial cells (VEC), expression of these genes was reduced, suggesting that VECs respond to Wnt/β-catenin signaling. Mechanistic investigations revealed that failure of the angiogenic switch could be attributed to reduced Vegfa mRNA and protein expression in VECs, a source of VEGFA mRNA in the tumor that was limiting in the absence of myeloid WNT7B. We also noted a dramatic reduction in lung metastasis associated with decreased macrophage-mediated tumor cell invasion. Together, these results illustrated the critical role of myeloid WNT7B in tumor progression, acting at the levels of angiogenesis, invasion, and metastasis. We suggest that therapeutic suppression of WNT7B signaling might be advantageous due to targeting multiple aspects of tumor progression.

The tumor microenvironment shapes lineage, transcriptional, and functional diversity of infiltrating myeloid cells

Myeloid cells play important regulatory roles within the tumor environment by directly promoting tumor progression and modulating the function of tumor-infiltrating lymphocytes, and as such, they represent a potential therapeutic target for the treatment of cancer. Although distinct subsets of tumor-associated myeloid cells have been identified, a broader analysis of the complete myeloid cell landscape within individual tumors and also across different tumor types has been lacking. By establishing the developmental and transcriptomic signatures of infiltrating myeloid cells from multiple primary tumors, we found that tumor-associated macrophages (TAM) and tumor-associated neutrophils (TAN), while present within all tumors analyzed, exhibited strikingly different frequencies, gene expression profiles, and functions across cancer types. We also evaluated the impact of anatomic location and circulating factors on the myeloid cell composition of tumors. The makeup of the myeloid compartment was determined by the tumor microenvironment rather than the anatomic location of tumor development or tumor-derived circulating factors. Protumorigenic and hypoxia-associated genes were enriched in TAMs and TANs compared with splenic myeloid-derived suppressor cells. Although all TANs had an altered expression pattern of secretory effector molecules, in each tumor type they exhibited a unique cytokine, chemokine, and associated receptor expression profile. One such molecule, haptoglobin, was uniquely expressed by 4T1 TANs and identified as a possible diagnostic biomarker for tumors characterized by the accumulation of myeloid cells. Thus, we have identified considerable cancer-specific diversity in the lineage, gene expression, and function of tumor-infiltrating myeloid cells.

Mechanisms driving macrophage diversity and specialization in distinct tumor microenvironments and parallelisms with other tissues

Macrophages are extremely versatile cells that adopt a distinct phenotype in response to a changing microenvironment. Consequently, macrophages are involved in diverse functions, ranging from organogenesis and tissue homeostasis to recognition and destruction of invading pathogens. In cancer, tumor-associated macrophages (TAM) often contribute to tumor progression by increasing cancer cell migration and invasiveness, stimulating angiogenesis, and suppressing anti-tumor immunity. Accumulating evidence suggests that these different functions could be exerted by specialized TAM subpopulations. Here, we discuss the potential underlying mechanisms regulating TAM specialization and elaborate on TAM heterogeneity in terms of their ontogeny, activation state, and intra-tumoral localization. In addition, parallels are drawn between TAM and macrophages in other tissues. Together, a better understanding of TAM diversity could provide a rationale for novel strategies aimed at targeting the most potent tumor-supporting macrophages.

The M1 and M2 paradigm of macrophage activation: time for reassessment

Macrophages are endowed with a variety of receptors for lineage-determining growth factors, T helper (Th) cell cytokines, and B cell, host, and microbial products. In tissues, macrophages mature and are activated in a dynamic response to combinations of these stimuli to acquire specialized functional phenotypes. As for the lymphocyte system, a dichotomy has been proposed for macrophage activation: classic vs. alternative, also M1 and M2, respectively. In view of recent research about macrophage functions and the increasing number of immune-relevant ligands, a revision of the model is needed. Here, we assess how cytokines and pathogen signals influence their functional phenotypes and the evidence for M1 and M2 functions and revisit a paradigm initially based on the role of a restricted set of selected ligands in the immune response.

Macrophages mediate a switch between canonical and non-canonical Wnt pathways in canine mammary tumors

Objective

According to the current hypothesis, tumor-associated macrophages (TAMs) are “corrupted” by cancer cells and subsequently facilitate, rather than inhibit, tumor metastasis. Because the molecular mechanisms of cancer cell–TAM interactions are complicated and controversial we aimed to better define this phenomenon.

Methods and Results

Using microRNA microarrays, Real-time qPCR and Western blot we showed that co-culture of canine mammary tumor cells with TAMs or treatment with macrophage-conditioned medium inhibited the canonical Wnt pathway and activated the non-canonical Wnt pathway in tumor cells. We also showed that co-culture of TAMs with tumor cells increased expression of canonical Wnt inhibitors in TAMs. Subsequently, we demonstrated macrophage-induced invasive growth patterns and epithelial–mesenchymal transition of tumor cells. Validation of these results in canine mammary carcinoma tissues (n = 50) and xenograft tumors indicated the activation of non-canonical and canonical Wnt pathways in metastatic tumors and non-metastatic malignancies, respectively. Activation of non-canonical Wnt pathway correlated with number of TAMs.

Conclusions

We demonstrated that TAMs mediate a “switch” between canonical and non-canonical Wnt signaling pathways in canine mammary tumors, leading to increased tumor invasion and metastasis.

Interestingly, similar changes in neoplastic cells were observed in the presence of macrophage-conditioned medium or live macrophages. These observations indicate that rather than being “corrupted” by cancer cells, TAMs constitutively secrete canonical Wnt inhibitors that decrease tumor proliferation and development, but as a side effect, they induce the non-canonical Wnt pathway, which leads to tumor metastasis.

These data challenge the conventional understanding of TAM–cancer cell interactions.

Immune chaperone gp96 drives the contributions of macrophages to inflammatory colon tumorigenesis

Macrophages are important drivers in the development of inflammation-associated colon cancers, but the mechanistic underpinnings for their contributions are not fully understood. Furthermore, Toll-like receptors have been implicated in colon cancer, but their relevant cellular sites of action are obscure. In this study, we show that the endoplasmic reticulum chaperone gp96 is essential in tumor-associated macrophages (TAM) to license their contributions to inflammatory colon tumorigenesis. Mice where gp96 was genetically deleted in a macrophage-specific manner exhibited reduced colitis and inflammation-associated colon tumorigenesis. Attenuation of colon cancer in these mice correlated strikingly with reduced mutation rates of β-catenin, increased efficiency of the DNA repair machinery, and reduced expression of proinflammatory cytokines, including interleukin (IL)-17 and IL-23 in the tumor microenvironment. The genotoxic nature of TAM-associated inflammation was evident by increased expression of genes in the DNA repair pathway. Our work deepens understanding of how TAM promote oncogenesis by altering the molecular oncogenic program within epithelial cells, and it identifies gp96 as a lynchpin chaperone needed in TAM to license their function and impact on expression of critical inflammatory cytokines in colon tumorigenesis.

The role of tumor-associated macrophages in tumor vascularization

Tumor vascularization is a highly complex process that involves the interaction between tumors and their surrounding stroma, as well as many distinct angiogenesis-regulating factors. Tumor associated macrophages (TAMs) represent one of the most abundant cell components in the tumor environment and key contributors to cancer-related inflammation. A large body of evidence supports the notion that TAMs play a critical role in promoting the formation of an abnormal tumor vascular network and subsequent tumor progression and invasion. Clinical and experimental evidence has shown that high levels of infiltrating TAMs are associated with poor patient prognosis and tumor resistance to therapies. In addition to stimulating angiogenesis during tumor growth, TAMs enhance tumor revascularization in response to cytotoxic therapy (e.g., radiotherapy), thereby causing cancer relapse. In this review, we highlight the emerging data related to the phenotype and polarization of TAMs in the tumor microenvironment, as well as the underlying mechanisms of macrophage function in the regulation of the angiogenic switch and tumor vascularization. Additionally, we discuss the potential of targeting pro-angiogenic TAMs, or reprograming TAMs toward a tumoricidal and angiostatic phenotype, to promote normalization of the tumor vasculature to enhance the outcome of cancer therapies.

PIIKA 2: an expanded, web-based platform for analysis of kinome microarray data

Kinome microarrays are comprised of peptides that act as phosphorylation targets for protein kinases. This platform is growing in popularity due to its ability to measure phosphorylation-mediated cellular signaling in a high-throughput manner. While software for analyzing data from DNA microarrays has also been used for kinome arrays, differences between the two technologies and associated biologies previously led us to develop Platform for Intelligent, Integrated Kinome Analysis (PIIKA), a software tool customized for the analysis of data from kinome arrays. Here, we report the development of PIIKA 2, a significantly improved version with new features and improvements in the areas of clustering, statistical analysis, and data visualization. Among other additions to the original PIIKA, PIIKA 2 now allows the user to: evaluate statistically how well groups of samples cluster together; identify sets of peptides that have consistent phosphorylation patterns among groups of samples; perform hierarchical clustering analysis with bootstrapping; view false negative probabilities and positive and negative predictive values for t-tests between pairs of samples; easily assess experimental reproducibility; and visualize the data using volcano plots, scatterplots, and interactive three-dimensional principal component analyses. Also new in PIIKA 2 is a web-based interface, which allows users unfamiliar with command-line tools to easily provide input and download the results. Collectively, the additions and improvements described here enhance both the breadth and depth of analyses available, simplify the user interface, and make the software an even more valuable tool for the analysis of kinome microarray data. Both the web-based and stand-alone versions of PIIKA 2 can be accessed via http://saphire.usask.ca.

Wiskott-Aldrich syndrome protein regulates leukocyte-dependent breast cancer metastasis

A paracrine interaction between epidermal growth factor (EGF)-secreting tumor-associated macrophages (TAMs) and colony-stimulating factor 1 (CSF-1)-secreting breast carcinoma cells promotes invasion and metastasis. Here, we show that mice deficient in the hematopoietic-cell-specific Wiskott-Aldrich syndrome protein (WASp) are unable to support TAM-dependent carcinoma cell invasion and metastasis in both orthotopic and transgenic models of mammary tumorigenesis. Motility and invasion defects of tumor cells were recapitulated ex vivo upon coculture with WASp(-/-) macrophages. Mechanistically, WASp is required for macrophages to migrate toward CSF-1-producing carcinoma cells, as well as for the release of EGF through metalloprotease-dependent shedding of EGF from the cell surface of macrophages. Our findings suggest that WASp acts to support both the migration of TAMs and the production of EGF, which in concert promote breast tumor metastasis.

Carcinoma cells misuse the host tissue damage response to invade the brain

The metastatic colonization of the brain by carcinoma cells is still barely understood, in particular when considering interactions with the host tissue. The colonization comes with a substantial destruction of the surrounding host tissue. This leads to activation of damage responses by resident innate immune cells to protect, repair, and organize the wound healing, but may distract from tumoricidal actions. We recently demonstrated that microglia, innate immune cells of the CNS, assist carcinoma cell invasion. Here we report that this is a fatal side effect of a physiological damage response of the brain tissue. In a brain slice coculture model, contact with both benign and malignant epithelial cells induced a response by microglia and astrocytes comparable to that seen at the interface of human cerebral metastases. While the glial damage response intended to protect the brain from intrusion of benign epithelial cells by inducing apoptosis, it proved ineffective against various malignant cell types. They did not undergo apoptosis and actually exploited the local tissue reaction to invade instead. Gene expression and functional analyses revealed that the C-X-C chemokine receptor type 4 (CXCR4) and WNT signaling were involved in this process. Furthermore, CXCR4-regulated microglia were recruited to sites of brain injury in a zebrafish model and CXCR4 was expressed in human stroke patients, suggesting a conserved role in damage responses to various types of brain injuries. Together, our findings point to a detrimental misuse of the glial damage response program by carcinoma cells resistant to glia-induced apoptosis.

A novel anti-CCN1 monoclonal antibody suppresses Rac-dependent cytoskeletal reorganization and migratory activities in breast cancer cells

CCN1, a secreted matrix-associated molecule, is involved in multiple cellular processes. Accumulating evidence supports that CCN1 plays an important role in tumorigenesis and progression of breast cancer. In this study, we have developed a novel CCN1 function-blocking monoclonal antibody (mAb), designated YM1B. YM1B binds to human CCN1 with high specificity, recognizing the native CCN1 structure with undisturbed disulfide linkages. Our analyses have mapped the YM1B recognition region to domain IV of CCN1, likely in proximity to the DM site. In breast cancer cells, CCN1 can induce actin reorganization, formation of lamellipodia, and cell migration/invasion through the αV integrins/Rac1/ERK signaling axis; these CCN1-dependent activities can be effectively suppressed by YM1B. Our results also suggest that YM1B may exert its CCN1-blocking effect by perturbing the interaction of CCN1 with vitronectin and fibronectin, which are ligands of αV integrins and instrumental for integrin activation. This CCN1-specific mAb may open a new potential avenue for therapeutic intervention of breast cancer progression.

Impaired mitochondrial metabolism and mammary carcinogenesis

Mitochondrial oxidative metabolism plays a key role in meeting energetic demands of cells by oxidative phosphorylation (OxPhos). Here, we have briefly discussed (a) the dynamic relationship that exists among glycolysis, the tricarboxylic acid (TCA) cycle, and OxPhos; (b) the evidence of impaired OxPhos (i.e. mitochondrial dysfunction) in breast cancer; (c) the mechanisms by which mitochondrial dysfunction can predispose to cancer; and (d) the effects of host and environmental factors that can negatively affect mitochondrial function. We propose that impaired OxPhos could increase susceptibility to breast cancer via suppression of the p53 pathway, which plays a critical role in preventing tumorigenesis. OxPhos is sensitive to a large number of factors intrinsic to the host (e.g. inflammation) as well as environmental exposures (e.g. pesticides, herbicides and other compounds). Polymorphisms in over 143 genes can also influence the OxPhos system. Therefore, declining mitochondrial oxidative metabolism with age due to host and environmental exposures could be a common mechanism predisposing to cancer.

Macrophage scavenger receptor a promotes tumor progression in murine models of ovarian and pancreatic cancer

Alternatively activated macrophages express the pattern recognition receptor scavenger receptor A (SR-A). We demonstrated previously that coculture of macrophages with tumor cells upregulates macrophage SR-A expression. We show in this study that macrophage SR-A deficiency inhibits tumor cell migration in a coculture assay. We further demonstrate that coculture of tumor-associated macrophages and tumor cells induces secretion of factors that are recognized by SR-A on tumor-associated macrophages. We tentatively identified several potential ligands for the SR-A receptor in tumor cell-macrophage cocultures by mass spectrometry. Competing with the coculture-induced ligand in our invasion assay recapitulates SR-A deficiency and leads to similar inhibition of tumor cell invasion. In line with our in vitro findings, tumor progression and metastasis are inhibited in SR-A(-/-) mice in two in vivo models of ovarian and pancreatic cancer. Finally, treatment of tumor-bearing mice with 4F, a small peptide SR-A ligand able to compete with physiological SR-A ligands in vitro, recapitulates the inhibition of tumor progression and metastasis observed in SR-A(-/-) mice. Our observations suggest that SR-A may be a potential drug target in the prevention of metastatic cancer progression.

Imaging interactions between macrophages and tumour cells that are involved in metastasis in vivo and in vitro

Tumour-associated macrophages participate in several protumour functions including tumour growth and angiogenesis, and facilitate almost every step of the metastatic cascade. Interfering with macrophage functions may therefore provide an important strategy in the clinical management of cancer and metastatic disease. Our understanding of macrophage functions has been greatly expanded by direct observations of macrophage-carcinoma cell interactions using light microscopy. Imaging approaches include intravital microscopy of tumours in mouse models of cancer and visualization of macrophage-carcinoma cell interactions in in vitro assays; whether atop 2D substrates, embedded in 3D matrices or in more complex assemblies of multiple cell types that mimic specific topologies of the tumour microenvironment. Such imaging and reconstitution approaches have provided us with a wealth of information on the motile behaviour and physical associations between macrophages and carcinoma cells and the role of the tumour microenvironment in influencing the movement of these cells. Finally, high-resolution imaging techniques have permitted researchers to correlate motility patterns with specific gene signatures and biochemical pathways in cells, pointing to potential targets for intervention. Here, we review experimental approaches employed in the study of macrophage interactions with carcinoma cells with an emphasis on imaging invasive and metastatic cell motility in breast carcinomas.

Pharmacological inhibition of the Wnt acyltransferase PORCN prevents growth of WNT-driven mammary cancer

Porcupine (PORCN) is a membrane bound O-acyltransferase that is required for Wnt palmitoylation, secretion, and biologic activity. All evaluable human Wnts require PORCN for their activity, suggesting that inhibition of PORCN could be an effective treatment for cancers dependent on excess Wnt activity. In this study, we evaluated the PORCN inhibitor Wnt-C59 (C59), to determine its activity and toxicity in cultured cells and mice. C59 inhibits PORCN activity in vitro at nanomolar concentrations, as assessed by inhibition of Wnt palmitoylation, Wnt interaction with the carrier protein Wntless/WLS, Wnt secretion, and Wnt activation of β-catenin reporter activity. In mice, C59 displayed good bioavailability, as once daily oral administration was sufficient to maintain blood concentrations well above the IC(50). C59 blocked progression of mammary tumors in MMTV-WNT1 transgenic mice while downregulating Wnt/β-catenin target genes. Surprisingly, mice exhibit no apparent toxicity, such that at a therapeutically effective dose there were no pathologic changes in the gut or other tissues. These results offer preclinical proof-of-concept that inhibiting mammalian Wnts can be achieved by targeting PORCN with small-molecule inhibitors such as C59, and that this is a safe and feasible strategy in vivo.

Selective gene-expression profiling of migratory tumor cells in vivo predicts clinical outcome in breast cancer patients

Introduction

Metastasis of breast cancer is the main cause of death in patients. Previous genome-wide studies have identified gene-expression patterns correlated with cancer patient outcome. However, these were derived mostly from whole tissue without respect to cell heterogeneity. In reality, only a small subpopulation of invasive cells inside the primary tumor is responsible for escaping and initiating dissemination and metastasis. When whole tissue is used for molecular profiling, the expression pattern of these cells is masked by the majority of the noninvasive tumor cells. Therefore, little information is available about the crucial early steps of the metastatic cascade: migration, invasion, and entry of tumor cells into the systemic circulation.

Methods

In the past, we developed an in vivo invasion assay that can capture specifically the highly motile tumor cells in the act of migrating inside living tumors. Here, we used this assay in orthotopic xenografts of human MDA-MB-231 breast cancer cells to isolate selectively the migratory cell subpopulation of the primary tumor for gene-expression profiling. In this way, we derived a gene signature specific to breast cancer migration and invasion, which we call the Human Invasion Signature (HIS).

Results

Unsupervised analysis of the HIS shows that the most significant upregulated gene networks in the migratory breast tumor cells include genes regulating embryonic and tissue development, cellular movement, and DNA replication and repair. We confirmed that genes involved in these functions are upregulated in the migratory tumor cells with independent biological repeats. We also demonstrate that specific genes are functionally required for in vivo invasion and hematogenous dissemination in MDA-MB-231, as well as in patient-derived breast tumors. Finally, we used statistical analysis to show that the signature can significantly predict risk of breast cancer metastasis in large patient cohorts, independent of well-established prognostic parameters.

Conclusions

Our data provide novel insights into, and reveal previously unknown mediators of, the metastatic steps of invasion and dissemination in human breast tumors in vivo. Because migration and invasion are the early steps of metastatic progression, the novel markers that we identified here might become valuable prognostic tools or therapeutic targets in breast cancer.

Tumor-associated macrophages: function, phenotype, and link to prognosis in human lung cancer

Macrophages are the dominant leukocyte population found in the tumor microenvironment. Accumulating evidence suggests that these tumor-associated macrophages (TAMs) actively promote all aspects of tumor initiation, growth, and development. However, TAMs are not a single uniform population; instead, they are composed of multiple distinct pro- and anti-tumoral subpopulations with overlapping features depending on a variety of external factors. Defining and differentiating these subsets remains a challenging work-in-progress. These difficulties are apparent in prognostic studies in lung cancer that initially demonstrated conflicting evidence regarding the significance of TAMs but which have more recently clarified and confirmed the clinical importance of these subsets through improved phenotypic capabilities. Thus, these cells represent potential targets for cancer therapeutic initiatives through translational approaches. In this review, we summarize the current understanding of how the tumor microenvironment takes advantage of macrophage plasticity to mold an immunosuppressive population, the phenotypic heterogeneity of TAMs, and their link to prognosis in human lung cancer.

Instruction of myeloid cells by the tumor microenvironment: Open questions on the dynamics and plasticity of different tumor-associated myeloid cell populations

The versatility and plasticity of myeloid cell polarization/differentiation has turned out to be crucial in health and disease, and has become the subject of intense investigation during the last years. On one hand, myeloid cells provide a critical contribution to tissue homeostasis and repair. On the other hand, myeloid cells not only play an important role as first line defense against pathogens but also they are involved in a broad array of inflammation-related diseases such as cancer. Recent studies show that macrophages can exist in different activation states within the same tumor, underlining their plasticity and heterogeneity. In this review, we will discuss recent evidence on how the tumor microenvironment, as it evolves, shapes the recruitment, function, polarization and differentiation of the myeloid cell compartment, leading to the selection of myeloid cells with immunosuppressive and angiogenic functions that facilitate tumor progression and dissemination.

Interaction between regulatory T cells and cancer stem cells

The concept that cancer stem cells (CSCs)/tumor stem cells/cancer-initiating cells are one of the key centers to cure neoplastic disease has drawn an increasing attention recent years. Because of their high resistance and potential to initiate tumors, CSCs are considered a critical factor associated with tumor relapse. Regulatory T(T(reg)) cells, a group of immune cells with tumor-promoting effect, exert their function through inhibition of effector T cells and regulation of the tumor microenvironment by producing a series of soluble factors. However, the interactions between T(reg)s and CSCs are less understood. The mechanisms of how T(reg)s, as tumor-promoting cells, manipulate CSCs remain obscure. In this review, we elucidate their interactions.

β-Catenin signaling regulates Foxa2 expression during endometrial hyperplasia formation

The Wnt/β-catenin signaling is essential for various organogenesis and is often implicated during tumorigenesis. Dysregulated β-catenin signaling is associated with the formation of endometrial adenocarcinomas (EACs), which is considered as the common form of endometrial cancer in women. In the current study, we investigate the downstream target of Wnt/β-catenin signaling in the uterine epithelia and the mechanism leading to the formation of endometrial hyperplasia. We report that conditional ablation and activation of β-catenin in the uterine epithelia lead to aberrant epithelial structures and endometrial hyperplasia formation, respectively. We demonstrate that β-catenin regulates Foxa2 with its candidate upstream region for the uterine epithelia. Furthermore, knockdown of Foxa2 leads to defects in cell cycle regulation, suggesting a possible function of Foxa2 in the control of cell proliferation. We also observe that β-catenin and Foxa2 expression levels are augmented in the human specimens of complex atypical endometrial hyperplasia, which is considered to have a greater risk of progression to EACs. Thus, our study indicates that β-catenin regulates Foxa2 expression, and this interaction is possibly essential to control cell cycle progression during endometrial hyperplasia formation. Altogether, the augmented expression levels of β-catenin and Foxa2 are essential features during the formation of endometrial hyperplasia.

Macrophages and angiogenesis: a role for Wnt signaling

Macrophages regulate many developmental and pathological processes in both embryonic and adult tissues, and recent studies have shown a significant role in angiogenesis. Similarly, Wnt signaling is fundamental to tissue morphogenesis and also has a role in vascular development. In this review, we summarize recent advances in the field of macrophage-regulated angiogenesis, with a focus on the role of macrophage-derived Wnt ligands. We review data that provide both direct and indirect evidence for macrophage-derived Wnt regulation of physiologic and pathologic angiogenesis. Finally, we propose that Wnt signaling plays a central role in differentiation of tumor associated and wound infiltrating macrophages to a proangiogenic phenotype.

Paracrine interactions between primary human macrophages and human fibroblasts enhance murine mammary gland humanization in vivo

INTRODUCTION

Macrophages comprise an essential component of the mammary microenvironment necessary for normal gland development. However, there is no viable in vivo model to study their role in normal human breast function. We hypothesized that adding primary human macrophages to the murine mammary gland would enhance and provide a novel approach to examine immune-stromal cell interactions during the humanization process.

METHODS

Primary human macrophages, in the presence or absence of ectopic estrogen stimulation, were used to humanize mouse mammary glands. Mechanisms of enhanced humanization were identified by cytokine/chemokine ELISAs, zymography, western analysis, invasion and proliferation assays; results were confirmed with immunohistological analysis.

RESULTS

The combined treatment of macrophages and estrogen stimulation significantly enhanced the percentage of the total gland humanized and the engraftment/outgrowth success rate. Timecourse analysis revealed the disappearance of the human macrophages by two weeks post-injection, suggesting that the improved overall growth and invasiveness of the fibroblasts provided a larger stromal bed for epithelial cell proliferation and structure formation. Confirming their promotion of fibroblasts humanization, estrogen-stimulated macrophages significantly enhanced fibroblast proliferation and invasion in vitro, as well as significantly increased proliferating cell nuclear antigen (PCNA) positive cells in humanized glands. Cytokine/chemokine ELISAs, zymography and western analyses identified TNFα and MMP9 as potential mechanisms by which estrogen-stimulated macrophages enhanced humanization. Specific inhibitors to TNFα and MMP9 validated the effects of these molecules on fibroblast behavior in vitro, as well as by immunohistochemical analysis of humanized glands for human-specific MMP9 expression. Lastly, glands humanized with macrophages had enhanced engraftment and tumor growth compared to glands humanized with fibroblasts alone.

CONCLUSIONS

Herein, we demonstrate intricate immune and stromal cell paracrine interactions in a humanized in vivo model system. We confirmed our in vivo results with in vitro analyses, highlighting the value of this model to interchangeably substantiate in vitro and in vivo results. It is critical to understand the signaling networks that drive paracrine cell interactions, for tumor cells exploit these signaling mechanisms to support their growth and invasive properties. This report presents a dynamic in vivo model to study primary human immune/fibroblast/epithelial interactions and to advance our knowledge of the stromal-derived signals that promote tumorigenesis.

The multi-faceted roles of prostaglandin E2 in cancer-infiltrating mononuclear phagocyte biology

Extensive research in the last two decades implemented that the inflammatory cell infiltrate, especially in solid tumors, is a major determinant for patient prognosis. Mononuclear phagocytes, i.e. monocytes/macrophages, dendritic cells and myeloid-derived suppressor cells, constitute the majority of tumor-associated immune cells. Instead of inducing anti-tumor immunity, mononuclear phagocytes are functionally subverted by tumor microenvironmental factors to support each stage of oncogenesis. Although mechanisms how tumors program their inflammatory infiltrate to support tumor development are ill-defined, few master regulators are beginning to emerge. One of them is the inflammatory eicosanoid prostaglandin E(2) (PGE(2)), produced by tumor cells or the infiltrating immune cells. In this review we summarize the impact of PGE(2) on mononuclear phagocytes in inflammation and cancer and discuss potential implications for cancer therapy.

Intratumoral hemorrhage, vessel density, and the inflammatory reaction contribute to volume increase of sporadic vestibular schwannomas

Vestibular schwannomas show a large variation in growth rate, making prediction and anticipation of tumor growth difficult. More accurate prediction of clinical behavior requires better understanding of tumor biological factors influencing tumor progression. Biological processes like intratumoral hemorrhage, cell proliferation, microvessel density, and inflammation were analyzed in order to determine their role in vestibular schwannoma development. Tumor specimens of 67 patients surgically treated for a histologically proven unilateral vestibular schwannoma were studied. Preoperative magnetic resonance imaging (MRI) scans were used to determine tumor size and to classify tumors as homogeneous, inhomogeneous, and cystic. Immunohistochemical studies evaluated cell proliferation (histone H3 and Ki-67), microvessel density (CD31), and inflammation (CD45 and CD68). Intratumoral hemorrhage was assessed by hemosiderin deposition. The expression patterns of these markers were compared with tumor size, tumor growth index, MRI appearance, patients’ age, and duration of symptoms. No relation between cell proliferation and clinical signs of tumor volume increase or MRI appearance was found. Intratumoral hemosiderin, microvessel density, and inflammation were significantly positively correlated with tumor size and the tumor growth index. Cystic and inhomogeneous tumors showed significantly more hemosiderin deposition than homogeneous tumors. The microvessel density was significantly higher in tumors with a high number of CD68-positive cells. The volume increase of vestibular schwannomas is not based on cell proliferation alone. Factors like intratumoral bleeding, (neo)vascularization, and intensity of the inflammatory reaction also influence tumor volume.

Macrophage-tumor crosstalk: role of TAMR tyrosine kinase receptors and of their ligands

Ample clinical and preclinical evidence indicates that macrophages interact with tumor cells as well as with virtually all populations of host cells present in the tumor microenvironment. This crosstalk can strongly promote malignancy, but also has in principle the potential to inhibit tumor growth. Thus, it is of the utmost importance to improve our understanding of the mechanisms driving the pro- and antimalignant behavior of tumor-associated macrophages (TAMs) in order to develop better anticancer therapies. In this review, we discuss the biological consequences of reciprocal interactions between TAMs, cancer cells, endothelial cells, fibroblasts and other leukocyte subfractions within tumors. It was recently elucidated that tumors specifically educate macrophages to secrete growth arrest-specific gene 6 (Gas6), the common ligand of the Tyro3, Axl, Mer receptor (TAMR) family. In turn, Gas6 fosters tumor growth by promoting cancer cell proliferation. Therefore, the Gas6-TAMR axis might represent a novel target for disrupting tumor-macrophage crosstalk. We summarize here what is known about TAMR and their ligands in (human) cancer biology. In order to shed more light on the role of macrophages in human cancer, we additionally provide an overview of what is currently known about the prognostic impact of TAMs in human cancer.

Basal-like breast cancer cells induce phenotypic and genomic changes in macrophages

Basal-like breast cancer (BBC) is an aggressive subtype of breast cancer that has no biologically targeted therapy. The interactions of BBCs with stromal cells are important determinants of tumor biology, with inflammatory cells playing well-recognized roles in cancer progression. Despite the fact that macrophage-BBC communication is bidirectional, important questions remain about how BBCs affect adjacent immune cells. This study investigated monocyte-to-macrophage differentiation and polarization and gene expression in response to coculture with basal-like versus luminal breast cancer cells. Changes induced by coculture were compared with changes observed under classical differentiation and polarization conditions. Monocytes (THP-1 cells) exposed to BBC cells in coculture had altered gene expression with upregulation of both M1 and M2 macrophage markers. Two sets of M1 and M2 markers were selected from the PCR profiles and used for dual immunofluorescent staining of BBC versus luminal cocultured THP-1s, and cancer-adjacent, benign tissue sections from patients diagnosed with BBCs or luminal breast cancer, confirming the differential expression patterns. Relative to luminal breast cancers, BBCs also increased differentiation of monocytes to macrophages and stimulated macrophage migration. Consistent with these changes in cellular phenotype, a distinct pattern of cytokine secretion was evident in macrophage-BBC cocultures, including upregulation of NAP-2, osteoprotegerin, MIG, MCP-1, MCP-3, and interleukin (IL)-1β. Application of IL-1 receptor antagonist (IL-1RA) to cocultures attenuated BBC-induced macrophage migration. These data contribute to an understanding of the BBC-mediated activation of the stromal immune response, implicating specific cytokines that are differentially expressed in basal-like microenvironments and suggesting plausible targets for modulating immune responses to BBCs.

Molecular networks that regulate cancer metastasis

Tumor metastases are responsible for approximately 90% of all cancer-related deaths. Although many patients can be cured, in the US and UK, cancer still causes 730,000 deaths every year, and it is second only to cardiovascular disease as a cause of death. The functional roles of many critical players involved in metastasis have been delineated in great detail in recent years, due to the draft of the human genome and to many associated discoveries. Here, we address several genetic events and critical factors that define the metastatic phenotype acquired during tumorigenesis. This involves molecular networks that promote local cancer-cell invasion, single-cell invasion, formation of the metastatic microenvironment of primary tumors, intravasation, lymphogenic metastasis, extravasation, and metastatic outgrowth. Altogether, these functional networks of molecules contribute to the development of a selective environment that promotes the seeding and malignant progression of tumorigenic cells in distant organs. We include here candidate target proteins and signaling pathways that are now under clinical investigation. Although many of these trials are still ongoing, they provide the basis for the development of new aspects in the treatment of metastatic cancers, which involves inhibition of these proteins and their molecular networks.

Coordinated regulation of myeloid cells by tumours

Myeloid cells are the most abundant nucleated haematopoietic cells in the human body and are a collection of distinct cell populations with many diverse functions. The three groups of terminally differentiated myeloid cells - macrophages, dendritic cells and granulocytes - are essential for the normal function of both the innate and adaptive immune systems. Mounting evidence indicates that the tumour microenvironment alters myeloid cells and can convert them into potent immunosuppressive cells. Here, we consider myeloid cells as an intricately connected, complex, single system and we focus on how tumours manipulate the myeloid system to evade the host immune response.

Accessories to the crime: functions of cells recruited to the tumor microenvironment

Mutationally corrupted cancer (stem) cells are the driving force of tumor development and progression. Yet, these transformed cells cannot do it alone. Assemblages of ostensibly normal tissue and bone marrow-derived (stromal) cells are recruited to constitute tumorigenic microenvironments. Most of the hallmarks of cancer are enabled and sustained to varying degrees through contributions from repertoires of stromal cell types and distinctive subcell types. Their contributory functions to hallmark capabilities are increasingly well understood, as are the reciprocal communications with neoplastic cancer cells that mediate their recruitment, activation, programming, and persistence. This enhanced understanding presents interesting new targets for anticancer therapy.

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.

GPCRs and cancer

G-protein-coupled receptors (GPCRs), which represent the largest gene family in the human genome, play a crucial role in multiple physiological functions as well as in tumor growth and metastasis. For instance, various molecules like hormones, lipids, peptides and neurotransmitters exert their biological effects by binding to these seven-transmembrane receptors coupled to heterotrimeric G-proteins, which are highly specialized transducers able to modulate diverse signaling pathways. Furthermore, numerous responses mediated by GPCRs are not dependent on a single biochemical route, but result from the integration of an intricate network of transduction cascades involved in many physiological activities and tumor development. This review highlights the emerging information on the various responses mediated by a selected choice of GPCRs and the molecular mechanisms by which these receptors exert a primary action in cancer progression. These findings provide a broad overview on the biological activity elicited by GPCRs in tumor cells and contribute to the identification of novel pharmacological approaches for cancer patients.

Global gene expression profiles of canine macrophages and canine mammary cancer cells grown as a co-culture in vitro

Background

Solid tumours comprise various cells, including cancer cells, resident stromal cells, migratory haemopoietic cells and other. These cells regulate tumour growth and metastasis. Macrophages constitute probably the most important element of all interactions within the tumour microenvironment. However, the molecular mechanism, that guides tumour environment, still remains unknown. Exploring the underlying molecular mechanisms that orchestrate these phenomena has been the aim of our study.

A co-culture of canine mammary cancer cells and macrophages was established and maintained for 72 hrs. Having sorted the cells, gene expression in cancer cells and macrophages, using DNA microarrays, was examined. The results were confirmed using real-time qPCR and confocal microscopy. Moreover, their ability for migration and invasion has been assessed.

Results

Microarray analysis showed that the up-regulated genes in the cancer cell lines are involved in 15 highly over-manifested pathways. The pathways that drew our diligent attention included: the inflammation pathway mediated by chemokine and cytokine, the Toll receptor signalling pathway and the B cell activation. The up-regulated genes in the macrophages were involved in only 18 significantly over-manifested pathways: the angiogenesis, the p53 pathway feedback loops2 and the Wnt signalling pathway. The microarray analysis revealed that co-culturing of cancer cells with macrophages initiated the myeloid-specific antigen expression in cancer cells, as well as cytokine/chemokine genes expression. This finding was confirmed at mRNA and protein level. Moreover, we showed that macrophages increase cancer migration and invasion.

Conclusions

The presence of macrophages in the cancer environment induces acquisition of the macrophage phenotype (specific antigens and chemokines/cytokines expression) in cancer cells. We presumed that cancer cells also acquire other myeloid features, such as: capabilities of cell rolling, spreading, migration and matrix invasion (what has also been confirmed by our results). It may, perhaps, be the result of myeloid-cancer cell hybrid formation, or cancer cells mimicking macrophages phenotype, owing to various proteins secreted by macrophages.

Tumor microenvironment: a main actor in the metastasis process

Over recent decades, various studies have argued that the metastatic tissue microenvironment is fully controlled by the intrinsic properties of the cancer cells (growth, motility and invasion, angiogenesis, extracellular matrix remodeling, immune escape) and additional cells types. Overall, the extrinsic factors and determinants mediate the contribution of the host microenvironment to metastasis formation. The tumor microenvironment carries out these functions by secretion of molecules that can influence and modulate its phenotype, making these complex interactions the basis for support for the progression of a cancer. Here, we undertake a summary of the "state of the art" of the functions and actions of these cells, as the main actors in the promotion of the formation of the microenvironment of the metastatic niche, and the associated network of interactions. The unraveling of the relationships between tumorigenic cells and their microenvironment represents an important issue for the development of new therapeutic agents that can fight both initiation and recurrence of cancer.